C.X. Shi(National Natural Science Foundation of China
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Beijing 100083
,
China Manuscript received 26 August 1996)
金属学报(英文版)
A comprehensive survey was made of various candidate high temperature materials for gas turbine use, and their relative merits and drawbacks were assessed. It is shown that superalloys, fine-tuned, will be persistent for the next few decades, to be followed up by high temperature intermetallics. For advanced ceramics, the problems of reliability and cost will have to be solved before they can be used in critical parts of engines.So are C/C composites with their oxidation problem. Surface modification and development of thermal barrier coatings can effectively overcome many problems of gas turbine materials and these technologies should be emphasized.
关键词:
:superalloy
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null
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null
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null
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WADSWORTH Jeffrey and FLUSS Michael(Chemistry and Materials Science Directorate
,
Lawrence Livermore National Laboratory
,
Livermore
,
CA 94551)
金属学报(英文版)
The role of the National Laboratories is summarized from the era of post World War II to the present time. The U.S. federal government policy for the National Laboratories and its influence on their materials science infrastructure is reviewed with respect to .determining overall research strategies, various initiatives to interact with industry (especially in recent years),building facilities that serve the nation, and developing leading edge research in the materials sciences. Despite reductions in support for research in the U.S. in recent years, and uncertainties regarding the specific policies for Research &Development (R&D) in the U.S., there are strong roles for materials research at the National Laboratories. These roles will be centered on the abilities of the National Laboratories to field multidisciplinary teams, the use of unique cutting edge facilities, a focus on areas of strength within each of the labs,increased teaming and partnerships, and the selection of motivated research areas. It is hoped that such teaming opportunities will include new alliances with China, in a manner similar, perhaps, to those recently achieved between the U.S. and other countries.
关键词:
: U.S. Materials Science. U.S. National Laboratories and Facilities
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null
自然科学进展﹒国际材料（英文）
Part of the results of the key project "Search for novel rare-earth functional materials" supported by the National Natural Science Foundation of China is reviewed. In combination with reports in literature, the effects of the third element M on the formation and stability of La-2(Co, M)(17), R(Fe, M)(12) and R-3(Fe, M)(29) intermetallic compounds are discussed by considering mixing enthalpy of M with rare-earth, Fe and Co, and atomic radius, electronegativity and electronic configurations, etc. It is concluded that the mixing enthalpy and atomic radius dominate the preferential sites and the minimum amount of M required to stabilize a structure, which ultimately affect the magnetic properties of a compound prominently. This review should provide some heuristic hints for exploiting novel rare-earth transition metal functional materials and for improving their performance.
关键词:
La-2 (Co, M)(17);R (Fe, M)(12);R-3(Fe, M)(29);crystal structure;magnetic properties;uniaxial magnetocrystalline anisotropy;subsolidus phase-relations;m;ternary-system;magnetic-properties;crystal-structure;neutron-diffraction;permanent-magnets;fe substitutions;nd;cr
Biomaterials
A natural self-reinforced composite material, bamboo, is studied for the first time as a biomedical material. Its anatomical structure was investigated and its mechanical properties were measured and compared with those of some common bone-bonding or bone-repairing biomaterials. It is found that, among all kinds of biomaterials, bamboo has the closest modulus of elasticity to human long bone. The cytotoxicity of bamboo was tested using the agar overlay method before and after heat or chemical treatments. The results reveal that ethanol, methanol and toluene can remove toxic leachable components from bamboo to some extent through extraction. After grafting a polymer whose molecule includes poly(ethylene glycol), alpha,omega-di(aminopropyl)poly(ethylene glycol) 800 on bamboo, bamboo has the ability to form a calcium phosphate coating after being immersed in calcification solution (simulated body fluid and accelerated calcification solution). The characteristics and the morphology of the mineral formed on bamboo were studied by infrared spectroscopy and scanning electron microscopy. (C) 1997 Elsevier Science Limited. All rights reserved.
关键词:
bamboo;grafts;calcium phosphate;corrosion films
Acta Chimica Sinica
A conventional high voltage wire-like plasma can be greatly enhanced and spread by pulsed microwave to form an umbrella-like plasma continuously distributed in reactor. By use of this plasma, methane is directly converted to C-2 hydrocarbons at high yield under the condition of atmospheric or higher pressure. The effect of pressure, microwave power, pulse duration, molar ratio of H-2/CH4 and flow rate on the methane conversion was investigated. Higher conversion of methane is achieved by proper choice of parameters, and the products only comprise ethylene and acetylene; The molar ratio of C2H2/C2H4 could be adjusted through changing the pressure. With total flow rate of 300 mL/min, H-2/CH4 molar ratio of 2, pressure of 0.13 MPa, peak microwave power of 120 W, pulse duty factor of 400/400 ms, conversion of methane and yield of C-2 could reached up to 59.2% and 52% respectively.
关键词:
higher pressure;low temperature;microwave plasma;natural gas;methane
