Calorimetric measurements in 0.8[xB2O3-（1 - x）SiO2]-0.2Na2O glasses and melts are performed in I-IF calorimetry at 298 K and lead borate calorimetry at 973 K, respectively. Mixing enthalpy is affected by both temper...Calorimetric measurements in 0.8[xB2O3-（1 - x）SiO2]-0.2Na2O glasses and melts are performed in I-IF calorimetry at 298 K and lead borate calorimetry at 973 K, respectively. Mixing enthalpy is affected by both temperature and composition. At 298 K, the mixing enthalpies are slightly negative and components are miscible at that temperature in the whole composition range. At 973 K, the sign of the mixing enthalpies reflect the tendency to phase separation at silica-rich compositions, which is avoided for kinetic reasons as shown by SEM results. Therefore, one is tempted to consider the quenched 0.8[xB2O3-（1 - x）SiO2-0.20Na2O] glasses and melts as single-phase materials.展开更多
The mixed alkali effect was investigated in the glass system 0.75B2O3-0.25[xNa2O-（1 -x）K20] through thermodynamic properties. The calorimetric measurements were performed in HF solution calorimetry at 298 K. The mix...The mixed alkali effect was investigated in the glass system 0.75B2O3-0.25[xNa2O-（1 -x）K20] through thermodynamic properties. The calorimetric measurements were performed in HF solution calorimetry at 298 K. The mixing enthalpy values show non-linear behaviour upon substitution of one alkali ion by another. This thermodynamic non-ideality is caused by the slight variations of distance between metallic cations, the macromolecular structure being unchanged. It can be explained, at least qualitatively, using electrolyte theory based on the Coulombic interactions of charged species originally developed by Debye and Hückel.展开更多
文摘Calorimetric measurements in 0.8[xB2O3-（1 - x）SiO2]-0.2Na2O glasses and melts are performed in I-IF calorimetry at 298 K and lead borate calorimetry at 973 K, respectively. Mixing enthalpy is affected by both temperature and composition. At 298 K, the mixing enthalpies are slightly negative and components are miscible at that temperature in the whole composition range. At 973 K, the sign of the mixing enthalpies reflect the tendency to phase separation at silica-rich compositions, which is avoided for kinetic reasons as shown by SEM results. Therefore, one is tempted to consider the quenched 0.8[xB2O3-（1 - x）SiO2-0.20Na2O] glasses and melts as single-phase materials.
文摘The mixed alkali effect was investigated in the glass system 0.75B2O3-0.25[xNa2O-（1 -x）K20] through thermodynamic properties. The calorimetric measurements were performed in HF solution calorimetry at 298 K. The mixing enthalpy values show non-linear behaviour upon substitution of one alkali ion by another. This thermodynamic non-ideality is caused by the slight variations of distance between metallic cations, the macromolecular structure being unchanged. It can be explained, at least qualitatively, using electrolyte theory based on the Coulombic interactions of charged species originally developed by Debye and Hückel.
