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D. Gopi,P.R. Bhalaji,V.C.A. Prakash,A.K. Ramasamy,L. Kavitha,J.M.F. Ferreira 한국물리학회 2011 Current Applied Physics Vol.11 No.3
A method to synthesize hydroxyapatite (HAP) ceramic powders using a metal-oxalate route with calcium chloride and phosphoric acid as calcium and phosphorus precursors respectively is described. Ethylene glycol was used as a reaction medium and oxalic acid as a chelating agent. The resulting HAP powders were calcined at 600 ℃ for 6 h and subsequently sintered at 900 ℃ for 2 h. FT-IR, XRD and SEM techniques were employed for the characterization of the synthesized particles. Moreover, the influence of reaction temperature on the HAP formation was also studied. The results have shown successful formation of the crystalline, uniform sized, uniform shaped and stoichiometric HAP powders at a reaction temperature of 75 ℃ which was found to be the optimum temperature for the preparation. The grain size of the synthesized sample was 680 nm in length and 440 nm in width.
Kim, Hee‐,Je,Yeo, Tae‐,Bin,Kim, Soo‐,Kyoung,Rao, S. Srinivasa,Savariraj, A. Dennyson,Prabakar, K.,Gopi, Chandu V. V. M. WILEY‐VCH Verlag 2014 European journal of inorganic chemistry Vol.2014 No.26
<P><B>Abstract</B></P><P>Metal sulfide electrodes were compared to a conventional platinum (Pt) counter electrode (CE) in quantum‐dot‐sensitized solar cells (QDSSCs), in which they were used to improve the short circuit current, fill factor, and conversion efficiency (<I>η</I>). We deposited optimal‐temperature‐based nickel sulfide (NiS) thin films on a fluorine‐doped tin oxide (FTO) substrate by a facile chemical bath deposition method and successfully employed them as a highly efficient CE for QDSSCs. The obtained NiS thin‐film nanoparticles exhibit high electrocatalytic performance and fast mass transfer rates toward the polysulfide electrolyte. Under the illumination of one sun (100 mW cm<SUP>–2</SUP>), the QDSSC with a NiS CE produces a higher <I>η</I> of 3.30 %, which is much higher than that of a Pt CE (1.89 %). Cyclic voltammetry, electrochemical impedance spectroscopy, and Tafel polarization measurements were performed to investigate the electrocatalytic activity of the NiS CE toward polysulfide electrolyte.</P>
Gopi, Chandu V.V. Muralee,Somasekha, A.,Reddy, Araveeti Eswar,Kim, Soo-Kyoung,Kim, Hee-Je Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.435 No.-
<P><B>Abstract</B></P> <P>Herein, for the first time, we demonstrate the fabrication of Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> hybrid nanostructures on Ni foam substrate by facile one-step hydrothermal technique. Morphological studies reveal that aggregated Fe<SUB>2</SUB>O<SUB>3</SUB> nanoflakes anchored on the surface of sphere-like LiCoO<SUB>2</SUB> nanoflakes. Electrochemical studies are used to examine the performance of the supercapacitor electrodes. The composite Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode exhibited excellent electrochemical performance than Fe<SUB>2</SUB>O<SUB>3</SUB> and LiCoO<SUB>2</SUB> electrodes, such as a low charge transfer resistance, a high specific capacitance of 489 F g<SUP>−1</SUP> at 5 mA cm<SUP>−2</SUP> and an enhanced capacity retention of 108% over 3000 cycles at 15 mA cm<SUP>−2</SUP>. The composite Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> holds great promise for electrochemical applications due to well-defined hierarchical morphology, synergetic effect of Fe<SUB>2</SUB>O<SUB>3</SUB> and LiCoO<SUB>2</SUB>, enhanced electrical conductivity, efficient electrolyte penetration and fast electron transfer.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> composites successfully fabricated by facile hydrothermal route. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> shows unique surface morphology with large surface area and superior conductivity. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode exhibit excellent supercapacitor performances. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>@LiCoO<SUB>2</SUB> electrode shows superior cycling stability with retention of 108%. </LI> </UL> </P>
P. Gopi Krishnan,R. Srinivasan,D. Pritima,A. Bovas Herbert Bejaxhin 한양대학교 청정에너지연구소 2023 Journal of Ceramic Processing Research Vol.24 No.6
Friction stir welding (FSW) is a green manufacturing process that does not liberate smoke, fume and odour unlike the conventionalarc welding. This research article aims at finding the ultimate tensile strength of the Aluminium matrix compositeswelded by FSW with the process parameters such as tool rotation speed, weld traverse speed and axial force. The searchoptimization is carried out in two phases using MATLAB environment. Firstly, the regression equation of the experimentsis utilized to find the better design points by Genetic Algorithm (GA) through pool generation, cross-over and mutation. Secondly, the top design points obtained in GA are stored in a new pool, from which the global best optimal design is selectedby Firefly Algorithm (FA). Since, every algorithm has different features and highlights, the coupled GA-FA algorithm isutilized to obtain the optimal point that gives the best ultimate tensile strength of the welded composite. The results demonstratethat the optimal points are distributed in several points of design space that needs to be searched out by the effectiveoptimization strategy. The convergence rate, speed of the optimization and coverage of the design points are also improved. The algorithm shows good agreement with the confirmation tests also with errors less than 5%.
Study on effect of welding speed on friction stir welded aluminium metal matrix hybrid composite
P. Gopi Krishnan,B. Suresh Babu,S. Madhu,S. J. Gowrishankar,C. Bibin,S. Saran,S. Shree Ram,A. R. Sri Hari,S.Vidyasagar 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.5
The development of aluminum series matrix hybrid composites with ceramic reinforcements has recently caught the interestof new researchers. The addition of more than one or two reinforcements in aluminium alloy leads to the fabrication of theAluminium Metal Matrix Hybrid Composite (AMMHC). The present investigation is aimed at the development of newlydeveloped AMMHC followed by friction stir welding for obtaining the improved mechanical properties. The stir castedAA6063 with reinforcement of 5%, 10% and 15% wt. Silicon Carbide (SiC) and 10% wt. Boron Carbide (B4C) werefabricated by stir casting technique and the AMMHC with 10% each of SiC and B4C showed higher mechanical properties. Further the AMMHC are joined by friction stir welding (FSW) route. A prime experimental work has been tried out in theFSW process by varying welding speed (20, 30, 40, 50 and 60 mm/min). The effect of welding speed on AMMHCs were studiedon macro and microstructural observations followed by micro hardness and ultimate tensile. Strength, in which 40 mm/minof welding speed gives better properties than other processing condition. The weldment reveals the better joint strength withthe presence of fine particle dispersion in the microstructure.
S.K. Chaudhary,A. B. Mandal,R.Bhar,M. Gopi,A. Kannan,S. E. Jadhav,J.J. Rokade 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.1
Objective: This study investigated the effects of soapnut (Sapindus mukorossi) shell powder (SSP) on serum hormone level, egg quality, semen characteristics and reproductive performance of broiler breeders fed with a maize-soybean meal based diet. Methods: Ninety six female and twenty four male CARIBRO-VISHAL broiler breeders, 38-week old, were individually caged and randomly allocated to four treatment groups (24 female breeders/treatment and 6 male breeders/treatment): an un-supplemented control (T1) and three groups with 0.0176% SSP (group T2), 0.026% SSP (group T3) and 0.0528% SSP (group T4), to have supplementary saponin at 0, 50, 75, and 150 ppm, respectively, for 42 days. Results: The results indicated that serum (p<0.001) and seminal plasma (p<0.05) testosterone level, semen volume (p<0.001), mass motility (p<0.001), and live spermatozoa count (p<0.001) was increased in groups T3 and T4 compared to T2 and control groups. Compared with control group, total sperm count was increased (p<0.001) and dead spermatozoa count was decreased (p<0.001) in SSP supplemented groups. Supplementation of SSP did not affected the quality of egg lay. Compared with control group, fertility (p<0.01) and hatchability (total eggs set and fertile eggs set) (p<0.001) were significantly improved in SSP supplemented groups with the highest improvement in T3 treatment group. Embryonic death was decreased (p< 0.001) in SSP supplemented groups compared to control; lowest embryonic death was recorded in T3 treatment group. Conclusion: Thus, it was concluded that dietary supplementation of 0.026% SSP (saponin equivalent 75 ppm) improved the reproductive performance of broiler breeders.
High performance of TiO2/CdS quantum dot sensitized solar cells with a Cu-ZnS passivation layer
Lee, Y. S.,Gopi, C. V.,EswarReddy, A.,Nagaraju, C.,Kim, H. J. CNRS 2017 NEW JOURNAL OF CHEMISTRY Vol.41 No.5
<P>The Cu-ZnS passivation layer is considered to be far more efficient than the most widely used ZnS passivation layer in terms of enhancement of light harvesting and suppression of surface charge recombination. As a result, a TiO2/CdS/Cu-ZnS quantum dot sensitized solar cell (QDSSC) exhibits a greatly improved efficiency of 3.35%, which is 30% and 82% higher than that of TiO2/CdS/ZnS and TiO2/CdS based QDSSCs, respectively.</P>
Kim, Ki Hean,Burns, James A.,Bernstein, Jonathan J.,Maguluri, Gopi N.,Park, B. Hyle,de Boer, Johannes F. Optical Society of America 2010 Optics express Vol.18 No.14
<P>We present in-vivo 3D human vocal fold images with polarization sensitive optical coherence tomography (PS-OCT). Characterizing the extent and location of vocal fold lesions provides useful information in guiding surgeons during phonomicrosurgery. Previous studies showed that PS-OCT imaging can distinguish vocal fold lesions from normal tissue, but these studies were limited to 2D cross-sectional imaging and were susceptible to sampling error. In-vivo 3D endoscopic imaging was performed by using a recently developed 2-axis MEMS scanning catheter and a spectral domain OCT (SD-OCT), running at 18.5 frames/s. Imaging was performed in the operating room with patients under general anesthesia and 3D images were acquired either by 2D scanning of the scanner on the sites of interest or by combining 1D scanning and manual sliding to capture whole length of the vocal fold. Vocal fold scar, polyps, nodules, papilloma and malignant lesions were imaged and characteristics of individual lesions were analyzed in terms of spatial distribution and variation of tissue structure and birefringence. The 3D large sectional PS-OCT imaging showed that the spatial extent of vocal fold lesions can be found non-invasively with good contrast from normal tissue.</P>
Oxidation of vanillin by peroxomonosulphate-thermodynamic and kinetic investigation
S. Kutti Rani,S. Nirmal Kumar,Crystal Y. Wilson,A. Gopi,D. Easwaramoorthy 한국공업화학회 2009 Journal of Industrial and Engineering Chemistry Vol.15 No.6
The oxidation of vanillin by peroxomonosulphate (PMS) in acetic acid–sodiumacetate bufferedmedium was carried out at 308 K. The rate was first order with respect to [vanillin] and [PMS]. The rate increased with increase in pH and the rate was too fast to be measured at pH 5.2. The rate increased with increase in [acetate] and the plot of kobs versus [acetate] was a straight line with positive intercept. Variation of ionic strength had no effect on the rate of the reaction. Effects of polarity were studied with five different solvents and in all the cases, log kobs versus 1/e were linear with negative slope. The reaction had been carried out at four different temperatures and the activation and thermodynamic parameters were calculated. The product of oxidation was confirmed as vanillic acid by IR, 1H NMR and GC-MS spectral analysis. Based on the results obtained a reaction scheme had been proposed and the rate law was derived.