Reactions between SiC and sintering aids in Si3N4/SiC nanocomposites and their consequences

Si3N4/SiC nanocomposites were fabricated by hot-pressing mixtures of submicron alpha -Si3N4, SiC nanopowders with sintering aids. XRD, TEM and SEM were used to study the effects of SiC additions on sintering behavior and microstructure of Si3N4; EDAX was employed to investigate the composition of interfaces. The results showed that nano-SiC addition led to loss and compositional modification of intergranular phases and limited the densification and phase transformation of Si3N4 Reactions between sintering aids and nano-SiC are thermodynamically calculated and the temperature and N-2 pressure dependence of the reactions are also theoretically analyzed. Influences of these reactions on the effects of SIC additions are discussed. (C) 2001 Elsevier Science Ltd and Techna S.r.l. All rights reserved.