The effect of pure iron in a nanocrystalline grain size on the corrosion inhibitor behavior of sodium benzoate in near-neutral aqueous solution

The effect of grain size reduction on the electrochemical and corrosion behavior of iron with different grain sizes (32–750 nm) produced by direct and pulsed current electrodeposition were characterized using Tafel polarization curves and electrochemical impedance spectroscopy. The grain size of deposits was determined by X-ray diffraction analysis and scanning electron microscopy. The tests were carried out in an aqueous electrolyte containing 30 mg L⁻¹ NaCl + 70 mg L⁻¹ Na₂SO₄. Results obtained suggested that the inhibition effect and corrosion protection of sodium benzoate inhibitor in near-neutral aqueous solutions increased as the grain size decreased from microcrystalline to nanocrystalline. The improvement on the inhibition effect is attributed to the increase of the surface energy.     

From uniform Cu thin films to 〈1 1 0〉 and 〈1 1 1〉 columns

This paper reports the transition phenomenon from uniform Cu thin films to 〈1 1 0〉 and 〈1 1 1〉 columns. Using magnetron sputtering technique, we deposit a series of Cu films on an SiO₂/Si(1 1 1) substrate. Characterizations using the scanning electron microscopy (SEM), the transmission electron microscopy (TEM), and the X-ray diffraction (XRD) reveal the morphology, the crystal orientation and the internal strain of the Cu films and columns. The Cu films are always uniform and 〈1 1 1〉 textured during the early stage of deposition. For higher sputtering power and shorter target-substrate distance, the 〈1 1 1〉 uniform film yields to columns as deposition continues. This transition correlates with the internal strain in the uniform film. At moderate strain, the columns are of 〈1 1 0〉 orientation and they nucleate at the grain boundaries of the uniform film. At even higher strain, the columns are of 〈1 1 1〉 orientation and they form by the breakup of grains in the uniform film. Based on the strain characterization and the column formation mechanism, we suggest that strain energy is the driving force of the transitions from uniform films to columns.     

Crystallography of magnetron sputtered TiN coatings on steel substrates

Structure formation processes in TiN coatings deposited by reactive CFUBMS on steel substrates have been investigated by X-ray diffraction experiments in symmetric Bragg-Brentano (B-B) and grazing incidence asymmetric Bragg diffraction (GIABD) modes and by SEM. The results show that the deposits with thicknesses of 500 and 4000 nm are built-up of polycrystalline stoichiometric TiN, in addition to which, some negligible amount of Ti-O and Ti-N-O phases have also been observed predominantly at their surfaces. In the thinner 500 nm films only columnar crystallites with {1 1 1}, {2 0 0} and {2 2 0} crystallographic planes parallel to the surface were formed. The share of the micro-volumes belonging to the 〈1 1 1〉 out-of-plane texture component varied between 70% and 80% depending on the target current (I_d) used (4 or 8 A in the present experiments). During the more advanced stages of growth the 〈1 1 1〉 texture weakens and new texture components appear; the process being more pronounced when the application has been performed at higher I_d values. The obtained crystallographic texture results for the thinner films and their changes during the more advanced stages of the coatings formation are discussed with particular consideration of the crystallography of the TiN lattice and the anisotropy of its elastic parameters. Based on a precise estimation of the interplanar distances, d_{〈u v w〉}, corresponding to the main texture components of the investigated films in the direction along the surface macro-normal, it has been revealed that the elastic strain, ε_{〈u v w〉}, caused by the compressive residual macro-stresses acting parallel to the film surfaces and the corresponding elastic stored energy, U_{〈u v w〉}, values obey the following relationships: ε_{〈1 1 1〉}>ε_{〈2 2 0〉}> ε_{〈2 0 0〉} and U_{〈1 1 1〉}>U_{〈2 2 0〉}>U_{〈2 0 0〉}, respectively. The observed ε_{〈u v w〉} and U_{〈u v w〉} anisotropy is found to be more pronounced in the thinner coatings and is such that, at more advanced stages of growth, it would be expected to favour the transition from 〈1 1 1〉 to 〈2 0 0〉 out-of-plane preferred orientation. However, the experimental results do not confirm this expectation, which points out that the texture-formation at these stages is not governed solely by the minimization of the stored elastic energy, but is a rather complicated process depending on a larger number of factors, some of which are discussed in the paper.     

Texture and mechanical properties of EUROFER 97 steel processed by ECAP

The EUROFER 97 steel was processed by equal channel angular pressing (ECAP) at 550 °C for four passes via route C. The starting material consisted of ferrite-martensite dual phase composed by small subgrains of about 0.5 μm and low angle boundaries less than 5°. The volume fraction of second phase particles was around 10 vol.%, besides a texture formed by several fibers orientations belonging to the zone axes 〈1 1 0〉, 〈1 1 1〉 and 〈1 1 2〉. Increasing ECAP deformation, this microstructure became into equiaxed grain structures of less than 1 μm, and the misorientation between contiguous grains increased. This refinement of the microstructure was accompanied by the development of a new texture described by a family of fiber orientations related by rotations around axes 〈1 1 0〉 and 〈1 1 1〉. Tensile tests have revealed that an ECAP treatment at 550 °C for two passes could significantly strengthen the tempered material still maintaining good ductility.     

Thin films of tetragonal zirconia (3Y-TZ) deposited by reactive sputtering

Thin films of tetragonal zirconia (TZ), comprised of 3 mol% Y₂O₃ (3Y-TZ), were deposited onto silicon, oxide-coated silicon, slide glass and aluminum oxide substrates by reactive sputtering of metallic targets in mixtures of oxygen and argon. The texture of deposited films varied with oxygen-to-argon flow ratios with which the target surface altered between metal and oxide compound constituents. Thin films of TZP with (2 0 0) preferred orientation were obtained from sputter deposition in the metallic mode whereas (1 1 1) texture was obtained in the compound mode at ambient temperature. The film texture tends to align along the 〈1 1 1〉 direction while the substrate was heated to 300 °C during the deposition. The texture of all these films was stable upon annealing at 900 °C in air. The reasons for the texture development are discussed.     

Microstructural evolution of copper clad steel bimetallic wire

We investigated the microstructure of two different bimetallic wires of Copper Clad Low Carbon Steel Wire (LCSW), which had a 1006 steel core, and Copper Clad High Carbon Steel Wire (HCSW), which had a 1055 steel core. The HCSW generally showed higher hardness than LCSW because of the pearlitic grain structure. A low temperature annealing at 720 °C to the drawn HCSW caused a significant reduction of hardness, which was as low as that of an annealed LCSW. In general, both LCSW and HCSW showed strong global textured features after drawing, with the steel having a strong 〈1 1 0〉 fiber texture and the copper having a 〈1 1 1 〉-〈1 1 2〉 deformation direction. At the interface, a grain size discrepancy at the steel-copper interface was observed. Post-drawing, the LCSW copper grains exhibited refined grain sizes near the interface and has been explained in terms of shear strain gradient. The HCSW did not exhibit this copper grain size distribution but did exhibit a coarsening of the steel grains near the interface after a subsequent 720 °C heat treatment. This is attributed to the large localized stress concentration at the perimeter of the steel region during the drawing process. The strain induced regions at the steel-copper interface have been simulated by finite element modeling. These grain size discrepancies caused the smooth variation in nanohardness across the interface.     

Modeling of large plastic deformation behavior and anisotropy evolution in cold rolled bcc steels using the viscoplastic ?-model-based grain-interaction

In this paper, a micromechanical approach is used to predict the mechanical response and anisotropy evolution in BCC metals. Particularly, cold rolling textures and the corresponding yield surfaces are simulated using the newly developed viscoplastic intermediate ?-model. This model takes into account the grain interactions but without the Eshelby theory. In this work, we compare our results to those predicted by the upper and lower bounds (Taylor and Static) as well as those of the viscoplastic self-consistent (VPSC) model. The results are compared in terms of predicted slip activity, texture evolution and yield loci. For the simulations, we considered two cases: the restricted slip, {1 1 0}〈1 1 1〉, and the pencil glide, {1 1 0}〈1 1 1〉 + {1 1 2}〈1 1 1〉 + {1 2 3}〈1 1 1〉. In addition, we present a qualitative comparison with experimental cold rolling textures taken from the literature for several BCC metals: electrical, ferritic, Interstitial-Free (IF) and low carbon steels. Our results show that the pencil glide assumption is adequate for low carbon and IF-steels and that the restricted slip assumption is well suited for ferritic and electrical steels.     

Characterization of TiO2 thin films prepared by electrolytic deposition for lithium ion battery anodes

The electrolytic deposition of TiO₂ thin films on platinum for lithium batteries is carried out in TiCl₄ alcoholic solution and the films are subsequently annealed. The as-prepared films are amorphous TiO(OH)₂·H₂O, transformed into anatase TiO₂ at 350 °C, and then gradually into rutile TiO₂ at 500 °C. Cyclic voltammograms show oxidation and reduction peaks at 2.20 and 1.61 V, respectively, corresponding to charge and discharge plateaus at 1.98 and 1.75 V vs. Li⁺/Li. The specific capacity decreases with increasing current density for film of 128-nm thickness in the initial discharge. It is observed that the diffusion flux of Li⁺ insertion/extraction into/from TiO₂ controls the reaction rate at higher current densities. Consequently, at low film thickness, high discharge capacity (per weight) is found for the initial cycle at a current density of 10 μA cm^− 2. However, the capacity of prepared films in various thicknesses approach 103 ± 5 mAh g^− 1 after 50 cycles, since the formation of cracks for thicker films offers shorter diffusion paths for Li⁺. In addition, TiO₂ films show electrochromic properties during lithiation and delithiation.     

RF diode reactive sputtering of n- and p-type zinc oxide thin films

We present the relationship between parameters of reactive RF diode sputtering from a zinc oxide (ZnO) target and the crystalline, electrical and optical properties of n-/p-type ZnO thin films. The properties of the ZnO thin films depended on RF power, substrate temperature and, particularly, on working gas mixtures of Ar/O₂ and of Ar/N₂. Sputtering in Ar+O₂ working gas (up to 75% of O₂) improved the structure of an n-type ZnO thin film, from fibrous ZnO grains to columnar crystallites, both preferentially oriented along the c-axis normally to the substrate (〈0 0 2〉 direction). These films had good piezoelectric properties but also high resistivity (ρ≈10³ Ω cm). ZnO:N p-type films exhibited nanograin structure with preferential 〈0 0 2〉 orientation at 25% N₂ and 〈1 0 0〉 orientation for higher N₂ content. The presence of nitrogen N_O at O-sites forming N_O-O acceptor complexes in ZnO was proven by SIMS and Raman spectroscopy. A minimum value of resistivity of 790 Ω cm, a p-type carrier concentration of 3.6×10¹⁴ cm⁻³ and a Hall mobility of 22 cm² V⁻¹ s⁻¹ were obtained at 75% N₂.     

Double electrodeposition and heat treatment process for the fabrication of superconducting oxides on the intensified {1 1 3} <1 2 1> Ag substrate

The Tl-1223 coated conductor (Tl_0.8Pb_0.2Bi_0.2Sr_1.8Ba_0.2Ca_2.2Cu₃O_δ) was synthesized by using electrodeposition on the intensified {1 1 3} <1 2 1> Ag substrate applying the new method of the repeating electrodeposition/heat treatment. The films were fabricated conducting the first electrodeposition and then heat treatment, after that the second electrodeposition on the first electrodeposition/heat treatment coated conductors. The second electrodeposition on the first electrodeposition/heat treatment/the first electrodeposition/heat treatment coated conductor showed the better quality of the Tl-1223 phases than that of the first electrodeposition/heat treatment coated conductor, showing more compact and dense grains on the films. The thin Tl-1223 films caused by the thinning process were discussed by considering the properties of Tl and the epitaxial growth aspects. The purer Tl-1223 grains obtained at the double electrodeposition/heat treatment are due to the growth from Tl-1223 grains already synthesized during the first electrodeposition/heat treatment, facilitating the epitaxial growth easier than that of the Ag substrate. The second electrodeposition process was successfully performed, obtaining 1.9 × 10⁵ A/cm² of J_c at 0 T at 10 K.     

Galvanostatic electrodeposition and microstructure of copper (I) oxide film

 Polycrystalline copper (I) oxide films were deposited on stainless steel substrate by galvanostatic electrodeposition method and were characterized by X-ray diffraction and scanning electron microscopy. The effect of bath temperature, bath pH and current density on the compositon, grain size, surface texture and surface morphology of the electrodeposited films were investigated. The films deposited at low bath pH (≤7) consisted of copper (I) oxide and metallic copper; while the films deposited at bath pH between 8 and 12 and bath temperature of 60°C were pure copper (I) oxide. The preferred orientation of the copper (I) oxide films depended on the relative growth rate of {111} and {200} faces and could be controlled by adjusting the bath pH and/or the cathodic current density. (100)-oriented copper (I) oxide films could be deposited at pH=9 and current densities in the range of 0.25–1 mA/cm², while (111)-oriented films could be prepared at pH=12 or at pH=9 using the current densities between 1.5–2.5 mA/cm². Computer simulated crystallite shapes showed that the crystal shape changed from octahedral for (100)-oriented film to trucated pyramids and cubs for (111)-oriented film. And they were approved by scanning electron microscopy. Received: 1 December 1997 / Accepted: 13 December 1997     

Rod- and wire-like morphologies of tin oxide developed with plasma oxidation after electrodeposition

A new manufacturing method has been developed to prepare films composed of Sn-rich SnO₂ wires and rods using electrodeposition and subsequent plasma oxidation of pure Sn. The morphology of Sn-rich tin oxide grains varied significantly depending on the deposition current density. After a DC plasma oxidation process, the Sn, SnO, and SnO₂ phases were obtained as spherical grains when the previous electrodeposition was carried out at 6 A/dm² current density. The wire morphology was obtained only when the electrodeposition current was below 3 A/dm². The film produced at 1.5 A/dm² and then plasma oxidized showed wire morphology with single crystals of SnO₂ that formed in the (110) direction.     

Carrier transport in polycrystalline transparent conductive oxides: A comparative study of zinc oxide and indium oxide

Highly doped indium-tin oxide films exhibit resistivities ρ as low as  1.2 × 10^− 4 Ω cm, while for ZnO films resistivities in the range of 2 to 4 × 10^− 4 Ω cm are reported. This difference is unexpected, if ionized impurity scattering would be dominant for carrier concentrations above 10²⁰ cm^− 3. By comparing the dependences of the effective Hall mobility on the carrier concentration of ZnO and ITO it is found that grain barriers limit the carrier mobility in ZnO for carrier concentrations as high as 2 × 10²⁰ cm^− 3, independently, if the films were grown on amorphous or single crystalline substrates. Depending on the deposition method, grain barrier trap densities between 10¹² and 3 × 10¹³ cm^− 2 were estimated for ZnO layers. Also, crystallographic defects seem to reduce the mobility for highly doped ZnO films. On the other hand, for ITO films such an influence of the grain barriers was not observed down to carrier concentrations of about 10¹⁸ cm^− 3. Thus the grain barrier trap densities of ZnO and ITO are significantly different, which seems to be connected with the defect chemistry of the two oxides and especially with the piezoelectricity of zinc oxide.     

On work function and characteristics of anomalous electrodeposited nickel-cobalt films

The anomalous cobalt content in the electrodeposited nickel-cobalt (Ni-Co) alloy films significantly influenced by the current density was related to the variation of morphology and electron work function (EWF) of the films. The characteristics and EWF of Ni-Co films were investigated by scanning electron microscope with an attached energy dispersive X-ray spectrometer, X-ray diffraction, ultraviolet photoelectron spectroscopy (UPS) and Kelvin probe technique, respectively. As the current density increased from 1 to 20 ampere per square decimeter (A/dm²), the Co atomic concentration (at.%) in Ni-Co greatly decreased from 22.5 at.% to 13.2 at.% correspondingly. The surface morphology of film obtained at low current density became smoother than that at high current density. Both UPS and Kelvin probe results showed the same trend of EWF variation which increased with increasing current density from 1 to 10 A/dm² and kept nearly unchanged at 10-20 A/dm². The smooth Ni-Co film with low EWF could be achieved at low current density. In comparison, Kelvin probe operated at atmosphere ambient could be a good candidate for EWF measurement because of the lower cost and easier operation than UPS at ultra high vacuum.     

The electrochemical corrosion of bulk nanocrystalline ingot iron in HCl solutions with different concentrations

We studied the corrosion properties of bulk nanocrystalline ingot iron (BNII) and conventional polycrystalline ingot iron (CPII) in HCl solutions from 0.1 mol L⁻¹ to 0.4 mol L⁻¹ at room temperature. The corrosion resistance of BNII was enhanced in comparison with CPII. We investigated the surface energy state densities of BNII and CPII with ultra-violet photoelectron spectroscopy. The energy state density of BNII 4s electrons was 13.73% less than that of CPII. The function work of BNII was 0.47 eV larger that of CPII. The corrosion resistance of BNII was enhanced in comparison with CPII due to its less energy state density of 4s electrons, larger work function and weaker Cl⁻ specific adsorption.     

Exploring the Nickel–Graphene Nanocomposite Coatings for Superior Corrosion Resistance: Manipulating the Effect of Deposition Current Density on its Morphology,Mechanical Properties,and Erosion‐Corrosion Performance

The use of graphene‐based composite as anti‐corrosion and protective coatings for metallic materials is still a provocative topic worthy of debate. Nickel–graphene nanocomposite coatings have been successfully fabricated onto the mild steel by electrochemical co‐deposition technique. This research demonstrates the properties of nickel–graphene composite coatings influenced by different electrodeposition current densities. The effect of deposition current density on the; surface morphologies, composition, microstructures, grain sizes, mechanical, and electrochemical properties of the composite coatings are executed. The coarseness of deposited coatings increases with the increasing of deposition current density. The carbon content in the composite coatings increases first and then decreases by further increasing of current density. The improved mechanical properties and superior anti‐corrosion performance of composite coatings are obtained at the peak value of current density of 9 A dm^?2. The incorporation of graphene sheets into nickel metal matrix lead to enhance the micro hardness, surface roughness, and adhesion strength of produced composite coatings. Furthermore, the presence of graphene in composite coating exhibits the reduced grain sizes and the enhanced erosion–corrosion resistance properties.

     

Oxidation states of molybdenum in oxide films formed in sulphuric acid and sodium hydroxide

X-ray photoelectron spectroscopy is used to investigate the oxidation states of molybdenum in thin films formed potentiostatically, over a range of potentials, in either 1 mol dm^− 3 H₂SO₄ or 10 mol dm^− 3 NaOH at 20 °C. Mo 3d spectra suggested that MoO₂ and Mo(OH)₂ were the main components of the films, with smaller amounts of MoO₃ and possibly Mo₂O₅. O 1s spectra indicated the presence of oxygen as oxide and hydroxide species and as bound water. Ion beam analysis revealed the formation of thin films at all potentials, with significant losses of oxidized molybdenum to the electrolyte.     

Characterizations of electrodeposited Ni–CeO2 nanocomposite coatings

The expansion of current machinery requires metallic materials with better surface properties. In the present investigation, CeO₂ reinforced nickel nanocomposite coatings were deposited on mild steel substrate by direct current electrodeposition process employing nickel acetate bath. The effect of incorporation of CeO₂ particles in the Ni nanocomposite coatings on the micro hardness and corrosion behaviour has been evaluated. Smooth and compact nanocomposite deposits containing well-distributed cerium oxide particles were obtained. The crystallite structure was fcc for electrodeposited nickel and Ni–CeO₂ nanocomposite coatings. It has been observed that, the presence of CeO₂ nanoparticles favours the [111] and [200] texture of nickel matrix. The co-deposition of CeO₂ nanoparticles with nickel was found to be favoured at applied current density of 8 A dm⁻². The micro hardness values of the nickel nanocomposite coatings (725 HV) was higher than that of pure nickel (265 HV).The decrease in I_corr values and increase in Constant Phase Element values were investigated in 3.5% NaCl solution which showed the higher corrosion resistant nature of Ni–CeO₂ coatings.     

Anodic oxidation of wastewater containing the Reactive Orange 16 Dye using heavily boron-doped diamond electrodes

Boron-doped diamond (BDD) films grown on the titanium substrate were used to study the electrochemical degradation of Reactive Orange (RO) 16 Dye. The films were produced by hot filament chemical vapor deposition (HFCVD) technique using two different boron concentrations. The growth parameters were controlled to obtain heavily doped diamond films. They were named as E1 and E2 electrodes, with acceptor concentrations of 4.0 and 8.0 × 10²¹ atoms cm⁻³, respectively. The boron levels were evaluated from Mott-Schottky plots also corroborated by Raman's spectra, which characterized the film quality as well as its physical property. Scanning Electron Microscopy showed well-defined microcrystalline grain morphologies with crystal orientation mixtures of (1 1 1) and (1 0 0). The electrode efficiencies were studied from the advanced oxidation process (AOP) to degrade electrochemically the Reactive Orange 16 azo-dye (RO16). The results were analyzed by UV/VIS spectroscopy, total organic carbon (TOC) and high-performance liquid chromatography (HPLC) techniques. From UV/VIS spectra the highest doped electrode (E2) showed the best efficiency for both, the aromaticity reduction and the azo group fracture. These tendencies were confirmed by the TOC and chromatographic measurements. Besides, the results showed a direct relationship among the BDD morphology, physical property, and its performance during the degradation process.     

The roles of grain orientation and grain boundary characteristics in the enhanced superelasticity of Cu71.8Al17.8Mn10.4 shape memory alloys

Through texture and grain boundary control by continuous unidirectional solidification, the continuous columnar-grained polycrystalline Cu_71.8Al_17.8Mn_10.4 shape memory alloys were prepared and possess a strong 〈0 0 1〉 texture along the solidification direction and straight low-energy grain boundary. The alloys show excellent superelasticity of 10.1% improved from 3% for ordinary polycrystalline counterpart and with a tiny residual strain of less than 0.3% after unloading. There are some reasons for the enhanced superelasticity: (1) The martensitic transformation of all grains with strong 〈0 0 1〉-oriented texture occur at the same time under the tensile loading, which can avoid the significant stress concentration problem and transformation strain incompatibility at the grain boundaries due to the high elastic anisotropy in ordinary polycrystalline alloy. (2) High phase transformation strain can be obtained along 〈0 0 1〉 grain orientation. (3) Straight low-energy grain boundary and the absence of grain boundary triple junctions of continuous columnar-grained polycrystals can significantly reduce the blockage of martensitic transformation at the grain boundaries. These results provide a reference to structure design of high-performance polycrystalline Cu-based shape memory alloys.