Macroporous ceramics with pore sizes from 400 nm to 4 mm and porosity within the range 20%–97% have been produced for a number of well-established and emerging applications, such as molten metal filtration, catalysis, refractory insulation, and hot gas filtration. These applications take advantage of the unique properties achieved through the incorporation of macropores into solid ceramics. In this article, we review the main processing routes that can be used for the fabrication of macroporous ceramics with tailored microstructure and chemical composition. Emphasis is given to versatile and simple approaches that allow one to control the microstructural features that ultimately determine the properties of the macroporous material. Replica, sacrificial template, and direct foaming techniques are described and compared in terms of microstructures and mechanical properties that can be achieved. Finally, directions to future investigations on the processing of macroporous ceramics are proposed.

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Processing Routes to Macroporous Ceramics: A Review

Processing and properties of macroporous silicon carbide ceramics: A review

https://iopscience.iop.org/article/10.1088/1468-6996/11/4/044303/pdf

Processing of polysiloxane-derived porous ceramics: a review

Gelcasting of alumina foams using agarose solutions

By using α- and/or β-SiC staring powders, the effects of the initial α-phase content on the microstructure, mechanical properties, and permeability of macroporous SiC ceramics were investigated. When β-SiC powder or a mixture of α/β powders containing a small amount (≤10%) of α-SiC powder was used, the microstructure consisted of large platelet grains. In contrast, when using α-SiC powder or α/β powders containing a large amount (>10%) of α powders, the microstructure consisted of small equiaxed grains. The development of large α-SiC platelet grains in the microstructure did not result in any improvement of the flexural strength of the macroporous SiC ceramics because of the accompanying pore growth and grain growth. The growth of the platelet-SiC grains was beneficial in increasing the gas permeability of the macroporous SiC ceramics from 4.12 × 10−13 m2 for macroporous SiC with an equiaxed microstructure to 1.89 × 10−12 m2 for macroporous SiC ceramics with large platelet grains.

Effects of the initial α-SiC content on the microstructure, mechanical properties, and permeability of macroporous silicon carbide ceramics

SiC foams were fabricated by gelcasting with a commercially available powder and agar as gelling agent. Ceramic foams processed by gel casting have dense struts and are therefore mechanically stronger than foams produced by the conventional poly-urethane replica method. First, special attention was given to the preparation and characterization of the powder suspension using silicon carbide powders which has been recognized as a high performance material.

SiC foams produced by gel casting: Synthesis and characterization

Silicon Carbide Foams by Polyurethane Replica Technique

A process according to the invention is a process to separate an initial fluid stream comprising phosgene and hydrogen chloride in at least a first and a second fluid stream, said first fluid stream being a hydrogen chloride enriched and phosgene depleted gaseous stream, said second fluid stream being a hydrogen chloride depleted and phosgene enriched stream. The separation is performed by feeding said initial fluid stream to a membrane separation unit, said membrane separation unit separating said initial fluid stream in a first and a second fluid stream.

Rabah Mouazer

Papers

SiC foams produced by gel casting: Synthesis and characterization

Silicon Carbide Foams by Polyurethane Replica Technique

A process to separate phosgene and hydrogen chloride from a fluid stream comprising phosgene and hydrogen chloride

Role of citrate and tartaric ligands for the stabilization of NASICON sols. Application to membrane preparation

Ionic exchange by electromigration on NASICON membranes: preparation and characterisation