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SiC-Si-ZrSiO4 Multiphase Oxidation Protective Coating for Carbon/Carbon Composites

Yulei ZHANG , Hejun LI , Qiangang FU , Kezhi LI , Dangshe HOU , null

材料科学技术(英文)

In order to improve the anti-oxidation property of carbon/carbon (C/C) composites, a novel SiC-Si-ZrSiO4 multiphase oxidation protective coating was produced on the surface of C/SiC coated carbon/carbon composites by a pack cementation technique. The phase composition and microstructure of the as-prepared coatings were characterized by XRD (X-ray diffraction), SEM (scanning electron microscopy) and EDS (energy dispersive spectroscopy). Oxidation behavior of the multiphase coated C/C composites was also investigated. It showed that the as-prepared coating characterized by excellent oxidation resistance and thermal shock resistance could effectively protect C/C composites from oxidation at 1773 K for 57 h in air and endure the thermal cycle between 1773 K and room temperature for 12 times, whereas the corresponding weight loss is only 1.47%. The excellent oxidation protective ability of the SiC-Si-ZrSiO4 coating could be attributed to the C/SiC gradient inner layer and the multiphase microstructure of the coating.

关键词: Carbon/carbon composites , null , null

Study on the Electromagnetic Interference of CFRC Composites by Reflectivity

Kezhi LI , Chuang WANG , Hejun LI , Gengsheng JIAO , Jian WEI

材料科学技术(英文)

The influence of dispersion of carbon fibers in carbon-fiber-reinforced cement-based composites (CFRC) on the mechanical properties of the composites was discussed. The microstructure of the fracture surface of the CFRC samples was observed with a scanning electron microscope (SEM). The electromagnetic interference (EMI) was evaluated indirectly by reflectivity in the Naval Research Laboratory (NRL) testing system. The reflectivity of the electromagnetic radiation by the composites was measured in the frequency range of 8.0–8.2 GHz for different carbon fiber contents of 0.2%, 0.4%, 0.6%, 0.8%, and 1.0% (in wt pct), respectively. The results showed that the reflectivity decreased with the growing fiber content till the percentage of 0.6%. The minimum reflectivity was -23 dB, far less than ¡10 dB, and the composites were strong wave absorbers. After this percentage, the curve increased abruptly as the fiber content proceeded. The electromagnetic waves were gradually reflected. When the fiber content reached 1.0% finally, the maximum reflectivity -7.5 dB appeared and there was stronger reflection. The shielding mechanism includes mainly reflection, absorption, and multiple reflections.

关键词: Carbon fibers , fibers , Cement-based , EMI , Reflectiv

ON SPINODAL BOUNDARIES OF Al-Li ALLOYS

WEI Yinghui , WANG Xiaotian (School of Materials Scince and Engineering , Xi'an Jiaotong University , Xi'an 710049 , China Manuscript received 10 Mareh , 1994)

金属学报(英文版)

The spinodal decomposition can occur in Al-Li alloys containing 5.8-14.2 at.% Li at room temperature. The modutated structure wavelength is approximately 3.1 nm for com mercial Al-LI alloys. The limit composition of the miscibility gap is 3.66 -16.06 at.%Li at 298 K. The highest temperature of the miscibility gap is 377 K.

关键词: : Al-Li alloy , null , null

大爆炸核合成相关的8Li(d, p)9Li反应截面测量

李志宏 , 柳卫平 , 白希祥 , 郭冰 , 连钢 , 颜胜权 , 王宝祥 , 陆昀 , 曾晟 , 苏俊

原子核物理评论 doi:10.3969/j.issn.1007-4627.2005.01.006

利用8Li次级束测量了质心系能量7.8 MeV 2H(8Li, 9Li)1H反应的角分布, 导出了8Li(d, p)9Li反应的天体物理S因子及9Li→8Li+n虚衰变的渐近归一化系数.

关键词: 8Li(d,p)9Li反应 , 角分布 , 天体物理S因子 , 渐近归一化系数

CRYSTAL STRUCTURE OF γ-Li_xFe_2O_3 WITH ELECTROCHEMICAL INSERTION OF Li

HUANG Jianshun CHEN Junming Shanghai Institute of Metallurgy , Academia Sinica , Shanghai , China Research Associate , Shanghai Institute of Metallurgy , Academia Sinica , Shanghai 200050 , China

金属学报(英文版)

Crystal structure of γ-Li_xFe_2O_3,inserted Li electrochemically,was studied by Moss- bauer spectroscopy together with X-ray diffraction,XPS and electrochemical method,On the insertion of Li at low current density,the crystal structure is keeping original spinel; while at higher current density or by thermal activation,owing to violent movement of Li~+ ions,part of crystal structure transforms into rock type similar to face-centered cubic structure of ferrous oxide.The transition channels during insertion of Li~+ ions and limitation of Li~+ ions inserted were discussed.

关键词: null , null , null

Al—Li合金的晶界断裂

姚大平 , 张匀 , 胡壮麒 , 李依依

材料研究学报

本文研究了两种晶粒组织的二元Al-Li 合金拉伸性能与断裂行为。结果表明Al-Li 合金力学性能与晶粒尺寸有关,其断裂行为决定于PFZ 内平面滑移或晶界沉淀相与滑移的交互作用。

关键词: Al—Li合金 , intergranular fracture , planar slip

Effect of Li(3)N additive on the hydrogen storage properties of Li-Mg-N-H system

Journal of Materials Research

The effect of Li(3)N additive on the Li-Mg-N-H system was examined with respect to the reversible dehydrogenation performance. Screening Study with varying Li(3)N additions (5, 10, 20, and 30 mol%) demonstrates that all are effective for improving the hydrogen desorption capacity. Optimally, incorporation of 10 mol% Li(3)N improves the practical capacity from 3.9 wt% to approximately 4.7 wt% hydrogen at 200 degrees C, which drives the dehydrogenation reaction toward completion. Moreover, the capacity enhancement persists well over 10 de-/rehydrogenation cycles. Systematic x-ray diffraction examinations indicate that Li(3)N additive transforms into LiNH(2) and LiH phases and remains during hydrogen cycling. Combined structure/property investigations suggest that the LiNH(2) "seeding" should be responsible for the capacity enhancement, which reduces the kinetic barrier associated with the nucleation of intermediate LiNH(2). In addition, the concurrent incorporation of LiH is effective for mitigating the ammonia release.

关键词: complex hydrides;improvement;mixtures;imides;amide;h-2

SUPERPLASTICITY OF A RAPIDLY SOLIDIFIED AI-Li ALLOY

MANG Weishi WANG Guozhi ZHANG Yongchang HU Zhuangqi SHI Changxu Institute of Metal Research , Academia Sinica , Shenyang , China Yongchang Associate Professor , Institute of Metal Research , Academia Sinica , Shenyang 110015 , China

金属学报(英文版)

A rapidly solidified microcrystalline Al-Li-Cu-Mg-Zr alloy and its superplasicity have been investigated.An optimum tensile elongation of 585% was obtained at 540℃ and strain rate 1.67×10~(-2)s~(-1).The superplastic Al-Li alloy is manufaetured using thermomechanical pro- cessing:solution,overaging,warm rolling and recrystallization.Microstructural changes in thermomechanical processing and cavitation occurred during superplastic deformation have been observed.The superplastic failure of alloy may be caused mainly by nucleation and growth of cavities as well as the linkage around grains.

关键词: superplasticity , null , null , null

Al-Li合金强韧化机理及途径

甘卫平 , 周兆锋 , 杨伏良

材料导报

概述了Al-Li合金强韧化的内部机理和外部机理,并在此基础上阐述了提高Al-Li合金强韧性的主要途径.

关键词: Al-Li合金 , 强韧性 , 途径

Preparation of Li-B alloy and study of its microstructure and discharge characteristics

Zhijian LIU , Zhiyou LI , Wei DUAN , Xuanhui QU , Baiyun HUANG , Siqi ZHANG

材料科学技术(英文)

A LI-B alloy has been prepared using a pretreated amorphous B powder and pure Li ingot as starting materials by continually slow addition of B powder and intensified stirring in the process of melting. The microstructure and the discharge characteristic of the materials have been investigated. Results show that the problem of temperature control in synthesis would be modified by means of continual addition of B powder, the Li7B6 would be more finery distributed in the metal Li by means of intensified stirring. The discharge characteristic of the Li-B alloy using amorphous B as starting materials is almost the same with that of using crystalline B.

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