Reactive wetting of Ni–Si alloys on graphite substrates: effects of Si and Ni
In recent years, the reactive wetting of Ni–Si on graphite has attracted increasing attention. However, most attention has been focused on the effect of Si on the wetting behavior of Ni–Si/C systems. In this work, the wetting process of Ni–Si alloys with different Si content (20, 28, 35, 45 and 55 wt%) on graphite substrates has been investigated at 1523 K in a high vacuum using a modified sessile drop method. The threshold activity of Si in liquid to form SiC at 1523 K can be calculated to be 0.0173, corresponding to a Si content of 33 at% (19 wt%). In addition, a minimum equilibrium contact angle of 20° can be observed in the Ni–45 wt% Si/C system. The adsorption energies of Si at the interface and at the surface of the Ni metal are 5.36 kJ mol−1 and −20.9 kJ mol−1, respectively; whereas, the adsorption energies of Ni at the interface and at the surface of the Si metal are −5.38 kJ mol−1 and 68.9 kJ mol−1, respectively. Moreover, the effects of Si and Ni on the change in the equilibrium contact angle have been evaluated in terms of the solid–liquid interfacial energy and the surface energy of the liquid alloy.