JP2020200219A - Method for producing aluminum nitride powder and method for controlling specific surface area of aluminum nitride powder - Google Patents

Abstract

To provide a method for producing an aluminum nitride powder capable of more strictly controlling a specific surface area of the aluminum nitride powder, and a method for controlling the specific surface area of the aluminum nitride powder.SOLUTION: A method for producing aluminum nitride powder comprises: a step of synthesizing aluminum nitride preliminary powder by reduction-nitriding alumina preliminary powder in advance, and measuring a specific surface area (SMAl2O3) of the aluminum preliminary powder and a specific surface area (SMAlN) of the aluminum nitride preliminary powder; a step of setting a target specific surface area (STAlN) of the aluminum nitride powder; a step of calculating a target specific surface area (STAl2O3) of alumina powder based on the SMAl2O3, the SMAlN, and the STAlN; a step of preparing alumina powder whose specific surface area coincides with the STAl2O3; and a step of synthesizing the aluminum nitride powder by reduction-nitriding the alumina powder.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing aluminum nitride powder and a method for controlling the specific surface area of aluminum nitride powder.

Aluminum nitride (AlN) has the property of easily transmitting lattice vibration while having no free electrons, and has the characteristics of being excellent in thermal conductivity and electrical insulation. Therefore, aluminum nitride powder is used for substrates of semiconductor parts such as ICs and CPUs and heat-dissipating parts by sintering it into a sintered body or kneading it with a resin to make a composite material. ..

Two methods, a direct nitriding method and a reduction nitriding method, are known as methods for synthesizing aluminum nitride powder. The direct nitriding method is a method of calcining metallic aluminum powder in a nitrogen atmosphere to obtain aluminum nitride, and the reaction is represented by 2Al + N ₂ → 2AlN. The aluminum nitride synthesized by this method is a block-shaped mass. Therefore, in order to obtain a powder, it is necessary to perform a multi-step pulverization treatment on this mass, which causes a problem that it is difficult to control the particle size and impurities are easily mixed during pulverization, and it is difficult to obtain a high-purity powder. ..

On the other hand, the reduction nitriding method is a method in which a reducing agent such as carbon powder is mixed with alumina (Al ₂ O ₃ ) powder, and the obtained mixture is calcined in a nitrogen atmosphere and then crushed to obtain aluminum nitride. When carbon is used as the reducing agent, the reaction is represented by Al ₂ O ₃ + 3C + N ₂ → 2AlN + 3CO. Since the reduction nitriding method can obtain high-purity aluminum nitride fine powder having a uniform particle size, it is considered to be the most suitable method for producing powder for a high thermal conductive material. Documents that disclose the synthesis of aluminum nitride powder by the reduction nitriding method include the following.

In Patent Document 1, alumina powder having an average particle diameter of 0.15 to 0.5 μm and carbon powder are mixed and nitrided at 1400 to 1700 ° C. in a nitrogen atmosphere, and then the nitrided powder is obtained in an amount of 5 to 30% by weight. A method for producing an aluminum nitride powder, which comprises pulverizing in the presence of carbon and then burning and removing excess carbon, has been disclosed. According to the method, fine particles with few aggregates, excellent moldability and stability, and excellent moldability and stability. Moreover, it is described that the aluminum nitride powder that can be sintered at normal pressure without any aid can be supplied (Patent Document 1 claim 2 and [0036]).

In Patent Document 2, in the method for producing aluminum oxide powder in the reduction nitriding method, the particle surface of the alumina particle powder is coated with a surface modifier as a starting material, and the surface of the surface modifier-coated alumina particle is coated with carbon powder. A method for producing an aluminum oxide powder, which is characterized by using a composite particle powder to which the powder is attached, is disclosed. According to the method, the aluminum oxide powder has excellent thermal conductivity and a sharp particle size distribution with few impurities, and is baked. It is described that aluminum nitride powder having a low thermal shrinkage at the time of baking can be obtained at a relatively low cost (claims 1 and [0014] of Patent Document 2).

Further, Patent Document 3 and Patent Document 4 disclose a method of reducing and nitriding alumina with ammonia gas. For example, in Patent Document 3, γ-Al ₂ O ₃ or a precursor thereof is heated at 1200 to 1700 ° C. in a mixed gas of a hydrocarbon gas containing 0.5% by volume or more of the hydrocarbon gas and an ammonia gas. Then, a porous aluminum nitride having a specific surface area of 10 m ² / g or more is produced, and then this is used as a gas atmosphere of any one of an inert gas, an ammonia gas and a mixed gas of an ammonia gas and an inert gas. Discloses a method for producing low oxygen concentration aluminum nitride, which comprises heating at 1600 to 2000 ° C. (claim 1 of Patent Document 3).

Patent Document 4 describes that in producing aluminum nitride by heating and nitriding alumina in a mixed gas of a hydrocarbon gas containing 0.5% by volume or more of hydrocarbon gas and ammonia gas, γ-Al ₂ is added to the alumina. A method for producing aluminum nitride, which comprises using γ-Al ₂ O _{3 in} which O ₃ or a precursor thereof is calcined to reduce the water content to 1% by weight or less, and the heating temperature is 1200 to 1700 ° C. Is disclosed (claim 1 of Patent Document 4).

Japanese Unexamined Patent Publication No. 05-017109 Japanese Unexamined Patent Publication No. 2006-256940 Japanese Unexamined Patent Publication No. 11-021113 Japanese Unexamined Patent Publication No. 11-130411

As described above, it has been conventionally proposed to synthesize aluminum nitride powder by reducing and nitriding the alumina powder. On the other hand, in response to the demand for higher characteristics of aluminum nitride parts, it is required to control the physical properties of the aluminum nitride powder more strictly. In particular, when the aluminum nitride powder is sintered to form a sintered body or a composite material with a resin, the physical properties such as the specific surface area of the aluminum nitride powder are stricter from the viewpoint of ensuring fluidity and filling property. It is required to control. However, it has been difficult to strictly control the specific surface area of the aluminum nitride powder after synthesis by the conventional method. That is, in the process of synthesizing aluminum nitride by the reduction diffusion method, the nitriding process and the grain growth process are intricately intertwined, and it is difficult to express by a simple reaction mechanism. Therefore, the aluminum nitride powder having a desired specific surface area could not be obtained by simply increasing or decreasing the specific surface area of the raw material alumina powder.

As a result of studying to deal with such a problem, the present inventor found that the grain growth behavior of aluminum oxide after synthesis differs between the low specific surface area region and the high specific surface area region of the alumina powder, and the low specific surface area region. By calculating the specific surface area target value of alumina by dividing it into the high specific surface area region and controlling the specific surface area of alumina based on the target value, it is possible to more strictly control the specific surface area of the aluminum oxide powder after synthesis. The present invention was completed with the finding that it would be possible.

Therefore, it is an object of the present invention to provide a method for producing aluminum nitride powder and a method for controlling the specific surface area of aluminum nitride powder, which makes it possible to control the specific surface area of the aluminum nitride powder more strictly.

The present invention includes the following aspects (1) to (6). In addition, in this specification, the expression "~" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".

(1) A method for producing aluminum nitride powder.
A step of preliminarily reducing and nitriding the alumina preliminary powder to synthesize an aluminum nitride preliminary powder, and measuring the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ).
The process of setting the target specific surface area (ST _AlN ) of the aluminum nitride powder, and
A step of calculating the target specific surface area (ST _Al2O3 ) of the alumina powder based on the SM _Al2O3 , the SM _AlN, and the ST _AlN .
A step of preparing an alumina powder whose specific surface area matches that of ST _Al2O3, and
A method comprising a step of reducing and nitriding the alumina powder to synthesize an aluminum nitride powder.
When calculating the target specific surface area (ST _Al2O3 ) of the alumina powder, the formula: ST _Al2O3 = SM _Al2O3 + k × (ST _AlN −SM _AlN ), where k is a real number and SM _Al2O3 ≦ 13 m ² / g. Is 0 <k, and in the case of SM _Al2O3 > 13 m ² / g, k <0, and ST _Al2O3 is calculated according to the method.

(2) The method of (1) above, wherein the absolute value (| k |) of k satisfies 2 <| k | <6.

(3) The method according to (1) or (2) above, wherein in the step of preparing the alumina powder, aluminum hydroxide is heat-treated to produce an alumina powder.

(4) At the time of synthesizing the aluminum nitride preliminary powder and / or aluminum nitride powder, a mixture of the alumina preliminary powder and / or the alumina powder and the carbon powder is prepared, and the mixture is heat-treated in a nitrogen atmosphere. Any of the above (1) to (3), wherein the reduced nitride is prepared, and the reduced nitride is heat-treated in an air atmosphere to remove residual carbon components to synthesize an aluminum nitride preliminary powder and / or an aluminum nitride powder. Method.

(5) The method of (4) above, wherein the heat treatment in the nitrogen atmosphere is performed at a temperature within the range of 1600 to 1800 ° C.

(6) A method for controlling the specific surface area of aluminum nitride powder.
A step of preliminarily reducing and nitriding the alumina preliminary powder to synthesize an aluminum nitride preliminary powder, and measuring the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ).
The process of setting the target specific surface area (ST _AlN ) of the aluminum nitride powder, and
A step of calculating the target specific surface area (ST _Al2O3 ) of the alumina powder based on the SM _Al2O3 , the SM _AlN, and the ST _AlN .
A step of preparing an alumina powder whose specific surface area matches that of ST _Al2O3, and
A method comprising a step of reducing and nitriding the alumina powder to synthesize an aluminum nitride powder.
When calculating the target specific surface area (ST _Al2O3 ) of the alumina powder, the formula: ST _Al2O3 = SM _Al2O3 + k × (ST _AlN −SM _AlN ), where k is a real number and SM _Al2O3 ≦ 13 m ² / g. Is 0 <k, and in the case of SM _Al2O3 > 13 m ² / g, k <0, and ST _Al2O3 is calculated according to the method.

According to the present invention, there is provided a method for producing an aluminum nitride powder and a method for controlling the specific surface area of the aluminum nitride powder, which makes it possible to control the specific surface area of the aluminum nitride powder more strictly.

It is a figure which shows the relationship between the calcined BET of an alumina powder, and the BET of an aluminum nitride powder. It is a figure which shows the relationship between the calcined BET of an alumina powder, and the pressure bulk density of an aluminum nitride powder.

Method for Producing Aluminum Nitride Powder The method for producing aluminum nitride powder of the present invention uses a reduction nitriding method. In this production method, the alumina preliminary powder is reduced-nitrided in advance to synthesize the aluminum nitride preliminary powder (pre-synthesis), and the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ) are obtained. A step of measuring, a step of setting a target specific surface area (ST _AlN ) of the aluminum nitride powder, a step of calculating a target specific surface area (ST _Al2O3 ) of the alumina powder based on SM _Al2O3 , SM _AlN and ST _AlN , It includes a step of preparing an alumina powder whose specific surface area matches that of ST _Al2O3, and a step of reducing and nitriding the alumina powder to synthesize (mainly synthesize) the aluminum nitride powder. Further, when calculating the target specific surface area of the alumina powder _{(ST Al2 O3), wherein:} calculating the _{ST Al2 O3} according to _{ST Al2O3 = SM Al2O3 + k ×} (ST AlN -SM AlN). However, k is a real number, which is 0 <k when SM _Al2O3 ≤ 13 m ² / g and k <0 when SM _Al2O3 > 13 m ² / g. Each step will be described in detail below.

<Preliminary synthesis and specific surface area measurement process>
In the pre-synthesis step, the alumina (α-Al ₂ O ₃ ) pre-powder is reduced and nitrided in advance to synthesize (pre-synthesize) the aluminum nitride (AlN) pre-powder. As the alumina preliminary powder, a known powder for synthesizing aluminum nitride can be used. Typically, the alumina preliminary powder has a specific surface area of ² to 25 m ² / g. Further, the alumina preliminary powder is preferably produced by the Bayer process, that is, by heat-treating aluminum hydroxide (gibbsite). Alumina powder produced by the Bayer process is inexpensive and therefore suitable for aluminum nitride synthesis. In addition, in this specification, a powder is an aggregate of particles and refers to the thing which shows fluidity as a whole. Therefore, it may be an aggregate of particles that are not bonded to each other, or there may be a bond (necking) between the particles as long as they show fluidity as a whole.

Further, the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ) are measured. The specific surface area may be measured by a known method. Examples of such a method include a permeation method and a gas adsorption method. Further, when an alumina preliminary powder having a bond (necking) between the particles is used, the specific surface area may be measured with the bond (necking). Therefore, when the alumina preliminary powder produced by the Bayer process is used, the specific surface area (calcined BET) of the powder may be measured without crushing or crushing after the heat treatment of aluminum hydroxide (gibbsite). This is because the calcined BET more accurately reflects the size of the primary particles in the alumina powder. On the other hand, the powder produced by crushing or crushing after the heat treatment contains a large amount of fine particles generated by the crushing or crushing treatment. Therefore, the specific surface area (crushed BET) is affected by the fine particles and does not accurately reflect the size of the primary particles.

Reduction nitriding may be performed by a known method. For example, a method of preparing a mixture of an alumina preliminary powder and a carbon powder and heat-treating the mixture in a nitrogen atmosphere to obtain a reduced nitride can be mentioned. In this case, the ratio of the alumina preliminary powder to the carbon powder is, for example, 8: 2 to 6: 4 in terms of mass ratio. The heat treatment is performed at a temperature in the range of, for example, 1600 to 1800 ° C. If necessary, the obtained reduced nitride may be further heat-treated in an air atmosphere. This makes it possible to effectively remove the residual carbon component contained in the reduced nitride.

<Step of setting the target specific surface area of aluminum nitride>
The target specific surface area (ST _AlN ) of the aluminum nitride powder is set. The target specific surface area (ST _AlN ) may be set according to the use of the aluminum nitride powder, and is not particularly limited. For example, when the aluminum nitride powder is used for the production of a sintered body, the target specific surface area may be set higher from the viewpoint of obtaining excellent sinterability. On the other hand, when the aluminum nitride powder is used as a filler, the target specific surface area may be set low from the viewpoint of dispersibility in the base material. The target specific surface area (ST _AlN ) is typically 2.0-6.0 m ² / g. The target specific surface area (ST _AlN ) may be set before or after the pre-synthesis and specific surface area measurement steps described above.

<Calculation process of target specific surface area of alumina powder>
Next, the target specific surface area (ST _Al2O3 ) of the alumina powder is calculated based on the specific surface area SM _Al2O3 of the alumina preliminary powder, the specific surface area SM _AlN of the aluminum nitride preliminary powder, and the target specific surface area ST _AlN of the aluminum nitride powder. Specifically, ST _Al2O3 is calculated according to the formula: ST _Al2O3 = SM _Al2O3 + k × (ST _AlN −SM _AlN ). Here, k is a real number, which is 0 <k when SM _Al2O3 ≤ 13m ² / g and k <0 when SM _Al2O3 > 13m ² / g.

k is a parameter indicating the relationship between the change in the specific surface area of the alumina preliminary powder and the change in the specific surface area of the aluminum nitride preliminary powder. When the specific surface area of the alumina preliminary powder is 13 m ² / g or less, k is a positive real number (0 <k), and when the specific surface area is more than 13 m ² / g, k is a negative real number (k <k). 0). As described above, the alumina powder is divided into a case where the specific surface area of the alumina preliminary powder is in the low specific surface area region (SM _Al2O3 ≤ 13 m ² / g) and a case where the specific surface area is in the high specific surface area region (SM _Al2O3 > 13 m ² / g). Calculate the target specific surface area of. Although the detailed mechanism is unknown, it is considered that the grain growth behavior of aluminum nitride after synthesis differs between the low specific surface area region and the high specific surface area region of the alumina powder. Therefore, by calculating the target specific surface area separately for the low specific surface area region and the high specific surface area region and preparing the alumina powder based on the target specific surface area, it is possible to obtain an aluminum nitride powder whose specific surface area is strictly controlled. it can. The absolute value (| k |) of k preferably satisfies 2 << k | <6, and more preferably 3 << k | <6.

<Preparation process of alumina powder>
After calculating the target specific surface area (ST _Al2O3 ), the alumina powder for this synthesis is prepared. At that time, an alumina powder having a specific surface area that matches ST _Al2O3 is prepared. As a result, an aluminum nitride powder having a strictly controlled specific surface area can be obtained. In addition, in this specification, the thing that the specific surface area is the same means the case where the specific surface area of the alumina powder is within the range of ST _Al2O3 ± 10%. For example _{ST Al2 O3} is in the case of ^{10 m} 2 / g is referred to as the specific surface area of the alumina powder is 9~11m specific surface area when it is in the range of ² / g to match.

As the alumina powder for this synthesis, it is preferable to use one produced by the same method (Bayer method) as the alumina preliminary powder. Therefore, in the step of preparing the alumina powder, it is preferable to heat-treat aluminum hydroxide (gibbsite) to produce the alumina powder. In that case, the specific surface area of the alumina powder can be controlled by adjusting the heat treatment conditions (temperature, holding time, etc.) of the aluminum hydroxide. At this time, as the specific surface area of the alumina powder, it is preferable to adopt the specific surface area (calcined BET) of the powder obtained without crushing or crushing after the heat treatment.

<Main synthesis process>
Next, the prepared alumina powder is reduced and nitrided to synthesize aluminum nitride powder (main synthesis). The reduction nitriding of this synthesis is carried out under the same conditions as the preliminary synthesis. For example, a method of preparing a mixture of alumina powder and carbon powder and heat-treating the mixture in a nitrogen atmosphere to obtain a reduced nitride can be mentioned. In this case, the heat treatment is performed at a temperature in the range of, for example, 1600 to 1800 ° C. Further, if necessary, the obtained reduced nitride may be further heat-treated in an air atmosphere.

Method of controlling the specific surface area of the aluminum nitride powder In the method of controlling the specific surface area of the aluminum nitride powder of the present invention, the alumina preliminary powder is preliminarily reduced and nitrided to synthesize the aluminum nitride preliminary powder (presynthesis), and the alumina preliminary powder A step of measuring the specific surface area (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ), a step of setting a target specific surface area (ST _AlN ) of the aluminum nitride powder, and a step of SM _Al2O3 , SM _AlN and ST _AlN. Based on the above, the step of calculating the target specific surface area (ST _Al2O3 ) of the alumina powder, the step of preparing the alumina powder whose specific surface area matches ST _Al2O3, and the step of reducing and nitriding the alumina powder to synthesize the aluminum nitride powder ( The step of main synthesis) and. Further, when calculating the target specific surface area of the alumina powder _{(ST Al2 O3), wherein:} calculating the _{ST Al2 O3} according to _{ST Al2O3 = SM Al2O3 + k ×} (ST AlN -SM AlN). However, k is a real number, which is 0 <k when SM _Al2O3 ≤ 13 m ² / g and k <0 when SM _Al2O3 > 13 m ² / g. The details of each step are the same as in the case of the method for producing aluminum nitride powder.

The present invention will be described in more detail with reference to the following examples.

(1) Preparation of Alumina (Spare) Powder Prior to the synthesis of the aluminum nitride powder, the alumina powder was prepared as follows. That is, the aluminum hydroxide obtained by the Bayer process is fired in an electric furnace set to the temperature shown in Table 1 so as to have a target specific surface area, and then used in a jet mill (air flow type crusher) or a ball mill (media crusher). And crushed. As a result, the No. 1 shown in Table 1 Samples 1 to 8 were obtained. In addition, No. 7 and No. Alumina powder of No. 8 was mixed to obtain No. Nine samples were prepared.

(2) Synthesis of Aluminum Nitride (Preliminary) Powder Next, the crushed alumina powder was reduced-nitrided to synthesize aluminum nitride powder. First, 5% by mass of ethanol was added as an auxiliary agent to 50 g of alumina powder and 22 g of carbon powder (Mitsubishi Chemical Corporation, MA600), and the mixture was mixed with a rotary ball mill for 1 hour. 12 g of the obtained mixed powder was thinly spread on a carbon jig. The mixed powder laid on the carbon jig was set in a multipurpose high temperature furnace (Fuji Dempa Kogyo Co., Ltd., Hi-Multi 10000) and reduced and nitrided. Reduction nitriding was carried out by heat treatment at 1650 ° C. for 5 hours while flowing nitrogen gas at a flow rate of 10 L / min. Next, in order to remove residual carbon, the reduced nitride was heat-treated at 600 ° C. for 10 hours in an air atmosphere. Then, using a vibrating ball mill, the reduced nitride after the heat treatment was subjected to a crushing treatment for 30 minutes to loosen the agglomerates, and an aluminum nitride powder was prepared.

(3) Evaluation of Alumina Powder and Aluminum Nitride Powder The following evaluation was performed on the alumina powder and aluminum nitride powder.

<D50>
The volume average particle diameter (D50) of the alumina powder and the aluminum nitride powder (both after crushing) was measured as follows. That is, the sample was dispersed in sodium hexametaphosphate (solvent), set in MT-3300 manufactured by Nikkiso Co., Ltd., and the particle size distribution (volume basis) of each was measured.

<BET>
The specific surface area (BET) of the alumina powder and the aluminum nitride powder was measured as follows. That is, nitrogen gas was adsorbed on the surface of the sample, and the surface area of the sample was determined from the adsorbed amount by the nitrogen gas adsorption method. An automatic specific surface area measuring device (Micromeritex, Flowsorb II2300 type) was used as the equipment used. For the alumina powder, the specific surface area before the crushing treatment (calcination BET) and the specific surface area after the crushing treatment (crushed BET) were measured. Further, the α particle size of the alumina powder was determined according to the formula: α particle size = 6 / (3.98 × calcined BET).

<Pressurized bulk density>
The pressurized bulk density of the alumina powder and the aluminum nitride powder (both after crushing) was measured as follows. That is, the sample was placed in a mold and pressure molded at a pressure of 250 kgf / cm ² . At this time, the holding time of pressurization was eliminated. The bulk density was calculated by measuring the mass and dimensions of the formed molded piece.

(4) Results Table 1 shows the obtained evaluation results. The relationship between the calcined BET of the alumina powder and the BET of the aluminum nitride powder shown in Table 1 is shown in FIG. 1, and the relationship between the calcined BET of the alumina powder and the pressurized bulk density of the aluminum nitride powder is shown in FIG. As shown in FIG. 1, in the region where the calcined BET of the alumina powder was 13 m ² / g or less, the BET of the aluminum nitride powder monotonously increased as the calcined BET of the alumina powder increased. The reciprocal of the slope (calcined BET of Δalumina powder / BET of Δaluminum nitride powder) was 3.9. On the other hand, in the region where the calcined BET of the alumina powder was more than 13 m ² / g, the BET of the aluminum nitride powder decreased monotonically as the calcined BET of the alumina powder increased. The reciprocal of the slope (calcined BET of Δalumina powder / BET of aluminum nitride powder) was -5.2.

From this, in the region where the calcined BET of the alumina powder is 13 m ² / g or less, k = (ST _Al2O3- SM _Al2O3 ) / (ST _AlN- SM _AlN ) is set to 3.9, and the calcined BET of the alumina powder is 13 m ² /. In the region over g, k is set to -5.2, the target specific surface area of the alumina powder (ST _Al2O3 ) is calculated, and the target is to use the alumina powder having a specific surface area that matches the target specific surface area (ST _Al2O3 ). It can be seen that aluminum nitride powder having a specific surface area (ST _AlN ) can be synthesized.

Claims (6)

A method for producing aluminum nitride powder.
A step of preliminarily reducing and nitriding the alumina preliminary powder to synthesize an aluminum nitride preliminary powder, and measuring the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ).
The process of setting the target specific surface area (ST _AlN ) of the aluminum nitride powder, and
A step of calculating the target specific surface area (ST _Al2O3 ) of the alumina powder based on the SM _Al2O3 , the SM _AlN, and the ST _AlN .
A step of preparing an alumina powder whose specific surface area matches that of ST _Al2O3, and
A method comprising a step of reducing and nitriding the alumina powder to synthesize an aluminum nitride powder.
When calculating the target specific surface area (ST _Al2O3 ) of the alumina powder, the formula: ST _Al2O3 = SM _Al2O3 + k × (ST _AlN −SM _AlN ), where k is a real number and SM _Al2O3 ≦ 13 m ² / g. Is 0 <k, and in the case of SM _Al2O3 > 13 m ² / g, k <0, and ST _Al2O3 is calculated according to the method. The method according to claim 1, wherein the absolute value (| k |) of k satisfies 2 <| k | <6. The method according to claim 1 or 2, wherein in the step of preparing the alumina powder, aluminum hydroxide is heat-treated to produce an alumina powder. At the time of synthesizing the aluminum nitride preliminary powder and / or aluminum nitride powder, a mixture of the alumina preliminary powder and / or the alumina powder and the carbon powder is prepared, and the mixture is heat-treated in a nitrogen atmosphere to reduce the nitride. The method according to any one of claims 1 to 3, wherein the reduced nitride is heat-treated in an air atmosphere to remove residual carbon components to synthesize an aluminum nitride preliminary powder and / or an aluminum nitride powder. The method according to claim 4, wherein the heat treatment in a nitrogen atmosphere is performed at a temperature in the range of 1600 to 1800 ° C. A method of controlling the specific surface area of aluminum nitride powder.
A step of preliminarily reducing and nitriding the alumina preliminary powder to synthesize an aluminum nitride preliminary powder, and measuring the specific surface area of the alumina preliminary powder (SM _Al2O3 ) and the specific surface area of the aluminum nitride preliminary powder (SM _AlN ).
The process of setting the target specific surface area (ST _AlN ) of the aluminum nitride powder, and
A step of calculating the target specific surface area (ST _Al2O3 ) of the alumina powder based on the SM _Al2O3 , the SM _AlN, and the ST _AlN .
A step of preparing an alumina powder whose specific surface area matches that of ST _Al2O3, and
A method comprising a step of reducing and nitriding the alumina powder to synthesize an aluminum nitride powder.
When calculating the target specific surface area (ST _Al2O3 ) of the alumina powder, the formula: ST _Al2O3 = SM _Al2O3 + k × (ST _AlN −SM _AlN ), where k is a real number and SM _Al2O3 ≦ 13 m ² / g. Is 0 <k, and in the case of SM _Al2O3 > 13 m ² / g, k <0, and ST _Al2O3 is calculated according to the method.

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