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Sample records for siliceous sinter deposit

  1. Compaction of lithium-silicate ceramics using spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Kubatík, Tomáš František; Lukáč, František; Mušálek, Radek; Brožek, Vlastimil; Stehlíková, K.; Chráska, Tomáš

    2017-01-01

    Roč. 61, č. 1 (2017), s. 40-44 ISSN 0862-5468 R&D Projects: GA ČR GB14-36566G Institutional support: RVO:61389021 Keywords : Li2Si2O5 * Li2SiO3 * Spark plasma sintering (SPS) * Quantitative Rietveld refinement * X-ray diffraction (XRD) Subject RIV: JG - Metallurgy OBOR OECD: Materials engineering Impact factor: 0.439, year: 2016 http://www.ceramics-silikaty.cz/index.php?page=cs_detail_doi&id=789

  2. Development of novel tricalcium silicate-based endodontic cements with sintered radiopacifier phase.

    Science.gov (United States)

    Xuereb, M; Sorrentino, F; Damidot, D; Camilleri, Josette

    2016-06-01

    All implants, bone and endodontic cements need to be sufficiently radiopaque to be able to be distinguished from neighbouring anatomical structures post-operatively. For this purpose, radiopacifying materials are added to the cements to render them sufficiently radiopaque. Bismuth oxide has been quite a popular choice of radiopacifier in endodontic materials. It has been shown to cause dental discoloration. The aim of this study was to develop, characterize and assess the properties of tricalcium silicate cement with alternative radiopacifiers, which are either inter-ground or sintered to the tricalcium silicate cement. Custom-made endodontic cements based on tricalcium silicate and 20 % barium, calcium or strontium zirconate, which were either inter-ground or sintered at high temperatures, were produced. The set materials stored for 28 days in Hank's balanced salt solution were characterized by scanning electron microscopy and X-ray diffraction analysis. Assessment of pH, leaching, interaction with physiological solution, radiopacity, setting time, compressive strength and material porosity were investigated. Mineral trioxide aggregate (MTA) Angelus was used as control. Addition of radiopacifying materials improved the radiopacity of the material. The sintered cements exhibited the formation of calcium zirconate together with the respective radiopacifier phase. All materials produced calcium hydroxide on hydration, which interacted with tissue fluids forming hydroxyapatite on the material surface. The physical properties of the tricalcium silicate-based cements were comparable to MTA Angelus. A novel method of producing radiopaque tricalcium silicate-based cements was demonstrated. The novel materials exhibited properties, which were either comparable or else improved over the control. The novel materials can be used to replace MTA for root-end filling, perforation repair and other clinical applications where MTA is indicated.

  3. Experimental measurements of the thermal conductivity of ash deposits: Part 2. Effects of sintering and deposit microstructure

    Energy Technology Data Exchange (ETDEWEB)

    A. L. Robinson; S. G. Buckley; N. Yang; L. L. Baxter

    2000-04-01

    The authors report results from an experimental study that examines the influence of sintering and microstructure on ash deposit thermal conductivity. The measurements are made using a technique developed to make in situ, time-resolved measurements of the effective thermal conductivity of ash deposits formed under conditions that closely replicate those found in the convective pass of a commercial boiler. The technique is designed to minimize the disturbance of the natural deposit microstructure. The initial stages of sintering and densification are accompanied by an increase in deposit thermal conductivity. Subsequent sintering continues to densify the deposit, but has little effect on deposit thermal conductivity. SEM analyses indicates that sintering creates a layered deposit structure with a relatively unsintered innermost layer. They hypothesize that this unsintered layer largely determines the overall deposit thermal conductivity. A theoretical model that treats a deposit as a two-layered material predicts the observed trends in thermal conductivity.

  4. Radiocarbon dating of silica sinter deposits in shallow drill cores from the Upper Geyser Basin, Yellowstone National Park

    Science.gov (United States)

    Lowenstern, Jacob B.; Hurwitz, Shaul; McGeehin, John P.

    2016-01-01

    To explore the timing of hydrothermal activity at the Upper Geyser Basin (UGB) in Yellowstone National Park, we obtained seven new accelerator mass spectrometry (AMS) radiocarbon 14C ages of carbonaceous material trapped within siliceous sinter. Five samples came from depths of 15-152 cm within the Y-1 well, and two samples were from well Y-7 (depths of 24 cm and 122 cm). These two wells, at Black Sand and Biscuit Basins, respectively, were drilled in 1967 as part of a scientific drilling program by the U.S. Geological Survey (White et al., 1975). Even with samples as small as 15 g, we obtained sufficient carbonaceous material (a mixture of thermophilic mats, pollen, and charcoal) for the 14C analyses. Apparent time of deposition ranged from 3775 ± 25 and 2910 ± 30 14C years BP at the top of the cores to about 8000 years BP at the bottom. The dates are consistent with variable rates of sinter formation at individual sites within the UGB over the Holocene. On a basin-wide scale, though, these and other existing 14C dates hint that hydrothermal activity at the UGB may have been continuous throughout the Holocene.

  5. Sintering of MnCo2O4 coatings prepared by electrophoretic deposition

    DEFF Research Database (Denmark)

    Bobruk, M.; Molin, Sebastian; Chen, Ming

    2018-01-01

    Sintering of MnCo2O4 coatings prepared by electrophoretic deposition on steel substrates has been studied in air and in reducing-oxidizing atmosphere. Effect of temperature and pO2 on the resulting coating density was evaluated from scanning electron microscopy images of polished cross sections...

  6. Stylolites, porosity, depositional texture, and silicates in chalk facies sediments

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke; Borre, Mai K.

    2007-01-01

    and sediments as counteracted by the pressure in the pore fluid, so the regional overpressure in the Central North Sea is one reason why the two localities have different relationships between temperature and effective burial stress. In the chalk of the Ontong Java Plateau the onset of calcite-silicate pressure......Comparison of chalk on the Ontong Java Plateau and chalk in the Central North Sea indicates that, whereas pressure dissolution is controlled by effective burial stress, pore-filling cementation is controlled by temperature. Effective burial stress is caused by the weight of all overlying water......-silica complexes causes an apparent super-saturation of Ca and retards cementation. The onset of massive pore-filling cementation at 1100 m bsf may be controlled by the temperature-dependent transition from opal-CT to quartz. In the stylolite-bearing chalk of two wells in the Gorm and Tyra fields, the nannofossil...

  7. Electrical Characterization of Ti-Silicate Films Grown by Atomic Layer Chemical Vapor Deposition

    Science.gov (United States)

    Lee, Seungjae; Yong, Kijung

    2007-08-01

    Electrical characterization was performed for Ti-silicate films, which were deposited by atomic layer chemical vapor deposition (ALCVD). Before the deposition of Ti-silicate films, the silicon substrates were pretreated differently using hydrofluoric acid (HF)-etching, chemical oxidation, and thermal oxidation. Regardless of the pretreatment methods, the grown films showed a highly smooth surface with rms below 0.52 nm. The electrical properties of the grown Ti-silicate films showed a strong dependence on the substrate pretreatments. The 5-nm-thick Ti-silicate films grown on hydrogen-passivated Si and chemically oxidized Si showed rather high leakage currents, whereas the films grown on thermally oxidized Si showed low leakage currents below 1× 10-7 A/cm2 at a bias of -1 V. All of the films showed a positive shift in the flatband voltage (VFB) upon annealing. Also, each film showed low a hysteresis below 180 mV and the hysteresis decreased upon annealing.

  8. The siliceous-calcareous-argillaceous rock type uranium deposit in south subzone of Western Qinling

    International Nuclear Information System (INIS)

    Qian Farong; Zhou Dean; Ji Hongfang

    1995-11-01

    The siliceous-calcareous-argillaceous rock type uranium deposit in south subzone of western Qinling is an inland found type deposit with specific mineralization and good potentiality. The mineralization distributes along definite horizons and occurs in siliceous layer and lenses of siliceous-calcareous rocks. Orebody presents in forms of stratoid, lenticular and irregular veins and controlled by factorial structures. Ore is identified as massive and sandy and each characterized by various mineral compositions and element associations. The study shows that the mineralizing materials are mainly derived from ore-bearing strata. The metallogenic environment has characteristics of middle-low temperature and supergene The metallogenesis underwent three stages: (1) Sedimentation-diagenesis of the ore-bearing strata led to preliminary concentration of uranium; (2) Polytectonic activities accompanied by underground hydrothermal process resulted in the industrial concentration of uranium; and (3) Orebody reworked by oxidation-denudation and leaching, locally has taken place secondary concentration. The deposit in origin attributes to polygenesis dominated by underground hydrothermal metallogenesis. Main metallogenic epoch happens during the periods of Late Yanshan and Himalayan. According to the geological-tectonic conditions the further prospecting direction in study area is proposed. (3 refs., 5 figs., 9 tabs.)

  9. Corrosion properties of aluminium coatings deposited on sintered NdFeB by ion-beam-assisted deposition

    Energy Technology Data Exchange (ETDEWEB)

    Mao Shoudong; Yang Hengxiu; Li Jinlong; Huang Feng [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 519 Zhuangshi Road, Ningbo 315201 (China); Song Zhenlun, E-mail: songzhenlun@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 519 Zhuangshi Road, Ningbo 315201 (China)

    2011-04-15

    Pure Al coatings were deposited by direct current (DC) magnetron sputtering to protect sintered NdFeB magnets. The effects of Ar{sup +} ion-beam-assisted deposition (IBAD) on the structure and the corrosion behaviour of Al coatings were investigated. The Al coating prepared by DC magnetron sputtering with IBAD (IBAD-Al-coating) had fewer voids than the coating without IBAD (Al-coating). The corrosion behaviour of the Al-coated NdFeB specimens was investigated by potentiodynamic polarisation, a neutral salt spray (NSS) test, and electrochemical impedance spectroscopy (EIS). The pitting corrosion of the Al coatings always began at the voids of the grain boundaries. Bombardment by the Ar{sup +} ion-beams effectively improved the corrosion resistance of the IBAD-Al-coating.

  10. CuFeO2 formation using fused deposition modeling 3D printing and sintering technique

    Science.gov (United States)

    Salea, A.; Dasaesamoh, A.; Prathumwan, R.; Kongkaew, T.; Subannajui, K.

    2017-09-01

    CuFeO2 is a metal oxide mineral material which is called delafossite. It can potentially be used as a chemical catalyst, and gas sensing material. There are methods to fabricate CuFeO2 such as chemical synthesis, sintering, sputtering, and chemical vapor deposition. In our work, CuFeO2 is prepared by Fused Deposition Modeling (FDM) 3D printing. The composite filament which composed of Cu and Fe elements is printed in three dimensions, and then sintered and annealed at high temperature to obtain CuFeO2. Suitable polymer blend and maximum percent volume of metal powder are studied. When percent volume of metal powder is increased, melt flow rate of polymer blend is also increased. The most suitable printing condition is reported and the properties of CuFeO2 are observed by Scanning Electron Microscopy, and Dynamic Scanning Calorimeter, X-ray diffraction. As a new method to produce semiconductor, this technique has a potential to allow any scientist or students to design and print a catalyst or sensing material by the most conventional 3D printing machine which is commonly used around the world.

  11. Aqueous deposition of calcium phosphates and silicate substituted calcium phosphates on magnesium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Satish S. [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Roy, Abhijit; Lee, Boeun [Department of Bioengineering University of Pittsburgh, Pittsburgh, PA 15261 (United States); Kumta, Prashant N., E-mail: pkumta@pitt.edu [Department of Chemical and Petroleum Engineering, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Bioengineering University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Craniofacial Regeneration, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Department of Mechanical Engineering and Materials Science, University of Pittsburgh, Pittsburgh, PA 15261 (United States); Center for Complex Engineered Multifunctional Materials, University of Pittsburgh, Pittsburgh, PA 15261 (United States)

    2011-12-15

    Attempts were made to deposit homogeneous films of calcium phosphates (CaPs) on two magnesium alloy systems, AZ31 and Mg-4Y, through an aqueous phosphating bath method. The deposition of silicate substituted CaPs by this aqueous method was also explored as silicate substitution is believed to increase the bioactivity of CaPs. The effect of doped and undoped coatings on the in vitro degradation and bioactivity of both alloy systems was studied. FTIR and EDX confirmed the deposition of Ca, P, and Si on both alloys and the coatings appeared to consist primarily biphasic mixtures of hydroxyapatite and {beta}-TCP. These largely inhomogeneous coatings, as observed by SEM, were not shown to have any significant effect on maintaining the physiological pH of the culture medium in comparison to the uncoated samples, as the pH remained approximately in the 8.4-8.7 range. Interestingly, despite similar pH profiles between the coated and uncoated samples, CaP coatings affected the degradation of both alloys. These doped and undoped calcium phosphate coatings were observed to decrease the degradation of AZ31 whereas they increased the degradation of Mg-4Y. In vitro studies on cell attachment using MC3T3-E1 mouse osteoblasts showed that between the uncoated alloys, Mg-4Y appeared to be the more biocompatible of the two. Silicate substituted CaP coatings were observed to increase the cell attachment on AZ31 compared to bare and undoped CaPs coated samples, but did not have as great of an effect on increasing cell attachment on Mg-4Y.

  12. A mid-Permian chert event: widespread deposition of biogenic siliceous sediments in coastal, island arc and oceanic basins

    Science.gov (United States)

    Murchey, B.L.; Jones, D.L.

    1992-01-01

    Radiolarian and conodont of Permian siliceous rocks from twenty-three areas in teh the circum-Pacific and Mediterranean regions reveal a widespread Permian Chert Event during the middle Leonardian to Wordian. Radiolarian- and (or) sponge spicule-rich siliceous sediments accumulated beneath high productivity zones in coastal, island arc and oceanic basins. Most of these deposits now crop out in fault-bounded accreted terranes. Biogenic siliceous sediments did not accumulate in terranes lying beneath infertile waters including the marine sequences in terranes of northern and central Alaska. The Permian Chert Event is coeval with major phosphorite deposition along the western margin of Pangea (Phosphoria Formation and related deposits). A well-known analogue for this event is middle Miocene deposition of biogenic siliceous sediments beneath high productivity zones in many parts of the Pacific and concurrent deposition of phosphatic as well as siliceous sediments in basins along the coast of California. Interrelated factors associated with both the Miocene and Permian depositional events include plate reorientations, small sea-level rises and cool polar waters. ?? 1992.

  13. Electrophoretic deposition of calcium silicate-reduced graphene oxide composites on titanium substrate

    DEFF Research Database (Denmark)

    Mehrali, Mehdi; Akhiani, Amir Reza; Talebian, Sepehr

    2016-01-01

    Calcium silicate (CS)/graphene coatings have been used to improve the biological and mechanical fixation of metallic prosthesis. Among the extraordinary features of graphene is its very high mechanical strength, which makes it an attractive nanoreinforcement material for composites. Calcium...... electrophoretic deposition (EPD). Compared to a pure CS coating on Ti, the CS-1. wt% rGO coating has improved adhesion by 70%, hardness by 150% and the elastic modulus by 240%. The CS-rGO composite coatings exhibit good apatite-forming ability in simulated body fluid (SBF). Moreover, the effect of addition of r...

  14. Coking- and sintering-resistant palladium catalysts achieved through atomic layer deposition.

    Science.gov (United States)

    Lu, Junling; Fu, Baosong; Kung, Mayfair C; Xiao, Guomin; Elam, Jeffrey W; Kung, Harold H; Stair, Peter C

    2012-03-09

    We showed that alumina (Al(2)O(3)) overcoating of supported metal nanoparticles (NPs) effectively reduced deactivation by coking and sintering in high-temperature applications of heterogeneous catalysts. We overcoated palladium NPs with 45 layers of alumina through an atomic layer deposition (ALD) process that alternated exposures of the catalysts to trimethylaluminum and water at 200°C. When these catalysts were used for 1 hour in oxidative dehydrogenation of ethane to ethylene at 650°C, they were found by thermogravimetric analysis to contain less than 6% of the coke formed on the uncoated catalysts. Scanning transmission electron microscopy showed no visible morphology changes after reaction at 675°C for 28 hours. The yield of ethylene was improved on all ALD Al(2)O(3) overcoated Pd catalysts.

  15. Functional properties of coated by chemical vapour deposition sintered tool materials investigated with use of tribological tests

    Directory of Open Access Journals (Sweden)

    J. Mikuła

    2017-01-01

    Full Text Available The purpose of the work is to present the results of investigations into the structure and properties of sintered carbides with deposited wear resistant coatings after a tribological test carried out with the method of combined examination of abrasion wear resistance and edge fracture resistance.

  16. An evaluation of the processing conditions, structure, and properties (biaxial flexural strength and antibacterial efficacy) of sintered strontium-zinc-silicate glass ceramics.

    Science.gov (United States)

    Looney, Mark; Shea, Helen O'; Gunn, Lynda; Crowley, Dolores; Boyd, Daniel

    2013-05-01

    The use of artificial bone grafts has increased in order to satisfy a growing demand for bone replacement materials. Initial mechanical stability of synthetic bone grafts is very advantageous for certain clinical applications. Coupled with the advantage of mechanical strength, a material with inherent antibacterial properties would be very beneficial. A series of strontium-doped zinc silicate (Ca-Sr-Na-Zn-Si) glass ceramics have been characterized in terms of their crystalline structure, biaxial flexural strength and antibacterial efficacy based on the identification of optimum sintering conditions. All three glass ceramics, namely, BT110, BT111, and BT112 were found to be fully crystalline, with BT111 and BT112 comprising of biocompatible crystalline phases. The biaxial flexural strengths of the three glass ceramics ranged from 70 to 149 MPa and were shown to be superior to those of clinically established ceramics in dry conditions and following incubation in simulated physiological conditions. The bacteriostatic effect for each glass ceramic was also established, where BT112 showed an inhibitory effect against three of the most common bacteria found at implantation sites, namely, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), and Pseudomonas aeruginosa. The results of the evaluation suggest that the materials studied offer advantages over current clinical materials and indicate the potential suitability of the glass ceramics as therapeutic bone grafts.

  17. Fundamental studies of the mechanisms of slag deposit formation: Studies on initiation, growth and sintering in the formation of utility boiler deposits: Topical technical report

    Energy Technology Data Exchange (ETDEWEB)

    Tangsathitkulchai, M.; Austin, L.G.

    1986-03-01

    Three laboratory-scale devices were utilized to investigate the mechanisms of the initiation, growth and sintering process involved in the formation of boiler deposits. Sticking apparatus investigations were conducted to study deposit initiation by comparing the adhesion behavior of the ash drops on four types of steel-based heat exchanger materials under the conditions found in a utility boiler and an entrained slagging gasifier. In addition, the adhesion behavior of the ash drops on a reduced steel surface were investigated. All the ash drops studied in this investigation were produced from bituminous coals.

  18. The integration of physical rock properties, mineralogy and geochemistry for the exploration of large zinc silicate deposits: A case study of the Vazante zinc deposits, Minas Gerais, Brazil

    Science.gov (United States)

    McGladrey, Alexandra J.; Olivo, Gema Ribeiro; Silva, Adalene Moreira; Oliveira, Gustavo Diniz; Neto, Basilio Botura; Perrouty, Stéphane

    2017-01-01

    The Vazante deposit, which is the world's largest zinc silicate deposit, occurs in brecciated dolomite and comprises mainly willemite with various proportions of hematite, Fe-carbonate, minor franklinite and magnetite. Exploration for this type of deposit is more challenging than zinc sulfide deposits, as they do not exhibit similar geophysical anomalies. To improve the application of geophysical surveys to the exploration of hypogene silicate zinc deposits, data from 475 samples were investigated from drill holes representative of the various types of ore and host rocks as well as barren zones of known geophysical anomalies in the Vazante District. Lithogeochemical and mineralogical (optical, SEM and MLA) data were integrated with physical rock properties (density, magnetic susceptibility and Ksbnd Usbnd Th gamma-ray spectrometry) to assist in exploring for this type of deposit. The most distinct physical property of the ore is density, compared with the host rocks due to high proportion of denser minerals (hematite and willemite). However, barren hematite breccias also have high densities. The zinc ore and hematite breccias yielded higher magnetic susceptibilities than the surrounding host rocks, with the highest values associated with greater proportions of franklinite and magnetite. The density and magnetic susceptibility contrasts are a result of hydrothermal fluids interacting with and altering the carbonate host rocks. Zinc ore also yielded elevated U concentrations relative to the various host rocks, yielding higher gamma-ray spectrometric values. The results of this investigation indicate that an integration of magnetic, gravimetric and radiometric surveys would be required to identify zinc silicate ore zones.

  19. An review on geology study of carbonaceous-siliceous-pelitic rock type uranium deposit in China and the strategy for its development

    International Nuclear Information System (INIS)

    Zhao Fengmin

    2009-01-01

    Carbonaceous-siliceous-pelitic rock type uranium deposit was founded by Chinese uranium geologist, it refers to the uranium deposit hosted by non or light metamophosed carbonate,siliceous rock, pelitic rock and their intermediates. It is one of the important types uranium deposit in China. A lot of this type deposits have been discovered in China and their temporal-spatial distribution pattern and mineralization features have been basically identified, and the rich experience have layed a good foundation for the future exploration. Although the ore of this type is not favourable economically, it is still available. Because carbonaceous-siliceous-pelitic rock type uranium deposit has great resource potential, metallogenic study and exploration efforts should be projected differentially according to their economic profit so as to meet the uranium resource demand of nuclear power development in China. (authors)

  20. Pulsed laser deposited amorphous chalcogenide and alumino-silicate thin films and their multilayered structures for photonic applications

    Energy Technology Data Exchange (ETDEWEB)

    Němec, P. [Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210 Pardubice (Czech Republic); Charrier, J. [FOTON, UMR CNRS 6082, Enssat, 6 rue de Kerampont, BP 80518, 22305 Lannion (France); Cathelinaud, M. [Missions des Ressources et Compétences Technologiques, UPS CNRS 2274, 92195 Meudon (France); Allix, M. [CEMHTI-CNRS, Site Haute Température, Orléans (France); Adam, J.-L.; Zhang, S. [Equipe Verres et Céramiques, UMR-CNRS 6226, Sciences Chimiques de Rennes (SCR), Université de Rennes 1, 35042 Rennes Cedex (France); Nazabal, V., E-mail: virginie.nazabal@univ-rennes1.fr [Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Studentská 573, 53210 Pardubice (Czech Republic); Equipe Verres et Céramiques, UMR-CNRS 6226, Sciences Chimiques de Rennes (SCR), Université de Rennes 1, 35042 Rennes Cedex (France)

    2013-07-31

    Amorphous chalcogenide and alumino-silicate thin films were fabricated by the pulsed laser deposition technique. Prepared films were characterized in terms of their morphology, chemical composition, and optical properties. Multilayered thin film stacks for reflectors and vertical microcavities were designed for telecommunication wavelength and the window of atmosphere transparency (band II) at 1.54 μm and 4.65 μm, respectively. Bearing in mind the benefit coming from the opportunity of an efficient wavelength tuning or, conversely, to stabilize the photoinduced effects in chalcogenide films as well as to improve their mechanical properties and/or their chemical durability, several pairs of materials from pure chalcogenide layers to chalcogenide/oxide layers were investigated. Different layer stacks were fabricated in order to check the compatibility between dissimilar materials which can have a strong influence on the interface roughness, adhesion, density, and homogeneity, for instance. Three different reflector designs were formulated and tested including all-chalcogenide layers (As{sub 40}Se{sub 60}/Ge{sub 25}Sb{sub 5}S{sub 70}) and mixed chalcogenide-oxide layers (As{sub 40}Se{sub 60}/alumino-silicate and Ga{sub 10}Ge{sub 15}Te{sub 75}/alumino-silicate). Prepared multilayers showed good compatibility between different material pairs deposited by laser ablation despite the diversity of chemical compositions. As{sub 40}Se{sub 60}/alumino-silicate reflector showed the best parameters; its stop band (R > 97% at 8° off-normal incidence) has a bandwidth of ∼ 100 nm and it is centered at 1490 nm. The quality of the different mirrors developed was good enough to try to obtain a microcavity structure for the 1.5 μm telecommunication wavelength made of chalcogenide layers. The microcavity structure consists of Ga{sub 5}Ge{sub 20}Sb{sub 10}S{sub 65} (doped with 5000 ppm of Er{sup 3+}) spacer surrounded by two 10-layer As{sub 40}Se{sub 60}/Ge{sub 25}Sb{sub 5}S{sub 70

  1. Microwave sintering of poly-ether-ether-ketone (PEEK) based coatings deposited on metallic substrate

    International Nuclear Information System (INIS)

    Zhang, G.; Leparoux, S.; Liao, H.; Coddet, C.

    2006-01-01

    In this paper, the feasibility of microwave (MW) sintering PEEK (poly-ether-ether-ketone) based coatings was investigated. Three coatings were studied: pure PEEK, micron-SiC and nano-SiC particles filled (wt.10%) PEEK coatings. The results indicate that, for the two composite coatings, the SiC particles distributed in the polymer matrix, as a good MW susceptor, could be heated preferentially by MW radiation. Consequently, the polymer matrix was heated by these particles

  2. Spark plasma sintering of cBN(core/SiO2(shell powder prepared by rotary chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Jianfeng Zhang

    2014-09-01

    Full Text Available SiO2 nanolayer coated cubic boron nitride (cBN, cBN(core/SiO2(shell powder, was prepared by rotary chemical vapor deposition. The cBN/SiO2 powder was densified by spark plasma sintering at 1873 K for 0.3 ks. The hexagonal boron nitride (hBN phase was not observed in the cBN–SiO2 composites, indicating that the SiO2 nanolayer depressed the phase transformation from cBN to hBN. The relative density of cBN–SiO2 increased with increasing SiO2 content (CSiO2. The highest hardness of the cBN–SiO2 composite was 17.5 GPa at CSiO2=38 wt% and a load of 0.98 N.

  3. Interface structure and properties of CNTs/Cu composites fabricated by electroless deposition and spark plasma sintering

    Science.gov (United States)

    Wang, Hu; Zhang, Zhao-Hui; Hu, Zheng-Yang; Song, Qi; Yin, Shi-Pan

    2018-01-01

    In this paper, we fabricated a novel copper matrix composites reinforced by carbon nanotubes (CNTs) using electroless deposition (ED) and spark plasma sintering technique. Microstructure, mechanical, electric conductivity, and thermal properties of the CNTs/Cu composites were investigated. The results show that a favorable interface containing C–O and O–Cu bond was formed between CNTs and matrix when the CNTs were coated with nano-Cu by ED method. Thus, we accomplished the uniformly dispersed CNTs in the CNTs/Cu powders and compacted composites, which eventually leads to the enhancement of the mechanical properties of the CNTs/Cu composites in the macro-scale environment. However, the interface structure can hinder the movement of carriers and free electrons and increase the interface thermal resistance, which leads to modest decrease of electrical and thermal conductivity of the CNTs/Cu composites.

  4. The relationship of carbonate-siliceous-pelitic uranium deposits with the plunging portions of down-faulted zones

    International Nuclear Information System (INIS)

    Liu Guihua; Liu Shouzhi; Zhou Huawen.

    1985-01-01

    Five uranium deposits of carbonate-siliceous-pelitic type occurred in different geological setting are studied. The geological data suggest that this type of uranium deposits is mostly located in the plunging portions of down-faulted zones. The cause of this kind of occurrence is tentatively discussed. It is proposed that uraniferous strata are the uranium source in deposits. The infiltration under arid climatic conditions promoted the uranium concentration up to ore grade. The mesozoic-cenozoic era which is characterized by the arid climate was the main ore-forming period. The converging condition of ground water in the plunging portions of down-faulted zones was better. Therefore, the plunging portions of down-faulted zones were more favourable for uranium ore formation compared with that of the uplifting portions. The preservation is the most important ore-controlling factor under the neotectonic movement and the plunging portions are the most favourable in this sence. The recognition criteria for the plunging portions of down-faulted zones which can be used in uranium exploration are proposed

  5. Solid oxide fuel cells with apatite-type lanthanum silicate-based electrolyte films deposited by radio frequency magnetron sputtering

    Science.gov (United States)

    Liu, Yi-Xin; Wang, Sea-Fue; Hsu, Yung-Fu; Wang, Chi-Hua

    2018-03-01

    In this study, solid oxide fuel cells (SOFCs) containing high-quality apatite-type magnesium doped lanthanum silicate-based electrolyte films (LSMO) deposited by RF magnetron sputtering are successfully fabricated. The LSMO film deposited at an Ar:O2 ratio of 6:4 on an anode supported NiO/Sm0.2Ce0·8O2-δ (SDC) substrate followed by post-annealing at 1000 °C reveals a uniform and dense c-axis oriented polycrystalline structure, which is well adhered to the anode substrate. A composite SDC/La0·6Sr0·4Co0·2Fe0·8O3-δ cathode layer is subsequently screen-printed on the LSMO deposited anode substrate and fired. The SOFC fabricated with the LSMO film exhibits good mechanical integrity. The single cell with the LSMO layer of ≈2.8 μm thickness reports a total cell resistance of 1.156 and 0.163 Ωcm2, open circuit voltage of 1.051 and 0.982 V, and maximum power densities of 0.212 and 1.490 Wcm-2 at measurement temperatures of 700 and 850 °C, respectively, which are comparable or superior to those of previously reported SOFCs with yttria stabilized zirconia electrolyte films. The results of the present study demonstrate the feasibility of deposition of high-quality LSMO films by RF magnetron sputtering on NiO-SDC anode substrates for the fabrication of SOFCs with good cell performance.

  6. The Setup Design for Selective Laser Sintering of High-Temperature Polymer Materials with the Alignment Control System of Layer Deposition

    Directory of Open Access Journals (Sweden)

    Alexey Nazarov

    2018-03-01

    Full Text Available This paper presents the design of an additive setup for the selective laser sintering (SLS of high-temperature polymeric materials, which is distinguished by an original control system for aligning the device for depositing layers of polyether ether ketone (PEEK powder. The kinematic and laser-optical schemes are given. The main cooling circuits are described. The proposed technical and design solutions enable conducting the SLS process in different types of high-temperature polymer powders. The principles of the device adjustment for depositing powder layers based on an integral thermal analysis are disclosed. The PEEK sinterability was shown on the designed installation. The physic-mechanical properties of the tested 3D parts were evaluated in comparison with the known data and showed an acceptable quality.

  7. Uranium-iron-silicate phases from the Balkan Metallogenic Zone and the Lenz im Kaltenegg (Styria, Austria) deposit

    International Nuclear Information System (INIS)

    Simova, F.G.

    1985-01-01

    The newly-found mineral phases of U 4+ of the UO 2 -FeO - SiO 2 homologuos series are reported. They have been established in a deposit of remobilized veinlet-disseminated type, falling within the scope of West-Balkan Metallogenic Zone and of the slightly metamorphized sedimentary type deposit, within the scope of the Semmering - Wechsel Massif, the Eastern Alpes. The presence of pyrite, hematite and peroxides, as well as uranium oxides and U-Fe silicates as small crystals determines the high iron content and radioactivity of the altered rocks. A complex of physical and chemical methods of investigation, radiography, scanning electron microscopy and X-ray microspectral analysis were employed to study the ore mineralization. Rour U-Fe-Si minerals, new to science, have been identified, one coming from Austria and three from the West-Balkan Metallogenic Zone of Bulgaria. The specific composition of the uranium mineralization made it possible to determine the Alpine and recent ages of the hydrothermal mineralization

  8. Electrochemically deposited sol-gel-derived silicate films as a viable alternative in thin-film design.

    Science.gov (United States)

    Deepa, P N; Kanungo, Mandakini; Claycomb, Greg; Sherwood, Peter M A; Collinson, Maryanne M

    2003-10-15

    Sol-gel-derived silicate films were electrochemically deposited on conducting surfaces from a sol consisting of tetramethoxysilane (TMOS). In this method, a sufficiently negative potential is applied to the electrode surface to reduce oxygen to hydroxyl ions, which serves as the catalyst for the hydrolysis and condensation of TMOS. The electrodeposition process was followed by the electrochemical quartz crystal microbalance and cyclic voltammetry. The electrodeposited films were characterized for their surface morphology, porosity, and film thickness using atomic force microscopy, electrochemical probe techniques, surface area and pore size analysis, and profilometry. The electrodeposited films were found to have a completely different surface structure and to be significantly rougher relative to spin-coated films. This is likely due in part to the separation of the gelation and evaporation stages of film formation. The electrodeposited films were found to be permeable to simple redox molecules, such as ruthenium(III) hexaammine and ferrocene methanol. Film thickness can be easily varied from 15 microm by varying the electrode potential from -600 mV to more than -1000 mV, respectively. The electrodeposition process was further applied for the electroencapsulation of redox molecules and organic dyes within the silicate network. Cyclic voltammograms for the gel-entrapped ferrocene methanol (FcCH2OH) and ruthenium(II) tris(bipyridine) (Ru(bpy)3(2+)) exhibited the characteristic redox behavior of the molecules. The electroencapsulation of organic dyes in their "native" form proved to be more difficult because these species typically contain reducible functionalities that change the structure of the dye.

  9. The Effect of Sintering Oxygen Partial Pressure on a SmBiO3 Buffer Layer for Coated Conductors via Chemical Solution Deposition

    Directory of Open Access Journals (Sweden)

    Xiaolei Zhu

    2016-10-01

    Full Text Available The application of high-temperature YBa2Cu3O7−δ (YBCO superconducting material is a considerable prospect for the growing energy shortages. Here, SmBiO3 (SBO films were deposited on (100-orientated yttrium-stabilized zirconia (YSZ simple crystal substrates via the chemical solution deposition (CSD approach for coated conductors, and the effects of sintering oxygen partial pressure on SBO films were studied. The crystalline structures and surface morphologies of SBO films were characterized by X-ray diffraction (XRD, scanning electron microscopy (SEM, and atomic force microscope (AFM. The optimized growth temperature, the intensity ratios of the SBO (200 peak to the SBO (111 peak, and the crystallinities of SBO films increased with the sintering oxygen partial pressure. The SEM and AFM images displayed a smooth and well-distributed surface in the argon atmosphere. The subsequent YBCO films with superconducting transition temperatures (Tc = 89.5 K, 90.2 K, and 86.2 K and critical current densities (Jc = 0.88 MA/cm2, 1.69 MA/cm2, and 0.09 MA/cm2; 77 K, self-field were deposited to further check the qualities of the SBO layer. These results indicated that sintering oxygen partial pressure had an effect on the epitaxial growth of the SBO buffer layer and YBCO superconducting properties. The experimental results may be a usable reference for the epitaxial growth of YBCO-coated conductors and other oxides.

  10. Investigation of Boron Thermal Diffusion from Atmospheric Pressure Chemical Vapor Deposited Boron Silicate Glass for N-Type Solar Cell Process Application

    Directory of Open Access Journals (Sweden)

    Ikuo Kurachi

    2016-01-01

    Full Text Available An atmospheric pressure chemical vapor deposition (AP-CVD system has been newly developed for boron silicate glass (BSG film deposition dedicating to solar cell manufacturing. Using the system, thermal boron diffusion from the BSG film is investigated and confirmed in terms of process stability for surface property before BSG deposition and BSG thickness. No degradation in carrier lifetime is also confirmed. A boron diffusion simulator has been newly developed and demonstrated for optimization of this process. Then, the boron thermal diffusion from AP-CVD BSG is considered to be the suitable method for N-type silicon solar cell manufacturing.

  11. Ash chemistry and sintering, verification of the mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Hupa, M.; Skrifvars, B.J. [Aabo Akademi, Turku (Finland)

    1996-12-01

    In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). In one part of study the melting behavior was calculated for ten biomass ashes and compared with lab measurements of sintering tendencies. The comparison showed that the T{sub 15} temperatures, i.e. those temperatures at which the ashes contained 15 % molten phase, correlated fairly well with the temperature at which the sintering measurements detected sintering. This suggests that partial melting can be predicted fairly accurate for some ashes already with the today existing thermodynamic calculation routines. In some cases, however the melting calculations did not correlate with the detected sintering temperatures. In a second part detailed measurements on ash behavior was conducted both in a semi full scale CFB and a lab scale FBC. Ashes and deposits were collected and analyzed in several different ways. These analyses show that the ash chemistry shifts radically when the fuel is shifted. Fuels with silicate based ashes behaved totally different than those with an oxide or salt based ash. The chemistry was also affected by fuel blending. The ultimate goal has been to be able to predict the ash thermal behavior during biomass thermal conversion, using the fuel and ash elemental analyses and a few operational key parameters as the only input data. This goal has not yet today been achieved. (author)

  12. High-rate deposition of Ta-doped SnO2 films by reactive magnetron sputtering using a Sn–Ta metal-sintered target

    International Nuclear Information System (INIS)

    Muto, Y.; Nakatomi, S.; Oka, N.; Iwabuchi, Y.; Kotsubo, H.; Shigesato, Y.

    2012-01-01

    Ta-doped SnO 2 films were deposited on glass substrate (either unheated or heated at 200 °C) by reactive magnetron sputtering with a Sn–Ta metal-sintered target using a plasma control unit (PCU) and mid-frequency (mf, 50 kHz) unipolar pulsing. The PCU feedback system precisely controlled the flow of the reactive and sputtering gases (O 2 and Ar, respectively) by monitoring either discharge impedance or the plasma emission of the atomic O* line at 777 nm. The planar target was connected to the switching unit, which was operated in unipolar pulse mode. Power density on the target was maintained at 4.4 W cm −2 during deposition. The lowest obtained resistivity for the films deposited on heated substrate was 6.4 × 10 −3 Ωcm, where the deposition rate was 250 nm min −1 .

  13. Preparation and characterization of amorphous SiO{sub 2} coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

    Energy Technology Data Exchange (ETDEWEB)

    Xu, J.L., E-mail: jlxu@nchu.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Xiao, Q.F.; Mei, D.D. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China); Zhong, Z.C., E-mail: zzhong2014@sina.com [The Institute for Rare Earth Magnetic Materials and Devices, Jiangxi University of Science and Technology, Ganzhou 341000 (China); Tong, Y.X. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Zheng, Y.F., E-mail: yfzheng@pku.edu.cn [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Li, L. [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China)

    2017-03-15

    Amorphous SiO{sub 2} coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO{sub 2} and a few amorphous Fe{sub 2}O{sub 3} and Nd{sub 2}O{sub 3}. The amorphous SiO{sub 2} coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO{sub 2} coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

  14. Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

    International Nuclear Information System (INIS)

    Xu, J.L.; Xiao, Q.F.; Mei, D.D.; Zhong, Z.C.; Tong, Y.X.; Zheng, Y.F.; Li, L.

    2017-01-01

    Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the “coral reef” like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 µm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO 2 and a few amorphous Fe 2 O 3 and Nd 2 O 3 . The amorphous SiO 2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees. - Highlights: • Amorphous SiO 2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation. • The coatings presented excellent thermal shock resistance. • The corrosion resistance could be enhanced by one order of magnitude. • The MAO coatings slightly decreased the magnetic properties of the NdFeB samples.

  15. Preparation and characterization of amorphous SiO2 coatings deposited by mirco-arc oxidation on sintered NdFeB permanent magnets

    Science.gov (United States)

    Xu, J. L.; Xiao, Q. F.; Mei, D. D.; Zhong, Z. C.; Tong, Y. X.; Zheng, Y. F.; Li, L.

    2017-03-01

    Amorphous SiO2 coatings were prepared on sintered NdFeB magnets by micro-arc oxidation (MAO) in silicate solution. The surface and cross-sectional morphologies, element and phase composition, corrosion resistance and magnetic properties of the coatings were investigated by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), X-ray photoelectron spectroscopy (XPS), potentiodynamic polarization test and physical properties measurements system (PPMS). The results showed that the surface morphologies of the coatings exhibited the "coral reef" like structure, different from the typical MAO porous structure. With increasing the voltages, the thickness of the coatings increased from 12.72 to 19.90 μm, the content of Si element increased, while the contents of Fe, Nd and P elements decreased. The coatings were mainly composed of amorphous SiO2 and a few amorphous Fe2O3 and Nd2O3. The amorphous SiO2 coatings presented excellent thermal shock resistance, while the thermal shock resistance decreased with increasing the voltages. The corrosion resistance of the coatings increased with increasing the voltages, and it could be enhanced by one order of magnitude compared to the uncoated NdFeB magnets. The MAO coatings slightly decreased the magnetic properties of the NdFeB samples in different degrees.

  16. Sinterable powders

    International Nuclear Information System (INIS)

    Zanghi, J.S.; Kasprzyk, M.R.

    1979-01-01

    A description is given of sinterable powders and methods of producing sintered products using such powders. The powders consist of (a) a particulate ceramic material, e.g. SiC, having specified particle size and surface area; (b) a carbon source material, e.g. sugar or a phenol-formaldehyde resin; and (c) a residue from a solution of H 3 BO 3 , B 2 O 3 , or mixtures of these as sintering aid. (U.K.)

  17. Immobilization of Uranium Silicides in Sintered Glass

    International Nuclear Information System (INIS)

    Mateos, P.; Russo, D.O.; Heredia, A.D.; Sanfilippo, M.

    2003-01-01

    High activity nuclear spent fuels vitrification by fusion is a well known technology which has industrial scale in France, England, Japan, EEUU. Borosilicates glasses are used in this process.Sintered glasses are an alternative to the immobilization task in which there is also a wide experience around the world.The available technics are: cold pressing and sintering , hot-pressing and hot isostatic pressing.This work compares Borosilicates and Iron silicates sintered glasses behaviour when different ammounts of nuclear simulated waste is added

  18. Exploration on relationship between uranium and organic materials in carbonate-siliceous pelite type uranium ore deposits

    International Nuclear Information System (INIS)

    Dong Yongjie

    1996-01-01

    The author determines the content of uranium and organic carbon of part specimen of surrounding rocks and ores, which sampled from carbonate and black shale type uranium deposits in Xiushui, Jiangxi Province, and Tongcheng, Hubei Province. According to the analytical operation regulations of organic materials, extraction and separation of chloroform pitch is carried out. Internal relationships between uranium and organic derivative is discussed. The conclusion shows that: (1) certain co-relationship between U and organic carbon and chloroform extract is detected; (2) evolutionary processes of organic materials in the exogenetic uranium deposits are not all the same; (3) non-hydrocarbon is closely related to uranium, so it can be regarded as indicator of uranium gathering in exogenetic uranium deposits

  19. Enhancement and retardation of thermal boron diffusion in silicon from atmospheric pressure chemical vapor deposited boron silicate glass film

    Science.gov (United States)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2014-03-01

    Thermal boron diffusion into silicon from boron silicate glass (BSG) prepared by atmospheric pressure CVD (AP-CVD) has been investigated in terms of the BSG boron concentration dependence on diffusion mechanism for N-type solar cell applications. With thermal diffusion at 950 °C in N2 for 20 min, the sheet resistance of the boron-diffused layer decreases with BSG boron concentration up to approximately 4 × 1021 cm-3 at which a boron-rich layer (BRL) is formed at the surface. However, the resistance increases with BSG boron concentration when the BSG boron concentration is higher than 4 × 1021 cm-3. It is also confirmed that the diffusion depth decreases with increasing BSG boron concentration within this BSG concentration region. To clarify this mechanism, the BSG boron concentration dependence on boron diffusivity has also been studied. From extracted diffusivities, the anomalous diffusion can be explained by silicon interstitials formed owing to kick-out by diffused boron atoms and by silicon interstitial generation-degradation due to BRL formation.

  20. Rapid assembly and rejuvenation of a large silicic magmatic system: Insights from mineral diffusive profiles in the Kidnappers and Rocky Hill deposits, New Zealand

    Science.gov (United States)

    Cooper, George F.; Morgan, Daniel J.; Wilson, Colin J. N.

    2017-09-01

    The timescales over which magmas in large silicic systems are reactivated, assembled and stored remains a fundamental question in volcanology. To address this question, we study timescales from Fe-Mg interdiffusion in orthopyroxenes and Ti diffusion in quartz from the caldera-forming 1200 km3 Kidnappers and 200 km3 Rocky Hill eruptions from the Mangakino volcanic centre (Taupo Volcanic Zone, New Zealand). The two eruptions came from the same source area, have indistinguishable 40Ar/39Ar ages (∼1.0 Ma) and zircon U-Pb age spectra, but their respective deposits are separated by a short period of erosion. Compositions of pumice, glass and mineral species in the collective eruption deposits define multiple melt dominant bodies but indicate that these shared a common magmatic mush zone. Diffusion timescales from both eruptions are used to build on chemical and textural crystal signatures and interpret both the crystal growth histories and the timing of magma accumulation. Fe-Mg interdiffusion profiles in orthopyroxenes imply that the three melt-dominant bodies, established through extraction of melt and crystals from the common source, were generated within 600 years and with peak accumulation rates within 100 years of each eruption. In addition, a less-evolved melt interacted with the Kidnappers magma, beginning ∼30 years prior to and peaking within 3 years of the eruption. This interaction did not directly trigger the eruption, but may have primed the magmatic system. Orthopyroxene crystals with the same zoning patterns from the Kidnappers and Rocky Hill pumices yield consistently different diffusion timescales, suggesting a time break between the eruptions of ∼20 years (from core-rim zones) to ∼10 years (outer rim zones). Diffusion of Ti in quartz reveals similarly short timescales and magmatic residence times of gestation time of the magmatic system of ∼200 kyr, as indicated by zircon age patterns. The magmatic system was able to recover after the

  1. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    Tsutsumi 1999; Xu et al 2008; Huang et al 2009). In vitro and in vivo investigations of a calcium magnesium silicate ... as a preparation process to produce homogeneous, very fine crystalline, unagglomerated, multicomponent oxide ... ing the oxides from sintering (Ekambaram and Patil 1995,. 1997; Chandrappa et al 1999).

  2. Constraints on silicates formation in the Si-Al-Fe system: Application to hard deposits in steam generators of PWR nuclear reactors

    Science.gov (United States)

    Berger, Gilles; Million-Picallion, Lisa; Lefevre, Grégory; Delaunay, Sophie

    2015-04-01

    Introduction: The hydrothermal crystallization of silicates phases in the Si-Al-Fe system may lead to industrial constraints that can be encountered in the nuclear industry in at least two contexts: the geological repository for nuclear wastes and the formation of hard sludges in the steam generator of the PWR nuclear plants. In the first situation, the chemical reactions between the Fe-canister and the surrounding clays have been extensively studied in laboratory [1-7] and pilot experiments [8]. These studies demonstrated that the high reactivity of metallic iron leads to the formation of Fe-silicates, berthierine like, in a wide range of temperature. By contrast, the formation of deposits in the steam generators of PWR plants, called hard sludges, is a newer and less studied issue which can affect the reactor performance. Experiments: We present here a preliminary set of experiments reproducing the formation of hard sludges under conditions representative of the steam generator of PWR power plant: 275°C, diluted solutions maintained at low potential by hydrazine addition and at alkaline pH by low concentrations of amines and ammoniac. Magnetite, a corrosion by-product of the secondary circuit, is the source of iron while aqueous Si and Al, the major impurities in this system, are supplied either as trace elements in the circulating solution or by addition of amorphous silica and alumina when considering confined zones. The fluid chemistry is monitored by sampling aliquots of the solution. Eh and pH are continuously measured by hydrothermal Cormet© electrodes implanted in a titanium hydrothermal reactor. The transformation, or not, of the solid fraction was examined post-mortem. These experiments evidenced the role of Al colloids as precursor of cements composed of kaolinite and boehmite, and the passivation of amorphous silica (becoming unreactive) likely by sorption of aqueous iron. But no Fe-bearing was formed by contrast to many published studies on the Fe

  3. Silicate calculi, a rare cause of kidney stones in children.

    Science.gov (United States)

    Taşdemir, Mehmet; Fuçucuoğlu, Dilara; Özman, Oktay; Sever, Lale; Önal, Bülent; Bilge, Ilmay

    2017-02-01

    Urinary silicate calculi in humans are extremely rare. Reported cases of silicate calculi are mostly documented in adults and are commonly related to an excessive intake of magnesium trisilicate in food or drugs. Published studies on the presence of silicate calculi in children are scarce. Three cases of silicate kidney stones without prior silicate intake are reported. Two patients underwent surgical treatment, and the third patient was treated using conservative methods. Urinalysis revealed no underlying metabolic abnormalities. Analyses revealed that silicate was the major component of the stones. Siliceous deposits in urinary stones may be more common than anticipated, and the underlying pathophysiology remains to be clarified.

  4. Sintering and densification; new techniques: sinter forging

    International Nuclear Information System (INIS)

    Winnubst, A.J.A.

    1998-01-01

    In this chapter pressure assisted sintering methods will be described. Attention will mainly be paid to sinter forging as a die-wall free uniaxial pressure sintering technique, where large creep strains are possible. Sinter forging is an effective tool to reduce sintering temperature and time and to obtain a nearly theoretically dense ceramic. In this way grain size in tetragonal zirconia ceramics can be reduced down to 100 nm. Another important phenomenon is the reduction of the number density and size of cracks and flaws resulting in higher strength and improved reliability, which is of utmost importance for engineering ceramics. The creep deformation during sinter forging causes a rearrangement of the grains resulting in a reduction of interatomic spaces between grains, while grain boundary (glassy) phases can be removed. The toughness and in some cases the wear resistance is enhanced after sinter forging as a result of the grain-boundary-morphology improvement. (orig.)

  5. Basic characteristics of Australian iron ore concentrate and its effects on sinter properties during the high-limonite sintering process

    Science.gov (United States)

    Liu, Dong-hui; Liu, Hao; Zhang, Jian-liang; Liu, Zheng-jian; Xue, Xun; Wang, Guang-wei; Kang, Qing-feng

    2017-09-01

    The basic characteristics of Australian iron ore concentrate (Ore-A) and its effects on sinter properties during a high-limonite sintering process were studied using micro-sinter and sinter pot methods. The results show that the Ore-A exhibits good granulation properties, strong liquid flow capability, high bonding phase strength and crystal strength, but poor assimilability. With increasing Ore-A ratio, the tumbler index and the reduction index (RI) of the sinter first increase and then decrease, whereas the softening interval (Δ T) and the softening start temperature ( T 10%) of the sinter exhibit the opposite behavior; the reduction degradation index (RDI+3.15) of the sinter increases linearly, but the sinter yield exhibits no obvious effects. With increasing Ore-A ratio, the distribution and crystallization of the minerals are improved, the main bonding phase first changes from silico-ferrite of calcium and aluminum (SFCA) to kirschsteinite, silicate, and SFCA and then transforms to 2CaO·SiO2 and SFCA. Given the utilization of Ore-A and the improvement of the sinter properties, the Ore-A ratio in the high-limonite sintering process is suggested to be controlled at approximately 6wt%.

  6. Silicate bonded ceramics of laterites

    International Nuclear Information System (INIS)

    Wagh, A.S.; Douse, V.

    1989-05-01

    Sodium silicate is vacuum impregnated in bauxite waste (red mud) at room temperature to develop ceramics of mechanical properties comparable to the sintered ceramics. For a concentration up to 10% the fracture toughness increases from 0.12 MNm -3/2 to 0.9 MNm -3/2 , and the compressive strength from 7 MNm -2 to 30 MNm -2 . The mechanical properties do not deteriorate, when soaked in water for an entire week. The viscosity and the concentration of the silicate solution are crucial, both for the success of the fabrication and the economics of the process. Similar successful results have been obtained for bauxite and lime stone, even though the latter has poor weathering properties. With scanning electron microscopy and energy dispersive analysis, an attempt is made to identify the crystals formed in the composite, which are responsible for the strength. The process is an economic alternative to the sintered ceramics in the construction industry in the tropical countries, rich in lateritic soils and poor in energy. Also the process has all the potential for further development in arid regions abundant in limestone. (author). 6 refs, 20 figs, 3 tabs

  7. Melting and Sintering of Ashes

    DEFF Research Database (Denmark)

    Hansen, Lone Aslaug

    1997-01-01

    , the biggest deviations being found for salt rich (i.e. straw derived) ashes.A simple model assuming proportionality between fly ash fusion and deposit formation was found to be capable of ranking deposition rates for the different straw derived fly ashes, whereas for the fly ashes from coal/straw co......-firing, the model only had a qualitative agreement with the measured ash deposit formation rates.Sintering measurements were carried out by means of compression strength testing of ash pellets. This method showed to not be applicable for the salt rich fly ash derived from straw combustion. For the fly ashes...... have been employed in a simple model for prediction of ash deposit formation, the results of which have been compared to ash deposition formation rates measured at the respective boilers.The ash fusion results were found to directly reflect the ash compositional data:a) Fly ashes and deposits from...

  8. Investigation of the hydration and bioactivity of radiopacified tricalcium silicate cement, Biodentine and MTA Angelus.

    Science.gov (United States)

    Camilleri, Josette; Sorrentino, François; Damidot, Denis

    2013-05-01

    calcium silicate was higher for Biodentine™ than for TCS-20-Z owing to its optimized particle size distribution, the presence of CaCO₃ and the use of CaCl₂. Tricalcium calcium silicate in MTA hydrated even more slowly than TCS-20-Z as evident from the size of reaction rim representative of calcium silicate hydrate (C-S-H) around tricalcium silicate grains and the calorimetry measurements. On the other hand, calcium oxide contained in MTA Angelus™ hydrated very fast inducing an intense exothermic reaction. Calcium hydroxide was produced as a by-product of reaction in all hydrated cements but in greater quantities in MTA due to the hydration of calcium oxide. This lead to less dense microstructure than the one observed for both Biodentine™ and TCS-20-Z. All the materials were bioactive and allowed the deposition of hydroxyapatite on the cement surface in the presence of simulated body fluid and the radiopacity was greater than 3mm aluminum thickness. All the cement pastes tested were composed mainly of tricalcium silicate and a radiopacifier. The laboratory manufactured cement contained no other additives. Biodentine™ included calcium carbonate which together with the additives in the mixing liquid resulted in a material with enhanced chemical properties relative to TCS-20-Z prototype cement. On the other hand MTA Angelus™ displayed the presence of calcium, aluminum and silicon oxides in the un-hydrated powder. These phases are normally associated with the raw materials indicating that the clinker of MTA Angelus™ is incompletely sintered leading to a potential important variability in its mineralogy depending on the sintering conditions. As a consequence, the amount of tricalcium silicate is less than in the two other cements leading to a slower reaction rate and more porous microstructure. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Thermal barrier coating resistant to sintering

    Science.gov (United States)

    Subramanian, Ramesh; Seth, Brij B.

    2004-06-29

    A device (10) is made, having a ceramic thermal barrier coating layer (16) characterized by a microstructure having gaps (18) with a sintering inhibiting material (22) disposed on the columns (20) within the gaps (18). The sintering resistant material (22) is stable over the range of operating temperatures of the device (10), is not soluble with the underlying ceramic layer (16) and is applied by a process that is not an electron beam physical vapor deposition process.

  10. Silicate glasses

    International Nuclear Information System (INIS)

    Lutze, W.

    1988-01-01

    Vitrification of liquid high-level radioactive wastes has received the greatest attention, world-wide, compared to any other HLW solidification process. The waste form is a borosilicate-based glass. The production of phosphate-based glass has been abandoned in the western world. Only in the Soviet Union are phosphate-based glasses still being developed. Vitrification techniques, equipment and processes and their remote operation have been developed and studied for almost thirty years and have reached a high degree of technical maturity. Industrial demonstration of the vitrification process has been in progress since 1978. This chapter is a survey of world-wide research and development efforts in nuclear waste glasses and its production technology. The principal glasses considered are silicate glasses which contain boron, i.e., borosilicate glasses

  11. Growth of superconducting Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} films by sedimentation deposition and liquid phase sintering and annealing technique

    Energy Technology Data Exchange (ETDEWEB)

    Manahan, R.L.C. [Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Llamas Science Hall, Rm. 3122, E. Quirino Street, Diliman, Quezon City 1101 (Philippines)]. E-mail: rcmanahan@nip.upd.edu.ph; Sarmago, R.V. [Condensed Matter Physics Laboratory, National Institute of Physics, University of the Philippines, Llamas Science Hall, Rm. 3122, E. Quirino Street, Diliman, Quezon City 1101 (Philippines)

    2006-10-01

    We report on a technique of growing highly c-axis oriented Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} (Bi-2212) thick films on MgO substrate using a combined sedimentation-deposition and liquid phase sintering and annealing process. The temperature profiles employed partial melting followed by rapid cooling to temperature below the melting point. Scanning electron micrographs show that the films have a smooth surface. No evidence of grain boundaries on the film's surface can be seen. The critical temperatures of the samples range from {approx}67 K to {approx}81 K. This method presents a quick and easy preparation for high quality epitaxial Bi-2212 films.

  12. Preparation and characterization of magnesium–aluminium–silicate ...

    Indian Academy of Sciences (India)

    A three-stage heating schedule involving calcination, nucleation and crystallization, has been evolved for the preparation of magnesium aluminium silicate (MAS) glass ceramic with MgF2 as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and ...

  13. Physical and electrical characteristics of atomic-layer-deposited Hf-silicate thin films using Hf[N(CH{sub 3})(C{sub 2}H{sub 5})]{sub 4} and SiH[N(CH{sub 3}){sub 2}]{sub 3} precursors

    Energy Technology Data Exchange (ETDEWEB)

    Chung, K. B.; Whang, C. N.; Yim, C. J.; Ko, D. H. [Yonsei University, Seoul (Korea, Republic of); Cho, M. H. [Korea Research Institute of Standards and Science, Daejeon (Korea, Republic of); Kim, Y. S.; Kim, M. J.; Lee, J. H.; Lee, N. I. [Samsung Electronics Co. Ltd., Yongin (Korea, Republic of)

    2006-04-15

    Hf-silicate films were grown by using atomic layer deposition with Hf[N(CH{sub 3})(C{sub 2}H{sub 5})]{sub 4} and SiH[N(CH{sub 3}){sub 2}]{sub 3} precursors. The composition of the Hf-silicate films was excellently well controlled by using the ratio of the deposition cycles of HfO{sub 2} and SiO{sub 2} (Hf/Si). The physical and the electrical characteristics of the Hf-silicate films were compared for Hf/Si = 3/1, Hf/Si = 1/1, and Hf/Si = 1/3. The relative Hf/(Hf+Si) compositions were 58 %, 41 %, and 25 % for Hf/Si = 3/1, Hf/Si = 1/1, and Hf/Si = 1/3, respectively. The binding characteristics of the Hf-silicate films were shifted in the direction of higher binding energy with increasing of SiO{sub 2} portion, resulting in electric charging. The molecular structure of the Hf-silicate films was changed by the relative compositions of HfO{sub 2} and SiO{sub 2}. In addition, the dielectric characteristics of the Hf-silicate films were directly proportional to the HfO{sub 2} portion.

  14. Deposition

    International Nuclear Information System (INIS)

    1984-01-01

    Monitoring of radionuclide contents in rainwater is a useful way to keep a check on any change in the external radiation dose caused by the deposited material. Thus analuses of 3 H, 89 Sr and 90 Sr as well as 137 Cs and other gamma radionuclide contents in deposition were continued both nationwide and in the vicinities of the nuclear power stations at Loviisa and Olkiluoto. The deposition of 90 Sr and 137 Cs was lower than in previous years, being only a small fraction of the highest deposition values measured in 1983. The tritium concentrations were also lower than in 1982. The total annual deposition of tritium at different sampling stations varied from 1.7 kBq/m 2 to 2.9 kBq/m 2

  15. Sintering of nonstoichiometric UO2

    International Nuclear Information System (INIS)

    Susnik, D.; Holc, J.

    1983-01-01

    Activated sintering of UO 2 pellets at 1100 deg C is described. In CO 2 atmosphere is UO 2 is nonstoichiometric and pellets from active UO 2 powders sinter at 900 deg C to high density. At 1100 deg C the final sintered density is practically achieved at heating on sintering temperature. After reduction and cooling in H 2 atmosphere which is followed sintering in CO 2 the structure is identical to the structured UO 2 pellets sintered at high temperature in H 2 . Density of activated sintered UO 2 pellets is stable, even after additional sintering at 1800 deg C. (author)

  16. Laser Sintered Calcium Phosphate Bone

    National Research Council Canada - National Science Library

    Vail, Neil

    1999-01-01

    ...) technology selective laser sintering (SLS). BME has successfully implemented a pilot facility to fabricate calcium phosphate implants using anatomical data coupled with the selective laser sintering process...

  17. A method for sintering

    DEFF Research Database (Denmark)

    2012-01-01

    The present invention provides a method for sintering, comprising in the following order the steps of: providing a body in the green state or in the pre-sintered state on a support; providing a load on at least one spacer on the support such that the load is located above said body in the green...

  18. Metasomatic silicate chemistry at the Bayan Obo Fe REE Nb deposit, Inner Mongolia, China: Contrasting chemistry and evolution of fenitising and mineralising fluids

    Science.gov (United States)

    Smith, M. P.

    2007-01-01

    Fenite aureoles around carbonatite dykes, and alteration associated with Fe-REE-Nb ore bodies at Bayan Obo, Inner Mongolia, China, show alkali silicate assemblages containing aegirine-augite, (magnesio-)riebeckite, (magnesio-)arfvedsonite, and phlogopite, accompanied by varying amounts of apatite, albite and quartz. In both fenites and orebodies simple thermodynamic constraints indicate mineral parageneses are consistent with rock buffered cooling accompanied by the infiltration of a range of externally buffered hydrothermal fluids. Statistical analysis of amphibole chemistry indicates that even in apparently texturally well constrained paragenetic stages wide variations in chemistry occur in both the ore bodies and fenites. Much of this variation is attributable to the Mg and F content of amphibole, and is therefore interpreted as a result of variation in externally controlled variables ( P, T, initial fluid composition) rather than internally controlled variables such as protolith composition. Similarities in chemistry exist between fenite and some ore body amphiboles. Thermodynamic analysis of the composition of biotite and apatite allows constraints to be placed on the F-content of hydrothermal fluids, and indicates relatively consistent compositions in fenites and orebodies (log aHF/ aH 2O = - 3.8 to - 3.6 at 300 °C and 1 kbar). Amphibole and biotite associated with niobate mineralization are both enriched in fluorine relative to the rest of the paragenesis, and biotite compositions indicate significantly higher HF activities in the hydrothermal fluid (log aHF/ aH 2O = - 2.6 at 300 °C and 1 kbar). The data presented here reinforce previous interpretations of the complex, multistage nature of mineralisation at Bayan Obo, but are still consistent with a direct involvement of carbonatite derived fluids during ore genesis.

  19. Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn–W deposit, Germany

    OpenAIRE

    T. Monecke; Peter Dulski; U. Kempe

    2007-01-01

    The chondrite-normalized rare earth element (REE) patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments, referred to as tetrads. In the present contribution, a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size. The method involves a detailed evaluation of element and sample specific random a...

  20. Sintering of beryllium oxide

    International Nuclear Information System (INIS)

    Caillat, R.; Pointud, R.

    1955-01-01

    This study had for origin to find a process permitting to manufacture bricks of beryllium oxide of pure nuclear grade, with a density as elevated as possible and with standardized shape. The sintering under load was the technique kept for the manufacture of the bricks. Because of the important toxicity of the beryllium oxide, the general features for the preliminary study of the sintering, have been determined while using alumina. The obtained results will be able to act as general indication for ulterior studies with sintering under load. (M.B.) [fr

  1. Silicate volcanism on Io

    Science.gov (United States)

    Carr, M. H.

    1986-03-01

    This paper is mainly concerned with the nature of volcanic eruptions on Io, taking into account questions regarding the presence of silicates or sulfur as principal component. Attention is given to the generation of silicate magma, the viscous dissipation in the melt zone, thermal anomalies at eruption sites, and Ionian volcanism. According to the information available about Io, it appears that its volcanism and hence its surface materials are dominantly silicic. Several percent of volatile materials such as sulfur, but also including sodium- and potassium-rich materials, may also be present. The volatile materials at the surface are continually vaporized and melted as a result of the high rates of silicate volcanism.

  2. Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn W deposit, Germany

    Science.gov (United States)

    Monecke, T.; Dulski, P.; Kempe, U.

    2007-01-01

    The chondrite-normalized rare earth element (REE) patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments, referred to as tetrads. In the present contribution, a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size. The method involves a detailed evaluation of element and sample specific random and systematic errors that are constrained on the basis of independent repeated preparations and analyses of sample and reference materials. Application of the proposed method to samples from the granite-hosted Zinnwald Sn-W deposit, Germany, revealed that at least two tetrads in normalized whole rock REE patterns have to be analytically significant to rule out that fractional crystallization led to the unusual behavior of the REEs. Based on the analysis of altered albite granite and greisen samples from the endocontact of the Zinnwald granite massif, it is demonstrated that the lanthanide tetrad effect is responsible for the formation of the convex tetrads. Geological and petrological evidence suggests that the tetrads in the samples developed prior to greisenization and related cassiterite precipitation. In contrast to the endocontact samples, the rhyolitic wall rocks are typified by normalized REE patterns having tetrads that are variable in size and frequently close to the limit of analytical significance. The sizes of the tetrads apparently correlate with the intensity of albitization, but show no relation to subsequent alteration processes including greisenization and low-temperature argillization. This observation proves that curved segments in normalized whole rock REE patterns can be introduced during hydrothermal fluid-rock interaction.

  3. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  4. Morphological analysis and modelling of sintering and of sintered materials

    International Nuclear Information System (INIS)

    Jernot, Jean-Paul

    1982-01-01

    This research thesis addresses the study of solid phase sintering of metallic powders, and aims at describing as precisely as possible the different involved matter transport mechanisms, first by using a thermodynamic approach to sintering. Sintering diagrams are also used to determine prevailing mechanisms. The microstructure of sintered materials has been studied by using image quantitative analysis, thus by using a morphological approach to sintering. Morphological parameters allow, on the one hand, the evolution of powders during sintering to be followed, and, on the other hand, sintered products to be correctly characterised. Moreover, the author reports the study of the evolution of some physical properties of sintered materials with respect to their microstructure parameters. This leads to the development of a modelling of the behaviour of these materials [fr

  5. Sintering of Synroc D

    International Nuclear Information System (INIS)

    Robinson, G.

    1982-01-01

    Sintering has been investigated as a method for the mineralization and densification of high-level nuclear defense waste powder. Studies have been conducted on Synroc D composite powder LS04. Optimal densification has been found to be highly dependent on the characteristics of the starting material. Powder subjected to milling, which was believed to reduce the level of agglomeration and possibly particle size, was found to densify better than powder not subjected to this milling. Densities of greater than 95% of theoretical could be achieved for samples sintered at 1150 to 1200 0 C. Mineralogy was found to be as expected for Synroc D for samples sintered in a CO 2 /CO atmosphere where the Fe +2 /Fe +3 ratio was maintained at 1.0 to 5.75. In a more oxidizing, pure CO 2 atmosphere a new phase, not previously identified in Synroc D, was found

  6. SinterHab

    Science.gov (United States)

    Rousek, Tomáš; Eriksson, Katarina; Doule, Ondřej

    2012-05-01

    This project describes a design study for a core module on a Lunar South Pole outpost, constructed by 3D printing technology with the use of in-situ resources and equipped with a bio-regenerative life support system. The module would be a hybrid of deployable (CLASS II) and in-situ built (CLASS III) structures. It would combine deployable membrane structures and pre-integrated rigid elements with a sintered regolith shell for enhanced radiation and micrometeorite shielding. The closed loop ecological system would support a sustainable presence on the Moon with particular focus on research activities. The core module accommodates from four to eight people, and provides laboratories as a test bed for development of new lunar technologies directly in the environment where they will be used. SinterHab also includes an experimental garden for development of new bio-regenerative life support system elements. The project explores these various concepts from an architectural point-of-view particularly, as they constitute the building, construction and interior elements. The construction method for SinterHab is based on 3D printing by sintering of the lunar regolith. Sinterator robotics 3D printing technology proposed by NASA JPL enables construction of future generations of large lunar settlements with little imported material and the use of solar energy. The regolith is processed, placed and sintered by the Sinterator robotics system which combines the NASA ATHLETE and the Chariot remotely controlled rovers. Microwave sintering creates a rigid structure in the form of walls, vaults and other architectural elements. The interior is coated with a layer of inflatable membranes inspired by the TransHab project. The life-support system is mainly bio-regenerative and several parts of the system are intrinsically multifunctional and serve more than one purpose. The plants for food production are also an efficient part of atmosphere revitalization and water treatment. Moreover

  7. Sintering and microstructure evolution of columnar nickel-based superalloy sheets prepared by EB-PVD

    International Nuclear Information System (INIS)

    Chen, S.; Qu, S.J.; Liang, J.; Han, J.C.

    2010-01-01

    Research highlights: → EB-PVD technology is commonly used to deposit thermal barrier coatings (TBCs) and columnar structure is commonly seen in EB-PVD condensates. The unique columnar structure can provide outstanding resistance against thermal shock and mechanical strains for TBCs. However, a number of researchers have found that the columnar structure can affect the mechanical properties of EB-PVD alloy thin sheet significantly. As yet, works on how to reduce this kind of effects are seldom done. In the present article, we tried to reveal the sintering effects on microstructure evolution and mechanical properties of columnar Ni-based superalloy sheet. The results suggests that after sintering, the columnar structure degrades. Degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering. - Abstract: A ∼0.15 mm-thick columnar nickel-based superalloy sheet was obtained by electron beam physical vapor deposition (EB-PVD). The as-deposited alloy sheet was sintered at different conditions. The microstructure of the specimens before and after sintering was characterized by using scanning electron microscopy. An X'Pert texture facility was used to determine the crystallographic orientation of the as-deposited alloy sheet. The phase transformation was investigated by X-ray diffraction. Tensile tests were conducted at room temperature on as-deposited and sintered specimens. The results show that the as-deposited sheet is composed of typical columnar structures. After sintering, however, the columnar structure degrades. The degradation depends on sintering temperature and time. Both the ultimate tensile strength and the elongation percentage are effectively improved after sintering.

  8. Chemical Stability between NiCr2O4 Material and Molten Calcium-Magnesium-Alumino-Silicate (CMAS at High Temperature

    Directory of Open Access Journals (Sweden)

    Zhuang Ma

    2017-12-01

    Full Text Available NiCr2O4 as a potential protection for thermal barrier coatings (TBCs against the attack of molten calcium-magnesium-alumino-silicate (CMAS was studied by a CMAS-contacting experiment. Atmospheric plasma sprayed coatings and sintered bulk materials were fabricated, covered with CMAS deposits, and exposed to 1200 °C for 24 h. Nano-sized CMAS-NiCr2O4 mixed powder was manufactured by ball milling and then conducted heat treatment under the same condition. The results show that no reacting product was found at the border between molten CMAS and NiCr2O4 and no element transportation occurred. It can be inferred that NiCr2O4 has outstanding chemical stability with the molten CMAS.

  9. Sintering of B4C by pressureless liquid phase sintering

    International Nuclear Information System (INIS)

    Rocha, Rosa Maria da; Melo, Francisco Cristovao Lourenco de

    2009-01-01

    The effect of three different sintering additive systems on densification of boron carbide powder was investigated. The sintering additives were Al 2 O 3 :Y 2 O 3 , AlN:Y 2 O 3 and BN:Y 2 O 3 compositions. Powder mixtures were prepared with 10 vol% of sintering aids following conventional powder technology processes. Samples were sintered by pressureless sintering at 2050 deg C/30min in argon atmosphere. Sintered samples were compared to a sintered B 4 C without sintering additive. Samples were characterized by XRD to analyze the crystalline phases after sintering and SEM to observe the microstructure and the second phase distribution. YB 4 and YB 2 C 2 were identified in all samples, indicating a reaction between Y 2 O 3 , B 4 C and B 2 O 3 present at the B 4 C particle surface. The best densification result was achieved with Al 2 O 3 :Y 2 O 3 additive system, showing 92.0 % of theoretical density, low porosity and 15.2 % of linear shrinkage. But this sample showed the highest weight loss. (author)

  10. Recovery of Al and Na Values from Red Mud by BaO-Na2CO3 Sinter Process

    Directory of Open Access Journals (Sweden)

    S.N. Meher

    2011-01-01

    Full Text Available The red mud BaO-Na2CO3 sinter process can be used in combination with the Bayer process to recover sodium and aluminium from the red mud waste and direct it back to the process stream. This is facilitated by the high temperature reaction of BaO-Na2CO3 and De-silication product (Sodalite (DSP in the red mud to produce an insoluble di-barium silicate, barium titanate, barium ferrite and a soluble sodium aluminate. A variation of the red mud BaO-Na2CO3 sintering process using half the barium oxide of existing methods has been investigated. The barium to silicon ratio was reduced from 2 to 1 producing a sodium barium silicate (Na2BaSiO4 rather than the di-barium silicate (Ba2SiO4 insoluble phase produced in the existing BaO-Na2CO3 sinter method. Synthetic BaO-Na2CO3 sinter products were investigated to understand the phases produced during sintering at varying temperatures and the chemistry of extraction. The target phases and morphological behaviors of sinter products were seen in XRD and SEM and the highest extractions were produced from a sinter temperature of 1000 °C for 4 h. A two-stage (105 °C / 60 min, 105 °C / 240 min water or caustic leaching process was found to be most effective for extraction. Sodium and aluminium extractions were 99% and 99.5% respectively. The experimental method devised was then used to treat red mud and the target phases were produced. An extraction of sodium and aluminium of 94% and 87% respectively was achieved. Silicon extractions were below 2%. Production benefits include sodium hydroxide savings, liquor burning, increased aluminium extraction and reduced cost of waste handling.

  11. Boric oxide or boric acid sintering aid for sintering ceramics

    International Nuclear Information System (INIS)

    Lawler, H.A.

    1979-01-01

    The invention described relates to the use of liquid sintering aid in processes involving sintering of ceramic materials to produce dense, hard articles having industrial uses. Although the invention is specifically discussed in regard to compositions containing silicon carbide as the ceramic material, other sinterable carbides, for example, titanium carbide, may be utilized as the ceramic material. A liquid sintering aid for densifying ceramic material is selected from solutions of H 3 BO 3 , B 2 O 3 and mixtures of these solutions. In sintering ceramic articles, e.g. silicon carbide, a shaped green body is formed from a particulate ceramic material and a resin binder, and the green body is baked at a temperature of 500 to 1000 0 C to form a porous body. The liquid sintering aid of B 2 O 3 and/or H 3 BO 3 is then dispersed through the porous body and the treated body is sintered at a temperature of 1900 to 2200 0 C to produce the sintered ceramic article. (U.K.)

  12. Sintering of magnesia: effect of additives

    Indian Academy of Sciences (India)

    % was studied on the sinter- ing and microstructural developments of the chemically pure magnesia using the pressureless sintering technique between 1500 and 1600◦C. Sintering was evaluated by per cent densification and microstructural ...

  13. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...... silicate nanocomposites and their structure-properties relationship. In the first part of the thesis, thermoplastic layered silicates were obtained by extrusion. Different modification methods were tested to observe the intercalation treatment effect on the silicate-modifier interactions. The silicate...... modification was studied at different silicate/modifier ratios and properties were investigated for obtained nanocomposites with different amounts of modified layered silicate loadings. The obtained nanocomposites presented improved mechanical properties such as toughness, stiffness or a good balance between...

  14. Laser sintering of copper nanoparticles

    International Nuclear Information System (INIS)

    Zenou, Michael; Saar, Amir; Ermak, Oleg; Kotler, Zvi

    2014-01-01

    Copper nanoparticle (NP) inks serve as an attractive potential replacement to silver NP inks in functional printing applications. However their tendency to rapidly oxidize has so far limited their wider use. In this work we have studied the conditions for laser sintering of Cu-NP inks in ambient conditions while avoiding oxidation. We have determined the regime for stable, low-resistivity copper (< ×3 bulk resistivity value) generation in terms of laser irradiance and exposure duration and have indicated the limits on fast processing. The role of pre-drying conditions on sintering outcome has also been studied. A method, based on spectral reflectivity measurements, was used for non-contact monitoring of the sintering process evolution. It also indicates preferred spectral regions for sintering. Finally, we illustrated how selective laser sintering can generate high-quality, fine line (<5 µm wide) and dense copper circuits. (paper)

  15. Silicates in Alien Asteroids

    Science.gov (United States)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  16. Measurement of the efficacy of calcium silicate for the protection and repair of dental enamel.

    Science.gov (United States)

    Parker, Alexander S; Patel, Anisha N; Al Botros, Rehab; Snowden, Michael E; McKelvey, Kim; Unwin, Patrick R; Ashcroft, Alexander T; Carvell, Mel; Joiner, Andrew; Peruffo, Massimo

    2014-06-01

    To investigate the formation of hydroxyapatite (HAP) from calcium silicate and the deposition of calcium silicate onto sound and acid eroded enamel surfaces in order to investigate its repair and protective properties. Calcium silicate was mixed with phosphate buffer for seven days and the resulting solids analysed for crystalline phases by Raman spectroscopy. Deposition studies were conducted on bovine enamel surfaces. Acid etched regions were produced on the enamel surfaces using scanning electrochemical cell microscopy (SECCM) with acid filled pipettes and varying contact times. Following treatment with calcium silicate, the deposition was visualised with FE-SEM and etch pit volumes were measured by AFM. A second set of bovine enamel specimens were pre-treated with calcium silicate and fluoride, before acid exposure with the SECCM. The volumes of the resultant acid etched pits were measured using AFM and the intrinsic rate constant for calcium loss was calculated. Raman spectroscopy confirmed that HAP was formed from calcium silicate. Deposition studies demonstrated greater delivery of calcium silicate to acid eroded than sound enamel and that the volume of acid etched enamel pits was significantly reduced following one treatment (pcalcium loss from enamel was 0.092 ± 0.008 cm/s. This was significantly reduced, 0.056 ± 0.005 cm/s, for the calcium silicate treatments (pCalcium silicate can transform into HAP and can be deposited on acid eroded and sound enamel surfaces. Calcium silicate can provide significant protection of sound enamel from acid challenges. Calcium silicate is a material that has potential for a new approach to the repair of demineralised enamel and the protection of enamel from acid attacks, leading to significant dental hard tissue benefits. © 2014 Elsevier Ltd. All rights reserved.

  17. INORGANIC PHOSPHORS IN GLASS BASED ON LEAD SILICATE GLASSES

    Directory of Open Access Journals (Sweden)

    V. A. Aseev

    2014-09-01

    Full Text Available We created and synthesized luminescent composite of the "phosphor in glass" type, based on the lead-silicate matrix and fine-dispersed powder of cerium-activated yttrium-aluminum garnet crystal. Lead-silicate system (40SiO2- 20PbO-(40-x PbF2-xAlF3, x = 0-25 was chosen as the glassy matrix. Initial glass was reduced to powder (frit for "phosphor in glass" composite with a particle size about 50 µm. Glass frit and powder of commercial YAG:Ce3+ phosphor were mixed in a ratio of 30 to 70 (wt %. Then this composite was pressed in a tablet and sintered on a quartz substrate at 823 К for 30 minutes. Thus, the plane parallel sheet for composite of the "phosphor in glass" was obtained with a diameter equal to 10 mm. For the purpose to reduce the loss of light in the presence of dispersion at a glass-phosphor boundary, optimization of glass mixture was done by adjusting the refractive index. X-ray phase and spectral-luminescent analysis of the derived composite were done. The results of these studies showed that there was no degradation of YAG: Ce powder during sintering. Dependence of luminescence intensity from temperature in the range from room temperature to 473 К was studied. It was shown, that with the phosphor in glass usage thermal quenching of luminescence was reduced in comparison with the silicone. The model of white LED was created with the "phosphor in glass" composite based on lead-silicate glasses with low temperature of vitrifying. The derived LED emits white light with a color temperature of 4370 K, and the luminous efficiency is equal to 58 lm/W. The developed luminescent composite based on the lead-silicate matrix can be used for the production of high-power white light LED.

  18. Models of current sintering

    Science.gov (United States)

    Angst, Sebastian; Engelke, Lukas; Winterer, Markus; Wolf, Dietrich E.

    2017-06-01

    Densification of (semi-)conducting particle agglomerates with the help of an electrical current is much faster and more energy efficient than traditional thermal sintering or powder compression. Therefore, this method becomes more and more common among experimentalists, engineers, and in industry. The mechanisms at work at the particle scale are highly complex because of the mutual feedback between current and pore structure. This paper extends previous modelling approaches in order to study mixtures of particles of two different materials. In addition to the delivery of Joule heat throughout the sample, especially in current bottlenecks, thermoelectric effects must be taken into account. They lead to segregation or spatial correlations in the particle arrangement. Various model extensions are possible and will be discussed.

  19. Production of pure sintered alumina

    International Nuclear Information System (INIS)

    Rocha, J.C. da; Huebner, H.W.

    1982-01-01

    With the aim of optimizing the sintering parameters, the strength of a large number of alumina samples was determined which were produced under widely varying sintering conditions and with different amounts of MgO content. The strength as a function of sintering time or temperature was found to go through a maximum. With increasing time, this maximum is shifted to lower temperatures, and with decreasing temperature to longer times. Data pairs of sintering times and temperatures which yeld the strength maximum were determined. The value of the strength at the maximum remains unchanged. The strength is high (= 400 MN/m 2 , at a grain size of 3 um and a porosity of 2 per cent) and comparable to foreign aluminas produced for commercial purposes, or even higher. The increase in the sintering time from 1 h to 16 h permits a reduction of the sintering temperature from 1600 to 1450 0 C without losing strength. The practical importance of this fact for a production of sintered alumina on a large scale is emphasized. (Author) [pt

  20. High activity wastes immobilization in sintered glasses: simulated wastes of the HWR (heavy water reactors) type in a new formulation glass

    International Nuclear Information System (INIS)

    Bevilacqua, A.M.; Messi de Bernasconi, N.B.; Audero, M.A.

    1987-01-01

    The new formulation of boron silicate glass, of German origin, SG7, was specifically developed for high activity wastes immobilization by a sintering process. Using the pressing technique at room temperature and subsequent sintering, the sintering conditions of the pure glass and the incorporation of the 10% in weight of simulated wastes of the HWR type recently developed, have been studied. Besides, three ways of incorporation of wastes are presented: a) incorporation of a coincidental compound obtained from chemical and thermal denitration; b) incorporation of a calcination only obtained from thermal denitration; c) incorporation of the nitric solution, mixing this one with the glass, and subsequent calcination. The results from the sintering studies and from the leaching assays of the MCC-1 are presented, and the microstructures observed are described. These results are compared with those previously obtained from boron silicate glasses of the VG type. Finally, results from long duration leaching assays, performed in samples obtained years before, are presented. (Author)

  1. CdS sintered films: growth and characteristics

    International Nuclear Information System (INIS)

    Sharma, Monika; Kumar, Sushil; Sharma, L.M.; Sharma, T.P.; Husain, M.

    2004-01-01

    Cadmium sulphide finds extensive applications in a variety of optoelectronic devices. CdS, with a band gap of 2.43 eV, is a suitable window material in heterojunction solar cells that employ CdTe, Cu 2 S or CuInSe 2 as an absorber. Polycrystalline films of CdS, thickness ∼15 μm, were grown onto chemically clean and optically plane glass substrates by sintering process. A 10 min sintering time and 500 deg. C sintering temperature were found to be optimum. As deposited films were characterized through optical, structural and electrical transport properties using optical reflection spectroscopy, X-ray diffractometry and I-V characteristics techniques

  2. Influence of silicate on the transport of bacteria in quartz sand and iron mineral-coated sand.

    Science.gov (United States)

    Dong, Zhe; Yang, Haiyan; Wu, Dan; Ni, Jinren; Kim, Hyunjung; Tong, Meiping

    2014-11-01

    The influence of silicate on the transport and deposition of bacteria (Escherichia coli) in packed porous media were examined at a constant 20 mM ionic strength with different silicate concentrations (from 0 to 1 mM) at pH 7. Transport experiments were performed in two types of representative porous media, both bare quartz sand and iron mineral-coated quartz sand. In bare quartz sand, the breakthrough plateaus in the presence of silicate in suspensions were lower and the corresponding retained profiles were higher than those without silicate ions, indicating that the presence of silicate in suspensions decreased cell transport in bare quartz sand. Moreover, the decrease of bacteria transport in quartz sand induced by silicate was more pronounced with increasing silicate concentrations from 0 to 1 mM. However, when EPS was removed from cell surfaces, the presence of silicate in cell suspensions (with different concentrations) did not affect the transport behavior of bacteria in quartz sand. The interaction of silicate with EPS on cell surfaces negatively decreased the zeta potentials of bacteria, resulting in the decreased cell transport in bare quartz sand when silicate was copresent in bacteria suspensions. In contrast, the presence of silicate in suspensions increased cell transport in iron mineral-coated sand. Silicate ions competed with bacteria for the adsorption sites on mineral-coated sand, contributing to the increased cell transport in mineral-coated sand with silicate present in cell suspensions. Copyright © 2014 Elsevier B.V. All rights reserved.

  3. Mineralogy and microstructure of sintered lignite coal fly ash

    Energy Technology Data Exchange (ETDEWEB)

    Marina Ilic; Christopher Cheeseman; Christopher Sollars; Jonathan Knight [Faculty of Technology and Metallurgy, Belgrade (Yugoslavia)

    2003-02-01

    Lignite coal fly ash from the 'Nikola Tesla' power plant in Yugoslavia has been characterised, milled, compacted and sintered to form monolithic ceramic materials. The effect of firing at temperatures between 1130 and 1190{sup o}C on the density, water accessible porosity, mineralogy and microstructure of sintered samples is reported. This class C fly ash has an initial average particle size of 82 {mu}m and contains siliceous glass together with the crystalline phases quartz, anorthite, gehlenite, hematite and mullite. Milling the ash to an average particle size of 5.6 m, compacting and firing at 1170{sup o}C for 1 h produces materials with densities similar to clay-based ceramics that exhibit low water absorption. Sintering reduces the amount of glass, quartz, gehlenite and anhydrite, but increases formation of anorthite, mullite, hematite and cristobalite. SEM confirms the formation of a dense ceramic at 1170{sup o}C and indicates that pyroplastic effects cause pore formation and bloating at 1190{sup o}C. 23 refs., 6 figs., 2 tabs.

  4. Decreased water flowing from a forest amended with calcium silicate

    Science.gov (United States)

    Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg

    2013-01-01

    Acid deposition during the 20th century caused widespread depletion of available soil calcium (Ca) throughout much of the industrialized world. To better understand how forest ecosystems respond to changes in a component of acidification stress, an 11.8-ha watershed was amended with wollastonite, a calcium silicate mineral, to restore available soil Ca to preindustrial...

  5. The sintering of nitrogen ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Hampshire, S.

    1986-01-01

    The mechanism of densification with oxide additives and the role of the ..cap alpha..-BETA phase transformation is investigated in a detailed kinetic study. Selected compositions in the Si-Al-O-N system are detailed, with and without additives. Although the work is mainly concerned with the identification of the mechanisms of sintering, some property measurements on a sintered BETA-sialon are reported and the feasibility of preparing pure ..cap alpha..-sialon phases is explored.

  6. Method of sintering ceramic materials

    Science.gov (United States)

    Holcombe, Cressie E.; Dykes, Norman L.

    1992-01-01

    A method for sintering ceramic materials is described. A ceramic article is coated with layers of protective coatings such as boron nitride, graphite foil, and niobium. The coated ceramic article is embedded in a container containing refractory metal oxide granules and placed within a microwave oven. The ceramic article is heated by microwave energy to a temperature sufficient to sinter the ceramic article to form a densified ceramic article having a density equal to or greater than 90% of theoretical density.

  7. Sintering of manganese ore in natura with different additions on activated carbon

    International Nuclear Information System (INIS)

    Lima, M.M.F.; Mapa, T.F.M.; Lima, R.M.F.

    2016-01-01

    Full text: The shortage of high grade manganese ore and the importance of economically viable processes suggest a necessity of the recovery of ore residues. So, this work presents a route to obtain by-products of economic interest from manganese ore residues in bench scale. The objective was the sintering of manganese ore in natura using a particle size below 0,037μm with different additions of activated carbon. For this, the fine residues were calcined at 800°C during 60 minutes, homogenized in an agate mortar with 12% humidity and additions of 9 and 12% of activated carbon. After homogenization, the sintering process was carried out at 1145°C and 1155°C during 5, 15 and 30 minutes at natural air. The products sintered were characterized by bulk density, BET surface area, OM, SEM / EDS and diffraction X-rays. During the calcination of the ore, the mass loss was (15.16 ± 0.02)% due to the elimination of volatiles and water. The surface area of the ore was reduced due to the diffusion process that occurred during sintering. While, the bulk density values had little variation, around (3.51 ± 0.06)g/cm³. The analyses of micro-regions EDS showed that the matrix is a silicate with a high Mn content. It was identified yet, other silicates with different proportions of Si, Al, Ti, Na, Mn, Mg and Ca. (author)

  8. Sintering of manganese ore in natura with different additions on activated carbon

    Energy Technology Data Exchange (ETDEWEB)

    Lima, M.M.F.; Mapa, T.F.M.; Lima, R.M.F. [Universidade Federal de Ouro Preto (UFOP), MG (Brazil)

    2016-07-01

    Full text: The shortage of high grade manganese ore and the importance of economically viable processes suggest a necessity of the recovery of ore residues. So, this work presents a route to obtain by-products of economic interest from manganese ore residues in bench scale. The objective was the sintering of manganese ore in natura using a particle size below 0,037μm with different additions of activated carbon. For this, the fine residues were calcined at 800°C during 60 minutes, homogenized in an agate mortar with 12% humidity and additions of 9 and 12% of activated carbon. After homogenization, the sintering process was carried out at 1145°C and 1155°C during 5, 15 and 30 minutes at natural air. The products sintered were characterized by bulk density, BET surface area, OM, SEM / EDS and diffraction X-rays. During the calcination of the ore, the mass loss was (15.16 ± 0.02)% due to the elimination of volatiles and water. The surface area of the ore was reduced due to the diffusion process that occurred during sintering. While, the bulk density values had little variation, around (3.51 ± 0.06)g/cm³. The analyses of micro-regions EDS showed that the matrix is a silicate with a high Mn content. It was identified yet, other silicates with different proportions of Si, Al, Ti, Na, Mn, Mg and Ca. (author)

  9. Natural Weathering Rates of Silicate Minerals

    Science.gov (United States)

    White, A. F.

    2003-12-01

    activities. For example, Huntington et al. (2000) show that extensive timber harvesting in the southeastern forests of the United States, which are underlain by intensely weathered saprolites, produces net calcium exports that exceed inputs from weathering, thus creating a long-term regional problem in forest management.The role of chemical weathering has long been recognized in economic geology. Tropical bauxites, which account for most of world's aluminum ores, are typical examples of residual concentration of silicate rocks by chemical weathering over long time periods (Samma, 1986). Weathering of ultramafic silicates such as peridotites forms residual lateritic deposits that contain significant deposits of nickel and cobalt. Ores generated by chemical mobilization include uranium deposits that are produced by weathering of granitic rocks under oxic conditions and subsequent concentration by sorption and precipitation ( Misra, 2000).Over the last several decades, estimating rates of silicate weathering has become important in addressing new environmental issues. Acidification of soils, rivers, and lakes has become a major concern in many parts of North America and Europe. Areas at particular risk are uplands where silicate bedrock, resistant to chemical weathering, is overlain by thin organic-rich soils (Driscoll et al., 1989). Although atmospheric deposition is the most important factor in watershed acidification, land use practices, such as conifer reforestation, also create acidification problems ( Farley and Werritty, 1989). In such environments, silicate hydrolysis reactions are the principal buffer against acidification. As pointed out by Drever and Clow (1995), a reasonable environmental objective is to decrease the inputs of acidity such that they are equal to or less than the rate of neutralization by weathering in sensitive watersheds.The intensive interest in past and present global climate change has renewed efforts to understand quantitatively feedback

  10. Selective light sintering of Aerosol-Jet printed silver nanoparticle inks on polymer substrates

    Energy Technology Data Exchange (ETDEWEB)

    Schuetz, K., E-mail: klaus.schuetz1@gmx.de, E-mail: hoerber@faps.uni-erlangen.de, E-mail: franke@faps.uni-erlangen.de; Hoerber, J., E-mail: klaus.schuetz1@gmx.de, E-mail: hoerber@faps.uni-erlangen.de, E-mail: franke@faps.uni-erlangen.de; Franke, J., E-mail: klaus.schuetz1@gmx.de, E-mail: hoerber@faps.uni-erlangen.de, E-mail: franke@faps.uni-erlangen.de [Institute for Factory Automation and Production Systems, University of Erlangen-Nuremberg (Germany)

    2014-05-15

    Printing silver nanoparticle inks to generate conductive structures for electronics on polymer substrates has gained increasing relevance in recent years. In this context, the Aerosol-Jet Technology is well suited to print silver ink on 3D-Molded Interconnect Devices (MID). The deposited ink requires thermal post-treatment to obtain sufficient electrical conductivity and adhesion. However, commonly used oven sintering cannot be applied for many thermoplastic substrates due to low melting temperatures. In this study a new sintering technology, selective light sintering, is presented, based on the focused, continuous light beam of a xenon lamp. Sintering experiments were conducted with Aerosol-Jet printed structures on various polycarbonate (PC) substrates. Especially on neat, light transparent PC, silver tracks were evenly sintered with marginal impact to the substrate. Electrical conductivities significantly exceed the values obtained with conventional oven sintering. Adhesive strength is sufficient for conductive tracks. Experiments with non-transparent PC substrates led to substrate damage due to increased light absorption. Therefore a concept for a variation of light sintering was developed, using optical filters. First experiments showed significant reduction of substrate damage and good sintering qualities. The highly promising results of the conducted experiments provide a base for further investigations to increase adhesion and qualifying the technology for MID applications and a broad spectrum of thermoplastic substrates.

  11. Selective light sintering of Aerosol-Jet printed silver nanoparticle inks on polymer substrates

    International Nuclear Information System (INIS)

    Schuetz, K.; Hoerber, J.; Franke, J.

    2014-01-01

    Printing silver nanoparticle inks to generate conductive structures for electronics on polymer substrates has gained increasing relevance in recent years. In this context, the Aerosol-Jet Technology is well suited to print silver ink on 3D-Molded Interconnect Devices (MID). The deposited ink requires thermal post-treatment to obtain sufficient electrical conductivity and adhesion. However, commonly used oven sintering cannot be applied for many thermoplastic substrates due to low melting temperatures. In this study a new sintering technology, selective light sintering, is presented, based on the focused, continuous light beam of a xenon lamp. Sintering experiments were conducted with Aerosol-Jet printed structures on various polycarbonate (PC) substrates. Especially on neat, light transparent PC, silver tracks were evenly sintered with marginal impact to the substrate. Electrical conductivities significantly exceed the values obtained with conventional oven sintering. Adhesive strength is sufficient for conductive tracks. Experiments with non-transparent PC substrates led to substrate damage due to increased light absorption. Therefore a concept for a variation of light sintering was developed, using optical filters. First experiments showed significant reduction of substrate damage and good sintering qualities. The highly promising results of the conducted experiments provide a base for further investigations to increase adhesion and qualifying the technology for MID applications and a broad spectrum of thermoplastic substrates

  12. Synthesis of radium silicate

    International Nuclear Information System (INIS)

    Garibov, A.A; Agayev, T.N; Mansimov, Z.A

    2010-01-01

    Full text :One of the possible ways of implementation of the processes of molecular hydrogen radiologic of the elements in the differential heat of water as a catalyst for the collapse of the creation of a special nuclear reactors. A chemical process in radiation-4-oxide-silicon compounds, which is one of the radium, is of great importance. Research in the silicon-oxide-radiumun different activity-4 has been synthesized. As initial substances for the synthesis of tetra etiolate silicate and radium chloride solutions were used. At the same time to remove reaction products from the reaction intermediate in acetate acid was used. The intermediate product was reacted with ethyl alcohol ethyl acetate ether acetate acid that forms from the reaction of the temperature effect is broken. As a result, 4-oxide was initially pure silicon.

  13. Sintering diagrams of UO2

    International Nuclear Information System (INIS)

    Mohan, A.; Soni, N.C.; Moorthy, V.K.

    1979-01-01

    Ashby's method (see Acta Met., vol. 22, p. 275, 1974) of constructing sintering diagrams has been modified to obtain contribution diagrams directly from the computer. The interplay of sintering variables and mechanisms are studied and the factors that affect the participation of mechanisms in UO 2 are determined. By studying the physical properties, it emerges that the order of inaccuracies is small in most cases and do not affect the diagrams. On the other hand, even a 10% error in activation energies, which is quite plausible, would make a significant difference to the diagram. The main criticism of Ashby's approach is that the numerous properties and equations used, communicate their inaccuracies to the diagrams and make them unreliable. The present study has considerably reduced the number of factors that need to be refined to make the sintering diagrams more meaningful. (Auth.)

  14. Recycling of mill scale in sintering process

    Directory of Open Access Journals (Sweden)

    El-Hussiny N.A.

    2011-01-01

    Full Text Available This investigation deals with the effect of replacing some amount of Baharia high barite iron ore concentrate by mill scale waste which was characterized by high iron oxide content on the parameters of the sintering process., and investigation the effect of different amount of coke breeze added on sintering process parameters when using 5% mill scale waste with 95% iron ore concentrate. The results of this work show that, replacement of iron ore concentrate with mill scale increases the amount of ready made sinter, sinter strength and productivity of the sinter machine and productivity at blast furnace yard. Also, the increase of coke breeze leads to an increase the ready made sinter and productivity of the sintering machine at blast furnace yard. The productivity of the sintering machine after 5% decreased slightly due to the decrease of vertical velocity.

  15. Phosphorus containing sintered alloys (review)

    International Nuclear Information System (INIS)

    Muchnik, S.V.

    1984-01-01

    Phosphorus additives are considered for their effect on the properties of sintered alloys of different applications: structural, antifriction, friction, magnetic, hard, superhard, heavy etc. Data are presented on compositions and properties of phosphorus-containing materials produced by the powder metallurgy method. Phosphorus is shown to be an effective activator of sintering in some cases. When its concentration in the material is optimal it imparts the material such properties as strength, viscosity, hardness, wear resistance. Problems concerning powder metallurgy of amorphous phosphorus-containing alloys are reported

  16. Environmental silicate nano-biocomposites

    CERN Document Server

    Pollet, Eric

    2012-01-01

    Environmental Silicate Nano-Biocomposites focuses on nano-biocomposites, which are obtained by the association of silicates such as bioclays with biopolymers. By highlighting recent developments and findings, green and biodegradable nano-composites from both renewable and biodegradable polymers are explored. This includes coverage of potential markets such as packaging, agricultures, leisure and the fast food industry. The knowledge and experience of more than twenty international experts in diverse fields, from chemical and biochemical engineering to applications, is brought together in four different sections covering: Biodegradable polymers and Silicates, Clay/Polyesters Nano-biocomposites, Clay/Agropolymers Nano-biocomposites, and Applications and biodegradation of Nano-biocomposites. By exploring the relationships between the biopolymer structures, the processes, and the final properties Environmental Silicate Nano-Biocomposites explains how to design nano-materials to develop new, valuable, environmenta...

  17. Radioanalysis of siliceous materials

    International Nuclear Information System (INIS)

    Das, H.A.

    2003-01-01

    Both natural and induced radioactivity as well as man-made radiotracers may be applied to assess quality and its maintenance a widely varying range of siliceous materials. One example of industrial application is given for each of these three branches. Natural Radioactivity: The measurement of 222-Rn emanation from building material components serves the determination of the internal diffusion and thus of the effective porosity as well as the usual environmental control. Radiotracers: The specific surface area of silica components can be obtained from measurements of the chemisorptions of fluoride and its kinetics, using acid fluoride solutions and carrier-free 18-F, Tl/2 = 110 min, as the radiotracer. This also enables the determination of fluoride in drinking water at the (sub-) ppm level by spiking isotope dilution and substoichiometric adsorption to small glass beads. Neutron activation analysis (NAA): Concentration profiles down to the micro m-range of trace elements in small electronic components of irregular shape are derived from combination of NAA with controlled sequential etching flux in dilute HF-solutions. The cases of Na, Mn, Co and Se by instrumental NAA and that of W by chemical isolation from the reagent solution are considered. (author)

  18. Constrained Sintering in Fabrication of Solid Oxide Fuel Cells.

    Science.gov (United States)

    Lee, Hae-Weon; Park, Mansoo; Hong, Jongsup; Kim, Hyoungchul; Yoon, Kyung Joong; Son, Ji-Won; Lee, Jong-Ho; Kim, Byung-Kook

    2016-08-09

    Solid oxide fuel cells (SOFCs) are inevitably affected by the tensile stress field imposed by the rigid substrate during constrained sintering, which strongly affects microstructural evolution and flaw generation in the fabrication process and subsequent operation. In the case of sintering a composite cathode, one component acts as a continuous matrix phase while the other acts as a dispersed phase depending upon the initial composition and packing structure. The clustering of dispersed particles in the matrix has significant effects on the final microstructure, and strong rigidity of the clusters covering the entire cathode volume is desirable to obtain stable pore structure. The local constraints developed around the dispersed particles and their clusters effectively suppress generation of major process flaws, and microstructural features such as triple phase boundary and porosity could be readily controlled by adjusting the content and size of the dispersed particles. However, in the fabrication of the dense electrolyte layer via the chemical solution deposition route using slow-sintering nanoparticles dispersed in a sol matrix, the rigidity of the cluster should be minimized for the fine matrix to continuously densify, and special care should be taken in selecting the size of the dispersed particles to optimize the thermodynamic stability criteria of the grain size and film thickness. The principles of constrained sintering presented in this paper could be used as basic guidelines for realizing the ideal microstructure of SOFCs.

  19. Sintering of nanoscale silver coated textiles, a new approach to attain conductive fabrics for electromagnetic shielding

    International Nuclear Information System (INIS)

    Kardarian, Kasra; Busani, Tito; Osório, Inês; Domingos, Helena; Igreja, Rui; Franco, Ricardo; Cortez, João

    2014-01-01

    The demand for conductive textiles is increasing, owing to the need for lightweight and flexible conductive materials for a variety of applications, including electromagnetic shielding of electronic equipment. Herein we propose a process that combines the in situ synthesis of silver nanoparticles at the textile fibre surface followed by sintering of the nanoparticles to obtain highly conductive fabrics. The formation of silver particles at the nanoscale allowed for sintering to be performed efficiently, at reduced temperature and time, bestowing fabrics with high conductivity and capability of shielding electromagnetic radiation. The nanoparticle synthesis method entailed the precipitation of 2.0 g L −1 silver nitrate and further reduction with citrate, with the formation of a deposit of silver nanoparticles at the fabric surface. The amount of silver deposited (up to 195 mg of silver per g of fabric) resulted in moderate electrical conductivity with sheet resistance of 803 Ω/sq. Upon sintering, this value decreased dramatically to 5.2 Ω/sq. The sintering process was monitored by SEM, which showed that sintering at 200 °C for 30 min resulted in maximal electrical conductivity with the lowest amount of silver deposited, while forming a homogenous surface. Fabrics submitted to these sintering conditions maintained their sheet resistance and shielding effectiveness values, even after eight washing cycles. - Highlights: • Assembly of highly conductive textiles capable of shielding electromagnetic radiation. • Procedure combines in situ synthesis of AgNPs at the textile surface and sintering. • AgNPs formed by precipitation of AgNO 3 and reduction with citrate, as observed by SEM. • Sintering increased dramatically conductivity and shielding effectiveness. • Treated fabrics maintained conductivity and shielding effectiveness after 8 washes

  20. Sintering of nanoscale silver coated textiles, a new approach to attain conductive fabrics for electromagnetic shielding

    Energy Technology Data Exchange (ETDEWEB)

    Kardarian, Kasra [REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Busani, Tito [CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Osório, Inês [REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Domingos, Helena; Igreja, Rui [CENIMAT/I3N, Departamento de Ciência dos Materiais, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Franco, Ricardo [REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal); Cortez, João, E-mail: j.cortez@fct.unl.pt [REQUIMTE, Departamento de Química, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Campus de Caparica, 2829-516 Caparica (Portugal)

    2014-10-15

    The demand for conductive textiles is increasing, owing to the need for lightweight and flexible conductive materials for a variety of applications, including electromagnetic shielding of electronic equipment. Herein we propose a process that combines the in situ synthesis of silver nanoparticles at the textile fibre surface followed by sintering of the nanoparticles to obtain highly conductive fabrics. The formation of silver particles at the nanoscale allowed for sintering to be performed efficiently, at reduced temperature and time, bestowing fabrics with high conductivity and capability of shielding electromagnetic radiation. The nanoparticle synthesis method entailed the precipitation of 2.0 g L{sup −1} silver nitrate and further reduction with citrate, with the formation of a deposit of silver nanoparticles at the fabric surface. The amount of silver deposited (up to 195 mg of silver per g of fabric) resulted in moderate electrical conductivity with sheet resistance of 803 Ω/sq. Upon sintering, this value decreased dramatically to 5.2 Ω/sq. The sintering process was monitored by SEM, which showed that sintering at 200 °C for 30 min resulted in maximal electrical conductivity with the lowest amount of silver deposited, while forming a homogenous surface. Fabrics submitted to these sintering conditions maintained their sheet resistance and shielding effectiveness values, even after eight washing cycles. - Highlights: • Assembly of highly conductive textiles capable of shielding electromagnetic radiation. • Procedure combines in situ synthesis of AgNPs at the textile surface and sintering. • AgNPs formed by precipitation of AgNO{sub 3} and reduction with citrate, as observed by SEM. • Sintering increased dramatically conductivity and shielding effectiveness. • Treated fabrics maintained conductivity and shielding effectiveness after 8 washes.

  1. Adhesion Strength of Biomass Ash Deposits

    DEFF Research Database (Denmark)

    Laxminarayan, Yashasvi; Jensen, Peter Arendt; Wu, Hao

    2015-01-01

    This study investigates the shear adhesion strength of biomass ash deposits on superheater tubes. Artificial biomass ash deposits were prepared on superheater tubes and sintered in an oven at temperatures up to 1000°C. Subsequently, the deposits were sheared off with the help of an electrically...

  2. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    ... involves compaction of polymeric powder under pressure and sintering of the preforms at temperature above its melting point. In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering temperatures and strength development.

  3. THE BIOCOMPATIBILITY OF MESOPOROUS SILICATES

    Science.gov (United States)

    Hudson, Sarah; Padera, Robert F.; Langer, Robert; Kohane, Daniel S.

    2008-01-01

    Micro- and nano- mesoporous silicate particles are considered potential drug delivery systems because of their ordered pore structures, large surface areas and the ease with which they can be chemically modified. However, few cytotoxicity or biocompatibility studies have been reported, especially when silicates are administered in the quantities necessary to deliver low-potency drugs. The biocompatibility of mesoporous silicates of particle sizes ~ 150 nm, ~ 800 nm and ~ 4 µm and pore sizes of 3 nm, 7 nm and 16 nm respectively are examined here. In vitro, mesoporous silicates showed a significant degree of toxicity at high concentrations with mesothelial cells. Following subcutaneous injection of silicates in rats, the amount of residual material decreased progressively over three months, with good biocompatibility on histology at all time points. In contrast, intra peritoneal and intra venous injections in mice resulted in death or euthanasia. No toxicity was seen with subcutaneous injection of the same particles in mice. Microscopic analysis of the lung tissue of the mice indicates that death may be due to thrombosis. Although local tissue reaction to mesoporous silicates was benign, they caused severe systemic toxicity. This toxicity could be mitigated by modification of the materials. PMID:18675454

  4. Master Sintering Surface: A practical approach to its construction and utilization for Spark Plasma Sintering prediction

    Directory of Open Access Journals (Sweden)

    Pouchly V.

    2012-01-01

    Full Text Available The sintering is a complex thermally activated process, thus any prediction of sintering behaviour is very welcome not only for industrial purposes. Presented paper shows the possibility of densification prediction based on concept of Master Sintering Surface (MSS for pressure assisted Spark Plasma Sintering (SPS. User friendly software for evaluation of the MSS is presented. The concept was used for densification prediction of alumina ceramics sintered by SPS.

  5. Sintering additives for zirconia ceramics

    International Nuclear Information System (INIS)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification

  6. Sintering additives for zirconia ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, S.

    1986-01-01

    This book is an overview of sintering science and its application to zirconia materials including CaO, MgO, and Y/sub 2/O/sub 3/-CeO/sub 2/ doped materials. This book is a reference for first-time exposure to zirconia materials technology, particularly densification.

  7. The Influence of Sintering Method on Kaolin-Based Geopolymer Ceramics with Addition of Ultra High Molecular Weight Polyethylene as Binder

    Science.gov (United States)

    Romisuhani, A.; AlBakri, M. M.; Kamarudin, H.; Andrei, S. V.

    2017-11-01

    The influence of sintering method on kaolin-based geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene as binder were studied. Geopolymer were formed at room temperature from kaolin and sodium silicate in a highly alkaline medium, followed by curing and drying at 80 °C. 12 M of sodium hydroxide solution were mixed with sodium silicate at a ratio of 0.24 to form alkaline activator. Powder metallurgy technique were used in order to produce kaolin geopolymer ceramics with addition of Ultra High Molecular Weight Polyethylene. The samples were heated at temperature of 1200 °C with two different sintering method which are conventional method and two-step sintering method. The strength and density were tested.

  8. Bioactivity studies of calcium magnesium silicate prepared from eggshell waste by sol–gel combustion synthesis

    Directory of Open Access Journals (Sweden)

    Rajan Choudhary

    2015-06-01

    Full Text Available The present study focused on the synthesis of calcium magnesium silicate (akermanite, Ca2MgSi2O7 using eggshell biowaste (as calcium source, magnesium nitrate and tetraethyl orthosilicate (TEOS as starting materials. Sol–gel combustion method was adopted to obtain calcium magnesium silicate. Citric acid was used as a fuel (reducing agent and nitrate ions present in the metal nitrates acts as an oxidizing agent during combustion process. The characterization of synthesized calcium magnesium silicate was carried out by powder X-ray diffraction (XRD, Fourier transform infrared (FTIR and scanning electron microscopy (SEM techniques. Calcium magnesium silicate crystallite size was observed in nano regime which can effectively mimic natural bone apatite composition. In-vitro bioactivity was investigated by immersing calcium magnesium silicate pellet in simulated body fluid (SBF for three weeks. Results show effective deposition of crystallized hydroxyapatite (HAP layer on its surface and predicting its possibilities for applications in hard tissue regeneration.

  9. Strain-enhanced sintering of iron powders

    Energy Technology Data Exchange (ETDEWEB)

    Amador, D.R.; Torralba, J.M. [Universidad Carlos III de Madrid, Departamento de Ciencias de Materiales e Ingenieria Metalurgica, Leganes, Madrid (Spain); Monge, M.A.; Pareja, R. [Universidad Carlos III de Madrid, Departamento de Fisica, Madrid (Spain)

    2005-02-01

    Sintering of ball-milled and un-milled Fe powders has been investigated using dilatometry, X-ray, density, and positron annihilation techniques. A considerable sintering enhancement is found in milled powders showing apparent activation energies that range between 0.44 and 0.80 eV/at. The positron annihilation results, combined with the evolution of the shrinkage rate with sintering temperature, indicate generation of lattice defects during the sintering process of milled and un-milled powders. The sintering enhancement is attributed to pipe diffusion along the core of moving dislocations in the presence of the vacancy excess produced by plastic deformation. Positron annihilation results do not reveal the presence of sintering-induced defects in un-milled powders sintered above 1200 K, the apparent activation energy being in good agreement with that for grain-boundary diffusion in {gamma}-Fe. (orig.)

  10. SPM nanolithography of hydroxy-silicates

    International Nuclear Information System (INIS)

    Valdrè, G; Moro, D; Hounsome, C M; Antognozzi, M

    2012-01-01

    Bio-nanopatterning of surfaces is becoming a crucial technique with applications ranging from molecular and cell biology to medicine. Scanning probe microscopy (SPM) is one of the most useful tools for nanopatterning of flat surfaces. However, these patterns are usually built on homogeneous surfaces and require chemical functionalization to ensure specific affinity. Layered magnesium–aluminum hydroxide–silicates have already shown unique self-assembly properties on DNA molecules, due to their peculiar crystal chemistry based on alternating positive and negative crystal layers. However, patterns on these surfaces tend to be randomly organized. Here we show etching and oxidation at the nanometer scale of magnesium–aluminum hydroxide–silicates using the same SPM probe for the creation of organized nanopatterns. In particular, it is possible to produce three-dimensional structures in a reproducible way, with a depth resolution of 0.4 nm, lateral resolution of tens of nm, and a speed of about 10 μm s −1 . We report, as an example, the construction of an atomically flat charged pattern, designed to guide DNA deposition along predetermined directions without the need of any chemical functionalization of the surface. (paper)

  11. Experimental simulation of evaporation-driven silica sinter formation and microbial silicification in hot spring systems.

    Science.gov (United States)

    Orange, François; Lalonde, Stefan V; Konhauser, Kurt O

    2013-02-01

    Evaporation of silica-rich geothermal waters is one of the main abiotic drivers of the formation of silica sinters around hot springs. An important role in sinter structural development is also played by the indigenous microbial communities, which are fossilized and eventually encased in the silica matrix. The combination of these two factors results in a wide variety of sinter structures and fabrics. Despite this, no previous experimental fossilization studies have focused on evaporative-driven silica precipitation. We present here the results of several experiments aimed at simulating the formation of sinters through evaporation. Silica solutions at different concentrations were repeatedly allowed to evaporate in both the presence and absence of the cyanobacterium Synechococcus elongatus. Without microorganisms, consecutive silica additions led to the formation of well-laminated deposits. By contrast, when microorganisms were present, they acted as reactive surfaces for heterogeneous silica particle nucleation; depending on the initial silica concentration, the deposits were then either porous with a mixture of silicified and unmineralized cells, or they formed a denser structure with a complete entombment of the cells by a thick silica crust. The deposits obtained experimentally showed numerous similarities in terms of their fabric to those previously reported for natural hot springs, demonstrating the complex interplay between abiotic and biotic processes during silica sinter growth.

  12. Elastic properties of silicate melts

    DEFF Research Database (Denmark)

    Clark, Alisha N.; Lesher, Charles E.

    2017-01-01

    Low seismic velocity regions in the mantle and crust are commonly attributed to the presence of silicate melts. Determining melt volume and geometric distribution is fundamental to understanding planetary dynamics. We present a new model for seismic velocity reductions that accounts for the anoma......Low seismic velocity regions in the mantle and crust are commonly attributed to the presence of silicate melts. Determining melt volume and geometric distribution is fundamental to understanding planetary dynamics. We present a new model for seismic velocity reductions that accounts...... for the anomalous compressibility of silicate melt, rendering compressional wave velocities more sensitive to melt fraction and distribution than previous estimates. Forward modeling predicts comparable velocity reductions for compressional and shear waves for partially molten mantle, and for low velocity regions...

  13. Sintered wire cesium dispenser photocathode

    Science.gov (United States)

    Montgomery, Eric J; Ives, R. Lawrence; Falce, Louis R

    2014-03-04

    A photoelectric cathode has a work function lowering material such as cesium placed into an enclosure which couples a thermal energy from a heater to the work function lowering material. The enclosure directs the work function lowering material in vapor form through a low diffusion layer, through a free space layer, and through a uniform porosity layer, one side of which also forms a photoelectric cathode surface. The low diffusion layer may be formed from sintered powdered metal, such as tungsten, and the uniform porosity layer may be formed from wires which are sintered together to form pores between the wires which are continuous from the a back surface to a front surface which is also the photoelectric surface.

  14. Nuclear tracks in sinterized gemstones

    International Nuclear Information System (INIS)

    Espinosa, G.; Rodriguez, L.V.; Golzarri, J.I.; Castano, V.M.

    1993-01-01

    The responses of sinterized gemstones to alpha particles attempt analyzed with the objective of finding new materials for SSNTD, and also to understand their interaction with radiation and the formation of tracks. In this work we present the results of the characterization of these materials as SSNTD. The micro structural changes observed by electron microscopy. The preparation, etching solution concentration, etching time and effects of temperature are discussed. (Author)

  15. Microwave sintering of ceramic materials

    Science.gov (United States)

    Karayannis, V. G.

    2016-11-01

    In the present study, the potential of microwave irradiation as an innovative energy- efficient alternative to conventional heating technologies in ceramic manufacturing is reviewed, addressing the advantages/disadvantages, while also commenting on future applications of possible commercial interest. Ceramic materials have been extensively studied and used due to several advantages they exhibit. Sintering ceramics using microwave radiation, a novel technology widely employed in various fields, can be an efficient, economic and environmentally-friendlier approach, to improve the consolidation efficiency and reduce the processing cycle-time, in order to attain substantial energy and cost savings. Microwave sintering provides efficient internal heating, as energy is supplied directly and penetrates the material. Since energy transfer occurs at a molecular level, heat is generated throughout the material, thus avoiding significant temperature gradients between the surface and the interior, which are frequently encountered at high heating rates upon conventional sintering. Thus, rapid, volumetric and uniform heating of various raw materials and secondary resources for ceramic production is possible, with limited grain coarsening, leading to accelerated densification, and uniform and fine-grained microstructures, with enhanced mechanical performance. This is particularly important for manufacturing large-size ceramic products of quality, and also for specialty ceramic materials such as bioceramics and electroceramics. Critical parameters for the process optimization, including the electromagnetic field distribution, microwave-material interaction, heat transfer mechanisms and material transformations, should be taken into consideration.

  16. Mechanical and physical properties of calcium silicate/alumina composite for biomedical engineering applications.

    Science.gov (United States)

    Shirazi, F S; Mehrali, M; Oshkour, A A; Metselaar, H S C; Kadri, N A; Abu Osman, N A

    2014-02-01

    The focus of this study is to investigate the effect of Al2O3 on α-calcium silicate (α-CaSiO3) ceramic. α-CaSiO3 was synthesized from CaO and SiO2 using mechanochemical method followed by calcinations at 1000°C. α-CaSiO3 and alumina were grinded using ball mill to create mixtures, containing 0-50w% of Al2O3 loadings. The powders were uniaxially pressed and followed by cold isostatic pressing (CIP) in order to achieve greater uniformity of compaction and to increase the shape capability. Afterward, the compaction was sintered in a resistive element furnace at both 1150°C and 1250°C with a 5h holding time. It was found that alumina reacted with α-CaSiO3 and formed alumina-rich calcium aluminates after sintering. An addition of 15wt% of Al2O3 powder at 1250°C were found to improve the hardness and fracture toughness of the calcium silicate. It was also observed that the average grain sizes of α-CaSiO3 /Al2O3 composite were maintained 500-700nm after sintering process. © 2013 Published by Elsevier Ltd.

  17. Development of import subtituting technologies for increasing productivity of sintering machines and strength of agglomerates

    Directory of Open Access Journals (Sweden)

    В. Л. Трушко

    2016-11-01

    Full Text Available A problem of industrial fluxed agglomerates self-destruction in the process of cooling after sintering has been examined. It has been revealed that the main reason of strength degradation is polymorphism of dicalcium silicate Ca2SiO4 (or short designation С2S: β-Ca2SiO4 ® γ-Ca2SiO4. Ways for increasing the  agglomerate  strength by physical and crystal-chemical stabilization of the high temperature modification of C2S have been proposed and tested. Physical stabilization of C2S agglomerate is increased with its structure reinforcement due to thickening of walls between large pores that is achieved by increasing height of the sintered layer through improvement of its gas permeability. The task is addressed by substituting the previously used import sintering ore with the  polydisperse ore from the Yakovlevo field, which improves the charge  pelletizing by 3-4 times and helps to bring the  height of the sintered layer and the strength of the domestic agglomerate up to the international best practice standards, while eliminating a need to purchase import high-vacuum   exhausters. In practice crystal-chemical stabilization of C2S within iron-ore  agglomerate is ensured by adding an  opti- mal multicomponent additive in the form of the    waste product  generated in production  of alumina  from bauxites, i.e. the red mud, to the initial sinter charge. Thus mechanical strength of agglomerates and pellets is increased by 5-10 % and their hot strength improves by 20-40 %. The productivity of sintering machines and blast furnaces improves by 5-10 %. Specific coke consumption reduces by 2-2.5 %. In production of iron-ore pellets red mud is substituting the import  bentonite.

  18. Development of membrane filters with nanostructured porous layer by coating of metal nanoparticles sintered onto a micro-filter

    International Nuclear Information System (INIS)

    Park, Seok Joo; Park, Young Ok; Lee, Dong Geun; Ryu, Jeong In

    2008-01-01

    The membrane filter adhered with nanostructured porous layer was made by heat treatment after deposition of nanoparticle-agglomerates sintered in aerosol phase onto a conventional micron-fibrous metal filter as a substrate filter. The Sintered-Nanoparticle-Agglomerates-coated NanoStructured porous layer Membrane Filter (SNA-NSMF), whose the filtration performance was improved compared with the conventional metal membrane filters, was developed by adhesion of nanoparticle-agglomerates of dendrite structure sintered onto the micron-fibrous metal filter. The size of nanoparticle-agglomerates of dendrite structure decreased with increasing the sintering temperature because nanoparticle-agglomerates shrank. When shrinking nanoparticle-agglomerates were deposited and treated with heat onto the conventional micron-fibrous metal filter, pore size of nanostructured porous layer decreased. Therefore, pressure drops of SNA-NSMFs increased from 0.3 to 0.516 KPa and filtration efficiencies remarkably increased from 95.612 to 99.9993%

  19. Constraints on astronomical silicate dust

    International Nuclear Information System (INIS)

    Sorrell, W.H.

    1990-01-01

    Numerical radiative-transfer models are used to discuss the properties of circumstellar dust grains around the premain-sequence star AB Aur (HD 31293). It is assumed that the dust consists of a silicate-graphite mixture with Draine and Lee (1984) optical properties. The modeling technique is to match the observed FUV through FIR energy distribution with the spectral energy distribution predicted for a spherical dust shell around a luminous hot star. Special attention is given to matching the observed 10-micron silicate emission feature and the observed circumstellar absorption curve at UV wavelengths, making it possible to strengthen constraints on dust-grain opacity and chemical composition. It is concluded that, although silicate grains can explain the observed 10-micron emission feature, the Draine and Lee silicate-graphite mixture cannot explain the observed FUV circumstellar absorption at the same time. The dust shell around AB Aur contains an additional population of small particles, the most likely candidate being amorphous carbon grains in a nonhydrogenated form. 18 refs

  20. Constraints on astronomical silicate dust

    Science.gov (United States)

    Sorrell, Wilfred H.

    1990-01-01

    Numerical radiative-transfer models are used to discuss the properties of circumstellar dust grains around the premain-sequence star AB Aur (HD 31293). It is assumed that the dust consists of a silicate-graphite mixture with Draine and Lee (1984) optical properties. The modeling technique is to match the observed FUV through FIR energy distribution with the spectral energy distribution predicted for a spherical dust shell around a luminous hot star. Special attention is given to matching the observed 10-micron silicate emission feature and the observed circumstellar absorption curve at UV wavelengths, making it possible to strengthen constraints on dust-grain opacity and chemical composition. It is concluded that, although silicate grains can explain the observed 10-micron emission feature, the Draine and Lee silicate-graphite mixture cannot explain the observed FUV circumstellar absorption at the same time. The dust shell around AB Aur contains an additional population of small particles, the most likely candidate being amorphous carbon grains in a nonhydrogenated form.

  1. Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

    OpenAIRE

    Changzhou Yu; Peng Cao; Mark Ian Jones

    2017-01-01

    Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P.) titanium in a graphite furnace backfilled with argon and stu...

  2. Production of sintered alumina from powder; optimization of the sinterized parameters for the maximum mechanical resistence

    International Nuclear Information System (INIS)

    Rocha, J.C. da.

    1981-02-01

    Pure, sinterized alumina and the optimization of the parameters of sinterization in order to obtain the highest mechanical resistence are discussed. Test materials are sinterized from a fine powder of pure alumina (Al 2 O 3 ), α phase, at different temperatures and times, in air. The microstructures are analysed concerning porosity and grain size. Depending on the temperature or the time of sinterization, there is a maximum for the mechanical resistence. (A.R.H.) [pt

  3. Amended Silicated for Mercury Control

    Energy Technology Data Exchange (ETDEWEB)

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where

  4. Alternative sintering methods compared to conventional thermal sintering for inkjet printed silver nanoparticle ink

    NARCIS (Netherlands)

    Niittynen, J.; Abbel, R.; Mäntysalo, M.; Perelaer, J.; Schubert, U.S.; Lupo, D.

    2014-01-01

    In this contribution several alternative sintering methods are compared to traditional thermal sintering as high temperature and long process time of thermal sintering are increasing the costs of inkjet-printing and preventing the use of this technology in large scale manufacturing. Alternative

  5. Protocol for Ultralow-Temperature Ceramic Sintering: An Integration of Nanotechnology and the Cold Sintering Process.

    Science.gov (United States)

    Guo, Hanzheng; Baker, Amanda; Guo, Jing; Randall, Clive A

    2016-11-22

    The sintering process is an essential step in taking particulate materials into dense ceramic materials. Although a number of sintering techniques have emerged over the past few years, the sintering process is still performed at high temperatures. Here we establish a protocol to achieve dense ceramic solids at extremely low temperatures (sustainable manufacturing practices.

  6. Impact of variable frequency microwave and rapid thermal sintering on microstructure of inkjet-printed silver nanoparticles

    OpenAIRE

    Cauchois, Romain; Saadaoui, Mohamed; Yakoub, Abdelwahhab; Inal, Karim; Dubois-Bonvalot, Béatrice; Fidalgo, Jean-Christophe

    2012-01-01

    International audience; The effect of thermal profile on microstructure is studied in the frame of thin films deposited by inkjet-printing technology. The role of sintering temperature and thermal ramp is particularly investigated. Fast heating ramps exhibit coarse grains and pores, especially when a hybrid microwave curing is performed. This enhanced growth is attributed to the quick activation of densifying sintering regimes without undergoing thermal energy loss at low temperature. Microst...

  7. Microwave combustion and sintering without isostatic pressure

    International Nuclear Information System (INIS)

    Ebadian, M.A.

    1998-01-01

    In recent years interest has grown rapidly in the application of microwave energy to the processing of ceramics, composites, polymers, and other materials. Advances in the understanding of microwave/materials interactions will facilitate the production of new ceramic materials with superior mechanical properties. One application of particular interest is the use of microwave energy for the mobilization of uranium for subsequent redeposition. Phase III (FY98) will focus on the microwave assisted chemical vapor infiltration tests for mobilization and redeposition of radioactive species in the mixed sludge waste. Uranium hexachloride and uranium (IV) borohydride are volatile compounds for which the chemical vapor infiltration procedure might be developed for the separation of uranium. Microwave heating characterized by an inverse temperature profile within a preformed ceramic matrix will be utilized for CVI using a carrier gas. Matrix deposition is expected to commence from the inside of the sample where the highest temperature is present. The preform matrix materials, which include aluminosilicate based ceramics and silicon carbide based ceramics, are all amenable to extreme volume reduction, densification, and vitrification. Important parameters of microwave sintering such as frequency, power requirement, soaking temperature, and holding time will be investigated to optimize process conditions for the volatilization of uranyl species using a reactive carrier gas in a microwave chamber

  8. Electrophoretic deposition of mesoporous bioactive glass on glass-ceramic foam scaffolds for bone tissue engineering.

    Science.gov (United States)

    Fiorilli, Sonia; Baino, Francesco; Cauda, Valentina; Crepaldi, Marco; Vitale-Brovarone, Chiara; Demarchi, Danilo; Onida, Barbara

    2015-01-01

    In this work, the coating of 3-D foam-like glass-ceramic scaffolds with a bioactive mesoporous glass (MBG) was investigated. The starting scaffolds, based on a non-commercial silicate glass, were fabricated by the polymer sponge replica technique followed by sintering; then, electrophoretic deposition (EPD) was applied to deposit a MBG layer on the scaffold struts. EPD was also compared with other techniques (dipping and direct in situ gelation) and it was shown to lead to the most promising results. The scaffold pore structure was maintained after the MBG coating by EPD, as assessed by SEM and micro-CT. In vitro bioactivity of the scaffolds was assessed by immersion in simulated body fluid and subsequent evaluation of hydroxyapatite (HA) formation. The deposition of a MBG coating can be a smart strategy to impart bioactive properties to the scaffold, allowing the formation of nano-structured HA agglomerates within 48 h from immersion, which does not occur on uncoated scaffold surfaces. The mechanical properties of the scaffold do not vary after the EPD (compressive strength ~19 MPa, fracture energy ~1.2 × 10(6) J m(-3)) and suggest the suitability of the prepared highly bioactive constructs as bone tissue engineering implants for load-bearing applications.

  9. Dry Sintered Metal Coating of Halloysite Nanotubes

    Directory of Open Access Journals (Sweden)

    James C. Nicholson

    2016-09-01

    Full Text Available Halloysite nanotubes (HNTs are a naturally-occurring aluminosilicate whose dimensions measure microns in length and tens of nanometers in diameter. Bonding defects between the alumina and silica lead to net negative and positive charges on the exterior and interior lumen, respectively. HNTs have been shown to enhance the material properties of polymer matrices and enable the sustained release of loaded chemicals, drugs, and growth factors. Due to the net charges, these nanotubes can also be readily coated in layered-depositions using the HNT exterior lumen’s net negative charge as the basis for assembly. These coatings are primarily done through wet chemical processes, the majority of which are limited in their use of desired chemicals, due to the polarity of the halloysite. Furthermore, this restriction in the type of chemicals used often requires the use of more toxic chemicals in place of greener options, and typically necessitates the use of a significantly longer chemical process to achieve the desired coating. In this study, we show that HNTs can be coated with metal acetylacetonates—compounds primarily employed in the synthesis of nanoparticles, as metal catalysts, and as NMR shift reagents—through a dry sintering process. This method was capable of thermally decaying the metal acetylacetonate, resulting in a free positively-charged metal ion that readily bonded to the negatively-charged HNT exterior, resulting in metallic coatings forming on the HNT surface. Our coating method may enable greater deposition of coated material onto these nanotubes as required for a desired application. Furthermore, the use of chemical processes using toxic chemicals is not required, thus eliminating exposure to toxic chemicals and costs associated with the disposal of the resultant chemical waste.

  10. Biomarkers and taphonomic processes in fresh and fossil biosignatures from Hot Spring silica deposits in El Tatio Chile, as a Mars Analogue

    Science.gov (United States)

    Carrizo, D.; Sánchez-García, L.; Parro, V.; Cady, S. L.; Cabrol, N. A.

    2017-09-01

    Biomarkers characterization and taphonomic process of recent and fossil biosignatures in extreme environments with analogies to Mars is essential to understanding how life could develop and survive in this conditions. Siliceous sinter deposits on Mars where similar to those found in the hydrothermal hot springs and geysers from El Tatio, Chile. Organic preservation have been shown in this study. Many different labile functional groups (i.e., carboxylic acids, alcohols, aldehydes, etc.) were found in both "age" samples. A shift in congener pattern for the different lipids families were found and discuss. This results give insight in taphonomic processes actin in this extreme environment, which could be used as a baseline in Mars exploration.

  11. Master sintering curves of two different alumina powder compacts

    Directory of Open Access Journals (Sweden)

    Vaclav Pouchly

    2009-12-01

    Full Text Available Concept of Master Sintering Curve is a strong tool for optimizing sintering schedule. The sintering behaviour can be predicted, and sintering activation energy can be calculated with the help of few dilatometric measurements. In this paper an automatic procedure was used to calculate Master Sintering Curves of two different alumina compacts. The sintering activation energies were determined as 640 kJ/mol for alumina with particle size of 240 nm, respective 770 kJ/mol for alumina with particle size of 110 nm. The possibility to predict sintering behaviour with the help of Master Sintering Curve was verified.

  12. Low-voltage bendable pentacene thin-film transistor with stainless steel substrate and polystyrene-coated hafnium silicate dielectric.

    Science.gov (United States)

    Yun, Dong-Jin; Lee, Seunghyup; Yong, Kijung; Rhee, Shi-Woo

    2012-04-01

    The hafnium silicate and aluminum oxide high-k dielectrics were deposited on stainless steel substrate using atomic layer deposition process and octadecyltrichlorosilane (OTS) and polystyrene (PS) were treated improve crystallinity of pentacene grown on them. Besides, the effects of the pentacene deposition condition on the morphologies, crystallinities and electrical properties of pentacene were characterized. Therefore, the surface treatment condition on dielectric and pentacene deposition conditions were optimized. The pentacene grown on polystyrene coated high-k dielectric at low deposition rate and temperature (0.2-0.3 Å/s and R.T.) showed the largest grain size (0.8-1.0 μm) and highest crystallinity among pentacenes deposited various deposition conditions, and the pentacene TFT with polystyrene coated high-k dielectric showed excellent device-performance. To decrease threshold voltage of pentacene TFT, the polystyrene-thickness on high-k dielectric was controlled using different concentration of polystyrene solution. As the polystyrene-thickness on hafnium silicate decreases, the dielectric constant of polystyrene/hafnium silicate increases, while the crystallinity of pentacene grown on polystyrene/hafnium silicate did not change. Using low-thickness polystyrene coated hafnium silicate dielectric, the high-performance and low voltage operating (1 × 10(4)) and complementary inverter (DC gains, ~20) could be fabricated.

  13. Sintering characteristics of nano-ceramic coatings

    NARCIS (Netherlands)

    de Hosson, J.T.M.; Popma, R.

    2003-01-01

    This paper concentrates on sintering characteristics of nano-sized ceramic SiO2 particles. The sintering process is studied as a function of temperature using a conventional furnace and using a laser beam. The underlying idea is to combine the nanoceramic sol-gel concept with inkjet technology and

  14. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    In firing of products by conventionally sintered process, SiC grain gets oxidized producing SiO2 (∼ 32 wt%) and deteriorates the quality of the product substantially. Partially sintered silicon carbide by such a method is a useful material for a varieties of applications ranging from kiln furniture to membrane material.

  15. Kinetic analysis of boron carbide sintering

    International Nuclear Information System (INIS)

    Borchert, W.; Kerler, A.R.

    1975-01-01

    The kinetics of the sintering of boron carbide were investigated by shrinkage measurements with a high-temperature dilatometer under argon atmosphere in dependence on temperature, grain size, and pressure. The activation energies and the reaction mechanisms of the different stages of sintering were determined. (orig.) [de

  16. Electro sinter forging of titanium disks

    DEFF Research Database (Denmark)

    Cannella, Emanuele; Nielsen, Chris Valentin; Bay, Niels Oluf

    Electro sinter forging (ESF) is a new sintering process based on the principle of electrical Joule heating. In the present work, middle frequency direct current (MFDC) was flowing through the powder compact, which was under mechanical pressure. The main parameters are the high electrical current,...

  17. Sintering of ultra high molecular weight polyethylene

    Indian Academy of Sciences (India)

    Abstract. Ultra high molecular weight polyethylene (UHMWPE) is a high performance polymer having low coefficient of friction, good abrasion resistance, good chemical ... In this study, we report our results on compaction and sintering behaviour of two grades of UHMWPE with reference to the powder morphology, sintering ...

  18. Sintered-to-size FBR fuel

    International Nuclear Information System (INIS)

    Rasmussen, D.E.; Schaus, P.S.

    1984-04-01

    Fabrication of sintered-to-size PuO 2 -UO 2 fuel pellets was completed for testing of proposed FBR product specifications. Approximately 6000 pellets were fabricated to two nominal diameters and two densities by cold pressing and sintering to size. Process control and correlation between test and production batches are discussed

  19. Sintering of zirconia in high-pressure

    International Nuclear Information System (INIS)

    Kunrath, A.O.; Strohaecker, T.R.; Pereira, A.S.; Jornada, J.A.H. da; Piermarini, G.J.

    1989-01-01

    A systematic study about the sintering of zirconia hyperfines powders in high-pressure is presented. The differents conditions effect of sintering in microstructure and in hardness and tenacity properties of zirconia samples with a very fine grain is also studied. (C.G.C.) [pt

  20. Modeling the microstructural evolution during constrained sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    A numerical model able to simulate solid state constrained sintering of a powder compact is presented. The model couples an existing kinetic Monte Carlo (kMC) model for free sintering with a finite element (FE) method for calculating stresses on a microstructural level. The microstructural respon...

  1. Modeling the Microstructural Evolution During Constrained Sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Pryds, Nini

    2015-01-01

    A numerical model able to simulate solid-state constrained sintering is presented. The model couples an existing kinetic Monte Carlo model for free sintering with a finite element model (FEM) for calculating stresses on a microstructural level. The microstructural response to the local stress as ...

  2. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    Unknown

    Central Glass and Ceramic Research Institute, Kolkata 700 032, India. Abstract. The present work deals with the sintering of ... recently become an attractive area of research and deve- lopment. The major advantages of ... without the usage of sintering aids (Lee and Case 1999;. Goldstein et al 1999). Several studies have ...

  3. THE POLARIZING EFFECTS IN SINTERED KAOLIN

    African Journals Online (AJOL)

    compacted and sintered density of the ceramic have been studied, and a density — pressure relationship for before- and after-sintering conditions obtained. INTRODUCTION. Ceramics have been known to mankind for thousands of years, and have been used in construction materials. In many applications, ceramics have.

  4. The Influence of Sintering Temperature of Reactive Sintered (Ti, MoC-Ni Cermets

    Directory of Open Access Journals (Sweden)

    Marek Jõeleht

    2015-09-01

    Full Text Available Titanium-molybdenum carbide nickel cermets ((Ti, MoC-Ni were produced using high energy milling and reactive sintering process. Compared to conventional TiC-NiMo cermet sintering the parameters for reactive sintered cermets vary since additional processes are present such as carbide synthesis. Therefore, it is essential to acquire information about the suitable sintering regime for reactive sintered cermets. One of the key parameters is the final sintering temperature when the liquid binder Ni forms the final matrix and vacancies inside the material are removed. The influence of the final sintering temperature is analyzed by scanning electron microscopy. Mechanical properties of the material are characterized by transverse rupture strength, hardness and fracture toughness.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7179

  5. Participation of bacteria in weathering processes of silicates

    Directory of Open Access Journals (Sweden)

    Peter Javorský

    2005-11-01

    Full Text Available Biological processes presented by the metabolic activity of different species of bacteria adhered at the mineral surfaces are a part of the geochemical processes. These bacteria accelerate, by the production of organic acids into the minerals structural bonds, the leaching of elements and their subsequent and gradual transformation to the secondary minerals. Microbial destructions of silicates are studied in order to processing low-quality mineral raw-materials and the remediation of soils, sediments and waters contaminated by industrial pollutants. The samples of material, used in our research, were obtained at 9 deposits of non-metallic raw-materials in Slovakia. The sediment sample was taken from the area of Baikal Lake. The presence of microorganisms in the matrix most frequently was determined by a subsequent isolation of microorganisms and identification of bacterial species presented in the silicate matrix. The species of Bacillus and Pseudomonas genus were the common representative of the microorganisms.

  6. Sintered ceramics having controlled density and porosity

    International Nuclear Information System (INIS)

    Brassfield, H.C.; DeHollander, W.R.; Nivas, Y.

    1980-01-01

    A new method was developed for sintering ceramic uranium dioxide powders, in which ammonium oxalate is admixed with the powder prior to being pressed into a cylindrical green body, so that the end-point density of the final nuclear-reactor fuel product can be controlled. When the green body is heated, the ammonium oxalate decomposes and leaves discrete porosity in the sintered body, which corresponds to the ammonium oxalate regions in the green body. Thus the end-point density of the sintered body is a function of the amount of ammonium oxalate added. The final density of the sintered product is about 90-97% of the theoretical. The addition of ammonium oxalate also allows control of the pore size and distribution throughout the fuel. The process leaves substantially no impurities in the sintered strucuture. (DN)

  7. Titanium Powder Sintering in a Graphite Furnace and Mechanical Properties of Sintered Parts

    Directory of Open Access Journals (Sweden)

    Changzhou Yu

    2017-02-01

    Full Text Available Recent accreditation of titanium powder products for commercial aircraft applications marks a milestone in titanium powder metallurgy. Currently, powder metallurgical titanium production primarily relies on vacuum sintering. This work reported on the feasibility of powder sintering in a non-vacuum furnace and the tensile properties of the as-sintered Ti. Specifically, we investigated atmospheric sintering of commercially pure (C.P. titanium in a graphite furnace backfilled with argon and studied the effects of common contaminants (C, O, N on sintering densification of titanium. It is found that on the surface of the as-sintered titanium, a severely contaminated porous scale was formed and identified as titanium oxycarbonitride. Despite the porous surface, the sintered density in the sample interiors increased with increasing sintering temperature and holding time. Tensile specimens cut from different positions within a large sintered cylinder reveal different tensile properties, strongly dependent on the impurity level mainly carbon and oxygen. Depending on where the specimen is taken from the sintered compact, ultimate tensile strength varied from 300 to 580 MPa. An average tensile elongation of 5% to 7% was observed. Largely depending on the interstitial contents, the fracture modes from typical brittle intergranular fracture to typical ductile fracture.

  8. Field assisted sintering of refractory carbide ceramics and fiber reinforced ceramic matrix composites

    Science.gov (United States)

    Gephart, Sean

    materials. While FAST sintered materials showed higher average values, in general they also showed consistently larger variation in the scattered data and consequently larger standard deviation for the resulting material properties. In addition, dynamic impact testing (V50 test) was conducted on the resulting materials and it was determined that there was no discernable correlation between observed mechanical properties of the ceramic materials and the resulting dynamic testing. Another study was conducted on the sintering of SiC and carbon fiber reinforced SiC ceramic matrix composites (CMC) using FAST. There has been much interest recently in fabricating high strength, low porosity SiC CMC.s for high temperature structural applications, but the current methods of production, namely chemical vapor infiltration (CVI), melt infiltration (MI), and polymer infiltration and pyrolysis (PIP), are considered time consuming and involve material related shortcomings associated with their respective methodologies. In this study, SiC CMC.s were produced using the 25 ton laboratory unit with a target sample size of 40 mm diameter and 3 mm thickness, as well as on the larger 250 ton industrial FAST system targeting a sample size of 101.6 x 101.6 x 3 mm3 to investigate issues associated with scaling. Several sintering conditions were explored including: pressure of 35-65 MPa, temperature of 1700-1900°C, and heating rates between 50-400°C/min. The SiC fibers used in this study were coated using chemical vapor deposition (CVD) with boron nitride (BN) and pyrolytic carbon to act as a barrier layer and preserve the integrity of the fibers during sintering. Then the barrier coating was coated by an outer layer of SiC to enhance the bonding between the fibers and the SiC matrix. Microstructures of the sintered samples were examined by FE-SEM. Mechanical properties including flexural strength-deflection and stress-strain were characterized using 4-point bend testing. Tensile testing was

  9. Thermodynamics and mechanisms of sintering

    International Nuclear Information System (INIS)

    Pask, J.A.

    1978-10-01

    A phenomenological overview and exploration of the thermodynamic and geometric factors play a role in the process of densification of model compact systems consisting of crystalline spheres of uniform size in regular and irregular packing that form grain boundaries at every contact point. A further assumption is the presence of isotropic surface and grain boundary energies. Although such systems are unrealistic in comparison with normal powder compacts, their potential sintering behavior can be analyzed and provided with a limiting set of behavior conditions which can be looked upon as one boundary condition. This approach is logically realistic since it is easier to understand and provide a basis for understanding the more complex real powder systems

  10. Science of sintering and its future

    International Nuclear Information System (INIS)

    Ristic, M.M.

    1975-01-01

    Some new books published by M.Yu. Baljshin, V.A. Ivensen, V.V. Skorohod and others are characterized by the wish to give a complete approach to the problems of sintering theory. Bearing just this in mind while writing the book ''An Essay on the Generalization of Sintering Theory'' (G.V.Samsonov, M.M. Ristic with the collaborators) an idea was born: to ask the most eminent scientists in this field to present their own opinions on the theme ''The Science of Sintering and Modern Views on its Future''. There were formed 18 questions, given in the appendix to be answered. The received answers were presented in 10 chapters of this book. The fourth part of the book consists of papers of eminent scientists engaged in the field of sintering science (some of which were published here for the first time). This material is published in the book with the consent of the authors and these original contributions provide a more profound knowledge of sintering. The initial idea, that the book should have a monograph character and in which the answers would serve as some data on the latest notions of the science of sintering, was somewhat changed since the original opinions of individual scientists are given in the book and these, are sometimes very contradictory. This, in fact, gives the book a special charm because the unsolved problems in the science of sintering are most evidently stressed in this way

  11. Silica phases in sinters and residues from geothermal fields of New Zealand

    Science.gov (United States)

    Rodgers, K. A.; Browne, P. R. L.; Buddle, T. F.; Cook, K. L.; Greatrex, R. A.; Hampton, W. A.; Herdianita, N. R.; Holland, G. R.; Lynne, B. Y.; Martin, R.; Newton, Z.; Pastars, D.; Sannazarro, K. L.; Teece, C. I. A.

    2004-06-01

    Five silica phases are major components of silica sinters, deposited from both near-neutral pH alkali-chloride and acid-sulfate thermal waters, and of silica residues formed at the surface of geothermal fields in New Zealand. In all cases, the initial silica is noncrystalline opal-A deposited commonly as microspheres that possess an underlying nanospherical substructure, upon different substrate templets, including microbes living in hot springs. Deposition may also occur monomerically upon earlier deposited silica. Following microsphere growth through Ostwald ripening, silica remains mobile throughout the postdepositional history of the sinter/residue deposits, resulting in a range of textures. These include the continuing growth of microspheres, the development of secondary microspheres and silica coatings, phase transformations, a reduction in sinter porosity, dissolution features, and late-stage deposition of drusy quartz and opal-A. The sinter mass attempts to achieve thermodynamic equilibrium through stepwise phase transformations (maturation): opal-A crystallises to paracrystalline opal-CT±opal-C, which recrystallises to microcrystalline α-quartz+moganite. No intermediate silica phases are produced, but gradual changes occur among different opal-A or opal-CT/-C phases. The phase maturation produces changes in particle densities, silanol water, and in X-ray powder response of the different silica phases, although the rates of change can be perturbed by heating, weathering, and dissolution of the sinter/residue. The properties of opal-A change little in a sinter/residue mass within the first 10,000 years, but reductions occur in the densities, silanol water, and X-ray scattering bandwidth of older sinters where opal-A can persist for up to 100,000 years. Eventually, opal-A transforms to opal-CT when silanol water is reduced sufficiently for enough -Si-O-Si- linkages to produce a crude diffraction-like X-ray response. The transformation is aided by heat, as

  12. Solidification of HLLW into sintered ceramics

    International Nuclear Information System (INIS)

    O-Oka, K.; Ohta, T.; Masuda, S.; Tsunoda, N.

    1979-01-01

    Simulated HLLW from the PNC reprocessing plant at Tokai was solidified into sintered ceramics by normal sintering or hot-pressing with addition of some oxides. Among various ceramic products obtained so far, the most preferable was nepheline-type sintered solids formed with addition of SiO 2 and Al 2 O 3 to the simulated waste calcine. The solid shows advantageous properties in leach rate and mechanical strength, which suggest that the ceramic solids were prepared with additions of ZrO 2 or MnO 2 , and some of them showed good characteristics

  13. Effect of sintering temperature and heating mode on consolidation of ...

    Indian Academy of Sciences (India)

    Microwave sintering was performed in 2.45 GHz multimode microwave furnace at temperatures ranging from 570–630 °C. Microwave sintering at a heating rate of as high as 22°C/min resulted in ∼55% reduction of processing time as compared to conventional sintering. A lower sintered density observed in the case of ...

  14. Sintering of nano crystalline o silicon carbide doping with

    Indian Academy of Sciences (India)

    Sinterable silicon carbide powders were prepared by attrition milling and chemical processing of an acheson type -SiC. Pressureless sintering of these powders was achieved by addition of aluminium nitride together with carbon. Nearly 99% sintered density was obtained. The mechanism of sintering was studied by ...

  15. Surface Morphology and Corrosion Behavior of Hydroxyapatite-Coated Co-Cr Implant: Effect of Sintering Conditions

    Science.gov (United States)

    Shirdar, Mostafa Rezazadeh; Taheri, Mohammad Mahdi

    2017-12-01

    The surface morphology and corrosion behavior of a hydroxyapatite (HA)-coated cobalt-chromium (Co-Cr) implant after sintering posttreatment using different times and temperatures were investigated. The substrates were electrophoretically coated with calcium phosphate in solution of Ca(NO3)·4H2O and NH4H2PO4. Sintering at four different conditions was then performed on the as-deposited samples. Scanning electron microscopy, contact angle measurement, and potentiodynamic polarization studies were employed to investigate the surface morphology, porosity, wettability, and corrosion behavior of the coated samples. The results revealed that the HA-coated substrate sintered at temperature of 600°C for 20 min showed fairly uniform microstructure with the highest density and corrosion resistance compared with the other conditions. Moreover, the highest wettability was exhibited by the HA surface sintered at temperature of 500°C for 60 min.

  16. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  17. Radiosynoviorthesis with yttrium-90 silicate

    International Nuclear Information System (INIS)

    Reichel, H.; Bergmann, H.; Kolarz, G.; Thumb, N.; Vienna Univ.

    1979-01-01

    The results of the radiosynoviorthesis with yttrium-90 silicate in 36 joints, are reported. In comparison to the radiogold therapy in 64 joints, yttrium-90 was a little more effective. Additionally, the body distribution of radioactive yttrium after radiosynoviorthesis of knee joints, was measured in 6 patients. It could be shown that the uptake of the regional lymphnodes was between 4 and 5% of the yttrium administered. The radiation dose of the regional lymphnodes certainly exceeds 1000 rad. These results point to the importance of a careful selection of patients for radiosynoviorthesis. (author)

  18. Silicate bonding properties: Investigation through thermal conductivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzini, M; Cesarini, E; Cagnoli, G; Campagna, E; Losurdo, G; Martelli, F; Piergiovanni, F; Vetrano, F [INFN, Istituto Nazionale di Fisica Nucleare, Sez. di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Haughian, K; Hough, J; Martin, I; Reid, S; Rowan, S; Veggel, A A van, E-mail: lorenzini@fi.infn.i [SUPA, University of Glasgow, Department of Physics and Astronomy, Kelvin Building G12 8QQ Glasgow, Scotland (United Kingdom)

    2010-05-01

    A direct approach to reduce the thermal noise contribution to the sensitivity limit of a GW interferometric detector is the cryogenic cooling of the mirrors and mirrors suspensions. Future generations of detectors are foreseen to implement this solution. Silicon has been proposed as a candidate material, thanks to its very low intrinsic loss angle at low temperatures and due to its very high thermal conductivity, allowing the heat deposited in the mirrors by high power lasers to be efficiently extracted. To accomplish such a scheme, both mirror masses and suspension elements must be made of silicon, then bonded together forming a quasi-monolithic stage. Elements can be assembled using hydroxide-catalysis silicate bonding, as for silica monolithic joints. The effect of Si to Si bonding on suspension thermal conductance has therefore to be experimentally studied. A measurement of the effect of silicate bonding on thermal conductance carried out on 1 inch thick silicon bonded samples, from room temperature down to 77 K, is reported. In the explored temperature range, the silicate bonding does not seem to affect in a relevant way the sample conductance.

  19. U3O8 microspheres sintering kinetics

    International Nuclear Information System (INIS)

    Godoy, A.L.E.

    1986-01-01

    U 3 O 8 microspheres sintering kinetics was determined using a hot-stage optical microscopy apparatus, able to reach temperature up to 1350 0 C in controlled atmospheres. The sintered material had its microstructure analysed by optical and electron microscopy. The microspheres were characterized initialy utilizing X-ray diffractometry and thermogravimetry. The equation which describes the microspheres shrinkage in function of the time was obtained using finite difference analysis X-ray diffractometry indicated hexagonal structure for the microspheres main starting material, ammonium diuranate thermogravimetric analysis showed reduction of this material to U 3 O 8 at 600 0 C. Ceramography results showed 5 hours sintered microspheres grain sizes G vary with the temperature. Sintered U 3 O 8 micrographs compared with published results for UO 2 , indicate similar homogeneity microstructural characteristics and suggest the processed micorspheres to be potentially useful as nuclear fuels. (Author) [pt

  20. Radiation effects in silicate glasses

    International Nuclear Information System (INIS)

    Bibler, N.E.; Howitt, D.G.

    1988-01-01

    The study of radiation effects in complex silicate glasses has received renewed attention because of their use in special applications such as high level nuclear waste immobilization and fiber optics. Radiation changes the properties of these glasses by altering their electronic and atomic configurations. These alterations or defects may cause dilatations or microscopic phase changes along with absorption centers that limit the optical application of the glasses. Atomic displacements induced in the already disordered structure of the glasses may affect their use where heavy irradiating particles such as alpha particles, alpha recoils, fission fragments, or accelerated ions are present. Large changes (up to 1%) in density may result. In some cases the radiation damage may be severe enough to affect the durability of the glass in aqueous solutions. In the paper, the authors review the literature concerning radiation effects on density, durability, stored energy, microstructure and optical properties of silicate glasses. Both simple glasses and complex glasses used for immobilization of nuclear waste are considered

  1. Evaluation of apatite silicates as solid oxide fuel cell electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Marrero-Lopez, D. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain); Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Martin-Sedeno, M.C.; Aranda, M.A.G. [Dpto. de Quimica Inorganica, Universidad Malaga, 29071 Malaga (Spain); Pena-Martinez, J. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Instituto de Energias Renovables, Parque Tecnologico, Universidad de Castilla La Mancha, 02006 Albacete (Spain); Ruiz-Morales, J.C.; Nunez, P. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Ramos-Barrado, J.R. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain)

    2010-05-01

    Apatite-type silicates have been considered as promising electrolytes for Solid Oxide Fuel Cells (SOFC); however studies on the potential use of these materials in SOFC devices have received relatively little attention. The lanthanum silicate with composition La{sub 10}Si{sub 5.5}Al{sub 0.5}O{sub 26.75} has been evaluated as electrolyte with the electrode materials commonly used in SOFC, i.e. manganite, ferrite and cobaltite as cathode materials and NiO-CGO composite, chromium-manganite and Sr{sub 2}MgMoO{sub 6} as anode materials. Chemical compatibility, area-specific resistance and fuel cell studies have been performed. X-ray powder diffraction (XRPD) analysis did not reveal any trace of reaction products between the apatite electrolyte and most of the aforementioned electrode materials. However, the area-specific polarisation resistance (ASR) of these electrodes in contact with apatite electrolyte increased significantly with the sintering temperature, indicating reactivity at the electrolyte/electrode interface. On the other hand, the ASR values are significantly improved using a ceria buffer layer between the electrolyte and electrode materials to prevent reactivity. Maximum power densities of 195 and 65 mWcm{sup -2} were obtained at 850 and 700 C, respectively in H{sub 2} fuel, using an 1 mm-thick electrolyte, a NiO-Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} composite as anode and La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} as cathode materials. This fuel cell was tested for 100 h in 5%H{sub 2}-Ar atmosphere showing stable performance. (author)

  2. Uranium-thorium silicates, with specific reference to the species in the Witwatersrand reefs

    International Nuclear Information System (INIS)

    Smits, G.

    1987-01-01

    (U,Th)-silicates form two complete series of anhydrous and hydrated species with general formulae (U,Th)SiO 4 and (U,Th)SiO 4 .nH 2 O respectively. The end-members of the anhydrous series are anhydrous coffinite and thorite, and those of the hydrated series, coffinite and thorogummite. Although the silicates are relatively rare in nature, coffinite is a common ore mineral in uranium deposits of the sandstone type. In the Witwatersrand reefs, (U,Th)-silicates are extremely rare in most reefs, except for the Elsburg Reefs on the West Rand Goldfield and the Dominion Reef. In these reefs detrital uraninite has been partly or entirely transformed to (U,Th)-silicates of coffinite composition, but thorite and thorogummite of detrital origin are also found in the Dominion Reef. In leaching tests on polished sections of rock samples containing (U,Th)-silicates, a dilute sulphuric acid solution, to which ferric iron had been added, was used as the lixiviant. It appeared that the dissolution of coffinite is less rapid than that of uraninite and uraniferous leucoxene. However, the reaction of silicates of high thorium content is much slower, and was not completed during the tests

  3. The use of Bacillus genus to dressing of silicate raw materials

    Directory of Open Access Journals (Sweden)

    Štyriaková Iveta

    2000-09-01

    Full Text Available Bacteria of Bacillus genus from Banská Hodruša ore deposit and from Horná Prievrana kaolin deposit caused a more intensive destruction of silicate minerals by their activity, especially by the metabolites production. Their activity resulted to the development of corrosive and enantiomorphic holes on silicate minerals surface when sulphidic minerals were released and the metals were extracted into solution.The monitoring of Bacillus spp. occurrence in various deposits with silicate minerals composition suggested that these bacteria can be found in several deposits and waste dumps with silicate minerals at Slovakia. The widest species representation was detected in samples from the Horná Prievrana kaolin deposit.The experiments with primary silicates showed either a more intensive destruction of silicate minerals accompanied by sulphides releasing from these minerals or a more intensive metals extraction from sulphidic minerals after ore dressing. The important percentage of precious metals extraction (30% of gold and 30% of argentine from silicate minerals can suggest a possibility of the regulation of cyanides use in precious metals winning. A process for biological removal of elements from the samples was the result of the cultivation of organic acids - producing strains of the genus Bacillus. Hovewer, these bacteria synthesized also polysaccharides during bioleaching. Extensive acidic mucopolysaccharide films, which entrapped mineral particles, were identified by the ruthenium red staining. Ore bioleaching can not compete with physical and chemical methods in the rapidity of metal extraction from rich ores without ecological criterion. However, biotechnology becomes an alternative way in metals extraction from poor ores or wastes from the economical as well as the ecological view.The laboratory experiments with secondary silicates confirmed various forms of iron binding in kaolins and an important influence of the iron binding form on the

  4. Trace fossils of Ordovician radiolarian chert and siliceous mudstone in Newfoundland, Canada

    Science.gov (United States)

    Kakuwa, Yoshitaka

    2017-08-01

    Ordovician radiolarian chert and siliceous mudstone in Newfoundland are examined to elucidate the development of trace fossils in and on the Early Paleozoic ocean bottom. Chert sedimentation in the Shoal Arm Formation (SAF) is limited to a short interval, but its sedimentation rate is high with few siliciclastic materials. Trace fossils are common in chert in the SAF, but their development is interrupted by frequent anoxic events. The trace fossils are larger than trace fossils in the contemporary chert of other areas. In contrast, trace fossils in the Strong Island Chert (SIC) are moderately-sized to small, with a few sandstone beds interbedded with chert. Those characteristics reflect differences in the sedimentary environments. Rocks of the SIC were deposited in a basinal part of a back-arc basin; whereas, those in the SAF were deposited on a small isolated basin. Red chert or siliceous rocks that underlie grey cherts and siliceous rocks of the SIC and the SAF bear small and simple trace fossils. This is a common feature of ;oceanic red rocks.; Radiolarian chert and siliceous rocks in Newfoundland also showed that trace fossils are widespread by the Middle Ordovician in the deep-sea environment. The Great Ordovician Biodiversification Event is confirmed in the radiolarian siliceous rocks there.

  5. Silicates materials of high vacuum technology

    CERN Document Server

    Espe, Werner

    2013-01-01

    Materials of High Vacuum Technology, Volume 2: Silicates covers silicate insulators of special importance to vacuum technology. The book discusses the manufacture, composition, and physical and chemical properties of technical glasses, quartz glass, quartzware, vycor glass, ceramic materials, mica, and asbestos.

  6. Electric field-assisted sintering of nanocrystalline hydroxyapatite for biomedical applications

    Science.gov (United States)

    Tran, Tien Bich

    consistent during varied heating rate (50--400ºC/min) and varied pressure application (25--90 MPa) studies. While in vitro cytocompatibility studies using MG63 osteoblast-like cells demonstrated the biocompatibility of the FAST-processed specimens, bioactivity was sensitive to processing parameters. Since extensive dehydroxylation reduces the surface charge of the sintered materials, apatite deposition during simulated body fluid immersion only occurred when dehydroxylation was mild---i.e., on specimens sintered at low temperatures (800--900ºC) or for short periods. Microstructural investigations revealed that HA sintered at temperatures above 900ºC under an applied electric field contained nanometric residual pores in grain interiors, as well as micron-sized dehydroxylation-related pores at grain boundaries and grain boundary junctions. These larger pores were responsible for the increasing embrittlement of specimens sintered at higher temperatures. Although grain size dependence could not be found in the 60--100 nm grain size range, fracture toughness (KIC = 1.92 MPa√m, maximum) increased with decreasing sintering temperature. Results from the suite of investigations conducted demonstrate that biocompatible and bioactive nanocrystalline hydroxyapatite with enhanced mechanical properties can be efficiently manufactured by field-assisted sintering under controlled processing conditions.

  7. Analysis of Laser Sintering Technology

    Directory of Open Access Journals (Sweden)

    Vladislav Markovič

    2014-02-01

    Full Text Available The new, high-tech development and customization is one ofthe most important factors in promoting the country‘s economicgrowth indicators. The economic downturn in the industryrequires technology and equipment using a minimumof raw materials and providing maximum performance. Thisstatement perfectly describes the innovative, forward-looking,cost-effective laser powder sintering (SLS technology. Here,thanks to the latest engineering achievements, product surfacesare modified and improved, they gain new characteristics. SLSis viable in automobile, engineering, construction, aerospace,aircraft, printing, medical and other areas.In order to create a product which meets the standards andtechnical documentation it is necessary to use and ensure highquality of raw materials, high-end equipment, qualified personnel,the working environment with proper climatic conditions, ergonomics,etc. But all of these, the quality of the product becomesthe decisive indicators meaningless if know how to properly selectthe laser processing operation. Scanning speed, beam power,pulse frequency, protective gases, powder layer thickness – allof them are the physical and mechanical characteristics of thechange in a small range changes the quality of the product of thefuture, the field of application and performance characteristics.

  8. Low Temperature Constrained Sintering of Cerium Gadolinium OxideFilms for Solid Oxide Fuel Cell Applications

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Jason Dale [Univ. of California, Berkeley, CA (United States)

    2007-01-01

    Cerium gadolinium oxide (CGO) has been identified as an acceptable solid oxide fuel cell (SOFC) electrolyte at temperatures (500-700 C) where cheap, rigid, stainless steel interconnect substrates can be used. Unfortunately, both the high sintering temperature of pure CGO, >1200 C, and the fact that constraint during sintering often results in cracked, low density ceramic films, have complicated development of metal supported CGO SOFCs. The aim of this work was to find new sintering aids for Ce0.9Gd0.1O1.95, and to evaluate whether they could be used to produce dense, constrained Ce0.9Gd0.1O1.95 films at temperatures below 1000 C. To find the optimal sintering aid, Ce0.9Gd0.1O1.95 was doped with a variety of elements, of which lithium was found to be the most effective. Dilatometric studies indicated that by doping CGO with 3mol% lithium nitrate, it was possible to sinter pellets to a relative density of 98.5% at 800 C--a full one hundred degrees below the previous low temperature sintering record for CGO. Further, it was also found that a sintering aid's effectiveness could be explained in terms of its size, charge and high temperature mobility. A closer examination of lithium doped Ce0.9Gd0.1O1.95 indicated that lithium affects sintering by producing a Li2O-Gd2O3-CeO2 liquid at the CGO grain boundaries. Due to this liquid phase sintering, it was possible to produce dense, crack-free constrained films of CGO at the record low temperature of 950 C using cheap, colloidal spray deposition processes. This is the first time dense constrained CGO films have been produced below 1000 C and could help commercialize metal supported ceria based solid oxide fuel cells.

  9. Discrimination symbol applying method for sintered nuclear fuel product

    International Nuclear Information System (INIS)

    Ishizaki, Jin

    1998-01-01

    The present invention provides a symbol applying method for applying discrimination information such as an enrichment degree on the end face of a sintered nuclear product. Namely, discrimination symbols of information of powders are applied by a sintering aid to the end face of a molded member formed by molding nuclear fuel powders under pressure. Then, the molded product is sintered. The sintering aid comprises aluminum oxide, a mixture of aluminum oxide and silicon dioxide, aluminum hydride or aluminum stearate alone or in admixture. As an applying means of the sintering aid, discrimination symbols of information of powders are drawn by an isostearic acid on the end face of the molded product, and the sintering aid is sprayed thereto, or the sintering aid is applied directly, or the sintering aid is suspended in isostearic acid, and the suspension is applied with a brush. As a result, visible discrimination information can be applied to the sintered member easily. (N.H.)

  10. Solid-state sintering of tungsten heavy alloys

    International Nuclear Information System (INIS)

    Gurwell, W.E.

    1994-10-01

    Solid-state sintering is a technologically important step in the fabrication of tungsten heavy alloys. This work addresses practical variables affecting the sinterability: powder particle size, powder mixing, and sintering temperature and time. Compositions containing 1 to 10 micrometer (μM) tungsten (W) powders can be fully densified at temperatures near the matrix solidus. Blending with an intensifier bar provided good dispersion of elemental powders and good as-sintered mechanical properties under adequate sintering conditions. Additional ball milling increases powder bulk density which primarily benefits mold and die filling. Although fine, 1 μm W powder blends have high sinterability, higher as-sintered ductilities are reached in shorter sintering times with coarser, 5 μm W powder blends; 10μm W powder blends promise the highest as-sintered ductilities due to their coarse microstructural W

  11. Sintering of Fine Particles in Suspension Plasma Sprayed Coatings.

    Science.gov (United States)

    Latka, Leszek; Goryachev, Sergey B; Kozerski, Stefan; Pawlowski, Lech

    2010-07-01

    Suspension plasma spraying is a process that enables the production of finely grained nanometric or submicrometric coatings. The suspensions are formulated with the use of fine powder particles in water or alcohol with some additives. Subsequently, the suspension is injected into plasma jet and the liquid additives evaporate. The remaining fine solids are molten and subsequently agglomerate or remain solid, depending on their trajectory in the plasma jet. The coating's microstructure results from these two groups of particles arriving on a substrate or previously deposited coating. Previous experimental studies carried out for plasma sprayed titanium oxide and hydroxyapatite coatings enabled us to observe either a finely grained microstructure or, when a different suspension injection mode was used, to distinguish two zones in the microstructure. These two zones correspond to the dense zone formed from well molten particles, and the agglomerated zone formed from fine solid particles that arrive on the substrate in a solid state. The present paper focuses on the experimental and theoretical analysis of the formation process of the agglomerated zone. The experimental section establishes the heat flux supplied to the coating during deposition. In order to achieve this, calorimetric measurements were made by applying experimental conditions simulating the real coatings' growth. The heat flux was measured to be in the range from 0.08 to 0.5 MW/m²,depending on the experimental conditions. The theoretical section analyzes the sintering during the coating's growth, which concerns the fine particles arriving on the substrate in the solid state. The models of volume, grain boundary and surface diffusion were analyzed and adapted to the size and chemistry of the grains, temperature and time scales corresponding to the suspension plasma spraying conditions. The model of surface diffusion was found to best describe the sintering during suspension plasma spraying. The formation

  12. Sintering of Fine Particles in Suspension Plasma Sprayed Coatings

    Directory of Open Access Journals (Sweden)

    Leszek Latka

    2010-07-01

    Full Text Available Suspension plasma spraying is a process that enables the production of finely grained nanometric or submicrometric coatings. The suspensions are formulated with the use of fine powder particles in water or alcohol with some additives. Subsequently, the suspension is injected into plasma jet and the liquid additives evaporate. The remaining fine solids are molten and subsequently agglomerate or remain solid, depending on their trajectory in the plasma jet. The coating’s microstructure results from these two groups of particles arriving on a substrate or previously deposited coating. Previous experimental studies carried out for plasma sprayed titanium oxide and hydroxyapatite coatings enabled us to observe either a finely grained microstructure or, when a different suspension injection mode was used, to distinguish two zones in the microstructure. These two zones correspond to the dense zone formed from well molten particles, and the agglomerated zone formed from fine solid particles that arrive on the substrate in a solid state. The present paper focuses on the experimental and theoretical analysis of the formation process of the agglomerated zone. The experimental section establishes the heat flux supplied to the coating during deposition. In order to achieve this, calorimetric measurements were made by applying experimental conditions simulating the real coatings’ growth. The heat flux was measured to be in the range from 0.08 to 0.5 MW/m2,depending on the experimental conditions. The theoretical section analyzes the sintering during the coating’s growth, which concerns the fine particles arriving on the substrate in the solid state. The models of volume, grain boundary and surface diffusion were analyzed and adapted to the size and chemistry of the grains, temperature and time scales corresponding to the suspension plasma spraying conditions. The model of surface diffusion was found to best describe the sintering during suspension

  13. Mesoporous Silicate Materials in Sensing

    Directory of Open Access Journals (Sweden)

    Paul T. Charles

    2008-08-01

    Full Text Available Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through cocondensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  14. Sintering behavior and property of bioglass modified HA-Al2O3 composite

    Directory of Open Access Journals (Sweden)

    Wang Li-li

    2012-01-01

    Full Text Available The bioglass modified HA-Al2O3 composites were successfully fabricated by mixing HA, synthesized by wet chemical method between precursor materials H3PO4 and Ca(OH2, with 25wt% Al2O3 and different content of bioglass (5%, 25%, 45%, 65wt% respectively, with a mole fraction of 53.9%SiO2, 22.6%Na2O, 21.8%CaO, and 1.7wt%P2O5, sintered in air at various temperatures (750-950°C for 2h. when the content of bioglass is below 45wt% in the composite, HA decomposes completely and transforms to β-TCP. The main phase in this case are β-TCP, Al2O3 and Ca3(AlO32.When the content of bioglass is above 45wt% in the composite, the decomposition of HA to β-TCP is suppressed and the main phases in this case are Al2O3 and HA, DCP□CaHPO4□ and β-TCP, which almost have the same chemical composition, forming ternary-glass phase, and have better bioactive than pure HA. It can also be found that at the certain addition of bioglass, the higher sintered temperature, the bigger volume density and flexural strength of the composite are, but when the sintered temperature reaches 950°C, they decrease. This modified HA-Al2O3 composites by calcium silicate glass have a much lower sintering temperature and decrease the production cost much.

  15. Gels composed of sodium-aluminum silicate, Lake Magadi, Kenya

    Science.gov (United States)

    Eugster, H.P.; Jones, B.F.

    1968-01-01

    Sodium-aluminum silicate gels are found in surftcial deposits as thick as 5 centimeters in the Magadi area of Kenya. Chemical data indicate they are formed by the interaction of hot alkaline springwaters (67?? to 82??C; pH, about 9) with alkali trachyte flows and their detritus, rather than by direct precipitation. In the process, Na2O is added from and silica is released to the saline waters of the springs. Algal mats protect the gels from erosion and act as thermal insulators. The gels are probably yearly accumulates that are washed into the lakes during floods. Crystallization of these gels in the laboratory yields analcite; this fact suggests that some analcite beds in lacustrine deposits may have formed from gels. Textural evidence indicates that cherts of rocks of the Pleistocene chert series in the Magadi area may have formed from soft sodium silicate gels. Similar gels may have acted as substrates for the accumulation and preservation of prebiological organic matter during the Precambrian.

  16. Effects of sintering atmosphere and initial particle size on sintering of gadolinia-doped ceria

    International Nuclear Information System (INIS)

    Batista, Rafael Morgado

    2014-01-01

    The effects of the sintering atmosphere and initial particle size on the sintering of ceria containing 10 mol% gadolinia (GdO 1.5 ) were systematically investigated. The main physical parameter was the specific surface area of the initial powders. Nanometric powders with three different specific surface areas were utilized, 210 m 2 /g, 36,2 m 2 /g e 7,4 m 2 /g. The influence on the densification, and micro structural evolution were evaluated. The starting sintering temperature was verified to decrease with increasing on the specific surface area of raw powders. The densification was accelerated for the materials with smaller particle size. Sintering paths for crystallite growth were obtained. Master sintering curves for gadolinium-doped ceria were constructed for all initial powders. A computational program was developed for this purpose. The results for apparent activation energy showed noticeable dependence with specific surface area. In this work, the apparent activation energy for densification increased with the initial particle size of powders. The evolution of the particle size distributions on non isothermal sintering was investigated by WPPM method. It was verified that the grain growth controlling mechanism on gadolinia doped ceria is the pore drag for initial stage and beginning of intermediate stage. The effects of the sintering atmosphere on the stoichiometry deviation of ceria, densification, microstructure evolution, and electrical conductivity were analyzed. Inert, oxidizing, and reducing atmospheres were utilized on this work. Deviations on ceria stoichiometry were verified on the bulk materials. The deviation verified was dependent of the specific surface area and sintering atmosphere. Higher reduction potential atmospheres increase Ce 3+ bulk concentration after sintering. Accelerated grain growth and lower electrical conductivities were verified when reduction reactions are significantly present on sintering. (author)

  17. Master sintering curve: A practical approach to its construction

    Directory of Open Access Journals (Sweden)

    Pouchly V.

    2010-01-01

    Full Text Available The concept of a Master Sintering Curve (MSC is a strong tool for optimizing the sintering process. However, constructing the MSC from sintering data involves complicated and time-consuming calculations. A practical method for the construction of a MSC is presented in the paper. With the help of a few dilatometric sintering experiments the newly developed software calculates the MSC and finds the optimal activation energy of a given material. The software, which also enables sintering prediction, was verified by sintering tetragonal and cubic zirconia, and alumina of two different particle sizes.

  18. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.

    2012-11-01

    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  19. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Sargent, B. A., E-mail: sfogerty@pas.rochester.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2016-10-20

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  20. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    International Nuclear Information System (INIS)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I.; Sargent, B. A.

    2016-01-01

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  1. Integrated analysis of oxide nuclear fuel sintering

    International Nuclear Information System (INIS)

    Baranov, V.; Kuzmin, R.; Tenishev, A.; Timoshin, I.; Khlunov, A.; Ivanov, A.; Petrov, I.

    2011-01-01

    Dilatometric and thermal-gravimetric investigations have been carried out for the sintering process of oxide nuclear fuel in gaseous Ar - 8% H 2 atmosphere at temperatures up to 1600 0 C. The pressed compacts were fabricated under real production conditions of the OAO MSZ with application of two different technologies, so called 'dry' and 'wet' technologies. Effects of the grain size growth after the heating to different temperatures were observed. In order to investigate the effects produced by rate of heating on properties of sintered fuel pellets, the heating rates were varied from 1 to 8 0 C per minute. Time of isothermal overexposure at maximal temperature (1600 0 C) was about 8 hours. Real production conditions were imitated. The results showed that the sintering process of the fuel pellets produced by two technologies differs. The samples sintered under different heating rates were studied with application of scanning electronic microscopy analysis for determination of mean grain size. A simulation of heating profile for industrial furnaces was performed to reduce the beam cycles and estimate the effects of variation of the isothermal overexposure temperatures. Based on this data, an optimization of the sintering conditions was performed in operations terms of OAO MSZ. (authors)

  2. Development of dense glass-ceramic from recycled soda-lime-silicate glass and fly ash for tiling

    Science.gov (United States)

    Mustaffar, Mohd Idham; Mahmud, Mohamad Haniza; Hassan, Mahadi Abu

    2017-12-01

    Dense glass-ceramics were prepared by sinter-crystallization process from a combination of soda-lime-silicate glass waste and fly ash. Bentonite clay that acted as a binder was also added in a prepared formulation. The powder mixture of soda-lime glass, fly ash and bentonite clay were compacted by using uniaxial hydraulic press machine and sintered at six (6) various temperatures namely 750, 800, 850, 900, 950 and 1000 °C. The heating rate and sintering time were set at 5 °C/min and 30 minutes respectively. The results revealed that modulus of rupture (MOR), density and linear shrinkage increase first from 750 to 800 °C but decrease later after 800 to 1000 °C. In the meantime, water absorption was showing completely an opposite trend. The glass-ceramic sintered at 800 °C was found to have the best combination of physical-mechanical properties and has the potential to be applied in the construction industry particularly as floor and wall tiles because of the simple manufacturing process at low temperature.

  3. Model Dust Envelopes Around Silicate Carbon Stars

    Directory of Open Access Journals (Sweden)

    Kyung-Won Suh

    2006-03-01

    Full Text Available We have modeled dust envelopes around silicate carbon stars using optical properties for a mixture of amorphous carbon and silicate dust grains paying close attention to the infrared observations of the stars. The 4 stars show various properties in chemistry and location of the dust shell. We expect that the objects that fit a simple detached silicate dust shell model could be in the transition phase of the stellar chemistry. For binary system objects, we find that a mixed dust chemistry model would be necessary.

  4. Thermal Conductivity and Sintering Behavior of Advanced Thermal Barrier Coatings

    Science.gov (United States)

    Zhu, Dongming; Miller, Robert A.

    2002-01-01

    Advanced thermal barrier coatings, having significantly reduced long-term thermal conductivities, are being developed using an approach that emphasizes real-time monitoring of thermal conductivity under conditions that are engine-like in terms of temperatures and heat fluxes. This is in contrast to the traditional approach where coatings are initially optimized in terms of furnace and burner rig durability with subsequent measurement in the as-processed or furnace-sintered condition. The present work establishes a laser high-heat-flux test as the basis for evaluating advanced plasma-sprayed and physical vapor-deposited thermal barrier coatings under the NASA Ultra Efficient Engine Technology (UEET) Program. The candidate coating materials for this program are novel thermal barrier coatings that are found to have significantly reduced thermal conductivities due to an oxide-defect-cluster design. Critical issues for designing advanced low conductivity coatings with improved coating durability are also discussed.

  5. New materials through a variety of sintering methods

    Science.gov (United States)

    Jaworska, L.; Cyboroń, J.; Cygan, S.; Laszkiewicz-Łukasik, J.; Podsiadło, M.; Novak, P.; Holovenko, Y.

    2018-03-01

    New sintering techniques make it possible to obtain materials with special properties that are impossible to obtain by conventional sintering techniques. This issue is especially important for ceramic materials for application under extreme conditions. Following the tendency to limit critical materials in manufacturing processes, the use of W, Si, B, Co, Cr should be limited, also. One of the cheapest and widely available materials is aluminum oxide, which shows differences in phase composition, grain size, hardness, strain and fracture toughness of the same type of powder, sintered via various methods. In this paper the alumina was sintered using the conventional free sintering process, microwave sintering, Spark Plasma Sintering (SPS), high pressure-high temperature method (HP-HT) and High Pressure Spark Plasma Sintering (HP SPS). Phase composition analysis, by X-ray diffraction of the alumina materials sintered using various methods, was carried out. For the conventional sintering method, compacts are composed of α-Al2O3 and θ-Al2O3. For compacts sintered using SPS, microwave and HP-HT methods, χ-Al2O3 and γ-Al2O3 phases were additionally present. Mechanical and physical properties of the obtained materials were compared between the methods of sintering. On the basis of images from scanning electron microscope quantitative analysis was performed to determine the degree of grain growth of alumina after sintering.

  6. Sintered cobalt-rare earth intermetallic product

    International Nuclear Information System (INIS)

    Benz, M.G.

    1975-01-01

    This patent describes a sintered product having substantially stable permanent magnet properties in air at room temperature. It comprises compacted particulate cobalt--rare earth alloy consisting essentially of a Co 5 R intermetallic phase and a CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase, where R is a rare earth metal. The Co 5 R intermetallic phase is present in an amount of at least 65 percent by weight of the sintered product and the CoR intermetallic phase which is richer in rare earth metal content than the Co 5 R phase is present in a positive amount having a value ranging up to about 35 percent by weight of the product. The sintered product has a density of at least 87 percent and has pores which are substantially noninterconnecting and wherein the component grains have an average size less than 30 microns

  7. Method of manufacturing sintered nuclear fuel

    International Nuclear Information System (INIS)

    Watarumi, Kazutoshi.

    1984-01-01

    Purpose: To obtain composite pellets with an improved strength. Method: A core mainly composed of fuel materials is previously prepared, embedded into the central portion of a pellet, silted therearound with cladding material, and then pressmolded and sintered. For instance, a rugby-ball like core body with the maximum outer diameter of 6 mm and the height of 6 mm is made by compressive molding with uranium dioxide powder, then coating material comprising the same powder incorporated with 0.1 % by weight of SiC fibers is filled around the core body, which is molded into a composite pellet by means of pressing and then sintered at 1600 0 C, to obtain a sintered pellet of 93.5 % theoretical density. As the result of the compression test for the pellet, it showed a strength greater by 15 % than that of the similar mono-layer pellet. (Kamimura, M.)

  8. Sintering of nickel steam reforming catalysts

    DEFF Research Database (Denmark)

    Sehested, Jens; Larsen, Niels Wessel; Falsig, Hanne

    2014-01-01

    The lifetimes of heterogeneous catalysts in many widely used industrial processes are determined by the loss of active surface area. In this context, the underlying physical sintering mechanism and quantitative information about the rate of sintering at industrial conditions are relevant....... In this paper, particle migration and coalescence in nickel steam reforming catalysts is studied. Density functional theory calculations indicate that Ni-OH dominate nickel transport at nickel surfaces in the presence of steam and hydrogen as Ni-OH has the lowest combined energies of formation and diffusion...... compared to other potential nickel transport species. The relation between experimental catalyst sintering data and the effective mass diffusion constant for Ni-OH is established by numerical modelling of the particle migration and coalescence process. Using this relation, the effective mass diffusion...

  9. Design of sintering-stable heterogeneous catalysts

    DEFF Research Database (Denmark)

    Gallas-Hulin, Agata

    the crystalline framework of a zeolite creates a steric hindrance against agglomeration into larger clusters. In the present study, experimental protocols for encapsulation of metal nanoparticles inside zeolites were developed. Two different methodologies were proposed to encapsulate gold, palladium and platinum......One of the major issues in the use of metal nanoparticles in heterogeneous catalysis is sintering. Sintering occurs at elevated temperatures because of increased mobility of nanoparticles, leading to their agglomeration and, as a consequence, to the deactivation of the catalyst. It is an emerging...... problem especially for the noble metals-based catalysis. These metals being expensive and scarce, it is worth developing catalyst systems which preserve their activity over time. Encapsulation of nanoparticles inside zeolites is one of the ways to prevent sintering. Entrapment of nanoparticles inside...

  10. Fabrication of 200 mm Diameter Sintering Body of Skutterudite Thermoelectric Material by Spark Plasma Sintering

    Science.gov (United States)

    Tomida, T.; Sumiyoshi, A.; Nie, G.; Ochi, T.; Suzuki, S.; Kikuchi, M.; Mukaiyama, K.; Guo, J. Q.

    2017-05-01

    Filled skutterudite is a promising material for thermoelectric power generation because its ZT value is relatively high. However, mass production of high-performance thermoelectric materials remains a challenge. This study focused on the sintering process of thermoelectric materials. Large-diameter n-type (Yb or La, Ca, Al, Ga, In)0.8(Co, Fe)4Sb12 skutterudite sintering bodies with a small thickness were successfully produced by the spark plasma sintering (SPS) method. When direct current flows through the thermoelectric sintering body during the SPS pulse, the Peltier effect causes a temperature difference within the sintering body. To eliminate the Peltier effect, an electrical insulating material was inserted between the punch (electrode) and the sintering body. In this way, an n-type La-filled skutterudite sample with a diameter of 200 mm, thickness of 21 mm, and weight of 5 kg was successfully produced. The thermoelectric properties and microstructures of the sample were almost the same throughout the whole sintering body, and the dimensionless figure of merit reached 1.0 at 773 K.

  11. PRODUCTION OF WELDMENTS FROM SINTERED TITANIUM ALLOYS

    Directory of Open Access Journals (Sweden)

    A. YE. Kapustyan

    2014-04-01

    Full Text Available Purpose. Limited application of details from powder titanium alloys is connected with the difficulties in obtaining of long-length blanks, details of complex shape and large size. We can solve these problems by applying the welding production technology. For this it is necessary to conduct a research of the structure and mechanical properties of welded joints of sintered titanium alloys produced by flash welding. Methodology. Titanium industrial powders, type PT5-1 were used as original substance. Forming of blanks, whose chemical composition corresponded to BT1-0 alloy, was carried out using the powder metallurgy method. Compounds were obtained by flash welding without preheating. Microstructural investigations and mechanical tests were carried out. To compare the results investigations of BT1-0 cast alloy were conducted. Findings. Samples of welded joints of sintered titanium blanks from VT1-0 alloy using the flash butt welding method were obtained. During welding the microstructure of basic metal consisting of grains of an a-phase, with sizes 40...70 mkm, is transformed for the seam weld and HAZ into the lamellar structure of an a-phase. The remaining pores in seam weld were practically absent; in the HAZ their size was up to 2 mkm, with 30 mkm in the basic metal. Attainable level of mechanical properties of the welded joint in sintered titanium alloys is comparable to the basic metal. Originality. Structure qualitative changes and attainable property complex of compounds of sintered titanium alloys, formed as a result of flash butt welding were found out. Practical value. The principal possibility of high-quality compounds obtaining of sintered titanium alloys by flash welding is shown. This gives a basis for wider application of sintered titanium alloys due to long-length blanks production that are correspond to deformable strand semi finished product.

  12. Phase characterisation in spark plasma sintered TiPt alloy

    CSIR Research Space (South Africa)

    Chikosha, S

    2011-12-01

    Full Text Available The conclusions drawn from this presentation are that Spark Plasma Sintering (SPS) of equiatomic BE TiPt powder produces fully sintered specimens, with incomplete homogenisation. There is a need for improved furnace atmosphere control so...

  13. Recent developments in the MOCVD and ALD of rare earth oxides and silicates

    International Nuclear Information System (INIS)

    Jones, Anthony C.; Aspinall, Helen C.; Chalker, Paul R.; Potter, Richard J.; Kukli, Kaupo; Rahtu, Antti; Ritala, Mikko; Leskelae, Markku

    2005-01-01

    Lanthanide, or rare-earth oxides are currently being investigated as alternatives to SiO 2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high-κ dielectric oxides and in this paper some of our recent research into the MOCVD and ALD of PrO x , La 2 O 3 , Gd 2 O 3 , Nd 2 O 3 and their related silicates are reviewed

  14. Process for microwave sintering boron carbide

    Science.gov (United States)

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  15. Fusibility and sintering characteristics of ash

    International Nuclear Information System (INIS)

    Ots, A. A.

    2012-01-01

    The temperature characteristics of ash fusibility are studied for a wide range of bituminous and brown coals, lignites, and shales with ratios R B/A of their alkaline and acid components between 0.03 and 4. Acritical value of R B/A is found at which the fusion temperatures are minimal. The sintering properties of the ashes are determined by measuring the force required to fracture a cylindrical sample. It is found that the strength of the samples increases sharply at certain temperatures. The alkali metal content of the ashes has a strong effect on their sintering characteristics.

  16. Highly silicic compositions on the Moon.

    Science.gov (United States)

    Glotch, Timothy D; Lucey, Paul G; Bandfield, Joshua L; Greenhagen, Benjamin T; Thomas, Ian R; Elphic, Richard C; Bowles, Neil; Wyatt, Michael B; Allen, Carlton C; Donaldson Hanna, Kerri; Paige, David A

    2010-09-17

    Using data from the Diviner Lunar Radiometer Experiment, we show that four regions of the Moon previously described as "red spots" exhibit mid-infrared spectra best explained by quartz, silica-rich glass, or alkali feldspar. These lithologies are consistent with evolved rocks similar to lunar granites in the Apollo samples. The spectral character of these spots is distinct from surrounding mare and highlands material and from regions composed of pure plagioclase feldspar. The variety of landforms associated with the silicic spectral character suggests that both extrusive and intrusive silicic magmatism occurred on the Moon. Basaltic underplating is the preferred mechanism for silicic magma generation, leading to the formation of extrusive landforms. This mechanism or silicate liquid immiscibility could lead to the formation of intrusive bodies.

  17. Carbon Monoxide Silicate Reduction System, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is an innovative method that for the first time uses the strong reductant carbon monoxide to both reduce iron...

  18. Adsorption of aqueous silicate on hematite

    International Nuclear Information System (INIS)

    Taylor, P.; Ticknor, K.V.

    1997-08-01

    During radioisotope sorption studies, adsorption of silicate from synthetic groundwaters by synthetic hematite was observed. To further investigate this observation, the adsorption of silicate onto hematite (α-Fe 2 O 3 ) powder from a neutral, aqueous NaC1 solution (0.1 mol/dm 3 ), containing 2.56 x 10 -4 mol/dm 3 of Si added as Na 2 SiO 3 ·9H 2 O, was measured at ∼21 deg C. Equilibrium adsorption of silicate amounted to ∼1.93 μmol/m 2 (one Si(O,OH) 4 moiety per 86 A 2 ). It is important to take this adsorption into account when evaluating the ability of iron oxides to adsorb other species, especially anions, from groundwaters. Silicate adsorption is known to diminish the ability of iron oxides to adsorb other anions. (author)

  19. Carbon Monoxide Silicate Reduction System, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — The Carbon Monoxide Silicate Reduction System (COSRS) is a novel technology for producing large quantities of oxygen on the Moon. Oxygen yields of 15 kilograms per...

  20. Siliceous microfossil extraction from altered Monterey rocks

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C.O.; Casey, R.E.

    1986-04-01

    Samples of altered Monterey rocks of differing lithologies were processed by various methods to develop new techniques for extracting siliceous microfossils. The preliminary use of thin sections made from the same rocks reduced the number of probable samples (samples worth further processing) by about one-third. Most of the siliceous microfossils contained in altered Monterey rocks appear to be highly recrystallized and are extremely fragile; however, some contained silicified and silica-infilled radiolarians and planktonic and benthonic foraminifera, which are very tough. In general the most useful techniques were gently hydrochloric acid, hydrogen peroxide, formic acid, monosodium glutamate, and regular siliceous microfossil extraction techniques. Unsuccessful techniques and a new siliceous microfossil flotation technique are also documented.

  1. Magnetic properties of sheet silicates

    International Nuclear Information System (INIS)

    Ballet, O.; Coey, J.M.D.

    1982-01-01

    Susceptibility, magnetisation and Moessbauer measurements are reported for a representative selection of 2:1 layer phyllosilicates. Eight samples from the mica, vermiculite and smectite groups include examples diluted in iron which are paramagnetic at all temperatures, as well as iron-rich silicates which order magnetically below 10 K. Anisotropic susceptibility of crystals of muscovite, biotite and vermiculite is quantitatively explained with a model where the Fe 2+ ions lie in sites of effective trigonal symmetry, the trigonal axis lying normal to the sheets. The ferrous ground state is an orbital singlet. Ferric iron gives an isotropic contribution to the susceptibility. Fe 2+ -Fe 2+ exchange interactions are ferromagnetic with Gapprox. equal to2 K, whereas Fe 3+ -Fe 3+ coupling is antiferromagnetic in the purely ferric minerals. A positive paramagnetic Curie temperature for glauconite may be attributable to Fe 2+ → Fe 3+ charge transfer. Magnetic order was found to set in inhomogeneously for glauconite at 1-7 K. One biotite sample showed an antiferromagnetic transition at Tsub(N) = 7 K marked by a well-defined susceptibility maximum. Its magnetic structure, consisting of ferromagnetic sheets with moments in their planes coupled antiferromagnetically by other, weak interactions, resembles that found earlier for the 1:1 mineral greenalite. (orig.)

  2. Intrinsic luminescence of alkali silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Arbuzov, V.I.; Grabovskis, V.Y.; Tolstoi, M.N.; Vitol, I.K.

    1986-09-01

    This study obtains additional information on L centers and their role in electron excitation and intrinsic luminescence of a whole series. (Li, Na, K, Rb, and Cs) of alkali silicate glasses. The authors compare the features of the interaction with radiation of specimens of glass and crystal of a similar chemical composition, since silicates of alkali metals can be obtained in both the glassy and crystalline states.

  3. Disk shaped radiation sources fabricated by compression and formation of sinter powder

    International Nuclear Information System (INIS)

    Kawano, Takao

    2008-01-01

    Sinters are deposits found at the bottom of hot springs, some of which contain naturally occurring radioisotopes of the uranium and thorium series. A disk-shaped radiation source was developed by compressing sinter powder. Ten disk-shaped radiation sources were fabricated by this method and their weight, thickness, mass density, and radioactivity were determined. The results indicated that special skills or techniques are not required for production of a radiation source with this method, and the production method is robust. Thus, the method is suitable for the simultaneous fabrication of multiple uniform radiation sources. To evaluate the ability of this fabrication method to produce sinter radiation sources applicable to courses involving radiation protection or similar investigations, the dependence of the radiation count rate on distance, shielding thickness, and shielding materials was examined using a conventional GM survey meter. The results showed that the sinter radiation source is suitable to comprehend characteristics of radiation and principle of radiation protection related to distance and shielding. (author)

  4. Thermodynamics and Kinetics of Silicate Vaporization

    Science.gov (United States)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  5. Production of a calcium silicate cement material from alginate impression material.

    Science.gov (United States)

    Washizawa, Norimasa; Narusawa, Hideaki; Tamaki, Yukimichi; Miyazaki, Takashi

    2012-01-01

    The purpose of this study was to synthesize biomaterials from daily dental waste. Since alginate impression material contains silica and calcium salts, we aimed to synthesize calcium silicate cement from alginate impression material. Gypsum-based investment material was also investigated as control. X-ray diffraction analyses revealed that although firing the set gypsum-based and modified investment materials at 1,200°C produced calcium silicates, firing the set alginate impression material did not. However, we succeeded when firing the set blend of pre-fired set alginate impression material and gypsum at 1,200°C. SEM observations of the powder revealed that the featured porous structures of diatomite as an alginate impression material component appeared useful for synthesizing calcium silicates. Experimentally fabricated calcium silicate powder was successfully mixed with phosphoric acid solution and set by depositing the brushite. Therefore, we conclude that the production of calcium silicate cement material is possible from waste alginate impression material.

  6. Identification of the man-made barium copper silicate pigments among some ancient Chinese artifacts through spectroscopic analysis.

    Science.gov (United States)

    Li, Q H; Yang, J C; Li, L; Dong, J Q; Zhao, H X; Liu, S

    2015-03-05

    This article describes the complementary application of non-invasive micro-Raman spectroscopy and energy dispersive X-ray fluorescence spectrometry to the characterization of some ancient Chinese silicate artifacts. A total of 28 samples dated from fourth century BC to third century AD were analyzed. The results of chemical analysis showed that the vitreous PbO-BaO-SiO2 material was used to sinter these silicate artifacts. The barium copper silicate pigments including BaCuSi4O10, BaCuSi2O6 and BaCu2Si2O7 were widely identified from colorful areas of the samples by Raman spectroscopy. In addition, other crystalline phases such as Fe2O3, BaSi2O5, BaSO4, PbCO3 and quartz were also identified. The present study provides very valuable information to trace the technical evolution of man-made barium copper silicate pigments and their close relationship with the making of ancient PbO-BaO-SiO2 glaze and glass. Copyright © 2014 Elsevier B.V. All rights reserved.

  7. Sintering of dioxide pellets in an oxidizing atmosphere (CO2)

    International Nuclear Information System (INIS)

    Santos, G.R.T.

    1992-01-01

    This work consists in the study of the sintering process of U O 2 pellets in an oxidizing atmosphere. Sintering tests were performed in an CO 2 atmosphere and the influence of temperature and time on the pellets density and microstructure were verified. The results obtained were compared to those from the conventional sintering process and its efficiency was confirmed. (author)

  8. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Administrator

    Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for conventional sintered (8–10 and 135–155 GPa) samples. Keywords. Microwave sintering; La-substituted SBTi ceramics; mechanical properties. 1. Introduction. In recent years, bismuth layer-structured ferroelectrics.

  9. Effect of aluminum silicate fiber modification on crack-resistance of a ceramic mould

    Directory of Open Access Journals (Sweden)

    Jiang Yehua

    2012-11-01

    Full Text Available To improve the crack-resistance of the mould for silica sol bonded quartz based ceramic mould casting, aluminum silicate fibers with the diameter ranging from 5 µm to 25 µm and the length about 1 mm were dispersed in the ceramic mould. The effect of the aluminum silicate fibers on the tensile strength, shrinkage rate and the cracking trend of the ceramic mould were investigated. In the ceramic slurry, quartz sand was applied as ceramic aggregate, silica sol containing 30% silicon dioxide as bonder, and the weight ratio of quartz sand to silica sol was 2.69; the dispersed fibers changed from 0 to 0.24vol.%. The mould samples were formed after the slurry was poured and gelled at room temperature, and then sintered at different temperatures ranging from 100 to 800 ℃ to measure the tensile strength and shrinkage rate. The results show that, with the aluminum silicate fiber addition increasing from 0 to 0.24vol.%, the tensile strength increases linearly from 0.175 MPa to 0.236 MPa, and the shrinkage rate decreases linearly from 1.75% to 1.68% for the ceramic mould sintered at 400 ℃, from 1.37% to 1.31% for the ceramic mould at room temperature. As the sintering temperature was raised from 100 ℃ to 800 ℃, the tensile strength increases, and the shrinkage rate decreases at all temperatures, compared with those without fiber dispersion, but their variation patterns remain the same. Furthermore, the cracking trend of the mould and its decreasing proportion were defined and analyzed quantitatively considering both effects of the fiber dispersion on the strength and shrinkage. The cracking trend appears to decrease linearly with increasing fiber content and to reach the maximum reduction of 28.8% when 0.24vol.% fiber was dispersed. Therefore, the investigation proposes a new method to improve the crack-resistance of the ceramic mould, i.e., inorganic fiber dispersion into the ceramic mould.

  10. Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

    International Nuclear Information System (INIS)

    Wang, G.P.; Liu, W.Q.; Huang, Y.L.; Ma, S.C.; Zhong, Z.C.

    2014-01-01

    Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively

  11. Effects of sintering temperature on the mechanical properties of sintered NdFeB permanent magnets prepared by spark plasma sintering

    Energy Technology Data Exchange (ETDEWEB)

    Wang, G.P., E-mail: wgp@jxnu.edu.cn [College of Physics and Communication Electronics, Jiangxi Normal University, Nanchang 330022 (China); Liu, W.Q. [Key Laboratory of Advanced Functional Materials Science and Engineering, Ministry of Education, Beijing University of Technology, Beijing 100022 (China); Huang, Y.L.; Ma, S.C.; Zhong, Z.C. [School of Materials Science and Engineering, Nanchang Hangkong University, Nanchang 330063 (China)

    2014-01-15

    Sintered NdFeB-based permanent magnets were fabricated by spark plasma sintering (SPS) and a conventional method to investigate the mechanical and magnetic properties. The experimental results showed that sintered NdFeB magnet prepared by the spark plasma sintering (SPS NdFeB) possesses a better mechanical properties compared to the conventionally sintered one, of which the maximum value of bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively. The effects of sintering temperature on bending strength and Vickers hardness were investigated. It was shown that the bending strength firstly increases to the maximum value and then decreases with the increase of sintering temperature in a certain range. The investigations of microstructures and mechanical properties indicated that the unique sintering mechanism in the SPS process is responsible for the improvement of mechanical properties of SPS NdFeB. Furthermore, the relations between the mechanical properties and relevant microstructure have been analyzed based on the experimental fact. - Highlights: • Studied the sintering temperature effect on strengthening mechanism of NdFeB magnet firstly. • It showed that sintering temperature may effectively affect the mechanical properties. • The maximum bending strength and Vickers hardness was 402.3 MPa and 778.1 MPa, respectively.

  12. Calcium silicate bioactive cements: Biological perspectives and clinical applications.

    Science.gov (United States)

    Prati, Carlo; Gandolfi, Maria Giovanna

    2015-04-01

    To introduce and to examine the research progress and the investigation on hydraulic calcium silicate cements (HCSCs), well-known as MTA (mineral trioxide aggregate). This review paper introduces the most important investigations of the last 20 years and analyze their impact on HCSCs use in clinical application. HCSCs were developed more than 20 years ago. Their composition is largely based on Portland cement components (di- and tri-calcium silicate, Al- and Fe-silicate). They have important properties such as the ability to set and to seal in moist and blood-contaminated environments, biocompatibility, adequate mechanical properties, etc. Their principal limitations are long setting time, low radiopacity and difficult handling. New HCSCs-based materials containing additional components (setting modulators, radiopacifying agents, drugs, etc.) have since been introduced and have received a considerable attention from laboratory researchers for their biological and translational characteristics and from clinicians for their innovative properties. HCSCs upregulate the differentiation of osteoblast, fibroblasts, cementoblasts, odontoblasts, pulp cells and many stem cells. They can induce the chemical formation of a calcium phosphate/apatite coating when immersed in biological fluids. These properties have led to a growing series of innovative clinical applications such as root-end filling, pulp capping and scaffolds for pulp regeneration, root canal sealer, etc. The capacity of HCSCs to promote calcium-phosphate deposit suggests their use for dentin remineralization and tissue regeneration. Several in vitro studies, animal tests and clinical studies confirmed their ability to nucleate apatite and remineralize and to induce the formation of (new) mineralized tissues. HCSCs play a critical role in developing a new approach for pulp and bone regeneration, dentin remineralization, and bone/cementum tissue healing. Investigations of the next generation HCSCs for

  13. Mechanical characteristics of microwave sintered silicon carbide

    Indian Academy of Sciences (India)

    Unknown

    tions ranging from kiln furniture to membrane material. Keywords. Microwave sintering; biaxial flexure; silicon carbide. 1. Introduction. Silicon carbide (SiC) ceramics is a very well known candidate material for a structural application. However, due to (i) poor densification due to highly directional bonding, (ii) susceptibility of ...

  14. Sintering behavior of LZSA glass-ceramics

    Directory of Open Access Journals (Sweden)

    Oscar Rubem Klegues Montedo

    2009-06-01

    Full Text Available The LZSA glass-ceramic system (Li2O-ZrO2-SiO2-Al2O 3 shows interesting properties, such as good chemical resistance, low thermal expansion, high abrasion resistance, and a low dielectric constant. However, in order to obtain a high performance material for specific applications, the sintering behavior must be better understood so that the porosity may be reduced and other properties improved. In this context, a sintering investigation for a specific LZSA glass-ceramic system composition was carried out. A 18.8Li2O-8.3ZrO2-64.2SiO2-8.7Al 2O3 glass was prepared by melting the solids, quenching the melt in water, and grinding the resulting solid in order to obtain a powder (3.68 μm average particle diameter. Subsequently, the glass powder was characterized (chemical analysis and determination of thermal properties and the sintering behavior was investigated using optical non-contact dilatometry measurements. The results showed that the crystallization process strongly reduced the sintering in the temperature interval from 785 to 940 °C, and a maximum thermal shrinkage of 15.4% was obtained with operating conditions of 1020 °C and 180 minutes.

  15. Low temperature sintering of hyperstoichiometric uranium dioxide

    International Nuclear Information System (INIS)

    Chevrel, H.

    1991-12-01

    In the lattice of uranium dioxide with hyperstoichiometric oxygen content (UO 2+x ), each additional oxygen atoms is introduced by shifting two anions from normal sites to interstitial ones, thereby creating two oxygen vacancies. The point defects then combine to form complex defects comprising several interstitials and vacancies. The group of anions (3x) in the interstitial position participate in equilibria promoting the creation of uranium vacancies thereby considerably increasing uranium self-diffusion. However, uranium grain boundaries diffusion governs densification during the first two stages of sintering of uranium dioxide with hyperstoichiometric oxygen content, i.e., up to 93% of the theoretical density. Surface diffusion and evaporation-condensation, which are considerably accentuated by the hyperstoichiometric deviation, play an active role during sintering by promoting crystalline growth during the second and third stages of sintering. U 8 O 8 can be added to adjust the stoichiometry and to form a finely porous structure and thus increase the pore area subjected to surface phenomena. The composition with an O/U ratio equal to 2.25 is found to densify the best, despite a linear growth in sintering activation energy with hyperstoichiometric oxygen content, increasing from 300 kj.mol -1 for UO 2.10 to 440 kJ.mol -1 for UO 2.25 . Seeds can be introduced to obtain original microstructures, for example the presence of large grains in small-grain matrix

  16. Study of ceramics sintering under high pressures

    International Nuclear Information System (INIS)

    Kunrath Neto, A.O.

    1990-01-01

    A systematic study was made on high pressure sintering of ceramics in order to obtain materials with controlled microstructure, which are not accessible by conventional methods. Some aspects with particular interest were: to achieve very low porosity, with fine grains; to produce dispersed metastable and denser phases which can act as toughening agents; the study of new possibilities for toughening enhancement. (author)

  17. Deformation behavior of sintered nanocrystalline silver layers

    International Nuclear Information System (INIS)

    Zabihzadeh, S.; Van Petegem, S.; Duarte, L.I.; Mokso, R.; Cervellino, A.; Van Swygenhoven, H.

    2015-01-01

    The microstructure of porous silver layers produced under different low temperature pressure-assisted sintering conditions is characterized and linked with the mechanical behavior studied in situ during X-ray diffraction. Peak profile analysis reveals important strain recovery and hardening mechanism during cyclic deformation. The competition between both mechanisms is discussed in terms of porosity and grain size

  18. Air-sintering mechanisms of chromites

    Energy Technology Data Exchange (ETDEWEB)

    Chick, L.A.; Bates, J.L.; Maupin, G.D.

    1991-07-01

    The sintering behaviors of La{sub 1-x}Sr{sub x}CrO{sub 3} and Y{sub 1-x}Ca{sub x}CrO{sub 3} in air at 1550{degrees}C are described as functions of alkaline earth concentration and chromium enrichment or depletion. Vapor-, liquid-, and solid-phase mass transport mechanisms appear to be operative in both systems. Liquid-phase sintering appears dominant an Y{sub 1-x}Ca{sub x}CrO{sub 3} with x = 0.15 to 0.40, especially with Cr enrichment. Either vapor- or solid-phase transport may dominate in the La{sub 1-x}Sr{sub x}CrO{sub 3} system. Slight depletion or enrichment of Cr in both systems has dramatic effects on air-sintered density and microstructure, probably due to modulation of vapor-phase transport and liquid-phase formation. Substantial Cr depletion enhances sintering. 10 refs., 9 figs.

  19. Mechanical characterization of microwave sintered zinc oxide

    Indian Academy of Sciences (India)

    Unknown

    Keywords. Zinc oxide; microwave sintering; microhardness. 1. Introduction. The application of microwave energy for the processing of ceramics has become an attractive area of research and innovation recently. The major advantages of the micro- wave processing of ceramic materials are accelerated densification rate as a ...

  20. Laser Sintering Technology and Balling Phenomenon.

    Science.gov (United States)

    Oyar, Perihan

    2018-02-01

    The aim of this review was to evaluate the balling phenomenon which occurs typically in Selective Laser Sintering (SLS). The balling phenomenon is a typical SLS defect, and observed in laser sintered powder, significantly reduces the quality of SLS, and hinders the further development of SLS Technology. Electronic database searches were performed using Google Scholar. The keywords "laser sintering, selective laser sintering, direct metal laser melting, and balling phenomenon" were searched in title/abstract of publications, limited to December 31, 2016. The inclusion criteria were SLS, balling phenomenon, some alloys (such as Cr-Co, iron, stainless steel, and Cu-based alloys) mechanical properties, microstructure and bond strength between metal-ceramic crown, laboratory studies, full text, and in English language. A total of 100 articles were found the initial search and yielded a total of 50 studies, 30 of which did not fulfill the inclusion criteria and were therefore excluded. In addition, 20 studies were found by screening the reference list of all included publications. Finally, 40 studies were selected for this review. The method in question is regulated by powder material characteristics and the conditions of laser processing. The procedure of formation, affecting factors, and the mechanism of the balling effect are very complex.

  1. Sintering of silicon nitride ceramics with magnesium silicon nitride and yttrium oxide as sintering aids

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J; Xu, J Y [Shanghai Institute of Technology, Shanghai 200235 (China); Peng, G H [Guangxi Normal University, Guilin 541004, Guangxi (China); Zhuang, H R; Li, W L; Xu, S Y [Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050 (China); Mao, Y J, E-mail: guojianjiang@sit.edu.cn [Shanghai University, Shanghai 200444 (China)

    2011-10-29

    Silicon nitride (Si{sub 3}N{sub 4}) ceramics had been produced through pressureless sintering and hot-pressing sintering with MgSiN{sub 2}-Y{sub 2}O{sub 3} or only MgSiN{sub 2} as sintering aids. The influences of the amount of MgSiN{sub 2} and Y{sub 2}O{sub 3} and sintering methods on the properties of Si{sub 3}N{sub 4} ceramics were investigated. The results show that the bend strength of Si{sub 3}N{sub 4} ceramic fabricated through pressureless sintering at 1820 deg. C for 4 h with 5.6 wt.% MgSiN{sub 2}-15.8 wt.% Y{sub 2}O{sub 3} as sintering additive could achieve 839 MPa. However, the bend strength of Si{sub 3}N{sub 4} ceramic produced by hot-pressing sintering at 1750 deg. C for 1 h under uniaxial pressure of 20 MPa with 4.76 wt.% MgSiN{sub 2} was 1149 MPa. The thermal conductivity of the Si{sub 3}N{sub 4} ceramic 2 3 4 could reach to 129 W{center_dot}m{sup -1{center_dot}}K{sup 1}. The present work demonstrated that MgSiN{sub 2} aids and hot-pressing sintering were effective to improve the thermal conductivity of Si{sub 3}N{sub 4} ceramic.

  2. Yttrium oxide transparent ceramics by low-temperature microwave sintering

    International Nuclear Information System (INIS)

    Luo, Junming; Zhong, Zhenchen; Xu, Jilin

    2012-01-01

    Graphical abstract: The figure shows the SEM photos of the surfaces of the Y 2 O 3 transparent ceramic samples obtained by microwave sintering and vacuum sintering. It is clearly demonstrated that the grain distribution of the vacuum sintering sample is not uniform with the smallest and the largest particle size at about 2 μm and 15 μm respectively, while the grain distribution of microwave sintering sample is uniform with the average diameter at about 2–4 μm (the smallest reported so far) and with no abnormal growth-up or coarsening phenomenon. We have further found out that the smaller the grain size, the higher the mechanical and optical properties. Display Omitted Highlights: ► The microwave sintering temperature of the sample is lower compared with vacuum. ► The microwave sintering time of the sample is shorter compared with vacuum. ► The mechanical properties of the microwave sintering sample is improved greatly. ► The Y 2 O 3 grain of microwave sintering sample is the smallest reported so far. -- Abstract: Yttrium oxide (Y 2 O 3 ) transparent ceramics samples have been successfully fabricated by microwave sintering processing at relatively low temperatures. In comparison with the vacuum sintering processing, Y 2 O 3 transparent ceramics can be obtained by microwave sintering at lower sintering temperature and shorter sintering time, and they possess higher transmittances and mechanical properties. The technologies of low-temperature microwave sintering and the relationships of the microstructures and properties of the specified samples have been investigated in detail. We have found out that the low-temperature microwave sintering technique has its obvious advantages over the conventional methods in manufacturing yttrium oxide transparent ceramics.

  3. TiO2 doped UO2 fuels sintered by spark plasma sintering

    Science.gov (United States)

    Yao, Tiankai; Scott, Spencer M.; Xin, Guoqing; Lian, Jie

    2016-02-01

    UO2 fuels doped with oxide additives Cr2O3 and TiO2 display larger grain size, improving fission product retention capability and thus accident tolerance. Spark plasma sintering (SPS) was applied to consolidate TiO2-doped UO2 fuel pellets with 0.5 wt % dopant concentration, above its solubility, in order to induce eutectic phase formation and promote sintering kinetics. The grain size can reach 80 μm by sintering at 1700 °C for 20 min, and liquid U-Ti-O eutectic phase occurs at the triple junction of grain boundaries and significantly improves grain growth during sintering. The oxide additive also impedes the reduction of the initial hyperstoichiometric fuel powders to more stoichiometric fuel pellets upon SPS process. Thermal-mechanical properties of the sintered doped fuel pellets including thermal conductivity and hardness are measured and compared with undoped fuel pellets. The enlarged grain size (80 μm) and densification within short sintering duration highlight the immense possibility of SPS in fabricating large grained UO2 fuel pellets to improve fuel performance.

  4. Sintering uranium oxide using a preheating step

    International Nuclear Information System (INIS)

    Jensen, N.J.; Nivas, Y.; Packard, D.R.

    1977-01-01

    Compacted pellets of uranium oxide or uranium oxide with one or more additives are heated in a kiln in a process having a preheating step, a sintering step, a reduction step, and a cooling step in a controlled atmosphere. The process is practiced to give a range of temperature and atmosphere conditions for obtaining optimum fluoride removal from the compacted pellets along with optimum sintering in a single process. The preheating step of this process is conducted in a temperature range of about 600 0 to about 900 0 C and the pellets are held for at least twenty min, and preferably about 60 min, in an atmosphere having a composition in the range of about 10 to about 75 vol % hydrogen with the balance being carbon dioxide. The sintering step is conducted at a temperature in the range of about 900 0 C to 1500 0 C in the presence of an atmosphere having a composition in the range of about 0.5 to about 90 vol % hydrogen with the balance being carbon dioxide. The reduction step reduces the oxygen to metal ratio of the pellets to a range of about 1.98 to 2.10:1 and this is accomplished by gradually cooling the pellets for about 30 to about 120 min from the temperature of the sintering step to about 1100 0 C in an atmosphere of about 10 to 90 vol % hydrogen with the balance being carbon dioxide. Thereafter the pellets are cooled to about 100 0 C under a protective atmosphere, and in one preferred practice the same atmosphere used in the reduction step is used in the cooling step. The preheating, sintering and reduction steps may also be conducted with their respective atmospheres having an initial additional component of water vapor and the water vapor can comprise up to about 20 vol %

  5. Comparative sinterability of combustion synthesized and commercial titanium carbides

    International Nuclear Information System (INIS)

    Manley, B.W.

    1984-11-01

    The influence of various parameters on the sinterability of combustion synthesized titanium carbide was investigaged. Titanium carbide powders, prepared by the combustion synthesis process, were sintered in the temperature range 1150 to 1600 0 C. Incomplete combustion and high oxygen contents were found to be the cause of reduced shrinkage during sintering of the combustion syntheized powders when compared to the shrinkage of commercial TiC. Free carbon was shown to inhibit shrinkage. The activation energy for sintering was found to depend on stoichiometry (C/Ti). With decreasing C/Ti, the rate of sintering increased. 29 references, 16 figures, 13 tables

  6. Authigenic Mineralization of Silicates at the Organic-water Interface

    Science.gov (United States)

    McEvoy, B.; Wallace, A. F.

    2015-12-01

    It is relatively common for some fraction of organic material to be preserved in the sedimentary rock record as disseminated molecular fragments. The survival of wholly coherent tissues from primarily soft-bodied organisms is far more unusual. However, the literature is now well- populated with spectacular examples of soft-tissue preservation ranging from a 2,600 year old human brain to the tissues of the Ediacaran biota that have survived ~600 million years. Some of the most exceptional examples of soft tissue preservation are from the Proterozoic-Cambrian transition, however, nearly all modes of fossil preservation during this time are debated. Clay mineral templates have been implicated as playing a role in several types of soft tissue preservation, including Burgess Shale and Beecher's Trilobite-type preservation, and more recently, Bitter Springs-type silicification. Yet, there is still much debate over whether these clay mineral coatings form during early stage burial and diagenesis, or later stage metamorphism. This research addresses this question by using in situ fluid cell Atomic Force Microscopy (AFM) to investigate the nucleation and growth of silicate minerals on model biological surfaces. Herein we present preliminary results on the deposition of hydrous magnesium silicates on self-assembled monolayers (-OH, -COOH, -CH3, and -H2PO3 terminated surfaces) at ambient conditions.

  7. Phase transformation of NiTi alloys during vacuum sintering

    Science.gov (United States)

    Wang, Jun; Hu, Kuang

    2017-05-01

    The aim of this study is to ascertain the Phase transformation of NiTi alloys during vacuum sintering. NiTi shape memory alloys (SMA) of atomic ratio 1:1 were prepared through press forming and vacuum sintering with the mixture of Ni and Ti powders. Different samples were prepared by changing the sintering time and the sintering temperature. Phase and porosity of the samples were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that in the process of sintering NiTi2 and Ni3Ti phases are formed firstly and then transform into NiTi phase. The quantity of NiTi2 and Ni3Ti phases gradually decreased but not eliminate completely with increase of sintering time. The porosity of specimen sintering at 900°C decreases slightly with increase of sintering time. With increase of sintering time the porosity of specimen sintering at 1050°C decreased firstly and then increased because of generation rich titanium liquid in the process of sintering.

  8. Spark plasma sintering of hydrothermally synthesized bismuth ferrite

    Directory of Open Access Journals (Sweden)

    Zorica Branković

    2016-12-01

    Full Text Available Bismuth ferrite, BiFeO3 (BFO, powder was synthesized by hydrothermal method from Bi(NO33·5 H2O and Fe(NO33·9 H2O as precursors. The synthesized powder was further sintered using spark plasma sintering (SPS. The sintering conditions were optimized in order to achieve high density, minimal amount of secondary phases and improved ferroelectric and magnetic properties. The optimal structure and properties were achieved after spark plasma sintering at 630 °C for 20 min, under uniaxial pressure of 90 MPa. The composition, microstructure, ferroelectric and magnetic properties of the SPS samples were characterized and compared to those of conventionally sintered ceramics obtained from the same powder. Although the samples sintered using conventional method showed slightly lower amount of secondary phases, the spark plasma sintered samples exhibited favourable microstructure and better ferroelectric properties.

  9. The kinetic fragility of natural silicate melts

    International Nuclear Information System (INIS)

    Giordano, Daniele; Dingwell, Donald B

    2003-01-01

    Newtonian viscosities of 19 multicomponent natural and synthetic silicate liquids, with variable contents of SiO 2 (41-79 wt%), Al 2 O 3 (10-19 wt%), TiO 2 (0-3 wt%), FeO tot (0-11 wt%); alkali oxides (5-17 wt%), alkaline-earth oxides (0-35 wt%), and minor oxides, obtained at ambient pressure using the high-temperature concentric cylinder, the low-temperature micropenetration, and the parallel plates techniques, have been analysed. For each silicate liquid, regression of the experimentally determined viscosities using the well known Vogel-Fulcher-Tammann (VFT) equation allowed the viscosity of all these silicates to be accurately described. The results of these fits, which provide the basis for the subsequent analysis here, permit qualitative and quantitative correlations to be made between the VFT adjustable parameters (A VFT , B VFT , and T 0 ). The values of B VFT and T 0 , calibrated via the VFT equation, are highly correlated. Kinetic fragility appears to be correlated with the number of non-bridging oxygens per tetrahedrally coordinated cation (NBO/T). This is taken to infer that melt polymerization controls melt fragility in liquid silicates. Thus NBO/T might form an useful ingredient of a structure-based model of non-Arrhenian viscosity in multicomponent silicate melts

  10. Calcareous sinter from ancient aqueducts as a source of data in paleoclimate, tectonics and hydrology

    Science.gov (United States)

    Surmelihindi, G.; Passchier, C. W.

    2010-12-01

    During the lifetime the Roman Empire (300BC-400AD), about 1200 major aqueducts were built to supply cities in the Mediterranean with drinking water. The ruins of many of these channels contain sinter (calcium carbonate), which was deposited at a rate of 0.5-5 mm/year over the life of the aqueduct, usually 50-200 but up to 1000 years. Calcareous sinter inside the ancient aqueduct channels can give important insight into paleoclimatology in the form of temperature and rainfall, reflect palaeohydrology of water, water chemistry, flow rate, bacterial activity and source area of the water. This type of data is important to build climate models and to understand earthquake and flood patterns in the Mediterranean, and can be a new, additional source of information besides speleothems, travertine and tufa deposits. In our study we focus on Mediterranean climate patterns, and selected four aqueduct sites from Southern Turkey, Greece and Italy. The calcareous sinter deposits may reflect annual or subannual lamination characterized by alternating light, dense, coarse-grained and dark, porous, microcrystalline layers which are thought to represent winter and summer conditions respectively. Moreover, abrupt changes in the sequence of lamination can be a signal of natural hazards such as earthquakes or flood events. Deposits from the aqueduct of Patara (Southern Turkey) show 40-50 laminae couples, which may be annual layers. δ18O and δ 13C stable isotope data indicate high cyclicity within the sinter samples from Patara during the Roman period. Higher δ18O values correspond with dark, porous layers and lower values with light, dense layers. Major geochemical analyses show similar seasonal changes. Electron microprobe study shows that within dark laminae, detrital Fe, Mg, K, Al and Si are enriched whereas the light layers have high Ca content. Trace element analyses by LA-ICP-MS also indicate higher Mg/Ca and Sr/Ca values in the dark layers, which can be interpreted in terms

  11. Sensitivity of novel silicate and borate-based glass structures onin vitrobioactivity and degradation behaviour.

    Science.gov (United States)

    Mancuso, Elena; Bretcanu, Oana; Marshall, Martyn; Dalgarno, Kenneth W

    2017-10-15

    Three novel glass compositions, identified as NCL2 (SiO 2 -based), NCL4 (B 2 O 3 -based) and NCL7 (SiO 2 -based), along with apatite-wollastonite (AW) were processed to form sintered dense pellets, and subsequently evaluated for their in vitro bioactive potential, resulting physico-chemical properties and degradation rate. Microstructural analysis showed the carbonated hydroxyapatite (HCA) precipitate morphology following SBF testing to be composition-dependent. AW and the NCL7 formulation exhibited greater HCA precursor formation than the NCL2 and NCL4-derived pellets. Moreover, the NCL4 borate-based samples showed the highest biodegradation rate; with silicate-derived structures displaying the lowest weight loss after SBF immersion. The results of this study suggested that glass composition has significant influence on apatite-forming ability and also degradation rate, indicating the possibility to customise the properties of this class of materials towards the bone repair and regeneration process.

  12. Effect of different sintering temperature on fly ash based geopolymer artificial aggregate

    Science.gov (United States)

    Abdullah, Alida; Abdullah, Mohd Mustafa Al Bakri; Hussin, Kamarudin; Tahir, Muhammad Faheem Mohd

    2017-04-01

    This research was conducted to study the mechanical and morphology of fly ash based geopolymer as artificial aggregate at different sintering temperature. The raw material that are used is fly ash, sodium hydroxide, sodium silicate, geopolymer artificial aggregate, Ordinary Portland Cement (OPC), coarse aggregate and fine aggregate. The research starts with the preparation of geopolymer artificial aggregate. Then, geopolymer artificial aggregate will be sintered at six difference temperature that is 400°C, 500°C, 600°C, 700°C, 800°C and 900°C to known at which temperature the geopolymer artificial aggregate will become a lightweight aggregate. In order to characterize the geopolymer artificial aggregate the X-ray Diffraction (XRD) and X-Ray Fluorescence (XRF) was done. The testing and analyses involve for the artificial aggregate is aggregate impact test, specific gravity test and Scanning Electron Microscopy (SEM). After that the process will proceed to produce concrete with two type of different aggregate that is course aggregate and geopolymer artificial aggregate. The testing for concrete is compressive strength test, water absorption test and density test. The result obtained will be compared and analyse.

  13. Bioactive Glass-Ceramic Foam Scaffolds from ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Directory of Open Access Journals (Sweden)

    Hamada Elsayed

    2018-02-01

    Full Text Available Highly porous bioactive glass-ceramic scaffolds were effectively fabricated by an inorganic gel casting technique, based on alkali activation and gelification, followed by viscous flow sintering. Glass powders, already known to yield a bioactive sintered glass-ceramic (CEL2 were dispersed in an alkaline solution, with partial dissolution of glass powders. The obtained glass suspensions underwent progressive hardening, by curing at low temperature (40 °C, owing to the formation of a C–S–H (calcium silicate hydrate gel. As successful direct foaming was achieved by vigorous mechanical stirring of gelified suspensions, comprising also a surfactant. The developed cellular structures were later heat-treated at 900–1000 °C, to form CEL2 glass-ceramic foams, featuring an abundant total porosity (from 60% to 80% and well-interconnected macro- and micro-sized cells. The developed foams possessed a compressive strength from 2.5 to 5 MPa, which is in the range of human trabecular bone strength. Therefore, CEL2 glass-ceramics can be proposed for bone substitutions.

  14. Chemical solution deposition of CaCu 3 Ti 4 O 12 thin film

    Indian Academy of Sciences (India)

    CaCu3Ti4O12 (CCTO) thin film was successfully deposited on boron doped silica substrate by chemical solution deposition and rapid thermal processing. The phase and microstructure of the deposited films were studied as a function of sintering temperature, employing X-ray diffractometry and scanning electron ...

  15. Nano filter from sintered rice husk silica membrane.

    Science.gov (United States)

    Lee, Soo Young; Han, Chong Soo

    2006-11-01

    A nano filter showing the Knudsen flow was demonstrated by a modification of a membrane constructed from rice husk silica. The membrane was prepared by pressing and sintering micron sized rice husk silica with 4 nm pores. The membrane showed a permeability of 5.2 x 10(-8) mol m(-1) sec(-1) Pa(-1) for H2 and ratios of gas permeability 2.1 and 3.2 for k(H2)/k(CH4) and k(H2)/k(CO2), respectively. When the membrane was treated by filtration of approximately 100 nm sized rice husk silica particles, the permeability decreased to 4.9 x 10(-8) mol m(-1) sec(-1) Pa(-1) and the ratios increased to 2.2 and 3.4. In the case of the membrane after treatments with the dispersion and chemical deposition of tetraethylorthosilicate (TEOS), the corresponding permeability and ratios of the membrane were 1.8 x 10(-8) mol m(-1) sec(-1) Pa(-1), and 2.9 and 4.5, respectively. From the change of the ratio of gas permeability for the membrane with modifications, it is suggested that approximately 100 nm sized rice husk silica particles pack the large pores among the micron sized rice husk silica particles while the chemical deposition of tetraethylorthosilicate (TEOS) reveals the gas flow through 4 nm pores in the rice husk silica by blocking large pores.

  16. Numerical simulation of electric field assisted sintering

    Science.gov (United States)

    McWilliams, Brandon A.

    A fully coupled thermal-electric-sintering finite element model was developed and implemented to explore electric field assisted sintering techniques (FAST). FAST is a single step processing operation for producing bulk materials from powders, in which the powder is heated by the application of electric current under pressure. This process differs from other powder processing techniques such as hot isostatic pressing (HIP) and traditional press and sinter operations where the powder or compact is heated externally, in that the powder is heated directly as a result of internal Joule heating (for conductive powders) and/or by direct conduction from the die and punches. The overall result is much more efficient heating which allows heating rates of >1000°C/min to be achieved which is desirable for sintering bulk nanocrystalline and other novel high performance materials. Previous modeling efforts on FAST have only considered the thermal-electric aspect of the problem and have neglected densification. In addition to the introduction of a sintering model, a detailed thermal-electric study of process parameters was carried out in order to identify key system variables and quantify their effect on the overall system response and subsequent thermal history of a consolidated sample. This analysis was compared to empirical data from a parallel experimental study and shown to satisfactorily predict the observed trends. This model was then integrated with a phenomenologically based sintering model to capture the densification of the sample. This fully coupled model was used to predict densification kinetics under FAST like conditions and examine the evolution of material properties as the sample transitions from a loose powder to a fully dense compact and the resulting effect on the electrical and thermal fields within the compact. This model was also used to explore the effect of non-uniform thermal, electrical, stress and density fields on the final geometry and local

  17. Distribution, microfabric, and geochemical characteristics of siliceous rocks in central orogenic belt, China: implications for a hydrothermal sedimentation model.

    Science.gov (United States)

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Gao, Le; Yang, Zhijun; Zhou, Yongzhang; He, Junguo; Liang, Jin; Zhou, Liuyu; Voudouris, Panagiotis Ch

    2014-01-01

    Marine siliceous rocks are widely distributed in the central orogenic belt (COB) of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian--Ordovician, and Carboniferous--Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08-95.30%), Ba (42.45-503.0 ppm), and ΣREE (3.28-19.75 ppm) suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn), Sc/Th, (La/Yb) N, and (La/Ce) N ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics.

  18. Distribution, Microfabric, and Geochemical Characteristics of Siliceous Rocks in Central Orogenic Belt, China: Implications for a Hydrothermal Sedimentation Model

    Directory of Open Access Journals (Sweden)

    Hongzhong Li

    2014-01-01

    Full Text Available Marine siliceous rocks are widely distributed in the central orogenic belt (COB of China and have a close connection to the geological evolution and metallogenesis. They display periodic distributions from Mesoproterozoic to Jurassic with positive peaks in the Mesoproterozoic, Cambrian—Ordovician, and Carboniferous—Permian and their deposition is enhanced by the tensional geological settings. The compressional regimes during the Jinning, Caledonian, Hercynian, Indosinian, and Yanshanian orogenies resulted in sudden descent in their distribution. The siliceous rocks of the Bafangshan-Erlihe ore deposit include authigenic quartz, syn-depositional metal sulphides, and scattered carbonate minerals. Their SiO2 content (71.08–95.30%, Ba (42.45–503.0 ppm, and ΣREE (3.28–19.75 ppm suggest a hydrothermal sedimentation origin. As evidenced by the Al/(Al + Fe + Mn, Sc/Th, (La/YbN, and (La/CeN ratios and δCe values, the studied siliceous rocks were deposited in a marginal sea basin of a limited ocean. We suggest that the Bafangshan-Erlihe area experienced high- and low-temperature stages of hydrothermal activities. The hydrothermal sediments of the former stage include metal sulphides and silica, while the latter was mainly composed of silica. Despite the hydrothermal sedimentation of the siliceous rocks, minor terrigenous input, magmatism, and biological activity partly contributed to geochemical features deviating from the typical hydrothermal characteristics.

  19. Bioactive Glass-Ceramic Scaffolds from Novel ‘Inorganic Gel Casting’ and Sinter-Crystallization

    Science.gov (United States)

    Elsayed, Hamada; Rincón Romero, Acacio; Ferroni, Letizia; Gardin, Chiara; Zavan, Barbara; Bernardo, Enrico

    2017-01-01

    Highly porous wollastonite-diopside glass-ceramics have been successfully obtained by a new gel-casting technique. The gelation of an aqueous slurry of glass powders was not achieved according to the polymerization of an organic monomer, but as the result of alkali activation. The alkali activation of a Ca-Mg silicate glass (with a composition close to 50 mol % wollastonite—50 mol % diopside, with minor amounts of Na2O and P2O5) allowed for the obtainment of well-dispersed concentrated suspensions, undergoing progressive hardening by curing at low temperature (40 °C), owing to the formation of a C–S–H (calcium silicate hydrate) gel. An extensive direct foaming was achieved by vigorous mechanical stirring of partially gelified suspensions, comprising also a surfactant. The open-celled structure resulting from mechanical foaming could be ‘frozen’ by the subsequent sintering treatment, at 900–1000 °C, causing substantial crystallization. A total porosity exceeding 80%, comprising both well-interconnected macro-pores and micro-pores on cell walls, was accompanied by an excellent compressive strength, even above 5 MPa. PMID:28772531

  20. Reheating of zinc-titanate sintered specimens

    Directory of Open Access Journals (Sweden)

    Labus N.

    2015-01-01

    Full Text Available The scope of this work was observing dimensional and heat transfer changes in ZnTiO3 samples during heating in nitrogen and air atmosphere. Interactions of bulk specimens with gaseous surrounding induce microstructure changes during heating. Sintered ZnTiO3 nanopowder samples were submitted to subsequent heating. Dilatation curves and thermogravimetric with simultaneous differential thermal analysis TGA/DTA curves were recorded. Reheating was performed in air and nitrogen atmospheres. Reheated samples obtained at different characteristic temperatures in air were analyzed by X-ray diffraction (XRD. Microstructures obtained by scanning electron microscopy (SEM of reheated sintered samples are presented and compared. Reheating in a different atmosphere induced different microstructures. The goal was indicating possible causes leading to the microstructure changes. [Projekat Ministarstva nauke Republike Srbije, br. OI172057 i br. III45014

  1. Foaming Glass Using High Pressure Sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    Foam glass is a high added value product which contributes to waste recycling and energy efficiency through heat insulation. The foaming can be initiated by a chemical or physical process. Chemical foaming with aid of a foaming agent is the dominant industrial process. Physical foaming has two...... variations. One way is by saturation of glass melts with gas. The other involves sintering of powdered glass under a high gas pressure resulting in glass pellets with high pressure bubbles entrapped. Reheating the glass pellets above the glass transition temperature under ambient pressure allows the bubbles...... to expand. After heat-treatment foam glass can be obtained with porosities of 80–90 %. In this study we conduct physical foaming of cathode ray tube (CRT) panel glass by sintering under high pressure (5-25 MPa) using helium, nitrogen, or argon at 640 °C (~108 Pa s). Reheating a sample in a heating...

  2. Sintering techniques for microstructure control in ceramics

    Science.gov (United States)

    Rosenberger, Andrew T.

    Sintering techniques can be manipulated to enhance densification in difficult to sinter materials and to produce property enhancing microstructures. However, the interplay between materials, sintering techniques, and end properties is not fully understood in many material systems, and some fundamental aspects of sintering such as the nature of the effects of electric fields remains unknown. The processing property relationships were examined in two classes of materials; zirconium diboride ultra high temperature ceramic composites, and all solid lithium-ion battery phosphate materials. Investigation of zirconium diboride ceramics focused on the effects of zirconium carbide as a secondary or tertiary phase in ZrB2 and ZrB2 -- SiC. Addition of zirconium carbide was observed to increase flexural strength of composites up to 590MPa at 50wt% ZrC, significantly higher than the flexural strength of 380MPa observed in similarly prepared ZrB2 -- SiC. This difference was attributed to the absence of CTE mismatch induced residual stresses in the ZrB2 -- ZrC composites. A high temperature reaction between ZrB2 and TiC producing Zr1-xTixB2 -- ZrC composites was discovered and found to enhance densification while reducing the average grain size to as small as 1.4mum, lower than the starting powder size of 1.8mum. While a high flexural strength of 670MPa was observed, a strength dependence on the ZrC grain size indicative of CTE mismatch residual stresses was also seen. Finally, the oxidation and ablation resistance of ZrB2 -- ZrC -- SiC composites as a function of ZrC fraction and ZrC:SiC ratio was investigated. Above 5vol% ZrC, the oxidation and ablation resistance of the composites was significantly reduced due to ZrC oxidation, regardless of SiC content. While ZrC can significantly enhance the mechanical properties of the composite, the volume fraction must be kept low to avoid an undesirable reduction in the oxidation resistance. The influence of applied electrical fields

  3. Reaction sintering of ceramic-metal composites

    International Nuclear Information System (INIS)

    Botta Filho, W.J.; Rodrigues, J.A.; Tomasi, R.; Pandolfelli, V.C.; Passos, J.F.S.S.; Folgueras, M.V.

    1990-01-01

    Reaction sintering experiments have been carried out in the system Al 2 O 3 -ZrAl 2 -Nb 2 O 5 with the objective of producing ceramic-metal composites of improved toughness. The sintering treatments have been done in the temperature range of 700 0 C to 1400 0 C under different conditions of vacuum and in air and argon atmospheres. The treated samples have been analysed by X-ray diffraction and analytical electron microscopy. The results are discussed in function of the degree of reaction, the development of microstructure and the densification. These results have shown that although an exchange reaction can occur to produce a composite, the control of the reaction to obtain a dense microstructure has not been possible yet. (author) [pt

  4. Photoluminescent layered Y/Er silicates

    International Nuclear Information System (INIS)

    Kostova, Mariya H.; Ananias, Duarte; Carlos, Luis D.; Rocha, Joao

    2008-01-01

    The synthesis of new layered rare-earth silicates K 3 [Y 1-a Er a Si 3 O 8 (OH) 2 ] (AV-22 materials) has been reported. The photoluminescence properties of Y/Er-AV-22 and the material resulting from its thermal degradation, K 3 [Y 1-a Er a Si 3 O 9 ] (Y/Er-AV-23), have been studied and compared. Both materials have a similar chemical makeup and structures sharing analogous building blocks, hence providing a unique opportunity for rationalising the evolution of the photoluminescence properties of lanthanide silicates across dimensionality

  5. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  6. Sintering Behavior, Microstructure, and Mechanical Properties: A Comparison among Pressureless Sintered Ultra-Refractory Carbides

    Directory of Open Access Journals (Sweden)

    Laura Silvestroni

    2010-01-01

    Full Text Available Nearly fully dense carbides of zirconium, hafnium, and tantalum were obtained by pressureless sintering at 1950°C with the addition of 5–20 vol% of MoSi2. Increasing the amount of sintering aid, the final density increased too, thanks to the formation of small amounts of liquid phase constituted by M-Mo-Si-O-C, where M is either Zr, Hf, or Ta. The matrices of the composites obtained with the standard procedure showed faceted squared grains; when an ultrasonication step was introduced in the powder treatment, the grains were more rounded and no exaggerated grains growth occurred. Other secondary phases observed in the microstructure were SiC and mixed silicides of the transition metals. Among the three carbides prepared by pressurless sintering, TaC-based composites had the highest mechanical properties at room temperature (strength 590 MPa, Young's modulus 480 GPa, toughness 3.8 MPa·m1/2. HfC-based materials showed the highest sinterability (in terms of final density versus amount of sintering aid and the highest high-temperature strength (300 MPa at 1500  °C.

  7. Fabrication of Sintered Annular Fuel Pellet

    International Nuclear Information System (INIS)

    Rhee, Young Woo; Kim, Dong Joo; Kim, Jong Hun; Yang, Jae Ho; Kim, Keon Sik; Kang, Ki Won; Song, Kun Woo

    2010-01-01

    A dual cooled annular fuel has been seriously considered as a favorable option for uprating the power density of a Pressurized Water Reactor fuel assembly. An annular fuel has a geometrically inherent advantage such as an increased heat transfer area and a thin pellet thickness. It results in a lot of advantages from the point of a fuel safety and its economy. In order to actualize the dual cooled fuel, an essential element is the annular pellet with precisely controlled diametric tolerance. However, the unique shape of annular fuel pellet causes challenging difficulties to satisfy a diametric tolerance specification. Because of an inhomogeneous green density distribution along the compact height, an hour-glassing usually occurred in a sintered cylindrical PWR fuel pellet fabricated by a conventional doubleacting press. Thus, a sintered pellet usually undergoes a centerless grinding process in order to secure a pellet's specifications. In the case of an annular pellet fabrication using a conventional double-acting press, the same hour-glass shape would probably occur. The outer diameter tolerance of an annular pellet can be controlled easily similar to that of a conventional cylindrical PWR pellet through a centerless grinding. However, it appears not to be simple in the case of an inner surface grinding. It would be the best way to satisfy the specifications for the inner diameter in an as-fabricated pellet. In the present study, we are trying to find a way to minimize the diametric tolerance of the sintered annular pellet without inner surface grinding. This paper deals with a new approach that we have tried to reduce the diametric tolerance of the sintered annular pellet

  8. Sintering of titanium alloy by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Cosme, C.R.M. [Universidade de Brasilia (UnB), DF (Brazil); Henriques, V.A.R.; Cairo, C.A.A.; Taddei, E.B. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    Full text: Titanium alloys are suitable for biomaterial applications, considering its biocompatibility and low elastic modulus compared to steel. Bone resorption in this case can be reduced by load sharing between the implant and natural bone.Starting powders were obtained by hydride method, carried out under positive hydrogen pressure at 500 deg C for titanium and 800 deg C for Nb, Zr and Ta powders. After reaching the nominal temperature, the material was held for 3h, with subsequent cooling to room temperature and milling of the friable hydride. Samples were produce by mixing of initial metallic powders followed by and cold isostatic pressing. Subsequent densification by sintering was performed at temperature range between 900 and 1700 deg C. Characterization was carried out with scanning electron microscopy, X-ray diffractometry and microhardness measurements. Microstructural examinations revealed higher amount of &⧣946;-phase for higher sintering temperature and dissolution of Ta and NB particles. In vitro tests revealed low cytotoxicity of sintered samples. (author)

  9. Sintering and deformation of nanocrystalline ceramics

    International Nuclear Information System (INIS)

    Hahn, H.; Averback, R.S.; Hofler, H.J.; Logas, J.

    1991-01-01

    Nanocrystalline ceramics have been produced by the method of inert gas condensation of ultra-small particles and in situ consolidation. Sintering characteristics and microstructural parameter such as grain size, porosity and pore size distributions have been investigated by a variety of techniques, including: X-ray diffraction, gravimetry, nitrogen adsorption, scanning electron microscopy and small angle neutron scattering. In pure TiO 2 , the sintering temperatures are drastically lowered compared to conventional ceramics, however, extensive grain growth occurs before full densification is achieved. High density, nanocrystalline ceramics can be prepared by pressure assisted sintering, doping and additions of second phases. High temperature microhardness and creep deformation in compression were measured and it was found that creep processes occur at lower temperatures than in ceramics with larger grain sizes. Nanocrystalline TiO 2 with densities >99% can be deformed plastically without fracture at temperatures below half the melting point. The total strains exceed 0.6 at strain rates as high as 10 -3 s -l . The stress exponent of the strain rate, n, is approximately 3 and the grain size dependence is G -q with q in the range of 1-1.5. In this paper it is concluded that the creep deformation occurs by an interface reaction controlled mechanism

  10. Mechanical properties of polymer-infiltrated-ceramic (sodium aluminum silicate) composites for dental restoration.

    Science.gov (United States)

    Cui, Bencang; Li, Jing; Wang, Huining; Lin, Yuanhua; Shen, Yang; Li, Ming; Deng, Xuliang; Nan, Cewen

    2017-07-01

    To fabricate indirect restorative composites for CAD/CAM applications and evaluate the mechanical properties. Polymer-infiltrated-ceramic composites were prepared through infiltrating polymer into partially sintered sodium aluminum silicate ceramic blocks and curing. The corresponding samples were fabricated according to standard ISO-4049 using for mechanical properties measurement. The flexural strength and fracture toughness were measured using a mechanical property testing machine. The Vickers hardness and elastic modulus were calculated from the results of nano-indentation. The microstructures were investigated using secondary electron detector. The density of the porous ceramic blocks was obtained through TG-DTA. The conversion degrees were calculated from the results of mid-infrared spectroscopy. The obtained polymer infiltrated composites have a maximum flexural strength value of 214±6.5MPa, Vickers hardness of 1.76-2.30GPa, elastic modulus of 22.63-27.31GPa, fracture toughness of 1.76-2.35MPam 1/2 and brittleness index of 0.75-1.32μm -1/2 . These results were compared with those of commercial CAD/CAM blocks. Our results suggest that these materials with good mechanical properties are comparable to two commercial CAD/CAM blocks. The sintering temperature could dramatically influence the mechanical properties. Restorative composites with superior mechanical properties were produced. These materials mimic the properties of natural dentin and could be a promising candidate for CAD/CAM applications. Copyright © 2017 Elsevier Ltd. All rights reserved.

  11. Ash transformation and deposition behavior during co-firing biomass with sewage sludge

    DEFF Research Database (Denmark)

    Wang, Liang; Wu, Hao; Jensen, Peter Arendt

    In the present work, the ash transformation and deposition behavior during wheat straw and wood waste combustion were investigated by combustion experiments in an entrained flow reactor. The influence of sewage sludge addition on ash chemistry and deposition tendency was also studied. During...... deposits, which mainly contain K-silicates, K-Al-silicates and K-Ca-silicates. The sewage sludge addition significantly reduced the water soluble K and Na in the fly ash from wheat straw and wood waste combustion. Compared to pure wheat straw and wood waste, the ash deposition rates were increased due...... to sewage sludge addition. However, the ash deposition propensity decreased significantly. In addition, the content of water soluble K and Cl in the deposits reduced as a result of sewage sludge addition. The results from present work suggest co-firing of sewage sludge could alleviate deposit formation...

  12. Co-Sintering behaviour of zirconia-ferritic steel composites

    Directory of Open Access Journals (Sweden)

    Alexander Michaelis

    2016-08-01

    Full Text Available The combination of metallic and ceramic materials allows the combination of positive properties of both and can be applied in various industrial fields. At the moment, the deployment of these composites faces difficult and complex manufacturing. One attempt, which offers a short process route and a high degree of flexibility regarding design is a combined shaping (co-shaping with a combined sintering (co-sintering. The article will show co-sintering results of different metal-ceramic symmetric and asymmetric multi-layered tapes, consisting of yttria stabilized zirconia combined with a ferritic iron chromium steel. Focus is on the densification and co-sintering behaviour of ceramic layers depending on the sintering behaviour of metallic layers. Co-sintered composites were characterized by field emission scanning electron microscopy, x-ray diffraction measurements and in terms of adhesive tensile strength.

  13. 21 CFR 172.410 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... CONSUMPTION (CONTINUED) FOOD ADDITIVES PERMITTED FOR DIRECT ADDITION TO FOOD FOR HUMAN CONSUMPTION Anticaking... agent in food in an amount not in excess of that reasonably required to produce its intended effect. (b... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and...

  14. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    Silicate based bioceramics are promising candidates as biomaterials for tissue engineering. The combustion synthesis method provides control on the morphology and particle size of the synthesized material. This paper discusses the combustion synthesis of akermanite (Ca2MgSi2O7 and Sr2MgSi2O7), which has been ...

  15. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...

  16. Dielectric properties of plasma sprayed silicates

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Neufuss, Karel; Dubský, Jiří; Chráska, Pavel

    -, č. 31 (2005), s. 315-321 ISSN 0272-8842 R&D Projects: GA ČR(CZ) GA202/03/0708 Institutional research plan: CEZ:AV0Z20430508 Keywords : Optical microscopy * electrical properties * silicates * insulators * plasma spraying Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.702, year: 2005

  17. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    Eu2+. Keywords. Biomaterials; silicates; akermanite; combustion synthesis; photoluminescence. 1. Introduction. It is essential to develop biocompatible, bioactive, biore- sorbable and durable materials for orthopaedic and dental implants, that are capable of bearing high stress and loads, and that invoke positive cellular and ...

  18. Thermoset polymer-layered silicic acid nanocomposites

    Science.gov (United States)

    Wang, Zhen

    Nanocomposites are formed when phase mixing occurs on a nanometer length scale. Due to the improved phase morphology and interfacial properties, nanocomposites exhibit mechanical properties superior to conventional composites. Toyota researchers first demonstrated that organoclay could be exfoliated in a nylon-6 matrix to greatly improve the thermal and mechanical properties of the polymer, which has resulted in a practical application in the automobile industry. A great deal of research has been conducted on organic-inorganic hybrid composites in which smectite clays are used as reinforcement agents. However, little work has been devoted to derivatives of other layered inorganic solids. In the present work, the first examples of organic polymer-layered silicic acid nanocomposites have been prepared by formation of a cured epoxy polymer network in the presence of organo cation exchange forms of magadiite. The exfoliation of silicate nanolayers in the epoxy matrix was achieved by in-situ intragallery polymerization during the thermosetting process. In general, the tensile properties, solvent resistance, barrier properties and chemical stability of the polymer matrix are greatly improved by the embedded silicate nanolayers when the matrix is flexible (sub-ambient Tg). The improvement of properties are dependent on the silicate loading, the degree of nanolayer separation and interfacial properties. Interestingly, the exfoliation also affects the polymer elasticity in a favorable way. The mechanism leading to nanocomposite formation is proposed. One exfoliated epoxy-magadiite nanocomposite/composition possessed unique transparent optical properties. The exfoliation chemistry was successfully extended to the other members of the layered silicic acid family. A new approach also was developed to prepare thermoset epoxy polymer-layered silicate nanocomposites in which curing agents can be directly intercalated into the intragallery without the need for alkylammonium ions

  19. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

  20. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Sodium silicate was dissolved in water in either a monomer form or polymer form; the effects of both forms of sodium silicate aqueous solution on rose powdery mildew and root rot diseases of miniature rose were examined. Both forms of sodium silicate aqueous solution were applied to the roots of the miniature rose.

  1. 21 CFR 182.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  2. 21 CFR 582.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  3. Reactive Sintering of Bimodal WC-Co Hardmetals

    OpenAIRE

    Marek Tarraste; Kristjan Juhani; Jüri Pirso; Mart Viljus

    2015-01-01

    Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal har...

  4. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Directory of Open Access Journals (Sweden)

    Barbara Malič

    2015-12-01

    Full Text Available The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions and different atmospheres (i.e., defect chemistry on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT.

  5. Sintering of Lead-Free Piezoelectric Sodium Potassium Niobate Ceramics

    Science.gov (United States)

    Malič, Barbara; Koruza, Jurij; Hreščak, Jitka; Bernard, Janez; Wang, Ke; Fisher, John G.; Benčan, Andreja

    2015-01-01

    The potassium sodium niobate, K0.5Na0.5NbO3, solid solution (KNN) is considered as one of the most promising, environment-friendly, lead-free candidates to replace highly efficient, lead-based piezoelectrics. Since the first reports of KNN, it has been recognized that obtaining phase-pure materials with a high density and a uniform, fine-grained microstructure is a major challenge. For this reason the present paper reviews the different methods for consolidating KNN ceramics. The difficulties involved in the solid-state synthesis of KNN powder, i.e., obtaining phase purity, the stoichiometry of the perovskite phase, and the chemical homogeneity, are discussed. The solid-state sintering of stoichiometric KNN is characterized by poor densification and an extremely narrow sintering-temperature range, which is close to the solidus temperature. A study of the initial sintering stage revealed that coarsening of the microstructure without densification contributes to a reduction of the driving force for sintering. The influences of the (K + Na)/Nb molar ratio, the presence of a liquid phase, chemical modifications (doping, complex solid solutions) and different atmospheres (i.e., defect chemistry) on the sintering are discussed. Special sintering techniques, such as pressure-assisted sintering and spark-plasma sintering, can be effective methods for enhancing the density of KNN ceramics. The sintering behavior of KNN is compared to that of a representative piezoelectric lead zirconate titanate (PZT). PMID:28793702

  6. The electric conductivity of some forms of sintered synthetic zeolites

    International Nuclear Information System (INIS)

    Susic, M.; Petrovic, V.; Ristic, M.; Petranovic, N.

    1978-01-01

    Some forms of synthetic zeolites were sintered and their electric conductivity was measured. The conductivity was observed in correlation with the conductivity of non-sintered pressed samples. Also the change in microstructural constituents in the course of the process of sintering was observed with an optical microscope. It has been found that there is a considerable change in conductivity due to sintering as well as a change in the activation energy for conduction. Also the porosity is noticeably changed. A marked affect of the nature of counter ions on the electric conductivity is shown

  7. Sintering, microstructural and dilatometric studies of combustion synthesized Synroc phases

    International Nuclear Information System (INIS)

    Muthuraman, M.; Patil, K.C.; Senbagaraman, S.; Umarji, A.M.

    1996-01-01

    Sintering, microstructure, and linear thermal expansion properties of Synroc-B and constituent phases, viz. perovskite CaTiO 3 , zirconolite ZrTi 2 O 7 , hollandite (ideal formula BaAl2Ti 6 O 16 ) have been investigated. Synroc-B powder when pelletized and sintered at 1250 C for 2 h achieved >95% theoretical density. Sintered Synroc-B has a linear thermal expansion coefficient α of 8.72 x 10 -6 K -1 and Vicker's microhardness 9.88 GPa. The linear thermal expansion curves did not show any hysteresis indicating the absence of microcracking in the sintered bodies

  8. Rapid laser sintering of metal nano-particles inks.

    Science.gov (United States)

    Ermak, Oleg; Zenou, Michael; Toker, Gil Bernstein; Ankri, Jonathan; Shacham-Diamand, Yosi; Kotler, Zvi

    2016-09-23

    Fast sintering is of importance in additive metallization processes and especially on sensitive substrates. This work explores the mechanisms which set limits to the laser sintering rate of metal nano-particle inks. A comparison of sintering behavior of three different ink compositions with laser exposure times from micro-seconds to seconds reveals the dominant factor to be the organic content (OC) in the ink. With a low OC silver ink, of 2% only, sintering time falls below 100 μs with resistivity <×4 bulk silver. Still shorter exposure times result in line delamination and deformation with a similar outcome when the OC is increased.

  9. Interpretation of Frenkel’s theory of sintering considering evolution of activated pores: III. Determination of equilibrium sintering time

    Directory of Open Access Journals (Sweden)

    Yu C.L.

    2015-01-01

    Full Text Available In this article, the Frenkel’s theory of liquid-phase sintering was interpreted regarding pores as the activated volume. The mathematical model established by Nikolić et al. was used to infer the equilibrium sintering time at varied sintering temperatures during the isothermal sintering of codierite glass by Giess et al. Through the calculation, the equilibrium time at 800ºC, 820ºC, 840ºC and 860ºC is inferred to be 7014.42mins, 1569.65mins, 368.92mins and 114.61mins, respectively. The equilibrium time decreases as the temperature increases. And the theoretical value is in good accordance with the experimental results. Thus, the model established by Nikolić et al. can be applied successfully to predict the equilibrium sintering time of the cordierite glass at varied temperatures during isothermal sintering.

  10. Effects of varied porosity on the physic-mechanical properties of sintered ceramic from Ifon clay

    Directory of Open Access Journals (Sweden)

    Fatai Olufemi ARAMIDE

    2017-12-01

    Full Text Available The effects of saw dust admixture on the physic-mechanical properties of sintered clay bonded carbonized palm kernel shell ceramic was investigated. Composite mixtures of powdered carbonized palm kernel shell and clay from Ifon deposit were produced using equal amount of clay and carbonized palm kernel shell. These were then mixed with varied amount of saw dust (0%, 5% and 10% in a ball mill for 6 hours. From this standard sample specimens were produced using uniaxial compression after mixing each mixture with 10% moisture of clay contents. The compressed samples were sintered at 9500C and soaked for one hour. The sintered samples were characterized for various physic-mechanical properties using state of the art equipment’s. The fired samples were also characterized using ultra-high-resolution field emission scanning electron microscope (UHR-FEGSEM equipped with energy dispersive spectroscopy (EDX. It was observed that the apparent porosity and water absorption of the clay bonded carbonized palm kernel shell ceramic increased with increased amount of saw dust admixture, cold crushing strength, Young’ modulus of elasticity and absorbed energy of the sample reduced with increased amount of saw dust admixture. It was concluded that the sample with 0% saw dust admixture is judged to possess optimum physic-mechanical properties.

  11. Residual stresses in a co-sintered SOC half-cell during post-sintering cooling

    DEFF Research Database (Denmark)

    Charlas, Benoit; Chatzichristodoulou, Christodoulos; Brodersen, Karen

    2014-01-01

    Due to the thermal expansion mismatch between the layers of a Solid Oxide Cell, residual stresses (thermal stresses) develop during the cooling after sintering. Residual stresses can induce cell curvature for asymmetric cells but more importantly they also result in more fragile cells. Depending...

  12. Powder densification maps in Selective Laser Sintering

    International Nuclear Information System (INIS)

    Bourell, D.; Wohlert, M.; Harlan, N.; Beaman, J.; Das, S.

    2002-01-01

    Selective Laser Sintering (SLS) is a manufacturing process in which a part is produced without the need for part-specific tooling. It competes effectively with other manufacturing processes when part geometry is complex and the production run is not large. Traditionally, this was limited to prototype production, although tooling applications are now appearing. This paper describes several applications of powder densification maps to advance solutions in direct SLS of metallic and ceramic powders. Time-dependent plasticity issues arise in pre-processing of powder to make it suitable for SLS and in post-processing of SLS parts to obtain desired density. (Abstract Copyright [2002], Wiley Periodicals, Inc.)

  13. Computer Modeling of Direct Metal Laser Sintering

    Science.gov (United States)

    Cross, Matthew

    2014-01-01

    A computational approach to modeling direct metal laser sintering (DMLS) additive manufacturing process is presented. The primary application of the model is for determining the temperature history of parts fabricated using DMLS to evaluate residual stresses found in finished pieces and to assess manufacturing process strategies to reduce part slumping. The model utilizes MSC SINDA as a heat transfer solver with imbedded FORTRAN computer code to direct laser motion, apply laser heating as a boundary condition, and simulate the addition of metal powder layers during part fabrication. Model results are compared to available data collected during in situ DMLS part manufacture.

  14. Selective laser sintering in biomedical engineering.

    Science.gov (United States)

    Mazzoli, Alida

    2013-03-01

    Selective laser sintering (SLS) is a solid freeform fabrication technique, developed by Carl Deckard for his master's thesis at the University of Texas, patented in 1989. SLS manufacturing is a technique that produces physical models through a selective solidification of a variety of fine powders. SLS technology is getting a great amount of attention in the clinical field. In this paper the characteristics features of SLS and the materials that have been developed for are reviewed together with a discussion on the principles of the above-mentioned manufacturing technique. The applications of SLS in tissue engineering, and at-large in the biomedical field, are reviewed and discussed.

  15. SEM hot stage sintering of UO2

    International Nuclear Information System (INIS)

    Miller, D.J.

    1976-06-01

    The sintering of hyperstoichiometric uranium dioxide powder compacts, in the hot stage of a scanning electron microscope, was continuously monitored using 16 mm time lapse movies. From alumina microspheres placed on the surface of the compacts, shrinkage measurements were obtained. Converting shrinkage measurements into densification profiles indicates that a maximum densification rate is reached at a critical density, independent of the constant heating rates. At temperatures above 1350 0 C, the movement of the reference microspheres made shrinkage measurements impossible. It is believed the evolution of UO 3 gas from hyperstoichiometric UO 2 is the cause of this limitation

  16. Study of the dissolution of three synthetic minerals: zirconolite, Y-britholite and mono-silicate fluor-apatite; Etude de la solubilite de trois mineraux synthetiques: la zirconolite, la britholite-Y et la fluorapatite monosilicatee

    Energy Technology Data Exchange (ETDEWEB)

    Kamel, N.E.H.; Telmoune, S.A. [Centre de Recherche Nucleaire d' Alger, Div. des Techniques Nucleaires, Alger (Algeria); Ait-Amar, H. [Unitersite des Sciences et de la Technologie Houari Boumediene, Dept. de Genie des Procedes, Alger (Algeria)

    2007-11-15

    In this study, we were interested in the synthesis by natural sintering of three minerals analogue of natural rocks: zirconolite, Y-britholite and mono-silicated fluor-apatite. Cerium was used as an actinide surrogate. A simple physical characterization of the materials was made by X-ray diffraction and by measuring both densities and hardnesses. A static leaching test allowed determining the cerium immobilization capacity of the minerals. The most stable mineral was mono-silicated fluor-apatite, with a maximum amount of released cerium less than 2 %. For zirconolite and Y-britholite, this amount reached 15 and 18 % of the total cerium in the minerals, respectively. For the latter compounds, the cerium content in the materials was too weak, and the chosen synthesis method gave less satisfactory physicochemical mineral properties compared to those obtained for mono-silicated fluor-apatite. (authors)

  17. Comparative study of the various methods of preparation of silicate solution and its effect on the geopolymerization reaction

    Directory of Open Access Journals (Sweden)

    N. Essaidi

    Full Text Available This paper is based on the characterization of synthesized geopolymer binders based on either powder or solution silicate, and the amount of water contained in synthesized binders is determined to evaluate their possibility to coat a brick. The structural evolution of the formed geopolymers was investigated using FTIR spectroscopy. The mechanical properties were evaluated using compression tests. The structural evolution ensured that the solutions prepared from silicate powder or liquid had different degrees of polymerization, which modified the polycondensation reaction of the mixture. Nevertheless, the use of aluminosilicate solutions based on powder or liquid display similar behavior in a polycondensation reaction. The obtained materials show good mechanical properties, and it is possible to deposit this binder on the brick depending on the water content. Keywords: Silicate powder, Bricks, Alkaline solution, Binders, Depolymerization, Metakaolin reactivity

  18. Studies on sintered titanates and zeolites as hosts for medium-level radioactive waste

    International Nuclear Information System (INIS)

    Forberg, S.; Westermark, T.; Faelth, L.

    1981-01-01

    In Sweden, a system for transferring long-lived activities from organic to inorganic ion exchangers such as titanates and zeolites was demonstrated on a bench scale. The stability of this system depends on the conditioning of the inorganic ion exchangers. The purpose of this paper was to study and compare the quality of the products obtained by hot pressing and hot isostatic pressing in order to guide the choice of full scale equipment. Due to the leakage of argon, the hot isostatic pressing did not appear to have an advantage. The extremely large surfaces of authentic titanates must be ascribed to this phenomenon. The merits of the two sintering methods could not be objectively compared from the results obtained. Therefore, more experiments are needed and planned. These are studies on the conditioning of the titanates previous to the sintering, on the welding technique and performance, and at a higher sintering temperature, 1300 0 C, known to yield very good results. Formally, a leach rate of 3 μg d -1 cm -2 for the zeolites corresponds to the leaching out of cesium from a surface layer of 0.15 cm during 300 years. The same leach rate of strontium from titanates corresponds to a depth of 0.08 cm for 300 years. Bearing in mind that the temperature of the deposit will be at least 80 0 C lower, and the water flow much lower, the examples mentioned here might be quite satisfying. After a more successful sintering, the leach rates may be still better and a leaching test at more realistic conditions might be worthwhile

  19. Silicon isotope fractionation by marine siliceous sponges

    Science.gov (United States)

    Hendry, K. R.; Maldonado, M.

    2016-02-01

    The stable isotope composition of benthic sponge spicule silica is a potential source of palaeoceanographic information about past deep seawater chemistry. The silicon isotope composition of spicules has been shown to relate to the silicic acid concentration of ambient water. However, existing calibrations do exhibit a degree of scatter in the relationship, and there are many open questions surrounding the mechanism behind isotopic fractionation during biosilicification. Here, we present a new study of silicon isotopes in siliceous sponges, covering a range of ancestral lineages, marine environments and geographical locations, and the impact of cleaning methods of silicon isotope compositions. We show that the cleaning method has minimal impact on silicon isotope composition of sponge spicules. Our results highlight the importance of environmental and biological factors on silicon isotope fractionation, and we discuss the implications of these results on the use of palaeoceanographic applications of sponge spicules.

  20. Cooling rate calculations for silicate glasses.

    Science.gov (United States)

    Birnie, D. P., III; Dyar, M. D.

    1986-03-01

    Series solution calculations of cooling rates are applied to a variety of samples with different thermal properties, including an analog of an Apollo 15 green glass and a hypothetical silicate melt. Cooling rates for the well-studied green glass and a generalized silicate melt are tabulated for different sample sizes, equilibration temperatures and quench media. Results suggest that cooling rates are heavily dependent on sample size and quench medium and are less dependent on values of physical properties. Thus cooling histories for glasses from planetary surfaces can be estimated on the basis of size distributions alone. In addition, the variation of cooling rate with sample size and quench medium can be used to control quench rate.

  1. Tailored Nanocomposites of Polypropylene with Layered Silicates

    Energy Technology Data Exchange (ETDEWEB)

    Xu, L.; Nakajima, H; Manias, E; Krishnamoorti, R

    2009-01-01

    The melt rheological properties of layered silicate nanocomposites with maleic anhydride (MA) functionalized polypropylene are contrasted to those based on ammonium-terminated polypropylene. While the MA functionalized PP based nanocomposites exhibit solid-like linear viscoelastic behavior, consistent with the formation of a long-lived percolated nanoparticle network, the single-end ammonium functionalized PP based nanocomposites demonstrated liquid-like behavior at comparable montmorillonite concentrations. The differences in the linear viscoelasticity are attributed to the presence of bridging interactions in MA functionalized nanocomposites. Further, the transient shear stress of the MA functionalized nanocomposites in start-up of steady shear is a function of the shear strain alone, and the steady shear response is consistent with that of non-Brownian systems. The weak dependence of the steady first normal stress difference on the steady shear stress suggests that the polymer chain mediated silicate network contributes to such unique flow behavior.

  2. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...... experiments in 0.01 m NaNO3 electrolyte (pH 3-6). The surface equilibrium constants were calculated according to the two-layer model by Dzombak & Morel (1990). Near equilibrium between protons/hydroxyls in solution and the ferrihydrite surface was obtained within minutes while equilibration with silicate...

  3. Sorption of Europium in zirconium silicate

    International Nuclear Information System (INIS)

    Garcia R, G.

    2004-01-01

    Some minerals have the property of sipping radioactive metals in solution, that it takes advantage to manufacture contention barriers that are placed in the repositories of nuclear wastes. The more recent investigations are focused in the development of new technologies guided to the sorption of alpha emissors on minerals which avoid their dispersion in the environment. In an effort to contribute to the understanding of this type of properties, some studies of sorption of Europium III are presented like homologous of the americium, on the surface of zirconium silicate (ZrSiO 4 ). In this work the results of sorption experiences are presented as well as the interpretation of the phenomena of the formation of species in the surface of the zirconium silicate. (Author)

  4. SILICATE EVOLUTION IN BROWN DWARF DISKS

    International Nuclear Information System (INIS)

    Riaz, B.

    2009-01-01

    We present a compositional analysis of the 10 μm silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 μm, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of ∼2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of ∼87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a ∼26% crystalline mass fraction for this object.

  5. Neutron diffraction studies of silicate glasses

    International Nuclear Information System (INIS)

    Urnes, S.; Herstad, O.

    1978-01-01

    The different ratios between the scattering amplitudes of X-rays and neutrons for various atomic constituents of glasses have been utilized to study the atomic ordering in silicate glasses. A comparison of corresponding atomic radial distribution curves obtained from neutron diffraction and electron radial distribution curves obtained with X-rays is made. The interatomic distances derived from the two methods are discussed. (Auth.)

  6. Submarine silicic volcanism: Processes and products

    Digital Repository Service at National Institute of Oceanography (India)

    Kalangutkar, N.G.; Iyer, S.D.

    and these are supported by several experimental studies (Annen et al., 2006). A silicic calc-alkalic magma can form by differentiation from a more mafic parent magma and by crustal anatexis. Several evidences show the origin of some rhyolitic and andesitic magma... to be related due to similar tectonic settings. Fractional crystallisation: This process produces a series of residual liquids of variable compositions as compared to their parental magmas and is best explained by the Bowen’s reaction principle (Bowen, 1922...

  7. Durability of metakaolin geopolymers with various sodium silicate/sodium hydroxide ratios against seawater exposure

    Science.gov (United States)

    Jaya, Nur Ain; Abdullah, Mohd Mustafa Al Bakri; Li, Long-Yuan; Sandu, Andrei Victor; Hussin, Kamarudin; Ming, Liew Yun

    2017-09-01

    This work presents an investigation of the performance of metakaolin geopolymers exposed to the continuous immersion of seawater. The geopolymers were prepared from metakaolin by activating with a mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) solutions and cured at 80°C. The ratios of sodium silicate to sodium hydroxide were varied from 0.20 to 0.32. The result showed that metakaolin geopolymers reduce in strength after immersion in seawater for 28 days. The unexposed samples with highest compressive strength attained greatest strength retention. White deposits were formed on the surface of the geopolymers after the exposure to seawater which was believed due to the depolymerisation process of the geopolymer network. Even so, the metakaolin geopolymers did not substantially change in dimension and remain structurally intact.

  8. Direct metal laser sintering: a digitised metal casting technology.

    Science.gov (United States)

    Venkatesh, K Vijay; Nandini, V Vidyashree

    2013-12-01

    Dental technology is undergoing advancements at a fast pace and technology is being imported from various other fields. One such imported technology is direct metal laser sintering technology for casting metal crowns. This article will discuss the process of laser sintering for making metal crowns and fixed partial dentures with a understanding of their pros and cons.

  9. Monitoring Sintering Burn-Through Point Using Infrared Thermography

    Directory of Open Access Journals (Sweden)

    Francisco G. Bulnes

    2013-08-01

    Full Text Available Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burnthrough point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

  10. Monitoring sintering burn-through point using infrared thermography.

    Science.gov (United States)

    Usamentiaga, Rubén; Molleda, Julio; Garcia, Daniel F; Bulnes, Francisco G

    2013-08-09

    Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burn-through point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process.

  11. Tool design and materials for electro sinter forging (ESF)

    DEFF Research Database (Denmark)

    Cannella, Emanuele; Nielsen, Chris Valentin

    A near net-shape forming process represents a suitable solution to obtain the final product by avoiding secondary machining processes. In this field, electro sinter forging is capable of accomplishing the advantages of sintering in a reduced amount of time. Classified as a high field mode (HFM...

  12. Effects of Sintering Temperature on the Density And Porosity of ...

    African Journals Online (AJOL)

    Effects of sintering temperature on the density and porosity of sodium chloride preforms for alu- minium foam manufacturing have been investigated. Cold pressed salt preforms were sintered at 30, 760 and 790 and di erent times ranging between 6- 18 hours in a carbolite furnace at a heating rate of 5/minute. The Results of ...

  13. Monitoring Sintering Burn-Through Point Using Infrared Thermography

    Science.gov (United States)

    Usamentiaga, Rubén; Molleda, Julio; Garcia, Daniel F.; Bulnes, Francisco G.

    2013-01-01

    Sintering is a complex industrial process that applies heat to fine particles of iron ore and other materials to produce sinter, a solidified porous material used in blast furnaces. The sintering process needs to be carefully adjusted, so that the combustion zone reaches the bottom of the material just before the discharge end. This is known as the burn-through point. Many different parameters need to be finely tuned, including the speed and the quantities of the materials mixed. However, in order to achieve good results, sintering control requires precise feedback to adjust these parameters. This work presents a sensor to monitor the sintering burn-through point based on infrared thermography. The proposed procedure is based on the acquisition of infrared images at the end of the sintering process. At this position, infrared images contain the cross-section temperatures of the mixture. The objective of this work is to process this information to extract relevant features about the sintering process. The proposed procedure is based on four steps: key frame detection, region of interest detection, segmentation and feature extraction. The results indicate that the proposed procedure is very robust and reliable, providing features that can be used effectively to control the sintering process. PMID:23939585

  14. Effect of sintering temperature on structural and electrical properties ...

    Indian Academy of Sciences (India)

    TECS

    vity measurement. The crystallinity and surface morphology of the samples improved with sintering tempera- ture. Further, the electrical conductivity measurement indicated that the conduction mechanism is mainly ionic. The conductivity of samples sintered at 1673 K and 1773 K at 800°C are of the order of 0⋅1 S-cm. –1.

  15. The sintering behavior of close-packed spheres

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Tikare, V.; Frandsen, Henrik Lund

    2012-01-01

    The sintering behavior of close-packed spheres is investigated using a numerical model. The investigated systems are the body-centered cubic (bcc), face-centered cubic (fcc) and hexagonal close-packed spheres (hcp). The sintering behavior is found to be ideal, with no grain growth until full dens...

  16. Field assisted hot pressing of sintering Inconel 718 MIM samples

    Science.gov (United States)

    Dugauguez, Olivier; Torralba, Jose Manuel; Barriere, Thierry; Gelin, Jean-Claude

    2016-10-01

    In this investigation on samples obtained by Metal Injection Molding (MIM), the conventional way of sintering in a furnace will be compared to Field Assisted Hot pressing (FAHP) sintering. The difficulty of this method is to be able to control the shrinkage of the sample and so its shape. It has yet not been investigated with a super alloy powder and so, the effects of a high sintering rate. By accelerating the sintering kinetics, the thermal behavior may be modified. Hence, the behavior of the Inconel 718 sintered by FAHP has been investigated. The sintered samples were all injected from a feedstock composed of a fine particle Inconel powder and a binder principally composed of Cellulose Acetate Butyrate CAB and Poly-Ethylene Glycol PEG. The effects of the two methods on the microstructure and the mechanical properties are then compared. There was no difference in distribution of pores between the conventional sintering and the FAHP sintering but a finer grain size showed better hardness.

  17. Sintering of Multilayered Porous Structures: Part I-Constitutive Models

    DEFF Research Database (Denmark)

    Olevsky, Eugene; Tadesse Molla, Tesfaye; Frandsen, Henrik Lund

    2013-01-01

    Theoretical analyses of shrinkage and distortion kinetics during sintering of bilayered porous structures are carried out. The developed modeling framework is based on the continuum theory of sintering; it enables the direct assessment of the cofiring process outcomes and of the impact of process...

  18. Microstructure and properties of sintered mullite developed from ...

    Indian Academy of Sciences (India)

    Dense mullite aggregates with 72% Al2O3 have been synthesized by reaction sintering of two varieties of Indian bauxite and silica sol. The bauxites used are of inferior grade with different levels of accessory impurities such as Fe2O3, TiO2, CaO. The phase and microstructure development of sintered samples were ...

  19. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    NiZnCu hexagonal ferrite (abbreviated as ZT/NZC) composite samples were prepared successfully by using restricted shrinkage sintering process (RSS) (Liu et al 2009a, b). But the electromagnetic performance degra- dation of co-sintered layer ...

  20. Corrosion behaviour of sintered duplex stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Utrilla, M. Victoria; Urena, Alejandro; Otero, Enrique; Munez, Claudio Jose [Escuela Superior de Ciencias Experimentales y Tecnologia, Universidad Rey Juan Carlos, C/ Tulipan s/n, 28933 Mostoles, Madrid (Spain)

    2004-07-01

    Duplex austenite-ferrite stainless steels were prepared by mixing austenitic (316L) and ferritic (434L) atomized powders. Although different 316L/434L ratios were prepared, present work centred its study on 50% ferrite - 50% austenite sintered steel. The powders were mixed and pressed at 700 MPa and sintered at 1250 deg. C for 30 min in vacuum. The cooling rate was 5 deg. C/min. Solution treatment was carried out to homogenize the microstructure at 1100 deg. C during 20 min. A microstructural study of the material in solution was performed, evaluating the microstructure, proportion and shape of porosity, and ferrite percentage. This last was measured by two methods, quantitative metallography and Fischer ferrito-metry. The materials were heat treated in the range of 700 to 1000 deg. C, for 10, 30 and 60 min and water quenched, to study the microstructural changes and the influence on the intergranular corrosion resistance. The method used to evaluate the sensitization to the intergranular corrosion was the electrochemical potentio-kinetic reactivation procedure (EPR). The test solution was 0.5 M H{sub 2}SO{sub 4} + 0,01 M KSCN at 30 deg. C. The criterion used to evaluate the sensitization was the ratio between the maximum reactivation density (Ir) and the maximum activation density (Ia). The results of the electrochemical tests were discussed in relation with the microstructures observed at the different heat treatments. (authors)

  1. Adsorption of dimeric surfactants in lamellar silicates

    Energy Technology Data Exchange (ETDEWEB)

    Balcerzak, Mateusz; Pietralik, Zuzanna [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Domka, Ludwik [Department of Metalorganic Chemistry, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań (Poland); Skrzypczak, Andrzej [Institute of Chemical Technology, Poznań University of Technology, Berdychowo 4, 60-965 Poznań (Poland); Kozak, Maciej, E-mail: mkozak@amu.edu.pl [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-12-01

    Highlights: • The intercalation of dimeric surfactants changed the morphology of MMT samples. • XRD indicated structures formed by surfactant molecules in interlayer space. • The four-step thermal decomposition of dimeric surfactant, confirms intercalation. - Abstract: The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d{sub 001}) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH{sub 2} and CH{sub 3} groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  2. The boron geochemistry of siliceous sponges

    Science.gov (United States)

    de Leon, A.; Wille, M.; Eggins, S. M.; Ellwood, M. J.

    2009-12-01

    The boron content and isotopic composition (δ11B) of marine carbonate organisms can be linked to the pH of the seawater in which they have grown, making carbonates a useful tool for palaeo-seawater pH reconstruction. A study by Furst (1981) documented unusually high boron concentrations in siliceous sponge spicules, in range from hundreds to a thousand ppm. This observation and the potential for preferential incorporation of the tetrahedral borate species into biogenic silica raises the question as to whether the boron chemistry of biogenic silica might also be influenced by seawater pH. We have measured the boron concentration and isotopic composition of siliceous sponges from the Southern Ocean region, with a view to (1) confirming the observations of Furst (1981), (2) assessing the factors that control boron incorporation and isotopic compositions of sponge silica, and (3) investigating the potentially significant role of siliceous sponges in the marine boron cycle. The measured boron concentrations in a diverse range of both demosponge and hexactinellid sponges confirm the high boron concentrations previously reported. The boron isotope compositions of these sponges vary from around +2‰ to +25‰ and greatly exceed the range in marine carbonates. This isotopic variation is inconsistent with seawater pH control but is correlated with ambient seawater silicon concentration, in a manner that suggests a link to silicon uptake kinetics and demand by sponges.

  3. Lead-silicate glass optical microbubble resonator

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Pengfei, E-mail: pengfei.wang@dit.ie [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Ward, Jonathan; Yang, Yong; Chormaic, Síle Nic [Light-Matter Interactions Unit, OIST Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Feng, Xian; Brambilla, Gilberto [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Farrell, Gerald [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)

    2015-02-09

    Microbubble whispering gallery resonators have the potential to become key components in a variety of active and passive photonic circuit devices by offering a range of significant functionalities. Here, we report on the fabrication, optical characterization, and theoretical analysis of lead-silicate glass and optical microbubble resonators. Evanescent field coupling to the microbubbles was achieved using a 1 μm diameter, silica microfiber at a wavelength of circa 775 nm. High Q-factor modes were efficiently excited in both single-stem and two-stem, lead-silicate glass, and microbubble resonators, with bubble diameters of 38 μm (single-stem) and 48 μm (two-stem). Whispering gallery mode resonances with Q-factors as high as 2.3 × 10{sup 5} (single-stem) and 7 × 10{sup 6} (two-stem) were observed. By exploiting the high-nonlinearity of the lead-silicate glass, this work will act as a catalyst for studying a range of nonlinear optical effects in microbubbles, such as Raman scattering and four-wave mixing, at low optical powers.

  4. The Emergence of Quantitative Sintering Theory from 1945 to 1955

    Science.gov (United States)

    German, Randall M.

    2017-04-01

    Particles flow and pack under stress, allowing shaping of the particles into target engineering geometries. Subsequently, in a process termed sintering, the particles are heated to induce bonding that results in a strong solid. Although first practiced 26,000 years ago, sintering was largely unexplained until recent times. Sintering science moved from an empirical and largely qualitative notion into a quantitative theory over a relatively short time period following World War II. That conceptual transition took place just as commercial applications for sintered materials underwent significant growth. This article highlights the key changes in sintering concepts that occurred in the 1945-1955 time period. This time span starts with the first quantitative neck growth model from Frenkel and ends with the quantitative shrinkage model from Kingery and Berg that includes several transport mechanisms.

  5. Preliminary investigation of liquid phase sintering in ferrous systems

    International Nuclear Information System (INIS)

    Klein, J.

    1975-04-01

    Liquid phase sintering was utilized to achieve, by a simple compaction and sintering procedure involving short times and moderate temperatures, a virtually full dense high carbon Fe:C alloy and high boron Fe:B alloy. Parameters such as powder characteristics and mixing, compacting pressure, heating program and the liquid phase fraction were found to influence the sintered density. The response of the Fe:C alloy to a heat treatment is reported along with preliminary experiments in the iron base ternary system Fe:W:C. Residual porosities observed in microstructures of certain liquid phase sintered compacts were accounted for by a proposed capillary flow of the liquid phase and a local densification competing against an overall densification. Some general recommendations are made for liquid phase sintering of powder aggregates. 15 fig., 7 tables

  6. Sintering with a chemical reaction as applied to uranium monocarbide

    International Nuclear Information System (INIS)

    Accary, A.; Caillat, R.

    1960-01-01

    The present paper provides a survey of different investigations whose aim was the preparation and fabrication of uranium monocarbide for nuclear use. If a chemical reaction takes place in the sample during the sintering operation, it may be expected that the atom rearrangements involved in this reaction should favour the sintering process and thereby lower the temperature needed to yield a body of a given density. With this hypothesis in mind, the following methods have been studied: - Sintering of U-C mixtures; - Sintering of UO 2 -C mixtures; - Hot pressing of U-C mixtures; - Extrusion of U-C mixtures. To generalize our result, it could be said that a chemical reaction does not lead to high densification, if one depends on a simple contact between discrete particles. On the contrary, a chemical reaction can help sintering if, as our hot pressing experiments shows, the densification can be achieved prior to the reaction. (author) [fr

  7. Sintered silver joints via controlled topography of electronic packaging subcomponents

    Science.gov (United States)

    Wereszczak, Andrew A.

    2014-09-02

    Disclosed are sintered silver bonded electronic package subcomponents and methods for making the same. Embodiments of the sintered silver bonded EPSs include topography modification of one or more metal surfaces of semiconductor devices bonded together by the sintered silver joint. The sintered silver bonded EPSs include a first semiconductor device having a first metal surface, the first metal surface having a modified topography that has been chemically etched, grit blasted, uniaxial ground and/or grid sliced connected to a second semiconductor device which may also include a first metal surface with a modified topography, a silver plating layer on the first metal surface of the first semiconductor device and a silver plating layer on the first metal surface of the second semiconductor device and a sintered silver joint between the silver plating layers of the first and second semiconductor devices which bonds the first semiconductor device to the second semiconductor device.

  8. Intense pulsed light sintering of copper nanoink for printed electronics

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Hak-Sung; Dhage, Sanjay R.; Shim, Dong-Eun [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); Hahn, H.T. [University of California, Mechanical and Aerospace Engineering Department, Los Angeles, CA (United States); University of California, Material Science and Engineering Department, California NanoSystems Institute, Los Angeles, CA (United States)

    2009-12-15

    An intense pulsed light (IPL) from a xenon flash lamp was used to sinter copper nanoink printed on low-temperature polymer substrates at room temperature in ambient condition. The IPL can sinter the copper nanoink without damaging the polymer substrates in extremely short time (2 ms). The microstructure of the sintered copper film was investigated using X-ray powder diffraction (XRD), optical microscopy, scanning electron microscopy (SEM), X-ray micro tomography, and atomic force microscopy (AFM). The sintered copper film has a grainy structure with neck-like junctions. The resulting resistivity was 5{mu}{omega} cm of electrical resistivity which is only 3 times as high as that of bulk copper. The IPL sintering technique allows copper nanoparticles to be used in inkjet printing on low-temperature substrates such as polymers in ambient conditions. (orig.)

  9. Microstructure evolution during pressureless sintering of bulk oxide ceramics

    Directory of Open Access Journals (Sweden)

    Karel Maca

    2009-06-01

    Full Text Available The author’s experience concerning the infl uence of the choice of different pressureless heating schedules on the fi nal microstructure of oxide ceramic materials is summarized in the paper. Alumina, ceria, strontium titanate, as well as tetragonal (3 mol% Y2O3 and cubic (8 mol% Y2O3 zirconia were cold isostatically pressed or injection moulded and pressureless sintered with different heating schedules – namely with Constant-Rate of Heating with different dwell temperatures (CRH, with Rate-Controlled Sintering (RCS and with Two-Step Sintering (TSS. It was examined whether some of these three sintering schedules, with the same fi nal density achieved, can lead to a decrease of the grain size of sintered ceramics. The results showed that only TSS (and only for selected materials brought significant decrease of the grain size.

  10. Ash chemistry and sintering, verification of the mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Hupa, M.; Skrifvars, B.J.; Backman, R.; Lauren, T.; Uusikartano, T.; Malm, H.; Stenstroem, P.; Vesterkvist, M. [Aabo Akademi, Turku (Finland). Combustion Chemistry Research Group

    1997-10-01

    In this project four sintering mechanisms have been studied, i.e., partial melting with a viscous liquid, partial melting with a non-viscous liquid, chemical reaction sintering and solid state sintering. The work has aimed at improving the understanding of ash sintering mechanisms and quantifying their role in combustion and gasification. The work has been oriented in particular on the understanding of biomass ash behavior. The work has not directly focused on any specific technical application. However, results can also be applied on other fuels such as brown coal, petroleum coke, black liquor and different types of wastes (PDF, RDF, MSW). During 1996 the work has focused on identifying bed agglomeration mechanisms and analysing bed agglomerates in both full scale and lab scale FB reactors, as well as comparing how well the compression strength based sintering test can predict bed agglomeration in an FB furnace. (orig.)

  11. Study on selective laser sintering of glass fiber reinforced polystyrene

    Science.gov (United States)

    Yang, Laixia; Wang, Bo; Zhou, Wenming

    2017-12-01

    In order to improve the bending strength of Polystyrene (PS) sintered parts by selective laser sintering, Polystyrene/glass fiber (PS/GF) composite powders were prepared by mechanical mixing method. The size distribution of PS/GF composite powders was characterized by laser particle size analyzer. The optimum ratio of GF was determined by proportioning sintering experiments. The influence of process parameters on the bending strength of PS and PS/GF sintered parts was studied by orthogonal test. The result indicates that the particle size of PS/GF composite powder is mainly distributed in 24.88 μm~139.8 μm. When the content of GF is 10%, it has better strengthen effect. Finally, the article used the optimum parameter of the two materials to sinter prototype, it is found that the PS/GF prototype has the advantages of good accuracy and high strength.

  12. Powder metallurgy: Solid and liquid phase sintering of copper

    Science.gov (United States)

    Sheldon, Rex; Weiser, Martin W.

    1993-01-01

    Basic powder metallurgy (P/M) principles and techniques are presented in this laboratory experiment. A copper based system is used since it is relatively easy to work with and is commercially important. In addition to standard solid state sintering, small quantities of low melting metals such as tin, zinc, lead, and aluminum can be added to demonstrate liquid phase sintering and alloy formation. The Taguchi Method of experimental design was used to study the effect of particle size, pressing force, sintering temperature, and sintering time. These parameters can be easily changed to incorporate liquid phase sintering effects and some guidelines for such substitutions are presented. The experiment is typically carried out over a period of three weeks.

  13. Structural Environments of Chloride in Silicate and Aluminosilicate Glasses: Cl-35 NMR of a Volatile Species

    Science.gov (United States)

    Sandland, T. O.; Du, L.-; Stebbins, J. F.

    2002-12-01

    As a volatile species, chloride behavior affects the nature and timing of magmatic degassing. Chloride is also recognized as an important complexing agent for metals in hydrothermal ore fluids and is directly related to many mineral deposits. In silicate melts, chloride solubilities have been observed to be strongly dependent on melt composition, and from these studies chlorine speciation has been inferred. However, little direct spectroscopic data is available to constrain the chemical and structural environments of chlorine in these systems. As such, the local environments of chlorine anions in several silicate and aluminosilicate glasses were probed using chlorine-35 MAS NMR. NMR spectra were obtained at 14.1 and 18.8 T fields for a series of Na- and Ca- silicate and aluminosilicate glasses with 1 wt % Cl. Peaks are roughly Gaussian in shape, much narrower than the total chemical shift range for the nuclei, and contributions to peak widths are primarily from quadrupole interactions (Wq) and to a lesser extent chemical shift distribution (Wcsd). Peak widths (FWHM), Wq, and Wcsd at 14.1 T, isotropic chemical shifts (relative to 1 M aq. NaCl), and mean quadrupole coupling constants (η =.7) for the samples probed are: Na-silicate (6210+/-80 Hz, 92+/-3 ppm, 50+/-2 ppm, -70+/-5 ppm, 3.3+/-.1 Hz), Ca-Na-silicate (11750+/-70 Hz, 186+/-4 ppm, 72+/-5 ppm, -50+/-15ppm, 3.2+/-.4 Hz), Ca-silicate (11250+/-590 Hz, 175+/-16 ppm, 78+/-6 ppm, 81+/-20 ppm, 4.4+/-.4 Hz), and Ca-aluminosilicate (12900+/-240 Hz, 217+/-6 ppm, 33+/-10 ppm, 14+/-39 ppm, 3.5+/-.9 Hz). Modeling of the mixed cation (Ca-Na) silicate glass suggests that most (>60%) Cl in the sample is in a mixed bonding environment with a significant amount (~25%) completely Na-coordinated and a minor amount (<10%) completely Ca-coordinated. There is no evidence for significant Cl-Al bonding and quantization of peak intensities suggests that there is little to no "NMR-invisible" Cl in the samples due to peak broadening

  14. Multiphysics modeling of selective laser sintering/melting

    Science.gov (United States)

    Ganeriwala, Rishi Kumar

    A significant percentage of total global employment is due to the manufacturing industry. However, manufacturing also accounts for nearly 20% of total energy usage in the United States according to the EIA. In fact, manufacturing accounted for 90% of industrial energy consumption and 84% of industry carbon dioxide emissions in 2002. Clearly, advances in manufacturing technology and efficiency are necessary to curb emissions and help society as a whole. Additive manufacturing (AM) refers to a relatively recent group of manufacturing technologies whereby one can 3D print parts, which has the potential to significantly reduce waste, reconfigure the supply chain, and generally disrupt the whole manufacturing industry. Selective laser sintering/melting (SLS/SLM) is one type of AM technology with the distinct advantage of being able to 3D print metals and rapidly produce net shape parts with complicated geometries. In SLS/SLM parts are built up layer-by-layer out of powder particles, which are selectively sintered/melted via a laser. However, in order to produce defect-free parts of sufficient strength, the process parameters (laser power, scan speed, layer thickness, powder size, etc.) must be carefully optimized. Obviously, these process parameters will vary depending on material, part geometry, and desired final part characteristics. Running experiments to optimize these parameters is costly, energy intensive, and extremely material specific. Thus a computational model of this process would be highly valuable. In this work a three dimensional, reduced order, coupled discrete element - finite difference model is presented for simulating the deposition and subsequent laser heating of a layer of powder particles sitting on top of a substrate. Validation is provided and parameter studies are conducted showing the ability of this model to help determine appropriate process parameters and an optimal powder size distribution for a given material. Next, thermal stresses upon

  15. Three-dimensional simulation of viscous-flow agglomerate sintering.

    Science.gov (United States)

    Kirchhof, M J; Schmid, H -J; Peukert, W

    2009-08-01

    The viscous-flow sintering of different agglomerate particle morphologies is studied by three-dimensional computer simulations based on the concept of fractional volume of fluid. For a fundamental understanding of particle sintering characteristics, the neck growth kinetics in agglomerate chains and in doublets consisting of differently sized primary particles is investigated. Results show that different sintering contacts in agglomerates even during the first stages are not completely independent from each other, even though differences are small. The neck growth kinetics of differently sized primary particles is determined by the smaller one up to a size difference by a factor of approximately 2, whereas for larger size differences, the kinetics becomes faster. In particular, the agglomerate sintering kinetics is investigated for particle chains of different lengths and for different particle morphologies each having ten primary particles and nine initial sintering contacts. For agglomerate chains, the kinetics approximately can be normalized by using the radius of the fully coalesced sphere. In general, different agglomerate morphologies show equal kinetics during the first sintering stages, whereas during advanced stages, compact morphologies show significantly faster sintering progress than more open morphologies. Hence, the overall kinetics cannot be described by simply using constant morphology correction factors such as fractal dimension or mean coordination number which are used in common sintering models. However, for the first stages of viscous-flow agglomerate sintering, which are the most important for many particle processes, a sintering equation is presented. Although we use agglomerates consisting of spherical primary particles, our methodology can be applied to other aggregate geometries as well.

  16. Lithofacies and biofacies of mid-Paleozoic thermal spring deposits in the Drummond Basin, Queensland, Australia

    Science.gov (United States)

    Walter, M. R.; Desmarais, D.; Farmer, J. D.; Hinman, N. W.

    1996-01-01

    The Devonian to Carboniferous sinters of the Drummond Basin, Australia, are among the oldest well established examples of fossil subaerial hot springs. Numerous subaerial and subaqueous spring deposits are known from the geological record as a result of the occurrence of economic mineral deposits in many of them. Some are reported to contain fossils, but very few have been studied by paleobiologists; they represent an untapped source of paleobiological information on the history of hydrothermal ecosystems. Such systems are of special interest, given the molecular biological evidence that thermophilic bacteria lie near the root of the tree of extant life. The Drummond Basin sinters are very closely comparable with modern examples in Yellowstone National Park and elsewhere. Thirteen microfacies are recognisable in the field, ranging from high temperature apparently abiotic geyserite through various forms of stromatolitic sinter probably of cyanobacterial origin to ambient temperature marsh deposits. Microfossils in the stromatolites are interpreted as cyanobacterial sheaths. Herbaceous lycopsids occur in the lower temperature deposits.

  17. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    OpenAIRE

    Cruz,Maria Fernanda; Rodrigues,Fabrício Ávila; Diniz,Ana Paula Cardoso; Moreira,Maurilio Alves; Barros,Everaldo Gonçalves

    2013-01-01

    The control of Asian Soybean Rust (ASR), caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS) and soil amendment with calcium silicate (CS) on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection ...

  18. Preparation of non-sintered fly ash filter (NSFF) for ammonia nitrogen adsorption.

    Science.gov (United States)

    Shao, Qing; Lu, Mingming; Zhou, Jingchun; Zhu, Zufu; Song, Yinqiang

    2018-02-15

    In accordance with China's goal of 'treating wastes with wastes, turning wastes into treasure', a non-sintered fly ash filter (NSFF) with sewage sludge as additive was prepared. It consists of 70.9% fly ash, 7% sewage sludge, 9% cement, 7.1% CaO, 1% NaHCO 3 and 5% sodium silicate solution. After mixing, 34 g/(100 g dry material) water was added, and then was granulated and steam cured under 80°C for 16 h. NSFF's main performance indexes include specific surface area (SSA) of 17.038 m 2  g -1 , filter media breaking rate (FMBR) of 2.2%, apparent density (AD) of 1140 kg m -3 , and porosity of 41.67%, meeting the Chinese Standard CJ/T 299-2008. This NSFF has a larger SSA and a lower AD comparing with the other similar non-sintered fly ash ceramsite products. Moreover, leaching toxicity of the NSFF has met the Chinese Standards for Hazardous Wastes (GB5085.3-2007). Therefore, the NSFF is effective and safe to use as a water treatment filter media. The NSFF's adsorption characteristics for ammonia nitrogen was investigated. Results showed that the optimized parameters for ammonia nitrogen adsorption are as follows, NSFF dosage at 5 g, initial ammonia nitrogen concentration of 225 mg L -1 , pH at 7, contact time of 12 h and temperature at 30°C. Under the optimum conditions, the adsorption capacity of NSFF for ammonia nitrogen was 4.25 mg g -1 . The adsorption process can be best described by Langmuir isotherm and pseudo-second-order kinetic model. The proposed adsorption mechanism include adsorption and cation exchange.

  19. Effects of serum protein on ionic exchange between culture medium and microporous hydroxyapatite and silicate-substituted hydroxyapatite.

    Science.gov (United States)

    Guth, Katharina; Campion, Charlie; Buckland, Tom; Hing, Karin A

    2011-10-01

    It has been proposed that one of the underlying mechanisms contributing to the bioactivity of osteoinductive or osteoconductive calcium phosphates involves the rapid dissolution and net release of calcium and phosphate ions from the matrix as alternatively a precursor to subsequent re-precipitation of a bone-like apatite at the surface and/or to facilitate ion exchange in biochemical processes. In order to confirm and evaluate ion release from sintered hydroxyapatite (HA) and to examine the effect of silicate substitution into the HA lattice on ion exchange under physiological conditions we monitored Ca(2+), PO(4)(3-) and SiO(4)(4-) levels in Earl's minimum essential medium (E-MEM) in the absence (serum-free medium, SFM) or presence (complete medium, C-MEM) of foetal calf serum (FCM), with both microporous HA or 2.6 wt% silicate-substituted HA (SA) sintered discs under both static and semi-dynamic (SD) conditions for up to 28 days. In SFM, variation in Ca(2+) ion concentration was not observed with either disc chemistry or culture conditions. In C-MEM, Ca(2+) ions were released from SA under static and SD conditions whereas with HA Ca(2+) was depleted under SD conditions. PO(4)(3-) depletion occurred in all cases, although it was greater in C-MEM, particularly under SD conditions. SiO(4)(4-) release occurred from SA irrespective of medium or culture conditions but a sustained release only occurred in C-MEM under SD conditions. In conclusion we showed that under physiological conditions the reservoir of exchangeable ions in both HA and SA in the absence of serum proteins is limited, but that the presence of serum proteins facilitated greater ionic exchange, particularly with SA. These observations support the hypothesis that silicate substitution into the HA lattice facilitates a number of ionic interactions between the material and the surrounding physiological environment, including but not limited to silicate ion release, which may play a key role in determining

  20. Regularities in Low-Temperature Phosphatization of Silicates

    Science.gov (United States)

    Savenko, A. V.

    2018-01-01

    The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.

  1. Sintered soft magnetic materials. Properties and applications

    Science.gov (United States)

    Bas, J. A.; Calero, J. A.; Dougan, M. J.

    2003-01-01

    A comparison is presented of the characteristics and production requirements of a variety of materials used to produce sintered soft magnetic parts. These include pure iron, phosphorous-iron, silicon-iron, nickel-iron, and cobalt-iron, together with new coated materials based on encapsulated iron powders. In these bonded materials an organic and/or inorganic insulator is used to coat the metallic powder particles giving a magnetic composite. The suitability of the different materials for use in both direct and alternating current applications is reviewed, and examples are provided of their application in both the automotive and other sectors. The results of a comparative study of motors using stators and rotors based on both conventional laminated materials and the insulated iron powders are presented, in which the new materials show advantages of reduced hysteresis losses at high frequencies, and isotropy of magnetic properties. Nevertheless, the applications of these materials in electrical motors requires the modification of existing designs.

  2. Sintering and microstructure evolution in columnar thermal barrier coatings

    International Nuclear Information System (INIS)

    Krishnamurthy, Ramanathan; Srolovitz, David J.

    2009-01-01

    Sintering of thermal barrier coatings changes their key properties, such as thermal conductivity and thermal shock resistance, thus adversely impacting their reliability. We present a novel modeling approach to study the evolution of coating structure during sintering. We model the sintering of individual columns using a thermodynamic principle, and incorporate the center-to-center approach rates for the columns calculated using this principle in a larger scale discrete dynamics model for the evolution of a large number of columns. Surface energies, grain boundary energies and strain energies associated with the deformation of the columns are all included in this framework, while sintering is assumed to occur by the concerted action of surface and grain boundary diffusion. Two sets of initial conditions corresponding to different extents of pre-sintering among neighboring columns are considered. When the extent of pre-sintering is small, we observe that small clusters containing 5-20 columns are formed. In contrast, where a larger amount of pre-sintering exists, we observe, especially at large column densities, that clusters containing 50-100 columns separated by large inter-cluster pores/channels that appear to organize themselves into a network are formed. These observations are in good agreement with recently published experimental observations. We also explain how these results can explain the development of a 'mud-crack'-like pattern

  3. Embrittling Components in Sintered Steels: Comparison of Phosphorus and Boron

    Science.gov (United States)

    Danninger, Herbert; Vassileva, Vassilka; Gierl-Mayer, Christian

    2017-12-01

    In ferrous powder metallurgy, both boron and phosphorus have been known to be sintering activators for a long time. However, the use has been widely different: while P is a standard additive to sintered iron and steels, boron has been frequently studied, but its use in practice is very limited. Both additives are also known to be potentially embrittling, though in a different way. In the present study the differences between the effects of both elements are shown: while P activates sintering up to a certain threshold, in part by stabilizing ferrite, in part by forming a transient liquid phase, boron is the classical additive enhancing persistent liquid phase, being virtually insoluble in the iron matrix. The consequence is that sintered steels can tolerate quite a proportion of phosphorus, depending on composition and sintering process; boron however is strongly embrittling in particular in combination with carbon, which requires establishing a precisely defined content that enhances sintering but is not yet embrittling. The fracture mode of embrittled materials is also different: while with Fe-P the classical intergranular fracture is observed, with boron a much more rugged fracture surface appears, indicating some failure through the eutectic interparticle network but mostly transgranular cleavage. If carbon is added, in both cases transgranular cleavage dominates even in the severely embrittled specimens, indicating that no more the grain boundaries and sintering necks are the weakest links in the systems.

  4. Seeking Signs of Life in Nili Patera with Icelandic Sinter Field Exploration.

    Science.gov (United States)

    Skok, J. R.; Farmer, J. D.; Parente, M.; Gaskin, J.; Kaasalainen, H.; Tobler, D.; Jerman, G.

    2015-12-01

    The past decade of Martian orbital and surface exploration has made it clear that the planet could have supported life as we know it in many places throughout much of it's history. The next step in exploration will be to find the evidence for and characterize any preserved Martian life. The jump from confirming habitability to finding life will be difficult and likely require a systemic surface exploration of multiple, specific sites. One site, the sinter mounds of the Nili Patera caldera, provides the ideal combination of hot, neutral to alkaline waters that can develop or support life and the sinter precipitation to preserve it. Nili Patera also provides deposits that are well mapped from orbit allowing a mission to pinpoint the target rocks. With this target known, we can develop the mission, the payload and the science to fit the goals. Several sinter field sites in Iceland were selected for mission testing. They were selected to provide diversity in scale, chemistry and complexity. At each site, we asked the same questions that would drive a mission to Mars. Was there life? What are its preserved properties? What are the environmental history of the sinters and the volcanic history of the local terrain? These questions were investigated with spectral, compositional and morphological analysis. By investigating these questions in Iceland, we will determine which observations, in terms of terrain access and instrument selection are required for mission success on Mars. We report the results from the August 2015 expedition, the first of two planned field seasons. This summer was focused on finalizing the field locations, acquiring mapping data and an initial sampling campaign to determine expected composition and calibrate instruments for year two. With this information, we will determine an investigation plan consistent with a range of mission types from robotic lander to sample return to human exploration. We will also determine the instruments required by the

  5. CO2 sequestration by magnesium silicate mineral carbonation in Finland

    International Nuclear Information System (INIS)

    Zevenhoven, R.; Kohlmann, J.

    2001-01-01

    Fixation Of CO 2 from fossil fuel combustion in the form of solid carbonates appears to be a realistic option for the capture and storage of this greenhouse gas. Vast amounts of magnesium silicate minerals exist worldwide that may be carbonated, with magnesium carbonate as stable and environmentally harmless product. Also in Finland magnesium silicate resources exist that could support Finnish commitments under the Kyoto Protocol. This paper describes the option Of CO 2 sequestration with magnesium silicates in Finland. Addressed are mineral resources, mineral quality and the mineral carbonation process, including some experimental results on magnesium silicate carbonation kinetics

  6. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2004-12-01

    Full Text Available The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca2+ ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of calcium ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca2+ ions on silicate level in the fluid and the fluid properties.

  7. Coordinated STEM/FIB/NanoSIMS Analyses of Presolar Silicates in Comet Dust and Primitive Meteorites

    Science.gov (United States)

    Keller, Lindsay; Nguyen, A.; Rahman, Z.; Messenger, S.

    2012-01-01

    Silicate grains were among the most abundant mineralogical building blocks of our Solar System. These grains were the detritus from earlier generations of stars that have been recycled in the early solar nebula. Rare sub-micrometer survivors of this processing have been identified in meteorites, micrometeorites and interplanetary dust particles (IDPs). These silicate grains are recognized as presolar in origin because of their extremely anomalous isotopic compositions that reflect nucleosynthetic processes in their stellar sources (evolved stars, novae and supernovae). We perform coordinated chemical, mineralogical and isotopic studies of these grains to determine their origins and histories. We examine the complex mineralogy and petrography of presolar silicates using imaging, diffraction and chemical data obtained from thin sections with the JSC JEOL 2500 field-emission STEM equipped with a Noran thin window energy dispersive x-ray (EDX) spectrometer and a Gatan Tridiem GIF. Quantitative element x-ray maps (spectrum images) are acquired by rastering a 4 nm incident probe whose dwell time is minimized to avoid beam damage and element diffusion during mapping. Successive image layers are acquired and combined in order to achieve approx 1% counting statistics for major elements. The IDP samples are prepared by ultramicrotomy of particles embedded in epoxy or elemental sulfur. After EDX mapping, the sections are subjected to C, N, and O isotopic imaging with the JSC NanoSIMS 50L ion microprobe. We prepare sections of some meteorite grains using the JSC FEI Quanta 3D focused ion beam (FIB) instrument. The specimen surface is protected from the FIB milling process by layers of electron beam-deposited C and Pt followed by an ion-deposited Pt layer. We also use the FIB to preferentially remove surrounding grains to reduce the background in subsequent NanoSIMS measurements. For mineralogical studies, we again employ the FIB instrument to deposit a protective cap over the

  8. Preparation of reactive beta-dicalcium silicate

    Science.gov (United States)

    Shen, M.S.; Chen, J.M.; Yang, R.T.

    1980-02-28

    This invention relates to the preparation of fine particles of reactive beta-dicalcium silicate by means of a solid state process which comprises firing a mixture of calcium sulfate, silica, and a reducing additive selected from the group consisting of calcium sulfide, carbon, carbon monoxide, methane, and hydrogen, at a temperature of about 850 to 1000/sup 0/C. A carrier gas such as nitrogen or carbon dioxide may also be added, if desired. A high concentration of sulfur dioxide is a by-product of this process.

  9. Pozzolanic activity of various siliceous materials

    Energy Technology Data Exchange (ETDEWEB)

    Agarwal, S.K. [Central Building Research Institute, Roorkee (India)

    2006-09-15

    The accelerated pozzolanic activity of various siliceous materials, like silica fume, fly ash (as received and fine ground), quartz, precipitated silica, metakaolin and rice husk ash (RHA; various fineness and carbon content), has been determined. The compressive strength of accelerated tests has been compared with cubes cured in water at 7 and 28 days. Maximum activity has been observed in case of RHA ({lt}45 g), followed by quartz and silica fume. The 10% replacement of cement by sand has shown accelerated pozzolanic index of 92% compared with 85% required in ASTM for silica fume as mineral admixture.

  10. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    Diatoms are highly abundant unicellular algae that often dominate pelagic as well as benthic primary production in the oceans and inland waters. Being strictly dependent on silica to build their biomineralized cell walls, marine diatoms precipitate 240 × 10(12) mol Si per year, which makes them...... the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d...

  11. NMR study of hydrated calcium silicates

    International Nuclear Information System (INIS)

    Klur, I.

    1996-01-01

    Radioactive wastes storage methods are developed by the CEA. As cements are important materials as well for hours living radioisotopes than for years living radioisotopes, a better knowledge of this material will allow to anticipate its behaviour and to obtain safer storage methods. The structure of calcium silicates (C-S-H) (main constituent of cements) have then been determined in this thesis by nuclear magnetic resonance. This method has allow to explain in structural terms, the different calcium rates that can be measured in the C-S-H too. (O.M.)

  12. Structure peculiarities of mixed alkali silicate glasses

    International Nuclear Information System (INIS)

    Bershtein, V.A.; Gorbachev, V.V.; Egorov, V.

    1980-01-01

    The thermal porperties and structure of alkali and mixed alkali (Li, Na, K) silicate glasses by means of differential scanning calorimetry (DSC), the positron annihilation method, X-ray fluorescence and infrared (300-30 cm -1 ) spectroscopy were studied. Introduction of different alkali cations in glass results in nonadditive change in their electron structure (bond covalence degree growth) and the thermal behaviour. The different manifestations of mixed alkali effect can be explained by the lessening of long distance Coulomb interactions and strengthening the short-range forces in the mixed alkali glasses. (orig.)

  13. Effects of various additives on sintering of aluminum nitride

    Science.gov (United States)

    Komeya, K.; Inoue, H.; Tsuge, A.

    1982-01-01

    Effects of thirty additives on sintering A/N were investigated. The addition of alkali earth oxides and rare earth oxides gave fully densified aluminum nitride. This is due to the formation of nitrogen-containing aluminate liquid in the system aluminum nitride-alkali earth oxides or rare earth oxides. Microstructural studies of the sintered specimens with the above two types of additives suggested that the densification was due to the liquid phase sintering. Additions of silicon compounds resulted in poor densification by the formation of highly refractory compounds such as A/N polytypes.

  14. Low temperature spark plasma sintering of YIG powders

    International Nuclear Information System (INIS)

    Fernandez-Garcia, L.; Suarez, M.; Menendez, J.L.

    2010-01-01

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 o C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 o C leads to dense samples with minimal formation of YFeO 3 , opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  15. Phenomenological theory of sintering and its application to swelling

    Directory of Open Access Journals (Sweden)

    Kornyushin Y.

    2004-01-01

    Full Text Available The general phenomenological theory of sintering, formulated by the author in 1998 is applied to the problem of swelling. Driving forces, caused by the presence of the evolution of heat in the volume of a sample (electric contact, hf, inductive heating or penetrating radiation, e.g., neutrons could be the sources of the heat in the bulk of a sample are considered. The influence of these driving forces on sintering, structure and properties is discussed. The role of mobile and immobile dislocations, grain boundaries, and pores is considered. Cycling and pulsing regimes of sintering are investigated.

  16. Microwave sintering of nanophase ceramics without concomitant grain growth

    Science.gov (United States)

    Eastman, Jeffrey A.; Sickafus, Kurt E.; Katz, Joel D.

    1993-01-01

    A method of sintering nanocrystalline material is disclosed wherein the nanocrystalline material is microwaved to heat the material to a temperature less than about 70% of the melting point of the nanocrystalline material expressed in degrees K. This method produces sintered nanocrystalline material having a density greater than about 95% of theoretical and an average grain size not more than about 3 times the average grain size of the nanocrystalline material before sintering. Rutile TiO.sub.2 as well as various other ceramics have been prepared. Grain growth of as little as 1.67 times has resulted with densities of about 90% of theoretical.

  17. Manufacturing of metal supported BSCF membranes by spark plasma sintering

    OpenAIRE

    Laptev, Alexander; Bram, Martin; Zivcec, Maria; Baumann, Stefan; Jarligo, Maria Ophelia; Sebold, Doris; Pfaff, Ewald; Broeckmann, Christoph

    2013-01-01

    Spark plasma sintering (SPS), also known as field assisted sintering technique (FAST), is a relatively new method for rapid consolidation of metallic or ceramic powders. In the present work, its suitability for the manufacturing of metal supported Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) based membrane by co-sintering of functional ceramic BSCF layer and porous metallic support has been investigated. The BSCF based membranes are highly attractive for oxygen separation from air due to mixed ionic and e...

  18. Cleanable sintered metal filters in hot off-gas systems

    International Nuclear Information System (INIS)

    Schurr, G.A.

    1981-01-01

    Filters with sintered metal elements, arranged as tube bundles with backflush air cleaning, are the equivalent of bag filters for high-temperature, harsh environments. They are virtually the only alternative for high-temperature off-gas systems where a renewable, highly efficient particle trap is required. Tests were conducted which show that the sintered metal elements installed in a filter system provide effective powder collection in high-temperature atmospheres over thousands of cleaning cycles. Such a sintered metal filter system is now installed on the experimental defense waste calciner at the Savannah River Laboratory. The experimental results included in this paper were used as the basis for its design

  19. Low temperature spark plasma sintering of YIG powders

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez-Garcia, L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Suarez, M., E-mail: m.suarez@cinn.e [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain); Fundacion ITMA, Parque Tecnologico de Asturias, 33428, Llanera (Spain); Menendez, J.L. [Department of Nanostructured Materials, Centro de Investigacion en Nanomateriales y Nanotecnologia (CINN). Principado de Asturias - Consejo superior de Investigaciones Cientificas (CSIC) - Universidad de Oviedo - UO, Parque Tecnologico de Asturias, 33428 Llanera, Asturias (Spain)

    2010-07-16

    A transition from a low to a high spin state in the magnetization saturation between 1000 and 1100 {sup o}C calcination temperature is observed in YIG powders prepared by oxides mixture. Spark plasma sintering of these powders between 900 and 950 {sup o}C leads to dense samples with minimal formation of YFeO{sub 3}, opening the way to co-sintering of YIG with metals or metallic alloys. The optical properties depend on the sintering stage: low (high) density samples show poor (bulk) optical absorption.

  20. Coating of ceramic powders by chemical vapor deposition techniques (CVD)

    International Nuclear Information System (INIS)

    Haubner, R.; Lux, B.

    1997-01-01

    New ceramic materials with selected advanced properties can be designed by coating of ceramic powders prior to sintering. By variation of the core and coating material a large number of various powders and ceramic materials can be produced. Powders which react with the binder phase during sintering can be coated with stable materials. Thermal expansion of the ceramic materials can be adjusted by varying the coating thickness (ratio core/layer). Electrical and wear resistant properties can be optimized for electrical contacts. A fluidized bed reactor will be designed which allow the deposition of various coatings on ceramic powders. (author)

  1. Sintering equation: determination of its coefficients by experiments - using multiple regression

    International Nuclear Information System (INIS)

    Windelberg, D.

    1999-01-01

    Sintering is a method for volume-compression (or volume-contraction) of powdered or grained material applying high temperature (less than the melting point of the material). Maekipirtti tried to find an equation which describes the process of sintering by its main parameters sintering time, sintering temperature and volume contracting. Such equation is called a sintering equation. It also contains some coefficients which characterise the behaviour of the material during the process of sintering. These coefficients have to be determined by experiments. Here we show that some linear regressions will produce wrong coefficients, but multiple regression results in an useful sintering equation. (orig.)

  2. Improvement of mechanical strength of sintered Mo alloyed steel by optimization of sintering and cold-forging processes with densification

    Science.gov (United States)

    Kamakoshi, Y.; Shohji, I.; Inoue, Y.; Fukuda, S.

    2017-10-01

    Powder metallurgy (P/M) materials have been expected to be spread in automotive industry. Generally, since sintered materials using P/M ones contain many pores and voids, mechanical properties of them are inferior to those of conventional wrought materials. To improve mechanical properties of the sintered materials, densification is effective. The aim of this study is to improve mechanical strength of sintered Mo-alloyed steel by optimizing conditions in sintering and cold-forging processes. Mo-alloyed steel powder was compacted. Then, pre-sintering (PS) using a vacuum sintering furnace was conducted. Subsequently, coldforging (CF) by a backward extrusion method was conducted to the pre-sintered specimen. Moreover, the cold-forged specimen was heat treated by carburizing, tempering and quenching (CQT). Afterwards, mechanical properties were investigated. As a result, it was found that the density of the PS specimen is required to be more than 7.4 Mg/m3 to strengthen the specimen by heat treatment after CF. Furthermore, density and the microstructure of the PS specimen are most important factors to make the high density and strength material by CF. At the CF load of 1200 kN, the maximum density ratio reached approximately 99% by the use of the PS specimen with proper density and microstructure. At the CF load of 900 kN, although density ratio was high like more than 97.8%, transverse rupture strength decreased sharply. Since densification caused high shear stress and stress concentration in the surface layer, microcracks occurred by the damages of inter-particle sintered connection of the surface layer. On the contrary, in case of the CF load of 1200 kN, ultra-densification of the surface layer occurred by a sufficient plastic flow. Such sufficient compressed specimens regenerated the sintered connections by high temperature heat treatment and thus the high strength densified material was obtained. These processes can be applicable to near net shape manufacturing

  3. Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers

    Energy Technology Data Exchange (ETDEWEB)

    Charnovych, S., E-mail: csari86@gmail.com [Department of Experimental Physics, University of Debrecen, Bem sq. 18/a, 4026 Debrecen (Hungary); Nemec, P. [Department of Graphic Arts and Photophysics, Faculty of Chemical Technology, University of Pardubice, Studentska 573, 53210 Pardubice (Czech Republic); Nazabal, V. [Equipe Verres et Ceramiques, UMR-CNRS 6226, Sciences Chimiques de Rennes (SCR), Universite de Rennes 1, 35042 Rennes Cedex (France); Csik, A. [Institute of Nuclear Research of Hungarian Academy of Sciences (ATOMKI), P.O. Box 51, H-4001 Debrecen (Hungary); Allix, M.; Matzen, G. [CEMHTI-CNRS, Site Haute Temperature, Orleans (France); Kokenyesi, S. [Department of Experimental Physics, University of Debrecen, Bem sq. 18/a, 4026 Debrecen (Hungary)

    2011-11-01

    Highlights: {yields} Amorphous chalcogenides were investigated in this work. {yields} Photo-induced effects were investigated in the created thin films. {yields} Limiting of photo induced changes in amorphous chalcogenide/alumino-silicate nanomultilayers have been studied. - Abstract: Photo induced changes in amorphous As{sub 20}Se{sub 80}/alumino-silicate nanomultilayers (NML) produced by pulsed laser deposition (PLD) method have been studied in this work. The aim was to investigate the photo induced optical and surface relief changes due to the band gap illumination under the size- and hard cover limited conditions. It was observed that the hard cover layer on the surface of the uniform film or alumino-silicate sub-layers in the NML structure influences the photo darkening and restricts surface relief formations in As{sub 20}Se{sub 80} film or in the related NML compared with this effect in a pure chalcogenide layer. The influence of hard layers is supposed to be connected with limiting the free volume formation at the initial stage of the transformation process, which in turn limits the atomic movement and so the surface relief formation.

  4. Late Eocene siliceous sponge fauna of southern Australia: reconstruction based on loose spicules record.

    Science.gov (United States)

    Łukowiak, Magdalena

    2015-02-09

    An abundant and diversified assemblage of siliceous loose sponge spicules has been identified in the Late Eocene deposits cropping out along the southern coasts of Australia. Based on the comparison of the obtained spicules with those of living sponges, representatives of at least 43 species within 33 genera, 26 families, and 9 orders of "soft" Demospongiae and Homoscleromorpha have been identified in the assemblage. Within the studied sediments, the spicules representing demosponge orders Poecilosclerida, Hadromerida, and Astrophorida were the most diverse. The rest of the five demosponge orders (Halichondrida, Agelasida, Haplosclerida, Spirophorida, and Chondrosida) are represented by single families. Also, a single family Plakinidae within the class Homoscleromorpha that includes two genera was present. The diversity of spicules is similar in all studied samples and areas, even distant geographically, and there are only minor differences between the sections. That indicates a homogenous character of this rich siliceous sponge assemblage. Most of the studied sponge spicules have Recent equivalents among present-day siliceous spicules. However, the fossil ones are bigger which is most likely due to different environmental conditions. Among the recognized sponge species, at least eleven (Agelas cf. axifera, Agelas cf. wiedenmayeri, Penares sclerobesa, Histodermella australis, Trikentrion flabelliforme, Cliona cf. mucronata, Tethya cf. omanensis, Terpios sp., Placinolopha cf. sarai, Dotona pulchella, and Sigmosceptrella quadrilobata) are noted for the first time in the fossil record.

  5. Vibrational investigation of calcium-silicate cements for endodontics in simulated body fluids

    Science.gov (United States)

    Taddei, Paola; Modena, Enrico; Tinti, Anna; Siboni, Francesco; Prati, Carlo; Gandolfi, Maria Giovanna

    2011-05-01

    Calcium-silicate MTA (Mineral Trioxide Aggregate) cements have been recently developed for oral and endodontic surgery. This study was aimed at investigating commercial (White ProRoot MTA, White and Grey MTA-Angelus) and experimental (wTC-Bi) accelerated calcium-silicate cements with regards to composition, hydration products and bioactivity upon incubation for 1-28 days at 37 °C, in Dulbecco's Phosphate Buffered Saline (DPBS). Deposits on the surface of the cements and the composition changes during incubation were investigated by micro-Raman and ATR/FT-IR spectroscopy, and pH measurements. Vibrational techniques disclosed significant differences in composition among the unhydrated cements, which significantly affected the bioactivity as well as pH, and hydration products of the cements. After one day in DPBS, all the cements were covered by a more or less homogeneous layer of B-type carbonated apatite. The experimental cement maintained a high bioactivity, only slightly lower than the other cements and appears a valid alternative to commercial cements, in view of its adequate setting time properties. The bioactivity represents an essential property to favour bone healing and makes the calcium-silicate cements the gold standard materials for root-apical endodontic surgery.

  6. Thermal ammonia nitridation on HfO2 and hafnium silicates thin films

    International Nuclear Information System (INIS)

    Ganem, J.-J.; Trimaille, I.; Vickridge, I.C.; Gusev, E.P.

    2006-01-01

    In this paper we use isotopic tracing experiments with 15 NH 3 and 14 NH 3 to investigate the nitridation mechanisms on both hafnium silicates films (40-175 A) and HfO 2 (50 A) films deposited by MOCVD on silicon substrate covered by a 10-15 A interfacial SiO 2 layer. Nitrogen profiles in the films were obtained through nuclear resonance profiling (NRP) with the 15 N(p,αγ) 12 C resonance at 429 keV and the total amounts of atomic species and the overall stoichiometry were obtained by RBS and NRA. In the silicate films, nitrogen is incorporated both into surface and bulk regions. For HfO 2 , lowering the ammonia pressure favors the fixation of nitrogen in the near surface region of film. This phenomenon is not observed in the case of silicate films. The pressure dependence of near surface nitrogen incorporation in HfO 2 films could be related to the formation of oxygen vacancies and opens a way to control the diffusion barrier needed in the gate dielectric

  7. Uniform thin film electrode made of low-temperature-sinterable silver nanoparticles: optimized extent of ligand exchange from oleylamine to acrylic acid

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Yung Jong; Kim, Na Rae; Lee, Changsoo; Lee, Hyuck Mo, E-mail: hmlee@kaist.ac.kr [Department of Materials Science and Engineering (Korea, Republic of)

    2017-02-15

    Lowering the sintering temperature of nanoparticles in the electrode deposition process holds both academic and industrial interest because of the potential applications of such electrodes in polymer devices and flexible electronics. In addition, achieving uniform electrode formation after ligand exchange is equally important as lowering the sintering temperature. Here, we report a simple chemical treatment by the addition of ligand-exchanging interfaces to lower the sintering temperature; we also determine the optimum extent of ligand exchange for crack-free electrode formation. First, we investigated the structural change of Ag thin films with respect to the concentration of acrylic acid (AA) solutions. Second, we used thermal analysis to evaluate the effects of changes in the sintering temperature. We observed that the resulting conductivity of the Ag patterns was only one order of magnitude lower than that of bulk Ag when the patterns were sintered at 150 °C. The simple chemical treatment developed in this work for solution-processed Ag electrode formation can be adopted for flexible electronics, which would eliminate the need for vacuum and high-temperature processes.

  8. Evidence for seismogenic fracture of silicic magma.

    Science.gov (United States)

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  9. Thermochemistry of dense hydrous magnesium silicates

    Science.gov (United States)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  10. Carbon Mineralization Using Phosphate and Silicate Ions

    Science.gov (United States)

    Gokturk, H.

    2013-12-01

    Carbon dioxide (CO2) reduction from combustion of fossil fuels has become an urgent concern for the society due to marked increase in weather related natural disasters and other negative consequences of global warming. CO2 is a highly stable molecule which does not readily interact with other neutral molecules. However it is more responsive to ions due to charge versus quadrupole interaction [1-2]. Ions can be created by dissolving a salt in water and then aerosolizing the solution. This approach gives CO2 molecules a chance to interact with the hydrated salt ions over the large surface area of the aerosol. Ion containing aerosols exist in nature, an example being sea spray particles generated by breaking waves. Such particles contain singly and doubly charged salt ions including Na+, Cl-, Mg++ and SO4--. Depending on the proximity of CO2 to the ion, interaction energy can be significantly higher than the thermal energy of the aerosol. For example, an interaction energy of 0.6 eV is obtained with the sulfate (SO4--) ion when CO2 is the nearest neighbor [2]. In this research interaction between CO2 and ions which carry higher charges are investigated. The molecules selected for the study are triply charged phosphate (PO4---) ions and quadruply charged silicate (SiO4----) ions. Examples of salts which contain such molecules are potassium phosphate (K3PO4) and sodium orthosilicate (Na4SiO4). The research has been carried out with first principle quantum mechanical calculations using the Density Functional Theory method with B3LYP functional and Pople type basis sets augmented with polarization and diffuse functions. Atomic models consist of the selected ions surrounded by water and CO2 molecules. Similar to the results obtained with singly and doubly charged ions [1-2], phosphate and silicate ions attract CO2 molecules. Energy of interaction between the ion and CO2 is 1.6 eV for the phosphate ion and 3.3 eV for the silicate ion. Hence one can expect that the selected

  11. Plutonium Immobilization Project Binder Burnout and Sintering Studies (Milestone 6.6a)

    Energy Technology Data Exchange (ETDEWEB)

    Chandler, G.

    1999-10-28

    The Plutonium Immobilization Team has developed an integrated test program to understand and optimize the controlling variables for the sintering step of the plutonium immobilization process. Sintering is the key process step that controls the product minerology. It is expected that the sintering will be the limiting process step that controls the throughput of the production line. The goal of the current sintering test program is to better understand factors that affect the sintering process.

  12. Plutonium Immobilization Project Binder Burnout and Sintering Studies (Milestone 6.6a)

    International Nuclear Information System (INIS)

    Chandler, G.

    1999-01-01

    The Plutonium Immobilization Team has developed an integrated test program to understand and optimize the controlling variables for the sintering step of the plutonium immobilization process. Sintering is the key process step that controls the product mineralogy. It is expected that the sintering will be the limiting process step that controls the throughput of the production line. The goal of the current sintering test program is to better understand factors that affect the sintering process

  13. Sintering and electrical properties of strontium-doped lanthanum manganite

    Energy Technology Data Exchange (ETDEWEB)

    Tarrago, Diego Pereira; Sousa, Vania Caldas de [Universidade Federal do Rio Grande do Sul (LABIOMAT/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Biomateriais], Email: dptarrago@gmail.com; Moreno Buriel, Berta; Chinarro Martini, Eva; Jurado Egea, Jose Ramon [Consejo Superior de Investigaciones Cientificas (ICV/CSIC), Madrid (Spain). Inst. de Ceramica y Vidrio; Malfatti, Celia de Fraga [Universidade Federal do Rio Grande do Sul (LAPEC/PPGEM/UFRGS), Porto Alegre, RS (Brazil). Programa de Pos-Graduacao em Engenharia de Minas, Metalurgica e de Materiais. Lab. de Pesquisa em Corrosao

    2010-07-01

    Lanthanum strontium manganites (LSM) are potential materials for cathode applications in solid oxide fuel cells (SOFC) due to their good catalytic activity, chemical stability and compatibility with electrolyte materials in high temperatures. The sinterability of single phase La{sub 1-x}Sr{sub x}Mn{sub O3} (x=0.18) perovskite powders and the electrical properties of the resulting samples are analyzed in this study. Using a heating microscope, the powders were pressed and sintered at different pressures and temperatures, resulting in an open porosity of 33.36% when compacted at 125 MPa and sintered at 1200 degree C. Top and cross-section s canning electron microscopy (SEM) micrographs revealed interconnected pores in the sintered body and, hence, a suitable microstructure for the application. The activation energy for conductance was 0.04 eV and the tested LSM bulk started to exhibit adequate electrical properties at about 500 degree C. (author)

  14. Zone refining of sintered, microwave-derived YBCO superconductors

    International Nuclear Information System (INIS)

    Warrier, K.G.K.; Varma, H.K.; Mani, T.V.; Damodaran, A.D.; Balachandran, U.

    1993-07-01

    Post-sintering treatments such as zone melting under thermal gradient has been conducted on sintered YBCO tape cast films. YBCO precursor powder was derived through decomposition of a mixture of nitrates of cations in a microwave oven for ∼4 min. The resulting powder was characterized and made into thin sheets by tape casting and then sintered at 945 C for 5 h. The sintered tapes were subjected to repeated zone refining operations at relatively high speeds of ∼30 mm/h. A microstructure having uniformly oriented grains in the a-b plane throughout the bulk of the sample was obtained by three repeated zone refining operations. Details of precursor preparation, microwave processing and its advantages, zone refining conditions, and microstructural features are presented in this paper

  15. Quartz crystal reinforced quartz glass by spark plasma sintering

    International Nuclear Information System (INIS)

    Torikai, D.; Barazani, B.; Ono, E.; Santos, M.F.M.; Suzuki, C.K.

    2011-01-01

    The Spark Plasma Sintering presents fast processing time when compared to conventional sintering techniques. This allows to control the grain growth during sintering as well as the diffusion rate of a multi-material compounds, and make possible obtainment of functionally graded materials and nanostructured compounds. Powders of high purity silica glass and crystalline silica were sintered in a SPS equipment at temperatures around 1350° C, i.e., above the softening temperature of silica glass and below the melting temperature of quartz crystal. As a result, glass ceramics with pure silica glass matrix reinforced with crystalline alpha-quartz grains were fabricated at almost any desired range of composition, as well as controlled size of the crystalline reinforcement. X-ray diffraction and density measurements showed the possibility to manufacture a well controlled density and crystallinity glass-ceramic materials. (author)

  16. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; de Florio, D. Z.

    2017-01-01

    Gadolinium, yttrium and samarium-doped barium cerate pressed pellets were submitted to flash sintering experiments isothermally in the temperature range 800-1300oC under 200 V cm-1 electric field. The pellets were positioned inside a dilatometer furnace with Pt-Ir electrodes connected either...... to a power supply or to an impedance analyzer to evaluate the bulk and the grain boundary contributions to the electrical resistivity. Near full density was achieved in the sintered samples. The combined results of dilatometry and impedance measurements in conventionally and flash sintered specimens show...... substantial improvement of the electrical conductivity. Joule heating is assumed to be the primary effect for sintering. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively, as the reasons for the decrease...

  17. Onset conditions for flash sintering of UO2

    Science.gov (United States)

    Raftery, Alicia M.; Pereira da Silva, João Gustavo; Byler, Darrin D.; Andersson, David A.; Uberuaga, Blas P.; Stanek, Christopher R.; McClellan, Kenneth J.

    2017-09-01

    In this work, flash sintering was demonstrated on stoichiometric and non-stoichiometric uranium dioxide pellets at temperatures ranging from room temperature (26 °C) up to 600 °C . The onset conditions for flash sintering were determined for three stoichiometries (UO2.00, UO2.08, and UO2.16) and analyzed against an established thermal runaway model. The presence of excess oxygen was found to enhance the flash sintering onset behavior of uranium dioxide, lowering the field required to flash and shortening the time required for a flash to occur. The results from this study highlight the effect of stoichiometry on the flash sintering behavior of uranium dioxide and will serve as the foundation for future studies on this material.

  18. Foam glass obtained through high-pressure sintering

    DEFF Research Database (Denmark)

    Østergaard, Martin Bonderup; Petersen, Rasmus Rosenlund; König, Jakob

    2018-01-01

    are subjected to a second heat treatment above the glass transition temperature at atmospheric pressure. This heat treatment causes expansion of the pores due to high internal gas pressure. We found that the foaming ability strongly depends on the gas pressure applied during sintering, and on the kinetic......Foam glasses are usually prepared through a chemical approach, that is, by mixing glass powder with foaming agents, and heating the mixture to a temperature above the softening point (106.6 Pa s) of the glass. The foaming agents release gas, enabling expansion of the sintered glass. Here, we use...... a physical foaming approach to prepare foam glass. First, closed pores filled with inert gases (He, Ar, or N2) are physically introduced into a glass body by sintering cathode ray tube (CRT) panel glass powder at high gas pressure (5‐25 MPa) at 640°C and, then cooled to room temperature. The sintered bodies...

  19. Efficient Radiation Shielding Through Direct Metal Laser Sintering

    Data.gov (United States)

    National Aeronautics and Space Administration — We have developed a method for efficient component-level radiation shielding that can be printed by direct metal laser sintering (DMLS) from files generated by the...

  20. Non-pressurized sintered silicon carbide with titanium carbide reinforcement

    International Nuclear Information System (INIS)

    Adler, J.

    1992-01-01

    A non-pressurized compression of SiC-TiC composite materials can be achieved via liquid phase sintering by the application of oxidic additives. Materials with TiC proportions up to 40% by volume of TiC and densities of 97 to 98% TD were produced at sintering temperatures around 1875 C. With SiC sintered in the liquid phase an increase of toughness at fracture of 80% compared with conventionally non-pressurized sintered SiC was achieved with B/C additive. No further increase could be achieved by the addition of TiC particles. However, the oxidation resistance at 1200 C was worsened. (orig.) [de

  1. Pressureless sintering behavior of injection molded alumina ceramics

    Directory of Open Access Journals (Sweden)

    Liu W.

    2014-01-01

    Full Text Available The pressureless sintering behaviors of two widely used submicron alumina (MgOdoped and undoped with different solid loadings produced by injection molding have been studied systematically. Regardless of the sinterability of different powders depending on their inherent properties, solid loading plays a critical role on the sintering behavior of injection molded alumina, which greatly determines the densification and grain size, and leads to its full densification at low temperatures. As compared to the MgO-doped alumina powder, the undoped specimens exhibit a higher sinterability for its smaller particle size and larger surface area. While full densification could be achieved for MgO-doped powders with only a lower solid loading, due to the fact that MgO addition can reduce the detrimental effect of the large pore space on the pore-boundary separation.

  2. Modeling constrained sintering of bi-layered tubular structures

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye; Kothanda Ramachandran, Dhavanesan; Ni, De Wei

    2015-01-01

    Constrained sintering of tubular bi-layered structures is being used in the development of various technologies. Densification mismatch between the layers making the tubular bi-layer can generate stresses, which may create processing defects. An analytical model is presented to describe...... the densification and stress developments during sintering of tubular bi-layered samples. The correspondence between linear elastic and linear viscous theories is used as a basis for derivation of the model. The developed model is first verified by finite element simulation for sintering of tubular bi-layer system....... Furthermore, the model is validated using densification results from sintering of bi-layered tubular ceramic oxygen membrane based on porous MgO and Ce0.9Gd0.1O1.95-d layers. Model input parameters, such as the shrinkage kinetics and viscous parameters are obtained experimentally using optical dilatometry...

  3. Verification of the Skorohod-Olevsky Viscous Sintering (SOVS) Model

    Energy Technology Data Exchange (ETDEWEB)

    Lester, Brian T. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-11-16

    Sintering refers to a manufacturing process through which mechanically pressed bodies of ceramic (and sometimes metal) powders are heated to drive densification thereby removing the inherit porosity of green bodies. As the body densifies through the sintering process, the ensuing material flow leads to macroscopic deformations of the specimen and as such the final configuration differs form the initial. Therefore, as with any manufacturing step, there is substantial interest in understanding and being able to model the sintering process to predict deformation and residual stress. Efforts in this regard have been pursued for face seals, gear wheels, and consumer products like wash-basins. To understand the sintering process, a variety of modeling approaches have been pursued at different scales.

  4. The potential for carbon bio-sequestration in China’s paddy rice (Oryza sativa L.) as impacted by slag-based silicate fertilizer

    Science.gov (United States)

    Song, Alin; Ning, Dongfeng; Fan, Fenliang; Li, Zhaojun; Provance-Bowley, Mary; Liang, Yongchao

    2015-12-01

    Rice is a typical silicon-accumulating plant. Silicon (Si), deposited as phytoliths during plant growth, has been shown to occlude organic carbon, which may prove to have significant effects on the biogeochemical sequestration of atmospheric CO2. This study evaluated the effects of silicate fertilization on plant Si uptake and carbon bio-sequestration in field trials on China’s paddy soils. The results showed (1) Increased Si concentrations in rice straw with increasing application rates of silicate fertilizer; (2) Strong positive correlations between phytolith contents and straw SiO2 contents and between phytolith contents and phytolith-occluded carbon (PhytOC) contents in rice straw; (3) Positive correlations between the phytolith production flux and either the above-ground net primary productivity (ANPP) or the PhytOC production rates; (4) Increased plant PhytOC storage with increasing application rates of silicate fertilizer. The average above-ground PhytOC production rates during China’s rice production are estimated at 0.94 × 106 tonnes CO2 yr-1 without silicate fertilizer additions. However, the potential exists to increase PhytOC levels to 1.16-2.17 × 106 tonnes CO2 yr-1 with silicate fertilizer additions. Therefore, providing silicate fertilizer during rice production may serve as an effective tool in improving atmospheric CO2 sequestration in global rice production areas.

  5. The potential for carbon bio-sequestration in China's paddy rice (Oryza sativa L.) as impacted by slag-based silicate fertilizer.

    Science.gov (United States)

    Song, Alin; Ning, Dongfeng; Fan, Fenliang; Li, Zhaojun; Provance-Bowley, Mary; Liang, Yongchao

    2015-12-01

    Rice is a typical silicon-accumulating plant. Silicon (Si), deposited as phytoliths during plant growth, has been shown to occlude organic carbon, which may prove to have significant effects on the biogeochemical sequestration of atmospheric CO2. This study evaluated the effects of silicate fertilization on plant Si uptake and carbon bio-sequestration in field trials on China's paddy soils. The results showed (1) Increased Si concentrations in rice straw with increasing application rates of silicate fertilizer; (2) Strong positive correlations between phytolith contents and straw SiO2 contents and between phytolith contents and phytolith-occluded carbon (PhytOC) contents in rice straw; (3) Positive correlations between the phytolith production flux and either the above-ground net primary productivity (ANPP) or the PhytOC production rates; (4) Increased plant PhytOC storage with increasing application rates of silicate fertilizer. The average above-ground PhytOC production rates during China's rice production are estimated at 0.94 × 10(6) tonnes CO2 yr(-1) without silicate fertilizer additions. However, the potential exists to increase PhytOC levels to 1.16-2.17 × 10(6) tonnes CO2 yr(-1) with silicate fertilizer additions. Therefore, providing silicate fertilizer during rice production may serve as an effective tool in improving atmospheric CO2 sequestration in global rice production areas.

  6. The potential for carbon bio-sequestration in China’s paddy rice (Oryza sativa L.) as impacted by slag-based silicate fertilizer

    Science.gov (United States)

    Song, Alin; Ning, Dongfeng; Fan, Fenliang; Li, Zhaojun; Provance-Bowley, Mary; Liang, Yongchao

    2015-01-01

    Rice is a typical silicon-accumulating plant. Silicon (Si), deposited as phytoliths during plant growth, has been shown to occlude organic carbon, which may prove to have significant effects on the biogeochemical sequestration of atmospheric CO2. This study evaluated the effects of silicate fertilization on plant Si uptake and carbon bio-sequestration in field trials on China’s paddy soils. The results showed (1) Increased Si concentrations in rice straw with increasing application rates of silicate fertilizer; (2) Strong positive correlations between phytolith contents and straw SiO2 contents and between phytolith contents and phytolith-occluded carbon (PhytOC) contents in rice straw; (3) Positive correlations between the phytolith production flux and either the above-ground net primary productivity (ANPP) or the PhytOC production rates; (4) Increased plant PhytOC storage with increasing application rates of silicate fertilizer. The average above-ground PhytOC production rates during China’s rice production are estimated at 0.94 × 106 tonnes CO2 yr−1 without silicate fertilizer additions. However, the potential exists to increase PhytOC levels to 1.16–2.17 × 106 tonnes CO2 yr−1 with silicate fertilizer additions. Therefore, providing silicate fertilizer during rice production may serve as an effective tool in improving atmospheric CO2 sequestration in global rice production areas. PMID:26621377

  7. Low temperature sintering of fluorapatite glass-ceramics.

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A

    2014-02-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Objective, our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Methods, glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disk-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. Results and Significance XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. Copyright © 2013 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  8. Process for preparing sintered uranium dioxide nuclear fuel

    International Nuclear Information System (INIS)

    Carter, R.E.

    1975-01-01

    Uranium dioxide is prepared for use as fuel in nuclear reactors by sintering it to the desired density at a temperature less than 1300 0 C in a chemically controlled gas atmosphere comprised of at least two gases which in equilibrium provide an oxygen partial pressure sufficient to maintain the uranium dioxide composition at an oxygen/uranium ratio of at least 2.005 at the sintering temperature. 7 Claims, No Drawings

  9. Corrosion Properties of Sintered and Wrought Stainless Seel

    DEFF Research Database (Denmark)

    Mathiesen, Troels; Maahn, Ernst Emanuel

    1997-01-01

    The corrosion properties of a range of stainless steels produced by powder metallurgy (PM) are compared with wrought AISI304 and AISI316 Steel. Characterisation of the passivation properties in 0.5M H2SO4 and pittingresistance in 0.3% chloride solution by polarisation show properties...... of the sintered PM150 that are comparable or better than those of wrought 316 steel depending on the applied sintering technique....

  10. Low temperature sintering of fluorapatite glass-ceramics

    Science.gov (United States)

    Denry, Isabelle; Holloway, Julie A.

    2014-01-01

    Fluorapatite glass-ceramics have been shown to be excellent candidates as scaffold materials for bone grafts, however, scaffold production by sintering is hindered by concurrent crystallization of the glass. Our goal was to investigate the effect of Ca/Al ratio on the sintering behavior of Nb-doped fluorapatite-based glasses in the SiO2-Al2O3-P2O5-MgO-Na2O-K2O-CaO-CaF2 system. Glass compositions with Ca/Al ratio of 1 (A), 2 (B), 4 (C) and 19 (D) were prepared by twice melting at 1525°C for 3h. Glasses were either cast as cylindrical ingots or ground into powders. Disc-shaped specimens were prepared by either sectioning from the ingots or powder-compacting in a mold, followed by heat treatment at temperatures ranging between 700 and 1050°C for 1h. The density was measured on both sintered specimens and heat treated discs as controls. The degree of sintering was determined from these measurements. XRD showed that fluorapatite crystallized in all glass-ceramics. A high degree of sintering was achieved at 775°C for glass-ceramic D (98.99±0.04%), and 900°C for glass-ceramic C (91.31±0.10). Glass-ceramics A or B were only partially sintered at 1000°C (63.6±0.8% and 74.1±1.5%, respectively). SEM revealed a unique microstructure of micron-sized spherulitic fluorapatite crystals in glass-ceramics C and D. Increasing the Ca/Al ratio promoted low temperature sintering of fluorapatite glass-ceramics, which are traditionally difficult to sinter. PMID:24252652

  11. Properties of Bulk Sintered Silver As a Function of Porosity

    Energy Technology Data Exchange (ETDEWEB)

    Wereszczak, Andrew A [ORNL; Vuono, Daniel J [ORNL; Wang, Hsin [ORNL; Ferber, Mattison K [ORNL; Liang, Zhenxian [ORNL

    2012-06-01

    This report summarizes a study where various properties of bulk-sintered silver were investigated over a range of porosity. This work was conducted within the National Transportation Research Center's Power Device Packaging project that is part of the DOE Vehicle Technologies Advanced Power Electronics and Electric Motors Program. Sintered silver, as an interconnect material in power electronics, inherently has porosity in its produced structure because of the way it is made. Therefore, interest existed in this study to examine if that porosity affected electrical properties, thermal properties, and mechanical properties because any dependencies could affect the intended function (e.g., thermal transfer, mechanical stress relief, etc.) or reliability of that interconnect layer and alter how its performance is modeled. Disks of bulk-sintered silver were fabricated using different starting silver pastes and different sintering conditions to promote different amounts of porosity. Test coupons were harvested out of the disks to measure electrical resistivity and electrical conductivity, thermal conductivity, coefficient of thermal expansion, elastic modulus, Poisson's ratio, and yield stress. The authors fully recognize that the microstructure of processed bulk silver coupons may indeed not be identical to the microstructure produced in thin (20-50 microns) layers of sintered silver. However, measuring these same properties with such a thin actual structure is very difficult, requires very specialized specimen preparation and unique testing instrumentation, is expensive, and has experimental shortfalls of its own, so the authors concluded that the herein measured responses using processed bulk sintered silver coupons would be sufficient to determine acceptable values of those properties. Almost all the investigated properties of bulk sintered silver changed with porosity content within a range of 3-38% porosity. Electrical resistivity, electrical conductivity

  12. Impact strength of sintered astaloy CrM powders

    International Nuclear Information System (INIS)

    Kazior, J.; Ploszczak, J.; Nykiel, M.; Pieczonka, T.

    2003-01-01

    In this paper results of a series of impact tests on sintered Astaloy CrM powders alloys modified by boron are presented and discussed. Boron in different forms, i.e. as elemental boron powder, boron carbide B 4 C powder or mixture of boron and carbon elemental powders, was used in different weight percentage to activate sintering of Astaloy CrM powder and to increase hardenability, with aim of increasing impact strength in view of structural applications. (author)

  13. Enhanced Sintering of Boron Carbide-Silicon Composites by Silicon

    Science.gov (United States)

    Zeng, Xiaojun; Liu, Weiliang

    2016-11-01

    Boron carbide (B4C)-silicon (Si) composites have been prepared by aqueous tape casting, laminating, and spark plasma sintering (SPS). The influences of silicon (Si) content on the phases, microstructure, sintering properties, and mechanical properties of the obtained B4C-Si composites are studied. The results indicate that the addition of Si powder can act as a sintering aid and contribute to the sintering densification. The addition of Si powder can also act as a second phase and contribute to the toughening for composites. The relative density of B4C-Si composites samples with adding 10 wt.% Si powder prepared by SPS at 1600 °C and 50 MPa for 8 min is up to 98.3%. The bending strength, fracture toughness, and Vickers hardness of the sintered samples are 518.5 MPa, 5.87 MPa m1/2, and 38.9 GPa, respectively. The testing temperature-dependent high-temperature bending strength and fracture toughness can reach a maximum value at 1350 °C. The B4C-Si composites prepared at 1600, 1650, and 1700 °C have good high-temperature mechanical properties. This paper provides a facile low-temperature sintering route for B4C ceramics with improved properties.

  14. Bending Behavior of Porous Sintered Stainless Steel Fiber Honeycombs

    Science.gov (United States)

    Zou, Shuiping; Wan, Zhenping; Lu, Longsheng; Tang, Yong

    2017-02-01

    A novel porous honeycomb-type substrate has been developed using solid-state sintering stainless steel fibers. The porous sintered stainless steel fiber honeycombs (PSSSFH) are composed of a skeleton of sintered stainless steel fibers, three-dimensionally interconnected porous structures and multiple parallel microchannels. The bending behavior of the PSSSFH is investigated using three-point bending tests. Four stages, including an elastic stage, a yielding stage with a plateau, a hardening stage and a failure stage, are observed during the bending process of the PSSSFH. In the initial yielding stage, the bending forces increase slowly with displacement increasing, and then a yielding plateau follows, which is unique compared with other porous materials. Moreover, the structure parameters of the PSSSFH are varied to investigate the influence on the bending strength. It is determined that the multiple parallel microchannels can enhance the bending strength of porous stainless steel fiber sintered substrates (PSSFSS) and do not influence the variation trend of bending strength of PSSFSS with porosity increasing. The open ratio is conducive to increasing the bending strength, and the microchannel diameters ranging from 0.5 mm to 1.5 mm have little influence on the bending strength. In addition, both the increasing of sintering temperature and sintering time can strengthen the PSSSFH.

  15. Industrial Sintering of Uranium Oxide in a Continuous Furnace

    International Nuclear Information System (INIS)

    Hauser, R.; Porneuf, A.

    1963-01-01

    Under a USAEC-EURATOM research contract, CICAF (Compagnie industrielle de combustibles atomiques frittes) was asked by the French Atomic Energy Commission to design and construct a continuous furnace sintering under a reducing atmosphere at high temperature. The characteristic features of the furnace are automatic operation, rigorous control of presintering and sintering atmospheres, flexibility of temperature regulation so that the thermal cycle can be adjusted to the product to be sintered and high output (5 t of uranium oxide per month). It can operate continuously up to 1700 deg. C, the presintering taking place at a lower temperature (800 deg. C) in a preliminary furnace which forms an integral part of the whole. The sintering atmosphere is cracked ammonia or pure hydrogen; the presintering atmosphere is a mixture o f about 10% hydrogen and 90% nitrogen. The sintered pellets densify to above 97% of theoretical density, with a total dispersion of less than 1%. Structurally, they are equi-axed grains of about 10μm. It was established that the stoichiometric variation of the uranium oxide sintered in a continuous furnace was less than 0.005. (author) [fr

  16. Manufacture of sintered bricks of high density from beryllium oxide

    International Nuclear Information System (INIS)

    Pointud, R.; Rispal, Ch.; Le Garec, M.

    1959-01-01

    Beryllium oxide bricks of nuclear purity 100 x 100 x 50 and 100 x 100 x 100 mm of very high density (between 2.85 and 3.00) are manufactured by sintering under pressure in graphite moulds at temperatures between 1,750 and 1,850 deg. C, and under a pressure of 150 kg/cm 2 . The physico-chemical state of the saw material is of considerable importance with regard to the success of the sintering operation. In addition, a study of the sintering of a BeO mixture with 3 to 5 per cent of boron introduced in the form of boric acid, boron carbide or elementary boron shows that high densities can only be obtained by sintering under pressure. For technical reasons of manufacture, only the mixture based on boron carbide is used. The sintering is carried out in graphite moulds at 1500 deg. C under 150 kg/cm 2 pressure, and bricks can be obtained with density between 2,85 and 2,90. Laboratory studies and the industrial manufacture of various sinters are described in detail. (author) [fr

  17. Uniaxial ratcheting behavior of sintered nanosilver joint for electronic packaging

    International Nuclear Information System (INIS)

    Chen, Gang; Yu, Lin; Mei, Yunhui; Li, Xin; Chen, Xu; Lu, Guo-Quan

    2014-01-01

    Uniaxial ratcheting behavior and the fatigue life of sintered nanosilver joint were investigated at room temperature. All tests were carried out under stress-controlled mode. Force–displacement data were recorded during the entire fatigue lifespan by a non-contact displacement detecting system. Effects of stress amplitude, mean stress, stress rate, and stress ratio on the uniaxial ratcheting behavior of the sintered nanosilver joint were discussed. Stress-life (S–N) curves of the sintered joints were also obtained. The Smith–Watson–Topper (SWT) model, the Gerber model and the modified Goodman model, all of which took effect of mean stress into consideration, were compared for predicting the fatigue life of the sintered joint. Both the ratcheting strain and its rate increased with increasing stress amplitude or mean stress. The increase in stress amplitude and mean stress both reduced the fatigue life of the sintered joint, while the fatigue life prolonged with the increase in stress rate and stress ratio. The modified Goodman model predicted the fatigue life of the sintered joints well

  18. Orange-red emitting europium doped strontium ortho-silicate phosphor prepared by a solid state reaction method.

    Science.gov (United States)

    Sahu, Ishwar Prasad

    2017-05-01

    In the present article we report europium-doped strontium ortho-silicates, namely Sr 2 SiO 4 :xEu 3+ (x = 1.0, 1.5, 2.0, 2.5 or 3.0 mol%) phosphors, prepared by solid state reaction method. The crystal structures of the sintered phosphors were consistent with orthorhombic crystallography with a Pmna space group. The chemical compositions of the sintered phosphors were confirmed by energy dispersive X-ray spectroscopy (EDS). Thermoluminescence (TL) kinetic parameters such as activation energy, order of kinetics and frequency factors were calculated by the peak shape method. Orange-red emission originating from the 5 D 0 - 7 F J (J = 0, 1, 2, 3) transitions of Eu 3+ ions could clearly be observed after samples were excited at 395 nm. The combination of these emissions constituted orange-red light as indicated on the Commission Internationale de l'Eclairage (CIE) chromaticity diagram. Mechanoluminescence (ML) intensity of the prepared phosphor increased linearly with increasing impact velocity of the moving piston that suggests that these phosphors can also be used as sensors to detect the stress of an object. Thus, the present investigation indicates that the piezo-electricity was responsible for producing ML in the prepared phosphor. Copyright © 2016 John Wiley & Sons, Ltd.

  19. [Adsorption characteristic and form distribution of silicate in lakes sediments].

    Science.gov (United States)

    Lü, Chang-Wei; Cui, Meng; Gao, Ji-Mei; Zhang, Xi-Yan; Wan, Li-Li; He, Jiang; Meng, Ting-Ting; Bai, Fan; Yang, Xu

    2012-01-01

    Taking surface sediments from the Wuliangsuhai Lake and Daihai Lake as adsorbent, the isothermal adsorption experiments of silicate on sediments were carried out and the adsorption behavior was explained by Langmuir, Freundlich and Temkin crossover-type equations, then the form distribution characters of silicate were studied after adsorption in this work. The results showed that the adsorption behavior of silicate on the two lakes sediments can be linear fitting in the lower concentration dose (Temkin crossover-type equations can be used to explain the adsorption behavior of silicate on the two lakes sediments, and the native adsorption silicate (NAS) and equilibrium silicate concentration (ESC(0)) calculated by the three equations could be used to explain the sink and source effects of the sediments from the two lakes; the silicate form distribution in the sediments after adsorption indicated that silicate adsorbed on particles were mainly added on the form of IEF-Si, CF-Si, IMOF-Si and OSF-Si, and the IMOF-Si and OSF-Si had important potential bioavailability.

  20. Petrology and Geochemistry of Calc-Silicate Schists and Calc ...

    African Journals Online (AJOL)

    Chemically the calc-silicate schists are characterized by relatively high CaO, MgO, Cr, Ni, Sr, La, Ce and Nd contents compared with the mica schist regionally associated with the marble as well as the Post-Archean Australian Shale (PAAS). Relative to the ultramafic schist the calc-silicate schists are characterized by higher ...

  1. Tsunami deposits

    International Nuclear Information System (INIS)

    2013-01-01

    The NSC (the Nuclear Safety Commission of Japan) demand to survey on tsunami deposits by use of various technical methods (Dec. 2011), because tsunami deposits have useful information on tsunami activity, tsunami source etc. However, there are no guidelines on tsunami deposit survey in JAPAN. In order to prepare the guideline of tsunami deposits survey and evaluation and to develop the method of tsunami source estimation on the basis of tsunami deposits, JNES carried out the following issues; (1) organizing information of paleoseismological record and tsunami deposit by literature research, (2) field survey on tsunami deposit, and (3) designing the analysis code of sediment transport due to tsunami. As to (1), we organize the information gained about tsunami deposits in the database. As to (2), we consolidate methods for surveying and identifying tsunami deposits in the lake based on results of the field survey in Fukui Pref., carried out by JNES. In addition, as to (3), we design the experimental instrument for hydraulic experiment on sediment transport and sedimentation due to tsunamis. These results are reflected in the guideline on the tsunami deposits survey and evaluation. (author)

  2. Deposit Shedding in Biomass-Fired Boilers: Shear Adhesion Strength Measurements

    DEFF Research Database (Denmark)

    Laxminarayan, Yashasvi; Jensen, Peter Arendt; Wu, Hao

    2017-01-01

    a significant effect under the investigated conditions. Addition of compounds which increase the melt fraction of the ash dposit, typically by forming a eutectic system, increases the adhesion strength, whereas addition of inert compounds with a high melting point decreases the adhesion strength. Furthermore......Ash deposition on boiler surfaces is a major problem encountered in biomass combustion. Timely removal of ash deposits is essentialfor optimal boiler operation. In order to improve the understanding of deposit shedding in boilers, this study investigates the adhesion strength of biomass ash from...... off by an electrically controlled arm, and the corresponding adhesion strength was measured. The effect of sintering temperature, sintering time, deposit composition, thermal shocks on the deposit, and steel type was investigated. The results reveal that the adhesion strength of ash deposits...

  3. Effect of sintering temperature on optical properties and microstructure of translucent zirconia prepared by high-pressure spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Haibin Zhang, Byung-Nam Kim, Koji Morita, Hidehiro Yoshida Keijiro Hiraga and Yoshio Sakka

    2011-01-01

    Full Text Available Aiming to characterize the effect of sintering temperature on transparency of zirconia, we have evaluated the optical properties and microstructure of translucent cubic zirconia prepared by high-pressure spark plasma sintering (SPS at 1000–1200 circleC. Color centers (oxygen vacancies with trapped electrons and residual pores were primary defects in the samples. In SPS samples, the total forward transmittance and in-line transmittance are mainly affected by color centers with a limited contribution from residual pores; in contrast, the changes in reflectance are only related to the porosity. The amounts of color centers and residual pores increase with sintering temperature that reduces the total forward and in-line transmittance of the as-sintered zirconia. Annealing in oxidizing atmosphere improves the total forward and in-line transmittance. During the annealing, the concentration of color centers decreases but the porosity increases.

  4. Effect Of Compaction Pressure And Sintering Temperature On The Liquid Phase Sintering Behavior Of Al-Cu-Zn Alloy

    Directory of Open Access Journals (Sweden)

    Lee S.H.

    2015-06-01

    Full Text Available The liquid phase sintering characteristics of Al-Cu-Zn alloy were investigated with respect to various powder metallurgy processing conditions. Powders of each alloying elements were blended to form Al-6Cu-5Zn composition and compacted with pressures of 200, 400, and 600 MPa. The sintering process was performed at various temperatures of 410, 560, and 615°C in N2 gas atmosphere. Density and micro-Vickers hardness measurements were conducted at different processing stages, and transverse rupture strength of sintered materials was examined for each condition, respectively. The microstructure was characterized using optical microscope and scanning electron microscopy. The effect of Zn addition on the liquid phase sintering behavior during P/M process of the Al-Cu-Zn alloy was also discussed in detail.

  5. Spectral properties of porphyrins in the systems with layered silicates

    International Nuclear Information System (INIS)

    Ceklovsky, A.

    2009-03-01

    This work is focused on investigation of hybrid materials based on layered silicates, representing host inorganic component, and porphyrin dyes as organic guest. Aqueous colloidal dispersions, as well as thin solid films of layered silicate/porphyrin systems were studied. Modification of photophysical properties, such as absorption and fluorescence of molecules, adsorbed or incorporated in layered silicate hosts, were studied mainly to spread the knowledge about the environments suitable for incorporating aromatic compounds, providing photoactive properties of potential technological interest. TMPyP cations interact with the surfaces of layered silicates via electrostatic interactions. The extent of dye adsorption on colloidal particles of the silicates is influenced by the CEC values and swelling ability of silicates. Interaction of porphyrins with layered silicate hosts leads to significant changes of dye spectral properties. One of the key parameters that has a crucial impact on this interaction is the layer charge of silicate template. Other factors influence the resulting spectral properties of hybrid systems, such as the method of hybrid material preparation, the material's type (colloid, film), and the modification of the silicate host. Molecular orientation studies using linearly-polarized spectroscopies in VIS and IR regions revealed that TMPyP molecules were oriented in almost parallel fashion with respect to the silicate surface plane. Slightly higher values of the orientation angle of TMPyP transition moment were observed for the TMPyP/FHT system. Thus, flattening of the guest TMPyP molecules is the next important factor (mainly in the systems with lower layer charge), influencing its spectral properties upon the interaction with layered silicates. Fluorescence was effectively quenched in the systems based on solid films prepared from the high concentration of the dye (10-3 mol.dm-3). The quenching is most probably related to the structure of the

  6. Effect of natural fiber types and sodium silicate coated on natural fiber mat/PLA composites: Tensile properties and rate of fire propagation

    Science.gov (United States)

    Thongpin, C.; Srimuk, J.; hipkam, N.; Wachirapong, P.

    2015-07-01

    In this study, 3 types of natural fibres, i.e. jute, sisal and abaca, were plain weaved to fibre mat. Before weaving, the fibres were treated with 5% NaOH to remove hemi cellulose and lignin. The weaving was performed by hand using square wooden block fit with nails for weaving using one and two types of natural fibres as weft and warp fibre to produce natural fibre mat. The fibre mat was also impregnated in sodium silicate solution extracted from rich husk ash. The pH of the solution was adjusted to pH 7 using H2SO4 before impregnation. After predetermined time, sodium silicate was gelled and deposited on the mat. The fabric mat and sodium silicate coated mat were then impregnated with PLA solution to produce prepreg. Dried pepreg was laminated with PLA sheet using compressing moulding machine to obtain natural fibre mat/PLA composite. The composite containing abaca aligned in longitudinal direction with respect to tension force enhanced Young's modulus more than 300%. Fibre mat composites with abaca aligned in longitudinal direction also showed tensile strength enhancement nearly 400% higher than neat PLA. After coating with sodium silicate, the tensile modulus of the composites was found slightly increased. The silicate coating was disadvantage on tensile strength of the composite due to the effect of sodium hydroxide solution that was used as solvent for silicate extraction from rice husk ash. However, sodium silicate could retard rate of fire propagation about 50%compare to neat PLA and about 10% reduction compared to fibre mat composites without sodium silicate coated fibre mat.

  7. Development of hydroxyapatite/calcium silicate composites addressed to the design of load-bearing bone scaffolds.

    Science.gov (United States)

    Sprio, Simone; Tampieri, Anna; Celotti, Giancarlo; Landi, Elena

    2009-04-01

    This work deals with the preparation of bioactive ceramic composites to be employed for the development of load-bearing bone substitutes, made of hydroxyapatite (Ca(10)(PO(4))(6)(OH)(2), HA) and bioactive dicalcium silicate (Ca(2)SiO(4), C(2)S) as a reinforcing phase. The composite materials were prepared by Fast Hot-Pressing (FHP), which allowed the rapid sintering of monolithic ceramics at temperatures up to 1500 degrees C, well above the commonly adopted temperatures for the consolidation of hydroxyapatite (1200-1300 degrees C). The purpose was to achieve the grain coalescence of both HA and the strengthening phase, so that to obtain a homogeneous ceramic material characterized by controlled phase composition and improved mechanical strength; the dwell time was reduced as much as possible to prevent HA decomposition and excessive grain growth. The most remarkable result, in terms of phase composition, was the absence of any secondary phases in the final ceramics other than HA and C(2)S, even after sintering at 1500 degrees C. The flexure strength of the composite materials was found to be much higher than that of HA alone. Further mechanical characterization was also carried out on HA and composites, sintered in different conditions, to evaluate the elastic properties and fracture toughness, and properties close to those of mineral bone were found. These preliminary results confirmed that composites of HA and Ca(2)SiO(4) are promising for the development of bioactive load-bearing ceramic bone substitutes with controlled phase composition.

  8. Thermal Analysis of Sintered Silver Nanoparticles Film

    Directory of Open Access Journals (Sweden)

    M. Keikhaie

    2014-07-01

    Full Text Available Thin bonded films have many applications in antireflection and reflection coating, insulating and conducting films and semiconductor industries. Thermal conductivity is one of the most important parameter for power packaging since the thermal resistance of the interconnections is directly related to the heat removal capability and thermal management of the power package. The defects in materials play very important role on the effective thermal conductivity. In this paper, finite element method (FEM was utilized to simulate the effect of pores on the effective thermal conductivity of sintered silver nanoparticles film. The simulation results indicate that the effective thermal conductivity of film is different at different directions and would be enhanced when the pore angle is 90. The simulation results will help us to further understand the heat transfer process across highly porous structures and will provide us a powerful guide to design coating with high thermal insulation or conductor property. Because of there is no similar experimental data for this simulation results, this paper is a comparative work among three different models.

  9. Polymer powders for selective laser sintering (SLS)

    Science.gov (United States)

    Schmid, Manfred; Amado, Antonio; Wegener, Konrad

    2015-05-01

    Selective Laser Sintering (SLS) is close to be accepted as a production technique (Additive Manufacturing). However, one problem limiting employment of SLS for additive manufacturing in a wide-ranging industrial scope is the narrow variety of applicable polymers. The commonly applied SLS powder to date is polyamide 12 (PA 12). PA 12 or ccompounds of PA 12 (dry blends) are approximately 90 % of complete industrial consumption. The remaining small quantity is distributed on polyamide 11 (PA11) and some other `exotic' polymers (TPU, PEBA, P(E)EK). Industry is awaiting commodity polymers like polypropylene (PP) or polyethylene (PE) crucial to open new market segments. But several approaches launching those polymers failed. But what are the reasons for the difficulties in developing new SLS powders? The contribution is to answer this and highlights the combination of intrinsic and extrinsic polymer properties necessary to generate a polymer powder promising for SLS application. Particle shape, powder distribution, thermal, rheological and optical requirements must be considered and only a particularly controlled property combination leads to successful SLS implementation. Thermal behavior, particle shape and -distribution is discussed in detail, although the other properties can't be disregarded for providing new commercially successful SLS powder finally.

  10. Damage Behavior of Sintered Fiber Felts

    Directory of Open Access Journals (Sweden)

    Nicolas Lippitz

    2015-04-01

    Full Text Available The reduction of aircraft noise is important due to a rising number of flights and the growth of urban centers close to airports. During landing, a significant part of the noise is generated by flow around the airframe. To reduce that noise porous trailing edges are investigated. Ideally, the porous materials should to be structural materials as well. Therefore, the mechanical properties and damage behavior are of major interest. The aim of this study is to show the change of structure and the damage behavior of sintered fiber felts, which are promising materials for porous trailing edges, under tensile loading using a combination of tensile tests and three dimensional computed tomography scans. By stopping the tensile test after a defined stress or strain and scanning the sample, it is possible to correlate structural changes and the development of damage to certain features in the stress-strain curve and follow the damage process with a high spatial resolution. Finally, the correlation between material structure and mechanical behavior is demonstrated.

  11. Mineralization enrichment of uranyl mineral in mid-low temperature hydrothermal of Shuanghuajiang uranium deposit

    International Nuclear Information System (INIS)

    Fang Shiyi; Liang Yongdong; Tao Zhijun; Chen Weifeng

    2009-01-01

    Based on field examination and mineral study by X-ray powder diffraction, electronic probe and back scatter electronic image, uranium mineral in Shuanghuajiang uranium deposit are analyzed and the mineral are divided into two classes: uranyl phosphate and uranyl silicate. After studying the forming condition of these uranylminerals, the deposit fall into low temperature hydrothermal genesis. The metallogenic model is hence established. (authors)

  12. Stress-corrosion mechanisms in silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Ciccotti, Matteo, E-mail: matteo.ciccotti@univ-montp2.f [Laboratoire des Colloides, Verres et Nanomateriaux, UMR 5587, CNRS, Universite Montpellier 2, Montpellier (France)

    2009-11-07

    The present review is intended to revisit the advances and debates in the comprehension of the mechanisms of subcritical crack propagation in silicate glasses almost a century after its initial developments. Glass has inspired the initial insights of Griffith into the origin of brittleness and the ensuing development of modern fracture mechanics. Yet, through the decades the real nature of the fundamental mechanisms of crack propagation in glass has escaped a clear comprehension which could gather general agreement on subtle problems such as the role of plasticity, the role of the glass composition, the environmental condition at the crack tip and its relation to the complex mechanisms of corrosion and leaching. The different processes are analysed here with a special focus on their relevant space and time scales in order to question their domain of action and their contribution in both the kinetic laws and the energetic aspects.

  13. Properties of BioRoot RCS, a tricalcium silicate endodontic sealer modified with povidone and polycarboxylate.

    Science.gov (United States)

    Siboni, F; Taddei, P; Zamparini, F; Prati, C; Gandolfi, M G

    2017-12-01

    To evaluate the chemical and physical properties of a tricalcium silicate root canal sealer containing povidone and polycarboxylate (BioRoot RCS), a calcium silicate MTA-based sealer containing a salicylate resin (MTA Fillapex), a traditional eugenol-containing sealer (Pulp Canal Sealer) and an epoxy resin-based root canal sealer (AH Plus). Calcium release, pH, setting time, water sorption, volume of open pores, volume of impervious portion, apparent porosity and weight loss were measured. The ability to nucleate calcium phosphates (CaP) after ageing 28 days in a simulated body fluid was evaluated using ESEM-EDX and micro-Raman spectroscopy. Data were statistically analysed (P = 0.05) using one-way anova (setting time, radiopacity, solubility, water sorption, porosity) or two-way anova (ion release tests). BioRoot RCS had a final setting time of 300 min and adequate radiopacity (5.2 mm Al). It demonstrated the highest (P pH (11-12) (P Pulp Canal Sealer and AH Plus; no CaP nucleation was detected on aged Pulp Canal Sealer, and some apatite deposits were found on aged AH Plus (chemi/physisorption-related CaP-deposition). Higher and significantly different (P < 0.05) porosity, water sorption and solubility were measured for the two calcium silicate sealers, especially for BioRoot RCS. BioRoot RCS had bioactivity with calcium release, strong alkalizing activity and apatite-forming ability, and adequate radiopacity. © 2017 International Endodontic Journal. Published by John Wiley & Sons Ltd.

  14. Co-settling of Chromite and Sulfide Melt Droplets and Trace Element Partitioning between Sulfide and Silicate Melts

    Science.gov (United States)

    Manoochehri, S.; Schmidt, M. W.; Guenther, D.

    2013-12-01

    Gravitational settling of immiscible, dense sulfide melt droplets together with other cumulate phases such as chromite, combined with downward percolation of these droplets through a cumulate pile, is thought to be one of the possible processes leading to the formation of PGE rich sulfide deposits in layered mafic intrusions. Furthermore some chromitite seams in the Merensky Reef (Bushveld Complex) are considered to be acting as a filter or barrier for further downward percolation of sulfide melts into footwall layers. To investigate the feasibility of such mechanical processes and to study the partitioning behavior of 50 elements including transition metals and REEs (but not PGEs) between a silicate and a sulfide melt, two separate series of high temperature (1250-1380 °C) centrifuge-assisted experiments at 1000 g, 0.4-0.6 GPa were conducted. A synthetic silicate glass with a composition representative of the parental magma of the Bushveld Complex (~ 55 wt% SiO2) was mixed with pure FeS powder. For the first series of experiments, 15 or 25 wt% natural chromite with average grain sizes of ~ 5 or 31 μm were added to a mixture of silicate glass and FeS (10 wt%) adding 1 wt% water. For the second series, a mixture of the same glass and FeS was doped with 50 trace elements. These mixtures were first statically equilibrated and then centrifuged. In the first experimental series, sulfide melt droplets settled together with, but did not segregate from chromite grains even after centrifugation at 1000 g for 12 hours. A change in initial chromite grain size and proportions didn't have any effect on segregation. Without chromite, the starting mixture resulted in the formation of large sulfide melt pools together with finer droplets still disseminated through the silicate glass and both at the bottom of the capsule. The incomplete segregation of sulfide melt is interpreted as being due to high interfacial energies between sulfide and silicate melts/crystals which hinder

  15. Hydrolytic Stability of 3-Aminopropylsilane Coupling Agent on Silica and Silicate Surfaces at Elevated Temperatures

    DEFF Research Database (Denmark)

    Okhrimenko, Denis; Budi, Akin; Ceccato, Marcel

    2017-01-01

    in coupling efficiency, thus decreasing the product quality and the mechanical strength of the polymer-inorganic material interface. Therefore, a better understanding of the chemical state and stability of APS on inorganic surfaces is needed. In this work, we investigated APS adhesion on silica wafers...... and compared its properties with those on complex silicate surfaces such as those used by industry (mineral fibers and fiber melt wafers). The APS was deposited from aqueous and organic (toluene) solutions and studied with surface sensitive techniques, including X-ray photoelectron spectroscopy (XPS), atomic......- and laboratory-scale APS deposition methods and increasing adhesion and stability, thus increasing the quality and effectiveness of materials where APS is used as a coupling agent....

  16. Microwave-Assisted Conversion of Levulinic Acid to γ-Valerolactone Using Low-Loaded Supported Iron Oxide Nanoparticles on Porous Silicates

    Directory of Open Access Journals (Sweden)

    Alfonso Yepez

    2015-09-01

    Full Text Available The microwave-assisted conversion of levulinic acid (LA has been studied using low-loaded supported Fe-based catalysts on porous silicates. A very simple, productive, and highly reproducible continuous flow method has been used for the homogeneous deposition of metal oxide nanoparticles on the silicate supports. Formic acid was used as a hydrogen donating agent for the hydrogenation of LA to effectively replace high pressure H2 mostly reported for LA conversion. Moderate LA conversion was achieved in the case of non-noble metal-based iron oxide catalysts, with a significant potential for further improvements to compete with noble metal-based catalysts.

  17. Synthesis, characterization of CaF2doped silicate glass-ceramics.

    Science.gov (United States)

    Riaz, Madeeha; Zia, Rehana; Mirza, Ambreen; Hussain, Tousif; Bashir, Farooq; Anjum, Safia

    2017-06-01

    This paper reports the fabrication and characterization of silicate glass-ceramics doped with (0-12mol%) CaF 2 . TGA-DSC analysis was carried out to determine the crystallization temperature and stability of glass measured by two glass parameters; Hruby parameter K H =(T x -T g )/(T L -T x ) and Weinberg parameter K W =(T c -T g )/T L . It was found that with CaF 2 doping improved sinterability at low temperature and provided stability to the glass. The XRD pattern exhibits a single phase of combeite and doping of CaF 2 cause increase in crystallite size. Microstructure of samples was also improved with CaF 2 addition, pores were significantly reduced. After 15days immersion in simulated body fluid all samples developed apatite layer onto its surface. Hence, the addition of CaF 2 provided bioactive glass-ceramic material having a low processing temperature. Copyright © 2017 Elsevier B.V. All rights reserved.

  18. Characteristics of products generated by selective sintering and stereolithography rapid prototyping processes

    Science.gov (United States)

    Cariapa, Vikram

    1993-01-01

    The trend in the modern global economy towards free market policies has motivated companies to use rapid prototyping technologies to not only reduce product development cycle time but also to maintain their competitive edge. A rapid prototyping technology is one which combines computer aided design with computer controlled tracking of focussed high energy source (eg. lasers, heat) on modern ceramic powders, metallic powders, plastics or photosensitive liquid resins in order to produce prototypes or models. At present, except for the process of shape melting, most rapid prototyping processes generate products that are only dimensionally similar to those of the desired end product. There is an urgent need, therefore, to enhance the understanding of the characteristics of these processes in order to realize their potential for production. Currently, the commercial market is dominated by four rapid prototyping processes, namely selective laser sintering, stereolithography, fused deposition modelling and laminated object manufacturing. This phase of the research has focussed on the selective laser sintering and stereolithography rapid prototyping processes. A theoretical model for these processes is under development. Different rapid prototyping sites supplied test specimens (based on ASTM 638-84, Type I) that have been measured and tested to provide a data base on surface finish, dimensional variation and ultimate tensile strength. Further plans call for developing and verifying the theoretical models by carefully designed experiments. This will be a joint effort between NASA and other prototyping centers to generate a larger database, thus encouraging more widespread usage by product designers.

  19. A primary study into graphene/polyether ether ketone (PEEK) nanocomposite for laser sintering

    Science.gov (United States)

    Chen, Binling; Berretta, Silvia; Evans, Ken; Smith, Kaylie; Ghita, Oana

    2018-01-01

    This paper proposes two methods of preparation of graphene/PEEK powders for Laser Sintering (LS) and investigates their behaviour in relation to their microstructure and their properties. Thin composite films were fabricated in an attempt to replicate the thin layer formation of the powder bed process. Both methods of composite powder preparation (wet and dry) led to enhanced mechanical performance of the composite films at 0.1 and 0.5 wt% graphene nano-platelets (GNP) concentrations. The TEM images show that the GNP act as a nucleation point in crystallisation of PEEK, being at the centre of the spherulites. The hot stage microscopy reveals a 20 s delay in the onset of GNP/PEEK nanocomposite coalescence in comparison with plain PEEK. This is a very important observation for laser sintering, as it will influence the build strategy and specific parameters (e.g. time between layers deposition, multiple exposures). The excellent electrical conductivity properties of graphene were noticeable in the nanocomposite films at concentrations above 1 wt% GNP.

  20. Fabrication of silicon nitride nanoceramics—Powder preparation and sintering: A review

    Directory of Open Access Journals (Sweden)

    Toshiyuki Nishimura et al

    2007-01-01

    Full Text Available Fine-grained silicon nitride ceramics were investigated mainly for their high-strain-rate plasticity. The preparation and densification of fine silicon nitride powder were reviewed. Commercial sub-micrometer powder was used as raw powder in the "as-received" state and then used after being ground and undergoing classification operation. Chemical vapor deposition and plasma processes were used for fabricating nanopowder because a further reduction in grain size caused by grinding had limitations. More recently, nanopowder has also been obtained by high-energy milling. This process in principle is the same as conventional planetary milling. For densification, primarily hot pressing was performed, although a similar process known as spark plasma sintering (SPS has also recently been used. One of the advantages of SPS is its high heating rate. The high heating rate is advantageous because it reduces sintering time, achieving densification without grain growth. We prepared silicon nitride nanopowder by high-energy milling and then obtained nanoceramics by densifying the nanopowder by SPS.

  1. Up-cycling waste glass to minimal water adsorption/absorption lightweight aggregate by rapid low temperature sintering: optimization by dual process-mixture response surface methodology.

    Science.gov (United States)

    Velis, Costas A; Franco-Salinas, Claudia; O'Sullivan, Catherine; Najorka, Jens; Boccaccini, Aldo R; Cheeseman, Christopher R

    2014-07-01

    Mixed color waste glass extracted from municipal solid waste is either not recycled, in which case it is an environmental and financial liability, or it is used in relatively low value applications such as normal weight aggregate. Here, we report on converting it into a novel glass-ceramic lightweight aggregate (LWA), potentially suitable for high added value applications in structural concrete (upcycling). The artificial LWA particles were formed by rapidly sintering (waste glass powder with clay mixes using sodium silicate as binder and borate salt as flux. Composition and processing were optimized using response surface methodology (RSM) modeling, and specifically (i) a combined process-mixture dual RSM, and (ii) multiobjective optimization functions. The optimization considered raw materials and energy costs. Mineralogical and physical transformations occur during sintering and a cellular vesicular glass-ceramic composite microstructure is formed, with strong correlations existing between bloating/shrinkage during sintering, density and water adsorption/absorption. The diametrical expansion could be effectively modeled via the RSM and controlled to meet a wide range of specifications; here we optimized for LWA structural concrete. The optimally designed LWA is sintered in comparatively low temperatures (825-835 °C), thus potentially saving costs and lowering emissions; it had exceptionally low water adsorption/absorption (6.1-7.2% w/wd; optimization target: 1.5-7.5% w/wd); while remaining substantially lightweight (density: 1.24-1.28 g.cm(-3); target: 0.9-1.3 g.cm(-3)). This is a considerable advancement for designing effective environmentally friendly lightweight concrete constructions, and boosting resource efficiency of waste glass flows.

  2. Sintering furnace for remote fuel fabrication

    International Nuclear Information System (INIS)

    Bowen, W.W.

    1978-10-01

    Component testing and evaluation of a chemical vapor deposition Re/W muffle has been initiated. Hydrogen permeation testing and thermal cycling behavior will be evaluated. Fabrication of prototype 10-12 Kg furnace is scheduled for completion late in 1979, at which time testing of the system will be initiated

  3. Computational model for microstructure and effective thermal conductivity of ash deposits in utility boilers

    Science.gov (United States)

    Kweon, Soon-Cheol

    The ash deposits formed in pulverized-coal fired power plants reduce heat transfer rate to furnace wall, super heater tubes, and other heat transfer surfaces. The thermal properties that influence strongly on this heat transfer depend mainly on the microstructure of the ash deposit. This dissertation examines three issues associated with the ash deposits in utility boilers: (1) the three-dimensional model for characterization of the ash deposit microstructures from the sample ash deposits, (2) the computational model for effective thermal conductivity of sintered packed beds with low conductive stagnant fluids, and (3) the application of thermal resistor network model for the effective thermal conductivity of ash deposits in utility boilers. The SEM image analysis was conducted on two sample ash deposits to characterize three-dimensional microstructure of the ash deposit with several structural parameters using stereology. A ballistic deposition model was adopted to simulate the deposit structure defined by the structural parameters. The inputs for the deposition model were chosen from the predicted and measured physical parameters, such as the size distribution, the probability of the particle rolling, and the degree of the particle sintering. The difference between the microstructure of the sample deposits and the simulated deposits was investigated and compared quantitatively based on the structural parameters defined. Both the sample and the simulated deposits agree in terms of the structural parameters. The computational model for predicting the effective thermal conductivity of sintered packed beds with low conductive stagnant fluid was built and the heat conduction through the contact area among sintered particles is the dominant mode of heat transfer. A thermal resistor network is used to model the heat conduction among the sintered particles and the thermal resistance among the contacting particles is estimated from both the contact area and the contact

  4. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Science.gov (United States)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB.

  5. Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

    Science.gov (United States)

    Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing

    2017-12-01

    The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.

  6. Stable emulsions in extraction systems containing zirconium and silicic acid

    International Nuclear Information System (INIS)

    Sinegribova, O.A.; Chizhevskaya, S.V.; Kotenko, A.A.

    1989-01-01

    The effect of zirconium nitrate compound nature and silicic acid on the rate of emulsions stratification in extraction systems depending on the components concentration, solution acidity, its past history, is studied. It is stated that stable multinuclear zirconium compounds have an influence on formation of stable emulsions in systems containing silicic acid. On the basis of results of chemical analysis and properties of interphase precipitates, being part of stable emulsion, suppositions on mechanism of interaction of zirconium nitrate compounds with silicic acid β-form are made

  7. Cell response to hydroxyapatite surface topography modulated by sintering temperature.

    Science.gov (United States)

    Mealy, Jacob; O'Kelly, Kevin

    2015-11-01

    Increased mesenchymal stem cell (MSC) activity on hydroxyapatite (HA) bone tissue engineering scaffolds will improve their viability in diffusion-based in vivo environments and is therefore highly desirable. This work focused on modulating the sintered HA surface topography with a view to increasing cell activity; this was achieved by varying the sintering temperature of the HA substrates. Cells were cultured on the substrates for periods of up to 19 days and displayed a huge variation in viability. MSC metabolic activity was measured using a resazurin sodium salt assay and revealed that surfaces sintered from 1250 to 1350°C significantly outperformed their lower temperature counterparts from day one (p ≤ 0.05). Surfaces sintered at 1300°C induced 57% more cell activity than the control at day 16. No significant activity was observed on surfaces sintered below 1200°C. It is suggested that this is due to the granular morphology produced at these temperatures providing insufficient contact area for cell attachment. In addition, we propose the average surface wavelength as a more quantitative surface descriptor than those readily found in the literature. The wavelengths of the substrates presented here were highly correlated with cell activity (R(2)  = 0.9019); with a wavelength of 2.675 µm on the 1300°C surface inducing the highest cell response. © 2015 Wiley Periodicals, Inc.

  8. Consolidation of metallic hollow spheres by electric sintering

    Science.gov (United States)

    Mironov, V.; Tatarinov, A.; Lapkovsky, V.

    2017-07-01

    This paper considers peculiarities of the technology of production of structures from metallic hollow spheres (MHS) using magnetic fields and electric sintering. In these studies, the raw material was MHS obtained by burning of polystyrene balls coated by carbon steel. MHS had an outer diameter of 3-5 mm and a steel wall thickness of 70-120 microns. Pulsed current generators were used for electric sintering of MHS to obtain different spatial structures. Since MHS have small strength, the compressive pressure during sintering should be minimal. To improve the adhesion strength and reduce the required energy for sintering, hollow spheres were coated with copper by ion-plasma sputtering in vacuum. The coating thickness was 10-15 microns. The ferromagnetic properties of MHS allowed using of magnet fields for orientation of the spheres in the structures, as well as using of perforated tapes acting as orienting magnetic cores. Ultrasonic testing of MHS structures has been tried using through propagation of ultrasound in low kilohertz frequency range. Sensitivity of the propagation parameters to water filling of inter-spheres space and sintering temperature was demonstrated.

  9. Leaching of metals from fresh and sintered red mud.

    Science.gov (United States)

    Ghosh, Indrani; Guha, Saumyen; Balasubramaniam, R; Kumar, A V Ramesh

    2011-01-30

    The disposal of red mud, a solid waste generated during the extraction of alumina from bauxite, is one of the major problems faced by the aluminum industry. Proper disposal followed by its utilization, for example as bricks, can provide a satisfactory solution to this problem. Pollution potential of red mud and its finished product, due to metals leaching out from them under certain environmental conditions, need to be studied. Sintering of red mud was performed in a resistance type vertical tube furnace to simulate the brick-making conditions in lab-scale. Leachability of metals in red mud and the sintered product was evaluated by performing sequential extraction experiments on both. The metals studied were the 'macro metals' iron and aluminum and the 'trace metals' copper and chromium. The total extractabilities of all the metals estimated by the microwave digestion of red mud samples decreased due to sintering. The leachability in sequential extraction of the macro metals iron and aluminum, on the other hand, increased due to sintering in all phases of sequential extraction. However, the effect of sintering on the leachability of the trace metals by sequential extraction was different for copper and chromium in different fractions of sequential extraction. Copyright © 2010 Elsevier B.V. All rights reserved.

  10. Low sintering temperature glass waste forms for sequestering radioactive iodine

    Science.gov (United States)

    Nenoff, Tina M.; Krumhansl, James L.; Garino, Terry J.; Ockwig, Nathan W.

    2012-09-11

    Materials and methods of making low-sintering-temperature glass waste forms that sequester radioactive iodine in a strong and durable structure. First, the iodine is captured by an adsorbant, which forms an iodine-loaded material, e.g., AgI, AgI-zeolite, AgI-mordenite, Ag-silica aerogel, ZnI.sub.2, CuI, or Bi.sub.5O.sub.7I. Next, particles of the iodine-loaded material are mixed with powdered frits of low-sintering-temperature glasses (comprising various oxides of Si, B, Bi, Pb, and Zn), and then sintered at a relatively low temperature, ranging from 425.degree. C. to 550.degree. C. The sintering converts the mixed powders into a solid block of a glassy waste form, having low iodine leaching rates. The vitrified glassy waste form can contain as much as 60 wt % AgI. A preferred glass, having a sintering temperature of 500.degree. C. (below the silver iodide sublimation temperature of 500.degree. C.) was identified that contains oxides of boron, bismuth, and zinc, while containing essentially no lead or silicon.

  11. The uranium deposits of Ontario

    International Nuclear Information System (INIS)

    Robertson, J.A.

    1981-01-01

    The principal types of uranium deposits in Ontario are carbonatites and fenites, alkalic volcanic rocks, pegiatites, calc-silicate rocks, pyritic quartz-pebble conglomerates, polymictic conglomerates and some pelitic rocks, and various 'pitchblende' deposits including late Precambrian unconformities, possibly late Precambrian diabase dikes, and other unconformities: carbonates, sandstones, lignites, and semi-pelitic rocks of middle and upper Precambrian age. Only red unzoned pegmatite and the pyritic quartz-pebble conglomerate have supported production. Ontario reasonably assured and estimated resources in the economic and subeconomic categories in 1977 amounted to 553 000 tonnes U, and 1977 production was 4000 tonnes U. Measured, indicated, and inferred resources in the Elliot Lake - Agnew Lake area are at least 400 000 tonnes U. The latter deposits are also a significant thorium resource. Geological features reflecting major changes in physics and chemistry are prime controls on distribution of uranium deposits. Geological province and subprovince boundaries, major faults, higher metamorphic grades, domain boundaries related to quartz monzonite batholiths, alkalic complexes, and the distribution of carbonate rocks are examples of such geological features

  12. Fabrication And Properties Of Silver Based Multiwall Carbon Nanotube Composite Prepared By Spark Plasma Sintering Method

    Directory of Open Access Journals (Sweden)

    Lis M.

    2015-06-01

    Full Text Available The paper presents results of investigations of the obtained nanocomposite materials based on silver with addition of multiwall carbon nanotubes. The powder of carbon nanotubes content from 0.1 to 3 wt. % was produced by application of powder metallurgy methods, through mixing and high-energetic milling, and also chemical methods. Modification of carbon nanotubes included electroless deposition of silver particles on the carbon nanotube active surfaces and chemical reduction with strong reducing agent – sodium borohydride (NaBH4. The obtained powder mixtures were consolidated by SPS – Spark Plasma Sintering method. The formed composites were subjected to tests of relative density, electrical conductivity and electro-erosion properties. Detailed examinations of the structure with application of X-ray microanalysis, with consideration of carbon nanotubes distribution, were also carried out. The effect of manufacturing methods on properties of the obtained composites was observed.

  13. Optical, structural and electrical properties of nanosized zinc oxide sintered films for photovoltaic applications

    Directory of Open Access Journals (Sweden)

    Kumar V.

    2013-01-01

    Full Text Available Zinc oxide films have been deposited on ultra-clean glass substrates by screenprinting method followed by sintering process. Optimum conditions for preparing good quality screen-printed films have been found. The optical band gap of the films has been studied using reflection spectra in wavelength range 325-600 nm by using double beam spectrophotometer. X-ray diffraction studies revealed that the films are polycrystalline in nature, single phase exhibiting wurtzite (hexagonal structure with strong preferential orientation of grains along the (101 direction. Surface morphology of films has been studied by scanning electron microscopy (SEM technique. The electrical resistivity of the films was measured in vacuum by two probe technique. PACS: 78.20.Ci; 78.50.Ge; 78.66.-w; 78.66.Hf.

  14. Sinter-Resistant Platinum Catalyst Supported by Metal-Organic Framework

    Energy Technology Data Exchange (ETDEWEB)

    Kim, In Soo [Materials Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA; Nanophotonics Center, Korea Institute of Science and Technology, Seoul 02792 South Korea; Li, Zhanyong [Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston IL 60208 USA; Zheng, Jian [Institute for Integrated Catalysis, Pacific Northwest National Lab, P.O. Box 999 Richland WA 99352 USA; Platero-Prats, Ana E. [X-ray Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA; Mavrandonakis, Andreas [Department of Chemistry, University of Minnesota, 207 Pleasant St. SE Minneapolis MN 55455 USA; Pellizzeri, Steven [Chemical and Biomolecular Engineering, Clemson University, 205 Earle Hall Clemson SC 29634 USA; Ferrandon, Magali [Chemical Sciences and Engineering Division, Argonne National Lab, 9700 S. Cass Ave. Argonne IL 60439 USA; Vjunov, Aleksei [Institute for Integrated Catalysis, Pacific Northwest National Lab, P.O. Box 999 Richland WA 99352 USA; Gallington, Leighanne C. [X-ray Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA; Webber, Thomas E. [Department of Chemistry, University of Minnesota, 207 Pleasant St. SE Minneapolis MN 55455 USA; Vermeulen, Nicolaas A. [Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston IL 60208 USA; Penn, R. Lee [Department of Chemistry, University of Minnesota, 207 Pleasant St. SE Minneapolis MN 55455 USA; Getman, Rachel B. [Chemical and Biomolecular Engineering, Clemson University, 205 Earle Hall Clemson SC 29634 USA; Cramer, Christopher J. [Department of Chemistry, University of Minnesota, 207 Pleasant St. SE Minneapolis MN 55455 USA; Chapman, Karena W. [X-ray Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA; Camaioni, Donald M. [Institute for Integrated Catalysis, Pacific Northwest National Lab, P.O. Box 999 Richland WA 99352 USA; Fulton, John L. [Institute for Integrated Catalysis, Pacific Northwest National Lab, P.O. Box 999 Richland WA 99352 USA; Lercher, Johannes A. [Institute for Integrated Catalysis, Pacific Northwest National Lab, P.O. Box 999 Richland WA 99352 USA; Department of Chemistry and Catalysis Research Institute, Technische Universität München, Lichtenbergstrasse 4 85748 Garching Germany; Farha, Omar K. [Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston IL 60208 USA; Hupp, Joseph T. [Materials Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA; Department of Chemistry, Northwestern University, 2145 Sheridan Rd. Evanston IL 60208 USA; Martinson, Alex B. F. [Materials Science Division, Argonne National Lab, 9700 S Cass Ave. Argonne IL 60439 USA

    2018-01-02

    Installed on the zirconia nodes of a metal-organic framework (MOF) NU-1000 via targeted vapor-phase synthesis. The catalytic Pt clusters, site-isolated by organic linkers, are shown to exhibit high catalytic activity for ethylene hydrogenation while exhibiting resistance to sintering up to 200 degrees C. In situ IR spectroscopy reveals the presence of both single atoms and few-atom clusters that depend upon synthesis conditions. Operando X-ray absorption spectroscopy and Xray pair distribution analyses reveal unique changes in chemical bonding environment and cluster size stability while on stream. Density functional theory calculations elucidate a favorable reaction pathway for ethylene hydrogenation with the novel catalyst. These results provide evidence that atomic layer deposition (ALD) in MOFs is a versatile approach to the rational synthesis of size-selected clusters, including noble metals, on a high surface area support.

  15. Short-Pulse Laser Sintering of Multilayer Hard Metal Coatings: Structure and Wear Behavior

    Science.gov (United States)

    Kharanzhevskiy, Evgeny; Ipatov, Alexey; Nikolaeva, Irina; Zakirova, Raushaniya

    2015-06-01

    This paper reports on the phase composition and properties of multilayer hard metal coatings deposited on steel by a process variant of Selective laser melting (SLM). The process is based on layer-wise short-pulse laser sintering of high-dispersive WC-Co powder on a steel substrate. High temperature in the molten zone and chemical interaction with the substrate explain high level of adhesion strength between the coating and the substrate. The technique allows obtaining both high quality hard-metal multilayer gradient coatings with thickness up to 200 μm, density near to the theoretical density (TD), hardness up to 21 GPa and complex 3D objects by layer-wise powder based process such as SLM.

  16. [Influence on microstructure of dental zirconia ceramics prepared by two-step sintering].

    Science.gov (United States)

    Jian, Chao; Li, Ning; Wu, Zhikai; Teng, Jing; Yan, Jiazhen

    2013-10-01

    To investigate the microstructure of dental zirconia ceramics prepared by two-step sintering. Nanostructured zirconia powder was dry compacted, cold isostatic pressed, and pre-sintered. The pre-sintered discs were cut processed into samples. Conventional sintering, single-step sintering, and two-step sintering were carried out, and density and grain size of the samples were measured. Afterward, T1 and/or T2 of two-step sintering ranges were measured. Effects on microstructure of different routes, which consisted of two-step sintering and conventional sintering were discussed. The influence of T1 and/or T2 on density and grain size were analyzed as well. The range of T1 was between 1450 degrees C and 1550 degrees C, and the range of T2 was between 1250 degrees C and 1350 degrees C. Compared with conventional sintering, finer microstructure of higher density and smaller grain could be obtained by two-step sintering. Grain growth was dependent on T1, whereas density was not much related with T1. However, density was dependent on T2, and grain size was minimally influenced. Two-step sintering could ensure a sintering body with high density and small grain, which is good for optimizing the microstructure of dental zirconia ceramics.

  17. Granulation of coke breeze fine for using in the sintering process

    Directory of Open Access Journals (Sweden)

    Mohamed F.M.

    2010-01-01

    Full Text Available Coke breeze is the main fuel used in the sintering process. The value of -3+1 mm. represents the most favorable particle size for coke breeze in the sintering process. About 20% of total coke fines (-0.5 mm are produced during different steps of preparation. Introducing these fines during the sintering process proves to be very harmful for different operating parameters. Thus ,this study aims at investigating the production of granules resulting from these fines using molasses as organic binder and its application in sintering of an iron ore. The results showed that the granules having the highest mechanical properties were obtained with 14.5 wt % molasses addition. The sintering experiments were performed by using coke breeze in different shapes (-3+1 mm in size, coke breeze without sieving and coke breeze granules -3+1 mm. The reduction experiments, microscopic structure and X-ray analysis for the produced sinter were carried out. The results revealed that, all sinter properties (such as shatter test, productivity of sinter machine and blast furnace, reduction time and chemical composition for produced sinter by using coke breeze with size -3+1 mm and coke breeze granules were almost the same. The iron ore sinter which was produced by using coke breeze without sieving yielded low productivity for both sinter machine and blast furnace. Furthermore, using coke breeze without sieving in sintering of an iron ore decreases the vertical velocity of sinter machine and increases the reduction time.

  18. Flame-sintered ceramic exoelectron dosimeter samples

    International Nuclear Information System (INIS)

    Petel, M.; Holzapfel, G.

    1979-01-01

    New techniques for the preparation of integrating solid state dosimeters, particularly exoelectron dosimeters, have been initiated. The procedure consists in melting the powdered dosimeter materials in a hot, fast gas stream and depositing the ceramic layer. The gas stream is generated either through a chemical flame or by an electrical arc plasma. Results will be reported on the system Al 2 O 3 /stainless steel as a first step to a usable exoelectron dosimeter

  19. Effects of Incorporating High-Volume Fly Ash into Tricalcium Silicate on the Degree of Silicate Polymerization and Aluminum Substitution for Silicon in Calcium Silicate Hydrate

    Directory of Open Access Journals (Sweden)

    Sungchul Bae

    2017-02-01

    Full Text Available This study assesses the quantitative effects of incorporating high-volume fly ash (HVFA into tricalcium silicate (C3S paste on the hydration, degree of silicate polymerization, and Al substitution for Si in calcium silicate hydrate (C–S–H. Thermogravimetric analysis and isothermal conduction calorimetry showed that, although the induction period of C3S hydration was significantly extended, the degree of hydration of C3S after the deceleration period increased due to HVFA incorporation. Synchrotron-sourced soft X-ray spectromicroscopy further showed that most of the C3S in the C3S-HVFA paste was fully hydrated after 28 days of hydration, while that in the pure C3S paste was not. The chemical shifts of the Si K edge peaks in the near-edge X-ray fine structure of C–S–H in the C3S-HVFA paste directly indicate that Al substitutes for Si in C–S–H and that the additional silicate provided by the HVFA induces an enhanced degree of silicate polymerization. This new spectromicroscopic approach, supplemented with 27Al and 29Si magic-angle spinning nuclear magnetic resonance spectroscopy and transmission electron microscopy, turned out to be a powerful characterization tool for studying a local atomic binding structure of C–S–H in C3S-HVFA system and presented results consistent with previous literature.

  20. High performance sinter-HIP for hard metals

    International Nuclear Information System (INIS)

    Hongxia Chen; Deming Zhang; Yang Li; Jingping Chen

    2001-01-01

    The horizontal sinter-HIP equipment with great charge capacity and high performance, developed and manufactured by Central Iron and Steel Research Institute(CISRI), is mainly used for sintering and condensation of hard metals. This equipment is characterized by large hot zone, high heating speed, good temperature uniformity and fast cooling system. The equipment can provide uniform hot zone with temperature difference less than 6 o C at 1500-1600 o C and 6-10 MPa by controlling temperature, pressure and circulation of gas precisely. Using large scale horizontal sinter-HIP equipment to produce hard matals have many advantages such as stable quality, high efficiency of production, high rate of finished products and low production cost, so this equipment is a good choice for manufacturer of hard metals. (author)

  1. Electric Field-Assisted Pressureless Sintering of Ceramic Protonic Conductors

    DEFF Research Database (Denmark)

    Muccillo, R.; Esposito, Vincenzo; Zanetti De Florio, Daniel

    2017-01-01

    -5 A the electric current pulse amplitude. The sintering experiments were carried out in ambient atmosphere with the pellets positioned inside a vertical dilatometer furnace with Pt-Ir electrodes connected either to a power supply for applying the electric field or to an impedance analyzer for collecting [-Z''(ω) x......Gadolinium, yttrium and samarium-doped barium cerate (BCGd, BCY and BCSm, respectively) polycrystalline green pellets were submitted to electric field-assisted pressureless sintering experiments isothermally in the temperature range 800-1200oC under 100-200 V cm-1 electric fields, limiting to 1...... of the electrical conductivity of flash sintered specimens. Joule heating is assumed to be the primary effect of the electric current pulse through the specimens. Improved grain-to-grain contact and the removal of depleted chemical species due to Joule heating at the space charge region are proposed, respectively...

  2. Modeling Macroscopic Shape Distortions during Sintering of Multi-layers

    DEFF Research Database (Denmark)

    Tadesse Molla, Tesfaye

    Ceramic multi-layered composites are being used as components in various technologies ranging from electronics to energy conversion devices. Thus, different architectures of multi-layers involving ceramic materials are often required to be produced by powder processing, followed by sintering...... the camber development during co-firing. The effect of extrinsic factors (e.g. gravity, thickness ratio and friction) on the shape evolution of bi-layers during co-firing has been studied using the developed model and experiments. Furthermore, a new analytical model describing stresses during sintering...... of tubular bi-layer structures has been developed by using the direct correspondence between elasticity and linear viscous problems. The finite element model developed in this study and sintering experiments of tubular bi-layer sample have been used to verify and validate the developed analytical model...

  3. Nano pores evolution in hydroxyapatite microsphere during spark plasma sintering

    Directory of Open Access Journals (Sweden)

    Lin C.

    2011-01-01

    Full Text Available Micron-spherical granules of hydroxyapatite (HAp nanoparticles were prepared by powder granulation methods. Through subsequent sintering, porous HAp microspheres with tailored pore and grain framework structures were obtained. Detailed microstructure investigation by SEM and TEM revealed the correlation of the pore structure and the necking strength with the sintering profiles that determine the coalescence features of the nanoparticles. The partially sintered porous HAp microspheres containing more than 50% porosity consisting of pores and grains both in nano-scale are active in inducing the precipitation of HAp in simulated body fluid. The nano-porous HAp microspheres with an extensive surface and interconnecting pores thus demonstrate the potential of stimulating the formation of collagen and bone and the integration with the newly formed bones during physiological bone remodeling.

  4. Immobilization of high-level wastes into sintered glass: 1

    International Nuclear Information System (INIS)

    Russo, D.O.; Messi de Bernasconi, N.; Audero, M.A.

    1987-01-01

    In order to immobilize the high-level radioactive wastes from fuel elements reprocessing, borosilicate glass was adopted. Sintering experiments are described with the variety VG 98/12 (SiO 2 , TiO 2 , Al 2 O 3 , B 2 O 3 , MgO, CaO and Na 2 O) (which does not present devitrification problems) mixed with simulated calcinated wastes. The hot pressing line (sintering under pressure) was explored in two variants 1: In can; 2: In graphite matrix with sintered pellet extraction. With scanning electron microscopy it is observed that the simulated wastes do not disolve in the vitreous matrix, but they remain dispersed in the same. The results obtained point out that the leaching velocities are independent from the density and from the matrix type employed, as well as from the fact that the wastes do no dissolve in the matrix. (M.E.L.) [es

  5. High efficiency particulate removal with sintered metal filters

    International Nuclear Information System (INIS)

    Kirstein, B.E.; Paplawsky, W.J.; Pence, D.T.; Hedahl, T.G.

    1981-01-01

    Because of their particle removal efficiencies and durability, sintered metal filters have been chosen for HEPA filter protection in the off-gas treatment system for the proposed Idaho National Engineering Laboratory Transuranic Waste Treatment Facility. Process evaluation of sintered metal filters indicated a lack of sufficient process design data to assume trouble-free operation. Subsequent pilot-scale testing was performed with fly ash as the test particulate. The test results showed that the sintered metal filters can have an efficiency greater than 0.9999999 for the specific test conditions used. Stable pressure drop characteristics were observed in pulsed and reversed flow blowback modes of operation. Over 4900 hours of operation were obtained with operating conditions ranging up to approximately 90 0 C and 24 volume percent water vapor in the gas stream

  6. Evaluation of dilatometric techniques for studies of sintering kinetics

    International Nuclear Information System (INIS)

    El-Sayed Ali, M.; Toft Soerensen, O.

    1985-04-01

    The kinetics of the initial sintering stage of CeO 2 is evaluated by three different techniques: constant heating rate dilatometry, constant shrinkage rate dilatometry and a new technique recently introduced by the authors called Stepwise Isothermal Dilatometry (SID). Comparative measurements with these techniques showed that too high activation energies were obtained with the two first techniques, both of which can be termed as nonisothermal, whereas activation energies comparable to those reported for cation diffusion in other fluorite oxides were obtained with the latter technique. Of the three techniques SID is thus considered to be the most accurate for studies of the sintering kinetics. In contrast to the two nonisothermal techniques SID has the further advantage that both the controlling mechanism and its activation energy can be determined in a single experiment. From the SID-measurement it was concluded that the initial sintering stage of CeO 2 is controlled by grain-boundary diffusion. (author)

  7. High efficiency particulate removal with sintered metal filters

    International Nuclear Information System (INIS)

    Kirstein, B.E.; Paplawsky, W.J.; Pence, D.T.; Hedahl, T.G.

    1981-01-01

    Because of their particle removal efficiencies and durability, sintered metal filters have been chosen for high efficiency particulate air (HEPA) filter protection in the off-gas treatment system for the proposed Idaho National Engineering Laboratory Transuranic Waste Treatment Facility. Process evaluation of sintered metal filters indicated a lack of sufficient process design data to ensure trouble-free operation. Subsequence pilot scale testing was performed with flyash as the test particulate. The test results showed that the sintered metal filters can have an efficiency greater than 0.9999999 for the specific test conditions used. Stable pressure drop characteristics were observed in pulsed and reversed flow blowback modes of operation. Over 4900 hours of operation were obtained with operating conditions ranging up to approximately 90 0 C and 24 vol % water vapor in the gas stream

  8. Reactive Sintering of Bimodal WC-Co Hardmetals

    Directory of Open Access Journals (Sweden)

    Marek Tarraste

    2015-09-01

    Full Text Available Bimodal WC-Co hardmetals were produced using novel technology - reactive sintering. Milled and activated tungsten and graphite powders were mixed with commercial coarse grained WC-Co powder and then sintered. The microstructure of produced materials was free of defects and consisted of evenly distributed coarse and fine tungsten carbide grains in cobalt binder. The microstructure, hardness and fracture toughness of reactive sintered bimodal WC-Co hardmetals is exhibited. Developed bimodal hardmetal has perspective for demanding wear applications for its increased combined hardness and toughness. Compared to coarse material there is only slight decrease in fracture toughness (K1c is 14.7 for coarse grained and 14.4 for bimodal, hardness is increased from 1290 to 1350 HV units.DOI: http://dx.doi.org/10.5755/j01.ms.21.3.7511

  9. Petrophysical Analysis of Siliceous Ooze Sediments, Ormen Lange Field, Norway

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    Skeletal remains of siliceous algae form biogenic fine grained highly porous pelagic siliceous ooze sediments that were found above the reservoir of the Ormen Lange gas field which is located in the southern part of the Norwegian Sea (Figure 1a). The Palaeocene sandstone of the “Egga” Formation...... structure is complex and the solids are mechanically fragile and hydrous. Normal petrophysical methods used in formation evaluation might not be suitable for interpreting siliceous ooze. For example, density and neutron logging tools are calibrated to give correct porosity readings in a limestone formation......, but apparent porosity indications in any other lithology, such as siliceous ooze, are wrong and they should be corrected. The apparent bulk density log should be influenced by the hydrogen in opal as also the neutron porosity tools because they are sensitive to the amount of hydrogen in a formation...

  10. Silicate Urolithiasis during Long-Term Treatment with Zonisamide

    Directory of Open Access Journals (Sweden)

    Satoru Taguchi

    2013-01-01

    Full Text Available Silicate urinary calculi are rare in humans, with an incidence of 0.2% of all urinary calculi. Most cases were related to excess ingestion of silicate, typically by taking magnesium trisilicate as an antacid for peptic ulcers over a long period of time; however, there also existed unrelated cases, whose mechanism of development remains unclear. On the other hand, zonisamide, a newer antiepileptic drug, is one of the important causing agents of iatrogenic urinary stones in patients with epilepsy. The supposed mechanism is that zonisamide induces urine alkalinization and then promotes crystallization of urine components such as calcium phosphate by inhibition of carbonate dehydratase in renal tubular epithelial cells. Here, we report a case of silicate urolithiasis during long-term treatment with zonisamide without magnesium trisilicate intake and discuss the etiology of the disease by examining the silicate concentration in his urine.

  11. Characterizations of Rapid Sintered Nanosilver Joint for Attaching Power Chips

    Directory of Open Access Journals (Sweden)

    Shuang-Tao Feng

    2016-07-01

    Full Text Available Sintering of nanosilver paste has been extensively studied as a lead-free die-attach solution for bonding semiconductor power chips, such as the power insulated gated bipolar transistor (IGBT. However, for the traditional method of bonding IGBT chips, an external pressure of a few MPa is reported necessary for the sintering time of ~1 h. In order to shorten the processing duration time, we developed a rapid way to sinter nanosilver paste for bonding IGBT chips in less than 5 min using pulsed current. In this way, we firstly dried as-printed paste at about 100 °C to get rid of many volatile solvents because they may result in defects or voids during the out-gassing from the paste. Then, the pre-dried paste was further heated by pulse current ranging from 1.2 kA to 2.4 kA for several seconds. The whole procedure was less than 3 min and did not require any gas protection. We could obtain robust sintered joint with shear strength of 30–35 MPa for bonding 1200-V, 25-A IGBT and superior thermal properties. Static and dynamic electrical performance of the as-bonded IGBT assemblies was also characterized to verify the feasibility of this rapid sintering method. The results indicate that the electrical performance is comparable or even partially better than that of commercial IGBT modules. The microstructure evolution of the rapid sintered joints was also studied by scanning electron microscopy (SEM. This work may benefit the wide usage of nanosilver paste for rapid bonding IGBT chips in the future.

  12. Nanostructure of Er3+ doped silicates.

    Science.gov (United States)

    Yao, Nan; Hou, Kirk; Haines, Christopher D; Etessami, Nathan; Ranganathan, Varadh; Halpern, Susan B; Kear, Bernard H; Klein, Lisa C; Sigel, George H

    2005-06-01

    We demonstrate nanostructural evolution resulting in highly increased photoluminescence in silicates doped with Er3+ ions. High-resolution transmission electron microscopy (HRTEM) imaging, nano-energy dispersed X-ray (NEDX) spectroscopy, X-ray diffraction (XRD) and photoluminescence analysis confirm the local composition and structure changes of the Er3+ ions upon thermal annealing. We studied two types of amorphous nanopowder: the first is of the composition SiO2/18Al2O3/2Er2O3 (SAE), synthesized by combustion flame-chemical vapor condensation, and the second is with a composition of SiO2/8Y2O3/2Er2O3 (SYE), synthesized by sol-gel synthesis (composition in mol%). Electron diffraction and HRTEM imaging clearly show the formation of nanocrystallites with an average diameter of approximately 8 nm in SAE samples annealed at 1000 degrees C and SYE samples annealed at 1200 degrees C. The volume fraction of the nanocrystalline phase increased with each heat treatment, eventually leading to complete devitrification at 1400 degrees C. Further XRD and NEDX analysis indicates that the nanocrystalline phase has the pyrochlore structure with the formula Er(x)Al(2-x)Si2O7 or Er(x)Y(2-x)Si2O7 and a surrounding silica matrix.

  13. Calcium Isotopic Composition of Bulk Silicate Earth

    Science.gov (United States)

    Kang, J.; Ionov, D. A.; Liu, F.; Zhang, C.; Zhang, Z.; Huang, F.

    2016-12-01

    Ca isotopes are used to study the accretion history of the Earth and terrestrial planets, but, Ca isotopic composition of the Bulk Silicate Earth (BSE) remains poorly constrained [1]. To better understand the Ca isotopic composition of BSE, we analyzed 22 well studied peridotite xenoliths from Tariat (Mongolia), Vitim (southern Siberia) and Udachnaya (Siberian Craton). These samples include both fertile and highly depleted garnet and spinel peridotites that show no or only minor post-melting metasomatism or alteration. Ca isotope measurements were done on a Triton-TIMS using double spike method at the Guangzhou Institute of Geochemistry, CAS. The data are reported as δ44/40Ca (relative to NIST SRM 915a). Results for geostandards are consistent with those from other laboratories. 2 standard deviations of SRM 915a analyses are 0.13‰ (n=48). δ44/40Ca of both and fertile and refractory peridotites range from 0.79 to 1.07‰ producing an average of 0.93±0.12‰ (2SD). This value defines the Ca isotopic composition of the BSE, which is consistent with the average δ44/40Ca of oceanic basalts ( 0.90‰)[2,3]. [1] Huang et al (2010) EPSL 292; [2] Valdes et al (2014) EPSL 394; [3]DePaolo (2004) RMG 55.

  14. Predicting sintering deformation of ceramic film constrained by rigid substrate using anisotropic constitutive law

    International Nuclear Information System (INIS)

    Li Fan; Pan Jingzhe; Guillon, Olivier; Cocks, Alan

    2010-01-01

    Sintering of ceramic films on a solid substrate is an important technology for fabricating a range of products, including solid oxide fuel cells, micro-electronic PZT films and protective coatings. There is clear evidence that the constrained sintering process is anisotropic in nature. This paper presents a study of the constrained sintering deformation using an anisotropic constitutive law. The state of the material is described using the sintering strains rather than the relative density. In the limiting case of free sintering, the constitutive law reduces to a conventional isotropic constitutive law. The anisotropic constitutive law is used to calculate sintering deformation of a constrained film bonded to a rigid substrate and the compressive stress required in a sinter-forging experiment to achieve zero lateral shrinkage. The results are compared with experimental data in the literature. It is shown that the anisotropic constitutive law can capture the behaviour of the materials observed in the sintering experiments.

  15. Preparation of Ni-Ti shape memory alloy by spark plasma sintering method

    Czech Academy of Sciences Publication Activity Database

    Salvetr, P.; Kubatík, Tomáš František; Novák, P.

    2016-01-01

    Roč. 16, č. 4 (2016), s. 804-808 ISSN 1213-2489 Institutional support: RVO:61389021 Keywords : Ni-Ti alloy * Powder metallurgy * Reactive sintering * Spark plasma sintering Subject RIV: JK - Corrosion ; Surface Treatment of Materials

  16. The analysis of adhesion failure between Ni-coating and sintered NdFeB substrate

    Energy Technology Data Exchange (ETDEWEB)

    Hengxiu, Y; Yong, D; Zhenlun, S, E-mail: yanghengxiu@nimte.ac.cn [Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, 315201 (China)

    2011-01-01

    Ni-coating was widely used to protect the sintered NdFeB magnet from corrosion by Watt electro-deposition solution. However, the protection failure always occurs due to poor adhesion strength between Ni-coating and NdFeB substrate. In present work, the adhesion strength of the Ni-coating on NdFeB substrate was measured by vertical tensile method to strip Ni-coating from NdFeB substrate. The results revealed that the adhesion failure was occurred in the side of the NdFeB substrate due to a weak zone sometimes shown cracks located inside of NdFeB substrate, rather than in the interface between Ni-coating and NdFeB substrate. Comparing with cross section morphology of NdFeB magnet after pretreatment, it is concluded that the crack could be formed during the electro-deposition process. The effect of the pH value of bath on adhesion strength indicated that the crack could be induced due to electrochemical hydrogenation of NdFeB substrate during electro-deposition.

  17. Comparison of silicon nanoparticles and silicate treatments in fenugreek.

    Science.gov (United States)

    Nazaralian, Sanam; Majd, Ahmad; Irian, Saeed; Najafi, Farzaneh; Ghahremaninejad, Farrokh; Landberg, Tommy; Greger, Maria

    2017-06-01

    Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO 2 particles, phytoliths, similar to SiO 2 -nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-lyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L.) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  18. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Gunther, E.

    1987-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and ''Li 6 SiO 5 '' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented

  19. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Guenther, E.

    1986-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and 'Li 6 SiO 5 ' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented. (author)

  20. PETROLOGY AND GEOCHEMISTRY OF CALC-SILICATE SCHISTS ...

    African Journals Online (AJOL)

    DR OKONKOWO

    2012-02-29

    silicate reaction bands have higher contents of CaO and Sr and lower concentrations of K2O, Rb, Ni, and Ba relative to the calc-silicate schists; and relatively higher SiO2, TiO2, Al2O3, Fe2O3, MgO, Na2O, K2O and P2O5 and lower ...

  1. Pressure sintering and creep deformation: a joint modeling approach

    International Nuclear Information System (INIS)

    Notis, M.R.

    1979-10-01

    Work related to microchemical and microstructural aspects of the joint modeling of pressure sintering and creep in ceramic oxides is reported. Quantitative techniques for the microchemical analysis of ceramic oxides and for the examination of impurity segregation effects in polycrystalline ceramic materials were developed. This has included fundamental absorption corrections for the oxygen anion species as a function of foil thickness. The evolution in microstructure during the transition from intermediate stage to final stage densification during hot pressing of cobalt oxide and preliminary studies with doped oxides were studied. This work shows promise in using time-integrated microstructural effects to elucidate the role of impurities in the sintering of ceramic materials

  2. In situ Transmission Electron Microscopy of catalyst sintering

    DEFF Research Database (Denmark)

    DeLaRiva, Andrew T.; Hansen, Thomas Willum; Challa, Sivakumar R.

    2013-01-01

    Recent advancements in the field of electron microscopy, such as aberration correctors, have now been integrated into Environmental Transmission Electron Microscopes (TEMs), making it possible to study the behavior of supported metal catalysts under operating conditions at atomic resolution. Here......, we focus on in situ electron microscopy studies of catalysts that shed light on the mechanistic aspects of catalyst sintering. Catalyst sintering is an important mechanism for activity loss, especially for catalysts that operate at elevated temperatures. Literature from the past decade is reviewed...

  3. Pressure sintering and creep deformation: a joint modeling approach

    Energy Technology Data Exchange (ETDEWEB)

    Notis, M.R.

    1979-10-01

    Work related to microchemical and microstructural aspects of the joint modeling of pressure sintering and creep in ceramic oxides is reported. Quantitative techniques for the microchemical analysis of ceramic oxides and for the examination of impurity segregation effects in polycrystalline ceramic materials were developed. This has included fundamental absorption corrections for the oxygen anion species as a function of foil thickness. The evolution in microstructure during the transition from intermediate stage to final stage densification during hot pressing of cobalt oxide and preliminary studies with doped oxides were studied. This work shows promise in using time-integrated microstructural effects to elucidate the role of impurities in the sintering of ceramic materials.

  4. Method and apparatus for radio frequency ceramic sintering

    Science.gov (United States)

    Hoffman, Daniel J.; Kimrey, Jr., Harold D.

    1993-01-01

    Radio frequency energy is used to sinter ceramic materials. A coaxial waveguide resonator produces a TEM mode wave which generates a high field capacitive region in which a sample of the ceramic material is located. Frequency of the power source is kept in the range of radio frequency, and preferably between 60-80 MHz. An alternative embodiment provides a tunable radio frequency circuit which includes a series input capacitor and a parallel capacitor, with the sintered ceramic connected by an inductive lead. This arrangement permits matching of impedance over a wide range of dielectric constants, ceramic volumes, and loss tangents.

  5. Sintering of Kernel UO2 for High Temperature Reactor Fuel

    International Nuclear Information System (INIS)

    Sukarsono; Dwi-Heru-Sucahyo; Hidayati; Evi-Hertiviana; Bambang-Sugeng

    2000-01-01

    Sintering investigation of UO 2 gel has been done. The gel was preparedthrough two ways. The first, gel was produced using PVA as additive agent.The second gel was produced using HMTA and Urea as additive agent. From thepreparation of gel, the PVA method better than the urea - HMTA method,because was not necessary the cold temperature for sol preparation and alsowas not necessary the hot temperature for gelation process. After nextprocessing, the sintered gel of gel through PVA, also better than HMTAprocess. (author)

  6. Sintering and microstructure of ZnO varistor

    International Nuclear Information System (INIS)

    Leite, E.R.; Longo, E.; Varela, J.A.

    1987-01-01

    The sintering and microstructure of ZnO-Bi 2 O 3 (ZB) and ZuO-Sb 2 O 3 -CoO-Bi 2 O 3 (ZSCB) varistors in several temperatures, for one hour in dry air temperature were studied. The compounds were analyzed by scanning electron microscopy, X-ray diffraction, differential thermal analysis and the density and porosity were determined by mercury picnometry. The experimental results showed that the ZB and ZSCB system sinters by liquid means and that liquid will control the density and grain growth mechanisms. (E.G.) [pt

  7. A silicified bird from Quaternary hot spring deposits.

    Science.gov (United States)

    Channing, Alan; Schweitzer, Mary Higby; Horner, John R; McEneaney, Terry

    2005-05-07

    The first avian fossil recovered from high-temperature hot spring deposits is a three-dimensional external body mould of an American coot (Fulica americana) from Holocene sinters of Yellowstone National Park, Wyoming, USA. Silica encrustation of the carcass, feathers and colonizing microbial communities occurred within days of death and before substantial soft tissue degradation, allowing preservation of gross body morphology, which is usually lost under other fossilization regimes. We hypothesize that the increased rate and extent of opal-A deposition, facilitated by either passive or active microbial mediation following carcass colonization, is required for exceptional preservation of relatively large, fleshy carcasses or soft-bodied organisms by mineral precipitate mould formation. We suggest physico-chemical parameters conducive to similar preservation in other vertebrate specimens, plus distinctive sinter macrofabric markers of hot spring subenvironments where these parameters are met.

  8. The application of silicon and silicates in dentistry: a review.

    Science.gov (United States)

    Lührs, A-K; Geurtsen, Werner

    2009-01-01

    Silicates and silicate-based compounds are frequently used materials in dentistry. One of their major applications is their use as fillers in different dental filling materials such as glass-ionomer cements, compomers, composites, and adhesive systems. In these materials, the fillers react with acids during the setting process or they improve the mechanical properties by increasing physical resistance, thermal expansion coefficient and radiopacity in acrylic filling materials. They also reduce polymerization shrinkage, and increase esthetics as well as handling properties. Furthermore, silicates are used for the tribochemical silication of different surfaces such as ceramics or alloys. The silicate layer formed in this process is the chemical basis for silanes that form a bond between this layer and the organic composite matrix. It also provides a micromechanical bond between the surface of the material and the composite matrix. Silicates are also a component of dental ceramics, which are frequently used in dentistry, for instance for veneers, inlays, and onlays, for denture teeth, and for full-ceramic crowns or as crown veneering materials.

  9. Silicates in orthopedics and bone tissue engineering materials.

    Science.gov (United States)

    Zhou, Xianfeng; Zhang, Nianli; Mankoci, Steven; Sahai, Nita

    2017-07-01

    Following the success of silicate-based glasses as bioactive materials, silicates are believed to play important roles in promoting bone formation and have therefore been considered to provide a hydroxyapatite (HAP) surface layer capable of binding to bone as well as potentially being a pro-osteoinductive factor. Natural silicate minerals and silicate-substituted HAPs are also being actively investigated as orthopaedic bone and dental biomaterials for application in tissue engineering. However, the mechanisms for the proposed roles of silicate in these materials have not been fully understood and are controversial. Here, we review the potential roles of silicate for bone tissue engineering applications and recent breakthroughs in identifying the cellular-level molecular mechanisms for the osteoinductivity of silica. The goal of this article is to inspire new ideas for the rational design of third-generation cell-and gene-affecting biomaterials. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2090-2102, 2017. © 2017 Wiley Periodicals, Inc.

  10. Silicate Removal in Aluminum Hydroxide Co-Precipitation Process

    Directory of Open Access Journals (Sweden)

    Chiharu Tokoro

    2014-02-01

    Full Text Available The removal mechanisms of silicate using an aluminum hydroxide co-precipitation process was investigated and compared with an adsorption process, in order to establish an effective and validated method for silicate removal from wastewater. Adsorption isotherms, XRD and FT-IR analyses showed that silicate uptake occurred by adsorption to boehmite for initial Si/Al molar ratios smaller than two, but by precipitation of poorly crystalline kaolinite for the ratios larger than two, in both co-precipitation and adsorption processes. Silicate was removed by two steps: (i an initial rapid uptake in a few seconds; and (ii a slow uptake over several hours in both processes. The uptake rate in the first step was higher in the co-precipitation process than in adsorption process, presumably due to increased silicate adsorption to boehmite and rapid precipitation of kaolinite. These results suggest that silicate removal using aluminum salts could be effectively achieved if the pH adjustment and aluminum concentration are strictly controlled.

  11. The distribution and composition characteristics of siliceous rocks from Qinzhou Bay-Hangzhou Bay joint belt, South China: constraint on the tectonic evolution of plates in South China.

    Science.gov (United States)

    Li, Hongzhong; Zhai, Mingguo; Zhang, Lianchang; Zhou, Yongzhang; Yang, Zhijun; He, Junguo; Liang, Jin; Zhou, Liuyu

    2013-01-01

    The Qinzhou Bay-Hangzhou Bay joint belt is a significant tectonic zone between the Yangtze and Cathaysian plates, where plentiful hydrothermal siliceous rocks are generated. Here, the authors studied the distribution of the siliceous rocks in the whole tectonic zone, which indicated that the tensional setting was facilitating the development of siliceous rocks of hydrothermal genesis. According to the geochemical characteristics, the Neopalaeozoic siliceous rocks in the north segment of the Qinzhou Bay-Hangzhou Bay joint belt denoted its limited width. In comparison, the Neopalaeozoic Qinzhou Bay-Hangzhou Bay joint belt was diverse for its ocean basin in the different segments and possibly had subduction only in the south segment. The ocean basin of the north and middle segments was limited in its width without subduction and possibly existed as a rift trough that was unable to resist the terrigenous input. In the north segment of the Qinzhou Bay-Hangzhou Bay joint belt, the strata of hydrothermal siliceous rocks in Dongxiang copper-polymetallic ore deposit exhibited alternative cycles with the marine volcanic rocks, volcanic tuff, and metal sulphide. These sedimentary systems were formed in different circumstances, whose alternative cycles indicated the release of internal energy in several cycles gradually from strong to weak.

  12. Determination of optimum thermal debinding and sintering process parameters using Taguchi Method

    CSIR Research Space (South Africa)

    Seerane, M

    2015-07-01

    Full Text Available on the basis of obtaining a defect-free part after sintering and also determining a sintering time that gives high sintering density. Thermal debinding was conducted after solvent debinding. The feedstock used to produce green compacts composed of Ti6Al4V... International Light Metals Technology Conference (LMT 2015), Port Elizabeth, South Africa, July 27-29 Determination of Optimum Process for Thermal Debinding and Sintering using Taguchi Method SEERANE Mandya,*, CHIKWANDA Hildab, MACHAKA Ronaldc CSIR...

  13. Effect of moisture and chitosan layered silicate on morphology and properties of chitosan/layered silicates films

    International Nuclear Information System (INIS)

    Silva, J.R.M.B. da; Santos, B.F.F. dos; Leite, I.F.

    2014-01-01

    Thin chitosan films have been for some time an object of practical assessments. However, to obtain biopolymers capable of competing with common polymers a significant improvement in their properties is required. Currently, the technology of obtaining polymer/layered silicates nanocomposites has proven to be a good alternative. This work aims to evaluate the effect of chitosan content (CS) and layered silicates (AN) on the morphology and properties of chitosan/ layered silicate films. CS/AN bionanocomposites were prepared by the intercalation by solution in the proportion 1:1 and 5:1. Then were characterized by infrared spectroscopy (FTIR), diffraction (XRD) and X-ray thermogravimetry (TG). It is expected from the acquisition of films, based on different levels of chitosan and layered silicates, choose the best composition to serve as a matrix for packaging drugs and thus be used for future research. (author)

  14. Effect of MnO2 doped on physical, structure and optical properties of zinc silicate glasses from waste rice husk ash

    Directory of Open Access Journals (Sweden)

    Ali Jabbar Abed Al-Nidawi

    Full Text Available In this study, an investigation was conducted to explore and synthesize silicate (SiO2 glass from waste rice husk ash (RHA. MnO2 doped zinc silicate glasses with chemical formula [(ZnO55 + (WRHA45]100-X[MnO2]X, (where X = 0, 1, 3 and 5 wt% was prepared by conventional melt quenching technique. The glass samples were characterized using energy dispersive X-ray fluorescence (EDXRF, X-ray diffraction (XRD, field emission scanning electron microscopy (FESEM, Fourier transform infrared (FTIR spectroscopy, and ultraviolet–visible (UV–Vis spectroscopy. The results revealed that by increasing the concentration of MnO2, the color of glass samples changed from colorless to brown and the density of glass increased. XRD results showed that a broad halo peak which centered on the low angle (2θ = 30° indicated the amorphous nature of the glass. FTIR results showed basic structural units of Si-O-Si in non-bridging oxygen, Si-O and Mn-O in the glass network. FESEM result showed a decreasing porosity with an increasing MnO2 content, which was attributed to the Mn ions resort to occupy interstitial sites inside the pores of glass. Besides, the absorption intensity of glass increased and the band gap value decreased with increasing the MnO2 percentage. In this synthesized glass system of MnO2 doped zinc silicate glasses using RHA as a source of silica, the MnO2 affect most of the properties of the glass system under investigation. Keywords: Rice husk, Manganese dioxide, Glass, Zinc silicate, Sintering, Optical properties

  15. Model for the evaluation and prediction of production rate of sinter ...

    African Journals Online (AJOL)

    A model has been derived for evaluation and prediction of production rate of sinter machine operating on vertical mode. The quadratic model expressed as: P = 0.4395 V – 0.0526 V2 + 0.54, showed that the production rate of the sinter machine was dependent on the vertical sintering height. The maximum deviation of the ...

  16. Influence of various manufacturing parameters on some characteristics of UO2 powders and their sintering behaviour

    International Nuclear Information System (INIS)

    Mintz, M.H.; Vaknin, Sh.; Kremener, A.; Hadari, Z.

    1977-02-01

    Various parameters in the process of manufacturing uranium dioxide are examined and their influence on the characteristics and sintering behaviour of the powders obtained established. In addition some correlations between the powder aggregates microstructure and their adhesion properties and sintering behaviour are indicated. Shrinkage during the sintering process is also discussed

  17. Application of fine-grained coke breeze fractions in the process of iron ore sintering

    Directory of Open Access Journals (Sweden)

    M. Niesler

    2014-01-01

    Full Text Available The testing cycle, described in the paper, included fine-grained coke breeze granulation tests and iron concentrate sintering tests with the use of selected granulate samples. The use of granulated coke breeze in the sintering process results in a higher process efficiency, shorter sintering duration and fuel saving.

  18. Sintering of uranium dioxide pellets (UO2) in an oxidizing atmosphere (C O2)

    International Nuclear Information System (INIS)

    Santos, G.R.T.

    1992-01-01

    This work consists in the study of the sintering process of U O 2 pellets in an oxidizing atmosphere. Sintering tests were performed in an CO 2 atmosphere and the influence of temperature and time on the pellets density and microstructure were verified. The results obtained were compared to those from the conventional sintering process and its efficiency was confirmed. (author)

  19. Fabrication of High Strength and Ductile Stainless Steel Fiber Felts by Sintering

    Science.gov (United States)

    Wang, J. Z.; Tang, H. P.; Qian, M.; Li, A. J.; Ma, J.; Xu, Z. G.; Li, C. L.; Liu, Y.; Wang, Y.

    2016-03-01

    Stainless steel fiber felts are important porous stainless steel products for a variety of industry applications. A systematic study of the sintering of 28- µm stainless steel fibers has been conducted for the first time, assisted with synchrotron radiation experiments to understand the evolution of the sintered joints. The critical sintering conditions for the formation of bamboo-like grain structures in the fiber ligaments were identified. The evolution of the number density of the sintered joints and the average sintered neck radius during sintering was assessed based on synchrotron radiation experiments. The optimum sintering condition for the fabrication of high strength and ductile 28- µm-diameter stainless steel fiber felts was determined to be sintering at 1000°C for 900 s. Sintering under this optimum condition increased the tensile strength of the as-sintered stainless steel fiber felts by 50% compared to conventional sintering (1200°C for 7200 s), in addition to much reduced sintering cycle and energy consumption.

  20. Spark Plasma Sintered AlN-BN Composites and Its Thermal Conductivity

    NARCIS (Netherlands)

    Zhao Haiyang, [No Value; Wang Weimin, [No Value; Wang Hao, [No Value; Fu Zhengyi, [No Value

    2008-01-01

    A series of samples of hexagonal boron nitride-aluminum nitride ceramic composites with different amounts of CaF(2) as sintering aid were prepared by spark plasma sintered at 1700-1850 degrees C for 5 min. The addition of CaF(2) effectively lowered the sintering temperature and promoted the

  1. Process for the production of metal nitride sintered bodies and resultant silicon nitride and aluminum nitride sintered bodies

    Science.gov (United States)

    Yajima, S.; Omori, M.; Hayashi, J.; Kayano, H.; Hamano, M.

    1983-01-01

    A process for the manufacture of metal nitride sintered bodies, in particular, a process in which a mixture of metal nitrite powders is shaped and heated together with a binding agent is described. Of the metal nitrides Si3N4 and AIN were used especially frequently because of their excellent properties at high temperatures. The goal is to produce a process for metal nitride sintered bodies with high strength, high corrosion resistance, thermal shock resistance, thermal shock resistance, and avoidance of previously known faults.

  2. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Cruz

    2013-01-01

    Full Text Available The control of Asian Soybean Rust (ASR, caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS and soil amendment with calcium silicate (CS on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection process of P. pachyrhizi was investigated by scanning electron microscopy. The uredia on leaves of plants sprayed with PS were smaller and more compact than those observed on the leaves of plants grown in soil amended with CS or in soil non-amended with CS (control treatment. On leaves of plants from the control treatment, uredia produced many urediniospores at 9 days after inoculation, and the ASR severity was 15, 8 and 9%, respectively, for plants from control, PS and CS treatments. In conclusion, the spray of PS contributed to reduce the number of uredia per cm² of leaf area and both PS spray and CS resulted in lower ASR symptoms.

  3. Dentine-pulp tissue engineering in miniature swine teeth by set calcium silicate containing bioactive molecules.

    Science.gov (United States)

    Tziafas, Dimitrios; Kodonas, Konstantinos; Gogos, Christos; Tziafa, Christina; Papadimitriou, Seraphim

    2017-01-01

    The present study aims to investigate whether reparative dentinogenesis could be guided at central pulpal sites or at a distance from the amputated pulp of miniature pig teeth, by using set calcium silicate-based carriers containing human recombinant bioactive molecules. Pulp exposures were performed in 72 permanent teeth of 4 healthy miniature swine. The teeth were capped with pre-manufactured implants of set calcium silicate-based material containing BMP-7, TGFβ1 or WnT-1, for 3 weeks. Conical-shaped intrapulpal implants were exposed in the central pulp core, while disc-shaped extrapulpal implants were placed at a distance from the amputated pulp. Implants without bioactive molecules were used as controls. Thickness and forms of new matrix mineralized deposition were assessed histologically at post-operative periods of 3 weeks by light microscopy. Intrapulpal applications: Calcified structures composed of osteodentine were found in contact with the BMP-7 implants. An inhomogeneous calcified tissue matrix was found around the WnT-1 carriers. A two-zone calcified structure composed of osteodentine and a thicker tubular matrix zone was seen at the TGFβ1 carrier-pulp interface. Extrapulpal applications: The space between WnT-1 implants and pulp periphery had been invaded by soft tissue with traces of calcified foci. Thick calcified structures composed of osteodentine were found surrounding pulp exposure sites in response to application of BMP-7. Spindle-shaped cells associated with atubular calcified matrix or elongated polarized cells associated with tubular dentine-like matrix were found along the cut dentinal walls of the TGFβ1 group. The present experiments indicated that set calcium silicate could be used as carrier for biologically active molecules. TGFβ1 was shown to be an effective bioactive molecule in guiding tertiary dentine formation. Copyright © 2016 Elsevier Ltd. All rights reserved.

  4. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Yiqin [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Li, Heqin, E-mail: lhqjs@hfut.edu.cn [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zuo, Min; Tao, Lei; Wang, Wei [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); Zhang, Jing; Tang, Qiong [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China); School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009 (China); Bai, Peiwen [School of Materials Science and Engineering, Hefei University of Technology, Hefei 230009 (China)

    2016-07-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  5. Corrosion resistance of sintered NdFeB coated with SiC/Al bilayer thin films by magnetron sputtering

    International Nuclear Information System (INIS)

    Huang, Yiqin; Li, Heqin; Zuo, Min; Tao, Lei; Wang, Wei; Zhang, Jing; Tang, Qiong; Bai, Peiwen

    2016-01-01

    The poor corrosion resistance of sintered NdFeB imposes a great challenge in industrial applications. In this work, the SiC/Al bilayer thin films with the thickness of 510 nm were deposited on sintered NdFeB by magnetron sputtering to improve the corrosion resistance. A 100 nm Al buffer film was used to reduce the internal stress between SiC and NdFeB and improve the surface roughness of the SiC thin film. The morphologies and structures of SiC/Al bilayer thin films and SiC monolayer film were investigated with FESEM, AFM and X-ray diffraction. The corrosion behaviors of sintered NdFeB coated with SiC monolayer film and SiC/Al bilayer thin films were analyzed by polarization curves. The magnetic properties were measured with an ultra-high coercivity permanent magnet pulse tester. The results show that the surface of SiC/Al bilayer thin films is more compact and uniform than that of SiC monolayer film. The corrosion current densities of SiC/Al bilayer films coated on NdFeB in acid, alkali and salt solutions are much lower than that of SiC monolayer film. The SiC/Al bilayer thin films have little influence to the magnetic properties of NdFeB. - Highlights: • The same thick Al, SiC and SiC/Al films are deposited on NdFeB by magnetron sputtering. • 510 nm SiC/Al bilayer films can improve the corrosion resistance of the NdFeB evidently. • Al buffer layer improves effectively the surface roughness of the SiC thin film. • SiC/Al bilayer films do not deteriorate the magnetic properties of NdFeB.

  6. Effects of sintering temperature on the density and porosity

    African Journals Online (AJOL)

    2013-03-01

    Mar 1, 2013 ... used as a model system for the investigation of ce- ramic sintering behavior [1, 2]. However, the system ... cially available metal foams are based on aluminium, copper, nickel and metal alloys [4]. ... Zhao et al [9] reported that the porosity of the as- manufactured foam is determined by the density of.

  7. Effect of sintering temperature and heating mode on consolidation of ...

    Indian Academy of Sciences (India)

    ventional vacuum furnace (10. −2 torr). The transverse rupture strength (TRS) samples (31·7 ... testing machine (model: 1195, INSTRON, UK) at a cross- head speed of 0·5 mm/min and SEM of fractured surfaces ... Photographs of 7775 alloy sintered under vacuum at. 590. ◦. C and 630. ◦. C in conventional furnace. where f is ...

  8. Novel sintered ceramic materials incorporated with EAF carbon steel slag

    Science.gov (United States)

    Karayannis, V.; Ntampegliotis, K.; Lamprakopoulos, S.; Papapolymerou, G.; Spiliotis, X.

    2017-01-01

    In the present research, novel sintered clay-based ceramic materials containing electric arc furnace carbon steel slag (EAFC) as a useful admixture were developed and characterized. The environmentally safe management of steel industry waste by-products and their valorization as secondary resources into value-added materials towards circular economy have attracted much attention in the last years. EAF Carbon steel slag in particular, is generated during the manufacture of carbon steel. It is a solid residue mainly composed of rich-in- Fe, Ca and Si compounds. The experimental results show that the beneficial incorporation of lower percentages of EAFC up to 6%wt. into ceramics sintered at 950 °C is attained without significant variations in sintering behavior and physico-mechanical properties. Further heating up to 1100 °C strongly enhances the densification of the ceramic microstructures, thus reducing the porosity and strengthening their mechanical performance. On the other side, in terms of thermal insulation behavior as well as energy consumption savings and production cost alleviation, the optimum sintering temperature appears to be 950 °C.

  9. Effect of sintering temperature and time on the mechanical ...

    Indian Academy of Sciences (India)

    Administrator

    partial sintering of the alloy particles on the cell walls. Pore size and pore interconnectivity are critical factors in porous material for tissue engineering. Micropores are scale to provide pathways for body fluid and nutrient transpor- tation, needed for bone regeneration and growth.25 In addition, these kinds of pores provide ...

  10. Diffusion of silver during sintering in high permittivity COG dielectrics

    NARCIS (Netherlands)

    Mikkenie, R.; Groen, W.A.; Drift, R. van der

    2010-01-01

    To achieve cost reduction in multi-layer ceramic capacitors and actuators, which use a silver-palladium alloy as internal electrode, the trend is to use alloys with the highest silver content possible. This requires ceramic materials which must be sintered at a relative low temperature. Goal is to

  11. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    Abstract. Zinc–magnesium titanate dielectrics/nickel–zinc–copper ferrite layer composites were prepared by tape- casting technique combined with a uniaxial pressure shaping technique. The sintering and camber development of the composites were investigated. The results show that the difference of shrinkage in the ...

  12. Electrical discharge machining studies on reactive sintered FeAl

    Indian Academy of Sciences (India)

    Electrical discharge machining (EDM) studies on reactive sintered FeAl were carried out with different process parameters. The metal removal rate and tool removal rate were found to increase with the applied pulse on-time. The surface roughness of machined surface also changed with the applied pulse on-time.

  13. Preparation and characterization of solid-state sintered aluminum ...

    Indian Academy of Sciences (India)

    AZO target; ZnAl2O4 spinel; resistivity; AZO thin film. 1. Introduction. Transparent conducting oxides ... (i) low cost, (ii) low growth temperature, (iii) non-toxicity, and (iv) easy adjustment of conductivity by adding ... strate via sputtering, a target with high sintering density is required. In this work, preparation of high quality AZO ...

  14. Sintering, camber development of layer composites and a new ...

    Indian Academy of Sciences (India)

    Home; Journals; Bulletin of Materials Science; Volume 37; Issue 1. Sintering ... To eliminate or decrease the camber, a new method semi-fixed uniaxial pressure technique (SUP) was proposed. ... Department of Materials Science and Engineering, Xi'an University of Science and Technology, Xi'an 710054, P. R. China ...

  15. Sintering Reaction of Pseudoleucite Syenite: Thermodynamic Analysis and Process Evaluation

    Science.gov (United States)

    TAN, Danjun; MA, Hongwen; LI, Ge; LIU, Hao; ZOU, Dan

    On the basis of comprehensive analysis of the modal composition of a pseudoleucite syenite ore sample, collected from the Zijin Hill of Lin County, Shanxi Province, thermodynamic analysis of the pseudoleucite syenite sintering process with sodium carbonate as the additive was carried out. It indicated that when the pseudoleucite syenite was sintered at 760-880°C for 1.0-1.5 h, with sodium carbonate as the additive. The decomposition rate of minerals in the pseudoleucite syenite could reach 97.1%. The thermodynamic calculation shows that it needs to consume Na 2CO 3, i.e., 0.65 t treating per ton pseudoleucite syenite ore and approximately 95% of Na 2CO 3 could be recycled. This process consumes heat energy (2.29-2.48)×10 -6 kJ, corresponding to standard coal 190.97-206.82 kg as the thermal efficiency was 40% and CO 2 emission was 0.77-0.81 t. Compared with the Russian limestone-sintering technique, the natural mineral resources and energy consumptions and greenhouse gas emissions of the soda-sintering technique were reduced by 65%, 63%, and 65%, respectively. It is, therefore, feasible that the procedure suggested in this article could be industrialized providing both economic benefit and environmental conservation.

  16. Effect of sintering temperature and heating mode on consolidation of ...

    Indian Academy of Sciences (India)

    sintering of various Al-based composites. Microwave heat- ing of metallic powders (Al–Cu–Fe) to single phase was first reported by Vauchera et al (2008). To the best of our know- ... insulation also consisted of graphite coated SiC rods. Tem- perature ... Figure 3 compares thermal profile for 7775 aluminum alloy compacts ...

  17. Coal fly ash utilization: low temperature sintering of wall tiles.

    Science.gov (United States)

    Chandra, Navin; Sharma, Priya; Pashkov, G L; Voskresenskaya, E N; Amritphale, S S; Baghel, Narendra S

    2008-01-01

    We present here a study of the sintering of fly ash and its mixture with low alkali pyrophyllite in the presence of sodium hexa meta phosphate (SHMP), a complex activator of sintering, for the purpose of wall tile manufacturing. The sintering of fly ash with SHMP in the temperature range 925-1050 degrees C produces tiles with low impact strength; however, the incremental addition of low alkali pyrophyllite improves impact strength. The impact strength of composites with >or=40% (w/w) pyrophyllite in the fly ash-pyrophyllite mix satisfies the acceptable limit (19.6 J/m) set by the Indian Standards Institute for wall tiles. Increasing the pyrophyllite content results in an increase in the apparent density of tiles, while shrinkage and water absorption decrease. The strength of fly ash tiles is attributed to the formation of a silicophosphate phase; in pyrophyllite rich tiles, it is attributed to the formation of a tridymite-structured T-AlPO(4) phase. Scanning electron micrographs show that the reinforcing rod shaped T-AlPO(4) crystals become more prominent as the pyrophyllite content increases in the sintered tiles.

  18. Optical properties of CdS sintered film

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Chemical method has been used to prepare cadmium sulphide by using cadmium, hydrochloric acid and H2S. The reflection spectra of covered and uncovered sintered films of CdS have been recorded by 'Hitachi spectrophotometer' over the wavelength range 300–700 nm. The energy band gaps of these films ...

  19. Preparation and Characterization of Sintered Microporous Polymeric Filters

    Directory of Open Access Journals (Sweden)

    Meysam Salari

    2017-09-01

    Full Text Available Nowadays filtration process is increasingly used in various areas such as water purification, food industries, filtering the air dust and other separation applications. In this work, the HDPE microporous filters have been fabricated at different pressure and time conditions via sintering process and then were characterized by different techniques. It can be expected that microstructure and mechanical properties of the samples could be controlled by changing the fabrication parameters like temperature, pressure, time of the process and also by changing the properties of the resin such as powder shape, particle size and rheological properties. In the first step, by using DSC, MFI, rheology test and optical microscope, the most suitable polymeric powder for sintering process was chosen. The sintering temperature was fixed in the vicinity of melting temperature of the used HDPE powder, based on DSC result. In order to evaluate mechanical properties and porosity of the samples, the results obtained from the shear punch test, acetone drop permeability, gas permeability, transition optical microscopy and SEM, have been used; then the effect of pressure and time parameters on the characteristics of the product has been studied. Finally, it was concluded that it is possible to make microporous filters with suitable mechanical properties, using sintering process at controlled pressure and temperature conditions.It can be seen that by increasing time and pressure, on the one hand the mechanical properties of the products increase, and on the other hand, their porosity and the gas permeability of the vents decrease.

  20. Effect of sintering on controlled release profile of diltiazem ...

    African Journals Online (AJOL)

    The study was designed to formulate and evaluate diltiazem hydrochloride wax matrix tablets for controlled release using sintering technique. Granules of diltiazem hydrochloride-wax were prepared by melt granulation technique. This was formed by triturating the drug powder with a melted carnauba wax (drug: wax ratio, ...

  1. The polarising effects in sintered kaolin | D'ujanga | Tanzania ...

    African Journals Online (AJOL)

    The polarizing effects in sintered kaolin samples were analysed in terms of the sample density (or porosity) using direct current (dc) techniques. More porous samples exhibited higher polarizing effects than the less porous ones. The conduction carriers in kaolin samples at room temperature were found to be mainly ...

  2. Electrical discharge machining studies on reactive sintered FeAl

    Indian Academy of Sciences (India)

    Unknown

    MS received 7 November 2005. Abstract. Electrical discharge machining (EDM) studies on reactive sintered FeAl were carried out with differ- ... electric breakdown process spreads at an explosive rate, resulting in the formation of a .... of cutting fluid takes place which would give out a car- bon residue. The visual black layer ...

  3. New membranes made of sintered clay application to crossflow ...

    African Journals Online (AJOL)

    The new mineral membranes made of sintered clay are performed and characterized in terms of porosity, hydraulic resistance, pore diameter and mechanical resistance. It is shown that these membranes can be used as microfiltration membrane. The variations of the filtrate flux as a function of time are measured during the ...

  4. Physical chemistry and modelling of the sintering of actinide oxides

    International Nuclear Information System (INIS)

    Lechelle, Jacques

    2013-01-01

    This report gives a synthesis of the work I have carried out or to which I have numerically contributed to from 1996 up to 2012 in the Department of Plutonium Uranium and minor Actinides in Cadarache CEA Center. Their main goal is the study and the modeling of the sintering process of nuclear fuels which is the unifying thread of this document. Both in order to take into account the physical and chemical features of the actinide bearing oxide material and in order to combine the different transport phenomena leading to sintering, a sub-granular scale model is under development. Extension to a varying chemical composition as well as exchanges with the gaseous phase are foreseen. A simulation on a larger scale (pellet scale) is ongoing in the framework of a PhD thesis. Validation means have been tested with (U,Pu)O 2 material on the scale of the pellet (Small Angle Neutron Diffusion), on the scale of powder granules (X-Ray High Resolution Micro-Tomography) and with CeO 2 at the 'Institut de Chimie Separative' in Marcoule on a single crystal scale (Environmental Scanning Electron Microscope). The required microstructure homogeneity for nuclear fuels has led to a campaign of experimental studies about the role of Cr 2 O 3 as a sintering aid. Whole of these studies improve our understanding of fuel sintering and hence leads to an improved mastering of this process. (author) [fr

  5. Microstructure and properties of sintered mullite developed from ...

    Indian Academy of Sciences (India)

    purpose are clay minerals such as kaolinite, pyrophyllite, si- llimanite group ... racterized in terms of bulk density, apparent porosity, phase .... density at 1650. ◦. C. Gradual removal of open pores with an increase in sintering temperature is the reason for higher den- sification. Formation of higher amount of low density glass.

  6. Synthesis and electrical field-assisted sintering behaviour of yttria ...

    Indian Academy of Sciences (India)

    Synthesis and electrical field-assisted sintering behaviour of yttria-stabilized tetragonal ZrO2 nanopowders by polyacrylamide gel method. XINGHUA SU. ∗. , BENPAN WANG, JIE ZHOU and HAOYU SUN. School of Materials Science and Engineering, Chang'an University, Xi'an 710061, China. MS received 5 May 2015; ...

  7. Effect of increasing lanthanum substitution and the sintering ...

    Indian Academy of Sciences (India)

    Compared with SBTi ceramics and other lanthanide-substituted compositions, the incorporation of La3+ results in clear improvement in properties for SBLT ( ∼ 0.75) with respect to the values of hardness and Young's modulus of the microwave sintered samples (8.8–12.5 and 160–180 GPa) are higher than that for ...

  8. High-level radioactive waste fixation in sintered vitreous matrix

    International Nuclear Information System (INIS)

    Russo, D.O.; Messi de Bernasconi, N.; Audero, M.A.

    1987-01-01

    The safe storage of high-level wastes from fuel elements reprocessing includes, as a first step, the fixation of the same in materials having a good resistance to the leaching in aqueous medium, such as borosilicate glass. As an alternative to the usual method of the molten glasses, a procedure for the sintering of a powdered glass and waste mixture at lower temperatures (600-700 deg C) has been developed, which minimizes the volatilization of active compounds during the process. Two glasses matrices of different composition and characteristics were used, to which the simulated wastes were added in the ratio of a 10% in weight of oxides. Two sintering techniques were employed 1: cold pressing and further sintering; 2: hot pressing and sintering under pressure. The densities were measured, the microstructure of the samples was analyzed and leaching essays were made in distilled water. The pellet's microstructure was observed by means of optical microscopy, by reflection in polished samples and by transparency in thin slices. The presence of crystalline compounds was analyzed by means of x rays and electron microprobe. The results have shown the convenience to continue with hot pressing essays, because a denser product with a higher resistance to the leaching is thus obtained. (M.E.L.) [es

  9. Strain in the mesoscale kinetic Monte Carlo model for sintering

    DEFF Research Database (Denmark)

    Bjørk, Rasmus; Frandsen, Henrik Lund; Tikare, V.

    2014-01-01

    Shrinkage strains measured from microstructural simulations using the mesoscale kinetic Monte Carlo (kMC) model for solid state sintering are discussed. This model represents the microstructure using digitized discrete sites that are either grain or pore sites. The algorithm used to simulate dens...

  10. Optical properties of CdS sintered film

    Indian Academy of Sciences (India)

    Chemical method has been used to prepare cadmium sulphide by using cadmium, hydrochloric acid and H2S. The reflection spectra of covered and uncovered sintered films of CdS have been recorded by 'Hitachi spectrophotometer' over the wavelength range 300–700 nm. The energy band gaps of these films have been ...

  11. Joining of β-SiC by spark plasma sintering

    Czech Academy of Sciences Publication Activity Database

    Grasso, S.; Tatarko, Peter; Rizzo, S.; Porwal, H.; Hu, Ch.; Katoh, Y.; Salvo, M.; Reece, M. J.; Ferraris, M.

    2014-01-01

    Roč. 34, č. 7 (2014), s. 1681-1686 ISSN 0955-2219 EU Projects: European Commission(XE) 264526 - GLACERCO Institutional support: RVO:68081723 Keywords : β-SiC * joining * Spark plasma sintering Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 2.947, year: 2014

  12. Binding Mechanisms in Selective Laser Sintering and Selective Laser Melting

    NARCIS (Netherlands)

    Kruth, J.P.; Mercelis, P.; Van Vaerenbergh, J.; van Vaerenbergh, J.; Froyen, L.; Rombouts, M.

    2005-01-01

    Purpose – This paper provides an overview of the different binding mechanisms in selective laser sintering (SLS) and selective laser melting (SLM), thus improving the understanding of these processes. Design/methodology/approach – A classification of SLS/SLM processes was developed, based on the

  13. New developments in laser sintering of diamond cutting disks

    NARCIS (Netherlands)

    Kovalenko, V.; Golovko, L.; Meijer, J.; Anyakin, M.

    2007-01-01

    The analysis of techniques and problems in the fabrication of cutting tools based on super hard composites results in a solution by the application of lasers. The results of systematic study of diamond composites sintering with laser radiation are discussed. A mathematical modeling of the heat

  14. Preparation and characterization of solid-state sintered aluminum ...

    Indian Academy of Sciences (India)

    Preparation and characterization of solid-state sintered aluminum-doped zinc oxide with different alumina contents. YU-HSIEN CHOU. ∗. , J L H CHAU, W L WANG, C S CHEN, S H WANG and C C YANG. Nanopowder and Thin Film Technology Centre, ITRI–South, Industrial Technology Research Institute, Tainan 70955,.

  15. Photoconductive cells from screen-printed and sintered cadmium sulfoselenide

    Czech Academy of Sciences Publication Activity Database

    Franc, Jiří; Nešpůrek, Stanislav

    2008-01-01

    Roč. 25, č. 3 (2008), s. 41-46 ISSN 1356-5362 Institutional research plan: CEZ:AV0Z40400503; CEZ:AV0Z40500505 Keywords : photoconductivity * detectors (circuits) * sintering * pastes Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 0.471, year: 2008

  16. Consolidation of copper and aluminium powders by spark plasma sintering

    Science.gov (United States)

    Saiprasad, M.; Atchayakumar, R.; Thiruppathi, K.; Raghuraman, S.

    2016-09-01

    Processing in the powder metallurgy route has emerged as an economical process for the production of near net shaped components with a wide range of desired mechanical properties suitable for various applications of industrial needs. This research work was conducted with an objective of studying the improvisation of density and hardness of Copper-Aluminium alloy prepared by spark plasma sintering. Cu-Al alloy with a composition of 95% copper and 5% aluminium was prepared by SPS process. SPS is a low voltage, DC pulse current activated, pressure-assisted sintering, which enables sintering at lower temperatures and shorter durations. The combination offered by Cu-Al alloy of high strength and high corrosion resistance results their applications under a wide variety of conditions. The density and hardness of the prepared sample were measured by conducting appropriate tests. Apparently, the values of hardness and density of the specimen prepared by SPS seemed to be better than that of conventional sintering. The experimental procedure, testing methodologies and analysis are presented.

  17. Fossilization processes in siliceous thermal springs: trends in preservation along thermal gradients

    Science.gov (United States)

    Cady, S. L.; Farmer, J. D.

    1996-01-01

    To enhance our ability to extract palaeobiological and palaeoenvironmental information from ancient thermal spring deposits, we have studied the processes responsible for the development and preservation of stromatolites in modern subaerial thermal spring systems in Yellowstone National Park (USA). We investigated specimens collected from silica-depositing thermal springs along the thermal gradient using petrographic techniques and scanning electron microscopy. Although it is known that thermophilic cyanobacteria control the morphogenesis of thermal spring stromatolites below 73 degrees C, we have found that biofilms which contain filamentous thermophiles contribute to the microstructural development of subaerial geyserites that occur along the inner rims of thermal spring pools and geyser effluents. Biofilms intermittently colonize the surfaces of subaerial geyserites and provide a favoured substrate for opaline silica precipitation. We have also found that the preservation of biotically produced microfabrics of thermal spring sinters reflects dynamic balances between rates of population growth, decomposition of organic matter, silica deposition and early diagenesis. Major trends in preservation of thermophilic organisms along the thermal gradient are defined by differences in the mode of fossilization, including replacement, encrustation and permineralization.

  18. Preparation and mechanism of the sintered bricks produced from Yellow River silt and red mud

    Energy Technology Data Exchange (ETDEWEB)

    He, Hongtao [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Yue, Qinyan, E-mail: qyyue@sdu.edu.cn [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China); Su, Yuan; Gao, Baoyu; Gao, Yue; Wang, Jingzhou; Yu, Hui [Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, Jinan 250100 (China)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer The best condition was red mud content of 40% and sintering at 1050 Degree-Sign C for 2 h. Black-Right-Pointing-Pointer Bricks' weight loss was caused by the removal of absorbed water and crystal water. Black-Right-Pointing-Pointer Bricks' sintering shrinkage depended on the sodium and iron compounds of red mud. Black-Right-Pointing-Pointer Sintering can strengthen bricks and decrease leaching concentration of toxic metal. - Abstract: The preparation, characteristics and mechanisms of sintered bricks manufactured by Yellow River silt and red mud were studied. The sintering shrinkage, weight loss on ignition, water absorption and compressive strength were tested to determine the optimum preparation condition. Sintering mechanisms were discussed through linear regression analysis. Crystalline components of raw materials and bricks were analyzed by X-ray diffraction. Leaching toxicity of raw materials and bricks were measured according to sulphuric acid and nitric acid method. Radiation safety of the sintered bricks was characterized by calculating internal exposure index and external exposure index. The results showed that at the chosen best parameters (red mud content of 40%, sintering temperature of 1050 Degree-Sign C and sintering time of 2 h), the best characteristics of sintered bricks could be obtained. The weight loss on ignition of sintered bricks was principally caused by the removal of absorbed water and crystal water. The sintering shrinkage of sintered bricks mainly depended on sodium compounds and iron compounds of red mud. The sintering process made some components of raw materials transform into other crystals having better thermostability. Besides, the leaching toxicity and radioactivity index of sintered bricks produced under the optimum condition were all below standards.

  19. Microstructural optimization of solid-state sintered silicon carbide

    Science.gov (United States)

    Vargas-Gonzalez, Lionel R.

    Silicon carbide armor, manufactured through solid-state sintering, liquid-phase sintering, and hot-pressing, is being used by the United States Armed Forces for personal and vehicle protection. There is a lack of consensus, however, on which process results in the best-performing ballistic armor. Previous studies have shown that hot-pressed ceramics processed with secondary oxide and/or rare earth oxides, which exhibit high fracture toughness, perform well in handling and under ballistic impact. This high toughness is due to the intergranular nature of the fracture, creating a tortuous path for cracks and facilitating crack deflection and bridging. However, it has also been shown that higher-hardness sintered SiC materials might perform similarly or better to hot-pressed armor, in spite of the large fracture toughness deficit, if the microstructure (density, grain size, purity) of these materials are improved. In this work, the development of theoretically-dense, clean grain boundary, high hardness solid-state sintered silicon carbide (SiC) armor was pursued. Boron carbide and graphite (added as phenolic resin to ensure the carbon is finely dispersed throughout the microstructure) were used as the sintering aids. SiC batches between 0.25--4.00 wt.% carbon were mixed and spray dried. Cylindrical pellets were pressed at 13.7 MPa, cold-isostatically pressed (CIP) at 344 MPa, sintered under varying sintering soaking temperatures and heating rates, and varying post hot-isostatic pressing (HIP) parameters. Carbon additive amounts between 2.0--2.5 wt.% (based on the resin source), a 0.36 wt.% B4C addition, and a 2050°C sintering soak yielded parts with high sintering densities (˜95.5--96.5%) and a fine, equiaxed microstructure (d50 = 2.525 mum). A slow ramp rate (10°C/min) prevented any occurrence of abnormal grain growth. Post-HIPing at 1900°C removed the remaining closed porosity to yield a theoretically-dense part (3.175 g/cm3, according to rule of mixtures). These

  20. COMPARISON OF SOL-GEL SILICATE COATINGS ON Ti SUBSTRATE

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    DIANA HORKAVCOVÁ

    2012-12-01

    Full Text Available The objective of the submitted work was to prepare and to characterize two types of silicate coatings prepared by the sol-gel method using the dip-coating technique on a titanium substrate. Efforts have been made to use mechanical properties of bio-inert titanium and bioactive properties of a silicate layer enriched with an admixture of compounds identified below. The first group consisted of silicate coatings containing silver, brushite and monetite. The other group of silicate coatings contained calcium nitrate and triethyl phosphate. Mechanically and chemically treated titanium substrates were dipped into sols and dried and fired. Silicate coatings from the first group were also chemically treated in 10 mol.l-1 solution of sodium hydroxide. All coatings were measured to determine their adhesive and bioactive properties and furthermore the antibacterial properties were tested in the case of first group. Surfaces of the coated substrates were investigated after the firing and after the individual tests with optical and electron microscopy and X-ray microdiffraction. A tape test demonstrated excellent adhesive property of all coatings to the substrate, classified with degree 5. A static in vitro test demonstrated bioactivity of nearly all the coatings. The basic silicate coating from the first group and one type of coating from the second group were identified as inert. Antibacterial properties of silicate coatings containing silver showed to be different when tested against Escherichia coli bacteria. A complete inhibition of the growth of bacteria under our experimental conditions was observed for the coating containing silver and monetite and a partial inhibition of the growth of bacteria for coatings containing silver and silver in combination with brushite.