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Enhanced critical current density (J(c)) and fractural strength of low and high Eu level doped bare bulk (Bi, Pb)-2223 rods for cryogenic applications
No full textThe effect of Eu doping (0 to 0.12 M%) on magnetic field dependence of transport critical current density (J(c)) and diametral fracture strength (sigma) of the bare bulk 100mm long (Bi, Pb)-2223 rods is reported. An enhancement in Jc on Eu doping has been observed for low Eu levels/low-magnetic fields and for high Eu levels in relatively high magnetic fields. The diametral fracture strength (sigma) has also increased for both low and high Eu levels. In addition these studies, contact resistivity and magneto are also explored. Thermal cycling tests were performed 50 times to check the long term reliability of these rods by observing any degradation in Jc and contact resistivity which exhibits nearly no change in their values. The nature of flux pinning centers responsible for the low Eu level/low field and high Eu level/high field has been discussed. The improvement in both the transport Jc as well as of s by low/high Eu doping evidences long-term reliability and high importance for potential applications of these bare bulk (Bi, Pb)-2223 rods in low as well as high fields
Enhanced multiferroic and magnetoelectric properties of Ni-0.92(Cu0.05Co0.03)Fe2O4/Ba1-xCaxZr0.10Ti0.90O3 lead-free composite films
No full textThe search for lead-free high performance magnetoelectric multiferroic materials at room temperature continues to be stimulated from the perspective of designing environmentally friendly multifunctional devices. In this context, lead-free composite thin films consisting of Ba1-xCaxZr0.10Ti0.90O3 (BCZT, x = 0, 0.10 and 0.15) as the ferroelectric/piezoelectric phase and Ni-0.92(Cu0.05Co0.03)Fe2O4 (NCCFO) as the ferromagnetic/magnetostrictive component have been grown on Pt/TiO2/SiO2/Si substrates via chemical solution spin-coating method. The phase and structural evolutions of two distinct pure phases of as grown NCCFO/BCZT composite films were confirmed using X-ray diffractrometry (XRD) and field emission scanning electron microscopy (FE-SEM). The multiferroic, magneto-dielectric and magnetoelectric properties of the NCCFO/BCZT composite films have been investigated. Moreover, significant enhancement of multiferroic properties and magnetoelectric effect was observed in these composite films when compared to those reported recently for other lead-free BCZT based multiferroic composites. The magnetic studies demonstrate that the NCCFO/Ba0.90Ca0.10Zr0.10Ti0.90O3 (NCCFO/BCZT10) composite film exhibits a large saturation and remnant magnetization of M-s similar to 346.2 emu/cm(3) and M-r similar to 73.5 emu/cm(3) respectively having a coercive field of H-c similar to 73.5 Oe. The NCCFO/BCZT10 composite film also exhibits good ferroelectric properties with saturation polarization P-s similar to 26.7 mu C/cm(2), remnant polarization P-r similar to 8.9 mu C/cm(2) and coercive field E-c similar to 82.7 kV/cm. The observed magneto-dielectric effect is of two orders higher than those reported for other lead-free multiferroic composites. A maximum magnetoelectric voltage coefficient of alpha(ME) similar to 22.4 mVcm(-1) Oe(-1) is obtained for the NCCFO/BCZT10 composite film. The observed results suggest that the NCCFO/BCZT composite films are potential lead-free multiferroic systems at room temperature
Enhanced near infrared luminescence in Ag@Ag2S core-shell nanoparticles
No full textAg-Ag2S core-shell nano-structured particles, prepared by soft chemical route, were found to be luminescent in the near-infrared (NIR) range. The silver nanoparticles were pre-synthesized with size control by poly-vinylpyrrolidone (PVP) polymer capping from silver nitrate solution, by reduction using sodium borohydride in solution, which were further subjected to reaction with sulfur ions in the later stage by mixing controlled amount of Na2S in the solution. With increasing concentration of sulfur ions, the plasmonic peak of Ag showed progressive blue shift and damping, leading to final diminishment. Enhanced NIR luminescence obtained from Ag@Ag2S core-shell nanoparticles were found to be asymmetric and blue shifting with reduced intensity and increasing sulfur ion concentration. The mechanism behind such a beha vior is predicted due to formation of composite layer of Ag2S-Ag both at the surface and the volume, with Ag core at the center, diminishing in size with increasing sulfur concentration. The structure, chemical composition, morphology and final core-shell structure formation were further established by combination of X-ray diffractometry (XRD), X-ray Photoelectron Spectroscopy (XPS) and Transmission Electron Microscopy (TEM) analysis
Enhancement of dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal mixture by dispersing nano-sized copper oxide
No full textHere, we present the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared ferroelectric liquid crystal (FLC) mixture, namely W302. The FLC mixture, comprising of pyrimidine compounds, was characterised through dielectric spectroscopy, differential scanning calorimetry (DSC), polarising optical microscopy (POM) and other electro-optical methods. The material parameters such as spontaneous polarisation, rotational viscosity, response time and tilt angle of W302 were found to be 14 nC/cm(2), 240 mPa.s, 150 mu s and 28(& x1d3c;), respectively. The phase transition temperatures of W302 were observed through DSC and further confirmed by the dependence of dielectric loss factor in homogeneously aligned FLC sample with temperature. We also demonstrate the observance of a low-frequency dielectric relaxation mode due to the unwinding of the helix, called as partially unwound helical mode (p-UHM) along with Goldstone mode. The behaviour of p-UHM has been systematically studied with temperature and applied bias field. Further, dispersion of nCuO into host W302 has shown a significant increase in dielectric permittivity. Also, the p-UHM relaxation peak in the dielectric regime has disappeared with the incorporation of nCuO. These studies would be useful to fabricate better electro-optical devices for display, switching and beam steering applications. The formulation and characterization of a ferroelectric liquid crystal (FLC) mixture W302 composed of pyrimidine compounds is presented. Then, we observed the effect of copper (II) oxide nanoparticles (nCuO) on dielectric and electro-optical parameters of a newly prepared and characterized FLC mixture
Magnetic field control of polarization/capacitance/voltage/resistance through lattice strain in BaTiO3-CoFe2O4 multiferroic nanocomposite
No full textMagnetoelectric (ME) nanocomposites is a topic of intensive research due to their superficial potential in spintronic applications. In the present work, the magnetic field controlled electrical polarization is studied in hydrothermally synthesized multiferroic 0.25BaTiO(3)-0.75CoFe(2)O(4) (BTO-CFO) nanocomposite. This multiferroic heterostructure is combined ferrimagnetic (CFO) with ferroelectric/piezoelectric (BTO) and achieved strain-mediated ME effect, which can effectively mediate magnetic anisotropy. The X-ray diffraction pattern confirmed polycrystalline phases of spinel CFO and tetragonal BTO, for which the compressive lattice strain is made. The microstructural study has evaluated BTO-CFO nanoparticles formation and the value of d-lattice spacing is calculated. The room temperature magnetic hysteresis is arising which depends on CFO inversion degree, and the change in bond-angle/length along A and B-sites. The ferroelectric hysteresis is measured at room temperature, which changed with applied magnetic field, i.e., the phenomenon of reduction in domain wall pinning related with oxygen vacancies and grain boundaries effect. The magnetic field is also influenced impedance spectra to induce magnetoimpedance effect and the positive value of magnetoresistance is obtained. A giant magnetodielectric coefficient up to - 27% is obtained at 1 kOe of field. A strain mediated ME coupling enhancement is obtained
Cauliflower-shaped ternary nanocomposites with enhanced power and energy density for supercapacitors
No full textThe present research work aimed to study the electrochemical performance of the rGO/PPY/PANI ternary nanocomposite electrodes for supercapacitor applications. The nanocomposites have been prepared by physical blending of rGO with conducting polymers PANI and PPY in five different ratios. The prepared nanocomposites were examined by XRD, IR, Raman, SEM, and XAS characterizations, and from the results, it was found that ternary nanocomposites formed in cauliflower shape, in which PPY and PANI nanoparticles are decorated on to the rGO matrix. In addition, the electrochemical performance of the prepared nanocomposites were studied using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopic studies. The highest values of capacitance, energy density, and power density values achieved were 317.5 F/g, 254 Wh/kg, and 1508.9 W/kg for nanocomposite, respectively, as expected from the synergistic properties of two types of electrode materials resulting in the nanocomposites with hybrid and improved properties. Further, the cyclic stability was also analyzed by performing 4000 long cycles, and the retained capacitance during such long cycles indicates the high potential of rGO/PPY/PANI ternary nanocomposites as electrodes for future energy requirement
Development and Long-Term Stability Assessment of Co-C Eutectic Fixed Point for Thermocouple Thermometry
No full textThe long-term stability assessment on the Co-C eutectic fixed point cell indigenously developed at CSIR-National Physical Laboratory, India is presented. Metal-carbon eutectic fixed points are promising candidates for the direct traceability to high-temperature thermometry and radiometry. The acceptance of any fixed point as a temperature reference cell depends on its repeatability, reproducibility, and long-term stability. In this paper, we report the detailed investigations on development and realization of Co-C cell and comparison of successive 3-year data to evaluate the long-term stability and robustness of cell. We assigned melting transition temperature to Co-C cell by using Type-S thermocouple, calibrated on ITS-90 fixed points. The cell has been subjected for 270h of melt-freeze cycle since its construction in 2014 and exhibits excellent thermo-mechanical stability. The Co-C melting transition temperature and measurement uncertainty were estimated by using the same Type-S thermocouple, for 3years from 2015 to 2017, and overall drift for the cell was estimated to be 0.1 degrees C, after normalizing the drift of the thermocouple
Development of electrochemical biosensor based on CNT-Fe3O4 nanocomposite to determine formaldehyde adulteration in orange juice
No full textAn electrochemical biosensor was developed to determine formaldehyde (HCHO) adulteration commonly found in food. The current responses of various electrodes based on multiwalled carbon nanotubes (CNTs) and synthesized nanocomposite (CNT-Fe3O4) were measured using cyclic voltammetry. The nanocomposite based biosensor shows comparatively high sensitivity (527 mu Amg/L(-1)cm(-2)), low detection limit (0.05mg/L) in linear detection range 0.05-0.5mg/L for formaldehyde detection using formaldehyde dehydrogenase (FDH) enzyme. In real sample analysis, the low obtained RSD values (less than 1.79) and good recovery rates (more than 90%) signify an efficient and precise sensor for the selective quantification of formaldehyde in orange juice. The developed biosensor has future implications for determining formaldehyde adulteration in citrus fruit juices and other liquid foods in agri-food chain to further resolve global food safety concerns, control unethical business practices of adulteration and reduce the widespread food borne illness outbreaks
Effect of spin-orbit interaction on the vortex dynamics in LaAlO3/SrTiO3 interfaces near the superconducting transition
Get PDFControlling spin-orbit interaction and its effect on superconductivity has been a long-standing problem in two-dimensional inversion-symmetry-broken superconductors. An open challenge is to understand the role of various energy scales in shaping the complex phase diagram in these systems. From a combined experimental and theoretical study of resistance fluctuations and its higher-order statistics, we propose a phase diagram for the superconducting phase in the magnetic-field-spin-orbit interaction energy plane for the quasi-two-dimensional electron gas at the interface of LaAlO3/SrTiO3 heterostructures. The relative variance of resistance fluctuations increases by few orders of magnitude below the spin-orbit field B-SO and a non-Gaussian component to the fluctuations arises for fields below the upper critical field B-c2. Theoretical calculations show that the non-Gaussian noise predominantly arises due to percolative nature of the superconducting transition. We quantify the strength and the relative importance of the spin-orbit interaction energy, Zeeman energy, and the pairing potential. Our work highlights the important role played by the interplay between these energy scales in framing the fascinating phases seen in two-dimensional inversion-symmetry-broken superconductors
Enhanced dielectric properties and theoretical modeling of PVDF–ceramic composites
No full textThe ceramic-polymer composites, consisting of (Bi0.5K0.5)(Fe0.5Nb0.5)O-3 [BKFN] as fillers and poly (vinylidene fluoride) (PVDF) as matrix, with different ratios (weight ratio of BKFN to PVDF, are 10%, 30% and 50%) have been prepared by using a solution casting method. The X-ray diffraction (XRD) pattern evidenced a semi-crystalline structure containing mixed alpha-, beta- and gamma- phases of PVDF which was further confirmed by Fourier transform-infrared spectroscopy. Using scanning electron micrograph, the dispersion of the particulate filler in PVDF matrix is examined. With an increase of BKFN content, in the BKFN-PVDF composite films, both the dielectric constant and remnant polarizations showed a remarkable increase as compared to those of PVDF. Different theoretical models were proposed with experimental data to determine the effective dielectric constants of the prepared composites. Also, increased optical band gap is observed due to addition of BKFN in PVDF