Three-dimensional hydrophobic and efficient electromagnetic shielding Cu/wood/Cu laminated composites were prepared by a simple one-step electroless Cu process. The number of electroless Cu on wood surface and the treatment time of electroless Cu were used as variables. The effects of independent variables in the range from 0.3 ×10−3 to 3.0 GHz (L-band) on the conductivity, water contact angle and electromagnetic shielding effectiveness of the composite were analyzed. The Cu particles are fully filled in the wood hierarchical porous structure, and the metal coating uniformly covers the entire wood surface. After three times of electroless Cu, the conductivity of the composite can reach 7255 S/cm, the contact angle is 130.8° when the time is 12 min, showing good hydrophobic properties, and the average electromagnetic shielding effectiveness is as high as 96 dB. Compared with the L-band (94 dB), the twice electroless sample has a maximum shielding effectiveness of 85.6 dB in the X-band (8.2-12.4 GHz), which can shield a large number of incident electromagnetic waves to achieve high absorption and low reflection. The anisotropic internal porous structure of wood matrix and the multi-interface polarization between wood and Cu are the main reasons for the effective electromagnetic interference shielding performance of Cu/wood/Cu laminated composites.
A wood-based composite with excellent electromagnetic shielding performance was prepared by constructing a multilayer structure with positive conductance gradient and negative magnetic gradient, and the electromagnetic waves underwent a special absorption-reflection-reabsorption process and an interfacial polarization loss-induced absorption process. The results showed that with the increase of the content of Fe3O4@Graphene compound, the surface morphology of wood gradually becomes flat. When the content of Fe3O4@Graphene compound is 300 mg, the surface roughness of metal coatings on the wood surface of the composites was only 13.525 μm. The maximum thickness of the coatings on the wood surface section was 88 μm. XRD patterns showed that the crystalline structure of the coatings on the wood surface was further strengthened, which confirmed the existence of Cu, Ni and Fe3O4@Graphene nanoparticles on the wood surface. When the content of Fe3O4@Graphene compound was 400 mg, the hydrophobic property of the composite reached the best, and the contact angle was 85.4°. The electromagnetic shielding of the composite can be up to 94.73 dB ranging from 300 kHz to 3.0 GHz.
With the aggravation of electromagnetic radiation pollution, it is urgent to develop green, lightweight, ultra-thin and high-performance electromagnetic interference shielding materials to eliminate unnecessary electromagnetic interference; however, the construction of wood-based high-performance electromagnetic shielding materials by simple methods remains a challenge. Based on the layer-by-layer assembly strategy, a lightweight Ni/Wood/Ni composite (NWNC) with an interlayer structure was constructed by a simple electroless plating method using natural wood as a substrate for electromagnetic interference shielding. The synthesized NWNC has a smooth surface, and its minimum surface roughness is only 8.34 μm. After 15 min of electroless nickel plating, the contact angle (CA) of NWNC with an ultra-thin nickel layer (65 μm) was 118.3°. When the thickness of the nickel layer is only 0.102 mm, the conductivity can reach 1659.59 S/cm when the three electroless nickel plating time is 15 min. In the L-band, the electromagnetic shielding effectiveness can reach 94.1 dB after three times electroless nickel plating for 20 min. This is due to the conductive loss, magnetic loss and interface polarization loss generated by the electromagnetic network constructed by the nickel layer, which makes the composite material produce an electromagnetic shielding mechanism dominated by absorption. The L-band absorption efficiency can reach 39.01 dB, and due to the porous structure of the original wood, the multiple reflection and absorption inside the wood further lose the electromagnetic wave. This study provides a low-cost and simple method for the design of light, ultra-thin and efficient controllable wood-based electromagnetic shielding materials and has broad application prospects in the fields of construction and aerospace.
Abstract The NiNiO/GR‐TiO 2 magnetic hollow rod composites based on lignocellulose was prepared via electroless Ni and sol‐gel method to effectively solve that the composites were difficult to recycle and reuse. Rapid degradation of organic dyes was conducted. The element distribution, surface morphology, and functional groups were characterized via SEM, TEM, LSCM and FT‐IR, respectively. The structure was characterized by XRD and XPS. The photocatalytic properties were tested via TU‐1950 UV spectrophotometer. The EDS demonstrated the increase of S and N elements and FT‐IR results, indicating that methylene blue has been degraded by ring‐opening reaction. The results showed that the surface elements of the hollow rod structure were evenly distributed. The composite catalytic efficiency could reached 57.65 % and catalytic material prepared in vacuum was 93.34 % when the dosage of graphene was 50 mg. The composite materials photocatalytic system with addition of 20 mL EDTA could greatly improve the catalytic efficiency, which was up to 97.43 %.
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