Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/26—Plasma torches
  • H05H1/30—Plasma torches using applied electromagnetic fields, e.g. high frequency or microwave energy
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H1/00—Generating plasma; Handling plasma
  • H05H1/24—Generating plasma
  • H05H1/26—Plasma torches
  • H05H1/32—Plasma torches using an arc
  • H05H1/34—Details, e.g. electrodes, nozzles
  • H05H1/36—Circuit arrangements
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2240/00—Testing
  • H05H2240/10—Testing at atmospheric pressure
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2240/00—Testing
  • H05H2240/20—Non-thermal plasma
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2245/00—Applications of plasma devices
  • H05H2245/30—Medical applications
  • H05H2245/36—Sterilisation of objects, liquids, volumes or surfaces
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05H—PLASMA TECHNIQUE; PRODUCTION OF ACCELERATED ELECTRICALLY-CHARGED PARTICLES OR OF NEUTRONS; PRODUCTION OR ACCELERATION OF NEUTRAL MOLECULAR OR ATOMIC BEAMS
  • H05H2245/00—Applications of plasma devices
  • H05H2245/40—Surface treatments

Definitions

• the invention relates to a plasma tool for the plasma-assisted treatment, modification and coating of inner and outer surfaces of materials in air by means of a cold plasma jet according to the preamble of claim 1.
• Plasma technology especially at high temperatures and high gas pressures, has long been known and described many times, e.g. in US Pat. No. 3,648,015, US Pat. No. 4,626,648, DE 41 08 499 A1 and DE 10.1 40 298 B4.
• WO 03/026365 Al a device is described which allows to generate a plasma by means of microwaves, wherein it allows the device described in WO 03/026365, despite any pressure fluctuations in the process gas to produce a stable plasma flame.
• German Auslegeschrift 1 639 257 Another plasma generator that produces a plasma at high temperatures is described in German Auslegeschrift 1 639 257. It is a high-frequency plasma jet generator with a cylindrical tube, on one end side of which to gas to be ionized and at the other end side of the generated plasma flows out, an induction coil whose one end is connected to ground and the other end is connected to a high-frequency generator. Between the two ends of the coil, a tap is arranged. The high-frequency voltage generated in the induction coil is higher than the excitation voltage.
• the tube in the area of the plasma outlet is made of metal and placed on the high-voltage end of the induction coil. The tube is concentrically and electrically isolated surrounded by a metallic housing. Due to the special arrangement, the gas discharge between the two adjacent ends of tube and housing takes place due to a capacitive coupling between these two components.
• this generator is not suitable for the generation of a cold normal pressure plasma at least due to its electrode shape.
• low-pressure plasmas have been used to date for these processes, in which the radicals, excited atoms, ions, electrons and UV radiation required for these applications can be generated to a defined extent by the selection of suitable process parameters.
• Low-pressure plasma processes are not suitable for numerous industrial processes in which a corresponding surface modification is required, both for cost reasons and for procedural reasons.
• Corona discharge which is suitable for the plasma treatment of surfaces.
• a gas stream is passed through a corona discharge gap between a rod-shaped inner and a tubular outer electrode.
• a process for the plasma treatment of surfaces is described, which is based on the generation of a plasma jet by arc discharge with non-transferred arc.
• the subject matter of US Pat. Nos. 6,194,036 and 6,262,523 are arrangements based on the RF excitation of atmospheric pressure plasmas.
• US 2002/122896 are various Arrangements for producing normal pressure plasmas based on RF excited discharges in tubes of insulating material are described.
• plasmas of this type are used for argon plasma coagulation (US 4,781,175, US 4,060,088, DE 19513338), for coatings on artificial implants to increase their biocompatibility, for controlling cell adhesion to surfaces, for disinfecting medical instruments (M. Laroussi: IEEE Trans. Plasma. 30: 4 (2002), 1409) and for the treatment of biological cells and tissues (E. Stoffels et al.: Plasma Sources Sei. Technol., 11 (2002), 383).
• Normal-pressure plasmas based on RF-excited discharges have the advantage that they can be operated at fixed frequencies (13, 56 MHz, 27.12 MHz, 40.68 MHz), which are released for industrial applications, and on the other hand at smaller
• High-frequency operated plasma reactors require a matching network (matchbox) for maximum power transmission from their RF generator.
• An often used circuit in the Matchbox is the ⁇ circuit. It consists of two capacitors C1 and C2 and a coil (see Fig. 1). In order to keep losses in the matchbox low, capacitors with air as a dielectric are used, which occupy a large volume. Since the current transport at these frequencies takes place mainly on the surface of an electrical conductor (skin effect), the coil and all other electrical leads consist of a relatively thick metal wire with high electrical conductivity on the surface (silver wire, silver-plated copper wire). As a result, such a matchbox is generally very voluminous. To ignite and maintain a gas discharge in the plasma reactor, high voltages are needed.
• the matchbox by the fact that the coil and the capacitor C2 form a series resonant circuit, which must be matched to the particular frequency of the RF generator used.
• the supply line Z2 should consist of an unshielded cable and should be kept as short as possible.
• the matchbox and the plasma reactor actually form a relatively rigid, unwieldy unit. If you want to realize a handy plasma nozzle as a plasma reactor, which can be performed for example by a robot, such a bulky plasma reactor is useless.
• the invention is therefore based on the object to realize a handy plasma nozzle, which can also be performed by hand and / or by robots.
• the coil and optionally the capacitor C2 is integrated into the plasma nozzle.
• a possibly required capacitor Cl may be located anywhere between the generator and the plasma nozzle, but preferably the capacitor Cl is positioned directly on the generator outside (short lead) or directly inside. This achieves the following improvements:
• the supply line Zl (coaxial cable) from the generator to the plasma nozzle can be designed much more flexible and longer than would ever have been possible for the lead Z2 according to the prior art.
• the supply line Z2 is formed by the coil end to the electrode El and can therefore be made extremely short. 4. The formed between the electrodes El and E2
• Capacity is parallel to C2. Changes in this capacity due to tolerances in the production of the plasma nozzle or upon ignition of the plasma can be compensated for by changing C2, so that the resonance condition is maintained. 5. Due to the very short lead Z2, the total capacity, formed by the capacitance C2 and the capacitance between El and E2, is automatically kept small, so that the inductance L can be maximally selected according to the fixed frequency and thus a high quality of the series resonant circuit (generation a high voltage overshoot) can be achieved.
• the plasma tool according to the invention for producing a cold plasma jet comprises a
• Adaptation network for generating the required voltage is characterized in that the matching network at least the coil is integrated into the plasma nozzle.
• the matching network integrates the coil L and the capacitor C2 into the plasma nozzle.
• the capacitor Cl of the matching network can be arranged directly on or in the frequency generator and it is advantageously arranged there.
• the plasma nozzle contains a capillary made of insulating material and the coil is arranged around this capillary.
• the matching network (matchbox) consists of one coil and two capacitors C1 and C2 with their connections.
• the coil and the capacitor C2 are integrated in the plasma nozzle and the capacitor Cl is arranged directly on or in the generator.
• the generator is a frequency-tunable RF generator and the matching network consists of a coil with leads, the coil being integrated into the plasma nozzle.
• Capacitors C1 and C2 it is clearly stated here that the capacitors C1 and C2 can be made up of several partial capacitors and that capacitors constructed from partial capacitors are likewise referred to as C1 and C2 in the context of this invention.
• the plasma reactor may be configured such that the matching network consists of a coil and either capacitor C1 or capacitor C2 and the corresponding lines.
• Invention is a plasma nozzle, in which at least one coil, preferably a coil and a capacitor C2 are integrated. These can, as described above and in the embodiments resp. the figures shown to be installed.
• the invention is a frequency generator in which either a capacitor suitable as a capacitor Cl of a matching network is integrated or mounted directly at the output of the generator.
• the embodiment with a capacitor Cl and a capacitor C2 relates in particular to commercially available RF generators having a fixed frequency, as described e.g. in Germany are released by the post office for technical concerns.
• a simplification, and therefore cheaper, of the combination RF generator - plasma nozzle results in the transition to lower frequencies (e.g., 3 MHz) and using a
• a plasma nozzle according to the invention generally comprises a body side, ie on the plasma respectively. the nozzle facing away from the plasma nozzle, with a hollow body connected to a process gas supply.
• This hollow body is preferably made of insulating material.
• the coil forming part of the matching network is arranged around a part of this hollow body.
• the dimensions of the hollow body, or these dimensions together with another body, preferably an insulating body, are to be chosen such that the coil with the desired winding diameter can be arranged thereon.
• This coil must - if the hollow body or other body on which it is arranged, not made of insulating material, be self-insulated.
• This coil is connected to the nozzle side with an electrode El and optionally a variable capacitor C2.
• the electrode E1 may optionally be a ring electrode disposed around the insulating hollow body or a rod electrode disposed in the hollow body.
• the capacitor C2 and the coil are connected in series, so that it can adjust the voltage required at a given frequency. On the side facing away from the coil, the capacitor C2 is connected to the grounded housing.
• a ring electrode E2 which is connected to the grounded housing.
• This housing has feeds for the electric current and feed openings for the process gas and a discharge opening for the plasma within the second electrode E2.
• a further insulating layer which is important in particular with a small clearance between the coil and the housing.
• the connecting line between the electrode El and the capacitor C2 is usually on the coil side on the housing shielding insulation and in turn is provided with an insulating layer.
• Suitable insulating materials are plastic, quartz glass, ceramics, etc., which may be used singly or in combination.
• Conductivity preferred at least on the surface such as silver-plated copper wire or pure silver wire.
• FIG. 1 shows the general connection of an RF-operated, capacitively coupled plasma tool
• FIG. 1a representing the plasma reactor in general
• FIG. 1b the plasma nozzle.
• FIG. 2 shows an inventive device
• FIG. 3 shows a further embodiment according to the invention with a variable frequency generator in which the capacitors C 1 and C 2 can be dispensed with.
• FIG. 4 shows a plasma nozzle according to the invention with an RF ring electrode.
• FIG. 5 shows a plasma nozzle according to the invention with an RF rod electrode.
• FIG. 6 shows a plasma broad-jet nozzle with an RF ring electrode according to the invention.
• Embodiments of the prior art relate in particular to commercially available RF generators having a fixed frequency.
• the matching network has been separated, the capacitor C1 in the RF generator and the capacitor C2 and the coil being integrated in the plasma nozzle.
• FIG. 4 shows an exemplary embodiment of a plasma nozzle with a capacitively coupled capillary discharge 1.
• Ring electrodes 2, 3 are mounted at a suitable distance on a hollow body made of insulating material (dielectric) 4.
• a coil 6 is wound, which is connected at one end to the RF electrode 3 and at the other end to the RF input 7 of the plasma nozzle.
• the RF electrode 3 is connected to the grounded case 8 via a rotary air capacitor C2.
• the process gas 9 preferably noble gas
• Both electrodes 2 and 3 and the dielectric 4 form a capacitance (a few pF), the parallel to C2.
• the coil 6 forms a series resonant circuit with these capacitances and can be adjusted via C2 to maximum voltage at the electrode 3.
• Suitable dimensions and materials for the embodiment described in FIG. 4 are:
• Width of metallic ring electrodes 5mm
• Insulating material (capillary): outer diameter 3mm, inner diameter lmm
• process gases noble gases, such as argon and helium
• Dielectric constant e.g. quartz glass
• Capacitor Cl 350 pF In Fig. 5 is another
• Embodiment of a plasma nozzle with a capillary discharge 1 shown.
• the RF energy is coupled via a rod electrode 3 into the capillary discharge.
• the rod electrode should be made of low work function materials to minimize the voltage needed for capillary discharge. She should also be pointed forward, so as to achieve a high field strength. Between the tip and the grounded electrode 2, at sufficiently high voltages, a capillary discharge is formed, the plasma of which is in turn blown outward by the gas flow.
• Essential dimensions / materials other than in the embodiment described above and in FIG. 4 are:
• Hollow body made of insulating material (capillary) 4 outer diameter 6mm, inner diameter 2mm.
• Diameter of the rod electrode lmm
• FIG. 6 shows a modified variant of the plasma nozzle. The discharge is again generated between the electrodes 2 and 3 and passes through a
• insulating material such as, for example, plastic, Quartz glass, ceramics, etc.
• plasma nozzle by means of an RF discharge generated by a nozzle, directed normal pressure blasting plasma with the desired properties (for example, non-thermal, floating, homogeneous and reactive) to which the In order to achieve their desired physicochemical change, the conditions in the jet plasma region may be changed by changing the geometric arrangements and dimensions within the plasma nozzle, by using other process gases, their admixtures and flow rates be controlled by the arrangement and choice of electrodes, by the type of ignition and / or by varying the electrical parameters of the discharge.
• desired properties for example, non-thermal, floating, homogeneous and reactive

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Electromagnetism (AREA)
• Plasma Technology (AREA)
• Treatment Of Fiber Materials (AREA)

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Cited By (14)

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Citations (4)

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• 2006
  • 2006-04-27 DE DE102006019664.3A patent/DE102006019664B4/de active Active
• 2007
  • 2007-04-26 ES ES07724599.1T patent/ES2548096T3/es active Active
  • 2007-04-26 WO PCT/EP2007/003669 patent/WO2007124910A2/de active Application Filing
  • 2007-04-26 PT PT77245991T patent/PT2016809E/pt unknown
  • 2007-04-26 PL PL07724599T patent/PL2016809T3/pl unknown
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