Facile, environmentally friendly, cost effective and scalable production of few-layered graphene

© 2017 Elsevier B.V. Commercialization of graphene is still one the biggest challenges in the carbon field despite the development of several methods for its production. The lack of simple, cost-effective and scalable methods for mass-production of graphene hampers its promotion to the market. Here, we propose a new method for large-scale p roduction of mono- and few-layered graphene via liquid phase exfoliation with the use of wet ball milling in the presence of organic solvents at extremely low temperatures. The wet ball milling combined with the temperature modulated high surface energy solvents affords exfoliation of bulk graphite into graphenes in a fast, scalable, cost effective and environmentally friendly process. The thorough statistical analysis of as-prepared graphene flakes demonstrates that more than 61% of the flakes comprise less than 5 layers, while ∼14% of the flakes were monolayer graphene. Combined with the ∼30% yield of few-layer graphene out of the graphite precursor, this method demonstrates incredible efficiency in just 45 min. In the presence of methanol, our method results in formation of predominantly bi-layer graphene, which is more difficult to obtain in scalable fashion, than mono-layer graphene. The high quality of as-obtained graphenes is fully confirmed by Raman spectroscopy, TEM, SAED, AFM and X-ray photoelectron spectroscopy

Facile, environmentally friendly, cost effective and scalable production of few-layered graphene

© 2017 Elsevier B.V. Commercialization of graphene is still one the biggest challenges in the carbon field despite the development of several methods for its production. The lack of simple, cost-effective and scalable methods for mass-production of graphene hampers its promotion to the market. Here, we propose a new method for large-scale p roduction of mono- and few-layered graphene via liquid phase exfoliation with the use of wet ball milling in the presence of organic solvents at extremely low temperatures. The wet ball milling combined with the temperature modulated high surface energy solvents affords exfoliation of bulk graphite into graphenes in a fast, scalable, cost effective and environmentally friendly process. The thorough statistical analysis of as-prepared graphene flakes demonstrates that more than 61% of the flakes comprise less than 5 layers, while ∼14% of the flakes were monolayer graphene. Combined with the ∼30% yield of few-layer graphene out of the graphite precursor, this method demonstrates incredible efficiency in just 45 min. In the presence of methanol, our method results in formation of predominantly bi-layer graphene, which is more difficult to obtain in scalable fashion, than mono-layer graphene. The high quality of as-obtained graphenes is fully confirmed by Raman spectroscopy, TEM, SAED, AFM and X-ray photoelectron spectroscopy

Faktorer som kan påverka egenvården hos etniska minoritetsgrupper med diabetes mellitus

Diabetes mellitus är en folksjukdom som trots preventiva åtgärder har en stadigt ökad prevalens i hela världen, förorsakar 5 % av dödsfallen globalt varje år och som sannolikt kommer att öka mer än 50 % de nästkommande 10 åren. I Sverige likt många andra länder i Europa har invandringen lett till att vi lever i samhällen med kulturella skillnader. Egenvården vid diabetes mellitus är en viktig del av behandlingen som minskar risken för diabeteskomplikationer. Internationellt sett har forskningen mestadels fokuserat på etniska minoritetsgrupper och sjukvård utifrån skillnader mellan sjukdom och dödlighet. Forskningen tenderar att påvisa att socioekonomiska skillnader och etnicitet är viktiga faktorer som påverkar dålig hälsa. Syftet med studien var att belysa faktorer som kan påverka egenvården hos personer med diabetes mellitus från etniska minoritetsgrupper. Metoden som använts är en litteraturstudie med kvalitativ ansats baserad på vetenskapliga artiklar. Resultatet visar att det föreligger stora skillnader i hälsa och hälsomedvetenhet i de olika etniska minoritetsgrupperna. Utbildningsnivå, religion, könsrelaterade kulturella skillnader och tidigare traumatiska migrationsupplevelser är något som bör tas hänsyn till i diabetesvården. Det framkom även att ett behov av tillgängliga och lämpliga tolkar är viktigt för att kunna säkra informationen mellan sjuksköterska och patient. De viktigaste slutsatserna är att det finns ett behov av utbildning i mångkulturell vård till sjuksköterskor samt att kulturellt anpassad diabetesvård är nödvändig för att egenvården ska fungera optimalt efter individens förutsättningar

Heat transfer performance of two-phase closed thermosyphon with oxidized CNT/water nanofluids

In this paper, the effects of different acids on the thermal performance of oxidized carbon nanotubes (CNT)/water nanofluids in a two-phase closed thermosyphon were studied. The structures morphology and functionalization degree were studied concurrently. The results indicated that strong oxidants increased dispersivity of CNT in the nanofluids. In other words, as the number of COOH groups increased in the nanofluids, an upward trend was also observed in the thermal efficiency of the thermosyphon

Water-based graphene quantum dots dispersion as a high-performance long-term stable nanofluid for two-phased closed thermosyphons

Water-based graphene quantum dots (GQD) suspension has great potential for different heat transfer applications as a novel coolant due to their unique colloidal stability, high thermal conductivity and low penalty for rheological properties once loading GQD. To this end, graphene quantum dots were firstly prepared through a new and cost-effective exfoliation procedure. Based on the morphological characterization, the average thickness and diameter of the synthesized amine treated-GQD (AGQD) were determined as mostly less than 1 nm and in the range of 5–20 nm, respectively. Case studies show that water-based AGQD nanofluid at very low weight fractions shows a considerably higher thermal conductivity than that of base fluid. In a detailed rheological investigation of the water-based AGQD nanofluid, no noteworthy increase was observed in comparison with the base fluid, which is considered as a major benefit for this novel generation of coolants. The water-based AGQD nanofluids were also found to be especially more effective in the thermosyphon in terms of overall thermal properties such as net heat transfer, and thermal efficiency, and rheological property such as effective viscosity, as well as, total pressure drop in comparison to the distilled water. Since the water-based AGQD nanofluids show no sedimentation, high thermal conductivity and fairly no effect on rheological properties, it would provide an economical approach for enhancing the performance of industrial heat pipes and thermosyphons

Effect of magnetic field on thermo-physical and hydrodynamic properties of different metals-decorated multi-walled carbon nanotubes-based water coolants in a closed conduit

In this paper, the thermo-physical and hydrodynamic properties of heat transfer nanofluids containing metal nanoparticles-decorated multi-wall carbon nanotube (MWCNT) are reported. To this end, Cu-decorated MWCNT, Fe-decorated MWCNT, and Ni-decorated MWCNT (covalently functionalized samples) were synthesized with pre-functionalization with the aspartic acid as the hydrophilic chain. To have a comprehensive comparison, water-based non-covalently functionalized MWCNT nanofluids were also synthesized. A significant increase in the thermal and electrical conductivities of heat transfer nanofluids containing metal nanoparticles-based MWCNT as compared to the non-covalently functionalized sample as well as water has been determined at the same operational conditions. All the prepared nanofluids are stable and the viscosity and density remained approximately the same after loading additives. The present paper also focused on the study of the role of weight concentrations of additives, flow rate and thermo-physical properties of the prepared nanofluids on the convective heat transfer rate and hydrodynamic performances in the laminar flow. Further, the convective heat transfer coefficient, pressure drop, friction factor, performance index and pumping power variation were also investigated under applied magnetic field, which improves the overall thermal performance of the closed conduit insignificantly

Microwave-Assisted Synthesis of Highly-Crumpled, Few-Layered Graphene and Nitrogen-Doped Graphene for Use as High-Performance Electrodes in Capacitive Deionization

Capacitive deionization (CDI) is a promising procedure for removing various charged ionic species from brackish water. The performance of graphene-based material in capacitive deionization is lower than the expectation of the industry, so highly-crumpled, few-layered graphene (HCG) and highly-crumpled nitrogen-doped graphene (HCNDG) with high surface area have been introduced as promising candidates for CDI electrodes. Thus, HCG and HCNDG were prepared by exfoliation of graphite in the presence of liquid-phase, microwave-assisted methods. An industrially-scalable, cost-effective, and simple approach was employed to synthesize HCG and HCNDG, resulting in few-layered graphene and nitrogen-doped graphene with large specific surface area. Then, HCG and HCNDG were utilized for manufacturing a new class of carbon nanostructure-based electrodes for use in large-scale CDI equipment. The electrosorption results indicated that both the HCG and HCNDG have fairly large specific surface areas, indicating their huge potential for capacitive deionization applications

Microwave-assisted direct coupling of graphene nanoplatelets with poly ethylene glycol and 4-phenylazophenol molecules for preparing stable-colloidal system

Herein, microwave-assisted direct coupling of Graphene Nanoplatelets (GNP) with polymers including hydroxyl ( OH) groups such as poly ethylene glycol (PEG) and bio-molecules like 4-phenylazophenol (Azo) are investigated. Among different water-soluble polymers, PEG has received unique consideration due to its biocompatibility. Moreover, Azo-treated GNP can easily employ in long-term solar thermal storage. Thus, an electrophilic addition reaction under microwave irradiation is presented as an efficient procedure to functionalize GNP with Azo and PEG. In order to compare the activities of different catalysts under microwave irradiation, the direct coupling of GNP with Azo and PEG were performed in the presence of ZnCl2, FeCl2,TiCl4 and AlCl3, separately. The use of simple Lewis acids loading provides an electrophilic addition reaction in as little as 30 min, which provide a shortcut and prevent time-consuming and multiple steps approaches. Interestingly, PEG-treated GNP has no cross-linking of the flakes, which this allows the production of more dispersed GNP in aqueous media. Investigation of colloidal stability using particle absorbance measurement showed successful results in terms of stability with very low sediment. (C) 2015 Elsevier B.V. All rights reserved