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31.
Takeshi Hashishin Takeshi Yamamoto Manshi Ohyanagi Zuhair A. Munir 《Journal of the American Ceramic Society》2003,86(12):2067-2073
The synthesis of titanium oxycarbide through a solid–gas combustion was investigated. Titanium powders containing TiC additive at levels ranging from 0 to 50 wt% were combusted in an atmosphere of carbon dioxide gas, at pressures ranging from 0.1 to 5.0 MPa. The characteristics of the synthesis process and the properties of the resulting product were found to depend on the level of the TiC additive and on the pressure of the carbon dioxide gas. Dense oxycarbides (∼96% relative density) with Vickers microhardness of ∼18 GPa were synthesized. In addition, the process presents a possible method for the fixation of carbon dioxide gas for the synthesis of useful materials. 相似文献
32.
K Haruta S Kobayashi S Hirose A Horiai M Ohyanagi M Tanaka T Kawano T Shirai Y Takasaki H Hashimoto 《Canadian Metallurgical Quarterly》1998,160(1):253-258
The reactivity with and affinity for thrombomodulin (TM) of monoclonal anti-cardiolipin Abs (MoaCL), derived from a New Zealand Black x New Zealand White F1 (NZB/W F1) mouse, were studied to investigate the pathogenicity of anti-cardiolipin Abs (aCL). Four of eighteen MoaCL were found to react with rabbit TM when examined using ELISA. These four MoaCL also reacted with synthetic peptide that included the epidermal growth factor-like domain of human TM, a binding site for thrombin. The reaction with TM of these four MoaCL was inhibited by bovine thrombin. When the affinity for TM of the MoaCL was determined, the dissociation constants (Kd) ranged from 4.8 x 10(-9) to 4.7 x 10(-8) M. By contrast, examination of the affinity for cardiolipin (CL) gave values from 8.3 x 10(-6) to 7.4 x 10(-5) M. Thus, these MoaCL reacted to TM with a higher affinity than to CL. Moreover, these MoaCL also bound to TM on HUVEC and down-regulated the expression level of TM on the surface of HUVEC due to internalization of TM. The binding of thrombin to TM is known to initiate rapid protein C activation, and complexes of activated protein C and protein S show anticoagulatory activity. Thus, the present studies suggest that certain pathogenic aCL cross-react with TM and induce down-regulation of TM on endothelial cells, followed by induction of thrombosis. 相似文献
33.
Masachika Shibuya Takanori Yoneda Yutaka Yamamoto Manshi Ohyanagi Zuhair A. Munir 《Journal of the American Ceramic Society》2003,86(2):354-356
Solid solutions of TiB2 –WB2 were densified and annealed simultaneously to cause the decomposition into the phases (Ti,W)B2 and (W,Ti)B2 . Ni and Co were added to solid solutions formed by induction field activated combustion synthesis. The presence of these metals as additives markedly enhanced the kinetics of the subsequent decomposition process. With these additives, decomposition to the two phases occurred within minutes (360 s) in contrast to hours when the solutions did not include the additives. The phases resulting from decomposition, (Ti,W)B2 and (W,Ti)B2 , were identified by X-ray to have the hexagonal AlB2 and W2 B5 structures, respectively. The precipitated phase, (W,Ti)B2 , occurred as elongated grains with aspect ratios of as high as about 10 in samples containing Ni as the additive. 相似文献
34.
Takeshi Yamamoto Hidetoshi Kitaura Yasuhiro Kodera Takashi Ishii Manshi Ohyanagi Zuhair A. Munir 《Journal of the American Ceramic Society》2004,87(8):1436-1441
Nanostructured β-SiC, with crystallite size in the range of 5–20 nm in agglomerates of 50–150 nm, was formed by reactive high-energy ball milling and consolidated to a relative density of 98% by sintering at 1700°C without the use of additives. X-ray line broadening analysis gave a crystallite size of 25 nm, while transmission electron microscopy observations showed the crystallite size to be in the range of 30–50 nm. Evidence demonstrating the role of a disorder–order transformation in the densification process is provided by changes in the diffraction peak patterns and in the integral width with temperature. 相似文献
35.
E. M. Heian S. K. Khalsa J. W. Lee Z. A. Munir T. Yamamoto M. Ohyanagi 《Journal of the American Ceramic Society》2004,87(5):779-783
Dense fine-grained B4 C was synthesized by the spark plasma sintering (SPS) method using mechanically activated elemental powders. Relative densities of up to 95% were achieved. When characterized by X-ray line broadening methods, the grains of the resulting product were determined to be nanometric in scale. However, transmission electron microscopy (TEM) observations showed the product to be composed of a mixture of fine (nanometric) crystallites and grains in the micrometer range. The TEM images showed a highly defective structure containing a high density of twins. Their presence is the reason for the discrepancy between the X-ray and TEM results. 相似文献
36.
Takeshi Hashishin Yasuhiro Kodera Takeshi Yamamoto Manshi Ohyanagi Zuhair A. Munir 《Journal of the American Ceramic Society》2004,87(3):496-499
The spinel (Mg,Si)Al2 O4 was synthesized from aluminum dross using an induction synthesis method. X-ray diffraction analyses on products formed at different temperatures provided an understanding of the formation mechanism of the spinel. After removal of soluble components, the induction heating of the dross resulted first in the oxidation of some of the AlN component and the subsequent formation of the spinel by the following reaction: x SiO2 + (1− x )MgO + [1−( x /3)]Al2 O3 + (2 x /3)AlN = (Mg1− x ,Si x )Al2 O4 + ( x /3)N2 ( g ). 相似文献
37.
Takeshi A. Yamamoto Takayuki Kondou Yasuhiro Kodera Takashi Ishii Manshi Ohyanagi Zuhair A. Munir 《Journal of Materials Engineering and Performance》2005,14(4):460-466
The consolidation of SiC nanopowder synthesized by the mechanical alloying method was subsequently accomplished by spark plasma
sintering of 1700 °C for 10 min under an applied pressure of 40 MPa. The SiC sintered compact with relative density of 98%
consisted of nano-sized particles smaller than 100 nm. This phenomenon resulted in the ordering process of stacking disordered
structure formed by mechanical alloying. In this work, the effect of grain size and relative density on the mechanical properties
were studied. The mechanical properties of sintered compacts were evaluated and compared with the reference samples fabricated
from the commercial SiC powder (β-SiC, 0.3 μm, IBIDEN Co., Gifu, Japan) with sintering additive (B–C mixture). The Vickers
hardness and bending strength of those sintered compacts increased with the increment of the density. However, the mechanical
properties were lower than those of reference samples in case of lower density, even though the mechanical property was close
to that of reference sample in case of higher density. This phenomenon was considered for the difference of bond strength
between grains because those sintered compacts were fabricated without any sintering additives, while those reference samples
were fabricated by accelerating the grain bonding with a sintering additive of B–C mixture. In other words, those results
indicated that the effect of sintering additive affected on mechanical properties directly.
This paper was presented at the International Symposium on Manufacturing, Properties, and Applications of Nanocrystalline
Materials sponsored by the ASM International Nanotechnology Task Force and TMS Powder Materials Committee on October 18–20,
2004 in Columbus, OH. 相似文献
38.
Manshi Ohyanagi Takahito Imai Naoki Toyofuku Daisuke Nakagawa Zuhair A. Munir 《Journal of the American Ceramic Society》2015,98(1):50-56
Nanometric silicon carbide (SiC) powder (~5 nm) with a stacking‐sequence disordered structure (SD‐SiC), synthesized from elemental powders of Si and C, was investigated by microscopic and several spectroscopic methods. The structure of SD‐SiC was characterized by transmission electron microscopy (TEM), 13C, and 29Si‐NMR, and by infrared (IR), Raman, and X‐ray photoelectron spectroscopy (XPS) methods. TEM characterizations showed relatively large deviations of the lattice parameters in the as‐synthesized SiC, indicative of the presence of stacking‐sequence disorder. IR analysis showed a weaker Si‐C bond in the SD‐SiC than in the 3C‐SiC. XPS determinations showed that C and Si in SD‐SiC are similar to those in 3C‐SiC. Broader peaks of 29Si and 13C MAS‐NMR also indicate that the structure of SD‐SiC is different from that of 3C‐SiC. Raman spectroscopy exhibited activities for the crystalline polytypes and the amorphous of SiC but lack of them for the SD‐SiC. The inactivity of Raman spectroscopy for the SD‐SiC along with large deviation of the lattice constant and the extremely broad X‐ray diffraction peaks would indicate that SD‐SiC is a possible intermediate state between conventional polytype SiC and amorphous SiC, that is, a possible new type of SiC. 相似文献