High temperature ceramics for use in membrane reactors: the development of microporosity during the pyrolysis of polycarbosilanes

• Published in: Journal of materials chemistry 2002-11, Vol.12 (12), p.3754-3760
• Main Authors: WILLIAMS, Howard M, DAWSON, Elizabeth A, BARNES, Philip A, RAND, Brian, BRYDSON, Rik M. D, BROUGH, Adrian R
• Format: Article
• Language: English
• Subjects: Applied sciences; Building materials. Ceramics. Glasses; Ceramic industries; Chemical industry and chemicals; Chemistry; Colloidal state and disperse state; Exact sciences and technology; General and physical chemistry; General studies; Inorganic and organomineral polymers; Membranes; Miscellaneous; Physicochemistry of polymers; Technical ceramics
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/b205892h

The pyrolysis of polycarbosilane (PCS), a ceramic precursor polymer, at temperatures up to 700 C under an inert atmosphere results in the development of amorphous microporous materials which have a number of potential applications, such as gas separation membranes. The development of microporosity was examined during pyrolysis under nitrogen, at temperatures ranging from 300 to 700 C, of both the cross-linked and non-cross-linked starting materials. The products are characterised by nitrogen adsorption, to determine surface areas and pore volumes, solid-state NMR, electron microscopy and FTIR, and their formation was studied using thermal analysis and evolved gas analysis with on-line mass spectrometry. The cross-linked and non-cross-linked PCSs have a maximum micropore volume of 0.2 cm3/g at pyrolysis temperatures of between 550 and 600 C. The microporosity is stable in air at room temperature, but is lost in oxidising atmospheres at elevated temperatures. 41 refs.