2-DIMENSIONAL PHASE-TRANSFORMATIONS ON SUBSTRATES OF INFINITE AND FINITE SIZE

Two general geometrical methods of calculating the coverage of a substrate electrode by overlapping growth centers are presented, and it is shown that the formalism due to Evans can be applied more directly than that due to Avrami. The Evans formalism is applied to predict the behavior of ensembles of transients due to the two-dimensional growth of a finite number of centers on a circular substrate: it is shown that the use of electrodes of finite size gives information about electrocrystallization reactions which cannot be derived from experiments on electrodes of effectively infinite area. The extension of Evans formalism allows the prediction of closed form solutions of the transient behavior (i.e., simulations are not required). While the integrals derived must be evaluated numerically for certain models, it is shown that simple closed form algebraic solutions can also be derived in other cases.