Abstract
The wettability of ceramics by liquid metals is discussed from both the fundamental point of view and the point of view of applications. The role of interfacial reactions (simple dissolution of the solid in the liquid or formation of a layer of a new compound) is illustrated and analysed. Several results are presented in order to illustrate the role of wettability in materials processing, namely infiltration processing, joining dissimilar materials by brazing and selecting crucibles for crystallising liquid metals and semiconductors. The review includes results obtained during the last 15 years mainly, but not only, by the Grenoble group.
Highlights
The intrinsic aptitude of a non-reactive liquid to wet a flat, smooth and chemically homogeneous solid surface is quantified by the value of Young’s contact angle θY, a unique characteristic of a solidS–liquid L–vapour V system (Figure 1). θY enters into all model equations describing the wetting of liquids on real solid surfaces, i.e., surfaces with a certain roughness and degree of heterogeneity, as well as into equations modelling wetting in reactive liquid–solid systems
This review focuses on liquid metal/ceramic systems, a limited number of results concerning liquid metal–solid metal systems are given because they are useful in understanding bonding at metal/ceramic interfaces
The thermodynamics and kinetics of reactive wetting with formation of a new compound at the interface are given by the Reaction Product Control (RPC) model which can be summarised as follows: [2]
Summary
The intrinsic aptitude of a non-reactive liquid to wet a flat, smooth and chemically homogeneous solid surface is quantified by the value of Young’s contact angle θY, a unique characteristic of a solid. By measuring θY and the surface energy (or surface tension) σLV of the liquid Dupré’s adhesion energy Wa can be evaluated This quantity characterises the thermodynamic stability of interfaces between dissimilar materials and is widely used in practice for predicting their potential bonding properties. Significant improvements have been made in the measurement of contact angles of high temperature systems [1] In this period, wetting studies have benefited from high resolution techniques for characterising the topological and chemical features of surfaces at nanometric scale. Another reason for this improvement has been the use of monocrystalline or vitreous solids to prepare the high-quality surfaces required for Young’s contact angle determinations. The results are mainly, but , from studies performed by the Grenoble group
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