Research of Heat Transfer Mechanisms in Glasses Using Modulation Polarimetry Technique

An optical method of registration of optical anisotropy (birefringence) in glasses is offered. The research of heat transfer processes was based on the occurrence and registration of the thermoelastic effect. This effect arises in the sample during radiative cooling. Change of heat balance and loss of internal energy are due to the thermal radiation. This leads to the formation of an inhomogeneous radiation, temperature, and deformation fields in the sample. The measurement method is based on the modulation of polarization of laser radiation transmitted through the anisotropic area and the definition of its anisotropy parameters by means of this modulation. Phase differences between orthogonal components of linearly polarized light are linearly dependent on a mechanical stress magnitude. The method allows obtaining several desired material parameters by measuring one stress s(t) value. Detectability of the modulation polarimetry technique was high and ensured the registration of the mechanical stresses during radiative cooling by a fraction of a degree. The mechanical stresses induced by the heat flow also have small values and are nonlinearly related to the temperature function. Time dependence of the stress s(t) in various coordinates of the sample demonstrates a complicated and variable dependence during the measurement. Components related to radiation, conductive and convective heat transfer mechanisms are obtained from the s(t) dependence. Relaxation parameters of these components are determined. The technique allows simulating high-temperature heating-cooling processes during the manufacture of materials and their technological application.