A study of polybromide chain formation using carbon nanomaterials via density functional theory approach

\ua9 2016 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license. We use a density functional theory approach under the local density approximation (DFT/LDA) to describe the formation of polybromide chain structures, their stretching frequency modes and charge transfer induced by the interaction of these molecules with a graphene sheet. In many cases, we find polybromides to be more thermodynamically stable than the equivalent Br2 molecular structures adsorbed on graphene sheet. This results in lower frequency stretch modes at around 170–190 cm−1. We propose that these are rarely observed experimentally due to the bromination techniques used, which introduces molecular Br2 into the carbon host material. Charge transfer with their host material means that these molecules and their associated hole charge in the neighbouring carbon materials, are then coulombically repelled from other bromine molecules which acts as a barrier to combination into polybromides. Our calculated barrier for polybromide formation (2Br2→Br4) on a graphene sheet was 0.35 eV which is an exothermic process with an enthalpy value of −0.28 eV. Therefore, thermodynamically, chain polybromide formation seems to be favourable but kinetically, is unlikely, since there is an activation barrier that needs to be overcome to give stable bromine chain structures

Synthesis and microstructural characterization of kaolin-polyethylene composites

In this article, the preparation and characterization of kaolin/polyethylene composites are presented. Microstructural characteristics of six different kaolin–polyethylene composites with varying percentage compositions of kaolin and polymer were produced using a modified melt compounding approach, was explored. The characterization methods employed are scanning electron microscopy (SEM), attenuated total reflectance mid Infrared (ATR-MIR), X-ray powder diffraction (XRD), thermogravimetric and differential thermal analysis (TGA-DTA), compressive, flexural strengths and impact resistance analysis. The implications of the results are discussed for the design of kaolin/polymer composites for constructional purposes.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1548-0569hb201

Nanomaterials in 2 dimensions for flexible solar cell applications a review

This review presents the progress, challenges and prospects of ultrathin flexible photovoltaic devices based on 2 dimensional 2D nanomaterials. These devices have shown very high performance in bending stabilities for up to 90 of their power conversion efficiencies PCEs after multiple bending deformations. They are thin film PVs with lightweight and mechanically robust structures that allow use in the continual advancing solar cell applications. In this paper, comprehensive assessments of 2D nanomaterials, their syntheses methods, performance, degradation, mechanical and opto electronic characterization in flexible photovoltaic PV cells are highlighted. Semi conductor materials such as conjugated donor and acceptor polymers, small donor acceptor molecules and organometal halide perovskites for use as active layers in such flexible solar cell structures are reviewed. The challenges and prospects associated with the adoption of 2D nanomaterials in flexible solar cells are presented. The review highlights the need to transition laboratory results on 2D nanomaterials based flexible solar cells into scale up and commercialized products despite the existing and also opens research areas for researchers to explore and achieve robust and high efficient solar device

Preparation and Characterization of Rubber Blends for Industrial Tire Tread Fabrication

The physico-mechanical properties of variable rubber blends including epoxide natural rubber (ENR), polybutadiene rubber (BR), and solution polymerized styrene-butadiene rubber (SBR) filled with silanized silica and carbon black mixtures were explored. The tensile, hardness, resilience, abrasion, and fatigue behavior were investigated. An optimized composition involving 30 phr of ENR and 70 phr SBR filled with mixtures of carbon blacks and silanized silica was proposed to be a suitable composition for the future development of green passenger truck tires, with low rolling resistance (fuel saving ability), high wear resistance, and desired fatigue failure properties

A study of polybromide chain formation using carbon nanomaterials via density functional theory approach

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Effects of pre-buckling on the bending of organic electronic structures

This paper explores the extent to which pre-buckling of layers (in thin film multilayered structures) can be used to increase the flexibility of organic electronic devices. The deformation of wavy/buckle profiles, with a range of nano- and micro-scale wavelengths, is modeled using finite element simulations. The predictions from the models are then validated using experiments that involve the bending of layered structures that are relevant to flexible organic electronics. The introduction of pre-buckled profiles is shown to increase the range of deformation that is applied to model structures, prior to onset of significant stresses and strains. The implications of the work are discussed for the design of robust flexible organic solar cells

Effects of substrates on the performance of optoelectronic devices: A review

This review discusses the effects of substrates on devices fabricated for optoelectronic applications. It includes the types and characteristics of substrates, synthesis and fabrication of substrates, and the influence of substrates on the optical properties, surface morphology and current-voltage behaviour of optoelectronic devices. The study showed that two main types of substrates: planar and textured are commonly used in the industry. Flexibility, semi-rigidity and rigidity are characteristics of the substrates and they vary in modulus, transparency and texture. Whereas glass and metal substrates can be produced via melt casting, polydimethylsiloxane (PDMS), polyethylene terephthalate (PET), etc are produced by crosslinking polymer base materials with curing agents. The mechanical and current-voltage characteristics are also shown for planar and textured substrate-based devices. The textured substrates showed ridges, wrinkles, buckled surface morphology whereas the planar showed uniform and largely flat morphology. Textured substrates also recorded higher optical absorbance and improved device efficiencies compared with planar substrates. The molecular configuration of the polymer chains are edged-on for planar substrates and both edge-on and face-on for textured substrates. The findings and their implications have been discussed to highlight the importance of substrates in the fabrication and performance of optoelectronic devices

Cold welding of organic light emitting diode: Interfacial and contact models

This paper presents the results of an analytical and computational study of the contacts and interfacial fracture associated with the cold welding of Organic Light Emitting diodes (OLEDs). The effects of impurities (within the possible interfaces) are explored for contacts and interfacial fracture between layers that are relevant to model OLEDs. The models are used to study the effects of adhesion, pressure, thin film layer thickness and dust particle modulus (between the contacting surfaces) on contact profiles around impurities between cold-welded thin films. The lift-off stage of thin films (during cold welding) is then modeled as an interfacial fracture process. A combination of adhesion and interfacial fracture theories is used to provide new insights for the design of improved contact and interfacial separation during cold welding. The implications of the results are discussed for the design and fabrication of cold welded OLED structures

Industrial Applications of Clay Materials from Ghana (A Review)

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Pressure effects on interfacial surface contacts and performance of organic solar cells

This paper explores the effects of pressure on the interfacial surface contacts and the performance of organic solar cells. A combination of experimental techniques and analytical/computational models is used to study the evolving surface contacts profiles that occur when compliant, semi-rigid and rigid particles are interlocked between adjacent layers in model solar cell structures. The effects of layer surface roughness and interlocked (trapped) particles are also considered along with the effects of surface energy, adhesion energy, and pressure. The results show that increased interfacial contact lengths and decreased void lengths are associated with the application of increased pressure. Increased pressure also results in significant improvements in power conversion efficiency. These improvements in power conversion efficiency are associated with the closure up of micro- and nano-voids due to the application of pressure to layers produced via spin coating and thermal evaporation. The results suggest that pressure-induced contacts can be used to enhance the performance of organic solar cells