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A recent research focus has been on developing sustainable and renewable high-performance electromagnetic shielding materials. We present here a robust and effective top-down method in which polydopamine (PDA) is added to delignified wood via in situ polymerization, and Ag particles are successfully deposited in the wood channel via PDA's adhesive property with a subsequent silver mirror reaction. According to our findings, when the AgNO3 content is 30 g/L, the conductivity of 2-mm-thick conductive wood reached 500 S/cm with an electromagnetic interference shielding efficiency of 50 dB in the X-band. The three-dimensional network structure of the wood is preserved, and thus it has good mechanical properties. Hence, silver-plated wood can be used as an electromagnetic shielding material that requires high strength. [ABSTRACT FROM AUTHOR]

A novel and cost-effective method for the fabrication of highly conductive Al/Ag core-shell structured microspheres was proposed and investigated. The oxidative co-deposition of catechol and polyamine was firstly performed to modify the surface of the aluminum microsphere. Then, a two-step electroless plating was conducted to fabricate the Al/Ag microspheres. During the first step of the electroless plating process, the surface of the aluminum microsphere was deposited with silver nanoparticle seeds using n-octylamine and ethylene glycol. Then, during the second step of the electroless plating process, silver particles grew evenly to form a compact silver shell on the surface of aluminum via a silver mirror reaction. According to the scanning electron microscope and energy dispersive X-ray results, a compact and continuous silver layer was successfully generated on the surface of the aluminum. The valence of the sliver on the surface of the aluminum was confirmed to be zero, based on the X-ray photoelectron spectrometer and X-ray diffractometer analyses. As a result, the as-prepared Al/Ag microspheres exhibited a high conductivity of 10,000 S/cm. The Al/Ag/MVQ composite demonstrated low electrical resistivity of 0.0039 Ω·cm and great electromagnetic interference shielding effectiveness at more than 70 dB against the X-band, and this result suggests that the as-prepared composite is a promising conductive and electromagnetic shielding material. [ABSTRACT FROM AUTHOR]

The thermoplastic polyurethane/multiwalled carbon nanotube (TPU/CNT) nanocomposites with high conductivity and low percolation threshold value were prepared by melting blending and annealing treatment. The effect of annealing process on the microphase structure and the properties of TPU/CNT nanocomposites was studied. It has been shown that CNT flocculation can occur in TPU/CNT nanocomposites during the annealing process. At a critical CNT content, which defined the percolation threshold, CNTs could form conductivity network. The conductive percolation threshold value of TPU/CNT nanocomposites was decreased from 10 to 4% after annealing process, and the conductivity of TPU/CNT nanocomposites with 10 vol % of CNT could reach 1.1 S/m after an annealing time of 1 h. The significant enhancement of electrical conductivity was influenced by the annealing time and the content of CNTs. The formation of CNT networks was also verified by dynamic viscoelastic characterization. The results of X-ray diffraction and differential scanning calorimetry indicated that annealing process reinforced the microphase separation of the nanocomposites. Mechanical properties test showed that the annealing treatment was in favor of improving the mechanical properties; however, further increase in the annealing time has negative effect on the mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

Abstract: A biomimetic method for the preparation of highly conductive silver-plated polyethylene terephthalate (PET) fiber was demonstrated. First, the PET fibers were functionalized with a bio-inspired polydopamine (PDA) coating, simply by being dispersed in a dopamine solution under mild stirring at room temperature. Electroless plating of silver was then carried out on the surface of the PET-PDA fiber. An aqueous solution of silver nitrate and glucose was used as silver precursor and reducing reagent, respectively. The overall procedure is fast, simple, efficient, nontoxic, as well as controllable. The PDA layer on the PET surface was characterized by X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, and contact angle measurement. The crystalline structure of the modified PET fiber was studied by X-ray diffraction (XRD). The morphology of the PET-PDA and the PET-Ag fiber was observed by scanning electron microscopy (SEM). SEM results showed that the silver layer coated on PET-PDA was continuous, uniform, and compact. The as-prepared PET-Ag fibers have good electrical conductivity, with surface resistivity as low as 0.4mΩcm. The binding force between the silver layer and PET-PDA fiber was strong enough that the silver layer remained compact and continuous after the PET-PDA/Ag fiber was rinsed under ultrasound for 4h. [Copyright &y& Elsevier]

Abstract: A facile method was developed to prepare silica–silver core–shell composite microspheres with continuous, compact, and conductive silver layers. The procedure involves dopamine oxidative self-polymerization and electroless plating. The poly(dopamine) layer was used as the chemi-sorption sites for silver ions and promoted the silver deposition. The electroless plating procedure involves a combination of surface activation, seeding growth, and deposition. The chemical composition and the crystal structure of the silica–silver core–shell composite microspheres were studied by X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD), respectively. In addition, the surface morphology and chemical composition of each composite microsphere were confirmed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The results demonstrated that the silver layer on the silica surface was continuous and compacted. [Copyright &y& Elsevier]

It is very important to improve the electrical conductivity of polymer nanocomposites (PNCs), which can be used under the external field. In this work, by employing a coarse-grained molecular dynamics simulation, the effect of the external fields (tensile field and shear field) on the conductive probability of PNCs has been investigated in details by tuning the nanofiller shape. By carefully analyzing the conductive network, compared with the rod filler and the sphere filler, the Y filler and the X filler can protect the conducive networks well from their breakage perpendicular to the external fields, which thus can significantly enhance the conductive probability under the external fields. In other words, compared with under the quiescent state, the decrease or the increase of the conductive probability under the external fields depends on the nanofiller shape. Meanwhile, it is interesting to find that both the directional conductive probabilities parallel to the shear field and perpendicular to the shear field increase with the shear rate for the Y fillers, which further reflects their high conductive probability under the shear field. The reason can be attributed to two aspects: (1) the gradual aggregation of Y fillers under the external field; (2) the multi-arm structures of Y fillers. In summary, this work presents some further understanding how to improve the electrical conductivity of PNCs under the external fields by tuning the nanofiller shape. Image 1 [ABSTRACT FROM AUTHOR]