Recent progress in the research on magnesium and magnesium alloy foils:A short review

Magnesium and magnesium alloy foils have great potential for application in battery anodes,electromagnetic shielding,optics and acoustics,and biology because of their excellent specific damping,internal dissipation coefficients,magnetic and electrical conductivities,as well as high theoretical specific capacity.However,magnesium alloys exhibit poor deformation ability due to their hexagonal close-packed crystal structure.Preparing magnesium and magnesium alloy foils with thicknesses of less than 0.1 mm is difficult because of surface oxidation and grain growth at high temperatures or severe anisotropy after cold rolling that leads to cracks.Numerous methods have been applied to prepare magnesium alloy foils.They include warm rolling,cold rolling,accumulative roll bonding,electric plastic rolling,and on-line heating rolling.Defects of magnesium and magnesium alloy foils during preparation,such as edge cracks and breakage,are important factors for consideration.Herein,the current status of the research on magnesium and magnesium alloy foils is summarized from the aspects of foil preparation,defect control,performance characterization,and application prospects.The advantages and disadvantages of different preparation methods and defect(edge cracks and breakage)mechanisms in the preparation of foils are identified.

Purification of copper foils driven by single crystallization

High-purity copper(Cu) with excellent thermal and electrical conductivity, is crucial in modern technological applications, including heat exchangers, integrated circuits, and superconducting magnets. The current purification process is mainly based on the zone/electrolytic refining or anion exchange, however, which excessively relies on specific integrated equipment with ultra-high vacuum or chemical solution environment, and is also bothered by external contaminants and energy consumption. Here we report a simple approach to purify the Cu foils from 99.9%(3N) to 99.99%(4N) by a temperature-gradient thermal annealing technique, accompanied by the kinetic evolution of single crystallization of Cu.The success of purification mainly relies on(i) the segregation of elements with low effective distribution coefficient driven by grain-boundary movements and(ii) the high-temperature evaporation of elements with high saturated vapor pressure.The purified Cu foils display higher flexibility(elongation of 70%) and electrical conductivity(104% IACS) than that of the original commercial rolled Cu foils(elongation of 10%, electrical conductivity of ~ 100% IACS). Our results provide an effective strategy to optimize the as-produced metal medium, and therefore will facilitate the potential applications of Cu foils in precision electronic products and high-frequency printed circuit boards.

Methods of controlled formation of instabilities during the electrical explosion of thin foils

The results of a study of the electrical explosion of aluminum foils with an artificial periodic surface structure created by laser engraving are presented.Experiments were carried out on pulsed high-current generators BIN(270 kA,300 kV,100 ns)and KING(200 kA,40 kV,200 ns)with Al foil of thicknesses 16 and 4μm,respectively.Images of the exploded foils were recorded by point projection radiography in the radiation from hybrid X-pinches.It is found that the application of an artificial periodic structure to the foil leads to a much more uniform and well-defined periodic structure of the exploded foil.Images recorded in the UV range using a microchannel-plate-intensified detector show that the radiation from a surface-modified foil is more uniform along the entire length and width of the foil than that from a foil without modification.

Optimized growth and dielectric properties of barium titanate thin films on polycrystalline Ni foils

Barium titanate（BTO） thin films were deposited on polycrystalline Ni foils by using the polymer assisted deposition（PAD） technique.The growth conditions including ambient and annealing temperatures were carefully optimized based on thermal dynamic analysis to control the oxidation processing and interdiffusion.Crystal structures,surface morphologies,and dielectric performance were examined and compared for BTO thin films annealed under different temperatures.Correlations between the fabrication conditions,microstructures,and dielectric properties were discussed.BTO thin films fabricated under the optimized conditions show good crystalline structure and promising dielectric properties with εr～ 400 and tan δ 〈 0.025 at 100 kHz.The data demonstrate that BTO films grown on polycrystalline Ni substrates by PAD are promising in device applications.

Experimental Investigation on Micro Deep Drawing of Stainless Steel Foils with Different Microstructural Characteristics

In the present work,austenitic stainless steel(ASS)304 foils with a thickness of 50μm were first annealed at temperatures ranging from 700 to 1100℃for 1 h to obtain different microstructural characteristics.Then the effects of microstructural characteristics on the formability of ASS 304 foils and the quality of drawn cups using micro deep drawing(MDD)were studied,and the mechanism involved was discussed.The results show that the as-received ASS 304 foil has a poor formability and cannot be used to form a cup using MDD.Serious wrinkling problem occurs on the drawn cup,and the height profile distribution on the mouth and the symmetry of the drawn cup is quite non-uniform when the annealing temperature is 700℃.At annealing temperatures of 900 and 950℃,the drawn cups are both characterized with very few wrinkles,and the distribution of height profile,symmetry and mouth thickness are uniform on the mouths of the drawn cups.The wrinkling becomes increasingly significant with a further increase of annealing temperature from 950 to 1100℃.The optimal annealing temperatures obtained in this study are 900 and 950℃for reducing the generation of wrinkling,and therefore improving the quality of drawn cups.With non-optimized microstructure,the distribution of the compressive stress in the circumferential direction of the drawn foils becomes inhomogeneous,which is thought to be the cause of the occurrence of localized deformation till wrinkling during MDD.

Preparation and Characterization of Mesoporous Al-MCM-41 Layers Deposited on FeCrAl Metallic Foils by an In-situ Hydrothermal Method

A new class of activated mesoporous Al-MCM-41 layers was deposited on Fe-CrAl metallic foils in the presence of cationic surfactant cetyltrimethylammonium bromide under basic conditions by an in-situ hydrothermal method. The characterization techniques including X-ray diffraction, nitrogen adsorption and transmission electron microscopy, as well as field-emission scanning electron microscopy were performed to investigate the pore structure and surface morphology of the Al-MCM-41 layers. The Al-MCM-41 materials are of amorphous structure but exhibit large BET surface area （up to 757.0 m2/g） and pore volume （up to 0.72 cm3/g）, as well as a mean pore diameter of 3 nm. The layers deposited on the FeCrAl foils are continuous despite with a few of holes on the surface.

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces fabricated by double rolling

Copper foils with gradient structure in thickness direction and different roughnesses on two surfaces were fabricated by double rolling. The two surface morphologies of double-rolled copper foils are quite different, and the surface roughness values are 61 and 1095 nm, respectively. The roughness value of matt surface can meet the requirement for bonding the resin matrix with copper foils used for flexible printed circuit boards, thus may omit traditional roughening treatment; the microstructure of double-rolled copper foils demonstrates an obviously asymmetric gradient feature. From bright surface to matt surface in thickness direction, the average grain size first increases from 2.3 to 7.4 μm and then decreases to 3.6 μm; compared with conventional rolled copper foils, the double-rolled copper foils exhibit a remarkably increased bending fatigue life, and the increased range is about 16.2%.

Response of structural and magnetic properties of ultra-thin FeCo–V foils to high-energy beam welding processes

Microstructural evolutions and grain-boundary-character distribution during high-energy-beam welding of ultra-thin Fe Co-V foils were studied. Detailed data about the boundaries, coincidence site lattice（CSL） relationships, grain sizes, and microstructural features were acquired from electron-backscatter diffraction（EBSD） maps. Moreover, the evolution of the magnetic properties during high-energy-beam welding was studied using vibrating sample magnetometry（VSM）. The fraction of low-angle boundaries was observed to increase in the fusion zones of both electron- and laser-beam-welded foils. The results showed that the fractions of low-Σ CSL boundaries（particularly twin boundaries, Σ3） in the fusion zones of the welded foils are higher than those in the base metal. Because the strain rates produced during high-energy-beam welding are very high（because of the extremely high cooling rate）, grain deformation by a slip mechanism is limited; therefore, deformation by grain twinning is dominant. VSM analysis showed that the magnetic properties of the welded foils, i.e., their remanence, coercive force, and energy product, changed significantly. The formation of large grains with preferred orientation parallel to the easy axis of magnetization was the main reason for the diminished magnetic properties.

Effect of Treatment Temperature on Iron Nitride Foils Irradiated with Nitrogen Plasma

We investigated the effect of treatment temperature on the magnetic property of iron nitride foils irradiated with nitrogen plasma. The iron nitride foils irradiated with nitrogen plasma were composed of ε-Fe2/3N, γ'-Fe4N and γ nitrogen austenite in α-Fe of the matrix. The saturation magnetization of the iron nitride foils decreased with increasing the surface temperature. The coercive force of the iron nitride foils increased with increasing the surface temperature.

Explosion dynamics of thin flat foils at high current density

This paper presents characteristic features of the explosion of thin flat foils for currents and pulse risetimes ranging from 8 kA at 350 ns to1000 kA at ∼100 ns. Foils made of aluminum, copper, nickel, and titanium with thicknesses of 1–100 μm are tested. Various diagnostics inthe optical, UV, and x-ray spectral ranges are used to image the exploding foils from initial breakdown to complete destruction or pinching.It is shown that foil explosion is a complex process that depends on many factors, but features common to all foils are found that do notdepend on the parameters of the generators or, accordingly, on the energy deposited in the foil: for example, the breakdown of flat foils underdifferent conditions occurs at the edges of the foil. For the first time, the formation of a precursor over the central part of the foil is shown,which significantly changes the dynamics of the foil explosion.

Evolution of recrystallization textures in high voltage aluminum capacitor foils

The evolution of recrystallization textures in high voltage aluminum capacitor foils which are produced with a high level of cold reduction was tracked by analysis of microstructure and crystallographic texture. The results show that the deformation textures are mainly composed of S orientation, Cu orientation and a little B s orientation. During the low temperature stages of final annealing, the iron precipitates first along the sub grain boundaries, and the Fe concentration in the matrix becomes low. Then, the cube grains nucleate preferably into the sub grains. At high temperature stages, the cube nuclei can grow preferably because of their 40°<111> orientation relationship to the S orientation, the main component of the rolling texture. Finally, the cube texture is sharply strong and the R orientation is very weak in the foils.

Numerical Study of Mechanisms of the Vortex Formation in the Wake of Dual-Flapping Foils

The vortex formation and organization are the key to understand the intrinsic mechanism in flying and swimming in nature. The vortex wake of dual-flapping foils is numerically investigated using the immersed boundary method. Beside the deflection of the reversed von-Kármán vortex street, an interesting phenomenon, the deflection of the von-Kármán vortex street, is observed behind the dual-flapping foils. The deflected direction is not according to the initial direction of biplane’s flapping motion. And the deflection angle is related to the difference between upward and downward deflecting velocities.

Evolution mechanism of the interfacial reaction layers in the joints of diffusion bonded Mo and Al foils

Mo foil （10 -20 μm in thickness） and Al foil （20 -60 μLm in thickness） were vacuum diffusion bonded at 600 - 640 ~C under 20 MPa for 54 min - 6 h. The joints were examined by scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS） to study the evolution mechanism of the reaction layers. The results show that Al atoms diffuse into Mo grain boundaries and form reaction products as Mo3Al8, MoAl4 , MoAl5 and MoAl12. The surface oxide film is eroded by the growths of the reaction products that plow into the lamellar texture of Mo grain boundaries. Mo3Al8 layer grows by ＂taking root＂ downwards and transforms into MoAl4 and MoAl5 phases upwards by absorbing Al atoms. MoAl12 layer grows up from MoAl5 layer in the same way. When the supplement of Al atoms ceases, MoAl12 transforms reversely into MoAl5 and MoAl5 into MoAl4 via the loss of Al atoms. However, MoAl4 continues to precipitate from Mo3Als layer. At last, there are MoAl4 and Mo3Al8 remained on the joint interface.

Effects of gravity on the electrodeposition and characterization of nickel foils

The effects of gravity on nickel electrodeposition,the morphology and mechanical properties of deposits were studied in a super gravity field.Predictions in a microgravity field were also presented based on the obtained experimental tendency.Linear sweep voltammetry reveals that the nickel electrodeposition process is enhanced by increasing the gravity coefficient（G）.The limiting current density changes from 10.2 to 293.0 mA·cm-2 with the increase of the G value from 10-4 to 354.The morphology of deposits was analyzed by scanning electron microscopy（SEM） and atomic force microscopy（AFM）.The images show that the morphology deposited in the super gravity field has finer grain sizes and denser and smoother surfaces.The roughness reduces from 48.3 to 4.9 nm with the increase of the G value from 10-4 to 354.Meanwhile,mechanical tests indicate that the mechanical properties of nickel foils are greatly improved due to introducing a super gravity field during electrodeposition.

Preparation of Ni-Co Alloy Foils by Electrodeposition

Electrodeposition of Ni-Co alloy foils on titanium substrate was performed in an acid chloride- sulphate bath. The influences of electrodeposition parameters such as current density, temperature, pH value, cobalt sulphate and saccharin concentration on composition and current efficiency were investigated in detail. The morphology and the microstructure of deposits were analyzed by SEM and XRD, respectively. The results indicated that the optimum parameters were current density 3-4 A/dm2, pH 2-3, temperature 40-50?C, cobalt sulphate 20 g/l and saccharin 2-3 g/l. Chemical analysis of the deposits by EDS revealed anomalous Ni-Co codeposition occured in this system. The SEM showed that hydroxide particles were not present on the surface and that fine-grain, smooth and compact Ni-Co alloy deposits were obtained. The crystallographic structures of Ni-Co alloy foils were the fcc Ni solid solution. The Ni-Co alloy foils with Co content 17.3-37.2 wt% and thickness of 20-45 μm were bright with low residual stress and super toughness.

Preparation of graphene on Cu foils by ion implantation with negative carbon clusters

We report on few-layer graphene synthesized on Cu foils by ion implantation using negative carbon cluster ions,followed by annealing at 950？C in vacuum. Raman spectroscopy reveals IG/I2 Dvalues varying from 1.55 to 2.38 depending on energy and dose of the cluster ions, indicating formation of multilayer graphene. The measurements show that the samples with more graphene layers have fewer defects. This is interpreted by graphene growth seeded by the first layers formed via outward diffusion of C from the Cu foil, though nonlinear damage and smoothing effects also play a role. Cluster ion implantation overcomes the solubility limit of carbon in Cu, providing a technique for multilayer graphene synthesis.

Morphology and Magnetic Properties of Electrodeposited Iron and Nickel Based Alloy Foils

An alternative to conventional process for the preparation of soft magnetic metal foils of Fe,Fe-Ni,Fe-Co and Fe-Ni-Co by electroforming was described.The microstructure and magnetic properties were observed.The results showed that the crystal size of the iron-based alloy foil is less than 10μm,while that of nickel-based alloy foil is about 2μm.Moreover,the electroformed Fe-Ni foil has better magnetic properties than the conventional milled permalloy 1J79 foil.

Simple and Rapid Spectrophotometric Determination of Titanium on Etched Aluminum Foils

Introduction of titanium oxides with high permittivity on etched aluminum foils’ surface has been successfully utilized to increase specific capacitance of anode foils for aluminum electrolytic capacitors. In order to quantify the concentration of titanium (IV) on the etched aluminum foil precisely, a simple and rapid spectrophotometric procedure has been developed. After optimizing a series of variables including absorbance wavelength, concentration of nitric acid, concentration of hydrogen peroxide, nitration time and developing time, analytical precision and accuracy were tested by using standard working solution containing known amount of titanium (IV). The results showed that Lambert-Beer’s law was obeyed in the range of 0.01 to 3.00 mmol·L﹣1. The relative standard deviation (RSD) ranged from 0.67% to 1.09% (n = 6), and the recovery was between 99.17% - 100.03%. Investigation on effect of Al3+ ion indicated that there was no interference in the absorbance of titanium (IV) at 410 nm. The proposed procedure was applied to real samples for the determination of titanium (IV), and the results were in a good agreement with the values certified by inductively coupled plasma-atomic emission spectrometry (ICP-AES).

CV-etched Nanostructured Ag Foils for Efficient Electrochemical CO_(2) Reduction

Electrochemical reduction of CO_(2) has attracted wide attention because it can realize an artificial carbon cycle.The key step to achieving efficient electrochemical conversion of CO_(2) is the preparation of catalysts with multiple active sites,prepared without additional strong alkaline solutions.In this work,the surfaces of Ag foils were nanosized by simple cyclic voltammetry(CV)pretreatment,which can supply an abundant specific surface area for the CO_(2) reduction reaction(CO_(2)RR).The results indicated that the CO_(2)RR performance of Ag catalysts was boosted,and the competitive reaction of H_(2) evolution was suppressed.For this catalyst,at-0.92 V vs.RHE(reversible hydrogen electrode),the current density of CO achieved 12.31 mA/cm^(2),a significant increase compared to that of the untreated Ag foils(0.81 mA/cm^(2)).The outstanding electrochemical properties are ascribed to the rich nanostructures on Ag foils after the CV pretreatment.The nanostructure has a very high specific surface area,so it can supply more reactive active sites in the process of CO_(2)RR.

Preliminary discussion on the ignition mechanism of exploding foil initiators igniting boron potassium nitrate

Exploding foil initiator(EFI)is a kind of advanced device for initiating explosives,but its function is unstable when it comes to directly igniting pyrotechnics.To solve the problem,this research aims to reveal the ignition mechanism of EFIs directly igniting pyrotechnics.An oscilloscope,a photon Doppler velocimetry,and a plasma spectrum measurement system were employed to obtain information of electric characteristics,impact pressure,and plasma temperature.The results of the electric characteristics and the impact pressure were inconsistent with ignition results.The only thing that the ignition success tests had in common was that their plasma all had a relatively long period of high-temperature duration(HTD).It eventually concludes that the ignition mechanism in this research is the microconvection heat transfer rather than the shock initiation,which differs from that of exploding foil initiators detonating explosives.Furthermore,the methods for evaluating the ignition success of semiconductor bridge initiators are not entirely applicable to the tests mentioned in this paper.The HTD is the critical parameter for judging the ignition success,and it is influenced by two factors:the late time discharge and the energy of the electric explosion.The longer time of the late time discharge and the more energy of the electric explosion,the easier it is to expand the HTD,which improves the probability of the ignition success.