Showing papers in "Results in physics in 2016"

WITHDRAWN: Preparation and characterization of high surface area activated carbon from Fox nut (Euryale ferox) shell by chemical activation with H3PO4

Abstract: Activated carbons were prepared from Fox nutshell by chemical activation with H 3 PO 4 in N 2 atmosphere and their characteristics were studied. The effects of activation temperature and impregnation ratio were examined. N 2 adsorption isotherms characterized the surface area, total pore volume, micropore volume and pore size distribution of activated carbons. Activated carbon was produced at 700 °C with a 1.5 impregnation ratio and one hour of activation time has found 2636 m 2 /g and 1.53 cm 3 /g of highest BET surface area and total pore volume, respectively. The result of Fourier-infrared spectroscopy analysis of the prepared activated carbon confirmed that the carbon has abundant functional groups on the surface. Field emission scanning electron micrographs of the prepared activated carbon showed that a porous structure formed during activation.

Boundary layer flow of Maxwell fluid in rotating frame with binary chemical reaction and activation energy

Abstract: Here we study the heat/mass transfer effects on revolving flow of Maxwell fluid due to unidirectional stretching surface. Mass transfer process is modeled in terms of binary chemical reaction and activation energy. Modified Arrhenius function for activation energy is invoked. Traditional boundary layer approximations are utilized to simplify the governing equations. Using similarity method, self-similar form of boundary layer equations are derived which are solved numerically. The solutions depend on dimensionless numbers such as the rotation parameter λ , the Deborah number β , the Prandtl number Pr , the Schmidt number Sc , activation energy E , fitted rate constant n and temperature difference parameter δ . We found that the solute concentration in binary mixture is proportional to both rotation parameter λ and activation energy E . The reaction rate σ and fitted rate n both provide reduction in the solute concentration. Thermal boundary layer becomes thicker and heat transfer rate diminishes when fluid is subjected to a larger rotation rate.

Structural and optical characterization of PVA:KMnO 4 based solid polymer electrolyte

Abstract: Solid polymer electrolyte films of polyvinyl alcohol (PVA) doped with a different weight percent of potassium permanganate (KMnO 4 ) were prepared by standard solution cast method. XRD and FTIR techniques were performed for structural study. Complex formation between the PVA polymer and KMnO 4 salt was confirmed by Fourier transform infrared (FTIR) spectroscopy. The description of crystalline nature of the solid polymer electrolyte films has been confirmed by XRD analysis. The UV-Visible absorption spectra were analyzed in terms of absorption formula for non-crystalline materials. The fundamental optical parameters such as optical band gap energy, refractive index, optical conductivity, and dielectric constants have been investigated and showed a clear dependence on the KMnO 4 concentration. The observed value of optical band gap energy for pure PVA is about 6.27 eV and decreases to a value 3.12 eV for the film sample formed with 4 wt% KMnO 4 salt. The calculated values of refractive index and the dielectric constants of the polymer electrolyte films increase with increasing KMnO 4 content.

Site location of Al-dopant in ZnO lattice by exploiting the structural and optical characterisation of ZnO:Al thin films

Abstract: The zinc oxide thin films, highly transparent, doped aluminium were prepared on glass substrates by the reactive chemical spray method. The incorporation nature of Al atoms in the ZnO lattice was determined by X-ray diffraction and optical analyses. Indeed, for low doping ⩽2%, the results of X-ray spectra analysis show a simultaneous reduction of lattice parameters (a and c), this variation, which follows VEGARD’s law, tends to indicate a substitution of Zn by Al. By against for doping >2% the increase in the lattice parameters thus the grain sizes, in accordance with the VEGARD’s law can be explained by occupation of the interstitial sites by Al atoms. Beyond 4%, the material tends to get disorderly and the crystallites orientation is random. The studied optical properties show that the variation of the optical gap follows a law of the x3/2 form for x

Ion acoustic solitary wave solutions of three-dimensional nonlinear extended Zakharov–Kuznetsov dynamical equation in a magnetized two-ion-temperature dusty plasma

Abstract: We consider the propagation of three-dimensional nonlinear magnetized two-ion-temperature dusty plasma. The problem formulation of this mathematical model leads to nonlinear extended Zakharov–Kuznetsov (EZK) dynamical equation in three-dimensional by applying the reductive perturbation theory. We found the families of dust and ion solitary wave solutions of the three-dimensional nonlinear EZK dynamical equation using the auxiliary equation mapping method and direct algebraic mapping method.

Neem leaves mediated preparation of NiO nanoparticles and its magnetization, coercivity and antibacterial analysis

Abstract: Nickel oxides nanoparticles (NiO NPs) were synthesized by biosynthesis method with the help of phytoconstituents present in the neem leaf. Further the synthesized NiO NPs were subjected for structural, optical, morphological and magnetic properties. The XRD patterns clearly infer the presence of polycrystalline nature of samples (0 1 0), (0 1 1) and (0 1 2) with hexagonal crystal phase. Morphological studies using Transmission Electron Microscope (TEM) reveals that the biosynthesized NiO NPs were in shape of oblong with 12 nm in size. Elemental analysis (EDAX) confirms the quantity of Ni is present at 51% and remaining O as 49% as well as the mass magnetization values of 61 emu/g are also recorded for NiO NPs and its coercivity values in the range of 0.2–0.4 of nanoparticles respectively. Finally the NiO NPs was studied for bacterial activity against Staphylococcus aureus (MTCC 1430) and followed by Escherichia coli (MTCC 739) by agar diffusion assay.

Numerical simulation for nonlinear radiative flow by convective cylinder

Abstract: Present study explores the effect of nonlinear thermal radiation and magnetic field in boundary layer flow of viscous fluid due to nonlinear stretching cylinder. An incompressible fluid occupies the porous medium. Nonlinear differential systems are obtained after invoking appropriate transformations. The problems in hand are solved numerically. Effects of flow controlling parameters on velocity, temperature, local skin friction coefficient and local Nusselt numbers are discussed. It is found that the dimensionless velocity decreases and temperature increases when magnetic parameter is enhanced. Temperature profile is also increasing function of thermal radiation.

Elucidation of the highest valence band and lowest conduction band shifts using XPS for ZnO and Zn0.99Cu0.01O band gap changes

Abstract: ZnO and Zn0.99Cu0.01O nanostructures were prepared by a simple sol–gel method. The band gaps of the materials were systematically studied based on the dependence of the dimensions of the nanostructures as well as the presence of a dopant material, Cu. ZnO and Zn0.99Cu0.01O nanostructures were found to exhibit band gap widening whilst substitution of Cu in the lattice of ZnO caused its band gap to narrow with respect to the pure ZnO materials. In order to understand the phenomenon of band gap change, structural, spectroscopic, particle size and morphological studies were done. The band gap change occurring when the materials were in the nanostructured phase was proven to be mainly due to the downward shift of the valence band. Interestingly, when the band gaps of the pure ZnO and Cu doped ZnO were compared, the band gap changes were due to different shifts of the valence bands.

Influence of Mn doping on the magnetic and optical properties of ZnO nanocrystalline particles

Abstract: The structural, optical and magnetic properties of Mn doped ZnO nanocrystalline particles, Zn1-xMnxO, with different percentages of Mn content have been studied. XRD and XPS measurements showed that all samples with Mn doping up to x = 0.1 possess typical wurtzite structure and have no other impurity phases. The incorporation of Mn ions into the ZnO lattice was also confirmed by FTIR and UV–Vis. spectroscopy results. Both XRD and SEM results indicated a slight decrease in the grain size with increasing the Mn doping level. The XPS results indicated an increase in the oxygen vacancies concentration with increasing the Mn doping level. The magnetization measurements revealed a weak ferromagnetic behavior at room temperature and a clear ferromagnetic behavior with relatively large coercive fields at low temperature. The ferromagnetic order is improved by increasing the Mn doping. In addition, we observed an increase in the concentration of oxygen vacancies, which is also induced by increasing the Mn doping level. A ferromagnetic coupling of the local moment of Mn dopants through the sp-d exchange interaction and oxygen vacancies, in addition to different magnetic contributions due to different forms of Mn ions that coexist in the Mn doped nanoparticles were presented in order to interpret the observed magnetic behavior. We observed a clear red shift in the direct band gap and an increase in the coercive field and saturation magnetization values with increasing the Mn doping level.

Darcy–Forchheimer flow of magneto Maxwell liquid bounded by convectively heated sheet

Abstract: The present work studies the MHD two-dimensional flow of Maxwell liquid over a stretched surface moving with linear velocity. Convective heat phenomenon characterizes the heat transfer process. Induced electric and magnetic fields are absent. The set of partial differential equations governing the Darcy–Forchheimer flow of Maxwell liquid is derived. Computations for strong nonlinear systems are presented after non-dimensionalization. Convergent relations for velocity and temperature distributions are achieved. Besides this local Nusselt number is computed and analyzed. Our findings reveal that the temperature field has an inverse relationship with the thermal relaxation parameter and Prandtl number.

Travelling wave solutions of generalized coupled Zakharov-Kuznetsov and dispersive long wave equations

Abstract: In this manuscript, we constructed different form of new exact solutions of generalized coupled Zakharov–Kuznetsov and dispersive long wave equations by utilizing the modified extended direct algebraic method. New exact traveling wave solutions for both equations are obtained in the form of soliton, periodic, bright, and dark solitary wave solutions. There are many applications of the present traveling wave solutions in physics and furthermore, a wide class of coupled nonlinear evolution equations can be solved by this method.

Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

Abstract: Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag + to prepare Ag/Ag + /Ag 3+ nanoparticle composites. UV–Vis was employed to detect and track the reduction of Ag + and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO 3 solution to produce Ag/Ag + /Ag 3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO 3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag + /Ag 3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of NH 2 , OH, and others were distributed on the surface of the newly synthesized Ag/Ag + /Ag 3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

Three-dimensional flow of nanofluid with Cattaneo–Christov double diffusion

Abstract: Three dimensional (3D) boundary-layer flow of viscous nanofluid has been investigated in the presence of Cattaneo–Christov double diffusion. A bi-directional linearly stretching sheet has been used to create the flow. Thermal and concentration diffusions are characterized by introducing Cattaneo–Christov fluxes. Novel attributes regarding Brownian motion and thermophoresis are retained. The conversion of nonlinear partial differential system to nonlinear ordinary differential system is done through suitable transformations. The resulting nonlinear systems are solved. Graphs have been sketched in order to investigate that how the temperature and concentration profiles are affected by distinct physical flow parameters. Further the skin friction and heat and mass transfer rates are numerically computed and discussed. Our findings depict that temperature and concentration distributions are decreasing functions of thermal and concentration relaxation parameters.

Investigations of the structural, morphological and electrical properties of multilayer ZnO/TiO 2 thin films, deposited by sol–gel technique

Abstract: Investigations of the structural, morphological and electrical properties of multilayer ZnO/TiO 2 thin films deposited by sol–gel technique on glass substrate. Sol–gel is a technique in which compound is dissolved in a liquid in order to bring it back as a solid in a controlled manner. TiO 2 solution was obtained by dissolving 0.4 g of TiO 2 nano powder in 5 ml ethanol and 5 ml diethylene glycol. ZnO solution was obtained by dissolving 0.88 g zinc acetate in 20 ml of 2-methoxyethanol. X-ray diffraction (XRD) (PW 3050/60 PANalytical X’Pert PRO diffractometer) results showed that the crystallinity is improved when the number of ZnO/TiO 2 layers increased. Also it shows the three phases (rutile, anatase and brookite) of TiO 2 . Surface morphology measured by scanning electron microscopy (SEM) (Quanta 250 fei) revealed that Crakes are present on the surface of ZnO/TiO 2 thin films which are decreased when the number of ZnO/TiO 2 layers increased. Four point probe (KIETHLEY instrument) technique used to investigate the electrical properties of ZnO/TiO 2 showed the average resistivity decreased by increasing the number of ZnO/TiO 2 layers. These results indicated that the multilayer thin films improved the quality of film crystallinity and electrical properties as compared to single layer.

MHD flow of Jeffrey liquid due to a nonlinear radially stretched sheet in presence of Newtonian heating

Abstract: This communication describes the magnetohydrodynamic (MHD) flow of Jeffrey liquid persuaded by a nonlinear radially stretched sheet. Heat transfer is characterized by Newtonian heating and Joule heating effects. The transformed nonlinear governing ordinary differential equations are solved employing homotopic approach. The obtained results of the velocity and temperature are analyzed graphically for various pertinent parameters. Skin friction coefficient and Nusselt number are tabulated and addressed for the various embedded parameters. Furthermore the temperature decays for increasing nonlinear parameter of axisymmetric stretching surface. The nonlinear parameter has reverse effect for temperature and skin friction coefficient.

Fabrication and characterization of semiconductor nickel oxide (NiO) nanoparticles manufactured using a facile thermal treatment

Abstract: In this paper, thermal treatment procedures were utilised to prepare crystalline nickel oxide semiconductor nanoparticles, derived from an aqueous solution. The solution consists of three compounds, primarily nickel nitrate, polyvinyl pyrrolidine and deionised H 2 O acting as metal precursor, capping agent and solvent, respectively. The solution was made prior to the drying, grinding and calcination at varying temperature settings up to 800 °C. The scanning Electron Microscopy (SEM) images allowed a detailed study on the morphological of the monocrystalline grains which were obviously observed in the specimen, showing them to be almost identical in shape and size. The Infrared Fourier Transform (FTIR) and X-ray diffraction (XRD) results demonstrated a transformation of the amorphous structure at room temperature to the crystalline structure at higher temperatures during calcination process. The mean particle diameter and particle distribution were found to be directly proportional to temperature increased. The transmission electron microscopic (TEM) analysis revealed that the particle diameters vary between 15 and 35 nm when temperature increased between 500 and 800 °C. The composition of the specimens was delineated by energy dispersed X-ray spectroscopy (EDX), which identified nickel and oxygen atomic percentages in the final products. Optical characteristics were deducted from a UV–Vis reflectance spectrophotometer, which demonstrated the energy band gap decrement as the calcination temperatures increased. Magnetic properties were determined through electron spin resonance spectroscopy (ESR), which revealed the presence of unpaired electrons. The magnetic field resonance decreases along with an increase of the g-factor value as the calcination temperature increased from 500 to 800 °C.

Adsorption and corrosion inhibition properties of thiocarbanilide on the electrochemical behavior of high carbon steel in dilute acid solutions

Abstract: The inhibition performance of thiocarbanilide on the electrochemical corrosion behavior of high carbon steel in 1 M H2SO4 and HCl acid solutions was studied through weight loss method and potentiodynamic polarization test. Data obtained showed that the organic compound performed effectively in acid solutions at all concentrations with an average thiocarbanilide inhibition efficiency above 70% in H2SO4 acid and 80% in HCl acid from weight loss and potentiodynamic polarization test respectively. Results from corrosion thermodynamic calculations showed that the adsorption of thiocarbanilide onto the steel was through chemisorption mechanism whereby the redox electrochemical process responsible for corrosion and the electrolytic transport of corrosive anions were simultaneously suppressed. Statistical derivations through ANOVA analysis confirm that the influences of both the inhibitor concentration and exposure time on inhibition efficiency values are negligible. Adsorption of the compound was determined to obey the Langmuir and Frumkin isotherm model.

Mixed convective flow of Maxwell nanofluid past a porous vertical stretched surface – An optimal solution

Abstract: Present investigation is devoted to examine the mixed convective flow of Maxwell nanofluid with Soret and Dufour effects through a porous medium. Effects of variable temperature and concentration over a linearly permeable stretched surface are also taken into account. An optimal solution is obtained for the highly nonlinear set of differential equations using BVPh 2.0 Mathematica package. Graphs of different emerging pertinent parameters against velocity, temperature and concentration distributions are plotted and discussed accordingly. Numerically tabulated values of local Nusselt and Sherwood numbers are also part of this investigation. It is witnessed that concentration field is decreasing and increasing function of Brownian motion and thermophoretic parameters respectively. Further, opposite behavior of Soret number on temperature and concentration distributions is seen.

Lie symmetry analysis, conservation laws and exact solutions of the seventh-order time fractional Sawada–Kotera–Ito equation

Abstract: In this paper Lie symmetry analysis of the seventh-order time fractional Sawada–Kotera–Ito (FSKI) equation with Riemann–Liouville derivative is performed. Using the Lie point symmetries of FSKI equation, it is shown that it can be transformed into a nonlinear ordinary differential equation of fractional order with a new dependent variable. In the reduced equation the derivative is in Erdelyi–Kober sense. Furthermore, adapting the Ibragimov’s nonlocal conservation method to time fractional partial differential equations, we obtain conservation laws of the underlying equation. In addition, we construct some exact travelling wave solutions for the FSKI equation using the sub-equation method.

MHD axisymmetric flow of power-law fluid over an unsteady stretching sheet with convective boundary conditions

Abstract: This paper examines the boundary layer flow and heat transfer characteristic in power law fluid model over unsteady radially stretching sheet under the influence of convective boundary conditions. A uniform magnetic field is applied transversely to the direction of the flow. The governing time dependent nonlinear boundary layer equations are reduced into nonlinear ordinary differential equations with the help of similarity transformations. The transformed coupled ordinary differential equations are then solved analytically by homotopy analysis method (HAM) and numerically by shooting procedure. Effects of various governing parameters like, power law index n , magnetic parameter M , unsteadiness A , suction/injection S , Biot number γ and generalized Prandtl number Pr on velocity, temperature, local skin friction and the local Nusselt number are studied and discussed. It is found from the analysis that the magnetic parameter diminishes the velocity profile and the corresponding thermal boundary layer thickness.

Assessment on characteristics of heterogeneous-homogenous processes in three-dimensional flow of Burgers fluid

Abstract: An analysis is performed to explore the characteristics of heterogeneous-homogeneous processes for the steady three-dimensional flow of Burgers fluid over a bidirectional stretching surface. In this paper, we utilized the advanced model of a homogeneous-heterogeneous reactions with equal diffusivities for reactant and autocatalysis. Additionally, heat transfer analysis is carried out in the presence of nonlinear thermal radiation and convective boundary conditions. The basic governing non-linear problem is presented and reduced into self-similar form with the aid of suitable similarity approach. The advanced non-linear problem is then tackled analytically by employing the homotpy analysis method (HAM). The effectiveness of relevant physical parameters on temperature and concentration profiles are taken into consideration. It is evident from the graphs that the concentration distribution diminishes by uplifting the homogeneous process parameter while it enhances for strength of Schmidt number. Moreover, it is observed that the surface heat transfer rate enhances for larger values of the Prandtl number.

Heat transfer squeezed flow of Carreau fluid over a sensor surface with variable thermal conductivity: A numerical study

Abstract: Present phenomenon is dedicated to investigate the heat transfer and squeezed flow of Carreau fluid over a sensor surface. The thermal conductivity of the fluid is assumed to be temperature dependent. After assimilating these assumptions, the appropriate transformations are used to formulate the partial differential equations into non-dimensional system of ordinary differential equations. Solutions for the boundary layer momentum and heat equations are accomplished by a well-known numerical technique namely shooting method. The related essential physical parameters are visualized through graphs and tables. It is found that the velocity profile increases by increasing squeezed flow parameter b, permeable velocity parameter f 0 , power law index n and Weissenberg number We Similarly, temperature profile increases by increasing small parameter ∊ .

Hubbard U calculations on optical properties of 3d transition metal oxide TiO2

Abstract: The optical properties of titanium dioxide (TiO 2 ) in rutile, anatase and brookite phases were investigated via density functional theory (DFT) framework. The Hubbard U term in Ti 3 d electrons of the TiO 2 phases was introduced to observe the optical behavior with the effect of U parameter. The calculated structural parameters from the optimized TiO 2 are in good agreement with the previous experimental and theoretical data. The values of static dielectric constant and refractive index from exchange-correlation functional in standard DFT are slightly higher than the DFT + U method. The energy peaks of reflectivity and loss function spectra show the good match with each other. The TiO 2 with rutile, anatase and brookite phases have optical absorption in the ultraviolet (UV) light region. Thus, the inclusion of U parameters turn out to shift the wavelength photon towards the low region. Furthermore, this work provides a good theoretical understanding of the optical properties of TiO 2 which helpful in a technological application such as photocatalysis and photovoltaics.

Investigation of magnetic and structural properties of copper substituted barium ferrite powder particles via co-precipitation method

Abstract: In this paper, it is proposed to synthesize copper-doped barium ferrite (BaCu x Fe 12− x O 19 ) using co-precipitation technique at different ratios in order to increase the coercivity value which in turn increases the magnetic storage capacity of the copper-doped barium ferrite powder. This technique is very compactable with lower cost. This method was used to prepare different ratio (0–8%) of copper-doped barium ferrite samples exposed to sintering process under the temperature 1200 °C for 6 h because the base and doped materials are combined to form a new compound. The sintered compound is involved the XRD analysis and the obtained values are matched with the constant standards ( a = b = 5.864 A and c = 23.098 A). Hence, the samples proved as hexagonal system. TGA/DTA used to establish selected characteristics of materials that exhibit decomposition and oxidation process. FT-IR spectroscopy used to confirm the chemical bonds and vibration mode of samples. Using beam of X-rays, XPS spectra obtained and the binding energy of the sample is measured. From the SEM analysis, the morphology and grain size of the copper-doped barium ferrite powder materials are found. The vibrating sample magnetometer measures the magnetic saturation, magnetic reminisce and coercivity of a sample. The magnetic saturation, magnetic remanence and coercivity values are found and tabulated.

Linear and nonlinear optical properties of Gd3+ doped zinc borotellurite glasses for all-optical switching applications

Abstract: In this work, linear and nonlinear optical parameters of zinc borotellurite glasses doped with Gd3+ have been studied for all-optical switching applications. A series of gadolinium zinc borotellurite glasses were synthesized by using conventional melt quenching technique. Optical absorption spectra were recorded by UV–vis spectroscopy. From the optical absorption spectra, the cut-off wavelength, optical band gap, Urbach energy and refractive index have been determined and are related to the structural changes in the glass systems. The nonlinear optical properties of Gd3+ doped glasses are investigated by using Z-scan technique. The values of nonlinear refractive index and absorption coefficient with closed and opened apertures of the Z-scan, respectively, were determined for proper utilization in nonlinear optical devices.

Effects of thermal-diffusion and viscous dissipation on peristaltic flow of micropolar non-Newtonian nanofluid: Application of homotopy perturbation method

Abstract: In this paper, a study of the peristaltic motion of incompressible micropolar non-Newtonian nanofluid with heat transfer in a two-dimensional asymmetric channel is investigated under long-wavelength assumption. The flow includes radiation and viscous dissipation effects as well as all micropolar fluid parameters. The fundamental equations which govern this flow have been modeled under long-wavelength assumption, and the expressions of velocity and microrotation velocity are obtained in a closed form, while the solutions of both temperature and nanoparticles phenomena are obtained using the homotopy perturbation method (HPM). Also, the skin friction, Nusselt number and Sherwood number are obtained at both lower and upper walls. The results have been discussed graphically to observe the effects the physical parameters of the problem have on the physical quantities.

Optimization and spectroscopic studies on carbon nanotubes/PVA nanocomposites

Abstract: Nanocomposite films of polyvinyl alcohol (PVA) containing constant ratio of both single and multi-wall carbon nanotubes had been obtained by dispersion techniques and were investigated by different techniques. The infrared spectrum confirmed that SWNTs and MWNTs have been covalently related OH and CAC bonds within PVA. The X-ray diffraction indicated lower crystallinity after the addition of carbon nanotubes (CNTs) due to interaction between CNTs and PVA. Transmission electron microscope (TEM) illustrated that SWNTs and MWNTs have been dispersed into PVA polymeric matrix and it wrapped with PVA. The properties of PVA were enhanced by the presence of CNTs. TEM images show uniform distribution of CNTs within PVA and a few broken revealing that CNTs broke aside as opposed to being pulled out from fracture surface which suggests an interfacial bonding between CNTs and PVA. Maximum value of AC conductivity was recorded at higher frequencies. The behavior of both dielectric constant (epsilon') and dielectric loss (epsilon'') were decreased when frequency increased related to dipole direction within PVA films to orient toward the applied field. At higher frequencies, the decreasing trend seems nearly stable as compared with lower frequencies related to difficulty of dipole rotation.

Sintering behavior, ac conductivity and dielectric relaxation of Li 1.3 Ti 1.7 Al 0.3 (PO 4 ) 3 NASICON compound

Abstract: The phenomenon of relaxation in dielectric materials is described as one of the powerful tools to determine the behavior and properties of ion transport. The kinetics of ionic species and dipole in solid-state electrolyte are dependent on frequency, temperature, and dielectric relaxation. Li 1+x Ti 2−x Al x (PO 4 ) 3 conducting solid state electrolyte with x = 0.3 was synthesized via conventional solid state technique using the raw materials Li 2 CO 3 , TiO 2 , Al 2 O 3 , and NH 4 H 2 PO 4 as starting materials. TGA/DTG and X-ray diffraction measurements were carried out to study the thermal behavior and phases of the composition. It was observed from the TGA/DTA curves that there is no mass loss above 500 °C. The XRD peaks were observed to start appearing at 500 °C which corresponds to small peaks in TGA. It was also pointed out that at increasing sintering temperatures from 700 °C to 1000 °C the number of phases drastically decreased which is attributed to the complete chemical reaction. Temperature and frequency dependence of dielectric relaxation and electric modulus of the compounds were investigated at temperatures 30–230 °C and at frequencies of 40 kHz–1 MHz. The findings showed that the dielectric relaxation peaks shift to higher temperature as frequency increases and the change in ac conductivity with frequency is in agreement with Jonscher’s power law.

Preparation and characterization of poly(vinylidene fluoride): A high dielectric performance nano-composite for electrical storage

Abstract: We have prepared films of polymer nano-composite (PNC) of poly[vinylidene-fluoride] (PVDF) and bismuth vanadate (BiVO4) nanoparticles. The α and γ electro-active phases were detected, and the addition of BiVO4 drastically increases the formation of the α-phase. Addition of BiVO4 produces up to 98% of electro-active phases. Robust electrostatic interactions arise between charges at the BiVO4-surfaces, and differences in electron affinity between CH2 and CF2 groups created dielectric dipoles. The addition of BiVO4 has not only enhanced the formation of the electrically active phases but also makes each dipole in the phase has its specific characteristics for example its own relaxation time. The AC-electrical permittivity showed that the dielectric constant of 10%wt- BiVO4 nanoparticles in PVDF has a value 44 e0, which is four times more than the dielectric constant of the as-prepared PVDF films. These data show the importance of these polymers as easy, flexible, and durable energy storage materials.

Prominent spectral features of Sm3+ ion in disordered zinc tellurite glass

Abstract: Trivalent rare earth doped glasses with modified spectroscopic features are essential for solid state lasers and diverse photonic applications. Glass composition optimisation may fulfil such demand. Stimulating the spectral properties of samarium (Sm3+) ions in tellurite glass host with desired enhancement is the key issue. Glasses with composition (80 − x)TeO2–20ZnO–(x)Sm2O3, where 0 ⩽ x ⩽ 1.5 mol% are prepared using melt quenching method. The role of varying Sm3+ contents to improving the absorption and emission properties of the prepared glasses are determined. XRD pattern verifies amorphous nature of synthesised glasses. FTIR spectroscopy has been used to observe the structural modification of (TeO4) trigonal bipyramid structural units. DTA traces display prominent transition peaks for glass transition, crystallisation and melting temperature. Samples are discerned to be stable with desired Hruby parameter and superior glass forming ability. The UV–Vis–NIR absorption spectra reveals nine peaks centred at 470, 548, 947, 1085, 1238, 1385, 1492, 1550 and 1589 nm. These bands arise due to 6H5/2 → 4I11/2, 4G5/2, 6F11/2, 6F9/2, 6F7/2, 6F5/2, 6F3/2, 6H15/2 and 6F1/2 transitions, respectively. The direct, indirect band gap and Urbach energy calculated from the absorption edge of UV–Vis–NIR spectra are found to appear within (2.75–3.18) eV, (3.22–3.40) eV, and (0.20–0.31) eV, respectively. The observed increase in refractive index from 2.45 to 2.47 is ascribed to the generation of non-bridging oxygen atoms via the conversion of TeO4 into TeO3 units. Conversely the decrease in refractive index to 2.39 is attributed to the lower ionic radii (1.079 A) of Sm3+. PL spectra under the excitation of 452 nm display four emission bands centred at 563, 600, 644 and 705 nm corresponding to 4G5/2 → 6H5/2, 6H7/2, 6H9/2 and 6H11/2 transitions of samarium ions. Excellent features of the results nominate these compositions towards prospective applications.