Improving the Interfacial Reaction Between Cristobalite Silica from Rice Husk and Al–Mg–Si by CVD-Si3N4 Deposition

Abstract

Wettability of silica and coated silica by Al–Mg–Si alloys has been determined by the sessile-drop method. Great deal of effort was devoted to the characterization of metal/particulate interfaces. It has been offered that Mg in the Al–Mg–Si alloy vaporizes and reacts with CVD deposited Si3N4 on rice husk ash (silica) and forms Mg3N2 which is in contact with molten aluminum. By precipitation of Mg3N2 particles as an intermediate phase in the molten Al–Mg–Si the fraction of AIN is formed. Formation of AlN induces wetting between Al alloy and silica. Contact angle, work of adhesion and surface tension between the droplet and substrates have been measured for silica–Al–Mg–Si and Si3N4 coated silica–Al–Mg–Si systems. Results show that at 1200 °C, in nitrogen atmosphere with high Mg content in alloy, the minimum contact angles obtained in RHA and Si3N4-coated RHA substrates are 72° and 35°, respectively, revealing the beneficial effect of modifying the surface of RHA with Si3N4 coating.