Formation of Aluminum Titanate with Small Additions of MgO and SiO2

Sintering and characterization of aluminum titanate ceramics with enhanced thermomechanical properties

“…to modulate the morphology of grains and grain boundary cracks, these additives have abilities to create some isostructural solid solutions such as Al 2 TiO 5 -MgTi 2 O 5 or Al 2 TiO 5 -Fe 2 TiO 5 due to the introduction of the corresponding cations (e.g., Mg 2+ , Fe 2+ ) into the lattice structure of aluminum titanate. 3,[13][14][15][16][17] Meanwhile AT ceramics doped with MgO and Fe 2 O 3 , and their mixture can form a certain amount of elongated grains by liquid phase sintering at high temperature leading to high mechanical strength, while low thermal expansion coefficient retained. 18,19 Other secondary phases (such as mullite, SiO 2 , etc.)…”

“…Aluminum titanate (Al 2 TiO 5 ; AT), a synthetic ceramic material, is isomorphous with pseudobrookite (Fe 2 TiO 5 ) structure in form of orthorhombic crystallographic structure, which bears the following corresponding lattice parameters of a = 3.591, b = 9.429, and c = 9.636 Å 1 . AT has a broad spectrum of superb properties: fairly low coefficient of thermal expansion (0.2–1 × 10 −6 K −1 ), 2 ultrahigh thermal shock resistance (up to 500 Wm −1 ), 3 high melting point (≈1860°C), 4 resistance to molten metal, and molten glass; hence these properties enable utilization as high‐temperature structural ceramic candidates such as ceramic components in molten metal casting under quenching and hot conditions, honeycomb ceramic exhaust filters, and catalyst support materials 5–8 . The low thermal expansion coefficient of aluminum titanate is mainly due to microcracks existing within the interior, and the microcracks matrix is triggered by the severe thermal expansion anisotropy of different crystal axes ( α a = −2.9–3.0 × 10 −6 K −1 , α b = 10.3–11.8 × 10 −6 K −1 , α c = 20.1–21.8 × 10 −6 K −1 ) 9 during the cooling stage from sintering temperature, which is in connection with poor mechanical properties 10–12 …”

Effect of Boron Impurities on the Properties of Magnesium Oxychloride Cement

“…It has been reported that the above limitations could be resolved by the formation of stable solid solutions and through the microstructure modification by adding secondary phases at the intergranular boundaries during processing [7,8]. Although MgO or Fe 2 O 3 as stabilising additives and MgTi 2 O 5 as heterogeneous nucleation agents could enhance the formation of Al 2 TiO 5 solid solutions at a low temperature by a classical solid phase reaction, effectively stabilising the crystal structure and depressing its medium-temperature thermal decomposition, the thermal expansion of the as-received samples usually becomes bigger [3,9,[10][11][12][13][14]. In the case of the addition of secondary phases, such as mullite, ZrO 2 and Al 2 O 3 , or the in situ formation of mullite through the addition of SiO 2 , though the presence of these reinforced secondary phases may produce a duplex microstructure and restrict the microcrack development as well as improving the mechanical properties of the bulk material, these phases usually have a high thermal expansion coefficient, conferring a slight detrimental effect on its thermal expansion behaviour [4,6,7,15].…”

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

“…Aluminum titanate (Al 2 TiO 5 , AT) has attracted widespread attention because of its considerable properties of low thermal expansion coefficient (1.5 Â l0 À6 /K) and high-temperature resistance. [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.…”