Composite structural supercapacitors (SSC) are an attractive technology for aerospace vehicles; however, maintaining strength whilst adding energy storage to composite structures has been difficult. Here, SSCs were manufactured using aerospace-grade composite materials and CNT mat electrodes. A new design methodology was explored where the supercapacitor electrolyte was localised within the composite structure, achieving good electrochemical performance within the active region, whilst maintaining excellent mechanical performance elsewhere. The morphologies of these localised SSC designs were characterised with synchrotron X-ray fluorescence microscopy and synchrotron X-ray micro-computed tomography and could be directly correlated with both electrochemical and mechanical performance. One configuration used an ionogel with an ionic liquid (IL) electrolyte, which assisted localisation and achieved 2640 mW h kg−1 at 8.37 W kg−1 with a corresponding short beam shear (SBS) strength of 71.5 MPa in the active area. A separate configuration with only IL electrolyte achieved 758 mW h kg−1 at 7.87 W kg−1 with SBS strength of 106 MPa in the active area. Both configurations provide a combined energy and strength superior to results previously reported in the literature for composite SSCs.

Graphitic nanoplatelets (GNPs) have been treated using an ultrasonicated ozonolysis procedure to produce stable aqueous dispersions that facilitate deposition of thin films using electrophoretic deposition. The thin GNP films were then coated with zero valence (ZV) iron nanocubes using a pulsed electrodeposition technique. Characterization of the ZV-iron coating with deposition time revealed that the changing magnetic character of the ferromagnetic-graphitic hybrid material was related to the nucleation density and growth of the ZV-iron nanocubes. Density functional theory calculations show a preference for ZV-iron adsorption at the oxygen sites of the GNPs, with ZV-iron displacement of oxygen groups favored in some configurations. Transmission electron microscopy studies confirm ZV-iron growth nucleates preferentially at the graphite nanoplatelet edges and the hybrid material magnetism is affected by the convergent crystalline grain boundaries formed between adjacent ZV-iron nanocubes.

Exposure to plasma can significantly increase the surface area of silver species and their resistance to oxidation. While some work investigating plasma-treated silver has been done, limited morphologies and applications have been explored. We hereby explore this effect on silver nanowires (AgNWs) through medium-vacuum air plasma exposure time ranging between 30 s to 60 min. These plasma-treated AgNW networks are directly applied as supercapacitor electrodes, without any carbon or polymer additives that are typically employed alongside silver in energy storage applications. The plasma treatment consequently affected the electrochemical performance of AgNWs, where longer treatment times resulted in higher energy storage capacity. An increase in resistance was observed for plasma treatment times greater than or equal to 5 min, due to the switch from the percolation threshold of the metallic Ag phase to the Ag2O phase. Despite an initial drop in stored energy, an overall improvement in energy storage capacity was observed throughout cycling, where the optimal plasma treatment time of 5 min resulted in an increase of 320% of its starting value with near 100% coulombic efficiency, through the development of stable redox-active surface nanostructures.

Boron nitride nanotubes (BNNTs) represent a relatively new class of materials that provides alternative electrical and thermal properties to the carbon analogue. The high chemical and thermal stability and large band gap combined with high electrical resistance make BNNTs desirable in several thin-film applications. In this study, stable BNNT and hexagonal boron nitride (hBN) particle dispersions have been developed using environmentally friendly advanced oxidation processing (AOP) that can be further modified for electrophoretic deposition (EPD) to produce thin films. The characterization of the dispersions has revealed how the hydroxyl radicals produced in AOP react with BNNT/hBN and contaminant boron nanoparticles (BNPs). While the radicals remove the carbon contaminant present on BNNT/hBN and increase dispersion stability, they also oxidize the BNPs and the boron oxide produced, which, conversely, reduces the dispersion stability. The use of high- or low-powered ultrasonication in combination with the AOP affects the rate of the competing reactions, with low-powered sonication and AOP providing the best combination for producing stable dispersions with high concentrations. BNNT/hBN dispersions were functionalized with polyethyleneimine to facilitate EPD, where films of several micrometer thickness were readily deposited onto stainless steel and glass-fiber fabrics. BNNT/hBN films produced on glass fabrics by EPD exhibited a consistent through-thickness macroporosity that was facilitated by platelet and nanotube stacking. The film macroporosity present on the coated fabrics was suitable for use as separator layers in supercapacitors and provided improved device robustness with a minimal impact on electrochemical performance.

Vanadium dioxide (VO2) has been identified as a material capable of transitioning from an insulator to a metal close to room temperature. Previous works have demonstrated potential applications of this material in various microwave components or devices. However, the complex permittivity and permeability characterization of the VO2 over X-band has not been previously reported. Knowledge of these properties is essential for accurate modeling of the components and devices utilizing VO2. This paper characterizes a VO2 film deposited on a quartz substrate in a WR90 waveguide using a vector network analyzer. The S-parameters, conductivity, relative complex permittivity, and permeability of the VO2 film are determined across the transition temperature.

A carbon nanotube (CNT) mat interspersed with metallic iron nanoparticles is investigated as a structural supercapacitor electrode material that could be incorporated into fiber-reinforced composites. Both ionic liquid and aqueous potassium hydroxide electrolytes are trialed to examine pseudocapacitive mechanisms and the long-term electrochemical stability of the CNT mat in symmetrical supercapacitors. High-resolution transmission electron microscopy showed the high level of interconnection of the CNTs and evenly distributed metallic iron nanoparticles, which enhances the structural and electrical performance of the electrode. Raman and X-ray photoelectron spectroscopies combined with thermogravimetric and surface area analyses are used to characterize the physico-chemical properties of the CNT mat and identify the different electrochemical mechanisms contributing to the supercapacitive behavior. Three electrode experiments demonstrated the relative contributions of the cathode and anode processes to the total capacitance. Symmetrical supercapacitor coin-cell trials used a structural glass-fiber separator and showed the ionic liquid electrolyte facilitated stable pseudocapacitance with the available iron nanoparticles, leading to specific energy and power as high as 18.3 Wh.kg(-1) at 0.15 kW kg(-1) and 5.6 Wh.kg(-1) at 2.4 kW kg(-1) after 5000 cycles. It is envisioned these materials can readily be incorporated into composite materials for structural energy storage technology. Crown Copyright (c) 2019 Published by Elsevier Ltd. All rights reserved.

This paper focuses on the design of microwave permittivity sensors based on microstrip lines loaded with shunt connected series LC resonators. The LC resonator is made of a thin inductive trace connected to a capacitive square patch in the ground plane using a via hole. By producing two branches of the same configuration connected to each other using a T junction, differential sensing is achieved enabling robust detections against environmental factors causing measurement errors and miscalibration. The sensor operation principle is analyzed and validated through lumped-element circuit analysis and practical measurements.

Carbon fiber reinforced polymer (CFRP) materials are anisotropic lossy conductors which restrict their use in high-performance lightweight and load-bearing waveguides. The attenuation of CFRP waveguides has been improved in this research by investigating and comparing three different manufacturing techniques. WR-90 waveguides have been manufactured from Cytec IM7/977-3 prepreg and their transmission performance was evaluated. Three different techniques were implemented to reduce waveguide losses including: copper foil lining, conductive paint, and a new integrated metalized carbon fiber veil (CFV) material. The new lightweight high conductivity CFV was integrated into the walls of a CFRP waveguide which reduced the per unit length attenuation to below 1 dB/m. This was an improvement of up to 5.5 dB over raw carbon fiber and similar to the performance of a copper foil-lined waveguide.