Regularities of ferritic-pearlitic structure formation during subcooled austenite decomposition

International Nuclear Information System (INIS)

Shkatov, V.V.; Frantsenyuk, L.I.; Bogomolov, I.V.

1997-01-01

Relationships of ferrite-pearlite structure parameters to austenite grain size and cooling conditions during γ -> α transformation are studied for steel 3 sp. A mathematical description has been proposed for grain evolution in carbon and low alloy steel cooling after hot rolling. It is shown that ferrite grain size can be controlled by changing temperature range of water spraying when the temperatures of rolling completion and strip coiling are the same

Microwave dielectric properties of nanostructured nickel ferrite

Indian Academy of Sciences (India)

Wintec

Abstract. Nickel ferrite is one of the important ferrites used in microwave devices. In the present work, we have synthesized nanoparticles of nickel ferrite using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The microwave dielectric properties of nanostructured.

Effect of nano-sized precipitates on the crystallography of ferrite in high-strength strip steel

Institute of Scientific and Technical Information of China (English)

Jing-jing Yang; Run Wu; Wen Liang; Meng-xia Tang

2014-01-01

For strip steel with the thickness of 1.6 mm, the yield and tensile strengths as high as 760 and 850 MPa, respectively, were achieved using the compact strip production technology. Precipitates in the steel were characterized by scanning and transmission electron microscopy to elucidate the strengthening mechanism. In addition, intragranular misorientation, Kernel average misorientation, and stored energy were measured using electron backscatter diffraction for crystallographic analysis of ferrite grains containing precipitates and their neighbors without precipitates. It is found that precipitates in specimens primarily consist of TiC and Ti4C2S2. Ferrite grains containing pre-cipitates exhibit the high Taylor factor as well as the crystallographic orientations with{012},{011},{112}, or{221}plane parallel to the rolling plane. Compared with the intragranular orientation of adjoining grains, the intragranular misorientation of grains containing precipi-tates fluctuates more frequently and more mildly as a function of distance. Moreover, the precipitates can induce ferrite grains to store a rela-tively large amount of energy. These results suggest that a correlation exists between precipitation in ferrite grains and grain crystallographic properties.

Processing–microstructure–properties relationship in a CuNiZn ferrite

Directory of Open Access Journals (Sweden)

Carolina Clausell

2018-01-01

The electromagnetic properties of the sintered ferrites were observed to improve as sintered relative density and average grain size increased, provided there was no evidence of exaggerated grain growth. In this sense, it seems there is a threshold of the grain size as of which the electromagnetic properties of the sintered specimens get worse. A linear relationship was observed between the imaginary part of the complex magnetic permeability and average grain size, provided each of the different magnetization mechanisms contributing to the complex permeability of the ferrite are taken into account (i.e. spin rotation and wall motion mechanisms.

Grain boundary precipitation strengthening mechanism in W containing advanced creep resistant ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Shibata, T.; Hasegawa, Y. [Tohoku Univ., Sendai (Japan)

2010-07-01

Grain boundary precipitation strengthening is expected to be a decisive factor in developing ferritic creep resistant steels. This study examined the grain boundary precipitation strengthening mechanism extracting the effect of the tempered martensitic microstructure and precipitates on the high angle grain boundary in M{sub 23}C4{sub 6} type carbide and the Fe{sub 2}W type Laves phase effect of the creep deformation fixing the grain boundary according to transmission electron microscope (TEM) observation. A creep test was carried out at high temperature in order to evaluate the high angle boundary strengthening effect simulating the long-term creep deformation microstructure by the lath structure disappearance. The correlation of the creep rupture time and the grain boundary shielding ratio were found to be independent of precipitate type. The creep deformation model represents block boundary shielding by precipitates as the decisive factor for W containing ferritic creep resistant steels. (orig.)

The effect of oxide particles on the strength and ductility of bulk iron with a bimodal grain size distribution

Energy Technology Data Exchange (ETDEWEB)

Casas, C.; Tejedor, R. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Rodríguez-baracaldo, R. [Department of Mechanical Engineering, Universidad Nacional de Colombia, Bogotá. Colombia (Colombia); Benito, J.A., E-mail: Josep.a.benito@upc.edu [Department of Materials Science and Metallurgical Engineering, EUETIB, Universitat Politècnica de Catalunya, Comte d' Urgell 187, 08036 Barcelona (Spain); Fundació CTM Centre Tecnològic de Manresa, Plaça de la Ciencia, 2, 08243 Manresa (Spain); Cabrera, J.M. [Department of Materials Science and Metallurgical Engineering, ETSEIB, Universitat Politècnica de Catalunya, Av. Diagonal 647, 08028 Barcelona (Spain); Fundació CTM Centre Tecnològic de Manresa, Plaça de la Ciencia, 2, 08243 Manresa (Spain)

2015-03-11

The strength and ductility of bulk nanostructured and ultrafine-grained iron containing 0.39% oxygen by weight was determined by tensile tests. Samples were obtained by consolidation of milled iron powder at 500 °C. Heat treatments were designed to cover a wide range of grain sizes spanning from 100 to 2000 nm with different percentages of coarse and nanostructured grain areas, which was defined as a bimodal grain size distribution. Transmission electron microscopy was used to determine the diameter, volume fraction and location of oxides in the microstructure. The strength was analysed following two approaches. The first one was based on the strong effect of oxides and involved the use of a mixed particle-grain boundary strengthening model, and the second one was based on simple grain boundary strengthening. The mixed model underestimated the strength of nanostructured samples, whereas the simple grain boundary model worked better. However, for specimens with a bimodal grain size, the fitting of the mixed model was better. In this case, the more effective particle strengthening was related to the dispersion of oxides inside the large ferrite grains. In addition, the bimodal samples showed an acceptable combination of strength and ductility. Again, the ferrite grains containing oxides promoted strain hardening due to the increase in dislocation activity.

Processing–microstructure–properties relationship in a CuNiZn ferrite

International Nuclear Information System (INIS)

Clausell, C.; Barba, A.

2018-01-01

CuNiZn ferrites are polycrystalline ceramic materials that are used widely in electronic devices for a number of reasons, including their high permeability in the RF frequency region, electrical resistivity, mechanical hardness and chemical stability. One of their main applications is in the production of specimens to prevent possible interferences between electronic devices, thanks to their ability to absorb electromagnetic waves. However, their electromagnetic properties are not solely dependent on their chemical composition, but also on the microstructure of the final piece (relative density or total porosity, grain size distribution, pore size distribution, the nature of the grain boundary, presence of secondary phases, dopants, etc.) and, therefore, on the morphology and size of the starting particles, and the processing method. The microstructure of the sintered specimens was designed in such a way as to optimize the electromagnetic properties of this ferrite. The solid-state sintering stage was also modeled with this optimization in mind. This sintering model enabled to propose the material transport mechanisms that controlled the densification and grain-growth rates, as well as the relative rates of these two simultaneous processes. The established relationships facilitate the design of a thermal cycle suitable for the manufacture of ferrite pieces with maximum relative density and the necessary microstructure. Together with the pre-configured chemical composition, the idea is that this ensures a strong set of final electromagnetic properties. The electromagnetic properties of the sintered ferrites were observed to improve as sintered relative density and average grain size increased, provided there was no evidence of exaggerated grain growth. In this sense, it seems there is a threshold of the grain size as of which the electromagnetic properties of the sintered specimens get worse. A linear relationship was observed between the imaginary part of the

Abnormal grain growth in Eurofer-97 steel in the ferrite phase field

Energy Technology Data Exchange (ETDEWEB)

Oliveira, V.B. [Lorena School of Engineering, University of Sao Paulo, Lorena, SP, 12602-810 (Brazil); Sandim, H.R.Z., E-mail: hsandim@demar.eel.usp.br [Lorena School of Engineering, University of Sao Paulo, Lorena, SP, 12602-810 (Brazil); Raabe, D. [Max-Planck-Institut für Eisenforschung, Düsseldorf, D-40237 (Germany)

2017-03-15

Reduced-activation ferritic-martensitic (RAFM) Eurofer-97 steel is a candidate material for structural applications in future fusion reactors. Depending on the amount of prior cold rolling strain and annealing temperature, important solid-state softening reactions such as recovery, recrystallization, and grain growth occur. Eurofer-97 steel was cold rolled up to 70, 80 and 90% reductions in thickness and annealed in the ferrite phase field (below ≈ 800 °C). Changes in microstructure, micro-, and mesotexture were followed by orientation mappings provided by electron backscatter diffraction (EBSD). Eurofer-97 steel undergoes abnormal grain growth above 650 °C and this solid-state reaction seems to be closely related to the high mobility of a few special grain boundaries that overcome pinning effects caused by fine particles. This solid-state reaction promotes important changes in the microstructure and microtexture of this steel. Abnormal grain growth kinetics for each condition was determined by means of quantitative metallography. - Highlights: • Abnormal grain growth (AGG) occurs in Eurofer-97 steel deformed to several strains. • Kinetics of abnormal grain growth has been determined at 750 and 800 °C. • Significant changes in crystallographic texture take place during AGG. • Grain boundaries with misorientations above 45° may explain abnormal grain growth. • Local microstructural instabilities (coarsening of M23C6 carbides) also explain AGG.

Grain refinement by cold deformation and recrystallization of bainite and acicular ferrite structures of C-Mn steels

International Nuclear Information System (INIS)

Hossein Nedjad, S.; Zahedi Moghaddam, Y.; Mamdouh Vazirabadi, A.; Shirazi, H.; Nili Ahmadabadi, M.

2011-01-01

Research highlights: → Bainite showed weak property improvement after rolling and annealing. → Additions of titanium and titanium oxide stimulated acicular ferrite. → Acicular ferrite obtained by nanoparticles exhibited very high strength. → Rolling and annealing of acicular ferrite gave substantial property improvement. - Abstract: The propensity of bainite and acicular ferrite structures of experimental C-Mn steels for enhanced grain refinement by combining phase transformation and plastic deformation has been investigated. Formation of acicular ferrite structures were stimulated with a small amount of titanium and titanium oxide nanoparticles added into the molten steels of high Mn concentrations. Isothermal transformations into the bainite and acicular ferrite structures were performed for 1.8 ks at 823 K after preliminary austenitization for 1.8 ks at 1523 K. Cold rolling for 50% thickness reduction was conducted on the isothermally transformed structures. Subsequent annealing of the deformed structures was conducted for 3.6 ks at 773, 873 and 973 K. Optical microscopy, scanning electron microscopy and tensile test were used for characterization of the studied steels. Cold rolling and annealing of the transformed structures at 873 K resulted in strengthening at the expense of ductility where an initial stage of recrystallization is realized. Acicular ferrite obtained by the addition of titanium into the molten steel exhibited the remarkable improvement of tensile properties. Discontinuous recrystallization of the deformed structures at 973 K leads to the formation of fine grains wherein acicular structures represented more enhanced grain refinement than bainite.

Ultrafine grained steels processed by equal channel angular pressing

International Nuclear Information System (INIS)

Shin, Dong Hyuk; Park, Kyung-Tae

2005-01-01

Recent development of ultrafine grained (UFG) low carbon steels by using equal channel angular pressing (ECAP) and their room temperature tensile properties are reviewed, focusing on the strategies overcoming their inherent mechanical drawbacks. In addition to ferrite grain refinement, when proper post heat treatments are imposed, carbon atom dissolution from pearlitic cementite during ECAP can be utilized for microstructural modification such as uniform distribution of nano-sized cementite particles or microalloying element carbides inside UFG ferrite grains and fabrication of UFG ferrite/martensite dual phase steel. The utilization of nano-sized particles is effective on improving thermal stability of UFG low carbon ferrite/pearlite steel but less effective on improving its tensile properties. By contrast, UFG ferrite/martensite dual phase steel exhibits an excellent combination of ultrahigh strength, large uniform elongation and extensive strain hardenability

Microstructural development of cobalt ferrite ceramics and its influence on magnetic properties

Science.gov (United States)

Kim, Gi-Yeop; Jeon, Jae-Ho; Kim, Myong-Ho; Suvorov, Danilo; Choi, Si-Young

2013-11-01

The microstructural evolution and its influence on magnetic properties in cobalt ferrite were investigated. The cobalt ferrite powders were prepared via a solid-state reaction route and then sintered at 1200 °C for 1, 2, and 16 h in air. The microstructures from sintered samples represented a bimodal distribution of grain size, which is associated with abnormal grain growth behavior. And thus, with increasing sintering time, the number and size of abnormal grains accordingly increased but the matrix grains were frozen with stagnant grain growth. In the sample sintered for 16 h, all of the matrix grains were consumed and the abnormal grains consequently impinged on each other. With the appearance of abnormal grains, the magnetic coercivity significantly decreased from 586.3 Oe (1 h sintered sample) to 168.3 Oe (16 h sintered sample). This is due to the magnetization in abnormal grains being easily flipped. In order to achieve high magnetic coercivity of cobalt ferrite, it is thus imperative to fabricate the fine and homogeneous microstructure.

Effect of Prior Austenite Grain Size on the Morphology of Nano-Bainitic Steels

Science.gov (United States)

Singh, Kritika; Kumar, Avanish; Singh, Aparna

2018-04-01

The strength in nanostructured bainitic steels primarily arises from the fine platelets of bainitic ferrite embedded in carbon-enriched austenite. However, the toughness is dictated by the shape and volume fraction of the retained austenite. Therefore, the exact determination of processing-morphology relationships is necessary to design stronger and tougher bainite. In the current study, the morphology of bainitic ferrite in Fe-0.89C-1.59Si-1.65Mn-0.37Mo-1Co-0.56Al-0.19Cr (wt pct) bainitic steel has been investigated as a function of the prior austenite grain size (AGS). Specimens were austenitized at different temperatures ranging from 900 °C to 1150 °C followed by isothermal transformation at 300 °C. Detailed microstructural characterization has been carried out using scanning electron microscopy and X-ray diffraction. The results showed that the bainitic laths transformed in coarse austenite grains are finer resulting in higher hardness, whereas smaller austenite grains lead to the formation of thicker bainitic laths with a large fraction of blocky type retained austenite resulting in lower hardness.

Kinetics of Sub-Micron Grain Size Refinement in 9310 Steel

Science.gov (United States)

Kozmel, Thomas; Chen, Edward Y.; Chen, Charlie C.; Tin, Sammy

2014-05-01

Recent efforts have focused on the development of novel manufacturing processes capable of producing microstructures dominated by sub-micron grains. For structural applications, grain refinement has been shown to enhance mechanical properties such as strength, fatigue resistance, and fracture toughness. Through control of the thermo-mechanical processing parameters, dynamic recrystallization mechanisms were used to produce microstructures consisting of sub-micron grains in 9310 steel. Starting with initial bainitic grain sizes of 40 to 50 μm, various levels of grain refinement were observed following hot deformation of 9310 steel samples at temperatures and strain rates ranging from 755 K to 922 K (482 °C and 649 °C) and 1 to 0.001/s, respectively. The resulting deformation microstructures were characterized using scanning electron microscopy and electron backscatter diffraction techniques to quantify the extent of carbide coarsening and grain refinement occurring during deformation. Microstructural models based on the Zener-Holloman parameter were developed and modified to include the effect of the ferrite/carbide interactions within the system. These models were shown to effectively correlate microstructural attributes to the thermal mechanical processing parameters.

Synthesis of Highly Uniform and Compact Lithium Zinc Ferrite Ceramics via an Efficient Low Temperature Approach.

Science.gov (United States)

Xu, Fang; Liao, Yulong; Zhang, Dainan; Zhou, Tingchuan; Li, Jie; Gan, Gongwen; Zhang, Huaiwu

2017-04-17

LiZn ferrite ceramics with high saturation magnetization (4πM s ) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10-50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li 0.415 Zn 0.27 Mn 0.06 Ti 0.1 Fe 2.155 O 4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πM s and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.

Effects of mechanical force on grain structures of friction stir welded oxide dispersion strengthened ferritic steel

International Nuclear Information System (INIS)

Han, Wentuo; Kimura, Akihiko; Tsuda, Naoto; Serizawa, Hisashi; Chen, Dongsheng; Je, Hwanil; Fujii, Hidetoshi; Ha, Yoosung; Morisada, Yoshiaki; Noto, Hiroyuki

2014-01-01

The weldability of oxide dispersion strengthened (ODS) ferritic steels is a critical obstructive in the development and use of these steels. Friction stir welding has been considered to be a promising way to solve this problem. The main purpose of this work was to reveal the effects of mechanical force on grain structures of friction stir welded ODS ferritic steel. The grain appearances and the misorientation angles of grain boundaries in different welded zones were investigated by the electron backscatter diffraction (EBSD). Results showed that the mechanical force imposed by the stir tool can activate and promote the recrystallization characterized by the transformation of boundaries from LABs to HABs, and contribute to the grain refinement. The type of recrystallization in the stir zone can be classified as the continuous dynamic recrystallization (CDRX)

Effects of mechanical force on grain structures of friction stir welded oxide dispersion strengthened ferritic steel

Energy Technology Data Exchange (ETDEWEB)

Han, Wentuo, E-mail: hanwentuo@hotmail.com [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Kimura, Akihiko [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Tsuda, Naoto [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Serizawa, Hisashi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Chen, Dongsheng [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Je, Hwanil [Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Fujii, Hidetoshi [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Ha, Yoosung [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Morisada, Yoshiaki [Joining and Welding Research Institute, Osaka University, Ibaraki, Osaka 567-0047 (Japan); Noto, Hiroyuki [Graduate School of Energy Science, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan)

2014-12-15

The weldability of oxide dispersion strengthened (ODS) ferritic steels is a critical obstructive in the development and use of these steels. Friction stir welding has been considered to be a promising way to solve this problem. The main purpose of this work was to reveal the effects of mechanical force on grain structures of friction stir welded ODS ferritic steel. The grain appearances and the misorientation angles of grain boundaries in different welded zones were investigated by the electron backscatter diffraction (EBSD). Results showed that the mechanical force imposed by the stir tool can activate and promote the recrystallization characterized by the transformation of boundaries from LABs to HABs, and contribute to the grain refinement. The type of recrystallization in the stir zone can be classified as the continuous dynamic recrystallization (CDRX)

Influence of the grain size on deleterious phase precipitation in superduplex stainless steel UNS S32750

International Nuclear Information System (INIS)

Pardal, J.M.; Tavares, S.S.M.; Fonseca, M. Cindra; Souza, J.A. de; Corte, R.R.A.; Abreu, H.F.G. de

2009-01-01

In the present work, the effect of grain size on deleterious phase precipitation in a superduplex stainless steel was investigated. The materials studied were heat treated isothermally at 800 deg. C, 850 deg. C and 900 deg. C for times up to 120 min. Hardness tests, light optical microscopy, scanning electron microscopy and X-ray diffraction were carried out to detect sigma and other harmful precipitate phases. The ferritic and austenitic grain sizes in the solution treated condition of the two steels analyzed were measured by electron backscattered diffraction (EBSD). Cyclic polarization corrosion tests were performed to evaluate the effect of grain size on the corrosion resistance. The results presented show that the precipitation of deleterious phases such as χ, σ and γ 2 , which can occur during welding and forming operations, is retarded by grain growth

Grain refinement and hardness distribution in cryogenically cooled ferritic stainless steel welds

International Nuclear Information System (INIS)

Amuda, M.O.H.; Mridha, S.

2013-01-01

Highlights: ► Grain refinement was undertaken in AISI 430 FSS welds using cryogenic cooling. ► Flow rates of the cryogenic liquid influenced weld grain structure. ► Cryogenic cooling of welds generates about 45% grain refinement in welds. ► Phase structure of welds is not affected by flow rates of cryogenic liquid. ► Hardness profile in cryogenically cooled and conventional welds is similar. - Abstract: The energy input and heat dissipation dynamics during fusion welding generates coarse grain in the welds resulting in poor mechanical properties. While grain refinement in welds via the control of the energy input is quite common, the influence of heat dissipation on grain morphology and properties is not fully established. This paper characterized cryogenically cooled ferritic stainless steel (FSS) welds in terms of grain structure and hardness distribution along transverse and thickness directions. Cryogenic cooling reduces the weld dimension by more than 30% and provides grain refinement of almost 45% compared to conventional weld. The hardness distribution in the thickness direction gives slightly higher profile because of decreased grain growth caused by faster cooling effects of cryogenic liquid

Influence of rare earth Ce3+ on structural, electrical and magnetic properties of Sr2+ based W-type hexagonal ferrites

International Nuclear Information System (INIS)

Sadiq, Imran; Khan, Imran; Aen, Faiza; Islam, M.U.; Rana, M.U.

2012-01-01

A series of single phase W-type Sr 3-x Ce x Fe 16 O 27 (x=0, 0.02, 0.04, 0.06, 0.08, 0.10) hexagonal ferrites prepared by the Sol-Gel method was sintered at 1050 °C for 5 h. The X-ray diffraction analysis reveals that all the samples belong to the family of W-type hexagonal ferrites. The c/a ratio falls in the range of W-type hexagonal ferrites. The grain size was measured by SEM varies from 0.7684 to 0.4366 μm which shows that the Ce 3+ substituted samples have smaller grain size than pure ferrite Sr 3 Fe 16 O 27 which results from the difference in ionic radii of Ce 3+ (1.034 Å) and Sr 2+ (1.12 Å). The room temperature resistivity of the present samples varies from 6.5×10 8 to 272×10 8 Ω-cm. The coercivity increases from 1370 to 1993 Oe which is consistent with the decrease in grain size. The coercivity values indicate that the present samples fall in the range of hard ferrites. The large value of H c may be due to domain wall pinning at the grain boundaries.

Structural and electrical properties of nickel substituted cadmium ferrite

Science.gov (United States)

Chethan, B.; Raj Prakash, H. G.; Vijayakumari, S. C.; Ravikiran, Y. T.

2018-05-01

Spinal nano-sized Cadmium ferrite (CD) and Nickel substituted cadmium ferrite (NSCF) were fabricated by sol-gel auto combustion method. The formation of spinal structure of ferrite materials was confirmed by X-ray diffraction (XRD) analysis. The crystallites size of CF and NSCF as determined by Scherrer's formula were found to be 24.73 nm and 17.70 nm respectively. comparative study of Fourier transform infrared spectroscopy (FTIR) of CF and NSCF revealed tetrahedral absorption bands shifted slightly towards higher frequency where as octahedral bands shifted towards lower frequency side confirming interfacial interaction between Ni and CF. The AC conductivity (σ), loss tangent (tan δ) and complex plane impedance plots for both CF and NSCF are determined at various frequencies ranging from 50 kHz to 5 MHz and comparatively analyzed. The increase in AC conductivity of the NSCF nano particles as compared to CF was explained in the light of hopping model. The impedance measurement of NSCF show presence of a semi-circle corresponding to the grain boundary resistance and hence shows that the conductivity takes place largely through grain boundaries.

Use of microstructure control to toughen ferritic steels for cryogenic use. I. Fe--Ni steels

International Nuclear Information System (INIS)

Syn, C.K.; Jin, S.; Morris, J.W. Jr.

1976-12-01

Alternation of austenitization and austenite + ferrite two-phase decomposition treatment in a cyclic thermal treatment allows the achievement of ultra-fine grain size in steels containing 8-12% Ni. The grain refinement leads to a substantial improvement in cryogenic mechanical properties. The ductile-brittle transition temperature of a ferritic Fe-12Ni-0.25Ti alloy was suppressed to below liquid helium temperature by this grain refinement procedure; the transition temperature of commercial ''9Ni'' cryogenic steel was similarly reduced by combining the grain refinement with a final temper which introduces a small admixture of retained austenite

Characterization and Modeling of Grain Boundary Chemistry Evolution in Ferritic Steels under Irradiation

Energy Technology Data Exchange (ETDEWEB)

Marquis, Emmanuelle [Univ. of Michigan, Ann Arbor, MI (United States); Wirth, Brian [Univ. of Tennessee, Knoxville, TN (United States); Was, Gary [Univ. of Michigan, Ann Arbor, MI (United States)

2016-03-28

Ferritic/martensitic (FM) steels such as HT-9, T-91 and NF12 with chromium concentrations in the range of 9-12 at.% Cr and high Cr ferritic steels (oxide dispersion strengthened steels with 12-18% Cr) are receiving increasing attention for advanced nuclear applications, e.g. cladding and duct materials for sodium fast reactors, pressure vessels in Generation IV reactors and first wall structures in fusion reactors, thanks to their advantages over austenitic alloys. Predicting the behavior of these alloys under radiation is an essential step towards the use of these alloys. Several radiation-induced phenomena need to be taken into account, including phase separation, solute clustering, and radiation-induced segregation or depletion (RIS) to point defect sinks. RIS at grain boundaries has raised significant interest because of its role in irradiation assisted stress corrosion cracking (IASCC) and corrosion of structural materials. Numerous observations of RIS have been reported on austenitic stainless steels where it is generally found that Cr depletes at grain boundaries, consistently with Cr atoms being oversized in the fcc Fe matrix. While FM and ferritic steels are also subject to RIS at grain boundaries, unlike austenitic steels, the behavior of Cr is less clear with significant scatter and no clear dependency on irradiation condition or alloy type. In addition to the lack of conclusive experimental evidence regarding RIS in F-M alloys, there have been relatively few efforts at modeling RIS behavior in these alloys. The need for predictability of materials behavior and mitigation routes for IASCC requires elucidating the origin of the variable Cr behavior. A systematic detailed high-resolution structural and chemical characterization approach was applied to ion-implanted and neutron-irradiated model Fe-Cr alloys containing from 3 to 18 at.% Cr. Atom probe tomography analyses of the microstructures revealed slight Cr clustering and segregation to dislocations and

A study of manufacturing tubes with nano/ultrafine grain structure by stagger spinning

International Nuclear Information System (INIS)

Xia, Qinxiang; Xiao, Gangfeng; Long, Hui; Cheng, Xiuquan; Yang, Baojian

2014-01-01

Highlights: • Proposing a method of manufacturing tubes with nano/ultrafine crystal. • Obtaining the refined ferritic grains with an size of 500 nm after stagger spinning. • Obtaining the equiaxial ferritic grains with an size of 600 nm after annealing. - Abstract: A new method of manufacturing tubes with nano/ultrafine grain structure by stagger spinning and recrystallization annealing is proposed in this study. Two methods of the stagger spinning process are developed, the corresponding macroforming quality, microstructural evolution and mechanical properties of the spun tubes made of ASTM 1020 steel are analysed. The results reveal that a good surface smoothness and an improved spin-formability of spun parts can be obtained by the process combining of 3-pass spinning followed by a 580 °C × 0.5 h static recrystallization and 2-pass spinning with a 580 °C × 1 h static recrystallization annealing under the severe thinning ratio of wall thickness reduction. The ferritic grains with an average initial size of 50 μm are refined to 500 nm after stagger spinning under the 87% thinning ratio of wall thickness reduction. The equiaxial ferritic grains with an average size of 600 nm are generated through re-nucleation and grain growth by subsequent recrystallization annealing at 580 °C for 1 h heat preservation. The tensile strength of spun tubes has been founded to be proportional to the reciprocal of layer spacing of pearlite (LSP), and the elongation is inversely proportional to the reciprocal of LSP. This study shows that the developed method of stagger power spinning has the potential to be used to manufacture bulk metal components with nano/ultrafine grain structure

Modeling of kinetics of isothermal idiomorphic ferrite formation in a medium carbon vanadium-titanium microalloyed steel

International Nuclear Information System (INIS)

Capdevila, C.; Caballer, E. G.; Garcia de Andres, C.

2002-01-01

A theoretical model is presented in this work to calculate the evolution of isothermal austenite-to-idiomorphic ferrite transformation in a medium carbon vanadium-titanium microalloyed steel. This model has been developed on the basis of the study of the nucleation and growth kinetics of idiomorphic ferrite, considering the influence of the nature, size and distribution of the inclusions, which are responsible of the intragranular nucleation of idiomorphic ferrite. Moreover, the influence of the austenite grain size on the isothermal decomposition of austenite in idiomorphic ferrite has been thoroughly analysed. An excellent agreement (85% in R''2) has been obtained between experimental and predicted values of volume fraction of idiomorphic ferrite. (Author) 32 refs

Effects of microstructure and CaO addition on the magnetic and mechanical properties of NiCuZn ferrites

Energy Technology Data Exchange (ETDEWEB)

Wang, Sea-Fue, E-mail: sfwang@ntut.edu.tw; Hsu, Yung-Fu; Liu, Yi-Xin; Hsieh, Chung-Kai

2015-11-15

In this study, the effects of grain size and the addition of CaCO{sub 3} on the magnetic and mechanical properties of Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics were investigated. The bending strength of the ferrites increased from 66 to 84 MPa as the grain size of the sintered ceramics decreased from 10.25 μm to 7.53 μm, while the change in hardness was insignificant. The addition of various amounts of CaCO{sub 3} densified the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramics at 1075 °C. In the pure Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic, second phase CuO was segregated at the grain boundaries. With the CaCO{sub 3} content ≥1.5 wt%, a small amount of discrete plate-like second phase Fe{sub 2}CaO{sub 4} was observed, together with the disappearance of the second phase CuO. The grain size of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic dropped from 7.80 μm to 4.68 μm, and the grain size distribution widened as the CaCO{sub 3} content increased from 0 to 5 wt%. Initially rising to 807 after CaCO{sub 3} addition up to 2.0 wt%, due to a reduced grain size, the Vickers hardness began to drop as the CaCO{sub 3} content increased. The bending strength grew linearly with the CaCO{sub 3} content and reached twice the value for the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic with an addition of 5.0 wt% CaCO{sub 3}. The initial permeability of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic decreased substantially from 402 to 103 as the addition of CaCO{sub 3} in ferrite increased from 0 to 5 wt%, and the quality factor of the Ni{sub 0.5}Cu{sub 0.3}Zn{sub 0.2}Fe{sub 2}O{sub 4} ceramic was maximized at 95 for 1.0 wt% CaCO{sub 3} addition. - Highlights: • Effects of grain size and CaCO{sub 3} on the properties of NiCuZn ferrite were studied. • Bending strength increased with grain size of the ferrite but not in the hardness. • Bending strength reached a twice value for

A revisited Johnson-Mehl-Avrami-Kolmogorov model and the evolution of grain-size distributions in steel

OpenAIRE

Hömberg, D.; Patacchini, F. S.; Sakamoto, K.; Zimmer, J.

2016-01-01

The classical Johnson-Mehl-Avrami-Kolmogorov approach for nucleation and growth models of diffusive phase transitions is revisited and applied to model the growth of ferrite in multiphase steels. For the prediction of mechanical properties of such steels, a deeper knowledge of the grain structure is essential. To this end, a Fokker-Planck evolution law for the volume distribution of ferrite grains is developed and shown to exhibit a log-normally distributed solution. Numerical parameter studi...

Grain boundary engineering for structure materials of nuclear reactors

Science.gov (United States)

Tan, L.; Allen, T. R.; Busby, J. T.

2013-10-01

Grain boundary engineering (GBE), primarily implemented by thermomechanical processing, is an effective and economical method of enhancing the properties of polycrystalline materials. Among the factors affecting grain boundary character distribution, literature data showed definitive effect of grain size and texture. GBE is more effective for austenitic stainless steels and Ni-base alloys compared to other structural materials of nuclear reactors, such as refractory metals, ferritic and ferritic-martensitic steels, and Zr alloys. GBE has shown beneficial effects on improving the strength, creep strength, and resistance to stress corrosion cracking and oxidation of austenitic stainless steels and Ni-base alloys.

Role of grain boundary engineering in the SCC behavior of ferritic-martensitic alloy HT-9

International Nuclear Information System (INIS)

Gupta, G.; Ampornrat, P.; Ren, X.; Sridharan, K.; Allen, T.R.; Was, G.S.

2007-01-01

This paper focuses on the role of grain boundary engineering (GBE) in stress corrosion cracking (SCC) of ferritic-martensitic (F-M) alloy HT-9 in supercritical water (SCW) at 400 deg. C and 500 deg. C. Constant extension rate tensile (CERT) tests were conducted on HT-9 in as-received (AR) and coincident site lattice enhanced (CSLE) condition. Both unirradiated and irradiated specimens (irradiated with 2 MeV protons at 400 deg. C and 500 deg. C to a dose of 7 dpa) were tested. Ferritic-martensitic steel HT-9 exhibited intergranular stress corrosion cracking when subjected to CERT tests in an environment of supercritical water at 400 deg. C and 500 deg. C and also in an inert environment of argon at 500 deg. C. CSL-enhancement reduces grain boundary carbide coarsening and cracking susceptibility in both the unirradiated and irradiated condition. Irradiation enhanced coarsening of grain boundary carbides and cracking susceptibility of HT-9 for both the AR and CSLE conditions. Intergranular (IG) cracking of HT-9 results likely from fracture of IG carbides and seems consistent with the mechanism that coarser carbides worsen cracking susceptibility. Oxidation in combination with wedging stresses is the likely cause of the observed environmental enhancement of high temperature IG cracking in HT-9

Development of a new ultrafine grained dual phase steel and examination of the effect of grain size on tensile deformation behavior

Energy Technology Data Exchange (ETDEWEB)

Saeidi, N., E-mail: navidsae@gmail.com; Ashrafizadeh, F.; Niroumand, B.

2014-04-01

Ultrafine grained dual phase (DP) steels are among the newest grades of DP steels that incorporate the uniform distribution of fine martensite particles (in the order of 1–2 μm) within a ferrite matrix. These new grades of steels have been developed in response to the world's demand for decreasing the fuel consumption in automobiles by increasing the strength to weight ratio. In the present research, a new kind of ultrafine grained DP (UFG-DP) steel with an average grain size of about 2 μm as well as a coarse grained DP (CG-DP) steel with an average grain size of about 5.4 μm was produced by consecutive intercritical annealing and cold rolling of low carbon AISI 8620 steel. The martensite volume fraction for both microstructures was the same and about 50 percent. Scanning electron microscopy (SEM) microstructural examination and room temperature tensile deformation analyses were performed on both UFG-DP and CG-DP steels and their deformation behavior in terms of strength, elongation and strain hardening was studied and compared. Room-temperature uniaxial tensile tests revealed that for a given martensite volume fraction, yield and tensile strengths were not very sensitive to martensite morphology. However, uniform and total elongation values were noticeably affected by refining martensite particles. The higher plasticity of fine martensite particles as well as the more uniform strain distribution within the UFG-DP microstructure resulted in higher strain hardenability and, finally, the higher ductility of the UFG-DP steel.

Grain-size sorting and slope failure in experimental subaqueous grain flows

NARCIS (Netherlands)

Kleinhans, M.G.; Asch, Th.W.J. van

2005-01-01

Grain-size sorting in subaqueous grain flows of a continuous range of grain sizes is studied experimentally with three mixtures. The observed pattern is a combination of stratification and gradual segregation. The stratification is caused by kinematic sieving in the grain flow. The segregation is

Annealing effect on the microstructure and magnetic properties of 14%Cr-ODS ferritic steel

International Nuclear Information System (INIS)

Ding, H.L.; Gao, R.; Zhang, T.; Wang, X.P.; Fang, Q.F.; Liu, C.S.

2015-01-01

Graphical abstract: TEM images of microstructure for 14%Cr-ODS ferritic steel annealed for 2 h at different temperatures: (a) 600 °C, (b) 800 °C, (c) 950 °C, and (d) 1150 °C, and the evolution trends of coercivity field (H_C) and Vickers microhardness for samples annealed at above temperatures for 2 h and 50 h. - Highlights: • The thermal stability of annealed 14%Cr-ODS ferritic steel was investigated. • The particle size keeps fairly constant with increasing annealing temperature. • The grain size is still 2–4 μm even after annealing for 50 h at 1150 °C. • The hardness and H_C are almost unchanged after annealing from 800 °C to 1150 °C. - Abstract: The microstructure and magnetic properties of the 14%Cr oxide dispersion strengthened (ODS) ferritic steel fabricated by sol–gel and HIP method were investigated by annealing in vacuum for 2 h (at 300, 600, 800, 950 and 1150 °C) and 50 h (at 600, 800, 950 and 1150 °C). Microstructure analysis shows that as the annealing temperature increases, the size of oxide nanoparticles becomes smaller and their dispersion in matrix becomes more homogeneous. Grain size remains stable when the annealing temperature is below 800 °C, while above 800 °C, grain size grows with the increasing annealing temperature and time. The Vickers microhardness and coercivity (H_C) display almost similar evolution trend with annealing temperature for 2 h and 50 h. No obvious recrystallization appears after 1150 °C annealing, which indicates the high microstructural stability of 14%Cr-ODS ferritic steel. The possible mechanism for above behaviors is discussed in this paper.

The effect of heating conditions on the properties of nano- and microstructured Ni-Zn ferrite

Energy Technology Data Exchange (ETDEWEB)

Sutka, A; Mezinskis, G [Institute of Silicate Materials, Riga Technical University, Azenes 14/24, LV-1048 (Latvia); Gross, K A [Department of Materials Engineering, Monash University, VIC 3168 (Australia); Bebris, G [State Forensic Science Bureau, Hospitalu 55, LV-1013 (Latvia); Knite, M, E-mail: andris.sutka@rtu.l [Institute of Technical Physics, Riga Technical University, Azenes 14/24, LV-1048 (Latvia)

2011-02-15

The structural, microstructural and morphological, as well as electric and dielectric, properties of nickel-zinc ferrite (Ni{sub 0.3}Zn{sub 0.7}Fe{sub 2}O{sub 4}) derived from sol-gel auto-combustion have been studied after sintering from 900 to 1300 deg. C. The effect of heating rate has not been previously investigated and is reported here. X-ray diffraction showed a pure cubic spinel after calcination. Atomic force microscopy revealed nanosized particles after calcination, but scanning electron microscopy showed nanosized grains after sintering at 900 deg. C. The heating rate has a marked effect on oxidation of Fe{sup 3+} to Fe{sup 2+}, showing an additional approach to control charge carrier concentration in Ni-Zn ferrites (powder and monoliths). The heating rate also influences the average particle size and distribution. Grain size and resistivity of sintered pellets do not show significant change with heating rate, proving that resistivity is mainly dictated by the number of grain boundaries. The dielectric loss tangent curves at room temperature exhibit dielectric relaxation peaks attributed to the similarity in frequency of charge hopping between the localized charge states and external fields. The relaxation peak shifts to higher frequencies for ferrites with nanosized grains.

Magnetic properties of nanostructured spinel ferrites and ...

Indian Academy of Sciences (India)

exchange interaction strength because of an increase in the magnetic ion concentration in the A-site on milling, ... By using a copper wheel, rotating with the ... Zn ferrite with a small applied field of 4 mT for two different grain sizes. The Néel ... By varying the concentration of the oxidant (KNO3) or ferric ions, we could achieve.

Influence of particle size on the magnetic spectrum of NiCuZn ferrites for electromagnetic shielding applications

Energy Technology Data Exchange (ETDEWEB)

Wu, Xiaohan; Yan, Shuoqing; Liu, Weihu [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Feng, Zekun, E-mail: fengzekun@mail.hust.edu.cn [School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, Hubei (China); Chen, Yajie; Harris, Vincent G. [Center for Microwave Magnetic Materials and Integrated Circuits, and Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115 (United States)

2016-03-01

The effect of ferrite particle size on the magnetic spectra (1 MHz to 1 GHz) of NiCuZn polycrystalline ferrites doped with Co{sub 2}O{sub 3} and Bi{sub 2}O{sub 3} were systematically investigated. The experiments indicate that the ferrite particle size tailored by grinding time and corresponding sintering temperatures is crucial to achieving high permeability, high Q-factor and low magnetic loss, at 13.56 MHz for electromagnetic shielding applications especially in the near field communication (NFC) field. It is evident that high-performance NiZnCu ferrite materials are strongly tailored by morphology and microstructure. It is conclusive that fine ferrite particles and relatively low sintering temperatures are favorable to lowering magnetic loss and enhancing permeability. This work has built a foundation for improvement of the ferrite slurry used for fabrication of large area tape-casting ferrite sheets. - Highlights: • Fine particles are favorable to lowering magnetic loss and enhancing permeability.

Effect of neutron irradiation on mechanical properties of ferritic steels

International Nuclear Information System (INIS)

Kass, S.B.; Murty, K.L.

1995-01-01

Effect of neutron radiation exposure was investigated in various ferritic steels with the main emphasis being the effects of thermal neutrons on radiation hardening. Pure iron of varied grain sizes was also used for characterizing the grain size effects on the source hardening before and after neutron irradiation. While many steels are considered in the overall study, the results on 1020, A516 and A588 steels are emphasized. Radiation hardening due to fast neutrons was seen to be sensitive to the composition of the steels with A354 being the least resistant and A490 the least sensitive. Majority of the radiation hardening stems from friction hardening, and source hardening term decreased with exposure to neutron radiation apparently due to the interaction of interstitial impurities with radiation produced defects. Inclusion of thermal neutrons along with fast resulted in further decrease in the source hardening with a slight increase in the friction hardening which revealed a critical grain size below which exposure to total (fast and thermal) neutron spectrum resulted in a slight reduction in the yield stress compared to the exposure to only fast neutrons. This is the first time such a grain size effect is reported and this is shown to be consistent with known radiation effects on friction and source hardening terms along with the observation that low energy neutrons have a nonnegligible effect on the mechanical properties of steels. In ferritic steels, however, despite their small grain size, exposure to total neutron spectrum yielded higher strengths than exposure to only fast neutrons. This behavior is consistent with the fact that the source hardening is small in these alloys and radiation effect is due only to friction stress

Carpel size, grain filling, and morphology determine individual grain weight in wheat

OpenAIRE

Xie, Quan; Mayes, Sean; Sparkes, Debbie L.

2015-01-01

Individual grain weight is a major yield component in wheat. To provide a comprehensive understanding of grain weight determination, the carpel size at anthesis, grain dry matter accumulation, grain water uptake and loss, grain morphological expansion, and final grain weight at different positions within spikelets were investigated in a recombinant inbred line mapping population of bread wheat (Triticum aestivum L.)?spelt (Triticum spelta L.). Carpel size, grain dry matter and water accumulat...

Methods of assessing grain-size distribution during grain growth

DEFF Research Database (Denmark)

Tweed, Cherry J.; Hansen, Niels; Ralph, Brian

1985-01-01

This paper considers methods of obtaining grain-size distributions and ways of describing them. In order to collect statistically useful amounts of data, an automatic image analyzer is used, and the resulting data are subjected to a series of tests that evaluate the differences between two related...... distributions (before and after grain growth). The distributions are measured from two-dimensional sections, and both the data and the corresponding true three-dimensional grain-size distributions (obtained by stereological analysis) are collected. The techniques described here are illustrated by reference...

Grain dissection as a grain size reducing mechanism during ice microdynamics

Science.gov (United States)

Steinbach, Florian; Kuiper, Ernst N.; Eichler, Jan; Bons, Paul D.; Drury, Martin R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-04-01

Ice sheets are valuable paleo-climate archives, but can lose their integrity by ice flow. An understanding of the microdynamic mechanisms controlling the flow of ice is essential when assessing climatic and environmental developments related to ice sheets and glaciers. For instance, the development of a consistent mechanistic grain size law would support larger scale ice flow models. Recent research made significant progress in numerically modelling deformation and recrystallisation mechanisms in the polycrystalline ice and ice-air aggregate (Llorens et al., 2016a,b; Steinbach et al., 2016). The numerical setup assumed grain size reduction is achieved by the progressive transformation of subgrain boundaries into new high angle grain boundaries splitting an existing grain. This mechanism is usually termed polygonisation. Analogue experiments suggested, that strain induced grain boundary migration can cause bulges to migrate through the whole of a grain separating one region of the grain from another (Jessell, 1986; Urai, 1987). This mechanism of grain dissection could provide an alternative grain size reducing mechanism, but has not yet been observed during ice microdynamics. In this contribution, we present results using an updated numerical approach allowing for grain dissection. The approach is based on coupling the full field theory crystal visco-plasticity code (VPFFT) of Lebensohn (2001) to the multi-process modelling platform Elle (Bons et al., 2008). VPFFT predicts the mechanical fields resulting from short strain increments, dynamic recrystallisation process are implemented in Elle. The novel approach includes improvements to allow for grain dissection, which was topologically impossible during earlier simulations. The simulations are supported by microstructural observations from NEEM (North Greenland Eemian Ice Drilling) ice core. Mappings of c-axis orientations using the automatic fabric analyser and full crystallographic orientations using electron

Grain size dependence of wear in ceramics

International Nuclear Information System (INIS)

Wu, C.C.; Rice, R.W.; Johnson, D.; Platt, B.A.

1985-01-01

Pin-On-Disk (POD), microwear tests of Al 2 O 3 , MgO, MgAl 2 O 4 , and ZrO 2 , most being dense and essentially single phase, showed the reciprocal of wear following a hall-petch type relationship. However, extrapolation to infinite grain size always gave a lower intercept than most or all single-crystal values; in particular, Al 2 O 3 data projects to a negative intercept. Initial macro wear tests of some of the same Al 2 O 3 materials also indicate a hall-petch type grain-size dependence, but with a greatly reduced grain-size dependence, giving a positive hall-petch intercept. Further, the macrowear grain-size dependence appears to decrease with increased wear. It is argued that thermal expansion anisotropy (of Al 2 O 3 ) significantly affects the grain size dependence of POD wear, in particular, giving a negative intercept, while elastic anisotropy is suggested as a factor in the grain-size dependence of the cubic (MgO, MgAl 2 O 4 , and ZrO 2 ) materials. The reduced grain-size dependence in the macrowear tests is attributed to overlapping wear tracks reducing the effects of enhanced wear damage, e.g., from elastic and thermal expansion anisotropies

Effect of alloying element partitioning on ferrite hardening in a low alloy ferrite-martensite dual phase steel

Energy Technology Data Exchange (ETDEWEB)

Ebrahimian, A., E-mail: ebrahimiana@yahoo.com; Ghasemi Banadkouki, S.S.

2016-11-20

In this paper, the effect of carbon and other alloying elements partitioning on ferrite hardening behavior were studied in details using a low alloy AISI4340 ferrite-martensite dual phase (DP) steel. To do so, various re-austenitised samples at 860 °C for 60 min were isothermally heated at 650 °C from 3 to 60 min and then water–quenched to obtain the final ferrite-martensite DP microstructures containing different ferrite and martensite volume fractions. Light and electron microscopic observations were supplemented with electron dispersive spectroscopy (EDS) and nanoindentation tests to explore the localized compositional and hardening variations within ferrite grains in DP samples. The experimental results showed that the ferrite hardness was varied with progress of austenite to ferrite phase transformation in DP samples. In the case of a particular ferrite grain in a particular DP sample, despite a homogeneous distribution of carbon concentration, the ferrite hardness was significantly increased by increasing distance from the central location toward the interfacial α/γ areas. Beside a considerable influence of martensitic phase transformation on adjacent ferrite hardness, these results were rationalized in part to the significant level of Cr and Mo pile-up at α/γ interfaces leading to higher solid solution hardening effect of these regions. The reduction of potential energy developed by attractive interaction between C-Cr and C-Mo couples toward the carbon enriched prior austenite areas were the dominating driving force for pile-up segregation.

Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

International Nuclear Information System (INIS)

Milasin, N.

1964-05-01

Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, σ y =σ i +k y d -1/2 between lower yield stress, σ y , and grain size, 2d, the information about the effect of irradiation on the parameters σ i and k y is obtained. Taking as a base interpretation of σ i and k y given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of the experimental results obtained the relative microstructure and

Grain size refinement of inconel 718 thermomechanical processing

International Nuclear Information System (INIS)

Okimoto, P.C.

1988-01-01

Inconel 718 is a Ni-Fe precipitation treated superalloy. It presents good thermal fatigue properties when the material has small grain size. The aim of this work is to study the grain size refinement by thermomechanical processing, through observations of the microstructural evolution and the influence of some of the process variables in the final grain size. The results have shown that this refinement occured by static recrystallization. The presence of precipitates have influenced the final grain size if the deformations are below 60%. For greater deformations the grain size is independent of the precipitate distribution in the matrix and tends to a limit size of 5 μm. (author)

Interlinking backscatter, grain size and benthic community structure

Science.gov (United States)

McGonigle, Chris; Collier, Jenny S.

2014-06-01

The relationship between acoustic backscatter, sediment grain size and benthic community structure is examined using three different quantitative methods, covering image- and angular response-based approaches. Multibeam time-series backscatter (300 kHz) data acquired in 2008 off the coast of East Anglia (UK) are compared with grain size properties, macrofaunal abundance and biomass from 130 Hamon and 16 Clamshell grab samples. Three predictive methods are used: 1) image-based (mean backscatter intensity); 2) angular response-based (predicted mean grain size), and 3) image-based (1st principal component and classification) from Quester Tangent Corporation Multiview software. Relationships between grain size and backscatter are explored using linear regression. Differences in grain size and benthic community structure between acoustically defined groups are examined using ANOVA and PERMANOVA+. Results for the Hamon grab stations indicate significant correlations between measured mean grain size and mean backscatter intensity, angular response predicted mean grain size, and 1st principal component of QTC analysis (all p PERMANOVA for the Hamon abundance shows benthic community structure was significantly different between acoustic groups for all methods (p ≤ 0.001). Overall these results show considerable promise in that more than 60% of the variance in the mean grain size of the Clamshell grab samples can be explained by mean backscatter or acoustically-predicted grain size. These results show that there is significant predictive capacity for sediment characteristics from multibeam backscatter and that these acoustic classifications can have ecological validity.

Magnetic and electrical properties of the La doped Mn-Zn ferrite nanoparticles synthesized by the co-precipitation method

International Nuclear Information System (INIS)

Chandel, Vipin; Vijeta; Thakur, Atul; Thakur, Preeti

2013-01-01

In the present study, nano crystalline Mn-Zn-La ferrite with chemical formula Mn 0.4 Zn 0.6 La 0.3 Fe 1.7 O 4 was successfully synthesized by a co-precipitation method. The prepared powders were presintered at 700℃. The pallets formed were finally sintered at 700℃, 800℃ and 900℃ for 3h reach. The structural and morphological behavior was investigated by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD confirms the formation of the expected spinel structure. Scanning Electron Microscopy (SEM) was used to characterize the microstructure of the ferrite samples i.e. grain morphology, grain size, grain size distribution and shape. Fourier transform infrared spectroscopy (FTIR) confirms the peaks of different molecules in the given sample. Electrical and magnetic properties were studied by using dc resistivity set up and vibrating sample magnetometer (VSM). (author)

Lithium ferrite: The study on magnetic and complex permittivity characteristics

Directory of Open Access Journals (Sweden)

Madhavaprasad Dasari

2017-03-01

Full Text Available Lithium ferrite (Li0.5Fe2.5O4 powder was prepared by solid state reaction method, which was finally pressed and sintered at 1150 °C. The spinel structure of the lithium ferrite was confirmed by X-ray diffraction and grain size estimation was obtained from scanning electron microscope (SEM. Fourier transform infrared spectroscopy (FTIR confirmed the presence of primary and secondary absorption bands characteristic for spinel structure. The force constants were estimated using absorption bands for the lithium ferrite. Magnetization and dielectric studies were carried out for the sintered sample. Saturation magnetization (Ms of 59.6 emu/g was achieved and variation of magnetization with temperature was used to identify the Curie temperature. The complex permittivity (ε∗ for the lithium ferrite sample was obtained for wide frequency range up to 3 GHz and discussed based on available models. The Curie temperature was estimated around 480 °C and verified from both magnetization versus temperature and dielectric constant versus temperature measurements.

Tsunami sediments and their grain size characteristics

Science.gov (United States)

Sulastya Putra, Purna

2018-02-01

Characteristics of tsunami deposits are very complex as the deposition by tsunami is very complex processes. The grain size characteristics of tsunami deposits are simply generalized no matter the local condition in which the deposition took place. The general characteristics are fining upward and landward, poor sorting, and the grain size distribution is not unimodal. Here I review the grain size characteristics of tsunami deposit in various environments: swale, coastal marsh and lagoon/lake. Review results show that although there are similar characters in some environments and cases, but in detail the characteristics in each environment can be distinguished; therefore, the tsunami deposit in each environment has its own characteristic. The local geological and geomorphological condition of the environment may greatly affect the grain size characteristics.

OKMC study of the effect of grain boundaries in martensitic Fe-Cr-C alloys

International Nuclear Information System (INIS)

Chiapetto, M.; Becquart, C.S.; Malerba, L.

2015-01-01

Fe-Cr-C alloys with chromium concentrations in the range from about 2 wt % to 12 wt % form ferritic-martensitic structures by rapid cooling from the austenite state already in the presence of relatively low carbon concentrations. In this process it is possible to obtain different ratios of ferrite and martensite, as well as formation of carbides, by varying the thermal treatment. The presence of ferrite or martensite might have an influence on the nano-structural evolution under irradiation of these alloys. Here, considering a tempered martensite reference alloy with 9% Cr, we make use of an already validated object kinetic Monte Carlo (OKMC) model in order to study the possible effect of the formation of martensite laths on the material nano-structural evolution under neutron irradiation, assuming that the relevant boundaries act as sinks for radiation defects. The results show that the reduction of the grain size (including in this definition the average size of prior austenite grains, blocks and laths) does not play any relevant role until sizes of the order of about 0.5 μm are reached: for smaller grains the number of defects being absorbed by the boundaries becomes dominant. However, this threshold is lower than the experimentally observed martensite lath dimensions, thereby suggesting that what makes the difference in martensitic Fe-Cr-C alloys with respect to ferrite concerning events and mechanisms taking place during irradiation are not the lath boundaries as sinks. Differences between the nano-structural evolution in ferrite and martensite should therefore be ascribed to other factors. This document is composed of an article and the presentation slides. (authors)

Effect of zirconium addition on the microstructure and mechanical properties of 15Cr-ODS ferritic Steels consolidated by hot isostatic pressing

Energy Technology Data Exchange (ETDEWEB)

Xu, Haijian, E-mail: haijianxu@eis.hokudai.ac.jp [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China); Material Science and Engineering, Faculty of Engineering, Hokkaido University, Sapporo 060-8628 (Japan); Lu, Zheng; Wang, Dongmei; Liu, Chunming [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China)

2017-01-15

The influence of Zr addition on the microstructure and mechanical properties of mechanically alloyed (MA) ODS ferritic steels were studied in this work. The microstructure characteristics included the grain size, oxide particles number densities, size distributions, crystal structures and compositions. TEM foils measurements were complemented by studies of alloys on carbon extraction replica and focus ion beam (FIB) foils. The tensile properties were carried out at different temperatures. The microstructure and mechanical properties were analyzed and compared with nominal compositions (wt.%): Fe-15Cr-2W-0.3Y{sub 2}O{sub 3} and Fe-15Cr −2W-0.3Zr-0.3Y{sub 2}O{sub 3}. The experimental revealed that the addition of Zr increased the volume fraction of the smallest and equiaxed ferritic grains, number density of nano-oxide particles and decreased the average size of oxide particles within the ferritic matrix, promoting the formation of fine trigonal δ-phase Y{sub 4}Zr{sub 3}O{sub 12} nano-oxides and leading to the enhancement of the mechanical properties of the ODS steels.

Intragranular ferrite morphologies in medium carbon vanadium-microalloyed steel

Directory of Open Access Journals (Sweden)

Fadel A.

2013-01-01

Full Text Available The aim of this work was to determine TTT diagram of medium carbon V-N micro-alloyed steel with emphasis on the development of intragranular ferrite morphologies. The isothermal treatment was carried out at 350, 400, 450, 500, 550 and 600°C. These treatments were interrupted at different times in order to analyze the evolution of the microstructure. Metallographic evaluation was done using optical and scanning electron microscopy (SEM. The results show that at high temperatures (≥ 500°C polygonal intragranulary nucleated ferrite idiomorphs, combined with grain boundary ferrite and pearlite were produced and followed by an incomplete transformation phenomenon. At intermediate temperatures (450, 500°C an interloced acicular ferrite (AF microstructure is produced, and at low temperatures (400, 350°C the sheave of parallel acicular ferrite plates, similar to bainitic sheaves but intragranularly nucleated were observed. In addition to sheaf type acicular ferrite, the grain boundary nucleated bainitic sheaves are observed. [Projekat Ministartsva nauke Republike Srbije, br. OI174004

A Rare Allele of GS2 Enhances Grain Size and Grain Yield in Rice.

Science.gov (United States)

Hu, Jiang; Wang, Yuexing; Fang, Yunxia; Zeng, Longjun; Xu, Jie; Yu, Haiping; Shi, Zhenyuan; Pan, Jiangjie; Zhang, Dong; Kang, Shujing; Zhu, Li; Dong, Guojun; Guo, Longbiao; Zeng, Dali; Zhang, Guangheng; Xie, Lihong; Xiong, Guosheng; Li, Jiayang; Qian, Qian

2015-10-05

Grain size determines grain weight and affects grain quality. Several major quantitative trait loci (QTLs) regulating grain size have been cloned; however, our understanding of the underlying mechanism that regulates the size of rice grains remains fragmentary. Here, we report the cloning and characterization of a dominant QTL, grain size on chromosome 2 (GS2), which encodes Growth-Regulating Factor 4 (OsGRF4), a transcriptional regulator. GS2 localizes to the nucleus and may act as a transcription activator. A rare mutation of GS2 affecting the binding site of a microRNA, OsmiR396c, causes elevated expression of GS2/OsGRF4. The increase in GS2 expression leads to larger cells and increased numbers of cells, which thus enhances grain weight and yield. The introduction of this rare allele of GS2/OsGRF4 into rice cultivars could significantly enhance grain weight and increase grain yield, with possible applications in breeding high-yield rice varieties. Copyright © 2015 The Author. Published by Elsevier Inc. All rights reserved.

Grain size measurements by ultrasonic Rayleigh surface waves

International Nuclear Information System (INIS)

Palanichamy, P.; Jayakumar, T.

1996-01-01

The use of Rayleigh surface waves to determine average grain size nondestructively in an austenitic stainless steel AISI type 316 stainless is discussed. Two commercial type 4MHz frequency surface wave transducers, one as transmitter and the other as receiver were employed for the measurement of surface wave amplitudes. Relative amplitudes of the Rayleigh surface waves were correlated with the metallographically obtained grain sizes. Results indicate that surface/sub-surface average grain sizes of AISI type 316 austenitic stainless steel can be estimated with a confidence level of more than 80% in the grain size range 30-170 μm. (author)

The Influence of the Induced Ferrite and Precipitates of Ti-bearing Steel on the Ductility of Continuous Casting Slab

Science.gov (United States)

Qian, Guoyu; Cheng, Guoguang; Hou, Zibing

2015-11-01

In order to investigate the loss of the ductility of Ti-bearing ship plate steel under 1000 °C, where the ductility begins to reduce rapidly, so the hot ductility of Ti-bearing ship plate steel has been obtained using the Gleeble 1500 thermal-mechanical simulator and also the studies about the effect of grain boundary ferrite films and precipitates containing Ti on the ductility has been carried out. The result showed that the TiN particles precipitating at 950 °C with a larger size and smaller volume fraction cannot effectively suppress the occurrence of recrystallization and the ductility still retains at a high level, although R.A. value presents a certain degree of decline compared with 1000 °C. A large number of smaller Ti(C,N) particles precipitate at 900 °C and can induce the formation of a very small amount of fine grain boundary ferrite, which deteriorates the adhesion strength of the grain boundary, so the R.A. value rapidly reduces to less than 50%. When the temperature falls to close Ae3 (827 °C), the amount of the grain boundary ferrite films increase due to the ferrite phase transformation, but the ferrite film thickness becomes more uneven at the same time, which results in the increase of strain concentration and plays a leading role in causing the decrease of ductility, so the R.A. value has been kept less than 40% as the temperature cooling to 800 °C from 850 °C. When the temperature further decreases, the ductility starts to recover due to the increase of average ferrite film thickness to a greater degree which greatly reduces the strain concentration of the grain boundary.

Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks

Energy Technology Data Exchange (ETDEWEB)

Milasin, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

1964-05-15

Irradiation hardening of steel for reactor pressure vessels has been studied extensively during the past few years. A great number of experimental results concerning the behaviour of these steels in the radiation field and several review papers (1,2) have been published. Most of the papers deal with the effects of specific metallurgical factors or irradiation conditions (temperature, flux) on irradiation hardening and embrittlement. In addition, a number of experiments are performed to give evidence on the mechanism of irradiation hardening of these steels. However, this mechanism is still unknown due to the complexity of steel as a system. Among different methods used in radiation damage studies, the changes of mechanical properties have been mainly investigated. By using Hall-Petch's empirical relation, {sigma}{sub y}={sigma}{sub i}+k{sub y} d{sup -1/2} between lower yield stress, {sigma}{sub y}, and grain size, 2d, the information about the effect of irradiation on the parameters {sigma}{sub i} and k{sub y} is obtained. Taking as a base interpretation of {sigma}{sub i} and k{sub y} given by Petch and his co-workers it has been concluded that radiation does not change the stress to start slip but that it increase the friction that opposes the passage of free dislocations across a slip plane. In attempting to apply Hall-Petch's relation to one unirradiated ferritic steel with a carbon content higher than 0.15% some difficulties were encountered. The results obtained indicate that the influence of grain size can not be isolated from other factors introduced by the treatments used to produce different grain sizes. This paper deals with a similar problem in the case of irradiated steel. The results obtained give the changes of the mechanical properties of steel in neutron irradiation field as a function of microstructure and grain size. In addition, the mechanical properties of irradiated steel are measured after annealing at 150 deg C and 450 deg C. On the basis of

Structure and electromagnetic properties of NiZn spinel ferrite with nano-sized ZnAl{sub 2}O{sub 4} additions

Energy Technology Data Exchange (ETDEWEB)

Zheng, Zongliang, E-mail: zzlma@163.com; Zhang, Huaiwu; Yang, Qinghui; Jia, Lijun

2015-11-05

In this study, nanocrystalline ZnAl{sub 2}O{sub 4} (ZA) (x = 0–20 wt%) were introduced into Ni{sub 0.4}Zn{sub 0.6}Fe{sub 2}O{sub 4} ferrite (NZ) by a solid-state reaction method combining a sol–gel auto-combustion method. The effects of ZA addition on the crystalline phase formation, microstructures, magnetic and dielectric properties were systematically investigated. X-ray diffraction and scanning electron microscope results reveal that the added ZA can fully solve into the NZ to form a ceramic with single-phase cubic spinel structure, and the grain size decreases obviously as x > 5 wt%. Meanwhile, the magnetic and dielectric properties exhibit significantly dependent on the ZA addition content. With the increasing addition level of ZA from 0 to 20 wt%, the initial permeability μ{sub i} is found increased initially and then decreased with the maximum 679 at x = 0.5 wt%. For the samples with x ≤ 5 wt%, permittivity ε′ is relatively higher at low frequencies (ε′ = 91–138 at 1 MHz) and dielectric loss tan δ{sub ε} shows distinct peak behavior. When x reaches 10 wt%, however, the ε′ and tan δ{sub ε} show very stable spectra from 1 MHz to 1 GHz. - Highlights: • Various amount of nanocrystalline ZnAl{sub 2}O{sub 4} (ZA) were introduced into NiZn ferrite. • NiZn ferrite can form single-phase spinel ceramic materials with ZA additives. • ZA has significant effects on magnetic and dielectric properties of the ceramics. • It provides a new method for fabricating NiZn ferrite with tunable properties.

Microstructure examination of Fe–14Cr ODS ferritic steels produced through different processing routes

Energy Technology Data Exchange (ETDEWEB)

Oksiuta, Z., E-mail: z.oksiuta@pb.edu.pl [Bialystok University of Technology, Mechanical Department (Poland); Hosemann, P. [University of California Berkeley, Nuclear Engineering, 4169 Etcheverry Hall, Berkeley, CA 94720 (United States); Vogel, S.C. [Los Alamos Neutron Science Center, Los Alamos National Laboratory, PO Box 1663, NM (United States); Baluc, N. [Ecole Polytechnique Fédérale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confédération Suisse, Villigen PSI 5232 (Switzerland)

2014-08-01

Various thermo-mechanical treatments were applied to refine and homogenise grain size and improve mechanical properties of hot-isostatically pressed (HIP) 14%Cr ODS ferritic steel. The grain size was reduced, improving mechanical properties, tensile strength and Charpy impact, however bimodal-like distribution was also observed. As a result, larger, frequently elongated grains with size above 1 μm and refined, equiaxed grains with a diameter ranging from 250 to 500 nm. Neutron diffraction measurements revealed that for HIP followed by hydrostatic extrusion material the strongest fiber texture was observed oriented parallel to the extrusion direction. In comparison with hot rolling and hot pressing methods, this material exhibited promising mechanical properties: the ultimate tensile strength of 1350 MPa, yield strength of 1280 MPa, total elongation of 21.7% and Charpy impact energy of 5.8 J. Inferior Charpy impact energy of ∼3.0 J was measured for HIP and hot rolled material, emphasising that parameters of this manufacturing process still have to be optimised. As an alternative manufacturing route, due to the uniform microstructure and simplicity of the process, hot pressing might be a promising method for production of smaller parts of ODS ferritic steels. Besides, the ductile-to-brittle transition temperature of all thermo-mechanically treated materials, in comparison with as-HIPped ODS steel, was improved by more than 50%, the transition temperature ranging from 50 to 70 °C (323 and 343 K) remains still unsatisfactory.

Carpel size, grain filling, and morphology determine individual grain weight in wheat.

Science.gov (United States)

Xie, Quan; Mayes, Sean; Sparkes, Debbie L

2015-11-01

Individual grain weight is a major yield component in wheat. To provide a comprehensive understanding of grain weight determination, the carpel size at anthesis, grain dry matter accumulation, grain water uptake and loss, grain morphological expansion, and final grain weight at different positions within spikelets were investigated in a recombinant inbred line mapping population of bread wheat (Triticum aestivum L.)×spelt (Triticum spelta L.). Carpel size, grain dry matter and water accumulation, and grain dimensions interacted strongly with each other. Furthermore, larger carpels, a faster grain filling rate, earlier and longer grain filling, more grain water, faster grain water absorption and loss rates, and larger grain dimensions were associated with higher grain weight. Frequent quantitative trait locus (QTL) coincidences between these traits were observed, particularly those on chromosomes 2A, 3B, 4A, 5A, 5DL, and 7B, each of which harboured 16-49 QTLs associated with >12 traits. Analysis of the allelic effects of coincident QTLs confirmed their physiological relationships, indicating that the complex but orderly grain filling processes result mainly from pleiotropy or the tight linkages of functionally related genes. After grain filling, distal grains within spikelets were smaller than basal grains, primarily due to later grain filling and a slower initial grain filling rate, followed by synchronous maturation among different grains. Distal grain weight was improved by increased assimilate availability from anthesis. These findings provide deeper insight into grain weight determination in wheat, and the high level of QTL coincidences allows simultaneous improvement of multiple grain filling traits in breeding. © The Author 2015. Published by Oxford University Press on behalf of the Society for Experimental Biology.

Structural, magnetic and dielectric investigations in antimony doped nano-phased nickel-zinc ferrites

Energy Technology Data Exchange (ETDEWEB)

Lakshmi, Ch.S. [Department of Physics, Regency Institute of Technology, Adivipolam Yanam 533464, Pondicherry (India); Sridhar, Ch.S.L.N. [Department of Physics, Vignana Bharathi Institute of Technology, Aushapur(v) Ghatkesar (M), Hyderabad 501301, Telangana (India); Govindraj, G. [Department of Physics, School of Physical, Chemical and Applied Sciences, Pondicherry University, R.V.Nagar, Kalapet, Pondicherry 605014 (India); Bangarraju, S. [Department of Physics, Andhra University, Visakhapatnam 530003, Andhrapradesh (India); Potukuchi, D.M., E-mail: potukuchidm@yahoo.com [Department of Physics, University College of Engineering, Jawaharlal Nehru Technological University:Kakinada, Kakinada 533003 (India)

2015-02-15

Nanocrystalline Ni–Zn–Sb ferrites synthesized by hydrothermal method are reported. Influence of Sb{sup 5+} ions on structural, magnetic and dielectric properties of ferrites is studied. Phase identification, lattice parameter and crystallite size studies are carried out using by X-ray diffraction (XRD). Addition of dopant resulted for decrease in lattice parameter. Crystallite size gets reduced from 62 nm to 38 nm with doping of Antimony. Crystallite size and porosity exhibit similar trends with doping. Morphological study is carried out by Field Emission Scanning Electron Microscopy (FESEM). Strong FTIR absorption bands at 400–600 cm{sup −1} confirm the formation of ferrite structure. Increase of porosity is attributed to the grain size. Doping with Antimony results for decrease in saturation magnetization and increase in coercivity. An initial increase of saturation magnetization for x=0.1 is attributed to the unusually high density. Reversed trend of coercivity with crystallite size are observed. Higher value of dielectric constant ε′(ω) is attributed to the formation of excess of Fe{sup 2+} ions caused by aliovalent doping of Sb{sup 5+} ions. Variation of dielectric constant infers hopping type of conductivity mechanism. The dielectric loss factor tanδ attains lower values of ∼10{sup −2}. High ac resistivity ρ(ω) of 10{sup 8} Ω cm is witnessed for antimony doped ferrites. Higher saturation magnetization and enhanced dielectric response directs for a possible utility as microwave oscillators and switches.

Effects of grain size and grain boundaries on defect production in nanocrystalline 3C-SiC

International Nuclear Information System (INIS)

Swaminathan, N.; Kamenski, Paul J.; Morgan, Dane; Szlufarska, Izabela

2010-01-01

Cascade simulations in single crystal and nanocrystalline SiC have been conducted in order to determine the role of grain boundaries and grain size on defect production during primary radiation damage. Cascades are performed with 4 and 10 keV silicon as the primary knock-on atom (PKA). Total defect production is found to increase with decreasing grain size, and this effect is shown to be due to increased production in grain boundaries and changing grain boundary volume fraction. In order to consider in-grain defect production, a new mapping methodology is developed to properly normalize in-grain defect production rates for nanocrystalline materials. It is shown that the presence of grain boundaries does not affect the total normalized in-grain defect production significantly (the changes are lower than ∼20%) for the PKA energies considered. Defect production in the single grain containing the PKA is also studied and found to increase for smaller grain sizes. In particular, for smaller grain sizes the defect production decreases with increasing distance from the grain boundary while for larger grain sizes the presence of the grain boundaries has negligible effect on defect production. The results suggest that experimentally observed changes in radiation resistance of nanocrystalline materials may be due to long-term damage evolution rather than changes in defect production rates from primary damage.

Grain size distributions and their effects on auto-acoustic compaction

Science.gov (United States)

Taylor, S.; Brodsky, E. E.

2013-12-01

A variety of geophysical and geomorphological processes depend on the response of granular mixtures to shear stress. For example, if shear sliding in a fault zone causes gouge to compact or dilate, this has implications on our understanding of earthquake nucleation and propagation. The behavior of granular flows has previously been found to be strongly dependent on shear rate. At relatively slow shear velocities, a granular flow will support stresses elastically through force chains in what is recognized as the 'quasi-static' regime. At relatively high shear velocities, it will support stresses by transferring momentum in higher velocity grain collisions in the 'grain-inertial' regime, which results in dilation of the flow. Recent experiments conducted using a commercial torsional rheometer found that at intermediate shear velocities, force chain collapse in angular sand samples produced sound waves capable of vibrating the shear zone enough to cause compaction. To expand on the characterization of this newly identified rheological regime, the 'auto-acoustic' regime, we used the same experimental set up to observe how volumetric and acoustic response to shear stress changes with grain size mean and range. Stepped velocity ramp experiments were conducted first on five separate grain size bins, and then on various mixtures of these grain sizes. As expected, larger grain sizes entered the mass-dependent grain-inertial regime at lower shear velocities than smaller grain sizes. Interestingly, smaller grain sizes exhibited more pronounced compaction at slower velocities resulting from the auto-acoustic regime, and the largest grain sizes showed no compaction, implying a grain size threshold for auto-acoustic compaction. In mixtures of different grain size bins, the response of the flow to intermediate shear velocities was consistent with the response of the smallest grain size bin included in the mixture, while the response of the flow to high shear velocities was most

Effects of grain size distribution on the interstellar dust mass growth

OpenAIRE

Hirashita, Hiroyuki; Kuo, Tzu-Ming

2011-01-01

Grain growth by the accretion of metals in interstellar clouds (called `grain growth') could be one of the dominant processes that determine the dust content in galaxies. The importance of grain size distribution for the grain growth is demonstrated in this paper. First, we derive an analytical formula that gives the grain size distribution after the grain growth in individual clouds for any initial grain size distribution. The time-scale of the grain growth is very sensitive to grain size di...

GRAIN SIZE CONSTRAINTS ON HL TAU WITH POLARIZATION SIGNATURE

International Nuclear Information System (INIS)

Kataoka, Akimasa; Dullemond, Cornelis P; Muto, Takayuki; Momose, Munetake; Tsukagoshi, Takashi

2016-01-01

The millimeter-wave polarization of the protoplanetary disk around HL Tau has been interpreted as the emission from elongated dust grains aligned with the magnetic field in the disk. However, the self-scattering of thermal dust emission may also explain the observed millimeter-wave polarization. In this paper, we report a modeling of the millimeter-wave polarization of the HL Tau disk with the self-polarization. Dust grains are assumed to be spherical and to have a power-law size distribution. We change the maximum grain size with a fixed dust composition in a fixed disk model to find the grain size to reproduce the observed signature. We find that the direction of the polarization vectors and the polarization degree can be explained with the self-scattering. Moreover, the polarization degree can be explained only if the maximum grain size is ∼150 μm. The obtained grain size from the polarization is different from that which has been previously expected from the spectral index of the dust opacity coefficient (a millimeter or larger) if the emission is optically thin. We discuss that porous dust aggregates may solve the inconsistency of the maximum grain size between the two constraints

GRAIN SIZE CONSTRAINTS ON HL TAU WITH POLARIZATION SIGNATURE

Energy Technology Data Exchange (ETDEWEB)

Kataoka, Akimasa; Dullemond, Cornelis P [Zentrum für Astronomie der Universität Heidelberg, Institut für Theoretische Astrophysik, Albert-Ueberle-Str. 2, D-69120 Heidelberg (Germany); Muto, Takayuki [Division of Liberal Arts, Kogakuin University, 1-24-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo 163-8677 (Japan); Momose, Munetake; Tsukagoshi, Takashi, E-mail: kataoka@uni-heidelberg.de [College of Science, Ibaraki University, 2-1-1 Bunkyo, Mito, Ibaraki 310-8512 (Japan)

2016-03-20

The millimeter-wave polarization of the protoplanetary disk around HL Tau has been interpreted as the emission from elongated dust grains aligned with the magnetic field in the disk. However, the self-scattering of thermal dust emission may also explain the observed millimeter-wave polarization. In this paper, we report a modeling of the millimeter-wave polarization of the HL Tau disk with the self-polarization. Dust grains are assumed to be spherical and to have a power-law size distribution. We change the maximum grain size with a fixed dust composition in a fixed disk model to find the grain size to reproduce the observed signature. We find that the direction of the polarization vectors and the polarization degree can be explained with the self-scattering. Moreover, the polarization degree can be explained only if the maximum grain size is ∼150 μm. The obtained grain size from the polarization is different from that which has been previously expected from the spectral index of the dust opacity coefficient (a millimeter or larger) if the emission is optically thin. We discuss that porous dust aggregates may solve the inconsistency of the maximum grain size between the two constraints.

Size-dependent antimicrobial properties of the cobalt ferrite nanoparticles

Science.gov (United States)

Žalnėravičius, Rokas; Paškevičius, Algimantas; Kurtinaitiene, Marija; Jagminas, Arūnas

2016-10-01

The growing resistance of bacteria to conventional antibiotics elicited considerable interest to non-typical drugs. In this study, antimicrobial investigations were performed on low-size dispersion cobalt ferrite nanoparticles (Nps) fabricated by co-precipitation approach in several average sizes, in particular, 15.0, 5.0, and 1.65 nm. A variety of experimental tests demonstrated that the size of these Nps is determinant for antimicrobial efficiency against S. cerevisiae and several Candida species, in particular, C. parapsilosis, C. krusei, and C. albicans. The small and ultra-small fractions of CoFe2O4 Nps possess especially strong antimicrobial activity against all tested microorganisms. The possible reasons are discussed. Nps were characterized by means of transmission and high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and atomic force microscopy, chemical analysis and magnetic measurements.

Size-dependent antimicrobial properties of the cobalt ferrite nanoparticles

International Nuclear Information System (INIS)

Žalnėravičius, Rokas; Paškevičius, Algimantas; Kurtinaitiene, Marija; Jagminas, Arūnas

2016-01-01

The growing resistance of bacteria to conventional antibiotics elicited considerable interest to non-typical drugs. In this study, antimicrobial investigations were performed on low-size dispersion cobalt ferrite nanoparticles (Nps) fabricated by co-precipitation approach in several average sizes, in particular, 15.0, 5.0, and 1.65 nm. A variety of experimental tests demonstrated that the size of these Nps is determinant for antimicrobial efficiency against S. cerevisiae and several Candida species, in particular, C. parapsilosis, C. krusei, and C. albicans. The small and ultra-small fractions of CoFe_2O_4 Nps possess especially strong antimicrobial activity against all tested microorganisms. The possible reasons are discussed. Nps were characterized by means of transmission and high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and atomic force microscopy, chemical analysis and magnetic measurements.Graphical Abstract

Synthesis of ferrite nanoparticle by milling process for preparation of single domain magnet

International Nuclear Information System (INIS)

Suryadi; Hasbiyallah; Agus S W; Nurul TR; Budhy Kurniawan

2009-01-01

Study of ferrite nanoparticle synthesis for preparation of single domain magnet by milling of scrap magnet material have been done. Sample preparation were done using disk mill continued with high energy milling (HEM). Some powder were taken after 5, 10 dan 20 hours milling using HEM-E3D. The powder were then characterized using X-Ray Fluorescence (XRF), X-Ray Diffractometer (XRD) and Scanning Electron Microscope (SEM). XRF characterization result, confirmed by XRD analysis result, showed that the sample are of Strontium ferrite phase. Microstructure analysis result showed the occurrence of grain refining process of ferrite particle with increasing of milling time. Particle having size of nanometers successfully obtained, although in unhomogeneous distribution. Magnetic properties characterization result showed the increasing of hysteresis curve area of sample for longer milling time and sintering process. (author)

Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

International Nuclear Information System (INIS)

Qi, B.; Andrew, J. S.; Arnold, D. P.

2017-01-01

This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe_6_6Co_3_4) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe_2O_4) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

Calcium-assisted reduction of cobalt ferrite nanoparticles for nanostructured iron cobalt with enhanced magnetic performance

Energy Technology Data Exchange (ETDEWEB)

Qi, B. [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States); Andrew, J. S. [University of Florida, Department of Materials Science and Engineering (United States); Arnold, D. P., E-mail: darnold@ufl.edu [University of Florida, Interdisciplinary Microsystems Group, Department of Electrical and Computer Engineering (United States)

2017-03-15

This paper demonstrates the potential of a calcium-assisted reduction process for synthesizing fine-grain (~100 nm) metal alloys from metal oxide nanoparticles. To demonstrate the process, an iron cobalt alloy (Fe{sub 66}Co{sub 34}) is obtained by hydrogen annealing 7-nm cobalt ferrite (CoFe{sub 2}O{sub 4}) nanoparticles in the presence of calcium granules. The calcium serves as a strong reducing agent, promoting the phase transition from cobalt ferrite to a metallic iron cobalt alloy, while maintaining high crystallinity. Magnetic measurements demonstrate the annealing temperature is the dominant factor of tuning the grain size and magnetic properties. Annealing at 700 °C for 1 h maximizes the magnetic saturation, up to 2.4 T (235 emu/g), which matches that of bulk iron cobalt.

The effect of heat treatment on recrystallized microstructure, precipitation and ductility of hot-rolled Fe–Cr–Al–REM ferritic stainless steel sheets

International Nuclear Information System (INIS)

Qu, H.P.; Lang, Y.P.; Yao, C.F.; Chen, H.T.; Yang, C.Q.

2013-01-01

This study presents research works about the effects of heat treatment on recrystallized equiaxed grain size, precipitation, room temperature (RT) toughness and ductile to brittle transition temperature (DBTT) of Fe–Cr–Al–REM ferritic stainless steel (FSS) hot-rolled sheet. Results showed that the recrystallization of hot-rolled Fe–Cr–Al–REM FSS sheet could be completed after annealing treatment at 750 °C for 15 min with the equiaxed grain diameter of approximately 50 μm. Inappropriate annealing treatment would inevitably leads to the unexpected grain coarsening. On the other hand, a great deal of needle-like or spot-like fine aluminum–lanthanum compound Al 11 La 3 precipitates were observed in the ferrite matrix after 1 h aging treatment at 750 °C. The microstructure observation results associated with the impact test definitely illustrated that the Al 11 La 3 precipitates was the reason for the brittle crack in the as-casted ingot and as-forged slab. The real DBTT of the annealed Fe–Cr–Al–REM FSS sheet with average grain size of about 50 μm was −4 °C. Meanwhile, the DBTT of the hot-rolled Fe–Cr–Al–REM stainless steel sheet was evidently increased as the recrystallized grain size increased.

The effect of heat treatment on recrystallized microstructure, precipitation and ductility of hot-rolled Fe-Cr-Al-REM ferritic stainless steel sheets

Energy Technology Data Exchange (ETDEWEB)

Qu, H.P., E-mail: quhuapeng0926@163.com [Institute for Special Steels (Formerly Institute for Structural Materials), Central Iron and Steel Research Institute (CISRI), 76 HaiDianNan Road, Beijing 100081 (China); Lang, Y.P. [Institute for Special Steels (Formerly Institute for Structural Materials), Central Iron and Steel Research Institute (CISRI), 76 HaiDianNan Road, Beijing 100081 (China); Yao, C.F. [Institute for Special Steels (Formerly Institute for Structural Materials), Central Iron and Steel Research Institute (CISRI), 76 HaiDianNan Road, Beijing 100081 (China); Zhuozhou Works, Central Iron and Steel Research Institute (CISRI), 2 HuoJuNan Road, Zhuozhou 072750, Hebei (China); Chen, H.T.; Yang, C.Q. [Institute for Special Steels (Formerly Institute for Structural Materials), Central Iron and Steel Research Institute (CISRI), 76 HaiDianNan Road, Beijing 100081 (China)

2013-02-01

This study presents research works about the effects of heat treatment on recrystallized equiaxed grain size, precipitation, room temperature (RT) toughness and ductile to brittle transition temperature (DBTT) of Fe-Cr-Al-REM ferritic stainless steel (FSS) hot-rolled sheet. Results showed that the recrystallization of hot-rolled Fe-Cr-Al-REM FSS sheet could be completed after annealing treatment at 750 Degree-Sign C for 15 min with the equiaxed grain diameter of approximately 50 {mu}m. Inappropriate annealing treatment would inevitably leads to the unexpected grain coarsening. On the other hand, a great deal of needle-like or spot-like fine aluminum-lanthanum compound Al{sub 11}La{sub 3} precipitates were observed in the ferrite matrix after 1 h aging treatment at 750 Degree-Sign C. The microstructure observation results associated with the impact test definitely illustrated that the Al{sub 11}La{sub 3} precipitates was the reason for the brittle crack in the as-casted ingot and as-forged slab. The real DBTT of the annealed Fe-Cr-Al-REM FSS sheet with average grain size of about 50 {mu}m was -4 Degree-Sign C. Meanwhile, the DBTT of the hot-rolled Fe-Cr-Al-REM stainless steel sheet was evidently increased as the recrystallized grain size increased.

Grain-to-grain variations in NbC particle size distributions in an austenitic stainless steel

International Nuclear Information System (INIS)

Barlow, C.Y.; Ralph, B.; Silverman, B.; Jones, A.R.

1979-01-01

Quantitative information has been obtained concerning the size distributions of NbC precipitate particles in different grains in a deformed and aged austenitic stainless steel specimen. The precipitate size distributions obtained differ from one grain to another. The average disparity measured between the mean precipitate sizes was a function of the distance between the grains compared. The results obtained are considered in terms of differences in precipitation behaviour due to variations in the levels of plastic strain in constituent grains of the deformed specimen. (author)

THE EFFECT OF SEDIMENT GRAIN SIZE ON HEAVY METAL CONTENT

Directory of Open Access Journals (Sweden)

Svetlana Maslennikova

2012-06-01

Full Text Available In the natural surroundings tectonical, climatological, dynamic and physico-chemical conditions of sedimentation are the crucial factors in the process of sediment composition formation. Grain size is one of the most investigated reasons of space and temporary variability in heavy metal concentration. In general, the data on grain size measurement afford to appreciate sorption capacity of sediments and arrange them. The dependence heavy metal content on grain size of sediments has been examined in the enormous amount of research works. The main conclusion is that if grain size decreases, metal content increases.We have carried out sediment grain size measurement of two lakes (Chebachje Lake, Piketnoye Lake located in the South of Western Siberia, Russia. To define grain size of these sediments the sorting of samples collected layer-by-layer has been conducted by nest of sieves (from 43 to 1000 µm. Accomplished examinations allow to state that layer-by-layer grain size measurement of sediments has significant importance in reconstruction of paleoecologic peculiarities and also influences organic and inorganic matter concentrating in the sediments in dynamics

Structural and magnetic Ni-Zn ferrite synthesized by combustion reaction and sintered in a conventional oven

International Nuclear Information System (INIS)

Vieira, D.A.; Diniz, V.C.S.; Costa, A.C.F.M.; Kiminami, R.H.G.A.; Cornejo, D.R.

2011-01-01

The Ni-Zn ferrite due to their electrical and magnetic properties allows use in various technological applications. These properties can be controlled through appropriate choice of chemical composition, structural characteristics and morphology of the powders used and the techniques used for sintering. Thus, this study aims to evaluate the sintering in a conventional oven at a temperature of 1200 deg C/2h samples of Ni-Zn ferrite synthesized by microwave energy. The samples were characterized by density measurement, XRD, SEM and magnetic measurements. The results indicate the phase formation of Ni-Zn ferrite crystalline phase with crystallite size of 80 nm. The sample was heterogeneous microstructure with grain size of about 1 μm high intergranular porosity. The sample showed the saturation magnetization of 7.57 emu/g, coercive field and remanent magnetization close to zero, thus indicating a behavior characteristic of superparamagnetic materials. (author)

Conception, definition, measuring procedure of grain size

International Nuclear Information System (INIS)

Yanagisawa, Kazuaki

1976-12-01

The conception, definition, measuring procedure of ''Grain Size'' were surveyed. A concept ''grain diameter'' was introduced after deriving a calculation formula for the grain diameter for using the Comparison (simple) and Intercept(detailed) procedure. As an example and putting into practice, the grain diameter determination was carried out by means of the Comparison procedure for a UO 2 pellet used in a densification experiment. (auth.)

Size-dependent antimicrobial properties of the cobalt ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Žalnėravičius, Rokas [State Research Institute Center for Physical Sciences and Technology (Lithuania); Paškevičius, Algimantas [Nature Research Centre, Laboratory of Biodeterioration Research (Lithuania); Kurtinaitiene, Marija; Jagminas, Arūnas, E-mail: arunas.jagminas@ftmc.lt [State Research Institute Center for Physical Sciences and Technology (Lithuania)

2016-10-15

The growing resistance of bacteria to conventional antibiotics elicited considerable interest to non-typical drugs. In this study, antimicrobial investigations were performed on low-size dispersion cobalt ferrite nanoparticles (Nps) fabricated by co-precipitation approach in several average sizes, in particular, 15.0, 5.0, and 1.65 nm. A variety of experimental tests demonstrated that the size of these Nps is determinant for antimicrobial efficiency against S. cerevisiae and several Candida species, in particular, C. parapsilosis, C. krusei, and C. albicans. The small and ultra-small fractions of CoFe{sub 2}O{sub 4} Nps possess especially strong antimicrobial activity against all tested microorganisms. The possible reasons are discussed. Nps were characterized by means of transmission and high-resolution transmission electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy and atomic force microscopy, chemical analysis and magnetic measurements.Graphical Abstract.

Effect of freeze-thaw cycling on grain size of biochar.

Science.gov (United States)

Liu, Zuolin; Dugan, Brandon; Masiello, Caroline A; Wahab, Leila M; Gonnermann, Helge M; Nittrouer, Jeffrey A

2018-01-01

Biochar may improve soil hydrology by altering soil porosity, density, hydraulic conductivity, and water-holding capacity. These properties are associated with the grain size distributions of both soil and biochar, and therefore may change as biochar weathers. Here we report how freeze-thaw (F-T) cycling impacts the grain size of pine, mesquite, miscanthus, and sewage waste biochars under two drainage conditions: undrained (all biochars) and a gravity-drained experiment (mesquite biochar only). In the undrained experiment plant biochars showed a decrease in median grain size and a change in grain-size distribution consistent with the flaking off of thin layers from the biochar surface. Biochar grain size distribution changed from unimodal to bimodal, with lower peaks and wider distributions. For plant biochars the median grain size decreased by up to 45.8% and the grain aspect ratio increased by up to 22.4% after 20 F-T cycles. F-T cycling did not change the grain size or aspect ratio of sewage waste biochar. We also observed changes in the skeletal density of biochars (maximum increase of 1.3%), envelope density (maximum decrease of 12.2%), and intraporosity (porosity inside particles, maximum increase of 3.2%). In the drained experiment, mesquite biochar exhibited a decrease of median grain size (up to 4.2%) and no change of aspect ratio after 10 F-T cycles. We also document a positive relationship between grain size decrease and initial water content, suggesting that, biochar properties that increase water content, like high intraporosity and pore connectivity large intrapores, and hydrophilicity, combined with undrained conditions and frequent F-T cycles may increase biochar breakdown. The observed changes in biochar particle size and shape can be expected to alter hydrologic properties, and thus may impact both plant growth and the hydrologic cycle.

Precipitation of Epsilon Copper in Ferrite Antibacterial Stainless Steel

Institute of Scientific and Technical Information of China (English)

Zhixia ZHANG; Gang LIN; Zhou XU

2008-01-01

The precipitation of epsilon copper at 1023 K ageing in ferrite antibacterial stainless steel was investigated by a combination of electron microscopy and micro-Vickers hardness measurement. The results show that epsilon copper precipitation occurs within 90 s. Complex rnultilayer structure confirmed as twins and stacking faults on {111}ε-Cu planes was observed in the precipitates. The precipitates grow by the lengthwise enlargement of a set of parallel layers, having [111]ε-Cu and [112]ε-Cu preferred growth orientations. The volume fraction of precipitates f formed within 120 min can be predicted by a modified Avrami equation (In 1/1-f= kt+b).Simultaneously, substituent atom clusters with a size of 5-10 nm was found to occur in the solution and cause matrix strain. The precipitate morphology and distribution on the surface of ferrite antibacterial stainlesss teel are associated with surface crystallographic orientation of the matrix. The precipitates are predominantly located within the ferrite grains of orientation. The precipitates located on {111}α-Fe surface planes have sphere or ellipse shape.

A new database sub-system for grain-size analysis

Science.gov (United States)

Suckow, Axel

2013-04-01

Detailed grain-size analyses of large depth profiles for palaeoclimate studies create large amounts of data. For instance (Novothny et al., 2011) presented a depth profile of grain-size analyses with 2 cm resolution and a total depth of more than 15 m, where each sample was measured with 5 repetitions on a Beckman Coulter LS13320 with 116 channels. This adds up to a total of more than four million numbers. Such amounts of data are not easily post-processed by spreadsheets or standard software; also MS Access databases would face serious performance problems. The poster describes a database sub-system dedicated to grain-size analyses. It expands the LabData database and laboratory management system published by Suckow and Dumke (2001). This compatibility with a very flexible database system provides ease to import the grain-size data, as well as the overall infrastructure of also storing geographic context and the ability to organize content like comprising several samples into one set or project. It also allows easy export and direct plot generation of final data in MS Excel. The sub-system allows automated import of raw data from the Beckman Coulter LS13320 Laser Diffraction Particle Size Analyzer. During post processing MS Excel is used as a data display, but no number crunching is implemented in Excel. Raw grain size spectra can be exported and controlled as Number- Surface- and Volume-fractions, while single spectra can be locked for further post-processing. From the spectra the usual statistical values (i.e. mean, median) can be computed as well as fractions larger than a grain size, smaller than a grain size, fractions between any two grain sizes or any ratio of such values. These deduced values can be easily exported into Excel for one or more depth profiles. However, such a reprocessing for large amounts of data also allows new display possibilities: normally depth profiles of grain-size data are displayed only with summarized parameters like the clay

Microstructural evaluation and magnetic Ni-Zn ferrite sintered by microwave energy

International Nuclear Information System (INIS)

Diniz, Veronica Cristhina S.; Vieira, Debora A.; Costa, Ana Cristina F.M.; Kiminami, R.H.G.A.; Cornejo, Daniel Reinaldo

2011-01-01

The present Ni-Zn ferrite magnetic properties sensitive to microstructure and obtain a ferrite with a uniform microstructure is the biggest challenge in the advancement of new technologies. This study proposes to evaluate the microstructure and magnetic properties of Ni-Zn ferrite sintered by microwave energy. The samples were previously synthesized by combustion reaction using urea and glycine, with 1200 deg C/2h sintered at a heating rate of 5 deg C/min, and characterized by density, XRD, SEM and magnetic measurements. The results show that the sample synthesized with glycine showed the formation of ferrite phase and traces of secondary phase hematite, grains with undefined format, and a high porosity and inter intragranular. The sample synthesized with urea gave only the ferrite phase, with hexagonal grains, and low intergranular porosity. The sample synthesized with urea showed better magnetic characteristics when compared with the samples synthesized with glycine. (author)

Grain boundary engineering for structure materials of nuclear reactors

Energy Technology Data Exchange (ETDEWEB)

Tan, L., E-mail: tanl@ornl.gov [Materials Science and Technology Division, Oak Ridge National Laboratory (United States); Allen, T.R. [Department of Engineering Physics, University of Wisconsin–Madison (United States); Busby, J.T. [Materials Science and Technology Division, Oak Ridge National Laboratory (United States)

2013-10-15

Grain boundary engineering (GBE), primarily implemented by thermomechanical processing, is an effective and economical method of enhancing the properties of polycrystalline materials. Among the factors affecting grain boundary character distribution, literature data showed definitive effect of grain size and texture. GBE is more effective for austenitic stainless steels and Ni-base alloys compared to other structural materials of nuclear reactors, such as refractory metals, ferritic and ferritic–martensitic steels, and Zr alloys. GBE has shown beneficial effects on improving the strength, creep strength, and resistance to stress corrosion cracking and oxidation of austenitic stainless steels and Ni-base alloys.

Resistance spot welding of AISI 430 ferritic stainless steel: Phase transformations and mechanical properties

International Nuclear Information System (INIS)

Alizadeh-Sh, M.; Marashi, S.P.H.; Pouranvari, M.

2014-01-01

Highlights: • Phase transformations during RSW of AISI430 are detailed. • Grain growth, martensite formation and carbide precipitation are dominant phase transformations. • Failure mode of AISI430 resistance spot welded joints are analyzed. • Larger FZ size provided improved load bearing capacity and energy absorption capability. - Abstract: The paper aims at investigating the process–microstructure–performance relationship in resistance spot welding of AISI 430 ferritic stainless steel. The phase transformations which occur during weld thermal cycle were analyzed in details, based on the physical metallurgy of welding of the ferritic stainless steels. It was found that the microstructure of the fusion zone and the heat affected zone is influenced by different phenomena including grain growth, martensite formation and carbide precipitation. The effects of welding cycle on the mechanical properties of the spot welds in terms of peak load, energy absorption and failure mode are discussed

Development of ODS ferritic-martensitic steels for application to high temperature and irradiation environment

International Nuclear Information System (INIS)

Lambard, V.

2000-01-01

Iron oxide dispersion strengthened alloys are candidate for nuclear fuel cladding. Therefore, it is crucial to control their microstructure in order to optimise their mechanical properties at temperatures up to 700 deg C. The industrial candidates, ODS ferritic alloys, present an anisotropic microstructure which induces a weakening of mechanical properties in transversal direction as well as the precipitation of brittle phases under thermal aging and irradiation. For this purpose, we tried to develop a material with isotropic properties. We studied several 9Cr-1Mo ferritic/martensitic alloys, strengthened or not by oxide dispersion. The mechanical alloying was performed by attribution and powders were consolidated by hot extrusion. In this work, different metallurgical characterisation techniques and modelling were used to optimise a new martensitic ODS alloy. Microstructural and chemical characterization of matrix has been done. The effect of austenitizing and isochronal tempering treatments on microstructure and hardness has been studied. Oxide distribution, size and chemical composition have been studied before and after high temperature thermal treatment. The study of phase transformation upon heating has permitted the extrapolation to the equilibrium temperature formation of austenite. Phase transformation diagrams upon cooling have been determined and the transformation kinetics have been linked to austenite grain size by a simple relation. Fine grain size is unfavourable for the targeted application, so a particular thermal treatment inducing a coarser grain structure has been developed. Finally, tensile properties have been determined for the different microstructures. (author)

Comparative study of eddy current and Barkhausen noise nondestructive testing methods in microstructural examination of ferrite-martensite dual-phase steel

Science.gov (United States)

Ghanei, S.; Kashefi, M.; Mazinani, M.

2014-04-01

The magnetic properties of ferrite-martensite dual-phase steels were evaluated using eddy current and Barkhausen noise nondestructive testing methods and correlated with their microstructural changes. Several routes were used to produce different microstructures of dual-phase steels. The first route was different heat treatments in γ region to vary the ferrite grain size (from 9.47 to 11.12 in ASTM number), and the second one was variation in intercritical annealing temperatures (from 750 to 890 °C) in order to produce different percentages of martensite in dual-phase microstructure. The results concerning magnetic Barkhausen noise are discussed in terms of height, position and shape of Barkhausen noise profiles, taking into account two main aspects: ferrite grain size, and different percentages of martensite. Then, eddy current testing was used to study the mentioned microstructural changes by detection of impedance variations. The obtained results show that microstructural changes have a noticeable effect on the magnetic properties of dual-phase steels. The results reveal that both magnetic methods have a high potential to be used as a reliable nondestructive tool to detect and monitor microstructural changes occurring during manufacturing of dual-phase steels.

Effects of grain size evolution on mantle dynamics

Science.gov (United States)

Schulz, Falko; Tosi, Nicola; Plesa, Ana-Catalina; Breuer, Doris

2016-04-01

The rheology of planetary mantle materials is strongly dependent on temperature, pressure, strain-rate, and grain size. In particular, the rheology of olivine, the most abundant mineral of the Earth's upper mantle, has been extensively studied in the laboratory (e.g., Karato and Wu, 1993; Hirth and Kohlstedt, 2003). Two main mechanisms control olivine's deformation: dislocation and diffusion creep. While the former implies a power-law dependence of the viscosity on the strain-rate that leads to a non-Newtonian behaviour, the latter is sensitively dependent on the grain size. The dynamics of planetary interiors is locally controlled by the deformation mechanism that delivers the lowest viscosity. Models of the dynamics and evolution of planetary mantles should thus be capable to self-consistently distinguish which of the two mechanisms dominates at given conditions of temperature, pressure, strain-rate and grain size. As the grain size can affect the viscosity associated with diffusion creep by several orders of magnitude, it can strongly influence the dominant deformation mechanism. The vast majority of numerical, global-scale models of mantle convection, however, are based on the use of a linear diffusion-creep rheology with constant grain-size. Nevertheless, in recent studies, a new equation has been proposed to properly model the time-dependent evolution of the grain size (Austin and Evens, 2007; Rozel et al., 2010). We implemented this equation in our mantle convection code Gaia (Hüttig et al., 2013). In the framework of simple models of stagnant lid convection, we compared simulations based on the fully time-dependent equation of grain-size evolution with simulations based on its steady-state version. In addition, we tested a number of different parameters in order to identify those that affects the grain size to the first order and, in turn, control the conditions at which mantle deformation is dominated by diffusion or dislocation creep. References Austin

Effect of Austenite Deformation on the Microstructure Evolution and Grain Refinement Under Accelerated Cooling Conditions

Science.gov (United States)

Zhao, H.; Palmiere, E. J.

2017-07-01

Although there has been much research regarding the effect of austenite deformation on accelerated cooled microstructures in microalloyed steels, there is still a lack of accurate data on boundary densities and effective grain sizes. Previous results observed from optical micrographs are not accurate enough, because, for displacive transformation products, a substantial part of the boundaries have disorientation angles below 15 deg. Therefore, in this research, a niobium microalloyed steel was used and electron backscattering diffraction mappings were performed on all of the transformed microstructures to obtain accurate results on boundary densities and grain refinement. It was found that with strain rising from 0 to 0.5, a transition from bainitic ferrite to acicular ferrite occurs and the effective grain size reduces from 5.7 to 3.1 μm. When further increasing strain from 0.5 to 0.7, dynamic recrystallization was triggered and postdynamic softening occurred during the accelerated cooling, leading to an inhomogeneous and coarse transformed microstructure. In the entire strain range, the density changes of boundaries with different disorientation angles are distinct, due to different boundary formation mechanisms. Finally, the controversial influence of austenite deformation on effective grain size of low-temperature transformation products was argued to be related to the differences in transformation conditions and final microstructures.

On Suspended matter grain size in Baltic sea

Science.gov (United States)

Bubnova, Ekaterina; Sivkov, Vadim; Zubarevich, Victor

2016-04-01

Suspended matter grain size data were gathered during the 25th research vessel "Akademik Mstislav Keldysh" cruise (1991, September-October). Initial quantitative data were obtained with a use of the Coulter counter and subsequently modified into volume concentrations (mm3/l) for size intervals. More than 80 samples from 15 stations were analyzed (depth range 0-355 m). The main goal of research was to illustrate the spatial variability of suspended matter concentration and dispersion in Baltic Sea. The mutual feature of suspended matter grain size distribution is the logical rise of particle number along with descending of particle's size. Vertical variability of grain size distribution was defined by Baltic Sea hydrological structure, including upper mixed layer - from the surface to the thermocline - with 35 m thick, cold intermediate layer - from the thermocline to the halocline- and bottom layer, which lied under the halocline. Upper layer showed a rise in total suspended matter concentration (up to 0.6 mm3/l), while cold intermediate level consisted of far more clear water (up to 0.1 mm3/l). Such a difference is caused by the thermocline boarding role. Meanwhile, deep bottom water experienced surges in suspended matter concentration owing to the nepheloid layer presence and "liquid bottom" effect. Coastal waters appeared to have the highest amount of particles (up to 5.0 mm3/l). Suspended matter grain size distribution in the upper mixed layer revealed a peak of concentration at 7 μ, which can be due to autumn plankton bloom. Another feature in suspended matter grain size distribution appeared at the deep layer below halocline, where both O2 and H2S were observed and red/ox barrier is. The simultaneous presence of Fe and Mn (in solutions below red/ox barrier) and O2 leads to precipitation of oxyhydrates Fe and Mn and grain size distribution graph peaking at 4.5 μ.

Hall measurements and grain-size effects in polycrystalline silicon

International Nuclear Information System (INIS)

Ghosh, A.K.; Rose, A.; Maruska, H.P.; Eustace, D.J.; Feng, T.

1980-01-01

The effects of grain size on Hall measurements in polycrystalline silicon are analyzed and interpreted, with some modifications, using the model proposed by Bube. This modified model predicts that the measured effective Hall voltage is composed of components originating from the bulk and space-charge regions. For materials with large grain sizes, the carrier concentration is independent of the intergrain boundary barrier, whereas the mobility is dependent on it. However, for small grains, both the carrier density and mobility depend on the barrier. These predictions are consistent with experimental results of mm-size Wacker and μm-size neutron-transmutation-doped polycrystalline silicon

Grain-size variations on a longitudinal dune and a barchan dune

Science.gov (United States)

Watson, Andrew

1986-01-01

The grain-size characteristics of the sand upon two dunes—a 40 m high longitudinal dune in the central Namib Desert and a 6.0 m high barchan in the Jafurah sand sea of Saudi Arabia—vary with position on the dunes. On the longitudinal dune, median grain size decreases, sorting improves and the grain-size distributions are less skewed and more normalized toward the crest. Though sand at the windward toe is distinct, elsewhere on the dune the changes in grain-size characteristics are gradual. An abrupt change in grain size and sorting near the crest—as described by Bagnold (1941, pp. 226-229)—is not well represented on this dune. Coarse grains remain as a lag on concave slope units and small particles are winnowed from the sand on the steepest windward slopes near the crest. Avalanching down slipfaces at the crest acts only as a supplementary grading mechanism. On the barchan dune median grain size also decreases near the crest, but sorting becomes poorer, though the grain-size distributions are more symmetric and more normalized. The dune profile is a Gaussian curve with a broad convex zone at the apex upon which topset beds had accreted prior to sampling. Grain size increases and sorting improves down the dune's slipface. However, this grading mechanism does not influence sand on the whole dune because variations in wind regime bring about different modes of dune accretion. On both dunes, height and morphology appear to influence significantly the grain-size characteristics.

Large polaron tunneling, magnetic and impedance analysis of magnesium ferrite nanocrystallite

Energy Technology Data Exchange (ETDEWEB)

Mahato, Dev K., E-mail: drdevkumar@yahoo.com [Department of Physics, National Institute of Technology Patna, Patna 800 005 (India); Majumder, Sumit [Department of Physics, Jadavpur University, Kolkata 700032 (India); Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India); Banerjee, S. [Surface Physics and Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

2017-08-15

Graphical abstract: The diffraction peaks corresponding to the planes (111), (220), (311), (222), (400), (422), (511), (440), (620), (533) and (444) provide a clear evidence for the formation of spinel structure of the ferrites. The lattice parameter ‘a’ determined as 8.392 Å matches well with JCPDS (73-2410) file for MgFe{sub 2}O{sub 4.} The volume of the unit cell is 591.012 Å{sup 3}. The crystallite size of the synthesized powder estimated from X-ray peak broadening of (311) highest intensity diffraction peak using Scherer formula was 56.4 nm. - Highlights: • Both the grain and grain boundaries contribution to conductivity of the Mg-ferrite has been observed. • Polydispersive nature of the material is checked using Cole – Cole relation. • The ac conductivity of magnesium ferrite followed σ{sub ac} ∝ ω{sup n} dependence. • The variation of the exponent ‘n’ with temperature suggests that overlapping large polaron tunnelling is the dominant conduction mechanism. • The superparamagnetic behavior of this Mg-ferrite has been observed for sample S1 annealed at 500 °C. - Abstract: Single phase MgFe{sub 2}O{sub 4} (MFO) ferrite was prepared through sol-gel auto-combustion route. The Rietveld analysis of X-ray patterns reveals that our samples are single phase. The increase in average particle size with annealing temperature and formation of nanoparticle agglomerates is observed in MgFe{sub 2}O{sub 4}. The structural morphology of the nanoparticles is studied using Scanning Electron Microscopy (SEM). Formation of spinel structure is confirmed using Fourier transform infrared spectroscopy (FTIR). The Zero-Field-Cooled (ZFC) and Field-Cooled (FC) magnetization measurements show the maximum irreversibility at 700 °C annealing temperature. The formation of a maximum at blocking temperature, T{sub B}∼ 180 K for sample annealed at 500 °C in the ZFC curve shows the superparamagnetic behavior of the sample. The increase of saturation magnetism (M

Grain-size distributions and grain boundaries of chalcopyrite-type thin films

International Nuclear Information System (INIS)

Abou-Ras, D.; Schorr, S.; Schock, H.W.

2007-01-01

CuInSe 2 , CuGaSe 2 , Cu(In,Ga)Se 2 and CuInS 2 thin-film solar absorbers in completed solar cells were studied in cross section by means of electronbackscatter diffraction. From the data acquired, grain-size distributions were extracted, and also the most frequent grain boundaries were determined. The grain-size distributions of all chalcopyrite-type thin films studied can be described well by lognormal distribution functions. The most frequent grainboundary types in these thin films are 60 - left angle 221 right angle tet and 71 - left angle 110 right angle tet (near) Σ3 twin boundaries. These results can be related directly to the importance of {112} tet planes during the topotactical growth of chalcopyrite-type thin films. Based on energetic considerations, it is assumed that the most frequent twin boundaries exhibit a 180 - left angle 221 right angle tet constellation. (orig.)

Grain-to-Grain Variations in NbC Particle Size Distributions in an Austenitic Stainless Steel

DEFF Research Database (Denmark)

Barlow, Claire; Ralph, B.; Silverman, B.

1979-01-01

Quantitative information has been obtained concerning the size distributions of NbC precipitate particles in different grains in a deformed and aged austenitic stainless steel specimen. The precipitate size distributions obtained differ from one grain to another. The average disparity measured be...

The grain-size lineup: A test of a novel eyewitness identification procedure.

Science.gov (United States)

Horry, Ruth; Brewer, Neil; Weber, Nathan

2016-04-01

When making a memorial judgment, respondents can regulate their accuracy by adjusting the precision, or grain size, of their responses. In many circumstances, coarse-grained responses are less informative, but more likely to be accurate, than fine-grained responses. This study describes a novel eyewitness identification procedure, the grain-size lineup, in which participants eliminated any number of individuals from the lineup, creating a choice set of variable size. A decision was considered to be fine-grained if no more than 1 individual was left in the choice set or coarse-grained if more than 1 individual was left in the choice set. Participants (N = 384) watched 2 high-quality or low-quality videotaped mock crimes and then completed 4 standard simultaneous lineups or 4 grain-size lineups (2 target-present and 2 target-absent). There was some evidence of strategic regulation of grain size, as the most difficult lineup was associated with a greater proportion of coarse-grained responses than the other lineups. However, the grain-size lineup did not outperform the standard simultaneous lineup. Fine-grained suspect identifications were no more diagnostic than suspect identifications from standard lineups, whereas coarse-grained suspect identifications carried little probative value. Participants were generally reluctant to provide coarse-grained responses, which may have hampered the utility of the procedure. For a grain-size approach to be useful, participants may need to be trained or instructed to use the coarse-grained option effectively. (c) 2016 APA, all rights reserved).

Magneto acoustical emission in nanocrystalline Mn–Zn ferrites

International Nuclear Information System (INIS)

Praveena, K.; Murthty, S.R.

2013-01-01

Graphical abstract: Mn 0.4 Zn 0.6 Fe 2 O 4 powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie temperature. It is found that the magneto-acoustic emission (MAE) activity along hysteresis loop is proportional to the hysteresis losses during the same loop. This law has been verified on series of polycrystalline ferrites and found that the law is valid whatever the composition, the grain size and temperature. It is also found that the domain wall creation/or annihilation processes are the origin of the MAE. - Highlights: • The AE been measured along the hysteresis loops from 80 K to Curie temperature. • The MAE activity along hysteresis loop is proportional to P h during the same loop. • It is found that the domain wall creation/or annihilation processes are the origin of the MAE. - Abstract: Mn 0.4 Zn 0.6 Fe 2 O 4 powders were prepared by microwave hydrothermal method. The powders were characterized by X-ray diffraction, transmission electron microscope. The powders were sintered at different temperatures 400, 500, 600, 700, 800 and 900 °C/30 min using microwave sintering method. The grain size was estimated by scanning electron microscope. The room temperature dielectric and magnetic properties were studied in the frequency range (100 kHz–1.8 GHz). The magnetization properties were measured upto 1.5 T. The acoustic emission has been measured along the hysteresis loops from 80 K to Curie temperature. It is found that the magneto

Dielectric and impedance study of praseodymium substituted Mg-based spinel ferrites

Energy Technology Data Exchange (ETDEWEB)

Farid, Hafiz Muhammad Tahir, E-mail: tahirfaridbzu@gmail.com [Department of Physics, Bahauddin Zakariya, University Multan, 60800 (Pakistan); Ahmad, Ishtiaq; Ali, Irshad [Department of Physics, Bahauddin Zakariya, University Multan, 60800 (Pakistan); Ramay, Shahid M. [College of Science, Physics and Astronomy Department, King Saud University, P.O. Box 2455, 11451 Riyadh (Saudi Arabia); Mahmood, Asif [Chemical Engineering Department, College of Engineering, King Saud University, Riyadh (Saudi Arabia); Murtaza, G. [Centre for Advanced Studies in Physics, GC University, Lahore 5400 (Pakistan)

2017-07-15

Highlights: • Magnesium based spinel ferrites were successfully synthesized by sol-gel method. • Dielectric constant shows the normal spinel ferrites behavior. • The dc conductivity are found to decrease with increasing temperature. • The samples with low conductivity have high values of activation energy. • The Impedance decreases with increasing frequency of applied field. - Abstract: Spinel ferrites with nominal composition MgPr{sub y}Fe{sub 2−y}O{sub 4} (y = 0.00, 0.025, 0.05, 0.075, 0.10) were prepared by sol-gel method. Temperature dependent DC electrical conductivity and drift mobility were found in good agreement with each other, reflecting semiconducting behavior. The dielectric properties of all the samples as a function of frequency (1 MHz–3 GHz) were measured at room temperature. The dielectric constant and complex dielectric constant of these samples decreased with the increase of praseodymium concentration. In the present spinel ferrite, Cole–Cole plots were used to separate the grain and grain boundary’s effects. The substitution of praseodymium ions in Mg-based spinel ferrites leads to a remarkable rise of grain boundary’s resistance as compared to the grain’s resistance. As both AC conductivity and Cole–Cole plots are the functions of concentration, they reveal the dominant contribution of grain boundaries in the conduction mechanism. AC activation energy was lower than dc activation energy. Temperature dependence normalized AC susceptibility of spinel ferrites reveals that MgFe{sub 2}O{sub 4} exhibits multi domain (MD) structure with high Curie temperature while on substitution of praseodymium, MD to SD transitions occurs. The low values of conductivity and low dielectric loss make these materials best candidate for high frequency application.

Competing Grain Boundary and Interior Deformation Mechanisms with Varying Sizes

Energy Technology Data Exchange (ETDEWEB)

Zhang, Wei [University of Tennessee (UT); Gao, Yanfei [ORNL; Nieh, T. G. [University of Tennessee, Knoxville (UTK)

2018-01-01

In typical coarse-grained alloys, the dominant plastic deformations are dislocation gliding or climbing, and material strengths can be tuned by dislocation interactions with grain boundaries, precipitates, solid solutions, and other defects. With the reduction of grain size, the increase of material strengths follows the classic Hall-Petch relationship up to nano-grained materials. Even at room temperatures, nano-grained materials exhibit strength softening, or called the inverse Hall-Petch effect, as grain boundary processes take over as the dominant deformation mechanisms. On the other hand, at elevated temperatures, grain boundary processes compete with grain interior deformation mechanisms over a wide range of the applied stress and grain sizes. This book chapter reviews and compares the rate equation model and the microstructure-based finite element simulations. The latter explicitly accounts for the grain boundary sliding, grain boundary diffusion and migration, as well as the grain interior dislocation creep. Therefore the explicit finite element method has clear advantages in problems where microstructural heterogeneities play a critical role, such as in the gradient microstructure in shot peening or weldment. Furthermore, combined with the Hall-Petch effect and its breakdown, the above competing processes help construct deformation mechanism maps by extending from the classic Frost-Ashby type to the ones with the dependence of grain size.

Standard test methods for characterizing duplex grain sizes

CERN Document Server

American Society for Testing and Materials. Philadelphia

2002-01-01

1.1 These test methods provide simple guidelines for deciding whether a duplex grain size exists. The test methods separate duplex grain sizes into one of two distinct classes, then into specific types within those classes, and provide systems for grain size characterization of each type. 1.2 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.3 This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult appropriate safety and health practices and determine the applicability of regulatory limitations prior to its use.

Concurrent microstructural evolution of ferrite and austenite in a duplex stainless steel processed by high-pressure torsion

International Nuclear Information System (INIS)

Cao, Y.; Wang, Y.B.; An, X.H.; Liao, X.Z.; Kawasaki, M.; Ringer, S.P.; Langdon, T.G.; Zhu, Y.T.

2014-01-01

A duplex stainless steel with approximately equal volume fractions of ferrite and austenite was processed by high-pressure torsion. Nano-indentation, electron backscatter diffraction and transmission electron microscopy were used to investigate the hardness and microstructure evolutions of the steel. Despite the different strain-hardening rates of individual ferrite and austenite, the microstructures of the two phases evolved concurrently in such a way that the neighbouring two phases always maintained similar hardness. While the plastic deformation and grain refinement of ferrite occurred mainly via dislocation activities, the plastic deformation and grain refinement process of austenite were more complicated and included deformation twinning and de-twinning in coarse grains, grain refinement by twinning and dislocation–twin interactions, de-twinning in ultrafine grains and twin boundary subdivision

Structural, morphological and electrical properties of Sn-substituted Ni-Zn ferrites synthesized by double sintering technique

Energy Technology Data Exchange (ETDEWEB)

Ali, M.A. [Department of Physics, Chittagong University of Engineering and Technology (CUET), Chittagong 4349 (Bangladesh); Uddin, M.M., E-mail: mohi@cuet.ac.bd [Department of Physics, Chittagong University of Engineering and Technology (CUET), Chittagong 4349 (Bangladesh); Khan, M.N.I. [Materials Science Division, Atomic Energy Center, Dhaka 1000 (Bangladesh); Chowdhury, F.U.-Z. [Department of Physics, Chittagong University of Engineering and Technology (CUET), Chittagong 4349 (Bangladesh); Haque, S.M. [Materials Science Division, Atomic Energy Center, Dhaka 1000 (Bangladesh)

2017-02-15

The Sn-substituted Ni-Zn ferrites, (0.0≤x≤0.30), have been synthesized by the standard double sintering technique from the oxide nanopowders of Ni, Zn, Fe and Sn. The structural and electrical properties have been investigated by the X-ray diffraction (XRD), scanning electron microscopy (SEM), DC resistivity and dielectric measurements. From XRD data, the single cubic spinel phase has been confirmed for x≤0.1, whereas for x>0.1 an extra intermediate phase has been detected along with the cubic spinel phase of Ni-Zn ferrite. The grain size is increased due to Sn substitution in Ni-Zn ferrites. DC resistivity as a function of temperature has been measured by two probe method. The semiconducting nature has been found operative in the samples. The DC resistivity was found to decrease whilst the dielectric constant increased with increasing Sn content in Ni-Zn ferrites. The unusual behavior of the dielectric loss factor of the ferrites was explained by the Rezlescu model. The electrical relaxation of the ferrites has been studied in terms of electric modulus formalism and the time for dielectric relaxation was calculated. The contribution of grain resistance has been studied from the Cole-Cole plot. The suitability to use the as prepared samples in the miniaturized memory devices based capacitive components or energy storage principles are confirmed from the values of dielectric constant. - Highlights: • Sn-substituted Ni-Zn ferrites with cubic spinel structure have been synthesized. • a{sub th} is calculated and well compared with a{sub expt}. • Dielectric unusual behavior has been successfully explained by the Rezlescu model. • Long τ (ns) is determined, can be utilized for memory and spintronics devices.

Grain size segregation in debris discs

Science.gov (United States)

Thebault, P.; Kral, Q.; Augereau, J.-C.

2014-01-01

Context. In most debris discs, dust grain dynamics is strongly affected by stellar radiation pressure. Because this mechanism is size-dependent, we expect dust grains to be spatially segregated according to their sizes. However, because of the complex interplay between radiation pressure, grain processing by collisions, and dynamical perturbations, this spatial segregation of the particle size distribution (PSD) has proven difficult to investigate and quantify with numerical models. Aims: We propose to thoroughly investigate this problem by using a new-generation code that can handle some of the complex coupling between dynamical and collisional effects. We intend to explore how PSDs behave in both unperturbed discs at rest and in discs pertubed by planetary objects. Methods: We used the DyCoSS code to investigate the coupled effect of collisions, radiation pressure, and dynamical perturbations in systems that have reached a steady-state. We considered two setups: a narrow ring perturbed by an exterior planet, and an extended disc into which a planet is embedded. For both setups we considered an additional unperturbed case without a planet. We also investigated the effect of possible spatial size segregation on disc images at different wavelengths. Results: We find that PSDs are always spatially segregated. The only case for which the PSD follows a standard dn ∝ s-3.5ds law is for an unperturbed narrow ring, but only within the parent-body ring itself. For all other configurations, the size distributions can strongly depart from such power laws and have steep spatial gradients. As an example, the geometrical cross-section of the disc is very rarely dominated by the smallest grains on bound orbits, as it is expected to be in standard PSDs in sq with q ≤ -3. Although the exact profiles and spatial variations of PSDs are a complex function of the set-up that is considered, we are still able to derive some reliable results that will be useful for image or SED

Modelling the joint variability of grain size and chemical composition in sediments

NARCIS (Netherlands)

Bloemsma, M.R.; Zabel, M.; Stuut, J.B.W.; Tjallingii, R.; Collins, J.A.; Weltje, G.J.

2012-01-01

The geochemical composition of siliciclastic sediments correlates strongly with grain size. Hence, geochemical composition may serve as a grain-size proxy. In the absence of grain-size variations, geochemical data of siliciclastic sediments may be used to characterise size-independent processes,

Tailoring the magnetic properties and magnetorheological behavior of spinel nanocrystalline cobalt ferrite by varying annealing temperature.

Science.gov (United States)

Sedlacik, Michal; Pavlinek, Vladimir; Peer, Petra; Filip, Petr

2014-05-14

Magnetic nanoparticles of spinel nanocrystalline cobalt ferrite were synthesized via the sol-gel method and subsequent annealing. The influence of the annealing temperature on the structure, magnetic properties, and magnetorheological effect was investigated. The finite crystallite size of the particles, determined by X-ray diffraction and the particle size observed via transmission electron microscopy, increased with the annealing temperature. The magnetic properties observed via a vibrating sample magnetometer showed that an increase in the annealing temperature leads to the increase in the magnetization saturation and, in contrast, a decrease in the coercivity. The effect of annealing on the magnetic properties of ferrite particles has been explained by the recrystallization process at high temperatures. This resulted in grain size growth and a decrease in an imposed stress relating to defects in the crystal lattice structure of the nanoparticles. The magnetorheological characteristics of suspensions of ferrite particles in silicone oil were measured using a rotational rheometer equipped with a magnetic field generator in both steady shear and small-strain oscillatory regimes. The magnetorheological performance expressed as a relative increase in the magnetoviscosity appeared to be significantly higher for suspensions of particles annealed at 1000 °C.

Structural and magnetic properties of nano-sized NiCuZn ferrites synthesized by co-precipitation method with ultrasound irradiation

Energy Technology Data Exchange (ETDEWEB)

Harzali, Hassen, E-mail: harzali@mines-albi.fr [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Saida, Fairouz; Marzouki, Arij; Megriche, Adel [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Baillon, Fabien; Espitalier, Fabienne [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi CT cedex 09 (France); Mgaidi, Arbi [Laboratory of Applied Mineral Chemistry, Faculty of Sciences, University Tunis ElManar, Campus University, Farhat Hached El-Manar, 2092 Tunis (Tunisia); Taibah University, Faculty of Sciences & art, Al Ula (Saudi Arabia)

2016-12-01

Sonochemically assisted co-precipitation has been used to prepare nano-sized Ni–Cu–Zn-ferrite powders. A suspension of constituent hydroxides was ultrasonically irradiated for various times at different temperatures with high intensity ultrasound radiation using a direct immersion titanium horn. Structural and magnetic properties were investigated using X-diffraction (XRD), FT-IR spectroscopy, transmission electron microscopy (TEM), Nitrogen adsorption at 77 K (BET) and Vibrating sample magnetometer (VSM). Preliminary experimental results relative to optimal parameters showed that reaction time t=2 h, temperature θ=90 °C and dissipated Power P{sub diss}=46.27 W. At these conditions, this work shows the formation of nanocrystalline single-phase structure with particle size 10–25 nm. Also, ours magnetic measurements proved that the sonochemistry method has a great influence on enhancing the magnetic properties of the ferrite. - Highlights: • Coprecipitation experiments were carried out with ultrasound. • The spinel ferrite NiCuZn was perfectly synthesized by ultrasound. • The saturation magnetization and crystals size are found to be correlated as the dissipated power was varied.

Structural and magnetic properties of nano-sized NiCuZn ferrites synthesized by co-precipitation method with ultrasound irradiation

International Nuclear Information System (INIS)

Harzali, Hassen; Saida, Fairouz; Marzouki, Arij; Megriche, Adel; Baillon, Fabien; Espitalier, Fabienne; Mgaidi, Arbi

2016-01-01

Sonochemically assisted co-precipitation has been used to prepare nano-sized Ni–Cu–Zn-ferrite powders. A suspension of constituent hydroxides was ultrasonically irradiated for various times at different temperatures with high intensity ultrasound radiation using a direct immersion titanium horn. Structural and magnetic properties were investigated using X-diffraction (XRD), FT-IR spectroscopy, transmission electron microscopy (TEM), Nitrogen adsorption at 77 K (BET) and Vibrating sample magnetometer (VSM). Preliminary experimental results relative to optimal parameters showed that reaction time t=2 h, temperature θ=90 °C and dissipated Power P_d_i_s_s=46.27 W. At these conditions, this work shows the formation of nanocrystalline single-phase structure with particle size 10–25 nm. Also, ours magnetic measurements proved that the sonochemistry method has a great influence on enhancing the magnetic properties of the ferrite. - Highlights: • Coprecipitation experiments were carried out with ultrasound. • The spinel ferrite NiCuZn was perfectly synthesized by ultrasound. • The saturation magnetization and crystals size are found to be correlated as the dissipated power was varied.

Improved electrical properties of cadmium substituted cobalt ferrites nano-particles for microwave application

Energy Technology Data Exchange (ETDEWEB)

Ahmad, Rabia [Institute of Chemical Sciences, Gomal University, D. I. Khan (Pakistan); Hussain Gul, Iftikhar, E-mail: iftikhar.gul@scme.nust.edu.pk [Thermal Transport Laboratory (TTL), Materials Engineering Department, School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology - NUST, H-12 Campus, Islamabad (Pakistan); Zarrar, Muhammad [Thermal Transport Laboratory (TTL), Materials Engineering Department, School of Chemical and Materials Engineering (SCME), National University of Sciences and Technology - NUST, H-12 Campus, Islamabad (Pakistan); Anwar, Humaira [Islamabad Model College for Girls G-10/2, Islamabad (Pakistan); Khan Niazi, Muhammad Bilal [Department of Chemicals Engineering, SCME, NUST, H-12 Campus, Islamabad (Pakistan); Khan, Azim [Institute of Chemical Sciences, Gomal University, D. I. Khan (Pakistan)

2016-05-01

Cadmium substituted cobalt ferrites with formula Cd{sub x}Co{sub 1−x}Fe{sub 2}O{sub 4} (x=0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye–Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15–19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd{sup 2+}concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner’s model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system Cd{sub x}Co{sub 1−x}Fe{sub 2}O{sub 4} the impedance analysis were performed. - Highlights: • Preparation of homogeneous, spherical and single phase well crystallized cobalt ferrites. • A simple and economical PEG assisted wet chemical co-precipitation method has been used. • Increased in DC electrical resistivity and activation energy. • Decease in dielectric constant used for microwave absorber. • AC conductivity of Cd{sup 2+} substituted Co-ferrites increases.

Improved electrical properties of cadmium substituted cobalt ferrites nano-particles for microwave application

International Nuclear Information System (INIS)

Ahmad, Rabia; Hussain Gul, Iftikhar; Zarrar, Muhammad; Anwar, Humaira; Khan Niazi, Muhammad Bilal; Khan, Azim

2016-01-01

Cadmium substituted cobalt ferrites with formula Cd x Co 1−x Fe 2 O 4 (x=0.0, 0.2, 0.35, 0.5), have been synthesized by wet chemical co-precipitation technique. Electrical, morphological and Structural properties of the samples have been studied using DC electrical resistivity and Impedance analyzer, Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD), respectively. XRD, SEM and AFM have been used to study the structural parameters such as measured density, lattice constant, X-ray density, crystallite size and morphology of the synthesized nano-particles. Debye–Scherrer formula has been used for the estimation of crystallite sizes. The estimated crystallite sizes were to be 15–19±2 nm. Hopping length of octahedral and tetrahedral sites have been calculated using indexed XRD data. The porosity and lattice constant increased as Cd 2+ concentration increases. DC electrical resistivity was performed using two probe technique. The decrease of resistivity with temperature confirms the semiconducting nature of the samples. The dielectric properties variation has been studied at room temperature as a function of frequency. Variation of dielectric properties from 100 Hz to 5 MHz has been explained on the basis of Maxwell and Wagner’s model and hoping of electrons on octahedral sites. To separates the grains boundary and grains of the system Cd x Co 1−x Fe 2 O 4 the impedance analysis were performed. - Highlights: • Preparation of homogeneous, spherical and single phase well crystallized cobalt ferrites. • A simple and economical PEG assisted wet chemical co-precipitation method has been used. • Increased in DC electrical resistivity and activation energy. • Decease in dielectric constant used for microwave absorber. • AC conductivity of Cd 2+ substituted Co-ferrites increases.

Effects by the microstructure after hot and cold rolling on the texture and grain size after final annealing of ferritic non-oriented FeSi electrical steel

Science.gov (United States)

Schneider, J.; Stöcker, A.; Franke, A.; Kawalla, R.

2018-04-01

The magnetic properties of fully processed non-oriented FeSi electrical steel are characterized by their magnetization behavior and specific magnetic losses. The magnetic properties are determined by the texture and microstructure. Less gamma fiber intensity and a high intensity of preferable texture components, especially cube fiber texture, are desirable to obtain an excellent magnetizing behavior. Furthermore, large grain sizes are necessary to reach low values of the specific magnetic losses. The fabrication route of the fully processed non-oriented electrical steels comprises a heavy cold rolling of the hot rolled material before final annealing. To fulfill the requirements on large grain size for low loss materials, grain growth, which appears after complete recrystallization, plays an important role. In this paper we will analyze the influence of different microstructures of the hot strip and the resulting microstructure after cold rolling on the appearance of recrystallization and grain growth after final annealing. The evolution of texture reflects the present ongoing softening processes: recovery, recrystallization and finally grain growth at the given annealing conditions. It will be shown that the image of texture at recrystallization is remarkable different from the texture at grain growth. Substantially grain growth is obtained at lower annealing temperatures for an optimum microstructure of the hot rolled material.

Effects by the microstructure after hot and cold rolling on the texture and grain size after final annealing of ferritic non-oriented FeSi electrical steel

Directory of Open Access Journals (Sweden)

J. Schneider

2018-04-01

Full Text Available The magnetic properties of fully processed non-oriented FeSi electrical steel are characterized by their magnetization behavior and specific magnetic losses. The magnetic properties are determined by the texture and microstructure. Less gamma fiber intensity and a high intensity of preferable texture components, especially cube fiber texture, are desirable to obtain an excellent magnetizing behavior. Furthermore, large grain sizes are necessary to reach low values of the specific magnetic losses. The fabrication route of the fully processed non-oriented electrical steels comprises a heavy cold rolling of the hot rolled material before final annealing. To fulfill the requirements on large grain size for low loss materials, grain growth, which appears after complete recrystallization, plays an important role. In this paper we will analyze the influence of different microstructures of the hot strip and the resulting microstructure after cold rolling on the appearance of recrystallization and grain growth after final annealing. The evolution of texture reflects the present ongoing softening processes: recovery, recrystallization and finally grain growth at the given annealing conditions. It will be shown that the image of texture at recrystallization is remarkable different from the texture at grain growth. Substantially grain growth is obtained at lower annealing temperatures for an optimum microstructure of the hot rolled material.

Tailoring and patterning the grain size of nanocrystalline alloys

International Nuclear Information System (INIS)

Detor, Andrew J.; Schuh, Christopher A.

2007-01-01

Nanocrystalline alloys that exhibit grain boundary segregation can access thermodynamically stable or metastable states with the average grain size dictated by the alloying addition. Here we consider nanocrystalline Ni-W alloys and demonstrate that the W content controls the grain size over a very broad range: ∼2-140 nm as compared with ∼2-20 nm in previous work on strongly segregating systems. This trend is attributed to a relatively weak tendency for W segregation to the grain boundaries. Based upon this observation, we introduce a new synthesis technique allowing for precise composition control during the electrodeposition of Ni-W alloys, which, in turn, leads to precise control of the nanocrystalline grain size. This technique offers new possibilities for understanding the structure-property relationships of nanocrystalline solids, such as the breakdown of Hall-Petch strength scaling, and also opens the door to a new class of customizable materials incorporating patterned nanostructures

Microstructure development of welding joints in high Cr ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Kubushiro, Keiji; Takahashi, Satoshi; Morishima, Keiko [IHI Corporation (Japan). Research Lab.

2010-07-01

Creep failure in high Cr ferritic steels welding joints are Type IV failure. Type IV-failure was ruptured in fine grained region of heat affected zone, microstructure and phase transformation process at welding in fine grained region were very important to clarify. Microstructure difference of heat affected zone was investigated in Gr.91, Gr.92, Gr.122 welding joint. The fraction of 60 degree block boundary, packet boundary, random boundary (including prior gamma boundary) length was compared in three ferritic steels by EBSP(Electron Backscatter Diffraction Pattern) analysis. HAZ was almost fully martensite phase in Gr.122 weld joint. On the other hand, HAZ in Gr.91 welding joint were some equiaxial grain and martensite structure. (orig.)

Some regularity of the grain size distribution in nuclear fuel with controllable structure

International Nuclear Information System (INIS)

Loktev, Igor

2008-01-01

It is known, the fission gas release from ceramic nuclear fuel depends from average size of grains. To increase grain size they use additives which activate sintering of pellets. However, grain size distribution influences on fission gas release also. Fuel with different structures, but with the same average size of grains has different fission gas release. Other structure elements, which influence operational behavior of fuel, are pores and inclusions. Earlier, in Kyoto, questions of distribution of grain size for fuel with 'natural' structure were discussed. Some regularity of grain size distribution of fuel with controllable structure and high average size of grains are considered in the report. Influence of inclusions and pores on an error of the automated definition of parameters of structure is shown. The criterion, which describe of behavior of fuel with specific grain size distribution, is offered

Experimental Phase Functions of Millimeter-sized Cosmic Dust Grains

Energy Technology Data Exchange (ETDEWEB)

Muñoz, O.; Moreno, F.; Guirado, D.; Escobar-Cerezo, J. [Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Vargas-Martín, F. [Department of Electromagnetism and Electronics, University of Murcia, E-30100 Murcia (Spain); Min, M. [SRON Netherlands Institute for Space Research, Sobornnelaan 2, 3584 CA Utrecht (Netherlands); Hovenier, J. W. [Astronomical Institute “Anton Pannekoek,” University of Amsterdam, Science Park 904, 1098 XH, Amsterdam (Netherlands)

2017-09-01

We present the experimental phase functions of three types of millimeter-sized dust grains consisting of enstatite, quartz, and volcanic material from Mount Etna, respectively. The three grains present similar sizes but different absorbing properties. The measurements are performed at 527 nm covering the scattering angle range from 3° to 170°. The measured phase functions show two well-defined regions: (i) soft forward peaks and (ii) a continuous increase with the scattering angle at side- and back-scattering regions. This behavior at side- and back-scattering regions is in agreement with the observed phase functions of the Fomalhaut and HR 4796A dust rings. Further computations and measurements (including polarization) for millimeter-sized grains are needed to draw some conclusions about the fluffy or compact structure of the dust grains.

TEM examination of microstructural evolution during processing of 14CrYWTi nanostructured ferritic alloys

International Nuclear Information System (INIS)

Kishimoto, H.; Alinger, M.J.; Odette, G.R.; Yamamoto, T.

2004-01-01

A transmission electron microscopy (TEM) study was carried out on the co-evolution of the coarser-scale microstructural features in mechanically alloyed (MA) powders and hot isostatic press (HIP) consolidated Fe-14Cr-3W-0 and 0.4Ti-0.25Y 2 O 3 nanostructured ferritic alloys (NFAs). The pancake shaped nanoscale grains in the as-MA powders are textured and elongated parallel to the particle surface. Powder annealing results in re-crystallization at 850 deg. C and grain growth at 1150 deg. C. The grains also recrystallize and may grow in the alloys HIPed at 850 deg. C, but appear to retain a polygonized sub-grain structure. The grains are larger and more distinct in the alloys HIPed at 1000 and 1150 deg. C. However, annealing resulted in bi-modal grain size distribution. Finer grains retained a significant dislocation density and populations of small precipitates with crystal structures distinct form the matrix. The grains and precipitates were much larger in alloys without Ti

Plasticity of oxide dispersion strengthened ferritic alloys

International Nuclear Information System (INIS)

Zakine, C.; Prioul, C.; Alamo, A.; Francois, D.

1993-01-01

Two 13%Cr oxide dispersion strengthened (ODS) ferritic alloys, DT and DY, exhibiting different oxide particle size distribution and a χ phase precipitation were studied. Their tensile properties have been tested from 20 to 700 C. Experimental observations during room temperature tensile tests performed in a scanning electronic microscope have shown that the main damage mechanism consists in microcracking of the χ phase precipitates on grain boundaries. These alloys are high tensile and creep resistant between 500 and 700 C. Their strongly stress-sensitive creep behaviour can be described by usual creep laws and incorporating a threshold stress below which the creep rate is negligible. (orig.)

XXIst Century Ferrites

International Nuclear Information System (INIS)

Mazaleyrat, F; Zehani, K; Pasko, A; Loyau, V; LoBue, M

2012-01-01

Ferrites have always been a subject of great interest from point of view of magnetic application, since the fist compass to present date. In contrast, the scientific interest for iron based magnetic oxides decreased after Oersted discovery as they where replaced by coil as magnetizing sources. Neel discovery of ferrimagnetism boosted again interest and leads to strong developments during two decades before being of less interest. Recently, the evolution of power electronics toward higher frequency, the down sizing of ceramics microstructure to nanometer scale, the increasing price of rare-earth elements and the development of magnetocaloric materials put light again on ferrites. A review on three ferrite families is given herein: harder nanostructured Ba 2+ Fe 12 O 19 magnet processed by spark plasma sintering, magnetocaloric effect associated to the spin transition reorientation of W-ferrite and low temperature spark plasma sintered Ni-Zn-Cu ferrites for high frequency power applications.

WIDE AND THICK GRAIN 1, which encodes an otubain-like protease with deubiquitination activity, influences grain size and shape in rice.

Science.gov (United States)

Huang, Ke; Wang, Dekai; Duan, Penggen; Zhang, Baolan; Xu, Ran; Li, Na; Li, Yunhai

2017-09-01

Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 (WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP-WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice. © 2017 The Authors The Plant Journal © 2017 John Wiley & Sons Ltd.

Effect of niobium clustering and precipitation on strength of an NbTi-microalloyed ferritic steel

International Nuclear Information System (INIS)

Kostryzhev, A.G.; Al Shahrani, A.; Zhu, C.; Cairney, J.M.; Ringer, S.P.; Killmore, C.R.; Pereloma, E.V.

2014-01-01

The microstructure–property relationship of an NbTi-microalloyed ferritic steel was studied as a function of thermo-mechanical schedule using a Gleeble 3500 simulator, optical and scanning electron microscope, and atom probe tomography. Contributions to the yield stress from grain size, solid solution, work hardening, particle and cluster strengthening were calculated using the established equations and the measured microstructural parameters. With a decrease in the austenite deformation temperature the yield stress decreased, following a decrease in the number density of >20 nm Nb-rich particles and ≈5 nm Nb-C clusters, although the grain refinement contribution increased. To achieve the maximum cluster/precipitation strengthening in ferrite, the austenite deformation should be carried out in the recrystallisation temperature region where there is a limited tendency for strain-induced precipitation. Based on the analysis of cluster strengthening increment, it could be suggested that the mechanism of dislocation–cluster interaction is closer to shearing than looping

Effect of niobium clustering and precipitation on strength of an NbTi-microalloyed ferritic steel

Energy Technology Data Exchange (ETDEWEB)

Kostryzhev, A.G., E-mail: kostryzhev@yahoo.com [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); Al Shahrani, A. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); Zhu, C.; Cairney, J.M.; Ringer, S.P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Killmore, C.R. [BlueScope Steel Limited, Five Islands Road, Port Kembla, NSW 2505 (Australia); Pereloma, E.V. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2500 (Australia); UOW Electron Microscopy Centre, University of Wollongong, NSW 2519 (Australia)

2014-06-01

The microstructure–property relationship of an NbTi-microalloyed ferritic steel was studied as a function of thermo-mechanical schedule using a Gleeble 3500 simulator, optical and scanning electron microscope, and atom probe tomography. Contributions to the yield stress from grain size, solid solution, work hardening, particle and cluster strengthening were calculated using the established equations and the measured microstructural parameters. With a decrease in the austenite deformation temperature the yield stress decreased, following a decrease in the number density of >20 nm Nb-rich particles and ≈5 nm Nb-C clusters, although the grain refinement contribution increased. To achieve the maximum cluster/precipitation strengthening in ferrite, the austenite deformation should be carried out in the recrystallisation temperature region where there is a limited tendency for strain-induced precipitation. Based on the analysis of cluster strengthening increment, it could be suggested that the mechanism of dislocation–cluster interaction is closer to shearing than looping.

Quantitative determination of grain sizes by means of scattered ultrasound

International Nuclear Information System (INIS)

Goebbels, K.; Hoeller, P.

1976-01-01

The scattering of ultrasounds makes possible the quantitative determination of grain sizes in metallic materials. Examples of measurements on steels with grain sizes between ASTM 1 and ASTM 12 are given

The NGDC Seafloor Sediment Grain Size Database

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The NGDC (now NCEI) Seafloor Sediment Grain Size Database contains particle size data for over 17,000 seafloor samples worldwide. The file was begun by NGDC in 1976...

Reduced activation ODS ferritic steel - recent development in high speed hot extrusion processing

Energy Technology Data Exchange (ETDEWEB)

Oksiuta, Zbigniew [Faculty of Mechanical Engineering, Bialystok Technical University (Poland); Lewandowska, Malgorzata; Kurzydlowski, Krzysztof [Faculty of Materials Science and Engineering, Warsaw University of Technology (Poland); Baluc, Nadine [Ecole Polytechnique Federale de Lausanne (EPFL), Centre de Recherches en Physique des Plasmas, Association Euratom-Confederation Suisse, Villigen PSI (Switzerland)

2010-05-15

The paper presents the microstructure and mechanical properties of an oxide dispersion strengthened (ODS), reduced activation, ferritic steel, namely the Fe-14Cr-2W-0.3Ti-0.3Y{sub 2}O{sub 3} alloy, which was fabricated by hot isostatic pressing followed by high speed hydrostatic extrusion (HSHE) and heat treatment HT at 1050 C. Transmission electron microscopy (TEM) observations revealed significant differences in the grain size and dislocation density between the as-HIPped and as-HSHE materials. It was also found that the microstructure of the steel is stable after HT. The HSHE process improves significantly the tensile and Charpy impact properties of the as-HIPped steel. The ultimate tensile strength at room temperature increases from 950 up to 1350 MPa, while the upper shelf energy increases from 3.0 up to 6.0 J. However, the ductile-to-brittle transition temperature (DBTT) remains relatively high (about 75 C).These results indicate that HSHE is a promising method for achieving grain refinement and thus improving the mechanical properties of ODS ferritic steels. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

Science.gov (United States)

Zhong, X. C.; Guo, X. J.; Zou, S. Y.; Yu, H. Y.; Liu, Z. W.; Zhang, Y. F.; Wang, K. X.

2018-04-01

Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

Improving soft magnetic properties of Mn-Zn ferrite by rare earth ions doping

Directory of Open Access Journals (Sweden)

X. C. Zhong

2018-04-01

Full Text Available Mn-Zn ferrites doped with different Sm2O3, Gd2O3, Ce2O3 or Y2O3 were prepared by traditional ceramic technology using industrial pre-sintered powders. A small amount of Sm2O3, Gd2O3, Ce2O3 or Y2O3 can significantly improve the microstructure and magnetic properties. The single spinel phase structure can be maintained with the doping amount up to 0.07 wt.%. A refined grain structure and uniform grain size distribution can be obtained by doping. For all rare earth oxides, a small amount of doping can significantly increase the permeability and reduce the coercivity and magnetic core loss. The optimized doping amount for Sm2O3 or Gd2O3 is 0.01 wt.%, while for Ce2O3 or Y2O3 is 0.03 wt.%. A further increase of the doping content will lead to reduced soft magnetic properties. The ferrite sample with 0.01 wt.% Sm2O3 exhibits the good magnetic properties with permeability, loss, and coercivity of 2586, 316 W/kg, and 24A/m, respectively, at 200 mT and 100 kHz. The present results indicate that rare earth doping can be suggested to be one of the effective ways to improve the performance of soft ferrites.

Estimating the average grain size of metals - approved standard 1969

International Nuclear Information System (INIS)

Anon.

1975-01-01

These methods cover procedures for estimating and rules for expressing the average grain size of all metals and consisting entirely, or principally, of a single phase. The methods may also be used for any structures having appearances similar to those of the metallic structures shown in the comparison charts. The three basic procedures for grain size estimation which are discussed are comparison procedure, intercept (or Heyn) procedure, and planimetric (or Jeffries) procedure. For specimens consisting of equiaxed grains, the method of comparing the specimen with a standard chart is most convenient and is sufficiently accurate for most commercial purposes. For high degrees of accuracy in estimating grain size, the intercept or planimetric procedures may be used

Computational Investigation of Effects of Grain Size on Ballistic Performance of Copper

Science.gov (United States)

He, Ge; Dou, Yangqing; Guo, Xiang; Liu, Yucheng

2018-01-01

Numerical simulations were conducted to compare ballistic performance and penetration mechanism of copper (Cu) with four representative grain sizes. Ballistic limit velocities for coarse-grained (CG) copper (grain size ≈ 90 µm), regular copper (grain size ≈ 30 µm), fine-grained (FG) copper (grain size ≈ 890 nm), and ultrafine-grained (UG) copper (grain size ≈ 200 nm) were determined for the first time through the simulations. It was found that the copper with reduced grain size would offer higher strength and better ductility, and therefore renders improved ballistic performance than the CG and regular copper. High speed impact and penetration behavior of the FG and UG copper was also compared with the CG coppers strengthened by nanotwinned (NT) regions. The comparison results showed the impact and penetration resistance of UG copper is comparable to the CG copper strengthened by NT regions with the minimum twin spacing. Therefore, besides the NT-strengthened copper, the single phase copper with nanoscale grain size could also be a strong candidate material for better ballistic protection. A computational modeling and simulation framework was proposed for this study, in which Johnson-Cook (JC) constitutive model is used to predict the plastic deformation of Cu; the JC damage model is to capture the penetration and fragmentation behavior of Cu; Bao-Wierzbicki (B-W) failure criterion defines the material's failure mechanisms; and temperature increase during this adiabatic penetration process is given by the Taylor-Quinney method.

Using the ''Epiquant'' automatic analyzer for quantitative estimation of grain size

Energy Technology Data Exchange (ETDEWEB)

Tsivirko, E I; Ulitenko, A N; Stetsenko, I A; Burova, N M [Zaporozhskij Mashinostroitel' nyj Inst. (Ukrainian SSR)

1979-01-01

Application possibility of the ''Epiquant'' automatic analyzer to estimate qualitatively austenite grain in the 18Kh2N4VA steel has been investigated. Austenite grain has been clarified using the methods of cementation, oxidation and etching of the grain boundaries. Average linear size of grain at the length of 15 mm has been determined according to the total length of grain intersection line and the number of intersections at the boundaries. It is shown that the ''Epiquant'' analyzer ensures quantitative estimation of austenite grain size with relative error of 2-4 %.

SMALL GRAIN 1, which encodes a mitogen-activated protein kinase kinase 4, influences grain size in rice.

Science.gov (United States)

Duan, Penggen; Rao, Yuchun; Zeng, Dali; Yang, Yaolong; Xu, Ran; Zhang, Baolan; Dong, Guojun; Qian, Qian; Li, Yunhai

2014-02-01

Although grain size is one of the most important components of grain yield, little information is known about the mechanisms that determine final grain size in crops. Here we characterize rice small grain1 (smg1) mutants, which exhibit small and light grains, dense and erect panicles and comparatively slightly shorter plants. The short grain and panicle phenotypes of smg1 mutants are caused by a defect in cell proliferation. The smg1 mutations were identified, using a map-based cloning approach, in mitogen-activated protein kinase kinase 4 (OsMKK4). Relatively higher expression of OsMKK4/SMG1 was detected in younger organs than in older ones, consistent with its role in cell proliferation. Green fluorescent protein (GFP)-OsMKK4/SMG1 fusion proteins appear to be distributed ubiquitously in plant cells. Further results revealed that OsMKK4 influenced brassinosteroid (BR) responses and the expression of BR-related genes. Thus, our findings have identified OsMKK4 as a factor for grain size, and suggest a possible link between the MAPK pathways and BRs in grain growth. © 2013 The Authors The Plant Journal © 2013 John Wiley & Sons Ltd.

Grain-Size Dynamics Beneath Mid-Ocean Ridges: Implications for Permeability and Melt Extraction

Science.gov (United States)

Turner, A. J.; Katz, R. F.; Behn, M. D.

2014-12-01

The permeability structure of the sub-ridge mantle plays an important role in how melt is focused and extracted at mid-ocean ridges. Permeability is controlled by porosity and the grain size of the solid mantle matrix, which is in turn controlled by the deformation conditions. To date, models of grain size evolution and mantle deformation have not been coupled to determine the influence of spatial variations in grain-size on the permeability structure at mid-ocean ridges. Rather, current models typically assume a constant grain size for the whole domain [1]. Here, we use 2-D numerical models to evaluate the influence of grain-size variability on the permeability structure beneath a mid-ocean ridge and use these results to speculate on the consequences for melt focusing and extraction. We construct a two-dimensional, single phase model for the steady-state grain size beneath a mid-ocean ridge. The model employs a composite rheology of diffusion creep, dislocation creep, dislocation accommodated grain boundary sliding, and a brittle stress limiter. Grain size is calculated using the "wattmeter" model of Austin and Evans [2]. We investigate the sensitivity of the model to global variations in grain growth exponent, potential temperature, spreading-rate, and grain boundary sliding parameters [3,4]. Our model predicts that permeability varies by two orders of magnitude due to the spatial variability of grain size within the expected melt region of a mid-ocean ridge. The predicted permeability structure suggests grain size may promote focusing of melt towards the ridge axis. Furthermore, the calculated grain size structure should focus melt from a greater depth than models that exclude grain-size variability. Future work will involve evaluating this hypothesis by implementing grain-size dynamics within a two-phase mid-ocean ridge model. The developments of such a model will be discussed. References: [1] R. F. Katz, Journal of Petrology, volume 49, issue 12, page 2099

Austenite Grain Size Estimtion from Chord Lengths of Logarithmic-Normal Distribution

Directory of Open Access Journals (Sweden)

Adrian H.

2017-12-01

Full Text Available Linear section of grains in polyhedral material microstructure is a system of chords. The mean length of chords is the linear grain size of the microstructure. For the prior austenite grains of low alloy structural steels, the chord length is a random variable of gamma- or logarithmic-normal distribution. The statistical grain size estimation belongs to the quantitative metallographic problems. The so-called point estimation is a well known procedure. The interval estimation (grain size confidence interval for the gamma distribution was given elsewhere, but for the logarithmic-normal distribution is the subject of the present contribution. The statistical analysis is analogous to the one for the gamma distribution.

Molecular dynamics study on microstructure of near grain boundary distortion region in small grain size nano- NiAl alloy

International Nuclear Information System (INIS)

Wang, J.Y.; Wang, X.W.; Rifkin, J.; Li, D.X.

2001-12-01

Using the molecular dynamics simulation method, the microstructure of distortion region near curved amorphous-like grain boundary in nano-NiAl alloy is studied. The results showed that due to the internal elastic force of high energy grain boundary, distortion layer exists between grain and grain boundary. The lattice expansion and structure factor decreasing are observed in this region. Stacking fault in sample with grain size 3.8nm is clearly observed across the distortion region at the site very close to grain. The influences of different grain sizes on average distortion degree and volume fractions of distortion region, grain and grain boundary are also discussed. (author)

Effect of rare earth substitution in cobalt ferrite bulk materials

International Nuclear Information System (INIS)

Bulai, G.; Diamandescu, L.; Dumitru, I.; Gurlui, S.; Feder, M.; Caltun, O.F.

2015-01-01

The study was focused on the influence of small amounts of rare earth (RE=La, Ce, Sm, Gd, Dy, Ho, Er, Yb) addition on the microstructure, phase content and magnetic properties of cobalt ferrite bulk materials. The X-Ray diffraction measurements confirmed the formation of the spinel structure but also the presence of secondary phases of RE oxides or orthoferrite in small percentages (up to 3%). Density measurements obtained by Archimedes method revealed a ~1 g cm −3 decrease for the RE doped cobalt ferrite samples compared with stoichiometric one. Both the Mössbauer and Fourier Transform Infrared Spectrocopy analysis results confirmed the formation of the spinel phase. The saturation magnetization and coercive field values of the doped samples obtained by Vibrating Sample Magnetometry were close to those of the pure cobalt ferrite. For magnetostrictive property studies the samples were analyzed using the strain gauge method. Higher maximum magnetostriction coefficients were found for the Ho, Ce, Sm and Yb doped cobalt ferrite bulk materials as related to the stoichiometric CoFe 2 O 4 sample. Moreover, improved strain derivative was observed for these samples but at higher magnetic fields due to the low increase of the coercive field values for doped samples. - Highlights: • Substitution by a large number of rare earth elements was investigated. • First reported results on magnetostriction measurements of RE doped cobalt ferrite. • The doped samples presented an increased porosity and a decreased grain size. • Increased magnetostrctive response was observed for several doped samples

Grain-size effect on the electrical properties of nanocrystalline indium tin oxide thin films

Energy Technology Data Exchange (ETDEWEB)

Lee, Jong Hoon [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); Kim, Young Heon, E-mail: young.h.kim@kriss.re.kr [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Ahn, Sang Jung [Korea Research Institute of Standards and Science, 267 Gajeong-Ro, Yuseong-Gu, Daejeon 305-340 (Korea, Republic of); University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Ha, Tae Hwan [University of Science & Technology, 217 Gajeong-Ro, Yuseong-Gu, Daejeon 305-350 (Korea, Republic of); Future Biotechnology Research Division, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 125 Gwahak-ro, Yuseong-Gu, Daejeon 305-806 (Korea, Republic of); Kim, Hong Seung [Department of Nano Semiconductor Engineering, Korea Maritime and Ocean University, 727 Taejong-Ro, Busan 606-791 (Korea, Republic of)

2015-09-15

Highlights: • Nanometer-sized small grains were observed in the ITO thin films. • The grain size increased as the post-thermal annealing temperature increased. • The mobility of ITO thin films increased with increasing grain size. • The ITO film annealed at 300 °C was an amorphous phase, while the others were polycrystalline structure. - Abstract: In this paper, we demonstrate the electrical properties, depending on grain size, of nanocrystalline indium tin oxide (ITO) thin films prepared with a solution process. The size distributions of nanometer-sized ITO film grains increased as the post-annealing temperature increased after deposition; the grain sizes were comparable with the calculated electron mean free path. The mobility of ITO thin films increased with increasing grain size; this phenomenon was explained by adopting the charge-trapping model for grain boundary scattering. These findings suggest that it is possible to improve mobility by reducing the number of trapping sites at the grain boundary.

Austenite grain growth and microstructure control in simulated heat affected zones of microalloyed HSLA steel

Energy Technology Data Exchange (ETDEWEB)

Zhang, Lei [Department of Machine Tools and Factory Management, Technical University of Berlin, Pascalstraße 8 – 9, 10587, Berlin (Germany); Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Kannengiesser, Thomas [Federal Institute for Materials Research and Testing, Unter den Eichen 87, 12205, Berlin (Germany); Institute of Materials and Joining Technology, Otto von Guericke University Magdeburg, Universitetsplatz 2, 39106, Magdeburg (Germany)

2014-09-08

The roles of microalloying niobium, titanium and vanadium for controlling austenite grain growth, microstructure evolution and hardness were investigated at different simulated heat affected zones (HAZ) for high strength low alloy (HSLA) S690QL steel. High resolution FEG-SEM has been used to characterize fine bainitic ferrite, martensite and nanosized second phases at simulated coarse and fine grain HAZs. It was found that for Ti bearing steel (Ti/N ratio is 2) austenite grain had the slowest growth rate due to the presence of most stable TiN. The fine cuboidal particles promoted intragranular acicular ferrite (IGF) formation. Nb bearing steel exhibited relatively weaker grain growth retardation compared with titanium bearing steels and a mixed microstructure of bainite and martensite was present for all simulated HAZs. IGF existed at coarse grain HAZ of Ti+V bearing steel but it was totally replaced by bainite at fine grain HAZs. Hardness result was closely related to the morphology of bainitic ferrite, intragranular ferrite and second phases within ferrite. The microstructure and hardness results of different simulated HAZs were in good agreement with welded experimental results.

The Relevance of Grain Dissection for Grain Size Reduction in Polar Ice: Insights from Numerical Models and Ice Core Microstructure Analysis

Directory of Open Access Journals (Sweden)

Florian Steinbach

2017-09-01

Full Text Available The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modeling and analyzed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD have been used together with c-axis orientations using an optical technique (Fabric Analyser. Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighboring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modeling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be

The relevance of grain dissection for grain size reduction in polar ice: insights from numerical models and ice core microstructure analysis

Science.gov (United States)

Steinbach, Florian; Kuiper, Ernst-Jan N.; Eichler, Jan; Bons, Paul D.; Drury, Martyn R.; Griera, Albert; Pennock, Gill M.; Weikusat, Ilka

2017-09-01

The flow of ice depends on the properties of the aggregate of individual ice crystals, such as grain size or lattice orientation distributions. Therefore, an understanding of the processes controlling ice micro-dynamics is needed to ultimately develop a physically based macroscopic ice flow law. We investigated the relevance of the process of grain dissection as a grain-size-modifying process in natural ice. For that purpose, we performed numerical multi-process microstructure modelling and analysed microstructure and crystallographic orientation maps from natural deep ice-core samples from the North Greenland Eemian Ice Drilling (NEEM) project. Full crystallographic orientations measured by electron backscatter diffraction (EBSD) have been used together with c-axis orientations using an optical technique (Fabric Analyser). Grain dissection is a feature of strain-induced grain boundary migration. During grain dissection, grain boundaries bulge into a neighbouring grain in an area of high dislocation energy and merge with the opposite grain boundary. This splits the high dislocation-energy grain into two parts, effectively decreasing the local grain size. Currently, grain size reduction in ice is thought to be achieved by either the progressive transformation from dislocation walls into new high-angle grain boundaries, called subgrain rotation or polygonisation, or bulging nucleation that is assisted by subgrain rotation. Both our time-resolved numerical modelling and NEEM ice core samples show that grain dissection is a common mechanism during ice deformation and can provide an efficient process to reduce grain sizes and counter-act dynamic grain-growth in addition to polygonisation or bulging nucleation. Thus, our results show that solely strain-induced boundary migration, in absence of subgrain rotation, can reduce grain sizes in polar ice, in particular if strain energy gradients are high. We describe the microstructural characteristics that can be used to

Microstructure and Mechanical Property of ODS Ferritic Steels Using Commercial Alloy Powders for High Temperature Service Applications

Energy Technology Data Exchange (ETDEWEB)

Noh, Sanghoon; Choi, Byoung-Kwon; Kang, Suk Hoon; Kim, Tae Kyu [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2016-10-15

Oxide dispersion strengthening (ODS) is one of the promising ways to improve the mechanical property at high temperatures. This is mainly attributed to uniformly distributed nano-oxide particle with a high density, which is extremely stable at the high temperature and acts as effective obstacles when the dislocations are moving. In this study, as a preliminary examination to develop the advanced structural materials for high temperature service applications, ODS ferritic steels were fabricated using commercial alloy powders and their microstructural and mechanical properties were investigated. In this study, ODS ferritic steels were fabricated using commercial stainless steel 430L powder and their microstructures and mechanical properties were investigated. Morphology of micro-grains and oxide particles were significantly changed by the addition of minor alloying elements such as Ti, Zr, and Hf. The ODS ferritic steel with Zr and Hf additions showed ultra-fine grains with fine complex oxide particles. The oxide particles were uniformly located in grains and on the grain boundaries. This led to higher hardness than ODS ferritic steel with Ti addition.

Factors Affecting Impact Toughness in Stabilized Intermediate Purity 21Cr Ferritic Stainless Steels and Their Simulated Heat-Affected Zones

Science.gov (United States)

Anttila, Severi; Alatarvas, Tuomas; Porter, David A.

2017-12-01

The correlation between simulated weld heat-affected zone microstructures and toughness parameters has been investigated in four intermediate purity 21Cr ferritic stainless steels stabilized with titanium and niobium either separately or in combination. Extensive Charpy V impact toughness testing was carried out followed by metallography including particle analysis using electron microscopy. The results confirmed that the grain size and the number density of particle clusters rich in titanium nitride and carbide with an equivalent circular diameter of 2 µm or more are statistically the most critical factors influencing the ductile-to-brittle transition temperature. Other inclusions and particle clusters, as well as grain boundary precipitates, are shown to be relatively harmless. Stabilization with niobium avoids large titanium-rich inclusions and also suppresses excessive grain growth in the heat-affected zone when reasonable heat inputs are used. Thus, in order to maximize the limited heat-affected zone impact toughness of 21Cr ferritic stainless steels containing 380 to 450 mass ppm of interstitials, the stabilization should be either titanium free or the levels of titanium and nitrogen should be moderated.

NON-COHESIVE SOILS’ COMPRESSIBILITY AND UNEVEN GRAIN-SIZE DISTRIBUTION RELATION

Directory of Open Access Journals (Sweden)

Anatoliy Mirnyy

2016-03-01

Full Text Available This paper presents the results of laboratory investigation of soil compression phases with consideration of various granulometric composition. Materials and Methods Experimental soil box with microscale video recording for compression phases studies is described. Photo and video materials showing the differences of microscale particle movements were obtained for non-cohesive soils with different grain-size distribution. Results The analysis of the compression tests results and elastic and plastic deformations separation allows identifying each compression phase. It is shown, that soil density is correlating with deformability parameters only for the same grain-size distribution. Basing on the test results the authors suggest that compaction ratio is not sufficient for deformability estimating without grain-size distribution taken into account. Discussion and Conclusions Considering grain-size distribution allows refining technological requirements for artificial soil structures, backfills, and sand beds. Further studies could be used for developing standard documents, SP45.13330.2012 in particular.

Importance and role of grain size in free surface cracking prediction of heavy forgings

Energy Technology Data Exchange (ETDEWEB)

Wang, Zhenhua [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Sun, Shuhua; Wang, Bo [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China); Shi, Zhongping [Key Laboratory of Advanced Forging & Stamping Technology and Science, Yanshan University, Ministry of Education of China, Qinhuangdao 066004 (China); Fu, Wantang, E-mail: wtfu@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, Qinhuangdao 066004 (China)

2015-02-11

The importance and role of grain size in predicting surface cracking of heavy forgings were investigated. 18Mn18Cr0.5N steel specimens with four different grain sizes were tensioned between 900 and 1100 °C at a strain rate of 0.1 s{sup −1}. The nucleation sites and crack morphology were analyzed through electron backscatter diffraction analysis, and the fracture morphology was examined using scanning electron microscopy. The nucleation sites were independent of the grain size, and cracks primarily formed at grain boundaries and triple junctions between grains with high Taylor factors. Grains with lower Taylor factors inhibited crack propagation. Strain was found to mainly concentrate near the grain boundaries; thus, a material with a larger grain size cracks more easily because there are fewer grain boundaries. Fine grains can be easily rotated to a lower Taylor factor to further inhibit cracking. The fracture morphology transformed from a brittle to ductile type with a lowering of grain size. At lower temperature, small dimples on the fracture surfaces of specimens with smaller grain sizes were left by single parent grains and the dimple edge was the grain edge. At higher temperature, dimples formed through void coalescence and the dimple edge was the tearing edge. Finally, the relationship between the reduction in area, grain size, and deformation temperature was obtained.

Characteristics of Laser Beam and Friction Stir Welded AISI 409M Ferritic Stainless Steel Joints

Science.gov (United States)

Lakshminarayanan, A. K.; Balasubramanian, V.

2012-04-01

This article presents the comparative evaluation of microstructural features and mechanical properties of friction stir welded (solid-state) and laser beam welded (high energy density fusion welding) AISI 409M grade ferritic stainless steel joints. Optical microscopy, microhardness testing, transverse tensile, and impact tests were performed. The coarse ferrite grains in the base material were changed to fine grains consisting duplex structure of ferrite and martensite due to the rapid cooling rate and high strain induced by severe plastic deformation caused by frictional stirring. On the other hand, columnar dendritic grain structure was observed in fusion zone of laser beam welded joints. Tensile testing indicates overmatching of the weld metal relative to the base metal irrespective of the welding processes used. The LBW joint exhibited superior impact toughness compared to the FSW joint.

Autonomous bed-sediment imaging-systems for revealing temporal variability of grain size

Science.gov (United States)

Buscombe, Daniel; Rubin, David M.; Lacy, Jessica R.; Storlazzi, Curt D.; Hatcher, Gerald; Chezar, Henry; Wyland, Robert; Sherwood, Christopher R.

2014-01-01

We describe a remotely operated video microscope system, designed to provide high-resolution images of seabed sediments. Two versions were developed, which differ in how they raise the camera from the seabed. The first used hydraulics and the second used the energy associated with wave orbital motion. Images were analyzed using automated frequency-domain methods, which following a rigorous partially supervised quality control procedure, yielded estimates to within 20% of the true size as determined by on-screen manual measurements of grains. Long-term grain-size variability at a sandy inner shelf site offshore of Santa Cruz, California, USA, was investigated using the hydraulic system. Eighteen months of high frequency (min to h), high-resolution (μm) images were collected, and grain size distributions compiled. The data constitutes the longest known high-frequency record of seabed-grain size at this sample frequency, at any location. Short-term grain-size variability of sand in an energetic surf zone at Praa Sands, Cornwall, UK was investigated using the ‘wave-powered’ system. The data are the first high-frequency record of grain size at a single location of a highly mobile and evolving bed in a natural surf zone. Using this technology, it is now possible to measure bed-sediment-grain size at a time-scale comparable with flow conditions. Results suggest models of sediment transport at sandy, wave-dominated, nearshore locations should allow for substantial changes in grain-size distribution over time-scales as short as a few hours.

Grain-size dependent accommodation due to intragranular distributions of dislocation loops

International Nuclear Information System (INIS)

Richeton, T.; Berbenni, S.; Berveiller, M.

2009-01-01

A grain-size dependent accommodation law for polycrystals is deduced from an inclusion/matrix problem (i.e., each grain is seen as embedded in a homogeneous equivalent medium) where plastic strain inside the inclusion is given as a discrete distribution of circular coaxial glide dislocation loops. The loops are assumed constrained at spherical grain boundaries. From thermodynamic considerations specific to a process of identical plastification in all the loops (considered as 'super-dislocations'), an average back-stress over the grain is derived. In order to compute the very early stages of plastic deformation in a face-centred cubic polycrystal, this back-stress is incorporated into a diluted model in terms of concentration of plastic grains. Contrary to conventional mean-field approaches, a grain-size effect is obtained for the initial overall strain-hardening behaviour. This size effect results from an intrinsic contribution of intragranular slip heterogeneities on the kinematical hardening

Synthesis and properties of Pr-substituted MgZn ferrites for core materials and high frequency applications

International Nuclear Information System (INIS)

Mukhtar, Muhammad Waqas; Irfan, Muhammad; Ahmad, Ishtiaq; Ali, Ihsan; Akhtar, Majid Niaz; Khan, Muhammad Azhar; Abbas, Ghazanfar; Rana, M.U.; Ali, Akbar; Ahmad, Mukhtar

2015-01-01

A series of single phase spinel ferrites having chemical formula Mg 0.5 Zn 0.5 Pr x Fe 2−x O 4 (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared using the sol–gel technique after sintering at 700 °C. The thermal decomposition behavior of an as prepared powder was investigated by means of DTA/TGA analyses. The sintered powders were then characterized by Fourier transform infrared spectroscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscope and vibrating sample magnetometer. X-ray diffraction patterns confirm the single phase spinel structure of prepared ferrites without the presence of any impurity phase. The value of lattice parameter (a) increases with the increase of Pr contents (x) into the spinel lattice. The grain size estimated from electron microscope images is in the range of 2.75–5.4 µm which confirms the spinel crystalline nature of the investigated samples. The saturation magnetization (M s ) decreases whereas coercivity (H c ) increases with the increase of Pr contents (x). The measured parameters suggest that these materials are favorable for high frequency applications and as core materials. - Highlights: • Pr-substituted spinel ferrites synthesized by autocombustion route have been investigated. • The average grain size was in the range of 2.75–5.4 µm estimated by SEM technique. • The (M s ) decreases whereas (H c ) increases with the increase of Pr contents (x). • These parameters are favorable for high frequency applications and as core materials

Manufacturing of Mn-Zn ferrite transformer cores

International Nuclear Information System (INIS)

Waqas, H.; Qureshi, A.H.; Hussain, N.; Ahmed, N.

2012-01-01

The present work is related to the development of soft ferrite transformer cores, which are extensively used in electronic devices such as switch mode power supplies, electromagnetic devices, computers, amplifiers etc. Mn-Zn Ferrite (soft ferrite) powders were prepared by conventional mixed oxide and auto combustion routes. These powders were calcined and then pressed in toroid shapes. Sintering was done at different temperatures to develop desired magnetic phase. Impedance resistance of sintered toroid cores was measured at different frequencies. Results revealed that Mn-Zn Ferrite cores synthesized by auto combustion route worked more efficiently in a high frequency range i.e. > 2MHz than the cores developed by conventional mixed oxide method. It was noticed that compact size, light weight and high impedance resistance are the prime advantages of auto combustion process which supported the performance of core in MHz frequency range. Furthermore, these compact size cores were successfully tested in linear pulse amplifier circuit of Pakistan Atomic Research Reactor-I. The fabrication of soft ferrite (Mn-Zn Ferrite) cores by different processing routes is an encouraging step towards indigenization of ferrite technology. (Orig./A.B.)

Relative effect(s) of texture and grain size on magnetic properties in a low silicon non-grain oriented electrical steel

International Nuclear Information System (INIS)

PremKumar, R.; Samajdar, I.; Viswanathan, N.N.; Singal, V.; Seshadri, V.

2003-01-01

Hot rolled low Si (silicon) non-grain oriented electrical steel was cold rolled to different reductions. Cold rolled material was subsequently recrystallized, 650 deg. C and 2 h, and then temper rolled (to 7% reduction) for the final grain growth annealing and decarburization treatment at 850 deg. C for 2-24 h. The development of texture, grain size and magnetic properties were characterized at different stages of processing. Effect of texture on magnetic properties (watt loss and permeability) was observed to be best represented by the ratio of volume fractions of (1 1 1) /(0 0 1) fibers, as estimated by convoluting X-ray ODFs (orientation distribution functions) with respective model functions. Such a ratio was termed as generalized texture factor (tf) for the non-grain oriented electrical steel. An effort was made to delink effects of grain size and texture, as represented by respective tf, on watt loss and permeability by careful analysis of experimental data. In general, low tf and/or high grain size were responsible for low watt loss and high permeability. However, individual effect of grain size or tf on magnetic properties was less significant at low tf or large grain size, respectively. An attempt was made to fit regression equations, namely--linear, exponential and power, relating magnetic properties with tf and grain size, limiting the fitting parameters to 3. Least standard deviations, between experimental and predicted values, were obtained by power regression equations for both magnetic properties

Influence of grain size in the near-micrometre regime on the deformation microstructure in aluminium

International Nuclear Information System (INIS)

Le, G.M.; Godfrey, A.; Hansen, N.; Liu, W.; Winther, G.; Huang, X.

2013-01-01

The effect of grain size on deformation microstructure formation in the near-micrometre grain size regime has been studied using samples of aluminium prepared using a spark plasma sintering technique. Samples in a fully recrystallized grain condition with average grain sizes ranging from 5.2 to 0.8 μm have been prepared using this technique. Examination in the transmission electron microscope of these samples after compression at room temperature to approximately 20% reduction reveals that grains larger than 7 μm are subdivided by cell block boundaries similar to those observed in coarse-grained samples, with a similar dependency on the crystallographic orientation of the grains. With decreasing grain size down to approx. 1 μm there is a gradual transition from cell block structures to cell structures. At even smaller grain sizes of down to approx. 0.5 μm the dominant features are dislocation bundles and random dislocations, although at a larger compressive strain of 30% dislocation rotation boundaries may also be found in the interior of grains of this size. A standard 〈1 1 0〉 fibre texture is found for all grain sizes, with a decreasing sharpness with decreasing grain size. The structural transitions with decreasing grain size are discussed based on the general principles of grain subdivision by deformation-induced dislocation boundaries and of low-energy dislocation structures as applied to the not hitherto explored near-micrometre grain size regime

Towards modeling intergranular stress corrosion cracks on grain size scales

International Nuclear Information System (INIS)

Simonovski, Igor; Cizelj, Leon

2012-01-01

Highlights: ► Simulating the onset and propagation of intergranular cracking. ► Model based on the as-measured geometry and crystallographic orientations. ► Feasibility, performance of the proposed computational approach demonstrated. - Abstract: Development of advanced models at the grain size scales has so far been mostly limited to simulated geometry structures such as for example 3D Voronoi tessellations. The difficulty came from a lack of non-destructive techniques for measuring the microstructures. In this work a novel grain-size scale approach for modelling intergranular stress corrosion cracking based on as-measured 3D grain structure of a 400 μm stainless steel wire is presented. Grain topologies and crystallographic orientations are obtained using a diffraction contrast tomography, reconstructed within a detailed finite element model and coupled with advanced constitutive models for grains and grain boundaries. The wire is composed of 362 grains and over 1600 grain boundaries. Grain boundary damage initialization and early development is then explored for a number of cases, ranging from isotropic elasticity up to crystal plasticity constitutive laws for the bulk grain material. In all cases the grain boundaries are modeled using the cohesive zone approach. The feasibility of the approach is explored.

Small-scale mechanical property characterization of ferrite formed during deformation of super-cooled austenite by nanoindentation

International Nuclear Information System (INIS)

Ahn, Tae-Hong; Um, Kyung-Keun; Choi, Jong-Kyo; Kim, Do Hyun; Oh, Kyu Hwan; Kim, Miyoung; Han, Heung Nam

2009-01-01

The mechanical properties of dynamically and statically transformed ferrites were analyzed using a nanoindentater-EBSD (Electron BackScattered Diffraction) correlation technique, which can distinguish indenting positions according to the grains in the specimen. The dilatometry and the band slope and contrast maps by EBSD were used to evaluate the volume fractions of two kinds of ferrite and pearlite. Fine ferrites induced by a dynamic transformation had higher nano-hardness than the statically transformed coarse ferrites. Transmission electron microscopy (TEM) showed the dynamic ferrites to have a higher dislocation density than the statically transformed ferrites.

Oxide dispersion strengthened ferritic alloys. 14/20% chromium: effects of processing on deformation texture, recrystallization and tensile properties

International Nuclear Information System (INIS)

Regle, H.

1994-01-01

The ferritic oxide dispersion strengthened alloys are promising candidates for high temperature application materials, in particular for long life core components of advanced nuclear reactors. The aim of this work is to control the microstructure, in order to optimise the mechanical properties. The two ferritic alloys examined here, MA956 and MA957, are obtained by Mechanical Alloying techniques. They are characterised by quite anisotropic microstructure and mechanical properties. We have investigated the influence of hot and cold working processes (hot extrusion, swaging and cold-drawing) and recrystallization heat treatments on deformation textures, microstructures and tensile properties. The aim was to control the size of the grains and their anisotropic shape, using recrystallization heat treatments. After consolidation and hot extrusion, as-received materials present a extremely fine microstructure with elongated grains and a very strong (110) deformation texture with single-crystal character. At that stage of processing, recrystallization temperature are very high (1450 degrees C for MA957 alloy and 1350 degrees C for MA956 alloy) and materials develop millimetric recrystallized grains. Additional hot extrusion induce a fibre texture. Cold-drawing maintains a fibre texture, but the intensity decreases with increasing cold-work level. For both materials, the decrease of texture intensities correspond to a decrease of the recrystallization temperatures (from 1350 degrees C for a low cold-work level to 750 degrees C for 60 % cold-deformation, case of MA956 alloy) and a refinement of the grain size (from a millimetric size to less than an hundred of micrometer). Swaging develop a cyclic component where the intensity increases with increasing deformation in this case, the recrystallization temperature remains always very high and the millimetric grain size is slightly modified, even though cold-work level increases. Technologically, cold-drawing is the only way

Determination of grain size by XRD profile analysis and TEM counting in nano-structured Cu

International Nuclear Information System (INIS)

Zhong Yong; Ping Dehai; Song Xiaoyan; Yin Fuxing

2009-01-01

In this work, a serial of pure copper sample with different grain sizes from nano- to micro-scale were prepared by sparkle plasma sintering (SPS) and following anneal treatment at 873 K and 1073 K, respectively. The grain size distributions of these samples were determined by both X-ray diffraction (XRD) profile analysis and transmission electronic microscope (TEM) micrograph counting. Although these two methods give similar distributions of grain size in the case of as-SPS sample with nano-scale grain size (around 10 nm), there are apparent discrepancies between the grain size distributions of the annealed samples obtained from XRD and TEM, especially for the sample annealed at 1073 K after SPS with micro-scale grain size (around 2 μm), which TEM counting provides much higher values of grain sizes than XRD analysis does. It indicates that for large grain-sized material, XRD analysis lost its validity for determination of grain size. It might be due to some small sized substructures possibly existed in even annealed (large grain-sized) samples, whereas there is no substructures in as-SPS (nanocrystalline) sample. Moreover, it has been found that the effective outer cut-off radius R e derived from XRD analysis coincides with the grain sizes given by TEM counting. The potential relationship between grain size and R e was discussed in the present work. These results might provide some new hints for deeper understanding of the physical meaning of XRD analysis and the parameters derived.

Structural, impedance and Mössbauer studies of magnesium ferrite synthesized via sol–gel auto-combustion process

Directory of Open Access Journals (Sweden)

Shahid Khan Durrani

2017-12-01

Full Text Available Crystalline magnesium ferrite (MgFe2O4 spinel oxide powder was synthesized by nitrate–citrate sol–gel auto-combustion process with stoichiometric composition of metal nitrate salts, urea and citric acid. The study was focused on the modification of synthesis conditions and effect of these modified conditions on the structural and electrical properties of synthesized MgFe2O4 ceramic materials. Phase composition, crystallinity, structure and surface morphology were studied by X-ray diffraction, FTIR and SEM. Pure single phase MgFe2O4 spinel ferrite was obtained after calcination at 850 °C. Rietveld refinement of XRD result confirmed the single cubic phase spinel oxide with the lattice constant of a = 8.3931 Å and Fd3m symmetry. UV–visible absorption study of calcined powder revealed an optical band gap of 2.17 eV. SEM images of sintered specimens (1050–1450 °C showed that the grain size increased with the increase in sintering temperature. From the impedance results of the sintered MgFe2O4 specimens, it was found that the resistance of grain, grain boundary and electrode effect decreased with an increase in sintering temperature and associated grain growth. In the intermediate frequency region lowering of impedance and dielectric values was observed due to the decrease in grain boundary areas. Mössbauer studies indicated that magnesium ferrite had a mixed spinel structure in calcined and sintered samples, however, the well refined single phase MgFe2O4 was observed due to well developed high crystalline structure at 1350 °C and 1450 °C. Keywords: Sol–gel auto-combustion, Magnesium ferrite, X-ray diffraction, SEM, Mössbauer spectroscopy, Impedance spectroscopy

Structural and magnetic Properties of TbZn-substituted calcium barium M-type nano-structured hexa-ferrites

Energy Technology Data Exchange (ETDEWEB)

Khan, Hasan M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Department of Electronics, University of York, York YO10 5DD (United Kingdom); Islam, M.U., E-mail: dr.misbahulislam@bzu.edu.pk [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Xu, Yongbing [Department of Electronics, University of York, York YO10 5DD (United Kingdom); Nanjing–York International Centre of Spintronics and Nano-Engineering, Nanjing University, Nanjing 210093 (China); Asif Iqbal, M. [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); National University of Science and Technology, College of E and ME, Islamabad (Pakistan); Ali, Irshad [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan)

2014-03-15

Highlights: • Tb–Zn substituted Ca{sub 0.5}Ba{sub 0.5}Fe{sub 12}O{sub 19} samples exhibit single magnetoplumbite phase. • Lattice parameters a and c have increasing values. • Coercivity can be tuned at lower substitution level • Crystallites size was found in the range 18–25 nm by TEM and by Scherrer formula. • These hexa-ferrites are suitable for microwave devices and magnetic recording media. -- Abstract: Effect of TbZn substitution on the structural and magnetic properties of Ca{sub 0.5}Ba{sub 0.5−x}Tb{sub x}Zn{sub y}Fe{sub 12−y}O{sub 19}, (x = 0.00–0.10; y = 0.00–1.00) ferrites prepared by sol–gel auto combustion is reported. The synthesized samples were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Vibrating Sample magnetometery. The X-ray diffraction analysis confirmed single phase M-type hexa-ferrite structure. The lattice parameters were found to increase as TbZn contents increases, which is attributed to the ionic sizes of the implicated cations. The TbZn seems to be completely soluble in the lattice. The results of scanning electron microscopy and transmission electron microscopy shows that the grain size decreases with increase of TbZn substitution. The coercivity values (1277–2025 Oe) of all samples lies in the range of M-type hexa-ferrite and indicate that an increase of anisotropy was achieved by substitution of TbZn, while the size of nanoparticles was drastically reduced between 18 and 25 nm. The increased anisotropy and fine particle size are useful for many applications, such as improving signal noise ratio of recording devices.

Effect of gamma irradiation on the structural and magnetic properties of Co–Zn spinel ferrite nanoparticles

International Nuclear Information System (INIS)

Raut, Anil V.; Kurmude, D.V.; Shengule, D.R.; Jadhav, K.M.

2015-01-01

Highlights: • Co–Zn ferrite nanoparticles were examined before and after γ-irradiation. • Single phase cubic spinel structure of Co–Zn was confirmed by XRD data. • The grain size was reported in the range of 52–62 nm after γ-irradiation. • Ms, Hc, n B were reported to be increased after gamma irradiation. - Abstract: In this work, the structural and magnetic properties of Co 1−x Zn x Fe 2 O 4 (0.0 ≤ x ≤ 1.0) ferrite nanoparticles were studied before and after gamma irradiation. The as-synthesized samples of Co–Zn ferrite nanoparticles prepared by sol–gel auto-combustion technique were analysed by XRD which suggested the single phase; cubic spinel structure of the material. Crystal defects produced in the spinel lattice were studied before and after Co 60 γ-irradiation in a gamma cell with a dose rate of 0.1 Mrad/h in order to report the changes in structural and magnetic properties of the Co–Zn ferrite nanoparticles. The average crystallite size (t), lattice parameter (α) and other structural parameters of gamma-irradiated and un-irradiated Co 1−x Zn x Fe 2 O 4 spinel ferrite system was calculated from XRD data. The morphological characterizations were performed using scanning electron microscopy (SEM). The magnetic properties were measured using pulse field hysteresis loop tracer by applying magnetic field of 1000 Oe, and the analysis of data obtained revealed that the magnetic property such as saturation magnetization (Ms), coecivity (Hc), magneton number (n B ) etc. magnetic parameters were increased after irradiation

The role of grain size in He bubble formation: Implications for swelling resistance

Science.gov (United States)

El-Atwani, O.; Nathaniel, J. E.; Leff, A. C.; Muntifering, B. R.; Baldwin, J. K.; Hattar, K.; Taheri, M. L.

2017-02-01

Nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas ranging from 3000 to 7500 nm2 show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm2 possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.

The role of grain size in He bubble formation: Implications for swelling resistance

Energy Technology Data Exchange (ETDEWEB)

El-Atwani, O., E-mail: oelatwan25@gmail.com [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States); Nathaniel, J.E.; Leff, A.C. [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States); Muntifering, B.R. [Department of Radiation Solid Interactions, Sandia National Laboratories, NM (United States); Baldwin, J.K. [Center for Integrated Nanotechnologies, Los Alamos National Laboratory, Los Alamos, NM (United States); Hattar, K. [Department of Radiation Solid Interactions, Sandia National Laboratories, NM (United States); Taheri, M.L. [Drexel University, Department of Materials Science & Engineering, Philadelphia, PA (United States)

2017-02-15

Nanocrystalline metals are postulated as radiation resistant materials due to their high defect and particle (e.g. Helium) sink density. Here, the performance of nanocrystalline iron films is investigated in-situ in a transmission electron microscope (TEM) using He irradiation at 700 K. Automated crystal orientation mapping is used in concert with in-situ TEM to explore the role of grain orientation and grain boundary character on bubble density trends. Bubble density as a function of three key grain size regimes is demonstrated. While the overall trend revealed an increase in bubble density up to a saturation value, grains with areas ranging from 3000 to 7500 nm{sup 2} show a scattered distribution. An extrapolated swelling resistance based on bubble size and areal density indicated that grains with sizes less than 2000 nm{sup 2} possess the greatest apparent resistance. Moreover, denuded zones are found to be independent of grain size, grain orientation, and grain boundary misorientation angle.

A study on low temperature transformation ferrite in ultra low carbon IF steels (I) - effects of manganese and annealing conditions

International Nuclear Information System (INIS)

Jeong, Woo Chang; Lee, Jae Yeon; Jin, Young Sool

2001-01-01

An investigation was made to determine the effects of Mn content and annealing conditions on the formation of the low temperature transformation products in ultra low carbon interstitial free steels. With increasing the Mn content, yield and tensile strengths increased, but yield ratio decreased. The Mn was found to be effective to decrease the yield point elongation, causing continuous yielding in 3% Mn steel. Low temperature transformation ferrites such as quasi-polygonal ferrite, granular bainitic ferrite, and bainitic ferrite more easily formed with higher Mn content, higher annealing temperature, longer annealing time, and faster cooling rate. Polygonal ferrite grain was readily identified in the light microscope and was characterized by the polyhedral and equiaxed shape while quasi-polygonal ferrite showed the irregular changeful grain boundaries. It was found that both granular bainitic and bainitic ferrites revealed some etching evidence of substructures in the light microscope

Microhardness and grain size of disordered nonstoichiometric titanium carbide

International Nuclear Information System (INIS)

Lipatnikov, V.N.; Zueva, L.V.; Gusev, A.I.

1999-01-01

Effect of the disordered nonstoichiometric titanium carbide on its microhardness and grain size is studied. It is established that decrease in defectiveness of carbon sublattice of disordered carbide is accompanied by microhardness growth and decrease in grain size. Possible causes of the TiC y microhardness anomalous behaviour in the area 0.8 ≤ y ≤ 0.9 connected with plastic deformation mechanism conditioned by peculiarities of the electron-energetic spectrum of nonstoichiometric carbide are discussed [ru

Anisotropy in tensile and ductile-brittle transition behavior of ODS ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Kasada, R., E-mail: r-kasada@iae.kyoto-u.ac.jp [Institute of Advanced Energy, Kyoto University, Uji, Kyoto (Japan); Lee, S.G.; Isselin, J.; Lee, J.H.; Omura, T.; Kimura, A. [Institute of Advanced Energy, Kyoto University, Uji, Kyoto (Japan); Okuda, T. [KOBELCO Research Institute, 1-5-5, Takatsukadai, Nishi-ku, Kobe 651-2271 (Japan); Inoue, M. [Japan Atomic Energy Agency, 4002 Narita, Oarai, Ibaraki 311-1393 (Japan); Ukai, S.; Ohnuki, S. [Materials Science and Engineering, Hokkaido University, N14 W8, Kita ku, Sapporo 060-8626 (Japan); Fujisawa, T. [Nagoya University, Furocho, Chikusa, Nagoya 464-8603 (Japan); Abe, F. [National Institute of Materials Science, Tsukuba, (NIMS), 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2011-10-01

Anisotropic fracture behavior of SOC-1 oxide dispersion strengthened (ODS) ferritic steel has been investigated for a hot-extruded bar by tensile tests and Charpy impact tests. These mechanical properties are better in the longitudinal direction than in the transverse directions against extrusion direction (ED). Fracture surface observations by scanning electron microscopy and auger electron spectroscopy indicated bundle-like morphology with existence of segregation/precipitation/inclusions along ED. Pole figures of the hot-extruded bar characterized using electron back scattering diffraction (EBSD) technique and X-ray diffraction exhibited <1 1 0> fiber texture formation along ED. The EBSD orientation map showed a complex bundle-like grain morphology which consists of elongated grains having a specific orientation <1 1 0>// ED and relatively isotropic and small grains having other orientation. The results conclude that the combined effects of observed elongated grain morphology and these small grains with segregation/precipitation/inclusions along ED can explain the anisotropic fracture behavior of the hot-extruded ODS ferritic steel.

Mapping soil degradation by topsoil grain size using MODIS data

OpenAIRE

XIAO, Jieying; SHEN, Yanjun; TATEISHI, Ryutaro

2005-01-01

[ABSTRACT] MODIS BRDF reflectance data at the end of April 2004 was selected to make a desertification map base on topsoil grain size by using Gain Size Index at arid and semiarid Asia. After data processing, GSI was applied into desertification mapping, and we find that high GSI area distributed at the desert and its’ marginal area, degraded grassland, desert steppe. The desertification map was output according to the correlation between GSI and grain size distribution, the classification of...

High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions

Energy Technology Data Exchange (ETDEWEB)

Li, Lulu, E-mail: lli18@ncsu.edu; Saber, Mostafa; Xu, Weizong; Zhu, Yuntian; Koch, Carl C.; Scattergood, Ronald O.

2014-09-08

The influence of 1–4 at% Hf additions on the thermal stability of mechanically alloyed nanocrystalline Fe–14Cr alloys was studied in this work. XRD-calculated grain size and microhardness results were reported versus isochronal annealing treatments up to 1100 °C. Microstructural evolution was investigated using channeling contrast FIB imaging and TEM. Grain size of samples with 4 at% Hf was found to be maintained in the nanoscale range at temperatures up to 1000 °C. Zener pinning was considered as a major source of high temperature grain size stabilization. By comparing the Orowan strengthening contribution to the total hardness, the deviation of grain size predictions from the actual grain size in Fe–14Cr–4Hf suggests the presence of thermodynamic stabilization by the solute segregation to grain boundaries (GBs). A predictive thermodynamic model indicates that the thermodynamic stabilization can be expected.

Structural and magnetic properties of Ni0.8M0.2Fe2O4 (M = Cu, Co) nano-crystalline ferrites

Science.gov (United States)

Vijaya Babu, K.; Satyanarayana, G.; Sailaja, B.; Santosh Kumar, G. V.; Jalaiah, K.; Ravi, M.

2018-06-01

Nano-crystalline nickel ferrites are interesting materials due to their large physical and magnetic properties. In the present work, two kinds of spinel ferrites Ni0.8M0.2Fe2O4 (M = Cu, Co) are synthesized by using sol-gel auto-combustion method and the results are compared with NiFe2O4. The structural properties of synthesized ferrites are determined by using X-ray powder diffraction; scanning electron microscope and Fourier transform infrared spectroscopy. The cation distribution obtained from X-ray diffraction show that cobalt/copper occupies only tetrahedral site in spinel lattice. The lattice constant increases with the substitution of cobalt/copper. The structural parameters like bond lengths, tetrahedral and octahedral edges have been varied with the substitution. The microstructural study is carried out by using SEM technique and the average grain size is increased with nickel ferrite. The initial permeability (μi) is improving with the substitution. The observed g-value from ESR is approximately equal to standard value.

Synthesis of a low loss Mn–Zn ferrite for power applications

Energy Technology Data Exchange (ETDEWEB)

Tsakaloudi, Vasiliki, E-mail: vikaki@cperi.certh.gr [Laboratory of Inorganic Materials, Chemical Process and Energy Resources Institute, Centre for Research and Technology Hellas, 57001 Thermi-Thessaloniki (Greece); Zaspalis, Vassilios [Laboratory of Inorganic Materials, Chemical Process and Energy Resources Institute, Centre for Research and Technology Hellas, 57001 Thermi-Thessaloniki (Greece); Laboratory of Materials Technology, Department of Chemical Engineering, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)

2016-02-15

Current market trends of the switching power supplies industry require even lower energy losses in power conversion systems with maintenance of satisfactory initial permeability levels. Typical operation conditions refer to a frequency of 100 kHz, an induction level of 200 mT and a steady state temperature of 100° C. In this work the development of a polycrystalline Mn–Zn ferrite material that exhibits initial relative magnetic permeability above 2500 and very low power losses at 100 kHz, 200 mmT and 100° C is presented. The Mn–Zn ferrite samples were prepared by the conventional solid state reaction method. Sintering was performed under controlled atmosphere conditions. The combinatorial role of TiO{sub 2} and CoO together with Zn content, as well as the effects of the process parameters on the magnetic performance of the Mn–Zn ferrite was evaluated. It is shown that the development of the adequate polycrystalline microstructure that is characterized by (a) high sintered density, (b) homogenous grain size that is free of morphological or chemical pinning defects and (c) high resistivity grain boundary structure, can be achieved by means of appropriate compositional and dopant adjustment, anisotropy control and specific resistivity optimization. The newly developed Mn–Zn ferrite is characterized by high sintered density of 4.91 g/cm{sup 3}, initial magnetic permeability of 2512 (at 10 kHz, 0.1 mT, 25 °C), high saturation magnetic flux density of 560 mT (at 10 kHz, 1200 A/m, 25 °C) and very low power losses (Pv) of 224 mW/cm{sup 3} (at 100 kHz, 200 mT, 100 °C) combined with very low power losses of 470 mW/cm{sup 3} even at room temperature, establishing it as ideal for power applications. - Highlights: • Mn–Zn ferrites for power applications are prepared by solid state reaction. • Optimal doping levels of TiO{sub 2} and CoO for low power losses are determined. • A slow cooling rate during sintering improves the resistivity and power losses. �

Influence of Fe(Cr) miscibility on thin film grain size and stress

Energy Technology Data Exchange (ETDEWEB)

Zhou, Xuyang; Kaub, Tyler; Martens, Richard L.; Thompson, Gregory B., E-mail: gthompson@eng.ua.edu

2016-08-01

During the post coalescence portion of thin film deposition, thin film stress is related to the grain size and adatom mobility of the depositing material. Using a Fe(Cr) alloy thin film, the manipulation of the tensile stress for thick films was studied as a function of Cr solute content up to 8 at.%. Solute concentrations up to 4 at.% resulted in an approximate 50% increase in grain size that resulted in a reduction of the tensile stress to be lower than either elemental film. Upon increasing the Cr content, the grain size refined and the tensile stress of the films increased. Atom probe characterization of the grain boundaries confirmed Cr chemical partitioning which refined the grain size and altered the film's texture, both of which contributed to the change in film stress. The use of intrinsic segregation, rather than deposition processing parameters, appears to be another viable option for regulating film stress. - Highlights: • Solute segregation to regulate grain size in controlling film stress • Quantification of Cr interfacial excess as a function of alloy content • Quantification of texture fiber alignment as a function of Cr content.

THE EFFECTS OF GRAIN SIZE AND TEMPERATURE DISTRIBUTIONS ON THE FORMATION OF INTERSTELLAR ICE MANTLES

Energy Technology Data Exchange (ETDEWEB)

Pauly, Tyler; Garrod, Robin T., E-mail: tap74@cornell.edu [Cornell Center for Astrophysics and Planetary Science, Cornell University, Ithaca, NY 14853-6801 (United States)

2016-02-01

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface–gas interactions.

The Effects of Grain Size and Temperature Distributions on the Formation of Interstellar Ice Mantles

Science.gov (United States)

Pauly, Tyler; Garrod, Robin T.

2016-02-01

Computational models of interstellar gas-grain chemistry have historically adopted a single dust-grain size of 0.1 micron, assumed to be representative of the size distribution present in the interstellar medium. Here, we investigate the effects of a broad grain-size distribution on the chemistry of dust-grain surfaces and the subsequent build-up of molecular ices on the grains, using a three-phase gas-grain chemical model of a quiescent dark cloud. We include an explicit treatment of the grain temperatures, governed both by the visual extinction of the cloud and the size of each individual grain-size population. We find that the temperature difference plays a significant role in determining the total bulk ice composition across the grain-size distribution, while the effects of geometrical differences between size populations appear marginal. We also consider collapse from a diffuse to a dark cloud, allowing dust temperatures to fall. Under the initial diffuse conditions, small grains are too warm to promote grain-mantle build-up, with most ices forming on the mid-sized grains. As collapse proceeds, the more abundant, smallest grains cool and become the dominant ice carriers; the large population of small grains means that this ice is distributed across many grains, with perhaps no more than 40 monolayers of ice each (versus several hundred assuming a single grain size). This effect may be important for the subsequent processing and desorption of the ice during the hot-core phase of star formation, exposing a significant proportion of the ice to the gas phase, increasing the importance of ice-surface chemistry and surface-gas interactions.

Application of carbon extraction replicas in grain-size measurements of high-strength steels using TEM

International Nuclear Information System (INIS)

Poorhaydari, Kioumars; Ivey, Douglas G.

2007-01-01

In this paper, the application of carbon extraction replicas in grain-size measurements is introduced and discussed. Modern high-strength microalloyed steels, used as structural or pipeline materials, have very small grains with substructures. Replicas used in transmission electron microscopes can resolve the grain boundaries and can be used for systematic measurement of grain size in cases where the small size of the grains pushes the resolution of conventional optical microscopes. The grain-size variations obtained from replicas are compared with those obtained from optical and scanning electron microscopy. An emphasis is placed on the importance of using the correct technique for imaging and the optimal magnification. Grain-size measurements are used for estimation of grain-boundary strengthening contribution to yield strength. The variation in grain size is also correlated with hardness in the base metal of several microalloyed steels, as well as the fine-grained heat-affected zone of a weld structure with several heat inputs

Metal-assisted chemical etching of CIGS thin films for grain size analysis

Energy Technology Data Exchange (ETDEWEB)

Xue, Chaowei [Research and Development Centre, Hanergy Thin Film Power Group Limited, Chengdu (China); Loi, Huu-Ha; Duong, Anh; Parker, Magdalena [Failure Analysis Department, MiaSole Hi-Tech Corp., Santa Clara, CA (United States)

2016-09-15

Grain size of the CIGS absorber is an important monitoring factor in the CIGS solar cell manufacturing. Electron backscatter diffraction (EBSD) analysis is commonly used to perform CIGS grain size analysis in the scanning electron microscope (SEM). Although direct quantification on SEM image using the average grain intercept (AGI) method is faster and simpler than EBSD, it is hardly applicable on CIGS thin films. The challenge is that, not like polycrystalline silicon, to define grain boundaries by selective chemical etching is not easily realizable for the multi-component CIGS alloy. In this Letter, we present direct quantification of CIGS thin film grain size using the AGI method by developing metal-assisted wet chemical etching process to define CIGS grain boundaries. The calculated value is similar to EBSD result. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

High-Temperature Confocal Laser Scanning Microscopy Studies of Ferrite Formation in Inclusion-Engineered Steels: A Review

Science.gov (United States)

Mu, Wangzhong; Hedström, Peter; Shibata, Hiroyuki; Jönsson, Pär G.; Nakajima, Keiji

2018-05-01

The concepts of oxide metallurgy and inclusion engineering can be utilized to improve the properties of low-alloy steels. These concepts aim at controlling the formation of intragranular ferrite (IGF), often a desirable microstructure providing good mechanical properties without the need for expensive alloying elements. IGF formation is stimulated to occur at non-metallic inclusions and form an arrangement of fine, interlocking ferrite grains. A method that has contributed significantly to investigations in this field lately is high-temperature confocal laser scanning microscopy (HT-CLSM). HT-CLSM is suited for in situ studies of inclusion behavior in liquid steel and phase transformations in solid-state steel, where in particular, displacive phase transformations can be studied, since they provide sufficient topographic contrast. The purpose of the present report is to provide a brief review of the state of the art of HT-CLSM and its application for in situ observations of ferrite formation in inclusion-engineered steels. The scientific literature in this field is surveyed and supplemented by new work to reveal the capability of HT-CLSM as well as to discuss the effect of factors such as cooling rate and parent grain size on IGF formation and growth kinetics. The report concludes with an outlook on the opportunities and challenges of HT-CLSM for applications in oxide metallurgy.

Forecasting grain size distribution of coal cut by a shearer loader

Energy Technology Data Exchange (ETDEWEB)

Sikora, W; Chodura, J; Siwiec, J

1983-02-01

Analyzed are effects of shearer loader design on grain size distribution of coal, particularly on proportion of the finest size group and proportion of largest coal grains. The method developed by the IGD im. A.A. Skochinski Institute in Moscow is used. Effects of cutting tool design and mechanical coal properties are analyzed. Of the evaluated factors, two are of decisive importance: thickness of the coal chip cut by a cutting tool and coefficient of coal disintegration which characterizes coal behavior during cutting. Grain size distribution is also influenced by cutting tool geometry. Two elements of cutting tool design are of major importance: dimensions of the cutting edge and angle of attack. Effects of cutting tool design and coal mechanical properties on grain size distribution are shown in 12 diagrams. Using the forecasting method developed by the IGD im. A.A. Skochinski Institute in Moscow grain size distribution of coal cut by three shearer loaders is calculated: the KWB-3RDU with a drum 1600 mm in diameter, the KWB-6W with a drum 2500 mm in diameter, and a shearer loader being developed with a 1550 mm drum. The results of comparative evaluations are shown in two tables. 5 references.

Colour characteristics of winter wheat grits of different grain size

Directory of Open Access Journals (Sweden)

Horváth Zs. H.

2015-01-01

Full Text Available Nowadays, wheat has spread all over the world due to its extensive usability. The colour of wheat grits is very important for the milling and baking industry because it determines the colour of the products made from it. The instrumental colour measuring is used, first of all, for durum wheat. We investigated the relationship between colour characteristics and grain size in the case of different hard aestivum wheats. We determined the colour using the CIE (Commission Internationale de l’Eclairage 1976 L*, a*, b* colour system measured by MINOLTA CR-300 tristimulus colorimeter. After screening the colour of the wheat fractions of different grain size, grits was measured wet and dry. We determined the L*, a*, b* colour co-ordinates and the whiteness index, too. To evaluate the values we had obtained, we used analysis of variance and regression analysis. We pointed out that the colour of wheat grits of different grain size is dependent on the hardness index of wheat. The lightness co-ordinate (L* of grits of the harder wheat is smaller, while a* and b* co-ordinates are higher. We also found that while grain size rises, the L* co-ordinate decreases and a*, b* values increase in the case of every type of wheat. The colour of grits is determined by the colour of fractions of 250-400 μm in size, independently from the average grain size. The whiteness index and the L* colour co-ordinate have a linear relation (R2 = 0.9151; so, the determination of whiteness index is not necessary. The L* value right characterizes the whiteness of grits.

Investigations of grain size dependent sediment transport phenomena on multiple scales

Science.gov (United States)

Thaxton, Christopher S.

Sediment transport processes in coastal and fluvial environments resulting from disturbances such as urbanization, mining, agriculture, military operations, and climatic change have significant impact on local, regional, and global environments. Primarily, these impacts include the erosion and deposition of sediment, channel network modification, reduction in downstream water quality, and the delivery of chemical contaminants. The scale and spatial distribution of these effects are largely attributable to the size distribution of the sediment grains that become eligible for transport. An improved understanding of advective and diffusive grain-size dependent sediment transport phenomena will lead to the development of more accurate predictive models and more effective control measures. To this end, three studies were performed that investigated grain-size dependent sediment transport on three different scales. Discrete particle computer simulations of sheet flow bedload transport on the scale of 0.1--100 millimeters were performed on a heterogeneous population of grains of various grain sizes. The relative transport rates and diffusivities of grains under both oscillatory and uniform, steady flow conditions were quantified. These findings suggest that boundary layer formalisms should describe surface roughness through a representative grain size that is functionally dependent on the applied flow parameters. On the scale of 1--10m, experiments were performed to quantify the hydrodynamics and sediment capture efficiency of various baffles installed in a sediment retention pond, a commonly used sedimentation control measure in watershed applications. Analysis indicates that an optimum sediment capture effectiveness may be achieved based on baffle permeability, pond geometry and flow rate. Finally, on the scale of 10--1,000m, a distributed, bivariate watershed terain evolution module was developed within GRASS GIS. Simulation results for variable grain sizes and for

Generalization of the existing relations between microstructure and yield stress from ferrite-pearlite to high strength steels

Energy Technology Data Exchange (ETDEWEB)

Iza-Mendia, A., E-mail: aiza@ceit.es [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain); Gutierrez, I. [CEIT and Tecnun (University of Navarra), Manuel de Lardizabal 15, 20018 Donostia-San Sebastian, Basque Country (Spain)

2013-01-20

A series of available equations allows the yield and the tensile strength of low carbon ferrite-pearlite microstructures to be expressed as a function of the optical grain size, steel composition and interstitials in solution. Over the years, as the complexity of steel microstructures has increased, some additional terms have been added to account for precipitation and forest dislocation contributions. In theory, this opens the door for an extension of these equations to bainitic microstructures. Nevertheless, there is a series of difficulties that needs to be overcome in order to improve prediction accuracy. In the present work, different microstructures (ferrite-pearlite, bainite, quenched, and quenched and tempered) were produced and tension tested in a C-Mn-Nb steel. Optical microscopy and EBSD (Electron Back Scattered Diffraction) were applied and the results were compared as a function of the tolerance angle. Based on this work, an adaptation to Pickering's equation is proposed, including its extension to other microstructures rather than ferrite-pearlite.

The effects of particle size distribution and induced unpinning during grain growth

International Nuclear Information System (INIS)

Thompson, G.S.; Rickman, J.M.; Harmer, M.P.; Holm, E.A.

1996-01-01

The effect of a second-phase particle size distribution on grain boundary pinning was studied using a Monte Carlo simulation technique. Simulations were run using a constant number density of both whisker and rhombohedral particles, and the effect of size distribution was studied by varying the standard deviation of the distribution around a constant mean particle size. The results of present simulations indicate that, in accordance with the stereological assumption of the topological pinning model, changes in distribution width had no effect on the pinned grain size. The effect of induced unpinning of particles on microstructure was also studied. In contrast to predictions of the topological pinning model, a power law dependence of pinned grain size on particle size was observed at T=0.0. Based on this, a systematic deviation to the stereological predictions of the topological pinning model is observed. The results of simulations at higher temperatures indicate an increasing power law dependence of pinned grain size on particle size, with the slopes of the power law dependencies fitting an Arrhenius relation. The effect of induced unpinning of particles was also studied in order to obtain a correlation between particle/boundary concentration and equilibrium grain size. The results of simulations containing a constant number density of monosized rhombohedral particles suggest a strong power law correlation between the two parameters. copyright 1996 Materials Research Society

Species distribution model transferability and model grain size - finer may not always be better.

Science.gov (United States)

Manzoor, Syed Amir; Griffiths, Geoffrey; Lukac, Martin

2018-05-08

Species distribution models have been used to predict the distribution of invasive species for conservation planning. Understanding spatial transferability of niche predictions is critical to promote species-habitat conservation and forecasting areas vulnerable to invasion. Grain size of predictor variables is an important factor affecting the accuracy and transferability of species distribution models. Choice of grain size is often dependent on the type of predictor variables used and the selection of predictors sometimes rely on data availability. This study employed the MAXENT species distribution model to investigate the effect of the grain size on model transferability for an invasive plant species. We modelled the distribution of Rhododendron ponticum in Wales, U.K. and tested model performance and transferability by varying grain size (50 m, 300 m, and 1 km). MAXENT-based models are sensitive to grain size and selection of variables. We found that over-reliance on the commonly used bioclimatic variables may lead to less accurate models as it often compromises the finer grain size of biophysical variables which may be more important determinants of species distribution at small spatial scales. Model accuracy is likely to increase with decreasing grain size. However, successful model transferability may require optimization of model grain size.

Effect of coal stress on grain size of the gotten

Energy Technology Data Exchange (ETDEWEB)

Sikora, W; Tront, A

1988-09-01

Presents investigation results on the effect of seam stress and strain state on winning as measured by the grain size of the gotten. The investigations were carried out at the Institute of Mining Mechanization of the Silesian Politechnical where the relations between parameters of seams and cutters and their effect on coal grain size and energy consumption have been studied for several years. The effect was examined on coal samples taken from 4 mines in the Upper Silesian coal basin using a model of the system: seam - cutter. Cubic samples (400x400x400 mm) were tested on the CMG KOMAG test stand equipped with the POS-1 cutting apparatus. Two types of coal were distinguished: that particularly sensitive to increased pressure on seam and that only negligibly susceptible. Corresponding graphs of coal grain size versus vertical pressure are shown. A function has been developed that characterizes this sensitivity depending on a material parameter that can be determined by workability tests. The relationship between coal strength and grain size yield greater than 10 mm in the gotten depending on dynamic crushability of coal is shown in graphs. 6 refs.

Charging of Individual Micron-Size Interstellar/Planetary Dust Grains by Secondary Electron Emissions

Science.gov (United States)

Tankosic, D.; Abbas, M. M.

2012-01-01

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper, we discuss experimental results on dust charging by electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). Currently, very limited experimental data are available for charging of individual micron-size dust grains, particularly by low energy electron impact. Available theoretical models based on the Sternglass equation (Sternglass, 1954) are applicable for neutral, planar, and bulk surfaces only. However, charging properties of individual micron-size dust grains are expected to be different from the values measured on bulk materials. Our recent experimental results on individual, positively charged, micron-size lunar dust grains levitated in an electrodynamic balance facility (at NASA-MSFC) indicate that the SEE by electron impact is a complex process. The electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Here we discuss the complex nature of SEE charging properties of individual micron-size lunar dust grains and silica microspheres.

Microstructure of warm rolling and pearlitic transformation of ultrafine-grained GCr15 steel

International Nuclear Information System (INIS)

Sun, Jun-Jie; Lian, Fu-Liang; Liu, Hong-Ji; Jiang, Tao; Guo, Sheng-Wu; Du, Lin-Xiu; Liu, Yong-Ning

2014-01-01

Pearlitic transformation mechanisms have been investigated in ultra-fine grained GCr15 steel. The ultrafine-grained steel, whose grain size was less than 1 μm, was prepared by thermo-mechanical treatment at 873 K and then annealing at 923 K for 2 h. Pearlitic transformation was conducted by reheating the ultra-fine grained samples at 1073 K and 1123 K for different periods of time and then cooling in air. Scanning electron microscope observation shows that normal lamellar pearlite, instead of granular cementite and ferrite, cannot be formed when the grain size is approximately less than 4(± 0.6) μm, which yields a critical grain size for normal lamellar pearlitic transformations in this chromium alloyed steel. The result confirms that grain size has a great influence on pearlitic transformation by increasing the diffusion rate of carbon atoms in the ultra-fine grained steel, and the addition of chromium element doesn't change this pearlitic phase transformation rule. Meanwhile, the grain growth rate is reduced by chromium alloying, which is beneficial to form fine grains during austenitizing, thus it facilitating pearlitic transformation by divorced eutectoid transformation. Moreover, chromium element can form a relatively high gradient in the frontier of the undissolved carbide, which promotes carbide formation in the frontier of the undissolved carbide, i.e., chromium promotes divorced eutectoid transformation. - Highlights: • Ultrafine-grained GCr15 steel was obtained by warm rolling and annealing technology. • Reduction of grain size makes pearlite morphology from lamellar to granular. • Adding Cr does not change normal pearlitic phase transformation rule in UFG steel. • Cr carbide resists grain growth and facilitates pearlitic transformation by DET

Epitaxial growth of zinc on ferritic steel under high current density electroplating conditions

International Nuclear Information System (INIS)

Greul, Thomas; Comenda, Christian; Preis, Karl; Gerdenitsch, Johann; Sagl, Raffaela; Hassel, Achim Walter

2013-01-01

Highlights: •EBSD of electroplated Zn on Fe or steel was performed. •Zn grows epitaxially on electropolished ferritic steel following Burger's orientation relation. •Surface deformation of steel leads to multiple electroplated zinc grains with random orientation. •Zn grows epitaxially even on industrial surfaces with little surface deformation. •Multiple zinc grains on one steel grain can show identical orientation relations. -- Abstract: The dependence of the crystal orientation of electrodeposited zinc of the grain orientation on ferritic steel substrate at high current density deposition (400 mA cm −2 ) during a pulse-plating process was investigated by means of EBSD (electron backscatter diffraction) measurements. EBSD-mappings of surface and cross-sections were performed on samples with different surface preparations. Furthermore an industrial sample was investigated to compare lab-coated samples with the industrial process. The epitaxial growth of zinc is mainly dependent on the condition of the steel grains. Deformation of steel grains leads to random orientation while zinc grows epitaxially on non-deformed steel grains even on industrial surfaces

Impact of grain size and rock composition on simulated rock weathering

Science.gov (United States)

Israeli, Yoni; Emmanuel, Simon

2018-05-01

Both chemical and mechanical processes act together to control the weathering rate of rocks. In rocks with micrometer size grains, enhanced dissolution at grain boundaries has been observed to cause the mechanical detachment of particles. However, it remains unclear how important this effect is in rocks with larger grains, and how the overall weathering rate is influenced by the proportion of high- and low-reactivity mineral phases. Here, we use a numerical model to assess the effect of grain size on chemical weathering and chemo-mechanical grain detachment. Our model shows that as grain size increases, the weathering rate initially decreases; however, beyond a critical size no significant decrease in the rate is observed. This transition occurs when the density of reactive boundaries is less than ˜ 20 % of the entire domain. In addition, we examined the weathering rates of rocks containing different proportions of high- and low-reactivity minerals. We found that as the proportion of low-reactivity minerals increases, the weathering rate decreases nonlinearly. These simulations indicate that for all compositions, grain detachment contributes more than 36 % to the overall weathering rate, with a maximum of ˜ 50 % when high- and low-reactivity minerals are equally abundant in the rock. This occurs because selective dissolution of the high-reactivity minerals creates large clusters of low-reactivity minerals, which then become detached. Our results demonstrate that the balance between chemical and mechanical processes can create complex and nonlinear relationships between the weathering rate and lithology.

Synthesis and properties of Pr-substituted MgZn ferrites for core materials and high frequency applications

Energy Technology Data Exchange (ETDEWEB)

Mukhtar, Muhammad Waqas; Irfan, Muhammad [Department of Physics, Federal Urdu University of Arts, Science and Technology, Islamabad 44000 (Pakistan); Ahmad, Ishtiaq; Ali, Ihsan [Department of Physics, Bahauddin Zakariya University, Multan 60800 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore (Pakistan); Khan, Muhammad Azhar [Department of Physics, Islamia University, Bahawalpur (Pakistan); Abbas, Ghazanfar [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Rana, M.U. [Center of Excellence in Solid State Physics, University of the Punjab, Lahore (Pakistan); Ali, Akbar [Department of Basic Sciences, Riphah International University, Islamabad-44000 (Pakistan); Ahmad, Mukhtar, E-mail: ahmadmr25@yahoo.com [Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

2015-05-01

A series of single phase spinel ferrites having chemical formula Mg{sub 0.5}Zn{sub 0.5}Pr{sub x}Fe{sub 2−x}O{sub 4} (x=0.00, 0.05, 0.10, 0.15, 0.20, 0.25) were prepared using the sol–gel technique after sintering at 700 °C. The thermal decomposition behavior of an as prepared powder was investigated by means of DTA/TGA analyses. The sintered powders were then characterized by Fourier transform infrared spectroscope, X-ray diffraction, scanning electron microscope, energy dispersive X-ray spectroscope and vibrating sample magnetometer. X-ray diffraction patterns confirm the single phase spinel structure of prepared ferrites without the presence of any impurity phase. The value of lattice parameter (a) increases with the increase of Pr contents (x) into the spinel lattice. The grain size estimated from electron microscope images is in the range of 2.75–5.4 µm which confirms the spinel crystalline nature of the investigated samples. The saturation magnetization (M{sub s}) decreases whereas coercivity (H{sub c}) increases with the increase of Pr contents (x). The measured parameters suggest that these materials are favorable for high frequency applications and as core materials. - Highlights: • Pr-substituted spinel ferrites synthesized by autocombustion route have been investigated. • The average grain size was in the range of 2.75–5.4 µm estimated by SEM technique. • The (M{sub s}) decreases whereas (H{sub c}) increases with the increase of Pr contents (x). • These parameters are favorable for high frequency applications and as core materials.

Impact of Nd{sup 3+} in CoFe{sub 2}O{sub 4} spinel ferrite nanoparticles on cation distribution, structural and magnetic properties

Energy Technology Data Exchange (ETDEWEB)

Yadav, Raghvendra Singh, E-mail: yadav@fch.vutbr.cz [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Havlica, Jaromir; Masilko, Jiri; Kalina, Lukas; Wasserbauer, Jaromir; Hajdúchová, Miroslava; Enev, Vojtěch [Materials Research Centre, Brno University of Technology, Purkyňova 464/118, 61200 Brno (Czech Republic); Kuřitka, Ivo; Kožáková, Zuzana [Centre of Polymer Systems, University Institute, Tomas Bata University in Zlín, Nad Ovčírnou 3685, 760 01 Zlín (Czech Republic)

2016-02-01

Nd{sup 3+} doped cobalt ferrite nanoparticles have been synthesized by starch-assisted sol–gel auto-combustion method. The significant role played by Nd{sup 3+} added to cobalt ferrite in changing cation distribution and further in influencing structural and magnetic properties, was explored and reported. The crystal structure formation and crystallite size were studied from X-ray diffraction studies. The microstructural features were investigated by field emission scanning electron microscopy and transmission electron microscopy that demonstrates the nanocrystalline grain formation with spherical morphology. An infrared spectroscopy study shows the presence of two absorption bands related to tetrahedral and octahedral group complexes within the spinel ferrite lattice system. The change in Raman modes in synthesized ferrite system were observed with Nd{sup 3+} substitution, particle size and cation redistribution. The impact of Nd{sup 3+} on cation distribution of Co{sup 2+} and Fe{sup 3+} at octahedral and tetrahedral sites in spinel ferrite cobalt ferrite nanoparticles was investigated by X-ray photoelectron spectroscopy. Room temperature magnetization measurements showed that the saturation magnetization and coercivity increase with addition of Nd{sup 3+} substitution in cobalt ferrite. - Highlights: • Nd{sup 3+} doped CoFe{sub 2}O{sub 4} nanoparticles by starch-assisted sol–gel auto-combustion method. • The change in Raman modes with Nd{sup 3+} substitution. • Presence of absorption infrared bands related to octahedral and tetrahedral site. • The impact of Nd{sup 3+} on cation distribution at octahedral and tetrahedral sites. • Influence of Nd{sup 3+} substitution in cobalt ferrite on magnetic properties.

Inhomogeneity of the grain size of aircraft engine turbine polycrystalline blades

Directory of Open Access Journals (Sweden)

J. Chmiela

2011-10-01

Full Text Available The determination of the behaviour of inhomogeneous materials with a complex microstructure requires taking into account the inhomogeneity of the grain size, as it is the basis for the process of designing and modelling effective behaviours. Therefore, the functional description of the inhomogeneity is becoming an important issue. The paper presents an analytical approach to the grain size inhomogeneity, based on the derivative of a logarithmic-logistic function. The solution applied enabled an effective evaluation of the inhomogeneity of two macrostructures of aircraft engine turbine blades, characterized by a high degree of diversity in the grain size. For the investigated single-modal and bimodal grain size distributions on a perpendicular projection and for grains with a non-planar surface, we identified the parameters that describe the degree of inhomogeneity of the constituents of weight distributions and we also derived a formula describing the overall degree of inhomogeneity of bimodal distributions. The solution presented in the paper is of a general nature and it can be used to describe the degree of inhomogeneity of multi-modal distributions. All the calculations were performed using the Mathematica® package.

Grain-size effects on thermal properties of BaTiO3 ceramics

Indian Academy of Sciences (India)

Administrator

decreasing grain size. Furthermore, the Curie temperature shifts to lower temperature with decreasing grain size. Keywords. Nanocrystalline ceramics; thermal properties; size effect. 1. Introduction. BaTiO3 has been widely used in the electronic industry for its high dielectric constant and low losses above room temperature ...

Preparation of bimodal grain size 7075 aviation aluminum alloys and their corrosion properties

Directory of Open Access Journals (Sweden)

Wenming TIAN

2017-10-01

Full Text Available The bimodal grain size metals show improved strength and ductility compared to traditional metals; however, their corrosion properties are unknown. In order to evaluate the corrosion properties of these metals, the bimodal grain size 7075 aviation aluminum alloys containing different ratios of coarse (100 μm in diameter and fine (10 μm in diameter grains were prepared by spark plasma sintering (SPS. The effects of grain size as well as the mixture degree of coarse and fine grains on general corrosion were estimated by immersion tests, electrochemical measurements and complementary techniques such as scanning electron microscope (SEM and transmission electron microscope-energy disperse spectroscopy (TEM-EDS. The results show that, compared to fine grains, the coarse grains have a faster dissolution rate in acidic NaCl solution due to the bigger size, higher alloying elements content and larger area fraction of second phases in them. In coarse grains, the hydrogen ions have a faster reduction rate on cathodic second phases, therefore promoting the corrosion propagation. The mixture of coarse and fine grains also increases the electrochemical heterogeneity of alloys in micro-scale, and thus the increased mixture degree of these grains in metal matrix accelerates the corrosion rate of alloys in acidic NaCl solution.

Precipitates and boundaries interaction in ferritic ODS steels

Energy Technology Data Exchange (ETDEWEB)

Sallez, Nicolas, E-mail: nicolas.sallez@simap.grenoble-inp.fr [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France); Hatzoglou, Constantinos [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Delabrouille, Fredéric [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Sornin, Denis; Chaffron, Laurent [CEA, DEN, Service de Recherches Métallurgiques Appliqué, 91191 Gif-sur-Yvette (France); Blat-Yrieix, Martine [EDF–EDF R& D, Les Renardières, 77818 Moret-sur-Loing (France); Radiguet, Bertrand; Pareige, Philippe [Groupe de Physique des Matériaux, Université et INSA de Rouen, UMR CNRS 6634, Normandie Université (France); Donnadieu, Patricia; Bréchet, Yves [Univ. Grenoble Alpes, SIMAP, F-38000 Grenoble (France)

2016-04-15

In the course of a recrystallization study of Oxide Dispersion Strengthened (ODS) ferritic steels during extrusion, particular interest was paid to the (GB) Grain Boundaries interaction with precipitates. Complementary and corresponding characterization experiments using Transmission Electron Microscopy (TEM), Energy Dispersive X-ray spectroscopy (EDX) and Atom Probe Tomography (APT) have been carried out on a voluntarily interrupted extrusion or extruded samples. Microscopic observations of Precipitate Free Zones (PFZ) and precipitates alignments suggest precipitate interaction with migrating GB involving dissolution and Oswald ripening of the precipitates. This is consistent with the local chemical information gathered by EDX and APT. This original mechanism for ODS steels is similar to what had been proposed in the late 80s for similar observation made on Ti alloys reinforced by nanosized yttrium oxides: An interaction mechanism between grain boundaries and precipitates involving a diffusion controlled process of precipitates dissolution at grain boundaries. It is believed that this mechanism can be of primary importance to explain the mechanical behaviour of such steels. - Highlights: • To study the microstructural evolution of a ferritic ODS steel during its extrusion, observations have been carried on samples resulting from a voluntarily interrupted extrusion and extruded materials. • A highly heterogeneous precipitate population have been observed. Nanosized coherent precipitates (2–5 nm) on both sides of the grain boundaries despite grain boundary migration after precipitation due to further thermo-mechanical processing as well as coarse precipitates (10–40 nm) alignments are observed on the grain boundaries and within the grains, parallel to the grain boundaries. • Asymmetrical PFZs can be observed around precipitates alignments and grain boundaries. Using TEM with EDX and APT we have been able to ensure that the PFZs are chemically depleted. �

Effect of microstructural evolution by isothermal aging on the mechanical properties of 9Cr-1WVTa reduced activation ferritic/martensitic steels

Energy Technology Data Exchange (ETDEWEB)

Park, Min-Gu [Korea Institute of Materials Science, Changwon 642-831 (Korea, Republic of); Lee, Chang-Hoon, E-mail: lee1626@kims.re.kr [Korea Institute of Materials Science, Changwon 642-831 (Korea, Republic of); Moon, Joonoh; Park, Jun Young; Lee, Tae-Ho [Korea Institute of Materials Science, Changwon 642-831 (Korea, Republic of); Kang, Namhyun [Pusan National University, Busan 609-735 (Korea, Republic of); Chan Kim, Hyoung [National Fusion Research Institute, Daejeon 305-806 (Korea, Republic of)

2017-03-15

The influence of microstructural changes caused by aging condition on tensile and Charpy impact properties was investigated for reduced activation ferritic-martensitic (RAFM) 9Cr-1WVTa steels having single martensite and a mixed microstructure of martensite and ferrite. For the mixed microstructure of martensite and ferrite, the Charpy impact properties deteriorated in both as-normalized and tempered conditions due to the ferrite and the accompanying M{sub 23}C{sub 6} carbides at the ferrite grain boundaries which act as path and initiation sites for cleavage cracks, respectively. However, aging at 550 °C for 20–100 h recovered gradually the Charpy impact toughness without any distinct drop in strength, as a result of the spheroidization of the coarse M{sub 23}C{sub 6} carbides at the ferrite grain boundaries, which makes crack initiation more difficult.

On the room temperature microstrain of vanadium of different grain size

International Nuclear Information System (INIS)

Timm, J.; Guttmann, V.

1977-01-01

The present work deals with the plastic behaviour of polycrystalline vanadium from the onset of plastic deformation to the upper yield point. The stress-strain relation was found to be omega approximately epsilonsub(p)sup(1/2). The influence of the grain size on stress followed a omega approximately d -1 relationship. The initial yield stress was independent of grain size. By means of optical and electron microscopy it was found, that the first dislocation movement starts at grain boundaries. (orig.) [de

Grain size dependent electrical studies on nanocrystalline SnO2

International Nuclear Information System (INIS)

Bose, A. Chandra; Thangadurai, P.; Ramasamy, S.

2006-01-01

Nanocrystalline tin oxide (n-SnO 2 ) with different grain sizes were synthesized by chemical precipitation method. Size variation was achieved by changing the hydrolysis processing time. Structural phases of the nanocrystalline SnO 2 were identified by X-ray diffraction (XRD). The grain sizes of the prepared n-SnO 2 were found to be in the range 5-20 nm which were estimated using the Scherrer formula and they were confirmed by transmission electron microscopy (TEM) measurements. The electrical properties of nanocrystalline SnO 2 were studied using impedance spectroscopy. The impedance spectroscopy results showed that, in the temperature range between 25 and 650 deg. C, the conductivity has contributions from two different mechanisms, which are attributed to different conduction mechanisms in the grain and the grain boundary regions. This is because of the different relaxation times available for the conduction species in those regions. However, for the temperatures above 300 deg. C, there is no much difference between these two different relaxation times. The Arrhenius plots gave the activation energies for the conduction process in all the samples

Effect of grain size on the high temperature mechanical properties of type 316LN stainless steel

Energy Technology Data Exchange (ETDEWEB)

Kim, D. W.; Lee, Y. S.; Ryu, W. S.; Jang, J. S.; Kim, S. H.; Kim, W. G.; Cho, H. D.; Han, C. H

2001-02-01

Nitrogen increases the high temeprature mechanical properties and decreases grain size. The effect of nitrogen on the high temperature mechanical properties was investigated in the viewpoint of grain size. Tensile strength increases with the decrease of grain size and agrees with the Hall-Petch relationship. Effect of grain size on the low cycle fatigue life properties were investigated as measuring the fatigue life from the results which had been obtained by the constant strain rate and various strain range. There was no effect on the low cycle fatigue properties by the grain size. The time to rupture decreased with the increase of grain size. The steady state creep rate decreased to a minimum and then increased as the grain size increased. This result agrees with the result predicted from Garofalo equation. The rupture elongation at the intermediate grain size showed a minimum due to the cavity formed easily by carbide precipitates in the grain boundaries.

Rapid heating effects on grain-size, texture and magnetic properties ...

Indian Academy of Sciences (India)

Administrator

oriented electrical steels (Kumar et ... through changes in recovery and recrystallization beha- viour during the final annealing treatment (Duan et .... recovery, recrystallization and grain coarsening (Doherty et al 1988). The size of recrystallized grain is ...

Effect of initial grain size on dynamic recrystallization in high purity austenitic stainless steels

International Nuclear Information System (INIS)

El Wahabi, M.; Gavard, L.; Montheillet, F.; Cabrera, J.M.; Prado, J.M.

2005-01-01

The influence of initial microstructure on discontinuous dynamic recrystallization (DDRX) has been investigated by using high purity and ultra high purity austenitic stainless steels with various initial grain sizes. After uniaxial compression tests at constant strain rates and various temperatures, the steady state microstructure or the state corresponding to the maximum strain (ε = 1) attained in the test was analyzed by scanning electron microscopy aided with automated electron back scattering diffraction. Recrystallized grain size d rec and twin boundary fraction f TB measurements were carried out. The mechanical behavior was also investigated by comparing experimental stress-strain curves with various initial grain sizes. DDRX kinetics was described by the classical Avrami equation. It was concluded that larger initial grain sizes promoted a delay in the DDRX onset in the two alloys. It was also observed that the softening process progressed faster for smaller initial grain sizes. The effect of initial grain size is larger in the HP material and becomes more pronounced at low temperature

Effect of gamma irradiation on the structural and magnetic properties of Co–Zn spinel ferrite nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Raut, Anil V., E-mail: nano9993@gmail.com [Vivekanand Arts, Sardar Dalipsingh Commerce and Science College, Aurangabad 431004, (M.S.) India (India); Kurmude, D.V. [Milind College of Science, Aurangabad 431004, (M.S.) India (India); Shengule, D.R. [Vivekanand Arts, Sardar Dalipsingh Commerce and Science College, Aurangabad 431004, (M.S.) India (India); Jadhav, K.M. [Department of Physics, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad 431004, (M.S.) India (India)

2015-03-15

Highlights: • Co–Zn ferrite nanoparticles were examined before and after γ-irradiation. • Single phase cubic spinel structure of Co–Zn was confirmed by XRD data. • The grain size was reported in the range of 52–62 nm after γ-irradiation. • Ms, Hc, n{sub B} were reported to be increased after gamma irradiation. - Abstract: In this work, the structural and magnetic properties of Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} (0.0 ≤ x ≤ 1.0) ferrite nanoparticles were studied before and after gamma irradiation. The as-synthesized samples of Co–Zn ferrite nanoparticles prepared by sol–gel auto-combustion technique were analysed by XRD which suggested the single phase; cubic spinel structure of the material. Crystal defects produced in the spinel lattice were studied before and after Co{sup 60} γ-irradiation in a gamma cell with a dose rate of 0.1 Mrad/h in order to report the changes in structural and magnetic properties of the Co–Zn ferrite nanoparticles. The average crystallite size (t), lattice parameter (α) and other structural parameters of gamma-irradiated and un-irradiated Co{sub 1−x}Zn{sub x}Fe{sub 2}O{sub 4} spinel ferrite system was calculated from XRD data. The morphological characterizations were performed using scanning electron microscopy (SEM). The magnetic properties were measured using pulse field hysteresis loop tracer by applying magnetic field of 1000 Oe, and the analysis of data obtained revealed that the magnetic property such as saturation magnetization (Ms), coecivity (Hc), magneton number (n{sub B}) etc. magnetic parameters were increased after irradiation.

Effect of Yttrium Addition on the Microstructure and Mechanical Properties of Cu-Rich Nano-phase Strengthened Ferritic Steel

Science.gov (United States)

Liu, Hongyu; He, Jibai; Luan, Guoqing; Ke, Mingpeng; Fang, Haoyan; Lu, Jianduo

2018-03-01

Due to the brittle problem of Cu-rich nano-phase strengthened ferritic steel (CNSFS) after air aging, the effect of Y addition in CNSFS was systemically investigated in the present work. The microstructure, tensile fracture morphology and oxide layer of the steels were surveyed by optical microscope and scanning electron microscope. Transmission electron microscope with the combination of energy-dispersive x-ray spectroscopy and selected area electron diffraction was used to analyze the morphology, size, number density, chemical compositions and crystal structure for nano-crystalline precipitates. Microstructural examinations of the nano-crystalline precipitates show that Cu-rich precipitates and Y compounds in the range of 2-10 and 50-100 nm, respectively, form in the Y-containing steel; meanwhile, the average size of nano-crystalline precipitates in Y-containing steel is larger, but the number density is lower, and the ferritic grains are refined. Furthermore, the tensile strength and ductility of Y-containing steel after air aging are improved, whereas the tensile strength is enhanced and the ductility decreased after vacuum aging. The drag effect of Y makes the oxide layer thinner and be compacted. Tensile properties of CNSFS after air aging are improved due to the refined grains, antioxidation and purification by the addition of Y.

The effect of grain size and cement content on index properties of weakly solidified artificial sandstones

Science.gov (United States)

Atapour, Hadi; Mortazavi, Ali

2018-04-01

The effects of textural characteristics, especially grain size, on index properties of weakly solidified artificial sandstones are studied. For this purpose, a relatively large number of laboratory tests were carried out on artificial sandstones that were produced in the laboratory. The prepared samples represent fifteen sandstone types consisting of five different median grain sizes and three different cement contents. Indices rock properties including effective porosity, bulk density, point load strength index, and Schmidt hammer values (SHVs) were determined. Experimental results showed that the grain size has significant effects on index properties of weakly solidified sandstones. The porosity of samples is inversely related to the grain size and decreases linearly as grain size increases. While a direct relationship was observed between grain size and dry bulk density, as bulk density increased with increasing median grain size. Furthermore, it was observed that the point load strength index and SHV of samples increased as a result of grain size increase. These observations are indirectly related to the porosity decrease as a function of median grain size.

Deformation mechanisms and grain size evolution in the Bohemian granulites - a computational study

Science.gov (United States)

Maierova, Petra; Lexa, Ondrej; Jeřábek, Petr; Franěk, Jan; Schulmann, Karel

2015-04-01

A dominant deformation mechanism in crustal rocks (e.g., dislocation and diffusion creep, grain boundary sliding, solution-precipitation) depends on many parameters such as temperature, major minerals, differential stress, strain rate and grain size. An exemplary sequence of deformation mechanisms was identified in the largest felsic granulite massifs in the southern Moldanubian domain (Bohemian Massif, central European Variscides). These massifs were interpreted to result from collision-related forced diapiric ascent of lower crust and its subsequent lateral spreading at mid-crustal levels. Three types of microstructures were distinguished. The oldest relict microstructure (S1) with large grains (>1000 μm) of feldspar deformed probably by dislocation creep at peak HT eclogite facies conditions. Subsequently at HP granulite-facies conditions, chemically- and deformation- induced recrystallization of feldspar porphyroclasts led to development of a fine-grained microstructure (S2, ~50 μm grain size) indicating deformation via diffusion creep, probably assisted by melt-enhanced grain-boundary sliding. This microstructure was associated with flow in the lower crust and/or its diapiric ascent. The latest microstructure (S3, ~100 μm grain size) is related to the final lateral spreading of retrograde granulites, and shows deformation by dislocation creep at amphibolite-facies conditions. The S2-S3 switch and coarsening was interpreted to be related with a significant decrease in strain rate. From this microstructural sequence it appears that it is the grain size that is critically linked with specific mechanical behavior of these rocks. Thus in this study, we focused on the interplay between grain size and deformation with the aim to numerically simulate and reinterpret the observed microstructural sequence. We tested several different mathematical descriptions of the grain size evolution, each of which gave qualitatively different results. We selected the two most

On the role of the grain size in the magnetic behavior of sintered permanent magnets

Science.gov (United States)

Efthimiadis, K. G.; Ntallis, N.

2018-02-01

In this work the finite elements method is used to simulate, by micromagnetic modeling, the magnetic behavior of sintered anisotropic magnets. Hysteresis loops were simulated for different grain sizes in an oriented multigrain sample. By keeping out other parameters that contribute to the magnetic microstructure, such as the sample size, the grain morphology and the grain boundaries mismatch, it has been found that the grain size affects the magnetic properties only if the grains are exchange-decoupled. In this case, as the grain size decreases, a decrease in the nucleation field of a reverse magnetic domain is observed and an increase in the coercive field due to the pinning of the magnetic domain walls at the grain boundaries.

Neutron depolarisation study of the austenite grain size in TRIP steels

International Nuclear Information System (INIS)

Dijk, N.H. van; Zhao, L.; Rekveldt, M.Th.; Fredrikze, H.; Tegus, O.; Brueck, E.; Sietsma, J.; Zwaag, S. van der

2004-01-01

We have performed combined neutron depolarisation and magnetisation measurements in order to obtain an in situ determination of the average grain size and volume fraction of the retained austenite phase in TRIP steels. The average grain size of the retained austenite was found to decrease for an increase in austenite volume fraction at two different annealing temperatures

Environmental monitoring of Columbia River sediments: Grain-size distribution and contaminant association

Energy Technology Data Exchange (ETDEWEB)

Blanton, M.L.; Gardiner, W.W.; Dirkes, R.L.

1995-04-01

Based on the results of this study and literature review, the following conclusions can be made: Sediment grain size and TOC (total organic carbon) influence contaminant fate and transport (in general, sediments with higher TOC content and finer grain-size distribution can have higher contaminant burdens than sediments from a given river section that have less TOC and greater amounts of coarse-grained sediments). Physiochemical sediment characteristics are highly variable among monitoring sites along the Columbia River. Sediment grain characterization and TOC analysis should be included in interpretations of sediment-monitoring data.

Environmental monitoring of Columbia River sediments: Grain-size distribution and contaminant association

International Nuclear Information System (INIS)

Blanton, M.L.; Gardiner, W.W.; Dirkes, R.L.

1995-04-01

Based on the results of this study and literature review, the following conclusions can be made: Sediment grain size and TOC (total organic carbon) influence contaminant fate and transport (in general, sediments with higher TOC content and finer grain-size distribution can have higher contaminant burdens than sediments from a given river section that have less TOC and greater amounts of coarse-grained sediments). Physiochemical sediment characteristics are highly variable among monitoring sites along the Columbia River. Sediment grain characterization and TOC analysis should be included in interpretations of sediment-monitoring data

Lanthana-bearing nanostructured ferritic steels via spark plasma sintering

Energy Technology Data Exchange (ETDEWEB)

Pasebani, Somayeh [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Charit, Indrajit, E-mail: icharit@uidaho.edu [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Wu, Yaqiao; Burns, Jatuporn; Allahar, Kerry N.; Butt, Darryl P. [Department of Materials Science and Engineering, Boise State University, Boise, ID 83725 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Cole, James I. [Idaho National Laboratory, Idaho Falls, ID 83401 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Alsagabi, Sultan F. [Department of Chemical and Materials Engineering, University of Idaho, Moscow, ID 83844 (United States); Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States)

2016-03-15

A lanthana-containing nanostructured ferritic steel (NFS) was processed via mechanical alloying (MA) of Fe-14Cr-1Ti-0.3Mo-0.5La{sub 2}O{sub 3} (wt.%) and consolidated via spark plasma sintering (SPS). In order to study the consolidation behavior via SPS, sintering temperature and dwell time were correlated with microstructure, density, microhardness and shear yield strength of the sintered specimens. A bimodal grain size distribution including both micron-sized and nano-sized grains was observed in the microstructure of specimens sintered at 850, 950 and1050 °C for 45 min. Significant densification occurred at temperatures greater than 950 °C with a relative density higher than 98%. A variety of nanoparticles, some enriched in Fe and Cr oxides and copious nanoparticles smaller than 10 nm with faceted morphology and enriched in La and Ti oxides were observed. After SPS at 950 °C, the number density of Cr–Ti–La–O-enriched nanoclusters with an average radius of 1.5 nm was estimated to be 1.2 × 10{sup 24} m{sup −3}. The La + Ti:O ratio was close to 1 after SPS at 950 and 1050 °C; however, the number density of nanoclusters decreased at 1050 °C. With SPS above 950 °C, the density improved but the microhardness and shear yield strength decreased due to partial coarsening of the grains and nanoparticles.

Influence of Cu-Cr substitution on structural, morphological, electrical and magnetic properties of magnesium ferrite

Science.gov (United States)

Yonatan Mulushoa, S.; Murali, N.; Tulu Wegayehu, M.; Margarette, S. J.; Samatha, K.

2018-03-01

Cu-Cr substituted magnesium ferrite materials (Mg1 - xCuxCrxFe21 - xO4 with x = 0.0-0.7) have been synthesized by the solid state reaction method. XRD analysis revealed the prepared samples are cubic spinel with single phase face centered cubic. A significant decrease of ∼41.15 nm in particle size is noted in response to the increase in Cu-Cr substitution level. The room temperature resistivity increases gradually from 0.553 × 105 Ω cm (x = 0.0) to 0.105 × 108 Ω cm (x = 0.7). Temperature dependent DC-electrical resistivity of all the samples, exhibits semiconductor like behavior. Cu-Cr doped materials can be suitable to limit the eddy current losses. VSM result shows pure and doped magnesium ferrite particles show soft ferrimagnetic nature at room temperature. The saturation magnetization of the samples decreases initially from 34.5214 emu/g for x = 0.0 to 18.98 emu/g (x = 0.7). Saturation magnetization, remanence and coercivity are decreased with doping, which may be due to the increase in grain size.

Radon emanation rate as a function of monazite grain size

International Nuclear Information System (INIS)

Yogesan, S.; Stanley, J.D.; Rosli Mahat; Yusof Md Amin

1995-01-01

In this study, a sample of monazite from local mining area was divided to 7 parts according to size (μm) and each sample was analysed using silicon surface barrier detector and multichannel analyser. From this study it has found that small grain monazite produced more radon that big grain monazite and radium is distributed on or near the surface of the monazite grain

Palaeoenvironmental implication of grain-size compositions of terrace deposits on the western Chinese Loess Plateau

Science.gov (United States)

Liu, Xingxing; Sun, Youbin; Vandenberghe, Jef; Li, Ying; An, Zhisheng

2018-06-01

Sedimentary sequences that developed on river terraces have been widely investigated to reconstruct high-resolution palaeoclimatic changes since the last deglaciation. However, frequent changes in sedimentary facies make palaeoenvironmental interpretation of grain-size variations relatively complicated. In this paper, we employed multiple grain-size parameters to discriminate the sedimentary characteristics of aeolian and fluvial facies in the Dadiwan (DDW) section on the western Chinese Loess Plateau. We found that wind and fluvial dynamics have quite different impacts on the grain-size compositions, with distinctive imprints on the distribution pattern. By using a lognormal distribution fitting approach, two major grain-size components sensitive to aeolian and fluvial processes, respectively, were distinguished from the grain-size compositions of the DDW terrace deposits. The fine grain-size component (GSC2) represents mixing of long-distance aeolian and short-distance fluvial inputs, whilst the coarse grain-size component (GSC3) is mainly transported by wind from short-distance sources. Thus GSC3 can be used to infer the wind intensity. Grain-size variations reveal that the wind intensity experienced a stepwise shift from large-amplitude variations during the last deglaciation to small-amplitude oscillations in the Holocene, corresponding well to climate changes from regional to global context.

Correlation of microstructure and strain hardening behavior in the ultrafine-grained Nb-bearing dual phase steels

Energy Technology Data Exchange (ETDEWEB)

Ghatei Kalashami, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Kermanpur, A., E-mail: ahmad_k@cc.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Ghassemali, E. [Jönköping University, School of Engineering, Department of Materials and Manufacturing, P.O. Box 1026, SE-551 11 Jönköping (Sweden); Najafizadeh, A. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Mazaheri, Y. [Department of Materials Engineering, Isfahan University of Technology, Isfahan 84156-83111 (Iran, Islamic Republic of); Department of Materials Engineering, Bu-Ali Sina University, Hamedan 65178-38695 (Iran, Islamic Republic of)

2016-12-15

Ultrafine-grained dual phase (DP) steels with different Nb contents (0.00, 0.06 and 0.12 wt%) were produced by cold-rolling followed by intercritical annealing of ferrite/martensite starting microstructure at 770 °C for different holding times. Scanning electron microscopy, equipped with electron backscattered diffraction (EBSD) detector, nanoindentation and tensile testing were used to characterize microstructural evolutions and their correlations to the strain hardening and fracture behavior. EBSD results confirmed the retardation effect of Nb on recrystallization. It was found that the strains stored in the grains and density of geometrically necessary dislocations (GNDs) were increased with the addition of Nb. Strain hardening analysis showed that plastic deformation of the DP steels occurred in three distinct stages, which based on the EBSD results, nanoindentation and fracture analysis, were controlled by microstructural features such martensite volume fraction and size, density of GNDs and individual ferrite and martensite tensile properties.

Sediment grain size and hydrodynamics in Mediterranean coastal ...

Indian Academy of Sciences (India)

Integrated classification maps were produced by combining sediment grain-size and hydrological data .... Integrated classification of abiotic parameters in lagoons. 1099. Figure 1. ...... spline with tension: I. Theory and implementation; Math.

Grain size effect on yield strength of titanium alloy implanted with aluminum ions

Energy Technology Data Exchange (ETDEWEB)

Popova, Natalya, E-mail: natalya-popova-44@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Nikonenko, Elena, E-mail: vilatomsk@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); National Research Tomsk Polytechnic University, 30, Lenin Str., 634050, Tomsk (Russian Federation); Yurev, Ivan, E-mail: yiywork@mail.ru [Tomsk State University of Architecture and Building, 2, Solyanaya Sq., 634003, Tomsk (Russian Federation); Kalashnikov, Mark, E-mail: kmp1980@mail.ru [Institute of Strength Physics and Materials Science, SB RAS, 2/4, Akademicheskii Ave., 634021, Tomsk (Russian Federation); Kurzina, Irina, E-mail: kurzina99@mail.ru [National Research Tomsk State University, 36, Lenin Str., 634050, Tomsk (Russian Federation)

2016-01-15

The paper presents a transmission electron microscopy (TEM) study of the microstructure and phase state of commercially pure titanium VT1-0 implanted by aluminum ions. This study has been carried out before and after the ion implantation for different grain size, i.e. 0.3 µm (ultra-fine grain condition), 1.5 µm (fine grain condition), and 17 µm (polycrystalline condition). This paper presents details of calculations and analysis of strength components of the yield stress. It is shown that the ion implantation results in a considerable hardening of the entire thickness of the implanted layer in the both grain types. The grain size has, however, a different effect on the yield stress. So, both before and after the ion implantation, the increase of the grain size leads to the decrease of the alloy hardening. Thus, hardening in ultra-fine and fine grain alloys increased by four times, while in polycrystalline alloy it increased by over six times.

The magnetized sheath of a dusty plasma with grains size distribution

International Nuclear Information System (INIS)

Ou, Jing; Gan, Chunyun; Lin, Binbin; Yang, Jinhong

2015-01-01

The structure of a plasma sheath in the presence of dust grains size distribution (DGSD) is investigated in the multi-fluid framework. It is shown that effect of the dust grains with different sizes on the sheath structure is a collective behavior. The spatial distributions of electric potential, the electron and ion densities and velocities, and the dust grains surface potential are strongly affected by DGSD. The dynamics of dust grains with different sizes in the sheath depend on not only DGSD but also their radius. By comparison of the sheath structure, it is found that under the same expected value of DGSD condition, the sheath length is longer in the case of lognormal distribution than that in the case of uniform distribution. In two cases of normal and lognormal distributions, the sheath length is almost equal for the small variance of DGSD, and then the difference of sheath length increases gradually with increase in the variance

Dielectric properties of Al-substituted Co ferrite nanoparticles

Indian Academy of Sciences (India)

Administrator

The particle size, D, decreases with increase in Al-content. The lattice parameter, a ... a significant saving in time and energy consumption over the traditional methods. ... electrical, and magnetic properties of spinel ferrites. Cobalt ferrite based ...

Grain size dependence of the critical current density in YBa2Cu3Ox superconductors

International Nuclear Information System (INIS)

Kuwabara, M.; Shimooka, H.

1989-01-01

The grain size dependence of the critical current density in bulk single-phase YBa 2 Cu 3 O x ceramics was investigated. The grain size of the materials was changed to range approximately from 1.0 to 25 μm by changing the conditions of power processing and sintering, associated with an increase in the sintered density of the materials with increasing grain size. The critical current density has been found to exhibit a significant grain size dependence, changing from 880 A/cm 2 to a value of 100 A/cm 2 with a small increase in the average grain size from 1.2 to 2.0 μm. This seems to provide information about the nature of the weak link between superconducting grains which might govern the critical current density of the materials

Notes on representing grain size distributions obtained by electron backscatter diffraction

International Nuclear Information System (INIS)

Toth, Laszlo S.; Biswas, Somjeet; Gu, Chengfan; Beausir, Benoit

2013-01-01

Grain size distributions measured by electron backscatter diffraction are commonly represented by histograms using either number or area fraction definitions. It is shown here that they should be presented in forms of density distribution functions for direct quantitative comparisons between different measurements. Here we make an interpretation of the frequently seen parabolic tales of the area distributions of bimodal grain structures and a transformation formula between the two distributions are given in this paper. - Highlights: • Grain size distributions are represented by density functions. • The parabolic tales corresponds to equal number of grains in a bin of the histogram. • A simple transformation formula is given to number and area weighed distributions. • The particularities of uniform and lognormal distributions are examined

Impact of grain sizes on the quantitative concrete analysis using laser-induced breakdown spectroscopy

Science.gov (United States)

Gottlieb, C.; Günther, T.; Wilsch, G.

2018-04-01

In civil engineering concrete is the most used building material for making infrastructures like bridges and parking decks worldwide. It is as a porous and multiphase material made of aggregates with a defined grain size distribution, cement and water as well as different additives and admixtures depending on the application. Different grain sizes are important to ensure the needed density and compressive strength. The resulting porous cement matrix contains a mixture of flour grains (aggregates with a grain size below 125 μm) and cement particles (particle size ≈ 50μm). Harmful species like chlorides may penetrate together with water through the capillary pore space and may trigger different damage processes. The damage assessment of concrete structures in Germany is estimated due to the quantification of harmful elements regarding to the cement content only. In the evaluation of concrete using LIBS a two-dimensional scanning is necessary to consider the heterogeneity caused by the aggregates. Therefore, a LIBS system operating with a low energy NdCr:YAG laser, a pulse energy of 3 mJ, a wavelength of 1064 nm, a pulse width of 1.5 ns and a repetition rate of 100 Hz has been used. Different Czerny-Turner spectrometers with CCD detectors in the UV and NIR range have been used for the detection. Large aggregates (macro-heterogeneity) can be excluded from the evaluation, whereas small aggregates in the range of the laser spot size (flour grains) cannot be spatially resolved. In this work the micro heterogeneity caused by flour grains and their impact on the quantification with LIBS will be discussed. To analyze the effect of changing grain sizes and ratios, the ablation behavior has been determined and compared. Samples with defined grain sizes were made and analyzed using LIBS. The grain size distributions were analyzed with laser diffraction (LDA).

Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

International Nuclear Information System (INIS)

Majeed, Abdul; Khan, Muhammad Azhar; Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F.; Murtaza, Ghulam; Akhtar, Majid Niaz; Shakir, Imran; Warsi, Muhammad Farooq

2016-01-01

Rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm −1. Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b VI ). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La 3+ , Nd 3+ , Gd 3+ , Tb 3+ , Dy 3+ ) doped Ba 2 NiCoRE x Fe 28−x O 46 (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba 2 NiCoRE x Fe 28−x O 46 ferrites. • The crystallite size was found in the range 7–19 nm. • The rare-earth incorporation enhanced the coercivity (664–926 Oe). �

Microstructural evolution of ferritic steel powder during mechanical alloying with iron oxide

Energy Technology Data Exchange (ETDEWEB)

Wen, Yuren; Liu, Yong; Liu, Donghua; Tang, Bei [Central South Univ., State Key Lab. of Powder Metallurgy, Changsha (China); Liu, C.T. [The Hong Kong Polytechnic Univ., Dept. of Mechanical Engineering, Hong Kong (China)

2011-02-15

Mechanical alloying of mixed powders is of great importance for preparing oxide dispersion strengthened ferritic steels. In this study, the microstructural evolution of ferritic steel powder mixed with TiH{sub x}, YH{sub 2} and Fe{sub 2}O{sub 3} in the process of mechanical alloying is systematically investigated by using X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy and microhardness tests. It is found that titanium, yttrium hydrides and iron oxide are completely dissolved during milling, and homogeneous element distribution can be achieved after milling for 12 h. The disintegration of the composite powder particles occurs at 24 h and reaches the balance of welding and fracturing after 36 h. The oxygen content increases sharply with the disintegration of powder particles due to the absorption of oxygen at the solid/gas interface from the milling atmosphere, which is the main source of extra oxygen in the milled powder. Grain refinement down to nanometer level occurs due to the severe plastic deformation of particles; however, the grain size does not change much with further disintegration of particles. The hardness increases with milling time and then becomes stable during further milling. The study indicates that the addition of iron oxide and hydrides may be more beneficial for the dispersion and homogenization of chemical compositions in the powder mixture, thus shortening the mechanical alloying process. (orig.)

Effects of Static Recrystallization and Precipitation on Mechanical Properties of 00Cr12 Ferritic Stainless Steel

Science.gov (United States)

Shao, Yi; Liu, Chenxi; Yue, Tengxiao; Liu, Yongchang; Yan, Zesheng; Li, Huijun

2018-05-01

The 00Cr12 ferritic stainless steel samples were isothermally held at different temperatures in the range of 700 °C to 1000 °C to investigate the effect of static recrystallization and precipitation on mechanical properties, such as microhardness, tensile strength, and yield strength. The results show that the formation of the fine recrystallized grain, as well as precipitation, coarsening, and dissolution of the second-phase particles, influences the mechanical properties remarkably. The fine recrystallized grain can provide a positive grain boundary-strengthening effect in the sample under a relatively high holding temperature. Coarsening and dissolution of M23C6 result in partial depletion of precipitate hardening. In contrast, the size and number density of MX particles are almost constant, regardless of the holding temperature; therefore, it can provide a better precipitation-hardening effect.

ON ESTIMATION AND HYPOTHESIS TESTING OF THE GRAIN SIZE DISTRIBUTION BY THE SALTYKOV METHOD

Directory of Open Access Journals (Sweden)

Yuri Gulbin

2011-05-01

Full Text Available The paper considers the problem of validity of unfolding the grain size distribution with the back-substitution method. Due to the ill-conditioned nature of unfolding matrices, it is necessary to evaluate the accuracy and precision of parameter estimation and to verify the possibility of expected grain size distribution testing on the basis of intersection size histogram data. In order to review these questions, the computer modeling was used to compare size distributions obtained stereologically with those possessed by three-dimensional model aggregates of grains with a specified shape and random size. Results of simulations are reported and ways of improving the conventional stereological techniques are suggested. It is shown that new improvements in estimating and testing procedures enable grain size distributions to be unfolded more efficiently.

Recent improvements in size effects correlations for DBTT and upper shelf energy of ferritic steels

International Nuclear Information System (INIS)

Kumar, A.S.; Louden, B.S.; Garner, F.A.; Hamilton, M.L.

1992-01-01

Currently available correlations for the effects of specimen size on the USE were developed for relatively ductile steels and will not serve as well when the steels become embrittled. Size effects correlations were developed recently for the impact properties of less ductile HT9 to be applied to other initially more ductile steels as they lose their ductility during irradiation. These new correlations successfully predict the ductile brittle transition temperature (DBTT) and the upper shelf energy (USE) of full size Charpy specimens based on subsize specimen data. The new DBTT and the USE correlations were tested against published experimental data on other ferritic steels and shown to perform successfully at lower USE particularly when both precracked and notched only specimens were employed

Studies of fracture processes in Cr-Mo-V ferritic steel with various types of microstructures

Energy Technology Data Exchange (ETDEWEB)

Dzioba, I., E-mail: pkmid@tu.kielce.p [Fundamentals of Machine Design Chair, Kielce University of Technology, Al.1000-lecia PP 7, 25-314 Kielce (Poland); Gajewski, M., E-mail: gajem@tu.kielce.p [Fundamentals of Machine Design Chair, Kielce University of Technology, Al.1000-lecia PP 7, 25-314 Kielce (Poland); Neimitz, A., E-mail: neimitz@tu.kielce.p [Fundamentals of Machine Design Chair, Kielce University of Technology, Al.1000-lecia PP 7, 25-314 Kielce (Poland)

2010-10-15

In this paper, the authors report on analysis of the influence of microstructure on ductile and cleavage fracture mechanisms. The question investigated was whether microstructure observations alone can provide sufficient information to predict the possible fracture mechanism or change in fracture mechanism. Four different microstructures of ferritic steel were tested after four different heat treatments. The microstructures examined were ferritic, ferritic-pearlitic, ferritic-bainitic, and tempered martensitic types. It was concluded that the ratio (S{sub C}/S{sub 0}) of the area covered by carbides to the total area of a ferritic grain (measured by taking into account large carbides) is the only possible quantitative measure that can be used to predict cleavage fracture.

Effects of grain size on high temperature creep of fine grained, solution and dispersion hardened V-1.6Y-8W-0.8TiC

Energy Technology Data Exchange (ETDEWEB)

Furuno, T. [Ehime Univerisity, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Kurishita, H., E-mail: kurishi@imr.tohoku.ac.jp [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Nagasaka, T.; Nishimura, A.; Muroga, T. [Fusion Engineering Research Center, National Institute for Fusion Science (NIFS), Oroshi-cho 322-6, Tok, Gifu 292 (Japan); Sakamoto, T.; Kobayashi, S.; Nakai, K. [Department of Materials Science and Biotechnology, Ehime Univerisity, 3 Bunkyo-cho, Matsuyama 790-8577 (Japan); Matsuo, S.; Arakawa, H. [International Research Center for Nuclear Materials Science, Institute for Materials Research (IMR), Tohoku University, Oarai, Ibaraki 311-1313 (Japan)

2011-10-01

Creep resistance is the major concern of vanadium and its alloys for fusion reactor structural applications. In order to elucidate the effects of grain size on the creep behavior of solution and dispersion strengthened vanadium alloys, V-1.6Y-8W-0.8TiC specimens with fine grain sizes from 0.58 to 1.45 {mu}m were prepared by mechanical alloying and HIP without any plastic working and tested at 1073 K and 250 MPa in vacuum. It is shown that the creep resistance of V-1.6Y-8W-0.8TiC depends strongly on grain size and increases with increasing grain size: The creep life for the grain size of 1.45 {mu}m is almost one order longer than that of 0.58 {mu}m, and about two orders longer than that of V-4Cr-4Ti (NIFS-Heat 2) although the grain size of V-4Cr-4Ti is as large as 17.8 {mu}m. The observed creep behavior is discussed in terms of grain size effects on dislocation glide and grain boundary sliding.

Numerical and Experimental Investigation of the Influence of Growth Restriction on Grain Size in Binary Cu Alloys

Directory of Open Access Journals (Sweden)

Andreas Cziegler

2017-09-01

Full Text Available Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude.

Grain-size data from four cores from Walker Lake, Nevada

International Nuclear Information System (INIS)

Yount, J.C.; Quimby, M.F.

1990-01-01

A number of cores, taken from within and near Walker Lake, Nevada are being studied by various investigators in order to evaluate the late-Pleistocene paleoclimate of the west-central Great Basin. In particular, the cores provide records that can be interpreted in terms of past climate and compared to proposed numerical models of the region's climate. All of these studies are being carried out as part of an evaluation of the regional paleoclimatic setting of a proposed high-level nuclear waste storage facility at Yucca Mountain, Nevada. Changes in past climate often manifest themselves in changes in sedimentary processes or in changes in the volume of sediment transported by those processes. One fundamental sediment property that can be related to depositional processes is grain size. Grain size effects other physical properties of sediment such as porosity and permeability which, in turn, affect the movement and chemistry of fluids. The purposes of this report are: (1) to document procedures of sample preparation and analysis, and (2) to summarize grain-size statistics for 659 samples from Walker Lake cores 84-4, 84-5, 84-8 and 85-2. Plots of mean particle diameter, percent sand, and the ratio of silt to clay are illustrated for various depth intervals within each core. Summary plots of mean grain size, sorting, and skewness parameters allow comparison of textural data between each core. 15 refs., 8 figs., 3 tabs

Microstructural characterization of ODS ferritic steels at different processing stages

Energy Technology Data Exchange (ETDEWEB)

Gil, E., E-mail: egil@ceit.es; Ordás, N.; García-Rosales, C.; Iturriza, I., E-mail: iiturriza@ceit.es

2015-10-15

Highlights: • ODS ferritic stainless steel produced by new route without mechanical alloying. • Fully dense ferritic stainless steels containing Y and Ti were obtained by HIPping. • Y and Ti-rich precipitates prevent grain growth during heat treatment up to 1320 °C. • HIPping at 1220 °C dissolves the metastable oxides on PPBs. - Abstract: Nanostructured Oxide Dispersion Strengthened Reduced Activation Ferritic Stainless Steels (ODS RAF) are promising structural materials for fusion reactors, due to their ultrafine microstructure and the presence of a dispersion of Y–Ti–O nanoclusters that provide excellent creep strength at high temperatures (up to 750 °C). The traditional powder metallurgical route to produce these steels is based on Gas Atomization (GA) + Mechanical Alloying (MA) + HIP + ThermoMechanical Treatments (TMTs). Recently, alternative methods have arisen to avoid the MA step. In line with this new approach, ferritic stainless steel powders were produced by gas atomization and HIPped, after adjusting their oxygen, Y and Ti contents to form Y–Ti–O nanoclusters during subsequent heat treatments. The microstructure of as-HIPped steels mainly consists of ferrite grains, Y–Ti precipitates, carbides and oxides on Prior Particle Boundaries (PPBs). Post-HIP heat treatments performed at high temperatures (1270 and 1300 °C) evaluated the feasibility of achieving a complete dissolution of the oxides on PPBs and a precipitation of ultrafine Ti- and Y-rich oxides in the Fe14Cr2W matrix. FEG-SEM with extensive EDS analysis was used to characterize the microstructure of the atomized powders and the ODS-RAF specimens after HIP consolidation and post-HIP heat treatments. A deeper characterization of atomized powder was carried out by TEM.

Modelling and experimental characterisation of a residual stress field in a ferritic compact tension specimen

International Nuclear Information System (INIS)

Wenman, M.R.; Price, A.J.; Steuwer, A.; Chard-Tuckey, P.R.; Crocombe, A.

2009-01-01

The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (∼5-10 μm grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.

Modelling and experimental characterisation of a residual stress field in a ferritic compact tension specimen

Energy Technology Data Exchange (ETDEWEB)

Wenman, M.R., E-mail: m.wenman@imperial.ac.u [Department of Materials, Imperial College London, London SW7 2AZ (United Kingdom); Price, A.J. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom); Steuwer, A. [ESS Scandinavia, Stora Algatan 4, 22350 Lund (Sweden) and Nelson Mandela Metropolitan University, Port Elizabeth 6031 (South Africa); Chard-Tuckey, P.R. [Nuclear Department, Defence College of Management and Technology, HMS Sultan, Gosport, Hants PO12 3BY (United Kingdom); Crocombe, A. [Faculty of Engineering and Physical Sciences (J5), University of Surrey, Guildford GU2 7XH (United Kingdom)

2009-12-15

The aim of the work is to elucidate the influence of plasticity behaviour on the residual stress field in a ferritic reactor pressure vessel steel. To this end, we investigate two compressively pre-loaded compact tension (CT) specimens to generate a mechanical residual stress field. One specimen was subsequently pre-cracked by fatigue before both specimens were measured using high-energy synchrotron X-ray diffraction. A fine grain size microstructure (approx5-10 mum grain size) allowed a small X-ray beam slit size and therefore gauge volume. The results provide an excellent data set for validation of finite element (FE) modelling predictions against which they have been compared. The results of both mechanical testing and modelling suggest that the use of a combined hardening model is needed to accurately predict the residual stress field present in the specimen after pre-loading. Some discrepancy between the modelled crack tip stress values and those found by X-ray diffraction remain which can be partly explained by volume averaging effects in the presence of very high stress/strain gradients.

Grain Size of Recall Practice for Lengthy Text Material: Fragile and Mysterious Effects on Memory

Science.gov (United States)

Wissman, Kathryn T.; Rawson, Katherine A.

2015-01-01

The current research evaluated the extent to which the grain size of recall practice for lengthy text material affects recall during practice and subsequent memory. The "grain size hypothesis" states that a smaller vs. larger grain size will increase retrieval success during practice that in turn will enhance subsequent memory for…

A study of interaction effect theoretical with combination size grain on magnetics in of permanent magnet

International Nuclear Information System (INIS)

Tarihoran, Doansi; Manaf, Azwar

2002-01-01

Stoner-Wohlfarth theory, SW shows a deviation around 30-40% to the measurement result of a permanent magnetic material with nanometer-sized grains. This is caused by this theory neglecting the interacting grain factor. This research modifies SW theory by calculating the grain interacting effect. The modification is made by assuming the interacting energy of a mono-domain grain has ellipsoidal shaped focused at the edge of the grain. SW grain in this calculation model is a box-shaped in a grain with edges of the box placed in the skin's grain. The result shows that interacting effect make remanent polarization increasing drastically and coercive field value decreasing when grain's size reaches 20% of size of the first mono-domain grain. For material with ND 2 Fe 14 B phase, the optimum coercive field value and remanent polarization that producing maximum product energy, (BH) m ax obtained in a material with 5 nanometer-size grains. Qualitatively there is as appropriate result between the calculation and measurement

Electromagnetic properties of NiZn ferrite nanoparticles and their polymer composites

Energy Technology Data Exchange (ETDEWEB)

Parsons, P. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States); Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Duncan, K. [U.S. Army, Communications-Electronics Research, Development and Engineering Center, Space and Terrestrial Communications Directorate, Aberdeen Proving Ground, Maryland 21005 (United States); Giri, A. K. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States); Bowhead Science and Technology, LLC, Belcamp, Maryland 21017 (United States); Xiao, J. Q. [Department of Physics and Astronomy, University of Delaware, Newark, Delaware 19716 (United States); Karna, S. P., E-mail: shashi.p.karna.civ@mail.mil [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States)

2014-05-07

The magnetic properties of polycrystalline NiZn ferrite nanoparticles synthesized using a polyol-reduction and coprecipitation reaction methods have been investigated. The effects on magnetization of synthesis approach, chemical composition, processing conditions, and on the size of nanoparticles on magnetization have been investigated. The measured room-temperature magnetization for the as-prepared magnetic nanoparticles (MNP) synthesized via polyol-reduction and coprecipitation is 69 Am{sup 2} kg{sup −1} and 14 Am{sup 2} kg{sup −1}, respectively. X-ray diffraction measurements confirm spinel structure of the particles with an estimated grain size of ∼80 nm obtained from the polyol-reduction and 28 nm obtained from these coprecipitation techniques. Upon calcination under atmospheric conditions at different temperatures between 800 °C and 1000 °C, the magnetization, M, of the coprecipitated MNP increases to 76 Am{sup 2} kg{sup −1} with an estimated grain size of 90 nm. The MNP-polymer nanocomposites made from the synthesized MNP in various loading fraction and high density polyethylene exhibit interesting electromagnetic properties. The measured permeability and permittivity of the magnetic nanoparticle-polymer nanocomposites increases with the loading fractions of the magnetic nanoparticles, suggesting control for impedance matching for antenna applications.

Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

International Nuclear Information System (INIS)

Liu, Junliang; Zeng, Yanwei; Zhang, Xingkai; Zhang, Ming

2015-01-01

Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%

Effects of magnetic pre-alignment of nano-powders on formation of high textured barium hexa-ferrite quasi-single crystals via a magnetic forming and liquid participation sintering route

Energy Technology Data Exchange (ETDEWEB)

Liu, Junliang, E-mail: liujunliang@yzu.edu.cn [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zeng, Yanwei [State Key Laboratory of Materials-Oriented Chemical Engineering, School of Materials Science and Engineering, Nanjing Tech University, Nanjing 210009 (China); Zhang, Xingkai [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Zhang, Ming [Key Laboratory of Environmental Materials and Engineering of Jiangsu Province, School of Chemistry and Chemical Engineering, Yangzhou University, Yangzhou 225002 (China); Testing Center of Yangzhou University, Yangzhou 225002 (China)

2015-05-15

Highly textured barium hexa-ferrite quasi-single crystal with narrow ferromagnetic resonance line-width is believed to be a potential gyromagnetic material for self-biased microwave devices. To fabricate barium hexa-ferrite quasi-single crystal with a high grain orientation degree, a magnetic forming and liquid participation sintering route has been developed. In this paper, the effects of the pre-alignment of the starting nano-powders on the formation of barium quasi-single crystal structures have been investigated. The results indicated that: the crystallites with large sizes and small specific surfaces were easily aligned for they got higher driving forces and lower resistances during magnetic forming. The average restricting magnetic field was about 4.647 kOe to overcome the average friction barrier between crystallites. The pre-aligned crystallites in magnetic forming acted as the “crystal seeds” for oriented growth of the un-aligned crystallites during liquid participation sintering to achieve a high grain orientation. To effectively promote the grain orientation degrees of the sintered pellets, the grain orientation degrees of the green compacts must be higher than a limited value of 15.0%. Barium hexa-ferrite quasi-single crystal with a high grain orientation degree of 98.6% was successfully fabricated after sintering the green compact with its grain orientation degree of 51.1%. - Highlights: • Aligned particles acted as “crystal seeds” for un-aligned ones' oriented growth. • Magnetic field of 4.647 kOe was needed to overcome crystallites' friction barrier. • GOD dramatically increased after sintering if starting GOD exceeded to 15.0%. • Quasi-single crystal was prepared by sintering green compact with GOD of 51.1%.

Corrosion behavior of ferritic stainless steel with 15wt% chromium for the automobile exhaust system

Science.gov (United States)

Li, Hua-bing; Jiang, Zhou-hua; Feng, Hao; Zhu, Hong-chun; Sun, Bin-han; Li, Zhen

2013-09-01

The effect of chloride ion concentration, pH value, and grain size on the pitting corrosion resistance of a new ferritic stainless steel with 15wt% Cr was investigated using the anodic polarization method. The semiconducting properties of passive films with different chloride ion concentrations were performed using capacitance measurement and Mott-Schottky analysis methods. The aging precipitation and intergranular corrosion behavior were evaluated at 400-900°C. It is found that the pitting potential decreases when the grain size increases. With the increase in chloride ion concentration, the doping density and the flat-bland potential increase but the thickness of the space charge layer decreases. The pitting corrosion resistance increases rapidly with the decrease in pH value. Precipitants is identified as Nb(C,N) and NbC, rather than Cr-carbide. The intergranular corrosion is attributed to the synergistic effects of Nb(C,N) and NbC precipitates and Cr segregation adjacent to the precipitates.

grain size and heavy mineral analyses of two boreholes in recent

African Journals Online (AJOL)

user

mineral composition and the grain sizes of the aquifer in the study areas. ... analysis of both wells show that mean, inclusive standard deviation, ..... colourless grains with rectangular outline. .... Nigeria; A Case Study of Onisha and Environ.

Ferrite channel effect on ductility and strain hardenability of ultra high strength dual phase steel

Energy Technology Data Exchange (ETDEWEB)

Ravi, Kumar B., E-mail: ravik@nmlindia.org [CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Patel, Nand Kumar [O.P Jindal University, Raigarh 496001 (India); Mukherjee, Krishnendu; Walunj, Mahesh; Mandal, Gopi Kishor [CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Venugopalan, T. [Tata Steel Limited, Jamshedpur 831001 (India)

2017-02-08

This study describes an effect of controlled austenite decomposition on microstructure evolution in dual phase steel. Steel sheets austenitized at various annealing temperatures were rapidly cooled to the inter-critical annealing temperature of 800 °C for the isothermal decomposition of austenite and then ultra fast cooled to room temperature. The scanning electron microscope analysis of evolving microstructure revealed ferrite nucleation and growth along prior austenite grain boundaries leading to ferrite network/channel formation around martensite. The extent of ferrite channel formation showed a strong dependence on the degree of undercooling in the inter-critical annealing temperature regime. Uniaxial tensile deformation of processed steel sheets showed extensive local inter-lath martensite damage activity. Extension/propagation of these local micro cracks to neighboring martensite grains was found to be arrested by ferrite channels. This assisted in delaying the onset of global damage which could lead to necking and fracture. The results demonstrated an alternate possible way of inducing ductility and strain hardenability in ultra high strength dual phase steels.

Effects of consolidation temperature, strength and microstructure on fracture toughness of nanostructured ferritic alloys

International Nuclear Information System (INIS)

Miao, P.; Odette, G.R.; Yamamoto, T.; Alinger, M.; Hoelzer, D.; Gragg, D.

2007-01-01

Fully consolidated nanostructured ferritic alloys (NFAs) were prepared by attritor milling pre-alloyed Fe-14Cr-3W-0.4Ti and 0.3 wt% Y 2 O 3 powders, followed by hot isostatic pressing (HIPing) at 1000 o C or 1150 o C at 200 MPa for 4 h. Transmission electron microscopy (TEM) revealed similar bimodal distributions of fine and coarse ferrite grains in both cases. However, as expected, the alloy microhardness decreased with increasing in HIPing temperature. Three point bend tests on single edge notched specimens, with a nominal root radius ρ = 0.15 mm, were used to measure the notch fracture toughness, K ρ , as a function of test temperature. The K ρ curves were found to be similar for both processing conditions. It appears that the coarser ferrite grains control cleavage fracture, in a way that is independent of alloy strength and HIPing temperature

Determining the effect of grain size and maximum induction upon coercive field of electrical steels

Science.gov (United States)

Landgraf, Fernando José Gomes; da Silveira, João Ricardo Filipini; Rodrigues-Jr., Daniel

2011-10-01

Although theoretical models have already been proposed, experimental data is still lacking to quantify the influence of grain size upon coercivity of electrical steels. Some authors consider a linear inverse proportionality, while others suggest a square root inverse proportionality. Results also differ with regard to the slope of the reciprocal of grain size-coercive field relation for a given material. This paper discusses two aspects of the problem: the maximum induction used for determining coercive force and the possible effect of lurking variables such as the grain size distribution breadth and crystallographic texture. Electrical steel sheets containing 0.7% Si, 0.3% Al and 24 ppm C were cold-rolled and annealed in order to produce different grain sizes (ranging from 20 to 150 μm). Coercive field was measured along the rolling direction and found to depend linearly on reciprocal of grain size with a slope of approximately 0.9 (A/m)mm at 1.0 T induction. A general relation for coercive field as a function of grain size and maximum induction was established, yielding an average absolute error below 4%. Through measurement of B50 and image analysis of micrographs, the effects of crystallographic texture and grain size distribution breadth were qualitatively discussed.

The effect of annealing on the structural and magnetic properties of Ni-ferrite nanocrystals

Energy Technology Data Exchange (ETDEWEB)

Ojha, Chaturbhuj, E-mail: cbophy@yahoo.co.in; Chauhan, S. S.; Shrivastava, A. K. [School of Studies in Physics, Jiwaji University, Gwalior (India); Verma, A. K. [Govt. Post Graduate College Dholpur, Rajasthan (India)

2015-06-24

Magnetic nanoparticles NiFe{sub 2}O{sub 4} were prepared by chemical co-precipitation technique using the chlorides of Ni, Fe (III) and oleic acid. The precursors were annealed at different temperature 500, 700, and 900 °C. The XRD of samples show the presence of inverse cubic spinel structure. Grain size was determined using Scherrer formula and SEM technique. The Particle size, Lattice parameter and X-ray density were also estimated from X-ray diffraction data. The particles size was found to vary from 17nm to 37 nm and largely depends on the annealing temperature. Magnetization measurements have also carried out using VSM and it was found that saturation magnetization (Ms), Remanance (Mr) and coercivity (H{sub c}) of nano ferrite materials are lower compared to bulk materials.

Passive acoustic measurement of bedload grain size distribution using self-generated noise

Directory of Open Access Journals (Sweden)

T. Petrut

2018-01-01

Full Text Available Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

Passive acoustic measurement of bedload grain size distribution using self-generated noise

Science.gov (United States)

Petrut, Teodor; Geay, Thomas; Gervaise, Cédric; Belleudy, Philippe; Zanker, Sebastien

2018-01-01

Monitoring sediment transport processes in rivers is of particular interest to engineers and scientists to assess the stability of rivers and hydraulic structures. Various methods for sediment transport process description were proposed using conventional or surrogate measurement techniques. This paper addresses the topic of the passive acoustic monitoring of bedload transport in rivers and especially the estimation of the bedload grain size distribution from self-generated noise. It discusses the feasibility of linking the acoustic signal spectrum shape to bedload grain sizes involved in elastic impacts with the river bed treated as a massive slab. Bedload grain size distribution is estimated by a regularized algebraic inversion scheme fed with the power spectrum density of river noise estimated from one hydrophone. The inversion methodology relies upon a physical model that predicts the acoustic field generated by the collision between rigid bodies. Here we proposed an analytic model of the acoustic energy spectrum generated by the impacts between a sphere and a slab. The proposed model computes the power spectral density of bedload noise using a linear system of analytic energy spectra weighted by the grain size distribution. The algebraic system of equations is then solved by least square optimization and solution regularization methods. The result of inversion leads directly to the estimation of the bedload grain size distribution. The inversion method was applied to real acoustic data from passive acoustics experiments realized on the Isère River, in France. The inversion of in situ measured spectra reveals good estimations of grain size distribution, fairly close to what was estimated by physical sampling instruments. These results illustrate the potential of the hydrophone technique to be used as a standalone method that could ensure high spatial and temporal resolution measurements for sediment transport in rivers.

The grain-size distribution of pyroclasts: Primary fragmentation, conduit sorting or abrasion?

Science.gov (United States)

Kueppers, U.; Schauroth, J.; Taddeucci, J.

2013-12-01

Explosive volcanic eruptions expel a mixture of pyroclasts and lithics. Pyroclasts, fragments of the juvenile magma, record the state of the magma at fragmentation in terms of porosity and crystallinity. The grain size distribution of pyroclasts is generally considered to be a direct consequence of the conditions at magma fragmentation that is mainly driven by gas overpressure in bubbles, high shear rates, contact with external water or a combination of these factors. Stress exerted by any of these processes will lead to brittle fragmentation by overcoming the magma's relaxation timescale. As a consequence, most pyroclasts exhibit angular shapes. Upon magma fragmentation, the gas pyroclast mixture is accelerated upwards and eventually ejected from the vent. The total grain size distribution deposited is a function of fragmentation conditions and transport related sorting. Porous pyroclasts are very susceptible to abrasion by particle-particle or particle-conduit wall interaction. Accordingly, pyroclastic fall deposits with angular clasts should proof a low particle abrasion upon contact to other surfaces. In an attempt to constrain the degree of particle interaction during conduit flow, monomodal batches of washed pyroclasts have been accelerated upwards by rapid decompression and subsequently investigated for their grain size distribution. In our set-up, we used a vertical cylindrical tube without surface roughness as conduit. We varied grain size (0.125-0.25; 0.5-1; 1-2 mm), porosity (0; 10; 30 %), gas-particle ratio (10 and 40%), conduit length (10 and 28 cm) and conduit diameter (2.5 and 6 cm). All ejected particles were collected after settling at the base of a 3.3 m high tank and sieved at one sieve size below starting size (half-Φ). Grain size reduction showed a positive correlation with starting grain size, porosity and overpressure at the vent. Although milling in a volcanic conduit may take place, porous pyroclasts are very likely to be a primary product

grain size analysis of beach sediment along the barrier bar lagoon

African Journals Online (AJOL)

PROF EKWUEME

sediment are medium grain and deposited in a moderate energy condition hence more stable to ... The grain size and amount of sand on a beach depends on wave energy and geological ..... Recent and Pleistocene history of Southeast.

Effects of grain size on the corrosion resistance of pure magnesium by cooling rate-controlled solidification

Science.gov (United States)

Liu, Yichi; Liu, Debao; You, Chen; Chen, Minfang

2015-09-01

The aim of this study was to investigate the effect of grain size on the corrosion resistance of pure magnesium developed for biomedical applications. High-purity magnesium samples with different grain size were prepared by the cooling rate-controlled solidification. Electrochemical and immersion tests were employed to measure the corrosion resistance of pure magnesium with different grain size. The electrochemical polarization curves indicated that the corrosion susceptibility increased as the grain size decrease. However, the electrochemical impedance spectroscopy (EIS) and immersion tests indicated that the corrosion resistance of pure magnesium is improved as the grain size decreases. The improvement in the corrosion resistance is attributed to refine grain can produce more uniform and density film on the surface of sample.

On grain-size-dependent void swelling in pure copper irradiated with fission neutrons

DEFF Research Database (Denmark)

Singh, Bachu Narain; Eldrup, Morten Mostgaard; Zinkle, S.J.

2002-01-01

The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms. The phenomenon had already been investigated in the 1970s and it was demonstrated that the grain......-size-dependent void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under...

Film Grain-Size Related Long-Term Stability of Inverted Perovskite Solar Cells.

Science.gov (United States)

Chiang, Chien-Hung; Wu, Chun-Guey

2016-09-22

The power conversion efficiency (PCE) of the perovskite solar cell is high enough to be commercially viable. The next important issue is the stability of the device. This article discusses the effect of the perovskite grain-size on the long-term stability of inverted perovskite solar cells. Perovskite films composed of various sizes of grains were prepared by controlling the solvent annealing time. The grain-size related stability of the inverted cells was investigated both in ambient atmosphere at relative humidity of approximately 30-40 % and in a nitrogen filled glove box (H 2 Operovskite film having the grain size larger than 1 μm (D-10) decreases less than 10 % with storage in a glove box and less than 15 % when it was stored under an ambient atmosphere for 30 days. However, the cell using the perovskite film composed of small (∼100 nm) perovskite grains (D-0) exhibits complete loss of PCE after storage under the ambient atmosphere for only 15 days and a PCE loss of up to 70 % with storage in the glove box for 30 days. These results suggest that, even under H 2 O-free conditions, the chemical- and thermal-induced production of pin holes at the grain boundaries of the perovskite film could be the reason for long-term instability of inverted perovskite solar cells. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Grain size of fine-grained windblown sediment: a powerful proxy for process identification

NARCIS (Netherlands)

Vandenberghe, J.

2013-01-01

Dust transport by the wind is not a uniform process but may occur in different modes according to source area conditions and transport height and distance. Subsequently, these differences are expressed in terms of grain-size and fluxes of the aeolian deposits. Transport distances may vary from

GS6, a member of the GRAS gene family, negatively regulates grain size in rice.

Science.gov (United States)

Sun, Lianjun; Li, Xiaojiao; Fu, Yongcai; Zhu, Zuofeng; Tan, Lubin; Liu, Fengxia; Sun, Xianyou; Sun, Xuewen; Sun, Chuanqing

2013-10-01

Grain size is an important yield-related trait in rice. Intensive artificial selection for grain size during domestication is evidenced by the larger grains of most of today's cultivars compared with their wild relatives. However, the molecular genetic control of rice grain size is still not well characterized. Here, we report the identification and cloning of Grain Size 6 (GS6), which plays an important role in reducing grain size in rice. A premature stop at the +348 position in the coding sequence (CDS) of GS6 increased grain width and weight significantly. Alignment of the CDS regions of GS6 in 90 rice materials revealed three GS6 alleles. Most japonica varieties (95%) harbor the Type I haplotype, and 62.9% of indica varieties harbor the Type II haplotype. Association analysis revealed that the Type I haplotype tends to increase the width and weight of grains more than either of the Type II or Type III haplotypes. Further investigation of genetic diversity and the evolutionary mechanisms of GS6 showed that the GS6 gene was strongly selected in japonica cultivars. In addition, a "ggc" repeat region identified in the region that encodes the GRAS domain of GS6 played an important historic role in the domestication of grain size in rice. Knowledge of the function of GS6 might aid efforts to elucidate the molecular mechanisms that control grain development and evolution in rice plants, and could facilitate the genetic improvement of rice yield. © 2013 Institute of Botany, Chinese Academy of Sciences.

Influence of temperature and grain size on the tensile ductility of AISI 316 stainless steel

International Nuclear Information System (INIS)

Mannan, S.L.; Samuel, K.G.; Rodriguez, P.

1985-01-01

The influence of tmeperature and grain size on the tensile ductility of AISI 316 stainless steel has been examined in the temperature range 300-1223 K for specimens with grain sizes varying from 0.025 to 0.650 mm at a nominal strain rate of 3 X 10 -4 s -1 . The percentage total elongation and reduction in area at fracture show minimum ductility at an intermediate temperature, and the temperature corresponding to this ductility minimum has been found to increase with increase in grain size. The total elongation is found to decrease with increase in grain size at high temperatures where failures are essentially intergranular in nature. At 300 K, both uniform and total elongation increase with increase in grain size and then show a small decrease for a very coarse grain size. The high ductility observed at low temperatures (300 K) is consistent with the observation of characteristic dimples associated with transgranular ductile fracture. The ductility minimum with respect to temperature is associated with the occurrence of intergranular fracture, as evidenced by optical and scanning electron microscopy. The present results support the suggestion that the ductility minimum coincides with the maximum amount of grain boundary sliding; at temperatures beyond the ductility minimum, grain boundary separation by cavitation is retarded by the occurrence of grain boundary migration, as evidenced by the grain boundary cusps. In tests conducted at various strain rates in the range 10 -3 -10 -6 s -1 at 873 K the ductility was found to decrease with decreasing strain rate, emphasizing the increased importance of grain boundary sliding at lower strain rates. (Auth.)

Effect of grain size on corrosion of nanocrystalline copper in NaOH solution

International Nuclear Information System (INIS)

Luo Wei; Xu Yimin; Wang Qiming; Shi Peizhen; Yan Mi

2010-01-01

Research highlights: → Coppers display an active-passive-transpassive behaviour with duplex passive film. → Grain size variation has little effect on the overall corrosion behaviour of Cu. → Little effect on corrosion may be due to duplex passivation in NaOH solution. → Bulk nanocrystalline Cu show bamboo-like flake corrosion structure. - Abstract: Effect of grain size on corrosion of bulk nanocrystalline copper was investigated using potentiodynamic polarization measurements in 0.1 M NaOH solution. Bulk nanocrystalline copper was prepared by inert gas condensation and in situ warm compress (IGCWC) method. The grain sizes of all bulk nanocrystalline samples were determined to be 48, 68 and 92 nm using X-ray diffraction (XRD). Results showed that bulk coppers displayed an active-passive-transpassive behaviour with duplex passive films. From polycrystalline to nanocrystalline, grain size variation showed little effect on the overall corrosion resistance of copper samples.

Electrical transport properties of CoMn0.2−xGaxFe1.8O4 ferrites using complex impedance spectroscopy

Directory of Open Access Journals (Sweden)

Chien-Yie Tsay

2016-05-01

Full Text Available In this study, we report the influence of Ga content on the microstructural, magnetic, and AC impedance properties of Co-based ferrites with compositions of CoMn0.2−xGaxFe1.8O4 (x=0, 0.1, and 0.2 prepared by the solid-state reaction method. Experimental results showed that the as-prepared Co-based ferrites had a single-phase spinel structure; the Curie temperature of Co-based ferrites decreased with increasing Ga content. All ferrite samples exhibited a typical hysteresis behavior with good values of saturation magnetization at room temperature. The electrical properties of Co-based ferrites were investigated using complex impedance spectroscopy analysis in the frequency range of 100 kHz-50 MHz at temperatures of 150 to 250 oC. The impedance analysis revealed that the magnitudes of the real part (Z’ and the imaginary part (Z” of complex impedance decreased with increasing temperature. Only one semicircle was observed in each complex impedance plane plot, which revealed that the contribution to conductivity was from the grain boundaries. It was found that the relaxation time for the grain boundary (τgb also decreased with increasing temperature. The values of resistance for the grain boundary (Rgb significantly increased with increasing Ga content, which indicated that the incorporation of Ga into Co-based ferrites enhanced the electrical resistivity.

Fracture toughness of WWER Uranium dioxide fuel pellets with various grain size

International Nuclear Information System (INIS)

Sivov, R.; Novikov, V.; Mikheev, E.; Fedotov, A.

2015-01-01

Uranium dioxide fuel pellets with grain sizes 13, 26, and 33 μm for WWER were investigated in the present work in order to determine crack formation and the fracture toughness.The investigation of crack formation in uranium oxide fuel pellets of the WWER-types showed that Young’s modulus and the microhardness of polycrystalline samples increase with increasing grain size, while the fracture toughness decreases. Characteristically, radial Palmqvist cracks form on the surface of uranium dioxide pellets for loads up to 1 kg. Transgranular propagation of cracks over distances several-fold larger than the length of the imprint diagonal is observed in pellets with large grains and small intragrain pores. Intergranular propagation of cracks along grain boundaries with branching occurs in pellets with small grains and low pore concentration on the grain boundaries. Blunting on large pores and at breaks in direction does not permit the cracks to reach a significant length

Fractographic examination of reduced activation ferritic/martensitic steel charpy specimens irradiated to 30 dpa at 370{degrees}C

Energy Technology Data Exchange (ETDEWEB)

Gelles, D.S.; Hamilton, M.L. [Pacific Northwest National Lab., Richland, WA (United States); Schubert, L.E. [Univ. of Missouri, Rolla, MO (United States)

1996-10-01

Fractographic examinations are reported for a series of reduced activation ferritic/Martensitic steel Charpy impact specimens tested following irradiation to 30 dpa at 370{degrees}C in FFTF. One-third size specimens of six low activation steels developed for potential application as structural materials in fusion reactors were examined. A shift in brittle fracture appearance from cleavage to grain boundary failure was noted with increasing manganese content. The results are interpreted in light of transmutation induced composition changes in a fusion environment.

Tailoring the magnetic properties of cobalt-ferrite nanoclusters

Energy Technology Data Exchange (ETDEWEB)

Vega, A. Estrada de la; Garza-Navarro, M. A., E-mail: marco.garzanr@uanl.edu.mx; Durán-Guerrero, J. G.; Moreno Cortez, I. E.; Lucio-Porto, R.; González-González, V. [Universidad Autónoma de Nuevo León, Facultad de Ingeniería Mecánica y Eléctrica (Mexico)

2016-01-15

In this contribution, we report on the tuning of magnetic properties of cobalt-ferrite nanoclusters. The cobalt-ferrite nanoclusters were synthesized from a two-step approach that consists of the synthesis of cobalt-ferrite nanoparticles in organic media, followed by their dispersion into aqueous dissolution to form an oil-in-water emulsion. These emulsions were prepared at three different concentrations of the cationic surfactant cetyltrimethylammonium bromide (CTAB), in order to control the size and clustering density of the nanoparticles in the nanoclusters. The synthesized samples were characterized by transmission electron microscopy and their related techniques, such as bright-field and Z-contrast imaging, electron diffraction and energy-dispersive X-ray spectrometry; as well as static magnetic measures. The experimental evidence indicates that the size, morphology, and nanoparticles clustering density in the nanoclusters is highly dependent of the cobalt-ferrite:CTAB molar ratio that is used in their synthesis. In addition, due to the clustering of the nanoparticles into the nanoclusters, their magnetic moments are blocked to relax cooperatively. Hence, the magnetic response of the nanoclusters can be tailored by controlling the size and nanoparticles clustering density.

Size distribution of dust grains: A problem of self-similarity

International Nuclear Information System (INIS)

Henning, TH.; Dorschner, J.; Guertler, J.

1989-01-01

Distribution functions describing the results of natural processes frequently show the shape of power laws. It is an open question whether this behavior is a result simply coming about by the chosen mathematical representation of the observational data or reflects a deep-seated principle of nature. The authors suppose the latter being the case. Using a dust model consisting of silicate and graphite grains Mathis et al. (1977) showed that the interstellar extinction curve can be represented by taking a grain radii distribution of power law type n(a) varies as a(exp -p) with 3.3 less than or equal to p less than or equal to 3.6 (example 1) as a basis. A different approach to understanding power laws like that in example 1 becomes possible by the theory of self-similar processes (scale invariance). The beta model of turbulence (Frisch et al., 1978) leads in an elementary way to the concept of the self-similarity dimension D, a special case of Mandelbrot's (1977) fractal dimension. In the frame of this beta model, it is supposed that on each stage of a cascade the system decays to N clumps and that only the portion beta N remains active further on. An important feature of this model is that the active eddies become less and less space-filling. In the following, the authors assume that grain-grain collisions are such a scale-invarient process and that the remaining grains are the inactive (frozen) clumps of the cascade. In this way, a size distribution n(a) da varies as a(exp -(D+1))da (example 2) results. It seems to be highly probable that the power law character of the size distribution of interstellar dust grains is the result of a self-similarity process. We can, however, not exclude that the process leading to the interstellar grain size distribution is not fragmentation at all

Grain Size Distribution in Mudstones: A Question of Nature vs. Nurture

Science.gov (United States)

Schieber, J.

2011-12-01

Grain size distribution in mudstones is affected by the composition of the source material, the processes of transport and deposition, and post-depositional diagenetic modification. With regard to source, it does make a difference whether for example a slate belt is eroded vs a stable craton. The former setting tends to provide a broad range of detrital quartz in the sub 62 micron size range in addition to clays and greenschist grade rock fragments, whereas the latter may be biased towards coarser quartz silt (30-60 microns), in addition to clays and mica flakes. In flume experiments, when fine grained materials are transported in turbulent flows at velocities that allow floccules to transfer to bedload, a systematic shift of grain size distribution towards an increasingly finer grained suspended load is observed as velocity is lowered. This implies that the bedload floccules are initially constructed of only the coarsest clay particles at high velocities, and that finer clay particles become incorporated into floccules as velocity is lowered. Implications for the rock record are that clay beds deposited from decelerating flows should show subtle internal grading of coarser clay particles; and that clay beds deposited from continuous fast flows should show a uniform distribution of coarse clays. Still water settled clays should show a well developed lower (coarser) and upper (finer) subdivision. A final complication arises when diagenetic processes, such as the dissolution of biogenic silica, give rise to diagenetic quartz grains in the silt to sand size range. This diagenetic silica precipitates in fossil cavities and pore spaces of uncompacted muds, and on casual inspection can be mistaken for detrital quartz. In distal mudstone successions close to 100 % of "apparent" quartz silt can be of that origin, and reworking by bottom currents can further enhance a detrital perception by producing rippled and laminated silt beds. Although understanding how size

Fatigue Failure Modes of the Grain Size Transition Zone in a Dual Microstructure Disk

Science.gov (United States)

Gabb, Timothy P.; Kantzos, Pete T.; Palsa, Bonnie; Telesman, Jack; Gayda, John; Sudbrack, Chantal K.

2012-01-01

Mechanical property requirements vary with location in nickel-based superalloy disks. In order to maximize the associated mechanical properties, heat treatment methods have been developed for producing tailored grain microstructures. In this study, fatigue failure modes of a grain size transition zone in a dual microstructure disk were evaluated. A specialized heat treatment method was applied to produce varying grain microstructure in the bore to rim portions of a powder metallurgy processed nickel-based superalloy disk. The transition in grain size was concentrated in a zone of the disk web, between the bore and rim. Specimens were extracted parallel and transversely across this transition zone, and multiple fatigue tests were performed at 427 C and 704 C. Grain size distributions were characterized in the specimens, and related to operative failure initiation modes. Mean fatigue life decreased with increasing maximum grain size, going out through the transition zone. The scatter in limited tests of replicates was comparable for failures of uniform gage specimens in all transition zone locations examined.

Fission gas release during post irradiation annealing of large grain size fuels from Hinkley point B

International Nuclear Information System (INIS)

Killeen, J.C.

1997-01-01

A series of post-irradiation anneals has been carried out on fuel taken from an experimental stringer from Hinkley Point B AGR. The stringer was part of an experimental programme in the reactor to study the effect of large grain size fuel. Three differing fuel types were present in separate pins in the stringer. One variant of large grain size fuel had been prepared by using an MgO dopant during fuel manufactured, a second by high temperature sintering of standard fuel and the third was a reference, 12μm grain size fuel. Both large grain size variants had similar grain sizes around 35μm. The present experiments took fuel samples from highly rated pins from the stringer with local burn-up in excess of 25GWd/tU and annealed these to temperature of up to 1535 deg. C under reducing conditions to allow a comparison of fission gas behaviour at high release levels. The results demonstrate the beneficial effect of large grain size on release rate of 85 Kr following interlinkage. At low temperatures and release rates there was no difference between the fuel types, but at temperatures in excess of 1400 deg. C the release rate was found to be inversely dependent on the fuel grain size. The experiments showed some differences between the doped and undoped large grains size fuel in that the former became interlinked at a lower temperature, releasing fission gas at an increased rate at this temperature. At higher temperatures the grain size effect was dominant. The temperature dependence for fission gas release was determined over a narrow range of temperature and found to be similar for all three types and for both pre-interlinkage and post-interlinkage releases, the difference between the release rates is then seen to be controlled by grain size. (author). 4 refs, 7 figs, 3 tabs

Fission gas release during post irradiation annealing of large grain size fuels from Hinkley point B

Energy Technology Data Exchange (ETDEWEB)

Killeen, J C [Nuclear Electric plc, Barnwood (United Kingdom)

1997-08-01

A series of post-irradiation anneals has been carried out on fuel taken from an experimental stringer from Hinkley Point B AGR. The stringer was part of an experimental programme in the reactor to study the effect of large grain size fuel. Three differing fuel types were present in separate pins in the stringer. One variant of large grain size fuel had been prepared by using an MgO dopant during fuel manufactured, a second by high temperature sintering of standard fuel and the third was a reference, 12{mu}m grain size fuel. Both large grain size variants had similar grain sizes around 35{mu}m. The present experiments took fuel samples from highly rated pins from the stringer with local burn-up in excess of 25GWd/tU and annealed these to temperature of up to 1535 deg. C under reducing conditions to allow a comparison of fission gas behaviour at high release levels. The results demonstrate the beneficial effect of large grain size on release rate of {sup 85}Kr following interlinkage. At low temperatures and release rates there was no difference between the fuel types, but at temperatures in excess of 1400 deg. C the release rate was found to be inversely dependent on the fuel grain size. The experiments showed some differences between the doped and undoped large grains size fuel in that the former became interlinked at a lower temperature, releasing fission gas at an increased rate at this temperature. At higher temperatures the grain size effect was dominant. The temperature dependence for fission gas release was determined over a narrow range of temperature and found to be similar for all three types and for both pre-interlinkage and post-interlinkage releases, the difference between the release rates is then seen to be controlled by grain size. (author). 4 refs, 7 figs, 3 tabs.

Effect of grain size on tensile stress and ductility in Al99.99

International Nuclear Information System (INIS)

Kovacs-Csetenyi, E.; Horvath, M.; Chinh, N.Q.; Kovacs, I.

1998-01-01

The effect of recrystallized grain size on the tensile stress and ductility of 99.99% purity aluminium was investigated at room temperature. It was proved that the grain size dependence of flow stress follows a modified Hall-Petch equation with coefficients depending linearly on ε 1/2 up to the stability limit. The uniform strain can also be described by a linear dependence on d -1/2 according to which the uniform elongation increases with increasing grain size. The post-uniform elongation changes inversely to that of the uniform one accompanied by the decrease of the strain rate sensitivity. (orig.)

Structural and magnetic properties of ball milled copper ferrite

DEFF Research Database (Denmark)

Goya, G.F.; Rechenberg, H.R.; Jiang, Jianzhong

1998-01-01

The structural and magnetic evolution in copper ferrite (CuFe2O4) caused by high-energy ball milling are investigated by x-ray diffraction, Mössbauer spectroscopy, and magnetization measurements. Initially, the milling process reduces the average grain size of CuFe2O4 to about 6 nm and induces....... The canted spin configuration is also suggested by the observed reduction in magnetization of particles in the blocked state. Upon increasing the milling time, nanometer-sized CuFe2O4 particles decompose, forming alpha-Fe2O3 and other phases, causing a further decrease of magnetization. After a milling time...... of 98 h, alpha-Fe2O3 is reduced to Fe3O4, and magnetization increases accordingly to the higher saturation magnetization value of magnetite. Three sequential processes during high-energy ball milling are established: (a) the synthesis of partially inverted CuFe2O4 particles with a noncollinear spin...

A pretreatment method for grain size analysis of red mudstones

Science.gov (United States)

Jiang, Zaixing; Liu, Li'an

2011-11-01

Traditional sediment disaggregation methods work well for loose mud sediments, but not for tightly cemented mudstones by ferric oxide minerals. In this paper, a new pretreatment method for analyzing the grain size of red mudstones is presented. The experimental samples are Eocene red mudstones from the Dongying Depression, Bohai Bay Basin. The red mudstones are composed mainly of clay minerals, clastic sediments and ferric oxides that make the mudstones red and tightly compacted. The procedure of the method is as follows. Firstly, samples of the red mudstones were crushed into fragments with a diameter of 0.6-0.8 mm in size; secondly, the CBD (citrate-bicarbonate-dithionite) treatment was used to remove ferric oxides so that the cementation of intra-aggregates and inter-aggregates became weakened, and then 5% dilute hydrochloric acid was added to further remove the cements; thirdly, the fragments were further ground with a rubber pestle; lastly, an ultrasonicator was used to disaggregate the samples. After the treatment, the samples could then be used for grain size analysis or for other geological analyses of sedimentary grains. Compared with other pretreatment methods for size analysis of mudstones, this proposed method is more effective and has higher repeatability.

Structural elucidation and magnetic behavior evaluation of rare earth (La, Nd, Gd, Tb, Dy) doped BaCoNi-X hexagonal nano-sized ferrites

Energy Technology Data Exchange (ETDEWEB)

Majeed, Abdul, E-mail: abdulmajeed2276@gmail.com [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Raheem, Faseeh ur; Hussain, Altaf; Iqbal, F. [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Murtaza, Ghulam [Centre for Advanced Studies in Physics, Government College University, Lahore 54000 (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Shakir, Imran [Deanship of Scientific Research, College of Engineering, King Saud University, PO Box 800, Riyadh 11421 (Saudi Arabia); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

2016-06-15

Rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route, which is a fast chemistry route for obtaining nano-sized ferrite powders. These nanomaterials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), as well as vibrating sample magnetometer (VSM). The XRD analysis exhibited that all the samples crystallized into single X-type hexagonal phase. The crystalline size calculated by Scherrer's formula was found in the range 7–19 nm. The variations in lattice parameters elucidated the incorporation of rare-earth cations in these nanomaterials. FTIR absorption spectra of these X-type ferrites were investigated in the wave number range 500–2400 cm{sup −1.} Each spectrum exhibited absorption bands in the low wave number range, thereby confirming the X-type hexagonal structure. The enhancement in the coercivity was observed with the doping of rare-earth cations. The saturation magnetization was lowered owing to the redistribution of rare-earth cations on the octahedral site (3b{sub VI}). The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Graphical abstract: Nano-sized rare-earth (RE=La{sup 3+}, Nd{sup 3+}, Gd{sup 3+}, Tb{sup 3+}, Dy{sup 3+}) doped Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} (x=0.25) hexagonal ferrites were synthesized for the first time via micro-emulsion route and the crystallite size was found in the range 7–19 nm. The enhancement in the coercivity was observed with the doping of rare-earth cations. The higher values of coercivity (664–926 Oe) of these nanomaterials suggest their use in longitudinal recording media. - Highlights: • Micro-emulsion route was used to synthesize Ba{sub 2}NiCoRE{sub x}Fe{sub 28−x}O{sub 46} ferrites. • The crystallite size was found

Effect of grain size on the hardness and reactivity of plasma-sintered beryllium

International Nuclear Information System (INIS)

Kim, Jae-Hwan; Nakamichi, Masaru

2014-01-01

Beryllium and its intermetallic compounds have attracted great attention as promising neutron multipliers in fusion reactors. In this study, mechanical and chemical properties of fabricated plasma-sintered beryllium (PS-Be) with different grain-sizes are investigated. Density and hardness analysis results of the fabricated PS-Be samples infer that a smaller grain size in the sintered Be indicates higher porosity and hardness. Sintered Be with a large grain size exhibits better resistance toward oxidation at 1273 K in dry air and at 1073 K in Ar/1% H 2 O, since oxidation at the grain boundaries of the determines the rate. In contrast, at 1273 K in Ar/1% H 2 O, a catastrophic oxidation is indicated by the increase of weight of the samples and the generation of H 2 from the bulk Be

Numerical modelling of intergranular fracture in polycrystalline materials and grain size effects

Directory of Open Access Journals (Sweden)

P. Wriggers

2011-07-01

Full Text Available In this paper, the phenomenon of intergranular fracture in polycrystalline materials is investigated using a nonlinear fracture mechanics approach. The nonlocal cohesive zone model (CZM for finite thickness interfaces recently proposed by the present authors is used to describe the phenomenon of grain boundary separation. From the modelling point of view, considering the dependency of the grain boundary thickness on the grain size observed in polycrystals, a distribution of interface thicknesses is obtained. Since the shape and the parameters of the nonlocal CZM depend on the interface thickness, a distribution of interface fracture energies is obtained as a consequence of the randomness of the material microstructure. Using these data, fracture mechanics simulations are performed and the homogenized stress-strain curves of 2D representative volume elements (RVEs are computed. Failure is the result of a diffuse microcrack pattern leading to a main macroscopic crack after coalescence, in good agreement with the experimental observation. Finally, testing microstructures characterized by different average grain sizes, the computed peak stresses are found to be dependent on the grain size, in agreement with the trend expected according to the Hall-Petch law.

Cohesion of Mm- to Cm-Sized Asteroid Simulant Grains: An Experimental Study

Science.gov (United States)

Brisset, Julie; Colwell, Joshua E.; Dove, Adrienne; Jarmak, Stephanie; Anderson, Seamus

2017-10-01

The regolith covering the surfaces of asteroids and planetary satellites is very different from terrestrial soil particles and subject to environmental conditions very different from what is found on Earth. The loose, unconsolidated granular material has angular-shaped grains and a broad size distribution. On small and airless bodies (Earth surface gravity, the cohesion behavior of the regolith grains will dictate the asteroid’s surface morphology and its response to impact or spacecraft contact.Previous laboratory experiments on low-velocity impacts into regolith simulant with grain sizes landing missions to small bodies such as asteroids or Martian moons.

[Characteristics and its forming mechanism on grain size distribution of suspended matter at Changjiang Estuary].

Science.gov (United States)

Pang, Chong-guang; Yu, Wei; Yang, Yang

2010-03-01

In July of 2008, under the natural condition of sea water, the Laser in-situ scattering and transmissometry (LISST-100X Type C) was used to measure grain size distribution spectrum and volume concentration of total suspended matter in the sea water, including flocs at different layers of 24 sampling stations at Changjiang Estuary and its adjacent sea. The characteristics and its forming mechanism on grain size distribution of total suspended matter were analyzed based on the observation data of LISST-100X Type C, and combining with the temperature, salinity and turbidity of sea water, simultaneously observed by Alec AAQ1183. The observation data showed that the average median grain size of total suspended matter was about 4.69 phi in the whole measured sea area, and the characteristics of grain size distribution was relatively poor sorted, wide kurtosis, and basically symmetrical. The conclusion could be drawn that vertically average volume concentration decreased with the distance from the coastline, while median grain size had an increase trend with the distance, for example, at 31.0 degrees N section, the depth-average median grain size had been increased from 11 microm up to 60 microm. With the increasing of distance from the coast, the concentration of fine suspended sediment reduced distinctly, nevertheless some relatively big organic matter or big flocs appeared in quantity, so its grain size would rise. The observation data indicated that the effective density was ranged from 246 kg/m3 to 1334 kg/m, with average was 613 kg/m3. When the concentration of total suspended matter was relatively high, median grain size of total suspended matter increased with the water depth, while effective density decreased with the depth, because of the faster settling velocity and less effective density of large flocs that of small flocs. As for station 37 and 44, their correlation coefficients between effective density and median grain size were larger than 0.9.

Evaluation of Pure Aluminium Inoculated with Varying Grain Sizes of an Agro-waste based Inoculant

Directory of Open Access Journals (Sweden)

Adeyemi I. Olabisi

2017-04-01

Full Text Available Pure Aluminium and its alloy are widely utilized in Engineering and Industrial applications due to certain significant properties such as softness, ductility, corrosion resistance, and high electrical conductivity which it possesses. Addition of an agro-waste based grain refiner to the melt can alter the characteristics positively or negatively. Therefore, the aim of this paper is to investigate the inoculating capability of an agro-waste based inoculant and the effect of adding varying sizes of its grains on some of the properties of pure aluminium after solidification. The beneficial outcome of this investigation would enhance the economic value of the selected agro-waste and also broaden the applications of aluminium in Engineering. The assessed properties include; microstructure, micro hardness, ductility, and tensile strength. The agro-waste used as the grain refiner is pulverised cocoa bean shells (CBS. Three sets of test samples were produced using dry sand moulding process, with each melt having a specified grain size of the inoculant added to it (150, 225 and 300microns respectively. Ladle inoculation method was adopted. The cast samples after solidification were machined to obtain various shapes/sizes for the different analysis. The microstructural examination showed that the mechanical properties are dependent on the matrix as the aluminium grains became more refined with increasing grain size of the inoculant. I.e. Due to increasing grain size of the inoculant, the micro hardness increased (56, 61, 72HB as the aluminium crystal size became finer. Meanwhile, the tensile strength (284, 251, 223N/mm2 and ductility (1.82, 0.91, 0.45%E decreased as grain size of the inoculant increased. The overall results showed that the used agro-waste based inoculant has the capability of refining the crystal size of pure aluminium as its grain size increases. This will make the resulting aluminium alloy applicable in areas where hardness is of

Structural and magnetic Ni-Zn ferrite synthesized by combustion reaction and sintered in a conventional oven; Caracterizacao estrutural e magnetica de ferrita Ni-Zn sintetizadas por reacao de combustao e sinterizadas em forno convencional

Energy Technology Data Exchange (ETDEWEB)

Vieira, D.A.; Diniz, V.C.S.; Costa, A.C.F.M., E-mail: deboralbq@hotmail.com [Universidade Federal de Campina Grande (UFCG), Campina Grande, PB (Brazil). Departamento de Engenharia de Materiais; Kiminami, R.H.G.A. [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Engenharia de Materiais; Cornejo, D.R. [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica. Departamento de Fisica dos Materiais e Mecanica

2011-07-01

The Ni-Zn ferrite due to their electrical and magnetic properties allows use in various technological applications. These properties can be controlled through appropriate choice of chemical composition, structural characteristics and morphology of the powders used and the techniques used for sintering. Thus, this study aims to evaluate the sintering in a conventional oven at a temperature of 1200 deg C/2h samples of Ni-Zn ferrite synthesized by microwave energy. The samples were characterized by density measurement, XRD, SEM and magnetic measurements. The results indicate the phase formation of Ni-Zn ferrite crystalline phase with crystallite size of 80 nm. The sample was heterogeneous microstructure with grain size of about 1 μm high intergranular porosity. The sample showed the saturation magnetization of 7.57 emu/g, coercive field and remanent magnetization close to zero, thus indicating a behavior characteristic of superparamagnetic materials. (author)

A universal approximation to grain size from images of non-cohesive sediment

Science.gov (United States)

Buscombe, D.; Rubin, D.M.; Warrick, J.A.

2010-01-01

The two-dimensional spectral decomposition of an image of sediment provides a direct statistical estimate, grid-by-number style, of the mean of all intermediate axes of all single particles within the image. We develop and test this new method which, unlike existing techniques, requires neither image processing algorithms for detection and measurement of individual grains, nor calibration. The only information required of the operator is the spatial resolution of the image. The method is tested with images of bed sediment from nine different sedimentary environments (five beaches, three rivers, and one continental shelf), across the range 0.1 mm to 150 mm, taken in air and underwater. Each population was photographed using a different camera and lighting conditions. We term it a “universal approximation” because it has produced accurate estimates for all populations we have tested it with, without calibration. We use three approaches (theory, computational experiments, and physical experiments) to both understand and explore the sensitivities and limits of this new method. Based on 443 samples, the root-mean-squared (RMS) error between size estimates from the new method and known mean grain size (obtained from point counts on the image) was found to be ±≈16%, with a 95% probability of estimates within ±31% of the true mean grain size (measured in a linear scale). The RMS error reduces to ≈11%, with a 95% probability of estimates within ±20% of the true mean grain size if point counts from a few images are used to correct bias for a specific population of sediment images. It thus appears it is transferable between sedimentary populations with different grain size, but factors such as particle shape and packing may introduce bias which may need to be calibrated for. For the first time, an attempt has been made to mathematically relate the spatial distribution of pixel intensity within the image of sediment to the grain size.

Influence of grain size distribution on dynamic shear modulus of sands

Directory of Open Access Journals (Sweden)

Dyka Ireneusz

2017-11-01

Full Text Available The paper presents the results of laboratory tests, that verify the correlation between the grain-size characteristics of non-cohesive soils and the value of the dynamic shear modulus. The problem is a continuation of the research performed at the Institute of Soil Mechanics and Rock Mechanics in Karlsruhe, by T. Wichtmann and T. Triantafyllidis, who derived the extension of the applicability of the Hardin’s equation describing the explicite dependence between the grain size distribution of sands and the values of dynamic shear modulus. For this purpose, piezo-ceramic bender elements generating elastic waves were used to investigate the mechanical properties of the specimens with artificially generated particle distribution. The obtained results confirmed the hypothesis that grain size distribution of non-cohesive soils has a significant influence on the dynamic shear modulus, but at the same time they have shown that obtaining unambiguous results from bender element tests is a difficult task in practical applications.

Gas tungsten arc welding and friction stir welding of ultrafine grained AISI 304L stainless steel: Microstructural and mechanical behavior characterization

Energy Technology Data Exchange (ETDEWEB)

Sabooni, S., E-mail: s.sabooni@ma.iut.ac.ir [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Karimzadeh, F.; Enayati, M.H. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of); Ngan, A.H.W. [Department of Mechanical Engineering, The University of Hong Kong, Pokfulam Road, Hong Kong (China); Jabbari, H. [Department of Materials Engineering, Isfahan University of Technology, 84156-83111 Isfahan (Iran, Islamic Republic of)

2015-11-15

In the present study, an ultrafine grained (UFG) AISI 304L stainless steel with the average grain size of 650 nm was successfully welded by both gas tungsten arc welding (GTAW) and friction stir welding (FSW). GTAW was applied without any filler metal. FSW was also performed at a constant rotational speed of 630 rpm and different welding speeds from 20 to 80 mm/min. Microstructural characterization was carried out by High Resolution Scanning Electron Microscopy (HRSEM) with Electron Backscattered Diffraction (EBSD) and Transmission Electron Microscopy (TEM). Nanoindentation, microhardness measurements and tensile tests were also performed to study the mechanical properties of the base metal and weldments. The results showed that the solidification mode in the GTAW welded sample is FA (ferrite–austenite) type with the microstructure consisting of an austenite matrix embedded with lath type and skeletal type ferrite. The nugget zone microstructure in the FSW welded samples consisted of equiaxed dynamically recrystallized austenite grains with some amount of elongated delta ferrite. Sigma phase precipitates were formed in the region ahead the rotating tool during the heating cycle of FSW, which were finally fragmented into nanometric particles and distributed in the weld nugget. Also there is a high possibility that the existing delta ferrite in the microstructure rapidly transforms into sigma phase particles during the short thermal cycle of FSW. These suggest that high strain and deformation during FSW can promote sigma phase formation. The final austenite grain size in the nugget zone was found to decrease with increasing Zener–Hollomon parameter, which was obtained quantitatively by measuring the peak temperature, calculating the strain rate during FSW and exact examination of hot deformation activation energy by considering the actual grain size before the occurrence of dynamic recrystallization. Mechanical properties observations showed that the welding

Dependency of annealing behaviour on grain size in Al–TiC ...

Indian Academy of Sciences (India)

This work investigates the effect of grain size on annealing behaviour in both coarse-grained and ultrafinegrained Al–TiC composite processed by accumulative roll bonding (ARB). Microstructural analysis indicates that annealingbehaviour of the specimens are essentially determined by the level of strain accumulation or ...

Size Distribution and Rate of Dust Generated During Grain Elevator Handling

Science.gov (United States)

Dust generated during grain handling is an air pollutant that produces safety and health hazards. This study was conducted to characterize the particle size distribution (PSD) of dust generated during handling of wheat and shelled corn in the research elevator of the USDA Grain Marketing and Product...

Spectral Profiler Probe for In Situ Snow Grain Size and Composition Stratigraphy

Science.gov (United States)

Berisford, Daniel F.; Molotch, Noah P.; Painter, Thomas

2012-01-01

An ultimate goal of the climate change, snow science, and hydrology communities is to measure snow water equivalent (SWE) from satellite measurements. Seasonal SWE is highly sensitive to climate change and provides fresh water for much of the world population. Snowmelt from mountainous regions represents the dominant water source for 60 million people in the United States and over one billion people globally. Determination of snow grain sizes comprising mountain snowpack is critical for predicting snow meltwater runoff, understanding physical properties and radiation balance, and providing necessary input for interpreting satellite measurements. Both microwave emission and radar backscatter from the snow are dominated by the snow grain size stratigraphy. As a result, retrieval algorithms for measuring snow water equivalents from orbiting satellites is largely hindered by inadequate knowledge of grain size.

Grain-size effects on PIXE and INAA analysis of IAEA-336 lichen reference material

Science.gov (United States)

Marques, A. P.; Freitas, M. C.; Wolterbeek, H. Th.; Verburg, T. G.; De Goeij, J. J. M.

2007-02-01

IAEA-336 lichen certified reference material was used to compare outcomes from INAA and PIXE elemental analyses, in relationship with grain size. The IAEA material (grain size lichen reference material's particle size distribution follows a bimodal distribution, which is turning more and more monomodal after further fine sieving. Replicates of each fraction were analysed by INAA and PIXE. Results for Cl, K, Mn, Fe and Zn by both techniques were compared by application of z-values tested against the criterion ∣ z∣ limited amount of lichen material as "seen" in the PIXE analysis and the grain size distribution in the lichen material were no causes of measurable differences between the results of both techniques. However, fractionation into smaller grain sizes showed to be associated with lower element content, for Na, Cl, K, Mn and Sr even up to a factor of 2. The observed increases of the proportion of algae in the smaller grain-size fractions and the possible accumulation capacity for certain elements in the fungal part of the lichen may explain the observed phenomenon. The sieving process and consequently the discarding of part of the material have lead to a change of the properties of the original sample, namely algae/fungus percentage and elemental contents.

Investigation on grain refinement and precipitation strengthening applied in high speed wire rod containing vanadium

Energy Technology Data Exchange (ETDEWEB)

Wu, Da-yong; Xiao, Fu-ren, E-mail: frxiao@ysu.edu.cn; Wang, Bin; Liu, Jia-ling; Liao, Bo, E-mail: cyddjyjs@263.net

2014-01-13

To obtain necessary information for the simulation of high speed wire production process, the effect of grain refinement and precipitation strengthening on two high speed wire rod steels with different vanadium and nitrogen contents was investigated by continuous cooling transformation (CCT) characteristics. CCT curves were constructed by the dilatometer test and microscopic observation. Results showed that the formation of intra-granular ferrite (IGF) could refine grain remarkably and accelerate the ferrite transformation. Schedules for high speed wire production process focused on the effect of cooling rate. Ferrite grain was refined by increasing cooling rate and the formation of IGF. The microhardness calculation revealed that the steels were strengthened mostly by a combined effect of grain refinement and precipitation hardening. Degenerated pearlite was observed at lower transformation temperature and the fracture morphology changed from cementite lamellar to nanoscale cementite particle with increasing cooling rate. Based on the analysis above, an optimal schedule was applied and the microstructure and microhardness were improved.

Influence of austenite grain size on recrystallisation-precipitation interaction in a V-microalloyed steel

International Nuclear Information System (INIS)

Quispe, A.; Medina, S.F.; Gomez, M.; Chaves, J.I.

2007-01-01

By means of torsion tests using small specimens, the influence of austenite grain size on strain induced precipitation kinetics has been determined in a vanadium microalloyed steel. Determination of recrystallisation-precipitation-time-temperature (RPTT) diagrams for two austenite grain sizes allows values of the aforementioned magnitudes to be determined. An ample discussion is made of the quantitative influence found and its relation with nucleation and growth mechanisms of precipitates. The results are compared with the quantitative influence exerted by the other variables, reaching the conclusion that the austenite grain size has a notable influence on strain induced precipitation kinetics which should not be underestimated. Finally, the influence of austenite grain size is included in a strain induced precipitation model constructed by the authors of this work and which also takes into account the other aforementioned variables

Preliminary study of determination of UO2 grain size using X-ray diffraction method

International Nuclear Information System (INIS)

Mulyana, T.; Sambodo, G. D.; Juanda, D.; Fatchatul, B.

1998-01-01

The determination of UO 2 grain size has accomplished using x-ray diffraction method. The UO 2 powder is obtained from sol-gel process. A copper target as radiation source in the x-ray diffractometer was used in this experiment with CμKα characteristic wavelength 1.54433 Angstrom. The result indicate that the UO 2 mean grain size on presintered (temperature 800 o C) has the value 456.8500 Angstrom and the UO 2 mean grain size on sintered (temperature 1700 o C) has value 651.4934 Angstrom

Effect of Al doping on structural and mechanical properties of Ni-Cd ferrites

Science.gov (United States)

Shidaganal, Lata C.; Gandhad, Sheela S.; Hiremath, C. S.; Mathad, S. N.; Jeergal, P. R.; Pujar, R. B.

2018-05-01

Ferrites are ceramic magnetic materials which behave like a conventional ferromagnetic. Ni-Zn ferrites are commercially used as electromagnetic interfaces in hard disc drives, laptops and other electronic devices. Here we are going to report on the structural and mechanical properties of Al doped Ni-Cd ferrites synthesized by standard double sintering ceramic method by using AR grade Al oxide, Ni oxide, Cd oxide and ferric oxide in molar proportions with a general chemical formula Ni0.5 Cd0.5 Alx Fe2-x O4 where x=0.1 to 0.4.X-ray analysis confirms the formation of single phase FCC spinel structure. The decrease in lattice constant with Al concentration is attributed to Vegard's law. IR spectra indicate prominent absorption bands near 400cm-1and 600cm-1 which are assigned to fundamental vibrations of complexes in A and B sites respectively. SEM micrographs exhibit fine grains without segregation of impurities. The average grain diameter is found vary from 1.00µm to 0.9 µm which is in agreement with Vegard's law.

Microwave Measurements of Ferrite Polymer Composite Materials

Directory of Open Access Journals (Sweden)

Rastislav Dosoudil

2004-01-01

Full Text Available The article focuses on the microwave measurements performed on the nickel-zinc sintered ferrite with the chemical formula Ni0.3Zn0.7Fe2O4 produced by the ceramic technique and composite materials based on this ferrite and a non-magnetic polymer (polyvinyl chloride matrix. The prepared composite samples had the same particle size distribution 0-250um but different ferrite particle concentrations between 23 vol% and 80 vol%. The apparatus for measurement of the signal proportional to the absolute value of scattering parameter S11 (reflexion coefficient is described and the dependence of measured reflected signal on a bias magnetic field has been studied. By means of experiments, the resonances to be connected with the geometry of microwave experimental set-up were distinguished from ferromagnetic resonance arising in ferrite particles of composite structure. The role of local interaction fields of ferrite particles in composite material has been discussed.

Interactive contribution of grain size and grain orientation to coercivity of melt spun ribbons

International Nuclear Information System (INIS)

Wang, N.; Li, G.; Yao, W.J.; Wen, X.X.

2010-01-01

During melt spinning process, the improvement of certain grain orientation and the refinement of grain size with surface velocity have interactive and contradictory effects on the magnetic properties. The contributions of these effects have seldom been taken into account and they were discussed in this paper via Fe-2, 4, 6.5 wt% Si alloys. Heat treatment at 1173 K for 1 h was performed to show the annealing impact. The X-ray diffraction patterns show that the high surface velocity and heat treatment increase the intensity ratio of line (2 0 0) to (1 1 0) of A2 phase. The (2 0 0) line corresponds to (2 0 0) plane in direction, easy magnetization direction of α-Fe phase in Fe-Si alloy. The improvement of this grain orientation with the surface velocity decreases the coercivity, which should increase due to the grain refinement. It is revealed that the texture promoted by the anisotropic heat release during melt spinning process is one factor to improve the magnetic properties and should be considered when preparing soft magnetic materials.

Microstructural examination of commercial ferritic alloys at 299 DPA

International Nuclear Information System (INIS)

Gelles, D.S.

1995-11-01

Microstructures and density change measurements are reported for Martensitic commercial steels HT-9 and Modified 9Cr-lMo (T9) and oxide dispersion strengthened ferritic alloys MA956 and NU957 following irradiation in the FFTF/MOTA at 420 degrees C to 200 DPA. Swelling as determined by density change remains below 2% for all conditions. Microstructures are found to be stable except in recrystallized grains of MA957, which are fabrication artifacts, with only minor swelling in the Martensitic steels and α' precipitation in alloys with 12% or more chromium. These results further demonstrate the high swelling resistance and microstructural stability of the ferritic alloy class

Correlation Between Grain Size Distribution and Silicon and Oxygen Contents at Wadi Arar Sediments, Kingdom of Saudi Arabia

Directory of Open Access Journals (Sweden)

M. A. M. Alghamdi

2017-08-01

Full Text Available Quartz is the major mineral of Wadi Arar sediments. The top two elements contents are oxygen with 63.96 wt%, followed by silicon with 16.35 wt%. There is a positive, weak to medium correlation between grain size and silicon and oxygen contents. The correlation between oxygen and grain size is four times higher than that of silicon. At grain size ranges between 0.8 and 1.0 mm, both oxygen and silicon show the maximum correlation, which decrease gradually with finer and coarser grain sizes. For each element, the correlation between the element content and grain size is a fourth degree polynomial in the grain size. Theoretically, the best two math models that represent the relation between the grain size distribution and each of individual oxygen and silicon content are y=8.84∙ln(x+39.5 and y=2.26∙ln(x+10.1 respectively, where y represents the element content percentage and x represents the corresponding grain size in mm.

The effect of the Tom Thumb dwarfing gene on grain size and grain number of wheat (Triticum aestivum)

International Nuclear Information System (INIS)

Gale, M.D.; Flintham, J.E.

1984-01-01

The Tom Thumb dwarfing gene, Rht3, like the related genes Rht1 and Rht2 from Norin 10, has pleiotropic effects on individual ear yields, and grain protein concentrations. An experiment was conducted in which tiller number per plant and grain number per spike were restricted to ascertain whether reduced grain size and protein content are primary or secondary competitive effects in near-isogenic lines. The potential for grain growth was shown to be identical in Rht3 and rht genotypes when grain set was restricted, indicating that the primary effect of the gene is to increase spikelet fertility. Nitrogen accumulation within the grain was also affected by inter-grain competition but decreased nitrogen yields per plant indicated that reduced protein levels are, in part, a primary effect of the gene. Analysis of individual grain yields within Rht3 and rht spikes showed that the gene affected developmental 'dominance' relationships within the spike. (author)

Magnetoabsorption and magnetic hysteresis in Ni ferrite nanoparticles

Directory of Open Access Journals (Sweden)

Torres C.

2013-01-01

Full Text Available Nickel ferrite nanoparticles were prepared by a modified sol-gel technique employing coconut oil, and then annealed at different temperatures in 400-1200 °C range. This route of preparation has revealed to be one efficient and cheap technique to obtain high quality nickel ferrite nanosized powder. Sample particles sizes obtained with XRD data and Scherrer’s formula lie in 13 nm to 138 nm, with increased size with annealing temperature. Hysteresis loops have been obtained at room temperature with an inductive method. Magnetic field induced microwave absorption in nanoscale ferrites is a recent an active area of research, in order to characterize and explore potential novel applications. In the present work microwave magnetoabsorption data of the annealed nickel ferrite nanoparticles are presented. These data have been obtained with a system based on a network analyzer that operates in the frequency range 0 - 8.5 GHz. At fields up to 400 mT we can observe a peak according to ferromagnetic resonance theory. Sample annealed at higher temperature exhibits different absorption, coercivity and saturation magnetization figures, revealing its multidomain character.

Incision and Landsliding Lead to Coupled Increase in Sediment Flux and Grain Size Export

Science.gov (United States)

Roda-Boluda, D. C.; Brooke, S.; D'Arcy, M. K.; Whittaker, A. C.; Armitage, J. J.

2017-12-01

The rates and grain sizes of sediment fluxes modulate the dynamics and timing of landscape response to tectonics, and dictate the depositional patterns of sediment in basins. Over the last decades, we have gained a good quantitative understanding on how sediment flux and grain size may affect incision and basin stratigraphy. However, we comparably still have limited knowledge on how these variables change with varying tectonic rates. To address this question, we have studied 152 catchments along 8 normal fault-bounded ranges in southern Italy, which are affected by varying fault slip rates and experiencing a transient response to tectonics. Using a data set of 38 new and published 10Be erosion rates, we calibrate a sediment flux predictive equation (BQART), in order to estimate catchment sediment fluxes. We demonstrate that long-term sediment flux is governed by fault slip rates and the tectonically-controlled transient incision, and that sediment flux estimates from the BQART, steady-state assumptions, and incised volumes are highly correlated. This is supported by our 10Be erosion rates, which are controlled by fault slip and incision rates, and the associated landsliding. Based on a new landslide inventory, we show that erosion rate differences are likely due to differences in incision-related landslide activity across these catchments, and that landslides are a major component of sediment fluxes. From a data set of >13000 grain size counts on hillslope grain size supply and fluvial sediment at catchment outlets, we observe that landslides deliver material 20-200% coarser than other sediment sources, and that this coarse supply has an impact on the grain size distributions being exported from the catchments. Combining our sediment flux and grain size data sets, we are able to show that for our catchments, and potentially also for any areas that respond to changes in climate or tectonics via enhanced landsliding, sediment flux and grain size export increase

The effects of surface finish and grain size on the strength of sintered silicon carbide

Science.gov (United States)

You, Y. H.; Kim, Y. W.; Lee, J. G.; Kim, C. H.

1985-01-01

The effects of surface treatment and microstructure, especially abnormal grain growth, on the strength of sintered SiC were studied. The surfaces of sintered SiC were treated with 400, 800 and 1200 grit diamond wheels. Grain growth was induced by increasing the sintering times at 2050 C. The beta to alpha transformation occurred during the sintering of beta-phase starting materials and was often accompanied by abnormal grain growth. The overall strength distributions were established using Weibull statistics. The strength of the sintered SiC is limited by extrinsic surface flaws in normal-sintered specimens. The finer the surface finish and grain size, the higher the strength. But the strength of abnormal sintering specimens is limited by the abnormally grown large tabular grains. The Weibull modulus increases with decreasing grain size and decreasing grit size for grinding.

Strain Amount Dependent Grain Size and Orientation Developments during Hot Compression of a Polycrystalline Nickel Based Superalloy

Directory of Open Access Journals (Sweden)

Guoai He

2017-02-01

Full Text Available Controlling grain size in polycrystalline nickel base superalloy is vital for obtaining required mechanical properties. Typically, a uniform and fine grain size is required throughout forging process to realize the superplastic deformation. Strain amount occupied a dominant position in manipulating the dynamic recrystallization (DRX process and regulating the grain size of the alloy during hot forging. In this article, the high-throughput double cone specimen was introduced to yield wide-range strain in a single sample. Continuous variations of effective strain ranging from 0.23 to 1.65 across the whole sample were achieved after reaching a height reduction of 70%. Grain size is measured to be decreased from the edge to the center of specimen with increase of effective strain. Small misorientation tended to generate near the grain boundaries, which was manifested as piled-up dislocation in micromechanics. After the dislocation density reached a critical value, DRX progress would be initiated at higher deformation region, leading to the refinement of grain size. During this process, the transformations from low angle grain boundaries (LAGBs to high angle grain boundaries (HAGBs and from subgrains to DRX grains are found to occur. After the accomplishment of DRX progress, the neonatal grains are presented as having similar orientation inside the grain boundary.

Development of ODS ferritic-martensitic steels for application to high temperature and irradiation environment; Developpement d'une nouvelle nuance martensitique ODS pour utilisation sous rayonnement a haute temperature

Energy Technology Data Exchange (ETDEWEB)

Lambard, V

2000-07-01

Iron oxide dispersion strengthened alloys are candidate for nuclear fuel cladding. Therefore, it is crucial to control their microstructure in order to optimise their mechanical properties at temperatures up to 700 deg C. The industrial candidates, ODS ferritic alloys, present an anisotropic microstructure which induces a weakening of mechanical properties in transversal direction as well as the precipitation of brittle phases under thermal aging and irradiation. For this purpose, we tried to develop a material with isotropic properties. We studied several 9Cr-1Mo ferritic/martensitic alloys, strengthened or not by oxide dispersion. The mechanical alloying was performed by attribution and powders were consolidated by hot extrusion. In this work, different metallurgical characterisation techniques and modelling were used to optimise a new martensitic ODS alloy. Microstructural and chemical characterization of matrix has been done. The effect of austenitizing and isochronal tempering treatments on microstructure and hardness has been studied. Oxide distribution, size and chemical composition have been studied before and after high temperature thermal treatment. The study of phase transformation upon heating has permitted the extrapolation to the equilibrium temperature formation of austenite. Phase transformation diagrams upon cooling have been determined and the transformation kinetics have been linked to austenite grain size by a simple relation. Fine grain size is unfavourable for the targeted application, so a particular thermal treatment inducing a coarser grain structure has been developed. Finally, tensile properties have been determined for the different microstructures. (author)

On grain size dependent void swelling in pure copper irradiated with fission neutrons

International Nuclear Information System (INIS)

Singh, B.N.; Eldrup, M.; Golubov, S.I.; Zinkle, S.J.

2001-03-01

The effect of grain size on void swelling has its origin in the intrinsic property of grain boundaries as neutral and unsaturable sinks for both vacancies and self-interstitial atoms (SIAs). The phenomenon was investigated already in the 1970s and it was demonstrated that the grain size dependent void swelling measured under irradiation producing only Frenkel pairs could be satisfactorily explained in terms of the standard rate theory (SRT) and dislocation bias. Experimental results reported in the 1980s demonstrated, on the other hand, that the effect of grain boundaries on void swelling under cascade damage conditions was radically different and could not be explained in terms of the SRT. In an effort to understand the source of this significant difference, the effect of grain size on void swelling under cascade damage conditions has been investigated both experimentally and theoretically in pure copper irradiated with fission neutrons at 623K to a dose level of ∼0.3 dpa (displacement per atom). The post-irradiation defect microstructure including voids was investigated using transmission electron microscopy and positron annihilation spectroscopy. The evolution of void swelling was calculated within the framework of the production bias model (PBM) and the SRT. The grain size dependent void swelling measured experimentally is in good accord with the theoretical results obtained using PMB. Implications of these results on modeling of void swelling under cascade damage conditions are discussed. (au)

Grain size effect of monolayer MoS2 transistors characterized by second harmonic generation mapping

KAUST Repository

Lin, Chih-Pin

2015-08-27

We investigated different CVD-synthesized MoS2 films, aiming to correlate the device characteristics with the grain size. The grain size of MoS2 can be precisely characterized through nondestructive second harmonic generation mapping based on the degree of inversion symmetry. The devices with larger grains at the channel region show improved on/off current ratio, which can be explained by the less carrier scattering caused by the grain boundaries.

Influence of the initial metallurgical state and the austenizing conditions on the distribution of austenitc grain size of the martensitic-ferritic steel T91(9%Cr-1%Mo-V-Nb)

International Nuclear Information System (INIS)

Zavaleta Gutierrez, N; Luppo, M.I; Danon, C.A; Garcia de Andres, C

2006-01-01

It is a known fact that the austenizing conditions (speed of heating to the austenite temperature and austenizing time) as well as the initial metallurgical state of the material strongly influence the distribution of austenitic grain size in steels. This distribution will be one of the parameters that will control the behavior of the material in a later transformation from the austenite -by continuous cooling or in the isothermal case - and this behavior will determine the product's final mechanical properties. Based on the published literature, we have studied the influence of the initial metallurgical state and the speed of heating to austenite on the distribution of austenitic grain size for a certain austenizing temperature and time for a martensitic-iron ASTM A213 grade T91 steel. Two-stage thermal cycles were designed for this, that is, tempering for a variable period of time at the industrial tempering temperature (780 o C) followed by the austenizing (1050 o C, 30 minutes) 'in situ'. We have analyzed the following as a whole: 1) the role of the stabilizing elements (Nb, V) that eventually control the anchoring of the austenitic grain boundary by carbide or carbonitride precipitation. Therefore, we have tried to vary the fraction of these elements present in solid solution by annealing before austenizing. 2) the role of the speed of heating to austenite. In this case, we have considered two different values (1 and 30 o C/s), previously reported as inferior and superior, respectively, to the speed of 'critical' heat needed to produce a distribution of heterogeneous austenitic grain size when the metallurgical state before the austenizing is quenched and tempered. Preliminary results suggest that a annealing stage after tempering in the plant and prior to eventual austenizing significantly reduces the influence of the heating to austenite speed in the development of a heterogeneous structure of austenitic grains (CW)

Particle-size distribution modified effective medium theory and validation by magneto-dielectric Co-Ti substituted BaM ferrite composites

Science.gov (United States)

Li, Qifan; Chen, Yajie; Harris, Vincent G.

2018-05-01

This letter reports an extended effective medium theory (EMT) including particle-size distribution functions to maximize the magnetic properties of magneto-dielectric composites. It is experimentally verified by Co-Ti substituted barium ferrite (BaCoxTixFe12-2xO19)/wax composites with specifically designed particle-size distributions. In the form of an integral equation, the extended EMT formula essentially takes the size-dependent parameters of magnetic particle fillers into account. It predicts the effective permeability of magneto-dielectric composites with various particle-size distributions, indicating an optimal distribution for a population of magnetic particles. The improvement of the optimized effective permeability is significant concerning magnetic particles whose properties are strongly size dependent.

The MAFLA (Mississippi, Alabama, Florida) Study, Grain Size Analyses

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — The MAFLA (Mississippi, Alabama, Florida) Study was funded by NOAA as part of the Outer Continental Shelf Program. Dr. L.J. Doyle produced grain size analyses in the...

Influence of grain size on the extraordinary Hall effect in magnetic granular alloys

International Nuclear Information System (INIS)

Granovsky, Alexander B.; Kalitsov, Alan V.; Khanikaev, Alexander B.; Kioussis, Nicholas

2003-01-01

A quantum statistical theory of the influence of grain size on the residual extraordinary Hall effect (EHE) in magnetic metal-insulator granular alloys is presented. It is shown that under certain conditions the quasi-classical size-effect (QSE) can lead to similar behaviors of EHE in metal-metal and metal-insulator alloys. The possible dependences of EHE coefficient on the grain size and the role of the QSE in the giant EHE in nanocomposites are discussed

Influence of grain size on the extraordinary Hall effect in magnetic granular alloys

Energy Technology Data Exchange (ETDEWEB)

Granovsky, Alexander B. E-mail: granov@magn.ru; Kalitsov, Alan V.; Khanikaev, Alexander B.; Kioussis, Nicholas

2003-03-01

A quantum statistical theory of the influence of grain size on the residual extraordinary Hall effect (EHE) in magnetic metal-insulator granular alloys is presented. It is shown that under certain conditions the quasi-classical size-effect (QSE) can lead to similar behaviors of EHE in metal-metal and metal-insulator alloys. The possible dependences of EHE coefficient on the grain size and the role of the QSE in the giant EHE in nanocomposites are discussed.

Effect of grain size on the melting point of confined thin aluminum films

Energy Technology Data Exchange (ETDEWEB)

Wejrzanowski, Tomasz; Lewandowska, Malgorzata; Sikorski, Krzysztof; Kurzydlowski, Krzysztof J. [Materials Design Division, Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02-507 Warsaw (Poland)

2014-10-28

The melting of aluminum thin film was studied by a molecular dynamics (MD) simulation technique. The effect of the grain size and type of confinement was investigated for aluminum film with a constant thickness of 4 nm. The results show that coherent intercrystalline interface suppress the transition of solid aluminum into liquid, while free-surface gives melting point depression. The mechanism of melting of polycrystalline aluminum thin film was investigated. It was found that melting starts at grain boundaries and propagates to grain interiors. The melting point was calculated from the Lindemann index criterion, taking into account only atoms near to grain boundaries. This made it possible to extend melting point calculations to bigger grains, which require a long time (in the MD scale) to be fully molten. The results show that 4 nm thick film of aluminum melts at a temperature lower than the melting point of bulk aluminum (933 K) only when the grain size is reduced to 6 nm.

Laboratory Measurements on Charging of Individual Micron-Size Apollo-11 Dust Grains by Secondary Electron Emissions

Science.gov (United States)

Tankosic, D.; Abbas, M. M.

2012-01-01

Observations made during Apollo missions, as well as theoretical models indicate that the lunar surface and dust grains are electrostatically charged, levitated and transported. Lunar dust grains are charged by UV photoelectric emissions on the lunar dayside and by the impact of the solar wind electrons on the nightside. The knowledge of charging properties of individual lunar dust grains is important for developing appropriate theoretical models and mitigating strategies. Currently, very limited experimental data are available for charging of individual micron-size size lunar dust grains in particular by low energy electron impact. However, experimental results based on extensive laboratory measurements on the charging of individual 0.2-13 micron size lunar dust grains by the secondary electron emissions (SEE) have been presented in a recent publication. The SEE process of charging of micron-size dust grains, however, is found to be very complex phenomena with strong particle size dependence. In this paper we present some examples of the complex nature of the SEE properties of positively charged individual lunar dust grains levitated in an electrodynamic balance (EDB), and show that they remain unaffected by the variation of the AC field employed in the above mentioned measurements.

Effect of grain size on superelasticity in Fe-Mn-Al-Ni shape memory alloy wire

Directory of Open Access Journals (Sweden)

T. Omori

2013-09-01

Full Text Available Effects of grain size on superelastic properties in Fe-34Mn-15Al-7.5Ni alloy wires with a ⟨110⟩ fiber-texture were investigated by cyclic tensile tests. It was confirmed that the critical stress for induced martensitic transformation and the superelastic strain are functions of relative grain size d/D (d: mean grain diameter, D: wire diameter, and that the critical stress is proportional to (1–d/D2 as well as in Cu-based shape memory alloys. A large superelastic strain of about 5% was obtained in the specimen with a large relative grain size over d/D = 1.

Microstructure and mechanical properties in the weld heat affected zone of 9Cr-2W-VTa reduced activation ferritic/martensitic steel for fusion

Energy Technology Data Exchange (ETDEWEB)

Moon, Joonoh; Lee, Changhoon; Lee, Taeho; Jang, Minho; Park, Mingu [Korea Institute of Materials Science, Changwon (Korea, Republic of); Kim, Hyoung Chan [National Fusion Research Institute, Daejeon (Korea, Republic of)

2014-05-15

Reduced activation ferritic/martensitic (RAFM) steel demonstrated excellent resistance to the neutron irradiation and mechanical properties. The investigation of weldability in company with the development of RAFM steel is essential for construction of the fusion reactor. Generally, the superior mechanical properties of the RAFM steel can be upset during welding process due to microstructural change by rapid heating and cooling in the weld heat affected zone (HAZ). The phase transformation and mechanical properties in the weld HAZ of RAFM steel were investigated. The base steel consisted of tempered martensite and two carbides. During rapid welding thermal cycle, the microstructure of the base steel was transformed into martensite and δ-ferrite. In addition, the volume fraction of δ-ferrite and grain size increased with increase in the peak temperature and heat input. The strength of the HAZs was higher than that of the base steel due to the formation of martensite, whereas the impact properties of the HAZs deteriorated as compared with the base steel due to the formation of δ-ferrite. The PWHT improved the impact properties of the HAZs, resulting from the formation of tempered martensite.

Synthesis and characterization of nano silver ferrite composite

International Nuclear Information System (INIS)

Murthy, Y.L.N.; Kondala Rao, T.; Kasi viswanath, I.V.; Singh, Rajendra

2010-01-01

We report the synthesis of nano sized silver ferrite composite having the empirical formula AgFeO 2 by a co-precipitation method. The resulting powders are thin platelets, transparent and a rich ruby red in color in transmission. The X-ray diffraction (XRD) powder data consisted of only nine reflections, and the analysis showed the unit cell to be rhombohedral. The powders showed extensive XRD line broadening and the sizes of the crystals are calculated to be in the range 4-36.5 nm. The morphology of the silver ferrite composite studied using scanning electron microscope showed nano sized particles. The particle size is found to increase with increase in annealing temperature. The magnetic behavior, measured using a vibrating sample magnetometer, indicated a change from paramagnetic to ferromagnetic with increase in particle size.

Influence of Cu-Cr substitution on structural, morphological, electrical and magnetic properties of magnesium ferrite

Directory of Open Access Journals (Sweden)

S. Yonatan Mulushoa

2018-03-01

Full Text Available Cu-Cr substituted magnesium ferrite materials (Mg1 − xCuxCrxFe21 − xO4 with x = 0.0–0.7 have been synthesized by the solid state reaction method. XRD analysis revealed the prepared samples are cubic spinel with single phase face centered cubic. A significant decrease of ∼41.15 nm in particle size is noted in response to the increase in Cu-Cr substitution level. The room temperature resistivity increases gradually from 0.553 × 105 Ω cm (x = 0.0 to 0.105 × 108 Ω cm (x = 0.7. Temperature dependent DC-electrical resistivity of all the samples, exhibits semiconductor like behavior. Cu-Cr doped materials can be suitable to limit the eddy current losses. VSM result shows pure and doped magnesium ferrite particles show soft ferrimagnetic nature at room temperature. The saturation magnetization of the samples decreases initially from 34.5214 emu/g for x = 0.0 to 18.98 emu/g (x = 0.7. Saturation magnetization, remanence and coercivity are decreased with doping, which may be due to the increase in grain size. Keywords: Solid state reaction, X-ray diffraction, Crystallite size, Magnetic and electrical properties, Saturation magnetization

Study of variation grain size in desulfurization process of calcined petroleum coke

Science.gov (United States)

Pintowantoro, Sungging; Setiawan, Muhammad Arif; Abdul, Fakhreza

2018-04-01

Indonesia is a country with abundant natural resources, such as mineral mining and petroleum. In petroleum processing, crude oil can be processed into a source of fuel energy such as gasoline, diesel, oil, petroleum coke, and others. One of crude oil potentials in Indonesia is petroleum coke. Petroleum coke is a product from oil refining process. Sulfur reducing process in calcined petroleum cokes can be done by desulfurization process. The industries which have potential to become petroleum coke processing consumers are industries of aluminum smelting (anode, graphite block, carbon mortar), iron riser, calcined coke, foundry coke, etc. Sulfur reducing process in calcined petroleum coke can be done by thermal desulfurization process with alkaline substance NaOH. Desulfurization of petroleum coke process can be done in two ways, which are thermal desulfurization and hydrodesulphurization. This study aims to determine the effect of various grain size on sulfur, carbon, and chemical bond which contained by calcined petroleum coke. The raw material use calcined petroleum coke with 0.653% sulfur content. The grain size that used in this research is 50 mesh, then varied to 20 mesh and 100 mesh for each desulfurization process. Desulfurization are tested by ICP, UV-VIS, and FTIR to determine levels of sulfur, carbon, chemical bonding and sulfur dissolved water which contained in the residual washing of calcined petroleum coke. From various grain size that mentioned before, the optimal value is on 100 mesh grain size, where the sulfur content in petroleum coke is 0.24% and carbon content reaches the highest level of 97.8%. Meanwhile for grain size 100 mesh in the desulfurization process is enough to break the chemical bonds of organic sulfur in petroleum coke.

Rapid Grain Size Reduction in the Upper Mantle at a Plate Boundary

Science.gov (United States)

Kidder, S. B.; Scott, J.; Prior, D. J.; Lubicich, E. J.

2017-12-01

A few spinel peridotite xenoliths found near the Alpine Fault, New Zealand, exhibit a mylonitic texture and, locally, an extremely fine 30 micron grain size. The harzburgite xenoliths were emplaced in a 200 km-long elongate dike zone interpreted as a gigantic tension fracture or Reidel shear associated with Alpine Fault initiation 25 Ma. The presence of thin ( 1 mm) ultramylonite zones with px-ol phase mixing and fine grain sizes, minimal crustal-scale strain associated with the dike swarm, and the absence of mylonites at four of the five xenolith localities associated with the dike swarm indicate that upper mantle deformation was highly localized. Strings of small, recrystallized grains (planes in 3D) are found in the interiors of olivine porphyroclasts. In some cases, bands 1-2 grains thick are traced from the edges of olivine grains and terminate in their interiors. Thicker zones of recrystallized grains are also observed crossing olivine porphyroclasts without apparent offset of the unrecrystallized remnants of the porphyroclasts. We suggest a brittle-plastic origin for these features since the traditional recrystallization mechanisms associated with dislocation creep require much more strain than occurred within these porphyroclasts. Analogous microstructures in quartz and feldspar in mid-crust deformation zones are attributed to brittle-plastic processes. We hypothesize that such fine-grained zones were the precursors of the observed, higher-strain ultramylonite zones. Given the size of the new grains preserved in the porphyroclasts ( 100 micron) and a moho temperature > 650°C, grain growth calculations indicate that the observed brittle-plastic deformation occurred <10,000 yrs. prior to eruption. It is likely then that either brittle-plastic deformation was coeval with the ductile shearing occurring in the ultramylonite bands, or possibly, if deformation can be separated into brittle-plastic (early) and ductile (later) phases, that the entire localization

Effect of Starting As-cast Structure on the Microstructure-Texture Evolution During Subsequent Processing and Finally Ridging Behavior of Ferritic Stainless Steel

Science.gov (United States)

Modak, Pranabananda; Patra, Sudipta; Mitra, Rahul; Chakrabarti, Debalay

2018-06-01

Effect of the initial as-cast structure on the microstructure-texture evolution during thermomechanical processing of 409L grade ferritic stainless steel was studied. Samples from the regions of cast slab having `columnar,' `equiaxed,' and a mixture of `columnar' and `equiaxed' grains were subjected to two different processing schedules: one with intermediate hot-band annealing before cold-rolling followed by final annealing, and another without any hot-band annealing. EBSD study reveals that large columnar crystals with cube orientation are very difficult to deform and recrystallize uniformly. Resultant variations in ferrite grain structure and retention of cube-textured band in cold-rolled and annealed sheet contribute to ridging behavior during stretch forming. Initial equiaxed grain structure is certainly beneficial to reduce or even eliminate ridging defect by producing uniform ferrite grain structure, free from any texture banding. Application of hot-band annealing treatment is also advantageous as it can maximize the evolution of beneficial gamma-fiber texture and eliminate the ridging defect in case of completely `equiaxed' starting structure. Such treatment reduces the severity of ridging even if the initial structure contains typically mixed `columnar-equiaxed' grains.

[Spatial change of the grain-size of aeolian sediments in Qira oasis-desert ecotone, Northwest China].

Science.gov (United States)

Lin, Yong Chong; Xu, Li Shuai

2017-04-18

In order to understand the environmental influence of oasis-desert ecotone to oasis ecological system, we comparatively analyzed the grain size characteristics of various aeolian sediments, including the sediments in oasis-desert ecotone, shelterbelt and the inside oasis and in Qira River valley. The results showed that the grain size characteristics (including grain-size distribution curve, grain size parameters, and content of different size classes) of sediments in the oasis-desert ecotone were consistent along the prevailing wind direction with a grain-size range of 0.3-200 μm and modal size of 67 μm. All of the sediments were good sorting and mainly composed of suspension components and saltation components, but not denatured saltation and creeping components (>200 μm). They were typically aeolian deposits being short-range transported. The grain sizes of sediments in oasis-desert ecotone were smaller than that in the material sources of Qira River valley and desert (0.3-800 μm), but very similar to those of the modern aeolian deposits in oasis-desert ecotone, shelterbelt and the inside oasis. The denatured saltation and creep components (>200 μm) were suppressed to transport into oasis-desert ecotone because of the high vegetation cover in oasis-desert ecotone. Therefore, like the shelterbelts, the oasis-desert ecotone could also block the invasion of desert. They safeguarded the oasis ecological environment together.

Grain-Size Analysis of Debris Flow Alluvial Fans in Panxi Area along Jinsha River, China

Directory of Open Access Journals (Sweden)

Wen Zhang

2015-11-01

Full Text Available The basic geometric parameters of 236 debris flow catchments were determined by interpreting SPOT5 remote sensing images with a resolution of 2.5 m in a 209 km section along the Jinsha River in the Panxi area, China. A total of 27 large-scale debris flow catchments were selected for detailed in situ investigation. Samples were taken from two profiles in the deposition zone for each debris flow catchment. The φ value gradation method of the grain size was used to obtain 54 histograms with abscissa in a logarithmic scale. Five types of debris flows were summarized from the outline of the histogram. Four grain size parameters were calculated: mean grain size, standard deviation, coefficient of skewness, and coefficient of kurtosis. These four values were used to evaluate the features of the histogram. The grain index that reflects the transport (kinetic energy information of debris flows was defined to describe the characteristics of the debris-flow materials. Furthermore, a normalized grain index based on the catchment area was proposed to allow evaluation of the debris flow mobility. The characteristics of the debris-flow materials were well-described by the histogram of grain-size distribution and the normalized grain index.

Resistance to fracture of carbon weldable structural steel with ferrite-pearlite and widmanstaetten structure

International Nuclear Information System (INIS)

Gulyaev, A.P.; Guzovskaya, M.A.

1977-01-01

Consideration is given to mechanical properties of St3 steel with varying ferritic-peartilic and widmanstaetten structures typical of a weld seam and adjacent zones. It has been found that mechanical properties determined at static tension are sensitive to structure variation in the limits under study. A considerable difference has been detected during impact tests CT 50 , asub(p)). The highest resistance to breakage is observed for the steel with a fine-grain ferritic-pearlitic structure (T 50 =-10 deg C, asub(p)=4.3 kgxm/cm 2 ). The enlargement of such a structure enhances transition temperature (T 50 =+20 deg C) and reduces resistance to crack development (asub(p)2.4 kgxm/cm 2 ). The appearance of widmanstaetten zones in the fine-grain structure leads also to a higher T 50 , up to +10 deg C, and at a completely widmanstaetten structure T 50 =+25 deg C. An especially unfavorable effect on the resistance of steel to breakage is produced by structure nonuniformity, i.e. accumulation of loop-like pearlitic and ferritic zones

Elaboration of austenitic stainless steel samples with bimodal grain size distributions and investigation of their mechanical behavior

Science.gov (United States)

Flipon, B.; de la Cruz, L. Garcia; Hug, E.; Keller, C.; Barbe, F.

2017-10-01

Samples of 316L austenitic stainless steel with bimodal grain size distributions are elaborated using two distinct routes. The first one is based on powder metallurgy using spark plasma sintering of two powders with different particle sizes. The second route applies the reverse-annealing method: it consists in inducing martensitic phase transformation by plastic strain and further annealing in order to obtain two austenitic grain populations with different sizes. Microstructural analy ses reveal that both methods are suitable to generate significative grain size contrast and to control this contrast according to the elaboration conditions. Mechanical properties under tension are then characterized for different grain size distributions. Crystal plasticity finite element modelling is further applied in a configuration of bimodal distribution to analyse the role played by coarse grains within a matrix of fine grains, considering not only their volume fraction but also their spatial arrangement.

The Effect of Grain Size and Strain on the Tensile Flow Stress of Aluminium at Room Temperature

DEFF Research Database (Denmark)

Hansen, Niels

1977-01-01

stress-grain size relationship was analyzed in terms of matrix strengthening and grain boundary strengthening according to the dislocation concept of Ashby. At intermediate strains this approach gives a good description of the effect of strain, grain size and purity on the flow stress.......Tensile-stress-strain data over a strain range from 0.2 to 30% were obtained at room temperature for 99.999 and 99.5% aluminium as a function of grain size. The yield stress-grain size relationship can be expressed by a Petch-Hall relation with approximately the same slope for the two materials....... The flow stress-grain size relationship can adequately be expressed by a modified Petch-Hall relation; for 99.999% aluminium material the slope increases with strain through a maximum around 15–20%, whereas for 99.5% aluminium the slope decreases with the strain to zero at strains about 10%. The flow...

Study on microstructure and mechanical characteristics of low-carbon steel and ferritic stainless steel joints

Energy Technology Data Exchange (ETDEWEB)

Sarkari Khorrami, Mahmoud; Mostafaei, Mohammad Ali; Pouraliakbar, Hesam, E-mail: hpouraliakbar@alum.sharif.edu; Kokabi, Amir Hossein

2014-07-01

In this work, examinations on the microstructure and mechanical properties of plain carbon steel and AISI 430 ferritic stainless steel dissimilar welds are carried out. Welding is conducted in both autogenous and using ER309L austenitic filler rod conditions through gas tungsten arc welding process. The results indicate that fully-ferritic and duplex ferritic–martensitic microstructures are formed for autogenous and filler-added welds, respectively. Carbide precipitation and formation of martensite at ferrite grain boundaries (intergranular martensite) as well as grain growth occur in the heat affected zone (HAZ) of AISI 430 steel. It is found that weld heat input can strongly affect grain growth phenomenon along with the amount and the composition of carbides and intergranular martensite. Acquired mechanical characteristics of weld in the case of using filler metal are significantly higher than those of autogenous one. Accordingly, ultimate tensile strength (UTS), hardness, and absorbed energy during tensile test of weld metal are increased from 662 MPa to 910 MPa, 140 Hv to 385 Hv, and 53.6 J m{sup −3} to 79 J m{sup −3}, respectively by filler metal addition. From fracture surfaces, predominantly ductile fracture is observed in the specimen welded with filler metal while mainly cleavage fracture occurs in the autogenous weld metal.

Retrieval of snow albedo and grain size using reflectance measurements in Himalayan basin

Directory of Open Access Journals (Sweden)

H. S. Negi

2011-03-01

Full Text Available In the present paper, spectral reflectance measurements of Himalayan seasonal snow were carried out and analysed to retrieve the snow albedo and effective grain size. The asymptotic radiative transfer (ART theory was applied to retrieve the plane and spherical albedo. The retrieved plane albedo was compared with the measured spectral albedo and a good agreement was observed with ±10% differences. Retrieved integrated albedo was found within ±6% difference with ground observed broadband albedo. The retrieved snow grain sizes using different models based on the ART theory were compared for various snow types and it was observed that the grain size model using two channel method (one in visible and another in NIR region can work well for the Himalayan seasonal snow and it was found consistent with temporal changes in grain size. This method can work very well for clean, dry snow as in the upper Himalaya, but sometimes, due to the low reflectances (<20% using wavelength 1.24 μm, the ART theory cannot be applied, which is common in lower and middle Himalayan old snow. This study is important for monitoring the Himalayan cryosphere using air-borne or space-borne sensors.

Effects of grain size and humidity on fretting wear in fine-grained alumina, Al{sub 2}O{sub 3}/TiC, and zirconia

Energy Technology Data Exchange (ETDEWEB)

Krell, A. [Fraunhofer Inst. for Ceramic Technologies and Sintered Materials, Dresden (Germany); Klaffke, D. [Federal Inst. for Materials Research and Testing, Berlin (Germany)

1996-05-01

Friction and wear of sintered alumina with grain sizes between 0.4 and 3 {micro}m were measured in comparison with Al{sub 2}O{sub 3}/TiC composites and with tetragonal ZrO{sub 2} (3 mol% Y{sub 2}O{sub 3}). The dependence on the grain boundary toughness and residual microstresses is investigated, and a hierarchical order of influencing parameters is observed. In air, reduced alumina grain sizes improve the micromechanical stability of the grain boundaries and the hardness, and reduced wear is governed by microplastic deformation, with few pullout events. Humidity and water slightly reduce the friction of all of the investigated ceramics. In water, this effect reduces the wear of coarser alumina microstructures. The wear of aluminas and of the Al{sub 2}O{sub 3}/TiC composite is similar; it is lower than observed in zirconia, where extended surface cracking occurs at grain sizes as small as 0.3 {micro}m.

Effect of grain size on high temperature low-cycle fatigue properties of inconel 617

International Nuclear Information System (INIS)

Hattori, Hiroshi; Kitagawa, Masaki; Ohtomo, Akira

1982-01-01

The effect of grain size on the high temperature low-cycle fatigue behavior and other material strength properties of Inconel 617 was studied at 1 273 K in air. The strain controlled low-cycle fatigue tests were conducted with a symmetrical (FF type) and an asymmetrical (SF type) strain wave forms. The latter wave form was used for the evaluation of creep-fatigue interaction. The main results obtained in this study are as follows: 1) The tensile strength slightly increased with the increase of the grain diameter. On the other hand, the tensile ductility remarkabley decreased with the increase of the grain diameter. 2) The creep rupture life remarkabley increased with the increase of the grain diameter, especially at the lower stress levels. The effect of grain size on creep ductility has not detailed. 3) The low-cycle fatigue life remarkably decreased with the increase of the grain diameter, especially at the lower strain ranges. 4) The creep-fatigue life was less sensitive to the grain diameter than the fatigue life, because the grain size effects on creep and on fatigue were contrary. It is seemed that the creep-fatigue life is determined by the proportion of the creep and fatigue contribution. 5) The fatigue and creep-fatigue test results have good relations with the tensile and creep ductilities at the test temperature. (author)

Absorption Efficiencies of Forsterite. I: DDA Explorations in Grain Shape and Size

Science.gov (United States)

Lindsay, Sean S.; Wooden, Diane; Harker, David E.; Kelley, Michael S.; Woodward, Charles E.; Murphy, Jim R.

2013-01-01

We compute the absorption efficiency (Q(sub abs)) of forsterite using the discrete dipole approximation (DDA) in order to identify and describe what characteristics of crystal grain shape and size are important to the shape, peak location, and relative strength of spectral features in the 8 - 40 micron wavelength range. Using the DDSCAT code, we compute Q(sub abs) for non-spherical polyhedral grain shapes with a(sub eff) = 0.1 micron. The shape characteristics identified are: 1) elongation/reduction along one of three crystallographic axes; 2) asymmetry, such that all three crystallographic axes are of different lengths; and 3) the presence of crystalline faces that are not parallel to a specific crystallographic axis, e.g., non-rectangular prisms and (di)pyramids. Elongation/reduction dominates the locations and shapes of spectral features near 10, 11, 16, 23.5, 27, and 33.5 micron, while asymmetry and tips are secondary shape effects. Increasing grain sizes (0.1 - 1.0 micron) shifts the 10, 11 micron features systematically towards longer wavelengths and relative to the 11 micron feature increases the strengths and slightly broadens the longer wavelength features. Seven spectral shape classes are established for crystallographic a-, b-, and c-axes and include columnar and platelet shapes plus non-elongated or equant grain shapes. The spectral shape classes and the effects of grain size have practical application in identifying or excluding columnar, platelet or equant forsterite grain shapes in astrophysical environs. Identification of the shape characteristics of forsterite from 8 - 40 micron spectra provides a potential means to probe the temperatures at which forsterite formed.

A triple-scale crystal plasticity modeling and simulation on size effect due to fine-graining

International Nuclear Information System (INIS)

Kurosawa, Eisuke; Aoyagi, Yoshiteru; Tadano, Yuichi; Shizawa, Kazuyuki

2010-01-01

In this paper, a triple-scale crystal plasticity model bridging three hierarchical material structures, i.e., dislocation structure, grain aggregate and practical macroscopic structure is developed. Geometrically necessary (GN) dislocation density and GN incompatibility are employed so as to describe isolated dislocations and dislocation pairs in a grain, respectively. Then the homogenization method is introduced into the GN dislocation-crystal plasticity model for derivation of the governing equation of macroscopic structure with the mathematical and physical consistencies. Using the present model, a triple-scale FE simulation bridging the above three hierarchical structures is carried out for f.c.c. polycrystals with different mean grain size. It is shown that the present model can qualitatively reproduce size effects of macroscopic specimen with ultrafine-grain, i.e., the increase of initial yield stress, the decrease of hardening ratio after reaching tensile strength and the reduction of tensile ductility with decrease of its grain size. Moreover, the relationship between macroscopic yielding of specimen and microscopic grain yielding is discussed and the mechanism of the poor tensile ductility due to fine-graining is clarified. (author)

Grain Size and Phase Purity Characterization of U3Si2 Pellet Fuel

Energy Technology Data Exchange (ETDEWEB)

Hoggan, Rita E. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Tolman, Kevin R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cappia, Fabiola [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wagner, Adrian R. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Harp, Jason M. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2018-05-01

Characterization of U3Si2 fresh fuel pellets is important for quality assurance and validation of the finished product. Grain size measurement methods, phase identification methods using scanning electron microscopes equipped with energy dispersive spectroscopy and x-ray diffraction, and phase quantification methods via image analysis have been developed and implemented on U3Si2 pellet samples. A wide variety of samples have been characterized including representative pellets from an initial irradiation experiment, and samples produced using optimized methods to enhance phase purity from an extended fabrication effort. The average grain size for initial pellets was between 16 and 18 µm. The typical average grain size for pellets from the extended fabrication was between 20 and 30 µm with some samples exhibiting irregular grain growth. Pellets from the latter half of extended fabrication had a bimodal grain size distribution consisting of coarsened grains (>80 µm) surrounded by the typical (20-30 µm) grain structure around the surface. Phases identified in initial uranium silicide pellets included: U3Si2 as the main phase composing about 80 vol. %, Si rich phases (USi and U5Si4) composing about 13 vol. %, and UO2 composing about 5 vol. %. Initial batches from the extended U3Si2 pellet fabrication had similar phases and phase quantities. The latter half of the extended fabrication pellet batches did not contain Si rich phases, and had between 1-5% UO2: achieving U3Si2 phase purity between 95 vol. % and 98 vol. % U3Si2. The amount of UO2 in sintered U3Si2 pellets is correlated to the length of time between U3Si2 powder fabrication and pellet formation. These measurements provide information necessary to optimize fabrication efforts and a baseline for future work on this fuel compound.

Thermal conductivity of nanocrystalline silicon: importance of grain size and frequency-dependent mean free paths.

Science.gov (United States)

Wang, Zhaojie; Alaniz, Joseph E; Jang, Wanyoung; Garay, Javier E; Dames, Chris

2011-06-08

The thermal conductivity reduction due to grain boundary scattering is widely interpreted using a scattering length assumed equal to the grain size and independent of the phonon frequency (gray). To assess these assumptions and decouple the contributions of porosity and grain size, five samples of undoped nanocrystalline silicon have been measured with average grain sizes ranging from 550 to 64 nm and porosities from 17% to less than 1%, at temperatures from 310 to 16 K. The samples were prepared using current activated, pressure assisted densification (CAPAD). At low temperature the thermal conductivities of all samples show a T(2) dependence which cannot be explained by any traditional gray model. The measurements are explained over the entire temperature range by a new frequency-dependent model in which the mean free path for grain boundary scattering is inversely proportional to the phonon frequency, which is shown to be consistent with asymptotic analysis of atomistic simulations from the literature. In all cases the recommended boundary scattering length is smaller than the average grain size. These results should prove useful for the integration of nanocrystalline materials in devices such as advanced thermoelectrics.

Effect of noise-induced nucleation on grain size distribution studied via the phase-field crystal method

International Nuclear Information System (INIS)

Hubert, J; Cheng, M; Emmerich, H

2009-01-01

We contribute to the more detailed understanding of the phase-field crystal model recently developed by Elder et al (2002 Phys. Rev. Lett. 88 245701), by focusing on its noise term and examining its impact on the nucleation rate in a homogeneously solidifying system as well as on successively developing grain size distributions. In this context we show that principally the grain size decreases with increasing noise amplitude, resulting in both a smaller average grain size and a decreased maximum grain size. Despite this general tendency, which we interpret based on Panfilis and Filiponi (2000 J. Appl. Phys. 88 562), we can identify two different regimes in which nucleation and successive initial growth are governed by quite different mechanisms.

Volatile and non-volatile elements in grain-size separated samples of Apollo 17 lunar soils

International Nuclear Information System (INIS)

Giovanoli, R.; Gunten, H.R. von; Kraehenbuehl, U.; Meyer, G.; Wegmueller, F.; Gruetter, A.; Wyttenbach, A.

1977-01-01

Three samples of Apollo 17 lunar soils (75081, 72501 and 72461) were separated into 9 grain-size fractions between 540 and 1 μm mean diameter. In order to detect mineral fractionations caused during the separation procedures major elements were determined by instrumental neutron activation analyses performed on small aliquots of the separated samples. Twenty elements were measured in each size fraction using instrumental and radiochemical neutron activation techniques. The concentration of the main elements in sample 75081 does not change with the grain-size. Exceptions are Fe and Ti which decrease slightly and Al which increases slightly with the decrease in the grain-size. These changes in the composition in main elements suggest a decrease in Ilmenite and an increase in Anorthite with decreasing grain-size. However, it can be concluded that the mineral composition of the fractions changes less than a factor of 2. Samples 72501 and 72461 are not yet analyzed for the main elements. (Auth.)

Radiation damage of the construction materials, Phase II, Microstructure and grain size effects on irradiation hardening of low carbon steel for reactor tanks; Radijaciono ostecenje konstrukcionih materijala, II faza, Uticaj velicine zrna i mikrostrukture na radijaciono otvrdnjavanje niskougljenicnih celika za reaktorske sudove

Energy Technology Data Exchange (ETDEWEB)

Lazarevic, Dj; Milasin, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

1964-05-15

Influence of grain size on radiation damage of different steel types was investigated intensely during past few years. But the obtained data did not enable complete answer. The objective of here described experiments was to obtain new data about the influence of grain size on radiation hardening of the steel for reactor vessel fabrication. The steel was exposed to integral fast neutron flux bigger than 10{sup 19} n/cm{sup 2} and irradiation temperature less than 100 deg C. As a part of VISA-2/1 project these investigations we redone in cooperation with the CEN Saclay. Simultaneously, experimental procedures applied for obtaining samples with different grain sizes produced steels with different macrostructure. For that reason possible influence of microstructure should ne taken into account. In fact, it was found that the performance of samples depended more on microstructure than on the grain size. The most important results obtain from this experiments indicate the following: (1) samples with different grain size having ferrite-perlite structure showed the same tensile strength; (2) samples with cementite on the grain boundaries showed more intensive hardening after irradiation; (3) samples exposed to {gamma} radiation for obtaining bigger grains showed decreased hardening than samples deformed under room temperature and exposed to {alpha} radiation. Experiments were performed under 150 deg C. samples with ferrite-perlite microstructure showed further smaller increase of tensile limit and hardening. Uticaj velicine zrna na radijaciono otvrdnjavanje razlicitih tipova celika intenzivno je proucavan u toku poslednjih nekoliko godina. Medjutim, dobijeni podaci nisu omogucili da se u potpunosti odgovori na pitanje. Opisani eksperimenti imali su za cilj da pruze nove podatke o uticaju velicine zrna na radijaciono otvrdnjavanje date vrste celika za reaktorski sud, pri integralnom fluksu brzih neutrona > 10{sup 19} n/cm{sup 2} i temperaturi ozracivanja < 100 deg C. Kao

A comparative study of NiZn ferrites modified by the addition of cobalt

Directory of Open Access Journals (Sweden)

Pereira S.L.

1999-01-01

Full Text Available Off-stoichiometric NiZn ferrite was obtained by hydrothermal process and compacted in torus form under different pressures. Two samples A1 and A2 - cobalt doped (0.5 % were sintered at 1573 K in air atmosphere during 3 h. The magnetic properties were studied by vibrating sample magnetometry, Mössbauer spectroscopy and complex impedanciometry. X-ray diffraction and Hg porosimetry were used in order to determine the average grain size and the type of packing in the samples. Both samples exhibited superparamagnetic behavior in the hysteresis loop. This effect does not agree with Mössbauer results, which were fitted using Normos, a commercial computer program. All samples parameters were compared.

Grain size and burnup dependence of spent fuel oxidation: Geological repository impact

International Nuclear Information System (INIS)

Kansa, E.J.; Hanson, B.D.; Stout, R.B.

1999-01-01

Further refinements to the oxidation model of Stout et al. have been made. The present model incorporates the burnup dependence of the oxidation rate and an allowance for a distribution of grain sizes. The model was tested by comparing the model results with the oxidation histories of spent-fuel samples oxidized in thermogravimetric analysis (TGA) or oven dry-bath (ODB) experiments. The experimental and model results are remarkably close and confirm the assumption that grain-size distributions and activation energies are the important parameters to predicting oxidation behavior. The burnup dependence of the activation energy was shown to have a greater effect than decreasing the effective grain size in suppressing the rate of the reaction U 4 O 9 r↓U 3 O 8 . Model results predict that U 3 O 8 formation of spent fuels exposed to oxygen will be suppressed even for high burnup fuels that have undergone restructuring in the rim region, provided the repository temperature is kept sufficiently low

In Situ Sampling of Relative Dust Devil Particle Loads and Their Vertical Grain Size Distributions.

Science.gov (United States)

Raack, Jan; Reiss, Dennis; Balme, Matthew R; Taj-Eddine, Kamal; Ori, Gian Gabriele

2017-04-19

During a field campaign in the Sahara Desert in southern Morocco, spring 2012, we sampled the vertical grain size distribution of two active dust devils that exhibited different dimensions and intensities. With these in situ samples of grains in the vortices, it was possible to derive detailed vertical grain size distributions and measurements of the lifted relative particle load. Measurements of the two dust devils show that the majority of all lifted particles were only lifted within the first meter (∼46.5% and ∼61% of all particles; ∼76.5 wt % and ∼89 wt % of the relative particle load). Furthermore, ∼69% and ∼82% of all lifted sand grains occurred in the first meter of the dust devils, indicating the occurrence of "sand skirts." Both sampled dust devils were relatively small (∼15 m and ∼4-5 m in diameter) compared to dust devils in surrounding regions; nevertheless, measurements show that ∼58.5% to 73.5% of all lifted particles were small enough to go into suspension (grain size classification). This relatively high amount represents only ∼0.05 to 0.15 wt % of the lifted particle load. Larger dust devils probably entrain larger amounts of fine-grained material into the atmosphere, which can have an influence on the climate. Furthermore, our results indicate that the composition of the surface, on which the dust devils evolved, also had an influence on the particle load composition of the dust devil vortices. The internal particle load structure of both sampled dust devils was comparable related to their vertical grain size distribution and relative particle load, although both dust devils differed in their dimensions and intensities. A general trend of decreasing grain sizes with height was also detected. Key Words: Mars-Dust devils-Planetary science-Desert soils-Atmosphere-Grain sizes. Astrobiology 17, xxx-xxx.

Size effect in tension perpendicular to the grain

DEFF Research Database (Denmark)

Pedersen, Martin Bo Uhre; Clorius, Christian Odin; Damkilde, Lars

1999-01-01

The strength in tension perpendicular to the grain is known to decrease with an increase in the stressed volume. Usually this size effect is explained on a stochastic basis, that is an explanation relying on an increased probability of encountering a strength reducing flaw when the volume...... of the material under stress is increased. This paper presents a small experimental investigation on specimens with well defined structural orientation of the material. The experiments exhibit a larger size effect than expected and furthermore the data and the nature of the failures encountered suggest...... that the size effect can be explained on a deterministic basis. Arguments for such a simple deterministic explanation of size effect is found in finite element modelling using the orthotropic stiffness characteristics in the transverse plane of wood....

On Techniques to Characterize and Correlate Grain Size, Grain Boundary Orientation and the Strength of the SiC Layer of TRISO Coated Particles: A Preliminary Study

Energy Technology Data Exchange (ETDEWEB)

I.J.van Rooyen; J.L. Dunzik Gougar; T. Trowbridge; Philip M van Rooyen

2012-10-01

The mechanical properties of the silicon carbide (SiC) layer of the TRi-ISOtropic (TRISO) coated particle (CP) for high temperature gas reactors (HTGR) are performance parameters that have not yet been standardized by the international HTR community. Presented in this paper are the results of characterizing coated particles to reveal the effect of annealing temperature (1000 to 2100°C) on the strength and grain size of unirradiated coated particles. This work was further expanded to include possible relationships between the grain size and strength values. The comparative results of two strength measurement techniques and grain size measured by the Lineal intercept method are included. Preliminary grain boundary characterization results determined by electron backscatter diffraction (EBSD) are included. These results are also important for future fission product transport studies, as grain boundary diffusion is identified as a possible mechanism by which 110mAg, one of the fission activation products, might be released through intact SiC layers. Temperature is a parameter known to influence the grain size of SiC and therefore it is important to investigate the effect of high temperature annealing on the SiC grain size. Recommendations and future work will also be briefly discussed.

Influence of phosphorous and sulphur as well as grain size on creep in pure copper

International Nuclear Information System (INIS)

Andersson, Henrik; Seitisleam, Facredin; Sandstroem, Rolf

1999-12-01

Uniaxial creep tests have been performed at 175 deg C for extruded oxygen-free copper. The effect of different contents of phosphorous and sulphur as well as different grain sizes have been studied. The copper with < 1 ppm phosphorous and with a 6 ppm sulphur content showed significantly lower creep life and ductility than batches with higher P content. An increase of the P content to 29 ppm increased the creep life and ductility, but a further increase did not affect the properties further. A similar drop in the creep properties was found in the material with a grain size of about 2000 μm. A reduction of the mean grain size to 800 μm had a beneficial effect on the creep ductility. A further reduction of the grain size did not give any further improvements. All tests except those with a phosphorous content of less than 1 ppm P and those with a mean grain size of about 2000 μm failed at an elongation greater than 20%, most of them at 30-40%. The variation in sulphur content from 6 to 12 ppm did not affect the creep properties. The main creep rupture mechanisms were found to be cavitation and microcracking at the grain boundaries. Master curves for extrapolation are provided for creep rupture as well as for 5% and 10% creep strain

Effects of laser power density and initial grain size in laser shock punching of pure copper foil

Science.gov (United States)

Zheng, Chao; Zhang, Xiu; Zhang, Yiliang; Ji, Zhong; Luan, Yiguo; Song, Libin

2018-06-01

The effects of laser power density and initial grain size on forming quality of holes in laser shock punching process were investigated in the present study. Three different initial grain sizes as well as three levels of laser power densities were provided, and then laser shock punching experiments of T2 copper foil were conducted. Based upon the experimental results, the characteristics of shape accuracy, fracture surface morphology and microstructures of punched holes were examined. It is revealed that the initial grain size has a noticeable effect on forming quality of holes punched by laser shock. The shape accuracy of punched holes degrades with the increase of grain size. As the laser power density is enhanced, the shape accuracy can be improved except for the case in which the ratio of foil thickness to initial grain size is approximately equal to 1. Compared with the fracture surface morphology in the quasistatic loading conditions, the fracture surface after laser shock can be divided into three zones including rollover, shearing and burr. The distribution of the above three zones strongly relates with the initial grain size. When the laser power density is enhanced, the shearing depth is not increased, but even diminishes in some cases. There is no obvious change of microstructures with the enhancement of laser power density. However, while the initial grain size is close to the foil thickness, single-crystal shear deformation may occur, suggesting that the ratio of foil thickness to initial grain size has an important impact on deformation behavior of metal foil in laser shock punching process.

Wavelength-Dependent Extinction and Grain Sizes in "Dippers"

Science.gov (United States)

Sitko, Michael; Russell, Ray W.; Long, Zachary; Bayyari, Ammar; Assani, Korash; Grady, Carol; Lisse, Carey Michael; Marengo, Massimo; Wisniewski, John

2018-01-01

We have examined inter-night variability of K2-discovered "Dippers" that are not close to being viewed edge-on (as determined from previously-reported ALMA images) using the SpeX spectrograph on NASA's Infrared Telescope facility (IRTF). The three objects observed were EPIC 203850058, EPIC 205151387, and EPIC 204638512 ( = 2MASS J16042165-2130284). Using the ratio of the fluxes from 0.7-2.4 microns between two successive nights, we find that in at least two cases, the extinction increased toward shorter wavelengths. In the case of EPIC 204638512, we find that the properties of the dust differ from that seen in the diffuse interstellar medium and denser molecular clouds. However, the grain properties needed to explain the extinction does resemble those used to model the disks of many young stellar objects. The best fit to the data on EPIC 204638512 includes grains at least 500 microns in size, but lacks grains smaller than 0.25 microns. Since EPIC 204638512 is seen nearly face-on, it is possible the grains are entrained in an accretion flow that preferentially destroys the smallest grains. However, we have no indication of significant gas accretion onto the star in the form of emission lines observed in young low-mass stars. But the He I line at 1.083 microns was seen to change from night to night, and showed a P Cygni profile on one night, suggesting the gas might be outflowing from regions near the star.

Grain size control method for the nozzles of AP1000 primary coolant pipes

Energy Technology Data Exchange (ETDEWEB)

Wang, Shenglong [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Sun, Yanhui [Collaborative Innovation Center of Steel Technology, University of Science & Technology Beijing, Beijing 100083 (China); Yang, Bin, E-mail: byang@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China); Collaborative Innovation Center of Steel Technology, University of Science & Technology Beijing, Beijing 100083 (China); Zhang, Mingxian [State Key Laboratory for Advanced Metals and Materials, University of Science & Technology Beijing, Beijing 100083 (China)

2017-04-01

Highlights: • Design a new forging technology for AP1000 primary coolant pipe. • Method combining FEM and scale-down experiments is adopted. • The grain size and distribution in simulation and experiment are consistent. • Get optimal forging parameters for production guiding. - Abstract: AP1000 primary coolant pipe is made of 316LN austenitic stainless steel. It is a large special-shaped pipe manufactured by integral forging technology. Owing to non-uniform temperature and deformation during forging, coarse grains often occur in the boss sections of the pipe especially in the nozzles’ parts. In the present study, a new forging technology was proposed to control the grain size. The finite element method was used to optimize the forging speed and friction coefficient, then the scale-down experiments were performed for comparison. The forging speed is suggested to be less than 20 mm/s, and effective lubricants should be used to decrease the friction coefficient. The errors of the grain size between the experiment and simulation are less than 20%.

Grain size control method for the nozzles of AP1000 primary coolant pipes

International Nuclear Information System (INIS)

Wang, Shenglong; Sun, Yanhui; Yang, Bin; Zhang, Mingxian

2017-01-01

Highlights: • Design a new forging technology for AP1000 primary coolant pipe. • Method combining FEM and scale-down experiments is adopted. • The grain size and distribution in simulation and experiment are consistent. • Get optimal forging parameters for production guiding. - Abstract: AP1000 primary coolant pipe is made of 316LN austenitic stainless steel. It is a large special-shaped pipe manufactured by integral forging technology. Owing to non-uniform temperature and deformation during forging, coarse grains often occur in the boss sections of the pipe especially in the nozzles’ parts. In the present study, a new forging technology was proposed to control the grain size. The finite element method was used to optimize the forging speed and friction coefficient, then the scale-down experiments were performed for comparison. The forging speed is suggested to be less than 20 mm/s, and effective lubricants should be used to decrease the friction coefficient. The errors of the grain size between the experiment and simulation are less than 20%.

Composition and grain size effects on the structural and mechanical properties of CuZr nanoglasses

International Nuclear Information System (INIS)

Adibi, Sara; Branicio, Paulo S.; Zhang, Yong-Wei; Joshi, Shailendra P.

2014-01-01

Nanoglasses (NGs), metallic glasses (MGs) with a nanoscale grain structure, have the potential to considerably increase the ductility of traditional MGs while retaining their outstanding mechanical properties. We investigated the effects of composition on the structural and mechanical properties of CuZr NG films with grain sizes between 3 to 15 nm using molecular dynamics simulations. Results indicate a transition from localized shear banding to homogeneous superplastic flow with decreasing grain size, although the critical average grain size depends on composition: 5 nm for Cu 36 Zr 64 and 3 nm for Cu 64 Zr 36 . The flow stress of the superplastic NG at different compositions follows the trend of the yield stress of the parent MG, i.e., Cu 36 Zr 64 yield/flow stress: 2.54 GPa/1.29 GPa and Cu 64 Zr 36 yield/flow stress: 3.57 GPa /1.58 GPa. Structural analysis indicates that the differences in mechanical behavior as a function of composition are rooted at the distinct statistics of prominent atomic Voronoi polyhedra. The mechanical behavior of NGs is also affected by the grain boundary thickness and the fraction of atoms at interfaces for a given average grain size. The results suggest that the composition dependence of the mechanical behavior of NGs follows that of their parent MGs, e.g., a stronger MG will generate a stronger NG, while the intrinsic tendency for homogeneous deformation occurring at small grain size is not affected by composition.

Grain-size effects on PIXE and INAA analysis of IAEA-336 lichen reference material

International Nuclear Information System (INIS)

Marques, A.P.; Freitas, M.C.; Wolterbeek, H.Th.; Verburg, T.G.; Goeij, J.J.M. de

2007-01-01

IAEA-336 lichen certified reference material was used to compare outcomes from INAA and PIXE elemental analyses, in relationship with grain size. The IAEA material (grain size <125 μm) was ground and sieved through nylon nets with 64 μm, 41 μm and 20 μm pores. Particle sizes were determined by Laser Light Scattering technique: the data indicate that, after sieving, the IAEA-336 lichen reference material's particle size distribution follows a bimodal distribution, which is turning more and more monomodal after further fine sieving. Replicates of each fraction were analysed by INAA and PIXE. Results for Cl, K, Mn, Fe and Zn by both techniques were compared by application of z-values tested against the criterion vertical bar z vertical bar < 3 for approval of results at the 99.7% confidence level. Under the conditions of this study, the limited amount of lichen material as 'seen' in the PIXE analysis and the grain size distribution in the lichen material were no causes of measurable differences between the results of both techniques. However, fractionation into smaller grain sizes showed to be associated with lower element content, for Na, Cl, K, Mn and Sr even up to a factor of 2. The observed increases of the proportion of algae in the smaller grain-size fractions and the possible accumulation capacity for certain elements in the fungal part of the lichen may explain the observed phenomenon. The sieving process and consequently the discarding of part of the material have lead to a change of the properties of the original sample, namely algae/fungus percentage and elemental contents

Grain size determination in zirconium alloys. Final report of a co-ordinated research programme, 1989-1992

International Nuclear Information System (INIS)

1995-04-01

A research programme was planned as an exercise to establish procedures and evaluate the success of technology transfer. The first programme under this scheme was proposed by the IAEA on the research topic: grain size determination in zirconium alloys. The host laboratory was Siemens AG Erlangen, in Germany. The programme was supervised by experts selected from participating countries. This report contains the results of the work carried out under this programme. The grain size of Zircaloy, the measurement methods, distribution of grain size in the matrix and dependence of grain size on temperature time of annealing are discussed in this report. The report also includes some information on the organizational arrangements and discusses possibilities for future collaboration. 38 figs, 11 tabs

A new look at grain size and load effects in the hardness of ceramics

Energy Technology Data Exchange (ETDEWEB)

Krell, A. [Fraunhofer-Institut fuer Keramische Technologien und Sinterwerkstoffe (IKTS), Dresden (Germany)

1998-05-01

A simple model describes the load effect (size effect) in the hardness, assuming an increasing microplastic deformability, when the further extension of the plastic zone growth and multiplication of pre-existing elements of plasticity are more effective than the generation of new dislocations or twins in the virgin material around the indentation site. The model explains experiments with sintered alumina which indicate a reduced load effect in increasingly fine-grained microstructures due to a grain size effect that is more pronounced at higher testing loads (larger indents) than in the microhardness range. A large difference between the hardness of plastically deformed volumes in single crystals and in polycrystalline microstructures consisting of grains with the same size, respectively, reveals a substantial contribution of the grain boundaries to plastic deformation at the indentation site even at room temperature and even for coarser microstructures. (orig.) 18 refs.

Structural characterization of ferrite nanoparticles and composite materials using synchrotron radiation

International Nuclear Information System (INIS)

Albuquerque, A.S.; Macedo, W.A.A.; Plivelic, T.; Torriani, I.L.; Jimenez, J.A.L.; Saitovich, E.B.

2001-01-01

During the last decade nanocrystalline magnetic materials have been widely studied due to the multiple technological applications. Amongst the magnetic materials of major technological interest are the soft magnetic ferrites and the granular solids formed by ferrites dispersed in non-magnetic matrices. It is a well known fact that the magnetic properties of these materials, such as coercivity, magnetic saturation and magnetization, depend on the shape, size and size distribution of the nanoparticles. For this reason, the general purpose of this work was to obtain structural information on ferrite nanoparticles (NiFe 2 O 4 and NiZnFe 2 O 4 ) and granular solids obtained by dispersion of these particles in non magnetic matrices, like SiO 2 and SnO 2 . The ferrite samples were prepared by co-precipitation and heat treated between 300 and 600 deg. C at the Applied Physics Laboratory of tile CDTN. The granular solids, with 30% in volume concentration of ferrite, were obtained by mechanical alloying with milling times (t m ) varying between 1.25 and 10 h, at the CBPF

DUST DYNAMICS IN PROTOPLANETARY DISK WINDS DRIVEN BY MAGNETOROTATIONAL TURBULENCE: A MECHANISM FOR FLOATING DUST GRAINS WITH CHARACTERISTIC SIZES

Energy Technology Data Exchange (ETDEWEB)

Miyake, Tomoya; Suzuki, Takeru K.; Inutsuka, Shu-ichiro, E-mail: miyake.tomoya@e.mbox.nagoya-u.ac.jp, E-mail: stakeru@nagoya-u.jp [Department of Physics, Nagoya University, Nagoya, Aichi 464-8602 (Japan)

2016-04-10

We investigate the dynamics of dust grains of various sizes in protoplanetary disk winds driven by magnetorotational turbulence, by simulating the time evolution of the dust grain distribution in the vertical direction. Small dust grains, which are well-coupled to the gas, are dragged upward with the upflowing gas, while large grains remain near the midplane of a disk. Intermediate-size grains float near the sonic point of the disk wind located at several scale heights from the midplane, where the grains are loosely coupled to the background gas. For the minimum mass solar nebula at 1 au, dust grains with size of 25–45 μm float around 4 scale heights from the midplane. Considering the dependence on the distance from the central star, smaller-size grains remain only in an outer region of the disk, while larger-size grains are distributed in a broader region. We also discuss the implications of our result for observations of dusty material around young stellar objects.

Dependence of corrosion properties of AISI 304L stainless steel on the austenite grain size

Energy Technology Data Exchange (ETDEWEB)

Sabooni, Soheil; Rashtchi, Hamed; Eslami, Abdoulmajid; Karimzadeh, Fathallah; Enayati, Mohammad Hossein; Raeissi, Keyvan; Imani, Reihane Faghih [Isfahan Univ. of Technology, Isfahan (Iran, Islamic Republic of). Dept. of Materials Engineering; Ngan, Alfonso Hing Wan [The Univ. of Hong Kong (China). Dept. of Mechanical Engineering

2017-07-15

The corrosion resistance of austenitic stainless steels is known to be hampered by the loss of chromium available for passive surface layer formation as a result of chromium carbide precipitation at austenite grain boundaries during annealing treatments. Although high-temperature annealing can promote carbide dissolution leading to better corrosion resistance, grain coarsening also results, which would lead to poorer mechanical properties. Processing methods to achieve both good corrosion resistance and mechanical properties are thus highly desirable for austenitic stainless steels. In the present study, we show that the corrosion resistance of AISI 304L stainless steel can be improved by grain refinement into the ultrafine-grained regime. Specifically, samples with different austenite grain sizes in the range of 0.65-12 μm were studied by potentiodynamic polarization and electrochemical impedance spectroscopy tests in a 3.5 wt.% NaCl solution. All samples showed a typical passive behavior with similar corrosion potential, but the corrosion current density decreased significantly with decreasing grain size. The results show that the sample with the finest grain size had the best corrosion resistance due to a higher resistance of the passive layer to pitting attacks. This study indicates that grain refinement which improves mechanical properties can also significantly improve the corrosion resistance of AISI 304L stainless steel.

Enhanced ductility of surface nano-crystallized materials by modulating grain size gradient

International Nuclear Information System (INIS)

Li, Jianjun; Soh, A K

2012-01-01

Surface nano-crystallized (SNC) materials with a graded grain size distribution on their surfaces have been attracting increasing scientific interest over the past few decades due to their good synergy of high strength and high ductility. However, to date most of the existing studies have focused on the individual contribution of three different aspects, i.e. grain size gradient (GSG), work-hardened region and surface compressive residual stresses, which were induced by surface severe plastic deformation processes, to the improved strength of SNC materials as compared with that of their coarse grained (CG) counterparts. And the ductility of these materials has hardly been studied. In this study, a combination of theoretical analysis and finite element simulations was used to investigate the role of GSG in tuning the ductility of SNC materials. It was found that the ductility of an SNC material can be comparable to that of its CG counterpart, while it simultaneously possessed a much higher strength than its CG core if the optimal GSG thickness and grain size of the topmost phase were adopted. A design map that can be used as a guideline for fabrication of SNC materials was also plotted. Our predictions were also compared with the corresponding experimental results. (paper)

Enhanced Sucrose Loading Improves Rice Yield by Increasing Grain Size.

Science.gov (United States)

Wang, Liang; Lu, Qingtao; Wen, Xiaogang; Lu, Congming

2015-12-01

Yield in cereals is a function of grain number and size. Sucrose (Suc), the main carbohydrate product of photosynthesis in higher plants, is transported long distances from source leaves to sink organs such as seeds and roots. Here, we report that transgenic rice plants (Oryza sativa) expressing the Arabidopsis (Arabidopsis thaliana) phloem-specific Suc transporter (AtSUC2), which loads Suc into the phloem under control of the phloem protein2 promoter (pPP2), showed an increase in grain yield of up to 16% relative to wild-type plants in field trials. Compared with wild-type plants, pPP2::AtSUC2 plants had larger spikelet hulls and larger and heavier grains. Grain filling was accelerated in the transgenic plants, and more photoassimilate was transported from the leaves to the grain. In addition, microarray analyses revealed that carbohydrate, amino acid, and lipid metabolism was enhanced in the leaves and grain of pPP2::AtSUC2 plants. Thus, enhancing Suc loading represents a promising strategy to improve rice yield to feed the global population. © 2015 American Society of Plant Biologists. All Rights Reserved.

Agriproteomics of Bread Wheat: Comparative Proteomics and Network Analyses of Grain Size Variation.

Science.gov (United States)

Dawkar, Vishal V; Dholakia, Bhushan B; Gupta, Vidya S

2015-07-01

Agriproteomics signifies the merging of agriculture research and proteomics systems science and is impacting plant research and societal development. Wheat is a frequently consumed foodstuff, has highly variable grain size that in effect contributes to wheat grain yield and the end-product quality. Very limited information is available on molecular basis of grain size due to complex multifactorial nature of this trait. Here, using liquid chromatography-mass spectrometry, we investigated the proteomics profiles from grains of wheat genotypes, Rye selection 111 (RS111) and Chinese spring (CS), which differ in their size. Significant differences in protein expression were found, including 33 proteins uniquely present in RS111 and 32 only in CS, while 54 proteins were expressed from both genotypes. Among differentially expressed proteins, 22 were upregulated, while 21 proteins were downregulated in RS111 compared to CS. Functional classification revealed their role in energy metabolism, seed storage, stress tolerance and transcription. Further, protein interactive network analysis was performed to predict the targets of identified proteins. Significantly different interactions patterns were observed between these genotypes with detection of proteins such as Cyp450, Sus2, and WRKY that could potentially affect seed size. The present study illustrates the potentials of agriproteomics as a veritable new frontier of plant omics research.

Microstructure and mechanical behavior of neutron irradiated ultrafine grained ferritic steel

Energy Technology Data Exchange (ETDEWEB)

Alsabbagh, Ahmad, E-mail: ahalsabb@ncsu.edu [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Sarkar, Apu [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Miller, Brandon [ATR National Scientific User Facility, Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Burns, Jatuporn [Center for Advanced Energy Studies, Idaho Falls, ID 83401 (United States); Squires, Leah; Porter, Douglas; Cole, James I. [ATR National Scientific User Facility, Idaho National Laboratory, Idaho Falls, ID 83415 (United States); Murty, K.L. [Department of Nuclear Engineering, North Carolina State University, Raleigh, NC 27695 (United States)

2014-10-06

Neutron irradiation effects on ultra-fine grain (UFG) low carbon steel prepared by equal channel angular pressing (ECAP) have been examined. Counterpart samples with conventional grain (CG) sizes have been irradiated alongside with the UFG ones for comparison. Samples were irradiated in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) to 1.37 dpa. Atom probe tomography revealed manganese and silicon-enriched clusters in both UFG and CG steel after neutron irradiation. Mechanical properties were characterized using microhardness and tensile tests, and irradiation of UFG carbon steel revealed minute radiation effects in contrast to the distinct radiation hardening and reduction of ductility in its CG counterpart. After irradiation, micro hardness indicated increases of around 9% for UFG versus 62% for CG steel. Similarly, tensile strength revealed increases of 8% and 94% respectively for UFG and CG steels while corresponding decreases in ductility were 56% versus 82%. X-ray quantitative analysis showed that dislocation density in CG increased after irradiation while no significant change was observed in UFG steel, revealing better radiation tolerance. Quantitative correlations between experimental results and modeling were demonstrated based on irradiation induced precipitate strengthening and dislocation forest hardening mechanisms.

Ion-induced swelling of ODS ferritic alloy MA957 tubing to 500 dpa

Energy Technology Data Exchange (ETDEWEB)

Toloczko, M.B., E-mail: mychailo.toloczko@pnnl.gov [Pacific Northwest National Laboratory, Richland, WA 99354 (United States); Garner, F.A. [Radiation Effects Consulting, Richland, WA 99354 (United States); Voyevodin, V.N.; Bryk, V.V.; Borodin, O.V.; Mel’nychenko, V.V.; Kalchenko, A.S. [Kharkov Institute of Physics and Technology, Kharkov (Ukraine)

2014-10-15

In order to study the potential swelling behavior of the ODS ferritic alloy MA957 at very high dpa levels, specimens were prepared from pressurized tubes that were unirradiated archives of tubes previously irradiated in FFTF to doses as high as 110 dpa. These unirradiated specimens were irradiated with 1.8 MeV Cr{sup +} ions to doses ranging from 100 to 500 dpa and examined by transmission electron microscopy. No co-injection of helium or hydrogen was employed. It was shown that compared to several tempered ferritic/martensitic steels irradiated in the same facility, these tubes were rather resistant to void swelling, reaching a maximum value of only 4.5% at 500 dpa and 450 °C. In this fine-grained material, the distribution of swelling was strongly influenced by the presence of void denuded zones along the grain boundaries.

Grain size effect in corrosion behavior of electrodeposited nanocrystalline Ni coatings in alkaline solution

International Nuclear Information System (INIS)

Wang Liping; Zhang Junyan; Gao Yan; Xue Qunji; Hu Litian; Xu Tao

2006-01-01

Effects of grain size reduction on the electrochemical corrosion behavior of nanocrystalline Ni produced by pulse electrodeposition were characterized using potentiodynamic polarization testing and electrochemical impedance spectroscopy; X-ray photoelectron spectroscopy were used to confirm the electrochemical measurements and the suggested mechanisms. The corrosion resistance of Ni coatings in alkaline solutions considerably increased as the grain size decreased from microcrystalline to nanocrystalline. The higher corrosion resistance of NC Ni may be due to the more rapid formation of continuous Ni(OH) 2 passive films compared with coarse-grained Ni coatings

A statistical mixture model for estimating the proportion of unreduced pollen grains in perennial ryegrass (Lolium perenne L.) via the size of pollen grains

NARCIS (Netherlands)

Jansen, R.C.; Nijs, A.P.M. den

1993-01-01

The size of pollen grains is commonly used to indicate the ploidy level of pollen grains. In this paper observations of the diameter of pollen grains are evaluated from one diploid accession of perennial ryegrass (Lolium perenne L.), which was expected to produce diploid (unreduced) pollen grains in

Correlation vs. Causation: The Effects of Ultrasonic Melt Treatment on Cast Metal Grain Size

Directory of Open Access Journals (Sweden)

J. B. Ferguson

2014-10-01

Full Text Available Interest in ultrasonic treatment of liquid metal has waxed and waned for nearly 80 years. A review of several experiments representative of ultrasonic cavitation treatment of Al and Mg alloys shows that the theoretical mechanisms thought to be responsible for grain refinement are (1 cavitation-induced increase in melting temperature predicted by the Clausius-Clapeyron equation and (2 cavitation-induced wetting of otherwise unwetted insoluble particles. Neither of these theoretical mechanisms can be directly confirmed by experiment, and though they remain speculative, the available literature generally assumes that one or the other or both mechanisms are active. However, grain size is known to depend on temperature of the liquid, temperature of the mold, and cooling rate of the entire system. From the reviewed experiments, it is difficult to isolate temperature and cooling rate effects on grain size from the theoretical effects. Ultrasonic treatments of Al-A356 were carried out to isolate such effects, and though it was found that ultrasound produced significant grain refinement, the treatments also significantly chilled the liquid and thereby reduced the pouring temperature. The grain sizes attained closely correlated with pouring temperature suggesting that ultrasonic grain refinement is predominantly a result of heat removal by the horn and ultrasonic stirring.

Grain size controls on sediment supply from debris-mantled dryland hillslopes

Science.gov (United States)

Michaelides, K.

2011-12-01

Debris-mantled hillslopes are common in arid and semiarid environments where low rates of chemical weathering give rise to thin, non-cohesive soils mantled with a layer of coarse rock fragments derived from weathered bedrock that can reach boulder size. The grain size distributions (GSDs) on the surface of these hillslopes interact with different magnitudes and frequencies of runoff-producing rainfall events that selectively transport grain sizes of different classes depending on flow, grain position on the slope, and hillslope attributes. Sediment transport over many runoff events determines sediment delivery to the slope base, which ultimately modifies the GSD of valley floors. The relationship between hillslope attributes and sediment flux forms the basis of geomorphic transport laws used to model the topographic evolution of drainage basins over >104 y timescales, but the specific responses of sediment flux across the hillslope and the corresponding changes in GSDs to individual storm events are poorly understood. Sheetwash erosion of coarse fragments presents a particular set of conditions for sediment transport that is poorly resolved in current models. A particle-based model for sheetwash sediment transport on debris-mantled hillslopes was developed within a rainfall-runoff model. The rainfall-runoff model produces spatial values of flow depth and velocity which are used to drive a particle-by-particle force-balance model derived from first principles for grain sizes > 1 mm. Particles on the hillslope surface are represented explicitly and can be composed of mixed grain sizes of any distribution or of uniform sizes of any diameter. The model resolves all the forces on each particle at each time and space step based on the flow hydraulics acting on them, so no assumptions are made about incipient motion using Shield's criterion. This research examines how the interplay between hillslope GSD, hillslope attributes (gradient and length) and runoff

Constraints on Circumstellar Dust Grain Sizes from High Spatial Resolution Observations in the Thermal Infrared

Science.gov (United States)

Bloemhof, E. E.; Danen, R. M.; Gwinn, C. R.

1996-01-01

We describe how high spatial resolution imaging of circumstellar dust at a wavelength of about 10 micron, combined with knowledge of the source spectral energy distribution, can yield useful information about the sizes of the individual dust grains responsible for the infrared emission. Much can be learned even when only upper limits to source size are available. In parallel with high-resolution single-telescope imaging that may resolve the more extended mid-infrared sources, we plan to apply these less direct techniques to interpretation of future observations from two-element optical interferometers, where quite general arguments may be made despite only crude imaging capability. Results to date indicate a tendency for circumstellar grain sizes to be rather large compared to the Mathis-Rumpl-Nordsieck size distribution traditionally thought to characterize dust in the general interstellar medium. This may mean that processing of grains after their initial formation and ejection from circumstellar atmospheres adjusts their size distribution to the ISM curve; further mid-infrared observations of grains in various environments would help to confirm this conjecture.

Optimization and testing results of Zr-bearing ferritic steels

Energy Technology Data Exchange (ETDEWEB)

Tan, Lizhen [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Yang, Ying [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Tyburska-Puschel, Beata [Univ. of Wisconsin, Madison, WI (United States); Sridharan, K. [Univ. of Wisconsin, Madison, WI (United States)

2014-09-01

The mission of the Nuclear Energy Enabling Technologies (NEET) program is to develop crosscutting technologies for nuclear energy applications. Advanced structural materials with superior performance at elevated temperatures are always desired for nuclear reactors, which can improve reactor economics, safety margins, and design flexibility. They benefit not only new reactors, including advanced light water reactors (LWRs) and fast reactors such as sodium-cooled fast reactor (SFR) that is primarily designed for management of high-level wastes, but also life extension of the existing fleet when component exchange is needed. Developing and utilizing the modern materials science tools (experimental, theoretical, and computational tools) is an important path to more efficient alloy development and process optimization. Ferritic-martensitic (FM) steels are important structural materials for nuclear reactors due to their advantages over other applicable materials like austenitic stainless steels, notably their resistance to void swelling, low thermal expansion coefficients, and higher thermal conductivity. However, traditional FM steels exhibit a noticeable yield strength reduction at elevated temperatures above ~500°C, which limits their applications in advanced nuclear reactors which target operating temperatures at 650°C or higher. Although oxide-dispersion-strengthened (ODS) ferritic steels have shown excellent high-temperature performance, their extremely high cost, limited size and fabricability of products, as well as the great difficulty with welding and joining, have limited or precluded their commercial applications. Zirconium has shown many benefits to Fe-base alloys such as grain refinement, improved phase stability, and reduced radiation-induced segregation. The ultimate goal of this project is, with the aid of computational modeling tools, to accelerate the development of a new generation of Zr-bearing ferritic alloys to be fabricated using conventional

One-pot production of copper ferrite nanoparticles using a chemical method