Determination of components in alumina-chrome refractories by X-ray fluorescence spectrometry using glass beads

Abstract

The chemical components in alumina-chrome (AC) refractories were determined by X-ray fluorescence spectrometry (XRF) using glass beads (GB). AC refractories which contain much Cr2O3 can not be fused with only Li2B4O7. Thus, LiNO3 must be added as an oxidizing agent. The fusing conditions for the GB were chosen as follows: sample (0.2000 g)-Li2B4O7 (3.0000 g)-LiNO3 (3.000 g), 1250 °C-10 min. Complete fusion of the Cr-containing sample was suspected to have been proceeded by the formation of CrO42-, caused by the oxidation of Cr(III), converting it to Cr(VI). This possibility was investigated by the CrK-edge X-ray absorption near-edge structure (XANES) spectra. According to preliminary results of Cr(VI) by XANES, the Cr(VI) content in a GB prepared with only Li2B4O7 was merely 7% against the total Cr, but in the GB with Li2B4O7 and LiNO3 it was 39%. Moreover, the Cr(VI) content in the GB with Na2B4O7 and NaNO3, which could be easily fused, but could not be used for actual analysis, because of the contain Na2O content, was 95%. The GBs used for the calibration curve were prepared by accuratly weighing alumina system reference materials and reagent Cr2O3 on a micro-balance of 1 μg accuracy limit and fusing them with Li2B4O7 and LiNO3. As a result, the accuracies (SD) of the calibration curves prepared with these GBs were very satisfactory for Al2O3: 0.21 mass%, Cr2O3: 0.07 mass %, SiO2: 0.027 mass% and so on.