Effects of chemical corrosion and thermal shock on the properties of mullite- and cordierite-bonded porous SiC ceramics prepared using waste fly ash

The chemical corrosion resistance properties of newly developed oxide (mullite-, cordierite)-bonded SiC ceramics prepared using mixture of waste fly ash and metal oxide additives were investigated in environments containing Na2SO4 at temperature 1000 degrees C for 8 h. The thermal shock resistance to cooling were evaluated as a function of quenching cycles. The changes in weight, flexural strength, and morphology due to thermal and chemical corrosion were examined. The mechanisms of flexural strength degradation due to chemical and thermal corrosion were analyzed, and the results were compared with literature data. In the hot corrosion by Na2SO4, the cordierite component was severely attacked in the cordierite-bonded SiC ceramics resulted similar to 34% strength degradation after 8 h corrosion; on the contrary, mullite-bonded SiC ceramics exhibited similar to 4% improvement of flexural strength. The chemical and thermal shock resistance results suggest a potential advantage of porous SiC ceramics prepared using waste fly ash for several industrial applications.