Enhanced microwave absorption property of reduced graphene oxide (RGO)-MnFe2O4 nanocomposites and polyvinylidene fluoride.

MnFe2O4 nanoparticles have been synthesized on a large scale by a simple hydrothermal process in a wild condition, and the RGO/MnFe2O4 nanocomposites were also prepared under ultrasonic treatment based on the synthesized nanoparticles. The absorption properties of MnFe2O4/wax, RGO/MnFe2O4/wax and the RGO/MnFe2O4/PVDF (polyvinylidene fluoride) composites were studied; the results indicated that the RGO/MnFe2O4/PVDF composites show the most excellent wave absorption properties. The minimum reflection loss of RGO/MnFe2O4/PVDF composites with filler content of 5 wt % can reach -29.0 dB at 9.2 GHz, and the bandwidth of frequency less than -10 dB is from 8.00 to 12.88 GHz. The wave absorbing mechanism can be attributed to the dielectric loss, magnetic loss and the synergetic effect between RGO+MnFe2O4, RGO+PVDF and MnFe2O4+PVDF.

Fabrication of Reduced Graphene Oxide (RGO)/Co3 O4 Nanohybrid Particles and a RGO/Co3 O4 /Poly(vinylidene fluoride) Composite with Enhanced Wave-Absorption Properties.

Reduced graphene oxide (RGO)/Co3 O4 nanohybrid particles, composed of reduced graphite oxide and Co3 O4 particles, have been fabricated by an in situ growth method under mild wet-chemical conditions (140 °C). A series of characterization results indicate that the as-prepared Co3 O4 particles with relatively uniform sizes are embedded in RGO layers to form unique core-shell nanostructures. The RGO/Co3 O4 /poly(vinylidene fluoride) composite was found to possess excellent absorption properties. Owing to the effect of the negative permeability, the position of the absorption peaks remains at the same frequency at different thicknesses without shifting to lower frequencies. For the composites with a filler loading of 10 wt %, the maximum peaks can reach -25.05 dB at 11.6 GHz with a thickness of 4.0 mm. These enhanced microwave absorbing properties can be explained based on the structures of the nanohybrid particles.

Facile Size-Controllable Synthesis of Colorful Quasi-Cubic α-Fe2 O3 Materials from Nanoscale to Microscale and Their Properties Related to the Size Effect.

A facile and environmentally friendly hydrothermal approach has been employed to synthesize size-controllable quasi-cubic α-Fe2 O3 nanocrystals by using an aqueous solution of FeCl3 without any alkaline materials and stabilizing agent. The as-prepared products were carefully characterized and the growth mechanism is also discussed. This hydrothermal synthesis of such quasi-cubic structures implies a simple and low-cost route to prepare monodisperse nanomaterials on a large scale. The size-controllable synthesis of α-Fe2 O3 is the first achieved successfully from 80 nm to 2 µm with constant structures. The synthesized α-Fe2 O3 materials have different optical properties and stabilities in water, which are caused by the change of their band-gap energy and specific surface areas. Finally, the dielectric properties of synthesized α-Fe2 O3 cubes were also investigated, and the differences caused by the particle sizes are discussed.