Pressure infiltration in a reactive system: Packed SiC particulates infiltrated by pure silver with dissolved oxygen

Abstract

The role played by interfacial reactions on pressure infiltration of ceramic preforms by liquid metals is still controversial. Experimental results for pressure infiltration of packed SiC particulates by pure silver with dissolved oxygen in a concentration near saturation are presented. In this system, SiC reacts with the large amount of oxygen which dissolves liquid silver. The results show that the threshold pressure for initiation of infiltration is higher than in SiC/aluminum, and, thus, do not reproduce the large drop in the threshold pressure found when packed alumina particles are infiltrated with silver instead of aluminum. On the other hand, the rate at which the infiltrated height increases as a function of the pressure drop in the liquid metal, is similar to that observed in alumina/silver. These results can be understood in terms of low wetting at the silver/SiC interface, which can be a consequence of a higher contact angle and a reduction in the contact area promoted by the gas evolved in the oxidation of SiC (mainly CO 2 as indicated by mass spectrometry). This indicates that reactivity at the interface should not always be associated with an improvement in the wetting performance.