Vortex fluidic exfoliation of graphite and boron nitride

Chen, Xianjue; Dobson, John F.; Raston, Colin L.

doi:10.1039/c2cc17611d

Cited by 261 publications

(284 citation statements)

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“…However, a recent paper has shown that graphite can be exfoliated to give graphene by generating shear in a very thin liquid layer in a rapidly rotating tube. 22 However, this method gives very small quantities of graphene and is inherently un-scalable. Here we demonstrate a method for shear-exfoliation of graphite to give graphene that is many times more efficient than sonication but which can be scaled-up to an industrial level.…”

Section: Main Textmentioning

confidence: 99%

“…14 We can understand these processes by modelling exfoliation as shear-induced intermonolayer sliding in a solvent. 14,22 This predicts a minimum shear rate given by: Equation 1 can be rewritten to express the minimum flake size that can be produced by shear exfoliation at a given  . 14 Then, the average flake size, L , is approximately the mean of this value and the maximum flake size retained after centrifugation, LCF.…”

Section: Main Textmentioning

confidence: 99%

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Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

et al. 2014

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Abstract:In order to progress from the lab 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. XPS and Raman spectroscopy show the exfoliated flakes to be unoxidised and free of basal plane defects. We have developed a simple model which shows exfoliation to occur once the local shear rate exceeds 10 4 s -1 . By fully characterizing the scaling behaviour of the graphene production rate, we show that exfoliation can be achieved in liquid volumes from 100s of ml up to 100s 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, MoS2 and a range of other layered crystals. Main Text:Due to its ultra-thin, 2-dimensional nature and its unprecedented combination of physical properties, graphene has become the most studied of all nano-materials. In the next decade graphene is likely to find commercial applications in many areas from high-frequency electronics to smart coatings.

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Section: Main Textmentioning

confidence: 99%

Section: Main Textmentioning

confidence: 99%

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

et al. 2014

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“…More recently it has been demonstrated that liquid exfoliation can be achieved by exposing graphite to high shear rates 34 using either rotor-stator high shear mixers 35,36 or simple kitchen blenders. 37,38 This gives graphene nanosheets of similar size and quality to those produced using sonication.…”

Section: Introductionmentioning

confidence: 99%

“…However, to date only preliminary results have been demonstrated for the scale-up of liquid phase exfoliation of inorganic layered materials such as MoS2, WS2 and BN. 34,35 To facilitate scaleup, it will be important to demonstrate an effective large-scale shear exfoliation of such materials with rotating blade mixers and to identify optimised processing parameters.…”

Section: Introductionmentioning

confidence: 99%

Large-Scale Production of Size-Controlled MoS₂ Nanosheets by Shear Exfoliation

Varrla¹,

Backes²,

et al. 2015

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In order to fulfil 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 disulphide 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 optimising 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 disulphide. ToC fig3

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“…The magnitude of the shear force cannot be estimated accurately because of the complexity of the velocity distribution in turbulence ow, but the exfoliation capability of the uidic shear force has been proved by the graphene exfoliation experiment done by Chen et al using a vortex uidic device. 36 Along with the exfoliation process, perforation takes place simultaneously. As shown in Fig.…”

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confidence: 99%

One-step green synthesis of graphene nanomesh by fluid-based method

et al. 2014

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A fluid-based method is demonstrated for preparing graphene nanomeshes (GNMs) directly from pristine graphite flakes by a one-step process. The high efficiency is attributed to the combination of fluidassisted exfoliation and perforation of the graphene sheets. Atomic force microscopy shows that the as-produced GNMs are less than 1.5 nm thick. The total area of the pores within 1 mm 2 of the GNM sheet is estimated as $0.15 mm 2 and the pore density as $22 mm À2, The yield of GNMs from pristine graphite powder and the power consumption for per gram GNM synthesis are evaluated as 5 wt% and 120 kW h, respectively. X-ray photoelectron spectroscopy, infrared spectroscopy, elemental analysis andRaman spectroscopy results indicate the purity of the GNMs and thus it is a green efficient method. The present work is expected to facilitate the production of GNMs in large scale.

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Vortex fluidic exfoliation of graphite and boron nitride

Abstract: Graphite is exfoliated into graphene by shearing vortex fluidic films of N-methyl-pyrrolidone (NMP), as a controlled process for preparing oxide free graphene, and for exfoliating the corresponding boron nitride sheets.

Cited by 261 publications

References 20 publications

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

Large-Scale Production of Size-Controlled MoS₂ Nanosheets by Shear Exfoliation

One-step green synthesis of graphene nanomesh by fluid-based method

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Vortex fluidic exfoliation of graphite and boron nitride

Abstract: Graphite is exfoliated into graphene by shearing vortex fluidic films of N-methyl-pyrrolidone (NMP), as a controlled process for preparing oxide free graphene, and for exfoliating the corresponding boron nitride sheets.

Cited by 261 publications

References 20 publications

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

Scalable production of large quantities of defect-free few-layer graphene by shear exfoliation in liquids

Large-Scale Production of Size-Controlled MoS2 Nanosheets by Shear Exfoliation

One-step green synthesis of graphene nanomesh by fluid-based method

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Large-Scale Production of Size-Controlled MoS₂ Nanosheets by Shear Exfoliation