High-toughness reaction-sintered boron carbide ceramic composite material and preparation method thereof

Abstract

The invention belongs to the technical field of ceramics, and relates to a high-toughness reaction-sintered boron carbide ceramic composite material and a preparation method thereof. Resorcinol, formaldehyde, deionized water, basic salt containing Fe, Co and Ni and B4C powder are used as raw materials, a B4C / C porous prefabricated body of a fiber interwoven structure is prepared through a gel injection molding technology, then the high-toughness reaction sintering boron carbide ceramic composite material is obtained through silicon infiltration, the silicon carbide phase exists in the two forms of nanocrystals and whiskers, and the high-toughness reaction sintering boron carbide ceramic composite material is obtained. The B4C particles are wrapped by a continuous silicon carbide network formed by the silicon carbide nanocrystals, the silicon carbide whiskers are dispersed and distributed around the B4C particles, and meanwhile, the bending strength and the fracture toughness of the composite material are improved.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramics and relates to a high-strength and toughness reaction-sintered boron carbide ceramic composite material and a preparation method thereof. Background Art

[0002] In modern military conflicts, it is crucial to improve the battlefield survivability of combatants and weapon systems. To achieve this goal, the armies of various countries widely use ballistic protective equipment to protect soldiers and vehicles from direct damage from enemy fire. Ceramic materials, especially boron carbide (B4C), have become ideal for manufacturing high-performance armor due to their excellent physical properties - low density, high hardness and high elastic modulus. These properties enable boron carbide to effectively resist the impact of high-speed projectiles and fragments, reduce the weight of protective equipment, and provide excellent protective performance.

[0003] Boron carbide is a compound tightly bound by covalent bonds. It has good chemical stability, strong wear resistance, and extremely high hardness, almost second only to diamond. However, due to its structural characteristics - 93.94% is covalently bonded - boron carbide has a low self-diffusion coefficient, which means that it is not easy to sinter and densify under conventional conditions. Therefore, high temperature and high pressure environment are usually required to make boron carbide ceramics reach the required density and strength, but this also brings several problems: higher sintering temperature and longer holding time increase the energy demand in the preparation process, thereby increasing the cost; too high sintering temperature may cause excessive growth of boron carbide grains, forming larger pores, reducing the overall density of the material, and thus weakening the hardness and toughness of the ceramic.

[0004] Faced with these problems, in the 1970s, the United States developed a new technical path - melt infiltration method, which is used to prepare reaction sintered boron carbide ceramic composites. This method greatly reduces production costs by infiltrating liquid metal or alloy into porous boron carbide blanks, filling pores and achieving densification. However, although this method reduces the difficulty and cost of preparation, the problem of insufficient toughness and strength of boron carbide ceramics is still difficult to solve, limiting the wider application and development of this material. For example, under high-intensity impact, traditional boron carbide ceramics are prone to crack propagation, resulting in protection failure.

[0005] In order to further improve the mechanical properties of boron carbide ceramics, scientists consider adding reinforcing phases, such as silicon carbide (SiC) whiskers. These whiskers not only have high strength and high elastic modulus, but also show good chemical stability. In theory, they can be added to the boron carbide matrix as an ideal toughening component. However, in actual operation, whiskers are prone to agglomeration, which affects the consistency of the internal structure of the material and may reduce the toughness of the material. In addition, the introduction of whiskers may also bring problems with interface bonding strength, because the difference in thermal expansion coefficients between different materials may cause stress concentration during the cooling process, further weakening the performance of the material.

[0006] The Chinese patent application document (publication number: CN110304923A) discloses a method for preparing a boron carbide-based ceramic composite material based on particle grading, which includes: mixing B4C powders of different specifications in proportion and grinding them for later use; using water as solvent, acrylamide, methylenebisacrylamide, and tetramethylammonium hydroxide as solutes, preparing a premixed liquid in proportion, adding the B4C mixed powder and then adding an initiator for injection molding and curing, and obtaining a B4C blank after drying and carbonization; placing Si on the B4C blank for vacuum infiltration to obtain a boron carbide ceramic composite material. However, the acrylamide used in the method is neurotoxic, easily carcinogenic, and poses a great threat to personnel; on the other hand, the method easily forms large-sized silicon carbide in the material, which has an adverse effect on the strength of the material.

[0007] A Chinese patent application document (publication number: CN110304923A) discloses a method for preparing a silicon carbide fiber reinforced boron carbide ceramic material. However, the added silicon carbide fiber is extremely difficult to disperse and it is difficult to increase its proportion in the material. The non-uniformity of the silicon carbide fiber and the thermal expansion mismatch with boron carbide can easily lead to stress concentration in the material to form microcracks, thereby reducing the material performance. The introduction of a small amount of fiber has limited effect on improving the toughness of the material. On the other hand, the silicon carbide fiber is expensive and difficult to promote industrialization.

[0008] A Chinese patent application document (publication number: CN105777130A) discloses a gel injection molding preparation method for reaction-sintered boron carbide ceramic composites. However, the use of sodium carbonate as a catalyst can only catalyze the polymerization of the gel system, and cannot catalyze the growth of nanowire structures. It is still difficult to solve the problem of low toughness of boron carbide ceramic composites. Summary of the invention

[0009] The purpose of the present invention is to solve the above problems existing in the prior art and to propose a method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material. The silicon carbide phase in the prepared reaction-sintered boron carbide ceramic composite material exists in the form of nanocrystals and whiskers. The B4C particles are wrapped by a continuous silicon carbide network formed by silicon carbide nanocrystals, and the silicon carbide whiskers are dispersed around the B4C particles, thereby improving the flexural strength and fracture toughness of the composite material.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] A method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, the method comprising the following steps:

[0012] S1, adding the B4C mixed powder into a resorcinol formaldehyde solution containing at least one of Fe, Co and Ni to obtain a mixed solution, and then ball milling to obtain a slurry;

[0013] S2, after vacuum degassing, pour the slurry into a mold and seal it, and obtain a solidified body after gelation and normal pressure drying;

[0014] S3, carbonizing the solidified body in a flowing argon atmosphere to obtain a preform;

[0015] S4. Spread silicon particles on the preform and perform high-temperature infiltration in a vacuum, and finally obtain a high-strength and tough reaction-sintered boron carbide ceramic composite material by cooling.

[0016] In the above-mentioned method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material, the resorcinol formaldehyde solution is prepared by mixing a basic salt containing at least one of Fe, Co, and Ni, resorcinol, formaldehyde, and deionized water, wherein the concentration of the basic salt containing at least one of Fe, Co, and Ni in the resorcinol formaldehyde solution is 0.0002 to 0.02 mol%.

[0017] In the present invention, basic salts of Fe, Co and Ni are used as catalysts. On the one hand, the "polymerization-induced phase separation" process between the resorcinol formaldehyde resin phase and water can be promoted to make the preform more compact. On the other hand, Fe, Co and Ni ions can promote the formation of silicon carbide nanocrystals and silicon carbide nanowires in the reaction-sintered boron carbide ceramics, thereby achieving the strengthening and toughening of the material.

[0018] However, the addition amount of basic salts of Fe, Co, and Ni needs to be controlled. Too much addition will cause the preform to be too dense, making it difficult for molten silicon to penetrate, and forming residual C and residual pores in the reaction-sintered boron carbide ceramics, reducing the mechanical properties of the ceramics; too little addition will not form a nanowire structure and cannot play a role in strengthening and toughening.

[0019] Preferably, the basic salt containing at least one of Fe, Co and Ni is basic nickel carbonate.

[0020] In the above-mentioned method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, the B4C mixed powder is graded according to the mass ratio, with an average particle size of 30-50 μm: an average particle size of 5-15 μm: an average particle size of 1-3 μm = (5-7): 1: (2-4).

[0021] In the above-mentioned method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, the content of B4C mixed powder in the mixed solution in step S1 is 40-75wt%,

[0022] Preferably, the ball milling process uses zirconium oxide balls as grinding media, and the ball milling time is 6 to 24 hours.

[0023] In the above-mentioned method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, the gelation temperature in step S2 is 70-90° C., the insulation time is 6-24 hours, and the drying temperature is 100-150° C., and the time is 6-24 hours.

[0024] In the above-mentioned method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material, the carbonization treatment temperature in step S3 is 800-1200°C, the carbonization holding time is 2-6h, the heating rate is 1-5°C / min, and the argon flow rate is 0.5-2mL / min. The present invention utilizes flowing argon to provide a growth path for the carbon nanowires in the preform while preventing oxidation of the carbon source and ensuring its graphitization degree, and can reduce the lattice defects of the carbon nanowires compared with other nitrogen or vacuum conditions.

[0025] In the above-mentioned method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material, the preform is composed of B4C particles and carbon nanowires, and the B4C particles are dispersed in the fiber interlaced structure formed by the carbon nanowires, wherein the carbon content is 5-20wt%. The present invention controls the carbon content by carbonization with resorcinol formaldehyde. If the carbon content is too high, the proportion of silicon carbide nanocrystals and silicon carbide whiskers in the composite material will increase, and silicon infiltration blockage will be easily caused, thereby reducing the hardness of the ceramic; if the carbon content is too low, the proportion of silicon carbide nanocrystals and silicon carbide whiskers will decrease, the proportion of residual silicon will increase, and the mechanical properties will be reduced.

[0026] In the above-mentioned method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, in step S4, the high-temperature infiltration is heated to 1450-1650° C. at a rate of 1-10° C. / min, and the holding time is 10-120 min.

[0027] In the above-mentioned method for preparing a high-strength and toughness reaction-sintered boron carbide ceramic composite material, the particle size of the silicon particles in step S4 is 1 to 5 mm, and the actual amount of silicon particles added is ≥1.5 times the theoretical amount.

[0028] The present invention also provides a strong and tough reaction-sintered boron carbide ceramic composite material, which is prepared by the above-mentioned preparation method. The silicon carbide phase in the prepared high-strength and tough reaction-sintered boron carbide ceramic composite material exists in the form of nanocrystals and whiskers. The B4C particles are wrapped by a continuous silicon carbide network formed by silicon carbide nanocrystals, and the silicon carbide whiskers are dispersed around the B4C particles.

[0029] Preferably, the ceramic composite material has a flexural strength of 510-525 MPa and a fracture toughness of 5.50-6.00 MPa·m 1 / 2 , Vickers hardness is 20~25GPa.

[0030] Preferably, the morphological difference of silicon carbide is regulated by the gas source gradient.

[0031] More preferably, the gas source is SiO and CO gas generated by the reaction of oxygen partial pressure with silicon and carbon respectively during the high-temperature infiltration process.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The present invention uses resorcinol, formaldehyde, deionized water, basic salt containing Fe, Co, Ni and B4C powder as raw materials, and uses a gel injection molding process to prepare a fiber interwoven structure B4C / C porous preform, and then obtains a high-strength and tough reaction-sintered boron carbide ceramic composite material by melt-infiltrating silicon. The silicon carbide phase exists in the form of nanocrystals and whiskers. The B4C particles are wrapped by a continuous silicon carbide network formed by silicon carbide nanocrystals, and silicon carbide whiskers are dispersed around the B4C particles, thereby improving the flexural strength and fracture toughness of the composite material.

[0034] 2. The present invention regulates the content of silicon carbide in the reaction-sintered boron carbide ceramic composite material by adjusting the carbon content, regulates the morphological distribution of silicon carbide by adjusting the gas source gradient, strengthens the composite material through a continuous silicon carbide nanocrystalline skeleton, and toughens the composite material through silicon carbide whiskers.

[0035] 3. The comprehensive physical properties of the boron carbide ceramic composite material prepared by the present invention are greatly improved, with a flexural strength of 510-525 MPa and a fracture toughness of 5.50-6.00 MPa·m 1 / 2 , Vickers hardness is 20~25GPa. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1This is a SEM image of the fiber interwoven structure B4C / C preform prepared in Example 1 of the present invention.

[0037] Figure 2 This is the XRD spectrum of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention.

[0038] Figure 3 This is a SEM image of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention.

[0039] Figure 4 This is a SEM image of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention after Si is etched. DETAILED DESCRIPTION

[0040] The following are specific embodiments of the present invention, which further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments. The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the invention, modifications and substitutions made to the inventive methods, steps or conditions all belong to the scope of the present invention.

[0041] The raw materials used in the embodiment are as follows:

[0042] F320B4C powder average particle size = 39.85μm, Dalian Jinma Boron Technology Group Co., Ltd.;

[0043] F800B4C powder average particle size = 9.01μm, Dalian Jinma Boron Technology Group Co., Ltd.;

[0044] W3.5B4C powder average particle size = 1.97μm, Dalian Jinma Boron Technology Group Co., Ltd.;

[0045] Resorcinol (C6H6O2), analytical grade, Sinopharm Chemical Reagent Co., Ltd.;

[0046] Formaldehyde (CH2O), analytical grade, Sinopharm Chemical Reagent Co., Ltd.;

[0047] Basic nickel carbonate (NiCO3·2Ni(OH)2·4H2O), analytical grade, from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0048] Basic cobalt carbonate (2C O CO3·3Co(OH)2), analytical grade, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0049] Basic iron carbonate (Fe2(CO3)3·Fe(OH)3), analytical grade, Shanghai MacLean Biochemical Technology Co., Ltd.;

[0050] Deionized water, P ≥ 18 MΩ / cm;

[0051] The equipment used for infiltration in the embodiment of the present invention is a graphite vacuum sintering furnace;

[0052] The test method for the flexural strength in the embodiment of the present invention is a three-point flexural strength method, and the electronic universal testing machine used is an AG-Xplus100kN electronic universal testing machine manufactured by Japan Co., Ltd.;

[0053] The fracture toughness test method in the embodiment of the present invention is the SENB method, and the electronic universal testing machine used is the AG-Xplus100kN electronic universal testing machine manufactured by Japan Co., Ltd.;

[0054] The Vickers hardness test method in the embodiment of the present invention is the Vickers indentation hardness method, using a 450SVD Vickers hardness tester;

[0055] The test method for the open porosity and bulk density in the embodiment of the present invention adopts the Archimedes drainage method;

[0056] The high-strength and tough reaction-sintered boron carbide ceramic composite material prepared in the embodiment of the present invention is composed of B x C. B 12 (B, C, Si)3, SiC and Si composition;

[0057] Compared with the preform before sintering, the size change of the sintered body obtained after sintering in the embodiment of the present invention is less than 1%.

[0058] Embodiment 1:

[0059] S1. Weigh 11.11 mol% of resorcinol, 22.22 mol% of formaldehyde, 66.65 mol% of deionized water, and 0.02 mol% of basic nickel carbonate respectively, add them into a beaker, and stir evenly to obtain a resorcinol formaldehyde solution;

[0060] S2. Weigh 53 wt% of B4C mixed powder according to the mass ratio of F320:F800:W3.5=5:1:4, add it to the resorcinol formaldehyde solution, and pour them into a ball mill together, use zirconium oxide balls as grinding media, and ball mill for 12 hours. After vacuum degassing the slurry after ball milling, pour it into a mold and seal it, place it in an 85°C forced air drying oven for gelation for 12 hours; then demold and transfer it to a 120°C forced air drying oven and dry it at normal pressure for 12 hours to obtain a solidified body;

[0061] S3, placing the solidified body in a tubular furnace in a flowing Ar environment with a gas flow rate of 1.0 mL / min, heating the body to 1100° C. at a heating rate of 2° C. / min, and keeping the temperature for 3 hours, and obtaining a fiber interwoven structure B4C / C preform after cooling, wherein the carbon content is 20 wt%;

[0062] S4. Spread silicon powder particles with an average particle size of 3 mm on the B4C / C preform (the amount of silicon powder particles is 1.5 times the theoretical silicon mass required), place them in a graphite crucible coated with a boron nitride coating, and place them together in a vacuum graphite furnace and heat them to 1480°C and keep them warm for 30 minutes at a heating rate of 5°C / min. After cooling in the furnace, a reaction-sintered boron carbide ceramic composite material is obtained.

[0063] Figure 1 This is a SEM image of the fiber interwoven structure B4C / C preform prepared in Example 1 of the present invention. As can be seen from the figure, carbon nanowires with a high aspect ratio and a diameter less than 100nm are generated in the B4C / C preform. The carbon nanowires show a typical bamboo-like structure and are intertwined and entangled to form a three-dimensional network of fiber interwoven structure, fixing the B4C particles in the structure.

[0064] Figure 2 The XRD spectrum of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention. As can be seen from the figure, the reaction-sintered boron carbide ceramic composite material is composed of B x C. B 12 (C,Si,B)3, SiC and Si.

[0065] Figure 3 This is a SEM image of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention. As can be seen from the figure, the various phases in the reaction-sintered boron carbide ceramic composite material are evenly distributed, and the black area is boron carbide (B x C and B 12 (C, Si, B) 3), the light gray area is residual Si, and the dark gray area is SiC. Among them, the residual Si is a continuous phase mainly distributed around the boron carbide particles, and SiC forms a ceramic skeleton to completely disperse the boron carbide particles, and there is no large-sized SiC and residual carbon.

[0066] Figure 4 This is a SEM image of the reaction-sintered boron carbide ceramic composite material prepared in Example 1 of the present invention after etching Si. It can be seen from the figure that the holes in the figure are left after etching the residual Si, the various phases in the composite material are evenly distributed, and the residual Si is in a network that runs through the interior of the composite material; SiC exists in two forms, nanocrystals and whiskers, in which SiC nanocrystals are concentrated in a quasi-spherical shape on the surface of the boron carbide particles, and form a continuous SiC network skeleton to wrap the boron carbide particles; and silicon carbide whiskers are dispersed around the boron carbide phase.

[0067] Embodiment 2:

[0068] S1. Weigh 11.11 mol% of resorcinol, 22.22 mol% of formaldehyde, 66.65 mol% of deionized water, and 0.02 mol% of basic ferric carbonate respectively, add them into a beaker, and stir evenly to obtain a resorcinol formaldehyde solution;

[0069] S2. Weigh 53 wt% of B4C mixed powder according to the mass ratio of F320:F800:W3.5=5:1:4, add it to the resorcinol formaldehyde solution, and pour them into a ball mill together, use zirconium oxide balls as grinding media, and ball mill for 12 hours. After vacuum degassing the slurry after ball milling, pour it into a mold and seal it, place it in an 85°C forced air drying oven for gelation for 12 hours; then demold and transfer it to a 120°C forced air drying oven and dry it at normal pressure for 12 hours to obtain a solidified body;

[0070] S3, placing the solidified body in a tubular furnace in a flowing Ar environment with a gas flow rate of 0.8 mL / min, heating the body to 1150° C. at a heating rate of 2° C. / min, and keeping the temperature for 3 hours, and obtaining a fiber interwoven structure B4C / C preform after cooling, wherein the carbon content is 20 wt%;

[0071] S4. Spread silicon powder particles with an average particle size of 2 mm on the B4C / C preform (the amount of silicon powder particles is 1.5 times the theoretical silicon mass required), place them in a graphite crucible coated with a boron nitride coating, and place them together in a vacuum graphite furnace and heat them to 1550°C and keep them warm for 15 minutes at a heating rate of 5°C / min. After cooling in the furnace, a reaction-sintered boron carbide ceramic composite material is obtained.

[0072] Embodiment 3:

[0073] S1. Weigh 11.11 mol% of resorcinol, 22.22 mol% of formaldehyde, 66.65 mol% of deionized water, and 0.02 mol% of basic cobalt carbonate respectively, add them into a beaker, and stir evenly to obtain a resorcinol formaldehyde solution;

[0074] S2. Weigh 53 wt% of B4C mixed powder according to the mass ratio of F320:F800:W3.5=5:1:4, add it to the resorcinol formaldehyde solution, and pour them into a ball mill together, use zirconium oxide balls as grinding media, and ball mill for 12 hours. After vacuum degassing the slurry after ball milling, pour it into a mold and seal it, place it in an 85°C forced air drying oven for gelation for 12 hours; then demold and transfer it to a 120°C forced air drying oven and dry it at normal pressure for 12 hours to obtain a solidified body;

[0075] S3, placing the solidified body in a tubular furnace in a flowing Ar environment with a gas flow rate of 0.6 mL / min, heating the body to 1050° C. at a heating rate of 2° C. / min, and keeping the temperature for 3 hours, and obtaining a fiber interwoven structure B4C / C preform after cooling, wherein the carbon content is 20 wt%;

[0076] S4. Spread silicon powder particles with an average particle size of 1 mm on the B4C / C preform (the amount of silicon powder particles is 1.5 times the theoretical silicon mass required), place them in a graphite crucible coated with a boron nitride coating, and place them together in a vacuum graphite furnace and heat them to 1610°C and keep them warm for 10 minutes at a heating rate of 5°C / min. After cooling in the furnace, a reaction-sintered boron carbide ceramic composite material is obtained.

[0077] Embodiment 4:

[0078] The only difference from Example 1 is that the B4C mixed powder is only F320B4C powder.

[0079] Embodiment 5:

[0080] The only difference from Example 1 is that the B4C mixed powder is only W3.5B4C powder.

[0081] Embodiment 6:

[0082] The only difference from Example 1 is that in step S3, after the tubular furnace is filled with Ar, the temperature is increased to 1100° C. at a heating rate of 2° C. / min and kept at this temperature for 3 h without providing a flowing argon atmosphere.

[0083] Embodiment 7:

[0084] The only difference from Example 1 is that the amount of basic nickel carbonate added is 0.0001 mol %.

[0085] Embodiment 8:

[0086] The only difference from Example 1 is that the amount of basic nickel carbonate added is 0.05 mol%.

[0087] Comparative Example 1:

[0088] The only difference from Example 1 is that basic nickel carbonate is replaced by sodium bicarbonate.

[0089] Comparative Example 2:

[0090] The only difference from Example 1 is that basic nickel carbonate is replaced by sodium carbonate.

[0091] Comparative Example 3:

[0092] The only difference from Example 1 is that the high-temperature infiltration is carried out under normal pressure.

[0093] Table 3: Performance test results of reaction-sintered boron carbide ceramic composite materials prepared in Examples 1-8 and Comparative Examples 1-3

[0094]

[0095] In summary, the present invention uses resorcinol, formaldehyde, deionized water, basic salt containing Fe, Co, Ni and B4C powder as raw materials, utilizes gel injection molding process to prepare fiber interwoven structure B4C / C porous preform, and then obtains high-strength and toughness reaction sintered boron carbide ceramic composite material by melt infiltration of silicon, wherein the silicon carbide phase exists in two forms of nanocrystals and whiskers, the B4C particles are wrapped by a continuous silicon carbide network formed by silicon carbide nanocrystals, and the silicon carbide whiskers are dispersed around the B4C particles, thereby improving the flexural strength and fracture toughness of the composite material.

[0096] The parts of the embodiments herein that are not exhaustive of the midpoint values ​​of the technical scope claimed for protection by the present invention and the new technical solutions formed by equivalent replacement of single or multiple technical features in the technical solutions of the embodiments are also within the scope claimed for protection by the present invention; at the same time, in all the listed or unlisted embodiments of the scheme of the present invention, each parameter in the same embodiment merely represents an example of its technical solution (i.e., a feasible solution), and there is no strict coordination and limitation relationship between the parameters, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present invention, unless otherwise stated.

[0097] The technical means disclosed in the scheme of the present invention are not limited to the technical means disclosed in the above technical means, but also include technical schemes composed of any combination of the above technical features. The above is a specific implementation of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications are also regarded as the protection scope of the present invention.

[0098] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

Claims

1. A method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material, characterized in that: The method comprises the following steps: S1, adding the B4C mixed powder into a resorcinol formaldehyde solution containing at least one of Fe, Co and Ni to obtain a mixed solution, and then ball milling to obtain a slurry; S2, after vacuum degassing, pour the slurry into a mold and seal it, and obtain a solidified body after gelation and normal pressure drying; S3, carbonizing the solidified body in a flowing argon atmosphere to obtain a preform; S4. Spread silicon particles on the preform and perform high-temperature infiltration in a vacuum, and finally obtain a high-strength and tough reaction-sintered boron carbide ceramic composite material by cooling.

2. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: The resorcinol formaldehyde solution is prepared by mixing a basic salt containing at least one of Fe, Co and Ni, resorcinol, formaldehyde and deionized water, wherein the concentration of the basic salt containing at least one of Fe, Co and Ni in the resorcinol formaldehyde solution is 0.0002-0.02 mol%.

3. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: The B4C mixed powder is graded according to the mass ratio, with an average particle size of 30-50 μm: an average particle size of 5-15 μm: an average particle size of 1-3 μm = (5-7): 1: (2-4).

4. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: The content of B4C mixed powder in the mixed solution of step S1 is 40-75wt%.

5. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: In step S2, the gelation temperature is 70-90° C., and the insulation time is 6-24 hours; the drying temperature is 100-150° C., and the drying time is 6-24 hours.

6. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: In step S3, the carbonization treatment temperature is 800-1200° C., the carbonization holding time is 2-6 hours, the heating rate is 1-5° C. / min, and the argon gas flow rate is 0.5-2 mL / min.

7. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: The preform is composed of B4C particles and carbon nanowires, wherein the B4C particles are dispersed in a fiber interlaced structure formed by the carbon nanowires, and the carbon content is 5-20wt%.

8. The method for preparing a high-strength and tough reaction-sintered boron carbide ceramic composite material according to claim 1, characterized in that: Step S4: high temperature infiltration: heating the temperature to 1450-1650°C at 1-10°C / min, and keeping the temperature for 10-120min, wherein the particle size of silicon particles is 1-5mm, and the actual amount of silicon particles added is ≥1.5 times the theoretical amount.

9. A high-strength and tough reaction-sintered boron carbide ceramic composite material, characterized in that: The ceramic composite material is prepared by the preparation method of claim 1, wherein the silicon carbide phase in the composite material exists in two forms: nanocrystals and whiskers, the B4C particles are wrapped by a continuous silicon carbide network formed by silicon carbide nanocrystals, and the silicon carbide whiskers are dispersed around the B4C particles.

10. The high-strength and toughness reaction-sintered boron carbide ceramic composite material according to claim 9, characterized in that: The flexural strength of ceramic composite materials is 510-525MPa, and the fracture toughness is 5.50-6.00MPa·m 1 / 2 , Vickers hardness is 20~25GPa.

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