A. Ibrahim

Tuning the optical and dielectric properties of calcium copper titanate CaxCu3−xTi4O12 nanopowders

Calcium copper titanate CaxCu3−xTi4O12 (CCTO) nanopowders have been synthesized using the organic acid precursor method based on commercially available materials. The results revealed that cubic CCTO phase was accomplished for the formed citrate precursors annealed at 1000 °C for 2 h. The crystallite size of the formed powders was found to increase from 44.2 to 64.8 nm upon increasing the molar ratio of Ca2+ ion from 1.0 to 2.0. A slight increase in the lattice parameter “a” and unit cell volume were observed, while a slight decrease in the porosity was evidenced as a result of increasing Ca2+ ion concentration. FE-SEM observations of these powders confirmed their homogeneous regular cubic-like structure. It can be noted that the transmittance of the sample was around 85% with Ca2+ ratio 1.0. Furthermore, the band gap energy increased from 3.8 to 4.2 eV, and the DC resistivity was increased from 6.4 × 104 to 6.8 × 104 cm Ω with increasing calcium content. We demonstrate that without any dopant, only by controlling the chemistry and engineering of the interfacial regions at the grain boundaries, the dielectric loss was suppressed remarkably while retaining the giant dielectric constant. These investigations would allow the application of these materials in transparency, microelectronics and memory devices.

Statistical Evaluation of Phenol Degradation by Ozone Oxidation

Abstract Phenol is a major environmental contaminant produced by various industries. In this study, phenol degradation was achieved using ozone treatment. The main parameter affecting the phenol degradation, i. e., ozone concentration, H2O2/phenol molar ratio and reaction time, were studied using statistical design of experiments to optimize the phenol degradation in terms of studied parameters. The results of the statistical design indicated that the ozone oxidation can be used for phenol degradation reaching high efficiency of 100 %. It was indicated that there is not only one condition at which the complete degradation can be carried out but also several design points lead to the same results. For instance, the complete degradation can be achieved at six hours reaction time, 0.03 H2O2/phenol molar ratio, and 10 g/m3 ozone concentration.

Solid-state dye-sensitized solar cells based on Zn1−xSnxO nanocomposite photoanodes

Solid-state dye-sensitized solar cells (ss-DSSCs) comprising Sn2+-substituted ZnO nanopowder were purposefully tailored via a co-precipitation method. The solar cells assembled in this work were sensitized with N719 ruthenium dye and insinuated with spiro-OMeTAD as a solid hole transport layer (HTL). Evidently, significant enhancement in cell efficiency was accomplished with Sn2+ ions-substituted ZnO photoelectrodes by maintaining the weight ratio of SnO at 5%. The overall power conversion efficiency was improved from 3.0% for the cell with pure ZnO to 4.3% for the cell with 5% SnO substitution. The improvement in the cell efficiency with Sn2+-substituted ZnO photoelectrodes is attributed to the considerably large surface area of the nanopowders for dye adsorption, efficient charge separation and the suppression of charge recombination provided by SnO. Furthermore, the energy distinction between the conduction band edges of SnO and ZnO implied a type II band alignment. Moreover, the durability as well as the stability of 15 assembled cells were studied to show the outstanding long-term stability of the devices made of Sn2+ ion substituted ZnO, and the PCE of each cell remained stable and ∼96% of its primary value was retained for up to 100 h. Subsequently, the efficacy was drastically reduced to ∼35% after 250 h of storage.