Cohesive assemblies comprising carbon are prepared by obtaining carbon in the form of powder, particles, flakes, or loose agglomerates, dispersing the carbon in a liquid halogen by mechanical mixing and/or sonication, and substantially removing the liquid halogen, typically by evaporation, whereby the cohesive assembly of carbon is formed. The method is especially suitable for preparing free-standing, monolithic assemblies of carbon nanotubes in the form of films, wafers, or discs, having high carbon packing density and low electrical resistivity. The assemblies have various potential applications, such as electrodes in batteries or supercapacitors or as electromagnetic interference shielding materials.