JPS6047204B2 - Method for manufacturing silicon nitride powder - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing silicon nitride powder.

More specifically, general formula (I): SiR1(R2)3(I) In the formula, R represents an alkyl group having 1 to 4 carbon atoms, and R
” represents a hydrogen atom or a chlorine atom.

A silicon compound represented by the general formula (Π)■ Si(R3)O(Π) In the formula, R゜ is a hydrogen atom, a chlorine atom, or a carbon number J1-4
represents an alkoxy group.

A mixture of at least one silicon compound represented by the formula and carbon powder is prepared in PHI Sanno, and the resulting precipitate is calcined at 400 to 1100°C in a non-oxidizing atmosphere containing nitrogen. The present invention relates to a method for producing silicon nitride powder, which comprises firing a substance in which part of the portion has been replaced with nitrogen at 1300 to 1550°C in a non-oxidizing atmosphere containing nitrogen.

Silicon nitride is a material with excellent high-temperature stability and high-temperature strength, and its application as a high-temperature structural material, particularly as a member for high-temperature gas turbines, is attracting attention.

Conventionally, methods for producing silicon nitride include (1) directly nitriding metal silicon, (2) reacting silicon tetrachloride or silane with ammonia in the gas phase, and (3) reducing silica powder with carbon and nitrogen.・Nitriding methods are known.

In method (1), since the reaction is exothermic,
In order to control the heat generation, it is necessary to take some measures in the process. For example, as the metal silicon powder, relatively coarse particles are selected, and after nitriding, they are finely pulverized to obtain silicon nitride powder.

In this case, the mixture of impurities during the pulverization process is unavoidable, and although the impurity-containing material can be used as a raw material for general heat-resistant materials, it is not suitable as a raw material for high-temperature gas turbine components. Since method (2) is a vapor phase method, it is suitable for, for example, coating the surface of a semiconductor element with silicon nitride, but it lacks mass productivity and cannot be used as an industrial method for producing inorganic heat-resistant materials. Method (3) has the advantage that the reaction operation is simple, but the product is α-type silicon nitride,
β-type silicon nitride, silicon oxynitride (Si2
It is a mixed system of ON2) and silicon carbide, and has the disadvantage of a low yield of α-type silicon nitride. The present invention aims to provide a new method for producing silicon nitride powder different from the above-mentioned conventional technology, and the inventors have conducted extensive research in order to obtain silicon nitride powder with better physical properties. As a result, they succeeded in developing silicon nitride powder and completed the present invention.

According to the manufacturing method of the present invention, silicon nitride powder is manufactured by the following steps.

In the first stage, general formula (1) 5,
R1 and R2 have the same meanings as above.

A silicon compound represented by the general formula (■) 4
−ー ＼ （
In the formula (2), R3 has the same meaning as above.

A mixture of at least one silicon compound represented by: In this process, the intermediate material is obtained by firing the intermediate material.

Trichloromethylsilane (C
H3SiCl2), methylsilane (CH3SiH3),
Examples include trichloroethylsilane (C2l(5SiC13)) and ethylsilane (C2H5SiH3).

As the silicon compound represented by the above general formula (■),
Silicon tetrachloride (SiCl4), tetrahydroxysilane (SiH4), tetraethoxysilane ((C2H5O)
4Si), etc. These silicon compounds are commercially available in high purity. Examples of the carbon powder include carbon black and the like, and it is preferable that the average particle size is 1 μm or less. The ratio of this mixture is such that the weight ratio of the silicon compound represented by the general formula (1), the silicon compound represented by the general formula (■), and the carbon powder is O~1.0:0~1.0:0.
0:0.3-4.0, preferably 0-1.0:0-1.
0:0.4.~2.0 (however, all silicon compounds are expressed as SiO2). This mixture is mixed with hydrochloric acid, ammonium hydroxide, water-soluble organic amines such as methylamine, ethylamine, propylamine, etc., preferably ammonium hydroxide, to bring the pH to 1, preferably 8 to 10.
prepared and hydrolyzed to obtain a precipitate.

Furthermore, when using an acid, it can be used to a moderate degree. In the precipitate thus obtained, silicon compounds containing hydrocarbons are adsorbed around carbon particles. This silicon compound has the general formula (■), where R4 represents an alkyl group having 1 to 4 carbon atoms, and! is 3
It represents the following integer, and y represents the amount of adsorbed water.

It is considered to be a silicon compound represented by

Preferably, the precipitate thus obtained is dehydrated by heat treatment at about 300°C. Next, this precipitate is fired in a non-acidic atmosphere containing nitrogen at 400 to 1100° C. for at least three minutes to obtain an intermediate material.

This reaction is carried out quickly because an alkyl group having 1 to 4 carbon atoms is easily substituted with nitrogen. The non-oxidizing atmosphere containing nitrogen is preferably nitrogen and/or ammonia, but nitrogen-argon, nitrogen-hydrogen, or nitrogen-carbon oxide may also be used.

Further, it is particularly preferable to use an atmosphere in which nitrogen and/or ammonia is activated by a plasma method. The firing temperature is 400 to 1100°C, preferably 600 to 900°C. At temperatures below 400°C, almost no nitrogen is substituted, and 1
At temperatures above 100° C., the particle size of the intermediate increases, impeding the formation of silicon nitride.

The intermediate material thus obtained has a partially nitrided silicon oxide adsorbed around the carbon powder particles, and contains more nitrogen than O and less than 8% by weight, preferably 0.5 to 7% by weight.
．． The content may be 5% by weight, and hydrogen may be dissolved in solid solution.

This intermediate is also a suitable raw material for the production of silicon nitride and can also be isolated. In addition, this intermediate substance has the general formula (■) in which X1 is greater than 0 and 0.5
Represents a smaller value.

It is thought that the structure is such that the substance shown in is adsorbed around the carbon powder particles. Next, this intermediate material is fired at 1300 to 1550°C in a non-oxidizing atmosphere containing nitrogen.

The non-oxidizing atmosphere containing nitrogen is the same as above. Firing temperature is 1300-15500C, preferably 1350-14
Perform at 80°C. If the temperature is below 1300°C, the yield of silicon nitride will be low, and if it is above 1550°C, silicon carbide will be produced, which is not preferable.

In this nitriding reaction, the intermediate compound contains nitrogen, and the reaction rapidly proceeds with this nitrogen as a core. Furthermore, since the intermediate compound is adsorbed on the fine carbon powder, the contact area is large, and carbon reduction proceeds smoothly, resulting in a rapid nitriding reaction. Note that if carbon powder is added in excess, carbon remains and can be removed by oxidation by heating at 600 to 700°C. The silicon nitride powder thus obtained is a fine powder with a high yield of α-type silicon nitride, generally having an average particle size of 1 μm or less, and is a high-quality powder as a sintering raw material.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
Example 1 A mixture was prepared by mixing a trichloromethylsilane solution, a tetraethoxysilane solution, and carbon powder in various proportions.

The mixture was adjusted to pH 10 with anonmonium hydroxide, hydrolyzed, and the resulting precipitate was filtered.
After heat treatment at 0 to 300'C for 5 hours, intermediate material 5 was obtained by heat treatment at 400 to 1100C for 2 to 5 hours in an ammonia-nitrogen atmosphere or an ammonia-nitrogen active atmosphere by plasma method. The average particle size, nitrogen content (wt%), and amount of metal impurities of this intermediate material were investigated. The results are shown in Table 1. Example 2 The intermediate material obtained in Example 1 was prepared in various proportions,
2 at 1350-1551°C in a non-oxidizing atmosphere containing nitrogen
After heat treatment for ~5 hours, heat treatment was performed at 700°C under an air atmosphere for 8 hours.
A silicon nitride powder was obtained by heat treatment for a period of time.

The average particle size, nitrogen content, and metal impurities of this powder were measured. The results are shown in Table 2. Comparative examples are also shown. As is clear from the above examples, if the method of the present invention is followed,
A fine powder of silicon nitride is obtained, which is an excellent sintering material.

Claims (1)

[Claims] Primary formula: SiR^1(R^2)_3 In the formula, R^1 represents an alkyl group having 1 to 4 carbon atoms,
R^2 represents a hydrogen atom or a chlorine atom. A silicon compound represented by the following formula: Si(R^3)_4 where R^3 is a hydrogen atom, a chlorine atom, or a carbon number of 1 to 4
represents an alkoxy group. A mixture of at least one silicon compound represented by the formula and carbon powder is adjusted to a pH of 12 or less, and the resulting precipitate is calcined at 400 to 1100°C in a non-oxidizing atmosphere containing nitrogen. 1. A method for producing silicon nitride powder, which comprises firing a substance in which a portion of the material is substituted with nitrogen at 1,300 to 1,550° C. in a non-oxidizing atmosphere containing nitrogen. Quadratic formula: Si_3O_6_−_3_x__1N_2_x__1 In the formula, x_1 represents a number greater than 0 and less than 0.5. A substance obtained by supporting the compound represented by on carbon powder was heated at 1300 to 1550°C in a non-oxidizing atmosphere containing nitrogen.
1. A method for producing silicon nitride powder, the method comprising firing the silicon nitride powder at