초록 ▼

A method and a device for generating a plasma in atmospheric-pressure, low-temperature conditions are described herein. The device described for the generation of the plasma comprises a first pair of electrodes, each of which separated by a dielectric layer and externally positioned with respect to

A method and a device for generating a plasma in atmospheric-pressure, low-temperature conditions are described herein. The device described for the generation of the plasma comprises a first pair of electrodes, each of which separated by a dielectric layer and externally positioned with respect to a tubular duct where the gas flows, and a second pair of electrodes, also in this case each of which separated by a dielectric layer and externally positioned with respect to said tubular duct where the same gas flows downstream with respect to the first pair with respect to the direction of the flow. A high-frequency excitation is applied to the first pair of electrodes while a Radio-Frequency excitation is applied to the second pair of electrodes. The plasma generated in this manner emerges from the gas flow at the outlet of the transport duct. The high-frequency excitation can be applied in pulse trains and the Radio-Frequency generator is substantially activated in said pulse trains for the purpose of limiting the thermal load on the treated substrate. Chemical precursors and reagents can be added to the plasma as vapors or aerosols by means of a central transport duct coaxial with the tubular duct for the gas.

대표청구항 ▼

1. Method for generating an atmospheric plasma jet which comprises: flowing a process gas that advances in a flow direction (202, 402, 502) through a tubular duct (201, 401, 501) made of dielectric material with an inlet section and an outlet section (207, 410) at atmospheric pressure;positioning a

1. Method for generating an atmospheric plasma jet which comprises: flowing a process gas that advances in a flow direction (202, 402, 502) through a tubular duct (201, 401, 501) made of dielectric material with an inlet section and an outlet section (207, 410) at atmospheric pressure;positioning a first pair of coaxial electrodes (203-204, 307-308, 404-405, 503-504) and a second pair of coaxial electrodes (205-206, 309-310, 406-407, 505-506) in contact with the external surface of said tubular duet (201, 401, 501); said first pair of electrodes (203-204, 307-308, 404-405, 503-504) being placed in position upstream of said second pair of electrodes (205-206, 309-310, 406-407, 505-506) in relation to the flow direction of said process gas in said tubular duct (202, 402, 502) and being connected to a high-frequency generator (208, 301); said second pair of electrodes (205-206, 309-310, 406-407, 505-506) being connected to a Radio-Frequency generator (209, 303);said high-frequency generator (208, 301) generating a filamentary plasma within said tubular duct (201, 401, 501), said filamentary plasma extending at least to said second pair of electrodes (205-206, 309-310, 406-407, 505-506);said Radio-Frequency generator (209, 303) generating a second RF plasma;flowing out said RF plasma and said filamentary plasma to outside the tubular duct (201, 401, 501) through said outlet section (207, 410), such plasmas at the outlet comprising at least one neutral gas at the outlet having temperature not higher than about 100° C. 2. Method according to claim 1, wherein during the generation of said RF plasma, by said Radio-Frequency generator (209, 303), said high-frequency generator (208, 301) is substantially always operative for generating said filamentary plasma. 3. Method according to claim 1, wherein the process gas, introduced into said tubular duct (201, 401, 501) through the inlet section thereof, comprises at least one from among the following substances: helium, hydrogen, oxygen, nitrogen, argon, air, neon, carbon oxide, hydrocarbons. 4. Method according to claim 3, wherein the process gas, introduced into said tubular duct (201, 401, 501) through the inlet section thereof, comprises a mixture containing at least one noble gas and at least one reactive gas. 5. Method according to claim 1, wherein the high-frequency generator (208, 301) generates pulse trains and the Radio-Frequency generator (209, 303) is substantially exclusively active in said pulse trains. 6. Method according to claim 5, wherein the Radio-Frequency generator (209, 303) operates in the frequency range comprised between 1 and 30 MHz. 7. Method according to claim 5, wherein the pulsed high-frequency generator (208, 301) operates in the frequency range comprised between 1 and 100 kHz; wherein the pulse duration is up to 20 ms with a duty cycle in the range comprised between 10 and 98%. 8. Atmospheric plasma minitorch device characterized in that it comprises: a tubular duct (201, 401, 501) made of dielectric material with an inlet section and an outlet section (207, 410) at atmospheric pressure;at least one supply source connected to the inlet section of said tubular duct (201, 401, 501) and arranged for introducing said process gas into said tubular duct (201, 401, 501);a first pair of coaxial electrodes (203-204, 307-308, 404-405, 503-504) and a second pair of coaxial electrodes (205-206, 309-310, 406-407, 505-506) in contact with the external surface of said tubular duct (201, 401, 501); said first pair of electrodes (203-204, 307-308, 404-405, 503-504) being placed in position upstream of said second pair of electrodes (205-206, 309-310, 406-407, 505-606) in relation to the flow direction of said process gas in said tubular duct (202, 402, 502) and being connected to a high-frequency generator (208, 301); said second pair of electrodes (205-206, 309-310, 406-407, 505-506) being connected to a Radio-Frequency generator;said high-frequency generator (208, 301) being arranged for generating a filamentary plasma within said tubular duct (201, 401, 501), said filamentary plasma extending at least to said second pair of electrodes (205-206, 309-310, 406-407, 505-506) and exiting from said tubular duct (201, 401, 501) through said outlet section;said Radio-Frequency generator (209, 303) being arranged for generating a RF plasma which exits from said tubular duct (201, 401, 501) through said outlet section (207, 410);said filamentary plasma and said RF plasma exiting from said tubular duct (201, 401, 501) comprising at least one neutral gas at the outlet having temperature not higher than about 100° C. 9. Atmospheric plasma minitorch device according to claim 8, characterized in that it comprises control means connected to said high-frequency generator (208, 301) and to said Radio-Frequency generator (209, 303) and arranged for controlling said high-frequency generator (208, 301) between a first non-operative state and a first operative state, in which said high-frequency generator (208, 301) generates said filamentary plasma; said control means being arranged for controlling said Radio-Frequency generator (209, 303) between a second non-operative state and a second operative state, in which said Radio-Frequency generator (209, 303) generates said RF plasma with said high-frequency generator (208, 301) in said first operative state. 10. Atmospheric plasma minitorch device according to claim 9, characterized in that said control means comprise at least one electronic control unit connected to said high-frequency generator (208, 301) and to said Radio-Frequency generator (209, 303), and programmed for controlling the activation of said Radio-Frequency generator (209, 303), controlled in said second operative state, during pulse trains generated by the high-frequency generator (208, 301) controlled in said first operative state. 11. Atmospheric plasma minitorch device according to claim 8, characterized in that it comprises at least one supply source connected to the inlet section of said tubular duct (201, 401, 501) and arranged for introducing said process gas into said tubular duct (201, 401, 501), which can be modulated both with regard to the entering flow and the composition, in mixture form containing at least one noble gas and at least one reactive gas. 12. Atmospheric plasma minitorch device according to claim 8, wherein the tubular duct (201) has circular section and is made of dielectric material such as glass, ceramic, polymer, composite or other dielectric material and wherein the external diameter of the tubular duct is comprised between 1 mm and 15 mm. 13. Atmospheric plasma minitorch device according to claim 8, wherein the body of the device is a tubular duct with rectangular section (501) and wherein the shorter side is comprised between 1 mm and 15 mm (509). 14. Atmospheric plasma minitorch device according to claim 8, wherein the high-frequency generator (208) operates in the range comprised between 1 and 100 kHz and wherein the duration of the pulse is comprised in the range between 1.25 and 20 ms with a duty cycle in the range comprised between 10 and 98%; wherein the Radio Frequency generator (209) operates in the range comprised between 1 and 30 MHz; and wherein the activation of said radio-frequency generator (209) is susceptible of being controlled by said pulse trains generated by the high-frequency generator. 15. Atmospheric plasma minitorch device according to claim 8, which also comprises: a transport duct (409), through which a liquid precursor or a precursor in the form of a particle suspension in a liquid can be flowed, such duct (409) positioned inside and coaxial with respect to the tubular duct (401), with the free emission end placed inside said tubular duct at a distal position from the outlet section of said tubular duct (401). 16. Atmospheric plasma mini torch device according to claim 15, which also comprises: a separation duct (408) made of dielectric material with larger internal diameter with respect to the transport duct (409) and with smaller external diameter with respect to the tubular duct (401), coaxially interposed between said transport duct (409) and said tubular duct (401), and it too equipped with an outlet section;an annular cavity being defined by the external surface of the transport duct (409) and by the internal surface of said separation duct (408), into which a nebulizer gas flows which, by intercepting the fluid exiting from the transport duct (409), generates an aerosol at the free emission end of said transport duct (409). 17. Atmospheric plasma minitorch device according to claim 15, which also comprises: a separation duct (408) made of dielectric material with larger internal diameter with respect to the transport duct (409) and with smaller external diameter with respect to the tubular duct (401), coaxially interposed between said tubular duct (401) and said transport duct (409);an annular cavity being defined by the external surface of the transport duct (409) and by the internal surface of said separation duct (408), into which a process has flows in the form of vapors or aerosols of chemical precursors, such process gas interacting with the RF plasma at the outlet section.