SiC nanofiber synergized in-situ ultrafine layered TiC x Method for producing reinforced siC composite

Abstract

The application relates to a SiC nanofiber synergistic in-situ self-grown ultrafine layered TiC x A preparation method of reinforced SiC composite material. Ti3AlC2 powder, SiC powder and dispersed SiC nanofiber are blended, high-energy ball milling, drying and sieving are carried out to obtain mixed powder, a green body is formed through die pressing, and finally hot-pressing sintering is carried out. In the application, high-toughness SiC nanofiber is used to synergize Ti3AlC2 to form TiC in-situ in the SiC ceramic matrix, which has good interface wettability and pure interface x A ceramic dispersion reinforcement body is obtained, and a high-density, super-tough high-strength, high-temperature-resistant and corrosion-resistant SiC nanofiber synergistic in-situ self-grown layered TiC x Ultrafine particle reinforced SiC composite material; compared with the interface wettability of externally added TiC and the matrix, the interface wettability is significantly improved; compared with the fracture toughness of traditional SiC ceramics, the fracture toughness is 2-5 MPa.m 1 / 2 , which jumps to more than 9 MPa.m 1 / 2 , and the structural ceramic is greatly toughened; compared with the preparation process of traditional SiC ceramic matrix composite material, the material has great potential in the fields of petrochemical industry, vehicle brake disc, hypersonic aircraft and the like.

Description

Technical Field

[0001] This invention belongs to the field of ceramic matrix composite material preparation technology, specifically relating to a SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC x Preparation method of reinforced SiC composite materials. Background Technology

[0002] Silicon carbide (SiC) ceramics possess numerous advantages, including low density, high elastic modulus, high strength, wear resistance, corrosion resistance, oxidation resistance, and excellent high-temperature performance. They hold immense application potential in fields such as mechanical seals, wear-resistant bearings, hard cutting tools, advanced refractory materials, aerospace, and bulletproof armor. However, SiC is a highly covalent compound, with strong C-Si bonds accounting for up to 90% of its composition. This can easily lead to stress concentration due to the inability to effectively release internal defects, ultimately resulting in brittle fracture and failure. Furthermore, the excessively strong covalent bonds result in a low self-diffusion coefficient (1.5 × 10⁻⁶) for elements such as C and Si. -10 -2.5×10 -13 cm 2 The inherent brittleness of SiC ceramics also leads to problems such as difficulty in sintering and densification, resulting in mechanical properties of SiC ceramics falling far short of expectations. This, in turn, causes defects such as a lack of toughness and poor impact resistance due to its inherent brittleness as a ceramic material, severely limiting its application in structural materials and related special materials.

[0003] To improve the mechanical properties of SiC ceramics, second-phase reinforcements, such as fibers, whiskers, or particles, are typically introduced into the matrix. This involves introducing highly tough, high aspect ratio reinforcements with a specific arrangement within the brittle matrix, or introducing dispersed isotropic reinforcement structures within the matrix. The synergistic effect between these heterogeneous components alleviates localized stress concentrations or improves the material's resistance to crack propagation, thus achieving toughening and strengthening of SiC ceramics. Existing research indicates that while high aspect ratio whisker or fiber reinforcements can significantly improve the toughness and strength of materials, they suffer from problems such as uncontrollable bonding with the matrix interface, the need for complex coating processes and difficulty in achieving uniform distribution, high porosity in the composite material, and excessively high sintering temperatures leading to coarse matrix grains and uncontrollable growth or reaction damage of the reinforcement. These issues severely limit the strengthening and toughening effect of such high aspect ratio reinforcements on the ceramic matrix. In contrast, second-phase particle reinforcements offer numerous advantages, including high dispersion, uniform distribution, stable and easily controllable bonding with the matrix interface, and high composite material density. Furthermore, their preparation process is simple, making them more suitable for the fabrication and large-scale production of complex components. However, the existing technology of using traditional non-in-situ synthesis to strengthen SiC ceramic materials has a series of key problems that are difficult to overcome, such as poor wettability of the heterogeneous interface formed with SiC ceramics, resulting in very limited effectiveness.

[0004] Ti3AlC2 ceramics, as an important member of the MAX phase material family, exhibit unique layered structures that distinguish them from traditional ceramics, including self-lubrication, ease of processing, and high electrical conductivity. Recent studies have confirmed that Ti3AlC2 can not only form highly dispersed, fine-grained, non-stoichiometric TiC in situ within metals or alloys... x The reinforcement, and the interfacial wettability with the metal phase is better with the addition of TiC or other in-situ synthesized TiC. x The reinforcement is significantly improved, and the mechanical properties of the resulting composite material are also significantly enhanced. Currently, research on obtaining in-situ ceramic reinforcements using MAX phase materials has only been partially explored in metal matrix materials. Unlike metal materials, ceramic materials often suffer from poor wettability at heterogeneous interfaces even under ultra-high temperature and high pressure conditions due to the prevalent strong covalent / ionic bonds. This can lead to unstable interfacial bonding or even complete non-wetting (only physical interlocking), resulting in the mechanical properties of the prepared composite materials often falling short of the expected design. Furthermore, no research has been reported on the application of this method in ceramic matrix materials. Therefore, introducing fiber reinforcements into ceramic matrix composites modified with MAX phase materials has great potential. Summary of the Invention

[0005] To address the problems and shortcomings of the existing technologies, the purpose of this invention is to provide a SiC nanofiber-assisted in-situ self-generated ultrafine layered TiC... x The preparation method of enhanced SiC composite materials significantly improves the mechanical properties of the composite materials, optimizes the sintering process, reduces energy consumption, and avoids the introduction of impurity phases such as sintering aids.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0007] A SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC x Methods for preparing reinforced SiC composite materials include:

[0008] S1. Add SiC nanofibers and an appropriate amount of distilled water to a container, stir magnetically to disperse for 12-16 hours, take out the dispersed SiC nanofibers, and dry them in an oven at 80-120℃ for 24-48 hours for later use.

[0009] S2. Ti3AlC2 powder, β-SiC powder, and appropriate amounts of polyethylene glycol and anhydrous ethanol are sequentially added to a grinding jar containing grinding balls. The jar is then placed in a planetary ball mill for high-energy ball milling at a speed of 280-300 r / min for 8-12 h. The grinding jar is then removed, and SiC nanofibers and an appropriate amount of anhydrous ethanol are added again. The mixture is then ball milled at high energy to obtain a ball milling slurry.

[0010] S3. Take out the ball mill slurry from S2, dry it, and obtain dry powder;

[0011] S4. The dried powder in S3 is crushed, sieved through a mesh of 300 or more, placed into a stainless steel mold, and held under pressure of 15-25MPa for 5-8 minutes to obtain a block blank.

[0012] S5. The bulk blank from S4 is loaded into a graphite mold and placed into a vacuum hot pressing sintering furnace. It is then hot-pressed and sintered in a vacuum or argon atmosphere to obtain the SiC composite material.

[0013] Preferably, in S2, the mass fraction of Ti3AlC2 powder is 30-40 wt%, the mass fraction of SiC nanofibers is 5-30 wt%, and the remainder is β-SiC powder.

[0014] Preferably, in S2, the purity of Ti3AlC2 powder is 95%-98% and the average particle size is 40-80μm, the purity of β-SiC powder is ≥98% and the average particle size is less than 1μm, and the size of SiC nanofibers is 200-500nm.

[0015] Preferably, after adding SiC nanofibers again in step S2, the ball milling time is 1-3 hours, the ball-to-material ratio is 3-5:1, and the rotation speed is 280-330 r / min to obtain the ball milling slurry.

[0016] Preferably, in step S3, the ball-milled slurry is dried in an oven at 80-120°C for more than 24 hours to obtain dried powder.

[0017] Preferably, in step S5, the bulk blank is placed in a vacuum atmosphere with a vacuum degree of 1×10⁻⁶. -2 -1×10 -5 Hot pressing and sintering in a Pa or argon positive pressure atmosphere.

[0018] Preferably, the hot pressing sintering parameters in S5 are set as follows: temperature 1500-2000℃, pressure 15-35 MPa, and holding time 1-3 h.

[0019] Preferably, the sintering temperature is 1750-1950℃ and the hot pressing sintering pressure is 20-30MPa.

[0020] Preferably, the heating rate is 5°C / min in the sintering temperature range of 20-100°C, 20-30°C / min in the 100-1200°C range, and 5-10°C / min from 1200°C to the maximum sintering temperature.

[0021] Preferably, when the temperature inside the vacuum hot pressing sintering furnace reaches the predetermined temperature, the pressurization program is started to gradually increase the pressure. After 5-8 minutes, the maximum pressure of 15-35 MPa is reached. After holding the pressure for 1-3 hours, the pressure is released. After 20-40 minutes, the pressure drops to 0 MPa. After the temperature inside the furnace cools to room temperature, the sample is taken out to obtain the SiC composite material.

[0022] The principle of the technical solution: In this invention, the ball milling time is controlled to be 1-3 hours after adding SiC nanofibers to S2 to prevent excessively long ball milling time from damaging the fiber structure. In this invention, the hot-pressing sintering parameters are set to a temperature of 1500-2000℃, a pressure of 15-35 MPa, and a holding time of 1-3 hours to achieve the synthesis and densification of the composite material. The densification process of the ceramic matrix composite material uses low-melting-point elemental aluminum precipitated from Ti3AlC2 at high temperature as a sintering aid, promoting pore expulsion, particle rearrangement, and volume shrinkage through liquid-phase sintering, thereby achieving high-density in-situ self-generated TiC. x The preparation of reinforced SiC composite materials involves no additional sintering aids during the entire sintering process. In this invention, the variation in heating rate at different temperature stages is based on the structural transformation characteristics caused by the breakdown and outward diffusion of weak bonds of Al elements in the special layered structure of Ti3AlC2 at high temperatures (>1200℃). This invention uses Ti3AlC2 powder and SiC nanofibers as raw materials, with Al released from the high-temperature decomposition of Ti3AlC2 as a sintering aid. Through a hot-pressing sintering process, ultrafine layered TiC composites with excellent surface wettability are obtained. x Particles and SiC nanofibers are used to toughen and reinforce SiC ceramics. This addresses the technical problems in existing technologies, such as large and unevenly distributed ceramic reinforcement particles, poor wettability at the reinforcement-matrix interface, impurities at the interface leading to low composite density, excessively high sintering temperatures causing reactions between the reinforcement and matrix, and the introduction of impurity phases due to the need for additional sintering aids. These issues hinder the full realization of the synergistic effect of the reinforcement and matrix in improving the mechanical properties of composite materials.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention addresses the problems of traditional SiC ceramics, such as excessively high sintering temperatures (>2100℃), over-reliance on sintering aids (e.g., YAG-based materials), difficulty in densification, and excessive grain growth caused by excessively high sintering temperatures. These issues lead to unsatisfactory overall mechanical properties of SiC ceramics, particularly fracture toughness, a key indicator for structural components. This invention provides a SiC nanofiber-assisted in-situ self-generated ultrafine layered TiC... x Preparation methods of reinforced SiC composite materials:

[0025] (1) This invention utilizes the metamorphic properties of the Ti3AlC2 layered structure to form, in situ, a material with ultra-fine dimensions (below submicron level) and a different stoichiometric ratio (TiC) from common (non-)stoichiometry in the SiC matrix at a certain sintering temperature (>1200℃). x TiC particles possess a unique layered structure, excellent surface / interface wettability, and a pure interfacial composition. x Ceramic dispersion reinforcement, synergistically introduced high aspect ratio, high toughness SiC nf A high-toughness, high-strength, high-temperature resistant, and corrosion-resistant SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC was prepared. x Reinforced SiC composites; significantly improved interfacial wettability between the composite and the matrix compared to externally added TiC; and improved fracture toughness (2-5 MPa·m) compared to traditional SiC ceramics. 1 / 2 A significant jump (>9 MPa·m) 1 / 2 The fracture toughness was increased by 2-5 times, achieving efficient toughening and reinforcement, and greatly enhancing its potential as a structural material.

[0026] (2) This invention utilizes the metamorphic properties of the Ti3AlC2 layered structure to induce the self-diffusion of Al atoms to form high-temperature Al elemental at temperatures far below the traditional SiC ceramic sintering temperature (>1200℃). This serves as a sintering aid, effectively promoting pore discharge, particle rearrangement, and volume shrinkage, thereby achieving in-situ self-generated TiC in synergy with SiC nanofibers. x The low-temperature, additive-free preparation technology for reinforced SiC composites is simple, energy-saving, and emission-reducing, making it suitable for large-scale production.

[0027] (3) The SiC nanofibers synergistically in-situ self-generated ultrafine layered TiC provided by this invention x Reinforced SiC composites have great potential in fields such as petrochemicals, vehicle brake discs, and hypersonic aircraft.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is the method provided in Example 1 of the present invention for preparing SiC nanofibers in situ with in-situ ultrafine TiC. x Process flow diagram of SiC composite materials;

[0030] Figure 2 This invention uses different SiC nf The proportion of SiC nanofibers provided in situ synergistically with in-situ ultrafine TiC x Line graph showing the changes in flexural strength and fracture toughness of SiC composite materials;

[0031] Figure 3The SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC provided in Example 1 of this invention x Scanning electron microscope (SEM) image of the polished surface of the reinforced SiC composite material;

[0032] Figure 4 The SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC provided in Example 1 of this invention x Scanning electron microscopy backscattered image (BD-SEM) of a polished surface of a reinforced SiC composite material;

[0033] Figure 5 The SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC provided in Example 1 of this invention x Scanning electron microscope (SEM) images of the cross-section of the reinforced SiC composite material;

[0034] Figure 6 The SiC nanofiber synergistic in-situ self-generated ultrafine layered TiC provided in Example 1 of this invention x Scanning electron microscope (SEM) images of the cross-section of the reinforced SiC composite material;

[0035] Figure 7 The SiC nanofibers synergistically in-situ self-generated ultrafine layered TiC provided in Examples 1-3 x X-ray characteristic diffraction peak pattern (XRD) of reinforced SiC composite material. Detailed Implementation

[0036] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0037] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0038] Unless otherwise specified, all raw materials used in this invention are commercially available products in the art.

[0039] Example 1: A SiC nanofiber-assisted in-situ self-generated ultrafine layered TiC x The preparation method of reinforced SiC composite materials includes the following steps:

[0040] S1. Add SiC nanofibers and an appropriate amount of distilled water to a container, stir magnetically to disperse for 12 hours, take out the dispersed SiC nanofibers, and dry them in an 80℃ oven for 24 hours for later use.

[0041] S2. 40wt% Ti3AlC2 powder (purity 96%, average particle size 54μm), 55wt% β-SiC powder (β-SiC powder purity 98%, average particle size 1μm), and appropriate amounts of polyethylene glycol and anhydrous ethanol are sequentially added to a grinding jar containing grinding balls. The jar is then placed in a planetary ball mill for high-energy ball milling at a speed of 280 r / min for 8 h. The grinding jar is then removed, and 5wt% SiC nanofibers (SiC nanofiber size 350nm) and appropriate amounts of anhydrous ethanol are added again. The mixture is then ball milled for 2 h, with a ball-to-material ratio of 4:1 and a grinding speed of 280 r / min to obtain a ball mill slurry.

[0042] S3. Take out the ball mill slurry from S2 and dry it in an oven at 80℃ for 48 hours to obtain dried powder.

[0043] S4. The dried powder in S3 is crushed, passed through a 300-mesh sieve, and placed into a stainless steel mold with a mold size of Ф=50mm. It is then held under a pressure of 25MPa for 6 minutes to obtain a block blank.

[0044] S5. Load the bulk blank from S4 into a graphite mold and place it in a vacuum hot pressing sintering furnace. Sinter at 1600℃ (vacuum degree 1×10⁻⁶) under a vacuum atmosphere. -2 Hot pressing sintering was performed under a pressure of 30 MPa. The heating program was set as follows: a heating rate of 5℃ / min in the 20-100℃ range, a heating rate of 20℃ / min in the 100-1200℃ range, and a heating rate of 10℃ / min in the 1200-1600℃ range, with a holding time of 1 hour. The pressurization program was set as follows: when the furnace temperature reached 1500℃, the pressurization program was started to gradually increase the pressure, reaching the maximum pressure of 30 MPa after 5 minutes. After holding for 1 hour, the pressure was released, and after 30 minutes, the pressure dropped to 0 MPa. After the furnace temperature cooled to room temperature, the sample was removed, thus obtaining the corresponding SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC. x Reinforced SiC composites.

[0045] Example 2: A SiC nanofiber-assisted in-situ self-generated ultrafine layered TiC x The preparation method of reinforced SiC composite materials includes the following steps:

[0046] S1. Add SiC nanofibers and an appropriate amount of distilled water to a container, stir magnetically to disperse for 14 hours, take out the dispersed SiC nanofibers, and dry them in an oven at 100℃ for 36 hours for later use.

[0047] S2. 40wt% Ti3AlC2 powder (purity 97%, average particle size 48μm), 50wt% β-SiC powder (β-SiC powder purity 98%, average particle size 1μm), and appropriate amounts of polyethylene glycol and anhydrous ethanol are sequentially added to a grinding jar containing grinding balls. The jar is then placed in a planetary ball mill for high-energy ball milling at a speed of 290 r / min for 10 h. The grinding jar is then removed, and 10wt% SiC nanofibers (SiC nanofiber size 350nm) and appropriate amounts of anhydrous ethanol are added again. The mixture is then ball milled for 2 h, with a ball-to-material ratio of 5:1 and a grinding speed of 290 r / min, to obtain a ball mill slurry.

[0048] S3. Dry the ball mill slurry from S2 in an oven at 100℃ for 36 hours to obtain dried powder.

[0049] S4. The dried powder in S3 is crushed, passed through a 350-mesh sieve, and placed into a stainless steel mold with a mold size of Ф=50mm. It is then held under pressure of 20MPa for 7 minutes to obtain a block blank.

[0050] S5. Load the bulk blank from S4 into a graphite mold and place it in a vacuum hot pressing sintering furnace. Sinter at 1800℃ (vacuum degree 1×10⁻⁶) in a vacuum atmosphere. -3 Hot pressing sintering was performed under a pressure of 20 MPa. The heating program was set as follows: a heating rate of 5℃ / min in the 20-100℃ range, a heating rate of 20℃ / min in the 100-1200℃ range, and a heating rate of 10℃ / min in the 1200-1800℃ range, with a holding time of 1 hour. The pressurization program was set as follows: when the furnace temperature reached 1700℃, the pressurization program was started to gradually increase the pressure, reaching the maximum pressure of 20 MPa after 7 minutes. After holding for 1 hour, the pressure was released, and after 30 minutes, the pressure dropped to 0 MPa. After the furnace temperature cooled to room temperature, the sample was removed, thus obtaining the corresponding SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC. x Reinforced SiC composites.

[0051] Example 3: A SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC x The preparation method of reinforced SiC composite materials includes the following steps:

[0052] S1. Add SiC nanofibers and an appropriate amount of distilled water to a container, stir magnetically to disperse for 12 hours, take out the dispersed SiC nanofibers, and dry them in an oven at 120℃ for 48 hours for later use.

[0053] S2. 40wt% Ti3AlC2 powder (purity 98%, average particle size 40μm), 45wt% β-SiC powder (β-SiC powder purity 98%, average particle size 1μm), and appropriate amounts of polyethylene glycol and anhydrous ethanol are sequentially added to a grinding jar containing grinding balls. The jar is then placed in a planetary ball mill for high-energy ball milling at a speed of 300 r / min for 12 h. The grinding jar is then removed, and 15wt% SiC nanofibers (SiC nanofiber size 350nm) and an appropriate amount of anhydrous ethanol are added again. The mixture is then ball milled for 3 h, with a ball-to-material ratio of 5:1 and a grinding speed of 280 r / min to obtain a ball mill slurry.

[0054] S3. Dry the ball mill slurry from S2 in an oven at 120°C for 24 hours to obtain dried powder.

[0055] S4. The dried powder in S3 is crushed, sieved through a 400-mesh sieve, and placed into a stainless steel mold with a mold size of Ф=50mm. It is then held under a pressure of 15MPa for 8 minutes to obtain a block blank.

[0056] S5. Load the bulk blank from S4 into a graphite mold and place it in a vacuum hot pressing sintering furnace. Sinter in a vacuum atmosphere at 1950℃ (vacuum degree 1×10⁻⁶). -5 Hot pressing sintering was performed under a pressure of 15 MPa. The heating program was set as follows: a heating rate of 5℃ / min in the 20-100℃ range, a heating rate of 20℃ / min in the 100-1200℃ range, and a heating rate of 10℃ / min in the 1200-1950℃ range, with a holding time of 1 hour. The pressurization program was set as follows: when the furnace temperature reached 1850℃, the pressurization program was started to gradually increase the pressure, reaching the maximum pressure of 15 MPa after 8 minutes. After holding for 1 hour, the pressure was released, and after 30 minutes, the pressure dropped to 0 MPa. After the furnace temperature cooled to room temperature, the sample was removed, thus obtaining the corresponding SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC. x Reinforced SiC composites.

[0057] The following experiments were conducted to evaluate the SiC nanofiber synergistic in-situ ultrafine TiC provided in each embodiment. x Performance verification of SiC composite materials:

[0058] (1) Using different SiC nf The proportion of SiC nanofibers provided in situ synergistically with in-situ ultrafine TiC x Mechanical properties of the / SiC composite material were tested, and the results are as follows: Figure 2 .

[0059] (2) The SiC nanofibers synergistically produced in-situ ultrafine TiC provided in Example 1 x The surface morphology of the / SiC composite material was observed, and the results are as follows: Figures 3-6 .

[0060] (3) X-ray diffraction experiments were conducted on the SiC composite materials prepared in Examples 1-3. The experimental results are as follows: Figure 7 As shown.

[0061] The test results are as follows:

[0062] (1) By Figure 2 It can be seen that different SiC nf The ratio of SiC nanofibers to in-situ ultrafine TiC x The flexural strength and fracture toughness of SiC composites are significantly affected. The composite prepared with 15 wt% SiC nanofibers exhibits a very high flexural strength exceeding 570 MPa, while its fracture toughness surpasses 9 MPa·m. 1 / 2 Because SiC ceramics typically have extremely poor or even almost no toughness (fracture toughness value 2-4 MPa·m), 1 / 2 Therefore, the SiC-based composite material prepared by this method exhibits significantly higher toughness than ordinary SiC ceramics (9 vs 2-4 MPa·m). 1 / 2 The toughness is increased by 2 to 5 times.

[0063] (2) By Figures 3-6 The provided SEM results show that the SiC nanofibers synergistically produce in-situ self-generated ultrafine layered TiC nanofibers obtained in Example 1 of this invention x The surface of the reinforced SiC composite material is smooth and free of obvious pores and microcracks, resulting in an ultrafine reinforced TiC. x The particles are extremely small (approximately a few micrometers to submicrometers) and dispersed within the SiC matrix, while TiC... x The SiC two-phase heterogeneous interface is tightly bonded with no obvious voids in the interface region. A small amount of Al2O3 phase is also present within the material, and this small amount of Al2O3, with its good wettability and excellent mechanical properties, can act as a substrate for TiC. x / SiC nf The SiC intermediate transition phase also contributes to the mechanical and high-temperature properties of the composite material to some extent. Overall, the composite material has a dense structure, uniform phase distribution, no protrusions or graininess on the surface, and low surface roughness.

[0064] (3) Figure 7 XDR results show that under the process conditions of sintering temperature of 1600-1950℃, sintering pressure of 15-30MPa, and holding time of 1h, the final product obtained regardless of the SiC nanofiber addition amount of 5wt%, 10wt%, or 15wt% has a relatively pure phase composition. The two sets of characteristic peaks are very significant, representing the TiC formed in situ by the decomposition of Ti3AlC2. xThe enhanced phase peaks, as well as the original SiC nanofibers and SiC matrix phase peaks (3C-SiC), were detected. At the same time, very weak Al2O3 and Ti3SiC2 peaks were also detected as impurity phases (Al2O3 is a common impurity phase in Al-containing ceramics due to the presence of residual oxygen on the surface of the raw material powder and lattice oxygen inside the powder, which usually does not affect the material properties).

[0065] By using Ti3AlC2 ceramic as a precursor, a TiC matrix with excellent interfacial wettability and a pure interface is formed in the ceramic matrix at a sintering temperature far lower than that of traditional SiC ceramics. x Ceramic dispersion reinforcement particles, combined with externally added high aspect ratio SiC nano-ceramic fibers with outstanding mechanical properties. nf By synergistically strengthening the SiC ceramic matrix, a highly dense, highly tough, and highly strong SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC was finally obtained. x Reinforced SiC Composites. The SiC-based composite material preparation method of the present invention can solve the problems of high energy consumption in the preparation of traditional SiC ceramics and their composites, the problem of impurity phase contamination introduced by adding sintering aids, the problem of poor bonding at ceramic / ceramic heterostructure interfaces, the common problems of coarse particles and uneven distribution of ceramic reinforcements in the ceramic matrix, and the problems of extremely poor toughness and insufficient strength in traditional SiC ceramics. In summary, the preparation method provided by the present invention can, within the relevant process parameter range, produce a novel SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC composite with relatively pure phase, high density, high toughness, and high strength. x Reinforced SiC composites.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. 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 still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC x A method for preparing reinforced SiC composite materials, characterized in that, Includes the following steps: S1. Add SiC nanofibers and an appropriate amount of distilled water to a container, stir magnetically to disperse for 12-16 hours, take out the dispersed SiC nanofibers, and dry them in an oven at 80-120℃ for 24-48 hours for later use. S2. Ti3AlC2 powder, β-SiC powder, and appropriate amounts of polyethylene glycol and anhydrous ethanol are sequentially added to a ball mill jar containing grinding balls. The jar is then placed in a planetary ball mill for high-energy ball milling at a speed of 280-300 r / min for 8-12 h. The ball mill jar is then removed, and SiC nanofibers and an appropriate amount of anhydrous ethanol are added again. The mixture is then ball milled at high energy to obtain a ball mill slurry. S3. Take out the ball mill slurry from S2, dry it, and obtain dry powder; S4. The dried powder in S3 is crushed, sieved through a sieve of 300 mesh or higher, placed into a stainless steel mold, and held under pressure of 15-25 MPa for 5-8 minutes to obtain a block blank. S5. The bulk blank in S4 is loaded into a graphite mold and placed into a vacuum hot pressing sintering furnace. It is then hot-pressed and sintered in a vacuum or argon atmosphere to obtain the SiC composite material. The mass fraction of Ti3AlC2 powder in S2 is 30-40 wt%, the mass fraction of SiC nanofibers is 15 wt%, and the remainder is β-SiC powder; The purity of Ti3AlC2 powder in S2 is 95%-98%, the average particle size is 40-80 μm, the purity of β-SiC powder is ≥98%, the average particle size is less than 1 μm, and the SiC nanofiber size is 200-500 nm. After adding SiC nanofibers again to S2, the ball milling time is 1-3 hours, the ball-to-material ratio is 3-5:1, and the rotation speed is 280-330 r / min to obtain the ball milling slurry.

2. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC nanofiber according to claim 1 x A method for preparing reinforced SiC composite materials, characterized in that, In S3, the ball-milled slurry is dried in an oven at 80-120℃ for more than 24 hours to obtain dried powder.

3. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC nanofiber according to claim 1 x A method for preparing reinforced SiC composite materials, characterized in that, In S5, the bulk blank is placed in a vacuum atmosphere with a vacuum degree of 1×10⁻⁶. -2 -1×10 -5 Hot pressing and sintering in a Pa or argon positive pressure atmosphere.

4. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC nanofiber according to claim 1 x A method for preparing reinforced SiC composite materials, characterized in that, The hot pressing sintering parameters in S5 are set as follows: temperature 1500-2000℃, pressure 15-35Mpa, and holding time 1-3h.

5. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC as described in claim 4 x A method for preparing reinforced SiC composite materials, characterized in that, The sintering temperature is 1750-1950℃, and the hot pressing sintering pressure is 20-30MPa.

6. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC according to any one of claims 4-5 x A method for preparing reinforced SiC composite materials, characterized in that, The heating rate is 5℃ / min in the sintering temperature range of 20-100℃, 20-30℃ / min in the 100-1200℃ range, and 5-10℃ / min from 1200℃ to the maximum sintering temperature.

7. The SiC nanofiber-synergistic in-situ self-generated ultrafine layered TiC according to any one of claims 4-5 x A method for preparing reinforced SiC composite materials, characterized in that, When the temperature inside the vacuum hot pressing sintering furnace reaches the predetermined temperature, the pressurization program is started to gradually increase the pressure. After 5-8 minutes, the maximum pressure of 15-35 MPa is reached. After holding the pressure for 1-3 hours, the pressure is released. After 20-40 minutes, the pressure drops to 0 MPa. After the temperature inside the furnace cools to room temperature, the sample is taken out to obtain the SiC composite material.

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