A polymer-derived C f -Si3N4 composite ceramic and its preparation method

Abstract

The present invention belongs to the technical field of the preparation of silicon nitride ceramic materials, and particularly relates to a polymer-derived C f -Si3N4 composite ceramic and a preparation method thereof. The preparation method of the polymer-derived C f -Si3N4 composite ceramic provided by the present invention adopts a polymer-derived combined with high temperature and high pressure method to prepare the composite ceramic. By designing the process of the precursor ceramic powder formed by the polymer, the present invention can effectively obtain an amorphous SiCN precursor at the micro-nano level; combining with the high temperature and high pressure technology can effectively promote the high temperature crystallization and densification of the polymer precursor ceramic. The above method provided by the present invention can not only realize the rapid preparation of the C f / Si3N4 composite ceramic, but also the prepared composite ceramic has excellent density, conductivity and mechanical properties, and is very suitable for preparing carbon-reinforced ceramic matrix composites, and has wide practical application value in the preparation and application fields of silicon nitride ceramic materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of preparation of silicon nitride ceramic materials, and particularly relates to a polymer-derived C f -Si3N4 composite ceramic and a preparation method thereof. Background Art

[0002] Si3N4 ceramics have excellent high-temperature strength, good oxidation resistance / thermal shock resistance, good thermal conductivity, high resistivity, low dielectric constant and other characteristics, and are considered to be emerging high-temperature structural functional materials. However, when the temperature is higher than 1500 °C, the high-temperature strength, conductivity and other properties of Si3N4 ceramics will degenerate significantly, which greatly limits their industrial applications. Under ideal processes, preparing short carbon fiber (C f ) reinforced ceramic matrix composites can significantly improve the high-temperature strength, toughness and creep resistance of single-phase ceramics, and at the same time have the advantages of low density, etc., which has attracted extensive attention of researchers at home and abroad. However, the main dilemma faced by the existing technologies is that there is still a lack of reliable and convenient preparation methods to obtain high-performance C f / Si3N4 composite ceramic materials.

[0003] The polymer precursor method is a process for preparing ceramic materials by using polymer precursor conversion. The converted ceramic materials are called polymer precursor ceramics (PDC), which are usually composed of an amorphous matrix of Si-C-N(O) tetrahedra and free carbon. The typical processes of this method include the crosslinking, inorganicization and crystallization processes of polymer precursors; the crosslinking process makes the polymer precursor macromolecular chains grow or form a network structure to improve thermal stability, ceramic yield and densification. The corresponding crosslinking methods include thermal crosslinking, high-energy electron beam / ray crosslinking, chemical crosslinking, etc.; the inorganicization process refers to the slow cracking of macromolecular chains to transform into amorphous inorganic materials, which includes chain breaking, discharge of low-molecular-weight polymers and small-molecule gases, etc.; the high-temperature crystallization process will improve the densification of the ceramic matrix and enhance the mechanical properties of the material.

[0004] Although the polymer precursor method can realize the preparation of ceramic materials, there are usually many pores generated inside the prepared ceramics, which affect the overall performance of the materials. At present, the commonly used methods to improve the material densification include repeated impregnation and hot pressing processes, etc.; however, the repeated impregnation densification method not only has a long cycle, but also the prepared ceramics have a large and uneven porosity; the hot pressing method is a method of sintering a green body with sinterability at high temperature (usually at the MPa level) into a ceramic, which has the advantages of low cost, simple equipment, convenient operation, etc., but its improvement of densification is limited. In particular, taking the atmospheric pressure or hot pressing crystallization of the polymer precursor SiCN ceramic as an example, both of them will produce SiC / Si3N4 composites, which will not only affect the high-temperature performance of the precursor ceramics, but also be unfavorable for the in-depth exploration of the mechanism.

[0005] Therefore, we seek a more suitable C f A method for preparing a Si3N4 composite ceramic material to enhance the density of the ceramic material and improve the performance of the composite material is a technical problem to be solved urgently in the present invention. Summary of the invention

[0006] In order to solve the above-mentioned shortcomings of the prior art, the first object of the present invention is to provide a polymer derived C f -The preparation method of Si3N4 composite ceramics, which adopts polymer derivatization combined with high temperature and high pressure method to prepare composite ceramics, not only has a simple process and is easy to realize rapid sintering preparation of composite ceramics, but also can effectively improve the density, electrical conductivity and mechanical properties of the material, and is very suitable for preparing carbon-reinforced ceramic-based composite materials.

[0007] The second object of the present invention is to provide a polymer derived C f -Si3N4 composite ceramics have a high density, and the Si3N4 phase contains graphite flakes, which can effectively improve the electrical conductivity and mechanical properties of the composite ceramics, making it suitable for use as a high-performance ceramic material.

[0008] In order to achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A polymer derived C f -A method for preparing Si3N4 composite ceramics, comprising the following steps:

[0010] (1) Preparation of amorphous SiCN ceramic powder: mixing a polysilazane precursor and a thermosetting agent under a protective atmosphere to obtain a mixture; thermally curing the mixture at a temperature of 110 to 200° C. under vacuum conditions to obtain a cured product; pyrolyzing the cured product at a temperature of 1000 to 1300° C. under a protective atmosphere to obtain a precursor ceramic; ball milling the precursor ceramic to obtain a micro-nano-level amorphous SiCN ceramic powder;

[0011] (2)C f Preparation of -Si3N4 composite ceramics: The amorphous SiCN ceramic powder obtained in step (1) is pre-pressed and then sintered at high temperature and high pressure to obtain a polymer-derived C f -Si3N4 composite ceramics; the high temperature and high pressure sintering pressure is 5 to 6 GPa and the temperature is 1300 to 1500°C.

[0012] As a further solution, in step (1), the structural formula of the polysilazane precursor is Wherein, in the structural formula, x is 0.2 and y is 0.8.

[0013] As a further solution, in step (1), the thermosetting agent is dicumyl peroxide; the dosage of the thermosetting agent is 1% - 2% of the mass of the polysilazane precursor.

[0014] As a further solution, in step (1), the time for thermosetting is 3 - 4 h.

[0015] There are obvious differences in the microstructures of the SiCN ceramic powders obtained at different pyrolysis temperatures, and it will have an obvious impact on the structures and properties of the subsequent C f -Si3N4 ceramics. Therefore, it is necessary to control the pyrolysis temperature and time. As a further solution, in step (1), the time for pyrolysis is 3 - 6 h.

[0016] As a further solution, in step (1), the time for ball milling is 1 - 2 h; the ratio of material to ball for ball milling is 1:1. Further, the temperature for ball milling is room temperature (10 - 30 °C).

[0017] As a further solution, in step (1), the protective atmosphere is nitrogen.

[0018] As a further solution, in step (2), the pressure for pre - pressing is 5 - 6 MPa, and the time is 1 - 3 min. The temperature for pre - pressing is room temperature (10 - 30 °C).

[0019] As a further solution, in step (2), the time for high - temperature and high - pressure sintering is 10 - 30 min.

[0020] A polymer - derived C f -Si3N4 composite ceramic prepared by the above - mentioned preparation method.

[0021] As a further solution, the phase of the polymer - derived C f -Si3N4 composite ceramic is crystalline Si3N4 and contains graphite flake phase.

[0022] Compared with the prior art, the outstanding advantages of the present invention are:

[0023] The polymer - derived C fPreparation method of C / Si3N4 composite ceramics, which combines polymer-derived and high-temperature high-pressure methods to prepare composite ceramics. Specifically, the preparation method of the present invention includes the following key steps. First, by specifically selecting polymer precursors, a polysilazane precursor containing specific elements and functional groups is obtained to ensure the performance required for the final composite ceramics. Subsequently, the polymer precursor is pyrolyzed under high-temperature conditions to transform it into amorphous ceramic powder. During the pyrolysis process, by precisely controlling process parameters such as temperature and atmosphere, the amorphous phase composition and microstructure required subsequently can be obtained. The next step is the key operation of densifying the amorphous ceramic powder into composite ceramics. High-temperature high-pressure technology is applied to provide a pressure of GPa level, promoting the high-temperature crystallization and densification of polymer precursor ceramics. The application of pressure promotes atomic rearrangement and particle bonding, which are tightly combined through the above steps, thereby synergistically improving the density, mechanical properties, and electrical conductivity of the composite ceramics. In addition, the high-temperature conditions during the densification process also contribute to the formation of the required crystalline phase.

[0024] The above method provided by the present invention can effectively obtain micro-nano level amorphous SiCN precursors by designing the process of polymer-derived precursor ceramic powder; combining high-temperature high-pressure technology can effectively promote the high-temperature crystallization and densification of polymer precursor ceramics, thereby realizing the rapid preparation of C / Si3N4 composite ceramics. In the method of the present invention, high-temperature high-pressure rapid sintering technology is adopted, and appropriate temperature and pressure parameters can ensure that the ceramics can quickly reach a dense state, while preventing damage to the material caused by excessive high temperature and high pressure. Moreover, the rapid sintering method of the present invention significantly shortens the sintering time, effectively reduces the energy consumption and manufacturing cost during the preparation process, and can make up for the deficiencies of the existing preparation methods of C / Si3N4 composite ceramics. f / Si3N4 composite ceramics. f

[0025] Especially, the C / Si3N4 composite ceramics prepared by the above method of the present invention can effectively improve the density, electrical conductivity, and mechanical properties of the material, and are very suitable for preparing carbon-reinforced ceramic matrix composites, and have high practical application value in a wide range of fields such as aerospace, electronics, and energy storage. f Description of the Drawings

[0026] Figure 1 XRD pattern of the amorphous SiCN ceramic powder obtained in step (1) of Example 1 of the present invention;

[0027] Figure 2 XRD pattern of the C / Si3N4 composite ceramics obtained in step (2) of Example 1 of the present invention; f

[0028] Figure 3C prepared in step (2) of Example 1 of the present invention f Raman spectra of the C / Si3N4 composite ceramics Detailed implementation manners

[0029] The technical solutions and effects of the present invention will be further described below in conjunction with the detailed implementation manners and the drawings. The following description is only for explaining the present invention and should not be construed as a limitation to the protection scope of the present invention. Unless otherwise specified in the following embodiments, the used methods are all conventional methods in the art. The materials used in the following embodiments, unless otherwise specified, are all conventional materials in the art and can be obtained from commercial channels.

[0030] Among them, in the following embodiments, the structural formula of the polysilazane precursor involved is x = 0.2, y = 0.8, from the Institute of Chemistry, Chinese Academy of Sciences; the thermosetting agent is dicumyl peroxide, from Sigma-Aldrich.

[0031] I. Embodiments

[0032] Example 1

[0033] This example provides a polymer-derived C f -Si3N4 composite ceramic, and its preparation method is specifically as follows:

[0034] (1) Preparation of amorphous SiCN ceramic powder:

[0035] (a) Under nitrogen protection, the polysilazane precursor is mixed with the thermosetting agent dicumyl peroxide (DP) to obtain a mixture; the dosage of the thermosetting agent is 1% of the mass of the polysilazane precursor; (b) Under vacuum conditions, the mixture obtained in step (a) is thermally cured at 110 °C for 4 h to obtain a cured product; (c) Under nitrogen protection, the cured product obtained in step (b) is pyrolyzed in a tubular furnace at 1000 °C for 4 h to obtain a precursor ceramic; (d) The precursor ceramic obtained in step (c) is ball-milled at room temperature for 1 hour (ball-to-material ratio = 1:1) using high-energy ball milling to obtain micro-nano amorphous SiCN ceramic powder.

[0036] (2) Preparation of C f -Si3N4 composite ceramic:

[0037] The amorphous SiCN ceramic powder obtained in step (1) is pre-pressed (5 MPa, time is 1 min) into a mold and then assembled using a high-temperature and high-pressure sintering component; then the assembled block is placed in a six-sided fixed press (CS-1B type, Guilin, China) for high-temperature and high-pressure sintering. The pressure of the high-temperature and high-pressure sintering is 5 GPa, the temperature is 1400 °C, and the sintering time is 30 min, and then it is cooled to obtain the polymer-derived C of this example f-Si3N4 composite ceramic.

[0038] Specifically, for the convenience of subsequent performance testing of the ceramic, when this step is specifically implemented, a composite ceramic with a specific size is prepared. In other embodiments, the size of the composite ceramic can be set as needed. The specific operation of this step is as follows: Pre-press the obtained amorphous SiCN ceramic powder into a cylinder with a diameter of 10 mm and a height of 6 mm; Assemble the pre-pressed cylinder using a high-temperature and high-pressure sintering assembly; Then place the assembled block in a six-sided fixed press (CS-1B type, Guilin, China) for sintering. The sintering conditions are a pressure of 5 GPa, a temperature of 1400 °C, and a sintering time of 30 min. After sintering, cool it to obtain a polymer-derived C f -Si3N4 composite ceramic, denoted as C f -Si3N4-1400 composite ceramic.

[0039] Example 2

[0040] This example provides a polymer-derived C f -Si3N4 composite ceramic, and the specific steps of its preparation method are as follows:

[0041] (1) Preparation of amorphous SiCN ceramic powder:

[0042] (a) Under nitrogen protection, mix the polysilazane precursor with the thermosetting agent dicumyl peroxide (DP) to obtain a mixture; The dosage of the thermosetting agent is 1% of the mass of the polysilazane precursor; (b) Under vacuum conditions, thermally cure the mixture obtained in step (a) at 110 °C for 4 h to obtain a cured product; (c) Under nitrogen protection, pyrolyze the cured product obtained in step (b) in a tubular furnace at 1000 °C for 4 h to obtain a precursor ceramic; (d) Use high-energy ball milling to ball mill the precursor ceramic obtained in step (c) at room temperature for 1 hour (ball-to-material ratio = 1:1) to obtain micro-nano amorphous SiCN ceramic powder.

[0043] (2) Preparation of C f -Si3N4 composite ceramic:

[0044] Pre-press the amorphous SiCN ceramic powder obtained in step (1) with a mold (5 MPa, time 1 min) into a shape and then perform high-temperature and high-pressure sintering (pressure 5 GPa, temperature 1500 °C, sintering time 30 min), and then cool it to obtain the polymer-derived C f -Si3N4 composite ceramic of this example.

[0045] Specifically, for the convenience of subsequent performance testing of the ceramic, when this step is specifically implemented, a composite ceramic with a specific size is prepared. In other embodiments, the size of the composite ceramic can be set as required. The specific operation of this step is as follows: The amorphous SiCN ceramic powder obtained above is pre-pressed into a cylinder with a diameter of 10 mm and a height of 6 mm; the pre-pressed cylinder is assembled using a high-temperature and high-pressure sintering assembly; then the assembled block is placed in a six-sided fixed press (CS-1B type, Guilin, China) for sintering. The sintering conditions are a pressure of 5 GPa, a temperature of 1500 °C, and a sintering time of 30 min. After sintering, it is cooled to obtain a polymer-derived C f -Si3N4 composite ceramic, denoted as C f -Si3N4-1500 composite ceramic.

[0046] II. Comparative Examples

[0047] Comparative Example 1

[0048] This comparative example provides a polymer-derived composite ceramic, and its preparation method is basically the same as that of Example 1, except that in step (2), the ceramic is sintered at normal pressure, the same temperature, and the same time. The specific process and conditions are as follows:

[0049] (1) Preparation of amorphous SiCN ceramic powder:

[0050] (a) Under nitrogen protection, a polysilazane precursor is mixed with a thermosetting agent dicumyl peroxide (DP) to obtain a mixture; the amount of the thermosetting agent is 1% of the mass of the polysilazane precursor; (b) Under vacuum conditions, the mixture obtained in step (a) is thermally cured at 110 °C for 4 h to obtain a cured product; (c) Under nitrogen protection, the cured product obtained in step (b) is pyrolyzed in a tubular furnace at 1000 °C for 4 h to obtain a precursor ceramic; (d) The precursor ceramic obtained in step (c) is ball-milled at room temperature for 1 hour (ball-to-material ratio = 1:1) using high-energy ball milling to obtain a micro-nano amorphous SiCN ceramic powder.

[0051] (2) The amorphous SiCN ceramic powder obtained above is pre-pressed (1 min) into a cylinder with a diameter of 10 mm and a height of 6 mm at room temperature and a pressure of 5 MPa; the pre-pressed cylinder is sintered at a high temperature in a tubular furnace, and the sintering temperature is 1400 °C and the holding time is 30 min.

[0052] Comparative Example 2

[0053] This comparative example provides a polymer-derived composite ceramic, and its preparation method is basically the same as that of Example 1, except that in step (2), the ceramic is sintered at normal pressure, the same temperature, and different times. The specific process and conditions are as follows:

[0054] (1) Preparation of amorphous SiCN ceramic powder:

[0055] (a) Under nitrogen protection, mix the polysilazane precursor with the thermosetting agent dicumyl peroxide (DP) to obtain a mixture; the dosage of the thermosetting agent is 1% of the mass of the polysilazane precursor; (b) Under vacuum conditions, thermally cure the mixture obtained in step (a) at 110 °C for 4 h to obtain a cured product; (c) Under nitrogen protection, pyrolyze the cured product obtained in step (b) in a tubular furnace at 1000 °C for 4 h to obtain a precursor ceramic; (d) Use high-energy ball milling to ball mill the precursor ceramic obtained in step (c) at room temperature for 1 hour (ball-to-material ratio = 1:1) to obtain amorphous SiCN ceramic powder at the micro-nano level.

[0056] (2) Pre-press the amorphous SiCN ceramic powder obtained above at room temperature and a pressure of 5 MPa (for 1 min) into a cylinder with a diameter of 10 mm and a height of 6 mm; sinter the pre-pressed cylinder in a tubular furnace at a high temperature of 1400 °C for a holding time of 4 h.

[0057] Comparative Example 3

[0058] This comparative example provides a polymer-derived composite ceramic, and its preparation method is the same as that of Example 2, except that in step (2), ceramic sintering is carried out at normal pressure, the same temperature, and different times. The specific process and conditions are as follows:

[0059] (1) Preparation of amorphous SiCN ceramic powder:

[0060] (a) Under nitrogen protection, mix the polysilazane precursor with the thermosetting agent dicumyl peroxide (DP) to obtain a mixture; the dosage of the thermosetting agent is 1% of the mass of the polysilazane precursor; (b) Under vacuum conditions, thermally cure the mixture obtained in step (a) at 110 °C for 4 h to obtain a cured product; (c) Under nitrogen protection, pyrolyze the cured product obtained in step (b) in a tubular furnace at 1000 °C for 4 h to obtain a precursor ceramic; (d) Use high-energy ball milling to ball mill the precursor ceramic obtained in step (c) at room temperature for 1 hour (ball-to-material ratio = 1:1) to obtain amorphous SiCN ceramic powder at the micro-nano level.

[0061] (2) Pre-press the amorphous SiCN ceramic powder obtained above at room temperature and a pressure of 5 MPa (for 1 min) into a cylinder with a diameter of 10 mm and a height of 6 mm; sinter the pre-pressed cylinder in a tubular furnace at a high temperature of 1500 °C for a holding time of 4 h.

[0062] Comparative Example 4

[0063] This comparative example provides a Si3N4 ceramic, which is the Si3N4 ceramic in "Zheng Youjin, Wang Junnan, Zhou Zhenxiang, et al. High-pressure synthesis and properties of high thermal conductivity Si3N4 ceramics [J]. Journal of Synthetic Crystals, 2019, 48(06): 1111-1115" in the prior art.

[0064] Comparative Example 5

[0065] This comparative example provides a SiCN ceramic, which is a ceramic prepared at high temperature under atmospheric pressure. Specifically, it is the SiCN ceramic in "Klausmann A, Morita K, Johanns K E, et al. Synthesis and high-temperature evolution of polysilylcarbodiimide-derived SiCN ceramic coatings [J]. Journal of the European Ceramic Society, 2015, 35(14): 3771-3780." in the prior art.

[0066] III. Test Examples

[0067] Test Example 1 Physical Property Test

[0068] The amorphous SiCN ceramic powder obtained in step (1) of Example 1 of the present invention was characterized by X-ray diffraction (XRD), and the results are as Figure 1 shown. Figure 1 The XRD analysis results confirm that the SiCN ceramic powder prepared in the present invention is indeed amorphous.

[0069] Furthermore, the C f / Si3N4 composite ceramic prepared by high-temperature and high-pressure sintering in step (2) of Example 1 of the present invention was characterized by X-ray diffraction (XRD), and the results are as Figure 2 shown. It can be Figure 2 seen that the composite ceramic has changed from the original amorphous state to a crystalline state, and the phase is Si3N4.

[0070] The C f / Si3N4 composite ceramic prepared by high-temperature and high-pressure sintering in step (2) of Example 1 of the present invention was characterized by Raman spectroscopy (Raman), and the results are as Figure 3 shown. Figure 3 It is confirmed that graphite platelet phase precipitates in the composite ceramic prepared in the present invention.

[0071] Therefore, the XRD and Raman results comprehensively confirm that the present invention realizes the rapid preparation of C f / Si3N4 composite ceramic by polymer-derived coupling high-temperature and high-pressure method.

[0072] Test Example 2 Performance Test

[0073] Performance index tests were conducted on the ceramic materials of the same specification prepared in Example 1 of the present invention and Comparative Examples 1-3.

[0074] Among them, the method used for density testing was the Archimedes drainage method. During the test, the mass of the dried specimen in air g, the weight of the specimen saturated with liquid in air g1, the floating weight of the specimen saturated with liquid in the liquid g2, and the density of the liquid r were measured respectively, and the density ρ of the sample was calculated according to the calculation formula ρ = rg / (g1 - g2).

[0075] The conductivity was calculated by combining the resistance and dimensions of the sample. The DC resistance was measured using a Keithley 2002 digital multimeter from the United States, while the high-resistance samples were recorded using a Keithley 2450 SourceMeter Unit to record the current-voltage relationship, and then the conductivity was calculated.

[0076] Hardness test and elastic modulus test: The hardness and elastic modulus of the samples were measured by nanoindentation. Nine points were measured for each sample, and five effective points were taken and averaged. Since the surface roughness affected the accuracy of the data, the samples were polished before the test. Through the above test methods, performance parameters such as density, conductivity, hardness, and elastic modulus related to the examples of the present invention were obtained. These parameters are very important for evaluating the characteristics and application potential of the materials.

[0077] The test results of the above indicators are shown in Table 1. Among them, Comparative Examples 4 and 5 are the data recorded in the prior art. "-" indicates that this test was not conducted.

[0078] Table 1

[0079]

[0080]

[0081] As can be seen from Table 1, compared with the SiCN ceramic materials (Comparative Examples 1-3) sintered at the same temperature under normal pressure, the density of the high-temperature and high-pressure sintered SiCN ceramic materials prepared in Example 1 of the present invention increased significantly, from no more than 2.30 g·cm -2 increasing to 2.75 g·cm -2 , indicating that the high-temperature and high-pressure conditions have an obvious promoting effect on the densification of polymer precursor ceramics. In addition, with the increase in density, the electrical and mechanical properties have also been significantly improved.

[0082] In terms of electrical properties, the high-temperature and high-pressure sintered SiCN ceramic material (phase: C f / Si3N4) prepared in Example 1 of the present invention has a conductivity of 2.78E-1 S / cm, which is more than 20 times higher than that of the SiCN ceramic material (Comparative Example 2) prepared at the same temperature under atmospheric pressure (1.01E-2 S / cm). This indicates that the SiCN ceramic sintered under high-temperature and high-pressure conditions has better electrical conductivity, which may be attributed to the promotion of the formation and arrangement of crystals by the action of high pressure, and at the same time promotes the precipitation and graphitization of free carbon, thus improving the conductivity.

[0083] At the same time, in terms of mechanical properties, the SiCN ceramic material obtained by high-temperature and high-pressure sintering exhibits excellent hardness and elastic modulus. The hardness reaches 21.5 GPa and the elastic modulus is 218.0 GPa, which are higher than those of the Si3N4 material (Comparative Example 4) sintered at high temperature and high pressure directly using silicon nitride powder (α-Si3N4, β-Si3N4) and the SiCN ceramic material prepared by high-temperature under atmospheric pressure (Comparative Example 5). These superior mechanical properties illustrate the improvement in the structure and composition of the high-temperature and high-pressure sintered SiCN ceramic material.

[0084] In summary, the present invention solves the problems of low density, average electrical properties and mechanical properties of the SiCN ceramic material prepared under atmospheric pressure in the prior art. By designing the process of the precursor ceramic powder formed by the polymer, the present invention can effectively obtain an amorphous SiCN precursor at the micro-nano level; combined with the high-temperature and high-pressure technology, it can effectively promote the high-temperature crystallization and densification of the polymer precursor ceramic, and can significantly improve the density, electrical properties and mechanical properties of the SiCN ceramic material. Therefore, the method of the present invention has good application prospects and can play an important role in the fields of electronics, energy, etc.

Claims

1. A preparation method of a polymer-derived C f -Si3N4 composite ceramic, characterized in that It includes the following steps: (1) Preparation of amorphous SiCN ceramic powder: Under a protective atmosphere, a polysilazane precursor is mixed with a thermosetting agent to obtain a mixture; under vacuum conditions, the mixture is thermally cured at a temperature of 110 - 200 °C to obtain a cured product; under a protective atmosphere, the cured product is pyrolyzed at a temperature of 1000 - 1300 °C to obtain a precursor ceramic; the precursor ceramic is ball-milled to obtain amorphous SiCN ceramic powder at the micro-nano level; the structural formula of the polysilazane precursor is Wherein, in the structural formula, x is 0.2 and y is 0.8; the thermosetting agent is dicumyl peroxide; the dosage of the thermosetting agent is 1% - 2% of the mass of the polysilazane precursor; (2)C f Preparation of C-Si3N4 composite ceramics: The amorphous SiCN ceramic powder obtained in step (1) is pre-pressed and then sintered at high temperature and high pressure to obtain polymer-derived C-Si3N4 composite ceramics; f the pressure of the high temperature and high pressure sintering is 5-6 GPa, the temperature is 1300-1500 °C; the time of the high temperature and high pressure sintering is 10-30 min; The polymer-derived C f -Si3N4 composite ceramic has a crystalline Si3N4 phase and contains graphite platelet phases.

2. The preparation method of the polymer-derived C f -Si3N4 composite ceramic, characterized in that In step (1), the time for thermal curing is 3 to 4 h; the time for pyrolysis is 3 to 6 h.

3. The preparation method of the polymer-derived C f -Si3N4 composite ceramic, characterized in that, In step (1), the time for ball milling is 1 to 2 h; the ball-to-material ratio for ball milling is 1:

1.

4. The preparation method of the polymer-derived C f -Si3N4 composite ceramic, characterized in that In step (1), the protective atmosphere is nitrogen or helium.

5. The preparation method of the polymer-derived C f -Si3N4 composite ceramic according to any one of claims 1 to 4, characterized in that In step (2), the pressure for pre-pressing is 5 to 6 MPa, and the time is 1 to 3 min.

6. A polymer-derived C f -Si3N4 composite ceramic prepared by the preparation method according to any one of claims 1 to 5.

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