High thermal shock resistance alumina ceramic material and method for manufacturing the same

Abstract

The application relates to the field of ceramic materials, in particular to a high-thermal-shock-resistance alumina ceramic material and a preparation method thereof, which comprises the following preparation raw materials in percentage by weight: 5-8% of organic silicon-coated carbon fibers, 5-10% of sintering aids, and the balance of alumina, wherein the prepared alumina ceramic material has excellent mechanical properties and good thermal shock resistance, and has a wide application range.

Description

Technical Field

[0001] This invention relates to the field of ceramic materials, specifically to a highly thermally shock resistant alumina ceramic material and its preparation method. Background Technology

[0002] Alumina ceramics possess many advantages, such as high strength, high hardness, good wear resistance and high-temperature resistance, good thermal conductivity, resistance to chemical corrosion, and electrical insulation. In modern engineering technology, alumina ceramics are widely used in many fields, including military weaponry, medical devices, optical components, aerospace, chemical engineering, and petroleum refining. However, alumina ceramics have a poor thermal shock resistance, which somewhat limits their application range. Summary of the Invention

[0003] Purpose of the invention: To address the above-mentioned technical problems, this invention proposes a highly thermally shock resistant alumina ceramic material and its preparation method.

[0004] The technical solution adopted is as follows:

[0005] A highly thermally shock resistant alumina ceramic material, by weight percentage, comprises the following raw materials:

[0006] The carbon fiber is coated with 5%-8% silicone, 5-10% sintering aid, and the balance is alumina.

[0007] Furthermore, the organosilicon-coated carbon fiber consists of a carbon fiber matrix and a polyethylene-based POSS-rare earth complex coated on the carbon fiber matrix.

[0008] Furthermore, the polyvinyl POSS-rare earth complex is obtained by reacting vinyl POSS with a mercapto compound, then reacting it with a rare earth salt, and finally undergoing free radical polymerization.

[0009] Furthermore, the method for preparing the organosilicon-coated carbon fiber is as follows:

[0010] Vinyl POSS, a mercapto compound, an initiator DMPA, and tetrahydrofuran were mixed, reacted under ultraviolet light, and concentrated under reduced pressure. Petroleum ether was added, crystallized at low temperature, filtered, and the resulting solid was dried and recorded as an intermediate. The intermediate and a rare earth salt in a 1:1 molar ratio were added to tetrahydrofuran, heated to reflux, concentrated under reduced pressure, and crystallized by adding methanol dropwise. The product was filtered and dried to obtain a vinyl POSS-rare earth complex. Carbon fibers were dispersed in a mixed solvent of DMSO / water, and the vinyl POSS-rare earth complex and a free radical initiator were added. The mixture was heated in a water bath, reacted, filtered, and the resulting product was dried.

[0011] Furthermore, the number of moles of vinyl in 1 mole of the vinyl POSS is ≥4, and the vinyl POSS is preferably an octavinyl POSS.

[0012] Furthermore, the thiol compound contains an ester group or a carboxyl group.

[0013] Furthermore, the structural formula of the thiol compound is shown below:

[0014] ;

[0015] R1 is a hydroxyl or methoxy group, and R2 is a hydrogen or carboxyl group.

[0016] Furthermore, the thiol compound is any one of the following compounds:

[0017] .

[0018] Furthermore, the rare earth salt is any one of water-soluble lanthanum salt, water-soluble neodymium salt, water-soluble samarium salt, water-soluble europium salt, and water-soluble ytterbium salt.

[0019] Furthermore, the rare earth salt is any one of lanthanum nitrate, neodymium nitrate, samarium nitrate, europium nitrate, and ytterbium nitrate.

[0020] Furthermore, the sintering aid is composed of magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, and magnesium fluoride.

[0021] Furthermore, the mass ratio of magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, and magnesium fluoride is 1-9:1-9:1-9:1-9:1-9, preferably 2:1:1:1:1.

[0022] This invention also provides a method for preparing alumina ceramic materials with high thermal shock resistance:

[0023] The carbon fiber coated with organosilicon, sintering aid and alumina are mixed, ball-milled and dried, granulated, pressed into shape and then debinded and sintered.

[0024] The beneficial effects of this invention are:

[0025] This invention provides a highly thermally shock resistant alumina ceramic material. The addition of carbon fibers allows external forces to be transferred to the alumina matrix through interfacial bonding, while the alumina matrix can also physically disperse stress to the carbon fibers. This synergistic effect enables the carbon fibers to bear the main load-bearing role when the ceramic material is subjected to external forces, while the alumina matrix enhances the overall strength of the ceramic material by transferring and dispersing stress, thereby improving the mechanical properties of the ceramic material.

[0026] During sintering, the polyethylene-based POSS-rare earth complex coating on the carbon fiber surface decomposes to generate silicon oxide and rare earth oxide. The silicon oxide, magnesium oxide, and aluminum oxide react during sintering to form cordierite, which has an extremely low coefficient of thermal expansion and excellent thermal shock resistance, thus coating the carbon fiber. This creates release channels within the ceramic material that resist thermal stress without causing damage. Furthermore, rare earth ions can replace the Mg in the cordierite lattice. 2+ Due to differences in ionic radius and charge, lattice distortion occurs, generating internal stress and strain, and forming stress vacancies. This helps to accelerate the sintering process, increase the ion diffusion rate, and promote the nucleation and growth of cordierite grains.

[0027] The addition of magnesium oxide can inhibit abnormal grain growth, reduce sintering temperature, promote sintering densification, and serve as a raw material for in-situ cordierite formation. Calcium oxide, zinc oxide, yttrium oxide, and magnesium fluoride can lower the sintering temperature, generate a liquid phase at a lower temperature, accelerate the elimination of pores in ceramics and the dissolution and precipitation of small grains onto the surface of large particles, inhibit excessive grain growth, promote grain refinement, and improve sintering density.

[0028] The alumina ceramic material prepared by this invention has excellent mechanical properties and good thermal shock resistance, and has a wide range of applications. Detailed Implementation

[0029] Unless otherwise specified in the examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products. Techniques not mentioned in this invention refer to existing technologies. Unless otherwise specified, the following examples and comparative examples are parallel experiments, using the same processing steps and parameters.

[0030] Example 1:

[0031] A highly thermally shock resistant alumina ceramic material, by weight percentage, comprises the following raw materials:

[0032] The composition is: 5% silicone-coated carbon fiber, 2% magnesium oxide, 1% calcium oxide, 1% zinc oxide, 1% yttrium oxide, 1% magnesium fluoride, and the balance is α-alumina.

[0033] The preparation method of organosilicon-coated carbon fiber is as follows:

[0034] 0.01 mol octavinylPOSS (CAS: 69655-76-1), 0.01 mol mercaptosuccinic acid (CAS: 70-49-5), 0.01 g initiator DMPA (CAS: 24650-42-8), and 100 ml tetrahydrofuran were added to a flask and stirred until completely dissolved. The mixture was then irradiated with 365 nm UV light at room temperature for 5 h. After the reaction was completed, the mixture was concentrated under reduced pressure to a volume of approximately 25 ml. 500 ml petroleum ether was added dropwise, and the mixture was crystallized in a cold trap at 0-5 °C for 10 h. The crystals were filtered, and the resulting solid was dried and recorded as an intermediate. The intermediate (1:1 molar ratio) and europium nitrate were added to tetrahydrofuran, and the mixture was heated to reflux for 24 h. The mixture was then concentrated under reduced pressure, and methanol was added dropwise to crystallize. The product was filtered and dried to obtain the vinylPOSS-europium complex. 1 g of carbon fiber (Toray T300 series, 2-3 mm in length and approximately 5 μm in diameter) was dispersed in 100 ml of... In a mixed solvent of DMSO and water (volume ratio 1:1), 1g of vinyl POSS-Eupoly complex and 0.01g of initiator BPO were added. After reacting in a water bath at 60°C for 5 hours, the mixture was filtered. The resulting product, after drying, became organosilicon-coated carbon fiber.

[0035] The preparation method of the above-mentioned high thermal shock resistant alumina ceramic material:

[0036] Organosilicon-coated carbon fibers, magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, magnesium fluoride, and α-alumina were placed in a ball mill jar. Anhydrous ethanol was selected as the dispersant (material-to-liquid mass ratio of 1:1.2), and an appropriate amount of zirconia balls were added as the milling medium. The mixture was ball-milled in a planetary ball mill for 2 hours at a speed of 500 r / min. After the milling time, the slurry mixture was removed and transferred to an oven to dry at 100℃ for 12 hours. The dried powder was then poured into an agate mortar and ground with the mortar head. Polyvinyl alcohol solution was then uniformly added to the powder mixture and thoroughly mixed. The powder was then sieved through a 250 μm sieve and pressed into shape in a steel mold at a pressure of 100 MPa for 1 minute. After molding, the blank is first debonded in a 650℃ debonding furnace for 2 hours. After cooling to room temperature, it is placed in a high-temperature box-type resistance furnace and sintered at 1450℃ for 2 hours at a rate of 5℃ / min. After sintering, it is naturally cooled to room temperature with the furnace.

[0037] Example 2:

[0038] A highly thermally shock resistant alumina ceramic material, by weight percentage, comprises the following raw materials:

[0039] The composition is: 6% silicone-coated carbon fiber, 2% magnesium oxide, 1% calcium oxide, 1% zinc oxide, 1% yttrium oxide, 1% magnesium fluoride, and the balance is α-alumina.

[0040] The preparation method of organosilicon-coated carbon fiber is the same as in Example 1.

[0041] The preparation method of the above-mentioned high thermal shock resistant alumina ceramic material:

[0042] Organosilicon-coated carbon fibers, magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, magnesium fluoride, and α-alumina were placed in a ball mill jar. Anhydrous ethanol was selected as the dispersant (material-to-liquid mass ratio of 1:1.2), and an appropriate amount of zirconia balls were added as the milling medium. The mixture was ball-milled in a planetary ball mill for 2 hours at a speed of 500 r / min. After the milling time, the slurry mixture was removed and transferred to an oven to dry at 100℃ for 12 hours. The dried powder was then poured into an agate mortar and ground with the mortar head. Polyvinyl alcohol solution was then uniformly added to the powder mixture and thoroughly mixed. The powder was then sieved through a 250 μm sieve and pressed into shape in a steel mold at a pressure of 100 MPa for 1 minute. After molding, the blank is first debonded in a 650℃ debonding furnace for 2 hours. After cooling to room temperature, it is placed in a high-temperature box-type resistance furnace and sintered at 1450℃ for 2 hours at a rate of 5℃ / min. After sintering, it is naturally cooled to room temperature with the furnace.

[0043] Example 3:

[0044] A highly thermally shock resistant alumina ceramic material, by weight percentage, comprises the following raw materials:

[0045] The composition is: 7% silicone-coated carbon fiber, 2% magnesium oxide, 1% calcium oxide, 1% zinc oxide, 1% yttrium oxide, 1% magnesium fluoride, and the balance is α-alumina.

[0046] The preparation method of organosilicon-coated carbon fiber is the same as in Example 1.

[0047] The preparation method of the above-mentioned high thermal shock resistant alumina ceramic material:

[0048] Organosilicon-coated carbon fibers, magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, magnesium fluoride, and α-alumina were placed in a ball mill jar. Anhydrous ethanol was selected as the dispersant (material-to-liquid mass ratio of 1:1.2), and an appropriate amount of zirconia balls were added as the milling medium. The mixture was ball-milled in a planetary ball mill for 2 hours at a speed of 500 r / min. After the milling time, the slurry mixture was removed and transferred to an oven to dry at 100℃ for 12 hours. The dried powder was then poured into an agate mortar and ground with the mortar head. Polyvinyl alcohol solution was then uniformly added to the powder mixture and thoroughly mixed. The powder was then sieved through a 250 μm sieve and pressed into shape in a steel mold at a pressure of 100 MPa for 1 minute. After molding, the blank is first debonded in a 650℃ debonding furnace for 2 hours. After cooling to room temperature, it is placed in a high-temperature box-type resistance furnace and sintered at 1450℃ for 2 hours at a rate of 5℃ / min. After sintering, it is naturally cooled to room temperature with the furnace.

[0049] Example 4:

[0050] A highly thermally shock resistant alumina ceramic material, by weight percentage, comprises the following raw materials:

[0051] The composition is: 8% silicone-coated carbon fiber, 2% magnesium oxide, 1% calcium oxide, 1% zinc oxide, 1% yttrium oxide, 1% magnesium fluoride, and the balance is α-alumina.

[0052] The preparation method of organosilicon-coated carbon fiber is the same as in Example 1.

[0053] The preparation method of the above-mentioned high thermal shock resistant alumina ceramic material:

[0054] Organosilicon-coated carbon fibers, magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, magnesium fluoride, and α-alumina were placed in a ball mill jar. Anhydrous ethanol was selected as the dispersant (material-to-liquid mass ratio of 1:1.2), and an appropriate amount of zirconia balls were added as the milling medium. The mixture was ball-milled in a planetary ball mill for 2 hours at a speed of 500 r / min. After the milling time, the slurry mixture was removed and transferred to an oven to dry at 100℃ for 12 hours. The dried powder was then poured into an agate mortar and ground with the mortar head. Polyvinyl alcohol solution was then uniformly added to the powder mixture and thoroughly mixed. The powder was then sieved through a 250 μm sieve and pressed into shape in a steel mold at a pressure of 100 MPa for 1 minute. After molding, the blank is first debonded in a 650℃ debonding furnace for 2 hours. After cooling to room temperature, it is placed in a high-temperature box-type resistance furnace and sintered at 1450℃ for 2 hours at a rate of 5℃ / min. After sintering, it is naturally cooled to room temperature with the furnace.

[0055] Comparative Example 1:

[0056] The process is basically the same as in Example 1, except that carbon fiber (Toray T300 series, 2-3 mm in length and about 5 μm in diameter) is used directly instead of silicone to coat the carbon fiber.

[0057] Comparative Example 2:

[0058] The method is basically the same as in Example 1, except that the preparation method of silicone-coated carbon fiber is as follows:

[0059] Take 1g of carbon fiber (Toray T300 series, length 2-3mm, diameter about 5μm) and disperse it in 100ml of mixed solvent of DMSO / water (volume ratio 1:1). Add 1g of octavinyl POSS (CAS:69655-76-1) and 0.01g of initiator BPO. React in a water bath at 60℃ for 5h and then filter. The resulting product is dried to obtain organosilicon-coated carbon fiber.

[0060] Comparative Example 3:

[0061] It is basically the same as Example 1, except that magnesium oxide is not added.

[0062] Comparative Example 4:

[0063] It is basically the same as Example 1, except that calcium oxide is not added.

[0064] Comparative Example 5:

[0065] It is basically the same as Example 1, except that zinc oxide is not added.

[0066] Comparative Example 6:

[0067] It is basically the same as Example 1, except that yttrium oxide is not added.

[0068] Comparative Example 7:

[0069] It is basically the same as Example 1, except that magnesium fluoride is not added.

[0070] Performance testing:

[0071] The alumina ceramic materials prepared in Examples 1-4 and Comparative Examples 1-7 of this invention were used as samples for performance testing.

[0072] According to GB / T 37246-2018 "Test Method for Thermal Shock Resistance of Fine Ceramics", the heating furnace is preheated to 1100±10℃ and held for 15 minutes. The sample is then quickly inserted into the sintering furnace and held for 20 minutes. The sample is then removed and quickly immersed in flowing water at 20±3℃. After rapid cooling in the water for 10 minutes, the sample is immediately removed and observed for cracks. If cracks are found, the test is stopped. If no cracks are found, the above process is repeated.

[0073] Bending strength refers to the ultimate stress at which the stress surface of a specimen breaks under bending stress. According to GB / T6569-2006 "Test Method for Bending Strength of Fine Ceramics", four-point 1 / 4 bending is adopted to calculate the room temperature bending strength of the specimen and the residual bending strength of the specimen without cracks after 20 water quenching cycles, and the strength retention rate is calculated.

[0074] The formula for calculating the strength retention rate is shown below;

[0075] σ = (λ2 / λ1) × 100%, where σ is the strength retention rate, λ1 is the room temperature bending strength, and λ2 is the residual bending strength after thermal shock.

[0076] The test results are shown in Table 1 below:

[0077] Table 1:

[0078]

[0079] As shown in Table 1 above, the alumina ceramic material prepared by this invention has excellent mechanical properties and good thermal shock resistance, and has a wide range of applications.

[0080] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A high thermal shock resistance alumina ceramic material, characterized by, The preparation raw materials include the following in percentage by weight: The silicone-coated carbon fiber 5%-8%, sintering aid 5-10%, and the balance of alumina; The silicone-coated carbon fiber is composed of a carbon fiber matrix and a polyvinyl POSS-rare earth complex coated on the carbon fiber matrix; The polyvinyl POSS-rare earth complex is obtained by reacting a vinyl POSS with a mercapto compound, then reacting and complexing with a rare earth salt, and finally free radical polymerization; The mercapto compound has the following structure: R1 is hydroxyl or methoxyl, and R2 is hydrogen or carboxyl; The sintering aid is composed of magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, and magnesium fluoride.

2. The high thermal shock resistance alumina ceramic material of claim 1, wherein, The number of moles of vinyl contained in 1 mole of the vinyl POSS is ≥4.

3. The high thermal shock resistance alumina ceramic material of claim 1, wherein, The rare earth salt is any one of a water-soluble lanthanum salt, a water-soluble neodymium salt, a water-soluble samarium salt, a water-soluble europium salt, and a water-soluble ytterbium salt.

4. The high thermal shock resistance alumina ceramic material of claim 1, wherein, The mass ratio of the magnesium oxide, calcium oxide, zinc oxide, yttrium oxide, and magnesium fluoride is 1-9:1-9:1-9:1-9:1-9.

5. A method of producing the high thermal shock resistance alumina ceramic material as claimed in any one of claims 1 to 4, characterized by, The silicone-coated carbon fiber, sintering aid, and alumina are mixed, ball milled, dried, granulated, pressed into shape, degreased, and sintered.

Images