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

Abstract

Aluminum titanate (Al 2 TiO 5) materials and aluminum titanate-mullite-zirconium titanate (Al 2 TiO 5-3Al 2 O 3 .2SiO 2-ZrTiO 4) composite materials were successfully processed from fine commercial powders and characterized. This was achieved by zircon (ZrSiO 4) addition to stoichiometric alumina-titania mixtures. Zircon addition was the principal processing variable explored. This additive stabilizes the unstable aluminum titanate phase, enhances the sintering process, restricts microcrack development and improves the mechanical properties of the bulk material, but has a slight detrimental effect on its thermal expansion behavior (α app from-1.5 to 2.5 x 10-6 °C-1 in the RT-800 °C range). With a clear microstructure configuration change, all the technological properties are directly (linearly) correlated with zircon proportion in the initial formulation in the range between 5 and 30 wt%. Developed phases were established, relatively dense ceramics were produced, and complex microstructures with multiphasic interlocked grains were identified. Also, an interconnected microcrack matrix was observed with no material integrity loss which explained the low or even negative thermal expansion behaviors observed in the developed materials. This, together with the mechanical behavior detected, encourages structural applications with high thermomechanical solicitations. The triplex composite material presented an excellent thermomechanical behavior and low porosity, 48 MPa flexural strength, low stiffness and high sintering grade with low thermal expansion.

High temperature mechanical behavior of low stiffness Al2TiO5 and Al2TiO5–3Al2O3.2SiO2–ZrTiO4 composite materials

“…The general microstructure features observed for each material are in agreement with those previously reported 13 . A matrix of microcracks apparently interconnected and the presence of pores can be seen in every case.…”

Sintering and characterization of aluminum titanate ceramics with enhanced thermomechanical properties

“…18,19 Other secondary phases (such as mullite, SiO 2 , etc.) [20][21][22][23][24][25] can also be used to achieve this goal. Silica is mainly aimed at forming a liquid phase at sintering temperature, leading to further densification.…”

Influence of Cooling Rates on the Microstructure and Mechanical Properties of Aluminum Titanate Flexible Ceramic

“…[5][6][7][8] Despite its low thermal expansion coefficient, AT exhibits high thermal expansion anisotropy (α a % 11 Â 10 À6 C À1 , α b % 21 Â 10 À6 C À1 , and α c % À3 Â 10 À6 C À1 ). [9][10][11] Accordingly, thermal stress would be easily generated during cooling, leading to spontaneous microcracks. [12,13] When stressed, these microcracks could provide space for AT grains to move, resulting in the flexibility of AT ceramics.…”