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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Effect of pH and chitosan concentration on precipitation and morphology of hierarchical porous silica
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Effect of pH and chitosan concentration on precipitation and morphology of hierarchical porous silica

机译：pH和壳聚糖浓度对分级多孔二氧化硅沉淀和形态的影响

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Understanding the interaction between chitosan molecules and sodium silicate is one of the principal objectives for the development of new environmentally benign strategies for the synthesis of low-cost porous silica with hierarchical structure. In this work, we have explored two essential factors simultaneously: chitosan/silica ratios (0.1, 0.4, 0.8 and 1.6) and pH values of the mixture (3, 5 and 6). The obtained silica-chitosan composite and the calcined products were investigated by using thermal gravimetric analysis, N_2-physisorption, scanning electron microscopy, and transmission electron microscopy. Rapid precipitation of silica-chitosan composite occurred because of the initial pH values of the chitosan and sodium silicate solutions. The amount of precipitating silica-chitosan composite was increased with increasing pH value of the mixture and chitosan/silica ratios but it did not change with the decrease of pH value of the mixture. The as-synthesized products prepared at pH 3 and 6 showed macroscopic two-solid phases (consisting of silica-rich phase and chitosan-rich phase), while those prepared at pH 5 displayed liquid and solid phases. At pH 3, a unimodal porous structure was found for the calcined products obtained from the silica-rich phase while a hierarchical structure was found for those obtained from the chitosan-rich phase; meanwhile, a hierarchical structure occurred for all calcined products prepared at pH 6. Different hierarchical structures of the silica products could be obtained by changing pH value of the mixture and chitosan/silica ratios.
机译：理解壳聚糖分子与硅酸钠之间的相互作用是开发新的对环境有益的新策略的主要目标之一，该策略可用于合成具有分层结构的低成本多孔二氧化硅。在这项工作中，我们同时探索了两个基本因素：壳聚糖/二氧化硅的比例（0.1、0.4、0.8和1.6）和混合物的pH值（3、5和6）。通过热重量分析，N_2-物理吸附，扫描电子显微镜和透射电子显微镜研究所得的二氧化硅-壳聚糖复合材料和煅烧产物。由于壳聚糖和硅酸钠溶液的初始pH值，导致二氧化硅-壳聚糖复合材料快速沉淀。二氧化硅-壳聚糖复合材料的沉淀量随混合物pH值和壳聚糖/二氧化硅比例的增加而增加，但不随混合物pH值的降低而变化。在pH 3和6下制备的合成产物显示出宏观的两个固相（由富含二氧化硅的相和富含壳聚糖的相组成），而在pH 5制备的那些则显示出液相和固相。在pH为3时，发现从富含二氧化硅的相中得到的煅烧产物为单峰多孔结构，而从富含壳聚糖的相中得到的则为分层结构。同时，在pH 6下制备的所有煅烧产品均出现分层结构。通过改变混合物的pH值和壳聚糖/二氧化硅比例，可以获得二氧化硅产品的不同分层结构。

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