System for preparing nanoparticles and production method

Abstract

The invention belongs to the technical field of nano-particle gas phase preparation, and particularly relates to a system for preparing nano-particles and a production method.The system comprises a precursor atomization device, a combustion reaction chamber and a product collector, the precursor atomization device is arranged at the bottom of the combustion reaction chamber and further connected with a plasma flame generator, and the plasma flame generator is connected with the combustion reaction chamber. The plasma flame generator comprises at least one pair of ignition needle pairs, the bottom ends of the ignition needle pairs are connected with a power source through a high-voltage pack, each ignition needle pair comprises two ignition needles, the two ignition needles are arranged in a mirror symmetry mode, and needle tips of the two ignition needles are opposite and both located above the precursor atomization device. The plasma technology is used for replacing methane-oxygen combustion-supporting flame in traditional flame spray pyrolysis equipment, the problems of safety and low efficiency of current combustible gas combustion-supporting are solved, and on the other hand, high-energy-density, high-temperature and high-speed active particles generated by plasma are used for strengthening efficient combustion of precursor atomized liquid.

Description

Technical Field

[0001] The invention belongs to the technical field of gas phase preparation of nanoparticles, and in particular relates to a system and a production method for preparing nanoparticles. Background Art

[0002] Nanoparticles have many special properties that are different from macroscopic solid materials, making them widely used in catalysis, optical materials, electronic devices, biomedicine and other fields. The flame combustion synthesis method of nanoparticles has the characteristics of simple process, high product purity and easy control. At present, in flame spray pyrolysis equipment, combustible gases such as methane, hydrogen, butane, etc. are generally used as supporting flames. However, these combustible gases pose great safety hazards to laboratories or factory workshops during storage and use. Therefore, it is urgent to design a flame spray pyrolysis method based on other non-combustible gases for gas phase combustion synthesis of nanoparticles. Summary of the invention

[0003] The problem to be solved by the present invention is to provide a system and a production method for preparing nanoparticles.

[0004] In view of the deficiencies of the prior art, the technical solution adopted by the present invention to solve the technical problems is: a system for preparing nanoparticles, the system comprising a precursor atomization device, a combustion reaction chamber and a product collector, the precursor atomization device is arranged at the bottom of the combustion reaction chamber, the precursor atomization device is also connected to a plasma flame generator, the plasma flame generator comprises at least one pair of ignition needles, the bottom ends of the ignition needles are connected to a power supply through a high-voltage package, the ignition needles comprise two ignition needles, the two ignition needles are arranged in mirror symmetry, the needle tips of the two ignition needles are opposite and both are located above the precursor atomization device.

[0005] Preferably, the diameter of the ignition needle is 1 mm to 5 mm, the distance between the needle tips of two ignition needles in the ignition needle pair is 0.5-2 cm, and the ignition needles are wrapped with ceramic except for the needle tips and needle tails.

[0006] Preferably, the ignition needle comprises a vertical rod and a horizontal rod, and the angle formed by the vertical rod and the horizontal rod is 75° to 135°.

[0007] Preferably, when the number of ignition pin pairs is more than one pair, the top view angle between adjacent ignition pins is 60° to 90°, and the vertical distance between two adjacent pairs of ignition pins is 2-4 cm.

[0008] Preferably, the number of the ignition pins is two pairs, and the top view angle between the two pairs of ignition pins is 90°.

[0009] Preferably, the number of the ignition pairs is three.

[0010] Preferably, the power supply configured for the plasma flame generator is a DC power supply or a DC power switch, the power supply voltage is 12-30V, and the current is 5-15A.

[0011] Preferably, the product collector is a membrane filter, a bag filter, an electrostatic precipitator, an electric bag precipitator or a liquid phase collector.

[0012] A method for producing barium titanate nanoparticles includes a plasma flame generator, a precursor atomization device, an oxygen intake structure, a combustion reaction chamber and a product collector, wherein the combustion reaction chamber is connected to the product collector through a connecting pipeline, and the connecting pipeline is connected to the product collector through a three-way valve, the product collector includes a collection box 1 and a collection box 2, and a vacuum gauge is provided between the product collector and the suction mechanism, including the following steps:

[0013] 1. Preparation of precursor liquid: 0.68 g of barium acetate was added to a container containing 50 mL of isooctanoic acid and mixed, heated to 160°C under magnetic stirring until completely dissolved, cooled to room temperature, 50 mL of isooctanoic acid was added, and then 0.75 mL of isopropyl titanate solution was added, and stirred evenly to obtain a precursor mixture;

[0014] 2. Combustion synthesis: Use a high-pressure infusion pump to deliver the heated atomized liquid to the capillary needle of the precursor atomization device at a rate of 3 mL / min. Oxygen is introduced into the oxygen inlet structure at an oxygen flow rate of 2.0 L / min. Turn on the plasma flame generator switch, and plasma flames and active particles are generated between the needle tips of the ignition needles, so that the precursor atomized liquid generated by the precursor atomization device is mixed and burned in the combustion reaction chamber to form products;

[0015] 3. Collection of barium titanate nanoparticles: The combustion products and tail gas in step 2 flow into the product collector through the suction mechanism. The three-way valve first connects the connecting pipeline and the collection box 1. When the collection box 1 is full, the three-way valve is then connected to the connecting pipeline and the collection box 2 to achieve alternating collection and thus achieve the purpose of continuous production. The filter in the product collector is removed to obtain the barium titanate nanopowder product.

[0016] The beneficial effects of the present invention are as follows: 1. The present invention utilizes the high temperature and high energy of the plasma flame to achieve rapid synthesis of nanoparticles and can control the size and composition of the nanoparticles by adjusting the reaction parameters, thereby improving the synthesis efficiency of the nanoparticles.

[0017] 2. The equipment provided by the present invention does not need to use traditional combustible gases, and plasma combustion has extremely high safety and stability, and can be produced continuously for a long time without the problem of combustible gas storage.

[0018] 3. The present invention does not require major changes to the flame spray pyrolysis equipment. The combustible gas energy source is replaced by a plasma generator based on the original system. It has the advantages of low cost, simple device structure, small footprint, low noise and low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the system structure of the present invention;

[0020] Figure 2 It is a schematic diagram of an ignition target according to the present invention;

[0021] Figure 3 It is a schematic diagram of an ignition needle according to the present invention;

[0022] Figure 4 is a schematic diagram of an ignition needle according to another embodiment of the present invention;

[0023] Figure 5 It is a schematic diagram of the arrangement of the ignition targets according to the present invention;

[0024] Figure 6 is a transmission electron microscope (TEM) image of barium titanate nanoparticles prepared according to the system of the present invention;

[0025] Explanation of the reference numerals in the accompanying drawings: 1. Plasma flame generator; 11. Ignition needle pair; 111. Ignition needle; 112. Vertical rod; 113. Horizontal rod; 114. Needle tip; 115. Needle tail; 116. Ceramic material layer; 12. Power supply; 13. High-pressure package; 2. Precursor atomization device; 3. Oxygen intake structure; 4. Air hole plate; 5. Combustion reaction chamber; 6. Connecting pipeline; 7. Product collector; 71. Collection box one; 72. Collection box two; 8. Vacuum gauge; 9. Suction mechanism. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. The embodiments of the present invention are provided for the purpose of illustration and description, and are not intended to be exhaustive or to limit the present invention to the disclosed forms. Many modifications and variations will be apparent to those of ordinary skill in the art. The embodiments are selected and described in order to better illustrate the principles and practical applications of the present invention, and to enable those of ordinary skill in the art to understand the present invention and thereby design various embodiments with various modifications suitable for specific uses.

[0027] As described in the background technology, currently, the flame spray pyrolysis equipment uses combustible gas combustion, such as methane, hydrogen, butane, etc. as supporting flames. However, the storage and use of these combustible gases in the laboratory or factory workshop bring great safety hazards. Therefore, the present invention proposes a system for preparing nanoparticles, the supporting flame of which does not require combustible gas, but is burned with the help of plasma. The system of the present invention includes a precursor atomization device 2, a combustion reaction chamber 5 and a product collector 7. The precursor atomization device 2 is arranged at the bottom of the combustion reaction chamber 5. The precursor atomization device 2 is also connected to a plasma flame generator 1, and the plasma flame generator 1 includes at least one pair of ignition pins 11, and the top view angle of adjacent ignition pins 11 is 60° to 90°. The bottom of the ignition pin 11 is connected to a power supply 12 through a high-voltage package 13. The power supply 12 is a DC power supply or a DC power switch. The voltage of the power supply 12 is 12-30V and the current is 5-15A. The ignition needle pair 11 includes two ignition needles 111, which are arranged in mirror symmetry, and the needle tips of the two ignition needles 111 are opposite and both are located above the precursor atomization device 2. The ignition needle pair 11 is connected to the power supply 12. After the power supply 12 is connected, the precursor liquid atomized droplets burn in the combustion reaction chamber 5. Specifically, the precursor atomization device 2 is equipped with a precursor solution delivery pipeline, and the precursor solution delivery is controlled by the delivery system. The outlet end of the precursor atomization device 2 is provided with an oxygen intake structure 3. Oxygen enters the outlet end of the precursor atomization device 2 through the oxygen intake structure 3, and the plasma flame generator 1 assists in combustion and produces nanoparticles and tail gas. The bottom of the combustion reaction chamber 5 is embedded with a vent plate 4, which is between the inner wall of the combustion reaction chamber 5 and the outer wall of the precursor atomization device 2. It is used to filter air to form an air flow to purge the inner wall of the combustion reaction chamber 5 to prevent nanoparticles from adhering to the inner wall surface of the combustion reaction chamber 5. The combustion reaction chamber 5 is connected to the product collector 7 via a connecting pipe 6. A vacuum gauge 8 is provided at the rear end of the product collector 7, and a pressure difference is generated through a suction mechanism 9 to provide filtering power to collect nanoparticles. The product collector 7 can adopt a filter membrane dust collector, a bag filter, an electrostatic precipitator, an electric bag dust collector or a liquid phase collector, and the specific use is not limited here.

[0028] The plasma flame generator 1 includes at least one pair of ignition needles 11, a high-voltage package 13, and a power supply 12. The high-voltage package 13 converts the low-voltage electricity of the power supply 12 into high-voltage electricity and supplies it to the ignition needle 11. The ignition needle 111 includes a vertical rod 112, a horizontal rod 113, a needle tip 114, a needle tail 115 and a ceramic material layer 116. The diameters of the vertical rod 112 and the horizontal rod 113 are 1 mm to 5 mm, and the angle between the two is in the range of 75° to 135°, which can meet the ignition requirements. Figure 3 The figure shows an embodiment of the ignition needle 111, wherein the angle formed by the vertical rod 112 and the horizontal rod 113 is 75°; Figure 2As shown, the angle between the vertical rod 112 and the horizontal rod 113 is 90°; Figure 4 Another embodiment of the ignition needle 111 is shown, and the angle formed by the vertical rod 112 and the horizontal rod 113 is 135°; Figure 2 As shown, the end of the horizontal rod 113 away from the vertical rod 112 is a needle tip 114, and the distance between the two opposite needle tips 114 in the ignition needle pair 11 is d, and the range of d is 0.5-2cm; the part of the horizontal rod 113 except the needle tip 114 and the part of the vertical rod 112 except the needle tail 115 are covered with a ceramic material layer 116, the needle tail 115 is used to connect to the power supply, and the needle tip 114 is used to generate an electric arc. The ceramic material layer 116 prevents the ignition needle 111 from generating an induced arc with the container wall, ensuring discharge in the area between the two needle tips 114.

[0029] like Figure 5 As shown in Figure b, when there are two pairs of ignition pins 11, the two pairs of ignition pins 11 are cross-released one above and one below, the vertical distance between the two pairs of ignition pins 11 is h, the range of h is 2-4cm, the top view angle between the two pairs of ignition pins 11 is β, the range of β is 60°~90°, and β is 90° as shown in Figure b, thus forming a layered support flame. Figure 5 As shown in Figure c, there are three pairs of ignition pins 11, which are stacked up and down, and the vertical distance between the upper and lower adjacent ignition pins 11 is h, and the range of h is 2-4 cm. The top view angle between the two pairs of ignition pins 11 with a vertical distance h is β, and the range of β is 60° to 90°. As shown in Figure c, β is 90°. The height difference between adjacent ignition pins 11 makes the supporting flame more layered, which is conducive to the precursor atomized liquid to participate in the combustion reaction more fully and improve the reaction efficiency.

[0030] The method for producing barium titanate nanoparticles by using the system of the present invention is as follows: the system components are connected in place, the system includes a plasma flame generator 1, a precursor atomization device 2, an oxygen intake structure 3, a combustion reaction chamber 5 and a product collector 7, the combustion reaction chamber 5 is connected to the product collector 7 through a connecting pipe 6, the connecting pipe 6 is connected to the product collector 7 through a three-way valve, the product collector 7 includes a collection box 1 71 and a collection box 2 72, a vacuum gauge 8 is provided between the product collector 7 and a suction mechanism 9, the vacuum gauge 8 detects the air pressure value, and the suction mechanism 9 is used to suck the combustion tail gas product of the combustion reaction chamber 5 into the product collector 7 for filtration to obtain nano powder. The method for producing barium titanate nanoparticles includes the following steps:

[0031] 1. Preparation of precursor liquid: 0.638 g of barium acetate was added to a container containing 50 mL of isooctanoic acid and mixed, heated to 160°C under magnetic stirring until completely dissolved, cooled to room temperature, added with 50 mL of isooctanoic acid, and then added with 0.75 mL of isopropyl titanate solution, and stirred evenly to obtain a precursor mixture;

[0032] 2. Combustion synthesis: Use a high-pressure infusion pump to deliver the heated atomized liquid to the capillary needle of the precursor atomization device 2 at a rate of 3 mL / min, and introduce oxygen into the oxygen inlet structure 3 at an oxygen flow rate of 2.0 L / min. Turn on the switch of the plasma flame generator 1, and a plasma flame is generated between the needle tips of the ignition needle 111, so that the precursor atomized liquid generated by the precursor atomization device 2 is mixed and burned in the combustion reaction chamber 5 to form products;

[0033] 3. Collection of barium titanate nanoparticles: The combustion products and tail gas in step 2 flow into the product collector 7 through the suction mechanism 9, and the three-way valve first connects the connecting pipe 6 and the collecting box 1 71. When the collecting box 1 71 is full, the three-way valve is then connected to the connecting pipe 6 and the collecting box 2 72 to achieve alternating collection and thus achieve the purpose of continuous production. The filter in the product collector 7 is removed to obtain the barium titanate nanopowder product.

[0034] Figure 6 The figure shows a transmission electron microscope (TEM) picture of barium titanate nanoparticles collected by the method of the present invention. The particle size of the barium titanate nanoparticles is about 20-30 nm, which meets the production requirements.

[0035] In summary, the present invention uses plasma-assisted combustion. As a very promising advanced combustion technology, plasma-assisted combustion does not require the use of combustible gases. It controls the size and composition of nanoparticles by adjusting the chemical reaction parameters during combustion, thereby improving the synthesis efficiency of nanoparticles, making the combustion process more efficient, rapid and low-pollution. Plasma-assisted combustion replaces combustible gases, which greatly ensures production safety.

Claims

1. A system for preparing nanoparticles, the system comprising a precursor atomization device (2), a combustion reaction chamber (5) and a product collector (7), wherein the precursor atomization device (2) is arranged at the bottom of the combustion reaction chamber (5), and is characterized in that: The precursor atomization device (2) is also connected to a plasma flame generator (1), wherein the plasma flame generator (1) comprises at least one pair of ignition pins (11), the bottom ends of the ignition pins (11) are connected to a power source (12) via a high-voltage package (13), the ignition pins (11) comprise two ignition needles (111), the two ignition needles (111) are arranged in mirror symmetry, and the needle tips of the two ignition needles (111) are opposite to each other and are both located above the precursor atomization device (2).

2. The device for preparing nanoparticles according to claim 1, characterized in that: The diameter of the ignition needle (111) is 1 mm to 5 mm, the distance between the needle tips of two ignition needles (111) in the ignition needle pair (11) is 0.5 to 2 cm, and the ignition needle (111) is wrapped with ceramic except for the needle tip and the needle tail.

3. The device for preparing nanoparticles according to claim 2, characterized in that: The ignition needle (111) comprises a vertical rod (112) and a horizontal rod (113), and the angle formed by the vertical rod (112) and the horizontal rod (113) is 75° to 135°.

4. The device for preparing nanoparticles according to claim 3, characterized in that: When the number of the ignition pins (11) is more than one pair, the top view angle between the adjacent ignition pins (11) is 60° to 90°, and the vertical distance between the two adjacent pairs of ignition pins (11) is 2-4 cm.

5. The device for preparing nanoparticles according to claim 4, characterized in that: The number of the ignition pins (11) is two pairs, and the top view angle between the two pairs of ignition pins (11) is 90°.

6. The device for preparing nanoparticles according to claim 4, characterized in that: The number of the ignition pair (11) is three.

7. A system for preparing nanoparticles according to any one of the preceding claims, characterized in that: The power supply (12) configured for the plasma flame generator (1) is a direct current power supply or a direct current power switch, and the voltage of the power supply (12) is 12-30V and the current is 5-15A.

8. The device for preparing nanoparticles according to claim 1, characterized in that: The product collector (7) is a filter membrane dust collector, a bag filter, an electrostatic precipitator, an electric bag dust collector or a liquid phase collector.

9. A method for producing barium titanate nanoparticles, comprising a plasma flame generator (1), a precursor atomization device (2), an oxygen intake structure (3), a combustion reaction chamber (5) and a product collector (7), wherein the combustion reaction chamber (5) is connected to the product collector (7) via a connecting pipe (6), the connecting pipe (6) is connected to the product collector (7) via a three-way valve, the product collector (7) comprises a collecting box 1 (71) and a collecting box 2 (72), a vacuum gauge (8) is provided between the product collector (7) and the suction mechanism (9), and characterized in that: The following steps are included:

1. Preparation of precursor liquid: 0.68 g of barium acetate was added to a container containing 50 mL of isooctanoic acid and mixed, heated to 160°C under magnetic stirring until completely dissolved, cooled to room temperature, 50 mL of isooctanoic acid was added, and then 0.75 mL of isopropyl titanate solution was added, and stirred evenly to obtain a precursor mixture; 2. Combustion synthesis: A high-pressure infusion pump is used to deliver the heated atomized liquid to the capillary needle of the precursor atomization device (2) at a rate of 3 mL / min. Oxygen is introduced into the oxygen inlet structure (3) at an oxygen flow rate of 2.0 L / min. The switch of the plasma flame generator (1) is turned on, and plasma flames and active particles are generated between the needle tips of the ignition needle (111), so that the precursor atomized liquid generated by the precursor atomization device (2) is mixed and burned in the combustion reaction chamber (5) to form products; 3. Collection of barium titanate nanoparticles: The combustion products and tail gas in step 2 flow into the product collector (7) through the suction mechanism (9), and the three-way valve first connects the connecting pipe (6) and the collecting box 1 (71). When the collecting box 1 (71) is full, the three-way valve is then connected to the connecting pipe (6) and the collecting box 2 (72), so as to realize alternating collection and achieve the purpose of continuous production. The filter in the product collector (7) is removed to obtain the barium titanate nanopowder product.

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