SURFACE-PROPERTIES OF COAL AND PYRITE POWDERS

We studied the surface properties and the tribo-electrification of coa l and pyrite powders by means of repeated-contact electrification (RCE ), X-ray photoelectron spectroscopy (XPS) and ultraviolet photoelectro n spectroscopy (UPS). The coal samples were from the USA, France and G reat Britain. RCE shows curves typical for the electrical conductivity of the samples. The surface chemical composition is found to be decis ive for the static electrification behaviour. The elemental concentrat ion of the surface differs not significantly from the bulk. High ash-c ontaining coal (US, France) showed different electrification behaviour compared to pyrite.