Aluminum nitride powder preparation method

Abstract

The present invention relates to the technical field of aluminum nitride synthesis, and specifically discloses a method for preparing aluminum nitride powder, S1, aluminum powder and aluminum nitride powder are mixed to obtain a first mixture; aluminum chloride powder and ammonium salt are mixed to obtain a second mixture; S2, the first mixture is spread on a material frame padded with a first carbon felt, and the second mixture is sealed in a closed container surrounded by the second carbon felt, and the closed container is on the upper surface, lower surface or middle position of the first mixture; S3, vacuuming and injecting nitrogen, and applying electricity to induce the first mixture to undergo a self-propagating combustion synthesis reaction, and to cause the second mixture to undergo a gas phase synthesis reaction. This key technology combines combustion synthesis with gas phase synthesis to overcome the problems of difficult control of combustion synthesis of aluminum nitride, low purity of the obtained product, and coarse and uneven grain size, and can simultaneously prepare micron-level powder and nano-level powder by partitioning.

Description

Technical Field

[0001] The invention relates to the technical field of aluminum nitride synthesis, and in particular to a method for preparing aluminum nitride powder. Background Art

[0002] Aluminum nitride is a new type of high-performance ceramic material and an important III-group wide-bandgap semiconductor material. It has excellent properties such as high thermal conductivity, low dielectric constant, and thermal expansion coefficient close to that of silicon. It is an ideal material for electronic circuit substrates and thermal conductive fillers, and has great application prospects in the field of microelectronic packaging. The preparation of high-quality aluminum nitride powder is the key to its application performance.

[0003] At present, the commonly used methods for preparing aluminum nitride powder are: carbon thermal reduction method, direct nitridation method, gas phase reaction method and combustion synthesis method. The carbon thermal reduction method is to use C powder to convert Al 2 O 3 The powder is reduced and nitrided at high temperature, and then decarbonized at 600-700°C to finally obtain aluminum nitride powder; the direct nitridation method refers to placing Al powder in a nitrogen and ammonia gas flow and applying high temperature to nitride to form aluminum nitride powder; the above two methods have long cycles, high energy consumption, low efficiency and high cost.

[0004] The gas phase reaction method refers to the use of aluminum alkoxide or halide and NH 3 or N 2 A chemical reaction occurs to deposit aluminum nitride from the gas phase; the combustion synthesis method is a method that uses necessary external energy to induce a local chemical reaction in the reaction system, and the reaction continues with the support of the heat released by itself, ultimately converting the reactants into products.

[0005] Most of the patents on gas-phase synthesis of aluminum nitride that have been disclosed so far focus on the preparation of aluminum nitride films, while the patents on combustion synthesis of aluminum nitride that have been disclosed all have some limitations. Chen Kexin et al. invented "A method for preparing high-performance aluminum nitride powder by combustion synthesis" (CN1321621A), first pre-treating the aluminum powder by pickling and other methods, then adding ammonium salts and other nitrides for 20 to 30 hours of wet grinding, drying, and then performing combustion synthesis under a nitrogen pressure of 1 to 4.5 MPa; this method is cumbersome and time-consuming, and too many types of additives are added, which greatly increases the impurity content of the product, which is not conducive to large-scale production. Zhuang Hanrui et al.'s invention patent "Self-propagating high-temperature synthesis of aluminum nitride powder preparation method" (CN1142477A) uses a higher content of Al powder, resulting in a higher reaction temperature and larger aluminum nitride particles. At the same time, the amount of ammonium salt added is too high, resulting in more impurities in the aluminum nitride product, which is not conducive to industrial application. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing aluminum nitride powder, which can prepare micron-level and nano-level aluminum nitride powders in different regions. The prepared aluminum nitride powder has good product uniformity and high purity, and the production method is simple and low in cost.

[0007] To achieve the above object, the technical solution adopted by the present invention is: A method for preparing aluminum nitride powder comprises the following steps: S1. Ingredients: Mix 20-40 parts of aluminum powder and 60-80 parts of aluminum nitride powder by weight to obtain a first mixture; mix aluminum chloride powder and ammonium salt by molar ratio to obtain a second mixture; S2, cloth: after vacuum drying the first mixture of step S1, evenly spread it on a material frame padded with a first carbon felt, place an ignition wire at the end of the material frame and add an ignition agent; after vacuum drying the second mixture of step S1, seal it in a sealed container surrounded by a second carbon felt; the sealed container is on the upper surface, lower surface or middle position of the first mixture; S3, combustion reaction: placing the material frame of step S2 into a high-pressure combustion synthesis reactor, evacuating the reactor, injecting nitrogen, and controlling the pressure at 1.0 MPa-2.0 MPa, then passing an electric current to induce the first mixture to undergo a self-propagating combustion synthesis reaction, and utilizing the heat released by the self-propagating combustion synthesis reaction to cause the second mixture to undergo a gas phase synthesis reaction; S4. After the reaction is completed, the mixture is cooled to room temperature, the pressure in the high-pressure combustion synthesis reactor is released, and the product is taken out, wherein the synthetic product of the first mixture is micron-grade powder after fine grinding, and the synthetic product of the second mixture is nano-grade powder.

[0008] Preferably, the mixing in step S1 is performed by mixing in a jar mill.

[0009] Preferably, the average particle size of the aluminum powder is in the range of 2 μm to 74 μm, and the average particle size of the aluminum nitride powder is in the range of 5 μm to 20 μm.

[0010] Preferably, the ammonium salt is ammonium chloride, and the molar ratio of the aluminum chloride powder to ammonium chloride is 1:1.

[0011] Preferably, the ammonium salt is ammonium carbonate, and the molar ratio of the aluminum chloride powder to ammonium carbonate is 1:2.

[0012] Preferably, the vacuum drying process of the first mixture and the second mixture in step S2 is as follows: vacuum degree is -0.2 MPa to -0.5 MPa, temperature is 100° C. to 110° C., and time is 45 min to 80 min.

[0013] Preferably, the ignition wire in step S2 is a spiral tungsten wire.

[0014] Preferably, the ignition agent in step S2 is titanium powder.

[0015] Preferably, the current in step S3 is 10A-30A, and the power-on time is 5 seconds-10 seconds.

[0016] Preferably, the average particle size of the synthetic product of the first mixture after fine grinding is in the range of 1 μm to 3 μm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The key technology of the aluminum nitride powder preparation method proposed in the present invention is the combination of combustion synthesis and gas phase synthesis to overcome the problems of difficult control of the combustion synthesis of aluminum nitride, low purity of the obtained product, coarse and uneven grain size, and micron-level powder and nano-level powder can be prepared in different areas at the same time.

[0018] The method of combining combustion synthesis with gas phase synthesis of the present invention has the advantages that: 1. Combustion synthesis combined with chemical furnace is adopted, which is easy to operate.

[0019] 2. The process is simple and the production cycle is short. When the first mixture is 0.5 kg to 2 kg, the self-propagating combustion synthesis reaction time is 10 min to 30 min.

[0020] 3. Low energy consumption. In addition to a small amount of energy input to start the combustion reaction, the synthesis of materials relies on the heat released by the reaction system itself, saving energy. The large amount of heat generated during the combustion synthesis process is used to promote the gas phase synthesis reaction, and micron- and nano-scale aluminum nitride powders with uniform morphology are synthesized in different regions at high efficiency and low cost.

[0021] 4. The present invention improves the problems of too high reaction temperature, too fast reaction speed, difficult reaction control and coarse product grains in the traditional combustion synthesis process. By regulating the coordination of the exothermic reaction of combustion synthesis and the endothermic reaction of gas phase synthesis, the endothermic balance of the reaction process is achieved, and aluminum nitride powder with high purity, uniform morphology and fine grains is synthesized. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the second mixture fabric of the present invention 1.

[0023] Figure 2 This is a schematic diagram of the second mixture fabric of the present invention 2.

[0024] Figure 3 This is a schematic diagram of the second mixture fabric of the present invention 3.

[0025] Figure 4 This is a SEM image of the nanoscale powder of Example 1 of the present invention.

[0026] Figure 5 This is the XRD image of the micron-sized powder of Example 1 of the present invention. DETAILED DESCRIPTION

[0027] Example 1 This embodiment provides a method for preparing aluminum nitride powder, comprising the following steps: S1. Ingredients: Mix 30 parts of aluminum powder and 70 parts of aluminum nitride powder by weight, wherein the average particle size range of the aluminum powder is 20 μm, and the average particle size range of the aluminum nitride powder is 8 μm, to obtain a first mixture. Mix aluminum chloride powder and ammonium salt by molar ratio, wherein the ammonium salt is ammonium chloride, and the molar ratio of the aluminum chloride powder to the ammonium chloride is 1:1, to obtain a second mixture. The mixing of the first mixture and the mixing of the second mixture are both mixed by a pot mill, with a rotation speed of 150 r / min and a mixing time of 30 min.

[0028] S2, cloth: before cloth, the first mixture and the second mixture are vacuum dried respectively, specifically: vacuum degree is -0.5MPa, temperature is 100℃, and time is 60min; after vacuum drying, the first mixture of step S1 is evenly spread on a material frame padded with a first carbon felt, a Φ0.5mm spiral tungsten wire is placed at the end of the material frame as an ignition wire and titanium powder is added as an ignition agent; after vacuum drying, the second mixture of step S1 is sealed in a sealed container surrounded by a second carbon felt; the sealed container is on the upper surface of the first mixture, such as Figure 1 shown.

[0029] S3, combustion reaction: the material frame of step S2 is placed in a high-pressure combustion synthesis reactor, evacuated, and nitrogen is injected. The pressure is controlled at 2.0 MPa, and then a 25A pulse current is introduced for a duration of 10 seconds to heat the spiral tungsten wire and heat the first mixture in contact with it to a temperature at which aluminum and nitrogen react. Then the pulse power supply is turned off, and the chemical reaction is promoted layer by layer in a self-propagating manner to carry out a self-propagating combustion synthesis reaction, and the heat released by the self-propagating combustion synthesis reaction is used to cause the second mixture to undergo a gas phase synthesis reaction.

[0030] S4. After the reaction is completed, a uniform product without a sandwich is obtained, which is cooled to room temperature, the pressure in the high-pressure combustion synthesis reactor is released, and the product is taken out, wherein the synthetic product of the first mixture is finely ground into a micron-sized powder with an average particle size range of 1.51 μm, and the XRD spectrum shows that the obtained product is aluminum nitride of wurtzite without impurity peaks, and the purity of the aluminum nitride powder is greater than 98%, and the synthetic product of the second mixture is a nanometer-sized powder.

[0031] Example 2 This embodiment provides a method for preparing aluminum nitride powder, comprising the following steps: S1. Ingredients: Mix 20 parts of aluminum powder and 80 parts of aluminum nitride powder by weight, wherein the average particle size range of the aluminum powder is 10 μm, and the average particle size range of the aluminum nitride powder is 5 μm, to obtain a first mixture. Aluminum chloride powder and ammonium salt are mixed in molar ratio to obtain a second mixture, wherein the ammonium salt is ammonium carbonate, and the molar ratio of the aluminum chloride powder to ammonium carbonate is 1:2. This design allows the hydrogen chloride generated by the reaction to react with the remaining ammonium carbonate and be consumed, thereby reducing the corrosion of hydrogen chloride to the reactor. The mixing of the first mixture and the mixing of the second mixture are both mixed by a pot mill, with a rotation speed of 150 r / min and a mixing time of 30 min.

[0032] S2, cloth: before cloth, the first mixture and the second mixture are vacuum dried respectively, specifically: vacuum degree is -0.5MPa, temperature is 100℃, and time is 60min; after vacuum drying, the first mixture of step S1 is evenly spread on a material frame padded with a first carbon felt, a Φ0.5mm spiral tungsten wire is placed at the end of the material frame as an ignition wire and titanium powder is added as an ignition agent; after vacuum drying, the second mixture of step S1 is sealed in a sealed container surrounded by a second carbon felt; the sealed container is at the middle position of the first mixture, such as Figure 2 shown.

[0033] S3, combustion reaction: the material frame of step S2 is placed in a high-pressure combustion synthesis reactor, evacuated, and nitrogen is injected. The pressure is controlled at 2.0 MPa, and then a 25A pulse current is introduced for a duration of 10 seconds to heat the spiral tungsten wire and heat the first mixture in contact with it to a temperature at which aluminum and nitrogen react. Then the pulse power supply is turned off, and the chemical reaction is promoted layer by layer in a self-propagating manner to carry out a self-propagating combustion synthesis reaction, and the heat released by the self-propagating combustion synthesis reaction is used to cause the second mixture to undergo a gas phase synthesis reaction.

[0034] S4. After the reaction is completed, a uniform product without a sandwich is obtained, which is cooled to room temperature, the pressure in the high-pressure combustion synthesis reactor is released, and the product is taken out, wherein the synthetic product of the first mixture is finely ground into a micron-sized powder with an average particle size range of 1.03 μm, and the XRD spectrum shows that the obtained product is aluminum nitride of wurtzite without impurity peaks, and the purity of the obtained aluminum nitride powder is greater than 98%, and the synthetic product of the second mixture is a nanometer-sized powder.

[0035] Example 3 This embodiment provides a method for preparing aluminum nitride powder, comprising the following steps: S1. Ingredients: Mix 40 parts of aluminum powder and 60 parts of aluminum nitride powder by weight, wherein the average particle size range of the aluminum powder is 30 μm, and the average particle size range of the aluminum nitride powder is 10 μm, to obtain a first mixture. Aluminum chloride powder and ammonium salt are mixed in molar ratio to obtain a second mixture, wherein the ammonium salt is ammonium carbonate, and the molar ratio of the aluminum chloride powder to ammonium carbonate is 1:2. This design allows the hydrogen chloride generated by the reaction to react with the remaining ammonium carbonate and be consumed, thereby reducing the corrosion of hydrogen chloride to the reactor. The mixing of the first mixture and the mixing of the second mixture are both mixed by a pot mill, with a rotation speed of 150 r / min and a mixing time of 30 min.

[0036] S2, cloth: before cloth, the first mixture and the second mixture are vacuum dried respectively, specifically: vacuum degree is -0.5MPa, temperature is 100℃, and time is 60min; after vacuum drying, the first mixture of step S1 is evenly spread on the material frame padded with the first carbon felt, a Φ0.5mm spiral tungsten wire is placed at the end of the material frame as an ignition wire and titanium powder is added as an ignition agent; after vacuum drying, the second mixture of step S1 is sealed in a sealed container surrounded by the second carbon felt; the sealed container is on the lower surface of the first mixture, such as Figure 3 shown.

[0037] S3, combustion reaction: the material frame of step S2 is placed in a high-pressure combustion synthesis reactor, evacuated, and nitrogen is injected. The pressure is controlled at 2.0 MPa, and then a 25A pulse current is introduced for a duration of 10 seconds to heat the spiral tungsten wire and heat the first mixture in contact with it to a temperature at which aluminum and nitrogen react. Then the pulse power supply is turned off, and the chemical reaction is promoted layer by layer in a self-propagating manner to carry out a self-propagating combustion synthesis reaction, and the heat released by the self-propagating combustion synthesis reaction is used to cause the second mixture to undergo a gas phase synthesis reaction.

[0038] S4. After the reaction is completed, a uniform product without a sandwich is obtained, which is cooled to room temperature, the pressure in the high-pressure combustion synthesis reactor is released, and the product is taken out, wherein the synthetic product of the first mixture is finely ground into a micron-sized powder with an average particle size range of 2.25 μm, and the XRD spectrum shows that the obtained product is aluminum nitride of wurtzite without impurity peaks, and the purity of the obtained aluminum nitride powder is greater than 98%, and the synthetic product of the second mixture is a nanometer-sized powder.

[0039] The chemical formula for synthesizing the micron powders of the above-mentioned embodiments 1-3 is: The main chemical equation (one of them) for the synthesis of the nanopowders in the above-mentioned Examples 1-3 is: The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for illustrating the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which shall fall within the scope of the present invention to be protected. The scope of protection of the present invention shall be defined by the attached claims and their equivalents.

Claims

1. A method for preparing aluminum nitride powder, characterized in that: The following steps are involved: S1. Ingredients: Mix 20-40 parts of aluminum powder and 60-80 parts of aluminum nitride powder by weight to obtain a first mixture; mix aluminum chloride powder and ammonium salt by molar ratio to obtain a second mixture; S2, cloth: after vacuum drying the first mixture of step S1, evenly spread it on a material frame padded with a first carbon felt, place an ignition wire at the end of the material frame and add an ignition agent; after vacuum drying the second mixture of step S1, seal it in a sealed container surrounded by a second carbon felt; the sealed container is on the upper surface, lower surface or middle position of the first mixture; S3, combustion reaction: placing the material frame of step S2 into a high-pressure combustion synthesis reactor, evacuating the reactor, injecting nitrogen, and controlling the pressure at 1.0 MPa-2.0 MPa, then passing an electric current to induce the first mixture to undergo a self-propagating combustion synthesis reaction, and utilizing the heat released by the self-propagating combustion synthesis reaction to cause the second mixture to undergo a gas phase synthesis reaction; S4. After the reaction is completed, the mixture is cooled to room temperature, the pressure in the high-pressure combustion synthesis reactor is released, and the product is taken out, wherein the synthetic product of the first mixture is micron-grade powder after fine grinding, and the synthetic product of the second mixture is nano-grade powder.

2. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The mixing in step S1 is performed by mixing in a jar mill.

3. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The average particle size of the aluminum powder is in the range of 2 μm to 74 μm, and the average particle size of the aluminum nitride powder is in the range of 5 μm to 20 μm.

4. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The ammonium salt is ammonium chloride, and the molar ratio of the aluminum chloride powder to the ammonium chloride is 1:

1.

5. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The ammonium salt is ammonium carbonate, and the molar ratio of the aluminum chloride powder to ammonium carbonate is 1:

2.

6. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The vacuum drying process of the first mixture and the second mixture in step S2 is specifically as follows: the vacuum degree is -0.2MPa to -0.5MPa, the temperature is 100°C to 110°C, and the time is 45min to 80min.

7. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The ignition wire in step S2 is a spiral tungsten wire.

8. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The ignition agent in step S2 is titanium powder.

9. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The current of step S3 is 10A-30A, and the power-on time is 5 seconds-10 seconds.

10. The method for preparing aluminum nitride powder according to claim 1, characterized in that: The average particle size of the synthetic product of the first mixture after fine grinding is in the range of 1 μm to 3 μm.

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