Preparation method of pressureless sintered B4C-(Zr, Ti) B2-C composite ceramic material

Abstract

The invention belongs to the technical field of composite ceramic materials, and particularly relates to a preparation method of a pressureless sintered B4C-(Zr, Ti) B2-C composite ceramic material. Aiming at the current situation that a pressureless sintered B4C ceramic material is extremely difficult to sinter and densify and is not easy to process, transition metal, transition metal oxide and transition metal carbide are used as additive phases, the temperature is increased to 1200-1500 DEG C through pressureless sintering, heat preservation is performed for 60-90 minutes, then the temperature is increased to 2000-2200 DEG C, and heat preservation is performed for 60-90 minutes, so that the densified B4C-(Zr, Ti) B2-C composite ceramic material is obtained. The composite ceramic contains a B4C phase, a solid solution phase (Zr, Ti) B2 and a C phase, the mass of the solid solution phase (Zr, Ti) B2 accounts for 10%-30%, the mass of the C phase accounts for 5%-10%, and the balance is 60%-85% of the B4C phase. The prepared B4C ceramic has good electrical properties and mechanical properties, the conductivity of the B4C ceramic is higher than 1S / m, complex shape cutting can be realized through electrosparking, and the application range of the B4C ceramic is further widened.

Description

Technical Field

[0001] The present invention belongs to the technical field of composite ceramic materials, and particularly relates to a method for preparing a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material. Background Art

[0002] Boron carbide (B4C) ceramics have the characteristics of low density, high hardness, high melting point, wear resistance, corrosion resistance and excellent neutron absorption performance, and are widely used in fields such as bulletproof armor, aerospace engines and nuclear power components. The existing hot pressing and spark plasma sintering methods are costly and difficult to fabricate large-sized complex components. In contrast, the pressureless sintering process is simple, low-cost and suitable for mass production. However, the strong covalent bond and low self-diffusion coefficient of B4C make its densification sintering difficult, and its high hardness and low electrical conductivity characteristics make it difficult to achieve complex shape cutting through electrical discharge machining, significantly increasing the difficulty of subsequent processing of the material.

[0003] In view of the difficulties in densification sintering and other problems existing in pressureless sintered B4C ceramics, researchers at home and abroad usually add different sintering aids to B4C to promote the densification sintering of the material. The commonly used sintering aids mainly include metals, carbon, oxides, carbides and borides, etc. Among them, borides have the characteristics of high hardness, high melting point and corrosion resistance. As an additive phase, they can maintain the performance advantages of B4C to the greatest extent, and the residual stress generated at the interface due to the mismatch of the thermal expansion coefficients of the boride and the B4C matrix can cause the deflection of cracks, thereby improving the toughness of B4C. Therefore, the preparation of pressureless sintered B4C-based composite ceramics by adding borides has received extensive attention.

[0004] At present, the relevant work of domestic and foreign scholars on the preparation of pressureless sintered B4C-based composite ceramics by adding borides mainly focuses on two strategies: one is to directly introduce borides (such as TiB2 and CrB2) into B4C, and the other is to generate borides in B4C through in-situ reaction. In the strategy of directly introducing borides, Baharvandiet et al. in Iran prepared a B4C-based composite material by adding 15 wt% of TiB2 at 2150 °C, and its relative density, fracture toughness and flexural strength were 96%, 2.85 MPa·m 1 / 2The hardness values are equivalent to those of pure B4C at 345 MPa. Another strategy is to generate borides through in-situ reactions. For example, the research team led by Professor Gong Hongyu from Shandong University prepared a B4C-ZrB2 composite material through in-situ reaction by adding 15 wt% of ZrO2 at 2100 °C. Its relative density is 96.7%, and the flexural strength is 365 MPa. In addition to oxides, adding transition metals or carbides can also generate borides through in-situ reactions. The research team led by Professor Fu Yudong from Harbin Engineering University prepared a B4C-TiB2 composite material with a relative density of 96% at 2250 °C by adding 5 wt% of Ti powder, and its fracture toughness is 3.75 MPa·m 1 / 2 . The research group also studied the effects of different carbides on B4C ceramics. Among them, the performance of the B4C-based composite material prepared by adding NbC at 2250 °C was improved most significantly. The relative density, flexural strength, and hardness are 96.1%, 368 MPa, and 27.3 GPa, respectively.

[0005] In the above research, single transition metal oxides, carbides, and borides were used as additive phases to prepare pressureless sintered B4C-based composite ceramic materials, and the solid solution strengthening mechanism was not involved. To retain the advantages of B4C ceramics themselves, the content of the second phase added has certain limitations. Therefore, the improvement of the mechanical properties of the prepared B4C-based composite ceramics is relatively limited, and the electrical properties of the materials were not evaluated. Summary of the Invention

[0006] Aiming at the current situation that pressureless sintered B4C ceramic materials are extremely difficult to sinter densification and are not easy to process, the purpose of the present invention is to design and add a multi-component composite additive with transition metals, transition metal oxides, and transition metal carbides as additive phases on the premise of adding a limited second phase, generate (Zr,Ti)B2 solid solution through in-situ reaction, and further improve the mechanical properties of the material by combining solid solution strengthening and carbon toughening mechanisms, evaluate the electrical properties of the material, and then prepare a new type of B4C-(Zr,Ti)B2-C composite ceramic with low cost, excellent mechanical properties, good electrical conductivity, and discharge machining performance.

[0007] The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material described in the present invention includes the following content:

[0008] The powdery sintering raw material composed of B4C, additive phase, and carbonaceous additive is pressureless sintered to obtain a densified composite ceramic material; the additive phase contains at least one of ZrO2, ZrC, and Zr element, and at the same time contains at least one of TiO2, TiC, and Ti element;

[0009] Preferably, the carbonaceous additive includes at least one of carbon black, phenolic resin, glucose, and graphite;

[0010] The pressureless sintering refers to first heating to 1200 °C to 1500 °C, holding for 60 min to 90 min, then heating to 2000 °C to 2200 °C, holding for 60 min to 90 min, and after the sintering is completed, a densified B4C-(Zr,Ti)B2-C composite ceramic material is obtained;

[0011] The B4C-(Zr,Ti)B2-C composite ceramic contains a B4C phase, a solid solution phase (Zr,Ti)B2 and a C phase. The mass of the solid solution phase (Zr,Ti)B2 accounts for 10% to 30%, the mass of the C phase is 5% to 10%, and the rest is the B4C phase with a content of 60% - 85%;

[0012] Preferably, the molar ratio of Zr element to Ti element in the solid solution phase (Zr,Ti)B2 is (1:9) to (9:1); preferably 1:9.

[0013] The amounts of various substances in the sintering raw materials are determined according to the composition of the B4C-(Zr,Ti)B2-C composite ceramic material. There is no strict limit between the amount of B4C powder and the amount of carbonaceous additive; since the by-products of sintering different materials added to B4C are different (for example, the by-product of adding ZrO2 is CO2, and the by-product of adding ZrC is C), the C phase content in the finally obtained B4C-(Zr,Ti)B2-C composite ceramic is 5% to 10%, the mass of the solid solution phase (Zr,Ti)B2 accounts for 10% to 30%, and the rest is the B4C phase (with a content of 60% to 85%). Combining different reaction formulas, the amount of carbonaceous additive and the amount of B4C powder in the sintering raw materials are determined.

[0014] A method for preparing a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to the present invention includes the following specific steps:

[0015] (1) Preparing a green body: After mixing, sieving and granulating the powdery sintering raw materials composed of B4C, an additive phase and a carbonaceous additive, pressing them into a green body;

[0016] (2) Pressureless sintering of the green body: First heating to 1200 °C to 1500 °C and holding for 60 min to 90 min, then continuing to heat to 2000 °C to 2200 °C and holding for 60 min to 90 min to obtain a densified B4C-(Zr,Ti)B2-C composite ceramic material;

[0017] The preparation method of the green body described in step (1) includes the following specific contents: The mixed powdery sintering raw materials are ball-milled horizontally for 12 h to 14 h with ethanol as the medium, the rotational speed of the ball mill is 120 r / min to 150 r / min, the grinding balls are composed of ZrO2, dried after grinding, and then 10% to 20% of the aqueous solution of polyvinyl alcohol (PVA) by the weight of the powder is added. The weight of PVA in this aqueous solution is 4% to 8%. Subsequently, continue grinding to make them fully and evenly mixed, and then pass the completely ground powder through a 60-mesh sieve, and let it stand for 12 h to 24 h to obtain a uniformly mixed granulated powder; The granulated powder is added to a mold and dry-pressed at 90 MPa to 120 MPa, and then cold isostatically pressed at 150 MPa to 200 MPa. After demolding, it is dried at 70 °C to 100 °C for 12 h to 24 h to obtain a green body for subsequent experiments.

[0018] The pressureless sintering described in step (2) includes the following specific contents: After adjusting the air pressure in the furnace ≤ 50 Pa, it is heated to 1200 °C to 1500 °C at a heating rate of 150 °C / h to 250 °C / h and kept warm for 60 min to 90 min. In the last 20 min of heat preservation, argon is introduced into the sintering furnace to raise the argon gas pressure in the furnace to 0.08 MPa, then the gas filling is closed. After the heat preservation is over, continue heating to 2000 °C to 2200 °C and keep warm for 60 min to 90 min to obtain a densified B4C-(Zr,Ti)B2-C composite ceramic material.

[0019] The beneficial effects of the present invention are as follows:

[0020] The present invention uses boron carbide as the main raw material, uses transition metals, transition metal oxides or transition metal carbides as additive phases, designs and adds multi-component composite additives, and through pressureless sintering, makes the ceramic green body in-situ react to generate a (Zr,Ti)B2 solid solution, promoting the improvement of the comprehensive properties of the material, thereby preparing a B4C-(Zr,Ti)B2-C composite ceramic material with excellent properties.

[0021] The B4C-(Zr,Ti)B2-C composite ceramic material of the present invention has good electrical and mechanical properties. Its electrical conductivity is higher than 1 S / m, and complex shape cutting can be realized by electrical discharge machining, further broadening the application range of B4C ceramics. The raw materials used in the present invention are cheap and easy to obtain, the process flow is simple and easy to implement, the equipment requirements are low, the production cost is low, and it is suitable for large-scale mass production. Description of the Drawings

[0022] Figure 1 is the preparation flow chart of the composite ceramic material of the present invention.

[0023] Figure 2 is the schematic diagram of the formation of the (Zr,Ti)B2 solid solution during the pressureless sintering process of the present invention.

[0024] Figure 3 It is a polished surface diagram of the composite ceramic material prepared in Example 1; among them, (a) is a backscattered microstructural diagram of the polished surface, and (b), (c), and (d) are EDS point analysis diagrams of different microregions of the polished surface.

[0025] Figure 4 It is a polished surface diagram of the composite ceramic material prepared in Example 1; among them, (a) is a backscattered microstructural diagram of the polished surface, and (b) is an elemental surface scan analysis diagram of the polished surface.

[0026] Figure 5 It is a scanning electron microscope diagram of crack propagation in the composite ceramic material prepared in Example 1; among them, (a) represents one crack, and (b) represents another crack.

[0027] Figure 6 It is a comparison diagram of the performance of the B4C-(Zr1,Ti9)B2-C composite ceramic material prepared in Example 2 and the literature data.

[0028] Figure 7 It is a polished surface diagram of the composite ceramic material prepared in Example 2; among them, (a) is a backscattered microstructural diagram of the polished surface, and (b), (c), and (d) are EDS point analyses of different microregions of the polished surface. Detailed implementation manners

[0029] Next, in combination with the examples and the drawings, the technical solutions of the present invention will be clearly and completely described. It should be noted that the examples described in the present invention are only used for further explanation and illustration, rather than limiting the scope of its application. Based on the present invention, all other examples obtained by those skilled in the art without creative efforts belong to the protection scope of the present invention.

[0030] The specific process of pressureless sintering is as follows:

[0031] a: Open the furnace lid, place the graphite crucible with the green body in the plasma sintering furnace, and close the furnace lid; turn on the circulating cooling water and the air compressor. After the air compressor stops running, turn on the vacuum pump to evacuate, and start the sintering furnace after the furnace pressure drops to 50 Pa.

[0032] b: Set the heating program: Manually control the power to heat up to 600 °C, then change to automatic program control. Heat up to 1200 °C - 1500 °C at a heating rate of 150 °C / h - 250 °C / h and hold for 1 h. In the last 20 min of holding, turn off the vacuum pump and introduce argon into the sintering furnace until the argon pressure in the furnace reaches 0.08 MPa, then turn off the gas injection. During this process, the organic binder, moisture or low-melting-point impurities in the material may start to volatilize or decompose. Holding for 1 hour ensures that these components are completely removed to avoid their residues in the subsequent high-temperature sintering stage, which may cause pores or cracks. At 1200 °C - 1500 °C, the material does not react violently yet. Switching the atmosphere at this time can effectively isolate oxygen and avoid the interference of introducing argon at the low-temperature stage on the volatilization of impurities. After the holding is completed, continue to heat up to 2000 °C - 2200 °C and hold for 1 h; after the sintering program is completed, the sample is cooled to room temperature in the furnace and taken out to obtain the densified B4C-(Zr,Ti)B2-C composite ceramic material.

[0033] Simulate the change trend of Gibbs free energy of all possible reactions during the pressureless sintering process through FactSage software to determine the process parameters such as the temperature, holding time, and staged sintering for the in-situ reaction to form solid solution.

[0034] The B4C used in the examples has a purity > 98.5%, a particle size of 0.5 μm - 1 μm, and is produced by Zhongpeng Technology (Weihai) Co., Ltd.; ZrC and TiC have a purity > 99.5%, a particle size of 0.5 μm - 1 μm, and are from Qinhuangdao Yinuo New Materials Co., Ltd.; ZrO2 has a purity > 94.7%, a particle size of 30 nm - 50 nm, and is produced by Hangzhou Jikang New Materials Co., Ltd.; Ti has a purity of 99.9%, a particle size of 50 μm, and is produced by Shanghai Shuitian Material Technology Co., Ltd.; the carbon black has a particle size of 20 nm.

[0035] The preparation process of the B4C-(Zr,Ti)B2-C composite ceramic material of the present invention is as Figure 1 shown, and the schematic diagram of the formation of (Zr,Ti)B2 solid solution during the pressureless sintering process is as Figure 2 shown.

[0036] Example 1

[0037] Using 84.5 wt% B4C as the raw material, 10% wt ZrO2, 2.5% wt Ti as the additive phase, and 3 wt% carbon black as the carbonaceous additive, mix them evenly to form the sintering raw material. During pressureless sintering, first heat up to 1450 °C and hold for 1 h, then heat up to 2000 °C and hold for 1 h. After sintering, the densified B4C-(Zr6,Ti4)B2-C composite ceramic material is obtained.

[0038] The specific preparation method is as follows:

[0039] (1) Preparation of green body: B4C, ZrO2, Ti, and carbon black were mixed and then horizontally ball-milled with ethanol as the ball-milling medium at a rotation speed of 120 r / min for 12 h to make the raw materials evenly mixed. After drying, it was sieved through a 60-mesh sieve, and a PVA aqueous solution accounting for 20% of the powder weight was added for granulation, and the PVA in this aqueous solution accounted for 4% by weight. After standing for 12 h, it was reserved for later use. Then the granulated powder was added into a mold and pressed into shape at 100 MPa, and then cold isostatically pressed at 160 MPa. After demolding, it was dried at 70 °C for 12 h, and finally a green body of 6 mm × 5 mm × 30 mm was obtained for subsequent experiments.

[0040] (2) Pressureless sintering of green body: After heating to 600 °C, it was heated to 1450 °C at a heating rate of 200 °C / h and held for 1 h. In the last 20 min of holding, the vacuum pump was turned off, and argon was introduced into the sintering furnace to raise the furnace pressure to 0.08 MPa and then the gas filling was turned off. After the holding was completed, it was heated to 2000 °C at a heating rate of 200 °C / h and held for 1 h to obtain the B4C-(Zr6,Ti4)B2-C composite ceramic material.

[0041] From Figure 3 (a), it can be seen that there are two white phases with different morphologies in the sample. One is approximately spherical with a smaller size, and the other is irregular in shape with a larger size; from Figure 3 (b) and Figure 3 (c), it can be seen that the elements Zr, Ti, and B are detected in both white phases, which proves that a (Zr,Ti)B2 solid solution is formed in Example 1; from Figure 3 (d), it can be proved that a dense B4C phase is also formed at the same time. The microstructure backscattering of the polished surface of the composite ceramic material is as shown in Figure 4 (a), and the surface scanning analysis of the elements B, C, Ti, and Zr on the polished surface is as shown in Figure 4 (b). From Figure 5 (a) and Figure 5 (b), it can be seen that due to the solid solution strengthening effect and the crack deflection and bridging between the (Zr,Ti)B2 grains in the composite ceramic sample added with ZrO2 and Ti, the fracture toughness of the sample is enhanced, reaching 4.01 MPa·m 1 / 2 .

[0042] Example 2

[0043] Using 82.3 wt% B4C as the raw material, 14.6 wt% TiC and 2.8 wt% ZrC as the additive phases, and 0.3% wt carbon black as the carbonaceous additive, they were evenly mixed to form the sintering raw materials. During pressureless sintering, it was first heated to 1450 °C and held for 1 h, and then heated to 2200 °C and held for 1 h. After the sintering was completed, a densified B4C-(Zr1,Ti9)B2-C composite ceramic material was obtained.

[0044] The specific preparation method is as follows:

[0045] (1) Preparation of green body: Mix B4C, TiC, and ZrC, then add carbon black and mix uniformly by ultrasonic stirring. Use ethanol as the ball milling medium for horizontal ball milling at a rotational speed of 120 r / min for 12 h to make the raw materials mix uniformly. After drying, sieve through a 60-mesh sieve, add a PVA aqueous solution accounting for 16% of the powder weight for granulation, where the weight of PVA in this aqueous solution accounts for 8%. Let it stand for 12 h and then set aside. Then, add the granulated powder into a mold and press it into shape at 100 MPa, followed by cold isostatic pressing at 160 MPa. After demolding, dry it at 70 °C for 12 h to finally obtain a green body of 6 mm × 5 mm × 30 mm for subsequent experiments.

[0046] (2) Pressureless sintering of green body: After heating to 600 °C, increase the temperature to 1450 °C at a heating rate of 200 °C / h and hold for 1 h. In the last 20 min of holding, turn off the vacuum pump and introduce argon into the sintering furnace to raise the argon gas pressure in the furnace to 0.08 MPa, then turn off the gas injection. After the holding ends, increase the temperature to 2200 °C at a heating rate of 200 °C / h and hold for 1 h to obtain the B4C-(Zr1,Ti9)B2-C composite ceramic material.

[0047] The prepared B4C-(Zr1,Ti9)B2-C composite ceramic sample has an open porosity of 0.1%, a relative density of 99%, a flexural strength of 460 MPa, and a conductivity of 2×10 4 S / m, and its strength is superior to that of the pressureless sintered B4C ceramics with different additives reported in most literatures. Figure 6 This is a comparison of the flexural strength and density of the composite ceramic sample (pentagram) prepared in this example and the B4C ceramic material without solid solution formation and only one additive phase. It can be seen that the performance of the present invention is the best. Figure 7 (a) It can be seen that there are two different morphologies of white phases in the sample. One is approximately spherical with a smaller size, and the other is irregular in shape with a larger size; Figure 7 (c) and Figure 7 (d) It can be seen that both Zr, Ti, and B elements are detected in the two white phases, which proves that the (Zr,Ti)B2 solid solution is formed in Example 2; Figure 7 (b) It can be proved that a dense B4C phase is also formed simultaneously.

[0048] Example 3

[0049] Using 81.5 wt% B4C as the raw material, 10.2 wt% TiC and 7.5 wt% ZrC as additive phases, and 0.8% wt carbon black as a carbonaceous additive, mix them uniformly to form the sintering raw material. During pressureless sintering, first heat to 1400 °C and hold for 1 h, then heat to 2150 °C and hold for 1 h. After sintering, a densified B4C-(Zr3,Ti7)B2-C composite ceramic material is obtained.

[0050] The specific preparation method is as follows:

[0051] (1) Preparation of green body: After mixing B4C, TiC, ZrC, and carbon black, horizontal ball milling is carried out with ethanol as the ball milling medium at a rotation speed of 140 r / min for 14 h to make the raw materials evenly mixed. After drying, it is sieved through a 60-mesh sieve, and a PVA aqueous solution accounting for 20% of the powder weight is added for granulation, and the weight of PVA in this aqueous solution accounts for 4%. After standing for 12 h, it is reserved for use. Then the granulated powder is added into a mold and pressed into shape at 120 MPa, and then cold isostatically pressed at 180 MPa. After demolding, it is dried at 70 °C for 12 h, and finally a green body of 6 mm × 5 mm × 30 mm is obtained for subsequent experiments.

[0052] (2) Pressureless sintering of green body: After heating to 600 °C, it is heated to 1400 °C at a heating rate of 180 °C / h and held for 1 h. In the last 20 min of holding, the vacuum pump is turned off, and argon is introduced into the sintering furnace to make the argon pressure in the furnace rise to 0.08 MPa and then the inflation is turned off. After the holding is completed, it is heated to 2150 °C at a heating rate of 200 °C / h and held for 1 h to obtain the B4C-(Zr3,Ti7)B2-C composite ceramic material.

[0053] The prepared B4C-(Zr3,Ti7)B2-C composite ceramic sample has an open porosity of 0.3%, a relative density of 98%, and a flexural strength of 386 MPa.

Claims

1. A preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material, characterized in that Includes the following: The powdered sintering raw material composed of B4C, an additive phase and a carbonaceous additive is subjected to pressureless sintering to obtain a densified B4C-(Zr,Ti)B2-C composite ceramic material; The added phase contains at least one of ZrO2, ZrC and Zr, and at the same time contains at least one of TiO2, TiC and Ti; the pressureless sintering refers to first heating the temperature to 1200°C~1500°C, keeping the temperature for 60min~90min, then heating the temperature to 2000°C~2200°C, keeping the temperature for 60min~90min, and after the sintering, a densified B4C-(Zr,Ti)B2-C composite ceramic material is obtained.

2. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 1, characterized in that, The carbonaceous additive includes at least one of carbon black, phenolic resin, glucose and graphite.

3. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 1, characterized in that, The B4C-(Zr,Ti)B2-C composite ceramic contains B4C phase, solid solution phase (Zr,Ti)B2 and C phase, wherein the mass of the solid solution phase (Zr,Ti)B2 accounts for 10% to 30%, the mass of the C phase accounts for 5% to 10%, and the rest is B4C phase accounting for 60% to 85%.

4. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 3, characterized in that, The molar ratio of the Zr element to the Ti element in the solid solution phase (Zr, Ti) B2 is (1:9) to (9:1).

5. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 4, characterized in that, The molar ratio of the Zr element to the Ti element in the solid solution phase (Zr, Ti) B2 is 1:

9.

6. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to any one of claims 1 to 5, characterized in that, The specific steps include: (1) Preparing a green body: mixing powdered sintering raw materials consisting of B4C, an additive phase and a carbonaceous additive, sieving and granulating, and then pressing into a green body; (2) Pressureless sintering of the green body: first raise the temperature to 1200°C ~ 1500°C and keep it for 60min ~ 90min, then continue to raise the temperature to 2000°C ~ 2200°C and keep it for 60min ~ 90min to obtain a densified B4C-(Zr,Ti)B2-C composite ceramic material.

7. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 6, characterized in that, The method for preparing the blank in step (1) includes the following specific contents: The mixed powdered sintering raw materials are ball-milled with ethanol as the medium for 12h to 14h, the ball mill speed is 120r / min to 150r / min, the composition of the grinding balls is ZrO2, and then a polyvinyl alcohol aqueous solution of 10% to 20% by weight of the powder is added, the weight of the polyvinyl alcohol in the aqueous solution is 4% to 8%, and the grinding is continued until the mixture is uniform. The ground powder is sieved and allowed to stand for 12h to 24h to obtain granulated powder; the granulated powder is first dry-pressed at 90MPa to 120MPa, and then cold isostatically pressed at 150MPa to 200MPa, and then dried at 70℃ to 100℃ for 12h to 24h to obtain the green body.

8. The preparation method of a pressureless sintered B4C-(Zr,Ti)B2-C composite ceramic material according to claim 6, characterized in that, The pressureless sintering in step (2) includes the following specific contents: After adjusting the gas pressure of the sintering equipment to ≤50Pa, the temperature is increased to 1200°C~1500°C at a heating rate of 150°C / h~250°C / h and kept at this temperature for 60min~90min. During the last 20min of the heat preservation, argon is introduced into the sintering furnace to raise the argon pressure in the furnace to 0.08MPa and then the inflation is closed. After the heat preservation is completed, the temperature is continued to be increased to 2000°C~2200°C and kept at this temperature for 60min~90min to obtain the densified B4C-(Zr,Ti)B2-C composite ceramic material.

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