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Anorthite ceramics (CaAl 2 Si 2 O 8) was obtained by slip casting of water suspension of kaolin (Al 2 O 3 ·2SiO 2 ·2H 2 O) and CaCO 3 as a source of CaO. A relative density of 87 % of the theoretical density was achieved after a 3-h-long sintering of green samples at 1200 °C. It was found that slip casting allows the fabrication of anorthite with relatively small pores (<8 μm) which was beneficial for achieving a high fracture strength of 129 MPa and good thermal shock resistance. For a quantitative measurement of thermal shock resistance, a critical temperature interval (ΔT c) was determined by a reduction in the mean fracture strength of at least 30 %. The experimentally determined ΔT c of 300 °C was higher than the value calculated by the equation assuming that the thermal stress created during quenching causes the fracture. It was found that the discrepancy between experimental and calculated values of ΔT c could be explained by an introduction of cracks of various sizes by indentation method and careful observation of crack growth initiation after quenching from various temperatures. It is believed that the reason for the discrepancy lies in the different nature of stress that was used in the theoretical calculation and the stress that acts during sample quenching. [ABSTRACT FROM AUTHOR]

Anorthite ceramics (CaAl 2 Si 2 O 8) was obtained by slip casting of water suspension of kaolin (Al 2 O 3 ·2SiO 2 ·2H 2 O) and CaCO 3 as a source of CaO. A relative density of 87 % of the theoretical density was achieved after a 3-h-long sintering of green samples at 1200 °C. It was found that slip casting allows the fabrication of anorthite with relatively small pores (<8 μm) which was beneficial for achieving a high fracture strength of 129 MPa and good thermal shock resistance. For a quantitative measurement of thermal shock resistance, a critical temperature interval (ΔT c) was determined by a reduction in the mean fracture strength of at least 30 %. The experimentally determined ΔT c of 300 °C was higher than the value calculated by the equation assuming that the thermal stress created during quenching causes the fracture. It was found that the discrepancy between experimental and calculated values of ΔT c could be explained by an introduction of cracks of various sizes by indentation method and careful observation of crack growth initiation after quenching from various temperatures. It is believed that the reason for the discrepancy lies in the different nature of stress that was used in the theoretical calculation and the stress that acts during sample quenching. [ABSTRACT FROM AUTHOR]

Cordierite-acicular mullite composites containing 0, 25, 50, 75 and 100 wt% of mullite were fabricated from waste MoSi 2 and commercial powders of Al 2 O 3 and spinel (MgAl 2 O 4). Careful oxidation of pulverised waste MoSi 2 rendered a precursor mixture of MoO 3 and amorphous SiO 2 , which served as pore forming agent and SiO 2 source, respectively. Evaporation of MoO 3 at ∼750 °C allowed production of highly porous cordierite-mullite ceramic composite after sintering in air at 1350 °C for 4 h. The combination of equiaxed cordierite grains and elongated (prism-like) mullite grains, resulted in unique microstructure with open porosity between 53.3 and 55.6 vol% which makes the obtained composite convenient for application as diesel particulate filter material. The presence of mullite affected four key thermo-mechanical properties which determine the thermal shock resistance of cordierite-mullite composite. The best thermal shock resistance was measured in composite containing 75 wt% of mullite. It was a result of improved thermal conductivity (1.081 W/mK) and bending strength (3.62 MPa) and relatively low values of coefficient of thermal expansion (3.8 × 10−6 K−1) and elastic modulus (2.27 GPa). [ABSTRACT FROM AUTHOR]