Method of forming aluminum nitride powder

Abstract

A method for forming aluminum nitride powder includes: (a) mixing alumina powder and carbon powder to form a mixture, wherein the specific surface area of ​​the carbon powder is 1000 m². 2 / g to 3000 m 2 / g; (b) heating the mixture under nitrogen to nitride the aluminum oxide powder to form aluminum nitride powder; and (c) heating the aluminum nitride powder and unreacted carbon powder under oxygen-containing gas to remove the unreacted carbon powder.

Description

Technical Field

[0001] The present disclosure relates to a method for forming aluminum nitride powder, and more particularly to the specific surface area of the carbon powder used therein. Prior Art

[0002] Aluminum nitride (AlN) has high thermal conductivity and excellent electrical insulation properties. Its coefficient of thermal expansion (4.5×10-6 / ˚C) is closer to that of gallium nitride (5.6×10-6 / ˚C) than other substrate materials such as silicon (4.2×10-6 / ˚C) or silicon carbide (3.7×10-6 / ˚C). Therefore, it is suitable for use in semiconductor and microelectronic circuit packaging substrates, high-brightness LED chip heat dissipation substrates, automotive electronics and lighting components, and high-frequency and high-power electronic component substrates.

[0003] The carbothermal reduction nitridation method produces aluminum nitride by heating a mixture of aluminum oxide and carbon powder under nitrogen. The aluminum oxide and carbon powder raw materials commonly used have relatively small specific surface areas (< 100 m² / g). The small interstices and contact area between the particles of the aluminum oxide and carbon powder mixture affect the reaction rate of the aluminum oxide to aluminum nitride, resulting in low batch yields and longer synthesis times for aluminum nitride powder, leading to higher production costs. Therefore, there is an urgent need to reduce the cost of aluminum nitride formation methods. Summary of the Invention

[0004] An embodiment of the present disclosure provides a method for forming aluminum nitride powder, comprising: (a) mixing aluminum oxide powder and carbon powder to form a mixture, wherein the carbon powder has a specific surface area of 1000 m2 / g to 3000 m2 / g; (b) heating the mixture under nitrogen to nitride the aluminum oxide powder to form aluminum nitride powder; and (c) heating the aluminum nitride powder and unreacted carbon powder under an oxygen-containing gas to remove the unreacted carbon powder.

[0005] In some embodiments, the average particle size of the carbon powder is 2 μm to 40 μm.

[0006] In some embodiments, the weight ratio of alumina powder to carbon powder is 1:0.5 to 1:1.

[0007] In some embodiments, the temperature of heating the mixture in step (b) is 1450°C to 1850°C.

[0008] In some embodiments, the oxygen-containing gas in step (c) comprises atmospheric air, oxygen, or a combination thereof.

[0009] In some embodiments, the temperature at which the aluminum nitride powder and the unreacted carbon powder are heated in step (c) is 600°C to 750°C.

[0010] In some embodiments, the weight of the alumina powder in step (a) is 100 g to 1000 g. Simple diagram description

[0011] FIG1 is an XRD pattern of the product, such as aluminum nitride powder, in the embodiments of the present disclosure. FIG. 2 is an XRD pattern of the product, such as aluminum nitride powder, in the embodiments of the present disclosure. FIG3 is an XRD pattern of the product, such as aluminum nitride powder, in the embodiments of the present disclosure. Implementation Method

[0012] One embodiment of the present disclosure provides a method for forming aluminum nitride powder, comprising: (a) mixing aluminum oxide powder and carbon powder to form a mixture, wherein the carbon powder has a specific surface area of 1000 m² / g to 3000 m² / g. In some embodiments, the carbon powder may have a specific surface area of 1500 m² / g to 2500 m² / g, such as 1900 m² / g to 2300 m² / g. The mixture essentially contains only aluminum oxide powder and carbon powder, without a binder such as a resin, an additive such as a fluoride or boride, or a combination thereof, to prevent impurities in the final product, such as aluminum nitride powder. If the specific surface area of the carbon powder is too small, the carbon powder and nitrogen gas will not react sufficiently with the aluminum oxide powder, thereby reducing the nitriding effect of the aluminum oxide powder. In some embodiments, the average particle size (D50) of the carbon powder is 2 μm to 40 μm. If the average particle size of the carbon powder is too large or too small, the carbon powder may not mix smoothly with the alumina powder, reducing the nitriding effect of the alumina powder. In some embodiments, the weight ratio of alumina powder to carbon powder is 1:0.5 to 1:1. If the carbon powder ratio is too low, the alumina powder cannot be fully nitrided. If the carbon powder ratio is too high, additional removal of unreacted carbon powder is required, increasing costs.

[0013] After step (a), the above method proceeds to step (b) of heating the mixture under nitrogen to nitride the aluminum oxide powder to form aluminum nitride powder. This step is known as the carbothermal reduction method, and the reaction is as follows: Al 2O 3+ N 2+ 3C → 2AlN + 3CO

[0014] In some embodiments, the temperature at which the mixture is heated in step (b) is between 1450°C and 1850°C. If the heating temperature in step (b) is too low, the nitriding effect of the aluminum oxide may be poor. If the heating temperature in step (b) is too high, the product, such as aluminum nitride powder, may easily agglomerate and grow into larger particles. Generally, step (b) requires continuous nitrogen flow and exhaust of nitrogen and reaction gases, such as carbon monoxide, at a nitrogen flow rate of 20 L / min to 40 L / min. The above nitrogen flow rate range is provided for illustrative purposes only and is not intended to limit the present disclosure. Those skilled in the art can adjust the nitrogen flow rate range based on parameters such as the volume of the apparatus used for step (b), the amounts of aluminum oxide and carbon powder used, or the reaction temperature.

[0015] After step (b), the method proceeds to step (c) of heating the aluminum nitride powder and unreacted carbon powder in an oxygen-containing gas to remove the unreacted carbon powder. In some embodiments, the oxygen-containing gas in step (c) comprises atmospheric air, oxygen, or a combination thereof. Generally, step (c) requires continuous introduction of the oxygen-containing gas and exhaust of the oxygen-containing gas and reaction-generated gases, such as carbon monoxide and / or carbon dioxide, with the oxygen-containing gas introduced at a flow rate of 20 L / min to 100 L / min. The above oxygen-containing gas flow rate range is provided for illustrative purposes only and is not intended to limit the present disclosure. Persons skilled in the art may adjust the oxygen-containing gas flow rate range based on parameters such as the volume of the apparatus performing step (c), the amount of unreacted carbon powder, or the reaction temperature.

[0016] In some embodiments, the temperature at which the aluminum nitride powder and unreacted carbon powder are heated in step (c) is between 600°C and 750°C. If the heating temperature in step (c) is too high, the aluminum nitride powder may be oxidized into aluminum oxide powder. If the heating temperature in step (c) is too low, the unreacted carbon powder may not be oxidized effectively, and the unreacted carbon powder may not be effectively removed.

[0017] In some embodiments, the weight of the aluminum oxide powder in step (a) is 100 g to 1000 g. Since the method disclosed herein can nitride a large amount of aluminum oxide powder into aluminum nitride powder in batches, the manufacturing cost can be reduced.

[0018] To make the above contents and other purposes, features, and advantages of the present disclosure more clearly understood, the following embodiments are specifically cited and described in detail with reference to the accompanying drawings: [Example]

[0019] In the following examples, the average particle size (D50) of the powder was measured using a laser particle size analyzer, and the specific surface area of the powder was measured according to ASTM D 6556. The nitridation rate of aluminum nitride powder was measured using X-ray diffraction. The peak intensities of the main peaks of aluminum nitride and aluminum oxide were compared. The nitridation rate was calculated using the formula "Nitridation rate (%) = (Q / R) × 100." Q is the aluminum nitride peak intensity, and R is the sum of the aluminum nitride peak intensity and the aluminum oxide peak intensity.

[0020] Example 1 50 g of aluminum oxide powder (AKP) (purchased from Sumitomo Chemical, with an average particle size (D50) of 0.65 μm and a specific surface area of 4.5 m2 / g) was mixed with 50 g of carbon powder (ACSCA, purchased from Zhongtan, with an average particle size (D50) of 6.51 μm and a specific surface area of 1923 m2 / g) and placed in a crucible. Nitrogen was introduced (at a flow rate of 40 L / min) and the mixture was heated to 1450°C for 10 hours to form aluminum nitride powder. Air was then introduced (at a flow rate of 60 L / min) and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 2 hours to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, which was then removed. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 1, and its nitridation yield is 82.86%.

[0021] Comparative Example 1 50 g of aluminum oxide powder (AKP) and 50 g of carbon powder (N330, purchased from CABOT, with an average particle size (D50) of 30 nm and a specific surface area of 85 m2 / g) were mixed and placed in a crucible. Nitrogen gas (at a flow rate of 40 L / min) was introduced and heated to 1450°C for 10 hours to form aluminum nitride powder. Air (at a flow rate of 60 L / min) was then introduced and the aluminum nitride powder and unreacted carbon powder were heated to 700°C for 2 hours to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, which was then removed. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 1, and its nitridation yield is 42.15%.

[0022] Comparative Example 2 50 g of aluminum oxide powder (AKP) and 50 g of carbon powder (N990, purchased from Cen Yi Chemical, with an average particle size (D50) of 300 nm and a specific surface area of 8 m2 / g) were mixed and placed in a crucible. Nitrogen gas was introduced (at a flow rate of 40 L / min) and heated to 1450°C for 10 hours to form aluminum nitride powder. Air was then introduced (at a flow rate of 60 L / min) and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 2 hours. The unreacted carbon powder was oxidized to carbon monoxide or carbon dioxide, which was then removed. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 1, and its nitridation yield is 39.73%.

[0023] It can be seen from Example 1, Comparative Example 1, and Comparative Example 2 that if the specific surface area of the carbon powder is too low, the nitriding rate of the product, such as aluminum nitride powder, will be low.

[0024] Example 2-1 50 g of aluminum oxide powder (AKP) and 50 g of carbon powder (ACSCA) were mixed and placed in a crucible to a thickness of 4 mm. Nitrogen was introduced (at a flow rate of 40 L / min) and heated to 1550°C for 10 hours under nitrogen to form aluminum nitride powder. Then, atmospheric air (at a flow rate of 100 L / min) was introduced and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 2 hours under atmospheric air to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, removing the unreacted carbon powder. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 2, and the nitridation yield is 99.53%.

[0025] Example 2-2 150 g of aluminum oxide powder (AKP) and 150 g of carbon powder (ACSCA) were mixed and placed in a crucible to a thickness of 12 mm. Nitrogen was introduced (at a flow rate of 40 L / min) and heated to 1550°C for 10 hours under nitrogen to form aluminum nitride powder. Then, atmospheric air (at a flow rate of 100 L / min) was introduced and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 2 hours under atmospheric air to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, removing the unreacted carbon powder. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 2, and the nitridation yield is 99.47%.

[0026] Example 2-3 250 g of aluminum oxide powder (AKP) and 250 g of carbon powder (ACSCA) were mixed and placed in a crucible to a thickness of 20 mm. Nitrogen was introduced (at a flow rate of 40 L / min) and heated to 1550°C for 10 hours under nitrogen to form aluminum nitride powder. Air was then introduced (at a flow rate of 100 L / min) and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 2 hours under atmospheric pressure to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, removing the unreacted carbon powder. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 2, and the nitridation yield is 99.27%.

[0027] As can be seen from Examples 2-1 to 2-3, the above method can produce aluminum nitride powder in large quantities, which is beneficial to reducing costs.

[0028] Example 3-1 250 g of aluminum oxide powder (AKP) and 250 g of carbon powder (ACSCA) were mixed and placed in a crucible. Nitrogen was introduced (at a flow rate of 40 L / min) and heated to 1680°C for 10 hours under nitrogen to form aluminum nitride powder. Air was then introduced (at a flow rate of 100 L / min) and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 3 hours under atmospheric pressure to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, removing the unreacted carbon powder. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 3, and the nitridation yield is 99.54%.

[0029] Example 3-2 666.6 g of aluminum oxide powder (AKP) and 333.3 g of carbon powder (ACSCA) were mixed and placed in a crucible. Nitrogen was introduced (at a flow rate of 40 L / min) and heated to 1680°C for 10 hours under nitrogen to form aluminum nitride powder. Air was then introduced (at a flow rate of 100 L / min) and the aluminum nitride powder and unreacted carbon powder were heated to 700°C and reacted for 3 hours under atmospheric pressure to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, removing the unreacted carbon powder. The product, aluminum nitride powder, was then cooled. Its XRD pattern is shown in Figure 3, and the nitridation yield is 99.27%.

[0030] Example 4 250 g of aluminum oxide powder (AKP) and 250 g of carbon powder (ACS20R4, purchased from Zhongtan, with an average particle size (D50) of 36.35 μm and a specific surface area of 2138 m² / g) were mixed and placed in a crucible. Nitrogen gas (at a flow rate of 40 L / min) was introduced and heated to 1680°C for 10 hours to form aluminum nitride powder. Air (at a flow rate of 100 L / min) was then introduced and the aluminum nitride powder and unreacted carbon powder were heated to 700°C for 3 hours to oxidize the unreacted carbon powder to carbon monoxide or carbon dioxide, which was then removed. The resulting aluminum nitride powder was then cooled, with a nitridation rate of 98.98%.

[0031] Although the present disclosure has been disclosed above with reference to several embodiments, this is not intended to limit the present disclosure. Anyone with ordinary skill in the art may make any changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the scope of protection of the present disclosure shall be determined by the scope of the appended patent applications.

[0032] none

Claims

1. A method for forming aluminum nitride powder, comprising: (a) Mixing alumina powder and carbon powder to form a mixture, wherein the carbon powder has a specific surface area of ​​1000 m² / g to 3000 m² / g and an average particle size of 2 μm to 40 μm; (b) Heating the mixture under nitrogen to nitrify the alumina powder to form aluminum nitride powder; and (c) Heating the aluminum nitride powder and unreacted carbon powder under oxygen-containing gas to remove the unreacted carbon powder.

2. The method for forming aluminum nitride powder as described in claim 1, wherein the weight ratio of the alumina powder to the carbon powder is 1:0.5 to 1:

1.

3. The method for forming aluminum nitride powder as claimed in claim 1, wherein step (b) involves heating the mixture at a temperature of 1450˚C to 1850˚C.

4. The method for forming aluminum nitride powder as described in claim 1, wherein the oxygen-containing gas in step (c) includes the atmosphere, oxygen, or a combination thereof.

5. The method for forming aluminum nitride powder as claimed in claim 1, wherein step (c) heats the aluminum nitride powder and the unreacted carbon powder at a temperature of 600˚C to 750˚C.

6. The method for forming aluminum nitride powder as described in claim 1, wherein the weight of the alumina powder in step (a) is from 100 g to 1000 g.

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