EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Heterogeneous catalysts are used under increasingly harsh conditions, requiring the use of high-performance ceramics with high thermal and chemical stability as carrier material. In addition, a high surface area for an effective reaction at the active sites and well tailored macroporous structures for high product flow are required. Currently, conventional ceramic processes are highly limited in meeting these shaping requirements, which calls for the use of additive manufacturing (AM). SiC-based ceramics, which are suitable candidate materials for these applications due to their excellent thermal and chemical properties, are notoriously difficult to produce via traditional powder and sinter routes, which in turn brings the use of polymer-derived ceramics (PDCs) into focus.
In this study, Lithography-based ceramic manufacturing (LCM) of preceramic organosilicone polymers was used as AM technique to produce macroporous preceramic polymer structures which were converted into silicon oxycarbide-based ceramics during a controlled pyrolysis treatment. The preceramic organosilicone polymers were used in combination with acrylate or thiol-ene systems enabling fast photopolymerization for the LCM process. As PDCs are limited in terms of part sizes due to their high shrinkage during pyrolysis, SiC particles were introduced as inert fillers. A variety of photo-curable formulations were evaluated both with and without the addition of particulate SiC fillers. The general feasibility of LCM for simple and complex silicon oxycarbide ceramic parts was assessed and demonstrated through iterative production development. The resulting ceramics were examined with regard to their elemental composition, and pyrolysis parameters were adjusted accordingly. The distribution of SiC filler particles and crack development during pyrolysis was shown to strongly affect mechanical material properties. It was possible to elucidate relationships between the photo-curable polymer composition, SiC particle content and resulting material properties, which will enable the production of specifically structured catalyst carrier materials.