D. Giuranno

Surface properties of Bi–Pb liquid alloys

Abstract The present work represents an experimentally based investigation of the applicability of a statistical mechanical theory in conjunction with a compound formation model (CFM) to describe surface properties of Bi–Pb liquid alloys. The surface tension of molten Pb, Bi and Bi–Pb alloys has been measured by the sessile-drop method over a temperature range. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values. Based on the phase diagram evidence about the existence of the e-Pb3Bi intermetallic compound, the phenomenon of compound formation in Bi–Pb liquid alloys has been analysed through the study of surface properties (surface tension and surface composition) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of CFM.

On the application of modelling to study the surface and interfacial phenomena in liquid alloy–ceramic substrate systems

Abstract The wetting phenomena of molten alloy/ceramic substrate depend on the bonding characteristics of liquid alloys and ceramics as well as on the magnitude of interactive forces at the interface. According to this, the first step of this investigation is to determine the surface properties of Ag–Cu, Ag–Ti and Cu–Ti liquid alloys. The energetics of mixing in liquid alloys has been analysed through the study of surface properties (surface tension and surface composition) and microscopic functions (concentration fluctuations in the long-wavelength limit and chemical short-range order parameter) in the frame of statistical mechanical theory in conjunction with the quasi-lattice theory (QLT). The results obtained for these binary systems have been extended to the ternary Ag–Cu–Ti system. Combining the Young and the Dupre equations, the computed results of surface tension together with contact angle data have been used to calculate the work of adhesion and, in the case of non-reactive wetting, the interfacial tension between the solid substrate and the liquid alloys over the whole concentration range. The evaluation of the interfacial tension values is determined from calculated and measured data using solid surface tension data from literature. These results provide more information on the characteristics of metal–ceramic systems, and are therefore useful in guiding experiments, or in predicting the surface properties of metallic systems with similar characteristics as well as their wetting behaviour in contact with ceramic materials.

Surface tension and wetting behaviour of molten Bi–Pb alloys

Abstract The present work represents an experimentally based investigation on the surface properties of molten Bi, Pb and Bi–Pb alloys. The surface tensions of the two pure elements and of seven alloys were measured by the sessile-drop method over the temperature range 623–773 K. In addition the wetting behaviour of the eutectic Bi–Pb alloy on AISI 316L substrate was also investigated in the same temperature range. The results obtained show general agreement with other reported measurements on pure elements and their alloys as well as with calculated surface tension values obtained by the application of the compound formation model (CFM).

Further Development of Testing Procedures for High Temperature Surface Tension Measurements

A new testing procedure combining in one test two methods for surface tension measurements of liquid metals [the pendant drop (PD) and the sessile drop] and carried out in the same device is discussed. The attention is focused on methodological aspects of the PD method due to the novelty of its application for high temperature metallic systems. It has been claimed that under the conditions applied in the present study, this method can be considered as a quasi-containerless one. Surface tension measurements of pure Cu, Ni, Al, and Fe performed using the new procedure are described. To confirm the validity of this procedure, the experimental results are discussed in the framework of the available literature data, particularly those obtained by the containerless methods.

Surface tension and density of Si-Ge melts

In this work, the surface tension and density of Si-Ge liquid alloys were determined by the pendant drop method. Over the range of measurements, both properties show a linear temperature dependence and a nonlinear concentration dependence. Indeed, the density decreases with increasing silicon content exhibiting positive deviation from ideality, while the surface tension increases and deviates negatively with respect to the ideal solution model. Taking into account the Si-Ge phase diagram, a simple lens type, the surface tension behavior of the Si-Ge liquid alloys was analyzed in the framework of the Quasi-Chemical Approximation for the Regular Solutions model. The new experimental results were compared with a few data available in the literature, obtained by the containerless method.

Graphene Translucency and Interfacial Interactions in the Gold/Graphene/SiC System

Integration of graphene into electronic circuits through its joining with conventional metal electrodes (i.e., gold) appears to be one of the main technological challenges nowadays. To gain insight into this junction, we have studied the physicochemical interactions between SiC-supported graphene and a drop of molten gold. Using appropriate high-temperature experimental conditions, we perform wetting experiments and determine contact angles for gold drops supported on graphene epitaxially grown on 4H-SiC. The properties of the metal/graphene interface are analyzed using a wide variety of characterization techniques, along with computational simulations based on density functional theory. In contrast with the established literature, our outcomes clearly show that graphene is translucent in the gold/graphene/SiC interface, and therefore its integration into electronic circuits primarily depends on the right choice of the support to produce favorable wetting interactions with liquid gold.