Synthesis of zinc and zinc oxide nanoparticles from zinc electrode using plasma in liquid

Nanoparticles are synthesized efficiently from zinc electrode by microwave plasma in liquid. The nanoparticles synthesized from alcohol resulted in pure zinc particles in the shape of spheres or hexagonal cylinders with a production rate of 3.3 g/h, and energy consumption of 267 J/mg for 1 mg. Whereas the nanoparticles synthesized in pure water are composed of Zn and ZnO. The Zn reacts with water through heat or the passage of time to become ZnO, releasing hydrogen gas. An upper disk placed 1 mm away from the electrode along with the bubbles generated simultaneously with the plasma ignition plays a key role in the synthesis of nanoparticles.     

Design considerations with zinc coated steel and zinc castings

Zinc castings and the various types of zinc coated steel all have different design considerations. Thick coatings applied by hot dipping, by sheradizing or by spraying are usually a final operation after fabrication. Continuously coated sheet or wire has virtually the same design flexibility as the uncoated steel but with longer life to first maintenance treatment. With zinc castings, technical development in the pressure die casting process — notably the ability to make thin and complex thin dimensional shapes — means that a zinc die casting can often economically replace an assembly of steel pressings. This article describes some of the design considerations for each group of materials with examples from practice.     

Preparation of extrapure zinc oxide and zinc acetate from diethylzinc

We have developed a process for the preparation of extrapure zinc oxide and zinc acetate from diethylzinc, which includes ultrapurification of this compound through low-pressure fractional distillation, oxygen oxidation of the purified diethylzinc in combustion mode, and heat treatment of the resultant zinc oxide. Zinc acetate was obtained by dissolving the zinc oxide in acetic acid. The content of regulated metallic impurities (iron, copper, aluminum, silicon, cadmium, nickel, cobalt, tin, lead, chromium, molybdenum, and magnesium) in the zinc oxide and zinc acetate was 10^?5 to 10^?6 wt %, and their net content was <5 × 10^?4 wt %.     

Fluorescence-based zinc ion sensor for zinc ion release from pancreatic cells

In this paper, we describe the synthesis and characterization of analytical properties of fluorescence-based zinc ion-sensing glass slides and their application in monitoring zinc ion release from beta pancreatic cells in cell cultures. To fabricate the sensors, the zinc ion indicator ZnAF-2 {6-[N-[N',N'-bis(2-pyridinylmethyl)-2-aminoethyl]amino-3',6'-dihydroxyspiro[isobenzofuran-1(3H),9'-[9H]xanthene]-3-one} was modified to include a sufficiently long linking aliphatic chain with a terminal carboxyl functional group. The recently synthesized ZnAF-2 zinc ion indicator provided high zinc ion selectivity in physiological solutions containing millimolar levels of calcium and other possible interfering cations. The carboxyl-modified ZnAF-2 was conjugated to the activated surface of glass slides, which then served as zinc ion sensors. It was possible to grow pancreatic cells directly on the zinc-sensing glass slide or on a membrane placed on these glass slides. The sensors were used to monitor zinc ion release events from glucose-stimulated pancreatic cells. The study showed that the zinc ion sensors responded effectively to the release of zinc ions from pancreatic cells at the nanomolar level with high selectivity and rapid subsecond response time.     

Synthesis and adsorption property of zinc rust of zinc hydroxynitrate

In order to clarify the formation condition of zinc rusts such as layered zinc hydroxynitrate (Zn₅(OH)₈(NO₃)₂·2H₂O: ZHN), ZnO particles were aged with aqueous Zn(NO₃)₂·6H₂O solution at 6–140 °C for 48 h. Further, adsorption of H₂O and CO₂ on ZHN was examined for simulating study of atmospheric corrosion of galvanized steel. The ZHN was formed at 6 °C and the ZnO completely disappeared, meaning the hydrolysis of ZnO particles in aqueous Zn(NO₃)₂·6H₂O solution to recrystallize as ZHN. Increasing the aging temperature improved the crystallinity of layered structure of ZHN, showing a maximum at 85 °C. The formed ZHN was hexagonal plate-like particles. The particle size was dependent of the crystallinity of layered structure of ZHN. The specific surface area of ZHN was decreased on elevating the aging temperature, showing a minimum at 85 °C. The adsorption of H₂O and CO₂ was enhanced on increasing the crystallinity of layered structure of ZHN, meaning that these molecules are adsorbed not only on particle surface but also in interlayer of ZHN. These facts infer that the preferred orientation of plate-like ZHN particles leads to the formation of compact rust layer on galvanized steel and to the enhancement of corrosion resistance.     

Rhizosphere characteristics of zinc hyperaccumulator Sedum alfredii involved in zinc accumulation

A hyperaccumulating ecotype (HE) and a non-hyperaccumulating ecotype (NHE) of Sedum alfredii were grown in a pot experiment to investigate the chemical characteristics of the rhizosphere. The results indicated that HE accumulated more Zn in the shoot than NHE after growing in both heavily and slightly polluted soil. The water soluble Zn and mobile Zn (extractable with 1M NH(4)NO(3)) fraction in both rhizosphere and bulk soils decreased considerably after growth of HE compared to NHE. However, the decreases in mobile fraction accounted for less than 8.5% of the total Zn uptake by HE indicating that HE was effective in mobilizing Zn from the non-mobile fractions. Zinc-induced root exudates reduced the soil pH (by 0.6-0.8 units) and increased dissolved organic carbon concentrations in the rhizosphere of HE compared to the bulk soil. The dissolved organic matter (DOM) from the rhizosphere of HE showed greater (1.7-2.5 times) extracting ability of Zn from various Zn minerals than those of NHE-DOM (P<0.05). Results from this study suggests that rhizosphere acidification and the exudation of high amounts of DOM with great metal extracting ability might be two important mechanisms by which HE S. alfredii is involved in activating metal in the rhizosphere.     

Direct synthesis of epitaxial zinc sulphide layers on zinc single-crystal substrates

Epitaxial thin zinc sulphide layers have been grown by direct synthesis on the basal face of zinc single crystals. Sulphur vapour reacted on the surface of the crystals, which were grown in sealed glass ampoules evacuated to 10^?6 torr. The thicknesses of the layers investigated varied from several hundred to 1000–1500 Å. The morphology, structure and epitaxy of the films were examined by electron microscope, electron and X-ray diffraction techniques. It was found that the film lattice had a sphalerite-type cubic structure, the perfection of the layer structure increasing with rise in both the substrate temperature and the sulphur vapour pressure. The layers were produced at substrate temperatures of 250°–400°C: polycrystalline ZnS films were obtained in the range 250°–300°C; at higher temperatures a definite texture gradually appeared and above 370°C, with a sulphur vapour pressure of 0.2–10 torr, the films became epitaxial. The following epitaxial relation was established:

$\text{{111} ZnS ∥ {0001} Zn}$

with

$\text{<110 > ZnS ∥ <11}\text{20}\text{> Zn}$

The zinc sulphide films reproduced the surface structure of the supporting zinc single crystals very well and could conveniently be used as electron microscope replicas.     

The chemistry of cements formed between zinc oxide and aqueous zinc chloride

A series of cements has been prepared from zinc oxide powder and aqueous zinc chloride, using solutions corresponding to concentrations of 20%, 30%, 40%, 50% and 60% and a ratio of ZnO powder to zinc chloride solution of 1:1. As with cements of the zinc oxide/zinc nitrate system, these ZnO/ZnCl2 cements were found to be weak in compression (not exceeding 10 MPa) with strength rising with increasing concentration of ZnCl2. The pH change as the reaction proceeded was monitored and generally showed a rapid increase, followed by a slight decrease, and a subsequent slower increase. This is assumed to arise because the doubly charged aquo-zinc cation, Zn(H2O)2+n (n=4 or 6) behaves as a weak acid, due to so-called salt hydrolysis: Zn(H2O)2+n+H2OZnOH(H2O)+(n-1)+H3O+ and reacts to form a salt, thus setting up a classic weak acid/salt buffer system. Finally, cements were stored in water for 1 month, and were generally found to increase in mass during the first week, with the greatest increase occurring in the cement made from 20% ZnCl2 solution. All cements lost mass between 1 week and 1 month, showing them to be sparingly soluble at room temperature. © 1998 Chapman & Hall     

Condensation of zinc aerosols

Condensation of zinc aerosols in the presence of argon was studied in the heat-pulse cloud chamber; as with cadmium, two distinct series of particles are produced as the wall temperature is increased, first prisms and then spheres. The prismatic particles are monocrystalline and include complicated dendrites and a species not previously seen, the capped prism. Whiskers grow from the basal surfaces of the simple prisms. The spherical particles include mono-, bi-, and poly-crystals.The production of simple prisms and dendrites is attributed to condensation of solid in the presence of particularly steep temperature and vapour-pressure gradients. Crystallographic evidence supports the view that the spheres condense as liquid droplets. It is concluded that the droplets solidfy from nuclei that grow rapidly into circular {00.1} rafts on the liquid surface, in the manner observed with large sessile drops by Mutaftschiev and Zell. The formation of hillocks on the basal raft or its conversion into a concave dish is evidence of growth in the vapour.The numbern of basal rafts on a solidified sphere may be identified with the number of nuclei. When unimpeded by other nuclei, a raft grows to a maximum radiusr0.55R, whereR is the droplet radius. The ratior/R is used to deduce the orientation of the pyramidal planes which develop at the edge of the raft as it begins to thicken. At low wall temperatures some of these planes tend to be very coarse, while when the growth front reaches the opposite side of the particle, the solid surface adopts a relatively smooth spherical outline.As the wall temperature is raised, the highest value observed forn increases from 1 to a maximum of 20 to 30 and then falls abruptly as the melting point of the metal is approached. The temporary increase inn may be an effect of drop size but the final fall is ascribed to the failure of supercooled droplets to nucleate until withdrawn from the apparatus. Spheres withn>1 deform on cooling as the result of thermal expansion anisotropy. Forn>2 cracking and slip are observed.     

Electrophoretic deposition of aqueous nano-sized zinc oxide suspensions on a zinc electrode

Electrophoretic deposition (EPD) was used to form ZnO deposits. ZnO with an average particle size of 40 nm was dispersed in water with the addition of an appropriate amount of anionic polyelectrolyte. Uniform and bubble-free ZnO deposits have been obtained via EPD on a zinc anode in an aqueous suspension. The obtained deposits showed good sinterability.     

Doughnut-shaped zinc oxide particles

Zinc oxide doughnut-shaped particles were synthesized using a chemical route. A possible growth model has been proposed from a detailed experiment in which samples were picked from the reaction chamber at various time intervals and characterized using scanning electron microscopy (SEM). Particles were also characterized using X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS).     

环氧富锌底漆不挥发分中金属锌含量测定及探讨

介绍了测定环氧富锌底漆不挥发分中金属锌含量的方法,探讨了影响实验结果的主要因素,并对现行富锌底漆标准规定的测定方法条件进行了一些调整,以便得到满意的实验结果。     

Investigations of diffusion behaviour in Al-doped zinc oxide and zinc stannate coatings

Multi-layer dielectric/silver/dielectric coating systems have excellent proprieties as heat insulators and for solar energy reflection and electrical conductivity. The largest market is dominated by low-emissivity (low-E) coatings, which are applied to large area architectural glazing to reduce heat losses from buildings. They combine high visible transparency with high reflectance in the far-infrared region, where the thin (~ 10 nm) silver layer reflects long wavelength IR back into the building and the dielectric layers both protect the silver and act as anti reflectance layers.In this study, a range of dielectric coatings has been deposited onto soda-lime glass substrates by reactive sputtering from metallic targets. The magnetrons were driven in DC mode and also in mid-frequency pulsed DC and AC modes. Process variables investigated include operating pressure, oxygen flow rate and magnetron configuration. Selected coatings were annealed at 650 °C and analysed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and atomic force microscope (AFM).The oxide samples were then over-coated with silver and annealed for a second time. These coatings were analysed by secondary ion mass spectroscopy (SIMS) to determine the diffusion rates of silver and sodium (from the substrate) through the oxide coatings.The results to date, presented here, show the diffusion of silver and sodium atoms through zinc oxide and zinc stannate thin films deposited under a vast range of conditions. Preliminary attempts have been made to estimate diffusion coefficients for these coating systems and to relate these values to processing conditions and the structural variations observed.     

Thin polycrystalline zinc oxide films obtained by oxidation of metallic zinc films

Thin polycrystalline ZnO films were obtained by thermal oxidation of metallic Zn films, thermally deposited on various substrates, such as silica, sapphire and glass, in both air and pure oxygen atmospheres. The quality of the ZnO layers was asserted by Hall effect, cathodoluminescence and atomic force microscopy measurements. Electron concentration of 7.32×10¹² cm⁻³ and mobility of 14.2 cm²/V s with root mean square roughness of 30 nm were obtained for the 900 °C annealed ZnO films in oxygen. Room temperature cathodoluminescence spectra consisted of a narrow near band edge luminescence band and a broad defect-related green band with peak positions at 380 and 500 nm, respectively. ZnO film luminescence properties improved dramatically with the increase of annealing temperature and decrease of O₂ pressure.     

Creep-sintering of zinc oxide

The simultaneous creep and densification of zinc oxide powder compacts was studied, using a loading dilatometer, at 725° C subjected to uniaxial stresses of up to 0.25 M Pa. Between relative densities of 0.50 and 0.85, the dependence of the uniaxial creep rate on density can be described in terms of a stress intensification factor,, of the form exp (aP), wherea is constant equal to 5.0 andP is the porosity. Comparison of the creep and densification rates showed that the ratio of the linear densification rate to the creep rate is nearly constant over a density range between 0.55 and 0.85, and permitted the evaluation of the sintering effective stress, which is found to decrease with increasing density. The results are compared with those obtained earlier for cadmium oxide and a soda-lime glass powder.     

Sulfidation of zinc plating sludge with Na2S for zinc resource recovery

A high amount of zinc disposed in the landfill sites as a mixed-metal plating sludge represents a valuable zinc source. To recover zinc from the plating sludge, a sulfidation treatment is proposed in this study, while it is assumed that ZnS formed could be separated by flotation. The sulfidation treatment was conducted by contacting simulated zinc plating sludge with Na(2)S solution at S(2-) to Zn(2+) molar ratio of 1.5 for a period of 1-48 h, while changing the solid to liquid (S:L) ratio from 0.25:50 to 1.00:50. The conversion of zinc compounds to ZnS was determined based on the consumption of sulfide ions. The reaction products formed by the sulfidation of zinc were identified by X-ray diffraction (XRD). As a result, it was found that the conversion of zinc compounds to ZnS increased with an increase in S:L ratio. A maximum conversion of 0.809 was obtained at an S:L ratio of 1.00:50 after 48 h. However, when the zinc sludge treated at S:L ratio of 1.00:50 for 48 h was subjected to XRD analyses, only ZnS was identified in the treated zinc sludge. The result suggested that the rest of zinc sludge remained unreacted inside the agglomerates of ZnS. The formation behavior of ZnS was predicted by Elovich equation, which was found to describe the system satisfactorily indicating the heterogeneous nature of the sludge.     

A new electropolishing technique for metallographic specimen preparation of zinc and zinc alloys

This article describes results obtained with a new method for electropolishing metallographic specimens of zinc and zinc alloys. An electrolyte containing ethanol, ethylene glycol, and sodium thiocyanate (or ammonium thiocyanate) has been developed. It is demonstrated that this solution has a good polishing action on pure zinc and zinc alloys in the systems Zn---Al---Cu, Zn---Cu---Mn, and Zn---Ni---Cd---Fe. The electropolishing process ensures that bright, defect-free surfaces are obtained for most of these alloys, irrespective of the different chemical compositions and phases present. The process is quick and preliminary specimen preparation is minimal.     

Annealing and oxidation mechanism of evaporated zinc thin films from zinc oxide powder

Zinc oxide (ZnO) thin films were deposited by thermal evaporation of a high quality ZnO powder; the obtained films were then oxidized in the air. We have systematically investigated the influence of annealing temperature ranged from 100 to 400 °C on the films composition and structural and optical properties by using Rutherford Back Scattering (RBS) analysis, X-ray Diffraction (XRD) and UV-Visible transmission respectively. The as grown films exhibit a hexagonal single phase of Zn with no preferential orientation and contain 28% oxygen. With an increase in the annealing temperature the oxygen content is enhanced to the detriment of Zn; samples were totally oxidized at 300 °C and the films are converted to stoichiometric ZnO material. However, in situ XRD pattern analysis shows that the oxidation starts at 250 °C. From the XRD results of annealed Zn samples under an electrical field we inferred that the oxidation mechanism is achieved by the ionization of oxygen atom at the film surface and subsequently followed by the diffusion of the produced ions in the film network.     

Structural aspects of Langmuir-Blodgett and cast films of zinc phthalocyanine and zinc hexadecafluorophthalocyanine

The processing of macrocyclic phthalocyanines (Pc) in the form of thin, nanostructured films has been usually carried out via evaporation techniques, owing to the low solubility exhibited by these compounds. The fabrication of Pc ultrathin films via the Langmuir-Blodgett technique may be advantageous from a technological point of view, since parameters such as film architecture and organization can be achieved without post-thermal treatments. In this study, a parent zinc phthalocyanine (ZnPc) and its fluorinated derivative (F₁₆ZnPc) were synthesized and manipulated in the form of LB films. The morphological and structural features of ZnPc and F₁₆ZnPc Langmuir-Blodgett films containing up to 31 layers were investigated using Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy and X-ray diffraction analyses and were compared to ZnPc and F₁₆ZnPc cast films. The interplanar distance obtained by X-ray specular reflection decreases from 12.64 Å for ZnPc to 12.16 Å for F₁₆ZnPc. FTIR spectra indicated absence of order in the LB films from ZnPc and F₁₆ZnPc, at least in the direction perpendicular to the substrate surface. Therefore, the order observed in the X-ray diffractograms means that the molecules might be organized in crystallites that are randomly oriented in the film.     

Synthesis of zinc oxide nanostructures during zinc oxidation by sub-and supercritical water

Solid zinc (Zn)_S and liquid zinc (Zn)_L are oxidized by water with the formation of zinc oxide (ZnO) nanostructures and the evolution of hydrogen. The maximum rate of this process, called chemical supercondensation by water (CSW), is realized on approaching the melting temperature of zinc from the left and right with increasing density of supercritical water. The CSW process begins with the formation of (ZnO) _n clusters via the reaction (Zn)_S,L + nH₂O = [(Zn)_S,L · (ZnO) _n ] + nH₂, followed by their subsequent growth at n > 7 in the exothermal process of epitaxy on (Zn)_S and coagulation of (ZnO) _n in (Zn)_L. The CSW of (Zn)_S leads predominantly to the formation of nanowires and nanorods, while the CSW of (Zn)_L practically always proceeds with the formation of nanoparticles. The rate of (Zn)_S oxidation increases with the thickness of a layer converted into ZnO. This is related to the self-heating and local melting of (Zn)_S in the course of CSW. The complete CSR of (Zn)_S plates and cylinders results in the formation of highly porous nanostructural ceramics.