Processing of a novel multilayered silicon nitride

A new type of silicon nitride with a layered structure of alternating dense and porous layers was obtained by addition of beta-Si3N4 whiskers to the porous layers, The materials consisted of dense layers 60 mu m thick and porous layers 40 mu m thick with a final porosity of about 30%, Highly anisotropic shrinkage behavior was observed during sintering, A large addition of whiskers to the porous layers resulted in layers with well-oriented and tightly tangled elongated grains, where porosity is represented by anisotropic shaped pores.