Manganese nitride stabilized on reduced graphene oxide substrate for high performance sodium ion batteries

( V. Sridhar ),서화원,박현 한국공업화학회 2020 한국공업화학회 연구논문 초록집 Vol.2020 No.-

Though the utility of manganese compounds such as oxides, sulphides has been well researched in energy storage applications such as super-capacitors and lithium-ion batteries, the utility of manganese nitrides hasn't been reported yet, especially as anode in sodium-ion batteries. In this manuscript we reported synthesis of manganese nitride decorated reduced graphene oxide (MnN@rGO) prepared by simple microwave nitridation technique and its utility as anode material in sodium-ion batteries. MnN@rGO electrodes exhibited sodium storage capacity of 716 mAhg^-1 whereas when used as electrodes in super-capacitors, a high capacitance value of 639.2 Fg^-1 at scan rates of 10 mVs^-1 in 1M Na₂SO₄ was achieved.

3D functional hetero-nanostructures of vertically anchored metal oxide nanowire arrays on porous graphene substrates

Sridhar, V.,Chun, H.H.,Park, H. Pergamon Press ; Elsevier Science Ltd 2014 Carbon Vol.79 No.-

Mesoporous three dimensional hierarchical structure of copper oxide nanowires vertically anchored on graphene substrate was synthesized by a facile and green 'alkali mediated synthesis' under microwave irradiation. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer-Emmett-Teller surface area tests showed highly crystalline nanowires vertically anchored on porous graphene to give a unique mesoporous, hierarchical nanostructures. When applied as anode in lithium ion batteries, our materials exhibit capacity of 770mAhg<SUP>-1</SUP> even after 100 cycles with a Columbic efficiency in excess of 97%, reflecting the ability of the hierarchical network to accommodate the extreme volume changes of metal anodes that occur during the lithiation/delithiation reactions. The utility of our newly developed to synthesize anisotropic titania nano-wires or zinc oxide nano-flowers on graphene substrate is also reported.

Dielectric and dynamic mechanical relaxation behavior of exfoliated nano graphite reinforced flouroelastomer composites

Sridhar, V.,Xu, Deng,Pham, Thanh Tu,Mahapatra, S.P.,Kim, Jin Kuk Wiley Subscription Services, Inc., A Wiley Company 2009 Polymer composites Vol.30 No.3

<P>Dynamic mechanical analysis and dielectric relaxation spectra of exfoliated nano graphite reinforced flouroelastomer composites were used to study their relaxation behavior as a function of temperature (−80°C to +40°C) and frequency (0.01 to 10<SUP>5</SUP> Hz). The effect of filler loadings on glass transition temperature was marginal for all the composites and T<SUB>g</SUB> value was in the narrow range of 7.8–8.4°C, which has been explained on the basis of relaxation dynamics of polymer chains in the vicinity of fillers. Strain-dependent dynamical parameters were evaluated at dynamic strain amplitudes of 0.01–10%. The nonlinearity in storage modulus has been explained on the concept of filler-polymer interaction and filler aggregation of the nano graphite platelets. The variation in real and complex part of impedance with frequency has been studied as a function of filler. The percolation of the nano graphite as studied by conductivity measurements is also reported. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers.</P>

Microwave extraction of graphene from carbon fibers

Sridhar, V.,Jeon, Jin-Han,Oh, Il-Kwon Elsevier 2011 Carbon Vol.49 No.1

<P><B>Graphical abstract</B></P><P><ce:figure id='f0030'></ce:figure></P><P><B>Research highlights</B></P><P>► Graphene synthesis from turbostratic carbon fibers. ► Eco-friendly chemicals. ► Microwave radiation.</P> <P><B>Abstract</B></P><P>A microwave method for extracting graphene and few-graphene stacks from turbostratic carbon fibers is reported. Microwave radiation is used as an additional energy source in the unzipping of tubular carbon structures in conjunction with hydrogen peroxide, a mild oxidizing agent. This minimizes the problems associated with excessive oxidation and considerably shortens the overall processing time.</P>

Microwave synthesis of three dimensional graphene-based shell-plate hybrid nanostructures

Sridhar, V.,Lee, I.,Yoon, H.S.,Chun, H.H.,Park, H. Pergamon Press ; Elsevier Science Ltd 2013 Carbon Vol.61 No.-

Though free standing graphene has excellent physical, chemical and electrical properties, its tendency to restack is a major hurdle in realizing its full potential especially in applications such as lithium ion batteries and super capacitors. In this manuscript, we report synthesis of graphene-based three dimensional (3D) shell-plate nanostructures composed of 'nano-cup arrays' anchored on few-layered graphene (FLG) substrates. The synthesis was carried out by a simple process using eco-friendly ionic liquids and microwave irradiation as the energy source. Morphological studies by scanning electron microscopy and transmission electron microscopy showed vertically anchored graphene nano-cups on graphene substrate. Super capacitor electrodes fabricated with FLG/gCup nano-hybrids and its electrochemical properties are studied by cyclic voltammetry (CV) and galvanostatic charge/discharge (DC) methods. FLG/gCup electrodes showed good electrochemical performance, with a maximum specific capacitance of 421Fg<SUP>-1</SUP> at the charge/discharge current density of 100mAg<SUP>-1</SUP> in 1M KOH electrolyte, which is four times higher than pristine graphene sheets. The utility of our developed technique in synthesis of graphene nano-cup arrays on arbitrary surfaces (glass substrate) is also reported.

Hollow SnO2@carbon core-shell spheres stabilized on reduced graphene oxide for high-performance sodium-ion batteries

Sridhar, V.,Park, H. Royal Society of Chemistry 2017 New journal of chemistry Vol.41 No.2

<P>Sodium ion batteries are rapidly emerging as attractive and costeffective devices in applications such as smart grids and large-scale energy storage. However, the large size of the sodium ion and its tendency to form NaC186 during electrochemical intercalation with carbon anodes necessitate the design of architectures which can accommodate the spatial requirements without sacrificing essential functional properties like good conductivity and high surface area. In this manuscript, we report the synthesis of three-dimensional, mesoporous, nano SnO2 cores encapsulated in carbon shells anchored on reduced graphene oxide (SnO2@ C-rGO) by a simple microwave induced catalytic transformation of diazoniumfunctionalized graphene oxide. The electrochemical results reveal that our SnO2@ C-rGO anodes have excellent electrochemical performance including high-capacity (493.12 mA h g(-1)), good capacity retention and large coulombic efficiency (96.2% after 150 cycles).</P>

Sugar-derived disordered carbon nano-sheets as high-performance electrodes in sodium-ion batteries

Sridhar, V.,Park, H. CNRS 2017 NEW JOURNAL OF CHEMISTRY Vol.41 No.11

<P>Inspired by the simple and spectacular experiment of dehydrogenation of sugar by sulphuric acid, we developed a microwave based solvothermal technique for the synthesis of activated carbon nanosheets (aCNS) using white sugar as the carbon source and potassium hydroxide as the activating agent. Morphological studies using SEM showed micrometer-long and nanometer-thick aCNS, whereas HRTEM showed the presence of semi-graphitic islands. When used as electrodes in sodium-ion batteries, our aCNS showed a high specific capacitance of 423 mA h g(-1) with a good rate capability even after 200 cycles.</P>

Synthesis of graphene nano-sheets using eco-friendly chemicals and microwave radiation

Sridhar, V.,Jeon, Jin-Han,Oh, Il-Kwon Elsevier 2010 Carbon Vol.48 No.10

<P><B>Abstract</B></P><P>A novel approach to synthesize graphene nano-sheets by combining chemical treatment and microwave radiation is demonstrated using eco-friendly chemicals. Microwave radiation was used to produce strong expansion of the graphite worm in the thickness direction. The graphene nano-sheets obtained in this study were characterized by morphology images, nanoprofilometry, Raman and X-ray photoelectron spectroscopy. Besides being eco-friendly, the proposed method has also the attractive advantage of being rapidly able to produce a lot of graphene nano-sheets.</P>

EFFICIENT CLOUD DATA HOSTING AVAILABILITY

P S V S Sridhar,Ronnie Caytiles 사단법인 미래융합기술연구학회 2017 아시아태평양융합연구교류논문지 Vol.3 No.2

More and additional enterprises and organizations square measure hosting their knowledge into the cloud, so as to cut back the IT maintenance price and enhance the info responsibility. However, facing the various cloud vendors further as their heterogenous valuation policies, customers would be confused with that cloud(s) square measure appropriate for storing their knowledge and what hosting strategy is cheaper. the overall establishment is that customers sometimes place their knowledge into one cloud (which is subject to the seller lock-in risk) then merely trust to luck. supported comprehensive analysis of assorted progressive cloud vendors, this paper proposes a completely unique knowledge hosting theme (named CHARM) that integrates 2 key functions desired. the primary is choosing many appropriate clouds associate degreed an applicable redundancy strategy to store knowledge with reduced financial price and warranted handiness. The second is triggering a transition method to re-distribute knowledge per the variations of knowledge access pattern and valuation of clouds. we tend to valuate the performance of CHARM victimisation each trace-driven simulations and model experiments. The results show that compared with the main existing schemes, CHARM not solely saves around two hundredth of financial price however additionally exhibits sound ability to knowledge and worth changes.

Asymmetric Formal Synthesis of (+)‐Lactacystin

Sridhar, Chirumarry,Vijaykumar, Bodduri V. D.,Radhika, Laghuvarapu,Shin, Dong‐,Soo,Chandrasekhar, Srivari WILEY‐VCH Verlag 2014 EUROPEAN JOURNAL OF ORGANIC CHEMISTRY Vol.2014 No.30

<P><B>Abstract</B></P><P>A formal synthesis of (+)‐lactacystin was achieved from commercially available isobutyraldehyde and ethyl acrylate. A Baylis–Hillman reaction, an intermolecular nucleophilic displacement under Mitsunobu conditions, a Sharpless asymmetric epoxidation, a palladium(0)‐catalyzed <I>syn</I>‐selective ring opening of an epoxide by treatment with an azide, a one‐pot azide reductive lactamization, and a ruthenium‐catayzed oxidation were employed as the key steps.</P>