Jean-Charles Joud

Tensions superficielles d'alliages liquides binaires présentant un caractère dimmiscibilité: Al-Pb, Al-Bi, Al-Sn et Zn-Bi

Abstract Experimental measurements of surface tensions of Al-Pb, Al-Bi, Al-Sn, Zn-Pb and Zn-Bi alloys have been performed using two different methods (maximum bubble pressure and sessile drop).The experimental results are compared with those given in the literature. In addition, calculations of surface adsorption are made from Gibbs equation for Al-Pb and Zn-Bi alloys.

Surface tensions of binary liquid alloys with strong chemical interactions

Abstract The statistical approach developed uses the concept of “surrounded atoms”. The strong chemical interactions existing between the atoms of the liquid alloys studied are expressed, to a great extent, by the energy of stabilization of “privileged surrounded atoms” (PSA) of the mixture. The model permits to show the effects of these PSA on the surface properties (particularly surface tension) of three systems: AlCu, FeSi and NiSi.

Surface tension of liquid tin-oxygen alloys and relationship with surface composition by Auger electron spectroscopy

Abstract The surface tension of liquid tin has been measured at 560 K by the sessile drop method, as a function of the oxygen surface content measured on the liquid surface by AES. The surface tension values range from 598 mN/m, for a clean surface, to 535 mN/m for a surface rich in oxygen. The surface tension isotherm consists roughly of two plateaux, with a transition at a oxygen-to-tin Auger peak height ratio close to 0.2. In the oxygen poor region some LEELS experiments have been performed on liquid tin in order to examine the chemical state of the liquid surface. For the oxygen rich region, a chemical shift of the tin Auger peak has been observed (− 3.4 eV). A simple model based on the existence of oxide islands is proposed, to explain the surface tension versus oxygen concentration behaviour. The model is consistent with the experimental results obtained in the regions poor or rich in oxygen, and describes the above-mentioned surface tension transition as due to the filling of the surface with SnO islands.

Tension superficielle d'alliages liquides aluminium-cuivre

Resume Experimental measurements of the surface tensions of AlCu alloys have been made using two different methods (maximum bubble pressure and sessile drop). A compilation of specific weight data for the system is presented. The experimental results are compared with both those given in the literature and those calculated from a statistical thermodynamic model. Finally, calculations of the surface adsorption are made for T = 1100° C from the Gibbs equation and from the statistical model.

Introduction du concept thermodynamique d'énergie élastique partielle dans l'analyse de la ségregation superficielle d'alliages solides binaires

Abstract Previous models of surface segregation have generally been interpreted by means of a decrease in surface free energy. Nevertheless the reduction in lattice strain-energy which accompanies the transfer of misfitting solute atoms from the lattice to the surface, constitutes also a driving force for that phenomenon. By the introduction of the concept of the partial elastic energy, it is possible to present a theory which combines the two different aspects into a single formalism, valid in a crude approximation, for all concentrations.

Average atomic order effect — Prediction of bulk and surface properties of liquid metallic systems

Abstract The average atomic order effect is studied in liquid alloys using a statistical model based on quasichemical approximation. In the first part an estimate of the composition dependence of this order effect is made assuming a good representation of thermodynamic data for segregating and ordering systems. In the second part corresponding surface properties of this systems are calculated with this model and compared with experimental surface tensions and surface concentration values. For the ordering system (NiSi), the local order in the surface layer is calculated.

Influence of the short-range chemical order effect on the partial interference functions of a dilute binary liquid alloy

Abstract An evaluation of the partial interference functions for a dilute binary liquid alloy in terms of the interference function of the solvent is presented. The calculation neglects size effects, but the influence of the short-range chemical order effect on the partial interference functions is studied. A quasichemical statistical treatment allows a calculation of the chemical effect to be made Results are presented for dilute alloys of Zn[sbnd]Al and Cu[sbnd]Sb and a direct comparison with experiment is made in the case of liquid Ag0.285 Li0.715.

An Auger Investigation of Oxygen-Enhanced Tin Segregation on a Liquid Pb-Sn Alloy.

SummaryAuger measurements of the surface composition have been performed on solid and molten Pb-5at%Sn alloys. They confirm the theoretical predictions that, in the absence of oxygen, liquid or solid alloys exhibit no significant surface segregation. On the contrary, surface composition measurements and simultaneous surface tension measurements clearly show that oxygen adsorption strongly affects the segregation of tin at the liquid-vapour interface. This surface enrichment is driven by the contribution of the reaction free energy and of the products surface tension.