J. Rogez

Thermodynamic study of the condensed phases of NaNO3, KNO3 and CsNO3 and their transitions

The heat capacities of solid and liquid NaNO3, KNO3 and CsNO3 and their enthalpies of transition have been measured by DSC. A review of the literature data and a comparison with the results of this investigation are presented.

Thermochemistry of nuclear waste glasses: an experimental determination

Abstract As part of a systematic study of the chemical stability of borosilicate glasses, we show that the Gibbs free energy of formation of a glass can be determined experimentally from a comprehensive, consistent set of measurements. For a sodium borosilicate glass with 14.2 mol%xa0Na2O and 18.4 mol%xa0B2O3, the relative enthalpy and entropy have been determined from heat capacities measured from 13 to 1480 K by adiabatic, differential scanning and drop calorimetry; the enthalpy of formation has been obtained from solution calorimetry at 970 K, whereas the configurational entropy of the glass has been derived from viscosity measurements through the Adam–Gibbs configurational entropy theory. The structural and thermochemical implications of the results are discussed in terms of short-range order and mixing of BO3 and BO4 units.

Thermodynamic analysis of the CsNO3-KNO3-NaNo3 system

The thermodynamic properties of the CsNO3-KNO3-NaNO3 system have been derived from an optimization procedure using experimental and published information concerning phase diagram and thermodynamic data for the constituent binary systems and ternary liquid phase. The results are in very close agreement with the experimental data.

Mixing properties in the continuous solid solution of the system AgNO3-NaNO3

Abstract The binary phase diagram for AgNO 3 -NaNO 3 has been previously reinvestigated and shows, in particular, a continuous subsolidus solid solution. The mixing enthalpies in this solid phase determined by solution calorimetry at 474 K are presented here. The results are fitted by the Van Laar model.

Heat capacities and enthalpies of transition of AgNO3

Abstract The heat capacities of AgNO 3 in the solid and liquid phases and the related enthalpies of transition have been measured by differential scanning calorimetry. A review of the literature data and a comparison with the present results are presented.

Thermal study of chromium–phosphorus-doped tricalcium aluminate

Abstract The evolution with the temperature of the composition of some mixtures of CaCO 3 , Al 2 O 3 , Cr 2 O 3 and P 2 O 5 has been investigated. The influence of chromium and phosphorus additions on the thermal decomposition of CaCO 3 and the formation of the tricalcium aluminate have been observed. The synthesized solid solutions have been characterized through X-ray diffraction (XRD). The free lime content has been determined by chemical analysis. The formation of the cubic polymorph of C 3 A with Cr and P additions less than 4.24 wt.% Cr 2 O 3 and 3.97 wt.% P 2 O 5 was shown. The temperatures of the decarbonation and the enthalpy variations during the raw firing have been studied. The results showed that the presence of the Cr 2 O 3 and P 2 O 5 oxides lowered the decomposition of CaCO 3 . The enthalpy of decarbonation and the enthalpy of the formation of the solid solutions based on tricalcium aluminate formation decreased when the concentrations of additives increased.

Enthalpie de melange du systeme vitreux albite-orthose (Na,K) AlSi3O8

Abstract Using a high temperature Calvet calorimeter the authors have measured the enthalpy of dissolution of vitreous albite, orthose and their mixtures into a 2PbO+B 2 O 3 liquid bath at 970 K. From these values, the enthalpy of mixing the vitreous system albite-orthose (Na, K) AlSi 3 O 8 at this temperature has been deduced.

Solution calorimetric investigation of AgCl-AgI ionic conductor composites at 298 K: observation of metastable AgI modifications

Abstract The enthalpies of solution of pure silver halides AgCl and AgI and a composite material with molar composition 0.5 AgCl–0.5 AgI were measured at 298xa0K in a mixture of Na 2 S 2 O 3 (1xa0M) and NH 4 OH (1xa0M). X-ray diffraction patterns showed that the composite material contained the metastable γ-AgI phase; different mechanisms for its stabilization were discussed. The phase transition enthalpies of AgI modifications and the enthalpy of formation of the composite material were deduced from the measurements. The latter could be related to a change of interfacial enthalpies.

Determination of the crystallization enthalpies of lithium ion conducting alumino-silicate glasses

Abstract An irreversible change of the electrical conductivity of Li+ ion-conducting lithium alumino–silicate glasses is observed during crystallization. The enthalpies of crystallization of the glasses are measured by solution calorimetry at 298 K in HF/HNO3 mixtures and compared with similar sodium glasses. The observed differences are related to the alumino–silicate crystal chemistry and the cation radii.

Phenomenological Hugoniot curves for transition metals up to 1 TPa

We study the volume dependence of the Hugoniot pressure obtained from shock-wave experiments by using the tight-binding (TB) potential. We observe that the Hugoniot P–V curve of one metal resembles an effective cold P–V curve of the same element but having a stiffer repulsive term in the TB potential. We show that our ansatz is in systematic good agreement with experimental data for 12 close-packed metals. This observation allows us to derive a phenomenological relation between the Hugoniot curve and the 293xa0K isotherm. Using finite strain theory, this relation is extended to metals having non-close-packed structures.