JPS616105A - Manufacture of aluminum nitride powder - Google Patents

Abstract

PURPOSE:To manufacture high purity AlN powder by dehydrating a hydrolyzate of an organoaluminum compound by heating mixing the resulting Al2O3 with a proper amount of fine C powder, calcining the mixture in an atmosphere of N2, and removing the unreacted C by heating at a proper temp. CONSTITUTION:The hydrolyzable organoaluminum compound such as aluminum alkoxide is hydrolyzed by contact with water or an org. solvent contg. water such as alcohol. The resulting hydrolyzate is dehydrated by heating at about 300-1,200 deg.C to form Al2O3 of a very small particle size. This Al2O3 is homogeneously mixed with fine C powder in a liq. dispersion medium such as alcohol in (1:0.36)-(1:2) weight ratio of Al2O3:C, and the mixtue is calcined at about 1,400-1,800 deg.C in an atmosphere of N2 or NH3. The unreacted C is removed from the resulting fine nitride powder by heating at 600-900 deg.C in an atmosphere contg. O2 to obtain high purity fine AlN powder giving a sintered body having such properties as high heat conductivity, high light transmittance and high corrosion resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing high purity aluminum nitride fine powder. In particular, the present invention is a method for producing high-purity aluminum nitride fine powder whose sintered body exhibits properties such as high thermal conductivity, high light transmittance, and high corrosion resistance.

Conventionally, the following two methods are known as methods for producing fine aluminum nitride powder. The first method is a method called a direct 9-composition method, in which aluminum gold powder is nitrogenized at high temperature in a nitrogen or ammonia atmosphere, and the resulting nitride is crushed to produce aluminum nitride powder.

The second method is the alumina reduction method, in which alumina and carbon powder are fired in a nitrogen or ammonia atmosphere, and the resulting nitride is heated in an oxygen-containing atmosphere to remove unreacted carbon. be. The former direct nitriding method has the disadvantage that the resulting aluminum nitride powder is not uniform because the pulverization step cannot be avoided. The latter method is also superior to the direct nitriding method in that it provides aluminum nitride powder with relatively uniform particle size. Published Japanese Patent Publication No. 59-5000
No. 8, it is reported that aluminum nitride powder, which imparts translucency to the sintered body, can be obtained by an alumina reduction method.

The present invention provides a method for producing high-purity aluminum nitride powder whose properties such as thermal conductivity and translucency can be further improved by selecting a specific production method.

R11: In the present invention, fine carbon powder is mixed in a liquid dispersion medium so that the ratio of hydrolyzable organic aluminum q alumina to carbon is 1-0.56 to 1:2, and the mixture is f! in a nitrogen or ammonia atmosphere. 8.
Next, the obtained fine powder was heated in an atmosphere containing oxygen for 600~
This is a method for producing high-purity aluminum nitride fine powder by heating at a temperature of 900°C to remove unreacted carbon.

The hydrolyzable 4-length aluminum compound used in the present invention is not particularly limited, and may include known organoaluminum compounds,
For example, aluminum alkyls such as trimethylaluminum, triethylaluminum, and diethylmonohaluminum; and particularly aluminum alphoxides such as aluminum propoxide, aluminum butoxide, and aluminum monobutoxydiisopropoxide can be suitably used. The use of aluminum alkoxide in the cavity is industrially most suitable because not only operations such as the hydrolysis reaction and dispersion treatment described later can be easily carried out, but also the properties of the obtained aluminum nitride powder are particularly improved. The above-mentioned hydrolyzable organoaluminum compound may be reacted directly with water, but is generally used after being dissolved or dispersed in an organic solvent. The organic solvent is not particularly limited and can be used as long as it dissolves or disperses the organoaluminum compound, but petroleum ether is usually used.

Hydrocarbons such as hexane, benzene, toluene, etc.: methanol, ethanol, propatool.

Aliphatic alcohols such as Improper Tool: Chlorinated solvents such as carbon tetrachloride are suitable.

In particular, the above-mentioned alcohols are suitable because operations such as hydrolysis reaction and carbon dispersion treatment FJ, which will be described later, can be carried out easily. The concentration of the organic solvent in which the organoaluminum compound is dissolved or dispersed is approximately
It varies depending on the type of organic solvent, hydrolysis conditions described below, etc., and cannot be definitively determined, but in general, the lower the concentration of the aluminum compound, the better. However, if the concentration of the aluminum compound is too low (h''-A1), the amount of oxidation used increases significantly, and if the jump is too high, reaction control becomes difficult and handling becomes inconvenient. It may be determined as appropriate in consideration of these factors, but in general IC, it is preferable to use a concentration of organoaluminum compound at a concentration of 50% or less, preferably 1% to 40% and 71%. .

The organoaluminum compound is heated with water or a water-containing organic solvent to perform hydrolysis. Although the organic solution mentioned above can be used without any particular limitation, Al-7-alcohol solution is the most preferred. When using the above-mentioned hydroalcoholic solution, the above-mentioned aliphatic alcohols are preferably used as the alcohol. The volume of water contained in the alcohol solution may be in an amount sufficient to hydrolyze the organoaluminum compound, and may be determined in advance and used depending on the hydrolysis conditions and other factors. If necessary, alkaline compounds such as ammonia and amines, nitric acid, hydrochloric acid, sulfur/T'? Bamboo mineral acid salts' hydrolysis accelerators can also be used.

The above 1ff + water decomposition is generally carried out in a heated state because the inter-core water decomposition reaction at wtB temperature is fast. . In addition, since the hydrolysis W1 reaction is often carried out under stirring, it is preferable that the four busy particle diameters are uniformly K11.
Moderate stirring/IZ is often effective for increasing the temperature. Furthermore, the particle size of particles obtained by VC size hydrolysis (/C) is also affected by the degree of organoaluminum compound and the type of solvent, so these values are determined by the required particle size. It is preferable to determine this in advance in a laboratory.

In the present invention, 71 obtained by the above-mentioned hydrolytic lit reaction
n Moisture > jl The product is layered and/or dried, then heated and heated to form alumina. The temperature of the Kaune instant water is not particularly limited, but is generally 300 to 1200.
It is sufficient to select a temperature Tt1M, preferably from Iloθ to 7000°C. The alumina thus obtained has a very small alumina particle size, and the aluminum nitride powder described later provides a uniform collection of fine particles. In addition, since the amount of impurities present in the alumina is extremely small, the resulting aluminum nitride powder is calcined.

Margin: The hydrolyzate of an organoaluminum compound obtained by the above method inevitably contains impurities in aluminum nitride obtained by a known method such as a direct nitriding method or an alumina reduction method due to the raw material. It contains significantly less impurities compared to other types.The particle size is 0.5 μm or less, and particles of 1 μm or less absorb at least 90% of the total volume.
It is also possible to obtain particles with very uniform particle sizes that account for the Such properties are mixed with materials that have a large effect on improving concretion (when obtaining an aluminum nitride sintered body) and improving the properties imparted to the sintered body, such as thermal conductivity and translucency. This is an essential process. In this case, the mixing ratio of carbon is 1:0.36 to 1:2, preferably 1:0.
It is preferable to select from the range of 4 to 1:1. If the amount of carbon used is less than the above range, the reduction reaction described below will not proceed sufficiently, and if it is too large, unreacted carbon will be removed. I like this because it takes more time than necessary to remove fC.
It's not right.

Takee Arashi Ikusho speed change λ, Neezoku 4-M Ko 2 Wa ≠ Matakura Miki, Male f-H Tokankei Suspension A'n mix =
1. It can be carried out in a liquid state that the extremely carbon σ and the extremely homogeneous 11? Not only does this have a great effect on the reactivity of aluminum nitride, but it also has the advantage of minimizing the amount of impurities mixed in with aluminum nitride. In addition, by adopting the above-mentioned liquid-type wet mixing method, it is possible to prevent the raw material particles from collapsing and becoming coarse. In the end, the aluminum nitride itself becomes fine particles with uniform particles, so there is no need to crush the resulting aluminum nitride, and it can be sintered as it is. The advantage of being able to omit this crushing process is valuable for the plant.
The size is small. If possible, the present invention can completely prevent impurities from entering during +'c grinding, and the surface of aluminum nitride will be oxidized during grinding, increasing the acid content. Since it is possible to completely prevent h'-emission, nitriding and impurity damage in aluminum are extremely reduced.

What about the wet mixing in the present invention? ! If possible, avoid contamination with impurity components that remain after firing into aluminum nitride.It is best to carry out the wet mixing in a device made of material that can be used. It is not affected by temperature and pressure.As long as the material is selected to avoid impurities that remain even under pressure after firing, any known device or method can be used as the crushing and mixing device. Vine.For example, it is common to use a mill with spheres or rods inside as a mixing device, but the materials of the inner wall of the mill, spheres or rods, etc. , Richio (Hachidemo'4
In order to avoid contamination with existing impurity components, it is preferable to use aluminum nitride itself or high purity alumina of 99.9% by weight or more. In addition, all of the surfaces in contact with the raw materials in the m and the rows can be made of plastic or coated with plastic. The plastics are not particularly limited, and include, for example, polyethylene, polypropylene, nylon, polyester, polyurethane, etc.
Can be used for F. In this case, the plastics may contain various gold components as stabilizers, so it should be checked in advance before use.

The fine carbon powder used as a raw material in the present invention has an ash content of 0.2% by weight, and a maximum of 0.1% by weight.
It is preferable to use one with a purity of % bone. Furthermore, since the particle size of the carbon affects the particle size of the aluminum nitride obtained, it is preferable to use it in the form of several particles with an average particle size of 1 μm or less. Carbon black, blackened carbon black, etc. can be used as the carbon, but carbon black/+Xm is also preferable for -U'.

The wet-mixed raw materials are filtered and/or dried if necessary, and then phosphoricated in an atmosphere of 9 elements or ammonia at a temperature of 1400 to 1800C. If the sintering temperature hS is lower than the above-mentioned temperature, the reaction is not favorable because the nitrogenation reaction will not proceed as efficiently as possible. Additionally, if the firing temperature increases above 100 degrees, a portion of the aluminum nitride obtained will undergo sintering. ．． Since aggregation between 1.5 particles and h'' occurs, aluminum nitride of the desired particle size is obtained and 'PR' is not desirable.

1. According to the nitride fine particles obtained by Yasei, the following f:'! 600~qoo'c in an atmosphere containing
The nitride particles are heat-treated in a manner similar to the above, and subjected to a step of oxidizing and removing unreacted carbon contained in the nitride fine particles.

If the above-mentioned adhesion degree is lower than the above-mentioned lower limit value, it will take a long time to remove unreacted carbon, which will be a disadvantage for the engineering, and if the above-mentioned back pressure degree exceeds the above-mentioned upper limit value, the surface of aluminum nitride will become heavy. , the acid content in the resulting aluminum nitride increases, causing deterioration of various properties and t(
I don't like it because it is.

The aluminum nitride laminated in this way has extremely low content of undesirable substances compared to the conventional aluminum compound.
J) Various physical properties of the aluminum nitride sintered body, such as thermal properties, light transmitting properties, etc., can be significantly improved. For example, the A4N content in the aluminum nitride obtained by the present invention is 97% or more. , the content of 4 lines of bound oxygen is 1.5% by weight or less, and the content of other gold components other than aluminum is 0.1% or less, preferably less than 0.1%, preferably less than 0.1% as a total shrinkage.

Further, the aluminum nitride powder A obtained in the present invention has an average particle size of 2 am or less. Average diameter h: If it is larger than this, the sinterability will be more likely to deteriorate.The aluminum nitride powder of the present invention is preferably used with an average diameter h of 1".
1. Contains powder having a particle size of 2 μm or less and a particle size of 5 nm or less in a ratio of 80% or more per volume.

As mentioned above, the aluminum nitride of the present invention has a high purity, for example, the combined oxygen content is preferably at most 1.031.
It is 1%. Conventionally, aluminum nitride fine powder with a combined oxygen content of less than 2% by weight has been found to have sufficient sintering properties, and in order to obtain good sinterability, a combined oxygen content of at least 2% by weight is required. Considering the state of the art believed to exist, the high-density aluminum nitride fine powder of the present invention
It is surprising that the material exhibits such good sinterability.

According to the present invention, high-purity and high-density aluminum nitride 4f is obtained from the high-purity aluminum nitride fine lead powder of the present invention! ,Q
The body is provided. Such a sintered body of aluminum nitride is obtained by molding the high-purity aluminum nitride fine powder of the present invention,
The obtained compact is sintered in an inert atmosphere at a temperature of 1,700 to 2,100°C to form an aluminum nitride compact.
By applying ljL! :1 construction Jl.

The aluminum nitride sintered body can also be manufactured by a method in which sintering is performed in the presence of a sintering aid. The above-mentioned sintering aid is not limited to OK and any known one can be used. A typical sintering aid that is generally suitably employed is at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals, and ythtrium, or its Q
It is generally advisable to add 0.01 to 5% by weight of the compound. The above-mentioned sintering aid is used in the hydrolysis step of the organoaluminum compound when producing the aluminum nitride powder of the present invention.
Sintering aids are added in processes such as the carbon addition process, and the resulting aluminum nitride powder contains sintering aids! The damaged product and -4
- You can also do that.

By sintering the aluminum monide powder containing the sintering aid at a temperature of 1,600 to 2,100° C. in an inert atmosphere, it becomes the excellent aluminum nitride sintered body.

The above-mentioned sintering method is not particularly limited, and any known sintering method can be used. For example, the hot press sintering method is carried out under pressure of 20 to 400 Kq/C, the gas pressure sintering method is sintering under nitrogen gas pressure of about 1 to 10 atm, and A pressureless sintering method performed under non-pressurized conditions may be employed as necessary.

The aluminum nitride sintered body thus obtained is an excellent high-density sintered body with a density of 6.12/- or more and a trench density of 3.29/- or more. 1. The holly sintered body has excellent thermal conductivity, and if it falls over, it will have a thermal conductivity of 1 [10 W/ro-K, preferably 110','l/m-K or more.

Furthermore, the translucency of the sintered body is also determined, for example, when the thickness of the sintered body is 0.5+m.
The phosphor vorticity of the qlC processed and polished product will be 35% or more for a wavelength of 6 μm.The sintered body thus obtained can be used, for example, as a highly heat conductive ceramic as a heat dissipation plate or a heat exchanger 4-1- , l-') ,
Board for stereo and video amplifiers.

I c: '(, +H, etc. and 1 to 1).Using its excellent translucency, it can be used as a window material for lamp arc tubes and sensors that use ultraviolet to infrared rays, as well as for radio wave transmittance. Window material for 1-noder.

Translucency at high temperatures 8 - Required use as special window material h' - Possible.

Furthermore, the aluminum nitride powder of the present invention is suitably used as a raw material for sialon-based materials, such as α-Flialon, α-Flialon,
A sialon compound with high purity and excellent properties that could not be achieved by using conventional AI and N as raw materials for β-8ialon, A/-N polytypes can be obtained.

In addition, since the aluminum q oxide powder of the present invention is a uniform fine powder with good dispersibility, it is effective as an additive to various ceramics such as silicon carbide, and as a powder for composites with polymers such as silicone rubber. Has rapid action.

The present invention will be explained in detail below using Examples, and the analytical methods or analytical devices used in each group in the Examples and Comparative Examples below are as follows.

Carbon analysis bimetallic carbon analyzer (manufactured by Ubabe Seisakusho gMI
A-3200) Acid 1 analysis: Kinbanchu 1':1 elemental analyzer (Gekto Susakusho fA
EMoA-1300) Nitrogen analysis: Melting separation neutralization titration xFi! Diffraction equipment: Seihon Denshi 13 JRx-12vn Scanning Hayaden Electronics Department 1 JEOL JSM-T200 Average particle size and particle size distribution measuring instrument: Baeba Manufacturing C! A'PA-500 Thermal Conductivity Oki 11
Fixing device: Rigaku Denki 1 Noser method heat fixing oil 1 fixing Wit
PS-7 Mitsuru, i! 3 rate i! 1++ constant equipment: Hitachi, Ltd. 6-recording spectrophotometer 630 model infrared spectrophotometer 260-30 model The light transmittance of the sintered body was calculated using the following formula.

■0 Work here. Intensity of throat incident light, 1 is intensity of transmitted light, Rf dimension reflection <! < , t Thickness of sintered body, μ ke absorption S = t
It is. R1d is determined by the refractive index of the sintered body, and if n is the refractive index, it can be expressed by the R order equation in air.

μ in the formula (1) is a finger indicating the translucency of the sintered body, and the value of μ shown in Example 1 (described later) was calculated according to the formula (1).

Example 1 Aluminum triyne brobogicide (At(o-is
o c3Hy )5) While stirring a solution of 200'' I dissolved in 1 ton of impropat tool, 2 ton of distilled water was added and the hydrolysis reaction was carried out for 1 hour, thereby converting the white precipitate into (1) The average particle size is Q, 45 pr
r'I Kagen Blank 101, a nylon pot and a nylon coated ball, and ethanol as a liquid dispersion medium. The mixture was uniformly mixed using a ball mill. After drying the obtained JL mixture, it was placed in a flat plate made of high-purity graphite and heated at a temperature of 1600° C. for 6 hours while continuously supplying nitrogen gas at 5 t/min into a lightning furnace. b) The reacted reaction mixture was heated in an atmosphere at a temperature of 750° C. for 4 hours to oxidize and remove unreacted carbon.

The obtained white powder was subjected to xR diffraction analysis (Xraydiff
ration analysis) results,
It was single phase (5 idle phase) A/=N. The average particle size of the powder is 1.20μm, and 6μm.
m or less accounted for 95% by volume. When observed using a scanning electron microscope, this powder was found to be uniform particles with an average particle size of 0.7/1 mP. In addition, as a result of analysis of this powder, O was found to be an impurity.
r + Si, Ni.

It is an extremely high-purity aluminum nitride powder that contains a trace amount of Fe metal, 1.0% by weight of oxygen, and 0.05% by weight of C.

Thus obtained J also vacated aluminum powder 1.0
gram was placed in a sumi-lead die coated with BN (boron nitride purple) with a diameter of 20 mm and heated to a temperature of 2000°C under a force of 100 Kf/- in one pot of gas at one pressure using a high frequency induction heating furnace. Hot pressed for 2 hours. The resulting baked product was a slightly yellowish, dense, translucent body.

The density of this sintered body was 6.26 f/-, and XS diffraction analysis showed that it was AtN in a single phase. In addition, the 3@conductivity+oS ratio of this sintered body is 3W/m-, and the thickness of this sintered body is 0.5
The light transmittance of the mIC processed and polished product was ν% for a wavelength of 6 μm. , and 40 drops in diameter hot pressed for the same moxibustion as above F7.

Approximately 2.8 x 5 x 6 cut from a disk with a thickness of about 6 sieves
Example 2 Aluminum nitride A powder (1
0F) to become 0-2 yt% as CaO
(No. 3) 2.4H20 was added to ethanol as a liquid medium, and mixed using a polyethylene pestle in a polyethylene mortar.

After drying this mixture, press it with the same method as in Example 1 to make a sintered body with a diameter of 20 parrots. Ta.

The density of this sintered body is 5.27? /r, l, and Xl
ζ. The light transmittance of a sintered body of octopus processed and polished to a thickness of 0.51 was 4% for light with a wavelength of 6 μm.

奎I dewo]F-毫1W はいきゅうい、 -2-One day's death on Saturdays and Sundays A white precipitate was obtained by adding 2 tons of prepared distilled water and carrying out a hydrolysis reaction at room temperature for 2 hours.

From the precipitate, aluminum nitride powder having the same properties as in Example 1 was obtained in the same manner as in Example 1. The powder was prepared by Tokuyama Soda Co., Ltd. in the same manner as in Example 2.

Claims (4)

[Claims] (1) A hydrolyzable organoaluminum compound is brought into contact with water or a water-containing organic solvent to perform hydrolysis, and the hydrolyzed product is heated and dehydrated, and the weight ratio of alumina:carbon is 1:0.36 or more. Fine carbon powder is mixed in a liquid dispersion medium at a ratio of 1:2, the mixture is fired in an atmosphere of nitrogen or ammonia, and the resulting fine powder is heated at 600 to 900°C in an atmosphere containing oxygen. A method for producing high-purity aluminum nitride powder, characterized by heating at a high temperature to remove unreacted carbon. (2) The production method according to claim (1), wherein the hydrolyzable organoaluminum compound is an aluminum alkoxide. (3) Claims (1) in which the organic solvent is alcohol
) manufacturing method described. (4) The manufacturing method according to claim (1), wherein the liquid dispersion medium is alcohol.