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Paton K.R.,Trinity College Dublin | Paton K.R.,Thomas Swan and Company Ltd | Varrla E.,Trinity College Dublin | Backes C.,Trinity College Dublin | And 27 more authors.
Nature Materials | Year: 2014

To progress from the laboratory to commercial applications, it will be necessary to develop industrially scalable methods to produce large quantities of defect-free graphene. Here we show that high-shear mixing of graphite in suitable stabilizing liquids results in large-scale exfoliation to give dispersions of graphene nanosheets. X-ray photoelectron spectroscopy and Raman spectroscopy show the exfoliated flakes to be unoxidized and free of basal-plane defects. We have developed a simple model that shows exfoliation to occur once the local shear rate exceeds 10 4 s â ̂'1. By fully characterizing the scaling behaviour of the graphene production rate, we show that exfoliation can be achieved in liquid volumes from hundreds of millilitres up to hundreds of litres and beyond. The graphene produced by this method performs well in applications from composites to conductive coatings. This method can be applied to exfoliate BN, MoS 2 and a range of other layered crystals. © 2014 Macmillan Publishers Limited.


Fraser I.S.,University of Cambridge | Motta M.S.,Thomas Swan and Co. | Motta M.S.,University of Cambridge | Schmidt R.K.,Akzo Nobel | And 2 more authors.
Science and Technology of Advanced Materials | Year: 2010

This work shows a simple, single-stage, scalable method for the continuous production of high-quality carbon nanotube-polymer transparent conductive films from carbon feedstock. Besides the ease of scalability, a particular advantage of this process is that the concentration of nanotubes in the films, and thus transparency and conductivity, can be adjusted by changing simple process parameters. Therefore, films can be readily prepared for any application desired, ranging from solar cells to flat panel displays. Our best results show a surface resistivity of the order of 300 Ω square-1 for a film with 80% transparency, which is promising at this early stage of process development. © 2010 National Institute for Materials Science.


Varrla E.,Trinity College Dublin | Backes C.,Trinity College Dublin | Paton K.R.,Trinity College Dublin | Paton K.R.,Thomas Swan and Co. | And 4 more authors.
Chemistry of Materials | Year: 2015

In order to fulfill their potential for applications, it will be necessary to develop large-scale production methods for two-dimensional (2D) inorganic nanosheets. Here we demonstrate the large-scale shear-exfoliation of molybdenum disulfide nanosheets in aqueous surfactant solution using a kitchen blender. Using standard procedures, we measure how the MoS2 concentration and production rate scale with processing parameters. However, we also use recently developed methods based on optical spectroscopy to simultaneously measure both nanosheet lateral size and thickness, allowing us to also study the dependence of nanosheet dimensions on processing parameters. We found the nanosheet concentration and production rates to depend sensitively on the mixing parameters (the MoS2 concentration, Ci; the mixing time, t; the liquid volume, V; and the rotor speed, N). By optimizing mixing parameters, we achieved concentrations and production rates as high as 0.4 mg/mL and 1.3 mg/min, respectively. Conversely, the nanosheet size and thickness were largely invariant with these parameters. The nanosheet concentration is also extremely sensitive to the surfactant concentration. However, more interestingly the nanosheet lateral size and thickness also varied strongly with the surfactant concentration. This allows the mean nanosheet dimensions to be controlled during shear exfoliation at least in the range ∼40-220 nm for length and ∼2-12 layers for thickness. We demonstrate the importance of this by showing that the MoS2 nanosheets prepared using different surfactant concentrations, and so displaying different nanosheets sizes, perform differently when used as hydrogen evolution catalysts. We find the nanosheets produced using high surfactant concentrations, which gives smaller flake sizes, perform significantly better, consistent with catalysis occurring at nanosheet edges. Finally, we also demonstrate that shear exfoliation using a kitchen blender is not limited to MoS2 but can also be achieved for boron nitride and tungsten disulfide. © 2015 American Chemical Society.


Brocchi E.A.,Pontifical Catholic University of Rio de Janeiro | Moura F.J.,Pontifical Catholic University of Rio de Janeiro | Solorzono I.G.,Pontifical Catholic University of Rio de Janeiro | Motta M.S.,Thomas Swan and Co
Advanced Materials Research | Year: 2010

It is well recognized the importance of nano-structured materials in the present technological stage. Due to their unique properties these materials can be used in a large number of applications. One example is the growing interest in nanocomposites, in which a very fine dispersion of a ceramic phase in a metal matrix will significantly improve the material properties. In view of that, extensive studies have been carried out on a variety of materials such as alloys and different types of composites. Recently, the authors have developed a novel chemical method for insitu formations of Cu-Al2O3 and Ni-Al2O3 nanoscale composites by decomposition of their mixed nitrate solutions, to co-form the nano oxides, followed by preferential reduction of CuO or NiO by hydrogen at very low temperature. Studies carried out by the authors on the kinetics of reduction of such fine oxides indicated that under low partial pressure of hydrogen (0.25 atm) in argon, the oxides of Ni and Cu can be reduced completely, in a low temperature range of 523 to 623 K. The composites containing nanosized metal-metal oxide particles have been found to be quite homogeneous in nature. In view of this, Cu-Ni and Ni-Co alloys was also produced by mixing the respective aqueous nitrate solutions, followed by decompositions of their nitrates to their mixed oxides and subsequent low temperature hydrogen reduction. In that context, the purpose of the present work is to address the fundamental aspects of the synthesis procedure, emphasizing the basic thermodynamics background of the two steps involved. Also, the work aims to illustrate the outcome, by presenting experimental conditions and providing relevant characterization of the obtained nano-materials, by means of electronic microscopy and X-Ray Diffraction. Examples are given in terms of the obtained nano-composites and alloys. © (2010) Trans Tech Publication.


Varrla E.,Trinity College Dublin | Paton K.R.,Trinity College Dublin | Paton K.R.,Thomas Swan and Co. | Backes C.,Trinity College Dublin | And 4 more authors.
Nanoscale | Year: 2014

To facilitate progression from the lab to commercial applications, it will be necessary to develop simple, scalable methods to produce high quality graphene. Here we demonstrate the production of large quantities of defect-free graphene using a kitchen blender and household detergent. We have characterised the scaling of both graphene concentration and production rate with the mixing parameters: mixing time, initial graphite concentration, rotor speed and liquid volume. We find the production rate to be invariant with mixing time and to increase strongly with mixing volume, results which are important for scale-up. Even in this simple system, concentrations of up to 1 mg ml-1 and graphene masses of >500 mg can be achieved after a few hours mixing. The maximum production rate was ∼0.15 g h-1, much higher than for standard sonication-based exfoliation methods. We demonstrate that graphene production occurs because the mean turbulent shear rate in the blender exceeds the critical shear rate for exfoliation. © 2014 the Partner Organisations 2014.


Istrate O.M.,Trinity College Dublin | Paton K.R.,Trinity College Dublin | Paton K.R.,Thomas Swan and Co. | Khan U.,Trinity College Dublin | And 3 more authors.
Carbon | Year: 2014

We have prepared polymer nanocomposites reinforced with exfoliated graphene layers solely via melt blending. For this study polyethylene terephthalate (PET) was chosen as the polymer matrix due to its myriad of current and potential applications. PET and PET/graphene nanocomposites were melt compounded on an internal mixer and the resulting materials were compression molded into films. Transmission electron microscopy and scanning electron microscopy revealed that the graphene flakes were randomly orientated and well dispersed inside the polymer matrix. The PET/graphene nanocomposites were found to be characterized by superior mechanical properties as opposed to the neat PET. Thus, at a nanofiller load as low as 0.07 wt%, the novel materials presented an increase in the elastic modulus higher than 10% and an enhancement in the tensile strength of more than 40% compared to pristine PET. The improvements in the tensile strength were directly correlated to changes in elongation at break and indirectly correlated to the fracture initiation area. The enhancements observed in the mechanical properties of polymer/graphene nanocomposites achieved at low exfoliated graphene loadings and manufactured exclusively via melt mixing may open the door to industrial manufacturing of economical novel materials with superior stiffness, strength and ductility. © 2014 Elsevier Ltd. All rights reserved.


Anastasaki A.,University of Warwick | Nikolaou V.,University of Warwick | Zhang Q.,University of Warwick | Burns J.,University of Warwick | And 11 more authors.
Journal of the American Chemical Society | Year: 2014

Photoinduced living radical polymerization of acrylates, in the absence of conventional photoinitiators or dye sensitizers, has been realized in "daylight'"and is enhanced upon irradiation with UV radiation (λmax ≈ 360 nm). In the presence of low concentrations of copper(II) bromide and an aliphatic tertiary amine ligand (Me6-Tren; Tren = tris(2-aminoethyl)amine), near-quantitative monomer conversion (>95%) is obtained within 80 min, yielding poly(acrylates) with dispersities as low as 1.05 and excellent end group fidelity (>99%). The versatility of the technique is demonstrated by polymerization of methyl acrylate to a range of chain lengths (DPn = 25-800) and a number of (meth)acrylate monomers, including macromonomer poly(ethylene glycol) methyl ether acrylate (PEGA 480), tert-butyl acrylate, and methyl methacrylate, as well as styrene. Moreover, hydroxyl- and vic-diol-functional initiators are compatible with the polymerization conditions, forming α,ω-heterofunctional poly(acrylates) with unparalleled efficiency and control. The control retained during polymerization is confirmed by MALDI-ToF-MS and exemplified by in situ chain extension upon sequential monomer addition, furnishing higher molecular weight polymers with an observed reduction in dispersity (Crossed D sign = 1.03). Similarly, efficient one-pot diblock copolymerization by sequential addition of ethylene glycol methyl ether acrylate and PEGA480 to a poly(methyl acrylate) macroinitiator without prior workup or purification is also reported. Minimal polymerization in the absence of light confers temporal control and alludes to potential application at one of the frontiers of materials chemistry whereby precise spatiotemporal "on/off" control and resolution is desirable. © 2013 American Chemical Society.


Patent
Thomas Swan and Co. | Date: 2013-08-15

A device and method for controlling light by wavelength in a device with a switch plane and a dispersion plane uses optics providing an imaging function in the dispersion plane, and a Fourier transform function in the switch plane, so as to enable crosstalk to be reduced


Patent
Thomas Swan And Co. | Date: 2011-10-05

A method of producing a phase-only computer generated hologram for a pixellated Spatial Light Modulator device (200) supporting a discrete number of modulation levels and having an integrated layer of liquid crystal material above a silicon circuit, the method comprising: determining punctuated replay coordinates in a Fourier transform plane (202) of the SLM (200); using said coordinates for calculating the size in pixels of a base cell;evaluating a holographic base cell pattern using a phase quantisation procedure and replicating said base cell in the plane of the said hologram device 200) until the entire aperture of the hologram device is filled.


A method of operating a pixellated liquid crystal spatial light modulator comprising:numerically determining a hologram cell pattern for a portion of the pixellated liquid crystal spatial light modulator (200), whereby the pattern provides a desired replay intensity distribution in a Fourier plane (202); writing the determined hologram pattern to one region of the portion of the pixellated liquid crystal spatial light modulator (200); illuminating (201) the portion of the pixellated liquid crystal spatial light modulator (200) whereby the desired replay intensity distribution is attained; numerically translating or scrolling the determined hologram pattern to form at least one shifted version of the pattern for said portion of the pixellated liquid crystal spatial light modulator (200); and writing the at least one shifted version of the hologram pattern to one shifted region of the portion of the spatial light modulator (200).

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