High-temperature Electromagnetic Interference Research Articles

Fabrication of conductive polyimide/metal composite fibers for high temperature EMI shielding

Surface metallization of high-performance polymer fibers via electroless plating represents a significant advancement in producing lightweight, flexible and durable electromagnetic interference (EMI) shielding fabrics. The conventional process for metallization of polyimide (PI) fibers faces challenges, including complex procedures and insufficient interfacial adhesion between the metal layer and fiber matrix. Herein, carboxylate-containing PI (PIC) fibers were developed to mitigate the mechanical degradation caused by traditional alkaline etching. Conductive composite fibers (PIC/Cu) were successfully produced through a continuous electroless copper plating process. The robust PIC/Cu interfacial bonding achieved based on nanoscale mechanical interlocking through Ni nanoparticles imparts excellent flexibility and durability, evidenced by only a 4 % increase in electrical resistance after 5000 bending cycles. The dense, uniform copper layer provides high conductivity (1.3 × 104 S/cm), resulting in an optimal EMI shielding efficiency of 63.4 dB for the corresponding fabric. Moreover, PIC/Cu-Ni fibers prepared by further electroless plating of nickel layer on the surface of PIC/Cu fibers demonstrate remarkable electrical stability across temperatures ranging from 50 to 350°C, with only a 1.2 % reduction in conductivity after exposure to 350°C for 1 h. These findings advance the development of high-performance conductive PI fibers for applications in aerospace vehicles and high-temperature environments.

A laminated carbon nanotubes/silicon boron carbonitride film for high-efficiency electromagnetic interference shielding with oxidation resistance

Constructing layer-structured carbon/ceramic composites is promising for achieving high-performance and high-temperature electromagnetic interference (EMI) shielding materials, in which the rational composition and structural manipulation is critical. Here, a laminated SiBCN@CNTs/SiBCN film with a unique hierarchical structure is prepared using multi-layered carbon nanotubes (CNTs) films as the skeleton by alternatively stacking SiBCN@CNTs layers and SiBCN layers, and its thickness varies from 0.13 to 1.10 mm depending on the number of stacked layers (i.e., 1 to 6 layers) and the concentration of polyborosilazane precursor for impregnation (i.e., 10–70 wt%). Enlarging the thickness of the SiBCN@CNTs layers from 60 to 130 μm in the film or increasing their stacking numbers could both enhance the shielding effectiveness due to the introduction of additional interfacial and interlayer multi-reflection to extend the propagation path of electromagnetic waves for effective wave interference. Consequently, a high EMI shielding effectiveness of 49.4 dB has been achieved on SiBCN@CNTs/SiBCN-50-3, corresponding to a high specific shielding effectiveness (SETotal/d) of 182.9 dB mm−1, higher than previous pure ceramic shielding materials and carbon/ceramic composites. Moreover, because of the effective protection of SiBCN for CNTs, the SETotal of the film is still up to 23.9 dB after oxidation at 1000 °C for 2 h. Therefore, the laminated SiBCN@CNTs/SiBCN film represents an ideal candidate for high-efficiency EMI shielding material used in oxidation environments.

Plasma-sprayed ZrB2/Al2O3 ceramics with excellent high temperature electromagnetic interference shielding properties

The preparation, microstructures, complex permittivity and the electromagnetic interference (EMI) shielding properties of plasma-sprayed ZrB2/Al2O3 ceramics were investigated. The sprayed ceramics displayed high dielectric losses in terms of a high imaginary part of the complex permittivity in the range of 120–150, indicative of exceptional EMI shielding performance. The total EMI shielding efficiency (EMI SE) of 30 wt% ZrB2 filled Al2O3 ceramics is greater than 31 dB at 25℃ and 44 dB at 600℃ in the range from 8.2–12.4 GHz with a thickness of 1.2 mm. In addition, the ZrB2/Al2O3 ceramics still maintain high EMI SE and a long-term life at high temperature (600℃ for 300 h). Therefore, ZrB2/Al2O3 ceramics may be good candidates for high temperature EMI shielding materials with high EMI shielding efficiency and a long-term life.

SiC encapsulated Fe@CNT ultra-high absorptive shielding material for high temperature resistant EMI shielding

Abstract Carbon nanotubes (CNTs) decorated with ferromagnetic materials have promising potential in electromagnetic interference (EMI) shielding applications. In this work, CNT sponges with increasing density were fabricated by filling them with magnetic Fe nanowires of mutative filling ratios via chemical vapor deposition (CVD). Results indicated that Fe@CNT composites with the highest density endowed the most remarkable average SET value of 70.01 dB (more than 99.99999% absorption), showing an ultra-high EMI shielding performance. However, the susceptibility to oxidation of carbon materials has restricted its further development in high-temperature EMI shielding applications. Therefore, the Fe@CNT composites were encapsulated by silicon carbide (SiC) with satisfactory oxidation resistance. Thereafter, the average SET value of SiC encapsulated a higher density Fe@CNT sponge decreased to an adequate value of 36.48 dB due to the huge loss of electrical conductivity. However, the SET value of it only dropped by about 1.20 as the temperature went up from 25 to 600 °C, demonstrating an excellent stability under high temperature conditions. As a proof of concept, the Fe@CNT/SiC composites with adequate EMI shielding performance and satisfactory oxidation resistance suggest its prospect in high temperature resistant EMI shielding.

Electromagnetic interference shielding performance of nano-layered Ti3SiC2 ceramics at high-temperatures

The X-band electromagnetic interference (EMI) shielding properties of nano-layered Ti3SiC2 ceramics were evaluated from room temperature up to 800°C in order to explore the feasibility of Ti3SiC2 as efficient high temperature EMI shielding material. It was found that Ti3SiC2 exhibits satisfactory EMI shielding effectiveness (SE) close to 30 dB at room temperature and the EMI SE shows good temperature stability. The remarkable EMI shielding properties of Ti3SiC2 can be mainly attributed to high electrical conductivity, high dielectric loss and more importantly the multiple reflections due to the layered structure.

Beta-manganese dioxide nanorods for sufficient high-temperature electromagnetic interference shielding in X-band

As the development of electronic and communication technology, electromagnetic interference (EMI) shielding and attenuation is an effective strategy to ensure the operation of the electronic devices. Among the materials for high-performance shielding in aerospace industry and related high-temperature working environment, the thermally stable metal oxide semiconductors with narrow band gap are promising candidates. In this work, beta-manganese dioxide (β-MnO2) nanorods were synthesized by a hydrothermal method. The bulk materials of the β-MnO2 were fabricated to evaluate the EMI shielding performance in the temperature range of 20–500 °C between 8.2 and 12.4 GHz (X-band). To understand the mechanisms of high-temperature EMI shielding, the contribution of reflection and absorption to EMI shielding was discussed based on temperature-dependent electrical properties and complex permittivity. Highly sufficient shielding effectiveness greater than 20 dB was observed over all the investigated range, suggesting β-MnO2 nanorods as promising candidates for high-temperature EMI shielding. The results have also established a platform to develop high-temperature EMI shielding materials based on nanoscale semiconductors.