Electrolytic Breakdown of Anodic Films on Aluminum

1971 ◽  
Vol 29 ◽  
pp. 206-207
Author(s):  
J. Zahavi ◽  
M. Metzger
Keyword(s):  
Electron Microscopy ◽  
Steady State ◽  
Sulfuric Acid ◽  
Large Scale ◽  
Film Growth ◽  
Film Formation ◽  
Constant Current ◽  
Anodic Films ◽  
Constant Current Density ◽  
The Stability

Electron microscopy has been used for some time in studying topography and structure of anodic films for identification and measurement of cell and pore structures and for detection of flaws or of various forms of breakdown, but usually at high forming voltages yielding relatively large scale features. For film formation with accompanying dissolution, leading to films of the porous type, the structure at cell voltages of several volts and below is of interest in regard to formation and dissolution mechanisms in general and to the stability and breakdown of corrosion films, in particular. As a first step, we have studied the films on aluminum, of known purity and microstructure, electropolished in a perchloric acid-ethanol bath and formed in 2.4 M sulfuric acid at a relatively low constant current density of 5 ma/cm2 giving steady state conditions of slow film growth at relatively low current efficiency.

The morphology and mechanism of formation of porous anodic films on aluminium

1970 ◽  
Vol 317 (1531) ◽  
pp. 511-543 ◽  
Keyword(s):  
Steady State ◽  
Layer Thickness ◽  
Current Density ◽  
Barrier Layer ◽  
Anodic Oxide ◽  
Constant Current ◽  
Cell Diameter ◽  
Anodic Films ◽  
Constant Current Density ◽  
Barrier Layer Thickness

The morphology of porous anodic oxide films formed on aluminium in phosphoric acid electrolytes at constant current density or voltage, and under changing electrical or electrolytic conditions, has been studied quantitatively by electron microscopy. Replicas from film sections and from both film interfaces have been prepared, as well as transmission micrographs of thin films, produced under accurately defined conditions. During formation at constant current density, pore initiation occurs by the merging of locally thickening oxide regions, which seem related to the substructure of the substrate, and the consequent concentration of current into the residual thin areas. The pores grow in diameter and change in number until the steady-state morphology is established. The film barrier layer thickness has been measured directly for the first time. The steady-state barrier-layer thickness, cell diameter and pore diameter are all observed to be directly proportional to the formation voltage. It becomes evident that the barrier-layer thickness, decided largely by an equilibrium established between oxide formation in the barrier-layer and field-assisted dissolution (probably thermally enhanced) at the pore bases, determines the cell and pore sizes by a simple geometrical mechanism. Anion incorporation into the film and its hydrogen-bonded structure play secondary roles to these factors in determining the actual film morphology, although not its subsequent properties. A consequence of the mechanism is that, at constant current density, relatively non-aggressive electrolytes give thicker barrier layers, larger cells and larger pores next to the barrier layer than aggressive media, although subsequent pore widening at the outer surface of the film by simple chemical dissolution is more severe in aggressive electrolytes.

Au-Based Transparent Conductors for Window Applications: Effect of Substrate Material

2010 ◽  
Vol 75 ◽  
pp. 25-30
Author(s):  
Pia C. Lansåker ◽  
Klas Gunnarsson ◽  
Arne Roos ◽  
Gunnar A. Niklasson ◽  
Claes Goran Granqvist
Keyword(s):  
Large Scale ◽  
Near Infrared ◽  
Film Growth ◽  
Film Formation ◽  
Optical Transmittance ◽  
Substrate Material ◽  
Transparent Conductors ◽  
Glass Substrates ◽  
Au Film ◽  
Window Applications

Thin films of Au were made by sputter deposition onto glass substrates with and without transparent and electrically conducting layers of SnO2:In. The Au films were up to ~11 nm in thickness and covered the range for thin film growth from discrete islands, via large scale coalescence and formation of a meandering conducting network, to the formation of a more or less “holey” film. Scanning electron microscopy and atomic force microscopy showed that the SnO2:In films were considerably rougher than the glass itself. This roughness influenced the Au film formation so that large scale coalescence set in at a somewhat larger thickness for films on SnO2:In than on glass. Measurements of spectral optical transmittance and electrical resistance could be reconciled with impeded Au film formation on the SnO2:In layer, leading to pronounced “plateaus” in the near infrared optical properties for Au films on SnO2:In and an accompanying change from such two-layer films having a lower resistance than the single gold film at thicknesses below large scale coalescence to the opposite behavior for larger film thicknesses.

20.8% slot-die coated MAPbI3 perovskite solar cells by optimal DMSO-content and age of 2-ME based precursor inks

2020 ◽  
Author(s):  
Jinzhao Li ◽  
Janardan Dagar ◽  
Oleksandra Shargaieva ◽  
Daniel Többens ◽  
Rahim Munir ◽  
...  
Keyword(s):  
Solar Cells ◽  
Large Scale ◽  
Film Growth ◽  
Intermediate Phase ◽  
Film Formation ◽  
Perovskite Solar Cells ◽  
Lead Iodide ◽  
Process Technology ◽  
Slot Die ◽  
The Right

Abstract Solar cells incorporating metal-halide perovskite (MHP) semiconductors are continuing to break efficiency records for solution-processed solar cell devices. Scaling MHP-based devices to larger area prototypes is a crucial step towards commercialization. This requires the development and optimization of scalable process technology for these devices. Here, we demonstrate a maximum power conversion efficiency (PCE) of 20.83% for slot-die coated gas-quenched small-area methylammonium lead iodide (MAPbI3) devices. Our ink is based on 2-methoxy-ethanol (2-ME) with the strongly coordinating solvent dimethyl-sulfoxide (DMSO) added in small amounts. We found that the amount of DMSO, as well as the age of the precursor solutions, are determining factors in achieving highly efficient and reproducible devices. Through in-depth insight into the film formation process as a function of DMSO content from in-situ X-ray diffraction experiments, we found that just the right amount of DMSO favorably affects thin film growth. Adding 11.77 mol% of DMSO prevents the formation of a crystalline intermediate phase related to MAPbI3 and 2-ME (MAPbI3 -2-ME), reported here for the first time, and inducing the formation of some (DMSO)2MA2Pb3I8 intermediate phase. These results demonstrate that ink composition and process control are critical to enable reproducible large-scale manufacturing of MHP-based devices for commercial applications.

Stability and EPD of Concentrated Suspensions of Alumina with Nanosized Titania

2012 ◽  
Vol 507 ◽  
pp. 203-207 ◽  
Author(s):  
Tamara Molina ◽  
Monica Vicent ◽  
Enrique Sánchez ◽  
Rodrigo Moreno
Keyword(s):  
Current Density ◽  
Deposition Time ◽  
Unit Area ◽  
Slip Casting ◽  
Constant Current ◽  
Concentrated Suspensions ◽  
Constant Current Density ◽  
Flaw Tolerance ◽  
Nanosized Titania ◽  
The Stability

Alumina-aluminium titanate (A-AT) composites and laminates have been recently investigated because they can provide improved flaw tolerance and toughness associated to a microcracking mechanism. A-AT composites have been produced by slip casting and reaction sintering of submicron sized alumina and titania powders. This work deals with the preparation of thick self-sustained A-AT films from mixtures of submicron sized alumina and nanosized titania. Suspensions were prepared in water to high solids loadings ranging from 30 to 50 vol.%. The stability of diluted suspensions was studied through zeta potential measurements as a function of pH and deflocculant type and concentration. The stability of the concentrated suspensions as a function of deflocculant content, sonication time and solids loadings was studied from rheological measurements. Self-sustained films were obtained by aqueous EPD using graphite substrates under constant current density conditions. The evolution of mass per unit area with current density and deposition time was recorded. The films were characterized in the green state and after debinding and sintering by density measurements, and electron microscopy observations.

Influence of Aggregate Volume Ratio of Mortar on the Migration of Cations Using the Accelerated Lithium Migration Technique

2011 ◽  
Vol 230-232 ◽  
pp. 400-404
Author(s):  
Wei Chien Wang ◽  
Chih Chien Liu ◽  
Chau Lee
Keyword(s):  
Steady State ◽  
Current Density ◽  
Linear Correlation ◽  
Volume Ratio ◽  
Constant Current ◽  
Constant Current Density ◽  
Pass Through ◽  
And Migration ◽  
Lithium Migration ◽  
Migration Technique

This study utilizes mortar specimens, to design 3 different a/c ratios of 2.25, 2.75, and 3.25. The aggregate volume ratios (Vf) are 46 %, 52 %, and 57 %, respectively, while the w/c ratio is 0.5, and undergoing a 9, 12, and 15 A/m2 constant current density Accelerated Lithium Migration Technique after curing for 3 months. Results show that, on specimens applied with the same current density, the time of Li+ to pass through the specimen, and steady state flux and migration coefficient all exhibit a positive linear correlation with Vf. At the same time, the non-steady state migration coefficient for Li+ have a negative linear correlation with Vf.

Stability of short-axial-wavelength internal kink modes of an anisotropic plasma

1987 ◽  
Vol 38 (3) ◽  
pp. 495-499 ◽  
Author(s):  
M. Faghihi ◽  
J. Scheffel
Keyword(s):  
Current Density ◽  
Anisotropic Plasma ◽  
Constant Current ◽  
Constant Current Density ◽  
The Stability ◽  
Z Pinch

The double adiabatic equations are used to study the stability of a cylindrical Z-pinch with respect to small axial wavelength, internal kink (m ≥ 1) modes. It is found that marginally (ideally) unstable, isotropic equilibria are stabilized. Also, constant-current-density equilibria can be stabilized for P⊥ > P∥ and large β⊥

scholarly journals An Optimal Fast-Charging Strategy for Lithium-Ion Batteries via an Electrochemical–Thermal Model with Intercalation-Induced Stresses and Film Growth

Energies ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2388 ◽  
Author(s):  
Guangwei Chen ◽  
Zhitao Liu ◽  
Hongye Su
Keyword(s):  
Lithium Ion Batteries ◽  
Thermal Model ◽  
Film Growth ◽  
Film Formation ◽  
Lithium Ion ◽  
Life Time ◽  
Constant Current ◽  
Charging Time ◽  
Fast Charging ◽  
Induced Stresses

Optimal fast charging is an important factor in battery management systems (BMS). Traditional charging strategies for lithium-ion batteries, such as the constant current–constant voltage (CC–CV) pattern, do not take capacity aging mechanisms into account, which are not only disadvantageous in the life-time usage of the batteries, but also unsafe. In this paper, we employ the dynamic optimization (DP) method to achieve the optimal charging current curve for a lithium-ion battery by introducing limits on the intercalation-induced stresses and the solid–liquid interface film growth based on an electrochemical–thermal model. Furthermore, the backstepping technique is utilized to control the temperature to avoid overheating. This paper concentrates on solving the issue of minimizing charging time in a given target State of Charge (SoC), while limiting the capacity loss caused by intercalation-induced stresses and film formation. The results indicate that the proposed optimal charging method in this paper offers a good compromise between the charging time and battery aging.

scholarly journals A Novel Radiation Method for Preparing MnO2/BC Monolith Hybrids with Outstanding Supercapacitance Performance

Nanomaterials ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 533
Author(s):  
Fan Yang ◽  
Xichuan Liu ◽  
Rui Mi ◽  
Lei Yuan ◽  
Xi Yang ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Specific Capacitance ◽  
High Performance ◽  
Electrochemical Impedance ◽  
Constant Current ◽  
Potential Range ◽  
Γ Irradiation ◽  
Constant Current Density ◽  
Transmission Electron ◽  
Potential Electrode

A novel facile process for fabrication of amorphous MnO2/bamboo charcoal monolith hybrids (MnO2/BC) for potential supercapacitor applications using γ-irradiation methods is described. The structural, morphological and electrochemical properties of the MnO2/BC hybrids have been investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. The combination of BC (electrical double layer charge) and MnO2 (pseudocapacitance) created a complementary effect, which enhanced the specific capacitance and good cyclic stability of the MnO2/BC hybrid electrodes. The MnO2/BC hybrids showed a higher specific capacitance (449 F g−1 at the constant current density of 0.5 A g−1 over the potential range from –0.2 V to 0.8 V), compared with BC (101 F g−1) in 1 M of Na2SO4 aqueous electrolyte. Furthermore, the MnO2/BC hybrid electrodes showed superior cycling stability with 78% capacitance retention, even after 10,000 cycles. The experimental results demonstrated that the high performance of MnO2/BC hybrids could be a potential electrode material for supercapacitors.

scholarly journals Effect of Aquo-glycolic Media and Added Anions on the Anodization of Zircaloy-4 in Sulphamic Acid

2011 ◽  
Vol 8 (1) ◽  
pp. 71-76
Author(s):  
Viplav Duth Shukla ◽  
CH. Anjaneyulu
Keyword(s):  
Dielectric Constant ◽  
Ethylene Glycol ◽  
Room Temperature ◽  
Film Formation ◽  
Constant Current ◽  
Constant Current Density ◽  
Phosphate Ions ◽  
Sulphamic Acid ◽  
Kinetics Of ◽  
Millimolar Concentration

Anodization of zircaloy-4 in 0.1 M sulphamic acid has been carried out. Kinetics of anodic oxidation of zircaloy-4 has been studied at a constant current density of 8 mA/cm2and at room temperature. Thickness estimates were made from capacitance data. The plots of formation voltagevs. time, reciprocal capacitancevs. time, reciprocal capacitancevs. formation voltage and thicknessvs. formation voltage were drawn and rate of formation, current efficiency and differential field were calculated. The addition of solvent (ethylene glycol) showed better kinetic results. For 25%, 50% and 75% aquo-glycolic media, the dielectric constant values are low leading to a marked improvement in the kinetics. In 80% ethylene glycol, though the dielectric constant value of solution is less, the kinetics was slow which may be attributed to the fact that the electrolyte becomes highly non-polar. Improvement in the kinetics of oxide film formation was observed by the addition of millimolar concentration of anions (CO32-, SO42-, PO43-). The presence of phosphate ions improved the kinetics of anodization to better extent.

Gyrokinetic stability theory of z–pinches

1990 ◽  
Vol 44 (1) ◽  
pp. 137-149 ◽  
Author(s):  
Hans O. Åkerstedt
Keyword(s):  
Growth Rate ◽  
Current Density ◽  
Stability Criterion ◽  
Stability Theory ◽  
Fluid Model ◽  
Constant Current ◽  
Constant Current Density ◽  
The Stability

From the Vlasov-fluid model a set of approximate stability equations describing the stability of the pure z–pinch is derived. The equations are valid for equilibria with small gyroradius compared with the pinch radius, but the perturbation wavenumber k may be of the order of the gyroradius ρi, δ = kρi = 0(1) - so-called gyrokinetic ordering. The equations are used to study the stability of the m = 0 and m = 1 internal modes of the z–pinch. In the limit of zero gyroradius δ → 0 we recover previously obtained results. For δ ≠ 0 we find that increasing δ at first gives a rapidly decreasing growth rate, and for δ ≈ l the growth rate compared with perpendicular MHD is γ/γMHD ≈ 0·09. For larger δ however, the growth rate increases to a quite large value. For the m = O mode we find, provided that drift resonances can be neglected, a stability criterion for δ ≥ 1, which is fulfilled both for the Bennett equilibrium and the constant-current-density equilibrium.

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