A multi-dimensional structure silicon carbide-silicon nitride composite material and a preparation method thereof

Abstract

The application discloses a multi-dimensional structure silicon carbide-silicon nitride composite material and a preparation method thereof. S As the core of the multi-dimensional structure, the prepared silicon carbide-silicon nitride composite material not only solves the long-term technical problems of'single dimension' and 'incomplete carbonization and nitridation', but also realizes the structural and functional integration of'mechanical strength and toughness' and 'electromagnetic wave absorption function', has the advantages of high purity, excellent mechanical properties, good electromagnetic wave absorption effect, low raw material cost, industrializable process and the like, and has a wide industrialization prospect.

Description

Technical Field

[0001] This invention belongs to the field of ceramics and structural materials technology, and specifically relates to a multidimensional silicon carbide-silicon nitride composite material and its preparation method. Background Technology

[0002] Silicon carbide-silicon nitride composites have attracted significant attention in aerospace, energy, and machinery manufacturing fields due to their high strength, high hardness, excellent high-temperature resistance, and chemical stability. However, traditional single-dimensional composite materials prepared using conventional methods have limitations in impact toughness, thermal conductivity, and adaptability to various environments, making it difficult to meet the demands of extreme operating conditions. While existing technologies attempt to improve performance by adding a second phase or optimizing processes, they generally suffer from weak phase interface bonding and poor controllability of microstructure, resulting in limited improvement in the overall material performance. Therefore, developing a method for preparing silicon carbide-silicon nitride composites that can construct a multi-dimensional architecture and achieve multi-phase synergistic reinforcement has become a key technological direction for overcoming performance bottlenecks and expanding application areas.

[0003] The development of silicon carbide-silicon nitride composites is undergoing a major paradigm shift from single-performance optimization to multi-dimensional synergistic design. Background technology indicates that while traditional processes can produce materials with satisfactory basic properties, they have limitations in addressing fundamental issues such as incomplete nitriding, dimensional uniformity, and weak interfacial bonding. In recent years, breakthroughs in technologies such as multi-dimensional structural design (0D / 1D / 2D synergy), biomimetic laminated structures (diamond-B4C-SiC / Si3N4-SiC), and external field-assisted sintering (SPS, microwave sintering) have continuously expanded the boundaries of material performance.

[0004] Future development in this field will focus more on four integrations: ① Structure-function integration, such as aerogel materials that combine load-bearing and electromagnetic control capabilities; ② Dimensional synergy integration, achieving multi-level inhibition of crack propagation through in-situ construction of multi-scale reinforcements; ③ Process-performance integration, using technologies such as SPS to precisely control phase composition and interface structure; ④ Application customization, developing specialized material systems for specific scenarios such as bone repair and aerospace thermal protection.

[0005] Therefore, developing high-performance multidimensional silicon carbide-silicon nitride composite materials has become a key research focus. Summary of the Invention

[0006] This invention addresses two major technical bottlenecks in the preparation of composite materials in existing technologies: "single-dimensionality" leading to limited structural performance and "incomplete carbonization and nitriding" affecting material purity and functional stability. It aims to prepare a structurally functional integrated composite material with both excellent mechanical properties and efficient electromagnetic wave absorption performance through low-cost raw materials and innovative processes. The invention proposes a multi-dimensional silicon carbide-silicon nitride composite material and its preparation method.

[0007] This invention utilizes three-roll differential milling (TRM) technology, leveraging the synergistic effect of the roller speed difference and the adhesion of phenolic resin (PF), to successfully exfoliate low-cost flake graphite (FG) into FG-type multilayer graphene sheets (MLG). F This process not only achieves MLG F The efficient dispersion, and more importantly, the foundation for subsequent MLG F In-situ formation of two-dimensional silicon carbide wafers (2D-SiC) with Si S This unique structure lays the foundation for ensuring the formation of SiC in the reaction. S Inherited MLG F The regular two-dimensional morphology is thus used to construct a uniformly distributed two-dimensional reinforcing phase inside the composite material.

[0008] From the perspective of mechanical property enhancement mechanism, Si and MLG F 2D-SiC generated by in-situ reaction S MLG can significantly hinder crack propagation and promote energy dissipation through the dual effects of "pull-out effect" and "bridging effect": when MLG is incorporated into composite materials... F At that time, its fracture toughness was higher than that without MLG. F The benchmark sample showed significant improvement, fully demonstrating the superior performance of 2D-SiC. S As a two-dimensional reinforcing phase, it plays a core role in breaking through the bottleneck of "single dimension" in composite materials and achieving multi-dimensional synergistic toughness.

[0009] In terms of electromagnetic absorption functionalization, 2D-SiC S With its unique two-dimensional sheet structure and interface properties, 2D-SiC can enhance dielectric loss through a synergistic effect of interface polarization and dipole polarization. S The numerous heterogeneous interfaces formed between the composite material and the matrix can induce strong interfacial polarization, while internal defects and charge accumulation can promote dipole polarization. The combined effect of these two polarization effects enables precise optimization of the dielectric loss characteristics of the composite material in the 12-18 GHz (Ku band) frequency band, significantly improving its electromagnetic wave absorption performance.

[0010] This invention uses low-cost silicon powder, phenolic resin, and flake graphite as raw materials, and employs a gradient in-situ reaction process to produce 2D-SiC. S The silicon carbide-silicon nitride composite material, which is ultimately prepared by constructing a multi-dimensional architecture around the core, not only solves the long-standing technical problems of "single dimension" and "incomplete carbonization and nitridation", but also achieves the integration of structure and function of "mechanical strengthening and toughening" and "electromagnetic wave absorption function". It has significant advantages such as high purity, excellent mechanical properties, good electromagnetic wave absorption effect, low raw material cost and industrialization of process, and has broad industrialization prospects.

[0011] Specifically, to achieve the above objectives, the present invention provides the following specific technical solutions:

[0012] A method for preparing a multidimensional silicon carbide-silicon nitride composite material, comprising:

[0013] Silicon powder (Si), yttrium oxide (Y2O3), aluminum oxide (Al2O3), and nickel nitrate hexahydrate (Ni(NO3)2·6H2O) were wet-milled, dried, and sieved to obtain the first mixture.

[0014] Phenolic resin (PF) and flake graphite (FG) were mixed and stirred, and then exfoliated using a three-roll milling process (TRM) to obtain multilayer graphene sheets (MLG). F The second mixture (PF-MLG) F );

[0015] The first mixture and the second mixture were mixed in anhydrous ethanol, and then heated and stirred in a water bath to obtain a slurry. The slurry was then vacuum dried to obtain a viscous powder.

[0016] The viscous powder is subjected to cold isostatic pressing to obtain a molded preform;

[0017] The preform is heated to 800-1000℃ at a rate of 2-10℃ / min and held for 1-3 hours under flowing argon gas. Then, it is heated to 1200-1350℃ at a rate of 1-5℃ / min and held for 1-3 hours. Next, it is heated to 1400-1420℃ at a rate of 1-5℃ / min and held for 1-2 hours. The argon gas is then switched to nitrogen gas, and the preform is held at 1400-1420℃ for 1-3 hours. Then, it is heated to 1450-1550℃ at a rate of 1-5℃ / min and held for 4-10 hours. Finally, it is heated to 1600-1800℃ at a rate of 1-5℃ / min under nitrogen gas and held for 1-3 hours to obtain the multidimensional silicon carbide-silicon nitride composite material.

[0018] Specifically, the molded preform is heated to 800-1000℃ at a rate of 2-10℃ / min and held for 1-3 hours under flowing argon (Ar) gas, causing the phenolic resin to pyrolyze into a carbon layer; then, the temperature is increased to 1200-1350℃ at a rate of 1-5℃ / min and held for 1-3 hours, causing Si to react with the carbon layer to form a silicon carbide layer; finally, the temperature is increased to 1400-1420℃ at a rate of 1-5℃ / min and held for 1-2 hours. During this process, the silicon carbide layer breaks down into zero-dimensional silicon carbide particles (0D SiC). p ), Si and MLG F In-situ reaction to generate two-dimensional silicon carbide wafers (2D SiC) SThe carbonized preform was obtained; the argon gas was switched to nitrogen (N2), and the temperature was maintained at 1400-1420℃ for 1-3 hours. Then, the temperature was increased to 1450-1550℃ at a rate of 1-5℃ / min and maintained for 4-10 hours to fully nitrid the free Si into one-dimensional silicon nitride whiskers (1D Si3N). 4w The silicon carbide-silicon nitride composite material is obtained by heating α-Si3N4 particles with nitrogen at a rate of 1-5℃ / min to 1600-1800℃ and holding for 1-3 hours. This completes the high-temperature sintering and simultaneously achieves a partial phase transformation of α-Si3N4 to β-Si3N4, ultimately yielding the multidimensional silicon carbide-silicon nitride composite material.

[0019] Specifically, the purity of Ar gas is ≥ 99.999%. The pyrolysis of PF also produces reducing gases that reduce Ni(NO3)2·6H2O to zero-dimensional Ni, subsequently forming zero-dimensional nickel silicide (0D Ni) with Si. x Si y ), where Si and MLG F Unique two-dimensional silicon carbide wafers (2D SiC) were synthesized in situ. S The structure plays a crucial role in the mechanical strength and electromagnetic wave absorption performance of the composite matrix itself.

[0020] Specifically, the purity of N2 gas was ≥ 99.999%. Switching from argon to nitrogen (N2) and maintaining the temperature at 1400-1420℃ for 1-3 hours was to pre-nitride the free Si in the carbonized preform, preventing silicon flow and black core phenomena. Switching from Ar to N2 gas ensured the rationality and controllability of the segmented and complete reactions of the preform carbonization and nitriding processes.

[0021] Furthermore, the mass ratio of silicon powder, yttrium oxide, aluminum oxide, and nickel nitrate hexahydrate is 100:0.5-6:0.1-3:0.1-3.

[0022] Specifically, the silicon powder (Si) has a purity ≥99 wt.% and a particle size ≤13 μm. Yttrium oxide (Y₂O₃) and aluminum oxide (Al₂O₃) are used as sintering aids, both with a purity ≥99.0 wt.% and a particle size ≤10 μm. Nickel nitrate hexahydrate (Ni(NO₃)₂·6H₂O) is used as a catalyst with a purity ≥99 wt.%.

[0023] Further, wet ball milling is performed using alcohol as a solvent for 1-3 hours; the alcohol is dried in an oven at 50-80℃ and sieved through a 200-500 mesh sieve.

[0024] Furthermore, the mass ratio of phenolic resin to flake graphite is 100:1-7.

[0025] Specifically, phenolic resin (PF) serves multiple purposes, including as a carbon source, green body binder, and adhesive release agent in three-roll milling, with a residual carbon content of ~40-50 wt.%. Flake graphite (FG) has a purity of ≥99.9 wt.% and a particle size of ≤100 μm.

[0026] Furthermore, the mixing time is 5-30 minutes.

[0027] Furthermore, the mass ratio of silicon powder to the second mixture in the first mixture is 100:15-30.

[0028] Further, the process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is feed roller: center roller: discharge roller = 1-2:3-5:8-10, the rotational speed is set to 200-400 rpm corresponding to the discharge roller, and 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 includes: firstly, peeling 3-6 times with the first gap being 22-26 μm and the second gap being 10-14 μm; then peeling 3-6 times with the first gap being 10-14 μm and the second gap being 4-8 μm; nextly, peeling 3-6 times with the first gap being 4-8 μm and the second gap being 2-3 μm; and finally, peeling 3-6 times with the first gap being 2-3 μm and the second gap being 1-1.9 μm, for a total of 12-24 peeling cycles.

[0029] Furthermore, the water bath heating and stirring are specifically: temperature 60-100℃, rotation speed 300-500r / min.

[0030] Specifically, this process belongs to the coating and mixing process, in which PF-MLG F Uniformly coated on the surface of Si powder particles, this ensures that the residual carbon layer from subsequent PF pyrolysis and MLG... F The silicon carbide reacts with Si to produce dispersed zero-dimensional silicon carbide particles (0DSiC). P ) and two-dimensional silicon carbide wafers (2D SiC) S ).

[0031] Furthermore, the specific conditions for cold isostatic pressing are hydraulic pressure of 100-300 MPa and pressure holding for 5-20 minutes.

[0032] The present invention also provides a multidimensional silicon carbide-silicon nitride composite material, which is prepared by the above method.

[0033] Beneficial effects:

[0034] 1. The Ni(NO3)2·6H2O added in this invention can be indirectly converted into Ni during the preparation process, and then combine with Si to form a zero-dimensional alloy compound, nickel silicide (0D Ni). x Si y This compound not only significantly shortens the carbide and nitridation reaction time of Si, but also optimizes the interfacial bonding state and refines the grains; more importantly, through growth mechanisms such as VLS (vapor-liquid-solid phase) and VS (vapor-solid phase), it can catalyze the generation of one-dimensional silicon nitride whiskers (1D Si3N) with a large aspect ratio. 4w This provides core support for the construction of multidimensional architectures of composite materials.

[0035] 2. The yttrium oxide (Y2O3) and aluminum oxide (Al2O3) added in this invention serve as sintering aids. They form a low-melting-point metastable phase with SiO2 in the raw materials, effectively destroying the oxide layer on the Si surface, allowing Si and N2 to directly contact and react, significantly improving the nitriding reaction rate and sintering densification effect, and fundamentally solving the technical problem of "incomplete nitriding".

[0036] 3. The commercial thermosetting phenolic resin (PF) used in this invention achieves "one agent, four uses": it is not only a carbon source supply agent required for carbonization reaction, but also a binder for raw material molding, and can also provide a reducing atmosphere during the reaction process to protect the raw materials from excessive oxidation. At the same time, as an adhesive stripping agent in the three-roll milling process (TRM), it provides key assistance for the efficient stripping of flake graphite, greatly improving the utilization rate of raw materials and the convenience of the process.

[0037] 4. This invention utilizes the synergistic effect of the roller speed difference in three-roll milling and the viscosity of PF to efficiently exfoliate low-cost flake graphite (FG) into FG-type multilayer graphene sheets (MLG). F The stripping process is low-cost and highly efficient, and MLG F Excellent dispersibility, making it suitable for subsequent two-dimensional silicon carbide wafers (2D SiC). S The in-situ generation of ) lays a high-quality structural foundation, which is conducive to industrial mass application.

[0038] 5. This invention employs a coating and mixing process to coat PF-MLG. F Uniform coating on the surface of Si particles can solve the problem of uneven dispersion of PF-MLGs at the source. This uniform coating structure ensures the formation of zero-dimensional silicon carbide particles (0D SiC) during the carbonization stage of the preform. P ) and two-dimensional silicon carbide wafers (2D SiC) S The material is evenly distributed in the matrix to avoid performance shortcomings caused by local agglomeration, thus providing structural protection for multi-dimensional synergistic toughening.

[0039] 6. The gradient reaction sintering method used in this invention: Under a low-temperature argon atmosphere, Si preferentially undergoes a carbonization reaction to generate ODSiC. P With 2D SiC S It can fully consume the carbon source and effectively solve the problem of residual carbon; under high temperature nitrogen environment, the remaining Si is further fully nitrided to generate 1D Si3N. 4w And silicon nitride grains / whiskers.

[0040] 7. By controlling the ratio of the two main raw materials, Si and PF, this invention can precisely regulate the content ratio of SiC and Si3N4 in the final composite material, meet the differentiated requirements of different application scenarios for the mechanical properties and electromagnetic wave absorption properties of the material, and improve the applicability and customization capability of the material.

[0041] 8. The apparent porosity of the multidimensional silicon carbide-silicon nitride composite material prepared by this invention is 10.55 (±0.45)%, and the bulk density is 2.37 (±0.04) g / cm³. 3 The room temperature flexural strength is 204 (±4) MPa, and the room temperature fracture toughness is 5.66 (±0.31) MPa·m. 1 / 2 At the 14.32 GHz band, the minimum reflection attenuation is -33.60 dB, and the effective absorption bandwidth is 1.04 GHz. Among them, Si and MLG... F 2D-SiC generated by in-situ reaction S From the perspective of mechanical property strengthening mechanism, it can significantly hinder crack propagation and promote energy dissipation through the dual effects of "pull-out effect" and "bridging effect," as well as 2D-SiC. S In terms of electromagnetic absorption functionalization, thanks to its unique two-dimensional sheet structure and interface characteristics, it can enhance dielectric loss through the synergistic effect of interface polarization and dipole polarization, and the large number of heterogeneous interfaces formed with the substrate can induce strong interface polarization.

[0042] In summary, this invention, through synergistic innovation in raw materials and processes, successfully solves two major technical bottlenecks in existing technologies: "single-dimensionality" and "incomplete carbonization and nitriding." Among these, 2D-SiC... S The existence of this material enables the manufactured material to possess both high mechanical strength and toughness, excellent electromagnetic wave absorption performance, and low raw material cost, and the process can be industrialized, thus possessing broad industrialization prospects. Attached Figure Description

[0043] Figure 1 This is a diagram showing the atmosphere switching system and sintering temperature regime for the formed preforms in Examples 1-3 of this invention;

[0044] Figure 2 This is the XRD analysis diagram of Example 2 in this invention;

[0045] Figure 3 XPS analysis images of Example 2 in this invention: full spectrum, Si spectrum, N spectrum, C spectrum, Ni spectrum;

[0046] Figure 4 The following are SEM images of Example 2 of this invention: (a) morphology of flake graphite (FG), (b) FG-type MLG. F Morphology, (c) FG and FG type MLG F The XRD values ​​(d)-(f) represent the 0D SiC in the sample. p 1D Si3N 4f and 2D SiC S structure;

[0047] Figure 5 The TEM analysis image of Example 2 in this invention is as follows: (a) 2D SiC in the sample S Structural and EDS analysis, (b)-(c) 2D SiC S Lattice analysis, (d)-(e) are MLG F Lattice analysis;

[0048] Figure 6 The following are SEM images of Comparative Example 1 in this invention: (a) morphology of expanded graphite (EG), (b) EG-type MLG. E Morphology, (c) EG and EG-type MLG E XRD, (d)-(e) show the broken flaky morphology of the sample, and (f) shows the surface EDS elemental spectrum. Detailed Implementation

[0049] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings, examples, and comparative examples.

[0050] In the following examples and comparative examples, apparent porosity and bulk density were tested using the drainage method, room temperature flexural strength was tested using the three-point bending method, room temperature fracture toughness was tested using the single-sided pre-crack method, and electromagnetic wave absorption performance was tested using the waveguide method.

[0051] Example 1:

[0052] (1) The mixture of silicon powder (Si): yttrium oxide (Y2O3): aluminum oxide (Al2O3): nickel nitrate hexahydrate (Ni(NO3)2·6H2O) was wet-milled in alcohol solvent for 1 hour, dried in an oven at 60°C, and passed through a 500-mesh sieve to obtain a mixed powder.

[0053] (2) Phenolic resin (PF): flake graphite (FG) are mixed and stirred for 30 minutes at a mass ratio of 100:1 to obtain PF-FG;

[0054] (3) Using a three-roll milling process (TRM) and the viscosity of PF, the FG in (2) is physically exfoliated by differential shearing to form FG-type multilayer graphene sheets (MLG). F ), to obtain PF-MLG F The rotational speed ratio between the rollers is 1:3:9 (feed roller: center roller: discharge roller), with the rotational speed set to 300 rpm for 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 parameters include: first, peeling 5 times with a first gap of 24 μm and a second gap of 12 μm; then peeling 5 times with a first gap of 12 μm and a second gap of 6 μm; next, peeling 5 times with a first gap of 6 μm and a second gap of 3 μm; and finally, peeling 5 times with a first gap of 3 μm and a second gap of 1 μm, for a total of 20 peeling cycles.

[0055] (4) Using a coating and mixing process: PF-MLG in (3) F According to Si:PF-MLG F Weigh out the powder at a mass ratio of 100:22.5 and mix it with the mixed powder obtained in (1) in anhydrous ethanol. Then, heat it in a water bath at 80°C and stir it at 400 r / min to obtain a slurry. Then, vacuum dry the slurry to obtain viscous powder D.

[0056] (5) The viscous powder in (4) is subjected to cold isostatic pressing to obtain the molded blank, specifically by hydraulic pressure of 200MPa and holding pressure for 10min;

[0057] (6) Under Ar gas, the preform formed in (5) is first heated to 1000℃ at 5℃ / min and held for 2h to allow PF to pyrolyze into a carbon layer. Then, the temperature is increased to 1350℃ at 2℃ / min and held for 2h to allow Si to react with the carbon layer to form a silicon carbide layer. Then, the temperature is increased to 1400℃ at 2℃ / min and held for 1h. During this process, the silicon carbide layer will break into zero-dimensional silicon carbide particles (0D SiC). p ), Si and MLG F In-situ reaction to generate two-dimensional silicon carbide wafers (2D SiC) S ), to obtain a carbonized preform;

[0058] (7) Replace Ar gas in (6) with N2 gas, and keep the carbonized preform obtained in (6) at 1400℃ for 2 hours. Then, raise the temperature to 1450℃ at 2℃ / min and keep it for 5 hours to fully nitrid the free Si into one-dimensional silicon nitride fibers (1D Si3N). 4f ) and Si3N4 particles / whiskers to obtain nitrided and carbide preforms;

[0059] (8) The nitrided and carbide preforms obtained in (7) are heated from 1450°C to 1700°C at 2°C / min under N2 gas and held for 1 hour to complete high-temperature sintering, thus obtaining the sample of the multidimensional structure silicon carbide-silicon nitride composite material of Example 1.

[0060] The apparent porosity of the multidimensional silicon carbide-silicon nitride composite material in Example 1 was 9.6 (±0.5)%, and the bulk density was 2.43 (±0.03) g / cm³. 3 The room temperature flexural strength is 169 (±1.5) MPa, and the room temperature fracture toughness is 4.14 (±0.18) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 15.02 GHz band is -25.30 dB, and the effective electromagnetic wave absorption bandwidth is 0.64 GHz.

[0061] Example 2:

[0062] The only difference from Example 1 is that PF-FG was obtained by stirring phenolic resin (PF): flake graphite (FG) at a mass ratio of 100:4, and finally the sample of the multidimensional silicon carbide-silicon nitride composite material of Example 2 was obtained.

[0063] The XRD analysis of the multidimensional silicon carbide-silicon nitride composite material sample in Example 2 is as follows: Figure 2 As shown, the sample contains two main phases: β-SiC, primarily formed by the reaction of residual carbon from the pyrolysis of Si and PF, and β-Si3N4, mainly generated by the nitridation of Si. Furthermore, a micro-peak in the NiSi2 phase was observed, formed by the combination of elemental Ni obtained from the reduction of Si with Ni(NO3)2·6H2O. No obvious peaks for residual carbon or free silicon were found, indicating that C and Si were almost entirely converted into two main phases. The XPS of the sample is as follows: Figure 3 As shown, corresponding Si-N, Si-C, CC, and CN bonds were detected. Furthermore, the Ni spectrum confirmed the presence of multiple valence states of Ni in the composite material. Figure 4 As shown in (a)-4(c), flake graphite (FG) was successfully physically exfoliated into fine, transparent, multilayer graphene sheets (FG-type MLG) through a three-roll milling process (TRM) and the adhesive action of PF. F Furthermore, XRD analysis showed that the MLG F The C diffraction peak of the (002) crystal plane is significantly lower and shifted to the left compared to FG, indicating that lattice distortion and increased interplanar spacing of the (002) crystal plane occurred after exfoliation. Figure 4 As shown in (d)-4(f), the multidimensional silicon carbide-silicon nitride composite material contains 2D SiCs and 0D SiCs. p and 1DSi3N 4f TEM analysis, such as Figure 5 As shown, the crystal structure of 2D SiCs in the sample is β-SiC stacked along the

[311] crystal plane, and the MLG obtained by exfoliation... F The (002) interplanar spacing is 0.346 nm > 0.335 nm (normal graphite (002) interplanar spacing), indicating the addition of MLG. F Indeed, it reacts with Si to form β-SiC type 2D SiCs.

[0064] The apparent porosity of the multidimensional silicon carbide-silicon nitride composite material in Example 2 was 10.55 (±0.45)%, and the bulk density was 2.37 (±0.04) g / cm³. 3 The room temperature flexural strength is 204 (±4) MPa, and the room temperature fracture toughness is 5.66 (±0.31) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 14.32 GHz band is -33.60 dB, and the effective electromagnetic wave absorption bandwidth is 1.04 GHz.

[0065] Example 3:

[0066] The only difference from Example 1 is that PF-FG was obtained by stirring phenolic resin (PF): flake graphite (FG) at a mass ratio of 100:7, and finally the sample of the multidimensional silicon carbide-silicon nitride composite material of Example 3 was obtained.

[0067] The apparent porosity of the multidimensional silicon carbide-silicon nitride composite material in Example 3 was 11.15 (±0.45)%, and the bulk density was 2.33 (±0.03) g / cm³. 3 The room temperature flexural strength is 160 (±3) MPa, and the room temperature fracture toughness is 3.64 (±0.08) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 13.52 GHz band is -38.72 dB, and the effective electromagnetic wave absorption bandwidth is 1.54 GHz.

[0068] Comparative Example 1:

[0069] The only difference between this example and Example 2 is that expanded graphite (EG) is used instead of flake graphite (FG) in Example 2. The expanded graphite (EG) has a purity of 99% and a particle size of 1-2 mm, and the silicon carbide-silicon nitride composite material sample of Comparative Example 1 is finally obtained.

[0070] like Figure 6 As shown in (a)-6(c), expanded graphite (EG) was successfully physically exfoliated into fine, transparent, multilayer graphene sheets (EG-type MLG) using a three-roll milling process (TRM) and the adhesive properties of PF. EFurthermore, XRD analysis showed that the MLG E Similarly, the C diffraction peak of the (002) crystal plane is significantly lower and shifted to the left compared to EG, indicating that lattice distortion and increased interplanar spacing of the (002) crystal plane occurred after exfoliation. Figure 6 As shown in (d)-6(f), the silicon carbide-silicon nitride composite material contains a lamellar structure, but its edges, when magnified, show severe reaction-induced breakage. EDS analysis revealed an atomic ratio of C to Si of 1:1, clearly indicating an EG-type MLG. E It is easily broken into SiC particles by the reaction, and a complete 2D SiC cannot be obtained. S The bridging and pulling effects are difficult to fully utilize in the matrix, and the overall electromagnetic wave absorption performance of the composite material is not optimized.

[0071] The apparent porosity of the silicon carbide-silicon nitride composite material in Comparative Example 1 was 10.8 (±0.4)%, and the bulk density was 2.32 (±0.04) g / cm³. 3 The room temperature flexural strength is 200 (±2) MPa, and the room temperature fracture toughness is 4.62 (±0.15) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 13.60 GHz band is -7.68 dB, and the effective electromagnetic wave absorption bandwidth is 0 GHz.

[0072] Comparative Example 2:

[0073] The only difference from Example 1 is that flake graphite (FG) is not added and three-roll milling is not performed. The final result is a sample of the silicon carbide-silicon nitride composite material of Comparative Example 2 (without 2D SiC). S ).

[0074] The apparent porosity of the silicon carbide-silicon nitride composite material in Comparative Example 2 was 9.75 (±0.65)%, and the bulk density was 2.42 (±0.03) g / cm³. 3 The room temperature flexural strength is 101 (±5) MPa, and the room temperature fracture toughness is 1.87 (±0.10) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 15.28 GHz band is -7.79 dB, and the effective electromagnetic wave absorption bandwidth is 0 GHz.

[0075] Comparative Example 3:

[0076] The only differences from Example 1 are: no flake graphite (FG) was added, no nickel nitrate hexahydrate was added, and three-roll milling was not performed. The final result was the silicon carbide-silicon nitride composite sample of Comparative Example 3 (without 2D SiC). s Free of 0D Ni x Si y ).

[0077] The apparent porosity of the silicon carbide-silicon nitride composite material in Comparative Example 3 was 11.45 (±0.45)%, and the bulk density was 2.29 (±0.03) g / cm³. 3 The room temperature flexural strength is 47 (±7) MPa, and the room temperature fracture toughness is 1.17 (±0.03) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 13.92GHz band is -2.57dB, and the effective electromagnetic wave absorption bandwidth is 0GHz.

[0078] Comparative Example 4:

[0079] The only difference between this example and Example 2 is that the molded preform was prepared by sintering in a N2 atmosphere throughout the process, and the final sample of the silicon carbide-silicon nitride composite material of Comparative Example 4 was obtained (there was residual carbon or incomplete reaction of residual silicon, resulting in uneven distribution of phases).

[0080] The apparent porosity of the silicon carbide-silicon nitride composite material in Comparative Example 4 was 14.10 (±0.5)%, and the bulk density was 2.18 (±0.03) g / cm³. 3 The room temperature flexural strength is 153 (±5) MPa, and the room temperature fracture toughness is 3.04 (±0.08) MPa·m. 1 / 2 The minimum electromagnetic wave reflection attenuation in the 13.95 GHz band is -20.52 dB, and the effective electromagnetic wave absorption bandwidth is 0.56 GHz.

[0081] Based on the above embodiments and comparative examples, this invention, through synergistic innovation in raw materials and processes, successfully solves two major technical bottlenecks in the prior art: "single-dimensionality" and "incomplete carbonization and nitriding." Among these, 2D-SiC... S The existence of this material enables the manufactured material to possess both high mechanical strength and toughness, excellent electromagnetic wave absorption performance, and low raw material cost, and the process can be industrialized, thus possessing broad industrialization prospects.

[0082] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for producing a multi-dimensional structure silicon carbide-silicon nitride composite material, characterized by, include: Silicon powder, yttrium oxide, aluminum oxide, and nickel nitrate hexahydrate were wet-milled, dried, and sieved to obtain the first mixture. After mixing and stirring phenolic resin and flake graphite, a three-roll differential milling process is used to peel off the mixture, resulting in a second mixture with multilayer graphene sheets. The first mixture and the second mixture were mixed in anhydrous ethanol, and then heated and stirred in a water bath to obtain a slurry. The slurry was then vacuum dried to obtain a viscous powder. The viscous powder is subjected to cold isostatic pressing to obtain a molded preform; The preform is heated to 800-1000℃ at a rate of 2-10℃ / min and held for 1-3 hours under flowing argon gas. Then, it is heated to 1200-1350℃ at a rate of 1-5℃ / min and held for 1-3 hours. Next, it is heated to 1400-1420℃ at a rate of 1-5℃ / min and held for 1-2 hours. The argon gas is then switched to nitrogen gas, and the preform is held at 1400-1420℃ for 1-3 hours. Then, it is heated to 1450-1550℃ at a rate of 1-5℃ / min and held for 4-10 hours. Finally, it is heated to 1600-1800℃ at a rate of 1-5℃ / min under nitrogen gas and held for 1-3 hours to obtain the multidimensional silicon carbide-silicon nitride composite material.

2. The method of claim 1, wherein, The mass ratio of silicon powder, yttrium oxide, aluminum oxide and nickel nitrate hexahydrate is 100:0.5-6:0.1-3:0.1-3.

3. The method of claim 1, wherein, Wet ball milling was performed using alcohol as a solvent for 1-3 hours; the alcohol was dried in an oven at 50-80℃ and sieved through a 200-500 mesh sieve.

4. The method of claim 1, wherein, The mass ratio of phenolic resin to flake graphite is 100:1-7.

5. The method of claim 1, wherein, The mixing time is 5-30 minutes.

6. The method of claim 1, wherein, The mass ratio of silicon powder to the second mixture in the first mixture is 100:15-30.

7. The method of claim 1, wherein, The process parameters of the three-roll grinding process are as follows: the rotational speed ratio between the rollers is feed roller: center roller: discharge roller = 1-2:3-5:8-10, the rotational speed is set to 200-400 rpm for the discharge roller, and 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 includes: first, peeling 3-6 times with the first gap being 22-26 μm and the second gap being 10-14 μm; then peeling 3-6 times with the first gap being 10-14 μm and the second gap being 4-8 μm; then peeling 3-6 times with the first gap being 4-8 μm and the second gap being 2-3 μm; and finally peeling 3-6 times with the first gap being 2-3 μm and the second gap being 1-1.9 μm, for a total of 12-24 peeling cycles.

8. The method according to claim 1, characterized in that, The water bath heating and stirring are specifically: temperature 60-100℃, rotation speed 300-500r / min.

9. The method of claim 1, wherein, The specific conditions for cold isostatic pressing are hydraulic pressure of 100-300 MPa and pressure holding for 5-20 minutes.

10. A multi-dimensional structured silicon carbide-silicon nitride composite material, characterized by, Prepared by the method described in any one of claims 1-9.

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