Composite structure transparent ceramic and method of making the same

Abstract

This invention discloses a composite transparent ceramic and its preparation method, belonging to the field of ceramic materials technology. To address the problems of poor uniformity, thermal shock resistance, and mechanical properties in existing yttrium-magnesium multiphase transparent ceramics, this invention provides a composite transparent ceramic and its preparation method, comprising: preparing Y₂O₃-MgO nanoparticles into multiphase transparent ceramic powder; obtaining a yttrium-magnesium multiphase layer through molding and sintering; then covering the yttrium-magnesium multiphase layer with zirconium oxide, etc., and through the bonding effect between zirconium oxide and the yttrium-magnesium multiphase layer, combined with molding, sintering, and polishing, to obtain the composite transparent ceramic. This invention adds a composite layer of materials such as zirconium oxide to the surface of the yttrium-magnesium multiphase transparent ceramic, ensuring the stability of the composite structure and significantly improving the thermal shock resistance and flexural strength of the composite transparent ceramic.

Description

Technical Field

[0001] This invention belongs to the field of ceramic materials technology, specifically relating to a composite transparent ceramic and its preparation method. Background Technology

[0002] Infrared imaging, infrared precision guidance, and infrared countermeasures technologies hold strategic importance in modern military applications. Infrared windows and radomes are key components of infrared technology. With the expansion of infrared material applications, infrared-transparent window and radome materials need to meet the following performance requirements: high mechanical strength, infrared transmittance, and thermal shock resistance. In recent years, researchers have made breakthroughs in some existing infrared materials, such as sapphire, magnesium aluminum spinel, ALON, and yttrium oxide. However, while these materials have their own advantages, they also face problems such as high thermal emissivity, short long-wavelength cutoff edges, or decreased mechanical properties with increasing temperature. Therefore, researchers have introduced the concept of multiphase ceramics into infrared-transparent ceramics, aiming to increase the mechanical properties of the ceramics while reducing their own radiation to meet the application requirements in high-speed environments.

[0003] Research has found that, theoretically, when yttrium oxide and magnesium oxide are uniformly distributed in a 1:1 volume ratio to form a nano-composite ceramic, this material would possess excellent mid-infrared transmittance, high flexural strength, and extremely low high-temperature emissivity, making it a promising candidate for infrared window materials in future hypersonic vehicles. However, due to the problem of uneven distribution, yttrium-magnesium composite transparent ceramics struggle to achieve the theoretically high performance.

[0004] As is well known, zirconia ceramics possess high flexural strength, fracture toughness, and Vickers hardness, making them among the strongest ceramic materials. Furthermore, due to their low thermal conductivity, zirconia ceramics perform exceptionally well in thermal insulation applications. Meanwhile, 3 mol yttrium-stabilized zirconia (3YSZ) theoretically boasts an infrared transmittance of up to 78%, excellent mechanical properties, and a sintering temperature close to that of yttrium-magnesium multiphase ceramics.

[0005] CN20131018681.0 discloses a method for preparing Y2O3 and MgO co-doped transparent ceramics at low temperature by microwave sintering. The method uses ZrO2 as a matrix, with Y2O3 at a ratio of 5-10 mol% and MgO at 0.05-0.2 mol%, and H2C2O4·2H2O at a corresponding concentration of 3 mol / L. Y(NO3)3·6H2O, Mg(NO3)3·6H2O, Zr(NO3)4·5H2O, and H2C2O4·2H2O are mixed together, and 0.3-0.6% of a surfactant is added. The raw material was placed in a ceramic ball mill jar with a mass ratio of 2:1 to ceramic balls. Ethanol was added as a lubricant, and the mixture was ball-milled at 200 r / min for 3 hours at room temperature. The product was washed 5 times with distilled water and then 3 times with ethanol. It was then dried in an oven at 80°C. The resulting precursor was ground and calcined at 900°C for 2 hours to obtain ZrO2 nanoparticles co-doped with Y2O3 and MgO. The nanoparticles were first dry-pressed at 50–90 MPa and then isostatically pressed at 250–350 MPa. After pressing, the powder was sintered at low temperature in a microwave sintering furnace to prepare ZrO2-based transparent ceramics.

[0006] CN20141049109.4 discloses a method for preparing transparent fluorescent ceramics for LEDs, comprising the following steps: A. Mixing ceramic raw material powder, sintering aid, and phosphor in a certain proportion; adding the mixture to a ball mill jar, along with milling media and milling balls, and milling for a certain time to obtain a mixture; B. Removing the mixture, drying it, grinding it, and sieving it; C. Sequentially performing dry pressing and cold isostatic pressing on the sieved powder to obtain a blank; D. Sequentially performing vacuum sintering and hot isostatic pressing sintering on the blank formed in step C; E. Annealing treatment to obtain the final product; wherein the ceramic raw material powder is selected from one or more of Al2O3, Y2O3, MgAl2O4, MgAlON, AlN, SiN, ZrO2, and SiC; the sintering aid is selected from one or more of CaO, MgO, TiO2, SiO2, MnO, and kaolin; the phosphor is composed of Y2O3. 15 O 12 Ce 3+ .

[0007] CN20191058678.7 discloses a method for preparing transparent ceramics, comprising the following steps: S1: placing oxide powder and sintering aid together in a ball mill jar at a certain weight percentage, while adding an appropriate amount of deionized water or anhydrous ethanol, and continuously ball milling at room temperature for 2-12 hours; S2: after ball milling, placing the slurry in an oven to dry; S3: crushing the dried sample and then passing it through a 200-400 mesh sieve; S4: subjecting the obtained powder to pre-pressing, cold isostatic pressing, and high-temperature sintering in sequence; S5: grinding and polishing the sintered material to obtain transparent ceramics; wherein the oxide powder is selected from any one or combination of Y2O3, Al2O3, Sc2O3, and Lu2O3, or a composite containing at least two of the aforementioned oxide elements; wherein the sintering aid is selected from any two or more of MgO, ZrO2, LiF, and SiO2.

[0008] CN20241090520.7 discloses a method for preparing yttrium magnesium multiphase transparent ceramics by non-aqueous injection molding, comprising the following steps: A. Mixing Y2O3 nanoparticles, MgO nanoparticles, dispersant, and non-aqueous solvent, performing a first ball milling, then adding epoxy resin and curing agent, and performing a second ball milling to obtain a ceramic slurry; B. After defoaming, curing, and drying, the ceramic slurry obtained in step A is obtained as a ceramic green body; C. Calcining the ceramic green body obtained in step B in air at 400–850℃ for debinding treatment, then heating to 1000–1500℃ for sintering densification, cooling, and then hot isostatic pressing sintering at 1000–1500℃ under high pressure and inert atmosphere, and finally annealing and polishing to obtain yttrium magnesium multiphase transparent ceramics.

[0009] Although all four methods described above disclose a transparent ceramic, they all use zirconium oxide as the dopant phase. Theoretically, yttrium-magnesium multiphase transparent ceramics have Y-Mg particles arranged uniformly in an ABAB pattern, resulting in excellent theoretical properties. However, in reality, it is difficult to achieve the theoretically ideal uniformity in yttrium-magnesium multiphase ceramics regardless of the method used. Furthermore, although single-phase zirconium oxide ceramics exhibit excellent hardness and thermal shock resistance, dispersing zirconium oxide in multiphase powders still fails to solve the uniformity problem.

[0010] It is evident that yttrium oxide-magnesium oxide nanocomposite ceramics prepared by existing technologies exhibit poor uniformity, poor thermal shock resistance, and poor mechanical properties. Consequently, the thermal shock resistance of large-size transparent multiphase ceramics is insufficient to meet the demands of high Mach applications. Furthermore, there are currently no reports on the preparation of yttrium-magnesium nanocomposite transparent ceramics using composite layer technology. Summary of the Invention

[0011] The purpose of this invention is to provide a composite transparent ceramic structure for preparing yttrium-magnesium multiphase ceramics using zirconia or other composite layer materials, overcoming the problem of poor thermal shock resistance in large-size Y₂O₃-MgO nano-multiphase infrared transparent ceramics. This invention utilizes 3YSZ and other materials to form a composite structure with yttrium-magnesium multiphase ceramics, adding a layer of zirconia or other materials to the yttrium-magnesium multiphase matrix, and then obtaining ZrO₂ (or alumina, or magnesium aluminum spinel)-Y₂O₃-MgO nano-multiphase infrared transparent ceramics through molding, sintering, and polishing. This method is expected to improve the thermal shock resistance of yttrium-magnesium multiphase ceramics.

[0012] This invention first provides a method for preparing a composite transparent ceramic, which includes the following steps:

[0013] A. Y2O3-MgO nanoparticles and organic solvents are mixed and ball-milled to obtain a ceramic slurry, which is then dried and sieved to obtain a multiphase transparent ceramic powder.

[0014] B1. The multiphase transparent ceramic powder obtained in step A is subjected to a first dry pressing to obtain a yttrium magnesium multiphase ceramic blank; the composite layer material nanopowder is uniformly covered or sprayed onto the yttrium magnesium multiphase ceramic blank, and then subjected to a second dry pressing, followed by cold isostatic pressing to obtain a composite structure ceramic blank; in step B1, the composite layer material is at least one of zirconium oxide, alumina, or magnesium aluminum spinel;

[0015] C1. The composite structure ceramic green body obtained in step B1 is pre-fired in air atmosphere, then heated for densification sintering to obtain a ceramic green body, and then hot isostatic pressing sintered in inert atmosphere.

[0016] D. After sintering (i.e., after hot isostatic pressing sintering in step C1, or after the second pressing sintering in step C), anneal in air atmosphere and polish to obtain a composite transparent ceramic.

[0017] In the preparation method of the above-mentioned composite transparent ceramic, in step A, the mass ratio of the Y2O3-MgO nanopowder to the organic solvent is 1 to 10:1.

[0018] In the preparation method of the above-mentioned composite transparent ceramic, the organic solvent in step A is ethanol.

[0019] In the preparation method of the above-mentioned composite transparent ceramic, in step A, during ball milling, zirconia balls or alumina balls are used as milling balls, and the mass ratio of the milling balls to Y2O3-MgO nanopowder is 30:1 to 10.

[0020] In the preparation method of the above-mentioned composite transparent ceramic, in step A, the ball milling conditions are: ball milling at a speed of 150-220 rad / s for 16-30 hours.

[0021] In the preparation method of the above-mentioned composite transparent ceramic, in step A, the mesh size of the sieve used for sieving is 100 to 200 mesh.

[0022] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the mass ratio of the composite layer material powder to the multiphase transparent ceramic powder is 1:1 to 4.

[0023] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the pressure of the first dry pressing is 5-20 MPa.

[0024] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the time for the first dry pressing is 2 to 10 minutes.

[0025] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the pressure of the second dry pressing is 5-20 MPa.

[0026] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the time for the second dry pressing is 2 to 10 minutes.

[0027] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the pressure of the cold isostatic pressing is 100-200 MPa.

[0028] In the preparation method of the above-mentioned composite transparent ceramic, in step B1, the cold isostatic pressing time is 2 to 5 minutes.

[0029] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the pre-firing temperature is 400-850℃.

[0030] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the pre-firing time is 1 to 10 hours.

[0031] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the densification sintering temperature is 1000-1500℃.

[0032] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the densification sintering time is 2 to 8 hours.

[0033] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the relative density of the ceramic green body is 90-99%.

[0034] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the inert gas is nitrogen or argon.

[0035] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the temperature of hot isostatic pressing sintering is 1000-1500℃.

[0036] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the pressure of hot isostatic pressing sintering is 100-200 MPa.

[0037] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, the hot isostatic pressing sintering time is 0.5 to 4 hours.

[0038] In the preparation method of the above-mentioned composite transparent ceramic, in step C1, in addition to the pre-firing and densification sintering mentioned above, the composite ceramic blank obtained in step B1 can also be vacuum sintered at 1200-1600℃ for 2-8 hours, and then hot isostatic pressing sintered under an inert atmosphere.

[0039] In the preparation method of the above-mentioned composite transparent ceramic, in step D, the annealing temperature is 1000-1400℃.

[0040] In the preparation method of the above-mentioned composite transparent ceramic, the annealing time in step D is 10-80 hours.

[0041] Based on the above-mentioned method for preparing composite transparent ceramics, the present invention also provides a method for preparing composite transparent ceramics, wherein steps B1 and C1 are replaced with steps B2 and C2.

[0042] B2. The multiphase transparent ceramic powder obtained in step A is subjected to dry pressing and cold isostatic pressing, or the multiphase transparent ceramic powder obtained in step A is subjected to a first pressing sintering to obtain a yttrium magnesium multiphase ceramic green body; in step B2, the first pressing sintering method is selected from hot pressing sintering or electric discharge plasma sintering.

[0043] C2. The composite layer material nanoparticles are uniformly covered or sprayed onto the yttrium magnesium multiphase ceramic green body obtained in step B2, and then subjected to a second pressing sintering to obtain a composite structure ceramic green body; in step C2, the composite layer material is at least one of zirconium oxide, alumina, or magnesium aluminum spinel; in step C2, the second pressing sintering method is selected from hot pressing sintering, encapsulated hot isostatic pressing sintering, or discharge plasma sintering.

[0044] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the pressure of dry pressing is 5-20 MPa.

[0045] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the dry pressing time is 2 to 10 minutes.

[0046] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the pressure of the cold isostatic pressing is 100-200 MPa.

[0047] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the cold isostatic pressing time is 2 to 5 minutes.

[0048] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the pressure of hot pressing sintering is 10-60 MPa.

[0049] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the hot pressing sintering time is 10-40 min.

[0050] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the hot pressing sintering temperature is 1150-1400℃.

[0051] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the temperature of the discharge plasma sintering is 1000-1200℃.

[0052] In the preparation method of the above-mentioned composite transparent ceramic, in step B2, the discharge plasma sintering time is 10-20 min.

[0053] In the above-mentioned method for preparing composite transparent ceramics, the mass ratio of the composite layer material powder in step C2 to the multiphase transparent ceramic powder in step B2 is 1:1 to 4.

[0054] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the pressure of hot pressing sintering is 40-100 MPa.

[0055] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the hot pressing sintering time is 60-150 min.

[0056] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the hot pressing sintering temperature is 1150-1400℃.

[0057] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the temperature of the cladding hot isostatic pressing sintering is 1000-1500℃.

[0058] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the pressure of the cladding hot isostatic pressing sintering is 100-200 MPa.

[0059] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the time for hot isostatic pressing sintering of the cladding is 0.5 to 4 hours.

[0060] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the temperature of the discharge plasma sintering is 1100-1400℃.

[0061] In the preparation method of the above-mentioned composite transparent ceramic, in step C2, the discharge plasma sintering time is 10-60 min.

[0062] Based on the above, the present invention also provides a type of composite transparent ceramic, which is prepared by the above two methods.

[0063] Among them, the relative density of the above-mentioned composite transparent ceramic is >99.9%, the average transmittance in the 3-5μm band at a thickness of 3mm is >73%, the maximum transmittance is 75-85%@5μm, and the three-point bending strength is 500-612MPa.

[0064] In this invention, the relative density of the ceramic green body and the relative density of the composite transparent ceramic are relative to the theoretical density of the yttrium magnesium composite transparent ceramic.

[0065] The beneficial effects of this invention are:

[0066] This invention first prepares a yttrium-magnesium (YMM) composite layer, then uniformly covers the YMM layer with composite material powders such as zirconium oxide, which have a melting temperature close to that of the YMM and can form bonds with it. Through the bonding effect between zirconium oxide and the YMM, and through molding, sintering, and polishing, a composite layer of zirconium oxide and other materials is added to the surface of the YMM transparent ceramic. This not only ensures the stability of the composite structure but also significantly improves the thermal shock resistance and flexural strength of the composite transparent ceramic. This invention can simply and quickly prepare high-performance composite transparent ceramics, which is of great significance for promoting their application in the field of optical windows. Attached Figure Description

[0067] Figure 1 This is a transmittance diagram of the transparent ceramic with a zirconium oxide-yttrium magnesium nanocomposite structure in Example 2 of the present invention.

[0068] Figure 2 This is a SEM image of the transparent ceramic with a zirconium oxide-yttrium magnesium nanocomposite structure according to Example 2 of the present invention. Detailed Implementation

[0069] The present invention will be further described in detail below through embodiments, but the scope of protection of the present invention is not limited to the embodiments described herein.

[0070] Example 1

[0071] Step 1, Powder preparation: Weigh out commercial Y2O3-MgO nanoparticle powder and anhydrous ethanol as organic solvent. Add the powder to a ball mill jar at a mass ratio of Y2O3-MgO powder: anhydrous ethanol: zirconium oxide balls = 10:1.5:40. Ball mill at 180 rad / s for 20 hours. Dry the resulting slurry and pass it through a 100-mesh sieve. Take the sieve-passing material to obtain yttrium magnesium multiphase transparent ceramic powder.

[0072] Step 2, Sample Forming: The powder obtained in Step 1 is subjected to a first dry pressing at 10 MPa for 3 min to obtain a yttrium magnesium composite ceramic green body. Zirconia nanoparticles are uniformly coated on the yttrium magnesium composite ceramic green body. The mass ratio of zirconia powder to the powder used in the first dry pressing is 1:3. A second dry pressing is then performed at 10 MPa for 5 min, followed by cold isostatic pressing at 180 MPa for 3 min to obtain a zirconia-yttrium magnesium composite ceramic green body.

[0073] Step 3, ceramic sintering: The ceramic green body is pre-fired in an air furnace at 600℃ for 6 hours, and then heated to 1000℃ for sintering and densification for 5 hours to obtain a ceramic green body with a relative density of 92%. Then, it is hot isostatically sintered at 1300℃ and 200MPa argon atmosphere for 1 hour.

[0074] Step 4, Annealing and Polishing: After sintering, anneal at 1200℃ in air atmosphere for 30 hours, and then polish on both sides to obtain zirconia-yttrium magnesium composite infrared transparent ceramic.

[0075] The 3mm thick sample was found to have a maximum transmittance of 76% at 5μm in the 3-5μm band, an average transmittance of >73%, and a three-point bending strength of 500MPa, demonstrating excellent performance.

[0076] Example 2

[0077] Step 1, Powder preparation: Weigh out commercial Y2O3-MgO nanoparticle powder and anhydrous ethanol as organic solvent. Add the powder to a ball mill jar at a mass ratio of Y2O3-MgO powder: anhydrous ethanol: zirconium oxide balls = 10:1.5:40. Ball mill at 180 rad / s for 20 hours. Dry the resulting slurry and pass it through a 100-mesh sieve. Take the sieve-passing material to obtain yttrium magnesium multiphase transparent ceramic powder.

[0078] Step 2, Sample Forming: The powder obtained in Step 1 is subjected to a first dry pressing at 10 MPa for 3 min to obtain a yttrium magnesium composite ceramic green body. Zirconia nanoparticles are uniformly coated on the yttrium magnesium composite ceramic green body. The mass ratio of zirconia powder to the powder used in the first dry pressing is 1:3. A second dry pressing is then performed at 10 MPa for 5 min, followed by cold isostatic pressing at 180 MPa for 3 min to obtain a zirconia-yttrium magnesium composite ceramic green body.

[0079] Step 3, ceramic sintering: The ceramic green body is pre-fired in an air furnace at 600℃ for 6 hours, and then heated to 1200℃ for sintering and densification for 5 hours to obtain a ceramic green body with a relative density of 95%. Then, it is hot isostatically sintered at 1300℃ and 200MPa argon atmosphere for 1 hour.

[0080] Step 4, Annealing and Polishing: After sintering, anneal at 1200℃ in air atmosphere for 30 hours, and then polish on both sides to obtain zirconia-yttrium magnesium composite infrared transparent ceramic.

[0081] The 3mm thick sample was found to have a maximum transmittance of 81% at 5μm in the 3-5μm band, an average transmittance of >78%, and a three-point bending strength of 500MPa, demonstrating excellent performance.

[0082] Example 3

[0083] Step 1, Powder preparation: Weigh Y2O 3- Commercial MgO nanoparticles were prepared by weighing anhydrous ethanol as an organic solvent and adding it to a ball mill jar at a mass ratio of Y2O3-MgO powder: anhydrous ethanol: zirconium oxide balls = 10:1.5:40. The mixture was ball-milled at a speed of 180 rad / s for 20 hours. The resulting slurry was dried and passed through a 100-mesh sieve. The sieve-passing material was collected to obtain yttrium magnesium multiphase transparent ceramic powder.

[0084] Step 2, Sample Forming: The powder obtained in Step 1 is subjected to a first dry pressing at 10 MPa for 3 min to obtain a yttrium magnesium composite ceramic green body. Zirconia nanoparticles are uniformly coated on the yttrium magnesium composite ceramic green body. The mass ratio of zirconia powder to the powder used in the first dry pressing is 1:3. A second dry pressing is then performed at 10 MPa for 5 min, followed by cold isostatic pressing at 180 MPa for 3 min to obtain a zirconia-yttrium magnesium composite ceramic green body.

[0085] Step 3, ceramic sintering: The ceramic green body is pre-fired in an air furnace at 600℃ for 6 hours, and then heated to 1400℃ for sintering and densification for 5 hours to obtain a ceramic green body with a relative density of 97%. Then, it is hot isostatically sintered at 1300℃ and 200MPa argon atmosphere for 1 hour.

[0086] Step 4, Annealing and Polishing: After sintering, anneal at 1200℃ in air atmosphere for 30 hours, and then polish on both sides to obtain zirconia-yttrium magnesium composite infrared transparent ceramic.

[0087] The 3mm thick sample was found to have a maximum transmittance of 80% at 5μm in the 3-5μm band, an average transmittance of >76%, and a three-point bending strength of 500MPa, demonstrating excellent performance.

[0088] Example 4

[0089] Step 1, Powder preparation: Weigh out commercial Y2O3-MgO nanoparticles and anhydrous ethanol as the organic solvent. Add them to a ball mill jar according to the mass ratio of Y2O3-MgO powder: anhydrous ethanol: zirconium oxide balls = 10:1.5:40. Ball mill at 180 rad / s for 20 hours. Dry the resulting slurry and pass it through a 100-mesh sieve. Take the sieve-passing material to obtain the desired yttrium magnesium multiphase powder.

[0090] Step 2: The powder obtained in Step 1 is subjected to a first hot pressing sintering at 50 MPa and 1250℃ for 30 min to obtain a yttrium magnesium multiphase ceramic green body.

[0091] Step 3: Zirconia nanoparticles are uniformly coated on the yttrium magnesium composite ceramic green body obtained in step 2, and then a second hot pressing sintering is performed. The mass ratio of zirconia powder to the powder used in the first hot pressing sintering is 1:3. After hot pressing sintering at 50 MPa and 1250℃ for 2 hours, a zirconia-yttrium magnesium composite ceramic green body is obtained.

[0092] Step 4, Annealing and Polishing: After sintering, anneal at 1200℃ in air atmosphere for 30 hours, and then polish on both sides to obtain zirconia-yttrium magnesium composite infrared transparent ceramic.

[0093] The 3mm thick sample was found to have a maximum transmittance of 78% at 5μm in the 3-5μm band, an average transmittance of >74%, and a three-point bending strength of 500MPa, demonstrating excellent performance.

[0094] Comparative Example 1

[0095] Step 1, Powder preparation: Weigh out commercial Y2O3-MgO nanoparticles and anhydrous ethanol as the organic solvent. Add them to a ball mill jar according to the mass ratio of Y2O3-MgO powder: anhydrous ethanol: zirconium oxide balls = 10:1.5:40. Ball mill at 180 rad / s for 20 hours. Dry the resulting slurry and pass it through a 100-mesh sieve. Take the sieve-passing material to obtain the desired yttrium magnesium multiphase powder.

[0096] Step 2, Sample forming: The powder obtained in Step 1 is dry-pressed at 10MPa for 3 minutes, and then cold isostatically pressed at 180MPa for 3 minutes to obtain yttrium magnesium multiphase ceramic green body.

[0097] Step 3, ceramic sintering: The ceramic green body is pre-fired in an air furnace at 600℃ for 6 hours, and then heated to 1000℃ for sintering and densification for 5 hours to obtain a ceramic green body with a relative density of 92%. Then, it is hot isostatically sintered at 1300℃ and 200MPa argon atmosphere for 1 hour.

[0098] Step 4, Annealing and Polishing: After sintering, anneal at 1200℃ in air atmosphere for 30 hours, and then polish on both sides to obtain yttrium magnesium multiphase infrared transparent ceramic.

[0099] The maximum transmittance of the 3mm thick sample in the 3-5μm band was measured to be 84%@5μm, the average transmittance was >78%, and the three-point bending strength was only 300MPa.

Claims

1. A method for preparing composite transparent ceramics, characterized in that: Includes the following steps: A. Y2O3-MgO nanoparticles and organic solvents are mixed and ball-milled to obtain a ceramic slurry, which is then dried and sieved to obtain a multiphase transparent ceramic powder. B1. The multiphase transparent ceramic powder obtained in step A is subjected to a first dry pressing to obtain a yttrium magnesium multiphase ceramic blank; the composite layer material nanopowder is uniformly covered or sprayed onto the yttrium magnesium multiphase ceramic blank, and then subjected to a second dry pressing, followed by cold isostatic pressing to obtain a composite structure ceramic blank; in step B1, the composite layer material is at least one of zirconium oxide, alumina, or magnesium aluminum spinel; C1. The composite structure ceramic green body obtained in step B1 is pre-fired in air atmosphere, then heated for densification sintering to obtain a ceramic green body, and then hot isostatic pressing sintered in inert atmosphere. D. After sintering, the ceramic is annealed in air and polished to obtain a composite transparent ceramic.

2. The method for preparing the composite transparent ceramic according to claim 1, characterized in that: At least one of the following must be met: In step A, the mass ratio of the Y2O3-MgO nanopowder to the organic solvent is 1 to 10:1; In step A, the organic solvent is ethanol; In step A, during ball milling, zirconia balls or alumina balls are used as milling balls, and the mass ratio of milling balls to Y2O3-MgO nanopowder is 30:1 to 10. In step A, the ball milling conditions are: ball milling at a speed of 150-220 rad / s for 16-30 hours; In step A, the mesh size of the sieve used for sieving is 100 to 200 mesh.

3. The method for preparing the composite transparent ceramic according to claim 1, characterized in that: At least one of the following must be met: In step B1, the mass ratio of the composite layer material powder to the multiphase transparent ceramic powder is 1:1 to 4; In step B1, the pressure of the first dry pressing is 5-20 MPa; In step B1, the time for the first dry pressing is 2 to 10 minutes; In step B1, the pressure of the second dry pressing is 5-20 MPa; In step B1, the second dry pressing molding time is 2 to 10 minutes; In step B1, the pressure of the cold isostatic pressing is 100-200 MPa; In step B1, the cold isostatic pressing time is 2 to 5 minutes.

4. The method for preparing the composite transparent ceramic according to claim 1, characterized in that: At least one of the following must be met: In step C1, the pre-firing temperature is 400–850°C; In step C1, the pre-firing time is 1 to 10 hours; In step C1, the densification sintering temperature is 1000–1500°C; In step C1, the densification sintering time is 2 to 8 hours; In step C1, the relative density of the ceramic green body is 90-99%; In step C1, the inert gas is nitrogen or argon; In step C1, the temperature of the hot isostatic pressing sintering is 1000–1500°C; In step C1, the pressure of hot isostatic pressing sintering is 100-200 MPa; In step C1, the hot isostatic pressing sintering time is 0.5 to 4 hours; In step C1, the composite structure ceramic green body obtained in step B1 is sintered in vacuum at 1200-1600℃ for 2-8 hours, and then subjected to hot isostatic pressing under an inert atmosphere.

5. The method for preparing the composite transparent ceramic according to claim 1, characterized in that: At least one of the following must be met: In step D, the annealing temperature is 1000–1400°C; In step D, the annealing time is 10 to 80 hours.

6. The method for preparing the composite transparent ceramic according to claim 1, 2 or 5, characterized in that: Replace steps B1 and C1 with steps B2 and C2; B2. The multiphase transparent ceramic powder obtained in step A is subjected to dry pressing and cold isostatic pressing, or the multiphase transparent ceramic powder obtained in step A is subjected to a first pressing sintering to obtain a yttrium magnesium multiphase ceramic green body; in step B2, the first pressing sintering method is selected from hot pressing sintering or electric discharge plasma sintering. C2. The composite layer material nanoparticles are uniformly covered or sprayed onto the yttrium magnesium multiphase ceramic green body obtained in step B2, and then subjected to a second pressing sintering to obtain a composite structure ceramic green body; in step C2, the composite layer material is at least one of zirconium oxide, alumina, or magnesium aluminum spinel; in step C2, the second pressing sintering method is selected from hot pressing sintering, encapsulated hot isostatic pressing sintering, or discharge plasma sintering.

7. The method for preparing the composite transparent ceramic according to claim 6, characterized in that: At least one of the following must be met: In step B2, the pressure for dry pressing is 5-20 MPa; In step B2, the dry pressing time is 2 to 10 minutes; In step B2, the pressure of the cold isostatic pressing is 100-200 MPa; In step B2, the cold isostatic pressing time is 2 to 5 minutes; In step B2, the pressure of the hot pressing sintering is 10-60 MPa; In step B2, the hot pressing sintering time is 10 to 40 minutes; In step B2, the hot pressing sintering temperature is 1150–1400°C; In step B2, the temperature of the discharge plasma sintering is 1000-1200℃; In step B2, the sintering time of the discharge plasma is 10 to 20 minutes.

8. The method for preparing the composite transparent ceramic according to claim 6, characterized in that: At least one of the following must be met: The mass ratio of the composite layer material powder in step C2 to the multiphase transparent ceramic powder in step B2 is 1:1 to 4; In step C2, the pressure of the hot pressing sintering is 40-100 MPa; In step C2, the hot pressing sintering time is 60–150 min; In step C2, the hot pressing sintering temperature is 1150–1400°C; In step C2, the temperature of the hot isostatic pressing sintering of the cladding is 1000-1500℃; In step C2, the pressure of the hot isostatic pressing sintering of the cladding is 100-200 MPa; In step C2, the hot isostatic pressing sintering time of the cladding is 0.5 to 4 hours; In step C2, the temperature of the discharge plasma sintering is 1100–1400°C; In step C2, the sintering time of the discharge plasma is 10 to 60 minutes.

9. A composite transparent ceramic prepared by the method described in any one of claims 1 to 8.

10. The composite transparent ceramic according to claim 9, characterized in that: The composite transparent ceramic has a relative density >99.9%, an average transmittance of >73% in the 3-5μm band at a thickness of 3mm, a maximum transmittance of 75-85%@5μm, and a three-point flexural strength of 500-612MPa.

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