276 results found
Finley JM, Shaffer MSP, Pimenta S, 2020, Data-driven intelligent optimisation of discontinuous composites, Composite Structures, Vol: 243, Pages: 1-19, ISSN: 0263-8223
Fibre composites, and especially aligned discontinuous composites (ADCs), offer enormous versatility in composition, microstructure, and performance, but are difficult to optimise, due to their inherent variability and myriad permutations of microstructural design variables. This work combines an accurate yet efficient virtual testing framework (VTF) with a data-driven intelligent Bayesian optimisation routine, to maximise the mechanical performance of ADCs for a number of single- and multi-objective design cases. The use of a surrogate model helps to minimise the number of optimisation iterations, and provides a more accurate insight into the expected performance of materials which feature significant variability. Results from the single-objective optimisation study show that a wide range of structural properties can be achieved using ADCs, with a maximum stiffness of 505 GPa, maximum ultimate strain of 3.94%, or a maximum ultimate strength of 1.92 GPa all possible. A moderate trade-off in performance can be achieved when considering multi-objective optimisation design cases, such as an optimal ultimate strength & ultimate strain combination of 982 MPa and 3.27%, or an optimal combination of 720 MPa yield strength & 1.91% pseudo-ductile strain.
Coulter GO, Clancy AJ, Au H, et al., Understanding and Controlling the Covalent Functionalisation of Graphene, Dalton Transactions, ISSN: 1477-9226
De Luca H, Anthony D, Greenhalgh E, et al., Piezoresistive structural composites reinforced by carbon nanotube-grafted quartz fibres, Composites Science and Technology, ISSN: 0266-3538
Johannisson W, Nguyen S, Lindbergh G, et al., 2020, A residual performance methodology to evaluate multifunctional systems, Multifunctional Materials, Vol: 3, ISSN: 2399-7532
The development of multifunctional materials and structures is receiving increasing interest for many applications and industries; it is a promising way to increase system-wide efficiency and improve the ability to meet environmental targets. However, quantifying the advantages of a multifunctional solution over monofunctional systems can be challenging. One approach is to calculate a reduction in mass, volume or other penalty function. Another approach is to use a multifunctional efficiency metric. However, either approach can lead to results that are unfamiliar or difficult to interpret and implement for an audience without a multifunctional materials or structures background.Instead, we introduce a comparative metric for multifunctional materials that correlates with familiar design parameters for monofunctional materials. This metric allows the potential benefits of the multifunctional system to be understood easily without needing a holistic viewpoint. The analysis is applied to two different examples of multifunctional systems; a structural battery and a structural supercapacitor, demonstrating the methodology and its potential for state-of-the-art structural power materials to offer a weight saving over conventional systems. This metric offers a new way to communicate research on structural power which could help identify and prioritise future research.
Valkova M, Anthony DB, Kucernak ARJ, et al., 2020, Predicting the compaction of hybrid multilayer woven composite reinforcement stacks, Composites Part A: Applied Science and Manufacturing, Vol: 133, ISSN: 1359-835X
A meso-scale finite element modelling strategy was developed to investigate the effect of hybridisation on the compaction response of multilayer stacks combining glass and carbon dry woven fabrics. It is expected that the electrochemical-mechanical properties of emerging multifunctional hybrid composites are strongly dictated by the morphology of the compacted reinforcements, yet no investigations into their compressibility have been reported. Model predictions were evaluated against compressibility measurements for monolithic and hybrid fabric stacks. The ply offset had a major influence on the predicted internal morphologies and fibre content, contributing to experimental variability thereof. Optical microscopy and micro X-ray computed tomography imaging indicated greater likelihood of intermediate ply offsets in physical specimens, over limit case model idealisations. Compressibility was slightly reduced in the hybrid multilayer stacks studied in this work. The model outputs presented are being used to analyse the electrochemical-mechanical response of hybrid woven structural power composites.
Leung AHM, García-Trenco A, Phanopoulos A, et al., 2020, Cu/M:ZnO (M = Mg, Al, Cu) colloidal nanocatalysts for the solution hydrogenation of carbon dioxide to methanol, Journal of Materials Chemistry A, Vol: 8, Pages: 11282-11291, ISSN: 2050-7488
Doped-ZnO nanoparticles, capped with dioctylphosphinate ligands, are synthesised by the controlled hydrolysis of a mixture of organometallic precursors. Substitutional doping of the wurtzite ZnO nanoparticles with 5 mol% Mg(II), Al(III) and Cu(I) is achieved by the addition of sub-stoichiometric amounts of the appropriate dopant [(n-butyl)(sec-butyl)magnesium, triethylaluminium or mesitylcopper] to diethylzinc in the precursor mixture. After hydrolysis, the resulting colloidal nanoparticles (sizes of 2–3 nm) are characterised by powder X-ray crystallography, transmission electron microscopy, inductively-coupled plasma optical emission spectrometry and X-ray photoelectron spectroscopy. A solution of the doped-ZnO nanoparticles and colloidal Cu(0) nanoparticles [M:ZnO : Cu = 1 : 1] are applied as catalysts for the hydrogenation of CO2 to methanol in a liquid-phase continuous flow stirred tank reactor [210 °C, 50 bar, CO2 : H2 = 1 : 3, 150 mL min−1, mesitylene, 20 h]. All the catalyst systems display higher rates of methanol production and better stability than a benchmark heterogeneous catalyst, Cu–ZnO–Al2O3 [480 μmol mmolmetal−1 h−1], with approximately twice the activity for the Al(III)-doped nanocatalyst. Despite outperforming the benchmark catalyst, Mg(II) doping is detrimental towards methanol production in comparison to undoped ZnO. X-Ray photoelectron spectroscopy and transmission electron microscopy analysis of the most active post-catalysis samples implicate the migration of Al(III) to the catalyst surface, and this surface enrichment is proposed to facilitate stabilisation of the catalytic ZnO/Cu interfaces.
Lee WJ, Paineau E, Anthony DB, et al., 2020, Inorganic nanotube mesophases enable strong self-healing fibers, ACS Nano, Vol: 14, Pages: 5570-5580, ISSN: 1936-0851
The assembly of one-dimensional nanomaterials into macroscopic fibers can improve mechanical as well as multifunctional performance. Double walled aluminogermanate imogolite nanotubes are geo-inspired analogs of carbon nanotubes, synthesized at low temperature, with complementary properties. Here, continuous imogolite based fibers are wet spun within a polyvinyl alcohol matrix. The lyotropic liquid crystallinity of the system produces highly aligned fibers with tensile stiffness and strength up to 24.1 GPa (14.1 N tex⁻¹) and 0.8 GPa (0.46 N tex⁻¹), respectively. Significant enhancements over the pure polymer control are quantitatively attributed to both matrix refinement and direct nanoscale reinforcement, by fitting an analytical model. Most intriguingly, imogolite-based fibers show a high degree of healability via evaporation induced self assembly, recovering up to 44%, and 19% of the original fiber tensile stiffness and strength, respectively. This recovery at high absolute strength highlights a general strategy for the development of high-performance healable fibers relevant to composite structures and other applications.
Au H, Rubio N, Buckley DJ, et al., 2020, Thermal decomposition of ternary sodium graphite intercalation compounds, Chemistry: A European Journal, Vol: 26, Pages: 6545-6553, ISSN: 0947-6539
Graphite intercalation compounds (GICs) are often used to produce exfoliated or functionalised graphene related materials (GRMs) in a specific solvent. This study explores the formation of the Na-tetrahydrofuran (THF)-GIC and a new ternary system based on dimethylacetamide (DMAc). Detailed comparisons of in situ temperature dependent XRD with TGA-MS and Raman measurements reveal a series of dynamic transformations during heating. Surprisingly, the bulk of the intercalation compound is stable under ambient conditions, trapped between the graphene sheets. The heating process drives a reorganisation of the solvent and Na molecules, then an evaporation of the solvent; however, the solvent loss is arrested by restacking of the graphene layers, leading to trapped solvent bubbles. Eventually, the bubbles rupture, releasing the remaining solvent and creating expanded graphite. These trapped dopants may provide useful property enhancements, but also potentially confound measurements of grafting efficiency in liquid-phase covalent functionalization experiments on 2D materials.
Au H, Rubio N, Buckley DJ, et al., 2020, Cover Feature: Thermal Decomposition of Ternary Sodium Graphite Intercalation Compounds (Chem. Eur. J. 29/2020), Chemistry – A European Journal, Vol: 26, Pages: 6291-6291, ISSN: 0947-6539
Sehmi SK, Lourenco C, Alkhuder K, et al., 2020, Antibacterial Surfaces with Activity against Antimicrobial Resistant Bacterial Pathogens and Endospores, ACS INFECTIOUS DISEASES, Vol: 6, Pages: 939-946, ISSN: 2373-8227
Gonzalez-Castillo EI, Costantini T, Shaffer MSP, et al., 2020, Nanocomposite coatings obtained by electrophoretic co-deposition of poly(etheretherketone)/graphene oxide suspensions, JOURNAL OF MATERIALS SCIENCE, Vol: 55, Pages: 8881-8899, ISSN: 0022-2461
Finley J, Henry J, Shaffer M, et al., 2020, The influence of variability and defects on the mechanical performance of tailorable composites, Journal of Composite Materials, Vol: 54, Pages: 565-589, ISSN: 0021-9983
Aligned hybrid-fibre discontinuous composites offer the ability to tailor their mechanical response through careful microstructural design. However, with tailorability comes microstructural complexity, which in turn leads to many sources of variability and defects. A virtual testing framework was further extended to investigate the influence of variability and defects on the mechanical performance of various aligned discontinuous composite material systems. This approach identified the most critical sources of variability as (i) fibre strength, (ii) the distance between fibre ends, or (iii) the level of fibre-type intermingling, depending on the material system. Fibre vacancy defects were shown to have the most significant influence on the strength and ductility of aligned discontinuous composites, although this sensitivity can be reduced through hybridisation of the fibre types.
Hart M, Chen J, Michaelides A, et al., 2019, One-Dimensional Pnictogen Allotropes inside Single-Wall Carbon Nanotubes, INORGANIC CHEMISTRY, Vol: 58, Pages: 15216-15224, ISSN: 0020-1669
Gonzalez Carter D, Goode A, Kiryushko D, et al., 2019, Quantification of blood-brain barrier transport and neuronal toxicity of unlabelled multiwalled carbon nanotubes as a function of surface charge, Nanoscale, Vol: 11, Pages: 22054-22069, ISSN: 2040-3364
Nanoparticles capable of penetrating the blood-brain barrier (BBB) will greatly advance the delivery of therapies against brain disorders. Carbon nanotubes hold great potential as delivery vehicles due to their high aspect-ratio and cell-penetrating ability. Studies have shown multiwalled carbon nanotubes (MWCNT) cross the BBB, however they have largely relied on labelling methods to track and quantify transport, or on individual electron microscopy images to qualitatively assess transcytosis. Therefore, new direct and quantitative methods, using well-defined and unlabelled MWCNT, are needed to compare BBB translocation of different MWCNT types. Using highly controlled anionic (-), cationic (+) and non-ionic (0) functionalized MWCNT (fMWCNT), we correlate UV-visible spectroscopy with quantitative transmission electron microscopy, quantified from c. 270 endothelial cells, to examine cellular uptake, BBB transport and neurotoxicity of unlabelled fMWCNT. Our results demonstrate that: i) a large fraction of cationic and non-ionic, but not anionic fMWCNT become trapped at the luminal brain endothelial cell membrane; ii) despite high cell association, fMWCNT uptake by brain endothelial cells is low (< 1.5% ID) and does not correlate with BBB translocation, iii) anionic fMWCNT have highest transport levels across an in vitro model of the human BBB compared to non-ionic or cationic nanotubes; and iv) fMWCNT are not toxic to hippocampal neurons at relevant abluminal concentrations; however, fMWCNT charge has an effect on carbon nanotube neurotoxicity at higher fMWCNT concentrations. This quantitative combination of microscopy and spectroscopy, with cellular assays, provides a crucial strategy to predict brain penetration efficiency and neurotoxicity of unlabelled MWCNT and other nanoparticle technologies relevant to human health.
Nguyen S, Anthony DB, Qian H, et al., 2019, Mechanical and physical performance of carbon aerogel reinforced carbon fibre hierarchical composites, Composites Science and Technology, Vol: 182, ISSN: 0266-3538
Carbon aerogel (CAG) is a potential hierarchical reinforcement to improve the matrix-dominated mechanical properties of continuous carbon fibre reinforced polymer (CFRP) composites in both multifunctional and purely structural applications. When using CAG to reinforce a polyethylene glycol diglycidyl ether (PEGDGE) matrix, the interlaminar shear strength, compressive modulus and strength increased approximately four-fold, whilst the out-of-plane electrical conductivity increased by 118%. These mechanical and electrical performance enhancements significantly improve the multifunctional efficiency of composite structural supercapacitors, which can offer weight savings in transport and other applications. However, CAG also has the potential to reinforce conventional continuous CF composites in purely structural contexts. Here, CAG reinforcement of structural epoxy resin composites marginally increased compressive (1.4%) and tensile (2.7%) moduli respectively, but considerably reduced compressive, tensile and interlaminar shear strengths. Fractographic analysis shows that the reduced performance can be attributed to poor interfacial adhesion; in the future, alternative processing routes may resolve these issues to achieve advances in both moduli and strengths over conventional structural CFRPs.
Lee C, Greenhalgh E, Shaffer M, et al., Optimized microstructures for multifunctional structural electrolytes, Multifuctional Materials, ISSN: 2399-7532
Multifunctional structural materials offer compelling opportunities to realize highly efficient products. However, the need to fulfil disparate functions generates intrinsically conflicting physical property demands. One attractive strategy is to form a bi-continuous architecture of two disparate phases, each addressing a distinct physical property. For example, structural polymer electrolytes combine rigid and ion-conducting phases to deliver the required mechanical and electrochemical performance. Here, we present a general methodology, based on topology optimization, to identify optimal microstructures for particular design considerations. The numerical predictions have been successfully validated by experiments using 3D printed specimens. These architectures are directly relevant to multifunctional structural composites whilst the methodology can easily be extended to identify optimal microstructural designs for other multifunctional material embodiments.
Leo BF, Fearn S, Gonzalez-Carter D, et al., 2019, Label-free TOF-SIMS imaging of sulfur producing enzymes inside microglia cells following exposure to silver nanowires, Analytical Chemistry, Vol: 91, Pages: 11098-11107, ISSN: 0003-2700
There are no methods sensitive enough to detect enzymes within cells, without the use of analyte labelling. Here we show that it is possible to detect protein ion signals of three different H2S-synthesizing enzymes inside microglia after pre-treatment with silver nanowires (AgNW) using time of flight-secondary ion mass spectrometry (TOF-SIMS). Protein fragment ions, including the fragment of amino acid (C4H8N+ - 70 amu), fragments of the sulfur producing cystathionine-containing enzymes and the Ag+ ion signal could be detected without the use of any labels; the cells were mapped using the C4H8N+ amino acid fragment. Scanning electron microscopy imaging and energy dispersive x-ray chemical analysis showed that the AgNWs were inside the same cells imaged by TOF-SIMS and transformed chemically into crystalline Ag2S within cells in which the sulfur producing proteins were detected. The presence of these sulfur producing cystathionine-containing enzymes within the cells was confirmed by Western Blots and confocal microscopy images of fluorescently labelled antibodies against the sulfur producing enzymes. Label-free ToF-SIMS is very promising for the label-free identification of H2S-contributing enzymes and their cellular localization in biological systems. The technique could in future be used to identify which of these enzymes are most contributory.
Basma N, Cullen PL, Clancy AJ, et al., 2019, The liquid structure of the solvents dimethylformamide (DMF) and dimethylacetamide (DMA), MOLECULAR PHYSICS, Vol: 117, Pages: 3353-3363, ISSN: 0026-8976
Kennedy OW, White R, Shaffer MSP, et al., 2019, Vapour-liquid-solid growth of ZnO-ZnMgO core-shell nanowires by gold-catalysed molecular beam epitaxy, Nanotechnology, Vol: 30, ISSN: 0957-4484
Nanowire heterostructures, combining multiple phases within a single nanowire, modify functional properties and offer a platform for novel device development. Here, ZnO/ZnMgO core–shell nanowires are grown by molecular beam epitaxy. At growth temperatures above 750 °C, Mg diffuses into ZnO making heterostructure growth impossible; at lower shell-growth temperatures (500 °C), the core–shell structure is retained. Even very thin ZnMgO shells show increased intensity photoluminescence (PL) across the ZnO band-gap and a suppression in defect-related PL intensity, relative to plain ZnO nanowires. EDX measurements on shell thickness show a correlation between shell thickness and core diameter which is explained by a simple growth model.
Lee W, Clancy A, Fernández-Toribio JC, et al., 2019, Interfacially-grafted single wall carbon nanotube / poly (vinyl alcohol) composite fibers, Carbon, Vol: 146, Pages: 162-171, ISSN: 0008-6223
Nanocomposites are critically influenced by interfacial interactions between the reinforcement and matrix. Polyvinyl alcohol (PVOH) of varying molecular weights were prepared and grafted to single-walled carbon nanotubes (SWCNTs), to improve the interfacial interaction with a homopolymer PVOH matrix. Nanocomposite fibers were coagulation spun across a broad range of loading fractions, controlled by the spinning dope composition. An intermediate grafted-PVOH molecular weight (10 kDa) maximized grafting ratio, and the final composite mechanical performance; the positive effects were attributed to the increased degree of dispersion of the SWCNTs in the dope, as well as the favorable interface. The PVOH grafting increased the stability of the SWCNT loading fractions (up to 45 wt.%), offering increased strength (up to 1100 MPa) and stiffness (up to 38.5 GPa); at the same time, strain to-failures remained high (up to 23.3%), resulting in high toughness (up to 125 J g-1).
Clancy A, Sirisinudomkit P, Anthony D, et al., 2019, Real-time mechanistic study of carbon nanotube anion functionalisation through open circuit voltammetry, Chemical Science, Vol: 10, Pages: 3300-3306, ISSN: 2041-6520
The mechanism of the functionalisation of reduced single walled carbon nanotubes with organobromides was monitored byopen circuit voltammetry throughout the reaction and further elucidated through a series of comparative reactions. Thedegree of functionalisation was mapped against the reagent reduction potential, degree of electron donation of substituents(Hammett parameter), and energies calculated, ab initio, for dissociation and heterolytic cleavage of the C-Br bond. Incontrast to the previously assumed reduction/homolytic cleavage mechanism, the reaction was shown to consist of a rapidassociation of carbon-halide bond to the reduced nanotube as a complex, displacing surface-condensed countercations,leading to an initial increase in the net nanotube surface negative charge. The complex subsequently slowly degradesthrough charge transfer from the reduced single-walled carbon nanotube to the organobromide, utilizing charge, and thecarbon-halide bond breaks heterolytically. Electron density on the C-Br bond in the initial reagent is the best predictor fordegree of functionalisation, with more electron donating substituents increasing the degree of functionalisation. Both themechanism and the new application of OCV to study such reactions are potentially relevant to wide range of related systems.
Kennedy OW, White ER, Howkins A, et al., 2019, Mapping the origins of luminescence in ZnO nanowires by STEM-CL, Journal of Physical Chemistry Letters, Vol: 10, Pages: 386-392, ISSN: 1948-7185
In semiconductor nanowires, understanding both the sources of luminescence (excitonic recombination, defects, etc.) and the distribution of luminescent centers (be they uniformly distributed, or concentrated at structural defects or at the surface) is important for synthesis and applications. We develop scanning transmission electron microscopy-cathodoluminescence (STEM-CL) measurements, allowing the structure and cathodoluminescence (CL) of single ZnO nanowires to be mapped at high resolution. Using a CL pixel resolution of 10 nm, variations of the CL spectra within such nanowires in the direction perpendicular to the nanowire growth axis are identified for the first time. By comparing the local CL spectra with the bulk photoluminescence spectra, the CL spectral features are assigned to internal and surface defect structures. Hyperspectral CL maps are deconvolved to enable characteristic spectral features to be spatially correlated with structural features within single nanowires. We have used these maps to show that the spatial distribution of these defects correlates well with regions that show an increased rate of nonradiative transitions.
Liu B, Liu C, De Luca H, et al., 2019, Synthesis of epoxidized poly(ester carbonate)-b-polyimide-b-poly(ester carbonate): reactive single-walled carbon nanotube dispersants enable synergistic reinforcement around multi-walled nanotube-grafted carbon fibers, Polymer Chemistry, Vol: 10, Pages: 1324-1334, ISSN: 1759-9954
Polyimides (PI) generally have a high affinity for single-walled carbon nanotubes (SWNTs), but they suffer from poor solubility in most low boiling point organic solvents and low compatibility with common resins (such as epoxy) used in composites, limiting their suitability as dispersants. PI block copolymer systems containing reactive poly(ester carbonate)s have not yet been reported and are expected to act as effective reactive dispersing agents of SWNTs. Herein, PI-derived block copolymers are synthesized via ring-opening copolymerization of lactide (LA) (a control monomer) and allyl-bearing 2-methyl-2-(allyloxycarbonyl)-propylene carbonate (MAC) from the OH-terminal ends of the PI block to produce PLA-PI-PLA (TB1, a control) and PMAC-PI-PMAC (TB2). The allyl pendant group of TB2 allows further facile functionalization to form a third series of epoxidized (EP) derivatives, i.e. PMACEP-block-PI-block-PMACEP (TB3). TB3 copolymer when mixed with a conventional structural epoxy resin forms blends that do not show inferior tensile properties compared with the epoxy, which is unusual. Furthermore, the mixing solvent tetrahydrofuran (THF) can be readily evaporated off after forming the blends. TB3-dispersed (2 wt%) SWNTs added to epoxy increased the tensile strength, modulus, and elongation at break of the resulting nanocomposite films by 40%, 34%, and 26% respectively, compared to the baseline epoxy resin. Furthermore, when TB3b triblock-dispersed SWNTs in epoxy were combined with fuzzy carbon fibers, i.e. carbon nanotube-grafted-carbon fibers (CNT-g-CF), a synergistic interfacial strength reinforcement was observed, together with shifting of the failure mode from the matrix interphase to the carbon fiber-grafted nanotube interface. The ultimate interfacial shear strength between the TB3-dispersed SWNT-epoxy matrix and the fuzzy carbon fibers (i.e., fibers having carbon nanotubes grown on them) measured via single fiber pull-out tests was 100 MPa, which was ca. 11% imp
Finley JM, Shaffer MSP, Pimenta S, 2019, Intelligent optimisation of aligned discontinuous composites
© 2019 by DEStech Publications, Inc. and American Society for Composites. All rights reserved. Aligned discontinuous composites offer a tailorable structural response, as their mechanical behaviour can be tailored by adjusting their microstructure. However, the stochastic nature of their microstructure, and the myriad permutations of different constituent properties makes optimisation of these materials difficult. In this work, an accurate yet efficient virtual testing framework is combined with an intelligent Bayesian optimisation routine to maximise the initial stiffness, ultimate strain, and ultimate strength of aligned discontinuous composites.
Stanier D, Radhakrishnan A, Gent I, et al., 2019, Matrix-graded and fibre-steered composites to tackle stress concentrations, COMPOSITE STRUCTURES, Vol: 207, Pages: 72-80, ISSN: 0263-8223
Zainol Abidin MS, Herceg T, Greenhalgh ES, et al., 2019, Enhanced fracture toughness of hierarchical carbon nanotube reinforced carbon fibre epoxy composites with engineered matrix microstructure, Composites Science and Technology, Vol: 170, Pages: 85-92, ISSN: 0266-3538
Clancy AJ, Leese HS, Rubio Carrero N, et al., 2018, Depleting depletion: maintaining single-walled carbon nanotube dispersions after graft-to polymer functionalization, Langmuir, Vol: 34, Pages: 15396-15402, ISSN: 0743-7463
Grafting polymers onto single-walled carbon nanotubes (SWCNTs) usefully alters properties but does not typically yield stable, solvated species directly. Despite the expectation of steric stabilization, a damaging (re)dispersion step is usually necessary. Here, poly(vinyl acetate)s (PVAc) of varying molecular weights are grafted to individualized, reduced SWCNTs at different concentrations to examine the extent of reaction and degree of solvation. The use of higher polymer concentrations leads to an increase in grafting ratio (weight fraction of grafted polymer relative to the SWCNT framework), approaching the limit of random sequentially adsorbed Flory ‘mushrooms’ on the surface. However, at higher polymer concentrations, a larger percentage of SWCNTs precipitate during the reaction; an effect which is more significant for larger weight polymers. The precipitation is attributed to depletion interactions generated by ungrafted homopolymer overcoming Coulombic repulsion of adjacent like-charged SWCNTs; a simple model is proposed. Larger polymers and greater degrees of functionalization favor stable solvation, but larger and more concentrated homopolymers increase depletion aggregation. By using low concentrations (25 μM) of larger molecular weight PVAc (10 kDa), up to 65% of grafted SWCNTs were retained in solution (at 65 μg mL-1) directly after the reaction.
Brandley E, Greenhalgh E, Shaffer M, et al., 2018, Mapping carbon nanotube orientation by fast fourier transform of scanning electron micrographs, Carbon, Vol: 137, Pages: 78-87, ISSN: 0008-6223
A novel method of applying a two-dimensional Fourier transform (2D-FFT) to SEM wasdeveloped to map the CNT orientation in pre-formed arrays. Local 2D-FFTs were integratedazimuthally to determine an orientation distribution function and the associated Hermanparameter. This approach provides data rapidly and over a wide range of lengthscales.Although likely to be applicable to a wide range of anisotropic nanoscale structures, themethod was specifically developed to study CNT veils, a system in which orientationcritically controls mechanical properties. Using this system as a model, key parameters forthe 2D-FFT analysis were optimised, including magnification and domain size; a model setof CNT veils were pre-strained to 5%, 10% and 15%, to vary the alignment degree. Thealgorithm confirmed a narrower orientation distribution function and increasing Hermanparameter, with increasing pre-strain.To validate the algorithm, the local orientation was compared to that derived from a commonpolarised Raman spectroscopy. Orientation maps of the Herman parameter, derived by bothmethods, showed good agreement. Quantitatively, the mean Herman parameter calculatedusing the polarised Raman spectroscopy was 0.42±0.004 compared to 0.32±0.002 for the 2DFFTmethod, with a correlation coefficient of 0.73. Possible reasons for the modest andsystematic discrepancy were discussed.
Basma NS, Headen TF, Shaffer MSP, et al., 2018, Local structure and polar order in liquid N-Methyl-2-pyrrolidone (NMP), Journal of Physical Chemistry B, Vol: 122, Pages: 8963-8971, ISSN: 1520-5207
N-Methyl-2-pyrrolidone (NMP) is an exceptional solvent, widely used in industry and for nanomaterials processing. Yet despite its ubiquity, its liquid structure, which ultimately dictates its solvation properties, is not fully known. Here, neutron scattering is used to determine NMP’s structure in unprecedented detail. Two dominant nearest-neighbor arrangements are found, where rings are parallel or perpendicular. However, compared with related solvents, NMP has a relatively large population of parallel approaches, similar only to benzene, despite its nonaromaticity and the presence of the normally structure-reducing methyl group. This arrangement is underpinned by NMP’s dipole moment, which has a profound effect on its structure: nearest-neighbor molecules arrange in an antiparallel but offset fashion. This polar-induced order extends beyond the first solvation shell, resulting in ordered trimers that reach the nanometer range. The degree of order and balance of interactions rationalize NMP’s high boiling point and versatile capabilities to solvate both charged and uncharged species.
Jia J, White ER, Clancy AJ, et al., 2018, Fast exfoliation and functionalisation of two-dimensional crystalline carbon nitride by framework charging, Angewandte Chemie, Vol: 57, Pages: 12656-12660, ISSN: 1521-3757
Two-dimensional (2D) layered graphitic carbon nitride (gCN) nanosheets offer intriguing electronic and chemical properties. However, the exfoliation and functionalisation of gCN for specific applications remain challenging. We report a scalable one-pot reductive method to produce solutions of single- and few-layer 2D gCN nanosheets with excellent stability in a high mass yield (35 %) from polytriazine imide. High-resolution imaging confirmed the intact crystalline structure and identified an AB stacking for gCN layers. The charge allows deliberate organic functionalisation of dissolved gCN, providing a general route to adjust their properties.
This data is extracted from the Web of Science and reproduced under a licence from Thomson Reuters. You may not copy or re-distribute this data in whole or in part without the written consent of the Science business of Thomson Reuters.