超高真空下过渡金属Nb与Nb、Ta、Ti、W相互间粘附特性的试验研究

An Experimental Investigation on Adhesive Characteristic of Niobium in Contact with Niobium, Tantalum, Tungsten and Titanium under Ultra-High-Vacuum

本文在超高真空(10^(-7)Pa)条件下量测了Nb-Nb(110)、Nb-Ta(110)、Nb-W(110)及Nb-Ti4个粘附对的粘附力,并从接触表面形貌的角度求得了真实接触面积,进而得到了各粘附对间的粘附强度,结果与采用简单紧束缚自洽矩方法计算所得理论结果一致。研究表明,超高真空下过渡金属间存在一种相互作用——由两金属间共用电子引起的化学键,而且主要由其外层d电子态密度所决定。过渡金属Nb与Nb、Ta、W、Ti之间粘附强度的实测值介于每对原子0.2～2.0eV之间。当样品受热升温后,由于C、N、B、S等少量非金属杂质的表面偏析致使粘附强度明显降低。

The adhesive forces of Nb-Nb(110), Nb-Ta(110), Nb-W(110) and Nb-Ti have been measured in ultra-high-vacuum(10-7Pa). The real contact areas were calculated by a multiasperities contact dynamic model. The experimental results of their adhesive strength range from 0.2 to 2.0 eV/atom, which are in agreement with theoretical values calculated by a simple tight-binding self-consistent moment method. These facts indicate that across the interface there is an interaction, which arises from chemical bonding is caused by sharing of electrons between two transition metals and mainly controlled by the density of states of their d-electrons. The adhesive strength decreases greatly because of the segregations of C, N, B and S etc. nonmetallic impurities with elevating the temperature of the samples.