KR101101244B1 - Method for manufacturing high density SiCf/SiC composites - Google Patents

Abstract

The present invention relates to a method for producing a high density silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC), and more particularly, ultra-high strength that can be used as a structural material for high efficiency radial heaters, engine parts, gas turbines and next-generation reactors The present invention provides a method for producing the composite, which enhances the density and mechanical strength of the sintered body containing the high temperature ceramic fibers.

Silicon Carbide Fiber Reinforced Silicon Carbide Composite, SiC Powder, SiC Woven Fiber, Vacuum Deposition

Description

Method for manufacturing high density silicon carbide fiber-reinforced silicon carbide composites (SiCb / SiC composite) {Method for manufacturing high density SiCf / SiC composites}

The present invention relates to a method for producing a high density silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC). More specifically, the present invention provides a method for producing the composite, which enhances the density and mechanical strength of a sintered body containing high-efficiency radial heaters, engine parts, gas turbines, and ultra-high-temperature high-temperature ceramic fibers that can be used as structural materials for next-generation reactors. It is about.

The demand for materials that function in extreme environments such as ultra-high temperatures is rapidly increasing due to the demand for advancement of industrial structure and improvement of energy efficiency. Ceramic fiber-reinforced composite materials are materials that maintain high strength, high toughness, corrosion resistance and high reliability even in extreme environments such as ultra high temperature, and are recognized as essential materials for industrial fields such as diesel dust filter for automobile, aerospace, aviation and nuclear power. In order to achieve excellent performance in extreme environments, fiber-reinforced composite materials are required to be made of high-strength heat-resistant ceramic fibers and a method of weaving and densifying the fibers in a desired form.

Silicon carbide (SiC) is a ceramic material with excellent thermal and mechanical properties. Since it was discovered by E. G. Acheson in 1891, it has been made into powder using electrochemical methods and CVD.

In the silicon carbide fiber has developed the Sylamic ^TM fibers of NASA, Textron and Dow Corning USA Inc. in conjunction in the mid-1970s, in Japan, Nippon Carbon Corp. has developed an extremely low oxygen-containing NiCalon ^TM fiber, Ube Corporation through the modification of the precursor polymer Fully crystallized fiber Tyranno ^™ was prepared. In particular, the Tyranno ^TM fiber has a C / Si stoichiometric ratio of 1.08, which is close to 1, and shows stability up to 1900 ° C in an oxygen-free atmosphere and up to 1000 ° C in an oxygen atmosphere. Suitable fibers.

High density and high mechanical strength are required for the application in the above fields. The manufacture of high density ceramics using silicon carbide (SiC) powder is possible, but has the disadvantage of causing brittle fracture in terms of mechanical strength. In order to solve this disadvantage, it is generally desirable to manufacture ceramic matrix composites (CMCs) containing woven fibers. Particles or short whisker reinforced ceramic composites do not exceed the breaking energy range of single phase ceramics, but woven fiber reinforced ceramic composites absorb the energy when the stress is applied to the base and propagates the cracks. Improve the fracture toughness of ceramics. In particular, the formation of an interface between the ceramic matrix and the fiber, which has a weak bonding force, can deflect crack propagation, thereby minimizing the problem of brittle fracture. For this purpose, 100-1000 nm thick pyrolytic carbon (C) is formed on the surface of the fiber. ) Or boron nitride (BN) layer.

Silicon carbide fiber-reinforced silicon carbide composites (SiC _f / SiC) are prepared by chemical vapor infiltration (CVI), polymer impregnation and pyrolysis (PIP), and reaction sintering. ) And methods combining them have been attempted. In particular, the CVI method has the advantage of minimizing the damage of the fiber due to high temperature because the SiC matrix phase is deposited between the SiC fibers by using a gas as a starting material by applying a process temperature of about 1000 ℃. However, there is a disadvantage in that dozens of hours of operation time are required for high density deposition, residual pores exist, and manufacturing costs are high. In particular, since the matrix is deposited on the surface of the composite preferentially during deposition, it is difficult to manufacture a matrix having a thickness of 4 mm or more because it is difficult to smoothly deposit the matrix onto the substrate. In the case of PIP and reaction sintering, the mechanical strength is low due to the relatively low purity and the presence of glass. Since the above methods generally contain 10-20% of pores, there is a disadvantage in that a composite having low mechanical properties is produced.

For the production of high density composites, a team of professors Koyayama, Kyoto University, Japan, prepared a polycarbosilane (PCS) slurry containing nano SiC powder, impregnated the unidirectional Tyranno SiC fibers, and then slid it to 1720-1780 ° C. A density of 2.77-2.93 g / cm ³ was achieved using pressure sintering at a temperature of. This is a very improved result compared to the composite density of 2.10-2.70 g / cm ³ produced by the conventional CVI and PIP methods.

The basic mechanism of densification used in this method is that the Al ₂ O ₃ -Y ₂ O ₃ sintering aid contained in about 10% by weight of the SiC slurry is changed into an eutectic liquid upon pressurization to promote densification. (nano-infiltrated transient eutectic) method.

However, this NITE method uses a slurry obtained by dispersing nano SiC powder in a polycarbosilane (PCS) binder to improve density, which is similar to the PIP method. In addition, since a method of simply impregnating unidirectional Tyranno fibers in the slurry is used, it is difficult to efficiently deposit SiC powder into the woven fibers. In particular, the nano SiC powders used have a strong tendency to agglomerate due to their high specific surface area, and therefore, it is necessary to find and apply the optimum dispersion conditions of the SiC powders in the slurry.

In order to improve the deposition rate of SiC powder into SiC woven fibers to produce high density SiC _f / SiC composites, 1) to obtain optimum SiC dispersion conditions in the slurry, 2) determine the slurry composition suitable for deposition 3) There is a need for a method for efficiently depositing SiC powder into fine gaps between woven fibers. The present invention finds conditions that meet these needs and produces the high density SiC _f / SiC composites of the present invention.

The present invention provides a dispersion method for efficiently dispersing nano SiC powder in a binder solution in which a polyvinyl butyral (PVB) binder is dissolved in a toluene / ethanol mixed solvent; A slurry composition for efficiently adsorbing SiC powder to SiC woven fibers; Provided is a method for efficiently depositing SiC powder into fine gaps between SiC woven fibers.

In addition, the present invention comprises the steps of mounting a plurality of SiC woven fibers in the middle of the inner cylinder, pouring a SiC slurry thereon, applying a vacuum, gradually injecting air into the cylinder to make the pressure of the cylinder to atmospheric pressure, and Provided is a method of depositing a SiC slurry onto SiC woven fibers comprising the step of depositing a SiC slurry in the pores of the SiC woven fibers.

Specifically, the present invention is to prepare a binder solution by dissolving a binder in a solvent, adding a plasticizer and a dispersing agent to the binder, adding a SiC powder to the binder solution to prepare a SiC slurry, and SiC to the SiC slurry Impregnating the woven fibers, to provide a method for producing a high density silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC) comprising the step of depositing SiC powder on the SiC woven fibers.

In another aspect, the present invention is characterized in that the electrostatic repulsive force is applied to the surface of the particles as a dispersing mechanism by applying a charge, or the steric hindrance repulsive force using a dispersant made of a polymer on the surface of the particle.

In particular, from the standpoint of electrostatic repulsion, the pH conditions for maximizing the charge on the surface are ensured, and in the steric hindrance repulsion, the type and amount of dispersant adsorbed on the surface of the SiC powder exhibiting the lowest slurry viscosity and the highest sedimentation density. Is based on determining.

Preferably, when using ethanol as the solvent, the absolute value of the zeta potential of the slurry exceeds 30 mV, which is characterized by a condition of pH 5.5 or lower, or 8.5 or higher which shows the maximum electrostatic repulsion. In addition, from the viewpoint of steric hindrance, 20 to 50% by weight of Hypermer KD1, a commercial dispersant showing the lowest viscosity, was added to 100% by weight of SiC powder, and a viscosity of 100 cPs or less at a shear rate of 132 s ⁻¹ was obtained. It is characterized by a suspension that achieves a settling density of at least 0.30 g / cm ³ .

In another aspect, the present invention provides a slurry composition containing β-SiC powder having an average particle size of 52 nm and a specific surface area of 80 m ² / g, comprising a composition of a solvent; Molecular weight and amount of PVB binder added; Content of SiC powder; Amount of plasticizer dioctyl phthalate (DOP) added; Milling methods for mechanical dispersion thereof, and the like.

Preferably, the present invention is characterized in that the dispersibility is secured through the optimization of the composition, the adsorption and deposition between the SiC woven fibers and the viscosity and rheological properties suitable for tape casting.

In another aspect, the present invention is a method for efficiently impregnating the prepared SiC slurry between the woven fibers, comprising a configuration of an experimental instrument for impregnation; Efficient impregnation method through the formation of pressure gradient using vacuum; Includes the number of vacuum impregnations.

By the method of the present invention, silicon carbide fiber-reinforced silicon carbide composites (SiC _f / SiC) of high density, especially up to 3.13 g / cm ³ , can be obtained which can be used as structural materials for high efficiency radial heaters, engine parts, gas turbines and next-generation reactors. Can be.

Other aspects than the above and the advantages of the present invention will become apparent from the following considerations of the preferred embodiments.

Figure 1 (a) shows a scanning electron micrograph of an average particle size of 52 nm SiC powder used as a ceramic matrix phase, Figure 1 (b) is a high magnification transmission electron micrograph for this, the surface of 1.7 nm thick SiO ₂ It can be seen that it is covered with layers.

FIG. 2 (a) shows a structure in which 7.5 μm-thick Tyranno ^™ fibers (Ube, Japan) are woven at 0/90 ^o of 1,600 strands, and FIG. 2 (b) shows methane (CH ₄ ) gas. Pyrolytically deposited 200 nm thick pyrolytic carbon shows Tyranno ^™ fiber coating.

The present invention is obtained by infiltrating and adsorbing the nano SiC powder of FIG. 1 (a) into the gap between the Tiranno ^™ fine fibers and the void space between the fiber bundles of FIG. do. However, since deposition using only SiC powder is difficult, the slurry is prepared by dispersing the powder in a binder solution.

Since nanopowders tend to agglomerate due to their high specific surface area, dispersion is essential for the deposition into microgaps between SiC fibers. Dispersion mechanisms include electrostatic repulsion that utilizes the repulsive force of the surface charge of SiC powder, and steric mechanism of dispersing by adsorbing a dispersant composed of a polymer on the surface of the powder. In the electrostatic repulsive force, the absolute value of the zeta potential as the surface charge is preferably 30 mV or more, and in the steric hindrance, the surface adsorption force to the powder is good, and therefore, a dispersant that provides repulsive force is preferable.

In particular, when the steric hindrance is not used, the repulsive force between particles cannot be directly measured. Therefore, a method of measuring the viscosity or sedimentation density of a slurry or a slurry to which a dispersant is added is mainly used. Means excellent acidity.

Figure 3 (a) shows the zeta potential value of the ethanol SiC slurry for electrostatic repulsive force utilization, Figure 3 (b) shows the change in zeta potential according to the addition amount of the four commercial dispersants.

For SiC dispersion of ethanol SiC slurry, the region showing zeta potential of 30 mV or more is preferably an acidic atmosphere having a pH of 5.5 or less or an alkaline region of 8.5 or more. In particular, in the pH = 7 region where the zeta potential is zero, there is no repulsive force due to the surface charge, so that dispersibility is deteriorated.

As shown in Figure 3 (b), the value of the zeta potential tends to decrease with the addition of the four dispersants used, it can be seen that the electrostatic repulsive force is reduced. The pH of SiC slurry using PVB as a binder is in the range of 7.5-8.5, and it can be inferred that the dispersion using the electrostatic repulsion in this case will not be effective.

In general, in a system using toluene or ethanol as a solvent, steric hindrance to improve dispersibility by using a dispersant is known effectively, and the present invention will also utilize this method. Four commercial dispersants used are listed in Table 1 for their manufacturer and properties.

Dispersant Supplier Disperser Rhodafac RE-610 Rhodia  Nonylphenol ethoxylate based phosphate esters Disperbyk-103 BYK  Copolymer with pigment affinic groups EFKA 5044 Ciba  Unsaturated polyamide and acid ester salts Hypermer KD1 ICI  A polyester / polyamine co-polymer

4 shows the viscosity of the SiC slurry according to the amount of the four dispersants added, and the viscosity of the dispersant Hypermer KD 1 is the lowest, so that the dispersibility is the maximum, and since the viscosity does not decrease from 20% by weight with respect to 100% by weight of SiC, the viscosity is appropriate. Determined by the addition amount.

The slurry showing the maximum dispersion showed a slow settling rate of the powder and a high packing density characteristic. The settling density comparison shown in Fig. 5 also showed the slowest settling rate and the highest settling density when Hypermer KD 1 was used as the dispersant. It can be seen that it is consistent with the viscosity behavior of FIG.

The sintering aid was mixed with Al ₂ O ₃ : Y ₂ O ₃ : MgO at a weight ratio of 6.4: 2.6: 1.0 and added in an amount of 8-12 wt%, preferably 10-12 wt%, based on 100 wt% of SiC powder. do. Their initial average particle size is several μm, which is larger than that of 52 nm SiC, which is used as a base phase, and then pulverized for 1 to 3 hours using 0.8 mm ZrO ₂ beads and a high energy mill using a rotational force of 3000 rpm. It is desirable to induce even mixing. More preferably, it is preferable to grind so that the average particle size of SiC powder may be within 100 nm.

A PVB binder having a molecular weight of 55,000 g / mol is dissolved in a mixed solvent having a weight ratio of toluene / ethanol of 6/4, and a binder of 5-45% by weight is added to 100% by weight of the solvent. After dissolving 60% by weight of the plasticizer DOP with respect to 100% by weight of the binder, 20% by weight of Hypermer KD 1 dispersant was added to 100% by weight of SiC powder to prepare a binder solution. After adding SiC powder so that PVB binder / SiC may be 0.4, the ball mill using a 6 mm SiC ball is performed for 36 hours. When SiC slurry dispersion is performed using a high energy mill using ZrO ₂ beads, the SiC hardness is larger than that of ZrO ₂ , so it is preferable to avoid Zr contamination. After the tape casting to a thickness of 40-60 μm using the SiC slurry prepared as described above, the green tape is stored.

In order to impregnate the slurry into SiC woven fiber, a specially prepared jig as shown in FIG. 6 is used. The jig consists of an inner cylinder with a sealed bottom, a thread for fixing a woven fiber having a diameter of 5 cm inside the cylinder, a separation ring for simultaneously mounting five woven fibers, and an outer cylinder for applying a vacuum.

Five woven fibers were mounted in the middle of the inner cylinder, and the prepared SiC slurry was poured on it, and then vacuum was applied so that the internal pressure was 0.1 Pa. Once the desired degree of vacuum is achieved, open the valve and slowly introduce air to bring the cylinder pressure to atmospheric pressure. In the process of increasing the pressure inside the cylinder, the slurry on the top of the woven fiber is moved to the lower side of the inner cylinder by the pressure gradient, during which the slurry is deposited in the pores of the woven fiber. This process is preferably slowed in vacuum to take more than 2 minutes to maximize the deposition of the slurry in the pores between the woven fibers. In addition, it is preferable to repeat the same process three or more times to promote the deposition of the slurry.

7 shows a scanning electron micrograph comparing the degree of deposition after vacuum deposition and the case of simple impregnation of SiC woven fiber in the slurry. It can be seen that the degree of slurry deposition in the case of using the vacuum pressure gradient is much larger than in the case of simple impregnation.

8 shows an electron micrograph of a specimen subjected to calcination after vacuum deposition on a woven fiber using a slurry having a changed binder content. Since the slurry was changed to 0, 5, 10 and 45% by weight after vacuum deposition, the calcination was carried out so that only SiC powder containing no binder was present.

Although the binder was burned during the calcination process, a small amount was expected to increase the degree of deposition, but the slurry containing 45% by weight of the binder also filled the large pores between the fiber bundles and showed the highest degree of deposition. Can be.

9 shows a picture of hot-sintered sintered specimens at 1750 ° C. and 20 MPa for 3 hours. have. It can be seen that the specimen laminated only the woven fiber still had pores between the fibers, while the tape-inserted specimen showed a very dense structure with no pores.

Figure 10 shows the fracture surface of the composite containing SiC weaving fibers, it can be seen that the fibers used in the breakage to reduce the brittle fracture. In particular, it can be seen that a coated pyrolytic carbon (PyC) layer remains on the fiber surface even at a high temperature of 1750 ° C for the purpose of low binding force between the fiber and the matrix.

FIG. 11 is a three-point bending test of monolithic SiC prepared by laminating a sample of 10 woven fabrics vacuum-deposited, a piece of tape laminated between 10 woven fibers, and SiC powder and a sintering aid. The results are shown.

Disruption of the specimens containing SiC woven fibers was larger than that of monoliths containing no fibers, increasing the resistance to brittle fracture. The maximum stress required for fracture is also higher in the samples containing woven fibers, especially in the case of specimens laminated with tape on impregnated woven fibers, showing a mechanical strength of 607 MPa at a density of up to 3.13 g / cm ³ compared to monolith. It can be seen that the increase more than two times.

Table 2 shows the various properties of the specimens prepared in the present invention, and Table 3 shows the density and mechanical strength values of the recently reported SiC composites.

In the case of specimens laminated with tape on the impregnated woven fiber implemented in the present invention, the density is higher than the value reported so far at a density of up to 3.13 g / cm ³ .

Manufacturing method Fiber fraction
(Vol.%) Sintered Density
(g / cm ³⁾ % Density ^* Flexural strength
(MPa) Vacuum deposition 62-72 2.90-3.02 90-94 312 ± 28 (Max. 342) Vacuum Deposition + Tape Insertion 48-55 3.04-3.13 94-97 562 ± 36 (Max. 607) SiC Powder Sintered Body 0 3.14-3.19 98-99 198 ± 36 (Max. 257) *:% Density compared to SiC theoretical density (3.21 g / cm ³ )

Researcher
Manufacturing method
Fiber Used (% Fiber Volume Fraction) Density ^* (g / cm ³ ) Max mechanical strength (MPa) Yano et al. [One] Slurry impregnation and tape stacking
Nicalon, Hi-Nicalon 2.38-3.07 260 Pasquier et al. [2] CVI
(35.1-38.2) 2.34-2.62 Yamada et al. [3] CVI and PIP
Hi-Nicalon (26-35) 380 Ortona et al. [4] CVI and PIP
NL 207 fiber (32-40) 1.58-1.80 247 Cheng et al. [5] CVI
Hi-Nicalon (40-45) 2.46-2.49 Yoshida et al. [6] Slurry impregnation and tape stacking
Hi-Nicalon (40-52) 2.79-3.05 460 Yang et al. [7] CVI
Tyranno-SA (43) 2.58-2.63 296 Lee et al. [8] Slurry infiltration and reaction sintering
Tyranno-SA (10-15) 2.20-3.00 505 Katoh et al. [9] Slurry infiltration
Tyranno-SA (30) 2.77-2.93 710 Nannetti et al. [10] CVI and PIP
Hi-Nicalon (40) 2.19-2.23 761 Kang et al. [11] Whisker growing and CVI
Tyranno-sa 2.54-2.67 Taguchi et al. [12] PIP-CVD and reaction bonding
Hi-Nicalon (33) 2.65-2.70 280 Katoh et al. [13] CVI
Tyranno-SA (35-40) 2.42-2.74 304 Yoshida et al. [14] Tape stacking and reaction sintering
Hi-icalon 2.90 200 Lim et al. [15] Slurry infiltration and tape stacking
Tyranno-sa 2.95-3.10 370 Yoshida et al. [16] EPD and tape stacking
Tyranno-sa 2.75-2.92 123 *: Fiber Density (g / cm ³ ): Nicalon (2.55), Hi-Nicalon (2.73) and Tyranno SA (3.10)

References

[1] Yano T, Budiyanto K, Yoshida K, Iseki T. woven of silicon carbide fiber-reinforced silicon carbide composite by hot-pressing. Fusion Eng Des 1998; 41: 157-63.

[2] Pasquier S, Lamon J, Naslain R. Tensile static fatigue of 2D SiC / SiC composites with multilayered (PyC-SiC) _n interphases at high temperatures in oxidizing atmosphere. Compos Part A-Appl S 1998; 29A: 1157-64.

[3] Yamada R, Taguchi T, Igawa N. Mechanical and thermal properties of 2D and 3D SiC / SiC composites. J Nucl Mater (2000); 283-287: 574-78.

[4] Ortona A, Donato A, Filacchioni G, De Angelis U, La Barbera A, Nannetti CA, Riccardi B, Yeatman J. SiC-SiC _f CMC manufacturing by hybrid CVI-PIP techniques: process optimization. Fusion Eng Des 2000; 51-52: 159-63.

[5] Cheng L, Xu Y, Zhang L, Yin X. Oxidation behavior of three-dimensional SiC / SiC composites in air and combustion environment. Compos Part A-Appl S 2000; 31: 1015-20.

[6] Yoshida K, Imai M, Yano T. Improvement of the mechanical properties of hot-pressed silicon-carbide-fiber-reinforced silicon carbide composites by polycarbosilane impregnation. Compos Sci Technol 2001; 61: 1323-29.

[7] Yang W, Araki H, Kohyama A, Yu J, Noda T. New Tyranno-SA fiber reinforced CVI-SiC / SiC composite. J Mater Sci Lett 2002; 21: 1411-13.

[8] Lee SP, Yoon HK, Park JS, Katoh Y, Kohyama A, Kim DH, Lee JK. Reaction sintering process of tyranno SA / SiC composites and their characterization. Fusion Eng Des 2002; 61-62: 717-22.

[9] Katoh Y, Dong SM, Kohyama A. Thermo-mechanical properties and microstructure of silicon carbide composites woven fiberated by nano-infiltrated transient eutectoid process. Fusion Eng Des 2002; 61-62: 723-31.

[10] Nannetti CA, Riccardi B, Ortona A, La Barbera A, ScafE, Vekinis. Development of 2D and 3D Hi-Nicalon fibers / SiC matrix composites manufactured by a combined CVI-PIP route. J Nucl Mater 2002; 307-311: 1196-99.

[11] Kang SM, Park JY, Kim WJ, Yoon SG, Ryu WS. Densification of SiC _f / SiC composite by the multi-step of whisker growing and matrix filling. J Nucl Mater 2004; 329-333: 530-33.

[12] Taguchi T, Igawa N, Yamada R, Jitsukawa S. Effect of thick SiC interphase layers on microstructure, mechanical and thermal properties of reaction-bonded SiC / SiC composites. J Phys Chem Solids 2005; 66: 576-80.

[13] Katoh Y, Nozawa T, Snead LL. Mechanical properties of thin pyrolitic carbon interphase SiC-matrix composites reinforced with near-stoichiometric SiC fibers. J Am Ceram Soc 2005; 88 (11): 3088-95.

[14] Yoshida K, Mukai H, Imai M, Hashimoto K, Toda Y, Hyuga H, Kondo N, Kita H, Yano T. Reaction sintering of two-dimensional silicon carbide fiber-reinforced silicon carbide composite by sheet stacking method. J Nucl Mater 2007; 367-370: 769-73.

[15] Lim KY, Jang DH, Kim YW, Park JY, Park DS. Fabrication of dense 2D SiC fiber-SiC matrix composites by slurry infiltration and a stacking process. Met Mater Int 2008; 14 (5): 589-91.

[16] Yoshida K, Matsukawa K, Imai M, Yano T. Formation of carbon coating on SiC fiber for two-dimensional SiC _f / SiC composites by electrophoretic deposition. Mater Sci Eng B 2009; In Press.

Figure 1 is a high magnification transmission electron micrograph showing (a) a scanning electron micrograph of the β-SiC powder used and (b) SiO ₂ adsorbed on the surface.

FIG. 2 is a scanning electron micrograph showing (a) Tyranno SA Grade 3 woven fibers used and (b) a 200 nm pyrolytic carbon layer.

3 is zeta potential behavior according to the type and amount of (a) pH and (b) dispersant in ethanol of β-SiC used.

4 is a viscosity behavior according to the type and amount of dispersant of the β-SiC slurry.

5 is a settling density according to the type of dispersant of the β-SiC slurry.

6 is a schematic diagram of slurry deposition utilizing a vacuum pressure gradient: (a) the entire system including the inner cylinder, the outer chamber and the vacuum pump, (b) the components and assembly of the inner cylinder, (c) when applying vacuum and ( d) Schematic diagram when releasing vacuum.

7 is a comparison of the degree of deposition during deposition utilizing (a) simple impregnation and (b) vacuum pressure gradient.

8 is a comparison of the degree of deposition according to the binder content contained in the slurry: (a) 0, (b) 5, (c) 10 and (d) 45 wt% PVB binders.

9 is a sintered structure of (a) and (b) SiC woven fibers subjected to vacuum impregnation; And (c) and (d) a sintered structure of a composite in which a SiC tape is inserted into a woven fiber subjected to vacuum impregnation.

10 is a fracture cross-sectional photograph of the prepared composite.

11 is a stress displacement behavior during the three-point bending strength test of the prepared composite.

Claims (17)

Dissolving the binder in toluene, ethanol or a mixture thereof, and adding a plasticizer and a dispersant thereto to prepare a binder solution, Adding SiC powder to the binder solution to prepare a SiC slurry having a pH of 5.5 or less or a pH of 8.5 or more; and Impregnating the SiC woven fibers in the SiC slurry to deposit SiC powder on the SiC woven fibers Method for producing a high density silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC) comprising a. The method according to claim 1, wherein the binder is a polyvinyl butyral (PVB) having a molecular weight of 55,000 g / mol (SiC _f / SiC) method for producing a high density silicon carbide fiber reinforced silicon carbide composite. The method of claim 1, wherein the SiC powder is a β-SiC powder having an average particle size of 52 nm and a specific surface area of 80 m ² / g, the method of producing a silicon carbide fiber-reinforced silicon carbide composite (SiC _f / SiC). delete delete The method according to claim 1, SiC powder, method for producing a high-density silicon carbide fiber reinforced silicon carbide composites (SiC _f / SiC), it characterized in that the binder / SiC weight ratio is added in an amount which is 0.4. delete delete delete The method according to claim 1, wherein the plasticizer is dioctyl phthalate of high density silicon carbide fiber reinforced silicon carbide composites (SiC _f / SiC), characterized in that. The high-density silicon carbide fiber according to claim 1, wherein at the time of addition of the SiC powder to the binder solution, a sintering aid Al ₂ O ₃ : Y ₂ O ₃ : MgO (weight ratio 6.4: 2.6: 1.0) is further added. Method of producing a reinforced silicon carbide composite (SiC _f / SiC). Method of producing a high-density silicon carbide fiber reinforced silicon carbide composites (SiC _f / SiC), characterized in that 12% by weight according to claim 11, the amount of sintering aid 8 with respect to 100% by weight of SiC powder. The method of claim 1, wherein after the addition of the SiC powder to the binder solution, a ball mill using a 6 mm SiC ball mill for 36 hours of a high density silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC) Manufacturing method. The method of claim 1, wherein the amount of binder is 5 to 45% by weight based on 100% by weight of the solvent, the amount of plasticizer is 60% by weight based on 100% by weight of the binder, the high density silicon carbide fiber reinforced silicon carbide composite (SiC _f / SiC) manufacturing method. Mounting a plurality of SiC woven fibers in the middle of the inner cylinder, Pouring the SiC slurry on it, and then applying a vacuum, Gradually injecting air into the cylinder to bring the cylinder to atmospheric pressure, and SiC slurry is deposited in the pores of SiC woven fibers Method for depositing SiC woven fibers of SiC slurry comprising a. The method of claim 15, wherein the SiC tape obtained by tape casting is sandwiched between a plurality of SiC woven fibers. A jig for use in the method of claim 15 comprising an inner cylinder with a lower seal, a thread for securing the woven fiber inside the cylinder, a separation ring for mounting the woven fiber simultaneously, and an outer cylinder for applying a vacuum.

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