Thermal-radiation properties of zirconia when heated by laser radiation upto the temperature of high-rate vaporization

The results are given of the investigation of the normally hemispherical re flectivity of engineering ceramics of zirconia stabilized with calcium oxid e. Measurements are performed at the wavelengths of 0.488, 0.633, 1.15, and 3.39 mcm in air and vacuum in the process of rapid heating of the test sam ples From room temperature up to the temperature of high-rate vaporization by concentrated radiation of CO2 laser, and in the process of subsequent co oling after the heating radiation is switched off. The correlation between the measured thermal-radiation properties and the temperature field in the sample is analyzed for different values of density of the heating heat Aux. It is found that an optically infinite layer is realized in the melt in th e entire spectral range under conditions when a melt layer approximately 15 0 mcm thick is present on the sample surface. It is demonstrated that the o ptical properties of samples heated in air differ considerably from those o f samples heated in vacuum.