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Structural characteristic of vanadium(V) oxide/sulfur composite cathode for magnesium battery applications

Abstract

Magnesium batteries are regarded as promising candidates for energy storage devices owing to their high volumetric capacity. The practical application is hindered, however, by strong electrostatic interactions between Mg2+ and the host lattice and due to the formation of a passivation layer between anode and electrolyte. V2O5 is a typical intercalation compound with a layered crystal structure ((0 0 1) interlayer spacing ~ 11.53 Å), which can act as a good host for the reversible insertion and extraction of multivalent cations. Herein, we have presented an investigation of the effects of S injection on the structure, electrochemical performance and Mg2+ diffusion in V2O5 cathode materials for Mg-ion batteries. The V2O5/S composite structure was investigated using X-ray diffraction, field-emission scanning electron microscope and energy dispersive X-ray spectroscopy. The integrated electrode exhibits an improvement in the electrical and electrochemical properties compared to the V2O5 electrode. The as-prepared V2O5/S composite has an initial discharge capacity of 310 mAh g−1 compared to 160 mAh g−1 for the V2O5 electrode. The V2O5/S composite is a promising cathode material for magnesium-ion battery applications.

Open access
Structural optical and electrical characterization of nanoparticle B doped ZnS films

Abstract

Structural, morphological, optical and electrical characteristics of zinc sulfide (ZnS) and boron doped zinc sulfide (ZnS:B) films deposited on glass substrates by ultrasonic spray pyrolysis (USP) method and heated up to 350±5 °C were studied. B doping at various concentrations did not change the crystal structure of the ZnS film and it also did not cause any significant change in the size of crystallites. Maximum transmittance values of the B doped ZnS films increased parallel to doping rate. Transmittance edges showed shifting towards smaller wavelengths due to the effect of B doping. B doping increased optical band gap values. Scanning electron microscopy (SEM) images of the film surfaces showed that B doping did not cause any significant change in grain sizes of the films. Presence of all expected elements in the films including Zn, S and B was confirmed through Energy Dispersive Spectrometry (EDS) analysis. Significant peaks of foreign phases on the film surfaces were observed through Fourier Transform Infrared (FT-IR) spectroscopy. The electrical resistivity values of the films were calculated by means of current-voltage characteristics.

Open access
Structure and performance optimization of phenol polyphosphazene grafted by 2,4-dinitroaniline containing small nonlinear optical molecules

Abstract

Electro-optic (EO) polymers, possessing high EO coefficient and low dielectric constant, are considered to be a new generation of nonlinear optical materials that have great application prospect in photo-communication, information storage, and data processing. The host-guest structure of EO polymers is the most typical one in this field. However, the phase separation during polarization between the host polymer and the guest nonlinear optical molecule (NLO) limits potential applications of the material. To solve the problem, a new synthetic method was designed in this paper. First, 2,4-dinitroaniline was grafted to phenol polyphosphazene by chemical method for polar improvement of the main chain. Then, another small NLO molecule was mixed into the polymer by physical method for further improvement of EO coefficient. The preparation process was studied and the structure of the product was characterized. The effects of different NLO mixing proportions and different polarizing temperatures on EO coefficient were investigated in details. Orientation stability of the sample was tested. Experimental results show that our products possess not only high EO coefficient but also good phase stability, which makes them good candidates for the application in information technology.

Open access
Study of crystallographic, optical and sensing properties of Na2WO4 films deposited by thermal evaporation with several thickness

Abstract

Na2WO4 films have been grown at 400 °C using thermal evaporation technique. Their structural properties were characterized by XRD, while their chemical composition was verified by both EDX and X-ray photoelectron spectroscopy (XPS). The evolution of crystallinity was studied as a function of film thickness that ranged from 500 nm to 3000 nm. The grain size increased with increasing film thickness. The surface morphology of the prepared films was studied using scanning electron microscope (SEM) and atomic force microscopy (AFM). It has been observed that the average transmittance of samples in the visible and near infrared range has varied from 90 % to 78 % with the film thickness. The optical band gap of the Na2WO4 films varied from 3.8 eV to 4.1 eV. The crystalline size increased with increasing thickness and showed better sensing response to gases. Thus, this study confirmed the possibility of using Na2WO4 thick films as a sensor element for detection of ethanol (C2H5OH), acetone (C3H6O) methanol (CH3OH) and ammonia hydroxide (NH4OH) vapor at room temperature, where thicker films exhibited sensing properties with a maximum sensitivity at 25 °C in air, especially for NH4OH.

Open access
Synthesis and characterization of mesoporous carbon spheres

Abstract

A three-step method was used for the synthesis of mesoporous carbon sphere (MCS) material: firstly, silica (SiO2) nanoparticles were synthesized by the modified Stöber procedure; secondly, tetraethyl orthosilicate (TEOS) and cetyltrimethylammonium chloride (CTAC) were grafted onto SiO2 core nanoparticles to prepare SiO2@SiO2-CTAC hard templates; lastly, MCS material was fabricated by carbonizing and selective leaching SiO2/resorcinol-formaldehyde (RF) composites. The influence of the mass ratio of R-F/silica on the structure, morphology and crystal form was studied. The results indicate that the MCS materials have a uniform morphology. The increase of the mass ratio of R-F/silica can increase the specific surface area and pore volume. The three-step method provides a cost-effective procedure for the fabrication of MCS materials with uniform morphology.

Open access
Synthesis, growth, and characterization of hexagonal shaped potassium-boro-phthalate (KBP) single crystal by slow solvent evaporation method for optoelectronics applications

Abstract

A novel nonlinear optical crystal of potassium-boro-phthalate (KBP) was grown by a slow solvent evaporation technique. The crystalline nature and cell parameters were analyzed using X-ray diffraction (XRD) study. The presence of various functional groups was determined by Fourier transform infrared spectroscopy (FT-IR) spectral analysis. The linear optical properties were determined by UV-Vis-NIR spectral analysis. The dielectric constant and dielectric loss of KBP were measured in the frequency range of 500 Hz to 5 MHz at different temperatures. The mechanical properties of KBP single crystal were studied using Vickers microhardness tester. The linear and nonlinear optical properties of the grown crystals were studied to assess its suitability for device fabrication.

Open access
Synthesis, morphology, electrical conductivity and electrochemical properties of α-Ni(OH)2 and its composites with carbon

Abstract

A simple and effective hydrothermal synthesis of spherical α-Ni(OH)2 particles and α-Ni(OH)2/carbon composites was proposed. The mechanism of ultrafine α-Ni(OH)2 phase forming and correlations between synthesis conditions, morphology, electrical conductivity were analyzed. It was found that carbon nanoparticles form an electric conductive cover on nickel hydroxide microparticles during synthesis which increases overall electronic conductivity of the composite material. α-Ni(OH)2 and α-Ni(OH)2/C samples were tested as electrodes for hybrid supercapacitors. It was found that carbon coverings stabilize α-Ni(OH)2 phase in the alkaline medium. The comparison of the influence of laser irradiation and ultrasonic treatment on the electrochemical performance of the obtained materials was made.

Open access
Thin film characterization of Ce and Sn co-doped CdZnS by chemical bath deposition

Abstract

Cerium and tin co-doped cadmium zinc sulfide nanoparticles (CdZnS:Ce)Sn were synthesized by chemical bath deposition method with a fixed concentration of Ce (3.84 mol%) and three different concentrations of Sn (2 mol % and 4 mol% and 6 mol%). They showed broad photoluminescence spectra in the visible region under the ultraviolet excitation with a wavelength of 325 nm. The photoluminescence emission peaks were obtained at 540 nm, 560 nm and 570 nm for CdZnS, CdZnS:Ce and (CdZnS:Ce)Sn thin films, respectively having different concentrations of Sn. It has been observed that the photoluminescence emission peak shifted to higher wavelength region with an increase in intensity by Ce doping and Ce–Sn co-doping. Further enhancement in luminescence peak intensity has been observed by increasing concentration of Sn in (CdZnS:Ce)Sn films. Average crystallite size, measured from XRD data, was found to be increased with increasing concentration of Sn. An increase in the concentration of Sn shifted the UV-Vis absorption edge toward the higher wavelength side. Energy band gap for undoped CdZnS and Ce–Sn co-doped CdZnS varied from 2.608 eV to 2.405 eV. The SEM micrographs of CdZnS and (CdZnS:Ce)Sn films showed the leafy-like and ball-like structures. The presence of Sn and Ce was confirmed by EDAX analysis.

Open access
Deposition time and annealing effects on morphological and optical properties of ZnS thin films prepared by chemical bath deposition

Abstract

Nanocrystalline zinc sulfide thin films were prepared on glass substrates by chemical bath deposition method using aqueous solutions of zinc chloride, thiourea ammonium hydroxide along with non-toxic complexing agent trisodium citrate in alkaline medium at 80 °C. The effect of deposition time and annealing on the properties of ZnS thin films was investigated by X-ray diffraction, scanning electron microscopy, optical transmittance spectroscopy and four-point probe method. The X-ray diffraction analysis showed that the samples exhibited cubic sphalerite structure with preferential orientation along 〈2 0 0〉 direction. Scanning electron microscopy micrographs revealed uniform surface coverage, UV-Vis (300 nm to 800 nm) spectrophotometric measurements showed transparency of the films (transmittance ranging from 69 % to 81 %), with a direct allowed energy band gap in the range of 3.87 eV to 4.03 eV. After thermal annealing at 500 °C for 120 min, the transmittance increased up to 87 %. Moreover, the electrical conductivity of the deposited films increased with increasing of the deposition time from 0.35 × 10−4 Ω·cm−1 to 2.7 × 10−4 Ω·cm−1.

Open access
Development of sol-gel derived gahnite anti-reflection coating for augmenting the power conversion efficiency of polycrystalline silicon solar cells

Abstract

The present research is focused on developing ZnAl2O4 (gahnite) spinel as an antireflection coating material for enhanced energy conversion of polycrystalline silicon solar cells (PSSC). ZnAl2O4 has been synthesized using dual precursors, namely aluminum nitrate nonahydrate and zinc nitrate hexahydrate in ethanol media. Diethanolamine has been used as a sol stabilizer in sol-gel process for ZnAl2O4 nanosheet fabrication. ZnAl2O4 nanosheet was deposited layer-by-layer (LBL) on PSSC by spin coating method. The effect of ZnAl2O4 coating on the physical, electrical, optical properties and temperature distribution in PSSC was investigated. The synthesized antireflection coating (ARC) material bears gahnite (ZnAl2O4) spinel crystal structure composed of two dimensional (2D) nanosheets. An increase in layer thickness proves the LBL deposition of ARC on the PSSC substrate. The ZnAl2O4 2D nanosheet comprising ARC on the PSSC was tested and it exhibited a maximum of 93 % transmittance, short-circuit photocurrent of 42.364 mA/cm2 and maximum power conversion efficiency (PCE) 23.42 % at a low cell temperature (50.2 °C) for three-layer ARC, while the reference cell exhibited 33.518 mA/cm2, 15.74 % and 59.1 °C, respectively. Based on the results, ZnAl2O4 2D nanosheets have been proven as an appropriate ARC material for increasing the PCE of PSSC.

Open access