Direct ink writing of SiOC ceramics from preceramic polymers

Ceramic fabrication from preceramic polymer by Direct ink writing, one of the Additive manufacturing techniques, has attracted a lot of attention due to the combination of fast and facile processing without de-binding and its ability to fabricate sophisticated structures for increasing requirements of advanced applications. This research focuses on the direct ink writing of SiOC ceramic components from different preceramic polymers with assistive techniques, aiming at addressing the limitations of direct ink writing on fabrication of complex ceramic structures (such as with large overhanging features). In this work, firstly origami was utilized for the secondary shaping on the printed 2D pattern for the structures with large spanning features in terms of high printability and flexibility of a commercially available silicone elastomer. Then, a robotic arm was employed for the printing of cylindrical lattices which is not possible for normal direct ink writing. Besides the controlling of macro ceramic structures achieved by direct ink writing, hierarchical porous structures with controllable pore size from several centimeters to hundreds of nanometers were fabricated with the assistance of sacrificial templates. In addition, to eliminate the influence of gravity on the suspended features, direct ink writing was performed by extruding an ink of preceramic polymer into a soft medium comprised of vegetable oil and fumed silica. Excellent printability was achieved by optimizing the content of fumed silica, printing speed and pressure. With this method, suspended coils and beams with large length-to-diameter ratio were fabricated without shape distortion both after printing and pyrolysis. We also explored the possibility of extending the method to other materials, including metal and ceramic powder, suggesting the high potential in the field of additive manufacturing of multi-materials components system. Finally, we investigated the mechanical properties and permeability of scaffolds with different structures fabricated by direct ink writing, showing the possibility of performance enhancement by structure designing without reducing the porosity. The structure-relationship from this work could also be extended to other ceramic systems or other materials.