The absorption properties of submicron SiC particles between 2.5 and 40 μm

Abstract Submicron α-SiC particles have been studied in the near and middle i.r. at room temperature and their properties measured after different treatment processes: namely, grinding, ultrasonic washing and sedimentation. TEM analysis allows determination of grain morphology and size distributions. The extinction curves reveal the presence of a central main peak at 11.4 μm and of two shoulders, respectively at 10.6 and 12.7 μm, due to phonon resonances. Our data show good agreement with those previously reported by the University of Jena Group. On the other hand, β-SiC spectra differ substantially, indicating their crucial dependence on the crystallographic characteristics of the samples. Experimental astronomical observations seem to indicate that α-SiC is the best candidate to simulate the actual SiC present in cosmic sources.