Method and device for preparing spherical nano aluminum nitride by using plasma

Abstract

The invention provides a method and a device for preparing spherical nano aluminum nitride by using plasma, and relates to the technical field of nano material preparation. According to the method, a plasma technology is adopted, micron aluminum nitride powder is introduced into a hot plasma reactor through carrier gas, and after being introduced into the reactor, the micron aluminum nitride powder is instantly heated to an evaporation state by hot plasma, is cooled to be condensed and nucleated from the evaporation state, and becomes spherical nanoparticles under the action of surface tension. By accurately controlling the feeding amount of the micron aluminum nitride powder and the heating temperature of the thermal plasma reactor, the effective regulation and control of the granularity of the aluminum nitride powder are realized; the cooling rate is high, the length of a heat insulation section of the device is shortened, the oxidation degree of the device is reduced, and produced aluminum nitride is high in purity, spherical in morphology, nanoscale in particle size, high in spheroidization rate and good in particle size uniformity. The spherical nano aluminum nitride prepared by the method provided by the invention has the advantages of large treatment capacity, high production efficiency, safety and controllability, and is suitable for continuous industrial large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of nano material preparation, and in particular to a method and a device for preparing spherical nano aluminum nitride by utilizing plasma. Background Art

[0002] As a key material for making high-frequency and high-power electrical ceramic substrates, aluminum nitride has outstanding advantages such as high thermal conductivity, high mechanical strength, suitable thermal expansion coefficient, good chemical stability, high isolation voltage, high volume resistivity, non-toxic and environmentally friendly, and easy processing. It is listed as a third-generation semiconductor material that needs to be focused on research and development. The quality index of aluminum nitride powder determines whether it has excellent physical and chemical properties. Therefore, in order to obtain aluminum nitride products with high thermal conductivity, it is necessary to prepare aluminum nitride powder with high purity, fine particles, uniform particle size, and good sphericity.

[0003] At present, the synthesis methods of ultrafine aluminum nitride powder mainly include carbon thermal reduction, direct nitridation, self-propagating high-temperature synthesis, liquid phase method and high-energy physics assisted method. However, the above preparation methods have problems such as high energy consumption, uneven product particle size, intermittent production and long cycle, and low yield. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a method and device for preparing spherical nano-aluminum nitride using plasma. The spherical nano-aluminum nitride prepared by the method provided by the present invention has uniform particle size, high spheroidization rate, high yield, high purity, short production cycle, large production process processing capacity, safety and controllability, and is suitable for continuous industrial scale-up production.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing spherical nano-aluminum nitride by using plasma, comprising the following steps:

[0007] Micron aluminum nitride powder is gasified by a carrier gas and sent into a thermal plasma reactor where it is heated to an evaporation state to obtain aluminum nitride vapor, which is then cooled to obtain spherical nano aluminum nitride.

[0008] The feed rate of the micron aluminum nitride powder is 0.5 to 3000 kg / h;

[0009] The heating temperature is 2000-3500K;

[0010] The cooling rate is ≥20000K / s.

[0011] Preferably, the particle size of the micron aluminum nitride powder is 1 to 100 μm, and the purity is 98.0 to 99.5%.

[0012] Preferably, the thermal plasma reactor comprises a radio frequency thermal plasma reactor, a microwave thermal plasma reactor or an arc thermal plasma reactor.

[0013] Preferably, the carrier gas includes one or more of argon, nitrogen, helium and ammonia.

[0014] Preferably, the heating time is in milliseconds.

[0015] Preferably, the cooling includes indirect cooling and / or direct cooling; the indirect cooling includes inter-wall heat exchange cooling; the direct cooling includes quenching gas cooling.

[0016] Preferably, the cooling medium of the inter-wall heat exchange cooling includes water or cooling liquid.

[0017] Preferably, the quenching gas used in the quenching gas cooling includes one or more of argon, nitrogen, helium and ammonia.

[0018] Preferably, the cooling rate is 20000-50000 K / s.

[0019] The present invention also provides a device used in the method described in the above technical solution, comprising a gas supply system 1, a plasma torch 2, a plasma power supply 3, a deposition chamber 4 and a cooling system;

[0020] The plasma torch 2 is connected to the gas supply system 1 and the plasma power supply 3 respectively;

[0021] The cooling system includes a quenching gas cooling system and / or a circulating medium cooling system; the air supply system 1 is connected to the deposition chamber 4 to form a quenching gas cooling system; the cooling medium storage device 5 is connected to the deposition chamber 4 to form the circulating medium cooling system.

[0022] The present invention provides a method for preparing spherical nano aluminum nitride by using plasma, comprising the following steps: micron aluminum nitride powder is gasified by a carrier gas into a thermal plasma reactor and heated to an evaporation state to obtain aluminum nitride vapor, and then cooled to obtain spherical nano aluminum nitride; the feeding amount of the micron aluminum nitride powder is 0.5-3000 kg / h; the heating temperature is 2000-3500 K; the cooling rate is ≥20000 K / s. The present invention adopts plasma technology, and the micron aluminum nitride powder is passed into the thermal plasma reactor through a carrier gas. After the micron aluminum nitride powder is passed into the reactor, it is instantly heated to an evaporation state by the thermal plasma, and is condensed into nuclei from the evaporation state after cooling, and becomes spherical nanoparticles under the action of surface tension. The present invention realizes effective regulation of the particle size of aluminum nitride powder by precisely controlling the feed amount of micron aluminum nitride powder and the heating temperature in the thermal plasma reactor; the present invention adopts a high cooling rate, shortens the length of the insulation section of the device, reduces the time that the aluminum nitride is in the high temperature zone, and thus reduces the degree of oxidation thereof; the produced aluminum nitride has high purity, spherical morphology, nanometer particle size, high spheroidization rate, and good particle size uniformity. The method provided by the present invention is used to produce spherical nano aluminum nitride, with a large processing capacity, high production efficiency, and safe and controllable properties, and is suitable for continuous industrial amplification of spherical nano aluminum nitride. Moreover, the method provided by the present invention does not require a subsequent deposition growth step, the spherical nano aluminum nitride does not agglomerate, the particles have high dispersibility, a simple process, simple operation, and low production cost.

[0023] The smaller the feed amount of micron aluminum nitride powder, the smaller the possibility of non-spheroidized raw materials appearing in the aluminum nitride product. However, too small a feed amount of aluminum nitride will result in too low a production efficiency of spherical nano aluminum nitride. The present invention achieves low-cost and high-efficiency preparation of spherical nano aluminum nitride by controlling the feed amount of micron aluminum nitride powder, and has good economic benefits.

[0024] The device provided by the present invention can produce aluminum nitride with high purity, spherical morphology, nanometer-level particle size, high spheroidization rate, good particle size uniformity, large processing capacity, safe and controllable production process, and is suitable for continuous industrial scale-up production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a diagram of a preparation device for spherical nano-aluminum nitride, wherein 1 is a gas supply system, 2 is a plasma torch, 3 is a plasma power supply, 4 is a deposition chamber, and 5 is a cooling medium storage device;

[0026] Figure 2 This is a production flow chart of spherical nano-aluminum nitride in the embodiment;

[0027] Figure 3 The SEM and XRD images of the flaky micron aluminum nitride powder used in the examples;

[0028] Figure 4 The SEM image and particle size distribution diagram of the spherical nano-aluminum nitride prepared in Example 1;

[0029] Figure 5 The SEM image and particle size distribution diagram of the spherical nano-aluminum nitride prepared in Example 2;

[0030] Figure 6 The SEM image and particle size distribution diagram of the spherical nano-aluminum nitride prepared in Example 3;

[0031] Figure 7 The SEM image and particle size distribution diagram of the spherical nano-aluminum nitride prepared in Example 4;

[0032] Figure 8 The SEM image and particle size distribution diagram of the spherical nano-aluminum nitride prepared in Example 5;

[0033] Fig. 9 XRD diagram of spherical nano-aluminum nitride prepared in Examples 1 to 3;

[0034] Fig.10 This is the XRD diagram of the spherical nano-aluminum nitride prepared in Example 1 and Examples 4-5. DETAILED DESCRIPTION

[0035] The invention provides a method for preparing spherical nano aluminum nitride by utilizing plasma, comprising the following steps: micron aluminum nitride powder is gasified by a carrier gas and fed into a thermal plasma reactor to be heated to an evaporation state to obtain aluminum nitride vapor, and then cooled to obtain spherical nano aluminum nitride; the feeding amount of the micron aluminum nitride powder is 0.5-3000 kg / h; the heating temperature is 2000-3500 K; and the cooling rate is ≥20000 K / s.

[0036] Unless otherwise specified, the materials and equipment used in the present invention are all commercially available products in the art.

[0037] In the present invention, the carrier gas preferably includes one or more of argon, nitrogen, helium and ammonia; when the carrier gas is a mixed carrier gas of two or more, the present invention has no special limitation on the volume ratio of different carrier gases, and any ratio is acceptable. The present invention has no special requirement on the flow rate of the carrier gas, and it only needs to be able to fluidize the micron aluminum nitride powder.

[0038] In the present invention, the particle size of the micron aluminum nitride powder is preferably 1 to 100 μm, and in specific embodiments it can be 1 μm, 3 μm, 5 μm, 7 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm or 100 μm; the purity of the micron aluminum nitride powder is preferably 98.0 to 99.5%, and in specific embodiments it can be 98.0%, 98.5%, 99.0% or 99.5%. In the present invention, the feed rate of the micron aluminum nitride powder is preferably 0.5 to 3000 kg / h, and in a specific embodiment, it can be 0.5 kg / h, 1 kg / h, 2 kg / h, 4 kg / h, 5 kg / h, 6 kg / h, 10 kg / h, 20 kg / h, 50 kg / h, 70 kg / h, 100 kg / h, 500 kg / h, 1000 kg / h, 1500 kg / h, 2000 kg / h, 2500 kg / h or 3000 kg / h. The present invention preferably selects a suitable plasma reactor according to the feed rate of micron aluminum nitride and the required temperature for heating. When the feed rate of micron aluminum nitride increases, the production of spherical nano aluminum nitride increases. The smaller the feed amount of micron aluminum nitride powder, the smaller the possibility of non-spheroidized raw materials appearing in the aluminum nitride product. However, too small a feed amount of aluminum nitride will result in too low a production efficiency of spherical nano aluminum nitride. The present invention achieves low-cost and high-efficiency preparation of spherical nano aluminum nitride by controlling the feed amount of micron aluminum nitride powder, and has good economic benefits.

[0039] In the present invention, the thermal plasma reactor preferably includes a radio frequency thermal plasma reactor, a microwave thermal plasma reactor or an arc thermal plasma reactor; the arc thermal plasma reactor is preferably a DC arc thermal plasma reactor, and more preferably a magnetic rotating arc thermal plasma reactor. In the present invention, the magnetic rotating arc thermal plasma reactor has high mass and heat transfer efficiency, and the material residence time is uniform and easy to control.

[0040] In the present invention, the heating temperature (i.e., the macroscopic temperature of the plasma) is 2000-3500K, and in specific embodiments, it can be 2000K, 2100K, 2200K, 2300K, 2400K, 2500K, 2600K, 2700K, 2800K, 2900K, 3000K, 3100K, 3200K, 3300K, 3400K or 3500K; the heating time is preferably in the millisecond order. After being pushed out by the feeder, the micron aluminum nitride powder is carried by the carrier gas into the high temperature zone of the plasma. Due to the huge temperature difference, the micron aluminum nitride powder can be instantly heated to an evaporation state. The present invention realizes effective regulation of the particle size of the aluminum nitride powder by accurately controlling the feed amount of the micron aluminum nitride powder and the heating temperature in the thermal plasma reactor.

[0041] In the present invention, the cooling preferably includes indirect cooling and / or direct cooling. In the present invention, the indirect cooling preferably includes interlayer heat exchange cooling, and the cooling medium of the interlayer heat exchange cooling preferably includes water or coolant; the present invention has no special limitation on the coolant, and a coolant that can meet the cooling rate of ≥20000K / s known to those skilled in the art can be used. In the present invention, the direct cooling preferably includes quenching gas cooling, and the quenching gas used in the quenching gas cooling preferably includes one or more of argon, nitrogen, helium and ammonia.

[0042] In the present invention, the cooling rate is preferably ≥ 20000K / s, more preferably 20000-50000K / s, and in specific embodiments may be 20000K / s, 21000K / s, 22000K / s, 23000K / s, 24000K / s, 250000K / s, 26000K / s, 27000K / s, 28000K / s, 29000K / s, 30000K / s, 31000K / s, 3200 0K / s, 33000K / s, 34000K / s, 350000K / s, 36000K / s, 37000K / s, 38000K / s, 39000K / s, 40000K / s, 41000K / s, 42000K / s, 43000K / s, 44000K / s, 45000K / s, 46000K / s, 47000K / s, 48000K / s, 49000K / s or 50000K / s. After the evaporated aluminum nitride is cooled, the particles will quickly condense into nuclei, and the particle morphology will become spherical due to the influence of surface tension. Since the cooling rate in the present invention is very fast, the particles can complete the phase change process from solid-liquid-gas to gas-liquid-solid in a very short time, and the process is dispersed by the quenching gas flow, thereby obtaining a nano aluminum nitride powder with good dispersibility, spherical morphology, and uniform particle size. Moreover, since aluminum nitride is particularly easy to be oxidized to form aluminum oxide at high temperatures, the present invention shortens the length of the insulation section of the device, greatly improves the quenching rate, reduces the time that aluminum nitride is in the high temperature zone, and thus reduces the degree of oxidation thereof. The aluminum nitride produced has high purity, spherical morphology, nanometer-level particle size, high spheroidization rate, and good particle size uniformity.

[0043] The method provided by the present invention is suitable for the continuous industrial production of spherical nano-aluminum nitride. Moreover, the method provided by the present invention does not require a subsequent deposition growth step, the spherical nano-aluminum nitride does not agglomerate, the particles have high dispersibility, the process is simple, the operation is simple, and the production cost is low.

[0044] In the present invention, the particle size of the spherical nano-aluminum nitride is preferably 20 to 80 nm, and in specific embodiments may be 37.17±12.67 nm, 44.25±19.55 nm, 54.09±22.86 nm, 56.38±21.88 nm or 57.12±22.11 nm.

[0045] The present invention also provides a device used in the method described in the above technical solution. Figure 1 , the following combination Figure 1 The device is described in detail.

[0046] The device provided by the present invention includes a gas supply system 1, a plasma torch 2, a plasma power supply 3, a deposition chamber 4 and a cooling system; the plasma torch 2 is connected to the gas supply system 1 and the plasma power supply 3 respectively; the cooling system includes a quenching gas cooling system and / or a circulating medium cooling system; the gas supply system 1 is connected to the deposition chamber 4 to form a quenching gas cooling system; the cooling medium storage device 5 is connected to the deposition chamber 4 to form the circulating medium cooling system, and the circulating medium preferably includes water or coolant.

[0047] The device provided by the present invention can produce aluminum nitride with high purity, spherical morphology, nanometer-level particle size, high spheroidization rate, good particle size uniformity, large processing capacity, safe and controllable production process, and is suitable for continuous industrial scale-up production.

[0048] In order to further illustrate the present invention, a method for preparing spherical nano-aluminum nitride by using plasma provided by the present invention is described in detail below in conjunction with embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0049] In the present invention, the device used in the method described in the above technical solution preferably includes a gas supply system, a plasma torch, a plasma power supply, a cooling system and a deposition chamber; the outlet of the gas supply system is connected to the inlet of the plasma torch; the plasma torch is connected to the plasma power supply; the cooling system includes a quenching gas cooling system and / or a circulating medium cooling system.

[0050] The micron aluminum nitride powder used is a flake micron-grade raw material. The SEM and XRD patterns are shown in Figure 3 .

[0051] Example 1

[0052] use Figure 2 The production flow chart for producing spherical nano-aluminum nitride.

[0053] Micron aluminum nitride powder (feed rate of 70 kg / h) is introduced into a rotating arc thermal plasma reactor through carrier gas blowing. After arcing, rotating arc plasma is formed. Under the condition of 3500K, aluminum nitride vapor is obtained after millisecond-level heating. The aluminum nitride vapor is water-cooled to 350K through the partition wall (cooling rate is 30000K / s) to obtain spherical nano aluminum nitride powder.

[0054] SEM images of spherical nano-aluminum nitride powders are shown in Figure 4 The particle size of the aluminum nitride product was statistically analyzed and calculated through SEM images, and the particle size of the spherical nano aluminum nitride powder was 57.12±22.11nm, the average particle size was 57.12nm, and the particle size was uniform.

[0055] The X-ray diffraction pattern of spherical nano-aluminum nitride powder is shown in Fig. 9 (3500K) and Fig.10 (70kg / h), and the results of X-ray diffraction analysis show that the spherical nano-aluminum nitride powder complies with the standard cards of cubic and hexagonal aluminum nitride, respectively, and the spherical nano-aluminum nitride powder prepared by the present invention has high purity.

[0056] Example 2

[0057] Spherical nano-aluminum nitride was prepared according to the method of Example 1, the only difference from Example 1 being that the heating temperature was 3300K.

[0058] SEM images of spherical nano-aluminum nitride powders are shown in Figure 5 The particle size of the aluminum nitride product was statistically analyzed and calculated through SEM images, and the particle size of the spherical nano aluminum nitride powder was 44.25±19.55nm, the average particle size was 44.25nm, and the particle size was uniform.

[0059] The X-ray diffraction pattern of spherical nano-aluminum nitride powder is shown in Fig. 9 (3300K), and the results of X-ray diffraction analysis show that the spherical nano-aluminum nitride powder complies with the standard cards of cubic and hexagonal aluminum nitride, respectively, and the spherical nano-aluminum nitride powder prepared by the present invention has high purity.

[0060] Example 3

[0061] Spherical nano-aluminum nitride was prepared according to the method of Example 1, the only difference from Example 1 being that the heating temperature was 3000K.

[0062] SEM images of spherical nano-aluminum nitride powders are shown in Figure 6 The particle size of the aluminum nitride product was statistically analyzed and calculated through SEM images, and the particle size of the spherical nano aluminum nitride powder was 54.09±22.86nm, the average particle size was 54.09nm, and the particle size was uniform.

[0063] The X-ray diffraction pattern of spherical nano-aluminum nitride powder is shown in Fig. 9 (3000K), and the results of X-ray diffraction analysis show that the spherical nano-aluminum nitride powder complies with the standard cards of cubic and hexagonal aluminum nitride, respectively, and the spherical nano-aluminum nitride powder prepared by the present invention has high purity.

[0064] Example 4

[0065] Micron aluminum nitride powder (feed rate of 20 kg / h) is introduced into a radio frequency thermal plasma reactor through carrier gas blowing. After starting the plasma power supply, thermal plasma is formed in the radio frequency device. Under the condition of 3500K, aluminum nitride vapor is obtained after millisecond-level heating. The aluminum nitride vapor is directly nitrogen quenched (cooling rate of 30000K / s) to 350K to obtain spherical nano aluminum nitride powder.

[0066] SEM images of spherical nano-aluminum nitride powders are shown in Figure 7 The particle size of the aluminum nitride product was statistically analyzed and calculated through SEM images, and the particle size of the spherical nano aluminum nitride powder was 56.38±21.88nm, the average particle size was 56.38nm, and the particle size was uniform.

[0067] The X-ray diffraction pattern of spherical nano-aluminum nitride powder is shown in Fig.10 (20kg / h), and the results of X-ray diffraction analysis show that the spherical nano-aluminum nitride powder complies with the standard cards of cubic and hexagonal aluminum nitride, respectively, and the spherical nano-aluminum nitride powder prepared by the present invention has high purity.

[0068] Example 5

[0069] Spherical nano-aluminum nitride was prepared according to the method of Example 4, the only difference from Example 4 being that the feed rate was 5 kg / h.

[0070] SEM images of spherical nano-aluminum nitride powders are shown in Figure 8 The particle size of the aluminum nitride product was statistically analyzed and calculated through SEM images, and the particle size of the spherical nano aluminum nitride powder was 37.17±12.67nm, the average particle size was 37.17nm, and the particle size was uniform.

[0071] The X-ray diffraction pattern of spherical nano-aluminum nitride powder is shown in Fig.10 (5kg / h), and the results of X-ray diffraction analysis show that the spherical nano-aluminum nitride powder complies with the standard cards of cubic and hexagonal aluminum nitride, respectively, and the spherical nano-aluminum nitride powder prepared by the present invention has high purity.

[0072] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing spherical nano-aluminum nitride using plasma, characterized in that: The following steps are involved: Micron aluminum nitride powder is gasified by a carrier gas and sent into a thermal plasma reactor where it is heated to an evaporation state to obtain aluminum nitride vapor, which is then cooled to obtain spherical nano aluminum nitride. The feed rate of the micron aluminum nitride powder is 0.5 to 3000 kg / h; The heating temperature is 2000-3500K; The cooling rate is ≥20000K / s.

2. The method according to claim 1, characterized in that The particle size of the micron aluminum nitride powder is 1-100 μm, and the purity is 98.0-99.5%.

3. The method according to claim 1 is characterized in that The thermal plasma reactor includes a radio frequency thermal plasma reactor, a microwave thermal plasma reactor or an arc thermal plasma reactor.

4. The method according to claim 1, characterized in that: The carrier gas includes one or more of argon, nitrogen, helium and ammonia.

5. The method according to any one of claims 1 to 4, characterized in that: The heating time is in millisecond order.

6. The method according to claim 1, characterized in that The cooling includes indirect cooling and / or direct cooling; the indirect cooling includes inter-wall heat exchange cooling; the direct cooling includes quenching gas cooling.

7. The method according to claim 6, characterized in that The cooling medium of the inter-wall heat exchange cooling includes water or cooling liquid.

8. The method according to claim 6, characterized in that The quenching gas used in the quenching gas cooling includes one or more of argon, nitrogen, helium and ammonia.

9. The method according to claim 1, 6, 7 or 8, characterized in that: The cooling rate is 20000-50000K / s.

10. The device used in the method according to any one of claims 1 to 9, comprising a gas supply system (1), a plasma torch (2), a plasma power supply (3), a deposition chamber (4) and a cooling system; The plasma torch (2) is connected to the gas supply system (1) and the plasma power supply (3) respectively; The cooling system comprises a quenching gas cooling system and / or a circulating medium cooling system; the air supply system (1) is connected to the deposition chamber (4) to form the quenching gas cooling system; the cooling medium storage device (5) is connected to the deposition chamber (4) to form the circulating medium cooling system.

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