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在纤维素-7% NaOH-12%尿素水溶液体系中加入少量无机盐诱导和促进体系形成凝胶,研究了不同种类和用量的无机盐对凝胶形成过程的促进作用,促进能力依次为:阴离子相同时,钾盐>钠盐>锂盐;阳离子相同时,氯盐>溴盐>硝酸盐.无机盐浓度越高对凝胶形成的促进作用越明显.在此基础上结合溶剂置换和超临界CO2干燥技术,提出了无机盐诱导凝胶法制备纤维素气凝胶的新工艺,用SEM、氮吸附仪和压汞仪对所制气凝胶材料进行了结构表征,材料具有介孔到大孔范围的多孔结构,介孔的比表面积为284m2/g,孔体积为2.0cm3/g,平均孔径为20.5nm;大孔的孔体积为13.95cm3/g,平均孔径为0.732μm,孔隙率达91%.
A small amount of inorganic salts was added to the system of cellulose-7% NaOH-12% urea aqueous solution to induce and promote the formation of gels. The effects of different types and amounts of inorganic salts on the gel formation were studied. The promoting ability was as follows: anion In the same way, potassium salt> sodium salt> lithium salt; when the cation is same, the chloride salt> bromine salt> nitrate salt.The higher the concentration of inorganic salt, the more obvious the promoting effect on the gel formation is.On the basis of the combination of solvent replacement and supercritical CO2 drying technology, a new technology of inorganic salt-induced gel method for the preparation of cellulose aerogels was proposed. The structure of the aerogels was characterized by SEM, nitrogen adsorption and mercury porosimetry. The material has mesopore to large Pore size of the porous structure, the mesoporous surface area of 284m2 / g, a pore volume of 2.0cm3 / g, an average pore diameter of 20.5nm; large pore volume of 13.95cm3 / g, an average pore diameter of 0.732μm, a porosity of up to 91%.