PNNL

Abstract

A multicomponent borosilicate glass containing several multivalent elements (Fe, Ni, Cr, Mn) and precipitating (Fe,Ni,Mn,Cr)(Fe,Cr,Mn)2O4 spinel as its primary phase, was equilibrated with the gas phase over the range of oxygen partial pressures, from 10^-13 Pa to 10^5 Pa and temperatures, T, from 850?C to 1300?C. The oxidation-reduction equilibrium of Fe in the glass was measured with Mossbauer spectroscopy and wet colorimetry. These data were combined with oxidation-reduction equilibria for Fe, Ni, and Cr in a borosilicate frit of a similar composition found in the literature to estimate concentrations of Fe(II), Fe(III), Ni(II), Cr(II), Cr(III), and Cr(VI) as functions of T. Measured liquidus temperature (TL) data for the test glasses within the same range were then added to a critically evaluated TL database composed of multicomponent borosilicate glasses within the spinel primary crystalline phase field. The set of partial molar liquidus temperatures for elements other than oxygen determined from this database was then augmented by values for Fe(II), Fe(III), Cr(II), Cr(III), and Cr(VI). A 0.1-mol% change in the metal ion concentration increases TL as follows: Fe(II) by 4.6?C, Fe(III) by 2.8?C, Cr(II) by 185?C, Cr(III) by 66?C, and Cr(VI) by -17?C. The calculated TL based on partial molar liquidus temperatures agreed with the measured TL in the range from 10^-13 Pa to 10^5 Pa.