Secrets of high thermal emission of transition metal disilicides TMSi2 (TM = Ta, Mo)

TMSi2 (TM = Ta, Mo) are extensively used as thermal emissivity agents in high emission coatings due to their well-known "high" emissivity in infrared range. However, there is a paucity of the high temperature (HT) emissivity property of these two silicides. Moreover, room temperature (RT) spectrometer measurements have demonstrated that the emittance in infrared range of two silicides was considerably low. Therefore, providing critical HT data and satisfactory elucidation on the emission incompatibility of TMSi2 is eagerly needed. In this contribution, combining first principles calculations and Drude model, the reflectance spectra of TMSi2 were predicted at both RT and HT. Consistent with spectrometer measurements, the intrinsic emittance of silicides was relatively low in the entire investigated temperatures. To explain the incompatible emission behavior, two simplified models including the majority of high emissivity coating, SiO2, were proposed. Intriguingly, with SiO2 considered in simulations, no matter covered on the surface or blended in the composites, the emittance of the TMSi2 enhanced significantly. Our theoretical results demonstrate the non-negligible significance of oxides on the high temperature performance of silicides and provide the guidelines for improving the emission performance of silicides and searching for potential high emissivity agents. (C) 2021 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.