Dense mullite–zirconia–zirconium titanate ceramic composites by reaction sintering

Abstract

Materials from the Al2O3-SiO2-ZrO2 and the Al2O3-SiO2-ZrO2-TiO2 systems have several high temperature applications because they present the good refractoriness, chemical inertness, adequate mechanical and thermo-mechanical behaviors with a relatively good cost: performance ratio. In this work stoichiometric (3:2:1) molar incompatible mixtures of alumina (Al2O3), zircon (ZrSiO4) and titania (TiO2) were slip casted and sintered in a 1300-1500 °C temperature range in order to obtain mullite (3Al2O3·2SiO2), zirconia (ZrO2) and zirconium titanate (ZrTiO4) dense triple ceramic composite. Both sintering and reaction occurred after the thermal treatments. Reaction progress and densification evolutions were established. Dense Triplex composite materials were achieved after 1500 °C treatments. The reaction-sintering was followed by XRD, TG-DTA, and dilatometry. Densification started at 1100 °C and the chemical reactions only started above 1300 °C. Aluminum titanate (Al2TiO5) was found to be an intermediate of the reaction after 1400 °C treatments. Materials treated below 1300 °C presented a partial densification of the unreacted starting powders. Resulting ceramic materials were characterized. The crystalline phases were evaluated, as well as the texture properties. The achieved microstructure consisted in interlocked multiphase ceramic with zirconia (monoclinic) grains. The achieved Hv and KIC reached 9 GPa and 4.3 MPa m1/2 respectively. The dense and interlocked ceramic microstructure and relative high mechanical properties of the developed material encourages several high temperature applications. Finally it can be pointed out that after 1500 °C treatments some detrimental grain growth was observed.