JP2642604B2 - Manufacturing method of fiber reinforced ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fiber-reinforced ceramics by combining ceramics with reinforcing fibers.

[0002]

2. Description of the Related Art The outer plate of a space plane is expected to be exposed to an unprecedented high temperature due to intense aerodynamic heating when starting from the earth and returning to the earth. The use of structural materials is essential.

[0003] As a high heat-resistant material, a ceramic material has excellent heat resistance and excellent characteristics in specific strength. However, ceramics are a typical brittle material. Problems remain in terms of gender. Therefore, as a lightweight heat-resistant structural material, ceramic matrix composites (Ceramic Matrix Composi) combined with a high heat-resistant fiber material as a reinforcing material with the aim of maintaining the excellent high heat resistance properties of ceramics and improving toughness
tes: CMC) is being developed.

[0004] As one of the methods for producing CMC, for example, a production method called a precursor method is disclosed in JP-A-62-260778. For example, it is known that an organic silicon polymer is converted into ceramics such as SiC when heat-treated at a high temperature, and ceramic fibers such as silicon carbide fibers, heat-resistant coating agents and the like are manufactured using these as ceramic precursors.

However, by impregnating a solution obtained by dissolving a matrix precursor in a solvent with a reinforcing fiber having a high strength such as carbon fiber and performing a baking treatment, the impregnation is performed in order to achieve a composite of the ceramic matrix and the carbon fiber. -In the firing treatment, there is a problem that the filling rate of the matrix is small, and the large voids between the reinforcing fiber layers are not easily filled with the matrix.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for producing fiber-reinforced ceramics by a precursor method which has been proposed in the prior art, and which has a simple process and has a large gap between reinforcing fiber layers. An object of the present invention is to provide a method for producing a fiber reinforced ceramic which can obtain a ceramic matrix filling rate.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a method for producing fiber-reinforced ceramics in which ceramics are combined with reinforcing fibers, comprising the steps of: adding a ceramic powder to a ceramic precursor solution; A step of impregnating the precursor solution with the reinforcing fibers to form a prepreg, and heating and pressurizing the laminate obtained by laminating the prepreg in a predetermined shape and size in an autoclave, removing the solvent and melting the ceramic precursor. Cooling and solidifying to form a preform of a predetermined shape; a primary firing step of heating the preform in an inert gas atmosphere;
Dipping the pre-fired preform and heating and pressurizing under an inert gas atmosphere, and a secondary firing step of heating the densified preform in an inert gas. This is a method for producing a fiber reinforced ceramics. Further, the present invention is characterized in that the densification step and the secondary firing step are alternately repeated a plurality of times. Also, the present invention provides a process in which the reinforcing fiber heats the non-oxide ceramic fiber to 700 to 1100 ° C. in the air to form an oxide layer on the surface of the fiber, and cools the non-oxide ceramic fiber in an inert gas atmosphere. And a crystallization step of heating to 1200 to 1600 [deg.] C. to have oxide crystals on the fiber surface. In addition, the present invention provides a method for coating SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , N
a method of applying a glass component composed of one or a mixture of two or more selected from a ₂ O, CaO, MgO, and Li ₂ O, drying and heating and curing the glass component to vitrify the glass component. Features. Further, in the present invention, the ceramic precursor solution is a xylene solution containing 45 to 75% (by weight) of the ceramic precursor, and the amount of the ceramic powder added to the ceramic precursor is 5 to 30% (by volume). There is a feature. Further, the present invention is characterized in that the conditions for treating the prepreg in an autoclave are a pressure in the can of ^{2 to} 10 kg / cm ² and a temperature in the can of 100 to 400 ° C. Further, in the present invention, the densification step may be performed at a tank pressure of 5 kg / cm.
It is characterized in that it is performed in a ceramic precursor solution bath having a liquid temperature of ² G or more and a liquid temperature of 120 ° C. or more.

[0008]

According to the present invention, a ceramic powder is added to a solution obtained by dissolving a ceramic precursor to be converted into ceramics in a solvent, and this solution is impregnated into reinforcing fibers to form a prepreg. The laminated body having the shape and dimensions is heated in an autoclave to melt the ceramic precursor, and then cooled to form a composite of the reinforcing fiber and the ceramic precursor in a predetermined shape to form a preform. The preform is primarily fired to form a ceramic matrix. However, since the filling rate of the ceramic matrix is low, the filling rate is improved by heating and pressurizing in a ceramic precursor solution containing no ceramic powder under an inert gas atmosphere. The densified ceramic precursor becomes a ceramic matrix by secondary firing, and the filling rate of the ceramic matrix can be significantly improved as compared with the conventional method.

By alternately repeating the densification step and the secondary firing step a plurality of times, it is possible to obtain a fiber-reinforced ceramic having a higher filling rate of the ceramic matrix and a higher strength.

Further, by using an oxide layer formed on the surface of the non-oxide ceramic fiber and crystallizing the oxide layer, high oxidation resistance can be obtained.

Further, a glass component is coated on the fiber reinforced ceramics manufactured as described above, and the glass component is vitrified and glass-coated, whereby even higher oxidation resistance can be obtained.

The solvent of the ceramic precursor solution is xylene, and the concentration of the ceramic precursor is 45 to 75%.
(Weight), and the addition amount of the ceramic powder is 5 to 30.
% (Volume) of the ceramic precursor solution is preferably used. Ceramic precursor concentration is 45% (weight)
In the following, it is not preferable because the matrix in the molded body becomes insufficient after firing. When the ceramic precursor concentration is 75
% (Weight) or more is not preferred because the viscosity of the solution increases. When the amount of ceramic powder added is 5% (volume) or less, the effect of the addition is not obtained, and when the amount is 30% (volume) or more, it is not completely dispersed in the solution. If a ceramic precursor solution outside of these ranges is used, a molded article having a predetermined shape cannot be obtained after the first firing.

The conditions for treating the prepreg in the autoclave are preferably a pressure in the can of ^{2 to} 10 kg / cm ² G and a temperature in the can of 100 to 400 ° C. When the temperature in the can is 100 ° C. or lower, the viscosity of the ceramic precursor solution is And the impregnation into the reinforcing fibers becomes insufficient and molding becomes difficult. If the temperature in the can is 400 ° C. or higher, the ceramic precursor is thermally decomposed. The pressure in the can is a pressure for obtaining a preform having a desired thickness.

The densification step is performed in a tank containing the ceramic precursor, and the temperature in the tank is preferably 120 ° C. or more, and the pressure in the tank is preferably 5 kg / cm ² G or more.
If the temperature in the bath is lower than 120 ° C., the viscosity is so high that a sufficient impregnation effect cannot be obtained. The tank pressure is a pressure for preventing the solvent from volatilizing. Considering the pressure resistance of the tank, the temperature in the tank is 120 to 1
More preferably, the temperature is 60 ° C. and the pressure in the tank is 5 to 9 kg / cm ² G.

[0015]

The present invention will be described more specifically with reference to the following examples.

As a reinforcing fiber, a silicon carbide-based tyrano fiber (manufactured by Ube Industries, Ltd.) was used. Polycarbosilane (manufactured by Nippon Carbon Co., Ltd.) 60% (by weight) was dissolved in a xylene solvent and used as a ceramic precursor solution (hereinafter abbreviated as a solution). This solution is used as an impregnating solution by adding ceramic powder and as a densification solution without adding ceramic powder. As the ceramic powder, silicon carbide-based powder (manufactured by IBIDEN Co., Ltd., trade name: beta random, average particle size: 0.27 μm) was used.

Using these materials, fiber reinforced ceramics were manufactured according to the process shown in FIG. The steps will be described below in order.

In step n1, the reinforcing fibers are prepared.
In step n2, the solution is prepared, and in step n3, 10% (by volume) of the ceramic powder is added to the solution to obtain an impregnating liquid. This is impregnated into the reinforcing fiber prepared in step n1 in step n4, and a prepreg having a predetermined size is formed in step n5. The prepreg is laminated in a predetermined shape, for example, a plate shape, in the configuration shown in FIG. 2 in step n6. In the method shown in FIG. 2, the prepreg 41 is placed on a molding jig 42 with a release film 43 interposed therebetween, placed on a plate 44 made of fluorine rubber or the like, and covered with an upper release film 45 and a glass cloth 46. The bag film 47 is covered from above, a sealant tape 48 is provided around the bag film 47 to maintain airtightness, and the air is evacuated from the exhaust port and pressurized.

The prepreg laminated in step n7 is
It is placed in an autoclave and heated and pressed in a nitrogen gas atmosphere according to the pattern shown in FIG. Maximum temperature is 10
The temperature may be in the range of 0 to 400 ° C., and the higher the temperature and the shorter the holding time, the better. However, in the present embodiment, the temperature was set to 300 ° C., 4 kg / cm ² G, and 0.5 hours in view of the pressure resistance of the autoclave. Then, cool and reheat in the air,
Leave for a time. The prepreg impregnated with the solution in the autoclave treatment is removed by evaporation of the xylene solvent in the solution,
The ceramic precursor is composited with the reinforcing fiber and reheated to 200 ° C. in the air, whereby the ceramic precursor itself is crosslinked and polymerized to form a preform.

In step n8, the preform is placed in a high-temperature firing furnace and first fired in an argon atmosphere in the pattern shown in FIG. This turns the ceramic precursor into ceramic. The maximum temperature for primary firing is 10
There is no particular problem as long as it is in the range of 00 to 1300 ° C.

The preform that has been subjected to the primary firing in step n9 is immersed in the solution prepared in step n2 to which the ceramic powder is not added, and is immersed in nitrogen gas for 9k.
g / cm ² , and enters a densification step of holding at 120 to 160 ° C. for 1 hour. This allows the ceramic precursor to penetrate into the voids of the preform, thereby improving the filling rate. The filling rate of the preform of the present example that had been subjected to densification at room temperature for 1 hour, at which the densification step was insufficient, was 25% as expressed by the following impregnation efficiency (%), but was 120 ° C., 1 hour The density was improved to 47% by the densification treatment of No. 1, and to 68% by the densification treatment at 160 ° C. for 1 hour.

Impregnation efficiency = (impregnation volume) / (pore volume before impregnation) × 100 The preform in which the solution is impregnated in the voids by the densification treatment in step n10 is taken out of the solution and is subjected to 120
After being dried at a temperature of 2 ° C. for 2 hours, it is secondarily fired. The secondary firing is performed in the same pattern as the primary firing. If necessary, the densification step of step n9 and the secondary firing step of step n10 are alternately repeated a plurality of times.

The fiber reinforced ceramics manufactured through the above steps may be directly used as a product in step n11. However, in order to further improve oxidation resistance in step n12, SiO ₂ , B ₂ O ₃ , Al ₂ O ₃ , Na ₂ O, Ca
It is preferable to coat the surface with a glass component containing one or a mixture of two or more selected from O, MgO, and Li ₂ O. For this purpose, a glass component composed of, for example, SiO ₂ —Na ₂ O was applied to the surface of the fiber-reinforced ceramic by brush, air-dried, and then heat-cured to vitrify the glass component. This significantly improved the oxidation resistance of the fiber reinforced ceramics.

In the present embodiment, silicon carbide-based tyrano fiber was used as the reinforcing fiber prepared in step n1, but other reinforcing fibers such as carbon fiber, glass fiber, silicon nitride fiber, alumina fiber, heat-resistant metal Fiber or the like is used. When non-oxide ceramic fibers such as carbides and nitrides are used, an oxide layer may be formed in step n13 on the surface of the fiber prepared in step n1, and the oxide layer may be crystallized and stabilized. preferable. Thereby, the oxidation resistance of the fiber itself and the oxidation resistance of the fiber reinforced ceramics using the fiber as the reinforcing fiber can be improved. The treatment method is as follows.
After cooling at 100 ° C. for 0.5 to 5.0 hours and cooling, it is kept at 1200 to 1600 ° C. for 2 to 3 hours in an argon gas atmosphere.

Next, the concentration of the ceramic precursor in the solution and the amount of ceramic powder added will be examined. By changing the ceramic precursor concentration and the amount of ceramic powder added,
The moldability was tested using a prepreg prepared by impregnating a reinforcing fiber (Tyranno fiber). The result is shown in FIG.
印 indicates that molding is possible, X indicates that molding is impossible, △ indicates molding is somewhat acceptable, and the dotted line indicates the scope of the present invention.

FIG. 6 shows a solution L1 containing 10% (by volume) of ceramic powder and a solution L2 containing no ceramic powder (ceramic precursor concentration is 50%).
5 is a graph showing the relationship between the bending strength and the number of densifications of fiber reinforced ceramics which were impregnated with Tyranno fibers and treated under the same conditions thereafter. From this graph, it can be seen that the one treated with the solution to which the ceramic powder is added has a higher flexural strength than the solution without the addition of the same number of densifications. Further, in order to obtain a fiber reinforced ceramic having the same bending strength, a large number of densifications are required in a treatment with a solution to which no ceramic powder is added.

FIG. 7 is a scanning electron micrograph of a fractured surface after the bending strength test. FIG. 7 (1) shows a case in which a solution to which no ceramic powder was added was impregnated.
(2) impregnated with a solution to which 10% (volume) of ceramic powder is added. The treatment after the impregnation is the same. In FIG. 7A, the fiber and the matrix are integrated and are torn at the fracture surface. On the other hand, in FIG. 7 (2), the interface of the matrix as a fiber is a loose bond, and the fiber is pulled out. It is considered that when the fiber was pulled out, the toughness was increased and the bending strength was increased.

[0028]

As described above, according to the present invention, the reinforcing fiber is impregnated with the ceramic precursor solution to which the ceramic powder is added, and the ceramic precursor and the ceramic powder impregnated into the reinforcing fiber are heated and pressed to form the reinforcing fiber. To form a preform in which ceramics are crosslinked.
In order to further improve the filling rate of the ceramic matrix, the preform is immersed under pressure in a ceramic precursor solution to which no ceramic powder is added, and densification for impregnating the ceramic precursor is performed. Thereby, the filling rate of the ceramic matrix is improved, and a fiber-reinforced ceramic having high bending strength after firing is obtained.

Further, according to the present invention, the densification and the subsequent heating are alternately performed a plurality of times to further improve the filling rate of the ceramic matrix.

Further, a fiber-reinforced ceramic having high oxidation resistance can be obtained by using a reinforcing fiber obtained by oxidizing the surface of the non-oxide ceramic fiber and crystallizing the generated oxide layer.

Further, by coating the surface of the fiber reinforced ceramics manufactured as described above with glass, a product having higher oxidation resistance can be obtained.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a flow of an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a step of producing a prepreg laminate.

FIG. 3 is a graph showing an example of a heating / pressing pattern in an autoclave process.

FIG. 4 is a graph showing an example of a heating / pressing pattern for firing.

FIG. 5 is a graph showing the relationship between the ceramic precursor concentration in the ceramic precursor solution, the amount of ceramic powder added, and the preform moldability.

FIG. 6 is a graph showing the relationship between the number of densification and bending strength.

FIG. 7 is a scanning electron micrograph of a surface broken by bending.

[Explanation of symbols]

L1 When ceramic powder is added to ceramic precursor solution L2 When ceramic powder is not added to ceramic precursor solution

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location B29K 105: 12 (72) Inventor Keiichi Tsukiki 1 Kawasaki-cho, Kakamigahara-shi, Gifu Prefecture Kawasaki Heavy Industries, Ltd. Gifu Inside the plant (72) Inventor Koji Nishio 1-1, Kawasaki-cho, Akashi-shi, Hyogo Prefecture Inside the Akashi Kawasaki Heavy Industries, Ltd. in the factory

Claims (7)

(57) [Claims] 1. A method for producing a fiber-reinforced ceramic in which a ceramic is combined with a reinforcing fiber, a step of adding a ceramic powder to a ceramic precursor solution, and impregnating the reinforcing fiber with the ceramic precursor solution to which the ceramic powder is added. And a step of forming a prepreg, and heating and pressurizing a laminate obtained by laminating the prepreg in a predetermined shape and size in an autoclave, removing a solvent and melting a ceramic precursor, and then cooling and solidifying to a predetermined shape. Forming a preform, a primary firing step of heating the preform in an inert gas atmosphere, and immersing the primary fired preform in a ceramic precursor solution under an inert gas atmosphere. And a densification step of heating and pressurizing, and heating the densified preform in an inert gas. And a secondary firing step. 2. The method according to claim 1, wherein the densification step and the secondary firing step are alternately repeated a plurality of times. 3. A step of heating the non-oxide ceramic fiber to 700 to 1100 ° C. in the air to form an oxide layer on the surface of the fiber, and cooling the fiber to an inert gas atmosphere after cooling. The method for producing fiber-reinforced ceramics according to claim 1 or 2, wherein the crystallization step of heating to 1200 to 1600 ° C has an oxide crystal on the fiber surface. 4. The method according to claim 1 or ₂ , wherein the surface of the fiber reinforced ceramics is SiO ₂ , B ₂
A glass component consisting of one or a mixture of two or more selected from O ₃ , Al ₂ O ₃ , Na ₂ O, CaO, MgO, and Li ₂ O is applied, dried, and then heat-cured to cure the glass component. A method for producing fiber-reinforced ceramics, which comprises a step of vitrification. 5. The ceramic precursor solution is a xylene solution containing 45 to 75% (by weight) of the ceramic precursor, and the amount of ceramic powder added to the ceramic precursor is 5 to 30% (by volume). The method for producing a fiber-reinforced ceramic according to any one of claims 1 to 4, wherein 6. The conditions in which the prepreg is treated in an autoclave are a pressure in the can of ^{2 to} 10 kg / cm ² and a temperature in the can of 100 to 400 ° C.
A method for producing the fiber-reinforced ceramics according to claim 5. 7. The method according to claim 1, wherein the densification step includes a pressure in the tank of 5 kg / cm.
7. The method is performed in a ceramic precursor solution bath having a temperature of ² G or more and a liquid temperature of 120 ° C. or more.
The method for producing a fiber-reinforced ceramic according to any one of the above.