Ultrathin Multilayer Textile Structure with Enhanced EMI Shielding and Air-Permeable Properties

A textile material’s electromagnetic interference (EMI) shielding effectiveness mainly depends on the material’s electrical conductivity and porosity. Enhancing the conductivity of the material surface can effectively improve the electromagnetic shielding effectiveness. However, the use of highly conductive materials increases production cost, and limits the enhancement of electromagnetic shielding effectiveness. This work aims to improve the EMI shielding effectiveness (EMSE) by using an ultrathin multilayer structure and the air-permeable textile MEFTEX. MEFTEX is a copper-coated non-woven ultrathin fabric. The single-layer MEFTEX SE test results show that the higher its mass per unit area (MEFTEX 30), the better its SE property between 56.14 dB and 62.53 dB in the frequency band 30 MHz–1.5 GHz. Through comparative testing of three groups samples, a higher electromagnetic shielding effect is obtained via multilayer structures due to the increase in thickness and decrease of volume electrical resistivity. Compared to a single layer, the EMI shielding effectiveness of five layers of MEFTEX increases by 44.27–83.8%. Due to its ultrathin and porous structure, and considering the balance from porosity and SE, MEFTEX 10 with three to four layers can still maintain air permeability from 2942 L/m2/s–3658 L/m2/s.

Electromagnetic Wave Shielding Properties of Amorphous Metallic Fiber-Reinforced High-Strength Concrete Using Waveguides

In this study, high-strength concrete containing hooked-end steel or amorphous metallic fibers was fabricated, and the electrical conductivity and electromagnetic shielding effectiveness were evaluated after 28 and 208 days based on considerations of the influences of the moisture content. Amorphous metallic fibers, which have the same length and length/equivalent diameter ratio as hooked-end steel fibers, were favored for the formation of a conductive network because they can be added in large quantities owing to their low densities. These fibers have a large specific surface area as thin plates. The electromagnetic shielding effectiveness clearly improved as the electrical conductivity increased, and it can be expected that the shielding effectiveness will approach the saturation level when the fiber volume fraction of amorphous metallic fibers exceeds 0.5 vol.%. Meanwhile, it is necessary to reduce the amount of moisture to conservatively evaluate the electromagnetic shielding performance. In particular, when 0.5 vol.% of amorphous metallic fibers was added, a shielding effectiveness of >80 dB (based on a thickness of 300 mm) was achieved at a low moisture content after 208 days. Similar to the electrical conductivity, excellent shielding effectiveness can be expected from amorphous metallic fibers at low contents compared to that provided by hooked-end steel fibers.

Electromagnetic shielding effectiveness for A16061 metal matrix composite based mesh wire reinforced with Flyash for oblique incidence of EM wave

Nowadays, flywire is used exclusively in aeronautical applications. A plane’s complete control is dependent on electronic technology, yet it suffers from high-intensity radiated fields. An electromagnetic shield may be necessary to protect this equipment from external electromagnetic pollution. The current project attempts to create a protective barrier around the operating equipment to enhance its efficiency. AL6061 composite material was used to create a metal matrix mesh shield. It is reinforced with fly ash in various volume fractions, and the electrical characteristics and Shielding Effectiveness are determined (SE). The maximum SE is 45.36dB obtained, which can be effectively used as a shield for aerospace and other applications.

Preparation And Properties of Electroless Cu/Ni Composite Materials Based On Wood

The changes of properties of wood-based Cu-Ni composites were studied via electroless Cu and Ni on wood surface to obtain Cu-Ni multilayer composites with excellent properties. The surface and interface morphology of the composite coatings were investigated via laser confocal microscopy and scanning electron microscope (SEM). The crystal structure was characterized by XRD. The hydrophobic properties of the composite coatings were tested via contact angle meter. The surface conductivity of composites was tested via four-probe. The results showed that the electrical conductivity of wood-based Cu-Ni composites was 2370.76 S/cm. The surface roughness was 9.99 μm and the thickness of uniform coating reached 157 μm via one time electroless Ni deposition and two times electroless Cu deposition. XRD analysis showed that the wood surface was uniformly covered with metal coating. The metal Cu and Ni were closely nested together to form a dense composite layer, and the composite material was light in weight. When the electroless Ni was 55 min, the contact angle could reach 123°, indicating that had best hydrophobicity. The average electromagnetic shielding effectiveness (EMSE) of Cu and Ni wood-based composites can reach 93.8 dB at L band ranging from 0.3×103 to 3.0×103 MHz) with a low thickness (157 μm), verified the multilayer composite materials can block over 99.99% of incident EM waves.