Device and method for preparing nano-powder by microwave plasma

Abstract

The present invention relates to a device and method for preparing nanopowders by microwave plasma. The device includes: an inner conductor tube, which includes a first inner conduit and a second inner conduit disposed on the outer periphery of the first inner conduit. Their lower ends are in an umbrella shape, and the inner side surface of the umbrella-shaped lower end of the second inner conduit has a corner portion bent in the axial direction; a plasma chamber, the lower end of the plasma chamber is open, and the upper end and the lower end are both narrowed structures, and the plasma chamber is a single-mode chamber; a cooling chamber, the cooling chamber is disposed below the plasma chamber, and the microwave plasma is distributed below the inner conductor tube, in the plasma chamber, and in part of the cooling chamber; a cyclone separator; and a filter. By setting the shapes of the inner conductor tube and the plasma chamber, the present invention makes the inner conductor tube have an umbrella-shaped lower end, and both the upper end and the lower end of the plasma chamber are narrowed structures, improving the shaping effect of the microwave plasma, and at the same time improving the powder processing efficiency and the nanopowder yield.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of additive manufacturing technology, and in particular to a device and method for preparing nanopowder using microwave plasma. Background Art

[0002] The technology of using micron-sized powder to prepare nano-sized powder usually involves feeding the micron-sized powder into plasma (arc plasma, inductively coupled plasma, microwave plasma), where the powder is heated and vaporized, and then cooled to form nano-sized powder. The micron-sized powder is collected after passing through a cyclone separator, and the nano-sized powder is collected after passing through a filter.

[0003] In related technologies, coaxial microwave plasma can only operate at low power and low temperature, making it difficult to reach the temperature for vaporizing powder, resulting in low efficiency in preparing nanopowders; inductively coupled plasma and compressed waveguide microwave plasma can easily burn quartz tubes or ceramic tubes; when using thermal arc plasma to make powder, the powder enters the plasma tail flame from the side, and the high temperature cannot be fully utilized to achieve powder vaporization.

[0004] Therefore, it is necessary to improve one or more problems existing in the above-mentioned related technical solutions.

[0005] It should be noted that this section is intended to provide background or context for the technical solutions of the present invention as stated in the claims. The description herein is not admitted to be prior art by virtue of being included in this section. Summary of the Invention

[0006] The object of the present invention is to provide an apparatus and method for preparing nanopowders using microwave plasma, thereby at least to a certain extent solving one or more problems caused by the limitations and defects of the related art.

[0007] The present invention first provides a device for preparing nanopowders using microwave plasma, comprising:

[0008] an inner conductor tube, the inner conductor tube comprising a first inner conduit and a second inner conduit disposed on an outer periphery of the first inner conduit, the gap between the first inner conduit and the second inner conduit forming a gas passage, the lower ends of the first inner conduit and the second inner conduit being umbrella-shaped, the inner side surface of the umbrella-shaped lower end of the second inner conduit having a corner portion, the corner portion being configured to bend toward a direction close to the axis of the second inner conduit;

[0009] a plasma chamber, wherein the lower end of the plasma chamber is open, the upper and lower ends of the plasma chamber are narrowed, the umbrella-shaped lower end of the inner conductor tube is disposed in the plasma chamber, and the plasma chamber is a single-mode chamber;

[0010] a cooling cavity, the cooling cavity being arranged below the plasma cavity and being in communication with the plasma cavity, wherein microwave plasma is distributed below the inner conductor tube, in the plasma cavity, and in a portion of the cooling cavity;

[0011] a cyclone separator, the cyclone separator being in communication with the cooling chamber;

[0012] A filter is connected to the cyclone separator.

[0013] In the present invention, the angle formed by the umbrella-shaped lower end of the inner conductor tube and the horizontal plane is 30-60°.

[0014] In the present invention, the side wall of the plasma chamber is provided with a double-layer water cooling structure.

[0015] In the present invention, the device further includes a microwave transmission zone, a quartz glass tube is provided in the microwave transmission zone, the second inner conduit portion is arranged in the microwave transmission zone, and a gap of 2 to 5 mm is provided between the quartz glass tube and the second inner conduit.

[0016] In the present invention, a first air inlet for blowing gas is provided on the side wall of the second inner conduit, a second air inlet for blowing gas obliquely downward is provided in the microwave transmission zone, and a third air inlet for blowing converging gas obliquely downward is provided on the side wall of the plasma chamber.

[0017] In the present invention, a fourth air inlet for blowing cooling gas obliquely downward is provided on the side wall of the cooling cavity, and a fifth air inlet for blowing cooling gas upward is provided below the cooling cavity.

[0018] In the present invention, the filter is provided with at least two filter elements, and each of the filter elements is provided with a valve group for opening and closing the filter element and a valve group for back-flushing control of the filter element.

[0019] In the present invention, an air extraction port is provided above the filter, and a bursting disc is provided on the side wall of the filter.

[0020] The present invention further provides a method for preparing nanopowder using microwave plasma, wherein the nanopowder is prepared using any of the above-mentioned devices, and the method comprises:

[0021] Raw material powder enters the plasma chamber through the first inner conduit. When the raw material powder flows out of the first inner conduit, gas blown from the gas channel between the first inner conduit and the second inner conduit gathers the raw material powder, bringing the raw material powder close to the microwave plasma for vaporization and spheroidization.

[0022] The raw material vapor formed after vaporizing the raw material powder enters the cooling chamber, forms a powder containing nano powder and unvaporized raw material micro powder, and enters the cyclone separator, and the cyclone separator collects the raw material micro powder in the powder;

[0023] The powder processed by the cyclone separator enters the filter, and the filter collects the nano powder in the powder.

[0024] In the present invention, the filter is provided with at least two filter elements, and each filter element is provided with a valve group for opening and closing the filter element and a valve group for controlling backwashing of the filter element;

[0025] During the process of the filter collecting the nano powder in the powder, one of the filter elements is used to filter the powder each time. When the filter element is blocked, another filter element is used to filter the powder, and the blocked filter element is cleaned by backwashing.

[0026] The technical solution provided by the present invention may include the following beneficial effects:

[0027] In the present invention, by setting the shapes of the inner conductor tube and the plasma chamber, the inner conductor tube has an umbrella-shaped lower end, and both the upper end and the lower end of the plasma chamber are narrowing structures, which improves the microwave plasma forming effect, improves the powder processing efficiency, increases the nano powder yield, and significantly improves the sphericity of the powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The drawings here are incorporated into the specification and form a part of this specification, showing embodiments consistent with the present disclosure, and are used together with the specification to explain the principles of the present disclosure. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0029] Figure 1 Showing a schematic structural diagram of a device for preparing nano powder by microwave plasma in an exemplary embodiment of the present invention;

[0030] Figure 2 Showing a schematic structural diagram of an inner conductor tube and a microwave transmission region in an exemplary embodiment of the present invention;

[0031] Figure 3 Showing a schematic structural diagram of a cooling chamber in an exemplary embodiment of the present invention;

[0032] Figure 4 Showing a schematic structural diagram of a filter in an exemplary embodiment of the present invention;

[0033] Figure 5The scanning electron microscope image of nano-silicon powder prepared by using a microwave power of 20 kW and a powder feeding rate of 2.0 g / min is shown;

[0034] Figure 6 Shows the transmission electron microscope image of nano-silicon powder.

[0035] Reference numerals:

[0036] 100, inner conductor tube; 101, first inner conduit; 102, second inner conduit; 1021, corner; 1022, first air inlet; 103, umbrella-shaped lower end; 200, plasma chamber; 201, third air inlet; 300, cooling chamber; 301, fourth air inlet; 302, fifth air inlet; 400, cyclone separator; 500, filter; 501, first filter element; 5011, first valve group; 5012, third valve group; 502, second filter element; 5021, second valve group; 5022, fourth valve group; 503, backflush mechanism; 504, air extraction port; 505, rupture disc; 600, microwave transmission zone; 601, quartz glass tube; 602, second air inlet. DETAILED DESCRIPTION

[0037] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be embodied in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concepts of the example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0038] In addition, the accompanying drawings are merely schematic illustrations of embodiments of the present invention and are not necessarily drawn to scale. Identical reference numerals in the drawings represent identical or similar parts, and thus repeated descriptions thereof will be omitted. Some of the blocks shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically separate entities.

[0039] In this exemplary embodiment, a device for preparing nanopowders using microwave plasma is first provided. Figure 1 As shown, the device includes: an inner conductor tube 100 , a plasma chamber 200 , a cooling chamber 300 , a cyclone separator 400 and a filter 500 .

[0040] Specifically, refer to Figure 2As shown, the inner conductor tube 100 includes a first inner conduit 101 and a second inner conduit 102 disposed on the outer periphery of the first inner conduit 101. The space between the first inner conduit 101 and the second inner conduit 102 forms a gas channel. The first inner conduit 101 and the second inner conduit 102 can be threadedly connected through the upper end portion, and the vertical position of the first inner conduit 101 can be adjusted to achieve the best coupling efficiency of the microwave plasma.

[0041] The lower ends of the first inner conduit 101 and the second inner conduit 102 are umbrella-shaped. The inner side surface of the umbrella-shaped lower end 103 of the second inner conduit 102 has a corner portion 1021, and the corner portion 1021 is arranged to bend towards the direction close to the axis of the second inner conduit 102. The corner portion 1021 provided here can be a bend of the second inner conduit 102 towards the axis of the tube, guiding the gas flowing through here, so that the gas is blown towards the axis of the tube, in order to gather the powder falling from the first inner conduit 101 towards the axis of the tube, so that it can be better vaporized and spheroidized under the action of the microwave plasma subsequently.

[0042] Reference Figure 3 As shown, the lower end of the plasma chamber 200 is open. The plasma chamber 200 has a structure that narrows both at the upper end and the lower end. For example, it can be an inclined surface structure. When the upper side wall of the plasma chamber 200 is an inclined surface, the upper surface of the inclined side wall is parallel to the lower surface of the second inner conduit 102. The middle part of the plasma chamber 200 can be in the shape of a vertical cylinder, and the lower end of the plasma chamber 200 can be an arc structure or an inclined surface structure, which can prevent powder from accumulating at the lower end of the plasma chamber 200.

[0043] The umbrella-shaped lower end 103 of the inner conductor tube 100 is disposed in the plasma chamber 200, and the plasma chamber 200 is a single-mode cavity. The structure of the plasma chamber 200 and the umbrella-shaped lower end 103 of the inner conductor tube 100 provided in this application can enable microwaves to form a high field strength at the center of the plasma chamber 200, and can form a high-power (10 - 75 kW) microwave plasma torch under normal pressure, and a microwave plasma with a high power density can be obtained, with a maximum temperature of up to 4000K, which can vaporize the powder. In addition, the central part of the umbrella-shaped lower end 103 (i.e., the part corresponding to the "umbrella top") is concave, which can maintain a certain distance from the microwave plasma, and the inner conductor tube 100 will not be damaged without water cooling.

[0044] The cooling chamber 300 is disposed below the plasma chamber 200 and communicates with the plasma chamber 200. The microwave plasma is distributed below the inner conductor tube 100, within the plasma chamber 200, and partially within the cooling chamber 300. The longer length of the microwave plasma increases the time the powder passes through the plasma, thereby improving the yield of nanopowder.

[0045] The cyclone separator 400 is connected to the cooling chamber 300 and is used to collect large-particle powder (such as micron-sized powder) in the powder. The filter 500 is connected to the cyclone separator 400 and is used to filter the powder processed by the cyclone separator 400 to obtain nanopowder.

[0046] In this embodiment, by setting the shapes of the inner conductor tube 100 and the plasma chamber 200, the inner conductor tube 100 has an umbrella-shaped lower end 103, and the upper and lower ends of the plasma chamber 200 are both narrowed structures, which can form a high-power microwave plasma torch to vaporize the raw material powder and then rapidly cool it to form nanopowder, while the sphericity of the powder is significantly improved.

[0047] It should be emphasized that, in one embodiment, the angle formed between the umbrella-shaped lower end 103 of the inner conductor tube 100 and the horizontal plane is 30-60°, for example, 45°, 50°, etc., but is not limited thereto. The umbrella-shaped lower end 103 makes it easier for the microwave plasma to form a longer torch. The longer the torch, the longer the action time on the powder, which improves the sphericity of the resulting powder and the yield of nanopowder.

[0048] In one embodiment, the side wall of the plasma chamber 200 is provided with a double-layer water-cooling structure. After the powder treated with microwave plasma is vaporized, it will approach the inner wall of the plasma chamber 200. The side wall of the plasma chamber 200 is provided with a double-layer water-cooling structure, which can quickly cool the vaporized powder to obtain nanopowder with finer particle size.

[0049] In one embodiment, the device further includes a microwave transmission zone 600, wherein a quartz glass tube 601 is provided in the microwave transmission zone 600, and the second inner conduit 102 is partially disposed in the microwave transmission zone 600. A gap of 2 to 5 mm is provided between the quartz glass tube 601 and the second inner conduit 102 to facilitate the airflow from the second air inlet 602 to enter the single-mode cavity, thereby facilitating the maintenance of the plasma torch in the single-mode cavity and preventing the torch from retreating into the microwave transmission zone 600.

[0050] In one embodiment, a first gas inlet 1022 for blowing gas is provided on the sidewall of the second inner conduit 102. Gas blown through the first gas inlet 1022 prevents powder from backflowing through the second inner conduit 102 and further gathers the powder below the inner conductor tube 100. The microwave transmission zone 600 is provided with a second gas inlet 602 for blowing gas diagonally downward. Gas blown through the second gas inlet 602 effectively prevents powder from backflowing within the plasma chamber 200, prevents powder from adhering to the quartz glass tube 601, extends the service life of the quartz glass tube 601, and ensures smooth powder production. A third gas inlet 201 is provided on the sidewall of the plasma chamber 200 for blowing converging gas diagonally downward. Gas blown through the third gas inlet 201 promotes the formation of microwave plasma in the center of the plasma chamber 200.

[0051] It should be noted that, in one embodiment, a fourth air inlet 301 for blowing cooling gas obliquely downward is provided on the side wall of the cooling chamber 300. The cooling gas blown through the fourth air inlet 301 can accelerate the cooling rate of the powder after microwave plasma treatment. A fifth air inlet 302 for blowing cooling gas upward is provided below the cooling chamber 300. The upward blowing of cooling gas prevents the powder from being deposited at the bottom of the cooling chamber 300 and accelerates the cooling rate of the powder. In addition, a water cooling structure can also be provided on the powder conveying channel between the cooling chamber 300 and the cyclone separator 400 to continuously cool the powder. In one embodiment, the outer wall of the cyclone separator 400 and the inner wall of the cooling chamber 300 can both adopt a water cooling structure to further reduce the temperature of the powder and gas entering the filter 500.

[0052] In one embodiment, reference Figure 4 As shown, the filter 500 is provided with at least two filter elements, each of which is equipped with a valve group for opening and closing the filter element and a valve group for controlling backflushing of the filter element. Specifically, taking two filter elements as an example, the two filter elements are: a first filter element 501 and a second filter element 502. The first filter element 501 is equipped with a first valve group 5011 for controlling its opening and closing, and the second filter element 502 is equipped with a second valve group 5021 for controlling its opening and closing. The filter 500 is also equipped with a third valve group 5012 for controlling backflushing of the first filter element 501, and a fourth valve group 5022 for controlling backflushing of the second filter element 502. Both the third valve group 5012 and the fourth valve group 5022 are connected to a backflushing mechanism 503 (e.g., a backflushing air bag).

[0053] Filter 500 usage: After powder enters filter 500 with the airflow, the first valve group 5011 is opened, and the second valve group 5021 is closed. The powder enters the first filter element 501 for filtration, and the filtered nanopowder is collected. If the first filter element 501 becomes clogged, the second valve group 5021 is opened, the first valve group 5011 is closed, and the third valve group 5012, which controls the backflushing of the first filter element 501, is opened. This backflushes the first filter element 501, and the powder enters the second filter element 502 for filtration. The nanopowder filtered by the second filter element 502 is collected. This cycle is repeated to achieve continuous powder production.

[0054] In one embodiment, an air extraction port 504 is provided above the filter 500 , and a bursting disc 505 is provided on the side wall of the filter 500 . When an explosion occurs inside the filter 500 , the bursting disc 505 can quickly release pressure.

[0055] It is understandable that multiple filter elements can be provided in the filter 500 to ensure continuous powder production for a long time.

[0056] The present invention further provides a method for preparing nanopowder using microwave plasma, wherein the nanopowder is prepared using any of the above-mentioned devices, and the method comprises:

[0057] In step S101, raw material powder enters the plasma chamber 200 through the first inner conduit 101. When the raw material powder flows out of the first inner conduit 101, gas blown from the gas channel between the first inner conduit 101 and the second inner conduit 102 gathers the raw material powder, bringing the raw material powder close to the microwave plasma for vaporization and spheroidization.

[0058] Step S102, the raw material vapor formed by vaporizing the raw material powder enters the cooling chamber 300, forming a powder containing nanometer powder and unvaporized raw material micron powder, and then enters the cyclone separator 400, and the cyclone separator 400 collects the raw material micron powder in the powder;

[0059] In step S103 , the powder processed by the cyclone separator 400 enters the filter 500 , and the filter 500 collects the nanopowder in the powder.

[0060] In this embodiment, by setting the shapes of the inner conductor tube 100 and the plasma chamber 200, the inner conductor tube 100 has an umbrella-shaped lower end 103, and the upper and lower ends of the plasma chamber 200 are both narrowed structures, thereby improving the microwave plasma forming effect, while improving the powder processing efficiency and the nanopowder yield, and the sphericity of the powder is significantly improved.

[0061] Based on the above embodiment, the filter 500 is equipped with at least two filter elements, each of which is equipped with a valve group for opening and closing the filter element and a valve group for controlling backflushing of the filter element. During the process of collecting nanopowder from the powder, the filter 500 uses one of the filter elements to filter the powder. When the filter element becomes clogged, the powder is filtered using the other filter element, and the clogged filter element is backflushed to clear it. The use of the filter 500 is the same as described above and will not be repeated here.

[0062] Figure 5 This is a scanning electron microscope image of nano-silicon powder prepared using a microwave power of 10kW and a powder feeding rate of 0.5g / min. Figure 6 This is a transmission electron microscope image of nano-silicon powder. It can be seen from the image that the spheroidization degree of nano-silicon powder is improved, the nano-powder yield is higher, and the particle size is smaller.

[0063] It should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. that may appear in the above description indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present invention.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the embodiments of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0065] In the embodiments of the present invention, unless otherwise expressly specified or limited, the terms "installed," "connected," "connected," "fixed," etc. should be understood in a broad sense. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection, electrical connection; direct connection, or indirect connection through an intermediate medium; internal communication between two components, or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0066] In the embodiments of the present invention, unless otherwise clearly specified or limited, the first feature being "above" or "below" the second feature may include the direct contact between the first and second features, or may include the contact between the first and second features through additional features therebetween rather than direct contact. Moreover, the first feature being "above", "over" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or merely means that the horizontal height of the first feature is higher than that of the second feature. The first feature being "below", "under" and "beneath" the second feature includes that the first feature is directly below and obliquely below the second feature, or merely means that the horizontal height of the first feature is less than that of the second feature.

[0067] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example" or "some examples", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0068] Those skilled in the art will readily conceive of other embodiments of the present invention after considering the specification and practicing the invention disclosed herein. This application is intended to cover any variations, uses or adaptations of the present invention, which follow the general principles of the present invention and include the common general knowledge or conventional technical means in the technical field not disclosed by the present invention. The specification and embodiments are only regarded as exemplary, and the true scope and spirit of the present invention are pointed out by the appended claims.

Claims

1. An apparatus for preparing nano-powders by microwave plasma, characterized in that, Comprising: An inner conductor tube, the inner conductor tube includes a first inner conduit and a second inner conduit disposed on the outer periphery of the first inner conduit. A gap between the first inner conduit and the second inner conduit forms a gas passage. The lower ends of the first inner conduit and the second inner conduit are umbrella-shaped. The inner side surface of the umbrella-shaped lower end of the second inner conduit has a corner portion, and the corner portion is configured to bend toward a direction close to the axis of the second inner conduit; A plasma chamber, the lower end of the plasma chamber is open, the plasma chamber has a structure that is narrowed at both the upper end and the lower end. The umbrella-shaped lower end of the inner conductor tube is disposed in the plasma chamber, and the plasma chamber is a single-mode chamber; A cooling chamber, the cooling chamber is disposed below the plasma chamber and is in communication with the plasma chamber. Microwave plasma is distributed below the inner conductor tube, in the plasma chamber, and in part of the cooling chamber; A cyclone separator, the cyclone separator is in communication with the cooling chamber; A filter, the filter is in communication with the cyclone separator; The structure of the plasma chamber and the umbrella-shaped lower end of the inner conductor tube cause microwaves to form a high field strength at the center of the plasma chamber, forming a 10 - 75 kW microwave plasma torch under atmospheric pressure. The central portion of the umbrella-shaped lower end is recessed, maintaining a distance from the microwave plasma, and the inner conductor tube will not be damaged by burning.

2. The apparatus for preparing nanopowder by microwave plasma according to claim 1, wherein, The angle formed by the umbrella-shaped lower end of the inner conductor tube and the horizontal plane is 30 - 60°.

3. The apparatus for preparing nanopowder by microwave plasma according to claim 1, wherein The side wall of the plasma chamber is provided with a double-layer water cooling structure.

4. The apparatus for preparing nano-powder by microwave plasma according to claim 1, wherein The device further includes a microwave transmission region, a quartz glass tube is provided in the microwave transmission region, a part of the second inner conduit is disposed in the microwave transmission region, and a 2 - 5 mm gap is provided between the quartz glass tube and the second inner conduit.

5. The apparatus for preparing nano-powder by microwave plasma according to claim 4, wherein, A first air inlet for blowing gas is provided on the side wall of the second inner conduit, a second air inlet for blowing gas obliquely downward is provided in the microwave transmission region, and a third air inlet for blowing converging gas obliquely downward is provided on the side wall of the plasma chamber.

6. The apparatus for preparing nano-powder by microwave plasma according to claim 1, wherein A fourth air inlet for blowing cooling gas obliquely downward is provided on the side wall of the cooling chamber, and a fifth air inlet for blowing cooling gas upward is provided below the cooling chamber.

7. The apparatus for preparing nano-powder by microwave plasma according to claim 1, characterized in that, The filter is provided with at least two filter elements, and each filter element is provided with a valve group for opening and closing the filter element and a valve group for controlling back blowing of the filter element.

8. The apparatus for preparing nano-powder by microwave plasma according to claim 7, characterized in that, An air extraction port is provided above the filter, and a rupture disk is provided on the side wall of the filter.

9. A method for preparing nanopowders by microwave plasma, characterized in that, Using the device according to any one of claims 1 - 8 to prepare nano-powders, the method includes: The raw material powder enters the plasma chamber from the first inner conduit. When the raw material powder flows out of the first inner conduit, the gas blown out from the gas passage between the first inner conduit and the second inner conduit gathers the raw material powder, causing the raw material powder to approach the microwave plasma for vaporization treatment; The raw material vapor formed after vaporizing the raw material powder enters the cooling chamber, forms a powder containing nano-powders and unvaporized raw material micro-powders and enters the cyclone separator, and the cyclone separator collects the raw material micro-powders in the powder; The powder processed by the cyclone separator enters the filter, and the filter collects the nanoflour in the powder.

10. The method for preparing nano-powder by microwave plasma according to claim 9, characterized in that, The filter is provided with at least two filter elements, and each filter element is provided with a valve group for opening and closing the filter element and a valve group for controlling backwashing of the filter element; During the process of the filter collecting the nanoflour in the powder, one of the filter elements is used to filter the powder each time. After the filter element is blocked, another filter element is used to filter the powder, and the blocked filter element is cleaned by backwashing.

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