PROBLEMS BY USING PRESSED POWDER PELLETS FOR XRF ANALYSIS OF FERROSILICON ALLOYS

The problems by using pressed powder pellets for XRF analysis of ferrosilicon alloys have been investigated. The origin of the problems is the heterogeneity of the solidified ferrosilicon. A variety of distinct crystallographic phases with varying X-ray absorption and grinding properties are formed from the molten metal resulting in large particle size effects. This in turn affects the accuracy and precision of the XRF analysis. A second effect that has to be accounted for is the stability of the powder pellets. The choice of binder agent is found to be essential to obtain stable pellets that are less affected by radiation and aging. The results show that grinding time, grinding vessel, grinding machine, cooling rate of the metal and choice of binder agent greatly influence the analysis results. To manage the problems it is of utmost importance to have a strict control of the sample preparation routines.