Thermal Properties of Ecological Phosphate and Silicate Glasses1

摘要

The present work deals with ecological phosphate and silicate glasses that belong to the oxide systems: Li2O-MgO-P2O5, Li2O-CaO-P2O5, Li2O-MgO-P2O5-Fe2O3; Li2O-CaO-P2O5-Fe2O3 and SiO2-R2O-R'O (R = Na, K; R' = Mg, Ca), the last system contains certain amounts of Zr02, ZnO, Ti02. These ecological glasses do not contain toxic substances as BaO, PbO, As2O3, As2O5, fluorine, CdS, CdSe and they have applications as regards the retention and counteracting action of the harmful compounds resulted from the nuclear plants. The replacement of MgO by CaO leads to an insignificant increasing of the thermal expansion index and a slight decreasing of the characteristic temperatures, except the softening point where the effect is opposite. Adding of iron oxide in the phosphate glass composition causes the increasing of characteristic temperatures and the decreasing of thermal expansion index, both in MgO and CaO-containing phosphate glasses. The ecological silicate glasses are used as opal glasses free of fluorine as well as for lead-free crystal glass (CFP) where BaO and PbO are replaced by non-toxic oxides as K2O, MgO, ZrO2, and TiO2. The paper presents different glass compositions and the technological parameters to prepare the ecological glass samples. Both ecological phosphate and silicate glasses have been characterized as regards the characteristic temperatures (vitreous transition point, low and high annealing points, softening point) and the thermal expansion coefficient. This study presents the changes of the thermal parameters when CaO replaces MgO in phosphate glass samples and the role of iron oxide in the vitreous network. In the case of silicate glasses, the viscosity and wetting angle dependency of temperature are presented. The elemental analysis of the ecological glasses was made by XPS (X-ray photoelectron spectroscopy) which also put in evidence the iron species from the vitreous network.