SINTERING ANISOTROPY IN SLIP-CAST SIC-WHISKER SI3N4-POWDER COMPACTS/

Sintering anisotropy in slip-cast SiC-whisker/Si3N4-powder compacts wa s studied at 1750-degrees-C in 0.1 MPa N2 or at 1825-degrees-C in 1.0 MPa N2. It was shown that whiskers oriented parallel to the mould surf ace and nearly 1.5-dimensionally along the slip flow direction when th e whisker content was 1 0 wt%. Linear shrinkage was largest perpendicu lar to the mould surface and smallest perpendicular to the whisker ali gnment. It was shown that the retardation of densification by whiskers is due to the formation of a rigid network along the whisker alignmen t, which is in accordance with percolation theory. The addition of up to 20 wt% whisker did not affect sintering kinetics but lowered sinter ability by 2-dimensional alignment of the whiskers. The anisotropy in fracture toughness is related to the orientation of the whiskers.