M. M. Shultz

The thermodynamic properties of oxide glasses and glass-forming liquids and their chemical structure

Abstract It is shown that the thermodynamic and other physical properties of oxide glasses and glass-forming liquids are adequately described on the basis of the model of ideal associated solutions using information on the corresponding properties of crystalline compounds which exist in the systems considered. The validity of the model used is illustrated by calculations performed for certain silicate and borate systems.

A thermodynamic, molecular dynamics and neutron diffraction investigation of the distribution of tetrahedral {;Si(n)} species and the network modifying cation environment in alkali silicate glasses

Abstract Previous molecular dynamics (MD) simulations of alkali silicate glasses are extended to keep a separate record of the bridging and non-bridging oxygen atoms and the SiO and NaO first neighbour distance distributions are compared with those extracted from neutron diffraction data. The model of ideal associated solutions is used to predict the distributions of Si ( n ) tetrahedral species for the glasses studied and these are in good agreement with nuclear magnetic resonance data. However, the corresponding distributions for the MD simulations indicate a much higher fictive temperature than for the real glasses. The spatial distribution of the Si (4) species for the MD simulations is more uniform than would pertain if the various Si ( n ) species were interconnected randomly, which has implications for the modified random network theory.

The thermodynamic modelling of glass properties: a practical proposition?

The model of associated solutions is used not only to calculate thermodynamic functions but also to predict physical properties and structural parameters for a range of binary borate, silicate and phosphate glasses. In each case, the model yields good agreement with the relevant experimental data.

Thermodynamic properties of the UO2ZrO2 system studied by the isothermal mass spectrometric vaporization method

Abstract The Knudsen effusion high-temperature mass spectrometric method was used to study the vaporization processes and thermodynamic properties of the UO2ZrO2 System in the temperature range 2200–2650 K. The work was carried out with the MS 1301 mass spectrometer developed for studies of physico-chemical properties of inorganic substances at high temperatures. Vaporization of the solid solutions containing 0.02–0.45 mol fractions of U02 was done using tungsten cells. The vaporization processes and the chemical potentials of ZrO2 in the U02Zr02 system and in the Y2O3ZrO2, Lu2O3ZrO2 and HfO2ZrO2 systems, available in the literature, were discussed from the point of view of the acid-base concept.

Mass spectrometric study of thermodynamic properties and vaporization processes in the Na2OB2O3GeO2 glass-forming melts

Abstract This work was performed using the Knudsen effusion method combined with the mass spectrometric analysis of the gaseous phase composition at temperatures from 1273K to 1373K. The vapour composition over the Na2OB2O3GeO3 melts was shown to depend on both the composition of condensed phase and the temperature, and the vapour composition over the Na2OB2O3, Na2OGeO2, B2O3GeO2 melts corresponds mainly to that over the pure oxides forming these systems. At 1273K the NaBO2 and (NaBO2)2 molecules were found in the vapour over the melts of the system containing 0.10 molar fraction of Na2O as well as B2O3 and GeO2 in molar ratio 4:1. Besides the indicated molecules, atomic sodium, germanium monoxide and oxygen were also found in the vapour over the 0.40Na2O0.30B2O30.30GeO2 and 0.40Na2O0.12B2O30.48GeO2 melts. The partial vapour pressures, activities, chemical potentials, partial molar enthalpies and entropies of the binary system components were determined. The thermodynamic functions of the Na2OB2O3, Na2OGeO2 and B2O3GeO2 melts agree with the structure of these melts adopted at present. The experimental values of excess free energy for the melts of a ternary system are compared with the values calculated from thermodynamic functions using the Kohler method.

Application op mass action law to glass forming oxide melts

Some difficulties in applying the m.a.l. to glass forming oxide melts due to their polymeric structure can be overcome by assuming statistical distribution of different structural groups in polymeric melts. On this basis the thermodynamic quantitative correlations between various borate and silicate formations in glass forming melts have been calculated.