Insights into the adsorption and interfacial products improving the wetting of the Ag-Ti/graphite and Cu-Ti/graphite systems: A first-principles calculation

Introducing actives into brazing alloys is a common way to improve their wettability. Typical interfacial be-haviors of added actives involve adsorbing at the liquid/solid interface and forming interfacial products. However, the mechanisms of the actives improving wettability are controversial. Here, first-principles calcula-tions are employed to investigate the Ti-adsorption and reacted interfaces in universal Ag/graphite and Cu/ graphite systems. For the clean interfaces, Ag (111)/graphite (0001) and Cu (111)/graphite (0001), quite low work of adhesion closing to 0 is obtained. The interfacial bonding is not enhanced even though the Ti atoms are introduced. However, as to the reacted interfaces, the work of adhesion of Ag (111)/TiC (111) and Cu (111)/TiC (111) interface reach to 3.637 J/m2 and 5.399 J/m2 , respectively. Additionally, the adoption of Ti enhances the interfacial bonding with the hybridizations of Ti -d and C -p at --2eV, and Ti -p and C -p at --3eV. Therefore, the addition of Ti is more effective in improving the wettability of Ag and Cu on graphite when it reacts with graphite to form TiC, as opposed to simply adsorbing at the melt/graphite interfaces. Furthermore, the adsorption of Ti at the melt/TiC interfaces enhances the wettability.