碳气凝胶的常压干燥制备及结构控制

研究了碳气凝胶在常压条件下的制备过程和干燥方法. 用扫描电镜、比表面测量仪及孔径分布仪对其结构进行了表征与测试. 通过改变催化剂和溶剂的用量，可以实现碳气凝胶的颗粒直径及孔洞由纳米到微米级的连续调节. 通过降低催化剂浓度并以丙酮进行溶剂替换，成功实现了碳气凝胶的常压干燥. 常压干燥样品具有250~650 kg/m3的低密度和250~550 m2/g的高比表面积. 分析了其溶胶-凝胶反应机理，围绕毛细压力和材料强度等方面探讨了其常压干燥的实现途径.

Preparation of Carbon Aerogels by Conventional Drying and Their Control in Microstructure

Carbon aerogels were dried successfully at ambient pressure by decreasing catalyst and exchanging solvents. SEM, BET and pore size distribution techniques were used to characterize the morphology and pore structure of the carbon aerogels. The structures of carbon aerogels are controlled from micro pore to macro pore by changing the concentration of catalyst and solvent. The size of the particles increases from less than 100 nm, 100~200 nm to 1~2 mm with R/C ratios increasing from 500, 1000 to 1500. The pore diameter of carbon aerogels decreases from 60 nm, 40 nm to 15 nm by increasing RF concentration from 30%, 40% to 50% while R/C ratio being 1000. The samples prepared by conventional drying have low density of 250~650 kg/m3 and a high specific surface area of 250~550 m2/g. The reaction mechanism of the sol-gel process and the way to dry aerogels at ambient pressure by enhancing material intensity and reducing capillary pressure were discussed.