COMPOSITE CATALYST SURFACES - EFFECT OF INERT AND ACTIVE HETEROGENEITIES ON PATTERN-FORMATION

Spatiotemporal dynamics in reaction-diffusion systems can be altered t hrough the properties (reactivity, diffusivity) of the medium in which they occur. We construct active heterogeneous media (composite cataly tic surfaces with inert as well as active inclusions) using microelect ronics fabrication techniques and study the spatiotemporal dynamics of heterogeneous catalytic reactions on these catalysts. In parallel, we perform simulations as well as numerical stability and bifurcation an alysis of these patterns using mechanistic models. At the limit of lar ge heterogeneity ''grain size'' (compared to the wavelength of spontan eously arising structures) the interaction of patterns with inert or a ctive boundaries dominates (e.g., pinning, transmission, and boundary breakup of spirals, interaction of pulses with corners, ''pacemaker'' effects). At the opposite limit of very small or very finely distribut ed heterogeneity, effective behavior is observed (slight modulation of pulses, nearly uniform oscillations, effective spirals). Some represe ntative studies of transitions between the two limits are presented.