Graphene is highly desirable as an electromagnetic wave absorber because of its high dielectric loss and low density. Nevertheless, pure graphene is found to be non-magnetic and contributes to microwave energy absorption mostly because of its dielectric loss, and the electromagnetic parameters of pure graphene, which are out of balance, result in a bad impedance matching characteristic. In this paper, we report a facile solvothermal route to synthesize laminated magnetic graphene. The results show that there have been significant changes in the electromagnetic properties of magnetic graphene when compared with pure graphene. Especially the dielectric Cole-Cole semicircle suggests that there are Debye relaxation processes in the laminated magnetic graphene, which prove beneficial to enhance the dielectric loss. We also proposed an electromagnetic complementary theory to explain how laminated magnetic graphene, with the combined advantages of graphene and magnetic particles, helps to improve the standard of impedance matching for electromagnetic wave absorbing materials. Besides, microwave absorption properties indicate that the reflection loss of the as-prepared composite is below À10 dB (90% absorption) at 10.4-13.2 GHz with a coating layer thickness of 2.0 mm. This further confirms that the nanoscale surface modification of magnetic particles on graphene makes graphenebased composites have a certain research value in electromagnetic wave absorption.
A carbon-bridge effect was adopted to explain the electromagnetic wave absorbing property related to the cross-linked framework structure of RGO–SCI composites.
N-doped ordered mesoporous carbon−Co composites (Co-N-OMC) with 2D hexagonal structure, uniform pore size (4.4 nm), high surface area (550 m 2 g −1 ), and medium pore volume (0.61 cm 3 g −1 ) were successfully fabricated through facile one-step template method. We employed resol as the carbon precursor, triblock copolymer as the template agent, and cobaltous acetate and urea as additives. XPS analysis revealed that nitrogen was successfully doped in ordered mesoporous carbon and existed in the form of pyridine-like and quaternary-N nitrogen atoms. More importantly, metallic Co nanoparticles with uniform diameter around 15 nm highly dispersed in carbon matrix without adding any dispersion agent, which was probably due to the confinement effect of mesoporous structure. It was unambiguously demonstrated by HRTEM analysis that there were layered graphitic sheets present around Co particles, resulting from in situ catalytic graphitization of amorphrous carbon by Co species. Pt catalyst deposited on Co-N-OMC composite showed an excellent electrocatalytic activity for both methanol oxidation and oxygen reduction reaction, which was probably due to its suitable pore structure, improved degree of graphitization, presence of nitrogen, and high dispersion of Pt nanoparticles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.