Reactive Multilayer Films Research Articles

Modeling and simulation of self-propagating exothermic reactions in Al/Ni reactive multilayer films and experimental validation

Modeling and simulation of self-propagating exothermic reactions in Al/Ni reactive multilayer films and experimental validation

Effects of Intermetallic Phase Formation and Bilayer Spacing on the Oxygen Exchange Process in Mg–CuO Reactive Multilayer Films

Effects of Intermetallic Phase Formation and Bilayer Spacing on the Oxygen Exchange Process in Mg–CuO Reactive Multilayer Films

Investigating the reaction mechanism of zirconium as a fuel in reactive multilayer films via multimodal analysis

In this report, we examine the intricate details of the mechanism driving Zr/CuO thermite system, shedding new light on the exceptional reactivity of Zr fuel with oxygen. Magnetron-sputtered Zr/CuO reactive multilayers were deposited, and thermo-physical techniques were employed to characterize the progression of the chemical reaction upon heating. Unlike commonly used Al fuel, Zr/CuO exhibited 100% heat release below 500 °C, contrasting with the ∼5% observed for conventional Al/CuO system. This enhanced reactivity at low temperature is attributed to the rapid oxygen consumption behavior of Zr, due to the poor barrier of ZrOx to oxygen diffusion. The oxidizing behavior of Zr was quantitatively analyzed using electron microscopy and spectroscopy. Our observations reveal a three-step process of Zr oxidation facilitated by a rapid reduction of CuO to metallic Cu accompanied by the formation of an intermediate Cu2O phase: (i) a preliminary low-temperature mass transport initiating at 275 °C, (ii) partial Zr oxidation forming ZrO2 and oxygen enriched Zr and finally (iii) complete conversion to zirconia at 450 °C. Finally, Zr/CuO reactive thin-films demonstrated a very high reactivity with an ignition delay time of 0.04 ± 0.016 ms and a burn rate of 3.5 m.s−1, in stark contrast to the same volume of Al/CuO, which failed to ignite and burn altogether. This study not only deepens our comprehension of Zr-based thermite system but also underscores its potential for diverse applications in energetic materials.

Enhancing laser-driven flyer velocity by optimizing of modulation period of Al/Ti reactive multilayer films

Reactive multilayer films (RMFs), a type of nanostructured energetic material, are recognized as an indispensable component for laser-driven flyer plate initiator systems. In this work, Al/Ti-RMF with three different modulation periods (600, 300, and 150 nm) were prepared and integrated into multilayer flyer plates, and energetic material with optimized performance for laser-driven flyers was obtained. Cross-sectional observations demonstrate that the modulation periods of the RMF are precisely regulated, with thickness errors falling within 3.4%. The velocity of the flyer plates was significantly higher with a modulation period of 150 nm, reaching 2174.16 m/s. Molecular dynamics simulation results show that as the modulation period decreases, the diffusion rate of atoms increases, enabling the reaction between the RMF to be completed in a shorter time span, which makes for higher velocity of the flyer. The energy coupling efficiency results indicate that the kinetic energy coupling efficiency of the RMF with a modulation period of 150 nm is 145.6% and 29.8% higher compared to those with modulation periods of 600 and 300 nm, respectively. It is proved that Al/Ti-RMF have high-energy output performance and can be a novel candidate for laser-driven flyer plates, which will play a critical role in complex electromagnetic interference environments in the future.

The Simulated Effect of Adding Solder Layers on Reactive Multilayer Films Used for Joining Processes

In order to introduce new bonding methods in the area of electronic packaging a theoretical analysis was conducted, which should give substantial information about the potential of reactive multilayer systems (rms) to create sufficient local heat for joining processes between silicon chips and ceramic substrates. For this purpose, thermal CFD (computational fluid dynamics) simulations have been carried out to simulate the temperature profile of the bonding zone during and after the reaction of the rms. This thermal analysis considers two different configurations. The first configuration consists of a silicon chip that is bonded to an LTCC-substrate (Low Temperature Co-fired Ceramics) using a bonding layer that contains an rms and a solder preform. The reaction propagation speed of the reactive multilayer was set to a value of 1 m/s, in order to partially melt a solder preform underneath a silicon chip. The second configuration, which consists only of the LTCC-substrate and the rms, was chosen to study the differences between the thermal outputs of the two arrangements. The analysis of the CFD simulations was particularly focused on interpretations of the temperature and liquid fraction contours. The CFD thermal simulation analysis conducted contains a melting/solidification model which can track the molten/solid state of the solder in addition to modelling the influence of latent heat. To provide information for the design of a test-substrate for experimental investigations, the real behaviour of Pt-100 temperature probes on the LTCC-substrate was simulated, in order to monitor an actual bonding in the experiment. All simulations were carried out using the ANSYS Fluent software.

Characteristics of micro energetic semiconductor bridge initiator by depositing Al/MoO3 reactive multilayered films on micro bridge with different bridge size

Four types of Al/MoO3 micro energetic semiconductor bridge (MESCB) initiators were prepared by integrating 3 µm Al/MoO3 reactive multilayer films (RMFs) on micro semiconductor bridge (MSCB) with different bridge areas. The bridge areas were varied from 11661 µm2 to 489 µm2, and the ratio of length to width, the thickness, V-type angle were fixed at 0.54, 2.5 µm, 90°, respectively. The heating process of MSCB before electrical explosive was analyzed with multi physical simulation (MPS). The electrical explosive characteristics of these MESCB as well as MSCB were investigated under the stimulation of 47 µF tantalum capacitor discharge. The MPS results reveal that the V-shaped sharp corner of MSCB has highest temperature and the completed melting time of MSCB is decreased with lowing of bridge area. The critical burst time and critical burst energy of MSCB and MESCB also decrease with the decreasing of bridge area. When bridge area is 11661 µm2, the critical burst time of MSCB and MESCB drops with applied voltage, while critical burst energy is independent on applied voltage. Besides, the critical burst time and energy of MESCB are the higher than that of MSCB with bridge area of 11661 µm2. When the bridge area is reduced to 2915 µm2, the critical burst time and critical burst energy for MESCB are no significant difference with the corresponding MSCB. In addition, the critical burst time MSCB and MESCB have no relationship with outer stimulation energy as the bridge area further decrease at 489 µm2. The flame duration time of MESCB barely decreases when lowing the bridge area, which suggests that the energy consumption of MESCB can be reduced by decreasing the bridge area without weakening its firing performance.

Development of Actuators for Repairing Cracks by Coating W Wires with Reactive Multilayers.

The aim of this research work was to optimize the coating of tungsten wires with reactive multilayer thin films and promote an exothermic self-propagating reaction. The ultimate goal is to use this heat to liquify low melting temperature materials, and thus block crack propagation in metallic materials. Ni/Me (Me = Al, Ti) multilayers were deposited by a DC (direct current) magnetron sputtering onto tungsten wires with diameters of 0.05 and 0.20 mm. The depositions were carried out to obtain films with near equiatomic average chemical composition and a modulation period (bilayer thickness) between 20 and 50 nm. The cross-section of the films was analyzed using electron microscopy before and after electrical ignition. A new substrate holder was developed to improve the quality of the Al/Ni films, allowing a reduction in the defects previously observed. The Ni/Ti thin films showed no discernible defects, regardless of the substrate holder. However, after ignition, the Ni + Ti reaction occurred in a non-self-propagating mode. Passing an electric current through a wire (ϕ = 0.05 mm) coated with an Al/Ni thin film, promoted a flash of light that was associated with the start of a self-propagating reaction. The reaction product was a B2-AlNi intermetallic phase. W wires coated with reactive multilayers may contribute to crack filling, and have potential to be self-healing actuators.

Effect of substrate–induced localized stress on the combustion properties of Al/CuO reactive multilayer films

Reactive multilayer films are a high energy dense configuration for energetics widely studied for various pyrotechnic applications. The objective of this study is to investigate the influence of substrate–induced localized stress on the combustion properties of Al/CuO reactive thin films. Square microbumps are patterned on glass substrates to serve as embedded stressor elements. Stress-induced structural or morphological changes of the materials deposited around the microbumps are characterized using high-magnification transmission and scanning electron microscopy, providing simultaneous nanometer imaging resolution and detailed chemical analysis. The structural and chemical changes (appearance of reactant intermixing and voids) around the microbumps modify the energetic reservoir and the thermophysical properties of the film. The heat of reaction, the flame temperature and the effective thermal conductivity of the film are altered (loss of ∼15%), leading to a global decrease in the material reactivity. The flame velocity of the film deposited on the substrate with microbumps drops by 9.2%, 32.4% and 48.7% for microbump heights of 0.15, 0.35 and 0.83 µm, respectively. This work helps deepen the understanding of the effect of stress-induced strain on reactive film combustion properties and provides perspectives for controlling the reaction of reactive thin films by tailoring the strain distributions within the films.

Al/Ni reactive multilayer films enhancing the properties of plasma induced by nanosecond pulsed laser

In this paper, the influence of Al/Ni reactive multilayer films on laser ablation induced plasma process is investigated. Laser ablation of single Ni layer and Al/Ni RMFs was performed by nanosecond pulsed laser beam with 1064 ​nm wavelength. The characterization methods were applied for researching the structure and chemical composition with transmission electron microscopy, X-ray photoelectron spectroscopy, and atom probe tomography. The effects of the Al/Ni RMFs on the plasma properties were then systematically investigated in terms of the electron temperature, density and ionization. Meanwhile, measurements of the plasma expansion velocity were performed using ICCD system. The results exhibit improved plasma behaviors with high electron temperature, fast expansion velocity and violent ablation phenomenon of Al/Ni RMFs in comparison with the Ni film, which is significant for broadening the potentials in military applications.

Combined Properties of Al/Ni Reactive Multilayer Films During High-Rate Heating Using a Pulse of Current

We use pulses of current to investigate the combined properties of Al/Ni multilayer films under high-rate heating by measuring current-voltage waveforms and the flyer velocity. Explosion occurs earlier in the Al/Ni multilayer foil than in the Al and Ni films, suggesting that the addition of Al/Ni affects the electrical exploding process, which is not controlled solely by resistance. The experiments indicates that the differences between the physical properties of the Al and Ni films is a factor to causing higher plasma electron temperature and absorb more electrical energy than the single Al or Ni film. The flyer velocity of the Al/Ni multilayer film is much lower than that of the Al film due to the high adiabatic index of Ni.

Ignition characteristics of energetic nichrome bridge initiator based on Al/CuO reactive multilayer films under capacitor discharge and constant current conditions

Four types of Al/CuO energetic nichrome bridges (ENCBs) initiators are reported, prepared by integrating Al/CuO reactive multilayer films (RMFs) on different V-shaped nichrome bridges (NCBs) through magnetron sputtering technology. V-type angles of NCBs are 150°, 136°, 120° and 90°. The fabrication, electrical explosive characteristics of these ENCBs initiators under capacitor discharge, as well as its firing process under constant current conditions are systematically described. The results reveal a ‘stagflation’ phenomenon in high-speed photograph of ENCBs at low discharge voltage, which is consistent with the result of optical microscope images. It is noted the electric explosion delay time decreases with an increase in the discharged voltages, while the critical ignition energy has no relationship with discharged voltages. Moreover, among the four ENCBs, the one with V-angle of 90° exhibits the shortest electric explosion delay time and lowest critical burst energy. This suggests that the electrical explosion performance of ESCBs can be adjusted by optimising the V-shaped angle and the discharge voltage. At last, the high combustion efficiency of ENCB is proved by comparative test with NCB at 0.6 A. And ENCBs have better heating efficiency than nichrome wire with the same resistance at 0.4A and 0.6A.

Influence of Interface Layer on the Properties of Exploding Foil Flyer Generator by Integrating Al/Ni Multilayers

Reactive multilayer films (RMFs) are a type of a thermite nanoenergetic multilayer film, which can be potentially applied to an exploding foil flyer generator (EFFG). Herein, Al/Ni RMFs with a bilayer thickness of 500 nm are integrated into an exploding foil layer by a magnetron sputtering method. The effects of interface layer on the properties of the EFFG are systematically investigated in terms of the electrical behavior and flyer velocity. The interface layer is controlled by annealing, whose structure and chemical composition are confirmed by X‐ray diffraction and transmission electron microscopy. The periodic multilayer structure can be clearly visible, and the thickness of interface layer increases with increasing annealing temperatures from room temperature to 573 K. The EFFG integrating as‐deposited Al/Ni RMFs exhibits improved exploding properties with a short exploding time, violent explosion region, and high flyer velocity phenomenon in comparison with generator at 573 K. Overall, the EFFGs integrated Al/Ni RMFs with larger interface layers can decrease the electrical plasma performances, which are significant for investigating the applicability in various engineering fields.

Laser welding of Ti6Al4V assisted with nanostructured Ni/Al reactive multilayer films

In this paper, the nanostructured reactive multilayer films (RMFs) are used as the intermediate layer to assist laser welding of Ti6Al4V alloy. During the welding process, the heat of the laser ignites the RMFs, and the heat released by the RMFs reaction instantaneously reaches the liquidus temperature in the center of the joint. This new joining method is helpful in reducing the laser energy input, minimizing the increasing brittleness and reducing strength effect of heat affected zone of the titanium alloy base material, and increase the joint strength of welds. The experiment confirmed that the joint with the Ni/Al RMFs as the intermediate layer can achieve a shear strength of 396 MPa at 700 W laser power, which is 3 times as high as that of the direct laser welded joints without using Ni/Al RMFs at the same power. Moreover, the Ni/Al RMFs as an intermediate layer can reduce the laser power required for welding by 10–20% without lowering the joint strength.

Characteristics of energetic semiconductor bridge initiator based on different stoichiometric ratios of Al/MoO3 reactive multilayer films under capacitor discharge conditions

Three types of Al/MoO3 energetic semiconductor bridge (ESCB) initiators were prepared by integrating Al/MoO3 reactive multilayer films (RMFs) of different stoichiometric ratios on semiconductor bridges through magnetron sputtering. The stoichiometric ratios of Al:MoO3 were 4:1, 2:1, and 4:3. An experimental investigation for obtaining the electrical explosive characteristics of the ESCBs with different stoichiometric ratios of Al/MoO3 RMFs was carried out under the stimulation of a 47 μF tantalum capacitor discharge. The results reveal a ‘stagflation’ phenomenon in the voltage–current–resistance curves of the ESCBs, which is obvious at low discharge voltages. The critical burst energy and critical burst time decrease with an increase in the MoO3 ratio in RMFs for initiators discharged with identical voltages. Moreover, among the three ESCBs, the one with a stoichiometric ratio of 4:3 exhibits the highest performance with the shortest critical burst time, lowest critical burst energy, and most violent explosion phenomenon. This suggests that the ignition performance of ESCBs can be enhanced by optimising the stoichiometric ratio of Al/MoO3 RMFs.

Metal–interlayer–metal structured initiator containing Al/CuO reactive multilayer films that exhibits improved ignition properties

Aluminum/cupric oxide (Al/CuO) reactive multilayer films (RMFs) are widely used for micro-chip energetic initiator applications; however, there are only a few examples where they are initiated through the direct input of electrical energy. This study describes the preparation of micro-chip energetic initiators containing Al/CuO RMFs as an interlayer between two Al electrical contact pads that are prepared using an image reversal lift-off process and the magnetron sputtering technology. This design enables the direct transfer of current from the contact pads to Al/CuO RMFs, which results in fast ignition (less than 1.0 μs) and produces luminous flame ball that spread over a wide area (maximum flame area of 13.8 mm2). A metal–interlayer–metal (MIM) structured initiator will not be fired until the external voltage has exceeded the breakdown field strength of CuO layers. These initiators achieved a critical breakdown voltage (VB) of 32–50 V and a complete electrical-explosion voltage (VC) of 72–84 V. The ignition threshold rises with increasing the bilayer thicknesses of the RMFs. These characteristics of this specially structured initiator are well suited for applications in highly efficient and insensitive initiating explosive devices.

Joining of Carbon Fiber Reinforced Plastic to Aluminum Alloy by Reactive Multilayer Films and Low Power Semiconductor Laser Heating

This study investigated the characteristics and strength of the dissimilar joints between carbon fiber reinforced plastic (CFRP) epoxy composites and aluminum alloys using two different heating methods, Ni/Al reactive multilayer films (RMF) and a low power continuous wave diode laser. To enhance the adhesion, the top resin layer of the CFRP and the surface of the aluminum alloy were patterned by femtosecond laser. Polycarbonate (PC) was used as a filler material during the joining processes. ANSYS simulation was applied to elucidate the thermal kinetics of the self-propagation reaction and the thermal profile, and evaluate the possibility of joining CFRP to aluminum using Ni/Al RMFs. The SEM image of the cross-section shows that melted PC flowed into the CFRP–aluminum alloy interface, suggesting strong mechanical bonding. A tensile strength of 9.5 MPa was reached using Ni/Al multilayers as heat sources, which provides a new way for joining CFRPs and aluminum alloys in space or under water.

Interaction between Ni/Ti Nanomultilayers and Bulk Ti-6Al-4V during Heat Treatment

The diffusion bonding of Ti-6Al-4V to NiTi alloys assisted by Ni/Ti reactive multilayer thin films indicates the diffusion of Ni from the filler material towards bulk Ti-6Al-4V. As a consequence, the fragile NiTi2 intermetallic phase is formed at the joint interface. In this context, the aim of this work is to investigate the occurrence of Ni diffusion from Ni/Ti nanomultilayers towards Ti-6Al-4V substrates. For this purpose, multilayer coated Ti alloys were studied in situ at increasing temperatures using synchrotron radiation. After heat treatment, scanning electron microscopy (SEM) analyses were carried out and elemental map distributions were acquired by electron probe microanalysis (EPMA). The EPMA maps confirm the occurrence of Ni diffusion; the presence of Ni in the substrate regions immediately underneath the nanomultilayers is clearly indicated and becomes more pronounced as the temperature increases. The presence of Ni is observed in the same locations where V is found, thus in β-Ti grains of Ti-6Al-4V. At the same time, the synchrotron results together with SEM analyses allow the increase of the amount of β-Ti phase in Ti-6Al-4V to be identified, while the thin films are mainly constituted by NiTi2. Therefore, the presence of the brittle NiTi2 intermetallic phase can be avoided if Ni diffusion is prevented.

Optimisation of modulation period of TiO2/Al reactive multilayer films for laser-driven flyer plates

Reactive multilayer films (RMFs) are a type of energetic nano-composite material and can be integrated into ablative layer structures using micro-electro-mechanical systems technology. They could potentially be applied to a laser-driven flyer detonator. In this study, TiO2/Al-based RMFs with two different modulation periods were integrated into multilayer flyer plates using magnetron sputtering technology, which produced nano-energetic multilayer films with optimised performance for laser-driven flyer plate systems. The effects of the TiO2/Al RMFs on the laser-driven properties of the RMF flyer were then systematically investigated in terms of the electron temperature and density using laser-induced breakdown spectroscopy. Measurements of the RMF flyer velocity were performed using a photonic Doppler velocimetry system. Electron temperatures of 6331.2–10563.0 K, electron densities of 4.03–12.69 × 1015 cm−3, and flyer velocities of 3854.7–6417.7 m/s were produced in the RMFs merely by changing the modulation period of the TiO2/Al RMF. This behaviour was also consistent with that found using a thermal conduction model in combination with a mass-diffusion reaction model. The RMF flyer exhibited a high level of integrity and promoted laser-driven energy efficiency, which are significant for improving the performance of a laser-driven flyer detonator for military and civilian applications.

Pulsed voltage breakdown of Al/CuO reactive multilayer films in metal-interlayer-metal structures

In this study, metal-interlayer-metal (MIM) structure samples are designed to investigate the breakdown properties of aluminum/cupric oxide (Al/CuO)-based reactive multilayer films (RMFs) and to evaluate the differences in the breakdown properties between the Al/CuO RMFs and the single-layer CuO film sample. The MIM structure samples use Al/CuO RMFs as the interlayers between the top and bottom aluminum electrodes, like a sandwich. The pulsed voltage is produced by a capacitor. The samples are not discharged until the external voltage exceeds the breakdown field strength (EB) of the Al/CuO RMFs. The results show that the EB of the Al/CuO RMFs can be improved by Al interlayers in the RMFs, but the destruction area caused by breakdown is smaller than that of the single-layer CuO film. A theoretical model indicates that the thermal conductivity and vaporization heat are crucial parameters for the breakdown of Al/CuO RMFs. The viewpoint from the breakdown of the Al/CuO RMFs proposed in this study might provide a new way for interpreting the electrical excitation process in RMFs.

Microstructures and Reaction Properties of Ti/Ni, Ti/Al and Ni/Al Multilayer Films

Reactive multilayer thin films are well-defined heterogeneous nanostructured energetic materials which can release chemical energy through a self-sustainable reaction. They have attracted intense interests due to potential applications in diverse fields such as joining, igniters, and high energy density power sources. In this paper, Ti/Ni, Ti/Al and Ni/Al multilayer films were prepared by magnetron sputtering. The reaction kinetics, microstructure and phase variation of these free-standing films are comparatively investigated. During slow heat reaction, the reaction products of reactive multilayer Ti/Ni nanofoils change from B2-TiNi austenite phase into TiNi3, illustrating an evolution of the phase transformation during reaction. These intermediate phases are also identified by slow heating and quenching. The fast speed imaging exhibits that the front speed is 0.47m/s, 0.8m/s and 3m/s respectively for as-deposited Ti/Ni, Ti/Al, and Ni/Al films. Differential thermal analysis yields that the corresponding releasing heat is 551.44 J/g, 434.18 J/g, and 562.5 J/g for these three composites. The theoretical minimum multilayer thickness for melting a tin solder layer has been calculated on the base of these characterizations, which proved the application potential of joining using the as-deposited film.