L. Yu. Fedorov

Method for producing nanomaterials in the plasma of a low-pressure pulsed arc discharge

A new method for the production of nanomaterials in the plasma of a low-pressure arc discharge is developed and experimentally studied. This method can be used to synthesize nanoparticles 5–10 nm in size with a narrow size distribution. In this method, a low-pressure arc discharge is used to melt a material, to disperse the molten material, to deliver liquid material droplets to the plasma, to cool the liquid nanoparticles forming in the plasma up to their solidification, and to deposit the solidified nanoparticles onto a substrate.

Specific features of the behavior of electroarc CuO nanoparticles in a magnetic field

The temperature and time dependences of the magnetization of copper oxide nanoparticles 8, 13, and 18 nm in size have been investigated. Specific features of the behavior of CuO nanoparticles formed by vacuum plasma-arc synthesis as compared to other antiferromagnetic particles have been revealed. It has been shown that the bifurcation of magnetization curves upon cooling in the zero (ZFC) and nonzero (FC) magnetic fields occurs above the Néel temperature, while the usual peak of the magnetization curve is absent in the ZFC mode. The problems associated with the nonequilibrium behavior of synthesized CuO nanoparticles have been discussed.

Plasmachemical synthesis and basic properties of CoFe2O4 magnetic nanoparticles

Cobalt-ferrite (CoFe2O4) nanoparticles (CFNPs) are obtained using direct plasmachemical synthesis in the plasma of a low-pressure arc discharge. The formation of the CFNPs with an average size of 9 nm and a narrow granulometric composition is established employing the methods of X-ray structure analysis and transmission microscopy. The CFNP behavior upon high-temperature annealing is analyzed. The CFNP functional groups are determined using the infrared Fourier spectrum. The results of the X-ray energy dispersion confirm the correspondence of the ratio of the number of atoms of each material to the nominal stoichiometry. The basic magnetic properties of the obtained and annealed samples are investigated at room temperature using the vibrating spectrum magnetometry (VSM).

Study of magnetic flux pinning in granular YBa2Cu3O7 − y/nanoZrO2 composites

In this work, the effect of ZrO2 nanoparticles prepared in a low-pressure arc discharge plasma on magnetic flux pinning of granular YBa2Cu3O7 − y/nanoZrO2 composites has been studied. It has been shown that the ZrO2 nanoparticles do not change the superconducting transition and the microstructure of superconductors. At a temperature of 5 K, the addition of 0.5 and 1 wt % of ZrO2 nanoparticles may lead to the additional effect of magnetic flux pinning and the increase in the critical current density Jc. The Jc value for composites with 1 wt % is two times larger than that for the reference sample. The fishtail effect is observed for YBa2Cu3O7 − y/nanoZrO2 composites at the temperatures of 20 and 50 K. The problems associated with the additional effect of magnetic flux pinning of granular YBa2Cu3O7 − y/nanoZrO2 composites and the appearance of the fishtail effect have been discussed.

Influence of pressure and hydrocarbons on carbide formation in the plasma synthesis of TiC nanoparticles

We examine the influence of pressure and gas mixture composition on the preparation of nanomaterials via vacuum arc sputtering of titanium cathodes in carbon-containing media. The formation of carbide phases in various gaseous atmospheres is accompanied by the formation of the low-temperature phase α-Ti (hcp lattice), characteristic of pure titanium. Carbide formation in the plasma synthesis of TiC nanoparticles is determined by the C/H ratio in the molecules of the hydrocarbons used. To raise the yield of carbon-rich carbide phases and reduce the percentage of the residual metal in the resulting nanopowders, it is necessary to use hydrocarbons with a large C/H ratio, for example, benzene and acetylene.

Physical, mechanical, and tribological properties of quasicrystalline Al-Cu-Fe coatings prepared by plasma spraying

The physical, mechanical, and tribological properties of quasicrystalline coatings based on the Al65Cu23Fe12 alloy prepared by plasma spraying have been investigated. The specific features of the phase formation due to the competitive interactions of the icosahedral ψ and cubic β phases have been elucidated. A correlation between the microhardness and the content of the icosahedral phase in the coating has been determined. The decisive role of the quasicrystalline phase in the formation of high tribological characteristics of the coatings has been revealed and tested.

Modification of the phase composition and structure of the quasicrystalline Al-Cu-Fe alloy prepared by plasma spraying

The structural-phase state of quasicrystalline coatings of the Al-Cu-Fe alloy produced under different thermal conditions of plasma spraying (different contact temperatures Tk of the substrate) has been investigated. It has been shown that sprayed coatings are heterophase with the dominant content of the icosahedral ψ and cubic β phases, the formation and fractional ratio of which depend on spraying conditions. The distribution of probabilities P(QS) of quadrupole splitting in experimental γ-resonance spectra has been analyzed. The dependence of hyperfine interaction parameters (QS, A) on spraying conditions of the coating has been established. Five nonequivalent positions of resonant iron atoms, the appearance and filling of which are determined by spraying conditions, have been revealed.

Plasma-chemical reactor based on a low-pressure pulsed arc discharge for synthesis of nanopowders

A reactor for producing nanopowders in the plasma of a low-pressure arc discharge has been developed. As a plasma source, a pulsed cold-cathode arc evaporator has been applied. The design and operating principle of the reactor have been described. Experimental data on how the movement of a gaseous mixture in the reactor influences the properties of nanopowders have been presented.

Study of Phase Composition of CuO/Cu2O Nanoparticles Produced in the Plasma of a Low-Pressure Arc Discharge

AbstractThe influence of synthesis parameters on peculiar features of the forming crystalline phases of copper oxide nanoparticles is inspected via electron microscopy, IR spectroscopy, X-ray diffraction, and differential thermal analysis. The nanopowders are produced through the evaporation of a bulk copper cathode by a low-pressure arc discharge with successive condensation of plasma-chemical reaction products on the substrate. The partial pressure of oxygen in the feeding Ar/O2 gas mixture is varied in a range of 3–30 Pa. The aforementioned methods reveal that particles are formed with controllable dispersion, phase composition, and structural features. The control of characteristics of nanodispersed oxides is based on their formation mechanisms that are brought by the competing impact of coagulation and diffusion processes. The synthesis products are spherical powders of copper oxides comprising a mixture of crystalline phases with the prevalence of CuO, whose average particle sizes are 10–20 nm. The qualitative differences in samples for the opposite partial pressures of oxygen (