Superconducting Ketjen black / boron carbide composite ceramic and preparation method and application thereof

Abstract

The invention discloses a superconducting Ketjen black / boron carbide composite ceramic and a preparation method and application thereof, and belongs to the technical field of ceramic materials, and the method comprises the following steps: uniformly mixing superconducting Ketjen black and boron carbide by wet mixing, and carrying out rotary evaporation, grinding, screening and sintering to obtain the superconducting Ketjen black / boron carbide composite ceramic. The superconductive Ketjen black is introduced, so that the superhigh hardness and the fracture toughness are synergistically improved, and the application potential of the boron carbide ceramic under extreme working conditions is expanded. A nanometer network structure is formed in the sintering process of the superconducting Ketjen black, so that the sintering performance and the mechanical performance of the boron carbide ceramic are remarkably enhanced. The prepared superconducting Ketjen black / boron carbide composite ceramic is suitable for application under extreme working conditions, including but not limited to armor materials, cutting tools and nuclear industry parts.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and in particular relates to a superconducting Ketjen black / boron carbide composite ceramic and a preparation method and application thereof. Background Art

[0002] Boron carbide ceramics are widely used in bulletproof armor, wear-resistant parts and other fields due to their extremely high hardness, low density and excellent wear resistance. However, their high brittleness and low toughness severely limit their engineering applications. Common reinforcement methods include the introduction of second phase particles, fibers or layered structures, but these methods have limitations in achieving high relative density, light weight, hardness and toughness.

[0003] In recent years, many papers have reported methods for preparing boron carbide ceramic composites with second phase additives. For example, Document 1 discloses a method for successfully preparing high-performance B4C-LaB6 composite ceramics by hot pressing and sintering. The addition of La2O3 significantly improves the densification and mechanical properties of the composite ceramics, especially at 4 wt% La2O3, the comprehensive mechanical properties of the composite ceramics reach the optimum. However, excessive La2O3 will lead to the generation of CO gas and reduce the degree of densification (Ming Y, Yan Z, Peng X, 2021, 47, 32675-32684). Document 2 discloses a method for preparing B4C-20 wt% TiB2 ceramics by hot pressing a mixture of B4C and ball milled TiB2 powders. The results show that the TiB2 particle size plays an important role in the mechanical properties of B4C-TiB2 ceramics. However, SiO2 introduced by ball milling is conducive to densification, but is not conducive to the mechanical properties of B4C-TiB2 ceramics (WenG, Qiang H, Ai W, ​​Tian T, Chun L, Lan H, Wei W, Hao W, Zheng F, 2023, 49,4403-4411). Reference 3 discloses a method for preparing Fe3Al-B4C-based ceramics by spark plasma sintering (SPS) at a relatively low temperature (1700 ℃), applying a pressure of 50 MPa in a vacuum, and maintaining it for 5 min. Although this method can obtain boron carbide ceramic composites at low temperatures, the content of Fe3Al added is as high as 7 wt%, and the theoretical density of the composite ceramic is 2.63 g / cm 3, limiting its application as lightweight armor (SS Rehman, Wei J,SA Khan, M. Asif, Zheng F, Wei W, Hao W, Jin Z, Yu W, 2014, 34, 2169-2175). Chinese patent application number CN202411397120.X discloses a method for preparing lightweight boron carbide ceramics using coconut shell as raw material. Using coconut shell as raw material, carbon powder is obtained by high-temperature carbonization, crushing, grinding and sieving, and a uniform mixture of carbon powder, boric acid and trishydroxymethylaminomethane is fully evaporated and cross-linked to obtain a gel, and the gel is converted into a precursor powder by combustion method, and finally a porous boron carbide ceramic is obtained by dry pressing and high-temperature sintering. Although this method can achieve process optimization for preparing lightweight boron carbide ceramics, the ceramic impurity phase is relatively large and the mechanical properties cannot meet the high requirements of the protection field. Chinese patent application number CN202411087181.6 discloses a method and application of preparing ceramic materials by boron carbide abrasives. The method comprises pre-treating the waste material, ball-milling or acid-leaching the pre-treated ground waste material to obtain a modified waste material, and hot-pressing and sintering the modified waste material to obtain a boron carbide ceramic material. Although the purpose of waste utilization is achieved, the process is complicated, requires acid treatment, has certain dangers, is difficult to operate, and the product is uncontrollable and has poor repeatability.

[0004] Currently, nanocarbon materials are used for ceramic reinforcement due to their excellent mechanical properties and special interface effects. As a carbon material with high specific surface area and excellent conductivity, the application of superconductive Ketjen Black (CCB) in ceramic matrix composites has not been fully studied. It is necessary to find a method to improve the toughness of boron carbide ceramics by using superconductive Ketjen Black additives while maintaining ultra-high hardness. Summary of the invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a superconducting Ketjen black / boron carbide composite ceramic and its preparation method and application, so as to solve how to achieve a significant improvement in the toughness of boron carbide ceramics through superconducting Ketjen black additives while maintaining its ultra-high hardness and lightweight properties, so as to break through the technical problems of traditional reinforcement methods in improving densification, simplifying processes and avoiding the introduction of impurities.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a preparation method of a superconducting Ketjen black / boron carbide composite ceramic, comprising: uniformly mixing superconducting Ketjen black and boron carbide by wet mixing, rotary evaporation, grinding, screening and sintering to obtain the superconducting Ketjen black / boron carbide composite ceramic.

[0007] Preferably, the mass ratio of superconducting Ketjen black to boron carbide is (1-10):(90-99); the purity of superconducting Ketjen black and boron carbide is greater than 99%; the particle size of boron carbide is 2.5-4.5 µm; and the particle size of superconducting Ketjen black is 0.24-0.44 nm.

[0008] Preferably, the wet mixing comprises adding superconducting Ketjen black into anhydrous ethanol, uniformly dispersing the superconducting Ketjen black in the anhydrous ethanol through ultrasonic treatment, and adding boron carbide and uniformly mixing through mechanical stirring.

[0009] More preferably, the power of the ultrasonic treatment is 200-500 W, and the time of the ultrasonic treatment is 30-60 min.

[0010] More preferably, the speed of mechanical stirring is 300-600 rpm, and the time of mechanical stirring is 60-120 min.

[0011] Preferably, the temperature of rotary evaporation is 30-35 °C, the vacuum degree of rotary evaporation is 100-300 mbar, and the time of rotary evaporation is 24-48 h.

[0012] Preferably, the grinding time is 30-45 min, the grinding speed is 20-30 rpm, and the sieved particle size is 60-100 mesh.

[0013] Preferably, the sintering is spark plasma sintering, and the conditions of spark plasma sintering are: applying a uniaxial pressure of 35-50 MPa, heating to 800-1000 °C at a heating rate of 50-200 °C / min, and keeping warm for 1-5 min; then heating to 1500-1600 °C at a heating rate of 50-150 °C / min; finally heating to 1750-1950 °C at a heating rate of 50-100 °C / min, and keeping warm for 3-10 min; the vacuum degree of sintering and keeping warm is 10 -2 ~10 -5 MPa.

[0014] The present invention also discloses a superconducting Ketjen black / boron carbide composite ceramic, which is prepared by the above-mentioned preparation method of the superconducting Ketjen black / boron carbide composite ceramic; the superconducting Ketjen black / boron carbide composite ceramic has a hardness of 33.2~36.8GPa; and a fracture toughness of 3.2~4.2 MPa·m 1 / 2 .

[0015] The present invention also discloses the application of the superconducting Ketjen black / boron carbide composite ceramics prepared by the preparation method of the superconducting Ketjen black / boron carbide composite ceramics in the manufacture of neutron absorption, protective armor, military materials, wear-resistant accessories or high-end wear-resistant parts.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a method for preparing superconducting Ketjen black / boron carbide composite ceramics, which adopts a method combining wet mixing, rotary evaporation and SPS to make the material have a more uniform microstructure, reduce pores and impurity aggregation, and improve overall mechanical properties. The process of liquid phase mixing and mechanical grinding is designed to avoid impurities that may be introduced in the ball milling process, ensure the refinement of the powder and improve the purity of the product.

[0017] The present invention also discloses a superconducting Ketjen black / boron carbide composite ceramic prepared by the above preparation method. Through the optimization effect of the CKB additive, the densification process of the boron carbide ceramic is promoted, the grain boundary defects are reduced, the hardness of the composite ceramic is improved, and an appropriate amount of toughening mechanism, such as microcrack deflection and particle bridging, is introduced. The hardness is 33.2~36.8 GPa; the fracture toughness is 3.2~4.2 MPa·m 1 / 2 .

[0018] The present invention also discloses the application of the superconducting Ketjen black / boron carbide composite ceramics prepared by the above-mentioned preparation method in the manufacture of neutron absorption, protective armor, military materials, wear-resistant accessories or high-end wear-resistant parts. Boron carbide itself has an extremely high thermal neutron absorption cross section, and the addition of CKB can optimize the microstructure of the material, improve the density and crack resistance, and further enhance its stability and service life in the fields of nuclear reactor control rods, radiation protection devices, etc. In addition, the introduction of CKB helps to improve the toughness of ceramics and reduce the risk of brittle fracture, so that the superconducting Ketjen black / boron carbide composite ceramics have both high hardness and impact resistance, and have broad application prospects in bullet-resistant ceramic armor (such as individual soldier protection, armored vehicle protection). Military materials working under high-intensity impact and extreme environments have extremely high requirements for the hardness, toughness and heat resistance of the materials. Superconducting Ketjen black / boron carbide composite ceramics have excellent mechanical properties and heat-resistant stability, and can be used for high-speed warhead armor-piercing core components, aerospace protection materials and ultra-high temperature protection systems to ensure that the material still maintains stable mechanical properties under extreme environments. At the same time, in high-end manufacturing fields such as semiconductor industry, aerospace and precision machining, materials not only require high wear resistance, but also high stability and low friction coefficient. Superconducting Ketjen Black / boron carbide composite ceramics have excellent wear resistance and high temperature resistance, and are suitable for high-end cutting tools, wear-resistant coatings, precision transmission parts and other fields, which can significantly improve the working efficiency and stability of equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is an optical micrograph of the indentation site of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 1 of the present invention; Figure 2This is a SEM image of the microstructure of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 2 of the present invention; Figure 3 The XRD spectrum of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 4 of the present invention; Figure 4 This is a relationship diagram between the Vickers hardness and the fracture toughness of the superconducting Ketjen black / boron carbide composite ceramics disclosed in Examples 4, 5 and 6 of the present invention. DETAILED DESCRIPTION

[0020] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0022] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0023] In the present invention, unless otherwise specified, percentage (%) or part refers to the weight percentage or weight part relative to the composition.

[0024] In the present invention, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0025] In the present invention, unless otherwise specified, the numerical range "a~b" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6~22" means that all real numbers between "6~22" have been listed in this document, and "6~22" is just an abbreviation of these numerical combinations.

[0026] The “range” disclosed in the present invention is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0027] In the present invention, the term "and / or" used herein refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0028] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0029] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0030] The present invention provides a method for preparing a superconducting Ketjen black / boron carbide composite ceramic, comprising the following steps: Step 1: Select high-purity boron carbide powder (B4C, 2.5~4.5 µm, purity ≥99%) and weigh a certain proportion of CKB (0.24~0.44 nm, purity ≥99%). The mass ratio of boron carbide powder to CKB can be adjusted according to specific needs, and the preferred range is 90:10 to 99:1.

[0031] Step 2: Using a wet mixing process, CKB is added to anhydrous ethanol, and CKB is evenly dispersed in the anhydrous ethanol through ultrasonic treatment.

[0032] The power of ultrasonic treatment is 200~500 W and the time is 30~60 min to ensure the dispersion effect.

[0033] Step 3: Add the weighed boron carbide powder to the CKB anhydrous ethanol dispersion and mix the powder evenly by mechanical stirring at a speed of 300-600 rpm for 60-120 min.

[0034] Step 4: Remove the ethanol solvent by rotary evaporation. Place the solution in a rotary evaporator, set the water bath temperature to 30-35 °C (lower than the boiling point of ethanol), rotate at a moderate speed, gradually reduce the vacuum to 100-300 mbar, avoid violent boiling, and dry for 24-48 hours. Continue evaporation until the solvent is completely removed to ensure that the powder is evenly dispersed.

[0035] Step 5: Use a small wheel mill to mechanically grind the composite powder. Place the powder evenly in the wheel mill, set the grinding time to 30-45 min, and control the speed at 20-30 rpm to ensure the uniformity and refinement of the powder. During the grinding process, the machine can be stopped at appropriate times to check the powder state to avoid overheating or agglomeration.

[0036] Step 6: To prevent particles from agglomerating, use a 60-100 mesh screen to sieve the ground powder. Pour the powder evenly into the screen for sieving to ensure separation of fine powder and coarse powder. The powder that passes through the screen is qualified fine powder and is collected for later use; the coarse powder that does not pass through the screen can be returned to the grinding equipment for secondary grinding until the target particle size is reached. Grind and sieve the mixed powder to ensure that the powder is evenly mixed and sufficiently refined.

[0037] Step 7: Place the composite ceramic powder in a high-purity graphite mold with a diameter of 30 mm. Place 2 mm thick graphite paper between the mold and the powder to facilitate demolding. When filling, ensure that the powder is evenly distributed to avoid density differences.

[0038] Step 8: Turn on the vacuum pump and diffusion pump. When the vacuum degree reaches -0.098 MPa and stabilizes, run the spark plasma sintering program.

[0039] Turn on the power supply, apply uniaxial pressure of 35~50 MPa, increase the temperature to 800~1000℃ at 50~200℃ / min, keep it warm for 1~5min, then increase the temperature to 1500~1600℃ at 50~150℃ / min, then increase the temperature to 1750~1950℃ at 50~100℃ / min, and keep it warm for 3~10min. The vacuum degree is kept at 10 -2 ~10 -5 MPa. Then turn off the power immediately to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The whole process is carried out in a vacuum environment. The sintering environment is vacuum or inert gas protection. The specific parameters of the sintering process are: pressure 35~50 MPa; heating rate 50~200 ℃ / min; insulation time 1~10 min.

[0040] Step 9: Perform necessary machining or surface treatment on the sintered boron carbide ceramics to optimize their final performance and obtain superconducting Ketjen black / boron carbide composite ceramics. Specific tests include: ceramic microstructure, Vickers hardness, fracture toughness and impact resistance, etc.

[0041] The present invention achieves a synergistic improvement of ultra-high hardness and toughness by introducing superconducting Ketjen black, expanding the application potential of boron carbide ceramics under extreme working conditions. The nano-network structure formed by CKB during the sintering process significantly enhances the fracture toughness and impact resistance of boron carbide ceramics. The prepared boron carbide ceramics are suitable for applications under extreme working conditions, including but not limited to armor materials, cutting tools and nuclear industry components.

[0042] The invention discloses a method for preparing a lightweight, ultra-high hardness and toughness-enhanced densified boron carbide (B4C) ceramic by spark plasma sintering with a CKB additive, which is suitable for manufacturing protective armor, military materials and high-end wear-resistant parts.

[0043] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0044] Example 1 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 200 W, and the time was 30 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 99:1 in the presence of anhydrous ethanol at a speed of 300 rpm for 60 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 30 °C, the vacuum degree of the rotary evaporation was 100 mbar, and the rotary evaporation time was 24 h to obtain CKB / boron carbide ceramic powder.

[0045] The composite powder was ground at 20 rpm for 30 min using a wheel mill, and then sieved at 100 mesh to ensure that the composite powder was evenly distributed and refined. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0046] The power was turned on, and a uniaxial pressure of 35 MPa was applied. The temperature was raised to 800 °C at a rate of 50 °C / min, kept at that temperature for 1 min, then raised to 1500 °C at a rate of 50 °C / min (power was 80%), and then raised to 1750 °C at a rate of 50 °C / min (power was 90%), and kept at that temperature for 3 min. The vacuum degree was kept at 10 -2 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0047] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500 and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0048] Figure 1 This is an optical micrograph of the indentation site of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 1 of the present invention; as can be seen from the figure, the indentation morphology is clear and crack extension occurs in the tip area.

[0049] Example 2 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 300 W and the time was 40 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 97:3 in the presence of anhydrous ethanol at a speed of 400 rpm for 80 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 32 °C, the vacuum degree of the rotary evaporation was 230 mbar, and the rotary evaporation time was 36 h to obtain CKB / boron carbide ceramic powder.

[0050] The composite powder was ground at 23 rpm for 35 min using a wheel mill, and then sieved at 80 mesh to ensure that the composite powder was evenly distributed and refined. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0051] The power was turned on, and a uniaxial pressure of 40 MPa was applied. The temperature was raised to 900°C at 100°C / min, kept at that temperature for 2 min, then raised to 1550°C at 100°C / min (power was 80%), and then raised to 1800°C at 65°C / min (power was 90%), and kept at that temperature for 5 min. The vacuum degree was kept at 10 -3 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0052] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500, and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0053] Figure 2 This is a SEM image of the microstructure of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 2 of the present invention; it can be seen from the image that the superconducting Ketjen black / boron carbide composite ceramic prepared by the present invention has an extremely high degree of densification and fewer pores.

[0054] Example 3 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 400 W and the time was 50 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 90:10 in the presence of anhydrous ethanol at a speed of 500 rpm for 100 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 34 °C, the vacuum degree of the rotary evaporation was 260 mbar, and the rotary evaporation time was 40 h to obtain CKB / boron carbide ceramic powder.

[0055] The composite powder was ground at 26 rpm for 40 min using a wheel mill and then sieved at 60 mesh to ensure uniform distribution and refinement of the composite powder. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0056] The power was turned on, and a uniaxial pressure of 50 MPa was applied. The temperature was raised to 1000°C at 200°C / min, kept at that temperature for 5 min, then raised to 1600°C at 150°C / min (power was 80%), and then raised to 1950°C at 100°C / min (power was 90%), and kept at that temperature for 10 min. The vacuum degree was kept at 10 -5 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0057] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500, and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0058] Example 4 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 500 W and the time was 60 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 95:5 in the presence of anhydrous ethanol at a speed of 600 rpm for 120 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 35 °C, the vacuum degree of the rotary evaporation was 300 mbar, and the rotary evaporation time was 48 h to obtain CKB / boron carbide ceramic powder.

[0059] The composite powder was ground at 30 rpm for 45 min using a wheel mill, and then sieved at 60 mesh to ensure that the composite powder was evenly distributed and refined. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0060] The power was turned on, and a uniaxial pressure of 45 MPa was applied. The temperature was raised to 950 °C at 175 °C / min, kept at this temperature for 3 min, then raised to 1575 °C at 125 °C / min (power was 80%), and then raised to 1850 °C at 80 °C / min (power was 90%), and kept at this temperature for 7 min. The vacuum degree was kept at 10 -4 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0061] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500, and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0062] Figure 3This is the XRD spectrum of the superconducting Ketjen black / boron carbide composite ceramic disclosed in Example 4 of the present invention; it can be seen from the figure that the main components of the superconducting Ketjen black / boron carbide composite ceramic prepared by the present invention are B4C and a small amount of residual carbon. Since the wet mixing method is adopted without introducing any other impurities, the product has a high purity.

[0063] Example 5 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 500 W and the time was 60 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 96:4 in the presence of anhydrous ethanol at a speed of 600 rpm for 120 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 35 °C, the vacuum degree of the rotary evaporation was 300 mbar, and the rotary evaporation time was 48 h to obtain CKB / boron carbide ceramic powder.

[0064] The composite powder was ground at 30 rpm for 45 min using a wheel mill, and then sieved at 60 mesh to ensure that the composite powder was evenly distributed and refined. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0065] The power was turned on, and a uniaxial pressure of 45 MPa was applied. The temperature was raised to 950 °C at 175 °C / min, kept at this temperature for 3 min, then raised to 1575 °C at 125 °C / min (power was 80%), and then raised to 1850 °C at 80 °C / min (power was 90%), and kept at this temperature for 7 min. The vacuum degree was kept at 10 -4 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0066] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500, and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0067] Example 6 A method for preparing a superconducting Ketjen black / boron carbide composite ceramic comprises the following steps: CKB was dispersed in anhydrous ethanol, and a uniformly dispersed solution was obtained by ultrasonic treatment. The power of ultrasonic treatment was 500 W and the time was 60 min. Boron carbide and CKB powder were mechanically stirred at a mass ratio of 97:3 in the presence of anhydrous ethanol at a speed of 600 rpm for 120 min to obtain a uniform mixed solution of CKB and boron carbide. Then, the mixed solution was subjected to a rotary evaporation process to remove anhydrous ethanol. The rotary evaporation temperature was 35 °C, the vacuum degree of the rotary evaporation was 300 mbar, and the rotary evaporation time was 48 h to obtain CKB / boron carbide ceramic powder.

[0068] The composite powder was ground at 30 rpm for 45 min using a wheel mill, and then sieved at 60 mesh to ensure that the composite powder was evenly distributed and refined. The composite ceramic powder was placed in a high-purity graphite mold with a diameter of 30 mm, and a 2 mm thick graphite paper was placed between the mold and the powder to facilitate demolding. The composite powder was pre-pressed using a hydraulic press.

[0069] The power was turned on, and a uniaxial pressure of 45 MPa was applied. The temperature was raised to 950 °C at 175 °C / min, kept at this temperature for 3 min, then raised to 1575 °C at 125 °C / min (power was 80%), and then raised to 1850 °C at 80 °C / min (power was 90%), and kept at this temperature for 7 min. The vacuum degree was kept at 10 -4 MPa. The power supply is then immediately turned off to ensure that no uniaxial pressure is applied during cooling, and the temperature naturally drops to room temperature. The entire process is carried out in a vacuum environment.

[0070] The mold was removed from the furnace and demolded. The ceramic was ground step by step using 180, 320, 800, 1500, 2500, and 3200 mesh diamond grinding discs, and polished with 50 and 80 µm diamond polishing agents. Finally, a black block superconducting Ketjen black / boron carbide composite ceramic was obtained. Scanning electron microscopy and X-ray diffraction analysis showed that the ceramic was almost completely dense and was a boron carbide ceramic.

[0071] Figure 4 The graph is a relationship between the Vickers hardness and the fracture toughness of the superconducting Ketjen black / boron carbide composite ceramics disclosed in Examples 4, 5 and 6 of the present invention; it can be seen from the graph that the hardness of the superconducting Ketjen black / boron carbide composite ceramics prepared by the present invention is 33.2~36.8 GPa, and the fracture toughness is 3.2~4.2 MPa·m 1 / 2 The hardness and toughness both reach a high level. In Example 4, the content of CKB is 5wt%, and the hardness and fracture toughness values ​​of the corresponding superconducting Ketjen black / boron carbide composite ceramic are 33.2 GPa and 4.2 MPa·m 1 / 2In Example 5, the content of CKB is 4wt%, and the corresponding hardness and fracture toughness values ​​are 36.8 GPa and 4.0 MPa·m 1 / 2 In Example 6, the content of CKB is 3wt%, and the corresponding hardness and fracture toughness values ​​are 34.9 GPa and 3.2 MPa·m 1 / 2 The hardness of superconducting Ketjen black / boron carbide composite ceramics increases first and then decreases with the increase of CKB content; the fracture toughness continues to increase.

[0072] The above examples show that the present invention adopts the spark plasma sintering process and selects CKB as an additive to efficiently prepare a lightweight, high-hardness and high-toughness superconducting Ketjen black / boron carbide composite ceramic. The superconducting Ketjen black / boron carbide composite ceramic can be used in the fields of neutron absorption, individual combat protection, armor protection, wear-resistant accessories, advanced composite materials, etc.

[0073] In summary, the present invention provides a method for preparing a superconducting Ketjen black / boron carbide composite ceramic. By precisely controlling the mixing process and the sintering process, and designing and selecting superconducting Ketjen black as an additive, the hardness and toughness of the boron carbide ceramic are significantly improved. The superconducting Ketjen black / boron carbide composite ceramic effectively enhances the impact resistance and crack propagation resistance on the basis of maintaining the excellent hardness of boron carbide, while optimizing the microstructure and improving the density and stability of the material. In addition, the boron carbide component of the superconducting Ketjen black / boron carbide composite ceramic has a high neutron absorption cross section, which is suitable for neutron shielding materials in the nuclear energy field; at the same time, it also shows a wide range of application potential in the fields of protective armor, military materials and wear-resistant accessories. With its excellent wear resistance, impact resistance and high temperature resistance, it provides a new technical approach for the research and development and application of multiple high-performance materials.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a superconducting Ketjen black / boron carbide composite ceramic, characterized in that: include: The superconducting Ketjen black and boron carbide are mixed uniformly by wet mixing, and after rotary evaporation, grinding, screening and sintering, the superconducting Ketjen black / boron carbide composite ceramic is obtained.

2. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 1, characterized in that: The mass ratio of the superconducting Ketjen black to boron carbide is (1-10): (90-99); the purity of the superconducting Ketjen black and boron carbide is greater than 99%; the particle size of the boron carbide is 2.5-4.5 µm; and the particle size of the superconducting Ketjen black is 0.24-0.44 nm.

3. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 1, characterized in that: The wet mixing method includes adding superconducting Ketjen black into anhydrous ethanol, uniformly dispersing the superconducting Ketjen black in the anhydrous ethanol through ultrasonic treatment, and adding boron carbide and uniformly mixing through mechanical stirring.

4. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 3, characterized in that: The power of the ultrasonic treatment is 200-500 W, and the time of the ultrasonic treatment is 30-60 min.

5. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 3, characterized in that: The speed of the mechanical stirring is 300-600 rpm, and the time of the mechanical stirring is 60-120 min.

6. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 1, characterized in that: The temperature of the rotary evaporation is 30-35 °C, the vacuum degree of the rotary evaporation is 100-300 mbar, and the time of the rotary evaporation is 24-48 h.

7. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 1, characterized in that: The grinding time is 30-45 min, the grinding speed is 20-30 rpm; the sieving particle size is 60-100 mesh.

8. The method for preparing the superconducting Ketjen black / boron carbide composite ceramic according to claim 1, characterized in that: The sintering is spark plasma sintering, and the conditions of spark plasma sintering are: applying a uniaxial pressure of 35-50 MPa, heating to 800-1000°C at a heating rate of 50-200°C / min, and keeping warm for 1-5 min; then heating to 1500-1600°C at a heating rate of 50-150°C / min; finally heating to 1750-1950°C at a heating rate of 50-100°C / min, and keeping warm for 3-10 min; the vacuum degree of sintering and keeping warm is 10 -2 ~10 -5 MPa.

9. A superconducting Ketjen black / boron carbide composite ceramic, characterized in that: The superconducting Ketjen black / boron carbide composite ceramic is prepared by the preparation method of any one of claims 1 to 8; the superconducting Ketjen black / boron carbide composite ceramic has a hardness of 33.2 to 36.8 GPa; and a fracture toughness of 3.2 to 4.2 MPa·m 1 / 2 .

10. Use of superconducting Ketjen black / boron carbide composite ceramics prepared by the preparation method of superconducting Ketjen black / boron carbide composite ceramics according to any one of claims 1 to 8 in the manufacture of neutron absorption, protective armor, military materials, wear-resistant accessories or high-end wear-resistant parts.

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