JPH0215514B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a method for producing a powdered refractory material in which short silicon carbide fibers are uniformly dispersed.

Prior Art As is well known, silicon carbide fibers have excellent heat resistance, low coefficient of thermal expansion, and excellent thermal shock resistance. In addition, it has a low specific gravity and a high strength-elastic modulus. For these reasons, silicon carbide fibers are used as materials for fiber-reinforced composite materials such as various heat-resistant materials.

Problems with the conventional technology The method of obtaining silicon carbide long fibers is
Although it is described in Japanese Patent Application No. 52-70122, the process of synthetically spinning an organic silicon polymer such as polycarbosilane and firing it is complicated, so the cost is very high. It has also been proposed to obtain silicon carbide whiskers from a mixed gas such as SiCl ₄ and methane, but it is difficult to mass produce and the cost is also very high. Also, this whisker is 10~15μm
It is too short to be used as a composite fiber.
Furthermore, when compounding, it is difficult to mix whiskers and powder uniformly and in large quantities.

Purpose of the Invention The purpose of the present invention is to solve the disadvantages of the conventional method in terms of cost and mixing process, to enable mass production at low cost, and to uniformly disperse silicon carbide staple fibers that are extremely good at uniform mixing. An object of the present invention is to provide a method for producing a powdered refractory material.

Summary of the Invention That is, according to the present invention, a silicon (Si) component (metallic Si, etc.) and a fibrous carbon (C) component (carbon fiber, etc.)
are bonded with an organic binder and brought into contact with each other, and fired in a non-oxidizing atmosphere to uniformly disperse silicon carbide short fibers produced by reaction of carbon fibers in a silicon carbide or silicon nitride powder matrix. A method of manufacturing a powdered refractory material is provided.

Preferred Embodiment Silicon components used in the present invention include metallic silicon, silica powder, colloidal silica, and SiCl ₄ . These silicon components may be used alone or in combination.

As the fibrous carbon component, carbon fibers themselves, graphite fibers, flame-resistant fibers, kynol fibers, and commercially available products thereof are used.

The organic binder used to closely bind the silicon component and the fibrous carbon component is
Organic polymers such as PVA, polyethylene oxide, CMC, and Metrose can be used. These binders are particularly effective when metallic silicon or silica powder is used as the silicon component. As described later, the organic binder turns into carbon during the firing process.

First, the silicon component, carbon component, and organic binder are mixed. In this case, the amount of silicon component and carbon component is determined by the following reaction formula: Si+C→SiC, SiO ₂ +3C
→ Considering SiC + 2CO, etc., Si and C are stoichiometrically
Determined by the weight ratio of

Regarding the amount of the organic binder, it is sufficient that the solid content binds the Si component and the C component and brings them into close contact. For example, the blending amount of Si component and C component
1 to 20 parts by weight per 100 parts by weight is suitable. The organic binder may be dissolved in a solvent in advance. The solvent used in this case may be water or any other organic solvent such as benzene, toluene, acetone, hexane, methyl alcohol, and ethyl alcohol. The organic binder may also be used in solid form.

The components thus mixed are formed into particles of an appropriate size in advance in order to facilitate the pulverization of the reactant, and the particle size is preferably 5 to 20 mm. This granulation step may be carried out by any suitable known means.

Next, the silicon component and the carbon component are combined with an organic binder and dried by an appropriate method in order to bring them into close contact with each other. The drying temperature and time vary depending on the organic binder used, but are approximately 1 hour at 50° to 100°C.

The dry product obtained in this _way was heated at ₅₀₀ ° to
Fired at a temperature range of 2100℃.

In this firing process, the following reactions occur at each temperature stage.

(i) Approximately 800 to 1400°C: The following reaction occurs on the surface of fibrous carbon.

Si+C→SiC (ii) Approximately 1400 to 2100°C: The reaction of Si+C→SiC occurs to the inside of fibrous carbon.

On the other hand, in the matrix, the following reaction
SiC, Si ₃ N ₄ powder is produced.

3Si＋2N ₂ →Si ₃ N ₄ (approximately 1400℃) Si＋C→SiC (over 1400℃) SiO ₂ +3C→SiC＋2CO (2000℃) 3SiO ₂ +2N ₂ +6C→Si ₃ N ₄ +6CO (over 1500℃) Heating during the firing process The solidified granular reaction product is then pulverized, which can be easily carried out using a mortar or the like. As mentioned above, the reaction product is obtained in a state in which short silicon carbide fibers are uniformly dispersed in a matrix of SiC or Si ₃ N ₄ powder.
The powder forming the matrix is composed of SiC, Si ₃ N ₄ or a mixture thereof depending on the raw material of the Si component and the firing conditions.

The reaction product obtained by pulverization is dispersed in water, and powder particles of silicon carbide short fibers and matrix can be easily separated using a filter.

As described above, the present invention provides a method for producing a powdered refractory material in which short silicon carbide fibers are uniformly dispersed in a SiC or Si ₃ N ₄ powder matrix. Furthermore, the silicon carbide short fibers separated from this are promising as reinforcing fibers.

Examples of this invention are shown below.

Example 1 100 parts by weight of metallic silicon powder (average particle size 5μ), 50 parts by weight of graphite fibers (Kuraray carbon fiber tips, average fiber length 6mm, average diameter 10μ), and 6% polyvinyl alcohol aqueous solution (Shin-Etsu Chemical C −17)
450 c.c. and knead with a mixer. After kneading,
The sample was granulated into spheres with a diameter of 10 mm, dried in a dryer at a temperature of 90°C for about 1 hour to solidify the sample, and then baked in an electric furnace at 1450°C in a nitrogen atmosphere for 5 hours. The sample, which had been reacted and solidified after firing, was ground in a mortar. The reaction product obtained by pulverization had short SiC fibers uniformly dispersed in a fine powder matrix.

Next, the reaction product was dispersed in water and passed through a filter to separate powder particles and fibrous material.

According to X-ray diffraction, the particle powder has α- and β-
Si ₃ N ₄ and the fiber was β-SiC. The average fiber length of the obtained fibers was 200μ.

Example 2 100 parts by weight of silica powder (Nipsil VN ₃ , Nippon Silica Kogyo Co., Ltd., average particle size 16 mμ, SiO ₂ 94%) and flame-resistant fiber (Toho Rayon, Chipp, average fiber length 3 mm, average diameter 13 to 15 μ) ) 60 parts by weight and 1% aqueous solution of Metrose (Shin-Etsu Chemical 90SH30000) 450
cc, kneaded in a mixer, and fired in an electric furnace at 1700° C. for 2 hours in an argon atmosphere in the same manner as in Example 1 to obtain a reaction product in which fibers were uniformly dispersed in a powder matrix.

According to X-ray diffraction, the reaction product, both powder and fiber, was β-SiC. The average fiber length of the obtained fibers was 250μ.

Effects of the Invention According to the present invention, it is possible to produce a powdered material of silicon carbide or silicon nitride in which short silicon carbide fibers are extremely uniformly dispersed, which is promising as a raw material for producing fiber-reinforced composite ceramics. It is.

Furthermore, the silicon carbide short fibers can be easily separated and are promising as raw materials for various composite materials (eg, fiber-reinforced metals).

In addition, according to the present invention, an inexpensive method for producing silicon carbide short fibers can be provided.

Claims (1)

[Claims] 1. An inorganic substance containing a silicon component and carbon fiber are bonded with an organic binder and brought into contact with each other, and this is fired in a non-oxidizing atmosphere to produce silicon carbide or silicon nitride powder. A method for producing a powdered fire-resistant material in which short silicon carbide fibers produced by reacting carbon fibers are uniformly dispersed in a matrix. 2. A method for producing a powdery refractory material in which short silicon carbide fibers are uniformly dispersed according to claim 1, wherein the inorganic substance is metal silicon powder, silica powder, colloidal silica, or SiCl ₄ . 3. A powdered fire-resistant material in which silicon carbide short fibers are uniformly dispersed according to claim 1, wherein the carbon fibers are carbon fibers themselves, graphite fibers, flame-resistant fibers, infusible fibers, or kynol fibers. Production method. 4 The organic binder is polyvinyl alcohol,
A method for producing a powdery refractory material in which short silicon carbide fibers according to claim 1, which are polyethylene oxide, CMC, and Metrose, are uniformly dispersed.