Xi-Xi Wang

Reduced graphene oxides: light-weight and high-efficiency electromagnetic interference shielding at elevated temperatures.

Chemical graphitized r-GOs, as the thinnest and lightest material in the carbon family, exhibit high-efficiency electromagnetic interference (EMI) shielding at elevated temperature, attributed to the cooperation of dipole polarization and hopping conductivity. The r-GO composites show different temperature-dependent imaginary permittivities and EMI shielding performances with changing mass ratio.

Ultrathin graphene: electrical properties and highly efficient electromagnetic interference shielding

Ultrathin graphene, a wonder material, exhibits great promise in various fields with its unique electronic structure and excellent physical, chemical, electrochemical, thermal and mechanical properties. Graphene presents great progress in electromagnetic interference (EMI) shielding. Herein, we review the advance in graphene-based EMI shielding materials. Towards graphene composites, we intensively evaluate EMI shielding efficiency and meaningfully describe the mechanism, such as polarization, hopping conduction and interface scattering. Moreover, we highlight an important direction for enhancing EMI shielding, the architectures, including alignment, paper, film and foam. Following that, the problems are summarized and the prospect is also highlighted for significant applications of ultrathin graphene in the field of EMI shielding.

Temperature dependent microwave absorption of ultrathin graphene composites

Ultrathin, lightweight graphene composites exhibit high-efficiency microwave absorption at elevated temperatures as well as thermal-stability permittivity. The minimum reflection loss reaches −42 dB and the widest bandwidth covers the entire X-band (−10 dB). More significantly, the composites possess one high-efficiency absorption belt with a value ≤−15 dB, as well as two ‘islands’ of reflection loss of ≤−17 dB and −30 dB. These excellent properties arise from the synergistic effect of polarization and conductivity. Our finding demonstrates that ultrathin graphene is a promising microwave absorber for microwave attenuation devices, information security and electromagnetic pollution defense.

Small magnetic nanoparticles decorating reduced graphene oxides to tune the electromagnetic attenuation capacity

High efficiency and lightweight are key factors for microwave absorption materials. Searching for the above necessary features is still a great challenge. Herein, we deposited small magnetic nickel ferrite nanoparticles on reduced graphene oxide nanosheets uniformly (NiFe2O4/r-GO) using a facile one-pot hydrothermal method with free of chemical agents, and investigated their permittivity, permeability and microwave absorption. Notably, we find an effective strategy for tuning microwave attenuation by the synergistic effect of dielectric and magnetic loss, which originates from inducing multiple relaxations and multiple resonances. The best impedance matching of NiFe2O4/r-GO was sought out. The minimum reflection loss (RL) can reach −42 dB with a broad bandwidth (RL ≤ −10 dB) of 5.3 GHz. Meanwhile, the multiple regions endow the absorbers with selectivity for efficient absorption. Our results demonstrate that the as-prepared NiFe2O4/r-GO is a promising candidate for application in communication devices, high speed processors, information security, electronic countermeasures and electromagnetic interference shielding.

Confinedly implanted NiFe2O4-rGO: Cluster tailoring and highly tunable electromagnetic properties for selective-frequency microwave absorption

Lightweight and high-efficiency microwave absorption materials with tunable electromagnetic properties is a highly sought-after goal and a great challenge for researchers. In this work, a simple strategy of confinedly implanting small NiFe2O4 clusters on reduced graphene oxide is demonstrated, wherein the magnetic clusters are tailored, and more significantly, the electromagnetic properties are highly tuned. The microwave absorption was efficiently optimized yielding a maximum reflection loss of –58 dB and ∼12 times broadening of the bandwidth (at –10 dB). Furthermore, tailoring of the implanted magnetic clusters successfully realized the selective-frequency microwave absorption, and the absorption peak could shift from 4.6 to 16 GHz covering 72% of the measured frequency range. The fascinating performances eventuate from the appropriately tailored clusters, which provide optimal synergistic effects of the dielectric and magnetic loss caused by multi-relaxation, conductance, and resonances. These findings open new avenues for designing microwave absorption materials in future, and the well-tailored NiFe2O4-rGO can be readily applied as a multi-functional microwave absorption material in various fields ranging from civil and commerce to military and aerospace.

Graphene nanohybrids: excellent electromagnetic properties for the absorbing and shielding of electromagnetic waves

Graphene has been long sought-after over the past few decades because of its multiple functions and broad applications in various fields, such as energy, information, medicine, military equipments, and aerospace. In particular, it has been significantly reported in electromagnetic wave absorbing and shielding fields, promoting it as the most cutting-edge topic. Herein, we systematically comb the structures and electromagnetic functions of graphene hybrids. We demonstrate the advances in the microwave response mechanism, including relaxation, charge transport, magnetic resonance, and eddy currents, as well as magnetic-dielectric synergistic effects. Furthermore, our review mainly focuses on graphene-dispersed systems, flexible graphene papers, graphene hybrids, and 3D graphene architectures.