Viscosities of CaO-SiO_2-Al_2O_3-(R_2O or RO) Melts

摘要

The effect of adding R_2O (R = Li, Na and K) or RO (R = Ba, Mg) on the viscosities of CaO-SiO_2-Al_2O_3 (CaO/SiO_2=0.67, 1.00 or 1.22, Al_2O_3=20 mass%) melts has been measured by rotating crucible viscometer. In addition, structural characterizations of these quenched vitreous samples have been investigated by ~(27)Al and ~(29)Si MAS-NMR spectra. The viscosities of CaO-SiO_2-Al_2O_3-R_2O quaternary melts decreased with increasing the additive content of Li_2O or Na_2O. However, the viscosity of the melts increased with increasing the additive content of K_2O. In the case of CaO-SiO_2-Al_2O_3-RO quaternary melts, the viscosities of the melts with CaO/SiO_2=0.67 decreased with increasing the additive content of BaO or MgO, however, the viscosities of the melts with CaO/SiO_2 = 1.00 and 1.22 increased with increasing the additive content of BaO. In the case of CaO-SiO_2-Al_2O_3-R_2O, the analysis of ~(27)Al MAS-NMR spectra and ~(29)Si MAS-NMR spectra indicated that the degree of polymerization of silicate anions in the glasses decreased with the addition of Li_2O or Na_2O, and that the degree of polymerization of aluminosilicate anions in the glasses increased with the addition of K_2O. It was estimated from the results that the increase in viscosities of CaO-SiO_2-Al_2O_3-K_2O melts was dependent on increase of aluminosilicate anions in the melts with the addition of K_2O. In the case of CaO-SiO_2-Al_2O_3-RO, the analysis of ~(27)Al MAS-NMR spectra and ~(29)Si MAS-NMR spectra indicated that the degree of polymerization of silicate and aluminosilicate anions in the glasses decreased with the addition of MgO. The degree of polymerization of aluminosilicate anions in the glasses increased with the addition BaO. It was estimated from the results that the increase in viscosities of CaO-SiO_2-Al_2O_3-BaO melts was dependent on increase of aluminosilicate anions in the melts with the addition of BaO.