Anisotropic\nand Lightweight\nCarbon/Graphene Composite\nAerogels for Efficient Thermal Insulation and Electromagnetic Interference\nShielding

Abstract

High-performance and lightweight\ncarbon aerogels (CAs)\nhave attracted\nconsiderable attention in various fields such as electrochemistry,\ncatalysis, adsorption, energy storage, and so on. However, finding\nan environmentally friendly and efficient preparation method and achieving\na controllable performance of CAs are still a challenge. Herein, a\nseries of anisotropic carbon/graphene composite aerogels were synthesized\nby unidirectional freezing of polyamic acid ammonium salt/graphene\noxide (PAS/GO) suspension followed by lyophilization, thermal imidization,\nand carbonization. The prepared aerogels presented a tubular pore\nstructure oriented along the freezing direction. The GO dispersed\nin the polymer matrix reinforced the skeleton of aerogels, which significantly\ninhibited the volume shrinkage during the preparation process, thus\ngiving low densities of 0.074–0.185 g cm^–3. In addition, the oriented pore structure endowed the composite\naerogels with obviously anisotropic heat insulation performance. The\nradial thermal conductivity was as low as 0.038 W m^–1 K^–1 at the density of 0.074 g cm^–3. When the initial content of GO rose to 20 phr, the resultant aerogels\nexhibited a high electrical conductivity of about 0.77 S cm^–1 in the radial direction and the electromagnetic interference shielding\neffectiveness (EMI SE) reached 54.6 dB at the same time. Therefore,\nthis study provided a facile and environmentally friendly method to\nprepare lightweight and anisotropic carbon aerogels.