THE DYNAMICS OF TRANSIENT OSTWALD RIPENING

We examine numerically the time-dependent behaviour of a two-phase system undergoing transient Ostwald ripening. The evolution of selected initial particle-radius-distribution (PRD) functions was followed to over three orders of magnitude in time. Although steady-state coarsening behaviour was never fully achieved, the existence of the Lifshitz-Slyozov (LS) attractor PRD and scaling laws for rBAR and N(v) was essentially confirmed for all the initial PRDS studied in systems with a zero volume fraction of coarsening phase. The transition path to steady-state coarsening was highly dependent upon the initial PRD. Phase-plane plots illustrated this dependence and showed the large basin of attraction for the LS PRD. In addition, changes in the initial form of a given PRD Within a fixed class of PRDS were found to affect strongly the transient coarsening rate; for example, wide log-normal PRDs evolved more rapidly than did narrow ones. Calculations were also done to examine the effect of a finite volume fraction of coarsening phase on the extent of the transient regime. The results showed that the system evolved to its steady-state form more rapidly at non-zero volume fraction than at zero volume fraction. Finally, we present a comparison of our calculations with other experimental and theoretical studies of transient coarsening behaviour.