A high-strength and tough interlocking structure ZrB2 ceramic and its preparation method and application

Abstract

The present invention discloses a high-strength and tough interlocking structure ZrB2 ceramic and its preparation method and application, belonging to the technical field of zirconium diboride ceramics. The method includes: first, pre-oxidizing ZrC powder and SiC powder, then mixing and ball-milling them with ZrB2 powder, and performing two-step sintering assisted by direct current to obtain a high-strength and tough interlocking structure ZrB2 ceramic. The pre-oxidized ZrC powder and SiC powder provide a process liquid phase at high temperature, and at the same time, a direct current is applied to induce anisotropic growth of ZrB2 grains and couple them into an interlocking structure, thus obtaining a high-strength and tough interlocking structure ZrB2 ceramic. The process liquid phase and the applied direct current can effectively promote the growth of ZrB2 grains into lamellar shapes, and the lamellar grains are coupled to form an interlocking structure, which not only improves the fracture toughness of ZrB2-based ceramics but also improves the strength of ZrB2-based ceramics; the process liquid phase formed at high temperature does not remain in the final ZrB2-based ceramics, improving the high-temperature mechanical properties of ZrB2-based ceramics; the preparation process is simple, with a short cycle and high efficiency, and can be mass-produced.

Description

Technical Field

[0001] The present invention belongs to the technical field of zirconium diboride ceramics, and particularly relates to a high-strength and tough interlocking structure ZrB2 ceramic, a preparation method thereof, and an application thereof. Background Art

[0002] Zirconium boride (ZrB2) ceramics have a low density, a high melting point, high strength, and excellent oxidation and ablation resistance, and are alternative materials for thermal structures and thermal protection components of aircraft. However, ZrB2 ceramics have a large intrinsic brittleness, low fracture toughness, and are prone to rapid crack propagation after crack initiation, resulting in brittle catastrophic failure of the material and low reliability, which limits their engineering applications.

[0003] Inducing anisotropic growth of ZrB2 grains into lamellar structures, and using the volume effect is expected to improve the fracture resistance of ZrB2 ceramics. Some researchers prepared gels using hydrated alumina as a raw material, and after drying, dry gel crushing, screening, high-temperature calcination, screening, and classification, ceramic corundum abrasives with a flaky structure were prepared. The flaky grains are in an interlocking structure, which improves the compressive strength of single abrasive grains. For ZrB2 ceramics, using this method will obviously cause ZrB2 to oxidize into zirconium dioxide (ZrO2), resulting in a decrease in the mechanical properties of ZrB2 ceramics, and the preparation process is complex and cumbersome. Some other researchers used Mo, Nb, Ti, W, and Si to assist the reaction of Zr and B to grow into flaky ZrB2 grains. However, the residual Mo, Nb, Ti, W, and Si will soften and melt at high temperatures, causing a sharp deterioration of the high-temperature mechanical properties of ZrB2 ceramics.

[0004] Therefore, in order to improve the comprehensive mechanical properties of ZrB2 ceramics, how to prepare high-strength and tough ZrB2 ceramics with a grain interlocking structure has become an urgent technical problem in this field. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a high-strength and tough interlocking structure ZrB2 ceramic, a preparation method thereof, and an application thereof, so as to solve the technical problem of how to prepare high-strength and tough ZrB2 ceramics with a grain interlocking structure.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention discloses a preparation method of a high-strength and tough interlocking structure ZrB2 ceramic, comprising the following steps:

[0008] First, the ZrC powder and SiC powder are pre-oxidized, and then mixed and ball-milled with the ZrB2 powder. After two-step sintering assisted by direct current, a high-strength and tough interlocked structure ZrB2 ceramic is obtained;

[0009] The conditions for the two-step sintering are as follows: First, apply a pressure of 18 - 22 MPa to compact the pre-sintered composite powder, pass a direct current, and heat it at a rate of 15 - 25 °C / min to 700 - 800 °C and hold for 20 - 40 min for the first-step sintering; then increase the pressure to 50 - 100 MPa within 1 min, adjust the direct current to a current density greater than 1000 A / cm 2 , and heat it to 1600 - 2000 °C and hold for 3 - 10 min for the second-step sintering;

[0010] After the ZrC powder and SiC powder are pre-oxidized, they provide a process liquid phase at high temperature. At the same time, under the action of direct current, the ZrB2 grains grow anisotropically, forming lamellar shapes and coupling with each other to form a high-strength and tough interlocked structure ZrB2 ceramic with a grain interlocked structure;

[0011] The fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramic is 7.1 - 7.6 MPa·m 1 / 2 , and the flexural strength is 810 - 900 MPa.

[0012] Preferably, the volume fraction ratio of the ZrC powder to the SiC powder is (2 - 15):(2 - 15); the sum of the volume fractions of the ZrC powder, SiC powder, and ZrB2 powder is 100.

[0013] Preferably, the particle size of the ZrC powder is less than 100 nm, the particle size of the SiC powder is less than 200 nm, and the particle size of the ZrB2 powder is less than 100 nm.

[0014] Preferably, the conditions for the pre-oxidation treatment are: ball-milling in air for 10 - 60 min.

[0015] Preferably, the conditions for the mixed ball-milling are: ball-milling in vacuum for 6 - 24 h.

[0016] Preferably, during the two-step sintering, a vacuum furnace with a vacuum degree of 1 - 2 Pa is used.

[0017] The present invention also discloses a high-strength and tough interlocked structure ZrB2 ceramic, which is prepared by using the preparation method of the above-mentioned high-strength and tough interlocked structure ZrB2 ceramic.

[0018] The present invention also discloses the application of the above-mentioned high-strength and tough interlocked structure ZrB2 ceramic in the preparation of thermal structures or thermal protection components of aircraft.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] A preparation method of a high-strength and tough interlocking structure ZrB2 ceramic disclosed by the present invention. By using pre-oxidized zirconium carbide (ZrC) powder and silicon carbide (SiC) powder, and combining with the action of direct current at high temperature, it promotes the growth of ZrB2 grains into lamellar shapes and couples with each other to form an interlocking structure. The pre-oxidation treatment can form a thin oxide layer on the powder surface, and this oxide layer can serve as a liquid phase source in the subsequent sintering process to promote the bonding between ZrB2 powder particles. During the sintering process, the process liquid phase formed by the pre-oxidized ZrC and SiC nano-powders plays a key role in assisting sintering, improving the density of the ZrB2-based ceramic. Moreover, these process liquid phases can escape in the form of gas at high temperature and will not remain in the final ZrB2-based ceramic. This characteristic avoids the common problem of residual low-melting-point phases in traditional ceramic preparation, thereby reducing the adverse effects of low-melting-point phase softening at high temperature on mechanical properties and significantly improving the high-temperature mechanical properties of the ZrB2-based ceramic. Compacting the pre-sintered composite powder by applying a pressure of 18 - 22 MPa reduces the contact resistance between powder particles and facilitates the passage of current. Passing a direct current can accelerate the diffusion and reaction between powder particles and improve the sintering efficiency. Heating the pre-sintered composite powder to 700 - 800 °C at a heating rate of 15 - 25 °C / min and holding for 20 - 40 min. Through a gentle heating rate and an appropriate holding time, the residual moisture and other impurities in the powder can be fully removed, which is beneficial to the densification of the ceramic. It can also ensure the preliminary bonding and diffusion between powder particles, realizing the pre-sintering process and laying a foundation for the subsequent densification process. Increase the pressure to 50 - 100 MPa within 1 min, adjust the current to a current density greater than 1000 A / cm 2 , heat up to 1600 - 2000 °C, and hold for 3 - 10 min; realizing the final densification and high performance of the ceramic. Set the current density greater than 1000 A / cm 2, a stable driving force can be provided through the electromigration effect to continuously drive the directional migration of atoms, achieving the preferred growth and directional arrangement of ZrB2 grains. The combined action of high pressure and high current density can rapidly increase the sintering temperature, promote the complete bonding and diffusion between powder particles, and form a dense microstructure. At the same time, the holding time at high temperature can ensure the stability and uniformity of the internal structure of the ceramic, further enhancing the fracture toughness and flexural strength of the ceramic. By precisely controlling the sintering parameters, the controllability and repeatability of the ceramic properties are achieved, providing a strong guarantee for batch production. Under the induction of direct current, the ZrB2 grains preferentially grow and are oriented, causing the ZrB2 grains to grow into lamellar shapes and couple with each other to form an interlocking structure. This unique structural design greatly enhances the fracture toughness of the ZrB2-based ceramic. When a crack propagates in the ceramic, the interlocking structure can effectively disperse stress and deflect the crack, increasing the crack propagation path and absorbing more fracture energy, thereby delaying the crack propagation speed and ultimately improving the fracture resistance of the material. In addition to the enhancement of fracture toughness, the interlocking structure also improves the overall strength of the ZrB2-based ceramic by increasing the contact area and bonding force between grains. This increase in strength enables the ceramic material to maintain better stability and durability under external forces. The preparation method of the present invention only includes simple steps such as pre-oxidation treatment, ball milling, and two-step sintering, without complex process equipment and cumbersome operation procedures. This simplified process not only reduces production costs but also improves the controllability and stability of the preparation process. Due to the adoption of an efficient sintering technology and optimized process parameters, the preparation method of the present invention can significantly shorten the preparation cycle and improve production efficiency. This makes the batch production of ZrB2-based ceramics possible, providing strong support for meeting the needs of large-scale industrial applications.

[0021] Furthermore, the volume fraction ratio of ZrC powder to SiC powder is (2 - 15):(2 - 15); the sum of the volume fractions of ZrC powder, SiC powder, and ZrB2 powder is 100; ensuring the uniformity of the three powders of ZrC, SiC, and ZrB2 during mixing and the optimization of their interactions. By precisely controlling the proportions of each component, precise regulation of the ceramic microstructure can be achieved, thereby enhancing the fracture toughness and flexural strength of the ceramic.

[0022] Furthermore, the particle size of ZrC powder is less than 100 nm, the particle size of SiC powder is less than 200 nm, and the particle size of ZrB2 powder is less than 100 nm; the use of nano-scale powders can significantly increase the surface area of the powders, improve the reaction activity during the sintering process, and contribute to achieving a denser sintered body and higher mechanical properties. At the same time, the small powder particle size also helps to form a more uniform microstructure, reduce internal defects, and further enhance the fracture toughness and flexural strength of the ceramic.

[0023] Further, the conditions for pre-oxidation treatment are: ball milling in air for 10 - 60 min; the pre-oxidation treatment can form a thin oxide layer on the powder surface. This oxide layer can serve as a liquid phase source during the subsequent sintering process, promoting the bonding between powder particles, and improving the density and mechanical properties of the sintered body.

[0024] Further, the conditions for hybrid ball milling are: ball milling in vacuum for 6 - 24 h; ball milling in a vacuum environment can avoid unnecessary reactions of ZrB2 powder with oxygen or other impurities in the air. At the same time, long-term ball milling can ensure sufficient mixing and uniform dispersion of powder particles, providing a strong guarantee for the formation of a uniform microstructure and excellent mechanical properties.

[0025] Further, during two-step sintering, a vacuum furnace with a vacuum degree of 1 - 2 Pa is used. Vacuum sintering can avoid the interference of oxygen during the sintering process, reduce the generation of internal pores and defects, and improve the density and mechanical properties of the ceramic; at the same time, it can also ensure that the pre-liquid phase can escape in the form of gas during the final sintering stage, improving the high-temperature mechanical properties of the ceramic.

[0026] The present invention also discloses a high-strength and tough interlocking structure ZrB2 ceramic, which is prepared by using the above-mentioned preparation method of high-strength and tough interlocking structure ZrB2 ceramic. The fracture toughness of the high-strength and tough interlocking structure ZrB2 ceramic is 7.1 - 7.6 MPa·m 1 / 2 , and the flexural strength is 810 - 900 MPa. This enables the ceramic material to exhibit stronger resistance and stability when subjected to complex stresses and extreme environmental conditions.

[0027] The present invention also discloses the application of the above high-strength and tough interlocking structure ZrB2 ceramic in the preparation of thermal structures or thermal protection components of aircraft. With excellent mechanical properties and high-temperature stability, the high-strength and tough interlocking structure ZrB2 ceramic prepared by the present invention has broad application prospects in thermal structures or thermal protection components of aircraft. It can withstand extreme high-temperature environments and complex mechanical stresses, providing a strong guarantee for the safe and reliable operation of aircraft. At the same time, this ceramic material is also expected to play an important role in fields such as aerospace, nuclear industry, and cutting tools, promoting the progress and development of related technologies. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the microstructure of the high-strength and tough interlocking structure ZrB2 ceramic in Example 1 of the present invention. Detailed Embodiments

[0029] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] In the present invention, if there is no special description, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0031] In the present invention, if there is no special description, all the technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0032] In the present invention, if there is no special description, the various components or their preferred components involved can be combined with each other to form a new technical solution.

[0033] In the present invention, unless otherwise stated, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where both a and b are real numbers. For example, the numerical range "6 - 22" means that all real numbers between "6 - 22" have been fully listed herein, and "6 - 22" is only an abbreviated representation of these numerical combinations.

[0034] The "range" disclosed in the present invention can be in the form of one or more lower limits and one or more upper limits, respectively.

[0035] 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.

[0036] In the present invention, unless otherwise stated, each reaction or operation step can be carried out sequentially or in order. Preferably, the reaction methods herein are carried out sequentially.

[0037] Unless otherwise stated, the professional and scientific terms used herein have the same meaning as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied to the present invention.

[0038] The present invention provides a preparation method of a high-strength and tough interlocking structure ZrB2 ceramic. Using pre-oxidized ZrC powder and SiC powder to provide a process liquid phase at high temperature, and applying a direct current at the same time to make the ZrB2 grains grow anisotropically, forming a ZrB2-based ceramic with a grain interlocking structure. The specific steps include:

[0039] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Based on the total volume fraction of ZrB2 powder, ZrC powder and SiC powder being 100 parts, the volume fraction of ZrC powder is 2 - 15, and the volume fraction of SiC powder is 2 - 15; the particle size of ZrC powder is less than 100 nm, and the particle size of SiC powder is less than 200 nm; the ZrC powder and SiC powder are ball-milled in air by ball milling method for 10 - 60 min to obtain pre-oxidation treated ZrC powder and SiC powder;

[0040] 2) Preparation of pre-sintered composite powder: ZrB2 powder with a particle size less than 100 nm, the pre-oxidation treated ZrC powder and SiC powder obtained in step 1) are ball-milled in vacuum by ball milling method for 6 - 24 h to obtain pre-sintered composite powder;

[0041] 3) Sintering of ZrB2-based ceramics: The pre-sintered composite powder is put into a sintering mold, the sintering mold is placed in a vacuum furnace with a vacuum degree of 1 - 2 Pa, a pressure of 18 - 22 MPa is applied to compact the pre-sintered composite powder, an electric current is passed, the pre-sintered composite powder is heated to 700 - 800 °C at a heating rate of 15 - 25 °C / min and held for 20 - 40 min, then the pressure is increased to 50 - 100 MPa within 1 min, and the current is adjusted to a current density greater than 1000 A / cm 2 , heated to 1600 - 2000 °C and held for 3 - 10 min, finally obtaining high-strength and tough interlocked structure ZrB2 ceramics.

[0042] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics disclosed by the present invention. The pre-oxidized ZrC nano-powder and SiC nano-powder can provide a process liquid phase at high temperature. At the same time, under the action of direct current, ZrB2 grains can grow into lamellar grains; these lamellar grains are coupled with each other to form an interlocked structure, which not only improves the fracture toughness of ZrB2-based ceramics, but also improves the strength of ZrB2-based ceramics. The liquid phase formed by the pre-oxidized ZrC nano-powder and SiC nano-powder at high temperature is a process liquid phase, and these liquid phases can escape in the form of gas during the high-temperature sintering process and will not remain in the final ZrB2-based ceramics, improving the high-temperature mechanical properties of ZrB2-based ceramics. Compared with traditional spark plasma sintering, traditional spark plasma sintering (SPS) uses pulsed current, which has the essential characteristics of intermittency and energy fluctuation. The intermittency and energy fluctuation of pulsed current change the dynamic conditions of electric field, temperature field and atomic diffusion, and will also cause thermal stress relaxation and atomic migration gap effect, thus weakening the driving force of grain orientation and arrangement. The traditional SPS current density is relatively low, less than 500 A / cm 2, the driving force for driving the directional migration of atoms is small. Therefore, during the traditional SPS sintering process, the degree of preferred growth of ZrB2 grains is low, and the degree of orientation arrangement is low. It is difficult to form a grain interlocking structure, and it is impossible to prepare a high-strength and tough interlocking structure ZrB2 ceramic. In the present invention, the direct current is a non-pulsating current, which is a continuous and constant current. And during the second sintering process, the set current density is greater than 1000 A / cm 2 , and a stable driving force can be provided through the electromigration effect to continuously drive the directional migration of atoms, realizing the preferred growth and directional arrangement of ZrB2 grains, so that a high-strength and tough interlocking structure ZrB2 ceramic can be prepared. The present invention has the advantages of simple process, short preparation cycle, high efficiency, etc., and can realize batch production. It improves the comprehensive mechanical properties of ZrB2 ceramics and promotes their engineering applications in aircraft thermal structures or thermal protection components.

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components described and shown in the accompanying drawings here can 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. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0044] Example 1

[0045] A preparation method of a high-strength and tough interlocking structure ZrB2 ceramic uses pre-oxidized ZrC powder and SiC powder to provide a process liquid phase at high temperature, and at the same time applies a direct current to make the ZrB2 grains grow anisotropically to form a ZrB2-based ceramic with a grain interlocking structure. The specific steps are as follows:

[0046] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Calculated based on the total volume fraction of ZrB2 powder, ZrC powder, and SiC powder being 100 parts, the volume fraction of ZrC powder is 10, and the volume fraction of SiC powder is 10; the particle size of ZrC powder is 50 nm, and the particle size of SiC powder is 100 nm; the ZrC powder and SiC powder are ball-milled in air by the ball-milling method for 20 min to obtain the pre-oxidized ZrC powder and SiC powder;

[0047] 2) Preparation of pre-sintered composite powder: ZrB2 powder with a particle size of 80 nm, pre-oxidized ZrC powder obtained in step 1), and SiC powder are ball-milled in a vacuum for 12 h by ball milling method to obtain pre-sintered composite powder;

[0048] 3) Sintering of ZrB2-based ceramics: The pre-sintered composite powder is placed in a sintering mold, and the sintering mold is placed in a vacuum furnace with a vacuum degree of 2 Pa. A pressure of 20 MPa is applied to compact the pre-sintered composite powder. An electric current is passed through, and the pre-sintered composite powder is heated to 750 °C at a heating rate of 20 °C / min and kept warm for 20 min. Then the pressure is increased to 60 MPa within 1 min, and the current is adjusted to a current density of 1300 A / cm 2 , heated to 1900 °C, and kept warm for 4 min, finally obtaining high-strength and tough interlocked structure ZrB2 ceramics. Please refer to Table 1. The fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in this Example 1 is 7.1 MPa·m 1 / 2 , and the flexural strength is 820 MPa.

[0049] Please refer to Figure 1 is the schematic diagram of the microstructure of the high-strength and tough interlocked structure ZrB2 ceramics in Example 1 of the present invention. It can be seen from the figure that a high-strength and tough interlocked structure ZrB2 ceramic of the present invention has a grain interlocked structure. The excellent mechanical properties are mainly attributed to the grain interlocked structure. When a crack propagates in the ceramic, the interlocked structure can effectively disperse stress and deflect the crack, increase the crack propagation path, absorb more fracture energy, thereby delaying the crack propagation speed and finally improving the fracture resistance of the material. In addition to the enhancement of fracture toughness, the interlocked structure also improves the overall strength of the ZrB2-based ceramics by increasing the contact area and bonding force between grains. The ZrB2-based ceramics with a grain interlocked structure not only have high fracture toughness and flexural strength, but may also exhibit good comprehensive properties such as thermal conductivity, oxidation resistance, and wear resistance. These excellent properties make this ceramic material have broad application prospects in extreme environments such as high temperature, high pressure, and strong corrosion.

[0050] Example 2

[0051] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics, comprising the following steps:

[0052] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Calculated according to the total volume fraction of ZrB2 powder, ZrC powder, and SiC powder being 100 parts, the volume fraction of ZrC powder is 5 parts, and the volume fraction of SiC powder is 15 parts; the particle size of ZrC powder is 50 nm, and the particle size of SiC powder is 100 nm; ZrC powder and SiC powder are ball-milled in air for 20 min by ball milling method to obtain pre-oxidized ZrC powder and SiC powder;

[0053] 2) Preparation of pre-sintered composite powder: ZrB2 powder with a particle size of 80 nm, the pre-oxidized ZrC powder obtained in step 1), and SiC powder are ball-milled in a vacuum for 12 h by ball milling method to obtain pre-sintered composite powder;

[0054] 3) Sintering of ZrB2-based ceramics: The pre-sintered composite powder is placed in a sintering mold, and the sintering mold is placed in a vacuum furnace with a vacuum degree of 2 Pa. A pressure of 20 MPa is applied to compact the pre-sintered composite powder. Current is passed through, and the pre-sintered composite powder is heated to 750 °C at a heating rate of 20 °C / min and held for 20 min. Then the pressure is increased to 60 MPa within 1 min, and the current is adjusted to a current density of 1300 A / cm 2 , heated to 1900 °C, and held for 4 min, finally obtaining high-strength and tough interlocked structure ZrB2 ceramics. Please refer to Table 1. The fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Example 2 is 7.2 MPa·m 1 / 2 , and the flexural strength is 900 MPa.

[0055] Example 3

[0056] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics, comprising the following steps:

[0057] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Calculated according to the total volume fraction of ZrB2 powder, ZrC powder and SiC powder being 100 parts, the volume fraction of ZrC powder is 10, and the volume fraction of SiC powder is 10; the particle size of ZrC powder is 50 nm, and the particle size of SiC powder is 100 nm; ZrC powder and SiC powder are ball-milled in air for 20 min by ball milling method to obtain pre-oxidized ZrC powder and SiC powder;

[0058] 2) Preparation of pre-sintered composite powder: ZrB2 powder with a particle size of 80 nm, the pre-oxidized ZrC powder obtained in step 1), and SiC powder are ball-milled in a vacuum for 12 h by ball milling method to obtain pre-sintered composite powder;

[0059] 3) Sintering of ZrB2-based ceramics: The pre-sintered composite powder is placed in a sintering mold, and the sintering mold is placed in a vacuum furnace with a vacuum degree of 2 Pa. A pressure of 20 MPa is applied to compact the pre-sintered composite powder. Current is passed through, and the pre-sintered composite powder is heated to 750 °C at a heating rate of 20 °C / min and held for 20 min. Then the pressure is increased to 60 MPa within 1 min, and the current is adjusted to a current density of 1300 A / cm 2, heat it to 2000 °C and keep it at this temperature for 10 min, and finally obtain high-strength and tough interlocked structure ZrB2 ceramics. Refer to Table 1, the fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Example 3 is 7.6 MPa·m 1 / 2 , and the flexural strength is 810 MPa.

[0060] Example 4

[0061] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics includes the following steps:

[0062] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Based on the total volume fraction of ZrB2 powder, ZrC powder and SiC powder being 100 parts, the volume fraction of ZrC powder is 2, and the volume fraction of SiC powder is 15; the particle size of ZrC powder is 50 nm, and the particle size of SiC powder is 150 nm; ball-mill the ZrC powder and SiC powder in air for 60 min by ball milling method to obtain pre-oxidation treated ZrC powder and SiC powder;

[0063] 2) Prepare pre-sintered composite powder: Ball-mill ZrB2 powder with a particle size of 50 nm, the pre-oxidation treated ZrC powder and SiC powder obtained in step 1) in vacuum for 6 h by ball milling method to obtain pre-sintered composite powder;

[0064] 3) Sinter ZrB2-based ceramics: Put the pre-sintered composite powder into a sintering mold, place the sintering mold in a vacuum furnace with a vacuum degree of 1 Pa, apply a pressure of 18 MPa to compact the pre-sintered composite powder, pass an electric current, heat the pre-sintered composite powder to 700 °C at a heating rate of 15 °C / min, and keep it at this temperature for 40 min, then increase the pressure to 100 MPa within 1 min, and adjust the electric current to a current density of 1300 A / cm 2 , heat it to 1600 °C and keep it at this temperature for 8 min, and finally obtain high-strength and tough interlocked structure ZrB2 ceramics. Refer to Table 1, the fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Example 4 is 7.1 MPa·m 1 / 2 , and the flexural strength is 810 MPa.

[0065] Example 5

[0066] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics includes the following steps:

[0067] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Based on the total volume fraction of ZrB2 powder, ZrC powder and SiC powder being 100 parts, the volume fraction of ZrC powder is 15, and the volume fraction of SiC powder is 5; the particle size of ZrC powder is 80 nm, and the particle size of SiC powder is 100 nm; the ZrC powder and SiC powder are ball-milled in air by ball-milling method for 40 min to obtain pre-oxidation treated ZrC powder and SiC powder;

[0068] 2) Preparation of pre-sintered composite powder: The ZrB2 powder with a particle size of 80 nm, the pre-oxidation treated ZrC powder and SiC powder obtained in step 1) are ball-milled in vacuum by ball-milling method for 18 h to obtain pre-sintered composite powder;

[0069] 3) Sintering of ZrB2-based ceramics: The pre-sintered composite powder is put into a sintering mold, the sintering mold is placed in a vacuum furnace with a vacuum degree of 2 Pa, a pressure of 22 MPa is applied to compact the pre-sintered composite powder, an electric current is passed, the pre-sintered composite powder is heated to 750 °C at a heating rate of 25 °C / min and held for 35 min, then the pressure is increased to 80 MPa within 1 min, the current is adjusted to a current density of 1200 A / cm 2 , heated to 1800 °C and held for 5 min, finally obtaining high-strength and tough interlocked structure ZrB2 ceramics. Please refer to Table 1, the fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Example 5 is 7.2 MPa·m 1 / 2 , and the flexural strength is 880 MPa.

[0070] Example 6

[0071] A preparation method of high-strength and tough interlocked structure ZrB2 ceramics, comprising the following steps:

[0072] 1) Pre-oxidation treatment of ZrC powder and SiC powder: Based on the total volume fraction of ZrB2 powder, ZrC powder and SiC powder being 100 parts, the volume fraction of ZrC powder is 15, and the volume fraction of SiC powder is 2; the particle size of ZrC powder is 50 nm, and the particle size of SiC powder is 100 nm; the ZrC powder and SiC powder are ball-milled in air by ball-milling method for 10 min to obtain pre-oxidation treated ZrC powder and SiC powder;

[0073] 2) Preparation of pre-sintered composite powder: The ZrB2 powder with a particle size of 80 nm, the pre-oxidation treated ZrC powder and SiC powder obtained in step 1) are ball-milled in vacuum by ball-milling method for 24 h to obtain pre-sintered composite powder;

[0074] 3) Sintered ZrB2-based ceramics: Put the pre-sintered composite powder into a sintering mold. Place the sintering mold in a vacuum furnace with a vacuum degree of 1.5 Pa. Apply a pressure of 20 MPa to compact the pre-sintered composite powder. Pass an electric current and heat the pre-sintered composite powder to 800 °C at a heating rate of 20 °C / min, and keep it warm for 30 min. Then increase the pressure to 50 MPa within 1 min, adjust the current to a current density of 1100 A / cm 2 , heat it up to 2000 °C, and keep it warm for 3 min to finally obtain high-strength and tough interlocked structure ZrB2 ceramics. Refer to Table 1. The fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Example 6 of this embodiment is 7.4 MPa·m 1 / 2 , and the flexural strength is 840 MPa.

[0075] Table 1 Comparison of mechanical properties of high-strength and tough interlocked structure ZrB2 ceramics prepared in Examples 1-6

[0076]

[0077] Refer to Table 1 for the comparison of the mechanical properties of the high-strength and tough interlocked structure ZrB2 ceramics prepared in Examples 1-6. It can be seen from the table that the fracture toughness of the high-strength and tough interlocked structure ZrB2 ceramics prepared by the present invention is 7.1-7.6 MPa·m 1 / 2 , which can better disperse stress when the material is under external force, delay crack propagation, improve the anti-fracture ability, and thus ensure the stability of the structure in extreme environments. The flexural strength is 810-900 MPa, and it is not easy to fracture when the material is subjected to a bending load, enhancing the reliability and durability of the structure. These properties enable the high-strength and tough interlocked structure ZrB2 ceramics prepared by the present invention to have broad application potential under extreme conditions such as high temperature, high pressure, and strong corrosion, and can significantly improve the service life and safety of products.

[0078] In summary, for the preparation method of a high-strength and tough interlocking structure ZrB2 ceramic of the present invention, ZrC powder and SiC powder are pre-oxidized and then mixed and ball-milled with ZrB2 powder. The pre-oxidation treatment can form a thin oxide layer on the powder surface. This oxide layer can serve as a liquid-phase source during the subsequent sintering process, promoting the bonding between ZrB2 powder particles, improving the density and mechanical properties of the sintered body. The process liquid phase formed by the pre-oxidized ZrC and SiC nano-powders plays a key role in assisting sintering and improves the density of the ZrB2-based ceramic. Moreover, these process liquid phases can escape in the form of gas at high temperature and will not remain in the final ZrB2-based ceramic. This avoids the problem of residual low-melting-point phases commonly found in traditional ceramic preparation, thereby reducing the adverse effect of the softening of low-melting-point phases at high temperature on mechanical properties and significantly improving the high-temperature mechanical properties of the ZrB2-based ceramic. By applying pressure to compact the pre-sintered composite powder, the contact resistance between powder particles is reduced, facilitating the passage of current. By passing a direct current, the diffusion and reaction between powder particles can be accelerated, improving the sintering efficiency. By using a gentle heating rate and an appropriate holding time, the residual moisture and other impurities in the powder can be fully removed, facilitating the densification of the ceramic. It can also ensure the preliminary bonding and diffusion between powder particles, realizing the pre-sintering process and laying a foundation for the subsequent densification process. By providing a stable driving force through the electromigration effect, continuously driving the directional migration of atoms, realizing the preferred growth and directional arrangement of ZrB2 grains. The combined action of high pressure and high current density can rapidly increase the sintering temperature, promoting the complete bonding and diffusion between powder particles and forming a dense microstructure. At the same time, the holding time at high temperature can ensure the stability and uniformity of the internal structure of the ceramic, further improving the fracture toughness and flexural strength of the ceramic. By precisely controlling the sintering parameters, the controllability and repeatability of the ceramic properties are realized, providing a strong guarantee for batch production. Through two-step sintering assisted by direct current, a high-strength and tough interlocking structure ZrB2 ceramic is obtained; under the induction of direct current, the ZrB2 grains preferentially grow and are oriented, prompting the ZrB2 grains to grow into lamellar shapes and couple with each other to form an interlocking structure. This unique structural design greatly improves the fracture toughness of the ZrB2-based ceramic. When a crack propagates in the ceramic, the interlocking structure can effectively disperse stress and deflect the crack, increasing the crack propagation path and absorbing more fracture energy, thereby delaying the crack propagation speed and ultimately improving the fracture resistance of the material. In addition to the enhancement of fracture toughness, the interlocking structure also improves the overall strength of the ZrB2-based ceramic by increasing the contact area and bonding force between grains. This improvement in strength enables the ceramic material to maintain better stability and durability when subjected to external forces.The present invention utilizes pre-oxidized ZrC powder and SiC powder to provide a process liquid phase at high temperature, and at the same time applies a direct current. ZrB2 grains can grow into lamellar grains; these lamellar grains are coupled with each other to form an interlocking structure, which not only improves the fracture toughness of ZrB2-based ceramics, but also improves the flexural strength of ZrB2-based ceramics; the preparation method of the present invention has the advantages of simple process, short preparation period and high efficiency, and can realize batch production.

[0079] The foregoing description of specific exemplary embodiments of the invention has been presented for purposes of illustration and example. These descriptions are not intended to limit the invention to the precise forms disclosed, and it is apparent that, according to the above teachings, many changes and variations are possible. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the invention and its practical applications, so that those skilled in the art can implement and utilize the various different exemplary embodiments of the invention, as well as various different selections and changes.

[0080] 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 them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A preparation method of a high-strength and tough interlocking structure ZrB2 ceramic, characterized in that, It includes the following steps: First, ball-mill ZrC powder and SiC powder in air for 10 - 60 min for pre-oxidation treatment, then mix and ball-mill them with ZrB2 powder in vacuum for 6 - 24 h to obtain composite powder, and obtain high-strength and tough interlocked structure ZrB2 ceramic through direct current-assisted two-step sintering; The conditions for the two-step sintering are as follows: First, apply a pressure of 18 - 22 MPa to compact the composite powder, pass a direct current, and heat it at a rate of 15 - 25 °C / min to 700 - 800 °C and hold for 20 - 40 min for the first-step sintering; then increase the pressure to 50 - 100 MPa within 1 min, adjust the direct current to a current density greater than 1000 A / cm 2 , and heat it to 1600 - 2000 °C and hold for 3 - 10 min for the second-step sintering; After the ZrC powder and SiC powder are pre-oxidized, they provide a process liquid phase at high temperature, and the process liquid phase escapes in the form of gas at high temperature. At the same time, under the action of direct current, ZrB2 grains grow anisotropically, form lamellar shapes, and are mutually coupled to form a high-strength and tough interlocked structure ZrB2 ceramic with a grain interlocked structure; The fracture toughness of the high-strength and tough interlocking structure ZrB2 ceramic is 7.1 - 7.6 MPa·m 1 / 2 , and the flexural strength is 810 - 900 MPa.

2. The preparation method of the high-strength and tough interlocking structure ZrB2 ceramic according to claim 1, characterized in that, The volume fraction ratio of the ZrC powder to the SiC powder is (2 - 15):(2 - 15); the sum of the volume fractions of the ZrC powder, SiC powder and ZrB2 powder is 100.

3. The preparation method of the high-strength and tough interlocking structure ZrB2 ceramic according to claim 1, wherein, The particle size of the ZrC powder is less than 100 nm, the particle size of the SiC powder is less than 200 nm, and the particle size of the ZrB2 powder is less than 100 nm.

4. The preparation method of the high-strength and tough interlocking structure ZrB2 ceramic according to claim 1, characterized in that, During two-step sintering, a vacuum furnace with a vacuum degree of 1 - 2 Pa is used.

5. A high-strength and tough interlocking structure ZrB2 ceramic, characterized in that, It is prepared by using the preparation method of the high-strength and tough interlocked structure ZrB2 ceramic according to any one of claims 1 - 4.

6. Application of the high-strength and tough interlocked structure ZrB2 ceramic prepared by using the preparation method of the high-strength and tough interlocked structure ZrB2 ceramic according to any one of claims 1 - 4 in the preparation of aircraft thermal structures or thermal protection components.

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