JPS60235708A - Production of fine powder of silicon nitride - Google Patents

Abstract

PURPOSE:A specific organosilicon compound is subjected to gas-phase reaction in the presence of ammonia to produce fine powders of Si3N4 of high alpha-phase content. CONSTITUTION:An organosilicon compound selected from aminosilanes of formula I (R, R', R'' are H, alkyl, allyl, phenyl where the case where all of them are simultaneously Hs is excluded; n is 0-3; n is 4-n), cyanosilanes of formula IIand silazanes of formula III or IV (R, R', R'' and R''' are H, alkyl, allyl, phenyl, methylamino where the case in which all of Rs are Hs simultaneously is excluded; n is 3 or 4) is gasified by heating, mixed with an ammonia-containing nonoxidative gas such as hydrogen, argon or helium, introduced into the reaction tube of external heating type to effect the reaction at 800-1,500 deg.C under the pressure of 0.01-several atms. for 0.01-120sec to give the objective fine powder of Si3N4 of less than 0.5mum particle sizes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing fine silicon nitride powder. More specifically, the general formula is Rn5i(NR").

R11) m (wherein R, R', R'' each represent hydrogen, an alkyl group, an allyl group or a phenyl group, except when R, R', R'' are simultaneously hydrogen, n
= o ~ 3, m = 4- n), the general formula is RnSi(CN)m (
In the formula, R represents hydrogen, an alkyl group, an allyl group, a phenyl group, n-0 to 3, m=4-n) or a cyanosilane compound represented by the general formula (R1R' + R''
S l)2 N R'''or MoRR' S j-
NR"-) n (wherein, R, R', R",
R"' each represents hydrogen, an alkyl group, an allyl group, or a phenyl group, and n is 5 or 4, provided that R, R
This invention relates to a method for producing fine silicon nitride powder, characterized by subjecting a silazane compound represented by ' , R'', and R'' to hydrogen at the same time to a gas phase reaction.

In recent years, non-oxidizing ceramics such as silicon nitride and silicon carbide have excellent high-temperature properties such as high-temperature strength and thermal shock resistance, so research into their manufacturing methods and applications has been actively conducted. Its use is also opening up as a heat-resistant structural material for heat exchangers, etc.

Among them, silicon nitride has 1) high mechanical strength and maintains its strength even at high temperatures. 2) - Excellent thermal shock resistance. 3) Chemically stable and has good corrosion resistance. 4] The coefficient of thermal expansion is extremely small. It is attracting particular attention because of its characteristics such as: However, physical and chemical stability and reliability at high temperatures are strictly required for silicon nitride sintered bodies made of high-temperature, high-stress materials, which are particularly important factors for silicon nitride sintered bodies. Since certain thermal and mechanical properties are greatly influenced by the raw material, it is desirable that the raw silicon nitride contains as few impurities as possible, is fine, and has a high α phase content if it is crystalline.

Conventionally, the following method has been known as the main method for producing silicon nitride.

(1) A method of nitriding metallic silicon powder by heating it to a high temperature in nitrogen or ammonia gas.

(2) A method of simultaneously reducing and nitriding a mixture of silicon powder and carbon by heating it to a high temperature in nitrogen.

(3) An amide or imide thermal decomposition method in which silicon tetrachloride and ammonia are reacted at room temperature or low temperature, the resulting silicon amide or silicon imide is separated, and then heated to a high temperature in a nitrogen or ammonia atmosphere.

(4) A method in which silicon tetrachloride and ammonia are reacted in a gas phase at high temperature.

However, each of these methods has the following problems that must be solved.

Regarding (1), although it is a method currently used industrially, it is difficult to obtain a fine powder with this method, and the product obtained by this method needs to be pulverized for a long time. Therefore, Fe, Ca, and A contained in the raw material Si
Impurities such as I may remain after nitriding, or may be mixed in during the grinding process.

Method (2) not only requires the use of sufficiently purified silica powder and carbon powder as raw materials, but also the resulting product is α-type Si sN4. β-type Si3N4. It is a mixture of silicon oxynitride, etc., and it is difficult to reduce particle size and variation in particle size.

Method (3) includes a liquid phase method and a gas phase method, but in both methods, a large amount of ammonium chloride is produced as a by-product along with silicon amide and silicon imide. For this reason, separation of the product and removal of ammonium chloride during the thermal decomposition process are troublesome, and impurities are likely to be mixed in due to corrosion or the use of solvents.

Furthermore, there are limits to the particle size and crystal type of the first powder obtained by thermally decomposing silicon amide or silicon imide, making it possible to form fine particles or regular equiaxed granules.

Among these, the gas phase method (4) is said to yield high quality products.

The gas phase method (4) is generally a method in which silicon tetrachloride and ammonia are reacted in a gas phase at 600°C to 15UO°C to obtain amorphous silicon nitride powder or amorphous silicon nitride powder containing some crystal grains. be. Usually, this product is used as raw material for molding,
A silicon nitride sintered body is obtained by sintering, but in addition to this method, a method for obtaining a crystalline powder with a high α phase content is also known, for example, as disclosed in Japanese Patent Application Laid-Open No. 1983-1982.

However, as long as silicon tetrachloride and ammonia are used as raw materials, this method has become difficult to operate due to expansion of production scale.
We will be subject to various constraints in terms of equipment, etc. For example, since the reaction between silicon tetrachloride and ammonia is fast, the reaction also occurs at the outlet of the gas supply pipe, blocking the outlet and making long-term continuous operation difficult; (3)
Similar to the method described above, the problems include the difficulty in removing crystallized ammonium chloride and the corrosion of equipment caused by ammonium chloride. Furthermore, even if the defects in the manufacturing process could be overcome, it would be extremely difficult to completely remove ammonium chloride, and even after special equipment and cumbersome removal processes, the chlorine filth from Huiho We have carried out intensive research on obtaining highly pure silicon nitride that does not contain chlorine and does not undergo β crystallization when obtaining crystalline silicon nitride powder or produce harmful by-products during the molding and sintering process.

+'h,:''As a result, a halogen-free nitrogen-containing organic silicon compound, 1 '゛=rm compound is mixed with ammonia and an inert compound such as hydrogen, nitrogen, alkali, 1゛1 1.1J two carbons, helium, etc. It has been discovered that an amorphous or partially crystallized silicon nitride fine powder can be obtained by carrying out a gas phase reaction in a gas or non-oxidizing gas atmosphere, and if necessary, it can also be obtained by the above method. The present inventors have discovered that a crystalline powder with a high alpha phase content can be obtained by crystallizing a fine powder in an inert gas or non-oxidizing gas atmosphere, and have completed the present invention.

According to the present invention, since the raw materials used do not contain chlorine,
Unlike conventional gas phase reactions, ammonium chloride is not produced as a by-product. Therefore, the method of the present invention not only enables long-term continuous operation, but also eliminates the need for an ammonium chloride removal process. No need for anti-corrosion or high-grade materials when used now.

Moreover, since the raw material can be easily purified by operations such as distillation or sublimation, it is extremely easy to supply the raw material to the molding and sintering processes of the present invention.

In the method of the present invention, the following organic silicon compounds are used as raw materials.

(1) The general formula is RnS i (NR', R'9m
(In the formula, R1R' and R1' each represent hydrogen, an alkyl group, an allyl group, or a phenyl group,
n=0~, except when R1 and R11 are hydrogen at the same time
3, m=4-tl), such as trimethylmethylaminosilane, dimethylbis(methylamino)silane, methyltris(methylaminofusilane, trimethyldimethylaminosilane, dimethylbis(dimethylamino)silane, or methyltris). (dimethylamino)silane etc.

(2) The general formula is RnSi(CN)m (wherein R represents hydrogen, an alkyl group, an allyl group, or a phenyl group, and n =
O-5, m=4-n), such as trimethylcyanosilane, dimethyldicyanosilane, dimethylcyanosilane, methylcyanosilane, methyldicyanosilane or cyanosilane.

(5) The general formula is (R, R', R'''5i)2NR...
or R) υS i -N R'' +11C In the formula, R, R', R'', R'''i:t each represents hydrogen, an alkyl group, an allyl group, or a phenyl group, and n is 3 or 4 years old. Certain silazane compounds represented by i,1,5.3-tetramethyldisilazane, hexamethyldisilazane, heptamethyldisilazane Silazane,
1, 1, 3. 5,5-hexamethylcyclotrisilazane, 1. Ro-divinyl-1.1,3.3-tetramethyldinerazai or 1,1,3,3,5,5,7,7-
Octamethylcyclotetrasilazane etc.

These raw materials are purified to extremely high purity by conventional distillation, sublimation, etc. Furthermore, when supplying to a gas phase reaction, there is no problem even if 281 or more of these raw materials are mixed.

These raw materials are gasified in advance and introduced into the reaction tube.
At the same time, NH3 is supplied mixed with an inert or non-oxidizing gas such as R2, Ar, or kle.

Although the amount of NH3 varies depending on the raw material used, it is usually appropriate to supply it in an amount of 1 to 50 times the amount of silicon compound. If the amount of NHs used is small, the product will contain a large amount of carbon, which will defeat the purpose of the present invention. Moreover, if the amount is too large, NHs will be consumed unnecessarily, which is not economical. In addition, entraining N2 is effective in discharging carbon components in silicon compounds out of the system as hydrocarbons such as methane and ethane through hydrogen decomposition, and gases such as inert Ar5He are used as raw materials in the reaction. This is important for changing the partial pressure and controlling the reaction time.

In the method of the present invention, the reaction temperature is 800"6~1500℃
It is appropriate to select it within the range of
On the other hand, if the temperature exceeds 1500° C., it is not economical due to equipment restrictions and a large amount of energy. The partial pressure of the raw material gas and the reaction time are determined by considering the particle size and yield of the product, but the raw material partial pressure is 0.01 to several aIm and the reaction time is 120 to 0.01 SeC. is preferred. If the raw material partial pressure is lower than these values and the reaction time is long, the reactor will be large-sized, which is industrially disadvantageous. On the other hand, if the partial pressure is high and the reaction time is short, the reaction may not proceed or carbon may be mixed into the product, which is not preferable.

As a specific implementation method, for example, if the raw material is a liquid, a predetermined amount of liquid is introduced into a preheater and gasified, and a predetermined amount of ammonia and an inert or non-oxidizing gas are sufficiently uniformly mixed. The mixing shaft is then led to an externally heated reaction tube. For the reaction tube i-piece type, empty column or packed column type flow type is used, but in order to obtain uniformity of the produced fine powder, it is necessary to have a structure in which the flow of waste is heated uniformly without pulsation or irregular pulses. is important.

The generated fine powder is led to a collector after cooling, but since there is no ammonium chloride by-product, there are no particular restrictions on the material, and the commonly used dust collectors, electric dust collectors, etc. It is possible to use a dust collector, cyclone, etc. as appropriate.

The resulting fine powder obtained in this way is either amorphous with no peak observed in X-ray diffraction, or partially crystallized with a slight peak, and has a uniform particle size. They are spherical particles of 0.5 μm or less. Further, the carbon component is contained only to the extent that it does not have an adverse effect on the production of the sintered body.

Normally, this fine silicon nitride powder is fed to the molding and sintering process as it is without any process, but it is also possible to perform further firing and crystallization if necessary.

The atmosphere during crystallization was N2. N1-13. I(2,
An inert or non-oxidizing gas such as Ar or He is used.

Firing temperature f: J1000''C to 1700C1, preferably 1200'C to 1600C. Firing time varies depending on the degree of crystallinity, but is usually 0.5 to 5 hours.

As for the specific method of carrying out the calcination, there is a method in which the product is filled in a crucible or a flow-type reaction tube and an inert or non-oxidizing gas is passed through it.

The crystalline silicon nitride fine powder that cannot be obtained in this way has an extremely high alpha phase, and can change into a spherical, whisker, or plate shape depending on the heating conditions and atmospheric gas.

The method of the present invention will be described in more detail below, but the method of the present invention is not limited to these Examples.

Example 1 The first tube installed in an electric furnace had an inner diameter of 25++Im and a length of 70O.
The temperature of the electric furnace was maintained at 1200° C. using a device consisting of a U high purity alumina reaction tube and a collector attached to the outlet of the reaction tube. C that has been turned into scum using a preheater
After thoroughly mixing H35i(NHCH3)3 with NH3 and Ar (volume ratio 7.2:20.6=72.2), 4 people were placed in a reaction tube and reacted.

The product powder obtained by the Retsu 1 collector had poor quality in X-ray diffraction, and was found to be spherical particles with a particle size of 0.4 microns or less.

The amount of carbon as an impurity was 1°81°.

Next 1 (This product was packed into an alumina tube and heat treated at 420°C for 10 hours under an Ar atmosphere.The obtained fine powder was α-8i3N4 by X-ray diffraction, and no formation of β phase was observed. The crystal particles were approximately equiaxed with a size of 0.6 microns or less.

Further, the amount of carbon as an impurity was 0.5Wt96.

Examples 2 to 6 Various organic silicon compounds were reacted using the same experimental method as in Example 1. The experimental conditions and the results obtained are shown in Table 1.

Table 1 Continued from page 1 0 Author: Hiroshi Izaki, Tayuhama, Niigata City, New Harm Research Institute, 0 Author: Riako Nakano, Tayuhama, Niigata City, Shinhagi Research Institute, +1828 Mitsubishi Gas Chemical Co., Ltd. Niigata 18:00 Place: Mitsubishi Gas Chemical Co., Ltd. Niigata Procedural Amendment II (Owner: RJ) June 3, 1980 Director General of the Patent Office Mr. 1, Indication of the case 1981 Patent Application No. 091554 Name of the invention Amendment to the manufacturing method of silicon nitride fine powder Relationship with the Patent Case Address of Patent Applicant: 5-2-5 Marunouchi Sara-chome, Chiyoda-ku, Tokyo Contents of Amendment (1) The scope of the patent claims will be amended as shown in the attached sheet.

(2) “Unexamined Japanese Patent Application Publication No. 1983-1970” on page 6, lines 5 to 6 of the specification
41712" is deleted.

(3) In the 3rd line of page 1ffita of the details, [Plat-like J is
Correct to.

The general formula of the appended claims is RnS i (NR', R'')m (in the formula,
R, R'.

R" each represents hydrogen, an alkyl group, an allyl group, or a phenyl group, and n=o~5, m-4-〇, except when R, R', and R" are all hydrogen at the same time) An aminosilane compound represented by RnSi(C
N)m (wherein, R represents hydrogen, an alkyl group, an allyl group, a phenyl group, and n-0 to 3, nl''-'4-n) or a cyanonerane compound represented by the general formula CR
, R', R″S i )2NR”’ or MoRI?
Si -NR hanging W (in the formula, R, R', R" RIll
each represents hydrogen, an argyl group, an allyl group, or a phenyl group, and n is 5 or 4, for example R, R'
, R" except when RI I 1 is hydrogen at the same time) A method for producing fine silicon nitride powder characterized by carrying out a gas phase reaction in the presence of ammonia. 5JH Item 1 Patent Application No. 91354 of 1981 2 Name of the invention (!■, Manufacturing method of silicon nitride fine powder) 3, Sleeve 1 ``Relationship with old 1 Patent applicant address Chiyoda, Tokyo Ward Marunouchi-J-1': ] 5522
Name: Shito - Ryo Gas Chemical Co., Ltd. Representative: Kazuyoshi Nagano 4, Agent address: Marunouchi, Chiyoda-ku, Tokyo: U' 15, 2 and 7", 1 phenyl group, methylamino group, etc. and correct it.

(2) "Silicon powder" on page 4, line 4, 11 of the specification is corrected to "silica powder."

(3) Indicates 1 phenyl group in specification No. 10 @ 3rd line.”
1 represents a phenyl group, methylamino group, etc. and is corrected to -1.

(4) "Octamethylcyclotetrasilazane, etc." on page 10-F to line 9 of the specification. Tris(N-methylamino)triN-methyl-cyclotrisilane, tris(N-methylamino)tris(N-methylamino)tris(N-methylamino)
-methylamino)tri-N-methyl-trimethylnocrotrilinolasan and the like. Correct it as j.

(5) "IO, 575 hours" in the fifth line from the bottom of page 13 of the specification is corrected to "10.5 to 15 hours".

(6) 1 Examples 2 to 6 on page 15 of the specification] to “Example 2
〜7''.

(7) 1 Table 1-1 shows the results of “Example 7” and the following (
1? Add f.

[Organosilicon compound knee IL+(CII+NII)Si
NCIL+3-z, temperature +1200℃, time: 1.2s
ec, organic silicon X: 1.0volχ, Nlh concentration: 1
5.3vo1χ, ^r? a degree: 83.7volX, u
J1 degree: 0volχ, particle size: 0.1 micron or less, Carbon Nikkei 1.5 revision χ, heat treatment temperature: ] 5500℃ time:
2.0 hours, atmospheric gas: N2, shape of heat-treated product, !
+ shape, lumpy, α/β: 10010, carbon content 0.1 W
tχ'' (8) As per the appended claims, the general formula of appended claim 1 is Rn5i(NR', R'') - (wherein, R,
11', R'' each represents hydrogen, a furkyl group, an allyl group, or a phenyl group, except when R, R', and R'' are hydrogen at the same time, n is O~3,...24-n
), the general formula is Rn
5i(CN), (wherein R represents hydrogen, an alkyl group, an allyl group, a phenyl group, n.0-3, m.4-n
) or the general formula is (R, R', R", Si ) 2NR"' or 1,000 R
R'5i-NR"3-.1 (in the formula ti, R', R", 1
1"' each represents an alkyl group, an allyl group, a phenyl group, a 7minomethyl w, etc., and n is 3 or 4, except when R, R', R", and R"' are all hydrogen at the same time. "A method for producing fine silicon nitride powder characterized by subjecting the noradine compound represented by Application No. 91354 2 Name of the invention Process for manufacturing silicon nitride fine powder 6 Person making the amendment (Relationship to matter J Kazu Nagano Zura 4 Agent address 2, 115 Saracho, Marunouchi, Chiyo LIJ-ku, Tokyo, Claims: Attachment JIIl Attachment Claims The general formula is Rn5i(NR', R”)m (wherein, R
, R'.

Claims (1)

[Claims] The general formula is RnS i (NR', R")m (wherein R, R'. R" each represents hydrogen, an alkyl group, an allyl group or a phenyl group, Aminosilane compounds represented by R, R'', and R'' are hydrogen at the same time, n = 0-5, m-4-n), the general formula is RnSi
(CN)m (wherein R represents hydrogen, an alkyl group, an allyl group, or a phenyl group, n=0 to 5, m=4-n)
The cyanosilane compound or general formula represented by (R,
R“R11Si)2NR”’or one! :RR'
5i-NR"±n (wherein R, R', R" and R each represent hydrogen, an alkyl group, an allyl group or a phenyl group, and n is 3 or 4, Tazoshi R, R' ,
A method for producing fine silicon nitride powder, characterized by subjecting a silazane compound represented by (except when R1+ and R2H are hydrogen at the same time) to a gas phase reaction.