Method for repairing processing defects of Y2O3-MgO-based nano complex-phase infrared transparent ceramic through atmosphere annealing

Abstract

The invention provides a method for repairing Y2O3-MgO-based nano complex-phase infrared transparent ceramic processing defects through atmosphere annealing, and belongs to the technical field of functional ceramic preparation. The preparation method comprises the following steps: performing high-temperature annealing on a Y2O3-MgO-based nano complex-phase infrared transparent ceramic sample piece in a vacuum atmosphere, wherein the annealing temperature is 600-1500 DEG C, and the annealing time is 1-10 hours; and after vacuum annealing is completed, a vacuum system is closed, oxygen is slowly introduced, the introduction amount of the oxygen is 5-100 sccm, the annealing temperature is 600-1500 DEG C, heat preservation is conducted for 1-10 hours in the oxygen atmosphere, and finally the temperature is slowly reduced to the room temperature. The ordered diffusion probability of atoms on the ceramic surface can be remarkably improved through vacuum atmosphere annealing, effective repairing of surface microcracks is achieved, oxygen vacancies and other microdefects can be eliminated through oxygen atmosphere annealing, and residual stress in a ceramic sample piece is released. The defect repair of the Y2O3-MgO-based nano complex-phase infrared transparent ceramic can be realized through atmosphere annealing, and the mechanical and optical properties of the Y2O3-MgO-based nano complex-phase infrared transparent ceramic are greatly improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional ceramic preparation, and particularly relates to a method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing. Background Art

[0002] Infrared transparent ceramics have important applications in the fields of infrared laser matrices, infrared windows / radomes, etc. As window / radome materials, the main wavelength bands of concern for infrared transparent ceramics are three: near-infrared (0.76 - 1.1 μm), mid-infrared (3 - 5 μm), and far-infrared (8 - 12 μm), which respectively correspond to the transmission windows of the atmosphere for radiant electromagnetic waves. Compared with traditional infrared glass and infrared crystal materials, infrared transparent ceramics have the advantages of both, such as high thermal conductivity, good mechanical properties, large preparation size, low production cost, etc., and have broad application prospects in new-generation optoelectronic devices such as infrared night vision devices, missiles, and laser guidance.

[0003] As a typical brittle material, ceramics are prone to fracture under external forces. In the processes of grinding, polishing, and other processing of ceramics, external mechanical stress will introduce microcracks and other microscopic defects on the surface of the sample, resulting in a decrease in the fracture strength of the material. In addition, local thermal stress during the preparation of ceramics, local mechanical stress during the processing, or local stress caused by microscopic defects (inclusions, pores, microcracks, etc.) will form residual stress inside the material. If the residual stress is tensile stress, it will further reduce the fracture strength of the ceramics and affect the service performance of Y2O3-MgO-based nanocomposite infrared transparent ceramics.

[0004] High-temperature annealing treatment has received extensive attention as an effective method for repairing internal microdefects in materials. During the annealing process, by appropriately heating the ceramic material, the atoms inside it obtain energy and rearrange, which helps to release the residual stress accumulated inside the ceramic. At the same time, the thermally activated effect generated during the annealing process can promote the healing of microcracks. The strength of the annealed ceramic material can be increased by 50% - 100%. Patent [CN114864410A] provides a reactive atmosphere annealing method for eliminating the surface damage layer of compound semiconductor crystals, which solves the problem of introducing new surface damage during the wafer surface treatment process, but leads to the deterioration of the wafer quality and affects the subsequent device fabrication. In 2015, Tavangarian et al. [Tavangarian, F.; Li, G. Crack-healing in spinel (MgAl2O4) ceramic. Materials Science and Engineering: A 2015, 641, 201 - 209.] reported the crack healing behavior of spinel ceramics during high-temperature annealing treatment, which solved the crack problem of spinel ceramics in high-temperature environments and achieved the restoration of strength. However, abnormal grain growth occurs at high temperatures, and further research and exploration are needed. In 2018, Fei Wang et al. [Wang, F.; Zhang, C.; Yan, X.; et al. Microstructure-property relation in alumina ceramics during post-annealing process after laser shock processing. 2018, 101, 4933 - 4941.] reported the healing of microcracks in α-Al2O3 ceramics after annealing treatment. However, when the annealing temperature is low, the residual stress inside the material can only be partially relaxed, and complete annealing can only be achieved above 1400 °C. And too high annealing temperature will lead to further growth of ceramic grains, which is not conducive to maintaining the high strength of the material.

[0005] For Y2O3-MgO-based nanocomposite infrared transparent ceramics, due to the relatively small grain size of the ceramics, there are many microdefects on the surface of the processed ceramics. During the long-term high-temperature annealing process, it will cause grain coarsening and precipitation at the microdefects with high surface energy, reduce the optical roughness of the ceramic surface, and affect the signal detection accuracy. At the same time, oxide ceramics cannot generate new substances through oxidation reactions to repair surface cracks, and new defect repair mechanisms need to be explored. For the above reasons, it is urgent to carry out research on new annealing technologies for Y2O3-MgO-based nanocomposite infrared transparent ceramics. Summary of the Invention

[0006] During the machining process of infrared transparent ceramics, microdefects such as microcracks and lattice defects are likely to occur on the surface, reducing the mechanical and optical properties of the ceramics. The purpose of the present invention is to provide a method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing, to overcome the problem of insufficient driving force for defect repair during the conventional annealing of nanoceramics, as well as the problem of grain precipitation caused by too high annealing temperature, and to further improve the comprehensive performance of ceramic materials.

[0007] Based on the above purpose, the present invention adopts the following technical solutions:

[0008] A method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing, first subjecting the Y2O3-MgO-based nanocomposite infrared transparent ceramic sample to vacuum high-temperature annealing; after the vacuum high-temperature annealing, closing the vacuum system and slowly introducing oxygen, at this time the vacuum annealing is transformed into oxygen annealing, and after the oxygen annealing is completed, it is slowly cooled to room temperature.

[0009] During the vacuum annealing process, on the one hand, impurities adsorbed on the surface cracks can be effectively released, and on the other hand, the vacuum environment is a weak reducing atmosphere, which causes the ceramic to easily generate oxygen vacancies at high-energy defect sites (such as crack tips, section edges, etc.). As the temperature rises, atoms at high-energy defect positions are easy to diffuse and migrate. When some atoms move and fill into the crack positions, the crack defects are repaired and the mechanical properties of the ceramic are improved. On the other hand, since the vacuum atmosphere will introduce lattice defects including additional oxygen vacancies, the crack healing temperature of the ceramic in the vacuum atmosphere is much lower than that in the air atmosphere, so that the precipitation of surface grains will not be caused, and the surface finish of the ceramic is basically not affected during the entire annealing stage.

[0010] After the vacuum annealing is completed, oxygen is slowly introduced, and the vacuum atmosphere transitions to an oxygen atmosphere. When annealing in an oxygen environment, oxygen vacancy defects on the surface and inside of the ceramic are repaired, which has a positive effect on improving the transmittance and reducing the emissivity of the infrared transparent ceramic. In addition, after the transition from vacuum to oxygen atmosphere annealing, the dangling bonds on the ceramic surface adsorb some oxygen atoms, thereby reducing the surface defect states and increasing the surface compressive stress of the ceramic. When the oxygen atmosphere annealing is completed and the temperature drops to room temperature, this compressive stress still exists.

[0011] After two-step annealing in vacuum and oxygen atmosphere, the mechanical and optical properties of the ceramic will be greatly improved.

[0012] Further, the vacuum degree during vacuum annealing is less than 10 -1 Pa, preferably 0.001 - 0.01 Pa.

[0013] Further, the vacuum annealing temperature is 600 - 1500 °C, preferably 800 - 1100 °C.

[0014] Furthermore, the holding time of vacuum annealing is 1 - 10 h, preferably 3 - 6 h.

[0015] After the vacuum annealing is completed, the vacuum system is closed and oxygen is introduced. The oxygen flow rate is 5 - 100 sccm, preferably 20 - 60 sccm.

[0016] , furthermore, the oxygen annealing temperature is 600 - 1000 °C, preferably 800 - 1000 °C.

[0017] When the annealing temperatures in the two stages of vacuum annealing and oxygen annealing are inconsistent, in the transition stage from vacuum annealing to oxygen annealing, the heating rate and cooling rate are 1 - 5 °C / min, preferably 2 °C / min.

[0018] Furthermore, the holding time of oxygen annealing is 5 - 10 h, preferably 5 - 8 h.

[0019] After the holding of oxygen annealing is completed, the system starts to cool down slowly. The cooling rate is 0.5 - 5 °C / min, preferably 2 °C / min.

[0020] The grain size of the Y2O3 - MgO - based nanocomposite infrared ceramic described in the present invention is 50 - 800 nm.

[0021] The annealed Y2O3 - MgO - based nanocomposite infrared transparent ceramic obtained based on the method of the present invention can be used as an infrared optical window material.

[0022] The method of the present invention is not only applicable to Y2O3 - MgO - based nanocomposite ceramics, but its technical principle can also be extended to the repair of processing defects of other types of infrared transparent ceramics. Specifically, it is applicable to doping one or more of oxides such as zirconia, ceria, hafnia, lutetia, gadolinia, zinc oxide, magnesium oxide, calcium oxide, aluminum oxide, titanium oxide, etc. in Y2O3 to form a general formula of (Y 1-x X x )2O3 - (Mg 1-Y Y Y )O - based nanocomposite infrared transparent ceramic processing defect repair.

[0023] The beneficial technical effects of the present invention are as follows:

[0024] The present invention provides an efficient and reliable solution for the processing and performance improvement of infrared transparent ceramics.

[0025] During the first-step vacuum high-temperature annealing process of the Y2O3-MgO-based nano-composite infrared transparent ceramic prepared by the present invention, the residual stress accumulated inside the ceramic is released and the micro-cracks gradually heal. With the release of stress and the repair of micro-cracks, the mechanical properties of the ceramic are improved, and it can be more stable when bearing external loads, effectively avoiding material failure caused by crack propagation.

[0026] During the second-step annealing process in an oxygen atmosphere, the oxygen vacancies inside the ceramic and a large number of dangling bonds on the surface are repaired. Therefore, the comprehensive properties of the material are improved, expanding the application of the ceramic material in extreme environments.

[0027] During the atmosphere annealing process of the present invention, a dynamic conversion from vacuum annealing to oxygen annealing is realized, solving the problem that it is difficult for traditional annealing methods to simultaneously take into account internal and surface defects, and significantly improving the mechanical properties and annealing efficiency of the material. Compared with the prior art, the annealing method of the present invention can achieve higher material properties in a shorter time, while reducing energy consumption and equipment loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a diagram of the flexural strength test before defect repair in Example 1.

[0029] Figure 2 It is a diagram of the flexural strength test after defect repair in Example 1.

[0030] Figure 3 It is a diagram of the flexural strength test of the crack sample in Example 2.

[0031] Figure 4 It is a diagram of the flexural strength test of the crack-healed sample in Example 2.

[0032] Figure 5 It is a scanning electron microscope image of the crack sample taken before defect repair in Example 3.

[0033] Figure 6 It is a scanning electron microscope image of the crack sample taken after defect repair in Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0034] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0035] Taking the Y2O3-MgO nano-composite oxide ceramic as an example, the present invention will be further described below in conjunction with examples and drawings. These examples are only used to illustrate the present invention and should not be used to limit the protection scope of the present invention.

[0036] Example 1

[0037] Take the same batch of Y2O3-MgO nanocomposite infrared transparent ceramics after grinding (with the specification of 3×4×36mm 3 ), and directly test the three-point bending strength of some without any treatment. Figure 1 It is the three-point bending strength tested without annealing directly after the processing of Example 1.

[0038] Another part of the samples is annealed according to the present invention. First, evacuate the furnace chamber system to make its vacuum degree less than 10 -3 Pa, then start heating at a heating rate of 1℃ / min to 800℃, and keep the samples at this temperature for 10h. Then break the vacuum of the system and introduce oxygen, with the amount of oxygen introduced being 50sccm, keep the samples at 800℃ for another 8h, then cool down. First, keep the cooling rate at 2℃ / min until it reaches 200℃, and then cool naturally to room temperature. Break the vacuum of the system and take out the samples. Test the three-point bending strength of the Y2O3-MgO nanocomposite infrared transparent ceramics after atmosphere annealing repair. Figure 2 It is the three-point bending strength tested after atmosphere annealing after the processing of Example 1.

[0039] Compared with the data before annealing, the bending strength of the Y2O3-MgO nanocomposite infrared transparent ceramics after atmosphere annealing is significantly improved, increasing from 150MPa to 300MPa.

[0040] Example 2

[0041] Take the same batch of Y2O3-MgO nanocomposite infrared transparent ceramics after grinding (with the specification of 3×4×36mm 3 ), and press cracks on its 4×36mm 2 surface with a Vickers hardness tester. Divide the samples containing cracks into two batches. Half of the cracked sample strips are directly tested for three-point bending strength without any heat treatment. The other half is annealed according to the present invention. First, evacuate the furnace chamber system to make its vacuum degree less than 10 -1 Pa, then start heating at a heating rate of 10℃ / min to 1500℃, and keep the samples at this temperature for 1h. Break the vacuum of the system and introduce oxygen, with the amount of oxygen introduced being 100sccm, and let the samples cool down at a cooling rate of 5℃ / min to 600℃, and keep them at this temperature for 10h. Then cool down. First, keep the cooling rate at 0.5℃ / min until it reaches 200℃, and then cool naturally to room temperature. Break the vacuum of the system and take out the samples. Test the three-point bending strength of the taken-out samples with healed cracks.

[0042] Figure 3 These are the test data of the flexural strength of the crack-like specimens. Figure 4 These are the test data of the flexural strength of the crack-healed specimens. It is found that the average flexural strength of the crack-healed specimens after the atmosphere annealing according to the present invention is 100 MPa higher than that of the crack-like specimens without any treatment, and the flexural strength is increased by 70%.

[0043] Example 3

[0044] Take two pieces of Y2O3-MgO nano-composite infrared transparent ceramics (with the specification of 3×4×36 mm 3 ) that are ground and processed in the same batch. Press cracks on the surface of their 4×36 mm 2 surface with a Vickers hardness tester. One of the specimens is not treated. The other specimen is subjected to the annealing treatment according to the present invention. First, evacuate the furnace cavity system to make its vacuum degree less than 10 - 2 Pa, and then start heating at a heating rate of 5 °C / min to 600 °C, and keep the specimen at this temperature for 6 h.

[0045] Perform a vacuum-breaking treatment on the system and introduce oxygen. The amount of oxygen introduced is 5 sccm. Let the sample heat up to 1000 °C at a heating rate of 1 °C / min and keep it at this temperature for 5 h. Then cool down. First, keep the cooling rate at 5 °C / min until it reaches 200 °C, and then cool it naturally to room temperature. Perform a vacuum-breaking treatment on the system and take out the specimen.

[0046] Observe the crack-like specimens without any treatment and the crack-healed specimens after the annealing treatment according to the present invention with a scanning electron microscope to see the change in the surface crack morphology.

[0047] Figure 5 This is the scanning electron microscope image of the crack-like specimen prefabricated on the surface with a Vickers hardness tester without annealing after the completion of Example 3.

[0048] Figure 6 This is the scanning electron microscope image of the specimen containing the crack-like specimen after the atmosphere annealing repair in Example 3. It can be clearly seen the crack-healing phenomenon after the atmosphere annealing.

[0049] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing, characterized in that, Including the following steps; S1 Vacuum annealing: The Y2O3-MgO-based nanocomposite infrared transparent ceramic sample is vacuum annealed at 600-1500 °C for 1-10 h; S2 Oxygen annealing: After the vacuum annealing is completed, the vacuum system is closed, oxygen is slowly introduced, and it is oxygen annealed at 600-1000 °C for 5-10 h; After slowly cooling to below 200 °C, the heating source is turned off and it is naturally cooled to room temperature.

2. The method for repairing processing defects of Y2O3-MgO-based nano-composite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that, In step S1, the vacuum degree is less than 10 -1 Pa, preferably 0.001 to 0.01 Pa.

3. The method for repairing processing defects of Y2O3-MgO-based nano-composite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that In step S1, the heating rate is 1-10 °C / min, preferably 5 °C / min.

4. The method for repairing processing defects of Y2O3-MgO-based nano-composite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that, In step S1, the vacuum annealing temperature is 800-1100 °C, and the vacuum annealing holding time is 3-6 h.

5. A method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that, When the annealing temperatures in the two stages of vacuum annealing and oxygen annealing are inconsistent, in the transition stage from vacuum annealing to oxygen annealing, the heating rate and the cooling rate are 1-5 °C / min, preferably 2 °C / min.

6. The method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that In step S2, the oxygen flow rate during oxygen annealing is 5-100 sccm, preferably 20-60 sccm.

7. A method for repairing processing defects of Y2O3-MgO-based nano-composite infrared transparent ceramics by atmosphere annealing according to claim 1 or 6, characterized in that, In step S2, the oxygen annealing temperature is 800-1000 °C, and the oxygen annealing holding time is 5-8 h.

8. The method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that, In step S2, the cooling rate of the slow cooling is 0.5-2 °C / min, preferably 2 °C / min.

9. The method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing according to claim 1, characterized in that, The grain size of the Y2O3-MgO-based nanocomposite infrared ceramic is 50-800 nm.

10. The method for repairing processing defects of Y2O3-MgO-based nanocomposite infrared transparent ceramics by atmosphere annealing according to claim 1, wherein The Y2O3-MgO-based nanocomposite infrared transparent ceramic is doped with one or more of zirconia, ceria, hafnia, lutetia, gadolinia, zinc oxide, magnesium oxide, calcium oxide, alumina, titanium oxide, etc.

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