Alternative Routes to Porous Silicon Carbide

Abstract

ABSTRACTA low-cost alternative route for large-scale fabrication of high purity porous silicon car-bide is reported. This allows a three-dimensional arrangement of pores with adjustable pore di-ameters from several 10 nanometers to several microns. The growth of SiC is here based on a combined sol-gel and carbothermal reduction process. Therein tetraethoxysilane is used as the primary silicon and sucrose as the carbon source. We provide two different sol-gel based ways for preparation of porous SiC, obtaining either a regular porous or a random porous type. Regu-lar porous SiC with monodisperse ordered spherical pores of predefined size is obtained via liq-uid infiltration of a removable opal matrix. Whereas random porous material with polydisperse pores of an adjustable size distribution range, but without order, can be achieved via free gas phase growth. This is performed by degradation of granulated sol-gel prepared material inside a sealed reaction chamber, resulting in a SiO/CO/SiC rich gas atmosphere, which causes SiC growth inside the granulate itself. For both types doping of the initially semi-insulating porous SiC is possible either during the sol-gel preparation or via the gas phase during the following annealing procedure. As probing dopants we have used P, N, B and Al, which are well known from 'conventional' SiC. Composition and structure of the obtained material was investigated using scanning electron microscopy, X-ray diffraction, nuclear magnetic resonance and Fourier transform infrared spectroscopy.