Tetrahedral amorphous carbon (ta-C) coatings for processing tools to reduce contamination in the analysis of trace elements

Abstract

The possibility of reducing contamination in trace element analysis by coating processing tools with tetrahedral amorphous carbon (ta-C) coating has been studied. The 0.5 μm thick ta-C coating was deposited on pressing tool pellets made of Mo, W and WC-Co hard metal using the plasma accelerator method. The method was optimised to get high adhesion and high sp3 fraction (approx. 80%) to ensure minimal wear. The contamination of sugar test samples pressed with uncoated pellets was clearly detected with particle induced X-ray emission method (PIXE) for all the pellet materials used. In the samples pressed with ta-C coated pellets contamination from the pellets was below the detection limit, i.e. < 0.1–1 ppm. Furthermore, ta-C coatings withstood the pressing and normal cleaning procedures without any delamination or other kind of damage. The results obtained should be applicable to other processing tools as well.