Atif Mossad Ali

Sol–gel synthesis of ZnO–SiO2 thin films: impact of ZnO contents on its photonic efficiency

Highly crystalline ZnO–SiO2 films obtained by a sol–gel method at different ZnO contents were deposited on silicon substrate (P(100)) using spin coating process. The XRD results revealed that the strong ZnO(100) peak isxa0grown with highly c-axis oriented film and the crystallinity isxa0progressively improved with increasing ZnO contents. SEM micrographs of the films deposited on silicon substrate show a homogeneous and uniformity structure at different ZnO content. The prepared ZnO–SiO2 filmsxa0are compared with either a film prepared from a commercial photocatalysts Hombikat UV-100 or Pilkington Glass Activ™ by the determination of their photonic efficiencies for degradation of methylene blue. The photocatalytic efficiency of the 10xa0wt% ZnO–SiO2 film was found to be about four times higher than film prepared from UV-100 or Pilkington Glass Activ™. The photocatalytic efficiencies of ZnO–SiO2 films arexa0increased with increasing ZnO content from 1xa0wt% to 10xa0wt% ZnO and then decreased at 15xa0wt% ZnO. The order of photocatalytic efficiencies of ZnO–SiO2 films at different ZnO content and commercial photocatalysts after 6xa0h illumination were as following: 10xa0wt% ZnOxa0>xa015xa0wt% ZnOxa0>xa01xa0wt% ZnOxa0> as-preparedxa010xa0wt% ZnO–SiO2 filmxa0>xa0UV-100xa0>xa0Pilkington Glass Activ™, which suggested that the ZnO–SiO2 films are photoactive than commercial photocatalysts. The improved efficiency and potentially the low-cost synthesis suggest that this material might be practically useful as a photocatalyst film.

The Structure and Kinetics of the Nanoscale Precipitation Processes in Al-1.0 wt pct Mg2Si-0.4 wt pct Mg-0.5 wt pct Ag Alloy

The influence of addition of 0.4 wt pct Mg on the precipitation sequence in the balanced Al-1.0 wt pct Mg2Si bearing 0.5 wt pct Ag has been investigated during the continuous heating of the quenched alloy from the solid solution state. Differential scanning calorimetry (DSC) and high-resolution transmission electron microscopy techniques have been used. The DSC experiments showed that all processes occurred are thermally activated. The activation energies of the precipitation processes have been determined and hence the kinetics of these precipitates have been determined. The obtained results have shown that the existence of excess Mg inhibits the formation of the early stage clusters of solute-vacancy clusters. These clusters can be assisted by the binding energies between solute Si, Mg, and Ag atoms and the excess vacancies. On the other hand, excess Mg accelerates the precipitation of random, β′-phase and β-phase precipitates.

The Effect of TiO2 on the Optical and Mechanical Properties of Heavy Metal Oxide Borosilicate Glasses

The density, the molar volume, the rigidity, the UV reflectance and the glass transition temperatures of the x TiO2 – 20Na2B4O7 – 30PbO – 20SiO2 – (30-x) Bi2O3 glass system were determined. These physical parameters were acquired by using the DTA, ultrasonic and UV techniques to explore the effect of TiO2. The replacement of Bi2O3 by TiO2 decreased these physical parameters, which suggested the glass modifier role of TiO2. This attitude can be attributed to the smaller ionic radii, the density and the polarizability of TiO2 than that of Bi2O3. Moreover, according to the FTIR, TiO2 created non-bridging oxygens in the network that decreased the bond strength of the glass system. The decreases of the rigidity, the glass transition temperature and the optical band gap are sensitive to the decrease of the bond strength and the created non-bridging oxygens in the lead alkali borosilicate network. The obtained results were discussed in relation to the role of TiO2 in the lead borosilicate glass system.

Fabrication and Characterization of Glass and Glass-Ceramic from Cement Dust and Limestone Dust

Recycling the solid wastes like cement dust and limestone dust and using in the manufacturing of glass and glass - ceramics are strongly needed. These glasses fabricated by melt-quench technique. The X-ray diffraction (XRD) patterns of all the studied samples confirmed the amorphous nature These glasses have been investigated for their physical properties using density and molar volume, structural properties using FTIR spectroscopy, optical properties using UV-Vis spectroscopy, thermal analysis and mechanical properties. The density, molar volume and refractive index vary with the concentration of CaO. The variations of various physical, structural, thermal analyses, mechanical and optical properties with the concentration of CaO in this glass system depict a strong structural influence of CaO. The ultrasonic velocity of these glasses has been decreased with addition of CaO, this decrease is connected to the decreasing the bonding strength between Calcium - oxygen are lower than the bond between silicon - oxygen (32-106 k cals).The elastic moduli of these glasses determined experimentally and calculated theoretically, according to Makishima–Mackenzie model decreased with increasing of CaO. This behavior may be related to changing the coordination number with an increasing of CaO and the decrease in the average force constant and crosslink density. The crystalline phase of the prepared glass ceramic is diopside with the chemical formula (Ca MgO6 Si) in all selected samples.

Highly Sensitive Ethanol Chemical Sensor Based on Novel Ag-Doped Mesoporous α–Fe 2 O 3 Prepared by Modified Sol-Gel Process

Mesoporous α–Fe2O3 has been synthesized via a simple sol-gel procedure in the presence of Pluronic (F-127) triblock copolymer as structure directing agent. Silver (Ag) nanoparticles were deposited onto α–Fe2O3 matrix by the photochemical reduction approach. Morphological analysis revealed the formation of Ag nanoparticles with small sizes <u200920xa0nm onto the mesoporous structure of α–Fe2O3 possessing <u200950xa0nm semi-spherical shape. The XRD, FTIR, Raman, UV-vis, PL, and N2 sorption isotherm studies confirmed the high crystallinity, mesoporosity, and optical characteristics of the synthesized product. The electrochemical sensing toward liquid ethanol has been performed using the current devolved Ag/α–Fe2O3-modified glassy carbon electrode (GCE) by cyclic voltammetry (CV) and current potential (I-V) techniques, and the obtained results were compared with bare GCE or pure α–Fe2O3. Mesoporous Ag/α–Fe2O3 was found to largely enhance the sensor sensitivity and it exhibited excellent sensing characteristics during the precision detection of low concentrations of ethanol. High and reproducible sensitivity of 41.27xa0μAmM−u20091xa0cm−u20092 at lower ethanol concentration region (0.05 to 0.8xa0mM) and 2.93xa0μAmM−u20091xa0cm−u20092 at higher concentration zone (0.8 to 15xa0mM), with a limit of detection (LOD) of 15.4xa0μM have been achieved. Investigation on reaction kinetics revealed a characteristic behavior of mixed surface and diffusion-controlled processes. Detailed sensing studies revealed also that the sensitivity toward ethanol was higher than that of methanol or isopropanol. With further effort in developing the synthesis and fabrication approaches, a proper utility for the current proposed protocol for fabricating a better sensor device performance is possible.

Photoluminescence features of magnetic nano-metric metal oxides

Copper oxide (CuO) and cobalt oxide (Co3O4) nanoparticles (NPs) have been synthesized using microwave irradiation method. These NPs have been prepared using copper nitrate and cobalt nitrate, respectively as the starting materials. The resulted powder of these NPs were explored by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), thermogravimetry and differential thermal analysis (DTA). XRD observations obtained the formation of nanostructure phase for both types of these NPs. The structural observations were helped for identifying the nano nature of these both materials. Optical properties such as photoluminescence (PL) and absorbance (A) of CuO and Co3O4 NPs have been studied. A resulted shift of PL with respect to absorption peak is 290 and 172xa0nm for CuO and Co3O4 NPs, respectively. Moreover, the magnetic hysteresis loop of both CuO and Co3O4 NPs were measured. The magnetic investigations obtained that the magnetic response with a maximum moment Mu2009≤u20090.07xa0emu/g is shown up to the maximum applied the field of 5xa0kOe for CuO NPs which is related to the uncompensated surface spins. On the other hand, the magnetization curve has linear shape in the field range used with the irreversible contribution for Co3O4 NPs.

Roles of SiH4 in Growth, Structural Changes and Optical Properties Of Nanocrystalline Silicon Thin Films

Nanocrystalline silicon (ns‐Si) thin films deposited through plasma‐enhanced chemical vapor deposition technique were studied. These films were grown at low deposition temperature of 200u2009°C and at different silane flow rates ([SiH4]). Characterization of these films with Raman spectroscopy, x‐ray diffraction and atomic force microscopy revealed that no films deposited at [SiH4]u2009=u20090.0u2009sccm. In addition, the structural change from an amorphous to a nanocrystalline phase at [SiH4]u2009=u20090.2u2009sccm. The Fourier transform infrared spectroscopic analysis showed at low values of [SiH4]u2009(0.1u2009sccm), no hydrogen incorporated in the nc‐Si thin film. However, the intensity of the spectra around 2100 cm−1 is likely to decreases with increasing [SiH4]. We have observed photoluminescence (PL) at room temperature in the range of 1.7 eV to 2.4 eV for all the films. Presence of the very small crystallites (the size less than 20 nm) responsible for quantum confinement effect. Variations of the PL intensity, width and position are...

Improved luminescence properties of nanocrystalline silicon films deposited by plasma enhanced chemical vapour deposition technique at low temperature

Nanocrystalline silicon (nc-Si) films have been prepared by plasma-enhanced chemical vapour deposition (PECVD). The feed gases were SiF4/SiH4/H2. The deposition temperature, Td and the air exposure time were varied. The optical properties of the films were evaluated by measurement of the photoluminescence (PL) and the structural properties were investigated by measurements of x-ray diffraction, Fourier transform infrared absorption and Raman scattering. The structural changed from an amorphous to a nanocrystalline phase at Td = 80°C. In addition, it suggests that Td low condition lead to the increase in the density of SiH-related bonds and a decrease in the average grain size, . The oxygen absorption peak increases with the air exposure time. The PL intensity increases and blue shifts consistently with the decrease of and increase of oxygen content.