A near fully dense carbon fiber reinforced ceramic matrix composite and its preparation method

Abstract

The present invention relates to an almost fully dense carbon fiber reinforced ceramic matrix composite material and a preparation method thereof, belonging to the technical field of ceramic matrix composite materials. The preparation method is as follows: performing high-temperature heat treatment on a carbon fiber preform, and then introducing a pyrolytic carbon interface into the heat-treated carbon fiber preform to obtain a C f / PyC green body; placing the C f / PyC green body in a resin mixture for vacuum impregnation, and then performing curing and carbonization to obtain a C f / PyC / BRC green body; the resin mixture is prepared from benzoxazine resin, ethanol, acetylacetone, and ethylene glycol; embedding the C f / PyC / BRC green body in metal powder for reactive infiltration to prepare an almost fully dense carbon fiber reinforced ceramic matrix composite material. The composite material prepared by the present invention can achieve almost full density, has a low preparation temperature, uniform distribution of ceramic phases, and excellent mechanical properties.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramic matrix composites, and particularly relates to an almost fully dense carbon fiber reinforced ceramic matrix composite and a preparation method thereof. Background Art

[0002] Due to a series of advantages such as low density, high specific strength, excellent fracture toughness, corrosion resistance, and wear resistance, carbon fiber reinforced ceramic matrix composites have shown broad application prospects in the fields of aerospace, automotive manufacturing, national defense technology, energy, and biomedicine. Nevertheless, the preparation of carbon fiber reinforced ceramic matrix composites still faces some technical problems, especially in improving the density of the materials.

[0003] At present, the main preparation methods of carbon fiber reinforced ceramic matrix composites include chemical vapor infiltration method, precursor infiltration and pyrolysis method, slurry infiltration method, reaction infiltration method, etc. Among them, the chemical vapor infiltration method, precursor infiltration and pyrolysis method, and slurry infiltration method can meet the performance requirements of the materials to a certain extent, but the composites prepared by them generally have the problem of high residual porosity (>10%), which limits the mechanical properties and long-term stability of the materials. The reaction infiltration method, with its low cost, short cycle, high density, and ability to adapt to complex-shaped components, has gradually become the preferred technology for the industrial preparation of carbon fiber reinforced ceramic matrix composites. However, the composites prepared by the reaction infiltration method still usually have about 5% residual porosity, which has a certain impact on the comprehensive performance of the materials. How to improve the density of carbon fiber reinforced ceramic matrix composites has become one of the key points in the current technological development.

[0004] Therefore, it is particularly important to develop an almost fully dense carbon fiber reinforced ceramic matrix composite and a preparation method thereof. By reducing the internal pore defects, the mechanical properties and stability of carbon fiber reinforced ceramic matrix composites can be further improved, and the application scope in various fields can be broadened. Summary of the Invention

[0005] In order to solve one or more technical problems existing in the prior art, the first object of the present invention is to provide a preparation method of an almost fully dense carbon fiber reinforced ceramic matrix composite. The composite prepared by the present invention can achieve almost full density (porosity ≤ 1%), has a low preparation temperature, uniform distribution of ceramic phases, and excellent mechanical properties.

[0006] The second object of the present invention is to provide an almost fully dense carbon fiber reinforced ceramic matrix composite prepared by the above preparation method.

[0007] In order to achieve the above objects, the present invention adopts the following technical solutions:

[0008] A preparation method of a nearly fully dense carbon fiber reinforced ceramic matrix composite material of the present invention uses a resin mixture as an impregnating agent, and impregnates, cures, and carbonizes the C f / PyC green body in sequence to obtain a C f / PyC / BRC green body. Finally, the C f / PyC / BRC green body is embedded in metal powder for reactive infiltration to obtain a nearly fully dense carbon fiber reinforced ceramic matrix composite material;

[0009] The resin mixture is composed of benzoxazine resin, ethanol, acetylacetone, and ethylene glycol. By mass ratio, benzoxazine resin: ethanol: acetylacetone: ethylene glycol = (40 - 85): (5 - 20): (5 - 20): (5 - 20).

[0010] In the preparation method of the present invention, a resin mixture composed of benzoxazine resin, ethanol, acetylacetone, and ethylene glycol is used to impregnate the C f / PyC green body. Among them, benzoxazine resin can undergo thermal ring-opening polymerization without an external curing agent to generate polybenzoxazine with a three-dimensional cross-linked network structure; in addition, benzoxazine resin has nearly zero shrinkage and small residual stress during the molding and curing process. Coupled with the fact that benzoxazine resin is a low molecular weight and low viscosity cyclic monomer before ring-opening polymerization and has good solubility, in the present invention, it is blended with solvents of various different boiling points such as ethanol, acetylacetone, and ethylene glycol. During curing, through solvent volatilization, benzoxazine resin forms hierarchical pores during carbonization to obtain porous benzoxazine resin carbon (BRC). This specific pore structure can enhance the capillary force of the green body during the reactive infiltration process and significantly accelerate the infiltration of the metal melt; in addition, benzoxazine resin carbon also has the characteristic of high activity, and can react violently with metal powder during the heating process of reactive infiltration, releasing a large amount of heat in a short time, causing the local temperature on the material surface to rise sharply and exceed the melting point of the metal powder, accelerating the melting of the metal powder and infiltrating under the action of capillary force. This can not only reduce the reaction temperature, but also promote the depth of infiltration and the degree of reaction, and promote the heterogeneous nucleation of the ceramic phase, thereby improving the distribution uniformity of the ceramic phase, reducing the residual metal phase in the material, increasing the density, and finally obtaining a nearly fully dense carbon fiber reinforced ceramic matrix composite material with excellent mechanical properties and excellent high-temperature thermal stability performance.

[0011] However, in the present invention, on the one hand, in addition to the need to simultaneously add ethanol, acetylacetone, and ethylene glycol as solvents to obtain hierarchical hierarchical pores, on the other hand, the proportion of the solvents also needs to be effectively controlled. If the addition amount is too small, the pore formation is incomplete or uneven; if too much, the efficiency is low and the residual carbon after resin carbonization is less, which is not conducive to the subsequent reactive infiltration to generate the ceramic phase.

[0012] Preferably, the C fThe method for obtaining the PyC preform is as follows: heat-treat the carbon fiber preform, and then introduce a pyrolytic carbon matrix into the carbon fiber preform by chemical vapor infiltration to obtain it.

[0013] Further preferably, the carbon fiber preform is selected from one of non-woven fabric / woven roving needle-punched carbon fiber preforms, satin fabric stitched preforms, three-dimensional punctured preforms, and three-dimensional braided preforms.

[0014] Further preferably, the heat treatment is carried out in an argon atmosphere, the temperature of the heat treatment is 1800 - 2000 °C, and the time of the heat treatment is 1 - 4 h.

[0015] Further preferably, during the chemical vapor infiltration, propylene or methane is used as the carbon source, and nitrogen or hydrogen is used as the carrier gas. The flow rate ratio of the carbon source to the carrier gas is (0.5 - 5):1; the deposition pressure is 0.5 - 1.5 kPa, the deposition temperature is 900 - 1100 °C, and the deposition time is 30 - 200 h. The flow rate unit in the present invention is L / min, which refers to the volume of gas passing through per unit time.

[0016] Preferably, the resin mixture is prepared as follows: weigh benzoxazine resin, ethanol, acetylacetone, and ethylene glycol according to the designed ratio and stir and mix them for 5 - 60 min.

[0017] Preferably, for the resin mixture, by mass ratio, benzoxazine resin:ethanol:acetylacetone:ethylene glycol = (40 - 70):(10 - 20):(10 - 20):(10 - 20).

[0018] Preferably, the impregnation is vacuum impregnation, the pressure of the impregnation is ≤ -0.10 MPa, and the time of the impregnation is 0.5 - 1.0 h.

[0019] Preferably, the curing process is as follows: first heat up to 40 - 60 °C and keep warm for 4 - 8 h, then heat up to 70 - 90 °C and keep warm for 12 - 20 h, then heat up to 130 - 150 °C and keep warm for 2 - 6 h, and finally heat up to 190 - 210 °C and keep warm for 2 - 6 h.

[0020] The resin mixture of the present invention, through the above-mentioned gradient heating-holding curing process, while realizing the curing of the benzoxazine resin, induces the multi-stage gradient volatilization of ethanol, acetylacetone, and ethylene glycol. This process promotes the formation of a microporous matrix carbon with a unique three-dimensional interconnected network structure after the carbonization of the benzoxazine resin. Its characteristics are as follows: supported by a submicron-scale carbon skeleton, a hierarchical pore structure containing nano- and submicron-scale pores is constructed, and high specific surface area characteristics are obtained through topological regulation.

[0021] Preferably, the carbonization temperature is 800~1200°C, and the carbonization time is 1~4 h; the temperature is raised to the carbonization temperature at a heating rate of 0.1~1.0°C / min.

[0022] Preferably, the number of times of impregnation, curing, and carbonization is 1~3 times in sequence.

[0023] Preferably, the metal powder is selected from at least one of Si powder, Ti powder, Zr powder, and Hf powder, and the particle size of the metal powder is ≤1000 μm.

[0024] Preferably, the reactive infiltration temperature is 1550~2000°C, preferably 1550~1800°C, more preferably 1550~1600°C, and the holding time is 1~4 h. Since the benzoxazine resin carbon also has the characteristic of high activity, it can react and infiltrate at a lower temperature, and the ultra-high temperature ceramic can be introduced into the matrix at 1550°C.

[0025] The present invention provides, in a second aspect, a near fully dense carbon fiber reinforced ceramic matrix composite prepared by the preparation method described in the first aspect of the present invention.

[0026] The porosity of the near fully dense carbon fiber reinforced ceramic matrix composite is ≤1%.

[0027] The present invention has at least the following beneficial effects compared with the prior art:

[0028] (1) By introducing porous benzoxazine resin carbon into the C f / PyC green body, the present invention regulates the pore structure, thereby enhancing the capillary force of the green body during the reactive infiltration process and significantly accelerating the infiltration of the molten metal. This method realizes the reactive infiltration process controlled by viscous resistance, effectively avoids the formation of closed pores inside the carbon fiber reinforced ceramic matrix composite due to reaction blockage, and prepares a near fully dense carbon fiber reinforced ceramic matrix composite.

[0029] (2) Using a resin mixture containing benzoxazine resin, ethanol solution, acetylacetone solution, and ethylene glycol solution as the carbon source precursor in C fIntroduce porous benzoxazine resin carbon into the PyC preform. The present invention discovers that the benzoxazine resin used in this resin mixture can undergo thermal ring-opening polymerization without an external curing agent to generate polybenzoxazine with a three-dimensional cross-linked network structure; in addition, the benzoxazine resin has almost zero shrinkage and small residual stress during the molding and curing process. Coupled with the fact that the benzoxazine resin is a low molecular weight and low viscosity cyclic monomer before ring-opening polymerization, it has good solubility and excellent processability, and can be used as a precursor for preparing the carbon matrix of composites. In addition, the present invention discovers that the ethanol solution, acetylacetone solution, and ethylene glycol solution added to this resin mixture can be used as pore-forming agents, forming multi-stage volatilization and discharging from the material during different temperature curing processes, enabling the benzoxazine resin to have porous characteristics after carbonization.

[0030] (3) The porous benzoxazine resin carbon introduced by the present invention has the characteristics of high activity and high specific surface area, and can react violently with metal powder during the heating process of reactive infiltration, releasing a large amount of heat in a short time, resulting in a sharp increase in the local temperature on the material surface exceeding the melting point of the metal powder, accelerating the melting of the metal powder and infiltrating under the action of capillary force, playing a role in reducing the preparation temperature.

[0031] (4) The highly active porous benzoxazine resin carbon introduced by the present invention can promote the heterogeneous nucleation of the ceramic phase, improve the distribution uniformity of the ceramic phase, as well as the mechanical properties and thermal shock resistance of the composite material; in addition, the benzoxazine resin carbon provides a highly active carbon source for the metal melt introduced by reactive infiltration, which can reduce the content of residual metal phases in the material and improve the high-temperature thermal stability of the material. Description of the Drawings

[0032] Figure 1 is the micrograph of the C f / PyC / BRC preform in Example 1.

[0033] Figure 2 is the micrograph of the BRC in Example 1.

[0034] Figure 3 is the micrograph of the nearly fully dense C / C-SiC composite material in Example 1.

[0035] Figure 4 is the micrograph of the nearly fully dense C / C-SiC composite material in Example 2.

[0036] Figure 5 is the micrograph of the nearly fully dense C / C-SiC-ZrC-HfC composite material in Example 3.

[0037] Figure 6 is the micrograph of the C / C-SiC composite material in Comparative Example 1.

[0038] Figure 7 is the microscopic morphology diagram of the C f / PyC / BRC green body obtained in Comparative Example 3.

[0039] Figure 8 is the microscopic morphology diagram of the C f / PyC / BRC green body obtained in Comparative Example 4. Specific Embodiments

[0040] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0041] The present invention will be further described by way of examples below, but the protection scope of the present invention is not limited to these embodiments. Unless otherwise specified, the raw materials and reagents used in the following examples are all commercially available products or can be prepared by known methods.

[0042] Example 1

[0043] (1) Using a three-dimensional winding carbon fiber preform with a density of 0.84 g / cm 3 as the initial green body, place the preform in a high-temperature heat treatment device, heat the carbon fiber preform to 2000 °C and hold for 2 h under an argon protective atmosphere; use propylene as the carbon source gas and nitrogen as the carrier gas, and introduce a pyrolytic carbon matrix into the carbon fiber preform by chemical vapor infiltration. The deposition temperature is 950 °C, the deposition pressure is 0.8 kPa, the flow ratio of propylene to nitrogen is 2:1, and the deposition time is 50 h to obtain a C 3 / PyC green body with a bulk density of 1.10 g / cm f .

[0044] (2) Place the above C f / PyC green body in a resin mixture for vacuum impregnation, and then cure and carbonize it to obtain a C 3 / PyC / BRC green body with a bulk density of 1.30 g / cm f .

[0045] Among them, a benzoxazine resin, an ethanol solution, an acetylacetone solution, and an ethylene glycol solution with a mass ratio of 7:1:1:1 are mixed and stirred thoroughly for 0.5 h to obtain a resin mixture; the vacuum impregnation is carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 1 h; the crosslinking and curing process is as follows: keep warm at 50 °C for 4 h, keep warm at 80 °C for 20 h, keep warm at 140 °C for 4 h, and keep warm at 200 °C for 4 h; the carbonization is carried out under an argon atmosphere, the carbonization temperature is 1000 °C, the heating rate to 1000 °C is 1.0 °C / min, and the pyrolysis carbonization time is 3 h.

[0046] (3) Embed the C f / PyC / BRC green body obtained in step (2) in pure Si powder and place it in a vacuum carbon tube furnace for reactive infiltration. The reactive infiltration temperature is 1600 °C, and the reactive infiltration time is 2 h to obtain a C / C-SiC composite material (nearly fully dense carbon fiber reinforced ceramic matrix composite material).

[0047] The C f / PyC / BRC green body obtained in this example has a microscopic morphology as Figure 1 shown. It can be seen that BRC effectively divides the large-scale pores inside the C f / PyC green body; the internal microscopic morphology of the porous benzoxazine resin carbon (BRC) formed directly after curing-pyrolysis carbonization of the resin mixture is as Figure 2 shown. It can be seen that BRC has a unique three-dimensional interconnected network structure; it has a hierarchical porous morphology; the microscopic morphology of the nearly fully dense C / C-SiC composite material obtained after reactive infiltration is as Figure 3 shown. It can be seen that the material exhibits high density characteristics, each phase is evenly distributed, and no obvious residual pores are found.

[0048] The volume density of the C / C-SiC composite material obtained in this example is measured to be 2.20 g / cm 3 , the porosity is 0.27%, the flexural strength is 285 MPa, and the compressive strength is 460 MPa.

[0049] Example 2

[0050] (1) Use a non-woven fabric / woven roving needle-punched carbon fiber preform with a density of 0.54 g / cm 3 as the initial green body. Place the preform in a high-temperature heat treatment device and heat the carbon fiber preform to 1800 °C and keep it warm for 4 h under an argon protective atmosphere; use propylene as the carbon source gas and nitrogen as the carrier gas, and introduce a pyrolytic carbon matrix into the carbon fiber preform by chemical vapor infiltration. The deposition temperature is 950 °C, the deposition pressure is 0.6 kPa, the flow ratio of propylene to nitrogen is 3:1, and the deposition time is 100 h to obtain a volume density of 1.24 g / cm3 of C f / PyC green body.

[0051] (2)Place the above C f / PyC green body in a resin mixture for vacuum impregnation, and then cure and carbonize to obtain a C 3 with a density of 1.38 g / cm f / PyC / BRC green body.

[0052] Among them, mix benzoxazine resin, ethanol solution, acetylacetone solution and ethylene glycol solution with a mass ratio of 5:2:1:2 and stir well for 0.5 h to obtain the resin mixture; the vacuum impregnation is carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 0.5 h; the cross-linking and curing process is: keep warm at 50 °C for 4 h, keep warm at 90 °C for 12 h, keep warm at 150 °C for 2 h, and keep warm at 210 °C for 2 h; the carbonization is carried out under an argon atmosphere, the carbonization temperature is 900 °C, the heating rate to 900 °C is 0.5 °C / min, and the pyrolysis carbonization time is 2 h.

[0053] (3)Embed the C f / PyC / BRC green body obtained in step (2) in pure Si powder and place it in a vacuum carbon tube furnace for reaction infiltration. The reaction infiltration temperature is 2000 °C, and the reaction infiltration time is 1 h to obtain a C / C-SiC composite material (near fully dense carbon fiber reinforced ceramic matrix composite material).

[0054] The micro-morphology of the near fully dense C / C-SiC composite material obtained after reaction infiltration in this example is as Figure 4 shown. It can be seen that the material shows high density characteristics, each phase is evenly distributed, and no obvious residual pores are found.

[0055] The volume density of the C / C-SiC composite material obtained in this example is measured to be 2.33 g / cm 3 , the porosity is 0.62%, the flexural strength is 258 MPa, and the compressive strength is 490 MPa.

[0056] Example 3

[0057] (1)With a density of 0.54 g / cm 3The non-woven fabric / net-shaped carbon fiber preform is used as the initial blank. The preform is placed in a high-temperature heat treatment equipment and heated to 1900 °C under an argon protective atmosphere and held for 3 h. Using propylene as the carbon source gas and nitrogen as the carrier gas, pyrolytic carbon matrix is introduced into the carbon fiber preform by chemical vapor infiltration method. The deposition temperature is 950 °C, the deposition pressure is 1.0 kPa, the flow rate ratio of propylene to nitrogen is 3:1, and the deposition time is 120 h, obtaining a C 3 / PyC blank with a bulk density of 1.31 g / cm f .

[0058] (2)The above C f / PyC blank is placed in a resin mixture for vacuum impregnation, and then cured and carbonized to obtain a C 3 / PyC / BRC blank with a density of 1.41 g / cm f .

[0059] Among them, a resin mixture is obtained by mixing benzoxazine resin, ethanol solution, acetylacetone solution and ethylene glycol solution with a mass ratio of 4:2:2:2 and stirring well for 0.5 h; the vacuum impregnation is carried out in a vacuum impregnation equipment containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 0.5 h; the crosslinking and curing process is: holding at 50 °C for 8 h, holding at 80 °C for 16 h, holding at 130 °C for 6 h, holding at 190 °C for 6 h; the carbonization is carried out under an argon atmosphere, the carbonization temperature is 900 °C, the heating rate to 900 °C is 0.6 °C / min, and the pyrolytic carbonization time is 2 h.

[0060] (3)The C f / PyC / BRC blank obtained in step (2) is embedded in a Si-Zr-Hf mixed powder with a mass ratio of 1:1:1 and placed in a vacuum carbon tube furnace for reactive infiltration. The reactive infiltration temperature is 1550 °C and the reactive infiltration time is 1 h, obtaining a C / C-SiC-ZrC-HfC composite material (near fully dense carbon fiber reinforced ceramic matrix composite material).

[0061] The microscopic morphology of the near fully dense C / C-SiC-ZrC-HfC composite material obtained after reactive infiltration in this example is as Figure 5 shown. It can be seen that the material exhibits high density characteristics, each phase is evenly distributed, and no obvious residual pores are found.

[0062] The bulk density of the C / C-SiC-ZrC-HfC composite material obtained in this example is measured to be 2.72 g / cm 3 , the porosity is 0.99%, the flexural strength is 323 MPa, and the compressive strength is 422 MPa.

[0063] Example 4

[0064] (1) Suture the carbon fiber preform with twill cloth having a density of 0.87 g / cm 3 to form an initial blank, place the preform in a high-temperature heat treatment device, heat the carbon fiber preform to 2000 °C and hold for 4 h under an argon protective atmosphere; use propylene as the carbon source gas and nitrogen as the carrier gas, and introduce a pyrolytic carbon matrix into the carbon fiber preform by chemical vapor infiltration. The deposition temperature is 950 °C, the deposition pressure is 1.2 kPa, the flow ratio of propylene to nitrogen is 3:1, and the deposition time is 150 h to obtain a C 3 / PyC blank with a bulk density of 1.28 g / cm f .

[0065] (2) Place the above C f / PyC blank in a resin mixture for vacuum impregnation, and then cure and carbonize to obtain a C 3 / PyC / BRC blank with a density of 1.40 g / cm f .

[0066] Among them, mix benzoxazine resin, ethanol solution, acetylacetone solution and ethylene glycol solution with a mass ratio of 6:1:1:2 and stir well for 1 h to obtain a resin mixture; the vacuum impregnation is carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 1 h; the crosslinking and curing process is: keep warm at 50 °C for 4 h, keep warm at 80 °C for 20 h, keep warm at 140 °C for 4 h, and keep warm at 200 °C for 4 h; the carbonization is carried out under an argon atmosphere, the carbonization temperature is 1000 °C, the heating rate to 1000 °C is 1.0 °C / min, and the pyrolytic carbonization time is 2 h.

[0067] (3) Embed the C f / PyC / BRC blank obtained in step (2) in Si powder and place it in a vacuum carbon tube furnace for reactive infiltration. The reactive infiltration temperature is 1800 °C and the reactive infiltration time is 3 h to obtain a C / C-SiC composite material (nearly fully dense carbon fiber reinforced ceramic matrix composite material).

[0068] It is measured that the bulk density of the C / C-SiC composite material obtained in this example is 2.18 g / cm 3 , the porosity is 0.81%, the flexural strength is 305 MPa, and the compressive strength is 469 MPa.

[0069] Comparative Example 1

[0070] (1) Suture the carbon fiber preform with twill cloth having a density of 0.84 g / cm 3The three-dimensional winding carbon fiber preform is used as the initial blank. The preform is placed in a high-temperature heat treatment equipment, and the carbon fiber preform is heated to 2000 °C and kept at this temperature for 2 h under an argon protection atmosphere. Using propylene as the carbon source gas and nitrogen as the carrier gas, a pyrolytic carbon matrix is introduced into the carbon fiber preform by chemical vapor infiltration. The deposition temperature is 950 °C, the deposition pressure is 0.8 kPa, the flow ratio of propylene to nitrogen is 2:1, and the deposition time is 50 h, obtaining a C 3 / PyC blank with a bulk density of 1.10 g / cm f .

[0071] (2)Embed the C f / PyC blank obtained in step (1) in pure Si powder and place it in a vacuum carbon tube furnace for reactive infiltration. The reactive infiltration temperature is 1600 °C and the reactive infiltration time is 2 h, obtaining a C / C-SiC composite material.

[0072] The microscopic morphology of the C / C-SiC composite material obtained by reactive infiltration in this comparative example is as shown in Figure 6 . It can be seen that there are large-scale residual pores that are not filled inside the material, and the density of the material is low.

[0073] The measured bulk density of the C / C-SiC composite material obtained in this comparative example is 1.62 g / cm 3 , the porosity is 19.83%, the flexural strength is 80 MPa, and the compressive strength is 145 MPa.

[0074] Comparative Example 2

[0075] (1)Use a non-woven fabric / woven roving needle-punched carbon fiber preform with a density of 0.54 g / cm 3 as the initial blank. The preform is placed in a high-temperature heat treatment equipment, and the carbon fiber preform is heated to 1800 °C and kept at this temperature for 4 h under an argon protection atmosphere. Using propylene as the carbon source gas and nitrogen as the carrier gas, a pyrolytic carbon matrix is introduced into the carbon fiber preform by chemical vapor infiltration. The deposition temperature is 950 °C, the deposition pressure is 0.6 kPa, the flow ratio of propylene to nitrogen is 3:1, and the deposition time is 100 h, obtaining a C 3 / PyC blank with a bulk density of 1.24 g / cm f .

[0076] (2)Embed the C f / PyC blank obtained in step (1) in pure Si powder and place it in a vacuum carbon tube furnace for reactive infiltration. The reactive infiltration temperature is 2000 °C and the reactive infiltration time is 1 h, obtaining a C / C-SiC composite material.

[0077] The measured bulk density of the C / C-SiC composite material obtained in this comparative example is 2.05 g / cm 3, the porosity is 6.88%, the flexural strength is 138 MPa, and the compressive strength is 229 MPa.

[0078] Comparative Example 3

[0079] Comparative Example 3 is basically the same as Example 1, except that:

[0080] (2) The above C f / PyC preform was placed in a resin mixture for vacuum impregnation, and then cured and carbonized to obtain a C 3 with a volume density of 1.33 g / cm f / PyC / BRC preform.

[0081] Among them, a resin mixture was obtained by mixing benzoxazine resin, ethanol solution, acetylacetone solution, and ethylene glycol solution with a mass ratio of 90:5:5:5 and stirring well for 0.5 h; the vacuum impregnation was carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree was -0.10 MPa, and the vacuum impregnation time was 1 h; the crosslinking and curing process was: keeping the temperature at 50 °C for 4 h, 80 °C for 20 h, 140 °C for 4 h, and 200 °C for 4 h; the carbonization was carried out in an argon atmosphere, the carbonization temperature was 1000 °C, the heating rate to 1000 °C was 1.0 °C / min, and the pyrolysis carbonization time was 3 h.

[0082] The C f / PyC / BRC preform obtained in this comparative example has a microscopic morphology as Figure 7 shown. It can be seen from Figure 7 that after the resin in this comparative example was carbonized and cracked, the pore formation was insufficient, and it was impossible to form a microporous matrix carbon with a three-dimensional interconnected network structure, which was not conducive to the subsequent reaction infiltration, and might even hinder the infiltration of the melt.

[0083] The volume density of the C / C-SiC composite material obtained in this comparative example was measured to be 1.60 g / cm 3 , the porosity was 20.11%, the flexural strength was 69 MPa, and the compressive strength was 133 MPa.

[0084] Comparative Example 4

[0085] Comparative Example 4 is basically the same as Example 1, except that:

[0086] (2) The above C f / PyC preform was placed in a resin mixture for vacuum impregnation, and then cured and carbonized to obtain a C 3 with a volume density of 1.30 g / cm f / PyC / BRC preform.

[0087] Among them, a resin mixture is obtained by mixing benzoxazine resin, acetylacetone solution and ethylene glycol solution with a mass ratio of 14:3:3 and stirring well for 0.5 h; the vacuum impregnation is carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 1 h; the cross-linking and curing process is: keeping warm at 50 °C for 4 h, keeping warm at 80 °C for 20 h, keeping warm at 140 °C for 4 h, and keeping warm at 200 °C for 4 h; the carbonization is carried out in an argon atmosphere, the carbonization temperature is 1000 °C, the heating rate to 1000 °C is 1.0 °C / min, and the pyrolysis carbonization time is 3 h.

[0088] The C f / PyC / BRC green body obtained in this comparative example is as Figure 8 shown. From Figure 8 it can be seen that after the resin in this comparative example is carbonized and pyrolyzed, the pore formation is uneven, and it is impossible to form a microporous matrix carbon with a three-dimensional interconnected network structure with uniform and controllable pore distribution, which is not conducive to the formation of a nearly fully dense and uniform-phase distributed C / C-SiC composite material.

[0089] The volume density of the C / C-SiC composite material obtained in this comparative example is measured to be 2.02 g / cm 3 , the porosity is 7.02%, the flexural strength is 192 MPa, and the compressive strength is 289 MPa.

[0090] Comparative Example 5

[0091] Comparative Example 5 is basically the same as Example 1, the difference is that:

[0092] (2) The above-mentioned C f / PyC green body is placed in the resin mixture for vacuum impregnation, and then cured and carbonized to obtain a C 3 / PyC / BRC green body with a volume density of 1.30 g / cm f .

[0093] Among them, a resin mixture is obtained by mixing benzoxazine resin, ethanol, acetylacetone solution and ethylene glycol solution with a mass ratio of 7:1:1:1 and stirring well for 0.5 h; the vacuum impregnation is carried out in a vacuum impregnation device containing the resin mixture, the vacuum degree is -0.10 MPa, and the vacuum impregnation time is 1 h; the cross-linking and curing process is: directly heating from room temperature to 200 °C and keeping warm for 28 h; the carbonization is carried out in an argon atmosphere, the carbonization temperature is 1000 °C, the heating rate to 1000 °C is 1.0 °C / min, and the pyrolysis carbonization time is 3 h.

[0094] The volume density of the C / C-SiC composite material obtained in this comparative example is measured to be 2.10 g / cm 3, the porosity is 3.43%, the flexural strength is 223 MPa, and the compressive strength is 380 MPa.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A preparation method of an almost fully dense carbon fiber reinforced ceramic matrix composite, characterized in that: Using a resin mixture as an impregnating agent, impregnation, curing, and carbonization are successively carried out on the C f / PyC preform to obtain a C f / PyC / BRC preform. Finally, the C f / PyC / BRC preform is embedded in metal powder for reactive infiltration to obtain a nearly fully dense carbon fiber reinforced ceramic matrix composite; The resin mixture is composed of benzoxazine resin, ethanol, acetylacetone and ethylene glycol, and the mass ratio of benzoxazine resin: ethanol: acetylacetone: ethylene glycol is 40-85: 5-20: 5-20: 5-20; The curing process is: firstly heating to 40-60°C, keeping warm for 4-8h, then heating to 70-90°C, keeping warm for 12-20h, then heating to 130-150°C, keeping warm for 2-6h, and finally heating to 190-210°C, keeping warm for 2-6h.

2. The preparation method of an almost fully dense carbon fiber reinforced ceramic matrix composite according to claim 1, characterized in that: The C f / PyC green body is obtained by heat-treating a carbon fiber preform and then introducing a pyrolytic carbon matrix into the carbon fiber preform by chemical vapor infiltration.

3. The method for preparing a nearly fully dense carbon fiber reinforced ceramic matrix composite material according to claim 2, characterized in that: The carbon fiber preform is selected from one of a non-woven fabric / net-based needle-punched carbon fiber preform, a satin fabric stitched preform, a three-dimensional puncture preform, and a three-dimensional winding preform; The heat treatment is carried out in an argon atmosphere, the heat treatment temperature is 1800-2000° C., and the heat treatment time is 1-4 hours; During the chemical vapor infiltration, propylene or methane is used as the carbon source, nitrogen or hydrogen is used as the carrier gas, and the flow ratio of the carbon source to the carrier gas is 0.5-5:1; the deposition pressure is 0.5-1.5 kPa, the deposition temperature is 900-1100° C., and the deposition time is 30-200 hours.

4. The method for preparing a nearly fully dense carbon fiber reinforced ceramic matrix composite material according to claim 1, characterized in that: The impregnation is vacuum impregnation, the impregnation pressure is ≤-0.10MPa, and the impregnation time is 0.5~1.0h.

5. The preparation method of an almost fully dense carbon fiber reinforced ceramic matrix composite according to claim 1, characterized in that: The carbonization temperature is 800-1200° C., and the carbonization time is 1-4 hours. The temperature is raised to the carbonization temperature at a heating rate of 0.1-1.0° C. / min.

6. The preparation method of a nearly fully dense carbon fiber reinforced ceramic matrix composite according to claim 1, characterized in that: The impregnation, curing and carbonization are performed sequentially 1 to 3 times.

7. The preparation method of a nearly fully dense carbon fiber reinforced ceramic matrix composite according to claim 1, wherein: The metal powder is selected from at least one of Si powder, Ti powder, Zr powder and Hf powder, and the particle size of the metal powder is ≤1000 μm; The temperature of the reaction infiltration is 1550-2000°C, and the insulation time is 1-4h.

8. A nearly fully dense carbon fiber reinforced ceramic matrix composite material prepared by the preparation method according to any one of claims 1 to 7.

9. The near fully dense carbon fiber reinforced ceramic matrix composite material according to claim 8, characterized in that: The porosity of the nearly fully dense carbon fiber reinforced ceramic matrix composite material is ≤1%.

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