A method for preparing a transparent ceramic material and a method for preparing the same

Abstract

The application belongs to the technical field of transparent ceramic material preparation, and particularly relates to a kind of transparent ceramic material and its preparation method. The transparent ceramic is prepared by first oscillating sintering the transparent ceramic powder, then heat treating and polishing, and finally forging by oscillation. The transparent ceramic is prepared by oscillating pre-sintering + heat treatment + dynamic sintering forging DSF, which successfully applies dynamic sintering forging to the preparation of transparent ceramic, directly improves the transmittance and strength of transparent ceramic, and further expands the application field and application environment of transparent ceramic.

Description

Technical Field

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

[0002] Transparent ceramics, with their wide-band high transmittance covering the ultraviolet to infrared spectrum, as well as excellent mechanical properties such as high strength, high hardness, wear resistance, and corrosion resistance, have become indispensable key materials in modern industry and defense. Typical applications include transparent armor, infrared radomes, optical lenses, and laser windows. With the continuous upgrading of weapon systems, more stringent requirements are being placed on the comprehensive performance of transparent ceramics: not only must the protection level be maintained or improved under lightweight and thin design conditions, but the long-term stability and reliability of optical and structural performance must also be ensured under multiple extreme conditions such as complex electromagnetic environments, extreme temperatures, and high-speed impacts. This means that the material faces the challenge of comprehensively improving key indicators such as optical transmittance, hardness, strength, and toughness.

[0003] In terms of manufacturing processes, existing sintering technologies still struggle to achieve an ideal balance between optical and mechanical properties. Hot pressing, a commonly used process, suffers from abnormal grain growth (reaching tens of micrometers) due to its high sintering temperature and frequent use of graphite molds, accompanied by carburization issues, resulting in a simultaneous decrease in both transmittance and mechanical properties. While spark plasma sintering can achieve material densification at lower temperatures, improving mechanical properties, its electric field environment exacerbates carbon diffusion, making carburization more pronounced and severely limiting optical transmittance. Although hot isostatic pressing performs well in eliminating porosity and improving transmittance, its complex equipment and high temperature and pressure requirements easily lead to grain coarsening, hindering further optimization of mechanical properties and limiting its application.

[0004] In contrast, dynamic pressure-assisted sintering (DPSA) technology, by introducing oscillating pressure with controllable magnitude and frequency, can effectively promote particle rearrangement, disrupt agglomeration structures, inhibit grain growth, improve grain boundary strength, accelerate porosity removal, and increase the density of ceramics. Studies have shown that this technology can also enhance grain boundary migration and mass diffusion, inducing an increase in dislocation density, which is beneficial for defect elimination and improved mechanical properties. However, DPSA currently still faces the problem of carburization caused by graphite molds, and high dislocation density can act as light scattering centers, affecting the light transmittance of ceramics. Therefore, in the development of high-performance transparent ceramics, how to effectively suppress carburization and control the microstructure while leveraging the advantages of DPSA technology has become a crucial technical challenge that urgently needs to be overcome. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a method for preparing a transparent ceramic material that combines high transmittance and high mechanical properties.

[0006] The technical solution adopted in this invention is as follows: A method for preparing a transparent ceramic material includes the following steps: 1) Transparent ceramic powder is loaded into a mold and sintered by vibration to obtain a pre-fired body; 2) Heat-treat the pre-fired body obtained in step 1); 3) Polish the pre-fired body after heat treatment; 4) Place the pre-fired body polished in step 3) between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict the heat. Heat to temperature T and hold at that temperature. At the same time, apply pressure to the preset pressure (50-200MPa) and apply oscillation force through the upper and lower pressure heads. After the holding time ends, stop the oscillation force and cool down to room temperature to obtain a transparent ceramic material.

[0007] In step 1), the sintering temperature of the oscillation sintering is 700-1200 ℃, the median value of the oscillation force is calculated based on the area as 30-100 MPa, the amplitude is 5-60 MPa, the frequency is 0.5-20 Hz, and the holding time is 5-60 min.

[0008] In step 2), the heat treatment temperature is 700-1600℃ and the holding time is 1-7h.

[0009] In step 4), the temperature T is 1200-1600℃, the median value of the oscillation force is 50-200MPa calculated based on the area, the amplitude is 5-70 MPa, the frequency is 0.5-20 Hz, and the heat preservation time is 1-3h.

[0010] The relative density of the pre-fired body is greater than 40%, and the shape of the pre-fired body is cylindrical or blocky.

[0011] Step 3) involves grinding and polishing the pre-burnt body until the surface roughness of the polished surface reaches 0.25-1μm.

[0012] The transparent ceramic powder is one of magnesium aluminum spinel powder, yttrium oxide powder, magnesium oxide powder, aluminum oxide powder, and yttrium aluminum garnet powder.

[0013] The transparent ceramic material obtained by the above preparation method has both high transmittance and high mechanical properties.

[0014] When the transparent ceramic material is magnesium aluminum spinel transparent ceramic, the transmittance at 800nm ​​is >84%, the average flexural strength is >400MPa, and the Vickers hardness is >18.4GPa. When the transparent ceramic material is yttrium oxide transparent ceramic, the transmittance at 800nm ​​is >82%, the average flexural strength is >170MPa, and the Vickers hardness is >9.8GPa; When the transparent ceramic material is magnesium oxide transparent ceramic, the transmittance at 800nm ​​is >71%, the average flexural strength is >236MPa, and the Vickers hardness is >8.5GPa. When the transparent ceramic material is yttrium aluminum garnet transparent ceramic, the transmittance at 800nm ​​is >79%, the average flexural strength is >310MPa, and the Vickers hardness is >14.3GPa.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are: 1. Compared with existing technologies, this invention organically combines oscillatory pre-sintering, heat treatment, and dynamic sintering forging (DSF), exhibiting a synergistic effect in improving the optical transmittance and mechanical properties of transparent ceramics. Specifically, oscillatory sintering first achieves preliminary densification of the ceramic powder, promoting orderly particle rearrangement and reducing defect proliferation, thereby improving the strength of the pre-sintered body and optimizing its microstructure. This pre-sintered body has a high initial density, which effectively reduces the contact area with the graphite mold in subsequent processes, thus significantly suppressing carburization. Based on this, specific high-temperature heat treatment of the pre-sintered body further removes residual carbon impurities and reduces oxygen vacancy concentration, preparing more suitable microstructure conditions for subsequent dynamic sintering forging. When the heat-treated and optimized pre-sintered body undergoes dynamic sintering forging, the reduced internal impurities and improved structural uniformity help eliminate porosity during dynamic sintering forging, fundamentally ensuring the high optical transmittance of the material. If heat treatment is placed after dynamic sintering and forging, it can alleviate some residual stress, but it cannot purify the material during the preceding sintering process. It is difficult to avoid performance loss caused by impurities and defects during DSF, and the synergistic enhancement effect is significantly limited.

[0016] 2. By using oscillatory pre-sintering, we can not only eliminate residual stress between particles and improve uniformity, but also lay a good foundation for subsequent dynamic sintering and forging. Furthermore, the shear force introduced during dynamic sintering and forging enhances the densification driving force. The combination of these two factors allows densification to be achieved at a lower sintering temperature (1200-1600℃). This not only inhibits abnormal grain growth and promotes the formation of a fine-grained structure, but the fine-grained interfaces also effectively pin and hinder dislocation movement. Simultaneously, due to the lower sintering temperature, the thermal stress experienced by the material is significantly reduced, thereby effectively suppressing dislocation multiplication caused by thermal stress. Ultimately, while achieving high material densification, the integrity of the microstructure is significantly optimized, and key mechanical properties such as hardness and fracture toughness are simultaneously improved.

[0017] 3. This invention successfully applies dynamic sintering and forging (DSF) to the preparation of transparent ceramics through oscillating pre-sintering + heat treatment + dynamic sintering and forging, achieving synergistic optimization of optical and mechanical properties. It effectively solves the contradiction that it is difficult to balance optical and mechanical properties in current ceramic preparation, and provides a reliable material basis for expanding the application of transparent ceramics in high-end optical windows, laser devices and national defense protection. Attached Figure Description

[0018] Figure 1 Photograph of the magnesium aluminum spinel transparent ceramic prepared in Example 1; Figure 2 Here is a surface SEM image of the magnesium aluminum spinel transparent ceramic prepared in Example 1; Figure 3 This is a high-magnification dark-field image of the magnesium aluminum spinel transparent ceramic prepared in Example 1; Figure 4 Photograph of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 1; Figure 5 SEM image of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 1; Figure 6 This is a high-magnification dark-field image of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 2. Figure 7 Photograph of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 2; Figure 8 SEM image of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 2; Figure 9 SEM image of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 3; Figure 10 Photograph of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 4; Figure 11 This is a high-magnification dark-field image of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 4; Figure 12 SEM image of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 4; Figure 13 SEM image of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 5; Figure 14 The transmittance curves are for the magnesium aluminum spinel transparent ceramics prepared in Example 1 and Comparative Examples 1-5. Detailed Implementation

[0019] The following examples illustrate specific implementations of the present invention. However, these examples are merely for illustrative purposes and do not limit the scope of the invention in any way.

[0020] Example 1: The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: 1) 5.7g of magnesium aluminum spinel powder was loaded into a cylindrical graphite mold with a diameter of 20mm, placed in an oscillating sintering furnace, heated to 1000℃, and pressurized to 50MPa at a pressure rate of 10KN / min. Then, an oscillating pressure of 40MPa, amplitude of 10MPa, and frequency of 10Hz was applied and held for 20min. After sintering was completed, the mixture was cooled to room temperature to obtain a magnesium aluminum spinel pre-sintered body with a relative density of 75%. 2) The obtained magnesium aluminum spinel pre-sintered body was placed in a muffle furnace for heat treatment. The temperature was increased to 1100℃ at a heating rate of 5℃ / min, held for 4 hours, and then cooled to room temperature at a cooling rate of 3℃ / min. 3) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict the heat. Heat to 1400℃ and pressurize to 120MPa at a rate of 10KN / min. Then apply a median pressure of 120MPa, an amplitude of 30MPa, and a frequency of 10Hz oscillation pressure. Hold for 1.5h. After the holding time is over, stop the oscillation force and cool to room temperature to obtain magnesium aluminum spinel transparent ceramic.

[0021] Magnesium aluminum spinel transparent ceramics were polished on both sides, and the transmittance was tested using a Shimadzu UV-3600i Plus ultraviolet spectrophotometer. The same applies to the following examples and comparative examples.

[0022] A 1cm square block was cut from the center of a magnesium-aluminate spinel transparent ceramic for density testing. The density was measured using Archimedes' displacement method, fracture toughness and Vickers hardness were tested using the indentation method, and strength was obtained using the three-point bending method. The same methods apply to the following examples and comparative examples.

[0023] Testing revealed that the magnesium aluminum spinel transparent ceramic achieved a hardness of 18.4 GPa and a fracture toughness of 2.5 MPa·m. 1 / 2 The average flexural strength is 400 MPa, the maximum flexural strength is 458 MPa, the transmittance at 400 nm is 73.8%, the transmittance at 800 nm is 84%, and the relative density is 99.7%.

[0024] Figure 1 The image shows a double-sided polished magnesium aluminum spinel transparent ceramic sample obtained in Example 1. Figure 1It can be seen that the text on the paper is still clearly visible when viewed from a distance of 10cm, indicating that the sample has good transmittance.

[0025] Figure 2 Here is a surface SEM image of the magnesium aluminum spinel transparent ceramic prepared in Example 1. Figure 2 As can be seen from the data, the average grain size of the prepared sample is about 503 nm, and the grains have no pores and are highly dense. Figure 3 This is a high-magnification dark-field image of the magnesium aluminum spinel transparent ceramic prepared in Example 1. As can be seen from the image, the sample has almost no dislocations and has a low-defect structure, which helps to improve the transmittance of the sample.

[0026] Comparative Example 1 The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: The difference from Example 1 is that step 2 is omitted, while the rest of the steps are the same.

[0027] Testing revealed that the final magnesium-aluminate spinel transparent ceramic had a relative density of 99.7%, a hardness of 17.7 GPa, and a fracture toughness of 2.4 MPa·m. 1 / 2 The average strength is 350 MPa, the maximum strength is 410 MPa, the transmittance at 400 nm is 69.4%, and the transmittance at 800 nm is 82.2%. It can be seen that the strength and transmittance of Example 1 are better than those of Comparative Example 1.

[0028] Figure 4 This is a photograph of the magnesium aluminum spinel transparent ceramic sample prepared in Comparative Example 1 after double-sided polishing. Figure 4 As can be seen, the sample is slightly darker because it has not undergone heat treatment. Defects such as pre-carburization and oxygen vacancies still remain, resulting in a lower transmittance than in Example 1.

[0029] Figure 5 Here are SEM images of the surface of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 1, by... Figure 5 As can be seen from the data, the average grain size of the prepared sample is about 524 nm, and there are a small number of pores at the grain boundaries.

[0030] Compared with Example 1, the high-temperature heat treatment of the pre-fired body was not performed in the early stage. During the preparation of the pre-fired body, there were some oxygen vacancy defects, carburization, and residual stress caused by powder agglomeration. As a result, after subsequent dynamic sintering and forging, the sample still had some defects, resulting in a decrease in transmittance and mechanical properties.

[0031] Comparative Example 2: The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: 6g of magnesium aluminum spinel powder was placed into a graphite mold with a diameter of 30mm and placed in an oscillating sintering furnace. The furnace was heated to 1500℃ and pressurized to 150MPa at a rate of 10KN / min. Then, an oscillating pressure of 150MPa, amplitude of 30MPa, and frequency of 10Hz was applied and held at that temperature for 1.5h. After the holding time was completed, the oscillation force was stopped and the furnace was cooled to room temperature to obtain the transparent magnesium aluminum spinel ceramic material after oscillation sintering.

[0032] Testing revealed that the final sintered magnesium-aluminate spinel transparent ceramic had a relative density of 99.3%, a hardness of 17.1 GPa, and a fracture toughness of 2.2 MPa·m. 1 / 2 The average strength is 314 MPa, the maximum strength is 350 MPa, the transmittance at 400 nm is 64%, and the transmittance at 800 nm is 75.7%.

[0033] from Figure 6 A small number of dislocations were observed in the sample. Under higher temperature conditions, thermal stress increased significantly, providing a stronger driving force for dislocation nucleation and multiplication; these dislocations, acting as light scattering centers, enhanced the scattering of incident light. Simultaneously, the direct and comprehensive contact between the powder and the graphite mold exacerbated carburization, further increasing light absorption and scattering, thereby reducing the overall transmittance of the material. Figure 7 The image shows the appearance of the magnesium-aluminate spinel transparent ceramic sample prepared in Comparative Example 2 after double-sided polishing. It exhibits a slightly darker overall tone, which is closely related to the light scattering caused by dislocations and carburization. Further analysis... Figure 8 SEM surface morphology analysis revealed that the average grain size of the sample was approximately 820 nm, and several large pores were present inside. These structural defects together led to a decrease in its optical transmittance and mechanical properties.

[0034] Comparative Example 3: The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: Steps 2)-4) are the same as in Example 1, except that: 1) 5.7g of magnesium aluminum spinel powder was loaded into a cylindrical graphite mold with a diameter of 20mm, placed in a hot press sintering furnace, heated to 1200℃, pressurized to 50MPa at a pressure rate of 5KN / min, and held for 30min to obtain a magnesium aluminum spinel pre-sintered body with a relative density of 70%.

[0035] Testing revealed that the final sintered magnesium-aluminate spinel transparent ceramic had a relative density of 99.5%, a hardness of 17.2 GPa, and a fracture toughness of 2.25 MPa·m. 1 / 2The average strength is 337 MPa, the maximum strength is 392 MPa, the transmittance at 400 nm is 68.7%, and the transmittance at 800 nm is 80.3%.

[0036] Figure 9 The image shows a surface SEM image of the magnesium aluminum spinel transparent ceramic prepared in Comparative Example 3. As can be seen from the image, the average grain size of the prepared sample is about 760 nm. Compared with the oscillating pre-firing in Example 1, there are residual pores at the grain boundaries, which reduces the transmittance. The grain size has increased, resulting in a decrease in mechanical properties.

[0037] Comparative Example 4: The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: Steps 1)-3) are the same as in Example 1. The difference from Example 1 is: 4) the pre-fired body after polishing in the previous step is placed between two graphite pressure heads and placed in an oscillating sintering furnace. This process is not limited by molds. The body is heated to 1700℃ and pressurized to 120MPa at a pressure rate of 10KN / min. Then, an oscillating pressure of 120MPa, amplitude of 30MPa, and frequency of 10Hz is applied and held for 1.5h. After the holding time is over, the oscillation force is stopped and the body is cooled to room temperature to obtain magnesium aluminum spinel transparent ceramic.

[0038] Testing revealed that the final sintered magnesium-aluminate spinel transparent ceramic had a relative density of 99.3%, a hardness of 16.9 GPa, and a fracture toughness of 2.1 MPa·m. 1 / 2 The average strength is 325 MPa, the maximum strength is 348 MPa, the transmittance at 400 nm is 41.2%, and the transmittance at 800 nm is 73.2%.

[0039] Dark-field images of the samples reveal a large number of dislocations. This is due to significant thermal stress caused by the high sintering temperature, which provides the primary driving force for dislocation nucleation and multiplication, thus acting as light scattering centers and reducing the material's optical transmittance. Simultaneously, the high temperature exacerbates carburization, further increasing light absorption and scattering. The magnesium-aluminate spinel transparent ceramic prepared in Comparative Example 4 has the following appearance: Figure 10 Its overall tone is slightly dark, a phenomenon closely related to the aforementioned scattering and absorption of light by dislocations. Further analysis using SEM... Figure 12 Analysis of the surface morphology revealed that the average grain size of the sample was approximately 1.2 μm, indicating significant grain coarsening and a reduction in the material's mechanical properties. Additionally, the sample contained several large pores, which were also a significant factor contributing to the decrease in its optical transmittance and mechanical properties.

[0040] Comparative Example 5: The preparation method of magnesium aluminum spinel transparent ceramics includes the following steps: Steps 1)-3) are the same as in Example 1, except that: 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in a hot pressing sintering furnace. Heat it to 1550℃, pressurize it to 150MPa at a rate of 10KN / min, hold the pressure, and keep it at the temperature for 2 hours. After the holding time is over, remove the pressure and cool it to room temperature to obtain magnesium aluminum spinel transparent ceramic.

[0041] Testing revealed that the final sintered magnesium-aluminate spinel transparent ceramic had a relative density of 99.3%, a hardness of 16.7 GPa, and a fracture toughness of 2.1 MPa·m. 1 / 2 The average strength was 332 MPa, the maximum strength was 365 MPa, the transmittance at 400 nm was 58.6%, and the transmittance at 800 nm was 73.8%. The average grain size of the prepared sample was approximately 692 nm, which is an increase compared to the grain size in Example 1. As can be seen from its SEM image, there are many pores in the grains and at the grain boundaries.

[0042] according to Figure 14 The transmittance curves show that the magnesium-aluminate spinel transparent ceramic prepared in Example 1 exhibits the best optical transmittance. In contrast, Comparative Example 1, lacking heat treatment, shows significant oxygen vacancy defects and carburization, which were not completely eliminated during subsequent dynamic sintering and forging, thus significantly reducing the material's transmittance. Comparative Example 2, using an oscillating sintering method, shows significantly lower transmittance than Example 1. This is because the powder is in full contact with the graphite mold during oscillating sintering, leading to more severe carburization; simultaneously, the slightly higher sintering temperature causes grain coarsening, collectively resulting in decreased optical transmittance and mechanical properties. Comparative Example 3, using hot-pressing pre-sintering, has greater internal stress compared to oscillating pre-sintering, resulting in a less uniform microstructure, affecting subsequent sintering. Residual pores at grain boundaries further reduce transmittance. Comparative Example 4, using a higher sintering temperature, introduces significant thermal stress, which becomes the main driving force for dislocation nucleation and multiplication. Numerous dislocations act as light scattering centers, severely reducing optical transmittance. Furthermore, high temperatures exacerbate carburization and lead to grain coarsening, further enhancing light absorption and scattering, thus affecting transmittance and mechanical properties. Comparative Example 5 uses hot-pressing sintering as the final process, requiring even higher temperatures to achieve densification. This results in increased grain growth and carburization, leading to lower transmittance and mechanical properties in its sample. In conclusion, the design of heat treatment processes, the selection of different pre-firing methods, and the determination of the final sintering process all have a significant impact on the final optical and mechanical properties of magnesium aluminate spinel transparent ceramics.

[0043] Example 2 The preparation method of yttrium oxide transparent ceramics includes the following steps: 1) 7.9g of yttrium oxide powder was loaded into a cylindrical graphite mold with a diameter of 20mm and placed in an oscillating sintering furnace. The sintering parameters were: median pressure 30MPa, amplitude 5MPa, frequency 10Hz, and temperature 1150℃. The temperature was held for 25min. After sintering was completed, the mixture was cooled to room temperature to obtain a yttrium oxide pre-sintered body with a relative density of 73%. 2) The obtained yttrium oxide pre-burnt body was placed in a muffle furnace for heat treatment. The temperature was increased to 1200℃ at a heating rate of 5℃ / min and held for 3 hours. Then it was cooled to room temperature at a cooling rate of 3℃ / min. 3) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 4) Place the pre-sintered body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict the heat. Heat to 1500℃ and pressurize to 80MPa at a rate of 10KN / min. Then apply a median pressure of 80MPa, an amplitude of 20MPa, and a frequency of 10Hz oscillation pressure. Hold for 2 hours. After the holding time is over, stop the oscillation force and cool to room temperature to obtain the yttrium oxide transparent ceramic material after dynamic pressure sintering.

[0044] Testing revealed that the final sintered yttrium oxide transparent ceramic had a relative density of 99.5%, a hardness of 9.8 GPa, and a fracture toughness of 2 MPa·m. 1 / 2 The average strength is 170 MPa, the maximum strength is 200 MPa, the transmittance at 400 nm is 70%, and the transmittance at 800 nm is 82%.

[0045] Comparative Example 6: The preparation method of yttrium oxide transparent ceramics includes the following steps: The difference from Example 2 is that step 2 is omitted, while the rest of the steps are the same.

[0046] Testing revealed that the final sintered yttrium oxide transparent ceramic had a relative density of 99.3%, a hardness of 8.5 GPa, and a fracture toughness of 1.7 MPa·m. 1 / 2 The average strength is 152 MPa, the maximum strength is 180 MPa, the transmittance at 400 nm is 61%, and the transmittance at 800 nm is 81%. It can be seen that the strength and transmittance of Example 2 are better than those of Comparative Example 6.

[0047] Comparative Example 7: The preparation method of yttrium oxide transparent ceramics includes the following steps: 1) 7.9g of yttrium oxide powder was loaded into a cylindrical graphite mold with a diameter of 20mm and placed in an oscillating sintering furnace. The sintering parameters were: median pressure 30MPa, amplitude 5MPa, frequency 10Hz, and temperature 1150℃. The temperature was held for 25min. After sintering was completed, the mixture was cooled to room temperature to obtain a yttrium oxide pre-sintered body with a relative density of 73%. 2) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 3) Place the pre-sintered body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict it. Heat it to 1500℃ and pressurize it to 80MPa at a rate of 10KN / min. Then apply a medium pressure of 80MPa, an amplitude of 20MPa, and a frequency of 10Hz. Hold it at this temperature for 2 hours. After the holding time is over, stop the oscillation and cool it to room temperature. 4) Place the sample obtained in the previous step into a muffle furnace for heat treatment. Heat the sample to 1200℃ at a heating rate of 5℃ / min, hold for 3 hours, and then cool it to room temperature at a cooling rate of 3℃ / min to obtain yttrium oxide transparent ceramic.

[0048] Testing revealed that the final sintered yttrium oxide transparent ceramic had a relative density of 99.4%, a hardness of 8 GPa, and a fracture toughness of 1.7 MPa·m. 1 / 2 The average strength is 143 MPa, the maximum strength is 166 MPa, the transmittance at 400 nm is 55%, and the transmittance at 800 nm is 78%. It can be seen that the strength and transmittance of Example 2 are significantly better than those of Comparative Example 7, while the strength of Comparative Example 7 is significantly reduced.

[0049] Comparative Examples 6 and 7 are comparisons with Example 2. By comparing the performance of the three, it was found that even in the yttrium oxide system, similar results were observed when heat treatment was lacking: decreased transmittance and reduced mechanical properties. Furthermore, it was found that the placement of heat treatment significantly impacted the sample performance. When the pre-sintered body optimized by heat treatment underwent dynamic sintering and forging, the reduced internal impurities and improved structural uniformity facilitated the elimination of porosity during dynamic sintering and forging, thus fundamentally ensuring the material's high optical transmittance. If heat treatment was placed after dynamic sintering and forging, although it could alleviate some residual stress, it could not purify the material during the preceding sintering process, making it difficult to avoid performance losses due to impurities and defects during DSF, significantly limiting the synergistic enhancement effect.

[0050] Example 3: The preparation method of transparent magnesium oxide ceramics includes the following steps: 1) 5.8g of magnesium oxide powder was loaded into a cylindrical graphite mold with a diameter of 20mm and placed in an oscillating sintering furnace. The furnace was held at sintering parameters of 50MPa, 15MPa, 10Hz and 1100℃ for 20min. After sintering was completed, the furnace was cooled to room temperature to obtain a magnesium oxide pre-sintered body with a relative density of 70%. 2) The obtained magnesium oxide pre-calcined body was placed in a muffle furnace for heat treatment. The temperature was increased to 1150℃ at a heating rate of 5℃ / min, held for 4 hours, and then cooled to room temperature at a cooling rate of 2℃ / min. 3) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process is not limited by molds. Heat to 1400℃ and pressurize to 100MPa at a rate of 10KN / min. Then apply a median pressure of 100MPa, an amplitude of 30MPa, and a frequency of 10Hz oscillation pressure. Hold for 2 hours. After the holding time is over, stop the oscillation force and cool to room temperature to obtain transparent magnesium oxide ceramic after dynamic pressure sintering.

[0051] Testing revealed that the final sintered transparent magnesium oxide ceramic had a relative density of 99.7%, a hardness of 9.3 GPa, and a fracture toughness of 2.3 MPa·m. 1 / 2 The average strength is 253 MPa, the maximum strength is 297 MPa, the transmittance at 400 nm is 69%, and the transmittance at 800 nm is 80%.

[0052] Comparative Example 8: The preparation method of transparent magnesium oxide ceramics includes the following steps: Steps 1)-3) are the same as in Example 3, except that: 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in a hot pressing sintering furnace. Heat it to 1400℃, pressurize it to 130MPa at a rate of 10KN / min, hold the pressure, and keep it at the temperature for 2 hours. After the holding time is over, remove the pressure and cool it to room temperature to obtain transparent magnesium oxide ceramic.

[0053] Testing revealed that the final sintered transparent magnesium oxide ceramic had a relative density of 99.3%, a hardness of 8 GPa, and a fracture toughness of 2.1 MPa·m. 1 / 2 The average strength is 196 MPa, the maximum strength is 210 MPa, the transmittance at 400 nm is 58%, and the transmittance at 800 nm is 71%.

[0054] Similar results were observed when hot pressing was used in the later stages of preparation in Comparative Example 8, with decreased transmittance and mechanical properties, indicating that the later preparation method is also crucial.

[0055] Example 4: The preparation method of transparent alumina ceramics includes the following steps: 1) 6.3g of alumina powder was loaded into a cylindrical graphite mold with a diameter of 20mm and placed in an oscillating sintering furnace. The furnace was held at sintering parameters of 60MPa, 15MPa, 10Hz and 1200℃ for 40min. After sintering was completed, the furnace was cooled to room temperature to obtain a pre-sintered alumina with a relative density of 78%. 2) The obtained alumina pre-calcined body was placed in a muffle furnace for heat treatment. The temperature was increased to 1250℃ at a heating rate of 5℃ / min, held for 4 hours, and then cooled to room temperature at a cooling rate of 2℃ / min. 3) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict the heat. Heat to 1500℃ and pressurize to 120MPa at a rate of 10KN / min. Then apply a median pressure of 120MPa, an amplitude of 20MPa, and a frequency of 10Hz oscillation pressure. Hold for 1 hour. After the holding time is over, stop the oscillation force and cool to room temperature to obtain alumina transparent ceramic material after dynamic pressure sintering.

[0056] Testing revealed that the final sintered transparent alumina ceramic had a relative density of 99.7%, a hardness of 20.6 GPa, and a fracture toughness of 4.7 MPa·m. 1 / 2 The average strength is 790 MPa, the maximum strength is 830 MPa, the transmittance at 400 nm is 70%, and the transmittance at 800 nm is 81%.

[0057] Comparative Example 9: The preparation method of transparent alumina ceramics includes the following steps: Steps 1)-3) are the same as in Example 4, except that: 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in a hot pressing sintering furnace. Heat it to 1700℃, pressurize it to 140MPa at a rate of 10KN / min, hold the pressure, and keep it at the temperature for 1 hour. After the holding time is over, remove the pressure and cool it to room temperature to obtain transparent alumina ceramic.

[0058] Testing revealed that the final sintered transparent alumina ceramic had a relative density of 99.5%, a hardness of 19.9 GPa, and a fracture toughness of 4.2 MPa·m. 1 / 2 The average strength is 702 MPa, the maximum strength is 748 MPa, the transmittance at 400 nm is 65%, and the transmittance at 800 nm is 77%.

[0059] Comparing the performance of Example 4 and Comparative Example 9, it was found that even in the alumina system, when Comparative Example 9 was subjected to hot pressing sintering for the final sintering, similar results were observed, with a decrease in transmittance and mechanical properties.

[0060] Example 5: The preparation method of yttrium aluminum garnet transparent ceramics is as follows: 1) 7.23g of yttrium aluminum garnet powder was loaded into a cylindrical graphite mold with a diameter of 20mm and placed in an oscillating sintering furnace. The furnace was held at 1100℃ for 30min under the sintering parameters of 40MPa medium pressure, 10MPa amplitude, 10Hz frequency, and 40MPa medium pressure. After sintering, the furnace was cooled to room temperature to obtain a pre-sintered alumina with a relative density of 78%. 2) Place the pre-burnt body into a muffle furnace for heat treatment. Heat the body to 1000℃ at a rate of 3℃ / min, hold for 5 hours, and then cool it to room temperature at a rate of 3℃ / min. 3) Grind and polish the pre-burned body obtained in the previous step on diamond sandpaper on both sides until the surface roughness is 0.5 micrometers, and grind and polish the two graphite indenters on diamond sandpaper until the surface roughness is 0.5 micrometers; 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in an oscillating sintering furnace. This process does not use molds to restrict the heat. Heat to 1400℃ and pressurize to 160MPa at a rate of 10KN / min. Then apply a median pressure of 160MPa, an amplitude of 20MPa, and a frequency of 10Hz. Hold for 1 hour. After the holding time is over, stop the oscillation and cool to room temperature to obtain yttrium aluminum garnet transparent ceramic after dynamic pressure sintering.

[0061] Testing revealed that the final sintered yttrium aluminum garnet transparent ceramic had a relative density of 99.9%, a hardness of 14.3 GPa, and a fracture toughness of 1.8 MPa·m. 1 / 2 The average strength is 310 MPa, the maximum strength is 350 MPa, the transmittance at 400 nm is 68%, and the transmittance at 800 nm is 79%.

[0062] Comparative Example 10: The preparation method of yttrium aluminum garnet transparent ceramics is as follows: Steps 1)-3) are the same as in Example 5, except that: 4) Place the pre-fired body after polishing in the previous step between two graphite pressure heads and place it in a hot pressing sintering furnace. Heat it to 1500℃, pressurize it to 180MPa at a rate of 10KN / min, hold the pressure, and keep it at the temperature for 1 hour. After the holding time is over, remove the pressure and cool it to room temperature to obtain yttrium aluminum garnet transparent ceramic.

[0063] Testing revealed that the final sintered yttrium aluminum garnet transparent ceramic had a relative density of 99.6%, a hardness of 13.5 GPa, and a fracture toughness of 1.5 MPa·m. 1 / 2 The average strength is 287 MPa, the maximum strength is 326 MPa, the transmittance at 400 nm is 64%, and the transmittance at 800 nm is 72.3%.

[0064] Comparing the performance of Example 5 and Comparative Example 10, it was found that even for yttrium aluminum garnet transparent ceramic materials, Comparative Example 10 showed similar results when hot-pressing sintering was used, with decreased transmittance and reduced mechanical properties. A better effect was achieved by using a combination of oscillation pre-firing, heat treatment, and DSF.

[0065] Table 1 Performance Data Sheet Material Sintering process Average flexural strength / MPa Maximum flexural strength / MPa Fracture toughness / MPa m1 / 2 Average grain size Hardness / GPa Relative density / % Transmittance at 400 nm % Transmittance at 800nm ​​% Example 1 Magnesium aluminum spinel Oscillating pre-firing + heat treatment + DSF 400 458 2.5 503nm 18.4 99.7 73.8 84 Comparative Example 1 Magnesium aluminum spinel Oscillation preheating + DSF 350 410 2.4 524nm 17.7 99.7 69.4 82.2 Comparative Example 2 Magnesium aluminum spinel Vibration sintering 314 350 2.2 820nm 17.1 99.3 64 75.7 Comparative Example 3 Magnesium aluminum spinel Hot pressing and preheating + heat treatment + DSF 337 392 2.25 760nm 17.2 99.5 68.7 80.3 Comparative Example 4 Magnesium aluminum spinel Oscillating pre-firing + heat treatment + DSF 325 348 2.1 1.2μm 16.9 99.3 41.2 73.2 Comparative Example 5 Magnesium aluminum spinel Vibration preheating + heat treatment + hot pressing 332 365 2.1 692nm 16.7 99.3 58.6 73.8 Example 2 Yttrium oxide Oscillating pre-firing + heat treatment + DSF 170 200 2 550nm 9.8 99.5 70 82 Comparative Example 6 Yttrium oxide Oscillation preheating + DSF 152 180 1.7 576nm 8.5 99.3 61 81 Comparative Example 7 Yttrium oxide Oscillating preheating + DSF + heat treatment 143 166 1.7 585nm 8 99.4 55 78 Example 3 magnesium oxide Oscillating pre-firing + heat treatment + DSF 253 297 2.3 674nm 9.3 99.7 69 80 Comparative Example 8 magnesium oxide Vibration preheating + heat treatment + hot pressing 196 210 2.1 718nm 8 99.3 58 71 Example 4 Alumina Oscillating pre-firing + heat treatment + DSF 790 830 4.7 569nm 20.6 99.7 70 81 Comparative Example 9 Alumina Vibration preheating + heat treatment + hot pressing 702 748 4.2 613nm 19.9 99.5 65 77 Example 5 Yttrium aluminum garnet Oscillating pre-firing + heat treatment + DSF 310 350 1.8 2.6μm 14.3 99.9 68 79 Comparative Example 10 Yttrium aluminum garnet Vibration preheating + heat treatment + hot pressing 287 326 1.5 3μm 13.5 99.6 64 72.3 Table 1 shows the performance data of the transparent ceramics prepared in Examples 1-5 and Comparative Examples 1-10 of this invention. DSF indicates dynamic sintering and forging technology. The combination of oscillating pre-firing, heat treatment, and DSF indicates that a pre-fired body is first prepared using oscillating sintering, then subjected to high-temperature heat treatment, and finally dynamic sintering and forging to obtain the final sample. The results show that the absence of heat treatment, changes in the pre-firing method, or changes in the dynamic sintering and forging method all affect the transmittance and strength of the product. The three methods—oscillating pre-firing, heat treatment, and DSF—complement each other and work synergistically; none can be omitted.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Any other modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention, as long as they do not depart from the spirit and scope of the technical solutions of the present invention, should be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing a transparent ceramic material, characterized in that, Includes the following steps: 1) Transparent ceramic powder is loaded into a mold and sintered by vibration to obtain a pre-fired body; 2) Heat-treat the pre-fired body obtained in step 1); 3) Polish the pre-fired body after heat treatment; 4) Place the pre-fired body polished in step 3) between two graphite pressure heads and place it in an oscillating sintering furnace. Heat it to temperature T and hold it at that temperature. At the same time, apply pressure to the preset pressure and apply oscillation force through the upper and lower pressure heads. After the holding time ends, stop the oscillation force and cool it down to room temperature to obtain a transparent ceramic material.

2. The preparation method according to claim 1, characterized in that: In step 1), the sintering temperature of the oscillation sintering is 700-1200 ℃, the median value of the oscillation force is calculated based on the area as 30-100 MPa, the amplitude is 5-60 MPa, the frequency is 0.5-20 Hz, and the holding time is 5-60 min.

3. The preparation method according to claim 1, characterized in that: In step 2), the heat treatment temperature is 700-1600℃ and the holding time is 1-7h.

4. The preparation method according to claim 1, characterized in that: In step 4), the temperature T is 1200-1600℃, the median value of the oscillation force is 60-200 MPa calculated based on the area, the amplitude is 5-70 MPa, the frequency is 0.5-20Hz, and the heat preservation time is 1-3h.

5. The preparation method according to claim 1, characterized in that: The relative density of the pre-fired body is greater than 40%, and the shape of the pre-fired body is cylindrical or blocky.

6. The preparation method according to claim 1, characterized in that: Step 3) involves grinding and polishing the pre-burnt body until the surface roughness of the polished surface reaches 0.25-1μm.

7. The preparation method according to claim 1, characterized in that: The transparent ceramic powder is one of magnesium aluminum spinel powder, yttrium oxide powder, magnesium oxide powder, aluminum oxide powder, and yttrium aluminum garnet powder.

8. A transparent ceramic material prepared by the method according to any one of claims 1-7.

9. The transparent ceramic material according to claim 8, characterized in that: When the transparent ceramic material is magnesium aluminum spinel transparent ceramic, the transmittance at 800nm ​​is >84%, the average flexural strength is >400MPa, and the Vickers hardness is >18.4GPa. When the transparent ceramic material is yttrium oxide transparent ceramic, the transmittance at 800nm ​​is >82%, the average flexural strength is >170MPa, and the Vickers hardness is >9.8GPa; When the transparent ceramic material is magnesium oxide transparent ceramic, the transmittance at 800nm ​​is >71%, the average flexural strength is >236MPa, and the Vickers hardness is >8.5GPa. When the transparent ceramic material is yttrium aluminum garnet transparent ceramic, the transmittance at 800nm ​​is >79%, the average flexural strength is >310MPa, and the Vickers hardness is >14.3GPa.

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