Diffusion Coefficient Of Iron Research Articles

Effect of a 0.05% Nickel Addition to Zinc Melt on the Mutual Diffusion Coefficient of Iron and Zinc in the Formation of a Zinc Coating

Effect of a 0.05% Nickel Addition to Zinc Melt on the Mutual Diffusion Coefficient of Iron and Zinc in the Formation of a Zinc Coating

Concentrated Ionic Fluids: Is There a Difference Between Chloride‐Based Brines and Deep Eutectic Solvents?

AbstractDeep Eutectic Solvents (DESs) have been lauded as novel solvents, but is there really a difference between them and concentrated aqueous brines? They provide a method of adjusting the activity of water and chloride ions which can affect mass transport, speciation and reactivity. This study proposes a continuum of properties across concentrated ionic fluids and uses metal processing as an example. Charge transport is shown to be governed by fluidity and there is no discontinuity between molar conductivity and fluidity irrespective of cation, charge density or ionic radius. Diffusion coefficients of iron(III) and copper(II) chloride in numerous concentrated ionic fluids show the same linear correlation between diffusion coefficient and fluidity. These oxidising agents were used to etch copper, silver and nickel and while the etching rate increased with fluidity for copper, etching of silver and nickel only occurred at high chloride and low water activity as passivation occurred when water activity increased. Overall, brines provide a high chloride content at a lower viscosity than DESs, but unlike DESs, brines are unable to prevent passivation due to their high water content. The results show how selective etching of mixed metal waste streams can be achieved by tuning chloride and water activity.

Concentrated Ionic Fluids: Is There a Difference Between Chloride-Based Brines and Deep Eutectic Solvents?

Deep Eutectic Solvents (DESs) have been lauded as novel solvents, but is there really a difference between them and concentrated aqueous brines? They provide a method of adjusting the activity of water and chloride ions which can affect mass transport, speciation and reactivity. This study proposes a continuum of properties across concentrated ionic fluids and uses metal processing as an example. Charge transport is shown to be governed by fluidity and there is no discontinuity between molar conductivity and fluidity irrespective of cation, charge density or ionic radius. Diffusion coefficients of iron(III) and copper(II) chloride in numerous concentrated ionic fluids show the same linear correlation between diffusion coefficient and fluidity. These oxidising agents were used to etch copper, silver and nickel and while the etching rate increased with fluidity for copper, etching of silver and nickel only occurred at high chloride and low water activity as passivation occurred when water activity increased. Overall, brines provide a high chloride content at a lower viscosity than DESs, but unlike DESs, brines are unable to prevent passivation due to their high water content. The results show how selective etching of mixed metal waste streams can be achieved by tuning chloride and water activity.

MD simulation of vacancy and interstitial diffusion in FeCr alloy

The diffusion mobility of iron and chromium atoms in Fe-9%Cr and Fe-20%Cr alloys for temperature up to 1000 K has been studied by molecular dynamics simulation. Both vacancy and interstitial migration of atoms has been considered. Corresponding diffusion coefficients of iron and chromium atoms, as well as the diffusion coefficients of a vacancy and self-interstitial configuration, have been evaluated. The values obtained for the vacancy diffusion satisfactory agree with experimental results taken from the literature.

Molecular dynamics simulation of corrosion and its inhibition: comparison of structural stability of Fe/FeNi/FeNiCr/FeNiCrTi steels under high-temperature liquid lead

The liquid lead used in fast nuclear reactor has been known to be able to cause a significant damage to the steels. Therefore, finding new materials with high corrosion resistance is the goal of much research current days. Likewise, developing a way to prevent corrosion is also the goal of designers of nuclear reactors. In the present study, we studied materials: Fe, FeNi, FeNiCr, and FeNiCrTi (a type of SS 316L austenite steel), comparing their structural stability when interacted with molten liquid lead at 750 °C. The performance of each steel is compared under high-temperature molten lead coolant, checking the structure's stability to see the material resistance to corrosion attack of liquid lead. The corrosion can also be seen from the data of iron diffusion coefficient. The larger of the iron diffusion coefficient can be associated with larger corrosion because there is a high solubility of iron atoms from the steel surface to the molten lead. The popular way to prevent more corrosion is by injecting oxygen into the lead coolant. This current work uses the molecular dynamics method to simulate the corrosion and inhibition phenomena. The research aims to compare the performance of Fe, FeNi, FeNiCr, and FeNiCrTi under liquid lead at a temperature of 750. The diffusion coefficient of iron of material will be calculated to describe quantitatively the corrosion level of those structural materials and the corrosion inhibition by oxygen injection. The study has produced important results that adding Ni, Cr, Ti into a pure iron crystal to build alloy steel will make the material stronger, structurally compact, and more resistant to corrosion. For specific composition of steels, from weaker to stronger that resist from corrosion attack, it is possible to make ordering: Fe<<FeNi<FeNiCr<FeNiCrTi. The composition of FeNiCrTi steel in this work is Fe(75)Ni(10.57)Cr(14.05)Ti(0.40). The high corrosion of FeNiCrTi in the liquid lead is effectively reduced by injecting 0.0112 wt % oxygen into lead coolant as a limit value for maximum corrosion inhibition

SOLID STATE DIFFUSION BONDING OF X70 STEEL TO DUPLEX STAINLESS STEEL

This paper deals with the solid state diffusion bonding of X70 steel to duplex stainless steel. Microstructure and mechanical properties of the welded dissimilar steels were investigated. Optical microscopy, Electron Backscatter Diffraction, energy dispersive spectrometry, Vickers hardness measurements, and X-Ray Diffraction were the main techniques of characterization. Microtructural variation was observed in the X70 steel side compared to duplex stainless steel. The diffusion coefficient of iron, chromium, and nickel across the interface X70 steel/duplex stainless steel was also measured. The diffusion coefficient of iron and chromium is higher than that of nickel. The Vickers microhardness profile across the bond joint showed an abrupt decrease in hardness from duplex stainless steel to X70 steel. In addition, a dynamic recrystallisation reaction was observed close to the interface in the X70 steel side.

Analysis of oxide scale thickness and pores position of HCM12A steel in supercritical water

Abstract More attention has been paid to the exfoliation of oxide scale on high-temperature heating surface of utility boiler. The oxidation mechanism of HCM12A steel in supercritical water is proposed and the growth of oxide film is simulated. The duplex scale contains an outer magnetite layer and an inner Cr-rich spinel layer. According to the data of Backhaus and Töpfer, the diffusion coefficient values of iron in magnetite layer are discussed and the function of R V, R I {R}_{\text{I}} for oxygen activity can be used for calculation of iron diffusion coefficients in Cr-rich spinel layer. Based on Wagner’s oxidation theory, the oxidation rate constants of HCM12A are calculated at 500 and 600°C in supercritical water, compared with experimental data of the relevant literatures. The oxygen activities at the interfaces of alloy/Cr-rich spinel oxide and magnetite/supercritical water are estimated. The simulation results of weight gain are matched with the test data. The iron diffusion mechanisms inside the magnetite layer and the Cr-rich spinel layer are analyzed. The iron diffusion coefficient at the interface of Cr-rich spinel/magnetite is discontinuous, while the oxygen activity is continuous in the whole double layer. The thickness of oxide scale on inner tube walls of the final superheater coils (T91) of a 600 MW supercritical boiler is calculated by using the calculation method provided by the paper. The modeling results, the measured data, and the calculation results by the method are compared. Accurate calculation of the thickness of the inner and outer oxide scales can provide a necessary basis for predicting the stress and exfoliation of oxide scales.

Experimental and simulation study of impurity transport response to RMPs in RF-heated H-mode plasmas at EAST

Spatial profiles of impurity emission measurements in the extreme ultraviolet (EUV) spectroscopic range in radiofrequency (RF)-heated discharges are combined with one-dimensional and three-dimensional transport simulations to study the effects of resonant magnetic perturbations (RMPs) on core impurity accumulation at EAST. The amount of impurity line emission mitigation by RMPs appears to be correlated with the ion Z for lithium, carbon, iron and tungsten monitored, i.e. stronger suppression of accumulation for heavier ions. The targeted effect on the most detrimental high-Z impurities suggests a possible advantage using RMPs for impurity control. Profiles of transport coefficients are calculated with the STRAHL one-dimensional impurity transport code, keeping $\nu /D$ fixed and using the measured spatial profiles of $\textrm{F}{\textrm{e}^{20 + }}$ , $\textrm{F}{\textrm{e}^{21 + }}$ and $\textrm{F}{\textrm{e}^{22 + }}$ to disentangle the transport coefficients. The iron diffusion coefficient ${D_{\textrm{Fe}}}$ increases from $1.0- 2.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ to $1.5- 3.0\;{\textrm{m}^2}\;{\textrm{s}^{ - 1}}$ from the core region to the edge region $(\rho \gt 0.5)$ after the onset of RMPs. Meanwhile, an inward pinch of iron convective velocity ${\nu _{\textrm{Fe}}}$ decreases in magnitude in the inner core region and increases significantly in the outer confined region, simultaneously contributing to preserving centrally peaked $\textrm{Fe}$ profiles and exhausting the impurities. The ${D_{\textrm{Fe}}}$ and ${\nu _{\textrm{Fe}}}$ variations lead to reduced impurity contents in the plasma. The three-dimensional edge impurity transport code EMC3-EIRENE was also applied for a case of RMP-mitigated high-Z accumulation at EAST and compared to that of low-Z carbon. The exhaust of ${\textrm{C}^{6 + }}$ toward the scrape-off layer accompanying an overall suppression of heavier ${\textrm{W}^{30 + }}$ is observed when using RMPs.

SIMULATION OF IRON CORROSION IN LEAD-MAGNESIUM EUTECTIC (LME) USING OXYGEN INHIBITOR

SIMULATION OF IRON CORROSION IN LEAD-MAGNESIUM EUTECTIC (LME) USING OXYGEN INHIBITOR. Lead-magnesium (Pb-Mg) is a metal that considered to have potential as a coolant raw material in the heat transfer system of nuclear reactors. However, the coolant in the form of Pb-Mg eutectic is corrosive to structured materials (eg steel cladding) used in reactors. In this research, steel material is represented by pure iron to simplify the simulation and calculation. This research aims to determine the effect of temperature on iron corrosion and the effect of adding oxygen as an inhibitor to reduce the iron corrosion rate in LME. In this study, corrosion was observed by looking at (coefficient) the diffusion of iron atoms into LME. A large iron diffusion coefficient represents high iron corrosion. To see inhibition effectivity with oxygen, the most effective oxygen concentration that can reduce the iron diffusion coefficient is searched. Simulations of iron corrosion and inhibition are performed using molecular dynamics simulation. The result of this research showed that oxygen concentration mixed into LME for effective inhibition of iron corrosion was in the range of 0.125 wt% - 0.135 wt% (for temperatures of 973K). Thus, oxygen is believed that able to inhibit iron corrosion in Pb-Mg eutectic up to 98.44%

Modeling of Ferrous Metal Diffusion in Liquid Lead Using Molecular Dynamics Simulation

Modeling of Iron metal diffusion in liquid lead using molecular dynamics simulation has been done. Molecular dynamics simulations are used to predict the value of physical quantities that we want to know based on the designed material model and on the input simulation data. In this research, effect of different geometry of material models was observed to know the diffusion coefficient. The material system was iron (Fe) in liquid lead (Pb). The material models is designed using Packmol software to get the initial configuration of atom's arrangement by inputting the material's characteristics such as mass, density, volume, number of atoms. This work examines the diffusion coefficient of iron in molten lead metal with the geometric shape of the simulation system in the form of iron in molten metal for various simulation models of boxes in a box, balls in a box and balls in balls. To design simulated geometric shapes we use the Packmol program. To calculate the diffusion coefficient we use the molecular dynamics simulation method. To find out which geometry is suitable, we compare the diffusion coefficient of the simulation results with existing references. The diffusion coefficient value of the spherical iron (Fe) system in the spherical liquid lead (Pb) has the best value compared to the other two forms with an accuracy rate of 99.94% because it is influenced by the even distribution of atoms in each part.

Temperature dependence diffusion coefficients of iron, boron and iron-boron calculated by molecular dynamics method

It has been calculated the diffusion coefficient of iron, boron and iron-boron system as temperature function using molecular dynamics simulation method. The diffusion coefficient is very important for knowing the physical processes. However, the diffusion coefficient data are not always available from experimental measurements, as so many applications using this data as an input of calculation. The computational molecular dynamics method shows a powerful tool for predicting the needed properties of material under consideration. In this work we predict the diffusion coefficient based on the Lennard-Jones potential under scheme of Lorentz-Berthelot mixing formula as the atomic interaction of material for molecular dynamics simulation. From this work we have determined the temperature dependence diffusion coefficient: DFe(T)=5.20×10−7.exp(-393.82/T), DB(T)=1.74×10−6.exp(-297.62/T, DB→Fe-B(T) = 2.50×10−6.exp(-411.29/T) and DFe→FeB(T)=5.274×10−9.exp(-930/T) in the unit of m2/s.

A computational model of gas tungsten arc welding of stainless steel: the importance of considering the different metal vapours simultaneously

A 2D computational model of the mixing of multiple metal vapours into a helium arc in gas tungsten arc welding of stainless steel is presented. The combined diffusion coefficient method, extended to three-gas mixtures, is used to treat helium–chromium–iron and helium–manganese–iron plasmas. It is found that all metal vapours penetrate to the arc centre and reach the cathode, with iron vapour confined near the cathode tip, while chromium and manganese vapours accumulate about 1.5 mm above the tip. The predicted distributions of chromium, manganese and iron show reasonable agreement with published photographic images and radial distributions of atomic line emission intensities. The results are also consistent with published measurements of the deposition of the metals on the cathode surface. A detailed examination of the influence of the different diffusion coefficients, net emission coefficients and vapour pressures of the metals on the metal vapour transport in the arc plasma is presented. It is shown that cataphoresis (diffusion due to applied electric fields) leads to the penetration of the metal vapours into the arc. The different distribution of iron vapour from those of chromium and manganese vapours near the cathode is strongly influenced by the lower ordinary diffusion coefficients of iron at low temperatures. Radiative emission is found to be important since it leads to cooling of the arc, which decreases the influence of cataphoresis. The vapour pressure only influences the concentration of the metal vapour close to the workpiece. Results for the two-gas helium–chromium and helium–iron systems are compared to those for the three-gas helium–chromium–iron system. It is shown that it is important to consider the different metal vapours simultaneously to obtain an accurate calculation of the metal vapour and arc temperature distributions.

Growth and Segregation of Intermenallic Phases in Zirconium Alloys

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Anodic Dissolution of Iron–Nickel Alloy under Non-Steady-State Conditions

Anodic dissolution of iron–nickel electrolytic alloy in the acidic chloride solution is studied by the non-steady-state electrochemical methods. It is shown that, in the initial period, selective dissolution of the alloy with prevailing iron ionization takes place. Then, the anodic dissolution rate is limited by the nonsteady-state bulk diffusion of the components in the solid phase. The effective diffusion coefficients of iron in the alloy are calculated.

Interdiffusion and phase formation in the Fe–TiO2 thin-film system

The interaction of magnetron-sputtered metal iron with titanium-oxide films upon isothermal vacuum annealing is studied by X-ray phase analysis, secondary-ion mass spectrometry, atomic-force microscopy, and mathematical simulation. A mechanism for the formation of complex oxides at grain boundaries is suggested. The mechanism is based on the reaction diffusion of metal iron into titanium oxide. A quantitative model of reaction interdiffusion in two-layer polycrystalline metal–oxide film systems with limited component solubility is developed. From numerical analysis of the experimental distributions of the metal concentrations in the Fe–TiO2 film system, the individual diffusion coefficients are determined. It is found that, under the conditions of vacuum annealing at 1073 K, the diffusion coefficients of iron and titanium are 8.0 × 10–13 and 3.0 × 10–15 cm2 s–1, respectively.

Effect of temperature on the corrosion inhibition of iron in liquid lead using oxygen inhibitor: studied by MD simulation

For corrosion mitigation of steels used in a fast nuclear reactor power plant, oxygen gas is one of promising candidates of inhibitors. Many experiments have been conducted to reveal the mechanism of corrosion and mechanism of how to overcome the corrosion. In the previous work, we had shown computationally that the oxygen atom can be used to reduce the corrosion and we had predicted the oxygen contents. In the current work, not only to explore deeeper the ability of oxygen gas to reduce the corrosion, but also to include the variation of used temperature. We still used iron material to represent a real steels. Using MD (molecular dynamics) simulation based on the Lennard-Jones interaction potential, we sought to understand the concentration of oxygen gas as variation of temperature used in the reactor for the best corrosion mitigation. From this work, we conclude that the temperature does not give effect in related with how concentration of injected oxygen. The temparature merely affects to rise the diffusion coefficient of iron in liquid lead, yet it does not influence how much oxygen needed for corrosion mitigation. In this work, all simulations on different series of temperatures (1023°K, 1073°K, 1123°K, 1173°K) reveals that oxygen content of 0.1151wt% will cause the lowest corrosion level of iron in liquid lead.

Estimation of Oxidation Kinetics and Oxide Scale Void Position of Ferritic-Martensitic Steels in Supercritical Water

Exfoliation of oxide scales from high-temperature heating surfaces of power boilers threatened the safety of supercritical power generating units. According to available space model, the oxidation kinetics of two ferritic-martensitic steels are developed to predict in supercritical water at 400°C, 500°C, and 600°C. The iron diffusion coefficients in magnetite and Fe-Cr spinel are extrapolated from studies of Backhaus and Töpfer. According to Fe-Cr-O ternary phase diagram, oxygen partial pressure at the steel/Fe-Cr spinel oxide interface is determined. The oxygen partial pressure at the magnetite/supercritical water interface meets the equivalent oxygen partial pressure when system equilibrium has been attained. The relative error between calculated values and experimental values is analyzed and the reasons of error are suggested. The research results show that the results of simulation at 600°C are approximately close to experimental results. The iron diffusion coefficient is discontinuous in the duplex scale of two ferritic-martensitic steels. The simulation results of thicknesses of the oxide scale on tubes (T91) of final superheater of a 600 MW supercritical boiler are compared with field measurement data and calculation results by Adrian’s method. The calculated void positions of oxide scales are in good agreement with a cross-sectional SEM image of the oxide layers.

Numerical study on non-axisymmetric wall thinning in pipelines with swirling flow

In order to understand the mechanisms of non-axisymmetric pipe-wall thinning in the Mihama nuclear power plant accident of 2004, a numerical simulation of pipe-wall thinning in an elbow-orifice pipeline with swirling flow was carried out based on mass and momentum transfer equations with a standard k-ε model of turbulence at a Reynolds number of 5.8×106. The pipe-wall thinning was evaluated on the basis of the mass transfer coefficient using the diffusion coefficient of ferrous iron in bulk water flow. The numerical simulation revealed that swirling flow with a certain level of swirl intensity generates a spiral motion downstream of the elbow and sustains a longer distance than expected from an elbow flow without swirl. This type of non-axisymmetrical flow triggers strongly biased flow at the orifice, which results in non-axisymmetric pipe-wall thinning downstream of the orifice.

Cations/Anions Effects of Imidazolium-based Ionic Liquids on the Diffusion Properties of Iron- and Ruthenium-bipyridine/phenanthroline Complexes

The diffusion coefficients of both iron(II)-bipyridine ([Fe(bpy)3]2+), ruthenium(II)-bipyridine ([Ru(bpy)3]2+) are reported in five of different imidazolium-based ionic liquids (ILs) and iron(II)-phenanthroline ([Fe(phen)3]2+), ruthenium(II)-phenanthroline ([Ru(phen)3]2+) in one of imidazolium-based ionic liquid, using cyclic voltammetry and chronoamperometry at microdisc electrodes. Activation energies of diffusion, ED, are calculated for each system. Diffusion coefficient ratios between oxidation and reduction species for both complexes were found to be close to 1. Plots of diffusion coefficients versus inverse viscosity deviate from expected linearity, especially for ILs with different kind of anions, suggesting that anions of the ILs contribute to the values of diffusion coefficients. ED for both complexes in ILs are found slightly larger compared to the activation energies of viscous flow (Eη) for the corresponding IL, indicating that the viscosity is not the only factor determining the diffusion of the complexes. Furthermore, the hydrodynamic radius of complexes in ILs were estimated based on the diffusion coefficient values. They are found to be independent of temperature and ILs viscosity.

Diffusion Coefficient of Iron in ZnSe Polycrystals from Metal Phase for mid-IR Gain Medium Application

Diffusion coefficient of Fe in polycrystalline host ZnSe as a mid-IR gain medium has been measured in the annealing temperature ranges of 850 to 950℃. The synthesis of the samples was carried out in quartz ampoule in which the Fe thin film deposited by physical vapor evaporation method on the ZnSe. One can realize that the diffusion coefficient strongly depends on the surface active surfactants through the cleaning process and the substrate temperature during the thin film deposition leading to 2.04×10 -9 cm²/s for Fe 2+ :ZnSe. The Annealing temperature dependence of the Fe ions diffusion in ZnSe was used to evaluate the activation energy, Ea=1.39 eV for diffusion and the pre-exponential factor D0 of 13.5 cm²/s.