Zinc Vapor Research Articles

Elucidation of the chemical environment for zinc species in an electron-rich zinc-incorporated zeolite

An electron-rich zinc-modified zeolite has been prepared by the incorporation of zinc vapor into the channels of a dehydrated HY (protonated zeolite Y). The chemical environment of the zinc species in the electron-rich zeolite has been elucidated on the basis of X-ray absorption spectroscopy. The formation of univalent zinc (Zn+) within the electron-rich zeolite was observed upon the irradiation of X-ray from either a synchrotron radiation source or a conventional X-ray diffractometer. The X-ray irradiation initiated the electron transfer from the electron-rich framework of zeolite Y to the nearby Zn2+ cations, generating Zn+ species. The variation of the coordination environment of the zinc species upon interaction with water molecules has also been investigated.

Role of a gas phase in the kinetics of zinc and iron reduction with carbon from slag melts

The influence of the mass transfer conditions in the gas phase having formed at the carbon-slag melt interface on CO regeneration is approximately estimated in the framework of a two-stage scheme of metal reduction from slag melts by carbon. The effect of zinc vapors on the combined reduction of iron and zinc from slags is considered. The influence of the slag composition and temperature on the critical concentration of zinc oxide above which no iron forms as an individual phase is explained.

The kinetics of the heterogeneous oxidation of zinc vapor by carbon dioxide

The heterogeneous oxidation of Zn(g) is a promising reaction pathway for the conversion of CO2 into CO in the two-step Zn/ZnO solar thermochemical cycle as it eliminates the solid-state diffusion limitation that plagues the oxidation of Zn(l,s). The rate of the heterogeneous oxidation of Zn(g) is measured gravimetrically in a quartz tubular flow reactor operated at atmospheric pressure for temperatures between 800 and 1150K, Zn(g) concentrations up to 36mol%, and CO2 concentrations up to 45mol%. The surface kinetics are extracted from the global reaction rate using a numerical reacting flow model that accounts for the transport of reacting species in the gas phase. The oxidation of Zn(g) by CO2 is rapid, on the order of 10−8–10−5molcm−2s−1, and the rate is proportional to the product of the Zn(g) and CO2 partial pressures at the reaction surface. The activation energy for the Arrhenius reaction rate parameter is 44±3kJmol−1 and the pre-exponential factor is (92±6)×10−3molcm−2s−1atm−2. As a result of the rapid rate of oxidation of Zn(g), less than 1s is required to convert more than 85% of Zn to ZnO.

Blowhole Generation Phenomenon and Quality Improvement in GMAW of Galvanized Steel Sheet

In the automotive industry, galvanized steel sheets have been applied for quality improvement. However, it has a problem of the weldability debasement by porosity defect (blowhole, pit) and spatter increase. In this study, the blowhole generating behavior which was not clarified until now has been observed by the high-intensity X-ray imaging apparatus. And the method to make reduce both of the porosity defects and the spatter has been examined. In the result, the measure was effective that the porosity defect is released as zinc vapor from just under the arc to outside of the molten pool. Based on this knowledge, a solution to problem was accomplished by optimizing (a) composition and size of welding wire, (b) shielding gas composition and (c) current pulse wave pattern.

Influence of contamination on the thermal evaporation of a zinc melt

In a thermal evaporation process, the melt will become enriched with elements of a lower vapor pressure than the evaporating species. Industrial coating facilities used in the steel industry are expected to run for days where the enrichment can become a serious problem because the accumulation of contaminants will influence the evaporation process. In this paper, two cases were investigated; a zinc melt contaminated with aluminum and a zinc melt contaminated with lead. These elements were chosen because they are present in significant amounts in commercially available zinc ingots, and at the tested temperature aluminum is completely soluble in zinc while lead and zinc form an emulsion. The results show that for a zinc melt at a constant temperature, the zinc evaporation rate is inversely proportional to the atomic percentage of aluminum. The influence that lead contamination has on the evaporation rate is much smaller and at 40atomic percentage lead the evaporation rate is still more than 95% of its original value.

Controllable growth of laterally aligned zinc oxide nanorod arrays on a selected surface of the silicon substrate by a catalyst-free vapor solid process – a technique for growing nanocircuits

We report a simple and effective vapor deposition method for directly growing ultra-long, laterally aligned, zinc oxide (ZnO) nanorod arrays only on the side edges of a bare silicon (Si) substrate without using any catalysts and precursors. The growth on the top surface of the substrate is restrained by controlling the flow of source vapor in a tube furnace through the chemical vapor solid process. The optimized growth parameters have been thoroughly investigated and identified. Direct growth of laterally aligned ZnO nanowire arrays on the desired surface of the substrate is successfully achieved. A vapor solid mechanism with source vapor flow rate control has been proposed to explain the synthesis: ZnO nanodots first form on the bare Si substrate side edges due to the local large binding energy and high zinc (Zn) vapor concentration, and then nanorods epitaxially grow from the nanodots. In addition, the lateral, ultra-long ZnO nanorods grown on orthogonal silicon microelectrodes are achieved and could be expected to find important applications in a bottom-up way of fabricating the next generation nanoelectronics.

Structural and Photoluminescence Properties of ZnO Nanowires

Arrays of ZnO nanowires are grown by the vapor-liquid-solid method on a silicon substrate. The results of XRD, SEM, and AFM studies show that the diameters of nanowires vary in the range (50–300) nm, and their length is up to 40 μm. The wires exhibit bright photoluminescence: the band corresponding to the near band edge region and one or two (depending on the growth conditions) defect-related bands. The intensity ratio of the bands reflects the non-stoichiometry of the material and can be controlled by the zinc evaporation temperature and the temperature in the growing zone.

Growth of High-Density Zinc Oxide Nanorods on Porous Silicon by Thermal Evaporation

The formation of high-density zinc oxide (ZnO) nanorods on porous silicon (PS) substrates at growth temperatures of 600–1000 °C by a simple thermal evaporation of zinc (Zn) powder in the presence of oxygen (O2) gas was systematically investigated. The high-density growth of ZnO nanorods with (0002) orientation over a large area was attributed to the rough surface of PS, which provides appropriate planes to promote deposition of Zn or ZnOx seeds as nucleation sites for the subsequent growth of ZnO nanorods. The geometrical morphologies of ZnO nanorods are determined by the ZnOx seed structures, i.e., cluster or layer structures. The flower-like hexagonal-faceted ZnO nanorods grown at 600 °C seem to be generated from the sparsely distributed ZnOx nanoclusters. Vertically aligned hexagonal-faceted ZnO nanorods grown at 800 °C may be inferred from the formation of dense arrays of ZnOx clusters. The formation of disordered ZnO nanorods formed at 1000 °C may due to the formation of a ZnOx seed layer. The growth mechanism involved has been described by a combination of self-catalyzed vapor-liquid-solid (VLS) and vapor-solid (VS) mechanism. The results suggest that for a more precise study on the growth of ZnO nanostructures involving the introduction of seeds, the initial seed structures must be taken into account given their significant effects.

A simple method to grow one-dimensional ZnO nanostructures in air

Using zinc foils as the only starting material, we synthesized one-dimensional ZnO nanostructures (nanorods, nanoneedles and nanowires) in air by zinc vapor condensation method at 500°C. The morphology, structure and photoluminescence of the synthesized one-dimensional ZnO nanostructures were investigated by scanning electron microscopy, X-ray diffractometry, transmission electron microscopy and spectrophotoscopy. It is found that the size, shape and photoluminescent properties of the one-dimensional ZnO nanostructures depend on the growth time of ZnO in the furnace. Mechanisms on the growth of the nanostructures were discussed, and controllable morphology and photoluminescence of the ZnO nanostructures were achieved by varying the growth time of ZnO in the furnace. It provides a simple, energy-saving and environment-benign route to synthesize one-dimensional ZnO nanostructures with controllable morphology and emission properties.

Zinc isotopic evidence for the origin of the Moon

Volatile elements have a fundamental role in the evolution of planets. But how budgets of volatiles were set in planets, and the nature and extent of volatile-depletion of planetary bodies during the earliest stages of Solar System formation remain poorly understood. The Moon is considered to be volatile-depleted and so it has been predicted that volatile loss should have fractionated stable isotopes of moderately volatile elements. One such element, zinc, exhibits strong isotopic fractionation during volatilization in planetary rocks, but is hardly fractionated during terrestrial igneous processes, making it a powerful tracer of the volatile histories of planets. Here we present high-precision zinc isotopic and abundance data which show that lunar magmatic rocks are enriched in the heavy isotopes of zinc and have lower zinc concentrations than terrestrial or Martian igneous rocks. Conversely, Earth and Mars have broadly chondritic zinc isotopic compositions. We show that these variations represent large-scale evaporation of zinc, most probably in the aftermath of the Moon-forming event, rather than small-scale evaporation processes during volcanism. Our results therefore represent evidence for volatile depletion of the Moon through evaporation, and are consistent with a giant impact origin for the Earth and Moon.

Activity of zinc in the liquid Bi-In-Sn-Zn alloys determined by knudsen method

The Knudsen effusion method was used for measurements of mass loss rate of liquid Bi-In-Sn-Zn alloys, in the temperature range from 572 to 768 K. The studies were carried out for the alloys with the ratio of Bi:In:Sn equal 2:6:2, 2:2:6 and 8:1:1. The obtained results were used for the calculation of zinc vapour pressure over liquid Bi-In-Sn-Zn alloys and next the activity of zinc in the Bi-In-Sn-Zn liquid phase. It was found that for the investigated alloys the activity of zinc shows the considerable positive deviation from the Raoult’s law.

Preparation of ZnO with various crystal morphologies from industrial zinc slag by oxidising zinc vapour

ZnO with various crystal morphologies were successfully prepared using industrial zinc slag. The condition of preparation of ZnO was systematically discussed. The microstructure and crystal morphology of ZnO were characterised by X-ray diffraction and scanning electron microscopy. The results show that five typical morphologies, such as powder, granular, needle, tetrapod and multipod-like ZnO, are obtained. The behaviour of the oxidising zinc vapour varies with the oxygen partial pressure, which leads to producing ZnO crystals of different morphologies that can be controlled by the change of preparing conditions. The additive is not a crucial factor for the crystal morphologies of ZnO but can expand the scope of nucleation and growth of tetrapod-like ZnO and adjust the preparation conditions.

Growth Kinetics of Needle-like Silicon Wires Formed via the Zinc Reduction Reaction of Silicon Tetrachloride

We studied the growth kinetics of needle-like silicon wires formed in the reduction reaction of silicon tetrachloride (SiCl4) with zinc vapor. Real-time monitoring of the silicon wire growth was performed using a quartz tube reactor with a charge-coupled device (CCD) camera. The formation of silicon wires was observed when SiCl4 was mixed with zinc vapor; the wires grew at a constant rate, which reached 20 mm min–1. We did not prepare catalytic metal particles in the reactor; however, since zinc metal can form a liquid alloy with silicon at reaction temperatures of ca. 900–950 °C, we proposed that a vapor–liquid–solid (VLS) mechanism was responsible for the formation of the silicon wires. We consider that the zinc acted both as a reducing agent for SiCl4 and as a metal catalyst for the wire formation. On the basis of the VLS mechanism, a simple kinetic model for wire growth was proposed. Our model described the experimental data well, and the rate-limiting step for the wire growth is the gas-phase reducti...

Effects of ultrathin layers on the growth of vertically aligned wurtzite ZnO nanostructures on perovskite single-crystal substrates

In this study, ZnO nanostructures were grown on various ultra-thin layers coated (100)-oriented SrTiO3 (STO) single-crystal substrates using thermal evaporation of metallic zinc at 600°C. This study used the ZnO seed layer and/or metal catalyst layer to grow high-density ZnO nanostructures on STO substrates. X-ray diffraction and scanning electron microscopy (SEM) measurements showed that the use of Au and Ag catalysts is crucial in producing ZnO nanostructures with a preferential c-axis direction. The as-grown ZnO nanostructures had a hexagonal facet. Among various STO substrates (Au/STO, Ag/STO, ZnO/STO, Au/ZnO/STO, and Ag/ZnO/STO), the ZnO nanostructures grown on the Au/STO substrate had the highest degree of vertical alignment, and the intensity ratio of the UV to visible emission band reached 55. Conversely, the ZnO nanostructures grown on the ZnO seed layer-coated STO substrate were more randomly oriented, and the intensity ratio of the UV to visible emission band was only 9.5. The cathodoluminescence (CL) results showed that higher vertically aligned ZnO nanostructures have lower-density crystal defects. The current–voltage measurements supported the structural analysis.

Effect of inorganic particulates on the condensation behavior of lead and zinc vapors upon flue gas cooling

This study aims to clarify the influence of particulates on the fate of Pb and Zn compound vapors upon flue gas cooling. Incineration of Pb and Zn-loaded model compounds has been separately carried out in a lab-scale quartz reactor. Three oxides of Fe2O3, Al2O3 and CaO as inorganic particulates were placed individually in flue gas cooling section to mimic pre-existing particulates in flue gas and examine their impact on the fate of Pb and Zn compound vapors. The effect of gaseous components including HCl, SO2 and H2O on the heterogeneous condensation of Pb and Zn compound vapors on particulates grains has also been clarified. The presence of particulates in flue gas exerted remarkable influence on the fate of Pb and Zn compound vapors. Pb compound vapor was found being captured by Al2O3 as Pb–Al–O at the temperature above 823K through chemical reaction, regardless flue gas composition. Zn preferentially transformed into ZnFe2O4, ZnAl2O4 and ZnO, respectively on the presence of Fe2O3, Al2O3 and CaO above 823K. The presence of SO2 inhibited the chemical reactions of Pb and Zn vapors with particulates. Such an inhibitory effect was however compensated by the introduction of steam to flue gas. The presence of particulates in flue gas promoted the condensation of Pb and Zn compound vapors at higher temperature in comparison to the blank conditions, through heterogeneous nucleation, which in turn offset the effect of super-cooling. Moreover, the formation of sulfate was increased since the presence of particulates in flue gas triggered the condensation of sulfates vapors at high temperature and then reduced its partial pressure in flue gas, facilitating the sulfation reaction. Adjusting the concentrations of SO2 and H2O in flue gas can prevent the formation of chloride of Pb and Zn, which is notorious for its toxicity and corrosion propensity during solid waste incineration.

The Research of De-Gassing with Silicon Powder Gapping for Remote Laser Welding of Zinc Coated Sheet Metal

There are the four types of defects during remote laser welding of zinc coated sheet metal. The root cause of all these defects is the explosion or ejection of molten weld metal caused by the escape of trapped high pressurized zinc vapor. De-gassing gapping is a method used to solve the defects. We have researched the silicon powder de-gassing gapping method for remote laser welding with coupons of zinc coated sheet metal. The result shows that silicon powder de-gassing gapping method works well.

The microwave and millimeter spectrum of ZnCCH ($\tilde {X}$X̃2Σ+): A new zinc-containing free radical

The pure rotational spectrum of the ZnCCH (X̃(2)Σ(+)) radical has been measured using Fourier transform microwave (FTMW) and millimeter direct-absorption methods in the frequency range of 7-260 GHz. This work is the first study of ZnCCH by any type of spectroscopic technique. In the FTMW system, the radical was synthesized in a mixture of zinc vapor and 0.05% acetylene in argon, using a discharge assisted laser ablation source. In the millimeter-wave spectrometer, the molecule was created from the reaction of zinc vapor, produced in a Broida-type oven, with pure acetylene in a dc discharge. Thirteen rotational transitions were recorded for the main species, (64)ZnCCH, and between 4 and 10 for the (66)ZnCCH, (68)ZnCCH, (64)ZnCCD, and (64)Zn(13)C(13)CH isotopologues. The fine structure doublets were observed in all the data, and in the FTMW spectra, hydrogen, deuterium, and carbon-13 hyperfine splittings were resolved. The data have been analyzed with a (2)Σ Hamiltonian, and rotational, spin-rotation, and H, D, and (13)C hyperfine parameters have been established for this radical. From the rotational constants, an r(m) ((1)) structure was determined with r(Zn-C) = 1.9083 Å, r(C-C) = 1.2313 Å, and r(C-H) = 1.0508 Å. The geometry suggests that ZnCCH is primarily a covalent species with the zinc atom singly bonded to the C≡C-H moiety. This result is consistent with the hyperfine parameters, which suggest that the unpaired electron is localized on the zinc nucleus. The spin-rotation constant indicates that an excited (2)Π state may exist ∼19,000 cm(-1) in energy above the ground state.

Characteristics of zinc behavior during laser welding of zinc “sandwich” sample

To address the problem of the zinc being easily gasified in laser welding of galvanized steel, laser welding of a zinc “sandwich” sample was performed to experimentally investigate the behavior and characteristics of the zinc inside and outside the keyhole, including the observation of the keyhole, the zinc vapor and zinc plasma, and the calculation of the electron temperature of the zinc plasma. Based on the principle of imaging amplification, the detected multi-points can be located precisely in order to study the distribution of the electron temperature of the zinc plasma. The results show that the zinc behavior played an important role in the formation of the weld-joint and the zinc plasma altered the energy distribution at the top of the keyhole whose diameter has been enlarged in the welding process. For both continuous-wave laser and pulsed laser welding of zinc “sandwich” sample, the average electron temperature of the zinc keyhole plasma was higher than that of the zinc plasma plume outside the keyhole. In the welding process, the continuous wave laser with higher input energy results in higher position of the zinc plasma with higher electron temperature above the sample surface. More zinc vapor resulted in a higher average electron temperature of the plasma.

Effects of sintering atmosphere on cement clinkers produced from chromium-bearing sludge

The purpose of this study was to investigate the effects of sintering atmosphere (oxidizing and reducing) on the polymorphs of dicalcium silicates (Ca2SiO4, C2S) and on the chromium leaching of the belite-rich clinkers made from a chromium-bearing sludge. This sludge was generated in an electroplating factory, and in addition to chromium, it contained nickel, copper, and zinc. In the clinker production, air was used as the oxidizing atmosphere, and carbon monoxide, which was produced by burning graphite with an insufficient amount of oxygen, was employed as the reducing atmosphere. Dicalcium silicates were substantially formed under both kinds of sintering atmosphere, but there was some nonhydraulic γ-C2S in the clinkers produced under the oxidizing atmosphere. In addition, the amount of γ-C2S decreased with the chromium-bearing sludge addition, whereas that of β-C2S increased. The clinkers produced under the reducing atmosphere had less residual chromium, a finding that shows that more chromium was evaporated. However, the reducing atmosphere can decrease the proportion of hexavalent chromium (Cr(VI)) in the resulting clinkers. For other heavy metals, the residual amounts of nickel and copper generally increased with the sludge addition, but zinc was absent in most of the clinkers produced under the reducing atmosphere. This implies that the evaporation of zinc is much more significant than that of the other heavy metals under a reducing atmosphere. In the leaching tests, the concentrations of nickel, copper, and zinc were below the detection limits in all the leachates. In terms of chromium, the total leaching concentration was highly related to Cr(VI). The clinkers produced under the oxidizing atmosphere had high leaching concentrations of chromium, and thus failed to meet the regulatory limit. In contrast, the reducing atmosphere was effective in decreasing the chromium leaching, and it therefore makes the resulting cement clinkers more environmentally sound. Implications: This study presents the effects of oxidizing/reducing atmosphere on the polymorphs of C2S and on the oxidation states of chromium in the clinkers. The chromium-bearing sludge from an electroplating factory was employed as a cement raw material. The reducing atmosphere was used to prevent the chromium from oxidizing to Cr(VI) during the sintering process, thus decreasing the chromium leaching concentrations of the resulting clinkers.

Real-time monitoring of laser welding of galvanized high strength steel in lap joint configuration

Two different cases regarding the zinc coating at the lap joint faying surface are selected for studying the influence of zinc vapor on the keyhole dynamics of the weld pool and the final welding quality. One case has the zinc coating fully removed at the faying surface; while the other case retains the zinc coating on the faying surface. It is found that removal of the zinc coating at the faying surface produces a significantly better weld quality as exemplified by a lack of spatters whereas intense spatters are present when the zinc coating is present at the faying surface. Spectroscopy is used to detect the optical spectra emitted from a laser generated plasma plume during the laser welding of galvanized high strength DP980 steel in a lap-joint configuration. A correlation between the electron temperature and defects within the weld bead is identified by using the Boltzmann plot method. The laser weld pool keyhole dynamic behavior affected by a high-pressure zinc vapor generated at the faying surface of galvanized steel lap-joint is monitored in real-time by a high speed charge-coupled device (CCD) camera assisted with a green laser as an illumination source.