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A new simplified low temperature deposition method to manufacture flexible transparent conductive electrodes (FTCE) based on conductive polymer composite filled with silver nanowires (AgNWs) was investigated. Polyurethane/AgNWs composite was deposed on a poly(ethylene terephthalate) substrate as a conductive paint in a thin layer lower than 2 μm. The high aspect ratio nanowires influence on the electrical behavior is followed with surface resistivity and optical transparency experiments. The best compromise was obtained with a conductive layer filled with 2.84 vol.% of AgNWs; it exhibits a surface resistivity of 143 Ω/sq with 73% in transmittance. These transparent conductive composites processing in one step with good touching manipulation resistance demonstrate the real interest for this kind of FTCEs technology without indium tin oxide. [ABSTRACT FROM AUTHOR]

Spray coating of the ferroelectric polymer P(VDF-TrFE) appears as an attractive approach for the fabrication of electromechanical transducers. However, it is important to elucidate how the crystallinity and the associated piezoelectric properties depend on the coating thickness and additives. To this aim, we have spray-coated various substrates both with pure and nanocomposite films of 70–30% copolymers in a broad thickness range (200 nm–30 μm). Using X-ray diffraction, differential scanning calorimetry, Raman spectroscopy and atomic force microscopy, we show that the obtained films are dense and homogeneous with ca. 50% crystallinity, which consists of a major polar phase, with slight alterations in the sub-micrometer thickness regime. Robust piezoelectricity and ferroelectricity are revealed at room temperature through both local hysteresis loops and lithography experiments using the piezoresponse force microscopy technique. After poling, the piezoelectric d33 coefficient displays values up to −19 and −11 pC N−1 for the pure copolymer and the composite, respectively. For a 33 vol% load of inorganic spin-crossover nanofillers, the switching properties are substantially improved and a coercive voltage of <10 V is demonstrated for micrometric films. Overall, this approach appears as a promising way for the in situ integration of high quality piezopolymer films into complex transducer geometries for sensing, actuating and energy harvesting purposes. [ABSTRACT FROM AUTHOR]

Polymer-based magnetoelectric composites are processed with an intrinsic piezoelectric poly(vinylidenefluoride-co-trifluoroethylene) (P(VDF-TrFE)) matrix and high-aspect-ratio magnetic nickel–decorated silver nanowires. These core/ shell wires are obtained by the polyol reduction of Ni2+ ions on high-aspect-ratio silver nanowires. Scanning electron microscopy and transmission electron microscopy analyses show a homogeneous and well-crystallized nickel layer. Magnetic properties of the intrinsic particles and their composites are measured and show a strong enhancement of the coercive field compared to spherical Ni nanopowders. They also show the existence of strong magnetic anisotropy in the composites. The composites processed with a small amount of metallic particles (0.3 vol%) allow the maintaining of the P(VDF-TrFE) crystalline phase and the ability of a macroscopic polarization. The latter is conducted under a 80 MV m−1 field, leading to a significant d33 (3.2 pC N−1). Thus, the magnetoelectric properties are analyzed and an important coupling coefficient αME equal to 1.8 V m−1 Oe−1 is measured. [ABSTRACT FROM AUTHOR]

For electromagnetic shielding in space environment, the metallization of carbon fiber reinforced polymer (CFRP) is required. A specific attention is paid due to the thermal expansion coefficient difference between substrate and metal coating. A surface metallization of a CFRP has been elaborated by electrodeposition. This study presents an original process based on an electrically conductive polymer coating elaborated from a polyurethane matrix filled with a low content of silver nanowires (<10%vol). A continuous and adherent deposit is obtained by an optimization of the electroplating parameters. A minimal volume fraction was determined at 3%vol associated with an applied current density estimated near 0.1 A/dm2. The growth speed is 7 μm/h at 0.1 A/dm2. The adhesion was checked in severe environmental conditions (−196 to 165°C). The effectiveness shielding obtained with this solution reaches an attenuation value higher than 90 dB between 1 and 26 GHz necessary for space communication applications. [ABSTRACT FROM AUTHOR]

In this work, three phase magnetoelectric nanocomposites are successfully prepared by solvent casting from α-PVDF. The extrinsic piezoelectric effect is insured by 20 vol% of NaNbO 3 ferroelectric nanoparticles prepared by the hydrothermal process. Nickel is chosen as the magnetic phase. In order to maintain insulation, electrical percolation is avoided by using nickel contents lower than the percolation threshold. Two different morphologies are employed: spherical nanoparticles (NiNPs) and nanochains (NNCs) with an aspect ratio of 80. NNCs are obtained by a polyol process under a magnetic field. Thin films of nanocomposites are processed by hot pressing. The real part of the dielectric permittivity (ε') of composites is governed by Maxwell-Wagner-Sillars polarization at the PVDF/Ni interfaces. An important increase of ε' at low frequency is observed for PVDF/NaNbO 3 /NNCs composites; it favors the magnetoelectric coupling. Piezoelectric properties of composites are dependent upon mechanical modulus so that the most higher d 33 is obtained for PVDF / NaNbO 3 / NiNPs. Magnetoelectric coupling coefficient (α ME) is determined from magnetoelectric intensity. PVDF / NaNbO 3 / NiNPs composites exhibit enhanced magnetoelectric coupling. The a ME coupling coefficient reaches 4.2V/(mOe). The magnetic properties are significantly improved by the NiNPs [ABSTRACT FROM AUTHOR]

Poly(ether ketone ketone) (PEKK)/unidirectional carbon fiber (CF) composites have a poor interface. Accordingly, PEKK oligomer (PEKKo) sizing with a chemical compatibility with PEKK is proposed for promoting interfacial interactions in order to enhance mechanical performances. The thermal stability until 500 °C has been shown by thermogravimetric analysis (TGA). In order to compare static and dynamic sizing methods, "lab sizing" and "pilot sizing" were carried out. Scanning electron microscopy images of freeze fractures of PEKK/unsized CF, PEKK/PEKKo lab‐sized CF and PEKK/PEKKo pilot‐sized CF show that the PEKKo sizing causes an improvement of fiber/PEKK interactions, regardless of the sizing method. Indeed, in both cases, there is a continuity of matter at the interface while we observe a poor wetting of CF by matrix in PEKK/unsized CF. Dynamic mechanical relaxations in shear were analyzed as a function of temperature. The increase of storage modulus upon sizing is observed for both methods but it is more important for PEKKo pilot sizing. In the same way, the mechanical energy loss increases, it reflects the optimization of stress transfer between matrix and fibers. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48818. [ABSTRACT FROM AUTHOR]

ABSTRACT: High performance thermoplastic poly(ether ketone ketone) (PEKK) polymers with various meta phenyl links ratio were investigated by dynamical mechanical analysis. Analyses were carried out in a wide range of temperature from solid state (torsion rectangular mode) to the melt state (torsion parallel plates mode) as function of thermal history and environmental conditions. In the solid state, this study was focused on the secondary relaxations in the vitreous state. A complementary investigation conducted with different poly(aryl ether ketones) allowed us to propose a molecular interpretation of PEKK sub‐vitreous relaxations. In the molten state, storage modulus (G′), loss modulus (G″), storage viscosity (η′), and loss viscosity (η″) were studied to determine zero shear‐rate viscosity (η0) and thermal activation energy Ea. Master curves were built and the shift factor aT was determined. Thermal activation energies were extracted from an Arrhenius model on the shift factor temperature's dependency. Finally, Ea and η0 were determined thanks to the dynamic viscosity fit with Cross model and Cole–Cole representation. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46456. [ABSTRACT FROM AUTHOR]