Densification of AlN using boron and carbon additives

The effects of boron and/or carbon on the densification of AlN were investigated. Sintering was promoted by adding the additives simultaneously. Thermo-chemical analysis indicated that a liquid phase composed of aluminum and boron were formed by the borothermal reduction of Al2O3 and AlN. Liquid phase sintering is believed to be the reason for the enhanced densification of AlN. The present investigation proposes a method to densify AlN using non-oxide sintering additives having high melting temperature (>2000 °C). The deterioration of AlN refractory is expected to be suppressed by preventing the formation of oxide grain boundary network which is vulnerable to corrosion caused by molten metal.