The effect of wall thickness distribution on mechanical reliability and strength in unidirectional porous ceramics

Abstract

Macroporous ceramics exhibit an intrinsic strength variability caused by the random distribution of defects in their structure. However, the precise role of microstructural features, other than pore volume, on reliability is still unknown. Here, we analyze the applicability of the Weibull analysis to unidirectional macroporous yttria-stabilized-zirconia (YSZ) prepared by ice-templating. First, we performed crush tests on samples with controlled microstructural features with the loading direction parallel to the porosity. The compressive strength data were fitted using two different fitting techniques, ordinary least squares and Bayesian Markov Chain Monte Carlo, to evaluate whether Weibull statistics are an adequate descriptor of the strength distribution. The statistical descriptors indicated that the strength data are well described by the Weibull statistical approach, for both fitting methods used. Furthermore, we assess the effect of different microstructural features (volume, size, densification of the walls, and morphology) on Weibull modulus and strength. We found that the key microstructural parameter controlling reliability is wall thickness. In contrast, pore volume is the main parameter controlling the strength. The highest Weibull modulus () and mean strength (198.2 MPa) were obtained for the samples with the smallest and narrowest wall thickness distribution (3.1 m) and lower pore volume (54.5%).

Mechanical properties and failure behavior of unidirectional porous ceramics

“…Ice-templated specimens were produced following the same procedure reported elsewhere 10 . Basically, suspensions were prepared by mixing distilled water with 3 mol% yttria-stabilized zirconia (TZ-3YS, Tosoh, Tokyo, Japan) at different weight ratios (from 45% to 70%), 0.75 wt.% of dispersant (Prox B03, Synthron, Levallois-Paris, France), and 3 wt.% of organic binder PVA (PVA2810, Wacker, Burghausen, Germany).…”

Synthesis of Functional Ceramic Supports by Ice Templating and Atomic Layer Deposition

“…First, templated monoliths of 3 mol% YSZ were prepared following the ice-templating process described previously (Seuba et al, 2016). The unidirectional freezing of water taking place during the ice-templating process enables to obtain regular macroporous materials.…”

“…Ice-templated monoliths of 3 mol% YSZ were prepared from aqueous ceramic slurry, following a procedure described previously (Seuba et al, 2016). Briefly, the aqueous slurry was prepared with 3 mol% YSZ (TZ-3YS, Tosoh, Japan), and 10 ml of the slurry was then poured into a PTFE mold (20 mm diameter and 25 mm height) placed on a copper plate.…”

The effect of gelation on statically and dynamically freeze‐cast structures

“…3 Anisotropy of pores is usually evaluated by simple visual comparison between perpendicular and parallel cross sections. Low tortuosity of macropores is often claimed as a characteristic for freeze-cast structures, 11,12,29,34,35 but is rarely calculated and evaluated with respect to freezing conditions. Miller et al 6 calculated tortuosities, however, only for static freezing conditions and only at one sample height.…”