)Preparation of ordered macroporous carbons by using ice crystal growth and control of their hierarchical structure

以间苯二酚和甲醛为原料，通过溶胶-凝胶缩聚、单向冷冻、冷冻干燥和热解等方法制备了炭冻凝胶微蜂窝。CMH具有大孔和介孔/微孔的分级结构。然而，CMHs的孔隙率低于通过常规方法制备的碳晶凝胶的孔隙率。研究了冷冻、HCl老化和CO_2活化对CMH孔性能的影响。冷冻操作大大降低了CMH的中孔体积。由于冷冻操作是制备CMH必不可少的步骤，因此CMH的孔隙率应在蜂窝结构形成后进行开发。有机微蜂窝的HCl老化可形成CMH的微孔或中孔。CO_2活化对提高CMH的孔隙率非常有效，因为活化过程中CMH保持了蜂窝结构。结合间苯二酚-甲醛水凝胶的合成条件和CO_2活化，可以制备出中孔结构较发达的CMH。将CMH浸渍在硅溶胶中，通过单向冷冻、溶剂交换和冷冻干燥制备了碳-硅复合材料。通过单向冷冻，可以在CMH内部形成硅胶蜂窝或纤维状硅胶。实验结果表明，以胶态二氧化硅为硅胶原料，可以制备出高结晶度、高抗压强度的碳-二氧化硅复合材料。

Carbon cryogel microhoneycombs (CMHs) were prepared via sol-gel polycondensation of resorcinol with formaldehyde, unidirectional freezing, freeze drying and pyrolysis. CMHs had a hierarchical structure of macropores and meso/micropores. However, the porosity of CMHs was lower than that of carbon cryogels prepared by a conventional method. The influence of freezing, HCl aging or CO_2 activation on their porous properties of CMHs was studied. The freezing operation greatly decreased the mesopore volume of CMHs. Since the freezing operation was indispensable to the preparation of CMHs, their porosity should be developed after the formation of honeycomb structure. The HCl aging of organic microhoneycombs could develop micropores or mesopores of CMHs. CO_2 activation was extremely useful for improving porosity of CMHs because the honeycomb structure was kept during activation. The CMH whose mesoporosity was much developed could be prepared by the combination of synthesis conditions of resorcinol-formaldehyde hydrogels and CO_2 activation. The CMHs were also immersed in silica sol under reduced pressure, and the carbon-silica composites were prepared via unidirectional freezing, solvent exchange and freeze drying. Silica gel honeycombs or fibrous silica gels could be formed inside the CMHs by unidirectional freezing. The experimental results suggested that the carbon-silica composites with high crystalinity and high compressive strength were prepared in the case where colloidal silica was used as a raw material for silica gels.