Wave-absorbing near-zero-expansion CMP / C-SiCN ceramic-based composite material as well as preparation method and application thereof

Abstract

The invention discloses a wave-absorbing near-zero-expansion CMP / C-SiCN ceramic-based composite material and a preparation method and application thereof. The preparation method comprises the following steps: preparing a CMP / C reinforcement material with ultrahigh modulus and negative thermal expansion effect by adopting chemical vapor deposition and high-temperature graphitization and taking mesophase pitch-based carbon fibers as a framework; a SiCN ceramic matrix is prepared in a reinforcement material in a compounding manner by adopting a polymer impregnation and pyrolysis method. The crystallinity and the thermal expansion coefficient of the SiCN ceramic are controlled through ceramic cracking and annealing processes, so that the negative thermal expansion of the CMP / C reinforcement material is compensated, and the near-zero expansion performance of the CMP / C-SiCN composite material is optimized. The wave-absorbing performance of the CMP / C-SiCN composite material is improved by regulating and controlling the content and dielectric properties of Si3N4 and SiC in the SiCN matrix, and the CMP / C-SiCN ceramic matrix composite material with near-zero expansion and wave-absorbing performance is prepared.

Description

Technical Field

[0001] The present invention belongs to the field of thermal expansion properties of ceramic matrix composites, and particularly relates to a wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite, its preparation method and application. Background Art

[0002] In today's era, space technology is an important symbol to measure a country's comprehensive national strength and scientific and technological capabilities. Among them, space satellites play an important role in many fields. High-resolution space satellites, as an important technology for winning modern information warfare, have become the "clairvoyant" for battlefield situation awareness and the basic guarantee for high-precision guided weapons with many advantages, and have great strategic and tactical value in earth observation. The space opto-mechanical structure is an important component of the space observation camera. In order to ensure the high-precision requirements of the space opto-mechanical structure for earth observation, the thermal expansion coefficient of the material is required to be as low as possible within a wide temperature range, preferably zero expansion. At present, most space satellites use the CFRP system, which can achieve a thermal expansion coefficient of 10 -6 ~10 -7 / K within the service temperature range, has a low density and excellent near-zero thermal expansion performance, but its space weather resistance is poor, and it will degrade during long-term exposure in space, resulting in failure. Therefore, the development of composites with low density, excellent environmental weather resistance and near-zero expansion performance is the key to ensuring the high-precision requirements of space satellites and extending their service life. Ceramic matrix composites have the advantages of low thermal expansion coefficient, excellent mechanical properties, low density, good space environmental stability and high designability, etc., and are the most potential future space opto-mechanical structure materials. However, the existing ceramic matrix composites have a long preparation cycle, high cost, and a thermal expansion coefficient of 10 -6 ~10 -7 / K, and there is still much room for improvement to meet the high requirements of advanced space opto-mechanical structures.

[0003] Through research on existing studies, the inventor found that polysilazane is an excellent choice as a ceramic precursor for the polymer impregnation pyrolysis method. It exists in a liquid form at room temperature, and the impregnation process does not require a solvent for dissolution, greatly improving the impregnation efficiency, thus shortening the preparation cycle and reducing the cost; at the same time, the SiCN ceramic component structure prepared by the pyrolysis of polysilazane has temperature sensitivity. As the annealing heat treatment temperature increases, the contents of Si3N4 and SiC components in its SiCN ceramic matrix will change, so that the SiCN matrix has different positive thermal expansion coefficients and dielectric constants at different temperatures; in addition, the C MP / C reinforcement prepared by weaving and chemical vapor deposition of mesophase pitch-based carbon fiber has different negative thermal expansion coefficients after being treated at different graphitization temperatures. Therefore, theoretically, through C MPThe compounding and post-treatment of C / C reinforcements and SiCN matrix can achieve the regulation of the thermal expansion coefficient of C / C-SiCN ceramic matrix composites. In addition, by regulating the content of Si3N4 and SiC component systems and their dielectric properties in the SiCN matrix, the wave absorption performance of C / C-SiCN composites is improved, and then a C / C-SiCN ceramic matrix composite with both near-zero expansion and wave absorption properties is prepared. MP The compounding and post-treatment of C / C and SiCN matrix can achieve the regulation of the thermal expansion coefficient of C / C-SiCN ceramic matrix composites. In addition, by regulating the content of Si3N4 and SiC component systems and their dielectric properties in the SiCN matrix, the wave absorption performance of C / C-SiCN composites is improved, and then a C / C-SiCN ceramic matrix composite with both near-zero expansion and wave absorption properties is prepared. MP / C-SiCN composites, and further prepare a C / C-SiCN ceramic matrix composite with both near-zero expansion and wave absorption properties. MP / C-SiCN ceramic matrix composites. Summary of the Invention

[0004] In summary, the present invention provides a wave-absorbing near-zero expansion C / C-SiCN ceramic matrix composite and its preparation method and application, realizing the application of near-zero thermal expansion performance in the temperature range of -150 to 400 °C and the wave absorption application of device structures. MP / C-SiCN ceramic matrix composites and their preparation methods and applications, realizing the application of near-zero thermal expansion performance in the temperature range of -150 to 400 °C and the wave absorption application of device structures.

[0005] The above object can be achieved by the following technical solutions:

[0006] In the first aspect, the present invention provides a wave-absorbing near-zero expansion C / C-SiCN ceramic matrix composite, including a C / C reinforcement material with mesophase pitch-based carbon fiber (MPCF) as the skeleton and a SiCN ceramic matrix; MP / C reinforcement material and SiCN ceramic matrix; MP / C reinforcement material and SiCN ceramic matrix;

[0007] The C / C reinforcement material is composed of mesophase pitch-based carbon fiber and pyrolytic carbon, and has ultra-high modulus and negative thermal expansion effect; MP / C reinforcement material is composed of mesophase pitch-based carbon fiber and pyrolytic carbon, and has ultra-high modulus and negative thermal expansion effect;

[0008] The SiCN ceramic matrix is formed by pyrolysis of polysilazane (PSN) and has wave absorption performance and positive expansion effect.

[0009] Preferably, the tensile strength of the mesophase pitch-based carbon fiber is 3.1 - 3.4 GPa, the tensile modulus is 800 - 950 GPa, and the volume fraction of the mesophase pitch-based carbon fiber preform (MPCF preform) obtained after the fiber is formed by unidirectional laying, two-dimensional weaving and / or three-dimensional weaving processes is 35 - 55%. Then, the C / C reinforcement material with a density of about 1.0 - 1.5 g / cm is obtained by pyrolytic carbon deposition. 3 of C / C MP / C reinforcement material; the SiCN ceramic is composed of free carbon, SiC, Si3N4 and the formed amorphous phase.

[0010] Preferably, the tensile strength of the mesophase pitch-based carbon fiber is 3.1 - 3.4 GPa, the tensile modulus is 895 GPa, and the volume fraction of the MPCF preform obtained after the fiber is formed by unidirectional laying, two-dimensional weaving and / or three-dimensional weaving processes is 42%. Then, the C / C reinforcement material with a density of 1.0 g / cm is obtained by pyrolytic carbon deposition.3 C of MP / C reinforcement material; the SiCN ceramic is composed of free carbon, SiC, Si3N4 and the amorphous phase formed.

[0011] In a second aspect, the present invention provides a method for preparing the above-mentioned near-zero expansion composite material, including step S1: preparing C MP / C reinforcement material by chemical vapor deposition and high-temperature graphitization process; S2: preparing a SiCN ceramic matrix in the reinforcement material by polymer impregnation pyrolysis method; S3: adopting an annealing heat treatment process to reasonably control the crystallinity and dielectric properties of the SiCN ceramic matrix, and then realizing the preparation and performance optimization of a wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material.

[0012] In a further embodiment of the present invention, the specific steps of S1 include: arranging the mesophase pitch-based carbon fiber in a unidirectional arrangement, two-dimensional weaving and / or three-dimensional weaving process to weave it into an MPCF preform, and after repairing and leveling, putting the MPCF preform into a chemical vapor deposition furnace for pyrolytic carbon deposition. Using natural gas or propane as the carbon source gas, nitrogen as the dilution gas and protective gas, the deposition temperature is 900-1100 °C, the deposition pressure is 0.5-3 kPa, the deposition time is 20-80 h, and the obtained C MP / C reinforcement material with a density of 1.0-1.5 g / cm 3 ; then putting the C MP / C reinforcement material into a high-temperature graphitization furnace, using argon as the protective atmosphere, the heat treatment temperature is 2000-3150 °C, and the heat treatment time is 0.5-2 h, so as to obtain a C MP / C reinforcement material with ultra-high modulus and negative thermal expansion effect.

[0013] In a further embodiment of the present invention, the specific steps of S2 include: S201: putting the C MP / C reinforcement material obtained in S1 into alcohol, ultrasonically cleaning and drying it, then putting it into an impregnation container, and then adding polysilazane (PSN) to the impregnation container to submerge the upper surface of the sample by 2-3 mm; putting the impregnation container into a vacuum impregnation device, controlling the vacuum degree to be 0.08-0.1 MPa, and controlling the vacuum impregnation time to be 6-8 h; putting the vacuum-impregnated sample into a mold and curing the polysilazane in a constant-temperature oven, the curing temperature is 100-250 °C, and the curing time is 3-4 h.

[0014] The molecular weight of the PSN is 3000-8000, and the kinetic viscosity is 200-2000 mPa·s.

[0015] S202: Put the solidified sample together with the mold into a heat treatment furnace for ceramic pyrolysis, using argon for protection, with an argon flow rate of 0.5 - 1 L / min, a pyrolysis temperature of 700 - 1500 °C, a heating rate of 5 °C / min, and an isothermal pyrolysis time of 2 - 4 h.

[0016] S203: Repeat the steps of S201 - S203 for the pyrolyzed sample until the single - weight gain rate is less than 1%, and then stop. The density range of the densified C MP / C - SiCN ceramic - matrix composite is 2.0 - 2.4 g / cm 3 .

[0017] In a further embodiment of the present invention, the specific steps of S3 include: Put the densified C MP / C - SiCN ceramic - matrix composite into an annealing furnace for annealing heat treatment, using argon as the protective atmosphere, with an argon flow rate of 0.5 - 1 L / min, controlling the annealing heat treatment temperature at 1100 - 1700 °C, a heating rate of 5 °C / min, and an isothermal annealing heat treatment time of 1 - 10 h.

[0018] Thirdly, the present invention provides the application of controlling the annealing heat treatment temperature to regulate the SiCN matrix components in the preparation of wave - absorbing near - zero - expansion C MP / C - SiCN ceramic - matrix composites.

[0019] The technical solution provided by the present invention has the following beneficial effects:

[0020] (1) Aiming at the characteristics of long cycle and high cost in the preparation of ceramic - matrix composites by the conventional polymer impregnation pyrolysis method, the present invention proposes to use polysilazane as a ceramic precursor, and rely on its advantages of no solvent and high ceramic yield to improve the densification efficiency of the SiCN matrix, thereby greatly shortening the preparation cycle, increasing the densification degree and reducing the cost.

[0021] (2) Prepare high - thermal - conductivity C MP / C reinforcement materials by high - temperature graphitization treatment, so as to improve the thermal conductivity of the subsequently prepared C MP / C - SiCN ceramic - matrix composites, realize the conduction of local heat in time during service, improve the temperature uniformity and thus improve the thermal deformation, which is beneficial to achieving near - zero expansion.

[0022] (3) Use annealing heat treatment to regulate the SiCN matrix structure components in the C MP / C - SiCN ceramic - matrix composites, and realize the preparation of C MP / C - SiCN ceramic - matrix composites with both near - zero expansion and wave - absorbing properties. This wave - absorbing structural near - zero - expansion C MP / C-SiCN composites show great application value in the aerospace field.

[0023] Additional aspects and advantages of the present invention will be given in the following description section, some will become apparent from the following description, or be learned through the practice of the present invention. Brief Description of the Drawings

[0024] Figure 1 Process flow chart for preparing C MP / C-SiCN ceramic matrix composites of the present invention;

[0025] Figure 2 SEM image with a magnification of 200 of the C MP / C-SiCN ceramic matrix composites prepared in the examples;

[0026] Figure 3 XRD pattern of the near-zero expansion C MP / C-SiCN ceramic matrix composites prepared in the examples;

[0027] Figure 4 XRD pattern of the SiCN ceramic matrix in the examples;

[0028] Figure 5 Reflection loss diagram of the SiCN ceramic matrix at different frequencies in the examples;

[0029] Figure 6 Impedance matching performance diagram of the SiCN ceramic matrix at different frequencies in the examples. Detailed Description of the Invention

[0030] The technical solutions in the embodiments of the present invention will be clearly and completely described below. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, so they are only examples and cannot be used to limit the protection scope of the present invention.

[0031] The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The test materials used in the following embodiments are all obtained from regular reagent manufacturers unless otherwise specified. Any parameters can be increased or decreased proportionally according to the actual situation.

[0032] Embodiment

[0033] This embodiment provides a wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite, including preparing an MPCF preform by laying out and weaving mesophase pitch-based carbon fibers; chemically vapor depositing C MP / C reinforcement at 900 °C; performing high-temperature graphitization treatment at 3000 °C to prepare high-thermal conductivity C MP / C reinforcement material; polymer impregnation pyrolysis method is used to prepare a densified SiCN ceramic matrix in the reinforcement material, the pyrolysis temperature is 1100 °C, and the density of the densified composite material is 2.28 g / cm 3 ; annealing heat treatment process at 1500 °C is used to prepare wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material.

[0034] The preparation method includes the following steps:

[0035] S1: The mesophase pitch-based carbon fiber is used to obtain an MPCF preform with a fiber volume fraction of 40% through laying and weaving. After being repaired and leveled, the MPCF preform is placed in a chemical vapor deposition furnace for pyrolytic carbon deposition. Propane is used as the carbon source gas, and nitrogen is used as the dilution gas and protective gas. The deposition temperature is 900 °C, the deposition pressure is 1.0 kPa, and the deposition time is 50 h. The obtained C MP / C reinforcement material has a density of 1.0 g / cm 3 . Then the C MP / C reinforcement material is placed in a high-temperature graphitization furnace. Using argon as the protective atmosphere, the heat treatment temperature is 3000 °C, and the heat treatment time is 0.5 h, so as to obtain a C MP / C reinforcement material with ultra-high modulus and negative thermal expansion effect.

[0036] S2: The sample treated in S1 is processed into a sample with dimensions of 25×4×4 mm 3 . It is cleaned ultrasonically with alcohol, weighed after drying, and the sample is placed in an impregnation container and numbered; polysilazane (PSN) is added to the impregnation container to submerge the upper surface of the sample by 2 - 3 mm. The impregnation container is placed in a vacuum impregnation device, and the vacuum degree is controlled to be 0.08 - 0.1 MPa, and the vacuum impregnation time is controlled to be 8 h; the vacuum-impregnated sample is placed in a mold according to the number and cured in a constant-temperature oven for polysilazane, the curing temperature is controlled to be 200 °C, and the curing time is controlled to be 3.5 h. The cured sample is placed in a tube furnace for pyrolysis. Using argon (Ar) as the protective atmosphere, the argon flow rate is 1 L / min, the pyrolysis temperature is controlled to be 1100 °C, the heating rate is 5 °C / min, and the isothermal pyrolysis time is 2 h. Repeat the above impregnation and pyrolysis steps until the single weight gain rate is less than 1% and then stop, to obtain a densified C 3 with a density range of 2.28 g / cm MP / C-SiCN ceramic matrix composite material.

[0037] S3: The densified C MPThe C / SiCN ceramic matrix composite is placed in an annealing furnace for annealing heat treatment. Argon is used as the protective atmosphere, with an argon flow rate of 1 L / min. The annealing heat treatment temperature is controlled at 1500 °C, the heating rate is 5 °C / min, and the constant temperature annealing heat treatment time is 2 h.

[0038] In the embodiment of the present invention, the annealed C MP / C-SiCN ceramic matrix composite preparation process is as Figure 1 shown. Its SEM characterization Figure 2 shows that the fiber interface and the ceramic matrix of the densified sample are tightly combined and have a high density; Figure 3 shows that the C MP / C-SiCN ceramic matrix composite has a carbon phase, a Si3N4 phase and a SiC phase, proving the successful composite of SiCN ceramic and C MP / C materials; Figure 4 shows that the SiCN ceramic matrix mainly has a Si3N4 phase and a SiC phase; Figure 5 and Figure 6 are the reflection loss (RL) value diagram and impedance matching performance of the SiCN ceramic matrix prepared in this embodiment, proving that the prepared composite material has excellent wave absorption performance.

[0039] It should be noted that in addition to the parameters in the preparation process involved in the above embodiments, it is also feasible to select other preparation parameters.

[0040] The commonly understood meaning; the numerical values mentioned in the embodiments of the present invention are only exemplary in nature, and the remaining numerical values should also belong to the present invention; the steps involved in the embodiments of the present invention have no order, so changing the order of the steps also belongs to the scope of the present invention. It should be noted that unless otherwise specified, the professional terms involved in the present invention should be those of a technical worker in this field.

Claims

1. A wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material, characterized in that: Including C with a mesophase pitch-based carbon fiber as the skeleton MP / C reinforcement material and SiCN ceramic matrix; The said C MP / C reinforcing material is composed of mesophase pitch-based carbon fiber and pyrolytic carbon, and has ultra-high modulus and negative thermal expansion effect; The SiCN ceramic matrix is pyrolyzed from polysilazane and has wave absorption performance and positive expansion effect.

2. The near-zero expansion C according to claim 1 MP / C-SiCN ceramic matrix composite, characterized in that: The tensile strength of the mesophase pitch-based carbon fiber is 3.1 to 3.4 GPa, and the tensile modulus is 800 to 950 GPa. After the fibers are formed by unidirectional laying, two-dimensional weaving and / or three-dimensional weaving processes, a mesophase pitch-based carbon fiber preform with a volume fraction of 35 to 55% is obtained. Then, a C 3 / C reinforcement material with a density of about 1.0 to 1.5 g / cm MP is obtained; the SiCN ceramic is composed of free carbon, SiC, Si3N4 and the amorphous phase formed thereby.

3. A method for preparing the wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material as claimed in claim 1 or 2, characterized in that The following steps are adopted: S1: Prepare C / C reinforcement materials by using chemical vapor deposition and high-temperature graphitization processes. MP / C reinforcement materials; S2: Using the polymer impregnation pyrolysis method, prepare the SiCN ceramic matrix in the reinforcing material. S3: Adopt an annealing heat treatment process to reasonably regulate the crystallinity and dielectric properties of the SiCN ceramic matrix, thereby realizing the preparation and performance optimization of a wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material.

4. The wave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material preparation method, characterized in that The S1 step includes: The mesophase pitch-based carbon fiber is woven into a mesophase pitch-based carbon fiber preform by using a unidirectional laying, two-dimensional weaving, and / or three-dimensional weaving process. Different preform structures exhibit different thermal expansion anisotropies. The mesophase pitch-based carbon fiber preform is placed in a chemical vapor deposition furnace for pyrolytic carbon deposition. Natural gas or propane is used as the carbon source gas, and nitrogen is used as the diluent gas and protective gas. The deposition temperature is 900 - 1100 °C, the deposition pressure is 0.5 - 3 kPa, and the deposition time is 20 - 80 h. The obtained C MP / C reinforcement material has a density of 1.0 - 1.5 g / cm 3 ; then the C MP / C reinforcement material is placed in a high-temperature graphitization furnace. With argon as the protective atmosphere, the heat treatment temperature is 2000 - 3150 °C, and the heat treatment time is 0.5 - 2 h, thereby obtaining a C MP / C reinforcement material with ultra-high modulus and negative thermal expansion effect.

5. The microwave-absorbing near-zero expansion C MP / C-SiCN ceramic matrix composite material preparation method according to claim 3, characterized in that The S2 step includes: S201: Clean the C reinforcing material of S1, dry it, and place it in an impregnation container. Then, add polysilazane to the impregnation container to submerge the upper surface of the sample by 2 - 3 mm. Place the impregnation container in a vacuum impregnation device, control the vacuum degree to be 0.08 - 0.1 MPa, and control the vacuum impregnation time to be 6 - 8 h. Place the vacuum-impregnated sample in a mold and cure the polysilazane in a constant-temperature oven. The curing temperature is 100 - 250 °C, and the curing time is 3 - 4 h; MP / C reinforcing material is cleaned and dried, then placed in an impregnation container. Next, polysilazane is added to the impregnation container to submerge the upper surface of the sample by 2 - 3 mm. The impregnation container is placed in a vacuum impregnation device, with the vacuum degree controlled at 0.08 - 0.1 MPa and the vacuum impregnation time controlled at 6 - 8 h. The vacuum-impregnated sample is placed in a mold and cured for polysilazane in a constant-temperature oven. The curing temperature is 100 - 250 °C, and the curing time is 3 - 4 h; The molecular weight of the polysilazane is 3000 - 8000, and the kinematic viscosity is 200 - 2000 mPa·s. S202: Put the cured sample into a heat treatment furnace for ceramic pyrolysis, use argon for protection, the argon flow rate is 0.5 - 1 L / min, the pyrolysis temperature is 700 - 1500 °C, the heating rate is 5 °C / min, and the constant temperature pyrolysis time is 2 - 4 h. S203: Repeat the steps of S201 - S203 for the pyrolyzed sample until the single - weight gain rate is less than 1%, and the densified C MP / C - SiCN ceramic matrix composite has a density range of 2.0 - 2.4 g / cm 3 .

6. The preparation method of the near-zero expansion C MP / C-SiCN ceramic matrix composite material according to claim 3, characterized in that The step S3 includes: putting the densified C MP / C-SiCN ceramic matrix composite into an annealing furnace for annealing heat treatment, using argon as the protective atmosphere, with an argon flow rate of 0.5 - 1 L / min, controlling the annealing heat treatment temperature to be 1100 - 1700 °C, the heating rate to be 5 °C / min, and the constant-temperature annealing heat treatment time to be 1 - 10 h; The annealing process is used to regulate the thermal expansion coefficient and dielectric properties of the SiCN ceramic that are sensitive to crystallinity, thereby developing a C MP / C-SiCN ceramic matrix composite with both good near-zero expansion and wave absorption properties.

7. The application of the C described in any one of claims 1 to 6 MP / C-SiCN ceramic matrix composite material for achieving near-zero thermal expansion performance in the temperature range of -150 to 400 °C and the application of wave absorption of the device structure.

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