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51.
52.
Jianghua Zeng Dingsheng Yuan Yingliang Liu Jingxing Chen Sanxiang Tan 《Frontiers of Chemistry in China》2009,4(2):127-131
Tungsten carbide (WC) nanocrystals have been prepared by a solvothermal method with Mg as the reductant and WO3 and anhydrous ethanol as the precursors. The effects of time and temperature on the synthesis of WC were investigated and
a probable formation mechanism was discussed. The obtained WC nanocrystals were characterized by X-ray diffraction, transmission
electron microscopy, energy dispersive spectroscopy and electrochemical methods. Hexagonal closepacked WC was successfully
synthesized when the temperature was as low as 500°C. The content of carbon was more than that of W, indicating that the composition
of the treated sample was C and WC only. The diameters of WC nanocrystals were ranged from 40 nm to 70 nm and the nanocrystals
were dispersed on carbon films. The electrochemical measurements reveal that WC nanocrystals obviously promote Pt/C electrocatalytic
ability for the oxygen reduction reaction.
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Translated from Chinese Journal of Catalysis, 2008, 29(7) (in Chinese) 相似文献
53.
本文研究荷能氢离子轰击对TiC薄膜的结构及其界面的影响。氢离子源为5A的脉冲离子注入器,能量25keV,脉冲宽度20ms。样品经轰击后发现。与受相同辐照的45~#钢样品相比,TiC薄膜表面无明显的损伤;TiC薄膜内的氢含量较高;薄膜的织构消除;TiC薄膜与基体间的结合力有明显提高。 相似文献
54.
Richard Nader Elie Moussaed Michel Kazan Joerg Pezoldt Pierre Masri 《Superlattices and Microstructures》2008,44(2):191-196
Structural and optical measurements were performed on silicon carbide (SiC) samples containing several polytypes. The SiC samples investigated were grown on (111) Si substrates by solid source molecular beam epitaxy (SSMBE). Several quantities of Ge were predeposited before the growth procedure. The influence of Ge on the SiC polytypes formation was studied by X-Ray, FTIR and μ-Raman characterizations methods. The spectra of the samples with less than one Ge monolayer exhibit a mixture of 2H, 15R and 3C–SiC polytypes. This mixture is due to the mismatch between the heterostructure layers. We propose that the Ge predeposition in the heterostructure can be used to stabilize and unify the polytypes formation. 相似文献
55.
Kang Ji Wang 《Applied Surface Science》2008,254(7):1981-1985
Deposition of HfO2 films on n-type 4H-SiC substrates by sol-gel spin-on coating technique has been performed and the physical and electrical characteristics of this film as a function of annealing temperature (550, 750, and 850 °C for 30 min) have been reported. The physical properties of the film have been characterized using a Filmetrics and X-ray diffractometer, while conduction atomic force microscope and semiconductor parameter analyzer were used for electrical characterization. Phase transformation has been revealed in the oxide as the annealing temperature changed. Refractive index, relative density, dielectric constant of the film, and oxide-semiconductor interface trap density have been extracted and related to the leakage current through the oxide. It has been recorded that, oxide annealed at 700 °C has demonstrated the lowest leakage current and the best oxide reliability. The reasons of these observations have been explained. 相似文献
56.
57.
Huimin Xiang Jiemin Wang Yue Chen Jingyang Wang Yanchun Zhou 《Journal of Raman spectroscopy : JRS》2014,45(2):202-207
In this paper, in situ Raman spectra of Ta2AlC are measured in the temperature range of 80–500 K at ambient pressure. The frequencies of the Raman modes decrease with increasing temperature, which have been explained by the anharmonic and thermal expansion effects. The line‐width of E2g (ω3) mode increases at elevated temperatures, which is found to be due to the anharmonic phonon–phonon scatterings. On the other hand, the line‐widths of E2g (ω1) and A1g (ω4) modes decrease continuously with increasing temperature, which is explained by the electron–phonon couplings of these two phonon modes with the Ta 5d electrons. The electron–phonon coupling strengths are obtained both in experiments and density functional calculations. Finally, Ta2AlC is predicted to be a new superconductive MAX phase. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
58.
反应烧结碳化硅复合材料的磨损机理研究 总被引:4,自引:3,他引:1
采用销-盘摩擦磨损试验机考察了反应烧结碳化硅及含Ni碳化硅复合材料在不同温度下的干摩擦磨损性能。结果表明,Ni有利于改善反应烧结碳化硅复合材料的摩擦磨损性能。SEM磨损表面和亚表面分析表明,复合材料在常温下的磨损机理为削和犁沟;600℃下反应烧结碳化硅的磨损机理为表面裂纹形成及断裂;而含Ni碳化硅复合材料的磨损机理为亚表面裂纹扩展导致表面局部剥落。 相似文献
59.
碳化硅(SiC)由于性能优异,已广泛应用于核技术领域.在辐照环境下,载能入射粒子可使材料中的原子偏离晶体格点位置,进而产生过饱和的空位、间隙原子、错位原子等点缺陷,这些缺陷将改变材料的热物性能,劣化材料的服役性能.因此,本文利用平衡分子动力学方法(Green-Kubo方法)采用Tersoff型势函数研究了点缺陷对立方碳化硅(β-SiC或3C-SiC)热传导性能的影响规律.研究过程中考虑的点缺陷包括:Si间隙原子(SiⅠ)、Si空位(SiⅤ)、Si错位原子(SiC)、C间隙原子(CⅠ)、C空位(CⅤ)和C错位原子(CSi).研究结果表明,热导率(λ)随点缺陷浓度(c)的增加而减小.在研究的点缺陷浓度范围(点缺陷与格点的比例范围为0.2%—1.6%),额外热阻率(ΔR-Rdefect-Rperfect,R=1/λ,Rdefect为含缺陷材料的热阻率,Rperfec... 相似文献
60.
碳化物抗氧化稳定性及其与基体的协同作用对Cr—Ni合金铸铁高温耐磨性的影响 总被引:3,自引:0,他引:3
通过改变Cr-Ni合金铸铁中共晶碳化物的抗氧化稳定性,在可控气氛高温磨料磨损试验机上研究了碳化物及其与基体的氧化协同性对合金耐高温磨料磨损能力的影响。结果表明:碳化物的抗氧化稳定性以及碳化物与基体的氧化大无畏同性对合金在大气气氛中的高温耐磨性起着重要的作用。在Cr-Ni合金铸铁中,碳化物在高温氧化气氛中将优先于合金基体发生氧化腐蚀,使合金的耐磨性得到极大损害,因此,使碳化物与合金基体在高温下保持协同的高温稳定性对合金的高温耐磨性非常有利。 相似文献