Measurement of Directional Spectral Emissivity at High Temperatures

Abstract

Emissivity is a significant parameter to describe the thermal radiation characteristics of the objects. It has important applications in thermal control of spacecrafts, highly efficient use of solar energy, buildings’ energy insulation and saving, and so on. Besides, more attention is attached to selective control of thermal emission by using micro-/nanostructures. In this work, to measure directional spectral emissivity, a measurement facility is developed which includes a sample heater with temperature control, a blackbody source, mirror assembly and a Fourier transform infrared spectrometer with different detectors. A sample heater is designed, and by using ceramic electric heaters, samples can be heated up to 1400 K at a high heating speed. And a new kind of water-cooled surface of the sample heating unit is designed to reduce the error by reducing the thermal radiation from surface of the heating unit so that measurement accuracy is improved. An electro-controlling rotating stage is adopted, and measuring angle is up to 60°. A SiC wafer is used as the reference to test the directional spectral emissivity measurement facility, and uncertainty is estimated.