Muralikrishna Molli

Enhanced dielectric properties and energy storage density of interface controlled ferroelectric BCZT-epoxy nanocomposites

Abstract Polymer nanocomposites with ferroelectric fillers are promising materials for modern power electronics that include energy storage devices. Ferroelectric filler, Ba0.85Ca0.15Zr0.1Ti0.9O3 (BCZT) nanopowder, was synthesized by sol-gel method. X-ray diffraction (XRD) studies confirmed the phase purity and the particle size distribution was determined by transmission electron microscopy (TEM). Extended aromatic ligand in the form of naphthyl phosphate (NPh) was chosen for surface passivation of BCZT nanoparticles. Surface functionalization was validated by thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS), and impedance spectroscopy using slurry technique. The dielectric constant of surface-passivated BCZT nanopowder was ~155, whereas pristine BCZT nanopowder dielectric constant could not be assessed due to high innate surface conductivity. Furthermore, BCZT–epoxy nanocomposite films were prepared and analyzed by differential scanning calorimetry (DSC), dielectric spectroscopy, dielectric breakdown strength (DBS), and scanning electron microscopy (SEM). Owning to stronger polymer–particle interface, dielectric measurements of 5 vol.% NPh surface functionalized BCZT–epoxy nanocomposites indicated improved DBS and glass transition temperature (Tg), reduced dielectric loss, and enhanced energy storage density compared to untreated BCZT–epoxy composites and pure epoxy. The energy storage density of 30 vol.% NPh surface functionalized BCZT–epoxy nanocomposite of 20 μm film thickness was almost three times that of pure epoxy polymer of identical film thickness.

Enhanced optical limiting of solubilized carbon nanotubesdecorated with Pt/Pd nanoparticles

We report here the nonlinear optical response of Solubilized Multiwalled Carbon Nanotubes (MWNTs) and these decorated with Platinum and Palladium Nanoparticles. Pristine MWNTs were functionalized with COOH group through microwave assisted synthesis route which rendered them soluble in water and other solvents too. Metal salts of Platinum and Palladium were further reduced to metal nanoparticles in presence of MWNT-COOH under microwave irradiation. These hybrid metal decorated carbon nanostructures were morphologically and functionally well characterized using SEM, EDAX, FTIR, UV-Visible etc., Using Z-scan technique, we carried out nonlinear optical studies on aqueous dispersions (stable) of these metal decorated (Pt/Pd-MWNT-COOH) using a high power Nd:YAG Laser with 532 nm excitation with 10 nanosecond pulse width. These samples exhibited significant nonlinear absorption and scattering. The metal decorated MWNT-COOH (Pt-MWNT-COOH:2 Jcm-2; Pd-MWNT-COOH: 1.7Jcm-2) exhibited enhanced optical limiting which is more than plain MWNT-COOH samples and similar Metal-Graphene hybrid dispersions reported earlier in literature. These could be ideally suited for optical power limiting applications.

Vanadium pentoxide nanoparticles based saturable absorbers

Vanadium pentoxide (V2O5) nanoparticles were synthesized by solution combustion method. The particle size reduction of the as-synthesized sample was achieved through ball milling. The as-synthesized and the ball milled samples were further characterized using XRD, TEM, EDX, UV-Visible and FTIR spectroscopy. Open-aperture z-scan technique was employed to study the nonlinear optical behavior of the synthesized samples and the commercially available V2O5 (bulk) using a second harmonic (532 nm) of Nd: YAG laser with 15 ns pulse width. We observed that the nonlinear absorption process was dependent on particle size as the synthesized and ball milled nanoparticles exhibited saturable absorption behavior while bulk V2O5 exhibited a transition to reverse saturable absorption behavior at the same incident laser intensity.

Low-Cost Plasmonic Carbon Spacer for Surface Plasmon-Coupled Emission Enhancements and Ethanol Detection: a Smartphone Approach

Surface plasmon-coupled emission (SPCE) has led to significant advancements in analytical techniques on account of its unique characteristics that include highly polarized photon-sorting ability. In this study, we report the use of a low-cost activated carbon as a plasmonic spacer in the SPCE substrate for achieving 30-fold enhancement in fluorescence emission. We extend the use of this spacer in the presence of Rhodamine B Base, a lactone dye as the sensing material for smartphone-based ethanol detection on the SPCE platform. Ethanol detection from 1 to 6% concentration highlights the potential use of this technique in monitoring fermentation processes.

DFT Study on the Carrier Concentration and Temperature-Dependent Thermoelectric Properties of Antimony Selenide

We present the thermoelectric properties of Antimony Selenide (Sb2Se3) obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Thermoelectric properties were calculated using BoltzTrap code using the constant relaxation time () approximation at three different temperatures 300 K, 600 K, and 800 K. Seebeck coefficient () was found to decrease with increasing temperature, electrical conductivity () was almost constant in the entire temperature range, and electronic thermal conductivity () increased with increasing temperature. With increase in temperature decreased from 1870 μV/K (at 300 K) to 719 μV/K (at 800 K), electronic thermal conductivity increased from 1.56 × 1015 W/m K s (at 300 K) to 3.92 × 1015 W/m K s (at 800 K), and electrical conductivity decreased from 22 × 1019/Ω m s (at 300 K) to 20 × 1019/Ω m s (at 800 K). The thermoelectric properties were also calculated for different hole concentrations and the optimum concentration for a good thermoelectric performance over a large range of temperatures (from 300 K to 1000 K) was found for hole concentration around 1019 cm−3.

Electronic band structure and optical properties of antimony selenide under pressure

In this work we present the optical properties of Antimony Selenide (Sb2Se3) under ambient conditions and under pressure of 9.2 GPa obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Optical properties like refractive index, absorption coefficient and optical conductivity are calculated using the WIEN2k code.

Effect of sulfur doping on thermoelectric properties of tin selenide – A first principles study

In this work we present the thermoelectric properties of tin selenide (SnSe) and sulfur doped tin selenide(SnSe(1-x)Sx, x= 0.125 and 0.25) obtained using first principles calculations. We investigated the electronic band structure using the FP-LAPW method within the sphere of the density functional theory. Thermoelectric properties were calculated using BOLTZTRAP code using the constant relaxation time approximation at three different temperatures 300, 600 and 800 K. Seebeck coefficient (S) was found to decrease with increasing temperature, electrical conductivity (σ/τ) was almost constant in the entire temperature range and thermal conductivity (κ/τ) increased with increasing temperature for all samples. Sulfur doped samples showed enhanced seebeck coefficient, decreased thermal conductivity and decreased electrical conductivity at all temperatures. At 300 K, S increased from 1500 µV/K(SnSe) to 1720μV/K(SnSe0.75S0.25), thermal conductivity decreased from 5 × 1015 W/mKs(SnSe) to 3 × 1015 W/mKs(SnSe0.75S0....