Effect of preheating on synthesis of tantalum nitride by self-propagating combustion

An experimental investigation of self-propagating high-temperature synthesis (SHS) of tantalum nitride (TaN) was conducted with tantalum compacts in nitrogen of 0.27–1.82 MPa. Effects of sample density, nitrogen pressure, and preheating temperature on the flame-front propagation velocity, combustion temperature, degree of conversion, and product composition were studied. Results showed that the SHS process of the tantalum/nitrogen reaction was characterized by the steady propagation of a planar combustion front, followed by a prolonged afterburning reaction. The flame-front velocity increased with nitrogen pressure, but decreased with sample density. Preheating the sample prior to ignition contributed higher combustion temperatures, thus leading to an increase in the conversion percentage. For the unpreheated samples, the conversion increased significantly with nitrogen pressure and reached around 80% at 1.82 MPa of N₂. With preheating temperatures between 150 and 300 °C, the conversion was increased by about 15% when compared with that without preheating. The nitride phase TaN was identified by XRD as the dominant composition in the combustion product.