Wettability of Hot-pressed Silicon Nitride Materials by Liquid Copper

The wettability of six different types of hot-pressed silicon nitride by liquid copper was evaluated at a temperature of 1373 K by the sessile drop method. The selected materials were such as to cover a wide range of additives (Y2O3, MgO, ZrO2 and Al2O3) and hot-pressing conditions. The experimental results were related to the microstructures of the substrates, and the equilibrium contact angle values were correlated with the physicochemical characteristics of the materials and with the mechanical status of their surfaces. A mean contact angle value of 135° was found for five out of the six types, leading to a value of 380 mJ m-2 for the work of adhesion. The sixth type exhibited a contact angle value of 144° and a value of 250 mJ m-2 for the work of adhesion. The different results obtained for the various types of substrate were ascribed to the effects induced by the roughness of the substrates, whereas the different ways of producing the materials and the oxide content did not markedly affect the materials' wettability.