US-12621922-B2 - Volumetric plasmas, and systems and methods for generation and use thereof

US12621922B2US 12621922 B2US12621922 B2US 12621922B2US-12621922-B2

Abstract

A volumetric plasma can be generated between first and second electrodes. The first and second electrodes can be spaced from each other by a gap. The first electrode can comprise a first base layer and a plurality of first projecting portions that extend along a first direction from the first base layer toward the second electrode. The first base layer can comprise a first electrically-conductive material. At least some of the first projecting portions can comprise a second electrically-conductive material. A melting temperature for the first electrically-conductive material and a melting temperature for the second electrically-conductive material can be at least 1000 K. During the generating, a temperature of the volumetric plasma between the first and second electrodes can be in a range of 1000-8000 K, inclusive.

Inventors

Liangbing Hu
Hua Xie
Yiguang Ju
Qian Zhang
Ji-Cheng Zhao

Assignees

UNIVERSITY OF MARYLAND, COLLEGE PARK
THE TRUSTEES OF PRINCETON UNIVERSITY

Dates

Publication Date: 20260505
Application Date: 20231003

Claims (20)

1 . A method comprising: generating a volumetric plasma between first and second electrodes spaced from each other by a gap, the first electrode comprising a first base layer and a plurality of first projecting portions that extend along a first direction from the first base layer toward the second electrode, wherein the first base layer comprises a first electrically-conductive material, at least some of the first projecting portions comprise a second electrically-conductive material, a melting temperature for the first electrically-conductive material and a melting temperature for the second electrically-conductive material are at least 1000 K, and during the generating, a temperature of the volumetric plasma between the first and second electrodes is in a range of 1000-8000 K, inclusive.
2 . The method of claim 1 , wherein: each of the first projecting portions has a maximum cross-sectional dimension in a plane substantially perpendicular to the first direction less than or equal to 500 μm; each of the first projecting portions has a length along the first direction less than or equal to 1 cm; each of the first projecting portions is spaced from adjacent ones of the plurality of first projecting portions by less than or equal 1 mm; or any combination of the above.
3 . The method of claim 1 , wherein the generating comprises: initiating the volumetric plasma by applying a first direct current (DC) voltage, a first alternating current (AC) voltage, or a first pulsed voltage waveform between the first and second electrodes; and maintaining the initiated volumetric plasma by applying a second DC voltage, a second AC voltage, or a second pulsed voltage waveform between the first and second electrodes, wherein an absolute value of a peak voltage of the second DC voltage, the second AC voltage, or the second pulsed voltage waveform is less than an absolute value of a peak voltage of the first DC voltage, the first AC voltage, or the first pulsed voltage waveform.
4 . The method of claim 1 , wherein a size of the generated plasma along a second direction is in range of 1 mm to 100 cm, inclusive, the second direction being in a plane substantially perpendicular to the first direction.
5 . The method of claim 1 , wherein: the second electrode comprises a second base layer and a plurality of second projecting portions that extend along the first direction from the second base layer toward the first electrode; the second base layer comprises a third electrically-conductive material; at least some of the second projecting portions comprise a fourth electrically-conductive material; and a melting temperature for the third electrically-conductive material and a melting temperature for the fourth electrically-conductive material are at least 1000 K.
6 . The method of claim 5 , wherein: the first electrode further comprises a plurality of third projecting portions that extend along the first direction from the first base layer toward the second electrode farther than the plurality of first projecting portions, at least some of the third projecting portions being formed of a fifth electrically-conductive material; the second electrode further comprises a plurality of fourth projecting portions that extend along the first direction from the second base layer toward the first electrode farther than the plurality of second projecting portions, at least some of the fourth projecting portions being formed of a sixth electrically-conductive material; at least one of the third projecting portions contacts with at least one of the fourth projecting portions in the gap or is separated from the at least one of the fourth projecting portions by no more than 5 μm; and a melting temperature for the fifth electrically-conductive material and a melting temperature for the sixth electrically-conductive material are at least 1000 K.
7 . The method of claim 6 , wherein the generating comprises: initiating the volumetric plasma via gas discharge between the third and fourth projecting portions; and maintaining the volumetric plasma via gas discharge between the first and second projecting portions.
8 . The method of claim 1 , wherein: the second electrode has a surface area facing the gap greater than that of the first electrode; and the method further comprises, during the generating, moving one of the first and second electrodes with respect to the other so as to change a location of the generated volumetric plasma.
9 . The method of claim 1 , further comprising, prior to or at a same time as the generating, disposing one or more precursors within or adjacent to the gap between the first and second electrodes such that the volumetric plasma heats the one or more precursors so as to form one or more products.
10 . The method of claim 1 , further comprising, during the generating, flowing one or more gases and/or one or more precursors through the volumetric plasma such that the volumetric plasma heats the one or more gases and/or the one or more precursors so at to form one or more products.
11 . The method of claim 1 , wherein the generating comprises: initiating the volumetric plasma by applying voltage between the first and second electrodes with the gap at a first distance; moving the first electrode away from the second electrode and/or moving the second electrode away from the first electrode; and maintaining the initiated volumetric plasma by applying voltage between the first and second electrodes with the gap being greater than the first distance.
12 . A system comprising: a first electrode comprising a first base layer and a plurality of first projecting portions, the first base layer comprising a first electrically-conductive material, at least some of the first projecting portions comprising a second electrically-conductive material, a melting temperature for the first electrically-conductive material and a melting temperature for the second electrically-conductive material being at least 1000 K; a second electrode spaced from the first electrode by a gap, the plurality of first projecting portions extending along a first direction from the first base layer toward the second electrode; an electrical power source electrically coupled to the first and second electrodes; and a control system operatively coupled to the electrical power source and configured to control operation thereof, the control system comprising one or more processors and computer-readable storage media storing instructions that, when executed by the one or more processors, cause the electrical power source to apply voltage between the first and second electrodes such that a volumetric plasma is generated within or adjacent to the gap, a temperature of the volumetric plasma being in a range of 1000-8000 K, inclusive.
13 . The system of claim 12 , wherein: each of the first projecting portions has a maximum cross-sectional dimension in a plane substantially perpendicular to the first direction less than or equal to 500 μm; each of the first projecting portions has a length along the first direction less than or equal to 1 cm; each of the first projecting portions is spaced from adjacent ones of the plurality of first projecting portions by less than or equal 1 mm; or any combination of the above.
14 . The system of claim 12 , wherein the electrical power source is configured to apply a direct current (DC) voltage, an alternating current (AC) voltage, or a pulsed voltage waveform between the first and second electrodes.
15 . The system of claim 12 , wherein the computer-readable storage media stores additional instructions that, when executed by the one or more processors, further cause the electrical power source to: initiate the volumetric plasma by applying a first direct current (DC) voltage, a first alternating current (AC) voltage, or a first pulsed voltage waveform between the first and second electrodes; and maintain the initiated volumetric plasma by applying a second DC voltage, a second AC voltage, or a second pulsed voltage waveform between the first and second electrodes, wherein an absolute value of a peak voltage of the second DC voltage, the second AC voltage, or the second pulsed voltage waveform is less than an absolute value of a peak voltage of the first DC voltage, the first AC voltage, or the first pulsed voltage waveform.
16 . The system of claim 12 , wherein a size of the first and second electrodes are such that a size of the generated plasma along a second direction is in a range of 1 mm to 100 cm, inclusive, the second direction being in a plane substantially perpendicular to the first direction.
17 . The system of claim 12 , wherein: the second electrode comprises a second base layer and a plurality of second projecting portions that extend along the first direction from the second base layer toward the first electrode; the second base layer comprises a third electrically-conductive material; at least some of the second projecting portions comprise a fourth electrically-conductive material; and a melting temperature for the third electrically-conductive material and a melting temperature for the fourth electrically-conductive material are at least 1000 K.
18 . The system of claim 12 , wherein: the first electrode further comprises a plurality of third projecting portions that extend along the first direction from the first base layer toward the second electrode farther than the plurality of first projecting portions, at least some of the third projecting portions being formed of a fifth electrically-conductive material; the second electrode comprises a plurality of fourth projecting portions that extend along the first direction from the second base layer toward the first electrode, at least some of the fourth projecting portions being formed of a sixth electrically-conductive material; at least one of the third projecting portions contacts with at least one of the fourth projecting portions in the gap or is separated from the at least one of the fourth projecting portions by no more than 5 μm; and a melting temperature for the fifth electrically-conductive material and a melting temperature for the sixth electrically-conductive material are at least 1000 K.
19 . The system of claim 12 , wherein the first electrode, the second electrode, or both have a non-planar geometry.
20 . The system of claim 12 , further comprising: (i) a first translation stage constructed to move the first electrode; (ii) a second translation stage constructed to move the second electrode; or (iii) both (i) and (ii), wherein the control system is operatively coupled to the first translation stage and/or the second translation stage and configured to control operation thereof, and the computer-readable storage media stores additional instructions that, when executed by the one or more processors, cause the first translation stage and/or the second translation stage to move one of the first and second electrodes with respect to the other of the first and second electrodes.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims the benefit of U.S. Provisional Application No. 63/378,215, filed Oct. 3, 2022, entitled “Tip-Enhanced Volumetric Plasma and Methods for Making and Using the Same,” and U.S. Provisional Application No. 63/513,567, filed Jul. 13, 2023, entitled “A Uniform, Ultrahigh-Temperature Stable Plasma Operating at Atmospheric Pressure for the Synthesis of Extreme Materials,” each of which is hereby incorporated by reference herein in its entirety. STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH This invention was made with government support under DE-SC0020233 awarded by the U.S. Department of Energy. The government has certain rights in the invention. FIELD The present disclosure relates generally to plasma systems and methods, and more particularly, to generation and use of a volumetric plasma, for example, by applying an electric field between electrodes. BACKGROUND Plasma is formed when an electric field electronically and vibrationally excites molecules via electron impact processes. While plasmas have been used for material processing, such as reactive ion etching and thin film deposition, it continues to be challenging to use conventionally-generated plasmas in the fabrication of large-scale bulk materials, in particular, materials have a high-melting point. For such fabrication, uniform high temperatures (e.g., >1000 K) over a large area or volume (e.g., >1 cm2) may be preferable. Volumetric plasmas, such as glow discharge, have been demonstrated. However, flow discharge typically requires low pressure (e.g., <150 torr), where the plasma neutral gas temperature (Tg) is significantly lower than the electron temperature (Te). As a result of the low neutral gas temperature (e.g., <1000 K), the ability of glow discharge to process high-temperature materials, particularly at a high yield is limited. While arc discharge can be used to generate high-temperature plasmas (e.g., up to 10,000 K) at atmospheric pressure, the generated plasmas have spatially non-uniform temperatures and can be unstable. In particular, atmospheric arc discharge between conventional plate electrodes contracts to a narrow, random arc channel (e.g., ˜1 mm in diameter), with the resulting temperature distribution being highly non-uniform. Pin-to-pin electrodes can help avoid random discharge. For example, the high curvature of the electrode (e.g., a radius of several mm) can increase the local electric field strength and promote the thermionic emission of secondary electrons. However, such a pin structure can limit the arc plasma to a narrow channel with a limited plasma volume. Use of a rotating gliding arc can increase the discharge volume, but the plasma channel remains a narrow filament with the concomitant non-uniform distribution of temperature and active species. Embodiments of the disclosed subject matter may address one or more of the above-noted problems and disadvantages, among other things. SUMMARY Embodiments of the disclosed subject matter provide systems and methods for generating volumetric plasmas, as well as use of such volumetric plasmas, for example, to subject a sample (e.g., precursor(s), reactant(s), or other material(s)) to high temperatures over relatively large areas with enhanced temporal stability and/or spatial uniformity. In some embodiments, the volumetric plasma can be generated by applying voltage between a pair of electrodes separated by a gap. A surface of at least one of the electrodes that faces the gap can have a dense array of first projecting portions that extend toward the other electrode. The array of first projecting portions can create numerous concentrated electric fields that merge across the electrodes, which can accelerate the Townsend-breakdown to arc-discharge transition and expand initial spark discharges into a volumetric plasma. In some embodiments, a surface of at least one of the electrodes that faces the gap can have one or more longer projecting portions that extend toward the other electrode farther than the first projecting portions so as to contact or be narrowly spaced from one or more portions of the other electrode. The longer projecting portions can help initiate plasmas through spark discharge at lower breakdown voltages. In one or more embodiments, a method can comprise generating a volumetric plasma between first and second electrodes spaced from each other by a gap. The first electrode can comprise a first base layer and a plurality of first projecting portions that extend along a first direction from the first base layer toward the second electrode. The first base layer can comprise a first electrically-conductive material. At least some of the first projecting portions can comprise a second electrically-conductive material. The melting temperature for the first electrically-conductive material and the melting temperature for the second electrically-conductive material can be at least 1000 K. During the ge