Inorganic nanotubes reinforced polyvinylidene fluoride composites as low-cost electromagnetic interference shielding materials

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region

Demonstration of Spatial Self Phase Modulation based photonic diode functionality in MoS2/h-BN medium

Spatial self-phase modulation (SSPM) is the optical nonlinear process and is a result of spatially varying refractive index profile along the line of propagation in a medium. SSPM is proved to be a method to demonstrate different photonic functionalities. Transition metal dichalcogenides play a key role in 2D nanophononics due to their unique and fascinating properties. MoS2 is the widely studied layered TMDs among all other 2D materials. This paper demonstrates such photonic functionality using thermally induced nonlinear optical response SSPM method, of MoS2 nano bottles. Thermally induced nonlinear optical parameters have been estimated by utilizing the saturable absorption response of h- BN, the nonreciprocal light propagation has been achieved. The diode actions have also been demonstrated in liquid-solid and solid-solid devices with the help of passive elements

Micromechanics of liquid-phase exfoliation of a layered 2D material: A hydrodynamic peeling model

We present a micromechanical analysis of flow-induced peeling of a layered 2D material suspended in a liquid, for the first time accounting for realistic hydrodynamic loads. In our model, fluid forces trigger a fracture of the inter-layer interface by lifting a flexible “flap” of nanomaterial from the surface of a suspended microparticle. We show that the so far ignored dependence of the hydrodynamic load on the wedge angle produces a transition in the curve relating the critical fluid shear rate for peeling to the non-dimensional adhesion energy. For intermediate values of the non-dimensional adhesion energy, the critical shear rate saturates, yielding critical shear rate values that are drastically smaller than those predicted by a constant load assumption. Our results highlight the importance of accounting for realistic hydrodynamic loads in fracture mechanics models of liquid-phase exfoliation.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Energy Technolog

High capacity silicon anodes enabled by MXene viscous aqueous ink

The ever-increasing demands for advanced lithium-ion batteries have greatly stimulated the quest for robust electrodes with a high areal capacity. Producing thick electrodes from a high-performance active material would maximize this parameter. However, above a critical thickness, solution-processed films typically encounter electrical/mechanical problems, limiting the achievable areal capacity and rate performance as a result. Herein, we show that two-dimensional titanium carbide or carbonitride nanosheets, known as MXenes, can be used as a conductive binder for silicon electrodes produced by a simple and scalable slurry-casting technique without the need of any other additives. The nanosheets form a continuous metallic network, enable fast charge transport and provide good mechanical reinforcement for the thick electrode (up to 450 µm). Consequently, very high areal capacity anodes (up to 23.3 mAh cm−2) have been demonstrated

Surfactant-exfoliated 2D molybdenum disulphide (2D-MoS2): the role of surfactant upon the hydrogen evolution reaction

© 2017 The Royal Society of Chemistry. Surfactant (sodium cholate, SC) mediated liquid (aqueous) phase exfoliation is a common approach to fabricate 2D molybdenum disulphide (2D-MoS 2 -SC) nanosheets since it is a facile methodology producing defect free flakes with nanometer lateral sizes. The electrocatalytic behaviour of 2D-MoS 2 -SC towards the Hydrogen Evolution Reaction (HER) is benchmarked within acidic media and found to exhibit inferior HER activity to an equivalent mass of pristine 2D-MoS 2 (2D-MoS 2 produced without a surfactant), with HER onset potentials, current densities and Tafel values of -0.61 V (vs. SCE), -2.19 mA cm -2 , 141 mV dec -1 and -0.42 V (vs. SCE), -4.96 mA cm -2 , 94 mV dec -1 respectively. This work demonstrates that sodium cholate has a detrimental effect upon the HER activity of 2D-MoS 2 . Future studies that utilise 2D materials, fabricated via liquid surfactant exfoliation, should consider the role of the surfactant in the observed electrochemical responses and perform the necessary control experiments

2D nanosheet molybdenum disulphide (MoS2) modified electrodes explored towards the hydrogen evolution reaction

We explore the use of two-dimensional (2D) MoS2 nanosheets as an electro-catalyst for the Hydrogen Evolution Reaction (HER). Using four commonly employed commercially available carbon based electrode support materials, namely edge plane pyrolytic graphite (EPPG), glassy carbon (GC), boron-doped diamond (BDD) and screen-printed graphite electrodes (SPE), we critically evaluate the reported electro-catalytic performance of unmodified and MoS2 modified electrodes towards the HER. Surprisingly, current literature focuses almost exclusively on the use of GC as an underling support electrode upon which HER materials are immobilised. 2D MoS2 nanosheet modified electrodes are found to exhibit a coverage dependant electrocatalytic effect towards the HER. Modification of the supporting electrode surface with an optimal mass of 2D MoS2 nanosheets results in a lowering of the HER onset potential by ca. 0.33, 0.57, 0.29 and 0.31 V at EPPG, GC, SPE and BDD electrodes compared to their unmodified counterparts respectively. The lowering of the HER onset potential is associated with each supporting electrodes individual electron transfer kinetics/properties. The effect of MoS2 coverage is also explored. We reveal that its ability to catalyse the HER is dependent on the mass deposited until a critical mass of 2D MoS2 nanosheets is achieved, after which its electrocatalytic benefits and/or surface stability curtail. The active surface site density and turn over frequency for the 2D MoS2 nanosheets is determined, characterised and found to be dependent on both the coverage of 2D MoS2 nanosheets and the underlying/supporting substrate. This work is essential for those designing, fabricating and consequently electrochemically testing 2D nanosheet materials for the HER

Liquid exfoliation of solvent-stabilized few-layer black phosphorus for applications beyond electronics

Few-layer black phosphorus (BP) is a new two-dimensional material which is of great interest for applications, mainly in electronics. However, its lack of environmental stability severely limits its synthesis and processing. Here we demonstrate that high-quality, few-layer BP nanosheets, with controllable size and observable photoluminescence, can be produced in large quantities by liquid phase exfoliation under ambient conditions in solvents such as N-cyclohexyl-2-pyrrolidone (CHP). Nanosheets are surprisingly stable in CHP, probably due to the solvation shell protecting the nanosheets from reacting with water or oxygen. Experiments, supported by simulations, show reactions to occur only at the nanosheet edge, with the rate and extent of the reaction dependent on the water/oxygen content. We demonstrate that liquid-exfoliated BP nanosheets are potentially useful in a range of applications from ultrafast saturable absorbers to gas sensors to fillers for composite reinforcement

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

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(-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, MoS2 and a range of other layered crystals

Towards scale‐up of graphene production via nonoxidizing liquid exfoliation methods

Graphene, the two‐dimensional form of carbon, has received a great deal of attention across academia and industry due to its extraordinary electrical, mechanical, thermal, chemical, and optical properties. In view of the potential impact of graphene on numerous and diverse applications in electronics, novel materials, energy, transport, and healthcare, large‐scale graphene production is a challenge that must be addressed. In the past decade, top–down production has demonstrated high potential for scale‐up. This review features the recent progress made in top–down production methods that have been proposed for the manufacturing of graphene‐based products. Fabrication methods such as liquid‐phase mechanical, chemical and electrochemical exfoliation of graphite are outlined, with a particular focus on nonoxidizing routes for graphene production. Analysis of exfoliation mechanisms, solvent considerations, key advantages and issues, and important production characteristics including production rate and yield, where applicable, are outlined. Future challenges and opportunities in graphene production are also highlighted

Synthesis of graphene oxide and graphene quantum dots from miscanthus via ultrasound-assisted mechano-chemical cracking method

Whilst graphene materials have become increasingly popular in recent years, the followed synthesis strategies face sustainability, environmental and quality challenges. This study proposes an effective, sustainable and scalable ultrasound-assisted mechano-chemical cracking method to produce graphene oxide (GO). A typical energy crop, miscanthus, was used as a carbon precursor and pyrolysed at 1200 ◦C before subjecting to edgecarboxylation via ball-milling in a CO2-induced environment. The resultant functionalised biochar was ultrasonically exfoliated in N-Methyl-2-pyrrolidone (NMP) and water to form GOs. The intermediate and endproducts were characterised via X-ray diffraction (XRD), Raman, high-resolution transmission electron microscopy (HR-TEM) and atomic force microscopy (AFM) analyses. Results show that the proposed synthesis route can produce good quality and uniform GOs (8–10% monolayer), with up to 96% of GOs having three layers or lesser when NMP is used. Ultrasonication proved to be effective in propagating the self-repulsion of negativelycharged functional groups. Moreover, small amounts of graphene quantum dots were observed, illustrating the potential of producing various graphene materials via a single-step method. Whilst this study has only investigated utilising miscanthus, the current findings are promising and could expand the potential of producing good quality graphene materials from renewable sources via green synthesis routes