Development and mechanical characterization of novel ceramic foams fabricated by gel-casting

Abstract

Porous ceramic materials are of considerable interest for a variety of chemical and industrial applications in extremely harsh conditions, particularly at very high temperatures for long times. A modified gelcasting process employing agar as a natural gelling agent and polyethylene spheres as pore formers was exploited to produce porous ceramic bodies. Alumina and alumina-ZrO 2 (AZ) powders were used to prepare samples having a porosity of about 65-70-75 vol%. The composite powder was produced by a surface modification route, i.e. by coating a well dispersed alphaalumina powder with a zirconium chloride aqueous solution. Upon thermal treatment, ultra-fine tetragonal zirconia grains formed on the surface of the alumina particles. SEM observations and image analysis were used to characterize the microstructure of porous samples and uniaxial compressive tests were used to measure their mechanical behavior.

Environmentally-Friendly Dense and Porous Geopolymers Using Fly Ash and Rice Husk Ash as Raw Materials

“…However, when porous samples were concerned, FA-R showed comparable or even higher strength than HL-R. In this case, the macro-porosity of the samples governs the material’s failure, as observed with other engineering ceramic foams [60]. Anyway, RHA addition to the geopolymeric composition proved to be effective either to produce dense or porous samples.…”

Fabrication of dense and porous biphasic calcium phosphates: Effect of dispersion on sinterability and microstructural development

“…The dry-milled material was characterized by a highly porous microstructure, embedding a diffused and micronic porosity. 42,43 Therefore, in order to improve the final density of drymilled material as well as to eliminate the residual porosity from the wet-milled one, it was investigated the role of the heating rate on the sintering behavior. However, some residual pores, with both spherical and elongated shape were detected as well, as shown in Figure 4D.…”

“…Such porosity can be partially explained by the gel-casting process, and precisely by the use of organic matter as gelling agent, which could give rise to a certain residual porosity in the sintered microstructure. 42,43 Therefore, in order to improve the final density of drymilled material as well as to eliminate the residual porosity from the wet-milled one, it was investigated the role of the heating rate on the sintering behavior. Precisely, samples were sintered at 1300°C for 3 hours at 1, 5 (as already reported in Figure 3) and 10°C/min.…”

Centrifugal Infiltration of Porous Ceramic Preforms by the Liquid Al Alloy – Theoretical Background and Experimental Verification

“…The most important are porosity (including the volume fraction of open and closed pores) as well as size distribution and morphology of pores. On the other hand, all the microstructural features depend closely on the selected route of manufacturing porous materials [8][9][10][11][12][13].…”

“…Generally, the macroporous ceramic foams (i.e. SiC, Al 2 O 3 ) with porosity in the range from 20% to 97% are produced usually by means of sintering granular materials with expanding agent [10], replication of polymer sponge [11], different direct foaming methods [12] and gel casting of foams [13].…”