JP2002211980A - SiC OR C FIBER/SiC COMPOSITE MATERIAL AND PRODUCTION METHOD TEHREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an SiC or C fiber/SiC composite material which has increased bond strength between SiC or C fiber and an SiC matrix by forming a thin C coating layer on the surface of the SiC or C fiber, and has excellent heat resistance and wear resistance. SOLUTION: In the SiC or C fiber/SiC composite material, an SiC matrix is bonded to SiC or C fiber via a C layer with a film thickness of 50 to 300 nm formed on the boundary of the SiC or C fiber/matrix, and the gaps of the SiC or C fiber are filled with the SiC matrix. The composite material is produced by forming a C layer with a film thickness of 50 to 300 nm on the surface of the SiC or C fiber by a vapor growth method, and thereafter filling the gaps of the SiC or C fiber with an SiC phase produced by the thermal decomposition of alkylchlorosilane.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a SiC or C-fiber / SiC composite material suitable as a structural material for a special environment or an extreme environment such as nuclear power, aerospace, and energy, and a manufacturing method thereof.

[0002]

2. Description of the Related Art Ceramic materials having excellent heat resistance and wear resistance have attracted attention as materials used in special or extreme environments such as the nuclear and aerospace fields. Ceramic materials are also used as members for heat exchangers, mechanical seals, and the like exposed to severe conditions. Above all,
Non-oxide ceramics such as SiC and Si ₃ N ₄ are materials that maintain excellent strength even in a high-temperature atmosphere. In particular, SiC and C are superior in strength, heat resistance, high thermal conductivity, and wear resistance, and they do not generate long-lived radionuclides even by neutron irradiation. It is a promising material in a wide range of fields up to the first partition of the furnace.

[0003] SiC has a high melting point and excellent high-temperature properties, but is itself a brittle material. Therefore, development of a composite material reinforced with C fibers or SiC fibers has been promoted. SiC or C-fiber / SiC composite material is reactive sintering,
Although it is manufactured by various methods such as a hot press method, there is an advantage that a gas-phase reaction permeation method (CVI) can be formed into an arbitrary shape close to the final product and high strength. In the gas phase reactive infiltration method (CVI), the internal voids of SiC or C fibers are filled with a SiC phase generated by thermal decomposition of alkylchlorosilane.

[0004]

SUMMARY OF THE INVENTION SiC or C fiber / S
The properties of iC composites are greatly influenced by the texture of the fiber / matrix interface. Therefore, C, SiC, B
After pre-coating SiC or C fibers with N or the like, a gas phase reactive infiltration method is performed. The coating layer applied to the SiC or C fiber has a high affinity for SiC generated by a thermal decomposition reaction, and improves the bonding strength at the fiber / matrix interface. However, since it is difficult to control the structure of the coating layer formed at the fiber / matrix interface, the optimum conditions are not clear, and high-stability characteristics cannot be imparted to SiC or C-fiber / SiC composite materials.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been devised to solve such a problem, and provides a mechanical layer by forming a C layer having a predetermined thickness as a coating layer at a fiber / matrix interface. Si with excellent properties and thermal properties
It is intended to provide a C or C fiber / SiC composite material.

In order to achieve the object, the SiC or C fiber / SiC composite material of the present invention has a thickness of 50 to 300 nm formed at the SiC or C fiber / matrix interface.
The SiC matrix is bonded to the SiC or C fibers via the layer, and the voids of the SiC or C fibers are filled with the SiC matrix.

This SiC or C fiber / SiC composite material has a thickness of 50 to 50% on the surface of the SiC or C fiber by a vapor phase growth method.
After forming a C layer of 300 nm, it is manufactured by filling voids of SiC or C fibers with a SiC phase generated by thermal decomposition of alkylchlorosilane. The coating layer formed on the fiber surface has a thickness of 5 as the first layer.
As long as there is a 0-300 nm C coating layer,
A multilayer structure in which iC and / or C layers are stacked may be used.

[0008]

The formation of a C coating layer on SiC or C fibers has been known per se. However, since the fibers are knitted after forming the C coating layer on the surface of each fiber, the coating layer is formed during knitting. Easily peels off.
Further, since knitting itself becomes difficult with a fiber having a thick coating layer formed thereon, the layer thickness of the coating layer is also 50 n.
m or less. Therefore, it cannot be said that the coating layer has a sufficient effect on improving the physical properties of the finally produced SiC or C fiber / SiC composite material. Therefore, the present inventors send a hydrocarbon gas such as methane, ethane, or propane into a fiber preform molded into a predetermined shape, and when depositing carbon generated by thermal decomposition of the hydrocarbon gas on the fiber surface, the carbon gas is uniform. They found that a dense C coating layer was formed, and filed a separate application (patent application filed simultaneously: serial number 12P382).

The present inventors have clarified in the course of investigating the effect of the thickness of the C coating layer formed as described above on the mechanical properties of SiC or C fiber / SiC composite material. When controlling the thickness of the C coating layer formed on the fiber surface in the range of 50 to 300 nm,
It is based on the finding that the mechanical properties of SiC or C-fiber / SiC composites are significantly improved. After a C coating layer having a predetermined thickness is formed, an SiC and / or C layer may be further laminated on the C coating layer. The multi-layer coating layer has the effect of dispersing the breaking stress and further improves the mechanical strength of the SiC or C fiber / SiC composite.

The C coating layer is made of SiC or C fiber /
As the SiC composite deforms, it buffers the crack propagation at the fiber / matrix interface and relaxes the fiber constraints. As a result, apparent deformation accompanied by slippage of the fiber with respect to the matrix occurs, the strength of the fiber itself is developed without reducing the strength of the composite material, and the effective strength of the composite material increases until the fiber is broken.

[0011] Such actions and effects are 50 to 300 n.
It becomes significant with a layer thickness of m. C coating layer thickness is 50
If it is less than nm, the fiber / matrix interface is too strong to bind the fiber, and the fiber is cut by the notch effect of cracks from the matrix, and the composite material breaks at low stress. Conversely, if the layer thickness exceeds 300 nm, the C coating layer is broken and the fibers fall off, so that the strength maintenance due to the fiber sliding effect is not exhibited, and the composite material is easily buckled with low stress.

[0012]

EXAMPLE A SiC fiber preform having a thickness of 2 mm was prepared by laminating seven layers of plain-woven SiC fiber fabrics. SiC fiber preform fiber laminate with diameter 40
It was shaped into a disk of mm and stored in a reactor. After vacuum suction of the reactor to 0.1 Pa, the resin adhering to the fibers was decomposed and removed by heating to 1200 ° C. for 1 hour. Then, methane was fed into the reactor at a flow rate of 200 cc / min as a reaction gas, and the internal pressure of the reactor was increased to 14.7 kPa.
, And C, which is a thermal decomposition product of methane, was precipitated around the preform fiber. In the case of multi-layer coating, a mixed gas of methyltrichlorosilane (reaction gas) and hydrogen (reducing carrier gas) was further fed into the reactor to precipitate an SiC phase. By repeating these operations a plurality of times, a multilayer film was formed on the surface of the SiC fiber.

After coating the SiC fibers, the internal voids of the fiber preform are removed by a gas-phase reactive infiltration method (CVI).
To prepare a SiC fiber / SiC composite material. In the gas-phase reaction permeation method (CVI), a mixed gas of methyltrichlorosilane: hydrogen = 1: 4 (volume ratio) is fed into a fiber preform accommodated in the same reactor, and a reaction temperature of 1: 1.
Methyltrichlorosilane was subjected to a thermal decomposition reaction under the conditions of 000 ° C. and a pressure of 13.3 kPa, and the generated SiC was deposited in the internal voids of the fiber preform.

The obtained SiC fiber / SiC composite material was subjected to a bending test, and the elastic limit strength and the bending strength were measured. When the measurement results were arranged by the C coating layer formed on the surface of the SiC fiber, the maximum strength was obtained at a film thickness of about 150 nm, and the strength tended to decrease when the film thickness exceeded 300 nm (FIG. 1). ). Even in the case of a SiC fiber / SiC composite material in which C and SiC are multi-layer coated, the strength is governed by the thickness of the C coating layer (first layer) formed on the surface of the SiC fiber, and the tendency is almost the same as in the case of a single C layer. there were.

A SiC fiber / SiC composite material having a C layer and a SiC layer of various thicknesses was subjected to a bending test, and the fracture surface was observed. As can be seen from the observation results in FIG. 2, in all cases, pulling out of the SiC fiber occurs mainly at the interface of the C coating layer. However, when the thickness of the C coating layer is less than 50 nm, many portions do not peel off from the SiC matrix. Was. When a multilayer coating layer was formed, cracks were propagated between the coating layers.

FIG. 2 shows that when a C coating layer having a thin film thickness of 50 to 300 nm is formed on the surface of the SiC fiber, the fiber / matrix interfacial bonding is not greatly reduced, and the crack propagation at the fiber interface is suppressed. It is inferred that the relaxation effect increased the strength of the SiC fiber / SiC composite material (FIG. 1). In the above embodiment, SiC
Although a fiber is used, even when a C fiber is used in place of a SiC fiber, a C coating layer having a film thickness of 50 to 300 nm is similarly formed to provide a C layer having excellent mechanical strength.
The mechanical strength of the fiber / SiC composite was made.

[0017]

As described above, the SiC of the present invention can be used.
Alternatively, the C-fiber / SiC composite binds the SiC or C-fiber to the SiC matrix through a thin-film C coating layer. Therefore, fiber / matrix interfacial separation is suppressed, and the excellent heat resistance and strength inherent in SiC are utilized, and it is used as a high-performance material for aerospace, reactor bulkheads, heat exchanger parts, and the like.

[Brief description of the drawings]

FIG. 1 is a graph showing the effect of the thickness of a C coating layer formed on the surface of a SiC fiber on elastic limit strength and bending strength.

FIG. 2: Si through single or multiple coating layers
SiC fiber / S combining C fiber and SiC matrix
Diagram showing crack growth and fracture surface structure when bending test of iC composite material

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yudai Kato Gokasho, Uji City, Kyoto Prefecture Inside the Institute of Energy Science and Engineering, Kyoto University (72) Inventor Hiroshi Araki 1-1-2 Sengen, Tsukuba City, Ibaraki Prefecture Inside the Materials Technology Research Institute (72) Inventor Tetsuji Noda 1-2-1, Sengen, Tsukuba, Ibaraki Pref.

Claims (2)

[Claims] An SiC matrix is bonded to a SiC or C fiber through a C layer having a thickness of 50 to 300 nm formed at an interface between the SiC or the C fiber and the matrix, and a void of the SiC or the C fiber is filled with the SiC matrix. SiC or C fiber / SiC composite material. 2. After forming a C layer having a thickness of 50 to 300 nm on the surface of SiC or C fiber by a vapor phase growth method, a SiC phase generated by thermal decomposition of alkyl chlorosilane is used as the SiC.
Alternatively, a method for producing a SiC or C fiber / SiC composite material, characterized by filling voids of the C fiber.