Nanostructure of wetting triple line in a Ag - Cu - Ti/Si₃N₄ reactive system

Nanometer scale structures around wetting triple lines were studied in a Ag-Cu-Ti/Si₃N₄ reactive system. Changes in the contact angle and radius of the molten metal on the substrate as a function of time were also measured in the system as macroscopic wetting behaviors. The macroscopic wetting behaviors showed two wetting stages and double layered reaction products consisting of upper Ti₅Si₃ and lower TiN layers were observed in both first and second stages. The reaction product always lay in front of the triple line defined as a triple junction of Ag - Cu - Ti alloy/Ti₅Si₃/atmosphere. At the front of the reaction product, a dominant phase changed from TiN in the first stage to Ti₅Si₃ in the second stage. It is considered that the structural change is one of the reasons why the macroscopic wetting behavior changed, and that the structural change was caused by a decrease of Ti activity as the reactive wetting progressed.