JPH1149569A - Composite member consisting of carbon fiber and ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite member which consists of carbon fiber and a ceramic material and has improved toughness, high strength with respect to impact load and improved heat resistance. SOLUTION: This member comprises: a core member 1 consisting of a carbon fiber nonwoven fabric; ceramic member 2 which is used for covering the core member 1 in such a way that the core member 1 is an unexposed state and which consists of a ceramic material converted from a slurry contg. an Si powder by sintering it; and a border layer 3 which is located at one of the borders between the ceramic material and the carbon fiber and consists of SiC converted from Si in the slurry and carbon by sintering them; wherein the ceramic material consists of at least any one of SiC and Si3 N4 and the slurry also contains Al2 O3 and Y2 O3 , both mixed in the slurry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composite member made of carbon fiber and ceramic which can be used for members such as a cylinder liner, a gas turbine combustor, a cylinder head, a combustion chamber structure, a port liner, and a valve.

[0002]

2. Description of the Related Art Conventionally, in order to effectively use the energy of exhaust gas, ceramics having excellent heat resistance and low thermal conductivity are used in exhaust manifolds, cylinder heads, combustion chamber members, gas passages of gas turbines, and the like. What you use is known. In addition, the heat resistance of ceramics,
High strength properties are expected to play an extremely important role in industrial equipment and components.

Japanese Patent Application Laid-Open No. HEI 6-117245 discloses a method of manufacturing a heat shield wall structure in which a heat insulating material is simply fixed to the outer surface of an inner wall member made of ceramics. The method of manufacturing the heat shield wall structure is applied to the manufacture of a heat shield exhaust passage. The exhaust port liner is made of a ceramic having an open pore structure and a low thermal conductivity and a low coefficient of thermal expansion, and the exhaust port liner is manufactured. The ceramic fiber is placed in uniformly mixed water or an organic solvent, and the inside of the exhaust port liner is suctioned to make a negative pressure. A heat insulating material made of a ceramic fiber layer is formed on the outer wall surface of the exhaust port liner, and the ceramic fibers enter the open pores of the exhaust port liner. Therefore, the heat shrinkage stress of the metal at the time of casting can be reduced by the heat insulating material, and the compression stress applied to the exhaust port liner can be reduced to prevent breakage.

[0004]

However, a drawback of the ceramic material is that it has low toughness, and when a ceramic component is subjected to an impact load, cracks and cracks are generated and the ceramic component is easily broken. In order to solve the above-mentioned drawbacks of ceramics, composites with fiber materials have been attempted in the past. However, due to problems such as the bondability of the two at the boundary between the ceramics and the fiber material and the deterioration of the fiber material during sintering, At present, the effect of the composite material by combining the ceramic and the fiber material cannot be exhibited.

It has been known that carbon graphite has high heat resistance. However, in an oxygen atmosphere, carbon graphite reacts with oxygen and is oxidized to be extremely weak. However, since carbon graphite has a high heat-resistant temperature of 3000 to 3500 ° C. in an atmosphere in which oxygen is not present and has sufficient high-temperature strength and toughness, when carbon ceramics are combined with carbon graphite, carbon graphite is used. It is required to construct a structure insulated from oxygen.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems. Parts such as a gas turbine, an exhaust manifold, a combustion chamber, a sub-chamber, and an exhaust port liner are made of heat-resistant ceramics. In this case, it is an object of the present invention to provide a composite member made of carbon fiber and ceramics, which is composited with ceramics and carbon fiber to increase toughness and is resistant to impact load.

According to the present invention, there is provided a ceramic member comprising a core member made of a nonwoven fabric of carbon fiber, and a ceramic covering the core member in a state where the core member is not exposed, and a slurry containing Si powder converted by sintering in N ₂ gas. A composite member made of carbon fiber and ceramics, comprising: a member; and a boundary layer made of SiC converted by sintering of carbon and Si in the slurry at a boundary between the ceramics and the carbon fiber. About.

The ceramics may be SiC or S
i ₃ N ₄ ceramics.

The slurry contains Al ₂ O ₃ and Y ₂ O
₃ is mixed. In addition, the slurry contains SiO
₂ is not included. SiO ₂ has a small bonding force between Si and C, so that Si and C are separated, C and oxygen are oxidized to generate gas, and a phenomenon that the composite member becomes brittle occurs. Further, when Si ₃ N ₄ powder is mixed into the slurry, the growth of Si ₃ N ₄ is promoted, and S ₃ N ₄
i ₃ N ₄ is properly contained.

[0010] The core member is formed into a molded body having a predetermined shape, and the molded body is solidified with a resin material. The resin material is a polymer precursor.

In the composite member made of carbon fibers and ceramics, carbon powder is adhered to the surface of the core member made of carbon fibers, placed in a molding die, and the slurry is injected and sintered. The carbon powder is converted to SiC, and a part of the core member is made of SiC.
The carbon fiber is maintained without being converted to carbon fiber.

Since the composite member composed of carbon fiber and ceramics is constructed as described above, the heat resistance and the toughness of the composite member depend on the characteristics of the carbon fiber and the ceramics such as SiC and Si ₃ N _{4 on the} outer periphery. A certain high-strength composite member can be provided. Further, Si ₃ N ₄ powder can be mixed with Si powder constituting the slurry to promote the growth of Si ₃ N ₄ during firing of a member formed from the slurry. Here, if a large amount of carbon fiber C is mixed with Si in the slurry, the slurry in which the carbon fibers are disposed is fired in a high-temperature N ₂ gas and sintering progresses. ₂ grows into Si ₃ N ₄ and Si and C
(Carbon) grows into SiC and a part of the carbon fiber is converted into SiC, but the remaining carbon fiber remains in the core, that is, the core of the member, and maintains the characteristics of the carbon fiber.

If carbon powder is adhered to the outer surface of the carbon fiber prior to placing the slurry on the carbon fiber, the slurry and the carbon powder first react during firing and grow into SiC. The carbon fiber inside remains as it is, and the toughness of the ceramic can be improved.

When manufacturing the composite member, it is difficult to maintain the carbon fiber in a predetermined shape. Therefore, the carbon fiber is formed in a predetermined shape, and the molded body is solidified with a resin material. The solidified carbon fiber compact is placed in a mold, and Si powder, Si ₃ N
After injecting a slurry to which ₄ powder, Ta, Al ₂ O ₃ , and Y ₂ O ₃ are added, degreasing and firing, an extremely strong and stable composite member of a sintered body can be produced. When the above resin material is composed of a polymer precursor such as polycarbosilane, that is, a preceramic material,
The polymer precursor can be converted into ceramics by sintering and can be used as a suitable solidifying material. That is, the polymer precursor is converted into ceramics by sintering, and the ceramics and the ceramics converted from the slurry are compounded to form a good composite member.

According to the present invention, when carbon is formed into carbon fiber, the carbon fiber is a soft material having elasticity. In particular, since the material has strong resistance to pulling, the carbon fiber is prevented from being oxidized. In this case, the surface of the carbon fiber is covered with a composite layer made of SiC so that oxygen does not exist, and high strength and high heat resistance of the carbon fiber are obtained. In the manufacturing process, a carbon fiber is wrapped around by a polymer precursor, put into a mold, a slurry of Si powder is put in, and solidified to produce a molded body. The solidified compact is sintered in N ₂ gas,
_{The two} gases react with Si to form Si ₃ N ₄ and C
Reacts with Si to form SiC. Usually, Si ₃ N ₄ in which the polymer precursor has been converted has a low strength due to a low sintering temperature. However, Al ₂ O ₃ , Y ₂
By arranging a slurry to which O ₃ and Si ₃ N ₄ powders are added, it is possible to sinter at a high temperature and grow into high-strength Si ₃ N ₄ .

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of a composite member made of carbon fiber and ceramic according to the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing an embodiment of a composite member composed of carbon fiber and ceramics according to the present invention, FIG. 2 is a perspective view showing a core molded body forming a core member, and FIG. FIG. 4 is an explanatory view showing a state in which the slurry is injected, and FIG. 4 is a cross-sectional view showing a compact.

The composite member made of carbon fiber and ceramics according to the present invention can be applied to, for example, an exhaust port and an intake port of an engine, a blade and a housing of a gas turbine, an exhaust manifold, a cylinder liner, a combustion chamber structure, a valve, and the like.

FIG. 1 shows an embodiment in which the composite member made of carbon fibers and ceramics is applied to a cylinder liner. The composite member of this embodiment is mainly
Core member 1 and core member 1 made of carbon fiber non-woven fabric
Member 2 made of ceramics in which the slurry containing Si powder is converted by sintering, covering the core member 1 in a state where the carbon is not exposed, and sintering of carbon located at the boundary between the ceramics and the carbon fibers and Si in the slurry. And a boundary layer 3 made of SiC converted by the method.

In the composite member made of carbon fiber and ceramic, the carbon fiber is sealed in the ceramic and the carbon fiber does not come into contact with oxygen, so that the fracture toughness K _1C of the composite member itself is improved to about 20. Since this composite member has a fracture toughness K _1C of about 5 to 8 in the case of a conventional ceramic simple substance, the fracture toughness is greatly improved, and breakage when an external force such as an impact load is applied can be avoided. .

Considering the manufacturing process of the composite member, it is as follows. A slurry containing Si powder, for example, a polymer precursor such as polycarbosilane (R ₃ S
When i.H, R: CH ₃ ) is arranged around the carbon fiber, a reaction in the step shown by the chemical formula occurs. (1) at _{25 ℃ ~200 ℃: R 3 Si} · H + NH 3 → R 3 Si · NH 2 + H 2 (2) at _{450 ℃ ~700 ℃: R 3 Si} · NH 2 + NH 3 → R 3 · SiNH 2 + CH ₄ (3) At 900 ° C. to 1000 ° C .: SiN _X H _Y → Si ₃ N ₄ + H ₂ (4) At 1200 ° C. to 1500 ° C .: Si ₃ N ₄ crystallizes.

Embedded image

This composite member can be manufactured, for example, as follows. First, a fiber material made of carbon graphite, that is, a carbon fiber is cut into long fibers, and a nonwoven fabric in which the long fibers are randomly entangled is formed into a mat-like sheet material. At this time, the carbon graphite has a linear expansion coefficient of 3 ×
Use a fiber material of about 10 ^-6 / ° C. In order to manufacture the sheet material into a core molded body having a shape such as a turbine housing shape or a combustion chamber structure shape, for example, as shown in FIG. Therefore, for example, the sheet material is passed through a resin material made of a polymer precursor such as polycarbosilane to impregnate the resin material into the resin material, and then formed into a predetermined shape and solidified. By doing so, the core molded body 5 having a predetermined shape can be easily produced. Also,
After forming the core molded body 5 having a predetermined shape, carbon graphite powder is adhered to the core molded body 5. The carbon powder adhered to the surface of the core molded body 5 reacts with Si powder of the slurry 6 described later. Thus, the carbon fiber can be sufficiently left as the core member 1 and the mechanical properties of the carbon fiber can be preserved.

As shown in FIG. 3, the core molded body 5 is placed on a molding die 4 such as a gypsum mold for slip casting, and a slurry or slurry 6 containing Si powder is placed around the core molded body 5 in the molding die 4. Injection is performed to produce a green molded body, which is dried and solidified to produce a molded body having a predetermined shape as shown in FIG. The slurry 6 includes Al ₂ O ₃ , Y in addition to the Si powder.
_{Although 2} to 3% of ₂ O ₃ is added and mixed, SiO ₂ is not mixed. The addition of SiO ₂ to the slurry 6, SiO ₂
Reacts with carbon to degrade carbon fibers, so that the slurry 6 contains SiO 2 to prevent oxidation of carbon.
₂ shall not be added.

The molded body 7 obtained in the above manufacturing process is primarily sintered at 1400 ° C. to 1500 ° C. in N ₂ gas to produce a calcined body. Next, the calcined body is heated at 1700 ° C. to 1800 ° C.
C. and sinter for about 10 hours. As the sintering of the slurry 6 proceeds in a high-temperature N ₂ gas during firing of the compact 7, Si and N ₂ react with Si ₃ N ₄ to grow, and S
i and C grow in response to SiC, and most of C in the carbon fiber grows into SiC. However, since the core portion has more carbon fibers than it reacts with Si, a part of the carbon fibers remains without reacting, and the characteristics of the carbon fibers can be exhibited. Therefore, as shown in FIG. 1, the ceramic member 2 is formed outside the core member 1 made of carbon fiber, and the boundary between the ceramic and the carbon fiber is formed by the boundary layer 3 made of SiC. The ceramic member 2 is made of SiC and Si ₃ N ₄
At least one of the ceramics.

In the manufacturing process of the composite member, when Si ₃ N ₄ powder is mixed in the slurry 6, Si ₃ N ₄
Is promoted, and the ceramic member 2 is composed of Si ₃ N ₄ . Further, when carbon powder is adhered to the surface of the core member 1 made of carbon fiber, the powder is placed in the molding die 4 and the slurry 6 is injected and sintered, so that S
The i-powder and the carbon powder react with each other to be converted into SiC, and a part of the core member 1 is kept in a state in which the carbon fibers are maintained without being converted into SiC, so that the characteristics of the carbon fibers can be secured.

[0025]

The composite member comprising carbon fibers and ceramics according to the present invention has the following effects because it is constructed as described above. That is, the composite member made of carbon fiber and ceramics has a structure in which the carbon fiber is sealed with ceramics, and the carbon fiber does not come into contact with oxygen. Moreover, the carbon fiber itself can exhibit extremely high heat resistance and high strength if it does not come into contact with oxygen. For example, in a high-temperature combustion gas atmosphere, the toughness of the composite member itself can be improved, and an impact load is applied. There is no risk of damage.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a composite member comprising carbon fiber and ceramics according to the present invention.

FIG. 2 is a perspective view showing a core molded body forming a core member.

FIG. 3 is an explanatory view showing a state where a core molded body is arranged in a molding die and slurry is injected.

FIG. 4 is a sectional view showing a compact.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core member 2 Ceramic member 3 Boundary layer 4 Mold 5 Core molded body 6 Slurry 7 Molded body

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02F 1/24 C04B 35/58 102M F23R 3/42 35/80 B

Claims (8)

[Claims] 1. A core member made of a nonwoven fabric of carbon fiber, and a ceramic member made of ceramics which covers the core member in a state where the core member is not exposed, and in which a slurry containing Si powder is converted by sintering in N ₂ gas. ,
And a boundary layer made of SiC converted by sintering of carbon and Si in the slurry at a boundary between the ceramics and the carbon fibers, and a composite member made of carbon fibers and ceramics. 2. The method according to claim 1, wherein the ceramic is SiC or Si _3.
Composite member comprising carbon fibers and ceramic according to claim 1, characterized in that the ceramic N _4. 3. The slurry comprises Al ₂ O ₃ and Y <sub>2
3. The method according</sub> to claim 1, wherein O ₃ is mixed.
A composite member comprising the carbon fiber and the ceramic according to the above. 4. The composite member according to claim 1, wherein the slurry does not contain SiO ₂ . 5. The composite member according to claim 1, wherein said slurry contains Si ₃ N ₄ powder. 6. The core member according to claim 1, wherein the core member is formed into a molded body having a predetermined shape, and the molded body is solidified with a resin material. Composite member made of carbon fiber and ceramics. 7. The composite member according to claim 6, wherein the resin material has a polymer precursor as a main component. 8. A carbon powder is attached to the surface of the core member made of the carbon fiber, placed in a molding die, the slurry is injected and sintered, and the carbon powder is converted into SiC. The composite member comprising carbon fibers and ceramics according to any one of claims 1 to 7, wherein a part of the core member maintains the carbon fibers without being converted to SiC.