High-purity Aluminum Foils Research Articles

Quantitative Determination on Fiber Textured Materials Derived by Particle Swarm Optimization

In this article presented, the maximum entropy method (MEM) assisted by the particle swarm optimization (PSO) algorithm with inertia weight factor was adopted to quantify the volume percentage of crystalline grains corresponding to the {100} fiber texture in high-purity Aluminum foils. The results derived from the inverse pole figures indicate a simpler and more convenient method than the ones derived by the conventional metallographic analysis in comparison, which possess a relative error less than 5% in general. In consideration of the measurement error relating to the metallographic method, this improved quantification is more accurate and acceptable.

Electrochemical Self-Assembly of Nanoporous Alumina Templates Title

Porous alumina was fabricated electrochemically through anodic oxidation of aluminum by means of such a self-organized method. Anodic aluminium oxide (AAO) template with nanopores was grown by two-steps anodization processes from a high purity aluminium foil. The anodization process was carried out in a phosphoric acid electrolyte at ambient temperature with a different duration of anodization. The analysis observation by Atomic Force Microscopy (AFM) showed that nanopore size increased with anodization time. The nanopore sizes of porous alumina were (16.04, 26.19 and 37.39 nm) for (1, 2 and 3 hour) respectively.

Fabrication of Nanoporous Aluminum Oxide via a Two-Step Anodisation Process

In this study, we report the fabrication of nanoporous aluminum oxide film from high purity aluminium foil via a two-step anodisation process controlled by a constant direct current potential ranging from 40 60 V from a DC power supply. The anodisation process was conducted at 20˚C in an electrochemical cell with the Al foil acting as anode, Pt as cathode and an acidic bath as electrolyte. Porous aluminium oxide films of pore diameters ranging between 30 90 nm were successfully fabricated. The morphologies and phase compositions of the anodized porous alumina films were investigated using scanning electron microscopy (SEM) and x-ray diffraction (XRD) for characterizations.

Improvement of pore distribution uniformity of nanoporous anodic aluminum oxide with pulse reverse voltage on low-and-high-purity aluminum foils

Many conventional anodic aluminum oxide (AAO) templates were performed using direct current anodization (DCA) at low temperature (0–5°C) to avoid Joule-heat-dissolution effect at relatively high temperature of 20–25°C. In this article, a small pulse reverse voltage added to normal-positive pulse anodization which is called hybrid pulse anodization (HPA) has been investigated for improving pore distribution uniformity of AAO at high temperature. The nanoporous AAO films were synthesized with both low-purity (99%) and high-purity (99.997%) aluminum (Al) foils in 0.3M oxalic acid by different voltage modes of HPA and DCA for comparison. The pore distribution uniformity can be much improved by small pulse reverse voltage in 3h duration anodization compared to DCA method. The small pulse reverse voltage presented the high uniformity of 88% and 91% for both low and high purity Al due to nearly zero cathodic current for reducing Joule-heat-dissolution. The effect of Al purity and voltage mode on uniformity improvement was further discussed.

Condensation of Acetone to Diacetone Alcohol over Structured MgO/Al<sub>2</sub>O<sub>3</sub>-Al Catalyst Packing

A novel solid base catalyst, structured MgO/Al2O3-Al catalyst packing, was prepared by supporting MgO onto a thin film of alumina that was formed by anodic oxidation of high purity aluminium foils. Some preparation parameters including the molar ratio of Mg(NO3)2•6H2O to CH3(CH2)16COOH, the aging time, the calcination temperature and time were investigated by using the catalyst for the condensation of acetone to diacetone alcohol. Each of those factors had some influence on the catalyst activity and an optimum value was obtained. The conversion of acetone was 20.2%, and the selectivity to diacetone alcohol was 100% under the optimized preparation conditions.

Effect of process parameters on growth rate and diameter of nano-porous alumina templates

Anodic aluminium oxide (AAO) template with hexagonal shaped nano-pores with high aspect ratio was fabricated by two-step anodization processes from high purity aluminium foil. It was observed that pore dimensions were affected by anodizing voltage, electrolyte temperature and the duration of anodization time. The vertical growth rate of the pores (10–250 nm/min) was found to vary exponentially with anodizing voltage; however, it exhibits linear increment with the electrolyte temperature. The measured pore diameter (50–130 nm) shows a linear variation with anodizing voltage. The bottom barrier oxide layer was etched out by pore widening treatment to obtain through holes.

Fabrication of enhanced anodic aluminum oxide performance at room temperatures using hybrid pulse anodization with effective cooling

Conventional anodic aluminum oxide (AAO) template was performed using potentiostatic method of direct-current anodization (DCA) on costly high-purity (99.997%) aluminum foils at low temperatures of 0–10°C to avoid dissolution effects which occurred frequently at room temperatures (RT) of 20–30°C. In this paper, we show the hybrid pulse anodization (HPA) method with pulsing normal-positive and small-negative potential differences at RT for enhancing performance of AAO structure for both the cheap low-purity (99%) and costly high-purity (99.997%) aluminum foils. The HPA mainly takes advantages of effective cooling that arise from the nearly zero cathodic current and high-thermal-conductivity liquid electrolyte on the foils. The HPA is different from the traditional pulse anodization with alternating both high and low positive potential differences (/currents) or both one-positive and one-zero potential differences. The HPA not only merits manufacturing convenience and cost reduction but also promotes pore distribution uniformity of AAO at severe conditions of cheap low-purity Al foils and relatively high room temperature. The pore distribution uniformity can be improved by HPA in a suitable duration compared with the DCA. Very good AAO distribution uniformity (91%) was achieved in high-purity aluminum foil by HPA because it can suppress the Joule's heat to diminish the dissolution reaction. The evolution of AAO distribution uniformity for both the HPA and DCA on Al foil purities and process durations were comparatively investigated.

Palladium coated porous anodic alumina membranes for gas reforming processes

Nanostructured ceramic membranes with ultrathin coatings of palladium metal have been demonstrated to separate hydrogen gas from a gas mixture containing nitrogen with 10% carbon dioxide and 10% hydrogen at temperatures up to 550 °C. The mechanically robust and thermally durable membranes were fabricated using a combination of conventional and high-efficiency anodisation processes on high purity aluminium foils. A pH-neutral plating solution has also been developed to enable electroless deposition of palladium metal on templates which were normally prone to chemical corrosion in strong acid or base environment. Activation and thus seeding of palladium nuclei on the surface of the template were essential to ensure uniform and fast deposition, and the thickness of the metal film was controlled by time of deposition. The palladium coated membranes showed improved hydrogen selectivity with increased temperature as well as after prolonged exposure to hydrogen, demonstrating excellent potential for gas separation technologies.

Ultrasonic-assisted ac etching of aluminum foils for electrolytic capacitor electrodes with enhanced capacitance

ac etching of high-purity aluminum foils in hybrid acids including hydrochloric acid, sulphuric acid and oxalic acid was investigated and the effects of ultrasonic-assisted stirring on the performances of the etched foils were investigated in this work. Scanning electron microscopy (SEM) was used for observation of the etched foils. Compared with the classically used mechanical stirring (magnetic stirring), the assistance of ultrasonic increased the performance of the etched foil. With 20 V forming voltage, the static capacitance and bending strength of the foils etched with ultrasonic stirring reached 76.5 μF cm −2 and 98 times compared with 71.2 μF cm −2 and 85 times respectively for the foils fabricated with magnetic stirring using 100 μm aluminum foils. The performance enhancement with the assistance of ultrasonic is probably due to the cavitation effects which are beneficial for the remove of protective layer and the dispersion effects which reduce concentration polarization in the bulk etchant solutions.

Porous anodic alumina formed by anodization of aluminum alloy (AA1050) and high purity aluminum

A two-step anodization process performed at 0 °C was used to prepare highly ordered porous anodic alumina on the AA1050 alloy and high purity aluminum foil. The anodizing of both substrates was carried out in 0.3 M sulfuric acid and 0.3 M oxalic acid baths at 25 V and 40 V, respectively. The effect of the extended duration of the second anodizing step on pore order degree and structural features of AAO membranes was studied. The presence of alloying elements affects not only the rate of oxide growth but also the microstructure of the anodic film. It was found that pore circularity and regularity of pore arrangement in AAO membranes formed on the AA1050 alloy were always worse than those observed on the pure Al substrate. The structural features, such as pore diameter, interpore distance, wall thickness, barrier layer thickness, porosity and pore density of porous anodic alumina formed on AA1050 are a little different from those obtained for high purity Al. The extended time of the second anodizing step, up to 16 h does not affect significantly the regularity of pore order and all structural features of AAO membranes, independently of the anodizing electrolyte.

Size dependency of mechanical properties of high purity aluminium foils

In order to study the size effect, tensile tests with high purity aluminium foils of different thicknesses from 5 μm to 540 μm were performed at room temperature and at 100 °C. A pronounced size effect was observed especially at elevated temperature. There are two major contributions to the size effect: first, the samples get weak if the fraction t/ g of thickness t to grain size g is smaller than 1, because the Hall–Petch model can no longer be applied if most of the grain boundaries are at the free surface. Second, the presence of an oxide layer increases the tensile strength of thin foils. Our results are relevant for the prediction of reliability and life time of electronic devices. It may be concluded that the grain size should be refined when the dimensions of electronic parts are reduced.

NANOSTRUCTURED ALUMINA CERAMIC MEMBRANES FOR GAS SEPARATION

Nanostructured alumina ceramic templates have been fabricated by anodizing annealed high-purity aluminium foil. Pore diameter, pore separation and thickness in these alumina ceramics can be controlled using a range of acid electrolytes and anodizing voltage profiles. Thermal development of the structure of these robust and optically clear templates have been compared using XRD, thermal analysis and 27 Al MAS NMR techniques, showing that species substituted in the alumina lattice from decomposition of the acid electrolyte play a major role in determining the chemical and physical stability of the ceramic template at elevated temperatures. Deposition of ultrathin palladium films on the surface of these alumina templates creates robust membranes that enable hydrogen separation from mixed gas streams at elevated temperatures. Gas permeability measurements through these membranes as a function of temperature have demonstrated their very high selectivity for hydrogen.

Characterization of electrodeposited Ni and Ni80Fe20 nanowires

In this work we use nanoporous alumina substrates as templates for the growth of Ni and Ni 80 Fe 20 nanowires. Our membranes were obtained by a two-step anodization process of high-purity aluminum foils: first anodizations were performed at 40 V for 15 h in 0.3 M oxalic acid, at 2–6 °C; the second anodization was carried out using the same conditions for 30 min, resulting in pore lengths of ∼1.3 μm. After the second anodization, the pore bottom barrier-layer was thinned, to allow the current to flow through electron tunneling. A pulsed electrodeposition method was then used to grow Ni and Ni 80 Fe 20 nanowires. Transport characterization and isothermal magnetization measurements performed on the produced arrays are presented.

Nonlinear wave effects of curvature solitons in surface layers of high-purity aluminum polycrystals under severe plastic deformation. II. The role of boundary conditions, interfaces, and nonequilibrium of a deformed state

Mechanisms of alternating severe plastic deformation at mesoscale levels of high-purity thin aluminum foils were investigated. Polycrystalline foils of varying thickness were glued to more rigid commercial titanium or aluminum substrates and the resulting two-layer specimens were then subjected to alternating bending. This provided a marked difference in boundary conditions between the front and back sides of the foils and enabled a crucial role of the combined effect of normal tensile and compressive stresses on the development of plastic deformation of the test materials to be demonstrated. The examined mechanisms of localized plastic deformation and its self-organization at mesoscale levels are controlled by the field of maximum tangential stresses and resulting rotational deformation modes. Free foil surfaces undergoing severe plastic deformation exhibit porosity strongly dependent on the foil thickness. No porosity is observed on back sides of all examined foils. Very thin slip and tweed structures seen in thin foils are attributed to “chessboard-like” distribution of tensile and compressive stresses over internal interfaces. The influence of the extent of nonequilibrium of the state of materials subjected to severe plastic deformation on the mechanisms of deformation involved is interpreted in terms of the nonequilibrium thermodynamics of local structural phase transformations in zones of hydrostatic tension.

On the need for quality assurance in superficial kilovoltage radiotherapy

External auditing of beam output and energy qualities of four therapeutic X-ray machines were performed in three radiation oncology centres in northeastern Brazil. The output and half-value layers (HVLs) were determined using a parallel-plate ionisation chamber and high-purity aluminium foils, respectively. The obtained values of absorbed dose to water and energy qualities were compared with those obtained by the respective institutions. The impact on the prescribed dose was analysed by determining the half-value depth (D(1/2)). The beam outputs presented percent differences ranging from -13 to +25%. The ratio between the HVL in use by the institution and the measurements obtained in this study ranged from 0.75 to 2.33. Such deviations in HVL result in percent differences in dose at D(1/2) ranging from -52 to +8%. It was concluded that dosimetric quality audit programmes in radiation therapy should be expanded to include dermatological radiation therapy and such audits should include HVL verification.

Fabrication of copper micro-tubes by electroless deposition with an etched porous aluminum template without using sensitization and activation

Cu micro-tubes were fabricated by electroless deposition in an etched porous aluminum membrane without sensitization and activation. The aluminum membrane having square holes was prepared from a high-purity aluminum foil electrochemically. The aluminum reduced Cu 2+ into Cu and the formed Cu nuclei served as the catalyst for the further reduction of Cu 2+. The auto-catalysis substituted the preparation of a novel metal catalyst through sensitization or activation and greatly simplified the deposition process. A two-step operation was developed to improve the deposition of copper, which enhanced the deposition reaction inside the micro-pores. With the help of the membrane, Cu micro-tubes with an outer diameter of about 1–2 μm and a wall thickness in the order of tens to several hundreds nanometers were obtained. The surface-deposited copper layer served as a substrate for the copper micro-tubes, and as the result the resulted material possessed strong mechanical strength as well as high surface area.

Influence of impurity hydrogen on coarse grain evolution in high purity aluminum foils for electrolytic capacitors

Two aluminum plates with 99.99 mass% purity with different hydrogen contents of 0.17 and 0.41 mass ppm were hot-rolled to 10 mm in thickness, cold-rolled by 99% to 130 μm in thickness, annealed at 250°C for 2 h, cold-rolled by 15% to 110 μm in thickness and finally annealed, which is similar to commercial processes of high purity aluminum foils for electrolytic capacitors. The foils were subjected to optical macro- and micro-scopies, thermal desorption spectroscopy (TDS), hydrogen micro-print technique (HMPT) and electron back-scattering diffraction pattern (EBSP) analysis and the effect of impurity hydrogen on the growth of off-cube grains in a recrystallized microstructure with a strong cube texture was investigated. It was confirmed that abnormal grain growth of off-cube grains becomes more conspicuous with the increase in the amount of impurity hydrogen in the original ingot. The HMPT analysis showed that hydrogen concentration in the cube-oriented region was larger than in the off-cube grain. The grain size in the cube-oriented region decreased with decreasing hydrogen content. From these facts and the result of TDS, supersaturated hydrogen atoms were presumed to segregate to low angle grain boundaries, the boundaries between cube-oriented grains, which can provide the driving force for the abnormal grain growth.

Windows for small-angle X-ray scattering cryostats

To determine the suitability of commonly used windows for small-angle X-ray scattering, a range of materials, including Kapton, (aluminized) Mylar, beryllium, high-purity aluminium foil, mica and silicon nitride have been studied. At small wavevector transfers, Q, in the range 2 x 10(-3) to 0.2 nm(-1), the scattering from Kapton, mica and beryllium is reasonably well described by power laws in Q with exponents of -3.25, -3.6 and -3.9, respectively. There are large variations in the scattering from mica, but a freshly cleaved natural mica window was by far the weakest scatterer. For applications where radiation in the infrared or visible range should be blocked, aluminized Mylar is the most suitable material. Both Mylar and Kapton can be used to make very simple demountable superfluid-tight windows using indium O-ring seals.

One-step anodization fabrication and morphology characterization of porous AAO with ideal nanopore arrays

A fabrication method for one-step anodization of an anodic aluminum oxide (AAO) template with nanopore arrays using pretreated high purity aluminum foil is reported in this article. Morphology of the AAO was characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). Results showed that porous AAO with ideal nanopore arrays can be fabricated by one-step anodization fabrication technology on high purity aluminum foil which had been anodized at 45 V direct current (DC), in 0°C, 0.5 M H2C2O4 solution for 48 hours. The average pore diameter and the interpore distance were 80 nm and 120 nm, respectively. Nanopores in porous AAO had very narrow size distribution and were arranged into hexagonal array. The formation mechanism of nanopore arrays in porous AAO is discussed. Porous AAO with ideal nanopore arrays provide an ideal template for preparation of many one-dimensional nanomaterials. One-step anodization of AAO is a simpler procedure and more applicable in industrial application than the previous two-step anodization technology.

Synthesis of palladium nanowire arrays with controlled diameter and length

Ordered palladium nanowire (NW) arrays with high aspect ratio have been synthesized using porous alumina templates and direct-current electrodeposition. The porous alumina films were prepared by double anodizing high purity aluminium foils in oxalic and sulphuric acids at 40 and 25 V, respectively. Final pore size of the processed (free-standing) alumina templates were determined to be ∼65 and 35 nm. The electrolyte consisted of 70 mM K 2PdCl 4 in 20 mM H 2SO 4 and the deposition voltage was 0.3 V (versus Ag/AgCl reference electrode). Under the employed conditions, a high filling rate (>90%) was obtained using 65 μm thick templates. The NWs synthesized in 65 nm pores were polycrystalline and textured, but those in 35 nm pores were single-crystalline. It is suggested that deposition in smaller pores proceeds under smaller overpotential due to diffusion-limitation which favors single-crystalline growth. In order to obtain self-standing Pd NWs, which may be interesting for realizing NW-array based gas sensor structures, the alumina template was dissolved away, leaving self-standing NWs supported on a conductive thin film. Such NWs were observed to form agglomerates and chemisorb O and C as surface impurities.