Zhou Wancheng

Graphene nanosheets/BaTiO3 ceramics as highly efficient electromagnetic interference shielding materials in the X-band

Graphene nanosheet (GN) filled BaTiO3 ceramics with high-performance electromagnetic interference (EMI) shielding were prepared via pressureless sintering. Both the real and imaginary parts of the complex permittivity increased with increasing GN content. The EMI shielding results showed that the absorption mechanism is the main contributor to the total EMI shielding effectiveness (SE). The total EMI SE is greater than 40 dB in the X-band at 1.5 mm thickness, which suggests the GN-BaTiO3 ceramics could be good candidates for highly efficient EMI shielding materials in the whole X-band.

Temperature dependence of the electromagnetic properties of graphene nanosheet reinforced alumina ceramics in the X-band

Graphene nanosheet (GN)/Al2O3 ceramics were prepared by hot press sintering with a significant improvement in both mechanical and electromagnetic properties. The excellent mechanical properties and electrical conductivity of the GN/Al2O3 ceramics contributed to the outstanding advantage of GNs as the reinforcing phase. The effects of GN content and temperature on complex permittivity, microwave absorption and electromagnetic interference (EMI) shielding performance of such ceramics have been studied in the frequency range of 8.2–12.4 GHz (X-band) and temperature range from 25 to 400 °C. Negative permittivity of the GN/Al2O3 ceramics with 2.0 vol% GNs appears throughout the whole X-band at 400 °C, and the mechanism was also investigated. The GN/Al2O3 ceramics show high mechanical properties, tunable electromagnetic properties, good microwave absorption and EMI shielding performance demonstrating their great potential to be applied in microwave applications.

Graphene nanosheets/E-glass/epoxy composites with enhanced mechanical and electromagnetic performance

Microwave absorbing composites with superior mechanical properties and electromagnetic absorption characteristics were fabricated using E-glass/epoxy composites containing graphene nanosheets (GNs). Compared with the composites without GNs, the incorporation of 2.0 wt% GNs enhanced the mechanical properties; the flexural strength and elastic modulus were improved by about 58.4 and 78.8%, respectively. Both the real and imaginary parts of the complex permittivity in the Ku-band increased with increasing GN content. Based on the complex permittivity of the composites, single and double layer absorbing composites were designed to obtain a wide reflection loss (RL) bandwidth below −10 dB. RL values less than −13 dB (larger than 95% absorption) can be obtained in the whole Ku-band for a double layer composite with a sample thickness of 3.4 mm.

Preparation of Ni-B Coating on Carbonyl Iron and Its Microwave Absorption Properties in the X Band

Ni-B coated carbonyl iron particles (CI@Ni-B) are prepared by the electroless plating technique. The structure, morphology, and antioxidant properties of the CI@Ni-B particles are analyzed. The results demonstrate that the CI particles have been coated with intact spherical-shell Ni-B coating, indicating the core-shell structure of CI@Ni-B particles, and the Ni-B coating can prevent the further oxidation of the CI particles. Compared with the raw CI particles/paraffin coatings with the same coating thickness of 2.0 mm and particles content of 70%, the CI@Ni-B particles/paraffin coatings possess higher microwave absorption (the RL exceeding −10 dB is obtained in the whole X band (8.2–12.4 GHz) with minimal RL of −35.0 dB at 9.2 GHz).

Microstructure and Dielectric Properties of Chopping SiCf/LAS Composites

Abstract The chopping SiC f /LAS composites were prepared by the hot-pressing method. The effects of hot-pressing time and pressures on the microstructures and the dielectric properties of the composites were researched. Compared with the LAS matrix and the SiC fibre, the results of dielectric constant testing in the range of 8-12 GHz indicate that the dielectric constant real part, imaginary part and dielectric dissipation of all samples increase by 1-3 orders of magnitude, and show obvious frequency dispersion effect. Their real parts increase while their imaginary parts and dielectric dissipations decline with the increase of the hot-pressing time or pressures. The SEM fractographs show that the composite interfacial films between the fibre and the matrix are thickened with the increase of the hot-pressing time or pressures.

Spinnability of Si(OC2H5)4-C2H5OH-H2O-HCl solutions

Abstract The spinnability of Si(OC 2 H 5 ) 4 -C 2 H 5 OH-H 2 O-HCl solutions, for the preparation of silica fibers, as a function composition was studied. The spinnability was measured in terms of the maximum length of the drawn fibers and the time suitable for fiber drawing. It was shown that H 2 O and HCl in solutions greatly affect the spinnability of the solutions, and that the total amount of the solution also has an effect on the spinnability. According to our experimental results, the composition range (H 2 O/ Si(OC 2 H 5 ) 4 :1.5–4.0; HCl/Si(OC 2 H 5 ) 4 :0.0003-0.3) can be divided into six small ranges with different spinnability.