JPH0442883A - Oxidation-resistant c/c material and its production - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a heat-resistant and oxidation-resistant C/C material (carbon fiber-reinforced carbon material) that exhibits excellent oxidation resistance in a high-temperature oxidizing atmosphere.
and its manufacturing method.

[Conventional technology]

C/C materials have outstanding specific strength and specific modulus, as well as excellent heat resistance and corrosion resistance, so they are in the spotlight as structural materials in many fields including aerospace applications.

Usually, the C/C material is reinforced with carbon fiber woven cloth, felt, tow, etc., which is impregnated or coated with a matrix resin liquid with a high carbonization residual rate, laminated and molded, and then hardened and sintered to carbonize. However, this material inherits the inherent material defects of carbon materials, which are easily oxidized in high-temperature atmospheres, and this is the biggest bottleneck that hinders its versatility. For this reason, attempts have been made to modify the surface of C/C materials by coating them with oxidation-resistant coatings, such as ZrO and Al.

A method of coating with a ceramic material such as Ch or SiC has been proposed. However, coating layers other than SiC cause peeling and cracking at the coating interface due to thermal cycles during use, and do not have the ability to sufficiently prevent the progress of oxidation.

Even in the SiC coating layer, peeling between the eyebrows may occur frequently depending on the method of film formation. That is, methods for coating the surface of a C/C base material with SiC include a conversion method in which carbon in the base material is used as a reaction source to convert it into SiC, and a CVD method in which SiC precipitated by a gas phase reaction is directly deposited. (chemical vapor deposition) method. Among these methods, the former method involves forming a Si layer on the substrate surface by hydrogen reduction of a silicon halide compound such as 5iCj2n,
The base material is forcibly impregnated with an organosilicon compound such as polycarbosilane in a solution state, or the base material surface is coated with 5iO7 and Si.
, C, etc. are brought into contact with each other, and these silicon components are heated to react with the carbon structure of the base material to form Si.
This method is based on the mechanism of converting SiC to C, and since the substrate surface forms a SiC layer as a continuous structure, there is no coating interface, and the film exhibits coating characteristics that prevent peeling between the eyebrows.On the other hand, the latter CVD method Sj that does not precipitate in the gas phase by heating reactions between silicon compounds and hydrocarbons (e.g. CJs) or reductive thermal decomposition of halogenated organic compounds containing hydrocarbons such as trichloromethylsilane (CLSiCIi).
C is precipitated and deposited on the surface of the base material, and in this case, since the coating interface is clearly separated, when a thermal shock is applied, the phenomenon of peeling between the eyebrows tends to occur frequently due to the mutual thermal expansion difference.

Therefore, as a method for forming an oxidation-resistant film by SiC coating on a C/C material, it is desirable to apply a conversion method, particularly a method of contacting with SiO gas that converts into a dense SiC layer.

[Problem to be solved by the invention]

In the conversion method using the SiO gas contact mechanism, a reaction occurs between the S10 gas and the carbon component of the C/C base material m weave surface as shown in the following equation.

S10+c-s1c+c.

Therefore, in the reaction stage of the coating process, the carbon component constituting the C/C base material texture surface becomes CO and does not degas and becomes Si.
Conversion to C progresses, and this gas desorption causes a situation in which minute voids (pinholes) are formed between SiC particles. Furthermore, even with a SiC film produced by the conversion method, depending on the layer thickness and other conditions, microscopic racks may be produced during the reaction, which, together with the aforementioned microporosity, reduces the oxidation resistance. .

As a result of repeated research on methods to solve the above problems, the inventors of the present invention added 5iOz
, BzOx, etc., it was confirmed that a dense, highly adhesive, and substantially gas-impermeable coating was formed.

The present invention was developed based on the above findings, and its purpose is to provide an oxidation-resistant C/CI exhibiting excellent oxidation resistance in a high-temperature oxidizing atmosphere and a method for producing the same.

[Means to solve the problem]

Oxidation resistant C/ according to the present invention to achieve the above object
C material has a SiC coating layer, S
iO□ fine particle coating layer, SiO□ glass coating layer or B2O
It is characterized by a structure in which three glass coating layers or B20, SiOx glass coating layers are laminated and coated in three layers.

In this configuration, the Si fine particle coating layer fills cracks generated in the SiC coating layer, and the S coating layer coats the upper layer.
iO□, Bz O* or a combination of these Bz O
It functions as an intermediate layer that is in close contact with the glass layer made of y・5iOz, and finally presents a three-layer dense coating layer to form a monolayer structure that completely blocks the oxidizing atmosphere on the outside and the C/C base material. do.

The method according to the present invention for producing the above-mentioned oxidation-resistant C/C material uses a carbon fiber-reinforced carbon substrate obtained by composite molding carbon fibers together with a matrix resin, hardening, and firing carbonization treatment as a base material. The first coating step involves contacting the surface of the material with SiO gas to form a SiC coating layer by the convergitan method, and the SiO□ fine particle suspension obtained by hydrolyzing an alcohol solution of Si (OCz Hs)4 in a basic region. Second coating step of vacuum impregnation, 5i
A third coating step of vacuum impregnation with a glass precursor solution obtained by hydrolyzing an alcohol solution of (OC, H,) in an acidic region is sequentially performed, followed by heat treatment at a temperature of 400'C or higher. It consists of the process of The above process is a manufacturing method for a structure in which a Si0-year-old glass layer is formed as the outermost coating layer.
In the case of forming a 2O3 glass layer, a method of applying B 2 (OC,,H2,)3 is applied instead of the third coating step in the above process.

In addition, when forming a structure in which the outermost coating layer is a B2O3・S+Oz glass coating layer, S
A method is used in which a glass precursor solution obtained by hydrolyzing an alcohol solution of i (OCz Hs)a in an acidic region is impregnated in vacuum, and then B (QC, □Hz7)4 is applied.

Details of the manufacturing process according to the present invention are as follows.

First, the carbon fibers that make up the base material are hand-woven, twilled, and other woven fabrics, felt, or tow made from various raw materials such as polyacrylonitrile, rayon, and pitch, and the matrix resin is phenolic, Furan-based or other liquid thermosetting resins with good carbonizability are used. The carbon fibers are sufficiently wetted with a matrix resin by dipping, impregnation, coating, etc., and then semi-cured to form a prepreg, which is then laminated and pressure-molded. The molded body is heated to completely harden the resin component, and then subjected to firing carbonization treatment or further graphitization according to a conventional method to obtain a C/C base material.

The obtained C/C base material may be subjected to repeated treatments of impregnating it with a matrix resin, hardening it, and carbonizing it to make its structure denser, if necessary.

A SiC coating layer is formed on the C/C substrate thus obtained by a conversion method as a first coating step. This step is carried out by mixing 5iOz powder with Si or C powder, storing the mixture in a closed heating system, and embedding or burying the C/C% material in the system to cause a heating reaction. The conditions at this time are preferably such that the molar ratio of 5iOz:Si or C is 2:1, the heating temperature is set in the range of 1850 to 2000°C, and the system is in a reducing or neutral atmosphere.

In the first coating step, SiO□ is Si or C
The components are heated and reduced to produce SiO gas, and this SiO
The gas reacts with the carbon structure constituting the C/C base material and converts the surface layer into SiC. The preferred thickness of the SiC coating layer is:
It is 100 to 300 μm.

The SiO□ fine particle suspension used in the second coating step is prepared by mixing S r (OC2Hs) and an alcohol such as ethanol or methanol at a molar ratio of 1:10 to 12, heating and stirring under reflux, and then Said S i
It is produced by adding NH and OH together with water in an amount such that the molar ratio to (OCz Hs)4 is 1:25, and hydrolyzing the mixture by heating and stirring in a basic region. At this time, the basic region is desirably adjusted to a pH range of 11.0 to 12.5. Susbenzi iy7 produced in this way has a thickness of 0.2-1.2am (7)S i
02 Spherical particles exhibit a uniformly dispersed suspension state.

The second coating step is carried out by immersing the C/C material on which the SiC coating layer has been formed in the first coating step in the above-mentioned Sin and fine particle suspension, performing vacuum impregnation treatment, and then drying. In addition, if necessary, the 5iO
The second coating step is completed by applying and drying the z particulate suspension.

The glass precursor solution used when the outermost coating layer is a SiO□ glass layer is prepared by mixing Si (QC2H5)a and alcohol at a molar ratio of 1:1.5 to 7.0 and stirring at room temperature. Then, in this solution, the above 5i (QC, H5),
H with an amount of water such that the molar ratio to
It is prepared by adding CI and stirring in an acidic region to hydrolyze it. The acidic region at this time is preferably in the pH range of 1 to 3.

The C/C substrate after the second coating step is immersed in this glass precursor solution, vacuum impregnated, and then dried to complete the third coating step.

In order to form the outermost coating layer with an 82O3 glass layer, a method is adopted in which the third coating step of vacuum impregnation with the 5iCh precursor described above is replaced with a step of coating and drying B (OClzHzt):+.

In addition, when the outermost coating layer is formed as a borosilicate glass layer consisting of B2O3.5102, a borosilicate glass layer obtained by hydrolyzing an alcohol solution of St (OCz Hs)4 in an acidic region according to the above procedure as the third coating step. After vacuum impregnation with the glass precursor solution and drying, B (OC1zH
zt) A method of applying and drying x is applied.

Note that the preferred thickness of the outermost glass layer is 5 to 10 μm.

The C/C substrate that has been sequentially subjected to the first to third coating processes as described above is then heated in a temperature range of 400°C or higher until the layer components formed in the third coating process convert into glass. do.

FIGS. 1 to 5 are schematic diagrams macroscopically showing the layer state at each stage in the above-mentioned coating process.

Of these, FIG. 1 shows the state in which the SiC coating layer 2 is formed on the surface of the C/C base material 1 by the first coating process, and the coating interface has a dense and strong form that is continuous with the C/C base material structure. However, the coating layer has minute voids and recesses such as cranks. FIG. 2 shows the state in which the Sin and fine particle coating layer 3 has been formed in the second coating step, and has a two-layered form in which the above-mentioned voids and crank portion are filled with 5ift of fine particles. Figure 3 shows the SiO□ glass layer or B! in the third coating step. 0. This figure shows an integral three-layer structure in which the glass layer 4 is formed as the outermost coating layer.

Figure 4 shows the steps in the process of forming a B2O3/SiO□ glass layer as the outermost coating layer.
are formed in layers. FIG. 5 shows a structure obtained by heating the state shown in FIG. 4 and converting it into a glassy state.
□ and the B2O3 component together form the outermost coating layer as the 82O3.Sin glass layer 6.

[For production]

According to the structure and manufacturing method of the oxidation-resistant C/C material according to the present invention, first, the surface layer of the C/C base material is converted into a dense SIC layer by a conversion method using the Si◯ contact mechanism. In this process, CO from the m-woven surface of the C/C base material is removed during heating.
Due to gas release, phenomena such as the formation of minute voids (pinholes) and cranks between SIC particles occur, but these defective areas are completely filled and sealed by the fine 5ift coating layer that serves as the intermediate layer. Furthermore, the 5102 glass coating layer forming the outermost layer or B! 0. Glass coating layer or B2O, ・Si
The O□ glass coating layer penetrates into the structure of the intermediate layer and converts into glass through the heating process.

Due to the above-mentioned anchoring action, the second and third coating layers have an extremely strong monolayer structure, and the outermost layer has a smooth surface with a non-porous structure.

With such a three-layer coating configuration, a dense, highly adhesive, substantially gas-impermeable, and highly oxidation-resistant coating is formed on the entire surface of the C/C substrate.

〔Example〕

Hereinafter, the present invention will be explained based on examples.

Example 1 (1) Preparation of C/C base material A polyacrylonitrile-based high-elasticity plain-woven carbon fiber cloth was impregnated by immersing it in a Matrix resin solution consisting of a phenolic resin initial condensate. Laminate 14 sheets of this and put it in a mold, heating temperature 110℃ 1 common pressure 20kg/
Composite molding was carried out under the conditions of "cm".

After the molded product was heated to a temperature of 250°C and completely cured, it was transferred to a firing furnace maintained in a nitrogen atmosphere, and the temperature was increased to 1000°C at a temperature increase rate of 5°C/hr and held for 5 hours to perform firing carbonization. .

The obtained C/C material was impregnated with a phenol resin liquid under vacuum pressure, and the process of firing at 1000''C in the same manner as above was repeated three times to produce a C/C base material with a dense structure.

(2) First coating step SiO□ powder and carbon powder are mixed at a molar ratio of 2:1, the mixed powder is placed in a graphite crucible, a C, /C base material is set on the top, and graphite is coated. I covered it with a lid.

Next, while maintaining the inside and outside of the crucible in an NZ gas atmosphere, a reaction was carried out at a temperature of 1850°C for 1 hour to convert the surface layer of the C/C material into SiC by a conversion method, and a thickness of 100°C was obtained.
A μ-SiC coating layer was formed.

(3) Second coating step S i (OCz H3)a and ethanol were blended in a molar ratio of 1:12, and after stirring under reflux at a temperature of 70°C, the above S 1 (QC, Hs) a 25 mol of water and 0.2 mol of NH per 1 mol.

The OH mixture was added dropwise with stirring. Solution p after dropping
H was 12.0. Subsequently, stirring was continued for 1 hour to prepare a suspension in which spherical fine particles of about 0.2 μm were uniformly suspended.

The C/C substrate subjected to the first coating step was immersed in this SiO□ fine particle suspension, vacuum impregnated for 1 hour, air-dried, and then dried at a temperature of 110°C. Next, the SiO□ fine particle suspension was applied to the surface and air-dried, followed by drying at a temperature of 110°C.

(4) Third coating step S i (QC2H,)4 and ethanol are blended in a molar ratio of 1, stirred at room temperature, and then the S
A mixed solution of 11 moles of water and 0.03 moles of HCi was added dropwise to 41 moles of i (OCz Hs) with stirring. The pH of the solution after dropping was 3.0. Stirring was continued for 1 hour to prepare a glass precursor solution.

The C/C substrate subjected to the second coating step was immersed in this glass precursor solution and vacuum impregnated for 1 hour. After air drying,
Drying was carried out for 30 minutes at each temperature step of 70°C, 1110°C and 200°C.

(5) Transfer the C/C base material subjected to the third coating step of vitrification treatment to an electric furnace,
The SiO□ coating layer formed in the third coating step was converted into a glass plate by heating at a temperature of 0° C. for 10 minutes. S in this case
In, the thickness of the glass layer was 8 μl.

(6) Heat resistance and oxidation resistance test Through the above steps, a SiC coating layer, S
A plasma flame exposure test was conducted under the following conditions on an oxidation-resistant C/C material coated with a three-layer laminated coating consisting of a fine particle coating layer and a SiO□ glass coating layer.

Specimen size 1OX50X2 - Plasma temperature: 1300℃ Atmosphere: Air exposure time 26 minutes Exposure number = 1 to 10 cycles Plasma gas generation conditions: Argon gas, flow rate 301 /
sin, current 275 A Distance from plasma to specimen: 25 mm Table 1 shows the weight loss rate of the specimen after the above exposure test.

Table I For comparison, an S dew test was conducted under the same conditions on a specimen on which only the SiC coating layer was formed in the first coating step, and the coating penetrated after 20 seconds of flame irradiation.

Example 2 An oxidation-resistant C/C material was manufactured by changing the third coating step and subsequent steps of Example 1 to the following steps.

B (OC+xH2?) on the C/C base material surface after the second coating step
) 3 was applied evenly and air-dried for one day and night to hydrolyze it to HzBO:+. Then, the C/C base material was heated at 600°C in an electric furnace.
Heat treatment for 10 minutes at a temperature of B10. Converted to glass.

The obtained oxidation-resistant C/C material was subjected to an oxidation consumption test by plasma flame exposure under the same conditions as in Example 1. The results are shown in Table 2.

Table 2 From the results in Table 2, it was recognized that excellent heat resistance and oxidation resistance were exhibited.

Example 3 Using the same C/C base material as in Example 1, a SiC coating layer, a SiO□ fine particle coating layer, and B, 0
A three-layer coated oxidation-resistant C/C material consisting of a 3.5iOz glass coating layer was manufactured.

(1) First coating step Sin, the powder and carbon powder are mixed at a molar ratio of 2:1, and the C/C base material is embedded in this mixed powder and filled into a graphite crucible. , 18 under N2 atmosphere
A temperature of 50°C was maintained. In this way, a 200 μm thick SiC coating layer was formed on the surface of the C/C base material.

(2) Second coating step A Sin fine particle coating layer was formed under the same conditions as in Example 1.

(3) Third coating step A SiO□ coating layer was formed under the same conditions as the third coating step of Example 1, and then B (OC+7Hzt)i was uniformly applied and air-dried for one day and night. At this stage, the surface of the second coating layer was coated with the SiO□ coating layer and the H, BO3 coating layer in a laminated manner.

(4) Vitrification treatment The coated C/C base material was transferred to an electric furnace and heated to 800°C.
The coating layer in the third coating step is heated to a temperature of B2O3.S.
It was reacted and converted into iO□ glass.

The thickness of the glass coating layer in this case was 10 μm.

(5) Heat resistance and oxidation resistance test The weight loss rate due to plasma flame exposure was measured in the same manner as in Example 1 in two temperature ranges of 1300°C and 1700°C. The results were as shown in Table 3.

Table 3 [Effects of the invention] As described above, the surface of the carbon fiber reinforced carbon base material is coated with SiC coating layer, SiO□ fine particle coating layer, Sin, glass layer or B.
The C/C material according to the present invention, which is coated with three layers of 2O3 glass coating layer or B20, .SiO□ glass coating layer, has excellent oxidation resistance.

Therefore, it can be used for structural members exposed to severe conditions under high-temperature oxidation cloud surroundings, resulting in effects such as ensuring stable performance and extending service life.

From the results in Table 3, it was confirmed that this C/C material had sufficient heat and oxidation resistance even under severe oxidation conditions of 1700° C., and the surface condition after the exposure test was also normal.

[Brief explanation of drawings]

1 to 5 are cross-sectional views schematically showing the coating state at each coating process step according to the manufacturing method of the present invention. 1... C/C base material 2... SiC coating layer 3.
...5iCh fine grain coating layer 4...5ift or B2O3 glass layer 4'...Si
O□Coating layer 5...B2O3 coating layer 6...B2O3
・SiO□ Glass layer 1 SiC coating layer C/C base material SiO□ Fine particle coating layer SiC coating layer C/C base material 5in2 Fine particle coating layer SiC coating layer C/C base material B2O3 Covering layer SiO□Coating layer Si○2 Fine particle coating layer SiC coating layer C/C base material B2O3・SiO□Glass layer SiO□Fine particle coating layer SiC coating layer C/C base material

Claims (4)

[Claims] 1. A SiC coating layer, S
iO_2 fine particle coating layer, SiO_2 glass coating layer or B
_2O_3 glass coating layer or B_2O_3・SiO
_2 An oxidation-resistant C/C material with a structure in which three glass coating layers are laminated and coated. 2. A carbon fiber-reinforced carbon body obtained by composite molding carbon fibers with a matrix resin, curing, and firing carbonization is used as a base material, and the surface of the base material is brought into contact with SiO gas to form a SiC coating layer by a conversion method. 1 coating step, a 2nd coating step of vacuum impregnating SiO_2 fine particle suspension obtained by hydrolyzing an alcohol solution of Si(OC_2H_5)_4 in a basic region;
_2H_5) Oxidation-resistant, characterized by sequentially performing a third coating step of vacuum impregnation with a glass precursor solution obtained by hydrolyzing the alcohol solution of _4 in an acidic region, and then heat-treating at a temperature of 400°C or higher. A method for manufacturing a carbon-resistant C/C material. 3. As the third coating step, B(OC_1_2H_2_7
3. The method for producing an oxidation-resistant C/C material according to claim 2, which uses a method of applying _3. 4. As the third coating step, Si(OC_2H_5)_4
After vacuum impregnation with the glass precursor solution obtained by hydrolyzing the alcohol solution of B(OC_1_2
The method for producing an oxidation-resistant C/C material according to claim 2, which uses a method of applying H_2_7)_3.