Μm Al Foil Research Articles

Revisiting the Anodic Stability of Aluminum Current Collectors in High-Voltage Li-Ion Batteries

High-voltage Li-ion batteries are anticipated to play a crucial role in the present transition towards electric vehicles, owing to their high energy density. However, a big challenge is the anodic stability (often referred to as corrosion) of the positive electrodes current collector, aluminum (Al), at potentials > 3.0 V vs. Li+/Li). In this work, we present a systematic study on the corrosion of 12 µm-thick Al foil (©Gränges, Sweden) up to 5.0 V vs. Li+/Li in a series of carbonate electrolytes containing lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl) imide (LiFSI) or lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salts. The selection of the 12 µm foil was motivated by the need to decrease the mass or volume of the dead weight components (i.e., current collector) to increase the energy density of the battery.The electrochemical behavior was investigated using voltammetric techniques, and the results indicated that the anodic oxidation of the 12 µm Al foil was similar to that of the conventionally used 20 µm-thick Al foil. Notably, the first anodic oxidation scan exhibited a two-step oxidation after 3.5 V vs. Li+/Li, suggesting carbonate solvent oxidation and a liberation of H+ ions attacking the native surface Al2O3 layer followed by oxidation of metallic Al. A passivation was observed on the subsequent scans in 1.0 M LiPF6 solutions due to formation of surface layer of AlF3, as confirmed by X-ray photoelectron spectroscopy (XPS) analyses. [1,2]However, in 1.0 M solutions of the imide salts (i.e., LiFSI or LiTFSI) a continuous anodic oxidation of aluminum was seen between 3.5 and 5.0 V vs. Li+/Li on the first few scans. After this the magnitude of the anodic current decreased significantly. The latter observations can be attributed to formation of soluble Al(TFSI) x or Al(FSI) x complexes [3] and a gradual saturation of the electrolyte. The voltammetric experiments showed that the magnitude of the anodic current increased when increasing the volume of the used imide electrolyte, supporting the saturation hypothesis.Results and analyses regarding the anodic oxidation of Al in a series of carbonate solvents and using different salt concentration, as well as effect of the use of carbon coated Al will also be presented.

Delta Electron Emission Yield of Relativistic Electron Passing Through Thin Aluminum Foils

The results of the experimental research of the δ-electrons yield from the thin aluminum foil are presented. The thickness range of the aluminum foils is \(8 \ldots 100\) µm. The energy of primary electrons varies from 2.5 to 30 MeV. The values of the average cross section for δ-electron production (generation and emission) from aluminum were obtained. It has been established that for 8 µm Al foil it is about \(8.17 \cdot 10^{ - 23}\) cm2. Finally, comparisons of the obtained results with the calculated ones are discussed.

Formation of ordered anodic alumina nanofibers during aluminum anodizing in oxalic acid at high voltage and electrical power

In this study, we modified the synthesis modes of aluminum anodizing in an aqueous solution of oxalic acid and suggested quick, one-step and convenient method for porous alumina surface modification to increase largely its surface area. Anodic alumina nanofibers consisting of pure aluminum oxide were formed by high field anodizing with evolving of Joule heating of aluminum foil of 60 and 100 μm thickness in 0.3 M aqueous solution of oxalic acid. It was shown that nanofibers formed on the surface of the films for an anodizing voltage of 90 V and a power range of 13.5–31.5 W cm−2. The thickness of the Al foil has proved to be responsible for the formation of the alumina nanofibers, which cannot be obtained in the same electrolyte and for similar current densities on 25 μm thick aluminum foil. We could show that during anodizing of 60 μm thick Al foil, regardless of anodic current density value, alumina nanofibers uniformly covered the entire surface of the films. However, during 100 μm Al foil anodizing, the pores were etched and the nanofibers partially dissolved and separated from the surface with increasing anodizing current density. Auger electron spectroscopy measurements showed that porous anodic alumina containing carbon impurities was obtained during anodizing of the 25 μm Al foil. Alternatively, the surface of the nanofibers formed on 60 and 100 μm Al foil consisted of pure alumina.

Recent measurements of soft X-ray emission from the DPF-1000U facility

Abstract Soft X-ray imaging is a very useful diagnostic technique in plasma-focus (PF) experiments. This paper reports results of four experimental sessions which were carried out at the DPF-1000U plasma-focus facility in 2013 and 2014. Over 200 discharges were performed at various experimental conditions. Measurements were taken using two X-ray pinhole cameras with a line of sight perpendicular to the z-axis, at different azimuthal angles (about 20° and 200°), and looking towards the centre of the PF-pinch column. They were equipped with diaphragms 1000 μm or 200–300 μm in diameter and coated with filters of 500 μm Al foil and 10 μm Be foil, respectively. Data on the neutron emission were collected with silver activation counters. For time-resolved measurements the use was made of four PIN diodes equipped with various filters and oriented towards the centre of the PF-column, in the direction perpendicular to the electrode axis. The recorded X-ray images revealed that when the additional gas-puff system is activated during the discharge, the stability of the discharge is improved. The data collected in these experiments confirmed the appearance of a filamentary fine structure in the PF discharges. In the past years the formation of such filaments was observed in many Z-pinch type experiments. Some of the recorded X-ray images have also revealed the appearance of the so-called hot-spots, i.e. small plasma regions of a very intense X-ray emission. Such a phenomenon was observed before in many PF experiments, e.g. in the MAJA-PF device, but it has not been investigated so far in a large facility such as the DPF-1000U. The time-resolved measurements provided the evidence of a time lapse between the X-ray emission from plasma regions located at different distance from the anode surface. The formation of distinct ‘hot-spots’ in different instants of the DPF-1000U discharge was also observed.

Modelling of non-LTE atomic physics processes in hot dense plasmas during the interaction with an intense short pulse laser

The implicit 2D3V particle-in-cell (PIC) code developed to study the interaction of intense lasers with matter (Petrov and Davis 2008 Comput. Phys. Commun. 179 868–80; 2011 Phys. Plasmas 18 073102) has been extended to include atomic physics under extreme energy density conditions. The atomic physics model is applied to aluminium. Each ionization stage contains two levels: one ground and one lumped excited state, for which various atomic physics processes such as optical field ionization, collisional ionization, excitation, de-excitation and radiative decay describe the population density. Two-dimensional PIC simulations have been carried out for laser pulses with peak intensity 1 × 1020 W cm−2, pulse duration 60 fs, spot size 3 µm and energy 0.75 J interacting with ultrathin (0.2 µm) Al foil. Radiation emitted during the laser–target interaction is computed by accounting for both bound–bound transitions and bremsstrahlung radiation. We demonstrate that the radiation signature of laser-produced plasma can be used as a complementary tool to other diagnostic techniques used in laser–plasma interactions. Finally, results from the PIC model are compared to equilibrium calculations (Maxwell–Boltzmann and Saha). In the early stages of laser–plasma interactions (<100 fs) the plasma is far from equilibrium and equilibrium models can not be applied with confidence to model the plasma.

Influence of the soft X-ray plasma focus radiation on live microorganisms

A 3 kJ plasma focus device was used to study the influence of the soft X-ray on live microorganisms. When Saccharomyces cerevisiae – (yeast) was treated with a dose of 65 mSv of the X-ray radiation (14 shots), no difference in the fertility activity between the control probe and the sample was observed. Also no change in the survival enzyme activity was found after irradiation through a 100 μm Al foil of another type of yeast – Kluyveromyces marxiamus. The irradiation of the Chlamydomonas reinhardtii samples by the PF-X-ray emission through 20 μm Al foil with a dose of 11 mSv produces a considerable change of the photosynthesis parameters. This result is similar to the results of previous studies with plasma focus radiation where strong effects were derived with low doses but with a high dose power.

Mechanism of Zn Vapour Suppressed by Al In Laser Lap Welding of High Strength Zinc Coated Sheet Steel

The basic feasibility of laser fusion welding for prefabrication and assembly of zinc-coated sheet steel auto body components has been demonstrated in a significant number of prior studies. For trouble-free high volume manufacturing, however, one leading key technical concern remains incompletely resolved. In lap or similar weld joint geometries, venting of trapped Zn vapour can seriously disturb the molten weld pool and give rise to gross fusion defects. In this paper, the technical status of the issue has been reviewed, and various experiments were planned to explore Al foil as an interlayer and dual beam laser for suppressing Zn vapour. The results have shown that the welding processing is very sTable when the lap 1+1 mm sheet steel is welded by using Nd-Yag laser at 3KW power and 4m/min travel speed (defined as single beam) with 75μm Al foil as interlayer. However, if first using 2KW power and 4m/min travel speed, secondly using 3KW power and4m/min travel speed (defined as dual beam), only 25 μm Al foil can stabilize welding fusion pool. It is found that Al foil just store the Zn vapour in the single beam method and cannot mix with Zn to form Al-Zn binary alloy, because the laser heating is too fast that Zn has been vaporized before Al was melted. But Al can mix with Zn to form Al-Zn binary alloy in the dual beam method, therefore, the boiling temperature is raised to about 1600°C. So that, in laser lap welding of Zn coated (galvanized) sheet steel, the Al-Zn alloy will be more effective than Al metal for stabilizing welding process.

Reversed scheme of thin foil acceleration

An alternative concept for accelerating thin foils to high velocity has been proposed and tested. The thin (10 μm) Al foil has been accelerated by the ablative plasma generated by means of the third harmonic (λ=0.438 μm, τ=250 ps) of the iodine laser pulse of the energies of 75 and 190 J irradiating a massive Cu target. Two separation distances of the foil from the massive target of 100 and 500 μm were used. It has been shown that this method of an indirect, two-step acceleration, named as the reversed acceleration scheme, can be more effective than the classic, direct-drive approach. The Al flyer foil has reached a velocity of ∼1.3×107 cm/s, i.e., significantly higher than that in the comparable “classic” ablative acceleration experiment.

Structural changes in helium implanted Zr0.8Y0.2O1.9 single crystals characterized by atomic force microscopy and EXAFS spectroscopy

The present work is devoted to investigate the local atomic environment (of Zr, Y and O) as well as surface modifications associated with excess helium in the cubic phase of (100)-oriented Zr0.8Y0.2O1.9 single crystal substrates. Commercially available oxide crystals have been implanted at various fluences in the range 0.15–2.0×1016 He-atoms/cm2 using a 2.74MeV He+ ion beam passing through a 8.0μm Al foil. The microstructure and surface morphology of the irradiated surface are examined using atomic force microscopy (AFM). The local atomic environments of Zr, Y and O in the implanted layer are studied using synchrotron radiation and by extended X-ray absorption fine structure (EXAFS) measured at glancing angles to probe the implanted layer. From AFM studies it was observed that the surface roughness increases as fluence increases and above a critical fluence stage, small blister-like structures originating from helium bubbles are scattered on the irradiated surface. The radial distribution functions (RDFs), derived from EXAFS data at the Zr K-edge, have been found to evolve continuously as a function of ion fluence describing the atomic scale structural modifications in YSZ by helium implantation. From the pristine data, long range order (beyond the first- and second-shell) is apparent in the RDF spectrum. It shows several nearest neighbour peaks at about 2.1, 3.6, 4.3 and 5.4Å. In the implanted specimens, all these peaks are greatly reduced in magnitude and their average positions are changed, typical of damaged material. A simple model taking into account only the existence of lattice vacancies has been used for the interpretation of measured EXAFS spectra.

Damage evolution and surface morphology of helium implanted yttria-stabilized zirconia single crystal

The effects of helium ion implantation on the surface morphology of (1 0 0)-oriented yttria-stabilized zirconia (YSZ) single crystals have been studied. Ion implantation at various fluences in the range 0.01–5.1 × 10 16 He-atoms/cm 2 has been carried out at room temperature using a 2.74 MeV He + ion beam passing through a 8.0 μm Al foil. The microstructure and surface morphology of the irradiated surface are examined using atomic force microscopy. Rutherford backscattering spectrometry combined with the channeling technique is applied for the investigation of lattice damage and for the thickness determination of the implanted layer. The ion-irradiated areas are found to protrude to different heights in nm scale. The fluence dependence of the magnitude of rms roughness exhibits a very sharp increase with the increase of the ion dose at higher fluences and in a narrow range between 2 × 10 16 and 5.1 × 10 16 cm −2, which is preceded by a linear increase at lower fluences. Given a sufficient concentration for implanted He, above 2 × 10 16 cm −2, surface blistering occurs directly during implantation. The size and distribution of blisters are dependent on the total helium content. For the specimen with a fluence 4.0 × 10 16 cm −2, an annealing has been conducted at 300 °C. After the annealing, some of the blisters are found to become larger in size, up to about 10 μm in diameter and 1 μm in height without rupture. Within the present experimental conditions, no signature of any surface exfoliation or flaking in YSZ is observed. A tentative explanation of the results is presented.

Superconducting UCN Polarizer for a New EDM Spectrometer.

A test experiment has shown that the number of ultracold neutrons (UCN) of one polarization state, transmitted through a 100 μm Al foil when placed in a 5 T magnetic field, is greater by 3.8 times. The increased transmission is due to the higher velocity of the UCN passing through the foil.

Superconducting UCN polarizer for a new EDM spectrometer

A test experiment has shown that the number of ultra cold neutrons (UCN) of one polarization transmitted through a 100 μm Al foil when placed in a 5 T magnetic field is greater by 3.8 times. The increased transmission is due to a higher velocity of the UCN passing through the foil.

Anormal growth of cavities in MeV He implanted Si covered with a thin Al foil

Cavities were created by MeV He implantation in silicon through a 1.5 μm Al foil. After a 800 °C-annealing, unexpected growth mechanism was found: a non-uniform layer of cavities with a distribution where bigger cavities are surrounded by smaller ones. Neither Oswald ripening nor migration-coalescence mechanisms can be applied to describe the growth of these cavities. The role of dislocations seem to be important in that distribution. Indeed some cavities seem to be trapped by dislocations. However the motion of the helium does not appear to be the origin of that anormal growth mechanism.

Extreme ultraviolet probing of laser imprint in a thin foil using an x-ray laser backlighter

For direct drive inertial confinement fusion, a capsule is imploded by directly illuminating the surface with laser light. Beam smoothing and uniformity of illumination affect the seeding of instabilities at the ablation front. We have developed a technique for studying the imprint of a laser beam on a thin foil using an x-ray laser as an extreme ultraviolet (XUV) backlighter. We use multilayer XUV optics to relay the x-ray laser onto the directly driven foil, and then to image the foil modulation onto a charged coupled device camera. This technique allows us to measure small fractional variations in the foil thickness. We have measured the modulation due to imprint from a low intensity 0.35 μm drive beam incident on a 3 μm Si foil using an yttrium x-ray laser on Nova. We present results from a similar technique to measure the imprinted modulation due to a low intensity 0.53 μm drive beam incident on a 2 μm Al foil using a germanium x-ray laser at the Vulcan facility.

Performance of thin foil scintillating screen for transmission electron microscopy

Scintillating screens made by coating a thin metal foil with a layer of phosphor appear to be attractive for transmission electron microscopy applications. We report here the brightness and resolution in the voltage range of 100–400 kV of such a screen made of a 10 μm layer of P20 phosphor on a 2 μm Al foil. Both brightness and resolution are superior to that of a screen made by coating a glass plate with a similar layer of phosphor. An exciting property of such a device is that its resolution improves slightly at higher voltages. This, combined with its excellent resistivity to radiation damage and stability under the electron beam, makes it a good candidate for high-voltage applications.

Simultaneous measurement of the hydrogen isotopes H, D, T and 3He with HIERD

The most straightforward method to measure simultaneously the amount and the depth distribution of different light atoms trapped in the surface layers of a solid, such as needed in investigations of the plasma-wall interaction in controlled thermonuclear fusion research, is the heavy ion elastic recoil detection (HIERD) technique. This technique has been applied using 30 MeV 35Cl ions to measure the light ions collected in a Ti target and in C targets. The recoiled atoms have been identified and detected by a ΔE − E telescope consisting of a 14 μm transmission detector and a SSB detector with a 12 μm Al foil at the entrance to stop all heavy ions. The hydrogen and helium isotopes are clearly identified. The sensitivity of this technique is the largest for H and decreases proportional to Mr3 i.e. proportional to 8 and 27 for the two heavier hydrogen isotopes, while the depth resolution is the best for tritium. Recoils heavier than He up to sodium are simultaneously detected by a Bragg ionization chamber.

High-performance transmission scintillating screen for TEM

A scintillating screen is an indispensable component of a slow-scan CCD (charge-coupled-device) camera system for transmission electron microscopy. Its performance is therefore of great concern because of its influence on the overall performance of the system. Screens produced by deposition of phosphor on a thin metal foil appear to be attractive particularly for intermediateand high voltage applications. The metal foil serves three purposes: (1) support for the phosphor; (2) charge conductor; and (3) light reflector. Vacuum deposited, thin aluminum foils serve these purposes well. We report here briefly the brightness and resolution of a scintillating screen composed of a 10 μm layer of P20 phosphor deposited on 2 μm Al foil. More detailed characterization of the screen can be found elsewhere. Results are compared to that of a screen made by depositing a similar layer of phosphor onto a glass plate, and that of a 0.5 mm YAG screen.Fig. 1 illustrates schematically the structure of the aluminum screen.

Fission fragment energy spectrum determination with solid state nuclear track detectors

Attempts are described to optimize the spectrometric response of a number of solid state nuclear track detectors (SSNTD), including fused silica, soda-lime glass and phosphate glass. Diameters of the etch pits resulting from normally incident beams of fission fragments from a 252Cf source in vacuum have been measured, by both optical and scanning-electron microscopy, as functions of the period of etching and of the thickness of Al absorber introduced in the path of the beam. The best resolution of the heavy and light fission fragment groups, as inferred from the diameter distributions, is obtained with phosphate glass SSTND covered with ≈5 μm Al foil during irradiation.