Fatma H. Margha

Electrocatalytic Oxygen Evolution on Nanoscale Crednerite (CuMnO2) Composite Electrode

Abstract In this study, nanoscale crednerite (CuMnO2) was prepared in the system xCuO–(70–x)MnO–30SiO2 , where x has values 10, 15, 20, 25 and 30, via melting quenching glass-ceramic technique. The electrocatalytic activity of the oxygen evolution reaction (OER) on CuMnO2 deposits has been studied in 1.0 M KOH (25 ℃) by means of cyclic voltammetry, linear sweep voltammetry, chronoamperometric and electrochemical impedance techniques. The study has shown that the catalytic activity had increased with the increase of Cu content in the electrode composition, where the optimum improvement in the apparent electrode catalytic activity was obtained at the M30 electrode (with x = 30). At E = 0.6 V versus Ag/AgCl, the apparent oxygen evolution current density observed at the M30 electrode is 4 times greater than that observed with M10 (x = 10). The order of the OER with respect to OH– concentration measured at low and high potentials is ∼ 1.0 and the roughness of the electrodes was decreased with the increase of the Cu content.

Transparent Nanocrystalline Glass-Ceramic System for Organic Pollutants Degradation

Because of the superior photocatalytic activities of nanocrystalline TiO2 and ZnO under UV irradiation, they were embedded into the glass system (SiO2, TiO2, ZnO, B2O3, Na2O, K2O, P2O5, Li2O and BaO) to provide easy separation from the aqueous system. Different contents of TiO2 and ZnO have been investigated. Conversion to glass-ceramic materials was carried out by heat treatment at 450 °C, which is the onset of the nucleation peak according to the differential thermal analysis (DTA) result, for different times. This heat treatment regime preserves the transparency of the prepared materials in the visible region and good absorption in the UV region. The high content of TiO2 or ZnO caused an improvement of microhardness of the prepared materials, though the presence of the two oxides with the same ratio decreased the microhardness values. Photocatalytic activity of the prepared glass-ceramic materials was investigated according to their efficiency for the degradation of humic acid (HA), the major precursor of disinfection by-products (DBPs), from water. All samples were proved to be photoactive with different extents. Four hours heat treatment at 450 °C appears to be the best conditions for the development of TiO2 and ZnO crystals leading to better photocatalytic activity.

Preparation and Electrical Characterization of Zn-Titanate / Borosilicate Glass Composites

A Composite materials from Zn-titanate/borosilicate glass of 10/0(ZT10), 9/1(ZT9), 7/3(ZT7) and 5/5(ZT5) ratios were prepared. Their XRD, SEM / EDX, electrical and dielectric properties were investigated. Willemite, rutile and Zn2TiO4 composite materials were developed through the sintering process. The incorporation of glass enhances the formation of willemite. The SEM micrographs show clear euhedral micro-size crystals of Zn2TiO4 spinel and willemite embedded in glassy groundmass. The EDX microanalysis shows the incorporation of Al- element into the structure of the formed phases. Both conductivity (σac) and dielectric constant (ε′)

Crystallization behaviour and hardness of glass ceramics rich in nanocrystals of ZrO2

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Investigating hydrogen storage behavior of CuMnO2 glass-ceramic material

, measured within frequency range 0.2 kHz -1 MHz, and temperature range 298- 573 (K). Glass-free sample showed the highest σac and ε′

Nanocrystalline Bi2O3–B2O3– (MoO3 or V2O5) glass-ceramic systems for organic pollutants degradation

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Effects of crystallization and microstructure on the dc electrical conductivity in the system xCuO–(70 − x) MnO–30SiO2

. Although, 5/5 sample exhibited relative higher values than those with 9/1 and 7/3. The dielectric constant of 9/1 and 7/3 and 5/5 samples show almost an independent behavior over a wide range of temperatures which was attributed to the micro-sized grains of crystalline phases and restraining effect of rigid glassy matrix. The results of ac conductivity may indicate the dominance of electronic conduction over the ionic transfer one in the studied samples. Therefore they may present good candidates for semiconductor materials in electronic devices.