Electrical Explosion Of Aluminum Wire Research Articles

Study on the properties of enhanced plasma injection driven by electrical explosion of aluminum wire in PTFE capillary in high-pressure SF6

Enhanced plasma injection (EPI) driven by the electrical explosion of a metal wire in a microcavity has been proven to be an effective method for triggering 10-cm-magnitude high-pressure SF6 gas gap at very low working coefficients and provides a potential technical routine for ultrafast bypass switches (UFBPSs). In this study, aiming to further promote the EPI strength and improve its triggering ability, the EPI actuator is optimized, and several vital parameters of the actuator structure, including diameter D and length L of the microcavity and nozzle shape, are investigated. EPI with a maximum height of ∼10 cm and an initial velocity of ∼1000 m/s can be realized in 0.5 MPa SF6 when a 600 μm aluminum wire is exploded by a ∼1000 J trigger pulse. The EPI strength vs D curve has an inverted V shape, and 2 mm D results in the most intense EPI, due to the competitive effect of the vent congestion inside a thin capillary and parasitic volume in a fat capillary. As L increases, the EPI strength increases to saturation and then decreases. A 20–23 mm L can yield suitable EPI strength with limited trigger energy. The nozzle shape has a remarkable influence, and a divergent-type nozzle leads to a much stronger EPI than the shrink-type or straight-type nozzle, generating an EPI with a maximum height of 12 cm and an initial velocity of 1600 m/s. This study provides a useful guidance for the EPI actuator design for triggering megavolt UFBPSs at very low working coefficients.

Numerical investigation of negative polarity electrical explosion of aluminum wire in vacuum

Numerical investigation was carried out on the evolution of inhomogeneous energy deposition of polarity effects in negative polarity electrical explosion of aluminum wire in vacuum. First, radial electric field distribution of the aluminum wire was simulated. The results showed that the initial electric field near electrodes was much smaller than that in the middle of the wire. A model of electrical wire explosion based on ZEUS-EW with artificial limitation on breakdown time of the aluminum wire was used to simulate the behavior of inhomogeneous energy deposition of the polarity effect. The complete evolution process of electrical explosion of the aluminum wire with inhomogeneous energy deposition was further explored and qualitatively divided into three stages according to the simulation results. Finally, the influence of some factors on the inhomogeneous energy deposition simulation was investigated. This study provides some help for a better understanding of the polarity effect in the process of wire explosion.

Preparation of Nano/Micro Bimodal Aluminum Powder by Electrical Explosion of Wires.

Electrical explosion of aluminum wires has been shown to be a versatile method for the preparation of bimodal nano/micro powders. The energy input into the wire has been found to determine the relative content of fine and coarse particles in bimodal aluminum powders. The use of aluminum bimodal powders has been shown to be promising for the development of high flowability feedstocks for metal injection molding and material extrusion additive manufacturing.

Stratification and filamentation instabilities in the dense core of exploding wires

We report experiments characterizing the stratified and filamentary structures formed in the dense core of nanosecond electrical explosion of aluminum wires to understand the physical scenario of electrothermal instability. Direct experimental observations for stratification and filamentation instabilities, as well as the coexistence state of azimuthal strata and vertical filament in the dense plasma column, are presented. The wire core exhibits remarkable different patterns of instability with the decreasing wire length. The shadowgram of shorter wires demonstrates that the instability is transformed from stratified structures to filamentary structures. According to a radial magnetohydrodynamic computation, the wire enters a phase state of negative temperature dependence of resistivity before voltage breakdown. However, filamentary structures are only observed in exploding wires of 1 cm and 0.5 cm in length. The analyses based on experimental and computational results indicate that the increase in internal energy determines the manifestation of instability in the dense core. Filamentation instability occurs when the total energy input is no less than 1.5 times the vaporization energy at the moment of voltage breakdown. The lower limit of energy deposition ensures that the increase in internal energy covers vaporization energy.

Electrical explosion of aluminum wire for preparation of nanoparticles: an experimental study

An experimental study on the characteristics of aluminum wire explosion in ambient gas is carried out. A compact experimental device is built to study the electrical parameters, morphology and size distribution of nanoparticles generated by wire explosion. The typical characteristics are obtained and the influence of the type and pressure of the ambient gas is investigated. The explosion process in argon indicates a longer time for breakdown development and larger deposited energy compared with those in helium. It is proposed that these differences are mainly due to different barrier effects on the formation of plasma channel. The nanoparticles formed in helium have a smaller average diameter, a more concentrated size distribution and a larger specific surface area. It is found that there exists a pressure of about 80 kPa, at which both the peak voltage and deposited energy possess the maximum values.

The formation and evolution of the core-corona structure in the electrical explosion of aluminum wire in vacuum: experimental and numerical investigations

Experimental and numerical investigations on the formation and evolution of the core-corona structure in the electrical explosion of aluminum wire in vacuum are presented. In the experiments of aluminum wire explosion, shadowgraphy, interferometry and schlieren optical diagnostics are constructed with a laser probe to study the morphological evolution and distribution of the core and corona. A set of computational models with cold start conditions, consisting of a thermodynamic calculation and magnetohydrodynamic model combined with a semi-empirical equation of state and transport coefficients, are established to reproduce the behavior of the electrical explosion of aluminum wire. The radial profiles of the density, temperature, current density and magnetic field, addressing the physical scenario of the formation and evolution of the core-corona structure are analyzed. The numerical results are also compared with relevant experimental data.

Numerical simulation of the initial plasma formation and current transfer in single-wire electrical explosion in vacuum**Project supported by the National Science Foundation of China (Grant Nos. 51322706, 51237006, and 51325705), the Program for New Century Excellent Talents in University, China (Grant No. NCET-11-0428), and the Fundamental Research Funds for the Central Universities, China.

In this paper, a computational model is constructed to investigate the phenomenon of the initial plasma formation and current transfer in the single-wire electrical explosion in a vacuum. The process of the single-wire electrical explosion is divided into four stages. Stage I: the wire is in solid state. Stage II: the melting stage. Stage III: the wire melts completely and the initial plasma forms. Stage IV: the core and corona expand separately. The thermodynamic calculation is applied before the wire melts completely in stages I and II. In stage III, a one-dimensional magnetohydrodynamics model comes into play until the instant when the voltage collapse occurs. The temperature, density, and velocity, which are derived from the magnetohydrodynamics calculation, are averaged over the distribution area. The averaged parameters are taken as the initial conditions for stage IV in which a simplified magnetohydrodynamics model is applied. A wide-range semi-empirical equation of state, which is established based on the Thomas–Fermi–Kirzhnits model, is constructed to describe the phase transition from solid state to plasma state. The initial plasma formation and the phenomenon of current transfer in the electrical explosion of aluminum wire are investigated using the computational model. Experiments of electrical explosion of aluminum wires are carried out to verify this model. Simulation results are also compared with experimental results of the electrical explosion of copper wire.

Characteristics and Diffusion of Electrical Explosion Plasma of Aluminum Wire in Argon Gas

Electrical explosion of aluminum wire is a very promising method for aluminum nanoparticle production. The exploding wire plasma has significant influence on the formation of the nanoparticles. In this paper, the electron temperatures and the electron densities in the plasma are estimated through Boltzmann plot and Stark broadening effect. The aluminum particle densities, charge state distributions, and the energy relaxation in the plasma are estimated accordingly. The diffusion of the plasma into protective argon gas is studied through its spatial distribution. The electron temperatures of the electrical explosion of wire (EEW) plasma with an aluminum wire in argon gas are 1~2 eV, and the electron densities are of the order of magnitude ~1019/cm3, which decrease rapidly over time after the EEW occurs. The diffusion of the EEW plasma of aluminum wire into ambient argon gas can be divided into two main phases, namely, the previous fast diffusion phase and the subsequent slow diffusion phase. The plasma is with quite different diffusion features due to the differences of the corresponding relative number density of the plasma to argon gas. For plasma with relative density much higher than 1, the diffusion velocity in the fast diffusion phase is significantly higher than that with relative density near 1, and in the slow diffusion phase, the distribution radius of the plasma can continue to increase significantly due to the considerable energy coupled from the circuit to the aluminum particles. Dependence of the plasma radii on the deposited energies are derived from the experimental data. For plasma with relative density near 1, due to the much longer relaxation time during the slow diffusion phase, very little energy can be transferred from the circuit to the aluminum particles and the plasma radii only increase slightly during this phase after the aluminum particles spent most of their kinetic energy in the previous fast diffusion phase.

Numerical investigation on the growth process and size distribution of nanoparticles obtained through electrical explosion of aluminum wire

Numerical investigations on the formation process and the final size distribution of nanoparticles during electrical explosion of Al wire are carried out. Firstly, the formation of the atomic vapor clusters is investigated. It indicates that the Al wire does not reach its atomization conditions. The size of the atomic vapor clusters is obtained, and it increases with the temperature at explosion. Then the growth process of Al nanoparticles from the formed atomic vapor clusters is modeled and the size distribution is predicted. The size distribution at different temperatures indicates that the growth process of Al nanoparticles becomes inactive gradually as the temperature decreases. The investigation of the size distribution under different cooling rates indicates that the bigger cooling rate is favorable for the formation of Al nanoparticles with smaller size dispersion and lower average dimension. The size distribution of Al nanoparticles obtained by the model is qualitatively consistent with the experimental data, which demonstrates the feasibility of this model.

Synthesis of Al nanoparticles and Al/AlN composite nanoparticles by electrical explosion of aluminum wires in argon and nitrogen

During the electrical explosion of aluminum wires in argon and nitrogen, Al nanoparticles and Al/AlN composite nanoparticles were synthesized. The as-prepared samples were characterized by transmission electron microscopy, energy dispersive X-ray microanalysis, X-ray diffraction and Brunauer–Emmett–Teller specific surface area measurements. The parameters of the electrical explosion of wires and the gas medium influenced the average size of the nanoparticles and the content of aluminum nitride in the powder. A nanoparticle formation mechanism caused by the coagulation of the primary particles generated in the early stages of the electrical explosion of the wires has been proposed.

Experimental investigation on the electrical explosion of single aluminum wire in vacuum

The electrical explosion of single wire occurs in many application fields, such as wire-array Z-pinch, synthesis of the nanopowder, high-intensity magnetic field source, etc. The initial stage of the electrical explosion of single wire has a critical influence on the stagnation and X-ray yield in the wire-array Z-pinch. The impressive result of X-ray yield from wire-array Z-pinch is a major motivation to promote the research in this field. Although numerous studies have been carried out to gain a deep insight into the physics of the electrical explosion of single wire, more experimental investigations are necessary to optimize the energy deposition and expansion rate. It is important to investigate the characteristics of the electrical explosion of single wire under the negative polarity pulsed-current, which is adopted in many Z-pinch facilities. In this paper, the electrical explosion of aluminum wire under negative polarity pulsed-current in vacuum is investigated. In the present experiments, the light emission is measured by the photomultiplier and streak camera. A laser probe EKSPLA-PL2251C (30 ps, 532 nm) is adopted to perform the shadowgraphy, schlieren and interferometry diagnostics. The radial knife-edge schlieren scheme is employed to translate the regions with plasma refractivity and gas-type refractivity. The interferometry is constructed based on Mach-Zehnder interferometer. The shadowgram, schlieren image and interferogram are recorded by Canon cameras. The typical waveforms of the voltage, current and light emission from the electrical explosion of 15 m-diameter, 2 cm-long aluminum wire are derived. The energy deposition at the instant of voltage collapse is about 2.4 eV/atom (vaporization energy is about 4 eV/atom). In order to increase the energy deposited into the wire, the 15 m-diameter, 2 cm-long aluminum wire with 2 m polyimide coating is exploded with the same electrical parameters. The energy deposition in the coated wire is about 5 eV/atom. From the shadowgram of the electrical explosion of uncoated aluminum wire, the expansion velocity of the high-density region can be estimated to be about 2.2 km/s. However, the expansion velocity of the high-density region of the polyimide-coated aluminum wire is about 5 km/s. The schlieren images show that the wire is exploded into a binary structure, i.e., a high-density core surrounded by the low-density corona. It should be noted that the energy deposition in the coated wire is larger than the vaporization energy, indicating that the aluminum wire is totally in gaseous state. Thus, the plasma region in the schlieren image of electrical explosion of coated wire is not distinct. The core-corona structure is depressed by the insulating coatings to a certain extent. The configuration of the parallel wire is adopted to estimate the expansion velocity of the plasma shell. The expansion velocity of the low-density plasma is about 5.8 km/s. Two-dimensional distribution of the phase shift is derived through the interferogram. The central part of the gas-type material with a radius of 0.1 cm exhibits a large positive phase shift, while the peripheral plasma shows a small negative phase shift. The three-dimensional atomic density distribution is reconstructed in the gas-type distribution area in which the contribution of electrons is negligible. In our experiments, the energy deposition of the electrical explosion of uncoated wire ranges from 2 to 4 eV/atom. This may be caused by the initial conditions of the wire surface and the connection between the wire and electrode. Further research should be carried out for a better understanding of this phenomenon.

Experimental investigation on the energy deposition and expansion rate under the electrical explosion of aluminum wire in vacuum

Experimental investigations on the electrical explosion of aluminum wire using negative polarity current in vacuum are presented. Current pulses with rise rates of 40 A/ns, 80 A/ns, and 120 A/ns are generated for investigating the influence of current rise rate on energy deposition. Experimental results show a significant increase of energy deposition into the wire before the voltage breakdown with the increase of current rise rate. The influence of wire dimension on energy deposition is investigated as well. Decreasing the wire length allows more energy to be deposited into the wire. The energy deposition of a 0.5 cm-long wire explosion is ∼2.5 times higher than the energy deposition of a 2 cm-long wire explosion. The dependence of the energy deposition on wire diameter demonstrates a maximum energy deposition of 2.7 eV/atom with a diameter of ∼18 μm. Substantial increase in energy deposition is observed in the electrical explosion of aluminum wire with polyimide coating. A laser probe is applied to construct the shadowgraphy, schlieren, and interferometry diagnostics. The morphology and expansion trajectory of exploding products are analyzed based on the shadowgram. The interference phase shift is reconstructed from the interferogram. Parallel dual wires are exploded to estimate the expansion velocity of the plasma shell.

Discharge Mode in Electrical Explosion of Aluminum Wire Under Various Argon Pressures

In this paper, spatial-resolved spectra of the electrical explosion of aluminum wire in argon gas were obtained through a imaging spectrometer. The distributions and compositions of the discharge plasmas after the secondary breakdown under various argon pressures were demonstrated and discussed based on the captured spectra. The discharge plasma presented significant difference under pressures below and above 30 kPa.

The Use of Alumina Nanoparticles as Modifiers of Galvanic Binder of Diamond Tools

This article presents results of a study of the surface topography of nickel composite electrochemical coatings (CEC), reinforced alumina nanoparticles, and the test results of the diamond tool. Used as a reinforcing phase alumina nanopowder was obtained by electrical explosion of aluminum wire in oxygenated atmosphere and had an average particle size of 60-70 nm. Experiments showed that the inclusion of alumina nanoparticles in a nickel matrix modifies its structure and increases the strength properties, so the wear resistance of diamond-plating increased by 3 times.

Influence of Energy Deposition on Characteristics of Nanopowders Synthesized by Electrical Explosion of Aluminum Wire in the Argon Gas

The energy deposition during the wire electrical explosion process plays an important role in the expansion of metallic vapor and conductive plasma for the nanopowders preparation. In this paper, aluminum nanopowders are synthesized by electrical exploding aluminum wire in the argon gas under different charging voltages of the capacitor. The influence of the deposited energy E and the argon gas pressure p on the characteristics of aluminum nanopowders is studied by the transmission electron microscope (TEM). Due to the effect of argon gas pressure on the energy deposition, a plasma expansion parameter $Ep^{-1}$ is proposed to summarize the synthesis conditions. The results show that the morphology of aluminum nanopowders was mainly dependent on the argon gas pressure rather than deposited energy. Lower deposited energy and higher pressure of argon gas could broaden the particle size distribution range of aluminum nanopowders evidently, which is ascribed to a smaller plasma expansion volume. The count mean diameter of aluminum nanopowders decreases monotonically with the increasing plasma expansion parameter $Ep^{-1}$. The value of relative standard deviation ranges from 0.38 to 0.5 in the experiments. It has been demonstrated that the size uniformity of nanoparticles can be improved by reducing the energy deposition rate when the pressure of argon gas and deposited energy remains virtually unchanged.

Numerical calculation of the current specific action integral at the electrical explosion of wires

The electrical explosion of aluminum wires is numerically simulated in the magnetohydrodynamic approximation for the current density ranging from 107 to 1010 A/cm2 and times to explosion varying from 10−10 to 10−6 s. It is shown that, at current densities of 108−109 A/cm2, low-temperature explosion conditions change to high-temperature ones, when inertial forces preventing the wire dispersion play a decisive role. This transition is accompanied by a sharp change in the thermodynamic parameters (the temperature and the energy deposited into the wire by the instant of explosion increase by several times), and the action integral for this transition increases smoothly approximately threefold as the explosion characteristics (current density and time to explosion) change by two orders of magnitude. The instant of transition from the low-temperature explosion to the high-temperature one depends on the radial dimensions of an exploding wire and does not depend on the properties of the environment.

Production of nanometer-sized ain powders by the exploding wire method

We have performed experiments to explore the possibility of making pure nanometer-sized AIN powders by electrical explosion of aluminum wire in an atmosphere of nitrogen-containing gases. It is shown that raising the density of the energy injected into the metal, applying increased pressures, and a high working-gas flow rate help assure the production of AIN powders with a specific surface up to 53 m 2/g, d BET =35 nm. Particle shape ranges from nearly spherical to rigorous-cut particles. The yield of such powder accounts for 50 % of the total mass of powder. The powder thus produced contains no more than 1 wt. % of impurities, including oxygen.