A new process to grow beta-Si3N4 whiskers using thermal decomposition and closed pores

Abstract

In this study, a novel and interesting method to grow beta-Si3N4 whiskers was developed using thermal decomposition Si3N4 and large pores introduced intentionally during liquid phase sintering. The pore size, pore vol%, pore morphology and nitrogen pressure were chosen as experimental variables to find proper conditions for growing whiskers. In this experiment, commercial alpha-Si3N4, Al2O3 and Y2O3 were selected as starting materials, and polymer beads with average diameters of 100 and 200 mu m were used as pore formers to make intentional pores in the sintered sample. A polyvinyl film was also used to make a film type of pore. beta-Si3N4 whiskers grew well on the inside of pores in the case of a low vol% of pores, 14 and 27 vol% or closed pores of a film shape, but not for a high vol% of pore, 39 and 50 vol% or open pores of a film shape. The variation of pore size, pore morphology and nitrogen pressure did not have any influence on whisker growth.