Four kinds of sugar (glucose, fructose, sucrose, and maltose) were selected as carbon precursors, and corresponding dense carbon products were prepared using a novel hydrogel carbonization method. The carbonization processes of sugar-polyacrylamide (sugar-PAM) hydrogels were studied in detail. The molecular structures in the raw materials were analyzed by proton nuclear magnetic resonance spectroscopy ((1)H NMR). Samples prepared at different temperatures were characterized by thermogravimetry analysis (TGA) and Fourier-transform infrared (FTIR...