Effect of sintering on TiO2-impregnated alumina foams
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The effect of sintering on the bulk properties, morphology and phase composition of ultralight Al2O3 foams impregnated with TiO2 was investigated in comparison with pure alumina foam in the temperature range of 900–1600°C in air. Impregnation was carried out by immersion of pre-sintered alumina foam in a sol of titanium isopropoxide-acetylacetone complex. The changes of the foam linear shrinkage, effective density and porosity were studied along with morphological evolution and relationship between these properties was demonstrated. Titania impregnation increased the linear shrinkage (LS) during sintering by a maximum of 5% relative to pure alumina foams. The change of LS and weight loss of TiO2/Al2O3 foams lead to a final density of 0.19 g/cm3 and porosity of 95%. The initial coating was found to develop a mosaic structure due to early shrinkage of the coating. After sintering at 1600°C the coating reacted with the underlying Al2O3 surface and became uniformly distributed. Finally, it was shown that the reacting TiO2 layer formed the tialite (Al2TiO5) phase below 1400°C. This Tialite coating remained intact under 1200°C without stabilizers.
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