Influence of F‐ doping on the microstructure,surface morphology and electrochemical properties of the lead dioxide electrode

The lead dioxide electrode (PbO₂) with Ti substrate and SnO₂‐Sb₂O₅ intermediate layer was doped by F^‐ ion through the potentiostatic anode co‐deposition method. The content of F in the coating can be controlled by adjusting deposition potential. The effect of F^‐ doping on the composition, surface morphology and electrochemical properties of the PbO₂ electrode was characterized by X‐ray diffraction, scanning electron microscope, X‐ray photoelectron spectroscopy and electrochemical measurement methods. The results have confirmed that the content of β‐PbO₂ increases with increasing that of F, and the doping can make the β‐PbO₂ grains become fine and the electrode surface become smooth; the specific surface areas and conductivity increase, and the initial potential of oxygen evolution shifts toward positive direction compared with the free‐doped PbO₂ electrode; the oxygen evolution potential increases with the increasing of the F^‐content in the PbO₂ film electrode. The bulk electrolysis result demonstrated that the performances of the F‐PbO₂ electrode for anodic oxidation aniline have been improved to some extent. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of Mn2+ on the chrome‐free colored Ti/Zr‐based conversion coating on 6063 aluminum alloy

The conversion coating with golden color and improved corrosion resistance had been prepared by adding Mn²⁺ in the Ti/Zr conversion coating solution. Comparing with that of conversion coating without Mn²⁺, the optimal treatment time of this conversion coating was much shorter and the corrosion resistance was obviously improved. The effect of Mn²⁺ on the formation of golden Ti/Zr conversion coating was thoroughly investigated by means of energy dispersive X‐ray spectroscopy, SEM, XPS, and Raman and electrochemical workstation. The results showed that the conversion coating had a double‐layer structure: the outer layer consisted of the metal‐organic complex and the inner layer was mainly made up of Na₃AlF₆. Mn²⁺ was oxidized into MnOOH in solution and precipitated on the substrate surface which provided the nucleus to Na₃AlF₆ crystal and accelerated Na₃AlF₆ crystal formation and also made the microstructure of conversion coating change to the cubic. The mechanism of the formation of the conversion coating can be deemed as nucleation, growth of Na₃AlF₆ crystal, and formation of metal‐organic complex. Copyright © 2015 John Wiley & Sons, Ltd.     

Optimization of electroless Ni?P coatings based on multiple roughness characteristics

This paper presents an experimental study of roughness characteristics of electroless Ni? P coatings. Optimization of coating process parameters is done with multiple surface roughness characteristics based on Taguchi method coupled with grey relational analysis. Experiments are carried out by utilizing the combination of process parameters based on L₂₇ Taguchi orthogonal design with three process parameters, viz. bath temperature, concentration of nickel source solution and concentration of reducing agent. Results show that concentration of the reducing agent and its interaction with concentration of the nickel source solution have significant influence in controlling the roughness characteristics of electroless Ni? P coating. Grey‐based Taguchi method is found to optimize the coating parameters fairly well. The surface morphology and composition of coatings are also studied with the help of scanning electron microscopy, energy dispersed X‐ray analysis and X‐ray diffraction analysis. No significant change in nickel and phosphorous content of coatings occurs with annealing. The Ni? P deposit is nanocrystalline in the as‐plated condition, and upon heat treatment at 400 °C it produces Ni₅P₂, Ni₂P, and NiP₂ as major compound constituents. Copyright © 2008 John Wiley & Sons, Ltd.     

Corrosion behavior of electroless Ni–P/TiO2 nanocomposite coatings

Composite Ni–P/nano‐TiO₂ coatings were prepared by simultaneous electroless deposition of Ni–P and nano‐TiO₂ on a low carbon steel substrate. The deposition was carried out from stirred solutions containing suspended nano‐TiO₂ particles. The Ni–P and Ni–P/nano‐TiO₂ coatings before and after heat treatment were characterized by X‐ray diffraction, scanning electron microscopy and energy dispersive X‐ray spectroscopy. The micro‐structural morphologies of the coatings significantly varied with the nano‐TiO₂ content. The corrosion resistance of as‐plated and heat‐treated Ni–P and Ni–P/nano‐TiO₂ coatings was investigated by anodic polarization, Tafel plots and electrochemical impedance spectroscopic (EIS) studies in 3.5% NaCl solution. Ni–P/nano‐TiO₂ coating exhibited superior corrosion resistance over Ni–P coating. Copyright © 2015 John Wiley & Sons, Ltd.     

Surface evaluation and electrochemical behavior of cerium conversion coating modified with silane on magnesium alloy

A new cerium conversion coating modified with the hydrolysis silane is designed for AZ31 magnesium alloy, which aims at assessing the surface characterizations and electrochemical behaviors between the cerium conversion coating with and without the silane modified. The effect of the silane addictive is studied by scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS). The adhesion of the coatings is undertaken according to the American Society for Testing and Materials (ASTM) standard D3359‐08 cross tape test. The electrochemical behavior is evacuated by polarization experiment and electrochemical impedance spectroscopy (EIS) in NaCl electrolyte. The results show that the addition of bis‐[triethoxysilylpropyl] tetrasulfide (BTESPT) to loosen and porous cerium conversion coating leads to the formation of a more compact and homogenous film, higher resistance to water uptake and better adhesion to substrate. Electrochemical measurements show that, compared with the non‐modified cerium conversion coating, the coating modified with the silane exhibits better anticorrosion properties. Copyright © 2014 John Wiley & Sons, Ltd.     

Corrosion behavior of tantalum alloying on γ‐TiAl by double‐glow plasma surface metallurgy technique

The Ta coating with corrosion resistance is grown on the γ‐TiAl substrate by double‐glow plasma surface metallurgy technique, followed by the electrochemical test in 10 wt%, 20 wt% HCl and 10 wt%, 40 wt% H₂SO₄ solution. The data of nanohardness and elastic modulus are collected by the nanoindention test. The adhesion strength of Ta coating is investigated by means of the scratch test. The study of corrosion resistance is performed using potentiodynamic polarization and electrochemical impedance spectroscopy and measured by SEM and X‐ray diffraction. Results highlight that the Ta coating is tightly bonded to the γ‐TiAl substrate, consisting of the deposition layer and diffusion layer. Experimental data indicate that the Ta coating presents excellent corrosion resistance, which is confirmed by the high values of polarization resistance (R_p) and the low values of corrosion current density (i_corr). The surface nanohardness of the Ta coating is improved from 3.41 to 7.29 GPa, nearly twice of that of the substrate. The Ta₂O₅ formed on the coating is able to hold back the penetration of adverse ions inwardly, owing to its dense structure and adhesion effect. Copyright © 2017 John Wiley & Sons, Ltd.     

The formation mechanism and biocorrosion property of CaSiO3/CaHPO4 · 2H2O composite conversion coating on the extruded Mg‐Zn‐Ca alloy for bone implant application·

In this work, a calcium silicate and calcium phosphate (CaSiO₃/CaHPO₄ · 2H₂O) composite coating was applied by a chemical reaction to an extruded Mg‐Zn‐Ca magnesium alloy. SEM observation showed that a flat and sand‐like conversion coating was formed. X‐ray diffractometer (XRD) analysis indicated that the conversion coating was composed of CaHPO₄ · 2H₂O and a little amount of CaSiO₃. The formation mechanism of CaSiO₃/CaHPO₄ · 2H₂O composite conversion coatings was discussed. The electrochemical polarization tests showed that the conversion coating markedly improved the biocorrosion resistance of Mg‐Zn‐Ca alloy in Hank's solution. Copyright © 2010 John Wiley & Sons, Ltd.     

Deposition and characterization of TiAlSiN coatings prepared by hybrid PVD coating system

TiAlSiN coatings with different Si contents were deposited on silicon and high‐temperature alloy by using a hybrid physical vapor deposition coating system, where the cathodic arc ion plating was combined with a twin target mid‐frequency magnetron sputtering. The chemical composition, microstructure, cross‐sectional structure and morphology were carried out by X‐ray photoelectron spectroscope (XPS), X‐ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscope (TEM), respectively. NanoTest 600 nanomechanical system and ball‐on‐disc friction tester were used to investigate the mechanical and friction properties of TiAlSiN coatings. The worn surface of the TiAlSiN coatings and counterballs were investigated by means of surface profilometer and optical microscope. The wear rates were also measured by surface profilometer. The results showed that the Si addition did not change the coatings growth orientation, and the coating transfered into amorphous phase when the Si content reached about 13.9 at.%. The tribological properties and the hardness were improved by solid solution of Si atoms and grain boundary strengthening of SiN_x amorphous phase with moderate Si content addition. In addition, the SiNx amorphous phase improved oxidation resistance of TiAlN coating, but with a high Si content (more than 8.3 at.% in this work) the agglomeration of SiN_x amorphous phase would reduce the mechanical properties and oxidation resistance of the coating. Copyright © 2014 John Wiley & Sons, Ltd.     

The influence of initial surface conditions on field crystallization of anodic aluminum oxide films determined by synchrotron X‐ray diffraction

X‐ray diffraction measurements were performed using synchrotron radiation at the SPring‐8 facility and electrochemical techniques to investigate the effect of polishing methods and storage conditions on the crystal structure of air‐formed oxide films and anodic oxide films formed on highly pure aluminum. Storage in an N₂ environment hinders local film breakdown during anodizing, and it was established that the X‐ray diffraction measurements showed the presence of a γ‐Al₂O₃ in the anodic oxide film formed on mechanically polished (MP) specimens. Formation of γ‐Al₂O₃ during anodizing was inhibited by electropolishing because of the removal of the work‐hardened layer that was formed on the MP by electro‐polishing. The X‐ray diffraction results do not show clear differences in the influence of the polishing method on the crystal structure of air formed oxide film. This is due to the very fast oxidation rate of the air‐formed oxide film and very long storage times for the X‐ray measurements. The anodic oxide film formed on aluminum, which has a very flat surface, shows color and the color depended on grain orientation. The electrochemical impedance of the MP specimen is slightly lower than that of the mechanically and then electrochemically polished specimen at the middle frequency range. This impedance difference may be due to formation of γ‐Al₂O₃ in the amorphous anodic oxide film and the thickness of the film. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and performance of electroless Ni–P–TiCN composite coatings on Al substrate

Electroless Ni–P and Ni–P–TiCN composite coatings have been deposited successfully on Al substrates. Scanning electron microscopy (SEM) and energy dispersive X‐ray (EDX) techniques were applied to study the surface morphology and the chemical composition of the deposited films. Moreover, X‐ray diffraction (XRD) proved that Ni–P and Ni–P–TiCN deposits have amorphous structures. The properties of Ni–P–TiCN/Al composite films such as hardness, corrosion resistance and electrocatalytic activity were examined and compared with that of Ni–P/Al film. The results of hardness measurements reveal that the presence of TiCN particles with Ni–P matrix improves its hardness. Additionally, the performance against corrosion was examined using Tafel lines and electrochemical impedance spectroscopy techniques in both of 0.6 M NaCl and a mixture of 0.5 M H₂SO₄ with 2 ppm HF solutions. The results indicate that the incorporation of high dispersed TiCN particles into Ni–P matrix led to a positive shift of the corrosion potential and an increase in the corrosion resistance for all aluminum substrates after their coating with Ni–P–TiCN. In addition, Ni–P–TiCN/Al electrodes showed a higher electrochemical catalytic activity and stability toward methanol oxidation in 0.5 M NaOH solution compared with that of Ni–P/Al. Copyright © 2014 John Wiley & Sons, Ltd.     

A One‐dimensional Lead(II) Coordination Polymer with Bridging Saccharinate and 2‐Aminomethylpyridine Ligands: Synthesis,IR Spectra,and Crystal Structure of [Pb(ampy)(μ‐sac)2]n

A complex with eight‐coordinate lead(II ) atom and saccharinate (sac) and 2‐aminomethylpyridine ligands was characterized by IR, elemental analysis and X‐ray crystallography. The lead(II ) complex crystallizes in the monoclinic crystal system with space group P2₁/c. The single crystal X‐ray analysis shows that the complex is a coordination polymer, [Pb(ampy)(μ‐sac)₂]_n, in which the lead(II ) ions have a highly distorted bicapped trigonal antiprism coordination. Lead(II ) ions are bridged by carboxyl groups of sac forming one‐dimensional linear chains, running parallel to the a axis. The intrachain Pb···Pb distances are 4.4490(3) and 4.4679(3)Å. The individual chains are connected by N—H···O_sulfonyl and C_ampy—H···O_sulfonyl type hydrogen bonds, resulting in a three‐dimensional network. The sac ligand acts as bidentate and bridging ligand, while ampy behaves as an N, N′ donor. The IR spectra of the lead(II ) complex are discussed in detail.     

Incorporation of Pure Fullerene into Organoclays: Towards C60‐Pillared Clay Structures

In this work, we demonstrate the successful incorporation of pure fullerene from solution into two‐dimensional layered aluminosilicate minerals. Pure fullerenes are insoluble in water and neutral in terms of charge, hence they cannot be introduced into the clay galleries by ion exchange or intercalation from water solution. To overcome this bottleneck, we organically modified the clay with quaternary amines by using well‐established reactions in clay science in order to expand the interlayer space and render the galleries organophilic. During the reaction with the fullerene solution, the organic solvent could enter into the clay galleries, thus transferring along the fullerene molecules. Furthermore, we demonstrate that the surfactant molecules, can be selectively removed by either simple ion‐exchange reaction (e.g., interaction with Al(NO₃)₃ solution to replace the surfactant molecules with Al³⁺ ions) or thermal treatment (heating at 350 °C) to obtain novel fullerene‐pillared clay structures exhibiting enhanced surface area. The synthesized hybrid materials were characterized in detail by a combination of experimental techniques including powder X‐ray diffraction, transmission electron microscopy, X‐ray photoemission, and UV/Vis spectroscopy as well as thermal analysis and nitrogen adsorption–desorption measurements. The reported fullerene‐pillared clay structures constitute a new hybrid system with very promising potential for the use in areas such as gas storage and/or gas separation due to their high surface area.     

Simultaneous Carbon Coating and Lithiation of Oxides by Contact Reaction

Chemical lithiation and carbon coating of cathode materials can lead to strongly improved electrochemical properties, especially if the active materials have low electronic conductivity. This behavior is quite often the case for new high‐capacity materials. A novel synthesis method is presented in which the two processes are performed simultaneously by employing Li₂C₂ as both the carbon and the lithium source. In this contact reaction, the acetylide anion C₂^2? is oxidized to carbon and deposited directly on the surface of the active material, while lithium is reductively inserted into the oxidant. Two different synthesis routes are demonstrated: a tribochemical approach at room temperature and heat treatments between 150 and 600 °C. The applicability of these new carbon‐coating methods are demonstrated on various crystalline and amorphous Li_xV₂O₅ phases. The composites obtained were characterized by powder X‐ray diffraction, transmission electron microscopy, and Raman spectroscopy. In addition, electrochemical data confirm the chemical lithiation and show that lithiated Li_xV₂O₅ with specific phases can be prepared selectively.     

Micropore formation mechanism in iridium coating after high‐temperature treatment

Noble metal iridium is of great interest for high‐temperature applications and extreme environments. A high (110)‐oriented iridium coating was prepared by a double glow plasma process on the surface of niobium substrate. The morphology and composition of the coating were determined by scanning electron microscopy, energy‐dispersive X‐ray spectroscopy and X‐ray photoelectron spectroscopy, respectively. The phase of the coating was identified by X‐ray diffraction analysis. The misorientation angle distributions of grains on the surface and cross section of the coating were characterized by electron backscatter diffraction system. The uniform and pure iridium coating consisted of the submicrometer‐sized columnar grains with high‐angle boundary. The mean misorientation angles on the surface and cross section of the coating were 38.6° and 45.6°, respectively. After high‐temperature treatment, the coating was composed of equiaxed grains with distinct grain boundaries. Micropores appeared on the fracture surface of the coating. The micropore formation mechanism in Ir coating after high‐temperature treatment was investigated. Copyright © 2016 John Wiley & Sons, Ltd.     

Inherent Electrochemistry of Layered Post‐Transition Metal Halides: The Unexpected Effect of Potential Cycling of PbI2

The development of two‐dimensional nanomaterials has expedited the growth of advanced technological applications. PbI₂ is a layered inorganic solid with important and unique properties suitable for applications in the detection of electromagnetic radiation. While the optical and electrical properties of layered PbI₂ have been generally established, its electrochemistry has remained largely unexplored. In this work, we examine the inherent electrochemistry of PbI₂ in relation to its morphological and structural properties. A direct comparison between commercially available and solution‐grown PbI₂ showed high similarity in properties based on characterizations by X‐ray photoelectron spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy. The respective layered PbI₂ materials also exhibited similar inherent electrochemistry. Electrochemical potential cycling of PbI₂ in phosphate buffer resulted in the dissolution of iodide ions from PbI₂ to form complex lead‐phosphate‐chloride with the oxygen groups of the phosphate ions while retaining the hexagonal structure. In the case of KCl solution, the formation of PbO₂ was observed.     

GDOES,XPS, and SEM with EDS analysis of porous coatings obtained on titanium after plasma electrolytic oxidation

In the paper, the glow discharge optical emission spectroscopy, X‐ray photoelectron spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray spectroscopy results of a commercial purity titanium grade 2 after plasma electrolytic oxidation (PEO), also known as micro arc oxidation (MAO), are presented. The PEO treatment was performed in the electrolyte containing concentrated (85%) phosphoric acid with copper nitrate at the voltage of 450 ± 10 V for 1 min. For the electrolyte, copper nitrate addition from 300 to 600 g/l was used. Porous coatings of specific properties were obtained. The measurements results allow to state that the copper and nitrogen ions can be introduced into the surface layer formed on pure titanium by the plasma electrolytic oxidation. The distributions of these elements were detected to depend on the electrolyte composition, with the highest amounts revealed in the coating created in the electrolyte containing 600 g Cu(NO₃)₂ in 1 l H₃PO₄. Three sub‐layers of the coating, displayed in this work by two models, were developed in the study. The analysis performed shows that under the PEO treatment in each of the electrolytes used, the formation of coating with the top sub‐layers always enriched in copper compounds was found. Copyright © 2016 John Wiley & Sons, Ltd.     

Schist‐like Nanostructured Manganese Oxides and Their Electrochemical Capacitance Properties

With an aim to develop environment friendly and inexpensive materials for electrochemical capacitor electrodes, nanocrystalline γ‐MnO₂ with layered architecture of schist‐like structure was successfully synthesized by reducing mixed MnSO₄×H₂O and CTAMnO₄ precursors in stoichiometric amounts through a hydrothermal process. The as‐prepared MnO₂ was characterized by field emission scanning electron microscopy, X‐ray diffraction, and thermal gravimetric analysis. Also, cyclic voltammetry was employed to investigate the electrochemical properties of the products in neutral KCl aqueous solution, showing a higher enhanced capacitive performance than that of the sample without a coating of schist‐like γ‐MnO₂, indicating that our MnO₂‐based electrode provides a promising opportunity for high‐performance energy storage devices.     

A Three—Dimensional Lead(II) Polymer with Bridging Saccharinate and Unusually Coordinated Acetate Ligands — Synthesis,IR Spectra,and Crystal Structure of [Pb(H2O)(μ‐OAc)(μ‐sac)]n

The complex [Pb(H₂O)(μ‐OAc)(μ‐sac)]n with acetate (OAc) and saccharinate (sac) ligands was characterized by IR, elemental analysis and X‐ray crystallography. The mixed‐anion lead(II) complex crystallizes in the triclinic crystal system with the space group of P1¯. The single crystal X‐ray analysis shows that the complex is a coordination polymer in which the lead(II) ions have a highly distorted pentagonal bipyramidal coordination geometry. Lead(II) ions are bridged by carboxylate groups in a zigzag arrangement forming one‐dimensional infinite chains, which are also linked by sac bridges and aromatic π‐π contacts between the adjacent phenyl rings of sac ligands, resulting in a three‐dimensional network. One water molecule coordinates the lead(II) ion and also forms weak hydrogen bonds with the sulfonyl oxygen atoms of the neighboring sac ligands. The sac ligand acts as a bridging ligand through the nitrogen and carbonyl oxygen atoms, while the carboxylate moiety of the acetate ligand shows an unusual (bidentate, and bridging) coordination behaviour, which was observed for the first time in the structure.     

Orange Peel Derived C‐dots Decorated CuO Nanorods for the Selective Monitoring of Dopamine from Deboned Chicken

A novel electrode based on orange peel derived C‐dots decorated CuO nanorods (CR@C‐dot) modified lead pencil (LP) electrode has been fabricated for highly sensitive and selective monitoring of dopamine (DA). Prior to the functionalization with C‐dot, electrochemical efficacy of CR was evaluated and compared with CuO nano‐needles (CN) and nano‐spheres (CS). The morphology, surface area and composition of synthesized nanoparticles was confirmed through field emission scanning electron microscopy (FE‐SEM), N₂‐adsorption‐desorption isotherm, X‐ray diffraction (XRD), Raman spectroscopy and X‐ray photoelectron spectroscopy (XPS). Our results indicated that CR has high electrocatalytic activity compared to CN and CS by expositing greater fraction of catalytic active sites, large surface area and short diffusion pathways. The electrochemical efficacy of CR is further enhanced by decorating with orange peel derived C‐dots, which surprisingly lead to the integrations of surface‐active sites with current collectors with minimum resistance by acting as an electron transport mediator and providing more surface defects. The developed CR@C‐dot sensor enables highly sensitive and selective recognition of DA detection (0.0007 μM), over good linear range (5–2250 μM) with rapid response time. the developed CR@C‐dot sensor was successfully used to monitor the DA from deboned chicken, thus suggesting reliability of the developed electrode.     

Sulfur Encapsulated in a TiO2‐Anchored Hollow Carbon Nanofiber Hybrid Nanostructure for Lithium–Sulfur Batteries

A hollow carbon nanofiber hybrid nanostructure anchored with titanium dioxide (HCNF@TiO₂) was prepared as a matrix for effective trapping of sulfur and polysulfides as a cathode material for Li–S batteries. The synthesized composites were characterized and examined by X‐ray diffraction, nitrogen adsorption–desorption measurements, field‐emission scanning electron microscopy, scanning transmission electron microscopy, and electrochemical methods such as galvanostatic charge/discharge, rate performance, and electrochemical impedance spectroscopy tests. The obtained HCNF@TiO₂–S composite showed a clear core–shell structure with TiO₂ nanoparticles coating the surface of the HCNF and sulfur homogeneously distributed in the coating layer. The HCNF@TiO₂–S composite exhibited much better electrochemical performance than the HCNF–S composite, which delivered an initial discharge capacity of 1040 mA h g^?1 and maintained 650 mAh g^?1 after 200 cycles at a 0.5 C rate. The improvements of electrochemical performances might be attributed to the unique hybrid nanostructure of HCNF@TiO₂ and good dispersion of sulfur in the HCNF@TiO₂–S composite.