Thermal Radiation Spectroscopy Diagnosis for Temperature and Microstructure of Surfaces(<Special Issue>Emerging Fields in Thermal Engineering)

Surface microstates of real surfaces of solid materials change in industrial environments, or they are changed in industrial surface processes positively. A real time diagnosis technique for the surface microstates should be developed for the process control. We propose a diagnosis technique for temperature and microstructure of real surfaces on a basis of the hardware performance of our wide-spectral-range high-speed spectrophotometer system. With respect to the temperature, an active spectral pyrometer technique is adopted, in which the reflection of the surface is measured as well as the self-emission. With respect to the microstructure, an attention is paid to the interference and diffraction of radiation in a new real surface model. An experiment is made on a metal surface in a high-temperature air-oxidation process to verify the performance of this technique. Spectra of emission and reflection energy of radiation in a near-infrared through infrared region are measured at every 2 s, and analyzed. Time transition of the surface temperature of an order of 1100 K is estimated within an inaccuracy of 10 K. The average thickness d and rms roughness σ_1 of the surface film are estimated to be in regions of d=0.08〜3.8 μm and σ_1=0.01〜0.71 μm, respectively.