The classic Lifshitz-Slezov-Wagner theory of ripening assumes that within a closed system, the total volume of the phase undergoing ripening remains constant while the total surface area of the phase decreases. We present here the ripening behavior in an open system in which the total surface area of the phase undergoing ripening remains constant while the total volume of the phase is growing. We define the latter growth to be flux-driven ripening. We compare these two types of ripening, one within a closed system and the other within an open system, in terms of the particles’ size distribution function, the scaling behavior of the distribution, and the rate of growth of the mean particle size.

A general method of obtaining hollow nanoparticles by utilizing the Kirkendall effect has been reported recently. We examine here the thermal instability of hollow nanoparticles. The difference of vacancy concentrations at the inner and outer surfaces of a nanoshell will generate an outflux of vacancies and transform it into a solid nanoparticle. Phenomenological as well as kinetic Monte Carlo modeling has been applied to analyse the shrinking kinetics of nanoshells, consisting of either a pure element or an intermetallic compound with large difference of partial diffusivities of the components. Shrinking kinetics and time to collapse to solid particles are demonstrated to be determined mainly by the slow diffusant, making compound nanoshells more stable than anticipated.