Papers by Keyword: Nanopowder

Abstract: Using XRD method it was revealed that in the stress-strain state of Al nanopowder lattice a non-significant amount of energy was stored (~0.385 J/g). Nevertheless, according to the data obtained by differential thermal analysis (DTA) the total amount of stored energy in the nanopowder was 348 J/g. The estimated value might be caused by the significant contribution of nanoparticles surface energy, which cannot be detected by means of XRD method. However, the method proposed in the paper can be applied to estimate changes in the structural and energy states of the lattice for nanoparticles or another micro-and nanopowders.

Abstract: Chemical activity of micro-and nanosized powders during open air heating after electron beam (up to 360 keV of electron kinetic energy) irradiation has been studied. A differential thermal analysis disclosed that an initial oxidation temperature for iron powders has been decreased to ~ 30°C after electron beam irradiation. Thus, the thermal oxidative stability of iron powders in air was improved without any detected changes in other activity parameters.

Abstract: Ceramic cordierite-based materials are widely used in metallurgy, mechanical engineering and in the chemical industry as refractories, filters and catalyst supports. In this article, the activation of the synthesis of cordierite ceramics additives obtained by SHS is described. These additives consist of a mixture of mineral and alumina nanopowder in various ratios.

Abstract: The paper describes the research into the effect of the energy supplied to the conductor at the time of explosion on the particle size distribution of aluminum powders obtained. Aluminum powders consist of at least three fractions with the average particle size of 20-100 μm, 1-5 μm, and 50-900 nm. The yield of each fraction and average particle size are determined by the level of energy supplied to the conductor.

Abstract: This article is devoted to the research of powders for the additive technologies made by EOS Company. Their analysis showed that the powders’ average diameter is about 30 microns. Powders are received by method of electrospark dispersion. The X-ray diffraction and metallographic analysis of these powders is presented.

Abstract: The paper gives the experimental data on physicochemical and sorption properties of aluminum hydroxides produced by electric spark dispersion of aluminum metal in water and electric explosion of an aluminum conductor in argon and further interaction with water. By comparing the phase composition, specific surface area, porosity, and functional dependence of the exchange capacity of products on the solution pH, we proved the influence of preparation conditions on the properties of the said products.

Abstract: The composite powder of AlN-BN is of interest from the point of view of the use for sintering the AlN-BN composite ceramics. The ceramics compared with AlN ceramics would have better thermal shock resistance, less britlleness, better machinability, good heat conductivity and tribological properties. Possibility of obtaining a composite powder of AlN-BN with the application of process of self-propagating high-temperature synthesis (SHS) from powder mixtures of NaN₃ and precursors of aluminum and boron was investigated. Halide salts AlF₃, Na₃AlF₆, KBF₄ and NH₄BF₄ were used as the precursors. It was shown that these mixtures are capable of burning and obtaining agglomerated composite powders from nanosized (50-170 nm) particles.

Abstract: The authors investigated the mechanical mixing and compacting briquettes of nickel powder (particle size 30...75 μm) and nanopowder modifier SiC+Si₃N₄ (particle size 70...100 nanometers), obtained by the azide technology SHS. The mixtures containing 5%, 10%, 15%, 20% of the modifier were investigated. Mechanical mixing was carried out during 60 minutes in planetary mill «Pulverizette-5». Some physic-technological properties of the obtained powder mixtures, such as, particle size distribution, density, bulk weight and flowability, are determined. The powder compositions' pressing was carried out on hydraulic press PSU-50 with pressure 65...700 MPa. Nanopowder ligature briquettes of 18.2 mm diameter, height to 4.2 mm, weighing 5 grams, with relative density 70...89% and porosity 11...30%, intended for subsequent input in aluminum melt with the aim of modification are obtained.

Abstract: The intermediate and final combustion products of pressed aluminum nanopowder are studied. It is found that the main combustion product is aluminum nitride. In the intermediate stages of combustion, aluminum oxide (γ-Al₂O₃) and oxynitride (Al₅O₆N) are the first to form on the sample surface, and aluminum nitride is formed next. The use of sliding (incident at a small angle to the surface) synchrotron radiation made it possible to determine with high accuracy (in time) the sequence of stages of formation of crystalline products during combustion of the aluminum nanopowder.

Abstract: The influence of the electron beam irradiation on the parameters of aluminum nanopowder oxidation by heating in air was studied. It was found that the oxidation starts at the temperature in the range from 410° C to 460° C and independent on the radiation dose. The degree of oxidation varied from 44.4 % to 58.3 % and its dependence on the radiation dose was not established. The heat energy release occurred in two stages: at the first stage (up to ~ 660° C) in general the increase of the thermal effect was observed. At the second oxidation stage of irradiated aluminum nanopowder the growth of the thermal effect also observed. The peak of heat effect achieved by irradiation (45.0 kGy absorbed dose) was 2576 J/g higher than the thermal effect for non-irradiated aluminum nanopowder. The energy stored is an additional motivating factor in the synthesis of composite materials, intermetallic compounds, hydrogen producing reactions and synthesis of various kinds.