Synthesis and enhanced electrochemical performance of Li₂CoPO₄F cathodes under high current cycling

Amaresh, S.,Kim, G. J.,Karthikeyan, K.,Aravindan, V.,Chung, K. Y.,Cho, B. W.,Lee, Y. S. The Royal Society of Chemistry 2012 Physical chemistry chemical physics Vol.14 No.34

<P>Lithium cobalt fluorophosphate, Li<SUB>2</SUB>CoPO<SUB>4</SUB>F, is successfully synthesized by a solid state reaction under Ar flow at 700 °C. X-ray diffraction and scanning electron microscopic studies are utilized to analyze the structural and morphological features of the synthesized materials, respectively. The presence of fluorine is also supported by energy-dispersive X-ray spectroscopy. The electrochemical properties are evaluated by means of Li/Li<SUB>2</SUB>CoPO<SUB>4</SUB>F half-cell configurations in both potentiostatic and galvanostatic modes. The Li/Li<SUB>2</SUB>CoPO<SUB>4</SUB>F cell delivers an initial discharge capacity of 132 mA h g<SUP>−1</SUP> at a current density of 0.1 mA cm<SUP>−2</SUP> between 2.0 and 5.1 V at room temperature. Due to the higher operating potential of the Co<SUP>2+/3+</SUP> couple in the fluorophosphate matrix, this cell shows a capacity retention of only 53% after 20 cycles, still the material delivered 108 mA h g<SUP>−1</SUP> at a high current rate of 1 C. Cyclic voltammetric studies corroborate the insertion and extraction of Li<SUP>+</SUP> ions by a single phase reaction mechanism during cycling.</P> <P>Graphic Abstract</P><P>A solid-state route was employed to synthesize high voltage cathode Li<SUB>2</SUB>CoPO<SUB>4</SUB>F by optimizing calcination temperature and duration, and Li-insertion properties were evaluated in half-cell configuration and the test cell delivered a reversible capacity of ∼132 mA h g<SUP>−1</SUP> with good cyclability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2cp41624g'> </P>

Investigations on Doping of Poly(3-methyl-thiophene) Composites for Supercapacitor Applications

G. Karthikeyan,S. Sahoo,G. C. Nayak,C. K. Das 한국고분자학회 2012 Macromolecular Research Vol.20 No.4

Zinc ion (Zn2+)-doped poly(3-methyl-thiophene)/multi-walled carbon nano tubes (MWCNT) composites (M-PMT-ZN) and poly(3-methyl-thiophene)/MWCNT composites (M-PMT) were synthesized by in situ chemical oxidative polymerization and investigated as electrode material for supercapacitors. The interactions of Zn2+ ions with sulfur sites on the polymer chains were characterized by Fourier transform infrared spectroscopy. The morphology of the nanocomposites was characterized by scanning electron microscopy and high resolution transmission electron microscopy. The electrochemical properties were investigated using cyclic voltammetry, cyclic chargingdischarging tests, and electrochemical impedance spectroscopy in a three-electrode system. Use of M-PMT-ZN resulted in a higher specific capacitance of 235 F/g. The specific capacitance retention after 500 cycles on M-PMTZN was also higher compared with that of the M-PMT composite. These results indicate that transition metal ion doping enhances the electrochemical properties of the conducting polymer.

Three dimensional electro catalytic oxidation of aniline by boron doped mesoporous activated carbon

S. Karthikeyan,K. Viswanathan,R. Boopathy,P. Maharaja,G. Sekaran 한국공업화학회 2015 Journal of Industrial and Engineering Chemistry Vol.21 No.1

In this report, boron doped mesoporous activated carbon (B-MAC) was synthesized by directhydrothermal route. The prepared B-MAC was characterized for HR-TEM, wide-angle XRD, SEM, XPS,FTIR and N2 sorption analyses. The results suggested that the B-MAC is mesoporous in structure andamorphous in nature, with surface area of 3.036 m2 g 1. The B-MAC was chosen as a catalyst for theelectrochemical oxidation of synthetic aniline solution. For the oxidations process, graphite rod waschosen as anode; SS 316 was chosen as cathode in the electrochemical catalytic oxidation process. Theelectro chemical oxidation of aqueous aniline solution was confirmed through UV–visible spectroscopy,Florescence emission spectrum and cyclic voltammetry analyses. The results revealed that, the removalefficiency of COD and aniline by B-MAC was found to be 76–80% and 80–85%, respectively, in electrocatalytic oxidation. MAC fluidized electro catalytic oxidation system removed COD by 40–45% andaniline by 50–62%, respectively. Thus, the B-MAC catalyst was found to be viable for the electrochemicaltreatment of aniline containing waste water.

Modified Graphene/Polyaniline Nanocomposites for Supercapacitor Application

Sumanta Sahoo,Chapal Kumar Das,G. Karthikeyan,G. C. Nayak 한국고분자학회 2012 Macromolecular Research Vol.20 No.4

This work explored the effect of graphene surface modification on the electrochemical performance of polyaniline-based nanocomposite. The surface modification of graphene was confirmed by Fourier transform infrared spectroscopy. Field emission scanning electron microscopy and high-resolution transmission electron microscopy showed uniform polyaniline coating of the modified graphene. The specific capacitance of the graphene/polyaniline composite was 242 F/g, but it decreased to 193 F/g after graphene modification. However, the capacitance retention increased from 86% to 89% after 500 cycles due to the graphene modification. The thermal stability of the composite also increased after the graphene modification.

Two Statistical Scrutinize of Impact Strength and Strength Reliability of Steel Fibre-Reinforced Concrete

G. Murali,R. Gayathri,V. R. Ramkumar,K. Karthikeyan 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.1

The variations in impact strength of steel Fibre Reinforced Concrete (FRC) were statistically, commanded in this research. For this purpose, the experimental impact test results of earlier researchers were investigated using two statistical approaches. Firstly, normality test was carried out on first crack strength (N1) and failure strength (N2) using distribution plot and its accuracy was verified with Kolmogorov-Smirnov, Shapiro-Wilk and Chen-Shapiro test. Secondly, strength reliability analysis was carried out using two parameter Weibull distribution and their Weibull parameters were determined using three methods viz., Empherical Method of Justus (EMJ), Method of Moments (MOM) and Empherical Method of Lysen (EML). Results suggested that, if three samples are used to determine the N1 value for researchers’ data, at 95% levels of confidence, then the error in the measured value is about 50%. The 0.1 reliability level of the impact strength values of EMJ, EML and MOM were 153, 120 and 153 respectively in case of N1 and were 198, 156, and 198 respectively in case of N2 based on earlier researcher’s data.

A porous activated carbon supported Pt catalyst for the oxidative degradation of poly[(naphthaleneformaldehyde)sulfonate]

Karthikeyan, S.,Jo, Wan-Kuen,Dhanalakshmi, R.,Isaacs, Mark A.,Wilson, Karen,Sekaran, G.,Lee, Adam F. Elsevier 2018 JOURNAL- TAIWAN INSTITUTE OF CHEMICAL ENGINEERS Vol.93 No.-

<P><B>Abstract</B></P> <P>Wet catalytic oxidation of sodium poly[(naphthaleneformaldehyde)sulfonate], a hazardous contaminant of wastewater streams from the textiles industry, by hydrogen peroxide under ambient conditions was explored over platinum supported on a porous activated carbon (PAC). Bulk and surface properties of the Pt/PAC catalyst were investigated by XRD, XPS, SEM, TEM, FTIR, EPR and thermogravimetric analysis. The parent PAC, derived from pyrolysis and subsequent activation of rice husks, exhibited significant micro- and mesoporosity, and a high degree of surface oxidation. Incorporation of 1.7 wt% Pt resulted in mesopore blockage, and a corresponding drop in surface area, associated with the formation of large ∼8 nm metallic nanoparticles. Poly[(naphthaleneformaldehyde)sulfonate] oxidative degradation was studied as a function of reactant concentration and solution pH, revealing first order decomposition kinetics and good activity over pH 3–9 at ambient temperature. Electron Paramagnetic Resonance (EPR)-DMPO spin trapping experiments confirm that oxidation of the organic pollutant proceeded via hydroxyl radical generation. The 1.7 wt% Pt/PAC catalyst showed excellent catalyst stability for five consecutive runs over 25 h in a fluidised bed reactor, delivering > 85% removal of 100 mg/L sulfonate with negligible Pt leaching or activity loss, and comparable performance for treatment of a real tannery effluent stream with a COD equivalent of 1860 mg/L.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A facile route to Pt functionalized biogenically sourced porous activated carbon. </LI> <LI> First heterogeneous catalyst for poly[(naphthaleneformaldehyde)sulfonate] oxidation. </LI> <LI> Excellent activity and stability over a broad concentration and pH range. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Analysis of flexural fatigue failure of concrete made with 100% coarse recycled and natural aggregates

G. Murali,T. Indhumathi,K. Karthikeyan,V.R. Ramkumar 사단법인 한국계산역학회 2018 Computers and Concrete, An International Journal Vol.21 No.3

In this study, the flexural fatigue performance of concrete beams made with 100% Coarse Recycled Concrete Aggregates (RCA) and 100% Coarse Natural Aggregates (NA) were statistically commanded. For this purpose, the experimental fatigue test results of earlier researcher were investigated using two parameter Weibull distribution. The shape and scale parameters of Weibull distribution function was evaluated using seven numerical methods namely, Graphical method (GM), Least-Squares (LS) regression of Y on X, Least-Squares (LS) regression of X on Y, Empherical Method of Lysen (EML), Mean Standard DeviationMethod (MSDM), Energy Pattern FactorMethod (EPFM) andMethod of Moments (MOM). The average of Weibull parameters was used to incorporate survival probability into stress (S)-fatigue life (N) relationships. Based on the Weibull theory, as single and double logarithm fatigue equations for RCA and NA under different survival probability were provided. The results revealed that, by considering 0.9 level survival probability, the theoretical stress level corresponding to a fatigue failure number equal to one million cycle, decreases by 8.77% (calculated using single-logarithm fatigue equation) and 6.62%(calculated using double logarithm fatigue equation) in RCAwhen compared to NAconcrete.

Strength and durability studies on high strength concrete using ceramic waste powder

B. Karthikeyan,G. Dhinakaran 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.61 No.2

This paper summarizes the study on effect of ceramic waste powder as partial substitute to cement in binary blend and along with silica fume in ternary blend high strength concrete in normal and aggressive environments. Strength parameters such as compression & tension and durability indices such as corrosion measurement, deterioration, water absorption and porosity were studied. Ceramic waste powder was used in three different percentages namely 5, 10 and 15 with constant percentage of silica fume (1%) as substitutes to cement in ternary blend high strength concrete was investigated. After a detailed investigation, it was understood that concrete with 15% ceramic waste powder registered maximum performance. Increase of ceramic waste powder offered better resistance to deterioration of concrete.

On-demand generation of heat and free radicals for dual cancer therapy using thermal initiator- and gold nanorod-embedded PLGA nanocomplexes

Guru Karthikeyan Thirunavukkarasu,G.R. Nirmal,이황재,이민규,박인규,이재영 한국공업화학회 2019 Journal of Industrial and Engineering Chemistry Vol.69 No.-

Dual cancer therapy is an attractive strategy that can generate synergistic effects and also reduce drug-related side effects. Here, we developed multifunctional nanocomplexes capable of remote on-demand production of hyperthermia and free radicals in response to near infrared (NIR) light irradiation To this end, thermal initiator and gold nanorods were embedded in nano-sized temperature-responsive poly(lactic acid-co-glycolic acid). In vitro studies demonstrated controllable heat and radical production from the nanocomplexes with NIR and effective eradication of CT26 colon cancer cells with our nanocomplexes. Hence, our smart nanomaterial will potentially contribute precise and effective dual cancer treatment.

Comparative Experimental and Analytical Modeling of Impact Energy Dissipation of Ultra-High Performance Fibre Reinforced Concrete

Murali G,Venkatesh J.,Lokesh N.,Nava Teja Reddy,Karthikeyan K. 대한토목학회 2018 KSCE Journal of Civil Engineering Vol.22 No.8

This study examines the impact energy dissipation capacity of Ultra High Performance Fibre Reinforced Concrete (UHPFRC). Forthis purpose, nine different mixes were fabricated with hooked end and crimped steel fibres at a dosage of 0.5, 1.0, 1.5 and 2.0percentage and tested under pendulum impact test. The impact energy dissipation capacity is assessed based on test (Charpy U-notch)procedure suggested by ASTM E23. Also, an analytical model was adopted to predict the impact energy dissipation value ofUHPFRC and its performance is verified against experimental results. Based on the test results, the impact energy dissipationcapacity of the mixtures containing crimped and hooked end steel fibres were significantly higher than that of Plain Concrete (PC). The hooked end steel fibres had an increased impact energy dissipation capacity compared to crimped steel fibres, which implies thathooked end steel fibre is more appropriate for enhancing the impact energy dissipation of UHPFRC. Also, the modelling datacompared well with experimental data for the fibre volume fraction beyond 0.5%.