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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>
Sridhar G.D. Sithu,Baskar Kuppusamy,Maniyarasan Subramaniyan,Hussain M. Sheik 한국지질과학협의회 2016 Geosciences Journal Vol.20 No.2
Seasonal observation on trace elements of shallow inner shelf sediments and their correlation with the population of recent benthic ostracoda off Rameswaram, Ramanathapuram District, Tamil Nadu, Southeast coast of India is the aim of this study. The sediments were analysed for trace elements Al, Fe, Mn, Zn, Cu, Pb, Cd, Ni, Co and Cr and being correlated with the population of benthic ostracoda for four different seasons. Cu has a positive correlation, and Fe, Mn, Zn, Pb, Cd, Ni, Co and Cr have negative correlation with the total population of ostracoda. Al has no considerable correlation with the total population of ostracoda. In the middle segment plenty of corals were found in the study area and their effect being discussed.
Sridhar Sundaram,Sidharth Harindranath,Praveen Kumar Rao,Nitin Ramani,Aditya Kale,Shraddha Patkar 소화기인터벤션의학회 2021 International journal of gastrointestinal interven Vol.10 No.4
Combined biliary and duodenal stent placement has been reported previously in multiple series. Rarely, colonic obstruction may present simultaneously with duodenal and biliary obstruction in advanced pancreaticobiliary cancers. Biliary, duodenal and colonic obstruction managed simultaneously using endoscopic modalities have been reported in only one case report previously. Here we report outcomes of a case of carcinoma of the gall bladder with biliary, gastric outlet and colonic obstruction managed by endoscopic placement of biliary, gastroduodenal and colonic self-expanding metal stents.
Sridhar, Vadahanambi,Kim, Hyun-Jun,Jung, Jung-Hwan,Lee, Changgu,Park, Sungjin,Oh, Il-Kwon American Chemical Society 2012 ACS NANO Vol.6 No.12
<P>The development of three-dimensional carbon-based nanostructures is the next step forward for boosting industrial applications of carbon nanomaterials such as graphenes and carbon nanotubes. Some defects, which have been considered as detrimental factors for maintaining exceptional materials properties of two-dimensional graphene, can be actively used to synthesize three-dimensional graphene-based carbon nanostructures. Here we describe a fast and heretofore unreported defect-engineered method to synthesize three-dimensional carbon nanohybrid structures with strong bonding between graphene nanoplatelets and carbon nanotubes using simple microwave irradiation and an ionic liquid. Our one-pot method utilizes defect-engineered sequential processes: microwave-based defect generation on graphene nanoplatelets, anchoring of palladium nanoparticles on these defects, and subsequent growth of carbon nanotubes by use of an ionic liquid. The unique three-dimensional nanostructures showed an ultrahigh redox capacitance due to high porosity, a high surface-to-volume ratio from the spacer role of vertically standing one-dimensional carbon nanotubes on graphene sheets, and capacitance-like redox response of the palladium nanoparticles. The proposed defect-engineered method could lead to novel routes to synthesizing three-dimensional graphene-based nanostructures with exceptionally high performance in energy storage systems.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/ancac3/2012/ancac3.2012.6.issue-12/nn3046133/production/images/medium/nn-2012-046133_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nn3046133'>ACS Electronic Supporting Info</A></P>
Synthesis of Cyclic Type Semi-Fluorinated Disodium Alkanesulfonate
Sridhar Chirumarry,고요한,장기완,신동수 대한화학회 2016 대한화학회지 Vol.60 No.4
A new perfluorobutyl substituted cyclic type disodium alkanesulfonate is designed, synthesized and characterized as alternative substance to perfluorooctane sulfonic acid (PFOS, 1), a well-known surfactant. Cylic type sulfonate was accomplished from commercially available 2,2,3,3,4,4,5,5-octafluoro-1,6-hexanediol in four steps. Bio-degradable perfluorobutyl moiety was introduced from fluorous diol, which is symmetrically substituted amphiphile via installation of an intermediate trifluoromethanesulfonyl ester and easily manipulated by double displacement of triflate using potassium malonate and further reduction followed by nucleophilic ring opening are key reactions to get target disodium alkanesulfonate. The efficiency and simplicity in the synthesis of this material offer a new strategy to design PFOS alternatives.
Damage evaluation of RC beams strengthened with hybrid fibers
Sridhar, Radhika,Prasad, Ravi Techno-Press 2019 Advances in concrete construction Vol.8 No.1
This paper describes an experimental investigation on hybrid fiber reinforced concrete (HYFRC) beams. And the main aim of this present paper is to examine the dynamic characteristics and damage evaluation of undamaged and damaged HYFRC beams under free-free constraints. In this experimental work, totally four RC beams were cast and analyzed in order to evaluate the dynamic behavior as well as static load behavior of HYFRCs. Hybrid fiber reinforced concrete beams have been cast by incorporating two different fibers such as steel and polypropylene (PP). Damage of HYFRC beams was obtained by cracking of concrete for one of the beams in each set under four-point bending tests with different percentage variation of damage levels as 50%, 70% and 90% of maximum ultimate load. And the main dynamic characteristics such as damping, fundamental natural frequencies, mode shapes and frequency response function at each and every damage level has been assessed by means of non-destructive technique (NDT) with hammer excitation. The fundamental natural frequency and damping values obtained through dynamic tests for HYFRC beams were compared with control (reference) RC beam at each level of damage which has been acquired through static tests. The static experimental test results emphasize that the HYFRC beam has attained higher ultimate load as compared with control reinforced concrete beam.
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.
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.
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>