Preparation method of C / SiC composite continuous single-bundle fiber with low thermal expansion coefficient

Abstract

The invention provides a preparation method of a C / SiC composite material continuous single-bundle fiber with a low thermal expansion coefficient. The problems that an existing method is long in preparation period, large in material thermal expansion coefficient and poor in performance consistency, and the overall performance of the material is poor due to microcracks can be solved. The method comprises the following steps: step 1, selecting a continuous carbon fiber bundle, winding the continuous carbon fiber bundle on a mold, and then placing the continuous carbon fiber bundle in a pyrolytic carbon deposition furnace for deposition until the continuous carbon fiber bundle with a pyrolytic carbon interface layer is obtained; step 2, constructing a pre-stress dipping and curing device, and performing dipping and curing on the continuous carbon fiber bundle obtained in the step 1 through the pre-stress dipping and curing device to obtain a continuous single-bundle fiber preform; and step 3, immersing the continuous single-bundle fiber preform obtained in the step 2 into a second SiC ceramic precursor prepared in advance for dipping, and then sequentially carrying out curing, cracking and SiC matrix deposition to obtain the C / SiC composite material continuous single-bundle fiber with the low thermal expansion coefficient.

Description

Technical Field

[0001] The invention relates to a method for preparing a continuous single-bundle fiber of a C / SiC composite material, and in particular to a method for preparing a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient. Background Art

[0002] Continuous Carbon Fiber Reinforced Silicon Ceramic Matrix Composites (C / SiC) is a high-performance material that combines the light weight and high strength of carbon fiber with the high temperature stability and wear resistance of silicon carbide. The density of C / SiC composites is only 1 / 3 of that of high-temperature alloys, but its strength is twice that of high-temperature alloys. It can withstand high temperatures of 1000℃ to 1500℃. Moreover, it has better durability, higher fracture toughness and damage tolerance, which makes C / SiC composites an internationally recognized thermal protection integrated material and has a place in the field of spacecraft. At present, C / SiC composites are usually prepared by chemical vapor deposition (CVI), polymer impregnation pyrolysis (PIP) and reactive melt infusion (RMI). Among them, the CVI method is to introduce a gas containing silicon and carbon into the fiber preform at high temperature, so that it reacts chemically on the fiber surface to form a SiC matrix. This method has good matrix density and excellent antioxidant properties, and is suitable for manufacturing ceramic-based composites with complex shapes. However, its preparation cycle is long, and the bottleneck effect causes residual pores in and between the fiber bundles, and the formation of matrix microcracks may occur during the cooling process, thereby affecting the overall performance of the composite material. The PIP method is to impregnate the polymer precursor into the fiber preform, and then pyrolyze it at high temperature to convert it into an inorganic ceramic matrix. The process temperature of this method is low and the cycle is short, which is suitable for the production of large structural parts. However, during the pyrolysis process, the matrix is ​​prone to produce holes and microcracks, resulting in poor overall performance of the composite material. The RMI method is to use liquid silicon to impregnate a solid preform and react with carbon to generate SiC, thereby forming a ceramic matrix. This method has a short preparation cycle and good matrix integrity, and low porosity, but its process temperature is high, which is easy to cause fiber damage, and residual silicon will reduce the use temperature of the product. In addition, the above three methods also have the problems of large thermal expansion coefficient and poor performance consistency of the obtained composite material. Summary of the invention

[0003] The purpose of the present invention is to solve the technical problems of the existing preparation method, such as long preparation cycle, large thermal expansion coefficient of composite materials, poor performance consistency and poor overall performance of composite materials due to the generation of microcracks, and to provide a method for preparing continuous single-bundle fibers of C / SiC composite materials with a low thermal expansion coefficient.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A method for preparing a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient is special in that it comprises the following steps:

[0006] Step 1: Preparation of pyrolytic carbon interface layer

[0007] Selecting a continuous carbon fiber bundle and winding it onto a mold, and then placing it in a pyrolytic carbon deposition furnace for deposition until a continuous carbon fiber bundle with a pyrolytic carbon interface layer is obtained;

[0008] Step 2: Dipping and curing

[0009] Step 2.1, constructing a prestressed impregnation and curing device; the prestressed impregnation and curing device comprises a tension controller, a precursor impregnation tank, a curing unit and a fiber winder which are sequentially arranged along the conveying direction of the continuous carbon fiber bundle; a fiber unwinding drum is installed on the tension controller;

[0010] Step 2.2, winding the continuous carbon fiber bundle obtained in step 1 on a fiber unwinding drum, and passing one end of the continuous carbon fiber bundle through a precursor impregnation tank and a curing unit in sequence, and then winding the bundle on a fiber winder;

[0011] Step 2.3, adjusting the torque of the tension controller so that the prestress value of the continuous carbon fiber bundle is the set value, adding the first SiC ceramic precursor to the precursor impregnation tank, setting the temperature of the curing unit, and then starting the fiber winder, so that the continuous carbon fiber bundle is sequentially impregnated with the first SiC ceramic precursor and cured by the curing unit, and then wound on the fiber winder to obtain a continuous single-bundle fiber preform;

[0012] Step 3: PIOP (polymer impregnation-online pyrolysis) and CVI (chemical vapor infiltration) treatment

[0013] The continuous single-bundle fiber preform obtained in step 2.3 is immersed in a pre-prepared second SiC ceramic precursor for impregnation, and then cured, cracked and SiC matrix is ​​deposited in sequence to obtain a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient.

[0014] Furthermore, in step 2.1, the prestressed impregnation and curing device further comprises a U-shaped guide wheel set arranged between the tension controller and the precursor impregnation tank, and a V-shaped guide wheel set arranged between the precursor impregnation tank and the curing unit; the fiber winder comprises a motor, a take-up drum connected to the motor drive end, and a plurality of take-up shafts uniformly distributed on the surface of the take-up drum along the circumference;

[0015] Step 2.2 is specifically as follows: winding the continuous carbon fiber bundle obtained in step 1 on a fiber unwinding drum, and winding one end of the continuous carbon fiber bundle on the take-up shaft after passing through a U-shaped guide wheel group, a precursor impregnation tank, a V-shaped guide wheel group, and a curing unit in sequence;

[0016] Step 2.3 is specifically as follows: adjusting the torque of the tension controller so that the prestress value of the continuous carbon fiber bundle is the set value, adding the first SiC ceramic precursor into the precursor impregnation tank, setting the temperature of the curing unit, and then starting the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the first SiC ceramic precursor by the U-shaped guide wheel group, converged by the V-shaped guide wheel group, and cured by the curing unit, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform.

[0017] Furthermore, in step 2.3, the temperature of the curing unit is 150-300° C.; and the take-up speed of the take-up reel is less than 0.5 cm / s.

[0018] Further, in step 2.3, the first SiC ceramic precursor is polycarbosilane PCS or hyperbranched polycarbosilane AHPCS;

[0019] In step 3, the second SiC ceramic precursor is polycarbosilane PCS or hyperbranched polycarbosilane AHPCS.

[0020] Furthermore, step 1 is specifically as follows:

[0021] A continuous carbon fiber bundle is selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. A precursor gas source is introduced for deposition at a deposition temperature of 880 to 920°C and a deposition pressure of 4 to 6 KPa until a continuous carbon fiber bundle with a pyrolytic carbon interface layer of 200 to 250 nm thickness is obtained. The bundle is then heat treated at a vacuum condition of 1750 to 1850°C for 1.5 to 2.5 hours to obtain a heat-treated continuous carbon fiber bundle; the thickness range of the continuous carbon fiber bundle is 1 to 12K.

[0022] Furthermore, step 3 is specifically as follows:

[0023] The continuous single fiber preform obtained in step 2.3 is immersed in the pre-prepared second SiC ceramic precursor for at least 40 seconds, and then placed in a tube furnace, cured at 200-250°C in an inert atmosphere for at least 2 hours, and then placed in a SiC deposition furnace, and the SiC matrix is ​​cracked and deposited when the furnace is heated to 950-1050°C until the dense density is greater than 2.0 g / cm 3 , stop the deposition, cool to room temperature, and obtain a continuous single bundle fiber of C / SiC composite material with a low thermal expansion coefficient.

[0024] Furthermore, step 1 is specifically as follows:

[0025] A 3K continuous carbon fiber bundle was selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. At a deposition temperature of 900°C and a deposition pressure of 5KPa, a precursor gas source C3H6 was introduced for deposition until a continuous carbon fiber bundle with a 230nm thick pyrolytic carbon interface layer was obtained. It was then heat treated at 1800°C under vacuum conditions for 2h to obtain a heat-treated continuous carbon fiber bundle.

[0026] Further, in step 2, the curing unit 3 is a heating table;

[0027] Step 2.3 is specifically as follows: adjusting the torque of the tension controller 1 to 0.18 Nm, so that the prestress value of the continuous carbon fiber bundle is 45 MPa, adding hyperbranched polycarbosilane AHPCS to the precursor impregnation tank 2, and setting the temperature of the heating table to 250°C, and then starting the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group 5, bundled by the V-shaped guide wheel group 6, and cured on the heating table, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform; the take-up speed of the take-up shaft is 0.45 cm / s.

[0028] Furthermore, step 3 is specifically as follows:

[0029] The continuous single fiber preform obtained in step 2.3 was immersed in the pre-prepared hyperbranched polycarbosilane AHPCS for 60 seconds, and then placed in a tube furnace, cured at 250 ° C in an Ar atmosphere for 3 hours, and then placed in a SiC deposition furnace. When the furnace temperature rises to 1000 ° C, the SiC matrix is ​​cracked and deposited for 2 hours, and then cooled to room temperature to obtain a dense density greater than 2.0 g / cm 3 Continuous single bundle fiber of C / SiC composite material with low thermal expansion coefficient.

[0030] Beneficial effects of the present invention:

[0031] 1. The present invention provides a method for preparing a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient. The preparation cycle is short and the production efficiency can be improved. The prepared continuous single-bundle fiber of the C / SiC composite material has a low thermal expansion coefficient, good performance consistency and good overall performance.

[0032] 2. In the present invention, under the prestress of the prestressed impregnation curing device, the straightness consistency of the fiber filaments in the continuous carbon fiber bundle is higher, the force in the load-bearing section is more uniform, the fiber filaments are in closer contact, and the fiber volume fraction is higher, so that the final C / SiC composite continuous single fiber bundle has higher tensile strength and better performance consistency. In addition, after the continuous carbon fiber bundle is cured under the action of prestress, the obtained continuous single fiber bundle preform is always subjected to compressive stress in the subsequent process, reducing the high-temperature thermal expansion, so that the continuous single fiber bundle of the C / SiC composite material has a lower thermal expansion coefficient.

[0033] 3. In the present invention, since compressive stress is introduced into the continuous single-bundle fiber preform, when the temperature is cooled, the cracking of the fiber under the action of prestress can be reduced, the microcracks inside the material can be reduced, and the crack resistance and service life of the continuous single-bundle fiber of the C / SiC composite material can be improved.

[0034] 4. In the present invention, the U-shaped guide wheel set can further improve the impregnation effect of the continuous carbon fiber bundle, and the take-up shaft can reduce the bending of the prestressed fiber. In addition, the take-up speed of the take-up shaft is less than 0.5 cm / s, which can ensure that the fiber is fully impregnated. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of a method for preparing a continuous single bundle fiber of a C / SiC composite material having a low thermal expansion coefficient of the present invention;

[0036] Figure 2 is a schematic diagram of winding a continuous carbon fiber bundle onto a graphite mold in step 1 of Example 1 of the present invention;

[0037] Figure 3 is a schematic structural diagram of a prestressed impregnation and curing device in step 2 of the first embodiment of the present invention;

[0038] Figure 4 1 is a schematic diagram of the structure of one of the U-shaped guide wheels of the U-shaped guide wheel assembly from different viewing angles in step 2.1 of the first embodiment of the present invention; wherein, Figure 4 (a) is a schematic diagram of the structure of the U-shaped guide wheel from one perspective. Figure 4 (b) is a schematic diagram of the structure of the U-shaped guide wheel from another perspective;

[0039] Figure 5 1 is a schematic diagram of the structure of one of the V-shaped guide wheels of the V-shaped guide wheel assembly from different viewing angles in step 2.1 of the first embodiment of the present invention; wherein, Figure 5 (a) is a schematic diagram of the structure of the V-type guide wheel from one perspective. Figure 5 (b) is a schematic diagram of the structure of the V-type guide wheel from another perspective;

[0040] Figure 6is a schematic diagram of multi-stage flattening of a U-shaped guide wheel assembly in other embodiments of the present invention;

[0041] Figure 7 is a curve diagram of the linear expansion variation of a continuous single bundle fiber of a C / SiC composite material obtained in Examples 1 to 5 of the present invention at different temperatures;

[0042] Figure 8 is a graph showing the change in thermal expansion coefficient of a continuous single bundle of C / SiC composite materials obtained in Examples 1 to 5 of the present invention at different temperatures;

[0043] Fig. 9 is a tensile stress-strain curve diagram of a continuous single bundle fiber of a C / SiC composite material obtained in Examples 1 to 5 of the present invention;

[0044] Fig.10 It is a graph of tensile strength and modulus of continuous single-bundle fibers of C / SiC composite materials obtained in Examples 1 to 5 of the present invention.

[0045] Description of reference numerals:

[0046] 1- tension controller, 2- precursor impregnation tank, 3- curing unit, 4- fiber winder, 5- U-type guide wheel set, 6- V-type guide wheel set. DETAILED DESCRIPTION

[0047] Embodiment 1

[0048] like Figure 1 As shown, a method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient is characterized by comprising the following steps:

[0049] Step 1: Preparation of pyrolytic carbon interface layer

[0050] like Figure 2 As shown, a continuous carbon fiber bundle of 3K T300 is selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. At a deposition temperature of 900°C and a deposition pressure of 5KPa, a precursor gas source C3H6 is introduced for deposition until a continuous carbon fiber bundle with a pyrolytic carbon interface layer of 230nm thickness is obtained. The reaction equation is shown in (1-1). Then, it is heat treated at 1800°C under vacuum conditions for 2h to increase the degree of crystallization of the pyrolytic carbon interface layer, and a continuous carbon fiber bundle after heat treatment is obtained.

[0051] C3H6(g)→3C(s)+3H2(g)(1-1)

[0052] Step 2: Dipping and curing

[0053] Step 2.1, build a prestressed impregnation and curing device; Figure 3-Figure 5As shown, the prestressed impregnation and curing device includes a tension controller 1, a precursor impregnation tank 2, a curing unit 3 and a fiber winder 4 which are arranged in sequence along the transmission direction of the continuous carbon fiber bundle, wherein a fiber unwinding drum with a diameter of 8 cm is installed on the tension controller 1, a U-shaped guide wheel group 5 is arranged between the tension controller 1 and the precursor impregnation tank 2, the U-shaped guide wheel group 5 includes a first U-shaped guide wheel located outside the precursor impregnation tank 2 and a second U-shaped guide wheel located inside the precursor impregnation tank 2, a V-shaped guide wheel group 6 is arranged between the precursor impregnation tank 2 and the curing unit 3, the V-shaped guide wheel group 6 includes a first V-shaped guide wheel located inside the precursor impregnation tank 2 and a second V-shaped guide wheel located outside the precursor impregnation tank 2, and the fiber winder 4 includes a motor, a take-up drum connected to the motor drive end, and eight take-up shafts with a diameter of 30 cm uniformly distributed on the surface of the take-up drum along the circumference. The tension controller 1 is used to ensure that the fiber maintains a constant tension during the entire preparation process. The fiber tension can be monitored in real time by a tension sensor. The curing unit 3 is used to accurately control the curing temperature. The motor of the fiber winder 4 is used to control the fiber winding speed and provide power. Figure 6 It is a schematic diagram of the multi-stage flattening of the U-shaped guide wheel set 5 in other embodiments.

[0054] Step 2.2, the continuous carbon fiber bundle obtained in step 1 is wound on the fiber unwinding drum, and one end of the continuous carbon fiber bundle passes through the U-shaped guide wheel group 5, the precursor impregnation tank 2, the V-shaped guide wheel group 6, and the curing unit 3 in sequence, and then is wound on the take-up shaft.

[0055] Step 2.3, adjust the torque of the tension controller 1 to 0.21Nm, so that the prestress value of the continuous carbon fiber bundle is 45MPa, add hyperbranched polycarbosilane AHPCS to the precursor impregnation tank 2, and set the temperature of the curing unit 3 to 250°C, then start the motor, the motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group 5, bundled by the V-shaped guide wheel group 6, and cured by the curing unit 3, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform, and the take-up speed of the take-up shaft is 0.45cm / s. Among them, the curing reaction mechanism is mainly hydrosilylation, dehydrogenation coupling and double bond self-polymerization reaction, which are respectively expressed as formulas (1-2), (1-3) and (1-4), as follows.

[0056] ≡Si-CH=CH2+H-Si≡→≡Si-CH2CH2-Si≡ (1-2)

[0057] ≡Si-H+H-Si≡→≡Si-Si≡+H2 (1-3)

[0058]

[0059] Step 3: PIOP and CVI processing

[0060] The continuous single fiber preform obtained in step 2.3 was immersed in the pre-prepared hyperbranched polycarbosilane AHPCS for 60 seconds, and then placed in a tube furnace, cured at 250 ° C in an Ar atmosphere for 3 hours, and then placed in a SiC deposition furnace. When the furnace temperature rises to 1000 ° C, the SiC matrix is ​​cracked and deposited for 2 hours, and then cooled to room temperature to obtain a dense density greater than 2.0 g / cm 3 Continuous single bundle fiber of C / SiC composite material with low thermal expansion coefficient.

[0061] Embodiment 2

[0062] Step 1: Preparation of pyrolytic carbon interface layer

[0063] A continuous carbon fiber bundle of 1K T300 was selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. At a deposition temperature of 880°C and a deposition pressure of 4KPa, a precursor gas source C3H6 was introduced for deposition until a continuous carbon fiber bundle with a 200nm thick pyrolytic carbon interface layer was obtained. It was then heat treated at 1850°C under vacuum conditions for 1.5h to increase the degree of crystallization of the pyrolytic carbon interface layer to obtain a continuous carbon fiber bundle after heat treatment.

[0064] Step 2.1 and step 2.2 in step 2 are the same as step 2.1 and step 2.2 in embodiment 1.

[0065] Step 2.3, adjust the torque of the tension controller 1 to 0.09Nm, so that the prestress value of the continuous carbon fiber bundle is 20MPa, add hyperbranched polycarbosilane AHPCS to the precursor impregnation tank 2, and set the temperature of the curing unit 3 to 150°C, and then start the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group 5, bundled by the V-shaped guide wheel group 6, and cured by the curing unit 3, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform. The take-up speed of the take-up shaft is 0.3cm / s.

[0066] Step 3: PIOP and CVI processing

[0067] The continuous single fiber preform obtained in step 2.3 was immersed in the pre-prepared hyperbranched polycarbosilane AHPCS for 55 seconds, and then placed in a tube furnace, cured at 230 ° C in a helium atmosphere for 2.5 hours, and then placed in a SiC deposition furnace. When the furnace temperature rises to 950 ° C, the SiC matrix is ​​cracked and deposited for 2 hours, and then cooled to room temperature to obtain a dense density greater than 2.0 g / cm 3 Continuous single bundle fiber of C / SiC composite material with low thermal expansion coefficient.

[0068] Embodiment 3

[0069] Step 1: Preparation of pyrolytic carbon interface layer

[0070] A continuous carbon fiber bundle of 12K T1000 was selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. At a deposition temperature of 920°C and a deposition pressure of 6KPa, a precursor gas source C3H6 was introduced for deposition until a continuous carbon fiber bundle with a 250nm thick pyrolytic carbon interface layer was obtained. It was then heat treated at 1750°C under vacuum conditions for 2.5h to increase the degree of crystallization of the pyrolytic carbon interface layer to obtain a continuous carbon fiber bundle after heat treatment.

[0071] Step 2.1 and step 2.2 in step 2 are the same as step 2.1 and step 2.2 in embodiment 1.

[0072] Step 2.3, adjust the torque of the tension controller 1 to 0.16Nm, so that the prestress value of the continuous carbon fiber bundle is 35MPa, add polycarbosilane PCS to the precursor impregnation tank 2, and set the temperature of the curing unit 3 to 300°C, and then start the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the polycarbosilane PCS through the U-shaped guide wheel group 5, gathered by the V-shaped guide wheel group 6, and cured by the curing unit 3, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform. The take-up speed of the take-up shaft is 0.3cm / s.

[0073] Step 3: PIOP and CVI processing

[0074] The continuous single fiber preform obtained in step 2.3 was immersed in the pre-prepared polycarbosilane PCS for 60 seconds, and then placed in a tube furnace, cured at 200 ° C in an Ar atmosphere for 3 hours, and then placed in a SiC deposition furnace. When the furnace temperature rises to 1050 ° C, the SiC matrix is ​​cracked and deposited for 2 hours, and then cooled to room temperature to obtain a dense density greater than 2.0 g / cm 3 Continuous single bundle fiber of C / SiC composite material with low thermal expansion coefficient.

[0075] Embodiment 4

[0076] Step 1, step 2.1 and step 2.2 in step 2, and step 3 are the same as step 1, step 2.1 and step 2.2 and step 3 in embodiment 1.

[0077] Step 2.3 is specifically as follows: adjusting the torque of the tension controller 1 to 0.25 Nm, so that the prestress value of the continuous carbon fiber bundle is 55 MPa, adding hyperbranched polycarbosilane AHPCS to the precursor impregnation tank 2, and setting the temperature of the curing unit 3 to 250°C, and then starting the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group 5, bundled by the V-shaped guide wheel group 6, and cured by the curing unit 3, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform. The take-up speed of the take-up shaft is 0.3 cm / s.

[0078] Embodiment 5

[0079] In this embodiment, all steps except step 2.3 are the same as those in the first embodiment.

[0080] Step 2.3 is specifically as follows: adjusting the torque of the tension controller 1 to 0 Nm, so that the prestress value of the continuous carbon fiber bundle is 0 MPa, adding hyperbranched polycarbosilane AHPCS to the precursor impregnation tank 2, and setting the temperature of the curing unit 3 to 250 ° C, and then starting the motor. The motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group 5, bundled by the V-shaped guide wheel group 6, and cured by the curing unit 3, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform. The take-up speed of the take-up shaft is 0.45 cm / s.

[0081] It should be noted that in Embodiments 1 to 5, the curing unit 3 is a heating platform.

[0082] Figure 7 and Figure 8 They are respectively the linear expansion variation curves and thermal expansion coefficient variation curves of the C / SiC composite continuous single bundle fibers obtained in Examples 1 to 5 of the present invention at different temperatures, Figure 7 and Figure 8 It can be concluded that the linear expansion coefficient of a continuous single fiber bundle of C / SiC composite material decreases with the increase of prestress, and the reduction reaches about 50% at 280°C and about 25% at 1200°C.

[0083] Fig. 9 and Fig.10 The tensile stress-strain curves and tensile strength and modulus curves of the continuous single-bundle fibers of the C / SiC composite materials obtained in Examples 1 to 5 of the present invention are shown in FIG. Fig. 9 and Fig.10It can be concluded that the tensile strength and modulus of the continuous single-bundle fiber of the C / SiC composite material change significantly with the increase of prestress. When the prestress is 45MPa, the tensile strength and modulus increase the most, increasing to about 1.75 times that of the case without prestress. However, when the prestress reaches 55MPa, the tensile strength will drop to a level similar to that without stress. Therefore, the best prestress value is 45MPa. The obtained continuous single-bundle fiber of the C / SiC composite material has the characteristics of high strength and low thermal expansion coefficient.

[0084] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient, characterized in that: The following steps are involved: Step 1: Preparation of pyrolytic carbon interface layer Selecting a continuous carbon fiber bundle and winding it onto a mold, and then placing it in a pyrolytic carbon deposition furnace for deposition until a continuous carbon fiber bundle with a pyrolytic carbon interface layer is obtained; Step 2: Dipping and curing Step 2.1, constructing a prestressed impregnation and curing device; the prestressed impregnation and curing device comprises a tension controller (1), a precursor impregnation tank (2), a curing unit (3) and a fiber winder (4) which are sequentially arranged along the conveying direction of the continuous carbon fiber bundle; the tension controller (1) is equipped with a fiber unwinding drum; Step 2.2, winding the continuous carbon fiber bundle obtained in step 1 onto a fiber unwinding drum, and passing one end of the continuous carbon fiber bundle through a precursor impregnation tank (2) and a curing unit (3) in sequence, and then winding the bundle onto a fiber winder (4); Step 2.3, adjusting the torque of the tension controller (1) so that the prestress value of the continuous carbon fiber bundle is a set value, adding a first SiC ceramic precursor to the precursor impregnation tank (2), setting the temperature of the curing unit (3), and then starting the fiber winder (4), so that the continuous carbon fiber bundle is sequentially impregnated with the first SiC ceramic precursor and cured by the curing unit (3), and then wound on the fiber winder (4), to obtain a continuous single-bundle fiber preform; Step 3: PIOP and CVI processing The continuous single-bundle fiber preform obtained in step 2.3 is immersed in a pre-prepared second SiC ceramic precursor for impregnation, and then cured, cracked and SiC matrix is ​​deposited in sequence to obtain a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient.

2. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 1, characterized in that: In step 2.1, the prestressed impregnation and curing device further comprises a U-shaped guide wheel group (5) arranged between the tension controller (1) and the precursor impregnation tank (2), and a V-shaped guide wheel group (6) between the precursor impregnation tank (2) and the curing unit (3); the fiber winder (4) comprises a motor, a take-up drum connected to the motor drive end, and a plurality of take-up shafts uniformly distributed on the surface of the take-up drum along the circumference; Step 2.2 specifically comprises: winding the continuous carbon fiber bundle obtained in step 1 onto a fiber unwinding drum, and winding one end of the continuous carbon fiber bundle onto the take-up shaft after passing through a U-shaped guide wheel group (5), a precursor impregnation tank (2), a V-shaped guide wheel group (6), and a curing unit (3) in sequence; Step 2.3 is specifically as follows: adjusting the torque of the tension controller (1) so that the prestress value of the continuous carbon fiber bundle is a set value, adding a first SiC ceramic precursor into the precursor impregnation tank (2), setting the temperature of the curing unit (3), and then starting the motor, which drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the first SiC ceramic precursor by the U-shaped guide wheel group (5), bundled by the V-shaped guide wheel group (6), and cured by the curing unit (3), and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform.

3. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 2, characterized in that: In step 2.3, the temperature of the curing unit (3) is 150-300° C.; and the take-up speed of the take-up reel is less than 0.5 cm / s.

4. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 3, characterized in that: In step 2.3, the first SiC ceramic precursor is polycarbosilane PCS or hyperbranched polycarbosilane AHPCS; In step 3, the second SiC ceramic precursor is polycarbosilane PCS or hyperbranched polycarbosilane AHPCS.

5. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 1, characterized in that: Step 1 is as follows: A continuous carbon fiber bundle is selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. A precursor gas source is introduced for deposition at a deposition temperature of 880 to 920°C and a deposition pressure of 4 to 6 KPa until a continuous carbon fiber bundle with a pyrolytic carbon interface layer of 200 to 250 nm thickness is obtained. The bundle is then heat treated at a vacuum condition of 1750 to 1850°C for 1.5 to 2.5 hours to obtain a heat-treated continuous carbon fiber bundle; the thickness range of the continuous carbon fiber bundle is 1 to 12K.

6. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 5, characterized in that: Step 3 is as follows: The continuous single fiber preform obtained in step 2.3 is immersed in the pre-prepared second SiC ceramic precursor for at least 40 seconds, and then placed in a tube furnace, cured at 200-250°C in an inert atmosphere for at least 2 hours, and then placed in a SiC deposition furnace, and the SiC matrix is ​​cracked and deposited when the furnace is heated to 950-1050°C until the dense density is greater than 2.0 g / cm 3 , stop the deposition, cool to room temperature, and obtain a continuous single bundle fiber of C / SiC composite material with a low thermal expansion coefficient.

7. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 6, characterized in that: Step 1 is as follows: A 3K continuous carbon fiber bundle was selected and wound onto a graphite mold, and then placed in a pyrolytic carbon deposition furnace. At a deposition temperature of 900°C and a deposition pressure of 5KPa, a precursor gas source C3H6 was introduced for deposition until a continuous carbon fiber bundle with a 230nm thick pyrolytic carbon interface layer was obtained. It was then heat treated at 1800°C under vacuum conditions for 2h to obtain a heat-treated continuous carbon fiber bundle.

8. The method for preparing a continuous single bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 4, characterized in that: In step 2, the curing unit (3) is a heating table; Step 2.3 is specifically as follows: adjusting the torque of the tension controller (1) to 0.18 Nm, so that the prestress value of the continuous carbon fiber bundle is 45 MPa, adding hyperbranched polycarbosilane AHPCS to the precursor impregnation tank (2), and setting the temperature of the heating table to 250°C, and then starting the motor, the motor drives the take-up shaft on the take-up disk to rotate, so that the continuous carbon fiber bundle is sequentially impregnated in the hyperbranched polycarbosilane AHPCS through the U-shaped guide wheel group (5), bundled by the V-shaped guide wheel group (6), and cured on the heating table, and then wound on the take-up shaft to obtain a continuous single-bundle fiber preform; the take-up speed of the take-up shaft is 0.45 cm / s.

9. The method for preparing a continuous single-bundle fiber of a C / SiC composite material with a low thermal expansion coefficient according to claim 8, characterized in that: Step 3 is as follows: The continuous single fiber preform obtained in step 2.3 was immersed in the pre-prepared hyperbranched polycarbosilane AHPCS for 60 seconds, and then placed in a tube furnace, cured at 250 ° C in an Ar atmosphere for 3 hours, and then placed in a SiC deposition furnace. When the furnace temperature rises to 1000 ° C, the SiC matrix is ​​cracked and deposited for 2 hours, and then cooled to room temperature to obtain a dense density greater than 2.0 g / cm 3 Continuous single bundle fiber of C / SiC composite material with low thermal expansion coefficient.

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