Effects of sintering temperature on the microstructure and properties of a W-Cu pseudo-alloy

This paper studies the feasibility of fabricating pseudo-alloys based on a W-Cu system through vacuum sintering of spherical bimetallic particles synthesized using the electric explosion of copper–tungsten wires in argon. The effects of the sintering temperature on the structure and hardness of the fabricated composites was studied. In terms of the structure of the samples, tungsten particles of predominantly spherical shapes with sizes ranging from submicrons to 80–90 μm were uniformly distributed throughout the copper matrix. Based on the analysis, the volume fractions of tungsten and copper were approximately equal. The calculated average phase compositions for all the samples were 58.9 wt% for W, 27.3 wt% for Cu, and 13.8 wt% WO2. When the annealing temperature increased from 1100 °C to 1250 °C, the wetting of tungsten by molten copper improved, which resulted in the porosity of the copper matrix being at the minimum, as observed in the contact zone. Due to good wetting and a decrease in the viscosity of copper, rearrangement of the solid phase of the tungsten in the bulk of the composites improved, and the density and hardness of the pseudo-alloy increased. The formation of coarse tungsten grains is caused by the fact that submicron and micron particles are growing in size and merging into agglomerates during the course of liquid-phase sintering, and this happens because of the high surface activity of ultrafine particles. Further research will be devoted to solving the discovered problems

The effect of low-temperature auto-ignition of W–Cu2O nanopowders with core-shell structure

In this work, the effect of in-vacuum low-temperature auto-ignition of a W–Cu2O nanopowders mixture obtained by natural oxidation of W–Cu composite nanopowders is demonstrated. The powder is obtained via electrical explosion of wire technique and consists of bimetallic particles instead of Cu and W mixture. The evolution of the phase composition has been studied using in situ X-ray diffraction technology during heating. The structural investigation shows that particles have a core-shell structure, increasing a contact surface between reactants. The ongoing reactions are described, and studies of the structure of powders and combustion products are given. Combustion occurs in the solid-phase temperature range, which is confirmed by the thermal imaging data

Review of the problems of additive manufacturing of nanostructured high-energy materials

This article dwells upon the additive manufacturing of high-energy materials (HEM) with regards to the problems of this technology’s development. This work is aimed at identifying and describing the main problems currently arising in the use of AM for nanostructured highenergy materials and gives an idea of the valuable opportunities that it provides in the hope of promoting further development in this area. Original approaches are proposed for solving one of the main problems in the production of nanostructured HEM—safety and viscosity reduction of the polymer-nanopowder system. Studies have shown an almost complete degree of deagglomeration of microencapsulated aluminum powders. Such powders have the potential to create new systems for safe 3D printing using high-energy materials

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

Investigation of the peculiarities of oxidation of Ti/Al nanoparticles on heating to obtain TiO2/Al2O3 composite nanoparticles

The creation of new nanomaterials with improved characteristics, as well as the development of new approaches to obtain such materials is an urgent task in science and technology. One of the promising directions in obtaining improved nanomaterials is the use of precursors in the form of multicomponent metal nanoparticles. Thermal oxidation of bimetallic Ti/ Al nanoparticles obtained by electrical explosion of wires was investigated in this work. Ti/Al nanoparticles have been found to be completely oxidized with the formation of composite TiO2/ Al2O3 nanoparticles after calcination at 900 °C. The formation of TiO2 phase with a rutile structure on heating to 500 °C, and the formation of TiO2 phases with a rutile and anatase structure, as well as α-Al2O3 on heating to 700 °C have been established, in addition to the residue of unoxidized metals. Complete oxidation of Ti/Al nanoparticles occurs when heated to 900 °C. The photochemical activity of TiO2/ Al2O3 composite nanoparticles obtained at 900 °C was studied. The degradation of methyl orange dye reached 55% under UV irradiation for 120 min

Controlled oxidation of cobalt nanoparticles to obtain Co/CoO/Co3O4 composites with different Co content

The paper studies patterns of interaction of electroexplosive Co nanoparticles with air oxygen during heating. The characteristics of Co nanoparticles and composite Co/CoO/Co3O4 nanoparticles formed as a result of oxidation were studied using transmission electron microscopy, X-ray phase analysis, thermogravimetric analysis, differential scanning calorimetry, and vibrating sample magnetometry. It was established that nanoparticles with similar morphology in the form of hollow spheres with different content of Co, CoO, and Co3O4 can be produced by varying oxidation temperatures. The influence of the composition of composite nanoparticles on their magnetic characteristics is shown

Antibacterial properties of PMMA functionalized with CuFe2O4/Cu2O/CuO nanoparticles

We have prepared a composite thin coating by incorporation of CuFe2O4/Cu2O/CuO nanoparticles in polymethyl methacrylate (PMMA) matrix by using the solution casting method. The electrical explosion of two twisted wires (EETW) was used to obtain multicomponent CuFe2O4/Cu2O/CuO nanoparticles with an average particle size of 20–70 nm. The microscopic studies showed that the nanoparticles in the composite coatings are evenly distributed. However, nanoparticles are strongly agglomerated as the powder concentration in the coating increases to 5 wt.% and 10 wt.%, as the size of particle agglomerates increases to 50 and 100 µm, respectively. Therefore, nanoparticles were pre-treated with ultrasound when introduced into the PMMA matrix. The thermal stability of the composite coating does not change with the introduction of CuFe2O4/Cu2O/CuO nanoparticles in the amount of 5 wt.%. The inclusion of nanoparticles in the PMMA matrix significantly enhances its antibacterial activity. The addition of 5 wt.% nanoparticles inhibited the growth of E. coli by 100% and the growth of MRSA by 99.94% compared to pure PMMA already after 3 h of exposure of bacteria on the surface of the composites. This research provides an easy-to-manufacture and cost-efficient method for producing a uFe2O4/Cu2O/CuO/PMMA composite coating with a broad application as an antibacterial material

Synthesis of novel hierarchical micro/nanostructures AlOOH/AlFe and their application for As(V) removal

Hierarchical micro/nanostructured composites, which contain iron and/or its (hydr)oxides, demonstrate high rate and capacity of arsenic adsorption. The main objective of this paper is the use of novel low toxicity AlOOH/AlFe hierarchical micro/nanostructures for arsenic removal. AlOOH/AlFe composite was obtained by simple water oxidation in mild conditions using AlFe bimetallic nanopowder as a precursor. AlFe bimetallic nanopowder was produced by electrical explosive of two twisted wires in argon atmosphere. The productivity of the electrical explosion assembly was 50 g/h, with the consumption of the electrical energy was 75 kW·h/kg. AlFe bimetallic nanoparticles were chemically active and interacted with water at 60 °C. This nanocomposite AlOOH/AlFe is low cost and adsorbs more than 200 mg/g As(V) from its aqueous solution. AlOOH/AlFe composite has flower-like morphology and specific surface area 247.1 m2/g. The phase composition of nanostructures is present AlOOH boehmite and AlFe intermetallic compound. AlOOH/AlFe composite was not previously used for this. The flower-shape AlOOH morphology not only facilitated deliverability, but increased the As(V) sorption capacity by up to 200 mg/g. The adsorption kinetics has been found to be described by a pseudo-second-order equation of Lagergren and Weber-Morris models while the experimental adsorption isotherm is closest to the Freundlich model. This indicates the energy heterogeneity of the adsorbent surface and multilayer adsorption. The use of non-toxic nanostructures opens up new options to treat water affected by arsenic pollution