Conductive silicon nitride composite ceramic and preparation method and application thereof

Abstract

The invention discloses conductive silicon nitride composite ceramic and a preparation method and application thereof. The method for preparing the conductive silicon nitride composite ceramic comprises the following steps: performing surface oxidation treatment on first ceramic powder to obtain the first ceramic powder with an oxidation film layer; mixing the second ceramic powder with the first ceramic powder with the oxide film to obtain a mixture; carrying out heating treatment on the mixture under the condition of 1700 DEG C to 2500 DEG C so as to obtain a precursor; and sintering the precursor to obtain the conductive silicon nitride composite ceramic, wherein the first ceramic powder comprises alpha-Si3N4, the second ceramic powder comprises metal oxide ceramic, the oxidation film layer comprises silicon oxide, and the oxidation film layer has active sites; the volume conductivity of the conductive silicon nitride composite ceramic at room temperature is not lower than 1 * 10 < 2 > S / m, and the volume conductivity of the conductive silicon nitride composite ceramic at 1000 DEG C is not lower than 1 * 10 < 3 > S / m. The conductive silicon nitride composite ceramic prepared by the invention has excellent mechanical properties and high conductivity.

Description

Technical Field

[0001] This application belongs to the field of semiconductors, specifically relating to a conductive silicon nitride composite ceramic, its preparation method, and its application. Background Technology

[0002] Silicon nitride ceramics, as a high-performance structural ceramic material, are widely used in aerospace, mechanical engineering, and electronic packaging due to their high strength, high hardness, excellent high-temperature resistance, and good chemical stability. However, the insulating properties of traditional silicon nitride ceramics typically result in a resistivity higher than 10 Ω·cm. 14 The low Ω·cm characteristic severely limits its application in components requiring electrical or electromagnetic conductivity, such as high-temperature electrodes, antistatic tools, and electromagnetic shielding materials. This limitation makes silicon nitride ceramics unable to meet the growing demand of modern industry for multifunctional materials, particularly in high-temperature electronic devices and advanced energy systems.

[0003] Related technologies primarily improve the conductivity of ceramic materials by introducing conductive phases. Common methods include metal-ceramic composites, carbon-based composites, and doping with conductive ceramic phases. However, while metal-ceramic composites (such as Al₂O₃ / Cu and SiC / Al) can improve conductivity, the metal phase is prone to oxidation or softening at high temperatures, leading to degradation of the material's mechanical properties. Carbon-based composite ceramics (such as SiC / C and ZrB₂ / C) possess high conductivity, but their poor stability in oxidizing environments limits their application under high-temperature, oxygen-containing conditions. While doping with conductive ceramic phases can improve conductivity, it affects the material's mechanical properties and sintering density, making it difficult to simultaneously meet the requirements of high strength and high conductivity. Summary of the Invention

[0004] The purpose of this application is to overcome the shortcomings of silicon nitride ceramics, which have high insulation properties but are difficult to combine with high strength and high conductivity. It provides a conductive silicon nitride composite ceramic with excellent mechanical properties, good conductivity, and high preparation efficiency, so as to transform traditional silicon nitride ceramics from insulators to conductive functional materials and obtain high-temperature structural and functional integrated ceramics.

[0005] The objective of this application can be achieved through the following technical solutions: A method for preparing conductive silicon nitride composite ceramics is disclosed, which solves the problem of densification in conductive composite ceramics and achieves high strength and high conductivity in the material. This method creates an oxygen-deficient state in metal oxides to construct a continuous conductive network and reinforcing phase distribution, significantly improving the conductivity of silicon nitride ceramics while maintaining their excellent mechanical properties.

[0006] In a first aspect of this application, a method for preparing conductive silicon nitride composite ceramics is provided, comprising: The first ceramic powder is subjected to surface oxidation treatment to obtain a first ceramic powder with an oxide film layer; The second ceramic powder is mixed with the first ceramic powder having an oxide film layer to obtain a mixture; The mixture was subjected to heat treatment at 1700℃-2500℃ to obtain a precursor; The precursor is sintered to obtain the conductive composite ceramic; wherein, The first ceramic powder comprises α-Si3N4, the second ceramic powder comprises metal oxide ceramic, the oxide film comprises silicon oxide, and the oxide film has active sites; the conductive composite ceramic has a volume conductivity of not less than 1×10⁻⁶ at room temperature. 2 The conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ S / m at 1000 °C. 3 S / m; During the sintering process, the active sites act as high-energy driving centers, significantly accelerating atomic migration and particle bonding, which is the key to achieving efficient densification of materials.

[0007] Preferably, the particle size D of the first ceramic powder is... 50 The first ceramic powder has a particle size of 30 nm to 1 μm and a purity of ≥99.9%. The second ceramic powder includes at least three of the following: zirconium oxide, cerium oxide, ytterbium oxide, yttrium oxide, lanthanum oxide, and gadolinium oxide.

[0008] Preferably, the mixture further includes a third ceramic powder, which comprises at least one powder selected from boron carbide and boron nitride; the conductive silicon nitride composite ceramic has a Vickers hardness ≥1800 HV1.0 and a fracture toughness ≥8 MPa·m. 1 / 2 .

[0009] Preferably, based on the total amount of the mixture, the proportion of the first ceramic powder is 50 mol.%-70 mol.% to ensure that the material maintains the excellent mechanical properties of silicon nitride ceramics; the proportions of the second ceramic powder and the third ceramic powder are independently 10 mol.%-20 mol.%, which not only provides sufficient functional phase to improve the overall performance of conductive silicon nitride composite ceramics, but also reduces the performance degradation caused by excessive addition of functional phase.

[0010] Preferably, the surface oxidation treatment includes atomic layer deposition, plasma ball milling, vapor phase oxidation, and wet chemical oxidation; and / or, the thickness of the oxide film is 2 nm-5 nm. Controlling the thickness of the oxide film within the aforementioned range can provide sufficient interfacial reactivity and reduce the negative impact of an excessively thick oxide film on material properties.

[0011] Preferably, the heat treatment satisfies one or more of the following conditions: the heat treatment method includes using a Joule heating device; the temperature of the heat treatment is 2000℃-2500℃, and the heat treatment time is 10s-20s; the environment of the heat treatment is one or more of vacuum, nitrogen, and argon; the total heating time of the heat treatment is 10-40s, and the extremely fast heating rate is beneficial to promoting the formation of a solid solution high entropy phase between various ceramic powders.

[0012] The enormous energy provided in an extremely short time greatly accelerates the atomic diffusion rate at the powder particle interface. This forces the ultrathin silicon oxide film pre-deposited on the surface of Si3N4 powder to undergo a violent solid-state reaction with the added oxide ceramic phase; at the same time, during Joule heating, local activation, melting, and preliminary necking occur on the surface of each ceramic powder, transforming the mixed powder from a simple physical mixture into a sintered precursor with high surface energy that has undergone preliminary sintering.

[0013] Preferably, the sintering treatment satisfies one or more of the following conditions: the sintering treatment method includes using a rapid hot press furnace; the sintering temperature is 1600 ℃-1700 ℃, and the sintering time is 5 min-10 min; the sintering pressure is 30 MPa-100 MPa. Controlling the sintering temperature and time within the aforementioned range can not only improve the densification degree of the sintered ceramic, but also control the grain size within an appropriate range. Short-term heat preservation is beneficial for maintaining a fine-grained microstructure; the heating rate of the sintering treatment is 120 ℃ / min-200 ℃ / min. This heating rate can improve the uniformity of the microstructure of the conductive silicon nitride composite ceramic, thereby further improving the consistency of material properties.

[0014] In a second aspect of this application, a conductive silicon nitride composite ceramic is provided, which is prepared by the aforementioned method.

[0015] The conductive silicon nitride composite ceramic comprises an α-Si3N4 matrix network and metal oxide ceramics dispersed within the matrix network. The metal oxide ceramics interconnected with the α-Si3N4 matrix undergo an oxygen-deficient state during sintering, thereby forming a continuous conductive network. The volume conductivity of the conductive composite ceramic at room temperature is not less than 1 × 10⁻⁶. 2 The conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ S / m at 1000 °C. 3 S / m.

[0016] In a third aspect, this application provides the application of dense conductive silicon nitride composite ceramics prepared by the aforementioned method in hot-end components of aerospace engines, leading-edge structures of hypersonic vehicles, high-temperature electronic devices, electromagnetic shielding, and plasma contact components.

[0017] Compared with existing technologies, this application achieves high strength and high conductivity of high-entropy ceramics through powder surface oxidation treatment and multi-component high-entropy composite method. It can be widely used in cutting-edge technology fields with stringent requirements for material strength, toughness, heat resistance and conductivity. At the same time, it breaks through the problem of poor sintering density of traditional conductive composite ceramics and obtains highly dense conductive composite ceramics. Attached Figure Description

[0018] Figure 1 This is a morphology diagram of the conductive silicon nitride composite ceramic in Example 1.

[0019] Figure 2 This is the elemental distribution diagram of the conductive silicon nitride composite ceramic in Example 1.

[0020] Figure 3 This is a morphology diagram of the conductive silicon nitride composite ceramic in Example 2.

[0021] Figure 4 This is the elemental distribution diagram of the conductive silicon nitride composite ceramic in Example 2.

[0022] Figure 5 This is a morphology diagram of the conductive silicon nitride composite ceramic in Example 3.

[0023] Figure 6 This is the elemental distribution diagram of the conductive silicon nitride composite ceramic in Example 3.

[0024] Figure 7 This is a morphology diagram of the conductive silicon nitride composite ceramic in Example 4.

[0025] Figure 8 This is the elemental distribution diagram of the conductive silicon nitride composite ceramic in Example 4. Specific Implementation The conductive silicon nitride composite ceramic of this application, its preparation method, and its application embodiments are disclosed in detail below with appropriate reference to the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0027] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0028] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0029] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0031] Traditional silicon nitride ceramics, due to their intrinsic insulating properties, cannot simultaneously possess high conductivity and excellent mechanical properties. When a conductive phase is introduced into silicon nitride ceramics, problems such as difficulty in sintering densification, weak interfacial bonding, and decreased high-temperature stability arise. Multiphase ceramic composite processes have narrow processing windows, making it difficult to coordinate the relationship between conductive network formation and matrix strengthening. Existing methods cannot achieve uniform distribution of conductive phase and interface control while ensuring high density.

[0032] To address the aforementioned issues, this application provides a high-entropy ceramic material primarily composed of silicon nitride, which, while maintaining its original high strength and high-temperature resistance, also possesses excellent electrical conductivity. This material can meet the stringent requirements for integrated material structure and function in fields such as hot-end components of aerospace engines, leading-edge structures of hypersonic vehicles, high-temperature electronic devices, electromagnetic shielding, and plasma contact components. This application achieves a significant improvement in the electrical conductivity of silicon nitride ceramics by optimizing the selection, distribution, and sintering process of the conductive phase, while simultaneously ensuring the material's mechanical properties and high-temperature stability, providing a new technical solution for the preparation of high-performance conductive ceramics.

[0033] This application details how conductive composite ceramics with high density, excellent mechanical properties, and outstanding electrical conductivity are prepared through processes such as precise construction of surface oxide film, multi-component high-entropy system, Joule heating-induced interface reaction, and rapid hot pressing sintering.

[0034] A method for preparing conductive silicon nitride composite ceramics includes the following steps: The first ceramic powder is subjected to surface oxidation treatment to obtain a first ceramic powder with an oxide film layer; The second ceramic powder is mixed with the first ceramic powder having an oxide film to obtain a mixture; The mixture is heated to obtain a precursor; The precursor was sintered at 1700℃-2500℃ to obtain a conductive composite ceramic; among which, The first ceramic powder comprises α-Si3N4, the second ceramic powder comprises metal oxide ceramic, the oxide film comprises silicon oxide, and the oxide film has active sites; the conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ at room temperature. 2 The volume conductivity (S / m) of conductive silicon nitride composite ceramics at 1000 ℃ is not less than 1×10⁻⁶. 3 S / m.

[0035] This application provides active sites for subsequent interfacial reactions by precisely controlling the thickness and chemical state of the surface oxide film. These active sites, acting as high-energy driving centers during sintering, significantly accelerate atomic migration and particle bonding, which is crucial for achieving efficient densification of the material. A suitable oxide film thickness effectively suppresses excessive reactions between silicon nitride and various oxide ceramics. During the mixing process, optimizing the powder ratio and mixing technology ensures uniform distribution of each component, resulting in a mixture with specific component gradients and microstructural characteristics. Rapid heating and short-time holding during high-temperature heat treatment promote interfacial reactions and preliminary sintering, forming a sintering precursor with high surface energy. Complete densification and performance optimization of the material are achieved through sintering temperature, pressure, and atmosphere control during sintering and post-treatment, ultimately yielding a conductive silicon nitride composite ceramic with excellent comprehensive performance.

[0036] The method for preparing conductive silicon nitride composite ceramics in this application has strong versatility in raw materials and is applicable to the preparation of high-entropy ceramics in various application fields, including but not limited to at least one of high-temperature resistant ceramics, high-strength ceramics, and high-toughness ceramics. The method in this application has good process compatibility and scalability, and the material composition and process parameters can be adjusted according to the needs of different application scenarios.

[0037] The second ceramic powder includes at least three of zirconium oxide, cerium oxide, ytterbium oxide, yttrium oxide, lanthanum oxide, and gadolinium oxide. This metal oxide ceramic powder not only acts as a sintering aid to promote the densification process, but also forms an oxygen-deficient state during sintering, thereby forming a continuous conductive network in the ceramic matrix.

[0038] Surface oxidation treatment can be used to construct a silicon oxide film of controllable thickness on the surface of silicon nitride powder. This film can promote interfacial bonding and the formation of a conductive network during subsequent sintering. A multi-component high-entropy ceramic system is employed, in which oxide ceramic powder is introduced to form a conductive phase. During high-temperature sintering, these oxide phases react with the silicon nitride matrix at the interface, forming a continuous conductive pathway and significantly improving the material's conductivity.

[0039] In some embodiments, the third ceramic powder includes at least one of high-strength ceramic powders such as boron nitride and boron carbide. By introducing a high-strength ceramic phase, a strong interfacial bond is formed with the matrix during sintering, improving the mechanical properties of the material through grain refinement and phase transformation toughening mechanisms. The rapid hot-pressing sintering process effectively suppresses grain growth and maintains the fine-grained structure of the material, thereby simultaneously achieving excellent mechanical and electrical properties.

[0040] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0041] Example 1: S1, Select D 50 =30nm, α-Si3N4 with a purity ≥99.9%, yttrium oxide, ytterbium oxide, cerium oxide, and boron nitride were mixed and then ball-milled in ethanol for 20 hours; after drying, the mixture was sieved to obtain a homogeneous mixture. Plasma-enhanced atomic layer deposition (PALD) was used to pretreat α-Si3N4 powder before ball milling. The method included the following steps: a sample boat containing silicon nitride powder was provided for transfer to a deposition chamber; a 0.15s pulse of trimethylaluminosilicate precursor was applied, followed by a 20s reaction period; a 40s nitrogen purging was applied to remove unreacted residues; a 1s ozone pulse was applied, followed by a 30s reaction period; and a 40s nitrogen purging was applied to remove unreacted residues. These steps constituted one deposition cycle. Silicon oxide films of varying thicknesses were prepared by changing the number of PALD cycles. This step, by precisely controlling the thickness and chemical state of the surface oxide film, provided active sites for subsequent interfacial reactions. The oxide film thickness effectively suppressed excessive reactions between silicon nitride and various oxide ceramics. The oxide film was silicon dioxide, and its thickness was 3nm.

[0042] α-Si3N4:boron nitride:ytterbium oxide:cerium oxide:yttrium oxide = 5:1:1:1:1 (mol.%); ball milling time was 12 h, and the rotation speed was 300 rpm.

[0043] S2. The above-mentioned uniformly mixed mixture is heat-treated by a Joule heating device: the mixture is placed in a quartz tube and heated to 2200℃ in an argon atmosphere, and then held for 10s to obtain the precursor; the total heating time is 10s, and the extremely fast heating rate is conducive to the formation of non-equilibrium microstructure.

[0044] The enormous energy provided in a very short time greatly accelerates the atomic diffusion rate at the powder particle interface. This forces the ultrathin SiO2 film pre-deposited on the surface of α-Si3N4 powder to undergo a violent solid-state reaction with the added oxide ceramic phase; at the same time, during Joule heating, local activation, melting, and preliminary necking occur on the particle surface, transforming the mixed powder from a simple physical mixture into a sintered precursor with high surface energy that has undergone preliminary sintering.

[0045] S3. The precursor is placed in a rapid hot press furnace for sintering; the sintering temperature is 1700℃, the holding time is 5min, and the sintering pressure is 80MPa; conductive silicon nitride composite ceramic is obtained (its specific microstructure is as follows). Figure 1-2 (As shown).

[0046] Temperature and reaction time ensure the densification of sintered ceramics and prevent grain growth. Short holding time helps maintain a fine-grained microstructure. Heating rate ensures the formation of a uniform microstructure and improves the consistency of material properties.

[0047] The density of the prepared conductive silicon nitride composite ceramic was tested using a density balance, and the results showed that it had a high density. The hardness of the prepared conductive silicon nitride composite ceramic was tested using a hardness tester, and the results showed that the conductive silicon nitride composite ceramic had high hardness and fracture toughness. The prepared conductive silicon nitride composite ceramic was tested using a four-probe tester, and the results showed that the conductive silicon nitride composite ceramic had high electrical conductivity, which was higher than that of general semiconductor materials. At 1000℃, its electrical conductivity was an order of magnitude higher than that at room temperature. The data results are shown in Table 1.

[0048] Example 2: In this embodiment, the material system is the same as in Example 1, and the only difference in the preparation method is the treatment of the silicon nitride oxide film, resulting in a conductive composite ceramic (its specific microstructure is as follows). Figure 3-4 (As shown).

[0049] Specifically, α-Si3N4 powder is treated using plasma ball milling technology, and the method includes the following steps: A1. Provide a plasma ball milling jar and silicon nitride balls for ball milling high-purity α-Si3N4 powder; A2. Evacuate the ball mill jar, then inject oxygen and evacuate again. Repeat this process 2-3 times to ensure that the ball mill jar is in a low-pressure and high-purity oxygen atmosphere, which is conducive to plasma discharge. A3. Provides a plasma ball mill with an oscillation frequency of 1350 rpm and a current of 65 mA for ball milling.

[0050] A4. Plasma ball milling of powder for different times to change the thickness of silicon oxide film on silicon nitride surface and silicon nitride surface defects to promote high-activity sintering of silicon nitride.

[0051] The density of the prepared conductive silicon nitride composite ceramic was tested using a density balance, and the results showed that it had a high density. The hardness of the prepared conductive silicon nitride composite ceramic was tested using a hardness tester, and the results showed that the conductive silicon nitride composite ceramic had high hardness and fracture toughness. The prepared conductive composite ceramic was tested using a four-probe tester, and the results showed that the conductive silicon nitride composite ceramic had high electrical conductivity, which was higher than that of general semiconductor materials. At 1000℃, its electrical conductivity was an order of magnitude higher than that at room temperature. The results are shown in Table 1.

[0052] Example 3: Compared to Example 1, the selected material in this embodiment is α-Si3N4:boron carbide:ytterbium oxide:cerium oxide:zirconium oxide = 5:1:1:1:1 (mol.%); other preparation conditions are the same as in Example 1, and a conductive composite ceramic is obtained (its specific microstructure is as follows). Figure 5-6 (As shown).

[0053] The density of the prepared conductive silicon nitride composite ceramic was tested using a density balance, and the results showed that it had a high density. The hardness of the prepared conductive silicon nitride composite ceramic was tested using a hardness tester, and the results showed that the conductive silicon nitride composite ceramic had high hardness and fracture toughness. The prepared conductive silicon nitride composite ceramic was tested using a four-probe tester, and the results showed that the conductive silicon nitride composite ceramic had high electrical conductivity, which was higher than that of general semiconductor materials. At 1000℃, its electrical conductivity was an order of magnitude higher than that at room temperature. The data results are shown in Table 1.

[0054] Example 4: Compared to Example 2, the selected material in this embodiment is silicon nitride: boron carbide: ytterbium oxide: cerium oxide: zirconium oxide = 5:1:1:1:1 (mol.%); other preparation conditions are the same as in Example 2, and a conductive composite ceramic is obtained (its specific microstructure is as follows). Figure 7-8 (As shown).

[0055] The density of the prepared conductive silicon nitride composite ceramic was tested using a density balance, and the results showed that it had a high density. The hardness of the prepared conductive silicon nitride composite ceramic was tested using a hardness tester, and the results showed that the conductive composite silicon nitride ceramic had high hardness and fracture toughness. The prepared conductive silicon nitride composite ceramic was tested using a four-probe tester, and the results showed that the conductive silicon nitride composite ceramic had high electrical conductivity, which was higher than that of general semiconductor materials. At 1000℃, its electrical conductivity was an order of magnitude higher than that at room temperature. The results are shown in Table 1.

[0056] Comparative Example 1: Compared to Example 1, this comparative example does not undergo silicon nitride surface treatment, nor does it undergo high-temperature treatment using a Joule heating device to obtain silicon nitride composite ceramics.

[0057] The density of the prepared silicon nitride composite ceramic was tested using a density balance, which showed that it had a low density. Under a light microscope, it was found that the surface had many pores. Because it was not sintered and dense, subsequent performance tests (such as electrical conductivity, fracture toughness, hardness, etc.) could not be performed.

[0058] Comparative Example 2: Compared to Example 3, this comparative example does not undergo silicon nitride surface treatment, nor does it undergo high-temperature treatment using a Joule heating device to obtain silicon nitride composite ceramics.

[0059] The density of the completed silicon nitride composite ceramic was tested using a density balance, which showed that it had a low density. Under a light microscope, it was found that the surface had many pores. Because it was not sintered and dense, subsequent performance tests (such as electrical conductivity, fracture toughness, hardness, etc.) could not be performed.

[0060] Table 1

[0061] In Table 1, "--" indicates that the silicon nitride composite ceramics obtained in Comparative Example 1 and Comparative Example 2 were not sintered and dense, so subsequent performance tests could not be performed, i.e., no performance test data was available.

[0062] As shown in Table 1, based on the density, hardness, toughness, and conductivity data of the conductive silicon nitride composite ceramics in Examples 1-4 and Comparative Examples 1-2, it can be seen that the preparation method of the conductive silicon nitride composite ceramics used in this application solves the problem of density reduction caused by the introduction of conductive phase, and realizes that silicon nitride has both excellent mechanical properties and high conductivity.

[0063] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for preparing conductive silicon nitride composite ceramics, characterized in that, include: The first ceramic powder is subjected to surface oxidation treatment to obtain a first ceramic powder with an oxide film layer; The second ceramic powder is mixed with the first ceramic powder having an oxide film to obtain a mixture; The mixture was subjected to heat treatment at 1700℃-2500℃ to obtain a precursor; The precursor is sintered to obtain the conductive silicon nitride composite ceramic; wherein, The first ceramic powder comprises α-Si3N4, the second ceramic powder comprises metal oxide ceramic, the oxide film comprises silicon oxide, and the oxide film has active sites; the conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ at room temperature. 2 The conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ S / m at 1000 °C. 3 S / m.

2. The method according to claim 1, characterized in that: The particle size D of the first ceramic powder 50 The first ceramic powder has a particle size of 30 nm to 1 μm and a purity of ≥99.9%. The second ceramic powder includes at least three of the following: zirconium oxide, cerium oxide, ytterbium oxide, yttrium oxide, lanthanum oxide, and gadolinium oxide.

3. The method according to claim 1, characterized in that: The mixture further includes a third ceramic powder, which comprises at least one powder selected from boron nitride and boron carbide; the conductive silicon nitride composite ceramic has a Vickers hardness ≥1800 HV1.0 and a fracture toughness ≥8 MPa·m. 1 / 2 .

4. The method according to claim 3, characterized in that: The third ceramic powder includes at least one of boron nitride and boron carbide.

5. The method according to claim 3 or 4, characterized in that: Based on the total amount of matter in the mixture, the proportion of the first ceramic powder is 50 mol.%-70 mol.%, and the proportions of the second ceramic powder and the third ceramic powder are each independently 10 mol.%-20 mol.%.

6. The method according to claim 1, characterized in that: The surface oxidation treatment method includes one or more of atomic layer deposition, plasma ball milling, vapor phase oxidation, and wet chemical oxidation; and / or, The thickness of the oxide film is 2 nm-5 nm.

7. The method according to claim 1, characterized in that: The heat treatment satisfies one or more of the following conditions; The heat treatment method includes using a Joule heating device; The temperature of the heat treatment is 2000℃-2500℃, and the time of the heat treatment is 10s-20s; The heating treatment environment is one or more of vacuum, nitrogen, and argon.

8. The method according to claim 1, characterized in that: The sintering process satisfies one or more of the following conditions: The sintering process includes processing using a rapid hot press furnace; The sintering temperature is 1600 ℃-1700 ℃, and the sintering time is 5 min-10 min; The sintering pressure is 30 MPa-100 MPa; The heating rate of the sintering process is 120℃ / min-200℃ / min.

9. A conductive silicon nitride composite ceramic, characterized in that, Prepared by the method according to any one of claims 1-8: The conductive silicon nitride composite ceramic includes an α-Si3N4 matrix network and metal oxide ceramics dispersed in the matrix network. The metal oxide ceramics connected to α-Si3N4 generate an oxygen-deficient state during the sintering process, thereby forming a continuous conductive network. The conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ at room temperature. 2 The conductive silicon nitride composite ceramic has a volume conductivity of not less than 1×10⁻⁶ S / m at 1000 °C. 3 S / m.

10. The application of a conductive silicon nitride composite ceramic prepared by the method of any one of claims 1-8, or the conductive silicon nitride composite ceramic as described in claim 9, in hot-end components of aerospace engines, leading-edge structures of hypersonic vehicles, high-temperature electronic devices, electromagnetic shielding, and plasma contact components.

Images