JPH1171190A - Production of silicon carbide-silicon composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a three-dimensional silicon carbide- silicon composite material, enabling to simply and rapidly obtain the three- dimensional composite material having a desired shape, a large strength and a density corresponding to that of a product produced by a method using a mold, in excellent profitability without using a mold. SOLUTION: This method for producing a three-dimensional silicon carbide- silicon composite material comprises a process for producing a three-dimensional shape product by excluding the heated melted product of a homogeneous mixture comprising a mesophase-containing pitch coated with a thermoplastic resin and silicon carbide powder from the opening of a nozzle 4, simultaneously scanning the opening of the nozzle on a support and subsequently hardening the melted product injected in a desired shape, a process for thermally treating the produced three-dimensional product in an inactive atmosphere to produce a calcined product comprising the silicon carbide and the carbon, and a subsequent process for impregnating the produced calcined product with silicon to produce the silicon carbide-silicon composite material.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a silicon carbide material having excellent properties such as heat resistance, chemical resistance, oxidation resistance and high strength.
The present invention relates to a method for manufacturing a silicon composite material. More specifically,
By forming a hardened layer using a process of melting and hardening a uniform mixture of silicon carbide powder and a thermoplastic resin, silicon carbide having a three-dimensional shape quickly without using a molding die.
The present invention relates to a method for producing a silicon carbide-silicon composite material from which a silicon composite material can be obtained.

[0002]

2. Description of the Related Art Silicon carbide-silicon composite materials are widely used for structural materials of various devices and various tools because of their high strength and excellent oxidation resistance. The silicon carbide-silicon composite material is usually formed by firing a mixture obtained by molding a mixture of silicon carbide powder and a phenol resin or carbon powder serving as a carbon source into a desired shape, and firing silicon carbide and carbon. Is manufactured by preparing a fired body made of and then impregnating the fired body with silicon. What significantly affects the characteristics of the fired body made of silicon carbide and carbon is a molding step for forming silicon carbide powder into a desired shape. Conventionally, as the molding method, a CIP (cold isostatic pressing) molding method,
A molding method using a specific mold such as a cast molding method using a water-absorbing mold such as a gypsum mold has been used. However, a molding method using such a molding die requires cost and production time for producing the mold, and furthermore, there is a restriction depending on the mold in molding a complicated three-dimensionally shaped body. For this reason,
For example, Japanese Patent Application Laid-Open No. 8-151267 discloses a rapid molding method in which a hardened layer having a desired shape is directly produced from a CAD model without using a mold, and the hardened layers are continuously laminated to form a three-dimensionally shaped body. Has been proposed. Furthermore, recently, as one of the same rapid molding methods, a thermoplastic resin-ceramics mixed system is melted by heat and extruded from a nozzle to form a hardened layer of a specific shape, and then hardened by repeating the same scanning. A forming method of stacking layers to form a three-dimensional shape (hereinafter, referred to as a melt deposition method) has been proposed [M. K. Agarwala et al., Solid Free
form Fabrication Symposiu
m Abstracts, page 1 (1995)].

[0003]

However, if the above-mentioned melt deposition method is applied directly to a method for forming a silicon carbide-silicon composite material, the following problems occur. That is, when the molded body is formed into a desired shape using a mixture mixed with silicon carbide powder using the thermoplastic resin as a molding aid (binder) as described above using the melt deposition method, Since the carbonization yield of the plastic resin is only 10% or less, it hardly becomes a carbon source in the obtained fired body, and the following problems occur. (I) When the residual carbon content of the fired body is small, the wettability of silicon when the fired body is impregnated with silicon deteriorates, and the fired body is not sufficiently impregnated with silicon. It becomes a silicon composite material. Also,
Since the residual carbon content is small, the strength of the fired body is low, and depending on the shape, the fired body is liable to be damaged when being carried in a manufacturing process, and the product yield is deteriorated. (Ii) If the carbon content of the fired body is small, the amount of silicon carbide generated from the reaction between carbon and silicon in the silicon impregnation step is small, and as a result, the proportion of silicon carbide in the composite material is low. The strength of the obtained silicon carbide-silicon composite material is reduced.

As one solution to these problems, it is conceivable to use a resin which shows a high carbonization yield when calcined, in combination with a thermoplastic resin. For example, a commonly used phenol resin has a carbonization yield of 50%.
Although high, the phenolic resin is a thermosetting resin, so when heating and melting a uniform mixture of silicon carbide powder and resin and extruding it from a nozzle, or heating the silicon carbide powder and resin to soften the resin In the case where an intermediate molded product is formed by uniformly mixing to form an intermediate molded product, and then the intermediate molded product is again heated and melted and used for molding, the fluidity of the heat-melted mixture is poor and molding is difficult. Occurs.

Accordingly, an object of the present invention is to form a three-dimensional body by heating and melting the above-mentioned thermoplastic resin-ceramics mixed system to form a hardened layer having a desired shape, and further laminating the hardened layer. Is effectively applied to a silicon carbide-silicon composite material to obtain a product having a desired three-dimensional shape without using a mold, and is comparable to a conventional method using a mold. An object of the present invention is to provide a highly economical silicon carbide-silicon composite material production method capable of easily and quickly obtaining such a dense and strong silicon carbide-silicon composite material.

[0006]

The above objects are achieved by the present invention described below. That is, the present invention heats and melts a uniform mixture having a silicon carbide powder and a thermoplastic resin coated with a mesophase-containing pitch, and scans and supports the molten product on a support while extruding the molten product from an opening of a nozzle. After injecting a melt into a desired shape on a table, a step (a) of preparing a three-dimensional body comprising a step (a) of curing the melt and forming a cured layer, and the above step (1). A step (2) of subjecting the obtained three-dimensionally shaped body to heat treatment in an inert atmosphere to form the three-dimensionally shaped body into a fired body composed of silicon carbide and carbon, and the fired body obtained in step (2). A method of producing a silicon carbide-silicon composite material, which comprises a step (3) of impregnating silicon into a silicon carbide-silicon composite material, and further producing the above-mentioned three-dimensional body depending on a three-dimensional shape. Step (1) comprises step (a) A silicon carbide-silicon composite comprising a step (b) of repeating the same operation as the step (a) and further laminating a cured layer to a desired height on the cured layer produced in the step (a). It is a method of manufacturing a material.

In the method for producing a silicon carbide-silicon composite material according to the present invention, a silicon carbide powder whose surface is coated with a pitch containing fine mesophase carbon particles having a structure similar to graphite is used as the silicon carbide powder. Since a thermoplastic resin having a low carbonization yield is used as a binder, when a molded body made of a homogeneous mixture of these is fired, the amount of carbon remaining in the fired body increases.
Furthermore, since the mesophase carbon fine particles maintain a spherical shape even after being fired, when the fired body is impregnated with silicon, the wettability of silicon into the fired body is improved,
The impregnation becomes easy, and the amount of carbon remaining after firing is high as described above, so that the strength of the fired body itself increases,
The ratio of silicon carbide in the silicon carbide-silicon composite material obtained by impregnating the fired body with silicon can be increased without being damaged by carrying or the like. As a result, the strength of the silicon carbide-silicon composite material increases.

Further, in the method for producing a silicon carbide-silicon composite material of the present invention, since a silicon carbide powder having a surface coated with pitch is used as a forming material, a uniform mixture of ceramic and resin is obtained. In the mixing step for forming the mixture and the forming step of obtaining a formed body from the mixture, the friction between the silicon carbide particles and the surface of each device is reduced, so that the inner surface of the device is prevented from being worn. As a result, a uniform mixture of the silicon carbide powder and the thermoplastic resin can be easily obtained, and the resulting mixture can be heated and melted and smoothly extruded from the nozzle, thereby improving the moldability. Further, since the silicon carbide particles are coated with the mesophase-containing pitch serving as the carbon source, the pitch serving as the carbon source is uniformly dispersed throughout the molded body. Therefore, carbon is uniformly present throughout the obtained fired body, and as a result, it is possible to obtain an extremely uniform silicon carbide-silicon composite material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to preferred embodiments of the present invention. In the method for producing a silicon carbide-silicon composite material according to the present invention, the silicon carbide powder coated with the mesophase-containing pitch as described above, and the thermoplastic resin added as a molding aid (binder) for the powder are used. Use a homogeneous mixture having the following,
The materials used for the mixture will be described.

First, silicon carbide powder used in the method for producing a silicon carbide-silicon composite material of the present invention includes:
Its average particle size is from 0.1 to 50 μm, preferably from 1 μm to
It is good to use a thing of 20 μm. That is, the particle size is 0.1μ
If it is smaller than m, it becomes difficult to mix with the thermoplastic resin, and since the viscosity of the mixture increases, a large amount of resin is required to give fluidity. This causes problems such as a decrease in strength and an increase in shrinkage in a heat treatment step. On the other hand, if the particle size is larger than 50 μm, clogging is likely to occur when the mixture is melted and injected from the opening of the nozzle, and when the diameter of the extrusion nozzle is increased to prevent clogging, fine molding is performed. Can not be done. Also, since the surface roughness of the compact depends on the particle size of the silicon carbide powder and the thickness of the line of the melt extruded from the nozzle, use a powder having a large particle size or scan a nozzle with a large diameter. Further, when a cured layer is formed by forming a cured product, and the cured layer is laminated as necessary to form a molded product, there is a problem that the surface roughness of the molded product is increased. In the present invention, a material obtained by adding another ceramic powder to silicon carbide powder may be used as long as the impregnation of silicon into the fired body and the silicidation reaction are not hindered.

As the silicon carbide coated with the mesophase-containing pitch used in the present invention, specifically, for example,
JP-A-61-136906 and JP-A-64-755
No. 66, for example, may be used which is produced by treating silicon carbide particles having a predetermined particle diameter and a mesophase pitch precursor. Usually, the processing temperature at this time is 350 to 550 ° C. In the present invention, the amount of the mesophase-containing pitch coated on the surface of the silicon carbide particles is preferably from 1 to 50 parts by weight, more preferably from 5 to 30 parts by weight, based on the amount of silicon carbide. . That is, when the amount of the mesophase-containing pitch exceeds 50 parts by weight, the carbon content becomes too large, and when impregnated with silicon in the fired body, a large amount of unreacted carbon remains, while less than 1 part by weight. If so, it becomes difficult to supply the required carbon content in the final product.

The mesophase-containing pitch coated on the surface of silicon carbide as described above has a high carbonization yield of 90 wt% when sintered, and can give a high concentration of carbon to the fired body. Further, the mesophase-containing pitch used in the present invention has a feature that it does not soften and melt in the heat treatment step.

In the method for producing a silicon carbide-silicon composite material of the present invention, a thermoplastic resin as a molding aid (binder) is used together with the silicon carbide coated with the above-mentioned mesophase-containing pitch. The thermoplastic resin that can be used at this time is not particularly limited as long as it has thermoplasticity.Specifically, for example, polyethylene, polybutylene, polystyrene, acrylic resin, methacrylic resin, polyethylene glycol, polyethylene oxide, ethyl cellulose, and ethyl cellulose Cellulose-based resins such as cellulose propionate, polyvinyl butyral, and the like are included. In the present invention, it is particularly preferable to use a resin having a carbon yield as high as possible when heat-treated and fired in an inert atmosphere.

The amount of the thermoplastic resin added is 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of silicon carbide coated with the mesophase-containing pitch, but is not limited thereto. It suffices if the homogeneous mixture can be heated and melted, and sufficient fluidity can be imparted to extrude it from a nozzle and mold it. In order to provide a high concentration of carbon to the final product, it is preferable that the addition amount of the thermoplastic resin in the homogeneous mixture be as small as possible. But,
If the addition amount of the thermoplastic resin is less than 5 parts by weight,
When the homogeneous mixture is heated and melted and extruded from the nozzle opening, the melt lacks fluidity, and the melt is not smoothly injected, which causes structural defects of the obtained molded body.

That is, for example, the nozzle is scanned while extruding the heated melt from the opening of the nozzle, and as shown in FIG. 3 (b), the extruded line-shaped melts are adjacent to each other. In the case of forming a flat plate shape, if the heat-melted mixture lacks fluidity, the respective line-shaped melts 9 do not spread horizontally. When observing the side surface of the formed flat plate, FIG. As shown, the gap 8 becomes large due to lack of adhesion to each other. In contrast,
If a mixture having some fluidity is used, FIG.
As shown in (b), each of the line-shaped melts spreads laterally and has a state in which there are few gaps in close contact with each other, so that a dense molded product is obtained.

On the other hand, if the amount of the thermoplastic resin as the binder in the homogeneous mixture increases, the fluidity becomes sufficient, but if the amount increases, the cured layer is laminated as necessary to produce a three-dimensional body. However, when the three-dimensional body is fired and carbonized, the shrinkage of the fired body increases. For this reason, there may be a problem that it is difficult to set dimensions when manufacturing a laminate before firing, a strength of the fired body is reduced, and a strength of a fired body impregnated with silicon is lowered.

Further, in the method for producing a silicon carbide-silicon composite material according to the present invention, as a melting / forming aid for facilitating the softening and melting of the material and the forming step, a low-mixing agent is added together with the thermoplastic resin in a homogeneous mixture. A wax or lubricant such as paraffin having a melting point may be added. As a lubricant,
Various fatty acids, aliphatic alcohols, fatty acid esters and the like can be used.

In the method for producing a silicon carbide-silicon composite material of the present invention, a homogeneous mixture having the above-described mesophase-containing pitch-coated silicon carbide powder and a thermoplastic resin is heated and melted. A step (a) of injecting a melt into a desired shape on the support by scanning over the support while extruding from the opening of the nozzle, and then curing the melt to form a hardened layer; According to the above, the same operation as in the step (a) is repeated to further laminate the cured layer until a desired height is obtained, and the three-dimensionally shaped body is produced by the step (b) in which the cured layer of the uniform mixture is laminated. Step (1)
A step (2) of subjecting the three-dimensional body obtained in the step (1) to a heat treatment in an inert atmosphere to form the three-dimensional body into a fired body composed of silicon carbide and carbon; (3) impregnating the fired body obtained in (2) with silicon to obtain a silicon carbide-silicon composite material. Hereinafter, each of these steps will be described.

First, the step (1) will be described. In the step (1), the homogeneous mixture described above is heated and melted, and the molten material is scanned on a support table while being extruded from a nozzle.
After injecting the melt into a desired shape on the support base, the method includes at least a step (a) of curing the melt to form a hardened layer, and further, if necessary according to a desired three-dimensional shape,
The same operation as the step (a) is repeated to repeat the above step (a)
(B) further laminating a similar cured layer to a desired height on the cured layer prepared in (1).

As the homogeneous mixture used in this case, when a heated melt containing silicon carbide powder coated with mesophase-containing pitch and a thermoplastic resin is extruded from a nozzle while being scanned and injected, these materials are used. Any material may be used as long as it is extruded in a uniformly mixed state.However, if an intermediate molded product in which the above-mentioned materials are uniformly mixed is prepared in advance, the intermediate molded product can be used as needed. It is preferable for convenience because it can be melted by heating and can be appropriately provided to the subsequent processes and steps.

When preparing the intermediate molded product, the silicon carbide powder coated with the mesophase-containing pitch as described above, a thermoplastic resin, and other melting or molding aids are provided with a heating function. Using an extruder,
The mixture is heated to a temperature of about 120 to 180 ° C. to soften and melt the thermoplastic resin and various auxiliaries, sufficiently kneaded, and then extruded, for example, into a rod-shaped intermediate mold having a diameter of about 0.2 to 2.0 mm. All you have to do is get your body. That is, when the silicon carbide powder and the thermoplastic resin are uniformly mixed, the thermoplastic resin is usually a solid powder at normal temperature, so that the powder is mixed without heating. However, if the powder is heated and kneaded with the silicon carbide powder in a state where the thermoplastic resin is softened and melted to have fluidity as described above, the powder can be more uniformly mixed as compared with the case where the powders are mixed.

In the step (a) of the step (1), the intermediate molded product made of such a homogeneous mixture is melted by heating.
The melt is extruded from the opening of the nozzle and scanned on the support table to inject the melt into a desired shape on the support table, and then the melt is cured to form a cured layer. As a specific procedure at this time, as shown in FIG. 1, the rod-shaped intermediate molded body 1 obtained as described above is supplied into a nozzle 4 having a heating device 3 and heated, and the rod-shaped molded body 1 is heated. The body 1 is heated and melted, and at the same time, while extruding the melt from the opening of the nozzle 4, the nozzle is continuously moved and scanned on the support table, for example, as shown in FIG. Inject the melt into the shape. The melt containing the extruded silicon carbide is spontaneously hardened by the temperature drop, and a hardened layer 5 having a desired shape is formed. If necessary,
The process of forming the hardened layer may be performed quickly by forcibly cooling the melt to accelerate the hardening rate. In the above description, as a method of forming the cured layer into a desired shape, for example, various kinds of scanning such as reciprocal scanning and rotational scanning of a nozzle controlled by a computer may be appropriately combined.

In the present invention, for example, when a plate-shaped material is formed, a step (1) of forming a hardened layer of a desired size by the above-mentioned step (a) to form a three-dimensional body is performed. ) May be terminated. However, depending on the desired three-dimensional shape, then, in step (b), the same operation as in step (a) is repeated, and a new cured layer is laminated on the cured layer prepared in step (a). This is repeated until the height reaches a height, and the cured layers are sequentially laminated to produce a three-dimensional body 7 composed of laminated cured layers made of a uniform mixture as shown in FIG. What is necessary is just to end 1).

As a specific procedure for forming the second hardened layer, for example, after the first layer is formed, the support having the hardened layer is lowered by a desired height, The second hardened layer 6 is formed by the same operation as the process (a) described above (see FIG. 2). At this time, the nozzle may be raised by a desired height while the position of the support table is fixed. In the above operation, the height of the support table to be lowered or the height of the nozzle to be raised is the thickness of the nozzle,
It depends on the degree of cooling shrinkage of the material and the like, and may be appropriately determined in consideration of these factors. As described above, in the present invention, the cured layers may be laminated until the desired height is reached, and when the desired height is reached in one-stage cured layer, the above-described cured layers are laminated. Step (b) is unnecessary. The thickness of the nozzle used in the present invention may be determined in consideration of the surface roughness of the target molded body, the particle size of the raw material powder to be used, but usually, for example, the inner diameter is 0.1 to 1.8
Use the one of about mm.

Further, in the above step (1), in order to obtain a denser three-dimensionally shaped body, when forming a three-dimensionally shaped body by sequentially laminating the hardened layer, a nozzle for forming the hardened layer is required. It is preferable to cross the scanning directions in such a manner as to intersect perpendicularly with the scanning direction when the cured layer is formed first. That is, as shown in FIGS. 5A and 5B,
The first layer (a) and the second layer (b) are sequentially laminated, and the nozzles are scanned such that the scanning directions of the adjacent cured layers cross each other, or FIG. As shown in (c) and (d), the first layer (c) and the second layer (d) are sequentially laminated, and the scanning directions of the adjacent cured layers cross each other perpendicularly. It is preferable to scan the nozzle obliquely so as to perform the scanning. By laminating the cured layers as described above, when the obtained three-dimensionally shaped body 7 is observed from the side, as shown in FIG. It is possible to obtain a dense three-dimensional body having a small gap 8 to be formed. In addition, the stability of each of the laminated cured layers is better if they are formed so as to cross each other.

Next, in the present invention, the three-dimensionally shaped body obtained in the above step (1) is subjected to a heat treatment in an inert atmosphere in a step (2) to be described below, so that silicon carbide and carbon are removed. And a fired body consisting of That is, as a specific means, a heat treatment is performed in an atmosphere of an inert gas such as argon or nitrogen to carry out thermal decomposition of the resin and carbonization of the pitch to obtain a fired body composed of silicon carbide and carbon. At this time, it is preferable to perform the firing in the range of 1400 to 1800 ° C. In the present invention, when heat treatment is performed at such a temperature in order to carbonize the three-dimensionally shaped body, the temperature rise in the range of 200 to 600 ° C., which is the normal decomposition temperature of a thermoplastic resin, is caused by damage to the molded body. It is preferable to perform the treatment gently in order to prevent this.

In the method for producing a silicon carbide-silicon composite material of the present invention, in the final step (3), the fired body obtained in the step (2) is impregnated with silicon.
A silicon carbide-silicon composite material is used. A known method can be applied to the impregnation of silicon. That is, the calcination can be performed by immersing the fired body in the molten silicon or by bringing the sintered body into contact with the molten silicon. In the present invention, the impregnation of the fired body with silicon performed at this time is preferably performed under an inert atmosphere such as argon or under vacuum.

[0028]

EXAMPLES Next, examples and comparative examples of the present invention will be described.
The present invention will be described in more detail. However, the present invention is not limited by the following examples. First, FIG.
Next, the rod-shaped molded body 1 having the silicon carbide powder coated with the mesophase-containing pitch and the thermoplastic resin used in the example of the present invention is inserted into the supply device 2 and heated and melted by the heating device 3, FIG. 2 is a conceptual explanatory diagram of an apparatus for forming a cured layer 5 by injecting the heated melt from a nozzle 4 and then curing the melt. In FIG. 1, a supply device 2,
The heating device 3 and the nozzle 4 are integrated, and can be freely scanned on the same plane by an XY control mechanism using a computer so that a hardened layer having a desired shape can be formed on the support base. Is configured. Further, a z-axis precision control device (not shown) is provided so that the cured layer thus formed can be freely raised and lowered to a desired height.

FIG. 2 is an explanatory view showing a state in which a second cured layer 6 is provided on the first cured layer 5 using the apparatus shown in FIG. That is, after the support on which the first hardened layer 5 is provided is lowered to a desired height by the z-axis precision control device, the same process as that for providing the first hardened layer 5 is performed. Then, by scanning while extruding the heated melt from the nozzle, the melt is laminated on the first hardened layer 5 and then hardened to form the second hardened layer 6. In the present invention, by using the apparatus shown in FIG. 1, the above-described operation is sequentially repeated, and a cured layer having a silicon carbide powder and a thermoplastic resin is laminated, and FIG. A molded article having a three-dimensional shape as shown in (1) is obtained.

Example 1 (Preparation of Silicon Carbide Powder Coated with Mesophase-Containing Pitch) The average particle size was 12 μm (# 1,000), 4 μm
m (# 3,000) and # 1.2 μm (# 8,000
0) silicon carbide was mixed at a weight ratio of 6: 10: 4, and treated with a mesophase pitch precursor of ethylene heavy end tar so that the coating amount of the mesophase-containing pitch became 10 wt%. 10wt
% Coated silicon carbide powder (hereinafter simply referred to as coated silicon carbide powder).

(Preparation of rod-shaped intermediate molded body and molding of three-dimensional molded body) With respect to 82 parts by weight of the coated silicon carbide powder obtained by the above method, 8.2 parts by weight of polymethyl methacrylate,
Using a material to which 4.5 parts by weight of polyethylene glycol having an average molecular weight of 20,000, 3.3 parts by weight of paraffin, and 2 parts by weight of methyl stearate was added, a rod-shaped intermediate molded body made of a homogeneous mixture was produced by the following method. . That is, using an extruder equipped with a heating device, the above materials are uniformly mixed while heating to 160 ° C. under reduced pressure, and then extruded to obtain a rod-shaped intermediate molded body having a diameter of 1.2 mm. Was.

Next, the rod-shaped intermediate body obtained above was supplied to the above-described apparatus shown in FIG. 1, and the heated portion was heated to 160 ° C. The apparatus for forcibly feeding the rod-shaped molded body to the heating section of the apparatus shown in FIG. 1 is operated to melt by heating, and the nozzle is scanned while extruding the melt from a nozzle 4 having a diameter of 0.8 mm, and the melt is scanned. Was injected onto a support to obtain a cured layer having a width of 30 mm and a length of 50 mm. Next, the first hardened layer obtained above is lowered by the z-axis controller, and then the same operation as above is performed thereon to obtain a second layer having a width of 30 mm and a length of 50 mm. A cured layer of the eyes was formed. Such an operation is continuously performed, and the width 30
A plate-shaped molded body having a thickness of 10 mm was formed with a thickness of 50 mm and a length of 50 mm.

(Firing) The plate-like molded body obtained as described above was heated to 700 ° C. for 40 hours in an argon atmosphere to thermally decompose organic substances. Further, the temperature was raised to 1600 ° C., and the temperature was maintained for 2 hours to carbonize the pitch covered with silicon carbide, thereby obtaining a fired body.

(Evaluation of silicon impregnation and product) Next, the fired body obtained as described above was heated at 1500 ° C. under vacuum conditions.
And then immersed in molten silicon and held for 1 hour. Then, after the impregnated body was pulled up in a state where silicon was molten, the furnace was cooled. Further, by removing excess silicon adhering to the surface, the width is about 30 mm and the length is about 50 mm.
A plate-shaped silicon carbide-silicon composite material having a thickness of about 10 mm and a thickness of about 10 mm was obtained. The density of this product was 2.93 g / cm ³ . From the obtained product, a test piece of 40 mm in length having a cross section of 4 mm in width and 3 mm in height was cut out, and the three-point bending strength at room temperature was measured. As a result, the bending strength was 360.
MPa, and had sufficient strength. Further, when the obtained product was visually observed, the product had a dense surface without any gap, and no structural defects such as cracks were observed. Further, as a result of observing the fracture surface of the obtained composite material by SEM, no unimpregnated portion of silicon was observed. Since the silicon carbide powder coated with the mesophase-containing pitch was used, the amount of carbon remaining in the sintered body was increased, and as a result, the wettability of silicon to the fired body was improved and the fired body was sufficiently impregnated with silicon. Therefore, it is considered that the amount of silicon carbide generated when impregnating silicon also increased.

Example 2 The same operation as in Example 1 was carried out except that the same material as in Example 1 was used and each of the cured layers was formed into an annular cured layer.
mm, a cylindrical molded body having an outer diameter of 42 mm and a height of 20 mm. Thereafter, carbonization, firing and impregnation of silicon were performed in the same manner as in Example 1 to obtain a cylindrical silicon carbide-silicon composite material. When this product was visually observed, it had a dense surface similarly to Example 1, and no structural defects such as cracks were observed. Furthermore, it was confirmed that shape retention was also good.

Comparative Example 1 The same silicon carbide powder as in Example 1 except that the surface was not treated was used, and polymethyl methacrylate 8.9 was added to 80 parts by weight of silicon carbide powder.
4. parts by weight, polyethylene glycol having an average molecular weight of 20,000
Using a material to which 3 parts by weight, 3.6 parts by weight of paraffin and 2.2 parts by weight of methyl stearate were added, kneading was performed at the same softening temperature in the same apparatus as in Example 1, and at the same time extrusion molding was performed. A rod-shaped intermediate molded body similar to that of Example 1 was obtained. Thereafter, in the same manner as in Example 1, after forming a flat molded body, the molded body is baked, and then subjected to a step of impregnating with silicon to obtain a plate having a width of 30 mm, a length of 50 mm, and a thickness of 8 mm. A silicon carbide-silicon composite material in a shape of was obtained. The density of the obtained composite material was 2.73 g / cm ³ .

The obtained composite material was measured for the three-point bending strength at room temperature in the same manner as in Example 1.
Met. Further, as a result of observing the fracture surface of the obtained composite material by SEM, a portion not impregnated with silicon was observed. As is clear from the comparison between Examples 1 and 2 and this comparative example, it was confirmed that by using the coated silicon carbide powder, the impregnation property of silicon was improved and the product strength was improved.

Reference Example 1 89 parts by weight of powder obtained by mixing silicon carbide powders having an average particle diameter of 12 μm and 1.2 μm at a weight ratio of 1: 1; 8.9 parts by weight of carbon powder having a primary particle diameter of 30 nm; 0.2 parts by weight of ammonium acid and 1.9 parts by weight of an emulsion type binder were added to about 27 parts by weight of water based on the total amount of the additives, and the mixture was stirred for 24 hours using a pot mill to obtain a forming material. Next, the slurry obtained above is poured into a gypsum mold, and then, by a casting method of curing,
A plate-shaped molded body having a thickness of 8 mm and a length and width of 50 mm was obtained. After the obtained compact was dried at room temperature, it was fired and impregnated in the same manner as in Example 1 to obtain a silicon carbide-silicon composite material. The bulk density was 2.95 g / cm ³ . The test piece was processed into a test piece in the same manner as in Example 1 and the three-point bending strength at room temperature was measured. As a result, it was 390 MPa. As a result of comparing Example 1 with Reference Example 1, Example 1
Is a simple method without using a molding die, but the obtained silicon carbide-silicon composite material
It has been confirmed that it has a bulk density and a bending strength close to those of a product obtained by a conventional casting method for obtaining a silicon carbide-silicon composite material by using a molding die performed in the above.

[0039]

As described above, according to the present invention,
Since it is not necessary to produce a mold for each desired shape, the time and cost required for producing the mold can be reduced, and various products having complicated shapes can be easily obtained with good yield without using a mold. An industrially useful method for producing a silicon carbide-silicon composite material is provided. Also,
According to the present invention, since silicon carbide powder coated with mesophase-containing pitch is used, even if a thermoplastic resin having a low carbonization yield is used as a binder, the amount of carbon remaining in the fired body is improved, and Impregnation with silicon becomes easy, and the amount of silicon carbide in the obtained silicon carbide-silicon composite material can be increased. As a result, it is dense and has excellent bending strength,
There is provided a method for producing a silicon carbide-silicon composite material which is extremely industrially useful, whereby a product having excellent properties comparable to the silicon carbide-silicon composite material obtained by a conventional method using a mold is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual explanatory view of one apparatus for forming a cured layer of a heated melt in the present invention.

FIG. 2 is an explanatory diagram showing a state in which a second cured layer is formed on a first cured layer.

3A is a perspective view, FIG. 3B is a plan view, and FIG. 3C is a three-dimensional body formed by laminating cured layers according to an embodiment of the present invention.
It is a side view.

FIG. 4 is an explanatory diagram showing a difference in the shape of a cured layer due to a difference in fluidity of a heated melt used in the present invention.

FIG. 5 is an explanatory diagram of a method of scanning a nozzle when laminating a cured layer according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rod-shaped intermediate molded object 2 Intermediate molded object supply device 3 Heating device 4 Nozzle 5 1st layer hardened layer 6 2nd layer hardened layer 7 Solid figure 8 Gap 9 Line-shaped melt

Claims (3)

[Claims] 1. A uniform mixture comprising silicon carbide powder coated with a mesophase-containing pitch and a thermoplastic resin is heated and melted, and the melt is extruded from an opening of a nozzle and scanned on a support base to be scanned. Step (1) of producing a three-dimensionally shaped body comprising a step (a) of injecting a melt into a desired shape above and curing the melt to form a cured layer
(2) heat-treating the three-dimensional body obtained in the step (1) in an inert atmosphere to form the three-dimensional body into a fired body made of silicon carbide and carbon; (3) impregnating the fired body obtained in (2) with silicon to obtain a silicon carbide-silicon composite material. 2. The step (1) of producing a three-dimensionally shaped body comprises the steps (a) and (a) repeated by repeating the same operation as the step (a) to further form a cured layer on the cured layer produced in the step (a). 2. The method for producing a silicon carbide-silicon composite material according to claim 1, comprising a step (b) of laminating to a desired height. 3. A thermoplastic resin is added to 100 parts by weight of silicon carbide powder coated with mesophase-containing pitch.
3. The method for producing a silicon carbide-silicon composite material according to claim 1, wherein the additive is added in an amount of from 100 to 100 parts by weight. 4.