Chalcogenide glasses of (Se₉₀Te₁₀)_100-x In_x (x = 0, 3, 6, 9, 11) alloys are prepared by melt quench technique. Differential scanning calorimetry (DSC) technique with different heating rate is used to study the dependence of the glass transition temperature (T_g) and fragility dynamics m on the In content in the Se-Te matrix. It is observed an increase of T_g with increasing In content. The glass transition temperature is differently defined according to the different degree of conversion of the glass. The activation energy of the glass transition (E_g) is evaluated using Kissinger, Moynihan kinetic and the partial area (isoconversional) methods. Analysis of experimental data shows that E_g changes with the degree of conversion from the glassy to the supercooled phase. The variation of the fragility with indium content is attributed to the formation of network structure. The employed theoretical models to describe the kinetics of the glass transition are valid.

In recent paper anodization of copper foams in 0.1 M K₂CO₃ is reported. Anodization was performed in the voltage range of 5–25 V and in all the cases oxides with a developed surface area were obtained. However, anodizing only at 20 and 25 V resulted in the formation of nanostruc-tures. In all the cases, the products of anodizing consisted of crystalline phases like cuprite (Cu₂O), tenorite (CuO), parameconite (Cu₄O₃) as well as spertiniite (Cu(OH)₂). Copper foams after ano-dizing were applied as catalysts in the photocatalytic decolorization of a model organic compound such as methylene blue. The highest photocatalytic activity was observed for samples anodized at 25 V and closely followed by samples anodized at 5 V. The anodized copper foams proved to be a useful material in enhancing the photocatalytic efficiency of organic dye decomposition.

This paper is aimed to perform an analytical study to identify the optimum operating conditions for the ozone generation in the dielectric barrier discharges. The dielectric barrier discharges have been formed inside a reactor in the form of two coaxial cylindrical electrodes. The reactor was fed by constant flow rates from the dry air and the oxygen gas separately at the normal atmospheric conditions, in parallel with applying a sinusoidal ac voltage to the discharge electrodes. The electric power consumed in the dielectric barrier discharges and the ozone concentration generated in the flowing gases through the reactor have been measured as a function in the peak value of the ac voltage applied to the reactor. The experimental results of the discharge power consumed inside the reactor were investigated by using Manley's equation. The optimum operating conditions for the ozone generated in the flowing gases through the reactor have been identified by applying Becker equation and Vasilʼev-Kobozev-Eremin equation on the experimental results measured in the dry air and the oxygen gas respectively. The obtained results showed that the optimum operating conditions for the ozone generation in both the dry air and the oxygen gas are only achieved with the lower flow rates for the gases through the reactor, and they in the oxygen gas are better than the dry air. The values of the coefficients of ozone formation and destruction in the oxygen gas are higher than their values in the dry air, and their values decrease with increasing the flow rate of the gases through the reactor. 

High altitude Venus ionosphere is characterized by the presence of H+ and O+ ions as well as electrons. Because of these two positive ions, the ion-acoustic wave (IAW) was observed. Propagation properties of nonlinear IAWs in the Venusian ionosphere are investigated. Korteweg de-Vries (KdV) equation is derived for weakly nonlinear behavior of the IAWs, while Sagdeev pseudo-potential is obtained to study an arbitrary amplitude IAWs. The region for the lower and upper limits of Mach number for the existence of soliton structures are determined. The physical parameters, such as density and temperature ratios, are investigated on the profiles of both weakly and fully nonlinear waves. Furthermore, subsonic waves can exist in the lower ionosphere whereas supersonic waves propagate at higher altitude. This is in good agreement with the observations.

Photoanode plays a crucial role in the operation of dye-sensitized solar cells due to its many functions:(1) provide a surface for the adsorption of the dye and (2) accepts photoinjected electrons from the excited dye and conducts them to the external circuit to produce an electric current. The research embodied in this thesis describes the synthesis of composite metal oxides nanostructure as well as pure binary metal oxides and evaluate their suitability as a photoanode in the dye-sensitized solar cells. Due to the advantageous properties such as favorable conduction band level of TiO2/ZnO, high electron mobility (150 cm2 V-1 s-1 for nanocrystals) and high electrical conductivity of SnO2, attention is devoted to these three materials. Composite metal oxides in the SnO2-TiO2 and SnO2-ZnO nanostructures are chosen for the current work to overcome the limitation of the single metal oxide; such as low conduction band edge of SnO2, low charge mobility of TiO2 and lack of stability of ZnO based photoanode in dye-sensitized solar cells. Electrospinning method is adopted for the synthesis of composite nanostructures morphologies due to the feasibility of this method for developing nanoscale materials in large scales. The composites formation is confirmed by X-ray diffraction, energy dispersive X-ray and X-ray photoelectron spectroscopy analyses. The morphology is examined by field emission scanning electron microscopy and transmission electron microscopy with selected area electron diffraction. Morphological studies show that SnO2-TiO2 formed in two structures, nanofibers and nanoflowers by adjusting the precursor’s concentration whereas …

EXTENDED ABSTRACT ZnO-SnO2 and TiO2-SnO2 composite nanofibers (CNFs) are synthesized by electrospinning a polymeric solution containing an equimolar concentration of the metals precursors and subsequent annealing. The composite formation is demonstrated by X-ray diffraction and energy dispersive X-ray measurements and morphology by scanning electron microscopy. Synergy in electronic and electrical properties are demonstrated by cyclic voltammetry, absorption spectroscopy, and electrochemical impedance spectroscopy. The TiO2-SnO2 and SnO2-ZnO CNFs offer valuable properties when utilized as a photoanode in dye-sensitized solar cells in terms of photoconversion efficiency (PCE~ 8.00%) and (~ 5.60%), respectively, compared to their binary counterparts SnO2 (~ 3.90%), TiO2 (~ 5.1%) and ZnO (~ 1.38%). Recently, one-dimensional nanofibers materials, have been widely growing interest because of their fundamental scientific interest as well as their potential applications in functional devices [1-3]. Among them, nanostructured metal oxide semiconductors (MOS), tin oxide (SnO2), zinc oxide (ZnO) and titanium dioxide (TiO2) have demonstrated excellent performance in various technological applications [4, 5] such as; in dye-sensitized solar cells (DSSCs). However, currently, the interests are shifting towards the synthesis of more complex structures employing two MOS for a range of applications including photoelectrode in DSSCs. These coupled MOS overcome the limitation of a single MOS, such as core-shell and composite nanostructures which possess qualities of both the component oxides and permit

Composites of functional materials have long been synthesized for achieving enhanced physical and chemical properties such that they serve improved functions for a range of nanoelectronic devices and architectures. This is because many nanoelectronic devices demands materials of multiple functions including high conductivity and high surface area. In particular, these two functions are mutually competing in nanostructured materials–when the surface area increases as a result of nanostructuring processes, the increased surface fraction imposes surface states that lie within the bandgap of the material and subsequently the electrical conductivity is lowered.[1] Many attempts have been adopted in the past to have high surface area and highly conducting materials in the single material system; however, making a composite is the most simple one and could be industrially accepted. Composite properties are achieved through many methods such as physical mixing of its components, chemical methods such as core/shell, hierarchical structures, nanoparticle-decorated nanowires, and carbon-reinforced porous materials are few examples.[2, 3] However, preparing a composite in the form of a nanowire or a 3D nanoflower is relatively new. Given the paramount importance of energy, recently energy conversion and storage devices are researched globally with high intensity. Optical transparency and workability at low light conditions enable the dye-sensitized solar cells (DSSCs) and the perovskite solar cells (PSCs) as desirable choice as smart windows in modern buildings for adding aesthetics with diverse choice of colors while producing …

Composite materials are aimed to combine properties of their components to achieve a desired device functionality; however, synthesizing them in morphologies such as one-dimensional nanofibers is challenging. This article compares optical and electrical properties of ZnO–SnO₂ composite nanofibers (CNFs) synthesized by electrospinning technique for energy-harvesting applications with similar CNFs (TiO₂–SnO₂) and their single-component nanofibers (NFs). The composite formation is confirmed by X-ray and electron diffraction, energy-dispersive X-ray, high-resolution transmission electron microscopy (HRTEM), and X-ray photoelectron spectroscopy analyses; the morphology is examined by HRTEM and field-emission scanning electron microscopy. The electrochemical properties of the CNFs are studied by cyclic voltammetry, absorption spectroscopy, and electrochemical impedance spectroscopy. The CNFs behaved as a single semiconducting material of band gap ∼3.32 (ZnO–SnO₂) and ∼3.15 (TiO₂–SnO₂) eV. The CNFs showed superior photoconversion efficiency (∼5.60% for ZnO–SnO₂ and ∼8.0% for TiO₂–SnO₂ CNFs) compared to its binary counterparts SnO₂ (∼3.90%), ZnO (∼1.38%), and TiO₂ (∼5.1%) when utilized as photoanodes in dye-sensitized solar cells.

Nanoparticles of Zn_1−xNi_xFe₂O₄ (x = 0.0–1.0 in step of 0.2) ferrites are synthesized by microwave combustion method using glycine as a fuel. The structure, site occupancy and ferrimagnetic behavior have been characterized by X-ray diffraction (XRD), Mössbauer Spectroscopy (MS) and Vibrating Sample Magnetometer (VSM). Special emphasis is given to the information provided by each of these techniques concerning the impact of the site occupancy on the magnetic properties. The results reveal the formation of single phase cubic spinel with crystallite sizes in the range of 30–42 nm. The lattice constants and the lattice strains decrease gradually with increasing Ni-content. Two well-defined Mössbauer sextets in the spectra at 78 K belong to octahedral [B] and tetrahedral (A) sites, respectively, confirming the formation of Zn_1−xNi_xFe₂O₄ spinel. The isomer shift (δ_Fe) values were assigned to Fe³⁺ ions distributed in both A and B sites. The quadrupole splitting (Δ) values showed also that the orientation of the magnetic hyperfine field (H_int) with respect to the principle axes of the electric field gradient (EFG) is random. The nanosize samples In the presence of an externally applied magnetic field prepared exhibit the hysteresis loops of the ferrimagnetic nature. The value of saturation magnetization increases with introducing Ni up to x = 0.8 and then it decreases. The magnetic data parameters of this structure are discussed as a function of the content of Ni ions.

The developments in mobile/portable electronics and alternative energy vehicles prompted engineers and researchers to develop electrochemical energy storage devices called supercapacitors, as the third-generation type capacitors. Most of the research and development on supercapacitors focus on electrode materials, electrolytes, and hybridization. Some attempts have been directed towards increasing the energy density by employing electroactive materials, such as metal oxides and conducting polymers. However, the high cost and toxicity of applicable metal oxides and poor long-term stability of the conducting polymers paved the way for alternative electrode materials. The electroactive materials with carbon particles in composites have been used substantially to improve the stability of supercapacitors. Furthermore, the use of carbon particles and metal oxides could significantly increase the energy density of supercapacitor electrodes compared to metal oxides. Recent developments in carbon materials, such as carbon nanotubes (CNTs), activated carbon, reduced graphene oxide, and graphene, have found applications in supercapacitors because of their enhanced double-layer capacitance due to the large surface area, electrochemical stability, and excellent mechanical and thermal properties.