Department of Physics

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The nanostructured Na3V2(PO4)3 (NVP) cathode material has been synthesized using the sol-gel route for different molar fractions of citric acid as a carbon source during the synthesis. The nanostructured NVP as cores with carbonic shell structures are fabricated with two different citric acid molar ratios. The thermal treatment has been optimized to convert the amorphous carbon shell into graphitic carbon to realize the better electrical conductivity and thus effective electron transfer during the electrochemical charge transfer process. The X-ray diffraction measurements confirmed the rhombohedral crystallographic phase (space group R-3c) with average crystallite size ~28 ± 5 nm. The coin cells are assembled in a hybrid rechargeable electrochemical cell configuration with lithium as a counter electrode and LiPF6-EC:DEC:DMC (1:1:1 ratio) as the electrolyte. The electrochemical charge/discharge measurements are carried out at C/10 and C/20 rates and the measured specific capacities are 80 and 120 mAhg−1 for samples with lower and higher citric acid molar ratios, respectively. The studies suggest that NVP can be used as an effective cathode material in hybrid electrochemical cells, and a higher concentration of citric acid may result in the effective carbonic shell for optimal electron transfer and thus enhanced electrochemical performance. © 2017, Springer-Verlag Berlin Heidelberg.

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Ionics

Electrochemical behavior of carbonic precursor with Na3V2(PO4)3nanostructured material in hybrid battery system

We investigated the effect of gadolinium doping (1-5 at.%) on the magnetic and dielectric properties of Fe3O4 nanoparticles, synthesized by the chemical co-precipitation technique, primarily to understand the onset of multifunctional properties such as ferroelectricity and magnetodielectric coupling. The substitution of larger Gd3+ ions at smaller Fe3+ octahedral sites in inverse spinel Fe3O4 has significantly influenced the morphology, average crystallite size, and more importantly, the magneto-crystalline anisotropy and saturation magnetization. The magneto-crystalline anisotropy and the saturation magnetization decreases substantially, however, significant increase in the average crystallite size is observed upon Gd doping. Furthermore, temperature-dependent dielectric studies suggest that these nanoparticle systems exhibit relaxor ferroelectric behavior, with much pronounced ferroelectric polarization moment recorded for 5 at.% Gd doped Fe3O4 as compared to its undoped counterpart. © 2017 The American Ceramic Society

Fulltext

Journal of the American Ceramic Society

Ferroic ordering and charge-spin-lattice order coupling in Gd-doped Fe3O4 nanoparticles relaxor multiferroic system

Quaternary compound semiconductor Cu2ZnSnS4 (CZTS) has been prepared using two different precursors sols, chlorides and nitrates, using spin coating process to get phase pure and less defective thin films for solar photovoltaics. The synthesized CZTS thin films are heat treated at different temperatures to achieve the kesterite crystallographic phase. The prepared thin films are highly textured along (112) axis. The surface microscopic images suggest that chloride precursor derived CZTS thin films are relatively uniform and densely packed as compared to nitrate precursors. The dislocation density is ∼1 × 1016 lines m-2 for the chloride precursor derived thin films, much lower than that of the nitride precursor derived CZTS thin films. The optical absorption measurements suggest the direct optical gap ∼1.52 eV for CZTS thin films derived from both the precursor routes. However, electrical resistivity measurements suggest that resistivity is uniform and much lower ∼0.025 Ω cm for chloride precursor CZTS thin films, alike nitride precursor CZTS thin films, where resistivity is three orders of magnitude higher ∼30 Ω cm. These studies suggest that chloride precursor derived CZTS thin films are of high quality and can be used for solar photovoltaic applications. © 2017 Author(s).

Journal of Renewable and Sustainable Energy

Effect of precursor and composition on the physical properties of the low-cost solution processed Cu2ZnSnS4 thin film for solar photovoltaic application

Nanostructured multiferroic BiFeO3 powder has been synthesized using sol–gel route followed by optimized post-annealing treatment. The phase pure rhombohedral structure of prepared powder was confirmed by X-ray diffraction and Fourier transform infrared studies. The room temperature weak ferromagnetic nature (~ 0.15 emu/g) exhibited by the nanocrystalline BiFeO3 sample (~ 50 nm) is attributed to the canted spin ordering in the sample. The BiFeO3/NBR rubber composites, with 50–80 wt% filler loading fractions, show the dual band resonating microwave (MW) absorption behavior. The reflection loss (R.L.) values enhanced and required absorber thickness reduced simultaneously with increasing BiFeO3 loading fraction in composite samples. These results confirm that the ferroelectric properties of multiferroic BiFeO3 are contributing significantly for the observed MW absorption with respect to the magnetic contribution. © 2017, Springer-Verlag GmbH Germany.

Applied Physics A: Materials Science and Processing

Ferroelectrically induced dual band microwave absorption in multiferroic BiFeO3/acrylo-nitrile butadiene rubber composites

The gel to carbonate precipitate route has been used for the synthesis of Ni1-x Znx Fe2 O 4 (x = 0, 0.25, 0.5 and 0.75) bulk inverse spinel ferrite powder samples. The optimal zinc (50%) substitution has shown the maximum saturation magnetic moment and resulted into the maximum magnetic loss tangent (tanδm) &gt; -1.2 over the entire 2-10 GHz frequency range with an optimum value ∼-1.75 at 6 GHz. Ni 0.5 Zn 0.5 Fe2 O 4 - Acrylo-Nitrile Butadiene Rubber (NBR) composite samples are prepared at different weight percentage (wt%) of ferrite loading fractions in rubber for microwave absorption evaluation. The 80 wt% loaded Ni 0.5 Zn 0.5 Fe2 O 4 /NBR composite (FMAR80) sample has shown two reflection loss (RL) peaks at 5 and 10 GHz. Interestingly, a single peak at 10 GHz for 3.25 mm thickness, can be scaled down to 5 GHz by increasing the thickness up to 4.6 mm. The onset of such twin matching frequencies in FMAR80 composite sample is attributed to the spin resonance relaxation at ∼5 GHz (f m1) and destructive interference at λm /4 matched thickness near ∼10 GHz (f m2) in these composite systems. These studies suggest the potential of tuning the twin frequencies in Ni 0.5 Zn 0.5 Fe2 O 4 /NBR composite samples for possible microwave absorption applications. © The Author(s) 2017.

Scientific Reports

Tunable twin matching frequency (fm1 /fm2) behavior of Ni1-x Znx Fe2 O 4 /NBR composites over 2-12.4 GHz: A strategic material system for stealth applications

Abstract: Here, synthesis and catalytic activity of a novel nanocatalyst (CuO@mTiO2@CF), consisting of CuO nanoparticles, mesoporous titanium oxide and Cobalt ferrite have been reported for the first time. The catalyst was synthesized using a simple aqueous solution based chemical methodology. Synthesized CuO@mTiO2@CF showed excellent catalytic activity towards various organic reactions such as (i) Epoxidation of styrene, (ii) Click reaction, (iii) Biginelli reaction, (iv) Reduction of 4-Nitrophenol and trifluralin in presence of excess NaBH4. Moreover, this novel nanocatalyst offered easy magnetic separation after the catalysis reaction and excellent reusability. Easy synthesis methodology, versatility, good reusability and easy separation make the nanocatalyst attractive in the field of heterogeneous catalysis. Graphical Abstract: [Figure not available: see fulltext.] © 2017, Springer Science+Business Media New York.

Catalysis Letters

CuO Nanoparticle Immobilised Mesoporous TiO2–Cobalt Ferrite Nanocatalyst: A Versatile, Magnetically Separable and Reusable Catalyst

The confirmation of excess in RD∗ at the LHCb is an indication of lepton flavor nonuniversality. Various different new physics operators and their coupling strengths, which provide a good fit to RD, RD∗, and q2 spectra, were identified previously. In this work, we try to find angular observables in B→D∗τν which enable us to distinguish between these new physics operators. We find that the D∗ polarization fraction fL(q2) is a good discriminant of scalar and tensor new physics operators. The change in fL(q2) induced by scalar and tensor operators, is about 3 times larger than the expected uncertainty in the upcoming Belle measurement. © 2017 American Physical Society.

Physical Review D

D* polarization as a probe to discriminate new physics in B¯→D*τν¯

MeV-scale magnetic fields in the interiors of magnetars suppress the pairing of neutrons and protons in the S-wave state. In the case of a neutron condensate the suppression is the consequence of the Pauli-paramagnetism of the neutron gas, i.e., the alignment of the neutron spins along the magnetic field. The proton S-wave pairing is suppressed because of the Landau diamagnetic currents of protons induced by the field. The Ginzburg-Landau and BCS theories of the critical magnetic fields for unpairing are reviewed. The macrophysical implications of the suppression (unpairing) of the condensates are discussed for the rotational crust-core coupling in magnetars and the neutrino-dominated cooling era of their thermal evolution. © Published under licence by IOP Publishing Ltd.

Journal of Physics: Conference Series

From microphysics to dynamics of magnetars

Ni-Co/Nanoporous Al2O3/Aluminum spectrally selective structures are grown using electrochemical anodization of alumina, followed by electrochemical pigmentation of Ni and Co metallic particles simultaneously. The pigmentation of Ni and Co particles into nanoporous anodized alumina (AA) is achieved using the reduction of metal ions in the aqueous electrolyte. The measured absorptivity and emittance are ∼ 0.90 ± 0.05 and 0.14 ± 0.04, respectively. These structures are subjected to the ten identical thermal cycling upto 300°C in inert N2 and air ambient conditions. The optical performance suggests that absorptivity is nearly same with slight enhancement in the emittance values as compared to the structure without any heat treatment. The accelerated corrosion studies suggest that Ni-Co co-pigmented AA structures are relatively corrosion robust as compared to that of the AA structure. © 2017. The Authors.

ISES Solar World Congress 2017 - IEA SHC International Conference on Solar Heating and Cooling for Buildings and Industry 2017, Proceedings

Ni-Co co-modified anodized spectrally selective coatings with enhanced corrosion and thermal stability

Li2MnSiO4 is a promising cathode material for lithium ion rechargeable batteries, however, synthesizing the desired crystallographic phase is challenging. We report the synthesis and electrochemical charge/discharge studies of carbon coated nanostructured Li2MnSiO4 in orthorhombic and monoclinic crystallographic phases. Li2MnSiO4 has been synthesized using solid state and sol-gel processes in bulk and nano-geometries without and with carbon coatings. The electrochemical performance of these Li2MnSiO4 samples was measured at a C/20 charge/discharge rate within 1.5-4.8 V voltage window. The first charge specific capacities are ∼290 mA h g-1 and ∼180 mA h g-1 for Li2MnSiO4 orthorhombic and monoclinic phase cathode materials. Charging-discharging of cells suggests that the degradation is lower for monoclinic Li2MnSiO4 cathode materials compared to that of orthorhombic Li2MnSiO4 cathode materials. This can be understood in terms of the relatively large electronic band gap and associated Jahn-Teller distortion observed in Li deficient Li2MnSiO4 materials, where Mn3+ intrinsically may lead to irreversible effective lithium insertion in distortion free starting Li2MnSiO4 materials for monoclinic materials. © 2017 The Royal Society of Chemistry.