Zinc Diffusion Research Articles

Surface modification of aluminum alloys using diffusion process

An applicability of solid diffusion of zinc (Zn) into an aluminum (Al) alloy for surface modification was investigated. A conventional Aluminum (Al) alloy (A5056) containing magnesium (Mg) was used for specimen. Liquefied Zn was plated on the Al alloy surface at a temperature of 450 degree Celsius (deg.) in air atmosphere then was aged for 5 hours was at various temperatures from 300 to 500 deg. As results, the increase in the diffusion distance of Zn from the surface and Al content into the Zn coated layer with the increase in the temperature was found. In addition, segregation of Mg was occurred near the surface and the coated layer was hardened. The tribological properties evaluated with 3 cast iron (FC250) pin in a lubricated condition showed that the difference of the friction coefficient depending on the heat treatment temperature was small and that the wear loss of the disc surface treated at a temperature of 300 deg. decreased. It was estimated that the transfer film containing Zn on the pin surface resulted in the low friction coefficient and the wear loss. Therefore, it is concluded that Zn coating accompanying with a heat treatment is effective means as the surface modification to decrease in the friction coefficient and the wear loss of Al alloy containing Mg.

Метод диффузии цинка в InP через узкий зазор с использованием планарного источника на основе Zn-=SUB=-3-=/SUB=-P-=SUB=-2-=/SUB=-

AbstractAn original technology of zinc diffusion into InP via a narrow gap is described, which allows reproducible formation of p–n junctions with preset depth of doping and retained surface morphology of the doped layers. Using the proposed method, desired charge carrier distribution profiles in Zn-doped InP layers were obtained. It has been experimentally confirmed that the method of cross-sectional scanning electron microscopy allows to precision measure of the zinc diffusion depth.

Computational and experimental analysis on Te-doped ZnSb thermoelectric material

We report a combined theoretical and experimental work on the tellurium doping of thermoelectric ZnSb. We investigated the influence of tellurium on the phase’s stabilities by DFT calculations. During experimental validation by SEM and EPMA characterization “needlelike” areas of Te-doped ZnSb were identified. The experimental results also highlight that for the compositions Zn0.5 Sb0.5-x Tex the system reaches a non-equilibrium state where ZnSb, ZnTe and Te-doped ZnSb are simultaneously present. The determination of the doping mechanism has demonstrated the formation of Te-doped Zn4Sb3 after quenching, leading to the formation of Te-doped ZnSb due to the zinc diffusion during annealing. Presumed from experimental observation oxygen prevents the tellurium diffusion. These results lead to the conclusion of an inert processing chain as a prerequisite for production of n-type ZnSb, which puts hurdles on a cheap and easily scalable tellurium doping for homogeneous and competitive products.

Formation of guard ring of avalanche photodiode based on the InGaAs/InP heterostructure

The suppression of the early edge breakdown in planar avalanche photodiodes based on the InP/InGaAs heteroepitaxial structures is analyzed. A structure with a sunken central part and shallow periphery fabricated with the aid of wet chemical etching with the subsequent one-step diffusion of zinc is employed. The etching rates of epitaxial InP are determined for several etching agents. The composition of etching agent and the optimal etching regimes are determined. A p–n junction with the 0.5-μm-sunk central part and 1.3-μm-deep shallow periphery (guard ring) is obtained with the aid of wet chemical etching of the upper InP epitaxial layer in the acid mixture HCl: HNO3: H3PO4 and one-step diffusion of zinc. The proposed method makes it possible to avoid early edge breakdown in the avalanche photodiode based on the InP/InGaAs heterostructure, in particular, in the production of commercial avalanche photodiodes.

Mode Behavior of VCSELs With Impurity-Induced Disordering

This letter explores the modal behavior of oxide-confined vertical-cavity surface-emitting lasers (VCSELs) with varying emission apertures defined by impurity-induced disordering (IID) via closed ampoule zinc diffusion. A 1-D plane wave propagation method is used to calculate the mirror loss as a function of IID strength and depth. The devices are fabricated with masked areas ranging from approximately 70%-110% of the oxide aperture defining an unmodified emission aperture designed to overlap mainly with the fundamental mode. An analysis of the transverse mode lasing characteristics and mode-dependent thermal characteristics demonstrates a decrease in thermal performance associated with the increasing overlap between the IID ring and supported optical modes of the VCSEL cavity. A single-mode output power of 1.6 mW with over 30 dBm side-mode suppression ration is achieved from a 3 μm device with an IID-defined output aperture of approximately 1.3 μm. The optimal IID emission aperture to oxide aperture ratio for maximizing the single-fundamental-mode output power is experimentally measured.

Shaping optimal zinc coating on the surface of high-quality ductile iron casting. Part II – Technological formula and value of diffusion coefficient

Abstract The completed research presented in the first part of the article has allowed linking the manufacturing technology of ductile iron castings with the process of hot dip galvanizing. On the basis of these data simulations were carried out to examine the behaviour of zinc diffusion coefficient D in the galvanized coating. The adopted model of zinc coating growth helped to explain the cases of excessive growth of the intermetallic phases in this type of coating. The paper analyzes covered the relationship between the roughness and phase composition of the top layer of product and the thickness and kinetics of zinc coating growth referred to individual sub-layers of the intermetallic phases.Roughness and phase composition in the surface layer of product were next related to the diffusion coefficient D examined in respective sublayers of the intermetallic phases.

Electrochemical behavior of tube-fin assembly for an aluminum automotive condenser with improved corrosion resistance

An aluminum automotive condenser was designed to exhibit high corrosion resistance in the seawater acetic acid test (SWAAT) combining zinc coated microchannel tubes and fins made with AA4343/AA3003(Zn)/AA4343 brazing sheet. Electrochemical measurements in SWAAT solution were carried out under laboratory conditions using tube-fin assembly and individual fin and tube samples withdrawn from the condenser core. The aim was to gain information on the protective role of the zinc sacrificial layer and about changes in corrosion behavior as a function of immersion time. External corrosion of the tube-fin system was simulated by immersion of mini-core samples under open circuit conditions. The corrosion rate increased rapidly during the first 6h and slowly afterwards. The short time behavior was related to the dissolution of the oxide film and fast dissolution of the outermost part of the zinc diffusion layer. With the aid of cross-sectional depth corrosion potential profiles, it was shown that as the sacrificial layer gets dissolved, the surface concentration of zinc decreases and the potential shifts to less negative values. The results of galvanic coupling of tube and fins in a mini-cell showed that the tube became the anode while the fins exhibited cathodic behavior. An evolution in the galvanic interaction was observed, due to the progressive dissolution of the sacrificial zinc layer. The difference of uncoupled potentials between tube and fins decreased from 71mV to 32mV after 84h of galvanic coupling. At the end of such period there was still a part of the zinc sacrificial layer remaining which would serve for protection of the tube material for even longer periods and there were indications of slight corrosion in the fins.

Influence of diffusion on the coating adhesion of zinc-magnesium thin films onto steel

Abstract In this study the zinc and magnesium diffusion in ZnMg thin PVD films is examined and linked to the crash adhesion performance of the coating-substrate system. The investigation is conducted at 175 °C because this temperature conforms to both the temperature range during production of the films and the post process steps at automotive customers. The results confirm that zinc is the faster diffusive specie and although the movement of zinc results in a phase transformation, first from magnesium into MgZn2 and later from MgZn2 into Mg2Zn11 this phase change does not seem to alter the crash adhesion performance of the coating substrate system. Additionally, the magnesium seems to diffuse along grain boundaries towards the steel substrate interface. This segregation of magnesium and the enrichment of magnesium at the interface results in a deterioration of the crash adhesion resistance. The time until the samples fail the crash adhesion test is determined by the distance the magnesium has to travel from the Mg containing layer to the steel-substrate interface.

Zinc Diffusion Coatings on Aluminium for Improved Pitting Resistance

The automotive industry has replaced copper tube based heat exchangers with all-aluminium solutions during the past years in order to reduce weight, material costs and environmental impact. Conversely, the use of aluminium tubing in the HVAC&R (Heat, Ventilation, Air Conditioning and Refrigeration) heat exchanger market is limited due to the much more demanding lifetime requirements. One way of obtaining the required level of safety against failure of aluminium tubing in such applications is corrosion protection by surface modification. This work investigates the effect of surface alloying with zinc on the pitting resistance of heat exchanger tubes. Pure zinc was applied on flat, thin-walled (≈ 400 µm) multi-port extruded Al-Mn alloy tubes by thermal arc spraying immediately after extrusion, resulting in a sub-micron thick metallic Zn layer on the surface. The tubes were subsequently heat treated to obtain various Zn-rich diffusion layers ranging up to about 70 µm into the alloy substrate. Zn depth profiles were determined by glow discharge optical emission spectroscopy (GD-OES). Corrosion testing was performed by exposure to a cyclic acidified (pH 3) synthetic seawater fog test (ASTM G85 annex A3), normally referred to as the SWAAT test. Open circuit potentials were measured on separate samples as a function of time during immersion in the SWAAT solution at 25 °C. The extent of corrosion as a function of time was determined by weight loss on samples retrieved from the salt spray cabinet at predetermined time intervals for a period of up to eight weeks. The maximum pit depth on each sample was measured by use of a light microscope with a micrometre focusing dial. Ten replicate samples (each 25 mm x 100 mm in size) for each substrate/coating combination were tested, allowing analysis of the maximum pit depth data from extreme value probability plots. The open circuit potential of the Zn diffusion coated samples in artificial seawater solution was about -0.95 V (SCE), shifting only 10 mV in positive direction during 24 h of immersion. The corrosion potential of the Al-Mn alloy substrate remained constant at -0.74 V (SCE) under similar conditions. The cathodic protection provided by the Zn-rich diffusion layers effectively protected the Al-Mn alloy tubes against formation of deep pits during SWAAT testing. No pits deeper than about 50 µm had formed on the Zn diffusion coated samples after eight weeks of exposure, whereas pit depths exceeding 200 µm was observed on uncoated reference samples already after two weeks. However, weight loss measurements showed that the (uniform) corrosion rate of the anodic Zn-rich diffusion layer was nearly two orders of magnitude higher than that of the Al-Mn alloy substrate under the aggressive low pH conditions prevailing during SWAAT exposure. The results suggest that a lower Zn load than that realizable by thermal arc spraying is required to obtain optimal Zn diffusion profiles in terms of service life of the heat exchanger tubing.

Surface analysis of InP and InGaAs after low temperature diffusion of Zinc

In order to develop III–V based devices integrated directly above post-processed silicon wafers, low temperature diffusion of zinc in n-type InP and InGaAs is studied at compatible temperatures, below 425 oC. We particularly focus on the resulting surface degradation. Efficient Zn diffusion is obtained for InGaAs samples, where the surface remains mirror-like after thermal treatment. Conversely, no significant diffusion occurs in InP where the surface is deeply deteriorated. The stability study for InP under thermal annealing in various ambients allows us to rule out thermal dephosphorization as the main cause of the surface degradation. On the basis of experimental observations and thermodynamic considerations, it is suggested that InP degradation is linked to the direct interaction of Zn and P, inducing the formation of parasitic ZnxP2 alloys, which also hinders the efficient diffusion of Zn into the InP substrate.

InGaAs/InP SPAD With Monolithically Integrated Zinc-Diffused Resistor

Afterpulsing and optical crosstalk are significant performance limitations for applications employing near-infrared single-photon avalanche diodes (SPADs). In this paper, we describe an InGaAs/InP SPAD with monolithically integrated resistor that is fully compatible with the planar fabrication process and provides a significant reduction of the avalanche charge and, thus, of afterpulsing and optical crosstalk. In order to have a fast SPAD reset ( $\text{k}\Omega $ , smaller than what is available in the literature. The resistor, fabricated with the zinc diffusions already used for avoiding premature edge-breakdown, promptly reduces the avalanche current to a low value ( $\sim 100~\mu \text{A}$ ) in less than 1 ns, while an active circuit completes the quenching and enforces a well-defined hold-off. The proposed mixed-quenching approach guarantees an avalanche charge reduction of more than 20 times compared with similar plain SPADs, enough to reduce the hold-off time down to 1 $\mu \text{s}$ . Finally, a compact single-photon counting module based on this detector and featuring 70-ps photon-timing jitter is presented.

α-Mg primary phase formation and dendritic morphology transition in solidification of a Mg-Nd-Gd-Zn-Zr casting alloy

Microstructure evolution in the commercial Mg-Nd-Gd-Zn-Zr alloy Elektron 21, solidified under nearly isothermal conditions, has been studied via in-situ X-ray radiography. For cooling rates T˙≤0.075 K/s, primary equiaxed α-Mg dendrites undergo a morphological transition after nucleation and an initial stage of growth. The growth regime is observed to change abruptly from a 3D to a more pronounced anisotropic sheet-like growth occurring predominantly along 112¯0 direction, with a 4–5 times increase in the growth velocity. The experimental results together with thermodynamic calculations and density functional theory simulations give support to relate the morphology transition to the formation of ordered rare earth-zinc dimers in the {0001} basal plane and {101¯1} pyramidal plane of α-Mg lattice. At the temperature where the morphological transition occurs, it is found that both the solute concentration and zinc diffusivity in α-Mg are high enough for dimer formation to occur within a diffusive layer extending a few micrometres from the solid-liquid interface into α-Mg, and thereby open for increased solute-partitioning at the growth front.

InGaAs/InP Avalanche Photodiode for Single Photon Detection with Zinc Diffusion Process Using Metal Organic Chemical Vapor Deposition.

In this paper, we describe a design, simulation, and fabrication of an InGaAs/InP single photon avalanche photodiode (SPAD), which requires a much higher gain, compared to APD's for conventional optical communications. To achieve a higher gain, an efficient multiplication width control is essential because it significantly affects the overall performance including not only gain but also noise characteristics. Normally, the multiplication layer width is controlled by the Zinc diffusion process. For the reliable and controllable diffusion process, we used metal organic chemical vapor deposition (MOCVD). The controllability of the proposed diffusion process is proved by the diffusion depth measurement of the fabricated devices which show the proportional dependence on the square root of the diffusion time. As a result, we successfully implemented the SPAD that exhibits a high gain enough to detect single photons and a very low dark current level of about 0.1 nA with 0.95 breakdown voltage. The single photon detection efficiency of 15% was measured at the 100 kHz gate pulse rate and the temperature of 230 K.

Synthesis, characterization and antimicrobial activity of alkaline ion-exchanged ZnO/bentonite nanocomposites

Nanocomposites of zinc/bentonite clay were synthesized for use as an antibacterial material by a quick and simple alkaline ion exchange method. The synthesis of zinc doped bentonite nanocomposite was accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The complexes were characterized by XRD, SEM and DRS. XRD analyses and SEM observations confirmed the diffusion of zinc to the clay surfaces. Antibacterial activity tests against Escherichia coli showed that bentonite did not present any antibacterial properties, but after alkaline ion exchange treatment, inhibition was noted. The highest antibacterial activity was observed with ZnO/bentonite composite alkaline ion exchange for 60 and 90 min. Interestingly, the leaching test indicated that ZnO/bentonite did not present any risk for drinking water treatment.

Synchrotron X-ray Fluorescence Microscopy study of the diffusion of iron, manganese, potassium and zinc in parboiled rice kernels

Parboiled rice is known to contain higher levels of nutrients than its non-parboiled counterpart. In order to study the diffusion of micronutrients into the starchy endosperm of the parboiled rice kernel, the parboiled paddy samples were prepared by combining different hydrothermal treatments (hydrated only, steamed-only, hydrated then steamed) employing two hydration temperatures (60 °C and 90 °C). The rice kernels were sectioned longitudinally into 90 μm thick sections after hydrothermal treatment, drying and milling. These rice kernels sections were analysed by Synchrotron X-Ray Fluorescence Microscopy (S-XFM) to determine the distribution of iron (Fe), manganese (Mn), potassium (K) and zinc (Zn). The S-XFM results showed that the bran and germ were rich in these minerals whereas the endosperm had a low concentration. Hydrothermal treatment of kernels increased the mineral diffusion into the endosperm from the bran layer and germ. The highest diffusion of Fe, Zn and Mn was observed in the sample treated with high temperature hydration for a longer time followed by steaming. However, K did not appear to diffuse into the endosperm as much as other the minerals.

Short range correlation length study in a single ZnO nanowire and its impact on phonon confinement

We report the influence of the short range correlation length ζL on the optical properties of a single non-centrosymmetric ZnO nanowire. Confocal Raman scattering and one-dimension phonon confinement model were employed to investigate the phonon and geometric properties of a single ZnO nanowire. The local optical results reveal a red shift in the non-polar E2 high frequency mode and a short range correlation length of ζL = 10(2) nm is obtained due to the enhancement of the zinc diffusion during the ZnO domain nucleating.

Erosion–corrosion interaction of Fe–B alloy in flowing zinc

The effect of erosion angle on the erosion–corrosion interaction of Fe–3.5 wt-%B alloy in flowing zinc was investigated. The total erosion–corrosion rate decreased linearly, whereas the pure erosion rate fluctuated slightly with increasing erosion angle, which was strongly dependent on the erosion–corrosion interaction. At an erosion angle of 0°, liquid zinc corrosion damaged the sample surface and facilitated erosion, which in turn increased corrosion via the removal of corrosion products. As the erosion angle increased, corrosion products accumulated and Fe2B flaked and cracked in front of the erosion interface, which resulted, in turn, in increased obstruction to the diffusion of liquid zinc. Accordingly, the erosion–corrosion interaction was reduced, thereby resulting in a low material loss at high erosion angles.

Electrodeposition of Nanocrystalline Zinc from Sulfate and Sulfate-Gluconate Electrolytes in the Presence of Additives

This study investigated electrodeposition of zinc from sulfate and sulfate-gluconate electrolytes in the presence and absence of additives such as Polyethylene glycol (PEG), hexadecyltrimethylammonium bromide (CTAB) and thiourea. Equilibrium distribution of zinc (II) species revealed that in both sulfate and sulfate-gluconate electrolytes, ZnSO4 was the predominant species at the pH range of 1 to 6. Voltammetric analysis and potentiostatic experiments showed that although ZnSO4 had higher concentration in both sulfate and sulfate-gluconate electrolytes, zinc-gluconate (Zn(GH4)+) species played a significant role in the reduction process. Due to strong effects of (Zn(GH4)+) species on the deposition process a negative shift in reduction potential and a decrease in zinc diffusion coefficient was observed. Effects of gluconate complex agent on the deposition of zinc was confirmed by evaluation of the surface morphology and the texture of electrodeposited zinc on mild steel substrate. Two distinct microstructures with different preferred orientations were produced from sulfate and sulfate-gluconate electrolytes under the same deposition conditions. Synergistic effects of additives resulted in the formation of zinc coatings with nano grain sizes for both sulfate and sulfate-gluconate electrolytes with the same preferred orientation. X-ray diffraction results indicated that the effects of ligands from which zinc deposition occurred became negligible in the presence of all additives.

Diffusion coupling in multiply associating electrolyte solutions

Diffusion coupling in multiply associating aqueous electrolyte solution is studied. The process is illustrated in the case of zinc(II) ion which forms a set of complexes, ZnCln2−n (with n=1,..,4), in the presence of chloride ions. The transport of zinc ion, taken in radioactive form 65Zn2+, in the electric field created by a gradient of LiCl, is investigated experimentally by employing an adaptation of the closed capillary technique. The transient diffusion process is modeled by using two different treatments: finite difference (FD) simulation and normal-mode (NM) analytic solution. Deviations from ideality are taken into account with the use of the mean spherical approximation (MSA), and the internal electric field is calculated using the dynamical electroneutrality condition. The theoretical FD and NM results are compared with the experimental data about the diffusion of zinc.

Low-loss passive waveguides in a generic InP foundry process via local diffusion of zinc.

Generic InP foundry processes allow monolithic integration of active and passive elements into a common p-n doped layerstack. The passive loss can be greatly reduced by restricting the p-dopant to active regions. We report on a localized Zn-diffusion process based on MOVPE, which allows to reduce waveguide loss from 2 dB/cm to below 0.4 dB/cm. We confirm this value by fabrication of a 73 mm long spiral ring resonator, with a record quality factor of 1.2 million and an extinction ratio of 9.7 dB.