Direct Nitridation of Aluminum Compacts at Low Temperature High Nitrogen Pressure

摘要

Direct nitridation of Al powder compactswith relative density of about 65percent was performedat 580 deg C, about 80 deg C below the melting pointof Al, and under nitrogen pressures of 4 and 7 MPa.In all eases, almost 100 percent nitridation wasachieved. The structure of the AlN products wasdrastically affected by the reaction conditions. Inhigh nitrogen pressure, the nitridation proceededrapidly, and the generated AlN exhibited a three-layerstructure, in which the inner layer was densified, andthe outer layers were porous with small particles ofa few #mu# m or less. It is considered that thisdensification and particle growth were caused by largeheat of nitridation reaction. However, in the caseof low nitrogen pressure, such phenomenon was notobserved. The nitriding at low temperature and thepre-heating in vacuum caused higher conversion ratiobecause of decreasing surface oxide or nitride layer.