Multilayer Foils Research Articles

Design and fabrication of energetic Al/Ni exploding foil with enhanced energy efficiency and plasma density for direct ignition

In order to lower the firing voltage, an energetic Al/Ni exploding foil (Al/Ni-EF) with enhanced energy efficiency and plasma density was prepared in this study, to realize the direct ignition of pyrotechnics. An Al/Ni reactive multilayer foil (Al/Ni-RMF) was firstly synthesized by magnetron sputtering and wet etch method, and its structure and exothermic behavior were investigated. Scanning Electron Microscopy, Atomic Force Microscope and X-ray Diffraction characterizations confirmed the periodic layer structure of Al/Ni-RMF with a total thickness of 4 μm. The highest heat release in Al/Ni-RMF could be achieved theoretically when the ratio of Al and Ni was 1.5, and thus the thickness of single Al and Ni layer was determined to be 300 nm and 200 nm, respectively. The obtained Al/Ni-RMF was subsequently fabricated to be an exploding foil, and its electric explosion performance was further studied. Energy efficiency of the Al/Ni-EF was measured to be 85.9% during the electric explosion process, which was 30.9% higher than that of Cu exploding foil (Cu-EF). The plasma generated at Al/Ni-EF had larger volume, longer duration time and higher temperature than Cu-EF due to the intermetallic reaction between Al and Ni, which was beneficial for the direct ignition of Boron/Potassium Nitrate composition (B/KNO3, BPN). Afterwards, a special Al/Ni-EF ignitor without slapper was constructed, and the fierce ignition of BPN at the minimum discharge voltage of 800 V was observed. Above results confirmed the feasibility of direct ignition, such a unique strategy was beneficial for the development of low-energy, low-cost and miniaturized ignitor.

Influence of environment on self-propagating reactions in Al/Ni multilayer foils

Reactive aluminum–nickel multilayer system shows exothermic energetic materials which act as a heat source for packaging and bonding of microsystems. The main challenge is controlling the self-propagation reaction velocity and temperature generated by thermal management through different thermal conductive substrate materials. The current work investigates the heat distribution of Al/Ni multilayer foils from different thermal conductive substrates which act as heat sink materials during the self-propagating reaction. A two-dimensional numerical model was developed to study thermal conductive heat loss and substrate thermal properties on the self-propagating reaction in Al/Ni multilayer foils. The self-propagating reaction was introduced on the surface of the foils by an electrical spark. Here we investigate the minimum critical thickness of Al/Ni multilayer foils which shows the self-propagation reaction on different substrates and verified from the two-dimensional numerical model. The outcomes of this investigation will facilitate the integration of Al/Ni multilayer foils on different substrates as intrinsic heat sources for different applications of micro/nanodevices.Graphical abstract

Modeling and Design of Full Electromagnetic Integration of a Symmetrical EMI Filtering Circuit With Flexible Multi-Layer Foil Technique

In a high-frequency power electronic converter with wide-bandgap device, electromagnetic interference (EMI) filter is an essential module for mitigating the conducted EMI issues. However, traditional discrete EMI filter will significantly increase total size and weight of the system. In this article, an UU-core based fully integrated symmetrical EMI filter is proposed using flexible multilayer foil technique, all the common-mode (CM) and differential-mode (DM) filtering components are integrated in the same unit for a more compact design. Moreover, a function-decoupling state is realized between the CM and DM elements, which contributes to predigesting the lumped equivalent CM and DM circuits. Then the parameter design procedure can be simplified. Prototypes of the proposed and other typical types of EMI filters are built for a 100 kHz SiC- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> voltage source inverter, contrastive experiments have verified the feasibility and validity of the full electromagnetic integration approach.

Effects of Ultrashort Pulsed Direct Laser Writing on Ni/Al Reactive Multilayer Foils

Reactive multilayer foils (RMFs) for joining processes have attracted a great deal of attention over the last few years. They are capable of exothermic self-propagating reactions and can serve as localized heat sources for joining applications when ignited by suitable means. Using short and ultrashort pulsed lasers with carefully selected parameters, cutting and shaping of RMFs makes it possible to tailor heat release characteristics without triggering the reaction. The present study is an investigation of microstructural changes induced by femtosecond laser machining of a commercially available Ni/Al-based RMF. The effects of the specific laser parameters pulse duration and repetition rate on the heat-affected zone (HAZ) are investigated by scanning and transmission electron microscopy. Debris consisting of oxide deposits can be found at a distance of several tens of microns from the cut edge. A negligible HAZ extending to less than 100 nm was observed for all parameters tested and no signs of ignition of a self-propagating reaction were observed. These results underline the suitability of femtosecond lasers for metal machining with minimal heat input.

Exothermic Reactions in AlNi Foils Produced by Rolling Powders

The possibility of manufacturing multilayer reaction foils of the Al-Ni system by rolling a powder mixture is considered. The sequence and temperatures of phase transformations during heating was established by the differential thermal analysis and X-ray phase analysis. The formation of the intermetallic compounds in the foils fabricated via rolling just mixed powder occurs only when a liquid phase appears (660°C). However, the foils fabricated from mechanically activated powders exhibit significant exothermic effect at temperature of 320°C unnecessarily for a liquid phase formation and can be proposed as a multilayer reactional foils for local heating in the technology of joining of various materials.

Optimization of process parameters of ultrasonic metal welding for multi layers foil of AL8011 material

When working with thin layers of comparable and/or different metals, resistance welding and conventional welding each have their own set of limits that they must overcome. When the input parameters include a high-frequency vibration, proper weld duration and pressure, ultrasonic metal welding performs at its highest level of efficiency. Ultrasonic welding uses a lot of power, force and energy, and if the right input parameters aren’t chosen, the quality of the weld and its durability suffer. This study takes into account the relationships between the input process parameters of welding pressure, welding time and vibration amplitude and the output responses of power, force and energy in ultrasonic metal welding (UMW). For multilayer AL-8011 foils, the author utilized UMW has experimented with central composite design by design professionals. The response surface approach, often known as RSM, has been used to improve the process parameters to get the best possible welding connections.

Terminal Configuration Principles for Achieving Various Electromagnetic Integration Units with Flexible Multilayer Foil Technique

Terminal Configuration Principles for Achieving Various Electromagnetic Integration Units with Flexible Multilayer Foil Technique

Hybrid Thermoplastic-Metal joining based on Al/Ni multilayer foils – Analysis of the joining zone

Multi material pairings like metal-plastic hybrid compounds are becoming increasingly important across all industrial sectors. However, the substitution of metals by plastics leads to a multitude of challenges based on the combination of dissimilar materials. The variations in the chemical and physical properties of the used materials require innovative joining processes. The application of reactive multilayers represents an advanced joining method for flexible and low-distortion joining of dissimilar joining partners by means of a short-term and localized application of thermal energy. In the context of this publication, the joining process between semi-crystalline polyamide 6 and austenitic stainless steel X5CrNi18–10(EN 1.4301 / AlSI304) based on reactive Al/Ni multilayers is investigated. In addition to evaluation of resulting joint strength, the focus of the work is in particular the characterization of the resulting failure behavior at the fracture interface under tensile load and the deriving binding mechanisms in the joint. From the results obtained, it is estimated that a direct bond can be generated between plastic and metal despite the presence of a residual reacted foil in the joining area. The structures present in the metal surface have a particularly positive influence on crack initiation and the resulting increased bond strength.

Investigations on the Load Capacity of Multilayer Foil Thrust Bearing Based on an Updated Complete Model

Abstract The multilayer gas foil thrust bearing (MLFTB) has four layers of foil structures with each having unique configuration and function. In this article, an updated complete model of the overlapped foil layers of MLFTB is established to calculate more accurate foil deformations and bearing performance by considering sufficient possibilities of separations between adjacent foil layers. The accuracy of the model is validated through the load capacity tests of MLFTB, which is presented for the first time in open publications. Based on the complete model, influences of individual and combined key foil structural factors on bearing load-carrying performance and top foil deformations are studied, revealing the function mechanism of each foil layer and obtaining the method of adjusting two-dimensional stiffness distributions. Furthermore, parametric optimizations toward improving the load capacity of this type of foil thrust bearing are conducted based on a developed algorithm. This study provides sufficient theoretical knowledge and designing methods for further investigations of MLFTB.

Investigation of phase equilibria of the Au–Ni–Sn ternary system and interfacial reactions in the Au/Sn/Ni/Cu multilayer couple

Au and Ni are widely used in the under-bump metallization, whereas Sn and Cu serve as common bonding materials and substrates, respectively. Solder joints consisting of an Au/Sn/Ni/Cu multilayer structure are widely found in the electronic packaging. Both phase equilibria of the Au–Ni–Sn ternary alloys and interfacial reactions of the Au/Sn/Ni/Cu multilayer structure were applied to the solid/solid-state reaction couple technique. The results showed that the Ni3Sn2 and AuSn4 phases respectively had a great solubility of the third element and the ternary AuNi2Sn4 phase existing in the Au–Ni–Sn ternary alloys was formed at 180 and 240 °C. The Sn/Ni/Cu multilayer structure was prepared by electroplating Sn/Ni layers on the Cu substrate. Afterward, the Sn/Ni/Cu multilayer and Au foil were screwed together to obtain the Au/Sn/Ni/Cu multilayer structure, followed by reactions at 150, 180 and 200 °C for different durations. The thickness of the intermetallic compounds (IMCs) increased with the increase in the reaction time and temperature. The IMC evolution in the couple remained unchanged at different temperatures. An increase in the reaction time converted the AuSn4 and AuSn2 phases to the AuSn phase. The voids formed in the couple were attributed to the volume shrinkage effect, which decreased with an increase in the reaction temperature. The (Ni, Au)3Sn2 phase was formed at the Ni side; the Ni layer functioned as an effective diffusion barrier to prevent the formation of the Cu–Sn IMCs.

Propeller-integrated airfoil heater system for small multirotor drones in icing environments: Anti-icing feasibility study

Atmospheric icing is one of the most common and hazardous environmental challenges for aircraft operations. So far, only large passenger aircraft, a few general aviation aircraft, and specialized rotorcraft are equipped with ice protection systems because of their additional energy consumption and weight. The emerging markets of small electric aircraft like Urban Air Mobility and Unmanned Aerial Vehicles for transportation, logistics, search and rescue, and other specialized operations will require efficient, lightweight and all-electric ice protection systems in order to allow operations in ice and snow conditions. In this work, an electrothermal ice protection system with an average heat power density of 1Wcm−2 was designed and developed for use on small multirotor drones. Commercially available propeller blades with diameters of 33cm were retrofitted with lightweight multilayer heating foils independently powered by super-capacitors. The heated propellers were tested in close-to-real icing conditions in a small-scale icing wind tunnel. Thrust, rotational speed, and power consumption of a non-heated reference propeller and a heated propeller were compared. In glaze ice conditions at air temperatures > −5°C the thrust of the non-heated propeller fluctuated between 60 and 90% with frequent cycles of ice accretion and shedding for the entire duration of the test. The heated propeller maintained a thrust of >95% in the same icing conditions. In rime ice conditions at air temperatures < −8°C the heating was not sufficient and the thrust of the non-heated and heated propellers similarly decreased over time. Heat flux calculations along the span of the propeller were made for different icing conditions and compared to the heat power density distribution of the tested ice protection system.

A Fully Integrated Common-Mode Choke Design Embedded With Differential-Mode Capacitances

The emerging flexible multilayer foils (FMLFs)-based winding design has a great potential to promote the magnetic integration technique in power electronic systems. This article investigates the full integration of a single-phase electromagnetic interference (EMI) choke with well-designed FMLFs. By sharing a UU-type core and configuring the windings reasonably, all the common-mode (CM) inductance and capacitances and differential-mode (DM) inductances and capacitances can be integrated into the same core unit. Moreover, the proper terminal configuration of conductive layers can realize function-decoupling between CM and DM filtering elements, which contributes to simplifying the equivalent CM and DM models, then predigesting the parameters design procedure. Following the modeling and theoretical analysis, prototypes of the proposed and existing EMI chokes have been built for a single-phase 200-kHz SiC-<small>mosfet</small> inverter system. Through experimental measurements, performance comparisons have been presented to demonstrate the validity of this model.

Effect of Inserted Ti Layers on the Phase Transformation of Al/Ni Multilayer Foils

The thin Ti layers were inserted in the interfaces of base Al/Ni multilayer foils to form the Al/Ti/Ni/Ti (ATNT) foils through magnetron deposition. Al and Ni were determined in the as-deposited foils, while the absence of Ti was due to the strongly textured polycrystalline structure. TEM analysis implied an asymmetric interface structure between the Ni/Ti/Al interfaces and Al/Ti/Ni interfaces. After annealing at 473 K and 573 K for 3 h, the phase composition was the same as the initial state, which changed to be Al3Ni2, Ni3(AlTi), Ni and a small amount of Al3Ti when the treating temperature reached 673 K. Further increasing the annealing temperature to 773 K and 873 K leads to the appearance of stable AlNi. The obtained results implied that the inserted Ti layers impeded atomic interdiffusion and the formation of Al3Ni at the early stage, but had less impact on the final products. This further indicated that adding the inserted transition layer provides a reference to balance the storage stability and reaction performance of Al/Ni foils with regard to the applications.

ДОСЛІДЖЕННЯ МОЖЛИВОСТІ ВИКОРИСТАННЯ ПРОМІЖНИХ ПРОШАРКІВ НА ОСНОВІ НІКЕЛЮ ПРИ ЗВАРЮВАННІ ОРТОАЛЮМІНІДУ ТИТАНУ З НІКЕЛЕВИМ СПЛАВОМ

Titanium aluminides have a low density and maintain high strength at elevated temperatures, which makes them prom-ising for the manufacture of aircraft engine elements. In the presented work, the problem of welding in the solid phase ortho-rhombic titanium aluminide based on the intermetallic compound Ti2AlNb and heat-resistant alloy ЭИ437Бon a nickel base is considered. A review of the state of the problem of welding heat-resistant alloy ЭИ437Бbased on nickel and titanium or-thoaluminide Ti2AlNb was carried out. It was established that the main problem in welding Ti2AlNb alloy with nickel alloy is a strong tendency to the formation of brittle phases in the joint zone, which negatively affect the mechanical properties. A promising method of joining this group of alloys is diffusion welding in a vacuum.The purpose of the work is to study the influence of multilayer and gradient foil on the formation of the zone of titanium orthoaluminide joints with a nickel-based alloy during vacuum diffusion welding.In the work, multilayer and gradient foil based on Al-Ni and Ni-Tisystems were used according to the original structure. The foils were obtained by electron beam evaporation and condensation in a vacuum. The deposition process consists in the layer-by-layer condensation of elements on a horizontal substrate.The work presents the method of conducting experiments, welding modes, chemical composition of materials and foil.The work shows for the first time that during the direct welding of titanium orthoaluminide with the ЭИ437Бalloy, as a result of the strong tendency ofthe materials to form brittle phases at the joint, a significant increase in microhardness is observed in the joint zone up to 2...4 times compared to the base material (up to 11.94 GPa). It was established that the useof layered foil (Ni/Ti, Al/Ni) as intermediate layers allows to significantly reduce the difference in microhardness values in the joint. At the same time, the microhardness in the central part of the joint zone reaches 6.69...8.79 GPa, which is close to the microhardness values of Ti2AlNb.The presented materials can be used as a basis for the development of welding technologies in the solid phase of heter-ogeneous titanium orthoaluminide materials with nickel-based alloys.

Influence of Initial Temperature and Convective Heat Loss on the Self-Propagating Reaction in Al/Ni Multilayer Foils.

A two-dimensional numerical model for self-propagating reactions in Al/Ni multilayer foils was developed. It was used to study thermal properties, convective heat loss, and the effect of initial temperature on the self-propagating reaction in Al/Ni multilayer foils. For model adjustments by experimental results, these Al/Ni multilayer foils were fabricated by the magnetron sputtering technique with a 1:1 atomic ratio. Heat of reaction of the fabricated foils was determined employing Differential Scanning Calorimetry (DSC). Self-propagating reaction was initiated by an electrical spark on the surface of the foils. The movement of the reaction front was recorded with a high-speed camera. Activation energy is fitted with these velocity data from the high-speed camera to adjust the numerical model. Calculated reaction front temperature of the self-propagating reaction was compared with the temperature obtained by time-resolved pyrometer measurements. X-ray diffraction results confirmed that all reactants reacted and formed a B2 NiAl phase. Finally, it is predicted that (1) increasing thermal conductivity of the final product increases the reaction front velocity; (2) effect of heat convection losses on reaction characteristics is insignificant, e.g., the foils can maintain their characteristics in water; and (3) with increasing initial temperature of the foils, the reaction front velocity and the reaction temperature increased.

Joining of copper foils via Al/Ni reactive multilayer nanofoils

Interconnected individual battery cells of lithium batteries are unavoidably involved in joining in parallel to improve the battery capacity. Due to the advantage of the small joint area and short process time, micro resistance welding is one of common applied joining techniques of copper foils. However, strength improvement of micro resistance welded copper foils was restricted by the insufficient Joule heat accumulation at the faying interface. Here we used the exothermic reaction of Al/Ni reactive multilayer nanofoils as a local heat source at the faying interface of micro resistance welding of copper foils, designing to increase the heat accumulation and improve the joints strength. Two faying interfaces were formed at the joints of copper foils, one was at the thickness direction of AlNi reactants caused by the diffusion of Cu element based on the high temperature and fracture of coating layer, and another was formed at the surface of AlNi reactants and copper foils. Due to grain boundary relaxation, grain refining of AlNi alloy compound of final product with the average grain size of 27.9 nm at the faying interface attributed to the hardness increase and improvement of joints strength. The joints strength of two-layer copper foils increased to 100 N and the value was 500 N for the joints of multilayer copper foils with the assistance of Al/Ni reactive multilayer nanofoils. These results pave the way for the application of micro resistance welding technique in the battery cells joining of lithium batteries manufacture.

A Review of Flexible Multilayer Foil Integration Technology for Passive Components

Passive integration technology is widely used in power electric converters since it can significantly reduce the volume of the passive components and improve the power density. This article highlights the flexible multilayer foil (FMLF) integration technology since it can meet the future requirements than other integration technologies. The realization, structures, and applications of the FMLF integration technology are summarized. The magnetic materials, dielectric materials, and conductive materials used in FMLF are investigated. Then, the approaches of the analysis and design for FMLF integrated units are introduced. Finally, it is compared with the planar printed circuit board integration technology to highlight the advantages of its characteristics and expounds its future research fields. Eventually, the power electronics engineers and researchers can comprehend the intrinsic properties of the FMLF integration technology.

Evaluation of Weldability based on Alignment Condition of Horns and Anvils used in Multilayered Battery Cell Welding Process in Ultrasonic Metal Welding

A battery cell has a foil-to-tab structure that is connected with multi-layer foils and a tab, and it is important to secure the weld quality to improve the battery performance. Ultrasonic metal welding (UMW) is widely applied as a technology suitable for battery cell welding because it provides a relative low heat input to welds owing to solid-state welding. In this study, 40 layers of 8 μm Cu foil and one layer of nickel-plated 0.2 mm Cu strip applied to a multilayered battery cell were used to evaluate the weldability of the materials for the UMW process. An experiment was conducted under four alignment conditions of a horn and an anvil to investigate the effect of the alignment on the weldability. The weld quality was classified based on the weld strength, discoloration, and failure mode of the test specimen to obtain a suitable welding range. The effect of the alignment condition on the deformation and weld shape was investigated by observing the cross-section of welds made under the four alignment conditions.

Analysis of structure and properties of multilayer polymer foil

Light and cheap composites are the main goal of manufacturing in many branches. Polymers, containing low weight and high relative strength, are suitable materials as matrix of composites reinforced with different metallic or ceramic fillers in the shape of fibres, plates, blocks or other types. This work takes into consideration optimisation and manufacturing of multilayer foil with different composition. To obtain the film has been used advanced blow molding process equipped with three extruders feeding material to the machine. Feeding of material is precisely controlled through gravimetric dosimeters. Final product of this technology is the polymer film which is obtained as combination of three films adherent together in the advanced head of blow molding machine.

Structural mechanism of plastic deformation of Al/а-Si multilayer foils at heating under load

Abstract Al/Si multilayer foils were produced by layer-by-layer vacuum deposition of component vapour phases on the substrate at 150°С temperature. It is shown that the structure of as-deposited foils is characterized by alternation of layers of aluminium and amorphous silicon. At foil heating under load in the temperature range of 180 … 230°С, an increase of plastic deformation rate is observed. Investigations of the change of foil structure showed that increased plasticity can be due to aluminium-induced silicon crystallization. The process of silicon crystallization is accompanied by fragmentation of its layers and formation of a composite structure, consisting of aluminium matrix, crystalline silicon particles and pores. When temperature of the order of 450–500°С is reached, the rate of foil plastic deformation rises abruptly. Analysis of structural changes in the foil leads to the assumption that intensive plastic deformation of the foil is realized by the mechanism of intergranular slipping of aluminium grains, accommodation of their displacement being facilitated by presence of pores.