Determination of components in refractories containing silicon carbide by X-ray fluorescence spectrometry using glass beads

The chemical components in refractories containing silicon carbide were det ermined by an Xray fluorescence analysis using glass beads. Good- quality g lass beads can be prepared by the following method. After 0.3000 g of a sil icon carbide sample is mixed with 3.0000 g of flux (Li2B4O7), the mixture i s placed in a Pt-Au alloy dish. It is then fused in a furnace under an O-2 atmosphere at 840 degrees C for 33 hours, and finally fused at 1150 degrees C. Since the mass of the resulting glass bead is increased by the oxidatio n of SiC, which produces SiO2 during sample heating, the ratio of 10 : 1 be tween the flux and the sample is changed. For this reason, the popular JIS method of using SiO2 - Al2O3 binary calibration curves could not be applied to obtain an accurate analysis with these glass beads. We therefore develo ped a new calibration method. In this method, the gain on ignition (GOI) is regarded as being a component in the sample, and the theoretical matrix co rrection coefficients (d(j)) of each component are calculated by the fundam ental parameter procedure (FP procedure) using the GOI as a base component. The GOI-SiO2 binary calibration curves (GOI correction curves) are made wi th the d(j)s obtained by the FP procedure. With this method the standard de viation (SD) of the GOI correction curves is very satisfactory. Our test re sults include an SD of 0.24 mass% for SiO2 and 0.096 mass% for Al2O3 The GO I correction curves are applicable to all components in the reference mater ials, except for Fe2O3.