Download COST1208-Bertinoro

BIOPLASMAS & PLASMAS WITH LIQUIDS - Joint Conference of COST ACTIONS TD1208 “Electrical discharges with liquids for future
applications” & MP1101 Biomedical Applications of Atmospheric Pressure Plasma Technology, Bertinoro, Italy, 13th-17th September 2015
Breakdown data for vapours of organic liquids
Nikola Škoro1, Jelena Sivoš1, Dragana Marić1, Gordana Malović1, Zoran Lj.
Petrović1,2
1
Institute of Physics, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia
Serbian Academy of Sciences and Arts, Knez Mihailova 35, 11000 Belgrade, Serbia
2
Non-equilibrium discharges operating in organic liquids and/or vapours of these liquids have become
subjects of great interest both from the point of fundamental research and due to the possibility of their
various applications. For instance, organic molecules (containing carbon and hydrogen atoms) are important
in manufacturing processes of graphene, carbon nanotubes and carbon nanowalls [1, 2]. Moreover,
discharges involving organic liquids have also found applications in biomedical field and environmental
remediation [3, 4]. Although plasma sources differ in sizes and geometry, as well as pressure and operating
environment (some of them produce plasma inside liquid while others operate in vapour above liquid)
common issue for all of them is how to resolve complicated phenomena taking place in these discharges.
This research requires extensive and realistic models which need complete and reliable data sets including,
among else, transport parameters [5]. Unfortunately, these parameters have seldom been measured
systematically in vapours over the past few decades [6].
In this work we show measurements of breakdown properties of several organic vapours i.e. primary and
secondary alcohols at low pressure. Alcohol vapours are obtained by evaporation of 99 % or higher purity
liquid samples of alcohols using the same procedure as for water vapour [7]. The breakdown is achieved in a
simple centimetre-size parallel-plate geometry electrode system, with copper cathode and quartz anode with
transparent and conductive platinum film, placed inside a cylindrical quartz tube. The electrical circuit with
high resistance provided highly reproducible and reliable determination of breakdown voltages [5]. High
reproducibility of measurements was also facilitated by cathode surface conditioning in moderate-current
hydrogen discharge prior to the measurements and tested by repeated measurements. Together with
measurement of breakdown voltages in a wide range of pd (pressure x electrode gap) parameter, we recorded
spatially and spectrally resolved light emission coming from low-current discharge. Time-integrated axial
profiles of emission in visible spectra coming from the vapour discharge running in steady state regime reveal
information on overall particle kinetics. The profiles show which elementary processes are important at
different breakdown conditions i.e. at different reduced electric fields (E/N). Spectrally resolved emission
recordings allow to identify dominant excited species produced in the discharge at different E/N conditions.
Additionally, profiles at lower E/N where dominant emission comes from electron-induced excitation are
employed to obtain ionization coefficient and consequently the effective secondary electron yield. Even
though these coefficients are obtained for narrow range of conditions, for some vapours they are obtained
for the first time.
The data obtained for several organic vapours is complete set of reliable breakdown data necessary for
modelling. Further studies will include time resolved measurements of breakdown, to follow kinetics of the
main elementary processes.
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