The characterization of cathodic plasma electrolysis of tungsten by means of optical emission spectroscopy techniques

Abstract

Cathodic plasma electrolysis (CPE) of tungsten is investigated by means of optical emission spectroscopy in order to measure the electron temperature Te and the electron number density Ne from CPE micro-arc discharges. The relative intensity of W I lines recorded from seven spectral ranges are used in conjunction with the Boltzmann plot (BP) technique to measure Te ≈ 10000 K. For Ne diagnostics, the complex line shape of the Hα and the H β lines are analyzed in the frame of the spectral line broadening theory. The results showed two Ne values, (7 ± 3) × 10 14 cm −3 and (7 ± 3) × 10 15 cm −3 , corresponding to different regions of CPE micro-arc discharges. The self-absorption effect on both studied H I lines was revealed and discussed as well. The SEM and XRD analysis showed a weak formation of rough oxide coating (WO3, W3O8) featured by the number of grains, channels, and holes.

The study of micro-arc discharges during cathodic plasma electrolysis of refractory metals using the spectral line shape of Na I lines

“…These N e values are intentionally chosen as the initial guess and they are based on the results of the H β analysis given in ref. [8]. In comparison to the initial N e values, a higher N e is determined from the shift of profiles Nos.…”

“…Based on our previous study of CPE micro-arc discharges [8], we assume that T e = 10000 K in the outer region while T e ∼ 5000 K, in the central region of the discharge. The gas temperature was T g = 3000-4000 K, while the hydrogen molecules were considered as a main perturbers in the van der Waals broadening calculations (p = 1 bar).…”

“…In our previous study, we applied spectroscopic diagnostics methods to estimate the electron temperature T e and the electron number density N e from CPE micro-arc (a) E-mail: jjovica@ff.bg.ac.rs discharges on tungsten. This was realized using a W I lines Boltzmann plot (BP) and applying the fitting procedure on the experimental H β profile [8], respectively. The main difficulty concerning the N e diagnostics procedure in ref.…”

“…The main difficulty concerning the N e diagnostics procedure in ref. [8] was related to the interference of the H β with neighboring spectral lines (originating from the cathode) as well as with the self-absorption effect on the H β line.…”

The spectroscopic study of metallic lines emitted from a pulsed atmospheric pressure gas discharge source with brass and stainless steel cathodes

“…When a treated sample is the cathode (so called cathodic plasma electrolysis-CPE), the same plasma phase occurs but with a detrimental effect on the deposited dielectric film. 10 It is worth mentioning that for a magnesium–aluminum alloy PEO, the spectral line shape of Mg I and Al II lines is analyzed for the purpose of T e and N e measurement in plasma. 11 The line shape of Fe I lines recorded from CPE experiments is also studied.…”