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91.
A new layered carbide, [Zr0.72(3)Y0.28(3)]Al4C4, has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and energy dispersive X-ray spectroscopy (EDX). The atom ratios [Zr:Y] were determined by EDX, and the initial structure model was derived by the direct methods, and further refined by Rietveld method. The crystal is trigonal (space group , Z=1) with lattice dimensions of a=0.333990(5) nm, c=1.09942(1) nm and V=0.106209(2) nm3. This compound shows an intergrowth structure with [Zr0.72Y0.28C2] thin slabs separated by Al4C3-type [Al4C4] layers. It is a new member with l=1 and m=1 of the homologous series, the general formula of which is (MC)l(T4C3)m (l=1, 2 and 3, m=1 and 2, M=Zr, Y and Hf, T=Al, Si and Ge). 相似文献
92.
93.
用高温X射线衍射装置对以B4C为供硼剂、以Y2O3为催WC-20Co硬质合金渗硼表面进行了从室温到1300℃连续升温渗硼过程的XRD动态物相分析,探讨了稀土-硼共渗机制。结果表明,在真空烧结升温期间,从WC-Co压坯表面B4C分解出来的活性硼原子除在压坯表面上形成硼化物外,所形成的高浓度活性硼原子还向压坯内钴中扩散形成三元含硼相W2Co21B6化合物。同单独渗硼相比,钇在稀土-硼共渗过程中有拓宽渗硼温度范围、促进B4C脱碳分解和活性硼原子向压坯内扩散等催化渗硼作用。 相似文献
94.
Keita Sugiura Hideto Yoshida Koichiro Fukuda 《Journal of solid state chemistry》2008,181(10):2864-2868
Two types of new ternary carbides, Zr2Al4C5 and Zr3Al4C6, have been synthesized and characterized by X-ray powder diffraction. The crystal structures were refined from laboratory X-ray powder diffraction data (CuKα1) using the Rietveld method. These carbides form a homologous series with the general formula (ZrC)mAl4C3 (m=2 and 3). The crystal structures can be regarded as intergrowth structures where the Al4C3-type [Al4C4] layers are the same, while the NaCl-type [ZrmCm+1] layers increase in thickness with increasing m value. The new carbides are most probably the end members of continuous solid-solutions (ZrC)m[Al4−xSix]C3 with 0?x?0.44. 相似文献
95.
Dr. Han Zhang Dr. Xiaohui Yang Prof. Huijuan Zhang Prof. Jinling Ma Prof. Zhengyong Huang Prof. Jian Li Prof. Yu Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(16):5074-5090
With the strengths of zero carbon emission and high gravimetric energy density, hydrogen energy is recognized as a primary choice for future energy supply. Electrochemical water splitting provides a promising strategy for effective and sustainable hydrogen production through renewable electricity, and one of the immediate challenges toward its large-scale application is the availability of low-cost and efficient electrocatalysts for the hydrogen evolution reaction (HER). Given the enormous efforts in the exploration of potential transition-metal carbide (TMC) electrocatalysts, this review aims to summarize the recent advances in synthetic methods and optimization strategies of TMC electrocatalysts. Additionally, the perspectives for the development of novel efficient TMC-based catalysts are also proposed. 相似文献
96.
镍基粉末高温合金FGH95的组织和性能 总被引:6,自引:0,他引:6
论文讨论了FGH95氩气雾化粉末颗粒的凝固组织,合金相组成,表面化学成分;粉末经过热等静压后的显微组织与相组成,原颗粒边界碳化物的本质和形成机制,热等静压坯再经热挤压后合金组织的改善,以及用改进的最终热处理使合金获得良好的显微组织,以提高合金的高温的拉伸,持久断裂,低周疲劳性能。 相似文献
97.
采用Gleeble 1500对WC-12Co硬质合金进行不同温度和应力场的压缩疲劳实验,测量疲劳前后合金硬度的变化,通过扫描电镜(SEM)、透射电镜(TEM)等手段观察其组织结构的变化并分析其变形失效机理.结果表明:随着实验温度与加载载荷的升高,WC-12Co合金硬度呈下降趋势,WC晶粒发生圆化,WC晶粒骨架的完整程度下降.WC-12Co合金的疲劳变形失效机理为:在较低变形温度和变形载荷下,塑性变形由WC相中的位错滑移和黏结相马氏体转变所提供,随着变形温度和变形载荷的升高,塑性变形则通过硬质相的层错运动和WC/WC的界面滑动形成黏结相条带来实现. 相似文献
98.
抑制硬质合金烧结中WC晶粒长大的研究 总被引:6,自引:0,他引:6
该文选择了VC和Cr3C2作为WC—Co硬质合金晶粒长大抑制剂,研究两种抑制剂加入量对合金组织、WC晶粒度和性能的影响以及抑制晶粒长大的机理.研究结果表明,VC和Cr3C2的加入十分有效地抑制了基体合金WC晶粒的长大,合金中的WC晶粒度随抑制剂加入量的增加而减小,可达到最小的WC晶粒度接近100nm,合金的硬度随抑制剂加入量增加而增加,但强度则下降。同时也会增加孔隙度,结果增加了脆性,降低了合金的强度.VC的有害影响比Cr3C2更大。 相似文献
99.
E. E. Goncharov I. I. Latyshev G. G. Ryabova 《Isotopes in environmental and health studies》2013,49(6):243-244
Compared are some of the properties of the solid state track detectors (SSTD) on the basis of nitrogen-free cellulose derivatives (cellulose acetate, triacetate and acetobutyrate), cellulose nitrate (LR-115, CN-85) and a CR-39 track detector. The optimum composition of the cellulose acetobutyrate has been established which will ensure the best mechanical properties. A simple device has been used to measure the α detection effectiveness over the energy range from 0 to 1.2 MeV of the cellulose acetobutyrate detectors in an electric field or under UV radiation or after catalytic etching. The proton detection effectiveness of the CN-85 detector has been measured. Also presented are the track autoradiograms of the distribution of B, Li, N and 3He in silicon, silicon carbide and steel. 相似文献
100.
The structural, electronic, and elastic properties of three mixed transition metal carbonitrides TiNxC1−x, ZrNxC1−x, and HfNxC1−x (0 ≤ x ≤ 1) with the rock-salt structure were calculated at ambient and elevated up to 50 GPa hydrostatic pressures in the framework of the density functional theory methods. The lattice constants, densities, and bulk moduli of the considered compounds were shown to behave as linear functions of the nitrogen concentration x. The obtained linear dependencies of all these parameters allow for getting their estimates at any value of x in the range from 0 to 1. Gradual enhancement of the ionicity of the chemical bonds with gradual replacement of carbon by nitrogen was demonstrated by calculating the bond orders and electron density difference distributions. 相似文献