THE DYNAMICS OF TRANSIENT OSTWALD RIPENING

We examine numerically the time-dependent behaviour of a two-phase sys tem undergoing transient Ostwald ripening. The evolution of selected i nitial particle-radius-distribution (PRD) functions was followed to ov er three orders of magnitude in time. Although steady-state coarsening behaviour was never fully achieved, the existence of the Lifshitz-Sly ozov (LS) attractor PRD and scaling laws for rBAR and N(v) was essenti ally confirmed for all the initial PRDS studied in systems with a zero volume fraction of coarsening phase. The transition path to steady-st ate coarsening was highly dependent upon the initial PRD. Phase-plane plots illustrated this dependence and showed the large basin of attrac tion for the LS PRD. In addition, changes in the initial form of a giv en PRD Within a fixed class of PRDS were found to affect strongly the transient coarsening rate; for example, wide log-normal PRDs evolved m ore rapidly than did narrow ones. Calculations were also done to exami ne the effect of a finite volume fraction of coarsening phase on the e xtent of the transient regime. The results showed that the system evol ved 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 transi ent coarsening behaviour.