Powder producing processes and properties
Kasimtsev A.V., Zhigunov V.V.
Phase and structural transformation in producing intermetallic compound powders
The mechanism and kinetics of intermetallic compound powder formation process have been studied when heating mixtures of oxides, metals, and calcium hydride in a range of t = 900-1200 °С (hydride-calcium method). As it has been deduced from the experiments, the synthesis of above indicated compounds covers two stages: at the first stage – reduction of metal oxides by calcium melt takes place (beginning at temperature of ~ 840 °С), at the second stage – diffusion interaction of the components takes place. It is shown that the component metals should dissolve in molten calcium or form eutectic among themselves with value t not exceeding the operating temperature of the process for the effective development of alloy-forming processes. With a rise in the last, the reduction of oxides and diffusion interaction of the components are intensified and completed at t < 1200 °С with formation of homogeneous intermetallic compound powders. A possibility to produce a wide range of intermetallic compound powders of various purposes is shown.
Key words: metal powders, oxide, calcium hydride, decomposition, intermetallic compound, diffusion, alloy formation.
Rudneva V.V., Galevskiy G.V., Yurkova E.K.
Investigation of silicon carbide nanopowder particle morphology and size with the methods of electron microscopy
Using electron transmission and scanning microscopy, the identification of silicon carbide and pyrolytic carbon nanopowder shape and particle size has been carried out, the results are compared with others methods of identification of sizing feature of nanopowders, the tendency of nanopowders for aggregating is estimated. It is established that silicon carbide nanopowders as delivered are represented as globular aggregates of sizes from 0,1 to 1 μm, which are generated as faceted nanoparticles of mainly 50–70 nm in size. Nanoparticles have characteristic faceting in the form of a cube, octahedron, and intermediate, i.e. the tendency to rounding of links and vertexes and forming of convex faces is recorded. Pyrolytic carbon nanoparticles form aggregates of sizes as high as 150–200 nm including globular particles of 30–40 nm in size.
Key words: electron microscopy, silicon carbide, pyrolytic carbon, nanopowders, particle shape and size.
Dovydenkov V.A., Yarmolyk M.V.
Granulation of copper based compositions in the course of reaction milling in attritor
The reacting milling time dependence of granule size (d) of compositions in the Cu–CuO–Al–C system in an attritor in a range of t = 5-75 min has been investigated. The process of granule formation is found to have two stages that differ in granule growth rate. Within each stage the d(t) dependence has linear character, as justified by the results of the process simulation in the attritor. The transition time from the first stage to the second one is reduced in increasing the specific processing energy from 1,5 to 2,5 kW/kg. The granule growth at the first stage is found to be realized mainly at the cost of <50 μm fraction powder particle consolidation and that at the second stage somewhat slows down, since the deformation of formed conglomerates takes place.
Key words: granule size, reaction milling, granule formation, attritor, specific processing energy.
Onishchenko D.V., Popovich A.A., Boiko Yu.N.
Anode composites of the carbon-silicon system for lithium-ionic (polymeric) storage batteries
Perspective anodic composite matrices of the “carbon-nanosized silicon” system for lithium ionic (polymeric) storage batteries have been produced by mechanoactivation; high dispersiveness and specific surface area of the composite powders were obtained.
Key words: lithium-ionic (polymeric) storage batteries, composite anodes, nanosized silicon, mechanoactivation, energy intensive mill, renewable vegetable resources.
Theory and processes of powder material forming and sintering
Basov V.V.
Comparative investigations of UO2 fuel pellet aftersintering process
The basic parameters of comparative tests of UO2 fuel pellets, produced with powder metallurgy processes, for aftersintering with the use of the procedures of their repeated thermal processing (aftersintering) in various gas environments — with and without humidity treatment are described. The results of the aftersintering level estimation of the same pellets by different standard techniques are given; their analysis has been carried out; and the substantiation of expediency of using the operating procedure developed at OAO “Machine-Building Plant”, Elektrostal city, Moscow Region for estimation of different fuel pellet type aftersintering with humidity treatment of gas environment is given.
Key words: fuel pellets, fuel compacting model, repeated thermal processing, aftersintering, standard technique of aftersintering, aftersintering plant, stoichiometric composition, dew point, isothermal sintering, thermosetting.
Self-propagating high-temperature synthesis
Kochetov N.A., Rogachyov A.S., Pogozhev Yu.S.
The effect of mechanical activation method of reaction mixture on speed of SHS-reaction wave propagation and microstructure of Ti-Ni solid alloy
The effect of mechanical activation (MA) of starting reaction mixture of the Ti–C–Ni composition on the combustion and structurization regularities in the process of self-propagating high-temperature synthesis (SHS) has been investigated. The preliminary MA of mixture is shown to affect the sequence of physical-chemical transformations in SHS-wave as well as on the dynamics of product structurization in which smaller grains with relatively narrow size distribution are formed. The prospect of applying the mechanical activation for modification of SHS-material structure is shown.
Key words: mechanical activation, self-propagating high-temperature synthesis, microstructure, solid alloy.
High-melting-point, ceramic, and composite materials
Antsiferov V.N., Kulmetieva V.B., Porozova S.E., Krasny B.L., Tarasovsky V.P., Krasny A.B.
Application of mechanochemical activation in producing zircon ceramic
Article is devoted to the processes of various zircon concentrate powders that have been preliminarily processed in producing zircon ceramic. It is shown from the results of Raman spectroscopy that samples of powders with low specific surface are prone to dissociation in the sintering process at t = 1600 °С even with insignificant content of impurities in zircon concentrate. Mechanochemical activation with additive of surface-active substances allows us to increase the efficiency of powder grinding and sinterability. Simultaneously the resistance of the specimens to thermal dissociation grows up. Practically monophasic zircon ceramic with residual porosity <10 % and thermal dissociation temperature above 1600 °С was produced on the base of activated powder without addition of any sintering activators.
Key words: mechanochemical activation, zircon, additive introduction, density, thermal dissociation.
Svistun L.I.
Carbidosteels for constructional purposes: production, properties, application (Review)
The information on chemical compositions, structures, properties, and application of industrial Ferro-TiC (USA) and Ferro-Titanit (Germany) type carbidosteels produced by sintering. The technologies of producing such materials based on the pressure sintering processes — hot isostatic compaction (HIC), hot extrusion (HE), and hot forming (HF) are now in progress. “Rapid steel – TiC” type composites (“UkrNIISpetsstal” and “Dneprospetsstal”, Zaporozhie city, the Ukraine) are produced by HIC and HE techniques in pilot scale. Carbidosteels with the use of TiC and Cr3C2 based on HF technique are now developed in the Ukraine and Russia. The prospects in creation of new types of composite materials with the use of boron carbide are shown.
Key words: powder metallurgy, carbidosteel, powder grinding, hot forming, microstructure of carbide-steel, properties of carbide-steels, composite materials, hot extrusion, hot isostatic compaction.
Surface modifying, including by charged beams, photon and plasma fluxes
Ilves V.G., Kamenetskikh A.S., Kotov Yu.A., Medvedev A.I., Sokovnin S. Yu.
Production of metal oxide nanopowders by evaporation in pulsed electron flow
Based on our experience, we updated the installation for production of metal oxide nanopowders. The technique used for production of nanopowders comprises evaporation of a target by pulsed electron beam, condensation of material vapor in low-pressure gas, and deposition of nanopowders on a cold crystallizer of great surface area. The new installation consists of a powerful electron-beam hollow-cathode gun to ensure forming up to 1 A electron beam with 100 ms pulse length and a crystallizer of great diameter (0,3 m) and length (0,5 m) to allow reducing nanopowder agglomeration. The results of evaporated targets from YSZ and CeGdOx are given. Using this method it is possible to produce oxide nanopowders with characteristic size of 3–5 nm and nanopowder agglomerates with characteristic size of 20–600 nm having specific surface up to 250 m2/g, production rate up to 10 g/h, and specific energy consumption ≥ 120 W·h/g.
Key words: nanopowders, pulsed electron beam, evaporation.
Information
Seminar exhibition “Up-to-date development of Russian and Bulgarian enterprises in the sphere of nanotechnologies and nanomaterials” within the frame of the Year of Bulgaria in Russia
