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Porous and high surface area silicon oxycarbide-based materials-A review

机译：多孔和高表面积碳氧化硅基材料-综述

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Silicon oxycarbide (SiOC)-based materials are a class of polymer-derived ceramics that enables the formation of a homogeneous structure at the molecular level starting from polymer precursors. In this system, oxygen and carbon atoms share bonds with silicon atoms in the amorphous network structure while elemental carbon, and possibly nanosized SiO_2 and SiC nanodomains may co-exist. Because of the flexibility of molecular level composition and microstructure designs, the systems can be made porous with high specific surface areas by changing the precursor compositions and the ceramization conditions. In this review, two strategies of creating porous SiOCs are discussed: conventional approach of using fugitive fillers, as well as pore formation and selective removal of certain SiOC matrix compositions (such as carbon, SiO_2, or SiC) at the molecular level. For the former, it includes ceramic replication of an organic template, direct foaming, and sacrificial pore formers. For the latter, it includes molecular level pore formation, molecular level species removal, and SiOC porous network creation through molecular templates. Direct pore formation can be achieved by changing processing conditions, using different precursor architectures, and using different hydrosilylation agents. For SiOC porous network creation through molecular level species removal, it includes molecular level free carbon removal, molecular level SiO_2 nanocluster removal, and molecular level carbon removal from SiC (and possibly BC_X for SiOBC). To understand single nanometer (＜10 nm) pore formation and phase separation for selective species removal, SiOC nanostructure models and composition descriptions after the pyrolysis are explained.
机译：碳氧化硅（SiOC）基材料是一类源自聚合物的陶瓷，能够从聚合物前体开始在分子水平上形成均质结构。在该系统中，氧和碳原子与非晶态网络结构中的硅原子共享键，而元素碳以及可能的纳米级SiO_2和SiC纳米域可能共存。由于分子水平组成和微结构设计的灵活性，可以通过更改前体组成和陶瓷化条件，使系统具有较高的比表面积。在这篇综述中，讨论了创建多孔SiOC的两种策略：使用逃逸性填料的常规方法，以及在分子水平上形成孔并选择性去除某些SiOC基质成分（例如碳，SiO_2或SiC）。对于前者，它包括有机模板的陶瓷复制，直接发泡和牺牲性成孔剂。对于后者，它包括分子水平的孔形成，分子水平的物质去除以及通过分子模板创建的SiOC多孔网络。通过改变加工条件，使用不同的前体结构和使用不同的氢化硅烷化剂，可以实现直接的孔形成。对于通过分子水平物质去除产生的SiOC多孔网络，它包括分子水平游离碳的去除，分子水平SiO_2纳米簇的去除以及从SiC中分子水平的碳去除（对于SiOBC，可能是BC_X）。为了了解单纳米（<10 nm）的孔形成和相分离以选择性去除物质的原因，我们解释了热解后的SiOC纳米结构模型和组成描述。

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