Thermodynamic properties and phase equilibria in the MnO-SiO{sub 2} system

Journal Article · Tue Aug 01 04:00:00 EDT 1995 · High Temperature and Materials Science

OSTI ID:218641

Zaitsev, A I; Litvina, A D; Tsaplin, A A; Mogutnov, B M ^[1]

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1. Inst. of Physical Metallurgy, Moscow (Russian Federation). Lab. of Thermodynamic Investigations

The Knudsen effusion technique with mass-spectrometric analysis of evaporated products has been applied for determination of thermodynamic properties of solid and liquid phases in the MnO-SiO{sub 2} system. To bring about volatile substances with measurable pressures, reduction reactions of MnO-SiO{sub 2} with molybdenum or niobium were conducted in effusion cells. Activities of the components have been calculated by several methods. The results coincided within the experimental error limits (2--3%). The following equations have been found for Gibbs energies of formation of the compounds MS and M{sub 2}S (M = MnO, S = SiO{sub 2}): {Delta}{sub f}G(MS) = {minus}(10,090 {+-} 616) {minus} (0.81 {+-} 0.42)T, J/mol (1,369 < T < 1,525 K) and {Delta}{sub f}G(M{sub 2}S) = {minus}(11,560 {+-} 588) {minus} (1.30 {+-} 0.38)T, J/mol (1,388 < T < 1,585 K). Temperature and concentration dependencies of {alpha}{sub MnO} and {alpha}{sub SiO{sub 2}} in liquid solutions have been described by the associated-solution model. Formation of associative complexes MnO-SiO{sub 2} and 2MnO-SiO{sub 2} as well as polymer SiO{sub 2} networks was taken into account. Thermodynamic computation of the phase diagram was carried out.

• OSTI ID: 218641
• Report Number(s): CONF-940468--
• Journal Information: High Temperature and Materials Science, Journal Name: High Temperature and Materials Science Journal Issue: 1-3 Vol. 34; ISSN HTMSFP; ISSN 1080-1278
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
EQUILIBRIUM
FORMATION FREE ENTHALPY
KNUDSEN FLOW
MANGANESE OXIDES
MASS SPECTROSCOPY
PHASE DIAGRAMS
PHASE STUDIES
SILICON OXIDES
THERMODYNAMIC PROPERTIES