Bionic Scarfskin-Inspired Hierarchy Configuration toward Tunable Microwave-Absorbing Performance.

Maintaining the dynamical microwave synchronization between a target and its background is the key to electromagnetical invisibility in real environment. Herein, we introduce an archetypical paradigm for ultraelastic films of graphene-functionalized ionic gel with tunable microwave-absorbing behaviors. Inspired by the local structural changes during the wing-spreading process of vespertilionids, the experimental and finite element simulations have revealed that proper shape changing of 3D wrinkled structure containing ridge walls with moderate impedance is the effective way to minimize reflected wave and promote energy attenuation. An optimal RL value of -43.6 dB and valid regulatory amplitude of 41.5 dB, covering a microwave-absorbing to shielding state, could be reached with only 0.2% weight fraction of the active ingredient RGO filler. The significant regulatory performance is attributed to the competitive effect between intrinsic dielectric attenuation of silicon nitride modified reduced graphene oxide (RGO-SiN), multiscattering of a 3D wrinkled structure, and evolution of the oriented RGO-SiN.

Structural instability and mechanical properties of MoS2 toroidal nanostructures.

Molybdenum disulfide (MoS2) nanostructures have received considerable research attention due to their outstanding physical and chemical properties. Recently, a form of MoS2 ring structure exhibiting unique transport properties has been experimentally identified. Herein, we present the first report describing direct molecular dynamics (MD) simulations of structural instability and mechanical properties of hypothetical MoS2 nanotube (NT) toroidal nanostructures. Nanorings with small diameter MoS2 NTs retain their circular shape because of the higher bending stability of NTs, while for those with large diameter MoS2 NTs buckling/kinking and displacive phase transformations appear to effectively reduce bending stress as a mechanism for stabilizing the nanorings. However, the nanorings which have to polygonize maintain a circular shape as thick multi-walled inner nanorings are presented. Furthermore, mechanical responses of various nanoweaves (nanochains, nanomailles, and nanochainmailles) by linking nanorings together are also studied. The results show that Young's modulus, stretchability and tensile strength of such nanoweaves depend not only on the helicity of MoS2 NTs but also on the woven pattern. For example, nanostructures with 4-in-1 weaves of nanorings exhibit much higher tensile strength and stiffness but lower extensibility than those with 2-in-1 weaves. The finding suggests that MoS2 NT nanorings and their woven hierarchical structures may be used in the development of new flexible, light-weight electromechanical and optoelectronic nanodevices.