Reactivity Of Zinc Research Articles

Effect of iron powder on zinc reactivity and anticorrosion performance of zinc-rich epoxy coatings

This study investigated the impact of iron powder on zinc reactivity and anticorrosion performance of zinc-rich epoxy (ZRE) coatings. Incorporating iron powder into ZRE coatings enhanced their overall anticorrosion performance, as evidenced by improved cathodic protection and reduced rust creep in salt spray tests. Furthermore, salt spray and EIS tests on cracked ZRE coatings demonstrated the enhanced sacrificial cathodic protection and physical barrier property with the inclusion of iron powder, attributed to the promoted sacrificial oxidation of zinc particles at damaged areas. The enhanced zinc dissolution in the presence of iron powder was also observed in immersion tests and potentiodynamic polarization tests on compressed Zn and ZnFe pellets.

Electrodeposition of Tin onto Zinc for the Electrochemical Synthesis of Zn/Sn/Cu Precursor Stack for CZTS‐Based Photoconversion Devices

AbstractIn this work, the synthesis of a Mo(sub)/Zn/Sn/Cu metallic stack through electrodeposition is achieved by using an ethylene‐glycol‐based solution designed to deposit Sn onto a Mo/Zn substrate. The displacement reaction with zinc is minimized through the formation of complexes with diethanolamine. A correlation between the electrochemical behavior of Sn(II) species and the reactivity of zinc upon immersion in the tin plating bath is shown. Morphological and compositional characterization is carried out on the Zn/Sn/Cu stack at the different synthesis steps. Reactive annealing is carried out to convert the metallic precursor into CZTS with a minor presence of secondary phases. The resulting CZTS/CdS/Pt photoelectrode shows a photocurrent density of −5.73 mA cm−2 at 0 V vs RHE under 1 sun (AM 1.5 G). This study demonstrates how the chemistry of the plating bath is crucial for the deposition of thin films onto reactive substrates, reducing the technological gap with vacuum‐based deposition methods.

Albumins inhibit the corrosion of absorbable Zn alloys at initial stages of degradation

Understanding the surface interactions and reactivity of zinc (Zn)-based biomaterials with constituents of physiological fluids such as proteins and ions is essential for an accurate evaluation of biomaterial corrosion initiation and progression. In this paper, the effect of the albumin addition on the corrosion behavior of pure Zn and Zn–4Ag alloy is discussed. The corrosion behavior of Zn-based materials was studied using potentiodynamic polarization, electrochemical impedance spectroscopy, immersion tests and X-ray photoelectron spectroscopy. It was found that the addition of albumins largely affects the chemical composition, morphology and compactness of the protective films formed on biomaterials. A shift of the corrosion regime from localized to more general was observed in the protein-containing electrolytes. The proteins acted as corrosion inhibitors, reducing the corrosion current density and promoting passivation of the metallic surfaces. The increase in the corrosion resistance of the Zn–4Ag alloy is attributed to a selective Zn ion leaching that leaves the metal surface enriched with electrochemically more stable alloying element.

(Invited) Zn-MnO2 Rechargeable Batteries Chemistry with Naturally Occurring Polymer Electrolyte Infused with Additives

Zinc based chemistries have attracted attention and revived research efforts due to their low cost, phenomenal inherent safety, and reliable electrochemical performance. Amongst various Zn-chemistries, Zn-MnO2 has received wide attention due to its cost-effectiveness, safety, eco-friendliness, high output voltage, and high capacity. Traditionally this chemistry has been developed and commercialized as primary batteries (Energizer, Duracell, etc.). Varied research efforts have been put toward making this chemistry rechargeable, however the majority utilize aqueous electrolytes. Zn based rechargeable batteries are notoriously known for failure due to dendrite generation and propagation. It is relatively easy for the propagation of dendrites to occur in secondary batteries that contain liquid electrolytes unless additional measures (suppressants, separators, etc.) are adopted. In an effort to overcome the latter issues, and to boost the overall performance of our Zn-MnO2 batteries, incorporation of polymer electrolytes (offers mechanical resistance to dendrite growth) have been implemented. However, issues such as the polymer itself acting as an insulator, high interfacial resistance from the small solubility of the zinc salts, poor adhesion between electrolytes and electrodes are frequently observed. Additionally, the majority of polymers used in battery application are synthetic, which are widely known for their very slow degradation rates that may cause environmental concerns unless adequately disposed of. Most synthetic polymers used as the base constituent for preparation of electrolytes are known to induce crystallinity (rigidity) and thus affecting flexibility, ionic conductivity, and overall performance of the complete cell.These overall limitations propelled our research to look and explore better alternatives. Our research focusses on exploring and preparing a zinc-manganese dioxide (Zn-MnO2) rechargeable battery using a novel and naturally occurring polysaccharide-based polymer gel film as the electrolyte. The novelty of the research lies in exploring and preparing polysaccharide-based electrolytes (flexible, biodegradable, safe, etc.) with various additives (for enhancing stability and performance) using non-conventional, low time, and low energy-consuming methods to attain an efficient optimized process. In this talk, I will discuss details of the polysaccharides explored, their performance with various salts incorporated in them. Effect on swellability of the polymer on ionic conductivities, reversibility and reactivity of Zinc in the system due to various molar concentrations (pH –variation) used in electrolyte preparation were extensively studied and will be discussed. Additionally, preliminary results for diffusion coefficient measurement, Zincate ions movements, and transference number performed to check performance efficiency and robustness of our gel electrolyte for cyclability will be presented. Our focus of research also extends towards generating an optimized cell construction technique to incorporate the prepared electrolyte in the cell to reduce the interfacial contact resistance. Also, few interesting non-conventional methods are being worked on currently to generate cathodes for this complete cell to achieve better performance. Finally, the overall performance of the constructed battery and performed ex-situ studies will be shown.

Evaluation of surface activity of hot-dip galvanized steel after alkaline cleaning

The surface activity of hot-dip galvanized steel was evaluated after alkaline cleaning by exposing the cleaned specimens in humid supercritical carbon dioxide, followed by extraction and quantification of the formed corrosion products. Different free alkalinities of the cleaning bath were studied to obtain information on the evolution of zinc surface activity at different levels of surface etching. Surface reactivity of uncleaned galvanized steel is restricted and local, with major contributions from grain boundaries and intermetallic particles. Formation of zinc corrosion products took place in uncleaned samples exclusively on and around these sites. Al2O3 removal by alkaline cleaning gradually increased the surface activity. The major increase in surface activity was achieved when increasing the free alkalinity from 0.5 to 4.0 mEq/L, which was shown by formation of zinc corrosion products within zinc grains. The surface activity was confirmed by applying a titanium hexafluoride pretreatment on the cleaned panels and measuring the lateral microscale uniformity of the formed layer. The uniformity increased when larger areas of galvanized steel became activated by alkaline cleaning. Reactivity of zinc is rather difficult to quantify when setting up an industrial cleaning sequence for galvanized steel. Controlled exposure of cleaned samples in humid supercritical carbon dioxide, followed by quantification of oxidized zinc, provides a straightforward method to evaluate zinc reactivity.

Mixed-ligand complexes of zinc(II) with 1,1-dicyanoethylene-2,2-dithiolate and N-donor ligands: A combined experimental and theoretical study

The fascinating structural chemistry of zinc(II) with 1,1-dicyanoethylene- 2,2-dithiolate [i-MNT2- = {S2C:C(CN)2}2-] ligand is presented. To elaborate, the reactivity of zinc(II) salt towards potassium salt of 1,1-dicyanoethylene-2,2-dithiolate (K2i-MNT) and 1,3-diaminopropane (dap) was studied in the presence of two distinct N-donor ligands, α-picoline (2-Methylpyridine) and γ-picoline (4-Methylpyridine), respectively. As a result, two different Zn(II) coordination complexes of formule [Zn2(dap)2(i-MNT)2] (1) and {[Zn(dap)(i-MNT)(4-MePy)]·2H2O}n (2) were obtained. They were isolated as stable crystalline solids and fully characterized, including by single crystal X-ray diffraction. Complex 1 is a discrete 0D dimer, whereas 2 is a 1D coordination polymer. Although α-picoline was used during the synthesis of 1, it is not involved in the metal coordination. Aiming at rationalizing the influence of the different noncovalent interactions, such as H-bonding, unconventional NH···π and anion–π, on the crystal packing of 1 and 2, DFT calculations (M06-2X/def2-TZVP) were performed. Moreover, luminescence property of the complex 2 was investigated. Finally, in vitro antifungal activity of complex 2 was also screened against five fungi viz. Synchitrium endobioticum, Pyricularia oryzae, Helminthosporium oryzae, Candida albicans (ATCC10231) and Trichophyton mentagrophytes by the disc diffusion method and found to be effective when compared to K2i-MNT.H2O.

The effect of synthetic zinc corrosion products on corrosion of electrogalvanized steel. II. Zinc reactivity and galvanic coupling zinc/steel in presence of zinc corrosion products

The reactivity of zinc under synthetic zinc patinas and the galvanic coupling in steel/patina/Zn are studied. Zn5(OH)6(CO3)2 and Na2Zn3(CO3)4⋅3H2O inhibit zinc anodic dissolution in NaCl, while Zn5(OH)8Cl2 H2O and Zn4(OH)6SO4nH2O do not. The galvanic current in steel/patina/NaCl/Zn is smaller as compared to steel/NaCl/Zn. The inhibiting effect decreases with time for Na2Zn3(CO3)4⋅3H2O or Zn4(OH)6SO4 nH2O due to the transformation into Zn(OH)2. In NaHCO3, the polarity between zinc and steel can reverse. The effect of confinement on the cathodic current is stronger than the initial effect of patina which is explained by the instability of the patinas under rapid pH-increase.

Reduction of N-Nitrosodimethylamine with zero-valent zinc

N-Nitrosodimethylamine (NDMA) is known as the disinfection by-product and the pollutant in the source water. Reduction with zero-valent zinc (Zn(0)) was investigated as a potential technology to treat NDMA. The results showed that Zn(0) was effective for NDMA reduction at initial pH 7.0. There were lag period and rapid period during the process, the corresponding zero-order rate constant (kzero) was 2.968 ± 0.245 μg L−1 h−1 ([Zn(0)]0 = 10g L−1),the mass normalized pseudo-first-order rate (kM) was 0.1215 ± 0.0171 L g−1 h−1. The reactivity of zinc on NDMA removal was consistent with the zinc corrosion rate. NDMA had little effect on the corrosion of zinc. Lower solution pH benefited the reduction of NDMA with Zn(0). The consumption of the oxygen and the localized acidification should be the cause of the shift from lag to rapid reaction period in the aerobic experiments. 1,1-dimethylhydrazine (unsymmetrical dimethylhydrazine, UDMH), dimethylamine (DMA) were detected as the products of NDMA degradation. The nitrogen mass balance at 24 h was 56%, the loss can be due to the formation of ammonium, the degradation of UDMH and other unmeasured products. DMA formed during the degradation of UDMH with Zn(0), the nitrogen loss could be caused by the formation of unmeasured products. Catalytic hydrogenation is proposed to be the mechanism based on the results and the redox properties of zinc and NDMA. One reduction process is: the active hydrogen atoms initially cleave and reduce the N=O bond in NDMA, generating UDMH. Then the N–N bond in UDMH is cleaved to form DMA and ammonium.

Reactivity of nanoparticles; interaction between zinc and copper oxide nanoparticles and iron ions in an alkaline medium

The reactivity of zinc and copper oxide nanoparticles was investigated upon their interaction with iron oxides. It was ascertained that, depending on the reaction conditions, nanoparticles of zinc and copper ferrites (ZnFe2O4 and CuFe2O4) or core/shell nanoparticles (Fe3O4/ZnO) are produced. Size, composition, and structure of the resulting nanoparticles were determined by transmission electron microscopy and X-ray diffraction analysis. The average size of zinc and copper ferrite nanoparticles was ascertained to be 9–10 and 2–3 nm, respectively. For core/shell Fe3O4/ZnO nanoparticles, the average size is 20 nm. It was experimentally proved that the photoluminescence radiative characteristics of ZnO nanoparticles are retained in core/shell Fe3O4/ZnO nanoparticles.

Zinc(II) complexes based on sterically hindered hydrotris(pyrazolyl)borate ligands: Synthesis, reactivity and solid-state structures

The coordination chemistry and reactivity of zinc(II) complexes supported by monoanionic hydrotris(pyrazolyl)borate ligands substituted by 3,3,3-mesityl groups (Tp Ms) and 3,3,5-mesityl groups (Tp Ms∗) have been investigated. Salt metathesis of ZnCl 2, ZnEt 2, and Zn(OAc) 2 with Tl[Tp Ms] or Tl[Tp Ms∗] cleanly afforded the corresponding compounds Tp MsZnCl ( 1), Tp MsZnEt ( 2), Tp Ms∗ZnEt ( 3), and Tp MsZnOAc ( 5). Compound 3 slowly disproportionates in benzene solution to afford the bis(ligand) complex (κ 2-Tp Ms∗) 2Zn ( 4). Acetate complex 5 as well as Tp MsZnOCOPh ( 6) and [Tp Ms∗ZnOAc] 2 ( 7) were alternatively prepared by acidolysis of the parent ethyl complexes ( 2, 3) with the corresponding carboxylic acid. No reaction was observed between 2 and 3 and alcohols (ROH; R = Et, iPr, Bn), while salt metathesis reactions of ZnEt(OR) with Tl[Tp Ms] led to 2 instead of the desired zinc-alkoxide complex. Compounds 1– 7 were characterized by elemental analysis, 1H and 13C NMR spectroscopy, as well as by X-ray diffraction studies for 1, 2, 4, 5 and 7. The former compounds adopt a monomeric structure in the solid state while [Tp Ms∗ZnOAc] 2 ( 7) exists as an anti- syn bridged acetate dimer. Complex 4 is four-coordinated, featuring a rare bidentate coordination mode of the Tp Ms∗ ligands. The results are rationalized in terms of the variable steric constraint around the zinc atom provided by the Tp Ms and Tp Ms∗ ligands.

Anodic Film Formation on Zinc in Alkaline Electrolytes Containing Silicate and Tetraborate Ions

The reactivity of zinc in sodium hydroxide electrolytes containing sodium silicate and sodium tetraborate was studied by electrochemical and microstructural examinations. Impedance measurements indicate that a porous surface layer is formed on zinc immersed in sodium hydroxide at its open circuit potential and on polarization in the prepassive region. This surface layer becomes compact at potentials in the passive region. The anodic reactions of a zinc electrode in a sodium hydroxide containing electrolyte are controlled by the mass transport of zincate ions away from the electrode. Silicate and tetraborate ions suppress the anodic dissolution of zinc. In the presence of silicate ions, a compact silicate containing film is formed upon anodic polarization. The electrode rotation affects the microstructure of the surface layer both in silicate-free and silicate-containing sodium hydroxide solutions. On addition of tetraborate ions, the polarization resistance increases and the formation of a surface layer is achieved at increased applied potential.

Excessive matrix metalloproteinase activity in diabetes: inhibition by tetracycline analogues with zinc reactivity.

Diabetes mellitus in rats is characterized by excessive activity of several matrix metalloproteinases (MMPs), notably collagenase(s) and gelatinase(s), in skin, gingiva, and other tissues. A number of tetracyclines (TCs), both antimicrobial compounds as well as chemically modified non-antimicrobial TC analogues (CMTs) are known to possess potent inhibitory activity against these enzymes. Three conventional antimicrobial TCs and six CMTs were used in this study. In vitro, doxycycline was shown to possess higher inhibitory capacity (i.e. lower IC(max)) against diabetic rat skin collagenase than either minocycline or tetracycline HCl. Addition of excess zinc partially reversed the proteinase inhibition by TCs. In vivo, using rats made diabetic with streptozotocin (STZ), oral administration of various TCs led to decreased weight loss and substantial reductions in the activity of both skin collagenase and skin gelatinase (primarily MMP-9, 92 kDa) without affecting blood glucose. Using an in vitro spectrophotometric technique, the Zn(++) reactivity of several CMTs was assessed and found to be positively related to the potency of these compounds as MMP inhibitors. One particular CMT (CMT-5, pyrazole analogue), which is neither antimicrobial nor capable of binding metal cations, did not inhibit the MMPs. TCs have potential utility in management of diabetic complications mediated by excessive activity of MMPs.

Elucidation of Sulfidation Mechanisms of Zinc Ferrite in a Reductive Gas Environment by in Situ X-ray Diffraction Analysis and Mössbauer Spectroscopy

A difference in reactivity of zinc and iron in zinc ferrite during sulfidation in a reductive gas environment is important to explain sulfur removal performance of the double oxide. We focused on their sulfidation characteristics under relatively lower sulfur concentration to determine the factors for a superior performance on sulfur removal. A series of sulfidation tests of the double oxide were performed in reductive gas environments at mainly 550 °C in an in situ X-ray diffraction instrument that identified products of reduction and sulfidation. Complementary information on valence and magnetic properties of iron in the products was obtained by 57Fe Mossbauer spectroscopy analysis. Reduction products of zinc ferrite were wustite, partly zinc-bearing magnetite, and pure magnetite, depending on the strength of the reductive environment. Sulfidation of the reduced zinc ferrite yields sulfides of both zinc and iron, when the concentration of hydrogen sulfide was sufficiently high. Zinc sulfides, however, w...

Reactivity of Zinc(II) 5-Oxoniaprotoporphyrin-IX: Synthesis of the First 5-Oxonia-15-phlorin

Reactivity of Zinc(II) 5-Oxoniaprotoporphyrin-IX: Synthesis of the First 5-Oxonia-15-phlorin

Growth and reactivity of zinc and cadmium oxide nano-particles in zeolites

Zinc and cadmium oxide particles in the size range of 1–10 nm grow inside a faujasite matrix, zeolites X and Y or its hexagonal analogue EMT starting from metal ion-exchanged zeolites subjected (i) to sodium hydroxide solutions (0.01–0.75 M) at elevated temperatures (293–353 K) and (ii) to subsequent calcination in air at 673 K. The oxide nano-particles are accommodated in mesopores forming simultaneously with the precipitation of the metal hydroxides. As revealed by adsorption measurements the maximum diameters and the overall volumes of the mesopores grow with increasing concentration of the lye used for the precipitation. The main portion of mesopores is formed as bubbles inside the zeolite matrix, only a small fraction as pockets at the outer surface of the zeolite crystallites. The embedded oxide nano-particles are physically and chemically uniform, i.e. they show (i) the expected quantum size effects in the diffuse reflectance spectra and (ii) a particle size effect concerning the reversible formation of cadmium carbonate.

Synthesis and reactivity of zinc and aluminum alkyl derivatives stabilized by oxygen tripod ligands

Zinc and aluminum alkyl derivatives L OEt ZnR (R=CH 3 , CH 2 CH 3 , CH(CH 3 ) 2 ) and L OEt Al(CH 3 ) 2 [Al(CH 3 ) 3 ] of the oxygen tripod ligand system L OEt ≡[CpCo{P(O)(OEt) 2 } 3 ] - (Cp=η 5 -C 5 H 5 ) have been synthesized by the reactions of the alkylis ZnR 2 and Al(CH 3 ) 3 with TlL OEt

Spectroscopy and reactivity of zinc 20‐oxaporphyrin‐IX dimethyl ester

AbstractA facile method of preparing zinc 20‐oxaprotoporphyrin‐IX dimethyl ester (1) from biliverdin‐IXα dimethyl ester has been found. According to NMR spectroscopy, the oxa substituent has a pronounced influence on the properties of the macrocyclic ring system. The 1H NMR spectrum reveals an aromatic structure and 13CNMR shows that in 1 a positive charge is delocalized, in agreement with the presence of one positive charge, and further that C‐1 and C‐19 have acquired the highest positive charge. This is corroborated by the reaction with nucleophiles, especially thiolates, leading to isolated adducts which could be well characterized. The adducts are the result of nucleophilic attack on the positions 1 and 19 exclusively, which agrees well with the charge on these positions in 1. The adducts show interesting spectroscopic properties. The study of oxaporphyrins and their nucleophilic adducts may contribute to a fuller understanding of the formation and properties of bile pigments.