The Fabrication and Characterization of Carbon Aerogels by Gelation and Supercritical Drying in Isopropanol (The research at MIT was supported by the Lawrence Livermore National Laboratory (LLNL) subcontract B518047 and was partially supported by the National Natural Science Foundation of China (59973028) and by the Talents Training Program Foundation of the Higher Education Department of Guangdong Province, China. Work at Duke University was in part supported by a grant from NASA (NAG-1-01061) through a subcontract from UNC.)