Thin Aluminum Foil Research Articles

Compression of crumpled aluminum thin foils and comparison with other cellular materials

The elasto-plastic behavior of aluminum crumpled thin foils was characterized in close die and uniaxial compressions within a wide range of relative density with different initial sizes of sheet. The experiments highlight that crumpled materials can present a hybrid behavior between foams and entangled materials with an auxetic behavior up to a relative density of 15%.

Growth time performance dependence of vertically aligned carbon nanotube supercapacitors grown on aluminum substrates

Vertically aligned carbon nanotubes (VACNTs) present a uniform pore size as compared to activated carbon or nonaligned carbon nanotubes, increasing the available surface area for electric double layer formation. In this study, we fabricate VACNTs grown directly on thin aluminum foils using only conductive support layers in a scalable, low-pressure chemical vapor deposition (LPCVD) process. These highly flexible and conductive electrodes were optimized by utilizing combinations of diffusion barrier layers and catalyst support layers to alter the electrode porosity and available surface area. Specific capacitances for five growth times (5, 10, 15, 20 and 25min) were measured to be 30–79Fg−1 and compare favorably to similar studies. Power densities for all supercapacitor sheets exceeded 3MWkg−1 and consistently exceeded other VACNT supercapacitor studies. Our study demonstrates the benefits and applicability of fabricating VACNTs on metal substrates using scalable techniques for flexible and conductive supercapacitors.

Thermal Performance of a Novel Flat Heat Pipe with Integral Micro-Grooved Wick for Energy Saving

A novel flat heat pipe is put forward. The novel flat heat pipe is characteristic of its integral wick structure of microgrooves, which is made of a series of thin aluminum foils folded side by side. The thermal performance of the novel flat heat pipe under the different heat loads and incline angles has been investigated experimentally. It is found that the equivalent thermal conductivity of the novel flat heat pipe can be 12.3 times higher than that of the heat pipe material. Moreover, the novel flat heat pipe with integral micro-grooved wick has good temperature uniformity. The novel flat heat pipe can play a pronounced role in heat transfer enhancement, and be expected to be good candidates for thermal management of electronic devices.

Thomson backscattering from laser-generated, relativistically moving high-density electron layers

We show experimentally that extreme ultraviolet radiation is produced when a laser pulse is Thomson backscattered from sheets of relativistic electrons that are formed at the rear surface of a foil irradiated on its front side with a high-intensity laser. An all-optical setup is realized using the Jena titanium:sapphire ten-terawatt laser system with an enhanced amplified spontaneous emission background of 10−12. The main pulse is split into two: one of them accelerates electrons from thin aluminium foil targets to energies of the order of some MeV and the other, counterpropagating probe pulse Thomson-backscatters off these electrons when they exit the target rear side. The process produced photons within a wide spectral range of some tens of eV as a result of the broad electron energy distribution. The highest scattering intensity is observed when the probe pulse arrives at the target rear surface 100 fs after irradiation of the target front side by the pump pulse, corresponding to the maximum flux of hot electrons at the interaction region. These results can provide time-resolved information about the evolution of the rear-surface electron sheath and hence about the dynamics of the electric fields responsible for the acceleration of ions from the rear surface of thin, laser-irradiated foils.

Stability limits of laser drilled hole arrays on large areas

Large area microdrilling utilizing short pulsed solid state lasers is a promising manufacturing technique for filtration technology. High degree of perforation and high quality of the drilled hole arrays regarding roundness and diameter variation of holes are the main challenges. The goal is to achieve a high degree of perforation with a high number of round holes on a constant pitch. The resulting variation of hole roundness and mechanical stability limitations of the percussion drilled foil using a ns pulsed laser source with a wavelength of 355 nm when drilling a 50 µm thin aluminum foil are presented here. Different drilling strategies are investigated in relation to roundness, hole diameter, and heat propagation. The quality of drilled holes decreases with decreasing pitch and hole diameter. This can be related to thermal effects and pointing stability of the laser beam. Both effects are directional in the setup used here and can, therefore, be superposed positively or negatively. Due to adapted superposition of the effects, the roundness of the holes can be maximized.

Measuring the absolute decay probability of82Sr by ion implantation

We have developed a method of implanted ion counting in order to determine the absolute decay probability of the 776.5 keV $\ensuremath{\gamma}$-ray transition in the decay sequence of ${}^{82}$Sr${\ensuremath{\rightarrow}}^{82}$Rb${\ensuremath{\rightarrow}}^{82}$Kr. A 215 MeV beam of ${}^{82}$Sr was produced at the Holifield Radioactive Ion Beam Facility and passed through an ionization chamber that counted and identified the ions before they were implanted into thin aluminum foils. Subsequent offline measurements using a Ge detector deduced the probability per decay of ${}^{82}$Rb for the 776.5 keV $\ensuremath{\gamma}$ ray in ${}^{82}$Kr to be 0.1493(37), in agreement with the accepted average value of 0.1508(16). This new technique measures directly the number of decaying nuclei in a given sample and significantly reduces the dependence on knowledge of the complete decay level scheme.

Method of Measuring Modulation Transfer Function in Computed Tomography Using Slit Method with Air Gap Phantom

There are several methods for measuring modulation transfer function (MTF) in computed tomography (CT) images. The aluminum slit method, scanning a phantom consisting of a thin aluminum foil sandwiched by flat plastic slabs, is a standard method for measuring field of view (FOV) in clinical CT scan. But this method requires extreme caution when handling metal foil of high precision. Therefore, we devised a more simple method named air gap slit (AS) method. This new technique is based on the aluminum slit method but use air gap instead of metal foil between phantoms. The MTF was calculated from a reversed profile curve of air slit which indicated minimum CT number. The aim of this study was to investigate a possibility of AS method evaluating MTF. We investigated fluctuation of MTF and FOV in clinical CT scan compared with the aluminum slit method. The result showed that the fluctuation of MTF was caused by statistics noise and is more affected by a bone kernel than standard kernel when reconstructing. Also, the MTF value in AS method was slightly higher than in aluminum slit method and did not correspond with. AS method is a useful method for measurement of MTF in clinical CT scan. When we use this method, we have to take into consideration the noise influence of data.

A Study of Closure of Tympanic Membrane Perforations by Chemical Cauterisation

To study the effectiveness of chemical cautery with patching on chronic tympanic membrane perforations of the pars tensa. Thirty-eight patients with dry tympanic membrane perforations due to inflammatory or traumatic etiology were selected after treating the primary etiological factors like septal deviation and allergic rhinitis. Fifty percentage silver nitrate was used to cauterize the margin and the perforation was covered with thin sterile aluminium foil as a patch. A maximum number of five applications were made, and the patients were followed up for the next 5years. In this series of 38 patients, highest success was noted among those patients with traumatic perforation, while larger perforations were reduced to small pinhole sizes which were successfully closed by myringoplasty. An overall success rate of 73.75% was achieved. This is a time tested useful method which was popularized by Derlacki (1953), to close small to moderate sized tympanic membrane perforation and should be considered as a first line management in the treatment of tympanic membrane perforation prior to any surgical intervention. Apart from being a simple and economical mode of treatment, it is associated with minimal complications. Though various materials have been used to modify this technique, the principle remains the same and the results obtained in this study is comparable with the previous ones.

Microcutting and Forming of Thin Aluminium Foils for MEMS

This paper presents a simple procedure for simultaneous cutting and forming of thin Al foils for use in MEMS components. The procedure makes use of scaled down macroscopic sheet forming and cutting techniques by using a hydraulic press, a soft counterpart, and a microfabricated stamp tool. The relation between applied pressure and forming and cutting features has been characterized for a specific set of stamp geometries and boundary conditions. The results show that 10 μm forming features can be transferred to 4 μm thick Al foils, which simultaneously can be cut into products by 25 μm wide cut lines. Using the procedure presented in this paper scaled to full 4–8 in. silicon wafer stamp tools, a fast and adequate method for high volume production of MEMS components is obtained.

Sub-surface fracture of a thin metallic foil under impact loading

We examine here sub-surface fracture of a thin metallic foil sandwiched between two elastomeric layers under impact. In particular we generate a vertical stack consisting of alternate layers of soft elastomers and thin aluminum foils and place it on a rigid substrate; we then allow a rigid sphere to impact the stack from a small vertical height. We show that under impact the foil at the top of the stack undergoes buckling deformation; however the foil sandwiched between the two elastic layers undergoes both deformation and fracture. We show that because of friction at the contacting interfaces with the elastomer, the sandwiched foil is subjected to in-plane stretching which when exceeds a threshold limit causes fracture. Experiments show that this threshold condition is reached within a range of critical thicknesses of the top and bottom elastomeric layers, for a given height of impact of the rigid spherical indenter. We present a theoretical analysis to predict the critical thickness of the stack below which the foil is expected to undergo fracture and also the critical heights within this stack at which the foil would fracture.

Visualization of Pressure Field over Rotating Blades Using Pressure Sensitive Foil Technique

This paper describes a new pressure measurement technique for measuring the pressure over rotating blades of an industrial axial flow fan. The new technique is called the pressure sensitive foil (PS-Foil) technique. In this technique, a very thin aluminum foil is coated with pressure sensitive paint using anodization. The resulting PS-Foil can be stuck on any blade using a very thin layer of silicon. The PS-Foil technique shows a very fast time response like conventional porous anodized aluminum and can be applied to any rotor blade without fabricating the blade from aluminum. The total thickness of the aluminum foil and silicon layer is as small as 200 μm. An intensity based method and prior calibration procedures are used to obtain the calibrated PSP image. The unsteady experimental setup presented here shows that the PS-Foil time response is on the order 30 μs which is close to the conventional porous anodized aluminum method. Two applications are considered here to assess the applicability of this technique. Subsonic jet-plate impingement, and rotating blade of industrial fan. The pressure distribution over the impingement plate at different plate angles, and over the rotating blade at various speeds could be obtained with sufficient spatial resolution.

Surface area analysis in edentulous jaws of patients with skeletal class I

Introduction. The surface area of edentulous jaw has been considered as an important functional and anthropometric parameter. The aim of this study was to assess the surface area of supporting tissue in edentulous jaws of patients with the skeletal class I. Material and Methods. Thin aluminum foils (0.5 mm of thickness) were adapted on plaster surfaces of 139 pairs of edentulous jaws casts. Foils were positioned on a millimeter-paper in order to measure their areas. Additionally, surface areas were measured using a mechanic plan-meter (G. Coradi, Zurich, Switzerland, serial no. 49823). The measurement error was 1%. Skeletal class of edentulous jaws was determined by analysis of lateral cephalometric radiographs, and assessing the ANB (SNA, SNB) angle. Results. The average surface area of edentulous upper jaws was 4654?407 mm2 in males, and 4212?368 mm2 in females. Edentulous lower jaws had average surface area of 2843?339 mm2 in males, and 2334?295 mm2 in females. Statistically significant difference (p<0.001) was found in comparison of surface areas and dimensions of upper and lower edentulous jaws in male and female. ANB values ranged from 2 to 4 degrees. Conclusion. The surface area is an important parameter in the analysis of edentulous jaws. Edentulous jaws in males had greater surface areas and dimensions as compared to females. Edentulous areas on the right side were not absolutely symmetric to areas on the left side.

Electronic sputtering of Gd 3Ga 5O 12 and Y 3Fe 5O 12 garnets: Yield, stoichiometry and comparison to track formation

The results of present paper have shown that sputtering of yttrium iron garnet (Y 3Fe 5O 12) under swift heavy ions in the electronic energy loss regime is non-stoichiometric. Here we are presenting additional experimental results for gadolinium gallium garnet (Gd 3Ga 5O 12) as target. The irradiations were performed with different ions ( 50Cr (589 MeV), 86Kr (195 MeV) and 181Ta (400 MeV)) impinging perpendicularly to the surface. As earlier, the sputtering yield was determined by collecting the emitted gadolinium and gallium atoms on a thin aluminium foil, placed upstream above the target and analyzing the Al catcher by Rutherford backscattering. Also for Gd 3Ga 5O 12, the emission of Gd and Ga is non-stoichiometric. Sputtering appears above a critical electronic stopping power of S th = 11.6 ± 1.5 keV/nm, which is larger than the threshold for track formation, in agreement with other amorphisable materials. In addition, the angular distribution of the sputtered species was measured for Y 3Fe 5O 12 and Gd 3Ga 5O 12 using 200 MeV Au ions impinging the surface at 20° relatively to the surface. For the two garnets the ratio of Y/Fe (and Gd/Ga) varies with the angle of emitted species and the stoichiometry seems to be preserved only for an emission perpendicular to the surface.

Effect of gallium focused ion beam milling on preparation of aluminium thin foils

Focussed ion beam milling has greatly extended the utility of the atom probe and transmission electron microscope because it enables sample preparation with a level of dimensional control never before possible. Using focussed ion beam it is possible to extract the samples from desired and very specific locations. The artefacts associated with this sample preparation method must also be fully understood. In this work, issues specifically relevant to the focussed ion beam milling of aluminium alloys are presented. After using the focussed ion beam as a sample preparation technique it is evident that gallium will concentrate in three areas of the sample: on the surface, on grain boundaries and at interphase boundaries. This work also shows that low-energy Ar ion nanomilling is potentially quite effective for removing gallium implantation layers and gallium from the internal surfaces of aluminium thin foils.

Comparison between the shock wave and chemical initiation in detonation of acetylene—oxygen mixtures

Detonation of different compositions of acetylene-oxygen mixtures by both chlorine gas injection and a shock wave as initiators is studied in this research. The chlorine gas is injected into the detonation tube through a reticular plate nozzle at the moment when a thin aluminum foil separating the injection system from the detonation tube is torn by a pressurized nitrogen gas. The results of experiments show that chemical initiation may be as effective as direct initiation of detonation and, therefore, replace more complicated methods of initiation. The best results are obtained in acetylene— oxygen mixtures with the molar ratio of 1: 1.

The Role of Alumina in Aluminum Corrosion and Passivation

The self passivation of aluminum in water generally prevents the generation of hydrogen from an aluminum-water reaction in conditions preferred for portable systems. However the corrosion rate of aluminum powders and thin foils is seen to greatly increase when in contact with alumina powder. This allows commercially useful amounts of hydrogen to be generated at moderate temperatures and neutral pH regions. Data is presented to support the claim that proton availability from the alumina surface is responsible for the increased hydrogen evolution rates, and hydrogen capture tests show passivation no longer stops the corrosion reaction.

Nanostructured phase boundaries in aluminum under severe cyclic plastic deformation

The mechanisms of plastic strain observed at high degrees of alternating bending of thin aluminum foils glued to elastically strained substrates have been investigated. As extrusion and intrusion develop on the surface of the aluminum foils, multiscale fragmentation of the structure is found to take place in the bulk of the materials to form nanostructured phase boundaries between subgrains. The width of the phase boundaries varies between 200 and 300 nm, with the size of the structure elements within the subgrain boundaries being 30–50 nm. Formation of the nanostructured phase boundaries between nonequilibrium subgrains is regarded to be the fragmentation mechanism operative at the submicrometer scale level in the foils subjected to bending-torsion at very high degrees of plastic strain.

X-ray characterization of thin foil gold mirrors of a soft X-ray telescope for ASTROSAT

X-ray reflectivity measurements were performed on several thin foil gold mirrors fabricated in TIFR for a Soft X-ray Imaging Telescope. The mirrors were made from thin aluminum foils with a reflecting layer of sputtered gold transferred from a smooth glass mandrel using an epoxy. X-ray reflectivity measurements were performed on a sample of randomly selected mirrors using CuKα (8.05 keV), CrKα (5.41 keV) X-rays and also at several energies in the energy range of 155–300 eV using the synchrotron source Indus-1. It was found that the roughness of the low-density top gold layer as obtained from the fitting of X-ray reflectivity data for CuKα radiation is relatively more as compared to that obtained from the CrKα radiation. This indicates that in the mirrors made by this process, the upper surfaces are smoother as compared to the deeper layers. It was also observed that the critical angle almost vanishes in the very low energy range of 290–300 eV due to strong absorption effects of the low density material sitting on top of these mirrors. Due to this absorption effect, efficiency of these mirrors reduces in this energy range. This is first time that reflectivity measurements are being reported for very soft X-rays (≤ 300 eV) for mirrors made for any X-ray astronomy mission.

Photoacoustic evaluation of the penetration of piroxicam gel applied with phonophoresis into human skin

The photoacoustic (PA) technique has been increasingly employed in biomedical studies, allowing in vivo skin measurements not easily performed with other techniques. It is possible to use PA measurements to evaluate transdermal delivery of products topically applied through manual massage or phonophoresis, that is the utilization of ultrasound waves to enhance drug absorption. The aim of this study was to analyze the influence of the period of phonophoresis application in the transdermal penetration of piroxicam gel. In vivo PA measurements employed a tungsten lamp as light source and a thin aluminum foil closing the PA chamber. The PA signals of the arm (i) clean; and (ii) after phonophoresis were utilized to estimate the concentration of piroxicam into skin. For all (4) volunteers, drug concentration in skin after phonophoresis application was the same for the different application times employed; in this way, phonophoresis for one minute seemed to be sufficient to enhance piroxicam penetration into skin. The actual amount of drug delivered into tissue depends on the person, suggesting a dependency with the skin type, which affects the PA signal level [2]. We conclude that drug delivery depends not only on the application method, but also on the specific skin type.

Single Point Micro Incremental Forming of Miniature Shell Structures

This study focuses on single point micro incremental forming (SPMIF) applied to the forming of miniature shell products in meso-scale. For this study, a desk-top type of CNC forming machine was newly constructed as an experimental apparatus. A thin aluminum foil with a thickness of 12 µm and a thin round-tip bar with a radius of 100 µm were utilized as a blank and a forming tool, respectively. Some fundamental and complex shell structures were formed for investigating the characteristics of the SPMIF process without using any die and backing plate. The analysis of contact region in forming polygonal pyramids confirmed that fracture on an edge of a polygonal pyramid, which determined the forming limit of SPMIF, was strongly affected by the size of re-contact area. Through the SPMIF process established in this study, complex shell structures were accomplished with elaborate tool paths.