第一性原理研究掺杂过渡元素对碳化钨性能的影响

First Principle Study on Tungsten Carbide with Transition Elements

摘要:

碳化钨（WC）在高温动力装备上应用越来越多，WC的脆性和高密度限制了其更广泛的使用，金属原子掺杂是提高WC性能的一种方法。采用基于第一原理的广义梯度作为近似交换相关函数，研究了A0.25W0.75C (A为Ti、V、Cr、Mn、Co和Ni)的弹性、电子和x射线吸收特性。数值分析结果显示，Ti0.25W0.75C的B/G值(B为体模量，G为剪切模量)为1.869，改性为延性材料，其它均为脆性材料。掺杂25%的V、Co原子可使WC的脆性降低，掺杂25%的Cr、Mn、Ni原子脆性增大。掺杂后化合物的态密度分布范围减小，费米能级处数值增大，金属性增强，其中Mn0.25W0.75C金属性最强。参杂后X射线吸收谱蓝移，在软X射线波段存在吸收波段，其中Cr，V，Ti在15.74～22.25nm波段出现强吸收峰。研究结果有助于塑性低密度WC类化合物的实验和应用研究。

Abstract:

Tungsten carbide (WC) is increasingly used in high-temperature power equipment. The brittleness and high density of WC limit its wider use. Metal atom doping is a method to improve the performance of WC. The generalized gradient based on the first principle is used as the approximate exchange correlation function. The elastic, electron and X-ray absorption characteristics of A0.25W0.75C (A is Ti, V, Cr, Mn, Co and Ni) were studied. According to the numerical analysis, the B/G value of Ti0.25W0.75c (B is the volume modulus, G is the shear modulus) is 1.869, the material is the modified ductile material, and the others are brittle materials. The brittleness of WC decreases with the doping of 25% V and Co atoms, and brittleness increases with the doping of 25% Cr, Mn and Ni atoms. After doping, the range of density of state decreases, the value of Fermi level increases, and the metallicity of the compounds increases. Among them, Mn0.25W0.75C has the strongest metallicity. The X-ray absorption spectrum shifts blue after doping, and there is an absorption band in a soft X-ray band. The strong absorption peaks of doping Cr, V, and Ti appears in the 15.74～22.25 nm band. The results are helpful to the experimental and application study of WC compounds with plasticity and low density.