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Aluminate glasses are important materials from a fundamental structural point of view because Al is the only network former. They present also a technological interest because of their good IR transmission and ultralow optical losses. Aluminum in glasses of the system MO–Al2O3 (M = Ca, Sr, Ba) can have different coordination numbers, essentially 4 and 6, as a function of the MO/Al2O3 ratio. Using Raman spectroscopy and high field 27Al NMR spectroscopy, we have determined the structure of aluminum network as a function of MO/Al2O3 ratio with M corresponds to different alkaline–earth cations. Al is essentially in four-fold coordination with different amounts for Al2O3 between 50 and 75% but varies between Q2 and Q4 species as a function of MO/Al2O3 ratio where Q is tetrahedral species and n the number of bridging oxygen.

New values of densities ρ and surface tensions σ of liquid aluminum obtained in the range 1600 to 2360 K by contactless techniques in neutral gases are reported. Conditions for oxygen-free aluminum are fulfilled which allow determination of the surface tension of aluminum. Extrapolation to the melting point, T m = 933 K, confirms the value of σ (T = 933K) = 1.05 N ⋅ m−1.

New data for the surface tension of liquid alumina from 2300 to 3200 K are reported. Aerodynamic levitation of CO2 laser-heated liquid drops allowed contactless measurement of vibration frequencies directly related to surface tension. Consistent data were obtained on drops of different mass ranging from 20 to 160 mg. It was also shown that the oxydo-reducing character of the atmosphere does not modify the results within experimental uncertainty.

Thermophysical properties of high temperature liquid iron heated with a CO2 laser have been determined in an aerodynamic levitation device equipped with a high-speed camera and a three-wavelength pyrometer. Characteristic curves of the free cooling and heating of the drop can be used to determine the same apparent emissivity of solid and liquid iron and to calibrate pyrometers based on the known value of the melting point of iron, i.e., 1808 K. Examination of the recalescence of undercooled liquid iron and further solidification are used to obtain the ratio of the melting enthalpy versus the heat capacity of liquid iron as \(\frac{{\Delta H_m }}{{c_P^l }} = 306 \pm 2.5{\text{ K}}\). The surface tension σ was determined from an analysis of the vibrations of liquid drops. Results are accurately described by σ (mJ⋅m−2)=(1888±31)−(0.285±0.015) (T−Tm) between 1750 K (undercooled liquid) and 2500 K. The density of liquid iron has been deduced from the image size and the mass of the liquid iron drops.

The density, surface tension, and spectral and total hemispherical emissivities of liquid boron obtained with contactless diagnostics are reported for temperatures between 2360 and 3100 K. It is shown that, contrary to previous expectations, liquid boron is denser than the solid at its melting point. It is also shown that the high total emissivity of 0.36 is not consistent with that of a liquid metal as recently claimed. Finally, good agreement is found with previously reported surface tensions and spectral emissivities of liquid boron.

It is shown that the essential issue in the controversy related to the nature of the driving force in the case of yttrium-doped zirconia placed between short-circuited reversible electrodes exposed to different chemical potentials is the omission of the potential drop occurring at the metal/solid electrolyte interface due to charges at the interface.

The behavior of ionic conducting oxides is discussed. It is shown that if such an oxide is placed between short-circuited reversible electrodes exposed to different chemical potentials, the oxygen ions are moving essentially under the influence of a gradient of electrical potential.

The density of liquid alumina drops maintained in levitation with an aerodynamic device and heated with CO2 lasers is determined by analysis of high-speed video digital images between 2000 and 3100 K in various gases. It is shown that consistent results can be achieved for the lighter drops (m

Oxygen self-diAusion measurements determined below and above the glass transition temperature in a cordierite glass are reported. The diAusion experiments were performed by the solid‐gas isotope exchange method using 18 Oa s a tracer in H2‐H2 18 O and Ar/ 18 O2 atmospheres. The 18 O diAusion profiles were established by secondary ion mass spectrometry (SIMS) after appropriate diAusion annealing. The oxygen diAusion coeAcients changed at the glass transition temperature as expected. The atmosphere aAected the oxygen diAusivity in agreement with other studies. The diAusion data were useful for comparisons with diAusion controlled process in the same glass. There is a diAerence between the activation enthalpies for crystal growth, viscous flow, and oxygen self-diAusion. Hence, bond-breaking and molecular reorientation required for crystallization and the atomic transport mechanism involved in viscous flow are not correlated in any obvious way to oxygen diAusion in cordierite glass. ” 1998 Elsevier Science B.V. All rights reserved.

The measurement of the surface tension of liquid silicon has a long history with many results but no general agreement between them. Two values at the melting temperature are cited in reviews (749 and 827 mN/m [N. Eustathopoulos, E. Ricci, B. Drevet, Note Technique DEM No. 97/58, CEA, 1997]) but there are few arguments to determine the correct one. In the present study, new data for the surface tension obtained with the analysis of characteristic frequencies of a levitating drop are presented. The effect of oxygen and nitrogen are also considered. These data are compared with former data obtained with contactless techniques. The most recent surface tension values obtained with drop weights ranging on two orders of magnitude and environments of different natures (argon, hydrogen and vacuum) show excellent agreement (within a 1.5% margin) at temperatures between 1350 K and 2400 K. The comparison of these data to others obtained with different techniques, reveal a good agreement, except those obtained with the sessile drop technique on some supports like BN, SiO2 and MgO. However, these special cases may be connected with the reactivity of silicon with these supports.

An infrared spectrometer (spectral range 2–6 μm), coupled with a 9 μm pyrometer (Christiansen’s wavelength), has been developed to collect time-resolved measurements (32 spectra/s) of the spectral emissivity of alumina droplets (d≈ 3 mm) freely cooling in an aerodynamic levitation system from the liquid-to-solid phases [2800 → 1500 K]. The temperature and nature of the gaseous atmosphere surrounding the droplet (oxidizing/neutral/reducing) are two important parameters affecting the spectral emissivity in the semi-transparent range. Observations are discussed in the framework of the thermal activation and of the chemical interactions of alumina with the environment.