Fabrication of mullite ceramics by rotary forging and pressureless sintering

Mullite ceramics were fabricated from boehmite/silica diphasic gels using a rotary forging compaction technique and pressureless sintering. Almost ful ly dense mullite samples were obtained after sintering at 1350 degrees C fo r 2 h. The microstructure of sintered samples comprised fine (average size <1 mu m), equiaxed grains. The samples showed superior sintering behaviour in comparison to those fabricated using conventional uniaxial and isostatic pressing. Powder compaction by rotary forging is thought to generate visco us deformation of the contact points increasing the interparticle contact a rea as well as increasing the packing density by breaking clo,vn hard agglo merates more effectively with concomitant rearrangement of the primary powd er particles, thus promoting-greater densification at relatively low temper atures.