A.I. Medvedev

Production and characteristics of composite nanopowders using a fiber ytterbium laser

A fiber ytterbium laser is used to obtain weakly aggregated nanopowders for yttria-stabilized zirconia solid electrolytes, ZnO and ZnS phosphors, and YAG- and Y2O3-based optical ceramics. The characteristics of the nanopowders are reported. The productivity and energy consumptions of the process with the use of fiber and CO2 lasers are compared. The influence of the buffer gas pressure in the evaporation chamber on the specific surface area of the nanopowder and particle size distribution is studied. The elemental composition of nanoparticles is found to change relative to the composition of the target when yttrium aluminum garnet is evaporated. In the pulsed mode of operation, the energy needed for nanopowder production is minimal when the radiation pulse is about 100 μs long.

Investigation of properties of ZnO-Zn-Cu nanopowders obtained by pulsed electron evaporation

ZnO-Zn and ZnO-Zn-Cu nanopowders with a high specific surface (up to 68 m2/g) is obtained by pulsed electron evaporation. The characteristics of nanopowders (NPs) are investigated by X-ray phase analysis (RPA), high-resolution transmission electron microscopy (HR TEM), electron diffraction analysis, differential scanning calorimetry (DSC), thermogravimetric (TG) analysis, inductively coupled plasma (ICP) method, and pulsed cathodoluminescence (PCL). For the first time, ferromagnetism at room temperature is found in ZnO-Zn-Cu nanopowders. The powder magnetism is connected with defects and magnetic Cu2+ ions in amorphous interlayers at interfaces between ZnO nanocrystallites. The connection of magnetic properties of nanopowders with the lattice constant of the fine-crystalline fraction of ZnO is shown.

Production of nanopowders of metal oxides by evaporation in the pulsed electron beam

Based on practical experience, the installation for production of metal oxide nanopowders is updated. The method involves evaporation of the target by a pulsed electron beam, condensation of the vapors of the material in a low-pressure gas, and deposition of nanopowders on a cold large-area crystallizer. In a new installation, a higher-power electron gun with a hollow cathode, which ensures the formation of the current pulse of the electron beam with an amplitude up to 1 A and a duration of 100 μs, and a crystallizer of a larger diameter (0.3 m) and length (0.5 m), which makes it possible to decrease the agglomeration of nanoparticles, are used. The results of the evaporation of targets made of YSZ and CeGdOx are presented. The proposed method makes it possible to obtain nanopowders of oxides with a characteristic particle size of 3–5 nm and agglomerates consisting of them 20–600 nm in size, specific surfaces of up to 250 m2/g, productivity of up to 10 g/h, and a specific power consumption ≥120 (W h)/g.

Forming a carbide coating on the surface of aluminum nanoparticles and producing nanopowders from Al-Al4C3 using the method of electric explosion of wire

The controlled feeding of butane to inert working gas in the process of producing aluminum nanopowders using the method of electrical explosion of wire (EEW) allows carbide coatings to be formed on the surface of aluminum particles, reducing the agglomeration of the particles and producing Al-Al4C3 nanopowders of various compositions and dispersivity. The dependences that the specific surface area of powder, the content of crystalline aluminum carbide, and the phase composition of powders have on the quantity of the butane fed at different values of energy input into the wire are presented. The morphology of the particles is examined. The powders were analyzed using BET, X-ray diffraction (XRD), thermogravimetry-differential scanning calorimetry-mass spectrometry (TG/DSC/MS), scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

Characteristics of ZrO2 nanopowders produced by electrical explosion of wire

A device and an experiment for obtaining zirconium dioxide nanopowders using the electrical explosion of a wire (EEW) with aerodynamical separation are described. The physicochemical and technological properties of powders depending on the conditions under which they are obtained are studied. It is shown that, like for other metals with high oxidation heat, there is an additional dispersion of powders due to combustion. The results are discussed from the point of view of current concepts of electrical explosion and the combustion of metal powders. The optimum technological conditions according to the criterion of the maximum nanofraction yield were found. It is shown that this method allows us to obtain weakly aggregated ZrO2 nanopowders with a spherical particle shape (the specific surface reaching 70 m2/g (average particle size <20 nm)) and a nanofraction yield of up to 28% of the theoretical weight of oxide.