JP2021191720A - Manufacturing method of sic/sic composite material - Google Patents

Abstract

To provide a manufacturing method of a SiC/SiC composite material capable of decreasing an amount of use of a matrix precursor to reduce manufacturing cost, and also removing easily a calcined material and the like that remains on a surface of the SiC/SiC composite material to improve surface smoothness.SOLUTION: The manufacturing method of a SiC/SiC composite material 10 includes: a coating step for obtaining a coated body 3 in which an oil-repellent coating 20 having a plurality of holes 20a is formed on an outer surface of an aggregate 2; an impregnation step for obtaining an impregnated body 7 by soaking the coated body 3 into an impregnation liquid 21 that contains a SiC matrix precursor made of a polycarbosilane-based resin; a curing step for obtaining a cured body 8 by heating the impregnated body 7; and a firing step for obtaining a fired body 9 by firing the cured body 8. Further, a surface cleaning step for removing effluent of the SiC matrix precursor that has flowed out to an outer surface of the aggregate 2 through the holes 20a at the curing step, is included after at least one of the curing step and the firing step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method for producing a SiC / SiC composite material.

Composites in which high-strength ceramic fibers are fixed with a matrix are widely used in various fields where strength is required. As the matrix, there are those using resin and those using a precursor fired to make ceramics, and there are various combinations of composite materials according to each application, and various molding methods according to the desired shape. Has been adopted.

For example, Patent Document 1 describes a method for forming a composite material in which a reinforcing fiber base material is laminated. In the above-mentioned method for forming a composite, first, a laminate in which a reinforcing fiber base material is laminated is placed on a molding surface of a molding jig for molding a composite material. Next, the laminate is covered with a film and hermetically sealed. Next, the resin is supplied to the laminate from the resin supply unit provided on the film side of the laminate. After that, the inside of the film is blocked from the passage of the resin in the film from the degassed and waterproof portion provided on the molding surface side of the laminated body and provided in one direction in the plane orthogonal to the laminated direction of the laminated body. The atmosphere of the above is sucked in, and the laminate is impregnated with the resin. After that, the resin in the film is discharged from the resin discharging portion provided on the film side of the laminated body.
In Patent Document 1, the composite material is suitably molded by suppressing the formation of an unimpregnated region even when the plate thickness of the composite material changes in one direction in the plane of the composite material. It is stated that it can be done.

Japanese Unexamined Patent Publication No. 2018-187806

However, the composite material described in Patent Document 1 is a composite material in which reinforcing fibers and a resin are combined, and the surface thereof has a structure covered with a resin, so that the smoothness of the surface is ensured. ..

On the other hand, in the SiC / SiC composite material having an aggregate containing SiC reinforcing fibers and a SiC matrix, a matrix precursor containing an organic polymer and an inorganic polymer adhering to the inside and the surface of the aggregate is fired. This firing step causes the matrix precursor to shrink. Here, the matrix precursor impregnated inside the aggregate has the function of firmly bonding the SiC reinforcing fibers to each other, but the matrix precursor adhering to the surface of the aggregate is a composite material after the firing step. May cause unevenness on the surface of the surface.
Further, due to the generation of fine cracks in the matrix after the firing step, the action of joining the SiC reinforcing fibers to each other is lost, and as a result, unevenness is formed on the surface of the composite material, and the appearance and dimensional accuracy are impaired.
Further, since a matrix precursor containing an expensive inorganic polymer or the like is used in the production of the SiC / SiC composite material, if there are many unnecessary matrix precursors adhering to the surface of the aggregate, the cost will increase. It becomes.

In view of the above problems, the present invention reduces the amount of the matrix precursor used by impregnating the aggregate with the necessary and sufficient matrix precursor, and at the same time, calcining the matrix precursor remaining on the surface of the SiC / SiC composite material. It is an object of the present invention to provide a method for producing a SiC / SiC composite material, which can easily remove an object and improve the smoothness of a surface.

The above object is achieved by the following method (1) for producing a SiC / SiC composite material according to the present invention.

(1) A method for producing a SiC / SiC composite material, which comprises an aggregate containing SiC fibers and a SiC matrix filled in the gaps between the aggregates.
A coating step of forming an oil-repellent coating having a plurality of holes on the outer surface of the aggregate to obtain a coating body,
The impregnation step of impregnating the coating body with an impregnating solution containing a SiC matrix precursor made of a polycarbosilane-based resin to obtain an impregnated body.
A curing step of heating the impregnated body to cure the SiC matrix precursor to obtain a cured product,
It has a firing step of firing the cured product to ceramicize the SiC matrix precursor to obtain a fired body.
Having at least one of the curing step and the firing step has a surface cleaning step of removing the effluent of the SiC matrix precursor that has flowed out to the outer surface of the aggregate through the pores in the curing step. A method for manufacturing a SiC / SiC composite material.

According to the method for producing a SiC / SiC composite material of the present invention, an oil-repellent film is formed on the outer surface of an aggregate made of SiC fibers. In the impregnation step, this oil-repellent coating allows the impregnating liquid to pass through the pores and impregnate the inside of the aggregate. It penetrates the entire area of the material. Therefore, the impregnated body obtained by the impregnation step can hold the impregnated liquid inside the aggregate and has an oil-repellent film on the surface thereof so that the impregnated liquid does not adhere to the impregnated body. It can be prevented from being used and the manufacturing cost can be reduced.

Further, the method for producing the SiC / SiC composite material according to the present invention is preferably the following (2) to (8).

(2) The surface cleaning step is performed between the curing step and the firing step, and is characterized in that the effluent that has become a dot-shaped cured product by the curing step is removed (2). The method for producing a SiC / SiC composite material according to 1).

According to the above manufacturing method, since the oil-repellent coating is present on the outer surface around the pores, the outflow of the SiC matrix precursor flowing out from the pores has a contact angle of 90 ° or more with the oil-repellent coating. It tends to be a dot shape. This dot-shaped outflow product becomes a dot-shaped cured product after the curing step, and it becomes easy to remove the cured product from the surface of the cured product by the surface cleaning step.

(3) The surface cleaning step is carried out after the firing step, and is characterized in that it is a step of removing the runoff that has become a dot-shaped fired product by the firing step (1) or (2). The method for producing a SiC / SiC composite material according to the above.

When the effluent is cured in a dot-shaped state, the shape does not change in the subsequent firing step, and a dot-shaped fired product is formed. Therefore, it becomes easy to remove the fired product from the surface of the fired body, and the SiC / SiC composite material 10 having excellent surface smoothness can be easily produced.

(4) The firing step is any one of (1) to (3), which is a step of ceramicizing the SiC matrix precursor cured by the curing step and carbonizing the oil-repellent film. The method for manufacturing a SiC / SiC composite material according to one.

Since the oil-repellent film formed on the surface of the aggregate is carbonized in the firing step, it can be easily peeled off after the firing step.

(5) The step according to (4), wherein the surface cleaning step is carried out after the firing step and is a step of removing the effluent and the carbide of the carbonized oil-repellent coating. A method for manufacturing a SiC / SiC composite material.

When the surface cleaning step is carried out after the firing step, the effluent of the SiC matrix precursor can be removed and at the same time, the carbide of the carbonized oil-repellent coating can be removed, and the surface of the SiC / SiC composite material can be removed with the oil-repellent coating after production. Does not remain, and a smooth surface can be obtained.

(6) The impregnation step is characterized by a reduced pressure pressure impregnation method in which the gas inside the aggregate is removed by depressurization and then the impregnated liquid is impregnated inside the aggregate by pressurization. The method for producing a SiC / SiC composite material according to any one of (1) to (5).

When the vacuum pressure impregnation method is used in the impregnation step, the gas inside the aggregate is removed during depressurization, and when the impregnating liquid is impregnated inside the aggregate by pressurization, the repulsion of the oil-repellent coating on the outer surface is countered. Then, the impregnating liquid can be easily introduced into the inside of the aggregate.

(7) The method for producing a SiC / SiC composite material according to any one of (1) to (6), wherein the SiC matrix precursor is an allylhydride polycarbosilane.

Allylhydride polycarbosilane has poor wettability with an oil-repellent film and can easily peel off a cured product or a fired product from the oil-repellent film, so that it can be suitably used as a SiC matrix precursor.

(8) The oil-repellent coating is characterized by containing at least one resin selected from silica-based resins containing polyvinyl alcohol, polyvinyl acetate, alkoxysilane and silanol (1) to (7). The method for producing a SiC / SiC composite material according to one.

When the oil-repellent film contains at least one resin selected from silica-based resins containing polyvinyl alcohol, polyvinyl acetate, alkoxysilane and silanol, there is no compatibility with the impregnating solution containing the polycarbosilane-based resin. In particular, since it has poor wettability with allylhydride polycarbosilane, which is preferably used as a SiC matrix precursor, the cured product can be easily removed from the oil-repellent film after the curing step.

According to the method for producing a SiC / SiC composite material according to the present invention, an oil-repellent film having a plurality of pores is formed on the outer surface of an aggregate made of SiC fibers, and therefore an impregnated liquid containing a SiC matrix precursor is formed. The impregnating liquid that has penetrated into the inside of the aggregate is easily permeated into the entire area of the aggregate and is retained inside the aggregate when the impregnated liquid is impregnated into the inside of the aggregate. Further, since the impregnating liquid does not adhere to the outer surface of the aggregate, it is possible to prevent the impregnating liquid from being used more than necessary, and it is possible to reduce the manufacturing cost. Further, since the effluent of the SiC precursor after the curing step and the firing step is cured and fired on the oil-repellent film, the effluent can be easily removed and the smoothness of the surface can be improved. It is possible to manufacture a possible SiC / SiC composite material.

1 (a) to 1 (g) are cross-sectional views schematically showing a method for producing a SiC / SiC composite material according to an embodiment of the present invention. 2 (a) to 2 (d) are cross-sectional views schematically showing a conventional method for manufacturing a SiC / SiC composite material.

The present inventor has made diligent studies in order to obtain a manufacturing method capable of reducing the amount of the matrix precursor used and improving the smoothness of the surface of the obtained SiC / SiC composite material. As a result, by appropriately selecting the impregnating liquid containing the SiC matrix precursor and forming an oil-repellent coating on the outer surface of the aggregate in advance, the impregnating liquid is less likely to adhere to the surface of the aggregate in the impregnation step. , It has been found that surface runoff can be easily removed after the curing and firing steps.

The present invention is based on such findings, and the method for producing a SiC / SiC composite material according to an embodiment of the present invention will be described in detail below.
The present invention is not limited to the embodiments described below, and can be arbitrarily modified and implemented without departing from the gist of the present invention.
Further, in the specification of the present application, "~" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value.

[Manufacturing method of SiC / SiC composite material]
1 (a) to 1 (g) are cross-sectional views schematically showing a method for producing a SiC / SiC composite material according to an embodiment of the present invention.

<Preparation of aggregate>
As shown in FIG. 1A, the aggregate 2 forms a woven fabric 6 by weaving strands 5 in which SiC fibers 4 are bundled as warp threads and weft threads, and a plurality of the obtained woven fabrics 6 are laminated. It is composed of. In this embodiment, for example, eight woven fabrics 6 are joined so as not to be peeled off in a laminated state. The method of joining is not particularly limited, but a method of sewing the woven fabric 6 in a bundled state, a method of temporarily fixing with an organic binder, or a method of impregnating the surface of SiC fibers with a chemical vapor deposition (CVI). Therefore, a method of forming a surface layer made of pyrolytic carbon, SiC, or the like and bonding SiC fibers to each other can be adopted.

<Coating process>
Next, as shown in FIG. 1 (b), the coating body 3 is formed by forming the oil-repellent coating 20 on the surface of the aggregate 2 having the predetermined thickness obtained as described above. The method for forming the oil-repellent coating 20 is not particularly limited, but a coating method such as applying an oil-repellent coating resin made of polyvinyl alcohol prepared into a paste to the surface and drying it, or attaching a sheet containing the oil-repellent resin is attached. The pasting method can be adopted.

In the coating method, the paste adheres only to the portion having the strand 5 made of the SiC fiber 4, and the paste does not remain in the opening portion without the strand 5, so that the step of forming the hole 20a is unnecessary and only the drying is performed. An oil-repellent coating 20 having holes 20a can be easily formed on the surface of the aggregate 2. Since the purpose of the coating method is to form the oil-repellent coating 20 only on the surface without penetrating into the inside of the aggregate 2, it is in the form of a paste so that the oil-repellent resin does not penetrate into the inside of the SiC fiber 4. It is preferable to apply the mixture.
Further, in the pasting method, since the sheet containing the oil-repellent resin having the holes 20a is pasted in advance, the oil-repellent coating 20 can be easily formed on the surface of the aggregate 2.
Regardless of which method is used, in the impregnation step described later, since the hole 20a serves as a passage for the impregnating liquid, it does not prevent the impregnating liquid 21 from impregnating the inside of the aggregate 2 and after impregnation. Can repel unnecessary impregnating liquid 21 on the surface of the aggregate 2 and prevent the outflow of the SiC matrix from adhering to the surface of the aggregate 2.

<Immersion process>
Next, as shown in FIG. 1 (c), the coating body 3 obtained by the above coating step is impregnated with an impregnating liquid 21 containing a SiC matrix precursor made of a polycarbosilane-based resin to impregnate the impregnating liquid 21. The impregnated body 7 is obtained by infiltrating the inside of the aggregate 2. Since the SiC fiber 4 has good wettability with the impregnating liquid 21 containing the polycarbosilane-based resin, the impregnating liquid 21 rapidly permeates the inside of the aggregate 2 by the impregnation step. On the other hand, since the oil-repellent coating 20 containing, for example, polyvinyl alcohol is formed on the surface of the aggregate 2, the impregnating liquid 21 is repelled and almost no impregnating liquid 21 remains.
As a method of impregnating the inside of the aggregate 2 with the impregnating liquid 21, a method that is easy to permeate can be selected because it passes through the holes 20a of the oil-repellent coating 20. For example, the coating body 3 on which the oil-repellent coating 20 is formed is placed in a vacuum atmosphere, the gas inside the aggregate 2 is removed, and then the impregnating liquid 21 is permeated into the inside of the aggregate 2 by pressurization. It is preferable to use the pressure impregnation method.

<Curing process>
Next, as shown in FIG. 1 (d), the impregnated body 7 is heated to cure the SiC matrix precursor to obtain a cured body 8. The curing step is a step of temporarily curing the SiC matrix precursor in the impregnating liquid 21 so that the impregnating liquid 21 does not flow out to the outside of the aggregate 2 in the firing step described later. Specifically, the temperature is slowly raised while gelling so as not to cause outflow due to a decrease in the viscosity of the impregnating liquid 21.
The rate of temperature rise in the curing step is preferably, for example, 10 to 60 ° C./min, and the treatment temperature is preferably 150 to 400 ° C. By carrying out under these conditions, it is possible to fix the impregnated liquid 21 inside the aggregate while suppressing the outflow. Further, by adjusting the temperature rise rate in the curing step, the curing step and the firing step described later can be continuously performed.

As described above, by appropriately adjusting the temperature in the curing step, it is possible to suppress the outflow due to the decrease in the viscosity of the impregnating liquid 21. However, since the solvent or low molecular weight component contained in the impregnating liquid 21 is generated as the decomposition gas 12 by heating, a certain amount of impregnation is performed from the inside of the aggregate 2 from the inside of the aggregate 2 with the decomposition gas 12. The liquid 21 flows out. Then, the impregnated liquid 21 that has flowed out is repelled on the surface of the oil-repellent coating 20, and for example, a cured product (outflow material) 21a of a dot-shaped SiC matrix precursor is formed on the surface of the cured body 8.

<Surface cleaning process (1st time)>
Next, as shown in FIG. 1 (e), the cured product 21a of the SiC matrix precursor on the surface of the cured product 8 formed in the curing step is removed. At this time, since the oil-repellent coating 20 is formed on the surface of the cured body 8, the cured product 21a of the SiC matrix precursor is not in close contact with the surface of the cured body 8, and the cured product 21a can be easily removed. Can be done.

<Baking process>
Next, as shown in FIG. 1 (f), by firing the cured product 8, the SiC matrix precursor made of the polycarbosilane-based resin cured by the curing step is ceramicized to form the SiC matrix 22. , Obtain a fired body 9. At this time, the cured product 21a of the SiC matrix precursor, which was slightly left on the surface of the cured product 8, is also fired in a dot shape to become a fired product (outflow) 22a. Further, the oil-repellent coating 20 on the surface of the cured body 8 is carbonized and easily peeled off.

The firing temperature in the firing step is preferably 1000 to 1500 ° C. When the firing temperature is 1000 ° C. or higher, the SiC matrix precursor is sufficiently fired, so that the heat resistance of the matrix is increased and the matrix is less likely to be deformed even at a high temperature. Further, when the firing temperature is 1500 ° C. or lower, the oxygen contained in the SiC fiber 4 reacts with the SiC, so that it is possible to prevent the formation of cavities that reduce the strength inside the SiC fiber, which is high. A strong SiC / SiC composite material can be obtained.

<Surface cleaning process (second time)>
Then, as shown in FIG. 1 (g), the SiC / SiC composite material 10 is obtained by removing the calcined product 22a of the SiC matrix precursor and the carbide of the oil-repellent coating 20 remaining on the surface of the fired body 9. Since the oil-repellent coating 20 is carbonized by the firing step and is in a state of being easily peeled off, the calcined product 22a of the SiC matrix precursor and the carbides of the oil-repellent coating 20 can be easily removed by the surface cleaning step. can do. Thereby, the SiC / SiC composite material 10 having a smooth surface can be manufactured.

The process from the series of coating steps to the surface cleaning step (second time) is not limited to one time, and may be repeated a plurality of times. By repeating it a plurality of times, the density can be further increased.

Subsequently, in order to explain in more detail the effect of the method for producing the SiC / SiC composite material according to the present embodiment, FIG. 2 shows a method for producing the SiC / SiC composite material when the above-mentioned coating step and surface cleaning step are not performed. This will be described below with reference to (a) to FIG. 2 (d). In FIG. 2, the same or equivalent parts as those of the embodiment shown in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted or simplified.

<Preparation of aggregate>
As shown in FIG. 2A, the aggregate 2 forms a woven fabric 6 by weaving strands 5 in which SiC fibers 4 are bundled as warp threads and weft threads, and a plurality of the obtained woven fabrics 6 are laminated. It is composed of.

<Immersion process>
Next, as shown in FIG. 2B, the impregnated body 7 is made by impregnating the impregnated liquid 21 containing the SiC matrix precursor with the aggregate 2 and allowing the impregnated liquid 21 to penetrate into the inside of the aggregate 2. obtain.

<Curing process>
Next, as shown in FIG. 2C, the impregnated body 7 is heated to cure the SiC matrix precursor to obtain a cured body 8. The curing step is a step of temporarily curing the SiC matrix precursor in the impregnating liquid 21 so that the impregnating liquid 21 does not flow out to the outside of the aggregate 2 in the firing step described later. Specifically, the temperature is slowly raised while gelling so as not to cause outflow due to a decrease in the viscosity of the impregnating liquid 21.
Since the solvent or low molecular weight component contained in the impregnating liquid 21 is generated as the decomposition gas 12 by this heating, a certain amount of the impregnating liquid 21 flows out to the outside of the aggregate 2 with the decomposition gas 12. Then, it becomes a cured product 21a of the SiC matrix precursor and adheres to the surface of the cured product 8.

<Baking process>
Next, as shown in FIG. 2D, the cured body 8 is fired to ceramicize the SiC matrix precursor to form the SiC matrix 22 and obtain the SiC / SiC composite material 10. At this time, the remaining cured product 21a of the SiC matrix precursor that had adhered to the surface of the cured body 8 is also fired while being attached to the surface of the cured body 8 to form the fired product 22a.

According to the conventional method for manufacturing a SiC / SiC composite material, the fired product 22a that has flowed out of the aggregate 2 and has been fired forms irregularities on the surface of the SiC / SiC composite material 10 and impairs smoothness. .. In addition, fine cracks may occur in the fired product 22a, which causes defects on the surface of the SiC / SiC composite material 10 to reduce the strength and form irregularities on the surface of the SiC / SiC composite material 10. ..

Further, according to the conventional manufacturing method, when the impregnating liquid 21 is impregnated inside the aggregate 2 in the impregnation step, a large amount of the impregnating liquid 21 adheres to the surface of the aggregate 2. As described above, since these are unnecessary fired products 22a due to the curing step and the firing step, a matrix precursor containing an expensive inorganic polymer or the like is used more than necessary.

Further, in the conventional manufacturing method, for the purpose of obtaining smoothness, for example, even if the surface of the SiC / SiC composite material 10 obtained after firing is to be polished or cut, an unnecessary fired product 22a and the SiC fiber 4 are used. Due to the high adhesion, the fired product 22a cannot be easily removed. As a result, the SiC fiber 4 is torn, the strength is lowered, and the smoothness of the surface is also lowered.

On the other hand, in the method for producing a SiC / SiC composite material according to the present embodiment shown in FIG. 1, an oil-repellent coating 20 is formed on the outer surface of the aggregate 2 made of the SiC fiber 4. In the impregnation step, the oil-repellent coating 20 passes through the holes 20a and impregnates the impregnating liquid 21 into the inside of the aggregate 2. Therefore, although the holes 20a act as a resistance to permeation, the impregnation penetrates into the inside of the aggregate 2. The liquid 21 easily permeates the entire area of the aggregate 2.
Therefore, the impregnated body 7 obtained by the impregnation step in the present embodiment is necessary because the impregnating liquid 21 can be held inside the aggregate 2 and the surface surface of the impregnating body 7 is not adhered by the oil-repellent coating 20. It is possible to prevent the above impregnating liquid 21 from being used, and it is possible to reduce the manufacturing cost.

Further, in the manufacturing method of the present embodiment, the SiC matrix precursor flows out to the outer surface of the aggregate 2 through the holes 20a in the curing step to become the cured product 21a, but the oil-repellent film on the surface of the aggregate 2 is formed. Due to the presence of 20, the cured product 21a can be easily removed.

Further, according to the manufacturing method of the present embodiment, since the oil-repellent coating 20 is present on the outer surface around the hole 20a, the outflow of the SiC matrix precursor flowing out from the hole 20a has a contact angle with the oil-repellent coating 20. Is 90 ° or more, and tends to have a dot shape. As described above, when the outflow material has a dot shape, it becomes a dot-shaped cured product 21a after the curing step, and it becomes easy to remove the cured product 21a from the surface of the cured body 8 by the surface cleaning step.

Further, even if the surface cleaning step is not performed after the curing step, when the outflow material is cured in a dot-shaped state and becomes a cured product 21a, the shape does not change in the subsequent firing step, and the dot-shaped firing is performed. The object 22a is formed. Therefore, the fired product 22a can be easily removed from the surface of the fired body 9, and the surface smoothness can be easily obtained regardless of whether the surface cleaning step is performed between the curing step and the firing step or after the firing step. An excellent SiC / SiC composite material 10 can be manufactured.

Furthermore, in the present embodiment, unlike the conventional manufacturing method, the oil-repellent coating 20 is formed on the surface of the aggregate, but since the oil-repellent coating 20 is carbonized in the firing step, it is easy after the firing step. Can be peeled off. Therefore, the oil-repellent coating 20 does not remain on the surface of the SiC / SiC composite material 10 after production, and desired quality can be obtained.
The oil-repellent coating 20 does not have to be formed on the entire outer surface of the aggregate 2, but may be formed on at least two surfaces orthogonal to the thickness direction of the aggregate 2. Since the two surfaces orthogonal to the thickness direction of the aggregate 2 occupy most of the total surface area of the aggregate 2, if impurities can be prevented from adhering to the two surfaces, the desired smoothness can be obtained. At the same time, the manufacturing cost can be reduced.

Further, in the production method of the present embodiment, after at least one of the curing step and the firing step, a surface cleaning step for removing the effluent of the SiC matrix precursor may be carried out, and in particular, a series of steps may be carried out. In the case of repeated impregnation, it is possible to carry out the surface cleaning step both between the curing step and the firing step and after the firing step, so that the calcined product 22a does not accumulate and a smoother SiC / SiC composite material can be obtained. It is preferable from the point of view that it can be obtained.

Further, in the manufacturing method of the present embodiment, the method of impregnating the inside of the aggregate with the impregnating liquid 21 is not particularly limited, but when the vacuum pressure impregnation method is used, the gas inside the aggregate 2 is removed at the time of depressurization. When the impregnating liquid 21 is impregnated inside the aggregate 2 by pressurization, the impregnating liquid can be easily introduced into the inside of the aggregate against the repulsion of the oil-repellent coating on the outer surface.

Subsequently, the forms of the impregnating liquid 21, the SiC matrix precursor, the oil-repellent coating 20, the SiC fiber 4, and the aggregate 2 that can be used in the production method of the present embodiment will be described below.

(Impregnated liquid)
The impregnating liquid 21 containing the SiC matrix precursor that can be used in the present embodiment is not particularly limited, but allylhydride polycarbosilane, polycarbosilane, and the like can be used. Since these impregnated liquids can form SiC in a high yield, they can be suitably used in the method for producing a SiC / SiC composite material according to the present embodiment. Further, the polycarbosilane-based resin as the SiC matrix precursor may be used as the impregnating liquid 21 by using the polymer or oligomer as it is, or may be diluted with a solvent and adjusted in viscosity to be used as the impregnating liquid 21.

(SiC matrix precursor)
The polycarbosilane-based resin used as a SiC matrix precursor is a precursor that becomes a SiC matrix by a firing step described later. In the present embodiment, the SiC matrix precursor is not particularly limited as long as it is a polycarbosilane-based resin, and for example, allylhydride polycarbosilane, polycarbosilane, and the like can be used.
Further, allylhydride polycarbosilane has poor wettability with the oil-repellent coating 20, and can easily peel off the cured product 21a or the fired product 22a from the oil-repellent coating 20, and is therefore suitably used as a SiC matrix precursor. can do.

(Oil-repellent coating)
The oil-repellent film (that is, the hydrophilic film) that can be used in the present embodiment is not particularly limited, but a film containing a resin having a hydrophilic group such as a hydroxyl group, an amino group, or a carboxyl group may be used. can. As the resin having such a hydrophilic group, for example, it is preferable to use at least one resin selected from silica-based resins containing polyvinyl alcohol, polyvinyl acetate, alkoxysilane and silanol. The oil-repellent coating containing these resins is incompatible with the impregnating liquid containing the polycarbosilane-based resin, and in particular, has poor wettability with allylhydride polycarbosilane, which is suitably used as a SiC matrix precursor. Therefore, after the curing step, the cured product 21a can be easily removed from the oil-repellent coating 20.

(SiC fiber)
The thickness of the SiC fiber 4 is not particularly limited, but for example, one having an average diameter of 7.5 to 15 μm can be used. When the thickness of the SiC fiber 4 is 7.5 μm or more, even if the surface is scratched, it is not easily affected, so that the SiC fiber 4 having high strength can be obtained. On the other hand, when the thickness of the SiC fiber 4 is 15 μm or less, it is difficult to break even when bent, so that a SiC / SiC composite material having a complicated shape and a portion having a small curvature can be obtained.

(aggregate)
The form of the aggregate 2 that can be used in the present embodiment is not particularly limited, and various forms of the aggregate 2 can be used, for example, a cloth (woven fabric), a filament winding body, and a braiding body. , Extracts, non-woven fabrics, etc. can be used. It is desirable that the cloth, the filament winding body and the braiding body are formed by using strands in which a plurality of SiC fibers are bundled. The number of SiC fibers 4 per strand can be, for example, 100 to 10,000.

2 Aggregate 3 Coating body 4 SiC fiber 6 Woven cloth 7 Impregnated body 8 Hardened body 9 Fired body 10 SiC / SiC composite material 20 Oil-repellent coating 20a Hole 21 Impregnated liquid 22 SiC matrix

Claims (8)

A method for producing a SiC / SiC composite material, which comprises an aggregate containing SiC fibers and a SiC matrix filled in the gaps between the aggregates.
A coating step of forming an oil-repellent coating having a plurality of holes on the outer surface of the aggregate to obtain a coating body,
An impregnation step of impregnating the coating body with an impregnating solution containing a SiC matrix precursor made of a polycarbosilane-based resin to obtain an impregnated body.
A curing step of heating the impregnated body to cure the SiC matrix precursor to obtain a cured product,
It has a firing step of firing the cured product to ceramicize the SiC matrix precursor to obtain a fired body.
Having at least one of the curing step and the firing step has a surface cleaning step of removing the effluent of the SiC matrix precursor that has flowed out to the outer surface of the aggregate through the pores in the curing step. A method for manufacturing a SiC / SiC composite material. The first aspect of claim 1 is characterized in that the surface cleaning step is carried out between the curing step and the firing step, and is a step of removing the runoff that has become a dot-shaped cured product by the curing step. The method for manufacturing a SiC / SiC composite material according to the above. The SiC / 2. The SiC / 2. A method for manufacturing a SiC composite material. The method according to any one of claims 1 to 3, wherein the firing step is a step of ceramicizing the SiC matrix precursor cured by the curing step and carbonizing the oil-repellent film. A method for manufacturing a SiC / SiC composite material. The SiC / SiC according to claim 4, wherein the surface cleaning step is performed after the firing step and is a step of removing the effluent and the carbide of the carbonized oil-repellent coating. Method of manufacturing composite material. The impregnation step is characterized by being carried out by a reduced pressure pressurization impregnation method in which the gas inside the aggregate is removed by depressurization and then the impregnated liquid is impregnated inside the aggregate by pressurization. The method for producing a SiC / SiC composite material according to any one of 1 to 5. The method for producing a SiC / SiC composite material according to any one of claims 1 to 6, wherein the SiC matrix precursor is an allylhydride polycarbosilane. The invention according to any one of claims 1 to 7, wherein the oil-repellent coating contains at least one resin selected from silica-based resins containing polyvinyl alcohol, polyvinyl acetate, alkoxysilane and silanol. A method for manufacturing a SiC / SiC composite material.

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