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排序方式: 共有7049条查询结果,搜索用时 15 毫秒
31.
研究了用微米级Ti2SiC2陶瓷与Cu制备纳米复合材料的工艺过程。分别选用钢球和玛瑙球进行球磨,对Ti2SiC2颗粒的细化和在Cu中分散性的影响进行了研究。结果表明,在其它实验参数相同的情况下,用两种不同材质的磨球所获得的混合粉形态有很大差异,用玛瑙磨球可以更好地使Ti2SiC2颗粒细化并均匀分散在Cu基体中,而用钢球则易产生混合粉的团聚。另外,随着球磨时间的延长,Ti2SiC2先后经历了颗粒细化、均匀镶嵌在基体中两个阶段。对球磨后的混合粉在850℃及20MPa的压力下成功地制备了组织成分均匀的大块纳米复合材料,其力学性能与同成分的普通复合材料相比有明显提高。 相似文献
32.
钨尾矿微晶玻璃的形状记忆效应 总被引:1,自引:1,他引:1
研究了钨尾矿微晶玻璃的形状记忆效应(SME),并用X射线衍射法(XRD)作了相分析。结果表明,钨尾矿微晶玻璃具有明显的SME;恢复应变随回复保温温度升高而增加;该材料随着变形量的减小,形状恢复率随之上升 相似文献
33.
34.
粉末冶金法制备SiC晶须增强MB15镁基复合材料 总被引:6,自引:0,他引:6
采用粉末冶金法制备了SiC晶须增强镁基复合材料(SiCW/MB15)试样。通过检测基体显微硬度探讨了SiCW对镁合金时效规律的影响,并借助扫描电镜(SEM)、透射电镜(TEM)和拉伸试验,研究了混粉方式对复合材料室温力学性能、SiCW分布及显微结构的影响。结果表明,MB15及其复合材料的时效硬化曲线上均存在双峰现象;SiCW的加入既提高了MB5的硬度,又加快了其时效速度:混粉方式对晶须分布及SiCW/MB15复合材料的室温力学性能影响很大。 相似文献
35.
36.
Michael Kmetz Steven L. Suib Francis S. Galasso 《Journal of the American Ceramic Society》1989,72(8):1523-1524
The strength and toughness of fibrous composites depend on the interface properties which control the bonding between the fibers and matrices. One method of controlling the interface involves coating the fiber with an appropriate material. In a previous study, it was found that there is a definite advantage in using low coating temperatures to prevent fibers from degrading. We therefore were interested in a report that Mo2 C could be deposited from Mo(CO)6 at temperatures as low as 300° to 475°C. Our studies indicated that the material was not Mo2 C, but an oxycarbide, which, with an analogous tungsten oxycarbide coating, was applied to SiC yarns. Both oxycarbides could be converted to the metals by heat-treating in N2 . 相似文献
37.
38.
High surface area carbon-supported platinum-based catalysts, Pt/C, PtWO
x
/C, PtRu/C and PtRuWO
x
/C, were prepared via a chemical reduction route using single metal precursor salts. The catalyst particles were found to
be in the nanoscale range, and the addition of Ru clearly decreased the particle size. The Ru was found to be partially incorporated
into the face centered cubic lattice of Pt and to form a single Ru catalyst component. X-ray diffraction and X-ray photon
spectroscopy did not provide evidence for electronic interactions between WO
x
and Pt as well as WO
x
and Ru. However, the addition of tungsten to the PtRuWO
x
/C catalyst resulted in a high degree of catalyst particle agglomeration. Both Ru containing catalysts showed significantly
higher activities for the CH3OH oxidation reaction in terms of Pt + Ru mass as well as electroactive Pt + Ru surface area than the Pt/C and PtWO
x
/C catalysts. The addition of tungsten appeared to mainly result in some ‘physical’ modification of the catalytically active
Pt and Ru surface components such as differences in electroactive surface area rather than promotion of the CH3OH oxidation reaction via a true catalytic mechanism. 相似文献
39.
Tateoki Iizuka Hideki Kita Hideki Hyuga Takene Hirai Kazuo Osumi 《Journal of the American Ceramic Society》2004,87(3):337-341
A W2 C-nanoparticle-reinforced Si3 N4 -matrix composite was fabricated by sintering porous Si3 N4 that had been infiltrated with a tungsten solution. During the sintering procedure, nanometer-sized W2 C particles grew in situ from the reaction between the tungsten and carbon sources considered to originate mainly from residual binder. The W2 C particles resided in the grain-boundary junctions of the Si3 N4 , had an average diameter of ∼60 nm, and were polyhedral in shape. Because the residual carbon, which normally would obstruct sintering, reacted with the tungsten to form W2 C particles in the composite, the sinterability of the Si3 N4 was improved, and a W2 C–Si3 N4 composite with almost full density was obtained. The flexural strength of the W2 C–Si3 N4 composite was 1212 MPa, ∼34% higher than that of standard sintered Si3 N4 . 相似文献