Synthesis of Magnesium Aluminum Oxynitride by Carbothermal Reduction and Nitridation Process

Abstract

Carbothermal reduction and nitridation (CRN) process was utilized to prepare magnesium aluminum oxynitride (MgAlON) and the influence of reaction variables, such as heating temperature, soaking time and the source of carbon, on the formation of MgAlON was investigated. In addition, the density of samples prepared under different route was compared. The results show that volatile gases, Mg (g) in chief, lead to variation in lattice constant and chemical composition at high temperature, and decrease the sintering effect. Since high temperature and low CO partial pressure are favorable to the CRN reaction in view of thermodynamic reason and high temperature also favors the transport of gases, the rate of CRN reaction increases with the increasing temperature. Due to the difference in reactivity between graphite and carbon black, CRN reaction may be the rate controlling step when graphite is used and solid solution of AIN may be the controlling step when carbon black is utilized. CRN reaction can increase surface energy of reaction materials and results in higher final density. However, gases in the system retard the densification effect.