WO2018202827A1

WO2018202827A1 - Plasma gun and plasma system for low melting point or low boiling point materials

Info

Publication number: WO2018202827A1
Application number: PCT/EP2018/061453
Authority: WO
Inventors: David Leamon; Thomas Conner; Dustin REITMEYER
Original assignee: Umicore Ag & Co. Kg
Priority date: 2017-05-04
Filing date: 2018-05-04
Publication date: 2018-11-08

Abstract

The present invention pertains to a plasma gun for use with low melting point materials or with materials that melt prematurely during processing in plasma guns and plasma systems is disclosed, along with methods for using such materials in a plasma apparatus. The plasma gun can also be used with low boiling point materials or with materials that boil prematurely during processing in plasma guns and plasma systems. The plasma gun and the methods disclosed can be used with materials such as nickel.

Description

Plasma Gun And Plasma System For Low Melting Point Or Low Boiling Point Materials

FIELD OF THE INVENTION

The invention pertains to plasma guns and plasma systems for use with low melting point or low boiling point materials, or materials susceptible to melting or boiling during plasma processing, such as nickel. The plasma guns and systems are used for materials processing. BACKGROUND OF THE INVENTION

Plasma processing is used in a wide variety of industrial processes. Plasma can be generated by using high energy input. DC voltage between an anode and a cathode, radiofrequency (RF) discharges, and microwave heating are common techniques for plasma generation. Plasmas are typically generated in plasma guns, which have a passageway for a working gas to flow into a plasma generation region. The high energy input is applied to the working gas in the plasma generation region to form the ionized plasma. By virtue of this high energy input, the plasma generation region is very hot, on the order of thousands or tens of thousands of degrees Kelvin. The plasma can then be combined with feed materials in order to process the feed materials at high temperatures. Examples of plasma guns are shown in U.S. Patent No. 8,803,025.

As noted in U.S. 8,803,025, plasma guns where materials are injected in or near the plasma generation region can suffer from clogging, requiring the plasma gun to be shut down in order to be cleaned. U.S. 8,803,025 provides certain solutions to this problem. The present invention provides additional solutions to this problem, which are particularly useful when the feed materials have relatively low melting points, or when the feed materials prematurely melt during processing in plasma guns and plasma systems. The present invention is also useful when the feed materials have relatively low boiling points, or when the feed materials prematurely boil during processing in plasma guns and plasma systems. BRIEF SUMMARY OF THE INVENTION

In one embodiment, the invention provides a plasma gun comprising a plasma generation region capable of generating a plasma stream; a feed material conduit for injection of feed material into the plasma stream; and a feed material cooling fluid conduit in thermal contact with the feed material conduit, for passing a feed material cooling fluid . The plasma gun can comprise a removable insert, which comprises the feed material conduit and the feed material cooling conduit, where the removable insert is inserted into the plasma gun, for example, by insertion into an opening in the plasma gun. The feed material conduit and the feed material cooling conduit can be passages which have been machined into the plasma gun. In any of these embodiments of the plasma gun, the feed material conduit can further comprise one or more of a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; and a removable inner tube. The feed material cooling fluid can comprise argon or can be argon.

In further embodiments, the invention provides a plasma system comprising a plasma gun for generating a plasma stream; a chamber for receiving the plasma stream from the plasma gun, where the chamber comprises a feed material conduit for injection of feed material into the plasma stream, and a feed material cooling fluid conduit in thermal contact with the feed material conduit, for passing a feed material cooling fluid. The system can comprise a removable insert, which comprises the feed material conduit and the feed material cooling conduit, wherein the removable insert is inserted into an opening in the chamber. The feed material conduit and the feed material cooling fluid conduit can be attached to the chamber. The feed material conduit and the feed material cooling fluid conduit can be passages which have been machined into the chamber. In any of these embodiments of the plasma system, the feed material conduit can further comprise one or more of a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; and a removable inner tube. The feed material cooling fluid can comprise argon or can be argon.

In further embodiments, the invention provides a plasma system comprising a plasma gun capable of generating a plasma stream; and a faceplate removably attached to the plasma gun, where the faceplate comprises a feed material conduit for injection of feed material into the plasma stream, and a feed material cooling fluid conduit in thermal contact with the feed material conduit for passing a feed material cooling fluid. The plasma system can further comprise a chamber for receiving the plasma stream from the plasma gun after injection of feed material from the feed material conduit. The system can comprise a removable insert, which comprises the feed material conduit and the feed material cooling conduit, wherein the removable insert is inserted into an opening in the faceplate. The feed material conduit and the feed material cooling fluid conduit can be passages which have been machined into the faceplate. In any of these embodiments of the plasma system, the feed material conduit can further comprise one or more of a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; and a removable inner tube. The feed material cooling fluid can comprise argon or can be argon.

In any of the embodiments of the plasma guns or the plasma systems disclosed herein, the feed material can be selected from one or more of the group consisting of cesium, gallium, rubidium, potassium, sodium, indium, lithium, selenium, tin, bismuth, thallium, cadmium, lead, zinc, tellurium, antimony, magnesium, aluminum, barium, strontium, arsenic, calcium, lanthanum, germanium, silver, gold, copper, manganese, beryllium, gadolinium, silicon, nickel, holmium, cobalt, and yttrium.

In any of the embodiments of the plasma guns or the plasma systems disclosed herein, the feed material can be nickel.

In further embodiments, the invention provides methods of treating material with plasma, comprising generating a plasma stream with a plasma gun; flowing feed material through a feed material conduit into the plasma stream; and flowing feed material cooling fluid through a feed material cooling fluid conduit in thermal contact with the feed material conduit, whereby the feed material cooling fluid cools the feed material conduit. The feed material cooling fluid cools the feed material in the feed material conduit. The feed material conduit and feed material cooling fluid conduit can be located in the plasma gun. The feed material conduit and feed material cooling fluid conduit can be located outside of the plasma gun. When the feed material conduit and feed material cooling fluid conduit are located outside of the plasma gun, after generating the plasma stream, the methods can further comprise flowing the plasma stream into a chamber; wherein the flowing of the feed material through a feed material conduit into the plasma stream, and the flowing of the feed material cooling fluid through a feed material cooling fluid conduit in thermal contact with the feed material conduit, occurs in the chamber.

When the feed material conduit and feed material cooling fluid conduit are located outside of the plasma gun, after generating the plasma stream, the methods can further comprise flowing the feed material through a feed material conduit into the plasma stream and flowing the feed material cooling fluid through a feed material cooling fluid conduit in thermal contact with the feed material conduit, via a faceplate removably attached to the plasma gun.

In any of the methods disclosed herein, the feed material cooling fluid can be argon. In any of the methods disclosed herein, the feed material can be selected from one or more of the group consisting of cesium, gallium, rubidium, potassium, sodium, indium, lithium, selenium, tin, bismuth, thallium, cadmium, lead, zinc, tellurium, antimony, magnesium, aluminum, barium, strontium, arsenic, calcium, lanthanum, germanium, silver, gold, copper, manganese, beryllium, gadolinium, silicon, nickel, holmium, cobalt, and yttrium. In any of the methods disclosed herein, the feed material can be nickel.

Any features from any embodiment disclosed herein can be combined with any features from any other embodiment, where possible. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a prior art plasma gun, where feed material is injected into the plasma generation zone.

FIG. 2 depicts one embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit, and where the feed material conduit and feed material cooling fluid conduit are located in a cavity or space in the plasma gun.

FIG. 3 depicts another embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit, and where the feed material conduit and feed material cooling fluid conduit are separate from the plasma gun.

FIG. 3A depicts another embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit, and where the feed material conduit and feed material cooling fluid conduit are located in a chamber separate from the plasma gun.

FIG. 3B depicts another embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit, and where the feed material conduit and feed material cooling fluid conduit are located in a faceplate attached to the plasma gun .

FIG. 4 depicts a top view of one embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit.

FIG. 5 depicts a top view of another embodiment of the invention, where a feed material conduit is in thermal contact with multiple feed material cooling fluid conduits.

FIG. 6 depicts another embodiment of the invention, where a feed material conduit is in thermal contact with a feed material cooling fluid conduit, where the feed material conduit and feed material cooling fluid conduit are located in a cavity or space in the plasma gun, and where the feed material conduit and feed material cooling fluid conduit form an acute angle with respect to the flow of the plasma stream. DETAILED DESCRIPTION OF THE INVENTION

Definitions

This disclosure provides several embodiments. It is contemplated that any features from any embodiment can be combined with any features from any other embodiment where possible. In this fashion, hybrid configurations of the disclosed features are within the scope of the present invention .

When numerical values are expressed herein using the term "about" or the term "approximately," it is understood that both the value specified, as well as values reasonably close to the value specified, are included . For example, the description "about 50° C" or "approximately 50° C" includes both the disclosure of 50° C itself, as well as values close to 50° C. Thus, the phrases "about X" or "approximately X" include a description of the value X itself. If a range is indicated, such as "approximately 50° C to 60° C," it is understood that both the values specified by the endpoints are included, and that values close to each endpoint or both endpoints are included for each endpoint or both endpoints; that is, "approximately 50° C to 60° C" is equivalent to reciting both "50° C to 60° C" and "approximately 50° C to approximately 60° C."

As used herein, the singular forms "a," "an," and "the" include the plural reference unless the context clearly dictates otherwise.

The terms "micro-particle," "micro-sized particle," "micron-particle," and "micron-sized particle" are generally understood to encompass a particle on the order of micrometers in diameter, typically between about 0.5 pm to 1000 pm, about 1 pm to 1000 pm, about 1 pm to 100 pm, or about 1 pm to 50 pm .

The terms "nanoparticle" and "nano-sized particle" are generally understood by those of ordinary skill in the art to encompass a particle on the order of nanometers in diameter, typically between about 0.5 nm to 500 nm, about 1 nm to 500 nm, about 1 nm to 100 nm, or about 1 nm to 50 nm .

Preferably, the nanoparticles have an average diameter less than 250 nanometers, or an average grain size less than 250 nanometers. In some embodiments, the nanoparticles have an average diameter of about 50 nm or less, about 30 nm or less, or about 20 nm or less. In additional embodiments, the nanoparticles have an average grain size of about 50 nm or less, about 30 nm or less, or about 20 nm or less. The aspect ratio of the particles, defined as the longest dimension of the particle divided by the shortest dimension of the particle, is preferably between one and one hundred, more preferably between one and ten, yet more preferably between one and two. "Grain size" is measured using the ASTM (American Society for Testing and Materials) standard (see ASTM E112 - 10). When calculating a diameter of a particle, the average of its longest and shortest dimension is taken; thus, the diameter of an ovoid particle with long axis 20 nm and short axis 10 nm would be 15 nm. The average diameter of a population of particles is the average of diameters of the individual particles, and can be measured by various techniques known to those of skill in the art.

It is understood that aspects and embodiments of the invention described herein include the "comprising," the "consisting," and/or the "consisting essentially of" aspects and embodiments. For all methods, systems, compositions, and devices described herein, the methods, systems, compositions, and devices can either comprise the listed components or steps, or can "consist of" or "consist essentially of" the listed components or steps. When a system, composition, or device is described as "consisting essentially of" the listed components, the system, composition, or device contains the components listed, and may contain other components which do not substantially affect the performance of the system, composition, or device, but either do not contain any other components which substantially affect the performance of the system, composition, or device other than those components expressly listed; or do not contain a sufficient

concentration or amount of the extra components to substantially affect the performance of the system, composition, or device. When a method is described as "consisting essentially of" the listed steps, the method contains the steps listed, and may contain other steps that do not substantially affect the outcome of the method, but the method does not contain any other steps which substantially affect the outcome of the method other than those steps expressly listed. The systems, compositions, substrates, and methods described herein, including any embodiment of the invention as described herein, may be used alone or may be used in combination with other systems,

compositions, substrates, and methods.

Plasma guns and systems with feed material cooling

The invention provides plasma guns and systems for use with low melting point materials, or with materials that melt prematurely during processing in plasma guns and plasma systems, such as nickel, and with feed materials that have relatively low boiling points, or feed materials that prematurely boil during processing in plasma guns and plasma systems. The plasma guns and systems can be used for processing materials with plasma. By maintaining the feed material fed into the plasma at a relatively low temperature until it contacts the plasma, the plasma guns and systems of the invention provide advantages over existing plasma guns and systems.

FIG. 1 illustrates one embodiment of a prior art plasma gun 100 used to process powder material . The plasma gun 100 is a DC plasma torch including a male electrode 120 and a female electrode 130. A power supply (not shown) is connected to the male electrode 120 and the female electrode 130 and delivers power through the plasma gun 100 by passing current across the gap 160 between the male electrode 120 and the female electrode 130. Furthermore, the plasma gun 100 includes a gas inlet 140 fluidly coupled to the gap 160 and configured to receive a working gas. The plasma gun 100 also includes a plasma outlet 150 fluidly coupled to the gap 160 on the opposite side of the plasma gun 100 from the gas inlet 140 and configured to provide a path through which a plasma stream 180 can be expelled from the plasma gun 100.

During operation, working gas flows through the gas inlet 140, through the gap 160 and out of the outlet 150. At the same time, power is supplied to the plasma gun 100. The current arcing across the gap 160 energizes the working gas and forms plasma 180, which flows out of the outlet 150. A feed material (such as a powdered material) 110 is fed into the plasma stream 180 through a channel 170 that is fluidly coupled to the pathway between the gap 160 and the plasma outlet 150 via a port 175 to the pathway. The plasma stream 180 entrains the powder, forming a plasma powder mixture that flows out of the plasma gun 100 through the outlet 150.

A problem can arise from this configuration of a plasma gun, as the radiant and conductive heat of the plasma 180 can melt the powder particles 110 before the particles travel completely down the channel 170 and exit the port 175 into the pathway between the gap 160 and the outlet 150. As a result, the melted particles agglomerate and adhere to the sides of the channel 170 and the port 175, and can block the channel and port.

Consequently, operation of the plasma gun has to be stopped in order to clean channel 170 and port 175, resulting in loss of productivity. This is particularly problematic with materials such as nickel, zinc, or copper, with materials that melt prematurely when being processed with plasma guns or plasma systems, or materials having low melting points, low heat capacities, or high thermal conductivities. Materials that have a relatively low boiling point can also pose problems in plasma systems. FIG. 2 illustrates one embodiment of the invention which solves this problem. As before, the plasma gun 200 is a DC plasma torch including a male electrode 220 and a female electrode 230. A power supply (not shown) is connected to the male electrode 220 and the female electrode 230 and delivers power through the plasma gun 200 by passing current across the gap 260 between the male electrode 220 and the female electrode 230. The plasma gun 200 includes a gas inlet 240 fluidly coupled to the gap 260 and configured to receive a working gas. The plasma gun 200 also includes a plasma outlet 250 fluidly coupled to the gap 260 on the opposite side of the plasma gun 200 from the gas inlet 240 and configured to provide a path through which a plasma stream 280 can be expelled from the plasma gun 200. During operation, working gas flows through the gas inlet 240, through the gap 260 and out of the outlet 250. At the same time, power is supplied to the plasma gun 200. The current arcing across the gap 260 energizes the working gas and forms plasma 280, which flows out of the outlet 250.

In contrast to the powder injection configuration of FIG. 1, however, in this configuration, feed material or powder 210 is injected into the plasma through a feed material conduit 276 (the feed material conduit is connected to a feed material supply chamber, not shown). In the embodiment shown in FIG. 2, feed material conduit 276 is located within another conduit, feed material cooling fluid conduit 274. In one embodiment, feed material conduit 276 is located within and coaxially with feed material cooling fluid conduit 274. A cooling fluid from a cooling fluid reservoir (not shown) is passed through the space 272 formed around feed material conduit 276 by feed material cooling fluid conduit 274. This feed material cooling fluid prevents premature melting or boiling of feed material or powder before the feed material or powder enters the extremely hot plasma 280.

The mixing of the feed material, feed material cooling fluid, and plasma may result in a somewhat cooler feed material-cooling fluid-plasma mixture compared to a plasma gun (such as that depicted in FIG. 1) that does not use a cooling fluid for the feed material . Given the high energy and extremely high temperature of the plasma, this may not be of concern. However, if it is desired to keep the temperature of the feed material- cooling fluid-plasma mixture at the same temperature as that of a plasma gun that does not use cooling fluid for the feed material, the power to the plasma gun can be increased, so that a hotter, more energetic plasma is generated before mixing with the feed material and feed material cooling fluid.

Another embodiment of the invention is shown in conjunction with the plasma gun 300 in FIG. 3. In FIG. 3, the feed material conduit 376 is located farther downstream of the plasma generation region. Feed material 310 encounters the plasma 380 in region 390 after the plasma has exited from outlet 350. Again, feed material cooling fluid is passed through the space 372 formed by feed material cooling fluid conduit 374 surrounding feed material conduit 376, which prevents premature melting or boiling of the feed material before it encounters plasma stream 380.

In FIG. 3, male electrode 320, female electrode 330, gap 360 between the male electrode 320 and the female electrode 330, gas inlet 340, plasma outlet 350, and plasma stream 380 correspond to those elements as depicted in FIG. 2.

In the embodiment shown in FIG. 3, the combination of feed material conduit 376 and feed material cooling fluid conduit 374 can be positioned either in, or as part of, a chamber in fluid communication with plasma outlet 350, or as part of a faceplate affixed to (for example, by bolts or other mechanical attachments) to plasma gun 300. FIG. 3A shows an

embodiment where the feed material conduit 376 and feed material cooling fluid conduit 374 are positioned in the initial portion of a chamber 395. The chamber 395 can be any chamber designed for further processing and treatment of the plasma, for example, the highly turbulent quench chambers described in U.S. Patent No. 9,180,423 or U.S. Patent

No. 9,599,405. FIG. 3B shows an embodiment where the where the feed material conduit 376 and feed material cooling fluid conduit 374 are contained in a faceplate 393 which can be removably attached to the plasma gun. The plasma 380 and feed material 310 combine at location 390, at which point the plasma-feed material mixture proceeds into chamber 395. Again, the chamber 395 can be any chamber designed for further processing and treatment of the plasma, for example, the highly turbulent quench chambers described in U .S. Patent No. 9,180,423 or U.S. Patent No. 9,599,405.

Thus, in the embodiments in FIG. 3A and FIG. 3B, the feed material conduit 376 and feed material cooling fluid conduit 374 are not contained in, nor part of, the plasma gun. This is in contrast to the embodiment in FIG. 2, where the feed material conduit 276 and feed material cooling fluid conduit 274 can be integrated into the plasma gun, or inserted as a separate assembly into a cavity or space in the plasma gun adapted to receive the feed material conduit 276 and feed material cooling fluid conduit 274. The embodiments in FIG. 3, FIG. 3A, and FIG. 3B are thus best described as plasma systems, which comprise a plasma gun 300, feed material conduit 376, and feed material cooling fluid conduit 374. Feed Materials for Use in the Invention

The plasma gun of the invention can be used with any feed material, and is particularly advantageous for use with materials which have low melting points, low heat capacities, and/or high thermal conductivities, or materials that melt prematurely during processing in plasma guns and plasma systems. Such materials can be susceptible to melting and clogging of feed material conduits, channels, tubes, or ports due to radiant and conductive heat from the plasma stream. These materials include elements such as (numbers in parentheses are melting points) : cesium (29°C), gallium (30°C), rubidium (39°C), potassium (63°C), sodium (98°C), indium

(156°C), lithium (181°C), selenium (217°C), tin (232°C), bismuth (271°C), thallium (304°C), cadmium (321°C), lead (328°C), zinc (420°C), tellurium (450°C), antimony (631°C), magnesium (649°C), aluminum (660°C), barium (725°C), strontium (769°C), arsenic (817°C), calcium (839°C), lanthanum (920°C), germanium (937°C), silver (962°C), gold (1064°C), copper (1083°C), manganese (1244°C), beryllium (1278°C), gadolinium (1311°C), silicon (1410°C), nickel (1453°C), holmium (1470°C), cobalt (1495°C), and yttrium (1523°C); and in general, any materials melting below 1,550°C.

The plasma gun of the invention is also advantageous for use with materials which have low boiling points, such as phosphorus (280°C), mercury (357°C), sulfur (445°C), cesium (678°C), rubidium (688°C), cadmium (765°C), potassium (774°C), zinc (907°C), magnesium (1090°C), and in general, any materials which boil below 1550°C.

In one embodiment, the plasma gun of the invention is used to process nickel powder, such as micron-sized nickel powder, by treating the micron- sized nickel powder with plasma, resulting in the production of nano-sized nickel powder. Feed Material Cooling Fluid for Use in the Invention

The feed material cooling fluid used to cool the feed material conduit can be selected from the group of inert gases and noble gases. Argon is a preferred feed material cooling fluid. Helium can also be used as a feed material cooling fluid . (While neon, krypton, and xenon are chemically inert, the high cost of those gases renders them much less preferred as feed material cooling fluids from an economic standpoint). The argon, helium, or other inert substance can be used in gaseous form or in liquid form. In one embodiment, the feed material cooling fluid comprises argon. In one embodiment, the feed material cooling fluid is argon. In one embodiment, the feed material cooling fluid comprises helium. In one embodiment, the feed material cooling fluid is helium.

In some embodiments, a reactive substance is added to the mixture of plasma and feed material by using the reactive substance as a feed material cooling fluid. Examples of such reactive substances are hydrogen and oxygen. The hydrogen, oxygen, or other reactive substance can be used in gaseous form or in liquid form. The reactive substance, such as hydrogen or oxygen, can be mixed with an inert gas such as argon or helium. Thus, in some embodiments, argon/hydrogen, helium/hydrogen, argon/oxygen, or helium/oxygen can be used as the feed material cooling fluid.

In preferred embodiments, the feed material cooling fluid is in gaseous form, and the temperature of the feed material cooling fluid fed into the feed material cooling fluid conduit can range from its boiling point to ambient temperature. For example, argon boils at about -185°C, and can be used as a feed material cooling fluid at any temperature between -185°C and the ambient temperature of the external environment in which the plasma gun is located . The temperature of the feed material cooling fluid can also be above ambient temperature in certain circumstances, for example, when heating the feed material cooling fluid results in better flow properties when injecting the feed material through the feed material conduit. In some embodiments, where maintaining the feed material conduit at as cold a temperature as possible is required, liquefied gases can be used as the feed material cooling fluid, where the temperature of the liquefied gas can range from its melting point to its boiling point. For example, argon melts at about -308°C and boils at about -185°C; thus, liquid argon between -308°C and -185°C can be fed into the feed material cooling fluid conduit to maintain the feed material conduit, and the feed material contained in the feed material conduit, at a lower temperature than a temperature attainable with gaseous argon.

The flow rate of the feed material cooling fluid can be determined by empirical testing, that is, by running the plasma gun with various rates of feed material injection and feed material cooling fluid flow rate, and determining the optimal rate to prevent clogging of the feed material conduit. The feed material flow rate can vary between, for example, 1 gram/minute to 60 grams/minute, while the feed material cooling fluid flow rate can vary between, for example, 1 liter/minute to 100 liters/minute, or higher if necessary.

Feed material conduit and feed material cooling fluid conduit

The conduits used for the feed material conduit and the feed material cooling fluid conduit typically comprise a very high melting point material so that the regions of the conduits closest to the plasma stream withstand the intense heat of the plasma. Examples of materials with high melting points include metals such as tungsten, carbides such as silicon carbide and tungsten carbide, and ceramics such as boron nitride. If the conduits are passages that are formed by machining or drilling into the body of the plasma gun (for example, conduits 574A, 574B, 576, etc. may be formed by machining or drilling into the female electrode 530 of the plasma gun of FIG. 5), then the conduits will comprise the same material that the female electrode comprises. Alternatively, in embodiments such as that shown in FIG. 2, the feed material conduit 276 and cooling fluid conduit 274 can be prepared as a separate insert or assembly which can be inserted into a cavity or space in the plasma gun adapted to receive the feed material conduit 276 and cooling fluid conduit 274. Using a separate assembly which contains both the feed material conduit 276 and cooling fluid conduit 274 enables rapid switching of the feed material conduit/cooling fluid conduit assembly for maintenance or other reasons. In one embodiment, the feed material conduit is thermally conductive (such as tungsten, another metal with a high melting point, or another thermally conductive material with a high melting point), so that heat can transfer from the feed material in the feed material conduit to the cooling fluid in the feed material cooling fluid conduit. In one embodiment, the feed material cooling fluid conduit is thermally insulating (such as a ceramic with a high melting point, or another thermally insulating material with a high melting point) in order to insulate the cooling fluid and feed material from heat from other elements of the plasma gun or plasma system. The feed material conduit can end shortly before the outer envelope of the plasma stream, for example, about 5 mm to about 30 mm before the outer envelope of the plasma stream, or about 5 mm to about 30 mm, about 10 mm to about 30 mm, about 15 mm to about 30 mm, about 20 mm to about 30 mm, about 25 mm to about 30 mm, about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, or about 5 mm to about 10 mm before the outer envelope of the plasma stream, in order to avoid degradation of the conduit by the plasma stream. The feed material cooling fluid conduit can end at the same location as the feed material conduit, or can end shortly before the feed material conduit (such as about 5 mm to about 30 mm before the end of the feed material cooling conduit, or about 5 mm to about 30 mm, about 10 mm to about 30 mm, about 15 mm to about 30 mm, about 20 mm to about 30 mm, about 25 mm to about 30 mm, about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, or about 5 mm to about 10 mm before the end of the feed material conduit), or can end after the feed material conduit (such as about 5 mm to about 30 mm after the end of the feed material cooling conduit, or about 5 mm to about 30 mm, about 10 mm to about 30 mm, about 15 mm to about 30 mm, about 20 mm to about 30 mm, about 25 mm to about 30 mm, about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, or about 5 mm to about 10 mm after the end of the feed material conduit), provided that it ends before the outer envelope of the plasma stream (such as about 5 mm to about 30 mm before the outer envelope of the plasma stream, or about 5 mm to about 30 mm, about 10 mm to about 30 mm, about 15 mm to about 30 mm, about 20 mm to about 30 mm, about 25 mm to about 30 mm, about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, or about 5 mm to about 10 mm before the outer envelope of the plasma stream). The particular shape and arrangement of the feed material conduit and the feed material cooling fluid conduit can vary, as long as the feed material conduit and the feed material cooling fluid conduit are in thermal contact such that the feed material cooling fluid conduit can be used to lower the temperature of at least a portion of the feed material conduit below the temperature that feed material conduit would attain without use of the feed material cooling fluid. FIG. 4 shows a top view of the plasma gun shown in FIG. 2, that is, looking down at the top of electrode 230 in FIG. 2. Plasma gun 400 has electrode 430 (corresponding to electrode 230 in FIG. 2), and feed material conduit 476 with lumen 479 for passage of feed material . Feed material conduit 476 is surrounded by the lumen 472 of feed material cooling fluid conduit 474. While both the feed material conduit and the feed material cooling fluid conduit are shown as having circular cross-sections, and the feed material conduit and the feed material cooling fluid conduit are in a co-axial arrangement, any other cross-section shape (including a cross- section shape which varies throughout the length of either the feed material conduit, the feed material cooling fluid conduit, or both the feed material conduit and the feed material cooling fluid conduit) and any other

arrangement can be used for the conduits.

The diameter or cross-section of the feed material conduit can be constant throughout its length. Alternatively, the diameter or cross-section of the feed material conduit can vary along the length of the conduit. In one embodiment, the feed material conduit can narrow as it approaches the plasma stream, in order to speed the flow of feed material in the region closest to the plasma stream. Increasing the speed at which the feed material flows decreases the time that the feed material spends in the region of the feed material conduit closest to the plasma stream, which will be the warmest region of the feed material conduit and the region where the feed material is most susceptible to melting or boiling. In another embodiment, the feed material conduit can widen as it approaches the plasma stream. Similarly, independently of the diameter or cross-section of the feed material conduit, the diameter or cross-section of the feed material cooling fluid conduit can be constant throughout its length or can vary along its length. In one embodiment, the feed material cooling fluid conduit can narrow as it approaches the plasma stream. In another embodiment, the feed material cooling fluid conduit can widen as it approaches the plasma stream.

The number of feed material conduits and feed material cooling fluid conduits can also vary; that is, one or more feed material conduits and one or more feed material cooling fluid conduits can be used. FIG. 5 shows a top view of a plasma gun with multiple feed material cooling fluid conduits surrounding one feed material conduit, that is, looking down at the top of the electrode 530 of plasma gun 500 (corresponding to electrode 230 of plasma gun 200 in FIG. 2). Only two feed material cooling fluid conduits 574A and 574B are labeled for simplicity, and only one lumen, lumen 572 of feed material cooling fluid conduit 574B, is labeled. The feed material cooling fluid conduits surround and are in thermal contact with feed material conduit 576 having lumen 579. Again, while both the feed material conduit and the feed material cooling fluid conduits are shown as having circular cross-sections, any other cross-section shape (including a cross-section shape which varies throughout the length of either the feed material conduit, the feed material cooling fluid conduits, or both the feed material conduit and the feed material cooling fluid conduits) can be used for the conduits. Additionally, while the feed material cooling fluid conduits are shown as surrounding the feed material conduit, any other arrangement which provides adequate thermal contact between the feed material conduit (or the plurality of feed material conduits, if more than one feed material conduits is used) and the feed material cooling fluid conduits (whether one feed material cooling fluid conduit is present or a plurality of feed material cooling fluid conduits are present) can be used for the conduits. For example, a spiral-shaped feed material cooling fluid conduit can wrap around the feed material conduit.

In any of the embodiments disclosed herein, the feed material conduit and feed material cooling fluid conduit (or conduits, if more than one feed material conduit and feed material cooling fluid conduit are used) can be angled, so as to add the feed material to the plasma stream at an angle. FIG. 6 depicts an embodiment of plasma gun 600 similar to FIG. 2, with plasma gun 600, male electrode 620, female electrode 630, power supply (not shown) connected to male electrode 620 and female electrode 630 which delivers power through the plasma gun 600 by passing current across the gap 660 between the male electrode 620 and the female electrode 630; gas inlet 640 fluidly coupled to the gap 660 and configured to receive a working gas; plasma outlet 650 fluidly coupled to the gap 660 on the opposite side of the plasma gun 600 from the gas inlet 640 and configured to provide a path through which a plasma stream 680 can be expelled from the plasma gun 600. However, in this configuration, feed material or powder 610 is injected into the plasma through a feed material conduit 676 which is at an angle Θ (theta); see arc 690 describing angle Θ. The angle Θ (theta) is defined such that it would be zero if the feed material were to be injected parallel to the flow of the plasma stream (that is, in the same direction as the plasma stream), and would be 180 degrees if the feed material were to be injected anti-parallel to the flow of the plasma stream (that is, opposite to the plasma stream). That is, when Θ (theta) is 90 degrees, the vector representing the direction of travel of the feed material is perpendicular to the plasma stream. When Θ (theta) is between zero degrees and 90 degrees, the vector representing the direction of travel of the feed material can be represented by two component vectors, one component vector perpendicular to the plasma stream, and one component vector parallel to and in the same direction as the plasma stream. Feed material cooling fluid conduit 674 is also at the same angle in order to provide cooling to feed material conduit 676 and feed material or powder 610, and cooling fluid from a cooling fluid reservoir (not shown) is passed through the space 672 formed around feed material conduit 676 by feed material cooling fluid conduit 674. The angle Θ (theta) formed by feed material conduit 676 and feed material cooling fluid conduit 674 can vary between about 30 degrees and 90 degrees; when angle Θ is 90 degrees, the embodiment shown in FIG. 6 is identical to the embodiment shown in FIG . 2. Angle Θ can range between about 30 degrees and 90 degrees, between about 30 degrees and 75 degrees, between about 30 degrees and 60 degrees, between about 30 degrees and 45 degrees, between about 45 degrees and 90 degrees, between about 60 degrees and 90 degrees, between about 75 degrees and 90 degrees, between about 45 degrees and 60 degrees, between about 45 degrees and 75 degrees, or between about 60 degrees and 75 degrees. Angle Θ can be about 45 degrees +/- about 15 degrees, about 60 degrees +/- about 15 degrees, or about 75 degrees +/- about 15 degrees. Angle Θ can be about 30 degrees, about 45 degrees, about 60 degrees, about 75 degrees, or about 90 degrees.

The feed material conduit and feed material cooling fluid conduit (or conduits, if more than one feed material conduit and feed material cooling fluid conduit are used) can be angled in any of the embodiments disclosed herein, such as the embodiment where the feed material conduit and feed material cooling fluid conduit are integrated into the plasma gun or are placed in an opening in the plasma gun; the embodiment where the feed material conduit and feed material cooling fluid conduit are in a chamber attached to the plasma gun; or the embodiment where the feed material conduit and feed material cooling fluid conduit are integrated into a faceplate attached to the plasma gun or are placed in an opening in a faceplate attached to the plasma gun .

Additional features for feed material conduit

Other features can be added to the feed material conduit if desired . U .S. Patent Application Publication Nos. 2014/0263190 and 2016/0030910 show various devices and methods for preventing clogs from developing in feed material conduits and ports. These devices and methods are depicted in FIG. 3A, FIG. 3B, and FIG. 3C of U .S. 2014/0263190; paragraphs [0044] - [0051] of U .S. 2014/0263190; FIG. 3A, FIG. 3B, FIG. 3C, FIG. 3D, FIG. 3E, and FIG. 3F of U.S. 2016/0030910; and paragraphs [0057] - [0064] of U .S. 2016/0030910. Specifically, any one or more of the following devices and methods from those patent applications can be used with the feed material conduit of the instant invention.

For example, the plasma gun or plasma system can comprise at least two feed material conduits, where the feed material conduits comprise removable tubes; if one of the feed material conduits becomes clogged, operation of the plasma gun or plasma system can continue using one of the other feed material conduits, while the removable tube of the clogged feed material conduit is removed and replaced with a fresh tube, or while the removable tube of the clogged feed material conduit is removed, unclogged, and returned to the plasma gun or plasma system.

In addition, the feed material conduit can further comprise a reciprocating plunger, for clearing or pushing any agglomerated feed material out of the conduit.

Also, the feed material conduit can further comprise a pulsing gas jet system, for supplying high-pressure pulses of gas into the feed material conduit, and clearing any agglomerated feed material in the conduit.

Chamber for receiving the plasma stream

The feed material conduit and feed material cooling fluid conduit can be located in a chamber which receives the plasma generated by the plasma gun, for example, a chamber such as the chamber 395 illustrated in

FIG. 3A. For any embodiment disclosed herein, the chamber into which the plasma stream flows can be any chamber designed for further processing and treatment of the plasma, for example, to produce small and highly uniform particles. Examples of chambers that can be used include the highly turbulent quench chambers described in U .S. Patent No. 9,180,423 or U.S. Patent No. 9,599,405. The chamber can be made of a high melting point metal, such as tungsten. The chamber can be made of a ceramic material, such as boron nitride or silicon carbide. The chamber can feed into a cool- down tube, or cooling conduit for the newly synthesized particles, such as that disclosed in U .S. Patent Application Publication No. 2016/0030910 at paragraphs [0081]-[0089] ("Laminar Flow Disruptor in a Cooling Conduit"). Other features of U .S. Patent Application Publication No. 2016/0030910 can also be combined as desired with the invention as disclosed herein.

The disclosures of all publications, patents, patent applications and published patent applications referred to herein by an identifying citation are hereby incorporated herein by reference in their entirety.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is apparent to those skilled in the art that certain changes and modifications will be practiced. Therefore, the description and examples should not be construed as limiting the scope of the invention.

Claims

1. A plasma gun comprising :

a plasma generation region capable of generating a plasma stream; a feed material conduit for injection of feed material into the plasma stream; and

a feed material cooling fluid conduit in thermal contact with the feed material conduit, for passing a feed material cooling fluid.

2. The plasma gun of claim 1, comprising a removable insert and wherein the feed material conduit and the feed material cooling conduit are part of the removable insert.

3. The plasma gun of claim 1, wherein the feed material conduit and the feed material cooling fluid conduit are machined passages of the plasma gun.

4. The plasma gun of any one of claims 1-3, wherein the feed material conduit further comprises a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; or a removable inner tube.

5. A plasma system comprising :

a plasma gun for generating a plasma stream;

a chamber for receiving the plasma stream from the plasma gun, said chamber comprising :

a feed material conduit for injection of feed material into the plasma stream, and

6. The plasma system of claim 5, comprising a removable insert and wherein the feed material conduit and the feed material cooling conduit are part of the removable insert, wherein the removable insert is inserted into an opening in the chamber.

7. The plasma system of claim 5, wherein the feed material conduit and the feed material cooling fluid conduit are attached to the chamber.

8. The plasma system of any one of claims 5-7, wherein the feed material conduit further comprises a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; or a removable inner tube.

9. A plasma system comprising :

a plasma gun capable of generating a plasma stream; and

a faceplate removably attached to the plasma gun comprising :

a feed material cooling fluid conduit in thermal contact with the feed material conduit for passing a feed material cooling fluid.

10. The plasma system of claim 9, further comprising a chamber for receiving the plasma stream from the plasma gun after injection of feed material from the feed material conduit.

11. The plasma system of claim 9 or claim 10, comprising a removable insert and wherein the feed material conduit and the feed material cooling conduit are part of the removable insert, wherein the removable insert is inserted into an opening in the faceplate.

12. The plasma system of claim 9 or claim 10, wherein the feed material conduit and the feed material cooling fluid conduit are machined passages of the faceplate.

13. The plasma system of any one of claims 9-12, wherein the feed material conduit further comprises a reciprocating plunger for clearing feed material from the feed material conduit; a pulsing gas jet system for clearing feed material from the feed material conduit; or a removable inner tube.

14. The plasma gun of any one of claims 1-4 or the plasma system of any one of claims 5-13, wherein the feed material is selected from one or more of the group consisting of cesium, gallium, rubidium, potassium, sodium, indium, lithium, selenium, tin, bismuth, thallium, cadmium, lead, zinc, tellurium, antimony, magnesium, aluminum, barium, strontium, arsenic, calcium, lanthanum, germanium, silver, gold, copper, manganese, beryllium, gadolinium, silicon, nickel, holmium, cobalt, and yttrium or wherein the feed material is nickel.

15. The plasma gun of any one of claims 1-4 or the plasma system of any one of claims 5-13, wherein the feed material conduit and feed material cooling fluid conduit are at an angle Θ (theta) between about 30° and 90° to the plasma stream.