Grain‐Boundary Microcracking Due to Thermal Expansion Anisotropy in Aluminum Titanate Ceramics

Abstract

The relation between grain size and grain‐boundary microcracking during cooling in aluminum titanate ceramics was studied. Microcracking temperature was determined by the measurement of thermal contraction and expansion, which was accompanied by acoustic emission. When the ceramics were cooled at a rate of 6°C/min, stress relaxation did not occur below the sintering temperature of 1500°C. The relation between the temperature difference from the sintering temperature to the microcracking temperature and the grain size showed good agreement with the prediction based on the energy criterion of grain‐boundary microcracking.

Microstructural evolution during high-temperature oxidation of spark plasma sintered Ti2AlN ceramics

“…Firstly, thermal expansion mismatch of phases in the oxide scale causes the cracks during rapid cooling. Secondly, the high anisotropy of thermal expansion in Al 2 TiO 5 is known to trigger spontaneous microcracking upon cooling when a critical size is exceeded [40,41] . Stress generated by formation of reaction products with larger volumes than the reactants can cause cracks to form [42].…”

Cation distribution of pseudobrookite-type titanates and their phase stability

“…3), 4) These grain boundary cracks cause low mechanical strength and low thermal expansion in ceramics. The latter property is attributed to the fact that thermal expansion in the direction of a large thermal expansion coefficient only fills the gap of a grain boundary crack.…”

Al2O3–TiO2/ZrO2–SiO2 based porous ceramics from particle-stabilized wet foam

“…Although being such a wonderful thermal shock resistive material, this ceramic has a big disadvantage related to its stability as a whole in the temperature range of 750-1280 ℃. During cooling, in this temperature range, Al 2 TiO 5 is  decomposed into Al 2 O 3 and TiO 2 [7,8], and this decomposition results in apparently useless materials for industrial applications because they no longer exhibit the low thermal expansion coefficient and thermal shock behavior. However, the enhancement of thermal durability of Al 2 TiO 5 can be possible by adding thermodynamical stabilizers such as MgO, Fe 2 O 3 , and TiO 2 , which are isomorphous with pseudo-brookite minerals like Fe 2 TiO 5 [9], MgTi 2 O 5 [10], Ti 3 O 5 (anosovite) [11], and MgAl 2 O 4 (spinel) [12].…”