MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Volume 52 , Issue 1
Showing 1-21 articles out of 21 articles from the selected issue
  • Hisanori Tanimoto, Takayuki Sugimori, Shoichiro Kumamoto, Hazuki Matsu ...
    2011 Volume 52 Issue 1 Pages 1-7
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    The Cu(111) texture evolution in Cu films sputter-deposited on 35-nm β-Ta barrier layers on Si(100) (Ta/Cu) and in those capped by 5-nm Ta (Ta/Cu/Ta) were studied by X-ray diffraction (XRD). The Cu thicknesses (tCu) ranged from 5 to 500 nm. For Ta/Cu, the intensity of the Cu 111 reflection exhibited a step-like increase for tCu between 22 and 33 nm, indicating that subsequent deposition of Cu caused the Cu(111) texture evolution in the already-deposited Cu film (Cu self-capping effect). For Ta/Cu/Ta, the 5-nm Ta capping caused the Cu(111) texture evolution in the already-deposited Cu films for tCu between 10 and 30 nm (Ta capping effect). These capping effects indicate that the texture evolution took place at room temperature in nanocrystalline Cu films. The capping effects and the initial growth stage of Cu on β-Ta are discussed as they relate to Ta and Cu interfacial and grain boundary energies in the nanocrystalline structures.
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  • M. Shaban, S. Gozalzadeh, B. Eghbali
    2011 Volume 52 Issue 1 Pages 8-11
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Ultra fine grained materials exhibit superior mechanical properties compared with the conventional coarse grained one. In the present work, the hot extrusion process was conducted on plain low carbon steel to achieve ultra fine ferritic structure. At first, with the aid of 3D finite element simulation an appropriate preheating temperature for the initiation of dynamic strain induced transformation of austenite to ferrite was predicted to be 930°C. After hot extrusion, the results of microstructural analysis by optical microscopy showed that the predicted temperature was suitable. Extruded samples showed ultra fine ferrite structure with average grain size of 1 μm on a plane perpendicular to material flow. Also, the microstructural developments with strain in the extrusion zone confirmed the occurrence of dynamic strain induced transformation of austenite to ferrite during deformation process. Tensile strength of processed steel is two times higher than coarse grained one.
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  • Wei-Chih Chung, Jiunn-Yuan Huang, Leu-Wen Tsay, Chun Chen
    2011 Volume 52 Issue 1 Pages 12-19
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: November 25, 2010
    JOURNALS FREE ACCESS
    In the nuclear power industry, dissimilar metal welding is widely used for joining low alloy steel to austenite stainless steel components with nickel-base filler metals. In this study, attention was paid to the weld metal in multi-pass Alloy 52-A508 dissimilar welds. An approximately 2 mm wide transition zone was observed that consisted of a martensitic layer (10∼20 um) along the weld interface and the austenite phase region with varying degrees of dilution. After post-weld heat treatment, the microstructures near the weld interface consisted of martensite, carbides and Type II boundaries. The presence of Type II boundaries significantly reduced the resistance to stress corrosion cracking (SCC) and formed intergranular cracking under simulated reactor coolant conditions. Constant extension rate tensile (CERT) tests were performed on the notched tensile specimens in 300°C water at two extension rates, 3×10−4 and 1×10−6 mm/s. A fast CERT test can be regarded to have no contribution of corrosion, and its results can be used as standards for comparison. In the slow CERT tests, the ductility losses of round-bar specimens with a circumferential notch at various regions in the weld metal were ranked accordingly. The relative susceptibility to SCC in terms of the ductility loss in increasing order of severity was as follows: the undiluted weld metal, the transition zone and the weld interface. SEM fractographic observations were consistent with the SCC results, i.e., an increased ductility loss or SCC susceptibility was associated with more brittle fractures.
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  • Katsuhiko Fujii, Koji Fukuya
    2011 Volume 52 Issue 1 Pages 20-24
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 08, 2010
    JOURNALS FREE ACCESS
    A micro tensile testing method for evaluating grain boundary strength was developed. Specimens of 2×2×10 μm having one grain boundary were made by focused ion beam (FIB) micro-processing and tensioned in an FIB system. The load was measured from the deflection of the Si cantilever and the displacement was also monitored in situ. The method was applied to aged and unaged Fe-Mn-P alloy specimens with different grain boundary P segregation. The load at intergranular fracture decreased with increasing P segregation.
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  • Hsu-Chi Chuang, Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen
    2011 Volume 52 Issue 1 Pages 25-30
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Electrical current process has been used in the thin plate metals and the fine wires because of its higher efficiency (rapidly recrystallization) and the advantage of avoiding oxidation without inert gas. This study investigated the transformation of twin structure and mechanical properties of 304 stainless steel after electrical current test by direct current. The results show the microstructure of matrix transported from preferred structure to equiaxed grains and a few annealed twins with increasing the current density of joule from 32 J to 188 J. The hardness of matrix remained stable under 83 J because of the number of twins increased, and the tensile properties were similar to the wire using furnace heating. After electrical current test at 188 J, the strain hardening exponent of wires was 0.44, was suitable to be used for cold work procedure.
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  • Yoichi Takahashi, Shigefumi Kihara, Takuo Nagamachi, Hiroaki Mizumoto, ...
    2011 Volume 52 Issue 1 Pages 31-36
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 08, 2010
    JOURNALS FREE ACCESS
    The effects of forming conditions on wrinkling in the neck of stainless-steel tubes were investigated using experiments and three-dimensional finite element simulations. The materials used for this study were tubes designed for automotive exhaust parts. When the axial or radial forming pitch of the rollers is large, the outside of the tube is subjected to considerable compressive stress in the circumferential direction by contact with the rollers. Simultaneously, the inside of the tube is subjected to considerable tensile stress in the circumferential direction. Consequently, the tube is subjected to excessive localized forming, which causes the curvature to become uneven in the circumferential direction, thereby resulting in wrinkling. The number of contact points with the rollers was determined. Results show that the optimum forming conditions were easily determined to achieve short forming times and high dimensional accuracy.
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  • Yorinobu Takigawa, Shin Wakayama, Isao Matsui, Tokuteru Uesugi, Kenji ...
    2011 Volume 52 Issue 1 Pages 37-40
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    Homogeneous bulk amorphous Ni-W alloy with thickness of more than 2 mm is fabricated by an electroforming process. By suppressing the side reaction and by preserving the mass balance between consumed ions by electrodeposition and supplemented ions by the solution of Ni and W anodes in the electroforming system, the standard deviation of W-concentration throughout the specimen is kept to 1.3 at%. As the result of micro-Vickers hardness tests, the standard deviation of micro-hardness decreases about 90% in bulk materials in comparison with thin-film materials fabricated by conventional electroforming process. This result indicates that it is important to minimize the fluctuation of W-concentration in the specimen for obtaining the micrometer-scale high reliability of hardness. The compressive strength of bulk amorphous Ni-W alloy is about 2.7 GPa. High compressive strength of amorphous Ni-W alloy can be clearly shown.
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  • Hongki Kim, Kaoru Kimura
    2011 Volume 52 Issue 1 Pages 41-48
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Samples of 1 at% metal (Al, Co, Cr, Cu, Mo, Nb, Ni, Ru, Si, V, W, Zr)-doped β-rhombohedral boron (β-boron) were prepared by spark plasma sintering and their thermoelectric properties were examined in the temperature range from 353 K to 1073 K. It was found that V-doped β-boron exhibited the largest dimensionless figure of merit (ZT value). The V concentration dependence of the thermoelectric properties of β-boron was investigated. We discuss the effects of V doping into β-boron and the precipitation of a second phase on the thermoelectric properties. The temperature dependences of electrical conductivity and the Seebeck coefficient in the single-phase range of V concentration can be explained by assuming a combination of the band conduction of holes and the variable-range hopping conduction of electrons. This is described using the band structure model with the intrinsic acceptor level and the hybridization between the orbitals of boron and V, which corresponds to the metallic-covalent bonding conversion. Among the samples of V-doped β-boron, V2.0B105 had the highest value of ZT (7.91×10−3 at 1079 K) due to both V doping and the precipitation of a metallic phase (VB2).
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  • Riki Kataoka, Toyoto Sato, Takahiro Kuriiwa, Atsunori Kamegawa, Masuo ...
    2011 Volume 52 Issue 1 Pages 49-53
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    New Li-based hydrides have been prepared under GPa-order by using a cubic-anvil-type apparatus. Novel compounds in Li-Zr and Li-Hf systems were obtained at 973 K under 5 GPa. For Li-Zr system, a novel compound has a primitive cubic structure with a=0.42188(3) nm. The compound was thermally stable up to 723 K under Ar flow. For Li-Hf system, two novel compounds were successfully synthesized. Crystal structures of these compounds were found to be a primitive cubic (a=0.4209(2) nm) and a body centered cubic (a=1.08369(4) nm). A structural model of the new compounds with the body-centered cubic structure was found to be an Ag8Ca3-type structure. The novel compound with a primitive cubic structure was thermally stable up to 723 K, but the compound with the body centered cubic structure was decomposed at 600 K with an endothermic reaction.
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  • Gong-An Lan, Chung-Wei Yang, Truan-Sheng Lui, Li-Hui Chen
    2011 Volume 52 Issue 1 Pages 54-60
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Microstructural features of Sn-xZn alloys with varying Zn content of 7, 9, 20, 30 mass% on the electrification-fusion phenomenon were investigated in this study. Experimental results showed that the critical fusion current density (CFCD) of Sn-xZn alloys increased with increasing Zn content. The enrichment of Zn-rich phase was the main factor in the improvement of electrical conductivity and the required electrical current density for triggering microstructural evolution for the hypereutectic Sn-30Zn alloy was much higher than the hypoeutectic Sn-7Zn alloy. There is an obvious difference in the increase rate of CFCD from the hypoeutectic composition (Sn-7Zn) to the eutectic composition (Sn-9Zn) due to the microstructural evolution with increasing Zn content. Through the in-situ examination of microstructural evolution during electrification-fusion tests, the initial site of electrification-fusion-induced failure was significantly emerged from the Sn/Zn eutectic phase for both the hypoeutectic composition (Sn-7Zn) and the hypereutectic composition (Sn-30Zn). The fusion behavior of Sn-7Zn was dominated by double massive fusion regions on Sn/Zn eutectic phase and β-Sn phase, whereas the fusion behavior of Sn-30Zn was dominated by massive fusion regions only on Sn/Zn eutectic phase.
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  • Z. Liu, K. C. Chan, L. Liu
    2011 Volume 52 Issue 1 Pages 61-67
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Two Ni- and Cu-free bulk metallic glasses (BMGs) of Zr65Pd17.5Fe10Al7.5 and Zr65Pd12.5Ag5Fe10Al7.5, with a critical casting diameter of 6 mm and a compressive strength above 1500 MPa, were developed. While the Zr65Pd17.5Fe10Al7.5 alloy showed little plastic strain before fracture, the Zr65Pd12.5Ag5Fe10Al7.5 alloy exhibited much larger plasticity by the relatively stable, intermittent propagation of the major shear band under compression. This unusual plastic deformation behavior was interpreted on the basis of the contribution of the icosahedral short-range order. Potentiodynamic polarization tests revealed that the Zr65Pd12.5Ag5Fe10Al7.5 alloy has a higher corrosion resistance than the Zr65Pd17.5Fe10Al7.5 alloy in phosphate buffered saline at 37°C. X-ray photoelectron spectroscopy analysis revealed that the passive film of Zr65Pd12.5Ag5Fe10Al7.5 alloy consisted mostly of ZrO2, which may be responsible for the excellent corrosion resistance of this alloy. Ni- and Cu-free BMGs with a critical diameter of 6 mm, together with enhanced mechanical properties and corrosion resistance, may be promising in biomedical applications.
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  • M. Tsukahara
    2011 Volume 52 Issue 1 Pages 68-72
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    Hydrogenation properties of the vanadium-rich ternary V-Ti-Cr alloy was investigated, which is of interest as a hydrogen carrier for fuel-cell vehicles. The dependence of hydrogen content of the hydrides with low plateau pressure (β phase) on the unit cell volume of the dehydrogenated alloys (α phase) is found to be different from that of the hydrides (γ phase) with high plateau pressure. By optimizing the alloy composition, a large effective hydrogen storage capacity of 2.62 mass% is obtained.
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  • Yoshitake Nishi, Tatsuya Yamamoto, Shinichiroh Namba, Hiroaki Takei, K ...
    2011 Volume 52 Issue 1 Pages 73-80
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    Homogeneous low voltage electron beam irradiation (HLEBI) improves the Charpy impact value (auc) of sandwich structural composite (CFRP/ABS/CFRP) of acrylonitrile butadiene styrene (ABS) resins cores (2 mm thickness) covered with carbon fiber reinforced epoxy polymers (CFRP) with 250 μm thickness at both side surfaces. The auc values of CFRP/ABS/CFRP at low (0.06) and mid (0.50) fracture probability (Pf) after irradiation at 0.30 MGy (kJg−1) were 35.9 and 53.0 kJm−2, which were approximately 20.3 and 25.2% higher than those (28.6 and 39.7 kJm−2) before treatment, respectively. Although the maximum auc value at mid Pf (0.50) after 0.30 MGy irradiation for the CFRP/ABS/CFRP is approximately equal to that for CFRP, it is also about 21.4% higher than that (41.7 kJm−2) of these CFRP before treatment. Although the use of ABS resin as the core reduced other mechanical properties of tensile and bending, the price of CFRP was apparently higher than that of ABS polymer. Thus, it is possible that the sandwich structural composites of CFRP/ABS/CFRP could be used for daily articles. Since the irradiated depth estimated is about 119±23 μm at their both sides surface, the irradiation effects mostly was acted within the CFRP sheet.
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  • Hideki Kamata, Shoichi Suzuki, Yuta Tanaka, Yusuke Tsutsumi, Hisashi D ...
    2011 Volume 52 Issue 1 Pages 81-89
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    Collagen is expected to work as a bonding agent of soft and hard tissues to solid materials. In this study, the electrodeposition of collagen to a titanium (Ti) surface under various conditions, i.e., the pH of the collagen solution, potential, and electrodeposition time, was performed to understand the optimal electrodeposition conditions for the immobilization of collagen to Ti. The effects of these conditions on the thickness and residual ratio of the collagen layer after shaking in water were evaluated by ellipsometry, scanning probe microscopy, and X-ray photoelectron spectroscopy. Collagen molecules were attracted to Ti cathode and immobilized with high durability by combining electrodeposition conditions, pH 5, alternating potential between −1 V and +1 V vs. SCE with 1 Hz, and 1800 s. The surface of this electrodeposited collagen layer was smooth and uniform maintaining the collagen fibril and natural structure. On the other hand, the collagen layer immobilized by immersion technique in a collagen solution, was rough and irregular. Electrodeposition with alternating potential at pH 5 for 1800 s is a much more appropriate technique to immobilize collagen to Ti than the conventional immersion technique.
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  • Kazuhiko Honda, Masaaki Sugiyama, Yoichi Ikematsu, Kohsaku Ushioda
    2011 Volume 52 Issue 1 Pages 90-95
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 01, 2010
    JOURNALS FREE ACCESS
    The primary Al phase crystallizes preferentially on TiAl3 fine precipitate during the solidification process of hot-dip Zn-11 mass%Al-3 mass%Mg-0.2 mass%Si coating, which leads to the formation of fine dendrite structures by the small amounts of Ti added to the coating bath. TiAl3 is thought to act as heterogeneous nucleation sites of the primary Al phase. Detailed TEM observation of the sectioned specimen by a micro-sampling unit equipped with an FIB system revealed that the TiAl3 fine precipitate is not a single crystal but polycrystals. However, a crystallographic relationship exists between the TiAl3 phase and the surrounding Al phase, namely, [001]TiAl3||[001]Al, [010]TiAl3||[010]Al and [100]TiAl3||[100]Al. High-resolution TEM observation of the interface indicates a good coincident relationship between the Al matrix and the precipitate. Therefore, the primary Al phase nucleated heterogeneously on the surface of the TiAl3 phase. Furthermore, detailed TEM observation revealed a monotectoid reaction by the primary Al phase to the extremely fine Al and Zn phases.
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  • Bing Xue, Yinshan Jiang, Darui Liu
    2011 Volume 52 Issue 1 Pages 96-101
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    A novel anticorrosion material, copper/linear low density polyethylene (Cu/LLDPE) nanocomposites, was prepared via melt-blend technique. X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive spectrometer (EDS), salt spray test, thermogravimetric analysis (TG), mechanical properties test and bactericidal properties test were employed to character the resultant nanocomposites. The results of XRD and SEM showed that the nanocomposites were a hybrid of the polymer and the copper nanoparticles, and the copper nanoparticles were distributed uniformly in general. The results of salt spay test showed that nano-Cu in LLDPE could react with permeated oxygen, leading to the improvement of anticorrosion properties of the Cu/LLDPE nanocomposites. The results of mechanical properties test and TG analysis indicated that the presence of a small amount of nano-Cu (no more than 5 mass%) could enhance the mechanical properties and thermal stability of the nanocomposites and excessive nano-Cu would cause performance degradation. The bactericidal properties evaluation showed that the bactericidal ability of the Cu/LLDPE nanocomposites increased with nano-Cu content remarkably.
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  • T. Kurosu, Y. Shimizu, Y. Tomota, J. Onuki
    2011 Volume 52 Issue 1 Pages 102-107
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    Thick (8 μm) Al-Si films both on poly Si (0.5 μm thick)/SiO2/Si and SiO2/Si substrates were subjected to cyclic current application or cyclic heating and cooling. Both the cyclic current application and the cyclic heating and cooling led to specimen surface roughening. The average roughness increased with the number of cycles, but the extent of roughness for the former was much larger than that for the latter. These results correspond to the fact that grain size and texture for the latter are two times larger and more [111] oriented than those for the former, respectively. According to Electron Back Scattering Pattern (EBSP) measurements, grains with an orientation deviating from [111] were found to deform heavily during the cyclic current charging or heating, resulting in grain extrusion on the surface.
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  • Kazuhito Shida, Ryoji Sahara, MN Tripathi, Hiroshi Mizuseki, Yoshiyuki ...
    2011 Volume 52 Issue 1 Pages 108-111
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 15, 2010
    JOURNALS FREE ACCESS
    Electric conductance of percolation clusters is calculated by means of random circuit approximation under a binary distribution in the size of the conducting particles. Although we have already investigated a similar size distribution model in 2D, a 3D version of this model has not been reported before. The size distribution of conducting particles induces a clear difference in the ensemble of a random circuit. Consequently, a significant change in the critical point and conductance compared to the monodisperse cases is observed.
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  • Ming-Hsiang Ku, Fei-Yi Hung, Truan-Sheng Lui, Li-Hui Chen
    2011 Volume 52 Issue 1 Pages 112-117
    Published: January 01, 2011
    Released: December 25, 2010
    JOURNALS FREE ACCESS
    7075-T6 Al alloy plates had a friction stir process (FSP) and then performed the natural aging to investigate the effects of various tool rotation speeds (1230 rpm, 1450 rpm, 1670 rpm) and natural aging (40°C, 96 h) on the microstructures and tensile fracture properties. The experimental results showed that the grain size became fine equiaxed and the average grain size were 5.2, 5.1, 4.2 μm from low to high tool rotation speeds in the stir zone (SZ). The tensile strength varied with the different rotation speeds of FSP. After natural aging, higher tool rotation speeds had an embrittlement phenomenon on the SZ (detected by nanoindenter) due to the contribution of stirred metal flow and precipitates. Decreasing the tool rotation speeds, the metal flow zones were refined and restrained the brittle behavior to improve the ductility.
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  • S. V. Jagadeesh Chandra, Myung-Il Jeong, Yun-Chang Park, Jong-Won Yoon ...
    2011 Volume 52 Issue 1 Pages 118-123
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 08, 2010
    JOURNALS FREE ACCESS
    We fabricated Ge metal-oxide-semiconductor (MOS) devices with Pt/HfO2 gate stacks and investigated the effect of thermal treatment on their structural and electrical properties in oxygen (O2) and forming gas (FG) environments. The annealing ambient dependency of the structural and electrical properties of Ge MOS devices was directly compared to that of Si MOS devices. For both Ge and Si MOS devices, the thermal treatment process led to a decrease in accumulation capacitance regardless of the annealing ambient. The interfacial layer (IL) at the HfO2/Ge stack was much thinner than the HfO2/Si stack. O2 annealing resulted in the improvement of the HfO2 interfacial quality of Ge and Si MOS devices, although the improvement of the Ge devices was greater than that of the Si devices. FG annealing was much more effective in the reduction of interface state density (Dit) in Si devices than in Ge devices. A negligible IL at a HfO2/Ge stack could be a main cause of degraded electrical performance of a Ge device with FG annealing.
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  • Ruisong Yang, Fangwei Luo, Renbo Xu
    2011 Volume 52 Issue 1 Pages 124-126
    Published: January 01, 2011
    Released: December 25, 2010
    [Advance publication] Released: December 15, 2010
    JOURNALS FREE ACCESS
    A novel process for synthesizing ceramic powders in molten salt was introduced in this paper. Dissimilar to traditional mechanochemical process, the novel process is based on chemical reaction in liquid phase (molten salt). The reaction temperature to synthesize tungsten carbide in molten salt could be reduced to 1000°C compared with traditional solid state methods. Results in this paper showed that nano W2C powder could be successfully synthesized through this method. The mechanism of the reaction in molten salt was discussed finally.
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