Effect of starting particle size and barium addition on flexural strength of polysiloxane-derived SiOC ceramics

Abstract

The effects of starting particle size and Ba addition on the flexural strength of bulk SiOC ceramics were investigated in polymerderived SiOC ceramics prepared by a conventional ceramic processing route. Crack-free, dense SiOC discs with 67 mm thickness and a 30 mm diameter were successfully fabricated from commercially-available polysiloxane without any fillers or 1 mol % barium isopropoxide-derived Ba as an additive. Agglomerates formed after pyrolysis of polysiloxane led to the formation of domain-like structures surrounded by pores after sintering. The flexural strength of bulk SiOC is strongly dependent on the domain size formed and Ba addition. Both minimization of the agglomerate size in the starting powders by milling after pyrolysis and judicious selection of additives which reinforce the SiOC structure are efficient ways to improve the flexural strength of bulk SiOC ceramics. The typical flexural strength of bulk Ba-doped SiOC ceramics fabricated from submicron-sized SiOC powders was 220 MPa.

Silicon oxycarbide glasses and glass‐ceramics: “All‐Rounder” materials for advanced structural and functional applications

“…Thermo‐mechanical analysis (TMA) is a useful tool to identify the best processing parameters. Two other ways are described to obtain monolithic green‐bodies: (a) casting of sol‐gel systems followed by careful aging and drying; (b) cold isostatic pressing (CIP) of pre‐crosslinked preceramic polymers . The subsequent transformation from the green‐body to the glass is performed upon pressureless pyrolysis in inert gas atmosphere (Ar, He, or N 2 ).…”

Effects of carbon addition on the electrical properties of bulk silicon-oxycarbide ceramics

“…The domains were enclosed with a series of pores. During hot-pressing, the agglomerates densified via a viscous flow of SiOC glass and C [29,44]. The densification led to removal of pores within the agglomerates and formed a series of inter-agglomerate pores, as shown in Fig.…”

“…Further decrease in the resistivity might be possible by optimizing the pyrolysis temperature. Since flexural strength of the SiOC16 specimen (195 ± 20 MPa) is 4-6 times higher than that of graphite (33)(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52) [53,54], the SiOC16 ceramics might be applicable to some structural parts which require excellent mechanical strength as well as electrical conductivity.…”