Yi Gang, Yu Yuxi
Fujian Key Laboratory of Advanced Materials, Department of Materials Science and Engineering, College of Materials, Xiamen University, Xiamen 361005, China.
Polymers (Basel). 2023 Jun 14;15(12):2676. doi: 10.3390/polym15122676.
Porous silicon oxycarbide (SiOC) ceramics with tailorable microstructure and porosity were fabricated using phenyl-substituted cyclosiloxane (C-Ph) as a molecular-scale porogen are analyzed in this study. A gelated precursor was synthesized via the hydrosilylation of hydrogenated and vinyl-functionalized cyclosiloxanes (CSOs), followed by pyrolysis at 800-1400 °C in flowing N gas. Tailored morphologies, such as closed-pore and particle-packing structures, with porosities in the range 20.2-68.2% were achieved by utilizing the high boiling point of C-Ph and the molecular aggregation in the precursor gel induced by the conjugation force of phenyl. Moreover, some of the C-Ph participated in pyrolysis as a carbon source, which was confirmed by the carbon content and thermogravimetric analysis (TGA) data. This was further confirmed by the presence of graphite crystals derived from C-Ph, as determined by high-resolution transmission electron microscopy (HRTEM). In addition, the proportion of C-Ph involved in the ceramic process and its mechanism were investigated. The molecular aggregation strategy for phase separation was demonstrated to be facile and efficient, which may promote further research on porous materials. Moreover, the obtained low thermal conductivity of 27.4 mW m K may contribute to the development of thermal insulation materials.
本研究分析了使用苯基取代的环硅氧烷（C-Ph）作为分子尺度致孔剂制备的具有可定制微观结构和孔隙率的多孔碳氧化硅（SiOC）陶瓷。通过氢化和乙烯基官能化的环硅氧烷（CSO）的硅氢加成反应合成了凝胶状前驱体，然后在流动的氮气中于800-1400°C下进行热解。利用C-Ph的高沸点和苯基共轭力在前驱体凝胶中诱导的分子聚集，实现了定制的形态，如闭孔和颗粒堆积结构，孔隙率在20.2-68.2%范围内。此外，部分C-Ph作为碳源参与了热解，这通过碳含量和热重分析（TGA）数据得到证实。高分辨率透射电子显微镜（HRTEM）确定存在源自C-Ph的石墨晶体，进一步证实了这一点。此外，研究了参与陶瓷过程的C-Ph的比例及其机制。结果表明，用于相分离的分子聚集策略简便有效，这可能会促进对多孔材料的进一步研究。此外，所获得的27.4 mW m K的低导热率可能有助于隔热材料的开发。
