High thermal conductivity aluminum oxide ceramic and preparation process thereof

Abstract

The application relates to the field of ceramic materials, and particularly discloses high-thermal-conductivity alumina ceramics and a preparation process thereof. The high-thermal-conductivity alumina ceramics are prepared from 50-70 parts of alumina powder, 40-50 parts of alumina fiber, 8-15 parts of a sintering aid, 0.7-1.5 parts of a dispersant and 0.2-0.3 parts of a binder, wherein the sintering aid is beryllium-zirconium composite fiber. The high-thermal-conductivity alumina ceramics have excellent thermal conductivity and mechanical properties, and have important application prospects in the field of heat dissipation of high-performance electronic devices. In addition, the preparation process can reduce the sintering temperature of the alumina ceramics, form a more uniform and refined grain system in the alumina ceramics, and significantly improve the thermal conductivity of the alumina ceramics.

Description

Technical Field

[0001] This application relates to the field of ceramic materials, and more specifically, to a high thermal conductivity alumina ceramic and its preparation process. Background Technology

[0002] Alumina ceramics are mainly made of alumina (Al2O3). Depending on the percentage of Al2O3 and the type of additives, various series of alumina materials can be prepared. As an important industrial oxide ceramic material, alumina ceramics possess excellent thermal conductivity and thermal stability, superior mechanical properties, wear resistance, and outstanding corrosion resistance, making them promising for applications in aerospace, automotive, construction, electronics, and semiconductor industries.

[0003] With the development of modern technology, the integration and power of electronic devices are increasing daily, making efficient heat transfer particularly important and heat dissipation a prominent issue. The thermal conductivity of traditional alumina ceramics is often insufficient to meet the growing heat dissipation requirements of high-performance electronic devices, thus limiting their application in such devices.

[0004] Regarding the aforementioned technologies, the inventors discovered that during the preparation of traditional alumina ceramics, the process is often affected by factors such as improper additive adaptation, sintering time, and temperature. This leads to anisotropic and anisotropic grain growth during the preparation of alumina ceramics, resulting in a non-uniform microstructure and even high internal porosity. This reduces the bonding strength between grains, making the heat conduction path of the alumina ceramic easily interrupted, increasing thermal resistance, and reducing thermal conductivity. Therefore, improving the thermal conductivity of alumina ceramics is of great significance for their application in high-performance electronic device heat dissipation, high-temperature furnaces, and thermocouple protection tubes. Summary of the Invention

[0005] To improve the thermal conductivity of alumina ceramics, this application provides a high thermal conductivity alumina ceramic and its preparation process.

[0006] In a first aspect, this application provides a high thermal conductivity alumina ceramic, which adopts the following technical solution:

[0007] A high thermal conductivity alumina ceramic, by weight, comprises 50-70 parts alumina powder, 40-50 parts alumina fiber, 8-15 parts sintering aid, 0.7-1.5 parts dispersant and 0.2-0.3 parts binder, wherein the sintering aid is beryllium oxide-zirconium composite fiber.

[0008] By adopting the above technical solution, using alumina powder and alumina fiber as the main components, the alumina ceramic of this application has high alumina purity and reduces the adverse effects of impurities on thermal conductivity.

[0009] When alumina fibers are mixed with alumina powder, the alumina fibers act as a thermal bridge, forming a three-dimensional thermally conductive network within the alumina powder. This network structure enables the formation of a fine-grained structure during subsequent sintering, optimizing the internal microstructure of the alumina ceramic, providing more pathways for heat diffusion, reducing phonon scattering, and lowering thermal resistance. On the other hand, the mutual filling between the alumina powder and alumina fibers significantly reduces the porosity of the ceramic material, increases its density, and significantly improves the thermal conductivity of the alumina ceramic.

[0010] As a sintering aid, beryllium oxide-zirconium composite fiber inhibits abnormal grain growth and promotes the formation of finer grains in alumina ceramics during sintering. The presence of beryllium further enhances the thermal conductivity of the beryllium oxide-zirconium composite fiber, thereby further optimizing the thermally conductive network formed between alumina powder and alumina fiber and improving the heat transfer efficiency.

[0011] Furthermore, zirconium oxide and beryllium oxide can form a composite solid solution with alumina, which reduces the energy barrier during the sintering process of alumina ceramics, further lowers the sintering temperature of alumina ceramics, and improves the sintering efficiency. Higher density can be formed at a lower sintering temperature, which significantly improves the thermal conductivity, mechanical properties and thermal shock resistance of alumina ceramics.

[0012] Optionally, by weight, the raw materials of the beryllium oxide-zirconium composite fiber include 5-10 parts of beryllium source, 3-6 parts of zirconium source and 10-15 parts of polyvinyl alcohol, wherein the beryllium source is selected from beryllium oxide, the zirconium source is selected from zirconium oxynitrate, and the beryllium oxide is in powder form.

[0013] Optionally, the preparation process of the beryllium oxide-zirconium composite fiber includes the following steps:

[0014] S1: Mix zirconium oxynitrate with nitric acid at a ratio of 1:(3-5) and stir until homogeneous. Then add beryllium oxide and ultrasonically disperse for 20-30 minutes to form a precursor solution.

[0015] S2: Add polyvinyl alcohol to water at 50-60℃ at a ratio of 1:(1-2.5) and stir until homogeneous to form a substrate solution; S3: Mix the precursor solution and the substrate solution and ultrasonically stir for 1.5-2 hours to form a spinning solution;

[0016] S4: The spinning solution is spun by electrospinning to obtain pretreated composite fibers;

[0017] S5: Heat-treat the pretreated composite fibers to obtain the final product.

[0018] By adopting the above technical solution, using beryllium oxide powder as the beryllium source and zirconium oxynitrate as the zirconium source, a precursor solution is prepared by sol-gel method. Then, through in-situ composite method, electrospinning and heat treatment, in-situ composite of beryllium oxide and zirconium oxide is realized, which effectively improves the interfacial bonding force of beryllium oxide-zirconium composite fiber and ensures the structural uniformity and performance stability of composite fiber.

[0019] Optionally, the conditions for electrospinning in step S4 are as follows: the positive spinning voltage is set to 15-20kV, the negative voltage to -5-1kV, the feed flow rate to 0.1-0.3mL / min, the diameter of the spinneret to 0.4-0.8mm, and the distance between the syringe spinneret and the receiver to 10-15cm.

[0020] By adopting the above technical solution, the uniformity and continuity of the fiber formation process can be effectively ensured, thereby guaranteeing the overall performance of the final beryllium oxide-zirconium composite fiber.

[0021] Optionally, the specific steps of heat treatment in step S5 are as follows: heat the pretreated composite fiber to 600-700℃ in an inert gas atmosphere, hold for 1.5-2.5h, and then cool to room temperature to obtain the final product.

[0022] By adopting the above technical solution, impurities in the system can be effectively removed, promoting the decomposition of zirconium oxynitrate to form zirconium oxide and promoting the interaction between beryllium oxide and zirconium oxide to form a more stable composite structure.

[0023] Optionally, the alumina powder is α-alumina with a particle size of 100-300 nm.

[0024] Optionally, the length of the alumina fiber is 200-300 μm.

[0025] By adopting the above technical solution, micron-sized alumina fibers and nano-sized alumina powder are mixed to form a size gradient, thereby forming a more optimized multi-scale three-dimensional heat conduction network. This multi-scale structure promotes the bridging effect of micron-sized fibers in the nano-powder matrix, forming a continuous heat conduction path and reducing interfacial resistance in heat conduction.

[0026] Meanwhile, nanoparticles can more fully fill the pores between micron fibers, forming a denser microstructure, further reducing the porosity of ceramic materials. Moreover, nano-alumina powder has higher surface activity, enabling it to form more interfaces with micron fibers. These interfaces can provide more diffusion paths during the subsequent sintering process of ceramics, promoting the densification of the internal structure of alumina ceramics and significantly improving the thermal conductivity of alumina ceramics.

[0027] Optionally, the dispersant is selected from any one or more combinations of acrylates, propylene glycol methyl ether acetate, and polyvinylpyrrolidone.

[0028] By adopting the above technical solutions, acrylate, propylene glycol methyl ether acetate, and polyvinylpyrrolidone as dispersants can effectively improve the uniform dispersion of raw materials, which helps alumina ceramics form a denser system during the preparation process, thereby improving the overall performance of alumina ceramics.

[0029] Secondly, this application provides a preparation process for high thermal conductivity alumina ceramics, employing the following technical solution: A preparation process for high thermal conductivity alumina ceramics includes the following steps:

[0030] S1: Alumina powder is mixed with ethanol at a material-to-liquid ratio of 1:(0.2-0.3) and ground for 6-8 hours to obtain blend A;

[0031] S2: Mix alumina fibers and sintering aids, mix with ethanol at a material-to-liquid ratio of 1:(0.2-0.3), and grind for 0.5-1h to obtain blend B;

[0032] S3: Mix blend A and blend B, add dispersant and binder, and then grind and disperse to obtain cast slurry;

[0033] S4: Cast the casting paste into a mold, and then let it stand and dry to obtain the blank;

[0034] S5: The blank is subjected to isostatic pressing and debinding to obtain a blank block. After hot pressing and sintering at 750-850℃ and 200-250MPa for 5-7 hours, the blank is then cooled to obtain the final product.

[0035] By employing the above technical solution and using ethanol as a solvent, dispersants and binders are introduced during the mixing process and can be rapidly removed in subsequent preparation processes. This reduces the formation of porosity and defects within the alumina ceramic, thereby increasing its density. It promotes ceramic densification and grain growth at lower temperatures, helps eliminate porosity, reduces grain boundary scattering, and produces alumina ceramics with high thermal conductivity and high strength. This effectively improves the sintering efficiency of the product, significantly saves energy and equipment costs, and reduces the sintering difficulty of high thermal conductivity alumina ceramics.

[0036] Optionally, the conditions for isostatic pressing in step S5 are as follows: first, press the billet to 100-110 MPa and hold the pressure for 1-2 minutes, then press it to 210-230 MPa and hold the pressure for 4-5 minutes.

[0037] By adopting the above technical solution, isostatic pressing can effectively improve the density and mechanical properties of alumina ceramics, resulting in alumina ceramics with high thermal conductivity and excellent mechanical properties.

[0038] In summary, this application has the following beneficial effects:

[0039] 1. This application uses nano-sized alumina powder and micron-sized alumina fibers as the main raw materials. The mutual filling between the fibers and powder forms a special three-dimensional network conduction network with size gradient, which forms a more continuous heat conduction path inside the alumina ceramic, and significantly reduces the porosity of the alumina ceramic, reduces the generation of cracks and defects, forms a denser structure, and significantly improves the thermal conductivity and mechanical properties of the prepared alumina ceramic.

[0040] 2. This application uses beryllium oxide-zirconium composite fiber, prepared by in-situ composite of beryllium oxide and zirconia, as a sintering aid. This fiber can form a composite solid solution with alumina, refine the grains inside the alumina ceramic, further optimize the thermal conductivity network and microstructure inside the alumina ceramic, and effectively reduce the energy barrier of alumina ceramic during the sintering process. This allows alumina ceramic with good thermal conductivity, mechanical properties and thermal shock resistance to be obtained at a lower sintering temperature.

[0041] 3. The alumina ceramics obtained by the method of this application have high alumina purity, which effectively reduces the adverse effects of impurities on thermal conductivity, improves the interfacial bonding force between fibers and powders inside the alumina ceramics, and effectively improves the thermal conductivity and mechanical properties of alumina ceramics. Detailed Implementation

[0042] The following embodiments provide a further detailed description of this application.

[0043] raw material

[0044] Unless otherwise specified, the raw materials used in the preparation examples, embodiments, and comparative examples in this application are all commercially available products, specifically:

[0045] Beryllium oxide, selected from Jizhi, B69330;

[0046] Zirconium oxynitrate, selected from Maclean's, Z820675;

[0047] Zirconia, selected from Maclean's, Z787450;

[0048] Acrylic ester, selected from Delun New Materials, Neocryl A-2092;

[0049] Propylene glycol methyl ether acetate, selected from Delun New Materials, T108;

[0050] Polyvinylpyrrolidone, selected from Huzhou Shenhua, PVP K90;

[0051] The binder is hydroxypropyl methylcellulose, selected from Zhiheng Zhiyuan, HPMC-001.

[0052] Preparation example of beryllium oxide-zirconium composite fiber

[0053] Preparation Example 1

[0054] The raw materials and dosages of beryllium oxide-zirconium composite fiber are shown in Table 1. The beryllium oxide is in powder form.

[0055] Table 1

[0056]

[0057] The above-mentioned beryllium oxide-zirconium preparation process includes the following steps:

[0058] S1: Zirconium oxynitrate is mixed with nitric acid at a ratio of 1:3 and stirred until homogeneous. Then beryllium oxide is added and ultrasonically dispersed for 30 minutes to form a precursor solution.

[0059] S2: Add polyvinyl alcohol to water at 60°C at a material-to-liquid ratio of 1:1.5, stir evenly to form a substrate solution;

[0060] S3: Mix the precursor solution and the substrate solution and ultrasonically stir for 2 hours to form a spinning solution;

[0061] S4: The spinning solution is spun by electrospinning to obtain pretreated composite fibers; the positive spinning voltage is 15kV, the negative voltage is -2kV, the feed flow rate is 0.2mL / min, the diameter of the spinneret is 0.4mm, and the distance between the syringe spinneret and the receiver is 10cm.

[0062] S5: The pretreated composite fiber is heat-treated at 600℃ in an inert gas atmosphere, held at that temperature for 2.5 hours, and then cooled to room temperature to obtain the final product.

[0063] Preparation Example 2

[0064] The beryllium oxide-zirconium composite fiber differs from that in Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, and its preparation process includes the following steps:

[0065] S1: Zirconium oxynitrate is mixed with nitric acid at a ratio of 1:4 and stirred until homogeneous. Then beryllium oxide is added and ultrasonically dispersed for 30 minutes to form a precursor solution.

[0066] S2: Add polyvinyl alcohol to water at 50°C at a material-to-liquid ratio of 1:2, stir until homogeneous, and form a substrate solution;

[0067] S3: Mix the precursor solution and the substrate solution, and ultrasonically stir for 1.5 hours to form a spinning solution;

[0068] S4: The spinning solution is spun by electrospinning to obtain pretreated composite fibers; the positive spinning voltage is 20kV, the negative voltage is 1kV, the feed flow rate is 0.1mL / min, the diameter of the spinneret is 0.4mm, and the distance between the syringe spinneret and the receiver is 12cm.

[0069] S5: The pretreated composite fiber is heat-treated at 700℃ in an inert gas atmosphere, held at that temperature for 2 hours, and then cooled to room temperature to obtain the final product.

[0070] Preparation Example 3

[0071] The beryllium oxide-zirconium composite fiber differs from that in Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, and its preparation process includes the following steps:

[0072] S1: Zirconium oxynitrate is mixed with nitric acid at a ratio of 1:5 and stirred until homogeneous. Then beryllium oxide is added and ultrasonically dispersed for 20 minutes to form a precursor solution.

[0073] S2: Add polyvinyl alcohol to water at 55°C at a material-to-liquid ratio of 1:1, stir until homogeneous, and form a substrate solution;

[0074] S3: Mix the precursor solution and the substrate solution and ultrasonically stir for 2 hours to form a spinning solution;

[0075] S4: The spinning solution is spun by electrospinning to obtain pretreated composite fibers; the positive spinning voltage is 15kV, the negative voltage is -5kV, the feed flow rate is 0.3mL / min, the diameter of the spinneret is 0.8mm, and the distance between the syringe spinneret and the receiver is 15cm.

[0076] S5: The pretreated composite fiber is heat-treated at 700℃ in an inert gas atmosphere, held at that temperature for 1.5 hours, and then cooled to room temperature to obtain the final product.

[0077] Preparation Example 4

[0078] The beryllium oxide-zirconium composite fiber differs from that in Preparation Example 1 in that the raw materials and their amounts are shown in Table 1, and its preparation process includes the following steps:

[0079] S1: Zirconium oxynitrate is mixed with nitric acid at a ratio of 1:4 and stirred until homogeneous. Then beryllium oxide is added and ultrasonically dispersed for 20 minutes to form a precursor solution.

[0080] S2: Add polyvinyl alcohol to water at 60°C at a material-to-liquid ratio of 1:2.5, stir evenly to form a substrate solution;

[0081] S3: Mix the precursor solution and the substrate solution and ultrasonically stir for 2 hours to form a spinning solution;

[0082] S4: The spinning solution is spun by electrospinning to obtain pretreated composite fibers; the positive spinning voltage is 20kV, the negative voltage is -3kV, the feed flow rate is 0.2mL / min, the diameter of the spinneret is 0.6mm, and the distance between the syringe spinneret and the receiver is 12cm.

[0083] S5: The pretreated composite fiber is heat-treated at 650℃ under an inert gas atmosphere, held at that temperature for 2 hours, and then cooled to room temperature to obtain the final product.

[0084] Example

[0085] Example 1

[0086] A high thermal conductivity alumina ceramic, the raw materials and their amounts are shown in Table 2, wherein the alumina powder is α-alumina with a purity ≥99% and a particle size range of 100-300nm; the alumina fiber has a length range of 200-300μm and a purity ≥99%; the sintering aid is the beryllium oxide-zirconium composite fiber prepared in Preparation Example 1; and the dispersant is selected from acrylate.

[0087] Table 2

[0088]

[0089]

[0090] The preparation process of the above-mentioned high thermal conductivity alumina ceramic includes the following steps:

[0091] S1: Alumina powder is mixed with ethanol at a material-to-liquid ratio of 1:0.2 and then milled in a sand mill for 6 hours to obtain blend A; S2: Alumina fiber and sintering aid are mixed and then mixed with ethanol at a material-to-liquid ratio of 1:0.3 and then milled in a ball mill for 0.5 hours to obtain blend B;

[0092] S3: Mix blend A and blend B, add dispersant and binder, and disperse evenly by ball milling to obtain cast slurry;

[0093] S4: Add the casting slurry to the casting machine for casting and shaping, and then let it stand and dry to obtain the blank;

[0094] S5: After adding the blank to the isostatic press for isostatic pressing and then debinding, first press the blank to 100MPa and hold for 2 minutes, then press to 210MPa and hold for 5 minutes to obtain the blank block.

[0095] S6: The billet is hot-pressed and sintered at 800℃ and 250MPa for 7 hours, and then cooled to obtain the final product.

[0096] Example 2

[0097] A high thermal conductivity alumina ceramic differs from Example 1 in that the raw materials and their amounts are shown in Table 2, and its preparation process includes the following steps:

[0098] S1: Alumina powder is mixed with ethanol at a material-to-liquid ratio of 1:0.25, and then milled in a sand mill for 7 hours to obtain blend A;

[0099] S2: Mix alumina fibers and sintering aids, mix with ethanol at a material-to-liquid ratio of 1:0.2, add to a ball mill and ball mill for 1 hour to obtain blend B;

[0100] S3: Mix blend A and blend B, add dispersant and binder, and then grind and disperse to obtain cast slurry;

[0101] S4: Add the casting slurry to the casting machine for casting and shaping, and then let it stand and dry to obtain the blank;

[0102] S5: After adding the blank to the isostatic press for isostatic pressing and then debinding, first press the blank to 110MPa and hold for 1 minute, then press to 230MPa and hold for 4 minutes to obtain the blank block.

[0103] S6: The billet is hot-pressed and sintered at 750℃ and 200MPa for 6 hours, and then cooled to obtain the final product.

[0104] Example 3

[0105] A high thermal conductivity alumina ceramic differs from Example 1 in that the raw materials and their amounts are shown in Table 2, and its preparation process includes the following steps:

[0106] S1: Alumina powder is mixed with ethanol at a material-to-liquid ratio of 1:0.3 and then milled in a sand mill for 6 hours to obtain blend A; S2: Alumina fiber and sintering aid are mixed and then mixed with ethanol at a material-to-liquid ratio of 1:0.25 and then milled in a ball mill for 0.5 hours to obtain blend B;

[0107] S3: Mix blend A and blend B, add dispersant and binder, and then grind and disperse to obtain cast slurry;

[0108] S4: Add the casting slurry to the casting machine for casting and shaping, and then let it stand and dry to obtain the blank;

[0109] S5: After adding the blank to the isostatic press for isostatic pressing and then debinding, first press the blank to 100MPa and hold for 2 minutes, then press to 230MPa and hold for 5 minutes to obtain the blank block.

[0110] S6: The billet is hot-pressed and sintered at 850℃ and 250MPa for 5 hours, and then cooled to obtain the final product.

[0111] Examples 4-6

[0112] A high thermal conductivity alumina ceramic, Examples 4-6 differ from Example 1 in that the raw materials and amounts are shown in Table 2, while the other steps are the same as in Example 1.

[0113] Example 7

[0114] A high thermal conductivity alumina ceramic differs from Example 1 in that the sintering aid is the beryllium oxide-zirconium composite fiber prepared in Example 2, while the other steps are the same as in Example 1.

[0115] Example 8

[0116] A high thermal conductivity alumina ceramic differs from Example 1 in that the sintering aid is the beryllium oxide-zirconium composite fiber prepared in Example 3, while the other steps are the same as in Example 1.

[0117] Example 9

[0118] A high thermal conductivity alumina ceramic differs from Example 1 in that the sintering aid is the beryllium oxide-zirconium composite fiber prepared in Example 4, while the other steps are the same as in Example 1.

[0119] Example 10

[0120] A high thermal conductivity alumina ceramic differs from Example 1 in that the dispersant in the raw materials is propylene glycol methyl ether acetate, while the other steps are the same as in Example 1.

[0121] Example 11

[0122] A high thermal conductivity alumina ceramic differs from Example 1 in that the dispersant in the raw materials is acrylate and polyvinylpyrrolidone in a mass ratio of 1:1, while the other steps are the same as in Example 1.

[0123] Comparative Example

[0124] Comparative Example 1

[0125] A high thermal conductivity alumina ceramic differs from Example 1 in that alumina fibers are not added, and the alumina fibers in the raw materials are replaced with an equal mass of alumina powder. All other steps are the same as in Example 1.

[0126] Comparative Example 2

[0127] A high thermal conductivity alumina ceramic differs from Example 1 in that beryllium oxide-zirconium composite fiber is not added as a sintering aid, and the beryllium oxide-zirconium composite fiber in the raw materials is replaced with an equal mass of alumina fiber. All other steps are the same as in Example 1.

[0128] Comparative Example 3

[0129] A high thermal conductivity alumina ceramic differs from Example 1 in that beryllium oxide-zirconium composite fiber is not added, and the beryllium oxide-zirconium composite fiber in the raw material is replaced with an equal mass of zirconia powder. All other steps are the same as in Example 1.

[0130] Comparative Example 4

[0131] A high thermal conductivity alumina ceramic differs from Example 1 in that beryllium oxide-zirconium composite fiber is not added, and the beryllium oxide-zirconium composite fiber in the raw material is replaced with an equal mass of beryllium oxide powder. All other steps are the same as in Example 1.

[0132] Performance testing

[0133] Mechanical and thermal conductivity tests were conducted on the alumina ceramics obtained in Examples 1-11 and Comparative Examples 1-4. Each test was performed three times, and the average value of the three tests was taken as the final result and recorded in Table 3. The relevant test standards and methods are as follows: 1. Fracture toughness: The alumina ceramics prepared in Examples 1-11 and Comparative Examples 1-4 were tested using a WDW type electronic universal testing machine and the single-sided notched beam method (SENB method). The loading rate was set to 0.05 mm / min.

[0134] The formula for calculating fracture toughness is: KIC = Y³PLa 1 / 2 / 2bw 2 , where P is the load at specimen fracture, N; L is the span between supports, mm; a is the specimen notch depth, mm; b is the specimen cross-sectional width, mm; w is the specimen cross-sectional height, mm.

[0135] 2. Bending strength: The bending strength of the alumina ceramics prepared in Examples 1-11 and Comparative Examples 1-4 were tested according to the methods and specifications of GB / T 6569-2006.

[0136] 3. Density: The density of the alumina ceramics prepared in Examples 1-11 and Comparative Examples 1-4 was tested according to the methods and specifications of GB / T 25995-2010.

[0137] 4. Thermal conductivity: Referring to the methods specified in GB / T 5598-2015, the alumina ceramic samples prepared in Examples 1-11 and Comparative Examples 1-4 were cut into circular pieces with a diameter of d = 10 mm. The thermal diffusivity α and specific heat Cp of the samples were obtained by testing them with a laser scintillation thermal diffusivity tester along with standard samples of the same thickness. The bulk density of the samples was tested by Archimedes method. The thermal conductivity of the samples was obtained by the formula λ = α·Cp·ρ.

[0138] Table 3

[0139]

[0140]

[0141] As can be seen from the performance test results in Table 3, the electrical conductivity of the high thermal conductivity alumina ceramic of this application is ≥57.7 W / (m·K), and the fracture toughness is ≥10.4 MPa·m. 1 / 2 With a bending strength of ≥593MPa, it not only exhibits excellent thermal conductivity but also excellent mechanical properties. This makes the high thermal conductivity alumina ceramic of this application have broad prospects for application in the field of heat dissipation of high-performance electronic devices, high-temperature furnaces, and high-temperature applications such as thermocouple protection tubes.

[0142] According to the performance test results of Examples 1-11 and Comparative Example 1, it can be seen that using nano-sized alumina powder and micron-sized alumina fibers as the main raw materials not only improves the purity of alumina ceramics and reduces the influence of impurities on the thermal conductivity of alumina ceramics, but also forms a special three-dimensional heat conduction network structure with size gradient, building a continuous heat conduction path inside the ceramic material. Furthermore, the filling effect between the fibers and powders increases the density of alumina ceramics, reduces the generation of cracks and defects, and significantly improves the thermal conductivity and mechanical properties of alumina ceramics.

[0143] The performance test results of Examples 1-11 and Comparative Examples 2-4 show that by preparing beryllium oxide-zirconium oxide composite fibers in situ as sintering aids, the grains of alumina ceramics during sintering are effectively refined, the generation of abnormal grains is reduced, and the fibers coordinate with the alumina fibers to further optimize the thermal conductivity network and grain arrangement inside the alumina ceramics, thereby reducing the sintering temperature of the alumina ceramics and forming a more stable and dense composite solid solution with alumina, significantly improving the thermal conductivity and mechanical properties of alumina ceramics.

[0144] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A high thermal conductivity alumina ceramic, characterized by, The raw materials include 50-70 parts of nano alumina powder, 40-50 parts of micrometer alumina fiber, 8-15 parts of sintering aid, 0.7-1.5 parts of dispersant and 0.2-0.3 parts of binder by weight, and the sintering aid is beryllium-zirconium composite fiber prepared by in-situ compounding of beryllium oxide and zirconium oxide.

2. The high thermal conductivity alumina ceramic of claim 1, wherein, The raw materials of the beryllium-zirconium composite fiber include 5-10 parts of beryllium source, 3-6 parts of zirconium source and 10-15 parts of polyvinyl alcohol by weight, and the beryllium source is selected from beryllium oxide in powder state.

3. The high thermal conductivity alumina ceramic of claim 2, wherein, The preparation process of the beryllium-zirconium composite fiber includes the following steps: S1: uniformly mix zirconium oxide nitrate with nitric acid in a liquid ratio of 1:(3-5), then add beryllium oxide, and ultrasonic dispersion for 20-30 min to form a precursor solution; S2: add polyvinyl alcohol to water at 50-60℃ in a liquid ratio of 1:(1-2.5), and stir uniformly to form a base solution; S3: mix the precursor solution and the base solution, and ultrasonic stirring for 1.5-2 h to form a spinning solution; S4: spin the spinning solution by electrospinning to obtain a pretreated composite fiber; S5: heat treat the pretreated composite fiber.

4. The high thermal conductivity alumina ceramic of claim 3, wherein, The electrospinning conditions in step S4 are as follows: set the positive voltage to 15-20 kV, the negative voltage to-5-1 kV, the push flow to 0.1-0.3 mL / min, the diameter of the spinneret to 0.4-0.8 mm, and the distance between the spinneret of the syringe and the receiver to 10-15 cm.

5. The high thermal conductivity alumina ceramic of claim 3, wherein, The specific steps of the heat treatment in step S5 are as follows: heat treat the pretreated composite fiber in an inert gas atmosphere at 600-700℃, and keep the temperature for 1.5-2.5 h, then cool to room temperature.

6. The high thermal conductivity alumina ceramic of claim 1, wherein, The nano alumina powder is alpha-alumina with a particle size of 100-300 nm.

7. The high thermal conductivity alumina ceramic of claim 1, wherein, The micrometer alumina fiber has a length of 200-300 μm.

8. The high thermal conductivity alumina ceramic of claim 1, wherein, The dispersant is selected from any one or a combination of multiple of acrylic ester, propylene glycol methyl ether acetate and polyvinyl pyrrolidone.

9. A process for the production of a high thermal conductivity alumina ceramic according to any one of claims 1 to 8, characterized in that, The method includes the following steps: S1: mix the nano alumina powder with ethanol in a liquid ratio of 1:(0.2-0.3), and grind and disperse for 6-8 h to obtain a blend A; S2: mix the micrometer alumina fiber and the sintering aid with ethanol in a liquid ratio of 1:(0.2-0.3), and grind and disperse for 0.5-1 h to obtain a blend B; S3: mix the blend A and the blend B, add the dispersant and the binder, and grind and disperse to obtain a casting slurry; S4: perform casting forming on the casting slurry, and obtain a blank after standing and drying; S5: perform isostatic pressing forming and degassing on the blank, obtain a blank block, and perform hot-pressing sintering at 750-850℃ and 200-250 MPa for 5-7 h, and cool to obtain the product.

10. The process for preparing high thermal conductivity alumina ceramic according to claim 9, characterized in that, ​

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