Sample records for zircon carburation studies

  1. Zircon Carburation Studies as Intermediate Stage in the Zirconium Fabrication; Estudios encaminados a la carburacion del circon como etapa intermedia en la obtencion de circonio

    Almagro Huertas, V.; Saenz de Tejada Gonzalez, L.; Lopez Rodriguez, M.


    Zirconium carbide and carbonitride mixtures were obtained by Kroll's method.Reaction products have been identified by micrography and X-ray diffraction analysis. The optimum graphite content in the initial charge for the carburation reaction has been studied. zirconium, silicon and carbon content in the final product has been controlled as a function of current in the furnace and reaction time.Further chlorination of the final product was performed successfully. (Author) 16 refs.

  2. Study on Carburizing Kinetics of Low-carbon Steel at High-temperature and Short-term

    Lu Sheng; Xiao Nianxin; Zhang Hailong


    In this paper, the carburizing kinetics of low-carbon steel at high-temperature and short-term in liquid cast-iron were studied by metallographic microscope, chemical analysis and so on, and the microstructure of carburized layer was also analyzed. The results show that the carburizing rate of low-carbon steel at high-temperature and short-term is so fast, and the microstructure of carburized layer possess higher carbon content, and cementite, pearlite and ferrite exist in carburized layer structure simultaneously. Besides, the kinetic equations of permeating layer forming have been presented, and the carburizing mechanism was preliminary discussed also.

  3. Kinetics and mechanical study of plasma electrolytic carburizing for pure iron

    Çavuşlu, F.; Usta, M.


    In this work, plasma electrolytic surface carburizing of pure iron in aqueous solution consisting of water, glycerin and NH4Cl was investigated. Surface carburizing was carried out in 20% glycerin solution treated at 750 °C, 800 °C, 900 °C and 950 °C temperatures for 5, 10 and 30 min. The formation of hard carbon-rich layer on the surface of pure iron was confirmed by XRD analysis. Metallographic and SEM studies revealed a rough and dense carburized layer on the surface of the pure iron. Experimental results showed that the thickness of the carburized layers changes with the time and temperature. The average thickness of the carburized layer ranged from 20 to 160 μm. The hardness of the carburized samples decreased with the distance from the surface to the interior of the test material. The average hardness values of the carburized layers on the substrate ranged 550-850 HV, while the hardness of the substrate ranged from 110 HV to 170 HV. The dominant phases formed on the pure iron were found to be a mixture of cementite (Fe3C), martensite (Fe + C) and austenite (FCC iron) confirmed by XRD. Wear resistance in all plasma electrolytic carburized samples is considerably improved in relation to the untreated specimen. After carburizing, surface roughness of the samples was increased. Friction coefficients were also increased because of high surface roughness.

  4. Study On The Effect Of Corrosion Behaviour Of Stainless Steel Before And After Carburizing Heat Treatment

    Sulaiman, S. A.; Alias, S. K.; Ahmad, S.; Fauzi, M. H. Mohd; Ahmad, N. N.


    This study investigates the effect of corrosion behaviour of stainless steel before and after carburizing process. All samples were prepared based on the testing specification requirement and the chemical compositions of the stainless steel were obtained using spectrometer tester. Samples were then undergoing pack carburizing process by adding 50g of carbon powder as the carburizing agent. Then the samples were heated at 900 °C and 950 °C for 8 hours. To obtain corrosion rate, weight loss test was conducted and the samples were immersed in three different solutions which were distilled water, hydrochloric acid and sodium chloride. Hardness and density test were employed to measure the physical properties of the ASTM 304 stainless steel. The microstructures of all samples were observed using Olympus BX41M optical microscope. The resulting phases after each heat treatment were tested by x-ray diffraction (XRD) tester. The percentage of corrosion values, determined from this technique, showed fairly good agreement. Carburizing process produced a carburizing layer improved mechanical properties and corrosion resistance abilities

  5. A study of internal oxidation in carburized steels by glow discharge optical emission spectroscopy and scanning electron microscopy

    An, X; Rainforth, W M; Chen, L


    The internal oxidation of Cr-Mn carburizing steel was studied. Internal oxidation was induced using a commercial carburizing process. Sputter erosion coupled with glow discharge optical emission spectroscopy (GDOES) was used to determine the depth profile elemental distribution within the internal oxidation layer (<10 mu m). In addition, scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS) studies were carried out on selected sputter eroded surfaces. Oxide type was identified primarily by transmission electron microscopy (TEM). The carburized surface was found to consist of a continuous oxide layer, followed by a complex internal oxidation layer, where Cr and Mn oxides were found to populate grain boundaries in a globular form in the near surface region. At greater depths (5-10 mu m), Si oxides formed as a grain boundary network. The internal oxides (mainly complex oxides) grew quickly during the initial stages of the carburizing process (2 h, 800 deg. C+3 h, 930 deg. C). G...

  6. Contribution to the study of gaseous Carburization of Uranium; Contribucion al estudio de la Carburacion gaesosa del uranio

    Esteban Hernandez, J. A.; Jimenez Moreno, J. M.; Villota Ruiz, P. de


    Thermal decomposition of uranium hydride powder obtained by hydrogenation of uranium turnings is studied on the first part of this paper. Carburization of the uranium hydride or metallic uranium powder with methane is studied in the second part. A method of uranium monocarbide fabrication under static atmosphere is described. On this method hydrogen is removed by means of an uranium getter. (Author) 6 refs.



    ABSTRACT In this study, retained austenite contents in carburized  SAE 8620 (21NiCrMo2) steel were investigated. Carburizing programs were carried out in gas atmosphere at 940°C. X-ray diffraction was used to determine retained austenite contents in the case-hardened microstructures of the carburized specimens. Test results indicated that maximum retained austenite contents at the microstructures of the carburized specimens that carburized 45 minute, 3 h and 5 h carburizing times at ...

  8. Accelerated Gas Carburizing (URX Gas Carburizing)

    Yoshikazu Shimosato; Mamoru Kamitani; Hiroyuki Nakatsu


    URX gas carburizing is an accelerated gas carburizing method with 50% CO + 50% H2 gas which comes from CH4 gas + CO2 gas. By using this gas composition, the carburizing reaction rate increases to the maximum and the controllability of carbon potential improves. A carbon mass flow rate is the product of the carburizing reaction rate multiplied by the difference of carbon percent between carbon potential of the gas and the carbon content of the surface of treated steel parts. We have obtained excellent results from the experimental tests at our laboratory as mentioned bellow. 1)Carburizing time can be shortened by 40% for 0.5 - 0.9 mm effective case depth. 2) Uniform carburizing case depth 3) Less internal oxidation with the same case depth. We have already developed the new roller hearth type continuous carburizing furnace and the new URX gas generator.

  9. Study of the 1.25Cr-1Mo-0.25V steel microstructure after a carburization phenomenon

    Simonetti, S., E-mail: [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Departamentos de Ciencias Basicas e Ingenieria Mecanica, Universidad Tecnologica Nacional, 11 de Abril 461, 8000 Bahia Blanca (Argentina); Lanz, C. [Departamento de Ingenieria, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina); Brizuela, G.; Juan, A. [Departamento de Fisica, Universidad Nacional del Sur, Av. Alem 1253, 8000 Bahia Blanca (Argentina)


    We studied the changes in the structure and carbide particle size in 1.25Cr-1Mo-0.25V steel under 600 deg. C and 168 MPa, after 4000 h service. We used microscopy and microanalysis techniques to analyze the carbide particles. We performed a complementary theoretical study on the chemical bonding and electronic structure of the carbide-Fe matrix interaction. The results contribute to the understanding of the changes in the alloy microstructure caused by the carburization phenomenon.

  10. Morphology and geochemistry of zircon: a case study on zircon from the microgranitoid enclaves

    汪相; KIENAST; Jean-Robert


    There are three types of zircon (i.e. Zircon A, Zircon B and Zircon C) in the microgranitoid enclaves from the Qingtian granite. Zircon A is of the smallest Ipr, Ipy and Iel values with the largest range of variations; Zircon C is of the largest Ipr, Ipy and Iel values with the smallest range of variations; and Zircon B is intermediate among the three types. The microprobe analysis of zircon demonstrates that the contents of trace elements (Hf, U, Y, Th) increase progressively with larger and larger variation from Zircon A through Zircon B to Zircon C. These characters snggest that the three types of zircon in the enclaves may have formed successively during the cooling process of enclave magma, corresponding to different sites along with the intrusion of enclave magma. Because of positive correlations of the UO2/HfO2 ratio with Ipr, the ThO2/Y2O3 ratio with Ipy, and the UO2/(ThO2 + Y2O3) ratio with Iel, it is suggested that the variation in zircon typology is caused

  11. Experimental Study on Vacuum Carburizing Process for Low-Carbon Alloy Steel

    Wei, Shaopeng; Wang, Gang; Zhao, Xianhui; Zhang, Xiaopeng; Rong, Yiming


    As a low-carbon alloy steel, 20Cr2Ni4A steel has an excellent mechanical properties. It has been used for producing heavy-duty gears, which require good wear and fatigue resistance. The vacuum carburizing process can improve the quality of gears and extend the service life. In this article, a complete heat-treatment process for 20Cr2Ni4A, with carburizing, tempering, quenching and cryogenic steps involved, was proposed. A numerical method was employed to design the carburizing step. The carburized samples were characterized by analysis of carbon profile, surface-retained austenite content, microstructure, and hardness profile. A good microstructure was obtained with acicular-tempered martensite, less-retained austenite, fine granular-dispersed carbides, and was oxide free. The final surface hardness was 64.2HRC, and the case depth was 0.86 mm, which meet the requirements of products. The relationships among process, performance, and microstructure were investigated to understand the inner connection.

  12. Mechanical properties of the CO{sub 2} free vacuum carburized in SCM415H

    Byun, Jae Hyuk; Ro, Seung Hoon; Lee, Jong Hyung; Lee, Chang Hun; Yang, Seong Hyeon [Kumoh Nat' l Institute of Technology, Gumi (Korea, Republic of)


    Vacuum carburizing is supposed to be the superior process to the gas carburizing. However, the vacuum carburizing has the stage in which hydrocarbon gas is supplied into the furnace to be pyrolysis, and consequently the stable heat treatment is hard to achieve due to the soot from the hydrocarbon pyrolysis. Recently, many studies have been made which utilize acetylene gas to overcome this defects. In this paper, the carburizing and the diffusion periods have been selected based on the Harris experimental formula, and the mechanical properties of the vacuum carburized specimen have been compared with those of the gas carburized SCM415H specimen to identify the feasibility of the CO{sub 2} free vacuum carburizing process. The result showed that the vacuum carburized materials used have no oxidization of the grain boundaries, and show the 29.8% higher effective hardness depth and the acceptable tensile strength.

  13. Positron annihilation lifetime study of radiation-damaged natural zircons

    Roberts, J. [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia); Gaugliardo, P. [Centre for Antimatter-Matter Studies, School of Physics, University of Western Australia (Australia); Farnan, I.; Zhang, M. [Department of Earth Sciences, University of Cambridge (United Kingdom); Vance, E.R.; Davis, J.; Karatchevtseva, I.; Knott, R.B. [Australian Nuclear Science and Technology Organisation (Australia); Mudie, S. [The Australian Synchrotron, Victoria (Australia); Buckman, S.J. [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia); Institute for Mathematical Sciences, University of Malaya, Kuala Lumpur (Malaysia); Sullivan, J.P., E-mail: [Centre for Antimatter-Matter Studies, Research School of Physics and Engineering, The Australian National University, Canberra (Australia)


    Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼10{sup 19} α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter. - Highlights: • Study of a range of naturally occurring zircons damaged by alpha radiation. • Characterised using a range of techniques, including PALS spectroscopy. • Effects on hydrous material appear important, rather than direct radiation damage. • Annealing is shown to remove the observed voids.

  14. Quality of carburizers and its influence on carburization process

    K. Janerka


    Full Text Available In the papers issue of production the synthetic cast iron obtaining on the basis of only steel scrap and carburizing materials are presented. Natural graphite, synthetic graphite, anthracite, petroleum coke, foundry coke and charcoal were used to carburization. Examinations covered evaluation of used carburizers taking into account chemical composition; carbon, sulphur and nitrogen content have been analyzed. Obtained effectiveness of carburization with method of inserting carburizing material into charge in solid, were especially taken into considerations. The comparison between mechanical properties (tensile strength and hardness of produced synthetic cast iron and cast iron obtained on the basis of pig iron have been carried out.

  15. Computation of carbon concentration curves in vacuum carburizing of steels

    Semenov, M. Yu.; Smirnov, A. E.; Ryzhova, M. Yu.


    The boundary conditions of the diffusion problem in parametric form are determined on the basis of an experimental study of formation of carbon-saturated layers in vacuum carburizing. The boundary conditions are applied in a model of a process with cyclic modes of carburizing. Adequacy of the developed model is confirmed.

  16. Acetylene Vacuum Carburizing

    Hitoshi Iwata


    Almost 30 years has passed since the publication of materials on vacuum carburizing technology, and is attracting a great deal of attention as a technology capable of being used as a substitute for gas carburizing technology.However, the technology was not popular except in specific fields. The main reason for this is due to a variety of harmful influences accompanying the sooting problems caused by CH4 or C3H8. We have succeeded in that the occurrence of sooting was suppressed by utilizing acetylene, at extremely low pressure for carburizing (below 1 kPa). This process is now showing the excellent quality and prospects for this technology in terms of quality, economy and safety. At present almost 70 practical mass production furnaces are used in production lines, in Japan and abroad. At this time, we will report summary of the present acetylene vacuum carbufizing process and the actual results obtained by these acetylene vacuum carbufizing furnaces for mass production.

  17. Enhancement of Stainless Steel's Mechanical Properties via Carburizing Process

    Ahmad, S.; Alias, S. K.; Abdullah, B.; Hafiz Mohd Bakri, Mohd.; Hafizuddin Jumadin, Muhammad; Mat Shah, Muhammad Amir


    Carburizing process is a method to disperse carbon into the steel surface in order to enhance its mechanical properties such as hardness and wear resistance. This paper study investigates the effect of carburizing temperature to the carbon dispersion layer in stainless steel. The standard AISI 304 stainless steel was carburized in two different temperatures which were 900°C and 950°C. The effect of carbon dispersion layers were observed and the results indicated that the increasing value of the average dispersion layer from 1.30 mm to 2.74 mm thickness was found to be related to increment of carburizing holding temperature . The increment of carbon thickness layer also resulted in improvement of hardness and tensile strength of carburized stainless steel.

  18. Tribological and corrosion behaviors of carburized AISI 4340 steel

    Thong-on, Atcharawadi; Boonruang, Chatdanai


    AISI 4340 steel is widely used in automotive and aircraft industries as gear components. In such applications, surface hardening processes such as carburizing are required in order to improve the life time of the components. There are many studies showing the tribological behavior of the carburized steel, but the corrosion behavior has not yet been clarified. This paper reports on both tribological and corrosion behaviors of the carburized AISI 4340 steel. Factor associated with carburizing, such as the quantities of deposited carbon, dissolved carbon, and formed Cr23C6 and Fe3C, affect the tribological and corrosion behaviors of the steel by improving hardness, friction, lubrication, and wear resistance; but corrosion resistance is reduced. The dissolved carbon affects the formation of the oxide layer of the carburized steel, by obstructing the continuous oxide layer formation and by decreasing the chromium content of the steel, leading to the decrease in the corrosion resistance of the steel.

  19. On the Plasma (ion) Carburized Layer of High Nitrogen Austenitic Stainless Steel

    Y. Ueda; N. Kanayama; K. Ichii; T. Oishi; H. Miyake


    The manganese concentration of austenitic stainless steel decreases from the inner layer towards the surface of the plasma (ion) carburized layer due to the evaporation of manganese from the specimen surface. The carbon concentration in the carburized layer is influenced by alloyed elements such as Ct, Ni, Si, and Mo, as well as Nitrogen. This study examined the effects of nitrogen on the properties of the carburized layer of high nitrogen stainless steel. Plasma (ion)carburizing was carried out for 14.4 ks at 1303 K in an atmosphere of CH4+H2 gas mixtures under a pressure of 350 Pa. The plasma carburized layer of the high nitrogen stainless steel was thinner than that of an austentric stainless steel containing no nitrogen. This suggested that the nitrogen raised the activity of carbon in the plasma carburized layer, GDOES measurement indicated that the nitrogen level in the layer did not vary after plasma (ion) carburizing.

  20. 钛表面辉光无氢渗碳动力学与耐蚀性能研究%Study on Kinetics and Corrosion Resistance of Plasma Non-hydrogen Carburizing on Titanium Surface

    华云峰; 李争显; 杨浩; 王宝云; 王彦峰; 姬寿长; 罗小峰; 杜继红


    C.P.Ti TA2 was carburized by double-glow plasma non-hydrogen carburizing technique. The carburizing kinetics was studied. The corrosion resistance of the carburized samples was evaluated in 3.5%NaCl and 80%H2SO4 water solution at 25 ℃. The results show that the thickness of carburized layer increases with increasing carburizing temperature and time. The relationship between the diffusion coefficient of carbon in carburized layer and the carburizing temperature accords with the Arrhenius manner. The value of diffusion activation energy is 13.6 kJ/mol (0.14 eV). The carburized sample has better corrosion resistance than Ti-0.2Pd and C.P.Ti. The corrosion rate of carburized layer is 0.00048 and 2.118 mm/a in 3.5%NaCl and 80%H2SO4 water solution, which is 77% and 50% of that of Ti-0.2Pd and 13% and 11% of that of C.P.Ti under the same condition, respectively.%采用辉光无氢渗碳方法,在工业纯钛TA2表面制备渗碳层,研究辉光无氢渗碳动力学以及渗碳试样在25℃、3.5% NaCl水溶液和25℃、80% H2SO4水溶液中的耐蚀性能.结果表明,渗碳层厚度随渗碳温度与时间的增加而增加,碳在渗碳层中的扩散系数与绝对温度之间符合Arrhenius关系式,扩散活化能为13.6 kJ/mol (0.14 eV).渗碳试样在25℃3.5% NaCl、80% H2SO4水溶液中的腐蚀速率分别为0.000 48 mm/a、2.118 mm/a,分别是Ti-0.2Pd的77%、50%,分别是TA2的13%、11%,耐蚀性能得到显著提高.

  1. Positron annihilation lifetime study of radiation-damaged natural zircons

    Roberts, J.; Gaugliardo, P.; Farnan, I.; Zhang, M.; Vance, E. R.; Davis, J.; Karatchevtseva, I.; Knott, R. B.; Mudie, S.; Buckman, S. J.; Sullivan, J. P.


    Zircons are a well-known candidate waste form for actinides and their radiation damage behaviour has been widely studied by a range of techniques. In this study, well-characterised natural single crystal zircons have been studied using Positron Annihilation Lifetime Spectroscopy (PALS). In some, but not all, of the crystals that had incurred at least half of the alpha-event damage of ∼1019 α/g required to render them structurally amorphous, PALS spectra displayed long lifetimes corresponding to voids of ∼0.5 nm in diameter. The long lifetimes corresponded to expectations from published Small-Angle X-ray Scattering data on similar samples. However, the non-observation by PALS of such voids in some of the heavily damaged samples may reflect large size variations among the voids such that no singular size can be distinguished or. Characterisation of a range of samples was also performed using scanning electron microscopy, optical absorption spectroscopy, Raman scattering and X-ray scattering/diffraction, with the degree of alpha damage being inferred mainly from the Raman technique and X-ray diffraction. The observed void diameters and intensities of the long lifetime components were changed somewhat by annealing at 700 °C; annealing at 1200 °C removed the voids entirely. The voids themselves may derive from He gas bubbles or voids created by the inclusion of small quantities of organic and hydrous matter, notwithstanding the observation that no voidage was evidenced by PALS in two samples containing hydrous and organic matter.

  2. Effects of Carburized Parts on Residual Stresses of Thin-Rimmed Spur Gears with Symmetric Web Arrangements Due to Case-Carburizing

    Kouitsu Miyachika; Wei-Dong Xue; Satoshi Oda; Hidefumi Mada; Hiroshige Fujio


    This paper presents a study on effects of carburized parts on residual stresses of thin-rimmed spur gears with symmetric web arrangements due to the case-carburizing. The carbon content of each element of the FEM gear model due to carburizing was obtained according to Vickers hardness Hv - carbon content C% and C% - d (distance from surface)charts. A heat conduction analysis and an elastic-plastic stress analysis during the case-carburizing process of thin-rimmed spur gears with symmetric web arrangements were carried out for various case-carburizing conditions by using the three-dimensional finite element method (3D-FEM) program developed by authors, and then residual stresses were obtained.The effects of the carburized part, the web structure, and the rim thickness on the residual stress were determined.

  3. Research on Eddy Current Testing System of the Carburized Layer Depth of 20CrMnTi Steel

    CHENG Xiao-min; LI Na; WU Xin- wen; FANG Hua-bin


    In this paper the carbon distribution in the carburized layer of 20CrMnTi steel was studied. The relationship between the depth of a carburized layer and the surface carbon distribution was established. Eddy current testing system of the case depth of this carburized steel was built by using ANSYS software as second development platform.

  4. Carburizer Effect on Cast Iron Solidification

    Janerka, Krzysztof; Kondracki, Marcin; Jezierski, Jan; Szajnar, Jan; Stawarz, Marcin


    This paper presents the effect of carburizing materials on cast iron solidification and crystallization. The studies consisted of cast iron preparation from steel scrap and different carburizers. For a comparison, pig iron was exclusively used in a solid charge. Crystallization analysis revealed the influence of the carburizer material on the crystallization curves as well as differences in the solidification paths of cast iron prepared with the use of different charge materials. The carburizers' influence on undercooling during the eutectic crystallization process was analyzed. The lowest undercooling rate was recorded for the melt with pig iron, then for synthetic graphite, natural graphite, anthracite, and petroleum coke (the highest undercooling rate). So a hypothesis was formulated that eutectic cells are created most effectively with the presence of carbon from pig iron (the highest nucleation potential), and then for the graphite materials (crystallographic similarity with the carbon precipitation in the cast iron). The most difficult eutectic crystallization is for anthracite and petroleum coke (higher undercooling is necessary). This knowledge can be crucial when the foundry plant is going to change the solid charge composition replacing the pig iron by steel scrap and the recarburization process.

  5. Final Scientific Report - "Novel Steels for High Temperature Carburizing"

    McKimpson, Marvin G.; Liu, Tianjun; Maniruzzaman, Md


    . For comparison, a control alloy of similar composition but without the microalloy additions exhibited a duplex prior austenite grain size with grains ranging from ASTM grain size 3 down to ASTM grain size 1 after similar processing and thermal exposure. These results confirm the potential for using microalloy additions of Ti, B, Nb, Al, rare earths and/or N for austenite grain size control in Cr-Mo (i.e. 4000-series) low alloy carburizing steels. They also demonstrate that these microalloy additions will not compromise the processability of the steel; all three materials produced under the program could be hot worked readily using normal steel processing protocols. To fully realize the technical and commercial potential of these steels, there is a need to continue development work using larger-scale heats. These larger-scale heats are needed to provide adequate material for fatigue testing of quenched and tempered alloys, to conduct more complete investigations of potential alloy chemistries and to provide additional material for processing studies. It will also be beneficial to carefully review intellectual property issues associated with this family of steels, since existing Japanese patent literature suggests that significant microstructural and/or process characterization work may be needed on new materials to confirm that these materials fall outside existing patent claims.

  6. Carbon diffusion and phase transformations during gas carburizing of high-alloyed stainless steels: Experimental study and theoretical modeling

    Turpin, T.; Dulcy, J.; Gantois, M.


    Gas carburizing of high-alloyed stainless steels increases surface hardness, as well as the overall mechanical characteristics of the surface. The growth of chromium-rich carbides during carbon transfer into the steel causes precipitation hardening in the surface, but decreases the chromium content in solid solution. In order to maintain a good corrosion resistance in the carburized layer, the stainless steel composition and the carburizing process need to be optimized. To limit the experimental work, a methodology using software for modeling the thermodynamic and kinetic properties in order to simulate carbon diffusion and phase transformations during gas carburizing is presented. Thermodynamic calculations are initially used to find the optimum parameters ( T, carbon wt pct, etc.) in order to maintain the highest Cr and Mo contents in the austenitic solid solution. In a second step, kinetic calculations using the diffusion-controlled transformations (DICTRA) software are used to predict how the amount of the different phases varies and how the carbon profile in the steel changes as a function of time during the process. Experimental carbon profiles were determined using a wavelength-dispersive spectrometer for electron-probe microanalysis (WDS-EPMA), while carbide compositions were measured by energy-dispersive spectroscopy_X (EDS_X) analyses. A good agreement between calculated and experimental values was observed for the Fe-13Cr-5Co-3Ni-2Mo-0.07C and the Fe-12Cr-2Ni-2Mo-0.12C (wt pct) martensitic stainless steels at 955 °C and 980 °C.

  7. A Raman spectroscopic study of zircons on micro-scale and Its significance in explaining the origin of zircons

    Bao, Xuezhao; Lu, Songnian


    The magmatic and metamorphic zircons were investigated with Raman spectrum microprobe analysis. We found notable differences between these two kinds of zircons exhibited by the variation trend of Raman peak intensity from core to rim of a crystal. In magmatic zircons, the intensity and the ratio H/W of Raman spectrum peaks gradually decrease from core to rim of a crystal, which is produced by an increase in metamictization degree and suggests an increase in U and Th concentrations from core to rim. In metamorphic zircons, there are two kinds of crystals according to their Raman spectra: the first group of zircons exhibits a variation trend opposite to those of magmatic zircons, tending to increase in the Raman peak intensity and H/W value from core to rim of a crystal, which is produced by a decrease in metamictization degree and indicates a decrease of U and Th concentrations from core to rim of a crystal. The second group of zircons exhibits no change in Raman peak intensity and H/W value through a crystal....

  8. 潜水渣浆泵的设计及应用研究%Study on Testing Method of Carburizing Gears for Heavy Duty Trucks

    张海平; 赵玉刚; 孟祥炎


    Driving gears are key components to ensure the running safety of automobiles, and the tests of the mierostrueture properties of gears are the important guarantee of its quality eontrol. Aiming at earburized gears for heavy duty trucks, the paper in detail studied the testing methods and demand of the chemical composition, microstructure, carbide rating, retained austenite and martensite rating, carburizing quenching effectively hardening depth, surface and core hardness. The results can provide a reference basis the design, manufacturing and test of carburizing gears for heavy duty trucks.%渣浆泵是固液混合物管道输送的核心部件,由于设计和材质方面的缺陷,我国目前应用的大部分渣浆泵不同程度存在运行效率较低和使用寿命短的问题。本文设计的潜水式渣浆泵通过采用先进的水力模型、合理选用耐磨材料和加工工艺,其抽渣运行效率大幅度提高、使用寿命也得到延长。

  9. A study of complex discordance in zircons using step-wise dissolution techniques

    Mattinson, James M.


    Step-wise dissolution techniques applied to a variety of zircon samples, including those with combined inheritance plus later isotopic disturbance, reveal both the complexity of zircon isotopic systematics, and successfully “see through” this complexity to extract high-quality age information. The chemical procedures for the partial dissolution steps must be designed to extract completely all the U and Pb associated with the zircon digested in each step, in order to avoid large, laboratory-induced fluctuations in U/Pb ratio from step to step. In general, relatively short initial partial dissolution steps remove disturbed zircon domains characterized by very high U concentrations and low 206Pb/238U ages. In some cases the initial step yields the lowest 206Pb/238U age, reflecting both the high accessibility and solubility of the most disturbed domains. In other cases, disturbed domains evidently reside deep within the zircons, and are attacked only when the second or third steps penetrate to the interior via cracks or flaws to “mine out” these domains. In all the samples in this study, and regardless of the details of the steps, about a week of digestion time at 80°C removed most of the highly disturbed domains, leaving further partial dissolution steps and/or the total digestion of the final residue to sample highly refractory (i.e., highly insoluble), relatively low U zircon domains. The early partial digestion steps also remove virtually all the common Pb associated with the zircons. Study of partially digested zircons by scanning electron microscope reveals that at least in part, the disturbed, high-U, highly soluble domains and the less (un-?) disturbed, low-U, highly refractory domains are defined by primary igneous zoning on a micron or even sub-micron scale, well below the resolution of the “SHRIMP”, for example. In the case of zircons lacking any inheritance, the residue analyses yield near-concordant, highly precise results. In the case of

  10. Study of Effect of Quenching Deformation Influenced by 17CrNiMo6 Gear Shaft of Carburization

    Pang, Zirui; Yu, Shenjun; Xu, Jinwu

    The 17CrNiMo6 steel is mainly used for the gear shaft of large modulus in many fields of heavy industry such as mining, transit, hoist, forging and so on[1]. The size of addendum circle and common normal line is changed a lot beyond the tolerance because of the long time of carburizing process and the out-of-step structural stress and thermal stress during the quenching process. And thus the posterior grinding efficiency and quality are influenced. In the paper comparison and analysis of the deformation affected by solid and hollow gear shafts were done and the methods of simulation and practice were both used. The results are as follows: the deformation of gear shaft was small before and after carburizing while that of gear shaft was large before and after quenching because of different cooling velocity, structure and hardness of each position. And the deformation of hollow was much smaller than that of solid. Therefore, if the hollow gear shaft is used, the waste of material will be decreased, and finishing cost will be reduced, and thus the technology of heat treatment will be optimized.

  11. Silica-calcium zirconate nanocomposite, studying its thermal and electrical properties

    Neda Kermani; Maryam Kargar Razi; Seyed Saeed Mirzaee; Reza Tayebee


    Silica–calcium zirconate nanocomposite was prepared in a two-step procedure. First, nanocalcium zirconate was synthesized by the modified sol–gel method; then, silica was added to the prepared sol and the resulting product was calcined at 700–1000° C. Dilatometric measurements were performed to determine the coefficient of thermal expansion (). It was concluded that was decreased from 15.96 × 10−6 to 10.26 × 10−6 1° C−1 with the increase in calcium zirconate/silica ratio. Moreover, studies on the dielectric properties and calcination temperature showed that the dielectric constant (r) was increased from 3.9 to 5.7.

  12. 20CrMnMo钢稀土渗碳研究%Study on RE Carburizing of 20CrMnMo Steel

    徐建军; 杜晓东


    RE carburization was carried out on 20CrMnMo steel. The carburizing kinetics of carburizing depth was dealed with, the microstructure of the carburized layer was observed, the hardness and abrasion resistance of the carburized layer were examined. The results show that a large amount of dispersed granular carbides precipitated in the carburized layer of 20CrMnMo steel RE carburized. The microstructure of surface layer after directly quenching consists of acicular martensite, fine granular carbides and a little residual austenite. The test results showed 10 persent improvement in hardness, 32 persent improvement in abrasion resistance,The touching fatigue life is sharply improved too.%采用稀土渗碳工艺对20CrMnMo钢进行渗碳处理,研究了渗层增厚的动力学、渗碳层组织和性能.结果表明:稀土渗碳层中沉淀析出了大量弥散分布的粒状碳化物,淬火后表层组织为针状马氏体、大量细小颗粒碳化物、少量残余奥氏体.渗碳层的硬度与传统工艺相比提高了10%,耐磨性提高了32%,接触疲劳寿命也有大幅提高.

  13. The properties and structure of the carburizers

    K. Janerka


    Full Text Available The results of examinations of the carburizers for foundry industry were presented in the article. The commonly used carburizers were selected for the experiments (anthracite, natural and synthetic graphite, petroleum coke of various grades, cupola coke and charcoal as well. The experiments consist of bulk and standard density, screen analysis (on the basis of it the equivalent diameter was calculated and the microstructure of the carburizers measurements. The chemical composition and basic properties of carburizers were described too.

  14. Cyclic strength of steel 16Kh3NVFBM-Sh (VKS-5) after vacuum carburizing

    Ryzhov, N. M.; Fakhurtdinov, R. S.; Smirnov, A. E.


    Cyclic strength of steel 16Kh3NVFMB-Sh is studied after vacuum and gas carburizing. It is shown that the fatigue resistance of the steel hardened by the method of vacuum carburizing is higher. The thickness of the layer and the concentration of carbon on the surface at which the cyclic endurance is the highest are determined.

  15. Optimization of the Process of Carburizing and Heat Treatment of Low-Carbon Martensitic Steels

    Ivanov, A. S.; Greben'kov, S. K.; Bogdanova, M. V.


    Steel 24Kh2G2NMFB is studied after carburizing and different heat treatments. The hardness and microhardness of the surface layer and of the matrix are measured. The content of retained austenite is determined by the method of x-ray diffraction analysis. Heat treatment modes improving the structure of the surface layer after carburizing are suggested.

  16. Effects of carburization time and temperature on the mechanical properties of carburized mild steel, using activated carbon as carburizer

    Fatai Olufemi Aramide


    Full Text Available Due to the complexity of controlling parameters in carburization, there has been relatively little work on process variables during the surface hardening process. This work focuses on the effects of the carburizing temperature and time on the mechanical properties of mild steel carburized with activated carbon, at 850, 900 and 950 ºC, soaked at the carburizing temperature for 15 and 30 minutes, quenched in oil, tempered at 550 ºC and held for 60 minutes. Prior carburization process, standard test samples were prepared from the as received specimen for tensile and impact tests. After carburization process, the test samples were subjected to the standard test and from the data obtained, ultimate tensile strength, engineering strain, impact strength, Youngs' moduli were calculated. The case and core hardness of the carburized tempered samples were measured. It was observed that the mechanical properties of mild steels were found to be strongly influenced by the process of carburization, carburizing temperature and soaking time at carburizing temperature. It was concluded that the optimum combination of mechanical properties is achieved at the carburizing temperature of 900 ºC followed by oil quenching and tempering at 550 ºC.

  17. Bending Fatigue of Carburized Steel at Very Long Lives

    Nelson, D. V.; Long, Z.


    The bending fatigue behavior of two carburized steels is investigated for lives between approximately 105 and 108 cycles. Cracks are observed to start at sub-surface inclusions and develop features on fracture surfaces resembling "fish eyes" in appearance. This type of sub-surface cracking tends to govern fatigue strength at long lives. Previous studies of "fish eye" fatigue in carburized steel have been relatively few and have mainly considered failures originating at depths beneath a carburized case, where compressive residual stresses are minimal and hardness values approach those in the core. This study provides fatigue data for cracks originating within cases at various depths where compressive residual stresses are substantial and hardness is much higher than in the core. Fatigue strength is predicted by a simple model, accounting for the influence of residual stresses and hardness values at the different depths at which cracks started. Predictions of fatigue strength are compared with data generated in this study.


    Osman ASİ


    Full Text Available In this study, the residual stresses developing in carburized and only quenched steel of SAE 8620 (21NiCrMo2 which is widely used as a carburized steel (shafts, gears etc. was investigated. Carburizing programs was carried out in gas atmosphere for 45 minute at 940 °C. X-ray analysis was used to determine residual stress in the microstructures of the only quenched and carburized specimens. The results of x-ray analysis have shown that while the carburized specimens have a residual compressive stress at the surface -551N/mm 2 , the only quenched specimens have a residual compressive stress at the surface -125 N/mm 2 .

  19. The Corrosion Behavior of Carburized Aluminum Using DC Plasma

    Somayeh Pirizadhejrandoost


    Full Text Available Because of the outstanding properties of aluminum, it is widely used in today's advanced technological world. However, its insufficient wear resistance limits its use for commercial and industrial applications. In this study, we performed DC diode plasma carburizing of aluminum in the gas composition of CH4–H2 (20–80% and at a temperature of about 350°C for 4 and 8 hours. The corrosion properties of the untreated and plasma-carburized samples were evaluated using anodic polarization tests in 3 N HCl solution according to ASTM: G5-94. The metallurgical characteristics were then investigated using XRD and SEM. The results showed that the carburizing process improves the corrosion resistance of treated specimens at low temperature.

  20. The effects of energizer and carburizing temperature and time on mechanical properties of hardened big knives in the pack carburizing process

    Narongsak Thammachot


    Full Text Available The purpose of this research is to study the effects of energizer and carburizing temperature and time on the mechanical properties of hardened big knives in the pack carburizing process. The mechanical properties of carburized and hardened big knives were compared to those of commercial hardened big knives made from leaf-spring steel that were forged, ground and quenched following the traditional forging processes. The experiment was conducted by forging big knives made of low carbon steel (grade AISI 1010. The first group of them was then pack-carburized using 10% by weight of calcium carbonate with 90% by weight of eucalyptus charcoal. The second group used 10% by weight of egg shell with 90% by weight of eucalyptus charcoal. The carburizing temperatures were 900, 950 and 1,000°C, with carburizing times of 30, 60 and 90 minutes followed by air cooling. The austenitizing temperature was 780°C with a holding time of 20 minutes, followed by quenching in water. Finally, the big knives were tempered at 180°C for 1 hour. Micro-Vickers hardness testing, impact testing and microstructure inspection were carried out. The results of this experiment show that the hardness of hardened big knives increased with an increase in the carburizing temperature and time. In contrast, the impact value of carburized steel decreased with an increase in the carburizing temperature and time. The hardness derived from using CaCO3 is slightly harder than that from using egg shell, however, the impact energy is higher when using egg shell, compared to using CaCO3.

  1. Depositional ages of clastic metasediments from Samos and Syros, Greece: results of a detrital zircon study

    Löwen, Kersten; Bröcker, Michael; Berndt, Jasper


    Siliciclastic metasediments from the islands of Samos and Syros, Cycladic blueschist unit, Greece, were studied to determine maximum sedimentation ages. Four samples from the Ampelos unit on Samos yielded age distribution spectra that range from ~320 Ma to ~3.2 Ga with a dominance of Cambrian-Neoproterozoic zircons (500-1,100 Ma). The youngest well-constrained age groups cluster at 500-550 Ma. Our results allow to link the Samos metasediments with occurrences showing similar age distribution patterns elsewhere in the eastern Mediterranean region (Greece, Turkey, Libya, Israel and Jordan) that record the influx of `Pan-African' detritus. The lack of post-500-Ma zircons in the Samos samples is in marked contrast to the data from Syros that indicates Triassic to Cretaceous depositional ages. The samples from Syros were collected from the matrix of a meta-ophiolitic mélange that is exposed near the top of the metamorphic succession as well as from outcrops representing the basal part of the underlying marble-schist sequence. The zircon populations from Syros were mainly supplied by Mesozoic sources dominated by Triassic protolith ages. Subordinate is the importance of pre-Triassic zircons, but this may reflect bias induced by the research strategy. Sediment accumulation continued until Late Cretaceous time, but the overall contribution of Jurassic to Cretaceous detritus is more limited. Zircon populations are dominated by grains with small degree of rounding suggesting relatively short sediment transportation. Available observations are in accordance with a model suggesting deposition close to the magmatic source rocks.

  2. The rate and effectiveness of carburization to the sort of carburizer

    K. Janerka


    Full Text Available The obtaining of demanded carbon contents during melting the cast iron with bounded pig iron’s portion is important problem for many foundries. There are searched the effective methods and carburizers, which would ensure obtaining of big carbon increases with great repeatability as quick as possible. The aim of presented researches was definition of influence of essential factors characterized the carburization and the sort of carburizer on the rate and effectiveness of process. The cast iron melts are presented only on the basis of steel scrap with the portion of graphitoidal, coke and anthracite carburizers. Two methods of carburization are taken into consideration during the experiments were carried out: the addition of carburizer to charge in solid in the initial period of melting and addition of carburizer on surface of liquid metal . The obtained researches results and their analyze allow to choose the corresponding method and the sort of carburizer. One can state, that the best carburizer is synthetic graphite, if the rate and effectiveness of process is considerate and the best method of carburization in the electric inductive furnace is addition of carburizer to charge in solid. In the subsequent part of researches the analyze of influence of carburizer on the structure of grey cast iron and ductile cast iron. The initial researches has showed the differences in obtained structures of synthetic cast iron melted only on the basis of steel scrap and defined kind of carburizer.

  3. 重型汽车用渗碳齿轮检验方法的分析研究%Study on Testing Method of Carburizing Gears for Heavy Duty Trucks

    张红梅; 郝爽; 孟丽


    变速器和车桥等部件中的传动齿轮是保证汽车行驶安全的核心部件,齿轮的组织性能的检验是其质量控制的重要保证。本文就重型汽车渗碳齿轮的化学成分、金相组织、碳化物评级、残余奥氏体和马氏体评级、渗碳淬火有效硬化层深、表面和心部硬度等检验方法和要求进行了详细的研究分析,可为重型汽车用渗碳齿轮的设计、制造及检验提供参考依据。%Driving gears are key components to ensure the running safety of automobiles, and the tests of the mierostrueture properties of gears are the important guarantee of its quality eontrol. Aiming at carburized gears for heavy duty trucks, the paper in detail studied the testing methods and demand of the chemical composition, mierostrueture, carbide rating, retained anstenite and martensite rating, carburizing quenching effectively hardening depth, surface and core hardness. The results can provide a reference basis the design, manufacturing and test of carburizing gears for heavy duty trucks.

  4. Pack Carburization of Mild Steel, using Pulverized Bone as Carburizer: Optimizing Process Parameters

    Joseph Olatunde BORODE


    Full Text Available Investigation was conducted into the mechanical properties of mild steel subjected to packed carburization treatment using pulverized bone as the carburizer, carburized at 850C, 900C and 950C, soaked at the carburizing temperature for 15 minutes and 30 minutes, quenched in oil and tempered at 550C. Prior carburization process, standard test samples were prepared from the as received specimen for tensile and impact tests. After carburization process, the test samples were subjected to the standard test and from the data obtained, ultimate tensile strength, engineering strain, impact strength, Youngs moduli were calculated. The case and core hardness of the carburized tempered samples were measured. It was observed that the mechanical properties of mild steels were found to be strongly influenced by the process of carburization, carburizing temperature and soaking time at carburizing temperature. It was concluded that the sample carburized at 900C soaked for 15 minutes and the one carburized at 850C soaked for 30 minutes followed by oil quenching and tempering at 550C were better because they showed a trend of hard case with softer core.

  5. Protoliths of enigmatic Archaean gneisses established from zircon inclusion studies:Case study of the Caozhuang quartzite, E. Hebei, China

    Allen P. Nutman; Ronni Maciejowski; Yusheng Wan


    A diverse suite of Archaean gneisses at Huangbaiyu village in the North China Craton, includes rare fuchsite-bearing (Cr-muscovite) siliceous rocks e known as the Caozhuang quartzite. The Caozhuang quartzite is strongly deformed and locally mylonitic, with silica penetration and pegmatite veining common. It contains abundant 3880e3600 Ma and some Palaeoarchaean zircons. Because of its siliceous nature, the presence of fuchsite and its complex zircon age distribution, it has until now been accepted as a (mature) quartzite. However, the Caozhuang quartzite sample studied here is feldspathic. The shape and cathodoluminescence petrography of the Caozhuang quartzite zircons show they resemble those found in immature detrital sedimentary rocks of local provenance or in Eoarchaean polyphase orthog-neisses, and not those in mature quartzites. The Caozhuang quartzite intra-zircon mineral inclusions are dominated by quartz, with lesser biotite, apatite (7%) and alkali-feldspar, and most inclusions are morphologically simple. A Neoarchaean orthogneiss from near Huangbaiyu displays morphologically simple inclusions with much more apatite (73%), as is typical for fresh calc-alkaline granitoids elsewhere. Zircons were also examined from a mature conglomerate quartzite clast and an immature feldspathic sandstone of the overlying weakly metamorphosed Mesoproterozoic Changcheng System. These zircons have oscillatory zoning, showing they were sourced from igneous rocks. The quartzite clast zircons contain only rare apatite inclusions (<1%), with domains with apatite habit now occupied by in-tergrowths of muscovite+quartz±Fe-oxides±baddeleyite. We interpret that these were once voids after apatite inclusions that had dissolved during Mesoproterozoic weathering, which were then filled with clays±±silica and then weakly metamorphosed. Zircons in the immature feldspathic sandstone show a greater amount of preserved apatite (11%), but with petrographic evidence of replacement of

  6. Protoliths of enigmatic Archaean gneisses established from zircon inclusion studies: Case study of the Caozhuang quartzite, E. Hebei, China

    Allen P. Nutman


    Full Text Available A diverse suite of Archaean gneisses at Huangbaiyu village in the North China Craton, includes rare fuchsite-bearing (Cr-muscovite siliceous rocks – known as the Caozhuang quartzite. The Caozhuang quartzite is strongly deformed and locally mylonitic, with silica penetration and pegmatite veining common. It contains abundant 3880–3600 Ma and some Palaeoarchaean zircons. Because of its siliceous nature, the presence of fuchsite and its complex zircon age distribution, it has until now been accepted as a (mature quartzite. However, the Caozhuang quartzite sample studied here is feldspathic. The shape and cathodoluminescence petrography of the Caozhuang quartzite zircons show they resemble those found in immature detrital sedimentary rocks of local provenance or in Eoarchaean polyphase orthogneisses, and not those in mature quartzites. The Caozhuang quartzite intra-zircon mineral inclusions are dominated by quartz, with lesser biotite, apatite (7% and alkali-feldspar, and most inclusions are morphologically simple. A Neoarchaean orthogneiss from near Huangbaiyu displays morphologically simple inclusions with much more apatite (73%, as is typical for fresh calc-alkaline granitoids elsewhere. Zircons were also examined from a mature conglomerate quartzite clast and an immature feldspathic sandstone of the overlying weakly metamorphosed Mesoproterozoic Changcheng System. These zircons have oscillatory zoning, showing they were sourced from igneous rocks. The quartzite clast zircons contain only rare apatite inclusions (<1%, with domains with apatite habit now occupied by intergrowths of muscovite + quartz ± Fe-oxides ± baddeleyite. We interpret that these were once voids after apatite inclusions that had dissolved during Mesoproterozoic weathering, which were then filled with clays ± silica and then weakly metamorphosed. Zircons in the immature feldspathic sandstone show a greater amount of preserved apatite (11%, but with petrographic

  7. The properties and structure of the carburizers

    K. Janerka; J. Jezierski; M. Pawlyta


    The results of examinations of the carburizers for foundry industry were presented in the article. The commonly used carburizers were selected for the experiments (anthracite, natural and synthetic graphite, petroleum coke of various grades), cupola coke and charcoal as well. The experiments consist of bulk and standard density, screen analysis (on the basis of it the equivalent diameter was calculated) and the microstructure of the carburizers measurements. The chemical composition and basic...

  8. A Probabilistic Approach to Examine the Effect of Chemistry Variations on Distortion During Industrial Gas Carburizing

    Sahay, Satyam S.; Deshmukh, Vinayak; El-Zein, Mohamad


    Industrial carburizing operations have been traditionally simulated for several decades by solving the diffusion equation. However, using this deterministic approach, it is difficult to capture batch-to-batch variations in the properties attributed to process and chemistry variations. In the current study, a probabilistic approach is used to capture the variations in process parameters and alloy chemistry. The advantage of this approach is illustrated through a case study on reduction in distortion variations as well as its absolute value during the carburizing operation. Finally, some of the opportunities and challenges in the carburizing simulation are discussed.

  9. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M


    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  10. Contribution of shot peening on carburized or carbonitrided parts

    Renaud, P.; Bristiel, P.; Barrallier, L.; Desvignes, M.; Kubler, R.


    The main purpose of car manufacturers is to design parts which are light and at the same time very resistant to fatigue efforts. Surface treatments are effective means to deal with this compromise. They bring surface hardness and introduce compressive residual stresses. This experimental study focuses on the influence of shot peening on parts initially treated by carburizing or carbonitriding.

  11. Effect of Carburizing and Hardening Temperature on the Endurance of Forming Dies from Steel R6M5

    Stepankin, I. N.; Ken'ko, V. M.; Boiko, A. A.


    Results of a study of the effect of carburizing of the forming surfaces of cold upset dies from high-speed steel R6M5 and of the hardening temperature on the structure and properties of the dies are presented. It is shown that the hardness and endurance of the carburized tools can be raised by hardening from lower temperatures.

  12. Structure-phase states of the nickel surface layers after electroexplosive carburizing

    Budovskikh; E.; A.; Bagautdinov; A.; Y.; Ivanov; Yu.; F.; Martusevich; E.; V.; Gromov; V.; E.


    The layer by layer study of the structure-phase states of the nickel surface layer carburizing with use the phenomena of the electrical explosion has conducted by the method TEM of the fine foils.……

  13. Deformation and fatigue behaviors of carburized automotive gear steel and predictions

    Bonglae Jo


    Full Text Available The fatigue behavior of carburized components such as automotive transmission gears is very complex due to hardness and microstructure difference, residual stresses and multi-axial stress states developed between the case and the core. In addition, automotive gears in service, commonly used in helical type, are actually subjected to complex stress conditions such as bending, torsion, and contact stress states. This study presents experimental and analytical results on deformation behavior of carburized steels, widely used in automotive gears, under cyclic stress conditions including axial and torsion loadings. Axial fatigue tests and rotating bending fatigue tests are also included. Predictions of cyclic deformation and fatigue behaviors of the carburized steel with two-layer model are compared with experimental results. The carburized steel investigated in this study exhibited cyclic softening under both axial loading and torsional loading. Predicted results with simple two-layer model for the cyclic deformation and fatigue behaviors were comparatively similar to the experimental data.

  14. A preliminary geochemical study of zircons and monazites from Deccan felsic dikes, Rajula, Gujarat, India: Implications for crustal melting

    Nilanjan Chatterjee; Somdev Bhattacharji


    Zircons of 10–100 m size and monazites of up to 10 m size are present in rhyolite and trachyte dikes associated with Deccan basalts around Rajula in the southern Saurashtra Peninsula of Gujarat. On the basis of structural conformity of the felsic and basaltic dikes, K-Ar ages and trace element considerations, a previous study concluded that the felsic rocks are coeval with the Deccan Volcanics and originated by crustal anatexis. The felsic rocks contain two populations of zircons and monazites, one that crystallized from the felsic melt and the other that contains inherited crustal material. Trace element variations in the rhyolites and trachytes indicate that zircons and monazites crystallized from the felsic melts, but compositional analysis of a zircon indicates the presence of a small core possibly inherited from the crust. Hf compositional zoning profile of this zircon indicates that it grew from the host rhyolitic melt while the melt differentiated, and Y and LREE contents suggest that this zircon crystallized from the host melt. Pb contents of some monazites also suggest the presence of inherited crustal cores. Hence, any age determination by the U-Th-Pb isotopic method should be interpreted with due consideration to crustal inheritance. Temperatures estimated from zircon and monazite saturation thermometry indicate that the crust around Rajula may have been heated to a maximum of approximately 900°C by the intruding Deccan magma. Crustal melting models of other workers indicate that a 1-2 million year emplacement time for the Deccan Traps may be appropriate for crustal melting characteristics observed in the Rajula area through the felsic dikes.

  15. 关于真空炉渗碳过程的初步试验研究%Preliminary experimental study about vacuum furnace carburizing process

    黄晓辉; 于滢


    通过对SG13Cr4Mo4Ni4V钢真空渗碳过程的主要影响因素进行试验分析,初步摸索了各工艺参数之间的关系,为提高该钢种真空渗碳热处理质量提供了试验数据。%Through test analysis on main affecting factors of vacuum carburizing process of SG13Cr4Ni4V steel, the relationship between the process parameters was tried to ifnd out initially in order to provide test data for improving the quality of the steel vacuum carburizing heat treatment.

  16. Surface properties and activation energy of superplastically carburized duplex stainless steel

    Ahamad, Nor Wahida, E-mail: [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Jauhari, Iswadi, E-mail: [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Azis, Sharidah Azuar Abdul, E-mail: [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia); Aziz, Nur Hafizah Abd, E-mail: [Department of Mechanical and Materials Engineering, Faculty of Engineering, University Malaya, Lembah Pantai, 50603 Kuala Lumpur (Malaysia)


    A new surface carburizing technique which combines superplastic phenomenon and carburizing process called superplastic carburizing (SPC) was introduced and compared with conventional carburizing (CC) process. Thermomechanically treated duplex stainless steel (DSS) with a fine grain microstructure that exhibits superplasticity was used as the superplastic material. SPC was carried out at temperatures of 1198-1248 K and a compression rate of 1 x 10{sup -4} s{sup -1} for various durations. Metallographic studies revealed that a carbon layer with a uniform, dense and smooth morphology formed on all carburized specimens. The case depth of the carbon layer was between 50.8 and 159.1 {mu}m. A remarkable increase in surface hardness was observed in the range 389.9-1129.0 HV. Activation energy for SPC was determined as 183.4 kJ mol{sup -1}, which is lower compare to CC process. The results indicate that SPC accelerates the diffusion of carbon atoms into the surface of DSS, thus increasing the thickness of the carburized layer and the surface hardness, at lower activation energy.

  17. Experimental Study and Computer Simulation on Multicomponent Diffusion in Multiphase Dispersions During Solid Carburizing of HP40Nb and KHR45A Alloys

    Zhao, Yanping; Gong, Jianming; Wang, Xiaowei; Shen, Limin; Li, Qingnan


    To simulate solid carburizing processes of HP40Nb and KHR45A alloys at 1273 K and 1373 K (1000 °C and 1100 °C), Thermo-Calc (Thermo-Calc Software, Inc., Stockholm, Sweden) and DICTRA (Thermo-Calc Software, Inc.) software analyses were performed. A model to treat multicomponent diffusion in multiphase dispersions was applied, where carbides are assumed to be distributed in face-centered cubic matrix and diffusion only occurs in the matrix. The time-dependent carbon flux determined by weight gain measurement was used as boundary condition in diffusion simulations. The calculated carbides are NbC, M23C6, and M7C3 ("M" stands for metal atoms), where M23C6 first precipitates, then M7C3 appears as carbon increases, and NbC covers the largest area of carbon content. The results show that carburization resistance is much better for KHR45A than HP40Nb due to the addition of elements (Si, Cr, Ni, and Nb). Microhardness measurements were also conducted to obtain the carburized case depths, and the results agreed well with the predicted calculations.

  18. Vacuum gas carburizing – fate of hydrocarbons

    Khan, Rafi Ullah


    This work focuses on gaseous reactive flows in ideal and non-ideal reactors. The objective of this research is the development of models for the numerical simulation of homogeneous reactive flows under vacuum carburizing conditions of steel with propane and acetylene. These models can be used for further investigations of heterogeneous reactions during vacuum carburizing of steel to predict the carbon flux on the complex shaped steel parts to understand and, eventually, optimize the behavior ...

  19. An investigation of rolling-sliding contact fatigue damage of carburized gear steels

    Kramer, Patrick C.

    The goal of this study was to evaluate the differences in RSCF performance between vacuum and gas carburized steels as well as to investigate the evolution of damage (wear and microstructure changes) leading to pitting. Vacuum and gas carburizing was performed on two gear steels (4120 and 4320) at 1010°C. The carburized specimens were tested in the as-carburized condition using a RSCF machine designed and built at the Colorado School of Mines. The tests were conducted at 3.2 GPa nominal Hertzian contact stress, based on pure rolling, 100°C, and using a negative twenty percent slide ratio. Tests were conducted to pitting failure for each condition for a comparison of the average fatigue lives. Pure rolling tests were also conducted, and were suspended at the same number of cycles as the average RSCF life for a comparison of fatigue damage developed by RCF and RSCF. Incremental tests were suspended at 1,000, 10,000, 100,000, and 200,000 cycles for the vacuum carburized steels to evaluate the wear and damage developed during the initial cycles of RSCF testing and to relate the wear and damage to pitting resistance. Incremental damage was not investigated for gas carburizing due to the limited number of available specimens. The vacuum carburized samples showed a decreased pitting fatigue resistance over the gas carburized samples, possibly due to the presence of bainite in the vacuum carburized cases. Pitting was observed to initiate from surface micropitting and microcracking. A microstructural change induced by contact fatigue, butterflies, was shown to contribute to micropitting and microcracking. Incremental testing revealed that the formation of a microcrack preceded and was necessary for the formation of the butterfly features, and that the butterfly features developed between 10,000 and 100,000 cycles. The orientation and depth of butterfly formation was shown to be dependent upon the application of traction stresses from sliding. RSCF butterflies formed

  20. Cu-Precipitation Strengthening in Ultrahigh-Strength Carburizing Steels

    Tiemens, Benjamin L.; Sachdev, Anil K.; Olson, Gregory B.


    Ultrahigh hardness levels greater than 700 VHN can be obtained in secondary hardening carburizing steels but depend on costly Co alloying additions to maximize hardness achieved through M2C-type carbide precipitation strengthening. This study aims to incorporate nanometer-scale bcc Cu precipitates to both provide strength as well as catalyze M2C nucleation in the absence of or with reduced Co. Cu additions of 1.0 and 3.7 wt pct were investigated, using a series of mechanistic models coupled with thermodynamic computational tools to derive final compositions. Thirty-pound experimental heats were cast of each designed alloy, samples of which were carburized and tempered to determine their hardness response. Characterization revealed the successful incorporation of Cu alloying additions into this family of steels, demonstrating a secondary hardening response even in the absence of Co. Matrix strength levels were close to those predicted by design models; however, all four alloys demonstrated a hardness deficit of approximately 200 VHN at the carburized surface, suggesting recalibration of the M2C precipitation strengthening model may be required in these alloys.

  1. Trace element features of hydrothermal and inherited igneous zircon grains in mantle wedge environment: A case study from the Myanmar jadeitite

    Lei, Weiyan; Shi, Guanghai; Santosh, M.; Ng, Yinok; Liu, Yingxin; Wang, Jing; Xie, Gen; Ju, Yan


    Jadeitites are considered to crystallise in ultramafic rocks in the subduction channel presumably from the overlying mantle wedge, and therefore zircons from these rocks provide important insights into mantle wedge processes. Here we investigate hydrothermal zircon (Group II) formed within a subduction zone and compare these with the igneous zircon cores (Group I) from the Myanmar jadeitite. Previous U-Pb studies reported ages of Groups I and II zircons as 163 Ma, and 147 Ma respectively, and both show isotope signature of the depleted mantle. Group I zircons have much higher total concentrations of rare earth elements (REEs) (500-1945 ppm) than those of Group II zircon (112-307 ppm), and contains relatively higher abundance of Y, Nb, Ta, Ti, Th and U with higher (Sm/La)N ratios (25.3-501) and Ce-anomalies (8.04-140) but lower (Yb/Gd)N ratios (9.76-57.0) than those of the Group II ((Sm/La)N ratios = 2.12-32.2, Ce-anomalies = 1.63-19.6, (Yb/Gd)N ratios = 44.8-142). Hf concentrations are broadly similar in both Groups. The Group I zircons are considered to be magmatic and crystallised from H2O-rich basaltic melt at relatively high pressure in the mantle wedge, whereas the Group II zircon overgrowth took place through recrystallisation and precipitation with distinct dissolution of the Group I zircons. Variation in the concentration of trace elements in zircons from Groups I to II in the mantle wedge is related to an intra-oceanic subduction system in the presence of Na-rich hydrothermal fluids under high-pressure and low-temperature. The Ti-in-zircon thermometer yield a mean crystallisation temperature of 742 ± 141 °C for Group I zircons, whereas the Group II zircons yield 339 ± 33 °C. The two groups of zircons also provide insights into the probable protolith involved in formation of the Myanmar jadeitite.

  2. A combined study of SHRIMP U-Pb dating, trace element and mineral inclusions on high-pressure metamorphic overgrowth zircon in eclogite from Qinglongshan in the Sulu terrane

    LI Qiuli; LI Shuguang; HOU Zhenhui1; HONG Jian; YANG Wei1


    Methods recently advanced for discrimination on the genesis of metamorphic zircon, such as analysis of mineral inclusions and trace elements, provide us powerful means to distinguish zircon overgrowth during high-pressure metamorphism. Zircons in ultrahigh-pressure eclogite from Qinglongshan in the Sulu terrane were studied by the SHRIMP U-Pb method in combining with trace element and mineral inclusion analyses. No inherited core was identified in the analyzed zircons by means of cathodoluminescence images. The occurrence of high-pressure metamorphic mineral inclusions in zircon, such as garnet, omphacite, rutile, and the flat HREE pattern in zircon indicate that the zircon formed at high-pressure metamorphic conditions. Therefore, a weighted average U-Pb age of 227.4 ± 3.5 Ma obtained from such a kind of zircon is interpreted to represent the timing of peak metamorphism for the Qinglongshan eclogite.

  3. Study On the Tribological Behavior of the Arc-added Glow Discharge Plasma Non-hydrogen Carburization On Titanium Alloy Surfaces

    CHEN Fei; ZHAHGYue-fei; Liu Yu; TANG Bin; PAN Jun-de


    This paper introduces a new titanium alloys surface strengthening treatment by using the arc-added glow discharge plasmas non-hydrogen carburization technique. High purity and high strength graphite is selected as cooling cathode arc source for supplying carbon atoms and particle, which migrate to the titanium alloy(Ti6Al4V) surface and form modified layer. Thus, the hydrogen embrittlement is avoided while the tribological behavior of the titanium alloy surface is improved in the respects of anti-friction and anti-wear ability. The tribological behavior of the modified layer under dry sliding against SAE52100 steel was evaluated on a ball-on-disc test rig. The results showed that the modified layer obtained a thickness of 30μm at 980℃, 30minutes. The microhardness of the Ti6A14V alloy surface attained 936 HV, which was much larger than that of the Ti6A14V alloy. The Ti6A14V alloy was characterized by adhesion wear and scuffing under dry sliding against the steel, while the surface modified layer experienced much abated adhesion wear and scuffing under the same testing condition. This could be attributed to the carbon element with different modalities exists in the modified layer.The modified layer showed good friction-reducing and fair anti-wear ability in dry sliding against the steel. Using the SEM,XRD and XPS, the phase structure and morphology of the carburization modified layer was analyzed.

  4. Holding time effect of pack carburizing on fatigue characteristic of v-notch shaft steel specimens

    Supriyono, Jamasri


    The objective of this research is to study the effect of the holding times of pack carburizing process on fatigue characteristic of v-notch shaft steel specimens. The carbon source was taken from charcoal of unused mahogany. The holding times were 2, 3 and 4 hours. The fatigue tests were conducted on rotary bending machine. The specimens were made of low carbon steel of 0.17% carbon content. Pack carburizing was conducted to the specimens at 930°C. V-notch was made to present the stress concentration on the specimens. To see the effects of the carburizing in changing the material properties, the micro-structures and hardness tests along the cross sectional area of the specimens were carried out. The results showed that the holding time of the carburizing process influences the fatigue strength of the material. The longer the holding time will be the higher the fatigue strength. The increase of the fatigue strength is due to the carbon content on the surface. It was confirmed by the micro-structures and the hardness tests results. The cross sectional area of carburized material is divided into two zones i.e. surface zone and core zone. The surface zone consists of hypereutectoid, eutectoid, and hypo eutectoid sub-zone. The core zone is the same as raw material. The longer the holding time will be the deeper the surface zone.


    Ahmet Çetin CAN


    Full Text Available Machine parts are surface hardened to increase fatigue strength and wear resistance. Carburization is the most common surface hardening process in practice. In order to have optimum properties, a machine part must have certain hardness depth. To obtain required hardness depth, the parts must be kept in a carburizing medium at certain temperature for certain time. As the time and temperature is increased hardness depth increases. In practice, carburization temperature is about 930 °C. Machine parts are kept at this temperature for required time depending on required hardness depth. The increase of temperature reduces treatment time, considerably. But, heat treaters do not tend to use high temperatures due to the concern of distortion of parts, and deterioration of mechanical properties. In this study, the increase of temperature for reducing carburization time in salt bath, and consequently change of mechanical properties have been investigated using DIN C20 case carburization steel. As a result of experiments, it was found that mechanical properties were not effected negatively.


    Claudio José Leitão


    Full Text Available This study compares the effects of nitriding and carburizing processes applied to gears subjected to contact stresses below 1300 MPa. The manufacturing cost, as well the depth of hardened layer and the distortion produced by two processes are analyzed. AISI 4140 gears quenched, tempered, liquid and gas nitriding and AISI 8620 gears after liquid carburizing, quenching and tempering are analyzed. The dimensional control of the gears was carried out before and after heat and thermochemical treatments. It is concluded that liquid or gas nitriding processes are about 30% more economical than liquid carburizing an also they reduce the dimensional changes. By the other hand liquid carburizing achieves greater case depth. Liquid nitriding process presents the lowest cost, dimensional changes and case depth.

  7. REE distribution in zircon from reference rocks of the Arctic region: Evidence from study by the LA-ICP-MS method

    Nikolaev, A. I.; Drogobuzhskaya, S. V.; Bayanova, T. B.; Kaulina, T. V.; Lyalina, L. M.; Novikov, A. I.; Steshenko, E. N.


    The results of the LA-ICP-MS analysis of the concentrations of REEs, U, Th, and Hf in zircon from Paleo- and Neoarchean reference rocks of the Kola region (garnet-amphibole gneiss, basic and acid granulites, and granite pegmatite) are reported. A new methodology of the study of accessory zircons has been validated and modified. The accuracy of the results is confirmed by analysis of standard zircons Temora 1 and 91 500 and by comparison with the data obtained in other laboratories.

  8. Zircon Recycling in Arc Intrusions

    Miller, J.; Barth, A.; Matzel, J.; Wooden, J.; Burgess, S.


    Recycling of zircon has been well established in arc intrusions and arc volcanoes, but a better understanding of where and how zircons are recycled can help illuminate how arc magma systems are constructed. To that end, we are conducting age, trace element (including Ti-in-zircon temperatures; TzrnTi) and isotopic studies of zircons from the Late Cretaceous (95-85 Ma) Tuolumne Intrusive Suite (TIS) in the Sierra Nevada Batholith (CA). Within the TIS zircons inherited from ancient basement sources and/or distinctly older host rocks are uncommon, but recycled zircon antecrysts from earlier periods of TIS-related magmatism are common and conspicuous in the inner and two most voluminous units of the TIS, the Half Dome and Cathedral Peak Granodiorites. All TIS units have low bulk Zr ([Zr]825°C), [Zr] in the TIS is a factor of 2 to 3 lower than saturation values. Low [Zr] in TIS rocks might be attributed to a very limited supply of zircon in the source, by disequilibrium melting and rapid melt extraction [1], by melting reactions involving formation of other phases that can incorporate appreciable Zr [2], or by removal of zircon at an earlier stage of magma evolution. Based on a preliminary compilation of literature data, low [Zr] is common to Late Cretaceous N.A. Cordilleran granodioritic/tonalitic intrusions (typically Tzrnsat [3]. A corollary is that slightly older zircon antecrysts that are common in the inner units of the TIS could be considered inherited if they are derived from remelting of slightly older intrusions. Remelting at such low temperatures in the arc would require a source of external water. Refs: [1] Sawyer, J.Pet 32:701-738; [2] Fraser et al, Geology 25:607-610; [3] Harrison et al, Geology 35:635- 638

  9. Numerical Simulation of Reaction-Diffusion during Carburization of HK40 Steel

    Meili ZHU; Qiang XU; Junshan ZHANG


    Two types of carbides M23C6 and M7C3 precipitate orderly as carbon concentration in a high Cr-Ni austenitic steel increases during carburization process. The mathematical model that describes diffusion of carbon and the precipitation of M23C6 and M7C3 has been studied. A criterion to judge when the transformation of M23C6 to M7C3 is over and M7C3 precipitates directly has been given in simulated calculation. By applying the model, the carburization of HK40 steel has been calculated by means of finite difference computation techniques. The pack carburization tests for the HK40 steel have been carried out at 1273 K. The comparison between the experimental and the calculated results show acceptable agreement.

  10. Study on Structure and Corrosion Resistance Analysis of Carburizing Organization of Austenitic Stainless Steel%奥氏体不锈钢渗碳层的组织及耐蚀强化性能研究

    李朋; 潘邻; 张良界; 杨闽红; 朱云峰; 马飞; 王成虎


    针对常规渗碳工艺会削弱奥氏体不锈钢耐蚀性的问题,通过对现有气体渗碳技术进行改进,采用前处理活化、降低渗碳温度的方法,实现了奥氏体不锈钢渗碳兼顾表面强度与耐蚀性能的目标.采用该工艺对AISI304和AISI316奥氏体不锈钢进行渗碳处理,并分析渗层组织和性能,结果表明,在470℃条件下,AISI316不锈钢经气体渗碳处理后,渗碳层具有优异的耐蚀强化性能.%In view of the conventional carburization weakening austenitic stainless steel corrosion resistance problem,based on the existing gas carburizing technology was improved,using pretreatment activation,carburizing temperature reduction methods,realized the austenitic stainless steel carburized surface strength and corrosion resistant properties of the target.Using this process on AISI304,AISI316 austenitic stainless steel carburizing processing,and get the austenitic stainless steel for low temperature carburizing organization performance carries on the analysis and research,research shows that under the condition of 470 ℃,AISI316 stainless steel carburization treated by low temperature gas carburizing layer has excellent corrosion resistance improved performance.

  11. The Effect of the Quenching Method on the Deformations Size of Gear Wheels after Vacuum Carburizing

    Dybowski K.


    Full Text Available This paper presents a comparison of the deformations and residual stresses in gear wheels after vacuum carburizing process with quenching in high-pressure nitrogen and oil. The comparison was made on a medium-sized gear wheels, made of AMS6265 (AISI 9310 steel. This steel is applied in the aerospace industry for gears. The study has provided grounds for an assessment of the effect of the method of quenching on the size of deformations. Compared to oil quenching, high-pressure gas quenching following vacuum carburizing resulted in more uniform and smaller deformations.

  12. Simultaneous oxidation and carburization under oxyfuel conditions

    Kranzmann, Axel; Schulz, Wencke [Federal Institute for Materials Research and Testing, Berlin (Germany). Div. V.1 Composition and Microstructure of Engineering Materials; Huenert, Daniela [National Institute for Standards and Technology, Gaithersburg, MD (United States). Group 855.13 Thermodynamics and Kinetics


    The combustion of coal in CO{sub 2}-reduced oxyfuel power plants requires creep resistant and corrosion resistant materials which can withstand high temperatures up to 600 C (873 K) and CO{sub 2}-rich atmospheres. Among the heat resistant materials, the 9-12 % chromium steels have been proven to resist high wall temperatures in conventional power plants and are suitable as membrane walls, superheaters and steam piping. During oxyfuel combustion a flue gas is generated which consists mainly of H{sub 2}O (x{sub H{sub 2}}{sub O}=0.3) and CO{sub 2} (x{sub CO{sub 2}}=0.7). The present paper is focused on the corrosion of 9-12 % chromium steels under oxyfuel conditions in a temperature range between 550 C (823 K) and 625 C (898 K). Depending on the chromium content of the 9-12 % chromium steels, carburization of the base material, perlite formation and carbide formation were observed. Alloys with lower chromium content form a non-protective oxide scale with perlite at the scale-alloy interface. Steels with 12 % chromium have a small growing oxide scale with enlarged M{sub 23}C{sub 6} particles at the scale-alloy interface. The carburization of the base material is found to be increased for the 9 % Cr steel. Higher pressure of the flue gas results in the formation of less resistant scales and causes accelerated carburization of the base materials. However, the carburization has an impact on the mechanical properties at the surface and leads to an embrittlement, which is deleterious during thermal cycling. Oxidation kinetics, phase analysis of the scale (transmission electron microscope) and carburization depths (microprobe) of the base materials are presented. (orig.)

  13. Study of samarium modified lead zirconate titanate and nickel zinc ferrite composite system

    Rani, Rekha [Department of Physics, SD PG College, Panipat 132103 (India); School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Juneja, J.K., E-mail: [Department of Physics, Hindu College, Sonepat 131001 (India); Singh, Sangeeta [Department of Physics, GVM Girls College, Sonepat 131001 (India); Raina, K.K. [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Prakash, Chandra [Solid State Physics Laboratory, Timarpur, Delhi 110054 (India)


    In the present work, composites of samarium substituted lead zirconate titanate and nickel zinc ferrite with compositional formula 0.95Pb{sub 1−3x/2} Sm{sub x}Zr{sub 0.65}Ti{sub 0.35}O{sub 3}–0.05Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4} (x=0, 0.01, 0.02 and 0.03) were prepared by the conventional solid state route. X-ray diffraction analysis was carried out to confirm the coexistence of individual phases. Microstructural study was done by using scanning electron microscope. Dielectric constant and loss were studied as a function of temperature and frequency. To study ferroelectric and magnetic properties of the composite samples, corresponding P–E and M–H hysteresis loops were recorded. Change in magnetic properties of electrically poled composite sample (x=0.02) was studied to confirm the magnetoelectric (ME) coupling. ME coefficient (dE/dH) of the samples (x=0 and 0.02) was measured as a function of DC magnetic field. - Highlights: • We are reporting the effect of Sm substitution on PZT–NiZn ferrite composites. • Observation of both P–E and M–H loops confirms ferroelectric and magnetic ordering. • With Sm substitution, significant improvement in properties was observed. • Increase in magnetization for electrically poled sample is evidence of ME coupling. • Electric polarization is generated by applying magnetic field.

  14. Zircon typology combined with SmNd whole-rock isotope analysis to study Brioverian sediments from the Armorican Massif

    Dabard, M. P.; Loi, A.; Peucat, J. J.


    The identification of source materials contributing to mature terrigenous clastic deposits is made difficult due to a lack of useful discriminant criteria. SmNd isotope analysis can provide some indication of the present of mantle-derived constituents in clastic rocks. However, since this method is based on whole-rock samples, it is only possible to obtain the averaged composition of the different source materials involved. Moreover, SmNd isotope systematics can be strongly influenced by the presence of heavy minerals rich in rare earth elements and/or displaying isotopic ratios very different to the sedimentary host. In this manner, 0.1% of zircon or 0.01% of monazite from an extraneous source is sufficient to modify significatively the SmNd signature of the whole-rock. The typological study of zircon populations is an extremely valuable tool, especially since this mineral is highly resistant and exhibits a morphology controlled by the physical and chemical conditions under which it crystallized. Zircons that have been reworked in a sedimentary deposit display typologies that make it possible to identify the different igneous rock-types present in the source region. Moreover the typological study can be associated with a single-grain PbPb dating. This twofold approach was applied to Brioverian sedimentary rocks (Neoproterozoic III to Early Palaeozoic in age) from the Central Brittany Domain (Armorican Massif, NW France). It is proposed that these deposits inherited a major component from juvenile crustal materials ( ɛND(540) = - 1.4 to - 6.3), reflecting the presence of igneous precursors with a dominantly mantle-derived origin (zircon sub-types S19, S20, S24, S25 etc.), to which was added another component of crustal anatectic affinity (zircon sub-types S2, S6, S7 etc.). Two igneous source regions are identified on the basis of the present study: the anatectic granitic massifs of the Mancellian Batholith (540 Ma), along with a coeval ignimbritic

  15. Carburizer particle dissolution in liquid cast iron – computer simulation

    D. Bartocha


    Full Text Available In the paper issue of dissolution of carburizing materials (anthracite, petroleum coke and graphite particle in liquid metal and its computer simulation are presented. Relative movement rate of particle and liquid metal and thermophsical properties of carburizing materials (thermal conductivity coefficient, specific heat, thermal diffusivity, density are taken into consideration in calculations. Calculations have been carried out in aspect of metal bath carburization in metallurgical furnaces.

  16. Numerical Simulation on Carburizing and Quenching of Gear Ring


    The carburizing process of the gear ring was simulated by taking into account the practical carburizing and quenching techniques of the gear ring and by solving the diffusion equation. The carbon content distribution in the carburized layer was obtained. Based on the results, the quenching process of the gear ring was then simulated using the metallic thermodynamics and FEM; it was found that the carburization remarkably affects the quenching process.Microstructures and stress distributions of the gear ring in the quenching process were simulated, and the results are confirmed by experiments.

  17. Packed bed carburization of tantalum and tantalum alloy

    Lopez, Peter C.; Rodriguez, Patrick J.; Pereyra, Ramiro A.


    Packed bed carburization of a tantalum or tantalum alloy object. A method for producing corrosion-resistant tantalum or tantalum alloy objects is described. The method includes the steps of placing the object in contact with a carburizing pack, heating the packed object in vacuum furnace to a temperature whereby carbon from the pack diffuses into the object forming grains with tantalum carbide along the grain boundaries, and etching the surface of the carburized object. This latter step removes tantalum carbides from the surface of the carburized tantalum object while leaving the tantalum carbide along the grain boundaries.

  18. About Reverted Austenite in Carburized Layers of Low-Carbon Martensitic Steels

    Ivanov, A. S.; Bogdanova, M. V.; Vylezhnev, V. P.


    Processes of surface hardening in low-carbon martensitic steel 24Kh2G2NMFTB under carburizing and subsequent quenching from the intercritical temperature range are studied. Special features of formation of reverted austenite with high strength and stability are considered.

  19. Magnetic Barkhausen Noise in quenched carburized steels

    De Campos, M F; Santos, R; Da Silva, F S; Lins, J F C [PUVR- Universidade Federal Fluminense, Av dos Trabalhadores 420, Vila Santa Cecilia, Volta Redonda, RJ, 27255-125 (Brazil); Franco, F A; Ribeiro, S B; Padovese, L R, E-mail:, E-mail: [Escola Politecnica, Universidade de Sao Paulo, Sao Paulo, SP (Brazil)


    Steels with different carbon content, 0.11%C and 0.48%C were submitted to a heat treatment for carburization in the surface. The samples were analyzed after several types of heat treatment, including quenching for producing martensite. The Magnetic Barkhausen Noise (MBN) is directly related to the microstructure. Samples with lower carbon content, have ferrite, a constituent where domain walls can move freely and present higher amplitude in the envelope of MBN. It is also found that the MBN peaks are quite distinct for the samples with martensite, which have lower permeability, and the results suggest that domain rotation contributes as mechanism for reversal of magnetization in martensite. The results also indicate that MBN is very suitable for monitoring the carburizing heat treatment.

  20. Magnetic Barkhausen Noise in quenched carburized steels

    de Campos, M. F.; Franco, F. A.; Santos, R.; da Silva, F. S.; Ribeiro, S. B.; Lins, J. F. C.; Padovese, L. R.


    Steels with different carbon content, 0.11%C and 0.48%C were submitted to a heat treatment for carburization in the surface. The samples were analyzed after several types of heat treatment, including quenching for producing martensite. The Magnetic Barkhausen Noise (MBN) is directly related to the microstructure. Samples with lower carbon content, have ferrite, a constituent where domain walls can move freely and present higher amplitude in the envelope of MBN. It is also found that the MBN peaks are quite distinct for the samples with martensite, which have lower permeability, and the results suggest that domain rotation contributes as mechanism for reversal of magnetization in martensite. The results also indicate that MBN is very suitable for monitoring the carburizing heat treatment.

  1. Rolling Contact Fatigue Performances of Carburized and High-C Nanostructured Bainitic Steels

    Yanhui Wang


    Full Text Available In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under lubrication. Results show that the RCF life of the carburized nanostructured bainitic steel is superior to that of the high-C nanostructured bainitic steel in spite of the chemical composition, phase constituent, plate thickness of bainitic ferrite, hardness, and residual compressive stress value of the contact surfaces of the two steels under roughly similar conditions. The excellent RCF performance of the carburized nanostructured bainitic steel is mainly attributed to the following reasons: finer carbide dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher work hardening ability, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface of the steel.

  2. Rolling Contact Fatigue Performances of Carburized and High-C Nanostructured Bainitic Steels.

    Wang, Yanhui; Zhang, Fucheng; Yang, Zhinan; Lv, Bo; Zheng, Chunlei


    In the present work, the nanostructured bainitic microstructures were obtained at the surfaces of a carburized steel and a high-C steel. The rolling contact fatigue (RCF) performances of the two alloy steels with the same volume fraction of undissolved carbide were studied under lubrication. Results show that the RCF life of the carburized nanostructured bainitic steel is superior to that of the high-C nanostructured bainitic steel in spite of the chemical composition, phase constituent, plate thickness of bainitic ferrite, hardness, and residual compressive stress value of the contact surfaces of the two steels under roughly similar conditions. The excellent RCF performance of the carburized nanostructured bainitic steel is mainly attributed to the following reasons: finer carbide dispersion distribution in the top surface, the higher residual compressive stress values in the carburized layer, the deeper residual compressive stress layer, the higher work hardening ability, the larger amount of retained austenite transforming into martensite at the surface and the more stable untransformed retained austenite left in the top surface of the steel.

  3. Roundness of heavy minerals (zircon and apatite) as a provenance tool for unraveling recycling: A case study from the Sefidrud and Sarbaz rivers in N and SE Iran

    Zoleikhaei, Yousef; Frei, Dirk; Morton, Andrew; Zamanzadeh, S. Mohammad


    In order to improve techniques for provenance studies, and especially to address the question of sediment recycling, morphological changes of two minerals with contrasting durability (zircon and apatite) were tracked during both fluvial transport and littoral reworking. The Sefidrud river system in northern Iran, which drains the Alborz volcano-sedimentary range into the Caspian Sea, and the Sarbaz river system in southeastern Iran, which drains the Makran Accretionary Prism into the Oman Sea, were chosen for this study. To determine source rocks of the grains, and thus their nature in terms of sedimentary cycles, zircon geochronology was conducted on both rivers. The zircon data indicate that most of the Sefidrud sediments are first cycle, derived from crystalline rocks, and the Sarbaz sediments are generally recycled from older wedges of the Makran. Results from SEM analysis show significant differences between the roundness of associated zircon and apatite grains. Zircon grains remain unrounded through several cycles, while apatite grains show abrasion from the early stages of their first cycle.

  4. Chemical evolution of Himalayan leucogranites based on an O, U-Pb and Hf study of zircon

    Hopkinson, Thomas N.; Warren, Clare J.; Harris, Nigel B. W.; Hammond, Samantha J.; Parrish, Randall R.


    Crustal melting is a characteristic process at convergent plate margins, where crustal rocks are heated and deformed. Miocene leucogranite sheets and plutons are found intruded into the high-grade metasedimentary core (the Greater Himalayan Sequence, GHS) across the Himalayan orogen. Previously-published Himalayan whole-rock data suggest that these leucogranites formed from a purely meta-sedimentary source, isotopically similar to those into which they now intrude. Bulk rock analyses carry inherent uncertainties, however: they may hide contributions from different contributing sources, and post-crystallization processes such as fluid interaction may significantly alter the original chemistry. In contrast, zircon is more able to retain precise information of the contributing sources of the melt from which it crystallises whilst its resistant nature is impervious to post-magmatic processes. This multi-isotope study of Oligocene-Miocene leucogranite zircons from the Bhutan Himalaya, seeks to differentiate between various geochemical processes that contribute to granite formation. Hf and O isotopes are used to detect discrete changes in melt source while U-Pb isotopes provide the timing of zircon crystallisation. Our data show that zircon rims of Himalayan age yield Hf-O signatures that lie within the previously reported whole-rock GHS field, confirming the absence of a discernible mantle contribution to the leucogranite source. Importantly, we document a decrease in the minimum ɛHf values during Himalayan orogenesis through time, correlating to a change in Hf model age from 1.4 Ga to 2.4 Ga. Nd model ages for the older Lesser Himalayan metasediments (LHS) that underthrust the GHS are significantly older than those for the GHS (2.4-2.9 Ga compared with 1.4-2.2 Ga), and as such even minor contributions of LHS material incorporated into a melt would significantly increase the resulting Hf model age. Hence our leucogranite data suggest either a change of source within

  5. Mechanical and Metallurgical Evaluation of Carburized, Conventionally and Intensively Quenched Steels

    Giordani, T.; Clarke, T. R.; Kwietniewski, C. E. F.; Aronov, M. A.; Kobasko, N. I.; Totten, G. E.


    Steels subjected to carburizing, quenching, and tempering are widely used for components that require hardness and superficial mechanical resistance together with good core toughness. Intensive quenching is a method that includes advantages including crack prevention, increased mechanical resistance, and improvement in fatigue performance when subjected to very fast (intensive) cooling. However, achieving these advantages requires the formation of sufficiently high surface compressive residual stresses and fine grains at the core of steel components. If the cooling rate is sufficiently high after intensive quenching, then low-hardenability, killed plain carbon steels may be used instead of higher-cost, low alloy steels because compressive residual stresses are formed at the surface of steel parts. The objective of this study was to compare between carburized non-killed AISI 1020 steel samples, which were not modified by Al that were subsequently conventionally and also intensively quenched to determine the effect of quenching on achieving the necessary formation of fine grain size. For comparison, carburized AISI 8620 steel test specimens were conventionally quenched. After quenching, all test specimens were characterized by metallurgical and mechanical analyses. The results of this study showed that when the two quenching methods were compared for carburized non-killed AISI 1020 steel, intensive quenching method was found to be superior with respect to mechanical and metallurgical properties. When comparing the different steels, it was found that intensively quenched, non-killed, AISI 1020 steel yielded grain sizes which were three times greater than those obtained with conventionally quenched, carburized AISI 8620 steel. Therefore, the benefits of intensive quenching were negated. These results show that plain carbon steels must be modified by Al to make fine grains if intensively quenched plain-carbon steel is to replace alloyed AISI 8620 steel.

  6. A poling study of lead zirconate titanate/polyurethane 0-3 composites

    Lau, S. T.; Kwok, K. W.; Shin, F. G.; Kopf, S.


    0-3 composites of lead zirconate titanate particles dispersed in a thermoplastic elastomer polyurethane matrix were fabricated. The dielectric permittivity and loss of the composite film were measured and compared to the theoretical values. The composites were polarized by the ac fields at different frequencies. With the application of the Sawyer-Tower circuit, the D-E hysteresis loops of the composites can be measured during the poling process. By decreasing the poling frequency, the composite sample shows a larger "remanent" polarization at the same poling field. To evaluate the poling effectiveness, the pyroelectric coefficients of the poled composite samples were measured by a dynamic method.

  7. Tracing the depositional history of Kalimantan diamonds by zircon provenance and diamond morphology studies

    Kueter, Nico; Soesilo, Joko; Fedortchouk, Yana; Nestola, Fabrizio; Belluco, Lorenzo; Troch, Juliana; Wälle, Markus; Guillong, Marcel; Von Quadt, Albrecht; Driesner, Thomas


    Diamonds in alluvial deposits in Southeast Asia are not accompanied by indicator minerals suggesting primary kimberlite or lamproite sources. The Meratus Mountains in Southeast Borneo (Province Kalimantan Selatan, Indonesia) provide the largest known deposit of these so-called "headless" diamond deposits. Proposals for the origin of Kalimantan diamonds include the adjacent Meratus ophiolite complex, ultra-high pressure (UHP) metamorphic terranes, obducted subcontinental lithospheric mantle and undiscovered kimberlite-type sources. Here we report results from detailed sediment provenance analysis of diamond-bearing Quaternary river channel material and from representative outcrops of the oldest known formations within the Alino Group, including the diamond-bearing Campanian-Maastrichtian Manunggul Formation. Optical examination of surfaces of diamonds collected from artisanal miners in the Meratus area (247 stones) and in West Borneo (Sanggau Area, Province Kalimantan Barat; 85 stones) points toward a classical kimberlite-type source for the majority of these diamonds. Some of the diamonds host mineral inclusions suitable for deep single-crystal X-ray diffraction investigation. We determined the depth of formation of two olivines, one coesite and one peridotitic garnet inclusion. Pressure of formation estimates for the peridotitic garnet at independently derived temperatures of 930-1250 °C are between 4.8 and 6.0 GPa. Sediment provenance analysis includes petrography coupled to analyses of detrital garnet and glaucophane. The compositions of these key minerals do not indicate kimberlite-derived material. By analyzing almost 1400 zircons for trace element concentrations with laser ablation ICP-MS (LA-ICP-MS) we tested the mineral's potential as an alternative kimberlite indicator. The screening ultimately resulted in a small subset of ten zircons with a kimberlitic affinity. Subsequent U-Pb dating resulting in Cretaceous ages plus a detailed chemical reflection make

  8. Subduction-accretion-collision history along the Gondwana suture in southern India: A laser ablation ICP-MS study of zircon chronology

    Sato, Kei; Santosh, M.; Tsunogae, Toshiaki; Chetty, T. R. K.; Hirata, Takafumi


    We report the petrological characteristics and preliminary zircon geochronology based on laser ablation ICP mass spectrometry of the various units in an accretionary belt within the Palghat-Cauvery Shear/Suture Zone in southern India, a trace of the Cambrian Gondwana suture. Zircons extracted from a plagiogranite in association with an ophiolite suite within this suture possess internal structure that suggests magmatic crystallization, and yield mid Neoproterozoic 206Pb/ 238U age of 817 ± 16 Ma (error: 1 σ) constraining the approximate timing of birth of the Mozambique Ocean floor. Compiled age data on zircons separated from a quartzite and metamorphosed banded iron formation within the accretionary belt yields a younger intercept age of 759 ± 41 Ma (error: 1 σ) which we relate to a mid Neoproteozoic magmatic arc. Detrital zircons extracted from the quartzite yield 207Pb/ 206Pb age peaks of about 1.9-2.6 Ga suggesting that they were sourced from multiple protolithis of Neoarchean and Paleoproterozoic. Metamorphic overgrowths on some zircon grains record ca. 500-550 Ma ages which are in good harmony with the known ages for the timing of high-grade metamorphism in this zone during the final stage of continent collision associated with the birth of the Gondwana supercontinent in the latest Neoproterozoic-Cambrian. The preliminary geochronological results documented in our study correlate with the subduction-accretion-collision history associated with the closure of the Mozambique Ocean and the final amalgamation of the Gondwana supercontinent.

  9. Gas-Carburizing Kinetics of a Low-Alloy Steel

    Nobili, Luca; Cavallotti, Pietro; Pesetti, Mariella


    Gas-carburizing kinetics of a low-alloy steel (Pyrowear 53) was investigated by thermogravimetric experiments. Kinetic curves were modeled by adapting the approximate integral method, and the diffusion coefficient of carbon as well as the rate constant of the surface reaction were estimated. These parameters were evaluated after several carburizing procedures, which differ from each other in the surface treatments performed before the carburizing step. It is known that the carbon enrichment is low when this steel is carburized without any pretreatment, and this behavior was found to be related to a low value of carbon diffusivity. The interaction between the selective oxidation of alloying elements by the carburizing atmosphere and carbon diffusion is discussed. The pretreatment procedures investigated in this work consist of different combinations of oxidation, reduction, and grit-blasting processes. The most effective procedures involve oxidation in dry air or oxidation in wet air followed by grit blasting.

  10. Evaluating the Paleomagnetic Potential of Zircons

    Fu, R. R.; Lima, E. A.; Weiss, B. P.; Glenn, D. R.; Kehayias, P.; Walsworth, R. L.


    Because zircon crystals commonly display high natural U/Pb ratios and excellent resistance to weathering, paleomagnetic data collected from zircons potentially enjoy the benefits of excellent age controls and minimal remagnetization from infiltrating fluids. We present rock magnetic and paleomagnetic experiments on two sets of zircons with contrasting geologic histories to determine the viability of zircons as paleomagnetic recorders. First, we characterize primary zircons from the Bishop Tuff, a pyroclastic deposit formed at 767±1 ka in a magnetic field of 43±3 µT. Magnetic field maps with ~10 µm resolution obtained with the nitrogen vacancy (NV) diamond magnetometer indicate that most ferromagnetic sources are situated within zircon interiors, suggesting a primary origin (Fig. 1A). Stepwise thermal demagnetization reveals well-defined components of magnetization blocked in most samples up to 580˚C, indicating the dominance of magnetite, which is the expected primary phase. The intensity of natural remanent magnetization (NRM) is typically 10-12 Am2. Ongoing Thellier-Thellier dual heating experiments will evaluate the accuracy of recovered paleointensities. Second, we study Hadean and Archean detrital zircons from the Jack Hills. In contrast to the Bishop Tuff samples, magnetic microscopy and stepwise thermal demagnetization demonstrate that the remanent magnetization of >80% of Jack Hills zircon are carried exclusively by secondary hematite situated on grain surfaces (Fig. 1B). NRM intensities range between 10-15 and 10-12 Am2 and decrease by a factor of several upon chemical removal of secondary hematite. Our analyses reveal a diversity of ferromagnetic mineralogies and distribution in natural zircons. While some zircon populations carry reliable paleomagnetic information, others are dominated by secondary ferromagnetic phases. Without the application of high-resolution magnetic microscopy techniques to identify the main ferromagnetic carrier, it is

  11. The effects of pack carburizing using charcoal of unused mahogany on fatigue characteristic of v-notch shaft steel specimens

    Supriyono, Jamasri


    The aim of this research is to study the fatigue characteristic of v-notch shaft steel specimens before and after pack carburizing. The carbon source is taken from charcoal of unused mahogany. The fatigue test is conducted on rotary bending machine. The specimens are made of low carbon steel of 0.17% carbon content. Pack carburizing is conducted to the specimens at 930°C. V-notch is made to present the stress concentration factor on the specimens. To see the effects of the carburizing in changing the material properties, micro-structures before and after carburizingare looked and micro hardness measurements along the cross sectional area are carried out. The results show that the carburizing process increases fatigue strength of the material. The micro-structures of the raw material are ferrite and pearlite. The carburized material is divided into two zones i.e. surface zone and core zone. The surface zone consists of hypereutectoid, eutectoid, and hypoeutectoid sub-zone. The core zone is the same as raw material

  12. Comparison of CaCO3 from Natural Sources and Artificial Carbonates as Activators of Solid-Phase Carburizing of Low-Carbon Steel

    González-Angeles, A.; López-Cuevas, J.; Pitalúa-Díaz, N.


    The process of solid-phase carburizing of steel with the use of carbonates of different origin including chemical reagents, limestone and oyster shells is studied. The highest microhardness is obtained in the case of SrCO3, wheres Na2CO3 is shown to be the cheapest and most economically expedient carbonate. A good carburized layer can be obtained using a mixture of limestone and oyster shells.

  13. Solidification of simulated actinides by natural zircon

    YANG Jian-Wen; LUO Shang-Geng


    Natural zircon was used as precursor material to produce a zircon waste form bearing 20wt% simulated actinides (Nd2O3 and UO2) through a solid state reaction by a typical synroc fabrication process. The fabricated zircon waste form has relatively good physical properties (density 5.09g/cm3, open porosity 4.0%, Vickers hardness 715kg/mm2). The XRD, SEM/EDS and TEM/EDS analyses indicate that there are zircon phases containing waste elements formed through the reaction. The chemical durability and radiation stability are determined by the MCC-1method and heavy ion irradiation; the results show that the zircon waste form is highly leach resistance and relatively stable under irradiation (amorphous dose 0.7dpa). From this study, the method of using a natural mineral to solidify radioactive waste has proven to be feasible.

  14. Trace-element study and age dating of zircon from chromitites of the Bushveld Complex (South Africa)

    Yudovskaya, Marina; Kinnaird, Judith; Naldrett, Anthony J.; Rodionov, Nickolay; Antonov, Anton; Simakin, Sergey; Kuzmin, Dmitry


    The layered Bushveld Complex hosts a number of chromitite layers, which were found to contain significant amounts of zircon grains compared with adjacent silicate rocks. Cathodoluminescent-dark, partially metamict cores and transparent rims of composite zircon grains were analyzed for trace elements with SIMS and LA-ICPMS techniques. The cores are enriched in REE, Y, Th and U and are characterized by distinctly flatter REE patterns in contrast to those of the rims and transparent homogenous crystals. Zircon from the different stratigraphic units has specific Th/U ratios, the highest of which (1.5-4) occurs in a Merensky Reef zircon core. The Ti content of Bushveld zircon ranges from 12 to 52 ppm correlating to a crystallization temperature range of 760-930 °C. The geochemical characteristics of the first zircon generation are consistent with its high-temperature crystallization as the first major U, Th and REE acceptor from a highly-evolved residue of the high-Mg basalt magma, whereas the rims and coreless crystals have crystallized from percolating intercumulus liquid of new influx of the same magma. U-Pb SHRIMP dating of zircon cores and rims does not reveal a distinguishable difference between their ages indicating the absence of inherited zircon. Concordia ages of 2,051 ± 9 Ma (2σ, MSWD = 0.1) and 2,056 ± 5 Ma (2σ, MSWD = 0.05) for zircons from the Merensky Reef and the Upper Platreef located equally near the top of the Critical Zone are in agreement with published ages for the Merensky Reef. Zircon from the deeper-seated Lower Group, Middle Group and Lower Platreef chromitites yields younger concordia ages that may reflect prolonged late-stage volatile activity.

  15. Fluid-assisted zircon and monazite growth within a shear zone: a case study from Finnmark, Arctic Norway

    Kirkland, Christopher L.; Whitehouse, Martin J.; Slagstad, Trond


    The U-Pb ages, REE content, and oxygen isotopic composition of zircon rims developed within a major shear zone in the Kalak Nappe Complex (KNC), Arctic Norway have been determined along with the age of monazite crystals. Different generations of granitic veins have been distinguished based on both field criteria and monazite ages of 446 ± 3 and 424 ± 3 Ma. Within each of these veins, inherited zircon cores are mantled by homogeneous low CL-response zircon rims which yield a range of concordant U-Pb dates of ca. 470-360 Ma. Significant numbers of zircon rims coincide with the timing of monazite crystallization. The zircon rims have moderate light REE enrichment compared to cores, distinctive (Sm/La) n values of less than 12, and La between 0.3 and 10 ppm. This indicates free elemental exchange between newly formed zircon rims and the surrounding matrix. The rims have calculated accumulated alpha-radiation dosages corresponding with a crystalline structure and δ18O values of 1‰. This implies rim crystallization directly from a zirconium-saturated hydrothermal fluid which was modified by some silicate melt. Growth of the zircon rims was prolonged and locally variable due to preferential fluid flow. A third type of zircon can be recognized, forming both rims and cores, with high alpha-radiation doses, and significant enrichment in La, Pr, and Eu. These are interpreted as low-temperature hydrothermally altered metamict zircons. The high volatile input and partial melting in the shear zone favoured prolonged zircon rim growth due to its ability to easily nucleate on inherited seeds. On the other hand, monazite, susceptible to dissolution and re-growth, crystallized in brief episodes, as has been predicted from theoretical phase diagrams. From a regional perspective, these results elucidate cryptic Ar-Ar cooling ages, providing the first record of a Late Ordovician heating and cooling phase within the KNC prior to the climactic Scandian collision.

  16. Evaluation of Carburized and Ground Face Gears

    Lewicki, David G.; Handschuh, Robert F.; Heath, Gregory F.; Sheth, Vijay


    Experimental durability tests were performed on carburized and ground AIS19310 steel face gears. The tests were in support of a Defense Advanced Research Projects Agency (DARPA) Technology Reinvestment Program (TRP) to enhance face-gear technology. The tests were conducted in the NASA Glenn spiral-bevel-gear/face-gear test facility. Tests were run at 2300 rpm face gear speed and at loads of 64, 76, 88, 100, and 112-percent of the design torque of 377 N-m (3340 in-lb). The carburized and ground face gears demonstrated the required durability when run for ten-million cycles at each of the applied loads. Proper installation was critical for the successful operation of the spur pinions and face gears. A large amount of backlash produced tooth contact patterns that approached the inner-diameter edge of the face-gear tooth. Low backlash produced tooth contact patterns that approached the outer-diameter edge of the face-gear tooth. Measured backlashes in the range of 0.178 to 0.254 mm (0.007 to 0.010 in) produced acceptable tooth contact patterns.

  17. Preliminary study of microscale zircon oxygen isotopes for Dabie-Sulu metamorphic rocks: Ion probe in situ analyses

    CHEN Daogong; Deloule Etienne; CHENG Hao; XIA Qunke; WU Yuanbao


    151 in situ analyses of oxygen isotopes were carried out by ion micro-probe for zircons from 8 localities of HP-UHP metamorphic rocks including eclogites in the Dabie-Sulu terrane. The results show significant heterogeneity inδ18O values, with variation in different rocks from -8.5‰ to +9.7‰ and within one sample from 2‰ to 12‰. No measurable difference inδ18O was observed between protolith magmatic (detrital) zircons and metamorphic recrystallized zircons within analytical uncertainties from the ion micro-probe measurements. This indicates that the metamorphic zircons have inherited the oxygen isotopic compositions of protolith zircons despite the HP to UHP metamorphism. According to their protolith ages from zircon U-Pb in situ dating by the same ion micro-probe, two groups of oxygen isotope composition are recognized, with one having δ18O values of 6‰-7‰ for old protolith of 1.9-2.5 Ga ages and the other 0‰-2‰ for young protolith of 0.7-0.8 Ga ages. The latter anomalously lowδ18O values of zircons indicate that the magma has had the obvious involvement of meteoric water when forming the young protolith of high-grade metamorphic rocks. This may be correlated with the snowball Earth event occurring in South China and the world elsewhere during the Neoproterozoic.

  18. Isotopic studies on detrital zircons of Silurian-Devonian siliciclastic sequences from Argentinean North Patagonia and Sierra de la Ventana regions: comparative provenance

    Uriz, Norberto J.; Cingolani, Carlos A.; Chemale, Farid; Macambira, Moacir B.; Armstrong, Richard


    The Silurian-Devonian siliciclastic sedimentary units known as Sierra Grande Formation and the upper part of the Ventana Group crop out in the eastern area of the North Patagonian Massif and in the Ventania system, toward the Atlantic border of Argentina. Both sequences show similar stratigraphical characteristics and were deposited in a shallow marine platform paleoenvironment. Previous contributions have provided evidence of an allochthonous Patagonia terrane that amalgamate to Gondwana during the Permian-Triassic. However, other lines of research support a crustal continuity southward, where the Pampean and Famatinian events extend into the northern Patagonia. In either case, the detrital input to the Eo-Mesopaleozoic basins generated along the passive margin tectonic setting should reflect the sedimentary sources. In this contribution, new age data on the sedimentary provenance of these units is provided by U-Pb and Lu-Hf isotopic studies on detrital zircons, using LA-ICP-MS and SHRIMP methodologies. The main sedimentary sources of detrital zircons for both regions are of Cambrian-Ordovician and Neoproterozoic age, while a secondary mode is Mesoproterozoic. Zircons from older cratonic sources (Mesoarchean-Paleoproterozoic ages) are scarcely recorded. The sample from the upper section of the Devonian Lolén Formation (Ventana Group) shows an important change in the sedimentary provenance, with a main mode of Mesoproterozoic detrital zircons. Detrital source areas considering the orogenic cycles known for southwest South America (Famatinian, Pampean-Brasiliano, Mesoproterozoic-`Grenvillian' and Paleoproterozoic-`Transamazonian') are proposed.

  19. Cryogenic Treatment of Carbide-free Bainite Steel After Carburizing

    SUN Shi-qing


    Full Text Available The cryogenic treatment (CT process of carbide-free bainite steel after carburizing was optimized by the method combining thermal magnetic analysis, microhardness analysis and direct reading spectrometric analysis. The results show that cryogenic treatment temperature of the hardened layer should be lower than 134K by measuring thermal magnetic curve of the sample after carburizing at 1193K and air cooling (AC. After cryogenic treatment at 123K and tempering (T at 463K, retained austenite content of the hardened layer is about 12.2% (mass fraction. The near surface layer of carburized steel is hardened dramatically through the cryogenic treatment, and the hardness of near surface layer reaches about 810HV1.0 after low temperature tempering. The distribution of hardness gradient of carburized steel tends to be reasonable.

  20. First principles study of nanoscale mechanism of oxygen adsorption on lanthanum zirconate surfaces

    Guo, Xingye; Wu, Linmin; Zhang, Yi; Jung, Yeon-Gil; Li, Li; Knapp, James; Zhang, Jing


    Lanthanum zirconate (La2Zr2O7) is a rare-earth pyrochlore material, which has been proposed as a promising thermal barrier coating (TBC) material due to its low thermal conductivity and high temperature phase stability. At elevated temperatures, degradation of La2Zr2O7 may occur due to adsorption of oxygen (O2) on La2Zr2O7 surfaces. This paper investigates nanoscale mechanism of O2 adsorption on La2Zr2O7 coating surfaces using the density functional theory (DFT) calculations. La2Zr2O7 surface energies on (001), (011) and (111) planes are calculated. The surface free energy of (011) plane is lower than those of (001) and (111) planes. On (001), (011) and (111) planes of La2Zr2O7, the lowest adsorption energy occurs at 4-fold site, bridge site, and 3-fold-FCC site, respectively. Among all calculated cases, the lowest adsorption energy site is 3-fold-FCC on (111) plane, which is confirmed by the Bader charge transfer analyses. Charge density difference analyses show that the 3-fold-FCC site on (111) surface has the largest charge density, suggesting the strongest interaction between O2 and La2Zr2O7 surface.

  1. Computer simulation of carburizers particles heating in liquid metal

    K. Janerka


    Full Text Available In this article are introduced the problems of computer simulation of carburizers particles heating (anthracite, graphite and petroleum coke, which are present in liquid metal. The diameter of particles, their quantity, relative velocity of particles and liquid metal and the thermophysical properties of materials (thermal conductivity, specific heat and thermal diffusivity have been taken into account in calculations. The analysis has been carried out in the aspect of liquid metal carburization in metallurgical furnaces.

  2. Electrochemical corrosion behavior of the carburized porous TiAl alloy

    Liao, Cuijiao [Hunan University of Technology, Zhuzhou, Hunan 412000 (China); Yang, Junsheng [Wuhan Polytechnic University, Wuhan, Hubei 430023 (China); He, Yuehui, E-mail: [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Ming, XingZu [Hunan University of Technology, Zhuzhou, Hunan 412000 (China)


    Highlights: • Ti{sub 2}AlC phase forms on porous TiAl alloy in a carburizing atmosphere. • The carburized sample at 1203 K for 10 h has continuous carburized layers. • Carburization can improve corrosion resistance of the porous TiAl alloy. • The passive film of the carburized sample at 1203 K for 10 h is very stable. - Abstract: Carburization was carried out to improve corrosion resistance of porous Ti–46.5 Al (at.%) intermetallic compound. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to analyze the carburized layers. Electrochemical corrosion behavior of the untreated and the carburized samples were investigated using potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and open circuit potential. The results reveal that the continuous and thick carburized layers form after carburization treatment at 1203 K for 10 h, whose main phase is a functional complex ceramic phase, Ti{sub 2}AlC. Carburization can improve corrosion resistance of the porous TiAl alloy. Among the carburized samples, the carburized one at 1203 K for 10 h presents the highest corrosion resistance and has the most stable oxide film.

  3. Combined garnet and zircon geochronology and trace elements studies - constraints of the UHP-(U)HT evolution of Orlica-Śnieżnik Dome (NE Bohemian Massif).

    Walczak, Katarzyna; Anczkiewicz, Robert; Szczepański, Jacek; Rubatto, Daniela


    The Orlica-Śnieżnik Dome (OSD), located on the NE margin of the Bohemian Massif, is predominantly composed of amphibolite-facies orthogneiss that contain bodies of HP and UHP eclogites and granulites. Numerous geochronological studies have been undertaken to constrain the timing of the ultra-high grade metamorphic event. Despite this, the exact timing of UHP-(U)HT conditions remain dubious (e.g. Brueckner et al., 1991; Anczkiewicz et al., 2007; Bröcker et al., 2009 & 2010). We have utilized garnet and zircon geochronology to provide time constraints on the evolution of the UHT-(U)HP rocks of the OSD. We have combined the ages with trace element analyses in garnet and zircon to better understand the significance of the obtained ages in petrological context. Lu-Hf grt-wr dating of peritectic garnet from two felsic granulites constrained the time of its initial growth at 346.9 ± 1.2 and 348.3 ± 2.0 Ma, recording peak conditions of 2.7 GPa and 950°C (e.g. Ferrero et al., 2015). In situ U-Pb SHRIMP dating of zircon from the same granulite gave a younger age of 342.2 ± 3.4 Ma. HREE partitioning between garnet rim and metamorphic zircon indicate their growth in equilibrium, hence, the U-Pb zircon date constrains the terminal phase of garnet crystallization. Similar ages were obtained from two eclogite bodies from Międzygórze and Nowa Wieś localities; Lu-Hf (grt-cpx-wr) dating provided ages of 346.5 ± 2.4 and 348.1 ± 9.1 Ma for samples from Międzygórze and Nowa Wieś, respectively. The same age (within error) of 346.3 ± 5.2 Ma was reported by Bröcker et al. (2010) for zircon from the Międzygórze eclogite. Comparison of REE concentrations in garnet (this study) and in metamorphic zircon (reported in Bröcker et al., 2010) indicate that garnet and zircon crystallized in equilibrium. Furthermore, M-HREE patterns observed in both garnet and zircon strongly suggest their growth at eclogite facies conditions. Sm-Nd garnet ages obtained for both felsic and mafic

  4. The Proper Process Parameter of Brush Copperplating and the Minimun Thickness of Copper Film for Prevention of Carburization%防渗碳刷镀镀铜的工艺参数及镀层厚度选择

    谢辅洲; 王桂芳; 郑玉丽


    In this paper, the effects of process parameter of brush copperplating on the copper film for prevention of carburization were studied; the relation between the time of carburization and the minimun thickness of copper film for prevention of carburization was established.%研究了用刷镀镀铜防渗碳时的工艺参数对镀层防渗碳效果的影响,及渗碳时间与防渗碳所需的最小镀层厚度之间的关系。

  5. Analysis on microstructure of carburized layer in cast-iron molten bath carburized 20 steel%20钢铸铁浴渗碳渗层组织的分析

    刘建华; 湛岩; 张瑞军; 于升学; 杨雪梅


    The microstructure of carburized layer in 20 steel cast-iron molten bath carburized at different temperature and time was studied in the paper.The research results show that the microstructure of carburized layer which is at 130~150μm from the surface is cementite+pearlite+ferrite,when specimen immevsed for 30s in 1270℃;the micvostruchre of carburized layer which is at 0~120μm from the surface is cementite+pearlite,and bar carbides is obtained in the base.%本文探讨了20钢在铸铁浴中经不同温度及时间渗碳的渗层组织。结果表明,试样在1270℃的铸铁浴中保留30秒,距表面130~150μm处,其渗层组织为渗碳体+珠光体+铁素体;试样在1300℃的铸铁浴中保留30秒,距表面0~120μm处,其渗层组织为渗碳体+珠光体,且在基体上形成棒条状的碳化物。

  6. Gradient boride layers formed by diffusion carburizing and laser boriding

    Kulka, M.; Makuch, N.; Dziarski, P.; Mikołajczak, D.; Przestacki, D.


    Laser boriding, instead of diffusion boriding, was proposed to formation of gradient borocarburized layers. The microstructure and properties of these layers were compared to those-obtained after typical diffusion borocarburizing. First method of treatment consists in diffusion carburizing and laser boriding only. In microstructure three zones are present: laser borided zone, hardened carburized zone and carburized layer without heat treatment. However, the violent decrease in the microhardness was observed below the laser borided zone. Additionally, these layers were characterized by a changeable value of mass wear intensity factor thus by a changeable abrasive wear resistance. Although at the beginning of friction the very low values of mass wear intensity factor Imw were obtained, these values increased during the next stages of friction. It can be caused by the fluctuations in the microhardness of the hardened carburized zone (HAZ). The use of through hardening after carburizing and laser boriding eliminated these fluctuations. Two zones characterized the microstructure of this layer: laser borided zone and hardened carburized zone. Mass wear intensity factor obtained a constant value for this layer and was comparable to that-obtained in case of diffusion borocarburizing and through hardening. Therefore, the diffusion boriding could be replaced by the laser boriding, when the high abrasive wear resistance is required. However, the possibilities of application of laser boriding instead of diffusion process were limited. In case of elements, which needed high fatigue strength, the substitution of diffusion boriding by laser boriding was not advisable. The surface cracks formed during laser re-melting were the reason for relatively quickly first fatigue crack. The preheating of the laser treated surface before laser beam action would prevent the surface cracks and cause the improved fatigue strength. Although the cohesion of laser borided carburized layer was

  7. Zircon LA-ICPMS study and petrogenesis simulation of Dahuabei pluton in the Wulashan area,Inner Mongolia

    Dapeng Li; Yuelong Chen; Liemeng Chen; Zhong Wang; Jinbao Liu


    Dahuabei pluton in the Wulashan area,Inner Mongolia,is an alkaline and peraluminous granitic pluton.LA-ICPMS U-Pb dating of zircons indicates that this pluton crystallized at 330±10 Myr.The pluton did not experience apparent zircon fractionation.The consistent temperatures between Zr saturation (765℃) and the average zircon-rutile Ti equilibrium (780℃),together with zircon ages and their CL images,indicated that there were no inherited zircons in this pluton.Through the simulation of the dry-system crystallization process of magma cooling at 200 MPa and 1100-709℃,the phase diagram and composition evolution tendency of different phases were obtained.The magma reached its liquidus at 1069℃.Sanidine was the first crystallized phase;at 709℃ the residual magma was less than 4%,and the range of 1069-719℃ should be the most suitable approach to the real condition.It is shown that at least some part of the pluton underwent such isobaric equilibrium crystallization processes during its crystallization.

  8. Analysis of methods of carburizing of gears from heat-resistant steels

    Ryzhov, N. M.; Fakhurtdinov, R. S.; Smirnov, A. E.; Fomina, L. P.


    Four methods of carburizing are compared with respect to the most significant factor, i.e., stability of maintenance of the specified parameters of carburized layer in hardening of gears from heat-resistant steels. The process advantages of vacuum carburizing (at low pressure) are shown.

  9. Effect of carbon on tribological property of plasma carburized TiAl based alloy

    LIU Xiao-ping; TIAN Wen-huai; GUO Chao-li; HE Zhi-yong; XU Zhong


    Plasma carburization at two different methane-to-argon gas ratios (5:5 and 6:5) was carried out on the cast TiAl based alloy of Ti-46.5Al-2.5V-1Cr (mole fraction, %) in order to enhance its wear resistance. The results show that after carburization under both carburizing atmospheres, Ti2AlC and TiC are the main carbides in the carburized layer and the value of surface hardness reaches more than HK 822, but for the carburized TiAl treated at CH4-Ar of 5-5, the surface carbon concentration is higher and the carburized depth is slightly thicker than that of alloy carburized at CH4-Ar of 6-5. The result of the ball-on-disk test against hardening-steel counter bodies shows that the wear resistance of the TiAl based alloy carburized under two different carburizing atmospheres is improved compared with non-carburized TiAl. The tribological property is related to the carbon content, and the carburized layer obtained at CH4:Ar of 5:5 possesses a stable friction coefficient, lower volume loss or wear rate and narrow wear scar. The characteristic of the carburized layer was examined by using optical microscopy, glow discharge spectrum and micro-hardness tester.

  10. Materials and Process Design for High-Temperature Carburizing: Integrating Processing and Performance

    D. Apelian


    The objective of the project is to develop an integrated process for fast, high-temperature carburizing. The new process results in an order of magnitude reduction in cycle time compared to conventional carburizing and represents significant energy savings in addition to a corresponding reduction of scrap associated with distortion free carburizing steels.

  11. A Comprehensive Numerical Study on Effects of Natural Gas Composition on the Operation of an HCCI Engine Une étude numérique complète sur les effets de la composition du gaz naturel carburant sur le réglage d’un moteur HCCI

    Jahanian O.


    Full Text Available Homogeneous Charge Compression Ignition (HCCI engine is a promising idea to reduce fuel consumption and engine emissions. Natural Gas (NG, usually referred as clean fuel, is an appropriate choice for HCCI engines due to its suitable capability of making homogenous mixture with air. However, varying composition of Natural Gas strongly affects the auto-ignition characteristics of in-cylinder mixture and the performance of the HCCI engine. This paper has focused on the influence of Natural Gas composition on engine operation in HCCI mode. Six different compositions of Natural Gas (including pure methane have been considered to study the engine performance via a thermo-kinetic zero-dimensional model. The simulation code covers the detailed chemical kinetics of Natural Gas combustion, which includes Zeldovich extended mechanism to evaluate NOx emission. Validations have been made using experimental data from other works to ensure the accuracy needed for comparison study. The equivalence ratio and the compression ratio are held constant but the engine speed and mixture initial temperature are changed for comparison study. Results show that the peak value of pressure/temperature of in-cylinder mixture is dependent of fuel Wobbe number. Furthermore, engine gross indicated power is linearly related to fuel Wobbe number. Gross indicated work, gross mean effective pressure, and NOx are the other parameters utilized to compare the performance of engine using different fuel compositions. Le moteur HCCI (Homogeneous Charge Compression Ignition, ou à allumage par compression d’une charge homogène est une idée prometteuse pour réduire la consommation de carburant et les émissions polluantes. Le gaz naturel, considéré généralement comme un carburant propre, est un choix approprié pour les moteurs HCCI en raison de sa capacité à former avec l’air un mélange homogène. Cependant, la composition du gaz naturel influe fortement sur les caract

  12. Widespread Occurrence of Zircon in Slow- and Ultraslow Spreading Ocean Crust: A Tool for Studying Ocean Lithospheric Processes

    Grimes, C. B.; John, B. E.; Cheadle, M. J.; Schwartz, J. J.


    The presence of igneous zircon in oceanic gabbro and peridotite provides a new opportunity to constrain absolute ages, and the processes and rates of crustal accretion in oceanic environments. Our recent investigations show zircon to be common in slow and ultraslow spreading oceanic crust including several locations along the Mid-Atlantic Ridge (MAR) and Southwest Indian Ridge (SWIR), and in rock types ranging from trondjhemite dikes to peridotite. Zircon is typically found in felsic intrusions and oxide gabbro, and in many cases may be due to late stage saturation in small pockets of residual melt. We report the morphologic and chemical characteristics of zircon grains collected from >100 rock samples recovered both from the seafloor by manned submersible and ROV, and with depth by ODP/IODP drilling. Grains range from euhedral and faceted to anhedral and fractured, with internal zonation that may be homogeneous, concentric, or patchy, and rarely contain relict cores. Sizes range from 1 mm. Measurements of major, minor, and trace element concentrations and high-resolution Pb/U ages were collected with the SHRIMP-RG. Chondrite-normalized rare earth element (REE) patterns for more than 50 zircon grains are uniform in shape and closely resemble patterns for known terrestrial igneous zircon. This is in contrast to mantle affinity zircon (e.g. kimberlite), which typically show depleted and relatively unfractionated patterns. Observed total REE concentrations range from 330-3765 ppm. Patterns are convex upward and rise sharply towards the HREE, with normalized Sm/La ratios = 16-320 and Lu/Gd ratios = 20-51. Positive Ce and negative Eu anomalies are ubiquitous. Hf abundances range from 5988 to 14,266 ppm. Other elements occurring at minor abundance levels include Y (463-6949 ppm), P (253-2288 ppm), U (7-2827 ppm), and Th (3-7403 ppm). Preliminary Ti concentrations range from 13 to 270 ppm, indicating crystallization temperatures of 765 to 1147°C based on Ti in zircon

  13. Carburizing of Duplex Stainless Steel (DSS) Under Compression Superplastic Deformation

    Ahamad, Nor Wahida; Jauhari, Iswadi


    A new surface carburizing technique which combines superplastic deformation with superplastic carburizing (SPC) is introduced. SPC was conducted on duplex stainless steel under compression mode at a fixed 0.5 height reduction strain rates ranging from 6.25 × 10-5 to 1 × 10-3 s-1 and temperature ranging from 1173 K to 1248 K (900 °C to 975 °C). The results are compared with those from conventional and non-superplastic carburizing. The results show that thick hard carburized layers are formed at a much faster rate compared with the other two processes. A more gradual hardness transition from the surface to the substrate is also obtained. The highest carburized layer thickness and surface hardness are attained under SPC process at 1248 K (975 °C) and 6.25 × 10-5 s-1 with a value of (218.3 ± 0.5) μm and (1581.0 ± 5.0) HV respectively. Other than that, SPC also has the highest scratch resistance.

  14. 低碳中铬钢渗碳层的耐磨粒磨损性能研究%Study on Abrasive Wear-Resistance of Carburized Low-carbon Medium-chromium Steel

    张黔; 孙小华; 李朝志


    The microstructure and abrasive wear-resistence of carburized layer of low-carbon medium-chromiun steel.compered with cemented 20 steel and Cr12Mo1V steel,was investigated.Carburized layer of 1Cr6Si2Mo steel contains large number of fine carbide(2.5~3.0 μm),which size smaller than that one of Cr12Mo1V.The wear-resistence of 1Cr6Si2Mo steel after carburizing and queching is obviously better than that of 20 steel.but less than that of Cr12Mo1V steel by vacuum heat treatment.%对低碳中铬钢(1Cr6Si2Mo)固体法稀土渗碳层的组织和耐磨性能与渗碳20钢及淬火Cr12Mo1V钢进行了对比试验研究。1Cr6Si2Mo钢的渗碳层内含有大量粒度为2.5~3.0 μm、弥散分布的铬碳化物,其尺寸比Cr12Mo1V钢中的共晶碳化物小。渗碳淬火后的1Cr6Si2Mo钢试样耐磨粒磨损性能大大优于渗碳淬火后的20钢,但不及真空热处理的Cr12Mo1V。

  15. African/Amazonian Proterozoic correlations of Iberia: A detrital zircon U-Pb study of early Cambrian conglomerates from the Sierra de la Demanda (northern Spain)

    ÁBalos, B.; Gil Ibarguchi, J. I.; SáNchez-Lorda, M. E.; Paquette, J. L.


    Unfoliated conglomerates define the base of an Early Cambrian transgressive system tract in the Sierra de la Demanda. Correlations allow us to bracket the corresponding sechron between 532 Ma and 520-521 Ma. These conglomerates contain sandstone and metamorphic quartzite pebbles carrying detrital tourmaline, rutile and zircon grains of plutonic or medium- to high-grade metamorphic derivation. Zircon detrital grains exhibit concordant or sub-concordant U/Pb ages clustered in various groups, including Neoarchean (2.52-2.56 Ga), Paleoproterozoic (1.71-2.02 Ga), and Mesoproterozoic (1.47 and ca. 1.1-1.0 Ga), the latter representative of orogenic magmatism related to Rodinia supercontinental assembly. The Neoproterozoic is represented by concordant ages in the range 750-880 Ma and by Cryogenian discordant ages. Ediacaran zircons cluster in two subsets ranging between 590 and 680 Ma and 560-585 Ma, both including several concordant ages. They reflect formation of juvenile crust in magmatic arc and back-arc basin settings. Zircon ages younger than 520-525 Ma postdate the depositional age of the conglomerate and may represent Hercynian overprinting. Bibliographic data overlooked in other provenance studies indicate that Mesoproterozoic relics as those presented here should no longer be considered of exotic origin with respect to a Gondwanan (West African) affinity of the Neoproterozoic to early Paleozoic of Iberia. The proposed source area, the "Ebro Massif" of central-north Iberia, currently is concealed under a kilometer-thick Paleozoic or younger cover. Its tectonic organization would compare to that of the North African or Amazonian cratons (including Mesoproterozoic components), rather than to the Neoproterozoic arc settings described in northwest and southwest Iberia.

  16. The Influence of Carburizing Parameters on Carbon Transfer Coefficient

    Tadeusz Sobusiak


    Definition of coefficient of carbon transfer in European Standard (EN 10052) is presented as: "Mass of carbon transferred from carburizing medium into the steel, per unit surface area per second for a unit difference between the carbon potential, and actual surface carbon content".In this paper, a model is presented of carbon transfer from endothermic atmospheres to carbon steel. The carbon transfer coefficient values were determined experimentally by the foil technique and on specimens, taking into account the following parameters: chemical composition of atmospheres, carbon potential, temperature and time of the carburizing process. Some examples of the variation of the carbon transfer coefficient for two steps of the carburizing process,including soaking before quenching, are given, based on results obtained. The effect of carbon transfer coefficient on carbon content at the steel surface is given.

  17. Investigation The Mechanical Properties of Carburized Low Carbon Steel

    Dr. Mohammed Abdulraoof Abdulrazzaq


    Full Text Available microstructure, mechanical properties; hardness and wear resistance has been investigated taken different temperatures; (850, 900, and 950 ˚C with constant time (2 hr of carburizing process. The experimental work shows that at carburizing temperature (850 ˚C, the hardness was increases from the inside to outside of specimen from ( 102 to HV 250., while increases for temperatures (900 and 950 ˚C from (105 to 272 HV, and (115 to 192 HV respectively. This experiment also been conducted for wear resistance for harder specimen which was at 950 ˚C carburized sample for three times (2, 4 and, 6 hr and the wear rate was (9.99*10-6 g/m at (2 hr, and for (4 hr it was (12.7*10-6 g/m and at (6 hr it was (15.13*10-6 g/m.

  18. Study of boron carbide evolution under neutron irradiation; Contribution a l'etude de l'evolution du carbure de bore sous irradiation neutronique

    Simeone, D. [CEA/Saclay, Dept. de Mecanique et de Technologie (DMT), 91 - Gif-sur-Yvette (France)]|[Universite Blaise Pascal, Clermont-Ferrand II, (CNRS), 63 - Aubiere (France)


    Owing to its high neutron efficiency, boron carbide (B{sub 4}C) is used as a neutron absorber in control rods of nuclear plants. Its behaviour under irradiation has been extensively studied for many years. It now seems clear that brittleness of the material induced by the {sup 10}B(n,{alpha}){sup 7}Li capture reaction is due to penny shaped helium bubbles associated to a high strain field around them. However, no model explains the behaviour of the material under neutron irradiation. In order to build such a model, this work uses different techniques: nuclear microprobe X-ray diffraction profile analysis and Raman and Nuclear Magnetic Resonance Spectroscopy to present an evolution model of B{sub 4}C under neutron irradiation. The use of nuclear reactions produced by a nuclear microprobe such as the {sup 7}Li(p,p'{gamma}){sup 7}Li reaction, allows to measure lithium profile in B{sub 4}C pellets irradiated either in Pressurised Water Reactors or in Fast Breeder Reactors. Examining such profiles enables us to describe the migration of lithium atoms out of B{sub 4}C materials under neutron irradiation. The analysis of X-ray diffraction profiles of irradiated B{sub 4}C samples allows us to quantify the concentrations of helium bubbles as well as the strain fields around such bubbles.Furthermore Raman spectroscopy studies of different B{sub 4}C samples lead us to propose that under neutron irradiation. the CBC linear chain disappears. Such a vanishing of this CBC chain. validated by NMR analysis, may explain the penny shaped of helium bubbles inside irradiated B{sub 4}C. (author)

  19. Carburization of tungsten filaments in a hot-wire chemical vapor deposition process using 1,1,3,3-tetramethyl-1,3-disilacyclobutane.

    Tong, L; Shi, Y J


    The alloying of tungsten filament when using 1,1,3,3-tetramethyl-1,3-disilacyclobutane (TMDSCB) in a hot-wire chemical vapor deposition reactor was systematically studied by scanning electron microscopy, Auger electron spectroscopy, analysis of the power consumed by the filament, and in situ mass spectrometric measurements of the gas-phase species produced in the process. Only carburization of the W filament was observed. The carburization is mainly caused by the interaction of methyl radicals with the filament. Graphite as well as both WC and W2C alloys can form on the filament surface, depending on the filament temperatures and source gas pressures. Both WC and graphite are converted to W2C with the diffusion of C into the filament. It is shown that filament carburization affects the consumption rate of the source gas and the intensities of gas-phase reaction products. Gas-phase reactions dominate at T or = 1800 degrees C.

  20. A new equilibrium form of zircon crystal

    WANG; Xiang


    [1]Hartman, P., Perdok, G., On the relationship between structure and morphology of crystals, Acta Cryst., 1955, 8: 525-529.[2]Woensdregt, C. F., Computation of surface of energies in an electrostatic point charge model, Ⅱ. Application to zircon (ZrSiO4), Phys. Chem. Minerals, 1992, 19: 417-423.[3]Kern, R., The equilibrium form of a crystal, in Morphology of Crystal (ed. Sunnagawa, I.), Tokyo: Terra Scientific Publishing Company, 1970, 77-206.[4]Machenzie, J. K., Moore, J. W., Nickolas, J. F., Bond broken at atomically flat crystal surface, I. Face-centered and body-centered cubic crystal, J. Phys. Chem. Solids, 1962, 23: 185-196.[5]?. Machenzie, J. K., Nicholas, J. F., Bond broken at atomically flat crystal surface, ?. Crystals containing many atoms in a primitive unit cell, J. Phys. Chem. Solids, 1962, 23: 197-205.[6]Hazen, R. M., Finger, L. W., Crystal structure and compressibility of zircon at high pressure, Am. Mineral, 1979, 64:196-201.[7]Pupin, J. P., Zircon and granite petrology, Contrib. Mineral Petrol., 1980, 73: 207-220.[8]Wang, X., Kienast, J. R., Morphology and geochemistry of zircon: a case study on zircon from the microgranitoid enclaves,Science in China, Series D, 1999, 42(5): 544-552.[9]Wang, X., Li, W. X., Discovery of the { 211 }-type of zircon and its petrogenetic implication, Chinese Sci. Bull., 2001 (inpress).[10]Wang, X., Quantitative description of zircon morphology and its dynamics analysis, Science in China, Series D, 1998,41(4): 422-428.

  1. MPPA-SSI12 automated module facility for "liquid" carburizing

    Syropyatov, V. Ya.


    An automated module facility of model MPPA-SSi12 for making controlled endothermic furnace atmospheres based on carbon-containing liquids is described. The facility is used for batching and feeding process liquids into carburizing shaft electric furnaces with automatic control of the carbon potential by changing the flow of added air.

  2. Provenance and Detrital-Zircon Studies of the Mint Canyon Formation and its Correlation to the Caliente Formation, Southern California

    hoyt, johanna


    The Middle Miocene Mint Canyon and Caliente formations represent sedimentation after triple-junction extension in southern California. Sandstone and conglomerate petrology, combined with detrital-zircon analysis, determines provenance of the Mint Canyon and Caliente formations. These data indicate that most detritus is locally derived, rather than being derived from the Chocolate Mountains across the San Andreas fault. The Mint Canyon and Caliente formations received Proterozoic anorthosite-s...

  3. An ion microprobe U-Th- Pb study of zircon xenocrysts from the Lahtojoki kimberlite pipe, eastern Finland

    Petri Peltonen


    Full Text Available Eleven relatively large (diameter 1–2 mm zircon grains extracted from the Lahtojoki kimberlite pipe (Eastern Finland Kimberlite Province have been analysed by the ion microprobe NORDSIM for their U- and Pb- isotopic composition. The 207Pb/206Pb ages fall into two concordant age groups: 2.7 Ga and 1.8 Ga. Discordant ages between these two groups are believed to result from partial resetting of Archaean grains in the 1.8 Ga thermal event. Since other datingmethods imply that kimberlites emplaced c. 0.6 Ga ago it is clear that the analysed zircons are xenocrysts inherited from older sources and do not provide the age of the kimberlite magmatism. Their unusual size and morphology, together with very low U- and Pb-concentrations, suggest, however, that these zircon grains are not derived from typical Archaean gneisses. More likely, they originate from lower crustal mafic pegmatites and from hydrous coarse-grained veins within the uppermost lithospheric mantle. The predominance of 1.8 Ga old xenocrystic grains, together with the recovery of mafic granulite xenoliths of similar age in the kimberlites (Hölttä et al. 2000, emphasises the importance of post-collisional lower crustal growth and reworking in central Fennoscandia.

  4. Hydrogen diffusion in Zircon

    Ingrin, Jannick; Zhang, Peipei


    Hydrogen mobility in gem quality zircon single crystals from Madagascar was investigated through H-D exchange experiments. Thin slices were annealed in a horizontal furnace flushed with a gas mixture of Ar/D2(10%) under ambient pressure between 900 ° C to 1150 ° C. FTIR analyses were performed on oriented slices before and after each annealing run. H diffusion along [100] and [010] follow the same diffusion law D = D0exp[-E /RT], with log D0 = 2.24 ± 1.57 (in m2/s) and E = 374 ± 39 kJ/mol. H diffusion along [001] follows a slightly more rapid diffusion law, with log D0 = 1.11 ± 0.22 (in m2/s) and E = 334 ± 49 kJ/mol. H diffusion in zircon has much higher activation energy and slower diffusivity than other NAMs below 1150 ° C even iron-poor garnets which are known to be among the slowest (Blanchard and Ingrin, 2004; Kurka et al. 2005). During H-D exchange zircon incorporates also deuterium. This hydration reaction involves uranium reduction as it is shown from the exchange of U5+ and U4+ characteristic bands in the near infrared region during annealing. It is the first time that a hydration reaction U5+ + OH- = U4+ + O2- + 1/2H2, is experimentally reported. The kinetics of deuterium incorporation is slightly slower than hydrogen diffusion, suggesting that the reaction is limited by hydrogen mobility. Hydrogen isotopic memory of zircon is higher than other NAMs. Zircons will be moderately retentive of H signatures at mid-crustal metamorphic temperatures. At 500 ° C, a zircon with a radius of 300 μm would retain its H isotopic signature over more than a million years. However, a zircon is unable to retain this information for geologically significant times under high-grade metamorphism unless the grain size is large enough. Refrences Blanchard, M. and Ingrin, J. (2004) Hydrogen diffusion in Dora Maira pyrope. Physics and Chemistry of Minerals, 31, 593-605. Kurka, A., Blanchard, M. and Ingrin, J. (2005) Kinetics of hydrogen extraction and deuteration in

  5. The Guarda structure (Portugal): Impact structure or not? Microstructural studies of Quartz, Zircon and Monazite

    Zalinge, M.E. van; Hamers, M.F.; Drury, M.R.


    The Guarda Structure in north-eastern Portugal has been proposed as a potential impact structure. We have studied the structure in detail, but no field or microscopic evidence has been found to support the impact hypothesis

  6. Modelling of the carburizing and quenching process applied to caterpillar track bushings

    Ferro, P.; Bonollo, F.


    The carburizing-quenching process applied to caterpillar track bushings was studied by means of experimental and numerical analyses. The numerical model was developed on the basis of the real cycle. The purpose of this work is to predict the carbon profiles, microstructural phase changes, hardness and residual stress that occur during quenching using finite element techniques. Good agreement was obtained between the experimental and numerical results in terms of carbon diffusion and hardness profiles. The Sysweld® numerical code was used to perform the simulations.

  7. The Effect of Thermo-mechanical Treatment of Substrate Preparation and Carburizing Temperature on The Morphology and Hardness of Carburizing on Low Carbon Steel

    Dadan Ramdan, Raden; Adetia, Andra; Suratman, Rochim


    Low carbon steel has a lot of applications in daily life because of its excellent properties. Among its excellent properties are good ductility, toughness, formability, and weldability. For the case of application that requires good wear resistant, carbon steel is not sufficient. For this case it is required to increase the hardness of carbon steel, such as by carburizing method. In this method one factor that affects the carburizing layer is metal substrate condition, i.e grain size. Another factor is temperature that could have significant role on the carburized layer characteristics. Therefore the present works focus in the correlation between degree of reduction of cold rolling and carburizing temperature on the carburized layer characteristic. Thermo-mechanical treatment was applied to the specimen with reduction of 0%, 30%, and 80% by mean of rolling before carburizing process. Carburizing processes were carried out at temperature of 850°C, 900°C, and 950°C. Examinations on carburized specimens were conducted by metallography and micro hardness test. The result showed that the specimen of 80% reduction giving the thickest layer and the hardest surface layer. In addition, at temperature of 900°C, the hardest layer was formed with the hardness at 1003 HV. However, the thickest layer was formed at the temperature of 950°C.

  8. Luminescence studies and infrared emission of erbium-doped calcium zirconate phosphor.

    Tiwari, Neha; Dubey, Vikas


    The near-infrared-to-visible upconversion luminescence behaviour of Er(3+)-doped CaZrO3 phosphor is discussed in this manuscript. The phosphor was prepared by a combustion synthesis technique that is suitable for less-time-taking techniques for nanophosphors. The starting materials used for sample preparation were Ca(NO3)2.4H2O, Zr(NO3)4 and Er(NO3)2, and urea was used as a fuel. The prepared sample was characterized by X-ray diffraction (XRD). The surface morphology of prepared phosphor was determined by field emission gun scanning electron microscopy (FEGSEM). The functional group analysis was determined by Fourier transform infrared (FTIR) spectroscopy. All prepared phosphors with variable Er(3+) concentrations (0.5-2.5 mol%) were studied by photoluminescence analysis. It was found that the excitation spectra of the prepared phosphor showed a sharp excitation peak centred at 980 nm. The emission spectra with variable Er(3+) concentrations showed strong peaks in the 555 nm and 567 nm range, with a dominant peak at 555 nm due to the ((2)H(11/2),(4)S(3/2)) transition and a weaker transition at 567 nm associated with 527 nm. Spectrophotometric determination of the peak was evaluated by the Commission Internationale de I'Eclairage (CIE) method These upconverted emissions were attributed to a two-photon process. The excitation wavelength dependence of the upconverted luminescence, together with its time evolution after infrared pulsed excitation, suggested that energy transfer upconversion processes were responsible for the upconversion luminescence. The upconversion mechanisms were studied in detail through laser power dependence. Excited state absorption and energy transfer processes were discussed as possible upconversion mechanisms. The cross-relaxation process in Er(3+) was also investigated.

  9. Double Glow Plasma Hydrogen-free Carburizing on Commercial Purity Titanium

    ZHANG Gaohui; PAN Junde; HE Zhiyong; ZHANG Pingze; GAO Yuan; XU Zhong


    A carburized layer with special physical and chemical properties was formed on the surface of commercial purity titanium by a double glow plasma hydrogen-free carburizing technique. High-purity netlike solid graphite was used as a raw material and commercial purity titanium was used as the substrate material. Argon gas was used as the working gas. The carburized layer can be obviously observed under a microscope. X-ray diffraction indicates that TiC phase with higher hardness and dissociate state carbon phase was formed in the carburized layer. The glow discharge spectrum (GDS) analysis shows that the carbon concentration distributes gradiently along the depth of carburized layer. The surface hardness of the substrate increases obviously. The hardness distributes gradiently from the surface to inner of carburized layer. The friction coefficient reduces by more than 1/2, the ratio wear rate decreases by above three orders of magnitude. The wear resistance of the substrate material is improved consumedly.

  10. Natural radioactivity and radon specific exhalation rate of zircon sands

    Righi, S.; Verita, S.; Bruzzi, L. [Bologna Univ., Centro Interdipartimentale di Ricerca per le Scienze Ambientali and Dipt. di Fisica, Ravenna (Italy); Albertazzi, A. [Italian Ceramic Center, Bologna (Italy)


    The study focuses on the radon emanation from zircon sands and their derivatives, which are widely used in many sectors of industry. In particular, the results obtained by experimental measurements on samples of zircon sands and zircon flours commonly used in Italian ceramic industries are reported. Zircon sands contain a significant concentration of natural radioactivity because Th and U may substitute zirconium in the zircon crystal lattice. The relevant routes of exposure of workers to T.E.N.O.R.M. from zircon materials are external radiation and internal exposure, either by inhalation of aerosols in dusty working conditions or by inhalation of radon in workplaces. The main objective of this investigation is to provide experimental data able to better calculate the internal exposure of workers due to radon inhalation. Zircon samples were surveyed for natural radioactivity, radon specific exhalation rate and emanation fraction. Measurements of radioactivity concentration were carried out using {gamma}-spectrometry. Methods used for determining radon consisted in determining the {sup 222}Rn activity accumulated in a vessel after a given accumulation build-up time. The average activity concentrations of {sup 238}U and {sup 232}Th in samples result about 2600 and 550 Bq kg-1, respectively; these concentrations are significantly higher than the world average noticed in soils, rocks and Earth crust. The {sup 222}Rn specific exhalation rates result very low probably due to the low porosity of the material and the consequent difficulty for radon to be released from the zircon crystal lattice. (author)

  11. Tribotechnical and Energy Assessment of Parts of Working Members of Cultivating Machines After Carburizing and Laser Hardening

    Pyndak, V. I.; Novikov, A. E.


    Results of experimental studies of low-carbon steel 20 and high-carbon steels of types 70 and 65G after carburizing, heat treatment and laser hardening are presented. The variation of the microhardness of the surface layers of the steels and of their wear resistance due to different variants of hardening is determined. Optimum modes of treatment aimed at raising the strength and wear resistance are suggested for the steels used for working members of cultivating machines.

  12. Extinct 244Pu in Ancient Zircons

    Turner, Grenville; Harrison, T. Mark; Holland, Greg; Mojzsis, Stephen J.; Gilmour, Jamie


    We have found evidence, in the form of fissiogenic xenon isotopes, for in situ decay of 244Pu in individual 4.1- to 4.2-billion-year-old zircons from the Jack Hills region of Western Australia. Because of its short half-life, 82 million years, 244Pu was extinct within 600 million years of Earth's formation. Detrital zircons are the only known relics to have survived from this period, and a study of their Pu geochemistry will allow us to date ancient metamorphic events and determine the terrestrial Pu/U ratio for comparison with the solar ratio.

  13. Graphene Growth via Carburization of Stainless Steel and Application in Energy Storage


    1697© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlinelibrary.comsmall 2011, 7, No. 12, 1697–1700 1. Introduction Carburization is order to achieve few-layers-thick graphene on stainless steel (SS) substrates. Though the carburization process is similar to the chemi cal...vapor deposition (CVD) tech- nique, which is generally used for growth of graphene on Graphene Growth via Carburization of Stainless Steel and

  14. Hydrogen uptake during Carburizing and Effusion of Hydrogen at Room Temperature and during Tempering

    Khodahami, Maryam


    The carburizing atmosphere during the case hardening process contains a large proportion of hydrogen. Due to the rapid diffusion of hydrogen a high amount of hydrogen can be absorbed by the carburizing component. The amount of absorbed hydrogen is dependent on some factors such as for example the carburizing time and component dimensions. Hydrogen diffused in material can then cause hydrogen embrittlement and in some cases cause cracking under a static load. This hydrogen must therefore be re...

  15. Precise gas carburizing quenching process of 18 Cr2 Ni4 WA steel bushes%18Cr2Ni4WA钢衬套的精密气体渗碳淬火热处理

    李锋; 王新宇; 李世键; 韩培培; 于浩


    The influence of precise gas carburizing and isothermal quenching process on carburized layer hardness , depth and the microstructure of 18Cr2Ni4WA steel was studied .The results show that the carburized layer depth increases with the increasing of the total holding time, but the hardness profile becomes flat gradually .The longer of strong carburizing time , the deeper of carburized depth with the same total holding time .The longer of strong carburizing time , the lower of surface hardness with the same diffusion carburizing time .The optimized precise heat treatment process consists of holding temperature at 910 ℃, by carbon potential of strong carburizing stage at 1.20%and holding for 3 h, and then by carbon potential of diffusion stage at 0.80%and holding for 1 h,and then isothermally quenched in nitrate bath.With this optimized process , the typical carburized depth of (1.2 ±0.1) mm with favorable microstructure distribution is obtained . The process has been successfully applied in bushes production with satisfactory requirement of carburized depth , hardness profile and microstructure .%研究了精密气体渗碳等温淬火工艺对18Cr2Ni4WA钢渗层硬度、深度及显微组织的影响。结果表明,随着总渗碳保温时间的延长,渗层深度增加,但硬度曲线变得平缓;在相同总保温时间的情况下,强渗时间越长,渗层越深;而当扩散时间相同时,强渗时间越长,淬火后表层的硬度较低。优化的精密气体渗碳工艺为:保温温度均为910℃,强渗阶段碳势1.20%,保温3 h;扩散阶段碳势0.80%,保温1 h,渗碳后进行等温淬火,可以获得(1.2±0.1) mm渗层深度。渗碳淬火后渗层组织良好。该工艺成功应用于衬套零件的实际生产,满足了设计要求。

  16. Low Temperature Surface Carburization of Stainless Steels

    Collins, Sunniva R; Heuer, Arthur H; Sikka, Vinod K


    Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys

  17. Hard Chromium Electroplating and Improvement the Properties by the Thermo Chemical Treatments (Solid Carburizing of Low Carbon Steel

    Ahmed Salloum Abbas


    Full Text Available In this research the hard chromium electroplating process, which is one of the common methods of overlay coating was used, by using chromium acid as source of chromium and sulphuric acid as catalyst since the ratio between chromic acid and sulphuric acid is (100 : 1 consequently. Plating process was made by applying current of density (40 Amp / dm2 and the range of solution temperature was (50 – 55oC with different time periods (1-5 hr. A low carbon steel type (Ck15 was used as substrate for hard chromium electroplating. Solid carburization was carried out for hard chromium plating specimen at temperature (925oC with time duration (2 hr to be followed with quenching and tempering. The phase analysis was conducted by using X– ray diffraction. The examination results show that the chromium carbides in plating layer were (Cr23C6, Cr7C3. The microhardness of hard chromium plating specimen was measured, and the results show that the high hardness was about (907HV. After solid carburization the hardness values increase and the results show that the higher hardness for chromium plating layer on low carbon steel surface was (1276 HV. Wear apparatus type (Pin on Disc was used to study dry sliding wear properties of low carbon steel (As received and hard chromium plating specimens and solid carburized. The effect of applied normal load on wear rate was studied with weighting method using five normal loads (5, 10, 15, 20, 25 N at constant sliding speed (2.198 m / sec. The results reveal that the wear rate increases with the increasing of applied normal load. A good improvement in wear resistance was noticed for hard chromium plating specimens as compared with substrate specimen. It was also seen that, the improvement in wear resistance was (94% as compared with substrate metal when carburizing treatment is carried out on hard chromium plating specimens.

  18. Nomograms to Determine the Controlling Factors in Vacuum-Carburizing Regimes

    Semenov, M. Yu.


    A method based on computer evaluation of mechanical properties and a mathematical model of vacuum carburizing are used for creating two nomograms, i.e., ( 1 ) for determining the parameters that the carburized layers of gears of steel 16Kh3NVFMB-Sh must have to obtain the required service properties and ( 2 ) for determining the values that the factors in periodic carburizing regimes must have to ensure that the layers have the prescribed parameters. The nomograms are used to determine the factors for two gears that are to undergo vacuum carburizing.


    S. P. Rudenko


    Full Text Available Results of studies of the kinetics of changes in actual grains during technological process at different stages of the manufacture of parts with the use of a universal metallographic etchant to identify borders of valid grains in rolling and stamping in carburizing layers and core parts made of alloy structure steel grades are presented.

  20. Formation history and protolith characteristics of granulite facies metamorphic rock in Central Cathaysia deduced from U-Pb and Lu-Hf isotopic studies of single zircon grains

    YU Jinhai; ZHOU Xinmin; Y. S. O'Reilly; ZHAO Lei; W. L. Griffin; WANG Rucheng; WANG Lijuan; CHEN Xiaomin


    The petrochemical as well as zircon U-Pb and Lu-Hf isotopic studies of granulite facies metamorphic rock from the Taoxi Group in eastern Nanling Range, Central Cathaysia indicate that its protolith is the sedimentary rock with low maturation index. The clastic materials are mostly from middle Neoproterozoic (~736 Ma) granitoid rocks with minor Neoarchaean and Paleoproterozoic rocks. The timing of this Neoproterozoic magmatism is in agreement with the second period of magmatism widespread surrounding the Yangtze Block. Hf isotopic data indicate that the Neoproterozoic granitoids resulted from the recycled Paleoproterozoic mantle-derived crustal materials. The sedimentary rock was deposited in Late Neoproterozoic Era, and carried into low crust in Early Paleozoic. The partial melting of the meta-sedimentary rock took place at about 480 Ma and subsequently granulite facies metamorphism occurred at ca. 443 Ma. The zircons forming during this time interval (Early Paleozoic) show large Hf isotope variations, and their -Hf(t) values increase from -13.2 to +2.36 with decreasing age, suggesting the injection of mantle-derived materials during partial melting and metamorphism processes in the Early Paleozoic. Calculation results show that this metamorphic rock, if evolved to Mesozoic, has similar isotopic composition to the nearby Mesozoic high Si peraluminous granites, implying that this kind of granulite facies metamorphic rock is probably the source material of some Mesozoic peraluminous granitoids in eastern Nanling Range.

  1. Enhanced wear and fatigue properties of Ti-6Al-4V alloy modified by plasma carburizing/CrN coating.

    Park, Y G; Wey, M Y; Hong, S I


    In this study, a newly developed duplex coating method incorporating plasma carburization and CrN coating was applied to Ti-6Al-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150 microm in depth and CrN coating film with 7.5 microm in thickness were formed after duplex coating. Hard carbide particles such as TiC And V(4)C(3) were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to about 1,960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex-coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex-coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.

  2. Evaluation of Important Factors Affecting Quench Distortion of Carburized Hypoid Gear with Shaft by Using Computer Simulation Methods

    Tsuyoshi Sugimoto; Youichi Watanabe


    To minimize quenching distortion and dispersion, carburizing and quenching process conditions must be optimized; this includes the parts racking design used for quenching. We investigated some factors affecting carburized quenching distortion with an experiment using a hypoid gear having a shaft and with numerical simulation methods. The experimental results and those obtained from simulation were generally in agreement. Focusing on the surface temperature distribution in the gear, we studied quenching distortion characteristics in terms of changes in tooth profile and helix deviation. In our experiments, distortions occur during quenching in 373 K oil after austenitized temperature treatments conducted with various attitudes. We calculated the distortions by simulating the carburized oil-quenching process for the hypoid gear. Our results show large differences between the cooling rates of the tooth toe, middle section, and heel edges,and these greatly influence the change in tooth profile and helix deviation. We found that reducing the differences in temperatures on the gear surfaces during quenching is most important for minimizing the quench distortion of the hypoid gear.

  3. Formation of nanocrystalline layers by surface severe plastic deformation and pulsed plasma electrolytic carburizing.

    Aliofkhazraei, M; Rouhaghdam, A Sabour


    Surfaces of various kinds of metallic materials spheres were treated by nanocrystalline surface severe plastic deformation and then pulsed nanocrystalline plasma electrolytic carburizing to study nanocrystalline substrate effect on formation and nano-hardness of hard nanocrystalline layer. The surface layers of the metallic materials developed by the nanocrystalline surface severe plastic deformation were characterized by means of high resolution scanning electron microscope. Nearly equiaxed nanocrystals with grain sizes ranging from 15 to 90 nm were observed in the near surface regions of all metallic materials, which are low carbon steel and commercially pure titanium. The effect of substrate nanocrystallization on growth kinetics and hardness of formed nanocrystalline carbide layer was studied with the means of figure analysis and nanohardness tests. Figure analysis show the length to diameter ratio and distribution curve of nanocrystals and it has been found that the achieved properties of hard layer (growth rate, nano-hardness, nanostructure...) are related to these factors. It was also clarified that these techniques and surface nanocrystallization can be easily achieved in most of metallic materials. Results indicate that the resultant hardened carburized layers exhibited excellent hardness profile. Investigation of the layer characteristics showed strong dependence followed from the treatment experimental parameters as well as the shape of nanocrystals.

  4. Analysis of Hardened Depth Variability, Process Potential, and Measurement Error in Case Carburized Components

    Rowan, Olga K.; Keil, Gary D.; Clements, Tom E.


    Hardened depth (effective case depth) measurement is one of the most commonly used methods for carburizing performance evaluation. Variation in direct hardened depth measurements is routinely assumed to represent the heat treat process variation without properly correcting for the large uncertainty frequently observed in industrial laboratory measurements. These measurement uncertainties may also invalidate application of statistical control requirements on hardened depth. Gage R&R studies were conducted at three different laboratories on shallow and deep case carburized components. The primary objectives were to understand the magnitude of the measurement uncertainty and heat treat process variability, and to evaluate practical applicability of statistical control methods to metallurgical quality assessment. It was found that ~75% of the overall hardened depth variation is attributed to the measurement error resulting from the accuracy limitation of microhardness equipment and the linear interpolation technique. The measurement error was found to be proportional to the hardened depth magnitude and may reach ~0.2 mm uncertainty at 1.3 mm nominal depth and ~0.8 mm uncertainty at 3.2mm depth. A case study was discussed to explain a methodology for analyzing a large body of hardened depth information, determination of the measurement error, and calculation of the true heat treat process variation.

  5. Paraequilibrium Carburization of Duplex and Ferritic Stainless Steels

    Michal, G. M.; Gu, X.; Jennings, W. D.; Kahn, H.; Ernst, F.; Heuer, A. H.


    AISI 301 and E-BRITE stainless steels were subjected to low-temperature (743 K) carburization experiments using a commercial technology developed for carburization of 316 austenitic stainless steels. The AISI 301 steel contained ~40 vol pct ferrite before carburization but had a fully austenitic hardened case, ~20- μm thick, and a surface carbon concentration of ~8 at. pct after treatment; this “colossal” paraequilibrium carbon supersaturation caused an increase in lattice parameter of ~3 pct. The E-BRITE also developed a hardened case, 12- to 18- μm thick, but underwent a more modest (~0.3 pct) increase in lattice parameter; the surface carbon concentration was ~10 at. pct. While the hardened case on the AISI 301 stainless steel appeared to be single-phase austenite, evidence for carbide formation was apparent in X-ray diffractometer (XRD) scans of the E-BRITE. Paraequilibrium phase diagrams were calculated for both AISI 301 and E-BRITE stainless steels using a CALPHAD compound energy-based interstitial solid solution model. In the low-temperature regime of interest, and based upon measured paraequilibrium carbon solubilities, more negative Cr-carbon interaction parameters for austenite than those in the current CALPHAD data base may be appropriate. A sensitivity analysis involving Cr-carbon interaction parameters for ferrite found a strong dependence of carbon solubility on relatively small changes in the magnitude of these parameters.

  6. Advances and directions of ion nitriding/carburizing

    Spalvins, Talivaldis


    Ion nitriding and carburizing are plasma activated thermodynamic processes for the production of case hardened surface layers not only for ferrous materials, but also for an increasing number of nonferrous metals. When the treatment variables are properly controlled, the use of nitrogenous or carbonaceous glow discharge medium offers great flexibility in tailoring surface/near-surface properties independently of the bulk properties. The ion nitriding process has reached a high level of maturity and has gained wide industrial acceptance, while the more recently introduced ion carburizing process is rapidly gaining industrial acceptance. The current status of plasma mass transfer mechanisms into the surface regarding the formation of compound and diffusion layers in ion nitriding and carbon build-up ion carburizing is reviewed. In addition, the recent developments in design and construction of advanced equipment for obtaining optimized and controlled case/core properties is summarized. Also, new developments and trends such as duplex plasma treatments and alternatives to dc diode nitriding are highlighted.

  7. Genesis of zircon and its constraints on interpretation of U-Pb age

    WU Yuanbao; ZHENG Yongfei


    Zircon U-Pb dating is the most commonly used method for isotopic geochronology. However, it has been a difficult issue when relating zircon U-Pb ages to metamorphic conditions in complex metamorphic rocks. Much progress has been made in the past decade with respect to the genesis of zircon and its constraints on interpretation of U-Pb age. Three methods have been proposed to link zircon U-Ph age to metamorphic conditions: ( I ) internal structure; (ii)trace element feature; (iii) mineral inclusion composition.Magmatic zircon shows typical oscillatory zoning and/or sector zoning, whereas metamorphic zircon has internal structures such as no zoned, weakly zoned, cloudy zoned,sector zoned, planar zoned, and patched zoned ones. Zircons formed in different geological environments generally have characteristic internal structures. Magmatic zircons from different rock types have variable trace element abundances,with a general trend of increasing trace element abundances in zircons from ultramafic through mafic to granitic rocks.Zircons formed under different metamorphic conditions have different trace element characteristics that can be used to relate their formation to metamorphic conditions. It is an effective way to relate zircon growth to certain P-T conditions by studying the trace element partitioning between coexisting metamorphic zircon and garnet in high-grade metamorphic rocks containing both zircon and garnet. Primary mineral inclusions in zircon can also provide unambiguous constraints on its formation conditions. Therefore,interpretation of zircon U-Pb ages can be constrained by its internal structure, trace element composition, mineral inclusion and so on.

  8. U-Pb geochronology of zircon and polygenetic titanite from the Glastonbury Complex, Connecticut, USA: An integrated SEM, EMPA, TIMS, and SHRIMP study

    Aleinikoff, J.N.; Wintsch, R.P.; Fanning, C.M.; Dorais, M.J.


    -Pb data from titanite indicate multiple growth episodes. In brown grains, oscillatory zoned cores formed at 443 ?? 6 Ma, whereas white (in BSE) cross-cutting zones are 425 ?? 9 Ma. Colorless grains and overgrowths on brown grains yield an age of 265 ?? 8 Ma (using the Total Pb method) or 265 ?? 5 Ma (using the weighted average of the 206Pb/238U ages). However, EMPA chemical data identify zoning that suggests that this colorless titanite may preserve three growth events. Oscillatory zoned portions of brown titanite grains are igneous in origin; white cross-cutting zones probably formed during a previously unrecognized event that caused partial dissolution of earlier titanite and reprecipitation of a slightly younger generation of brown titanite. Colorless titanite replaced and grew over the magmatic titanite during the Permian Alleghanian orogeny. These isotopic data indicate that titanite, like zircon, can contain multiple age components. Coupling SHRIMP microanalysis with EMPA and SEM results on dated zones as presented in this study is an efficient and effective technique to extract additional chronologic ?? 2002 Elsevier Science B.V. All rights reserved.

  9. Development of a carburizing and quenching simulation tool: numerical simulations of rings and gears

    Anderson, C.; Godlman, P.; Rangaswamy, P. [and others


    The ability to accurately calculate temperatures, stresses and metallurgical transformations in a single calculation or in a sequence of calculations is the key to prediction of distortion, residual stress and phase distribution in quench hardened automotive parts. Successful predictions in turn rely on the adequacy of the input data to the calculational procedure. These data include mechanical and thermal properties of the alloy phases over the range of temperature and strain rates experienced during the heat treat process, the mathematical description of the transformation kinetics, and the accuracy of the heat transfer boundary conditions. In this presentation we describe a calculational procedure using the ABAQUS{sup (1)} finite element code that simulates a carburizing and quench heat treat cycle for automotive gears. The calculational procedure features a numerically efficient 2-phase constitutive model, developed as part of the NCMS-Heat Treatment Distortion Prediction program, to represent transformational plasticity effects for the austenite/martensite Deformation together with refined finite element meshes to capture the steep gradients in stress and composition near the gear surfaces. The calculational procedure is illustrated on carburizing and quenching of a thick ring and comparison of model predictions for distortion, phase distribution, and residual stress with experimental measurements are discussed. Included in this model study is an investigation of the sensitivity of the predictions to mesh refinement.

  10. Low Temperature Surface Carburization of Stainless Steels

    Collins, Sunniva R; Heuer, Arthur H; Sikka, Vinod K


    Low-temperature colossal supersaturation (LTCSS) is a novel surface hardening method for carburization of austenitic stainless steels (SS) without the precipitation of carbides. The formation of carbides is kinetically suppressed, enabling extremely high or colossal carbon supersaturation. As a result, surface carbon concentrations in excess of 12 at. % are routinely achieved. This treatment increases the surface hardness by a factor of four to five, improving resistance to wear, corrosion, and fatigue, with significant retained ductility. LTCSS is a diffusional surface hardening process that provides a uniform and conformal hardened gradient surface with no risk of delamination or peeling. The treatment retains the austenitic phase and is completely non-magnetic. In addition, because parts are treated at low temperature, they do not distort or change dimensions. During this treatment, carbon diffusion proceeds into the metal at temperatures that constrain substitutional diffusion or mobility between the metal alloy elements. Though immobilized and unable to assemble to form carbides, chromium and similar alloying elements nonetheless draw enormous amounts of carbon into their interstitial spaces. The carbon in the interstitial spaces of the alloy crystals makes the surface harder than ever achieved before by more conventional heat treating or diffusion process. The carbon solid solution manifests a Vickers hardness often exceeding 1000 HV (equivalent to 70 HRC). This project objective was to extend the LTCSS treatment to other austenitic alloys, and to quantify improvements in fatigue, corrosion, and wear resistance. Highlights from the research include the following: • Extension of the applicability of the LTCSS process to a broad range of austenitic and duplex grades of steels • Demonstration of LTCSS ability for a variety of different component shapes and sizes • Detailed microstructural characterization of LTCSS-treated samples of 316L and other alloys

  11. In situ neutron diffraction studies of a commercial, soft lead zirconate titanate ceramic: response to electric fields and mechanical stress

    Pramanick, Abhijit; Prewitt, Anderson D.; Cottrell, Michelle A.; Lee, Wayne; Studer, Andrew J.; An, Ke; Hubbard, Camden R.; Jones, Jacob L.


    Structural changes in commercial lead zirconate titanate (PZT) ceramics (EC-65) under the application of electric fields and mechanical stress were measured using neutron diffraction instruments at the Australian Nuclear Science and Technology Organisation (ANSTO) and the Oak Ridge National Laboratory (ORNL). The structural changes during electric-field application were measured on the WOMBAT beamline at ANSTO and include non-180° domain switching, lattice strains and field-induced phase transformations. Using time-resolved data acquisition capabilities, lattice strains were measured under cyclic electric fields at times as short as 30 μs. Structural changes including the (002) and (200) lattice strains and non-180° domain switching were measured during uniaxial mechanical compression on the NRSF2 instrument at ORNL. Contraction of the crystallographic polarization axis, (002), and reorientation of non-180° domains occur at lowest stresses, followed by (200) elastic strains at higher stresses.

  12. High temperature carburizing of a stainless steel with uranium carbide

    Sar Latin-Small-Letter-Dotless-I kaya, Yueksel, E-mail: [Ankara University, Faculty of Science, Department of Chemistry, Tandogan, 06100 Ankara (Turkey); Oenal, Mueserref [Ankara University, Faculty of Science, Department of Chemistry, Tandogan, 06100 Ankara (Turkey)


    Graphical abstract: Temperature dependence of diffusion coefficient for carbon atoms in steel by carburizing with uranium carbide was found as: D = 2.6 Multiplication-Sign 10{sup -11} exp (-66753/RT) in m{sup 2} s{sup -1} microhardness measurements. Changes in thermodynamic quantities by formation of an activated complex with temperature were obtained as follows: {Delta}H{sup numbersign} = 66741-8.3T J mol{sup -1}, {Delta}C{sub p}{sup numbersign} = 8.3 J K{sup -1} mol{sup -1}, ln K{sup numbersign} = -66741/RT = (8.3/R)lnT-48.3, {Delta}G{sup numbersign} = 66741 + 8.3T lnT + 48.3RT J mol{sup -1}, and {Delta}S{sup numbersign} = -409.9-8.3 lnT in J K{sup -1} mol{sup -1}. Highlights: Black-Right-Pointing-Pointer Diffusion and activated complex theories were applied on the carburizing of steel. Black-Right-Pointing-Pointer Carburizing of steel was investigated by microhardness measurements. Black-Right-Pointing-Pointer Diffusion coefficient of carbon in the steel was determined. Black-Right-Pointing-Pointer Thermodynamic quantities by formation an activated complex were determined. - Abstract: Diffusion theory (DT) and activated complex theory (ACT) were applied to the carburizing process of austenitic stainless steel 1.4988 with uranium carbide by sodium bonding at 773, 873, 973 and 1073 K for 1000 h. Microhardness profiles of the carburized steel specimens were obtained. Diffusion coefficient (D) of carbon atoms into the steel were calculated for each temperature by using the microhardness values instead of the carbon concentrations in the approximate solution of the second Fick's equation. Arrhenius equation for the carburizing process was found as: D = 2.6 Multiplication-Sign 10{sup -11} exp (-66753/RT) in m{sup 2} s{sup -1}. Equilibrium constant (K{sup numbersign}) and enthalpy of activation ({Delta}H{sup numbersign}) for the formation of an activated complex calculated for each temperature from the Eyring equation using the diffusion coefficient instead of the

  13. Acetylene Flow Rate as a Crucial Parameter of Vacuum Carburizing Process of Modern Tool Steels

    Rokicki P.


    Full Text Available Carburizing is one of the most popular and wide used thermo-chemical treatment methods of surface modification of tool steels. It is a process based on carbon diffusive enrichment of the surface material and is applied for elements that are supposed to present higher hardness and wear resistance sustaining core ductility. Typical elements submitted to carburizing process are gears, shafts, pins and bearing elements. In the last years, more and more popular, especially in highly advanced treatment procedures used in the aerospace industry is vacuum carburizing. It is a process based on chemical treatment of the surface in lower pressure, providing much higher uniformity of carburized layer, lower process cost and much lesser negative impact on environment to compare with conventional carburizing methods, as for example gas carburizing in Endo atmosphere. Unfortunately, aerospace industry requires much more detailed description of the phenomena linked to this process method and the literature background shows lack of tests that could confirm fulfilment of all needed requirements and to understand the process itself in much deeper meaning. In the presented paper, authors focused their research on acetylene flow impact on carburized layer characteristic. This is one of the most crucial parameters concerning homogeneity and uniformity of carburized layer properties. That is why, specific process methodology have been planned based on different acetylene flow values, and the surface layer of the steel gears have been investigated in meaning to impact on any possible change in potential properties of the final product.

  14. Cast aluminum alloys containing dispersions of zircon particles

    Banerji, A.; Surappa, M. K.; Rohatgi, P. K.


    A process for preparing Al-alloy castings containing dispersions of zircon particles is described. Composites were prepared by stirring zircon particles (40 to 200 µm size) in commercially pure Al (99.5 pct)* and Al-11.8 pct Si melts and subsequently casting these melts in permanent molds. It was found to be necessary to alloy the above two melts with 3 pct Mg to disperse substantial amounts of zircon particles (25 to 30 pct). Further, it was possible to disperse up to 60 wt pct zircon by adding up to 5 pct Mg; however, the melts containing above 30 wt pct zircon showed insufficient fluidity for gravity diecasting and had to be pressure diecast. Microstructural studies of cast composites indicated the presence of a reaction zone at the periphery of zircon particles, and electron probe microanalysis showed concentrations of Mg and Si at the particle-matrix interface. Hardness, abrasive wear resistance, elastic modulus, 0.2 pct proof stress, and tensile strength of cast Al-3 pct Mg alloy were found to improve with the dispersions of zircon particles. Scanning electron micrographs of abraded and fractured surfaces did not show any evidence of particle pull-outs or voids at the particle matrix interface, indicating strong continuous bonding.

  15. 渗碳温度对22Si2MnCrNi2MoA钢渗碳层的影响%Influence of carburizing temperature on microstructure and properties of carburized layers of a 22Si2MnCrNi2MoA steel

    黄斌; 朱洪武; 杨忠; 周乐育; 刘雅政


    Influence of carburizing temperature on carburized layers of a 22Si2MnCrNi2MoA steel solid-carburized was studied by OM,SEM,XRD and hardness measurements.The relationship between carburizing temperature and carbon concentration,micro-hardness and retained austenite of the carburized layers were examined.The results indicate that with the carburizing temperature increasing for carburizing time of 6 h,the carbon concentration of the carburized layers gradually increases,and the distribution gradient of the carbon concentration gets smoother.The relationship between the micro-hardness of the carburized layers and carbon concentration obeys normal distribution.It is recommended that the surface carbon concentration of the carburized steel should be controlled in the range of 0.80% and 0.90% in order to obtain martensite microstructure with high hardness.When the surface carbon concentration is more than 0.80%-0.90%,aging treatment for a long time or deep cryogenic treatment are required to remove retained austenite in the carburized layers.%通过固体渗碳试验研究了加热温度对钎具用钢22Si2MnCrNi2MoA渗碳层的影响,分析了渗碳温度-碳浓度-显微硬度-残留奥氏体的关系以及残留奥氏体的控制措施.结果表明:当渗碳时间为6h时,随着渗碳温度的升高,渗碳层的碳浓度逐渐增加,碳浓度分布梯度越来越平缓.22Si2MnCrNi2MoA钢渗碳层的显微硬度-碳浓度关系符合正态分布.在渗碳处理过程中,为了使渗碳表层获得硬度很高的马氏体组织,22Si2MnCrNi2MoA钢渗碳层表面碳浓度应该控制在0.80% ~0.90%之间.当表面碳浓度超过0.80%~0.90%时,渗碳完成后需采取后续的工艺措施来消除已经存在的残留奥氏体,如采用长时间自然时效或深冷处理等.

  16. Sliding wear behaviour of steel carburized using Na2CO3-NaCl

    Liew Willey Y. H.


    Full Text Available Experiments have been carried out to investigate the effect of carburization process on the sliding wear resistance of mild steel. The carburization process was conducted in carbonate salts mixtures of Na2CO3-NaCl. Carburization followed by water quenching resulted in the formation of martensite with a hardness of 900 HV in the subsurface, up to the depth of 400 μm. This hardness value was substantially higher than the non-carburized steel which had a hardness of 520 HV. In the initial stage of sliding in air, abrasive wear and cluster of fine cavities due to adhesion were formed. This was followed by the formation of large-scale fracture at the cavities. The high hardness of the carburized steel reduced the severity of adhesive wear and thus the tendency of the worn surface to fracture.

  17. In Situ Observation for Abnormal Grain Coarsening in Vacuum-Carburizing Process

    Yogo, Yasuhiro; Tanaka, Kouji


    An in situ observation method was developed to investigate abnormal grain coarsening which occurs around the surface of steel during the vacuum-carburizing process. In this method, diffusion of carbon atoms in the vacuum carburizing was simulated by a cementite and steel diffusion couple. Abnormal grain coarsening, which appeared around the cementite and steel interface, was observed by a confocal scanning laser microscope. With this method, it was observed that when holding time was 60 seconds, the temperature at which the abnormal grain coarsening appeared in a specimen was higher when carburized than the temperature when not carburized. On the contrary, when holding time was 120 seconds, the temperature at which the abnormal grain coarsening appeared in a specimen was 10 K to 20 K lower than that in a non-carburized specimen. The validity of the observed results was confirmed by the calculated NbC fraction using Nb solubility and measured carbon content.

  18. Effect of carburization on electrochemical corrosion behaviours of TiAl alloy

    Liao, Cuijiao [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Hunan University of Technology, Zhuzhou, Hunan 412000 (China); He, Yuehui, E-mail: [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Yang, Junsheng; Nan, Bo; Liu, Xinli [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China)


    Highlights: ► The functional complex ceramic phase Ti{sub 2}AlC was formed by pack carburizing. ► The anodic polarization curve of the carburized TiAl alloy shows a larger passivation interval (about 1.246 V). ► The polarization resistance of the carburized TiAl alloy is at least seventeen times higher, compared to the untreated TiAl alloy. ► The corroded surface of the carburized TiAl alloy was covered with passive film. -- Abstract: Electrochemical corrosion behaviours of the untreated and the carburized of Ti-46.5Al (mol %) alloy were investigated. X-ray diffractometry (XRD) and scanning electron microscopy (SEM) were applied to characterize the carburized layer. Potentiodynamic polarization curve, electrochemical impedance spectroscopy (EIS) and SEM morphology of the corroded surface were used to evaluate corrosion resistance of both carburized and untreated TiAl alloy in 1 mol/L HCl. The outer layer of the carburized TiAl alloy is a continuous Ti{sub 2}AlC scale. Polarization curve and electrochemical impedance spectroscopy (EIS) of the carburized TiAl alloy present a nobler corrosion potential, a more positive pitting potential and a higher polarization resistance, respectively, compared with the untreated sample. After anodic corrosion or immersion corrosion, a deposited layer can be observed on the surface of the carburized titanium aluminide alloy. By contrast, pitting and crevasse corrosion occur on the surface of the untreated TiAl alloy after anodic corrosion and some corrosion products and slight corrosion appear on the surface of the untreated TiAl alloy after immersion corrosion.

  19. An in situ zircon Hf isotopic,U-Pb age and trace element study of banded granulite xenolith from Hannuoba basalt:Tracking the early evolution of the lower crust in the North China craton

    ZHENG Jianping; LU Fengxiang; YU Chunmei; TANG Huayun


    Backscattered electron images, in situ Hf isotopes, U-Pb ages and trace elements of zircons in a banded granulite xenolith from Hannuoba basalt have been studied. The results show that the banded granulite is a sample derived from the early lower crust of the North China craton. It is difficult to explain the petrogenesis of the xenolith with a single process. Abundant information on several processes, however, is contained in the granulite. These processes include the addition of mantle material, crustal remelting, metamorphic differentiation and the delamination of early lower crust. About 80% of zircons studied yield ages of 1842±40 Ma, except few ages of 3097-2824 Ma and 2489-2447 Ma. The zircons with ages older than 2447 Ma have high εHf (up to +18.3) and high Hf model age (2.5-2.6 Ga), indicating that the primitive materials of the granulite were derived mainly from a depleted mantle source in late Archean. Most εHf of the zircons with early Proterozoic U-Pb age vary around zero, but two have high εHf up to +9.2-+10.2, indicating mantle contribution during the collision and assembly between the Eastern and Western blocks in the early Proterozoic that resulted in the amalgamation of the North China craton.

  20. Nanostructural Evolution of Hard Turning Layers in Carburized Steel

    Bedekar, Vikram

    The mechanisms of failure for components subjected to contact fatigue are sensitive to the structure and properties of the material surface. Although, the bulk material properties are determined by the steel making, forming and the heat treatment; the near surface material properties are altered during final material removal processes such as hard turning or grinding. Therefore, the ability to optimize, modulate and predict the near surface properties during final metal removal operations would be extremely useful in the enhancement of service life of a component. Hard machining is known to induce severely deformed layers causing dramatic microstructural transformations. These transformations occur via grain refinement or thermal phenomena depending upon cutting conditions. The aim of this work is to engineer the near surface nanoscale structure and properties during hard turning by altering strain, strain rate, temperature and incoming microstructure. The near surface material transformations due to hard turning were studied on carburized SAE 8620 bearing steel. Variations in parent material microstructures were introduced by altering the retained austenite content. The strain, strain rate and temperature achieved during final metal cutting were altered by varying insert geometry, insert wear and cutting speed. The subsurface evolution was quantified by a series of advanced characterization techniques such as transmission electron microscopy (TEM), glancing angle X-ray diffraction (GAXRD), X-ray stress evaluation and nanoindentation which were coupled with numerical modeling. Results showed that the grain size of the nanocrystalline near surface microstructure can be effectively controlled by altering the insert geometry, insert wear, cutting speed and the incoming microstructure. It was also evident that the near surface retained austenite decreased at lower cutting speed indicating transformation due to plastic deformation, while it increased at higher cutting

  1. Paleozoic magmatism and metamorphism in the Central Tianshan block revealed by U-Pb and Lu-Hf isotope studies of detrital zircons from the South Tianshan belt, NW China

    Zhang, Xiaoran; Zhao, Guochun; Eizenhöfer, Paul R.; Sun, Min; Han, Yigui; Hou, Wenzhu; Liu, Dongxing; Wang, Bo; Liu, Qian; Xu, Bing


    As a major Precambrian microcontinent in the southernmost Central Asian Orogenic Belt (CAOB), the Central Tianshan block (CTS) in the Chinese Tianshan is essential for understanding the final assembly of the southern CAOB. It experienced multistage Paleozoic magmatism and metamorphism, but the detailed processes are still controversial and far from being completely understood. This paper reports coupled U-Pb and Lu-Hf isotopic data of detrital zircons from late Paleozoic (meta-)sedimentary strata in the South Tianshan belt, which can provide new insight into deciphering the Paleozoic evolution of the eastern segment of the CTS block. Characterized by typical oscillatory zoning and high Th/U ratios (> 0.2), detrital zircons in the Permian sedimentary samples yield dominant age populations at ca. 505-490 Ma, 475-440 Ma, 430-400 Ma and 340-250 Ma, pinpointing the development of four episodes of magmatism in the eastern CTS block. Particularly, Ordovician-Silurian (475-440 Ma) zircons, possessing low negative εHf(t) values, predominate in sedimentary strata in and surrounding the CTS block, indicating that the 475-440 Ma magmatic rocks probably constitute the main body of the CTS block. The origin of this (early Paleozoic) episode of magmatism was most likely related to the southward subduction of the Junggar Ocean beneath the CTS block. Carboniferous-Triassic (340-250 Ma) zircons have dominantly positive εHf(t) values, probably derived from the post-collisional juvenile rocks in the CTS block. Combined with previous studies, our data suggest that the single source terrane for the sampled strata was the CTS block, which had been a topographic high providing substantial detritus to the surrounding areas at least since the Early Permian. In the metasedimentary sample, detrital zircons mostly show partially/fully recrystallized internal textures and low Th/U ratios (isotopes and Ti-in-zircon thermometer of metamorphic zircons in this study, as well as previous

  2. On the genesis of molybdenum carbide phases during reduction-carburization reactions

    Guil-Lopez, R., E-mail: [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain); Nieto, E. [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain); Departamento de Tecnologia Quimica y Energetica, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, 28933-Mostoles (Spain); Botas, J.A. [Departamento de Tecnologia Quimica y Energetica, ESCET, Universidad Rey Juan Carlos, C/Tulipan s/n, 28933-Mostoles (Spain); Fierro, J.L.G., E-mail: [Grupo de Energia y Quimica Sostenibles, ICP-CSIC, Marie Curie 2, Cantoblanco, 28049-Madrid (Spain)


    Molybdenum carbide has been prepared according to the carbothermal reduction method. Carbon black substrate was used as C-source whereas a H{sub 2}-flow was the reducing agent. Two different H{sub 2} consumption steps were identified during the carburization treatment. The low temperature step is related to the reduction of Mo{sup 6+}-to-Mo{sup 4+}, the higher temperature process accounts for the deep reduction of Mo{sup 4+}-to-metal Mo{sup 0} and its subsequent reaction with C to form the Mo-carbide. The influences of the maximum carburization temperature, carburization time, gas hourly space velocity regarding Mo-loading, heating rate and temperature of Ar pre-treatment were analyzed. All these conditions are interrelated to each other. Thus, the carburization process ends at 700 Degree-Sign C when Mo-loading is 10 wt%, however Mo-loading higher than 10 wt% requires higher temperatures. Carburization temperatures up to 800 Degree-Sign C are needed to fulfill Mo-carbide formation with samples containing 50 wt% Mo. Nevertheless, Ar pre-treatment at 550 Degree-Sign C and slow heating rates favor the carburization, thus requiring lower carburization temperatures to reach the same carburization level. - Graphical Abstract: H{sub 2}-consumption profile (TPR) during the molybdenum carburization process, XRD patterns of the reduced Mo-samples after carburization and TEM-micrographs with two different enlargement of the samples with 5, 20 and 50 wt% Mo. Highlights: Black-Right-Pointing-Pointer Control of carburization variables: tailor the reduced/carbide Mo-phases (single/mixture). Black-Right-Pointing-Pointer Mo carburization in two stages: (1) Mo{sup 6+}-Mo{sup 4+}; (2) Mo{sup 4+}-Mo{sup 0} and, at once, MoC. Black-Right-Pointing-Pointer The carburization process is faster than Mo{sup 4+} reduction. Black-Right-Pointing-Pointer XPS probed: reduced Mo particles show core-shell structure. Black-Right-Pointing-Pointer Core: reduced Mo (Mo{sub 2}C, MoO{sub 2} and/or Mo

  3. Plutonium ion emission from carburized rhenium mass spectrometer filaments

    Kelley, J.M.; Robertson, D.M.


    Physicochemical processes important to the application of thermal emission mass spectrometry were identified and clarified. Effects of filament carbon concentration and temperature on plutonium ion emissions from a carburized rhenium filament were determined. Filament carbon concentration profoundly affected the appearance and duration of an ion signal. A useful ion signal was produced only when the carbon saturation temperature of the filament was exceeded, at which point first-order kinetics were either achieved or closely approached. This paper explains observed ion emission behavior in terms of pausible carbothermic reduction reactions and carbon diffusion processes that direct the course of those reactions. 31 references, 5 figures.

  4. Complicated secondary textures in zircon record evolution of the host granitic rocks: Studies from Western Tauern Window and Ötztal-Stubai Crystalline Complex (Eastern Alps, Western Austria)

    Kovaleva, Elizaveta; Harlov, Daniel; Klötzli, Urs


    Samples of metamorphosed and deformed granitic rocks were collected from two Alpine complexes with well-constrained metamorphic history: Western Tauern Window and Ötztal-Stubai Crystalline Complex. Zircon grains from these samples were investigated in situ by a combination of scanning electron microscope techniques, cathodoluminescence (CL) imaging and Raman spectroscopy. The aims were: to describe and interpret complicated secondary textures and microstructures in zircon; based on cross-cutting relationships between secondary microstructures, reconstruct the sequence of processes, affecting zircon crystals; link the evolution of zircon with the history of the host rocks. The results indicate that zircon in the sampled granitic rocks forms growth twins and multi-grain aggregates, which are unusual for this mineral. Moreover, various secondary textures have been found in the sampled zircon, often cross-cutting each other in a single crystal. These include: distorted oscillatory CL zoning with inner zones forming inward-penetrating, CL-bright embayments, which are the evidence of dry recrystallization via annealing/lattice recovery; CL mosaicism with no preservation of growth zoning, but abundant nano- and micro-scale pores and mineral inclusions, which are the evidence of recrystallization by coupled dissolution-reprecipitation and/or leaching; embayed zircon boundaries filled with apatite, monazite, epidote and mylonitic matrix, indicating mineral-fluid reactions resulting in zircon dissolution and fragmentation; overgrowth CL-dark rims, which contain nano-pores and point to transport and precipitation of dissolved zircon matter. We conclude that zircon in our meta-granites is sensitive to metamorphism/deformation events, and was reactive with metamorphic fluids. Additionally, we have found evidence of crystal-plastic deformation in the form of low angle boundaries and bent grain tips, which is a result of shearing and ductile deformation of the host rock. We

  5. Direct reduction of carburized pre-reduced pellets by microwave heating

    胡兵; 黄柱成; 易凌云; 姜涛


    A new iron-making process using carburized pre-reduced iron ore pellets and microwave heating is investigated. The pre-reduced pellets, with a porous structure, and fine particles are carburized homogeneously at 400-650 °C in a CO atmosphere. The carburized carbon not only acts reaction as a reduction agent, but also absorbs microwave in the reduction process. Hence, the carburized pre-reduced pellets can be rapidly reduced by microwave heating. There are three procedures involved in the process, namely, gas-based pre-reduction, low-temperature carburization and deep reduction by microwave heating. Carburized pre-reduced iron ore pellets show a rapid temperature rise that is twice as fast as the results for pre-reduced pellets in the laboratory. This not only improves the efficiency of the microwave heating, but also accelerates the reduction of iron oxides. The temperature of the pre-reduced pellets rises to 1050 °C in 45 min when the carburization rate is 2.02%, and the metallization rate and compressive strength reach 94.24%and 1725 N/pellet, respectively.

  6. Spectroscopic determination of optimal hydration time of zircon surface

    Ordonez R, E. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Garcia R, G. [Instituto Tecnologico de Toluca, Division de Estudios del Posgrado, Av. Tecnologico s/n, Ex-Rancho La Virgen, 52140 Metepec, Estado de Mexico (Mexico); Garcia G, N., E-mail: eduardo.ordonez@inin.gob.m [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, Av. Colon y Av. Tollocan, 50180 Toluca, Estado de Mexico (Mexico)


    When a mineral surface is immersed in an aqueous solution, it develops and electric charge produced by the amphoteric dissociation of hydroxyl groups created by the hydration of the solid surface. This is one influential surface property. The complete hydration process takes a time which is specific for each mineral species. The knowledge of the aqueous solution contact time for complete surface hydration is mandatory for further surface phenomena studies. This study deals with the optimal hydration time of the raw zircon (ZrSiO{sub 4}) surface comparing the classical potentiometric titrations with a fluorescence spectroscopy technique. The latter is easy and rea liable as it demands only one sample batch to determine the optimal time to ensure a total hydration of the zircon surface. The analytical results of neutron activation analysis showed the presence of trace quantities of Dy{sup 3+}, Eu{sup 3+} and Er{sup 3} in the bulk of zircon. The Dy{sup 3+} is structured in the zircon crystalline lattice and undergoes the same chemical reactions as zircon. Furthermore, the Dy{sup 3+} has a good fluorescent response whose intensity is enhanced by hydration molecules. The results show that, according to the potentiometric analysis, the hydration process for each batch (at least 8 sample batches) takes around 2 h, while the spectrometric method indicates only 5 minutes from only one batch. Both methods showed that the zircon surface have a 16 h optimal hydration time. (Author)

  7. Influence of the Inclusion Shape on the Rolling Contact Fatigue Life of Carburized Steels

    Neishi, Yutaka; Makino, Taizo; Matsui, Naoki; Matsumoto, Hitoshi; Higashida, Masashi; Ambai, Hidetaka


    It has been well known that the flaking failure in rolling contact fatigue (RCF) originates from nonmetallic inclusions in steels, and their apparent size is one of the important factors affecting RCF life. However, the influence of inclusion shape on the RCF life has not been fully clarified. In this study, attention was paid to the influence of the inclusion shape on the RCF life. This was evaluated by using carburized JIS-SCM420 (SAE4320) steels that contained two different shapes of MnS—stringer type and spheroidized type—as inclusions. Sectional observations were made to investigate the relation between the occurrence of shear crack in the subsurface and the shape of MnS. It was found that the RCF life was well correlated with the length of MnS projected to the load axis, and the initiation of shear crack in subsurface was accelerated as the length of MnS increased.

  8. Control of Heat-Resistant Steel Carburized Layer Structure. Part II

    Semenov, M. Yu.


    In the first part of the article, published in the previous issue of this journal, on the basis of studying features of the process a physical and mathematical model is presented of carbide formation during heat-resistant steel vacuum carburizing based on the example of VKS-5. In the second part of this article on the basis of analyzing the calculation model physical features are presented for formation of cementite type carbide phase taking account of steel VKS-5 alloying with chromium and nickel, and also temperature. Simultaneously, features of special molybdenum, tungsten, vanadium and niobium carbide formation are considered. The expediency of increasing chromium content in a new generation of heat-resistant steels alloyed with nickel is substantiated.

  9. Modeling of acetylene pyrolysis under steel vacuum carburizing conditions in a tubular flow reactor.

    Khan, Rafi Ullah; Bajohr, Siegfried; Graf, Frank; Reimert, Rainer


    In the present work, the pyrolysis of acetylene was studied under steel vacuum carburizing conditions in a tubular flow reactor. The pyrolysis temperature ranged from 650 degrees C to 1050 degrees C. The partial pressure of acetylene in the feed mixture was 10 and 20 mbar, respectively, while the rest of the mixture consisted of nitrogen. The total pressure of the mixture was 1.6 bar. A kinetic mechanism which consists of seven species and nine reactions has been used in the commercial computational fluid dynamics (CFD) software Fluent. The species transport and reaction model of Fluent was used in the simulations. A comparison of simulated and experimental results is presented in this paper.

  10. Effect of Rare Earths on Diffusion Coefficient and Transfer Coefficient of Carbon during Carburizing


    The diffusion coefficient of carbon in surface layer of steel-20 rare earth carburized at 880 ℃ and 900 ℃ for 8 h was calculated by substituting the measured layer depths into the diffusion equation. The mathematical model of the transfer coefficient of carbon was deduced based on the kinetics of weight gain during gas carburizing. The calculated results show that the main reason why the gas carburizing process is accelerated is due to the obvious increase in the diffusion coefficient and transfer coefficient of carbon resulted from the addition of RE.

  11. On the Notch Effect in Low Temperature Carburized Stainless Steel under Fatigue

    Minak G.


    Full Text Available The present paper describes the fatigue behaviour of carburized notched AISI 316 austenitic stainless steel specimens. Rotary four point bending fatigue tests have been performed using carburized smooth specimens with two different values of surface rugosity and notched specimen with two different stress concentration factors Kt, of 3.55 and 6.50 and the effects of carburizing on fatigue strength and notch sensitivity were discussed. Results show a general improvement of the fatigue life due to the treatment for all the series with an apparent notch sensitivity lower than one in the case of blunt notches due to secondary effects that were singled out.

  12. On the Notch Effect in Low Temperature Carburized Stainless Steel under Fatigue

    Minak, G.


    The present paper describes the fatigue behaviour of carburized notched AISI 316 austenitic stainless steel specimens. Rotary four point bending fatigue tests have been performed using carburized smooth specimens with two different values of surface rugosity and notched specimen with two different stress concentration factors Kt, of 3.55 and 6.50 and the effects of carburizing on fatigue strength and notch sensitivity were discussed. Results show a general improvement of the fatigue life due to the treatment for all the series with an apparent notch sensitivity lower than one in the case of blunt notches due to secondary effects that were singled out.

  13. Deformation Behavior across the Zircon-Scheelite Phase Transition

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang


    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO4 ) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO4 develops a (001) compression texture associated with dominant slip along ⟨100 ⟩{001 } starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  14. Deformation Behavior across the Zircon-Scheelite Phase Transition.

    Yue, Binbin; Hong, Fang; Merkel, Sébastien; Tan, Dayong; Yan, Jinyuan; Chen, Bin; Mao, Ho-Kwang


    The pressure effects on plastic deformation and phase transformation mechanisms of materials are of great importance to both Earth science and technological applications. Zircon-type materials are abundant in both nature and the industrial field; however, there is still no in situ study of their deformation behavior. Here, by employing radial x-ray diffraction in a diamond anvil cell, we investigate the dislocation-induced texture evolution of zircon-type gadolinium vanadate (GdVO_{4}) in situ under pressure and across its phase transitions to its high-pressure polymorphs. Zircon-type GdVO_{4} develops a (001) compression texture associated with dominant slip along ⟨100⟩{001} starting from 5 GPa. This (001) texture transforms into a (110) texture during the zircon-scheelite phase transition. Our observation demonstrates a martensitic mechanism for the zircon-scheelite transformation. This work will help us understand the local deformation history in the upper mantle and transition zone and provides fundamental guidance on material design and processing for zircon-type materials.

  15. Application of geochronology/geochemistry of zircon in understanding the construction of the Peninsular Range Batholith

    Kylander-Clark, A. R.; Johnston, S. M.


    Trace-element signatures of zircon are becoming increasingly used as a tool to infer the petrologic history of the rock from which that zircon crystallized. In this study, we sampled 11 igneous rocks from west to east across the northern Peninsular Ranges Batholith (PRB) to test how well REE patterns in zircon reflect those of the whole rock in arc magmas (granodiorite-tonalite). Previous studies of the PRB show two transitions from west to east, with respect to their REE patterns; transition 1) a decrease in HREE, from the west to the central PRB, and 2) an increase in LREE from the central to the eastern PRB. Whole rock samples in this study, analyzed by XRF and ICPMS, reproduce this pattern and thus provide a variety of REE signatures with which to test whether zircon can be used as a proxy for whole-rock data. Zircon from the 11 samples was analyzed by LASS (Laser Ablation Split Stream) ICP-MS, to measure both the age of the zircons and their trace-element compositions. In general, as expected, ages young from west (ca. 104 Ma) to east (ca. 90 Ma). Patterns of HREE in zircon correlate well with those of the whole rock, whereas the LREE correlation is weak. The distribution coefficient for HREE between zircon and whole rock, however, decreases with increasing HREE. Possibilities for this negative relation include: 1) minor changes in whole-rock chemistry, as samples become slightly more felsic from west to east, 2) changes in crystallization temperature from west to east, and 3) sampling bias of HREE-poor zircon rims with HREE fractionated in zircon cores. Other trace element data measured in zircon and whole rock include P, Ti, Y, Nb, Hf, Ta, Th, and U and provide interesting results. Nb and Ta show a moderate correlation between zircon and whole rock, but the Nb/Ta ratio does not. Also, though U correlates well between whole rock and zircon and Th/U correlates well between zircon and age, the Th/U ratio of the zircon is negatively correlated with the whole

  16. Thermoluminescence of zircon: a kinetic model

    Turkin, A A; Vainshtein, D I; Hartog, H W D


    The mineral zircon, ZrSiO sub 4 , belongs to a class of promising materials for geochronometry by means of thermoluminescence (TL) dating. The development of a reliable and reproducible method for TL dating with zircon requires detailed knowledge of the processes taking place during exposure to ionizing radiation, long-term storage, annealing at moderate temperatures and heating at a constant rate (TL measurements). To understand these processes one needs a kinetic model of TL. This paper is devoted to the construction of such a model. The goal is to study the qualitative behaviour of the system and to determine the parameters and processes controlling TL phenomena of zircon. The model considers the following processes: (i) Filling of electron and hole traps at the excitation stage as a function of the dose rate and the dose for both (low dose rate) natural and (high dose rate) laboratory irradiation. (ii) Time dependence of TL fading in samples irradiated under laboratory conditions. (iii) Short time anneali...

  17. Study on Preparation and Leaching Properties of Zirconate Synroc%锆酸盐人造岩石的制备及其浸出性能的研究

    李倩; 赖振宇; 卢忠远; 潘社奇; 赵颜红


    Using the analysis reagent of oxygen cerium(CeO2) , zirconium oxide(ZrO2) and calcium oxide(CaO) , calcium carbonate(CaCO3) , calcium flouride(CaF2) as raw material, CaCeZr2O7 is synthetized though the solid phase reaction. By XRD, SEM, density, porosity and leaching rate to study synthesis and the leaching properties of zirconate. The results show that the zirconate mineral is more pure by CaO as calcium materials in 1 500 C heat preservation under three hours, its density and porosity show were 3. 26 g/cm3 and 32. 4%, respectively. The leaching rate of cerium is 7. 14 × 10-6 g/(m2·d) , and its capacity of Ce can reach to 24. 38% , so it can be used as base material for high level radioactive waste.%采用分析纯氧化铈(CeO2)、氧化锆(ZrO2)和氧化钙(CaO)、碳酸钙(CaCO3)、氟化钙(CaF2)为原料,经固相反应合成具有烧绿石结构的CaCeZr2O7.通过XRD、SEM、密度和显气孔率以及浸出率的测试,对锆酸盐矿物的合成以及对Ce的浸出性能进行了研究.结果表明,在1 500 ℃下保温3h用CaF2做钙质原料可得到浸出率较低的锆酸盐固化体样品,其密度和显气孔率分别为3.26 g/cm3和32.4%,铈的归一化浸出率为7.14×10-6 g/(m2·d),对Ce的包容量可达24.38%.由于其包容量大等优良性能,可作为高放废物人造岩石固化的基材.

  18. Modeling of Carbon Concentration Profile Development During Both Atmosphere and Low Pressure Carburizing Processes

    Wei, Y.; Zhang, L.; Sisson, R. D.


    Heat treaters need an effective simulation tool to predict the carburization performance of a variety of steels. The tool is needed to not only predict the carbon profile but also optimize the process in terms of the cycle time and the total cost. CarbToolhas been developed to meet these needs for gas and vacuum carburization. In this article, CarbToolpredictions were compared with industrial experimental results for three types of steels (AISI 8620, 5120, and 4320), heat treated by both gas and vacuum carburizing processes. Based on the agreement of model predictions and experimental results, it is found that CarbToolcould be used to predict the carbon concentration profile for a variety of alloys in both gas and vacuum carburizing processes.

  19. Wettability Modification for Biosurface of Titanium Alloy by Means of Sequential Carburization

    Yong Luo; Shirong Ge; Zhong-min Jin


    Microporous titanium carbide coating was successfully synthesized on medical grade titanium alloy by using sequential carburization. Changes in the surface morphology of titanium alloy occasioned by sequential carburization were characterized and the wettability characteristics were quantified. Furthermore, the dispersion forces were calculated and discussed. The results indicate that sequential carburization is an effective way to modify the wettability of titanium alloy. After the carburization the surface dispersion force of titanium alloy increased from 76.5 × 10-3 J·m-2 to 105.5 × 10-3 J·m-2, with an enhancement of 37.9 %. Meanwhile the contact angle of titanium alloy decreased from 83° to 71.5°, indicating a significant improvement of wettability, which is much closer to the optimal water contact angle for cell adhesion of 70°.

  20. Computational Evaluation of Cyclic Strength of Carburized Gears from Heat-Resistant Steels

    Semenov, M. Yu.


    An advanced model for computing the fatigue bending strength of gears fabricated from a complexly alloyed heat-resistant steel 16Kh3NVFMB-Sh (VKS-5) subjected to vacuum carburizing in acetylene is suggested. The model matches experimental data satisfactorily and has been used to develop a mode for vacuum carburizing of gears from the heat-resistant steel to provide a high fatigue resistance.

  1. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature

    K. B. Kale


    Full Text Available The CO2 adsorption by calcium zirconate was explored at pre- and post- combustion temperature condition. The several samples of the calcium zirconate were prepared by different methods such as sol-gel, solid-solid fusion, template and micro-emulsion. The samples of the calcium zirconate were characterized by measurement of surface area, alkalinity/acidity, and recording the XRD patterns and SEM images. The CO2 adsorptions by samples of the calcium zirconate were studied in the temperature range 100 to 850 oC and the CO2 adsorptions were observed in the ranges of 6.88 to 40.6 wt % at 600 0C and 8 to 16.82 wt% at in between the temperatures 200 to 300 oC. The effect of Ca/Zr mol ratio in the samples of the calcium zirconate on the CO2 adsorption and alkalinity were discussed. The adsorbed moisture by the samples of the calcium zirconate was found to be useful for the CO2 adsorption. The promoted the samples of the calcium zirconate by K+, Na+, Rb+, Cs+, Ag+ and La3+ showed the increased CO2 adsorption. The exposure time of CO2 on the samples of the calcium zirconate showed the increased CO2 adsorption. The samples of the calcium zirconate were found to be regenerable and reusable several times for the adsorption of CO2 for at the post- and pre-combustion temperature condition. Copyright © 2012 by BCREC Undip. All rights reservedReceived: 23rd June 2012, Revised: 28th August 2012, Accepted: 30th August 2012[How to Cite: K. B. Kale, R. Y. Raskar, V. H. Rane and A. G.  Gaikwad (2012. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (2: 124-136. doi:10.9767/bcrec.7.2.3686.124-136] [How to Link / DOI: ] | View in 

  2. «Granulite» zircons of the Lapland granulite belt

    Kaulina, T.


    An age of the main stage of granulite metamorphism, which followed the overthrusting of the Lapland granulite belt (LGB) is estimated at about 1.91-1.95 Ga (Tugarinov, Bibikova, 1980; Bernard-Griffiths et al., 1984; Bibikova et al., 1993; Mitrofanov et al., 1993). This high-grade metamorphism is dated by U-Pb method on short prismatic gem-quality zircons that are typical for granulites and are interpreted as formed under stress and space-shortage conditions of the high pressure. And the common belief is that these zircon ages are dating the peak conditions of a metamorphic P-T path, since zircon has a high closure temperature of its U-Pb system. We studied rocks with different degree of metamorphism from Yavr and Pados rivers district (Kola Peninsula, Russia) located in the connection zone of the Tanaelv belt and LGB. Samples from the Tanaelv belt were taken from: 1) leucocratic garnet-clinopyroxene-amphibole plagiogneiss, chemically corresponds to andesite and formed under amphibolite facies 2) leucocratic biotite-pyroxene plagiogneiss with mineral association of granulite facies. Lapland granulites are represented by sillimanite-garnet-biotite gneiss from khondalite complex and leuco-mesocratic amphibole-pyroxene-plagioschist, belonging to the charnockite complex. Metamorphic zircons in all studied samples are represented practically by crystals of the same image. These are round or isometric (rarely subidiomorphic-prismatic in mafic granulites) large crystals with bright luster and high transparency. They are colorless or weakly colored into yellowish-pinkish tones. Crystals are zoneless but may contain cores, especially zircons from khondalite, 60% of which contain zoned cores. Thus typically “granulitic” zircon, described in many works, is the dominant type both in granulites of the Lapland belt and in amphiboles gneisses of the Tanaelv belt. Zircons are distinguished by low U contents (up to 100 ppm) and high Th/U and Zr/Hf ratios (0.6-0.7 and 42

  3. Paleoproterozoic mojaveprovince in northwestern Mexico? Isotopic and U-Pb zircon geochronologic studies of precambrian and Cambrian crystalline and sedimentary rocks, Caborca, Sonora

    Lang, Farmer G.; Bowring, S.A.; Matzel, J.; Maldonado, G.E.; Fedo, C.; Wooden, J.


    Whole-rock Nd isotopic data and U-Pb zircon geochronology from Precambrian crystalline rocks in the Caborca area, northern Sonora, reveal that these rocks are most likely a segment of the Paleoproterozoic Mojave province. Supporting this conclusion are the observations that paragneiss from the ??? 1.75 Ga Bamori Complex has a 2.4 Ga Nd model age and contains detrital zircons ranging in age from Paleo- proterozoic (1.75 Ga) to Archean (3.2 Ga). Paragneisses with similar age and isotopic characteristics occur in the Mojave province in southern California. In addition, "A-type" granite exposed at the southern end of Cerro Rajon has ca 2.0 Ga Nd model age and a U-Pb zircon age of 1.71 Ga, which are similar to those of Paleoproterozoic granites in the Mojave province. Unlike the U.S. Mojave province, the Caborcan crust contains ca. 1.1 Ga granite (Aibo Granite), which our new Nd isotopic data suggest is largely the product of anatexis of the local Precambrian basement. Detrital zircons from Neoproterozoic to early Cambrian miogeoclinal arenites at Caborca show dominant populations ca. 1.7 Ga, ca. 1.4 Ga, and ca. 1.1 Ga, with subordinate Early Cambrian and Archean zircons. These zircons were likely derived predominately from North American crust to the east and northeast, and not from the underlying Caborcan basement. The general age and isotopic similarities between Mojave province basement and overlying miogeoclinal sedimentary rocks in Sonora and southern California is necessary, but not sufficient, proof of the hypothesis that Sonoran crust is allochthonous and was transported to its current position during the Mesozoic along the proposed Mojave-Sonora megashear. One viable alternative model is that the Caborcan Precambrian crust is an isolated, autochthonous segment of Mojave province crust that shares a similar, but not identical, Proterozoic geological history with Mojave province crust found in the southwest United States ?? 2005 Geological Society of America.

  4. Influence of vacuum carburizing treatment on fatigue crack growth characteristic in DSG2

    K. Nambu


    Full Text Available The aim of this research is to clarify the influence of vacuum carburizing on the fatigue-crack progress characteristics of DSG2 steel. The test specimen tempering material (QT material and vacuum carburizing material (VC material has been used. The fatigue-crack progress was examined by subjecting the samples to four-point bending. The loading-capacity fixed experiment was done using a maximum load of Pmax = 4000– 7000 N. The ΔK fixed experiment was done using a load of ΔK = 18–36 MPa√m. The crack progress speed of VC material fell, after the high crack progress speed was shown, and after it showed the minimum, it showed the tendency to go up again. This is considered to be what is depended on the compressive residual stress given to the carburizing layer. From this, it is thinkable that there is a crack progress depression effect in a carburizing layer. In VC material, a carburizing layer has a crack progress depression effect from a plunger-helix bottom to about 2.6 mm, and it turned out that it is larger than an effective carburizing layer. Moreover, in each ΔK, it was shown that depression effect revelation differs and the crack progress process accompanying it was able to be shown typically.

  5. Carbide precipitation in austenitic stainless steel carburized at low temperature

    Ernst, F. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)]. E-mail:; Cao, Y. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Michal, G.M. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)


    Low-temperature gas-phase carburization can significantly improve the surface mechanical properties and corrosion resistance of austenitic stainless steel by generating a single-phase 'case' with concentrations of interstitially dissolved carbon exceeding the equilibrium solubility limit by orders of magnitude. Upon prolonged treatment, however, carbides (mostly {chi}, M{sub 5}C{sub 2}) can precipitate and degrade the properties. High-resolution and spatially resolved analytical transmission electron microscopy revealed the precise carbide-austenite orientation relationship, a highly coherent interface, and that precipitation only occurs when (i) the carbon-induced lattice expansion of the austenite has reached a level that substantially reduces volume-misfit stress and (ii) diffusional transport of nickel, chromium, and iron - enhanced by structural defects - can locally reduce the nickel concentration to the solubility limit of nickel in {chi}-carbide.

  6. Effects of niobium additions on the structure, depth, and austenite grain size of the case of carburized 0.07% C steels

    Islam, M. A.; Bepari, M. M. A.


    Carbon (0.07%) steel samples containing about 0.04% Nb singly and in combination with nitrogen were carburized in a natural Titas gas atmosphere at a temperature of 1223 K (950 °C) and a pressure of about 0.10 MPa for 1/2 to 4 h, followed by slow cooling in the furnace. Their microstructures were studied by optical microscopy. The austenite grain size of the case and the case depths were determined on baseline samples of low-carbon steels and also on niobium and (Nb + N) microalloyed steel samples. It was found that, when compared to the baseline steel, niobium alone or in combination with nitrogen decreased the thickness of cementite network near the surface of the carburized case of the steels. However, niobium in combination with nitrogen was more effective than niobium in reducing the thickness of cementite network. Niobium with or without nitrogen inhibited the formation of Widmanstätten cementite plates at grain boundaries and within the grains near the surface in the hypereutectoid zone of the case. It was also revealed that, when compared to the baseline steel, niobium decreased the case depth of the carburized steels, but that niobium with nitrogen is more effective than niobium alone in reducing the case depth. Niobium as niobium carbide (NbC) and niobium in the presence of nitrogen as niobium carbonitride, [Nb(C,N)] particles refined the austenite grain size of the carburized case, but Nb(C,N) was more effective than NbC in inhibiting austenite grain growth.

  7. Etude d'un procédé d'hydroliquéfaction du charbon pour la production simultanée de gaz et de carburant . . . . . Studies of a Coal Hydrogenation Process to Produce CO-Currently Gas and Gasoline

    Franckowiak S.


    Full Text Available Un des principaux moyens de réintroduire le charbon dans le marché énergétique français est de le transformer en produits utiles comme le gaz de réseau ou les carburants. Les procédés d'oxyvapogazéification permettent d'obtenir un gaz de synthèse qui peut être ensuite converti en gaz riche ou en produits liquides. L'hydrogénation en phase liquide (ou hydroliquéfaction se présente pour le long terme comme une seconde voie qui offre des avantages spécifiques - taux de conversion du charbon et rendement élevés, - production directe de gaz de substitution (GNS et de carburant, - possibilité d'utilisation d'hydrogène provenant de l'électricité nucléaire. Un programme d'étude a été lancé avec la participation du Gaz de France (GDF, du Centre d'études et de recherches des Charbonnages de France (Cerchar, de l'institut Français du Pétrole (lFP et du Centre National de la Recherche Scientifique (CNRS dans le cadre du Groupe d'Étude de la Conversion du Charbon par Hydrogénation (GECH. Un banc d'essai d'hydroliquéfaction situé au Cerchar, d'un débit de 10 kg/h de mélange charbon-solvant, permet d'obtenir des hydrogénats dans des conditions variées et en présence de divers catalyseurs. L'étude de la valorisation de ces hydrogénats est effectuée dans les laboratoires de l'lFP. Les essais et les études effectués permettent d'envisager la production à volonté du GNS, de carburants ou des deux ensemble. Un modèle d'optimisation a été réalisé au GDF pour étudier et comparer les différentes filières en prenant en compte l'utilisation d'hydrogène d'électrolyse ou d'hydrogène produit sur place à partir du résidu de liquéfaction. One of the main ways to bring coal in the future french energy market is to transform it into valuable products. The oxygen steam gasification processes give a synthesis gas which can be converted into SNG or gasoline in a catalytic stage. The liquid phase hydrogenation process is a

  8. 剪毛机支架体渗碳工艺的优化%The Optimum of Carburize Industrial Art on Shearing Machine Frame Foundation

    吐尔逊·斯地克; 熊辉林


    By the shearing machine frame foundation with its material (number 08 steel), using solid-state carburize method, the carburize industrial art, organization and property have been studied in order to provide reasonable theoretical foundation for increasing resistance to wear of carburize layers. From test the optimal version has been reached in heating temperature of 950℃, insulated time of 4 h, catalyst proportion of 30%.%本文以剪毛机支架体材料08钢为研究对像,采用固体渗碳法,对渗碳的工艺,组织和性能进行研究,为提高渗碳层的耐磨性提供可靠的理论依据.通过试验得出加热温度为950℃,保温时间为6 h,催渗剂比例为30%的最优方案.

  9. Microstructural constraints on the mechanisms of the transformation to reidite in naturally shocked zircon

    Erickson, Timmons M.; Pearce, Mark A.; Reddy, Steven M.; Timms, Nicholas E.; Cavosie, Aaron J.; Bourdet, Julien; Rickard, William D. A.; Nemchin, Alexander A.


    Zircon (ZrSiO4) is used to study impact structures because it responds to shock loading and unloading in unique, crystallographically controlled manners. One such phenomenon is the transformation of zircon to the high-pressure polymorph, reidite. This study quantifies the geometric and crystallographic orientation relationships between these two phases using naturally shocked zircon grains. Reidite has been characterized in 32 shocked zircon grains (shocked to stages II and III) using a combination of electron backscatter diffraction (EBSD) and focused ion beam cross-sectional imaging techniques. The zircon-bearing clasts were obtained from within suevite breccia from the Nördlingen 1973 borehole, close to the center of the 14.4 Ma Ries impact crater, in Bavaria, Germany. We have determined that multiple sets (up to 4) of reidite lamellae can form in a variety of non-rational habit planes within the parent zircon. However, EBSD mapping demonstrates that all occurrences of lamellar reidite have a consistent interphase misorientation relationship with the host zircon that is characterized by an approximate alignment of a {100}zircon with a {112}reidite and alignment of a {112}zircon with a conjugate {112}reidite. Given the tetragonal symmetry of zircon and reidite, we predict that there are eight possible variants of this interphase relationship for reidite transformation within a single zircon grain. Furthermore, laser Raman mapping of one reidite-bearing grain shows that moderate metamictization can inhibit reidite formation, thereby highlighting that the transformation is controlled by zircon crystallinity. In addition to lamellar reidite, submicrometer-scale granules of reidite were observed in one zircon. The majority of reidite granules have a topotaxial alignment that is similar to the lamellar reidite, with some additional orientation dispersion. We confirm that lamellar reidite likely forms via a deviatoric transformation mechanism in highly crystalline

  10. Direct evidence for anisotropic He diffusivity in zircon provided by laser depth profiling (Invited)

    Hodges, K.; van Soest, M. C.; Monteleone, B. D.; Boyce, J. W.


    While zircon (U-Th)/He dating has become an increasingly popular tool for studies of the thermal evolution of orogenic systems, several issues complicate interpretations of the geologic significance of zircon “dates”. Zircons frequently exhibit complex U-Th zoning, which makes corrections for alpha ejection loss uncertain. It has been known for decades that radiation damage enhances the rate of diffusive loss of helium in zircon, sometimes making the unique assignment of a (U-Th)/He closure temperature difficult. Here we consider another complicating factor: the proposal by Reich et al. (2007) - based on computer simulations - that He diffusion is anisotropic in zircon, which also may have significant implications regarding (U-Th)/He closure temperature. We present, for the first time, direct measurements of crystallographically controlled, anisotropic diffusion profiles in zircon that appear to support the conclusions of Reich et al. (2007). For this study, we conducted replicate vacuum heating experiments on slices from euhedral crystals of Cretaceous De Beers zircon from South Africa and Proterozoic Mud Tank zircon from Australia. (All slices were cut from the central portions of very large crystals in order to avoid natural alpha ejection profiles near crystal margins.) In each experiment, we heated slices of the two zircons cut both parallel and perpendicular to their c-axes for 24 hours at 415° C. Depth profiling of the resulting 4He diffusion profiles using an ArF excimer laser revealed extremely similar c-axis parallel diffusion profiles for both zircons, and extremely similar c-axis perpendicular diffusion profiles for both zircons. However, the c-axis parallel and perpendicular profiles were markedly different. The loss profiles parallel to c extended over twice as far into the crystals as did the perpendicular profiles, implying much more rapid thermally activated diffusion parallel to the c direction, as predicted by the Reich et al. models

  11. Mechanisms of radon loss from zircon: Microstructural controls on emanation and diffusion

    Eakin, Marty; Brownlee, S. J.; Baskaran, M.; Barbero, L.


    Understanding how radon escapes from minerals is important for many fields in Earth science, yet few studies have focused on the mechanisms for radon escape. We measured radon emanation rate and radon loss upon heating for crushed aliquots of three large zircon crystals from three localities: Mud Tank (Australia), Bancroft (Canada), and Malawi (Africa). Our study, in conjunction with published data, shows that the room temperature radon emanation coefficient (REC) varies over 5 orders of magnitude in zircon. For low U zircon, Mud Tank, there are variations in REC that appear to be related to annealing at different temperatures, possibly due to annealing of fission tracks, however, all REC values for Mud Tank zircon are within error of one another. Bancroft and Malawi zircons have higher U content and do not show any systematic relationship of REC to annealing temperature. Results from Mud Tank zircon suggest that partial annealing of fission tracks decreases REC, but when all fission tracks are annealed REC reaches a maximum. REC in zircons with high U content, Bancroft and Malawi, is slightly higher than in zircon with lower U, although results are within error. Results of measurements of radon loss upon heating suggest that radon diffusion is slow, ∼30% of the radon is lost during heating at 975 °C for 48 h. Samples heated a second time yield less fractional radon loss, ∼10%, suggesting that diffusion parameters are changed during heating at temperatures ⩾975 °C, which is likely the result of annealing of radiation damage. Diffusion parameters calculated from the fractional loss experiments reflect diffusion in highly radiation damaged or metamict zircons. Our results indicate that internal microstructures in zircon, such as fission tracks and alpha-radiation damage, influence radon escape for diffusion and recoil mechanisms, and hence if these effects can be further characterized, measurements of 222Rn escape have the potential to be useful for probing

  12. Short-term creep properties of Ti-6Al-4V alloy subjected to surface plasma carburizing process

    Verônica Mara Cortez Alves de Oliveira


    Full Text Available The aim of this study was to investigate the short-time creep behavior of Ti-6Al-4V by plasma carburizing, which was performed at 725 °C for 6 h in a 50% Ar – 45% H2 – 5% CH4 gas mixture. Nano and microhardness testing, optical microscopy, TEM, X-ray diffraction and optical profilometry were used to characterize the samples. Furthermore, short-term creep tests were performed under a constant tensile load in air at 600 °C using a dead-weight-creep-rupture machine. The carburizing treatment resulted in a compound layer measuring approximately 1.7 μm in thickness with a hardness of 815 HV and a composition of TiC0.66. The creep properties of the “Widmanstätten + carburized” specimens were improved relative to those of untreated specimens. TEM and fracture analysis indicated creep deformation process attributed mainly to α phase deformation and fracture by intergranular decohesion.

  13. TiC nanocrystal formation from carburization of laser-grown Ti/O/C nanopowders for nanostructured ceramics.

    Leconte, Y; Maskrot, H; Herlin-Boime, N; Porterat, D; Reynaud, C; Gierlotka, S; Swiderska-Sroda, A; Vicens, J


    Refractory carbide ceramics (TiC and ZrC) raise interest as promising materials for high-temperature applications such as structural materials for the future generation of nuclear reactors. In this context, nanostructured ceramics are expected to exhibit improved thermomechanical properties as well as better behavior under irradiation when compared to conventional materials. It is therefore necessary to synthesize carbide nanocrystals of such materials to elaborate the ceramics. We report here the formation study of TiC nanocrystals through the direct carburization of Ti/O/C nanopowders grown by laser pyrolysis. A spray of titanium tetraisopropoxide was laser pyrolyzed with ethylene as the sensitizer, leading to Ti/O/C nanopowders with various C contents controlled by the synthesis conditions. Annealing treatments performed on these nanopowders under an inert atmosphere without any C addition enabled the formation of TiC grains through the carburization of the oxide phase by free C incorporated during the synthesis. The powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The final TiC grain size was about 80 nm, and the grains were monocrystalline. The influence of the free C content on the grain growth during the annealing step, together with its effects on the densification of the ceramics after sintering by high-pressure flash sintering, was examined. A 93% densification was finally achieved.

  14. Lithium in low-temperature fluid-affected zircons. Paleoproterozoic weathering horizon (Karelia, the Baltic shield).

    Alfimova, Nadezhda; Klimova, Ekaterina; Matrenichev, Vjacheslav; Zinger, Tatjana


    Zircon is a mineral, which is widely used in geochronology. At the same time, low-temperature fluids had been shown to affect the inner structure, chemical and even isotopic composition of zircons (Geisler et al., 2007, Pidgeon et al., 2013). Here we report changes in the inner structure and chemical composition of zircon grains, preserved in Paleoproterozoic weathering horizon from Karelia craton (N. Ladoga region, Russia) in spite of greenschist metamorphism. Detailed zircon SEM and CL study revealed that zircons in weathered samples can be classified into two groups depending on their microstructural characteristics: 1- the zircons with an unusual and complex (breccia-like) structure with almost no relics of magmatic zonation. The inner structure of that grains is often composed of a mosaic of angular crystal pieces cemented with silicates or even other generation of zircon itself. Group 2- zircons with clearly seen relics of magmatic (oscillatory) zonation. Both groups have outer rims which are forming the facets of the grains. These two groups are also different in chemistry. Group 1 zircons contain more than 10 ppm of Ba and Sr, >1000 ppm U and Th/U there is ≤0.1, REE spectra show LREE/HREE > 0.5, positive Cean (0.3, Ba and Sr are less than 10 ppm each, LREE/HREE+2.0, Euan ≤ +1.0, Li is from 19 to 73 ppm with average meaning 49 ppm. A separate geochemical group can be identified within "a-structural" grains (group 1) -parts of zircons and grains light-colored in SEM. These part of group 1 zircons demonstrate specific REE spectra - LREE/HREE sources. Paleo-weathering had changed not only chemical composition (major element and REEs) but the inner structure of grains with higher U concentration more, then with low U content. Li had demonstrated strong ability to resist changes during the low-temperature fluid-mineral interaction.

  15. Laws of alloyed cementite particles nucleation during heat-resistant steels carburizing

    M. Yu. Semenov


    Full Text Available The article considers a problem analyzing a nucleation of cementite type carbides in carburized heat-resistant steels for the turbofan engines gear wheels.The verification of previously hypothesized mechanism of dislocation nucleation particles chromium-alloyed cementite during process of carburizing was accepted as an objective of the work.As a methodological basis of this paper were accepted the numerical experiments based on the kinetic theory of nucleation, as well as on the known results of experimental studies.According to the kinetic theory of nucleation, a new phase in the solid solutions take place in the defects of the crystal structure of the metal such as inter-grain boundaries and dislocations clusters. A principle feature of the inter-grain boundary mechanism of nucleation is formation of carbide lattice. It is of great practical interest because the cementite lattice drops mechanical properties of hardened parts.According to the experimental studies, the average chromium concentration in the alloyed cementite twice exceeds its Cr content in the heat-resistant steels. Furthermore, the areas of abnormally high (more than ten times in comparison with the average content chromium concentration in cementite have been experimentally revealed.Numerical experiments have revealed that the nucleation of cementite particles alloyed with chromium (chromium concentration of 3% or more occurs, mainly, by the dislocation mechanism on the concentration fluctuations of the alloying element. According to calculations, an obligatory prerequisite to start an active nucleation process of new phase in the solid solution is a local increase of the chromium concentration up to 40%.Despite the lack of physical prerequisites for the formation of chromium precipitates, this phenomenon is explained by a strong chemical affinity of chromium and carbon, causing diffusion of chromium atoms in the region of the carbon atoms clusters. The formation of carbon

  16. Metallic Pb nanospheres in ultra-high temperature metamorphosed zircon from southern India

    Whitehouse, M. J.; Kusiak, M. A.; Wirth, R.; Ravindra Kumar, G. R.


    A transmission electron microscope (TEM) study of Paleoproterozoic zircon that has experienced ultra-high temperature (UHT) metamorphism at ca. 570 Ma in the Kerala Khondalite Belt (KKB), southern India, documents the occurrence of metallic Pb nanospheres. These results permit comparison with a previous report from UHT zircon in Enderby Land, Antarctica, and allow further constraints to be placed on possible mechanisms for nanosphere formation. As in Enderby Land, the nanospheres in the KKB occur in non-metamict zircon, emphasising that radiogenic Pb redistribution can occur with only partial interconnectivity of radiation damaged zircon. In contrast, the nanospheres reported here are not closely associated with Si-rich glass inclusions, which is inconsistent with a silicate liquid-metal immiscibility model proposed in the earlier study. Formation of these Pb nanospheres effectively halts Pb-loss from zircon, even under extreme conditions, and can adversely affect geochronological interpretations due to decoupling of Pb from U.

  17. The sort of carburization and the quality of obtained cast iron

    K. Janerka


    Full Text Available In the production of cast iron, the pig iron’s amount in charge material is more and more often limited, and replaced by steel scrap. That extorts the necessity of know-how the carburization and one is looking for carburizers, which ensure obtaining big carbon increment as quickly as possible with the high repeatability and the ones which ensure getting the adequate quality of cast iron. The object of presented research was definition of the influence of charge materials’ sort on the structure, course of solidification, and the effectiveness of process. The cast iron melts, which are presented below, are made only on the basis of steel scrap with portion of graphitoidal, coke and anthracite carburizers, which were added to the charge in solid. In the article one compared the carburizers in respect of their structure, chemical constitution and the effectiveness obtained during the carburization of liquid metal. The melting of cast iron, based on the special pig iron, was carried out as well. The course of melts, chemical constitution of obtained cast iron and its structure were presented. The comparison between quality distribution and the volume fraction of graphite in classes of size for the individual melts were achieved and the TDA curves were inserted.

  18. Modeling Growth and Dissolution Kinetics of Grain-Boundary Cementite in Cyclic Carburizing

    Ikehata, Hideaki; Tanaka, Kouji; Takamiya, Hiroyuki; Mizuno, Hiroyuki; Shimada, Takeyuki


    In vacuum carburizing of steels, short-time carburizing is usually followed by a diffusion period to eliminate the filmlike cementite ( θ GB ) grown on the austenite ( γ) grain boundary surface. In order to obtain the θ GB amount during the process, the conventional model estimates the amount of cementite ( θ) with the equilibrium fractions for local C contents within a framework of the finite difference method (FDM), which overestimates the amount of θ GB observed after several minutes of carburizing. In our newly developed model, a parabolic law is assumed for the growth of θ GB and the rate controlling process is considered to be Si diffusion rejected from θ under the isoactivity condition. In contrast, the rate constant for the dissolution of θ GB is considered to be controlled by Cr diffusion of θ. Both rate coefficients ( α) were validated using multicomponent diffusion simulation for the moving velocity of the γ/ θ interface. A one-dimensional (1-D) FDM program calculates an increment of θ GB for all grid points by the updated diffusivities and local equilibrium using coupled CALPHAD software. Predictions of the carbon (C) profile and volume fraction of cementite represent the experimental analysis much better than the existing models, especially for both short-time carburization and the cyclic procedure of carburization and diffusion processes.

  19. Influence of Al on the microstructure and carburization performance of a Ni-based alloy coating

    Cangue, Feliciano Jose Ricardo, E-mail: [Federal University of Parana, Centro Politecnico, s/n - Bairro Jardim das Americas, Curitiba, Parana, Cx P. 19011, CEP: 81531-990 (Brazil); D' Oliveira, Ana Sofia Climaco Monteiro, E-mail: [Mechanical Engineering Department, Federal University of Parana, Centro Politecnico, s/n - Bairro Jardim das Americas, Curitiba, Parana, Cx P. 19011, CEP: 81531-990 (Brazil)


    Carburization is a degradation mechanism involving the diffusion of carbon into a metal alloy and its accumulation on the surface. Coke forms on the internal walls of crude oil refining equipment and adversely affects its efficiency and service life. In an attempt to enhance the service life of materials exposed to these aggressive environments, this work investigated the development of a protective coating to reduce the diffusion of carbon into the surfaces of components. Coatings were tailored by mixing the atomized Ni alloy (Hastealloy C) with 5 wt% and 15 wt% Al powders and deposited by Plasma Transferred Arc hardfacing. Pack carburizing was carried out at 650 deg. C and 850 deg. C for 6 h, and temperature stability was tested in an air furnace to evaluate the performance of the coatings. Characterization included measurement of Vickers microhardness profiles and microstructure analysis by optical and scanning electron microscopy and X-ray diffraction. The good weldability of the original Ni-based alloy was not altered by the presence of Al. Richer Al coatings developed ordered aluminide compounds in a Ni matrix and exhibited increased hardness and dilution. Exposure to temperatures of 650 deg. C and 850 deg. C in an air furnace and to a carburizing environment neither compromised coating hardness nor produced a carburizing layer, although carbides were identified at the top surface. Our results will be of benefit in the development of an alternative solution for the protection of components operating in carburizing environments.

  20. Isotope ratio measurements of pg-size plutonium samples using TIMS in combination with "multiple ion counting" and filament carburization

    Jakopic, Rozle; Richter, Stephan; Kühn, Heinz; Benedik, Ljudmila; Pihlar, Boris; Aregbe, Yetunde


    A sample preparation procedure for isotopic measurements using thermal ionization mass spectrometry (TIMS) was developed which employs the technique of carburization of rhenium filaments. Carburized filaments were prepared in a special vacuum chamber in which the filaments were exposed to benzene vapour as a carbon supply and carburized electrothermally. To find the optimal conditions for the carburization and isotopic measurements using TIMS, the influence of various parameters such as benzene pressure, carburization current and the exposure time were tested. As a result, carburization of the filaments improved the overall efficiency by one order of magnitude. Additionally, a new "multi-dynamic" measurement technique was developed for Pu isotope ratio measurements using a "multiple ion counting" (MIC) system. This technique was combined with filament carburization and applied to the NBL-137 isotopic standard and samples of the NUSIMEP 5 inter-laboratory comparison campaign, which included certified plutonium materials at the ppt-level. The multi-dynamic measurement technique for plutonium, in combination with filament carburization, has been shown to significantly improve the precision and accuracy for isotopic analysis of environmental samples with low-levels of plutonium.

  1. Gondwana to Pangea: a detrital zircons tale from NW Iberia

    Pastor-Galán, Daniel; Gutiérrez-Alonso, Gabriel; Brendan Murphy, J.; Fernández-Suárez, Javier; Hofmann, Mandy; Linnemann, Ulf


    The Cantabrian Zone of NW Iberia preserves a voluminous, almost continuous, sedimentary sequence that ranges from Neoproterozoic to Early Permian in age. Its tectonic setting is controversial and recent hypotheses include (i) passive margin deposition along the northern margin of Gondwana or (ii) an active continental margin or (iii) a drifting ribbon continent. In this paper we present detrital zircon U-Pb laser ablation age data from 13 samples from the Cantabrian Zone sequence ranging from Early Silurian to Early Permian in depositional age, which, together with previously published detrital zircon ages from Ediacaran-Ordovician strata, allow a comprehensive analysis of changing provenance through time. Laser ablation U-Pb geochronological analysis of detrital zircons in thirteen samples of the Cantabrian Zone of the NW Iberian Variscan belt reveal that this portion of Iberia was part of the northern passive-margin of Gondwana from the Ordovician to Late Devonian, until the onset of collision between Gondwana and Laurentia. Zircon populations in these samples show important similarities with zircons found in coeval detrital rocks from central North Africa. Additionally, the populations found in NW Iberia are coherent with a Saharan source. We suggest that NW Iberia was situated from Ordovician to Late Devonian along the Gondwana northern passive margin close to the paleoposition of central North Africa and Saharan craton. Additionally, the Carboniferous-Permian samples studied record the provenance changes produced during the Variscan collision and basement exhumation, the Cantabrian orocline formation and the subsequent detachment of the lithospheric mantle. The provenance changes reflect major topographic variations due to the afore mentioned processes during Late Devonian to Early Permian times. Detrital zircon studies are a useful tool that can complement regional syntheses in deducing paleogeographic locations, the occurrence of major tectonic events such

  2. Matrix cracking and creep behavior of monolithic zircon and zircon silicon carbide fiber composites

    Anandakumar, Umashankar

    In this study, the first matrix cracking behavior and creep behavior of zircon matrix silicon carbide fiber composites were studied, together with the fracture and creep behavior of the monolithic zircon. These behaviors are of engineering and scientific importance, and the study was aimed at understanding the deformation mechanisms at elevated temperatures. The first matrix cracking behavior of zircon matrix uniaxially reinforced with silicon carbide fiber (SCS-6) composites and failure behavior of monolithic zircon were studied as a function of temperature (25°C, 500°C, and 1200°C) and crack length in three point bending mode. A modified vicker's indentation technique was used to vary the initial crack length in monolithic and composite samples. The interfacial shear strength was measured at these temperatures from matrix crack saturation spacing. The composites exhibited steady state and non steady state behaviors at the three different temperatures as predicted by theoretical models, while the failure stress of zircon decreased with increasing stress. The intrinsic properties of the composites were used to numerically determine the results predicted by three different matrix cracking models based on a fracture mechanics approach. The analysis showed that the model based on crack bridging analysis was valid at 25°C and 500°C, while a model based on statistical fiber failure was valid at 1200°C. Microstructural studies showed that fiber failure in the crack wake occurred at or below the matrix cracking stress at 1200°C, and no fiber failure occurred at the other two temperatures, which validated the results predicted by the theoretical models. Also, it was shown that the interfacial shear stress corresponding to debonding determined the matrix cracking stress, and not the frictional shear stress. This study showed for the first time, the steady state and non-steady state matrix cracking behavior at elevated temperatures, the difference in behavior between

  3. Zircon SHRIMP dating of granite from Qaidamshan,NW China


    Zircon SHRIMP dating from Qaidamshan granite shows that the granite age is 446 Ma, similar to that of eclogite in the UHP belt. We think that both granite and eclogite may be formed at different stages during tectonic evolution of this area. Together with other studies we suggested that the collision of ocean and continent plates may occur at the early Caledonian in this area, forming the eclogite, and the collision of continent and continent plates at the late Caledonian, forming the Qaidamshan granite with the zircon SHRIMP age of 446 Ma.

  4. Evaluation of the carburized surface of steels with Magnetic Barkhausen Noise; Avaliacao de superficie cementada de acos com efeito Barkhausen

    Campos, M.F. de; Santos, R.; Silva, F.S. da; Ribeiro, S.B.; Lins, J.F.C., E-mail: mcampos@metal.eeimvr.uff.b [Universidade Federal Fluminense (PUVR/UFF), Volta Redonda, RJ (Brazil). Polo Universitario de Volta Redonda; Franco, F.A.; Padovese, L.R. [Universidade de Sao Paulo (EPUSP), SP (Brazil). Escola Politecnica


    Steels with different carbon content, 0.11%C and 0.48%C were submitted to a heat treatment for carburization in the surface. The samples were analyzed in the conditions: normalized, only carburized and carburized and quenched as received. The Magnetic Barkhausen Noise (MBN) was measured in all samples. A better understanding of the relation between microstructure and MBN is of large interest for nondestructive characterization. X-ray diffraction (XRD) has revealed large peak broadening for the samples carburized and quenched, which have martensite. This is due to the high density of dislocations and high internal stress in the martensite. It is also found that the MBN peaks are quite distinct for the samples with martensite, which present nanocrystalline structure. When martensite is present, domain rotation occurs more significantly, reducing the permeability and the MBN envelope signal intensity. MBN is a suitable method for non-destructive evaluation of the quality of the carburization process. (author)

  5. Zircon Senstive High Resolution Ion Microprobe (SHRIMP) study of granitoid intrusions in Zhaoye Gold Belt of Shandong Province and its implication

    苗来成; 罗镇宽; 黄佳展; 关康; N.J. McNaughton; D. I. Groves


    The zircon Sensitive High Resolution Ion Microprobe (SHRIMP) results show that granitoid intrusions in Zhaoyc Gold Belt were emplaced at two periods of Mesozoic: Linglong and Luanjiahe types of granitic intrusions were emplaced between 160 Ma and 150 Ma (late Jurassic); Guojialing type of granodioritic intrusions, 130 Ma and 126 Ma (early Cretaceous). All the three types contain at least two major generations of inherited zircons with Precambrian ( >650 Ma) and early Mesozoic ages (200-250 Ma), respectively. The former suggests that these plu-tonic rocks are of crustal origin and that Precambrian basement with component of sialic crust up to 3.4 Ga old ( Middle Archean) exists in the region. The presence of abundant inherited zircons with early Mesozoic age indicates that the Precambrian basement was affected by a major tectono-thermal event, that is the collision of the North and South China blocks, at 250 Ma to 200 Ma. SHRIMP results also indicate that the gold mineralization in the region took place

  6. Non-vacuum electron-beam carburizing and surface hardening of mild steel

    Bataev, I.A., E-mail: [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Golkovskii, M.G., E-mail: [Budker Institute of Nuclear Physics SB RAS, Lavrentieva Prospect 11, 630090 Novosibirsk (Russian Federation); Losinskaya, A.A., E-mail: [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Bataev, A.A., E-mail: [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Popelyukh, A.I., E-mail: [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation); Hassel, T., E-mail: [Leibniz University, Welfengarten 1, 30167 Hannover (Germany); Golovin, D.D., E-mail: [Novosibirsk State Technical University, K. Marks 20, 630092 Novosibirsk (Russian Federation)


    Highlights: • Steel specimens were carburized by non-vacuum electron-beam cladding. • The depth of the clad layers reached 2.6 mm. • The cladding rate was 1.8 m{sup 2}/h, the quenching rate 12.6 m{sup 2}/h. • The microhardness of the quenched and tempered layers reached 8 GPa. - Abstract: In this paper, we study the structure, microhardness, and tribological properties of surface layers of mild (0.19% C) steel, which was formed by electron-beam cladding with an iron–graphite powder mixture followed by quenching and tempering. A 1.4 MeV electron beam that was extracted into air was used. Cladding of steel with the iron–graphite mixture at a beam current of 24 and 26 mA formed a hypoeutectic cast iron layer (2.19% C) and a hypereutectoid steel (1.57% C) layer, which were 2.0 and 2.6 mm thick, respectively. The microhardness of the surface-quenched and tempered steel and cast iron layers was 7 and 8 GPa, respectively. Electron-beam quenching of the surface layers of hypoeutectic cast iron was accompanied with multiple cracking. During the quenching of the 1.57% C steel layer, crack formation was not observed. In friction tests against fixed and loose abrasive particles, the surface layers of hypereutectoid steel and hypoeutectic cast iron that were produced by electron-beam cladding and quenching had lower wear rates than mild steel after pack carburizing, quenching, and tempering. In the sliding wear tests, the cast iron clad layer, which was subjected to electron-beam quenching and tempering, exhibited the highest wear resistance. Electron-beam treatment can be used to harden local areas of large workpieces. It is reasonable to treat clad layers of high-carbon steel with electron-beam quenching and tempering. To prevent multiple cracking, white cast iron layers should not be quenched.

  7. Synthetic Or Reformulated Fuels: a Challenge for Catalysis Carburants de synthèse ou reformulés : un défi pour la catalyse

    Courty P.


    Full Text Available Despite comparative figures for wordwide crude oil and natural gas proven reserves, present time contribution of syngas chemistry to motorfuels remains marginal when the refining industry is faced to main constraints: market demand evolution, stringent specifications and environmental issues. Actually natural gas upgrading via syngas chemistry yields key products (e. g. methanol among which clean motorfuels (ethers, FT products should develop despite the huge investments required, mostly for syngas production. Main challenges and corresponding issues for catalysts and related technologies are identified for Fischer-Tropsch synthesis and motorfuels long-term reformulation. Among other, mastering the chain-growth (FT synthesis improving the FCC products: gasoline, and LCO for Diesel pool. All these issues need significant progresses in catalyst and technology to be solved. Lastly, our economical study, focused on Diesel-fuel production, shows up that clean diesel (from SR-LCO mixtures and FT Diesel reach similar production costs when cheap NG is available. In the future, FT middle distillates should amount to a few percent (5-150 Mt of the 1700-2000 Mt of transport middle distillates expected from oil refining. However they should more and more be a compulsory part of diesel pool if the level of investment for an FT process continues to decrease significantly. Malgré des réserves prouvées en pétrole et en gaz du même ordre de grandeur, la contribution de la chimie du gaz de synthèse à la production de carburants reste marginale, alors que l'industrie du raffinage est confrontée à des contraintes majeures : évolution de la demande, durcissement des spécifications des produits et contraintes environnementales. Cependant, la conversion chimique du gaz, via la chimie du gaz de synthèse, fournit des produits stratégiques (e. g. méthanol parmi lesquels les carburants propres (éthers, produits Fischer-Tropsch devraient se développer, bien

  8. Mathematical modeling and validation of the carburizing of low carbon steels

    García Mariaca, A.; Cendales, E. D.; Chamarraví, O.


    This paper shows the mathematical modeling of heat and mass transfer in transient state of cylindrical bars of low carbon steel subjected to carburizing process. The model solution for the two phenomena was performed using a one-dimensional analysis in the radius direction, using the numerical method of finite differences; also a sensitivity analysis by varying the coefficient of convective heat transfer (h) is performed. The modeling results show that this carburization steel is strongly dependent on h. These results suggest that if it can increase the value of h in this kind of process could reduce the time of process for this heat treatment. Additionally, an experimental procedure was established by carburization of a steel AISI SAE 1010, which develops cementing solid phase and the specimen steel and micrographic hardness profiles obtained from samples of the specimen analysis was performed, to determine the penetration depth of the carbon and validate this result over the values obtained by the computer model.

  9. The advantages of Low Pressure Carburizing in the Heat Treatment Subcontracting Business



    Low Pressure Carburizing (LPC) was introduced in the 90's in the western Europe Heat Treatment business,mainly for in-house applications where it was especially appreciated for carburizing of transmission parts. However the success of the LPC units installed for gears carburizing in the automotive industry has hindered the development of the process in other fields - like subcontracting business -, where its advantages deserve to be enlightened.After a brief review of the principle of the process, the interest of its classical application to transmission parts is described,underlining peculiarly the reduction of the distortion observed when LPC is associated with high pressure gas quenching.Then the less-known advantages of the LPC process, like the high accuracy and reproducibility of the results, the modeling possibility and the simulation easiness, the case-depth uniformity and the full flexibility of the units are considered,showing how they can be beneficial to subcontracting business.

  10. Carbon supersaturation due to paraequilibrium carburization: Stainless steels with greatly improved mechanical properties

    Michal, G.M. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail:; Ernst, F. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail:; Kahn, H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail:; Cao, Y. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Oba, F. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Agarwal, N. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States); Heuer, A.H. [Department of Materials Science and Engineering, Case Western Reserve University, 10900 Euclid Ave., Cleveland, OH 44106 7204 (United States)]. E-mail:


    Low-temperature gas-phase carburization has been used to generate very high surface interstitial carbon contents, up to {approx}12 at.%, in a 316L austenitic stainless steel. The high interstitial content leads to substantial surface hardening (Vickers hardness of {approx}12 GPa, equivalent to Rockwell C of {approx}71.5) with essentially no loss of ductility and with no carbide formation. Residual compressive stresses accompanying the low-temperature carburization enhance the high-cycle fatigue resistance, while the hardening enhances the wear resistance. These remarkable improvements in mechanical properties arise because the carburization is carried out at temperatures where 'paraequilibrium', rather than conventional thermodynamic equilibrium, determines the phase composition; paraequilibrium can be realized under conditions where substitutional solutes such as Cr and Ni are immobile whereas interstitial solutes such as carbon are not.

  11. Effect of Carburization on the Mechanical Properties of Biomedical Grade Titanium Alloys

    Yong Luo; Haibo Jiang; Gang Cheng; Hongtao Liu


    Titanium cermets were successfully synthesized on the surface of biomedical grade titanium alloys by using sequential carburization method. The mechanical properties such as hardness, fracture toughness and plasticity were measured to estimate the potential application of titanium cermets. The results show that after carburization the surface hardness of titanium cermets was 778 HV, with a significant improvement of 128% compared with that of titanium alloys. In addition, the fracture toughness of titanium cermets was 21.5×106 Pa·m1/2, much higher than that of other ceramics. Furthermore, the analysis of the loading-unloading curve in the nanoindentation test also indicates that the plasticity of titanium cermet reached 32.1%, a relatively high value which illustrates the combination of the metal and ceramics properties. The results suggest that sequential carburization should be an efficient way to produce titanium cermets with hard surface, high toughness and plasticity.

  12. Detrital Zircon Geochronology of Cretaceous and Paleogene Strata Across the South-Central Alaskan Convergent Margin

    Bradley, Dwight; Haeussler, Peter; O'Sullivan, Paul; Friedman, Rich; Till, Alison; Bradley, Dan; Trop, Jeff


    Talkeetna Mountains (schist of Hatcher Pass) and, immediately to the south, the northernmost sedimentary sequence of the Matanuska forearc basin (Arkose Ridge Formation). Detrital zircons from the Paleogene Arkose Ridge Formation are as young as 61 and 70 Ma; the population is dominated by a single Late Cretaceous peak at 76 Ma; the oldest zircon is 181 Ma. Sedimentological evidence clearly shows that the conglomeratic Arkose Ridge Formation was derived from the Talkeetna Mountains; our detrital zircon data support this inference. Zircons dated at ca. 90 Ma in the Arkose Ridge sample suggest that buried or unmapped plutons of this age may exist in the Talkeetnas. This is a particularly interesting age as it corresponds to the age of the supergiant Pebble gold-molybdenum-copper porphyry prospect near Iliamna and suggests a new area of prospectivity for Pebble-type deposits. The schist of Hatcher Pass, which was previously assigned a Jurassic depositional age, yielded surprisingly young Late Cretaceous detrital zircons, the youngest at 75 Ma. The probability density curve has four Cretaceous peaks from 76 to 102 Ma, a pair of Late Jurassic peaks at 155 and 166 Ma, three Early Jurassic to Late Triassic peaks at 186, 197, and 213 Ma, minor Carboniferous peaks at 303 and 346 Ma, and a minor Paleoproterozoic peak at 1828 Ma. The schist of Hatcher Pass was largely derived from Mesozoic arc sources, most likely the Wrangellia composite terrane, with some contribution from one or more older, inboard sources, probably including the Yukon-Tanana terrane. We postulate that the schist of Hatcher Pass represents metamorphosed rocks of the Valdez Group that were subducted and then exhumed along the Chugach terrane's 'backstop' during Paleogene transtension. Western Alaska Range - Six detrital zircon samples were collected from a little studied belt of turbidites in Tyonek quadrangle on strike with the Kahiltna assemblage of the central Alaska Range. Many of the sandstones ar

  13. Enhancing the wear resistance of case carburized steel (En 353) by cryogenic treatment

    Bensely, A.; Prabhakaran, A.; Mohan Lal, D.; Nagarajan, G.


    All mechanical components that undergo sliding or rolling contact are subject to some degree of wear. So wear is an important tribological phenomenon while studying the failure of components. The observed frequent failure of crown and pinion due to wear and fatigue lead to this study on effect of cryogenic treatment on the wear resistance of case carburized steel (En 353). This paper deals with the pin on disk wear test without lubrication as per ASTM standard, designation: G 99-95A. The test was carried out for three different load conditions and seven sliding speeds for the samples, which has undergone three different treatment conditions namely conventional heat treatment (CHT), shallow cryogenic treatment (SCT) and deep cryogenic treatment (DCT). It has been found that the wear resistance has been considerably increased due to shallow cryogenic treatment and deep cryogenic treatment includes much more improvement in wear resistance when compared to conventional heat treatment. Also it is concluded that for better wear resistance, it is advisable to go for deep cryogenic treatment. The results are consistent with the previous studies reported in the literature on cryogenic treatments for other materials.

  14. U-Pb-Hf zircon study of two mylonitic granite complexes in the Talas-Fergana fault zone, Kyrgyzstan, and Ar-Ar age of deformations along the fault

    Konopelko, D.; Seltmann, R.; Apayarov, F.; Belousova, E.; Izokh, A.; Lepekhina, E.


    A 2000 km long dextral Talas-Fergana strike-slip fault separates eastern terranes in the Kyrgyz Tien Shan from western terranes. The aim of this study was to constrain an age of dextral shearing in the central part of the fault utilizing Ar-Ar dating of micas. We also carried out a U-Pb-Hf zircon study of two different deformed granitoid complexes in the fault zone from which the micas for Ar dating were separated. Two samples of the oldest deformed Neoproterozoic granitoids in the area of study yielded U-Pb zircon SHRIMP ages 728 ± 11 Ma and 778 ± 11 Ma, characteristic for the Cryogenian Bolshoi Naryn Formation, and zircon grains analyzed for their Lu-Hf isotopic compositions yielded εHf(t) values from -11.43 to -16.73, and their calculated tHfc ages varied from 2.42 to 2.71 Ga. Thus varying Cryogenian ages and noticeable heterogeneity of Meso- to Paleoproterozoic crustal sources was established for mylonitic granites of the Bolshoi Naryn Formation. Two samples of mylonitized pegmatoidal granites of the Kyrgysh Complex yielded identical 206Pb/238U ages of 279 ± 5 Ma corresponding to the main peak of Late-Paleozoic post-collisional magmatism in the Tien Shan (Seltmann et al., 2011), and zircon grains analyzed for their Lu-Hf isotopic compositions yielded εHf(t) values from -11.43 to -16.73, and calculated tHfc ages from 2.42 to 2.71 Ga indicating derivation from a Paleoproterozoic crustal source. Microstructural studies showed that ductile/brittle deformation of pegmatoidal granites of the Kyrgysh Complex occurred at temperatures of 300-400 °C and caused resetting of the K-Ar isotope system of primary muscovite. Deformation of mylonitized granites of the Bolshoi Naryn Formation occurred under high temperature conditions and resulted in protracted growth and recrystallization of micas. The oldest Ar-Ar muscovite age of 241 Ma with a well defined plateau from a pegmatoidal granite of the Kyrgysh Complex is considered as a “minimum” age of dextral motions

  15. Repeated granitoid intrusions during the Neoproterozoic along the western boundary of the Saharan metacraton, Eastern Hoggar, Tuareg shield, Algeria: An AMS and U-Pb zircon age study

    Henry, B.; Liégeois, J. P.; Nouar, O.; Derder, M. E. M.; Bayou, B.; Bruguier, O.; Ouabadi, A.; Belhai, D.; Amenna, M.; Hemmi, A.; Ayache, M.


    The N-S oriented Raghane shear zone (8°30') delineates the western boundary of the Saharan metacraton and is, with the 4°50' shear zone, the most important shear zone in the Tuareg shield. It can be followed on 1000 km in the basement from southern Aïr, Niger to NE Hoggar, Algeria. Large subhorizontal movements have occurred during the Pan-African orogeny and several groups of granitoids intruded during the Neoproterozoic. We report U-Pb zircon datings (laser ICP-MS) showing that three magmatic suites of granitoids emplaced close to the Raghane shear zone at c. 790 Ma, c. 590 and c. 550 Ma. A comprehensive and detailed (158 sites, more than 1000 cores) magnetic fabric study was performed on 8 plutons belonging to the three magmatic suites and distributed on 200 km along the Raghane shear zone. The main minerals in all the target plutons do not show visible preferential magmatic orientation except in narrow shear zones. The AMS study shows that all plutons have a magnetic lineation and foliation compatible with the deformed zones that are zones deformed lately in post-solidus conditions. These structures are related to the nearby mega-shear zones, the Raghane shear zone for most of them. The old c. 793 Ma Touffok granite preserved locally its original structures. The magnetic structures of the c. 593 Ma Ohergehem pluton, intruded in the Aouzegueur terrane, are related to thrust structures generated by the Raghane shear zone while it is not the case of the contemporaneous plutons in the Assodé-Issalane terrane whose structures are only related to the subvertical shear zones. Finally, the c. 550 Ma granite group has magnetic structure related to the N-S oriented Raghane shear zone and its associated NNE-SSW structures when close to them, but NW-SE oriented when further. These NW-SE oriented structures appear to be characteristic of the late Neoproterozoic evolution of the Saharan metacraton and are in relation to the convergence with the Murzuq craton. This

  16. A numerical model for vacuum carburization of an automotive gear ring

    Kim, Dong-Wan; Cho, Yi-Gil; Cho, Hoon-Hwe; Kim, Sung-Hwan; Lee, Won-Beom; Lee, Myoung-Gyu; Han, Heung Nam


    A vacuum carburizing-heat treatment of an annulus gear ring is simulated via a carburized predictive finite element model that accounts for both heat transfer and carbon diffusion. Profiles of carbon concentration along the depth of the gear ring were calculated and are congruent with measured values, which were obtained by a glow discharge spectrometer (GDS). While sensitive to carbon content, rigorous observation of the microstructures in the gear ring after heat treatment was attempted by transmission electron microscopy (TEM). The finial various martensitic microstructures in several parts of the gear ring may be well explained on the basis of the calculated carbon concentration.

  17. Influence of vacuum carburizing treatment on fatigue crack growth characteristic in DSG2

    K. Nambu; Egami, N.


    The aim of this research is to clarify the influence of vacuum carburizing on the fatigue-crack progress characteristics of DSG2 steel. The test specimen tempering material (QT material) and vacuum carburizing material (VC material) has been used. The fatigue-crack progress was examined by subjecting the samples to four-point bending. The loading-capacity fixed experiment was done using a maximum load of Pmax = 4000– 7000 N. The ΔK fixed experiment was done using a load of ΔK = 18...

  18. Monitoring preparation and phase transitions of carburized W(1 1 0) by reflectance difference spectroscopy

    Bachmann, Magdalena [Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria); Memmel, Norbert, E-mail: [Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria); Bertel, Erminald [Institute of Physical Chemistry, University of Innsbruck, Innrain 52a, A-6020 Innsbruck (Austria); Denk, Mariella; Hohage, Michael; Zeppenfeld, Peter [Institute of Experimental Physics, Johannes Kepler University Linz, Altenbergerstr. 69, A-4040 Linz (Austria)


    Highlights: Black-Right-Pointing-Pointer Real-time in situ monitoring of W(1 1 0) surface cleaning. Black-Right-Pointing-Pointer Real-time in situ monitoring of carburazation kinetics on W(1 1 0) by RDS. Black-Right-Pointing-Pointer Phase transformation R(15 Multiplication-Sign 3)-C/W(1 1 0)-R(15 Multiplication-Sign 12)-C/W(1 1 0) studied by RDS, AES and LEED. - Abstract: Reflectance difference spectroscopy (RDS) is applied to follow in situ the preparation of clean and carburized W(1 1 0) surfaces and to study the temperature-induced transition between the R(15 Multiplication-Sign 3) and R(15 Multiplication-Sign 12) carbon/tungsten surface phases. RDS data for this transition are compared to data obtained from Auger-electron spectroscopy and low-energy electron diffraction. All techniques reveal that this transition, occurring around 1870 K, is reversible with a small hysteresis, indicating a first-order-like behaviour. The present results also prove a high surface sensitivity of RDS, which is attributed to the excitation of electronic p-like surface resonances of W(1 1 0).

  19. Pitting and Bending Fatigue Evaluations of a New Case-Carburized Gear Steel

    Krantz, Timothy; Tufts, Brian


    The power density of a gearbox is an important consideration for many applications and is especially important for gearboxes used on aircraft. One approach to improving power density of gearing is to improve the steel properties by design of the alloy. The alloy tested in this work was designed to be case-carburized with surface hardness of Rockwell C66 after hardening. Test gear performance was evaluated using surface fatigue tests and single-tooth bending fatigue tests. The performance of gears made from the new alloy was compared to the performance of gears made from two alloys currently used for aviation gearing. The new alloy exhibited significantly better performance in surface fatigue testing, demonstrating the value of the improved properties in the case layer. However, the alloy exhibited lesser performance in single-tooth bending fatigue testing. The fracture toughness of the tested gears was insufficient for use in aircraft applications as judged by the behavior exhibited during the single tooth bending tests. This study quantified the performance of the new alloy and has provided guidance for the design and development of next generation gear steels.

  20. Developing Zircon as a Probe of Planetary Impact History

    Wielicki, Matthew


    the Hadean population remains difficult and this study hopes to develop criteria to recognize impact zircon and possibly provide constraints on the early impactor flux. Five large terrestrial craters, Vredefort and Morokweng, South Africa, Sudbury and Manicouagan, Canada, and Popigai, Russia, are the focus of this study as smaller craters do not have the energy to produce thick melt sheets, which persist over time-scales sufficient for crystallization of zircon, permitting geochemical and geochronological analysis. Geochemical analysis of these impact-produced zircons yields similar chemical signatures to endogenic igneous zircon from crustal melts and highlights the need for well-developed criteria for discriminating impact and endogenic grains for impact geochronology. One such criterion is modeling of impact zircon crystallization temperature spectra for simulated impact events on targets of varying composition. Provided some assumptions the zircon crystallization spectra can be estimated from well established Zr systematics in crustal melts. Results for impacts into an Archean terrestrial surface (used as a proxy for the Hadean as little to no rock record exists >4.0 Ga) yields a crystallization spectra significantly higher than that reported for the Hadean zircon population and appears to rule out impacts as a dominant source for these ancient grains. When no dateable impact melt sheet exists, either due to the lack of energy of the impact itself or from subsequent erosion at Earth's surface, loss of radiogenic lead, Pb*, has been suggested as an alternative method to date the event. Pb*-loss was investigated from target rocks from Vredefort and Morokweng and suggests that Pb* diffusion, even in zircon isolated from shocked and brecciated target rocks, is remarkably slow. This may explain the seeming lack of 'reset' zircon in terrestrial impactites. Little is known about Pb* diffusion pathways associated with shock microstructures introduced during impact

  1. 1.8 Billion Years of Detrital Zircon Recycling Calibrates a Refractory Part of Earth's Sedimentary Cycle.

    Hadlari, Thomas; Swindles, Graeme T; Galloway, Jennifer M; Bell, Kimberley M; Sulphur, Kyle C; Heaman, Larry M; Beranek, Luke P; Fallas, Karen M


    Detrital zircon studies are providing new insights on the evolution of sedimentary basins but the role of sedimentary recycling remains largely undefined. In a broad region of northwestern North America, this contribution traces the pathway of detrital zircon sand grains from Proterozoic sandstones through Phanerozoic strata and argues for multi-stage sedimentary recycling over more than a billion years. As a test of our hypothesis, integrated palynology and detrital zircon provenance provides clear evidence for erosion of Carboniferous strata in the northern Cordillera as a sediment source for Upper Cretaceous strata. Our results help to calibrate Earth's sedimentary cycle by showing that recycling dominates sedimentary provenance for the refractory mineral zircon.

  2. Zircon U-Pb dating and geochemical study of the Xianggou granite in the Ma’anqiao gold deposit and its relationship with gold mineralization

    LEE; Ben


    Single zircon LA-ICP-MS U-Pb dating and lithogeochemical studies have been performed on the Xianggou monzonitic granitic porphyry outcropped in the Ma’anqiao gold deposit.A weighted average U-Pb age of 242.0±0.8 Ma for Xianggou monzonitic porphyry has been obtained.This corresponds with the conclusions of previous studies indicating a syn-orogenic age (242±21 Ma) of the Qinling Orogenic Belt,suggesting that the formation of the Xianggou granite should be associated with the collisional event of the North China Plate and the Yangtze Plate in the Indosinian period.The Xianggou granite is characterized by the high silicon and alkali of high K calc-alkaline series granites.It is rich in Al (Al2O3=14.49%-15.61%) and Sr (457.10-630.82 ppm),poor in Y (<16 ppm) and HREE (Yb<0.45 ppm),and exhibits high ratios of Sr/Y (76.24-97.34) and (La/Yb)N (29.65-46.10),as well as strongly fractionated REE patterns.These geochemical characteristics suggest the Xianggou granite can be classified as C-type adakitic rock.The initial Sr isotope ratios for the Xianggou granite vary from 0.70642 to 0.70668,εNd(t) values from -4.54 to -3.98,and TDM values from 1152 Ma to 1220 Ma.The low εNd(t) and ISr and high TDM values,as well as Na2O/K2O ratios of the Xianggou granite are close to 1 (Na2O/K2O=0.95-1.10),indicating that it is not an I-type adakite formed by partial melting of the subducting oceanic crust,nor adakitic rock formed by melting of the underplated basaltic lower crust,but the product of partial melting of the nonunderplated basaltic thickened lower crust.Zircons from the Xianggou pluton have a homogeneous Hf isotopic composition with negative εHf(t) values (between -9.7 and -5.9,with an average of -6.9),indicating that the rock-forming materials were mostly extracted from the ancient crust,not from the depleted mantle.The Xianggou monzonitic granitic porphyry is rich in LILE and LREE and depleted in HSFE,HREE and Y;the composition of trace element and REE are similar to

  3. Zircon U-Pb and Lu-Hf isotope study of the Neoproterozoic Haizhou Group in the Sulu orogen: Provenance and tectonic implications

    Zhou, Jian-Bo; Wilde, Simon A.; Liu, Fu-Lai; Han, Jie


    The Neoproterozoic Haizhou Group crops out sporadically in the Sulu orogen in east-central China. It is divided into the Jinping and Yuntai formations and consists of quartzite, quartz schist, marble and graphite- and apatite-bearing sequences. Major and trace element data for quartz schist from the two formations indicate that these rocks have a greywacke protolith and have been deposited during strong tectonic activity. LA-ICPMS U-Pb dating of detrital zircon yields ages of 635 to 1074 Ma for three samples from the Jinping Formation and 611 to 943 Ma for two samples from the Yuntai Formation. More than 78% of the detrital zircons from the two formations have U-Pb ages grouped between 700 and 890 Ma, with two clusters peaking at 758 Ma and 828 Ma, respectively. This indicates that their provenance is magmatic rocks of Neoproterozoic age that have a tectonic affinity to the South China Block (SCB). A few older zircon populations with peak U-Pb ages at 943 and 1074 Ma are also present. A younger population shows peaks at 661 and 611 Ma. This suggests that deposition of the Haizhou Group was later than ~ 611 Ma rather than during the Mesoproterozoic as previously thought. Zircon Lu-Hf isotope data collected from the same U-Pb sites show negative ɛHf(t) values of - 22.8 to - 7.4 and Hf model ages of 2341 to 3100 Ma. This indicates that the Neoproterozoic magmatic rocks were derived from reworking of ancient Paleoproterozoic to Archean crust. The results support the contention that the Haizhou Group is similar to the Wulian Group at the northwestern edge of the Sulu orogen, both having a SCB affinity, but that the Penglai Group does not belong to the SCB because of the absence of Neoproterozoic ages. This lends support to the conclusion that the Triassic suture between the North China and South China blocks is located along the Baichihe-Yantai Fault, which lies north of the Wulian Complex and south of the Jiaobei Terrane; thus the Wulian-Yantai Fault is not the suture

  4. Optical amplification in disordered electrooptic Tm3+ and Ho3+ codoped lanthanum-modified lead zirconate titanate ceramics and study of spectroscopy and communication between cations

    Zhao, Hua; Zhang, Kun; Xu, Long; Sun, Fankui; Chen, Xuesheng; Li, Kewen K.; Zhang, Jingwen


    Rare earth doped electro-optic (EO) ceramics of lanthanum-modified lead zirconate titanate (PLZT) are promising in building multifunctional optical devices, by taking advantage of both EO effect and optical activity. In this work, the combination of the measured spectra of absorption and photoluminescence, the fluorescent decay, the calculated Judd-Ofelt parameters, and measured single pass gain in Tm3+, Ho3+ codoped PLZT ceramics have marked them out as promising gain media in building electrically controllable lasers/optical amplifiers and other multifunctional devices. Optical energy storage was also observed in the optical amplification dynamics.

  5. Significance of zircon trace element geochemistry, the Shihu gold deposit,western Hebei Province, North China

    CAO Ye; LI Shengrong; ZHANG Huafeng; LIU Xiaobin; LI Zhenzhen; AO Chong; YAO Meijuan


    sources of ore-forming materials were from Precambrian host rocks. Our results significantly enhanced the usefulness of zircon in crustal studies of the North China craton and as an indicator mineral in mineral exploration of the Taihang region.

  6. 圆锥从动齿轮的渗碳工艺探析%Explore and Analysis of Carburization Process for Driven Bevel Gear Carburizing



    通过多次试验,解决了圆锥从动齿轮渗碳后淬火变形及二次压淬时出现的氧化脱碳问题,并提出了合理建议.%The problems of quenching deformation, oxidation and decarburization of driven bevel gear after carburizing and then the second pressure quenching were solved through several experiments, and the reasonable proposal was put forward.

  7. The zircon evidence of temporally changing sediment transport—the NW Gondwana margin during Cambrian to Devonian time (Aoucert and Smara areas, Moroccan Sahara)

    Gärtner, Andreas; Youbi, Nasrrddine; Villeneuve, Michel; Sagawe, Anja; Hofmann, Mandy; Mahmoudi, Abdelkader; Boumehdi, Moulay Ahmed; Linnemann, Ulf


    Detrital zircon provenance studies are an established tool to develop palaeogeographic models, mostly based on zircon of siliciclastic rocks and isotope data. But zircon is more than just istopes and features well definable morphological characteristics. The latter may indicate single grain transport histories independent of the individual grade of concordance. This additional tool for palaeogeoraphic reconstructions was tested on zircon from siliciclastic and carbonate sedimentary rocks of Palaeozoic age from the Aoucert and Smara areas of the Souttoufides, while findings of zircon in limestone generally open new archives for sedimentary provenance analysis. The morphologies—length, width, roundness, grain surfaces—of 834 detrital zircons from sediments of allochthonous Cambrian, and (par-)autochthonous Ordovician, and Devonian units were studied, while 772 of them were analysed for their U-Th-Pb isotopes by LA-ICP-MS. Mesoproterozoic zircon contents of more than 10% in the Cambrian sediments exclude the West African Craton (WAC) as exclusive source area. Thus, at least one additional external source is suggested. This is likely the western Adrar Souttouf Massif with its significant Mesoproterozoic zircon inheritance, or comparable, yet unknown sources. Decreasing Mesoproterozoic zircon age populations in Ordovician sediments are thought to be linked to the rifting of the terranes in the course of the Rheic Ocean opening and a predominant supply of WAC detritus. The Devonian sediments likely contain reworked material from the Cambrian siliciclastics, which is shown by the zircon age distribution pattern and the zircon morphologies. Therefore, multiple shifts in the direction of sedimentary transport are indicated.

  8. Thermoluminescence of zircon : a kinetic model

    Turkin, AA; van Es, HJ; Vainshtein, DI; den Hartog, HW


    The mineral zircon, ZrSiO4, belongs to a class of promising materials for geochronometry by means of thermoluminescence (TL) dating. The development of a reliable and reproducible method for TL dating with zircon requires detailed knowledge of the processes taking place during exposure to ionizing

  9. Mineral zircon : A novel thermoluminescence geochronometer

    Van Es, HJ; Vainshtein, DI; De Meijer, RJ; Den Hartog, HW; Donoghue, JF; Rozendaal, A


    Mineral zircon contains trace amounts (typically 10-1000 ppm) of the alpha-emitters uranium and thorium, which irradiate this mineral internally. This outstanding feature of zircon turns out to be extremely useful when this mineral is applied as a thermoluminescence (TL) dating medium, because the b

  10. Grenville Zircon Fertility, Baby Boom, and Baby Boom Echo; Natural Bias in the Detrital Zircon Record

    Moecher, D. P.; Samson, S. D.


    Grenville-aged (~1150-1050 Ma) granitoids of eastern Laurentia exposed in Appalachian basement massifs are as much as 20 times more Zr-rich and much more fertile for crystallizing zircon compared to Paleozoic Laurentian granitoids of the Eastern Blue Ridge, Inner Piedmont, and Carolina terranes. Erosion of Grenville source rocks generates disproportionately large numbers and/or sizes of detrital zircon compared to less fertile magmatic sources. The latter are essentially undetectable by standard detrital zircon provenance methods (SHRIMP or LA-ICP-MS analysis of magmatic cores of >100 micron grains). Grenvillian zircon fertility biased the Neoproterozoic to Recent detrital record as a result of: (1) zircon durability and insolubility in aqueous fluids means detrital zircons eroded from Grenville basement terranes are recycled during repeated orogenesis; (2) inertness of zircon below upper amphibolite facies (onset of anatexis), and high Zr resulting from concentration of detrital zircon in sedimentary protoliths, means dominantly metasedimentary terranes will fail to generate sufficient new zircon corresponding in age to the time of accretion of those terranes to Laurentia. Zircon growth under incipient anatectic conditions generates new zircon as overgrowths on detrital magmatic cores; overgrowths are often too thin to analyze by ion or laser beam. In this case, metasedimentary terranes may be rendered essentially undetectable. New `magmatic' zircon may be generated with greater degrees of anatexis, but might be inferred to be of plutonic, not metamorphic, parentage. Grenville modes dominate detrital zircon age distributions for: Laurentian Neoproterozoic rift basins; Neoproterozoic to Lower Ordovician passive margin sequences; Appalachian Paleozoic syn-orogenic clastic sequences; Appalachian metasedimentary terranes; and modern rivers. The latter is surprising since Grenville terranes comprise baby boom' that echoed through later orogenies. The natural Grenville

  11. Structural recovery of self-irradiated natural and {sup 238}Pu-doped zircon in an acidic solution at 175 deg. C

    Geisler, Thorsten [Institut fuer Mineralogie, University of Muenster, Corrensstrasse 24, 48149 Muenster (Germany)]. E-mail:; Burakov, Boris [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation); Yagovkina, Maria [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation); Garbuzov, Vladimir [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation); Zamoryanskaya, Maria [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation); Zirlin, Vladimir [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation); Nikolaeva, Larisa [Laboratory of Applied Mineralogy and Radiogeochemistry, V.G. Khlopin Radium Institute, 28, 2nd Murinskiy ave., St. Petersburg, 194021 (Russian Federation)


    We have investigated the aqueous stability of self-irradiated natural and synthetic {sup 238}Pu-doped zircon (4.7 wt% of {sup 238}Pu) in an acidic solution at 175 deg. C. Both zircon samples have suffered a similar deg.ree of self-irradiation damage, as given by their deg.ree of amorphization. X-ray diffraction measurements revealed that during the hydrothermal treatment only the disordered crystalline remnants recovered in the natural zircon, whereas in the {sup 238}Pu-doped zircon the amorphous phase strongly recrystallized. Such a different alteration behavior of natural and Pu-doped zircon is discussed in terms of two fundamentally different alteration mechanisms. Our results demonstrate that further experimental studies with Pu-doped zircon are required before any reliable prediction about the long-term aqueous stability of an actinide waste form based on zircon can be made.

  12. Microstructure and Cavitation Erosion Properties of Ceramic Coatings Fabricated on Ti-6Al-4V Alloy by Pack Carburizing

    Li, Haibin; Cui, Zhenduo; Li, Zhaoyang; Zhu, Shengli; Yang, Xianjin


    In this study, Ti-6Al-4V alloy was processed by pack carburizing to improve the cavitation erosion behavior. X-ray diffraction and scanning-electron microscopy (SEM) analysis showed that a uniform and crack-free ceramic coating formed on the surface of the treated samples. The coating layer comprised primary TiC and less oxide. Cavitation erosion experiment results indicated that the treated samples have the factor of 3.44 to 6.68 increase in cavitation erosion resistance ( R e) as compared with the as-received sample. The ceramic coatings with high hardness and good metallurgical bonding were responsible for the enhanced cavitation erosion properties. When the coatings were treated at condition of high temperature and/or long time, the R e was enervated due to the thin oxide film formed at the outermost surface. Cavitation erosion mechanism for the coatings was characterized as brittle mode by SEM observation of the worn surfaces.

  13. Monitoring preparation and phase transitions of carburized W(1 1 0) by reflectance difference spectroscopy.

    Bachmann, Magdalena; Memmel, Norbert; Bertel, Erminald; Denk, Mariella; Hohage, Michael; Zeppenfeld, Peter


    Reflectance difference spectroscopy (RDS) is applied to follow in situ the preparation of clean and carburized W(1 1 0) surfaces and to study the temperature-induced transition between the R(15 × 3) and R(15 × 12) carbon/tungsten surface phases. RDS data for this transition are compared to data obtained from Auger-electron spectroscopy and low-energy electron diffraction. All techniques reveal that this transition, occurring around 1870 K, is reversible with a small hysteresis, indicating a first-order-like behaviour. The present results also prove a high surface sensitivity of RDS, which is attributed to the excitation of electronic p-like surface resonances of W(1 1 0).

  14. Porous molybdenum carbide nano-octahedrons synthesized via confined carburization in metal-organic frameworks for efficient hydrogen production.

    Wu, Hao Bin; Xia, Bao Yu; Yu, Le; Yu, Xin-Yao; Lou, Xiong Wen David


    Electrochemical water splitting has been considered as a promising approach to produce clean and sustainable hydrogen fuel. However, the lack of high-performance and low-cost electrocatalysts for hydrogen evolution reaction hinders the large-scale application. As a new class of porous materials with tunable structure and composition, metal-organic frameworks have been considered as promising candidates to synthesize various functional materials. Here we demonstrate a metal-organic frameworks-assisted strategy for synthesizing nanostructured transition metal carbides based on the confined carburization in metal-organic frameworks matrix. Starting from a compound consisting of copper-based metal-organic frameworks host and molybdenum-based polyoxometalates guest, mesoporous molybdenum carbide nano-octahedrons composed of ultrafine nanocrystallites are successfully prepared as a proof of concept, which exhibit remarkable electrocatalytic performance for hydrogen production from both acidic and basic solutions. The present study provides some guidelines for the design and synthesis of nanostructured electrocatalysts.

  15. Carburization and heat treatment to cause carbide precipitation in gamma/gamma prime-delta eutectic alloys

    Tewari, S. N.; Dreshfield, R. L.


    In an attempt to improve their longitudinal shear strength, several directionally solidified eutectic alloy compositions with minor element modifications were pact, carburized, and heat treated to provide selective carbide precipitation at the cell and grain boundaries. The directionally solidified Ni-17.8 Nb-6Cr-2.5Al-3Ta (weight percent) alloy was selected for the shear strength evaluation because it showed the shallowest delta-denuded zone at the carburized surface. The carburization-carbide precipitation treatment, however, did not appear to improve the longitudinal shear strength of the alloy.

  16. Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

    Latif, Saadia; Mehmood, Mazhar; Ahmad, Jamil; Aslam, Muhammad; Ahmed, Maqsood; Zhang, Zhi-dong


    In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 °C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

  17. Ni-WC composite coatings by carburizing electrodeposited amorphous and nanocrystalline Ni-W alloys

    Latif, Saadia [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Mehmood, Mazhar, E-mail: [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmad, Jamil; Aslam, Muhammad [National Centre for Nanotechnology, Department of Chemical and Materials Engineering, Pakistan Institute of Engineering and Applied Sciences (PIEAS), Nilore, Islamabad 45650 (Pakistan); Ahmed, Maqsood [Physics Division, PINSTECH, P.O. Nilore, Islamabad (Pakistan); Zhang Zhidong [Institute of Metals Research, Chinese Academy of Science, Shenyang (China)


    In situ formation of tungsten carbide in the matrix of FCC nickel has been achieved by carburizing of the electrodeposited Ni-W alloy coatings. The size of the carbide particles ranges between 100 and 500 nm. The carbide phase is also present in the form of very small precipitates inside the nickel grains. The size of such precipitates is between 10 and 40 nm. The carburizing environment was created by introducing a flowing mixture of vaporized 95.5% alcohol (0.25 ml/min, liquid) and argon (0.5 L/min, gas) into the carburizing furnace. Supersaturated nature of electrodeposited amorphous and nanocrystalline alloys, in addition to high diffusivity, have been attributed for the formation of carbide phase in the deposits at a temperature range of 700-850 deg. C. The carbide-metal interface is clean and the composite coatings are compact. Hardness values up to about 1100 KHN are achieved. Hardness increases with tungsten content and carburizing temperature.

  18. Deciphering tectonic provenance signatures from the trace element geochemistry of igneous zircon

    Grimes, C. B.; Wooden, J. L.; Vazquez, J. A.


    The ability to correlate stable isotope ratios and trace element signatures with age on single crystals, coupled with resistance to chemical and physical weathering make zircon a useful complement in a wide range of geologic investigations. Zircon trace element concentrations broadly reflect parental magma composition, although studies show that crystal chemistry also imparts a significant control on the shape of REE patterns. Concentrations of select elements (e.g., Hf) and various trace element ratios (e.g., Th/U, Yb/Gd, Eu/Eu*) commonly correlate with crystallization temperature (from Ti-in-zircon thermometry) for suites of zircon precipitated during magmatic fractionation in zircon-saturated systems. Other trace element ratios, primarily U/Yb and Th/Yb plotted against Hf or Y discriminate zircon sampled in situ from mid-ocean ridges from those formed in arc-related ('continental') settings. However, these geochemical discriminations are limited in that ~20% of published mid-ocean ridge zircon compositions plot within the 'continental' zircon field and they fail to distinguish zircon from other magmatic settings such as ocean islands. To improve geochemical zircon discrimination diagrams for diverse tectonic environments, trace element criteria that distinguish lavas from different tectonic settings are considered along with a broad suite of elements routinely measured by the Stanford-USGS SHRIMP-RG ion probe. Arc-related magmas exhibit enrichment in large ion lithophile (LIL) elements (i.e., U, Th) with respect to typical MORB, and are depleted in niobium (Nb) with respect to both OIB and MORB lavas. OIB lavas are typically enriched in LIL with respect to MORB, but lack the Nb-depletion characteristic of arcs. The ratios U/Yb, Yb/Nb, and Th/Nb can therefore be used to discriminate lavas from these different settings. Discrimination diagrams based on these elemental ratios in zircon also define separate (though partly overlapping) fields for modern mid

  19. Annealing of natural metamict zircons: II high degree of radiation damage

    Colombo, M


    In situ time-dependent high-temperature X-ray powder diffraction was used to study the amorphous to crystalline transition in natural zircons which are characterized by a high degree of radiation damage. It was possible to distinguish two stages of the annealing process: (i) the recovery of the heavily disturbed but still crystalline domains and (ii) the recrystallization of the amorphous regions. The first stage is very fast under the chosen experimental conditions and, at least apparently, is not thermally activated. The second stage is a diffusion-controlled process, whose products (zircon or zircon and zirconia phases) are strongly correlated to the annealing temperature.

  20. Interpretation of zircon coronae textures from metapelitic granulites of the Ivrea–Verbano Zone, northern Italy: two-stage decomposition of Fe–Ti oxides

    E. Kovaleva


    Full Text Available In this study, we report the occurrence of zircon coronae textures in metapelitic granulites of the Ivrea–Verbano Zone. Unusual zircon textures are spatially associated with Fe–Ti oxides and occur as (1 vermicular-shaped aggregates 50–200 µm long and 5–20 µm thick and as (2 zircon coronae and fine-grained chains, hundreds of micrometers long and ≤ 1 µm thick, spatially associated with the larger zircon grains. Formation of such textures is a result of zircon precipitation during cooling after peak metamorphic conditions, which involved: (1 decomposition of Zr-rich ilmenite to Zr-bearing rutile, and formation of the vermicular-shaped zircon during retrograde metamorphism and hydration; and (2 recrystallization of Zr-bearing rutile to Zr-depleted rutile intergrown with quartz, and precipitation of the submicron-thick zircon coronae during further exhumation and cooling. We also observed hat-shaped grains that are composed of preexisting zircon overgrown by zircon coronae during stage (2. Formation of vermicular zircon (1 preceded ductile and brittle deformation of the host rock, as vermicular zircon is found both plastically and cataclastically deformed. Formation of thin zircon coronae (2 was coeval with, or immediately after, brittle deformation as coronae are found to fill fractures in the host rock. The latter is evidence of local, fluid-aided mobility of Zr. This study demonstrates that metamorphic zircon can nucleate and grow as a result of hydration reactions and mineral breakdown during cooling after granulite-facies metamorphism. Zircon coronae textures indicate metamorphic reactions in the host rock and establish the direction of the reaction front.

  1. Theoretical study of silicon carbide under irradiation at the nano scale: classical and ab initio modelling; Etude theorique a l'echelle nanometrique du carbure de silicium sous irradiation: modelisation classique et ab initio

    Lucas, G


    The behaviour of silicon carbide under irradiation has been studied using classical and ab initio simulations, focusing on the nano scale elementary processes. First, we have been interested in the calculation of threshold displacement energies, which are difficult to determine both experimentally and theoretically, and also the associated Frenkel pairs. In the framework of this thesis, we have carried out simulations in classical and ab initio molecular dynamics. For the classical approach, two types of potentials have been used: the Tersoff potential, which led to non satisfactory results, and a new one which has been developed during this thesis. This potential allows a better modelling of SiC under irradiation than most of the empirical potentials available for SiC. It is based on the EDIP potential, initially developed to describe defects in silicon, that we have generalized to SiC. For the ab initio approach, the feasibility of the calculations has been validated and average energies of 19 eV for the C and 38 eV for the Si sublattices have been determined, close to the values empirically used in the fusion community. The results obtained with the new potential EDIP are globally in agreement with those values. Finally, the elementary processes involved in the crystal recovery have been studied by calculating the stability of the created Frenkel pairs and determining possible recombination mechanisms with the nudged elastic band method. (author)

  2. Enhanced wear and corrosion resistance of plasma electrolytic carburized layer on T8 carbon steel

    Wu, Jie; Wang, Bin; Zhang, Yifan; Liu, Run [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Xia, Yuan; Li, Guang [Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190 (China); Xue, Wenbin, E-mail: [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)


    A hardening layer of 70 μm on T8 carbon steel was fabricated by plasma electrolytic carburizing (PEC) in glycerol solution at 380 V with 3 min treatment. The discharge process was characterized using optical emission spectroscopy (OES), and the electron temperature in plasma envelope was determined. Meanwhile, diffusion coefficient of carbon was calculated on the basis of carbon concentration profile. The tribological property of carburized steel under dry sliding against ZrO{sub 2} ball was measured by a ball-disc friction and wear tester. The corrosion behaviors were evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). It was found that the carburized layer mainly contained α-Fe and Fe{sub 3}C phases with maximum hardness of 620 HV. The PEC treatment significantly decreased the friction coefficient from 0.4 to 0.1. The wear rate of PEC treated steel was about 5.86 × 10{sup −6} mm{sup 3}/N·m, which was less than 1/4 of T8 steel substrate. After PEC treatment, the wear and corrosion resistance of T8 steel were improved. Particularly, the pitting corrosion of steel substrate was obviously suppressed. - Highlights: • Electron temperature in plasma electrolytic carburizing process is determined. • Diffusion coefficient of carbon in PEC is higher than conventional carburizing. • Wear and corrosion resistance of T8 steel are both improved after PEC treatment. • Pitting corrosion of steel substrate is obviously suppressed by PEC treatment.

  3. Rhyolite magma evolution recorded in isotope and trace element composition of zircon from Halle Volcanic Complex

    Słodczyk, E.; Pietranik, A.; Breitkreuz, C.; Fanning, C. M.; Anczkiewicz, R.; Ehling, B.-C.


    Voluminous felsic volcanic magmas were formed in Central Europe at the Carboniferous/Permian boundary in numerous pull-apart basins; one of which is the Saale Basin, which holds the Halle Volcanic Complex (HVC), the focus of this study. The rhyolites in the HVC formed laccoliths and scarce lavas, and occur in two different textural types: fine and coarse porphyritic. Zircon isotope and trace element composition was analysed in four units, two per each textural type. Zircon from the different units shows similar ranges in εHf (- 4.1 to - 8.1) and δ18O values (6.51-8.26), indicating similar sources and evolution processes for texturally diverse rhyolites from the HVC. Scarce inherited zircon ranges from ~ 315 Ma to ~ 2100 Ma with the major groupings around 315-550 Ma. These ages are typical for Devonian arc magmatic activity (350-400 Ma) and Cadomian igneous rocks (500-600 Ma), which occur in the basement presently underlying the HVC. Therefore, the source of the rhyolites was multicomponent and probably represented by a basement composed of various crystalline rocks. Trace elements in zircon show similar distributions in all analysed samples, which is broadly consistent with zircon cores crystallizing in a less evolved magma undergoing limited fractional crystallization, whilst the zircon rims crystallized from a magma undergoing extensive fractional crystallization of major and accessory minerals. Interestingly, comparison of the zircon composition in HVC rhyolites and other rhyolites worldwide shows that the observed trends are similar in such rhyolites despite the values being different. This may suggest that most of the zircon in rhyolites crystallizes at a similar stage in the rhyolite magma evolution, from magmas undergoing extensive crystallization of major phases and apatite. The implication is that most of the zircon represents late stage crystallization, but also that antecrystic component may be present and preserve information on the development of

  4. Dispersants in an organic medium: synthesis and physicochemical study of dispersants for fuels and lubricants; Dispersants en milieu organique: synthese et etude physicochimique de dispersants pour carburants et lubrifiants

    Dubois-Clochard, M.C.


    Carbonaceous deposits coming from the fuel and the lubricant are known to form over time at critical locations in an engine. In general, the deposits have an adverse effect on four functional areas which are the fuel metering system, the intake system, the lubrication system and the combustion chambers. These deposits can degrade vehicle performance and drive-ability, reduce fuel economy, increase fuel consumption and pollutant emissions and may lead to the destruction of the engine. In order to remedy these problems, detergent-dispersant additives are used in fuels and lubricants to avoid or decrease deposit adhesion on metallic surfaces and prevent from deposit aggregation. These products are mainly polymer surfactants and in this work, poly-iso-butenyl-succinimide of different structures have been studied. Firstly, 'comb like' polymers have been synthesized. Then they have been compared to classical di-bloc additives in terms of performance and action mechanism. These additives are adsorbed from their hydrophilic polyamine part on the acidic functions of the carbon black surface chosen as an engine deposit model and on the aluminium oxide function of an aluminium powder chosen as an engine wall model. The adsorption increases with temperature on the two solids. Their affinity with the solid surface increases with the length of the hydrophilic part. In the same way, changing the di-bloc structure for a comb like one lead to a better adsorption. At low concentration, it has been shown that the adsorption phenomenon was irreversible, due to the polymer structure of the polar part. Depending on the space required by the hydrophilic part on the solid surface, a more of less dense monolayer is formed. At higher concentrations, an important increase of the adsorbed amount appears. This phenomenon is totally reversible showing that the interactions additive / additive are weak. The dispersing efficiency of a comb like structure is better than a di-bloc one as

  5. Experimental Study on Pre-oxidization and Cyanide Carburizing of Refractory Gold Concentrate Containing High Sulphur Content%难浸高硫金精矿细菌预氧化--氰化浸出试验研究

    范道焱; 董博文


    Biological oxidation-leaching experiments of refractory gold concentrate containing high sulfur was carried out.The relationships of leaching rate of gold with the process parameter of pulp density,pH value,the reaction temperature,grinding fineness,oxidation time were studied by experiment,and the oxidated liquid was under the reuse treatment.Under the optimal process conditions,including slurry concentration of 16%,the pH value 1.2~1.4,the reaction temperature was 40 ℃,grinding fineness of less than 0.043 mm accounted for more than 94.8%,the oxidation time condition for 8 days.The ore sample was dealed with the bacterial oxidation processing technology,the oxidation rate of sulfur reached 86.0%,the leaching rate of gold was improved from 23.4%to 92.6%.%针对甘肃亚特含高硫难浸金精矿开展了生物预氧化-氰化浸出试验研究,考察了细菌预氧化过程中矿浆浓度、pH值、反应温度、磨矿细度和氧化时间等参数条件对浸出的影响,并对氧化后液进行回用处理。结果表明,在矿浆浓度为16%、pH值为1.2~1.4、反应温度为40℃、磨矿细度<0.043 mm占94.8%以上以及氧化时间为8 d的条件下,采用细菌预氧化处理技术对矿样进行处理,硫氧化率达86.0%,金浸出率由直接氰化浸出率的23.4%提高到92.6%。

  6. Formation of carburized layer structure with reverted austenite on low-carbon martensitic steel 12Kh2G2NMFT

    Ivanov, A. S.; Bogdanova, M. V.


    The structure of surface layer in low-carbon martensitic steel 12Kh2G2NMFT obtained by carburizing followed by high-temperature tempering and quenching from the intercritical temperature range is investigated.

  7. Zircon LA-ICP-MS U-Pb dating and Sr-Nd isotope study of the Guposhan granite complex, Guangxi, China

    GU Shengyan; HUA Renmin; QI Huawen


    Zircon U-Pb dating by the LA-ICP-MS method was applied to determining the ages of different units of the Guposhan granite complex, among which the East Guposhan unit is 160.8±1.6 Ma, the West Guposhan unit is 165.0±1.9 Ma, and the Lisong unit is 163.0±1.3 Ma in age. Much similarity in ages of the three units has thus proved that the whole Guposhan granite complex was formed in the same period of time. They were the products of large-scale granitic magmatism through crust-remelting in the first stage of the Middle Yanshanian in South China. However, the three units have differences both in petrology and in geochemistry. Besides the differences in major, trace and rare-earth elements, they are distinct in their Rb-Sr and Sm-Nd isotopic compositions. The East Guposhan unit and Lisong unit and its enclaves have a similar (87Sr/86Sr)i value of 0.7064 with an average of εNd(t)=-3.03, indicating that more mantle material was evolved in the magma derivation; whereas the West Guposhan unit has a higher (87Sr/86Sr)i value of 0.7173 but a lower εNd(t) value of -5.00, and is characterized by strong negative Eu anomalies and higher Rb/Sr ratios, suggesting that its source materials were composed of relatively old crust components and new mantle-derived components. In addition, an inherited zircon grain in the East Guposhan unit (GP-1) yielded a 206Pb/238U age of 806.4 Ma, which is similar to the ages of the Jiulin cordierite granite in northern Jiangxi and of the Yinqiao migmatic granite in Guangxi in the HZH granite zone. All this may provide new evidence for Late Proterozoic magmatism in the HZH granite zone.

  8. Detrital Zircon Ages of Hanjiang River:Constraints on Evolution of Northern Yangtze Craton, South China

    Yang Jie; Gao Shan; Yuan Honglin; Gong Hujun; Zhang Hong; Xie Shiwen


    Clastic sedimentary rocks are natural samples of the exposed continental crust over large ideal sample for studying the formation and evolution of the northern Yangtze craton. Here we report laser ablation inductively coupled plasma mass spectrometer U-Pb ages of 122 detrital zircons from one sand sample of the Hanjiang River. The 110 concordant zircons reveal four major age groups of 768,444, 212, and 124 Ma, which well correlate with known magmatic events in the northern Yangtze craton. A minor group is present at 1 536 Ma, which is less known in the study area. Only seven zircons have ages of >1 750 Ma. Our results show that the Early Paleozoic, Late Triassic, and Early Cretaceous are important episodes of zircon growth and crustal growth/reworking in addition to the previously documented Neoproterozoic event. Our results suggest very limited exposures of Paleoproterozoic and Archean rocks in the northern parts of the Yangtze craton.

  9. Elucidating the magmatic history of the Austurhorn silicic intrusive complex (southeast Iceland) using zircon elemental and isotopic geochemistry and geochronology

    Padilla, A. J.; Miller, C. F.; Carley, T. L.; Economos, R. C.; Schmitt, A. K.; Coble, M. A.; Wooden, J. L.; Fisher, C. M.; Vervoort, J. D.; Hanchar, J. M.


    The Austurhorn intrusive complex (AIC) in southeast Iceland comprises large bodies of granophyre and gabbro, and a mafic-silicic composite zone (MSCZ) that exemplifies magmatic interactions common in Icelandic silicic systems. Despite being one of Iceland's best-studied intrusions, few studies have included detailed analyses of zircon, a mineral widely recognized as a valuable tracer of the history and evolution of its parental magma(s). In this study, we employ high spatial resolution zircon elemental and isotopic geochemistry and U-Pb geochronology as tools for elucidating the complex construction and magmatic evolution of Austurhorn's MSCZ. The trace element compositions of AIC zircon crystals form a broad but coherent array that partly overlaps with the geochemical signature for zircons from Icelandic silicic volcanic rocks. Typical of Icelandic zircons, Hf concentrations are relatively low (mush-like material and a prolonged lifetime for the complex.

  10. New Gas Carburizing Method for Minimizing CO2 Emission by Saving Resources and Selective Removal of H2 in Furnace

    Mizukoshi, Tomoyuki; Yokoyama, Yujiro; Hoshino, Hideaki; Ishigami, Itsuo; Usui, Tateo

    An attempt has been made to develop a new gas carburizing furnace with the system that discharges H2 gas selectively from the atmosphere in the furnace. Polyimide hollow-fiber membrane filter on the market was selected as a filter that was expected to have good H2 gas permeability and selectivity. The results of the various gas permeability measurements of this filter showed that it had superior H2 gas permeability and selectivity. Using this gas filter module, a new industrial gas carburizing furnace that had ‘H2 gas selective discharging system’ was produced as a trial. Use of this furnace made possible to stabilize the gas carburizing atmosphere in the furnace under the lower carrier gas flow rate condition (below 25% of standard condition). It was confirmed that the carbon concentration profile of the steel carburized with the new carburizing furnace under lower carrier gas flow rate condition was comparable to that of the specimen carburized under standard carrier gas flow rate condition.

  11. Geochemistry, geochronology and zircon Hf isotopic study of peralkaline-alkaline intrusions along the northern margin of the North China Craton and its tectonic implication for the southeastern Central Asian Orogenic Belt

    Zhao, Pan; Jahn, Bor-ming; Xu, Bei; Liao, Wen; Wang, Yanyang


    A giant Permian alkaline magmatic belt has recently been identified in southern Inner Mongolia, along the northern margin of the North China Craton (NCC). This belt is mainly composed of syenite, quartz syenite, alkaline granite and mafic microgranular enclaves (MME)-bearing granodiorite. In order to study the petrogenesis and tectonic implications of these rocks, we undertook zircon U-Pb dating and geochemical analysis of two Permian alkaline plutons. The first Guangxingyuan Pluton occurs in the Hexigten area and is composed of MME-bearing tonalite, K-feldspar granite and syenite. The second Durenwuliji Pluton, located in the Xianghuangqi area, comprises syenite, quartz syenite and K-feldspar granite. Zircon U-Pb dating on tonalite, K-feldspar granite, syenite and quartz syenite from the two plutons yielded a tight range of ages from 259 to 267 Ma. The peralkaline-alkaline rocks show high abundance of total alkalis (K2O + Na2O = 7.9-12.9%) and K2O contents (3.9-8.0%), enrichment in large ion lithophile elements (LILE) and light rare earth element (LREE), and depletion of high field strength elements (HFSE). The associated tonalite and MMEs display I-type granitic geochemical affinity, with less total abundance of trace elements than the peralkaline-alkaline rocks. Zircon Hf isotopic analysis of the Guangxingyuan pluton yielded a large range of εHf(t) values from - 15.5 to + 6.7 and model ages (TDMC) from 781 to 2012 Ma. By contrast, the Hf isotopic data of the Durenwuliji pluton shows a small range of εHf(t) from + 6.2 to + 8.9 and TDMC from 667 to 816 Ma. The geochemical and Hf isotopic characteristics indicate that the parental magma was derived from a mixing of metasomatic mantle-derived mafic magma with different amount of crust-derived felsic magma, and followed by fractional crystallization. Considering previous tectonic studies in Inner Mongolia, a Permian post-orogenic extension was proposed to account for these peralkaline-alkaline intrusions following

  12. Evaluation of Process Capability in Gas Carburizing Process to Achieve Quality through Limit Design Concept

    K. Palaniradja; N. Alagumurthi; V. Soundararajan


    Steel is the most important metallic material used in industry. This is because of the versatility of its engineering properties under different conditions. In one condition it can be very mild, soft and suitable for any forming operation. In another condition the same steel can be very hard and strong. This versatility is made possible by the different heat treatments that the steel can be subject to. One such treatment is Gas carburizing. This is the most widely used process for surface hardening of low carbon steels. In this method the surface composition of the steel changes by diffusion of carbon and or nitrogen and result in hard outer surface with good wear resistance properties. A striking feature of Gas Carburizing process is that in this process the original toughness and ductility remains unaffected even after heat treatment. 3% nickel chromium case hardened low carbon steels are widely used for critical automotive and machine applications such as rack and pinion, gears, camshaft, valve rocker shafts and axles which requires high fatigue resistance. Fatigue behaviour of case carburized parts depends to a great extent on the correct combination of Hardness Penetration Depth (HPD) and the magnitude of hardness at the surface and beneath the surface with low size and shape distortion. In order to reduce the manufacturing costs in terms of material consumption and elimination of the number of processing steps, the effect of Gas carburizing parameters on the fatigue behaviour should already be considered in the parameter design stage. Therefore it is of importance to optimize the gas carburizing process variables to attain quality products with respect to hardness and case depth. In the present paper, the evaluation of process capability was carried out through a Limit Design Concept called orthogonal array design of experiment. To optimize the process variables the influence of several parameters (Holding time,Carbon potential, Furnace temperature and Quench

  13. Comparison of SHRIMP U-Pb dating of monazite and zircon

    WAN Yusheng; LIU Dunyi; JIAN Ping


    Monazite dating is an important technique in geochronological studies. However, monazite U-Pb dating by SHRIMP is much less popular than zircon in geochronological applications. This paper compares the results of SHRIMP U-Pb dating of monazites and zircons separated from two granite samples, indicating that monazite SHRIMP U-Pb dating at the Beijing SHRIMP Centre is feasible and provides identical results within error.

  14. Finite lattice distortion patterns in plastically deformed zircon grains

    E. Kovaleva


    Full Text Available This study examines finite deformation patterns of zircon grains from high-temperature natural shear zones. Various zircon-bearing rocks were collected in the Western Tauern Window, Eastern Alps, where they were deformed under amphibolite facies conditions, and in the Ivrea-Verbano Zone (IVZ, Southern Alps, where deformation is related with granulite-facies metamorphism. Among the sampled rocks are: granitic orthogneisses, meta-lamprophyres and paragneisses, all of which are highly deformed. The investigated zircon grains ranging from 10 to 50 microns were studied in situ using a combination of scanning electron microscope (SEM techniques, including secondary electron (SE, backscattered electron (BSE, forward scattered electron (FSE, cathodoluminescence (CL imaging, and crystallographic orientation mapping by electron backscatter diffraction analysis (EBSD, as well as micro-Raman spectroscopy. Energy-dispersive X-ray spectrometry (EDS was applied to host phases. Microstructural analysis of crystal-plastically deformed zircon grains was based on high-resolution EBSD maps. Three general types of finite lattice distortion patterns were detected: Type (I is defined by gradual bending of the zircon lattice with orientation changes of about 0.6° to 1.4° per μm without subgrain boundary formation. Type (II represents local gradual bending of the crystal lattice coupled with the formation of subgrain boundaries that have concentric semicircular shapes in 2-D sections. Cumulative grain-internal orientation variations range from 7° to 40° within single grains. Type (III is characterized by formation of subgrains separated by a well-defined subgrain boundary network, where subgrain boundaries show a characteristic angular closed contour in 2-D sections. The cumulative orientation variation within a single grain ranges from 3° to 10°. Types (I and (II predominate in granulite facies rocks, whereas type (III is restricted to the amphibolite facies

  15. The composition of zircon in Variscan granites from Northern Portugal

    Martins, H. C.B.


    Full Text Available A group of slightly peraluminous Variscan plutons in Northern Portugal were selected from the study of zircon composition. The selected plutons are: the Vila Pouca de Aguiar and the Lavadores-Madalena plutons with I-type affinities and the Vieira do Minho pluton, an l-S transitional type. Zircon occurs as euhedral to subhedral crystals and exhibit finely concentric oscillatory magmatic zoning mainly related to variations of Hf, Y, U and Th concentrations. Most zircon crystals show the dominant “xenotime” substitution. The zircon crystals have Zr/Hf ratio in the range of 21 to 52, with no significant differences between the different granites. These values are in the same range of other peraluminous granites and are in accordance with a crustal signature of zircon. Moreover, the range of Zr/Hf values in zircon crystals overlaps with that of crustal sources and consequently to the potential protoliths proposed in the genesis of the Vieira do Minho and the Vila Pouca de Aguiar plutons, namely meta-igneous crustal sources at different levels. Although zircon from the Lavadores-Madalena pluton has a compositional range similar to the other plutons, an origin by hibridisation has been proposed. However, similar zircon chemistry between this pluton and Vila Pouca de Aguiar and Vieira do Minho plutons could also suggest a similar crustal source.Se han seleccionado tres plutones graniticos variscos en el norte de Portugal para el estudio de la composición del circón. Los plutones son: Vila Pouca de Aguiar y Lavadores-Madalena con afinidad de tipo-I y el plutón de Vieira do Minho de tipo transicional I-S. Los circones se presentan en cristales euhédricos a subhédricos y tienen zonados magmáticos, concéntricos oscilatorios finos ligados principalmente a variaciones de las concentraciones del Hf, Y, U y Th. La mayoría de los cristales de circón muestran la sustitución dominante “xenotima”. Los zircones tienen relaciones Zr/Hf que var

  16. Non-vacuum electron-beam carburizing and surface hardening of mild steel

    Bataev, I. A.; Golkovskii, M. G.; Losinskaya, A. A.; Bataev, A. A.; Popelyukh, A. I.; Hassel, T.; Golovin, D. D.


    In this paper, we study the structure, microhardness, and tribological properties of surface layers of mild (0.19% C) steel, which was formed by electron-beam cladding with an iron-graphite powder mixture followed by quenching and tempering. A 1.4 MeV electron beam that was extracted into air was used. Cladding of steel with the iron-graphite mixture at a beam current of 24 and 26 mA formed a hypoeutectic cast iron layer (2.19% C) and a hypereutectoid steel (1.57% C) layer, which were 2.0 and 2.6 mm thick, respectively. The microhardness of the surface-quenched and tempered steel and cast iron layers was 7 and 8 GPa, respectively. Electron-beam quenching of the surface layers of hypoeutectic cast iron was accompanied with multiple cracking. During the quenching of the 1.57% C steel layer, crack formation was not observed. In friction tests against fixed and loose abrasive particles, the surface layers of hypereutectoid steel and hypoeutectic cast iron that were produced by electron-beam cladding and quenching had lower wear rates than mild steel after pack carburizing, quenching, and tempering. In the sliding wear tests, the cast iron clad layer, which was subjected to electron-beam quenching and tempering, exhibited the highest wear resistance. Electron-beam treatment can be used to harden local areas of large workpieces. It is reasonable to treat clad layers of high-carbon steel with electron-beam quenching and tempering. To prevent multiple cracking, white cast iron layers should not be quenched.


    Emilia Wołowiec-Korecka


    Full Text Available This paper presents the findings of research of a short-pulse low pressure carburizing technology developed for a new large-chamber furnace for high-performance and precision thermal treatment of parts of mechanical gear. Sections of the article discuss the novel constructions of the device in which parts being carburized flow in a stream, as well as the low-pressure carburizing experiment. The method has been found to yield uniform, even and repeatable carburized layers on typical gear used in automotive industry.

  18. Eburnean and Pan-African granitoids and the Raghane mega-shear zone evolution: Image analysis, U-Pb zircon age and AMS study in the Arokam Ténéré (Tuareg shield, Algeria)

    Nouar, O.; Henry, B.; Liégeois, J. P.; Derder, M. E. M.; Bayou, B.; Bruguier, O.; Ouabadi, A.; Amenna, M.; Hemmi, A.; Ayache, M.


    In the Arokam Ténéré, the three studied massifs of granitoids are located around the N-S oriented Raghane mega-shear zone, which separates two of the main domains of the Tuareg shield, the Saharan metacraton and the Central Hoggar. The field observations, AMS analyses and U-Pb zircon dating were completed by a study of Landsat images because of the scarcity of outcrops in several parts of the studied area. The image analysis allows to distinguish Arokam-East and Abdou granitoids in the eastern plutonic complex. It has also shown that the western plutonic complex corresponds to two different intrusions: the Yvonne granite and granodiorite. This is confirmed by the magnetic fabric that presents different characteristics in the different granitoids. U-Pb zircon dating and field observations show that the Arokam-West basement granite is much older (1915 Ma) than the Hanane granodiorite (582 Ma) in the central plutonic complex. Arokam-East and -West granites then belong to the Eburnean basement. The magnetic fabric of these granites is mainly associated with a post-magmatic deformation, probably of Pan-African age. Yvonne granodiorite is likely contemporaneous of the main displacement along the Raghane shear zone. The Yvonne granite (594 Ma) and Hanane granodiorite have a fabric similar to that previously obtained in most plutons of the Tiririne area. This fabric is related to the regional stress field, associated with the activity of the Raghane shear zone, during the late-magmatic phase in the plutons. On the contrary, the magnetic fabric of the Abdou pluton is still reflecting only the magma flow.

  19. Age and compositional data of zircon from sepiolite drilling mud to identify contamination of ocean drilling samples

    Andrews, Graham D. M.; Schmitt, Axel K.; Busby, Cathy J.; Brown, Sarah R.; Blum, Peter; Harvey, Janet. C.


    Zircon extracted from drilled oceanic rocks is increasingly used to answer geologic questions related to igneous and sedimentary sequences. Recent zircon studies using samples obtained from marine drill cores revealed that drilling muds used in the coring process may contaminate the samples. The JOIDES Resolution Science Operator of the International Ocean Discovery Program has been using two types of clays, sepiolite and attapulgite, which both have salt water viscosifier properties able to create a gel-like slurry that carries drill cuttings out of the holes several hundred meters deep. The dominantly used drilling mud is sepiolite originating from southwestern Nevada, USA. This sepiolite contains abundant zircon crystals with U-Pb ages ranging from 1.89 to 2889 Ma and continental trace element, δ18O, and ɛHf isotopic compositions. A dominant population of 11-16 Ma zircons in sepiolite drilling mud makes identification of contamination in drilled Neogene successions particularly challenging. Interpretation of zircon analyses related to ocean drilling should be cautious of zircon ages in violation of independently constrained age models and that have age populations overlapping those in the sepiolite. Because individual geochronologic and geochemical characteristics lack absolute discriminatory power, it is recommended to comprehensively analyze all dated zircon crystals from cores exposed to drill mud for trace element, δ18O, and ɛHf isotopic compositions. Zircon analyzed in situ (i.e., in petrographic sections) are assumed to be trustworthy.

  20. Provenance of zircon of the lowermost sedimentary cover, Estonia, East-European Craton

    Konsa, M.


    Full Text Available Bulk and accessory mineral composition of fresh and weathered crystalline rocks, and sedimentary deposits overlying the crystalline-sedimentary unconformity have been examined in core samples from 28 drill holes in Estonia. Before the Late Vendian to Early Cambrian regional subsidence and sedimentation, the region represented a flat plateau within the Svecofennian Domain. Palaeo-and Mesoproterozoic crystalline rocks, regardless their different initial mineral composition, subcrop under the Upper Vendian/Lower Cambrian sedimentary cover as usually intensely weathered rocks (saprolites composed of residual quartz, altered micas and prevailing clay minerals mainly of the kaolinite group. Thus, the bulk mineral composition of any basement crystalline rocks imparts no specific inherited rock-forming minerals into the covering sedimentary rocks. From the variety of accessory and opaque minerals of crystalline rocks, only zircon populations survived in saprolites. Crystalline rocks of different origin yield different zircons. Relationships between the zircon typology of the basement rocks having specific areas of distribution and the sedimentary rocks immediately overlying those crystalline rocks were the main subject of this study. The result is that siliciclastic sedimentary rocks covering weathered crystalline rocks only in places inherited zircons with typological features characteristic of specific basement areas. In northeastern Estonia, local lenses of the Oru Member (the earliest Upper Vendian sedimentary rocks in Estonia resembling the debris of weathered crystalline rocks yield accessory zircon which in a 1-2 m thick layer above the basement surface is similar to the zircons of the underlying weathering mantle of certain crystalline rocks. In the next unit, the Moldova Member, up to 43 m above the basement surface, a mixture of zircons resembling those of various local basement rocks has been found. Further upwards, in the Vendian and Lower

  1. Zircon saturation in silicate melts: a new and improved model for aluminous and alkaline melts

    Gervasoni, Fernanda; Klemme, Stephan; Rocha-Júnior, Eduardo R. V.; Berndt, Jasper


    The importance of zircon in geochemical and geochronological studies, and its presence not only in aluminous but also in alkaline rocks, prompted us to think about a new zircon saturation model that can be applied in a wide range of compositions. Therefore, we performed zircon crystallization experiments in a range of compositions and at high temperatures, extending the original zircon saturation model proposed by Watson and Harrison (Earth Planet Sci Lett 64:295-304, 1983) and Boehnke et al. (Chem Geol 351:324-334, 2013). We used our new data and the data from previous studies in peraluminous melts, to describe the solubility of zircon in alkaline and aluminous melts. To this effect, we devised a new compositional parameter called G [ {( {3 \\cdot {{Al}}2 {{O}}3 + {{SiO}}2 )/({{Na}}2 {{O}} + {{K}}2 {{O}} + {{CaO}} + {{MgO}} + {{FeO}}} )} ] (molar proportions), which enables to describe the zircon saturation behaviour in a wide range of rock compositions. Furthermore, we propose a new zircon saturation model, which depends basically on temperature and melt composition, given by (with 1σ errors): ln [ {{Zr}} ] = ( {4.29 ± 0.34} ) - ( {1.35 ± 0.10} ) \\cdot ln G + ( {0.0056 ± 0.0002} ) \\cdot T( °C ) where [Zr] is the Zr concentration of the melt in µg/g, G is the new parameter representing melt composition and T is the temperature in degrees Celsius. The advantages of the new model are its straightforward use, with the G parameter being calculated directly from the molar proportions converted from electron microprobe measurements, the temperature calculated given in degrees Celsius and its applicability in a wider range of rocks compositions. Our results confirm the high zircon solubility in peralkaline rocks and its dependence on composition and temperature. Our new model may be applied in all intermediate to felsic melts from peraluminous to peralkaline compositions.

  2. The Influence of Method of Carburizing and Nitrocarburizing on the Microstructure and Properties of Tool Steels

    Tomasz Babul; Natalia Kucharieva; Aleksander Nakonieczny; Jan Senatorski


    The paper presents the results of wear and metallography tests of tool steel grades: ASTM A681, Chl2M and Ch12FS per GOST, AMS 6437E i BS X46Cr13, all surface hardened by the Carbo process (carburizing) and by the NiCar process (nitrocarburizing). The thermo-chemical treatment was conducted in powder pack for a duration of 6 h (carburizing)and for 4 h in the case of nitrocarburizing. Factors investigated were: morphology, depth and microhardness of the cases obtained, their microstructure, as well as phase composition. Wear tests were conducted by the three cylinder-cone method.Wear velocity was 0.58 m/s, unit load was 50 MPa and 400Mpa, wear path was 3470 m. Oil SAE30 was applied at the rate of 30 drops per minute.

  3. Ablation behavior of monolayer and multilayer Ir coatings under carburizing and oxidizing oxyacetylene flames

    Wu, Wangping; Jiang, Jinjin; Chen, Zhaofeng


    Iridium is one of the most promising candidates for protective barrier of refractory materials to endure high service temperature. The multilayer iridium coating was produced by a double glow plasma process on the polished tungsten carbide substrates, compared with monolayer. The ablation behaviors of the monolayer on the unpolished and polished substrates were investigated under carburizing and oxidizing oxyacetylene flames, respectively, at the same time the multilayer coating ablated under oxidizing flames. Multilayer coating was a polycrystalline phase with the preferential (220) orientation. Monolayer on the unpolished substrate had fine coarse grains and some small microcracks were present. Multilayer consisted of columnar grains with some voids between the grains boundaries. The formation of a WIr phase in the as-deposited multilayer was attributed to high deposition temperature. The monolayer could endure high temperature up to 1800 °C in carburizing flame. The substrates could be protected more effectively by multilayer than monolayer at 2000- 2200 °C in oxidizing flame.

  4. Development of Nitrogen-Hydrocarbon Atmospheric Carburizing and Process Control Methods

    Wang, Xiaolan; Zurecki, Zbigniew; Sisson, Richard D.


    Atmospheric pressure carburizing and neutral carbon potential annealing in nitrogen containing small additions of hydrocarbon gases can offer cost and steel surface quality alternatives to the comparable, endothermic atmosphere, or vacuum operations. An experimental program was conducted for refining real-time process control methods in carburizing of AISI 8620 steel under N2-CH4, N2-C3H8 blends containing <5 vol.% of hydrocarbon gas at 900 and 930 °C. Multiple types of gas analyzers were used to monitor residual concentrations of H2, CO, CO2, H2O, O2, CH4, C3H8, and other hydrocarbons inside furnace. A modified shim stock technique was additionally evaluated for correlation with gas analysis and diffusional modeling using measured carbon mass flux values (g/cm2/s). Results of this evaluation work are presented.

  5. Modeling of numerical simulation and experimental verification for carburizing-nitriding quenching process



    A model considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is presented to examine metallo-thermo-mechanical behavior during carburized and nitrided quenching. Coupled simulation of diffusion,phase transformation and stress/strain provides the final distribution of carbon and nitrogen contents as well as residual stress and distortion. Effects of both transformation and lattice expansion induced by carbon and nitrogen absorption were introduced into calculating the evolution of the internal stress and strain. In order to verify the method and the results,the simulated distributions of carbon and nitrogen content and residual stress/strain of a ring model during carburized and nitrided quenching were compared with the measured data.

  6. Early Paleozoic tectonic reconstruction of Iran: Tales from detrital zircon geochronology

    Moghadam, Hadi Shafaii; Li, Xian-Hua; Griffin, William L.; Stern, Robert J.; Thomsen, Tonny B.; Meinhold, Guido; Aharipour, Reza; O'Reilly, Suzanne Y.


    In this study we use detrital zircons to probe the Early Paleozoic history of NE Iran and evaluate the link between sediment sources and Gondwanan pre-Cadomian, Cadomian and younger events. U-Pb zircon ages and Hf isotopic compositions are reported for detrital zircons from Ordovician and Early Devonian sedimentary rocks from NE Iran. These clastic rocks are dominated by zircons with major age populations at 2.5 Ga, 0.8-0.6 Ga, 0.5 Ga and 0.5-0.4 Ga as well as a minor broad peak at 1.0 Ga. The source of 2.5 Ga detrital zircons is enigmatic; they may have been supplied from the Saharan Metacraton (or West African Craton) to the southwest or Afghanistan-Tarim to the east. The detrital zircons with age populations at 0.8-0.6 Ga probably originated from Cryogenian-Ediacaran juvenile igneous rocks of the Arabian-Nubian Shield; this inference is supported by their juvenile Hf isotopes, although some negative εHf (t) values suggest that other sources (such as the West African Craton) were also involved. The age peak at ca 0.5 Ga correlates with Cadomian magmatism reported from Iranian basement and elsewhere in north Gondwana. The variable εHf (t) values of Cadomian detrital zircons, resembling the εHf (t) values of zircons in magmatic Cadomian rocks from Iran and Taurides (Turkey), suggest an Andean-type margin and the involvement of reworked older crust in the generation of the magmatic rocks. The youngest age population at 0.5-0.4 Ga is interpreted to represent Gondwana rifting and the opening of Paleotethys, which probably started in Late Cambrian-Ordovician time. A combination of U-Pb dating and Hf-isotope data from Iran, Turkey and North Gondwana confirms that Iran and Turkey were parts of Gondwana at least until late Paleozoic time.

  7. Surface carburizing of Ti-6Al-4V alloy by laser melting

    Saleh, A. F.; Abboud, J. H.; Benyounis, K. Y.


    Surface carburizing of a Ti-6Al-4V alloy using laser melting has been investigated experimentally, with the aim of increasing surface hardness and hence improving related properties such as wear and erosion resistance. The surface of the material was coated with graphite prior to laser irradiation. Carburizing was achieved by a laser alloying mechanism, which includes melting the substrate and dissolution of the graphite in the liquid state. Two different types of lasers were used: (i) a continuous wave CO 2 (CW CO 2) laser with a maximum power of 3 kW, and (ii) a pulsating Nd-YAG laser with a maximum power per pulse of 100 W. Optical microscopy, scanning electron microscopy, EDS-analysis, and X-ray diffraction were carried out to analyze the microstructure and identify phases of the carburized layers. The results show that the carburized layers produced by CW CO 2 and Nd-YAG lasers are macroscopically homogeneous and have gradient features. The microstructures consisted of TiC crystals in the matrix of α'-Ti. The TiC crystals are either in the form of particles or dendrites. The depths to which these layers extend ranged from about 0.2-0.5 mm, depending on the treatment parameters. The volume fraction of the dendrites was found to decrease with increasing laser power or increasing traverse speed. Microhardness has been found to be directly related to the volume fraction and the size of the TiC phase. It increased to a value ranging from 500 to 800 Hv as compared to 350 Hv for the as-received substrate.

  8. Characteristic Features of Nanoscale Сarbide Inclusions Nucleation and Growth When Carburizing Steels

    L.I. Roslyakova


    Full Text Available Thermodynamic calculations of the free energy of the formation of cementite type nanoscale carbides in supersaturated austenite alloyed with chromium and manganese are presented. It is shown that when carburizing steel, chromium stabilizing cementite facilitates its separation, in the form of dispersed inclusions. Manganese stabilizes cementite much weaker than chromium, though facilitates the growth of carbide inclusions due to the formation of the intermediate ε-phase at a reduced carbon content.

  9. Structural Characterization of Natural and Processed Zircons with X-Rays and Nuclear Techniques

    Laura C. Damonte


    Full Text Available In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD, Positron Annihilation Lifetime Spectroscopy (PALS, and Perturbed Angular Correlations (PAC in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and the modifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line. Additionally, HPGe gamma-ray spectroscopy confirms the occurrence of significant levels of natural radioactivity responsible for metamictization in the investigated zircon samples. Results from XRD, PALS, and PAC analysis confirm that the metamict state of zircon is a dispersion of submicron disordered domains in a crystalline matrix of zircon.

  10. EPDM composite membranes modified with cerium doped lead zirconate titanate

    Zaharescu, T.; Dumitru, A.; Lungulescu, M. E.; Velciu, G.


    This study was performed on γ-irradiated ethylene-propylene diene terpolymer (EPDM) loaded with lead zirconate titanate. The inorganic phase has a perovskite structure with general formula Pb(Zr0.65-xCexTi0.35)O3. The three composites with different Ce dopant concentrations revealed the stabilization activity of filler against oxidation proved by chemiluminescence investigation in respect to pristine polymer. The presence of cerium low concentrations in the solid lead zirconate titanate nanoparticles causes significant slowing of oxidation rate during radiation exposure. The improvement in the stabilization feature of filler is correlated with the existence of traps, whose interaction with free radicals assumes medium energy due to their convenient depth.

  11. RJJ-75-9TG井式气体渗碳炉工艺渗碳软件的应用%RJJ-75-9TG pit gas carburizing furnace carburizing process software applications



    选用北京培特公司技术开发的HT8002AC 井式炉渗碳/碳氮共渗工艺过程计算机控制系统,技术改进2台RJJ-75-9TG 井式气体渗碳炉的渗碳控制系统,实现计算机对整个工艺渗碳全过程的模拟控制,并时刻跟踪和修正现场设备参数的动态变化。提升了渗碳件的产品质量,确保汉德公司两到三年之内的自制件,能够达到国际出口标准。%Selection of Beijing tissue culture technology development company HT8002AC pit furnace carburizing / carbonitriding process computer control systems, technical improvements 2 RJJ-75-9TG pit gas carburizing carburizing furnace control system, the entire computer analog control the whole process of carburizing process and time tracking and dynamic correction field device parameters. Improve product quality carburizing, ensuring homemade pieces Hande within two to three years to reach the international export standards.

  12. Radiation damage in zircon and monazite

    Meldrum, A.; Boatner, L.A. [Oak Ridge National Lab., TN (United States). Solid state Div.; Weber, W.J. [Pacific Northwest National Lab., Richland, WA (United States); Ewing, R.C. [Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Nuclear Engineering and Radiological Sciences


    Monazite and zircon respond differently to ion irradiation and to thermal and irradiation-enhanced annealing. The damage process (i.e., elastic interactions leading to amorphization) in radioactive minerals (metamictization) is basically the same as for the ion-beam-irradiated samples with the exception of the dose rate which is much lower in the case of natural samples. The crystalline-to-metamict transition in natural samples with different degrees of damage, from almost fully crystalline to completely metamict, is compared to the sequence of microstructures observed for ion-beam-irradiated monazite and zircon. The damage accumulation process, representing the competing effects of radiation-induced structural disorder and subsequent annealing mechanisms (irradiation-enhanced and thermal) occurs at much higher temperatures for zircon than for monazite. The amorphization dose, expressed as displacements per atom, is considerably higher in the natural samples, and the atomic-scale process leading to metamictization appears to develop differently. Ion-beam-induced amorphization data were used to calculate the {alpha}-decay-event dose required for amorphization in terms of a critical radionuclide concentration, i.e., the concentration above which a sample of a given age will become metamict at a specific temperature. This equation was applied to estimate the reliability of U-Pb ages, to provide a qualitative estimate of the thermal history of high-U natural zircons, and to predict whether actinide-bearing zircon or monazite nuclear waste forms will become amorphous (metamict) over long timescales.

  13. Jurassic zircons from the Southwest Indian Ridge

    Cheng, Hao; Zhou, Huaiyang; Yang, Qunhui; Zhang, Lingmin; Ji, Fuwu; Dick, Henry


    The existence of ancient rocks in present mid-ocean ridges have long been observed but received less attention. Here we report the discovery of zircons with both reasonably young ages of about 5 Ma and abnormally old ages of approximate 180 Ma from two evolved gabbroic rocks that were dredged from the Southwest Indian Ridge (SWIR) in the Gallieni fracture zone. U-Pb and Lu-Hf isotope analyses of zircons were made using ion probe and conventional laser abrasion directly in petrographic thin sections. Young zircons and their host oxide gabbro have positive Hf isotope compositions (ɛHf = +15.7-+12.4), suggesting a highly depleted mantle beneath the SWIR. The spread ɛHf values (from-2.3 to-4.5) of abnormally old zircons, together with the unradiogenic Nd-Hf isotope of the host quartz diorite, appears to suggest an ancient juvenile magmatism along the rifting margin of the southern Gondwana prior to the opening of the Indian Ocean. A convincing explanation for the origin of the unusually old zircons is yet to surface, however, an update of the theory of plate tectonics would be expected with continuing discovery of ancient rocks in the mid-oceanic ridges and abyssal ocean basins.

  14. Jurassic zircons from the Southwest Indian Ridge.

    Cheng, Hao; Zhou, Huaiyang; Yang, Qunhui; Zhang, Lingmin; Ji, Fuwu; Dick, Henry


    The existence of ancient rocks in present mid-ocean ridges have long been observed but received less attention. Here we report the discovery of zircons with both reasonably young ages of about 5 Ma and abnormally old ages of approximate 180 Ma from two evolved gabbroic rocks that were dredged from the Southwest Indian Ridge (SWIR) in the Gallieni fracture zone. U-Pb and Lu-Hf isotope analyses of zircons were made using ion probe and conventional laser abrasion directly in petrographic thin sections. Young zircons and their host oxide gabbro have positive Hf isotope compositions (εHf = +15.7-+12.4), suggesting a highly depleted mantle beneath the SWIR. The spread εHf values (from-2.3 to-4.5) of abnormally old zircons, together with the unradiogenic Nd-Hf isotope of the host quartz diorite, appears to suggest an ancient juvenile magmatism along the rifting margin of the southern Gondwana prior to the opening of the Indian Ocean. A convincing explanation for the origin of the unusually old zircons is yet to surface, however, an update of the theory of plate tectonics would be expected with continuing discovery of ancient rocks in the mid-oceanic ridges and abyssal ocean basins.

  15. Effect of carburizing temperature and time on mechanical properties of AISI/SAE 1020 steel using carbonized palm kernel shell

    Olanike M. OLUWAFEMI


    Full Text Available The effects of varied carburizing temperatures and holding time on the mechanical properties of AISI/SAE1020 steel have been investigated. Standard test samples prepared from the steel sample were subjected to pack hardening process using carbonized palm kernel shell as a carburizer at 800°, 850°, 900° and 950°C and held for 60, 90 and 120 minutes, quenched in oil and temper at 500°C for 60 minutes. After pack hardening process, the test samples were subjected to tensile, impact and hardness tests. and from the data obtained Ultimate tensile strength (UTS and impact strength were calculated, the case and the core hardness of the carburized samples were taken and optical microscope was also used to observe the micro structural features of the case hardened, quenched and tempered samples. It was observed that at 800°, 850° and 900°C, the UTS and the micro hardness initially reduces to minimum and then increased as the carburizing temperature increased, but at 950°C, it was observed that the UTS increases with increase in holding time. It was concluded that the optimum combination of mechanical properties is achieved at the carburizing temperature of 950°C soaked for 120 minutes followed by oil quenching and tempered at 500°C for 60 minutes.

  16. Damage prediction of HP40Nb steel with coupled creep and carburization based on the continuum damage mechanics

    Limin SHEN; Jianming GONG; Yong JIANG; Luyang GENG


    HP40Nb steel,used as a candidate material for ethylene cracking furnace tube,suffers creep and carburization damage from the complex environment of high temperature,high carbon potential and low oxygen partial pressure,and they lead to failure of the furnace tubes ahead of designed life.In order to investigate damage evolution under the complex condition,coupled creep damage and carburization damage constitutive equations were developed according to continuum damage mechanics theory.Based on the finite element ABAQUS code,user subroutines were developed for analyzing damage evolution of ethylene furnace tube under the action of coupled creepcarburization.The results show that carburization accelerates the damage process dramatically,damage value reaches the critical value along the inner surface after serving for 75,000 h under the action of creep-carburization,meanwhile the damage value is only 0.53 along the outer surface after operating the same time under the action of creep alone,which means that microcracks are generated along the inner surface under the action of coupled creep-carburization,fracture begins along the outer surface of tube under the action of creep alone.

  17. Optimization of Modes of Vacuum Carburizing of Gears from Heat-Resistant Steel VKS-7 on the Basis of Computational Design

    Semenov, M. Yu.; Smirnov, A. E.; Fakhurtdinov, R. S.; Ospennikova, O. G.; Gromov, V. I.


    Mathematical simulation is used to develop modes of vacuum carburizing providing the specified level of operating properties in high-load gears from steel VKS-7. The computed values of the operating properties are compared to experimental data obtained by testing check pieces subjected to vacuum carburizing by the modes developed.

  18. Morphological Characteristics of Detrital Zircon Grains from Source to Sink (Western Australia)

    Markwitz, V.; Kirkland, C.


    Detrital zircon studies have become the tool of choice to address a wide range of geological questions including basin evolution, geodynamic setting, paleogeographic reconstructions, and determining source-sink relationships. However, grain destruction during transportation may be critical in understanding the detrital zircon record, yet it has not been explored in detail. In the magmatic crystallization environment zircon crystal shape is effectively a function of the magma chemistry and temperature. We address to what extent the zircon population represents an artefact of preservation, or a meaningful record of the magmatic events within the source terrain. We use image analysis of previously SIMS U-Pb dated zircon crystals to quantify how zircon grain shapes relate to the chemical composition of magmatic and detrital zircon crystals. We achieve this by testing the correlation between shape factors and the uranium, thorium content, apparent alpha dose, and isotopic signature of individual zircons with statistical methods. We focus our investigation on two different areas of Western Australia: (1) the Archean of the Yilgarn Craton and (2) the Proterozoic of the Musgrave Province, and their associated Proterozoic basin sediments: (1) The Yilgarn craton represents a Neoarchean amalgamation of c. 3.8 Ga and 2.6 Ga granite-greenstone belts including a variety of gneisses, metasedimentary and metavolcanic rock formations, and granites. Along the northern edge of the craton a series of four Proterozoic basins, with variable tectonic and metamorphic overprinting overlay this basement. (2) The West Musgrave Province consists of an east-west trending Meso- to Neoproterozoic belt dominated by granites and volcanics deformed by several major orogenic events between c. 1.35 Ga and 350 Ma. Based on age and Hf isotopic relationships the bedrock of the Musgrave Province is the source for the Neoproterozoic to Early Carboniferous Amadeus Basin to its north. Using rigorous

  19. Influence of Surface Carburization of Machinable Ceramics on Its Pulsed Flashover Characteristics in Vacuum%Influence of Surface Carburization of Machinable Ceramics on Its Pulsed Flashover Characteristics in Vacuum

    郑楠; 黄学增; 穆海宝; 张冠军


    For pulsed power devices, surface flashover phenomena across solid insulators greatly restrict their overall performance. In recent decades, much attention has been paid on enhancing the surface electric withstanding strength of insulators, and it is found that surface treatment of material is useful to improve the surface flashover voltage. The carburization treatment is employed to modify the surface components of newly-developed machinable ceramics (MC) materials. A series of MC samples with different glucose solution concentration (0%, 10%, 20%, 30% and 40%) are prepared by chemical reactions for surface carburization modification, and their surface fiashover characteristics are investigated under pulsed voltage in vacuum. It is found that the surface carburization treatment greatly modifies the surface resistivity of MCs and hence the flashover behaviors. Based on the reduction of surface resistivity and the secondary electron emission avalanche (SEEA) theory, the adjustment of flashover withstanding ability can be reasonably explained.

  20. Geochemistry of zircons from basic rocks of the Korosten anorthosite-mangerite-charnockite-granite complex, north-western region of the Ukrainian Shield

    Shumlyanskyy, Leonid; Belousova, Elena; Petrenko, Oksana


    The concentrations of 26 trace elements have been determined by laser ablation ICP-MS in zircons from four samples of basic rocks of the Korosten anorthosite-mangerite-charnockite-granite plutonic complex, the Ukrainian Shield. Zircons from the Fedorivka and Torchyn gabbroic intrusions and Volynsky anorthosite massif have distinctive abundances of many trace elements (REE, Sr, Y, Mn, Th). Zircons from the gabbroic massifs are unusually enriched in trace elements, while zircons from pegmatites in anorthosite are relatively depleted in trace elements. High concentrations of trace elements in zircons from gabbroic intrusions can be explained by their crystallization from residual interstitial melts enriched in incompatible elements. The zircons studied demonstrate a wide range of Ti concentrations, which reflects their temperature of crystallization: the zircons most enriched in Ti, from mafic pegmatites of the Horbuliv quarry (20-40 ppm), have the highest temperature of crystallization (845 ± 40 °C). Lower (720-770 °C) temperatures of zircon crystallization in gabbroic rocks are explained by its crystallization from the latest portions of the interstitial melt or by simultaneous crystallization of ilmenite. The Ce anomaly in zircons correlates with the degree of oxidation of the coexisting ilmenite.

  1. In situ zircon Hf isotopic, U-Pb age and trace element study of monzonite xenoliths from Pingquan and Fuxin basalts: Tracking the thermal events of 169 Ma and 107 Ma in Yanliao area

    ZHENG; Jianping; ZHANG; Ruisheng; YU; Chunmei; TANG; Huay


    K-Ar ages of the Mesozoic (92-100 Ma) Fuxin alkalic basalts (western Liaoning Province) and the Tertiary (23-45 Ma) Pingquan alkalic basalts (eastern Hebei Province), and the results of in situ zircon U-Pb dating, Hf isotope and the trace elements from three monzonite xenoliths carried in the alkalic basalts are reported. The crust-mantle interaction occurring in the Yanshan intracontinental orogenic belt is also discussed. Fuxin zircons show highly uniform U-Pb age ((169±3) Ma). More than 95% Pingquan zircons display the age of (107±10) Ma except two are 2491 Ma and 513 Ma respectively. Zircons with the ages of (169±3) Ma have εHf close to zero. εHf of the zircons with the ages of (107±10) Ma are mainly at -11.5--16.3, showing the crustal derivation. Fuxin zircons contain low Nb, Ta, Sr, Th, U contents, low and narrow Hf model ages (0.87-1.00 Ga), which reflect that the source materials of the monzonite xenoliths are young to Pingquan (focus at (1.28±0.08) Ga). High contents of the incompatible elements, and wide range of Hf model ages (0.89-2.56 Ga) in Pingquan zircons suggest a more complex source and the highly crustal maturity in their petrogenesis. Comprehensive information including the published data indicates that J3-K1 is the key period of the deep processes and shallow tectonic reverse in the Yanliao area. However, the processes were highly heterogeneous in spatial and in temporal.

  2. In situ zircon Hf isotopic, U-Pb age and trace element study of monzonite xenoliths from Pingquan and Fuxin basalts:Tracking the thermal events of 169 Ma and 107 Ma in Yanliao area

    ZHENG Jianping; ZHANG Ruisheng; YU Chunmei; TANG Huayun; ZHANG Pei


    K-Ar ages of the Mesozoic (92-100 Ma) Fuxin alkalic basalts (western Liaoning Province) and the Tertiary (23-45 Ma) Pingquan alkalic basalts (eastern Hebei Province), and the results of in situ zircon U-Pb dating, Hf isotope and the trace elements from three monzonite xenoliths carried in the alkalic basalts are reported. The crust-mantle interaction occurring in the Yanshan intracontinental orogenic belt is also discussed. Fuxin zircons show highly uniform U-Pb age ((169±3) Ma). More than 95% Pingquan zircons display the age of (107±10) Ma except two are 2491 Ma and 513 Ma respectively. Zircons with the ages of (169±3) Ma have εHf close to zero. εHf of the zircons with the ages of (107±10) Ma are mainly at -11.5--16.3, showing the crustal derivation. Fuxin zircons contain low Nb, Ta, Sr, Th, U contents, low and narrow Hf model ages (0.87-1.00 Ga), which reflect that the source materials of the monzonite xenoliths are young to Pingquan (focus at (1.28±0.08) Ga). High contents of the incompatible elements, and wide range of Hf model ages (0.89-2.56 Ga) in Pingquan zircons suggest a more complex source and the highly crustal maturity in their petrogenesis. Comprehensive information including the published data indicates that J3-K1 is the key period of the deep processes and shallow tectonic reverse in the Yanliao area. However, the processes were highly heterogeneous in spatial and in temporal.

  3. Geochemistry and U-Pb geochronology of detrital zircons in the Brujas beach sands, Campeche, Southwestern Gulf of Mexico, Mexico

    Tapia-Fernandez, Hector J.; Armstrong-Altrin, John S.; Selvaraj, Kandasamy


    This study investigated the bulk sediment geochemistry, U-Pb ages and rare earth element (REE) geochemistry of one hundred detrital zircons recovered from the Brujas beach sands in southwestern Gulf of Mexico to understand the provenance and age spectra. The bulk sediments are high in Zr and Hf contents (∼1400-3773 ppm and ∼33-90 ppm, respectively) suggested the abundance of resistant mineral zircon. The chondrite normalized REE patterns of the bulk sediments are less fractionated with enriched low REE (LREE; LaCN/SmCN = ∼491-693), depleted heavy REE (HREE; GdCN/YbCN = ∼44-69) and a negative Eu anomaly (Eu/Eu∗ = ∼0.44-0.67) suggested that the source rock is felsic type. The results of this study revealed highly varied contents of Th (∼4.2-321 ppm), U (∼20.7-1680 ppm), and Hf (∼6970-14,200 ppm) in detrital zircons compared to bulk sands. The total REE content (∼75 and 1600 ppm) and its chondrite-normalized pattern with positive Ce and negative Eu anomalies as well as low Th/U ratio of zircon grains indicated that they were dominantly of magmatic origin. U-Pb data of zircons indicated two age populations, with predominance of Permian-Triassic (∼216-286 Ma) and Neoproterozoic (∼551-996 Ma). The Permian-Triassic zircons were contributed by the granitoids and recycled metasedimentary rocks of the Chiapas Massif Complex. The major contribution of Neoproterozoic zircons was from the Chaucus, Oaxacan, and Chiapas Massif Complexes in Grenville Province, southern Mexico. U-Pb ages of zircons from the Brujas beach are consistent to the reported zircon ages from the drainage basins of Usumacinta, Coatzacoalcos, and Grijalva Rivers in southern Mexico, suggesting that the sediments delivered by the rivers to the beach area are vital in defining the provenance of placers.

  4. Detrital zircon geochronology and provenance of the Chubut Group in the northeast of Patagonia, Argentina

    Navarro, Edgardo L.; Astini, Ricardo A.; Belousova, Elena; Guler, M. Verónica; Gehrels, George


    The Chubut Group constitutes the most widespread sedimentary unit in NE Patagonia, characterized by variable-energy fluvial deposits. U-Pb analysis of detrital zircons from two sections of the Chubut Group constraint the age of the oldest sedimentary rocks in the northeast of the Somuncurá - Cañadón Asfalto Basin. In the Cañadón Williams area, at San Jorge section, 20 km NW of Telsen locality, dating of 56 detrital zircons from a medium to coarse sandstone indicated a maximum depositional age of 109 ± 1 Ma (n = 4). These sandstones were interpreted to represent shallow channels, associated with a lacustrine system. In the Telsen locality, a laser ablation analysis of 115 detrital zircons from a medium to coarse-grained sandstone, from fluvial channel facies, yielded a maximum depositional age of ca. 106 ± 1 Ma (n = 8). Both ages are consistent with volcanic events of the Barremian to Albian age in the central Patagonian Andes Region. Cathodoluminescence images of zircons from the San Jorge sample suggest an igneous origin, which is further supported by Th/U values above 0.5 in most of the grains. The distribution of the statistical modes of the main age populations of detrital zircons for the two samples [182, 185 and 189 Ma for Telsen sample (T2S) and 181 ± 1 Ma for San Jorge sample (SJS)] matches the age of the volcanic Marifil Formation. The rocks of the Marifil Formation of these ages are exposed NE to SE of the study area. The abundance of zircons of similar Jurassic ages (n = 52 for SJS and n = 105 for T2S) and the external morphology of the zircons in the sample SJS, implies a close proximity of the source area. Suggestion that the Marifil Formation was the main provenance source is also supported by northeast-southeasterly paleocurrents measured at the San Jorge and Telsen sections.

  5. 气体渗碳CAD软件的试验验证%Experimental Verification of CAD Software for Gas Carburizing

    孙炳超; 张戈; 钱初钧; 田禾; 沙云卿


    According to technical requirement of 1.2mm and 1.4mm carburizing depth, steel 20CrMnTi and 20CrMo test pieces were carburized in Unicase furnace with a gas carburizing dynamic control CAD system.The results show that this system has a powerful function and control exactly,the deviation of surface carbon concentration is less than 0.05%(weight),carbon concentration gradient curve in carburized layer is smooth and shows “S” shape,the deviation of carburizing depth is less than 0.05mm when the carburizing depth is 1.2mm or 1.4mm.The experimental results are fit well with that designed by software system.%用20CrMnTi和20CrMo钢制的试样,根据渗碳层深度分别为1.2mm和1.4mm的齿轮的技术要求,在装备有气体渗碳动态碳势控制CAD软件的渗碳炉上分别进行了试验,对模拟结果进行了验证,证实了该软件功能强劲、控制准确。其表面碳浓度(质量分数)偏差<0.05%;渗层内的碳浓度梯度曲线平滑,呈“S”型平台分布;渗层深度为1.2mm和1.4mm时,渗层深度的偏差<0.05mm。用该软件设计的渗碳工艺与实际检测结果能很好地吻合。

  6. Multi-mode Li diffusion in natural zircons: Evidence for diffusion in the presence of step-function concentration boundaries

    Tang, Ming; Rudnick, Roberta L.; McDonough, William F.; Bose, Maitrayee; Goreva, Yulia


    Micron- to submicron-scale observations of Li distribution and Li isotope composition profiles can be used to infer the mechanisms of Li diffusion in natural zircon. Extreme fractionation (20-30‰) within each single crystal studied here confirms that Li diffusion commonly occurs in zircon. Sharp Li concentration gradients frequently seen in zircons suggest that the effective diffusivity of Li is significantly slower than experimentally determined (Cherniak and Watson, 2010; Trail et al., 2016), otherwise the crystallization/metamorphic heating of these zircons would have to be unrealistically fast (years to tens of years). Charge coupling with REE and Y has been suggested as a mechanism that may considerably reduce Li diffusivity in zircon (Ushikubo et al., 2008; Bouvier et al., 2012). We show that Li diffused in the direction of decreasing Li/Y ratio and increasing Li concentration (uphill diffusion) in one of the zircons, demonstrating charge coupling with REE and Y. Quantitative modeling reveals that Li may diffuse in at least two modes in natural zircons: one being slow and possibly coupled with REE+Y, and the other one being fast and not coupled with REE+Y. The partitioning of Li between these two modes during its diffusion may depend on the pre-diffusion substitution mechanism of REE and Y in the zircon lattice. Based on our results, sharp Li concentration gradients are not indicative of limited diffusion, and can be preserved at temperatures >700 °C on geologic timescales. Finally, large δ7 Li variations observed in the Hadean Jack Hills zircons may record kinetic fractionation, rather than a record of ancient intense weathering in the granite source materials.

  7. Three-Dimensional (3-D) Atom Probe Tomography of a Cu-Precipitation-Strengthened, Ultrahigh-Strength Carburized Steel

    Tiemens, Benjamin L.; Sachdev, Anil K.; Mishra, Raja K.; Olson, Gregory B.


    In an effort to reduce material cost, experimental steel alloys were developed that incorporated Cu precipitation in lieu of costly Co alloying additions in secondary hardening carburizing gear steels. This work utilizes three-dimensional atom probe tomography to study one of these prototype alloys and quantify the nanoscale dispersions of body-centered cubic (bcc) Cu and M2C alloy carbides used to strengthen these steels. The temporal evolution of precipitate, size, morphology, and interprecipitate interactions were studied for various tempering times. Findings suggest that Cu precipitation does act as a catalyst for heterogeneous nucleation of M2C carbides at relatively high hardness levels; however, the resultant volume fraction of strengthening carbides was noticeably less than that predicted by thermodynamic equilibrium calculations, indicating a reduced potency compared with Co-assisted precipitation. Microstructural information such as precipitate size and volume fraction was measured at the peak hardness condition and successfully used to recalibrate alloy design models for subsequent alloy design iterations.

  8. A kinetic model of zircon thermoluminescence

    Turkin, A.A.; Es, H.J. van; Vainshtein, D.I.; Hartog, H.W. den

    A kinetic model of zircon thermoluminescence (TL) has been constructed to simulate the processes and stages relevant to thermoluminescent dating such as: filling of electron and hole traps during the excitation stage both for natural and laboratory irradiation; the time dependence of fading after

  9. What can zircon ages from the Jack Hills detrital zircon suite really tell us about Hadean geodynamics?

    Whitehouse, Martin; Nemchin, Alexander


    As the only direct sample of the Hadean Earth, detrital zircon grains from the Jack Hills, Western Australia, have been the subject of intense investigation over the almost three decades since their discovery. A wide variety of geochemical and isotopic analyses of these grains, as well as their mineral inclusions, have been used variously to support two fundamentally different models for Hadean geodynamics: (i) Some form of (not necessarily modern-style) plate recycling generating felsic (continental-type?) crust at the boundaries [1, 2], or conversely (ii) the persistence of a long-lived, stagnant basaltic lid within which magmatism occurred as a result of internal temperature perturbations and/or impacts [3, 4], a model also generally consistent with a wide range of observations from post-Hadean geochemical reservoirs. Despite the considerable time and resources expended, the majority of these studies uncritically accept the individual U-Pb zircon ages, even though their veracity is key to many of the interpretations [5, 6]. We report here the results of an in-depth evaluation of all published (and new) U-Pb ages from the Jack Hills zircon suite in order to define age populations that can be used with a high degree of confidence in geodynamic interpretations. A notable problem in the interpretation of U-Pb data from ancient zircon grains (including those as young as the Neoarchean) is that disturbance of the systematics even several 100 Ma after crystallization causes data to spread along the concordia curve without becoming discernably discordant within the relatively large error bounds associated with U/Pb ages from in situ dating methods (e.g. SIMS). While 207Pb/206Pb ages are typically more precise, individually they provide no means to detect Pb-loss-induced younging. However, if two or preferably more analyses have been made in the same zircon growth zone, a reasonable evaluation of the possibility of Pb-loss can be made. In the available Jack Hills zircon

  10. Élaboration de nanostructures à une dimension à base de carbure de silicium

    Ollivier, Maelig


    Le carbure de silicium est pressenti comme un matériau prometteur dans plusieurs domaines de l’électronique tels que la nano-électronique, l’électronique de puissance ou les capteurs travaillant en milieux hostiles (hautes températures, milieux corrosifs, milieux biologiques) du fait de ses propriétés physicochimiques supérieures à celles du silicium, notamment. Cependant, parmi les différentes méthodes d’élaboration par voie descendante ou ascendante permettant de fabriquer des nano-objets à...

  11. Control of heat-resistant steel carburized layer structure. Part I

    Semenov, M. Yu.


    A physical model of carbide formation with vacuum carburizing is developed with the aim of controlling complexly-alloyed steel diffusion layer structure, taking account of excess phase formation of both the cementite type, and special carbides. A mathematical model is developed on the basis of the physical model adopted, adequate for experimental results. Analysis of calculated results is used as a basis for demonstrating the effect on carbide formation of alloying with chromium and strong carbide-forming elements, and also production factors.

  12. Neoproterozoic-middle Paleozoic tectono-magmatic evolution of the Gorny Altai terrane, northwest of the Central Asian Orogenic Belt: Constraints from detrital zircon U-Pb and Hf-isotope studies

    Chen, Ming; Sun, Min; Buslov, Mikhail M.; Cai, Keda; Zhao, Guochun; Zheng, Jianping; Rubanova, Elena S.; Voytishek, Elena E.


    The Gorny Altai terrane (GA) is a key area in understanding the crustal evolution of the Central Asian Orogenic Belt (CAOB). This paper reports U-Pb and Hf-isotope data for detrital zircons from Cambrian to early Devonian sedimentary sequences to constrain their provenance, as well as the tectono-magmatic events and crustal growth in this region. Nearly all the detrital zircons are characterized by euhedral to subhedral morphology, high Th/U ratios (ca. 0.1-1.6) and typical oscillatory zoning, indicating a magmatic origin. The three samples from the Gorny Altai Group (middle Cambrian to early Ordovician) yield detrital zircon populations that are composed predominantly of 530-464 Ma grains, followed by a subordinate group of 641-549 Ma old. The Silurian and Devonian samples exhibit similar major zircon populations (555-456 Ma and 525-463 Ma, respectively), but a significant amount of additional 2431-772 Ma zircons occur in the early Devonian sample. Our results suggest that detritus from the nearby Kuznetsk-Altai intra-oceanic island arc served as a unitary source for the Cambrian-Silurian sedimentary sequences, but older detritus from other sources added to the early Devonian sequence. The low abundance of ca. 640-540 Ma detrital zircons may testify that this island arc was under a primitive stage in this period, when mafic volcanic rocks probably dominated. In contrast, the dominant population of ca. 530-470 Ma zircons may indicate an increased amount of granitic rocks in the source area, suggesting that the Kuznetsk-Altai island arc possibly evolved into a mature one in the Cambrian to early Ordovician. The ca. 530-470 Ma detrital zircons are almost exclusively featured by positive εHf(t) values and have two-stage Hf model ages of ca. 1.40-0.45 Ga, indicating that the precursor magmas were sourced predominantly from heterogeneous juvenile materials. We conclude that the late Neoproterozoic to early Paleozoic magmatism in the Kuznetsk-Altai arc made a

  13. Sample-scale zircon geochemical and geochronological heterogeneities as indicators of residual liquid infiltration events in the incrementally assembled Caleu Pluton, Central Chile

    Molina, P. G.; Parada, M. A.; Gutiérrez, F. J.; Ma, C.; Li, J.; Liu, Y.


    . Inconsistencies in whole-rock major and some trace elements concentrations are observed in the studied samples, these differences are attributable to open-system compositional perturbations. The sample-scale heterogeneities in zircon age and composition, points out to remobilization of a zircon-bearing interstitial melt, possibly by segregation from a locked-crystal mush, or infiltration of a zirconium-rich melt (and other incompatible elements) capable of crystallize zircons, even across a nearly solidified system during rapid exhumation. This study is financed by the CONICYT-FONDAP project 15090013, Centro de Excelencia en Geotermia de los Andes (CEGA).

  14. The U-Th-Pb systematics of zircon from the Bishop Tuff: A case study in challenges to high-precision Pb/U geochronology at the millennial scale

    Ickert, Ryan B.; Mundil, Roland; Magee, Charles W.; Mulcahy, Sean R.


    Dating zircon by U-Pb in the Pleistocene Bishop Tuff is challenging because the concentration of radiogenic Pb is low and the correction required for disequilibrium in the intermediate daughter products is large. The dates can be difficult to interpret, because their absolute precision is similar in magnitude to purported timescales of crystallization. Previous estimates of the duration of zircon crystallization span two orders of magnitude and appear to depend on the analytical approach. To reconcile the differing interpretations, we present new SIMS and ID-TIMS zircon Pb/U dates, including some crystals that are dated by both techniques. Both the SIMS and ID-TIMS dates have similar distributions as previous results. Normalized to a Th/Umelt = 2.81, SIMS spot dates from interior regions of sectioned grains range from 769 ± 31 ka to 845 ± 28 ka (2σ) and ID-TIMS dates have a range from 760 ± 7 ka to 793 ± 6 ka. Individual crystals dated by both methods have an average difference of 31 ka, with the SIMS dates being consistently older than the bulk crystal dates. This level of variability precludes the assignment of a geological significance to a mean (or weighted-mean) zircon date. A previous ID-TIMS investigation of single BT zircon that showed apparent statistically significant clustering of zircon ages was compromised by an incorrect treatment of the covariance structure of 230Th-corrected Pb/U data. We show approximate and exact methods for the correct treatment and demonstrate substantially more scatter in that data than previously recognized. Close scrutiny of available partition coefficient data show that they are not adequately precise for Bishop Tuff to <775 ka, which conflicts with some estimates of the 40Ar-39Ar sanidine age of eruption.

  15. U-Pb Dating of Zircons and Phosphates in Lunar Meteorites, Acapulcoites and Angrites

    Zhou, Q.; Zeigler, R. A.; Yin, Q. Z.; Korotev, R. L.; Joliff, B. L.; Amelin, Y.; Marti, K.; Wu, F. Y.; Li, X. H.; Li, Q. L.; Lin, Y. T.; Liu, Y.; Tang, G. Q.


    Zircon U-Pb geochronology has made a great contribution to the timing of magmatism in the early Solar System [1-3]. Ca phosphates are another group of common accessory minerals in meteorites with great potential for U-Pb geochronology. Compared to zircons, the lower closure temperatures of the U-Pb system for apatite and merrillite (the most common phosphates in achondrites) makes them susceptible to resetting during thermal metamorphism. The different closure temperatures of the U-Pb system for zircon and apatite provide us an opportunity to discover the evolutionary history of meteoritic parent bodies, such as the crystallization ages of magmatism, as well as later impact events and thermal metamorphism. We have developed techniques using the Cameca IMS-1280 ion microprobe to date both zircon and phosphate grains in meteorites. Here we report U-Pb dating results for zircons and phosphates from lunar meteorites Dhofar 1442 and SaU 169. To test and verify the reliability of the newly developed phosphate dating technique, two additional meteorites, Acapulco, obtained from Acapulco consortium, and angrite NWA 4590 were also selected for this study as both have precisely known phosphate U-Pb ages by TIMS [4,5]. Both meteorites are from very fast cooled parent bodies with no sign of resetting [4,5], satisfying a necessity for precise dating.

  16. Himalaya evolution at Paleogene-Neogene boundary unraveled by zircon age spectrum from Arabian Sea Sediments

    Feng, Han; Lu, Huayu; Zhang, Hanzhi


    Although virtually all the intensive orogenic activities of Himalaya occurred in Neogene, the tectonic evolution of this high mountain range in Paleogene is poorly understood. Investigations of tectonic change pattern at Paleogene-Neogene boundary are important to better understand the interaction between mountain building and climate evolution. Here we present new U-Pb ages of zircon grains from Indus Fan sediments to constrain the orogenic history of Himalaya at Paleogene-Neogene boundary. 11 samples between late Oligocene and early Miocene from ODP 117 cores are dated by the zircon U-Pb technique. We calculate relative contributions of potential sources by counting zircon grains for each sample, and the quantized results indicate Himalaya contributed sediments to the coring site, and an extremely high input from Great and Tethyan Himalaya during late Oligocene-early Miocene. Four samples in Pleistocene are also dated for comparison, which indicates that high proportion of Lesser Himalaya has contributed to the sediment in Pleistocene. Our results suggest that the high contribution of Great and Tethyan Himalaya at Paleogene-Neogene boundary might correlate with the beginning of activity of MCT and extension of STD with leucogranite intrusion along Himalaya, which give rise to the extensive Great Himalaya exhumation. Our study demonstrates that zircon U-Pb dating technique is a good tool to reconstruct erosional history of mountain building on a tectonic timescale. Key words: ODP, Himalaya, Indus Fan, zircon U-Pb dating, Paleogene-Neogene boundary

  17. U-Pb dating by zircon dissolution method using chemical abrasion

    Takehara, Lucy, E-mail: [Servico Geologico do Brasil (CPRM), Brasilia, DF (Brazil); Chemale Junior, Farid [Universidade de Brasilia (UnB), Brasilia, DF (Brazil). Inst. de Geociencias. Lab. de Geocronologia; Hartmann, Leo A. [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Inst. de Geociencias; Dussin, Ivo A.; Kawashita, Koji [Universidade de Sao Paulo (USP), SP, (Brazil). Centro de Pesquisa Geocronologicas


    Chemical abrasion was carried out on zircons grains of the Temora II standard for U-Pb dating prior to analyses using in situ Laser Ablation-Multi Collector Ion Coupled Plasma Mass Spectrometer (LA-ICPMS) followed by the Isotope Dissolution Thermal Ionization Mass Spectrometer (ID-TIMS) method. The proposed methodology was herein applied in order to reduce primarily the effects of secondary Pb loss, the presence of common lead and/or silicate impurities. Nine Temora II zircon grains were analyzed by the laser ablation method yielding an age of 418.3 +- 4.3 Ma. Zircon grains of a same population were separated for chemical abrasion before dissolution and mass spectrometry analyses. Six fractions of them were separated for isotope dissolution using {sup 235}U-{sup 205}Pb mixed spike after we have checked and assured the laboratory conditions of low blank values for total Pb of less than 2 pg/g. The obtained U-Pb zircon age by the ID-TIMS method was 415.7 +- 1.8 Ma (error 0.43 %) based on four successful determinations. The results are consistent with the published ages for the Temora diorite (Temora I - 416.75 +- 1.3 Ma; Temora II - 416.78 +- 0.33 Ma) and established as 416 +- 0.33 Ma. The technique is thus recommended for high precision U-Pb zircon analyses (error < 1 %), mainly for high resolution stratigraphic studies of Phanerozoic sequences. (author)

  18. Zircon xenocryst resorption and magmatic regrowth at El Chichón Volcano, Chiapas, Mexico

    Pack, Brenda; Schmitt, Axel K.; Roberge, Julie; Tenorio, Felipe Garcia; Damiata, Brian N.


    El Chichón volcano is the only active volcano located within the Chiapanecan Volcanic Arc in southern Mexico, which lies between the Trans-Mexican Volcanic Belt and the Central American Volcanic Arc. Previous studies have shown that ~ 12 eruptions have occurred at El Chichón within the last 8000 years, forming a complex of lava domes with a central crater and surrounding pyroclastic deposits. Here, we report the discovery of zircon in Holocene El Chichón rocks, which were analyzed by high spatial resolution imaging (color cathodoluminescence CCL) and isotopic (secondary ionization mass spectrometry SIMS) methods to resolve core and rim crystallization ages. Pumice samples from five proximal pyroclastic flow and fall-out deposits were collected based on published stratigraphy. Two of the samples were further (re-)classified by new 14C dates. In addition, we sampled two lavas from the 1982 eruption and from remnants of the older Somma lava complex. Zircon crystals were dated using 230Th/238U disequilibrium (U-Th) and U-Pb geochronology. U-Th zircon ages fall between near eruption ages and ca. 84 ka, with overlapping ages in all samples. By contrast, zircon core U-Pb ages range between ca. 290 Ma and 1.9 Ga. These ages are consistent with xenocrystic origins and their heterogeneity indicates derivation from clastic country rocks. Strong age contrasts between inherited xenocrystic and young magmatic domains in individual zircon crystals are evidence for arrested assimilation of crustal rocks where initially zircon-undersaturated magmas cooled rapidly to form a crystal mush or subsolidus amalgamate as a crustally contaminated boundary layer. This layer contributed zircon crystals to eruptible magma during episodic recharge events followed by partial melt extraction, mixing and homogenization. Zircon overgrowths are significantly older than major minerals whose U-series ages and sharp zonation boundaries suggest crystallization only within a few ka before eruption

  19. Late magmatic stage of the zoned Caleu pluton (Central Chile): insights from zircon crystallization conditions

    Molina, P. G.; Parada, M.; Gutierrez, F. J.; Chang-Qiang, M.; Jianwei, L.; Yuanyuan, L.


    (IV)/Ce(III) decrease with temperature gives rise to separate trends for each zone, suggesting an independent unbuffered development at time of zircon formation. Taking into account variations in zircon ages, morphologies and crystallization ranges in the collected samples, it is suggested that zircon crystallization took place independent of the magma composition. Furthermore, old inherited zircon grains in the GDZ could be antecrysts, or products of a restricted and not major host rock assimilation, owing to the impossibility of basaltic magmas to saturate zircon crystals, and the isotopically depleted signature. This study is financed by CONICYT-FONDAP grant 15090013, Centro de Excelencia en Geotermia de los Andes (CEGA); and the CONICYT PBCT-PDA07, Programa Bicentenario de Ciencia y Tecnología.

  20. Catalytic Effect of Cerium Oxide on Carburization of Steel%氧化铈在钢表面气相渗碳时的催化作用

    袁泽喜; 谭平; 余宗森; 徐庭栋


    Comparing the kinetics of gas carburization of steel 20 with the carburization agent containing cerium oxide or without it,it is found that cerium oxide in carburant can accelerate carburizing process greatly,which almost has the same effect at 850℃ and 910℃.This effect is accomplished by catalyzing mechanism of cerium oxide.RE in steel can also accelerate carburizing process,but its effect is less than RE in carburant. RE in steel can improve the catalysis of RE in carburant.%在20钢气相渗碳时对比了渗剂中加入CeO2或不加CeO2时的渗碳动力学,发现在渗剂中加入CeO2可以显著加快渗碳速率。稀土催渗剂的效果在850℃和910℃基本相同。认为CeO2加速渗碳的机制是催化。冶炼时在钢中加入的稀土对渗碳也起加速作用,但作用小于渗剂中的稀土。它还可以增强渗剂中稀土的催渗作用。

  1. U-Pb zircon geochronology and phase equilibria modelling of a mafic eclogite from the Sumdo complex of south-east Tibet: Insights into prograde zircon growth and the assembly of the Tibetan plateau

    Weller, O. M.; St-Onge, M. R.; Rayner, N.; Waters, D. J.; Searle, M. P.; Palin, R. M.


    The Sumdo complex is a Permian-Triassic eclogitic metamorphic belt in south-east Tibet, which marks the location of a suture zone that separates the northern and southern Lhasa terranes. An integrated geochronological and petrological study of a mafic eclogite from the complex has constrained its tectonometamorphic history and provides a case study of zircon growth in eclogite as a product of prograde dissolution-precipitation. In situ U-Pb geochronology indicates that the eclogite contains a single population of zircon with a crystallisation age of 273.6 ± 2.8 Ma. The morphology and chemistry of the zircon grains are consistent with growth by dissolution-precipitation of protolith magmatic zircon. The presence of zircon grains as inclusions in the cores of peak phases indicates that zircon dissolution-precipitation occurred during prograde metamorphism, and calculated pressure and temperature conditions over which mineral inclusions in zircon are stable suggest that the zircon most likely precipitated at 15.5-16.5 kbar and 500-560 °C. Subsequent peak metamorphism is calculated to have reached pressure-temperature conditions of 27 ± 1 kbar and 670 ± 50 °C. Previous studies, which have documented a range of peak metamorphic conditions from high- to ultrahigh-pressure at c. 266-230 Ma, indicate that the Sumdo complex is a composite belt that experienced protracted eclogite exhumation. The results of this study are consistent with this interpretation, and extend the age range of high-pressure metamorphism in the complex to over 40 Myr. Analysis of published pressure-temperature-time data indicates two systematic behaviours within this spread. First, peak metamorphic temperatures declined over time. Second, eclogite exhumation occurred in two discrete intervals: soon after formation, and during the demise of the subduction zone. The latter behaviour serves as a reminder that eclogite exhumation is the exception rather than the rule.

  2. 低碳钢固体渗碳的实验与研究%Experiment and Research on Solid-carburizing for Low Carbon Steel



    The experiment of solid-carburizing process on 20 steel and 20CrMoV steel has been fully developed, which includes preparatory heat-treatment, carburizing craft, metallographic structure, the final heat- treatment, etc. This experiment analyzed the factors of carburizing coating and hardness, and the basic law and technology of solid- carburizing process have been worked out. The experiment has proved that solid- carburizing craft has several advantages such as simple process, easily to operate and control, low cost, and without special devices. The solid- carburizing product completely meets conventional requirement. However, solid-carburizing process has its disadvantages such as thin carburizing coating and too long total operating time, thus solid- carburizing only fits for the production of single-piece on small scale.%对20、20CrMoV钢的固体渗碳进行了较全面的实验及研究,包括钢的预备热处理、渗碳工艺、金相组织、最终热处理等;分析了渗碳层、硬度的影响因素,并总结摸索出固体渗碳的基本规律和工艺技术;实验证明:固体渗碳工艺简单、操作简单、成本低廉,不需要专门设备;渗碳件在性能上完全能够达到常规渗碳的要求,但固体渗碳的渗碳层偏薄,时间较长,只能适应单件、小批量的生产。

  3. Green fuels, growth engines after petroleum; Les carburants verts, moteurs de la croissance apres le petrole

    Mili, Dino


    The contribution of the new fuels to a greener environment is important and immediate. Thanks to clean novel technologies and to commercial plant projects in development, companies like Enerkem contribute to satisfy increasing global demand for clean energy. They stimulate local economies by creating jobs in an industry that offers real growth potential. Green fuels will gradually allow us to let go of non sustainable energy sources like oil to adopt a way of life based on sustainable development. They will also allow a shift towards a green economy. [French] La contribution des nouveaux carburants a un environnement plus vert est importante et immediate. Grace a des technologies propres novatrices et a des projets d'sines commerciales en developpement, des entreprises comme Enerkem contribuent a satisfaire a la demande mondiale croissante en energie propre. Elles stimulent les economies locales par la creation d'emplois dans une industrie qui offre un veritable potentiel de croissance. Les carburants verts permettront graduellement de nous affranchir des sources d'energie non renouvelables comme le petrole pour adopter un mode de vie base sur le developpement durable. Ils permettront aussi un virage vers une economie verte.

  4. Boronization and Carburization of Superplastic Stainless Steel and Titanium-Based Alloys

    Masafumi Matsushita


    Full Text Available Bronization and carburization of fine-grain superplastic stainless steel is reviewed, and new experimental results for fine grain Ti88.5Al4.5V3Fe2Mo2 are reported. In superplastic duplex stainless steel, the diffusion of carbon and boron is faster than in non-superplastic duplex stainless steel. Further, diffusion is activated by uniaxial compressive stress. Moreover, non-superplastic duplex stainless steel shows typical grain boundary diffusion; however, inner grain diffusion is confirmed in superplastic stainless steel. The presence of Fe and Cr carbides or borides is confirmed by X-ray diffraction, which indicates that the diffused carbon and boron react with the Fe and Cr in superplastic stainless steel. The Vickers hardness of the carburized and boronized layers is similar to that achieved with other surface treatments such as electro-deposition. Diffusion of boron into the superplastic Ti88.5Al4.5V3Fe2Mo2 alloy was investigated. The hardness of the surface exposed to boron powder can be increased by annealing above the superplastic temperature. However, the Vickers hardness is lower than that of Ti boride.

  5. Analyses of quenching process during turn-off of plasma electrolytic carburizing on carbon steel

    Wu, Jie; Liu, Run [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Xue, Wenbin, E-mail: [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China); Wang, Bin; Jin, Xiaoyue; Du, Jiancheng [Key Laboratory for Beam Technology and Materials Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875 (China); Beijing Radiation Center, Beijing 100875 (China)


    Highlights: • Cooling rate of carburized steel at the end of PEC treatment is measured. • The quench hardening in the fast or slow turn-off mode hardly takes place. • Decrease of the surface roughness during slow turn-off process is found. • A slow turn-off mode is recommended to replace the conventional turn-off mode. - Abstract: Plasma electrolytic carburizing (PEC) under different turn-off modes was employed to fabricate a hardening layer on carbon steel in glycerol solution without stirring at 380 V for 3 min. The quenching process in fast turn-off mode or slow turn-off mode of power supply was discussed. The temperature in the interior of steel and electron temperature in plasma discharge envelope during the quenching process were evaluated. It was found that the cooling rates of PEC samples in both turn-off modes were below 20 °C/s, because the vapor film boiling around the steel sample reduced the cooling rate greatly in terms of Leidenfrost effect. Thus the quench hardening hardly took place, though the slow turn-off mode slightly decreased the surface roughness of PEC steel. At the end of PEC treatment, the fast turn-off mode used widely at present cannot enhance the surface hardness by quench hardening, and the slow turn-off mode was recommended in order to protect the electronic devices against a large current surge.

  6. Carburizing plasma in a low temperature austenitic stainless steel AISI 304; Cementacao a plasma em baixa temperatura de um aco inoxidavel austenitico AISI 304

    Mota, W.T.; Ramos, F.D.; Rocha, R.C.; Barcelos, M.V.; Barcelos, M.A., E-mail: [Instituto Federal do Espirito Santo (IFES), ES (Brazil)


    The industrial use of thermochemical treatment assisted by the cold plasma has been widely employed in recent years, mainly oriented to the excellent results obtained in the surface modification of engineering materials, when compared to more traditional methods. In this work, we studied the plasma carburizing low temperature steel AISI 304 mechanical parts used in construction. The thermochemical treatment was performed at a fixed gas atmosphere 7% CH{sub 4} (g) and 93 % H{sub 2} (g), 350 ° C and times of 1, 3 and 5 hours. Samples being tested for Vickers hardness, abrasive microwear, microstructure evaluation by optical microscopy and SEM and X-ray diffraction. The results show significant improvement in surface hardness, wear resistance and good formation of expanded austenite layer and no identifiers peaks of carbides. The results achieved are due to diffusion/adsorption of carbon present in the gaseous atmosphere to the evaluated samples. (author)

  7. A comparison of zircon U-Pb age results of the Red Clay sequence on the central Chinese Loess Plateau

    Gong, Hujun; Nie, Junsheng; Wang, Zhao; Peng, Wenbin; Zhang, Rui; Zhang, Yunxiang


    Single grain zircon U-Pb geochronology has demonstrated great potentials in extracting tectonic and atmospheric circulation signal carried by aeolian, fluvial, and fluviolacustrine sediments. A routine in this sort of studies is analyzing 100-150 grains and then compares zircon U-Pb age spectra between the measured sample and the potential sources. Here we compared the zircon U-Pb age results of the late Miocene-Pliocene Red Clay sequence of two neighboring sites from the Chinese Loess Plateau where similar provenance signal is expected. Although the results from the 5.5 Ma sediment support this prediction, the results from the 3 Ma sediment at these two sites differ from each other significantly. These results emphasize the importance of increasing analysis number per sample and combining the zircon U-Pb geochronology with other provenance tools in order to get reliable provenance information.


    杨久流; 罗家珂


    Ultrafine zircon powder with high purity is a kind of brightening agent in glaze for making high-grade cleaning whiteware. Wet ultrafine grinding is the key operation for producing ultrafine zircon power with high purity, and directly affects the size distribution, d50 and whiteness of the final products. This paper lays emphasis on researching wet grinding process parameters for producing ultrafine zircon power, such as the weight ratio of ball to feed material, grinding density and time, and weight assignment with different ball sizes, and their effects on quality of zircon power.%高纯超细锆英石粉是制造高档卫生洁具陶瓷所用釉料中的乳浊增白剂。湿法超细磨矿是生产高纯超细锆英石粉的关键工序之一,它直接影响最终产品粒度分布、中位粒径和白度。本文着重研究锆英石超细磨矿工艺参数球料比、磨矿浓度、磨矿时间及磨矿介质球径的配比等对锆英石微粉产品质量的影响。

  9. 大别山高压-超高压片麻岩锆石的拉曼光谱学研究%Laser-Raman spectroscopic studies on zircons from the HP-UHP gneisses of Dabie Mountains

    刘文元; 刘景波


    The zircons from gneisses in high and ultrahigh-pressure (HP-UHP) metamorphic zones of the Dabie Mountains have been investigated by using Laser Raman microprobe analysis, cathodoluminescence (CL) images, U-Pb ages and trace elements measured by LA-ICP-MS. Most of the FWHMs (full widths at half-maximum) of 1008cm~(-1) band of zircons are less than 20cm~(-1), suggesting that zircons are well crystallized to moderately damaged. The early inherited zircons from gneisses had undergone significant annealing and recrystallization during the HP-UHP metamorphic event. The α-doses that zircons suffered are probably accumulated from about 200Ma, indicating that HP-UHP metamorphic rocks have been exhumed to the surface of the earth at this time. The magmatic events of Cretaceous age in North Dabie may exert little effect on the HP-UHP rocks, which most of FWHMs and frequencies of zircons in Dabie Moutains fall into the natural radiation damage trend (RDT) , indicating completely recrystalization of zircons during the HP-UHP metamorphic event.%对大别山高压-超高压片麻岩的锆石进行了激光拉曼探针、阴极发光(CL)、U-Pb年龄和U、Th等微量元素的测定分析.研究结果表明:锆石拉曼光谱1008cm~(-1)峰的半高宽普遍小于20cm~(-1),指示锆石结晶程度较好到中等程度的蜕晶化;早期继承锆石在三叠纪高压-超高压变质作用中经历了退火和重结晶作用,所受的放射性通量是从200Ma的早侏罗纪开始积累的,表明高压-超高压岩石在这一时间已出露地表;北大别白垩纪岩浆热事件对高压-超高压岩石的影响很小;大多数锆石数据都落在天然锆石的放射性破坏趋势(RDT)中,表明锆石在高压、超高压过程中基本发生了完全的重结晶.

  10. Theoretical modeling of zircon's crystal morphology according to data of atomistic calculations

    Gromalova, Natalia; Nikishaeva, Nadezhda; Eremin, Nikolay


    Zircon is an essential mineral that is used in the U-Pb dating. Moreover, zircon is highly resistant to radioactive exposure. It is of great interest in solving both fundamental and applied problems associated with the isolation of high-level radioactive waste. There is significant progress in forecasting of the most energetically favorable crystal structures at the present time. Unfortunately, the theoretical forecast of crystal morphology at high technological level is under-explored nowadays, though the estimation of crystal equilibrium habit is extremely important in studying the physical and chemical properties of new materials. For the first time, the thesis about relation of the equilibrium shape of a crystal with its crystal structure was put forward in the works by O.Brave. According to it, the idealized habit is determined in the simplest case by a correspondence with the reticular densities Rhkl of individual faces. This approach, along with all subsequent corrections, does not take into account the nature of atoms and the specific features of the chemical bond in crystals. The atomistic calculations of crystal surfaces are commonly performed using the energetic characteristics of faces, namely, the surface energy (Esurf), which is a measure of the thermodynamic stability of the crystal face. The stable crystal faces are characterized by small positive values of Esurf. As we know from our previous research (Gromalova et al.,2015) one of the constitutive factors affecting the value of the surface energy in calculations is a choice of potentials model. In this regard, we studied several sets of parameters of atomistic interatomic potentials optimized previously. As the first test model («Zircon 1») were used sets of interatomic potentials of interaction Zr-O, Si-O and O-O in the form of Buckingham potentials. To improve playback properties of zircon additionally used Morse potential for a couple of Zr-Si, as well as the three-particle angular harmonic

  11. Zircon-apatite U-Pb geochronology, zircon Hf isotope composition and geochemistry of granite batholith in the northern Mexico: Implications for Tectonomagmatic evolution of southern Cordillera.

    Mahar, M. A.; Goodell, P.


    We present the zircon-apatite U-Pb ages and zircon Hf isotope composition of the granite batholith exposed at the western boundary of Chihuahua. Granidiorite samples were analyzed from both, north and south of the Rio El Fuerte and Sinforosa Lineament. Based on previous studies, the WWN-EES trending Sinforosa Lineament is proposed as the manifestation of a terrane boundary between Seri in the north and Tahue terrane in the south. Zircon U-Pb data indicate that the magmatism spans a time period of 36 Ma from 89 to 53 Ma to the north of the Sinforosa Lineament while granodiorites in the south of the Sinforosa Lineament are dated at 59 Ma. The U-Pb apatite ages are variable in the north of the Sinforosa Lineament and range from 86-51 Ma. These apatite dates are 1-28 Ma younger than the corresponding zircon U-Pb crystallization ages. This indicates variable cooling rates and moderate to shallow emplacement. In contrast, in the south of the Sinforosa Lineament, the U-Pb apatite ages (64-59 Ma) are indistinguishable from the zircon U-Pb age (59 Ma), indicating rapid cooling and shallow emplacement. Zircon morphology and U-Pb dating revealed the absence of inherited component in the zircon ages, as no inheritance of any age has been observed. Most of the northwestern Mexico is underlain by Precambrian-Paleozoic-Jurassic basement. However, in the study area, U-Pb dating does not support the involvement of the older basement in generating the granite magmas. The weighted mean initial ɛHf (t) isotope composition of granodiorites on both sides of the Sinforosa Lineament varies from +2 to +5. However, Hf isotope composition in the south of the Sinforosa Lineament is more heterogeneous and relatively evolved with weighted Mean ɛHf (t) = +1.45. The Hf isotope composition is consistent with the previously reported near bulk silicate Sr-Nd isotope values. We suggest that the magmatic rocks in this region are not derived from melting of a felsic older crust beneath the batholith

  12. The Crystal Structure of Lanthanide Zirconates

    Clements, Richard; Kennedy, Brendan; Ling, Christopher; Stampfl, Anton P. J.


    The lanthanide zirconates of composition Ln2Zr2O7 (Ln = La-Gd) are of interest for use in inert matrix fuels and nuclear wasteforms. The series undergoes a pyrochlore to fluorite phase transition as a function of the Ln atomic radii. The phase transition has been attributed to disordering of both the cation and the anion [1]. We have undertaken a synthesis of the lanthanide zirconate series Ln2Zr2O7 (Ln = La-Gd), Ln0.2Zr0.8O1.9 (Ln = Tb-Yb) and NdxHo2-xZr2O7 (0ANSTO's new high resolution powder diffractometer Echidna, in order to obtain accurate data on atomic displacement parameters and O 48f position across the series. These results will be presented, along with details of the analysis and synthetic techniques used.

  13. The crystallization age of eucrite zircon.

    Srinivasan, G; Whitehouse, M J; Weber, I; Yamaguchi, A


    Eucrites are a group of meteorites that represent the first planetary igneous activity following metal-silicate differentiation on an early planetesimal, similar to Asteroid 4 Vesta, and, thus, help date geophysical processes occurring on such bodies in the early solar system. Using the short-lived radionuclide (182)Hf as a relative chronometer, we demonstrate that eucrite zircon crystallized quickly within 6.8 million years of metal-silicate differentiation. This implies that mantle differentiation on the eucrite parent body occurred during a period when internal heat from the decay of (26)Al and (60)Fe was still available. Later metamorphism of eucrites took place at least 8.9 million years after the zircons crystallized and was likely caused by heating from impacts, or by burial under hot material excavated by impacts, rather than from lava flows. Thus, the timing of eucrite formation and of mantle differentiation is constrained.

  14. Hydrogen Effect on Coke Removal and Catalytic Performance in Pre-Carburization and Methane Dehydro-Aromatization Reaction on Mo/HZSM-5

    Hongtao Ma; Ryoichi Kojima; Satoshi Kikuchi; Masaru Ichikawa


    In this study,the effects of pre-carburization of catalyst,hydrogen addition to methane feed and the space velocity of methane on the catalytic performance in methane to benzene (MTB) reaction were discussed in detail over Mo/HZSM-5 catalyst at 1023 K and 0.3 MPa. Compared with the non-precarburized catalyst,the Mo catalyst pre-carburized under the flow of CH4+4H2 at 973 K was found to have the higher activity and better stability. Further 6% H2 addition to the methane feed suppressed the aromatic type of coke formation effectively,and improved the stability of catalyst markedly,moreover gave a much longer reaction life of catalyst (53 h at 1023 K and 5400 ml/(g·h)) and much more formation amounts of benzene and hydrogen. With increase of methane space velocity,both the naphthalene formation selectivity and the coke formation selectivity were decreased by the shortened contact time;the benzene formation selectivity and total formation amount before the complete deactivation of catalyst were increased ly,while the total naphthalene and coke formation amounts did not change much.At high methane space velocity (≥5400 ml/(g·h)),a new middle temperature coke derived from the high temperature aromatic coke was formed on the catalyst; all the coke formed could be burnt off at lower temperature in oxygen,compared with those obtained at low space velocity. Considering the benzene formation amount and catalyst stability together,5400 ml/(g·h) was proved to be the most efficient methane space velocity for benzene production.

  15. Detrital zircon U-Pb geochronology and provenance of the Carboniferous-Permian glaciomarine pebbly slates in the Tibetan Plateau

    Wang, Q.; Zhu, D.; Zhao, Z.; Chung, S.; Li, C.; Sui, Q.; Fu, X.; Mo, X.


    Glaciomarine diamictites (including pebbly slate, pebbly siltstone, and pebbly sandstone) in the Tibetan Plateau are widely interpreted to have been associated with the deglaciation of the Indian continent. Guiding by zircon cathodoluminescence images, we determined U-Pb ages for detrital zircons from five typical Carboniferous-Permian pebbly slate samples from the Qiangtang, Lhasa, and Tethyan Himalaya of the Tibetan Plateau. The age distributions of detrital zircons from two samples (180 analyses) from Qiwu and Gangma Tso of the Qiangtang Terrane are similar, with two main age peaks ca. 579 and ca. 816 Ma and one minor age peak ca. 2490 Ma. Two samples (177 analyses) from Jiangrang and Damxung of the Lhasa Terrane define similar age distributions with two main age peaks ca. 539 and ca. 1175 Ma. Ages of detrital zircons from one sample (110 analyses) from Kangmar of the Tethyan Himalaya display main age peaks ca. 535, ca. 949, and ca. 2490 Ma. The ca. 816-Ma detrital zircons from the Qiangtang Terrane were most likely derived from the Lesser Himalaya, and the ca. 950-Ma detrital zircons from the Tethyan Himalaya might have been sourced from the High Himalaya, Eastern Ghats Province of the Indian plate and the Rayner Province of East Antarctica. The distinctive ca. 1175-Ma age population characteristic of zircons in the pebbly slates from the Lhasa Terrane is identical to the detrital zircons from the late Paleozoic sandstones (Zhu et al., 2011a) and the inherited zircons from the Mesozoic peraluminous granites (Zhu et al., 2011b) in this terrane, but significantly absent in the pebbly slates from both the Qiangtang and the Tethyan Himalayan terranes. The ca. 1175-Ma detrital zircons in the Lhasa Terrane were most likely sourced from the Albany-Fraser-Wilkes in southwestern Australia and East Antarctica. These new data obtained in this study reveal a distinct difference of detrital zircon provenance for the coeval Carboniferous-Permian glaciomarine pebbly slates

  16. Zircon SHRIMP U-Pb age of garnet olivine pyroxenite at Hujialin in the Sulu terrane and its geological significance

    GAO Tianshan; CHEN Jiangfeng; XIE Zhi; YANG Shenghong; YU Gang


    Garnet olivine pyroxenite at Hujialin is situated in the Sulu ultrahigh pressure (UHP) metamorphic belt, Shandong Province. Most of the zircon separated from the rock is well crystallized, prismatic and granular with a length to width ratio of 1︰1.3-1︰2.5. CL and BSE images show the magmatic oscillatory zoning in the zircon. Th/U ratio ranges from 0.99 to 2.81. These suggest a magmatic origin for the zircon studied. SHRIMP dating yields 206Pb/238U ages of 207-223 Ma, with a weighted average of 216±3 Ma. This age corresponds to zircon growth during exhumation of UHP slab and thus the timing of amphibolite-facies retrogression. The garnet olivine pyroxenite was wrapped and brought to the crust by the UHP slab during exhumation, and then suffered from metasomatism by fluid from the UHP slab itself. The zircon U-Pb age records the timing of the crystallization of metasomatic melt. Therefore, fluid that was released during exhumation of deeply subducted continental slab may be the important source for zircon growth.

  17. An in vitro evaluation of novel NHA/zircon plasma coating on 316L stainless steel dental implant

    Ebrahim Karamian; Mahmood Reza Kalantar Motamedi; Amirsalar Khandan; Parisa Soltani; Sahel Maghsoudi


    The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon (NHA/zircon) nanobiocomposite coating on 316L stainless steel (SS) dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0 (control), 5, 10, and 15 wt%of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method. Scanning electron microscopy (SEM) was used to evaluate surface morphology, and X-ray diffraction (XRD) was used to analyze phase composition and crystallinity (Xc). Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30-40 nm in diameter and a bone-like composition, which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity (Xc = 41.1%) and maximum bioactivity occurred in the sample containing 10 wt%of zircon because of minimum Xc and maximum biodegradation of the coating sample.

  18. An in vitro evaluation of novel NHA/zircon plasma coating on 316L stainless steel dental implant

    Ebrahim Karamian


    Full Text Available The surface characteristics of an implant that influence the speed and strength of osseointegration include crystal structure and bioactivity. The aim of this study was to evaluate the bioactivity of a novel natural hydroxyapatite/zircon (NHA/zircon nanobiocomposite coating on 316L stainless steel (SS dental implants soaking in simulated body fluid. A novel NHA/zircon nanobiocomposite was fabricated with 0 (control, 5, 10, and 15 wt% of zircon in NHA using ball mill for 1 h. The composite mixture was coated on SS implants using a plasma spray method. Scanning electron microscopy (SEM was used to evaluate surface morphology, and X-ray diffraction (XRD was used to analyze phase composition and crystallinity (Xc. Further, calcium ion release was measured to evaluate the coated nanobiocomposite samples. The prepared NHA/zircon coating had a nanoscale morphological structure with a mean crystallite size of 30–40 nm in diameter and a bone-like composition, which is similar to that of the biological apatite of a bone. For the prepared NHA powder, high bioactivity was observed owing to the formation of apatite crystals on its surface. Both minimum crystallinity (Xc=41.1% and maximum bioactivity occurred in the sample containing 10 wt% of zircon because of minimum Xc and maximum biodegradation of the coating sample.

  19. U-Pb Age and Hf Isotope Study of Detrital Zircons from the Wanzi Supracrustals: Constraints on the Tectonic Setting and Evolution of the Fuping Complex, Trans-North China Orogen

    Xiaoping XIA; Min SUN; Guochun ZHAO; WU Fuyuan; XU Ping; Jian ZHANG; Yanhong HE; ZHANG Jiheng


    Located in the middle segment of the Trans-North China Orogen, the Fuping Complex is considered as a critical area in understanding the evolution history of the North China Craton (NCC).The complex is composed of various high-grade and multiply deformed rocks, including gray gneiss,basic granulite, amphibolite, fine-grained gneiss and marble, metamorphosed to upper amphibolite or granulite facies. It can be divided into four rock units: the Fuping TTG gneisses, Longquanguan augen gneisses, Wanzi supracrustals, and Nanying granitic gneisses. U-Pb age and Hf isotope compositions of about 200 detrital zircons from the Wanzi supracrustals of the Fuping Complex have been analyzed.The data on metamorphic zircon rims give ages of 1.82-1.84 Ga, corresponding to the final amalgamation event of the NCC, whereas the data for igneous zircon cores yield two age populations at ~2.10 and ~2.51 Ga, with some inherited ages scattering between 2.5 and 2.9 Ga. These results suggest that the Wanzi supracrustals were derived from the Fuping TTG gneisses (~2.5 Ga) and the Nanying granitic gneisses (2.0-2.1 Ga) and deposited between 2.10 and 1.84 Ga. All zircons with ~2.51 Ga age have positive initial εHf values from +1.4 to +10.9, suggesting an important crustal growth event at ~2.5 Ga through the addition of juvenile materials from the mantle. The Hf isotope data for the detrital zircons further imply that the 2.8 Ga rocks are important components in the lower crust, which is consistent with a suggestion from Nd isotope data for the Eastern Block. The zircons of 2.10 Ga population have initial εHf values of-4.9 to +6.1, interpreted as mixing of crustal re-melt with minor juvenile material contribution at 2.1 Ga. These results are distinct from that for the Western Block,supporting that the Fuping Complex was emplaced in a tectonic active environment at the western margin of the Eastern Block.

  20. Chemical abrasion-SIMS (CA-SIMS) U-Pb dating of zircon from the late Eocene Caetano caldera, Nevada

    Watts, Kathryn E.; Coble, Matthew A.; Vazquez, Jorge A.; Henry, Christopher D.; Colgan, Joseph P.; John, David A.


    Zircon geochronology is a critical tool for establishing geologic ages and time scales of processes in the Earth's crust. However, for zircons compromised by open system behavior, achieving robust dates can be difficult. Chemical abrasion (CA) is a routine step prior to thermal ionization mass spectrometry (TIMS) dating of zircon to remove radiation-damaged parts of grains that may have experienced open system behavior and loss of radiogenic Pb. While this technique has been shown to improve the accuracy and precision of TIMS dating, its application to high-spatial resolution dating methods, such as secondary ion mass spectrometry (SIMS), is relatively uncommon. In our efforts to U-Pb date zircons from the late Eocene Caetano caldera by SIMS (SHRIMP-RG: sensitive high resolution ion microprobe, reverse geometry), some grains yielded anomalously young U-Pb ages that implicated Pb-loss and motivated us to investigate with a comparative CA and non-CA dating study. We present CA and non-CA 206Pb/238U ages and trace elements determined by SHRIMP-RG for zircons from three Caetano samples (Caetano Tuff, Redrock Canyon porphyry, and a silicic ring-fracture intrusion) and for R33 and TEMORA-2 reference zircons. We find that non-CA Caetano zircons have weighted mean or bimodal U-Pb ages that are 2–4% younger than CA zircons for the same samples. CA Caetano zircons have mean U-Pb ages that are 0.4–0.6 Myr older than the 40Ar/39Ar sanidine eruption age (34.00 ± 0.03 Ma; error-weighted mean, 2σ), whereas non-CA zircons have ages that are 0.7–1.3 Myr younger. U-Pb ages do not correlate with U (~ 100–800 ppm), Th (~ 50–300 ppm) or any other measured zircon trace elements (Y, Hf, REE), and CA and non-CA Caetano zircons define identical trace element ranges. No statistically significant difference in U-Pb age is observed for CA versus non-CA R33 or TEMORA-2 zircons. Optical profiler measurements of ion microprobe pits demonstrate consistent depths of ~ 1.6

  1. The efficiency of different types of wood charcoal on increasing carbon content on surfaces of low carbon steel in the pack carburizing process

    Narongsak Thammachot


    Full Text Available The purpose of this research is to compare the efficiency of five types of wood charcoal, eucalyptus, coconut shell, tamarind, bamboo and cassava root in increasing carbon content on surfaces of low carbon steel by the pack carburizing process. The experiment for pack carburized low carbon steel (grade AISI 1020 was conducted by using the different wood charcoals as carburizers, mixed with 10% limestone (by weight as the energizer. The carburizing temperature of 950°C, and carburizing times of 2, 4 and 6 hours were used in the experiment. After grinding, the specimens in each case were checked for carbon content by optical emission spectroscopy. Micro-Vickers hardness testing and microstructure inspections were carried out. The results of the experiment showed that the efficiency of eucalyptus charcoal as the carburizer (for increasing carbon content on surfaces of low carbon steel was higher than that of tamarind, cassava root, coconut shell and bamboo charcoals. The averages for carbon content were: 1.16, 1.06, 0.97, 0.83 and 0.77% respectively.

  2. Development and application of intelligent vacuum carburizing and quenching furnace%智能型真空渗碳淬火炉研制及应用

    孙强; 胡东彪; 杨建军; 李宝军; 封亮


    Intelligent vacuum carburizing and quenching furnace with a powerful computer control system and expert system,according to workpiece material properties and the diffusion layer requirements automatically generated the initial parameters of vacuum carburizing process,solves the problems of vacuum carburizing carbon black,tar pollution and carburized layer uniformity and improves production stability and quality consistency,vacuum carburized to achieve intelligent automated production,improves quality of cementation,has been used successfully in the aviation industry carburizing high alloy steel and stainless steel.%智能型真空渗碳淬火炉具有功能强大的计算机控制系统和专家系统,可以根据工件材料特性和渗层要求等初始参数自动生成真空渗碳工艺,解决了困扰真空渗碳碳黑、焦油污染和渗层均匀性问题,提高了生产稳定性和质量一致性,实现真空渗碳淬火的智能化自动生产,提高了渗碳质量,已成功用于航空工业中高合金钢和不锈钢的渗碳。

  3. Effect of mass transfer limitations on catalyst performance during reduction and carburization of iron based Fischer-Tropsch synthesis catalysts

    Akbar; Zamaniyan; Yadollah; Mortazavi; Abbas; Ali; Khodadadi; Ali; Nakhaei; Pour


    Existence of intraparticle mass transfer limitations under typical Fischer-Tropsch synthesis has been reported previously,but there is no suitable study on the existence of intraparticle diffusion limitations under pretreatment steps (reduction and activation) and their effect on catalytic performance for iron based catalysts.In this study,Fe-Cu-La-SiO2 catalysts were prepared by co-precipitation method.To investigate the intraparticle mass transfer limitation under reduction,activation and reaction steps,and its effect on catalytic performance,catalyst pellets with different sizes of 6,3,1 and 0.5 mm have been prepared.All catalysts were calcined,pretreated and tested under similar conditions.The catalysts were activated in hydrogen (5%H2in N2) at 450℃ for 3 h and exposed to syngas (H2/CO=1) at 270℃ and atmospheric pressure for 40 h.Afterwards,FTS reaction tests were performed for approximately 120 h to reach steady state conditions at 290℃,17 bar and a feed flow (syngas H2/CO=1) rate of 3 L/h (STP).Using small pellets resulted in higher CO conversion,FT reaction rate and C5+ productivity as compared with larger pellets.The small pellets reached steady state conditions just 20 h after starting the reaction.Whereas for larger pellets,CO conversion,FT reaction rate and C5+ productivity increased gradually,and reached steady state and maximum values after 120 h of operation.The results illustrate that mass transfer limitations exist not only for FTS reaction but also for the reduction and carburization steps which lead to various phase formation through catalyst activation.Also the results indicate that some effects of mass transfer limitations in activation step,can be compensated in the reaction step.The results can be used for better design of iron based catalyst to improve the process economy.

  4. Carburization of austenitic and ferritic alloys in hydrocarbon environments at high temperature

    Serna, A.


    Full Text Available The technical and industrial aspects of high temperature corrosion of materials exposed to a variety of aggressive environments have significant importance. These environments include combustion product gases and hydrocarbon gases with low oxygen potentials and high carbon potentials. In the refinery and petrochemical industries, austenitic and ferritic alloys are usually used for tubes in fired furnaces. The temperature range for exposure of austenitic alloys is 800-1100 °C, and for ferritic alloys 500-700 °C, with carbon activities ac > 1 in many cases. In both applications, the carburization process involves carbon (coke deposition on the inner diameter, carbon absorption at the metal surface, diffusion of carbon inside the alloy, and precipitation and transformation of carbides to a depth increasing with service. The overall kinetics of the internal carburization are approximately parabolic, controlled by carbon diffusion and carbide precipitation. Ferritic alloys exhibit gross but uniform carburization while non-uniform intragranular and grain-boundary carburization is observed in austenitic alloys.

    La corrosión a alta temperatura, tal como la carburación de materiales expuestos a una amplia variedad de ambientes agresivos, tiene especial importancia desde el punto de vista técnico e industrial. Estos ambientes incluyen productos de combustión, gases e hidrocarburos con bajo potencial de oxígeno y alto potencial de carbono. En las industrias de refinación y petroquímica, las aleaciones austeníticas y ferríticas se utilizan en tuberías de hornos. El rango de temperatura de exposición para aleaciones austeníticas está entre 800-1.100°C y para aleaciones ferríticas está entre 500-700°C, con actividades de carbono ac>1 en algunos casos. En tuberías con ambas aleaciones, el proceso de carburación incluye deposición de carbón (coque en el diámetro interno, absorción de carbono en la superficie

  5. Nitrocarburizing with independently-controlled nitriding and carburizing potentials; Nitrocarburieren mit unabhaengig geregeltem Nitrier- und Carburierpotenzial

    Winter, K.M. [PROCESS-ELECTRONIC GmbH, Heiningen (Germany)


    Nitrocarburizing, a short-cycle nitriding, is a well-known heat treatment for improving corrosion and wear resistance of work pieces. In contrast to long-cycle nitriding, where nitrogen diffuses into the steel surface to achieve a case depth similar to carburizing, nitrocarburizing over saturates the surface with nitrogen and carbon in order to change the iron alpha structure into gamma prime (Fe{sub 4}N) and later into epsilon (Fe{sub 2-3}[NC]). The hexagonal closed-packed epsilon has a very low friction and a high chemical resistance. This article will show the influence of different compositions in N and C created using a standard industrial pit-type furnace equipped with a control system capable of measuring and controlling K{sub N} and K{sub C} independently and at the same time. (orig.)

  6. Reference measurements in a carburizing atmosphere. Pt. 1; Referenzmessungen in der Aufkohlungsatmosphaere. T. 1

    Mikulovic, Dzo; Ehmeier, Florian [MESA Electronic GmbH, Geretsried (Germany); Zivanovic, Dragan [Nis Univ. (RS). Fakultaet fuer Elektrotechnik; MESA Electronic GmbH, Nis (RS)


    The most important parameters for control of carburizing process are the temperature and the C-potential of atmosphere. Temperature normally is measured by means of thermocouples. For control of C-potential measurement of oxygen partial pressure of furnace atmosphere by in-situ O{sub 2}-probes and Lambda probes became accepted. The thermocouples as well as the probes for measurement of residual oxygen gradually lose in accuracy. Therefore reference measurements for adjustment of temperature and C-potential are essential for an exact control. Within this article the reasons for incorrect measurements with thermocouples and O{sub 2}-probes, respectively L-probes will be explained. The appropriate reference measurements for correction of these faults are also described. Furthermore it is explained what has to be observed with these reference measurements and which information is given thereby about furnace atmosphere, especially with the gas analysis by means of a gas analyzer. (orig.)

  7. Surface fatigue life of CBN and vitreous ground carburized and hardened AISI 9310 spur gears

    Townsend, Dennis P.; Patel, P. R.


    Spur gear surface endurance tests were conducted to investigate CBN ground AISI 9310 spur gears for use in aircraft applications, to determine their endurance characteristics and to compare the results with the endurance of standard vitreous ground AISI 9310 spur gears. Tests were conducted with VIM-VAR AISI 9310 carburized and hardened gears that were finish ground with either CBN or vitreous grinding methods. Test conditions were an inlet oil temeprature of 320 K (116 F), an outlet oil temperature of 350 K (170 F), a maximum Hertz stress of 1.71 GPa (248 ksi), and a speed of 10,000 rpm. The CBN ground gears exhibited a surface fatigue life that was slightly better than the vitreous ground gears. The subsurface residual stress of the CBN ground gears was approximately the same as that for the standard vitreous ground gears for the CBN grinding method used.

  8. Rolling Contact Fatigue Properties of SAE 8620 Steel after Case Carburizing

    Yan-guang CAO; Le XU; Gou-qiang ZHANG; Jie SHI; Mao-qiu WANG


    Rolling contact fatigue (RCF)properties of SAE 8620 steel after case carburizing have been investigated under two contact stresses of 4·0 and 5·5 GPa.Results show that the RCF life ranges from 2·5×106 to 3×107 cycles un-der the contact stress of 5·5 GPa,while it can be more than 1×108 cycles under the contact stress of 4·0 GPa.The rated fatigue life L10 (lives with the 10% failure)is also drastically shortened from 9·8×106 to 5·4×105 cycles when the contact stress is increased from 4·0 to 5·5 GPa.Theoretical calculations and fractographs show that the maximum shear stress and the contact area increase with increasing the contact stress,making RCF tend to occur earlier.

  9. Zircon oxygen isotopes reveal Ivrea-Verbano Zone source characteristics of the Sesia Valley Caldera

    Economos, R. C.; Quick, J. E.; Sinigoi, S.; de Silva, S. L.


    much broader range of δ18O(zircon) values, from +6 to +10‰. These values, when corrected for melt-zircon isotopic fractionation, are an excellent match for mafic and felsic sources in the Ivrea-Verbano Zone. Thus, volcanic rocks of the Sesia Valley share spatial, temporal, and geochemical affinities for Ivrea-Verbano Zone sources, strengthening the body of evidence that the Sesia Valley Caldera represents the upper crustal portions of a complete crustal section contiguous with these mid- and lower-crustal Alpine exposures. These data demonstrate a difference in extent of hybridization of source signals in the rhyodacite (little homogenization) compared to the caldera-forming eruption (more homogenization). This suggests a record of variation in magmatic processes for precursor and climactic eruptions that is potentially related to the thermal maturation of the volcanic system and warrants additional study. Additional work on trace element concentrations, including Ti thermometry, on these grains will further elucidate these processes and their relationship to known zircon-bearing sources in the mid- to deep-crust of the Ivrea-Verbano Zone.

  10. The not-so-sublime early Earth recorded in Hadean zircons

    Cavosie, A. J.


    The first few hundred million years following accretion is the least understood eon in the geologic time scale- the Hadean. This poorly defined eon continues to both challenge and fascinate scientists seeking to understand the early Earth, as the most profound planet-wide transition in Earth history occurred during the Hadean: the post-accretion transformation from a meteorite impact dominated, partially molten, steam covered mafic surface on a 'Hot Earth', to a solidified, granitoid-bearing, water covered, life-supporting 'Cool Earth'. Intact rocks from the Hadean have not been identified; other means are thus required to study early Earth processes, such as the appearance, formation, and processing of evolved crust, duration of early impacts and magma oceans, the appearance of liquid water and oceans, and ultimately, stabilization of habitats for life. Hadean detrital zircons found in younger sedimentary rocks in Australia, China, and the USA constitute a mineral record from the early Earth that enables 'ground truth' constraints to be placed on early Earth processes. Hadean zircons are complicated and originate from myriad sources; identification of grains that preserve magmatic composition is critical (as evidenced by growth zoning in CL, concordant U-Pb systematics, trace element abundances and ratios), as many have been modified by secondary processes. Detailed documentation of analyzed material is paramount. A generally consistent understanding of processes on the Hadean Earth is emerging, based on data from well-documented igneous zircons with concordant U-Pb systems: (1) A record of continuous magmatism and rock-forming events starting at 4.4 Ga is recorded in U-Pb ages of Hadean zircons; no periods of magmatic quiescence occur in the Hadean. (2) Coupled Lu/Hf and U/Pb data require formation of evolved crust from extracted Hadean reservoirs by 4.5 to 4.4 Ga. (3) Mineral inclusion suites, low Ti and high Li abundances, trace elements (U-Yb), and elevated

  11. Thermoelectric generating system attached to a carburizing furnace at Komatsu Ltd., Awazu Plant

    Kaibe, H.; Makino, K.; Kajihara, T.; Fujimoto, S.; Hachiuma, H.


    At the end of October 2009, KELK Ltd. started a field test of the thermoelectric generation system at a carburizing furnace of Komatsu Ltd., Awazu Plant. Residual carburizing gas based on CO, H2 and N2 is burned resulting that 20-30 kW range of flame constantly heats up the hot side of TEG. A single unit of TEG consists of 16 of the Bi-Te thermo-modules, each of which has a size of 50 × 50 × 4.2 mm3 and can generate 24W under the circumstance of 280 °C and 30 °C of hot side and cold side temperature, respectively [1]. 16 modules are separated into 4 groups and they are connected electrically depending on design concept, namely in case of focusing on reliability, parallel connection are used and in case of on simplicity and high-voltage transmission, series connection is preferably employed. The module is being life-time tested at various conditions. For instance, 10,000 of heat cycling under the hot side temperature between 250 and 50 °C with a constant cold side temperature at 30 °C gives within a few percent degrade. Both buck-and booster-type DC/DC converters controlled by one chip computer were set up and Maximum Power Point Tracking (MPPT) was well facilitated to search for the maximum output power depending on the hot and cold temperature. The electric output power from the 16 modules is summed up to charge 4 lead storage batteries (12V-65Ah) and then through DC/AC inverters electricity goes to LED light tubes inside the factory. 214 W can be generated and 180 W is delivered to the batteries.

  12. Impact of hydrothermal alteration on the U-Pb isotopic system of zircons from the Fangcheng syenites in the Qinling orogen, Henan Province, China

    BAO Zhiwei; WANG Qiang; BAI Guodian; ZHAO Zhenhua


    Disturbance of the zircon U-Pb isotopic system has been investigated extensively, but mostly in lab, in the last decades. Here, we reported a field-based study on intensive sericitization, K-feldsparthization and the impacts of mylonitization on zircons from the Fangcheng syenites.The Fangcheng syenites occur in the eastern part of the Qinling orogen and consist mainly of aegirine-augite syenite, aegirine nepheline syenite, biotite syenite and hornblende nepheline syenite. Zircons from the slightly sericitized aegirine augite syenite are colorless, transparent crystals and exhibit well-developed oscillatory and sector zoning on the cathodoluminescence (CL) images which are typical of magmatic zircons from alkaline rocks. Zircon U-Pb determinations by laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) showed that the syenite was formed in Neoproterozoic time, the weighted average of 206Pb/238U ages is 844.3±1.6 Ma (MSWD=0.86). In contrast, the hydrothermally altered zircons (hydrothermal zircon) from the intensively sericitized, K-feldsparthized, and weakly mylonitized aegirine augite syenite are conglomerates, yellowish to brown in color, generally translucent and internally textureless. The CL and backscatter electron (BSE) images of hydrothermal zircons exhibit fractured, textureless or mosaic textures, and occasionally show "sponge texture" with the veinlets and inclusions of K-feldspar; however, relicts of magmatic oscillatory zoning can still be discerned locally in individual grains. LA-ICPMS analyses of the hydrothermal zircons demonstrated that the zircons are chemically inhomogeneous, with enhanced and widely varied Pb, U, and Th contents. The U and Th contents of the hydrothermal zircons are estimated to be 32×10-6-1550×10-6 and 188×10-6-4059×10-6, respectively, with Th/U ratios within the range of 0.7-44.9. 206Pb/238U apparent ages of the hydrothermal zircons are negatively correlated with the contents of U, and radiogenic and

  13. Phase relations and conductivity of Sr-zirconates and La-zirconates

    Poulsen, F.W.; Vanderpuil, N.


    The formation of the strontium zirconates SrZrO3, Sr4Zr3O10, Sr3Zr2O7 and Sr2ZrO4, and of the lanthanum zirconates La2Zr2O7 and La2-xYZr2O7 at 1450-degrees-C was investigated by x-ray powder diffraction and DTA. Three different routes of synthesis were tested. In the Sr-zirconate system, single...... phase orthorhombic SrZrO3 and somewhat impure, tetragonal Sr2ZrO4 were observed, whereas the formation of ordered Ruddlesden-Popper phases, SrnZrn-1O3n-2, where n = 4 and 3, could not be verified. The conductivity of La2Zr2O7 was 3.7 X 10(-6) S/cm at 750-degrees-C and 3.8 x 10(-5) S/cm at 1000-degrees......-C. The conductivity of the Sr-zirconates increases with increasing Sr/Zr ratio. Samples with a nominal composition corresponding to Sr2ZrO4 have a conductivity of 7.5 x 10(-5) and 5.9 x 10(-4) S/cm at 750 and 1000-degrees-C, respectively. For all samples one observes low activation energies for ionic conduction (0...

  14. Enhanced diffusion of Uranium and Thorium linked to crystal plasticity in zircon

    Reddy Steven M


    Full Text Available Abstract The effects of crystal-plasticity on the U-Th-Pb system in zircon is studied by quantitative microstructural and microchemical analysis of a large zircon grain collected from pyroxenite of the Lewisian Complex, Scotland. Electron backscatter diffraction (EBSD mapping reveals a c.18° variation in crystallographic orientation that comprises both a gradual change in orientation and a series of discrete low-angle (207Pb/206Pb ages for individual analyses show no significant variation across the grain, and define a concordant, combined mean age of 2451 ± 14 Ma. This indicates that the grain was deformed shortly after initial crystallization, most probably during retrograde Inverian metamorphism at amphibolite facies conditions. The elevated Th over U and consistent 207Pb/206Pb ages indicates that deformation most likely occurred in the presence of a late-stage magmatic fluid that drove an increase in the Th/U during deformation. The relative enrichment of Th over U implies that Th/U ratio may not always be a robust indicator of crystallization environment. This study provides the first evidence of deformation-related modification of the U-Th system in zircon and has fundamental implications for the application and interpretation of zircon trace element data.

  15. 渗碳气体对201奥氏体不锈钢低温离子渗碳效果的影响%Effect of Carburizing Gases on Low Temperature Plasma Carburization of 201 Austenitic Stainless Steel

    王宇; 赵程


    用不同的渗碳气体对201奥氏体不锈钢进行了低温离子渗碳(DCPC)处理.实验证明,甲烷和乙炔均可在不锈钢表面形成一层无碳化铬析出的碳的过饱和固溶体(Sc相),使其表面的硬度和耐蚀性均有较大幅度的提高.但用甲烷作为渗碳气体处理的不锈钢表面有一层黑膜,破坏了不锈钢原有的光泽;而用乙炔作为渗碳气体不仅可以获得较为光亮的表面色泽,同时其硬度和耐蚀性也有进一步的提高.%The low temperature plasma carburization (DCPC) of 201 austenitic stainless steel has been done by using different carburizing gases. The results show that CH4 and C2 H2 can form a layer of carbon supersaturated solid solution (i. e. the Sc phase) on the steel surface without chromium carbide precipitation, so the surface hardness and corrosion resistance are greatly improved. But a layer of black film will form on the metal surface when CH4 is used as carburizing gases, which will destroy the original luster of stainless steel, when C2 H2 is used as carburizing gases, not only bright surface luster can be obtained, but also the hardness and corrosion resistance can be greatly improved.

  16. Inherited igneous zircons in jadeitite predate high-pressure metamorphism and jadeitite formation in the Jagua Clara serpentinite mélange of the Rio San Juan Complex (Dominican Republic)

    Hertwig, Andreas; McClelland, William C.; Kitajima, Kouki; Schertl, Hans-Peter; Maresch, Walter V.; Stanek, Klaus; Valley, John W.; Sergeev, Sergey A.


    This study utilizes zircon SIMS U-Pb dating, REE and trace-element analysis as well as oxygen isotope ratios of zircon to distinguish jadeite-rich rocks that formed by direct crystallization from a hydrous fluid from those that represent products of a metasomatic replacement process. Zircon was separated from a concordant jadeitite layer and its blueschist host, as well as from loose blocks of albite-jadeite rock and jadeitite that were all collected from the Jagua Clara serpentinite-matrix mélange in the northern Dominican Republic. In the concordant jadeitite layer, three groups of zircon domains were distinguished based on both age as well as geochemical and oxygen isotope values: age groups old (117.1 ± 0.9 Ma), intermediate (three dates: 90.6, 97.3, 106.0 Ma) and young (77.6 ± 1.3 Ma). Zircon populations from the blueschist host as well as the other three jadeite-rich samples generally match zircon domains of the old age group in age as well as geochemistry and oxygen isotope ratios. Moreover, these older zircon populations are indistinguishable from zircon typical of igneous oceanic crust and hence are probably inherited from igneous protoliths of the jadeite-rich rocks. Therefore, the results suggest that all investigated jadeite-rich rocks were formed by a metasomatic replacement process. The younger domains might signal actual ages of jadeitite formation, but there is no unequivocal proof for coeval zircon-jadeite growth.

  17. Continental Arc Magmatism and its Abrupt Termination by Ridge Subduction or Ridge Jump Along the Proto-Pacific Margin of Gondwana, Marie Byrd Land, Antarctica: A Zircon U-Pb Study

    Mukasa, S. B.


    The Paleozoic and Mesozoic development and subsequent fragmentation of Gondwanaland's Pacific margin is recorded in igneous and metamorphic rocks cropping out in the Marie Byrd Land (MBL) continental block of West Antarctica, recognized on geologic and paleomagnetic grounds to comprise a distinct microplate. Widespread occurrence of metaluminous granitoids dated by the zircon U-Pb method as mid- to late Paleozoic shows that convergence-related magmatism dominated the early evolution of this margin. Dates for granodiorites, monzogranites and granites from the Ruppert and Hobbs Coasts of western MBL reveal a prolonged period of subduction-related calc-alkaline magmatism between at least 320 ñ 3 Ma (age of the oldest granodiorite dated) and 110 ñ1 Ma (the age of the Mt. Prince granite). The latter is intruded by swarms of mafic and intermediate dikes believed to record the onset of rifting that led to separation of the New Zealand microcontinent from MBL. The dikes have been dated by zircon U-Pb at 101 ñ 1 Ma. Thus, the regime along the Ruppert and Hobbs Coasts had shifted from subduction-related to rift-related magmatism within a mere ~9-m.y. period. In the Kohler Range and the Pine Island Bay areas of eastern MBL, the calc-alkaline magmatism did not terminate until 96 ñ 1 Ma, based on U-Pb dating of zircons from one granitoid sample, or 94 ñ 3 Ma based on zircons from another. No continental separation occurred to the east of MBL. The margins of the Thurston Island and Antarctic Peninsula blocks went directly from convergent to inactive. With their zircon U-Pb ages clustering around 100 ñ 2 Ma, dike-free "anorogenic" syenites and quartz syenites along the Ruppert and Hobbs Coasts show that the transition to extensional magmatism was rapid in the west. This is also reflected by the fact that from the onset of rifting at 101 ñ 1 Ma to formation of oceanic crust between MBL and Greater New Zealand (Campbell Plateau, Chatham Rise, North Island and South Island

  18. Structure and stability of monazite- and zircon-type LaVO4 under hydrostatic pressure

    Cheng, Xuerui; Guo, Dongjie; Feng, Shiquan; Yang, Kun; Wang, Yongqiang; Ren, Yufen; Song, Yang


    Pure monazite (m)- and zircon (t)-type LaVO4 and LaVO4:Eu3+ were successfully synthesized by a hydrothermal method. The high pressure behavior of m- and t-LaVO4 nanoparticles has been investigated using Raman scattering techniques at room temperature. Raman measurements reveal a slight change for m-LaVO4 at 11.2 GPa because of an isostructural phase transition. However, striking changes in Raman spectra indicate a pressure-induced irreversible phase transition from the zircon to monazite structure for t-LaVO4 at around 5.9 GPa. The evolution of the luminescence spectra of t-LaVO4:Eu3+ has also been studied during the pressure-induced phase transition. It is observed that pressure has a great influence on the fluorescence intensity and the energy levels, which allows a more in-depth understanding of the nature of the pressure-induced phase transition for t-LaVO4. This result further confirms the conclusion that zircon-type RVO4 compounds with larger rare-earth cations will experience zircon to monazite phase transition.

  19. The carbide M{sub 7}C{sub 3} in low-temperature-carburized austenitic stainless steel

    Ernst, Frank, E-mail: [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States); Li, Dingqiang; Kahn, Harold; Michal, Gary M.; Heuer, Arthur H. [Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, OH 44106-7204 (United States)


    Prolonged low-temperature gas-phase carburization of AISI 316L-type austenitic stainless steel can cause intragranular precipitation of the carbide M{sub 7}C{sub 3} (M: randomly dispersed Fe, Cr, Ni). Transmission electron microscopy revealed that the carbide particles have the shape of needles. They grow by a ledge-migration mechanism and in a crystallographic orientation relationship to the austenite matrix that enables highly coherent interphase interfaces. A small solubility limit of Ni in the carbide and restricted Ni diffusivity at the processing temperature leads to Ni pileup around the particles and may explain the extreme aspect ratio of the particle shape. These characteristics closely resemble what has been observed earlier for precipitates of M{sub 5}C{sub 2} under slightly different processing conditions and can be rationalized by considering the particular constraints imposed by carburization at low temperature.

  20. Enhanced wear and fatigue properties of Ti-6Al-4V alloy modified by plasma carburizing/CrN coating%通过等离子渗碳/CrN覆层改性处理提高Ti-6Al-4V合金的耐磨性和抗疲劳特性



    In this study, a newly developed duplex coating method incorporating plasma carburization and CrN coating was applied to Ti-6Al-4V and its effects on the wear resistance and fatigue life were investigated. The carburized layer with approximately150 μm in depth and CrN coating film with 7.5μm in thickness were formed after duplex coating. Hard carbide particles such as TiC And V4 C3 were formed in the carburized layer. XRD diffraction pattern analysis revealed that CrN film had predominant [111] and [200] textures. The hardness (Hv) was significantly improved up to about 1960 after duplex coating while the hardness value of original Ti-6Al-4V was 402. The threshold load for the modification and/or failure of CrN coating was measured to be 32 N using the acoustic emission technique. The wear resistance and fatigue life of duplex coated Ti-6Al-4V improved significantly compared to those of un-treated specimen. The enhanced wear resistance can be attributed to the excellent adhesion and improved hardness of CrN coating film for the duplex coated Ti-6Al-4V. The initiation of fatigue cracks is likely to be retarded by the presence of hard and strong layers on the surface, resulting in the enhanced fatigue life.

  1. 倒车雷达用锆钛酸铅压电陶瓷材料的研究%Study on Lead Zirconate Titanate Piezoelectric Ceramic Materials for Reversing Radar

    文理; 刘玉红


    对锆钛酸铅陶瓷材料进行了Nb2 O5、 SrCO3微量掺杂改性研究,观察了掺杂后陶瓷样品的显微结构,研究了其相对介电常数、压电常数、机电耦合系数及电容量变化率随测试温度变化的规律。实验结果表明: Nb2 O5、 SrCO3掺杂后,陶瓷结构致密,介电损耗减少,相对介电常数、压电常数、机电耦合系数明显提高,电容量变化率明显改善。当Nb2 O5、 SrCO3的添加量为0.6wt%时,制得的压电陶瓷材料具有最佳的压电性能:εr=2100, D33=450 pC/N, Kp=0.81,ΔC/C<10%(-55~85℃),可以满足高性能的汽车倒车雷达的应用要求。%The lead zirconate titanate ceramic materials doped with Nb2 O5 , SrCO3 were studied.The microstructures of the doped ceramic samples were observed.Relative dielectric constant, piezoelectric constant, electromechanical coupling coefficient and capacitance change rates with test temperature were studied.The experimental results showed that Nb2 O5 , SrCO3 doping on ceramic, the ceramic becomes denser, the dielectric loss reduces, the relative dielectric constants, piezoelectric constant, electromechanical coupling coefficient increased evidently, the capacitance change rate improved obviously.When the adding amount of Nb2 O5 , SrCO3 was 0.6wt%, the piezoelectric ceramic material prepared had the best piezoelectric poperties,εr=2100, D33=450 pC/N, Kp=0.81, ΔC/C<10%(-55~85 ℃), can meet the requirements of high performance car reversing radar’s.

  2. Geochronologic, Isotopic, and Trace Element Constraints on Zircon Recycling in Sierra Crest Intrusive Suites, Sierra Nevada Batholith, USA

    Miller, J. S.; Lackey, J.; Memeti, V.; Hirt, W. H.; Wooden, J. L.


    Owing to its ubiquity and chemical properties, zircon is the primary tool for obtaining age information from felsic igneous rocks. Numerous geochronologic studies in ancient and recent plutonic and volcanic rocks over the last decade have shown: (1) that assemblages of zircons from single hand samples rarely crystallized at the same time; (2) that zircons from single hand samples may have variable geochemistry and isotopic compositions requiring distinct growth environments. Nonetheless, the conditions under which diverse assemblages of magmatic zircons crystallize, are dispersed and then gathered within such magma systems are less well understood. We have initiated a systematic geochemical (trace element) and isotopic (δ18O, 176Hf/177Hf) investigation of zircons from dated plutons within several of the Cretaceous Sierran Crest zoned intrusive suites of the Sierra Nevada Batholith to better understand melt sources and zircon recycling within these large magma systems. Preliminary O and Hf isotopic results indicate that zircon assemblages between different intrusive suites have variable isotopic compositions with multiple crustal and mantle sources involved. Preliminary trace element analysis of some of the zircon suites also show appreciable variability but important trends have emerged from the data. In particular, there are pronounced differences between trace element patterns and ratios of the youngest, interior, K-feldspar megacryst-bearing granodiorites (e.g. Cathedral Peak, Mono Creek, Whitney) and the older outer units of the intrusive suites, which are generally more mafic granodiorites and tonalites. In contrast to the more mafic outer units, zircons from the inner megacryst-bearing intrusions are overwhelmingly characterized by low Ti-in-zircon (Tzrn,Ti) model temperatures (regardless of uncertainties in aTiO2), low concentrations of MREEs, high Yb/Gd, low Th/U, high Hf, and high Eu/Eu*. These characteristics, and generally low Zr contents of the

  3. Isotope U-Pb age on single zircon and REE distribution in rocks and zircon from paleoproterozoic Kandalaksha-Kolvitsa complex Baltic shield

    Steshenko, Ekaterina; Bayanova, Tamara; Drogobuzhskaya, Svetlana; Lyalina, Ludmila; Serov, Pavel; Chashchin, Viktor; Elizarov, Dmitriy


    -05-00305, 16-05-00367, 16-05-00427) and theme of state assignment № 0231-2015-0005. References: 1. Boynton W.V. Cosmochemistry of the rare earth elements: meteorite studies // Ed. Henderson P. Rare earth element geochemistry. Amsterdam: Elsevier. 1984. P. 63-114. 2. Watson E. B., Wark D.A., Thomas J.B. Crystallization thermometers for zircon and rutile // Contrib. Miner. Petrol. 2006. V. 151. P. 413-433. 3. Hoskin P.W.O. and Schaltegger U. The Composition of zirconand igneous and metamorphic petrogenesis // Reviews in mineralogy & geochemistry. 2003. V. 53. P. 27-62.

  4. The Synergy of the Surface Layer after Carburizing of Tool Steel as a Measure of Operational Quality

    Wencel, Z.


    Full Text Available In the paper the results of the investigation on surface layer of carburized X150CrMoV12-1 tool steel are presented. Abrasive wearing of the surface was determined according the ASTM G77-98 method. The microstructure of the matrix and distribution of carbides were observed in a Scanning Electron Microscope (SEM. A correlation between the investigated parameters (microstructure/carbides distribution was found.

  5. First U-Pb detrital zircon ages from Numidian sandstones in Southern Apennines (Italy): Evidences of African provenance

    Fornelli, Annamaria; Micheletti, Francesca; Langone, Antonio; Perrone, Vincenzo


    Two samples of quartz-rich sandstones collected in the Numidian Flysch of Southern Apennines (Italy) have been studied to highlight the provenance of detritus using radiometric dating by LA-ICP-MS of detrital zircons and to compare the obtained ages with those of the Betic and Maghrebian Chains. The provenance of quartzose detritus from European or African Plates is still debated in these Chains, accordingly the ages of the detrital zircons can contribute significantly to discriminate the origin of the quartzose supply. The U-Pb zircon ages (n = 47) vary from 3047 ± 13 Ma (Mesoarchean) to 516 ± 19 Ma (Cambrian). The predominance of Paleo-Proteozoic ages (2500-1600 Ma) and the lack of Hercynian and Alpine ones suggest a provenance of the Numidian supply from North-African cratonic areas during the early-middle Langhian, when the Numidian successions of Southern Apennines were deposited. In addition, a cluster of ages at 773 ± 24 Ma and 668 ± 12 Ma in one sample and at 664 ± 17 Ma in the other sample, calculated on zircon domains with magmatic zoning, testify to an important contribution from Neo-proterozoic "granitic" rocks widely outcropping in the North-African Craton. The age data on detrital zircons from Numidian sandstones in Southern Apennines overlap those found in the Numidian sandstones widespread in the Betic Cordillera and in the Maghrebian Chain from south Spain to Sicily. This suggests that the entire depositional zone in which Numidian Flysch deposited, was fed from a southerly source represented by the African Craton where Archean, Proterozoic and Cambrian rocks widely crop out from the Atlantic coast to the Hoggar and Tibesti Massifs. Finally, it must be outlined that a Meso-Archean zircon age (3047 Ma) has been found in the Numidian Flysch of the Southern Apennines whereas in the Numidian Flysch of the Maghrebian Chain, zircons older than Paleo-proterozoic (1840 Ma) have not yet been found.

  6. Rational Formulation of Alternative Fuels using QSPR Methods: Application to Jet Fuels Développement d’un outil d’aide à la formulation des carburants alternatifs utilisant des méthodes QSPR (Quantitative Structure Property Relationship: application aux carburéacteurs

    Saldana D.A.


    Full Text Available Alternative fuels are a promising solution for road transport but also for aircraft. In the aviation field, a huge amount of work has been done in the past years with the approval to use up to 50 % by volume of SPK (Synthetic Paraffinic Kerosene in blends with conventional fossil Jet A-1. SPK are Fischer-Tropsch (FT fuels but also Hydroprocessed Esters and Fatty Acids (HEFA. However, these alternative fuels can have different chemical properties depending on the process used for their production. These properties include normal to iso paraffin ratio, carbon chain length and level of branching. R&D studies of alternative fuels are based on the evaluation of products coming from identified production processes. However, it appears that a better way of studying them could be firstly to determine the best chemical composition regarding aviation problems and secondly to find the best process and finishing process in order to obtain such a product. The objective of this work is to design a tool that aims to guide the future formulation of alternative fuels for aviation through the prediction of targeted physical properties. Thus, it is proposed to apply a methodology that identifies relationships between the structure and properties of a molecule (QSPR for Quantitative Structure Property Relationship, with the aim of establishing predictive models. These models will be built for hydrocarbons (normal and iso paraffins, naphthenes, aromatics, etc. and oxygenated compounds (esters and alcohols. For aviation, oxygenated compounds are not considered as a drop-in fuel. It could be seen as a disruptive solution in a long term view. There are concerns with oxygenates in aviation that are covered in this paper such as the flash point but others such as the energetic content, the water affinity that are not taken into account in this paper. The properties currently studied are flash point, cetane number, density and viscosity. The data sets will contain data

  7. Genetic Mechanism of Mineral Inclusions in Zircons from the Khondalite Series, Southeastern Inner Mongolia


    The early Precambrian khondalite series is widely distributed in the Jining-Zhuozi-Fengzhen- Liangcheng area, southeastern Inner Mongolia. The khondalite series mainly consists of sillimanite garnet potash feldspar (or two-feldspar) gneiss and garnet biotite plagioclase gneiss. These gneissic rocks have commonly experienced granulite-facies metamorphism. In zircons separated from sillimanite garnet potash feldspar gneisses, many mineral inclusions, including Sil, Grt, Ky, Kfs, Qtz and Ap, have been identified by the Laser Raman spectroscopy. Generally, prograde metamorphic mineral inclusion assemblages such as Ky + Kfs + Qtz + Ap and Ky + Grt + Kfs + Qtz are preserved in the core of zircon, while peak granulite-facies metamorphic minerals including Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap are identified in the mantle and rim of the same zircon. However, in some zircons are only preserved the peak metamorphic minerals such as Sil + Grt + Kfs + Qtz and Sil + Grt + Kfs + Qtz + Ap from core to rim, and in others are inherited the primary cores with minor mineral inclusions of Kfs + Qtz, with peak metamorphic mineral inclusions around the inherited cores. These data indicate that the mineral assemblage evolution of sillimanite garnet potash feldspar gneisses in the study are did experience a polymorphic transformation of kyanite to sillimanite. In garnet biotite plagioclase gneisses, secondary electron microscopic images reveal that most zircons display distinct zoning textures, which comprise cores and rims, each with distinctive inclusion assemblages. The inherited mineral inclusions, mainly consisting of Kfs + Pl + Qtz, Kfs + Qtz and Kfs + Qtz + Ap, are preserved in the primary cores, while peak granulite-facies mineral asemblages, including Grt + Bt + Pl + Qtz + Ap, Grt + Bt + Pl + Qtz and Grt + Bt + Pl + Qtz + Rt, are identified on the rims. The occurrence of peak metamorphic mineral inclusions in zircons indicates that these gneissic rocks, including

  8. The Effect of Surface Finish on Low-Temperature Acetylene-Based Carburization of 316L Austenitic Stainless Steel

    Ge, Yindong; Ernst, Frank; Kahn, Harold; Heuer, Arthur H.


    We observed a strong influence of surface finish on the efficacy of low-temperature acetylene-based carburization of AISI 316L austenitic stainless steel. Steel coupons were prepared with different surface finishes prior to carburization, from P400 SiC grit paper to 1- µm-diameter-diamond-paste. The samples with the finer surface finish developed a thicker "case" (a carbon-rich hardened surface layer) and a larger surface carbon concentration. Transmission electron microscopy revealed that the differences arose mainly from the nature of the deformation-induced disturbed layer on the steel surface. A thick (>400 nm) disturbed layer consisting of nano-crystalline grains (≈10 nm diameter) inhibits acetylene-based carburization. The experimental observations can be explained by assuming that during machining or coarse polishing, the surface oxide layer is broken up and becomes incorporated into the deformation-induced disturbed layer. The incorporated oxide-rich films retard or completely prevent the ingress of carbon into the stainless steel.

  9. Experimental method for characterization of fatigue behaviour of carburized layers; Pruefkonzept zur experimentellen Bestimmung des Ermuedungsverhaltens von einsatzgehaerteten Werkstoffzustaenden

    Kleemann, Andreas; Thumser, Rayk; Kleemann, Susanne; Winge, Joerg; Gerth, Uwe [Bauhaus Univ. Weimar (Germany). Materialforschungs- und -pruefanstalt


    Fatigue data of material states with different carbon contents are necessary for calculation of carburized parts. Experimental results on the correlation of local material structure and local endurance are not available. Up to now only carburized notched specimens and components have been investigated. In this investigation a new tube specimen with homogenous carbon content in the wall resulting from carburization process was developed. Carbon contents of 0.18 %, 0.40 %, 0.55 % und 0.70 % in the thin wall tube specimen have been tested. Specimens were loaded with cyclic internal and monotonic external pressures. Special test rig with two pressure intensifier is introduced. With the aid of the cyclic internal and constant external pressure the whole Haigh-diagram with ratios of pressure or stress of R = {infinity} until R = 0.5 could be covered. Main load direction in the tube specimen is perpendicular to the steel rods axis. Results obtained for the used 20MnCrB5 steel grade show the same endurance limit for different carbon contents or hardness, respectively, and are significantly affected by big non-metallic inclusions. (orig.)

  10. Duration of a large Mafic intrusion and heat transfer in the lower crust: A SHRIMP U-Pb zircon Study in the Ivrea-Verbano Zone (Western Alps, Italy)

    Peressini, G.; Quick, J.E.; Sinigoi, S.; Hofmann, A.W.; Fanning, M.


    The Ivrea-Verbano Zone in the western Italian Alps contains one of the world's classic examples of ponding of mantle-derived, mafic magma in the deep crust. Within it, a voluminous, composite mafic pluton, the Mafic Complex, intruded lower-crustal, high-grade paragneiss of the Kinzigite Formation during Permian-Carboniferous time, and is now exposed in cross-section as a result of Alpine uplift. The age of the intrusion is still debated because the results of geochronological studies in the last three decades on different rock types and with various dating techniques range from 250 to about 300 Ma. Sensitive high-resolution ion microprobe (SHRIMP) U-Pb zircon age determinations on 12 samples from several locations within the Mafic Complex were performed to better constrain the age of the igneous event. The results indicate a long history of magma emplacement and cooling, which reconciles the spread in previously published ages. The main intrusive phase took place at 288 ?? 4 Ma, causing a perturbation of the deep-crustal geotherm, which relaxed to the Sm-Nd closure temperature in garnet-free mafic rocks after about 15-20 Myr of sub-solidus cooling at c. 270 Ma. These results suggest that large, deep crustal plutons, such as those identified geophysically at depths of 10-20 km within extended continental crust (e.g. Yellowstone, Rio Grande Rift, Basin and Range) may have formed rapidly but induced a prolonged thermal perturbation. In addition, the data indicate that a significant thermal event affected the country rock of the Mafic Complex at about 310 Ma. The occurrence of an upper amphibolite- to granulite-facies thermal event in the Kinzigite Formation prior to the main intrusive phase of the Mafic Complex has been postulated by several workers, and is corroborated by other geochronological investigations. However, it remains uncertain whether this event (1) was part of a prolonged perturbation of the deep-crustal geotherm, which started long before the onset of

  11. On the valency state of radiogenic lead in zircon and its consequences

    Kramers, J.; Frei, R; Newville, M.; Kober, B.; Villa, I.; (UCopenhagen); (Universitä); (t Bern); (UC); (University of Heidelberg)


    In zircon U-Pb systematics, extreme robustness up to the temperatures of granulite facies and anatexis contrasts with apparently easy loss of radiogenic Pb at low temperatures, often without any metamorphic event being in evidence. Here we propose that this paradoxical behaviour can be understood with the hypothesis that radiogenic Pb in zircon is tetravalent. We review data and arguments in favour of this hypothesis. Diffusion profiles calculated for Pb{sup 2+} in a 25 {micro}m radius zircon xenocryst in a melt at 1000 C, combined with the incompatibility of Pb{sup 2+}, or for a zircon core inside a younger zircon rim at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during the final evaporation steps. The distribution of residual Pb in a leached titanite, revealed by PIXE, is similar to that of Ti. Lastly, XANES spectra of a 1 Ga old titanite (predominantly radiogenic Pb) and an Alpine one (predominantly common Pb) are significantly different, although the former does not resemble that of PbO{sub 2}. The arguments why radiogenic Pb should be tetravalent are based on analogies with studies relating to the tetravalent state of {sup 234}Th and the hexavalent state of {sup 234}U, which show that {alpha}-recoil in silicates generates a strongly oxidizing environment at the site where the recoiling nucleus comes to rest. Further, a zircon grain, being small, should remain highly oxidizing in its interior by the constant loss of {beta}-particles, maintaining the 4+ state of radiogenic Pb. From its effective ion radius, similar to that of Zr{sup 4+}, and its charge, Pb{sup 4+} has to be compatible in the zircon lattice. Also, by analogy with U{sup 4+}, Th{sup 4+} and Hf{sup 4+}, its diffusivity should be several

  12. Hf isotopic compositions of the standard zircons for U-Pb dating

    XU Ping; WU Fuyuan; XIE Liewen; YANG Yueheng


    Using the newly published Yb isotopic abundances and the mass bias relationship between Yb and Hf, we carried out an analysis of Hf isotopes in the standard zircon 91500 by means of 193 nm laser attached to Neptune multi-collector ICP-MS (LA-MC-ICPMS). The obtained Hf isotopic data, in either in situ or line scan modes, are not only identical for different spot sizes, but also are consistent with previously published results obtained on TIMS or other MC-ICPMS machines within errors. This indicates that it is possible to obtain reliable 176Hf/177Hf isotopic ratios for zircon in either in situ or line scan conditions on LA-MC-ICPMS machine, and the applied procedures in our study for elemental interfering correction are appropriate for the purpose of acquiring satisfactory accuracy for Hf isotope analyses. The Hf isotopic compositions of four zircon standards in high spatial resolution U-Pb dating, 91500, CZ3,CN92-1 and TEMORA, are measured, respectively. The obtained 176Hf/177Hf ratios are 0.282316+4 (n = 34, 2σ) for 91500, 0.281704±6 (n = 16, 2σ) for CZ3, 0.282200±6 (n = 20,2σ-) for CN92-1 and 0.282684±14 (n = 24, 2σ) for TEMORA,respectively, with 176Lu/177Hf ratios of ~0.00031, 0.000036,0.00083 and 0.00127. Zircons 91500 and CZ3 show narrower variations in 176Hf/177Hf and 176Lu/177Hf ratios than those of zircons CN92-1 and TEMORA, and thus are appropriate standards for the Hf isotope analysis.

  13. Cosmogenic and nucleogenic 3He in apatite, titanite, and zircon

    Farley, K. A.; Libarkin, J.; Mukhopadhyay, S.; Amidon, W.


    Cosmogenic 3He was measured in apatite, titanite, and zircon and cosmogenic 21Ne in quartz at 13 depth intervals in a 2.7-m long drill core in a Miocene ignimbrite from the Altiplano of Bolivia. All three 3He depth profiles as well as the 21Ne profile attenuate exponentially with depth, indicating that both of these isotopes are cosmogenic in origin with no significant contribution from other sources. The attenuation lengthscale for 3He production of Λ = 180 ± 11 g/cm 2 is consistent with expectations for neutron spallation, and is identical to that found for the cosmogenic 21Ne in quartz. By normalizing the measured 3He concentrations to 21Ne and using the independently known cosmogenic 21Ne production rate, the apparent cosmogenic 3He production rates in apatite, titanite, and zircon were respectively found to be 112, 97, and 87 atoms/g/yr at sea-level and high latitude. The formal uncertainty on these estimates is ˜ 20% (2 σ), and arises in equal parts from uncertainties in the measured 3He/ 21Ne ratios and the uncertainty in the 21Ne production rate. However an additional factor affecting the apparent 3He production rate in these phases arises from the long stopping range of spalled 3He and tritium (which decays to 3He). Because all three accessory phases have higher mean atomic number than major rock-forming minerals, they will have lower 3He production rates than their surroundings. As a consequence the long stopping ranges will cause a net implantation of 3He and therefore higher apparent production rates than would apply for purely in-situ production. Thus these apparent production rates apply only to the specific grain sizes analyzed. Analysis of sieved zircon aliquots suggests that a factor of 2 increase in grain size (from ˜ 50 to ˜ 100 μm cross-section) yields a 10% decrease in apparent production rate. While this effect warrants further study, the grain sizes analyzed here are typical of the accessory phases commonly encountered, so the apparent

  14. Selection of Raw Materials for the Reactive Sinterling of Zircon Porous Ceramics

    SHENYi; ZHANGWenli; 等


    The effect of three kinds of zircon raw materials on the sinterability and properties of porous zircon ceramics have been investigated.The results have shown that all the tested fired compacts are of high porosity,However,the sintering process are different for different raw materials.The preferable selected raw materials for porous zircon ceramics were commercials zircon and quartz.

  15. Interaction of rhyolite melts with monazite, xenotime, and zircon surfaces

    Rustad, James R.


    The interfacial contact region between a rhyolite melt and the accessory minerals monazite, xenotime, and zircon is investigated using molecular dynamics simulations. On all surfaces, major structural rearrangement extends about 1 nm into the melt from the interface. As evidenced by the structural perturbations in the ion distribution profiles, the affinity of the melt for the surface increases in going from monazite to xenotime to zircon. Alkali ions are enriched in the melt in contact with an inert wall, as well as at the mineral surfaces. Melt in contact with zircon has a particularly strong level of aluminum enrichment. In xenotime, the enrichment of aluminum is less than that in zircon, but still notable. In monazite, the aluminum enrichment in the contact layer is much less. It is expected that the relative surface energies of these accessory minerals will be a strong function of the aluminum content of the melt and that nucleation of zircon, in particular, would be easier for melts with higher aluminum concentration. The crystal growth rate for zircon is expected to be slower at a higher aluminum concentration because of the effectiveness of aluminum in solvating the zircon surface. The variable interfacial concentration profiles across the series of accessory minerals will likely affect the kinetics of trace element incorporation, as the trace elements must compete with the major elements for surface sites on the growing accessory minerals.

  16. Detrital Zircon of 4100 Ma in Quartzite in Burang, Tibet

    DUO Ji; WEN Chunqi; FAN Xiaoping; GUO Jianci; NI Zhiyao; LI Xiaowen; SHI Yuruo; WEN Quan


    A detrital zircon aged 4.1 Ga is discovered by the SHRIMP U-Pb method in a quartzite in Burang County, western Tibet. This is presently the oldest single-grain detrital zircon in China. The Th-U ratios of the two testing points of the >4.0 Ga zircon are between 0.76 and 0.86, indicating their magmatic origin. This discovery has offered an important age for investigating the geological evolution of the Qinghai-Tibet Plateau.

  17. Thermal expansion in lead zirconate titanate


    The volume anomalies with temperature variations in tin-modified lead zirconate titanate ceramics are investigated. Experimental results show that the volume changes are related to the phase transitions induced with temperature. The magnitude and orientation of crystal volume changes are dependent on the particular phase transition. When antiferroelectrics is transformed to ferroelectrics or paraelectrics the volume expands. Oppositely when ferroelectrics is transformed to antiferroelectrics or paraelectrics the volume contracts. In the transition of antiferroelectric orthorhombic structure to tetragonal structure or ferroelectric low-temperature rhombohedral structure to high-tem- perature rhombohedral structure, there are also revealed apparent anomalies in the curves of thermal expansion. Among them, the volume strain caused by the transition between antiferroelectrics and ferroelectrics is the biggest in magnitude, and the linear expansion dL/L0 and the expansion coefficient (dL/L0)/dT can reach 2.810?3 and 7.5 × 10?4 K?1 respectively.

  18. Integrated single crystal laser ablation U/Pb and (U-Th)/He dating of detrital accessory minerals - Proof-of-concept studies of titanites and zircons from the Fish Canyon tuff

    Horne, Alexandra M.; van Soest, Matthijs C.; Hodges, Kip V.; Tripathy-Lang, Alka; Hourigan, Jeremy K.


    Excimer laser technologies enable a rapid and effective approach to simultaneous U/Pb geochronology and (U-Th)/He thermochronology of a wide range of detrital accessory minerals. Here we describe the 'laser ablation double dating' (LADD) method and demonstrate its viability by applying it to zircon and titanite crystals from the well-characterized Fish Canyon tuff. We found that LADD dates for Fish Canyon zircon (206Pb/238U - 28.63 ± 0.11 Ma; (U-Th)/He - 28.38 ± 0.73 Ma) are statistically indistinguishable from those obtained through established, traditional methods of single-crystal dating. The same is true for Fish Canyon titanite LADD dates: 206Pb/238U - 28.08 ± 0.90 Ma; (U-Th)/He - 27.98 ± 0.86 Ma. As anticipated, given that LADD involves the analysis of smaller amounts of material than traditional methods, it yields dates with higher analytical uncertainty. However, this does not substantially reduce the utility of the results for most applications to detrital datasets. An important characteristic of LADD is that it encourages the chemical characterization of crystals by backscattered electron, cathodoluminescence, and/or Raman mapping prior to dating. In addition, by permitting the rapid and robust dating of crystals regardless of the degree of their abrasion during sedimentary transport, the method theoretically should yield dates that are more broadly representative of those of the entire population of detrital crystals in a natural sample.

  19. 1Cr11Ni2W2MoV不锈钢气体渗碳工艺%Gas Carburizing Process for 1Cr11Ni2W2MoV Stainless Steel

    杨亚宁; 张波; 卢华


    介绍了1Cr11Ni2W2MoV不锈钢在多用炉中低温气体渗碳的方法,解决了该材料低温渗碳层不均匀的问题.结果表明:零件渗碳前经吹砂或磷化,渗碳时通人NH,能够保证渗碳层均匀.%The gas carburizing process at low temperature in multi-furnace for 1Cr11Ni2W2MoV stainless steel was introduced.The problem of non uniform carburizing coating was solved.The results show that the carburized case uniformity can be ensured through sand blasting or phosphating before carburizing, and NH3 is filled during carburizing.

  20. The wetting behaviour of silver on carbon, pure and carburized nickel, cobalt and molybdenum substrates

    Hula, Robert C., E-mail: [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164, A-1060 Wien (Austria); Edtmaier, Christian; Holzweber, Markus; Hutter, Herbert [Institute of Chemical Technologies and Analytics, Vienna University of Technology, Getreidemarkt 9/164, A-1060 Wien (Austria); Eisenmenger-Sittner, Christoph [Institute of Solid State Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10, A 1040 Wien (Austria)


    Properties such as thermal and electrical conductivity or the expansion behaviour of silver matrix composites with carbon based inclusions are strongly affected by the contact angle between carbon and silver. In order to promote wetting of carbon, insertion of metallic interlayers such as nickel, cobalt or molybdenum is a feasible approach. This paper presents contact angle measurements done with the sessile drop method on carbon substrates (glassy carbon, polycrystalline graphite) and on pure nickel, cobalt and molybdenum foils. The ability of these interlayer elements to lower the high contact angles of silver on glassy carbon (117 deg.) and polycrystalline graphite (124 deg.) under vacuum conditions was verified. Unlike nickel (30 deg.) and cobalt (26 deg.), molybdenum (107 deg.) nevertheless was not wettable by liquid silver (at 1273 K) under vacuum conditions. ToF-SIMS was used to identify oxygen on the surface, causing higher contact angles than expected. After oxide reduction a contact angle of 18 deg. on molybdenum was detected. Furthermore, the influence of carbon diffusion on the contact angle was investigated by gas phase carburization of the metal foils. ToF-SIMS and XRD identified dissolved carbon (Ni, Co) and carbide formation (Mo). However, only nickel and cobalt showed a slight decrease of the contact angle due to carbon uptake.

  1. Austenite Grain Growth and Precipitate Evolution in a Carburizing Steel with Combined Niobium and Molybdenum Additions

    Enloe, Charles M.; Findley, Kip O.; Speer, John G.


    Austenite grain growth and microalloy precipitate size and composition evolution during thermal processing were investigated in a carburizing steel containing various additions of niobium and molybdenum. Molybdenum delayed the onset of abnormal austenite grain growth and reduced the coarsening of niobium-rich precipitates during isothermal soaking at 1323 K, 1373 K, and 1423 K (1050 °C, 1100 °C, and 1150 °C). Possible mechanisms for the retardation of niobium-rich precipitate coarsening in austenite due to molybdenum are considered. The amount of Nb in solution and in precipitates at 1373 K (1100 °C) did not vary over the holding times evaluated. In contrast, the amount of molybdenum in (Nb,Mo)C precipitates decreased with time, due to rejection of Mo into austenite and/or dissolution of fine Mo-rich precipitates. In hot-rolled alloys, soaking in the austenite regime resulted in coarsening of the niobium-rich precipitates at a rate that exceeded that predicted by the Lifshitz-Slyozov-Wagner relation for volume-diffusion-controlled coarsening. This behavior is attributed to an initial bimodal precipitate size distribution in hot-rolled alloys that results in accelerated coarsening rates during soaking. Modification of the initial precipitate size distribution by thermal processing significantly lowered precipitate coarsening rates during soaking and delayed the associated onset of abnormal austenite grain growth.

  2. Analyses of quenching process during turn-off of plasma electrolytic carburizing on carbon steel

    Wu, Jie; Liu, Run; Xue, Wenbin; Wang, Bin; Jin, Xiaoyue; Du, Jiancheng


    Plasma electrolytic carburizing (PEC) under different turn-off modes was employed to fabricate a hardening layer on carbon steel in glycerol solution without stirring at 380 V for 3 min. The quenching process in fast turn-off mode or slow turn-off mode of power supply was discussed. The temperature in the interior of steel and electron temperature in plasma discharge envelope during the quenching process were evaluated. It was found that the cooling rates of PEC samples in both turn-off modes were below 20 °C/s, because the vapor film boiling around the steel sample reduced the cooling rate greatly in terms of Leidenfrost effect. Thus the quench hardening hardly took place, though the slow turn-off mode slightly decreased the surface roughness of PEC steel. At the end of PEC treatment, the fast turn-off mode used widely at present cannot enhance the surface hardness by quench hardening, and the slow turn-off mode was recommended in order to protect the electronic devices against a large current surge.

  3. A metastable chromium carbide powder obtained by carburization of a metastable chromium oxide

    Loubiere, S. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Laurent, C. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Bonino, J.P. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique; Rousset, A. [Univ. Paul-Sabatier, Toulouse (France). Lab. de Chimie des Materiaux Inorganique


    A metastable Cr{sub 3}C{sub 2-x} carbide powder is prepared by carburization of a metastable chromium oxide in H{sub 2}-CH{sub 4} atmosphere under the appropriate conditions (temperature, dwell time and CH{sub 4} content). A very high specific surface area (greater than 210 m{sup 2} g{sup -1}) of the starting oxide is necessary to avoid the formation of the sole stable Cr{sub 3}C{sub 2} phase. The transformation from the stable Cr{sub 3}C{sub 2} to the metastable Cr{sub 3}C{sub 2-x} is observed for the first time. The driving force could be an epitaxial effect between Cr{sub 3}C{sub 2-x} and the surrounding graphite layer. This is consistent with the observation that the formation of graphite layers by CH{sub 4} cracking is easier in the Cr{sub 3}C{sub 2-x}-containing powders. (orig.)

  4. Calibration of eddy current carburization measurements in ethylene production tubes using ion beam analysis

    Stevens, K J [Materials Performance Technologies, Industrial Research Ltd, PO Box 31-310, Lower Hutt (New Zealand); Trompetter, W J [Rafter Laboratory, Institute of Geological and Nuclear Sciences, PO Box 31-312, Lower Hutt (New Zealand)


    Nuclear reaction analysis using a {sup 12}C(d, p{sub 0}){sup 13}C reaction and a {sup 16}O(d, p{sub 1}){sup 17}O reaction, with 1.02 MeV deuterons in an accelerator microprobe, has been used to produce quantitative linescans of the carbon and oxygen levels in ex-service ethylene pyrolysis tubes of HPM, HK40 and Manaurite XM alloy. Particle induced x-ray emission in the ion beam microprobe and energy dispersive analysis of x-rays in a scanning electron microscope were used for linescans of the heavier elements (Cr, Ni, Fe, Si and Ti). The composition linescans were used to calibrate the response and accuracy of an eddy current probe system for measuring carburization near the inner surface of the tubes. The influence of the ferromagnetic outer oxide surface layers has been clarified. A two-dimensional ANSYS finite element model (FEM) was used for interpretation of the eddy current scans. Good correlation was obtained between the ion beam analysis results, the impedance scans and the FEM.

  5. Calibration of eddy current carburization measurements in ethylene production tubes using ion beam analysis

    Stevens, K. J.; Trompetter, W. J.


    Nuclear reaction analysis using a 12C(d, p0)13C reaction and a 16O(d, p1)17O reaction, with 1.02 MeV deuterons in an accelerator microprobe, has been used to produce quantitative linescans of the carbon and oxygen levels in ex-service ethylene pyrolysis tubes of HPM, HK40 and Manaurite XM alloy. Particle induced x-ray emission in the ion beam microprobe and energy dispersive analysis of x-rays in a scanning electron microscope were used for linescans of the heavier elements (Cr, Ni, Fe, Si and Ti). The composition linescans were used to calibrate the response and accuracy of an eddy current probe system for measuring carburization near the inner surface of the tubes. The influence of the ferromagnetic outer oxide surface layers has been clarified. A two-dimensional ANSYS finite element model (FEM) was used for interpretation of the eddy current scans. Good correlation was obtained between the ion beam analysis results, the impedance scans and the FEM.


    R. Zamani Foroshani


    Full Text Available The aim of this work was to study the effect of fluorine and chlorine ions on the formation of mullite during the reaction sintering of mechanically activated zircon-alumina powder mixture. The results showed that mechanical activation of zirconalumina powder mixture for 20 h led to grain refinement and partial amorphization. In the presence of fluorine and chlorine ions, complete formation of mullite in the mechanically activated sample occurred after 2 h of reaction sintering at 1300oC and 1400oC, respectively. In the sample lacking fluorine and chlorine ions, mullitization was not completed even after 2 h of reaction sintering at 1400oC. It was concluded that presence of fluorine and chlorine ions enhance the dissociation of zircon and formation of mullite during the reaction sintering of mechanically activated zircon-alumina mixture.

  7. A new generation of more pH stable reversed phases prepared by silanization of zirconized silica.

    Silva, César R; Airoldi, Claudio; Collins, Kenneth E; Collins, Carol H


    To further extend our studies in the search for reversed phases with enhanced durability at high pH, zirconized silica has now been explored as an alternative support. The synthesis of the new stationary phases involves silanization of a zirconium-modified silica support with a C(18) trifunctional silane, followed by endcapping. The chromatographic properties of the C(18) phases based on zirconized silica are similar to their titanized silica counterparts. Accelerated high pH stability tests, using phosphate mobile phases and elevated temperature, have shown that the zirconized silica phases have promising advantages not only over similarly prepared non-metalized phases but also over titanized silica C(18) phases.

  8. Chemical characterisation of zircon-cadmium sulfoselenide ceramic pigments; Caracterizacion quimica de pigmentos ceramicos a base de sulfoseleniuro de cadmio

    Gazulla Barreda, M. F.; Rodrigo Edo, M.; Blasco Roca, E.; Orduna Cordero, M.


    The present paper addresses the development of a methodology that allows the complete chemical characterisation of zircon cadmium sulfoselenide ceramic pigments including minor and major elements. To develop the methodology, five zircon-cadmium sulfoselenide pigments with different hues were selected, studying the different measurement process steps, from sample preparation to the optimisation of the measurement of the different components of the pigments by spectroscopic techniques (WD-XRF and elemental analysis by combustion and IR detection). The chemical characterisation method developed was validated with synthetic standards prepared from the mixture of certified reference materials and pure oxides because no certified referenced materials of this type of pigments were commercially available. The developed method can be used for a complete chemical characterization of zircon-cadmium sulfoselenide ceramic pigments with a very low uncertainty for all the elements analysed. (Author)

  9. Cenozoic foreland basins of Central Andes: a preliminary provenance U-Pb zircon analysis of sedimentary sequences of Calchaqui Valley

    Oliveira, Alisson Lopes; Hauser, Natalia; Pimentel, Marcio Martins; Matteini, Massimo, E-mail: [Universidade de Brasilia (UnB), DF (Brazil). Laboratorio de Geocronologia; Galli, Claudia Ines [Faculdad de Ingenieria, Universidad Nacional de Jujuy (Argentina); Coira, Beatriz [CIT Jujuy, CONICET. Instituto de Geologia y Mineria (Argentina); Alonso, Ricardo; Barrientos, Andrea [Instituto CEGA, CONICET. Universidad Nacional de Salta (Argentina)


    The Eocene of northwestern Argentina records complex basin and structural evolution, including continental sedimentation of the post-rift Salta Basin and the beginning of the Andean uplift and foreland system evolution. This illuminates a significant period of evolutionary history of this and surrounding basins in northwestern Argentina. U-Pb zircon analyses by LA-ICP-MS for three formations representing post-rift to foreland stages allowed interpretation about provenance terrains. The Lumbrera Formation, representing the post-rift stage, shows bimodal sources with a main zircon population around 462 Ma, and a second population around 1023 Ma. The Los Colorados and Angastaco Formations representing the sedimentation in a foreland basin, show a unimodal source around 490 Ma, and 517 Ma respectively. Zircons younger than 50 Ma were not identified during this study. (author)

  10. Provenance and sediment dynamics within river basins in Western Peru through detrital zircons U-Pb ages

    Camille, Litty; Pierre, Lanari; Marco, Burn; Fritz, Schlunegger


    U-Pb dating of detrital zircons from clastic sediments by LA-ICPMS has become a popular method in sedimentary correlation and provenance studies. Because of remarkable durability, detrital zircons may be reworked through multiple sedimentary cycles and provide an ideal material to study the sedimentary provenance in rivers and the erosional characteristics. The Western side of the Peruvian Andes has experienced multiple pluvial periods induced phases of erosion and the formation of subsequent cut-and-fill terrace sequences since the Pleistocene. The aim of the study is to estimate the source areas of the terrace and modern deposits to infer changes in sediment dynamics through time and correlate them with the climatic change and especially precipitation patterns. To this extent, we determined the provenance of 4 dated terrace deposits along with modern sediments from the same streams by matching detrital-zircon ages with crystallization ages of source rocks. Age populations of detrital zircons are derived using U-Pb LA-ICP-MS analysis of about 50 zircons. Results show changes in the sediment provenance through time. Nowadays, sediment source areas are mainly located on the uppermost reach of the rivers whereas during the Pleistocene, sediment source areas were both located in the headwaters and along the middle reach of the rivers. These differences in terms of provenance could correlate with a change in precipitation locations and rates. Indeed a scenario where the locus of precipitation occurrence shifted from the middle reaches including the Altiplano during the past, to the Altiplano only as observed today, along with higher precipitation rates during the periods of terraces formation, offers an explanation to explain the erosional patterns recorded by detrital zircons.

  11. Design method of hardened depth for carburized gear%渗碳齿轮硬化层深度设计方法

    肖伟中; 刘忠明; 袁玉鹏


    Based on the calculating method of contact strength , the shear stress distribution along the depth direction of gear surface was calculated, from the relationship of shear stress and shear strength , the lowest hardness distribution curve for carburized gear was obtained . Based on the lowest hardness distribution curve , the hardness distribution for carburized gears was designed , and the available hardened depth of carburized gears was obtained .%基于接触强度计算方法,计算出了齿轮沿齿面深度方向的剪切应力分布,通过剪切应力与剪切强度的关系,得到了渗碳齿轮最低要求的硬度分布曲线,在此基础上,设计出了齿轮硬化层硬度分布,得到有效硬化层深度。

  12. Extrusion and properties of lead zirconate titanate piezoelectric ceramics

    Cai, S.; Millar, C.E.; Pedersen, L.


    The purpose of this work was to develop a procedure for fabricating electroceramic actuators with good piezoelectric properties. The preparation of lead zirconate titanate (PZT) piezoelectric ceramic rods and tubes by extrusion processing is described. The microstructure of extrudates was investi......The purpose of this work was to develop a procedure for fabricating electroceramic actuators with good piezoelectric properties. The preparation of lead zirconate titanate (PZT) piezoelectric ceramic rods and tubes by extrusion processing is described. The microstructure of extrudates...

  13. SHRIMP U-Pb dating of the preeruption growth history of zircons from the 340 ka Whakamaru Ignimbrite, New Zealand: Evidence for >250 k.y. magma residence times

    Brown, Stuart J. A.; Fletcher, Ian R.


    The Whakamaru group ignimbrites are products of one of the largest caldera-forming eruptions from the central Taupo Volcanic Zone, New Zealand, ca. 340 ka. Imaging of zircons separated from low-silica rhyolite pumice from Whakamaru group ignimbrite reveals a complex magmatic crystallization history; some grains contain resorbed cores. Cores and rims of individual zircons were dated using the sensitive high-resolution ion microprobe. Due to the high U contents of the zircons, 206Pb count rates were sufficiently high to obtain 206Pb/238U ages with precisions of 5% 10% (1 σS) using longer than usual 206Pb+ count times, and this has allowed zircon core and rim ages to be distinguished. Zircon rim and outer growth zone ages range from within 1 σS error of the eruption age to 449 ± 20 ka, whereas zircon cores produced ages to 608 ± 20 ka, indicating magmatic residence times exceeding 250 k.y. for some zircons. The data are consistent with a prolonged evolution of the magma system over hundreds of thousands of years, involving magma replenishment and mixing with residual phases of older silicic magma chambers, in addition to crystal fractionation processes, prior to eruption. The study has shown that 206Pb/238U dating using high-resolution ion microprobe can be used to determine zircon preeruptive growth histories in Quaternary lavas and pyroclastic rocks.

  14. Trace element composition and U-Pb age of zircons from Estherville: Constraints on the timing of the metal-silicate mixing event on the mesosiderite parent body

    Haba, Makiko K.; Yamaguchi, Akira; Kagi, Hiroyuki; Nagao, Keisuke; Hidaka, Hiroshi


    Mesosiderites are a group of stony-iron meteorites, which are thought to be the result of mixing of silicates with Fe-Ni metal. In this study, we combined textural observations with geochemical and chronological studies of two zircon grains found in the Estherville mesosiderite. One of the zircons (Zrc1) occurs with pyroxene, plagioclase, troilite, and silica, and the other (Zrc2) is located at a boundary between Fe-Ni metal and a silicate part mainly composed of pyroxene and plagioclase. The textural observations demonstrate that Zrc1 is relatively homogenous, whereas Zrc2 is composed of at least two chemically distinct domains. Trace element analyses of Zrc2 resolve large concentration gradients within this single grain with variations that are an order of magnitude for rare earth elements (REE) and two orders of magnitude for U and Th. The lowest trace element concentration in Zrc2 is more than an order of magnitude lower than those of lunar and eucritic zircons. However, it is similar to those of Zrc1 and a zircon from the Vaca Muerta mesosiderite. The calculated REE composition of the melt in equilibrium with Zrc2 shows that Zrc2 and perhaps also Zrc1 did not crystallize from a melt that was produced by fractional crystallization of the primary magmatic mineral assemblages. The zircons with low REE, U, and Th concentrations can be interpreted to have formed in a residual melt after incorporation of large amounts of REE, U, and Th into secondary phosphate minerals, which formed during the metal-silicate mixing event. The large concentration gradients observed in Zrc2 suggest significant heterogeneities in the melt from which the zircon crystallized. Alternatively, either mixing or diffusion between a relict zircon and a newly formed zircon could explain the observed concentration gradients. However, the REE patterns of Zrc2 cannot be explained by mixing or diffusion between the two distinct generations of zircons. These considerations suggest that Zrc1 and Zrc2

  15. Paleoproterozoic basement beneath the southern Jiangxi Province: Evidence from U-Pb ages and Lu-Hf isotopes in zircons from the Doushui Iamprophyre

    YU JinHai; WANG LiJuan; O'REILLY S Y; SHU LiangShu; UN Tao


    This paper presents geochemical analyses of a lamprophyre intruding the Caledonian Doushui granite body in Shangyou County, southern Jiangxi Province. U-Pb dating and Hf-isotope analyses are especially carried out for zircons from it. Petrological and geochemical features show that the lamprophyre belongs to a high-K, weakly alkaline pyroxene-biotite iamprophyre. It is characterized by high Mg# (0.74),Ni (253 μg/g) and Cr (893 μg/g) contents, and also enriched in incompatible elements, such as REE, Rb, Sr, Ba and K. It is suggested that its primitive melt probably derived from enriched mantle metasomatized by non-crust-derived agent. Morphology and LAM-ICPMS dating results of zircons in the lam prophyre indicate that they are xenocrysts captured from deep crustal rocks. Most xenocrystic zircons formed at -1.86 Ga, and a few in different Phanerozoic periods. The Paleoproterozoic zircons are of magmatic origin and have similar 176Hf/177Hf and 176Lu/177Hf ratios, indicating that they probably are from the same igneous basement rock. The ages and Hf-isotope compositions of zircons from this basement rock are similar to those of Paleoproterozoic Danzhu granite in the southern Zhejiang Province, but extremely distinguished from the Nanling basement, suggesting that the study area probably is a westward extension part of Paleoproterozoic Wuyishan terrane in the eastern Cathaysia Block. These Paleoproterozoic zircons have low Hf-isotope compositions, characteristic of crustal source. Hf model ages of these zircons and the presence of older inherited cores within them, coupled with available other data reported by previous studies, suggest that the source of Paleoproterozoic magma is Neoarchaean crust, implying the existence of older basement in the Wuyishan terrane. U-Pb ages and Hf isotopes of five Phanerozoic zircons indicate that Paleoproterozoic basement underwent multi-reworking occurring in Caledonian, Indosinian and early Yanshanian, respectively. The Caledonian

  16. Creation of a continent recorded in zircon zoning

    Moser, D.E.; Bowman, J.R.; Wooden, J.; Valley, J.W.; Mazdab, F.; Kita, N.


    We have discovered a robust microcrystalline record of the early genesis of North American lithosphere preserved in the U-Pb age and oxygen isotope zoning of zircons from a lower crustal paragneiss in the Neoarchean Superior province. Detrital igneous zircon cores with ??18O values of 5.1???-7.1??? record creation of primitive to increasingly evolved crust from 2.85 ?? 0.02 Ga to 2.67 ?? 0.02 Ga. Sharp chemical unconformity between cores and higher ??18O (8.4???-10.4???) metamorphic overgrowths as old as 2.66 ?? 0.01 Ga dictates a rapid sequence of arc unroofing, burial of detrital zircons in hydrosphere-altered sediment, and transport to lower crust late in upper plate assembly. The period to 2.58 ?? 0.01 Ga included ???80 m.y. of high-temperature (???700-650 ??C), nearly continuous overgrowth events reflecting stages in maturation of the subjacent mantle root. Huronian continental rifting is recorded by the youngest zircon tip growth at 2512 ?? 8 Ma (??? 600 ??C) signaling magma intraplating and the onset of rigid plate behavior. This >150 m.y. microscopic isotope record in single crystals demonstrates the sluggish volume diffusion of U, Pb, and O in zircon throughout protracted regional metamorphism, and the consequent advances now possible in reconstructing planetary dynamics with zircon zoning. ?? 2008 The Geological Society of America.

  17. Research on Parts Process of V-shape Slot Carburizing Quenching%V型槽渗碳淬火零件加工工艺研究

    陈惠娟; 黄玉方; 梁壮; 王健


    通过对V型槽渗碳淬火类零件的特性及加工难点的分析,研究V型槽渗碳淬火类零件的工艺总方案及加工工艺.主要针对2种不同结构类型的V型槽渗碳淬火类零件的加工工艺及加工过程进行分析,探讨V型槽渗碳淬火零件的特殊加工方法.通过对V型槽渗碳淬火类零件的生产加工和加工过程中的工艺改进与完善,摸索到了加工V型槽渗碳淬火零件的一些经验,供大家参考.%By analyzing the characteristics of V-shape slot carburizing quenching parts and the difficulties of processing, the paper mainly focused on the general plan and processing technology of the V-shape slot carburizing quenching parts. By analyzing parts processing technology and processing procedure of two different structures of the V-shape slot carburizing quenching, the paper discussed the specific processing method of the V-shape slot carburizing quenching parts. By making improvements and perfection of the production processing and the process technology of the V-shape slot carburizing quenching parts, we have got some experiences from the processing of the V-shape slot carburizing quenching parts for your reference.

  18. What Hf isotopes in zircon tell us about crust-mantle evolution

    Iizuka, Tsuyoshi; Yamaguchi, Takao; Itano, Keita; Hibiya, Yuki; Suzuki, Kazue


    The 176Lu-176Hf radioactive decay system has been widely used to study planetary crust-mantle differentiation. Of considerable utility in this regard is zircon, a resistant mineral that can be precisely dated by the U-Pb chronometer and record its initial Hf isotope composition due to having low Lu/Hf. Here we review zircon U-Pb age and Hf isotopic data mainly obtained over the last two decades and discuss their contributions to our current understanding of crust-mantle evolution, with emphasis on the Lu-Hf isotope composition of the bulk silicate Earth (BSE), early differentiation of the silicate Earth, and the evolution of the continental crust over geologic history. Meteorite zircon encapsulates the most primitive Hf isotope composition of our solar system, which was used to identify chondritic meteorites best representative of the BSE (176Hf/177Hf = 0.282793 ± 0.000011; 176Lu/177Hf = 0.0338 ± 0.0001). Hadean-Eoarchean detrital zircons yield highly unradiogenic Hf isotope compositions relative to the BSE, providing evidence for the development of a geochemically enriched silicate reservoir as early as 4.5 Ga. By combining the Hf and O isotope systematics, we propose that the early enriched silicate reservoir has resided at depth within the Earth rather than near the surface and may represent a fractionated residuum of a magma ocean underlying the proto-crust, like urKREEP beneath the anorthositic crust on the Moon. Detrital zircons from world major rivers potentially provide the most robust Hf isotope record of the preserved granitoid crust on a continental scale, whereas mafic rocks with various emplacement ages offer an opportunity to trace the Hf isotope evolution of juvenile continental crust (from εHf[4.5 Ga] = 0 to εHf[present] = + 13). The river zircon data as compared to the juvenile crust composition highlight that the supercontinent cycle has controlled the evolution of the continental crust by regulating the rates of crustal generation and intra

  19. Zircon record of fractionation, hydrous partial melting and thermal gradients at different depths in oceanic crust (ODP Site 735B, South-West Indian Ocean)

    Pietranik, A.; Storey, C.; Koepke, J.; Lasalle, S.


    Felsic veins (plagiogranites) are distributed throughout the whole oceanic crust section and offer insight into late-magmatic/high temperature hydrothermal processes within the oceanic crust. Despite constituting only 0.5% of the oceanic crust section drilled in IODP Site 735B, they carry a significant budget of incompatible elements, which they redistribute within the crust. Such melts are saturated in accessory minerals, such as zircon, titanite and apatite, and often zircon is the only remaining phase that preserves magmatic composition and records processes of felsic melt formation and evolution. In this study, we analysed zircon from four depths in IODP Site 735B; they come from the oxide gabbro (depth approximately 250 m below sea floor) and plagiogranite (depths c. 500, 860, 940 m below sea floor). All zircons have similar ɛHf composition of c. 15 units indicating an isotopically homogenous source for the mafic magmas forming IODP Site 735B gabbro. Zircons from oxide gabbro are scarce and variable in composition consistent with their crystallization from melts formed by both fractionation of mafic magmas and hydrous remelting of gabbro cumulate. On the other hand, zircon from plagiogranite is abundant and each sample is characterized by compositional trends consistent with crystallization of zircon in an evolving melt. However, the trends are different between the plagiogranite at 500 m bsf and the deeper sections, which are interpreted as the record of plagiogranite formation by two processes: remelting of gabbro cumulate at 500 m bsf and fractionation at deeper sections. Zircon from both oxide gabbro and plagiogranite has δ18O from 3.5 to 6.0‰. Values of δ18O are best explained by redistribution of δ18O in a thermal gradient and not by remelting of hydrothermally altered crust. Tentatively, it is suggested that fractionation could be an older episode contemporaneous with gabbro crystallization and remelting could be a younger one, triggered by

  20. Did the First Iron Blacksmiths Learn to Carburize Iron? Part II: Experiments Showing That it is Very Likely That They Did

    Verhoeven, J. D.; Pendray, A. H.; Dauksch, W. E.


    Results of short-time carburizing of wrought iron in a charcoal-fired furnace present strong evidence that our earliest blacksmith ancestors probably discovered how to carburize their bloomery iron and produced cutting and scraping tools superior to bronze tools shortly after they had learned to make this iron in the 1200-900 BC time period. Their bloomery iron needed to be forged to make useful tools and it seems likely that at least some of them heated the iron to the forging temperature in charcoal burning in their bloomery furnaces, the same arrangement as used here.

  1. Timing of metasomatism in a subcontinental mantle: evidence from zircon at Finero (Italy)

    Badanina, I. Yu.; Malitch, K. N.


    The Finero phlogopite-peridotite represents a metasomatized residual mantle harzburgite, exposed at the base of the lower-crust section in the Ivrea Zone, Western Alps (Hartmann and Wedepohl 1993). It forms the core of a concentrically zoned sequence of internal layered gabbro, amphibole-rich peridotite and external gabbro. The phlogopite peridotite contains small-size chromitite bodies, with a suite of accessory minerals such as phlogopite, apatite, Ca-Mg carbonates, zirconolite, zircon, thorianite and uraninite, proposed to form during alkaline-carbonatitic metasomatism process within the mantle (Zaccarini et al. 2004). In this study, the combined application of a non-destructive technique to separate zircon from their host rocks (see details at and in-situ analytical technique for compositional and isotopic analysis (SHRIMP-II at Russian Geological Research Institute, St. Petersburg) has provided new more detailed age constraints on the formation of chromitite and related metasomatic events within a mantle tectonite at Finero. Chromitite samples derived from the dump in the prospecting trenches of Rio Creves. In thin sections, zircon occurs as relatively large (up to 200 μm) grains characterized by subhedral to euhedral shapes. Separated grains of zircon form two distinct populations. Dominant zircon population is pale pink and characterized by different shapes (subhedral, subrounded or elongated). In cathodoluminescense, the main set of population is represented by complex grains, which show development of core-rim relationship (most likely recrystallized rim on a preserved core). Subordinate zircon grains are colourless. They are characterized by a smoky cathodoluminescense, with almost no internal pattern. Three main U-Pb age clusters have been recognized. The youngest age cluster, typical for subordinate colourless zircon population and rims in complex grains of dominant pale pink population, show two concordant 206Pb/238U ages (e

  2. Investigation of zircon/zirconia ceramics doped with {sup 239}Pu and {sup 238}Pu

    Burakov, B.E.; Anderson, E.B.; Zamoryanskaya, M.V.; Nikolaeva, E.V.; Strykanova, E.E.; Yagovkina, M.A. [V.G. Khlopin Radium Institute, Saint Petersburg (Russian Federation)


    Several samples of crystalline double-phase ceramics based on zircon, (Zr,Pu)SiO{sub 4} and zirconia, (Zr,Pu)O{sub 2}, were synthesized by sintering in air, precursors containing approximately 5-6 and 10 wt% {sup 239}Pu, respectively. One sample doped with 5-6 wt% {sup 238-39-40}Pu was also obtained under the same conditions. All ceramic samples were studied by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and MCC-1 leach test in deionized water at 90 C. Results indicate that even radiation damaged zircon/zirconia ceramics retain high chemical resistance and mechanical durability. (author)

  3. Critical scattering of synchrotron radiation in lead zirconate-titanate with low titanium concentrations

    Andronikova, D. A.; Bosak, A. A.; Bronwald, Iu. A.; Burkovsky, R. G.; Vakhrushev, S. B.; Leontiev, N. G.; Leontiev, I. N.; Tagantsev, A. K.; Filimonov, A. V.; Chernyshov, D. Yu.


    Diffuse scattering in the lead zirconate-titanate single crystal with a titanium concentration of 0.7 at % has been studied by the synchrotron radiation scattering method. Measurements have been performed both in the vicinity of the Brillouin zone center and at the M-point. Highly anisotropic diffuse scattering has been revealed in the paraelectric phase near the Brillouin zone center; diffuse scattering anisotropy is similar to that previously observed in pure lead zirconate. The temperature dependence of this diffuse scattering obeys a critical law with T c ≈ 480 K. Diffuse scattering in the vicinity of the M-point weakly depends on temperature; this dependence behaves differently at M-points with various indices.

  4. Precise U-Pb Zircon Dating of the Syenite Phase from the Ditrau Alkaline Igneous Complex

    Pană Dinu


    Full Text Available The Ditrău igneous complex represents the largest alkaline intrusion in the Carpathian-Pannonian region consisting of a plethora of rock types formed by complicated magmatic and metasomatic processes. A detailed U-Pb zircon age study is currently underway and the results for the syenite intrusion phase is reported herein. The U-Pb zircon emplacement age of the syenite of 229.6 +1.7/-1.2 Ma documents the quasi-contemporaneous production and emplacement of the gabbro and syenite magmas. We suggest that the syenite and associated granite formed by crustal melting during the emplacement of the mantle derived gabbroic magma around 230 Ma. The thermal contact aureole produced by the Ditrău alkaline igneous complex constrains the main tectonism recorded by surrounding metamorphic lithotectonic assemblages to be pre-Ladinian.

  5. On the valency state of radiogenic lead in zircon and its consequences

    Kramers, J.; Frei, Robert; Newville, M.


    at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during...... not resemble that of PbO2. The arguments why radiogenic Pb should be tetravalent are based on analogies with studies relating to the tetravalent state of 234Th and the hexavalent state of 234U, which show that a-recoil in silicates generates a strongly oxidizing environment at the site where the recoiling......-recoil damaged sites could be leached out by any electrolyte solution that reduces it to the divalent state, making it both incompatible and soluble. Thus, discordia can be generated in weathering. The curious observation that discordant Archaean zircon suites generally define trends to lower intercepts at up...

  6. Archean Arctic continental crust fingerprints revealing by zircons from Alpha Ridge bottom rocks

    Sergeev, Sergey; Petrov, Oleg; Morozov, Andrey; Shevchenko, Sergey; Presnyakov, Sergey; Antonov, Anton; Belyatsky, Boris


    Whereas thick Cenozoic sedimentary cover overlapping bedrock of the Arctic Ocean, some tectonic windows were sampled by scientific submarine manipulator, as well as by grabbing, dredging and drilling during «Arctic-2012» Russian High-Arctic expedition (21 thousands samples in total, from 400-km profile along Alpha-Mendeleev Ridges). Among others, on the western slope of Alpha Ridge one 10x10 cm fragment without any tracks of glacial transportation of fine-layered migmatitic-gneiss with prominent quartz veinlets was studied. Its mineral (47.5 vol.% plagioclase + 29.6% quartz + 16.6% biotite + 6.1% orthoclase) and chemical composition (SiO2:68.2, Al2O3:14.9, Fe2O3:4.44, TiO2:0.54, MgO:2.03, CaO:3.13, Na2O:3.23, K2O:2.16%) corresponds to trachydacite vulcanite, deformed and metamorphozed under amphibolite facies. Most zircon grains (>80%) from this sample has an concordant U-Pb age 3450 Ma with Th/U 0.8-1.4 and U content of 100-400 ppm, epsilon Hf from -4 up to 0, and ca 20% - ca 3.3 Ga with Th/U 0.7-1.4 and 90-190 ppm U, epsilon Hf -6.5 to -4.5, while only 2% of the grains show Proterozoic age of ca 1.9 Ga (Th/U: 0.02-0.07, U~500 ppm, epsilon Hf about 0). No younger zircons were revealed at all. We suppose that magmatic zircon crystallized as early as 3450 Ma ago during acid volcanism, the second phase zircon crystallization from partial melt (or by volcanics remelting) under amphibolite facies metamorphism was at 3.3 Ga ago with formation of migmatitie gneisses. Last zircon formation from crustal fluids under low-grade metamorphic conditions was 1.9 Ga ago. There are two principal possibilities for the provenance of this metavolcanic rock. The first one - this is ice-rafted debris deposited by melted glacial iceberg. However, presently there are no temporal and compositional analogues of such rocks in basement geology of peri-oceanic regions, including Archean Itsaq Gneiss Complex, Lewisian Complex and Baltic Shield but these regions are far from the places of

  7. Influence of gadolinium concentration on the EMR spectrum of Gd{sup 3+} in zircon

    Biasi, R.S. de, E-mail: rsbiasi@ime.eb.b [Secao de Engenharia Mecanica e de Materiais, Instituto Militar de Engenharia, 22290-270 Rio de Janeiro, RJ (Brazil); Grillo, M.L.N., E-mail: mluciag@uerj.b [Instituto de Fisica, Universidade do Estado do Rio de Janeiro, 20550-013 Rio de Janeiro, RJ (Brazil)


    Electron magnetic resonance (EMR) spectra of gadolinium-doped zircon (ZrSiO{sub 4}) powders have been studied at room temperature for gadolinium concentrations between 0.20 and 1.0 mol%. The results suggest that Gd{sup 3+} ions occupy substitutional sites in the zircon lattice, that the electron magnetic resonance linewidth increases with increasing gadolinium concentration and that the range of the exchange interaction between Gd{sup 3+} ions is about 1.17 nm, larger than that of the same ion in other host lattices, such as ceria (CeO{sub 2}), strontium oxide (SrO) and calcium oxide (CaO). The fact that the electron magnetic resonance linewidth of the Gd{sup 3+} ion in polycrystalline zircon increases, regularly and predictably, with Gd concentration, shows that the Gd{sup 3+} ion can be used as a probe to study, rapidly and non-destructively, the crystallinity and degradation of ZrSiO{sub 4}.

  8. Late Triassic uplift of southern Norway revealed by detrital zircons in the Norwegian-Danish Basin

    Olivarius, Mette; Nielsen, Lars H.; Weibel, Rikke; Kristensen, Lars; Thomsen, Tonny B.


    Zircon U/Pb geochronometry is used to identify the sediment source areas of the Upper Triassic to Lower Jurassic shallow marine to paralic Gassum Formation in the Norwegian-Danish Basin. The analyses of zircon grains from geographically and stratigraphically widely distributed cores take advantage of the detailed sequence stratigraphic framework existing for the succession. The zircon ages indicate that the sediment in the lower part of the Gassum Formation in the northern and central parts of the basin was supplied solely from the Telemarkia Terrane in the southern part of southern Norway. However, age signatures from other basement terranes were added during periods of transgression presumably as a result of longshore reworking. The sediment in the eastern part of the basin has a different provenance signature that reflects supply from various sources of which some or all seemingly include older sediments. The basinwide fluvial incision that occurred during a relative sea-level fall in the Rhaetian is interpreted to be related to uplift of southern Norway since a pronounced content of zircon grains with U/Pb ages of 1.65 Ga were introduced in the Norwegian-Danish Basin at the time. This age is dominant in the upper part of the Gassum Formation and is present in all studied younger sediments in the Norwegian-Danish Basin, whereas it is missing in older sediments in the basin. Rocks with corresponding ages are presently exposed in the Jotun Nappe Complex and the Western Gneiss Complex in the central and northern parts of southern Norway. Thus, major faulting activity must have occurred in southern Norway during the Late Triassic that made such rocks available for erosion with permanent southeastwards drainage.

  9. Synthesis of ZrO2 -SiC Composite by Carbothermal Reduction of Zircon


    Zircon (mesh size ≤ 44μm ) and carbon black (mesh size≤30 μm) were used as the starting materials,weighed with m(zircon): m(carbon black) of 100:20 and mixed fully. The specimens with the diameter of 20mm and length of 5mm were prepared by pressing at 100 MPa, then dried at 120℃ for 12h, put into a furnace with 1. 5L · min-1 argon gas and fired at 1450℃, 1500℃, 1550℃, 1600℃ and 1650℃ for 4h, respectively. The chemical composition, phase composition and microstructure of the specimens were studied by chemical analysis, X-ray diffraction and scanning electronic microscope, and the carbothermal reduction reaction process was discussed by thermodynamic analysis.The results showed that the ZrO2-SiC composite could be synthesized by carbothermal reduction reaction using zircon and carbon black as the starting materials in argon atmosphere. The composite with different composition was obtained by controlling the firing temperature and partial pressure of CO gas. The proper temperature to synthesize ZrO2-SiC composite was 1600℃ in this experiment.

  10. Two stages of zircon crystallization in the Jingshan monzogranite, Bengbu Uplift: Implications for the syn-collisional granites of the Dabie-Sulu UHP orogenic belt and the climax of movement on the Tan-Lu fault

    Wang, X.; Chen, J.; Griffin, W. L.; O'Reilly, S. Y.; Huang, P. Y.; Li, X.


    The detailed study of zircon can provide vital clues about the petrogenetic environment of granitoid rocks. Morphological and chemical studies of zircon grains from the Jingshan monzogranite in the Bengbu Uplift (Anhui province, eastern China) identify three phases of growth. Zircon I is brown, translucent, ovoid, and occurs as inherited cores. It shows two groups of 206Pb/ 238U ages, corresponding to the country rock of the Jingshan monzogranite and the basement of the Bengbu Uplift. Zircon II is colorless, transparent and idiomorphic-hypidiomorphic with Ipr = 0.34-0.52, Ipy = 0.03-0.24 and Iel = 0.26-0.34. It shows a very bright CL due to high contents of trace elements (e.g., Y, U and Th), and the oscillatory zoning associated with sector zoning. It contains 1.40-1.66 wt.% HfO 2 with a mean ɛ Hf (t) of - 17.88. These features indicate the igneous crystallization of Zircon II from a peraluminous granite of mainly crustal origin. Based on the field geology, petrography, geochemical analysis, and especially a weighted mean age of 222 Ma for Zircon II, we argue that the Jingshan monzogranite is a syn-collisional granite of the Dabie UHP orogenic belt. This provides new evidence for the northward subduction of the South China Block beneath the North China Block just before 222 Ma, and allows quantitative estimates of the rate of post-UHP exhumation in the Dabie orogenic belt. Zircon III is also colorless and transparent, but is totally idiomorphic with Ipr = 0.41-1.00, Ipy = 0.88-1.00 and Iel = 0.39-0.83. It occurs only as overgrowths on Zircon II, and shows weak CL due to its depletion in trace elements. Zircon III has widely variable contents of HfO 2 (1.12 to 3.01 wt.%) and Hf-isotope compositions very similar to those of Zircon II. These features suggest crystallization of Zircon III from small volumes of leucosome, probably in the beginning stages of migmatisation. Zircon III has a weighted mean age of 156 Ma, interpreted as representing the climax of movement

  11. Latest Pleistocene crustal cannibalization at Baekdusan (Changbaishan) as traced by oxygen isotopes of zircon from the Millennium Eruption

    Cheong, Albert Chang-sik; Sohn, Young Kwan; Jeong, Youn-Joong; Jo, Hui Je; Park, Kye-Hun; Lee, Youn Soo; Li, Xian-Hua


    The silicic volcanism of Baekdusan (Changbaishan), which is on the border between North Korea and China, was initiated in the Late Pleistocene and culminated in the 10th century with a powerful (volcanic explosivity index = 7) commendite-trachyte eruption commonly referred to as the ;Millennium Eruption.; This study presents oxygen isotope data of zircon in trachydacitic pumices ejected during the Millennium Eruption, together with whole-rock geochemical and Sr-Nd-Pb isotopic data that manifest once again the A-type and EM1 affinities of the Millennium Eruption magma. The zircon crystals, dated by previous studies at ca. 12-9 ka, show a moderate inter-grain variation in δ18O from 3.69‰ to 5.03‰. These values are consistently lower than the normal mantle range, and interpreted to have resulted from the digestion of meteoric-hydrothermally altered intracaldera rocks in the shallow magma chamber beneath Baekdusan just prior to the crystallization of the zircons, rather than from derivation from low-δ18O sources deep in the mantle. The whole-rock geochemical/isotopic considerations suggest that the magma mainly self-cannibalized the earlier erupted volcanic carapace around the magma chamber. This study highlights the usefulness of zircon oxygen isotopes for characterizing past volcanic activity that has now been commonly eroded away and implies that the generation of Yellowstone-type low-δ18O magma is not a rare phenomenon in large-volume silicic eruptions.

  12. Single-step thermal carburization synthesis of supported molybdenum carbides from molybdenum-containing methyl-silica

    Juan Zou; Minglin Xiang; Bo Hou; Dong Wu; Yuhan Sun


    A novel synthesis route to obtain highly dispersed molybdenum carbides in porous silica is described. The synthesis was carried out by a single-step heat treatment of molybdenum-containing and methyl-modified silica (Mo-M-SiO2) in argon atmosphere at 973 K. Mo-M-SiO2 precursor was facilely obtained via a one-pot synthesis route, using (NH4)6Mo7O24·4H2O (AHM) as molybdenum sources and polymethylhydrosiloxane (PMHS) as silica sources at the initial synthetic step. The optimal C/Mo molar ratio in reaction system for complete carburization of molybdenum species was 7. The carburization process of molybdenum species followed a nontopotactic route involving a MoO2 intermediate phase, which was evidenced by XRD, N2 adsorption-desorption and in situ XPS. Formation mechanism of Mo-M-SiO2 precursor was also proposed by observation of the reaction between AHM and PMHS with TEM. Furthermore, by adding TEOS into silica sources and adjusting TEOS/PMHS mass ratio, crystal phase of molybdenum carbides transferred fromβ-Mo2C to α-MoC1-x, and SiO2 structure changed from microporous to micro/mesoporous. Catalytic performances of samples were tested using CO hydrogenation as a probe reaction. The supported molybdenum carbides exhibited high selectivity for higher alcohol synthesis compared with bulkβ-Mo2C and α-MoC1-x.

  13. The influence of surface microstructure and chemical composition on corrosion behaviour in fuel-grade bio-ethanol of low-alloy steel modified by plasma nitro-carburizing and post-oxidizing

    Boniatti, Rosiana; Bandeira, Aline L.; Crespi, Ângela E.; Aguzzoli, Cesar; Baumvol, Israel J. R.; Figueroa, Carlos A.


    The interaction of bio-ethanol on steel surfaces modified by plasma-assisted diffusion technologies is studied for the first time. The influence of surface microstructure and chemical composition on corrosion behaviour of AISI 4140 low-alloy steel in fuel-grade bio-ethanol was investigated. The steel surfaces were modified by plasma nitro-carburizing followed plasma oxidizing. X-ray diffraction, scanning electron microscopy, optical microscopy, X-ray dispersive spectroscopy, and glow-discharge optical emission spectroscopy were used to characterize the modified surface before and after immersion tests in bio-ethanol up to 77 days. The main corrosion mechanism is pit formation. The pit density and pit size were measured in order to quantify the corrosion resistance which was found to depend more strongly on microstructure and morphology of the oxide layer than on its thickness. The best corrosion protection was observed for samples post-oxidized at 480 °C and 90 min.

  14. Silica-templated synthesis of ordered mesoporous tungsten carbide/graphitic carbon composites with nanocrystalline walls and high surface areas via a temperature-programmed carburization route.

    Wu, Zhangxiong; Yang, Yunxia; Gu, Dong; Li, Qiang; Feng, Dan; Chen, Zhenxia; Tu, Bo; Webley, Paul A; Zhao, Dongyuan


    Ordered mesostructured tungsten carbide and graphitic carbon composites (WC/C) with nanocrystalline walls are fabricated for the first time by a temperature-programmed carburization approach with phosphotungstic acid (PTA) as a precursor and mesoporous silica materials as hard templates. The mesostructure, crystal phase, and amount of deposited graphitic carbon can be conveniently tuned by controlling the silica template (SBA-15 or KIT-6), carburizing temperature (700-1000 degrees C), the PTA-loading amount, and the carburizing atmosphere (CH(4) or a CH(4)/H(2) mixture). A high level of deposited carbon is favorable for connecting and stabilizing the WC nanocrystallites to achieve high mesostructural regularity, as well as promoting the carburization reaction. Meanwhile, large pore sizes and high mesoporosity of the silica templates can promote WC-phase formation. These novel, ordered, mesoporous WC/C nanocomposites with high surface areas (74-169 m(2) g(-1)), large pore volumes (0.14-0.17 cm(3) g(-1)), narrow pore-size distributions (centered at about 3 nm), and very good oxidation resistance (up to 750 degrees C) have potential applications in fuel-cell catalysts and nanodevices.

  15. Effect of the Content of Retained Austenite and Grain Size on the Fatigue Bending Strength of Steels Carburized in a Low-Pressure Atmosphere

    Kula, P.; Dybowski, K.; Lipa, S.; Januszewicz, B.; Pietrasik, R.; Atraszkiewicz, R.; Wołowiec, E.


    The effect of the content of retained austenite and of the initial austenite grain size on high-cycle fatigue of two low-alloy steels 16MnCr5 and 17CrNi6-6 after carburizing in a low-pressure atmosphere (acetylene, ethylene and hydrogen) and subsequent high-pressure gas quenching is investigated.

  16. Mixing and melt sources in the Miocene Aztec Wash pluton (Nevada, USA) as revealed by zircon Hf and O and whole rock Sr, Nd, and Hf isotopes

    Ryan, M.; Miller, J. S.; Miller, C. F.; Bromley, S.; Davies, G. R.; Schmitt, A. K.


    The 15.6 Ma Aztec Wash Pluton (AWP) is one of several Miocene intrusions located within the northern Colorado River extensional corridor. Extensive E-W tilting of fault blocks has exposed the pluton from the roof to 5 km structural depth. Earlier field and petrologic studies subdivided the AWP into two distinct zones: (1) a Granite Zone (GZ) comprised of relatively homogeneous granite with subtle differences in textures and mineralogy; (2) a Heterogeneous Zone (HZ), which interfingers the GZ, contains evidence for mafic and felsic magma input with a wide compositional range (42-78 wt% SiO2), and abundant field evidence for hybridization. Previous whole rock geochemistry and zircon trace element analyses indicated that compositional variation was produced by multi-component mixing between mafic and felsic melts within the HZ. New whole rock Sr, Nd, and Hf isotope data from the HZ show that all rocks (including high-silica granites) formed by mixing Precambrian crust and enriched mantle, with mixtures having a large mantle fraction (≥50%). New Hf (n=189) and O (n=241) isotope analyses of zircon from samples in the HZ confirm these melt sources and provide a broader perspective on hybridization processes within the AWP. Zircon grains from all samples show heterogeneous Hf and O isotopic compositions (-5 to -18 ɛHf; 4.5-7.5% δ18O), but despite the clear signature of Precambrian crust in the whole rock data, obvious Precambrian zircons (or cores) were mostly absent; only one zircon was clearly Precambrian (ɛHf = -25). Resolvable intragrain variability is relatively limited (including the Precambrian grain, which is unzoned). Zircons from hand samples and from compositional groups also show heterogeneous ɛHf and δ18O values, although the spreads are more restricted than in the whole data set (6-10 ɛHf in granites, 5-7 ɛHf in intermediate "hybrids", 5-6 ɛHf in gabbro/diorite sheets). Oxygen isotope values for the zircons also show intra-handsample heterogeneity

  17. Detrital zircon evidence for progressive underthrusting in Franciscan metagraywackes, west-central California

    Snow, C.A.; Wakabayashi, J.; Ernst, W.G.; Wooden, J.L.


    We present new U/Pb ages for detrital zircons separated from six quartzose metagraywackes collected from different Franciscan Complex imbricate nappes around San Francisco Bay. All six rocks contain a broad spread of Late Jurassic-Cretaceous grains originating from the Klamath-Sierra Nevada volcanic-plutonic arc. Units young structurally downward, consistent with models of progressive underplating and offscraping within a subduction complex. The youngest specimen is from the structurally lowest San Bruno Mountain sheet; at 52 Ma, it evidently was deposited during the Eocene. None of the other metagraywackes yielded zircon ages younger than 83 Ma. Zircons from both El Cerrito units are dominated by ca. 100-160 Ma grains; the upper El Cerrito also contains several grains in the 1200-1800 Ma interval. These samples are nearly identical to 97 Ma metasedimentary rock from the Hunters Point shear zone. Zircon ages from this m??lange block exhibit a broad distribution, ranging from 97 to 200 Ma, with only a single pre-Mesozoic age. The Albany Hill specimen has a distribution of pre-Mesozoic grains from 1300 to 1800 Ma, generally similar to that of the upper El Cerrito sheet; however, it contains zircons as young as 83 Ma, suggesting that it is significantly younger than the upper El Cerrito unit. The Skaggs Spring Schist is the oldest studied unit; its youngest analyzed grains were ca. 144 Ma, and it is the only investigated specimen to display a significant Paleozoic detrital component. Sedimentation and subduction-accretion of this tract of the trench complex took place along the continental margin during Early to early-Late Cretaceous time, and perhaps into Eocene time. Franciscan and Great Valley deposition attests to erosion of an Andean arc that was active over the entire span from ca. 145 to 80 Ma, with an associated accretionary prism built by progressive underthrusting. We use these new data to demonstrate that the eastern Franciscan Complex in the northern and

  18. 孔雀河斜坡与库鲁克塔格隆起构造事件的裂变径迹证据%Detrital zircon and apatite fission track study of key tectonic events of Kongquehe slope and Kuruketage uplift, north-eastern Tarim Basin, China

    肖晖; 任战利; 王起琮; 赵靖舟


    文章以塔里木盆地东北缘库鲁克塔格隆起与孔雀河斜坡盆山系统为主要研究对象,在该地区露头和钻井样品开展碎屑磷灰石、锆石裂变径迹研究,对库鲁克塔格构造演化中关键构造事件提供热年代学约束.锫石样品在加里东晚期-早海西期达到最大古地温,之后经历了长期的抬升降温过程,锆石最小峰值年龄记录了371~392 Ma 和328~305.7 Ma二次构造抬升年龄;在晚侏罗-晚白垩世,样品逐渐退出磷灰石部分退火带底界,磷灰石裂变径迹记录了134.5~164 Ma、73~100 Ma和35.4 Ma三次构造抬升事件年龄,其中73~100 Ma为主要构造抬升年龄.海西期构造事件年龄反映了孔雀河斜坡由沉降转入剥蚀演化阶段,对油气藏的形成具有重要意义;晚白垩世构造事件则反映了库鲁克塔格山的强烈隆升.%This paper focuses on the study of basin-and-range relations about Kongquehe slope and Kuruketage uplift. Thermochronology constraints were made to the key tectonic events in the Kuruketage tectonic evolution history, using the methods of detrital zircon and apatite fission track, sampled from outcrop area and well cores. The time of the maximum palaeotemperature from zircon samples was determined during late-Caledonian to early-Hercynian cycle, and from then on, the samples experienced the procedure of tectonic uplifts and temperature drop times.Two thermochronology ages of zircon fission track were recorded, which reflect two tectonic events happened in 371~392 Ma and 328~305.7 Ma. Three later tectonic uplifting events were recorded by apatite fission track, whose thermochronology ages are 134.5~164 Ma, 73~100 Ma and 35.4 Ma respectively, after the palaeotemperature of samples was decreased out of the partial annealing zone's base level. The Hercynian ages from the zircon samples indicate the tectonic transformation from subsidence to uplift in the Kongquehe slope, which is significant to oil

  19. Fuel Penalty Comparison for (Electrically Heated Catalyst Technology Comparaison de l’augmentation de consommation de carburant pour la technologie de catalyseurs chauffés à l’électricité

    Kessels J. T.B.A.


    Full Text Available The conversion efficiency of three way catalytic converters is mainly defined by the temperature range wherein they are operating. Traditionally, ignition retard has been used to reduce the light-off time of the catalyst. This is however associated with a fuel penalty. With increasing vehicle electrification, electrically heating facilities present an alternative, especially for hybrid vehicles. Nevertheless, system complexity of hybrid vehicles prevents engineers to evaluate possible heating technologies and their corresponding fuel penalty with respect to traditional solutions. This paper evaluates the application of an electrically heated catalyst on a hybrid vehicle equipped with a Natural Gas (NG engine. The effect of heating power on light-off time and fuel penalty is determined, using analysis techniques emerging from integrated powertrain control. By means of a case study, the importance of an integral approach is explained by comparing the fuel penalty and conversion efficiency improvement of electric heating with that of ignition retard. In this process, a mix of simulation and test data were combined, forming the foundations for future control developments of a suitable light-off strategy. L’efficacité de conversion des catalyseurs est principalement définie par la gamme de température dans laquelle ils fonctionnent. Un retard du point d’allumage a traditionnellement été utilisé pour réduire le temps d’amorçage du catalyseur. Ceci est cependant associé à une augmentation de la consommation de carburant. Avec l’électrification des véhicules, la possibilité de chauffage électrique représente véritablement une alternative, tout particulièrement pour les véhicules hybrides. Cependant, la complexité des véhicules hybrides rend difficile l’évaluation des technologies de chauffage éventuelles ainsi que l’augmentation de la consommation de carburant associée ; il est aussi difficile de comparer ces r

  20. Electrochemical characterization of praseodymia doped zircon. Catalytic effect on the electrochemical reduction of molecular oxygen in polar organic solvents

    Domenech, Antonio, E-mail: [Departament de Quimica Analitica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain); Montoya, Noemi; Alarcon, Javier [Departament de Quimica Inorganica, Universitat de Valencia, Dr. Moliner, 50, 46100 Burjassot, Valencia (Spain)


    Highlights: > Electrochemical characterization of Pr centers in praseodymia-doped zircon. > Study of the catalytic effect on the reduction of peroxide radical anion in nonaqueous solvents. > Assessment of non-uniform distribution of Pr centers in the zircon grains. - Abstract: The voltammetry of microparticles and scanning electrochemical microscopy methodologies are applied to characterize praseodymium centers in praseodymia-doped zircon (Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4}; y + z = x; 0.02 < x < 0.10) specimens prepared via sol-gel synthetic routes. In contact with aqueous electrolytes, two overlapping Pr-centered cathodic processes, attributable to the Pr (IV) to Pr (III) reduction of Pr centers in different sites are obtained. In water-containing, air-saturated acetone and DMSO solutions as solvent, Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} materials produce a significant catalytic effect on the electrochemical reduction of peroxide radical anion electrochemically generated. These electrochemical features denote that most of the Pr centers are originally in its 4+ oxidation state in the parent Pr{sub x}Zr{sub (1-y)}Si{sub (1-z)}O{sub 4} specimens. The variation of the catalytic performance of such specimens with potential scan rate, water concentration and Pr loading suggests that Pr is not uniformly distributed within the zircon grains, being concentrated in the outer region of such grains.

  1. Age and genesis of the Myanmar jadeite: Constraints from U-Pb ages and Hf isotopes of zircon inclusions

    QIU ZhiLi; WU FuYuan; YANG ShuFeng; ZHU Min; SUN JinFeng; YANG Ping


    Myanmar jadeite (jadeitite) is well known for its economical value and distinctive tectonic locality within the collisional belt between India and Eurasian plates. However, it is less studied for its genesis and geodynamic implications due to precipitous topography, adverse weather and local military conflicts in the area. By means of combined ICP-MS and LA-MC-ICPMS techniques, we have carried out in-situ trace elements, U-Pb and Lu-Hf isotopes for zircon inclusions in a piece of jadeite gem sample. CL imaging suggests that the zircons are metasomatic in origin, and contain mineral inclusions of jadeite and omphacite. Seventy-five analyses on 16 grains of the zircons yield a U-Pb age of 158±2 Ma. The Myanmar zircons differ from other types in that they have no significant Eu anomalies despite high HREE concentrations. Measured 176Hf/177Hf ratios range from 0.282976 to 0.283122, with an average value of 0.283066±7;εHf(t) value of 13.8±0.3 (n=75). These results indicate that the Myanmar jadeite was formed in the Late Jurassic, probably by interaction of fluid released from subducted oceanic slab with mantle wedge. Therefore, its formation has no genetic relationship to the continental collision between Indian and Euroasian plates.

  2. 12CrNi3A凸轮轴渗碳激光强化复合处理工艺%The Intensification and Recombination Treatment of Carburization Laser of Cam Shaft 12CrNi3A



    he technique for the intensification and recombination treatment of carburization laser of cam shaft 12CrNi3A have been studied in this paper.The tests results show that,with using the carburization technique to increase the carbon density of surface and through the reasonable and effective technology of laser quenching treatment an ideal and uniform harden quench surfaceis obtained.The hardness of surface has been strengthened.The wear resistance and fatigue strength resistance of cam shaft has been enhanced.The problem of abrasive failure of cam shaft has also been resolved. It is a new attempt to develop and apply the technology of laser surface heat treating.%对12CrNi3A凸轮轴渗碳激光强化复合处理进行了研究。研究结果表明,采取表面渗碳工艺增加表层的碳浓度,并通过采用合理有效的激光淬火处理工艺,获得理想的淬硬层分布,提高了表层的硬度,增强了凸轮轴表面的耐磨性和抗疲劳强度,解决了凸轮轴磨损失效问题,是开发和应用激光表面热处理技术的一个新的尝试。

  3. Protocol for TL dating with zircon : Computer simulation of temperature and dose rate effects

    Turkin, AA; Van Es, HJ; Vainshtein, DI; den Hartog, HW


    Natural zircon is irradiated internally by U and Th impurities. After exposure to ionizing irradiation zircon exhibits thermoluminescence (TL), which can be used to calculate the irradiation dose and the sample age. A kinetic model for TL of zircon developed earlier is used to model the processes

  4. Evidence for multi-cycle sedimentation and provenance constraints from detrital zircon U-Pb ages: Triassic strata of the Lusitanian basin (western Iberia)

    Pereira, M. F.; Gama, C.; Chichorro, M.; Silva, J. B.; Gutiérrez-Alonso, G.; Hofmann, M.; Linnemann, U.; Gärtner, A.


    Laser ablation ICP-MS U-Pb analyses were conducted on detrital zircons of Triassic sandstone and conglomerate from the Lusitanian basin in order to: i) document the age spectra of detrital zircon; ii) compare U-Pb detrital zircon ages with previous published data obtained from Upper Carboniferous, Ordovician, Cambrian and Ediacaran sedimentary rocks of the pre-Mesozoic basement of western Iberia; iii) discuss potential sources; and iv) test the hypothesis of sedimentary recycling. U-Pb dating of zircons established a maximum depositional age for this deposit as Permian (ca. 296 Ma), which is about sixty million years older compared to the fossil content recognized in previous studies (Upper Triassic). The distribution of detrital zircon ages obtained points to common source areas: the Ossa-Morena and Central Iberian zones that outcrop in and close to the Porto-Tomar fault zone. The high degree of immaturity and evidence of little transport of the Triassic sediment suggests that granite may constitute primary crystalline sources. The Carboniferous age of ca. 330 Ma for the best estimate of crystallization for a granite pebble in a Triassic conglomerate and the Permian-Carboniferous ages (< ca. 315 Ma) found in detrital zircons provide evidence of the denudation of Variscan and Cimmerian granites during the infilling of continental rift basins in western Iberia. The zircon age spectra found in Triassic strata are also the result of recycling from the Upper Carboniferous Buçaco basin, which probably acted as an intermediate sediment repository. U-Pb data in this study suggest that the detritus from the Triassic sandstone and conglomerate of the Lusitanian basin is derived from local source areas with features typical of Gondwana, with no sediment from external sources from Laurussia or southwestern Iberia.

  5. U-Pb isotopic ages and Hf isotope composition of zircons in Variscan gabbros from central Spain: evidence of variable crustal contamination

    Villaseca, Carlos; Orejana, David; Belousova, Elena; Armstrong, Richard A.; Pérez-Soba, Cecilia; Jeffries, Teresa E.


    Ion microprobe U-Pb analyses of zircons from three gabbroic intrusions from the Spanish Central System (SCS) (Talavera, La Solanilla and Navahermosa) yield Variscan ages (300 to 305 Ma) in agreement with recent studies. Only two zircon crystals from La Solanilla massif gave slightly discordant Paleoproterozoic ages (1,848 and 2,010 Ma). Hf isotope data show a relatively large variation with the juvenile end-members showing ɛHfi values as high as +3.6 to +6.9 and +1.5 to +2.9 in the Navahermosa and Talavera gabbros, respectively. These positive ɛHfi values up to +6.9 might represent the composition of the subcontinental mantle which generates these SCS gabbros. This ɛHfi range is clearly below depleted mantle values suggesting the involvement of enriched mantle components on the origin of these Variscan gabbros, and is consistent with previous whole-rock studies. The presence of zircons with negative ɛHfi values suggest variable, but significant, crustal contamination of the gabbros, mainly by mixing with coeval granite magmas. Inherited Paleoproterozoic zircons of La Solanilla gabbros have similar trace element composition (e.g. Th/U ratios), but more evolved Hf-isotope signatures than associated Variscan zircons. Similar inherited ages have been recorded in zircons from coeval Variscan granitoids from the Central Iberian Zone. Granitic rocks have Nd model ages (TDM) predominantly in the range of 1.4 to 1.6 Ga, suggesting a juvenile addition during the Proterozoic. However, Hf crustal model ages of xenocrystic Proterozoic zircons in La Solanilla gabbro indicate the presence of reworked Archean protoliths (TDM2 model ages of 3.0 to 3.2 Ga) incorporated into the hybridized mafic magma.

  6. Provenance from zircon U-Pb age distributions in crustally contaminated granitoids

    Bahlburg, Heinrich; Berndt, Jasper


    The basement of sedimentary basins is often entirely covered by a potentially multi-stage basin fill and therefore removed from direct observation and sampling. Melts intruding through the basin stratigraphy at a subsequent stage in the geological evolution of a region may assimilate significant volumes of country rocks. This component may be preserved in the intrusive body either as xenoliths or it may be reflected only by the age spectrum of incorporated zircons. Here we present the case of an Ordovician calc-alkaline intrusive belt in NW Argentina named the "Faja Eruptiva de la Puna Oriental" (Faja Eruptiva), which in the course of intrusion sampled the unexposed and unknown basement of the Ordovician basin in this region, and parts of the basin stratigraphy. We present new LA-ICP-MS U-Pb ages on zircons from 9 granodiorites and granites of the Faja Eruptiva. The main part of the Faja Eruptiva intruded c. 445 Ma in the Late Ordovician. The zircon ages obtained from the intrusive rocks have a large spread between 2683.5 ± 21.6 and 440.0 ± 4.9 Ma and reflect the underlying crust and may be interpreted in several ways. The inherited zircons may have been derived from the oldest known unit in the region, the thick siliciclastic turbidite successions of the upper Neoproterozoic-lower Cambrian Puncoviscana Formation, which is inferred to represent the basement of the NW Argentina. The basement to the Puncoviscana Formation is not known. Alternatively, the inherited zircons may reflect the geochronological structure of the entire unexposed Early Paleozoic crust underlying this region of which the Puncoviscana Formation was only one component. This crust likely contained rocks pertaining to and detritus derived from earlier orogenic cycles of the southwestern Amazonia craton, including sources of Early Meso- and Paleoproterozoic age. Detritus derived, in turn, from the Faja Eruptiva intrusive belt reflects the origin of the granitoids as well as the inherited

  7. 耐热钢HP40Nb的中温粉末法渗铝及其抗渗碳特性%Pack aluminizing at moderate temperature on HP40Nb heat-resistant steel and its anti-carburization behaviour

    潘建伟; 谢飞; 孙力; 焦世辉; 翟建祥


    Pack aluminizing at temperature of 800-900 ℃ was investigated on HP40Nb heat-resistant steel with a media composed of master alloy of Fe-Al powder as Al supplier,NH4Cl as activator and SiC as filler.The anti-carburizing behaviour of the treated specimen was studied by employing an intensified pack carburization test.The results show that the aluminizing case has high surface quality and adheres very well with the substrate.The case is mainly composed of a deposition zone and a following transition zone.The thickness of the case is thinner than that by higher temperature aluminizing.Direct current field has few influence on the types of phase structure of the aluminized cases,while it can enhance the aluminizing rate at 800 ℃ by nearly 7 times.The aluminized cases studied show excellent anti-carburization ability in the intensified carburization test at 1000 ℃.%以铝铁为供铝剂、氯化氨为活化剂、碳化硅为填充剂,研究了耐热钢HP40Nb在800~900℃间的粉末法渗铝特性,采用固体强化渗碳方式来研究不同状态试样的抗渗碳能力。研究表明:渗层表面质量很高,渗层与基体结合良好,渗层主要由沉积区和过渡区两部分组成,较之高温渗铝,渗层厚度较薄;采用直流电场增强法对HP40Nb粉末法渗铝渗层相组成种类影响不大,但能使其800℃时的渗铝速度提高近7倍。所试验渗铝层在1000℃强化渗碳条件下表现出优良的抗渗碳特性。

  8. Magmatic and metasomatic imprints in a long-lasting subduction zone: Evidence from zircon in rodingite and serpentinite of Kochi, SW Japan

    Hu, Chao-Nan; Santosh, M.; Yang, Qiong-Yan; Kim, S. W.; Nakagawa, M.; Maruyama, S.


    Southwest Japan, as an active convergent margin, is one of the world's natural laboratories to investigate magmatic and metasomatic processes associated with a long-lived subduction zone. Rocks that carry the imprints of mantle metasomatism in this region include serpentinite, jadeitite, omphacitite, albitite, and rodingite. Here we investigate rodingites, serpentinites and pyroxenites from the accretionary complex of Kochi in the Shikoku island from within the Kurosegawa serpentinite mélange. We present petrology, zircon U-Pb geochronology, rare earth element (REE) geochemistry and Lu-Hf isotope data which indicate multiple pulses of magmatism and metasomatism. The zircon grains in these rocks yield major age peaks at 485 Ma and 469 Ma, marking the timing of formation of the protoliths. The wide range of minor age peaks including those at 152 Ma and 104 Ma suggest continuous fluid- and melt-induced mantle metasomatism in an active subduction zone from Cambrian to Paleogene associated with subduction of the Pacific plate. Our data suggest that the serpentinite-rodingite association might belong to various stages of subduction with the 450 Ma marking the initial phase. This is also close to the serpentinite zircon age of ca. 490 Ma. The REE patterns of zircons in all the rocks analyzed in this study show a distinct negative Eu-anomaly, particularly in the case of hydrothermal zircons. However, few zircons show only a slight negative Eu-anomaly suggesting that they might have crystallised from melts with high H2O content generated by partial melting of mantle wedge during the interaction of fluids released by the downgoing slab and the overlying sediments. Although the εHf(t) values of zircons in our samples show wide variation from - 9 to 18, most zircon grains that are younger than 485 Ma are typically characterised by positive εHf(t) values (ranging from 2 to18). This feature indicates that the zircon grains crystallised during serpentinisation and

  9. The effect of weathering on U-Th-Pb and oxygen isotope systems of ancient zircons from the Jack Hills, Western Australia

    Pidgeon, R. T.; Nemchin, A. A.; Whitehouse, M. J.


    We report the result of a SIMS U-Th-Pb and O-OH study of 44 ancient zircons from the Jack Hills in Western Australia with ages ranging from 4.3 Ga to 3.3 Ga. We have investigated the behaviour of oxygen isotopes and water in the grains by determining δ18O and OH values at a number of locations on the polished surfaces of each grain. We have divided the zircons into five groups on the basis of their U-Th-Pb and OH-oxygen isotopic behaviour. The first group has concordant U-Th-Pb ages, minimal common Pb, δ18O values consistent with zircons derived from mantle source rocks and no detectable OH content. U-Th-Pb systems in zircons from Groups 2, 3 and 4 vary from concordant to extremely discordant where influenced by cracks. Discordia intercepts with concordia at approximately zero Ma age are interpreted as disturbance of the zircon U-Th-Pb systems by weathering solutions during the extensive, deep weathering that has affected the Archean Yilgarn Craton of Western Australia since at least the Permian. Weathering solutions entering cracks have resulted in an influx of Th and U. δ18O values of Group 2 grains fall approximately within the "mantle" range and OH is within background levels or slightly elevated. δ18O values of Group 3 grains are characterised by an initial trend of decreasing δ18O with increasing OH content. With further increase in OH this trend reverses and δ18O becomes heavier with increasing OH. Group 4 grains have a distinct trend of increasing δ18O with increasing OH. These trends are explained in terms of the reaction of percolating water with the metamict zircon structure and appear to be independent of analytical overlap with cracks. Group five zircons are characterised by U-Pb systems that appear to consist of more than one age but show only minor U-Pb discordance. Nevertheless trends in δ18O versus OH in this group of grains resemble trends seen in the other groups. The observed trends of δ18O with OH in the Jack Hills zircons are similar

  10. Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff

    Fu, Roger R; Lima, Eduardo A; Kehayias, Pauli; Araujo, Jefferson F D F; Glenn, David R; Gelb, Jeff; Einsle, Joshua F; Bauer, Ann M; Harrison, Richard J; Ali, Guleed A H; Walsworth, Ronald L


    Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the earliest geodynamo, which holds broad implications for the early Earth interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been fully demonstrated. Here we conduct thermal and room temperature alternating field (AF) paleointensity experiments on 767.1 thousand year old (ka) zircons from the Bishop Tuff, California. The rapid emplacement of these zircons in a well-characterized magnetic field provides a high-fidelity test of the zircons intrinsic paleomagnetic recording accuracy. Successful dual heating experiments on nine zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of 46.2 +/- 18.8 microtesla (1sigma), which agrees closely with high-precision results from Bishop Tuff whole rock (43...

  11. Etudes sur la phase carbure de bore. Corrélations propriétés-composition


    No english abstract; La connaissance du diagramme de phases bore-carbone, des propriétés physico chimiques et la structure du carbure de bore ont été approfondies. Dans ce but, nous avons mis en œuvre principalement deux méthodes de préparation de nos échantillons : ¤ la fusion au canon à électrons, ¤ la compression à chaud. Il faut noter que nous avons considérablement amélioré cette dernière méthode pour la rendre apte à la préparation en particulier d'échantillons constitués de bore pur ou...

  12. Quantification of some elements of nuclear and industrial interest from zircon mineral using neutron activation analysis and passive gamma-ray spectroscopy.

    Attallah, M F; Hilal, M A; Moussa, S I


    A combined of various nuclear and analytical techniques were used for characterization of Egyptian zircon ore. Neutron activation analysis has been used for determination of the major, minor and trace elements from zircon ore. Non-destructive gamma-ray technique is also used for the radiometric analysis of zircon ore to quantify the natural radionuclides such as (238)U, (235)U, (232)Th, (226)Ra and (40)K. Zircon ore has been characterized by different analytical tools such as Fourier transformer infrared (FTIR), X-ray fluorescence (XRF), powder X-ray diffraction (XRD), and scanning electron microscopy (SEM). In this study, a significant concentration of U, Th and rare earth elements (REEs) has been reported. The obtained results showed that the average activity concentration of (238)U, (235)U, (226)Ra, (232)Th and (40)K are 4771±338, 230±17.1, 3588±125, 982±47.7 and 217±48.5Bq/kg, respectively. The results indicated that 297, 318 and 838mg/Kg for U, Th, REEs, respectively, using NAA. These results are consistent with those obtained by gamma-ray spectroscopy and/or XRF. It can be concluded that zircon ore is a riche with a valuable nuclear materials such as U, Th, Zr, and Hf. It is also containing a REEs of economic and industrial interest. Also, the different radiation hazardous parameters were found much higher than the permissible values. Copyright © 2017 Elsevier Ltd. All rights reserved.

  13. SHRIMP zircon dating and LA-ICPMS Hf analysis of early Precambrian rocks from drill holes into the basement beneath the Central Hebei Basin, North China Craton

    Yusheng Wan; Runlong Fan; Huiyi Sun; Xianzheng Zhao; Zejiu Wang; Dunyi Liu; Alfred Kröner; Chunyan Dong; Hangqian Xie; Yuansheng Geng; Yuhai Zhang


    The Central Hebei Basin (CHB) is one of the largest sedimentary basins in the North China Craton, extending in a northeastesouthwest direction with an area of>350 km2. We carried out SHRIMP zircon dating, Hf-in-zircon isotopic analysis and a whole-rock geochemical study on igneous and metasedi-mentary rocks recovered from drill holes that penetrated into the basement of the CHB. Two samples of gneissic granodiorite (XG1-1) and gneissic quartz diorite (J48-1) have magmatic ages of 2500 and 2496 Ma, respectively. Their zircons also record metamorphic ages of 2.41e2.51 and w2.5 Ga, respec-tively. Compared with the gneissic granodiorite, the gneissic quartz diorite has higher SREE contents and lower Eu/Eu* and (La/Yb)n values. Two metasedimentary samples (MG1, H5) mainly contain w2.5 Ga detrital zircons as well as late Paleoproterozoic metamorphic grains. The zircons of different origins haveεHf (2.5 Ga) values and Hf crustal model ages ranging from 0 to 5 and 2.7 to 2.9 Ga, respectively. Therefore, w2.5 Ga magmatic and Paleoproterozoic metasedimentary rocks and late Neoarchean to early Paleoproterozoic and late Paleoproterozoic tectono-thermal events have been identified in the basement beneath the CHB. Based on regional comparisons, we conclude that the early Precambrian basement beneath the CHB is part of the North China Craton.

  14. Evaluation of antibacterial properties of Barium Zirconate Titanate (BZT nanoparticle

    Simin Mohseni


    Full Text Available So far, the antibacterial activity of some organic and inorganic compounds has been studied. Barium zirconate titanate [Ba(Zr xTi1-xO3] (x = 0.05 nanoparticle is an example of inorganic materials. In vitro studies have provided evidence for the antibacterial activity of this nanoparticle. In the current study, the nano-powder was synthesized by sol-gel method. X-ray diffraction showed that the powder was single-phase and had a perovskite structure at the calcination temperature of 1000 ºC. Antibacterial activity of the desired nanoparticle was assessed on two gram-positive (Staphylococcus aureus PTCC1431 and Micrococcus luteus PTCC1625 and two gram-negative (Escherichia coli HP101BA 7601c and clinically isolated Klebsiella pneumoniae bacteria according to Radial Diffusion Assay (RDA. The results showed that the antibacterial activity of BZT nano-powder on both gram-positive and gram-negative bacteria was acceptable. The minimum inhibitory concentration of this nano-powder was determined. The results showed that MIC values for E. coli, K. pneumoniae, M. luteus and S. aureus were about 2.3 µg/mL, 7.3 µg/mL, 3 µg/mL and 12 µg/mL, respectively. Minimum bactericidal concentration (MBC was also evaluated and showed that the growth of E. coli, K. pneumoniae, M. luteus and S. aureus could be decreased at 2.3, 14, 3 and 18 µg/mL of BZT. Average log reduction in viable bacteria count in time-kill assay ranged between 6 Log10 cfu/mL to zero after 24 h of incubation with BZT nanoparticle.

  15. Low temperature oxidation, co-oxidation and auto-ignition of olefinic and aromatic blending compounds: Experimental study of interactions during the oxidation of a surrogate fuel; Oxydation, co-oxydation et auto-inflammation a basses temperatures d'alcenes et aromatiques types: etude experimentale des interactions au sein d'un carburant-modele

    Vanhove, G.


    The low-temperature (600-900 K) and high-pressure (5-25 bar) oxidation and auto-ignition of the three position isomers of hexene, of binary mixtures of 1-hexene, toluene and iso-octane, and of a surrogate fuel composed of these three compounds were studied in motor conditions using a rapid compression machine. Auto-ignition delay times were measured as long as intermediate products concentrations during the delay. The results show that the oxidation chemistry of the hexenes is very dependent on the position of the double bond inside the molecule, and that strong interactions between the oxidation mechanisms of hydrocarbons in mixtures can occur. The data obtained concerning the surrogate fuel give a good insight into the behaviour of a practical gasoline after an homogeneous charge compression. (author)

  16. Study of irradiation effects in the silicon carbide cubic polytype by photoluminescence and electron spin resonance spectroscopies; Etude des effets d'irradiation dans le polytype cubique du carbure de silicium par les techniques spectroscopiques de photoluminescence et de resonance paramagnetique electronique

    Lefevre, J


    This experimental work has consisted in the study of point defects induced by an electronic irradiation in the cubic crystallographic structure of silicon carbide with low temperature photoluminescence and electron spin resonance spectroscopies. The first one of these measurement tools has allowed to estimate the displacement threshold energy in the silicon sub-lattice and then to analyze the thermal stability of the irradiation defects in the low temperature range: (10-300 K) and then in the high temperature range: (300-1400 K). Besides, on the base of a recent theoretical model, this thesis has confirmed the proposition of the isolated silicon antisite for the D1 center whose running beyond the nominal running temperature of fission nuclear reactors (generation IV), for which SiC is in part intended, seems to be particularly problematic. Measurements carried out by ESR under lighting have at last allowed to detect a new defect in its metastable spin state S=1, possibly associated to a silicon interstitial configuration. (O.M.)

  17. Zircon U-Pb ages of the basement rocks beneath the Songliao Basin, NE China


    The basement of the Songliao Basin is mainly composed of slightly-metamorphosed or unmetamorphosed Paleozoic strata, granites and gneiss. Petrographical studies indicate that the gneiss was originally the granitic intrusions which were deformed in the later stage. One undeformed granitic rock sample gives a U-Pb age of (305±2) Ma, and the mylonitic granite yields a U-Pb age of (165±3) Ma. Both of the two samples contain no inherited zircon, which suggests that there is no large-scale Precambrian crystalline basement beneath the Songliao Basin.

  18. Creep behavior of plasma carburized Ti-6Al-4V alloy; Comportamento em fluencia da liga Ti-6Al-4V carbonetada por plasma

    Oliveira, Veronica Mara Cortez Alves de; Barboza, Miguel Justino Ribeiro; Silva, Mariane Capellari Leite da; Pinto, Catia Gisele; Suzuki, Paulo Atsushi [Universidade de Sao Paulo (EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Reis, Danieli Aparecida Pereira; Piorino Neto, Francisco [Instituto de Aeronautica e Espaco (IAE/DCTA), Sao Jose dos Campos, SP (Brazil); Machado, Joao Paulo B. [Instituto Nacional de Pesquisas Espaciais (INPE), Sao Jose dos Campos, SP (Brazil)


    This paper aims to evaluate the effect of plasma carburizing on the Ti-6Al-4V alloy submitted to creep tests. The results showed that the alloy Ti-6Al-4V had a hardness of 334 ± 18 HV. After treatment thermochemical by plasma, was observed the formation of a layer of average thickness of 1,5 μm and hardness of 809 ± 79 HV due to the presence of TiC phase identified by X-ray diffraction. The treatment increased the values of average roughness of 1,28 to 2,02 μm. The creep properties of carburized specimens were improved in comparison with those of the uncarburized Ti-6Al-4V alloy. (author)

  19. 拖拉机齿轮的稀土低温渗碳%Low-temperature Carburizing with Rare Earth Elements for Tractor Gears



    介绍了稀土低温渗碳工艺在拖拉机齿轮上的应用。通过具体的数据说明该工艺实施的方便性和节能效果。通过试验得出稀土低温渗碳工艺用于井式气体渗碳炉,生产周期可缩短15%,齿轮的质量也有所提高。%The application of low-temperature carburizing with rare earth elements for tractor gears is presented in this paper.The convenience and energy saving of the technology is demonstrated in details.It is concluded that by applying rare-earth low-temperature carburizing in pit-type furnace the production period can be shorten by 15 percent and the quality of the gears is improved.

  20. Reaction Sintering of Mexican Dolomite – Zircon Mixtures

    Rodríguez-Galicia, J. L.


    Full Text Available The present work has been conducted aiming to develop additional phase [Ca3SiO5, Ca2SiO4 and/or Ca3Mg(SiO42]-bonded magnesia refractory materials via reaction sintering of dolomite-zircon mixtures, employing a Mexican dolomite containing an excess of 3 wt% of CaCO3. The study was based on phase equilibrium data extracted from the quaternary system CaO – MgO – SiO2 – ZrO2, to put it more precisely, base on the projection from the MgO-apex of the liquidus surface of the primary crystallization volume of MgO onto the opposite face of the above mentioned quaternary system. The refractory materials designed within this system were obtained by attrition milling, followed by cold isostatic pressing and high temperature reaction sintering. All initial and produced materials were characterized by ICP-AES, XRF, XRD, SEM-EDX, DTA and TG analyses. The results obtained indicated that reaction sintering of dolomite-zircon mixtures is an interesting route to produce MgO-CaZrO3-additional phase refractory materials.

    El propósito de este trabajo ha sido obtener materiales refractarios de magnesia, aglomerados con una fase adicional [Ca3SiO5, Ca2SiO4 y/o Ca3Mg(SiO42], mediante la sinterización reactiva de mezclas de dolomita-circón, empleando para ello una dolomita mexicana que contiene un exceso de 3% en peso de CaCO3. El estudio se basa en la información relativa al equilibrio de fases del sistema CaO – MgO – SiO2 – ZrO2. En concreto se usa la proyección, desde el vértice del MgO, de la superficie de liquidus del volumen de cristalización primaria de este, hacia la cara opuesta de sistema cuaternario. Los materiales refractarios diseñados se han obtenido por molienda de atrición, seguida de un prensado isostático en frío y sinterización reactiva a alta temperatura. Todos los materiales, iniciales y finales, han sido caracterizados mediante ICPAES, FRX, DRX, MEB-EDX, ATD y TG. Los resultados obtenidos indican que la sinterizaci

  1. 浙江临安夏色岭钨矿含矿岩体特征及LA-ICP-MS锆石铀-铅年代学研究%Characteristics and LA-ICP-MS Zircon U-Pb Geochronology Study of Metallogenic Intrusion in the Xiaseling Tungsten Deposit in Lin'an,Zhejiang Province

    黄国成; 王登红; 吴小勇


    夏色岭钨矿是浙江省内已知规模最大的石英脉型钨矿,其形成与夏色岭花岗岩体关系密切,前人对该岩体的年代学研究方法比较局限.本研究采集了夏色岭钨矿区的新鲜花岗岩样品,从岩石的矿物学特征及地球化学特征出发,讨论了岩体与成矿作用之间的关系.通过分析精度更高、结果更可靠的激光剥蚀-电感耦合等离子体质谱( LA - ICP - MS)锆石U- Pb测年技术,获得206Pb/238 U加权平均年龄为( 126.9±1.7)Ma,表明为燕山晚期早阶段(早白垩世)的产物,结合区域上的找矿成果,对本地区的地质找矿具有一定指导意义.%The Xiaseling tungsten deposit is the largest discovered quartz-veined tungsten deposit in Zhejiang Province, which is closely related to Xiaseling Granite. The geochronological study on this granite has been very limited in previous studies. Fresh granite samples were collected from the Xiaseling tungsten deposit. The relationship between Xiaseling Granite and mineralization is discussed by mineralogy and geochemical characteristics of the rocks. The in-situ zircon U-Pb dating was performed with Laser Ablation-Multicollector Inductively Coupled Plasma-Mass Spectrometry ( LA-MC-ICPMS) with higher accuracy and greater reliability than previously achieved. Our result indicates that the weighted average 206Pb/238U ages for zircons from the Xiaseling granite is ( 126. 9 ?.7) Ma, suggesting the granite was intruded in the early stage of the late Yenshanian Period of the early Cretaceous era. Together with regional prospecting findings, it is also important for ore exploration work in this area.

  2. Environmental Transmission Electron Microscopy (ETEM) Studies of Single Iron Nanoparticle Carburization in Synthesis Gas

    Liu, Xi; Zhang, Chenghua; Li, Yongwang


    Structuralevolution of iron nanoparticles involving the formationand growth of iron carbide nuclei in the iron nanoparticle was directlyvisualized at the atomic level, using environmental transmission electronmicroscopy (TEM) under reactive conditions mimicking Fischer–Tropschsynthesis. Formation...... and electronenergy-loss spectra provides a detailed picture from initial activationto final degradation of iron under synthesis gas....

  3. Zircon-scale insights into the history of a Supervolcano, Bishop Tuff, Long Valley, California, with implications for the Ti-in-zircon geothermometer

    Reid, M.R.; Vazquez, J.A.; Schmitt, A.K.


    Zircon has the outstanding capacity to record chronological, thermal, and chemical information, including the storage history of zoned silicic magma reservoirs like the one responsible for the Bishop Tuff of eastern California, USA. Our novel ion microprobe approach reveals that Bishop zircon rims with diverse chemical characteristics surround intermediate domains with broadly similar compositions. The highest Y, REE, U, and Th concentrations tend to accompany the largest excesses in Y + REE3+:P beyond what can be explained by xenotime substitution in zircon. Apparent Ti-in-zircon temperatures of Bishop Tuff compositional spectrum may have evolved to broadly similar chemical and thermal conditions and therefore it is possible that there was no significant thermal gradient in the magma reservoir at some stage in its evolution. There is also no compelling evidence for punctuated heat ?? chemical influxes during the intermediate stages of zircon growth. Judging by the zircon record, the main volume of the erupted magma evolved normally by secular cooling but the latest erupted portion is characterized by a reversal in chemistry that appears to indicate perfusion of the magma reservoir by-or zircon entrainment in-a less evolved melt from the one in which the zircons had previously resided. ?? 2010 Springer-Verlag.

  4. Petrological and zircon evidence for the Early Cretaceous granulite-facies metamorphism in the Dabie orogen, China

    Gao, Xiao-Ying; Zhang, Qiang-Qiang; Zheng, Yong-Fei; Chen, Yi-Xiang


    An integrated study of petrology, mineralogy, geochemistry, and geochronology was carried out for contemporaneous mafic granulite and diorite from the Dabie orogen. The results provide evidence for granulite-facies reworking of the ultrahigh-pressure (UHP) metamorphic rock in the collisional orogen. Most zircons from the granulite are new growth, and their U-Pb ages are clearly categorized into two groups at 122-127 Ma and 188 ± 2 Ma. Although these two groups of zircons show similarly steep HREE patterns and variably negative Eu anomalies, the younger group has much higher U, Th and REE contents and Th/U ratios, much lower εHf(t) values than the older group. This suggests their growth is associated with different types of dehydration reactions. The older zircon domains contain mineral inclusions of garnet + clinopyroxene ± quartz, indicating their growth through metamorphic reactions at high pressures. In contrast, the young zircon domains only contain a few quartz inclusions and the garnet-clinopyroxene-plagioclase-quartz barometry yields pressures of 4.9 to 12.5 kb. In addition, the clinopyroxene-garnet Fe-Mg exchange thermometry gives temperatures of 738-951 °C. Therefore, the young zircon domains would have grown through peritectic reaction at low to medium pressures. The younger granulite-facies metamorphic age is in agreement not only with the adjacent diorite at 125 ± 1 Ma in this study but also the voluminous emplacement of coeval mafic and felsic magmas in the Dabie orogen. Mineral separates from both mafic granulite and its adjacent diorite show uniformly lower δ18O values than normal mantle, similar to those for UHP eclogite-facies metaigneous rocks in the Dabie orogen. In combination with major-trace elements and zircon Lu-Hf isotope compositions, it is inferred that the protolith of mafic granulites shares with the source rock of diorites, both being a kind of mafic metasomatites at the slab-mantle interface in the continental subduction channel

  5. Electron Microprobe Analysis of Hf in Zircon: Suggestions for Improved Accuracy of a Difficult Measurement

    Fournelle, J.; Hanchar, J. M.


    It is not commonly recognized as such, but the accurate measurement of Hf in zircon is not a trivial analytical issue. This is important to assess because Hf is often used as an internal standard for trace element analyses of zircon by LA-ICPMS. The issues pertaining to accuracy revolve around: (1) whether the Hf Ma or the La line is used; (2) what accelerating voltage is applied if Zr La is also measured, and (3) what standard for Hf is used. Weidenbach, et al.'s (2004) study of the 91500 zircon demonstrated the spread (in accuracy) of possible EPMA values for six EPMA labs, 2 of which used Hf Ma, 3 used Hf La, and one used Hf Lb, and standards ranged from HfO2, a ZrO2-HfO2 compound, Hf metal, and hafnon. Weidenbach, et al., used the ID-TIMS values as the correct value (0.695 wt.% Hf.), for which not one of the EPMA labs came close to that value (3 were low and 3 were high). Those data suggest: (1) that there is a systematic underestimation error of the 0.695 wt% Hf (ID-TIMS Hf) value if Hf Ma is used; most likely an issue with the matrix correction, as the analytical lines and absorption edges of Zr La, Si Ka and Hf Ma are rather tightly packed in the electromagnetic spectrum. Mass absorption coefficients are easily in error (e.g., Donovan's determination of the MAC of Hf by Si Ka of 5061 differs from the typically used Henke value of 5449 (Donovan et al, 2002); and (2) For utilization of the Hf La line, however, the second order Zr Ka line interferes with Hf La if the accelerating voltage is greater than 17.99 keV. If this higher keV is used and differential mode PHA is applied, only a portion of the interference is removed (e.g., removal of escape peaks), causing an overestimation of Hf content. Unfortunately, it is virtually impossible to apply an interference correction in this case, as it is impossible to locate Hf-free Zr probe standard. We have examined many of the combinations used by those six EPMA labs and concluded that the optimal EPMA is done with Hf

  6. The pre-orogenic detrital zircon record of the Variscan orogeny: Preliminary results

    Stephan, Tobias; Kroner, Uwe


    To test plate-tectonic constellations in consideration of the long-term development of sedimentary transport paths, temporally and spatially highly resolved records of provenance analysis are mandatory. The interpretation of existing studies focus on small-scale areas within an orogen thereby neglecting the differing distribution of provenance data in the entire orogenic system. This study reviews a large data set of compiled geochronological data to document the development of pre-orogenic tectonic units on the example of the Variscan orogeny. Constrained by tectonic and geological models, the temporal distribution of U-Pb detrital zircon ages, used as a proxy for sedimentary provenance, shows that some minima and maxima of zircon abundance are nearly synchronous for thousands of kilometres along the orogeny. Age spectra of Precambrian to Lower Palaeozoic samples were constructed on the basis of 38729 U-Pb ages from 685 samples that were compiled from 102 publications. The age compilation combines thermal ionization mass spectrometry (TIMS), laser ablation-inductively coupled plasma-mass spectrometer (LA-ICP-MS), sensitive high-resolution ion microprobe (SHRIMP), and secondary ion mass spectrometry (SIMS) analyses. The data was re-processed using a common age calculation and concordance filter to ensure comparability. The concordance of each zircon grain was calculated from 206Pb/238U and 207Pb/235U ages to guarantee that only concordant grains, i.e., with 3) is used for the maximum age of deposition. In addition to the location of >600 samples, the precise depositional ages result in a spatially and temporally high resolution. To avoid the different levels of analytical precision of the compiled TIMS, LA-ICP-MS, SHRIMP, and SIMS data, detrital zircon ages are plotted as kernel density estimates. Spatial and temporal distribution of the kernel density estimates, as well as further statistical techniques (e.g. multidimensional scaling) are used to discriminate

  7. The formation of Luoboling porphyry Cu-Mo deposit: Constraints from zircon and apatite

    Li, Cong-ying; Hao, Xi-luo; Liu, Ji-qiang; Ling, Ming-xing; Ding, Xing; Zhang, Hong; Sun, Wei-dong


    The Luobuling porphyry Cu-Mo deposit belongs to the Late Cretaceous Zijinshan Cu-Au-Mo mineralization field in southeastern China. Due to intensive hydrothermal alteration and weathering, it is very difficult to collect fresh whole rock samples for geochemical and isotopic studies in Luobuling. Zircon and apatite are accessory minerals that are resistant to hydrothermal alterations. In this study, we compared the trace element and isotope compositions of zircon and apatite from ore-bearing and barren samples to understand the formation of the Luoboling Cu-Mo deposit. Zircon U-Pb LA-ICP-MS dating shows that the Luoboling porphyries formed at 100 Ma (100.3 ± 1.2 Ma, 100.6 ± 1.5 Ma and 98.6 ± 1.2 Ma), which belongs to the late stage mineralization of the Zijinshan mineralization field. Zhongliao porphyritic granodiorite has the same age as the deposit (99.5 ± 1.6 Ma). The age of barren Sifang granodiorite is slightly older (109.7 ± 0.8 Ma). All these zircon grains have high Ce4+/Ce3+ ratios, indicating high oxygen fugacities. The ore-bearing samples show variable εHf(t) of - 7.3 to 0.2, suggesting either heterogeneous sources or mixing of two different magmas. Interestingly, the Hf isotope composition of barren samples is systematically higher (εHf(t) of - 3.6 to 5.5), implying a lower contribution of crustal materials. The OH mole percent of apatite grains from barren samples (LBL22-03 and SF09-05) is 0.5, which is higher than that of apatite from the ore-bearing samples (LBL20-01 LBL20-02 and LBL22-02), indicating lower F, Cl contents or higher water contents in the magma. In apatite from the ore-bearing samples, Sr is high, indicating the absence of plagioclase crystallization. In contrast, barren samples have varied and lower Sr, indicating that apatite crystallization was accompanied by plagioclase. These patterns were controlled by water contents because the crystallization of plagioclase is suppressed by high water contents in magmas. It also suggests

  8. Application of Carburization Technique in Nodular Iron Production%增碳技术在球墨铸铁生产中的应用



    简单介绍了增碳剂的类型及选用原则;对影响增碳剂增碳率和增碳作用的因素进行了分析,指出在球墨铸铁生产中,应用增碳及铁液预处理工艺,可减少铁液杂质元素和有害元素的含量,降低炉料遗传性影响,增加石墨球数,改善球化率,提高材料的力学性能.%The sorts of carburizer and their selection and usage principle were introduced briefly. The factors influencing the carburizing rate and carburizing effect were analyzed. It was pointed out that application of carhurizing procesa and preconditioning process in the nodular iron production makes it possible to reduce content of the impurity elements and harmful elements. decrease the heredity effect of the melting charges, increase nodule count, improve nodularity and improve material mechanical properties.

  9. 齿轮激光淬火和渗碳淬火的经济性比较%Economic Comparison of Laser-hardened Gear and Carburized Gear

    张欣; 郭子峰


    激光淬火是齿轮表面硬化的一个新工艺,与渗碳淬火相比,具有变形小等特点,具有广阔的应用前景。针对齿轮激光淬火和渗碳淬火两种不同工艺,从材料、工艺流程、制造成本等方面进行了比较,结果表明:齿轮激光淬火比渗碳淬火更加经济。%Laser hardening is a new method for surface hardening of gear tooth. It characteristics of little deformation after hardening compared with carburized gears, which can be widely used in the industries. According to the two dif-ferent heat treatments of gears, laser hardening and carburizing, the base materials, manufacturing process and produc-tion cost of two different hardened-gears are compared. The research results show that laser-hardened gears are eco-nomical compared to carburized gears.

  10. Influence of Plastic Deformation in Zircon on its Chemical Composition: Evdence for Gabbros in the Spreading Zone of the Mid-Atlantic Ridge, Markov Deep, 6oN

    Zinger, T. F.; Bortnikov, N. S.; Sharkov, E. V.


    We studied 150 grains of zircon from 8 gabbro samples, dragged at 4 sites in axial part of the MAR, Markov Deep, 6oN, during 10th cruise of R/V “Academic Ioffe” (2001-2002) and 22nd cruise of R/V “Professor Logachev” (2003). The region is located at southern continuation of the Central Atlantic oceanic core complex (OCC), where lower crustal gabbros and mantle peridotites expose on seafloor. We shown that zircon in gabbros of oceanic lower crust from axial part of the MAR, during their plastic flowage, was undergone by plastic creep under temperature interval from 815 to 680oC (according to Ti-in-zircon thermometry). How we shown earlier, two types of zircon occurs here: (1) “young” with SHRIMP-II age of 0.7-2.3 Ma, related to gabbro-host, and (2) “ancient” with age ranged from 87 to 3117 Ma, xenogenic (Bortnikov et al., 2008). Judging on appearance in grains of dislocation translation surfaces, both types of the zircon were involved in such flowage. Deformations occurred locally and irregularly, because of the zircon grains were altered in a variable extent. Zircon was enriched during deformations by diversity of rare elements (U, Th, Hf, P and Y) and REE. We suggest that it was linked both with appearance of deformation-related crustal-plastic microstructures in zircon, which enhanced diffusion of these components, how Reddy et al. (2006) think, and circulation of intergranular fluid as demonstrated processes of delution and redeposition of the zircon material with appearance of secondary small pyramidal zircons on another side of the crystal. Nature of this high-temperature fluid is not clear yet: it can be residual fluid, formed under solidification of host-gabbros, or result of involving of fluids, circulated in upper oceanic lithosphere, under it heating by these intrusions; most likely both factors were setting in motion. Introducing U, Th and Hf into zircon crystals can change their original isotopic systematics and influence on results of

  11. Synchronistic preparation of fibre-like SiC and cubic-ZrO{sub 2}/SiC composite from zircon via carbothermal reduction process

    Xu, Youguo; Liu, Yangai [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Huang, Zhaohui, E-mail: [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Fang, Minghao [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China); Hu, Xiaozhi [School of Mechanical and Chemical Engineering, University of Western Australia, Perth, WA 6009 (Australia); Yin, Li; Huang, Juntong [School of Materials Science and Technology, China University of Geosciences (Beijing), Beijing 100083 (China)


    Graphical abstract: Display Omitted Highlights: ► Zircon carbothermal reduction was carried out in a tailor-made device at high-temperature air atmosphere. ► Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were obtained synchronically. ► Zirconium and silicon in zircon ore was initial separated. ► [SiO{sub 4}] was mutated to fibre-like SiC, while [ZrO{sub 8}] was transformed to cubic ZrO{sub 2}. ► The SiC were surprisingly enriched in the reducing atmosphere charred coal particles layers by gas–solid reaction. -- Abstract: Fibre-like SiC and cubic-ZrO{sub 2}/SiC composite were prepared respectively from zircon with yttrium oxide addition via carbothermal reduction process at 1600 °C for 4 h in an air atmosphere furnace, where the green samples were immerged in charred coal particles inside a high-temperature enclosed corundum crucible. The reaction products were characterized by XRD, XRF, XPS and SEM. The results indicate that ZrO{sub 2} in the products was mainly existed in the form of cubic phase. The reacted samples mainly contain cubic ZrO{sub 2}, β-SiC and trace amounts of zircon, with the SiC accounting for 14.8 wt%. Furthermore, a large quantity of fibre-like SiC was surprisingly found to concentrate in the charred coal particles layers around the samples. This study obtains fibre-like SiC and cubic-ZrO{sub 2}/SiC composite synchronically from zircon via carbothermal reduction process, which also bring a value-added high-performance application for natural zircon.

  12. U-Pb zircon geochronology and Nd-Hf-O isotopic systematics of the Neoproterozoic Hadb adh Dayheen ring complex, Central Arabian Shield, Saudi Arabia

    Ali, Kamal A.; Jeon, Heejin; Andresen, Arild; Li, Shuang-Qing; Harbi, Hesham M.; Hegner, Ernst


    A combined study of single zircon U-Pb dating, Hf-O zircon isotopic analyses and whole-rock Nd isotopic compositions was carried out to infer the magma sources of Neoproterozoic post-collisional A-type granitoids in Saudi Arabia. U-Pb zircon dating of magmatic zircons of two samples from the Hadb adh Dayheen ring complex yielded ages of 625 ± 11 Ma for a hornblende-biotite granite sample, and 613 ± 4 Ma for a monzogranite sample. The granitic rocks show initial εNd values of + 4.1 to + 5.3 and εHf of + 4.5 to + 8.4 that are lower than those of a model depleted mantle (εHf ~+ 14 and εNd ~+ 6.5) and consistent with melting of subduction-related crustal protoliths that were formed during the Neoproterozoic assembly of the Arabian-Nubian Shield (ANS). Crustal-model ages (Hf-tNC) of 0.81 to 1.1 Ga are inconsistent with depleted-mantle Nd model ages of 0.71 to 0.81 Ga and indicate that the post-collisional Hadb adh Dayheen granites were derived mostly from juvenile crust formed in Neoproterozoic time. Single zircons data show a wide range in δ18O values from + 3.2‰ to + 6.4‰, possibly indicating crystallization of zircon from magma derived from magmatic rocks altered by meteoric water in a magma chamber-caldera system.

  13. Fingerprinting the K/T impact site and determining the time of impact by U-Pb dating of single shocked zircons from distal ejecta

    Krogh, T. E.; Kamo, S. L.; Bohor, B. F.


    U-Pb isotopic dating of single 1 - 3 micrograms zircons from K/T distal ejecta from a site in the Raton Basin, Colorado provides a powerful new tool with which to determine both the time of the impact event and the age of the basement at the impact site. Data for the least shocked zircons are slightly displaced from the 544 +/- 5 Ma primary age for a component of the target site, while those for highly shocked and granular grains are strongly displaced towards the time of impact at 65.5 +/- 3.0 Ma. Such shocked and granular zircons have never been reported from any source, including explosive volcanic rocks. Zircon is refractory and has one of the highest thermal blocking temperatures; hence, it can record both shock features and primary and secondary ages without modification by post-crystallization processes. Unlike shocked quartz, which can come from almost anywhere on the Earth's crust, shocked zircons can be shown to come from a specific site because basement ages vary on the scale of meters to kilometers. With U-Pb zircon dating, it is now possible to correlate ejecta layers derived from the same target site, test the single versus multiple impact hypothesis, and identify the target source of impact ejecta. The ages obtained in this study indicate that the Manson impact site, Iowa, which has basement rocks that are mid-Proterozoic in age, cannot be the source of K/T distal ejecta. The K/T distal ejecta probably originated from a single impact site because most grains have the same primary age.

  14. Effect of dopants on ferroelectric and piezoelectric properties of lead zirconate titanate thin films on Si substrates

    Nguyen, Duc Minh; Trinh, Thong Q.; Dekkers, Jan M.; Houwman, Evert Pieter; Vu, Hung Ngoc; Rijnders, Augustinus J.H.M.


    Lead zirconate titanate Pb(Zr0.52Ti0.48)O3 (undoped PZT) and doped PZT thin films with thickness of about 500 nm were grown on Pt/Ti/SiO2/Si substrates by pulsed laser deposition (PLD). In this study, 1.0 mol% Nb-doping (at Zr/Ti site) as donor, 1.0 mol% Fe-doping (at Zr/Ti) as acceptor and 10 mol%

  15. Petrology of Zircon-Bearing Diogenite Northwest Africa 10666

    Tanner, T. B.; Jeffcoat, C. R.; Righter, M.; Berger, E. L.; Lapen, T. J.; Irving, A. J.; Kuehner, S. M.; Fujihara, G.


    The howardite, eucrite, and diogenite (HED) meteorites are a group of achondrites thought to be derived from the asteroid 4 Vesta, though there is active debate as to whether all diogenites are part of the HED suite. Petrologic investigation of the HED meteorite group provides a means of understanding early planetary differentiation processes and early evolution of planets in our solar system. Diogenites are predominantly coarse grained ortho-pyroxenites with some samples containing appreciable amounts of clinopyroxene, olivine, chromite, and plagioclase. Accessory metal, troilite, and apatite are common. Many diogenites are brecciated, however, there are few poorly to unbrecciated samples. Diogenites are important because they may represent the lower crust of 4 Vesta. Although Mg isotope data indicates that the sources of diogenites are ancient, their crystallization ages are difficult to constrain due to their protracted thermal histories. The limited chronologic data for diogenites also limits the ability to test petrogenetic connections with eucrites and even parent body. A reliable and high closure-temperature isotope system, such as U-Pb in zircon, is needed to address the timing of diogenite igneous crystallization. Description of the textures and mineralogy of diogenites are essential to their classification and understanding their formation, in particular, whether all phases are petrogenetically related. Here, we present detailed petrographic data from a rare zircon-bearing feldspathic diogenite, Northwest Africa (NWA) 10666 and provide textural evidence for igneous crystallization of the zircon.

  16. Dating sub-20 micron zircons in granulite-facies mafic dikes from SW Montana: a new approach using automated mineralogy and SIMS U-Pb geochronology

    Ault, A. K.; Mahan, K. H.; Flowers, R. M.; Chamberlain, K.; Appleby, S. K.; Schmitt, A. K.


    Geochronological data is fundamental to all tectonic studies, but a major limitation for many lithologies is a paucity of sizeable zircons suitable for conventional U-Pb techniques. In particular, mafic dike swarms provide important time markers for tectonometamorphic activity in Precambrian terranes, but commonly yield little or no zircon or baddeleyite sufficient for TIMS or standard ion-probe analysis of crystal separates. We apply a new approach involving in-situ automated mineralogy and high spatial resolution Secondary Ion Mass Spectrometry (SIMS) geochronology to a mafic dike swarm exposed in the Northern Madison Range of SW Montana. The dikes cross-cut early fabrics but are also variably deformed and metamorphosed to P-T conditions as high as 1.2 GPa and 850 C. The swarm emplacement age is inferred to be ca. 2.1 Ga based on similarities to dated dikes in the adjacent Tobacco Root Mountains. Resolving the timing of dike emplacement and high-grade metamorphism in the study area is important for understanding the extent of post-Archean modification to the northwest margin of the Wyoming craton. Identification and textural characterization of zircons were facilitated by in-situ automated mineralogical analysis, in contrast to a standard elemental X-ray mapping approach. Our technique uses an SEM-based platform coupling calibrated BSE data with X-ray data collected by multiple energy dispersive spectrometers to rapidly identify target accessory phases at high spatial resolution. Whole thin section search maps were generated in ~30 minutes at 4 µm pixel resolution. Our dike thin sections commonly contained >300 zircons in a variety of textural settings, with 80% having a short dimension 95% for 206Pb. SIMS data for 22 zircons from a granulite-facies mafic dike thin section define a chord with upper and lower intercepts of 1753.1 ± 9.5 Ma and 63.2 ± 7.9 Ma, respectively (2 sigma error, MSWD = 1.6). A positive correlation between U concentration and degree of

  17. Synthesis and characterization of mixture of nanozirconia and nanosilica obtained from commercially available zircon flour by sol–gel method

    A J K Prasad; S M Shashidhara; B K Muralidhara


    In this paper we present the results of our patented (application filed in India) process for synthesizing a mixture of nanozirconia and nanosilica, obtained by the sol–gel method from commercially available zircon flour and hydrofluoric acid at low temperatures (∼ 100°C). Within the scope of this study, 99.2% dissolution of zircon was obtained by using 40% HF for a solid–liquid (S/L) ratio of 0.05 for a digestion period of 120 h. The nanoparticles, characterized by XRD, SEM and TEM techniques, were found to be largely spherical in shape and the average size of the particles was found to be less than 5 nm. Within the product, zirconiarich and silica-rich regions were found to exist.

  18. Evaluating the paleomagnetic potential of single zircon crystals using the Bishop Tuff

    Fu, Roger R.; Weiss, Benjamin P.; Lima, Eduardo A.; Kehayias, Pauli; Araujo, Jefferson F. D. F.; Glenn, David R.; Gelb, Jeff; Einsle, Joshua F.; Bauer, Ann M.; Harrison, Richard J.; Ali, Guleed A. H.; Walsworth, Ronald L.


    Zircon crystals offer a unique combination of suitability for high-precision radiometric dating and high resistance to alteration. Paleomagnetic experiments on ancient zircons may potentially constrain the history of the earliest geodynamo, which would hold broad implications for the early Earth's interior and atmosphere. However, the ability of zircons to record accurately the geomagnetic field has not been demonstrated. Here we conduct thermal and alternating field (AF) paleointensity experiments on 767.1 thousand year old (ka) zircons from the Bishop Tuff, California. The rapid emplacement of these zircons in a well-characterized magnetic field provides a high-fidelity test of the zircons' intrinsic paleomagnetic recording accuracy. Successful dual heating experiments on eleven zircons measured using a superconducting quantum interference device (SQUID) microscope yield a mean paleointensity of 54.1 ± 6.8μT (1σ; 42.6 ± 5.3μT after excluding possible maghemite-bearing zircons), which is consistent with high-precision results from Bishop Tuff whole rock (43.0 ± 3.2μT). High-resolution quantum diamond magnetic (QDM) mapping, electron microscopy, and X-ray tomography indicate that the bulk of the remanent magnetization in Bishop Tuff zircons is carried by Fe oxides associated with apatite inclusions, which may be susceptible to destruction via metamorphism and aqueous alteration in older zircons. As such, while zircons can reliably record the geomagnetic field, robust zircon-derived paleomagnetic results require careful characterization of the ferromagnetic carrier and demonstration of their occurrence in primary inclusions. We further conclude that a combination of quantum diamond magnetometry and high-resolution imaging can provide detailed, direct characterization of the ferromagnetic mineralogy of geological samples.

  19. Residence, resorption and recycling of zircons in Devils Kitchen rhyolite, Coso Volcanic Field, California

    Miller, J.S.; Wooden, J.L.


    Zircons from the Devils Kitchen rhyolite in the Pleistocene Coso Volcanic field, California have been analyzed by in situ Pb/U ion microprobe (SHRIMP-RG) and by detailed cathodoluminescence imaging. The zircons yield common-Pb-corrected and disequilibrium-corrected 206Pb/238U ages that predate a previously reported K-Ar sanidine age by up to 200 kyr, and the range of ages exhibited by the zircons is also approximately 200 kyr. Cathodoluminescence imaging indicates that zircons formed in contrasting environments. Most zircons are euhedral, and a majority of the zircons are weakly zoned, but many also have anhedral, embayed cores, with euhedral overgrowths and multiple internal surfaces that are truncated by later crystal zones. Concentrations of U and Th vary by two orders of magnitude within the zircon population, and by 10-20 times between zones within some zircon crystals, indicating that zircons were transferred between contrasting chemical environments. A zircon saturation temperature of ???750??C overlaps within error a previously reported phenocryst equilibration temperature of 740 ?? 25??C. Textures in zircons indicative of repeated dissolution and subsequent regrowth are probably caused by punctuated heating by mafic magma input into rhyolite. The overall span of ages and large variation in U and Th concentrations, combined with calculated zircon saturation temperatures and resorption times, are most compatible with crystallization in magma bodies that were emplaced piecemeal in the crust at Coso over 200 kyr prior to eruption, and that were periodically rejuvenated or melted by subsequent basaltic injections. ?? Oxford University Press 2004; all rights reserved.

  20. Direct Comparison of Detrital Garnet, Monazite, and Zircon Ages from a Southern Appalachian Tributary System for the French Broad River, North Carolina, USA

    Maneiro, K. A.; Baxter, E. F.; Samson, S. D.; Marschall, H.


    Nineteen detrital garnet ages from a tributary draining into the French Broad River of North Carolina represent the first full-scale deployment of a new detrital garnet geochronometer. Under the new geochronometer, inclusions within the garnet serve as a proxy for the original source rock and eliminate required assumption of a single source for detritus. Additionally, method development has advanced techniques for small sample Nd and Sm analysis by thermal ionization mass spectrometry (TIMS), allowing for Sm-Nd analysis of single detrital garnet grains for the first time. This is also the first dataset allowing direct comparison of detrital garnet, monazite, and zircon. The three proximate tributaries sampled drain a limited source lithology, and prior studies provide detrital monazite and zircon ages (e.g. Hietpas et al., 2010, Geology; Moecher et al., 2011, Geosphere). The weighted average age for tributary detrital monazite is 460.9 ± 2.5 Ma (95% confidence). Zircon cores failed to record Paleozoic metamorphism, while zircon rims gave a weighted average age of 443.5 ± 8.7 Ma (95% confidence). The tributary system is garnet-bearing, with garnet grains exceeding the current minimum volume required for single grain analysis (≥ 0.4 mm max. diameter). Previously reported initial ages from the garnet grains (Maneiro-Eccles, 2015, Goldschmidt) have been updated to include blank correction accounting for extremely small Nd loads; clean garnet analyses contain 17-445 pg Nd and repeat blanks indicate contribution of 4.31 ± 0.59 pg Nd. The resulting weighted average age for garnet is 438.8 ± 8.1 Ma (95% confidence). The weighted average ages for zircon rims and garnet overlap within error, while the monazite age is older (22.1 ± 8.5 Myr older than garnet, 17.4 ± 9.1 Myr older than zircon). Age variance between minerals could be attributed to monazite sampling bias, limited sample size, and either influence by a secondary tectonic event (e.g. the Cherokee Orogeny

  1. U-Pb zircon and biostratigraphic data of high-pressure/low-temperature metamorphic rocks of the Talea Ori: tracking the Paleotethys suture in central Crete, Greece

    Zulauf, G.; Dörr, W.; Krahl, J.; Lahaye, Y.; Chatzaras, V.; Xypolias, P.


    Inherited deformation microfabrics of detrital quartz grains and U-Pb (Laser ablation (LA)-ICPMS and ID TIMS) ages of detrital zircons separated from the Phyllite-Quartzite Unit s.l. of the Talea Ori, central Crete, suggest strikingly different source rocks. Albite gneiss of the lower Rogdia Beds includes Cambrian and Neoproterozoic rounded zircons with main U-Pb age peaks at 628 and 988 Ma. These and minor Paleoproterozoic and Archean peaks, together with the lack of Variscan-aged and Mesoproterozoic zircons, are similar to the age spectra obtained from the Phyllite-Quartzite Unit s.str. of the Peloponnesus and eastern Crete and from the Taurides. All of these zircons should be derived from the northeastern passive margin of Gondwana (Cimmeria). Metatuffites of the uppermost Rogdia Beds and metasandstone of Bali beach, on the other hand, include euhedral detrital zircons displaying a Variscan U-Pb age spectra at ca. 300 Ma with concordia ages at 291 ± 3, 300 ± 1 Ma (Rogdia) and 286 ± 3, 300 ± 3, 313 ± 2 Ma (Bali). Both types of metasediments and their zircons are similar to those of the pre-Alpine basement and overlying Tyros Beds of eastern Crete, revealing a provenance at the southern active margin of Laurasia. Thus, in central Crete the Paleotethys suture should be situated inside the Rogdia Beds. Magmatic zircons separated from a rhyolite boulder of the lower Achlada Beds yielded a concordant U-Pb zircon age at 242 ± 2 Ma placing a maximum age for the deposition of the (meta)conglomerate from which the boulder was collected. This age is compatible with an Olenekian-early Anisian age of the underlying Vasilikon marble suggested by new findings of the foraminifera Meandrospira aff. pusilla. Both the Achlada Beds and the Vasilikon marble can be attributed to the lower Tyros Beds of eastern Crete. The Alpine deformation led to a pervasive mylonitic foliation, which is affecting most of the studied rocks. This foliation results from D2 top

  2. Fifty Shades of Grey: Zircon Perspectives on the Timing and Chemistry of Magma Interactions Reflected in the Bishop Tuff

    Chamberlain, K. J.; Wilson, C. J.; Wooden, J. L.; Baker, J. A.; Charlier, B. L.


    The ~0.76 Ma Bishop Tuff eruption in eastern California is an archetypal example of the products of a compositionally stratified magma chamber. Key issues regarding the melt-dominant magma body that have arisen from recent studies include the role of horizontal variability versus vertical stratification, and the nature and timing of a late-stage ingress of compositionally contrasting melt. The latter is reflected in, for example, CL-bright rims on quartz, and Sr- and Ba-rich rims on sanidines, both of which are reported in samples from ignimbrite erupted from vents along the northern caldera rim. Various studies have placed contrasting temporal constraints on assembly and evacuation of the Bishop Tuff magma body and the processes occurring within it from one or two mineral phases. Although the overall crystal specific record is more complex, it has the potential to distinguish between mixing, in-situ crystallisation and other magmatic processes, and resolve the associated timings of these events. Zircon has been widely utilised in the Bishop Tuff and other silicic systems because of its unique records of information about the ages and P-T-X environments of growth. Here we present SHRIMP-RG ion probe data from Bishop Tuff zircons, collected from samples spanning the full eruptive sequence. A combination of age data, textural analysis and trace element analysis is used to yield insights into magma chamber development and the pre-eruptive state of the melt-dominant magma body, as evidenced in material erupted from different vent areas around what became the Long Valley caldera. U-Pb dating of 307 spots from all zones in crystals from all samples yields a strongly unimodal age spectrum, with a mean age of 794+/-3 ka (10 spots rejected, MSWD = 2.0). CL images of the dated zircon suites show the appearance of bright-rimmed zircons in later-erupted ignimbrite packages (accompanied generally by bright-rimmed sanidine and quartz crystals), but with diversity in the

  3. Fabrication and Characterization of a Lead Zirconate Titanate Micro Energy Harvester Based on Eutectic Bonding

    LI Yi-Gui; SUN Jian; YANG Chun-Sheng; LIU Jing-Quan; SUGIYAMA Susumu; TANAKA Katsuhiko


    A lead zirconate titanate(PZT)-Si energy harvester cantilever with PZT bulk ceramics is fabricated by eutectic bonding, polishing and dicing processes. The feasibility of this process is studied using a successful operation of the cantilever in both actuation and harvesting modes. The first prototype made from a PZT-Au-Si cantiliever is tested. The testing results show the voltage output of 632mV at the frequency of 815Hz when the excitation acceleration is 0.5 g. The PZT and silicon layers are bonded together to form a sandwiched structure using a gold layer as an intermediate layer.%@@ A lead zirconate titanate(PZT)-Si energy harvester cantilever with PZT bulk ceramics is fabricated by eutectic bonding, polishing and dicing processes.The feasibility of this process is studied using a successful operation of the cantilever in both actuation and harvesting modes.The first prototype made from a PZT-Au-Si cantiliever is tested.The testing results show the voltage output of 632mV at the frequency of 815 Hz when the excitation acceleration is 0.5 g.The PZT and silicon layers are bonded together to form a sandwiched structure using a gold layer as an intermediate layer.

  4. Paragneiss zircon geochronology and trace element geochemistry, North Qaidam HP/UHP terrane, western China

    Mattinson, C.G.; Wooden, J.L.; Zhang, J.X.; Bird, D.K.


    In the southeastern part of the North Qaidam terrane, near Dulan, paragneiss hosts minor peridotite and UHP eclogite. Zircon geochronology and trace element geochemistry of three paragneiss samples (located within a ???3 km transect) indicates that eclogite-facies metamorphism resulted in variable degrees of zircon growth and recrystallization in the three samples. Inherited zircon core age groups at 1.8 and 2.5 Ga suggest that the protoliths of these rocks may have received sediments from the Yangtze or North China cratons. Mineral inclusions, depletion in HREE, and absence of negative Eu anomalies indicate that zircon U-Pb ages of 431 ?? 5 Ma and 426 ?? 4 Ma reflect eclogite-facies zircon growth in two of the samples. Ti-in-zircon thermometry results are tightly grouped at ???660 and ???600 ??C, respectively. Inclusions of metamorphic minerals, scarcity of inherited cores, and lack of isotopic or trace element inheritance demonstrate that significant new metamorphic zircon growth must have occurred. In contrast, zircon in the third sample is dominated by inherited grains, and rims show isotopic and trace element inheritance, suggesting solid-state recrystallization of detrital zircon with only minor new growth. ?? 2009 Elsevier Ltd.

  5. Carburization of W- and Re-rich Ni-based alloys in impure helium at 1000 {sup o}C

    Adharapurapu, Raghavendra R., E-mail: [Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Kumar, Deepak; Zhu Jun [Materials Science and Engineering, University of Michigan, Ann Arbor, MI 48109 (United States); Pollock, Tresa M. [Materials Department, University of California, Santa Barbara, CA 93106 (United States)


    Research highlights: This work investigates the surface and bulk stability of W- and Re-rich Ni-based alloys under carburizing/oxidizing conditions (1000 {sup o}C) in order to understand the fundamental mechanisms of material degradation due to impurities in helium environment of the very high temperature helium-cooled reactor (VHTR). Depending on the alloy composition, carbides of type M{sub 6}C, M{sub 7}C{sub 3} or M{sub 23}C{sub 6} were observed, with a maximum carbon pickup between 0.06 and 0.12 wt.%. Alloys with high W content exhibited M{sub 6}C type carbides, whereas high Cr and low W alloys formed Cr-rich M{sub 23}C{sub 6} carbides. High additions of Re stabilized the M{sub 23}C{sub 6} phase due to its high solubility in these chromium-rich carbides. A continuous film of contiguous carbides (M{sub 6}C and M{sub 23}C{sub 6}) was observed in the grain boundaries; this is likely to be detrimental to the ductility and creep properties. During the first 50 h exposure, carbides were observed on the alloy surface as well as in the bulk with carbides precipitating in the grain interior and on the grain boundary. The (transient) surface carbides oxidized after prolonged exposure (100-225 h) forming stable Cr{sub 2}O{sub 3} oxide on the alloy surface. The work is particularly relevant to the development of strategies towards improvement of Ni-based alloys for intermediate heat exchangers (IHX) for service at 1000 {sup o}C in impure-He environment of the Next Generation Nuclear Plant (NGNP). - Abstract: The surface and microstructure stability of experimental W- and Re-rich Ni-based alloys in an impure-helium environment containing only CO and CO{sub 2} as impurities (ppm level) have been investigated at 1000 {sup o}C. All the alloys carburized during 50 h of exposure, and, depending on the alloy composition, different carbides of the type M{sub 6}C, M{sub 7}C{sub 3} and M{sub 23}C{sub 6} formed on the alloy surface, in grain interiors and at grain boundaries

  6. Monazite and zircon as major carriers of Th, U, and Y in peraluminous granites: examples from the Bohemian Massif

    Breiter, Karel


    The chemical compositions of zircon and monazite and the relationships between the contents of Th, U, Y, and REE in both minerals and in the bulk samples of their parental rocks were studied in three Variscan composite peraluminous granite plutons in the Bohemian Massif. It was established that granites of similar bulk composition contain zircon and monazite of significantly different chemistry. Monazite typically contains 5-13 wt% (rarely up to 28 wt%) ThO2, 0.4-2 wt% (up to 8.2 wt%) UO2, and 0.5-2 wt% (up to 5 wt%) Y2O3, whereas zircon typically contains less than 0.1 wt% (rarely up to 1.7 wt%) ThO2, less than 1 wt% UO2 (in the Plechý/Plockenstein granite, commonly, 1-2 wt% and scarcely up to 4.8 wt% UO2), and less than 1 wt% Y2O3 (in the Nejdek pluton often 2-5, maximally 7 wt% Y2O3). Monazite is an essential carrier of thorium, hosting more than 80 % of Th in all studied granites. Monazite also appears to be an important carrier of Y (typically 14-16 %, and in the Melechov pluton, up to 81 % of the total rock content) and U (typically 18-35 % and occasionally 6-60 % of the total rock budget). The importance of zircon for the rock budget of all the investigated elements in granites is lower: 4-26 % U, 5-17 % Y, and less than 5 % Th.

  7. Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil.

    Hartmann, Léo A; Liu, Dunyi; Wang, Yenbin; Massonne, Hans-Joachim; Santos, João O S


    U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on anamphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 +/- 9 Ma and 2006 +/- 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 +/- 18 Ma and 2031 +/- 40 Ma). However, protolith ages for the granodiorite (2366 +/- 8 Ma) and the granulite (2489 +/- 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites.

  8. Protolith age of Santa Maria Chico granulites dated on zircons from an associated amphibolite-facies granodiorite in southernmost Brazil

    Hartmann, Leo A. [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil). Inst. de Geociencias; Liu, Dunyi; Wang, Yenbin [Chinese Academy of Geological Sciences, Beijing (China); Massonne, Hans-Joachim [Universitaet Stuttgart (Germany). Inst. fuer Mineralogie und Kristallchemie; Santos, Joao O.S. [University of Western Australia, Perth, WA (Australia). Centre for Global Targeting


    U-Pb dating of zircon was undertaken with the Beijing SHRIMP II (sensitive high resolution ion microprobe) on an amphibolite facies granodiorite and an almandine-albite granulite from the Santa Maria Chico Granulitic Complex, southern Brazilian Shield. This work was also done to unravel protolith ages which are often hidden in the array of partly reset data. The obtained metamorphic ages of the granodiorite gneiss and the granulite are 2035 {+-} 9 Ma and 2006 {+-} 3 Ma, respectively. These data are within the range of metamorphic ages determined in previous studies (2022 {+-} 18 Ma and 2031 {+-} 40 Ma). However, protolith ages for the granodiorite (2366 {+-} 8 Ma) and the granulite (2489 {+-} 6 Ma) were obtained which are outside the previously recognized range (> 2510-2555 Ma). The magmatic protolith age of the granodiorite refers to a previously little known magmatic event in the shield. Further investigations may demonstrate that amphibolite facies zircon crystals are useful as a window into geological events in associated granulites, because zircon ages are blurred in the studied granulites. (author)

  9. Application of PT9800 software to optimization of carburizing process for heavy-duty locomotive gear%PT9800软件在重载机车齿轮渗碳工艺优化中的应用

    文超; 董雯; 谭小明; 王晓华


    利用PT9800软件进行了两段式渗碳工艺强扩比的模拟计算,据此优化了重载机车齿轮渗碳工艺并节省了20%的工艺时间。相应的验证试验也获得了满意的渗层金相组织、硬度梯度和预期的渗碳层深度,证明了PT9800计算的准确性,从而为渗碳工艺强扩比的合理选择和优化提供了依据。%The carburizing-diffusion ratio of two-stage carburizing technology was simulated by using PT9800 software.According to this simulation calculation,the carburizing process for heavy-duty locomotive gear was optimized and the process time was saved 20%.The expected microstructure,hardness distribution and case depth of the carburized layer were obtained by the relevant experiments,it is approved the reasonability and accuracy of PT9800 software,and provides evidence for choice and optimization of the carburizing-diffusion ratio.

  10. Equilibration of plain carbon and alloy steels with endothermic carburizing atmospheres: Part II. Oxidation of plain carbon and Armco steels during carburizing at 1000 °C and 1038 °C

    Hwang, Jong-Il; Jhee, Tae-Gu; Kim, Young-Kyu; Hwang, Tae-Young


    Carbon contents by the weight gain of AISI type 1010 steel foils equilibrated with CO-CO2 mixtures at 1000 °C were 0.03 wt.% to 0.07 wt.% higher than those by chemical analysis at carbon potentials of 0.2 wt.%C to 0.7 wt.%C. The lower the carbon potential, the bigger the difference became. This difference of 0.05 wt.% to 0.08 wt.% was also measured when the same materials were equilibrated with CO-CO2 mixtures at 1038 °C at carbon potentials below 0.4 wt.%C. Oxygen analyses of these equilibrated steel foils confirmed that those differences of 0.03 wt.% to 0.07 wt.% and 0.05 wt.% to 0.08 wt.% were mainly due to the selective oxidation of manganese. When Armco steels and type 1010 steels were equilibrated simultaneously with endothermic-base carburizing atmospheres at 1038 °C, oxidation was negligible and the carbon contents of the both steels were identical at carbon potentials of 0.2 wt.%C to 1.4 wt.%C.

  11. Effect of rheological properties of zircon-alumina suspensions on density of green casts

    L.B. Garrido


    Full Text Available Rheological properties of aqueous suspensions (48 vol% of zircon-alumina mixtures containing different amounts of polyelectrolyte as dispersant were studied. Slip casting in a plaster mold and pressure filtration at 8 MPa experiments were performed to correlate the rheological properties of the suspensions with the relative density of green casts. Flow curves fitted satisfactorily to the Casson model. The Casson viscosity values remained nearly constant whereas Casson yield stress parameter decreased to a minimum and then increased with increasing the amount of dispersant added. The influence of particle size distribution (PSD of the powder mixtures on Casson yield stress parameter and on the minimum viscosity was also examined. Green densities increased as yield stress Casson parameter decreased. The mixture of alumina and zircon as fine and coarse powders produced bimodal PSD which maximized the green density of the compacts. Some weakly flocculated suspensions having low apparent viscosity and small yield stress produced casts with relatively high densification. This is attributed to a slight higher viscosity at low shear rates of these suspensions in which settling of particles and /or segregation of components can not occur.

  12. Water-Induced Degradation in Lead Zinc Niobate-Lead Zirconate Titanate Soft Piezoelectric Ceramics

    JIANG Xiang-Ping; CHEN Wan-Ping; PENG Zhi; ZENG Min; CHANWANG Li-Hua; YIN Qing-Rui


    @@ Water-induced degradation of lead zinc niobate-lead zirconate titanate (Pb(Zn1/3Nb2/3)O3-Pb(ZrTi)O3) soft piezoelectric ceramics is studied using electrochemical hydrogen charging, in which the silver electrodes of the piezoelectric ceramics constitute a cathode in 0.01-M NaOH solution to evolve hydrogen by electrolysis of water.It is found that with the increasing hydrogen charging time, the resonance impedance increases, the difference between the resonance frequency and the anti-resonance frequency decreases, the spontaneous polarization, the remanent polarization and the piezoelectric coefficient d33 decrease. The degradation behaviour of the soft piezoelectric ceramics can be explained to hydrogen incorporating into the lattice and forming hydroxy (OH-)bonds in the perovskite structure, which prevents the Ti ions from switching and increases the coercive field Ec.The degradation characteristics of the soft piezoelectric ceramics are quite different from that of lead zirconate titanate hard piezoelectric ceramics.

  13. [The characteristics of microstructure and chemical compositions of K-feldspar, sphene and zircon with zoning structure].

    Liu, Chun-Hua; Wu, Cai-Lai; Lei, Min; Qin, Hai-Peng; Li, Ming-Ze


    K-feldspar, sphene and zircon in quartz monzonite from Shahewan, south Qinling, showing strong zoning structure. Characteristics of microstructure and chemical compositions of K-feldspar, sphene and zircon with zoning structure were investigated using advanced instruments of electron probe micro analyses equipped with wavelength dispersive spectrometer (EPM-WDS), scanning electron microscopy with energy dispersive spectrometer (SEM-EDS) and laser ablation--inductively coupled plasma--mass spectrometry (LA-ICP-MS). Our study suggests that K+ could be substituted by small amounts of Na+, Ca2+, Ba2+, Fe2+ and Ce3+. Ca2+ in sphene could be replaced by V3+, Ce3+, Ba2+ and Ti4+ could be substituted by both Fe2+ and Al3+. Zircon contains trace elements like Fe, Th, U, Nb, Ta, Y, Hf, Yb and Pb. Concentration of Si, Al, K, Ca, Na, Mg and Ba in K-feldspar ranked from high to low, among which the contents of K and Na are negatively correlated, the lighter part of BSE images featuring K-feldspar is attributed to comparably higher Ba content, additionally, Si and K contents are elevated while Na content decreased rimward. Ca, Si, Ti, Ba, V, Ce, Al and Fe concentration listed downward, among which higher iron content corresponds to brighter portion of BSE images. Element concentration of zircon could be ranked from high to low as Zr, Si, Nd, Ce, Hf, U, Pb and Th, in which Hf and Zr exhibit negatively correlated. Zr concentration increased while Hf, U and Th concentration decreased from core to rim.

  14. Sm-Nd and zircon SHRIMP U-Pb dating of Huilanshan mafic granulite in the Dabie Mountains and its zircon trace element geochemistry

    HOU; Zhenhui; LI; Shuguang; CHEN; Nengsong; LI; Qiuli; LIU


    The mafic granulites from Huilanshan are outcropped on the center of the Luotian dome in the northern Dabie Mountains. The Sm-Nd isochron defined by granulite-facies metamorphic minerals (garnet + clinopyroxene + hypersthene) yields an age of 136(±)18 Ma indicating the early Cretaceous granulite-facies metamorphism. The cathodoluminescence (CL) images of zircons from the granulite show clearly core-mantle-rim structures. The zircon cores are characterized by typical oscillatory zoning and highly HREE enriched patterns, which suggests their magma origin. Some zircon cores among them with little Pb loss give SHRIMP U-Pb ages ranging from 753 to 780 Ma, which suggests that the protolith of Huilanshan granulite is Neoproterozoic mafic rocks. The zircon mantles usually cut across the oscillatory zone of the zircon cores have 3―10 times lower REE, Th, U, Y, Nb and Ta contents than the igneous zircon cores but have high common Pb contents. These characteristics suggest that they were formed by hydrothermal alteration of the igneous zircons. The part of zircon mantles with little Pb loss give a similar SHRIMP U-Pb age (716―780 Ma) to the igneous zircon cores, which implies that the hydrothermal events occurred closely to the magmatic emplacement. In view of the strong early Cretaceous magmatism in the Luotian dome, consequently, the Huilanshan mafic granulite was formed by heating of the Neoproterozoic mafic rocks in mid-low crust, which caused the granulite-facies metamorphism underneath the Dabie Mountains. The similarity between the granulite metamorphic age (136±18 Ma) defined by Sm-Nd isochron and K-Ar age of 123―127 Ma given by amphible from the gneiss in Luotian dome suggests a rapid uplifting of the Luotian dome, which may result in further exhumation of the ultrahigh pressure metamorphic rocks in the Dabie Mountains.

  15. Proterozoic basement and Palaeozoic sediments in the Ringkøbing–Fyn High characterized by zircon U–Pb ages and heavy minerals from Danish onshore wells

    Olivarius, Mette; Friis, Henrik; Kokfelt, Thomas F.


    New data from the Proterozoic basement and scattered Palaeozoic sediments in the Ringkøbing–Fyn High including zircon U–Pb geochronometry, heavy mineral compositions and whole rock geochemistry is presented here to provide a frame of reference for detrital provenance studies. The Ringkøbing–Fyn H...

  16. Proterozoic basement and Palaeozoic sediments in the Ringkøbing–Fyn High characterized by zircon U–Pb ages and heavy minerals from Danish onshore wells

    Olivarius, Mette; Friis, Henrik; Kokfelt, Thomas F.


    New data from the Proterozoic basement and scattered Palaeozoic sediments in the Ringkøbing–Fyn High including zircon U–Pb geochronometry, heavy mineral compositions and whole rock geochemistry is presented here to provide a frame of reference for detrital provenance studies. The Ringkøbing...

  17. SHRIMP U-Pb geochronology of the detrital zircons from the Longshoushan Group and its tectonic significance

    KuoAn TUNG; HoungYi YANG; LIU DunYi; ZHANG JianXin; ChienYuan TSENG; WAN YuSheng


    Sixty-two geologically meaningful U-Pb dates were obtained by using SHRIMP technique for the detrital zircons in three mettasedimentary rocks from stratigraphically uppermost parts of the Longshoushan Group in the present study.Eighty percents of these dates range from 1.7 Ga to 2.2 Ga with a peak at 1.8-2.0 Ga and twenty percents from 2.3 Ga to 2.7 Ga.The youngest detrital zircon is dated at 1724±19Ma which is interpreted as the maximum depositional age of the metasedimentary rocks.Therefore,the age for the diagenesis and lithification of the original sedimentary rocks of the Longshoushan Group before the metamorphism must be younger than 1724±19 Ma.Comparison of the age histograms of these detrital zircons with the ages of the igneous rocks on the surrounding older massifs suggests that the sediments of the Longshoushan Group were most likely derived from the Alaxa Block and Tarim Craton.This implies that the affinity between Alaxa Block and Tarim Craton was strong and that they might have been a unified craton during middle-early Proterozoic time

  18. The Use and Abuse of Th-U Ratios in the Interpretation of Zircon

    Möller, A.; ÓBrien, P. J.; Kennedy, A.; Kröner, A.


    In the interpretation of geochronological data the distinction between magmatic and metamorphic zircon is mainly based on morphology, internal zoning or Th-U ratio. This distinction is of doubtful benefit in partially molten high grade metamorphic rocks where partial melting and zircon growth or dissolution may have occurred in several phases. It is proposed that instead of classifying zircon into magmatic and metamorphic groups, differences and changes in chemistry from inherited core to overgrowth can be attributed to growth or recrystallization mechanisms. Taking the distinction literally, only zircon grown by solid state (metamorphic) reactions may be called metamorphic, whereas zircon crystallized from melt is magmatic, and zircon crystallized from fluids is hydrothermal. Trace element characteristics together with the criteria mentioned above may help to link zircon growth to these environments or to other processes altering existing zircon (i.e. metamictisation, annealing, recrystallization, dissolution-reprecipitation). In-situ ion microprobe analysis has been used to track Th-U ratios of zircon through time in polymetamorphic rocks. Several different trends can be distinguished and attributed to different growth mechanisms when combined with cathodo-luminescence and backscatter electron imaging. Unchanged Th/U through time is interpreted to reflect closed system behaviour, lower Th/U in overgrowths can indicate competition for Th with high Th minerals (monazite, allanite etc.), higher Th/U is also observed and interpreted to reflect open system behaviour, breakdown of minerals with high Th/U, or competition with high U minerals (e.g. xenotime). In summary, zircon grown during metamorphic events may not be characterized by low Th/U, and classifying zircon as "metamorphic" solely based on its Th/U as occasionally seen in the literature can lead to gross misinterpretations.

  19. EBSD analysis of tungsten-filament carburization during the hot-wire CVD of multi-walled carbon nanotubes.

    Oliphant, Clive J; Arendse, Christopher J; Camagu, Sigqibo T; Swart, Hendrik


    Filament condition during hot-wire chemical vapor deposition conditions of multi-walled carbon nanotubes is a major concern for a stable deposition process. We report on the novel application of electron backscatter diffraction to characterize the carburization of tungsten filaments. During the synthesis, the W-filaments transform to W2C and WC. W-carbide growth followed a parabolic behavior corresponding to the diffusion of C as the rate-determining step. The grain size of W, W2C, and WC increases with longer exposure time and increasing filament temperature. The grain size of the recrystallizing W-core and W2C phase grows from the perimeter inwardly and this phenomenon is enhanced at filament temperatures in excess of 1,400°C. Cracks appear at filament temperatures >1,600°C, accompanied by a reduction in the filament operational lifetime. The increase of the W2C and recrystallized W-core grain size from the perimeter inwardly is ascribed to a thermal gradient within the filament, which in turn influences the hardness measurements and crack formation.

  20. 缩短渗碳周期与强烈淬火相结合的节能热处理技术%Energy Savings Using a Combination of Carburizing Cycle Reduction and Intensive Quenching

    Lauralice C. F. Canale; Eduardo Merheb; Jo(a)o C. Vendramim; George E. Totten


    在热处理行业,人们一直在探索降低生产成本、节约能源和减少环境污染的方法.汽车制造业在这方面将是大有作为的,其中包括:大幅度缩短渗碳时间,以节能和降低生产成本;开发新型淬火剂替代易燃、有毒的矿物油基淬火剂.采用非易燃的对环境友好的水基淬火剂进行强烈淬火(IQ)是达到这些目标的途径之一.此外,IQ还能使渗碳的扩散时间缩短50%或更多.本文论述了巴西圣保罗大学、巴西Combustol公司以及美国强烈淬火公司合作进行的采用一种强烈淬火工艺成功达到上述目标的研究成果.从长远看,这些成果对热处理工业将具有重要意义.%There is an ongoing interest in the heat treatment industry to identify methods of reducing production cost, energy consumption and to reduce environmental impact of heat treatment practices and materials. Automobile industry offers a number of opportunities in this regard including: reduction of substantial carburizing times which would result in substantial energy savings and reduction in production costs due to shorter processing times and the potential replacement of flammable and relatively toxic petroleum-based quenchants. One way of achieving these goals is to use intensive quenching processes (IQ) which utilize non-flammable and environmentally benign aqueous-based quenchants. Furthermore, IQ offers the potential of significantly reducing total carburizing diffusion times by 50%, or more. This paper will discuss the results of a collaborative study conducted by the University of Sao Paulo at Sao Carlos, Combustol, and Intensive Quenching Technologies to utilize an IQ process to successfully achieve the afore mentioned goals. These results are potentially of major importance to the heat treatment industry.

  1. 井式炉渗碳工艺过程控制SE-607系统的应用%Application of carburizing process control system SE-607 for pit-type furnace



    The application case in Hangzhou Advance Gearbox Group Co.,Ltd.,of SE-607 pit-type furnace carburizing control system that was developed and researched by STANGE Electronic GmbH was introduced for the construction of hardware and software,carburizing workmanship,working principle of carbon potential regulation,carburizing process simulation and computer monitoring system.%以德国斯坦格电气有限公司设计制造的SE-607井式炉渗碳工艺过程控制系统在杭州前进齿轮箱厂的项目应用为实例,对该过程控制系统的软硬件结构、渗碳工艺、碳势控制原理、渗碳扩散模拟模块及上位机监控系统的组成进行介绍。

  2. Geology, zircon geochronology, and petrogenesis of Sabalan volcano (northwestern Iran)

    Ghalamghash, J.; Mousavi, S. Z.; Hassanzadeh, J.; Schmitt, A. K.


    Sabalan Volcano (NW Iran) is an isolated voluminous (4821 m elevation; > 800 km2) composite volcano that is located within the Arabia-Eurasia collision zone. Its edifice was assembled by recurrent eruptions of trachyandesite and dacite magma falling into a relatively restricted compositional range (56-67% SiO2) with high-K calc-alkaline and adakitic trace element (Sr/Y) signatures. Previous K-Ar dating suggested protracted eruptive activity between 5.6 and 1.4 Ma, and a two stage evolution which resulted in the construction of the Paleo- and Neo-Sabalan edifices, respectively. The presence of a topographic moat surrounding Neo-Sabalan and volcanic breccias with locally intense hydrothermal alteration are indicative of intermittent caldera collapse of the central part of Paleo-Sabalan. Volcanic debris-flow and debris-avalanche deposits indicate earlier episodes of volcanic edifice collapse during the Paleo-Sabalan stage. In the Neo-Sabalan stage, three dacitic domes extruded to form the summits of Sabalan (Soltan, Heram, and Kasra). Ignimbrites and minor pumice fall-out deposits are exposed in strongly dissected drainages that in part have breached the caldera depression. Lavas and pyroclastic rocks are varyingly porphyritic with Paleo-Sabalan rocks being trachyandesites carrying abundant phenocrysts (plagioclase + amphibole + pyroxene + biotite). The Neo-Sabalan rocks are slightly more evolved and include dacitic compositions with phenocrysts of plagioclase + amphibole ± alkali-feldspar ± quartz. All Sabalan rock types share a common accessory assemblage (oxides + apatite + zircon). High spatial resolution and sensitivity U-Pb geochronology using Secondary Ionization Mass Spectrometry yielded two clusters of zircon ages which range from 4.5 to 1.3 Ma and 545 to 149 ka, respectively (all ages are averages of multiple determinations per sample). U-Th zircon geochronology for selected Neo-Sabalan rocks agrees with the U-Pb ages, with the youngest zircon rims dating

  3. Etching zircon age standards for fission-track analysis

    Garver, J.I. E-mail:


    Nineteen laboratories that routinely measure fission-track ages in zircon were surveyed as to their principal methodology used for track revelation using chemical attack and counting procedures. The survey results show the following: (a) researchers in most labs count fission tracks with a optical microscope using at a total magnification between 1250x and 1600x ({approx}80%) with about an equal number using either a dry or oil objective (b) the majority of laboratories etch zircon with a KOH:NaOH eutectic heated in an oven between temperatures of 210 deg. C and 230 deg. C; (c) ag standards in zircon analysis do not have uniformly accepted etch times. Etching times for the widely used 28 Ma Fish Canyon Tuff (FCT) (4-60 h) and the lesser-used 16 Ma Buluk Tuff (13-55 h) vary significantly from lab to lab. Between {approx}220 deg. C and 230 deg. C, the principal range fo etching times for the FCT is between 20 and 30 h, and the mode for the Buluk Tuff is between 30 and 55 h. Three or fewer labs report etching times for the Tardee Rhyolite (22-40 h), the Bishop Tuff (10-46 h), and the Mt. Dromedary Banite (5-24 h). Variation in etching times may result in a bias in U-content which affects counting statistics. If etching is successful, strict criteria must be followed to ensure that the analyst only counts well-etched grains and that all tracks are successfully identified.

  4. Modelling of optically stimulated luminescence of zircon : assessment of the suitability for dating

    Turkin, A.A.; Vainshtein, D.I.; Hartog, H.W. den


    The mineral zircon, ZrSiO4, is a candidate material for optical dating because it exhibits luminescence after exposure to natural radioactivity. The kinetic model of zircon thermally stimulated luminescence proposed before has been modified and used to investigate optically Stimulated luminescence (

  5. Extreme lithium isotopic fractionation in three zircon standards (Plešovice, Qinghu and Temora).

    Gao, Yu-Ya; Li, Xian-Hua; Griffin, William L; Tang, Yan-Jie; Pearson, Norman J; Liu, Yu; Chu, Mei-Fei; Li, Qiu-Li; Tang, Guo-Qiang; O'Reilly, Suzanne Y


    To understand the behavior of Li in zircon, we have analyzed the abundance and isotopic composition of Li in three zircon standards (Plešovice, Qinghu and Temora) widely used for microbeam analysis of U-Pb ages and O-Hf isotopes. We have mapped Li concentration ([Li]) on large grains, using a Cameca 1280HR Secondary Ion Mass Spectrometer (SIMS). All zircons have a rim 5-20 μm wide in which [Li] is 5 to 20 times higher than in the core. Up to ~20‰ isotopic fractionation is observed on a small scale in the rims of a single zircon grain. The measured δ(7)Li values range from -14.3 to 3.7‰ for Plešovice, -22.8 to 1.4‰ for Qinghu and -4.7 to 16.1‰ for Temora zircon. The [Li] and δ(7)Li are highly variable at the rims, but relatively homogenous in the cores of the grains. From zircon rim to core, [Li] decreases rapidly, while δ(7)Li increases, suggesting that the large isotopic variation of Li in zircons could be caused by diffusion. Our data demonstrate that homogeneous δ(7)Li in the cores of zircon can retain the original isotopic signatures of the magmas, while the bulk analysis of Li isotopes in mineral separates and in bulk-rock samples may produce misleading data.

  6. Microwave-assisted hydrothermal synthesis of lead zirconate fine powders

    Apinpus Rujiwatra


    Full Text Available A rapid synthesis of lead zirconate fine powders by microwave-assisted hydrothermal technique is reported. The influences of type of lead precursor, concentration of potassium hydroxide mineraliser, applied microwave power and irradiation time are described. The synthesised powders were characterised by powder X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopic microanalysis and light scattering technique. The merits of the microwave application in reducing reaction time and improving particle mono-dispersion and size uniformity as well as the drawbacks, viz. low purity of the desired phase and increasing demand of mineraliser, are discussed in relation to conventional heating method.

  7. Characterization and microstructure of porous lead zirconate titanate ceramics

    B Praveenkumar; H H Kumar; D K Kharat


    Porous lead zirconate titanate (PZT) ceramics are widely used because of their low acoustic impedance, high figure of merit and high hydrostatic sensitivity. In the present work, porous PZT ceramics were fabricated by incorporating polyethylene oxide (PEO) as pore-forming agent. Both PZT powder and PEO were mixed with a binder at different ratios and compaction was carried out. The samples were slowly heated to remove the pore-forming agent and binder without cracks, followed by controlled sintering and electrode forming. Samples were poled using corona poling technique. The ferroelectric properties and microstructure of the prepared ceramics were characterized. The correlation of porosity with microstructure and ferroelectric properties were discussed.

  8. 奥氏体不锈钢低温气体渗碳的组织性能%Structure and Properties of Anti-corrosion Carburized Layers in Austenitic Stainless Steels

    李朋; 潘邻; 张良界; 杨闽红; 朱云峰; 马飞


    Low temperature carburizing process, such as salt bath carburizing and plasma carburizing can improve the surface strength of the austenite stainless steel, but reduce the corrosion resistant performance. A gas carburizing technology at low temperature was developed, which can both improve the surface strength and corrosion resistant performance. 304 and 316 austenitic stainless steel were carburized by low temperature carburizing process, and the hardness and performance was analized. The results show that the surface strength enhances, however, the corrosion resistance reduces with the temperature increase. The austenitic stainless steel shows good strength and corrosion resistance under the condition of 470 ℃.%低温盐浴渗碳、等离子渗碳等低温渗碳工艺在提高奥氏体不锈钢表面强度的同时,会降低其耐蚀性能.为克服上述缺陷,开发了一种高效兼顾表面强度与耐蚀性能的表面强化工艺的低温气体渗碳技术.采用该工艺对304、316奥氏体不锈钢进行渗碳处理,并对得到的奥氏体不锈钢低温渗碳组织性能进行分析.结果表明,随着温度升高,试样表面强度提高,而腐蚀性能下降.470℃是兼顾强化与耐蚀性能的低温气体渗碳工艺参数.

  9. Carburizing Inspection of Cracking Furnace Tube Using Magnetic Hysteresis Non-Destructive Evaluation Technique%磁滞无损评估技术在裂解炉管渗碳检测中的应用

    刘德宇; 王宁辉; 张国庆; 李国瑞


    Large tube type fuel heating furnaces are important and essential equipments, with a wide range of applications in the petroleum and chemical industry, in which the failure modes of furnace tubes are mostly caused by carburizing. To estimate the effect of magnetic hysteresis non-destructive evaluation technique on carburizing inspection, both new and the three-years-service cracking furnace tubes were performed carburizing test. Different carburized depth of tubes were got and their coercivity was tested. The results showed that there is a good relationship between the coercivity and carburized case depth, which would be a great potential applications in the carburizing inspection of tube.%大型管式燃料加热炉是石油化工企业里广泛应用且必不可少的重要设备,其中炉管的失效大多由渗碳引起。为了评价磁滞无损评估技术在渗碳层厚度检测中应用的有效性,对未服役和服役3年的裂解炉炉管进行渗碳实验,得到不同渗碳层厚度的炉管,并采集磁滞参数矫顽力,结果表明,矫顽力与渗碳层厚度具有很好的对应关系,在炉管渗碳检测中具有很大的应用前景。

  10. Disturbed Sr and Nd Isotope Systematics in Zircons With Concordant SHRIMP U-Pb Ages

    Weaver, K. L.; Bennett, V. C.; Depaolo, D. J.; Mundil, R.


    Little is known about the Sr- and Nd-isotopic systematics of zircon. With slow diffusion rates and a high resistance to weathering, zircon should preserve accurate age information and initial Sr and Nd isotopic ratios. As a common accessory mineral, it could provide petrogenetic information for rocks that have been altered, weathered, or metamorphosed. We have investigated the Sm-Nd and Rb-Sr systematics of zircons from unmetamorphosed granitic rocks that have yielded concordant U-Pb SHRIMP (Sensitive High Resolution Ion Microprobe) ages and have depleted mantle signatures for Nd and Sr isotopes. Zircon populations from mantle-derived igneous rocks with ages of 0.1, 1.7, and 3.8 Ga were chosen for Sr and Nd isotopic analysis. Low concentrations (Sr, 4 to 8 ppm and Nd, 6 to 12 ppm) and small grain size necessitate the use of multigrain aliquots. Meaningful results can be obtained only if all of the zircons in the rock are a coherent population with homogeneous ages throughout and among grains. Zircon U-Pb ages were characterized using the SHRIMP RG, and trace element concentrations were measured by LA-ICPMS. The populations are homogeneous and the material ablated by the ion beam ( ˜~20 μ m spot size) shows little evidence of lead loss. Results on zircons of 100 Ma and 1700 Ma indicate that both the Rb-Sr and Sm-Nd systems have been severely disturbed. For the 1700 Ma granitic rocks from the Yavapai sequence of Arizona, zircon Sm-Nd apparent ages are ca. 1000 Ma! Leaching was used to remove contributions from adhering or included minerals, but leached residues that presumably most closely approximate the composition of the pure zircon (e.g. have high Sm/Nd) are no less disturbed than unleached samples. Despite the U-Pb SHRIMP ages indicating a closed system, the zircons have failed to preserve a reasonable age or initial isotopic composition for Sr and Nd, indicating that parts of the crystal might be severely affected by radiation damage resulting in disturbed

  11. Zircon and apatite fission track analyses on mineralization ages and tectonic activities of Tuwu-Yandong porphyry copper deposit in northern Xinjiang, China


    The mineralization ages reported in the past in the Tuwu-Yandong copper district not only are different, but also fall into the Hercynian epoch. This study has achieved 9 zircon and 7 apatite fission track analysis results. The zircon fission track ages range from 158 Ma to 289 Ma and the apatite ages are between 64 Ma and 140 Ma. The mineralization accords with the regional tectonics in the copper district. We consider that the zircon fission track age could reveal the mineralization age based on annealing zone temperature of 140-300℃ and retention temperature of ~250℃ for zircon fission track, and metallogenetic temperature of 120-350℃ in this ore district. Total three mineralization epochs have been identified, i.e., 289-276 Ma,232-200 Ma and 165-158 Ma, and indicate occurrence of the mineralization in the Indosinian and Yanshan epochs. Corresponding to apatite fission track ages, the three tectonic-mineralizing epochs are 140-132 Ma, 109-97 Ma and 64 Ma, which means age at about 100℃ after the mineralization. The three epochs lasted 146 Ma, 108 Ma and about 100 Ma from ~250℃ to ~100℃ and trend decrease from early to late. It is shown by the fission track modeling that this district underwent three stages of geological thermal histories, stable in Cretaceous and cooling both before Cretaceous and after 20 Ma.

  12. Effect of the temperature and oxalic acid in the uranyl sorption in zircon; Efecto de la temperatura y acido oxalico en la sorcion de uranilo en circon

    Ordonez R, E.; Almazan T, M. G.; Garcia G, N. [ININ, Departamento de Quimica, Carretera Mexico-Toluca s/n, 52750 Ocoyoacac, Estado de Mexico (Mexico); Hernandez O, R., E-mail: [Instituto Tecnologico de Veracruz, Ingenieria Quimica, Miguel Angel de Quevedo No. 2779, 91860 Veracruz (Mexico)


    In this work the results of the temperature effect study are presented on uranyl solutions adsorbed on zirconium silicate (ZrSiO{sub 4}) and also on the compounds formed in surface with oxalic acid. The adsorption isotherms of uranyl on hydrated zircon with NaClO{sub 4} 0.5 M, show an increase of the uranyl sorption efficiency when increasing the temperature from 20 to 4 C with a sudden descent in this efficiency when changing the temperature at 60 C. The uranyl sorption efficiency increases to hydrate the zircon with a solution of oxalic acid 0.1 M, maintaining the same tendency regarding to the temperatures of the sorption in medium NaClO{sub 4} 0.5 M. The complex formation in the zircon surface with organic acids of low molecular weight increases the fixation of the uranyl in solution due to the formation of ternary systems, in the order Zircon/A. Organic/Uranyl, without altering their response to the temperature. (Author)

  13. Zircon U-Pb Ages from an Ultra-High Temperature Metapelite, Rauer Group, East Antarctica: Implications for Overprints by Grenvillian and Pan-African Events

    Wang, Yanbin; Tong, Laixi; Liu, Dunyi


    SHRIMP U-Pb dating of zircon from an ultra-high temperature (UHT, ~1000 °C) granulite-facies metapelite from the Rauer Group, Mather Peninsula, east Antarctica, has yielded evidence for two episodes of metamorphic zircon growth, at ~1.00 Ga and ~530 Ma, and two episodes of magmatism in the source region for the protolith sediment, at ~2.53 and ~2.65 Ga, were identified from the zircon cores. Successive zircon growth at ~1.00 Ga and ~530 Ma records a sequence of distinct, widely spaced high-temperature metamorphic and/or anatectic events related to Grenvillian and Pan-African orogenesis. This study presents the first robust geochronological evidence for the timing of UHT metamorphism of the Rauer Group, supporting arguments that the peak UHT metamorphic event occurred at ~1.00 Ga and was overprinted by a separate high-grade event at ~530 Ma. The new age data indicate that the UHT granulites of the Rauer Group experienced a complex, multi-stage tectonothermal history, which cannot simply be explained via a single Pan-African (~500 Ma) high-grade tectonic event. This is critical in understanding the role of the eastern Prydz Bay region during the assembly of the east Gondwana supercontinent, and the newly recognized inherited Archaean ages (~2.53 and ~2.65 Ga) suggest a close tectonic relationship between the Rauer Group and the adjacent Archaean of the Vestfold Hills

  14. The effect of titanite crystallisation on Eu and Ce anomalies in zircon and its implications for the assessment of porphyry Cu deposit fertility

    Loader, Matthew A.; Wilkinson, Jamie J.; Armstrong, Robin N.


    The redox sensitivity of Ce and Eu anomalies in zircon has been clearly demonstrated by experimental studies, and these may represent an important tool in the exploration for porphyry Cu deposits which are thought to be derived from oxidised magmas. These deposits are significant because they are the source of much of the world's copper and almost all of the molybdenum and rhenium, key elements in many modern technologies. However, Ce and Eu anomalies in zircon are also affected by the co-crystallisation of REE bearing phases, such as titanite. Here, we report the trace element chemistry of zircons from titanite-bearing intrusions associated with mineralisation at the world class Oyu Tolgoi porphyry Cu-Au deposit (Mongolia). Based on these data, we suggest that neither zircon Eu/Eu*, nor Ce4+/Ce3+ are robust proxies for melt redox conditions, because they are both too strongly dependent on melt REE concentrations, which are usually poorly constrained and controlled by the crystallisation of titanite and other REE-bearing phases. In spite of this, Eu/Eu* can broadly distinguish between fertile and barren systems, so may still be an indicator of porphyry magma fertility, and a useful tool for exploration.

  15. SHRIMP Dating and Recrystallization of Metamorphic Zircons from a Granitic Gneiss in the Sulu UHP Terrane

    LI Hongyan


    An unusual zircon SHRIMP dating result of a granitic gneiss from the Qinglongshan eclogite-gneiss roadcut section is presented in this paper. The very peculiar and complicated internal structures, as well as the very low Th/U ratios (0.01-0.08) of the zircons indicate that they were formed by metamorphic recrystallization. Strongly in contrast with previously published zircon U-Pb ages of the Dabie-Sulu UHP metamorphic rocks where protolith ages of 600-800 Ma are commonly recorded, only metamorphic age of 218+5 Ma, defined by 18 analytical spots either in rim or in core of zircons, are recorded in this granitic gneiss. This age represents the time of the complete metamorphic recrystallization overprint on primary magmatic zircons. The recrystallization was derived by the UHP metamorphism,and was strengthened by the early stage of retrograde metamorphic fluid activity.

  16. 汽车零部件丙烷气体渗碳时气氛净化工艺及效果%Atmosphere Purification Technology and Effect of Gas Carburizing for Automobile Spare Parts

    张道于; 张铁军


    采用分子筛作为净化剂,可使渗碳气氛中的水分稳定地控制在较低水平.采用净化后的丙烷气体渗碳,产品质量得到明显提高,生产成本显著下降.%Using molecular sieve as the purifying agent, water in the carburizing atmosphere can be stably controlled at a lower level. Using purified propane gas carburizing, the product quality can be significantly improved, production costs decrease significantly.

  17. U-Pb (LA-PIMMS) Ages of Inherited Zircons from Early Palaeozoic Granitoids of the W Sudetes, N Bohemian Massif, Central Europe: Implications for Neoproterozoic Continental Reconstructions

    Crowley, Q. G.; Patocka, F.; Kachlík, V.


    A U-Pb laser ablation plasma ionisation multi-collector mass spectrometry (LA-PIMMS) geochronological study of zircons from early Palaeozoic (meta)granitoids of the Czech W Sudetes (E Saxothuringian Zone), NW Bohemian Massif, was carried out in order to determine the range of inherited age spectra preserved in these lithologies. Backscattered SEM images indicate that many zircons have distinct cores and rims. The majority of inherited zircon components yield concordant U-Pb ages that fall into the following age ranges: (1) 520-770 Ma, (2) 1.9-2.2 Ga and (3) ca. 3.0 Ga. These three age populations are typical of the W African Craton and the Armorican Terrane Assemblage of Europe. The age spectra correspond to Cadomian, Birimian / Icartian / Eburnean / Burkinian and Leonian events respectively. Some previous Pb-Pb zircon and whole rock Nd studies of similar lithologies from the W Sudetes (e.g. Hegner &Kröner, 2000) have attributed the presence of Mesoproterozoic 207Pb/206Pb ages to a peri-Amazonian provenance. Although some zircons from this study have yielded apparent Mesoproterozoic ages, they are discordant and can be resolved into early Palaeozoic to Neoproterozoic lower intercept and Palaeoproterozoic to Archaean upper intercept components. This unequivocally proves that an inherited Grenvillian component does not exist in these lithologies. We therefore favour derivation of the Saxothuringian zone and associated members of the Armorican Terrane Assemblage from a W African Craton Gondwanan setting. References: Hegner, E, &Kröner, A. 2000. Review of Nd data and xenocrystic and detrital ages from the pre-Variscan basement in the Eastern Bohemian Massif: speculations on palinspastic reconstructions. In: Franke, W., Altherr, R., Haak, V. &Oncken, O. (eds.), Orogenic Processes: Quantification and Modelling in the Variscan Belt of Central Europe Geological Society of London Special Publication, 179, 113-129.

  18. Processing of Lead Zirconate Titanate-graphite 3-3 Piezocomposites

    B. Praveenkumar


    Full Text Available The lead zirconate titanate (PZT-graphite piezocomposites have potential for higherpiezoelectric sensitivity, lower acoustic impedance, higher piezoelectric voltage constants, higherelectromechanical coupling coefficient, and higher hydrostatic coefficients as compared to densePZT materials. In addition, the properties of piezocomposites can be tailored for various weightpercentage of graphite powder. To study the phenomena, PZT-graphite 3-3 composites wereprepared by mixing calcined PZT and commercially available graphite powder. The mixed powderwas compacted, sintered, and poled by corona poling technique. Scanning electron microstructureswere recorded to study the effect of graphite on processing of 3-3 piezocomposites. The polarisingbehaviour, piezoelectric and dielectric properties of PZT-graphite composites were studied.

  19. Scanning ion imaging - a potent tool in SIMS U -Pb zircon geochronology

    Whitehouse, M. J.; Fedo, C.; Kusiak, M.; Nemchin, A.


    The application of high spatial resolution (BSE) characterisation, has revolutionised geochronology over the past 25 years, re-vealing complexities of crustal evolution from zoned zircons. In addition to ge-ochronology, such studies now commonly form the basis of broader investigations using O- and Hf- isotopes and trace elements obtained from the same growth zone as age, circumventing ambiguities commonly present in bulk-rock isotope studies. The choice of analytical beam diameter is often made to maximise the precision of data obtained from a given area of analysis within an identifiable growth zone. In cases where zircons yield poorly constrained internal structures in SEM, high spatial resolution spot analyses may yield uninterpretable and/or meaningless mixed ages by inadvertent sampling across regions with real age differences. Scanning ion imaging (SII) has the potential to generate accurate and precise geochrono-logical data with a spatial resolution down to ca. 2 μm, much higher than that of a normal spot analysis. SII acquisition utilises a rastered primary beam to image an area of the sample with a spatial resolution dependent on the selected primary beam diameter. On the Cameca ims1270/80 instruments, the primary beam scanning is coupled with the dynamic transfer optical system (DTOS) which deflects the secondary ions back on to the ion optical axis of the instrument regardless of where in the raster illuminated area the ions originated. This feature allows retention of a high field magnification (= high transmission) mode and the ability to operate the mass spectrometer at high mass resolution without any compromise in the quality of the peak shape. Secondary ions may be detected either in a sequential (peak hopping) mono-collection mode or simultaneous multicollection mode using low-noise pulse counting electron multipliers. Regardless of the detection mode, data are acquired over sufficient cycles to generate usable counting statistics from selected

  20. Improvement of Fracture Toughness Lanthanum Zirconate



    La2 Zr2 O7 (LZ) is a promising thermal barrier coating material for the high temperature applications. The fracture toughness and microhardness of nanocrystalline LZ (n-LZ), microcrystalline LZ (m-LZ) and LZ-5mol%8YSZ (LZ-5-8YSZ) composite (8YSZ for zirconia stabilized by 8 mol% ytrria) were studied. The n-LZ had a thermal expansion coeffinanofication was an efficient way to increase the toughness and thermal expansion coefficient of LZ. The composite LZ-5-superhigh pressure (SHP).

  1. Synthesis, Characterization and Thermal Diffusivity of Holmium and Praseodymium Zirconates

    Stopyra M.


    Full Text Available A2B2O7 oxides with pyrochlore or defected fluorite structure are among the most promising candidates for insulation layer material in thermal barrier coatings. The present paper presents the procedure of synthesis of holmium zirconate Ho2Zr2O7 and praseodymium zirconate Pr2Zr2O7 via Polymerized-Complex Method (PCM. Thermal analysis of precursor revealed that after calcination at relatively low temperature (700°C fine-crystalline, single-phase material is obtained. Thermal diffusivity was measured in temperature range 25-200°C, Ho2Zr2O7 exhibits lower thermal diffusivity than Pr2Zr2O7. Additionally, PrHoZr2O7 was synthesized. The powder in as-calcined condition is single-phase, but during the sintering decomposition of solid solution took place and Ho-rich phase precipitated. This material exhibited the best insulating properties among the tested ones.

  2. Origin and age of zircon-bearing chromitite layers from the Finero phlogopite peridotite (Ivrea-Verbano Zone, Western Alps) and geodynamic consequences

    Zanetti, Alberto; Giovanardi, Tommaso; Langone, Antonio; Tiepolo, Massimo; Wu, Fu-Yuan; Dallai, Luigi; Mazzucchelli, Maurizio


    An investigation has been performed on three chromitite layers segregated in dunite bodies of the Phlogopite Peridotite mantle unit in the Finero complex (FPP, Ivrea-Verbano Zone, Southern Alps) aimed at providing new constraints to their origin and evolution. Field relationships, the sub-chondritic Hf isotopic composition of the zircons (εHf(188) as low as - 5.4), the heavy O isotopic composition of zircons and pyroxenes (δ18O up to 6.9‰), the strict similarity of the trace element composition between the clinopyroxenes and amphiboles from the chromitites and those from the phlogopite harzburgites and pyroxenites forming the typical FPP association, as well as the REE composition of zircons, which approaches equilibrium with the associate clinopyroxene, suggest that the studied chromitites were segregated from melts, highly contaminated from continental crust, during the pervasive cycle of metasomatism recorded by the FPP. An LA-ICP-HRMS survey of chromitite zircon grains has provided Early Jurassic U-Pb ages mostly between 199 ± 3 Ma and 178 ± 2 Ma, with a pronounced peak at 187 Ma. Relevant exceptions are inherited domains of two grains giving Triassic ages of 242 ± 7 Ma and 229 ± 7 Ma, and a third homogeneous zircon giving 208 ± 3 Ma. Our geochronological data and those reported in the literature show that the FPP chromitites have zircon populations with different internal CL textures, but the same sub-chondritic Hf isotopic composition, which define an overall U-Pb age span from ~ 290 Ma to 180. The segregation of the chromitite layers and the main pervasive metasomatism likely occurred in the Early Permian (in a post-collisional, transtensional setting) or before (possibly, in a subduction-related setting). The rejuvenation of the zircon ages was accompanied by a progressive disappearance of the internal zoning, interpreted as the result of a prolonged residence at mantle depths with progressive re-equilibration of the U-Pb system due to thermal

  3. Detrital zircon geochronology and Nd isotope geochemistry of an early Paleozoic succession in Korea:

    Lee, Yong Il; Choi, Taejin; Lim, Hyoun Soo; Orihashi, Yuji


    This study reports the results of an analysis of U-Pb ages of detrital zircons and Nd isotope compositions from the well-established lower Paleozoic platform succession developed on the Precambrian gneiss and metasedimentary rocks in South Korea. The three stratigraphic units in the basal part of the succession are the Jangsan, Myeonsan, and Myobong Formations. The unfossiliferous Jangsan (white­to­pink quartz sandstone) and Myeonsan (dark-gray ilmenite-rich sandstone/shale) Formations are in fault contact and are generally considered to be coeval (Early Cambrian). Both formations are also generally considered to be conformably overlain by the dark­ gray, fossiliferous, fine-grained Myobong Formation (late Early-early Middle Cambrian). We here report U-Pb ages of detrital zircons and Nd isotopic data from the Jangsan, Myeonsan, and Myobong Formations. The Jangsan and Myeonsan Formations provide Archean-Paleoproterozoic U-Pb ages, but the former is characterized by Archean Sm-Nd model ages and the latter by late Paleoproterozoic Sm-Nd model ages, which is indicative of a significant change in provenance. This suggests that the Jangsan Formation predates the Myeonsan Formation. The Myobong Formation provides dominantly Meso- to Neoproterozoic U-Pb ages and Sm-Nd model ages that are slightly younger than those of the Myeonsan Formation. Contrary to the conventional wisdom, the combined evidence of unconformable contact and marked changes in zircon U-Pb ages and Nd isotopic compositions suggests that the Myobong Formation overlies the Jangsan and Myeonsan Formations unconformably. Considering the metamorphic age of the immediately underlying Precambrian basement metasediments (0.8 to 0.9 Ga), this stratigraphic relationship strongly suggests that the Jangsan Formation may be Neoproterozoic in age and that the Myeonsan Formation may be latest Neoproterozoic to Early Cambrian and calls for reevaluation of Precambrian-Paleozoic history of the Korean Peninsula. The

  4. Detrital zircon and apatite (U-Th)/He thermochronology of intercalated baked sediments: a new approach to dating young basalts

    Cooper, F. J.; van Soest, M. C.; Hodges, K.


    Placing accurate age constraints on young volcanic eruptions, particularly in populated areas such as New Mexico, is important for not only tectonic and climate studies, but also for geohazard analysis. A primary lack of zircon and apatite crystals in basaltic rocks leaves K/Ar and 40Ar/39Ar dating as the most favored methods, though extraneous Ar and low K contents can often reduce precision. Alternative techniques suggested in recent years include (U-Th)/He dating of U and Th rich inclusions in olivine phenocrysts and other phenocrysts (Min et al., 2006; Aciego et al., 2007), (U-Th)/He dating of zircon xenocrysts (Blondes et al., 2007), and (U-Th)/He dating of magnetite phenocrysts (Blackburn et al., 2007). Unfortunately, zircon xenocrysts are not very abundant in basalts, and not all basalts contain suitably sized olivine, magnetite, or other phenocrysts. Here, we present a new application of the (U-Th)/He method to dating young volcanic eruptions in an area where the emplacement of basalt flows has reset the (U-Th)/He systematics of zircons and apatites in intercalated baked sediments. The Taos Plateau volcanic field (TPVF) in New Mexico formed in Middle to Late Miocene time in association with extensional processes in the Rio Grande Rift. The voluminous (>200 km3) basalt flows of the TPVF have been carefully dated with 40Ar/39Ar (Appelt, 1998) and therefore provide a sound basis for comparison with the (U-Th)/He results. Two fluvial sand and gravel samples were collected from directly beneath the Upper member of the Servilleta Basalt (40Ar/39Ar age: 3.57 ± 0.19 Ma [2 S.E., n = 3]; Appelt, 1998) in the Rio Grande River Gorge just west of Taos. These two samples yielded a distinct population of single-crystal (U-Th)/He zircon and apatite ages of 3.54 ± 0.11 Ma [2 S.E., n = 4] and 3.44 ± 0.25 Ma [2 S.E., n = 2] respectively. Sixteen additional grains (6 zircons and 10 apatites) gave significantly older dates (~ 9 to 27 Ma). We interpret the older dates as

  5. The effect of molybdenum on niobium, titanium carbonitride precipitate evolution and grain refinement in high-temperature vacuum carburizing alloys

    Enloe, Charles M.

    Existing commercial carburizing alloys can be processed at higher temperatures and shorter processing times utilizing vacuum carburizing due to the suppression of intergranular oxidation. To provide resistance to undesired grain coarsening at these elevated temperatures and associated reduction in fatigue performance, microalloyed steel variants have been developed which employ fine Ti- and Nb-carbonitrides to suppress grain growth. Grain coarsening resistance is believed to be limited by the coarsening resistance of the precipitates themselves at high temperature, so further alloy/processing developments to enhance microalloy precipitate coarsening resistance based on a greater mechanistic understanding of solute interaction with microalloy precipitates would be beneficial. Molybdenum is known to affect microalloy precipitate evolution during processing in ferrite and austenite, but a unified explanation of the role of Mo in precipitate evolution is still lacking. Accordingly, the effect of molybdenum on microalloy precipitate size and composition evolutions and the associated onset of abnormal grain growth in austenite was investigated in Mo-bearing and Mo-free, Nb,Ti-microalloyed SAE 4120 steels. Molybdenum additions of 0.30 wt pct to alloys containing Nb additions of 0.05 and 0.10 wt pct Nb delayed the onset of abnormal grain growth in hot-rolled alloys reheated and soaked at 1050 °C and 1100 °C. The coarsening rate of microalloy precipitates was also reduced in Mo-bearing alloys relative to Mo-free alloys during isothermal soaking at 1050 °C, 1100 °C, and 1150 °C. The observed microalloy precipitate coarsening rates exceeded those predicted by the Lifshitz-Slyozov-Wagner relation for volume-diffusion-controlled coarsening, which is attributed to an initial bimodal precipitate size distribution prior to reheating to elevated temperature. Heat-treatments of hot-rolled alloys (tempering and solutionizing) prior to reheating to elevated temperature in

  6. Analysis of U-Pb, O, Hf, and trace elements of horizontally oriented outer and inner zones of zircons from the Boulder batholith, Montana

    Aleinikoff, J. N.; Lund, K.; Du Bray, E. A.; Wooden, J. L.; Kozdon, R.; Kita, N.; Valley, J. W.; Kamenov, G. D.; Mueller, P. A.


    The Late Cretaceous Boulder batholith, southwestern MT, is composed of the Butte Granite and at least a dozen smaller granodiorite to syenogranite plutons. These plutons (81-73 Ma) were dated by zircon U-Pb geochronology using the SHRIMP. Typically for SIMS analysis of igneous zircon, the analytical spot is located midway between core and rim on an area that displays fine oscillatory zoning, thus sampling a ~25-30 µm area of vertically oriented zones to a depth of 1-2 µm. For this study, preliminary LA-ICP-MS analysis of Hf isotopes in zircons from several plutons suggested that some grains show significant variation (>5 ɛHf unit