Plastic deformation of silicon nitride/boron nitride fibrous monoliths

High-temperature compressive creep of unidirectional Si3N4/BN fibrous monol iths has been investigated at 1300-1500 degreesC in an inert atmosphere. Th e results were then compared to those for deformation of the Si3N4 and BN b ase materials. Plasticity of the fibrous monoliths was limited to very low stresses when the Si3N4 cells were oriented perpendicular to the stress axi s because the BN cell boundaries failed, followed by failure of the Si3N4 c ells. In the fibrous monolith in which cells were oriented parallel to the stress axis, steady-state deformation controlled by deformation of the Si3N 4 cells was achieved. (C) 2001 Elsevier Science Ltd. All rights reserved.