Ultrathin graphene (UG) has been prepared by exfoliation of graphite oxide by a novel technique based on focused solar radiation. Graphene based engine oil nanofluids have been prepared and their frictional characteristics (FC), antiwear (AW), and extreme pressure (EP) properties have been evaluated. The improvement in FC, AW, and EP properties of nanofluids is respectively by 80, 33, and 40% compared with base oil. The enhancement can be attributed to the nanobearing mechanism of graphene in engine oil and ultimate mechanical strength of graphene. © 2011 American Chemical Society.

Sankaranarayanan V

Department Of Physics

Sundara Ramaprabhu

ANTI-WEAR

BASE OIL

Engine oil

EXTREME PRESSURE

FRICTIONAL CHARACTERISTICS

Frictional coefficients

grapheme

GRAPHITE OXIDE

Nanofluids

Novel techniques

SOLAR EXFOLIATION

TRIBOLOGICAL APPLICATIONS

Ultra-thin

Friction

LUBRICATING OILS

Nanofluidics

tribology

Wear resistance

Graphene

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

ACS Applied Materials and Interfaces

Graphite oxide (GO) with N doping is synthesized from the waste carbon source. The GO products obtained at 1200–1400 °C are utilized as nano-additive in synthetic engine oil. The GO is produced in the form of layered structure with Ca compound incorporation and functional groups. GO addition has improved the friction (2.8–21.1% reduction) and wear (8.2–18.5% reduction in worn volume) properties due to its easy shear force of layered structure. The maximum performance is achieved in the GO synthesized at 1300 °C. Study reveals the potential use of a waste carbon source converted to GO that can be directly used as nano-additive. © 2019 Elsevier Ltd

Tribology International

Tribological properties of graphite oxide derivative as nano-additive: Synthesized from the waster carbon source

Large-scale electrorheology (ER) response has been reported for dilute graphene nanoflake-based ER fluids that have been engineered as novel, readily synthesizable polymeric gels. Polyethylene glycol (PEG 400) based graphene gels have been synthesized and a very high ER response (∼125 000% enhancement in viscosity under influence of an electric field) has been observed for low concentration systems (∼2 wt.%). The gels overcome several drawbacks innate to ER fluids. The gels exhibit long term stability, a high graphene packing ratio which ensures very high ER response, and the microstructure of the gels ensures that fibrillation of the graphene nanoflakes under an electric field is undisturbed by thermal fluctuations, further leading to mega ER. The gels exhibit a large yield stress handling caliber with a yield stress observed as high as ∼13 kPa at 2 wt.% for graphene. Detailed investigations on the effects of graphene concentration, electric field strength, imposed shear resistance, transients of electric field actuation on the ER response and ER hysteresis of the gels have been performed. In-depth analyses with explanations have been provided for the observations and effects, such as inter flake lubrication/slip induced augmented ER response. The present gels show great promise as potential ER gels for various smart applications. © 2016 IOP Publishing Ltd.

Fulltext

Nanotechnology

Large electrorheological phenomena in graphene nano-gels

A solution-free green method using focused solar electromagnetic radiation is used to synthesize graphene and graphene-multiwalled carbon nanotube (MWNT) composite. Stable nanofluids are prepared by dispersing the nanomaterials in polar base fluids. Thermal conductivity of the nanofluids improves with graphene-MWNT nanocomposites as additives, which could be due to prevention of restacking of graphene sheets by MWNT along with a synergistic effect of intrinsic high thermal conductivity of graphene and MWNT. The advantage of the present synthesis method in particular to nanofluids application is that the presence of oxygen functional groups resulting from pre-functionalized MWNT rules out the need for functionalizing the hybrid composite again, thereby preserving the high thermal properties of graphene. Thermal conductivity enhancement of 9.2% and 10.5% is obtained with graphene and graphene-MWNT nanofluids in de-ionized water at room temperature for 0.04% volume fraction. The high thermal transport characteristics of graphene-MWNT composite nanofluids is ascribed to the high aspect ratio of MWNT and graphene, which in turn can form tightly bonded clusters and, by suppressing the interface resistance, can become excellent additives to attain high thermal conductivity. Further, an enhancement in heat-transfer coefficient of 193% at Reynolds number 2000 for 0.02% volume fraction of aqueous graphene-MWNT nanofluids suggests the potential application of the present hybrid material-based nanofluids in cooling circuits. © The Royal Society of Chemistry 2013.

RSC Advances

Graphene-multiwalled carbon nanotube-based nanofluids for improved heat dissipation

Advanced Powder Technology

Enhanced heat transfer in liquid thin film flow of non-Newtonian nanofluids embedded with graphene nanoparticles

Novel foam composites comprising functionalized graphene (f-G) and polyvinylidene fluoride (PVDF) were prepared and electrical conductivity and electromagnetic interference (EMI) shielding efficiency of the composites with different mass fractions of f-G have been investigated. The electrical conductivity increases with the increase in concentration of f-G in insulating PVDF matrix. A dramatic change in the conductivity is observed from 10 -16 S · m-1 for insulating PVDF to 10-4 S · m-1 for 0.5 wt.% f-G reinforced PVDF composite, which can be attributed to high-aspect-ratio and highly conducting nature of f-G nanofiller, which forms a conductive network in the polymer. An EMI shielding effectiveness of ≈20 dB is obtained in X-band (8-12 GHz) region and 18 dB in broadband (1-8 GHz) region for 5 wt.% of f-G in foam composite. The application of conductive graphene foam composites as lightweight EMI shielding materials for X-band and broadband shielding has been demonstrated and the mechanism of EMI shielding in f-G/PVDF foam composites has been discussed. © 2011 WILEY-VCH Verlag GmbH &amp; Co. KGaA, Weinheim.

Macromolecular Materials and Engineering

Functionalized graphene-PVDF foam composites for EMI shielding

Functionalized graphene-polyvinylidene fluoride (f-G-PVDF) nanocomposite films were synthesized using a simple solvent casting technique. The investigation demonstrates the real time strain response of f-G-PVDF nanocomposites on the macro-scale under tensile loads and the use of this nanocomposite as strain sensor. This is ascribed to the variation of electrical properties of graphene-polymer upon mechanical deformation at the nanoscale. © 2011 The Royal Society of Chemistry.

Journal of Materials Chemistry

Functionalized graphene reinforced thermoplastic nanocomposites as strain sensors in structural health monitoring

The fabrication of a cholesterol biosensor using gold nanoparticles decorated graphene nanoplatelets has been reported. Thermally exfoliated graphene nanoplatelets act as a suitable support for the deposition of Au nanoparticles. Cholesterol biosensor electrodes have been constructed with nafion solubilized functionalized graphene nanoplatelets (f-G) as well as Au nanoparticles decorated f-G, immobilized over glassy carbon electrode. f-G and Au/f-G thin film deposited glassy carbon electrodes were further functionalized with cholesterol oxidase by physical adsorption. Au nanoparticles dispersed over f-G demonstrate the ability to substantially raise the response current. The fabricated electrodes have been tested for their electrochemical performance at a potential of 0.2 V. The fabricated Au/f-G based cholesterol biosensor exhibits sensitivity of 314 nA/μM cm2 for the detection of cholesterol with a linear response up to 135 μM. Furthermore, it has been observed that the biosensor exhibits a good anti-interference ability and favorable stability over a month's period. © 2011 Elsevier B.V. All rights reserved.

Thin Solid Films

A cholesterol biosensor based on gold nanoparticles decorated functionalized graphene nanoplatelets

ACS Applied Materials & Interfaces

LiNi1/3Co1/3Mn1/3O2–Graphene Composite as a Promising Cathode for Lithium-Ion Batteries

The Journal of Physical Chemistry C

Preparation and Tribological Study of Functionalized Graphene–IL Nanocomposite Ultrathin Lubrication Films on Si Substrates

Graphene-based engine oil nanofluids for tribological applications

Journal	ACS Applied Materials and Interfaces
ISSN	19448244
Open Access	No