Direct nitridation of Al-alloys such as Al-Y, Al-Ca, and Al-Li was inv
estigated with particular emphasis on the alloy composition, reaction
temperature and reaction time. The alloys Al-2.3 wt%Li, Al-5.0 wt%Li a
nd Al-5.0 wt%Ca converted completely to AlN in very short soaking time
at 1000-degrees-C. For Al-1.0 wt%Li and Al-0.5 wt%Li conversion ratio
s at 1000-degrees-C for 5h were 28.2 and 12.6%, respectively. On the o
ther hand, no noticeable reaction was seen for Al-Y alloy and pure Al.
The product from Al-Ca alloy was difficult to crush, which seemed to
be a disadvantage for AlN powder synthesis. The reaction using Al-2.3
wt%Li alloy could be divided into three categories: namely, surface ni
tridation, volume nitridation and breakaway nitridation. In the surfac
e nitridation, the conversion ratio was very low, indicating the thick
ness of AlN layer was several tens of micron meters. In the volume nit
ridation the conversion ratio was in the extent of about 10%, and AlN
porous surface layer formed. In the breakaway nitridation, complete co
nversion to AlN was attained, and the product greatly expanded to show
no trace of the original form. The AlN product in the breakaway nitri
dation consisted of rod-like, plate-like and spherical grains. The siz
e increased with increasing reaction temperature.