A kind of high-strength corrosion-resistant alumina ceramic and preparation method thereof

Abstract

The invention discloses a high-strength corrosion-resistant alumina ceramic and a preparation method thereof, and belongs to the technical field of ceramic materials. The ceramic material is made of the following raw materials in parts by weight: 80-100 parts of alumina micropowder, 10-20 parts of modified nano alumina, 5-10 parts of corrosion-resistant agent, 0.3-0.8 parts of metal oxide additive, 1-1.5 parts of nanocomposite fiber, 5-10 parts of kaolin, and 1-3 parts of dispersant. The prepared alumina ceramic has excellent corrosion resistance and good mechanical properties, is suitable for use in various strong corrosion environments, and has good application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic materials, and in particular relates to a high-strength corrosion-resistant alumina ceramic and a preparation method thereof. Background Art

[0002] Ceramic materials are a type of inorganic non-metallic materials made from natural or compound materials through molding and high-temperature sintering. It has the advantages of high melting point, high hardness, high wear resistance, etc. Ceramic materials can be roughly divided into two categories. One is ordinary ceramic materials, which are mainly sintered from natural raw materials such as feldspar, clay and quartz, and are typical silicate materials. This type of ceramic material has abundant sources, low costs, and mature processes. According to performance characteristics and uses, it can be divided into daily ceramics, building ceramics, electrical insulation ceramics, chemical ceramics, etc. The other is special ceramic materials, also known as advanced ceramics or fine ceramics, which are mainly made of high-purity synthetic raw materials and are formed and sintered through precision control processes. It has a series of superior physical, chemical and biological properties and a wide range of applications. The main components of special ceramic materials include oxide ceramics (such as aluminum oxide, zirconium oxide, etc.), non-oxide ceramics (such as silicon nitride, silicon carbide, etc.) and metal ceramics. Alumina ceramics are mainly composed of aluminum oxide (Al2O3), which has physical and chemical properties such as high melting point, high hardness (second only to diamond), good wear resistance, good corrosion resistance, high chemical stability, high insulation and low dielectric loss. They are widely used in mechanical processing, aerospace, refractory materials, composite materials, electronic devices, energy engineering, bioengineering, wear resistance / corrosion resistance and other fields. Especially in occasions with corrosive environments, such as chemical industry, petroleum, metallurgy, etc., equipment often needs to operate in a corrosive environment. If the equipment material does not have sufficient corrosion resistance, it will cause equipment damage, performance degradation and even safety accidents. Therefore, the selection of materials with excellent corrosion resistance is crucial to ensure the safe operation of equipment and extend its service life. Alumina ceramics is such a material, and its excellent corrosion resistance makes it widely used in these fields.

[0003] However, conventional alumina ceramics still have problems of insufficient strength and limited corrosion resistance in certain extreme environments. Therefore, it is of great significance to develop an alumina ceramic material with both high strength and high corrosion resistance. Summary of the invention

[0004] The invention provides a high-strength corrosion-resistant alumina ceramic and a preparation method thereof. The prepared alumina ceramic has excellent corrosion resistance and good mechanical properties, is suitable for use in various strong corrosion environments, and has good application prospects.

[0005] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0006] A high-strength corrosion-resistant alumina ceramic is made from the following raw materials in parts by weight: 80-100 parts of alumina micropowder, 10-20 parts of modified nano alumina, 5-10 parts of corrosion resist, 0.3-0.8 parts of metal oxide additive, 1-1.5 parts of nano composite fiber, 5-10 parts of kaolin and 1-3 parts of dispersant.

[0007] Preferably, the alumina powder has a particle size of 5-10 μm.

[0008] Preferably, the preparation method of the modified nano-alumina is as follows: accurately weigh 5 g of stearic acid, add it to 100 ml of anhydrous ethanol, ultrasonically disperse it for 5-10 minutes, then add 5 g of nano-alumina, heat it to 55°C in a water bath, react with magnetic stirring for 2 hours, centrifuge, wash it with anhydrous ethanol several times, and dry it in an oven at 80°C for 2 hours; the particle size of the nano-alumina is 20-50 nm.

[0009] Preferably, the corrosion resist is composed of modified nano silicon dioxide and manganese dioxide in a mass ratio of 1:1.

[0010] Preferably, the preparation method of the modified nano-silica is as follows: 5 mL of TEOS is added to 50 mL of anhydrous ethanol, magnetically stirred in a 40°C water bath, the pH value is adjusted to 8.5 with dilute ammonia water, and magnetically stirred for 3.5 h, and then 6 mL of hexamethyldisilazane and 5 mL of anhydrous ethanol are added to the mixed solution, and magnetic stirring is continued for 2 h to obtain a milky white sol solution, which is allowed to stand at room temperature for 24 h, placed in an oven at 120°C for vacuum drying for 12 h, and then ground into powder.

[0011] Preferably, the metal oxide additive is composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:1.

[0012] Preferably, the nanocomposite fiber is prepared by the following method:

[0013] (a) First, 2.0 g of copper acetate (Cu(COOCH3)2·H2O) and 2.6 g of cobalt acetylacetonate (C 15 H 21 CoO6) was dissolved in 30 g of DMF solution and stirred until fully dissolved, then 2.1 g of polyacrylonitrile was added to the mixture and stirred at room temperature for 12 h to obtain a precursor solution after complete mixing;

[0014] (b) The precursor solution was injected into an electrospinning machine for spinning. During the spinning process, the distance between the spinning needle and the roller collector was set to 14 cm, the working voltage was set to 12 kV, and the injection speed was set to 0.02 mm / min. The prepared nanofiber membrane was collected and then placed in an oven for drying before use.

[0015] (c) The nanofiber membrane obtained in step (b) is placed in a tubular furnace, nitrogen is introduced, and heated to 200°C in a N2 atmosphere. After keeping the temperature for 1 h, it is then heated to 800°C at a rate of 5°C / min and naturally cooled to room temperature to obtain nanocomposite fibers.

[0016] Preferably, the dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1.

[0017] The present invention also provides a method for preparing the above-mentioned high-strength corrosion-resistant alumina ceramic, comprising the following steps:

[0018] (1) Alumina powder, modified nano-alumina, kaolin and dispersant are mixed in proportion and ball-milled for 6 hours to obtain a mixture;

[0019] (2) The remaining raw materials are mixed evenly with the mixture obtained in step (1), and anhydrous ethanol is used as the ball milling medium. The ball milling speed is set to 100 r / min, and the ball milling is continued for 20 hours to obtain a slurry;

[0020] (3) The mixed slurry is placed in a drying oven, dried at a constant temperature of 60°C for 24 hours, and then passed through an 80-mesh sieve. It is then placed in a hot press furnace and the pressure is set to 25-30 MPa. The first hot press sintering is performed at 500-600°C. After keeping the temperature for 1-2 hours, the second hot press sintering is performed at 800-900°C. After keeping the temperature for 2 hours, the third hot press sintering is performed at 1200-1350°C. After keeping the temperature for 2 hours, the product is obtained.

[0021] The raw materials used in the present invention are all commercially available unless otherwise specified.

[0022] In the above technical solution, micron-sized alumina and nano-sized alumina are compounded to optimize the particle grading, the small size effect and surface interface effect of nano-alumina, so that the nano-particles can more effectively fill and strengthen the microstructure of the ceramic material, reduce the pore size during the forming process of the ceramic blank, and improve the density and forming performance of the blank. At the same time, the nano-alumina used by the applicant is stearic acid-modified nano-alumina. Stearic acid is a low surface energy substance that can reduce the surface energy of alumina particles and change it from hydrophilic to hydrophobic. The hydrophobic nano-alumina and alumina powder work together to not only improve the corrosion resistance of alumina ceramic materials, but also improve the sintering performance of the material, reduce the sintering temperature, increase the sintering densification speed, and further improve the mechanical properties of the material.

[0023] The corrosion resist of the invention is composed of modified nano silicon dioxide and manganese dioxide. Hydrophilic SiO2 nanoparticles are generated by hydrolysis reaction and self-condensation reaction of tetraethyl orthosilicate (TEOS). The surfaces of the nanoparticles contain a large number of -OH groups, which can react with hexamethyldisilazane to make the hydrophilic silanol groups (Si-OH) generate ≡Si-O-Si(CH3)3 structures, so as to obtain hydrophobic groups. The surfaces of the hydrophilic SiO2 nanoparticles are covered with a large number of hydrophobic methyl groups, so as to obtain hydrophobic groups. The hydrophobic groups are then used together with manganese dioxide by physical mixing. The mixing produces a synergistic effect, further enhances the hydrophobicity and dispersibility of the nanoparticles, makes the highly hydrophobic nanoparticles more evenly distributed on the surface of the ceramic material matrix, forms a dense structure, and jointly improves the strength and corrosion resistance of the alumina ceramic material.

[0024] Further, a specific proportion of metal oxide additives is used to improve the sintering performance of alumina ceramics. Related studies have shown that sintering additives of different properties and different contents have great differences in the microstructure and mechanical properties of alumina ceramic system composite materials. The metal oxide additive composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:1 can effectively reduce the grain boundary migration rate of ceramics, so that the pores can be eliminated by using the grain boundaries as vacancy transfer channels, and finally promote the densification of alumina ceramics. At the same time, these additives can work synergistically to further reduce the sintering temperature, improve the density and mechanical properties of ceramics, and the addition of a specific content of additives can optimize the grain structure of alumina ceramics and improve the hardness and thermal shock resistance of alumina ceramics.

[0025] Due to the high hardness of alumina ceramic materials, it has high rigidity and lacks toughness, which makes alumina ceramics brittle and prone to cracks and fractures. The nanocomposite fiber used in the present invention has carbon elements as the skeleton, and copper and cobalt elements are evenly distributed on the surface of the fiber. From the results of scanning electron microscopy tests, it can be seen that its structural feature is that the cross-linked nanofibers form a nearly ordered 3D network structure, which can significantly improve the mechanical properties of alumina ceramics. When the nanocomposite fibers are composited with alumina ceramics, the carbon fibers, as a reinforcing phase, can effectively share the load and improve the tensile strength, flexural strength and compressive strength of the composite material. The addition of nanocomposite carbon fibers can also improve the fracture toughness of alumina ceramics, thereby delaying the expansion of cracks and improving the material's resistance to fracture; at the same time, the composite nanofibers doped with copper and cobalt elements can also significantly improve the acid and alkali resistance of alumina ceramic materials.

[0026] The dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1. The two work together to effectively disperse the alumina powder evenly in the liquid medium, prevent the powder from settling and agglomerating, thereby improving the uniformity and stability of the ceramic slurry. The dispersant can be adsorbed on the surface of the alumina particles to form a protective film, hindering the agglomeration between the particles, thereby improving the suspension stability of the ceramic slurry, preventing the particles from settling, and facilitating subsequent processing and forming.

[0027] The beneficial effects of the present invention are:

[0028] (1) Alumina powder and modified nano-alumina are used together to optimize the particle size distribution, effectively fill and strengthen the microstructure of ceramic materials, and have low porosity ( Figure 1 As shown in the figure, the hydrophobic nano-alumina and alumina powder work together to not only improve the corrosion resistance of alumina ceramic materials, but also improve the sintering performance of the materials, reduce the sintering temperature, increase the sintering densification speed, and further enhance the mechanical properties of the materials.

[0029] (2) The composite corrosion-resistant agent of the present invention works synergistically with alumina micropowder and modified nano-alumina, which increases the mechanical properties of alumina ceramics while also improving the corrosion resistance of the material. When facing erosion in extreme environments such as seawater or chemical industry, the internal structure is not easily destroyed, allowing the alumina ceramics to maintain a long-term stable structure.

[0030] (3) The nanocomposite fibers used in the present invention work together with alumina ceramics to effectively improve the tensile strength, flexural strength and compressive strength of the composite material, and the copper and cobalt elements ( Figure 2 The nanocomposite fiber, corrosion resistant agent and multi-level alumina powder work together to form a fiber bridge reinforcement structure, which strengthens the strength of the internal structure and provides strong support for the internal structure, forming an excellent corrosion-resistant alumina ceramic material with good structural stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a scanning electron microscope image of the surface of the alumina ceramic material prepared in Example 3 of the present invention;

[0032] Figure 2 These are scanning electron microscope images and local transmission electron microscope images of the nanocomposite fiber used in Example 3 of the present invention, wherein a) is a SEM image and b) is a TEM image. DETAILED DESCRIPTION

[0033] The technical solution of the present invention is further described below in conjunction with specific embodiments, but is not limited thereto.

[0034] Example 1

[0035] A high-strength corrosion-resistant alumina ceramic is made from the following raw materials in parts by weight: 80 parts of alumina micropowder, 10 parts of modified nano alumina, 5 parts of corrosion-resistant agent, 0.3 parts of metal oxide additive, 1 part of nano composite fiber, 5 parts of kaolin and 1 part of dispersant.

[0036] The particle size of the alumina powder is 5-10 μm.

[0037] The preparation method of the modified nano-alumina is as follows: accurately weigh 5g of stearic acid, add it to 100ml of anhydrous ethanol, ultrasonically disperse it for 5-10min, then add 5g of nano-alumina, heat it to 55°C in a water bath, react with magnetic stirring for 2h, centrifuge, wash it with anhydrous ethanol several times, and dry it in an oven at 80°C for 2h; the particle size of the nano-alumina is 20-50nm.

[0038] The corrosion resist is composed of modified nano silicon dioxide and manganese dioxide in a mass ratio of 1:1.

[0039] The preparation method of the modified nano-silica is as follows: 5 mL of TEOS is added to 50 mL of anhydrous ethanol, magnetically stirred in a water bath at 40° C., the pH value is adjusted to 8.5 with dilute ammonia water, and magnetically stirred for 3.5 hours, and then 6 mL of hexamethyldisilazane and 5 mL of anhydrous ethanol are added to the mixed solution, and the magnetic stirring is continued for 2 hours to obtain a milky white sol solution, which is placed at room temperature for 24 hours, placed in an oven at 120° C. and vacuum dried for 12 hours, and then ground into powder.

[0040] The metal oxide additive is composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:1.

[0041] The nanocomposite fiber is prepared by the following method:

[0042] (a) First, 2.0 g of copper acetate (Cu(COOCH3)2·H2O) and 2.6 g of cobalt acetylacetonate (C 15 H 21 CoO6) was dissolved in 30 g of DMF solution and stirred until fully dissolved, then 2.1 g of polyacrylonitrile was added to the mixture and stirred at room temperature for 12 h to obtain a precursor solution after complete mixing;

[0043] (b) The precursor solution was injected into an electrospinning machine for spinning. During the spinning process, the distance between the spinning needle and the roller collector was set to 14 cm, the working voltage was set to 12 kV, and the injection speed was set to 0.02 mm / min. The prepared nanofiber membrane was collected and then placed in an oven for drying before use.

[0044] (c) The nanofiber membrane obtained in step (b) is placed in a tubular furnace, nitrogen is introduced, and heated to 200°C in a N2 atmosphere. After keeping the temperature for 1 h, it is then heated to 800°C at a rate of 5°C / min and naturally cooled to room temperature to obtain nanocomposite fibers.

[0045] The dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1.

[0046] The preparation method of the above-mentioned high-strength corrosion-resistant alumina ceramic is as follows:

[0047] (1) Alumina powder, modified nano-alumina, kaolin and dispersant are mixed in proportion and ball-milled for 6 hours to obtain a mixture;

[0048] (2) The remaining raw materials are mixed evenly with the mixture obtained in step (1), and anhydrous ethanol is used as the ball milling medium. The ball milling speed is set to 100 r / min, and the ball milling is continued for 20 hours to obtain a slurry;

[0049] (3) The mixed slurry is placed in a drying oven, dried at a constant temperature of 60°C for 24 hours, and then passed through an 80-mesh sieve. It is then placed in a hot press furnace and the pressure is set to 25-30 MPa. The first hot press sintering is performed at 500-600°C. After keeping the temperature for 1-2 hours, the second hot press sintering is performed at 800-900°C. After keeping the temperature for 2 hours, the third hot press sintering is performed at 1200-1350°C. After keeping the temperature for 2 hours, the product is obtained.

[0050] Example 2

[0051] A high-strength corrosion-resistant alumina ceramic is made from the following raw materials in parts by weight: 90 parts of alumina micropowder, 15 parts of modified nano alumina, 8 parts of corrosion-resistant agent, 0.5 parts of metal oxide additive, 1.2 parts of nano composite fiber, 8 parts of kaolin and 2 parts of dispersant.

[0052] The particle size of the alumina powder is 5-10 μm.

[0053] The preparation method of the modified nano-alumina is as follows: accurately weigh 5g of stearic acid, add it to 100ml of anhydrous ethanol, ultrasonically disperse it for 5-10min, then add 5g of nano-alumina, heat it to 55°C in a water bath, react with magnetic stirring for 2h, centrifuge, wash it with anhydrous ethanol several times, and dry it in an oven at 80°C for 2h; the particle size of the nano-alumina is 20-50nm.

[0054] The corrosion resist is composed of modified nano silicon dioxide and manganese dioxide in a mass ratio of 1:1.

[0055] The preparation method of the modified nano-silica is as follows: 5 mL of TEOS is added to 50 mL of anhydrous ethanol, magnetically stirred in a water bath at 40° C., the pH value is adjusted to 8.5 with dilute ammonia water, and magnetically stirred for 3.5 hours, and then 6 mL of hexamethyldisilazane and 5 mL of anhydrous ethanol are added to the mixed solution, and the magnetic stirring is continued for 2 hours to obtain a milky white sol solution, which is placed at room temperature for 24 hours, placed in an oven at 120° C. and vacuum dried for 12 hours, and then ground into powder.

[0056] The metal oxide additive is composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:1.

[0057] The nanocomposite fiber is prepared by the following method:

[0058] (a) First, 2.0 g of copper acetate (Cu(COOCH3)2·H2O) and 2.6 g of cobalt acetylacetonate (C 15 H 21 CoO6) was dissolved in 30 g of DMF solution and stirred until fully dissolved, then 2.1 g of polyacrylonitrile was added to the mixture and stirred at room temperature for 12 h to obtain a precursor solution after complete mixing;

[0059] (b) The precursor solution was injected into an electrospinning machine for spinning. During the spinning process, the distance between the spinning needle and the roller collector was set to 14 cm, the working voltage was set to 12 kV, and the injection speed was set to 0.02 mm / min. The prepared nanofiber membrane was collected and then placed in an oven for drying before use.

[0060] (c) The nanofiber membrane obtained in step (b) is placed in a tubular furnace, nitrogen is introduced, and heated to 200°C in a N2 atmosphere. After keeping the temperature for 1 h, it is then heated to 800°C at a rate of 5°C / min and naturally cooled to room temperature to obtain nanocomposite fibers.

[0061] The dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1.

[0062] The preparation method of the above-mentioned high-strength corrosion-resistant alumina ceramic is as follows:

[0063] (1) Alumina powder, modified nano-alumina, kaolin and dispersant are mixed in proportion and ball-milled for 6 hours to obtain a mixture;

[0064] (2) The remaining raw materials are mixed evenly with the mixture obtained in step (1), and anhydrous ethanol is used as the ball milling medium. The ball milling speed is set to 100 r / min, and the ball milling is continued for 20 hours to obtain a slurry;

[0065] (3) The mixed slurry is placed in a drying oven, dried at a constant temperature of 60°C for 24 hours, and then passed through an 80-mesh sieve. It is then placed in a hot press furnace and the pressure is set to 25-30 MPa. The first hot press sintering is performed at 500-600°C. After keeping the temperature for 1-2 hours, the second hot press sintering is performed at 800-900°C. After keeping the temperature for 2 hours, the third hot press sintering is performed at 1200-1350°C. After keeping the temperature for 2 hours, the product is obtained.

[0066] Example 3

[0067] A high-strength corrosion-resistant alumina ceramic is made from the following raw materials in parts by weight: 100 parts of alumina micropowder, 20 parts of modified nano alumina, 10 parts of corrosion-resistant agent, 0.8 parts of metal oxide additive, 1.5 parts of nano composite fiber, 10 parts of kaolin and 3 parts of dispersant.

[0068] The particle size of the alumina powder is 5-10 μm.

[0069] The preparation method of the modified nano-alumina is as follows: accurately weigh 5g of stearic acid, add it to 100ml of anhydrous ethanol, ultrasonically disperse it for 5-10min, then add 5g of nano-alumina, heat it to 55°C in a water bath, react with magnetic stirring for 2h, centrifuge, wash it with anhydrous ethanol several times, and dry it in an oven at 80°C for 2h; the particle size of the nano-alumina is 20-50nm.

[0070] The corrosion resist is composed of modified nano silicon dioxide and manganese dioxide in a mass ratio of 1:1.

[0071] The preparation method of the modified nano-silica is as follows: 5 mL of TEOS is added to 50 mL of anhydrous ethanol, magnetically stirred in a water bath at 40° C., the pH value is adjusted to 8.5 with dilute ammonia water, and magnetically stirred for 3.5 hours, and then 6 mL of hexamethyldisilazane and 5 mL of anhydrous ethanol are added to the mixed solution, and the magnetic stirring is continued for 2 hours to obtain a milky white sol solution, which is placed at room temperature for 24 hours, placed in an oven at 120° C. and vacuum dried for 12 hours, and then ground into powder.

[0072] The metal oxide additive is composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:1.

[0073] The nanocomposite fiber is prepared by the following method:

[0074] (a) First, 2.0 g of copper acetate (Cu(COOCH3)2·H2O) and 2.6 g of cobalt acetylacetonate (C 15 H 21CoO6) was dissolved in 30 g of DMF solution and stirred until fully dissolved, then 2.1 g of polyacrylonitrile was added to the mixture and stirred at room temperature for 12 h to obtain a precursor solution after complete mixing;

[0075] (b) The precursor solution was injected into an electrospinning machine for spinning. During the spinning process, the distance between the spinning needle and the roller collector was set to 14 cm, the working voltage was set to 12 kV, and the injection speed was set to 0.02 mm / min. The prepared nanofiber membrane was collected and then placed in an oven for drying before use.

[0076] (c) The nanofiber membrane obtained in step (b) is placed in a tubular furnace, nitrogen is introduced, and heated to 200°C in a N2 atmosphere. After keeping the temperature for 1 h, it is then heated to 800°C at a rate of 5°C / min and naturally cooled to room temperature to obtain nanocomposite fibers.

[0077] The dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1.

[0078] The preparation method of the above-mentioned high-strength corrosion-resistant alumina ceramic is as follows:

[0079] (1) Alumina powder, modified nano-alumina, kaolin and dispersant are mixed in proportion and ball-milled for 6 hours to obtain a mixture;

[0080] (2) The remaining raw materials are mixed evenly with the mixture obtained in step (1), and anhydrous ethanol is used as the ball milling medium. The ball milling speed is set to 100 r / min, and the ball milling is continued for 20 hours to obtain a slurry;

[0081] (3) The mixed slurry is placed in a drying oven, dried at a constant temperature of 60°C for 24 hours, and then passed through an 80-mesh sieve. It is then placed in a hot press furnace and the pressure is set to 25-30 MPa. The first hot press sintering is performed at 500-600°C. After keeping the temperature for 1-2 hours, the second hot press sintering is performed at 800-900°C. After keeping the temperature for 2 hours, the third hot press sintering is performed at 1200-1350°C. After keeping the temperature for 2 hours, the product is obtained.

[0082] Comparative Example 1

[0083] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the modified nano alumina is replaced by an equal amount of alumina powder.

[0084] Comparative Example 2

[0085] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the modified nano-alumina is replaced by an equal amount of unmodified nano-alumina.

[0086] Comparative Example 3

[0087] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the corrosion-resistant agent is only modified nano-silicon dioxide.

[0088] Comparative Example 4

[0089] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the corrosion-resistant agent is only manganese dioxide.

[0090] Comparative Example 5

[0091] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that it does not contain a corrosion-resistant agent.

[0092] Comparative Example 6

[0093] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that it does not contain a nano-composite fiber component.

[0094] Comparative Example 7

[0095] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the dispersant is only polyacrylamide.

[0096] Comparative Example 8

[0097] A high-strength, corrosion-resistant alumina ceramic, which is different from Example 3 in that the dispersant is only cocamidopropyl betaine.

[0098] Performance Testing

[0099] The properties of the alumina ceramics prepared in Examples 1-3 and Comparative Examples 1-8 were tested, and the specific test results are shown in the following table.

[0100] The apparent porosity was determined by microscopic analysis. The compressive strength of each sample was tested according to GB / T4740-1999 "Test method for compressive strength of ceramic materials". The flexural strength of each sample was tested according to GB / T 6569-2006 "Test method for flexural strength of fine ceramics". The fracture toughness value of each sample was tested according to GB / T23806-2009 "Test method for fracture toughness of fine ceramics - single-edge pre-cracked beam (SEPB) method". The breakdown strength of the samples was determined at room temperature using a ZYS-75 high-voltage testing device.

[0101] Table 1 Performance test results

[0102]

[0103] From the data in Table 1, it can be seen that the high-strength corrosion-resistant alumina ceramics prepared in Examples 1-3 of the present invention have low apparent porosity, and their compressive strength, flexural strength and fracture toughness are all higher than those of Comparative Examples 1-8. This indicates that the raw materials in the present invention work together to achieve a synergistic effect, and the effect will be weakened if one of them is missing.

[0104] Corrosion resistance effect verification: The high-strength corrosion-resistant alumina ceramics of Example 1-3 and Comparative Example 1-8 were made into 10cm*10cm*2cm samples, and the samples were washed with clean water. After draining, the mass of the sample m1 was recorded. Then the samples were immersed in 3 mmol / L HNO3 solution and NaOH solution for 60 days, and the samples were washed with clean water after being taken out. After draining, the mass of the sample m2 was recorded again. The mass loss rate was calculated according to the formula and recorded in Table 2. Mass loss rate (%) = ×100%. At the same time, the bending strength of the samples treated with HNO3 solution and NaOH solution was tested again, and the specific results are shown in Table 2.

[0105] Table 2 Corrosion resistance test results

[0106]

[0107] From the data in Table 2, it can be seen that by comparing the results of Examples 1-3 with Comparative Examples 1-2, it can be found that no matter in acid solution or alkaline solution, the mass loss rate of the present invention is significantly lower than that of Comparative Examples 1-2, and the bending strength change is also small. This is mainly due to the combined effect of alumina micropowders of different particle sizes and hydrophobically modified alumina nanoparticles. On the one hand, through the small size effect and surface interface effect of nano-alumina, the nanoparticles can more effectively fill and strengthen the microstructure of the ceramic material to form a denser alumina ceramic matrix, thereby reducing the entry of corrosive liquids. On the other hand, the modified nano-alumina has strong hydrophobicity, which makes it difficult for corrosive liquids to enter the alumina ceramic matrix. The two effects work together to achieve a good corrosion resistance effect.

[0108] Comparing the data of comparative examples 3-5 with the data of embodiments 1-3, it can be seen that the increase of corrosion inhibitor can significantly improve the corrosion resistance of alumina ceramics. Although a single modified nano-silicon dioxide and a single manganese dioxide can also play a certain role in corrosion resistance, the two have a synergistic effect when used together, and their mass loss rate in acid and alkali solutions is much lower than the sum of the effects of the two substances acting alone.

[0109] Comparison of the results of Comparative Example 6 with those of Examples 1-3 shows that the addition of nanocomposite fibers can effectively share the load and improve the tensile strength, bending strength and compressive strength of the composite material. At the same time, the addition of nanocomposite carbon fibers can also significantly improve the acid and alkali resistance of alumina ceramic materials.

[0110] Comparison of the data of Comparative Examples 7-8 with Examples 1-3 shows that the use of different dispersants will also affect the mechanical properties and corrosion resistance of alumina ceramics. This is because the dispersant can effectively disperse the alumina powder evenly in the liquid medium, prevent the deposition and aggregation of the powder, thereby improving the uniformity and stability of the ceramic slurry, and the dispersant can be adsorbed on the surface of the alumina particles to form a protective film to hinder the agglomeration between the particles, thereby improving the suspension stability of the ceramic slurry, preventing the particles from settling, facilitating subsequent processing and molding, and thus improving the mechanical properties of the ceramic material.

[0111] It should be noted that the above embodiments are only partial embodiments of the preferred methods of implementing the present invention, rather than all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

Claims

1. A high-strength, corrosion-resistant alumina ceramic, characterized in that: It is made of the following raw materials in parts by weight: 80-100 parts of alumina powder, 10-20 parts of modified nano alumina, 5-10 parts of corrosion resistant agent, 0.3-0.8 parts of metal oxide additive, 1-1.5 parts of nano composite fiber, 5-10 parts of kaolin, and 1-3 parts of dispersant; The preparation method of the modified nano-alumina is as follows: accurately weigh 5g of stearic acid, add it to 100ml of anhydrous ethanol, ultrasonically disperse it for 5-10min, then add 5g of nano-alumina, heat it to 55°C in a water bath, stir it with a magnetic stirrer for 2h, centrifuge it, wash it with anhydrous ethanol several times, and dry it in an oven at 80°C for 2h to obtain the nano-alumina; the particle size of the nano-alumina is 20-50nm; The corrosion resist is composed of modified nano silicon dioxide and manganese dioxide in a mass ratio of 1:1; The dispersant is composed of polyacrylamide and cocamidopropyl betaine in a mass ratio of 2:1; The nanocomposite fiber is prepared by the following method: (a) First, 2.0 g Cu(COOCH3)2·H2O and 2.6 g cobalt acetylacetonate were dissolved in 30 g DMF solution and stirred until fully dissolved. Then, 2.1 g polyacrylonitrile was added to the mixture and stirred at room temperature for 12 h. After complete mixing, a precursor solution was obtained. (b) The precursor solution was injected into an electrospinning machine for spinning. During the spinning process, the distance between the spinning needle and the roller collector was set to 14 cm, the working voltage was set to 12 kV, and the injection speed was set to 0.02 mm / min. The prepared nanofiber membrane was collected and then placed in an oven for drying before use. (c) The nanofiber membrane obtained in step (b) is placed in a tubular furnace, nitrogen is introduced, and heated to 200°C in a N2 atmosphere. After being kept warm for 1 hour, it is then heated to 800°C at a rate of 5°C / min and naturally cooled to room temperature to obtain nanocomposite fibers.

2. The high-strength corrosion-resistant alumina ceramic according to claim 1, characterized in that: The particle size of the alumina powder is 5-10 μm.

3. The high-strength corrosion-resistant alumina ceramic according to claim 1, characterized in that: The preparation method of the modified nano-silica is as follows: 5 mL of TEOS is added to 50 mL of anhydrous ethanol, magnetically stirred in a water bath at 40° C., the pH value is adjusted to 8.5 with dilute ammonia water, and magnetically stirred for 3.5 hours, and then 6 mL of hexamethyldisilazane and 5 mL of anhydrous ethanol are added to the mixed solution, and the magnetic stirring is continued for 2 hours to obtain a milky white sol solution, which is placed at room temperature for 24 hours, placed in an oven at 120° C. and vacuum dried for 12 hours, and then ground into powder.

4. The high-strength corrosion-resistant alumina ceramic according to claim 1, characterized in that: The metal oxide additive is composed of lanthanum fluoride, magnesium oxide and zinc oxide in a mass ratio of 1:2:

1.

5. A method for preparing the high-strength corrosion-resistant alumina ceramic according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Alumina powder, modified nano-alumina, kaolin and a dispersant are mixed in proportion and ball-milled for 6 hours to obtain a mixture; (2) The remaining raw materials are mixed evenly with the mixture obtained in step (1), and anhydrous ethanol is used as the ball milling medium. The ball milling speed is set to 100 r / min, and the ball milling is continued for 20 hours to obtain a slurry; (3) The mixed slurry is placed in a drying oven, dried at a constant temperature of 60°C for 24 hours, and then passed through an 80-mesh sieve. It is then placed in a hot press furnace and the pressure is set to 25-30 MPa. The first hot press sintering is performed at 500-600°C. After keeping the temperature for 1-2 hours, the second hot press sintering is performed at 800-900°C. After keeping the temperature for 2 hours, the third hot press sintering is performed at 1200-1350°C. After keeping the temperature for 2 hours, the product is obtained.

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