Elastic Properties of Mullite

Abstract

Using ultrasonic methods, we determined the ambienttemperature elastic constants of dense (99.7%) hot-pressed polycrystalline 3:2 mullite (3Al 2 O 3 ؒ2SiO 2 ). We report the usual polycrystal elastic constants: Young's, shear, and bulk moduli, and the Poisson's ratio (). The Poisson's ratio ( = 0.280) suggests interatomic bonding that is very different from that of either alumina or silica. Temperature dependences of the elastic constants show a strong irregularity; for example, decreases as the temperature increases. This irregularity suggests an internal-state change that is perhaps related to the incommensurate structural modulation.

Design and production of ceramic laminates with high mechanical reliability

“…7. Young modulus and Poisson's ratio values for AM and AZ composites shown in Table 1 correspond to Voigt-Reuss bounds [17]; according to previous results [26], Young modulus and Poisson's ratio equal to 229 GPa and 0.27, respectively, were considered for pure mullite. The elastic modulus for pure alumina and zirconia was measured on monolithic samples as reported elsewhere [27].…”

Novel mullite-based ceramics manufactured from inorganic wastes

“…In this work, however, it is noted that the values (Table 1) are nearly independent upon the porosity, in the range investigated (0.1-50%). The mean value of obtained was 0.20 which is lower than that of 3:2 mullite (0.28) but intermediate between values of ␣-alumina (0.23) and silica (0.17) (Ledbetter et al, 1998). The presence of voids, cracks and elastically softer phases, such as a glassy phase enveloping the mullite particles, are expected to affect elastic stiffness.…”

“…This suggests that the Spriggs equation can be used to fit reasonably well the measured data of Young's modulus and shear modulus and therefore to correlate the dependence of the modulus of elasticity on porosity. However, the E values in Table 1 (Ledbetter et al, 1998;Ledbetter et al, 2001) and quartz (E = 96 GPa and G = 44 GPa) (Ledbetter et al, 1998) are much lower than those of mullite (E = 228 GPa and G = 89 GPa) (Ledbetter et al, 1998).The Poisson's ratios of the sintered bars were calculated from the mean E and G values, assuming that these materials are isotropic. In case of elastic isotropy, E and G are related by the equation:…”

Modeling thermal shock damage in refractory materials via direct numerical simulation (DNS)

“…7, based on the data given in Refs. [16][17][18][19]. A linear relation between the Cauchy stresses and logarithmic strains is adopted and heat fluxes are determined by Fourier's law of heat conduction.…”