Improving the microstructure of Si 3N 4–TiN composites using various PEIs to disperse raw TiO 2 powder

Abstract

An in situ synthesis route was developed for the preparation of dense and homogenous Si 3N 4–TiN (5 vol% TiN) composites, with TiN grains formed from TiO 2 and AlN. The dispersion of TiN grains in the Si 3N 4 matrix using various polyethyleneimines (PEIs) as dispersing agents for raw TiO 2 powder was investigated by scanning electron microscopy (SEM). We found that the microstructure of Si 3N 4–TiN composites was improved with the aid of PEI to disperse TiO 2 particles in the mixture. It was critical to disperse original TiO 2 particles with the appropriate dispersant before the sintering process, because the size of TiN grains in the Si 3N 4–TiN composites was strongly dependent on the size of TiO 2 particles. PEI molecules modified the surface of TiO 2 particles and protected the TiO 2 particles in the slurry from aggregations. It was a practical and useful way to obtain the Si 3N 4–TiN composites with homogeneous microstructures without the alteration of the preparation procedure.