Viscosity and thermal evolution of density and wetting angle of a commercial glaze by means of hot stage microscopy

In the present work we attempt to describe the results of the thermal behavior analysis of a commercial glaze obtained in a thermal microscope developed by the research group. At the same time, the density and the wetting angle of the glaze with an alumina surface was evaluated. Particularly the sintering temperature, the sphere, semi-sphere and fusion temperatures were also determined. These present characteristic viscosities. Afterward, by means of the de Vogel-Fulcher-Tammann equation, the viscosity as a function of temperature was estimated. In the first part the developed equipment is described together with the image analysis carried out for the in-situ cylindrical samples (2,5 mm of height and diameter). The thermal cycle was up to 1200 degrees C with a heating rate of 5 degrees C/min. The developed equipment presents the following characteristics: some problems with the temperature evaluation, it was slightly affected by air currents and difficulties for achieving an adequate parallelism. On the other hand, the potentialities of the equipment for development and study of the thermal behavior of glasses was established. (C) 2015 The Authors. Published by Elsevier Ltd.