Freeze drying for preparation of aerogel-like carbon

RF hydrogels were synthesized by the sol-gel polycondensation of resorcinol with formaldehyde and RF cryogels were prepared by freeze drying of the hy drogels with t-butanol. The cryogels were characterized by nitrogen adsorpt ion, density measurements, and scanning electron microscope. Their porous p roperties were compared with those of the aerogels prepared by supercritica l drying with carbon dioxide. RF cryogels were mesoporous materials with la rge mesopore volumes > 5.8 x 10(-4) m(3)/kg. Although surface areas and mes opore volumes of the cryogels were smaller than those of the aerogels, the cryogels were useful precursors of mesoporous carbons. Aerogel-like carbons (carbon cryogels) were obtained by pyrolyzing RF cryogels in an inert atmo sphere. The carbon cryogels were mesoporous materials with high surface are as > 8.0 x 10(5) m(2)/kg and large mesopore volumes > 5.5 x 10(-4) m(3)/kg. When pyrolyzed, micropores were formed inside the cryogels more easily tha n inside the aerogels.