Surface Chemistry and Structure of Ultrafine Silicon Carbide: An FT‐IR Study

Abstract

Using transmission FT‐IR, surface characterizations are performed on ultrafine SiC powders produced by a laser‐driven method. The surface species sensitive to thermal treatments (OH, CHx,, C = O, SiHx) are identified on samples evacuated at various temperatures. Absorption bands attributed to overtones of the fundamental Si—C modes are also present in the IR spectra and remain unchanged after treatment. The reaction of SiC with oxygen and water vapor produces a layer of silica on the sample and gaseous CO2; the reaction with ammonia results in a partial nitridation of the surface, with the formation of NHx groups that apparently increase the stability of the SiC against oxidation; and reaction with hydrogen produces methane in the gas phase and causes the disappearance of the bands due to surface CHx groups.