Spectroscopic diagnostics for an electrical discharge plasma in a liquid

Abstract

We conducted spectroscopic studies of an electrical discharge plasma in a liquid, used for synthesis of nanosized particles of metals and their compounds. From the intensity ratio of the copper lines, we estimated the electron temperature, and from the Stark broadening of the hydrogen lines H α we determined the electron density in the electrical discharge plasma. Information about the concentration of copper atoms in the discharge was obtained from analysis of the spectra in the region of resonance lines of copper. We carried out a comparative analysis of the plasma parameters for spark and arc discharges in water, ethanol, and air. Based on the equation of state for an ideal plasma, taking into account the Debye correction, we estimated the pressure in the plasma channel.Key words: electrical discharge in a liquid, electron concentration and temperature, spectral line reversal, Stark broadening of spectral lines, plasma particle concentration.Introduction. Electrical discharges in a liquid are used for machining metals and melting refractory materials, sterilizing drinking water and wastewater [1, 2], as sources of sound in hydroacoustic and hydrogeological studies; and in recent years, the electrical discharge method has shown promise for synthesis of nanosized particles of metals [3], their oxides, [4,5] and their carbides [6,7]. Advantages of the electrical discharge method for nanoparticle synthesis include: the possibility of controlling the parameters of the final products by varying the discharge regimes; the rather high throughput, with the possibility of scaling up the synthesis process (in this case, the refractory nature of the metals is not important); the relatively simple equipment needed in the reactor design; the uncomplicated process for preparation of the starting materials. Application of this method also makes it possible to significantly expand the variety of materials that can be obtained (metal powders, metal oxides and carbides, composite materials, particles of mixed composition) [8,9]. The conditions for synthesis of nanosized particles in a plasma may be more favorable than conditions in a gaseous medium [10]. This is connected with the fact that generally particles in a plasma are charged and repulsion between particles of like sign limits their growth, promoting formation of a narrower final particle size distribution.Despite the promise shown by the electrical discharge method and the growing number of papers on nanoparticle synthesis in electrical discharges in a liquid [3][4][5][6][7][8][9][10][11][12], in the literature we can only find scattered papers directly studying the discharge itself that is used to obtain the nanoparticles. Nevertheless, such discharge characteristics as electron temperature and the concentration of atoms and electrons are important for optimizing the synthesis process and controlling the parameters of the synthesized particles. The electrical parameters of the discharge determine to a significant extent the erosion of the electrodes of the material, th...

Synthesis and modification of molecular nanoparticles in electrical discharge plasma in liquids

“…We previously showed [48] that the electron temperature and the concentrations of atoms and electrons can be determined from the plasma emission spectrum.…”

Interpretation of Stark broadening measurements on a spatially integrated plasma spectral line

“…For the experimental characterisation of an electric arc, emission spectroscopy is the diagnostic method of choice for the measurement of the plasma temperature or species densities. Among the different spectroscopic diagnostic methods, those based on the measurement of the Stark broadening of a spectral line are widely used [1][2][3][4][5][6].…”

“…However, when none of these methods can be applied, because the plasma is not axisymmetric, the time constraints are too great, the intensity of the discharge is not sufficient to allow the selection of light rays or because the experimental setup does not allow a complex optical setup, it is common to collect the light emitted by the plasma using a focusing optical setup or selecting a direction with pinholes [1,3,5,9]. In this case the light is collected over the entire thickness of the plasma and the broadening measurement is made on the spectral line resulting from the integration over the thickness of the plasma.…”

Optimizing critical parameters for the directly measurement of particle flow with PF-SIBS

“…The selection of electrode materials is of significance to the accurate measurement and there are no specific research about it so far. Molybdenum 16 , platinum 17 , copper 18 , 19 and tungsten 10 – 13 were chosen as the electrode materials for experiment as they are the common electrode materials, and the spectral interference, plasma characteristic, delay time were studied to obtain optimal plasma observation state. Different size of quartz sands were also tested to investigate the size effect.…”