AIRBORNE FIBROUS AND NONFIBROUS PARTICLES IN A SILICON-CARBIDE MANUFACTURING PLANT

Silicon carbide (SiC) fibre generation is reported to occur during commercial SiC crystal production. Dust levels and fibre concentrations were measured by static sampling in an Italian plant operating 24 Acheson furnaces. X-ray Diffraction (XRD) was used to assess the quartz content in the dust collected. Optical microscopy (OM) and scanning electron microscopy (SEM) were used for fibre counting and identification of fibres. Only alpha-quartz was identified, but airborne concentrations were found to be higher than the concentration of crystalline silica reported in other similar studies. Two types of fibre, coarse and fine, were identified by OM and SEM: for both, only the peak of silicon (Si) was evident at energy dispersive X-ray analysis (EDXA). Coarse fibres are irregular in shape, with a diameter greater than 5-mu-m. Fine (respirable) fibres are straight, regular in shape, with a typical diameter between 1 and 2-mu-m. Fine fibre concentration does not appear to be related either to total dust or to total fibre concentration. It cannot therefore be predicted from the nature of the various processes involved.