Mechano-chemical synthesis of titanium silicide using allyl hydrido polycarbosilane as the chemical binder

This project attempts to develop a technology to produce bulky, nanocrystalline ceramic products with superior mechanical behavior. The research focuses on two issues: (a) use of mechanical alloying to produce nanostructured powder optimally and (b) preservation of fine scale structure by low temperature chemical consolidation using an appropriate chemical binder. The fusion of mechanical alloying and chemical binding to produce nanocrystalline ceramic products in bulk form makes this project distinctive.; Titanium silicide (Ti₅Si₃) in powder form was chosen as the candidate material as it showed better tendency for amorphization when subjected to mechanical alloying. The optimum milling conditions to obtain the smallest crystallite size with high hardness values were established by conducting experiments based on the statistical design of experiments approach. The significance of the milling variables, namely, milling speed, ball to powder ratio and milling time, was examined with respect to the average microhardness of the compacts. The milled powder was mixed with a chemical binder, Allyl Hydrido Polycarbosilane (AHPCS), in different mass percentages to enable the binder to form a film over the nanostructured powder particles. This holds the powder particles together when compacted. The chemical binder forms a hard amorphous interface between the powder particles when cured and fired at lower temperatures. This preserves the fine grain size and structure of the final product. The optimum combination of the milling variables and the optimum percentage of the binder were determined. Compression test was performed on the sample prepared with the optimum variables to determine the compressive strength of the product. The results were analyzed and suggestions for further research to enhance the mechanical properties of the products were given.