【摘要】 用低软化点线性酚醛树脂和糠醛为原料以正丙醇为溶剂在盐酸催化下经溶液-溶胶-凝胶过程合成了醇凝胶,将其在石油醚(30℃～60℃)中,超临界条件250℃,7MPa下干燥1h获得酚醛-糠醛有机气凝胶,将有机气凝胶在氮气保护下,以5℃ min速率升温到850℃并在该温度下保持3h裂解生成了炭气凝胶。用氮气吸附和透射电镜(TEM)表征了所得炭气凝胶。结果表明:炭气凝胶富含中大孔。随酚醛-糠醛比的增加,炭气凝胶的大孔和中孔孔容分别减小,大孔孔容变化幅度较大,微孔孔容很小。TEM图片表明:炭气凝胶的纳米骨架随酚醛-糠醛比的增加而增大。更多还原

【Abstract】 Alcogels were formed by solutionsolgel polymerization of phenolic novolac and furfural in 1propanol. The alcogels, after drying in supercritical petroleum ether at 250?℃ and 7?MPa for one hour, were pyrolyzed to yield carbon aerogels at 850?℃ for three hours under a nitrogen atmosphere. The effect of ratios of phenolic to furfural on volume shrinkage of the gels during the drying and pyrolyzing process, and on micro, meso and macropore volume and morphologies of carbon aerogels was investigated. It is found that, with increasing ratios of phenolic to furfural under otherwise identical condition, volume shrinkage of gels in the drying process increases whereas volume shrinkage of organic aerogels in the pyrolysis process decreases. Although the overall volume shrinkage is the sum of the two, the overall volume shrinkage increases with increasing ratio, indicating that the total volume shrinkage is governed by the drying process. The macropore volume decreases with the ratio much more than the meso-pore and micropore volumes, while the latter two volumes simultaneously decrease and then increase with increasing ratio. The porosity of carbon aerogels, when the concentration of reactants is defined, is determined by the volume shrinkage of gels in the drying and pyrolysis steps, and this is dependent on the cross-linking density of the polymers that form the alcogels. The domain sizes of a carbon aerogel formed at low ratio are smaller than that at high ratio where sintering is apparently occurring.更多还原