High-temperature metal oxide spectral emissivities for pyrometry applications

A study was conducted to determine the functional wavelength dependence of the emissivities of magnesium oxide, titanium dioxide, zirconium dioxide, and iron (III) oxide at elevated temperatures within the visible and near-infrared regions of the spectrum. A highly controlled, optically thin, inert environment created in a shock tube was used for these measurements to limit contributions from impurities and other effects, such as multiple scattering. A discussion on the optical depth effects for the materials reported was provided, based upon the findings of earlier studies. Particles were injected approximately 0.5m upstream of the endwall before the diaphragm bursting. The suspended particles were heated to the spatially uniform test temperature behind the reflected shock. The shock velocity was obtained by measuring the time of arrival of the shock at several axial locations using pressure transducers.