This work is devoted to the investigation of plasma parameters (excitation temperature and electron density) of the underwater discharge between two types of metal granules, in particular: between single-component granules of copper or molybdenum, copperized molybdenum, and both copper and molybdenum with a volume ratio of 50%. Optical emission spectroscopy was used to study such plasma of underwater spark discharges between different types of granules. Namely, the excitation temperature was determined by the Boltzmann plot technique, and the electron density was obtained from the width of the spectral lines of hydrogen and individual lines of metal atoms, assuming that the Stark effect is the dominant mechanism of broadening.

The radiation from the arc plasma ignited between the flat ends of copper electrodes in atmospheric pressure air at a direct current of 3.5 A is analyzed to determine the plasma temperature and composition. Side-on spectra in the range (430 – 650) nm are recorded using a CMOS camera connected to a spectrograph. The spectral emission coefficient is evaluated from the spectral radiance, which provides the radiator number density. The excitation temperature is obtained by applying the Boltzmann plot technique to at least two spectral lines and a series of radial positions in the midplane of the arc. Subsequently, the plasma composition is determined. The equation of radiative transfer is solved along lines of sight considered in the experiment. The spectral intensity of Cu I lines is computed and compared with the experimental ones. The arc properties are obtained by assuming axial symmetry and mapping the evaluated values in the midplane.

This work is devoted to optical emission spectroscopy of plasma of underwater electric discharge, which is used for the synthesis of silver nanoparticles. The main aim of this work is to investigate the possibility and validity of using plasma optical emission spectroscopy to determine its main physical characteristics, such as excitation temperature, electron density, the degree of ionization, etc. The specially developed pulse power source was used to initiate a discharge between silver granules immersed into the deionized water. Typical values of voltage vary from 40 to 200 V, the current is up to 150 A, and pulse frequency is in the range of 0.2–2 kHz. Applied to electrodes, the voltage caused a current flow along the chain of closely arranged granules in the stochastic switching mode. Special attention is paid to methods of spectrum treatment of underwater discharge plasma between silver granules. The method of Boltzmann plots and the method of relative intensities on the basis of both atomic and ionic silver spectral lines are used in order to determine the excitation temperature. The spectral lines, which were investigated and treated in detail, were used. Exposed to the Stark mechanism of spectral line broadening, the spectral profile of Hα spectral line is used to determine the electron density. The degree of ionization of the studied plasma was calculated using the obtained values of the electron density and temperature.

Plasma of electric arc discharge burning between different types of composite Cu-W electrodes was investigated. Electrodes manufactured of Cu-W composite materials (30/70% by mass) by shock sintering technology at temperatures of 750, 850, 950, and 1050°C were used. Optical emission spectroscopy techniques were applied to determine the main plasma parameters. Specifically, the side-on spectra of plasma emission were registered using a space-resolved spectrograph with a CMOS camera as a sensor device. The plasma thermodynamics properties were calculated based on the equilibrium plasma composition, which was determined using experimentally obtained radial distributions of temperatures and atom concentrations of the metals.

In this work, the radial distributions of parameters of plasma with copper and nickel vapours admixtures in positive column of electric arc discharge were investigated by optical emission spectroscopy. The plasma temperature was determined by the Boltzmann plot technique on the basis of absolute values of radiation intensity of both copper and nickel atomic spectral lines. Concentrations of both kinds of metal atoms of electrode origin were determined by the method of absolute intensities of the corresponding spectral lines of radiation of such plasma.

This study investigates the control of input energy and plasma parameters during the electric discharge erosive process for nanoparticle generation. The total energy supplied to the discharge chamber was controlled by varying the switching phase of the thyristor. Electrical parameters, including current and voltage waveforms, were analyzed to estimate the total input energy delivered to the reactor with zinc granules immersed in water. Additionally, the correlation between electrical parameters and plasma characteristics in the underwater discharge plasma with zinc vapors was examined. It was found that decreasing the switching phase increased the total input energy and influenced the electron density and emission intensity of the plasma. A decrease in switching phase within the range of 145–135 degrees resulted in better erosion of zinc material and more efficient generation of nanoparticles in the plasma. These findings contribute to the optimization of nanoparticle synthesis processes.

Faculty of Radio Physics, Electronics and Computer Systems, Taras Shevchenko National University of Kyiv, 64/13, Volodymyrska str., Kyiv, 01601, Ukraine E-mail: murmantsev.aleksandr@gmail.com Abstract. This work is devoted to the peculiarities of optical emission spectroscopy of plasma of electric arc discharge between Cu-Cr composite electrodes manufactured by pressing and sintering technologies at different temperatures, namely: 650, 750, 850, 950, 1050 and 1150°C. The investigations are carried out at arc current of 3.5 A. The comparison of radial distributions of plasma temperatures, which were determined by Boltzmann plot technique both on the base of Cu I and Cr I spectral lines, are performed and discussed.

This work is a part of acomplex investigation of the interaction of Cu-W composite materials with thermal electric arc discharge plasma. The plasma of 3.5 A DC arc discharge between novel Cu-W composite materials, fabricated by shock pressing technology at the temperature of 750°C, was studied at this stage. Spectra of such plasma emission were registered and treated to determine the radial distributions of plasma temperature in three different cross-sections of the plasma channel, namely in near-cathode, near-anode and middle cross-sections.

This work is devoted to diagnostics of thermal electric arc discharge plasma with copper and nickel vapour admixtures by optical emission spectroscopy and possibility of its usage for investigation of plasma regions near-electrodes surfaces. The spectra of plasma emission from such areas were obtained by registration device with spatial and spectral resolution. The Boltzmann plot technique was used to determine the radial distribution of plasma temperature of arc discharge channel in different cross-sections. Namely, the regions of arc discharge plasma in the vicinity of cathode and anode surfaces in the two different configuration of electrodes assembly (copper as a cathode, nickel as an anode and vice versa) were investigated.

This work is devoted to the plasma diagnostics of an underwater electric spark discharge, specially developed for the synthesis of metal nanoparticles by electro erosion of metal granules immersed into water. To improve the process of metal nanoparticle generation, the main plasma parameters for different modes of discharges between molybdenum and, separately, iron granules were investigated. The optical emission spectroscopy as a non-perturbing method was used. Namely, the Boltzmann plots on the basis of metal atomic lines’ (in particular Fe I and Mo I) intensities are used to determine the electron temperatures in plasma. Profile of Hα spectral line, exposed to the Stark mechanism of spectral lines’ broadening, is used to determine the electron density in such plasma. The black-body radiation is found in the spectrum of the discharge between molybdenum granules. It was found that the background emission in the spectral regions with densely spaced spectral lines can be caused by the overlapping of spectral lines’ contours for the underwater discharge between metal granules.

The results of optical emission spectroscopy (OES) investigation of plasma of electric arc discharges in steadystate mode between Cu-Cr composite electrodes, manufactured at different sintered temperatures: 750, 850, 950 or 1050 °C, is presented. In particular, the impact of sintering temperature on erosion resistanceof such composite materials, which was determined in indirect manner by estimation of metal vapours content in the midsection of discharge gaps, is studied by the analysis of plasma parameters. These contents were calculated in assumption of local thermodynamic equilibrium (LTE) on the base of experimentally obtained radial distributions of plasma temperature and electron density.

This work is devoted to spectroscopy peculiarities of electric arc discharge plasma with iron vapours. The solution of the main issue of optical emission spectroscopy, namely, selection of iron spectral lines, to study the parameters of non-uniform and non-steady-state plasma source, was considered within this paper. Specifically, the Boltzmann plots technique was used for detailed analysing of application possibility of Fe I spectral lines as well as for determination of plasma temperature. The spatial profiles of selected spectral line emission intensities were used to measure the radial distributions of plasma temperature of free-burning arc discharge between consumable electrodes at 3.5 A.

This work is devoted to investigation of the radiation in the plasma of electric arc discharge between Cu-C composite electrodes and estimation of its contribution during the determination of electron density from the energy balance equation (Elenbaas-Heller). The contribution of radiation energy in heat transfer is estimated as well. The calculation is carried out based on the preliminary experimentally obtained radial distribution of plasma temperature. For the correct solution of the energy balance equation, a Gaussian approximation of the plasma temperature profile is used. Estimation of the total current was used as a criterion for the need to take into account the radiation in the diagnostics of electric arc plasma.

Pulsed underwater discharges are used for the synthesis of nanoparticles, through electrode tip vaporization and material condensation. The resulting colloid solution can have applications in biomedical (sterilization) or agriculture (plants fertilizing) field. The plasma formed from vaporized water and electrode material constitutes a key step in the process. This work is dedicated to studying plasma parameters as a function of current and used electrode material. Optical emission spectroscopic diagnostic is used to measure electronic temperature (based on copper or molybdenum lines) and density (based on $\mathrm{H}_{\alpha}$ and $\mathrm{H}_{\beta}$ lines). The setup allows spatially resolved study over the discharge cross-section. Results show that with molybdenum the core temperature is 30 to 90 % higher but the radial gradient is stronger when compared to copper. Electron density is also twice higher with molybdenum electrodes. High speed imaging confirms that with this metal the spark light intensity is much stronger and the formed cavitation bubble is larger. These results can be explained by the lower thermal conductivity of molybdenum electrodes, leading to a more energetic discharge.

The underwater electric spark discharge was ignited to generate colloidal solution with nanoparticles. Optical emission spectroscopy was used to obtain temperatures and electron densities in such discharge plasmas. Structure and morphology of generated nanoparticles were studied by scanning and transmission electron microscopy and diffractometry methods. Several biological applications of obtained nanoparticles were carried out. The application of the nanoparticles as microelements increased the vegetative mass of watercress plants. The foliar processing of wheat plants by colloidal metal solutions showed increasing of crop capacity and quality of grown grain.

This paper deals with development of optical emission spectroscopy techniques for diagnostic of underwater discharge plasma between iron granules. The difficulties in selection of iron spectral lines, as well as the approximation of their profiles for determination of excitation temperature are discussed. A method of spectral lines resolving with close wavelengths is considered. Simulation of a narrow rangeof the plasma emission spectrum is carried out to estimate the excitation temperatures in underwater discharge plasma.

The behavior of the Balmer series spectral line profiles in the underwater electric spark discharge plasma between copper granules is investigated. Specially developed pulse power source is used to initiate a discharge between copper granules immersed into the deionized water. Typical values of voltage are of 40 - 200 V, current is up to 600A and pulse frequency is in the range of 0.2 - 2 kHz. The voltage, applied to electrodes, caused a current flow along the chain of closely arranged granules in the stochastic switching mode. Optical emission spectroscopy methods are used for diagnostics of such discharge plasma. Profiles of H alpha and H beta hydrogen lines, exposed to the Stark mechanism of spectral lines' broadening, are used to determine electron density. The Boltzmann plot of copper lines' intensities are used to determine the plasma temperature.

This work deals with investigations of thermal plasma of electric arc discharge between sintered composite Cu-Cr electrodes, which can be used in electrical contacts of vacuum circuit breakers. Breaking arcs between composite Cu-Cr as well as single-component copper electrodes were used to study the electrical properties, plasma optical emission and electrodes surface modification behavior. In particular, the temporal evolution of plasma emission spectra of electric breaking arcs in air atmosphere was investigated by Optical Emission Spectroscopy (OES). Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray Spectroscopy (EDXS) were applied to analyze the cross-section of working layer of electrodes surface modified by the heat flux from the discharge.

In this work, we present for the first time a unified model of a low-current short-length arc between copper electrodes. The model employs one-dimensional fluid description of the plasma in argon and copper vapour at atmospheric pressure and the heat transfer in the electrodes made of copper. The solution of the particle and energy conservation of electrons and heavy particles is coupled with the solution of the Poisson equation, from which the self-consistent electric field is obtained. The operation of the non-refractory cathode is based on thermo-field emission. Heat fluxes from the plasma to the electrodes are considered so that a phase change and evaporation from the cathode and a release of copper atoms into the plasma are taken into account. The influence of the copper atoms and ions on the plasma properties is analysed and discussed. The model’s predictions are compared with experimental data and a qualitative agreement is obtained besides the restrictions of the one-dimensional fluid model.

In this work the plasma of electric arc discharges between Cu-Cr composite electrodes, which material were pressured and sintered at different temperatures 750 or 1050°С, are investigated by Optical Emission Spectroscopy (OES). The Scanning Electron Microscopy (SEM) with Energy-Dispersive X-ray Spectroscopy (EDXS) are used to study the working surface of electrodes, modified by thermal effect of breaking electrical arc in the air atmosphere. The erosion intensity of electrodes’ material due to plasma-surface interaction is estimated in indirect way by determination of metal vapours content in the discharge gap in an assumption of local thermodynamic equilibrium (LTE). The plasma composition is calculated in this case on the base of experimentally determined plasma parameters: temperature and electron density.