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    High surface area carbonous components from emulsion derived SiOC and their gas sensing behavior
    (Elsevier Sci Ltd, 2015) Vakıfahmetoğlu, Cekdar; Buldu, Merve; Karakuscu, Aylin; Ponzoni, Andrea; Assefa, Dawit; Soraru, Gian Domenico
    A commercially available liquid polysiloxane polymer was emulsified via stirring in the presence of water and surfactant. After curing, porous microbead/capsule thermosets were obtained. The samples kept their shape upon pyrolysis and resulted in SiOC ceramics which were etched by hydrofluoric acid at room temperature. The specific surface area of the components increased considerably reaching to 310 m(2)/g when etching process was conducted. It was shown that the samples had hierarchical porosity including micro-meso and macro porosity (5-10 micron range). The etching process affected the conductivity and the room temperature NO2 sensing capability of the SiOC samples. It is shown that porous SiOC and carboneous materials produced via hydrofluoric acid etching, can be used to detect NO2 (5 ppm) at room temperature (for the etched sample) with an easy-to-read conductance (mS range) as well as fast response kinetics (few minutes) and a complete signal recovery. (C) 2015 Elsevier Ltd. All rights reserved.
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    Polymer-derived SiOC aerogel with hierarchical porosity through HF etching
    (Elsevier Sci Ltd, 2016) Assefa, Dawit; Zera, Emanuele; Campostrini, Renzo; Soraru, Gian Domenico; Vakıfahmetoglu, Cekdar
    Silicon oxycarbide (SiOC) aerogels have been synthesized from preceramic polymers via pyrolysis in inert atmosphere at 1200 and 1300 degrees C. The as synthesized materials have a typical colloidal microstructure with mesoporosity in the range 10-50 nm and no microporosity. HF acid attack of the SiOC aerogels dissolves preferentially the SiO2-rich phase and creates micro-and (small)mesopores (<10 nm) in the aerogels microstructure finally leading to a materials with hierarchical porosity. The HF post-pyrolysis treatment is more efficient for the SiOC aerogels pyrolyzed at the maximum temperature, i.e. 1300 degrees C, leading to a maximum value of specific surface area of 530 m(2)/g and total porosity of 0.649 cc/g. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.