Hierarchically ordered micro/meso/macroporous polymer-derived ceramic monoliths fabricated by freeze-casting

A hierarchically-ordered macro/meso/microporous SiOC monolith was obtained via freeze-casting using commercial polysiloxane as a raw material and silica sol as a binder and template source. The pre-ceramic polymer polysiloxane was pyrolyzed at 600 degrees C to produce a hydrophilic surface; higher temperatures would fully decompose the organic groups. When silica sol and polysiloxane precursor were combined in freeze-casting method, after pyrolysis a polymer-derived SiOC ceramic monolith with a lamellar pore morphology and a hierarchically-ordered pore structure was obtained. Decomposition of the polysiloxane precursors results in the development of micropores, and particle packing is believed to be responsible for the mesopore formation. Macro/mesoporous hierarchically-ordered ceramics with a specific surface area of 74 m(2)/g are preserved at pyrolysis temperatures as high as 1000 degrees C. The influence of H44-derived filler amount (10 wt-40 wt%), freezing temperature (-20 degrees C, -80 degrees C, -150 degrees C), and pyrolysis temperature (600 degrees C, 700 degrees C, 1000 degrees C) on open porosity, pore size distribution, and surface characteristics were investigated. (C) 2015 Elsevier Ltd. All rights reserved.