Method for forming aluminum nitride powder

Abstract

The invention discloses a method for forming aluminum nitride powder, which comprises the following steps: (a) mixing aluminum oxide powder and carbon powder to form a mixture, and the specific surface area of the carbon powder is 1000m < 2 > / g to 3000m < 2 > / g; (b) heating the mixture under nitrogen to nitride the alumina powder to form an aluminum nitride powder; and (c) heating the aluminum nitride powder and the unreacted carbon powder under oxygen-containing gas to remove the unreacted carbon powder.

Description

Technical Field

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

[0002] Aluminum nitride (AlN) has high thermal conductivity, good electrical insulation, and a thermal expansion coefficient (4.5×10 -6 / °C) 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 can be applied to products such as semiconductor and microelectronic circuit packaging substrates, high-brightness LED chip heat dissipation substrates, automotive electronics and lighting components, high-frequency and high-power electronic component substrates, etc.

[0003] The carbothermal reduction nitridation method is a method of obtaining aluminum nitride by heating a mixture of aluminum oxide and carbon powder under nitrogen to nitride aluminum oxide. Generally used raw materials of aluminum oxide and carbon powder have relatively small specific surface areas (<100 m 2 / g). The voids and contact areas between the particles of the mixed powder of aluminum oxide and carbon powder are small, which affects the reaction rate of nitriding aluminum oxide into aluminum nitride, resulting in a small batch production of aluminum nitride powder and a long synthesis time, leading to a relatively high production cost. In summary, there is an urgent need to reduce the cost of the method for forming aluminum nitride at present. Summary of the Invention

[0004] A method for forming aluminum nitride powder provided by an embodiment of the present invention includes: (a) mixing aluminum oxide powder and carbon powder to form a mixture, wherein the specific surface area of the carbon powder is 1000 m 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 the 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 the aluminum oxide powder to the carbon powder is 1:0.5 to 1:1.

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

[0008] In some embodiments, the oxygen-containing gas in step (c) includes air, oxygen, or a combination of the above.

[0009] In some embodiments, the temperature for heating the aluminum nitride powder and the unreacted carbon powder 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is the XRD pattern of the product such as aluminum nitride powder in the embodiments of the present invention.

[0012] Figure 2 This is the XRD pattern of the product such as aluminum nitride powder in the embodiments of the present invention.

[0013] Figure 3 This is the XRD pattern of the product such as aluminum nitride powder in the embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] A method for forming aluminum nitride powder provided by an embodiment of the present invention includes: (a) mixing alumina powder and carbon powder to form a mixture, wherein the specific surface area of the carbon powder is 1000 m 2 / g to 3000 m 2 / g. In some embodiments, the specific surface area of the carbon powder can be 1500 m 2 / g to 2500 m 2 / g, such as 1900 m 2 / g to 2300 m 2 / g. The above mixture substantially contains only alumina powder and carbon powder, and does not contain binders such as resins, additives such as fluorides or borides, or combinations thereof, so as to avoid generating 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 cannot react sufficiently with the alumina powder, reducing the nitriding effect of the alumina powder. In some embodiments, the average particle size (D 50 ) 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 be smoothly mixed with the alumina powder, reducing the nitriding effect of the alumina powder. In some embodiments, the weight ratio of the alumina powder to the carbon powder is 1:0.5 to 1:1. If the proportion of the carbon powder is too low, the alumina powder cannot be fully nitrided. If the proportion of the carbon powder is too high, it is necessary to additionally remove the unreacted carbon powder, increasing the cost.

[0015] After the above method in step (a), step (b) is then carried out to heat the mixture under nitrogen to nitride the alumina powder to form aluminum nitride powder. This step is the so-called carbothermal reduction method, and its reaction is as follows:

[0016] Al2O3 + N2 + 3C → 2AlN + 3CO

[0017] In some embodiments, the temperature for heating the mixture in step (b) is 1450°C to 1850°C. If the heating temperature in step (b) is too low, the nitriding effect of alumina is poor. If the heating temperature in step (b) is too high, the product such as aluminum nitride powder is likely to cause agglomeration of particles and grow into larger particles. Generally, nitrogen gas needs to be continuously introduced and nitrogen gas and reaction-generated gases such as carbon monoxide are discharged in step (b), and the flow rate of the introduced nitrogen gas is 20 L / min to 40 L / min. The above nitrogen gas flow rate range is only for illustration and not to limit the present invention. Those skilled in the art can adjust the nitrogen gas flow rate range according to parameters such as the volume of the device for performing step (b), the usage amounts of alumina and carbon powder, or the reaction temperature.

[0018] After the above method in step (b), step (c) is then carried out to heat the aluminum nitride powder and the unreacted carbon powder in an oxygen-containing gas to remove the unreacted carbon powder. In some embodiments, the oxygen-containing gas in step (c) includes air, oxygen, or a combination of the above. Generally, the oxygen-containing gas needs to be continuously introduced and the oxygen-containing gas and reaction-generated gases such as carbon monoxide and / or carbon dioxide are discharged in step (c), and the flow rate of the introduced oxygen-containing gas is 20 L / min to 100 L / min. The above oxygen-containing gas flow rate range is only for illustration and not to limit the present invention. Those skilled in the art can adjust the oxygen-containing gas flow rate range according to parameters such as the volume of the device for performing step (c), the usage amount of the unreacted carbon powder, or the reaction temperature.

[0019] In some embodiments, the temperature for heating the aluminum nitride powder and the unreacted carbon powder in step (c) is 600°C to 750°C. If the heating temperature in step (c) is too high, the aluminum nitride powder may be oxidized into alumina powder. If the heating temperature in step (c) is too low, the oxidation effect of the unreacted carbon powder is poor and the unreacted carbon powder cannot be effectively removed.

[0020] In some embodiments, the weight of the alumina powder in step (a) is 100 g to 1000 g. Since the method of the present invention can batch-nitridate a large amount of alumina powder into aluminum nitride powder, the manufacturing cost can be reduced.

[0021] To make the above content, other objects, features, and advantages of the present invention more obvious and understandable, specific embodiments are given below and detailed descriptions are made in conjunction with the accompanying drawings as follows:

[0022] [Embodiment]

[0023] In the following embodiments, the average particle size (D 50) The measurement method for () is a laser particle size analyzer, and the measurement method for the specific surface area of the powder is ASTM D 6556. The measurement method for the nitridation rate of aluminum nitride powder is X-ray diffraction. The peak intensities of the main peaks of aluminum nitride and the main peaks of aluminum oxide are used to calculate the nitridation rate from the peak intensities by "Nitridation rate (%) = (Q / R) × 100". Q is the peak intensity of aluminum nitride, and R is the sum of the peak intensity of aluminum nitride and the peak intensity of aluminum oxide.

[0024] Example 1

[0025] Take 50 g of alumina powder AKP (purchased from Sumitomo Chemical), with an average particle size (D 50 ) of 0.65 μm and a specific surface area of 4.5 m 2 / g), and 50 g of carbon powder ACSCA (purchased from Zhongtan), with an average particle size (D 50 ) of 6.51 microns and a specific surface area of 1923 m 2 / g). After mixing, place them in a crucible. After introducing nitrogen (flow rate: 40 L / min), heat the mixture to 1450 °C under nitrogen for 10 hours to carry out a nitridation reaction to form aluminum nitride powder. Then introduce air (flow rate: 60 L / min), and heat the aluminum nitride powder and the unreacted carbon powder to 700 °C under air and react for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then cool the product such as aluminum nitride powder. Its XRD pattern is as shown in Figure 1 , and its nitridation rate is 82.86%.

[0026] Comparative Example 1

[0027] Take 50 g of alumina powder AKP and 50 g of carbon powder N330 (purchased from CABOT), with an average particle size (D 50 ) of 30 nm and a specific surface area of 85 m 2 / g). After mixing, place them in a crucible. After introducing nitrogen (flow rate: 40 L / min), heat the mixture to 1450 °C under nitrogen for 10 hours to carry out a nitridation reaction to form aluminum nitride powder. Then introduce air (flow rate: 60 L / min), and heat the aluminum nitride powder and the unreacted carbon powder to 700 °C under air and react for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then cool the product such as aluminum nitride powder. Its XRD pattern is as shown in Figure 1 , and its nitridation rate is 42.15%.

[0028] Comparative Example 2

[0029] Take 50 g of alumina powder AKP and 50 g of carbon powder N990 (purchased from Cenyi Chemical), with an average particle size (D 50 ) of 300 nm and a specific surface area of 8 m 2 / g) After mixing, it is placed in a crucible. After introducing nitrogen gas (flow rate: 40 L / min), the mixture is heated to 1450 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air is introduced (flow rate: 60 L / min), and the aluminum nitride powder and the unreacted carbon powder are heated to 700 °C under air and reacted for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder is cooled, and its XRD pattern is as shown in Figure 1 shown, and its nitridation rate is 39.73%.

[0030] From Example 1, Comparative Example 1, and Comparative Example 2, it can be seen that if the specific surface area of the carbon powder is too low, the nitridation rate of the product such as aluminum nitride powder is low.

[0031] Example 2-1

[0032] Take 50 g of alumina powder AKP and 50 g of carbon powder ACSCA, mix them and place them in a crucible, and the laying thickness is 4 mm. After introducing nitrogen gas (flow rate: 40 L / min), the mixture is heated to 1550 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air is introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder are heated to 700 °C under air and reacted for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder is cooled, and its XRD pattern is as shown in Figure 2 shown, and its nitridation rate is 99.53%.

[0033] Example 2-2

[0034] Take 150 g of alumina powder AKP and 150 g of carbon powder ACSCA, mix them and place them in a crucible, and the laying thickness is 12 mm. After introducing nitrogen gas (flow rate: 40 L / min), the mixture is heated to 1550 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air is introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder are heated to 700 °C under air and reacted for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder is cooled, and its XRD pattern is as shown in Figure 2 shown, and its nitridation rate is 99.47%.

[0035] Example 2-3

[0036] 250 g of alumina powder AKP and 250 g of carbon powder ACSCA were mixed and placed in a crucible, and the thickness of the laid material was 20 mm. After introducing nitrogen (flow rate: 40 L / min), the mixture was heated to 1550 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air was introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder were heated to 700 °C under air and reacted for 2 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder was cooled, and its XRD pattern was as shown in Figure 2 shown, and its nitridation rate was 99.27%.

[0037] As can be seen from Examples 2-1 to 2-3, the above method can mass-produce aluminum nitride powder, which is beneficial to cost reduction.

[0038] Example 3-1

[0039] 250 g of alumina powder AKP and 250 g of carbon powder ACSCA were mixed and placed in a crucible. After introducing nitrogen (flow rate: 40 L / min), the mixture was heated to 1680 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air was introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder were heated to 700 °C under air and reacted for 3 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder was cooled, and its XRD pattern was as shown in Figure 3 shown, and its nitridation rate was 99.54%.

[0040] Example 3-2

[0041] 666.6 g of alumina powder AKP and 333.3 g of carbon powder ACSCA were mixed and placed in a crucible. After introducing nitrogen (flow rate: 40 L / min), the mixture was heated to 1680 °C under nitrogen for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air was introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder were heated to 700 °C under air and reacted for 3 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as aluminum nitride powder was cooled, and its XRD pattern was as shown in Figure 3 shown, and its nitridation rate was 99.27%.

[0042] Example 4

[0043] 250 g of alumina powder AKP and 250 g of carbon powder ACS20R4 (purchased from Zhongtan), with an average particle size (D 50 ) of 36.35 microns and a specific surface area of 2138 m 2 / g) After mixing, it is placed in a crucible. After introducing nitrogen gas (flow rate: 40 L / min), the mixture is heated to 1680 °C under nitrogen gas for 10 hours for a nitridation reaction to form aluminum nitride powder. Then, air is introduced (flow rate: 100 L / min), and the aluminum nitride powder and the unreacted carbon powder are heated to 700 °C under air and reacted for 3 hours to oxidize the unreacted carbon powder into carbon monoxide or carbon dioxide to remove the unreacted carbon powder. Then, the product such as the aluminum nitride powder is cooled, and its nitridation rate is 98.98%.

[0044] Although the present invention has been disclosed above with several embodiments, it is not intended to limit the present invention. Any person having ordinary knowledge in the technical field to which the present invention pertains may make any changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the appended claims.

Claims

1. A method for forming aluminum nitride powder, comprising: (a) Mix alumina powder and carbon powder to form a mixture, wherein the specific surface area of the carbon powder is 1000 m 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 the unreacted carbon powder under an oxygen-containing gas to remove the unreacted carbon powder.

2. The method for forming aluminum nitride powder according to claim 1, wherein the average particle size of the carbon powder is 2 μm to 40 μm.

3. The method for forming aluminum nitride powder according to claim 1, wherein the weight ratio of the aluminum oxide powder to the carbon powder is 1:0.5 to 1:

1.

4. The method for forming aluminum nitride powder according to claim 1, wherein the temperature for heating the mixture in step (b) is 1450 °C to 1850 °C.

5. The method for forming aluminum nitride powder according to claim 1, wherein the oxygen-containing gas in step (c) comprises air, oxygen, or a combination thereof.

6. The method for forming aluminum nitride powder according to claim 1, wherein the temperature for heating the aluminum nitride powder and the unreacted carbon powder in step (c) is 600 °C to 750 °C.

7. The method for forming aluminum nitride powder according to claim 1, wherein the weight of the aluminum oxide powder in step (a) is 100 g to 1000 g.

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