Feng He

This study addresses the corrosion problem of refractory materials during high-temperature molten treatment of pharmaceutical waste salt, and systematically investigates the interface behavior and corrosion mechanism of MgO-based refractory materials in simulated pharmaceutical waste salt (65 wt% NaCl-30 wt% Na₂SO₄-5 wt% CaCO₃). Through sessile drop wetting infiltration experiments, static corrosion tests (950 °C and 1150 °C/48 h), combined with SEM-EDS, XRD characterization, and FactSage thermodynamic calculations, the corrosion resistance of high-purity MgO phase (HM-97) refractory materials and magnesium–aluminum spinel composite phase (MA-85) refractory materials was compared and analyzed. The results show that due to the fine periclase grains and rich grain boundaries, the molten salt infiltration rate of HM-97 material in the 644–800 °C range is significantly higher than that of MA-85. After corrosion at 950 °C, HM-97 and MA-85 formed 47 μm and 53 μm transition layers respectively, and the HM-97 surface generated Ca₃Mg(SiO₄)₂ phase leading to uneven corrosion morphology. At 1150 °C, HM-97 produced long cracks and the transition layer thickness remained almost unchanged due to dissolution, while MA-85 formed an approximately 72 μm transition layer and a dense metamorphic layer. Phase analysis and thermodynamic calculations suggest that the MgAl₂O₄ phase in MA-85 is likely stable at high temperatures, which appears to effectively prevent molten salt infiltration and contribute to forming a protective metamorphic layer, thereby potentially enhancing the material’s corrosion resistance. The MgAl₂O₄ phase is proposed to improve the service performance of MgO-based refractory materials in the molten pharmaceutical waste salt environment.

Large-scale reuse of copper tailings can mitigate environmental hazards and recover strategic elements; this work investigates the feasibility of producing foam glass-ceramics with high copper-tailing content (>70 wt%) by tuning the CaO/SiO₂ ratio to couple melt viscosity and crystallisation. The comprehensive utilisation of these tailings helps mitigate environmental pollution and enhance resource efficiency. In this study, foam glass-ceramics with varying CaO/SiO₂ ratios were synthesised through melt quenching followed by foaming heat treatment. The effects of different CaO/SiO₂ ratios on the foaming behaviour, crystallisation, and microstructure were investigated using DSC, FTIR, viscosity, XRD, SEM, and CT. The results indicate that increasing the CaO/SiO₂ ratio disrupts the three-dimensional network structure of the glass, which lowers the glass viscosity and influences the bubble size and distribution in the foam glass-ceramics. Additionally, the increased CaO content promotes crystal precipitation and enhances the compressive strength of the foam glass-ceramics. At a CaO/SiO₂ mass ratio of 0.22, the foam glass-ceramics exhibited the lower bulk density (240 kg/m³) and thermal conductivity (0.07 W/m·K). The materials also demonstrated good water absorption and compressive strength. This study highlights the potential of using copper tailings in foam glass-ceramics to improve their overall performance, offering promising energy-saving and environmentally friendly solutions.

A systematic investigation was conducted into the effects of varying Al₂O₃ and SrO contents on the structure, sintering kinetics, crystallization patterns, and properties of the SrO-BaO-ZnO-MgO (RO)-B₂O₃-Al₂O₃-SiO₂ (RBAS) system. This glass-ceramic demonstrates effective applicability for low-temperature co-firing of alumina ceramics. Increasing Al₂O₃ content densified the glass network and reduced crystallinity, thereby promoting sintering densification. It led to improved acid resistance and a lower coefficient of thermal expansion (CTE). The composition with 17.50 mol% Al₂O₃ sintered at 800 °C exhibited optimal properties: a well-matched CTE of 7.45 × 10⁻⁶ K⁻¹, a high flexural strength of 130.58 MPa, and excellent chemical stability. Furthermore, it demonstrated excellent compatibility when co-sintered with an Al₂O₃ substrate.