Investigation of microstructural evolution during nitridation of aluminium using simultaneous thermal analysis

Abstract Aluminium powders with different average particle sizes were synthesised into aluminium nitride in nitrogen atmosphere using simultaneous thermal analysis (TG/DTA). Experiments showed that reaction of Al powders started below the melting point of aluminium (660°C) in the solid–gas state, however most of the reaction took place above the melting point, in the liquid–gas state. Further conversion of Al to AlN took place up to 1200°C. The influence of particle size on the nitridation process was demonstrated by the use of different Al powders. Microstructural characterisation showed that two kinds of whisker were formed in the original Al powder bed, one with wool-like morphology and the other with needlelike morphology and sharp changes of direction.