Abstract

The phase separation process in silica-based gelling systems in the presence of a polymer (polyethylene oxide, PEO) is shown to result in the formation of porous materials with the open-cell foam structure. The PEO concentration range in the reaction mixture where these foam-like structures are observed is determined. It is shown that phase separation begins with the formation of discrete droplets of solvent in the gel phase similar to the phase separation in some polymerizing organic systems. Further, liquid droplets grow and coalesce that leads to the formation of a system of interconnected macropores with a shape close to the spherical one. The macropore sizes are shown to depend on the PEO content, but no significant difference in the mesoporosity and surface area of the monoliths is observed. Dried and calcined porous silica monoliths are obtained with macropore sizes from 0.8 to 41 μm. The maximal compressive strength is 2.2 MPa, porosity is 85%, permeability coefficient is 3.5·10⁻¹² m², and the specific surface area is 210 m² g⁻¹. The materials can be used as supports in flow-through catalytic systems.

中文翻译：

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在基于四乙氧基硅烷的胶凝体系中开孔泡沫结构的形成

摘要

显示出在存在聚合物（聚环氧乙烷，PEO）的情况下，基于二氧化硅的胶凝体系中的相分离过程可导致形成具有开孔泡沫结构的多孔材料。确定观察到这些泡沫状结构的反应混合物中的PEO浓度范围。结果表明，相分离开始于凝胶相中离散的溶剂液滴的形成，类似于某些聚合有机体系中的相分离。此外，液滴生长并聚结，导致形成相互连接的大孔系统，其形状接近球形。示出大孔尺寸取决于PEO含量，但是没有观察到整体孔隙的介孔率和表面积的显着差异。获得干燥和煅烧的多孔二氧化硅整料，其大孔尺寸为0.8至41μm。最大抗压强度为2.2 MPa，孔隙率为85％，渗透系数为3.5·10^-12  m ²，比表面积为210 m ²  g ^-1。该材料可用作流通催化系统中的载体。