JPS6172607A - Production of silicon ceramic - Google Patents

Abstract

PURPOSE:A novel reaction between ammonia and a dihalosilane is effected and the resultant polysilazane is used as a starting material to effect heat treatment under vacuum or in an inert atmosphere to give silicon ceramics easily in high yield. CONSTITUTION:Ammonia is brought into contact with a dihalosilane of the formula: RHSiX2 (R is monovalent hydrocarbon group of 1-6 carbon atoms; X is halogen) to give a polysilazene. The polysilazane is heat-treated at a temperature over 1,200 deg.C in an inert atmosphere or under vacuum to give the desired silicon ceramics. The molecular weight of the polysilazane is preferably more than 10,000. After polysilazane is brought into contact with ammonia and dihalosilane, it is preferably heated at 50-500 deg.C in an inert and anhydrous atmosphere to increase the molecular weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method for producing silicon ceramics, and more particularly, the present invention relates to a method for producing silicon ceramics. The present invention relates to a method for producing a complex with.

[Technical background of the invention and its problems] Only the following four studies have been reported regarding the production of silicon ceramics using silazane or polysilazane having a silicon-nitrogen-silicon bond as a starting material. .

West German Patent No. 2,238,078 (1974) discloses a method of contacting dimethyldichlorosilane and ammonia in the gas or liquid phase to obtain a polysilazane oligomer, which is then heat treated.

In addition, the Journal of Applied Polymer 9 Science
tionpolymer 5science), 27
, 3751 (+982), methyltrichlorosilane and methylamine are brought into contact to produce methyltrictylaminosilane, heat treated at 52°C to form 11t of polycarbosilazane, and then further heat treated at about 1.2QO°C. A method has been reported.

However, it is difficult to obtain high-molecular-weight silazane 7 using any of these methods, and even in the heat treatment of polysilazane, the yield of silicon ceramics decreases due to heat treatment.
difficult to obtain.

In addition, communication φ of American φ Ceramics Society (Gosmun, ofAme
r, Ceram, 5ociety), G-13(1
983), dichlorosilane is brought into contact with ammonia to obtain borine razan, which is then mixed with 1
, 150'O is disclosed. However, this method has the problem that the resulting vorinolazan has poor stability and is easily decomposed at room temperature in the presence of acids, resulting in a portion of it becoming silochitinated.

Furthermore, as shown in Japanese Patent Application Laid-Open No. 558-83725, l! ! A method is disclosed in which polysilazane is obtained by contacting J-containing disilane and ammonia, and silicon ceramics are obtained by heat treatment. According to this method,
It has been reported that it is possible to polymerize polysilazane (although it is reported that disilane containing I!! primes as a raw material is used in the state of different 1!! prime numbers, so it is possible to polymerize polysilazane with certain properties. It has been reported that it is difficult to obtain polysilazane, and that only β-silicon carbide is obtained when polysilazane is heat-treated at 1800°C.Therefore, it is impossible to produce silicon nitride according to the purpose with this method.゛[Objective of the Invention] The present invention is directed to obtaining a high molecular weight polysilazane using as a starting material a herosilane having a silicon-hydrogen bond that is relatively easily separated, and further producing silicon ceramics using this polysilazane as a starting material. The purpose is to

[Summary of the Invention 1 As a result of repeated studies to achieve the above object, the present inventors found that when using a dihalosilane represented by the general formula R) (S + We have found that a silazane oligomer with a higher molecular weight than dihalosilane can be obtained, and that although the obtained silazane oligomer is relatively stable at room temperature, it is easily further polymerized by heating. The present inventors have discovered that silicon ceramics can be produced in good yield by heat-treating them at high temperatures, leading to the completion of the present invention.

That is, the present invention relates to a method for manufacturing silicon ceramics using polysilazane.

As polysilazane, ammonia and general formula: % formula % (wherein, R represents a monovalent hydrocarbon group having 1 to 6 carbon atoms,
or a halogen atom) by contacting with a dihalosilane represented by ().
The method is characterized in that the polysilazane is heat-treated at a temperature of 1200'O or more in an inert atmosphere or vacuum.

That is, the first feature of the present invention is that ammonia and a dihalosilane represented by the general formula: % (wherein R and X have the same meanings as above) are used as polysilazane as a raw material for silicon ceramics. It is to use polysilazane obtained by a novel reaction of contact.

The dihalosilane used in the above reaction has the general formula RHS i
It is represented by X 2, where the number of carbon atoms represented by R is 1 to
6 monovalent hydrocarbon groups include methyl group, ethyl group,
Examples include alkyl groups such as propyl, butyl, and hexyl groups; alkenyl groups such as vinyl and allyl groups; is a halogen atom with fluorine, chlorine, 7 odor, and 7 odor, but -1! 11 in terms of λ! It is an elementary atom.

When producing polysilazane, dihalosilanes having only the same R group may be used, or dihalosilanes having different R groups may be mixed in a predetermined ratio. Note that dihalosilanes are generally It is produced industrially by direct process products, decomposition of chlorine-containing disilane with hydrochloric acid, Grignard reaction, etc.

The ammonia used in the present invention is preferably ligneously anhydrous in order to prevent hydrolysis of the dihalosilano and the resulting silazane oligomer. Here, essentially anhydrous means absolutely anhydrous. It doesn't have to be,
This means that some moisture can be tolerated.

The reaction proceeds simultaneously when ammonia and dihalosilane come into contact with each other, and a polysilazane intermediate is formed via an aminosilane compound. Add raw materials, 1,
Although there are no restrictions on the order in which they are added, since ammonia is in the form of dregs, generally the method of introducing ammonia into dihalosilane is υ. In this case, Shibaronran 1
Normally, 7 moles of ammonia gas is 1 atm at room temperature.
As the 0 reaction that supplies 0 to +001 progresses, 371
The amount of ammonium oxide formed increases and the viscosity of the reaction mixture increases significantly. Therefore, it is desirable to add dihalosilane to a solvent with a low boiling point so that stirring of the reaction mixture is uniformly performed. Examples of such a low boiling point solvent include pentane, heptane, hexane, benzene, and toluene. These solvents are preferably essentially anhydrous for the reasons mentioned above and are generally used after drying. When such a solvent is used, it is usually added in an amount of 100 to 1,000 parts by weight per 100 parts by weight of dihalosilane.

The reaction can also be carried out at room temperature since ammonia and dihalosilane come into contact with each other and pass through at the same time. In order to promote one reaction, the reaction system may be heated. Generally, when one reaction is carried out under normal pressure, the reaction system is heated to a temperature at which the low boiling point solvent refluxes. Furthermore, for the purpose of promoting the reaction, the 0 reaction time, which may be carried out under electrical sealing, is usually 0.
．． 5 to 5 hours.

Polysilazane is produced by the above reaction.

In order to obtain desirable ceramics in the next heat treatment step, it is preferable to use a polysilazane with a molecular weight of 10,000 or more. In this heat treatment, the reaction mixture containing the polysilazane may be directly subjected to the treatment, or the polysilazane may be isolated from the reaction mixture according to a conventional method and then subjected to the treatment. Isolation of the polysilazane from the reaction mixture may be carried out, for example, by filtration of the by-product ammonium salt,
This is carried out by subjecting the filtrate to heat or vacuum treatment to remove low-boiling solvents and volatile products. In the reaction described in item 1 for polymerizing polysilazane, the degree of polymerization of polysilazane can be determined by heating temperature and time, and a polysilazane having a degree of polymerization of several tens to tens of thousands or more can be arbitrarily obtained.

The reaction is usually carried out at a temperature of 50 to 500°C, preferably 150 to 35°C.
It is carried out within a temperature range of 0°C, but if it is less than 50°C, a t-polymerization reaction will occur, and if it exceeds 500°C, it will be difficult to control the degree of polymerization.9 The reaction time is usually 0.2~ It is 10 hours.

The second feature of the present invention lies in the discovery of a new use in which the dihalosilane obtained by the above reaction can be used as a raw material for producing silicon ceramics. That is, in the present invention, finally, the polysilazane obtained by the contact reaction of ammonia and dihalosilane, or the polysilazane obtained by subjecting it to a reaction to further polymerize it, either as it is or after being purified, 1. 2
The heat treatment is performed at a temperature of 00°C or higher. This heat treatment is performed under an inert atmosphere such as nitrogen gas or argon gas or in vacuum in order to prevent the polysilazane from brewing. Heating temperature is 1.200℃ or higher, preferably 1,300℃
The temperature range is ~1,800°C.

1. If it is below 200°C, it will be difficult to obtain silicon ceramics of 1M crystal, and from the viewpoint of economical efficiency and the elevation and prevention of the produced ceramic fuchs, it is not preferable to raise the temperature too high, and the heating time is usually 0. .1 to 30 hours. Furthermore, in order to prevent damage to the heating furnace due to gas produced by-product during heat treatment of polysilazane, 1.2.
Before processing at 00°C or above, apply 500% polysilazane in advance.
It is preferable to perform heat treatment within the temperature range of ~1,000°C for 0.1 to 10 hours to remove by-products.

In the reaction L, one or more polysiloxanes can be optionally used. Polysiloxanes having hydrocarbon groups with a small number of carbon atoms as organic groups (e.g.
When a dihalosilane in which R is a lower alkyl group is used as a raw material by reacting with ammonia, silicon nitride is mainly obtained; obtained by reacting dihalosilane with ammonia)
When using as a raw material, mainly silicon carbide, 1
The raw material is obtained. Further, by blending both polysiloxanes in an appropriate ratio, a silicon, +; ceramic composite in which silicon nitride and silicon carbide are mixed in a ratio of tiI can be obtained.

[Effects of the Invention] According to the present invention, silicon ceramics can be easily obtained with high yield. Furthermore, the organic group bonded to the silicon atom of the dihalosilane as the starting material or the polysilazane as the direct raw material is appropriately added to 1! ! Depending on the selection, a silicon ceramic made of silicon nitride or silicon carbide, or a silicon ceramic composite containing a mixture of silicon nitride and silicon carbide can be obtained. Furthermore, by appropriately using two or more types of raw materials having different organic groups, the mixing ratio of silicon nitride and silicon carbide in the silicon ceramic composite can be freely adjusted. Therefore, the present invention is industrially extremely useful as a method for producing silicon ceramics.

[Embodiments of the Invention] Example 1 Polysilazane' A pressure-resistant reaction vessel equipped with a stirrer was charged with a weighted part of methyldichlorosilane cHH9+CfL2too and 4 parts of n-hexane as a low-boiling melt, and then the pressure-resistant reaction vessel was charged. Dry ammonia was blown in through the gas inlet attached to the gas inlet. At the same time as ammonia was blown in, the pressure rose and the reaction temperature also rose. 0The ammonia gas was gradually introduced so that the reaction temperature decreased to below 80°C. Continue to introduce, 30
After a few minutes, no heat generation due to the reaction and no decrease in the pressure of ammonia gas were observed. Ammonia gas supply amount is 50
Parts by weight. Then, the introduction of ammonia gas was stopped.

After continuing stirring for an additional 30 minutes, the 5 reactants were taken out from the pressure-resistant reaction vessel. After that, filter the ammonium salt,
The resulting liquid was distilled under reduced pressure to remove low boiling products and n
- Hexane removed, relatively viscous polysilazane oligo q-35,8ff! −% parts were obtained.

Next, this polysilazane oligomer 3offia portion was placed in the pressure-resistant reaction vessel again, and after nitrogen gas substitution, heat treatment was performed under various heating conditions. After the heat treatment was completed, when it was cooled to room temperature, decomposed gas was generated, and a residual pressure was observed.1 When the decomposed gas was released and the decomposed products were removed, a white to transparent polysilazane resin was obtained. The results are shown in Table 1.

The polysilazane Nos. 1 to 4 of E-ceramix Table 1 were placed in a silicon nitride crucible and heated at 750° C. for 1 hour while introducing nitrogen gas first to obtain a black solid.

This solid was then heated at 1,800° C. for 1 hour to obtain a solid with a gray appearance. The obtained solid is harder as it is produced from polysilazane with a smaller molecular weight.

This solid was subjected to X-ray diffraction decomposition, and the production ratios of various components in the silicon ceramics were calculated using the 1 weight method from the calibration curve of known samples. The results obtained are shown in Table 2.

Implementation fP42 A gray silicon ceramic solid was obtained in the same manner as in Example 1, except that the heating temperature of the black solid was 1,700"0. The production ratios and yields of various components were determined in the third example. Shown in the table.

Example 3 Phenyldichlorosilane C6H3H as polysilazane
The reaction temperature was increased to a maximum of 81"O, but after 40 minutes, a temperature drop was observed. The pressure drop of ammonia gas was also reduced.The amount of ammonia gas supplied was 40 parts by weight.Then, 1 hour after the start of the reaction, the introduction of ammonia gas was stopped, and stirring was continued for an additional 30 minutes. When the salt was filtered off and n-hexane was removed under reduced pressure, 38 parts by weight of a viscous polysilazane oligomer was obtained.

Next, 38 parts by weight of this polysilazane oligomer was heat treated at a temperature of 300°C for 2 hours in the same manner as in Example 1. In addition to a small amount of liquid, solid polysilazane resin 3
4 parts by weight were obtained.

Silicon ceramics The polysilazane obtained by the above reaction was heated in the same manner as in Example 1 to obtain silicon ceramics. The obtained ceramic was composed of β-3iC in which β-5i3N4 was present in a very small Wi amount, and the yield was 23%.

Example 4 The polysilazane resins No. 4 in Table 1 and the polysilazane resin obtained in Example 3 were each ground into powder, mixed in various proportions, and then heated in the same manner as in Example 1. By doing so, silicon ceramics shown in Table 4 were obtained.

Claims (4)

[Claims] (1) In a method for producing silicon ceramics using polysilazane, as polysilazane, ammonia and general formula: RHSiX
_2 (wherein, R represents a monovalent hydrocarbon group having 1 to 6 carbon atoms,
Production of silicon ceramics using a polysilazane obtained by contacting a dihalosilane represented by Method. (2) The method for producing silicon ceramics according to claim 1, wherein the polysilazane has a molecular weight of 10,000 or more. (3) After the polysilazane is brought into contact with ammonia and dihalosilane, 50 to 50
The method for producing silicon ceramics according to claim 1, wherein the silicon ceramics are polymerized by heating at 0°C. (4) The heat treatment temperature of polysilazane is 1,300 to 1,
The method for producing silicon ceramics according to claim 1, wherein the temperature is 800°C.