Thermal Cyclic Fatigue Behavior of Porous Ceramics for Gas Cleaning

Abstract

The thermal shock fatigue resistance of cordierite and SiC filters with a mullite filtration layer was evaluated under simulated reverse cleaning conditions. O‐ring specimens were thermally shocked by cyclically blowing cold air outward through them while they were exposed to high‐temperature flue gas. The calculated values of the tangential tensile stresses induced by the temperature differences between the inner and outer surfaces were found to be largest at the inner surfaces. It was also found that the elastic modulus and the thermal expansion coefficient of the filters affect the magnitude of the thermal stresses more than the thermal diffusivity and thermal transfer area, which were directly related to the microstructure of the filters. Failure of both filters is believed to have initiated at the inner subsurfaces because of the effects of thermal shock. The thermal shock fatigue lifetimes increased as thermal stresses decreased. The fatigue parameters for the SiC and cordierite filters were found to be 41 and 22, respectively. These parameters probably vary over different operating temperature ranges, especially in the case of SiC filters, where changes in their composite microstructures affect their high‐temperature strength.

Effect of template size on microstructure and strength of porous silicon carbide ceramics

“…The heat-treated compacts were further JCS-Japan sintered at 1850°C for 1 h with a heating rate of 20°C/min in argon and subsequently annealed at 1950°C for 4 h for the β →α phase transformation of SiC and grain growth. 10) The porosity of the porous ceramics was calculated from the bulk density (Db) of the porous ceramics and the theoretical density (Dth, 3.349 g/cm 3 ) of the strut material according to…”

Effect of aluminum source on flexural strength of mullite-bonded porous silicon carbide ceramics

“…The weight loss due to decomposition of Al(OH)3 during sintering is probably responsible for the observed low density for MBSC4. Furthermore, MBSC1 specimen prepared with the green density of 1.82 g/cm 3 showed high strength of ~27 MPa when compared against ~23 MPa strength and 1.94 g/cm 3 density for MBSC4 ( Fig. 7(d)).…”

“…7(a). MBSC2 specimen prepared with the compacts of lowest green density of 1.73 g/cm 3 consisted of a maximum porosity of ~37%, while MBSC3 specimen prepared with compacts of highest green density of 2.22 g/cm 3 exhibited a minimum porosity of ~17%. However, the corresponding relationship between the green density and sintered density of the specimen is not observed (Fig.…”

“…7(b)). Particularly, 1.94 g/cm 3 green density resulted in a low sintered density of 1.85 g/cm 3 in case of MBSC4, when compared against 1.82 g/cm 3 green density and 1.86 g/cm 3 sintered density for MBSC1. This deviation in case of MBSC4 is also observed in relationship between green porosity and sintered porosity (Fig.…”

Effects of silicon particle size on microstructure and permeability of silicon-bonded SiC ceramics

“…16), 17) On these bases, they have found many applications including filtration of molten metal, filtration of particles from diesel engine exhaust gases, filtration of hot corrosive gases in various industrial applications, gas-burner media, membrane supports for gas separation and light-weight structural parts for high temperature applications. For filters, vacuum chucks, and air spindle applications, the achievement of high gas permeability is a key factor in the development of porous SiC ceramics.…”