Ti、V、Ni、Mo对CVD金刚石涂层形核影响

基于密度泛函理论,计算分析了CH₃基团在含有过渡金属元素Ti、V、Ni、Mo的孕镶金刚石颗粒硬质合金基底表面的吸附能、Mulliken电荷分布、电荷密度差和态密度(density of states, DOS)等一系列性质,研究Ti、V、Ni、Mo对孕镶金刚石颗粒硬质合金基底化学气相沉积(chemical vapor deposition, CVD)金刚石涂层形核阶段的影响及其作用机理。计算结果表明:与CH₃基团在WC表面及金刚石表面的吸附相比,Ti、V、Ni、Mo与C原子间有较强的弱相互作用,这使得其对CH₃基团有更强的吸附能力(其中Ti>V>Mo>Ni);吸附能力大小与各原子的价电子结构相关,含有Ti元素的表面对CH₃的吸附最稳定;CH₃基团与Ni原子间更易发生电荷的转移形成共价键,Mo有利于促进CH₃基团的脱氢反应;形核阶段适当添加Ti、V、Ni、Mo这几种过渡金属元素将有利于增加形核密度,改善CVD金刚石膜基界面结合强度。

Effect of Ti,V, Ni and Mo on Nucleation of CVD Diamond Coating

To better understand the influence mechanism of transition metal elements (Ti, V, Ni, Mo) on the nucleation of chemical vapor deposition (CVD) diamond coating, the intrinsic mechanism of the CH₃ adsorption on impregnated diamond cemented carbides through geometry, interaction energy, Mulliken charge distribution, visualization of the interactions, charge density difference and density of state (DOS) were investigated theoretically. All the calculations were performed by density functional theory. The calculated results indicate that diamond surface doped with Ti/V/Ni/Mo, rather than pure diamond surface, exhibits stronger interactions. The adsorption capacity is related to the valence electron structure of each atom, and the surface doped with Ti has the most stable adsorption capacity. The charge transfer between CH₃ and Ni is more easier to form covalent bond, Mo is beneficial to promote the dehydrogenation reaction of CH₃. Ti, V, Ni and Mo are conducive to increasing the nucleation density and improving the strength of CVD diamond coating.