Besides a typical high-density plasma source, electrical explosion of conductors is also indispensable in switches, nanomaterial synthesis, shock-wave sources, etc. In this paper, an experimental study regarding plasma dynamics of electrical wire explosions (μstimescale) is presented, with spatiotemporal resolved diagnostics. Pure Cu/Ni wire and Cu-Ni alloy wire were used and compared. The alloy wire usually has a higher resistivity, resulting in a higher initial energy deposition (heating) rate. Abel inverse transformation indicated that the plasma radiation focussed on the outer region of the discharge channel for the alloy wire. In addition, the metallic vapour determined by the material properties had a considerable influence on the plasma process and resulting nanomaterials. In particular, both transverse and axial-layered structures were observed in alloy wire vapour. In addition, for the first time, the expanding arc-like plasma of explosion products was understood and examined from aspects of material properties and energy relaxation. The later stage of wire explosion resembled the state of regular metal vapour arcs under 1 MPa pressure. Finally, the core factor for the fast energy deposition stage of wire explosion was ascertained. Correlations between pre-exposition circuit parameters and post-explosion dynamic effects were found, which is significant for practical applications.

2D nanosheet is indispensable for the design and production of functional materials and devices. [1,2] Particularly, 2D layered materials, including graphene, phosphorene, and 2D bismuth selenide (Bi 2 Se 3 ), exhibit massive potential due to their unique electrical, optical, thermal, and mechanical properties. [3,4] Compared with classical graphene, phosphorene, 2D Bi 2 Se 3 , and other materials have shown more intriguing features and application prospects. [5][6][7][8] For example, single-and few-layer BP (2D BP) endow with a direct and tunable bandgap ranging from 0.3 eV (bulk) to 2.0 eV (monolayer), [9] which is favorable for making electric devices and photoelectric detectors. Bi and Se elements contained compounds are always selected as the electrode materials for supercapacitors and achieve satisfactory performance. [10][11][12] Khalafallah et al. designed the selenium-enriched reduced graphene oxide hybridized hetero-structured nickel bismuth selenide (RGO/Ni-Bi-Se) and bismuth selenide (RGO/Bi 2 Se 3 )based materials as positive and negative electrodes, respectively. The synthesized two electrode materials showed desirable performances (electrochemical behavior, pseudocapacitive properties, etc.). Furthermore, the established supercapacitor achieved admirable energy density with great capacity retention. [13] In addition, the layer 2D material has a considerable value of specific surface area and can be feasible for surface modification as catalysts. [14] The mainstream methodology to synthesize 2D thin nanosheets would be the exfoliation from the layered bulk form. [2] Due to the relatively weak van der Waals interlayer interaction of the materials, sometimes the exfoliation can be achieved via mechanical methods directly. [15] However, not all 2D materials can be easily exfoliated by the mechanical approach. The most prevalent and feasible way is the liquid exfoliation, where the layered bulk is immersed in suitable solutions. [16] In this case, chemical reactions intentionally introduce to facilitate the exfoliation process, such as oxidation reaction, intercalation, etc. Additional tools, including ultrasonic wave and electrochemical reaction, are also proposed to enhance liquid exfoliation. [2] Electrical explosion, characterized by ultrafast atomization and quenching rate (dT/dt ≈ 10 10 -10 12 K s -1 ) of the sample, is a unique approach for "onestep" synthesis of nanomaterials. Experiments are carried out with layered graphite and Bi 2 Se 3 under the action of electrical explosion in a confined reaction tube. High-speed photography and electrophysical diagnostics are applied to characterize dynamic processes. SEM and EDS are used to characterize surface micro-morphology of reaction products. The layered materials are first exfoliated to thin nanosheets/nanocrystals by shock waves and turbulent flow of the explosion. As the ionized explosion products (>10 000 K) contacts the sample, intense heat transfer happens, simultaneously atomizing the sample and quenching the plasmas. As a result, nanoparti...

The physical image of the confined electrical explosion in the source region is depicted. Metallic plasma/vapor dynamics and its fragmentation effect (on the confining structure) under μs-timescale are diagnosed via high-speed photography, electrophysical, and spectral measurements. When adding a 1-mm-thick Teflon tube outside the exploding wire, the growth of spatial heterogeneity by electro-thermal instability (ETI) is largely compressed and the deposited energy almost doubled from about 85 to 150 J. During the short period after breakdown, considerable energy depositing into the confined space, e.g., 100 J for 0.1 cm3, drives the fast inflation and burst of the 0.5 g confining tube to ~500 m/s (kinetic energy of ~62.5 J). Intense plasma jets eruption with supersonic speed >1.5 km/s and induced shock waves of 2-3 km/s are observed from cracks of the inflated tube. Besides, the erupted plasma jets gradually evolve Rayleigh-Taylor instability (RTI) and finally cause turbulent mixing with the ambient medium. This mechanism is very likely to explain the plasma cavity evolution in underwater explosion. Interestingly, although the confining effect of water is stronger than a Teflon tube, the latter has a better response to the high-rate impulse loading and absorbs more deposited energy by deformation, phase transition, and acceleration.

Fe-Ni-based nanocrystalline coatings with unique magnetic properties are widely used as soft magnetic materials and usually act as the core component in electronic devices. Nanocrystallized particles and thin films have become a popular contemporary research direction. Electrical explosion, characterized by an ultrafast atomization and quenching rate (dT/dt ~ 109–1011 K/s) for the material, is a unique approach for the rapid “single-step” synthesis of nanomaterials and coatings. In this study, experiments were carried out with intertwined wire under a directional spraying device in atmospheric Ar ambience. Two load systems of Fe-Ni and Fe-Ni-Co were considered in this work. Electrical parameters and high-speed camera images were obtained to reveal the physical mechanism and dynamic process of explosive spraying. The morphologic and crystallographic results were characterized by SEM and XRD. The magnetic properties were measured via VSM equipment, and the parameters of saturation magnetization Ms, residual magnetization Mr, and coercivity Hc were emphasized in the hysteresis loop pattern. The experimental results indicate that a dense coating was prepared with extremely low porosity, and the morphology of the coating surface shows different regions characterized by solidified chunks and loose particles. XRD patterns showed that crystalline structures were discrepant under two load systems with different Ni weight proportions. Magnetic measurements gave a thin and narrow hysteresis loop, which represents loops with good soft magnetic properties. Quantitatively, coercivity Hc decreased from 59.3 to 52.6 and from 121.0 to 49.9 for the coatings not containing and containing Co under parallel and perpendicular fields, respectively.

Nanomaterials with unique structural and properties can be synthesized by rapid transition of the thermodynamic state. One promising method is through electrical explosion, which possesses ultrafast heating/quenching rates (dT/dt~109 K/s) of the exploding conductor. In this study, experiments were performed with fine metallic wire exploding in liquid nitrogen (liq N2, 77 K) under different applied voltages. For the first time in the literature, the physical image of the electrical explosion dynamics in liq N2 is depicted using electro-physical diagnostics and spatial-temporal-resolved photography. Specifically, the pulsation and collapse processes of the vapor bubble (explosion products) have been carefully observed and analyzed. As a comparison, an underwater electrical explosion was also performed. The experimental results suggest that the vapor bubble behavior in liq N2 differs from that in water, especially in the collapse phase, characterized by secondary small-scale bubbles in liq N2, but multiple bubble pulses in water; correspondingly, the products’ characteristics are discrepant.