Zinc Chloride Hydroxide Research Articles

Transformation of zinc hydroxide chloride monohydrate to crystalline zinc oxide.

Thermal decomposition of layered zinc hydroxide double salts provides an interesting alternative synthesis for particles of zinc oxide. Here, we examine the sequence of changes occurring as zinc hydroxide chloride monohydrate (Zn5(OH)8Cl2·H2O) is converted to crystalline ZnO by thermal decomposition. The specific surface area of the resultant ZnO measured by BET was 1.3 m(2) g(-1). A complicating and important factor in this process is that the thermal decomposition of zinc hydroxide chloride is also accompanied by the formation of volatile zinc-containing species under certain conditions. We show that this volatile compound is anhydrous ZnCl2 and its formation is moisture dependent. Therefore, control of atmospheric moisture is an important consideration that affects the overall efficiency of ZnO production by this process.

Corrosion measurement on shear strength of Cu/Sn–9Zn/Cu lap joints

Corrosion of the Cu/Sn–9Zn/Cu lap joints in 3.5wt.% NaCl solution showed reduction in the ultimate shear strength with increasing immersion time. The highest ultimate shear strength value obtained was at 122.67MPa before immersion while the lowest value was 85.32MPa after immersion for 28days. Corrosion products consist of tin (II) chloride and zinc hydroxide chloride had been obtained due to the active dissolution of tin. The formation of pits observed on the lap joints marked as stress concentration points which are detrimental toward the shear strength. Upon longer immersion period, the pit coalescence and propagation led to the existence of long, deep cracks. The fracture paths nucleates from the cracks clearly established the mechanism of the fracture formation for the Cu/Sn–9Zn/Cu lap joints. The fracture analysis together with the presence of the corrosion by-products fully reiterated that corrosion activities was the main factor for the decrease in shear strength of Cu/Sn–9Zn/Cu lap joints.

Similarities between Zinc Hydroxide Chloride Monohydrate and Its Dehydrated Form: A Theoretical Study of Their Structures and Anionic Exchange Properties

The electronic structures of zinc hydroxide chloride monohydrate (ZHC) and its dehydrated form were calculated by ab initio density functional theory methodology in order to study some of their properties, such as anionic exchange. It was observed that the dehydrated structure showed no major differences in the unit cell parameters compared to hydrated one, except for the basal parameter c, which was smaller in the dehydrated structure. Charge difference plots and projected densities of states were computed to study the interactions between water molecules and the grafted chlorides. Differences between this kind of layered hydroxide salt and hydrotalcite-type compounds could be noticed and understood by the calculations. It could be observed that there were no drastic changes due to the dehydration. The calculated dehydration potentials were used to predict the water loss temperature and the thermodynamic features of the chloride anionic exchange reactions of Zn5(OH)8Cl2·H2O using different halide anions, and it was found that only the exchange with iodine can be performed spontaneously at 298.15 K.

Synthesis of ZnO‐CuO Nanocomposite Aerogels by the Sol‐Gel Route

The epoxide addition sol‐gel method has been utilized to synthesize porous zinc‐copper composite aerogels in the zinc‐to‐copper molar ratios of 50 : 50 to 90 : 10. A two‐step mixing approach has been employed to produce aerogels composed of nano‐ to micrometer sized particles. The aerogels were characterized by ultrahigh resolution scanning electron microscopy, transmission electron microscopy, and powder X‐ray diffraction. The as‐synthesized aerogels had a thin flake‐ or petal‐like microstructure comprised of clustered flakes on two size scales; they were identified as being crystalline with the crystalline species identified as copper nitrate hydroxide, zinc hydroxide chloride hydrate, and zinc hydroxide nitrate hydrate. Annealing of the aerogel materials at a relatively low temperature (400°C) resulted in a complete phase transition of the material to give highly crystalline ZnO‐CuO aerogels; the aerogels consisted of networked nanoparticles in the ~25–550 nm size range with an average crystallite size of ~3 nm and average crystallinity of 98%. ZnO‐CuO aerogels are of particular interest due to their particular catalytic and sensing properties. This work emphasizes the versatility of this sol‐gel route in synthesizing aerogels; this method offers a possible route for the fabrication of aerogels of different metal oxides and their composites.

End-of-life Zn–MnO2 batteries: electrode materials characterization

Physical and chemical characterization of several sizes and shapes of alkaline and saline spent Zn–MnO2 batteries was carried out, aiming at contributing for a better definition of the applicable recycling processes. The characterization essays included the mass balance of the components, cathode and anode elemental analysis, the identification of zinc and manganese bearing phases and the morphology analysis of the electrode particles. The electrode materials correspond to 64–79% of the total weigh of the batteries, with the cathodes having clearly the highest contribution (usually more than 50%). The steel components, mainly from the cases, are also important (17–30%). Elemental analysis showed that the electrodes are highly concentrated in zinc (from 48–87% in anodes) and manganese (from 35–50% in cathodes). X-Ray powder diffraction allowed for identifying several phases in the electrodes, namely zinc oxide, in the anodes of all the types of saline and alkaline batteries tested, while zinc hydroxide chloride and ammine zinc chloride only appear in some types of saline batteries. The manganese found in the cathode materials is present as two main phases, MnO·Mn2O3 and ZnO·Mn2O3, the latter corroborating that zinc migration from anode to cathode occurs during the batteries lifespan. A unreacted MnO2 phase was also found presenting a low crystalline level. Leaching trials with diluted HCl solutions of alkaline and saline battery samples showed that all zinc species are reactive attaining easily over than 90% leaching yields, and about 30% of manganese, present as Mn(ii/iii) forms. The MnO2 phase is less reactive and requires higher temperatures to achieve a more efficient solubilization.

Synthesis and Structure of Zinc Oxide Aerogel

The zinc-based aerogel was synthesized via a sol-gel route that it was processed using Zinc chloride as precursor, polyacrylic acid as the template and propylene oxide as the gelation agent. The Zn-based aerogel is formed the length and cross-link of the zinc chloride hydroxide chain, owing to a dominant influence of PAA on the nucleation and growth position of sol nucleus. Nevertheless, ZnO aerogel was prepared with the method that the zinc-based aerogel was calcined at 400°C. Consequently, the RWP value was in reasonable 7.35% according to X-ray diffraction pattern (XRD) refinement. The crystal system of the ZnO aerogel was monoclinic.

Intercalation studies of zinc hydroxide chloride: Ammonia and amino acids

Zinc hydroxide chloride (ZHC) is a layered hydroxide salt with formula Zn5(OH)8Cl2·2H2O. It was tested as intercalation matrix for the first time and results were compared with intercalation products of the well-known zinc hydroxide nitrate and a Zn/Al layered double hydroxide. Ammonia was intercalated into ZHC, while no significant intercalation occurred in ZHN. Aspartic acid intercalation was only achieved by co-precipitation at pH=10 with ZHC and pH=8 with zinc hydroxide nitrate. Higher pH resistance in ZHC favored total deprotonation of both carboxylic groups of the Asp molecule. ZHC conferred more thermal protection against Asp combustion presenting exothermic peaks even at 452°C while the exothermic event in ZHN was 366°C and in the LDH at 276°C.

Anionic iron(III) porphyrins immobilized on zinc hydroxide chloride as catalysts for heterogeneous oxidation reactions

This work describes the immobilization of an anionic iron(III) porphyrin (FePor) family on zinc hydroxide chloride (ZHC), a layered hydroxide salt prepared by reacting an aqueous zinc chloride solution with an ammonium hydroxide solution. The FePor immobilization was performed at room temperature under magnetic stirring, under air atmosphere, of each complex ethanol solution and the ZHC solid support suspension. The materials obtained were characterized by X-ray powder diffraction (XRPD), ultraviolet-visible spectroscopy (UV–vis) (solid samples), Fourier transform infrared spectroscopy (FTIR) and electron paramagnetic resonance (EPR). The catalytic activity of the solids was investigated in cyclooctene, cyclohexane and n-heptane heterogeneous catalytic oxidation reactions with iodosylbenzene as the oxygen donor. The solid catalyst's reutilization capacity was also investigated and the heterogeneous character of the catalytic process was confirmed. The compounds and the catalytic activity of FePor-ZHC were compared with the synthesis and catalytic activity of the same FePor immobilized on zinc hydroxide nitrate (ZHN). Though the matrixes are similar, the results obtained were exactly the opposite when the selectivity was analyzed.

One-step large-scale synthesis of porous ZnO nanofibers and their application in dye-sensitized solar cells

A one-step thermal evaporation and vapor-phase transport method was utilized to synthesize porous ZnO nanofibers in large scale. The synthesized nanofibers are highly porous, with diameters in the range of 200–700 nm and lengths of several micrometers. The addition of the CuCl 2·2H 2O into the Zn precursor powder was proved to be critical for the formation of the porous structures, which were proposed to be resulted from the decomposition of the unstable Cl-containing intermediate products such as zinc hydroxide chloride or zinc oxide chloride hydrate phases. In addition, a demonstration of applying the porous ZnO nanofibers as the photoanode of dye-sensitized solar cells is provided.

Initial corrosion protection of Zn–Mn alloys electrodeposited from alkaline solution

The effects of a deposition current density (c.d .) on the corrosion behaviour of Zn–Mn alloy coatings, deposited from alkaline pyrophosphate solution, were investigated by atomic absorption spectrophotometry (AAS), X-ray diffraction (XRD), atomic force microscopy (AFM), optical microscopy, electrochemical impedance spectroscopy (EIS) and measurement of corrosion potential ( E corr). XRD analysis disclosed that zinc hydroxide chloride was the main corrosion product on Zn–Mn coatings immersed in 0.5 mol dm −3 NaCl solution. EIS investigations revealed that less porous protective layer was produced on the alloy coating deposited at c.d . of 30 mA cm −2 as compared to that deposited at 80 mA cm −2.

Effect of water vapor on the thermal decomposition process of zinc hydroxide chloride and crystal growth of zinc oxide

Thermal decomposition process of zinc hydroxide chloride (ZHC), Zn 5(OH) 8Cl 2·H 2O, prepared by a hydrothermal slow-cooling method has been investigated by simultaneous X-ray diffractometry and differential scanning calorimetry (XRD–DSC) and thermogravimetric-differential thermal analysis (TG-DTA) in a humidity-controlled atmosphere. ZHC was decomposed to ZnO through β-Zn(OH)Cl as the intermediate phase, leaving amorphous hydrated ZnCl 2. In humid N 2 with P H 2 O =4.5 and 10 kPa, the hydrolysis of residual ZnCl 2 was accelerated and the theoretical amount of ZnO was obtained at lower temperatures than in dry N 2, whereas significant weight loss was caused by vaporization of residual ZnCl 2 in dry N 2. ZnO formed by calcinations in a stagnant air atmosphere had the same morphology of the original ZHC crystals and consisted of the c-axis oriented column-like particle arrays. On the other hand, preferred orientation of ZnO was inhibited in the case of calcinations in 100% water vapor. A detailed thermal decomposition process of ZHC and the effect of water vapor on the crystal growth of ZnO are discussed.

Comparison of corrosion behaviour of zinc in NaCl and in NaOH solutions. Part I: Corrosion layer characterization

The corrosion layer formed on zinc sample in 0.6 M NaCl and 0.5 M NaOH solution under ambient conditions has been investigated. The corrosion layer morphology was analyzed using scanning electron microscopy (SEM). X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to characterize the corrosion products of zinc. The thickness evolution of the corrosion layer was investigated by glow discharge optical emission spectroscopy (GDEOS). The corrosion layer formed in 0.5 M NaOH solution appeared more compact than that formed in 0.6 M NaCl solution. Zinc hydroxide chloride (Zn 5(OH) 8Cl 2·2H 2O) and zinc hydroxide carbonate (Zn 5(CO 3) 2(OH) 6) were formed on zinc surface in 0.6 M NaCl solution while in 0.5 M NaOH solution, zinc oxide (ZnO), zinc hydroxide (Zn(OH) 2) and zinc hydroxide carbonate (Zn 5(OH) 6(CO 3) 2·H 2O) were detected. Probable mechanisms of zinc corrosion products formation are presented.

Influence of Potassium Chloride on the Electrochemical Deposition of ZnO Plate Films

KCl is usually used as the supporting electrolyte in electrochemical deposition of Zinc oxide materials. Besides the role of supporting electrolyte, it can also influence the morphology of the fabricated materials. In this work, ZnO and zinc hydroxide chloride hydrate (Zn5(OH)8Cl2•H2O) mixture with platelet-like morphology were electrochemically deposited directly on ITO-coated glass substrates at 65°C. The electrolyte was 0.1M Zn(NO3)2•6H2O with KCl concentration varied from 0 to 3.2M. It was found that only ZnO thin film was obtained when the concentration of KCl was below 0.02M. Plates structure appeared as the concentration of KCl increased to 0.04M. Plentiful plates were obtained when the concentration of KCl was 0.05M-0.2M. From the X-ray diffraction, it was confirmed that the plate films was the mixture of ZnO and Zn5(OH)8Cl2•H2O. The plates showed perfect single crystal structure confirmed by selected area electron diffraction. Zn and Zn5(OH)8Cl2•H2O were obtained when the concentration of KCl was above 0.8M.

One‐step synthesis of ZnO/MgO core‐sheath structures

AbstractA kind of ZnO/MgO core‐sheath structure has been prepared directly by the pyrolysis of a mixture of polyvinyl alcohol, magnesium acetate, and zinc chloride coating on glass fiber mats at 450 °C for 60 min. The growing process and effect of the anions on the morphology of ZnO/MgO structures have been preliminarily discussed. The results indicate that ZnCl2 will transform to ZnO crystal through an intermediate of zinc hydroxide chloride. ZnO crystal act as the core of the micorod, and MgO lamellas act as the sheath. The concurrence of chloride and acetate anions in the precursor is necessary for the growth of ZnO/MgO core‐sheath structures. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Preparation of nano-ZnO supported on porous carbon and the growth mechanism

A novel kind of porous carbon embedding ZnO nano-particles has been prepared by pyrolysis of poly vinyl alcohol (PVA) and ZnCl 2 mixture coated on glass fiber mats. The structure of the composite was investigated through scanning electron microscopy, X-ray powder diffraction, X-ray energy spectrum analysis, N 2 adsorption at 77 K and thermogravimetry analysis. The results indicate that the pyrolysis time is the key factor that controls the morphology and size of ZnO particles growing in carbonous materials. Various nanostructures, including zinc hydroxide chloride (ZHC) lamellae-packed ellipsoid particles, hexagonal pencil-like ZnO nanorods, oriented ZnO nanorods array, and ZnO microrods sized range of 30 nm–3 μm could be prepared by controlling the pyrolysis time from 30 to 180 min. Specific surface areas of carbon supports were in range of 380–630 m 2/g. The growth process of nano-crystal of ZnO is believed to undergo the conversion of ZnCl 2 to ZHC, and then the decomposition of ZHC to ZnO while they were heated at 450 °C.

Preparation and characterization of ZnO porous plates

This article presents two main steps to prepare zinc oxide porous plates. Firstly, the precursor zinc hydroxide chloride hydrate (Zn 5(OH) 8Cl 2·H 2O) was synthesized by ZnCl 2 and ethylenediamine ((CH 2NH 2) 2). Secondly, the precursor was put into a furnace and annealed at 500 °C. And then the zinc oxide porous plates were successfully obtained. The crystal structures and the microstructures of the precursor and the final product were analyzed and compared by XRD, SEM and TEM. The specific surface area and gas adsorption isotherm of the final product were tested by Brunauer–Emmett–Teller equipment.

Hydrothermal Synthesis of Zinc Hydroxide Chloride Sheets and Their Conversion to ZnO

We report a simple hydrothermal slow cooling process to synthesize zinc hydroxide chloride (ZHC) powders consisting of large-sized single-crystal sheets. The lateral size of the sheetlike products can be tuned from 20 to 500 μm through the control of pH condition of the starting zinc chloride solution and the amount of the solute. The growth mechanism of the ZHC sheets is explained by dissolution at high temperatures and precipitation during slow cooling. The ZHC single-crystal sheets were converted to highly oriented polycrystalline zinc oxide sheets by calcination at 500 °C for 5 h in air.

Anion-exchange and thermal change of layered zinc hydroxides formed in the presence of Al(III)

Zinc hydroxide chloride particles of ZHC (simonkolleite, Zn 5(OH) 8Cl 2·H 2O) and layered double hydroxides (LDH, Zn–Al–Cl) were prepared by hydrolysis of ZnCl 2 solutions dissolving AlCl 3 at Al/Zn = 0.1 and 0.6 in atomic ratio, respectively. The anion-exchange and thermal change of ZHC and LDH were investigated by XRD, TEM, FTIR, analysis of Zn, Al, and Cl and gas adsorption of N 2, H 2O, and CCl 4. The formed ZHC and LDH particles were hexagonal thin plates and irregularly shaped thin plates, respectively. LDH was more easily ion-exchanged with CO 3 2− and SO 4 2− compared to ZHC. The layered structure of LDH was damaged by the ion-exchange with SO 4 2− but not CO 3 2−, whereas that of ZHC was kept after the ion-exchange with both the anions. The TEM observation of the ZHC and LDH particles outgassed at different temperatures of 75–400 °C revealed that exfoliation takes place on outgassing ZHC at 100–150 °C but not occurs in LDH. ZHC showed a high H 2O adsorption selectivity when outgassed below 100 °C, however the adsorption selectivity completely disappeared above 125 °C where the exfoliation took place. On the other hand, LDH exhibited less adsorption selectivity than ZHC though the selectivity was held after outgassed at 400 °C. The facilitated delamination of ZHC indicates that ZHC exhibits weaker interlalyer attractive force than LDH in vacuo.

Synthesis of layered zinc hydroxide chlorides in the presence of Al(III)

Zinc hydroxide chloride particles were synthesized by hydrolysis of ZnCl 2 solutions dissolving AlCl 3 at different atomic Al/Zn ratios from 0 to 1.0 and characterized by various techniques. Increasing Al/Zn ratio changed the crystal phases of the products as ZnO→ZnO+ZHC (Zn 5(OH) 8Cl 2·H 2O)→ZHC→LDH (layered double hydroxides, Zn–Al–Cl) and the particle morphology as agglomerates (ZnO)→fine particles (ZnO)→plates (ZHC)+rods (ZnO)→plates (ZHC)→plates (LDH). The atomic Cl/Zn ratios of LDH particles formed at Al/Zn⩾0.3 were ca. 0.3 despite the increase of Al/Zn ratio, being due to the intercalation of CO 3 2− into the LDH crystal. The OH − content of LDH estimated by TG was reduced by the deprotonation of OH − to counteract the excess positive charge produced by replacing Zn(II) with Al(III). ZHC exhibited a high adsorption selectivity of H 2O.

Influence of the alloying component on the protective ability of some zinc galvanic coatings

The composition of the corrosion products of pure Zn galvanic coatings as well as of some zinc alloys (Zn–Mn and Zn–Co) after treatment in selected free aerated model media (5% NaCl and 1N Na 2SO 4) is studied and discussed. X-ray diffraction and X-ray photoelectron spectroscopy investigations are used for this purpose. It is concluded that the corrosion products (zinc hydroxide chloride hydrate in 5% NaCl and zinc hydroxide sulfates hydrates in 1N Na 2SO 4) play a very important role for the improved protective ability of the zinc alloys toward the iron substrate, compared to the pure Zn coatings. Another result is that, for a given medium, the corrosion products are one and the same for both alloys independently of the fact that the alloying component is electrically more positive or negative than the zinc. Some suggestions about the models of the appearance of these products and their protective influence are also discussed.