Direct Nitridation of Aluminum Compacts in Low Temperature and Pressured Nitrogen Atmosphere

Complete nitridation of aluminum compacts was achieved at temperatures from 580 to 600°C (lower than the melting point of aluminum) and under a pressured nitrogen atmosphere of 1 and 4MPa. The structure of the generated aluminum nitride compact was strongly dependent of reaction condition. In the case of preheating in low vacuum or reaction under a low nitrogen pressure, a rather uniform structure was generated. On the other hand, in the case preheating in high vacuum and reaction under a high nitrogen pressure, the generated structure consisted of three layers: two dense outer layers and a porous inner layer. Melting of aluminum was not observed during nitridation when the uniform structure was generated, which suggests that the nitridation proceeded as a solid-gas reaction.