A silicon carbide fiber-reinforced silicon nitride-silicon carbide ceramic matrix composite and a method of making the same

Abstract

The application provides a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material and a preparation method thereof. Phenolic resin, multilayer graphite and hexagonal boron nitride are mixed, and then a PF-MLGs-MBN slurry A is obtained through three-roll differential grinding treatment. Silicon powder and nickel nitrate hexahydrate are mixed to obtain powder B. Then, the powder B and the slurry A are fully mixed again through a TRM process to obtain slurry C. The slurry C is coated on a SiC fiber cloth to perform multilayer stacking to form a blank and is dried to obtain a formed blank D. The blank D is carbonized at low temperature under vacuum; then, N2 is introduced to nitride at medium temperature; finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material is prepared through sintering at high temperature and high pressure. The product has excellent electromagnetic wave absorption performance on the basis of high mechanical strength, and can meet the key requirements of structure-function integrated materials in the fields of aerospace and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ceramic composite materials, and particularly relates to a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material and a preparation method thereof. BACKGROUND

[0002] The silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material combines the high-temperature resistance and high hardness of silicon carbide ceramic and the thermal shock resistance and fracture toughness of silicon nitride ceramic, and has a comprehensive performance far superior to single ceramic and traditional SiC / SiC composite material under extreme high-temperature alternating load, and is a key structural material for high-end equipment such as aerospace engine hot end components (combustion chamber, turbine blade) and nuclear device cladding. f The material solves the problems of poor thermal shock resistance of single silicon carbide and insufficient high-temperature strength of pure silicon nitride through silicon carbide fiber toughening and composite matrix synergistic effect, and provides support for long-term reliable service of high-end equipment under high-temperature complex working conditions.

[0003] However, its industrialization and engineering application faces multiple bottlenecks: first, the composite matrix preparation process is limited, and the reaction sintering method needs to strictly control the atmosphere and temperature, which is easy to cause uneven composition of the matrix and generate pores and cracks; although the chemical vapor deposition method can densify the matrix, the preparation period is as long as several months, and it is difficult to uniformly coat the fibers and easy to form interface defects. Second, the fiber-matrix interface regulation is difficult, because of the difference in thermal expansion coefficient and chemical compatibility between the two, the interface is easy to generate transition phase (SiO2, Si3N4-C solid solution), and if the combination is too strong, the fracture toughness will be reduced and brittle fracture will be caused, and if the combination is too weak, the load transfer will be invalid and the fiber-matrix will be peeled off. Third, the long-term service stability is insufficient, and in the high-temperature oxidation and complex medium environment, silicon nitride is easy to react with oxygen and water vapor to generate volatile SiO2, which causes the matrix to be loose, the interface is easy to be oxidized and eroded, the microcrack propagation is aggravated, the mechanical properties are sharply attenuated, and it is difficult to meet the service demand of tens of thousands of hours of high-end equipment.

[0004] Therefore, it is of great significance to develop a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material and a preparation method thereof which can solve the defects of existing preparation process, realize accurate interface regulation and improve the long-term service stability of the material, and promote the large-scale application of advanced ceramic matrix composite materials in the field of high-end equipment. SUMMARY

[0005] In view of the above problems in the prior art, the present application provides a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material and a preparation method thereof. A three-roll grinding (TRM) technology is used to perform exfoliation treatment on a phenolic resin (PF), multi-layer graphite and hexagonal boron nitride (h-BN) mixed system, two-dimensional multi-layer graphene / multi-layer boron nitride microsheet (2D MLGs / MBNs) is introduced, and through subsequent multi-stage temperature control reaction in a vacuum-nitrogen atmosphere, in-situ catalytic conversion synthesis of "zero-dimensional silicon carbide particle / nickel silicide particle + one-dimensional silicon carbide whisker / silicon nitride whisker" (0D SiC p / Ni x Si y +1D SiC w / Si3N 4w ) and other multi-component reinforcing phases is performed, and at the same time, a silicon carbide (SiC) fiber cloth lamination and high-temperature sintering densification process is combined, so that the mechanical strength and structural stability of the silicon nitride-silicon carbide ceramic matrix are effectively improved. The synergistic effect of the multi-component reinforcing phases can precisely control the electromagnetic properties of the ceramic matrix, so that the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material has excellent mechanical strength and electromagnetic absorption performance, and is suitable for structural-functional integrated application scenarios of high-end equipment.

[0006] To achieve the above-mentioned purpose, the present application provides the following specific technical solutions:

[0007] A preparation method of a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material, comprising:

[0008] After the phenolic resin, the multi-layer graphite and the hexagonal boron nitride are stirred and mixed, they are placed in a three-roll grinding machine for exfoliation to obtain a first mixture with multi-layer graphene and multi-layer boron nitride microsheet;

[0009] Silicon powder and nickel nitrate hexahydrate are wet ball milled, dried and sieved to obtain a second mixture;

[0010] After the first mixture and the second mixture are stirred and mixed, they are further mixed in a three-roll grinding machine to obtain a third mixture;

[0011] The third mixture is coated on a silicon carbide fiber cloth, and is stacked in a laminated manner, and after drying and shaping, a green body is obtained;

[0012] The shaped body is placed in a hot pressing furnace, first kept in a vacuum environment and pressurized to 25-35 MPa and pressure maintained for 10-20 min; then the pressure is reduced to 10-20 MPa, the temperature is raised from room temperature to 600-800°C at a rate of 50-100°C / min, and then raised to 900-1100°C at a rate of 20-80°C / min for 20-40 min; then raised to 1350-1420°C at a rate of 20-80°C / min for 1-3 h; then the vacuum environment is switched to a nitrogen atmosphere, and the pressure is maintained at 10-20 MPa, and the shaped body is further heated at 1350-1420°C for 1-3 h, then heated to 1450-1550°C at a rate of 5-20°C / min and maintained for 1-3 h; continue to pressurize to 45-55 MPa, and heat to 1800-1900°C at a rate of 20-80°C / min and maintain for 20-40 min; finally, natural slow cooling and slow release of pressure to obtain the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material.

[0013] Specifically, S1) first keep the vacuum environment and pressurize to 25-35 MPa and maintain the pressure for 10-20 min to ensure that the third mixture in the middle is fully diffused to each interface of the SiC fiber; then the pressure is reduced to 10-20 MPa, the temperature is raised from room temperature to 600-800°C at a rate of 50-100°C / min, and then raised to 900-1100°C at a rate of 20-80°C / min for 20-40 min to completely pyrolyze PF into residual carbon; then raised to 1350-1420°C at a rate of 20-80°C / min for 1-3 h, the Si and C in the body react to form a SiC layer, and under the action of external pressure and thermal stress, the SiC layer is broken into zero-dimensional SiC particles (0D SiC p ) and the carbonization of the body is completed;

[0014] S2) then the vacuum environment is switched to a nitrogen atmosphere, and the pressure is maintained at 10-20 MPa, and the shaped body is heated at 1350-1420°C for 1-3 h, then heated to 1450-1550°C at a rate of 5-20°C / min and maintained for 1-3 h, the free Si in the body is fully nitrided into one-dimensional silicon nitride whiskers (1D Si3N 4w ) and Si3N4 particles (Si3N 4p), the green body is nitrided to obtain a carbonized and nitrided green body; the pressure is continuously increased to 45-55 MPa, the temperature is increased to 1800-1900°C at a rate of 20-80°C / min and the temperature is maintained for 20-40 min, so that the carbonized and nitrided green body is sintered at high temperature, and the phase transition process of α-Si3N4 to β-Si3N4 occurs at the same time of the densification of SiC particles and whiskers, Si3N4 particles and whiskers, MLGs and MBNs and SiC fibers; finally, the temperature is slowly decreased and the pressure is slowly released, to obtain the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material.

[0015] In the S1) process, the PF pyrolysis also produces reducing gases such as CH4, CO and C2H4, which reduce the Ni(NO3)2·6H2O to zero-dimensional Ni element, and then the Ni and Si form zero-dimensional nickel silicide (0D Ni x Si y In combination with the reducing gas and SiO gas phase, one-dimensional silicon carbide whiskers (1D SiC x Si y The 1D SiC w ) organization is produced by the VLS (gas-liquid-solid) mechanism, which optimizes the mechanical strength and electromagnetic wave absorption performance of the composite material matrix itself.

[0016] In the S2), the purity of N2 is ≥99.999%, and the purpose of maintaining the shaped green body at 1350-1420°C for 1-3 h is to pre-nitride the free Si in the carbonized green body to prevent the flow of silicon and black core phenomenon. The operation of switching the vacuum environment to N2 realizes the rationality and controllability of the segmented full reaction of the carbonization and nitridation of the green body.

[0017] Further, the mass ratio of the phenolic resin, the multi-layer graphite and the hexagonal boron nitride is 100:1-4:5-20.

[0018] Specifically, the multi-layer graphite is expanded graphite or flaky graphite.

[0019] Specifically, the mass ratio of the phenolic resin, the multi-layer graphite and the hexagonal boron nitride is preferably 100:2-4:5-8; more preferably 100:4:8.

[0020] Specifically, the phenolic resin serves as a carbon source supply agent, a green body binder and a viscous stripping agent for three-roll grinding, and one dose serves multiple purposes, and the residual carbon content is 40-50 wt.%. The purity of the expanded graphite is 99%, and the particle size is 1-2 mm. The purity of the flaky graphite is ≥99.9 wt.%, and the particle size is ≤100 μm. The purity of the hexagonal boron nitride is ≥99.7%, and the particle size is ≤100 μm.

[0021] Further, the mass ratio of the silicon powder and the nickel nitrate hexahydrate is 100:0.1-3.

[0022] Specifically, the purity of the silicon powder is ≥99wt.%, and the particle size is ≤13μm. The nickel nitrate hexahydrate is used as the catalyst, and the purity is ≥99wt.%.

[0023] Further, the mass ratio of the silicon powder in the second mixture to the first mixture is 100:50-70.

[0024] Further, the temperature for stirring and mixing the phenolic resin, the multi-layer graphite and the hexagonal boron nitride is 40-60℃.

[0025] Further, the wet ball milling is performed with alcohol as the solvent, and the time is 1h-3h; the alcohol is dried in an oven at 50-80℃, and the sieving is performed through a 200-500 mesh sieve.

[0026] Further, the conditions for drying and shaping are drying at 80-100℃ for 2-4h.

[0027] Further, the process parameters of the three-roll grinding process are as follows: the speed ratio between the rollers is feed roller:center roller:discharge roller=1-2:3-5:8-10, the speed is set to 200-400rpm corresponding to the discharge roller, the first gap between the center roller and the feed roller is always greater than the second gap between the center roller and the discharge roller; the peeling further comprises: first, the first gap is 22-26μm, the second gap is 10-14μm, and the cycle peeling is performed for 3-6 times; then, the first gap is 10-14μm, the second gap is 4-8μm, and the cycle peeling is performed for 3-6 times; then, the first gap is 4-8μm, the second gap is 2-3μm, and the cycle peeling is performed for 3-6 times; finally, the first gap is 2-3μm, the second gap is 1-1.9μm, and the cycle peeling is performed for 3-6 times, a total of 12-24 times.

[0028] Further, the parameters for further mixing are as follows: the speed ratio between the rollers is feed roller:center roller:discharge roller=1:3:9, the speed is set to 200-400rpm corresponding to the discharge roller, the roller gap is always kept at 13-16μm, and the mixing is performed for 10-25 times.

[0029] Specifically, the roller gap is always kept at 13-16μm, which is greater than or equal to the particle size of the silicon powder, so as to avoid damaging the rollers.

[0030] Further, the multi-layer stacking is preferably 5-10 layers of stacking; more preferably, 8 layers of stacking.

[0031] Further, the stacking mode is specifically as follows: the third mixture is uniformly applied between every two layers of silicon carbide fiber cloth to form a stacking structure.

[0032] Specifically, for example, 8 portions of continuous silicon carbide fiber cloth discs with a diameter of 50 mm and 48-72 g of the third mixture which is not fully cured can be prepared first; then, 6-9 g of the third mixture is evenly applied between every two layers of silicon carbide fiber cloth, and 3-4.5 g of the third mixture is applied on the uppermost and lowermost layers of silicon carbide fiber cloth, to form a stacked structure containing 8 layers of silicon carbide fiber cloth.

[0033] The application also provides a silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material, which is prepared by the above method.

[0034] Beneficial effects:

[0035] The application breaks the traditional single reinforcement mode, forms a 2D MLGs-MBNs composite system by precisely stripping the raw material system with a novel TRM technology, in combination with a vacuum-nitrogen atmosphere multi-stage temperature control process, to in-situ construct a multi-element reinforced phase of “SiC w + Si3N 4w ”, realize multi-dimensional synergistic optimization of the microstructure, and provide a new path for performance improvement of the material; the phenolic resin is innovatively used as “one dose for three purposes”, to simultaneously supply a carbon source, bond a green body, and perform a three-roll grinding viscosity stripping function, in combination with a SiC fiber cloth quantitative stacking process, to not only greatly simplify the preparation process, but also further strengthen the structural stability of the material by regulating the phase transition process of α-Si3N4 to β-Si3N4; in terms of practicality, the prepared silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material not only has high mechanical strength, excellent high-temperature resistance, and electromagnetic wave absorption performance, can directly meet the demand for structure-function integrated materials in the fields of aerospace, high-end equipment, etc., and the whole set of process parameters is clear and controllable, easy to realize large-scale production, can quickly adapt to industrial application scenarios, and has significant technical transformation value. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 The atmosphere switching system and sintering temperature-pressure schedule diagram of embodiments 1-3 of the application;

[0037] Figure 2 The SEM analysis diagram in embodiment 3 of the application: (a) MLGs morphology after EG stripping, (b) MBNs morphology after h-BN stripping, (c) MLGs, (d) MBNs, (e) SiC fiber, (f) SiC whisker, and (g) Si3N4 whisker. DETAILED DESCRIPTION

[0038] The embodiments of the application will be described in detail below in combination with the drawings, examples, and comparative examples.

[0039] In the following examples and comparative examples, the apparent porosity and the bulk density are tested by the drainage method, the bending strength at room temperature is tested by the three-point bending method, the fracture toughness at room temperature is tested by the single-edge pre-crack method, and the electromagnetic wave absorption performance is tested by the waveguide method.

[0040] Example 1:

[0041] (1) A slurry A (PF-EG-BN) was prepared by pre-mixing phenolic resin (PF), expanded graphite (EG) and hexagonal boron nitride (h-BN) with a mass ratio of 100:2:5 under stirring at 50°C in a water bath;

[0042] (2) The slurry A obtained in (1) was poured into a three-roll mill (TRM) for peeling operation to obtain a slurry B (PF-MLGs-MBNs); the speed ratio between the rollers was feed roller:center roller:discharge roller = 1:3:9, and the rotation speed was set to 300 rpm corresponding to the discharge roller; the first gap between the center roller and the feed roller was always larger than the second gap between the center roller and the discharge roller; the peeling parameters included: first gap 24 μm, second gap 12 μm, 5 cycles of peeling; then first gap 12 μm, second gap 6 μm, 5 cycles of peeling; then first gap 6 μm, second gap 3 μm, 5 cycles of peeling; finally first gap 3 μm, second gap 1 μm, 5 cycles of peeling, a total of 20 times of peeling;

[0043] (3) A mixture powder C was prepared by ball milling silicon powder (Si) and nickel nitrate hexahydrate (Ni(NO3)2·6H2O) with a mass ratio of 100:1 in an alcohol solvent for 1 h, drying the alcohol at 60°C in an oven, and sieving through a 500-mesh screen;

[0044] (4) The slurry B in (2) was weighed according to a mass ratio of Si:PF-MLGs-MBNs = 100:60, mixed with the mixture powder C in (3), and then poured into a three-roll mill for further uniform mixing to obtain a final slurry D; the parameters for TRM mixing were as follows: the speed ratio between the rollers was feed roller:center roller:discharge roller = 1:3:9, the rotation speed was set to 300 rpm corresponding to the discharge roller, the roller gap was always kept at 14 μm, and the mixing was performed for 20 times.

[0045] (5) The slurry obtained in (4) was uniformly coated on a SiC fiber cloth to realize the close connection between the slurry and the fiber, and then 8 layers were stacked in a laminated manner to form a blank;

[0046] (6) The blank prepared in (5) was dried at 90°C for 3 h to complete the preliminary shaping of the sample, and a shaped blank was obtained;

[0047] (7) Put the green body in graphite mold and then into the hot-pressing furnace. First, maintain the vacuum environment and pressurize to 30 MPa and keep for 15 min to ensure that the intermediate slurry is fully diffused to each interface of the SiC fiber. Then, reduce the pressure to 15 MPa, increase the temperature from room temperature to 700 ℃ at a rate of 80 ℃ / min, and then increase the temperature to 1000 ℃ at a rate of 50 ℃ / min and keep for 30 min to make the PF completely pyrolyze into residual carbon. Then, increase the temperature to 1400 ℃ at a rate of 50 ℃ / min and keep for 1 h. The Si and C in the green body fully react to form a SiC layer. At the same time, under the dual action of external pressure and thermal stress, the SiC layer is broken into zero-dimensional SiC particles (0D SiC p ), and the carbonization of the green body is completed;

[0048] (8) Switch the vacuum environment in (7) to a nitrogen (N2) atmosphere environment, continue to keep the pressure at 15 MPa, and let the SiC green body obtained in (7) be kept at 1400 ℃ for 1 h. Increase the temperature to 1450 ℃ at a rate of 10 ℃ / min and keep for 2 h. The free Si in the green body is fully nitrided into one-dimensional silicon nitride whiskers (1D Si3N 4w ) and Si3N4 particles (Si3N 4p ). The nitridation of the green body is completed, and a carbonitrided green body is obtained.

[0049] (9) Continue to pressurize to 50 MPa, increase the temperature to 1850 ℃ at a rate of 50 ℃ / min and keep for 30 min. High-temperature sintering of the carbonitrided green body obtained in (8) is ensured to make the SiC and Si3N 4w powder and the fiber more dense. Finally, naturally and slowly cool down, slowly release the pressure, and obtain the SiC fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 1.

[0050] The apparent porosity of the SiC fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 1 is 3.57(±0.05)%, the bulk density is 3.10(±0.02) g / cm 3 , the room temperature bending strength is 643(±32) MPa, the room temperature fracture toughness is 30.36(±1.45) MPa·m 1 / 2 , and the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -33.07 dB and the effective absorption bandwidth is 4.62 GHz.

[0051] Example 2:

[0052] The difference between Example 1 and Example 2 is only that the phenolic resin (PF): expanded graphite (EG): hexagonal boron nitride (h-BN) = 100:4:5 by mass ratio is compounded, and finally the SiC fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 2 is obtained.

[0053] The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 2 is 3.89 (±0.045) %, the bulk density is 3.08 (±0.02) g / cm 3 , the room temperature bending strength is 672 (±38) MPa, and the room temperature fracture toughness is 32.93 (±1.23) MPa·m 1 / 2 , and the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -35.78 dB, and the effective absorption bandwidth is 5.33 GHz.

[0054] Example 3:

[0055] The difference between Example 1 and Example 3 is only that the phenolic resin (PF): expanded graphite (EG): hexagonal boron nitride (h-BN) = 100: 4: 8 mass ratio is prepared, and finally the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 3 is obtained.

[0056] As shown in Figure 2 , the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 3 contains 2DMLGs-MBNs, SiC fibers and 1D SiC w +Si3N 4w .

[0057] The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 3 is 4.11 (±0.07) %, the bulk density is 3.03 (±0.02) g / cm 3 , the room temperature bending strength is 696 (±14) MPa, and the room temperature fracture toughness is 36.57 (±1.72) MPa·m 1 / 2 , and the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -38.35 dB, and the effective absorption bandwidth is 5.68 GHz.

[0058] Example 4:

[0059] The difference between Example 3 and Example 4 is only that (9) is continued to be pressurized to 50 MPa, and the temperature is increased to 1800°C at 50°C / min and kept for 30 min. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 4 is obtained.

[0060] Compared with Example 3, the sintering temperature of Example 4 is low, so the density is also low, so that there are many pores in the final composite material. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 4 is 6.36 (±0.02) %, the bulk density is 2.94 (±0.02) g / cm 3, the room temperature bending strength is 589 (± 15) MPa, and the room temperature fracture toughness is 28.36 (± 1.35) MPa·m 1 / 2 The wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -31.87 dB, and the effective absorption bandwidth is 4.40 GHz.

[0061] Example 5:

[0062] The difference between Example 5 and Example 3 is only that: (9) is continued to pressurize to 50 MPa, and is heated to 1900℃ at a rate of 50℃ / min and kept for 30min. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 5 is obtained.

[0063] Compared with Example 3, the higher sintering temperature of Example 5 will cause excessive grain growth and reduce the number of grain boundaries. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Example 5 is 2.39 (± 0.035) %, the bulk density is 3.15 (± 0.02) g / cm 3 , the room temperature bending strength is 622 (± 28) MPa, and the room temperature fracture toughness is 30.97 (± 1.19) MPa·m 1 / 2 The wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -28.67 dB, and the effective absorption bandwidth is 3.96 GHz.

[0064] Comparative Example 1:

[0065] The difference between Comparative Example 1 and Example 3 is only that: the peeling operation in Example 3 (2) is not performed. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 1 is obtained.

[0066] Compared with Example 3, Comparative Example 1 does not contain MLGs and MBNs in the final composite material due to not performing the peeling operation. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 1 is 4.58 (± 0.03) %, the bulk density is 3.02 (± 0.02) g / cm 3 , the room temperature bending strength is 552 (± 27) MPa, and the room temperature fracture toughness is 23.95 (± 1.42) MPa·m 1 / 2 The wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -25.93 dB, and the effective absorption bandwidth is 3.49 GHz.

[0067] Comparative Example 2:

[0068] The difference between Example 3 and Comparative Example 2 is only that the phenolic resin (PF): expanded graphite (EG): hexagonal boron nitride (h-BN) = 100: 4: 0 mass ratio is compounded, and finally the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 2 is obtained.

[0069] Compared with Example 3, Comparative Example 2 does not add h-BN, so that the final composite material does not contain MBNs. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 2 is 3.78 (±0.025) %, the bulk density is 3.13 (±0.02) g / cm 3 , the room temperature bending strength is 576 (±17) MPa, and the room temperature fracture toughness is 21.46 (±1.06) MPa·m 1 / 2 , and the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -26.57 dB, and the effective absorption bandwidth is 3.58 GHz.

[0070] Comparative Example 3:

[0071] The difference between Example 3 and Comparative Example 3 is only that the phenolic resin (PF): expanded graphite (EG): hexagonal boron nitride (h-BN) = 100: 0: 8 mass ratio is compounded, and finally the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 3 is obtained.

[0072] Compared with Example 3, Comparative Example 3 does not add EG, so that the final composite material does not contain MLGs. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 3 is 3.55 (±0.03) %, the bulk density is 3.10 (±0.02) g / cm 3 , the room temperature bending strength is 521 (±23) MPa, and the room temperature fracture toughness is 24.74 (±1.18) MPa·m 1 / 2 , and the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -20.93 dB, and the effective absorption bandwidth is 3.19 GHz.

[0073] Comparative Example 4:

[0074] The difference between Example 3 and Comparative Example 4 is only that the operation of “uniformly coating the slurry obtained in (4) on the SiC fiber cloth to realize the close connection of the slurry and the fiber, and then stacking 8 layers in a laminated manner to form a blank” in (5) of Example 3 is not performed, and (6) of Example 3 is changed to “drying the slurry prepared in (4) at 90°C for 3 h, and then grinding into powder”. Finally, the multi-structure-function ceramic matrix composite material of Comparative Example 4 is obtained.

[0075] Compared with Example 3, the difference between Example 3 and Comparative Example 4 is that no SiC fiber cloth is added in Comparative Example 4, so that the final composite material lacks the main reinforcing phase. The apparent porosity of the carbon multi-structure and function ceramic matrix composite of Comparative Example 4 is 1.45 (±0.02) %, the bulk density is 3.17 (±0.02) g / cm 3 , the room temperature bending strength is 323 (±8) MPa, and the room temperature fracture toughness is 7.25 (±0.93) MPa·m 1 / 2 , the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -15.27 dB, and the effective absorption bandwidth is 1.95 GHz.

[0076] Comparative Example 5:

[0077] The difference between Example 3 and Comparative Example 5 is that no nickel nitrate hexahydrate is added, and the operation of Example 3 (3) is not performed, and Example 3 (4) is changed to “directly mix the silicon powder and the slurry B in the three-roll mill to be uniform”. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 5 is obtained.

[0078] Compared with Example 3, the difference between Example 3 and Comparative Example 5 is that no nickel nitrate hexahydrate is added, and the operation of Example 3 (3) is not performed, and Example 3 (4) is changed to “directly mix the silicon powder and the slurry B in the three-roll mill to be uniform”. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 5 is obtained. x Si y , not only lacks the substance that can catalyze to improve the reaction rate, but also makes the aspect ratio of 1D Si3N4 reduced, and the grain cannot be refined. The apparent porosity of the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 5 is 3.92 (±0.04) %, the bulk density is 3.08 (±0.02) g / cm 3 , the room temperature bending strength is 486 (±28) MPa, and the room temperature fracture toughness is 27.73 (±1.26) MPa·m 1 / 2 , the wave absorption performance test shows that the minimum reflection loss of the composite ceramic is -23.85 dB, and the effective absorption bandwidth is 2.89 GHz.

[0079] Comparative Example 6:

[0080] The difference between Example 3 and Comparative Example 6 is that the operation of Example 3 (8) is not performed, and the “then heated to 1400℃ at a rate of 50℃ / min and kept for 1 h” in Example 3 (7) is changed to “then heated to 1400℃ at a rate of 50℃ / min and kept for 2h, and then heated to 1450℃ at a rate of 10℃ / min and kept for 2h”. Finally, the silicon carbide fiber reinforced silicon carbide ceramic matrix composite material of Comparative Example 6 is obtained.

[0081] Compared with Example 3, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 6 has a porosity of 6.11 (±0.05) %, a bulk density of 2.95 (±0.02) g / cm 3 , a room temperature bending strength of 382 (±25) MPa, a room temperature fracture toughness of 14.61 (±1.32) MPa·m 1 / 2 , and a minimum reflectivity loss of -14.25 dB and an effective absorption bandwidth of 0.72 GHz.

[0082] Comparative Example 7:

[0083] The difference between Comparative Example 7 and Example 3 is that the “maintaining a vacuum environment” in Example 3 (7) is replaced by “introducing nitrogen gas”, “then heating to 1400℃ at a rate of 50℃ / min and maintaining for 1 h” is replaced by “then heating to 1400℃ at a rate of 50℃ / min and maintaining for 2 h, and then heating to 1450℃ at a rate of 10℃ / min and maintaining for 2 h”, and the operation in Example 3 (8) is not performed. Finally, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 7 is obtained.

[0084] Compared with Example 3, the silicon carbide fiber reinforced silicon nitride-silicon carbide ceramic matrix composite material of Comparative Example 7 has a porosity of 4.22 (±0.035) %, a bulk density of 3.04 (±0.02) g / cm 3 , a room temperature bending strength of 557 (±16) MPa, a room temperature fracture toughness of 28.29 (±1.51) MPa·m 1 / 2 , a minimum reflectivity loss of -26.87 dB and an effective absorption bandwidth of 3.53 GHz.

[0085] Based on the above examples and comparative examples, the three-roll grinding technology adopted in the present application can not only efficiently exfoliate the expanded graphite and hexagonal boron nitride into multi-layer graphene (MLGs) and boron nitride micro-nano sheets (MBNs) while ensuring the yield of the products, but also can rely on the viscosity of phenolic resin to assist the exfoliation without the need for additional exfoliating agents, thereby simplifying the process and reducing the cost, and further ensuring the uniformity of the slurry composition through secondary TRM mixing, thereby laying a foundation for the quality of the subsequent green body.

[0086] As the key reinforcing phase, the 2D structure MLGs and MBNs can be uniformly dispersed in the matrix, on the one hand, the load bearing and transmission capacity of the composite material is improved by virtue of the excellent mechanical properties of the reinforcing phase, and the toughening effects such as crack branching and deflection are assisted; on the other hand, the dielectric properties of the material can be synergistically regulated, and the impedance matching and loss capacity required for electromagnetic wave absorption are optimized, which provides core support for the material to have high strength and excellent electromagnetic function.

[0087] Nickel nitrate as a catalyst is first reduced to zero-dimensional Ni element by the reducing gas generated by pyrolysis of phenolic resin, and then reacts with Si in situ to generate 0D nickel silicide (Ni x Si y ); Ni x Si y can induce the generation of SiC whiskers (SiC w ) and Si3N4 whiskers (Si3N 4w ) through the VLS mechanism, further enhancing the mechanical strength of the matrix, while Ni x Si y itself as a zero-dimensional dispersion reinforcing phase can regulate the magnetic permeability of the material, and cooperate with MLGs and MBNs to optimize electromagnetic loss and improve electromagnetic wave absorption effect.

[0088] The 0D SiC p generated in situ can fill the voids of the matrix, and the 1D Si3N 4w and the 0D Si3N 4p can form a stable bond with the SiC fiber, which not only solves the problem of flowing silicon and black core, but also synergistically improves the density and mechanical strength of the material through multi-dimensional reinforcing phases (0D SiC p , 1D SiC w / Si3N 4w , 2D MLGs / MBNs); and the phase transition of alpha-Si3N4 to beta-Si3N4 during high-temperature sintering further optimizes the crystal structure and enhances the stability of the material, while the dielectric difference between SiC and Si3N4 can assist in regulating electromagnetic parameters and improving wave absorption performance.

[0089] The above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for producing a silicon carbide fiber-reinforced silicon nitride-silicon carbide ceramic matrix composite material, characterized by, The method comprises the following steps: mixing phenolic resin, multi-layer graphite and hexagonal boron nitride by stirring, and then placing the mixture in a three-roll mill to perform exfoliation, to obtain a first mixture of multi-layer graphene and multi-layer boron nitride microsheets; wet ball milling silicon powder and nickel nitrate hexahydrate, drying and sieving to obtain a second mixture; mixing the first mixture and the second mixture by stirring, and then placing the mixture in a three-roll mill to perform further mixing, to obtain a third mixture; coating the third mixture on a silicon carbide fiber cloth, and performing multi-layer stacking in a laminated manner, and then drying and shaping to obtain a shaped blank; placing the shaped blank in a hot-pressing furnace, maintaining a vacuum environment, and pressurizing to 25-35 MPa and keeping the pressure for 10-20 min; then reducing the pressure to 10-20 MPa, increasing the temperature from room temperature to 600-800 ℃ at a rate of 50-100 ℃ / min, and then increasing the temperature to 900-1100 ℃ at a rate of 20-80 ℃ / min and keeping the temperature for 20-40 min; then increasing the temperature to 1350-1420 ℃ at a rate of 20-80 ℃ / min and keeping the temperature for 1-3 h; then switching the vacuum environment to a nitrogen atmosphere, keeping the pressure at 10-20 MPa, and keeping the shaped blank at 1350-1420 ℃ for 1-3 h, and then increasing the temperature to 1450-1550 ℃ at a rate of 5-20 ℃ / min and keeping the temperature for 1-3 h; continuing to pressurize to 45-55 MPa, increasing the temperature to 1800-1900 ℃ at a rate of 20-80 ℃ / min and keeping the temperature for 20-40 min; and finally naturally and slowly reducing the temperature and slowly releasing the pressure, to obtain the silicon carbide fiber-reinforced silicon nitride-silicon carbide ceramic matrix composite material.

2. The method of claim 1, wherein, The mass ratio of the phenolic resin, the multi-layer graphite and the hexagonal boron nitride is 100:1-4:5-20.

3. The method of claim 1, wherein, The mass ratio of the silicon powder and the nickel nitrate hexahydrate is 100:0.1-3.

4. The method of claim 1, wherein, The mass ratio of the silicon powder in the second mixture to the first mixture is 100:50-70.

5. The method of claim 1, wherein, The wet ball milling is performed with alcohol as the solvent, and the time is 1-3 h; the alcohol is dried in an oven at 50-80 ℃, and sieving is performed to pass through a 200-500 mesh sieve.

6. The method of claim 1, wherein, The drying and shaping condition is drying at 80-100 ℃ for 2-4 h.

7. The method of claim 1, wherein, The process parameters of the three-roll milling process are as follows: the rotation speed ratio between the rollers is feed roller:center roller: discharge roller = 1-2:3-5:8-10, the rotation speed is set to 200-400 rpm corresponding to the discharge roller, the first gap between the center roller and the feed roller is always greater than the second gap between the center roller and the discharge roller; the exfoliation further comprises the following steps: first, the first gap is 22-26 μm, the second gap is 10-14 μm, and the exfoliation is performed for 3-6 cycles; then, the first gap is 10-14 μm, the second gap is 4-8 μm, and the exfoliation is performed for 3-6 cycles; then, the first gap is 4-8 μm, the second gap is 2-3 μm, and the exfoliation is performed for 3-6 cycles; finally, the first gap is 2-3 μm, the second gap is 1-1.9 μm, and the exfoliation is performed for 3-6 cycles, a total of 12-24 times of exfoliation.

8. The method of claim 1, wherein, The further mixing parameters are a rotation speed ratio between the rollers of 1:3:9 for the entry roller: middle roller: exit roller, a rotation speed setting of 200-400 rpm for the exit roller, a roller distance of 13-16 μm at all times, and 10-25 mixing passes.

9. The method of claim 1, wherein, The lamination manner is specifically: uniformly applying the third mixture between every two layers of the silicon carbide fiber cloth to form a stacking structure.

10. A silicon carbide fiber-reinforced silicon nitride-silicon carbide ceramic matrix composite, characterized by, prepared by the method of any one of claims 1-9.

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