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排序方式: 共有485条查询结果,搜索用时 15 毫秒
51.
Yibin Zhang Toshimi Yamane Keiichi Hirao Yoritoshi Minamino 《Journal of Materials Science》1991,26(21):5799-5805
Al-Cu alloys near the Al-Al2Cu equilibrium eutectic composition were rapidly solidified by the single-roller method. Two-zone structures were observed in transverse sections of Al-24.8, 30.0, 32.7, 33.2, 37.0 and 40.3 mass % Cu alloy ribbons, which were interpreted on the basis of the difference in cooling rates and of the temperature gradients between the chilled and free-surface sides of the ribbons. Non-equilibrium eutectic structures, cellular and irregular lamellar, were seen at the chilled side because the alloy liquids were directionally solidified with coupled eutectic growth. The coupled zone of the Al-Cu alloy expanded over the composition range 24.8–40.3 mass % Cu by rapid solidification. Dendritic structures were formed at the unchilled side of Al-24.8, 30.0, 37.0 and 40.3 mass % Cu alloys. Vickers hardness values at the chilled side differed from those at the unchilled side due to the difference in the microstructure. 相似文献
52.
Hisanori Tanaka Shin-ichi Ito Satoshi Kameoka Keiichi Tomishige Kimio Kunimori 《Applied Catalysis A: General》2003,250(2):255-263
K-promoted Rh/USY (molar ratio: K/Rh=3) catalyst was found to exhibit high performance in preferential oxidation of CO in rich hydrogen. Such high performance was maintained in the presence of steam and CO2. The CO oxidation activity of the K-Rh/USY catalyst was independent of the partial pressure of H2, while the activity of the unpromoted Rh/USY catalyst was decreased significantly in hydrogen-rich stream. The effect of potassium addition on the catalyst structure was investigated and is discussed in terms of the differences in the catalytic performance. 相似文献
53.
A ceramic/metal nanocomposite in tetragonal zirconia-molybdenum system possesses a novel microstructural feature composed of a mutual intragranular nanostructure, in which either nanometer sized Mo particles or equivalent sized zirconia particles are located within the zirconia grains or Mo grains, respectively. It achieves a simultaneous improvement in strength and toughness that overcomes the strength-toughness tradeoff relation. 相似文献
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55.
Summary Tactic and atactic poly(crown ether)s, poly(methacryloyloxymethylbenzo-15-crown-5), were synthesized by polymer reaction of the respective poly(methacrylic acid) with chloromethylbenzo-15-crown-5 and radical polymerization of methacryloyloxymethylbenzo-15-crown-5. By solvent extraction of alkali metal picrates with these poly(crown ether)s, the isotactic poly(crown ether) was found to be a little more selective for K+ and Rb+ than the syndiotactic and atactic ones. 相似文献
56.
Keiichi Ikegami Shin-Ichi Kuroda Mitsuyoshi Saito Kazuhiro Saito Michio Sugi Takayoshi Nakamura Mutsuyoshi Matsumoto Yasujiro Kawabata 《Thin solid films》1988,160(1-2):139-143
An electron spin resonance (ESR) investigation is performed on Langmuir-Blodgett films consisting of a surface-active 1:2 complex of N-docosylpyridinium and tetracyanoquinodimethane (TCNQ), whose temperature-dependent spin susceptibility has been so far found to be consistent with the random-exchange Heisenberg antiferromagnetic chain (REHAC) model of Soos and Bondeson. An out-of-plane anisotropy in the ESR spectra shows that the long axes of TCNQ molecules are preferentially oriented along the plane normal to the sample, where the negligible in- plane anisotropy indicates the random distribution of the short and the pπ orbital axes in the film plane. A heat treatment applied to the samples results in an increase in the concentration of disorder, showing the possibility of controlling it in the present REHAC system. 相似文献
57.
Electrochemical studies showed that tri(2-deoxy-2-L-ascorbyl)amine (), a new compound isolated as one of the products of reaction of dehydro-L-ascorbic acid with phenylalanine (with added L-ascorbic acid) in ethanol, is oxidized in aqueous solution in two reversible one-electron transfer steps, on mercury or platinum electrode. The first step occurs through the dianion, and its product is an unusually stable blue anion radical giving a characteristic ESR signal. The product of the second step of oxidation is labile and is slowly converted into the oxidized form of di(2-deoxy-2-L-ascorbyl)amine, presumably by hydrolysis with splitting of L-ascorbic acid. 相似文献
58.
Toshimi Yamane Masatoshi Yasunaga Keiichi Hirao Shinsuke Yamasaki Keizo Kazama Kosei Yoshida Rikio Takeda Minoru Hiratani 《Journal of Materials Science》1988,23(1):305-310
Repetition numbers of bending of Cu-0.81 wt% Cr, Cu-0.81 wt% Cr-0.14 wt% Sn and Cu-0.26 wt% Cr-0.10 wt% Sn alloys were investigated. After solution treatment, the first two types of copper alloys have a primary chromium phase; this is not so in the last alloy. The primary chromium phase does not influence the repetition numbers of bending of cold-rolled specimens; the repetition numbers of bending of specimens aged at 723 K for 1.8 × 103 sec after cold rolling are higher than those of cold-rolled specimens. The cause of this is considered to be a recovery of work-hardening during ageing. 相似文献
59.
60.