EMISSIVITY MODEL OF ALUMINUM 6063 WITH AN OXIDE FILM AT A WAVELENGTH OF 1.5 mu m IN THE TEMPERATURE RANGE 800-910 K

摘要

This paper models the variation of emissivity with temperature or/and surface oxidation. The emissivity measurements were done at a wavelength of 1.5 mu m over the temperature range from 800 to 910 K. The sample was heated to a certain temperature in air and kept at that temperature for approximately 6 h during the experiment. The radiation was received by an InGaAs detector. The surface temperature of samples was measured by two thermocouples, which were symmetrically welded on the surface of the samples. The average of their readings was regarded as the true temperature. Eleven models were used to investigate the variation of emissivity with growth of an oxide layer on the sample surface at a certain temperature. The effect of the number of parameters used in the models on the fitting quality was evaluated. The fitting quality of the emissivity models with the same number of parameters was compared. The variation of emissivity with temperature was studied at a certain thickness of the oxide film. Three approximate models were used to explore the variation in emissivity with temperature and thickness of the oxide layer, with two of them being found to accurately reproduce the emissivity. The strong oscillations of emissivity were observed during the initial heating period, which were affirmed to arise from the interference effect between the two radiations stemming from the oxide film and coming from the substrate.