Room-temperature-impregnated c / sialc ceramic matrix composite material and preparation method thereof

Abstract

The application provides a novel room-temperature-impregnated C / SiAlC ceramic matrix composite material and a preparation method thereof, and comprises the following steps: preparing liquid polyaluminum carbosilane with gradient aluminum element content; impregnating carbon fiber reinforcement in liquid polyaluminum carbosilane under vacuum condition and at room temperature; cross-linking and curing the impregnated carbon fiber reinforcement after pressurization and heat preservation; pyrolyzing the cured preform in an inert gas atmosphere; repeating the impregnation-curing-pyrolysis process, gradually reducing the viscosity of the impregnant liquid polyaluminum carbosilane with the increase of impregnation cycles, until the sample weight increase is not more than the required value or the sample density reaches the required density, and then the C / SiAlC ceramic matrix composite material is obtained. The preparation method adjusts the rheological property of the liquid polyaluminum carbosilane by regulating the aluminum content, and has the advantages of high densification efficiency, simple and controllable process, good thermal stability, improved high-temperature resistance and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-temperature-resistant ceramic matrix composites, and particularly relates to a novel C / SiAlC ceramic matrix composite that can be impregnated at room temperature and a preparation method thereof. BACKGROUND

[0002] C / SiC ceramic matrix composites have a wide application prospect in high-temperature thermal structural materials such as aerospace due to their high strength, high hardness, oxidation resistance, creep resistance, good wear resistance at high temperatures, excellent chemical corrosion resistance, small thermal expansion coefficient and relative density, etc. At present, the precursors for preparing the C / SiC composite matrix are mainly solid polycarbosilane and liquid polycarbosilane. In order to meet the continuous demand of new generation aircraft for high-temperature-resistant materials and oxidation resistance, a new impregnation matrix for C / SiC composite materials needs to be found.

[0003] Polyaluminum carbosilane (PACS) is a new type of ceramic precursor. The synthesis of polyaluminum carbosilane is usually obtained by the reaction of organosilicon polymers and aluminum-containing compounds such as aluminum acetylacetone and aluminum isopropyl alcohol. PACS can be obtained by melt spinning, infusibilization treatment and high temperature sintering, which is a ceramic fiber with a near stoichiometric ratio and a temperature resistance of 2200℃. It is currently the ceramic fiber with the best temperature resistance. The introduction of aluminum, a heterogeneous element, into SiC ceramic precursors can promote ceramic sintering, help densification and effectively improve the mechanical properties of ceramics.

[0004] Due to the high synthesis temperature of the current polyaluminum carbosilane synthesis method, the prepared polyaluminum carbosilane has poor rheological properties, and the prepared polyaluminum carbosilane is mostly in the form of a block solid. When using the impregnation-curing-pyrolysis process to prepare ceramic matrix composites, the solid impregnation phase needs to be used with a solvent, which often needs to be dissolved at high temperature and cannot be directly used as an impregnation matrix. Therefore, polyaluminum carbosilane is currently mainly used for the preparation of SiC fibers with high temperature resistance, oxidation resistance and creep resistance, and the use of polyaluminum carbosilane as a composite impregnation matrix is still a blank.

[0005] Therefore, in view of the above problems, how to obtain polyaluminum carbosilane that can be directly used as an impregnation matrix and prepare a new C / SiAlC ceramic matrix composite is a key problem. SUMMARY

[0006] In order to overcome the deficiencies in the prior art, the inventors have made intensive research and provided a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material and a preparation method thereof. The viscosity-controllable liquid polyaluminum carbosilane is prepared by adjusting the aluminum content in the polyaluminum carbosilane. In the preparation of the ceramic matrix composite material by using the impregnation-curing-pyrolysis process (PIP process), the high-viscosity liquid polyaluminum carbosilane is used as the impregnant in the first several rounds, and the low-viscosity liquid polyaluminum carbosilane is used as the impregnant in the last several rounds. The C / SiAlC ceramic matrix composite material can be quickly obtained by gradient-viscosity impregnation, and the impregnation rounds are reduced.

[0007] The technical scheme provided by the present application is as follows:

[0008] In a first aspect, a preparation method of a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material comprises the following steps:

[0009] The methylaluminoxane and polydimethylsiloxane (PDMS) with different mass ratios are dissolved in an organic solvent, and then reacted at 50-90 DEG C for 2-12 hours. After the reaction is completed, the organic solvent is removed, and the liquid polyaluminum carbosilane with gradient aluminum content is prepared.

[0010] The carbon fiber reinforcement is impregnated in the liquid polyaluminum carbosilane under vacuum and at room temperature.

[0011] The impregnated carbon fiber reinforcement is crosslinked and cured after being pressed and heat treated.

[0012] The cured preform is pyrolyzed under an inert gas atmosphere.

[0013] The above impregnation-curing-pyrolysis process is repeated. With the increase of the impregnation rounds, the liquid polyaluminum carbosilane with gradually decreasing aluminum content is selected, and the viscosity of the impregnant liquid polyaluminum carbosilane is gradually reduced until the sample weight increase is not more than the required value or the sample density reaches the required density, and the C / SiAlC ceramic matrix composite material is obtained.

[0014] In a second aspect, a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material is prepared by the preparation method of the novel room-temperature-impregnable C / SiAlC ceramic matrix composite material.

[0015] The novel room-temperature-impregnable C / SiAlC ceramic matrix composite material and the preparation method thereof have the following beneficial effects:

[0016] (1) The application provides a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material and a preparation method thereof, wherein the content of aluminum elements in the polyaluminum carbosilane is adjusted by adjusting the raw material ratio, the content of aluminum elements in the liquid polyaluminum carbosilane is increased, the viscosity of the liquid polyaluminum carbosilane is increased, and when the ceramic matrix composite material is prepared by using the impregnation-curing-pyrolysis process (PIP process), the high-viscosity liquid polyaluminum carbosilane is used as the impregnant in the first several cycles to quickly improve the densification degree of the composite material, and the low-viscosity liquid polyaluminum carbosilane is used as the impregnant in the last several cycles to effectively reduce the impregnation cycles and improve the densification degree of the C / SiAlC composite material.

[0017] (2) The application provides a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material and a preparation method thereof, wherein the prepared liquid polyaluminum carbosilane has good flowability and good fiber wettability, can be directly impregnated at room temperature without using an organic solvent, and has simple steps and simple operation; compared with a traditional hot-pressing sintering method, the method has the advantages of low preparation temperature and uniform element composition distribution, and is suitable for preparing composite materials with various shapes and sizes. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 Macroscopic photos (a) and micro-morphology photos (b) of a novel gradient-viscosity-impregnated C / SiAlC ceramic matrix composite material prepared in Example 1;

[0019] Figure 2 Typical densification curves of different cycle composite cycles of the novel gradient-viscosity-impregnated C / SiAlC ceramic matrix composite material prepared in Example 1 and a densification curve comparison of a comparative composite platelet;

[0020] Figure 3 A thermal weight loss curve of the novel gradient-viscosity-impregnated C / SiAlC ceramic matrix composite material prepared in Example 1 under 1200 DEG C air. DETAILED DESCRIPTION

[0021] The characteristics and advantages of the application will become more apparent with the following detailed description of the application.

[0022] The special word "exemplary" herein means "serving as an example, embodiment or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as superior or better than the other embodiments.

[0023] The application provides a novel room-temperature-impregnable C / SiAlC ceramic matrix composite material, which comprises the following steps:

[0024] (1) Gradient viscosity impregnant preparation: the impregnant is liquid polyaluminum carbosilane, which is prepared by the following steps: taking methylaluminoxane and polydimethylsiloxane (PDMS) with different mass ratios as raw materials, dissolving in an organic solvent, and then reacting at 50-90°C for 2-12 hours. After the reaction is completed, the organic solvent is removed to obtain liquid polyaluminum carbosilane with gradient aluminum content. The viscosity of the liquid polyaluminum carbosilane increases with the increase of the aluminum content in the liquid polyaluminum carbosilane.

[0025] In this step, the mass ratio of methylaluminoxane to polydimethylsiloxane (PDMS) is 1:1-1:100, the mass percentage of aluminum element in the prepared liquid polyaluminum carbosilane is 0%-10%, and the viscosity of the liquid polyaluminum carbosilane is 10-10000 mPa·s.

[0026] In this step, the organic solvent is one or a combination of more than one of toluene, xylene, tetrahydrofuran or n-hexane.

[0027] (2) Impregnation: the carbon fiber reinforcement is impregnated in the liquid polyaluminum carbosilane under vacuum and at room temperature.

[0028] In this step, the carbon fiber in the carbon fiber reinforcement is one or a combination of more than one of T300 grade carbon fiber, T700 grade carbon fiber, T800 grade carbon fiber, T1000 grade carbon fiber, M40J grade carbon fiber or M55J grade carbon fiber.

[0029] In this step, the weaving form of the carbon fiber reinforcement includes one or a combination of more than one of two-dimensional fiber cloth layer stitching, two-dimensional half-weaving, orthogonal three-way, three-dimensional yarn winding, three-dimensional five-way or three-dimensional six-way.

[0030] In this step, the carbon fiber reinforcement is deposited or not deposited with an interface layer, and the interface layer is pyrolytic carbon PyC or boron nitride BN.

[0031] In this step, the temperature during impregnation is room temperature, the vacuum state is maintained for 0.5-1 hour, the pressure is increased to 0.1-1.5 MPa, and the impregnation time is 0.5-3 hours. The viscosity of the liquid polyaluminum carbosilane during impregnation can be adjusted according to the different aluminum contents, and is between 10-10000 mPa·s.

[0032] (3) Curing: the impregnated carbon fiber reinforcement is crosslinked and cured after being pressurized and heat treated.

[0033] In this step, the curing temperature is 180-240°C, the curing pressure is 0.3-3 MPa, and the heat preservation time is 2-8 hours.

[0034] (4) Pyrolysis: the cured preform is pyrolyzed in an inert gas atmosphere.

[0035] In this step, the inert atmosphere during the pyrolysis is argon or nitrogen, the pyrolysis temperature is 900-1600℃, and the holding time is 1-2 hours.

[0036] The above impregnation-curing-pyrolysis process is repeated, preferably 6-12 times. With the increase of the impregnation cycles, liquid polycarbosilane with gradually decreasing aluminum element content is selected, and the viscosity of the impregnant liquid polycarbosilane is gradually reduced until the sample weight gain is not more than 2% or the density of the sample is more than 2 g / cm 3 , thereby obtaining the C / SiAlC ceramic matrix composite.

[0037] Examples

[0038] Example 1

[0039] (1) Gradient viscosity impregnant preparation: methylaluminoxane and polydimethylsiloxane (PDMS) with different mass ratios are used as raw materials, an organic solvent is dissolved, and then reacted at 80℃ for 6h. After the reaction is completed, the organic solvent is removed, and liquid polycarbosilane with gradient aluminum element content is obtained.

[0040] (2) Impregnation: orthogonal three-dimensional structure T300-3K carbon fiber fabric is used as a reinforcing body to make a 400mm×500mm flat plate sample. The sample is impregnated in the liquid polycarbosilane at room temperature and under vacuum conditions. The impregnation pressure of 8 cycles is 0.3, 0.3, 0.5, 0.5, 1, 1, 1, and 1.5 MPa, respectively, and the impregnation time of each cycle is 2 hours.

[0041] (3) Curing: the impregnated carbon fiber flat plate sample is pressurized to 2 MPa and crosslinked and cured in an oven at 200℃ for 2h.

[0042] (4) Pyrolysis: the cured flat plate sample in the above step is pyrolyzed at 900℃ in an argon atmosphere for 2h.

[0043] After repeating the above impregnation-curing-pyrolysis process 8 times, a new gradient viscosity impregnated C / SiAlC ceramic matrix composite is obtained. The macroscopic photograph and micro-morphology diagram of the C / SiAlC ceramic matrix composite are shown in Figure 1 . The viscosity of the impregnation phase used in each cycle and the density of the composite are shown in Table 1. The related information of the comparative composite is also shown in Table 1.

[0044] The polycarbosilane used in the comparative composite is a liquid phase polycarbosilane solution prepared by dissolving solid polycarbosilane and toluene at 80℃. The impregnation-curing-pyrolysis parameters are consistent with those of the new gradient viscosity impregnated C / SiAlC ceramic matrix composite. After 8 cycles of impregnation, the weight gain of the composite prepared by the method of the present application is only 1.3%, and the density has reached 1.95 g / cm 3Densification curve as shown Figure 2 As shown; however, after 12 rounds of impregnation, the density of the comparative composite material ② only reached 1.93 g / cm³. 3 .

[0045] Table 1

[0046]

[0047] The C / SiAlC ceramic matrix composite material prepared by the method of this invention has a room temperature tensile strength of 332 MPa, exhibiting good mechanical properties. After sintering in air at 1200℃ for 60 min, its total weight loss is 12%, demonstrating excellent high-temperature oxidation resistance. Figure 3 .

[0048] Example 2

[0049] (1) Preparation of gradient viscosity impregnating agent: Methylaluminoxane and polydimethylsiloxane (PDMS) with different mass ratios were used as raw materials. After being dissolved in an organic solvent, they were reacted at 75°C for 8 hours. After the reaction was completed, the organic solvent was removed to obtain liquid polyaluminosiloxane with gradient aluminum content.

[0050] (2) Impregnation: Using orthogonal triaxial T700 carbon fiber fabric as reinforcement, a 100mm×100mm flat sample was made and impregnated in polyaluminum carbosilane under room temperature and vacuum conditions. The impregnation pressures for 11 rounds were 0.3, 0.3, 0.3, 0.5, 0.5, 0.5, 1, 1, 1, 1, 1.5MPa, and the impregnation time for each round was 2 hours.

[0051] (3) Curing: The impregnated carbon fiber flat sample was pressurized to 2MPa and cross-linked and cured in an oven at 220℃ for 2h;

[0052] (4) Pyrolysis: The plate sample cured in the previous step was pyrolyzed at 1000℃ for 2 hours in an argon atmosphere;

[0053] After repeating the above impregnation-curing-pyrolysis process 11 times, a novel gradient viscosity impregnated C / SiAlC ceramic matrix composite material was obtained. The viscosity of the impregnating phase and the density of the composite material used in each round are shown in Table 2. Relevant information about the composite material is also shown in Table 2.

[0054] The polyaluminocarbosilane used in the composite material was a liquid-phase polyaluminocarbosilane solution prepared by adding toluene solution to solid polyaluminocarbosilane at 80℃. The impregnation-curing-pyrolysis parameters were consistent with those of the novel gradient viscosity impregnated C / SiAlC ceramic matrix composite material. After 11 rounds of impregnation, the density of the composite material ① prepared using the method of this invention reached 1.99 g / cm³. 3After 12 rounds of impregnation, the density of comparative composite 2 only reaches 1.93g / cm 3 .

[0055] Table 2

[0056]

[0057] The tensile strength of the new C / SiAlC ceramic matrix composite prepared by the above method is 346MPa at room temperature, and the composite has good mechanical properties; after sintering at 1200℃ in air for 60min, the total weight loss is 10.8%, and the composite has excellent high-temperature oxidation resistance.

[0058] The above detailed description of the present application is made in conjunction with the specific embodiments and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that various equivalent substitutions, modifications or improvements can be made to the technical solutions and embodiments of the present application without departing from the spirit and scope of the present application, and these all fall within the scope of the present application. The protection scope of the present application is subject to the appended claims.

[0059] The contents not described in detail in the specification of the present application are the known technology of those skilled in the art.

Claims

1. A method for preparing a room-temperature impregnated C / SiAlC ceramic matrix composite material, characterized in that, Includes the following steps: Methylaluminoxane and polydimethylsiloxane (PDMS) in different mass ratios were dissolved in an organic solvent and reacted at 50–90 °C for 2–12 h. After the reaction was completed, the organic solvent was removed to obtain liquid polyaluminosiloxane with a gradient aluminum content. The mass ratio of methylaluminoxane to PDMS was 1:1 to 1:100, and the viscosity of the liquid polyaluminosiloxane was 10–10000 mPa·s. The carbon fiber reinforcement was impregnated in liquid polyaluminosilane under vacuum conditions and at room temperature. The impregnated carbon fiber reinforcement is cross-linked and cured after being pressurized and kept at a heat source. The cured preform was decomposed under an inert atmosphere; Repeat the above impregnation-curing-pyrolysis process. As the number of impregnation rounds increases, use liquid polyaluminum carbide with gradually decreasing aluminum content and gradually reduce the viscosity of the impregnating agent liquid polyaluminum carbide until the sample weight gain does not exceed the required value or the sample density reaches the required density, and then obtain C / SiAlC ceramic matrix composite material.

2. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, In the step of preparing liquid polyaluminosilane with gradient aluminum content, the organic solvent is one or more of toluene, xylene, tetrahydrofuran, or n-hexane.

3. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The carbon fiber reinforcement is composed of one or more of the following: T300 grade carbon fiber, T700 grade carbon fiber, T800 grade carbon fiber, T1000 grade carbon fiber, M40J grade carbon fiber, or M55J grade carbon fiber.

4. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The weaving form of the carbon fiber reinforcement includes one or more of the following: two-dimensional fiber cloth lay-up stitching, two-dimensional semi-weaving, orthogonal three-dimensional, three-dimensional yarn wrapping, three-dimensional five-dimensional or three-dimensional six-dimensional.

5. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The impregnation process is carried out at room temperature, under vacuum for 0.5 to 1 hour, pressurized to 0.1 to 1.5 MPa, and for 0.5 to 3 hours.

6. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The curing temperature during the curing process is 180–240℃, the curing pressure is 0.3–3MPa, and the holding time is 2–8 hours.

7. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The inert atmosphere during pyrolysis is argon or nitrogen, the pyrolysis temperature is 900–1600℃, and the holding time is 1–2 hours.

8. The method for preparing room temperature impregnated C / SiAlC ceramic matrix composite material according to claim 1, characterized in that, The sample weight gain is no more than 2% or the sample density is more than 2 g / cm³. 3 C / SiAlC ceramic matrix composite material was obtained.

9. A room-temperature impregnated C / SiAlC ceramic matrix composite material, characterized in that, The composite material was prepared by the method described in any one of claims 1 to 8, which is a room temperature impregnated C / SiAlC ceramic matrix composite material.

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