Papers by Keyword: Zinc Oxide (ZnO)

Abstract: ZnO nanostructures with controllable morphology were synthesized by confining the reaction of Zn(NO3)2 and MEA in Reverse Micellar system composed with CCl4-AOT-Water. It was found that the ratio of MEA/ Zn(NO3)2 is decisive on the morphology of ZnO nanostructures. As the lower ratio of MEA/ Zn(NO3)2 is lower than 2:1, ZnO nanodots with a size about 5 nm were generated; the increase in the ratio of MEA/ Zn(NO3)2 leads to the formation of ZnO nanorods.

Abstract: Different types of Li-doped ZnO (LDZ) (Li = 0 to 10%) powders were prepared by following a novel pyro-hydrolysis route at 450°C, and were thoroughly characterized by means of thermo-gravimetry (TG), differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared (FT-IR) spectroscopy, Fourier-transform Raman spectroscopy (FT-Raman), diffuse reflectance spectroscopy (DRS), ultra-violet visible (UV-vis.) spectroscopy, BET SA, and zeta potential (ζ) measurements. Photocatalytic activity of these powders was evaluated by means of methylene blue (MB) degradation experiments conducted under the irradiation of simulated and natural solar light. Characterization results suggest that both pure and LDZ powders are quite thermally stable up to a temperature of 700°C and possess band gap (BG) energies in the range of 3.16 to 3.2 eV with a direct band to band transition and ζ values of-31.6 mV to-56.4 mV. The properties exhibited by LDZ powders were found to be quite comparable to those exhibited by p-type semi-conducting LDZ powders. In order to study the kinetics of MB degradation reaction under the irradiation of simulated solar light, the Li (0.2 to 10%) and Al (0.5%) co-doped ZnO powders were also synthesized and employed for this purpose. The photocatalytic degradation of MB over Al and Li co-doped ZnO powders followed the Langmuir-Hinshelwood (L-H) first order reaction rate relationship. The 10% Li and 0.5% Al co-doped ZnO exhibited highest photocatalytic activity among various powders investigated in this study.

Abstract: In this study, Zn0.99Co0.01Al0.015O thin film has been prepared by sol-gel method. The structural and magnetic properties of the sample were investigated. X-ray diffraction spectroscopy analyses indicate that the Co and Al codoping can not disturb the structure of ZnO. No additional peaks are observed in the Zn0.99Co0.01AlxO and Al3+ and Co2+ substitute for Zn2+ without changing the wurtzite structure. The resistance measurements confirm that Al ions increase the free carriers concentration. Based on the above experiments we think the ferromagnetic behavior of the sample could not originate from Co nanoclusters. The presence of free carriers and localized d spins is a prerequisite for the appearance of ferromagnetism. As the result, the carriers generated by Al doping is considered a main factor to induce the ferromagnetic phenomenon.

Abstract: Zinc oxide (ZnO) nanorods have been grown on silicon substrate by chemical bath deposition method in an aqueous solution that contained zinc nitrate hexahydrate and hexamethylenetetramine. The ZnO seed layer was deposited on substrate to promote growth of ZnO nanorods. Growth temperature was varying in order to form well aligned ZnO nanorods From XRD analysis confirmed that grown ZnO nanorods has wurtzite crystal structure and grown in the [10 direction. Well aligned and better size distribution of ZnO nanorods obtained at 75°C for 1h.

Abstract: Zinc oxides nanowires (ZnO NWs) were successfully synthesized on bare silicon substrates using Chemical vapour deposition (CVD) method without foreign catalyst. The ZnO NWs had good crystal quality as they exhibited a strong UV emission (373 nm) corresponding to the free exciton emission and a weak green arising from defect-related emission in PL measurement. Measurement of low temperature photoluminescence spectra show a peak of free exciton and defect bound excitons. The growth of these catalyst-free ZnO NWs was governed by Vapour-Solid (VS) mechanism.

Abstract: Metal oxide surge arrestors (MOSA) are commonly used in the electrical power system to protect the insulation from the damaging effect of lightning. This paper presents the damage characteristics and possible root cause of two exploded ZnO type arrestors. Both failures were not caused by lightning surge. They had degraded due to moisture ingress, leading to contamination and corrosion, accelerating thermal runaway effect in the ZnO elements and eventually caused early voltage breakdown under normal operating voltage. This indicated an inadequacy in the sealing components.

Abstract: The N, S codoped ZnO was synthesized by microwave assisted hydrothermal method. The N, S codoping narrowed the band gap of ZnO (formed impurity states in the band gap), hence shift light response to range of visible light. Furthermore, the doped ZnO exhibits significantly higher photocatalytic activity than that of pure ZnO for degradation of reactive brilliant blue KN-R aqueous solution under simulative solar irradiation.

Abstract: The effect of Zinc-Oxide (ZnO) thin film annealed in different ambiences is presented. To achieve low cost and environmentally friendly process, ZnO aqueous solution is synthesized by dissolving zinc acetate dihydrate in deionized water directly. Zinc oxide aqueous solution of high solubility and stability is presented. High quality and dense Zinc oxide thin film is formed by spin coating. Annealing temperatures are in the range of 300 °C~500 °C, and annealing ambiences of both air and N2 are discussed.

Abstract: The ZnO nanorods with sharp tip have been fabricated via water cooling treatment during the hydrothermal growth. The morphology and crystal structure of the zinc oxide nanostructure were examined by field-emission scanning electron microscopy and x-ray diffraction, respectively. The structural characterizations revealed that the as-synthesized nanorods were single crystalline, with a hexagonal phase. It has been demonstrated that the cooling rate is the critical factor of the synthesis of the sharp tip ZnO nanorods by comparing the different cooling conditions. The growth mechanism for the sharp tip ZnO nanorods has been proposed on the basis of the different crystallographic habits of wurtzite hexagonal ZnO crystals.

Abstract: ZnO hierarchical microstructures with uniform sea urchin-like morphology have been successfully synthesized through a facile and reliable ultrasound irradiation route by using Zn(CH3COO)2•2H2O and KOH as raw materials. The ZnO sample is investigated with XRD, SEM, TEM and HRTEM. Results indicate that the as-prepared sea urchin-like ZnO microstructures are assembled by numerous needle-like nanocrystals with the size about 2µm in length and about 100nm in diameter. The preferred growth orientation of these ZnO nanoneedles are along [101] direction. A blue shift in UV-vis absorption spectrum of the as-prepared ZnO sample is observed.