Search

The rapid development of modern electronic technology has provided high efficiency for social production, but it also brings serious electromagnetic interference (EMI). Although traditional metals and their alloys can serve as good electromagnetic shielding materials, their heavy weight, high cost as well as poor corrosion resistance limit their application in EMI shielding. Therefore, electromagnetic shielding materials with lightweight are gradually attracting more and more attention to meet the trend of lightweight and highly integrated electronic equipment. Polymers are widely used in EMI shielding materials because of their unique characteristics, such as lightweight, high flexibility and excellent corrosion resistance. This review is focused on the well-studied polymer-based lightweight composites, with the aim of providing a comprehensive review of the existing EMI shielding mechanism, preparation and application of polymer-based lightweight composites, along with retrieving new general insights into the advantages and limitations associated with the different measurement and prediction techniques, as well as the EMI shielding effectiveness of polymer-based lightweight composites including metal-containing composites, intrinsic conductive polymers, filler-containing polymers and newly discovered materials. These lightweight materials with fine EMI shielding performance will find more and more potential applications in communications, electronics, aerospace, military, environmental protection, etc.

In this study, a relatively light and high strength high entropy alloy thermoelectric material (Al2CoCrFeNi) for extreme service conditions was prepared by arc melting method. We find that the microstructure of the high entropy alloy (HEA) can be changed by annealing. By the tuning of proper annealing process, the microstructure evolution of the HEA can be adjusted to improve its mechanical and TE properties. Ultimate compressive strength can reach about 1.3 GPa after 1000 ℃ annealing. Fine-grain and precipitation strengthening are the main reasons for the improvement of the mechanical properties. The conductivity, Seebeck coefficient and thermal conductivity are all affected by grain size, precipitates, structural complexity and so on. The present work provides an effective means of preparing and regulating microstructures for the energy-conversion technique, and also supplies a feasible reference for the future development of lightweight, high-strength HEA TE materials.

Sulfur-free expanded graphite (EG) was prepared by chemical oxidation, then EG-based cobalt-nickel alloy hybrid (EG@CoNi) was obtained via hydrothermal method in this work. CoNi particles with the diameter of 0.1–0.5 µm were tightly attached to the surface of the layered EG. The incorporation of CoNi was conducive to the absorption of electromagnetic waves due to the increase in Ms and Hc, which enhanced the soft magnetization of EG@CoNi hybrids. The resulting EG@CoNi hybrids exhibited better dielectric loss than CoNi particles, and the optimal value of reflection loss (RL) reached − 50 dB, while the optimal bandwidth less than − 10 dB was 4 GHz, indicating enhanced microwave absorption characteristics. The well impedance matching and electromagnetic wave attenuation of EG@CoNi hybrids benefited from the synergy and double-loss mechanism between CoNi nanoparticles and EG. The dielectric loss in the double-loss mechanism was mainly dipole polarization and interface polarization, while the magnetic loss was mainly the natural ferromagnetic resonance and eddy current loss of CoNi nanoparticles. These multi-layer EG@CoNi hybrids with light weight and high dielectric characteristics would show good application prospects in high-efficiency electromagnetic wave absorbers.

In this research, the rolling of Mg-9Li-1Zn alloy at different temperatures was simulated, and it was found that the temperature control had an effect on the grain size and temperature field of the sheet. Combined with the experimental analysis, the results showed that the alloy with proper rolling temperature control had fine microstructure and plasticity. Under the conditions of 300 °C for the first pass and 275 °C for the second pass, the β-Li phase was recrystallized dynamically and most of the α-Mg phase was spheroidized. The tensile strength was 233 MPa, and a large number of dimples were produced on the tensile fracture, which was ductile fracture with an elongation of 45%. In addition, according to Gibbs-Thomson theorem and metallographic analysis, the mechanism of α-Mg spheroidization was explained.