Zinc Nitrate Concentration Research Articles

Urchin-like ZnO microspheres synthesized by thermal decomposition of hydrozincite as a copper catalyst promoter for the Rochow reaction

Urchin-like ZnO microspheres were successfully prepared by thermal decomposition of hydrozincite synthesized via homogeneous precipitation of zinc nitrate and urea in the presence of a nonionic surfactant polyethylene glycol. The synthesis conditions, such as reaction temperature and time, precursor concentration, and the amount of surfactant added, as well as the catalytic properties of urchin-like ZnO microspheres as promoters for a commercial copper catalyst in dimethyldichlorosilane synthesis were investigated. In addition, the formation mechanism of urchin-like microspheres from hydrozincite to ZnO was proposed. The ZnO samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, and N2 adsorption. It was found that zinc nitrate concentration and the amount of surfactant are the key factors that lead to the formation of urchin-like ZnO microspheres. These ZnO samples had BET surface areas of 16–30 m2 g−1 and an average diameter of 3–8 μm. Compared with commercial Zn microspheres and ZnO nanoparticles, urchin-like ZnO microspheres showed a better performance in dimethyldichlorosilane synthesis via the Rochow reaction due to their larger surface area, which created more interfacial contacts with the copper catalyst and active Cu3Si species. The work is helpful for developing novel catalyst promoters and understanding the role of the promoter in the Rochow reaction.

Improvement of rate capability of spinel lithium titanate anodes using microwave-assisted zinc nanocoating

In this study, the deposition of microwave-assisted Zn layers onto spinel lithium titanate (Li 4Ti 5O 12) crystals as superior anode materials for Li-ion batteries has been investigated. Microwave heating is capable of rapidly depositing Zn layers over the surface of spinel Li 4Ti 5O 12 within 6 min. The thickness of Zn layer (i.e., 1–10 nm) is an increasing function of zinc nitrate concentration under the microwave irradiation. The charge–discharge curve of Zn–Li 4Ti 5O 12 anode still maintains the plateau at 1.5 V, contributing to the major portion in the overall specific capacity. The presence of Zn coating significantly facilitates the capacity retention (78.1% at 10 C/0.2 C) of the composite anodes with high Coulombic efficiency (>99.9%), indicating an excellent reversibility of insertion/de-insertion of Li ions. This can be ascribed to the fact that well-dispersed Zn layer offers an electronic pathway over the Li 4Ti 5O 12 powder, thus imparting electronic conduction and reducing cell polarization. Accordingly, the deposition of Zn coating, prepared by the rapid microwave heating, shows a positive effect on the rate-capability improvement of Li 4Ti 5O 12 anodes.

Lactic acid aided electrochemical deposition of c-axis preferred orientation of zinc oxide thin films: Structural and morphological features

Compact and homogeneous c-axis preferred orientation of zinc oxide (ZnO) films on indium tin oxide (ITO) coated glass have been prepared electrochemically at −1.2 V vs. Ag|AgCl in a weak acidic condition from 0.06 M Zn(NO 3) 2 with 3 mM lactic acid (LA) added. LA was found having strong influence on the electrodeposition of c-axis preferred orientation of zinc oxide films. Other experimental variables such as deposition temperature, potential, and precursor concentration were also conducted in this article. Among these variables, it was found that precursor concentration of zinc nitrate influenced significantly on growth direction and crystal diameter of zinc oxide. Cyclic voltammetry was used to observe the electrochemistry of the deposition. Crystallinities of the films were examined by X-ray diffractometer. The morphologies of zinc oxide films were observed with a field emitting scanning electron microscope. Optical characteristics of zinc oxide layers were measured with UV–vis spectrophotometer. The band gap of the deposited zinc oxide thin films was evaluated from the Tauc relationship of ( αhν) 2 vs. hν, which was found to be 3.31 eV.

Electrodeposited ZnO films with high UV emission properties

We report here our results in the preparation of ZnO films with high UV band to band characteristic luminescence emission by potentiostatic electrodeposition. Zinc nitrate aqueous baths with different concentration and additives were employed for the preparation of the films on platinum substrates. We focused our research in determining how the electrodeposition bath composition, i.e. zinc nitrate concentration and addition of KCl or polyvinyl pyrolidone and applied overpotential influence the morphological and optical properties of the oxide films. Scanning electron microscopy was employed for characterizing the films in terms of morphology. Optical reflection, photoluminescence spectroscopy and cathodoluminescence were used for determining the optical characteristics of the samples. The morphology of the deposit varies from hexagonal prisms to platelets as a function of the deposition rate. This experimental parameter also influences the luminescence properties. We found that at low deposition rates high UV luminescent material is obtained.

Structural and Antireflective Properties of ZnO Nanorods Synthesized Using the Sputtered ZnO Seed Layer for Solar Cell Applications

We report the structural and antireflective properties of ZnO nanorod arrays (NRAs) on silicon (Si) substrate by wet chemical growth using the sputtered ZnO seed layer for solar cell applications. The size, height, shape, and number of ZnO nanorods depend strongly on the ZnO seed layer thickness as well as the molar zinc nitrate concentration. Clearly, the ZnO nanorods are of wurzite crystal structure from the X-ray diffraction analysis. To achieve the low reflectance over a wide wavelength range, the ZnO seed layer thickness, molar concentration, and growth time are optimized. It is found that the specular reflection spectrum of ZnO NRAs is closely related to the ZnO seed layer thickness. The solar weighted reflectance, Rw, of ZnO NRAs as antireflection coatings for Si solar cells is estimated under AM1.5 g illumination. For ZnO NRAs with 50 nm ZnO seed layer in 10 mM aqueous solution for 12 hours, the low specular reflectance (i.e., <7%) is obtained at wavelengths of 300-1200 nm, indicating a low Rw of 3.86%.

Effect of zinc nitrate concentration on the structural and the optical properties of ZnO nanostructures

ZnO nanorods and nanodisks were formed on indium-tin-oxide-coated glass substrates by using an electrochemical deposition method. Scanning electron microscopy images showed that the ZnO nanorods were transformed into nanodisks with increasing Zn(NO 3) 2 concentration. X-ray diffraction patterns showed that the ZnO nanostructures had wurzite structures. The full widths at half maxima of the near band-edge emission peak of photoluminescence spectra at 300 K for ZnO nanorods were small, indicative of the high quality of the nanorods. These results indicate that the structural and the optical properties of ZnO nanostructures vary by changing Zn(NO 3) 2 concentration.

Relation Between the Morphology of Electrodeposited ZnO Films and the Efficiency of Dye-Sensitized Solar Cells

The morphology of ZnO films electrodeposited from zinc(II) nitrate solution depends on the reactant concentrations and the deposition current density. The relationship between the film morphology and suitability for application in dye-sensitized solar cells was evaluated, and it was observed that a leaves-type morphology obtained at low current density and high zinc(II) nitrate concentration gives the best performance, related to a high accessible surface area for dye adsorption.

Effect of Supersaturation on the Growth of Zinc Oxide Nanostructured Films by Electrochemical Deposition

The changes in crystal growth habit of electrodeposited zinc oxide with zinc nitrate concentration are explained by changes in the levels of saturation at the electrode. Three growth regimes are found between 0.5 and 50 mM. For concentrations less than 2 mM, the growth is one-dimensional. Nanorods grow by screw dislocations from the outside inward, no coalescence is observed, and their surface shows pyramid-like features. For concentrations above 20 mM, the growth is two-dimensional. Large levels of supersaturation favor the nucleation on the low indexes faces and large sheets are observed. In the intermediate regime of growth, the growth is pseudo three-dimensional. Nanorods with a conical ends grow initially before coalescing and forming dense films.

Preparation of ZnO nanoparticles and characteristics of dye-sensitized solar cells based on nanoparticles film

ZnO nanoparticles were synthesized by hydrolization method and the effects of zinc nitrate concentration and reaction temperature on the resulted particle properties were studied. The transmission of the as-prepared and calcined films and their optical band gaps are measured and calculated respectively. Furthermore, as an application of the ZnO nanoparticles film, dye-sensitized solar cells based on it were successfully fabricated and the cell performances were characterized. The short circuit current for ZnO nanoparticles film DSSCs is 1.35 mA cm −2, which indicates good value of the prepared film using this technique.

PH-dependent growth of zinc oxide nanorods

Here we study the effect of pH variation on the dimension and morphology of zinc oxide (ZnO) nanorods grown through hydrothermal process at temperatures less than 100 °C. ZnO nanorods were grown on pre-seeded glass substrates using zinc nitrate hexahydrate as the source of Zn ions and hexamethylenetetramine as the source of hydroxyl ions. The pH of the reaction bath was found to change gradually from 6.4 to 7.3 in 5 h during the growth process. The growth of the ZnO nanorods was observed to be faster, both laterally and longitudinally, when the growth solution was in basic conditions. However, flower petal like ZnO nanostructures were obtained when the growth process was initiated in basic condition (pH 8–12), indicating that initial acidic conditions were required to obtain nanorods with well-defined hexagonal facets. ZnO is known to erode in acidic condition and the final dimension of the nanorods is determined by a competition between crystal growth and etching. ZnO nanorods of different dimensions, both laterally (diameters ranging from 220 nm to 1 μm) and longitudinally (lengths ranging from 1 to 5.6 μm) were successfully synthesized using the same concentration of zinc nitrate and hexamine in the reaction bath and the same growth duration of 5 h simply through appropriate control of the pH of the reactant solution between 6 and 7.3.

Controlled synthesis of ZnO from nanospheres to micro-rods and its gas sensing studies

1D ZnO rods are synthesized using less explored hydrazine method. Here we find, besides being combustible hydrazine can also be used as a structure-directing agent. The ratio of zinc nitrate (ZN) to hydrazine is found to control the morphology of ZnO. At lower concentration of ZN as compared with hydrazine the morphology of ZnO is found to be spherical. As we increase the hydrazine content the morphology changes from spherical (diameter ∼ 100 nm) to the elongated structures including shapes like Y, T as well dumbbell (diameter ∼ 40 nm and length ∼ 150 nm). Interestingly for more than 50% of hydrazine ZnO micro-rods are formed. Such rods are of diameter ∼ 120 nm having length of about 1 μm for ZN to hydrazine ratio of 1:9, isolated as well as bundle of rods are seen in scanning electron microscopy (SEM). The X-ray diffraction (XRD) reveals the phase formation with average particle size of 37 nm as calculated using Scherrer's formula. The high-resolution transmission electron microscopy (HRTEM) is also done to confirm the d-spacing in ZnO. Gas sensing study for these samples shows high efficiency and selectivity towards LPG at all operating temperatures. Photoluminescence (PL) study for these samples is performed at room temperature to find potential application as photoelectric material.

Modifying Effect of Zinc Oxide Nano-coating on the Different Pore Size of α-Alumina Microfiltration Membrane

Differentα-Al_2O_3 micro-powders with grain size of 0.5-3μm were coated onα-Al_2O_3 sub- strate by the dipping process,and microfiltration membranes with different pore sizes were prepared. The thickness of all the membranes was controlled to be about 25μm.Then the membranes were modified by nano zinc oxide coating deposited by coprecipitation process with zinc nitrate and urea as starting materials.The influences of the size ofα-alumina micro-powders for preparing the membranes and the concentration of zinc nitrate in the precursor of the zinc oxide coating on the water flux of the modified filtration membranes were studied.The results show that the flux of the modified membranes is increased and the amplitude of the flux increasing reaches maximum for the membrane which is made ofα-alumina micro-powers with size of 0.5μm.When the concentration of zinc nitrate is 0.3mol/L,the twice coated membrane possessed the best modification effect and the amplitude of the flux increase reaches 46.4%.Furthermore,the mechanism of zinc oxide modification is discussed initially.

Low-temperature growth and optical properties of ZnO nanorods

Zinc oxide (ZnO) nanorods were grown on ITO conducting glass by the chemical solution deposition method (CBD) in an aqueous solution that contained zinc nitrate hexahydrate (Zn(NO 3) 2·6H 2O) and methenamine (C 6H 12N 4). The size of ZnO nanorods increased with molar concentration of zinc nitrate, and the nanorods with different aspect ratios also formed through tuning the reaction time when the molar concentration was 0.1 M. The length of nanorods increased significantly with the reaction time, but the thickness of the film deposited on the substrate only slightly increased. From the X-ray measurement results, it can be seen that the growth orientation of the as-prepared ZnO nanorods was [0 0 2]. Photoluminescence measurements were also carried out, the result showed a blue shift in violet emission with the reduction in crystal size.

Nanobeads of crystalline ZnO synthesis from pyrolytic decomposition

Pyrolytic decomposition of aqueous zinc nitrate for crystalline ZnO nanobeads architecture oriented along (0 0 2) plane with hexagonal crystal structure is presented as a concentration of aqueous zinc nitrate solution. As-observed ZnO nanobeads were used for surface morphological, optical and electrical properties. Decrease in zinc nitrate concentration results in the destruction of the foggy-like morphology with newly formed dense nanograins and finally, porous nanobeads. The optical absorption studies revealed that the ZnO nanobeads exhibit the optical band gap of 3.30 eV. However, an increase in electrical resistivity with decrease in concentration of zinc nitrate solution was observed.

Chemical deposition of zinc oxide thin films on silicon substrate

Zinc oxide (ZnO) thin films were prepared chemically on silicon substrates by immersing the substrates in an aqueous solution containing zinc nitrate and dimethylamineborane. Chemical deposition enables film formation for electronic devices with arbitrary shapes, such as spherical silicon solar cells. An increase in zinc nitrate concentration and solution temperature resulted in columnar growth of high density hexagonal crystals, yielding a high refractive index. The lowest reflectance of the ZnO/Si of less than 1% was achieved by the optimization of deposition conditions, indicating that the film can be utilized as an antireflective coating on spherical silicon solar cells.

Low‐Temperature Synthesis of Zinc Oxide Nanoparticles

Crystalline zinc oxide nanoparticles have been prepared by mixing aqueous solutions of zinc nitrate and hexamethylenetetramine (HMT) at 60°C and 80°C. Transmission electron microscopy and X‐ray diffraction show that the ZnO nanoparticles of diameters ranging from 15–33 nm and 25–43 nm long are formed. Aspect ratio is observed to range from 1.18 to 1.74 at 60°C and 1.22 to 1.70 at 80°C as the HMT to zinc nitrate concentration ratio increases from 10 to 150. Nanoparticle size decreases as the concentration of HMT increases. Much larger ZnO particles are formed with ammonium hydroxide as a hydrolysis agent without HMT. In summary, HMT is an ammonium‐hydroxide source in the reaction, a surfactant for retaining nanosize, and not necessarily a template for ZnO nucleation.

Development of physicochemical nitrogen removal process for high strength industrial wastewater

The biological nitrogen removal (BNR) process is the most common method for removing low quantities of ammonium from wastewater, but this method is not used for wastewater rich with ammonium. In this study, we have developed the physicochemical nitrogen removal process to remove the nitrogen content for a real industrial wastewater. The denitrification was accomplished by the physicochemical denitrification process using zinc powder and sulfamic acid in pH 2–4. The experimental parameters were examined by varying various reaction conditions such as pH, zinc feeding time, amount of sulfamic acid, and amount of nitrate concentration. For each experimental condition, the physicochemical denitrification process was determined by pH, amount of zinc powder and sulfamic acid, zinc feeding time and nitrate concentration.

Preparation and characterization of zinc sulfide nanoparticles under high-gravity environment

Nanosized ZnS particles were prepared under high-gravity environment generated by the rotating packed bed reactor (RPBR) using zinc nitrate solution and hydrogen sulfide gas as raw materials. The effects of experimental conditions such as reactant concentration, reaction temperature, rotating speed of the RPBR and aging time, on the preparation of nanosized ZnS particles were investigated. A set of suitable operating parameters (the aging time of 48 h, concentration of zinc nitrate of 0.1 mol/l, reaction temperature of 45 °C and rotating speed of the RPBR of 1500–1800 rotation/min) for the preparation of nanosized ZnS were recommended. Under these optimum conditions, well-dispersed ZnS nanoparticles was obtained. The crystal structure, optical properties, size and morphology of the product were also characterized by XRD, UV-Vis spectrophotometer, and TEM, respectively. Results indicate that the prepared ZnS has a good absorption for light in the wavelength range of 200–330 nm. XRD analysis also shows the prepared ZnS is in a sphalerite crystal phase. The process has great potential of commercialization.

Growth and characterization of electrosynthesised zinc oxide thin films

Zinc oxide (ZnO) films have been electrodeposited from an aqueous solution containing 0.1 M zinc nitrate as the electrolyte with pH around 5±0.1. The deposition was carried out by galvanostatic reduction with an applied cathodic current density in the range between 5 and 20 mA cm −2. The influence of bath composition on the preparation of ZnO films is studied. The effects of zinc nitrate concentration and cathodic current density on the deposition rate of ZnO films were also studied. An optimum current density of 10 mA cm −2 is identified for the growth of ZnO film with improved crystallinity and optical transmittance. The crystalline structure of the deposits studied by X-ray diffraction reveals the possibility of growing hexagonal ZnO films under suitable electrochemical conditions. The surface morphological studies by scanning electron micrographs revealed the presence of nodular appearance for films deposited at 800 °C bath temperatures.

The effect of Cd, Co, and Zn as additives on nickel hydroxide opto-electrochemical behavior

Nickel hydroxide films were coprecipitated with the additives Cd(OH) 2, Co(OH) 2, and Zn(OH) 2 by galvanostatic electrodeposition process. The effects of the Cd(OH) 2, Co(OH) 2, and Zn(OH) 2 additions on electrode properties such as charge–discharge, reversibility of the electrode reaction, espectroelectrochemical behavior, superficial morphology by atomic force microscopy (AFM) images, were studied. An anomalous coprecipitation of Zn(OH) 2 was observed. The different concentration of zinc nitrate on the solution affects the amount of zinc hydroxide found on the film; this behavior must be attributed to the differences on the solubility products ( K ps) of the nickel and zinc hydroxides and also to the remarkable zinc amphoteric character. All additives studied displaced the oxygen evolution reaction (OER) to more positive values, and reduced the difference between the oxidation and reduction peaks (Ni(II)/Ni(III)), leading to an augmentation of the process reversibility. However, a significant loss on the electrode efficiency was observed for composite films with zinc. Lithium hydroxide solution as electrolyte showed an augmentation of the difference between the peak potential for the oxidation process and the oxygen evolution reaction, and also increased the reversibility of the redox nickel process. AFM images showed similar superficial morphologies for nickel hydroxide films and films with cobalt; on the other hand, films containing cadmium and zinc showed an inhomogeneous morphology. Nickel hydroxide film shows a differentiated spectroelectrochemical behavior when compared with composite films.