Zinc Oxide Synthesis from Extreme Ratios of Zinc Acetate and Zinc Nitrate: Synergistic Morphology

The synthesis of ZnO comprising different ratios of zinc acetate (ZA) and zinc nitrate (ZN) from the respective zinc precursor solutions was successfully completed via a simple precipitation method. Zinc oxide powders with different mole ratios of ZA/ZN were produced—80/1, 40/1, and 20/1. The crystallinity, microstructure, and optical properties of all produced ZnO powders were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and UV-Vis-NIR spectrophotometry. The average agglomerated particle sizes of ZnO-80/1, ZnO-40/1, and ZnO-20/1 were measured at 655, 640, and 620 nm, respectively, using dynamic light scattering (DLS). The optical properties of ZnO were significantly affected by the extreme ratio differences in the zinc precursors. ZnO-80/1 was found to have a unique coral-sheet structure morphology, which resulted in its superior ability to reflect near-infrared (NIR) radiation compared to ZnO-40/1 and ZnO-20/1. The NIR-shielding performances of ZnO were assessed using a thermal insulation test, where coating with ZnO-80/1 could lower the inner temperature by 5.2 °C compared with the neat glass substrate. Due to the synergistic effects on morphology, ZnO-80/1 exhibited the property of enhanced NIR shielding in curtailing the internal building temperature, which allows for its utilization as an NIR-reflective pigment coating in the construction of building envelopes.

Simultaneously Enhanced Potential Gradient and Nonlinearity of ZnO Varistor Ceramics by MnO Doping with Nano-Sized ZnO Powders

ZnO varistor ceramics with a high potential gradient, as well as a high nonlinear coefficient, were reported and analyzed in this paper. With the use of nano-sized ZnO powders, the average grain size was reduced to about 2.6 μm, which successfully raised the potential gradient to 1172 V/mm. Moreover, the nonlinear coefficient increased to 48, and the leakage current was decreased to 8.4 μA/cm2 by doping a moderate amount of MnO (0.9 mol%). This was proven to be caused by the high Schottky barrier height formed at the grain boundary, where the Mn element segregated and, consequently, led to the increased density of interface states. Therefore, this could be considered as a potential method to simultaneously enhance the potential gradient and the nonlinear coefficient of ZnO varistor ceramics.

Synthesis of ZnO thin film by chemical spray pyrolysis using its nano powder

The deposition of metal oxides powder faces several problems, including poor adhesion to the bases deposited on them, the presence of many cracks, poor thickness control, and other disadvantages. The current study gives a new and simple idea to deposit thin films using two ZnO powders with nano and microparticle sizes on glass substrates. This was done by transforming the powders to Zinc acetate and then using chemical spray pyrolysis to deposit ZnO thin films. Scanning electron microscope (SEM) images showed that the prepared film from the nanopowder (ZnONano) lost the independence of powder’s nanoparticles and became a homogeneous film with nano projections. But the deposited one from the micro powder (ZnOMicro) had both nanorods and nanoplates. The different shapes and sizes of ZnO particles in ZnOMicro powder were disappeared after the Spray process. The two deposited films were homogeneous, crack-free and there were controllable thicknesses during the deposition. X-ray spectroscopy (EDS) was used to measure weights and atomic percentages of elements for the deposited films. The structures of the deposited films were approximately identical as the X-ray diffraction (XRD) technique showed. The optical properties of these two films were studied and their parameters were measured and calculated.

Soft X-ray nanospectroscopy for quantification of X-ray linear dichroism on powders

X-ray linear dichroism (XLD) is a fundamental property of many ordered materials that can for instance provide information on the origin of magnetic properties and the existence of differently ordered domains. Conventionally, measurements of XLD are performed on single crystals, crystalline thin films, or highly ordered nanostructure arrays. Here, it is demonstrated how quantitative measurements of XLD can be performed on powders, relying on the random orientation of many particles instead of the controlled orientation of a single ordered structure. The technique is based on a scanning X-ray transmission microscope operated in the soft X-ray regime. The use of a Fresnel zone plate allows X-ray absorption features to be probed at ∼40 nm lateral resolution – a scale small enough to probe the individual crystallites in most powders. Quantitative XLD parameters were then retrieved by determining the intensity distributions of certain diagnostic dichroic absorption features, estimating the angle between their transition dipole moments, and fitting the distributions with four-parameter dichroic models. Analysis of several differently produced ZnO powders shows that the experimentally obtained distributions indeed follow the theoretical model for XLD. Making use of Monte Carlo simulations to estimate uncertainties in the calculated dichroic model parameters, it was established that longer X-ray exposure times lead to a decrease in the amplitude of the XLD effect of ZnO.

A new Approach on Electrochemical Properties of Poly Aniline and Polymer Binders Impregnated Zn/ZnO Powders as Anodic Electrodes for Energy Storage Devices

A novel battery consisted of Zn/ZnO anode with polymer binders has been developed by the direct mixing method. The influence of PANI on the performances of Zn/ZnO anode surfaces has been studied using cyclic voltammetry, Tafel polarization, and Impedance studies. The additions of PANI have not formed any coatings on Zn/ZnO anodes. However, a thin layer of PANI has formed. XRD studies revealed that influence of PANI on the Zn/ZnO anodes had not shown any significant changes in the hexagonal phase. SEM images confirmed that Zn's dendrite structure is prevented by polymers such as PVP, PVA, and microemulsion of castor oil. The impedance studies have demonstrated that there is a reduction in Rct values accounted for enhanced conductance of Zn/ZnO anodes.

Structural, Optical and Electrical Properties of Cu doped ZnO Thin Films Grown by RF Magnetron Sputtering: Application to Solar Photocatalysis

RF sputtered undoped and Cu doped ZnO (CZO) thin films were deposited on unheated glass substrates using a mixed Cu2O and ZnO powders target at different Cu concentrations of 0, 1, 2, 3 and 4 wt.%. The effects of copper concentration on the structural, electrical, optical and photocatalytic properties of CZO films have been studied. From XRD and Raman spectroscopy studies, it was found that the deposited films were polycrystalline with a predominant hexagonal wurtzite structure along the c-axis perpendicular to the substrate surface. The presence of multiple interference fringes in the transmittance and reflectance spectra shows the good homogeneity of the films. All the films are highly transparent with transparency reaching 80% indicating the possibility to use these films as an optical window. The absorption tail gradually shifted towards a higher wavelength side, which resulted in the decrease of bandgap energy from 3.35 to 3.26 eV. All the sputtered films are highly conductive with a conductivity reaching 104 S.cm− 1.The effect of Cu-doping on the photocatalytic activity of ZnO thin films for the degradation of methylene blue (MB) dye was studied under sunlight irradiation and the results showed that the Cudoping provokes appreciable degradation of MB and reached a maximum for the 1 wt.% Cu doped ZnO film.

Mechanical and antibacterial properties of ZnO/chitosan bio-composite films

In the current study, ZnO/chitosan bio-composite films were produced via solution-casting method. Two different ZnO powders, micrometer (d50 ≅ 1.5 μm) and nanometer sized (d50 ≅ 100 nm), were used to investigate the effect of ZnO particle size and concentration (0, 2, and 8% w/w of chitosan) on the mechanical and antibacterial properties of the ZnO/chitosan bio-composite films. The incorporation of the ZnO powders into the chitosan film resulted in an increase in the tensile strength (TS) and a decrease in the elongation at break (EB) values. Mechanical test results revealed that TS and EB properties were considerably affected (p < 0.05) by the concentration and particle size of the ZnO reinforcement. Disc diffusion method demonstrated good antibacterial activities of bio-composite films containing high amount of ZnO (8% w/w of chitosan) against Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Bacillus subtilis. The growth-limiting effect of the films was more pronounced for S. aureus and K. pneumoniae. Due to enhanced TS and imparted antibacterial activity of the produced ZnO/chitosan bio-composite films, these materials are promising candidates for applications such as food packaging, wound dressing, and antibacterial coatings for various surfaces.