Iron Foil Research Articles

Making Superhydrophobic Surfaces with Microstripe Array Structure by Diffusion Bonding and Their Applications in Magnetic Control Microdroplet Release Systems

AbstractHundreds of copper foils and iron foils with different thicknesses are alternatingly stacked and diffusion bonded, respectively. Cross‐sections of the diffusion bonded bulks are investigated via scanning electron microscopy (SEM) and energy dispersive spectroscopy. Hierarchical microstripe array structures with different groove depths and widths are successfully manufactured via selective corrosion followed by oxidation of the cross‐sections of the diffusion bonded bulks. The products are characterized via X‐ray diffraction, SEM, and transmission electron microscopy. In addition, the as‐obtained surfaces are modified with 1‐dodecanethiol to afford anisotropic superhydrophobicity. The chemical composition of the as‐obtained surfaces before and after modification is investigated by X‐ray photoelectron spectroscopy. The contact angles (CAs) and sliding angles (SAs) are measured parallel and perpendicular to the grooves. The surface with a groove depth‐to‐width ratio of 0.75 and a groove‐width‐to‐bulge‐width ratio of five shows the best superhydrophobicity, on which the CAs and SAs are 162.5° and 2.0° in the direction perpendicular to the grooves and 161.1° and 0.9° in the direction parallel to the grooves, respectively. A magnetic control microdroplet release system is built using the reversible transformation of the contact states of the superparamagnetic microdroplet on the as‐prepared superhydrophobic microstripe array surface.

Effect of metallic iron on the oxidative dissolution of UO2 doped with a radioactive alpha emitter in synthetic Callovian-Oxfordian groundwater

In the hypothesis of direct disposal of spent fuel in a geological nuclear waste repository, interactions between the fuel mainly composed of UO2 and its environment must be understood. The dissolution rate of the UO2 matrix, which depends on the redox conditions on the fuel surface, will have a major impact on the release of radionuclides into the environment. The reducing conditions expected for a geological disposal situation would appear to be favorable as regards the solubility and stability of the UO2 matrix, but may be disturbed on the surface of irradiated fuel. In particular, the local redox conditions will result from a competition between the radiolysis effects of water under alpha irradiation (simultaneously producing oxidizing species like H2O2, hydrogen peroxide, and reducing species like H2, hydrogen) and those of redox active species from the environment. In particular, Fe2+, a strongly reducing aqueous species coming from the corrosion of the iron canister or from the host rock, could influence the dissolution of the fuel matrix. The effect of iron on the oxidative dissolution of UO2 was thus investigated under the conditions of the French disposal site, a Callovian-Oxfordian clay formation chosen by the French National Radioactive Waste Management Agency (Andra), here tested under alpha irradiation. For this study, UO2 fuel pellets doped with a radioactive alpha emitter (238/239Pu) were leached in synthetic Callovian-Oxfordian groundwater (representative of the French waste disposal site groundwater) in the presence of a metallic iron foil to simulate the steel canister. The pellets had varying levels of alpha activity, in order to modulate the concentrations of species produced by water radiolysis on the surface and to simulate the activity of aged spent fuel after 50 and 10,000years of alpha radioactivity decay. The experimental data showed that whatever the sample alpha radioactivity, the presence of iron inhibits the oxidizing dissolution of UO2 and leads to low uranium concentrations (between 4×10−10 and 4×10−9M), through a reactional mechanism located in the very first microns of the UO2/water reactional interface. The mechanism involves consumption of oxidizing species, in particular of H2O2 by Fe2+ at the precise place where these species are produced, and is accompanied by the precipitation of an akaganeite-type Fe3+ hydroxide on the surface. The higher the radioactivity of the samples, the greater the precipitation induced. Modeling has been developed, coupling chemistry with transport and based on the main reactional mechanisms identified, which enables accurate reproduction of the mineralogy of the system under study, giving the nature of the phases under observation as well as the location of their precipitation. Obviously without excluding a potential contribution from the hydrogen produced by the anoxic corrosion of the iron foil, this study has shown that iron plays a major role in this oxidizing dissolution inhibition process for the system investigated (localized alpha radiolysis). This inhibitor effect associated with iron is therefore strongly dependent on the location of the redox front, which is found on the surface in the case of alpha irradiation UO2/water reactional interface.

Fabrication of robust gold superhydrophobic surface on iron substrate with properties of corrosion resistance, self-cleaning and mechanical durability

Well-defined gold nanoflower superhydrophobic surface (SHS) was constructed on iron foil by chemical deposition and anneal. The as-fabricated sample exerts excellent superhydrophobicity with water contact angle (WCA) up to 169°, a sliding angle of about 3°. The samples were characterized via scanning electron microscopy (SEM), X-ray diffraction pattern (XRD) and energy dispersive analysis of X-ray (EDX) to determine the morphology, structure and composition. The electrochemical measurements showed that the resultant surface displayed good corrosion resistance in 3.5 wt% sodium chloride aqueous solution. The effect of pH on the SHS and corrosion resistance ability of the samples at pH = 2, 7 and 9 were explored. The self-cleaning property of the SHS was analyzed. Also, the surface withstood abrasion by 400 grid SiC sandpaper for 2.0 m under 30 kPa, or water impacting for 120 min without losing its superhydrophobicity, indicating prominent mechanical durability. This successful manufacture of the gold SHS with anti-corrosion, self-cleaning, and mechanical durability can pave a prospective way for a variety of practical situations.

Spatially Resolved Mapping of Hydrogen Permeation with a Novel in-Situ Scanning Kelvin Probe (SKP) Based Setup

The detection of localized diffusible hydrogen is a key issue in investigating hydrogen embrittlement and crucial energy conversion issues. Several methods based on SKP and SECM techniques have been developed so far to trace diffusible hydrogen [1]-[7]. Most of these methods use pre-charged samples, through this way important information is usually lost due to the escape of diffusible hydrogen before the measurement can start and also it takes long time for a single measurement. The use of a “static” SKP based permeation setup inspired by the Devanathan-Stachurski electrochemical double cell was reported before [1],[5] using Pd thin film at the exit side for a potentiometric hydrogen measurement by Kelvin Probe. However, once H/Pd reaches the atomic ratio ~ 0.02 at room temperature, the onset of palladium hydride formation (i.e. of the binary phase region) will pin the potential value and all information of further hydrogen permeation will disappear. This drawback is overcome by using a dynamic ORR/Hads-H+ redox competition, which prevents reaching the binary phase point and provides a potential output value determined by a dynamic equilibrium of the redox competition. Furthermore, the potential output value measured can be correlated to the permeation rate obtained in electrochemical double cell under same charging condition. With the combination of Scanning Kelvin Probe and the ORR/Hads-H+redox competition method, localized hydrogen permeation maps can be obtained in an oxygen-purged atmosphere. Here on as an example the study of three differently microstructured samples with same composition will be presented (A: annealed, CR: cold-rolled, RK: recrystallized), and it was found that in large area scan (2000μm*2000 μm) A & RK showed no big difference in spatial permeation rate, but CR revealed strong differences. In a detailed investigation, it was found that in areas where blisters formed the hydrogen diffusion through the material was significantly decreased. The results showed that the resolution of this novel technique is from mm to μm scale range. [1] S. Evers, M. Rohwerder, The hydrogen electrode in the “dry”: A Kelvin probe approach to measuring hydrogen in metals, Electrochem. Commun. 24 (2012) 85-88. [2] C. Larignon, J. Alexis, E. Andrieu, L. Lacroix, G. Odemer, C. Blanc, Combined Kelvin probe force microscopy and secondary ion mass spectrometry for hydrogen detection in corroded 2024 aluminium alloy, Electrochimica Acta 110 (2013) 484–490 [3] G. Williams, H.N. McMurray, R.C. Newman, Surface oxide reduction by hydrogen permeation through iron foil detected using a scanning Kelvin probe, Electrochem. Commun. 27 (2013) 144-147 [4] R.F. Schaller, S. Thomas, N. Birbilis, J.R. Scully, Spatially resolved mapping of the relative concentration of dissolved hydrogen using the scanning electrochemical microscope, Electrochem. Commun. 51 (2015) 54-58 [5] M. Koyama, A. Bashir, M. Rohwerder, S. Merzlikin, E. Akiyama, K. Tsuzaki, D. Raabe, Spatially and kinetically resolved mapping of hydrogen in a twinning-induced plasticity steel by use of scanning Kelvin probe force microscopy, J. Electrochem. Soc. 162 (2015) 638–647 [6] G. Schimo, W. Burgstaller, A. W. Hassel, Potentiodynamic hydrogen permeation on Palladium-Kelvin probe compared to 3D printed microelectrochemical cell, Electrochem. Commun. 60 (2015) 208-211 [7] R.F. Schaller, J.R. Scully, Spatial determination of diffusible hydrogen concentrations proximate to pits in a Fe–Cr–Ni–Mo steel using the Scanning Kelvin Probe, Electrochem. Commun. 63 (2016) 5-9

Observation on Sodium p-Toluenesulfonate Doped Polypyrrole Cathode for Sodium Ion Battery

Sodium p-toluenesulfonate (TsONa)-doped polypyrrole (PPy) was synthesized as the cathode active material of sodium ion battery by way of facile one-step electrodeposition on iron (Fe) foil. The mic...

Analyzing the anodic reactions for iron surface with a porous Al2O3 cluster with the scanning vibrating electrode

The Scanning Vibrating Electrode Technique (SVET) was used to analyze the anodic reactions inside and around a porous Al2O3 cluster embedded onto an iron foil. The tests were carried out at −0.7 V vs. Saturated Calomel Electrode, in naturally aerated solutions of 0.1, 0.2, 0.35, and 0.5 M bicarbonate concentration. During 10 h of testing, the SVET showed evidence for a formation of a passive film in and around the cluster, in the scanning area shown in the graphical abstract. In the dilute 0.1 and 0.2 M solutions, the passive films formed slower than those in 0.35 and 0.5 M solutions. In the SVET maps, the passive films showed that they could suppress dissolution to currents comparable to those of slower dissolution under the porous Al2O3 cluster.

Effects of anodizing conditions and annealing temperature on the morphology and crystalline structure of anodic oxide layers grown on iron

Anodic iron oxide layers were formed by anodization of the iron foil in an ethylene glycol-based electrolyte containing 0.2M NH4F and 0.5M H2O at 40V for 1h. The anodizing conditions such as electrolyte composition and applied potential were optimized. In order to examine the influence of electrolyte stirring and applied magnetic field, the anodic samples were prepared under the dynamic and static conditions in the presence or absence of magnetic field. It was shown that ordered iron oxide nanopore arrays could be obtained at lower anodizing temperatures (10 and 20°C) at the static conditions without the magnetic field or at the dynamic conditions with the applied magnetic field. Since the as-prepared anodic layers are amorphous in nature, the samples were annealed in air at different temperatures (200–500°C) for a fixed duration of time (1h). The morphology and crystal phases developed after anodization and subsequent annealing were characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The results proved that the annealing process transforms the amorphous layer into magnetite and hematite phases. In addition, the heat treatment results in a substantial decrease in the fluorine content and increase in the oxygen content.

Kinetics of Light-Driven Oxygen Evolution at Nanostructured Hematite Semiconductor Electrodes

Hematite nanostructures have been electrochemically grown by ultrasound-assisted anodization of iron substrates in an ethylene glycol based medium. This hematite nano-architecture has been tuned from a 1-D nanoporous layer (grown onto a bare iron foil substrate) to a high aspect self-organized nanotube one (grown onto a pretreated iron foil). Well-developed hematite nanotube arrays perpendicular to the substrate with a 1 μm in length have been obtained. The nanoporous sample was characterized by pores of a mean diameter of 30 nm and an interpore distance of 150 nm, whereas the self-organized nanotube layer consisted of nanotube arrays with a single tube inner diameter of approximately 50 nm and average spacing of approximately 90 nm. The wall thickness of the hematite nanotubes was of approximately 30 nm. A comparative study of the photoelectrochemical properties of these two different hematite nanostructures under water-splitting conditions have been studied through EIS and PEIS methods. The strong correlation between the CSS increase with the RSS,ct decrease and the photocurrent development as the potential is made more anodic, indicated that holes transfer for the water splitting reaction takes place through the surface states and not directly from valence band holes. From the PEIS spectra the rate constants of the elementary reactions responsible for the competing processes of interfacial charge transfer (ktr and electron–hole recombination (krec have been determined. A better photoresponse kinetic was observed from the hematite nanotubular structure as compared to the nanoporous one. The last indicates that in the hematite nanotubular structure it exists a very well length scale matching between the nanotube wall thickness and the hole diffusion length (maximize light absorption while maintaining the bulk within hole collection length), diminishing then the recombination processes.

Characterization of prompt neutron spectrum of the Missouri University of Science and Technology Reactor

An activation-foil method was used to obtain the energy spectrum of the prompt-neutron flux at the Missouri University of Science and Technology Reactor (MSTR). The foils were irradiated at the center of the reactor core (120W configuration). The neutron spectrum was determined using the unfolding method implemented in the SAND-II code. Multiple foils of dysprosium, vanadium, indium, gold, aluminum, copper, cobalt, silver, nickel, and iron were placed at the source holder position and irradiated for 3min each at 100kW. The foil set cover energies from 0.025eV to 7.2MeV for a broad spectrum analysis. After irradiation, the sample was cooled using water until the dose rate reached a level that allowed safe handling. For each material, both bare and cadmium covers were used to obtain the thermal and epithermal neutron flux. The activity of each foil was determined by counting for 3min with a high-purity germanium detector, and the results were used in SAND-II to obtain the neutron flux spectrum for the MSTR. Monte Carlo N-particle (MCNP) model was used to obtain the initial guess of the spectrum at the source holder position, which was used as input for SAND-II. The spectrum is unfolded using two different energy binning structures in the initial guess for SAND-II. As expected, the results provided highly thermal neutron spectra in source-holder environment, where water thermalizes most of the neutrons; 93% of the total flux at the source-holder position is no greater than 0.55eV for the 120W reactor-core configuration. The epithermal and fast neutrons were 6% and 1%, respectively at fast/epithermal energy boundary of 100keV. A similar experiment and analysis in the past determined that 7%, 38% and 55% of the total flux at the source-holder position were respectively thermal, epithermal and fast for the 101W configuration. Notwithstanding the difference between the two configurations, the current determination is an improvement to the characterization of the MSTR flux. This is because 7% thermal flux is unlikely in an environment primarily surrounded by water. The total neutron flux calculated by MCNP is 4.98×1011±1.72×1010n/cm2s. The flux determined through SAND-II is 4.79×1011±6.10×1010n/cm2s; a difference of 4%.

Hydrothermal synthesis of WO3/Fe2O3 nanosheet arrays on iron foil for photocatalytic degradation of methylene blue

The growth of WO3/Fe2O3 nanosheet arrays on iron foil was fabricated by a facile and efficient hydrothermal treatment. The morphology and optical property of as-prepared WO3/Fe2O3 nanocomposites were characterized by using field-emission scanning electron microscopy, energy-dispersive X-ray spectrometry, transmission electron microscopy, X-ray diffraction and UV–Vis diffuse reflectance spectra. The photocatalytic activity of the as-synthesized WO3/Fe2O3 nanocomposite was evaluated by the degradation of methylene blue (MB) in aqueous solution under visible-light (λ > 420 nm) irradiation. It was observed that the sample obtained with a hydrothermal reaction time for 2 h exhibited the best photocatalytic performance. The kinetics of the MB degradation was found to comply with the Langmuir–Hinshelwood model. The photocatalytic efficiencies of WO3/Fe2O3NSAs correlated with the effective separation of photogenerated electron–hole pairs. Hence, the WO3/Fe2O3NSAs are excellent candidate for visible-light-driven photocatalysts.

Growth of Fe2O3/SnO2 nanobelt arrays on iron foil for efficient photocatalytic degradation of methylene blue

Tin(IV) oxide has been intensively employed in optoelectronic devices due to its excellent electrical and optical properties. But the high recombination rates of the photogenerated electron-hole pairs of SnO2 nanomaterials often results in low photocatalytic efficiency. Herein, we proposed a facile route to prepare a novel Fe2O3/SnO2 heterojunction structure. The nanobelt arrays grown on iron foil naturally form a Schottky-type contact and provide a direct pathway for the photogenerated excitons. Hence, the Fe2O3/SnO2 nanobelt arrays exhibit much improved photocatalytic performance with the degradation rate constant on the Fe2O3/SnO2 film of approximately 12 times to that of α-Fe2O3 nanobelt arrays.

Improving the growth of monolayer CVD-graphene over polycrystalline iron sheets

A high quality graphene film, mostly composed of monolayer graphene, was successfully grown on polycrystalline iron foil by atmospheric CVD process using methane as carbonaceous source.

Towards stable Fe-based catalysts with suitable active phase for Fischer-Tropsch synthesis to lower olefins

The Fe-based catalysts have been facile fabricated on iron foil by a controllable process involving the hydrothermal growth and calcinations. The catalysts show a distinguished catalytic performance with CO conversion of 86.7% and long-term stability (200h). The high O/P ratio of C2–4 shows the better selectivity of the catalysts for lower olefins. The Fe2O3 changes into Fe3O4@Fe5C2 nanoparticles with suitable active phase particle size after reaction, maintaining a carburized surface with suitable carbides particle size and thus increasing the CO conversion.

Electrodeposition preparation of Ni–Fe alloy foil

In this study, the electrodeposition of a nickel (Ni)–iron (Fe) alloy foil was thoroughly investigated. Linear potential sweep and cyclic voltammetry method were used to investigate the electrochemical behaviour of the nickel–iron alloy foil. In addition, single-factor experimental studies were combined with an orthogonal test analysis to obtain optimum experimental conditions. Scanning electron microscopy and X-ray diffraction were used to investigate the surface morphology and the crystalline structure of the nickel–iron alloy foil. The obtained nickel–iron alloy foil was a face-centred cubic crystal with a bright and smooth surface, in which no pinholes or cracks appeared. The average hardness value, electrical resistivity, maximum permeability, saturation magnetic flux density (B s) and residual magnetism (B r) of the obtained nickel–iron foil were 280 HV, 38–41 μΩ cm, 0·172 mH/m, 1·093 T and 0·0088 T, respectively. Lastly, the obtained nickel–iron foil displayed good soft magnetic properties, toughness and low residual stress.

Fe2O3/Reduced Graphene Oxide/Fe3O4 Composite in Situ Grown on Fe Foil for High-Performance Supercapacitors.

A Fe2O3/reduced graphene oxide (RGO)/Fe3O4 nanocomposite in situ grown on Fe foil was synthesized via a simple one-step hydrothermal growth process, where the iron foil served as support, reductant of graphene oxide, Fe source of Fe3O4, and also the current collector of the electrode. When it directly acted as the electrode of a supercapacitor, as-synthesized Fe2O3/RGO/Fe3O4@Fe exhibited excellent electrochemical performance with a high capability of 337.5 mF/cm2 at 20 mA/cm2 and a superior cyclability with 2.3% capacity loss from the 600th to the 2000th cycle.

The ternary Fe-C-N system: Homogeneous distributions of nitrogen and carbon

Porous iron foils were used for synthesizing homogeneous samples of iron carbides and (carbo)nitrides. Homogeneous distributions of interstitial nitrogen and carbon were obtained without long treatment times due to limited required diffusion distances in the porous material. By adjustments of the nitriding and carburizing potentials, tailored nitrogen and carbon contents can be achieved, which allows assessment of a phase stability diagram for the Fe-N-C system, for which available experimental data is limited.Thermal decomposition sequences were established for the various iron carbides and (carbo)nitrides using in situ synchrotron X-ray diffraction. Hägg carbide (χ) and ε-carbonitride, Fe2(N,C)1-z, with high carbon content decompose to cementite (θ) above 850 K, while ferrite (α) forms above 950 K and austenite (γ) above 1025 K. For high nitrogen contents ζ- Fe2(N,C) is transformed to ε from 680 to 770 K, which decomposes to γ′-Fe4(N,C)1+x between 795 and 900 K as nitrogen is released as N2. Ferrite forms above 850 K while austenite may be briefly formed around 900 K.The two iron carbides, cementite and Hägg carbide, exhibit different coefficients of thermal expansion. Below approximately 480 K, cementite is ferromagnetic and a volumetric thermal expansion coefficient of αV = 1.5 × 10−5 K−1 is obtained. The average value in the paramagnetic state is αV = 4.3 (3) × 10−5 K−1. For Hägg carbide the average value is αV = 3.8 (5) × 10−5 K−1 and only a minor change in unit cell volume is observed at the magnetic transition temperature.

A Facile Surface Passivation of Hematite Photoanodes with Iron Titanate Cocatalyst for Enhanced Water Splitting.

The surface modification of semiconductor photoelectrodes with passivation overlayers has attracted great attention as an effective strategy to improve the charge separation and charge transfer processes across the semiconductor-electrolyte interface. In this work, a thin Fe2 TiO5 layer was decorated on nanostructured hematite nanoflake and nanocoral photoanodes (by thermal oxidation of iron foils) by a facile water-based solution method. Photoelectrochemical measurements show that the Fe2 O3 /Fe2 TiO5 heterostructure exhibits an obvious enhancement in photoelectrochemical water oxidation performance compared to the pristine hematite. For example, at 1.23 V versus the reversible hydrogen electrode (VRHE ) in 1 m KOH under AM 1.5 G (100 mW cm(-2) ) illumination, a 4-8× increase in the water oxidation photocurrent is achieved for Fe2 O3 /Fe2 TiO5 , and a considerable cathodic shift of the onset potential up to 0.53-0.62 VRHE is obtained. Moreover, the performance of the Fe2 O3 /Fe2 TiO5 heterostructure can be further improved by decoration with a SnOx layer. The enhancement in photocurrent can be attributed to the synergistic effect of Fe2 TiO5 /SnOx overlayers passivating surface states, and thus reducing surface electron-hole recombination.

Phosphate recovery from livestock wastewater using iron oxide nanotubes

The key parts of this study included the fabrication of self-organized cylindrical nanotubes on the surface of iron (Fe) foil through anodization and the experimental evaluation of the adsorption and desorption performance of iron oxide nanotubes (INTs) for phosphate recovery with synthetic wastewater and raw livestock wastewater. Nanostructured INTs were achieved more than 95% of phosphate adsorption and desorption from synthetic wastewater in 30min whereas pure Fe foil showed only less than 40% of phosphate adsorption in 60min. Also, the INTs maintained the high efficiency of adsorption and desorption through three cycles of consecutive adsorption and desorption with the same INTs. In the case of raw livestock wastewater, the INTs adsorbed 43% of phosphate in 60min in a continuous column experiment. The Freundlich isotherm model was more suitable than the Langmuir model for describing phosphate isotherms on INTs. Based on results of point of zero charge, the adsorption of phosphate was more effective in the acidic range of pH. For phosphate recovery using INTs, an additional recovery step to separate iron particles from treated wastewater is not necessary, which indicates that this method has great advantages for saving the operating cost in actual application.

EFFECT OF PRE-ANNEALING TEMPERATURE ON THE GROWTH OF ALIGNED α-Fe2O3 NANOWIRES VIA A TWO-STEP THERMAL OXIDATION

Pre-annealing as part of a two-step thermal oxidation process has a significant effect on the growth of hematite ([Formula: see text]-Fe2O3) nanowires on Fe foil. High-density aligned nanowires were obtained on iron foils pre-annealed at 300[Formula: see text]C under a dry air flow for 30[Formula: see text]min. The X-ray diffraction (XRD) patterns indicate that the nanowires are transformed from the small [Formula: see text]-Fe2O3 grains and uniquely grow in the (110) direction. The formation of a high-density of small grains by pre-annealing improved the alignment and density of the [Formula: see text]-Fe2O3 nanowires.

Defect-induced enhanced photocatalytic activities of reduced α-Fe2O3 nanoblades

Bicrystalline α-Fe2O3 nanoblades (NBs) synthesized by thermal oxidation of iron foils were reduced in vacuum, to study the effect of reduction treatment on microstructural changes and photocatalytic properties. After the vacuum reduction, most bicrystalline α-Fe2O3 NBs transform into single-layered NBs, which contain more defects such as oxygen vacancies, perfect dislocations and dense pores. By comparing the photodegradation capability of non-reduced and reduced α-Fe2O3 NBs over model dye rhodamine B (RhB) in the presence of hydrogen peroxide, we find that vacuum-reduction induced microstructural defects can significantly enhance the photocatalytic efficiency. Even after 10 cycles, the reduced α-Fe2O3 NBs still show a very high photocatalytic activity. Our results demonstrate that defect engineering is a powerful tool to enhance the photocatalytic performance of nanomaterials.