Microwave-synthesized freestanding iron-carbon nanotubes on polyester composites of woven Kevlar fibre and silver nanoparticle-decorated graphene

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.ope

Conductive textiles for signal sensing and technical applications

Conductive textiles have found notable applications as electrodes and sensors capable of detecting biosignals like the electrocardiogram (ECG), electrogastrogram (EGG), electroencephalogram (EEG), and electromyogram (EMG), etc; other applications include electromagnetic shielding, supercapacitors, and soft robotics. There are several classes of materials that impart conductivity, including polymers, metals, and non-metals. The most significant materials are Polypyrrole (PPy), Polyaniline (PANI), Poly(3,4-ethylenedioxythiophene) (PEDOT), carbon, and metallic nanoparticles. The processes of making conductive textiles include various deposition methods, polymerization, coating, and printing. The parameters, such as conductivity and electromagnetic shielding, are prerequisites that set the benchmark for the performance of conductive textile materials. This review paper focuses on the raw materials that are used for conductive textiles, various approaches that impart conductivity, the fabrication of conductive materials, testing methods of electrical parameters, and key technical applications, challenges, and future potential

Electrically Conductive 2D Material Coatings for Flexible & Stretchable Electronics: A Comparative Review of Graphenes & MXenes

There is growing interest in transitioning electronic components and circuitry from stiff and rigid substrates to more flexible and stretchable platforms, such as thin plastics, textiles, and foams. In parallel, the push for more sustainable, biocompatible, and cost-efficient conductive inks to coat these substrates, has led to the development of formulations with novel nanomaterials. Among these, 2D materials, and particularly graphenes and MXenes, have received intense research interest due to their increasingly facile and scalable production, high electrical conductivity, and compatibility with existing manufacturing techniques. They enable a range of electronic devices, including strain and pressure sensors, supercapacitors, thermoelectric generators, and heaters. These new flexible and stretchable electronic devices developed with 2D material coatings are poised to unlock exciting applications in the wearable, healthcare and Internet of Things sectors. This review has surveyed key data from more than 200 articles published over the last 6 years, to provide a quantitative analysis of recent progress in the field and shade light on future directions and prospects of this technology. We find that despite the different chemical origins of graphenes and MXenes, their shared electrical properties and 2D morphology, guarantee intriguing performance in end applications, leaving plenty of space for shared progress and advancements in the future

Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region

Manipulating Light at Micro- and Nano-Scale: Enable Photonic Structures Toward Real-World Applications

Recent advances in fabrication and processing methods have spurred many breakthroughs in the field of nano- and micro-structures that provide novel ways of manipulating light interaction in a well controllable manner, thereby enabling various innovative applications. In this dissertation, new photonic design concepts and materials featuring high performance and long-term stability are investigated for bridging the gap between the research and the real-world applications. Firstly, angle-insensitive and high-purity structural color filters based on one-dimensional layered structures that are suitable for mass-production are studied. Various scenarios including reducing the layer number and depositing the whole device via an all-solution process have been proposed to simplify the fabrication, thereby lowering the manufacturing cost. The proposed structures offer significant advantages over existing colorant-based filters in terms of high efficiency, slim dimension, and being free from photobleaching. They have been successfully adapted into practical applications including decorative paints, visibly-opaque but near-infrared-transmitting camouflage coatings, and highly-efficient colored photovoltaics. As a special color, ‘black’ has been studied separately based on ultrabroadband absorbers that are achieved by simultaneously exciting multiple absorption resonances. It can significantly enhance the efficiency of energy harvesting and conversion in various applications. In addition, optical designs are incorporated into vehicle interiors, opening up a new path to the extensive use of optics in automobiles: Anti-glare colored dashboard with the potential for high-resolution dashboard displays are demonstrated with micro-scale lenticular lenses; Invisible vehicle pillars for safe driving are realized with compact optical cloaks using different optical components, including polarizers and mirrors. The next part is the research into a cost-effective and easy-to-fabricate method for flexible transparent electrodes employing ultrathin (thickness < 10 nm), ultra-smooth (roughness < 1 nm), and low-loss copper-doped silver. This novel silver alloy requires only room-temperature deposition and presents outstanding optical and electrical properties, mechanical flexibility, and environmental stability, which are greatly desired in potential high-performance flexible optoelectronic devices. Lastly, other optical structures inspired by methods employed in above researches that have impactful applications, including retro-reflective particles that can be embedded in transparent glasses for light detection and ranging and omnidirectional planar solar concentrators based on curved micro-reflectors, are briefly discussed. All the strategies and methodologies proposed here could bring optical researches out of the labs and open up more opportunities for further advancement.PHDElectrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/149791/1/jichg_1.pd

Electromagnetic Interference Shielding Effectiveness of Interlayered Systems Containing Metal-Oxide, Conducting Polymer and Carbon Nanotube Reinforced Polymeric Composites

The Electromagnetic Interference (EMI) Shielding Effectiveness (SE) has become one of the important requirements for the devices associated with telecommunication systems consisting of large frequency bands. The degradation of the quality of transmitting signal influenced by frequencies emitting from external sources can be reduced by covering the circuits of the devices by EMI Shielding materials like polymer composites, metal-based nanofiber mats, the metal of oxide films, etc. The investigation strives for the attenuation of EMI by introducing two composite mats from conducting polymer-based, multiwalled carbon nanotubes (MWCNTs) coated Nylon 6 nanofiber composites. Two other composite mats are also developed by the Forcespinning® method using sol solution of functionalized multiwalled carbon nanotubes (f-MWCNTs) and magnetite (Fe3O4) into as-prepared polyacrylonitrile (PAN) which is then carbonized at elevated temperature to convert it into carbon nanofiber (CNF). A total of four layers of mats are stacked and compression molded together to develop one multilayered composite (MLC 1). The Fe3O4 has higher magnetic properties which may provide a good magnetic loss effect. The focus is to investigate the synergistic effects between higher magnetic Fe3O4, conductive MWCNTs nanofillers with the dielectric CNF, conducting polymer, and functionalized MWCNTs coated nanofiber composite which can provide information about the dominating mechanism. (Absorption, reflection, or multiple reflections) for EMI SE. The multilayered composite (MLC 2) consisting 8 layers (repeating the stacking sequence again) has given the highest obtained value more than 40 dB EMI SE in the frequency range from 300–500 MHz. The results will bring some findings of optimized materials yielding good EMI SE in lightweight applications

Tailoring the electrical and thermal conductivity of multi-component and multi-phase polymer composites

The majority of polymers are electrical and thermal insulators. In order to create electrically active and thermally conductive polymers and composites, the hybrid-filler systems is an effective approach, i.e. combining different types of fillers with different dimensions, in order to facilitate the formation of interconnected conducting networks and to enhance the electrical, thermal, mechanical and processing properties synergistically. By tailoring polymer-filler interactions both thermodynamically and kinetically, the selective localisation of fillers in polymer blends and at the interface of co-continuous polymer blends can enhance the electrical conductivity at a low percolation threshold. Moreover, selective localisation of different filler types in different co-continuous phases can result in multiple functionalities, such as high electrical conductivity, thermal conductivity or electromagnetic interference shielding. In this review, we discuss the latest progress towards the development of electrically active and thermally conductive polymer composites, and highlight the technical challenges and future research directions