Thermotherapy
is a widespread technique that provides relief for
muscle spasms and joint injuries. A great deal of energy is used to
heat the surrounding environment, and heat emitted by the human body
is wasted on our surroundings. Herein, a woven Kevlar fiber (WKF)-based
personal thermal management device was fabricated by directly growing
vertical copper–nickel (Cu–Ni) nanowires (NWs) on the
WKF surface using a hydrothermal method. The treated WKF was combined
with reduced graphene oxide (rGO) dispersed in polydimethylsiloxane
(PDMS) to form composites using vacuum-assisted resin transfer molding
(VARTM). This WKF-based personal thermal management system contained
a conductive network of metallic NWs and rGO that promoted effective
Joule heating and reflected back the infrared (IR) radiation emitted
by the human body. It thus behaved as a type of thermal insulation.
The Cu–Ni NWs were synthesized with a tunable Ni layer on Cu
core NWs to enhance the oxidation resistance of the Cu NWs. The combined
effect of the NW networks and rGO enabled a surface temperature of
70 °C to be attained on application of 1.5 V to the composites.
The Cu3Ni1–WKF/PDMS provided 43% more
thermal insulation and higher IR reflectance than bare WKF/PDMS. The
absorbed impact energy and tensile strength was highest for the Cu1Ni3- and rGO-integrated WKF/PDMS samples. Those
Cu–Ni NWs having higher Ni contents displayed better mechanical
properties and those with higher Cu contents showed higher Joule heating
performance and IR reflectivity at a given rGO loading. The composite
shows sufficient breathability and very high durability. The high
flexibility of the composites and their ability to generate sufficient
heat during various human motions ensures their suitability for wearable
applications.
Well-aligned NiCoS nanowires, synthesized hydrothermally on the surface of woven Kevlar fiber (WKF), were used to fabricate composites with reduced graphene oxide (rGO) dispersed in polyester resin (PES) by means of vacuum-assisted resin transfer molding. The NiCoS nanowires were synthesized with three precursor concentrations. Nanowire growth was characterized using scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. Hierarchical and high growth density of the nanowires led to exceptional mechanical properties of the composites. Compared with bare WKF/PES, the tensile strength and absorbed impact energy were enhanced by 96.2% and 92.3%, respectively, for WKF/NiCoS/rGO (1.5%)/PES. The synergistic effect of NiCoS nanowires and rGO in the fabricated composites improved the electrical conductivity of insulating WKF/PES composites, reducing the resistance to ∼10 Ω. Joule heating performance depended strongly on the precursor concentration of the nanowires and the presence of rGO in the composite. A maximum surface temperature of 163 °C was obtained under low-voltage (5 V) application. The Joule heating performance of the composites was demonstrated in a surface deicing experiment; we observed that 17 g of ice melted from the surface of the composite in 14 min under an applied voltage of 5 V at -28 °C. The excellent performance of WKF/NiCoS/rGO/PES composites shows great potential for aerospace structural applications requiring outstanding mechanical properties and Joule heating capability for deicing of surfaces.
We synthesized Ag nanoparticle-decorated multilayered graphene nanosheets (Ag-graphene) from graphite nanoplatelets and silver nitrate through 90–100 s of microwave exposure, without the use of any mineral acids or harsh reducing agents. Fe nanoparticle-decorated carbon nanotubes (Fe-CNTs) were grown on polypyrrole (PPy) deposited on woven Kevlar fibre (WKF), using ferrocene as a catalyst, under microwave irradiation. Fe-CNTs grown on WKF and Ag-graphene dispersed in polyester resin (PES) were combined to fabricate Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites by vacuum-assisted resin transfer moulding. The combined effect of Fe-CNTs and Ag-graphene in the resulting composites resulted in a remarkable enhancement of tensile properties (a 192.56% increase in strength and 100.64% increase in modulus) as well as impact resistance (a 116.33% increase). The electrical conductivity significantly increased for Ag-graphene/Fe-CNT/PPy-coated WKF/PES composites. The effectiveness of electromagnetic interference shielding, which relies strongly on the Ag-graphene content in the composites, was 25 times higher in Ag-graphene/Fe-CNT/PPy-coated WKF/PES than in neat WKF/PES composites. The current work offers a novel route for fabricating highly promising, cost effective WKF/PES composites through microwave-assisted synthesis of Fe-CNTs and Ag-graphene.
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