Publications
312 results found
Li Y, Shaffer MSP, 2023, Confocal microscopy for in situ multi-modal characterization and patterning of laser-reduced graphene oxide, Advanced Functional Materials, Vol: 33, Pages: 1-13, ISSN: 1616-301X
Graphene oxide (GO) films can be readily prepared at wafer scale, then reduced to form graphene-based conductive circuits relevant to a range of practical device applications. Among a variety of reduction methods, laser processing has emerged as an important technique for localized reduction and patterning of GO films. In this study, the novel use of confocal microscopy is demonstrated for high-resolution characterization, in situ laser reduction, and versatile patterning of GO films. Multi-modal imaging and real-time tracking are performed with 405 and 488 nm lasers, enabling large-area direct observation of the reduction progress. Using image analysis to cluster flake types, the different stages of reduction can be attributed to thermal transfer and accumulation. Delicate control of the reduction process over multiple length scales is illustrated using millimeter-scale stitched patterns, micropatterning of single flakes, and direct writing conductive 2D wires with sub-micrometer resolution (530 nm). The general applicability of the technique is shown, allowing fabrication of both conductive reduced graphene oxide (rGO) films (sheet resistance: 2.5 kOhm sq−1) and 3D microscale architectures. This simple and mask-free method provides a valuable tool for well-controlled and scalable fabrication of reduced GO structures using compact low-power lasers (< 5 mW), with simultaneous in situ monitoring and quality control.
Cowie BE, Häfele L, Phanopoulos A, et al., 2023, Matched ligands for small, stable colloidal nanoparticles of copper, cuprous oxide and cuprous sulfide, Chemistry: A European Journal, Vol: 29, Pages: 1-18, ISSN: 0947-6539
This work applies organometallic routes to copper(0/I) nanoparticles and describes how to match ligand chemistries with different material compositions. The syntheses involve reacting an organo-copper precursor, mesitylcopper(I) [CuMes]z (z=4, 5), at low temperatures and in organic solvents, with hydrogen, air or hydrogen sulfide to deliver Cu, Cu2 O or Cu2 S nanoparticles. Use of sub-stoichiometric quantities of protonated ligand (pro-ligand; 0.1-0.2 equivalents vs. [CuMes]z ) allows saturation of surface coordination sites but avoids excess pro-ligand contaminating the nanoparticle solutions. The pro-ligands are nonanoic acid (HO2 CR1 ), 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (HO2 CR2 ) or di(thio)nonanoic acid, (HS2 CR1 ), and are matched to the metallic, oxide or sulfide nanoparticles. Ligand exchange reactions reveal that copper(0) nanoparticles may be coordinated by carboxylate or di(thio)carboxylate ligands, but Cu2 O is preferentially coordinated by carboxylate ligands and Cu2 S by di(thio)carboxylate ligands. This work highlights the opportunities for organometallic routes to well-defined nanoparticles and the need for appropriate ligand selection.
Shaffer M, Moore J, Paineau E, et al., 2023, Wet spinning imogolite nanotube fibres: an in situ process study, Nanoscale Advances, Vol: 5, Pages: 3376-3385, ISSN: 2516-0230
Imogolite nanotubes (INTs) form transparent aqueous nematic solutions, with strong birefringence and X-ray scatteringpower. They provide an ideal model system for studying the assembly of one-dimensional nanomaterials into fibres, as wellas offering interesting properties in their own right. Here, in-situ polarised optical microscopy is used to study the wetspinning of pure INTs into fibres, illustrating the influence of process variables during extrusion, coagulation, washing anddrying on both structure and mechanical properties. Tapered spinnerets were shown to be significantly more effective thanthin cylindrical channels for forming homogeneous fibres; a result related to simple capilliary rheology by fitting a shearthinning flow model. The washing step has a strong influence of structure and properties, combining the removal of residualcounter-ions and structural relaxation to produce a less aligned, denser and more networked structure; the timescales andscaling behviour of the processes are compared quantitatively. Both strength and stiffness are higher for INT fibres with ahigher packing fraction and lower degree of alignment, indicating the importance of forming a rigid jammed network totransfer stress through these porous, rigid rod assemblies. The electrostatically-stabilised, rigid rod INT solutions weresuccessfully cross-linked using multivalent anions, providing robust gels, potentially useful in other contexts.
Yang SM, Shaffer MSP, Brandt-Talbot A, 2023, High Lignin Content Carbon Fiber Precursors Wet-Spun from Low-Cost Ionic Liquid Water Mixtures, ACS Sustainable Chemistry and Engineering, Vol: 11, Pages: 8800-8811
Lignin is an abundant biopolymer present in wood biomass and a promising renewable precursor for carbon materials. Lignin-derived carbon fibers (CFs) are an attractive target for sustainable composite applications, due to the global scope for achieving energy efficiencies, if cost-effective manufacturing technologies can be developed. Here, a mixture of a low-cost (<$1/kg) ionic liquid (IL), N,N-dimethylbutylammonium hydrogen sulfate, [DMBA][HSO4], and water is shown to be an effective solvent for the continuous wet-spinning of high lignin content fibers. Homogeneous solutions formed of unmodified lignins (Kraft or ionoSolv) and partially hydrolyzed poly(vinyl alcohol) were prepared in aqueous IL mixtures (60:40 wt/wt % [DMBA][HSO4]:H2O) and spun into continuous fibers with circular cross-sections using 1 M aqueous Na2SO4 or pure water as a coagulant. The lignin precursor fibers with 75-90% lignin content had tensile strengths of 25-50 MPa and moduli of 3-5 GPa. After oxidative stabilization and carbonization at 1000 °C, a carbon yield of up to 40% was achieved, with tensile strengths and moduli of up to 450 MPa and 40 GPa, respectively. With further process optimization, the new lignin spinning approach has the promise to be scalable and provide biobased CFs that are low-cost and environmentally benign.
Asfaw HD, Kucernak A, Greenhalgh ES, et al., 2023, Electrochemical performance of supercapacitor electrodes based on carbon aerogel-reinforced spread tow carbon fiber fabrics, Composites Science and Technology, Vol: 238, ISSN: 0266-3538
Fabric-based supercapacitor electrodes were fabricated by embedding spread tow carbon fiber fabrics, in monolithic, bicontinuous carbon aerogels (CAG). The incorporation of CAG, at less than 30 wt%, increased the specific surface area of the CAG-CF fabric to above 230 m2 g−1 and the pore volume to about 0.35 cm3 g−1, orders of magnitude higher than that for the as-received carbon fibres. The presence of the CAG not only improves the electrochemical performance of the composite electrodes but may enhance the mechanical response due to the high stiffness of the aerogel structure. Cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance measurements were performed on symmetric supercapacitor cells consisting of two CAG-reinforced fabrics in an ionic liquid electrolyte. The specific capacitance of the symmetric supercapacitor was determined to be in the range 3–5 F g−1, considerably higher than that for the plain carbon fibers. Since optimum structural electrolytes are not yet available, this value was normalized to the total mass of both electrodes to place an upper bound on future structural supercapacitors using this spread tow CAG-CF system. The maximum specific energy and specific power, normalized to the total mass of the electrodes, were around 2.64 W h kg−1 and 0.44 kW kg−1, respectively. These performance metrics demonstrate that the thin CAG-modified spread tow fabrics are promising electrodes for future use in structural supercapacitors. In principle, in future devices, the reduced ply thickness offers both improved mechanical properties and shorter ion diffusion distance, as well as opportunities to fabricate higher voltage multicell assemblies within a given component geometry.
Valkova M, Nguyen S, Senokos E, et al., 2023, Current collector design strategies: The route to realising scale-up of structural power composites, Composites Science and Technology, Vol: 236, Pages: 1-9, ISSN: 0266-3538
Multifunctional structural power composites, which combine mechanical load-bearing and electrochemical energy storage, will transform electric vehicle design. This work focuses on structural supercapacitors, based on carbon aerogel-modified carbon fibre electrodes with copper current collectors. In common with many structural power embodiments, scale-up of these devices is currently limited by large internal resistances and the mass associated with current collection. There is a trade-off between the overall resistive power loss and the additional mass for the current collector material. However, in these devices, mechanical integrity is provided by the structural electrodes, allowing a range of collector designs to be considered. Using finite element simulations, these current collection strategies are explored quantitatively across a range of design space variables. The key conductivity parameters were measured experimentally, using the best existing materials, to inform direct current conduction simulations of the electrode/current collector assembly. For the present device configuration, the performance trade-off is governed by the area of the current collector. The most effective near-term strategy for power loss mitigation lies in reducing the contact resistance; however, improvements can also be obtained by modifying the collector geometry. The findings of this paper can be generalised to other structural power composites and monofunctional energy storage devices, which are relevant in many mass-sensitive electrochemical applications.
Senokos E, Anthony DB, Rubio N, et al., 2023, Robust single‐walled carbon nanotube‐infiltrated carbon fiber electrodes for structural supercapacitors: from reductive dissolution to high performance devices, Advanced Functional Materials, Vol: 33, Pages: 1-11, ISSN: 1616-301X
Multifunctional electrodes for structural supercapacitors are prepared by vacuum infiltration of single-walled carbon nanotubes (SWCNTs) into woven carbon fibers (CFs); the use of reductive charging chemistry to form nanotubide solutions ensured a high degree of individualization. The route is highly versatile, as shown by comparing four different commercial nanotube feedstocks. In film form, the pure nanotubide networks (“buckypapers”) are highly conductive (up to 2000 S cm−1) with high surface area (>1000 m2 g−1) and great electrochemical performance (capacitance of 101 F g−1, energy density of 27.5 Wh kg−1 and power density of 135 kW kg−1). Uniformly integrating these SWCNT networks throughout the CF fabrics significantly increased electrical conductivity (up to 318 S cm−1), surface area (up to 196 m2 g−1), and in-plane shear properties, all simultaneously. The CNT-infiltrated CFs electrodes exhibited intrinsically high specific energy (2.6–4.2 Wh kg−1) and power (6.0–8.7 kW kg−1) densities in pure 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (EMIM TFSI) electrolyte. Multifunctional structural supercapacitors based on CNT-coated CFs offer a substantial increase in capacitive performance while maintaining the tensile mechanical properties of the as-received CF-based composite. This non-damaging approach to modify CFs with highly graphitic, high surface area nanocarbons provides a new route to structural energy storage systems.
Greenhalgh ES, Nguyen S, Valkova M, et al., 2023, A critical review of structural supercapacitors and outlook on future research challenges, Composites Science and Technology, Vol: 235, Pages: 1-19, ISSN: 0266-3538
Structural composites and electrochemical energy storage underpin electrification of transportation, but advances in electric vehicles are shackled by parasitic battery mass. The emergence of structural power composites, multifunctional materials that simultaneously carry structural loads whilst storing electrical energy, promises dramatic improvements in effective performance Here, we assess the literature on structural supercapacitors, not only providing a comprehensive and critical review of the constituent (i.e., structural electrode, structural electrolyte and structural separator) developments, but also considering manufacture, characterisation, scale-up, modelling and design/demonstration. We provide a rigorous analysis of the multifunctional performance data reported in the literature, providing the reader with a detailed comparison between the different structural supercapacitor developments. We conclude with insights into the future research and adoption challenges for structural supercapacitors. There are several significant hurdles which must be addressed to mature this technology. These include development of a processable structural electrolyte; optimisation of current collection to facilitate device scale-up; identification of load-transmitting encapsulation solutions; standard protocols for characterisation and ranking of structural supercapacitors and; predictive multiphysics models for structural supercapacitors. Through addressing such issues, these emerging multifunctional materials will deliver a novel lightweighting strategy that can contribute to managing the ongoing climate crisis.
Anthony DB, Nguyen SN, Qian H, et al., 2023, Silica aerogel infused hierarchical glass fiber polymer composites, Composites Communications, Vol: 39, Pages: 1-7, ISSN: 2452-2139
Hierarchical systems can address the matrix-dominated failures of structural fiber polymer composites. Here, a new synergistic hierarchical structure combines conventional structural glass fibers with a bi-continuous silica-based aerogel matrix; both pure-silica and organically-modified silicate aerogels are demonstrated. When infused with an epoxy matrix, this type of hierarchical architecture showed a marked improvement in mechanical properties: without any loss in modulus, both the compressive strength and the interlaminar shear strength increased by up to 27%, relative to the equivalent glass-fiber reinforced epoxy composite baseline. The bi-continuous network modification strategy uses industrially-relevant infusion techniques, at or near room temperature, and retains a similar final composite density (within 2%). The strategy presented here provides a versatile and readily applicable means to improve state-of-the art continuous fiber reinforced composite systems in compression and offers an opportunity to develop a new generation of composite materials.
Govada L, Rubio N, Saridakis E, et al., 2022, Graphene-based nucleants for protein crystallization, Advanced Functional Materials, Vol: 32, ISSN: 1616-301X
Protein crystallization remains a major bottleneck for the determination of high resolution structures. Nucleants can accelerate the process but should ideally be compatible with high throughput robotic screening. Polyethylene glycol grafted (PEGylated) graphenes can be stabilized in water providing dispensable, nucleant systems. Two graphitic feedstocks are exfoliated and functionalized with PEG using a non-destructive, scalable, chemical reduction method, delivering good water dispersibility (80 and 750 µg mL−1 for large and small layers, respectively). The wide utility of these nucleants has been established across five proteins and three different screens, each of 96 conditions, demonstrating greater effectiveness of the dispersed PEGylated graphenes. Smaller numbers of larger, more crystalline flakes consistently act as better protein nucleants. The delivered nucleant concentration is optimized (0.1 mg mL−1 in the condition), and the performance benchmarked against existing state of the art, molecularly imprinted polymer nucleants. Strikingly, graphene nucleants are effective even when decreasing both the nucleant and protein concentration to unusually low concentrations. The set-up to scale-up nucleant production to liter volumes can provide sufficient material for wide implementation. Together with the optimized crystallization conditions, the results are a step forward toward practical synthesis of a readily accessible “universal” nucleant.
Ishfaq A, Nguyen S, Greenhalgh ES, et al., 2022, Multifunctional design, feasibility and requirements for structural power composites in future electric air taxis, Journal of Composite Materials, Vol: 57, Pages: 817-828, ISSN: 0021-9983
This study investigates the viability of implementing multifunctional structural power composites in a four-seater air taxi, the CityAirbus. For a given specific energy of the power source, the cruise endurance can be approximately doubled by using structural power composites as opposed to conventional batteries. Replacing all the eligible composite mass and batteries with structural power composites can reduce the CityAirbus weight by 25%. To achieve the current design performance, the minimum required elastic modulus, strength, specific energy and power for the structural power composite are 54 GPa, 203 MPa, 74 Wh/kg and 376 W/kg, respectively: current state-of-the-art structural power composites are now approaching this level of performance. Hence, structural power composites are considered feasible for adoption in the urban air mobility sector and have the potential to improve endurance and facilitate commercialization. This paper also discusses several key challenges that must be addressed to realize the adoption of structural power composites in future electric air taxis.
Rubio N, Suter T, Rana Z, et al., 2022, Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 10, Pages: 20121-20127, ISSN: 2050-7488
Bayazit MK, Yau HC, Leese H, et al., 2022, Mono-Acetylenes as New Crosslinkers for All-Carbon Living Charge Carbon Nanotubide Organogels, CHEMISTRYSELECT, Vol: 7, ISSN: 2365-6549
Wang J, Anthony DB, Fuentes CA, et al., 2022, Wettability of carbon nanotube-grafted carbon fibers and their interfacial properties in polypropylene thermoplastic composite, Composites Part A: Applied Science and Manufacturing, Vol: 159, Pages: 1-10, ISSN: 1359-835X
The interfacial properties of carbon fiber (CF) reinforced thermoplastic composites depend strongly on the wettability and surface characteristics of the reinforcing fibers, and their compatibility with a chosen matrix. The interface between conventional fibers and thermoplastic matrices is generally weak, due to a lack of specific chemical interaction, especially in the case of polyolefins. Carbon nanotube-grafted-carbon fibers (CNT-g-CF) are considered to be potential reinforcements as they provide additional mechanical interlocking. Commercial CFs were successfully grafted with nanotubes using a continuous, and hence scalable, CVD method. X-ray photoelectron spectroscopy, Wilhelmy wetting measurements, and scanning electron microscopy confirmed the successful grafting and resulting hydrophobic surface chemistry, dominated by van der Waals interactions. The grafted CNTs, with diameters and lengths around 10 nm and 140 nm respectively, were well suited to improve the overall wettability and interfacial shear strength (+53.4 %) of the CNT-g-CF in a polypropylene matrix when compared to as-received unsized CFs.
Yousefi N, Fisher SJ, Burgstaller C, et al., 2022, Hierarchical carbon fibre composites incorporating high loadings of carbon nanotubes, Composites Science and Technology, Vol: 222, ISSN: 0266-3538
Uncured solid bisphenol-A epoxy resins containing up to 20 wt% carbon nanotubes (CNTs) were prepared usingmelt blending in a high shear mixer. The extrudate was ground to produce fine nanocomposite (NC) powders.This simple method produced well-dispersed NC, with CNT agglomerate sizes below 1 μm. Consolidated NCsdisplayed improved tensile moduli and strengths up to 3.3 GPa (+32%) and 78 MPa (+19%), respectively at 15wt% CNT, compared to the pure cured epoxy matrix. The relatively high Tg of 39 ◦C for the uncured NC powderssimplified the manufacture of composite prepregs using wet powder impregnation. The prepregs were laminatedinto hierarchical carbon fibre reinforced composites with improved through-thickness properties. Interlaminarshear strength improved for intermediate CNT loadings in the matrix up to 65 MPa (10 wt% CNT, +19%) butdecreased at higher concentrations. Compression moduli remained constant irrespectively of CNT loading butcompression strength increased with a CNT loading of 2.5 wt% to 772 MPa (+31%). The mechanical propertiesof the hierarchical composites reflect good consolidation (void content <3%) and excellent fibre alignment(<±0.8◦). In addition to the improved mechanical properties, incorporation of CNTs improved the through-thickness electrical conductivity up to 115 S/m
Oates RP, Murawski J, Hor C, et al., 2022, How to Minimise Hydrogen Evolution on Carbon Based Materials?, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 169, ISSN: 0013-4651
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Valkova M, Anthony DB, Kucernak ARJ, et al., 2022, Predicting the mechanical behaviour of structural supercapacitor composites, Composites Part A: Applied Science and Manufacturing, Vol: 156, ISSN: 1359-835X
Multifunctional structural power composites may transform transport electrification, and other applications, but require performance and reliability improvements. Computational modelling has the potential to accelerate their development and deployment. This work addresses the lack of predictive models for the mechanical behaviour of structural supercapacitor composites exploiting carbon aerogel-modified carbon fabric electrodes. The elastic behaviour was investigated using finite element analysis of quasi-meso-scale periodic unit cell models, considering the effects of constituent properties, defects, stacking geometry, and boundary conditions. Nanoindentation was used to evaluate the Young’s modulus of carbon aerogel. Parametric modelling demonstrated a strong influence of the ply offset and matrix materials on the composite elastic properties. The initial numerical results overpredicted the actual performance measured from tensile and in-plane shear experiments in the literature. Optical, scanning electron and micro X-ray imaging revealed extensive pre-cracking and voidage in the physical laminates. Additional computational investigations showed that the pre-cracks were associated with a degradation of shear stiffness. The remaining performance gap was attributed to voidage. The present study highlights that challenges for mechanical performance and its prediction stem from the presence of processing defects and a lack of in-situ material data. Nevertheless, the models identify the potential of hierarchical laminates containing aerogels to generate sizable performance improvements, both in multifunctional and purely structural contexts.
Pernice MF, Qi G, Senokos E, et al., 2022, Mechanical, electrochemical and multifunctional performance of a CFRP/carbon aerogel structural supercapacitor and its corresponding monofunctional equivalents, Multifunctional Material, Vol: 5
Xu Z, Tonry C, Beckwith C, et al., 2022, High-speed imaging of the ultrasonic deagglomeration of carbon nanotubes in water, JOM, Vol: 74, ISSN: 1047-4838
Ultrasonic treatment is effective in deagglomerating and dispersing nanoparticles in various liquids. However, the exact deagglomeration mechanisms vary for different nanoparticle clusters, owing to different particle geometries and inter-particle adhesion forces. Here, the deagglomeration mechanisms and the influence of sonotrode amplitude during ultrasonication of multiwall carbon nanotubes in de-ionized water were studied by a combination of high-speed imaging and numerical modeling. Particle image velocimetry was applied to images with a higher field of view to calculate the average streaming speeds distribution. These data allowed direct comparison with modeling results. For images captured at higher frame rates and magnification, different patterns of deagglomeration were identified and categorized based on different stages of cavitation zone development and for regions inside or outside the cavitation zone. The results obtained and discussed in this paper can also be relevant to a wide range of carbonaceous and other high aspect ratio nanomaterials.
Lamoriniere S, Jones MP, Ho K, et al., 2022, Carbon nanotube enhanced carbon Fibre-Poly(ether ether ketone) interfaces in model hierarchical composites, COMPOSITES SCIENCE AND TECHNOLOGY, Vol: 221, ISSN: 0266-3538
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Leese HS, Tejkl M, Vilar L, et al., 2022, High-k dielectric screen-printed inks for mechanical energy harvesting devices, MATERIALS ADVANCES, Vol: 3, Pages: 1780-1790
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Navarro Suarez A, Shaffer M, 2022, Designing structural electrochemical energy storage systems: a perspective on the role of device chemistry, Frontiers in Chemistry, Vol: 9, ISSN: 2296-2646
Structural energy storage devices (SESDs), designed to simultaneously store electrical energy and withstand mechanical loads, offer great potential to reduce the overall system weight in applications such as automotive, aircraft, spacecraft, marine and sports equipment. The greatest improvements will come from systems that implement true multifunctional materials as fully as possible. The realization of electrochemical SESDs therefore requires the identification and development of suitable multifunctional structural electrodes, separators, and electrolytes. Different strategies are available depending on the class of electrochemical energy storage device and the specific chemistries selected. Here, we review existing attempts to build SESDs around carbon fiber (CF) composite electrodes, including the use of both organic and inorganic compounds to increase electrochemical performance. We consider some of the key challenges and discuss the implications for the selection of device chemistries.
Li Q, Markcoons D, Xu Z, et al., 2022, NANOPARTICLE REINFORCED LIGHTWEIGHT METAL COMPOSITES, Pages: 981-985
The interest to use carbon nanotubes (CNTs) to reinforce light metals has increased in recent years due to their potential application as lightweight high performance materials. One challenge in producing CNT composites is to achieve a homogenous dispersion of CNTs in the metal matrix. In order to effectively disperse CNTs in the Mg melt, we for the first time introduced the idea of using metal coated CNTs to promote the integration into Mg matrix. In this paper, Pt was selected to coat the CNT surface. TEM and EDX confirm that atomic Pt has been successfully deposited onto CNTs. The dispersion and stability of metal coated CNTs in solution have been investigated and compared to CNTs without metal coating. The Pt coated CNT reinforced Mg composites were also produced via a melt stirring process. The mechanical properties of such composites also showed a clear upward tendency, which we attribute to the Pt coating to help the dispersion of CNTs.
Xu Z, Tonry C, Beckwith C, et al., 2022, HIGH SPEED IMAGING OF THE ULTRASONIC DEAGGLOMERATION OF NANOPARTICLES IN WATER, Pages: 1048-1055
Ultrasonic treatment is effective in deagglomerating and dispersing nanoparticles during composite manufacturing via liquid state processing route. However, the exact deagglomeration mechanisms were difficult to observe owning to opaque metal melt and containers. Here, an analogue experiment was carried out in de-ionize water to study the deagglomeration mechanisms and the influence of sonotrode amplitude during ultrasonication of multiwall carbon nanotubes in light-weight metal melt. Particle image velocimetry was applied to the captured images with a higher Field of View to calculate the average streaming speeds distribution. These data allowed direct comparison with modelling results. For images captured at higher frame rates and magnification, different patterns of deagglomeration were identified, and categorized based on different stages of cavitation zone development and for regions inside or outside the cavitation zone. The results obtained and discussed in this paper can be also relevant to a wide range of carbonaceous and other high aspect ratio nanomaterials.
Rubio N, Au H, Coulter GO, et al., 2021, Effect of graphene flake size on functionalisation: quantifying reaction extent and imaging locus with single Pt atom tags, Chemical Science, Vol: 12, Pages: 1-13, ISSN: 2041-6520
Here, the locus of functionalisation on graphene-related materials and the progress of the reaction is shown to depend strongly on the starting feedstock. Five characteristically different graphite sources were exfoliated and functionalized using a non-destructive chemical reduction method. These archetypical examples were compared via a model reaction, grafting dodecyl addends, evaluated with TGA-MS, XPS and Raman data. A general increase in grafting ratio (ranging from 1.1 wt% up to 25 wt%) and an improvement in grafting stoichiometry (C/R) were observed as flake radius decreased. Raman spectrum imaging of the functionalised natural flake graphite identified that grafting is directed towards flake edges. This behaviour was further corroborated, at atomistic resolution, by functionalising the graphene layers with bipyridine groups able to complex single platinum atoms. The distribution of these groups was then directly imaged using aberration-corrected HAADF-STEM. Platinum atoms were found to be homogeneously distributed across smaller graphenes; in contrast, a more heterogeneous distribution, with a predominance of edge grafting was observed for larger graphites. These observations show that grafting is directed towards flake edges, but not necessary at edge sites; the mechanism is attributed to the relative inaccessibility of the inner basal plane to reactive moieties, resulting in kinetically driven grafting nearer flake edges. This phenomenology may be relevant to a wide range of reactions on graphenes and other 2d materials.
Suter TAM, Clancy AJ, Rubio Carrero N, et al., 2021, Scalable sacrificial templating to increase porosity and platinum utilisation in graphene-based polymer electrolyte fuel cell electrodes, Nanomaterials, Vol: 11, Pages: 1-13, ISSN: 2079-4991
Polymer electrolyte fuel cells hold great promise for a range of applications but require advances in durability for widespread commercial uptake. Corrosion of the carbon support is one of the main degradation pathways; hence, corrosion-resilient graphene has been widely suggested as an alternative to traditional carbon black. However, the performance of bulk graphene-based electrodes is typically lower than that of commercial carbon black due to their stacking effects. This article reports a simple, scalable and non-destructive method through which the pore structure and platinum utilisation of graphene-based membrane electrode assemblies can be significantly improved. Urea is incorporated into the catalyst ink before deposition, and is then simply removed from the catalyst layer after spraying by submerging the electrode in water. This additive hinders graphene restacking and increases porosity, resulting in a significant increase in Pt utilisation and current density. This technique does not require harsh template etching and it represents a pathway to significantly improve graphene-based electrodes by introducing hierarchical porosity using scalable liquid processes.
Karadotcheva E, Nguyen SN, Greenhalgh ES, et al., 2021, Structural power performance targets for future electric aircraft, Energies, Vol: 14, ISSN: 1996-1073
The development of commercial aviation is being driven by the need to improve efficiency and thereby lower emissions. All-electric aircraft present a route to eliminating direct fuel burning emissions, but their development is stifled by the limitations of current battery energy and power densities. Multifunctional structural power composites, which combine load-bearing and energy-storing functions, offer an alternative to higher-energy-density batteries and will potentially enable lighter and safer electric aircraft. This study investigated the feasibility of integrating structural power composites into future electric aircraft and assessed the impact on emissions. Using the Airbus A320 as a platform, three different electric aircraft configurations were designed conceptually, incorporating structural power composites, slender wings and distributed propulsion. The specific energy and power required for the structural power composites were estimated by determining the aircraft mission performance requirements and weight. Compared to a conventional A320, a parallel hybrid-electric A320 with structural power composites >200 Wh/kg could potentially increase fuel efficiency by 15% for a 1500 km mission. For an all-electric A320, structural power composites >400 Wh/kg could halve the specific energy or mass of batteries needed to power a 1000 km flight.
Wendong Q, Dent J, Arrighi V, et al., 2021, Biphasic epoxy-ionic liquid structural electrolytes: minimising feature size through cure cycle and multifunctional block-copolymer addition, Multifunctional Materials, Vol: 4, Pages: 1-12, ISSN: 2399-7532
Structural electrolytes provide mechanical properties approaching structural resin combined with a high degree of ionic conductivity. Here, structural electrolytes based on bisphenol A diglycidyl ether and the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIM-TFSI) were synthesised through reaction induced phase separation (RIPS) using isophorone diamine (iPDA) as a curing agent. The microstructure and properties of the resulting materials were controlled through both the initial formulations and the curing temperature. Curing at room temperature generated a bi-continuous structure and improved both mechanical performance and ionic conductivity of the resulting structural electrolytes. The balance between properties can be systematically adjusted; for example, a promising Young's modulus of 800 MPa was obtained simultaneously with an ionic conductivity of 0.28 mS cm−1, for a formulation containing 35 vol% EMIM-TFSI. The lengthscale of the structural features was reduced by an order of magnitude by introducing multifunctional block-copolymers (MF-bcP) based on glycidyl methacrylate (GMA) and quaternised (2-dimethylamino)ethyl methacrylate (DMAEMA). Small angle neutron scattering (SANS), obtained during curing, identified at least two structural phases of different length scale, for the formulations containing MF-bcP, in agreement with microstructures observed using scanning electron microscopy. Such structural electrolytes may be required when using structural electrodes that also have finer characteristic lengthscales. The addition of the MF-bcP to formulations containing 35 vol% EMIM-TFSI produced structural electrolytes with a Young's modulus of 530 MPa and an ionic conductivity of 0.64 mS cm−1.
Qi G, Nguyen S, Anthony DB, et al., 2021, The influence of fabrication parameters on the electrochemical performance of multifunctional structural supercapacitors, Multifunctional Materials, Vol: 4, ISSN: 2399-7532
Multifunctional structural supercapacitors based on carbon fibre electrodes (CF) and structural electrolytes (SEs) can realise multifunctionality by simultaneously bearing load and providing electrochemical energy storage. Structural supercapacitor constituents (i.e. electrodes and electrolytes) have undergone significant development to enhance their electrochemical and mechanical properties. However, the fabrication of fully functional devices presents a number of practical challenges to achieve optimal multifunctional properties, particularly those associated with assembly and lamination. This work investigated the effect of separator selection and processing parameters on the electrochemical performance of structural supercapacitors, as well as evaluating the repeatability of the SE filming process. Two layers of glass fibre fabrics were the most effective separator for preventing short-circuiting of the structural supercapacitors. The weight fraction of the SE matrix had a significant effect on the capacitance, energy and power of the structural supercapacitors. By addressing such fabrication challenges, high performance structural supercapacitors can be manufactured with greater reproducibility and at larger scales such that they are suitable for integration in industrial applications.
Said SA, Roberts CS, Lee JK, et al., 2021, Direct organometallic synthesis of carboxylate intercalated layered zinc hydroxides for fully exfoliated functional nanosheets, Advanced Functional Materials, Vol: 31, Pages: 1-11, ISSN: 1616-301X
Intercalation of organic anions into 2D materials can enable exfoliation, improve dispersion stability, increase surface area, and provide useful functional groups. In layered metal hydroxides, intercalation of bulk structures is commonly achieved by cumbersome and typically incomplete anion exchange reactions. In contrast, here, a series of carboxylate-intercalated layered zinc hydroxides (LZH-R) are synthesized directly, at room temperature, by reacting an organozinc reagent with a precise sub-stoichiometric quantity of the desired carboxylic acid and water. A range of carboxylic acids are used to make new LZH-R materials which are crystalline, soluble, and functionalized, as established by X-ray diffraction, spectroscopic, and microscopy techniques. When R is an alkyl ether carboxylate, this direct synthesis method results in the spontaneous exfoliation of the LZH-R into monolayer nanosheets with high yields (70–80%) and high solubilities in alcohols and water of up to 180 mg mL−1. By altering the carboxylate ligand, functional groups suitable for post-synthetic modification or for detection by fluorescence are also introduced. These examples demonstrate a versatile synthetic route for functional exfoliated nanosheets.
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