AlON transparent ceramic material and preparation method thereof
By using a BN composite crucible vapor phase volatile additive method that eliminates the need for pre-addition of sintering aids, the problems of coarse grains and uneven transparency in AlON transparent ceramic materials have been solved, enabling the preparation of AlON transparent ceramics with high strength and high transparency.
Patent Information
- Application Number
- CN202410958952.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-17
- Publication Date
- 2026-01-20
AI Technical Summary
In the preparation process of existing AlON transparent ceramic materials, the introduction of sintering aids leads to coarse grains, low mechanical properties, and uneven internal transparency, especially in large-sized samples.
A method without the need for pre-addition of sintering aids was adopted, using the gaseous volatiles of the BN composite crucible as aids at high temperature, and through steps such as atmosphere sintering, pressureless pre-firing, and hot isostatic pressing sintering, to prepare high-strength AlON transparent ceramics with uniform internal and external properties.
AlON transparent ceramic material with high transparency and high strength was obtained, with uniform grain size, transmittance of 82.5%, and bending strength of 350-450MPa.
Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the technical field of ceramic material preparation, and particularly relates to an AlON transparent ceramic material and a preparation method thereof. BACKGROUND
[0002] Among the existing transparent ceramic material systems, aluminum oxynitride (commonly known as AlON or gamma-AlON) is one of the materials with excellent mechanical and optical properties, and has been concerned since its advent. AlON transparent ceramic has good transmittance in the near-ultraviolet, visible and mid-infrared wavebands, and has the significant advantages of high strength and high hardness, and can be applied to the fields of infrared guidance seeker, fighter photoelectric pod, tank observation window, deep water periscope and space optical cabin, and is also expected to be applied to safety protection, POS machine window, optical components and special instruments.
[0003] Generally, in order to obtain high-performance AlON transparent ceramic, a small amount of sintering aid is often added in the preparation process to promote the densification of AlON powder, reduce the sintering temperature and shorten the sintering time. Commonly used sintering aids are lanthanum oxide (La2O3), yttrium oxide (Y2O3), magnesium oxide (MgO), silicon dioxide (SiO2), lithium fluoride (LiF), aluminum oxide (Al2O3) and the like. The introduction of such sintering aids can effectively improve the sintering process of AlON and the optical and mechanical properties of the corresponding ceramic, but at the same time, it also causes new problems. For example, rare earth oxides such as La2O3 and Y2O3 sintering aids can easily cause twinning; the AlON ceramic prepared by using MgO and LiF as sintering aids has relatively coarse grain size and low mechanical properties.
[0004] Li reported in J.Euro.Ceram.Soc., 2021, 41(7): 4327 that SiO2 was used as an aid to obtain small-grained, high-strength AlON transparent ceramic with an average grain size of 45 μm under hot isostatic pressing at about 1800℃, and it was also found that the SiO2 sintering aid would volatilize during the pre-sintering stage, which would easily cause a large number of micro-pores in the AlON pre-sintered body, and the density of the inner layer was smaller than that of the surface layer, thereby causing the sample or product to be opaque, especially as the size of the AlON ceramic increases, this problem becomes more and more obvious. Therefore, it is still a difficult problem to prepare AlON ceramic with uniform optical quality, high transparency and high strength. SUMMARY
[0005] In view of the above technical problems, the purpose of the present application is to provide a high-strength AlON transparent ceramic material and a preparation method thereof.
[0006] In a first aspect, the present application provides a preparation method of an AlON transparent ceramic material, which comprises the following steps: (1) AlON high-purity powder is grinded to slurry, dried, sieved and calcined to obtain AlON raw material powder; (2) The AlON raw material powder is pressed to obtain an AlON transparent ceramic green body; (3) The AlON raw material powder, SiO2 raw material powder and BN raw material powder are mixed and subjected to atmosphere sintering to obtain a BN composite crucible; (4) The AlON transparent ceramic green body obtained in step (2) is placed in the BN composite crucible obtained in step (3) for pressureless pre-sintering, and the gas phase volatiles of the BN composite crucible at high temperature are used as sintering aids, and then hot isostatic pressing sintering and annealing treatment are performed to obtain the AlON transparent ceramic material.
[0007] Preferably, in step (1), the AlON high-purity powder is grinded to slurry in a nylon ball mill tank, alumina balls are used as grinding balls, alcohol is used as solvent, the weight ratio of balls to powder is controlled to be 3-5, the mass ratio of powder to alcohol is 1:0.75-1, and after mixing, the mixture is placed on a planetary ball mill, the rotation speed is set to 120-350 r / min, and the ball milling time is 6-48 h. In step (1), the drying temperature is 45-100℃, and the drying time is 6-24 h; the mesh size of sieving is 60-200 mesh.
[0008] Preferably, in step (1), the calcination is performed in a muffle furnace, and the temperature is raised from room temperature to 500-650℃ for 2-20 h and kept for 1-10 h, and then the furnace is cooled to room temperature.
[0009] Preferably, in step (2), the AlON raw material powder is pressed in a steel mold, first subjected to axial bidirectional pressing at a pressure of 1-20 MPa at room temperature for 1-10 minutes, and then subjected to cold isostatic pressing at a pressure of 180-300 MPa for 3-10 minutes using a cold isostatic pressing machine.
[0010] Preferably, in step (3), based on the total mass of the AlON raw material powder, BN raw material powder and SiO2 raw material powder, the content of AlON is 10-50 wt%, the content of SiO2 is 1-5 wt%, and the content of BN is 45-89 wt%; preferably, the mass ratio of AlON to BN is 1:2. In step (3), the atmosphere sintering is performed in N2 atmosphere, the atmosphere sintering temperature is 1800-1900℃, and the atmosphere sintering time is 6-24 h.
[0011] Preferably, in step (4), the AlON transparent ceramic green body is first covered with powder having the same composition as the BN composite crucible, and then subjected to pressureless pre-sintering.
[0012] Preferably, in step (4), the pressureless pre-sintering is performed in a N2 atmosphere, the temperature of the pressureless pre-sintering is 1840-1950℃, and the time of the pressureless pre-sintering is 3-24h; preferably, the relative density of the green body after the pressureless pre-sintering is 92-99%.
[0013] Preferably, in step (4), the hot isostatic sintering is performed in a tungsten crucible, the temperature of the hot isostatic sintering is 1800-1900℃, the sintering pressure is 150-200MPa, the sintering time is 3-6h, and the sintering atmosphere is Ar.
[0014] Preferably, in step (4), the annealing treatment is performed in a N2 atmosphere furnace, the annealing temperature is 1800-1900℃, and the annealing time is 4-24h.
[0015] In the second aspect, the application provides an AlON transparent ceramic material prepared by the above preparation method, the AlON transparent ceramic material has a transmittance of 82.5% at 4mm thickness and 600nm wavelength, an average grain size of 50-80μm, and a bending strength of 350-450MPa.
[0016] Advantages The preparation method provided by the application does not need to add a sintering aid in the powder in advance, but uses the gas phase volatiles of the BN composite crucible at high temperature as the sintering aid, so that the high-strength AlON transparent ceramic with uniform internal and external can be obtained. DETAILED DESCRIPTION
[0017] The application is further illustrated by the following embodiments, and it should be understood that the following embodiments are only used to illustrate the application, but not to limit the application.
[0018] Hereinafter, the preparation method of the AlON transparent ceramic material provided by the application is exemplarily illustrated. The preparation method can include the following steps: (1) grinding, drying, and sieving AlON high-purity powder, and then calcining to obtain AlON raw material powder; (2) pressing and forming the AlON raw material powder to obtain an AlON transparent ceramic green body; (3) mixing the AlON raw material powder, SiO2 raw material powder, and BN raw material powder, and performing atmosphere sintering to obtain a BN composite crucible; (4) placing the AlON transparent ceramic green body obtained in step (2) in the BN composite crucible obtained in step (3) to perform pressureless pre-sintering, and then performing hot isostatic sintering and annealing treatment to obtain the AlON transparent ceramic material.
[0019] In some embodiments, in step (1), the purity of the AlON high-purity powder can be 99.9%.
[0020] In some embodiments, in step (1), the AlON high-purity powder grinding and slurry preparation can be performed in a nylon ball mill jar, with alumina balls as the grinding balls, alcohol as the solvent, a ball: powder weight ratio of 3-5, and a powder: alcohol mass ratio of 1:0.75-1. After mixing, the mixture is placed in a planetary ball mill, set to a rotation speed of 120-350 r / min, and ball-milled for 6-48 h.
[0021] In some embodiments, in step (1), the drying temperature can be 45-100°C, and the drying time can be 6-24 h; the mesh size of the sieving can be 60-200 mesh.
[0022] Calcination can be used to purify the AlON powder. In some embodiments, in step (1), the calcination can be performed in a muffle furnace, with the temperature being raised from room temperature to 500-650°C over a period of 2-20 h, and then held at 500-650°C for 1-10 h, and then cooled to room temperature.
[0023] In some embodiments, in step (2), the AlON raw material powder can be pressed and formed in a steel mold, with a pressure of 1-20 MPa applied axially in both directions for 1-10 min, and then cold isostatic pressing at a pressure of 180-300 MPa for 3-10 min.
[0024] In some embodiments, in step (3), the total mass of the AlON raw material powder, BN raw material powder, and SiO2 raw material powder is taken as 100%, the content of AlON can be 10-50 wt%, the content of SiO2 can be 1-5 wt%, and the content of BN can be 45-89 wt%; preferably, the mass ratio of AlON to BN can be 1:2.
[0025] In some embodiments, in step (3), the atmosphere sintering can be performed in a N2 atmosphere, with an atmosphere sintering temperature of 1800-1900°C and an atmosphere sintering time of 6-24 h.
[0026] In some embodiments, in step (4), the AlON transparent ceramic green body can be first covered with the same powder as the BN composite crucible component before pressureless pre-sintering.
[0027] In some embodiments, in step (4), the pressureless pre-sintering is performed in a N2 atmosphere, with a pressureless pre-sintering temperature of 1840-1950°C and a pressureless pre-sintering time of 3-24 h; preferably, the relative density of the green body after pressureless pre-sintering can be controlled to be 92-99%.
[0028] In some embodiments, in step (4), the hot isostatic pressing sintering is performed in a tungsten crucible, the temperature of the hot isostatic pressing sintering can be 1800-1900℃, the sintering pressure can be 150-200MPa (such as 190MPa), the sintering time can be 3-6 hours, and the sintering atmosphere can be Ar. The hot isostatic pressing sintering can promote the densification of the green body.
[0029] In some embodiments, in step (4), the annealing treatment can be performed in an N2 atmosphere furnace, the annealing temperature can be 1800-1900℃, and the annealing time can be 4-24 hours.
[0030] The AlON transparent ceramic material prepared by the preparation method provided by the present application has a transmittance of 82.5% at a thickness of 4mm and a wavelength of 600nm, an average grain size of 50-80μm, and a bending strength of 350-450MPa.
[0031] The preparation method provided by the present application does not need to add a sintering aid in the powder in advance, but uses the gas phase volatilization of the BN composite crucible at high temperature as the sintering aid, thereby obtaining an AlON transparent ceramic with uniform internal and external strength.
[0032] The following examples are further provided to illustrate the present application in detail. It should also be understood that the following examples are only used to further illustrate the present application, and cannot be understood as limiting the protection scope of the present application. Some non-essential improvements and adjustments made by those skilled in the art according to the above content of the present application all belong to the protection scope of the present application. The specific process parameters in the following examples are only one example in the appropriate range, i.e., those skilled in the art can make appropriate selection within the range through the description herein, and are not limited to the specific values in the following examples. If not specifically indicated, the technical means used in the examples are conventional means known to those skilled in the art.
[0033] Example 1
[0034] The preparation method of the AlON transparent ceramic material provided by the present embodiment comprises the following steps: (1) 1000g of AlON high-purity powder is weighed and added into a nylon ball mill jar, alumina balls are used as the grinding balls, the ball: powder weight ratio is controlled to be 3-5, 750g of alcohol is further added, the mixture is shaken gently and then placed on a planetary ball mill, the rotation speed is set to be 270r / min, and the ball milling time is 20h; the slurry is taken out and dried in an oven at 60℃, and then the dried powder is sieved through a 100 mesh nylon sieve; subsequently, the sieved powder is loaded into an alumina crucible, and then heated in a muffle furnace from room temperature to 600℃ for 2h and then cooled to room temperature, thereby obtaining an AlON raw material powder; (2) The AlON raw material powder in step (1) is loaded into a steel mold, and is axially bidirectionally pressed at a pressure of 5 MPa for 1 minute at room temperature, and then is cold isostatic pressed at a pressure of 200 MPa for 5 minutes by a cold isostatic pressing machine to obtain an AlON transparent ceramic green body; (3) The AlON raw material powder obtained in step (2) is mixed with high-purity hexagonal BN powder at a weight ratio of 1:2, and 4 wt% of SiO2 powder is additionally added as a raw material, and then is sintered in a N2 atmosphere to obtain a BN composite crucible; (4) The AlON transparent ceramic green body obtained in step (2) is placed in the BN composite crucible obtained in step (3) for pressureless pre-sintering, the temperature for pressureless pre-sintering is 1880 °C, the sintering time is 3 hours, and the pre-sintering atmosphere is N2; then the sample is placed in a tungsten crucible for hot isostatic pressing sintering, the sintering temperature is 1860 °C, the pressure is 190 MPa, the sintering time is 3 hours, and the hot isostatic pressing sintering atmosphere is Ar; finally, the sample after hot isostatic pressing sintering is annealed in a N2 atmosphere furnace at 1800 °C for 4 hours to obtain the AlON transparent ceramic material.
[0035] The AlON transparent ceramic material prepared in Example 1 is machined and polished to 4.0 mm by using a surface grinding machine and a polishing disc. It is detected that the transmittance of the sample with a thickness of 4 mm can reach 82.5% at a wavelength of 600 nm, the average grain size is 80 μm, and the bending strength is 380 MPa.
[0036] Example 2
[0037] The preparation method of the AlON transparent ceramic material provided in the example mainly differs from that in Example 1 in that, in step (4), the AlON green body is first placed in the BN composite crucible and is covered with the powder having the same composition as the BN composite crucible before pressureless pre-sintering, the temperature for pressureless pre-sintering is 1840 °C, the sintering time is 5 hours, the temperature for hot isostatic pressing sintering is 1800 °C, the pressure is 180 MPa, and the sintering time is 6 hours.
[0038] The AlON transparent ceramic material prepared in Example 2 is machined and polished to 4.0 mm by using a surface grinding machine and a polishing disc. It is detected that the transmittance of the sample with a thickness of 4 mm can reach 82.0% at a wavelength of 600 nm, the average grain size is 50 μm, and the bending strength is 420 MPa.
[0039] Although the content of the present application has been described in detail by means of the above preferred embodiments, it should be recognized that the above description should not be considered as limiting the present application. Various modifications and substitutions will be apparent to those skilled in the art after reading the above description. Therefore, the scope of protection of the present application should be defined by the appended claims.
Claims
1. A method for preparing an AlON transparent ceramic material, characterized in that, The preparation method includes the following steps: (1) The high-purity AlON powder is ground into a slurry, dried, sieved and then calcined to obtain AlON raw material powder; (2) Press the AlON raw material powder into shape to obtain AlON transparent ceramic blank; (3) The AlON raw material powder, SiO2 raw material powder and BN raw material powder are mixed and sintered under an atmosphere to obtain a BN composite crucible; (4) The AlON transparent ceramic blank obtained in step (2) is placed in the BN composite crucible obtained in step (3) for pressureless pre-firing. The gaseous volatiles of the BN composite crucible at high temperature are used as sintering aids. Then, hot isostatic pressing and annealing are performed to obtain the AlON transparent ceramic material.
2. The preparation method according to claim 1, characterized in that, In step (1), the AlON high-purity powder is ground and slurried in a nylon ball mill jar. Alumina balls are used as grinding balls, alcohol is used as solvent, the weight ratio of balls to powder is controlled to be 3-5, and the mass ratio of powder to alcohol is 1:0.75-1. After mixing, the mixture is placed on a planetary ball mill, the rotation speed is set to 120-350 r / min, and the ball milling time is 6-48 h. In step (1), the drying temperature is 45-100℃ and the drying time is 6-24h; the sieve mesh size is 60-200 mesh.
3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the calcination is carried out in a muffle furnace, where the temperature is raised from room temperature to 500-650°C in 2-20 hours and held for 1-10 hours, and then cooled to room temperature in the furnace.
4. The preparation method according to any one of claims 1-3, characterized in that, In step (2), the AlON raw material powder is pressed and molded in a steel mold. First, it is axially and bidirectionally pressed for 1-10 minutes at room temperature with a pressure of 1-20MPa, and then cold isostatically pressed for 3-10 minutes at a pressure of 180-300MPa using a cold isostatic press.
5. The preparation method according to any one of claims 1-4, characterized in that, In step (3), based on the total mass percentage of AlON raw material powder, BN raw material powder and SiO2 raw material powder being 100%, the content of AlON is 10-50wt%, the content of SiO2 is 1-5wt%, and the content of BN is 45-89wt%; preferably, the mass ratio of AlON to BN is 1:
2. In step (3), the atmosphere sintering is carried out in a N2 atmosphere, the atmosphere sintering temperature is 1800-1900℃, and the atmosphere sintering time is 6-24h.
6. The preparation method according to any one of claims 1-5, characterized in that, In step (4), the AlON transparent ceramic blank is first covered with powder of the same composition as the BN composite crucible, and then pressureless pre-firing is performed.
7. The preparation method according to any one of claims 1-6, characterized in that, In step (4), the pressureless pre-firing is carried out under N2 atmosphere, the pressureless pre-firing temperature is 1840-1950℃, and the pressureless pre-firing time is 3-24h; preferably, the relative density of the green blank after pressureless pre-firing is 92-99%.
8. The preparation method according to any one of claims 1-7, characterized in that, In step (4), the hot isostatic pressing sintering is carried out in a tungsten crucible. The hot isostatic pressing sintering temperature is 1800-1900℃, the sintering pressure is 150-200MPa, the sintering time is 3-6h, and the sintering atmosphere is Ar.
9. The preparation method according to any one of claims 1-8, characterized in that, In step (4), the annealing process is carried out in an N2 atmosphere furnace at an annealing temperature of 1800-1900℃ for 4-24 hours.
10. A method for preparing AlON transparent ceramic material according to any one of claims 1-9, characterized in that, The AlON transparent ceramic material has a transmittance of 82.5% at a wavelength of 600nm with a thickness of 4mm, an average grain size of 50-80μm, and a flexural strength of 350-450MPa.