JP2008222462A - METHOD OF MANUFACTURING SiC FIBER-BONDED CERAMIC - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a SiC fiber-bonded ceramic efficiently utilizing an effective surface area of a manufacturing apparatus while keeping the characteristics of the SiC fiber-bonded ceramic having excellent high temperature characteristics and fracture toughness. <P>SOLUTION: A prescribed inorganic fiber is obtained by adding a compound containing at least one or more kinds of metal elements of IIA group, IIIA group and IIIB group metal element into polysilane or a reactant resulting from heating it and after reacting the resultant by heating in an inert gas to obtain a metal element-containing organic silicon polymer, melt spinning the metal element-containing organic silicon polymer and further infusibilizing and mineralizing it. The inorganic fiber is formed into a preliminary formed body as a woven fabric and the SiC fiber-bonded ceramic is manufactured by placing the preliminary formed body with the side surfaces opened between carbon made upper and lower punches and heating at 1,700-2,200°C under 100-1,000 kg/cm<SP>2</SP>pressure in the vertical direction of the preliminary formed body in an atmosphere of one of vacuum, an inert gas, a reducing gas and hydrocarbon. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a dense SiC fiber-bonded ceramic having excellent heat resistance. In particular, the present invention relates to a method for producing SiC fiber-bonded ceramics that can be used for dense members that are required to have thermal shock resistance and high temperature characteristics, such as combustors, thermal protection plates, sintering shelves, jigs for high temperature testing, and the like.

  In the space / aircraft field and the energy / environment field, there is a need for a structural material that has excellent oxidation resistance and can be used for a long time even at high temperatures in order to improve efficiency and performance. Examples of the promising candidate materials include single-piece ceramics, SiC fiber-reinforced SiC-based composite materials (hereinafter referred to as “SiC / SiC”), and SiC fiber-bonded ceramics.

  Simple ceramics represented by silicon carbide, silicon nitride, etc. have high heat resistance and hardness, and also exhibit excellent surface smoothness by surface processing, so in a high temperature region or a very low temperature region where lubricating oil cannot be used, It is used as sliding parts such as rolling bearings and sliding bearings. Moreover, since these simple ceramics exhibit excellent characteristics even at a high temperature of 1300 ° C. or higher, they are also expected as members for high-efficiency gas turbines. However, simple ceramics have brittleness as an inherent defect and are sensitive to minute defects, so that there is a problem that reliability as a high-temperature structural material is lacking.

  SiC / SiC is a material in which the brittleness of a single ceramic is improved by a mechanism such as fiber bridging or crack deflection. This SiC / SiC is manufactured by the CVI method (Chemical Vapor Infiltration), the PIP method (Polymer Information and Pyrolysis), and the MI method (Melt Information). The CVI method is a gas phase method and is a method in which SiC is precipitated between fibers by a reaction between gases. However, in the CVI method, since the deposition rate of SiC is slow, production takes time. In addition, there is a problem that denseness cannot be obtained in a portion where the gas flow is not uniform. The PIP method is a liquid phase method in which SiC is generated by impregnation and thermal decomposition of an organosilicon polymer. Also in the PIP method, since the impregnation and thermal decomposition are repeated several times, the production takes time, or the same problem as in the CVI method that the denseness cannot be obtained in the non-impregnated portion occurs. The MI method is a method in which molten Si is impregnated, and is a method in which molten Si is impregnated in a preform in which a carbon source is dispersed between fibers, and a SiC matrix is generated by a reaction between C and Si to be combined. In the MI method, although the production time is short, there arises a problem that unreacted Si remains or denseness cannot be obtained in a non-uniform portion of the reaction. As described above, SiC / SiC has a fracture toughness superior to that of a single ceramic, but has a problem that it is inferior in compactness even if manufactured by any of the above methods.

  SiC fiber-bonded ceramics are manufactured by hot pressing only amorphous Si-M-C-O fibers (M is at least one metal element of 2A group, 3A group, and 3B group). Is done. The structure of the amorphous fiber changes to a polycrystalline SiC fiber under high temperature and high pressure, and at the same time, deforms into a hexagonal column having a close-packed structure. Therefore, the SiC fiber bonded ceramics are very dense. Further, in the process of changing the structure of the fiber, surplus carbon in the amorphous fiber is discharged to the fiber surface and generated in a layered manner on the fiber surface. Since the carbon layer on the fiber surface becomes a slip layer that deflects the progress of cracks, the SiC fiber-bonded ceramic exhibits excellent fracture toughness. As described above, the SiC fiber-bonded ceramic improves the brittleness of the single ceramic and the insufficient denseness of SiC / SiC.

  Conventionally, SiC fiber-bonded ceramics are placed in a carbon die reinforced by a C / C mold, and a preformed body with inorganic fibers laminated is placed and heated and pressurized using a hot press method or the like. (See, for example, JP-A-2004-131365). By disposing the preform in a carbon die reinforced with a C / C mold, it is possible to prevent the ceramic powder and the like from flowing out when pressure-sintering the ceramic powder and the like.

JP 2004-131365 A

  However, in the conventional manufacturing method of SiC fiber-bonded ceramics, the space for the C / C mold and the carbon die is required in the apparatus furnace. Therefore, the size of the SiC fiber-bonded ceramics that can be manufactured is the effective area of the apparatus furnace. There is a problem that it becomes smaller than. For example, when using a hot press apparatus having a maximum pressure of 350 ton and an effective diameter of 400 mm, the carbon die occupies a large proportion, and the size capable of forming the SiC fiber-bonded ceramic is only about 180 mm × 180 mm. Since the molding pressure at this time is about 200 tons, the pressurization capacity of the apparatus has a margin. Therefore, the conventional method cannot be said to be a manufacturing method that efficiently utilizes the performance of the apparatus. In addition, the introduction of new dedicated equipment suitable for the production of SiC fiber-bonded ceramics requires enormous capital investment, so the existing equipment capacity was fully utilized and the space in the equipment furnace was effectively utilized. A method for producing SiC fiber bonded ceramics is desired.

  Accordingly, the present invention provides a method for producing SiC fiber-bonded ceramics that efficiently utilizes the effective area of the production apparatus while maintaining the excellent characteristics of SiC fiber-bonded ceramics produced by a conventional method. With the goal.

In order to achieve the above object, as a result of intensive studies, the present inventors use a C / C mold and a carbon die by using a preform formed of a woven fabric of a specific mineralized fiber. Without knowing that it is possible to form SiC fiber-bonded ceramics with only carbon upper and lower punches, and as a result, the effective area in the equipment furnace is utilized to the maximum, and existing equipment is used to make it larger than before. It has been found that SiC fiber bonded ceramics of a size can be manufactured. That is, in the present invention, a compound containing at least one metal element among the metal elements of 2A group, 3A group, and 3B group is added to polysilane or a heating reaction product thereof, and the reaction is performed by heating in an inert gas. Thus, a first step of obtaining a metal element-containing organosilicon polymer, a second step of obtaining a spun fiber by melt spinning the metal element-containing organosilicon polymer, and the spinning fiber in an oxygen-containing atmosphere 50 A third step of obtaining an infusible fiber by heating at ~ 170 ° C, a fourth step of obtaining an inorganic fiber by mineralizing the infusible fiber in an inert gas, and the inorganic fiber Weaving, cutting and laminating the woven fabric into a predetermined shape, and stacking the pre-formed body with a fifth step for obtaining a preform, and placing the preform between the upper and lower punches made of carbon, vacuum Inert gas, in a reducing gas and hydrocarbon either atmosphere, the sixth step of performing heating and pressing treatment under a pressure of 100 to 1000 / cm ² in the vertical direction of the temperature and the preform 1700-2200 ° C. And a method for producing SiC fiber-bonded ceramics.

  As described above, according to the manufacturing method of SiC fiber bonded ceramics according to the present invention, the effective area of the manufacturing apparatus can be efficiently increased while maintaining the characteristics of SiC fiber bonded ceramics excellent in high temperature characteristics and fracture toughness. It can be used to produce SiC fiber bonded ceramics. Therefore, SiC fiber-bonded ceramics having a larger size than conventional ones can be manufactured using existing equipment, which is effective in reducing manufacturing costs and capital investment.

  The SiC fiber-bonded ceramic manufacturing method according to the present invention uses the mineralized fibers obtained in the first to fourth steps, and weaves the mineralized fibers into a woven shape to produce a preform. It is characterized by doing. When mineralized fibers other than the mineralized fibers obtained in the first to fourth steps are used, the same effects as in the present invention cannot be obtained even if the mineralized fibers are woven into a woven shape.

  As described above, according to the method for producing SiC fiber-bonded ceramics according to the present invention, the effective area of the production apparatus is efficiently maintained while maintaining the excellent characteristics of the SiC fiber-bonded ceramics produced by the conventional method. The manufacturing method of the SiC fiber bond type ceramics utilized for can be provided.

  The method for producing a SiC fiber-bonded ceramic according to the present invention includes the following first to sixth steps.

First Step In the first step, a metal element-containing organosilicon polymer that is a precursor polymer is prepared. The polysilane used in the first step is, for example, a chain obtained by dechlorinating one or more dichlorosilanes using sodium according to the method described in “Chemistry of organosilicon compounds” (Chemical Dojin, 1972). The average molecular weight is 300-1000 normally. This polysilane can have a hydrogen atom, a lower alkyl group, a phenyl group or a silyl group as a side chain of silicon, as shown in the general formula in Chemical Formula 1. It is desirable that the ratio is 1.5 or more in molar ratio. When the ratio of carbon atoms to silicon atoms is less than 1.5 in terms of molar ratio, the carbon in the fiber is desorbed as carbon dioxide in the temperature rising process until sintering, together with the oxygen introduced during infusibilization. For this reason, the boundary carbon layer between the fibers is hardly formed uniformly, which is not preferable.

  Instead of the polysilane used in the first step, the heated reaction product may be used. The heated reaction product of polysilane includes an organosilicon polymer partially containing a carbosilane bond in addition to the polysilane bond unit obtained by heating the above-described chain or cyclic polysilane. Such an organosilicon polymer can be prepared by a method known per se. Examples of the preparation method include a method in which a linear or cyclic polysilane is heated and reacted at a relatively high temperature of 400 to 700 ° C., and a phenyl group-containing polyborosiloxane is added to the polysilane to a relatively high temperature of 250 to 500 ° C. Examples thereof include a method of performing a heat reaction at a low temperature. The average molecular weight of the organosilicon polymer thus obtained is usually 1000 to 5000.

  The phenyl-containing polyborosiloxane can be prepared according to the methods described in JP-A-53-42300 and JP-A-53-50299. For example, phenyl-containing polyborosiloxane can be prepared by a dehydrochlorination condensation reaction between boric acid and one or more diorganochlorosilanes, and the average molecular weight is usually 500 to 10,000. The addition amount of the phenyl group-containing polyborosiloxane is usually 15 parts by weight or less with respect to 100 parts by weight of the polysilane.

  A compound containing at least one kind of metal element of 2A group, 3A group and 3B group metal element is added to the above polysilane or the organosilicon polymer which is a heated product thereof, and further inert. By reacting in a gas at a temperature of usually 250 to 350 ° C. for 1 to 10 hours, a metal element-containing organosilicon polymer as a raw material can be prepared. The metal element is used in such a ratio that the content ratio of the metal element in the finally obtained SiC fiber-bonded ceramic is 0.05 to 4.0% by weight. The specific ratio is the teaching of the present invention. Can be determined appropriately by those skilled in the art. The metal element-containing organosilicon polymer is a crosslinked polymer having a structure in which at least a part of silicon atoms of polysilane are bonded with or without metal atoms and oxygen atoms.

  Examples of the compound containing at least one metal element selected from the group 2A, 3A and 3B metal elements added in the first step include alkoxides of the metal elements, acetylacetoxide compounds, carbonyl compounds, and A cyclopentadienyl compound etc. can be mentioned. Specific examples include beryllium acetylacetonate, magnesium acetylacetonate, yttrium acetylacetonate, cerium acetylacetonate, butanoic acid borate, and aluminum acetylacetonate. . All of these react with the Si-H bond in the organosilicon polymer produced during the reaction with polysilane or its heated reactant, and each metal element is bonded to Si directly or via other elements. It can be generated.

Second Step In the second step, a spun fiber is obtained by melt spinning the metal element-containing organosilicon polymer obtained in the first step. The spun fiber can be obtained by spinning a metal element-containing organosilicon polymer as a precursor polymer by a method known per se such as melt spinning and dry spinning.

Third Step In the third step, an infusible fiber is prepared by heating the spun fiber obtained in the second step at 50 to 170 ° C. in an oxygen-containing atmosphere. The purpose of infusibilization is to form a bridging point by oxygen atoms between the polymers constituting the spun fiber so that the infusible fiber does not melt in the next mineralization step and adjacent fibers do not fuse. It is to be. Examples of the gas constituting the oxygen-containing atmosphere include air, oxygen, and ozone. The infusibilization time depends on the infusibilization temperature, but is usually several minutes to 30 hours. It is desirable to adjust the oxygen content in the infusible fiber to 8 to 16% by weight. Most of this oxygen remains in the fiber even after mineralization in the next step, and plays an important role in desorbing excess carbon in the inorganic fiber as CO gas in the temperature rising process until the final sintering. To do. When the oxygen content is less than 8% by weight, excess carbon in the inorganic fiber remains more than necessary, and segregates around the SiC crystal in the temperature rising process and stabilizes. Sintering is inhibited without going through the second phase of the grain boundary. Further, when the oxygen content is more than 16% by weight, surplus carbon in the inorganic fiber is completely desorbed, and a boundary carbon layer between the fibers is not generated. In either case, it adversely affects the mechanical properties of the resulting material, which is not preferable.

  The infusible fiber is preferably preheated in an inert atmosphere. Nitrogen, argon, etc. can be illustrated as gas which comprises an inert atmosphere. The heating temperature is usually 150 to 800 ° C., and the heating time is several minutes to 20 hours. By preheating the infusibilized fiber in an inert atmosphere, while preventing the incorporation of oxygen into the fiber, the cross-linking reaction of the polymer constituting the fiber is further advanced, and the infusible fiber from the precursor polymer is excellent. The strength can be further improved while maintaining the elongation. Thereby, the mineralization of the next process can be performed stably with good workability.

Fourth Step In the fourth step, mineralized fibers are obtained by mineralizing the infusible fibers obtained in the third step in an inert gas. The mineralization of the infusible fiber is performed by heat treatment at a temperature of 1000 to 1700 ° C. in an inert gas atmosphere such as argon by a continuous method or a batch method.

  The mineralized fiber obtained by the above method is a mineralized fiber mainly composed of a sintered structure of SiC, oxygen (O) 0.01 to 1% by weight, and metals of 2A group, 3A group, and 3B group It contains at least one metal atom among atoms. The inorganic fiber having a sintered structure of SiC is mainly composed of a polycrystalline sintered structure of β-SiC or crystalline fine particles of β-SiC and C. In a region in which β-SiC crystal particles containing at least one of C crystallites and a trace amount of oxygen (O) are sintered without intergranular second phase, strong bonds between SiC crystals are present. can get. If fracture occurs in the fiber, at least 30% of the region proceeds in the SiC crystal grains. In some cases, intergranular fracture regions and intergranular fracture regions between SiC crystals coexist.

  Moreover, the ratio of the element which comprises said mineralized fiber is normally Si: 55-70 weight%, C: 30-45 weight%, O: 0.01-1 weight%, M (2A group, 3A group) And 3B group metal element): 0.05 to 4.0% by weight, preferably 0.1 to 2.0% by weight. The group 2A metal elements include Be, Mg, Ca, and Sr, the group 3A metal elements include Sc and Y, and the group 3B metal elements include B, Al, and Ga. Among these, Be, Mg, Y, B and Al are particularly preferably used. All of these are known metal elements as SiC sintering aids, and there are chelate compounds and alkoxide compounds that can react with the Si—H bond of the organosilicon polymer. If the proportion of this metal element is excessively small, sufficient crystallinity of the fiber material cannot be obtained, and conversely, if the proportion is excessively high, grain boundary fracture increases, leading to deterioration of mechanical properties. Therefore, it is not preferable.

Fifth Step In the fifth step, the mineralized fiber obtained in the fourth step is woven, and the woven fabric is cut into a predetermined shape and laminated to prepare a preform. The mineralized fiber is woven in an orientation state similar to the laminated state of the two-dimensional fabric. The weaving method consists of a plain weave that circulates with two warp yarns and weft yarns, and each yarn floats and crosses one by one, and is made up of three or more warp yarns and weft yarns. Examples thereof include a twill weave that shows a twill line obliquely at the texture points that are continuously floated and submerged, and a satin weave that is made of five or more warps and wefts and has only one crossing point arranged at a constant interval. However, the types of these fabrics and the orientation directions of the fibers are selected as needed depending on the properties required for the target shape, and are not limited to these, and may be a combination of various fabrics. Good.

  In the method for producing a SiC fiber-bonded ceramic according to the present invention, the mineralized fibers obtained in the first to fourth steps are woven, and a preform is produced from the woven fabric. Further, from the characteristics of the mineralized fibers, a preform can be produced without adding ceramic powder or the like serving as a matrix component. Therefore, unlike the conventional manufacturing method, it is possible to heat and press the preform using only carbon upper and lower punches without placing a carbon die or C / C mold in the apparatus furnace. it can. Therefore, a preform having a larger size can be used for the same effective diameter of the apparatus furnace as compared with the conventional manufacturing method.

In the sixth step, the sixth step, the preform obtained in the fifth step is arranged with the side surfaces opened between the upper and lower punches made of carbon, and any of vacuum, inert gas, reducing gas and hydrocarbon In an atmosphere, a SiC fiber-bonded ceramic is formed by heating and pressing at a temperature of 1700 to 2200 ° C. and a pressure of 100 to 1000 kg / cm ^{2 in} the vertical direction of the preform. For the heat and pressure treatment in the sixth step, a publicly known hot press apparatus can be used.

  In the sixth step, unlike the conventional manufacturing method, the pre-molded body is heated and pressurized using only the upper and lower carbon punches without placing the carbon die or C / C mold in the apparatus furnace. I do. As a result, the effective area in the apparatus furnace can be utilized to the maximum, and a SiC fiber-bonded ceramic having a larger size than the conventional one can be manufactured using the existing apparatus.

  The carbon upper punch set on the upper side of the preform may be fixed to the movable rod side of the pressurizing device and brought into contact with the preform at the start of pressurization. Moreover, in order to pressurize a preforming body in a completely perpendicular direction, you may provide a guide in one or more side surfaces of an upper punch and a preforming body.

  It is preferable that all or most of the mineralized fibers constituting the obtained SiC fiber bonded ceramic are deformed into a polygonal shape and bonded to a structure extremely close to closest packing. Moreover, it is preferable that the boundary layer which has 1-100 nm of carbon (C) as a main component is formed in the boundary area | region between mineralized fibers. Reflecting this structure, the obtained SiC fiber-bonded ceramic exhibits very high mechanical properties such that the strength at 1600 ° C. is 80% or more of the room temperature strength.

  Next, the manufacturing method of the SiC fiber bond type ceramics according to the present invention will be described based on examples. In order to evaluate the mechanical properties of the obtained SiC fiber-bonded ceramics, a tensile test was conducted on the notched material and the smooth material. Since SiC fiber-bonded ceramics are hardly affected by stress concentration due to the notch, it is known that the tensile strength of the notch material substantially follows the net cross-sectional stress standard. In other words, it can be said that the tensile strength of the notched material is substantially the same as the tensile strength of the smooth material having the same cross-sectional area as the net cross-sectional area excluding the notched portion. From this, it is excellent if the tensile strength of the notch material of the SiC fiber bonded ceramic according to the example is substantially the same as the tensile strength of the smooth material having the same cross-sectional area as the net cross-sectional area excluding the notch part. It means having high fracture toughness.

[Tensile test]
The high-temperature tensile test of the notched material and the smooth material was performed in the atmosphere at 1400 ° C. and a crosshead speed of 0.5 mm / min using a hydraulic chuck type servo-type tester. The actual breaking strength of the notched material was obtained by dividing the breaking load by the cross-sectional area (width 10 mm × thickness 2 mm). Further, the breaking strength of the smooth material was also obtained by dividing the breaking load by the cross-sectional area (width 10 mm × thickness 2 mm), similarly to the notched material.

(Example 1)
Under an atmosphere of nitrogen gas, 1 L of dimethyldichlorosilane was added dropwise while heating and refluxing anhydrous xylene containing 400 g of sodium, followed by heating and refluxing for 10 hours to generate a precipitate. The precipitate was filtered and washed with methanol and then with water to obtain 420 g of white polydimethylsilane. The general formula of this polydimethylsilane is shown in Chemical Formula 2. As apparent from Chemical Formula 2, the Si: C atomic ratio in the obtained polydimethylsilane is 1: 2, and therefore the ratio of carbon atoms to silicon atoms is 1.5 or more in terms of molar ratio. Next, in a nitrogen gas atmosphere, 750 g of diphenyldichlorosilane and 124 g of boric acid are heated at 100 to 120 ° C. in n-butyl ether, and the resulting white resinous material is further heated at 400 ° C. for 1 hour in vacuum. As a result, 530 g of a phenyl group-containing polyborosixane was obtained. 4 parts of a phenyl group-containing polyborosiloxane was added to 100 parts of the obtained polydimethylsilane, followed by thermal condensation at 350 ° C. for 5 hours in a nitrogen gas atmosphere to obtain a high molecular weight organosilicon polymer. Polyaluminocarbosilane was synthesized by adding 7 parts of aluminum-tri- (sec-butoxide) to a xylene solution in which 100 parts of this organosilicon polymer was dissolved, and performing a crosslinking reaction at 310 ° C. under a nitrogen gas stream. .

  The obtained polyaluminocarbosilane was melt-spun at 245 ° C., heat-treated in air at 140 ° C. for 5 hours, and further heated in nitrogen at 300 ° C. for 10 hours to obtain infusible fibers. Subsequently, the infusible fiber was continuously fired at 1500 ° C. in nitrogen to synthesize a silicon carbide-based continuous inorganic fiber.

  Subsequently, the obtained silicon carbide-based continuous inorganic fiber was woven to produce a satin woven fabric sheet, cut into a length of 300 mm and a width of 180 mm, and then laminated with 50 sheets to obtain a preform. Although the size of the preform is limited by the effective diameter in the apparatus furnace, in Example 1, since the carbon die and the C / C mold are not arranged in the apparatus furnace, they are the same as in Comparative Example 1 described later. Larger preforms could be used for the effective diameter of.

  Next, the preform was set in a hot press apparatus and subjected to heat and pressure treatment. 1 is a plan view showing the inside of an apparatus furnace used in Example 1. FIG. FIG. 2 is a cross-sectional view in the A-A ′ direction in the apparatus furnace. The heat and pressure treatment was performed as follows. First, the preform 2 was placed between the upper punch 1 and the lower punch 4 made of carbon in the apparatus furnace 3. Subsequently, the preform 2 was hot press molded under an argon atmosphere at a temperature of 1900 ° C. and a pressure of 50 MPa to obtain a SiC fiber-bonded ceramic having a length of 300 mm × width of 180 mm and a thickness of 4 mm. The obtained SiC fiber-bonded ceramic was about 1.67 times larger in area ratio than Comparative Example 1 described later, and the space in the apparatus furnace could be used more effectively.

A notch material and a smooth material were sampled from the obtained SiC fiber-bonded ceramic material, and a tensile test was performed. 3 is a plan view of the notch material, FIG. 4 is a front view of the notch material, and FIG. 5 is an enlarged view of the notch portion. 6 is a plan view of the smoothing material, and FIG. 7 is a front view of the smoothing material. Both the notch material and the smooth material had a length of 150 mm and a width of 10 mm. In the cutout material, cutout portions having a length of 1 mm and a width of 0.5 mm were provided on both side surfaces of the test piece. Copper tabs were attached to the upper and lower surfaces of both ends of the notched material and the smooth material. The attachment of the copper tab was carried out by adhering with an inorganic adhesive (Aron Ceramic) and holding at 90 ° C. for 10 to 12 hours with a commercially available clip. The copper tab is attached to prevent the breakage of the grip portion that occurs when the specimen is directly gripped and to measure the exact high temperature strength of the specimen. When the tensile strength of the notched material and the smooth material was measured by the above-described method, the average was 154 MPa and 198 MPa, respectively. Assuming that the tensile strength of the notch material follows the net cross-sectional standard without being affected by the stress concentration at the notch tip, the tensile strength σ _g of the notch material can be expressed by equation (1). Here, σ _f is the tensile strength (198 MPa) of the smooth material, a is the notch length (1 mm) on one side, and W is the width (10 mm) of the test piece. From the formula (1), the notch material has a tensile strength of 158.4 MPa. The actual fracture strength of the notched material actually measured is 154 MPa, which is substantially equal to the value obtained by the equation (1). From this, it can be seen that the SiC fiber-bonded ceramic according to Example 1 is excellent in fracture toughness at high temperature without causing strength reduction due to stress concentration due to notches or the like. This result is almost equivalent to the result of the SiC fiber bonded ceramic of Comparative Example 1 formed using a carbon die or the like. From the above, in Example 1, SiC fiber-bonded ceramics having a size 1.67 times larger than the conventional one can be manufactured by utilizing the effective area in the apparatus furnace without deteriorating the characteristics of the SiC fiber-bonded ceramics. I understand that.

(Comparative Example 1)
Weaving silicon carbide-based continuous inorganic fibers synthesized by the same method as in Example 1 to produce a satin fabric sheet, cutting it into a length of 180 mm × width of 180 mm, laminating 50 sheets, Obtained. In Comparative Example 1, as described later, since the carbon die and the C / C mold were installed in the apparatus furnace, only a preform having a relatively small size with respect to the effective diameter in the apparatus furnace can be used. It was. Subsequently, the preform was set in a hot press apparatus and subjected to heat and pressure treatment. FIG. 8 is a plan view showing the inside of the apparatus furnace used in Comparative Example 1. FIG. FIG. 9 is a cross-sectional view in the AA ′ direction in the apparatus furnace. In Comparative Example 1, the carbon die 5 reinforced by the C / C mold 6 was placed on the upper surface of the lower punch 4 in the apparatus furnace 3, and the preform 2 was placed in the carbon die 5. Further, a carbon die 5 ′ is arranged on the upper surface of the preform 2 and hot press molding is performed in an argon atmosphere under the conditions of a temperature of 1900 ° C. and a pressure of 50 MPa, so that SiC of length 180 mm × width 180 mm and thickness 4 mm is obtained. A fiber-bonded ceramic was obtained.

A notch material and a smooth material were sampled from the obtained SiC fiber-bonded ceramic material, and the same tensile test as in Example 1 was performed. The shapes of the notch material and the smooth material used in the tensile experiment of Comparative Example 1 are the same as those shown in FIGS. 3 to 7 according to Example 1. As a result of conducting the same high-temperature tensile test as in Example 1, the tensile strengths of the notched material and the smooth material were 155 MPa and 201 MPa on average, respectively. Assuming that the tensile strength of the notch material follows the net cross-sectional standard without being affected by the stress concentration at the notch tip, the tensile strength σ _g of the notch material can be expressed by the above equation (1). Here, σ _f is the tensile strength (201 MPa) of the smooth material, a is the notch length (1 mm) on one side, and W is the width (10 mm) of the test piece. From equation (1), the tensile strength of the notch is 160.8 MPa. The actual fracture strength of the notch material actually measured is 155 MPa, which is substantially equal to the value obtained by the equation (1). From the above, it can be seen that the SiC fiber-bonded ceramic according to Comparative Example 1 is excellent in fracture toughness at a high temperature without causing a decrease in strength due to stress concentration due to a notch or the like. However, for the effective diameter of 400 mm in the apparatus furnace, the obtained SiC fiber bonded ceramic was 180 mm long × 180 mm wide, and the effective area in the apparatus furnace could not be fully utilized.

(Comparative Example 2)
Silicon carbide-based continuous inorganic fibers were synthesized in the same manner as in Example 1 to prepare short fibers having a length of 1 mm to 2 mm. After mixing this short fiber with a 10% by weight polyvinyl alcohol (PVA) solution, it is put in a mold coated with a release agent and dried at 100 ° C., and this is cut into a length of 180 mm × a width of 180 mm and a thickness of 30 mm. Thus, a preform was obtained. In the same manner as in Example 1, this preform was placed between the upper and lower carbon punches with the side surfaces opened, and hot press molded in an argon atmosphere under conditions of a temperature of 1900 ° C. and a pressure of 50 MPa.

  In Comparative Example 2, the short fibers at the end of the preform formed out of the upper and lower punches during molding, so that sufficient pressure was not applied to the end and pores were formed at the end of the obtained molded body. Had occurred. Furthermore, since the end portion of the preform was out of shape, the pressure was concentrated on a portion other than the end portion, and the upper punch was cracked. In Comparative Example 2, unlike Example 1, the silicon carbide-based continuous inorganic fibers were not woven into a woven shape, so that it was difficult to maintain the shape of the preform with only the upper and lower punches, and the molded product having a stable shape. It is thought that it was not able to get.

2 is a plan view showing the inside of an apparatus furnace according to Embodiment 1. FIG. 2 is a cross-sectional view in the A-A ′ direction in the apparatus furnace according to Embodiment 1. FIG. 3 is a plan view of a notch material used in a tensile experiment according to Example 1. FIG. 3 is a front view of a notch material used in a tensile experiment according to Example 1. FIG. 3 is an enlarged view of a notch portion of a notch material used in a tensile experiment according to Example 1. FIG. 3 is a plan view of a smooth material used in a tensile experiment according to Example 1. FIG. 1 is a front view of a smooth material used in a tensile experiment according to Example 1. FIG. 6 is a plan view showing the inside of an apparatus furnace according to Comparative Example 1. FIG. 6 is a cross-sectional view in the B-B ′ direction in the apparatus furnace according to Comparative Example 1. FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Upper punch, 2 ... Preliminary molded object, 3 ... Apparatus furnace, 4 ... Lower punch, 5, 5 '... Carbon die, 6 ... C / C mold

Claims (2)

By adding a compound containing at least one metal element among the metal elements of 2A group, 3A group, and 3B group to polysilane or its heated reaction product, and reacting by heating in an inert gas, the metal element content A first step of obtaining an organosilicon polymer;
A second step of obtaining a spun fiber by melt spinning the metal element-containing organosilicon polymer;
A third step of obtaining an infusible fiber by heating the spun fiber at 50 to 170 ° C. in an oxygen-containing atmosphere;
A fourth step of obtaining the mineralized fiber by mineralizing the infusible fiber in an inert gas;
A fifth step of weaving the mineralized fiber, cutting the fabric into a predetermined shape and laminating to obtain a preform,
The preform is placed with an open side surface between upper and lower carbon punches, and in a vacuum, an inert gas, a reducing gas, or a hydrocarbon atmosphere, a temperature of 1700 to 2200 ° C. and A sixth step of performing heat and pressure treatment under pressure of 100 to 1000 kg / cm ^{2 in} the vertical direction;
A method for producing SiC fiber-bonded ceramics, comprising:   2. The method for producing a SiC fiber-bonded ceramic according to claim 1, wherein in the fourth step, the infusible fiber is mineralized after preheating the infusible fiber in an inert gas.

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