AU2021100590A4

AU2021100590A4 - Method for preparing high-purity aluminum nitride through auto-catalysis

Info

Publication number: AU2021100590A4
Application number: AU2021100590A
Authority: AU
Inventors: Yuwei Tian; Shiming XU; Yongbin Xu
Original assignee: Shandong Hengjing New Material Co Ltd
Current assignee: Shandong Hengjing New Material Co Ltd
Priority date: 2020-07-31
Filing date: 2021-01-29
Publication date: 2021-04-22
Anticipated expiration: 2029-01-29
Also published as: CN111825066A; CN111825066B

Abstract

The present disclosure discloses a method for preparing high-purity AIN through auto-catalysis and belongs to the technical field of synthesis of AIN. The method includes the following steps of: (1) mixing of materials: uniformly mixing aluminum hydroxide powder, carbon powder and AIN powder as raw materials according to a certain weight ratio to obtain a material mixture; (2) high-temperature synthesis: subjecting the material mixture to reaction in a mixed gas flow of nitrogen and propane at a certain pressure for 1.5 h to 3 h at 13500C to 14200C to obtain a reaction product; and (3) decarbonization: decarbonizing the reaction product to obtain AIN powder. According to the method for preparing high-purity AIN through auto-catalysis of the present disclosure, the AIN is used as seed crystal, and the reaction is conducted in the mixed gas flow of the nitrogen and the propane at a certain pressure. Therefore, thermal motion of reactive molecules is enhanced, diffusion rate and permeation rate are increased, an auto-catalysis effect is achieved, the reaction synthesis time is shortened, and the temperature for reaction synthesis is lowered by 2000 C to 4000 C. Moreover, pollution caused by impurity elements introduced by adding other additives is avoided, and therefore the purity of the prepared AIN is guaranteed.

Description

AUSTRALIA

Patents Act 1990

COMPLETE SPECIFICATION

Invention title:

"METHOD FOR PREPARING HIGH PURITY ALUMINUM NITRIDE THROUGH AUTO-CATALYSIS"

Applicant:

SHANDONG HENGJING NEW MATERIAL CO., LTD.

Associated provisional applications:

The following statement is a full description of the invention, including the best method of performing it known to me:

"METHOD FOR PREPARING HIGH-PURITY ALUMINUM NITRIDE THROUGH AUTO-CATALYSIS"

Field of the Invention

[0001] The present disclosure relates to a method for preparing high-purity aluminum nitride (AIN) through auto-catalysis, and belongs to the technical field of synthesis of AIN.

Background to the Invention

[0002] AIN features high thermal conductivity, low dielectric constant, desirable insulativity, high mechanical strength, and an expansion coefficient matched with a silicon chip. Therefore, it is extremely suitable for preparing circuit substrates and red phosphor (CaASiN3:Eu) for white light-emitting diodes (LEDs), with a huge demand and wide application potential in the market.

[0003] The shape, purity, particle size, oxygen content and content of other impurities of the AIN directly affect the properties, such as thermal conductivity, of an AIN ceramic material, as well as a sintering and forming process of the material. For example, a high content of impurities in AIN powder will result in poor sintering property of the AIN powder. As a result, it is difficult to prepare compact AIN ceramics, and the thermal conductivity of the ceramic will be far lower than a theoretical value. Moreover, AIN is a covalent compound with a low self-diffusion coefficient, and it is difficult to implement sintering densification due to uneven particle size and shape. Therefore, an AIN product with excellent properties can be obtained only by AIN powder with a high purity, a small particle size, narrow particle size distribution and a stable performance.

[0004] There are various methods for preparing AIN, such as a direct aluminum powder nitriding method, a carbothermic reduction method, a chemical vapor deposition method, a self-propagating combustion synthesis method and a microwave synthesis method. All these methods have the disadvantages of high cost, difficulty in mass production, defective crystal form and low purity of synthesized AIN. Moreover, the prepared AIN powder is complicated in shape, which leads to poor fluidity, relatively low packing density and influences on thermal conductivity of a material. A conventional carbothermal reduction method can realize mass production, but the obtained AIN has a low purity due to a high synthesis temperature and a long reaction time. Therefore, the current method for preparing AIN is to be further improved.

[0005] It should be noted that the above descriptions belong to the technical cognitive category of the inventor and do not necessarily constitute the prior art.

Summary of the Invention

[0006] To address the problems in the prior art, the present disclosure provides a method for preparing high-purity AIN through auto-catalysis to achieve an auto-catalysis effect, shorten the reaction synthesis time, lower the temperature for reaction synthesis and improve the purity of an obtained product.

[0007] The above objective of the present disclosure is realized by the following technical solution.

[0008] A method for preparing high-purity AIN through auto-catalysis includes the following steps of: (1) mixing of materials: uniformly mixing aluminum hydroxide powder, carbon powder and AIN powder as raw materials according to a certain weight ratio to obtain a material mixture; (2) high-temperature synthesis: subjecting the material mixture to reaction in a mixed gas flow of nitrogen and propane at a certain pressure for 1.5 h to 3 h at 13500 C to 1420 0C to obtain a reaction product; and (3) decarbonization: decarbonizing the reaction product to obtain AIN powder.

[0009] Optionally, the weight ratio of the aluminum hydroxide powder to the carbon powder to the AIN powder may be (60-72):(30-39):(1.6-2.2).Optionally, the aluminum hydroxide powder may have a purity of 5N and a particle size of 1 pm to 2 pm, and preferably 1 pm to 1.5 pm.

[0010] Optionally, the AIN powder may have a purity of 5N and a particle size of 0.05 pm to 0.075 pm, and preferably 0.05 pm to 0.06 pm.

[0011] Optionally, the carbon powder may have a purity of 4N and a particle size of 2 pm to 4 pm, preferably 2 pm to 3 pm.

[0012] Optionally, the carbon powder maybe prepared from graphite, carbon black or activated carbon, preferably from activated carbon; and the activated carbon powder can accelerate carbonization due to its high specific surface area and optimal porosity.

[0013] Optionally, the pressure of the mixed nitrogen and propane may be 0.2 MPa to 0.6 MPa, and preferably 0.4 MPa to 0.5 MPa.

[0014] Optionally, a volume ratio of the nitrogen to the propane may be 1:(0.01-0.02), and preferably 1:(0.011-0.013).

[0015] Optionally, the high-temperature synthesis instep (2) may specifically include: (2.1) introducing nitrogen into a pusher tunnel furnace to completely exhausttheairin the pusher tunnel furnace, heating the pusher tunnel furnace until a temperature of a high-temperature zone in the pusher tunnel furnace reaches 1350 0C to 14200 C, introducing propane into the pusher tunnel furnace, heating continuously to maintain the temperature in the pusher tunnel furnace, and maintaining a velocity of the mixed gas flow of the nitrogen and the propane to be 0.2 L/min to 0.5 L/min; and (2.2) putting the material mixture in a carbonaceous crucible, moving the crucible at a certain velocity in a reaction furnace, and allowing the material mixture to be in the high-temperature zone in the reaction furnace for 1.5 h to 3 h.

[0016] Further, there may be seven temperature control zones in the tunnel furnace, and the temperatures in the seven temperature control zones are controlled to be: 300C+/-5C, 600C+/-5C, 900C+/-5C, 1200C+/-5C, (1350-1420)°C+/-5 0 C, (1350-1420)°C+/-5 0 C, 0 C, and (1350-1420)°C+/-5 respectively.

[0017] Optionally, the carbonaceous crucible may be a graphite crucible.

[0018] Optionally, the pusher tunnel furnace may adopt a graphite push plate.

[0019] Optionally, the decarbonization in step (3) may specifically include: after the reaction product is discharged from the reaction furnace, decarbonizing it in an oxidation furnace for 1 h to 3 h at 6000 C to 7000 C, and cooling it to room temperature to obtain AIN powder.

[0020] Further, the decarbonization may be conducted preferably at 6400 C to 6600 C preferably for 2.2 h.

[0021] Optionally, the mixing of the materials in step (1) may specifically include: mixing the aluminum hydroxide powder, the carbon powder and the AIN powder in a mixer for 12 h to 18 h at a rotating speed of 12 rpm to 20 rpm.

[0022] Further, the materials may be mixed preferably for 12 h to 14 h preferably at a rotating speed of 14 rpm to 16 rpm.

[0023] Optionally, the method for preparing high-purity AIN may further include a step (4) of purification: stirring and mixing the obtained AIN powder with pure water with a conductivity smaller than 0.06 S/m for 25 min to 35 min to obtain first slurry, dehydrating the first slurry to obtain a first powder cake, uniformly mixing the obtained first powder cake with pure water to obtain second slurry, dehydrating the second slurry to obtain a second powder cake, and repeating these steps for a plurality of times to obtain a pure AIN powder cake, wherein a weight ratio of the pure water to the AIN is (3-4):(0.1-1.2); and drying the obtained powder cake at 100 0C to 110 0 C and sieving it through a 100-mesh sieve to obtain high-purity AIN powder.

[0024] Further, the weight ratio of the pure water to the AIN during purification may be preferably (3-4):1.

[0025] The beneficial effects of the present disclosure include, but are not limited to, the following.

[0026] According to the method for preparing high-purity AIN through auto catalysis provided by the present disclosure, (1) AIN with fine crystal grains and a large specific surface area is used as seed crystal. During reaction, the AIN seed crystal induces carbonized aluminum ions and nitrogen ions to be gathered toward the seed crystal. In this way, thermal motion of reactive molecules is enhanced, diffusion rate and permeation rate are increased, an auto-catalysis effect is achieved and reaction synthesis time is shortened. In addition, the binding capacity of the aluminum ions and the nitrogen ions is increased due to addition of the AIN seed crystal, and thus formation of a covalent-bond compound is facilitated. Furthermore, the use of the AIN as the seed crystal also prevents pollution caused by impurity elements introduced by adding other additives, and therefore the purity of the prepared AIN is guaranteed. (2) The synthesis reaction is conducted in the mixed gas flow of the nitrogen and the propane at a certain pressure. Therefore, the concentration of CO generated in the reaction is lowered to facilitate forward reaction. In addition, the propane facilitates generation of intermediate-phase aluminum carbide, thereby facilitating binding of the aluminum ions and the nitrogen ions to form an AIN covalent-bond compound, and improving the reaction efficiency. Furthermore, according to the method for preparing high-purity AIN through auto-catalysis provided by the present disclosure, the high- temperature synthesis reaction is preferably conducted in a pusher tunnel furnace, and continuous production is achieved. Therefore, the synthesis reaction is kept consistent in temperature and time, to guarantee the stability and uniformity of properties as well as high purity of an AIN product.

Detailed Description

[0027] The present disclosure will be further described in detail below. It should be noted that the following detailed description merely provides specific operation examples of the present disclosure in an exemplary manner, without limiting the protection scope of the present disclosure. The protection scope of the present disclosure is defined by the claims only. Those skilled in the art can apparently know that various other improvements and substitutions of the description of the present disclosure can be provided within the protection scope limited by the claims of the present disclosure, which can still achieve the same technical effects and realize the final technical purpose of the present disclosure.

[0028] The present disclosure will be described in detail below in conjunction with examples.

[0029] Unless otherwise specified, each raw material mentioned in the description is commercially available. To avoid repetition, technical parameters involved in each example are jointly described as follows: the aluminum hydroxide powder has a purity of 5N and a particle size of 1 pm to 2 pm and is purchased from Shandong Hengjing New Material Co., Ltd; the activated carbon powder has a purity of 4N and a particle size of 2 pm to 4 pm and is purchased from Liyang Chenfeng Activated Carbon Co., Ltd; the AIN powder has a purity of 5N and a particle size of 0.05 pm to 0.075 pm and is purchased from Shandong Hengjing New Material Co., Ltd; parameters of the pusher tunnel furnace: a furnace chamber has effective dimensions of 12,000 mm x 270 mm x 220 mm (length x width x height); a tungsten wire heating tube and a graphite push plate (with dimensions of 250 mm x 250 mm x 40 mm) are adopted; the interior of the pusher tunnel furnace is sequentially divided into a furnace body feeding transition zone with a length of 500 mm, a feeding zone with a length of 1,000 mm, temperature control zones (seven temperature zones in total, where each temperature zone has a length of 800 mm) with a total length of 5,600 mm, and a cooling zone with a length of 4,900 mm.

[0030] An inlet of the pusher tunnel furnace is in a temperature of 500 C to 0C and an outlet in a temperature of 800 C to 1000 C.

[0031] Example 1: A method for preparing high-purity AIN through auto catalysis in this example includes the following steps of: (1) mixing of materials: (1.1) feeding of materials: dust and foreign matters on the surfaces of raw material bags containing aluminum hydroxide powder, carbon powder and AIN powder respectively were wiped away with a clean towel; 72 kg of the aluminum hydroxide powder, 39 kg of the carbon powder and 2.0 kg of the AIN powder were respectively added into a mixing barrel on a mixer; a screw which was arranged on the mixing barrel and used for fixing a barrel cover was tightened; and the mixer was started to mix the materials for 12 h at a rotating speed of 15 rpm to obtain a material mixture; (1.2) discharging of the materials: after the materials were mixed for a specified time, a switch of the mixer was controlled to make sure that a discharging port of the mixer was vertically downward; dust on the outer surface of the mixing barrel and a discharging port was wiped away with a clean towel; a prepared raw material barrel was placed below the discharging port; a valve was opened to discharge the material mixture; and (1.3) charging of the materials: during charging, an operator held a graphite crucible with the left hand, charged the material mixture into the graphite crucible in a way that an upper opening of the crucible abutted against the edge of the raw material barrel, and pushed the crucible to the front end of the tunnel furnace.

(2) High-temperature synthesis:

(2.1) a nitrogen flow with a pressure of 0.4 MPa was introduced into the tunnel furnace; the tunnel furnace was electrified and heated when it was full of nitrogen; temperatures of the seven temperature zones were set to be 300 0C, 600 0C, 900 0C, 1200 0C, 1420 0 C, 14200 C and 14200 C, respectively, where the temperature zones at 14200 C were high-temperature zones; after the temperature of each high-temperature zone reached 1420 0 C, a propane flow with a volume which is 1.2% of the total volume of the nitrogen was replenished into the nitrogen flow to form a mixed gas flow of the nitrogen and the propane; the tunnel furnace was heated again for 3 h under a condition that a velocity of the mixed gas flow was controlled to be 0.2 L/min and a pressure of the mixed gas flow was controlled to be 0.4 MPa to guarantee a uniformity of a synthesis atmosphere for later feeding; and (2.2) nitridation synthesis: the crucible with the material mixture was placed on a push plate; a pushing time of a push plate timer was regulated; and the crucible was automatically moved a distance equal to a length of one push plate every 17 min (the movement distance of the push plate was equal to the length of the push plate) to obtain a reaction product. (3) Decarbonization: the reaction product was discharged from the reaction furnace, cooled in air, decarbonized in an oxidation furnace for 1.5 h at 6500 C, cooled to a room temperature and discharged from the oxidation furnace to obtain AIN powder. (4) Purification: the obtained AIN powder was added into pure water with a conductivity smaller than 0.06 S/m, where a weight ratio of the pure water to the AIN powder was 3:1; the resulting mixture was stirred for 30 min to obtain first slurry; the first slurry was dehydrated in a centrifugal machine to obtain a first AIN powder cake; the dehydrated first AIN powder cake was added into pure water with a weight which was 3 times the weight of the first powder cake; the resulting mixture was stirred for 30 min to obtain second slurry; the second slurry was dehydrated in the centrifugal machine; and after these steps were repeated three times, the obtained second AIN powder cake was transferred to an enamelled tray, dried at 1050 C and sieved through a 100-mesh sieve to obtain high-purity AIN powder.

[0032] Example 2: The difference between this example and Example 1 was: 70 kg of the aluminum hydroxide powder, 36 kg of the carbon powder and 2.2 kg of the AIN powder were used; during mixing, the mixer worked for 18 h at a rotating speed of 12 rpm; in the reaction furnace, a velocity of the mixed gas flow was controlled to be 0.4 L/min; a pressure of the mixed gas flow was controlled to be 0.2 MPa; an amount of the introduced propane was 1.0% of that of the nitrogen; a temperature in the reaction furnace was 1350°C; the crucible was placed on the push plate and was automatically pushed a distance equal to a length of one push plate every 12 min; the decarbonization was conducted for 2 h at 6000 C in the oxidation furnace; and the other operations were the same.

[0033] Example 3: The difference between this example and Example 1 was: 60 kg of the aluminum hydroxide powder, 30 kg of the carbon powder and 1.6 kg of the AIN powder were used; during mixing, the mixer worked for 12 h at a rotating speed of 20 rpm; in the reaction furnace, a velocity of the mixed gas flow was controlled to be 0.5 L/min; a pressure of the mixed gas flow was controlled to be 0.3 MPa; an amount of the introduced propane was 1.2% of that of the nitrogen; a temperature in the reaction furnace was 1400°C; the crucible was placed on the push plate and was automatically pushed a distance equal to a length of one push plate every 14 min; the decarbonization was conducted for 1.7 h at 7000 C in the oxidation furnace; and the other operations were the same.

[0034] Example 4: The difference between this example and Example 1 was:

65 kg of the aluminum hydroxide powder, 35 kg of the carbon powder and 2.1 kg of the AIN powder were used; during mixing, the mixer worked for 14 h at a rotating speed of 18 rpm; in the reaction furnace, a velocity of the mixed gas flow was controlled to be 0.3 L/min; a pressure of the mixed gas flow was controlled to be 0.5 MPa; an amount of the introduced propane was 1.1% of that of the nitrogen; a temperature in the reaction furnace was 1380°C; the crucible was placed on the push plate and was automatically pushed a distance equal to a length of one push plate every 15 min; the decarbonization was conducted for 1.5 h at 6200 C in the oxidation furnace; and the other operations were the same.

[0035] Example 5: The difference between this example and Example 1 was: 63 kg of the aluminum hydroxide powder, 33 kg of the carbon powder and 1.8 kg of the AIN powder were used; during mixing, the mixer worked for 13 h at a rotating speed of 17 rpm; in the reaction furnace, a velocity of the mixed gas flow was controlled to be 0.2 L/min; a pressure of the mixed gas flow was controlled to be 0.6 MPa; an amount of the introduced propane was 1.2% of that of the nitrogen; a temperature in the reaction furnace was 1420°C; the crucible was placed on the push plate and was automatically pushed a distance equal to a length of one push plate every 13 min; the decarbonization was conducted for 2.2 h at 6700 C in the oxidation furnace; and the other operations were the same.

Detection Results (1) Contents of Elements(%)

[0036] The contents of key elements in the AIN product prepared by each example of the present disclosure were detected by using inductively coupled plasma (ICP) spectrometry, and the results were shown in Table 1 below.

Table 1 Contents of Key Elements in the AIN Product Prepared by Each Example of the Present Disclosure

Element Contents Measured Contents ppm wt s ppm wt Example Example 2 Example 3 Example4 Example

>99.9 99.999:2 99.99917 99.99915 99.99931

C ] <3 2 1.6 1.5 1.5 1.0 0 ][ <2 | 1.5 ][ 1.8 ] 2 [ 1.6 | 1.5 Cu <0.5 0.5 0.5 0.5 0.5 0.5 Fe <1 1 1 1 1 1 Mg ] <1 0.5 0.5 0.5 0.5 0.5 Na <3 1 1 1 1 1 Ca ] <1 0.5 0.7 0.5 0.5 0.2 Si <3 1 1.2 1.5 1.0 1.3

Particle Size

[0037] The AIN products prepared by the examples of the present disclosure were subjected to particle size analysis by using a Bettersize laser particle size analyzer (BT-9300S), where a diameter (D50) was 2.118 pm.

[0038] Comparative Example 1: The difference between this comparative example and Example 1 was: The aluminum hydroxide powder was replaced with aluminum oxide powder (with a purity of 5N and a particle size of 2 pm to 3 pm); 100 kg of the aluminum oxide powder, 39 kg of the carbon powder and 2 kg of the AIN powder were used; and the other operations were the same.

[0039] Comparative Example 2: The difference between this comparative example and Example 1 was: 0.5 kg of the AIN powder was used; and the other operations were the same.

[0040] Comparative Example 3: The difference between this comparative example and Example 1 was: the step (2.1) included: a nitrogen flow with a pressure of 0.4 MPa was introduced into the tunnel furnace; the tunnel furnace was electrified and heated to 1420 0C after it was full of the nitrogen and was heated again for 3 h under a condition that a velocity of the nitrogen flow was controlled to be 0.2 L/min for later feeding; and the other operations were the same.

[0041] Comparative Example 4: The difference between this comparative example and Example 1 was: the step (2.1) included: a nitrogen flow with a pressure of 0.4 MPa was introduced into the tunnel furnace; the tunnel furnace was electrified and heated after it was full of the nitrogen; after a temperature in each high temperature zone in the tunnel furnace reached 14200 C, a propane flow with a volume which was 3.0% of the total volume of the nitrogen was replenished into the nitrogen flow to form a mixed gas flow of the nitrogen and the propane; the tunnel furnace was heated again for 3 h under a condition that a velocity of the mixed gas flow was controlled to be 0.2 L/min and a pressure of the mixed gas flow was controlled to be 0.4 MPa for later feeding; and the other operations were the same.

[0042] Comparative Example 5: The difference between this comparative example and Example 1 was: the step (2.1) included: a nitrogen flow with a pressure of 0.4 MPa was introduced into the tunnel furnace; the tunnel furnace was electrified and heated after it was full of the nitrogen; after a temperature in each high temperature zone in the tunnel furnace reached 11000 C, a propane flow with a volume which was 1.2% of the total volume of the nitrogen into the nitrogen flow to form a mixed gas flow of the nitrogen and the propane; the tunnel furnace was heated again for 3 h under a condition that a velocity of the mixed gas flow was controlled to be 0.2 L/min and a pressure of the mixed gas flow was controlled to be 0.4 MPa for later feeding; and the other operations were the same.

Detection Results of Contents of Elements

[0043] The contents of key elements in the AIN product prepared by each comparative example of the present disclosure were detected by using inductively coupled plasma (ICP) spectrometry, and the results were shown in Table 2 below.

Table 2 Contents of Key Elements in the AIN Product Prepared by Each Comparative Example of the Present Disclosure

Eleme Measured Contents ppm wt nts Comparative Comparative Comparative Comparative Comparative Example 1 Example 2 Example 3 Example 4 Example 5 C 60 >200 50 27 >200 0 >200 ]| >200 75 32 >200

[Cu ~ 1 1 1 1 1 Fe 1.2 1.2 1.2 1.2 1.2 Mg 0.5 0.5 0.5 0.5 0.5

[Na ~ 1 1 1 1 1 Ca 0.5 0.5 0.5 0.5 0.5

[Si] 1 1 1 1 1 1

[0044] The results of comparison between the Comparative Example 1 and the examples of the present disclosure showed that aluminum hydroxide had a higher activity than aluminum oxide and lowered the requirements of synthesis. High-purity aluminum oxide was a product generated by high temperature dehydration and phase transfer of aluminum hydroxide. During this process, the cost was greatly increased. Moreover, pollution and cross pollution were generated by extraneous elements during phase transfer. According to the present disclosure, the aluminum oxide powder was replaced with the aluminum hydroxide powder, and during nitridation, hydroxyl ions facilitated the reaction. By comparing the data in Table 1 with the data in Table 2, it can be seen that the contents of impurity elements in the AIN product prepared by the Comparative Example 1 were higher, and the contents of impurity elements in the AIN products prepared by the examples of the present disclosure were extremely low.

[0045] The results of comparison between the Comparative Example 2 and the examples of the present disclosure showed that when too little AIN seed crystal was added, incomplete reaction was caused at the same synthesis temperature within the same synthesis time, and impurity phases were generated in the product.

[0046] The results of comparison between the Comparative Example 3 and the examples of the present disclosure showed that if no propane was introduced into the reaction furnace, namely the reaction was conducted in a nitrogen atmosphere only, the reaction velocity was lowered, incomplete reaction was caused, and the obtained AIN contained aluminum hydroxide.

[0047] The results of comparison between the Comparative Example 4 and the examples of the present disclosure showed that when a large amount of propane was introduced into the reaction furnace, water molecules were generated during reaction, and an actual synthesis temperature was lowered. As a result, the nitrodation velocity was affected, and aluminum hydroxide in the obtained product was not transformed completely.

[0048] The results of comparison between the Comparative Example 5 and the examples of the present disclosure showed that when the temperature for the reaction was excessively low, incomplete reaction occurred within the same synthesis time, and an impurity phase was generated in the product.

[0049] The above examples cannot be considered as a limitation to the protection scope of the present disclosure. Any substitution, improvement or modification of the present disclosure made by those skilled in the art shall fall within the protection scope of the present disclosure.

[0050] Anything not described in detail in the present disclosure may be a widely-known technology for those skilled in the art.

Claims

Claims 1. A method for preparing high-purity aluminum nitride (AIN) through auto catalysis, comprising the following steps of: (1) mixing of materials: uniformly mixing aluminum hydroxide powder, carbon powder and AIN powder as raw materials according to a certain weight ratio to obtain a material mixture; (2) high-temperature synthesis: subjecting the material mixture to reaction in a mixed gas flow of nitrogen and propane at a certain pressure for 1.5 h to 3 h at 13500 C to 1420 0C to obtain a reaction product; and (3) decarbonization: decarbonizing the reaction product to obtain AIN powder.
2. The method for preparing high-purity AIN through auto-catalysis according to claim 1, wherein the weight ratio of the aluminum hydroxide powder to the carbon powdertotheAINpowder is (60-72):(30-39):(1.6-2.2); wherein the aluminum hydroxide powder has a purity of 5N and a particle size of 1 pm to 2 pm; the AIN powder has a purity of 5N and a particle size of 0.05 pm to 0.075 pm; and the carbon powder has a purity of 4N and a particle size of 2 pm to 4 pm, and is prepared from graphite, carbon black or activated carbon, preferably from activated carbon; wherein a pressure of the mixed nitrogen and propane is 0.2 MPa to 0.6 MPa; wherein a volume ratio of the nitrogen to the propane is 1:(0.01-0.02)%.
3. The method for preparing high-purity AIN through auto-catalysis according to claim 1, wherein the high-temperature synthesis in step (2) specifically comprises: (2.1) introducing nitrogen into a pusher tunnel furnace to completely exhaust the air in the pushertunnel furnace, heating the pushertunnel furnace until a temperature of a high-temperature zone in the pusher tunnel furnace reaches 1350 0C to 14200 C, introducing propane into the pusher tunnel furnace, heating continuously to maintain the temperature in the pusher tunnel furnace, and maintaining a velocity of the mixed gas flow of the nitrogen and the propane to be 0.2 L/min to 0.5 L/min; and (2.2) putting the material mixture in a carbonaceous crucible, moving the crucible at a certain velocity in a reaction furnace, and allowing the material mixture to be in the high-temperature zone in the reaction furnace for 1.5 h to 3 h; wherein there are seven temperature control zones in the tunnel furnace, and the temperatures in the seven temperature control zones are controlled to be: 300C+/-5C, 600C+/-5C, 900C+/-5C, 1200C+/-5C, (1350-1420)°C+/-5 0 C, (1350-1420)°C+/-5 0 C, 0 C, and (1350-1420)°C+/-5 respectively.
4. The method for preparing high-purity AIN through auto-catalysis according to claim 1, wherein the decarbonization in step (3) specifically comprises: after the reaction product is discharged from the reaction furnace, decarbonizing it in an oxidation furnace for 1 h to 3 h at 6000 C to 7000 C, and cooling it to room temperature to obtain AIN powder; wherein the mixing of the materials in step (1) specifically comprises: mixing the aluminum hydroxide powder, the carbon powder and the AIN powder in a mixer for 12 h to 18 h at a rotating speed of 12 rpm to 20 rpm.
5. The method for preparing high-purity AIN through auto-catalysis according to claim 1, further comprising a step (4) of purification: stirring and mixing the obtained AIN powder with pure water with a conductivity smaller than 0.06 S/m for 25 min to 35 min to obtain first slurry; dehydrating the first slurry to obtain a first powder cake; uniformly mixing the obtained first powder cake with pure water to obtain second slurry; dehydrating the second slurry to obtain a second powder cake; repeating these steps for a plurality of times to obtain a pure AIN powder cake, wherein a weight ratio of the pure water to the AIN is (3-4):(0.1-1.2); and drying the obtained powder cake at 100 0C to 110 0 C and sieving it through a 100-mesh sieve to obtain high-purity AIN powder.

SHANDONG HENGJING NEW MATERIAL CO., LTD. By its Patent Attorneys ARMOUR IP

P2411AUOO