The effect of the temperature and the conditions of the reducing atmosphere
on the sintering behaviour of pressureless-sintered sol-gel alumina matrix
composites are studied by scanning electron microscopy (SEM), X-ray diffra
ction (XRD), and density measurements. The results are compared with those
obtained with fine commercial alumina/SiCw composites, and analyzed by mean
s of a thermodynamic study of the system.
A notable improvement in sintering behaviour and a more extensive grain gro
wth as the sintering temperature increases are determined for sol-gel alumi
na matrix samples.
The amount of melt observed in the microstructural analysis of sol-gel alum
ina matrix. materials is lower than that detected in fine alumina matrix sa
mples. The mechanisms of formation of the glassy phase due to the reducing
conditions of the atmosphere can operate in both series of samples, but the
higher content of impurities in fine alumina matrix materials produces a m
ore extensive liquid formation.
The presence of glassy phase, higher starting densities, and lower weight l
osses during sintering, contribute to the higher final densities of fine al
umina matrix composites. (C) 2000 Elsevier Science B.V, All rights reserved
.