Plasma Of Low-pressure Arc Discharge Research Articles

Resistive switching properties of a nanostructured layer of mixed ZrO2 phases obtained in low-pressure arc discharge plasma

The controlled vacuum-arc synthesis of zirconium dioxide (ZrO2) nanoparticles is considered, which makes it possible to regulate the percentage ratio of the monoclinic and tetragonal phases. The samples were characterized using XRD analysis, SEM, HRTEM analysis, FT-IR analysis, TG/DTA analysis and EPR spectroscopy. It has been established that the formation of the tetragonal phase is associated with the formation of a large number of oxygen vacancies formed due to high-speed quenching of nanoparticles. Reducing the operating gas pressure in a vacuum chamber from 180 Pa to 30 Pa makes it possible to obtain nanoparticles up to 2 nm in size. The synthesized ZrO2 nanoparticles do not contain foreign impurities and when heated, the weight loss is up to 7 %. The process of local resistive switching in the contact of an atomic force microscope (AFM) probe to a nanostructured ZrO(2-x) layer on a conducting substrate has been studied. Cyclic current-voltage characteristics demonstrate the existence of stable states of high and low resistance, switched by changing the polarity of the applied voltage. The coexistence of the m- and t-ZrO2 phases (and the resulting oxygen nonstoichiometry in the interboundary regions) provides conditions for the formation/destruction of a filament from oxygen vacancies, which determine the conductivity of the dielectric in the LRS state.

Effects of ion-plasma treatment temperature of the aluminium coating on the structure and phase composition of the VT6 titanium alloy

In this study, we studied the effects of aluminum coating treatment temperature on the microstructure and phase composition when applied to a VT6 titanium alloy substrate within a low-pressure arc discharge plasma environment. The ion-plasma treatment was conducted at 450 and 500 °C, employing argon shielding, while the aluminum coating was deposited using the vacuum-arc process, resulting in a coating thickness of ~3 μm. Microstructural analysis was performed using a scanning electron microscope, and the structural and phase composition were examined using X-ray diffraction (XRD) imaging in symmetric imaging mode with CuKα radiation. Our findings demonstrate that the application of the aluminum coating initiates the formation of a near-surface α-stabilized layer, extending up to 2.5 μm in thickness due to the heat generated during the ion cleaning process. Subsequent ion-plasma treatment further results in the development of a TiAl3 intermetallide site, reaching thicknesses of up to 1.5 μm, while the α-stabilized region expands to 5.5 μm. Higher temperatures during the treatment process contribute to an increase in the thickness of these aforementioned layers and also lead to the emergence of an intermediate TiAl intermetallic layer.

Features of Interaction of Molecular Oxygen with Condensation Surface in Low-Pressure Arc Discharge Plasma

Features of Interaction of Molecular Oxygen with Condensation Surface in Low-Pressure Arc Discharge Plasma

Magnetic State of the Nickel Oxide Nanoparticles Formed in Low-Pressure Arc Discharge Plasma

Magnetic State of the Nickel Oxide Nanoparticles Formed in Low-Pressure Arc Discharge Plasma

Vacuum-arc synthesis of metal-organic framework structures based on ZrO2

The vacuum-arc synthesis of nanopowders based on zirconium oxide and metal-organic framework structures was carried out using a low-pressure arc discharge plasma. The obtained material was studied by several methods (XRF, IR, TEM, DTA). The TEM method showed that Zr-MOK is a highly agglomerated particle of an almost spherical shape. The image clearly shows the crystalline ordering of nanoparticles with a large (about 2 nm) lattice parameter. Particle sizes range from 5 to 30 nm. Average particle size 9.4 nm. XRD showed that the proportion of ZrO relative to Zr-MOK, calculated from the most intense lines of the diffractogram, is 65%. XRF results are in good agreement with IR studies. The DTA curve demonstrates a continuous exothermic process associated with a number of features of the plasma-chemical synthesis and morphology of the resulting nanoparticles, which is in full agreement with studies using transmission microscopy.

Investigation of Microstructural Features, Phase Composition, and Magnetic Characteristics of YBCO-Based Composites and Additives of CuO Non-Superconducting Component Prepared in Low-Pressure Arc Discharge Plasma

A method making it possible to form HTS ceramics of non-superconducting coating consisting of self-organizing CuO crystals, whose sizes are less than the coherence length, i.e., within several tens of nanometers, has been developed. It has been shown that the combination of self-organizing structures in the form of whiskers and nanoparticles which arise as a result of combined sintering of YBa2Cu3O(7–x) powders and electric arc CuO nanopowders results in a significant increase in the current density and appearance of peak effect at high magnetic fields. Very high current density arises from the complex vortex pinning, where whisker defects provide high pinning energy and nanoparticles suppress flux creep. The morphology of such structures can be controlled by a simple change in the concentration of nanodisperse additives. It has been shown that 20 wt % of CuO additive is optimal.

Synthesis of Metal-Organic Framework Structures Based on Copper in a Low-Pressure Arc Discharge Plasma

Plasma-chemical synthesis of nanopowders based on copper oxide and metal-organic framework structures was carried out using low-pressure arc discharge plasma. The study of the obtained material was carried out by several methods (XRD, FTIR, TEM, TGA and EIS). TEM showed that the obtained powder is highly agglomerated particles with an average particle size of 13 nm, and the crystalline ordering of nanoparticles with a large (about 2 nm) lattice parameter is clearly visible. XRD showed the presence of four crystalline phases corresponding to [Cu3 (BTC)2], Cu, Cu2O and CuO. XRD results are in good agreement with FTIR studies. The DTA curve demonstrates a continuous exothermic process associated with a number of features of plasma-chemical synthesis and the morphology of the obtained nanoparticles. The study of the electrochemical properties of the materials obtained by the method of impedance spectroscopy revealed an anomalous accumulation of electrical charges around the electrodes due to electrochemical reactions for [Cu3 (BTC)2], which are associated with various reactions involving copper species in the organic framework.

The pulse vacuum-arc plasma generator for nanoengineering application

In paper described the results of work on the application of vacuum-arc machine in nanoengineering area. Researches were carried out to optimize the operation of this machine for the synthesis of nanomaterials in low-pressure arc-discharge plasma, plasma diagnosis and production of nanopowders. An electrode system based on the grounded cathode with impulse ignition has been developed. The anode current was measured and the mass output of the product was calculated. Experimental data on energy density were obtained, confirming the presence of plasma focusing on the electrode system axis due to its own magnetic field, the focus value of which reaches about 18 kJ/m2. Powder samples were also obtained in the form of clusters containing the copper particles (up to 98%) and spherical powder with size from 116 nm to 1.2 µm. Homogeneity and dispersion of powder depended on the time of the processes accompanying the deposition.

Physicochemical Properties of Zirconium Oxide Nanopowder Synthesized in Low-Pressure Arc Discharge Plasma

The method for synthesis of zirconium oxide nanopowder in low-pressure arc plasma was developed. The physicochemical properties of the nanopowder were studied. The estimation was carried out by means of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). The sequence and kinetics of structural transformations occurring in the specified time-temperature heating regimes have been examined using differential thermal analysis. It was shown that the particles have a nanometer size, a narrow particle size distribution and an amorphous-crystalline structure. The maximum specific surface area detected by the method of sorption of surfactants was 470 m2/g. The issues of crystallization were discussed. From comparison between the results of experimental studies from earlier works with the results obtained for zirconium oxide, it is concluded that the proposed method for producing NPs in a low-pressure arc discharge plasma is universal.

Особенности магнитного состояния наночастиц оксида никеля, полученного в плазме дугового разряда низкого давления

Особенности магнитного состояния наночастиц оксида никеля, полученного в плазме дугового разряда низкого давления

Morphological and Structural Features of Iron Oxide-Based Nanoparticle Formation under Arc Vacuum Sputtering

Ferrite Fe3O4 nanoparticles have been formed in low-pressure arc discharge plasma. It has been shown that the obtained nanoparticles have an average size of 9.4 nm and a blocking temperature of 89 K, crystallize in the magnetite phase, and are superparamagnetic at room temperature. The features in the behavior of nanoparticles in a magnetic field related to their large specific surface are discussed.

Investigation of the residual stresses effect on the magnetic properties of CuO nanoparticles synthesized in a low-pressure arc discharge plasma

Abstract The laws governing the formation of residual stresses in copper oxide nanoparticles in the process of their direct plasma-chemical synthesis in a low-pressure arc discharge plasma are studied. Correlation dependences of the residual stress and the magnetization of nanoparticles on the pressure of the gas mixture of 10% O 2 + 90% Ar are presented. The problems associated with the bifurcation of the magnetization curves during cooling in zero (ZFC) and non-zero (FC) magnetic field, non-equilibrium behavior, relaxation of magnetization and magnetic viscosity of the obtained CuO nanoparticles are discussed.

Морфологические и структурные особенности формирования наночастиц на основе оксида железа при вакуумно-дуговом распылении

Ferrite nanoparticles (Fe3O4) were obtained in low-pressure arc discharge plasma. Studies have shown that the obtained nanoparticles have an average particle size of 9.4 nm, the crystalline phase of magnetite, have superparamegnets at room temperature, and a blocking temperature of 89 K. The behavior of nanoparticles in a magnetic field associated with a large specific surface is discussed.

Peculiarities of Magnetic Behavior of CuO Nanoparticles Produced by Plasma-Arc Synthesis in a Wide Temperature Range

Copper oxide nanoparticles, produced by direct plasmochemical synthesis in a low-pressure arc discharge plasma, show a wide variety of magnetic properties depending on the strength of the external magnetic field and the temperature. At low strength of the field and throughout the studied temperature range, the ferromagnetic state dominates. This state is caused by disordering of the spins on the surface of the nanoparticles. At high strength of the field and under temperatures of less than 200 K, nanoparticles exhibit a paramagnetic state due to the spin-glass behavior of copper atoms. At high strength of the field (more than 3 kOe) and under temperatures of above 300 K, the diamagnetic state of nanoparticles is observed, due to local eddy currents caused by oxygen vacancies. The temperature of antiferromagnetic ordering under study is significantly lowered (down to ∼ 100 K).

Formation of the structure and physicomechanical properties of a quasicrystalline Al–Cu–Fe alloy upon plasma spraying

Quasicrystalline coatings prepared under various thermal conditions of spraying have been studied. Initial quasicrystalline powders with dispersion of 10–50 μm were prepared in a low-pressure arc discharge plasma. The coatings have been sprayed on copper rings using a swinging plasmatron. It is found that the increase in the quenching rate of melt droplets increases the chemical homogeneity and leads to formation of nanostructured formations. The precipitation of nanostructured grains (d < 100 nm) in the sprayed alloy leads to an increase in the mechanical characteristics (hardness, deformation, and ductility) and can be considered as an additional factor of hardening of the material.

Influence of the oxygen concentration on the formation of crystalline phases of TiO2 during the low-pressure arc-discharge plasma synthesis

The synthesis of titanium dioxide (TiO2) nanoparticles with different percentage of anatase and rutile phases is investigated. The synthesis is performed by controlling the oxygen percentage in the gas mixture in the plasmachemical evaporation–condensation process employing a low-pressure arc discharge. In all our experiments, the pressure in the plasmachemical reactor and the average size of particles remain constant and are 60 Pa and 6 nm, respectively. The crystal structure of synthesized TiO2 is studied using X-ray diffraction; the morphology of the particles is analyzed employing transmission electron microscopy. Using X-ray phase analysis, it is established that the concentration of the TiO2 anatase phase decreases upon a decrease in the oxygen concentration in the gas mixture. It is shown that the TiO2 anatase phase is more efficient for photocatalytic decomposition of methylene blue than the rutile phase.

Influence of the oxygen concentration on the formation of crystalline phases of ZrO2 nanoparticles during the low-pressure arc-discharge plasma synthesis

The synthesis of nanoparticles of zirconium dioxide with different contents of the monoclinic and tetragonal phases has been investigated. The synthesis has been performed by controlling the oxygen content in the gas mixture in the plasma-chemical evaporation–condensation process in low-pressure arc-discharge plasma. The crystal structure of synthesized ZrO2 nanoparticles has been studied using X-ray diffraction. The morphology of the particles has been analyzed using transmission electron microscopy. The nanoparticle growth in arc-discharge plasma has been examined using optical emission spectroscopy. The X-ray powder diffraction analysis has revealed that the content of the monoclinic phase of ZrO2 increases with a decrease in the oxygen content in the oxygen–argon gas mixture.

Nanocomposite material based on ultra-high-molecular-weight polyethylene and titanium dioxide electroarc nanopowder

The effect of nanodisperse TiO2 powder additions obtained in low-pressure arc discharge plasma on the physicomechanical properties of the ultra-high-molecular-weight polyethylene (UHMW-PE) samples obtained by hot molding was studied. Vacuum plasma-arc modification of UHMW-PE led to an increase in its deformation and strength characteristics. X-Ray diffraction analysis and electron microscopy showed that vacuum plasma-arc modification led to changes in the structure of UHMW-PE.

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.

Mechanical and tribological properties of complex-modified material based on ultra high molecular weight polyethylene and CuO

Results of studying nanocomposite materials based on ultra-high-molecular-weight polyethylene filled with copper oxide nanopowder produced in plasma of low-pressure arc discharge are presented. The process of the vacuum-plasma synthesis of powdered composite mixtures, which involves the treatment of powders of the polymer matrix material in a device for synthesizing nanopowders at low temperatures, is described. Results of the experimental study of the specimens are presented.