A thermoanalytical study on the reaction of ZrC in air
Abstract
In this investigation the non-isothermal oxidation of zirconium carbide particles was studied using simultaneous thermal analysis (STA), mass spectrometry (MS) and in situ x-ray diffraction (XRD). The thermoanalytical analysis was carried out in the temperature range of 25 - 1000 °C with heating rates of 2, 5, 10, 20 and 30 °C min-1. CO2 evolution during oxidation was detected by MS for the lower heating rates 2 and 10 °C min-1. Theoretical values were adjusted according to the experimental values obtained in the thermogravimetric analysis (TGA). For the evaluation of the kinetic parameters a kinetic model based on diffusion-controlled Jander's equation is used. The activation energies were estimated 200 and 208 kJ mol-1 for the first step, 315 and 333 kJ mol-1 for the second step of the reaction as a function of the heating rate. Oxide growth was investigated using XRD in the temperature range of 25 - 1200 °C and revealed the formation of monoclinic and orthorhombic ZrO2. A particle characterization was carried out using scanning electron microscope imaging (SEM), the specific surface area was determined according to the BET theory of adsorption and the particle size distribution was measured by laser diffraction. The heat of combustion of the sample was determined in a bomb calorimeter.
