Diffusion Coefficients Of Aluminum Research Articles

Effects of Electropulsing Treatment on the Element Diffusion Between Ti6Al4V and Commercially Pure Titanium

AbstractPrevious studies show that the phase transition temperature of Ti6Al4V can be effectively reduced by electropulsing treatment, which may be related to the promotion effect of current on element diffusion. In order to verify the above conjecture, the diffusion experiments of the Ti6Al4V-pure titanium system under the action of electropulsing and heat treatment are carried out. The results show that the current can effectively improve the diffusion coefficients of aluminum and vanadium, and the promotion effect has no relationship with the direction of the current. Considering the inhomogeneity of the Joule heat distribution of the microscopic scale of the material, the hypothesis of “local hot spot” is proposed to explain the experimental phenomena. It is found that the hypothesis can make effective predictions of diffusion coefficients and explain the promotion effect of electropulsing on Ti6Al4V phase transition reasonably.

Effect of Aluminum Coating on Corrosion and Heat Transfer Performance of Magnetic Refrigerant Gadolinium

The surface of gadolinium was covered with a layer of Al film(10–15 µm) by hot-press. Corrosion resistance, thermal conductivity and diffusivity of the composites were studied. As a result, temperature and pressure are the main factors that influence the combination of Gd and Al, and the effect of pressure is especially obvious. When the pressure exceeds 700 MPa, the binding force reaches 9 MPa. After coating, corrosion resistance of the composites is significantly improved, Corrosion rate is significantly reduced and mass loss reduced to one-tenth of pure Gd after 15 days. The current density decreases by an order of magnitude and corrosion potential increases by 0.3 V. The thermal conductivity of the composites is 11.12 W·m−1·K−1. Due to good thermal diffusion coefficient of aluminum, the magnetic work piece coated with Al film might show better heat transfer performance.

Slanted Ag-Al alloy nanorods arrays for highly active and stable surface-enhanced Raman scattering substrates

Aluminum has been established as an earth-abundant and low-cost alternative to gold and silver for plasmonic applications. Particularly, aluminum largely tends to combines with oxygen compared with silver. Here, a simple glancing angle deposition technique is presented to prepare Ag-Al alloy nanorods (NRs) with a small amount of aluminum. The effect of aluminum is to combine oxygen or corroded substances under certain conditions, such as in the air and in etchants. Beside this, owing to the large diffusion coefficient of aluminum in a Si wafer, the aluminum diffuses easily into a Si wafer, so the bonding force between the Ag-Al alloy NRs and Si wafer can be improved accordingly. In this work, 3.5 at% Al alloy NRs are optimal to exhibit high surface-enhanced Raman scattering (SERS) sensitivity, long-time stability as well as strong bonding force with a Si wafer. Ag-Al alloy NRs make a metal-metal alloy a promising material platform to develop pretty sensitive as well as stable SERS substrates.

Influence of the Polarization of Molecules of Metal Oxides on the Diffusion Coefficient in Smoky Plasmas

We study the influence of the polarization of molecules of metal oxides on the diffusion coefficient in a smoky plasma that is formed by the combustion of a metal powder in air. It is shown that the electrostatic dipole–charged grain interaction leads to a decrease in the diffusion coefficient. The values of the diffusion coefficients of aluminum and magnesium oxides in a smoky plasma as functions of the plasma temperature and the size and the charge of grains are determined.

Residual and intentional n-type doping of ZnO thin films grown by metal-organic vapor phase epitaxy on sapphire and ZnO substrates

ZnO epilayers usually exhibit high n-type residual doping which is one of the reasons behind the difficulties to dope this material p-type. In this work, we aimed at determining the nature of the involved impurities and their potential role as dopant in ZnO thin films grown by metalorganic vapor phase epitaxy (MOVPE) on sapphire and ZnO substrates. In both cases, secondary ion mass spectroscopy (SIMS) measurements give evidence for a strong diffusion of impurities from the substrate to the epilayer, especially for silicon and aluminum. In the case of samples grown on sapphire substrates, aluminum follows Fick's diffusion law on a wide growth temperature range (800−1000°C). Thus, the saturation solubility and the diffusion coefficient of aluminum in ZnO single crystals have been determined. Furthermore, the comparison between SIMS impurity and effective dopant concentrations determined by capacitance-voltage measurements highlights, on one hand a substitutional mechanism for aluminum diffusion, and on the other hand that silicon acts as a donor in ZnO and not as an amphoteric impurity. In addition, photoluminescence spectra exhibit excitonic recombinations at the same energy for aluminum and silicon, indicating that silicon behaves as an hydrogenic donor in ZnO. Based on these experimental observations, ZnO thin films with a controlled n-type doping in the 1016−1019cm−3 range have been carried out. These results show that MOVPE growth is fully compatible with the achievement of highly Al-doped n-type thin films, but also with the growth of materials with low residual doping, which is a crucial parameter to address ZnO p-type doping issues.

Diffusion of aluminum in MgO: A thermodynamic approach study

We have applied a thermodynamical model to calculate the diffusion coefficient of aluminum in MgO with the aid of bulk elastic properties. Our calculated diffusivities as a function of temperature and pressure are compared with the existing results derived from experimental or theoretical investigations. We find that the present model provides a satisfactory estimation for the activation volume and the activation enthalpy.

Mass transfer through a single grain boundary in alumina bicrystals under oxygen potential gradients

The mass-transfer behavior through grain boundaries (GBs) in alumina was systematically investigated using four types of alumina bicrystals. The alumina bicrystal wafers were exposed to the constant oxygen potential gradient \( \left( {\Updelta P_{{{\text{O}}_{ 2} }} } \right) \) generated by the combination of two different oxygen partial pressures \( P_{{{\text{O}}_{ 2} }} \left( {\text{II}} \right) \) and \( P_{{{\text{O}}_{ 2} }} \left( {\text{I}} \right) \) of 105 and 1 Pa, respectively, at 1923 K. Ridges were formed along the GBs on the surface subjected to \( P_{{{\text{O}}_{ 2} }} \left( {\text{II}} \right) \), and deep GB ditches were developed on the \( P_{{{\text{O}}_{ 2} }} \left( {\text{I}} \right) \) surface mainly during the migration of aluminum thorough GBs from the \( P_{{{\text{O}}_{ 2} }} \left( {\text{I}} \right) \) surface to \( P_{{{\text{O}}_{ 2} }} \left( {\text{II}} \right) \) surface. The surface morphology changes in the vicinity of the GBs were observed by atomic force microscopy. It was found that the surface morphology changes indicative of the aluminum GB diffusion were strongly dependent on the GB characteristics. The GB diffusion coefficients of aluminum estimated from the volume of the GB ridges showed a clear correlation to the local bonding environments of GB cores estimated from theoretical calculations reported previously.

Effect of a pulsed magnetic field on the diffusion of aluminum in iron and the fine-structure parameters of iron

The effect of a pulsed magnetic field with a strength in the range 0–557.2 kA m−1 and a frequency in the range 0–8 Hz at a temperature of 730°C on the diffusion of aluminum in iron, the microhardness of iron, and the dislocation density in iron has been experimentally investigated by metallography and X-ray diffraction. It is established that a pulsed magnetic field significantly affects the diffusion coefficient of aluminum and the dislocation density in iron. Possible mechanisms of the influence of a pulsed magnetic field on the characteristics measured are discussed.

DIFFUSION OF ALUMINUM IN DOUBLE QUANTUM WELL STRUCTURE UPON RAPID THERMAL ANNEALING

We have investigated theoretically and experimentally the impurity-free vacancy induced disordering for GaAs/AlGaAs double quantum well laser structure grown by MBE with capped SiO2 by repid thermal annealing. The position of the photoluminescence peaks, due to the n=1 electron to heavy-hole transition, was measured before and after annealing the samples. As a result, the samples annealed rapidly show blue shift in the position of photoluminescence peaks and the magnitude of shift increases with increasing temperature. We analyzed theoretically the Al-Ga interdiffusion process in GaAs/AlGaAs quantum well structure and the experimental energy shifts were compared with a theoretical model to obtain the diffusion coefficient of aluminum into the quantum well at different temperatures and the activation energy of aluminum diffusion process. The aluminum diffusion coefficient in the sample annealed at 950 ℃ for 30 s is 6.6×10-16 cm2/s. The activation energy found is 5.0 eV.

Postgrowth control of GaAs/AlGaAs quantum well shapes by impurity-free vacancy diffusion

The control of quantum well shapes in GaAs/AlGaAs material after growth has been investigated both theoretically and experimentally. Double quantum well samples capped either by SiO/sub 2/ or fluorides of the group IIA elements were annealed, and energy gap shifts were measured by photoluminescence. These experimental energy shifts were compared to a theoretical model to obtain the diffusion coefficient of aluminum into the quantum wells. Fluorides were found to inhibit the intermixing process almost completely, whereas SiO/sub 2/ is known to enhance it. The aluminum diffusion coefficients for samples annealed at 920/spl deg/C for 30 s are 4.0/spl times/10/sup -17/ cm/sup 2//s and 2.1/spl times/10/sup -15/ cm/sup 2//s for SrF/sub 2/ and SiO/sub 2/ caps, respectively. The activation energies found were 4.09 and 6.40 eV for the same two caps.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Determination of the diffusion coefficient of aluminum along the grain boundaries of gold films by the surface accumulation method

Grain boundary diffusion coefficients of aluminium in polycrystalline gold films were determined in the temperature range 75–110°C by the surface accumulation method. The time dependence of the average surface concentration of aluminium was followed by X-ray photoelectron spectroscopy (XPS). The obtained grain boundary diffusion parameter could be represented by w b D b = 2.90 × 10 −12 exp(−1.057 × 10 −19J/ kT) cm 3 s −1. Using the angle-resolved XPS technique the thickness of the surface accumulation layer was estimated to be 0.6 nm, giving for the boundary diffusion coefficient D b = 4.8 × 10 −5 exp(−1.057 × 10 −19 J/ kT) cm 2 s −1 . The values of the diffusion coefficients determined from the rate of aluminum accumulation on the surface agreed well with the value estimated from the delay time required for the aluminium to penetrate to the gold surface.

Diffusion of aluminum in ion-implanted alpha iron

The bulk diffusion coefficient of aluminum in ion-implanted paramagnetic iron-aluminum alloys has been determined to have an activation energy of 3.17±0.15 eV and preexponential factor of 1.6±4.60.2 cm2/s by measuring the time evolution of aluminum profiles in the temperature range 775–900 °C.

Aluminum redistribution in EFG of silicon ribbon

Impurity transport in EFG of silicon ribbon has been studied with the help of spreading resistance measurements and infrared transmission spectroscopy taken on ribbon grown from aluminum-doped melts. Redistribution of aluminum do pant is observed both in the ribbon thickness and width dimensions. The redistribution pattern across the ribbon width can be explained with the help of a two-dimensional model of impurity transport in the melt ahead of the growth interface. The model predictions have been used to obtain a value for the diffusion coefficient of aluminum in liquid silicon.

ChemInform Abstract: MEASUREMENT OF THE DIFFUSION COEFFICIENT OF ALUMINUM IN MERCURY

Abstract The diffusion coefficient of aluminum in mercury was measured over a concentration of 0.9 to 14 mM. It was found to increase with increasing concentration from 1.2 × 10−5 to 1.9 × 10−5 cm2 sec −1. This unusual dependence of D on C was attributed to the formation of aggregates of several aluminum atoms in the amalgam.

Measurement of the diffusion coefficient of aluminum in mercury

The diffusion coefficient of aluminum in mercury was measured over a concentration of 0.9 to 14 mM. It was found to increase with increasing concentration from 1.2 × 10 −5 to 1.9 × 10 −5 cm 2 sec −1. This unusual dependence of D on C was attributed to the formation of aggregates of several aluminum atoms in the amalgam.