Comparison of thermal expansion and heat capacity properties of various borosilicate glass-bonded strontium chloroapatite composites loaded with simulated pyrochemical waste

Abstract

Four different glass compositions were used to encapsulate strontium chloroapatite (SrApCl) ceramics along with 10 mass/% simulated chloride waste to fabricate glass-bonded composites for nuclear waste immobilization applications. The glass compositions chosen were borosilicate glass (BSG), aluminoborosilicate glass (AlBSG), barium borosilicate glass (BaBSG) and lead borosilicate glass (PbBSG). The composites were fabricated by heat-treating the reaction mixtures at 1,073 K in air. The Products were characterised by powder XRD. The % linear thermal expansion of these composites was measured by dilatometry. The average thermal expansion coefficients (αav) of these composites were found to be in the range of 14.5 ± 0.29 × 10−6–16.4 ± 0.32 × 10−6 K−1 at 323–715 K range of measurement. The glass transition temperature (Tg) of the glass–ceramic composites were also measured by dilatometry. Tg and heat capacity (Cp) of SrApCl-10w20BSG, SrApCl-10w20AlBSG, SrApCl-10w20BaBSG and SrApCl-10w20PbBSG were also measured by differential scanning calorimetry (DSC), and the values obtained are 730 ± 22, 718 ± 21, 700 ± 20 and 700 ± 20 K, respectively. The Cp values for SrApCl-10w20BSG, SrApCl-10w20AlBSG, SrApCl-10w20BaBSG and SrApCl-10w20PbBSG are 0.57 ± 0.006, 0.60 ± 0.006, 0.52 ± 0.005 and 0.54 ± 0.005 J K−1 g−1, respectively.