Modified zirconium boride ceramic, preparation method and application thereof in electrolytic aluminum

Abstract

The application provides a modified zirconium boride ceramic, a preparation method and application thereof in electrolytic aluminum, and belongs to the technical field of ceramics. The preparation method comprises the steps of preparing zirconium dioxide sol, preparing a reinforcing phase, coating and sintering. In the step of preparing the zirconium dioxide sol, a rare earth solution is added to a zirconium source solution, the adding rate of the rare earth solution is controlled to be 1.5-2.0 g / min, stirring is carried out at the same time, stirring is carried out at 42-45 DEG C for 30-35 min, stirring is carried out at 60-63 DEG C for 40-50 min, the pH is adjusted to 3.2-3.5, polyethylene glycol 2000 is added after aging, and stirring is carried out for 50-60 min to obtain the zirconium dioxide sol. The modified zirconium boride ceramic prepared by the application has high strength, excellent high-temperature oxidation resistance, excellent thermal shock resistance and excellent corrosion resistance, and can effectively ensure the stability of the electrolysis process.

Description

Technical Field

[0001] This invention belongs to the field of ceramic technology, specifically relating to a modified zirconium boride ceramic, its preparation method, and its application in electrolytic aluminum. Background Technology

[0002] Electrolytic aluminum is aluminum obtained through electrolysis, and it is an important part of the modern metallurgical industry. The modern electrolytic aluminum industry usually uses the cryolite-alumina melt electrolysis method, in which molten cryolite is the solvent, alumina is the solute, carbon is the anode, and aluminum liquid is the cathode. After a strong direct current is applied, an electrochemical reaction takes place at the two electrodes of the electrolytic cell at high temperature.

[0003] However, in traditional electrolysis processes, carbon anodes are continuously oxidized and consumed during electrolysis, generating large amounts of waste gases such as carbon dioxide, which does not meet the requirements for low-carbon and environmental protection. Furthermore, carbon anodes have low electrolysis efficiency, high energy consumption, and affect production stability. Their short lifespan limits their application in electrolytic aluminum.

[0004] Zirconium boride ceramic, as a typical ultra-high temperature ceramic material, has a high melting point of up to 3245℃, low resistivity, and good conductivity. It can maintain good conductivity even at high temperatures, meeting the electron transport requirements in the electrolysis process. Zirconium boride has good chemical inertness, and its corrosion resistance in the cryolite-alumina molten salt system is significantly better than that of traditional carbon materials and metal alloys. It can effectively extend the service life of the electrolytic cell and improve the electrolytic stability.

[0005] Therefore, zirconium boride ceramics are considered one of the ideal inert anode materials, and the application of zirconium boride ceramics in electrolytic aluminum has important research significance.

[0006] However, existing zirconium boride ceramics have the following problems in electrolytic aluminum applications:

[0007] First, zirconium boride ceramics have poor thermal shock resistance, and their coefficient of thermal expansion is not well matched with other components of the electrolytic cell. Temperature fluctuations during the electrolysis process can easily cause the ceramics to crack, affecting the electrolysis process.

[0008] Secondly, zirconium boride ceramics have insufficient oxidation resistance. In high-temperature oxidizing environments, they rapidly oxidize and fail, resulting in a sharp decline in physical properties such as strength. When used in electrolytic aluminum, their poor wettability with molten aluminum leads to uneven current distribution.

[0009] Therefore, it is essential to provide a modified zirconium boride ceramic that enhances its strength, strengthens its structural stability under various complex working conditions, improves its corrosion resistance and thermal shock resistance in the electrolytic aluminum environment, reduces energy consumption in the electrolytic aluminum production process, increases production efficiency, and reduces the number of electrode replacements, so as to meet the stringent requirements of electrolytic aluminum and other fields.

[0010] Existing technologies for modifying zirconium boride ceramics to improve ceramic strength typically involve adding second-phase particles, such as silicon carbide particles. However, the interfacial bonding between these particles and the zirconium boride matrix is ​​limited, making them prone to becoming crack initiation sites under stress. This fails to effectively improve the overall strength of the ceramic and may even reduce its toughness. In electrolytic aluminum applications, while some modification methods can improve the corrosion resistance of ceramics to some extent, the modified layer will gradually fail under long-term exposure to high-temperature, high-electrolyte environments, failing to meet the electrolytic aluminum industry's demand for low-cost, high-performance electrode materials. Summary of the Invention

[0011] To address the technical problems existing in the prior art, this invention provides a modified zirconium boride ceramic and its preparation method. The zirconium boride ceramic exhibits excellent strength and toughness, superior thermal shock resistance and high-temperature oxidation resistance, good electrical conductivity, and strong corrosion resistance, and can be used stably and sustainably in electrolytic aluminum production for a long period of time.

[0012] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0013] A method for preparing modified zirconium boride ceramics includes the steps of preparing zirconium dioxide sol, preparing a reinforcing phase, coating, and sintering, as detailed below:

[0014] 1. Preparation of Zirconia Sol

[0015] Gadolinium nitrate and neodymium nitrate were added to an ethanol solution and stirred until homogeneous at 30-34°C to obtain a rare earth solution; zirconium oxychloride was added to the ethanol solution and stirred until homogeneous at 60-62°C to obtain a zirconium source solution.

[0016] The ethanol solution has a mass concentration of 60-66%;

[0017] In the rare earth solution, the mass ratio of the ethanol solution, gadolinium nitrate, and neodymium nitrate is 200:6.5-7.0:3.0-3.5;

[0018] In the zirconium source solution, the mass ratio of zirconium oxychloride to ethanol solution is 65-70:500;

[0019] Rare earth solution was added to the zirconium source solution at a rate of 1.5-2.0 g / min, while stirring was performed at a speed of 110-120 rpm and a temperature of 30-34℃. After stirring, the temperature was increased to 42-45℃ at a rate of 1.5-2.0℃ / min and stirred for 30-35 min. The temperature was then increased to 60-63℃ at a rate of 1.0-1.5℃ / min and stirred for 40-50 min. Nitric acid solution was added to adjust the pH to 3.2-3.5. The solution was aged at 60-63℃ for 2.0-2.5 h. Polyethylene glycol 2000 was then added and stirred for 50-60 min. After washing and drying, zirconium dioxide sol was obtained.

[0020] The mass ratio of the zirconium source solution, rare earth solution, and polyethylene glycol 2000 is 570:100-120:3.0-3.5;

[0021] The mass concentration of the nitric acid solution is 20-25%.

[0022] 2. Preparation of reinforcing phase

[0023] TiB2 and AlN powders were impregnated in a pretreatment solution for 1.0-1.5 h at a temperature of 45-50 °C. After pretreatment, they were added to a modification solution, and the temperature was increased to 60-65 °C at a rate of 1.0-1.5 °C / min. The mixture was kept warm and stirred for 3.0-4.0 h. After stirring, the mixture was filtered, washed, and dried to obtain a modified mixed powder. The modified mixed powder was dispersed in tetrahydrofuran. After uniform dispersion, a trimesoyl chloride solution was added at a rate of 1.0-1.5 g / min. After addition, the mixture was kept warm and stirred at 0-4 °C for 2.0-2.5 h. After stirring, the mixture was allowed to return to room temperature and stirred for another 4.0-4.5 h. The mixture was then centrifuged, washed, and dried to obtain the reinforcing phase.

[0024] The TiB2 has a particle size of 120-150 nm;

[0025] The particle size of the AlN powder is 90-100 nm;

[0026] The mass ratio of TiB2 powder, AlN powder, pretreatment solution, and modification solution is 10-15:7-10:130-140:120-125;

[0027] The mass ratio of the modified mixed powder, tetrahydrofuran, and trimesoyl chloride solution is 10:80-85:50-55;

[0028] The pretreatment solution is a mixture of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol, wherein the mass ratio of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol is 100:1.5-2.0:0.5-0.8.

[0029] The modified solution is a mixture of deionized water and γ-aminopropyltriethoxysilane, wherein the mass ratio of deionized water to γ-aminopropyltriethoxysilane is 100:2.0-3.0.

[0030] The pyromellitic chloride solution is a mixture of pyromellitic chloride and tetrahydrofuran, with a mass ratio of pyromellitic chloride to tetrahydrofuran of 0.4-0.5:50.

[0031] 3. Covering

[0032] The reinforcing phase was placed in a zirconium dioxide sol and ultrasonically dispersed for 30-35 min at a power of 120-130 W and a frequency of 30-36 kHz. After ultrasonication, the temperature was raised to 72-76 °C and stirred for 2.0-2.5 h. After drying, the temperature was raised to 350-360 °C at a rate of 2.0-3.0 °C / min under an argon atmosphere and held for 30-40 min. Then, the temperature was raised to 600-620 °C at a rate of 1.5-2.0 °C / min and held for 2.0-2.2 h. After natural cooling to room temperature, the zirconium oxide-coated reinforcing phase was obtained.

[0033] The mass ratio of the reinforcing phase to the zirconium dioxide sol is 15-18:90-100.

[0034] 4. Sintering

[0035] Zirconium boride, zirconium oxide-coated reinforcing phase, LaB6, and Y2O3 were mixed and ball-milled for 30-35 minutes at a speed of 210-220 rpm and a ball-to-material ratio of 3-5:1. After ball milling, the mixture was shaped and sintered at 1200-1250℃ for 1.0-1.2 hours and then at 1810-1830℃ for 2.0-2.3 hours. The mixture was then cooled to room temperature in the furnace to obtain modified zirconium boride ceramic.

[0036] The mass ratio of the zirconium boride, zirconium oxide-coated reinforcing phase, LaB6, and Y2O3 is 85-90:6-10:3-5:2-3.

[0037] A modified zirconium boride ceramic was prepared using the above-described preparation method.

[0038] The modified zirconium boride ceramics prepared by the above method are used in aluminum electrolysis, which effectively promotes electrolytic stability and improves electrolysis efficiency.

[0039] This invention prepares modified zirconium boride ceramics, primarily using TiB2 and AlN powders as reinforcing phases to modify the zirconium boride ceramics. Zirconia sol is prepared using zirconium oxychloride precursor and doped with rare earth metal ions, which can be incorporated into the zirconium dioxide lattice. Combined with polyethylene glycol, this enhances stability, inhibits abnormal grain growth, improves conductivity, and prevents nanoparticle aggregation. Using TiB2 and AlN as reinforcing phases, they are first treated with surfactants and silane coupling agents to further enhance their surface dispersion properties, introducing amino active sites onto the powder surface. Then, they are processed with trimesoyl pyromellitic acid... Chlorine, acting as a bridge, can not only combine with TiB2 and AlN, but also with zirconium dioxide sol during the coating process. This achieves chemical bonding and coating of zirconium oxide particles on the surface of TiB2 and AlN powders, effectively improving the strength and toughness of the product, alleviating the problem of thermal expansion coefficient mismatch. Combined with LaB6 and Y2O3 components, it modifies zirconium boride ceramics, improving the ceramic's electrical conductivity, oxidation resistance, and thermal shock resistance, enhancing corrosion resistance, increasing electrolysis efficiency, and ensuring the stability of the electrolysis process, making it extremely valuable for applications in electrolytic aluminum.

[0040] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0041] 1. The modified zirconium boride ceramic of the present invention has a flexural strength of 476.7-488.5 MPa and a fracture toughness of 12.4-13.2 MPa·m. 1 / 2 The conductivity is 6.5-7.2×10⁻⁶. 5 S / m;

[0042] 2. The modified zirconium boride ceramic of the present invention has a corrosion rate of 7.3-7.7 mm / a;

[0043] 3. The modified zirconium boride ceramic of the present invention, when heated to 1300℃ at a rate of 10℃ / min and held at that temperature for 120h, exhibited a flexural strength of 447.1-464.6MPa and a fracture toughness of 11.8-12.7MPa·m. 1 / 2 ;

[0044] 4. The modified zirconium boride ceramic of the present invention is subjected to a process in which the temperature is increased to 1200°C at a rate of 50°C / min in air, held at that temperature for 1.0 h, and then immersed in deionized water at 20°C for 1.0 h. This process constitutes one treatment cycle, and after 20 consecutive treatment cycles, the flexural strength is measured again to be 441.9-457.2 MPa, and the fracture toughness is 11.6-12.4 MPa·m. 1 / 2 . Detailed Implementation

[0045] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0046] Example 1

[0047] 1. Preparation of Zirconia Sol

[0048] Add 7.0g gadolinium nitrate and 3.5g neodymium nitrate to 200g ethanol solution, stir evenly at 34℃ to obtain rare earth solution; add 70g zirconium oxychloride to 500g ethanol solution, raise the temperature to 62℃ and stir evenly to obtain zirconium source solution;

[0049] The ethanol solution has a mass concentration of 660%.

[0050] 120g of rare earth solution was added to 570g of zirconium source solution at a rate of 2.0g / min. The solution was stirred at 120rpm and 34℃. After stirring, the temperature was increased to 45℃ at a rate of 1.5℃ / min and stirred for 35min. The temperature was then increased to 63℃ at a rate of 1.5℃ / min and stirred for 50min. The pH was adjusted to 3.5 by adding 25wt% nitric acid solution and aged at 63℃ for 2.0h. Then, 3.5g of polyethylene glycol 2000 was added and stirred for 60min. After washing and drying, zirconium dioxide sol was obtained.

[0051] 2. Preparation of reinforcing phase

[0052] 15g of TiB2 and 10g of AlN powder were impregnated in 140g of pretreatment solution for 1.5h at 50℃. After pretreatment, the powder was added to 120g of modification solution, and the temperature was increased to 65℃ at a rate of 1.5℃ / min. The mixture was kept warm and stirred for 4.0h. After stirring, the powder was filtered, washed, and dried to obtain the modified mixed powder. 10g of the modified mixed powder was dispersed in 85g of tetrahydrofuran. After uniform dispersion, 55g of trimesoyl chloride solution was added at a rate of 1.5g / min. After addition, the mixture was kept warm and stirred at 4℃ for 2.5h. After stirring, the mixture was allowed to return to room temperature and stirred for another 4.5h. After centrifugation, washing, and drying, the reinforcing phase was obtained.

[0053] The TiB2 has a particle size of 150 nm;

[0054] The particle size of the AlN powder is 100 nm;

[0055] The pretreatment solution is a mixture of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol, wherein the mass ratio of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol is 100:2.0:0.8.

[0056] The modified solution is a mixture of deionized water and γ-aminopropyltriethoxysilane, wherein the mass ratio of deionized water to γ-aminopropyltriethoxysilane is 100:3.0.

[0057] The pyromellitic chloride solution is a mixture of pyromellitic chloride and tetrahydrofuran, with a mass ratio of pyromellitic chloride to tetrahydrofuran of 0.5:50.

[0058] 3. Covering

[0059] 18g of the reinforcing phase was placed in 100g of zirconium dioxide sol and ultrasonically dispersed for 35min, with an ultrasonic power of 130W and an ultrasonic frequency of 36kHz. After ultrasonication, the temperature was raised to 76℃ and stirred for 2.5h. After drying, the temperature was raised to 360℃ at a rate of 3.0℃ / min under an argon atmosphere and held for 40min. Then the temperature was raised to 620℃ at a rate of 2.0℃ / min and held for 2.0h. After natural cooling to room temperature, the zirconium dioxide-coated reinforcing phase was obtained.

[0060] 4. Sintering

[0061] 90g of zirconium boride, 10g of zirconium oxide-coated reinforcing phase, 5g of LaB6, and 3g of Y2O3 were mixed and ball-milled for 35 minutes at a speed of 220 rpm with a ball-to-material ratio of 5:1. After ball milling, the mixture was shaped and sintered at 1250℃ for 1.0 h and then at 1830℃ for 2.3 h. The mixture was then cooled to room temperature in the furnace to obtain modified zirconium boride ceramic.

[0062] Example 2

[0063] 1. Preparation of Zirconia Sol

[0064] Add 6.8g gadolinium nitrate and 3.3g neodymium nitrate to 200g ethanol solution, stir evenly at 32℃ to obtain rare earth solution; add 67g zirconium oxychloride to 500g ethanol solution, raise the temperature to 62℃ and stir evenly to obtain zirconium source solution;

[0065] The ethanol solution has a mass concentration of 62%.

[0066] 110g of rare earth solution was added to 570g of zirconium source solution at a rate of 1.8g / min. The mixture was stirred at 120rpm and 32℃. After stirring, the temperature was increased to 43℃ at a rate of 1.5℃ / min and stirred for 35min. The temperature was then increased to 62℃ at a rate of 1.2℃ / min and stirred for 45min. The pH was adjusted to 3.3 by adding 22wt% nitric acid solution. The mixture was aged at 62℃ for 2.5h. Then, 3.3g of polyethylene glycol 2000 was added and stirred for 55min. After washing and drying, zirconium dioxide sol was obtained.

[0067] 2. Preparation of reinforcing phase

[0068] 12g of TiB2 and 8g of AlN powder were impregnated in 135g of pretreatment solution for 1.2h at 45℃. After pretreatment, the powder was added to 125g of modification solution, and the temperature was increased to 62℃ at a rate of 1.2℃ / min. The mixture was kept warm and stirred for 3.5h. After stirring, the powder was filtered, washed, and dried to obtain the modified mixed powder. 10g of the modified mixed powder was dispersed in 82g of tetrahydrofuran. After uniform dispersion, 52g of trimesoyl chloride solution was added at a rate of 1.2g / min. After addition, the mixture was kept warm and stirred at 2℃ for 2.3h. After stirring, the mixture was allowed to return to room temperature and stirred for another 4.2h. After centrifugation, washing, and drying, the reinforcing phase was obtained.

[0069] The TiB2 has a particle size of 130 nm;

[0070] The particle size of the AlN powder is 100 nm;

[0071] The pretreatment solution is a mixture of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol, wherein the mass ratio of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol is 100:1.7:0.6.

[0072] The modified solution is a mixture of deionized water and γ-aminopropyltriethoxysilane, wherein the mass ratio of deionized water to γ-aminopropyltriethoxysilane is 100:2.5.

[0073] The pyromellitic chloride solution is a mixture of pyromellitic chloride and tetrahydrofuran, with a mass ratio of pyromellitic chloride to tetrahydrofuran of 0.5:50.

[0074] 3. Covering

[0075] 17g of the reinforcing phase was placed in 100g of zirconium dioxide sol and ultrasonically dispersed for 30min at a power of 125W and a frequency of 32kHz. After ultrasonication, the temperature was raised to 74℃ and stirred for 2.3h. After drying, the temperature was raised to 360℃ at a rate of 2.5℃ / min under an argon atmosphere and held for 35min. Then the temperature was raised to 610℃ at a rate of 2.0℃ / min and held for 2.2h. After natural cooling to room temperature, the zirconium dioxide-coated reinforcing phase was obtained.

[0076] 4. Sintering

[0077] 88g of zirconium boride, 7g of zirconium oxide-coated reinforcing phase, 4g of LaB6, and 3g of Y2O3 were mixed and ball-milled for 32 minutes at a speed of 220 rpm with a ball-to-material ratio of 4:1. After ball milling, the mixture was shaped and sintered at 1230℃ for 1.2 hours and then at 1820℃ for 2.2 hours. The mixture was then cooled to room temperature in the furnace to obtain modified zirconium boride ceramic.

[0078] Example 3

[0079] 1. Preparation of Zirconia Sol

[0080] Add 6.5g gadolinium nitrate and 3.0g neodymium nitrate to 200g ethanol solution, stir evenly at 30℃ to obtain rare earth solution; add 65g zirconium oxychloride to 500g ethanol solution, raise the temperature to 60℃ and stir evenly to obtain zirconium source solution;

[0081] The ethanol solution has a mass concentration of 60%.

[0082] 100g of rare earth solution was added to 570g of zirconium source solution at a rate of 1.5g / min. The solution was stirred at 110rpm and 30℃. After stirring, the temperature was increased to 42℃ at a rate of 2.0℃ / min and stirred for 30min. The temperature was then increased to 60℃ at a rate of 1.0℃ / min and stirred for 40min. The pH was adjusted to 3.2 by adding 20wt% nitric acid solution. The solution was aged at 60℃ for 2.5h. Then, 3.0g of polyethylene glycol 2000 was added and stirred for 50min. After washing and drying, zirconium dioxide sol was obtained.

[0083] 2. Preparation of reinforcing phase

[0084] 10g of TiB2 and 7g of AlN powder were impregnated in 130g of pretreatment solution for 1.0h at 50℃. After pretreatment, the powder was added to 120g of modification solution, and the temperature was increased to 60℃ at a rate of 1.0℃ / min. The mixture was kept warm and stirred for 3.0h. After stirring, the powder was filtered, washed, and dried to obtain the modified mixed powder. 10g of the modified mixed powder was dispersed in 80g of tetrahydrofuran. After uniform dispersion, 50g of trimesoyl chloride solution was added at a rate of 1.0g / min. After addition, the mixture was kept warm and stirred at 0℃ for 2.0h. After stirring, the mixture was allowed to return to room temperature and stirred for another 4.0h. After centrifugation, washing, and drying, the reinforcing phase was obtained.

[0085] The TiB2 has a particle size of 120 nm;

[0086] The particle size of the AlN powder is 90 nm;

[0087] The pretreatment solution is a mixture of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol, wherein the mass ratio of deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol is 100:1.5:0.5.

[0088] The modified solution is a mixture of deionized water and γ-aminopropyltriethoxysilane, wherein the mass ratio of deionized water to γ-aminopropyltriethoxysilane is 100:2.0.

[0089] The pyromellitic chloride solution is a mixture of pyromellitic chloride and tetrahydrofuran, with a mass ratio of pyromellitic chloride to tetrahydrofuran of 0.4:50.

[0090] 3. Covering

[0091] 15g of the reinforcing phase was placed into 90g of zirconium dioxide sol and ultrasonically dispersed for 30min at a power of 120W and a frequency of 30kHz. After ultrasonication, the temperature was raised to 72℃ and stirred for 2.0h. After drying, the temperature was raised to 350℃ at a rate of 2.0℃ / min under an argon atmosphere and held for 30min. Then the temperature was raised to 600℃ at a rate of 1.5℃ / min and held for 2.2h. After natural cooling to room temperature, the zirconium dioxide-coated reinforcing phase was obtained.

[0092] 4. Sintering

[0093] 85g of zirconium boride, 6g of zirconium oxide-coated reinforcing phase, 3g of LaB6, and 2g of Y2O3 were mixed and ball-milled for 30 minutes at a speed of 210 rpm with a ball-to-material ratio of 3:1. After ball milling, the mixture was shaped and sintered at 1200℃ for 1.2 hours and then at 1810℃ for 2.0 hours. The mixture was then cooled to room temperature in the furnace to obtain modified zirconium boride ceramic.

[0094] Comparative Example 1

[0095] The changes made in Example 2 are as follows:

[0096] 1. The preparation step of zirconium dioxide sol is omitted; in the coating step, an equal amount of zirconium dioxide sol is used as a zirconium dioxide mixture, wherein the zirconium dioxide mixture is a mixture of zirconium dioxide and deionized water, and the mass ratio of zirconium dioxide to deionized water is 10:90.

[0097] 2. In the step of preparing the reinforcing phase, the following steps are omitted: "Disperse 10g of modified mixed powder in 82g of tetrahydrofuran. After uniform dispersion, add 52g of trimesoyl chloride solution, controlling the addition rate at 1.2g / min. After addition, keep warm at 2℃ and stir for 2.3h. After stirring, allow to return to room temperature naturally and continue stirring for 4.2h. After centrifugation, washing, and drying, the reinforcing phase is obtained." The modified mixed powder obtained is the reinforcing phase.

[0098] The rest of the operations are exactly the same.

[0099] Comparative Example 2

[0100] The changes made in Example 2 are as follows:

[0101] 1. In the step of preparing zirconium dioxide sol, the rare earth liquid component is omitted, and the rare earth liquid is replaced with an equal amount of zirconium source solution;

[0102] 2. In the sintering step, replace an equal amount of LaB6 with zirconium boride;

[0103] The rest of the operations are exactly the same.

[0104] Performance testing

[0105] The modified zirconium boride ceramics prepared in Examples 1-3 and Comparative Examples 1-2 were subjected to performance testing, and the test results are as follows:

[0106]

[0107] The corrosion rate was determined by electrolytic testing of the modified zirconium boride ceramics prepared in Examples 1-3 and Comparative Examples 1-2 in a molten salt system at 1000℃. The molten salt system consisted of NaF·AlF3 + CaF2 + Al2O3, with a molar ratio of NaF·AlF3 of 2.0, a mass concentration of CaF2 of 5.0%, a mass concentration of Al2O3 of 5.0%, and an anolyte current density of 1.0 A / cm². 2 The electrolysis time was 48 hours, and the annual corrosion rate was calculated by testing the corrosion amount after 48 hours.

[0108] The high-temperature oxidation resistance was tested by placing the modified zirconium boride ceramics prepared in Examples 1-3 and Comparative Examples 1-2 in air, raising the temperature to 1300°C at a rate of 10°C / min, holding it at that temperature for 120 hours, and then testing the flexural strength and fracture toughness again.

[0109] The thermal shock resistance was tested by placing the modified zirconium boride ceramics prepared in Examples 1-3 and Comparative Examples 1-2 in an air environment, raising the temperature to 1200°C at a rate of 50°C / min, holding it at that temperature for 1.0h, and then immersing it in deionized water at 20°C for 1.0h. This process was repeated as one treatment cycle, and after 20 consecutive treatment cycles, the bending strength and fracture toughness were tested again.

[0110] According to the results in the table above, Comparative Example 1 directly added zirconium dioxide, which had poor bonding with the zirconium boride matrix, poor dispersion performance, and a large number of voids at the particle interface. Under stress, stress concentration easily occurred, reducing overall performance and increasing electron transport resistance, resulting in poor conductivity, strength, and stability. Comparative Example 2 omitted rare earth components in the zirconium dioxide sol preparation step, which caused zirconium dioxide to undergo a crystal transformation, making it easy to generate cracks inside the material and resulting in poor overall strength. The omission of LaB6 components further reduced conductivity, increased interface defects, and reduced overall stability.

[0111] Unless otherwise stated, all percentages used in this invention are mass percentages.

[0112] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing a modified zirconium boride ceramic, characterized by, The method comprises the steps of preparing zirconia sol, preparing reinforcing phase, coating and sintering; The step of preparing zirconia sol is adding rare earth solution into zirconium source solution, controlling the adding rate of rare earth solution to be 1.5-2.0 g / min, stirring while adding, stirring at 42-45℃ for 30-35 min, stirring at 60-63℃ for 40-50 min, adding nitric acid solution to adjust pH to 3.2-3.5, adding polyethylene glycol 2000 after aging, and stirring for 50-60 min to obtain zirconia sol; The zirconium oxychloride is added into ethanol solution, and stirred uniformly at a temperature of 60-62℃ to obtain the zirconium source solution; The rare earth solution is a mixture of ethanol solution, gadolinium nitrate and neodymium nitrate; The step of preparing reinforcing phase is dipping and pretreating TiB2 and AlN powders into pretreatment solution, the pretreatment time is 1.0-1.5 h, the pretreatment temperature is 45-50℃, after the pretreatment, the powders are put into modification solution, the temperature is increased to 60-65℃ at a rate of 1.0-1.5℃ / min, and the mixture is stirred for 3.0-4.0 h, after the stirring, the mixture is filtered, washed and dried to obtain modified mixed powders, the modified mixed powders are dispersed in tetrahydrofuran, and uniform benzene tricarboxylic acid chloride solution is added, the mixture is stirred at 0-4℃ for 2.0-2.5 h, and stirred at room temperature for 4.0-4.5 h to obtain reinforcing phase; The pretreatment solution is a mixture of deionized water, dodecyl dimethyl betaine and polyvinyl alcohol; The modification solution is a mixture of deionized water and γ-aminopropyl triethoxysilane; The coating step is ultrasonic dispersion of the reinforcing phase in zirconia sol, after the ultrasonic dispersion, the temperature is increased to 72-76℃, the mixture is stirred for 2.0-2.5 h, and after drying, the temperature is increased to 350-360℃ at a rate of 2.0-3.0℃ / min under argon atmosphere, the temperature is increased to 600-620℃ at a rate of 1.5-2.0℃ / min, the mixture is kept for 2.0-2.2 h, and the mixture is naturally cooled to room temperature to obtain zirconia coated reinforcing phase; The sintering step is ball milling of zirconium boride, zirconia coated reinforcing phase, LaB6 and Y2O3, after the ball milling, the mixture is shaped and sintered, the mixture is sintered at 1200-1250℃ for 1.0-1.2 h, and sintered at 1810-1830℃ for 2.0-2.3 h, and the mixture is cooled to room temperature in the furnace to obtain modified zirconium boride ceramic.

2. The method according to claim 1, wherein in the step of preparing zirconia sol, the mass ratio of zirconium source solution, rare earth solution and polyethylene glycol 2000 is 570:100-120:3.0-3.5; The mass concentration of the nitric acid solution is 20-25%.

3. The method according to claim 1, wherein in the rare earth solution, the mass ratio of ethanol solution, gadolinium nitrate and neodymium nitrate is 200:6.5-7.0:3.0-3.

5. ​ ​ The mass ratio of the zirconium oxychloride, ethanol solution in the zirconium source solution is 65-70:

500.

4. The method of claim 1, wherein the mass ratio of the modified mixed powder, tetrahydrofuran, and trimesoyl chloride solution in the step of preparing the reinforcing phase is 10:80-85:50-55. The trimesoyl chloride solution is a mixture of trimesoyl chloride and tetrahydrofuran, and the mass ratio of trimesoyl chloride to tetrahydrofuran is 0.4-0.5:

50.

5. The method of claim 1, wherein the TiB2 powder has a particle size of 120-150 nm. The AlN powder has a particle size of 90-100 nm. The mass ratio of the TiB2 powder, AlN powder, pretreatment solution, and modification solution is 10-15:7-10:130-140:120-125.

6. The method of claim 5, wherein the mass ratio of the deionized water, dodecyl dimethyl betaine, and polyvinyl alcohol in the pretreatment solution is 100:1.5-2.0:0.5-0.

8. The mass ratio of the deionized water to γ-aminopropyl triethoxysilane in the modification solution is 100:2.0-3.

0.

7. The method of claim 1, wherein the ultrasonic time in the coating step is 30-35 min, the ultrasonic power is 120-130 W, and the ultrasonic frequency is 30-36 kHz. The mass ratio of the reinforcing phase to the zirconia sol is 15-18:90-100.

8. The method of claim 1, wherein the ball milling time in the sintering step is 30-35 min, the ball milling speed is 210-220 rpm, and the ball-to-material ratio is 3-5:

1. The mass ratio of the boride zirconium, zirconia-coated reinforcing phase, LaB6, and Y2O3 mixture is 85-90:6-10:3-5:2-3. The modified boride zirconium ceramic is prepared by the method of any one of claims 1-8. The modified boride zirconium ceramic is prepared by the method of any one of claims 1-8. ​ ​ ​ 9. A modified zirconium boride ceramic characterized by, ​ 10. Use of a modified zirconium boride ceramic in electrolytic aluminium, characterized in that, ​

Images