Flexural strength evaluations and fractography analyses of slip cast mesoporous submicron alumina

Abstract

Mesoporous submicron α−Al2O3 green compacts were fabricated using slip casting of ultrafine alumina powders. The pre-sintered samples were sintered in air atmosphere at 1300 °C, 1350 °C, 1400 °C, and 1500 °C to obtain a variety of grain morphologies namely submicron equiaxed and micro rod structures. The resulting grain diameters lie between ∼270 nm and ∼1590 nm and total porosity fraction between 0.05 % and 13 %. The room temperature flexural strength (σ) evaluations and fractography analyses of sintered alumina samples were performed. It was observed that the total porosity fraction dictates the flexural strength as compared to grain diameter. Further, it was found that the flexural strength exhibited a decreasing trend for an increase in the total porosity fraction, and proved to be a better effective parameter than open porosity fraction. The fractography analyses suggest that samples sintered at 1300 °C and 1350 °C predominantly underwent intergranular fracture, while those sintered at 1400 °C and 1500 °C underwent a mixture of intergranular and transgranular fracture.

Perfluoropolyether-Impregnated Mesoporous Alumina Composites Overcome the Dewetting–Tribological Properties Trade-Off

“…FC exhibits the same trend as that of surface roughness ( R a ), as expected, and also depend on the grain diameters ( d grain ) and amount of OP . Wear-resistance, in addition to aforementioned parameters, is inversely dependent on TP, because the wear debris in this material are formed by local intergranular and transgranular fracture mechanisms . This is because, the flexural strength of the MPA samples, which strongly influences the wear-debris morphology and contents, are dictated by the total porosity fraction .…”

“…Mesoporous α-Al 2 O 3 green compacts were synthesized by employing a slip-casting process. ,, Both cuboidal and cylindrical green compacts were manufactured to utilize them as a tribo-pair. The green compacts were pre-sintered in air atmosphere in a tubular furnace to remove the binder that was utilized to prepare alumina suspensions for slip casting. ,, A heating rate of 1 °C min –1 used to heat to 600 °C, followed by 1 h of isothermal holding, produced ∼59% relative density pre-sintered samples. The pre-sintered samples were eventually sintered in air at 1150 ± 5, 1205 ± 5, 1250 ± 5, 1325 ± 10, and 1500 ± 10 °C in a tubular furnace with a 10 °C min –1 heating rate and 1 h of isothermal holding at the corresponding highest temperature to achieve 70 ± 3, 80 ± 3, 90 ± 3, 95 ± 1, and 99 ± 0.5% theoretical densities, respectively.…”

“…23 Wear-resistance, in addition to aforementioned parameters, is inversely dependent on TP, because the wear debris in this material are formed by local intergranular and transgranular fracture mechanisms. 29 This is because, the flexural strength of the MPA samples, which strongly influences the wear-debris morphology and contents, are dictated by the total porosity fraction. 29 Therefore, the lowest FC and smallest wear coefficients are achievable for the smallest ratios of S5.…”

“…29 This is because, the flexural strength of the MPA samples, which strongly influences the wear-debris morphology and contents, are dictated by the total porosity fraction. 29 Therefore, the lowest FC and smallest wear coefficients are achievable for the smallest ratios of S5. In Figure 8a, three regimes are expressed in checked green (regime I), yellow (regime II), and striped red (regime III).…”

A numerical investigation on ultrasonic bulk wave propagation features in functionally graded plates

“…Since in ceramics the wave propagation is affected by ceramics grain size, it could have the major effect on wave divergence, scattering, and reflection. Considering the wavelength of 3000 mm for a 4-MHz probe and the alumina grain size of $10 mm, 37,38 about 300 grains would exist in each wave length which decreases the effect of grain boundary on the wave propagation features. In other words, the effect of grain size on wave propagation can be neglected if significant numbers of grain exist in each wavelength.…”