DETAILED KINETICS OF TITANIUM NITRIDE SYNTHESIS

A thermogravimetric analyzer is used to study the synthesis of TiN fro m Ti powder over a wide range of temperature, conversion and heating r ate, and for two Ti precursor powders with different morphologies. Con versions to TiN up to 99% are obtained with negligible oxygen contamin ation. Nonisothermal initial rate and isothermal data are used in a no nlinear least-squares minimization to determine the most appropriate r ate law. The logarithmic rate law offers an excellent agreement betwee n the experimental and calculated conversions to TiN and can predict a fter-burning, which is an important experimentally observed phenomenon . Due to the form of the logarithmic rate law, the observed activation energy is a function of effective particle size, extent of conversion , and temperature even when the intrinsic activation energy remains co nstant. This aspect explains discrepancies among activation energies o btained in previous studies. The frequently used sedimentation particl e size is a poor measure of the powder reactivity. The BET surface are a indicates the powder reactivity much better.