A preparation method and preparation system of nano metal oxide powder

Abstract

The invention discloses a preparation method and a preparation system of nano metal oxide powder. The preparation method comprises the following steps: adding a batch of metal blocks into a smelting furnace to form metal liquid after smelting, the metal liquid enters a plasma furnace through a connecting pipe, and when the metal liquid levels in the smelting furnace and the plasma furnace reach a set height; turning on a plasma gun arranged on the top of a plasma cover, the plasma gun gasifies the metal liquid in the plasma furnace into gaseous metal, air enters the plasma cover during the gasification process, the gaseous metal and the air undergo oxidation reaction to obtain metal oxide, the metal oxide enters a powder collector driven by the air and is quickly cooled to obtain nano metal oxide; while turning on the plasma gun, metal blocks are added into the smelting furnace through a feeder, and the adding speed of the metal blocks is controlled by the feeder to maintain the metal liquid level change in the smelting furnace and the plasma furnace within ±5 mm.

Description

Technical Field

[0001] The invention belongs to the technical field of nano powder preparation, and in particular relates to a method and a system for preparing nano metal oxide powder. Background Art

[0002] Nano metal oxide powders are widely used in semiconductors, scientific instruments, new energy and other fields due to their unique quantum size effect, small size effect, surface and interface effect, macro quantum tunneling effect, excellent optical, electrical, chemical and other physical and chemical properties, high purity, narrow particle size distribution range, uniform geometry, stable crystal phase and other advantages. For example: Nano indium oxide powders are widely used in optoelectronics, gas sensors, catalysts, solar cells, photocatalysis, gas sensors, optoelectronic devices, flat-panel liquid crystal displays and other scientific fields; Nano gallium oxide powders are used in semiconductor optoelectronics industry, new energy fields, semiconductor materials fields, etc.; Nano tin oxide is used in electronics, optoelectronics, gas sensors, electrochemical energy storage and other fields.

[0003] Nano indium oxide powder is the main raw material for preparing transparent conductive film ITO (indium tin oxide) target materials, and the powder properties have a significant impact on the quality of the prepared ITO target materials. At present, there are three main methods for preparing nano indium oxide, namely, gas phase method, liquid phase method and solid phase method, among which the liquid phase method has been industrialized. A method for preparing nano indium oxide with a large specific surface area is disclosed in the patent with application number CN202011460456.8, which is to add a precipitant, a converter, and a neutralizer to an indium acid solution, and control the pH of the precipitation, conversion and neutralization process, and then filter, dry, crush, calcine, and screen to obtain nano indium oxide powder. However, this method has high processing costs, long processing procedures, and low yields.

[0004] The preparation methods of nano-gallium oxide mainly include electrospinning, thermal evaporation, precipitation and calcination. At present, the precipitation method is the main method for industrialization. In the patent with application number CN202410407494.9, a filamentous nano-gallium oxide and its preparation method are disclosed. The method in the invention is to use NaHCO3 as a precipitant, add it dropwise to a gallium salt solution, obtain a precipitate after precipitation reaction and room temperature aging, and then wash, centrifuge, dry, grind and screen to obtain the precursor gallium hydroxide oxide; then, the filamentous gallium oxide is obtained after gradient heating and cooling treatment. However, this method has high processing cost, long processing flow, low yield, and large amount of wastewater.

[0005] Nano antimony oxide powder is an important raw material for preparing nano antimony tin oxide film (ATO). The preparation methods of nano antimony oxide powder mainly include mechanical ball milling and chemical method. Application No. CN201110407345.5 discloses a method for preparing nano antimony oxide, which uses industrial antimony powder as raw material, adds mixed hydrogen peroxide and liquid additives, and then performs ball milling. After ball milling, nano antimony oxide is obtained by filtering and drying. However, this method requires long time for ball milling, resulting in high impurities in the powder (zirconium or aluminum impurities are easily introduced during ball milling).

[0006] In summary, given that the current industrial preparation methods of nano-oxides all have certain defects, it is very necessary to develop a method for preparing nano-oxide powders with uniform particle size, excellent performance, high purity and low cost. Summary of the invention

[0007] The purpose of the present invention is to provide a method and a system for preparing nano metal oxide powder with uniform particle size, high purity and low cost.

[0008] In a first aspect, the present invention provides a method for preparing nano metal oxide powder, comprising the following steps: A batch of metal blocks are added to the smelting furnace to form molten metal after smelting. The molten metal enters the plasma furnace through a connecting pipe. When the metal liquid levels in the smelting furnace and the plasma furnace reach a set height; a plasma gun arranged on the top of the plasma hood is turned on. The plasma gun gasifies the molten metal in the plasma furnace into gaseous metal. During the gasification process, air enters the plasma hood. The gaseous metal reacts with the air to obtain metal oxides. The metal oxides enter the powder collector driven by the air and are quickly cooled to obtain nano metal oxides. While the plasma gun is turned on, metal blocks are added to the smelting furnace through a feeder, and the speed of adding the metal blocks is controlled by the feeder to maintain the change of the metal liquid level in the smelting furnace and the plasma furnace within ±5mm; and an electromagnetic winding coil is provided under the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the metal liquid in the plasma furnace.

[0009] Preferably, the metal block is one of gallium, indium, tin, bismuth, cerium and antimony metal blocks; and the smelting temperature is higher than the melting point of the metal.

[0010] Preferably, the average particle size of the nano metal oxide is not greater than 100 nm.

[0011] Preferably, the air flow rate into the plasma hood is 5000-10000m 3 / h.

[0012] Preferably, the method of controlling the adding speed of the metal block by the feeder is: clamping one end of the metal block by the feeder, then lowering the lower end of the metal block by the feeder until it contacts the molten metal in the smelting furnace, and then controlling the descending speed of the metal block by the feeder, so that the metal block is gradually melted in the molten metal and the height of the molten metal level is increased.

[0013] Preferably, the adding speed of the metal block is 20-80 kg / h.

[0014] Preferably, the metal block is a rectangular metal block; when the feeder adds the metal block to the smelting furnace, the side of the rectangular metal block with the smallest area is used as the contact surface with the molten metal and is added to the smelting furnace.

[0015] Preferably, the power of the plasma gun is 50-100 kW, more preferably 100 kW.

[0016] Preferably, the operating frequency of the electromagnetic winding coil is 50 Hz, and the alternating current is 100-200 A.

[0017] Preferably, the wind speed in the powder collector is 0.1-1 m / min, and the pore size of the filter cloth in the powder collector is 0.1-0.5 μm.

[0018] In a second aspect, the present invention provides a system for preparing nano metal oxide powder, comprising a feeder, a smelting furnace, a plasma chamber, a powder collector and an exhaust system; The feeder is used to add metal blocks into the smelting furnace; The lower end of the smelting furnace is provided with a molten metal outlet; The plasma chamber comprises a plasma furnace, a plasma hood and a plasma gun; a metal liquid inlet is provided at the lower end of the plasma furnace, and a metal liquid outlet of the smelting furnace is connected with the metal liquid inlet of the plasma furnace through a connecting pipe; the plasma hood is placed directly above the plasma furnace, and the plasma hood and the plasma furnace are not completely closed, so as to introduce air; a plasma gun is provided at the top of the plasma hood, so as to gasify the metal liquid in the plasma furnace; a gas outlet is provided at the top of the plasma hood, so as to output metal oxides; and the gas outlet at the top of the plasma hood is connected with the powder inlet of the powder collector; The powder collector is used to cool and collect the metal oxides generated by the reaction in the plasma cover; the air extraction port of the powder collector is connected to the air extraction system; The exhaust system is used to introduce air into the plasma hood and to extract the generated metal oxides to the powder collector; An electromagnetic winding coil is arranged below the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the molten metal in the plasma furnace.

[0019] Preferably, the feeder comprises a rotating table, a lifting platform and a manipulator; wherein: the rotating table and the lifting platform are connected by a connecting rod, the rotating table drives the lifting platform to rotate in the horizontal direction; the manipulator is installed under the lifting platform, and the lifting platform controls the manipulator to rise and fall in the vertical direction.

[0020] Preferably, a laser rangefinder is provided below the lifting platform of the feeder, and the laser rangefinder can monitor the height of the metal liquid level in the smelting furnace when feeding, and adjust the descending speed of the lifting platform according to the change of the metal liquid level.

[0021] Preferably, the manipulator is provided with a visual device, which can identify the shape of the metal block, thereby achieving directional grasping of the metal block.

[0022] Preferably, a bracket is provided below the plasma hood, and the bracket is used to make the plasma hood and the plasma furnace incompletely closed.

[0023] Beneficial effects of the present invention: (1) The metal oxide powder prepared by the method for preparing nano metal oxide powder of the present invention has small particle size, high purity and uniform distribution, and the corresponding process is energy-saving and environmentally friendly, and no waste water or waste gas is generated.

[0024] (2) In the preparation method of nano metal oxide powder of the present invention, a feeder is used to control the adding speed of the metal block, and at the same time, the principle of communicating vessels is used to make the metal liquid level in the plasma furnace vary within ±5 mm, thereby ensuring a stable reaction interface, thereby effectively ensuring the uniformity of the nano metal oxide and reducing the particle size of the nano metal oxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the structure of the system for preparing nano metal oxide powder in the equipment embodiment.

[0026] Figure 2 It is a schematic diagram of the structure of the preparation system of nano metal oxide powder in the equipment comparison example.

[0027] Among them, 1. feeder; 11. rotating table; 12. manipulator; 13. lifting platform; 14. laser rangefinder; 15. metal block; 2. smelting furnace; 3. connecting pipe; 31. conduit; 4. plasma chamber; 41. plasma furnace; 42. plasma cover; 43. plasma gun; 44. bracket; 45. electromagnetic winding coil; 5. powder collector; 6. exhaust system. DETAILED DESCRIPTION

[0028] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively and meticulously below in conjunction with the accompanying drawings and preferred embodiments of the present invention, but the protection scope of the present invention is not limited to the following specific embodiments. Unless otherwise defined, all the professional terms used below have the same meanings as those generally understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention. Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] As mentioned above, in the first aspect, the present invention provides a method for preparing nano metal oxide powder, comprising the following steps: A batch of metal blocks are added to the smelting furnace to form molten metal after smelting. The molten metal enters the plasma furnace through a connecting pipe. When the metal liquid levels in the smelting furnace and the plasma furnace reach a set height; a plasma gun arranged on the top of the plasma hood is turned on. The plasma gun gasifies the molten metal in the plasma furnace into gaseous metal. During the gasification process, air enters the plasma hood. The gaseous metal reacts with the air to obtain metal oxides. The metal oxides enter the powder collector driven by the air and are quickly cooled to obtain nano metal oxides. While the plasma gun is turned on, metal blocks are added to the smelting furnace through a feeder, and the speed of adding the metal blocks is controlled by the feeder to maintain the change of the metal liquid level in the smelting furnace and the plasma furnace within ±5mm; and an electromagnetic winding coil is provided under the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the metal liquid in the plasma furnace.

[0030] In the present invention, the smelting furnace and the plasma furnace are connected through a connecting pipe; the connecting pipe adopts the principle of a communicating vessel to keep the height of the metal liquid level in the solution furnace consistent with that in the plasma furnace; at the same time, the adding speed of the metal block is controlled by a feeder to make the metal liquid level in the smelting furnace and the plasma furnace change within ±5mm, thereby improving the uniformity of the nano-oxide and reducing the particle size of the nano-oxide.

[0031] In the present invention, electromagnetic stirring is performed on the molten metal in the plasma furnace, so that the temperature of the molten metal is more uniform, the particle size of the produced nano-metal oxide is smaller, and the powder particle size distribution is narrow.

[0032] Preferably, the metal block is one of gallium, indium, tin, bismuth, cerium and antimony metal blocks; and the smelting temperature is higher than the melting point of the metal.

[0033] Preferably, the average particle size of the nano metal oxide is not greater than 100 nm.

[0034] Preferably, the air flow rate into the plasma hood is 5000-10000m 3 / h.

[0035] Preferably, the method of controlling the adding speed of the metal block by the feeder is: clamping one end of the metal block by the feeder, then lowering the lower end of the metal block by the feeder until it contacts the molten metal in the smelting furnace, and then controlling the descending speed of the metal block by the feeder, so that the metal block is gradually melted in the molten metal and the height of the molten metal level is increased.

[0036] Preferably, the adding speed of the metal block is 20-80 kg / h.

[0037] When the molten metal level in the smelting furnace is slightly lower than the set height, the descending speed of the metal block is accelerated to quickly raise the molten metal level; when the molten metal level is slightly higher than the set height, the descending speed of the metal block is reduced. When the consumption rate of the molten metal in the plasma furnace is greater than the amount of metal blocks added, the molten metal level in the smelting furnace will drop. Therefore, by controlling the descending speed of the metal block, the molten metal level in the smelting furnace and the plasma furnace can be changed within ±5mm.

[0038] Preferably, the metal block is a rectangular metal block; when the feeder adds the metal block to the smelting furnace, the side of the rectangular metal block with the smallest area is used as the contact surface with the molten metal and is added to the smelting furnace.

[0039] In the present invention, the surface of the rectangular metal block with the smallest area in contact with the molten metal is added into the smelting furnace, which can reduce the damage to the metal oxide film when the metal block is added, thereby reducing the loss caused by the oxidation of the molten metal.

[0040] Preferably, the power of the plasma gun is 50-100 kW, more preferably 100 kW; the operating frequency of the electromagnetic winding coil is 50 Hz, and the alternating current is 100-200 A.

[0041] Preferably, the wind speed in the powder collector is 0.1-1 m / min, and the pore size of the filter cloth in the powder collector is 0.1-0.5 μm.

[0042] In a second aspect, the present invention provides a system for preparing nano metal oxide powder, comprising a feeder, a smelting furnace, a plasma chamber, a powder collector and an exhaust system; The feeder is used to add metal blocks into the smelting furnace; The lower end of the smelting furnace is provided with a molten metal outlet; The plasma chamber comprises a plasma furnace, a plasma hood and a plasma gun; a metal liquid inlet is provided at the lower end of the plasma furnace, and a metal liquid outlet of the smelting furnace is connected with the metal liquid inlet of the plasma furnace through a connecting pipe; the plasma hood is placed directly above the plasma furnace, and the plasma hood and the plasma furnace are not completely closed, so as to introduce air; a plasma gun is provided at the top of the plasma hood, so as to gasify the metal liquid in the plasma furnace; a gas outlet is provided at the top of the plasma hood, so as to output metal oxides; and the gas outlet at the top of the plasma hood is connected with the powder inlet of the powder collector; The powder collector is used to cool and collect the metal oxides generated by the reaction in the plasma cover; the air extraction port of the powder collector is connected to the air extraction system; The exhaust system is used to introduce air into the plasma hood and to extract the generated metal oxides to the powder collector; An electromagnetic winding coil is arranged below the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the metal liquid in the plasma furnace.

[0043] Preferably, the feeder comprises a rotating table, a lifting platform and a manipulator; wherein: the rotating table and the lifting platform are connected by a connecting rod, the rotating table drives the lifting platform to rotate in the horizontal direction; the manipulator is installed under the lifting platform, and the lifting platform controls the manipulator to rise and fall in the vertical direction.

[0044] Preferably, a laser rangefinder is provided below the lifting platform of the feeder, and the laser rangefinder is used to monitor the height of the metal liquid level in the smelting furnace when feeding, and adjust the descending speed of the lifting platform according to the change of the metal liquid level.

[0045] Preferably, the manipulator is provided with a visual device, which can identify the shape of the metal block, thereby achieving directional grasping of the metal block.

[0046] Preferably, a bracket is provided below the plasma hood, and the bracket is used to make the plasma hood and the plasma furnace incompletely closed.

[0047] Device Embodiment Schematic diagram of the structure of the preparation system of nano metal oxide powder in the present invention Figure 1 As shown, it includes a feeder 1, a smelting furnace 2, a connecting pipe 3, a plasma chamber 4, a powder collector 5 and an exhaust system 6.

[0048] Wherein: the feeder 1 includes a rotating table 11, a manipulator 12, a lifting platform 13 and a laser rangefinder 14; the rotating table 11 is connected to the lifting platform 13 through a connecting rod, the rotating table 11 controls the lifting platform 13 to rotate in the horizontal direction, the manipulator 12 is installed on the lifting device of the lifting platform, and the manipulator 12 is lifted and lowered in the vertical direction by controlling the lifting device; a laser rangefinder 14 is installed under the lifting platform 13 for detecting the height of the metal liquid level in the smelting furnace 2.

[0049] The lifting platform 13 lowers the manipulator 12 into the pile of metal blocks through the lifting device. The visual device installed on the manipulator 12 automatically identifies the grabbing position of the metal block 15. After the manipulator 12 grabs the metal block 15 in a directional manner, the lifting device lifts the manipulator 12; then the lifting platform 12 is rotated to the top of the smelting furnace 2 through the rotating table 11, and the lifting device lowers the metal block 15 to contact the metal liquid surface in the smelting furnace 2; when the plasma gun 43 begins to vaporize the metal liquid, the laser rangefinder 14 measures the change in the height of the metal liquid surface, thereby controlling the descending speed of the metal block 15 through the lifting device, so that the metal block 15 is gradually melted in the metal liquid and the metal liquid surface is raised.

[0050] A molten metal outlet is provided below the smelting furnace 2 , and the molten metal outlet is connected to a molten metal inlet below the plasma furnace 41 through a connecting pipe 3 .

[0051] The plasma chamber 4 includes a plasma furnace 41, a plasma cover 42, and a plasma gun 43; a bracket 44 is arranged below the plasma cover 42; the plasma cover 42 is placed directly above the plasma furnace 41 through the bracket 44; the bracket 44 allows a hollow portion between the plasma cover 42 and the plasma furnace 41, which will not be completely closed, and is used to introduce air into the plasma cover 42. A plasma gun 43 is arranged at the top of the plasma cover 42, which is used to gasify the molten metal in the plasma furnace 41; an electromagnetic winding coil 45 is installed at the bottom of the plasma furnace 41, which can play an electromagnetic stirring role to make the temperature distribution of the molten metal in the plasma furnace 41 uniform; the electromagnetic winding coil is preferably a Cramer winding coil.

[0052] A gas outlet is provided at the top of the plasma cover 42 for outputting the generated metal oxides, and the gas outlet is connected to the powder inlet of the powder collector 5; The powder collector 5 is used for cooling and collecting the generated metal oxides. The exhaust port at the rear end of the powder collector 5 is connected to the exhaust system 6.

[0053] The exhaust system 6 is used to introduce air into the plasma hood and to extract the generated metal oxides to the powder collector 5 .

[0054] Equipment comparison Schematic diagram of the structure of the preparation system of nano metal oxide powder in the equipment comparison example Figure 2 As shown, it is basically the same as the preparation system of nano metal oxide powder in the equipment embodiment, the difference is that the molten metal outlet at the bottom of the smelting furnace 2 is connected to the conduit 31, and the molten metal inlet is not opened at the lower end of the plasma furnace 41; the conduit 31 transports the molten metal to the plasma furnace 41 through the top of the plasma furnace 41.

[0055] Preparation method example Example 1 This embodiment adopts Figure 1 The preparation system of the nano metal oxide powder shown in the figure prepares the nano indium oxide powder, which specifically includes the following steps: 1) A batch of 4N indium ingots is first added to the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 300°C. The metal indium liquid is smelted to obtain the metal indium liquid, and the metal indium liquid enters the plasma furnace 41 through the connecting pipe 3. At this time, the metal indium liquid level in the smelting furnace 2 and the plasma furnace 41 is the same, the liquid level of the metal indium liquid is half of the height of the plasma furnace 41, and the metal indium liquid level reaches a stable level.

[0056] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 50kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 100A; the air volume of the exhaust system 6 to 5000m 3 / h; the wind speed in the powder collector 5 is 0.1m / min, and the pore size of the filter cloth of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metal indium liquid in the plasma furnace 41. After the gasification, the indium vapor contacts with the air and undergoes an oxidation reaction in the plasma cover 42 to generate indium oxide. The indium oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano indium oxide. After the nano indium oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0057] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the indium ingot (the indium ingot is a rectangular parallelepiped with a size of 500mm*30mm*30mm) until it contacts the metal indium liquid in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the metal liquid level, the lifting platform 13 adjusts the descending speed of the indium ingot to gradually melt the indium ingot in the metal indium liquid and raise the height of the metal liquid level (at this time, the manipulator 12 always clamps the indium ingot, and melts the indium ingot in the contact part in the metal indium liquid by descending, instead of completely placing the entire indium ingot into the metal indium liquid; when one indium ingot is added, the feeder 1 will grab another indium ingot within 20s, and continue to add indium ingots to the melting furnace 2 according to the indium ingot adding method. During the feeding period, the manipulator indium ingot descending speed will match the height of the metal liquid in the furnace). The metal indium liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the indium ingot, the metal liquid level change in the smelting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; in the equilibrium state, the consumption rate of the metal indium liquid in the plasma chamber 4 is about 20kg / h. When the indium ingot is added to the smelting furnace 2 by the manipulator 12, the side of the indium ingot with the smallest area (the side of 30mm*30mm) is used as the contact surface with the metal indium liquid, and is added to the metal indium liquid in the smelting furnace 2.

[0058] The analysis results of the nano-indium oxide powder obtained in this example are as follows: purity 99.99%, average particle size 90nm, specific surface area (BET) 24m 2 / g. The surface oxidation rate of the indium liquid in the smelting furnace 2 is 0.01kg / h.

[0059] Example 2 This embodiment adopts Figure 1 The preparation system of the nano metal oxide powder shown in the figure prepares nano gold and nano tin oxide powder, which specifically includes the following steps: 1) A batch of 4N tin ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 400°C. The molten metal tin is smelted and enters the plasma furnace 41 through the connecting pipe 3. At this time, the liquid level of the metal tin in the smelting furnace 2 and the plasma furnace 41 is the same, the liquid level of the metal tin is half of the height of the plasma furnace 41, and the liquid level of the metal tin reaches a stable state.

[0060] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 75kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 100A; the air volume of the exhaust system 6 to 7000m 3 / h; the wind speed in the powder collector 5 is 0.3m / min, and the filter cloth aperture of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metallic tin liquid in the plasma furnace 41. After the gasification, the tin vapor contacts with the air and undergoes an oxidation reaction in the plasma cover 42 to generate tin oxide. The tin oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano-tin oxide. After the nano-tin oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0061] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the tin ingot (the tin ingot is a rectangular parallelepiped with a size of 300mm*20mm*20mm) until it contacts the molten tin in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the molten metal level, the lifting platform 13 adjusts the descending speed of the tin ingot so that the tin ingot is gradually melted in the molten metal and the height of the molten metal level is raised (at this time, the manipulator 12 is always clamping the tin ingot, and the contact part of the tin ingot is melted in the molten metal by descending, instead of completely placing the entire tin ingot into the molten metal; when one tin ingot is added, the feeder 1 will grab another tin ingot within 20s, and continue to add tin ingots to the melting furnace 2 according to the method of adding tin ingots. During the feeding period, the descending speed of the manipulator indium ingot will match the height of the molten metal in the furnace). The tin liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the tin ingot, the change of the metal liquid level in the smelting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; in the equilibrium state, the consumption rate of the metal tin liquid in the plasma chamber 4 is about 40kg / h. When the tin ingot is added to the smelting furnace 2 by the manipulator 12, the side of the tin ingot with the smallest area (20mm*20mm side) is used as the contact surface with the metal tin liquid, and it is added to the metal tin liquid in the smelting furnace 2.

[0062] The analysis results of the nano-tin oxide powder obtained in this example are as follows: purity 99.99%, average particle size 80nm, specific surface area (BET) 26m 2 / g. The surface oxidation rate of tin liquid in the smelting furnace is 0.01kg / h.

[0063] Example 3 This embodiment adopts Figure 1 The nano metal oxide powder preparation system shown in the figure prepares nano bismuth oxide powder, which specifically includes the following steps: 1) A batch of 4N bismuth ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 450° C., and smelting is performed to obtain metal bismuth liquid, which enters the plasma furnace 41 through the connecting pipe 3. At this time, the metal bismuth liquid levels in the smelting furnace 2 and the plasma furnace 41 are the same, and the liquid level of the metal bismuth liquid is 2 / 3 of the height of the plasma furnace 41, and the metal bismuth liquid level reaches a stable state.

[0064] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 90kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 100A; the air volume of the exhaust system 6 to 8000m 3 / h; the wind speed in the powder collector 5 is 0.5m / min, and the filter cloth pore size of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metallic bismuth liquid in the plasma furnace 41. After the gasification, the bismuth vapor contacts the air and undergoes an oxidation reaction in the plasma cover 42 to generate bismuth oxide. The bismuth oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano-bismuth oxide. After the nano-bismuth oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0065] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the bismuth ingot (the bismuth ingot is a rectangular parallelepiped with a size of 500 mm*20 mm*20 mm) until it contacts the metal bismuth liquid in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the metal liquid, the lifting platform 13 adjusts the descending speed of the bismuth ingot so that the bismuth ingot is gradually melted in the metal bismuth liquid and the height of the metal liquid is raised (at this time, the manipulator 12 is always holding the bismuth ingot and the contact part of the bismuth ingot is melted in the metal bismuth liquid by descending, instead of completely placing the entire bismuth ingot into the metal bismuth liquid). When one bismuth ingot is added, the feeder 1 will grab another bismuth ingot within 20 seconds, and continue to add bismuth ingots to the melting furnace 2 according to the method of adding bismuth ingots. During the feeding period, the descending speed of the manipulator indium ingot will match the height of the molten metal in the furnace); the bismuth liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the bismuth ingot, the change of the molten metal level in the melting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; under the equilibrium state, the consumption rate of the bismuth liquid in the plasma chamber 4 is about 60kg / h. When the bismuth ingot is added to the melting furnace 2 by the manipulator 12, the side with the smallest area of ​​the bismuth ingot (the side with 20mm*20mm) is used as the contact surface with the molten metal, and it is added to the bismuth liquid in the melting furnace 2.

[0066] The analysis results of the nano-bismuth oxide powder obtained in this example are as follows: purity 99.99%, average particle size 50nm, specific surface area (BET) 28m 2 / g. The surface oxidation rate of bismuth liquid in the smelting furnace is 0.02kg / h.

[0067] Example 4 This embodiment adopts Figure 1 The nano-metal oxide powder preparation system shown in the figure prepares nano-gallium oxide powder, which specifically includes the following steps: 1) A batch of 4N gallium ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 50°C. Metal gallium liquid is smelted and enters the plasma furnace 41 through the connecting pipe 3. At this time, the metal gallium liquid levels in the smelting furnace 2 and the plasma furnace 41 are the same, and the metal gallium liquid level is 2 / 3 of the height of the plasma furnace 41, and the metal gallium liquid level reaches a stable level.

[0068] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 100kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 200A; the air volume of the exhaust system 6 to 10000m 3 / h; the wind speed in the powder collector 5 is 0.5m / min, and the pore size of the filter cloth of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metal gallium liquid in the plasma furnace 41. After the gasification, the gallium vapor contacts the air and undergoes an oxidation reaction in the plasma cover 42 to generate gallium oxide. The gallium oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano-gallium oxide. After the nano-gallium oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0069] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the gallium ingot (the gallium ingot is a rectangular parallelepiped with a size of 450mm*20mm*20mm) until it contacts the metal gallium liquid in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the metal liquid, the lifting platform 13 adjusts the descending speed of the gallium ingot so that the gallium ingot is gradually melted in the metal gallium liquid and the height of the metal liquid is raised (at this time, the manipulator 12 is always clamping the gallium ingot, and the contact part of the gallium ingot is melted in the metal gallium liquid by descending, instead of completely placing the entire gallium ingot into the metal gallium liquid). When one gallium ingot is added, the feeder 1 will grab another gallium ingot within 20 seconds, and continue to add gallium ingots to the melting furnace 2 according to the method of adding gallium ingots. During the feeding period, the descending speed of the manipulator indium ingot will match the height of the molten metal in the furnace); the gallium liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the gallium ingot, the change of the metal liquid level in the melting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; in the equilibrium state, the consumption rate of the metal gallium liquid in the plasma chamber 4 is about 80kg / h. When the gallium ingot is added to the melting furnace 2 by the manipulator 12, the side of the gallium ingot with the smallest area (the side of 20mm*20mm) is used as the contact surface with the molten metal, and it is added to the metal gallium liquid in the melting furnace 2.

[0070] The analysis results of the nano-gallium oxide powder obtained in this example are as follows: purity 99.99%, average particle size 30nm, specific surface area (BET) 32m 2 / g. The surface oxidation rate of gallium liquid in the smelting furnace 2 is 0.01kg / h.

[0071] Example 5 This embodiment adopts Figure 1 The nano metal oxide powder preparation system shown in the figure prepares nano cerium oxide powder, which specifically includes the following steps: 1) A batch of 4N cerium ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 950°C. The cerium metal liquid is smelted and enters the plasma furnace 41 through the connecting pipe 3. At this time, the cerium metal liquid levels in the smelting furnace 2 and the plasma furnace 41 are the same, and the cerium metal liquid level is 2 / 3 of the height of the plasma furnace 41, and the cerium metal liquid level reaches a stable level.

[0072] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 80kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 180A; the air volume of the exhaust system 6 to 9000m 3 / h; the wind speed in the powder collector 5 is 1.0m / min, and the pore size of the filter cloth of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metal cerium liquid in the plasma furnace 41. After the gasification, the cerium vapor contacts with the air and undergoes an oxidation reaction in the plasma cover 42 to generate cerium oxide. The cerium oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano cerium oxide. After the nano cerium oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0073] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the cerium ingot (the cerium ingot is a rectangular parallelepiped with a size of 400mm*15mm*15mm) until it contacts the metal cerium liquid in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the metal liquid, the lifting platform 13 adjusts the descending speed of the cerium ingot so that the cerium ingot is gradually melted in the metal cerium liquid and the height of the metal liquid is raised (at this time, the manipulator 12 is always clamping the cerium ingot, and the contact part of the cerium ingot is melted in the metal cerium liquid by descending, instead of putting the entire cerium ingot completely into the cerium liquid). In the metal cerium liquid; when one cerium ingot is added, the feeder 1 will grab another cerium ingot within 20s, and continue to add cerium ingots to the melting furnace 2 according to the method of adding cerium ingots. During the feeding period, the descending speed of the manipulator indium ingot will match the height of the molten metal in the furnace); the cerium liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the cerium ingot, the change of the metal liquid level in the melting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; under the equilibrium state, the feeding speed of the metal cerium ingot is 50kg / h. When the cerium ingot is added to the melting furnace 2 by the manipulator 12, the side with the smallest area of ​​the cerium ingot (the side with 20mm*20mm) is used as the contact surface with the molten metal, and it is added to the metal cerium liquid in the melting furnace 2.

[0074] The analysis results of the nano-cerium oxide powder obtained in this example are as follows: purity 99.99%, average particle size 40nm, specific surface area (BET) 30m 2 / g. The surface oxidation rate of cerium liquid in the smelting furnace is 0.03kg / h.

[0075] Example 6 This embodiment adopts Figure 1 The nano metal oxide powder preparation system shown in the figure prepares nano antimony oxide powder, which specifically includes the following steps: 1) A batch of 4N antimony ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 850°C. Metal antimony liquid is smelted and enters the plasma furnace 41 through the connecting pipe 3. At this time, the metal antimony liquid levels in the smelting furnace 2 and the plasma furnace 41 are the same, and the liquid level of the metal antimony liquid is 2 / 3 of the height of the plasma furnace 41, and the metal antimony liquid level reaches a stable level.

[0076] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 100kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 200A; the air volume of the exhaust system 6 to 10000m 3 / h; the wind speed in the powder collector 5 is 0.8m / min, and the pore size of the filter cloth of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metal antimony liquid in the plasma furnace 41. After the gasification, the antimony vapor contacts with the air and undergoes an oxidation reaction in the plasma cover 42 to generate antimony oxide. The antimony oxide is pumped from the gas outlet to the powder collector 5 and is quickly cooled to generate nano antimony oxide. After the nano antimony oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0077] 3) While the plasma gun 43 is turned on, the lifting platform 13 lowers the lower end of the antimony ingot (the antimony ingot is a rectangular parallelepiped with a size of 600mm*15mm*15mm) until it contacts the metal antimony liquid in the smelting furnace 2. After the laser rangefinder 14 measures the change in the height of the metal liquid, the lifting platform 13 adjusts the descending speed of the antimony ingot so that the antimony ingot is gradually melted in the metal antimony liquid and the height of the metal liquid is raised (at this time, the manipulator 12 is always clamping the antimony ingot, and the contact part of the antimony ingot is melted in the metal antimony liquid by descending, instead of completely placing the entire antimony ingot in the antimony liquid). into the metal antimony liquid; when one antimony ingot is added, the feeder 1 will grab another antimony ingot within 20 seconds, and continue to add antimony ingots to the melting furnace 2 according to the method of adding antimony ingots. During the feeding period, the descending speed of the manipulator indium ingot will match the height of the molten metal in the furnace); the antimony liquid will flow into the plasma furnace 41 through the connecting pipe 3. Therefore, by controlling the descending speed of the antimony ingot, the change of the metal liquid level in the melting furnace 2 and the plasma furnace 41 can be maintained within ±5mm; in the equilibrium state, the feeding speed of the metal antimony ingot is 50kg / h. When adding antimony ingots to the melting furnace 2 through the manipulator 12, the side with the smallest area of ​​the antimony ingot (the side with 15mm*15mm) is used as the contact surface with the molten metal, and added to the metal antimony liquid in the melting furnace 2.

[0078] The analysis results of the nano antimony oxide powder obtained in this example are as follows: purity 99.99%, average particle size 30nm, specific surface area (BET) 33m 2 / g. The surface oxidation rate of antimony liquid in the smelting furnace is 0.03kg / h.

[0079] Comparative Example 1 The method is basically the same as Example 1, except that: the laser rangefinder 14 is not turned on, and 10 kg of metal indium ingots are added to the smelting furnace 2 through the feeder 1 every 30 minutes.

[0080] The liquid level fluctuated significantly during the test. During the period without adding material, the liquid level dropped, and during the addition process, the liquid level suddenly increased. The analysis results of the nano-indium oxide powder obtained in this example are: purity 99.99%, average particle size 250nm, specific surface area (BET) 13m 2 / g. The surface oxidation rate of the indium liquid in the smelting furnace 2 is 0.01kg / h.

[0081] Example 7 The method is basically the same as Example 3, except that: in step 2), the bismuth ingot is added to the smelting furnace 2 with the side with the largest area of ​​the bismuth ingot (the side with an area of ​​500 mm*30 mm) as the contact surface with the molten metal; that is, when the manipulator 12 grabs the bismuth ingot, it controls the side with the largest area of ​​the bismuth ingot to be grabbed by the visual device; The analysis results of the nano-bismuth oxide powder obtained in this example are as follows: purity 99.99%, average particle size 55nm, specific surface area (BET) 27m 2 / g. The surface oxidation rate of the bismuth liquid in the heating furnace is 1kg / h.

[0082] Comparative Example 2 It is basically the same as the embodiment 4, except that the electromagnetic winding coil 45 is not turned on and there is no electromagnetic stirring effect.

[0083] The analysis results of the obtained nano-gallium oxide powder are as follows: purity 99.99%, average particle size 400nm, specific surface area (BET) 7m 2 / g. The surface oxidation rate of gallium liquid in the smelting furnace 2 is 0.01kg / h.

[0084] Comparative Example 3 This comparative example 1 adopts Figure 2 The preparation system of the metal oxide powder shown is used to prepare metal nano-tin oxide; specifically, the following steps are included: 1) A batch of 4N tin ingots is first added into the smelting furnace 2 through the feeder 1, and the temperature of the smelting furnace 2 is set to 400°C. The molten metal tin is smelted and enters the plasma furnace 41 through the conduit 31. When the liquid level of the molten metal tin is half the height of the plasma furnace 41.

[0085] 2) Turn on the plasma gun 43, the electromagnetic winding coil 45, the powder collector 5 and the exhaust system 6, and set the output power of the plasma gun 43 to 75kW; the electromagnetic winding coil 45 to set the operating frequency to 50Hz, the alternating current to 100A; the air volume of the exhaust system 6 to 7000m 3 / h; the wind speed in the powder collector 5 is 0.3m / min, and the filter cloth aperture of the powder collector 5 is 0.1μm. The plasma gun 43 gasifies the metallic tin liquid in the plasma furnace 41. After the gasification, the tin vapor contacts with the air and undergoes an oxidation reaction in the plasma cover 42 to generate tin oxide. The tin oxide is pumped from the gas outlet to the powder collector 5 and is rapidly cooled to generate nano-tin oxide. After the nano-tin oxide is intercepted by the powder collector 5, it is collected at the powder outlet of the powder collector 5.

[0086] 3) While the plasma gun 43 is turned on, the metal tin ingot is added to the smelting furnace 2 at the adding speed of the metal tin ingot under the equilibrium state in Example 2; when the tin ingot is added to the smelting furnace 2 by the manipulator 12, the side of the tin ingot with the smallest area (the side with an area of ​​20 mm*20 mm) is used as the contact surface with the molten metal, and is added to the molten metal in the smelting furnace 2.

[0087] Since there is no connecting vessel, the liquid level is determined by the melting speed of the molten metal in the furnace. When the surface temperature of the metal ingot in the furnace reaches the melting point, a large amount of molten metal is formed, which flows into the plasma furnace and causes a sudden increase in the liquid level, affecting the stability of the reaction interface and reducing the powder particle size. The analysis results of the obtained nano-tin oxide powder are: purity 99.99%, average particle size 200nm, specific surface area (BET) 15m 2 / g; the surface oxidation rate of tin liquid in the smelting furnace is 0.02kg / h.

[0088] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing nano metal oxide powder, characterized in that: The following steps are involved: A batch of metal blocks are added to the smelting furnace to form molten metal after smelting. The molten metal enters the plasma furnace through a connecting pipe. When the metal liquid levels in the smelting furnace and the plasma furnace reach a set height; a plasma gun arranged on the top of the plasma hood is turned on. The plasma gun gasifies the molten metal in the plasma furnace into gaseous metal. During the gasification process, air enters the plasma hood. The gaseous metal reacts with the air to obtain metal oxides. The metal oxides enter the powder collector driven by the air and are quickly cooled to obtain nano metal oxides. While the plasma gun is turned on, metal blocks are added to the smelting furnace through a feeder, and the speed of adding the metal blocks is controlled by the feeder to maintain the change of the metal liquid level in the smelting furnace and the plasma furnace within ±5mm; and an electromagnetic winding coil is provided under the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the metal liquid in the plasma furnace.

2. The method for preparing nano metal oxide powder according to claim 1, characterized in that: The set height is 1 / 3 to 3 / 4 of the height of the plasma furnace; The metal block is one of gallium, indium, tin, bismuth, cerium and antimony metal blocks; The smelting temperature is higher than the melting point of the metal.

3. The method for preparing nano metal oxide powder according to claim 1, characterized in that: The method for controlling the adding speed of the metal block by the feeder is: clamping one end of the metal block by the feeder, then lowering the lower end of the metal block by the feeder until it contacts the molten metal in the smelting furnace, and then controlling the descending speed of the metal block by the feeder, so that the metal block is gradually melted in the molten metal and the height of the molten metal level is increased.

4. The method for preparing nano metal oxide powder according to claim 1 or 3, characterized in that: The metal block is a rectangular metal block; when the feeder adds the metal block into the smelting furnace, the side of the rectangular metal block with the smallest area is used as the contact surface with the molten metal and added into the smelting furnace.

5. The method for preparing nano metal oxide powder according to claim 1, characterized in that: The average particle size of the nano metal oxide is not greater than 100 nm; The air flow rate into the plasma hood is 5000~10000m 3 / h.

6. The method for preparing nano metal oxide powder according to claim 1, characterized in that: The power of the plasma gun is 50-100 kW; The electromagnetic winding coil has an operating frequency of 50 Hz and an alternating current of 100-200 A; The wind speed in the powder collector is 0.1-1 m / min, and the pore size of the filter cloth in the powder collector is 0.1-0.5 μm.

7. A system for preparing nano metal oxide powder, characterized in that: It includes a feeder, a smelting furnace, a plasma chamber, a powder collector and an exhaust system; The feeder is used to add metal blocks into the smelting furnace; The lower end of the smelting furnace is provided with a molten metal outlet; The plasma chamber comprises a plasma furnace, a plasma hood and a plasma gun; a metal liquid inlet is provided at the lower end of the plasma furnace, and a metal liquid outlet of the smelting furnace is connected with the metal liquid inlet of the plasma furnace through a connecting pipe; the plasma hood is placed directly above the plasma furnace, and the plasma hood and the plasma furnace are not completely closed, so as to introduce air; a plasma gun is provided at the top of the plasma hood, so as to gasify the metal liquid in the plasma furnace; a gas outlet is provided at the top of the plasma hood, so as to output metal oxides; and the gas outlet at the top of the plasma hood is connected with the powder inlet of the powder collector; The powder collector is used to cool and collect the metal oxides generated by the reaction in the plasma cover; the air extraction port of the powder collector is connected to the air extraction system; The exhaust system is used to introduce air into the plasma hood and to extract the generated metal oxides to the powder collector; An electromagnetic winding coil is arranged at the bottom of the plasma furnace, and the electromagnetic winding coil is used to generate an electromagnetic field to electromagnetically stir the molten metal in the plasma furnace.

8. The system for preparing nano metal oxide powder according to claim 7, characterized in that: The feeder includes a rotating table, a lifting platform and a manipulator; wherein: the rotating table and the lifting platform are connected by a connecting rod, the rotating table drives the lifting platform to rotate in the horizontal direction; the manipulator is installed under the lifting platform, and the lifting platform controls the manipulator to rise and fall in the vertical direction.

9. The system for preparing nano metal oxide powder according to claim 7 or 8, characterized in that: A laser rangefinder is provided below the lifting platform, and the laser rangefinder is used to monitor the height of the metal liquid level in the smelting furnace when feeding; The robot is provided with a visual device, and the visual device can identify the shape of the metal block.

10. The system for preparing nano metal oxide powder according to claim 7, characterized in that: A bracket is arranged below the plasma hood, and the plasma hood is placed directly above the plasma furnace through the bracket. The bracket is used to make the plasma hood and the plasma furnace incompletely closed.

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