D.V. Tikhonov

Combustion of Agglomerated Ultrafine Aluminum Powders in Air

It is shown experimentally that agglomeration of ultrafine aluminum powders decreases their reactivity during nonisothermal oxidation in air. Under normal and low pressures, the concentration of bound nitrogen in combustion products is lower for agglomerated powders than for unagglomerated powders, and under high pressures (>120 kPa), it is higher for agglomerated powders. Key words: ultrafine powder, aluminum, agglomeration, combustion, reactivity, aluminum nitride.

Electroexplosive Technology of Nanopowders Production: Current Status and Future Prospects

The current situation of the nanopowders production technology based on the process of electrical explosion of wires is described. The advantages and disadvantages of the electroexplosive technology are indicated. The results of studies characterizing the effect of the electrical explosion conditions on the nanopowders properties are presented, including latest results: conditions of nanopowders passivation, conditions of nanopowders production having narrow size distribution, the methods of nanopowders diagnostic and standartization. In addition, the application and area of future research on this technology are proposed.

Properties of Ultrafine Aluminum Powder Stabilized by Aluminum Diboride

The paper studies properties of an ultrafine aluminum powder produced by electric explosions of conductors, whose particles are stabilized by coating with aluminum diboride immediately during the synthesis of the powder. The ultrafine aluminum powder stabilized in such a manner has special properties: narrow particle size distribution, increased dispersity, and higher resistance to oxidation upon heating.

Effect of Electrical Parameters and Surrounding Gas on the Electroexplosive Tungsten Nanopowders Characteristics

Tungsten nanopowders were produced by the method of wires electrical explosion in the different gases. The study of phase and dispersed composition of the powders was carried out. The influence of electrical parameters such as the value of energy input in wire and the arc stage of the explosion was discussed. The factors that make for decreasing the particles size are the lower pressure of surrounding gas and the use of addition of chemically reactive gas.

Characteristics of nanopowders produced by electrical explosion of copper wires in argon with air additives

In this paper the dispersed, phase and chemical compositions of nanopowders produced by electrical explosion of wires in various gaseous medium were investigated. It is found that electrical explosion of copper wires in argon with little additives of air (1...2 vol.%) results in producing the nanopowders having high specific surface area (10.5...11 m2/g) and containing ~80 % of metal copper. The size of copper nanopowders decreases with increasing the content of reactive gas in argon (up to 30 vol. %) and their phase composition changes: the output of CuO is observed.

Stability and activity of ultrafine powders obtained by wire electrical explosion method

A perspective method of small particles reception is the electrical explosion of conductors. As against known methods of evaporation condensation, electrical explosion is characterized by strong nonequilibrium of electrical energy transfer processes in metal dissociation during energy transfer. The process nonequilibrium causes simultaneous coexistence of substances in various conditions: liquid, vaporized, plasma and other. The products of electrical explosion are dependent on the electrical and magnetic field conditions. The properties of received powders strongly depend on the electrical parameters of reception.

Scientific research on nanopowders diagnostics

The four parameters of chemical activity are proposed in the paper for testing of metal nanopowders and their mixtures stability to oxidation and chemical interaction. For estimation the thermodynamic conditions of the “metal nanopowder-gas” systems it is suggested to investigate their electrochemical characteristics.

Effect of the Gas Composition at the Electrical Explosion of Wires on the Nanopowders Properties

In this paper we present the study results of nanopowders properties produced by electrical explosion of wires in argon-oxygen and argon-air mixtures with different ratios of oxygen and air (0.5-30 vol. %). The products of aluminum, titanium and copper wires explosions were studied. The effect of the synthesis conditions on the metal content in the nanoparticles and their phase, chemical and size composition is discussed. The oxygen addition of 10-30 vol. % leads to a reduction in the metal content in the particles and to the formation of metals oxide. The small additives of reactive gases (< 2 vol. %) into the inert gas in the discharge chamber can be used for production of metal powder.

The mechanism of nitride phases formation at burning of metal powders in air

The research stages of nitrogen chemical accumulation during metal powders combustion in air, with the formation of independent crystal phases of nitrides are presented in the paper. The extraordinary characteristic of this phenomenon is connected with a contradiction: thermodynamic calculations show that nitrides are being oxidized by oxygen. It has been shown that the phenomenon is interdisciplinary: its manifestations are applicable in many spheres of science and technique. A probable mechanism is proposed regarding the formation of nitrides under high temperature conditions in the presence of air oxygen.

Characterization of nanopowders produced by electrical explosion of titanium wires

In this work the study results of nanopowders properties produced by electrical explosion of titanium wires in various medium (air, oxygen-argon mixture, and water) are presented. It was observed that the phase and size composition of nanopowders depends on the synthesis conditions: energy consumed by wire before explosion, material of wires, kind of working medium. Detailed study of the reactions mechanism of nanoparticles formation of chemical compounds under EEW was carried out.