JPS60180906A - Method for removing carbon powder from aluminum nitride powder - Google Patents

Abstract

PURPOSE:To remove excess carbon sticking to powdery AlN manufactured by the reaction of fine Al powder with fine C powder in N2 by treating the powdery AlN at a high temp. in gas contg. CO2. CONSTITUTION:Fine Al powder having 2mum average particle size is wet-mixed with carbon black having <=0.2% ash content and <=1mum average particle size in a liq. dispersion medium such as water, hydrocarbon or aliphatic alcohol in 1:0.36-1:1 weight ratio. The mixture is dried and calcined at 1,400-1,700 deg.C in an N2 or NH3 atmosphere to manufacture AlN powder. Since excess carbon sticks to AlN, the AlN powder is treated by contact with gas contg. >=0.5vol% CO2 at 700-1,100 deg.C and 0.5-5cm/sec flow rate for 30min-1hr to remove fine C particles sticking to the fine AlN particles. Thus, high purity AlN is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION A method for removing powder. Specifically, this is a method for removing carbon powder from aluminum nitride, which is characterized by bringing aluminum nitride powder containing carbon powder into contact with a gas containing carbon dioxide gas at a temperature of 700"C to 1100C.

Conventionally, various ceramics or ceramic composites have been used in various industrial and consumer machines, equipment materials, electronic equipment materials, and the like.

However, it is often difficult to industrially produce a material that satisfies the needs of a particular application.

The present inventors have been earnestly involved in the development of ceramic manufacturing technology. As a result of continuing research on aluminum nitride in particular, we have succeeded in producing a new aluminum nitride and have already proposed it. As a result of further research, we completed a new method for producing aluminum nitride l1 and proposed it here.

The present invention is a method for removing carbon powder from aluminum nitride. Specifically, aluminum nitride powder containing carbon powder is heated at 700°C or more with gas containing carbon dioxide gas.
This is a method for removing carbon powder from aluminum nitride, which is characterized by contacting at a temperature of 1100°C.

The aluminum nitride used in the present invention is obtained by reacting alumina and carbon in a nitrogen atmosphere. For example, (1) fine aluminum particles with an average particle size of 2 μm or less and fine carbon powder with an ash content of 0.2 coul% and an average particle size of 1 μm or less are intimately mixed in a liquid dispersion medium; The weight ratio of the powder to the fine carbon powder is i:o, ae~l:l: (2) The resulting intimate mixture is optionally dried and heated under an atmosphere of nitrogen or ammonia at l″ at 400-1700°C. Calcinate at high temperature to obtain aluminum nitride powder.

According to the above method, it is possible to avoid the step of pulverizing aluminum nitride obtained by firing the raw material. By avoiding the pulverization process, it is possible to remove impurity components mixed in during the pulverization process, and it is also possible to prevent the surface of the aluminum nitride from being oxidized during the pulverization and increasing the oxygen content. The advantages of omitting the process of crushing aluminum nitride are also extremely large. In order to omit the above-mentioned pulverization step and obtain aluminum nitride with good properties, it is important to adopt a so-called wet mixing method in which the fine alumina powder and the fine carbon powder are mixed in a liquid dispersion medium in the manufacturing process. be. The wet mixing blade not only allows the raw materials to be mixed closely, but also prevents the raw material particles from agglomerating and becoming coarse.

The resulting intimate mixture is then calcined to yield fine-grained and uniformly grained aluminum nitride. Moreover, as mentioned above, it is possible to completely prevent impurity components mixed in during the grinding process, etc., and it is also possible to prevent oxidation of the aluminum nitride surface, resulting in superior sinterability and high purity compared to conventional methods. As the body, aluminum nitride with excellent properties can be produced, which can provide a sintered body with high thermal conductivity and translucency. The liquid dispersion medium that can be used in the wet mixing is not particularly limited, and any known wet mixed solvent can be used. Generally, industrially, water, hydrocarbons, aliphatic alcohols, petroleum ether, hexa:
Benzene, toluene, etc., and aliphatic anomucoles include, for example, methanol, ethanol, isopropanol, etc.

It is preferable to carry out the process in an apparatus made of a material that can avoid contamination with residual impurity components.

- Generally, the wet mixing can be carried out at normal temperature and normal pressure. It is not adversely affected by temperature and pressure.

In addition, as long as the mixing device is selected from a material that does not produce residual impurity components even after firing, any known device, 1.
steps can be adopted. For example, it is common to use a mill with balls or rods built into it as a mixing device, but the inner wall of the mill, the materials of the balls or rods, etc., remain in the resulting aluminum nitride even after firing. In order to avoid contamination with remaining impurity components, it is preferable to use aluminum nitride UNO 1 itself or high purity alumina of 99.9% by weight or more. Furthermore, all surfaces of the mixing device that come into contact with the raw materials may be made of plastic or may be covered with plastic. The plastic is not particularly limited, and includes, for example, polyethylene, polypropylene, nylon,
Polyester, polyurethane, etc. can be used. In this case, since the plastic may contain various metal components as stabilizers, it should be checked before use.

Further, in the above method, it is necessary to use alumina and carbon having specific properties. Generally, it is preferable to use fine alumina powder having an average particle diameter of 2 μm or less, preferably at least 99.9 μm. Oli amount % more preferably at least 99.9. A purity of 1% is used. Further, it is preferable to use fine carbon powder having an ash content of 0.2% by weight at most, preferably 0.1% by weight at most. Further, the carbon needs to be used as fine particles with an average particle diameter of 1 μm or less. Further, as the carbon, carbon black, graphitized carbon, etc. can be used, but carbon black is generally preferred.

The raw material usage ratio of alumina and carbon varies depending on the properties of the alumina and carbon, such as their purity and particle diameter, and is therefore preferably determined by conducting a preliminary test in advance. Usually, alumina and carbon are mixed at a weight ratio of alumina to carbon of 1.
:0.36~1:1. Preferably, warm mixing may be carried out in the range of 1:4 to 1:1. The hot mixed raw materials are heated at 1400 to 1700°C under a nitrogen atmosphere after drying if necessary.
Bake at a temperature of Is the firing temperature J? If it is lower than t, sufficient reductive nitrogenation reaction is proceeding bifurcated.
L/No, so it's not preferable. Furthermore, if the firing temperature is higher than the above temperature, a part of the aluminum nitride obtained will sinter, causing agglomeration between particles, making it difficult to obtain aluminum nitride having the desired particle size, which is not preferable.

Since the aluminum nitride powder thus obtained contains excess carbon added as a raw material or unreacted carbon powder, it is necessary to remove the carbon from the obtained aluminum nitride powder. In the present invention, the carbon is removed by contacting it with a gas containing carbon dioxide gas at a temperature of 700 to 1100°C.

In the present invention, the above-mentioned waste temperature is an important factor. That is, if the temperature is lower than the above gas temperature, carbon is not removed sufficiently, and conversely, if it is higher than the above gas temperature, aluminum nitride is converted to alumina, resulting in a decrease in the purity of the aluminum nitride and the present invention. cannot achieve its purpose. Therefore, the gas temperature is 700 to 1100°C, preferably 750 to 9σO°C.
It is preferable to select from the range of .

The gas containing carbon dioxide used in the present invention is not particularly limited, but is generally 0.5% by volume or more, preferably l
It is preferred to use a gas containing at least % by volume.

Furthermore, since the flow rate of the gas brought into contact with the aluminum nitride powder affects the oxidation rate of the carbon, it is preferable to appropriately determine the flow rate of the gas at the time of contact, such as the gas temperature and contact time. . Generally, the gas flow rate is 0.
It is sufficient to select from the range of 2 to IOe*/sec and 0.5 to 5 cm+/sec.

The above-mentioned contact time varies depending on gas concentration, temperature, flow rate, etc., and may be appropriately determined based on these conditions. - Generally: It is sufficient to choose from the range of 30 minutes to 10 hours.

The apparatus for contacting aluminum nitride powder and carbon dioxide gas in the present invention is not particularly limited, and any known apparatus may be used as is.

The aluminum nitride powder obtained according to the present invention can be obtained in a stable state with almost no change in N% content even during the carbon removal.

EXAMPLES In order to explain the present invention in more detail, examples will be given below, but the present invention is not limited to these examples.

Example 1 100 parts by weight of alumina with a purity of 99.99% (impurity analysis values are shown in Table 1) and a content of 95% by volume of particles with an average particle diameter of 0.52 μm and 371 m or less, and an ash content of 0.0
50 parts of carbon black having an average particle diameter of 0.45 μm and weighing 8% by weight were uniformly ball-milled by wet mixing using a nylon pot and ball and using ethanol as a liquid dispersion medium.

After drying the mixture thus obtained, it was placed in a high-purity graphite blank and heated at 1600° C. for 6 hours while continuously supplying high-purity nitrogen gas into an electric furnace.

The reaction mixture thus obtained was transferred to a quartz Hei 1 plate, and carbon dioxide gas (dew point -70°C) with an oxygen content of 10 PI) M or less was supplied at a linear velocity of 2 an + 7 seconds and heated at 80° C.
Heating was carried out at a temperature of 0° C. for 3 hours.

As a result of X-ray diffraction analysis, the obtained white powder was found to be single-phase AL.
It was N, and the diffraction lines of other crystals were almost absent. The average particle diameter of the powder was 1058 μm, and particles of 3 μm or less accounted for 82% by volume. The analytical values of this powder are shown in Table 2.

(Left below) Table I AlaO+:+Powder analysis value AI. 03 Content 99.99% Element Content 11 (1'l'M) Mg < 5 Cr < 10 St 30 Zri < 5 Fe 22 Cu < 5 Ca < 2O N1 15' Sono < 5 (Margins below) Table 2 AIN Powder analysis value Element Content (PPM) Mg <5 Cr 23 Si )) ;3 Zn 9 Fe 18 Cu < 5 Mn 5 N1 31 71'+ <5 Co < 5 AI 65.2 N 33.7 0 0 .7 CO,12 3.0% of Ca(NOs) 2' 41190 was added to the aluminum nitride powder thus obtained as a sintering aid.
1% was added and mixed uniformly in ethanol. 0.6 g of this mixed powder was uniaxially pressed in a mold with an inner diameter of 13+U, and then pressed to a pressure of 2000 kg/C1♂ to form a rubber-press disc-shaped compact. This compact was placed in a graphite crucible whose inner wall was coated with boron nitride powder, and fired at 1800° C. for 2 hours in nitrogen at 1 atmosphere. The density of the sintered body after firing is 3.23 g/Cze, and this sintered body is
The thermal conductivity of the material polished to mm was measured by the laser flash method and found to be 122 w/mk.

In addition, the mixed powder containing the sintering aid was filled into a graphite mold (inner wall of which was coated with boron nitride) with an inner diameter of 20 mm, and the mixture was heated at 200 kg/cv/, 2000 kg/cv/ in 1 atm nitrogen.
Hot press sintering was performed at ℃ for 3 hours. The obtained Reta sintered body was ground and polished to a thickness of 0.5 mm and had excellent translucency for visible light to infrared light, and the linear transmittance for light with a wavelength of 6 μm was 46%. Example 2 The same alumina powder as in Example 1 was mixed and dried in the same manner as in Example 1, followed by a nitriding reaction. The reaction mixture was transferred to a flat quartz booklet and heat treated under various conditions. Table 3 shows the results. (N004.5 in Table 3 is a comparative example.) The following margin patent applicant: Tokuyama Soda Co., Ltd.

Claims (2)

[Claims] (1) A method for removing carbon powder from aluminum nitride, which comprises bringing aluminum nitride powder containing carbon powder into contact with a gas containing carbon dioxide gas at a temperature of 70θ°C to 1100°C. (2) The method according to claim (1), wherein the gas containing carbon dioxide gas is a gas containing 0.5% by volume or more of carbon dioxide gas.