Miloš Klíma

The high pressure torch discharge plasma source

We present a plasma source which works on the principle of the arc torch discharge. The powered electrode of the arc torch discharge was made from a thin pipe that simultaneously acts as the nozzle through which the working gas flows to the discharge region. The flow of the working gas stabilizes the arc torch discharge and a well defined plasma channel is created. The advantage of this system is that it is able to work at high pressure of working gas up to atmospheric pressure inside the plasma-chemical reactor and also in free space.

Diagnostics and Applications of High Frequency Plasma Pencil

The so called high frequency plasma pencil is a source of highly active environment (electrons, ions, reactive radicals, excited atoms, and molecules) which can be generated at atmospheric, reduced or increased pressure, preserving a good control of the performance. The discharge can be either unipolar or bipolar. The properties of unipolar atmospheric pressure discharges are discussed on the basis of simple theoretical considerations and electric probe measurements. The plasma pencil discharge is studied by optical emission spectroscopy in the gas phase at atmospheric pressure as well as immersed in liquid using argon as a working gas. From the emission spectra the electron, vibrational and rotational temperatures are calculated for various distances from the plasma pencil electrode. Several technological applications like restoration of archaeological glass and metal artifacts, fragmentation of molecules for microelectrophoresis and plasma polymerization are summarized. An advantage of the plasma pencil is that it can be easily operated and controlled.

Deposition of polymer films by rf discharge at atmospheric pressure

In this contribution we report some typical properties of the discharge which has been used for deposition of thin films and some mechanical parameters of thin films. RF plasma nozzle can burn very well even at atmospheric pressure. Special properties of RF discharges offer hopeful technological applications like deposition of thin solid films. The knowledge of physical parameters of plasma has been required. The parameters of the plasma were investigated by spectral and optical methods. The powered RF electrode of the torch discharge plasma source is made from the metal or dielectric pipe with an inner diameter of 1÷2 mm and with a length of several centimeters. The electrode is connected through the matching unit to the RF generator driven at the frequency of 13.56 MHz. The mixture of argon andn-hexane or HMDSO (hexamethyldisiloxane, C6H18Si2O) gas flows through the RF electrode at the pipe Fig. 1. Polymer films were deposited on the several substrates e.g. glass, brass polished plates and Si wafers.

Plasma-liquid technologies for treatment of archaelogical artifacts

Plasma-liquid technologies at atmospheric pressure provide a wide range of possibilities for applications. One of them, the treatment of archaeological artifacts, is presented in this paper. The effects of discharges between a metal electrode and a solution surface and/or an interaction of hollow cathode plasma jet, plasma pencil, with liquid on the corroded surface of bronze and glass artifacts were studied. It was compared with standard low pressure plasma techniques and with the effects of electrolysis. Original and treated objects were characterized by means of scanning electron microscope (SEM) with energy dispersive analyser used for the spot elemental analyses.

HF-Plasma Pencil in Liquids

The plasma pencil in liquids is a new device for the treatment of archeological artifacts. Plasma jets out from the pencil so that it makes radical changes in the conductivity and reactivity of liquids. An artifact is immersed in liquid and the plasma has a local and rapid effect on materials.

Plasma pencil — A new small scale source for atmospheric surface modifications

Plasma pencil is a device which can produce plasma jet at atmospheric pressure and low power (10–200 W) from DC to HF. The jet character of the plasma makes this device very efficient in aimed local (1 – 102 mm2) modifications of surfaces. Great variability in possible power sources allow to achieve a broad range of effects on materials. We have tested bipolar discharges with a metal object and a unipolar HF discharge to burn the glazing on ceramics. Both technologies could be prospective.

The high pressure plasma source for the surface treatment technology based on the torch discharge stabilized by working gas flow

The RF torch discharge has been described as a source of the plasma channel. The advantage of this system is that it is possible to use it up to atmospheric pressure for surface coating. The torch discharge works even in the liquid environment.

Influence of Chemical Precleaning on the Plasma Treatment Efficiency of Aluminum by RF Plasma Pencil

This paper is aimed to show the influence of initial chemical pretreatment prior to subsequent plasma activation of aluminum surfaces. The results of our study showed that the state of the topmost surface layer (i.e. the surface morphology and chemical groups) of plasma modified aluminum signiticantly depends on the chemical precleaning. Commonly used chemicals (isopropanol, trichlorethane, solution of NaOH in deionized water) were used as precleaning agents. The plasma treatments were done using a radio frequency driven atmospheric pressure plasma pencil developed at Masaryk University, which operates in Ar, Ar/O2 gas mixtures. The efectiveness of the plasma treatment was estimated by the wettability measurements, showing high wettability improvement already after 0.3 s treatment. The efects of surface cleaning (hydrocarbon removal), surface oxidation and activation (generation of OH groups) were estimated using infrared spectroscopy. The changes in the surface morphology were measured using scanning electron microscopy. Optical emission spectroscopy measurements in the near-to-surface region with temperature calculations showed that plasma itself depends on the sample precleaning procedure.

Optical diagnostics of special types of RF and DC discharges burning at atmospheric pressure

Special properties of RF discharges burning at atmospheric pressure or near the at mospheric pressure offer manyperspective technological applications. Using the emission spectroscopy, we compare the behaviour of RF discharges with the spark discharge controlled bymagnetic field.

Possibilities of effective fullerene and nanotubes production by radiofrequency dicharges

In our work, we are trying to find new more effective ways of fullerene and nanotube production by decomposition of hydrocarbons in radiofrequency discharges. So far, we have studied several radiofrequency energy sources by which hydrocarbons can be decomposed and the fullerenes produced. The conditions of experiments are similar to those in the classic way of fullerene production. He atmosphere, pressure around 100 – 200 Torr. We also try to modify those conditions by using of Ar and different pressures and energies (50 W – 2 kW). The latest application of hydrocarbon decomposition is also a controlled nanotube production reported by several teams which we try to obtain too.