JPS5837271B2 - Method for manufacturing high-density silicon carbide sintered body - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for manufacturing a high-density silicon carbide sintered body.

Initially, high-density silicon carbide sintered bodies were manufactured by adding sintering aids such as boron and aluminum to silicon carbide powder and hot pressing the mixture.

Recently, a method of sintering without using a hot press has been developed by adding boron or boron carbide and carbon as sintering aids.

High-density silicon carbide sintered bodies are expected to be used as gas turbine parts, heat exchanger parts, pop-up parts, other high-temperature structural materials, and corrosion-resistant materials.

However, if the silicon carbide powder is sintered without pressure, the average particle size must be about 1.0 μm or less, optimally about 0.5 μm, or about 98% of the theoretical density (3.21 g). There is a problem that it cannot be easily sintered until it gets cold.

Further, since the amount of the sintering aid is several percent or less, it is difficult to disperse the sintering aid uniformly unless the particle size is even smaller than that of the silicon carbide powder, and it is not uniformly dispersed unless the particle size is smaller than 0.1 μm.

However, it is impossible to obtain such ultrafine powder using conventional methods.

The purpose of the present invention is to uniformly disperse the sintering aid and to
3.2 1 El/cat') about 96%, preferably 9
An object of the present invention is to provide a method for manufacturing a high-density silicon carbide sintered body sintered to 8%.

The present invention comprises silicon carbide powder, an amine complex of boron halide,
It is characterized by mixing and molding a sintering aid consisting of an amine salt of a halogenated boric acid or a mixture thereof and a thermosetting fat, and then sintering in a vacuum, a nitrogen atmosphere, or an inert gas atmosphere. The present invention relates to a method for producing a high-density silicon carbide sintered body.

In the present invention, the boron halide compound dissolves in one solvent and becomes a solution, so it can easily coat the surface of silicon carbide powder evenly by mixing, compared to conventional non-dissolving powdered sintering aids. It has the advantage of being superior in comparison to the previous one, and has the feature that relatively high density can be achieved easily.

The amine complex of halogenated boron is represented by BX3・A, and the amine salt of halogenated boron acid is represented by H B
It is represented by A, where B is boron, X is a halogen element such as fluorine, chlorine, bromine, or iodine, and A is aniline, monoethylamine triethylamine, piperidine, P-toluidine,
These include N-methylaniline, N-ethylaniline, 2,4-dimethylaniline, N,N-dimethylaniline, triethanolamine, and other amines.

In addition, phenolic resins, cresol-based Jugetsu L furan-based resins, epoxy-based resins, etc. are used as thermosetting resins.
There is no limit.

This thermosetting resin prevents the sintering aid from scattering as halogenated boron gas, and allows the decomposition reaction to take place in the thermosetting resin, liberating it as boron or boron carbide in a near atomic state. added.

Further, the particle size of the silicon carbide powder used in the present invention is preferably 10 μm or less in maximum particle size and 1.0 μm or less in average particle size.

The amount of boron in the boron halide compound is preferably 0.2 to 3 parts by weight per 100 parts by weight of silicon carbide powder.

In addition, the amount of thermosetting resin is sintered {from silicon carbide powder 100
An amount corresponding to 0.5 to 5 parts by weight of carbon is preferred.

When mixing the above components, it is preferable to add a solvent such as water, alcohols, ethers, benzene, etc., and mold the mixture by pouring it into a mold, or by drying and pulverizing it and then molding it with a mold. do.

In this case, a general shaping method can be employed, such as granulating the molded powder with an excipient and shaping it in a mold, or creating a slip using an appropriate dispersant and casting it.

Further, the sintering must be performed in a vacuum, a nitrogen atmosphere, or an inert gas atmosphere.

A suitable sintering temperature is 1900 to 2300°C.

The present invention will be explained below with reference to Examples.

Example 1 B with a purity of 99.4% obtained by processing silica powder with a purity of 99.5% and coke powder with a carbon content of 99.0% at 1900°C
100 parts by weight of SiC powder, 10 parts by weight of boron trifluoride monoethylamine complex (BF3-C2H5NH2) (0.958 parts by weight as boron amount), novolac type phenol resin (manufactured by Mitsubishi Gas Chemical KK, trade name SM-P 107)
A) 6 parts by weight (3 parts by weight as carbon content) and 100 parts by weight of ethyl alcohol were mixed in a ball mill for 30 minutes, dried at 80° C. for 10 hours, and pulverized.

Further, 10 parts by weight of a 10% aqueous polyvinyl alcohol solution was added as an excipient, stirred, and passed through a 36 mesh sieve to obtain a molded product.

Next, the powder was molded at a pressure of 1000 kg/1, and the outer diameter was 5
A molded product having a height of 10 mm was obtained.

After drying this precept at 80°C, the temperature was raised to 2000°C at a rate of 5000G/hour in a vacuum of 0.04 Torr.
Sintered for 5 minutes.

As a result, the theoretical density (3.z
A 96.0% high-density silicon carbide sintered body of 1 g/i) was obtained.

Comparative Example 1 100 parts by weight of the same B-SiC powder as in Example 1, 0.5 parts by weight of boron powder with an average particle size of 15 μm, novolak-type ferresin (manufactured by Mitsubishi Gas Chemical KK, trade name: SM) as in Example 1. -P 107A) 6 parts by weight (3 parts by weight as carbon content) and 100 parts by weight of ethyl alcohol were mixed, and a sintered body was obtained through the same steps as in the examples.

The resulting density was 2.99/1, which was 93.1% of the theoretical density.

Actual fiber example 2 A-S with a maximum particle size of 3 μm, an average particle size of 0.5 μm, and a purity of 95.0% obtained by crushing silicon carbide powder manufactured by a conventional method.
100 parts by weight of iC powder, boron trichloride monoethylamine (
BCl3-C2H5NH2) 15 parts by weight (1 part by weight as boron amount), 6 parts by weight of novolac type phenol resin (manufactured by Mitsubishi Gas Chemical KK, trade name SM-P 107A) (
3 parts by weight of carbon and 100 parts by weight of methyl alcohol were mixed, mixed in a ball mill for 30 minutes, treated in the same manner as in Example 1, and after molding, sintered in the same manner as in Example 1.

The result was 3.16g/cI11. The theoretical density is 9 with the density of
A high-density silicon carbide sintered body having a density of 8.4% was obtained.

Comparative Example 2 1.00 parts by weight of a-SiC powder similar to Example 2, 1.3 parts by weight of boron carbide with an average particle size of 15 μm (1.00 parts by weight as boron amount)
(parts by weight), Example 2 and 6 parts by weight of eye-like novolac fiber resin (1 part by weight as carbon content, 1 part by weight of methyl alcohol)
After mixing in a ball mill for 30 minutes, the same steps as in Example 1 were carried out to obtain a sintered body.

The resulting density was 3.05g/i, 95.0% of the theoretical density.
Met.

Example 3 Maximum particle size obtained by crushing green silicon carbide abrasive material 5 1tm
, a-SiC powder 100 with an average particle size of 0.7 μm
Parts by weight, aniline fluoroborate (HBF4Ca H5
NH2) 20 parts by weight (1.2 parts by weight as boron content), 4 parts by weight of novolac type phenol resin (manufactured by Mitsubishi Gas Chemical KK, trade name SM-P, 107A) (2 parts by weight as carbon content), methyl Blended with 15 parts by weight of alcohol,
After naturally evaporating methyl alcohol while mixing with a crusher, add 10% polyvinyl alcohol aqueous solution 1 as an excipient.
0 parts by weight was added, further mixed, and passed through a 36 mesh sieve to obtain a shaped powder.

Next, the molded powder was molded under a pressure of 1000 kg/CTL to obtain a molded product with an outer diameter of 50 mm and a height of 10 mm.

After drying this precept at 80°C, 2 T or
The temperature was raised to 2100° C. at a rate of 400° C./hour in a vacuum of 30° C., and sintered for 30 minutes.

As a result, a high-density silicon carbide sintered body having a density of 3.15 and 98.4% of the theoretical density was obtained.

According to the present invention, a high-density silicon carbide sintered body can be easily produced compared to conventional powdered sintering aids.

Claims (1)

[Claims] 1. A sintering aid consisting of silicon carbide powder, an amine complex of boron halide, an amine salt of halogenated boric acid, or a mixture thereof, and a thermosetting resin are mixed and shaped, and then heated in a vacuum, in a nitrogen atmosphere, or in a nitrogen atmosphere. A method for producing a high-density silicon carbide sintered body characterized by sintering in an active gas atmosphere.