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Sathiyanathan, P.,Manjula Dhevi, Dhevagoti,Prabu, Arun Anand,Kim, Kap Jin Trans Tech Publications, Ltd. 2012 Advanced materials research Vol.584 No.-
<P>Thin films of polyvinylidene (PVDF) and its copolymers containing 50 to 30 mole % of trifluoroethylene (TrFE) demonstrate rapid reversal of polarization under applied electric field, and can be used as ferroelectric materials in non-volatile memory devices. In this study, Fourier-transform infrared transmission (FTIR-TS) and grazing incident reflection absorption (FTIR-GIRAS) spectroscopy techniques were used to examine the changes in Curie transition temperature (Tc), chain and dipole orientation in selected VDF copolymer spun-cast films as a subjected to a reversible thermal-cycling treatment. A reversible solid-to-solid β-crystalline phase transition with thermal hysteresis and a favorable C-F dipole orientation along the electric field direction were observed for the sample subjected to thermal-cycling below its melting point (Tm). An irreversible β-crystalline phase transition with unfavorable C-F dipole orientation was observed for the sample treated to heating-cooling cycle above Tm. The results are reported in detail here.</P>
Design and Analysis of Universal Power Converter for Hybrid Solar and Thermoelectric Generators
Sathiyanathan M.,Jaganathan S.,Josephine R. L. 전력전자학회 2019 JOURNAL OF POWER ELECTRONICS Vol.19 No.1
This work aims to study and analyze the various operating modes of universal power converter which is powered by solar andthermoelectric generators. The proposed converter is operated in a DC–DC (buck or boost mode) and DC–AC (single phase)inverter with high efficiency. DC power sources, such as solar photovoltaic (SPV) panels, thermoelectric generators (TEGs), andLi-ion battery, are selected as input to the proposed converter according to the nominal output voltage available/generated bythese sources. The mode of selection and output power regulation are achieved via control of the metal-oxide semiconductorfield-effect transistor (MOSFET) switches in the converter through the modified stepped perturb and observe (MSPO) algorithm. The MSPO duty cycle control algorithm effectively converts the unregulated DC power from the SPV/TEG into regulated DCfor storing energy in a Li-ion battery or directly driving a DC load. In this work, the proposed power sources and converter aremathematically modelled using the Scilab-Xcos Simulink tool. The hardware prototype is designed for 200 W rating with adsPIC30F4011 digital controller. The various output parameters, such as voltage ripple, current ripple, switching losses, andconverter efficiency, are analyzed, and the proposed converter with a control circuit operates the converter closely at 97% efficiency.
Ponnan Sathiyanathan,Dhevagoti Manjula Dhevi,Arun Anand Prabu,김갑진 한국고분자학회 2019 Macromolecular Research Vol.27 No.8
In this study, neat polyvinylidene fluoride (PVDF), PVDF/polyoctafluoropentyl acrylate (PFA, 90/10 w/w) and PVDF-PFA/hydroxyapatite (HAP, 0 to 20 wt% HAP w.r.t. PVDF-PFA content) were electrospun under controlled conditions, and studied for their piezo-responsive behaviours as a function of nanoweb stacking arrangement (constructive and destructive) and folding architectures (simple, series and parallel connection of electrodes between each folding). Influence of varying HAP content (0, 3, 7, 10, and 20 wt%) on the molecular orientation of CH2-CF2 dipoles in PVDF-PFA/HAP blends were investigated using FTIR, XRD and SEM analysis. Quantitative analysis showed increased β-crystalline content for the 7 wt% HAP sample. From the peak-to-peak output voltage, 7 wt% HAP sample exhibited significantly higher output voltage (Vp-p = 1.21 V) compared to neat PVDF-PFA sample (Vp-p = 0.46 V). Overall, the combinative effect of HAP addition and folding played a vital role in improving the piezoelectric output signals of PVDF-PFA/HAP, which signifies the importance of this study.
Synthesis of Pt Decorated Copper Oxide Nanoleaves and Its Electrochemical Detection of Glucose
Felix, Sathiyanathan,Chakkravarthy, Bala Praveen,Jeong, Soon Kwan,Grace, Andrews Nirmala The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.6
<P>A novel platinum decorated CuO nanoleaves were synthesized through a facile co-precipitation method and further utilized as a sensing platform for glucose based on immobilization of Pt-CuO hybrid nanostructures with Nafion matrix. The prepared composites were characterized by X-ray Diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The modified electrode exhibits excellent electrocatalytic activity towards glucose as probed by cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Comparing with pure CuO/Nf/GCE, Pt-CuO/Nf/GCE, as non-enzymatic electrode materials, exhibited a good response towards glucose with linear range 2–1000 μM with a higher sensitivity of 1681.7 μA mM<SUP>−1</SUP>cm<SUP>−2</SUP> and detection limit of 11 μM. The excellent electrocatalytic performances could be attributed to the Cu(II)/Cu(III) multiple oxidation states system could promote the redox reactions between electrode materials and glucose, and the electroactive sites became more active due to the synergic effect. The results, high sensitivity, excellent selectivity and long term stability showing that, Pt-CuO is a promising material for the future development of nonenzymatic glucose sensors.</P>
Ponnan Sathiyanathan,Arun Anand Prabu,김갑진 한국고분자학회 2016 Macromolecular Research Vol.24 No.8
In this study, neat polyvinylidene fluoride (PVDF) and its blend with polyoctafluoropentyl acrylate (POFPA) were electrospun under controlled conditions, and studied for their physico-mechanical and piezo-responsive behaviours. Initial FTIR studies confirmed the effect of thermal annealing on the crystalline phase transformations and chaindipole orientation in PVDF as a function of POFPA content. SEM data exhibited “root-shaped” morphology in the blend sample. Higher tensile strength (65.2±0.4 kPa) for the blend compared to that of neat PVDF (1.5±0.03 kPa) confirmed the elastic nature of the blend nanoweb. Peak-to-peak piezoelectric output signal (Vp-p 0.976 V) and capacitance hysteresis showed reduced tendency, whereas the capacitance maxima is higher for the blend sample (Cmax 0.182 nF) compared to that of neat PVDF (Vp-p 1.195, Cmax 0.147 nF). Overall, even 10 wt% addition of POFPA in PVDF greatly enhanced the tensile strength of nanofiber web along with improved piezocapacitive characteristics, a combination of great potential for many commercial sensor applications.
가줄라 프라사드,Ponnan Sathiyanathan,Arun Anand Prabu,김갑진 한국고분자학회 2017 Macromolecular Research Vol.25 No.10
In this paper, the crystallinity changes in polyvinylidene fluoride (PVDF) as function of varying phase-separation temperatures (0 to 90 oC) and chloride salts (BaCl2, CaCl2, CoCl2, NaCl, SnCl2, N2H6Cl2) were investigated. FTIR quantitative analysis showed higher β-crystalline and lower α-crystalline content for 70oC phase-separated PVDF and 70 oC phase-separated PVDF-CaCl2 (15wt%) samples. XRD and DSC studies also confirmed the influence of 70 oC phase-separation temperature and CaCl2 salt in improving the β-crystallinity in PVDF compared to the neat PVDF sample. Since higher β-crystalline content is favoured for use in piezoelectric applications, these two sample preparation conditions were optimized for use in piezoelectric studies. Electrospun nanowebs of the selected samples were measured for their piezoelectric output signals under applied pressure of 1 kgf and released periodically at 0.5 Hz. From the peak-to-peak output voltage, 70 oC phase-separated PVDF-CaCl2 sample exhibited significantly higher output voltage (+0.89 V) compared to neat PVDF (+0.48 V) and 70 oC phase-separated PVDF (+0.53 V) samples. These results conclude that the combinative effect of phase-separation temperature and metal salt addition plays a vital role in improving the piezoelectric characteristics of PVDF, which signifies the importance of this study.
Synthesis of Cobalt Sulfide–Graphene (CoS/G) Nanocomposites for Supercapacitor Applications
Ramachandran, Rajendran,Felix, Sathiyanathan,Saranya, Murugan,Santhosh, Chella,Velmurugan, Venugopal,Ragupathy, Bala Praveen Chakkravarthy,Soon Kwan Jeong,Grace, Andrews Nirmala IEEE 2013 IEEE TRANSACTIONS ON NANOTECHNOLOGY Vol.12 No.6
<P>Cobalt sulfide (CoS) and graphene nanocomposites were prepared from cobalt nitrate, thioacetamide, and graphene as starting materials in the presence of poly(vinylpyrrolidone) as surfactant. Furthermore, its morphology and properties were characterized by X-ray diffraction (XRD), field-emission scanning electron microscope, diffusive reflectance ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, and electrochemical measurements. The XRD reveals the amorphous nature of the nanocomposites. The as-prepared nanocomposites were tested for its supercapacitance property by cyclic voltammetric (CV) experiment in 6M KOH electrolyte. CV was performed at a potential range of 0 to -0.8 V at different scan rates, and results show an excellent capacitive behavior of the nanocomposites. A maximum specific capacitance of 2423.3 F/g was obtained at a scan rate of 5 mV/s.</P>