Abstract:

SiC is widely used in the field of refractories because of its excellent mechanical properties.The synthesis of SiC powder by catalytic reaction has a bright future.However,it is difficult to separate the catalysts,which act as impurities.While the influence of catalysts on the properties of SiC has not been studied.Therefore,the first-principles plane-wave pseudopotential method was used to study the catalysts (Fe,Co and Ni) and the doping concentration (1.56%,3.125%,6.25%,and 12.5%,by atom) on the thermodynamic properties,the mechanical properties and the density of states (DOS) of 3C-SiC.The results show that:(1)the structure stability of 3C-SiC crystals doped with Fe,Co and Ni atoms decreases in the order of Fe-SiC,Co-SiC and Ni-SiC.(2)When the Fe doping concentration is 1.56%,compared with the undoped 3C-SiC crystal,the changes of the elasticity modulus,the shear modulus and the Young’s modulus of Fe-SiC are 0.023%,3.57% and 2.77%,and the hardness and the brittleness do not change obviously,and DOS diagram is basically unchanged,which shows that low concentration Fe doping has negligible effect on the mechanical properties of 3C-SiC system.Therefore,SiC powder prepared by catalytic reaction method with Fe as the catalyst can be used in the field of refractories in theory.

Key words: silicon carbide, Fe,Co and Ni, catalytic reaction method, first-principles calculation, mechanical properties

摘要：

碳化硅以其优异的性能被广泛应用于耐火材料领域。催化反应法合成碳化硅粉体的前景广阔,但加入的催化剂作为杂质却难以分离,而催化剂对产物碳化硅性能的影响尚缺乏研究。采用第一性原理平面波赝势法研究了催化剂种类(Fe、Co及Ni)和元素掺杂浓度(x,1.56%、3.125%、6.25%、12.5%)对3C-SiC热力学性质、力学性能、电子态密度等的影响。结果表明:1)Fe、Co及Ni掺杂3C-SiC晶体的结构稳定性由大到小依次为Fe-SiC、Co-SiC、Ni-SiC;2)当Fe元素掺杂浓度为1.56%(x)时,与未掺杂3C-SiC晶体相比,Fe-SiC体系体弹性模量值变化量为0.023%,剪切模量和杨氏模量变化量为3.57%与2.77%,硬度值和脆韧性基本未发生明显变化,态密度图也基本不变,说明低浓度Fe元素掺杂基本不影响3C-SiC体系的力学性能。因此,用Fe作催化剂,采用催化反应法制备的碳化硅粉体理论上是可以应用于耐火材料领域的。

关键词: 碳化硅, Fe、Co及Ni, 催化反应法, 第一性原理计算, 力学性能