An FT-IR based instrument for measuring spectral emittance of material at high temperature

Abstract

For surfaces at high temperature the emitted spectrum of electromagnetic radiation is the most convenient probe of temperature, if the spectral emittance (emissivity) of the sample at that temperature is known. A bench top instrument has been developed that, when coupled to a Fourier transform infrared (FT-IR) spectrometer, allows for the measurements of emission, directional-hemispherical reflection, and directional-hemispherical transmission from materials at elevated temperatures. From these radiative property measurements, the temperature at the measurement point and the spectral emittance of the surface can both be obtained. The method has been applied to a variety of materials (i.e., metals, dielectrics, coal slags) with a variety of surface properties (i.e., partially transmitting and nontransmitting; specularly reflecting and diffusely reflecting) at temperatures up to 2226 K. The article describes the technique, presents the results for several materials, and compares results with those for other investigators.