Numerical simulation of concentrated laser radiation heating of refractory oxides

The behaviour of refractory oxides under intense laser radiation heating and subsequent cooling after removal of the heating radiation has been studied numerically. A mathematical model has been developed for one-dimensional transient conditions which included combined radiation and conduction heat transfer in semitransparent nonscattering material, a generalised phase change model with the presence of a two-phase region, overheating and undercooling, arbitrary nonlinear boundary conditions at the front and rear surfaces of the sample, general dependence of all thermophysical properties on temperature, and dependence of thermal radiative properties on temperature and wavelength. Numerical calculation was performed for alumina as a reference material. The formation of a broad two-phase region was discovered during cooling of the molten part of the sample. The results of numerical calculation can be applied to understanding the behaviour of brightness temperatures at the solidification plateau, for obtaining data on temperature distribution in the material, for the investigation of optical and thermophysical properties, and for experimental estimation of the true melting point of the material from the results of brightness temperature measurements.