Aluminum oxide-aluminum nitride composite ceramic material and preparation method thereof

Abstract

The invention belongs to the technical field of special ceramic materials, and particularly relates to an aluminum oxide-aluminum nitride composite ceramic material and a preparation method thereof.The preparation method of the aluminum oxide-aluminum nitride composite ceramic material comprises the steps that surface passivation treatment is conducted on aluminum nitride powder, specific materials are mixed, and the surface of the passivated aluminum nitride powder is evenly wrapped with aluminum oxide powder to form a wrapping structure; and granulating, preparing a green body, discharging glue in two steps, and carrying out staged heat preservation and sintering. According to the technical scheme, aluminum nitride is subjected to surface passivation treatment firstly, and a specific material mixing step is adopted, so that the problems that the aluminum nitride is not uniformly dispersed in aluminum oxide and the interface bonding is poor are solved, and then the composite ceramic material with the advantages of aluminum nitride ceramic and aluminum oxide ceramic is prepared through subsequent treatment. On the premise of ensuring the original mechanical properties of the aluminum oxide ceramic, the heat conductivity of the composite material is greatly improved, and a microstructure beneficial to phonon transmission is further constructed.

Description

Technical Field

[0001] This invention belongs to the field of special ceramic materials technology, specifically relating to a high thermal conductivity, high densification alumina-alumina nitride composite ceramic material for electrostatic chucks in semiconductor process equipment and its preparation method, particularly relating to a composite ceramic material that achieves uniform dispersion of the second phase and interface optimization through passivation treatment. Background Technology

[0002] Alumina ceramics are widely used in electrostatic chuck components in semiconductor manufacturing due to their excellent insulation properties, high mechanical strength, good chemical stability, and relatively low cost. During operation, the electrostatic chuck needs to support the silicon wafer and achieve efficient heat exchange via back-blown helium to precisely control the wafer's process temperature. Therefore, the thermal conductivity of the electrostatic chuck substrate material is a key performance indicator affecting its thermal response speed and temperature uniformity.

[0003] However, the thermal conductivity of traditional pure alumina ceramics is generally low, typically in the range of 20–30 W / m·K. This value is insufficient to meet the growing demands of advanced semiconductor manufacturing processes for rapid and precise temperature control. To improve the thermal conductivity of alumina ceramics, high-purity, fine-grained alumina raw materials are usually used, and the sintering process is optimized. However, the improvement in thermal conductivity achieved by this method is limited, and it is difficult to break through the bottleneck of 35 W / m·K.

[0004] Aluminum nitride (ANT) is a ceramic material with extremely high intrinsic thermal conductivity (theoretically exceeding 200 W / m·K), making it an ideal choice for preparing high thermal conductivity ceramics. However, pure ANT ceramics are expensive, and their mechanical and electrical insulation properties differ from those of alumina ceramics. Theoretically, if ANT could be introduced into an alumina matrix as a second phase, a composite material combining the advantages of both could be prepared. However, direct and simple physical mixing leads to poor interfacial bonding, high porosity, and the introduction of numerous phonon scattering centers, resulting in an actual thermal conductivity of the composite material that is far lower than theoretically expected, and may even be lower than that of pure alumina. Existing technologies, such as patent CN110467443A, disclose an aluminum nitride / alumina composite ceramic and its preparation method. This involves doping an alumina ceramic mixture with a carbon source, reshaping it, and then performing vacuum carbonization to obtain an alumina ceramic green body. The green body is then subjected to carbothermic reduction nitriding treatment, and aluminum nitride ceramic is introduced in situ into the alumina green body. Decarburization and sintering are then performed sequentially to obtain the aluminum nitride / alumina composite ceramic. However, the thermal conductivity of this composite ceramic is at most 40-45 W / (m·K). Another example is patent US12404215B2, which discloses a ceramic substrate and its manufacturing method. The ceramic substrate is prepared by mixing, drying, pressing, and sintering alumina, aluminum nitride, yttrium oxide, alcohol compounds, and binders. It also adds dopants such as graphene and rare earth composite oxides, resulting in a final thermal conductivity of up to 50 W / (m·K).

[0005] The aforementioned solutions still suffer from poor interfacial compatibility and insufficient thermal conductivity, making them unsuitable for the electrostatic chuck field. Therefore, developing a composite ceramic material that can effectively combine the advantages of alumina and aluminum nitride while overcoming interfacial compatibility issues and achieving a significant leap in thermal conductivity has become a pressing practical problem in this field. Summary of the Invention

[0006] This invention addresses the problems of poor interfacial compatibility and insufficient thermal conductivity in existing composite ceramic materials. It provides an alumina-alumina nitride composite ceramic material and its preparation method. By passivating the surface of aluminum nitride powder and lightly oxidizing the aluminum nitride powder, a transition layer of aluminum nitride and alumina is formed, overcoming the problems of uneven dispersion and poor interfacial bonding of aluminum nitride between alumina. Through innovative material mixing technology, not only is uniform dispersion of the second phase achieved, but the thermal conductivity of the material is also significantly improved while ensuring the original mechanical properties of alumina ceramics. Furthermore, a microstructure conducive to phonon transport is constructed.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Surface passivation treatment of aluminum nitride powder: aluminum nitride powder is placed in an oxygen-containing atmosphere and heat-treated at 800~1100℃ for 0.5~2.0h to obtain passivated aluminum nitride powder; (2) Passivated aluminum nitride powder is uniformly dispersed in ethanol. Under stirring, pre-mixed alumina powder and sintering aid are slowly added, and the pH is controlled at 3.5~4.5 so that the alumina powder is uniformly coated on the surface of the passivated aluminum nitride powder. After filtration and drying, coated particles are obtained. (3) Mix the coated particles with the binder, spray granulate to obtain composite granulated powder; (4) The composite granulated powder is formed into a green body, and then subjected to two-step debinding and staged heat preservation sintering to obtain alumina-alumina nitride composite ceramic material.

[0008] This invention involves surface passivation treatment of aluminum nitride powder. The powder is heat-treated at 800–1100°C for 0.5–2.0 h in an oxygen-containing atmosphere, causing mild oxidation and forming a dense alumina layer on the surface. This thin layer serves as a transition layer, forming a strong chemical bond with the subsequent alumina matrix, significantly improving the interfacial compatibility between the two phases. This solves the problems of uneven dispersion and poor interfacial bonding of aluminum nitride between alumina particles.

[0009] Meanwhile, an innovative material mixing technique is employed. First, passivated aluminum nitride powder is uniformly dispersed in ethanol. Then, pre-mixed alumina powder and sintering aids are added, and the pH is controlled at 3.5–4.5. Due to electrostatic adsorption, the alumina powder uniformly coats the surface of the passivated aluminum nitride powder. In other words, the passivated aluminum nitride powder acts as the core, while the highly compatible alumina acts as the shell. This method not only achieves uniform dispersion of the second phase but also facilitates the construction of effective heat flow channels, i.e., a microstructure conducive to phonon transport. While maintaining the original mechanical properties of the alumina ceramic, the thermal conductivity of the composite ceramic material is significantly improved.

[0010] Based on this, a composite ceramic material combining the advantages of both aluminum nitride and alumina ceramics was successfully prepared through a two-step debinding and staged heat preservation sintering process. The two-step debinding allows for step-by-step control of temperature and atmosphere, removing most of the organic binder at low temperature and removing residual carbon at medium temperature, while preventing deep oxidation of aluminum nitride that would affect interfacial compatibility. The staged heat preservation sintering gradually densifies the material and promotes limited interdiffusion at the AlN-Al2O3 interface, ultimately forming a dense ceramic material with high thermal conductivity.

[0011] Preferably, the mass ratio of the passivating aluminum nitride powder, alumina powder and sintering aid is 100:(30~70):(1~5).

[0012] Preferably, the sintering aid is selected from one or more of yttrium oxide, calcium oxide, yttrium fluoride, and calcium fluoride.

[0013] Preferably, the particle size D of the aluminum nitride powder is... 50 The particle size D of alumina powder is 0.5~2.0μm. 50 The range is 0.2~1.0μm.

[0014] Preferably, the mass ratio of the coated particles to the binder is 100:(3~8), and the binder is selected from at least one of PVB, ethyl cellulose and PVA.

[0015] Preferably, the composite granulated powder has a particle size D 50 The value is 50~150μm.

[0016] Preferably, the molding method is dry pressing or cold isostatic pressing.

[0017] Preferably, the two-step adhesive removal process is as follows: the first step is carried out in an air atmosphere at a temperature of 300~400℃ for 1~2.0h, and the second step is carried out in an inert atmosphere at a temperature of 500~600℃ for 1~2.0h.

[0018] A two-step adhesive removal method is adopted, with staged adhesive removal and atmosphere control. The first step is to remove most of the organic binder at low temperature in an air atmosphere. The second step is to remove residual carbon in an inert atmosphere at medium temperature and prevent aluminum nitride from being deeply oxidized.

[0019] Preferably, the staged heat preservation sintering is carried out in a nitrogen or argon atmosphere, with the temperature increased to 1500-1600°C at a rate of 5-10°C / min and held for 0.5-1.0 h, followed by a further increase in temperature to 1700-1850°C at a rate of 3-5°C / min and held for 1-3 h.

[0020] The process is carried out under a flowing nitrogen or argon atmosphere, using a staged heat-holding sintering method. First, the temperature is raised to 1500~1600℃ at a relatively rapid rate and held for 0.5~1.0h to promote the initial densification of the alumina matrix. Then, the temperature is raised to the final sintering temperature of 1700~1850℃ and held for 1~3h to completely densify the material and promote limited interdiffusion at the AlN-Al2O3 interface, forming a dense ceramic material with high thermal conductivity.

[0021] On the other hand, the present invention also provides an alumina-alumina nitride composite ceramic material, which is prepared by the above preparation method. The composite ceramic material has a thermal conductivity of 55~65 W / m·K and a relative density of not less than 99.0%.

[0022] This alumina-alumina composite ceramic material combines the advantages of both aluminum nitride ceramics and alumina ceramics. It has a thermal conductivity of 55~65 W / m·K, which is significantly improved compared with the existing technology, and a relative density of not less than 99.0%. At the same time, in terms of microstructure, the alumina ceramic acts as an integral framework to ensure the overall mechanical properties of the ceramic, while the embedded aluminum nitride ceramic phase constructs an effective heat flow channel, which is beneficial to phonon transport.

[0023] Therefore, the present invention has the following beneficial effects: (1) The aluminum nitride powder is passivated to make it slightly oxidized, and a dense aluminum oxide thin layer is formed on its surface. It can form a strong chemical bond with the subsequent aluminum oxide matrix, thereby greatly improving the interfacial compatibility between the aluminum nitride phase and the aluminum oxide phase. (2) After passivation, aluminum nitride powder is uniformly dispersed in ethanol, and then alumina powder and sintering aid are added. The pH value is controlled and electrostatic adsorption is used to make the alumina powder uniformly coat the surface of the passivated aluminum nitride powder, forming coated particles with "aluminum nitride as the core and alumina as the shell", thereby achieving uniform dispersion of the second phase. Moreover, the specific core-shell structure is conducive to building heat flow channels for ceramic materials, and ultimately, while ensuring the original mechanical properties of alumina ceramics, the thermal conductivity of composite ceramic materials is greatly improved. (3) Alumina-alumina composite ceramic materials combine the advantages of both aluminum nitride ceramics and alumina ceramics. The thermal conductivity is 55~65 W / m·K. In terms of microstructure, alumina ceramics serve as the overall framework to ensure the overall mechanical properties of the ceramics, while the embedded aluminum nitride ceramic phase constructs the microstructure for phonon transmission. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0025] General Implementation Examples A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Surface passivation treatment of aluminum nitride powder: aluminum nitride powder is placed in an oxygen-containing atmosphere and heat-treated at 800~1100℃ for 0.5~2.0h to obtain passivated aluminum nitride powder; (2) Passivated aluminum nitride powder is uniformly dispersed in ethanol. Under stirring, pre-mixed alumina powder and sintering aid are slowly added, and the pH is controlled at 3.5~4.5 so that the alumina powder is uniformly coated on the surface of the passivated aluminum nitride powder. After filtration and drying, coated particles are obtained. (3) Mix the coated particles with the binder, spray granulate to obtain composite granulated powder; (4) The composite granulated powder is formed into a green body, and then subjected to two-step debinding and staged heat preservation sintering to obtain alumina-alumina nitride composite ceramic material.

[0026] In one specific implementation, the mass ratio of passivating aluminum nitride powder, alumina powder and sintering aid is 100:(30~70):(1~5).

[0027] In one specific embodiment, the sintering aid is selected from one or more of yttrium oxide, calcium oxide, yttrium fluoride, and calcium fluoride.

[0028] As one specific implementation method, the particle size D of the selected aluminum nitride powder is... 50 The particle size D of alumina powder is 0.5~2.0μm. 50 The range is 0.2~1.0μm.

[0029] In one specific implementation, the mass ratio of the coating particles to the binder is 100:(3~8).

[0030] In one specific embodiment, the adhesive is selected from at least one of PVB, ethyl cellulose, and PVA.

[0031] As one specific implementation method, the particle size D of the composite granulated powder obtained by spray granulation is... 50 The value is 50~150μm.

[0032] As one specific implementation method, the composite granulated powder is formed by dry pressing or cold isostatic pressing.

[0033] As a specific implementation method, the two-step debinding process is as follows: the first step is to keep the product in an air atmosphere at a temperature of 300~400℃ for 1~2.0h, and the second step is to keep the product in an inert atmosphere at a temperature of 500~600℃ for 1~2.0h.

[0034] As a specific implementation method, the staged heat preservation sintering is as follows: under a nitrogen or argon atmosphere, the temperature is increased to 1500~1600℃ at 5~10℃ / min and held for 0.5~1.0h, and then the temperature is increased to 1700~1850℃ at 3~5℃ / min and held for 1~3h.

[0035] Example 1 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1000℃ for 1.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 4. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0036] Example 2 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 800℃ for 1.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50 The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 4. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0037] Example 3 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1100℃ for 1.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50 The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 4. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0038] Example 4 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1100℃ for 0.5 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50 The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 4. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0039] Example 5 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1100℃ for 2.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50 The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 4. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0040] Example 6 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1100℃ for 2.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 3.0. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0041] Example 7 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1100℃ for 2.0 h to obtain passivated aluminum nitride powder. (2) 100g of passivated aluminum nitride powder is uniformly dispersed in ethanol, and 50g of pre-mixed alumina powder (particle size D) is slowly added while stirring. 50 The alumina powder was uniformly coated on the surface of the passivated aluminum nitride powder by adding 2g of sintering aid Y2O3 powder (0.5μm) and controlling the pH to 5.0. The coated particles were then filtered and dried to obtain the coated particles. (3) Mix 152g of coated particles with 7.6g of PVB binder, spray granulate to obtain particle size D 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0042] Comparative Example 1 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) 100g aluminum nitride powder, 50g alumina powder (particle size D) 50 After being mixed evenly with 0.5 μm powder and 2 g of sintering aid Y2O3 powder, the mixture was ball-milled at a speed of 250 r / min, a ball-to-material ratio of 3:1, and a milling time of 15 h to obtain a mixed powder. (3) Mix 152g of the mixed powder with 7.6g of PVB binder, and spray granulate to obtain a particle size D. 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0043] Comparative Example 2 A method for preparing an alumina-alumina nitride composite ceramic material includes the following steps: (1) Regarding particle size D 50 Surface passivation treatment was performed on 1.0 μm aluminum nitride powder by placing the aluminum nitride powder in an air atmosphere and heat-treating it at 1000℃ for 1.0 h to obtain passivated aluminum nitride powder. (2) 100g passivated aluminum nitride powder, 50g alumina powder (particle size D) 50 After being mixed evenly with 0.5 μm powder and 2 g of sintering aid Y2O3 powder, the mixture was ball-milled at a speed of 250 r / min, a ball-to-material ratio of 3:1, and a milling time of 15 h to obtain a mixed powder. (3) Mix 152g of the mixed powder with 7.6g of PVB binder, and spray granulate to obtain a particle size D. 50 Composite granulated powder with a particle size of 100μm; (4) The composite granulated powder is formed into a green body by cold isostatic pressing. The cold isostatic pressing pressure is 200 MPa. Then it is placed in a high-temperature furnace. First, the binder is removed in an air atmosphere at a temperature of 350℃ and held for 1.5 h. Then, the binder is removed in a nitrogen atmosphere at a temperature of 550℃ and held for 1.5 h. Finally, the sintering is carried out in stages. Under a flowing nitrogen atmosphere, the temperature is increased to 1550℃ at 8℃ / min and held for 1.0 h. Then, the temperature is increased to 1800℃ at 4℃ / min and held for 2.0 h to obtain the alumina-aluminum nitride composite ceramic material.

[0044] Test case The thermal conductivity and relative density of the composite ceramic materials in Examples 1-7 and Comparative Examples 1-2 were determined. The room temperature thermal conductivity was measured using the laser scintillation method, and the relative density was measured using the Archimedes displacement method. The test results are shown in Table 1.

[0045] Table 1. Performance of alumina-alumina nitride composite ceramic materials in the examples and comparative examples. sample Relative density / % Thermal conductivity at room temperature / (W / m·K) Example 1 Heat treated at 1000℃ for 1.0 h; pH 4. 99.2 60.574 Example 2 Heat treated at 800℃ for 1.0 h; pH 4. 99.0 58.148 Example 3 Heat treated at 1100℃ for 1.0 h; pH 4. 99.1 59.662 Example 4 Heat treated at 1000℃ for 0.5 hours; pH 4. 99.1 59.581 Example 5 Heat treated at 1000℃ for 2.0 h; pH 4. 99.2 58.825 Example 6 Heat treatment at 1000℃ for 1.0 h; pH 3. 98.8 56.457 Example 7 Heat treatment at 1000℃ for 1.0 h; pH 5. 98.9 57.315 Comparative Example 1 No passivation treatment; direct ball milling mixing 97.8 28.587 Comparative Example 2 Heat treatment at 1000℃ for 1.0 h; direct ball milling mixing. 98.0 48.341 Comparing the test results of Example 1 with those of Comparative Examples 1 and 2, the relative density of the alumina-alumina nitride composite ceramic material was increased. Simultaneously, the room temperature thermal conductivity increased from 28.587 W / m·K in Comparative Example 1 and 48.341 W / m·K in Comparative Example 2 to 60.574 W / m·K. This indicates that surface passivation treatment of aluminum nitride powder and solvent-based coating treatment with alumina powder both benefit the performance of the composite ceramic material. The preparation method provided by this invention significantly improves the thermal conductivity of the composite ceramic material while maintaining the original mechanical properties of alumina ceramics. Furthermore, it constructs effective heat flow channels in the microstructure, which is beneficial for phonon transport.

[0046] The main principle is that aluminum nitride powder is heat-treated at 800-1100℃ in air, which causes slight oxidation, forming a dense alumina layer on the surface. This thin layer acts as a transition layer, forming a strong chemical bond with the subsequent alumina matrix, greatly improving the interfacial compatibility between the two phases. Furthermore, by mixing and passivating aluminum nitride powder and alumina powder in a solvent, and controlling the pH through electrostatic adsorption, a coating structure is formed with "passivated aluminum nitride powder as the core and alumina powder with excellent compatibility with the matrix as the shell," achieving uniform dispersion of the second phase. Therefore, surface passivation treatment and specific material mixing steps solve the problems of uneven dispersion and poor interfacial bonding of aluminum nitride between alumina and alumina.

[0047] Based on this, subsequent granulation, green body preparation, two-step debinding, and staged heat preservation sintering are carried out to finally obtain a composite ceramic material that combines the advantages of both aluminum nitride ceramics and alumina ceramics. Among them, the staged heat preservation sintering first promotes the initial densification of the alumina matrix, and then the temperature is raised to make the material completely densified, and promotes limited interdiffusion at the AlN-Al2O3 interface, thereby achieving the formation of a dense ceramic material with high thermal conductivity.

[0048] Comparing Examples 1-5, it is evident that excessively low or high heat treatment temperatures, or excessively short or long heat treatment times, can slightly affect the room-temperature thermal conductivity of the composite ceramic. The main reason is that inappropriate heat treatment temperature or time hinders the formation of a suitable alumina thin layer. For example, excessively high temperatures can cause deep oxidation of the aluminum nitride, preventing it from interacting with the subsequent alumina matrix and affecting the interfacial compatibility, thus impacting the composite ceramic's performance. Maintaining a heat treatment temperature of 800-1100℃ for 0.5-2 hours resulted in a room-temperature thermal conductivity of 58.148-60.574 W / m·K for the final composite ceramic material, significantly higher than the existing technology's 50 W / m·K.

[0049] Comparing Examples 1 and 6-7, it is evident that the second step of material mixing requires controlling the pH value to leverage electrostatic adsorption and form a stable core-shell coating structure, facilitating the subsequent formation of a dense ceramic material. At pH 4, the alumina-alumina nitride composite ceramic material exhibits a relative density exceeding 99.0%, while at pH 3 or 5, the relative densities are 98.8% and 98.9%, respectively, slightly lower than at pH 4. Furthermore, the room temperature thermal conductivity remains within the range of 56.457–60.574 W / m·K, significantly higher than the existing 50 W / m·K thermal conductivity. Therefore, during the preparation of composite ceramics, the pH of the material mixing step must be controlled within the range of 4 ± 0.5 to ultimately produce a material with excellent mechanical properties and thermal conductivity.

Claims

1. A method for preparing an alumina-alumina nitride composite ceramic material, characterized in that, Includes the following steps: (1) Surface passivation treatment of aluminum nitride powder: place aluminum nitride powder in an oxygen-containing atmosphere and heat treat it at 800~1100℃ for 0.5~2h to obtain passivated aluminum nitride powder; (2) Passivated aluminum nitride powder is uniformly dispersed in ethanol. Under stirring, pre-mixed alumina powder and sintering aid are slowly added, and the pH is controlled at 3.5~4.5 so that the alumina powder is uniformly coated on the surface of the passivated aluminum nitride powder. After filtration and drying, coated particles are obtained. (3) Mix the coated particles with the binder, spray granulate to obtain composite granulated powder; (4) The composite granulated powder is formed into a green body, and then subjected to two-step debinding and staged heat preservation sintering to obtain alumina-alumina nitride composite ceramic material.

2. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The mass ratio of the passivated aluminum nitride powder, alumina powder and sintering aid is 100:(30~70):(1~5).

3. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1 or 2, characterized in that, The sintering aid is selected from one or more of yttrium oxide, calcium oxide, yttrium fluoride, and calcium fluoride.

4. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The particle size D of the aluminum nitride powder 50 The particle size D of alumina powder is 0.5~2.0μm. 50 The range is 0.2~1.0μm.

5. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The mass ratio of the coated particles to the binder is 100:(3~8).

6. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The particle size D of the composite granulated powder 50 The value is 50~150μm.

7. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The forming method is dry pressing or cold isostatic pressing.

8. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The two-step adhesive removal process is as follows: the first step is to keep the adhesive at 300~400℃ in an air atmosphere for 1~2 hours, and the second step is to keep the adhesive at 500~600℃ in an inert atmosphere for 1~2 hours.

9. The method for preparing the alumina-alumina nitride composite ceramic material according to claim 1, characterized in that, The staged heat preservation sintering process specifically involves: heating to 1500-1600℃ at a rate of 5-10℃ / min under a nitrogen or argon atmosphere, holding at that temperature for 0.5-1h, and then continuing to heat to 1700-1850℃ at a rate of 3-5℃ / min, holding at that temperature for 1-3h.

10. An alumina-alumina nitride composite ceramic material, characterized in that, The product is prepared by any one of claims 1 to 9, and has a thermal conductivity of 55 to 65 W / m·K and a relative density of not less than 99.0%.