Wollastonite uses

The natural wollastonite in our study consisted of three samples. The laser-induced time-resolved technique enables us to detect Mn +, Fe " and possibly Cr emission centers (Fig. 4.42). 

Spectra with narrow gates where the centers with a short decay time are emphasized enables us to detect broad bands at 794 nm with a decay time of 5 ps and broad band at 840 nm with a decay time of 190 ps (Fig. 4.42). These bands maybe ascribed to Cr luminescence centers, in addition to Cr with narrow -lines at 720 nm, detected by steady-state spectroscopy (Min ko et al. 1978). Wollastonite structure has three different types of six-coordinated calcium-oxygen groups, which enables the formation of several types of Cr " limiinescence centers. Nevertheless, luminescence of Cr " as result of Ca substitution has not been confidently found yet and another interpretation is also possible. For example, ions of V maybe considered, which have similar luminescence properties with Cr + and may substitute in Ca + sites. 

Other fillers with significant shares of the world market in plastics are wollastonite (4%) and mica (2%), both chiefly in PP and polyamides. Consumption patterns for mica vary from region to region. Only about 5,000 tonnes of (mainly) dry ground mica was consumed in plastics in the US in 2002, which represents a mere 5% of total US consumption. 

The authors gratefully acknowledge the valuable contributions of Dr D R Brown (Croxton Garry Ltd, Curtis Road, Dorking, Surrey, RH4 IXA, UK) to the sections on calcium sulfate and wollastonite, of Joseph L Scaries (US Silica Company, PO Box 187, Berkeley Springs, WV 25411, USA) to the section on crystalline silica, and of Mrs Caryl Gould (EGC International, Europe) for the SEM micrographs of mineral fillers. 

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