Multilayer Foils Research Articles

Enhancing Ni–Ti shape memory alloy diffusion bonding with Ti/Ni reactive multilayer foils

This study investigates the utilization of Ti/Ni reactive multilayer foils as an energy source for facilitating the joining of Ni–Ti shape memory alloys through diffusion bonding. Multilayered samples were prepared using a 10-cycle accumulative roll bonding (ARB) process to be used for the bonding process. Diffusion bonding employing reactive multilayers was conducted over a temperature range of 600 °C to 900 °C, at 5 MPa pressure, with a 1-h hold time. Additionally, a comparison was made with a diffusion-bonded Nitinol sample at 900 °C without a reactive multilayer. Materials characterization and testing involved scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), shear strength testing, and differential scanning calorimetry (DSC), which were conducted on the bonded samples. The findings underscored the advantages of using reactive multilayers for diffusion bonding. These benefits included the formation of TiNi and the induction of a shape memory effect in the joint region, alongside a 1.5 times shear strength compared to identical diffusion bonding conditions without reactive multilayers. Moreover, employing reactive multilayers in the diffusion bonding of Nitinol holds promise for significantly reducing the energy needed to achieve robust and seamless bonded boundaries in the joining area.

Simulation of Heat Transfer and Propagation Velocity for Different Heat Loss Conditions for Guided Propagation Fronts in Reactive Multilayer Foils

Engineering self‐propagating reactions in reactive material systems requires an understanding of critical ignition and propagation conditions. These conditions are governed by the material properties of the reactive materials responsible for net heat generation, as well as by external environmental conditions that primarily determine net heat loss. In this study, it is aimed to utilize a numerical model to investigate the critical conditions for reaction propagation based solely on the heat‐transfer equation, enabling thorough examination with significantly low computational effort. Comparing simulations with experiments demonstrates a high level of agreement in predicting reaction propagation. Additionally, this numerical model provides valuable information regarding heat distribution in substrate materials.

Theoretical and experimental research on static stiffness, performance, and lift-off characteristics of multi-layer gas foil thrust bearings

In this study, a new comprehensive fully coupled elastic-hydrodynamic model is developed for a multi-layer gas foil thrust bearing (GFTB). The interaction effects among the top foil, back board, middle foil, and bottom foil, as well as the Coulomb friction effect, are considered. The stiffness and static characteristics obtained by the experimental and theoretical approaches are in good agreement, which verifies the accuracy of the model. The contribution of each foil layer to the overall stiffness and the load-carrying mechanism are analyzed. Interaction effects of the load, preload, and rotational speed on the static performance are investigated comprehensively. Furthermore, start-stop tests are performed to achieve the lift-off speed, start-up torque, and shut-down torque under various operating conditions.

Orthogonal experiments and bonding analysis of ultrasonic welded multi-layer battery foils and tabs

The motivation for this research stems from the growing demand for solid-phase welding technology to join multilayers metals, particularly in green electric vehicles. Welding of foils and tabs inside battery is a challenging task due to poor joint formation at the interface and low strength. Ultrasonic welding is an efficient, reliable and environmentally friendly bonding method to firmly connect multi-layer copper foils and tabs. Therefore, this is used to achieve electrical bonding within the lithium-ion batteries. This is widely used in production of new energy vehicle batteries. In this work, 40 layers of copper foil were bonded to 0.3 mm nickel-plated copper tabs using ultrasonic metal welding technology. The effect of ultrasonic welding parameters on T-peel strength of joints was systematically investigated by orthogonal experimental design. The maximum T-peel strength of 359.17 N was obtained under optimal parameters (e.g., welding energy 600 J, pressure 0.3 MPa and amplitude 55 %). The variation of welding temperature and amplitude under different welding parameters was measured using infrared thermometer and laser vibrometer. Moreover, the surface, cross-sectional and failure fracture analysis and characterization of specimens with different weld qualities were performed using optical microscopy and scanning electron microscopy (SEM). In addition, the state of Ni layer in cross-section was analyzed using the energy dispersive spectroscopy (EDS) technique after ultrasonic welding. This approach can be straightforward and more appropriate to the development of solid-phase welding method for automotive industry.

Enhanced broadband sound absorption of multi-layer composite material based on three-dimensional warp-knitted spacer fabric

Compared with other sound-absorbing materials, spacer fabric with a “sandwich” structure has many advantages, such as light weight, an environmentally friendly production process, recyclability, versatility, low production cost and high efficiency, and strong designability of the organizational structure. However, as a porous sound-absorbing material, the effective sound-absorbing frequency band of the spacer fabric is concentrated at high frequencies, so the sound-absorbing performance needs to be improved. This paper establishes a Johnson–Champoux–Allard theoretical model by using a genetic algorithm to characterize the sound absorption performance of the three-dimensional (3D) warp-knitted spacer fabric. The theoretical model is validated through finite element analysis and experimental methods. Based on this model, two composite materials are designed to improve the sound absorption performance: (1) multi-layer spacer fabric composite material and (2) multi-layer spacer fabric-aluminum foil composite material. Numerical simulation and experimental results show that the sound absorption performance is significantly improved by widening the effective frequency band and increasing the sound absorption coefficient. The contribution of this paper is twofold. Firstly, the theoretical acoustic model of 3D warp-knitted spacer fabric is established. Secondly, the superior sound absorption performance is achieved by proposing multi-layer and multi-material composite material. The spacer fabric-based composite material has broad application prospects in the field of noise reduction and sound insulation. The paper provides a theoretical basis and more strategies for the acoustic and multifunctional design of spacer fabric in the future.

Influence of Oxide Formation Following Ultrashort Pulsed Laser Micromachining on Self‐Propagating Reactions in Free‐Standing Ni/Al Reactive Multilayer Foils

Reactive metallic multilayers, renowned for their exothermic self‐propagating reactions, show a distinct ability to achieve minimal thermal influence in processes such as welding and soldering, where minimizing the thermal impact on the material being joined is crucial. Ultrashort pulsed lasers offer precision micromachining with negligible thermal damage, making them ideal for processing such sensitive materials. However, the formation and redeposition of oxide phases is a commonly observed side effect, especially when structuring in ambient air. This study investigates the effects of oxide formed after femtosecond laser treatment on self‐propagating properties, including propagation velocity and microstructure of Ni/Al reactive multilayer foils. Samples with varied line spacings between laser‐cut trenches are created. Scanning electron microscopy, high‐speed camera videography, and image analysis are employed to analyze the microstructure and quantify velocities. Thermal simulations enhance the understanding of the oxide's role in self‐propagating dynamics. The findings suggest that even a small oxide layer significantly decelerates the self‐propagating reaction. The oxide functions as a thermal ballast by absorbing the thermal energy generated during the reaction, without actively participating in the reaction mechanism.

Influence of Metal Surface Structures on Composite Formation during Polymer–Metal Joining Based on Reactive Al/Ni Multilayer Foil

Progressive developments in the field of lightweight construction and engineering demand continuous substitution of metals with suitable polymers. However, the combination of dissimilar materials results in a multitude of challenges based on different chemical and physical material properties. Reactive multilayer systems offer a promising joining method for flexible and low‐distortion joining of dissimilar joining partners with an energy source introduced directly into the joining zone. Within this publication, hybrid lap joints between semicrystalline polyamide 6 and surface‐structured austenitic steel X5CrNi18–10 (EN 1.4301) are joined using reactive Al/Ni multilayer foils of the type Indium–NanoFoil. The main objective is to examine possibilities of influencing crack initiation in the foil plane by variation of joining pressure and different metal surface structures with regard to geometry, density, and orientation. Thus, the position of foil cracks is superimposed onto the metal structure and associated filling with molten plastic is improved. Consequently, characterization of occurring crack positions as a function of joining pressure and metal structure, analysis of the composite in terms of structural filling and joint strength, as well as possible causes of crack initiation are evaluated.

Effect of al/si multilayer foil on microstructure and mechanical properties of SiCр/Al composites vacuum diffusion bonded joints

The peculiarities of joint formation in vacuum diffusion bonding through an intermediate multilayer foil (MF) of Al/Si produced by electron beam physical vapour deposition (EB-PVD) in vacuum were studied on SiCр/Al aluminium matrix composites with different alloying systems of the aluminium matrix. It is shown that Al/Si interlayer enables making permanent joints without degradation of the composite properties at the temperature of 500°С, which corresponds to the start of intensive plastic deformation of the interlayer at thermomechanical loading. It is found that the microstructure and phase composition of the joint zone (JZ) depend on the interlayer and aluminium matrix of the composite. It is demonstrated that reduction of the bilayer thickness of Al/Si MF and its alloying by manganese ensures intensive mass transfer of the components in the butt joint and equivalent joint formation. The maximum value of shear strength was 105 MPa in the case of an interlayer with a nano-scale period of the layers.

Effect of continuous dynamic-recrystallisation on high-property multilayer Cu foils joint by friction-stir-welding

In this experiment, friction-stir-welding was proposed to research the flexible connection of multilayer Cu foils. It studies the correlation between hardness, conductivity, and continuous dynamic-recrystallisation. New grains of continuous dynamic-recrystallisation have a correlation between the dislocation density and the grain size, such that a lower dislocation density corresponds to a higher grain size and vice versa. It is shown that after friction-stir-welding of multilayer Cu foils, the hardness increases and the conductivity decreases due to the combined effect of fine grain strengthening and dislocation strengthening for new grains of continuous dynamic-recrystallisation of the weld zone. However, the hardness gradually decreases and conductivity gradually increases within the weld zone with continuous dynamic-recrystallisation degree.

Review on Ultrasonic and Laser Welding Technologies of Multi-Layer Thin Foils for the Lithium-Ion Pouch Cell Manufacturing

Emission-reduction initiatives within the automotive sector have amplified the demand for electric and hybrid vehicles. An essential component in lithium-ion batteries for these vehicles is the pouch-type battery cell, which necessitates the welding of electrodes and tabs. Welding multi-layered thin foils, especially those only a few micrometers thick, is vital to ensure optimal performance and safety. The predominant techniques for this are ultrasonic and laser welding. This paper aims to provide a comprehensive review of contemporary advancements in ultrasonic and laser welding of multi-layer thin foils.

Achievement of defect-free and high-properties multilayer copper foils flexible connection by friction stir welding

Achievement of defect-free and high-properties multilayer copper foils flexible connection by friction stir welding

Analytical Double-2D Frequency-Dependent Leakage Inductance Model for Litz-Wired High-Frequency Transformer

Accurate and fast calculation of frequency-dependent leakage inductance is critical for the optimization of the high-frequency transformer with Litz wire winding. The analytical method is widely used due to its high computation speed. However, its computation accuracy is limited due to the following factors. i) One-dimensional (1D) or two-dimensional magnetic field model (2D) has unsatisfying accuracy for the transformer with a rotationally asymmetric structure. ii) The skin and proximity effect factors based on the multilayer foil winding are inaccurate for the Litz wire winding in the calculation of frequency-dependent magnetic energy. This paper proposes a double-2D frequency-dependent leakage inductance model for the transformer with Litz wire winding. It uses the image method to calculate the 2D leakage magnetic field inside and outside the core window, respectively, which considers the rotationally asymmetric structure in leakage inductance calculation. The round conductor model is proposed for the frequency-dependent magnetic energy calculation. The single strand in a Litz wire is taken as the basic modeling object of the round conductor model, which is more detailed than the multilayer foil winding model for the Litz wire winding. The comparison between the experiment, FEM, state-of-the-art models and the proposed model is conducted for eight transformers with E-core, U-core, round or rectangular Litz wire winding. The proposed model shows satisfying computation accuracy in the whole frequency band. And the computational speed of the proposed model is 100 times that of the FEM.

A novel integrated process-performance model for laser welding of multi-layer battery foils and tabs

A novel integrated process-performance model for laser welding of multi-layer battery foils and tabs

Utilization of Multilayered Polyethylene Terephthalate (PET)-Based Film Packaging Waste Using Reactive Compatibilizers and Impact Modifier

This research aimed to evaluate the material properties of reactive extrusion-modified blends containing PET multilayered foil waste. Three types of PET-based multilayer foil waste were used as the compound during the reprocessing of standard bottle-grade PET. Flakes used for this purpose were made from laminated foils: (A) PET/PE, (B) PET/EVOH/PE, and PET/PE/met. All types of the prepared materials were compounded with 30% of the waste foil flakes. Additionally, the blend was modified with an epoxy-based chain extender and polyolefin-based impact modifier. The prepared blends were processed using two methods; initially, the materials were prepared by injection molding, while cast-film samples were also prepared. All samples were subjected to full characterization using mechanical testing methods, thermal analysis, and structural observations. The study shows that the addition of multilayered foil waste is leading to significant deterioration of PET-based material properties. While, in most cases, the use of a chain extender led to some improvement in mechanical characteristics, the impact modifier addition strongly influenced most of the properties. It was also observed that the reactive extrusion procedure led to melt strength improvement, which greatly facilitates the film production process. Due to the limited possibility of separating the film components, the developed method of foil recycling might be useful for the utilization of multilayered packaging.

In-situ preparation of Zr-Al-Ni-Cu amorphous alloy by friction stirring using a tool consisting of multiple metal foils

Zr-Al-Ni-Cu amorphous alloy was prepared on an Al2O3 substrate by layering Zr, Al, Ni, and Cu foils, rolling them into a cylinder to fabricate a tool, and then pressing the tool onto the Al2O3 substrate while rotating the tool with a drilling machine. At the contact point between the multilayer metal foil tool and the Al2O3 substrate, Zr-Al-Ni-Cu amorphous alloy was formed by friction stir heating and mixing of the metal foils. The elastic modulus and hardness of the specimen were 173.0±7.9 and 11.7±0.7 GPa, respectively.

Optimal design of top-foil wedge shape for a specific multi-layer gas foil thrust bearing by considering aerodynamic and thermal performances

Optimal design of top-foil wedge shape for a specific multi-layer gas foil thrust bearing by considering aerodynamic and thermal performances

Thermo-elasto-hydrodynamic analysis of a specific multi-layer gas foil thrust bearing under thermal-fluid–solid coupling

Gas foil bearing faces severe and complex thermal-fluid–solid coupling issues when in ultra-high speed and miniaturized impeller machineries. In this study, a Thermo-Elasto-Hydrodynamic (TEHD) analysis of a specific multi-layer gas foil thrust bearing on the continuous loading process within a steady rotational speed is numerically investigated by a three-dimensional thermal-fluid–solid coupling method. Results indicate that the multi-layer foil exhibits nonlinear overall stiffness, with the thrust bottom foil serving as the primary elastic deformation structure, while the thrust top foil maintains a well-defined aerodynamic shape during a loading process, which helps reduce frictional damage and achieve an adequate loading capacity. For low loads, the fluctuation of the gas film is extremely sensitive, and it weakens dramatically as the load increases. The viscous heating and friction torque exhibit a linear relationship with an increasing bearing load after a rapid growth. Depending on the exact stacking sequence and contact position of the multi-layer gas foil, the overlapping configuration allows for efficient transfer of viscous-shearing heat accumulated at the smallest air film through thermal conduction while providing elastic support. Due to the strong inhomogeneity of the viscous heat under varying loads, the temperature distribution on the top foil surface shows pronounced variations, while the difference between the peak and average temperatures of the thrust plate and top foil surfaces widens substantially with an increasing load.

A comparative study on inflow schemes of radial throughflow cooling for thermal management of a specific multi-layer gas foil thrust bearing

In order to illustrate the effects of radial cooling throughflow on the aerodynamic and thermal behaviors of gas foil thrust bearing, a three-dimensional fluid-solid coupled numerical investigation is conducted for a specific multi-layer gas foil thrust bearing under stable operating conditions in the present study, with two inflow schemes adopted, referred as radially-inward inflow scheme and radially-outward inflow scheme, respectively. The results show that the flow fields and the thermal behavior within the gas foil thrust bearings under the two inflow schemes are significantly different due to the difference in the inflow direction and the effect of centrifugal force caused by the high-speed rotation. The radial cooling throughflow can greatly alleviate the high temperatures in the film layer and improve the cooling capacity, but the increase of mass flow rate causes a non-monotonic change of static bearing load and an enhancement of viscous-shearing heat, as well as a significant rise of the air supply pressure. The radially-inward inflow scheme allows a lower peak temperature and a more uniform temperature distribution on the thrust plate and foil surfaces, while the radially-outward inflow scheme provides a lower area-averaged temperature and consumes less air supply pressure.

Full Electromagnetic Integration of Impedance-Balanced EMI Filters for Single-Phase Power Converters

Utilizing passive electromagnetic interference (EMI) filters is the most widely used approach to restrain the conducted emissions from power converters. However, the introduction of these filters will significantly raise the weight and size of the systems. Using the emerging flexible multi-layer foil (FMLF) technique, this paper investigates a complete electromagnetically integrated design concept of single-phase EMI filters based on EE-type cores, which can be applicable to engineering application scenarios with different EMI noise attenuation requirements. Two types of integrated structures are constructed with different well-designed FMLF-windings and terminal configurations. One is a common-mode (CM) choke with controllable leakage inductances, which is able to realize the integration design of CM inductor, CM capacitors and differential-mode (DM) inductors. The other is an EMI choke with integrating the CM and DM inductances & capacitances, which achieves electromagnetic integration of all the CM and DM filtering components. Compared to the existing UU-type core based integration methods, the proposed methods can ameliorate the noise suppression performance while reducing filter's weight and volume. Theoretical analyses for modeling and design of the EMI chokes is presented. Then prototypes of different FMLFs based EMI filters have been built for a 500W 100kHz SiC-MOSFET inverter, experiments demonstrate the feasibility and validity of the proposed structures.

Study on theoretical model for electrical explosion resistivity of Al/Ni reactive multilayer foil

Al/Ni reactive multilayer foil (RMF) possesses excellent comprehensive properties as a promising substitute for traditional Cu bridge. A theoretical resistivity model of Al/Ni RMF was developed to guide the optimization of EFIs. Al/Ni RMF with different bilayer thicknesses and bridge dimensions were prepared by MEMS technology and electrical explosion tests were carried out. According to physical and chemical reactions in bridge, the electrical explosion process was divided into 5 stages: heating of condensed bridge, vaporization and diffusion of Al layers, intermetallic combination reaction, intrinsic explosion, ionization of metal gases, which are obviously shown in measured voltage curve. Effects of interface and grain boundary scattering on the resistivity of film metal were considered. Focusing on variations of substance and state, the resistivity was developed as a function of temperature at each stage. Electrical explosion curves were calculated by this model at different bilayer thicknesses, bridge dimensions and capacitor voltages, which showed an excellent agreement with experimental ones.