| Interfacial phenomena in binary metallic systems have been studied by a variety of techniques, including experimental studies, computer simulations and the development of analytical models.; The interfacial energies of the Al/Pb {lcub}111{rcub} and {lcub}100{rcub} interfaces have been determined by a solid-state wetting technique in which Pb crystallites were equilibrated on Al single crystal substrates of {lcub}111{rcub} and {lcub}100{rcub} orientations. All experiments were carried out in ultra-high vacuum conditions to avoid any contamination. The contact angle of Pb crystallites was measured to be 27.3 +/- 0.8° and 41.1 +/- 0.8° for the {lcub}111{rcub} and {lcub}100{rcub} interface, respectively. Auger electron spectroscopy was employed to measure possible adsorption. The spectra showed that Pb was adsorbed on the Al substrates while no Al was found on the Pb crystallites. After quantification, the amount of Pb adsorption on the Al substrates was determined to be 1.81 monolayers and 1.77 monolayers on {lcub}111{rcub} and {lcub}100{rcub} substrates, respectively. The adsorbed Pb was distributed among the near-surface layers of Al by taking advantage of a multi-layer surface adsorption model. By means of the Gibbs adsorption isotherm, the surface energy of Al was corrected for the adsorption, and determined to be 715 +/- 30mJ/m2 for {lcub}111{rcub} surface and 752 +/- 35mJ/m2 for {lcub}100{rcub} surface. The corrected surface energy, together with the surface energy of pure Pb, and the measured contact angle, yield an energy of 217 +/- 35 Pb/Al {lcub}111{rcub} and 330 +/- 40 mJ/m -2 for the Pb/Al(100) interface.; Molecular dynamics (MD) simulations, in conjunction with semi-empirical glue type potentials, have been used to model the melting behavior of nanosized Pb particles embedded in an Al matrix. We found that all the Pb particles studied melt well above the bulk melting temperature predicted by the same potential. In addition, the melting point elevation displays a damped periodic trend with increasing Pb particle size. A phenomenological model has been developed to describe this interesting melting behavior based on considerations of interfacial energy, volume expansion and lattice mismatch. Our model leads to the conclusion that the periodic variation of melting point with size is due to an oscillatory strain energy contribution arising from the large size mismatch of Pb and Al atoms. By inspecting snapshots derived from the simulations, it is also possible to conclude that melting occurs via nucleation at {lcub}100{rcub} interfaces. (Abstract shortened by UMI.)... |
