Structural Phase Transformations in Titanium Powders during Mechanosynthesis in Liquid Hydrocarbons

A number of nanocomposite titanium carbohydrides are prepared via high-energy mechanosynthesis in liquid hydrocarbons (n-heptane and toluene) using a planetary ball mill. X-ray diffraction analysis reveals that at the initial stages of mechanochemical treatment titanium powder consists of a mixture of fcc and hcp phases with different contents of carbon and hydrogen. The composites become monophasic after 15 h of mechanosynthesis in both heptane and toluene as a result of the hcp -> fcc structural phase transition. Differential scanning calorimetry and thermal desorption are used to perform a comparative analysis of thermally-induced hydrogen desorption in powder samples prepared in heptane and toluene with different synthesis time. Experimental evidence shows that thermally stable titanium carbohydrides and carbides can be obtained at prolonged synthesis time, with their chemical composition and rate of formation depending on the medium used in mechanosynthesis.