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

Abstract

Materials from the Al 2 O 3 -SiO 2 -ZrO 2 and the Al 2 O 3 -SiO 2 -ZrO 2 -TiO 2 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 (Al 2 O 3 ), zircon (ZrSiO 4 ) and titania (TiO 2 ) were slip casted and sintered in a 1300-1500 1C temperature range in order to obtain mullite (3Al 2 O 3 Á 2SiO 2 ), zirconia (ZrO 2 ) and zirconium titanate (ZrTiO 4 ) 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 1C treatments. The reaction-sintering was followed by XRD, TG-DTA, and dilatometry. Densification started at 1100 1C and the chemical reactions only started above 1300 1C. Aluminum titanate (Al 2 TiO 5 ) was found to be an intermediate of the reaction after 1400 1C treatments. Materials treated below 1300 1C 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 K IC reached 9 GPa and 4.3 MPa m 1/2 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 1C treatments some detrimental grain growth was observed.

Low (and negative) thermal expansion Al2TiO5 materials and Al2TiO5 - 3Al2O3.2SiO2 - ZrTiO4 composite materials. Processing, initial zircon proportion effect, and properties

“…The manufacturer's capability to achieve the desired properties and behaviors is enhanced by combining two or more different materials; however, the final properties are not necessarily between those of pure materials [1][2][3][4][5][6]. In the manufacture of structural ceramics, the composite ceramic-ceramic strategy has been used for decades [5,[7][8][9]. Once the constituent phases and the processing conditions are chosen, the phase proportion becomes one of the most important processing variables [10].…”

“…It has received significant attention during the last decades as a potential structural material for high-temperature applications. Mullite-based composite structural ceramics have particularly been developed [7,10,29,30]. Zirconium titanate (ZT = ZrTiO 4 ) is commonly used as a dielectric in microwave devices due to its high permittivity at microwave frequencies [33][34][35].…”

“…Recently, we studied a family of composites of the same quaternary system with a continuous-dispersed phase microstructural configuration. Particularly, the studied material presented mullite as the continuous phase, and zirconia together with zirconium titanate as dispersed phases [7]. In that work, alumina, zircon and titania were chosen as starting powders in a 3:2:1 molar ratio.…”

Preparation of mullite whiskers from kaolin via the addition of tribasic calcium phosphate

“…The mullite forms in high alumina‐containing rocks at very high temperature but low pressure, thus, mullite rarely exists in natural rocks. However, mullite is an attractive engineering material as it has low thermal expansion and conductivity, high creep resistance, and corrosion stability together with suitable strength and fracture toughness, and is one of the crystalline phases most frequently found in the final phase composition of both traditional ceramics and new inorganic functional materials . The significant role of mullite in various materials has been reported in the large number of publications in recent years …”

“…However, mullite is an attractive engineering material as it has low thermal expansion and conductivity, high creep resistance, and corrosion stability together with suitable strength and fracture toughness, and is one of the crystalline phases most frequently found in the final phase composition of both traditional ceramics and new inorganic functional materials. [2][3][4][5][6][7][8] The significant role of mullite in various materials has been reported in the large number of publications in recent years. [9][10][11][12][13][14][15][16][17] Mullite whiskers, a special morphology of mullite crystal, have been considered as reinforcements in the high-temperature composites and porous ceramics for its excellent performance.…”