Novel Method To Optimize the Structure of Reticulated Porous Ceramics

Abstract

A novel method has been developed for the fabrication of silicon nitride reticulated porous ceramics (RPCs) with regulated structure, using polyurethane sponge as the template. This technique includes two centrifuging steps. In the first stage, the polyurethane sponges are coated with thin slurry through high‐speed centrifuging. After the slurry on sponges dried, a high‐strength green body without filled cells is obtained. In the second stage, because of improved adhesion between the body and the slurry after the first coating, the body with uniformly thick strut is produced by recoating the as‐prepared green body with thixotropic slurry and centrifuging again. The loading content of slurry and the pore diameter of the RPCs body greatly depend on the slurry viscosity in the process of recoating. The strut diameter and pore diameter of the RPCs are effectively optimized by modulating the slurry viscosity.

Processing Routes to Macroporous Ceramics: A Review

“…68 Figure 4 shows that the strut flaws reduce the compressive strength of replica-derived porous ceramics to levels usually lower than the strength theoretically predicted for open cell structures. 76 Many attempts have been made to avoid this shortcoming by, for instance, improving the wetting of the suspension on the sponge with the help of additives, 21,25 performing a second impregnation step to fill the cracks in the ceramic struts, [17][18][19]22 and introducing fibers 77,28 or reactive compounds 25 to enhance the material's Impregnation with preceramic polymers SiOC-C composites 63 Liquid precipitation of precursors Macroporous zeolites, 64 Calcium phosphate-based composites integrity. In contrast to ceramic suspension-derived reticulated structures, cellular materials obtained from preceramic polymers have crack-free struts due most likely to the improved wetting on the sponge and the partial melting of the cross-linked polymer during pyrolysis.…”

Increased Mechanical Stability and Thermal Conductivity of Alumina Reticulated Porous Ceramics (RPC) by Nanoparticle Infiltration Processing

“…Recoating the RPC for filling cracks with additional slurry also increases the strut thickness and, therefore, decreases the size of 1st order pores. [10,11] Another approach is the infiltration of the hollow struts with a melt. [12,13] The infiltration with a fluid is limited to filling materials with a melting temperature below that of the strut materials.…”

Processing of Ceramic Foams with Hierarchical Cell Structure

“…[24] A pronounced increase in crushing strength by a factor of 3 or more was achieved by over-coating of conventional reticulated ceramic foams with low viscous slurry, chemical vapor deposition, or sol-gel coating, respectively. [25,26] Post-infiltration of hollow struts was successfully demonstrated to reduce defect size and morphology giving rise for a substantial improvement of fatigue strength. [27] The challenge is to improve mechanical properties of ceramic foams without increasing the fractional density substantially and to realize structures at smaller scale levels with cell sizes <10 mm.…”