Synthesis of nanocrystalline titanium diboride and titanium diboride containing nanocomposites by solution-phase processing

Recent interest in the synthesis of nanocrystalline materials arises from predictions that they may combine the desired mechanical properties of strength and fracture toughness. Nanometer-sized particles can also be used as reinforcements in fine-scale composites. This dissertation reports the solution-phase synthesis of nanocrystalline titanium diboride by the reduction of titanium (IV) chloride by sodium borohydride. Subsequent thermal treatment results in the formation of nanocrystalline titanium diboride (particle sizes 10-100 nm). The processing conditions have been shown to influence the nanostructure of the resulting material. A novel size-morphology relationship is also reported.; The titanium diboride ultrafine particles are used as nano-scale reinforcements for metal-matrix composite materials. The methods for the synthesis of two composite nanostructures are reported. These involve a nanocrystallite jacketing strategy for the formation of intragranular composite materials, and a nanocrystallite interdispersion strategy for the formation of intergranular composite materials. Cu/TiB{dollar}sb2{dollar} nanoreinforced composites are prepared by the intragranular strategy, and Ti/TiB{dollar}sb2{dollar} nanoreinforced composites are prepared by the intergranular strategy. The synthesis of nanocrystalline copper and nanocrystalline TiN is also reported.; An appendix chapter discusses non-hydrolytic sol-gel processing using diacetone alcohol as a condensation agent. Diacetone alcohol and metal alkoxides undergo alcohol interchange reactions to give aldolate intermediates. The aldolate intermediates participate in a designed thermal decomposition reaction to form oxide phases without the addition of external water. The reaction between diacetone alcohol and metal alkoxides in the titanium, barium and mixed metal barium-titanium system are described and thermal decomposition to oxide phases is reported.