SIZE-SELECTED SILICON PARTICLES IN SOL-GEL GLASS BY CENTRIFUGAL PROCESSING

Centrifugal processing was used to induce size selectivity in Si parti cles suspended in a silica sol-gel precursor solution. A model was dev eloped to describe Stokes settling of the silicon particles in the sol -gel medium whose viscosity increases exponentially with time eventual ly leading to hardening to a solid glassy material. An empirical modif ication to the theoretical model accounts for settling of particle agg lomerates. Experimental results for polydisperse silicon particulates centrifuged in a sol-gel of tetraethyl orthosilicate catalyzed by phos phoric acid are reported; the particle size and spatial distribution i n the gelled matrix are explained by the model. The utility of centrif ugal processing to produce functionally graded materials and semicondu ctor nanostructures is discussed. (C) 1998 American Institute of Physi cs.