Z.I. Zaki

Bio: Z.I. Zaki is an academic researcher from Taif University. The author has contributed to research in topics: Photocatalysis & Materials science. The author has an hindex of 12, co-authored 43 publications receiving 531 citations.

Zinc oxide thin films prepared by thermal evaporation deposition and its photocatalytic activity

Abstract: Thin zinc oxide (ZnO) films have been grown on silicon substrates by thermal physical vapor deposition approach. X-ray diffraction (XRD) analyses reveal that the deposited films are polycrystalline ZnO phase. Atomic force microscopy images (AFM) show needle-like shape highly oriented ZnO crystals. Thin film thickness ranges from 10 to 80 nm. X-ray photoelectron spectroscopy (XPS) results declare that the films compose mainly of Zn and O. Nevertheless, Si is not detected in the films and consequently no possibility of any silicide formation as is confirmed by XRD analysis. Photocatalytic decomposition of azo-reactive dye on ZnO films is tested. The results show that the dye decomposition efficiency increases with decreasing pH. Maximum photodecomposition, 99.6% is obtained at pH 2 with 10 mg/l dye concentration.

Chemical activation of calcium aluminate cement composites cured at elevated temperature

Abstract: The influence of sodium sulfate, as an activator, on the hydration of calcium aluminate cement (CAC)–fly ash (FA)–silica fume (SF) composites was investigated. Different mixes of CAC with 20% pozzolans (20% FA, 20% SF and 10% FA + 10% SF) were prepared and hydrated at 38 °C for up to 28 days. The hydration products were investigated by XRD, DSC and SEM. The results showed that sodium sulfate accelerated the hydration reactions of calcium aluminate cement as well as the reactions of FA and SF with CAH10 and C2AH8 to form the stratlingite (C2ASH8). The later reactions prevent the strength loss by preventing the conversion of CAH10 and C2AH8 to the cubic C3AH6 phase. The acceleration effect of Na2SO4 on the reactivity of fly ash was more pronounced than on the reactivity of silica fume with respect to reaction with CAH10 and C2AH8 phases.

Structural and magnetic properties of cadmium substituted manganese ferrites prepared by hydrothermal route

Abstract: Cd-substituted manganese ferrite Mn 1− x Cd x Fe 2 O 4 powders with x having values 00, 01, 03 and 05 have been synthesized by hydrothermal route at 180 °C in presence of NaOH as mineralizer The obtained ferrite samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM) and vibrating sample magnetometer (VSM) The XRD analysis showed that pure single phases of cubic ferrites were obtained with x upto 03 However, sample with x ≥ 05 showed hexagonal phase of cadmium hydroxide (Cd(OH) 2 ) besides the ferrite phase The increase in Cd-substitution upto x =03 leads to an increase in the lattice parameter as well as the average crystallite size of the prepared ferrites The average crystallite size increased by increasing the Cd-content and was in the range of 39–57 nm According to VSM results, the saturation magnetization increased with Cd ion substitution

Reduced graphene oxide-supported PbTiO3 nanospheres: Improved ceramic photocatalyst toward enriched photooxidation of thiophene by visible light

Abstract: Perovskite titanate-based nanostructures have got enough attraction for environmental remediation as active and stable photocatalysts. More, the removal of stable organic compounds such as thiophene (ThP) is of great importance in different industries. Here, we have synthesized PbTiO3 nanospheres using a modified sol-gel method. The PbTiO3 loaded on different amounts of reduced graphene oxide (rGO) to yield PbTiO3@rGO nanocomposite. The improved PbTiO3@rGO exhibited a complete photooxidation of ThP after 60 min of applying visible light with outstanding recyclability. The PbTiO3@rGO nanocomposites demonstrated an enlargement in the visible light absorption with a reduction of its bandgap energy from 2.45 to 1.90 eV at 9 wt.% of rGO loading. Also, we noticed the decrease of electron-hole recombination rate by photoluminescence and photocurrent measurements as well. This work proves the applicability of using rGO supported perovskites structured photocatalysts for several environmental remediation-related purposes.

In situ synthesis of high density magnetic ferrite spinel (MgFe2O4) compacts using a mixture of conventional raw materials and waste iron oxide

Abstract: A mixture of magnesite ore and waste iron oxide (mill scale) was used to synthesize high density magnesium ferrite compacts. The effect of different mixture composition (weight percentage of magnesite ore to mill scale) as well as the sintering temperatures on the phase change, compressive strength, physical and magnetic properties of sintered compacts was investigated. The results indicated that a single phase ferrite spinel is obtained in a compact produced from a mixture consisting of 40 wt% magnesite ore and 60 wt% mill scale and sintered at different temperatures. On the other hand, this mixture composition produced compacts possessing low porosity and high saturation magnetization of 6% and 31.89 emu/g, respectively when it is sintered at 1550 °C for 2 h.

Strategies of making TiO2 and ZnO visible light active.

Abstract: In modern purification techniques employing semiconductor mediated photooxidation of toxic substances, zinc oxide (ZnO) and titanium dioxide (TiO2) are the most widely used metal oxides due to their unique blend of properties. However, the band edges of these semiconductors lie in the UV region which makes them inactive under visible light irradiation. Researchers have been interested in the modification of electronic and optical properties of these metal oxides for their efficient use in water and air purification under visible light irradiation. Visible light activity has been induced in TiO2 and ZnO by surface modification via organic materials/semiconductor coupling and band gap modification by doping with metals and nonmetals, co-doping with nonmetals, creation of oxygen vacancies and oxygen sub-stoichiometry. This paper encompasses the progress and developments made so far through these techniques in the visible light photocatalysis with TiO2 and ZnO. Recently, nitrogen doping in titania has been extensively carried out and therefore somewhat detailed discussion in this respect has been presented. Visible light activation of titania clusters encapsulated in zeolite-Y by nitrogen doping and incorporation of dye or organic sensitizers inside the zeolite framework, has also been highlighted in this review.

Inorganic-modified semiconductor TiO2 nanotube arrays for photocatalysis

Abstract: Semiconductor photocatalysis is a promising physicochemical process for the photodegradation of organic contaminants and bacterial detoxification. Among various oxide semiconductor photocatalysts, TiO2 has garnered considerable attention because of its outstanding properties including strong oxidizing activity, chemical and mechanical stability, corrosion resistance, and nontoxicity. This Review briefly introduces the key mechanisms of photocatalysis, highlights the recent developments pertaining to pure TiO2 nanotube arrays and TiO2 nanotube arrays modified by non-metals, metals and semiconductors, and their applications in the photocatalytic degradation of organic dyes. The improved photocatalytic efficiencies of modified TiO2 nanotube arrays are compared with unmodified counterparts. Current challenges and prospective areas of interest in this rich field are also presented.

Thermal and Environmental Stability of Semi-Transparent Perovskite Solar Cells for Tandems Enabled by a Solution-Processed Nanoparticle Buffer Layer and Sputtered ITO Electrode.

Abstract: A sputtered oxide layer enabled by a solution-processed oxide nanoparticle buffer layer to protect underlying layers is used to make semi-transparent perovskite solar cells. Single-junction semi-transparent cells are 12.3% efficient, and mechanically stacked tandems on silicon solar cells are 18.0% efficient. The semi-transparent perovskite solar cell has a T 80 lifetime of 124 h when operated at the maximum power point at 100 °C without additional sealing in ambient atmosphere under visible illumination.

Degradation of wastewaters containing organic dyes photocatalysed by zinc oxide: a review

Abstract: Organic dyes are one of the largest groups of pollutants discharged into wastewaters from textile and other industrial processes. Owing to the potential toxicity of the dyes and their visibility in surface waters, removal and degradation of them have attracted considerable attention worldwide. A wide range of approaches have been developed, amongst which the heterogeneous photocatalysis involving zinc oxide (ZnO) emerges as a promising new route for water purification process. For the first time, we attempt to review and summarize the recent research on ZnO photocatalytic systems for organic dyes degradation. The photocatalysis on modified ZnO is also discussed, in particular aiming at enhancing the degradation efficiency and activity in visible region as well as solar irradiation. The effects of key operational parameters on the photocatalytic performance in terms of the degradation and mineralization of dyes are detailed. This review also highlights the utilization of multivariate analysis to d...

Comparison of dye degradation efficiency using ZnO powders with various size scales.

Abstract: ZnO powders with various size scales (mean diameter size: 10, 50, 200 and 1000nm) have been prepared by two different preparation methods, thermal evaporation method and chemical deposition method, and examined as photocatalysts for the UV-induced degradation of methyl orange in water solution. ZnO nanoparticle with diameter size 50nm prepared by thermal evaporation method showed the highest photocatalytic activity. In addition, the tetrapod ZnO nanopowders had the higher efficiency than irregular ZnO particles. However, the smallest 10nm ZnO nanoparticle prepared by chemical deposition method indicated the lower efficiency contrast to 200nm ZnO powders prepared by thermal evaporation method. The results indicated preparation method was the decisive factor rather than size and morphology. Moreover, the effect of catalyst loading, pH value and the initial dye concentration on the final degradation efficiency were discussed through the photocatalytic experiments using 50nm ZnO nanoparticle as photocatalyst.