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Keynote Lecture

Fabrication of porous oxide and non-oxide ceramics for gas separation, sensing and catalysis

Thursday (25.10.2018)
08:50 - 09:30
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Several fabrication routes towards micro-, meso- and macroporous ceramics will be presented. Case studies include: (i) micro- and mesoporous polymer-derived ceramics (PDCs) and their nanocomposites for gas separation and catalysis and (ii) control over pore size and geometry in ordered mesoporous silica COK-12. Micro- and mesoporous PDCs with variable pore geometry, microstructure and specific surface area have been synthesized by the thermolysis of preceramic polymers (so-called polymer thermolysis route). The polymer-to-ceramic transformation occurs through several distinctive stages, such as the decomposition of organic groups, accompanied by the release of gaseous species such as hydrogen, methane and other volatile compounds. The evolution of these gaseous species nucleates an intrinsic microporosity in as-formed products. This transient microporosity collapses as the thermolysis temperature increases; this process is driven by the spontaneous trend towards reduced surface energy. Therefore, one of the challenges is to preserve the microporosity, developed in the PDCs during the polymer-to-ceramic transformation, at least up to 750 °C for applications such as gas capture and gas separation. Ordered mesoporous silica materials are known for their high surface area and highly ordered structure. One of the main advantages of the synthesis of ordered mesoporous silica by soft-templating with amphiphilic molecules is the ability to tailor the mesostructure by using micellar swelling agents. In this context, the addition of hexane and polypropylene glycol (PPG) as micellar swelling agents in the facile room-temperature synthesis of COK-12 was studied to tailor the mesoporous structure of the system. Hexane was used as a micelle expander and as an agent to produce silica mesocellular foams. By adding PPG into the synthesis, a shift of the mesostructure of COK-12 from 2D hexagonal to a multilamellar vesicular configuration was observed.