Mechanical Behavior of Tubular Freeze-Cast Substrates with Organized Pore Structure

Abstract

Despite the high potential of the freeze-casting technique for production of porous inorganic substrates, there is a lack of studies on tubular geometries and their mechanical behavior under different pressure scenarios. In this work, the mechanical behavior of tubular freeze-cast alumina substrates was assessed by mathematical models from experimental O-ring tests. The stress distributions revealed a concentration of tensile stresses (within 0.2-25.0 MPa) on the plane of the load, causing brittle fracture. Furthermore, the results confirmed that the honeycomb model for brittle material adequately predicted the mechanical strength of the tubular freeze-cast substrates. Finally, fracture criteria from honeycomb model was used to estimate the maximum homogeneously distributed pressures, such as in fluids, that the substrates can withstand. This configuration represents more precisely practical conditions, though is hard to experimentaly replicate. Therefore, the developed procedure is paramount to simulate the mechanical behaviour of the tubular freeze-cast substrates under real operating conditions.

Microstructure Evolution During the Sintering of Freeze-Cast Alumina

“…The alumina freeze-cast tubes produced in this study have already been reported in previous studies describing the structure of the macropores produced by freeze-casting and its influence on the mechanical behavior 21,47 , as well as for production of membranes 14,57 . Representative micrographs of the radially aligned porosity are reproduced for reader's ease in Figure 1a, with pore sizes ranging within 5-10 µm 57 .…”

“…Therefore, this study aims to evaluate the sintering process on freeze-cast alumina substrates and compare the results from different characterization methods, such as stereological analysis of SEM micrographs, N 2 adsorption and X-ray diffraction analysis. Since the macroporosity and the mechanical behavior of the alumina freeze-cast substrate produced in this study has already been described elsewhere 21,47 , this report focuses mainly on the interparticle porosity, as well as the effects of sintering temperature on the crystallite size and lattice strain. The N 2 adsorption isotherms were analyzed using both the BET/classical and DFT methods, allowing estimation of the presence of pores and pore size distribution.…”