Diffusion Coefficient Of Nickel Research Articles

Atomic diffusion in liquid gallium and gallium-nickel alloys probed by quasielastic neutron scattering and molecular dynamic simulations

The atomic mobility in liquid pure gallium and a gallium-nickel alloy with 2 at% of nickel is studied experimentally by incoherent quasielastic neutron scattering. The integral diffusion coefficients for all-atom diffusion are derived from the experimental data at different temperatures. DFT-based ab-initio molecular dynamics (MD) is used to find numerically the diffusion coefficient of liquid gallium at different temperatures, and numerical theory results well agree with the experimental findings at temperatures below 500 K. Machine learning force fields derived from ab-initio molecular dynamics (AIMD) overestimate within a small 6% error the diffusion coefficient of pure gallium within the genuine AIMD. However, they better agree with experiment for pure gallium and enable the numerical finding of the diffusion coefficient of nickel in the considered melted alloy along with the diffusion coefficient of gallium and integral diffusion coefficient, that agrees with the corresponding experimental values within the error bars. The temperature dependence of the gallium diffusion coefficient DGa(T) follows the Arrhenius law experimentally for all studied temperatures and below 500 K also in the numerical simulations. However, DGa(T) can be well described alternatively by an Einstein–Stokes dependence with the metallic liquid viscosity following the Arrhenius law, especially for the MD simulation results at all studied temperatures. Moreover, a novel variant of the excess entropy scaling theory rationalized our findings for gallium diffusion. Obtained values of the Arrhenius activation energies are profoundly different in the competing theoretical descriptions, which is explained by different temperature-dependent prefactors in the corresponding theories. The diffusion coefficient of gallium is significantly reduced (at the same temperature) in a melted alloy with natural nickel, even at a tiny 2 at% concentration of nickel, as compared with its pure gallium value. This highly surprising behavior contradicts the existing excess entropy scaling theories and opens a venue for further research.

Kinetics of Nickel Diffusion into Austenitic Stainless Steels AISI 304 and 316L and Calculation of Diffusion Coefficients.

Diffusion bonding has many advantages, but it also has its specifics. When creating heterogeneous joints, problems arise with the creation of intermetallic phases. For this reason, an interlayer is needed to prevent the creation of these unfavorable phases. It is important to ensure that the interlayer is of sufficient thickness to prevent the elements from diffusing through the entire interlayer and the intermetallic phases from being formed again. Conversely, too thick an interlayer causes an increase in the heterogeneity of the bond properties. The creation of the initial diffusion bonds in a heterogeneous diffusion joint of AISI 304 and AISI 316L steel with a 0.2 mm thick nickel interlayer was made in a Gleeble 3500. The experiments to determine the diffusion kinetics were carried out in a vacuum furnace, with subsequent evaluation by EDX (Energy Dispersive X-ray Spectroscopy) analysis. Subsequently, the diffusion coefficients of nickel into both steels were determined, and generalized equations were formulated to calculate the diffusion coefficients for temperatures in the range of 950 to 1150 °C and holding times in the range of 3600 to 18,000 s. Equations are also given to determine the width of the diffused zone between each steel and the Ni interlayer.

Quantitative estimate of the contribution of the surface diffusion process to mass transfer during electrochemical deposition of metals

In this study, an attempt was made to quantify the contribution of the surface diffusion process to mass transfer during electrochemical deposition of metals. The maximum density of nucleation centers is calculated, at which only diffuse overgrowth of a continuous layer of a new phase is possible. The time of diffusion overgrowth of a continuous monomolecular layer of a new phase is calculated. The results of independent experiments on the determination of boundery diffusion coefficients in a two-layer platinum-nickel thin-film system are analyzed. The value of the boundery diffusion coefficient of nickel at a temperature of 393K was found. The part of mass transfer due to surface diffusion of physically adsorbed atoms in relation to the total mass transfer during electrochemical deposition of metals has been quantified. It is proved that the role of the surface diffusion process in the formation of the coating during electrochemical deposition of metals is insignificant. It is shown that this is an indirect proof of the formation of an amorphous coating structure during electrochemical deposition of metal.

Acceleration of nickel diffusion by high tensile stress in cold-worked type 316 stainless steel at 450°C

ABSTRACTThe effect of tensile stress on diffusion was studied by the diffusion couple method. A diffusion couple was prepared by electroless plating a nickel thin layer on the round notch surface of a compact tension-type specimen of 20% cold-worked Type 316 stainless steel. The couple was diffused at 450°C for 4003 h under the maximum tensile stress of 553 MPa in the load direction. A rapid diffusion coefficient of nickel in the Type 316 stainless steel was observed at the high tensile stress zone that was 6.5 times faster than that at the low-stress zone.

Rapid nickel diffusion in cold-worked type 316 austenitic steel at 360–500 °C

Abstract The diffusion coefficient of nickel in cold-worked Type 316 austenitic steel was determined by the diffusion couple method in the temperature range between 360 and 500 °C. A diffusion couple was prepared by electroless nickel plating on the surface of a 20 % cold-worked Type 316 austenitic steel specimen. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time until 14 055 h. The diffusion coefficient of nickel (D Ni) in cold-worked Type 316 austenitic steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 11 at.% of nickel. The value of D Ni at 360 °C was about 5 000 times higher than the lattice diffusion coefficient of nickel in Type 316 austenitic steel. The determined activation energy 117 kJ mol−1 was 46.6 % of the activation energy 251 kJ mol−1 for the lattice diffusion of nickel in Type 316 austenitic steel.

Electrodeposition Study of Ni Coatings on Copper from Choline Chloride-Based Deep Eutectic Solvents

Nickel was electrodeposited from choline chloride (ChCl)-based deep eutectic solvents (DESs) containing ethylene glycol (EG) and urea (U) on Cu substrate. The influence of the temperature and of DESs nature was evaluated. The diffusion coefficients of nickel varied from 2.2 × 10-9 to 3.7 × 10-8 cm2 s-1 for ChCl:2U and from 1.3 × 10-8 to 5.8 × 10-8 cm2 s-1 for ChCl:2EG with increasing temperature. The nucleation process of Ni on Cu at 70 °C was determined as instantaneous in ChCl:2EG and progressive in ChCl:2U using Scharifker and Hills model. The SEM characterization showed that with increasing temperature, more compact coatings were obtained. Linear polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion performance of the obtained deposits in 3.5% NaCl. The coatings were more protective as higher the temperature of deposition, with polarization resistance (Rp) values from 3.53 to 19.11 kΩ cm2.

Rapid nickel diffusion in cold-worked carbon steel at 320–450 °C

The diffusion coefficient of nickel in cold-worked carbon steel was determined with the diffusion couple method in the temperature range between 320 and 450 °C. Diffusion couple was prepared by electro-less nickel plating on the surface of a 20% cold-worked carbon steel. The growth in width of the interdiffusion zone was proportional to the square root of diffusion time to 12,000 h. The diffusion coefficient (DNi) of nickel in cold-worked carbon steel was determined by extrapolating the concentration-dependent interdiffusion coefficient to 0% of nickel. The temperature dependence of DNi is expressed by DNi = (4.5 + 5.7/−2.5) × 10−11 exp (−146 ± 4 kJ mol−1/RT) m2s−1. The value of DNi at 320 °C is four orders of magnitude higher than the lattice diffusion coefficient of nickel in iron. The activation energy 146 kJ mol−1 is 54% of the activation energy 270.4 kJ mol−1 for lattice diffusion of nickel in the ferromagnetic state iron.

The effect of multiple martensitic transformations on diffusion of Fe and Ni atoms in Fe-31.7%Ni-0.06%C alloy.

Diffusion characteristics of iron and nickel atoms were investigated using radioactive isotopes method in phase-hardened metastable iron-nickel Fe-31.7%Ni-0.06%C alloy with nanofragmented structure. It has been found that diffusion mobility of nickel and iron atoms in reverted austenite of Fe-31.7%Ni-0.06%C alloy significantly increases as the result of multiple γ-α-γ martensitic transformations. The diffusion coefficients of nickel and iron in the austenite at 400°C corresponded to the stationary diffusion coefficients at the temperatures above 900°C. The revealed diffusion acceleration at low temperatures is caused by high-density dislocations and additional low-angle subboundaries of disoriented nanofragments of reverted austenite and deformation twin subboundaries formed during multiple γ-α-γ cycles.

A LATTICE MONTE CARLO ANALYSIS ON CHEMICAL REACTION WITH MOVING BOUNDARY

The current paper aims to simulate combined mass diffusion and chemical reaction. Two solid reactants are brought into contact and the product is formed at the interface. Chemical reaction is assumed to occur instantaneously, thus the reaction rate is limited only by the interdiffusion of the two solid constituents. First, parametric studies for a range of constant diffusivities are performed and simple relations for the growth of the product phase are obtained. It is found that the thickness of the product layer increases proportionally to the square root of the product of diffusivity and time. In the second part of the analyses the formation of NiAl by interdiffusion of nickel and aluminum is simulated. This self-propagating exothermic reaction is of great interest for joining temperature-sensitive components. Within the limits of these calculations, the concentration dependence of the diffusion coefficients of nickel and aluminum is considered in order to improve the accuracy of the simulation.

Diffusion of nickel and tin in p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3 thermoelectric materials

The diffusion and spatial distribution of tin from solder, and nickel from diffusion barrier in p-type (Bi,Sb)2Te3 and n-type Bi2(Te,Se)3 thermoelectric materials were investigated using electron microscopy. The results indicate that nickel is a suitable diffusion-barrier material for tin in both (Bi,Sb)2Te3 and Bi2(Te,Se)3. However, even though it is not an issue in the (Bi,Sb)2Te3, the nickel diffuses several microns into the Bi2(Te,Se)3 during the soldering processing and degrades its performance. Diffusion coefficients of nickel in p-type (Bi,Sb)2Te3 and in n-type Bi2(Te,Se)3 were also quantitatively studied.

Mobility of Ni(II) Ions in Inorganic Ion Exchangers Based on Zirconium Hydroxophosphate

The mobility of Ni(II) ions in inorganic ion exchangers based on zirconium hydroxophosphate with varying phosphorus content was studied using electromigration and kinetic methods. It was found that the effective diffusion coefficient of nickel in the ion exchanger phase increased with increasing phosphorus content within the range 1·10−13 to 2·10−12 m2/s.

The production of nickel-zinc alloys by powder injection

Alloys of nickel and zinc are used for the hot dip galvanizing of reactive steels containing around 0.1 pct Si. The production of these alloys is hindered by the low solubility of nickel in molten zinc at normal zinc alloying temperatures (450 °C to 550 °C). The kinetics of the dissolution of nickel in molten zinc were investigated in the temperature range 450 °C to 550 °C to show that the dissolution rate is controlled by mass transfer in the liquid boundary layer. The experiments involved dipping nickel plates into a crucible of zinc, which could be rotated to provide controlled convection around the stationary nickel plates. The dissolution rate of nickel plates immersed vertically in a static zinc melt was measured to determine the diffusion coefficient of nickel in zinc as a function of temperature and the activation energy of diffusion. A mathematical model was formulated to predict the dissolution time of nickel particles suspended in molten zinc. The dissolution times observed during plant-scale alloying tests to produce 0.15 wt pct Ni alloys using powder injection to introduce the nickel into the zinc melt agreed with the predictions of the mathematical model. The plant tests demonstrated that alloying times of less than 10 minutes can be achieved at normal alloying temperatures if the nickel is added as a powder.

Estimation of the mass transfer coefficients and diffusion coefficients of nickel and vanadium in Kuwait crude oils: Prediction of long term leaching under simple experimental conditions

Abstract One of the major concerns following the Iraqi invasion is the possibility of ground water contamination caused due to massive oil spillage. Nickel and vanadium are the major metals which exist in trace amounts in crude oils. Leaching of nickel and vanadium was studied on a laboratory scale using four different crude oils, Kuwait export (KE), Burgan (B), Ratawi (R) and Weathered (W). Nitric, sulphuric and acetic acids (pH 4 and 6) were the leaching medium. The rate of leaching was found to be significantly dependent on the type of crude and the pH value of the leaching medium. The values for the mass transfer coefficient of nickel and vanadium are in the range 0.3 ‐ 3.18×10‐3 cm3min‐1 and 0.04 ‐ 6.4×10‐3 cm3 min‐1. The diffusion coefficient values for nickel and vanadium are in the range 0.17–22.2×10‐9 cm2 day‐1 and 0.06–45.4×10‐7 cm2 day‐1. An overall study of these values suggest that nitric acid is the most effective leachant for both metals in the four crude oils. Time for 10% leaching of nick...

Investigation of grain-boundary diffusion of nickel in molybdenum by auger electron spectroscopy

The dependence of the grain-boundary diffusion coefficient of nickel in molybdenum on annealing temperature was investigated. Possible causes are analyzed for differences in the values of the grain-boundary diffusion coefficients and the activation energies for this process from those obtained by earlier researchers.

Determination of sink concentrations in ion irradiated nickel and copper by diffusion measurements

Diffusion coefficients of nickel in nickel and in copper were measured after 300 keV self-ion irradiation at temperatures between 293 and 1000 K with dose rates between 10 −5 and 3 × 10 −2 dpa/s and doses between 0.2 and 102 dpa. The results were analyzed by means of a rate equation model characterizing the sink strength of the substructure by an effective sink concentration. At lower temperatures, sink concentrations (in terms of atomic units) of 2 × 10 −6 in nickel and 2 × 10 −5 in copper were deduced. Above 850 K. in nickel and 500 K in copper these sink concentrations decreased considerably. In nickel the effective sink concentration became stationary for doses greater than 0.2 dpa. The present results indicate a higher effective sink concentration than has been deduced so far from electron microscopy investigations.

Determination of sink concentrations in ion irradiated nickel and copper by diffusion measurements

Diffusion coefficients of nickel in nickel and in copper were measured after 300 keV self-ion irradiation at temperatures between 293 and 1000 K with dose rates between 10−5and 3 × 10−2 dpa/s and doses between 0.2 and 102 dpa. The results were analyzed by means of a rate equation model characterizing the sink strength of the substructure by an effective sink concentration. At lower temperatures, sink concentrations (in terms of atomic units) of 2 × 10−6 in nickel and 2 × 10−5 in copper were deduced. Above 850 K. in nickel and 500 K in copper these sink concentrations decreased considerably. In nickel the effective sink concentration became stationary for doses greater than 0.2 dpa. The present results indicate a higher effective sink concentration than has been deduced so far from electron microscopy investigations.

Fe-Ni系合金を用いた等軸晶生成機構の検討

The formation mechanism of equiaxed grains during solidification has been investigated in Fe-Ni alloys, since the diffusion coefficient of nickel in the solid iron is small and this system has the peritectic reaction as the Fe-C system does. Alloys were melted in the vacuum induction furnace and the melt was cast in the ingot mold made of MgO. In this ingot mold, fine thermocouples covered by thin quartz tubes were set to measure the temperature change. The ingot was cut and metallographically investigated. The equiaxed ratio was then measured as a function of superheat and nickel content.When superheat was less than 50 K globular grains were found independent of composition. In the center of the globular grains, a higher concentration region was found in the alloys with high nickel contents in which the γ-phase was solidified as a primary phase. The globular grains found in this study are formed by the nucleation in the slightly undercooled alloy melt. The mathematical model for nucleation has been also established to estimate the value of the undercooling and concentration difference. The result of this model agrees well with the result of temperature measurement.

A spectroscopic study of nickel oxide films on polycrystalline nickel

The growth of nickel oxide films has attracted much attention over the years, and various diffusion mechanisms have been proposed to model the process. The popular techniques used to study the mass transport mechanisms have been Auger electron spectroscopy and secondary ion mass spectroscopy (SIMS). Another approach that has been suggested is the study of isotope separation during thin film growth. This type of analysis can give the mechanism of reaction during the film growth and is the technique used in this study. A normal isotope separation implies either grain boundary or lattice diffusion, whereas a reverse separation explicity implies grain boundary diffusion. This study looks at nickel oxides grown on polycrystalline nickel at 400, 600 and 800°C, and which range from 1.5 to 18 μm in thickness. Oxides were grown under atmospheric oxygen partial pressure conditions. X-ray diffraction was used to determine the nature of the oxide, and SIMS, in conjunction with Auger spectroscopy and argon ion sputtering, was used to determine the isotope separation if any. It was found that the oxide grown at 800°C exhibited reverse isotope separation, whereas the oxides grown at lower temperatures showed normal separation. Simplified calculations of the chemical diffusion coefficients of nickel in nickel oxide have also been made at the temperatures of interest, and activation energies ranging from 55.2 to 190.4 kJ mol -1 were obtained.

Material transport parameters for irradiated nickel and austenitic Fe-Cr-Ni alloys

Abstract Diffusion coefficients of nickel in nickel, and of nickel and silicon in Fe-20Cr-60Ni and Fe-20Cr-20Ni have been measured by SIMS after irradiation with 300 keV Ni-ions. The irradiation temperature was varied between 293 K and 966 K, the displacement rate between 1.2 × 10 −4 dpa/s and 3.2 × 10 −2 dpa/s. The diffusion coefficients of all tracer/matrix-combinations are temperature dependent above 800 K. At these temperatures nickel diffuses about ten times faster in nickel than in Fe-20Cr-60Ni and about three times faster than in Fe-20Cr-20Ni. In the alloys silicon diffuses about a factor of five as fast as nickel. The data are discussed with a simple rate equation model. It will be shown that the effective sink concentration in nickel during heavy ion irradiation decreases above 900 K strongly with increasing temperature and that the production rate of freely migrating defects has a temperature independent value of only 1.5% of the calculated displacement rate.

Short-Circuit Diffusion Processes in Oxidation Films

ABSTRACTThe rate ofoxidation of metalsat high temperatures is usually controlled by the transport of metal ions or oxygen through the growing film of oxide on the surface. Since many technologically useful alloys (eg steels, nickelbased alloys) are based on the 3d transition metals, the transport properties of the oxides of these elements are of particular interest. In the temperature range 500–1000°C, where these alloys are used, the important transport paths in the oxide are not those that involve diffusion in the bulk crystal lattice, but other “short-circuit” paths. Basic experiments on the oxidation of nickel and direct tracer measurements of diffusion coefficients show that rain boundaries are the most important short-circuit paths under protective oxidation conditions. Similar conclusions can be drawn for other metals including chromium. The methods used in this work have been extended to study the way in which a surface treatment withCeO2reduces the oxidation rate of nickel, apparently by inhibiting the outward transport of metal ions along grain boundaries. Segregation of cerium ions to grain boundaries increases the diffusion coefficient of nickel; the inhibition is caused instead by particulates of CeO2in the middle region of the scale.