the invention relates to a method for preparing a carbon aerogel from agglomerated carbon nanotubes , that comprises the following steps : preparing an aqueous dispersion of carbon nanotubes in water in the presence of a dispersing agent ; forming a foam from the nanotubes aqueous dispersion of step by bulking under the action of a gas in the presence of a foaming agent ; and freezing the foam obtained in step and removing the water by sublimation . the invention also relates to the carbon aerogels thus obtained , and to their use essentially as partition materials or biomaterials .