High-toughness ZrB2 ceramic with interlocking structure as well as preparation method and application of high-toughness ZrB2 ceramic

Abstract

The invention discloses a high-toughness interlocking structure ZrB2 ceramic and a preparation method and application thereof, and belongs to the technical field of zirconium diboride ceramic, and the method comprises the following steps: carrying out pre-oxidation treatment on ZrC powder and SiC powder, mixing and ball-milling with ZrB2 powder, and carrying out direct current assisted two-step sintering to obtain the high-toughness interlocking structure ZrB2 ceramic. The preparation method comprises the following steps: providing a process liquid phase at a high temperature by using pre-oxidized ZrC powder and SiC powder, and meanwhile, applying direct current to induce anisotropic growth of ZrB2 crystal grains and couple the ZrB2 crystal grains into an interlocking structure, thereby obtaining the high-toughness ZrB2 ceramic with the interlocking structure. The process liquid phase and the applied direct current can effectively promote ZrB2 crystal grains to grow into a lamellar shape, and the lamellar crystal grains are coupled to form an interlocking structure, so that not only is the fracture toughness of the ZrB2-based ceramic improved, but also the strength of the ZrB2-based ceramic is improved; a process liquid phase formed at a high temperature is not left in the final ZrB2-based ceramic, so that the high-temperature mechanical property of the ZrB2-based ceramic is improved; the preparation process is simple, short in period, high in efficiency and capable of realizing batch production.

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 ZrB 2 Ceramics and their preparation methods and applications. Background Art

[0002] Zirconium boride ceramics (ZrB 2 ) Ceramics have low density, high melting point, high strength, and excellent anti-oxidation and ablation properties, and are candidate materials for aircraft thermal structures and thermal protection components. However, ZrB 2 Ceramics have great intrinsic brittleness and low fracture toughness. Cracks tend to expand rapidly after initiation, leading to brittle catastrophic failure of the material and low reliability, which limits its application in engineering.

[0003] Induced ZrB 2 The grains grow anisotropically into lamellar shapes, and the volume effect is expected to improve the ZrB 2 The fracture resistance of ceramics. Some researchers used hydrated alumina as raw material to prepare gel. After drying, dry gel crushing, screening, high-temperature calcination, screening and grading, they prepared ceramic corundum abrasives with flaky structures. The flaky grains are interlocked, which improves the compressive strength of single abrasive particles. 2 For ceramics, this method will obviously cause ZrB 2 Oxidized to zirconium dioxide (ZrO 2 ), causing ZrB 2 The mechanical properties of ceramics are reduced, and the preparation process is complicated and cumbersome. Some researchers have also used Mo, Nb, Ti, W and Si to assist Zr and B to react and grow into sheet-like ZrB 2 However, the residual Mo, Nb, Ti, W and Si will soften and melt at high temperature, causing ZrB 2 The mechanical properties of ceramics deteriorate dramatically at high temperatures.

[0004] Therefore, in order to increase the ZrB 2 Comprehensive mechanical properties of ceramics, how to prepare high-strength and tough ZrB with interlocking grain structure 2 Ceramics has become a technical problem that needs to be solved urgently in this field. Summary of the invention

[0005] In order to overcome the above-mentioned shortcomings of the prior art, the present invention aims to provide a high-strength and tough interlocking structure ZrB 2 Ceramics and their preparation methods and applications to solve the problem of how to prepare high-strength and tough ZrB with grain interlocking structure 2 Technical issues of ceramics.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: The invention discloses a high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: First, ZrC powder and SiC powder are pre-oxidized and then mixed with ZrB 2 The powders were mixed and ball-milled, and then sintered in two steps with the assistance of direct current to obtain a high-strength and tough interlocking structure ZrB 2 ceramics; The two-step sintering conditions are as follows: first, apply a pressure of 18-22MPa to compact the pre-sintered composite powder, pass a direct current, and heat to 700-800℃ at a rate of 15-25℃ / min and keep at this temperature for 20-40min for the first step of sintering; then increase the pressure to 50-100MPa within 1min, and adjust the direct current to a current density greater than 1000A / cm 2 , heat to 1600-2000℃ and keep warm for 3-10min for the second step of sintering; After pre-oxidation treatment, ZrC powder and SiC powder provide process liquid phase at high temperature. At the same time, under the action of direct current, ZrB 2 The grains grow anisotropically to form lamellar shapes and couple with each other to form a high-strength and tough interlocking structure ZrB 2 ceramics; High strength and toughness interlocking structure ZrB 2 The fracture toughness of ceramics is 7.1-7.6MPa·m 1 / 2 , the bending strength is 810-900MPa.

[0007] Preferably, the volume ratio of ZrC powder to SiC powder is (2-15): (2-15); ZrC powder, SiC powder and ZrB 2 The sum of the volume fractions of the powders is 100.

[0008] Preferably, 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 ZrB 2 The particle size of the powder is less than 100 nm.

[0009] Preferably, the pre-oxidation treatment conditions are: ball milling in air for 10-60 min.

[0010] Preferably, the conditions for the mixed ball milling are: ball milling in vacuum for 6-24 hours.

[0011] Preferably, during the two-step sintering, a vacuum furnace with a vacuum degree of 1-2 Pa is used.

[0012] The present invention also discloses a high-strength and tough interlocking structure ZrB 2 Ceramics, using the above high-strength and tough interlocking structure ZrB 2 The ceramic is prepared by a method for preparing the ceramic.

[0013] The present invention also discloses the above-mentioned high-strength and tough interlocking structure ZrB 2 The application of ceramics in the preparation of aircraft thermal structures or thermal protection components.

[0014] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a high-strength and tough interlocking structure ZrB 2 The ceramic preparation method uses pre-oxidized zirconium carbide (ZrC) powder and silicon carbide (SiC) powder, and combines the action of direct current at high temperature to promote ZrB 2 The grains grow into lamellar shapes and couple with each other to form an interlocking structure. Pre-oxidation treatment can form a thin oxide layer on the powder surface, which can serve as a liquid source in the subsequent sintering process to promote the ZrB 2 The bonding between the powder particles, during the sintering process, the liquid phase formed by the pre-oxidized ZrC and SiC nanopowders plays a key role in assisting sintering and improves the ZrB 2 In addition, these process liquid phases can escape in the form of gas at high temperatures and will not remain in the final ZrB 2 This feature avoids the common low-melting-point phase residue problem in traditional ceramic preparation, thereby reducing the adverse effect of low-melting-point phase softening at high temperature on mechanical properties and significantly improving ZrB 2 High temperature mechanical properties of base ceramics. By applying a pressure of 18-22MPa to compact the pre-sintered composite powder, the contact resistance between powder particles is reduced to facilitate 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℃ at a heating rate of 15-25℃ / min and keeping it warm for 20-40min; through a gentle heating rate and appropriate holding time, the residual moisture and other impurities in the powder can be fully removed, which is beneficial to the densification of ceramics; it can also ensure the initial bonding and diffusion between powder particles, realize the pre-sintering process, and lay the foundation for the subsequent densification process. Increase the pressure to 50-100MPa within 1min, and adjust the current to a current density greater than 1000A / cm 2 , heating to 1600-2000℃ and keeping warm for 3-10min; the final densification and high performance of the ceramic are achieved. The current density is set to be greater than 1000A / cm 2, can provide a stable driving force through the electromigration effect, continuously drive the directional migration of atoms, and realize ZrB 2 The preferential growth and directional arrangement of grains, the combined effect of high voltage and high current density can quickly 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, and further improve the fracture toughness and bending strength of the ceramic. By precisely controlling the sintering parameters, the controllability and repeatability of ceramic performance are achieved, providing a strong guarantee for mass production. Under the induction of direct current, ZrB 2 The grains grow preferentially and are oriented, which promotes the ZrB 2 The grains grow into lamellar shapes and couple with each other to form an interlocking structure. This unique structural design greatly improves the performance of ZrB 2 The interlocking structure can effectively disperse stress and deflect cracks when cracks propagate in ceramics, increase crack propagation paths, absorb more fracture energy, and thus slow down crack propagation, ultimately improving the material's fracture resistance. In addition to enhancing fracture toughness, the interlocking structure also increases the contact area and bonding strength between grains, thereby improving the fracture toughness of ZrB 2 The overall strength of the base ceramic. This improvement in strength allows the ceramic material to maintain better stability and durability when subjected to external forces. The preparation method of the present invention only includes simple steps such as pre-oxidation treatment, mixed ball milling and two-step sintering, without the need for complex process equipment and cumbersome operating procedures. This simplified process not only reduces production costs, but also improves the controllability and stability of the preparation process. Due to the use of 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 ZrB 2 Mass production of base ceramics becomes possible, providing strong support for meeting the needs of large-scale industrial applications.

[0015] Furthermore, the volume fraction ratio of ZrC powder to SiC powder is (2-15): (2-15); ZrC powder, SiC powder and ZrB 2 The volume fractions of the powders add up to 100; ensuring that ZrC, SiC and ZrB 2 The uniformity and interaction of the three powders when mixed are optimized. By precisely controlling the proportion of each component, the microstructure of the ceramic can be precisely controlled, thereby improving the fracture toughness and bending strength of the ceramic.

[0016] Furthermore, the particle size of ZrC powder is less than 100nm, the particle size of SiC powder is less than 200nm, and the particle size of ZrB 2The particle size of the powder is less than 100nm; the use of nano-scale powder can significantly increase the surface area of ​​the powder, improve the reactivity during sintering, and help achieve a denser sintered body and higher mechanical properties. At the same time, the fine powder particle size also helps to form a more uniform microstructure, reduce internal defects, and further improve the fracture toughness and bending strength of the ceramic.

[0017] Furthermore, the pre-oxidation treatment conditions are: ball milling in air for 10-60 minutes; the pre-oxidation treatment can form a thin oxide layer on the surface of the powder. This oxide layer can serve as a liquid source in the subsequent sintering process to promote the bonding between powder particles and improve the density and mechanical properties of the sintered body.

[0018] Furthermore, the conditions for mixed ball milling are: ball milling in vacuum for 6-24h; ball milling in vacuum environment can avoid ZrB 2 The powder reacts unnecessarily with oxygen or other impurities in the air. At the same time, long-term ball milling can ensure the full mixing and uniform dispersion of powder particles, providing a strong guarantee for the formation of uniform microstructure and excellent mechanical properties.

[0019] Furthermore, during the two-step sintering, a vacuum furnace with a vacuum degree of 1-2Pa 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 ceramics; at the same time, it can also ensure that the pre-liquid phase can escape in the form of gas in the final sintering stage, thereby improving the high-temperature mechanical properties of the ceramics.

[0020] The present invention also discloses a high-strength and tough interlocking structure ZrB 2 Ceramics, using the above high-strength and tough interlocking structure ZrB 2 The preparation method of ceramics is obtained, and the high-strength and tough interlocking structure ZrB 2 The fracture toughness of ceramics is 7.1-7.6MPa·m 1 / 2 , the bending strength is 810-900MPa. This makes the ceramic material show stronger resistance and stability when subjected to complex stress and extreme environmental conditions.

[0021] The present invention also discloses the above-mentioned high-strength and tough interlocking structure ZrB 2 The application of ceramics in the preparation of aircraft thermal structures or thermal protection components, with excellent mechanical properties and high temperature stability, the high-strength and tough interlocking structure ZrB prepared by the present invention 2 Ceramics have broad application prospects in aircraft thermal structures or thermal protection components. They can withstand extreme high temperature environments and complex mechanical stresses, providing strong guarantees for the safe and reliable operation of aircraft. At the same time, this ceramic material is also expected to play an important role in aerospace, nuclear industry, cutting tools and other fields, promoting the progress and development of related technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The high-strength and tough interlocking structure ZrB in Example 1 of the present invention 2 Schematic diagram of the microstructure of ceramics. DETAILED DESCRIPTION

[0023] The technical solution of the present invention will be described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] In the present invention, unless otherwise specified, all the embodiments and preferred implementation methods mentioned herein can be combined with each other to form a new technical solution.

[0025] In the present invention, unless otherwise specified, all technical features and preferred features mentioned herein can be combined with each other to form a new technical solution.

[0026] In the present invention, unless otherwise specified, the components or preferred components involved can be combined with each other to form a new technical solution.

[0027] In the present invention, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are real numbers. For example, the numerical range "6-22" means that all real numbers between "6-22" have been listed in this document, and "6-22" is just an abbreviation of these numerical combinations.

[0028] The “range” disclosed in the present invention is in the form of a lower limit and an upper limit, which can be one or more lower limits, and one or more upper limits, respectively.

[0029] 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.

[0030] In the present invention, unless otherwise specified, each reaction or operation step can be carried out sequentially or in accordance with the sequence. Preferably, the reaction method herein is carried out sequentially.

[0031] Unless otherwise specified, the professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. In addition, any method or material similar or equivalent to the described content may also be applied to the present invention.

[0032] The present invention provides a high-strength and tough interlocking structure ZrB 2The method for preparing ceramics comprises providing a process liquid phase by pre-oxidizing ZrC powder and SiC powder at a high temperature and applying a direct current to make ZrB 2 The grains grow anisotropically, forming ZrB with an interlocking grain structure. 2 Base ceramics, the specific steps include: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 2-15, and the volume fractions of the SiC powder are 2-15; the particle size of the ZrC powder is less than 100 nm, and the particle size of the SiC powder is less than 200 nm; the ZrC powder and the SiC powder are ball-milled in air for 10-60 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size less than 100 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 6-24 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: Place the pre-sintered composite powder into a sintering mold, place the sintering mold in a vacuum furnace with a vacuum degree of 1-2Pa, apply a pressure of 18-22MPa to compact the pre-sintered composite powder, pass current, heat the pre-sintered composite powder to 700-800℃ at a heating rate of 15-25℃ / min, and keep it warm for 20-40min, then increase the pressure to 50-100MPa within 1min, adjust the current to a current density greater than 1000A / cm 2 , heating to 1600-2000℃ and keeping warm for 3-10min, finally obtaining high-strength and tough interlocking structure ZrB 2 ceramics.

[0033] The invention discloses a high-strength and tough interlocking structure ZrB 2 Preparation method of ceramics, pre-oxidized ZrC nanopowder and SiC nanopowder can provide process liquid phase at high temperature, and under the action of direct current, ZrB 2 The grains can grow into lamellar grains; these lamellar grains are coupled to each other to form an interlocking structure, which not only improves the ZrB 2 The fracture toughness of the base ceramics also improves the ZrB 2 The liquid phase formed by the pre-oxidized ZrC nanopowder and SiC nanopowder at high temperature is the process liquid phase. During the high-temperature sintering process, these liquid phases can escape in the form of gas and will not remain in the final ZrB 2 In base ceramics, ZrB 2Compared with traditional spark plasma sintering, traditional spark plasma sintering (SPS) uses pulsed current, which has the essential characteristics of intermittent and energy fluctuations. The intermittent and energy fluctuations of pulsed current change the kinetic conditions of electric field, temperature field and atomic diffusion, and also cause thermal stress relaxation and atomic migration gap effect, thereby weakening the driving force of grain orientation and arrangement. The current density of traditional SPS is relatively low, less than 500A / cm 2 , the driving force for directional migration of atoms is small. Therefore, in the traditional SPS sintering process, ZrB 2 The degree of preferential growth of grains is low, 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 ZrB 2 In the present invention, the direct current is not a pulse current, but a continuous and constant current, and in the second step of sintering, the current density is set to be greater than 1000A / cm 2 , can provide a stable driving force through the electromigration effect, continuously drive the directional migration of atoms, and realize ZrB 2 The grains grow preferentially and are oriented, which enables the preparation of high-strength and tough interlocking structure ZrB 2 Ceramics. The present invention has the advantages of simple process, short preparation cycle, high efficiency, etc., and can realize mass production. 2 The comprehensive mechanical properties of ceramics promote their engineering applications in aircraft thermal structures or thermal protection components.

[0034] In order to make the purpose, 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 in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0035] Example 1 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises providing a process liquid phase by pre-oxidizing ZrC powder and SiC powder at a high temperature and applying a direct current to make ZrB 2 The grains grow anisotropically, forming ZrB with an interlocking grain structure. 2The base ceramic specifically comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 10, and the volume fractions of the SiC powder are 10; the particle size of the ZrC powder is 50 nm, and the particle size of the SiC powder is 100 nm; the ZrC powder and the SiC powder are ball-milled in air for 20 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 80 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 12 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 2Pa. A pressure of 20MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 750℃ at a heating rate of 20℃ / min and kept warm for 20min. Then the pressure was increased to 60MPa within 1min and the current was adjusted to a current density of 1300A / cm 2 , heating to 1900℃ and keeping it warm for 4min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 1 2 The fracture toughness of ceramics is 7.1MPa·m 1 / 2 , the bending strength is 820MPa.

[0036] See also Figure 1 The high-strength and tough interlocking structure ZrB in Example 1 of the present invention 2 Schematic diagram of the microstructure of ceramics. It can be seen from the figure that the high-strength and tough interlocking structure ZrB 2 Ceramics have a grain interlocking structure. The excellent mechanical properties are mainly attributed to the grain interlocking structure. When a crack propagates in the ceramic, the interlocking structure can effectively disperse the stress and deflect the crack, increase the crack propagation path, absorb more fracture energy, thereby slowing down the crack propagation speed, and ultimately improving the material's fracture resistance. In addition to the enhancement of fracture toughness, the interlocking structure also increases the contact area and bonding force between grains, thereby improving the ZrB 2 The overall strength of the base ceramic. ZrB with interlocking grain structure 2The base ceramic not only has high fracture toughness and bending strength, but also may show good comprehensive properties such as thermal conductivity, oxidation resistance and wear resistance. These excellent properties make this ceramic material have a wide range of application prospects in extreme environments such as high temperature, high pressure and strong corrosion.

[0037] Example 2 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 5, and the volume fractions of the SiC powder are 15; the particle size of the ZrC powder is 50 nm, and the particle size of the SiC powder is 100 nm; the ZrC powder and the SiC powder are ball-milled in air for 20 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 80 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 12 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 2Pa. A pressure of 20MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 750℃ at a heating rate of 20℃ / min and kept warm for 20min. Then the pressure was increased to 60MPa within 1min and the current was adjusted to a current density of 1300A / cm 2 , heating to 1900℃ and keeping it warm for 4min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 2 2 The fracture toughness of ceramics is 7.2MPa·m 1 / 2 , the bending strength is 900MPa.

[0038] Example 3 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 10, and the volume fractions of the SiC powder are 10; the particle size of the ZrC powder is 50 nm, and the particle size of the SiC powder is 100 nm; the ZrC powder and the SiC powder are ball-milled in air for 20 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 80 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 12 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 2Pa. A pressure of 20MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 750℃ at a heating rate of 20℃ / min and kept warm for 20min. Then the pressure was increased to 60MPa within 1min and the current was adjusted to a current density of 1300A / cm 2 , heating to 2000℃ and keeping warm for 10min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 3 2 The fracture toughness of ceramics is 7.6MPa·m 1 / 2 , the bending strength is 810MPa.

[0039] Example 4 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 2, and the volume fractions of the SiC powder are 15; the particle size of the ZrC powder is 50 nm, and the particle size of the SiC powder is 150 nm; the ZrC powder and the SiC powder are ball-milled in air for 60 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 50 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 6 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 1Pa. A pressure of 18MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 700℃ at a heating rate of 15℃ / min and kept warm for 40min. Then the pressure was increased to 100MPa within 1min and the current was adjusted to a current density of 1300A / cm 2 , heating to 1600℃ and keeping it warm for 8min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 4 2 The fracture toughness of ceramics is 7.1MPa·m 1 / 2 , the bending strength is 810MPa.

[0040] Example 5 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 15, and the volume fractions of the SiC powder are 5; the particle size of the ZrC powder is 80 nm, and the particle size of the SiC powder is 100 nm; the ZrC powder and the SiC powder are ball-milled in air for 40 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 80 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 18 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 2Pa. A pressure of 22MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 750℃ at a heating rate of 25℃ / min and kept warm for 35min. Then the pressure was increased to 80MPa within 1min and the current was adjusted to a current density of 1200A / cm 2 , heating to 1800℃ and keeping warm for 5min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 5 2 The fracture toughness of ceramics is 7.2MPa·m 1 / 2 , the bending strength is 880MPa.

[0041] Example 6 A high-strength and tough interlocking structure ZrB 2 The method for preparing ceramics comprises the following steps: 1) Pre-oxidation treatment of ZrC powder and SiC powder: 2 The total volume fractions of the powder, ZrC powder and SiC powder are 100 parts, the volume fractions of the ZrC powder are 15, and the volume fractions of the SiC powder are 2; the particle size of the ZrC powder is 50 nm, and the particle size of the SiC powder is 100 nm; the ZrC powder and the SiC powder are ball-milled in air for 10 minutes by a ball milling method to obtain pre-oxidized ZrC powder and SiC powder; 2) Preparation of pre-sintered composite powder: ZrB with a particle size of 80 nm 2 The powder, the pre-oxidized ZrC powder and the SiC powder obtained in step 1) are ball-milled in vacuum for 24 hours to obtain a pre-sintered composite powder; 3) Sintered ZrB 2 Base ceramics: The pre-sintered composite powder was placed in a sintering mold, and the sintering mold was placed in a vacuum furnace with a vacuum degree of 1.5 Pa. A pressure of 20 MPa was applied to compact the pre-sintered composite powder. Current was passed and the pre-sintered composite powder was heated to 800 °C at a heating rate of 20 °C / min and kept warm for 30 min. Then the pressure was increased to 50 MPa within 1 min and the current was adjusted to a current density of 1100 A / cm 2 , heating to 2000℃ and keeping warm for 3min, finally obtaining high-strength and tough interlocking structure ZrB 2 Refer to Table 1, the high-strength and tough interlocking structure ZrB prepared in Example 6 2 The fracture toughness of ceramics is 7.4MPa·m 1 / 2 , the bending strength is 840MPa.

[0042] Table 1 High-strength and tough interlocking structure ZrB prepared in Examples 1-6 2 Comparison of Mechanical Properties of Ceramics

[0043] See Table 1 for the high-strength and tough interlocking structure ZrB prepared in Examples 1-6. 2 The mechanical properties of ceramics are compared. It can be seen from the table that the high-strength and tough interlocking structure ZrB 2 The fracture toughness of ceramics is 7.1-7.6MPa·m 1 / 2 , when the material is subjected to external force, it can better disperse stress, delay crack expansion, and improve fracture resistance, thereby ensuring the stability of the structure in extreme environments. The bending strength is 810-900MPa, and the material is not prone to fracture when subjected to bending load, which enhances the reliability and durability of the structure. These properties make the high-strength and tough interlocking structure ZrB prepared by the present invention2 Ceramics have broad application potential under extreme conditions such as high temperature, high pressure and severe corrosion, and can significantly improve the service life and safety of products.

[0044] In summary, the high-strength and tough interlocking structure ZrB 2 The ceramic preparation method comprises pre-oxidizing ZrC powder and SiC powder, and then mixing with ZrB 2 Powder mixing and ball milling, pre-oxidation treatment can form a thin oxide layer on the powder surface, this oxide layer can be used as a liquid source in the subsequent sintering process to promote ZrB 2 The bonding between powder particles improves the density and mechanical properties of the sintered body. The liquid phase in the process of pre-oxidized ZrC and SiC nanopowders plays a key role in sintering, improving the ZrB 2 In addition, these process liquid phases can escape in the form of gas at high temperatures and will not remain in the final ZrB 2 It avoids the common problem of low melting point phase residue in traditional ceramic preparation, thereby reducing the adverse effect of low melting point phase softening at high temperature on mechanical properties and significantly improving ZrB 2 The high-temperature mechanical properties of the base ceramics. By applying pressure to compact the pre-sintered composite powder, the contact resistance between the powder particles is reduced, which facilitates the passage of current; by passing a direct current, the diffusion and reaction between the powder particles can be accelerated, and the sintering efficiency can be improved; through a gentle heating rate and appropriate holding time, the residual moisture and other impurities in the powder can be fully removed, which is conducive to the densification of the ceramics; it can also ensure the initial bonding and diffusion between the powder particles, realize the pre-sintering process, and lay the foundation for the subsequent densification process. Through the electromigration effect, a stable driving force is provided to continuously drive the directional migration of atoms to achieve ZrB 2 The preferential growth and directional arrangement of grains, the combined effect of high voltage and high current density can quickly 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, and further improve the fracture toughness and bending strength of the ceramic. By precisely controlling the sintering parameters, the controllability and repeatability of the ceramic performance are achieved, providing a strong guarantee for mass production. After two-step sintering assisted by DC current, a high-strength and tough interlocking structure ZrB 2 Ceramics; ZrB induced by direct current 2 The grains grow preferentially and are oriented, which promotes the ZrB 2 The grains grow into lamellar shapes and couple with each other to form an interlocking structure. This unique structural design greatly improves the performance of ZrB 2The interlocking structure can effectively disperse stress and deflect cracks when cracks propagate in ceramics, increase crack propagation paths, absorb more fracture energy, and thus slow down crack propagation, ultimately improving the material's fracture resistance. In addition to enhancing fracture toughness, the interlocking structure also increases the contact area and bonding strength between grains, thereby improving the fracture toughness of ZrB 2 The overall strength of the base ceramic is improved. This strength improvement enables the ceramic material to maintain better stability and durability when subjected to external forces. The present invention uses pre-oxidized ZrC powder and SiC powder to provide a process liquid phase at high temperature, and simultaneously applies a direct current to ZrB 2 The grains can grow into lamellar grains; these lamellar grains are coupled to each other to form an interlocking structure, which not only improves the ZrB 2 The fracture toughness of the base ceramics also improves the ZrB 2 The preparation method of the present invention has the advantages of simple process, short preparation cycle and high efficiency, and can realize batch production.

[0045] The foregoing description of specific exemplary embodiments of the present invention is for the purpose of illustration and demonstration. These descriptions are not intended to limit the present invention to the precise form disclosed, and it is obvious that many changes and variations can be made in accordance with the above teachings. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various different exemplary embodiments of the present invention and various different selections and changes.

[0046] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high-strength and tough interlocking structure ZrB2 ceramic, characterized in that: The following steps are involved: First, ZrC powder and SiC powder are pre-oxidized, then mixed with ZrB2 powder and ball-milled, and then sintered in two steps with the assistance of direct current to obtain high-strength and tough interlocking structure ZrB2 ceramics; The conditions of the two-step sintering are as follows: first, a pressure of 18-22 MPa is applied to compact the pre-sintered composite powder, a direct current is passed, and the temperature is raised to 700-800°C at a rate of 15-25°C / min and kept at this temperature for 20-40 min to perform the first step of sintering; then, the pressure is increased to 50-100 MPa within 1 min, and the direct current is adjusted to a current density greater than 1000 A / cm 2 , heat to 1600-2000℃ and keep warm for 3-10min for the second step of sintering; After the ZrC powder and the SiC powder are pre-oxidized, a process liquid phase is provided at a high temperature, and at the same time, under the action of a direct current, the ZrB2 grains grow anisotropically to form a lamellar shape, and are mutually coupled to form a high-strength and tough interlocking structure ZrB2 ceramic with a grain interlocking structure; The fracture toughness of the high-strength interlocking structure ZrB2 ceramic is 7.1-7.6 MPa·m 1 / 2 , the bending strength is 810-900MPa.

2. The method for preparing 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, the SiC powder and the ZrB2 powder is 100.

3. The method for preparing the high-strength and tough interlocking structure ZrB2 ceramic according to claim 1, characterized in that: 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 method for preparing the high-strength and tough interlocking structure ZrB2 ceramic according to claim 1, characterized in that: The conditions of the pre-oxidation treatment are: ball milling in air for 10-60 minutes.

5. The method for preparing high-strength and tough interlocking structure ZrB2 ceramics according to claim 1, characterized in that: The conditions of the mixed ball milling are: ball milling in vacuum for 6-24 hours.

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

7. A high-strength and tough interlocking structure ZrB2 ceramic, characterized in that: The high-strength and tough interlocking structure ZrB2 ceramic is prepared by the preparation method of any one of claims 1-6.

8. Use of the high-strength and tough interlocking structure ZrB2 ceramics prepared by the preparation method of high-strength and tough interlocking structure ZrB2 ceramics according to any one of claims 1 to 6 in the preparation of aircraft thermal structures or thermal protection components.

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