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Bimodal nano / micro powders are in demand in powder injection molding (PIM) and additive manufacturing (AM) technologies. Feedstocks with bimodal powder have a higher flowability, and the resulting products have a higher density. In this work, a bimodal 316L steel powder obtained by the electric explosion of a wire (EEW) was investigated. The bimodal powder is formed directly during the explosion and does not require a mixing step. The powder was obtained at different explosion energy densities. A feedstock was obtained with a powder content of 94 wt%. The powders have a different micro: nano ratio depending on the energy density. Feedstocks with these powders have different rheological behavior. The morphology and chemical composition of the powders and the homogeneity and rheological properties of feedstock with bimodal powder were studied and discussed. A comparison of feedstock properties with bimodal and micron powder is carried out.

Enhanced activity in low-temperature water-gas shift (LT-WGS) reaction of some ceramometal catalysts compared to conventional Cu–Zn–Al oxide catalyst was demonstrated. Porous ceramometals were synthesized from powdered CuAl alloys prepared by mechanical alloying with the addition of either CuAlexp powders produced by current spark explosion of Cu+Al wires or CuZnAl oxide obtained by coprecipitation. Their structural, microstructural, and textural characteristics were examined by means of X-ray diffraction, scanning electron microscopy with energy-dispersive X-ray spectrometry, NMR, and adsorption methods, and catalytic properties were studied in the LT-WGS reaction. CuAlO/CuAl ceramometals were found to have mostly the egg-shell microstructure with the metallic cores (AlxCu1–x, Al2Cu, and Al4Cu9) and the oxide shell containing copper oxides and/or mixed oxides of copper and aluminum and, at same time, CuAlO/CuAl ceramometal with incorporated additives was found to create a more complicated microstructure. A large amount of X-ray amorphous oxides of copper and aluminum is typical for all composites. CuAl ceramometal was shown to be more active than the CuZnAl oxide catalyst in spite of a much lower specific surface area. The CuAl+CuZnAl catalyst consisting of prismatic granules showed a higher activity in comparison with CuZnAl oxide consisting of cylindrical granules. The activity of the composite granulated catalyst referred to its unit weight was more than 6-fold higher as compared to the oxide catalyst, while the activity per the surface area was found to be more than an order of magnitude higher due to much higher specific activity of small fraction and additively much lower diffusion limitation of granules.

This research aims to determine consistent patterns in the formation of structure-phase states of bimetallic nanoparticles in the course of non-synchronous electrical explosion of two intertwined wires made of dissimilar metals (EEIW). It was shown by the example of Al Ag, Al Cu and Al Zn binary systems that EEIW can be used to obtain bimetallic nanoparticles with controllable phase composition. The phase composition of the nanoparticles is determined by the ratio between the diameters of the exploded wires. It was found that if the interval between non-synchronous explosions lies within 0.0 ÷ 1.82 μs, then the nanoalloying of clusters during coagulation is not limited. The research findings can be used for making use of EEIW to obtain a wide range of bimetallic nanoparticles with controllable phase composition.

Nanostructured W-31wt.%Cu composite was for the first time produced via magnetic pulse compaction from bimetallic particles obtained using electric explosion of intertwisted copper/tungsten wires in argon and then characterized for microstructures, mechanical strength and tribological behavior at high temperatures. Microstructure of the composite is characterized by recrystallized copper grains with mean grain size of 59 ± 3 nm and unreacted spherical tungsten particles. The composite density was in the range 93–99%. Flexural and compression strengths were 560 ± 10 and 1035 ± 150 MPa, respectively. Tribological high temperature tests showed that this composite develops reduced wear starting from the testing at 250 °C. Such an adaptation mechanisms is related to generation of copper tungstate CuWO4 on the worn surfaces.

The work researches the influence of metal mixing enthalpy on spontaneous nanoalloying of coagulated clusters formed when intertwined Fe/Ag, Ni/Ag, Nb/Сu and Pb/Сu wires with equiatomic composition are exploded. The analysis of temporal dependencies of currents and voltages has shown that the intervals between the successive explosions of Fe/Ag, Ni/Ag, Nb/Сu and Pb/Сu wires are 0.38, 0.26, 0.43 and 0.4 μs, respectively. This explains their asynchronous destruction. It has been found that when wires are exploded, bimetallic Janus and core-shell nanoparticles are formed. The obtained data makes it possible to conclude that when wires explode non-synchronously, clusters coagulate and atoms of metals subsequently intermix. The results of the research demonstrate that the explosion of two wires made of metals with positive mixing enthalpy (from 8 to 116 kJ/g) is a process that can be used to obtain bimetallic nanoparticles with complex structures.

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.

Bimetallic nanoparticles with core-shell structure and Janus nanoparticles attract much attention because of their unique properties. In this article we demonstrate the capabilities of an efficient method of synthesizing a wide range of bimetallic nanoparticles by the electrical explosion of two wires made of immiscible metals. To synthesize bimetallic nanoparticles, we have chosen model metals whose liquid phase undergoes lamination only within a limited temperature and concentration interval (Cu Nb and Pb Cu) and metals whose components laminate in the liquid state over a wide interval of temperatures and concentrations (Ag Ni and Ag Fe). It has been shown that the structure type of the resulting bimetallic nanoparticles (homogeneous distribution of the components, core-shell nanoparticles or Janus nanoparticles) depends on the surface energy and the crystalline structure of the metals.

The authors consider and evaluate the physical parameters and regularities of the process of consolidation of Fe–Cu, Cu–Nb, Ag–Ni, Fe–Pb nanoparticles when creating composite materials by means of shock wave compaction. As a result of theoretical consideration of explosive compaction process, researchers established and discussed the physical process conditions, established a number of threshold pressure values corresponding to different target indicators of the state of the compact. The time of shock wave impact on powders for powder consolidation was estimated.

Based on the statistical approach to the description of the structure of liquid metals, it has been shown that during wire heating with a current pulse, the drastic local increase in the electric resistance of the liquid metal leads to the development of overheating instability. The increase in the electric resistance of the liquid metal is a consequence of the destruction of individual atom clusters that form short range order in the liquid metal. Non-uniform heating leads to the transition of liquid metal into a two-phase “gas-liquid” state formed by the expanding products of the explosion of wires. The majority of the expanding wire explosion products are liquid phase particles; those coagulate to form a binary melt. It has been shown by the example of Pb/Al, Ag/Cu and Cu/Al nanoparticles forming during the electric explosion of two wires made of different metals that the structure and phase state of the particles is determined by the probability of the formation of the binary melt that depends on the temperature of the coagulating particles.

This work studies the impact of the size of grains/crystallites on the structural characteristics of the nanoparticles formed as a result of the electric explosion of wires. The temporal dependencies of the current and voltage in the conditions of EEW experiments were analyzed. It was concluded that an increase in the grain/crystallite size does not result in a significant change in the electric resistance of the wires that are in solid state. It was demonstrated that an increase in the grain/crystallite size does not result in an increase in the average nanoparticle size. The structure of the nanoparticles with the size between 80 and 110 nm is close to a monocrystalline one. This data allows for making an assertion that certain models suggested in research papers to explain non-equilibrium phase transitions cannot be applied when describing the electric explosion of wires.

Four bimetal Al–Ni nano-powders with compositions varied from 5 to 45 at% of nickel were synthesized by explosion of electrically heated twisted pure Al and Ni wires in argon. The nano-powders were characterized using electron microscopy, x-ray diffraction, and thermal analysis. Materials were ignited using an electrically heated filament coated with powder and electrostatic discharge (ESD). The results were compared to those for pure nano-aluminum powder (n-Al) prepared using the same wire explosion technique. The nano-powders with high nickel concentrations contain fully reacted intermetallic phases, which are difficult to oxidize making them unattractive for energetic formulations. Nano-powders with lower nickel concentrations do not contain significant amounts of the intermetallic phases. No intermetallics were detected in the powder with 5 at% Ni, which oxidized qualitatively similar to n-Al. The overall mass gain during oxidation for the bimetal powder was nearly identical to that of n-Al, suggesting the same heat release anticipated from their combustion. Oxidation kinetics assessed for this material accounting directly for the measured particle size distribution was compared to that of n-Al. The bimetal powder oxidized slower than n-Al, indicating its greater stability during handling and storage. The bimetal powder was less ESD-ignition sensitive than n-Al, but generated a stronger emission signal when ignited. Therefore, the bimetal powder with 5 at% Ni is an attractive replacement of n-Al for advanced energetics with lower ESD sensitivity, better stability, and improved combustion performance.

In this study, Cu/Ag, Сu/Pb and Al/Pb binary metallic nanoparticles were synthesized by the electrical explosion of two twisted wires from immiscible elements (i.e., Сu–Ag, Cu–Pb and Al–Pb). The distribution of metallic components in the nanoparticles depended on the melting temperature, metal density, and degree of initial wire superheating. Different types of nanoparticles, such as nanoparticles with no separation between the metal phases, as well as core-shell and Janus nanoparticles were formed depending on the process parameters and the characteristics of the metals. Certain binary metallic nanoparticles were formed when the metal clusters were combined and formed during the initial stages of dispersing the two wires using a pulse of electrical current.

This research shows the possibility of obtaining composite W-Cu nanoparticles with the core-shell structure and high content of copper by means of electrical explosion of intertwined W and Cu wires. The use of electric pulse plasma sintering on the obtained W-Cu composite nanoparticles in vacuum in the temperature range 900-1030 °С over 10 minutes has allowed us to fabricate 3D materials with the relative density of 95.3 ... 98.9 % and a conductivity that is close to the theoretical one (63.5-64.1 %IACS). Also, despite a significant content of copper, the microhardness of the 3D material was (2.68-2.7 GPa). High microhardness of the two-phase composite is attributed to its fine-grain structure. The conductivity and microhardness of the 3D W-Cu composite make it a promising material for different electrical engineering applications.

Bimetallic 73 wt.% Fe&ndash, Cu nanoparticles have been produced using electric explosion of two immiscible metal wires and then consolidated into disks using magnetic pulse compaction. The compacted disks have been characterized for phase composition, mechanical strength, and high-temperature steel ball-on-disk sliding friction. The sample possessed good flexural and compression strength. Friction and wear reduction were observed during sliding test at 400 &deg, C, which was explained by intense tribosynthesis of cuprospinel CuFe2O4 nanoparticles, which served to reduce adhesion between the ball and disk.

In this article, we present the results of the research into the characteristics of the conditions of heating and explosive destruction of Al-Cu, Fe-Ti, Fe-Cu, and Fe-Pb wires under a pulse of current with the density of 107 A/cm2. It has been shown that the energy that is deposited into the wire may depend on the relation between the thermophysical parameters and specific electric resistivity of the metals. It has been determined that under a pulse of current, the wires may explode synchronously or non-synchronously. During a synchronous explosion of wires, a single voltage pulse is generated. In the case of non-synchronous explosion, the wires explode in a succession, thus generating two voltage pulses. We suggested a dimensionless parameter that allows for predicting whether an electrical explosion of two wires of dissimilar metals is synchronous or non-synchronous. According to the research findings, non-synchronous nature of wire explosion may impact the formation of bimetallic particles through the explosion of two intertwined wires made of dissimilar metals.

The paper covers the evolution of the liquid phase formed under heating metal conductors by a pulse of current with the density of [j=~106-:106] A/cm{2}. Following the theoretical assessment and experimental data, it was shown that the two-phase state (condensed phase - gas) during the early expansion of products of electric explosion of wires can be caused by the development of density fluctuations in the liquid phase of the metal. The density fluctuation formation is caused by the destruction of liquid phase clusters of short-range order. The study demonstrated the absence of the complete transition of the semiconductor matter into gas after the injection of energy exceeding the energy of sublimation E s.

The work is focused on revealing the mechanism of structure and phase transformations in the metal wires under heating with a high-density current pulse (the electric explosion of wires, EEWs). It has been demonstrated on the example of brass and zinc wires that the transition of a current pulse with the density of j ≈ 3.3 × 107 A/cm2 results in homogeneous heating of the crystalline structure of the metal/alloy. It has been determined that under heating with a pulse of high-density current pulse, the electric resistance of the liquid phases of zinc and brass decreases as the temperature increases. The results obtained allow for a conclusion that the presence of the particles of the condensed phase in the expanding products of EEW is the result of overheating instabilities in the liquid metal.