Study on preparation of thermal storage ceramic by using clay shale

Shale was used as main raw material for developing thermal storage ceramics. The samples were fabricated via semi-dry pressing followed by pressureless sintering. The result showed that the sample (75% shale, 10% kaolin, 10% potash feldspar and 5% soda feldspar) fired at 1080 °C exhibited the best comprehensive performance. Ocular examination reveals that no cracks were observed after 30 cycle times thermal shock tests (wind cooling from 600 °C to room temperature). The results presented that the high bending strength remained after 20 cycle times thermal shock tests but plummeted at the thirtieth time. Other properties were given as follows: bulk density: 2.60 g/cm3; thermal conductivity: 2.33 W/(m °C); and heat storage density: 578.50 mJ/m3. XRD analysis indicated that the quartz and hematite were the main solid phases in the sample. Some isolated pores, quartz crystals, granular hematite crystals and needle-like mullite crystals were observed in the matrix according to the SEM (Scanning Electron Microscope) analysis. More pores were found with temperature rizing according to SEM analysis. The relatively high content of Fe2O3 contributed to the formation of the vitreous phase and favored the densification. Overall, the introduction of shale effectively reduced the firing temperature and performed the better thermal storage properties.