Micro- and macroscopic thermal expansion of stabilized aluminum titanate

Microcrack orientation in porous aluminum titanate

“…Therefore, Al 2 TiO 5 was described as an orthorhombic crystal with a b-facecentered unit cell, space group Bbmm, and the following lattice parameters: a = 9.439 Å , b = 9.647 Å , c = 3.593 Å . According to present data and previous work [12,23], the micro-and macroscopic thermal expansion curves of porous AT, fitted from ND data and measured by dilatometry, have the shapes shown in Fig. 3a and b, respectively.…”

“…Many other details of the model, as well its advantages over and drawbacks with respect to more sophisticated approaches, are thoroughly described elsewhere [7,8,23] and will not be discussed here, since the main point of this discussion is the impact of the hypothesis that w b = 0 at all temperatures.…”

“…The model presented above provides a powerful tool for reproducing the measured macroscopic expansion on the basis of microscopic (lattice) dilation data and calculating the internal micro-stress variation during cooling [23]. However, it rests on the working hypothesis that the b-axis is disconnected.…”

Microstructure–Property Connections for Porous Ceramics: The Possibilities Offered by Micromechanics

“…Microcracking is responsible for hysteresis in the thermal expansion and stiffness versus temperature curves (see data on magnesium titanate, aluminum titanate, NZP ceramics, and cordierite) and has been directly observed in SEM studies (e.g., Shyam et al; Harada). Microcracking is also responsible for the nonlinearity of the stress–strain curves, especially in porous ceramics .…”

“…Instead, in modeling the stress–strain curve of AT, we use constants for a single crystal (possessing orthorhombic symmetry) that were obtained by molecular dynamics simulations, and then average the elastic constants over the polycrystal using Kröner's self‐consistent scheme for the isotropic polycrystalline aggregates. For a single crystal, the stiffnesses are (in GPa) as follows:Kröner's averaging procedure then yields E 0 = 309 GPa and ν 0 = 0.33.…”