Yuchang Qing

Effect of magnetic fillers on the electromagnetic properties of CaCu3Ti4O12–epoxy composites within the 2–18 GHz range

The electromagnetic properties of the CaCu3Ti4O12 (CCTO)-magnetic particles–epoxy composite in the frequency range of 2–18 GHz are reported in this paper. The results showed that both the dielectric loss and the magnetic loss of the CCTO–epoxy composite were lower, and the dielectric constant was nearly independent of frequency over the measured frequency range. In order to improve the microwave absorption of the CCTO–epoxy composite, soft magnetic particles (barium ferrite, Fe–Si–Al and carbonyl iron flakes) were introduced. The effect of the magnetic fillers on the electromagnetic properties of the CCTO–epoxy composites within the 2–18 GHz range was also investigated. The experimental results showed that the complex permittivity and permeability of the composites were dependent on the type of filler and the frequency band, and the increasing rates of the real and imaginary parts with respect to the types of fillers were all different. These different rates can have a great effect on the thickness and microwave absorption in the design of single-layer microwave absorbers.

Nitrogen-doped graphene and titanium carbide nanosheet synergistically reinforced epoxy composites as high-performance microwave absorbers

The electromagnetic (EM) properties of both nitrogen-doped graphene (N-GP) and Ti3C2 nanosheets as hybrid absorbers were investigated in the frequency range of 2–18 GHz. The values and frequency dependencies of EM properties of such hybrid absorbers can be adjusted by the combination of the unique microstructure and dielectric characteristics of the N-GP and Ti3C2 nanosheets. The minimum reflection loss (RL) reaches up to −52 dB and the bandwidth below −10 dB can be obtained in the frequency range of 10.9–18 GHz with a sample thickness of 1.4 mm. These results suggest that N-GP and Ti3C2 nanosheets as hybrid absorbers are highly promising fillers for dielectric and EM applications, especially for thin-thickness, broadband absorption microwave absorbers.

Effect of Heat Treatment on the Microwave Electromagnetic Properties of Carbonyl Iron/Epoxy-Silicone Resin Coatings

Microwave absorbing properties of the carbonyl iron particles filled epoxy-silicone resin coatings showed visible degression when the coatings were heat treated at 300°C with different time. The complex permittivity and permeability of the coatings before and after heat treatment were measured. After heat treatment at 300°C, the real part of permittivity of the coatings increased with increasing treatment time and showed frequency dependence dielectric response. The complex permeability showed remarkable variation while the resonance frequency of the coatings heat treated at 300°C shifted from 7 to 12 GHz. The electromagnetic results indicated that microwave absorbing properties of the coatings showed more dependent on the complex permeability. The results showed that the difference of the electromagnetic and microwave absorbing properties before and after heat treatment was mainly attributed to the crystalline state transition of carbonyl iron particles.

Single-Layer and Double-Layer Microwave Absorbers Based on Graphene Nanosheets/Epoxy Resin Composite

Graphene nanosheets/epoxy resin (GN/EP) composites with enhanced microwave absorption properties were prepared. The influence of GNs content on the electromagnetic and microwave-absorbing properties of single-layer GN/EP composites was investigated in the frequency range of 2–18GHz. A novel double-layer microwave absorber by combining absorbers with different contents of graphene was designed to achieve absorbers with wide absorption band and optimal microwave absorption. The calculated microwave absorption properties indicated that broader absorption band was obtained by the double-layer GN/EP composites. Reflection loss (RL) values below −5dB can be obtained in the frequency range of 4.4–18GHz by the double-layer GN/EP composites at thickness of 3.9mm.