JP6703866B2 - Method for producing silicon carbide based composite - Google Patents

Description

The present invention relates to a method for manufacturing a silicon carbide based composite. More particularly, the present invention relates to a process for the production of simple and convenient silicon carbide based composite material having excellent bending strength in the process to obtain a silicon carbide based composite material.

Conventionally, a silicon carbide-based composite has been manufactured by the following manufacturing method (see Patent Document 1). First, an interface layer made of boron nitride is formed on a silicon carbide fiber (SiC fiber) by boron nitride-chemical vapor deposition (BN-CVD: Boron nitride-Chemical Vapor Deposition). Next, the obtained fiber is woven to form a preform made of silicon carbide fiber having a desired shape. After that, silicon carbide is produced in the obtained preform by polymer impregnation firing (PIP), and a silicon carbide-based composite is obtained.

JP, 11-49570, A

However, in the manufacturing method described in Patent Document 1, since BN-CVD is used, the manufacturing cost is high, and it is difficult to apply BN-CVD to the fabric.

The present invention has been made in view of the above problems of the conventional technology. The present invention aims to provide a method for producing a simple and convenient silicon carbide based composite material having excellent bending strength in the process to obtain a silicon carbide based composite material.

The present inventors have earnestly studied to achieve the above object. As a result, a silicon carbide fiber having a content of oxygen element of 5 to 15% by mass and having a structure including a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon is formed. The inventors have found that the above object can be achieved by forming an interface layer containing silicon, nitrogen, boron and carbon on the reform, and have completed the present invention.

The method for producing a silicon carbide-based composite of the present invention is a method for producing a silicon carbide-based composite including a skeleton made of silicon carbide fibers, an interface layer covering the skeleton, and a matrix layer, wherein oxygen A preform made of a silicon carbide fiber having a structure having an element content of 5 to 15 mass% and containing silicon carbide, and a coating part formed on the surface of the core and containing carbon, An interfacial layer forming treatment of impregnating a compound containing silicon, nitrogen, boron and carbon, drying and firing is performed to obtain a pre-composite, and then the pre-composite is impregnated with a compound containing carbon and silicon and heated. A matrix layer forming process is performed.

Further, a preferred embodiment of the method for producing a silicon carbide-based composite of the present invention is characterized in that the compound containing silicon, nitrogen, boron and carbon is polyboroorganosilazane.

Furthermore, another preferred embodiment of the method for producing a silicon carbide-based composite of the present invention is characterized in that the compound containing carbon and silicon is polycarbosilane.

According to the present invention, a silicon carbide fiber having a content of oxygen element of 5 to 15 mass% and having a structure including a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. An interfacial layer containing silicon, nitrogen, boron and carbon was formed on the preform consisting of. Therefore, it is possible to provide a method for producing a simple and convenient silicon carbide based composite material having excellent bending strength in the process to obtain a silicon carbide based composite material.

A method for fabricating a silicon carbide based composite material is described in detail according to an embodiment of the carbonization silicon-based composite and the present invention.

First, it will be described in detail charcoal of silicon-based complex. Carbonization silicon-based complex includes a skeleton made of silicon carbide fibers, and an interfacial layer and the matrix layer covering the skeleton. The silicon carbide fiber has an oxygen element content of 5 to 15% by mass, and has a structure including a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. The interface layer also contains silicon, nitrogen, boron and carbon. Furthermore, the matrix layer contains silicon carbide.

Carbonization having a content of oxygen element of 5 to 15% by mass, preferably 5 to 13% by mass, and a structure including a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. By forming an interface layer containing silicon, nitrogen, boron and carbon on a preform made of silicon fibers and then forming a matrix layer containing silicon carbide, a silicon carbide based composite having excellent bending strength is obtained.

When the oxygen element content in the core is less than 5% by mass or more than 15% by mass, the silicon carbide-based composite does not have excellent bending strength. This is not particularly limited, but it is considered that the bonding strength between the coating portion containing carbon and the core portion containing silicon carbide is not sufficient. Further, even when the interface layer containing silicon, nitrogen, boron and carbon is not provided, a silicon carbide based composite having excellent bending strength cannot be obtained. Furthermore, an interfacial layer containing silicon, nitrogen, boron, and carbon in a preform made of silicon carbide fibers containing 5 to 15% by mass of oxygen element and having no carbon-containing coating portion and containing silicon carbide. The silicon carbide-based composite obtained by forming a matrix layer containing silicon carbide after forming the above does not have a coating part containing carbon, and has an oxygen element content of 5 to 15 mass%. In a preform consisting of silicon carbide fibers containing, silicon, nitrogen, without forming an interface layer containing boron and carbon, compared with a silicon carbide-based composite obtained by forming a matrix layer containing silicon carbide, Bending strength tends to be low. Although it is not particularly limited, it is considered that oxygen reacts with nitrogen. In addition, although not particularly limited, since it has a coating layer containing carbon and silicon, nitrogen, an interface layer containing boron and carbon, than when not having an interface layer containing silicon, nitrogen, boron and carbon, It is also considered that the interface between the coating layer and the interface layer became more slippery and the bending strength was improved. Further, although not particularly limited, since it is a quaternary interface layer containing silicon, nitrogen, boron and carbon, the composition of the matrix layer is greater than that of a binary interface layer containing nitrogen and boron. And is easy to integrate with the matrix layer. It is considered that, as a result, slippage became easier at the interface between the coating layer and the interface layer, and bending strength was improved.

Further, a preform made of silicon carbide fibers having a content of oxygen element of 5 to 15% by mass and having a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. Since it has been decided to use, it not only has excellent bending strength, but there is no need to use BN-CVD, so there is a secondary advantage that the manufacturing cost can be reduced.

Further, a preform made of a silicon carbide fiber having a content of oxygen element of 5 to 15% by mass and having a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. Therefore, the use of silicon carbide fibers having not only excellent bending strength but also having an oxygen element content of less than 5% by mass, particularly less than 1% by mass, which is one of the factors that increase the manufacturing cost. Since it is not necessary, there is a secondary advantage that the manufacturing cost can be reduced.

Next, a method for manufacturing the silicon carbide based composite according to one embodiment of the present invention will be described in detail. The method for producing a silicon carbide-based composite of the present embodiment is a method for producing a silicon carbide-based composite including a skeleton made of silicon carbide fibers, an interface layer that covers the skeleton, and a matrix layer, and is described above . is one embodiment of a method of manufacturing a carbonization silicon-based complex.

The method for manufacturing the silicon carbide based composite according to the present embodiment includes the following step (1) and step (2).

In the step (1), the content of oxygen element is 5 to 15% by mass, and the silicon carbide fiber has a structure composed of a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. To obtain a pre-composite by impregnating a preform comprising the above with a compound containing silicon, nitrogen, boron and carbon, and drying and firing to obtain a pre-composite, that is, an interface layer in the intended silicon carbide-based composite. Is a step of forming.

The step (2) is performed after the step (1), and is a step of subjecting the pre-composite to a matrix layer forming treatment in which a compound containing carbon and silicon is impregnated and heated, that is, a target silicon carbide-based composite. Is a step of forming a matrix layer to obtain the intended silicon carbide-based composite.

By going through such steps (1) and (2), it is not necessary to use BN-CVD, so that the manufacturing cost can be reduced. In addition, since it is not necessary to use silicon carbide fibers having an oxygen element content of less than 5% by mass, particularly less than 1% by mass, which is one of the factors that increase the manufacturing cost, the manufacturing cost can be reduced. Furthermore, it is not necessary to apply BN-CVD to the woven fabric, and a silicon carbide-based composite having excellent bending strength can be obtained.

Here, the preform in the step (1) is not particularly limited, and for example, it can be obtained by a known method such as a blade weaving method, a filament winding method, a 2D laminating method using a predetermined silicon carbide fiber. It can be applied. Further, the predetermined silicon carbide fiber has an oxygen element content of 5 to 15% by mass, and has a structure including a core portion containing silicon carbide and a coating portion formed on the surface of the core portion and containing carbon. It is not particularly limited as long as it is one, but for example, a silicon carbide fiber having a content of oxygen element of 5 to 15 mass% and containing silicon carbide coated with carbon by chemical vapor deposition. Can be applied. Furthermore, the compound containing silicon, nitrogen, boron and carbon in the step (1) is not particularly limited, but examples thereof include polyboroorganosilazane. This compound forms an interfacial layer on the skeleton made of carbon silicon fibers described above, and from this point, polyboroorganosilazane may be called an interfacial layer precursor.

The interface layer precursor can be coated by a conventionally known wet method such as dipping which is simpler than BN-CVD. For example, drying can be performed at 150 to 200°C, and firing can be performed at 800 to 1000°C. The impregnation, drying and firing of these may be performed by so-called PIP. Further, the wet method can directly process the woven fabric, which has been difficult by BN-CVD.

The polyboroorganosilazane is synthesized by the following reaction formula. It may be referred to as a SiNBC-based polymer, and one having a mixing ratio of Si/B=1/2 may be abbreviated as "SiNBC-1/2".

Further, the compound containing carbon and silicon in the step (2) is not particularly limited, but for example, polycarbosilane (PCS) can be applied. Although the above compound functions as a matrix layer precursor, it can be used after diluting it with a diluting solvent such as toluene or xylene. It is also preferable to dilute with xylene. Furthermore, when diluting, the concentration of polycarbosilane is preferably 20 to 40% by mass, and more preferably 30 to 40% by mass.

As the polycarbosilane, for example, PCS-UH manufactured by Nippon Carbon Co., Ltd. may be used.

The formation of the matrix layer in which the compound is impregnated in the pre-composite and heated can be repeated a plurality of times, and for example, it is preferably performed about 6 to 12 times. The impregnation and heating of these may be performed by so-called PIP. Further, for example, heating can be usually performed by drying and firing, drying can be performed at about 80 to 120° C., and firing can be performed at about 800 to 1000° C. in a nitrogen gas (N ₂ ) atmosphere. The drying and firing may be performed by raising the temperature from room temperature to about 1000° C. in a nitrogen gas (N ₂ ) atmosphere.

Further, in the manufacturing method of the present embodiment, if necessary, a predetermined heat treatment can be further performed after the step (2). The predetermined heat treatment is to heat-treat the silicon carbide-based composite obtained in the step (2) at 1000 to 1500° C. in an inert gas, whereby the silicon carbide-based composite is crystallized and the quality is improved. Can be made uniform.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to such Examples.

(Example 1)
As the silicon carbide fiber woven fabric, carbon-coated silicon carbide fiber woven fabric (manufactured by NGS Advanced Fiber Co., Ltd., grade: type CG (with C coat), NL501-5HS, 5 sheets satin weave was used. Dimensions: 1000 mm x 2000 mm, Number of threads: warp; 22 threads/inch, weft: 22 threads/inch, thickness: 0.29 mm, basis weight 388 g/m ² , sizing agent type: P, cloth strength: warp direction; 2087 N/ 25 mm, weft direction: 2274 N/25 mm, and the specified yarn characteristics (representative value) are: yarn product name: NL-501, average fiber diameter: 14 μm, density: 2.55 g/cm ³ , tensile strength: ³ GPa. And tensile elastic modulus: 220 GPa.

A 40 mass% toluene solution of polyboroorganosilazane (“SiNBC-1/2” having an atomic ratio of Si/B=1/2) (manufactured by Art Science Co., Ltd.) was used as the interface layer precursor.

Further, as a matrix layer precursor, a 40 mass% xylene solution of polycarbosilane (PCS) (manufactured by NGS Advanced Fiber Co., Ltd., grade UH) was used.

First, carbon-coated silicon carbide fiber woven fabric was cut into a size of 50 mm×70 mm, and 12 sheets were laminated. Next, in the glove box, the obtained woven fabric laminate was vacuum impregnated with a 40% by mass toluene solution of SiNBC-1/2. Further, the obtained impregnated woven fabric laminate was set in a mold and pressure-molded. After that, the obtained woven fabric molded body is dried at 100° C. to evaporate the excess toluene, and heated to 1000° C. at a temperature rising rate of 200° C./hr in a nitrogen gas atmosphere and baked to obtain a pre-composite body. It was

Next, in the glove box, the obtained pre-molded body was vacuum-impregnated with a 40 mass% xylene solution of PCS-UH. Then, the obtained impregnated pre-composite is set in a mold, the impregnated pre-composite is dried at 100° C. to evaporate the excess xylene, and the temperature rising rate is 200° C./hr in a nitrogen gas atmosphere. It was heated to 1000° C. and baked.

The above PCS impregnation and firing were repeated 12 times to obtain a silicon carbide based composite of this example.

(Comparative Example 1)
First, carbon-coated silicon carbide fiber woven fabric was cut into a size of 50 mm×70 mm, and 12 sheets were laminated. Next, the obtained woven fabric laminate was set in a mold and pressure-molded. Further, the obtained woven fabric formed body was dried at 100° C. and heated to 1000° C. at a temperature rising rate of 200° C./hr in a nitrogen gas atmosphere to obtain a pre-composite body.
Further, in the glove box, the obtained pre-molded body was vacuum impregnated with a 40 mass% xylene solution of PCS-UH. Further, the obtained impregnated pre-composite is set in a mold, the impregnated pre-composite is dried at 100° C. to evaporate the excess xylene, and further, the temperature rising rate of 200° C./hr in a nitrogen gas atmosphere. It was heated to 1000° C. and baked.
The above PCS impregnation and firing were repeated 12 times to obtain a silicon carbide based composite of this example.

(Comparative example 2)
First, carbon-coated silicon carbide fiber woven fabric was cut into a size of 50 mm×70 mm, and 12 sheets were laminated. Next, the obtained woven fabric laminate was set in a mold and pressure-molded. Further, the obtained woven fabric formed body was dried at 100° C. and heated to 1000° C. at a temperature rising rate of 200° C./hr in a nitrogen gas atmosphere to obtain a pre-composite body.
Further, in the glove box, the obtained pre-molded body was vacuum impregnated with a 40 mass% xylene solution of PCS-UH. Further, the obtained impregnated pre-composite is set in a mold, the impregnated pre-composite is dried at 100° C. to evaporate the excess xylene, and further, the temperature rising rate of 200° C./hr in a nitrogen gas atmosphere. It was heated to 1000° C. and baked.
The above PCS impregnation and firing were repeated 6 times to obtain a silicon carbide based composite of this example.

(Comparative example 3)
As the silicon carbide fiber woven fabric, a silicon carbide fiber woven fabric not coated with carbon (manufactured by NGS Advanced Fiber Co., Ltd., grade: type CG (without C coat), NL201-8HS), 8 sheets satin weave was used. Specific specifications are dimensions: 1000 mm x 2000 mm, number of threads: warp; 22 threads/inch, weft: 22 threads/inch, thickness: 0.29 mm, basis weight 388 g/m ² , sizing agent type: P, cloth strength : Warp direction: 2087 N/25 mm, weft direction: 2274 N/25 mm. In addition, the specified yarn characteristics (representative value) are as follows: yarn product name: NL-201, average fiber diameter: 14 μm, density: 2.56 g/cm ³ , tensile strength: 2.95 GPa, tensile elastic modulus: 194 GPa, sizing adhesion Amount: 1.2% by mass.

First, a silicon carbide fiber woven fabric not coated with carbon was cut into a size of 50 mm×70 mm, and 12 sheets were laminated. Next, in the glove box, the obtained woven fabric laminate was vacuum impregnated with a 40% by mass toluene solution of SiNBC-1/2. Further, the obtained impregnated woven fabric laminate was set in a mold and pressure-molded. After that, the obtained woven fabric molded body is dried at 100° C. to evaporate the excess toluene, and heated to 1000° C. at a temperature rising rate of 200° C./hr in a nitrogen gas atmosphere and fired to obtain a pre-composite body. It was

Next, in the glove box, the obtained pre-molded body was vacuum-impregnated with a 40 mass% xylene solution of PCS-UH. Then, the obtained impregnated pre-composite is set in a mold, the impregnated pre-composite is dried at 100° C. to evaporate the excess xylene, and the temperature rising rate is 200° C./hr in a nitrogen gas atmosphere. It was heated to 1000° C. and baked.

The above PCS impregnation and firing were repeated 6 times to obtain a silicon carbide based composite of this example.

(Comparative example 4)
First, a silicon carbide fiber woven fabric not coated with carbon was cut into a size of 50 mm×70 mm, and 12 sheets were laminated. Next, the obtained woven fabric laminate was set in a mold and pressure-molded. Further, the obtained woven fabric formed body was dried at 100° C. and heated to 1000° C. at a temperature rising rate of 200° C./hr in a nitrogen gas atmosphere to obtain a pre-composite body.
Further, in the glove box, the obtained pre-molded body was vacuum impregnated with a 40 mass% xylene solution of PCS-UH. Further, the obtained impregnated pre-composite is set in a mold, the impregnated pre-composite is dried at 100° C. to evaporate the excess xylene, and further, the temperature rising rate of 200° C./hr in a nitrogen gas atmosphere. It was heated to 1000° C. and baked.
The above PCS impregnation and firing were repeated 6 times to obtain a silicon carbide based composite of this example.

[Performance evaluation]
A test piece of 5×50×2 (thickness) mm was cut out from the silicon carbide-based composite of each example, and the test piece was subjected to a three-point bending test at room temperature (25° C.). The results obtained are shown in Table 1.

From Table 1, it can be seen that the silicon carbide-based composite of Example 1 belonging to the scope of the present invention has a bending strength superior to that of the silicon carbide-based composite of Comparative Example 1 outside the scope of the present invention. Further, a silicon carbide fiber woven fabric not coated with carbon is subjected to an interface layer forming treatment of impregnating a compound containing silicon, nitrogen, boron and carbon, drying and firing to obtain a precomposite, and then a precomposite. Even when the matrix layer formation treatment of impregnating with a compound containing carbon and silicon and heating was carried out, the strength development of the composite was not recognized. Furthermore, it was found that the strength manifestation effect of the composite becomes remarkable by increasing the number of times of treatment with PIP.

Although the present invention has been described above with reference to some embodiments and examples, the present invention is not limited to these and various modifications can be made within the scope of the gist of the present invention.

Carbonization silicon-based complexes, for example, can be applied, such as a turbine blade for a gas generator for and nuclear generators, can be dense, high density products obtained with good production efficiency.

Claims (3)

A method for producing a silicon carbide based composite comprising a skeleton made of silicon carbide fibers, and an interface layer and a matrix layer covering the skeleton,
A preform made of a silicon carbide fiber having a structure including an oxygen element content of 5 to 15% by mass, a core portion containing silicon carbide, and a coating portion formed on the surface of the core portion and containing carbon. , A compound containing silicon, nitrogen, boron and carbon is impregnated, dried and baked to obtain an interfacial layer forming treatment to obtain a pre-composite,
Next, a method for producing a silicon carbide based composite, which comprises subjecting the pre-composite to a matrix layer forming treatment in which a compound containing carbon and silicon is impregnated and heated. The method for producing a silicon carbide based composite according to claim 1 , wherein the compound containing silicon, nitrogen, boron and carbon is polyboroorganosilazane. The method for producing a silicon carbide based composite according to claim 1, wherein the compound containing carbon and silicon is polycarbosilane.