A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics and its application

Abstract

A method and application for preparing high-strength and ultra-hard boride-carbide complex component ceramics, which belongs to the technical field of ceramic materials. The present invention aims to prepare high-strength and ultra-hard boride-carbide complex component ceramics with a wide range of compositions by directly mixing transition metals, boron powder and carbon powder. Method: 1. Prepare a composite powder; 2. Place the fully mixed composite powder in a mold, and then place it in a spark plasma sintering furnace for sintering to obtain high-strength and ultra-hard boride-carbide complex component ceramics. The high-strength and ultra-hard boride-carbide complex component ceramics prepared by the present invention have a finer grain size, and both the strength and hardness are significantly improved. The room temperature hardness is 32-36GPa, the three-point bending strength is 600-800MPa, and the fracture toughness is 6-7MPa·m 1 / 2 The present invention can obtain a high-strength and ultra-hard boride-carbide complex composition ceramic.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and in particular relates to a method for preparing high-strength and ultra-hard boride-carbide complex-component ceramics. Background Art

[0002] High-entropy ceramics have excellent thermal stability, amorphous thermal conductivity, high hardness, giant dielectric constant and superionic conductivity, and have broad application prospects in terms of structure and function. However, most high-entropy ceramic research to date has focused on equimolar compositions of five components or more, and the space for composition adjustment and performance optimization is limited. In 2020, Wright proposed the concept of compositionally complex ceramics (CCCs), which covers intermediate-entropy and non-equimolar ceramics. Many studies have shown that intermediate-entropy or non-equimolar ceramics are superior to high-entropy ceramics in certain specific properties.

[0003] Since single-phase CCCs have strong covalent bonds and low self-diffusion coefficients, sintering and densification are difficult. Research results show that transition metal diboride-carbide composite CCCs are easier to sinter than single-phase systems, with greatly reduced grain size and significantly improved mechanical properties. However, existing transition metal diboride-carbide composite CCCs are usually prepared by directly mixing different types of borides and carbides and then sintering, or by thermally reducing different types of transition metal oxides with carbon and boron and then sintering. Both process routes have the problems of high sintering temperature, complex process, and narrow design space for boride-carbide composition. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics.

[0005] The present invention utilizes low-speed oscillation combined with high-energy ball milling to greatly improve the uniformity of the mixed powders of transition metals, non-metallic boron and carbon powders, and broadens the composition and performance design space of boride-carbide complex composition ceramics by regulating the composition ratio of non-metallic powders.

[0006] A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is completed by the following steps:

[0007] 1. Obtaining composite powder:

[0008] ①, weighing 3 to 6 metal powders selected from the group consisting of titanium powder, zirconium powder, hafnium powder, vanadium powder, niobium powder, tantalum powder, chromium powder, molybdenum powder, and tungsten powder in equal molar ratios to obtain metal powder I;

[0009] ②. Weigh crystalline boron powder and carbon black separately to obtain non-metallic powder II;

[0010] ③. Preliminary mixing of metal powder I and non-metallic powder II is performed by low-speed pendulum vibration to obtain composite powder III;

[0011] ④. Further mixing and refining the composite powder III by high-energy ball milling to obtain a composite powder IV that is fully and evenly mixed and has a fine particle size;

[0012] Second, the fully and evenly mixed composite powder IV with a relatively fine particle size is placed in a sintering mold and sintered in a spark plasma sintering furnace under the protection of an inert atmosphere to obtain a high-strength and ultra-hard boride-carbide complex composition ceramic.

[0013] A high-strength and ultra-hard boride-carbide complex composition ceramic is used in the fields of ultra-high temperature thermal protection and cutting tools.

[0014] Principle of the present invention:

[0015] Transition metal borides include MeB, Me3B4, Me2B3, MeB2 (Me represents transition metal) and other borides; a certain amount of carbon vacancies can be allowed to exist in transition metal carbides to form non-stoichiometric carbides; the presence of different types of borides and carbon vacancies can greatly broaden the performance control space of composite CCCs; the present invention aims to provide a preparation method of boride-carbide complex composition ceramics, by directly mixing transition metal powder, crystalline boron powder and carbon black, simplifying the material composition design process, reducing process complexity and improving material sintering activity; the use of a two-step powder mixing method of low-speed vibration combined with high-energy ball milling can successfully achieve uniform mixing of transition metal powders with large differences in characteristics and ceramic powders; by regulating the content of boron and carbon in the system, the boride composition in the boride-carbide complex composition ceramics and the carbon vacancy content in the carbide can be designed, thereby optimizing material properties.

[0016] The present invention has the following beneficial effects:

[0017] First, the present invention directly mixes transition metal powder, crystalline boron powder and carbon black. By regulating the molar ratio between the three powders, it greatly expands the composition design space of boride-carbide complex composition ceramics, can cover various boride phases and non-stoichiometric carbide phases, and prepare multiphase complex composition ceramics with uniform microstructure;

[0018] Second, the present invention utilizes transition metals to react with crystalline boron powder and carbon black to generate corresponding transition metal borides and carbides, and selects a spark plasma furnace to carry out the reaction sintering under the protection of an inert atmosphere to obtain a high-strength, ultra-hard boride-carbide complex composition ceramic. The multiple transition metal powders, crystalline boron powder, and carbon black react in situ during the sintering process, and solid solution coupling occurs simultaneously, greatly promoting the mass transfer process. The density of the prepared composite ceramics is greater than 99%. In addition, the complex interface relationships and multi-component effects of the composite ceramics make grain growth more difficult than that of single-phase ceramics.

[0019] 3. The high-strength and ultra-hard boride-carbide complex ceramics prepared by the present invention have a finer grain size, and both strength and hardness are significantly improved. The hardness of the material at room temperature can reach 32-36GPa, and the fracture toughness can reach 6-7MPa·m 1 / 2 , the elastic modulus can reach 560GPa, and the three-point bending strength can reach 600-800MPa.

[0020] The invention can obtain a high-strength and ultra-hard boride-carbide complex component ceramic. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 The XRD pattern of the high-strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2;

[0022] Figure 2 This is a SEM microstructure photograph of the high-strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2;

[0023] Figure 3 A fracture photograph of a high-strength, ultra-hard boride-carbide complex composition ceramic having the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2;

[0024] Figure 4 A photograph of crack growth of the high-strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2;

[0025] Figure 5 The XRD pattern of the high-strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb)3B4-(Ti, Zr, Nb)C prepared in Example 5;

[0026] Figure 6This is a SEM microstructure photograph of the high-strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb)3B4-(Ti, Zr, Nb)C prepared in Example 5;

[0027] Figure 7 This is a SEM microstructure photograph of the boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 1;

[0028] Figure 8 This is the SEM microstructure photograph of the boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 2. DETAILED DESCRIPTION

[0029] Specific embodiment 1: This embodiment is a method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics, which is completed by the following steps:

[0030] 1. Obtaining composite powder:

[0031] ①, weighing 3 to 6 metal powders selected from the group consisting of titanium powder, zirconium powder, hafnium powder, vanadium powder, niobium powder, tantalum powder, chromium powder, molybdenum powder, and tungsten powder in equal molar ratios to obtain metal powder I;

[0032] ②. Weigh crystalline boron powder and carbon black separately to obtain non-metallic powder II;

[0033] ③. Preliminary mixing of metal powder I and non-metallic powder II is performed by low-speed pendulum vibration to obtain composite powder III;

[0034] ④. Further mixing and refining the composite powder III by high-energy ball milling to obtain a composite powder IV that is fully and evenly mixed and has a fine particle size;

[0035] Second, the fully and evenly mixed composite powder IV with a relatively fine particle size is placed in a sintering mold and sintered in a spark plasma sintering furnace under the protection of an inert atmosphere to obtain a high-strength and ultra-hard boride-carbide complex composition ceramic.

[0036] Specific Embodiment 2: This embodiment differs from Specific Embodiment 1 in that the purity of the titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten powders described in step 1 (1) above is greater than 99.0 wt.%, and their particle sizes are all between 10 and 90 μm. Other steps are the same as those in Specific Embodiment 1.

[0037] Specific embodiment 3: This embodiment differs from specific embodiments 1 or 2 in that the purity of the carbon black and crystalline boron powder described in step 1 (2) is >98.0 wt.%, and the particle size is between 1 and 20 μm. The molar ratio of the crystalline boron powder to the carbon black weighed in step 1 (2) is (1 to 4):1. Other steps are the same as those in specific embodiments 1 or 2.

[0038] Specific embodiment 4: This embodiment differs from specific embodiments 1 to 3 in that the molar ratio of metal powder I to non-metal powder II in step 1 ③ is 1:(0.75-2). The other steps are the same as specific embodiments 1 to 3.

[0039] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that the parameters for the preliminary mixing of metal powder I and non-metallic powder II using low-speed pendulum vibration described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation, forming a complete cycle; forward rotation is clockwise rotation, and reverse rotation is counterclockwise rotation; in each cycle, the forward rotation time is 10 to 300 minutes, the reverse rotation time is 10 to 300 minutes, the pause time is 5 to 60 minutes, the forward rotation speed is 100 to 500 r / min, the reverse rotation speed is 100 to 500 r / min, and the total number of cycles is 2 to 20. The other steps are the same as specific embodiments 1 to 4.

[0040] Specific embodiment 6: This embodiment differs from specific embodiments 1 to 5 in that the specific parameters for further mixing and refining the composite powder III using high-energy ball milling in step 1 (4) are as follows: the ball-to-material ratio during ball milling is (10-60):1, the main disc speed during high-energy ball milling is 200-500 rpm, the planetary disc speed is 300-700 rpm, the running time during each cycle is 20-100 min, the rest time is 10-30 min, the total number of cycles is 8-40, and the total time for the entire ball milling process is 10-40 h. The ball mill jar and the grinding ball media are all cemented carbide. The other steps are the same as specific embodiments 1 to 5.

[0041] Specific embodiment 7: This embodiment differs from specific embodiments 1 to 6 in that: in step 2, under the protection of an inert atmosphere, the spark plasma sintering furnace is heated from room temperature to 1800-2400°C at a heating rate of 50-200°C / min, maintained at 1800-2400°C for 5-20 minutes, and then cooled to room temperature at a cooling rate of 50-300°C / min. Throughout the entire process, the applied pressure is ensured to reach 25-100 MPa when the temperature reaches 800-1200°C, and then maintained at 25-100 MPa until the cooling stage ends. After the cooling stage ends, the mold is removed and demolded to obtain a high-strength, ultra-hard boride-carbide complex composition ceramic. The other steps are the same as specific embodiments 1 to 6.

[0042] Specific embodiment 8: This embodiment differs from specific embodiments 1 to 7 in that the inert atmosphere is argon, helium or neon. The other steps are the same as those of specific embodiments 1 to 7.

[0043] Specific embodiment 9: The difference between this embodiment and specific embodiments 1 to 8 is that the relative density of the high-strength and ultra-hard boride-carbide complex ceramic described in step 2 is >99%, the room temperature hardness is 32-36GPa, and the fracture toughness is 6-7MPa·m 1 / 2 , the elastic modulus can reach 560GPa, and the three-point bending strength is 600-800MPa. The other steps are the same as those in the first to eighth embodiments.

[0044] Specific embodiment 10: This embodiment is an application of high-strength and ultra-hard boride-carbide complex composition ceramics in the field of ultra-high temperature thermal protection and cutting tools.

[0045] The following examples are used to verify the beneficial effects of the present invention:

[0046] Example 1: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0047] 1. Obtaining composite powder:

[0048] ①, weighing metal titanium powder, metal zirconium powder and metal niobium powder in an equal molar ratio to obtain metal powder I;

[0049] The purity of the titanium powder, zirconium powder and niobium powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size of the powder is between 20 and 50 μm;

[0050] ②, respectively weighing crystalline boron powder and carbon black to obtain non-metallic powder II; the molar ratio of the weighed crystalline boron powder to carbon black is 2.5:1;

[0051] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0052] ③. Preliminarily mixing the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I and the non-metallic powder II is 1:1.4, to obtain a preliminarily mixed composite powder III;

[0053] The parameters for the preliminary mixing of the metal powder I and the non-metallic powder II by low-speed pendulum vibration described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation constitute a complete cycle process; the forward rotation is clockwise rotation, and the reverse rotation is counterclockwise rotation; the forward rotation time in each cycle is 100 min, the reverse rotation time is 100 min, the pause time is 40 min, the forward rotation speed is 150 r / min, the reverse rotation speed is 150 r / min, and the total number of cycles is 2 times;

[0054] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0055] The specific parameters of the high-energy ball milling process for further mixing and refining the preliminarily mixed composite powder III described in step 1 (4) are as follows: the ball-to-material ratio of the ball milling is 10:1, the main disk speed during the high-energy ball milling process is 200 rpm, the planetary disk speed is 700 rpm, the running time of each cycle is 40 minutes, the rest time is 20 minutes, the total number of cycles is 30, and the total time of the entire ball milling process is 30 hours. The ball milling jar and the grinding ball media are all cemented carbide;

[0056] 2. The fully uniformly mixed and fine-particle composite powder IV is placed in a sintering mold and sintered in a spark plasma sintering furnace under argon atmosphere protection. The temperature is raised from room temperature to 1900°C at a heating rate of 50°C / min, and kept at 1900°C for 20 minutes, and then cooled to room temperature at a cooling rate of 100°C / min. During the whole process, the pressure is ensured to reach 30MPa when the temperature is raised to 800°C, and then the pressure of 30MPa is maintained until the end of the cooling stage; after the cooling stage, the mold is removed and demolded to obtain (Ti,Zr,Nb)B2-(Ti,Zr,Nb)C high-strength and ultra-hard boride-carbide complex composition ceramics.

[0057] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb) B2-(Ti, Zr, Nb) C prepared in Example 1 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness was 32.6 GPa, and the fracture toughness was 6.1 MPa·m 1 / 2, the elastic modulus is 565GPa and the three-point bending strength is 634MPa.

[0058] Example 2: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0059] 1. Obtaining composite powder:

[0060] ①, weighing metal titanium powder, metal zirconium powder, metal niobium powder and metal tantalum powder in equal molar ratios to obtain metal powder I;

[0061] The purity of the titanium powder, zirconium powder, niobium powder and tantalum powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size is between 20 and 50 μm;

[0062] ②, respectively weighing crystalline boron powder and carbon black to obtain a mixed non-metallic powder II; the molar ratio of the weighed crystalline boron powder to the carbon black is 4:1;

[0063] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0064] ③. Preliminarily mixing the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I and the non-metallic powder II is 1:1.4, to obtain a preliminarily mixed composite powder III;

[0065] The parameters for the initial mixing of metal powder I and non-metallic powder II using low-speed oscillation described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation, forming a complete cycle. Forward rotation is clockwise, and reverse rotation is counterclockwise. Each cycle has a forward rotation time of 150 minutes, a reverse rotation time of 150 minutes, a pause time of 60 minutes, a forward rotation speed of 200 rpm, and a reverse rotation speed of 200 rpm. The total number of cycles is 3.

[0066] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0067] The specific parameters of the process of further mixing and refining the preliminarily mixed composite powder III using high-energy ball milling as described in step 1④ are as follows: the ball-to-material ratio of the ball milling is 20:1, the main disk speed during the high-energy ball milling process is 300 r / min, the planetary disk speed is 600 r / min, the running time during each cycle is 70 min, the intermittent time is 20 min, the total number of cycles is 10 times, the total time of the entire ball milling process is 15 h, and the ball milling jar and grinding ball media are all cemented carbide.

[0068] 2. The fully and uniformly mixed composite powder IV with fine particle size is placed in a sintering mold and sintered in a spark plasma sintering furnace under the protection of a helium atmosphere. The temperature is raised from room temperature to 2000°C at a heating rate of 75°C / min, and kept at 2000°C for 15 minutes, and then cooled to room temperature at a cooling rate of 150°C / min. During the whole process, the pressure is ensured to reach 40MPa when the temperature is raised to 1000°C, and then the pressure of 40MPa is maintained until the end of the cooling stage; after the cooling stage, the mold is taken out and demolded to obtain (Ti,Zr,Nb,Ta)B2-(Ti,Zr,Nb,Ta)C high-strength and ultra-hard boride-carbide complex composition ceramics.

[0069] The high strength and ultra-hard boride-carbide complex composition ceramics with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2 were subjected to XRD testing. The test results are as follows: Figure 1 As shown in the figure, "*" is the diffraction peak corresponding to (Ti, Zr, Nb, Ta) C, and "◆" is the diffraction peak corresponding to (Ti, Zr, Nb, Ta) B2. As can be seen from the figure, during the spark plasma sintering process, the transition metal powder reacts with the crystalline boron powder and carbon black to generate corresponding diborides and carbides. Various borides and carbides undergo mutual solid dissolution, and eventually two solid solution phases are generated. From the diffraction peaks, it can be seen that the sintered material is a complex phase. By calibrating the diffraction peaks, it can be found that the main phases are respectively a carbide phase with a face-centered cubic structure and a boride phase with a close-packed hexagonal structure. This proves that the technical solution of Example 2 can be used to obtain a high-strength, ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C.

[0070] The high strength and ultra-hard boride-carbide complex composition ceramics with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2 were subjected to SEM testing. The test results are shown in FIG. Figure 2 shown by Figure 2 It can be seen that the high-strength and ultra-hard boride-carbide complex composition ceramics are composed of a black diboride phase and a white carbide phase; the material contains almost no pores and is basically densified; the material structure is evenly distributed and the grain size is small.

[0071] The fracture analysis of the high strength and ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2 was performed. The test results are as follows: Figure 3As shown in the figure, the sintering of high-strength and ultra-hard boride-carbide complex ceramics is basically dense, and river patterns and the extraction of boride grains are observed, that is, the fracture mode of high-strength and ultra-hard boride-carbide complex ceramics is a mixed fracture along the grain and through the grain. The crack propagation analysis of the high-strength and ultra-hard boride-carbide complex ceramics with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2 is carried out, and the test results are as follows Figure 4 As shown in the figure, deflection occurs during the crack propagation process.

[0072] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Example 2 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness of the material was 32.3 GPa, and the fracture toughness was 6.2 MPa·m 1 / 2 , the elastic modulus is 554GPa and the three-point bending strength is 724MPa.

[0073] Example 3: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0074] 1. Obtaining composite powder:

[0075] ①, weighing metal titanium powder, metal zirconium powder, metal niobium powder and metal tungsten powder in equal molar ratios to obtain metal powder I;

[0076] The purity of the titanium powder, zirconium powder, niobium powder and tungsten powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size is between 10 and 40 μm;

[0077] ②, respectively weighing crystalline boron powder and carbon black to obtain non-metallic powder II; the molar ratio of the weighed crystalline boron powder to carbon black is 4:1;

[0078] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0079] ③. Preliminarily mixing the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I to the non-metallic powder II is 1:1.67, to obtain a preliminarily mixed composite powder III;

[0080] The parameters for the preliminary mixing of the metal powder I and the non-metallic powder II by low-speed pendulum vibration described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation constitute a complete cycle process; the forward rotation is clockwise rotation, and the reverse rotation is counterclockwise rotation; the forward rotation time in each cycle is 30 minutes, the reverse rotation time is 30 minutes, the pause time is 30 minutes, the forward rotation speed is 350 r / min, the reverse rotation speed is 350 r / min, and the total number of cycles is 10 times;

[0081] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0082] The specific parameters of the high-energy ball milling process for further mixing and refining the preliminarily mixed composite powder III described in step 1 (4) are as follows: the ball-to-material ratio of the ball milling is 25:1, the main disk speed during the high-energy ball milling process is 250 r / min, the planetary disk speed is 700 r / min, the running time of each cycle is 100 min, the rest time is 20 min, the total number of cycles is 10, and the total time of the entire ball milling process is 20 h. The ball milling jar and the grinding ball media are all cemented carbide;

[0083] 2. The fully uniformly mixed and fine-particle composite powder IV is placed in a sintering mold and sintered in a spark plasma sintering furnace under argon atmosphere protection. The temperature is increased from room temperature to 2000°C at a heating rate of 150°C / min, and kept at 2000°C for 10 minutes, and then cooled to room temperature at a cooling rate of 150°C / min; during the whole process, the applied pressure is ensured to reach 80MPa when the temperature is increased to 1100°C, and then the pressure of 80MPa is maintained until the end of the cooling stage; after the cooling stage, the mold is removed and demolded to obtain (Ti,Zr,Nb,W)B2-(Ti,Zr,Nb,W)C high-strength and ultra-hard boride-carbide complex composition ceramics.

[0084] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb, W) B2-(Ti, Zr, Nb, W) C prepared in Example 3 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness of the material was 35.2 GPa, and the fracture toughness was 6.7 MPa·m 1 / 2 , the elastic modulus is 546GPa, and the three-point bending strength is 698MPa.

[0085] Example 4: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0086] 1. Obtaining composite powder:

[0087] ①, weighing metal titanium powder, metal zirconium powder, metal niobium powder, metal hafnium powder, metal vanadium powder, and metal tantalum powder in equal molar ratios to obtain metal powder I;

[0088] The purity of the titanium powder, zirconium powder, niobium powder, hafnium powder, vanadium powder, and tantalum powder described in step 1 (1) is >99.0 wt.%, and the particle size is between 10 and 40 μm.

[0089] ②, respectively weighing crystalline boron powder and carbon black to obtain non-metallic powder II; the molar ratio of the weighed crystalline boron powder to carbon black is 4:1;

[0090] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0091] ③. Preliminarily mixing the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I to the non-metallic powder II is 1:1.67, to obtain a preliminarily mixed composite powder III;

[0092] The parameters for the initial mixing of the metal powder I and non-metallic powder II using low-speed oscillation described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation, forming a complete cycle. Forward rotation is clockwise, and reverse rotation is counterclockwise. Each cycle has a forward rotation time of 10 minutes, a reverse rotation time of 10 minutes, a pause time of 10 minutes, a forward rotation speed of 500 rpm, and a reverse rotation speed of 500 rpm. The total number of cycles is 20.

[0093] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0094] The specific parameters of the high-energy ball milling process for further mixing and refining the preliminarily mixed composite powder III described in step 1 (4) are as follows: the ball-to-material ratio of the ball milling is 50:1, the main disk speed during the high-energy ball milling process is 300 rpm, the planetary disk speed is 650 rpm, the running time of each cycle is 60 minutes, the rest time is 30 minutes, the total number of cycles is 16, and the total time of the entire ball milling process is 24 hours. The ball milling jar and the grinding ball media are all cemented carbide;

[0095] Second, the uniformly mixed, finely sized composite powder IV was placed in a sintering mold and sintered in a spark plasma sintering furnace under an argon atmosphere. The temperature was raised from room temperature to 2300°C at a rate of 100°C / min, held at 2300°C for 15 minutes, and then cooled to room temperature at a rate of 200°C / min. Throughout the entire process, the applied pressure reached 60 MPa at 1000°C and was maintained at 60 MPa until the cooling stage. After the cooling stage, the mold was removed and demolded to obtain a high-strength, ultra-hard boride-carbide complex ceramic (Ti, Zr, Hf, V, Nb, Ta)B2-(Ti, Zr, Hf, V, Nb, Ta)C.

[0096] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Hf, V, Nb, Ta) B2-(Ti, Zr, Hf, V, Nb, Ta) C prepared in Example 4 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness of the material was 33.1 GPa, and the fracture toughness was 6.9 MPa·m 1 / 2 , the elastic modulus is 559GPa and the three-point bending strength is 663MPa.

[0097] Example 5: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0098] 1. Obtaining composite powder:

[0099] ①, weighing metal titanium powder, metal zirconium powder and metal niobium powder in an equal molar ratio to obtain metal powder I;

[0100] The purity of the titanium powder, zirconium powder and niobium powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size of the powder is between 20 and 50 μm;

[0101] ②, respectively weighing crystalline boron powder and carbon black to obtain non-metallic powder I; wherein the molar ratio of the weighed crystalline boron powder to the carbon black is 1:1;

[0102] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 99.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0103] ③. Preliminary mixing of the metal powder I and the non-metallic powder II was performed using a low-speed pendulum vibration, wherein the molar ratio of the metal powder I to the non-metallic powder II was 1:0.92, to obtain a preliminarily mixed composite powder III;

[0104] The parameters for the preliminary mixing of the mixed metal powder I and non-metallic powder II by low-speed pendulum vibration described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation constitute a complete cycle process; the forward rotation is clockwise rotation, and the reverse rotation is counterclockwise rotation; the forward rotation time in each cycle is 60 minutes, the reverse rotation time is 60 minutes, the pause time is 30 minutes, the forward rotation speed is 300 r / min, the reverse rotation speed is 300 r / min, and the total number of cycles is 4 times;

[0105] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0106] The specific parameters of the high-energy ball milling process for further mixing and refining the preliminarily mixed composite powder III described in step 1 (4) are as follows: the ball-to-material ratio of the ball milling is 15:1, the main disk speed during the high-energy ball milling process is 400 rpm, the planetary disk speed is 400 rpm, the running time of each cycle is 35 minutes, the rest time is 25 minutes, the total number of cycles is 20, and the total time of the entire ball milling process is 20 hours. The ball milling jar and the grinding ball media are all cemented carbide;

[0107] 2. The fully uniformly mixed and fine-particle composite powder IV is placed in a sintering mold and sintered in a spark plasma sintering furnace under argon atmosphere protection. The temperature is raised from room temperature to 2000°C at a heating rate of 150°C / min, and kept at 2000°C for 15 minutes, and then cooled to room temperature at a cooling rate of 150°C / min. During the whole process, the pressure applied when the temperature is raised to 1000°C is ensured to reach 60MPa, and then the pressure of 60MPa is maintained until the end of the cooling stage. After the cooling stage, the mold is removed and demolded to obtain (Ti,Zr,Nb)3B4-(Ti,Zr,Nb)C high-strength and ultra-hard boride-carbide complex composition ceramics.

[0108] The high strength and ultra-hard boride-carbide complex composition ceramics with the chemical formula (Ti, Zr, Nb) 3B 4 -(Ti, Zr, Nb) C prepared in Example 5 were subjected to XRD testing. The test results are shown in FIG. Figure 5As shown in the figure, "*" is the diffraction peak corresponding to (Ti, Zr, Nb) C, and "◆" is the diffraction peak corresponding to (Ti, Zr, Nb) 3 B 4. As can be seen from the figure, during the spark plasma sintering process, the transition metal powder reacts with the crystalline boron powder and carbon black to generate the corresponding boride and carbide, and the boride and carbide undergo mutual solid dissolution, eventually forming two solid solution phases; from the diffraction peaks, it can be seen that the sintered material is a complex phase. By calibrating the diffraction peaks, it can be found that the main phases are the carbide phase with a face-centered cubic structure and the boride phase with an orthorhombic structure, respectively. This proves that the technical solution of Example 5 can be used to obtain a high-strength, ultra-hard boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb) 3 B 4 -(Ti, Zr, Nb) C.

[0109] The high strength and ultra-hard boride-carbide complex composition ceramics with the chemical formula (Ti, Zr, Nb) 3B 4 -(Ti, Zr, Nb) C prepared in Example 5 were subjected to SEM testing. The test results are shown in FIG. Figure 6 shown by Figure 6 It can be seen that the high-strength and ultra-hard boride-carbide complex composition ceramics are composed of a black boride phase and a white carbide phase; the material contains almost no pores and is basically densified; the material structure is evenly distributed and the grain size is small.

[0110] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb)3B4-(Ti, Zr, Nb)C prepared in Example 5 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness was 36.2 GPa, and the fracture toughness was 6.1 MPa·m 1 / 2 , the elastic modulus is 552GPa and the three-point bending strength is 694MPa.

[0111] Example 6: A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics is specifically completed by the following steps:

[0112] 1. Obtaining composite powder:

[0113] ①, weighing metal titanium powder, metal zirconium powder and metal niobium powder in an equal molar ratio to obtain metal powder I;

[0114] The purity of the titanium powder, zirconium powder and niobium powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size of the powder is between 20 and 50 μm;

[0115] ②, respectively weighing crystalline boron powder and carbon black to obtain non-metallic powder II; the molar ratio of the weighed crystalline boron powder to the carbon black is 1:1;

[0116] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0117] ③. Preliminarily mixing the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I to the non-metallic powder II is 1:0.79, to obtain a preliminarily mixed composite powder III;

[0118] The parameters for the preliminary mixing of the mixed metal powder I and non-metallic powder II by low-speed pendulum vibration described in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation constitute a complete cycle process; the forward rotation is clockwise rotation, and the reverse rotation is counterclockwise rotation; the forward rotation time in each cycle is 30 minutes, the reverse rotation time is 30 minutes, the pause time is 15 minutes, the forward rotation speed is 400 r / min, the reverse rotation speed is 400 r / min, and the total number of cycles is 8 times;

[0119] ④. Further mixing and refining the preliminarily mixed composite powder III by high-energy ball milling to obtain a fully uniformly mixed composite powder IV with a finer particle size;

[0120] The specific parameters of the high-energy ball milling process for further mixing and refining the preliminarily mixed composite powder III described in step 1 (4) are as follows: the ball-to-material ratio of the ball milling is 25:1, the main disk speed during the high-energy ball milling process is 300 rpm, the planetary disk speed is 700 rpm, the running time of each cycle is 50 minutes, the rest time is 10 minutes, the total number of cycles is 15, and the total time of the entire ball milling process is 15 hours. The ball milling jar and the grinding ball media are all cemented carbide;

[0121] Second, the uniformly mixed, finely sized composite powder IV was placed in a sintering mold and sintered in a spark plasma sintering furnace under an argon atmosphere. The temperature was raised from room temperature to 2000°C at a rate of 100°C / min, held at 2000°C for 10 minutes, and then cooled to room temperature at a rate of 150°C / min. Throughout the entire process, the applied pressure reached 55 MPa at 1100°C and was maintained at 55 MPa until the cooling stage. After the cooling stage, the mold was removed and demolded, yielding a high-strength, ultrahard boride-carbide complex ceramic (Ti, Zr, Nb)B-(Ti, Zr, Nb)C.

[0122] The mechanical properties of the high-strength and ultra-hard boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb) B-(Ti, Zr, Nb) C prepared in Example 6 were tested. The results showed that the relative density of the composite ceramic at room temperature was 99%, the hardness was 35.7 GPa, and the fracture toughness was 6.2 MPa·m 1 / 2 , the elastic modulus is 534GPa and the three-point bending strength is 701MPa.

[0123] Comparative Example 1: Preparation method of boride-carbide complex composition ceramics, specifically completed according to the following steps:

[0124] 1. Obtaining composite powder:

[0125] ①, weighing metal titanium powder, metal zirconium powder, metal niobium powder and metal tantalum powder in equal molar ratios to obtain metal powder I;

[0126] The purity of the titanium powder, zirconium powder, niobium powder and tantalum powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size is between 20 and 50 μm;

[0127] ②, respectively weighing crystalline boron powder and carbon black to obtain a mixed non-metallic powder II; the molar ratio of the weighed crystalline boron powder to the carbon black is 4:1;

[0128] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0129] ③. Directly mix the metal powder I and the non-metallic powder II by low-speed pendulum vibration, wherein the molar ratio of the metal powder I to the non-metallic powder II is 1:1.4, to obtain a mixed composite powder III;

[0130] The parameters for mixing metal powder I and non-metallic powder II using low-speed oscillation in step 1 (3) are set as follows: one forward rotation, one pause, and one reverse rotation, forming a complete cycle. Forward rotation is clockwise, and reverse rotation is counterclockwise. Each cycle has a forward rotation time of 150 minutes, a reverse rotation time of 150 minutes, a pause time of 60 minutes, a forward rotation speed of 200 rpm, and a reverse rotation speed of 200 rpm. The total number of cycles is 3.

[0131] 2. The composite powder III directly mixed by low-speed pendulum vibration is placed in a sintering mold and sintered in a spark plasma sintering furnace under the protection of a helium atmosphere. The temperature is increased from room temperature to 2000°C at a heating rate of 75°C / min, and kept at 2000°C for 15 minutes, and then cooled to room temperature at a cooling rate of 150°C / min. During the whole process, the pressure is ensured to reach 40MPa when the temperature is increased to 1000°C, and then the pressure of 40MPa is maintained until the end of the cooling stage; after the cooling stage, the mold is removed and demolded to obtain (Ti,Zr,Nb,Ta)B2-(Ti,Zr,Nb,Ta)C boride-carbide complex composition ceramics.

[0132] The boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 1 was subjected to SEM testing. The test results are as follows: Figure 7 shown by Figure 7 It can be seen that direct mixing of powders using low-speed vibration is less effective. Direct mixing using vibration results in insufficient system energy, and there is a clear phenomenon of incomplete and uneven diffusion of transition metal elements. The material has low density, poor microstructure uniformity, and large grain size.

[0133] The mechanical properties of the boride-carbide complex ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 1 were tested. The results showed that the relative density of the complex ceramic at room temperature was 95.7%, the hardness of the material was 23.1 GPa, the elastic modulus was 492 GPa, the three-point bending strength was 502 MPa, and the fracture toughness was 3.9 MPa·m 1 / 2 ; Through comparative example 1, it can be found that the technical solution of the present invention has significant advantages in improving the strength and hardness of ceramic materials.

[0134] Comparative Example 2: Preparation of boride-carbide complex composition ceramics, specifically completed by the following steps:

[0135] 1. Obtaining composite powder:

[0136] ①, weighing metal titanium powder, metal zirconium powder, metal niobium powder and metal tantalum powder in equal molar ratios to obtain metal powder I;

[0137] The purity of the titanium powder, zirconium powder, niobium powder and tantalum powder described in step 1 (1) is greater than 99.0 wt.%, and the particle size is between 20 and 50 μm;

[0138] ②, respectively weighing crystalline boron powder and carbon black to obtain a mixed non-metallic powder II; the molar ratio of the weighed crystalline boron powder to the carbon black is 4:1;

[0139] The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size of the two powders is between 1 and 20μm;

[0140] ③. Using high-energy ball milling to mix the metal powder I and the non-metallic powder II to obtain composite powder III;

[0141] The specific parameters of the mixing process using high-energy ball milling in step 1 (3) are as follows: the ball-to-material ratio of the ball milling is 20:1, the main disc speed during the high-energy ball milling process is 300 rpm, the planetary disc speed is 600 rpm, the running time of each cycle is 70 minutes, the rest time is 20 minutes, the total number of cycles is 10, and the total time of the entire ball milling process is 15 hours. The ball milling jar and the grinding balls are all cemented carbide;

[0142] Second, the composite powder III, directly mixed using high-energy ball milling, was placed in a sintering mold and sintered in a spark plasma sintering furnace under a helium atmosphere. The temperature was increased from room temperature to 2000°C at a rate of 75°C / min, held at 2000°C for 15 minutes, and then cooled to room temperature at a rate of 150°C / min. Throughout the entire process, the applied pressure reached 40 MPa at 1000°C and was maintained at 40 MPa until the end of the cooling phase. After the cooling phase, the mold was removed and demolded to produce a (Ti, Zr, Nb, Ta)B2-(Ti, Zr, Nb, Ta)C boride-carbide complex ceramic.

[0143] The boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 2 was subjected to SEM testing. The test results are as follows: Figure 8 shown by Figure 8 It can be seen that the direct mixing effect of composite powders using high-energy ball milling is not good. The porosity of the material is high, the densification process is incomplete, the material structure is uneven, and the grain size is also large.

[0144] The mechanical properties of the boride-carbide complex composition ceramic with the chemical formula (Ti, Zr, Nb, Ta) B2-(Ti, Zr, Nb, Ta) C prepared in Comparative Example 2 were tested. The results showed that the relative density of the complex composition ceramic at room temperature was 96.3%, the hardness of the material was 23.5 GPa, the elastic modulus was 477 GPa, the three-point bending strength was 489 MPa, and the fracture toughness was 4.1 MPa·m 1 / 2 Through comparative example 2, it can be found that the technical solution of the present invention has significant advantages in improving the strength and hardness of ceramic materials.

Claims

1. A method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics, characterized in that The method is completed in the following steps:

1. Obtaining composite powder: ①, weighing 3 to 6 metal powders selected from the group consisting of titanium powder, zirconium powder, hafnium powder, vanadium powder, niobium powder, tantalum powder, chromium powder, molybdenum powder, and tungsten powder in equal molar ratios to obtain metal powder I; ②. Weigh crystalline boron powder and carbon black separately to obtain non-metallic powder II; The molar ratio of the crystalline boron powder and carbon black weighed in step 1② is (1-4):1; ③. Preliminary mixing of metal powder I and non-metallic powder II is performed by low-speed pendulum vibration to obtain composite powder III; In step 1 (3), the molar ratio of metal powder I to non-metal powder II is 1:(0.75-2); In the process of preliminary mixing of metal powder I and non-metal powder II by low-speed oscillation described in step 1 (3), the parameters are set as follows: one forward rotation, a pause, and one reverse rotation to form a complete cycle process; Forward rotation is clockwise rotation, and reverse rotation is counterclockwise rotation; in each cycle, the forward rotation time is 10~300min, the reverse rotation time is 10~300min, the rest time is 5~60min, the forward rotation speed is 100~500r / min, the reverse rotation speed is 100~500r / min, and the total number of cycles is 2~20 times; ④. Further mixing and refining the composite powder III by high-energy ball milling to obtain a composite powder IV that is fully and evenly mixed and has a fine particle size; 2. Place the fully and evenly mixed and fine-particle composite powder IV in a sintering mold, and under the protection of an inert atmosphere, heat the spark plasma sintering furnace from room temperature to 1800~2400℃ at a heating rate of 50~200℃ / min, keep it at 1800~2400℃ for 5~20min, and then cool it to room temperature at a cooling rate of 50~300°C / min; during the entire process, ensure that the applied pressure reaches 25~100MPa when the temperature is raised to 800~1200℃, and then maintain the pressure of 25~100MPa until the end of the cooling stage; after the cooling stage, remove the mold and demould to obtain a high-strength and ultra-hard boride-carbide complex composition ceramic.

2. The method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics according to claim 1, characterized in that The purity of the metal titanium powder, metal zirconium powder, metal hafnium powder, metal vanadium powder, metal niobium powder, metal tantalum powder, metal chromium powder, metal molybdenum powder and metal tungsten powder described in step 1① is greater than 99.0wt.%, and the particle size is between 10 and 90μm.

3. The method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics according to claim 1, characterized in that The purity of the carbon black and crystalline boron powder described in step 1② is greater than 98.0wt.%, and the particle size is between 1 and 20μm.

4. The method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics according to claim 1, characterized in that The specific parameters for further mixing and refining the composite powder III using high-energy ball milling as described in step 1④ are as follows: the ball-to-material ratio of the ball milling is (10~60):1, the main disk speed during the high-energy ball milling process is 200~500r / min, the planetary disk speed is 300~700r / min, the running time in each cycle is 20~100min, the intermittent time is 10~30min, the total number of cycles is 8~40 times, the total time of the entire ball milling process is 10~40h, and the ball milling jar and grinding ball media are all cemented carbide.

5. The method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics according to claim 1, characterized in that The inert atmosphere is argon, helium or neon.

6. The method for preparing high-strength and ultra-hard boride-carbide complex composition ceramics according to claim 1, characterized in that The high-strength and ultra-hard boride-carbide complex ceramics described in step 2 have a relative density of >99%, a room temperature hardness of 32-36 GPa, and a fracture toughness of 6-7 MPa·m 1 / 2 , the elastic modulus can reach 560GPa, and the three-point bending strength is 600~800MPa.

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