Low Temperature Chemical Routes to Synthesis and Processing of TitaniumAluminides Intermetallics

摘要

The goal of this project was to synthesize gamma-TiAl using low temperaturechemical processing techniques. Four different chemical processes based on the electropositive and reducing power of lithium were used to investigate their potential for the synthesis of the aluminides. The reactions conducted in polar solvents resulted in the formation of TiAl along with TiC as a secondary phase. Among the various polar solvents attempted, THF appears to be the most suitable solvent since the carbide phase was very much reduced. It also appears from these preliminary studies that subjecting the precursors to pre-treatment in H2 makes them stable towards oxidation. Washing the preheated powders in water at this stage helps in minimizing and even elimination to a large extent impurity phases which may be related to lithium. The uses of inert solvents were found to be unsuitable due to the formation of insoluble adducts that lead to the generation of the formation of unknown phases in addition to TiC. The presence of TiC as an impurity is related to the coordination of TiCl with the solvent.