Preface to the view point set Jean-Marc Chaix et al

Thermodynamics and Kinetics of Grain Boundary Triple Junctions in Metals – Recent Developments

G Gottstein et al

We assess the contribution of grain boundary triple junctions to the driving force for grain growth and the “energetic” effect of boundary junctions on grain growth in nanocrystalline materials. The first measurement of grain boundary line tension allows to estimate quantitatively the fraction of the driving force due to boundary triple junctions. For polycrystals with a grain size in the range of not, vert, similar50 nm, it is comparable with the driving force from grain boundaries.

On the triple line in infiltration of liquid metals into porous preforms

J M Molina et al

We address here two questions of current interest: i) are contact angles measured by means of the sessile drop technique of any help to understand liquid metal infiltration into solid porous preforms?, and, ii) to what extent are contact angles derived from either the capillary law or drainage curves valid?. These questions have neither a simple nor a unique answer, as infiltration may occur under very different scenarios, namely, non-reactive and reactive infiltration, both spontaneous and forced. On the other hand, while the use of the simplest version of the capillary law relies upon the questionable slug-flow hypothesis, analyzing drainage curves by means of Brooks and Corey model seems only justified for particular distributions of pore sizes such as a power law. Anyhow, experimental studies indicate that threshold pressures, and therefore contact angles, derived from those two methods are not so different.