Fabrication of hierarchically porous silicon carbonitride monolith using branched polysilazane and freeze casting method without crosslinking step: Effect of polymer additive to aligned macropore structure

Abstract

A hierarchically porous SiCN monolith with aligned macropores was prepared using a branch-structured polysilazane, silsesquiazane (SSQZ), as a precursor and polymer additive, through the freeze casting method. As polymer additives, polystyrene (PS) and poly(methyl methacrylate), which have different compatibilities with SSQZ, were used to confirm the effect on the pore formation. In addition, the pore formability according to the molecular weight was investigated using PSs with different molecular weights. When the SSQZ and high-molecularweight PS (HPS) were used, a porous SiCN with micro/meso/macropore structure could be fabricated because of the structural stability of the SSQZ and high molecular weight of HPS. The hierarchically porous SiCN monolith was successfully manufactured using SSQZ and HPS with 639 m 2 /g of specific surface area, 0.36 cm 3 /g of pore volume, and 2.1 nm of average pore size. The hierarchically porous SiCN monolith with high HPS content has improved dimensional stability to show its compressive fracture energy.

Development of Inkjet Printable Formulations Based on Polyorganosilazane and Divinylbenzene

“…In addition, they contain hydrogen as a side group [36]. Polyorganosilazanes can be formulated with initiators, catalysts, or fillers to form processable matrix composites that can be fabricated by casting [37,38], coating [4,39], or additive manufacturing [18,[40][41][42][43]. Crosslinking is usually carried out thermally [44,45] or photochemically [46] after processing to reduce the loss of low-molecular-weight components and consequently leading to a high ceramic yield after pyrolysis at high temperature [47].…”