Preparation method of magnesium aluminate spinel nano infrared transparent ceramic

Abstract

The invention provides a preparation method of magnesium aluminate spinel nano infrared transparent ceramics, and relates to the technical field of infrared transparent ceramics. The magnesium aluminate spinel nano infrared transparent ceramic is prepared by preparing MgAl2O4 nano powder from magnesium acetate tetrahydrate and nano aluminum oxide powder as raw materials and then carrying out spray granulation, isostatic pressing molding, pre-sintering, hot isostatic pressing sintering, annealing, polishing and other processes, has the characteristics of high density and high light transmittance, and has the average transmittance of more than 85% in infrared 3-5 [mu] m.

Description

Technical Field

[0001] The present invention relates to the technical field of infrared transparent ceramics, and in particular to a method for preparing magnesium-aluminum spinel nano-infrared transparent ceramics. Background Art

[0002] Magnesium-aluminum spinel has important military applications. Its ballistic resistance far surpasses that of bulletproof glass and sapphire crystals, making it ideal for use in windows of tanks and armored vehicles, as well as individual soldier's protective visors. Its transparency in the mid-infrared band also surpasses that of sapphire and aluminum oxynitride, making it an ideal material for missile infrared windows. With the development of supersonic vehicles, missile infrared windows / dome covers face new challenges, requiring spinel transparent ceramics to exhibit high transmittance across a wide wavelength range. For use in armor, windows, and other components, which must withstand external impact and abrasion, the material must possess high hardness and wear resistance.

[0003] In recent years, the performance of magnesium-aluminum spinel transparent ceramics has also made significant progress. By adopting advanced preparation techniques and composition control strategies, such as co-doping and microstructure control, magnesium-aluminum spinel transparent ceramics with significantly improved flexural strength have been successfully prepared. These improvements have made magnesium-aluminum spinel transparent ceramics show great potential in the application of mid-infrared window materials in hypersonic aircraft. However, despite these advances, the flexural strength of existing magnesium-aluminum spinel transparent ceramics is still difficult to meet the more stringent requirements of hypersonic aircraft for infrared window materials. Therefore, in order to meet the application requirements in high- and extreme environments, it is crucial to develop new high-performance infrared light window materials. Against this background, the design concept of nano-complex phase modified magnesium-aluminum spinel came into being.

[0004] However, the existing common methods for preparing magnesium-aluminum spinel transparent ceramics, such as pressureless sintering, hot pressing sintering, and spark plasma sintering, all have certain limitations. In the prior art, the patent document entitled "A Method for Preparing Magnesium-Aluminum Spinel Nano Transparent Ceramics" with application number 200610022318.5 and publication date May 16, 2007, utilizes magnesium salts and aluminum salts to prepare magnesium-aluminum spinel nanopowders, and further produces magnesium-aluminum spinel ceramics. The ceramics have a transmittance greater than 70% in the infrared band of 760-2200nm and a transmittance greater than 50% in the visible light band of 500-760nm. This patent has academic value as an early exploration of the application of nanopowders in transparent ceramics. However, due to the sintering technology in 2007 (HIP was not popular), its process design has fundamental defects, and its optical performance has not reached the application threshold, which cannot meet the requirements of modern high-performance spinel ceramics. Therefore, no subsequent industrialization reports have been reported, and industrialization cannot be achieved.

[0005] In view of this, it is necessary to design an improved preparation method of magnesium-aluminum spinel nano-infrared transparent ceramics to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide a method for preparing magnesium aluminum spinel nano-infrared transparent ceramics.

[0007] To achieve the above-mentioned object of the invention, the present invention provides a method for preparing magnesium-aluminum spinel nano-infrared transparent ceramics, comprising the following steps:

[0008] The MgAl2O4 nano powder is ball-milled and granulated, then pressed into a shape, and then subjected to sintering and annealing treatments in sequence to obtain the MgAl2O4 nano infrared transparent ceramic.

[0009] The MgAl2O4 nanopowder is obtained by calcining a mixed solution containing a magnesium source and an aluminum source. The aluminum source is nano-alumina powder with a particle size of 20-50 nm.

[0010] Preferably, the calcination temperature is 400-800° C. and the calcination time is 1-3 hours.

[0011] Preferably, the pressing is performed by isostatic pressing, and the process parameters are: pressure 200-300 MPa, time 30-60 min.

[0012] Preferably, the sintering treatment adopts hot isostatic pressing sintering, and its process parameters are: temperature 1500-1900° C., pressure 100-150 MPa, heating rate 3-5° C. / min, and time 3-6 h.

[0013] Preferably, the annealing treatment is performed at a temperature of 1100-1220° C. for 5-15 hours.

[0014] Preferably, the magnesium source is one of magnesium sulfate, magnesium acetate and magnesium nitrate, preferably magnesium acetate.

[0015] Preferably, the ball milling uses 1-3 mm zirconia balls as the medium, anhydrous ethanol as the dispersant, and the ball milling time is 8-12 hours.

[0016] The beneficial effects of the present invention are:

[0017] 1. The magnesium aluminum spinel nano infrared transparent ceramic provided by the present invention uses magnesium acetate tetrahydrate and nano alumina powder as raw materials to prepare MgAl2O4 nano powder, and then undergoes spray granulation, isostatic pressing, pre-sintering, hot isostatic pressing sintering, annealing, polishing and other processes to obtain MgAl2O4 infrared transparent ceramic with an average particle size of 240nm. Its average transmittance in the infrared 3-5μm is greater than 85%.

[0018] 2. The preparation method of the magnesium aluminum spinel nano infrared transparent ceramic provided by the present invention adopts the thermal decomposition method of magnesium acetate and simultaneous reaction with nano Al2O3 to prepare MgAl2O4 nano powder. The grains are small and uniform, no additives are added, the preparation process is simple, no toxic gas is generated, and it is easy to industrialize and mass-produce with high yield.

[0019] 3. The preparation method of magnesium aluminum spinel nano infrared transparent ceramics provided by the present invention is to prepare MgAl2O4 nano powder by using magnesium acetate tetrahydrate and nano alumina powder as raw materials. This combination is significantly superior to traditional salt or oxide raw materials in purity, reaction efficiency and product performance. Combined with the low-temperature sintering process, the density of the obtained sample reaches 85% of the theoretical value, and the transmittance reaches 75% of the theoretical value. The finally obtained magnesium aluminum spinel nano infrared transparent ceramics are suitable for high-end optical devices. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 1 of the present invention;

[0021] Figure 2 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 2 of the present invention;

[0022] Figure 3 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 3 of the present invention;

[0023] Figure 4 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 4 of the present invention;

[0024] Figure 5 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 5 of the present invention;

[0025] Figure 6 This is the XRD pattern of the MgAl2O4 infrared transparent ceramic prepared in Example 5 of the present invention;

[0026] Figure 7 This is a SEM image of the MgAl2O4 infrared transparent ceramic prepared in Example 5 of the present invention;

[0027] Figure 8 This is the XRD pattern of the MgAl2O4 nanopowder prepared in Example 5 of the present invention;

[0028] Figure 9 This is an SEM image of the MgAl2O4 nanopowder prepared in Example 5 of the present invention;

[0029] Figure 104 is a particle size distribution histogram of the MgAl2O4 nanopowder prepared in Example 5 of the present invention;

[0030] Figure 11 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 6 of the present invention;

[0031] Figure 12 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 7 of the present invention;

[0032] Figure 13 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 8 of the present invention;

[0033] Figure 14 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 9 of the present invention;

[0034] Figure 15 This is the infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in Example 10 of the present invention. DETAILED DESCRIPTION

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] It should also be noted here that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the solutions of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0037] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0038] The present invention provides a method for preparing magnesium aluminum spinel nano infrared transparent ceramics, comprising the following steps:

[0039] A magnesium source and an aluminum source are prepared into a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution is 1:2; and the mixed solution is calcined at 400-800° C. for 1-3 hours to obtain MgAl 2 O 4 nanopowder;

[0040] MgAl2O4 nanopowder is ball-milled and spray-granulated, then is pressed into shape by isostatic pressing, and then hot isostatic pressing and sintering are performed. Finally, annealing is performed to obtain magnesia-alumina spinel nano-infrared transparent ceramics.

[0041] In some embodiments, the magnesium source is a soluble magnesium salt such as magnesium sulfate, magnesium acetate, magnesium nitrate, etc., preferably magnesium acetate. The aluminum source is preferably nano-alumina powder with a particle size of 20-50 nm.

[0042] In some embodiments, the isostatic pressing pressure is 200-300 MPa, and the time is 30-60 min.

[0043] In some embodiments, the hot isostatic pressing sintering temperature is 1500-1900° C., the pressure is 100-150 MPa, the heating rate is 3-5° C. / min, and the time is 3-6 h.

[0044] In some embodiments, the annealing treatment is performed at a temperature of 1100-1220° C. for a time of 5-15 hours.

[0045] In some embodiments, the ball milling process uses 1-3 mm zirconia balls as the medium, anhydrous ethanol as the dispersant, and the ball milling time is 8-12 hours.

[0046] In the above preparation process, the Mg in the magnesium salt 2+ Uniformly adsorbed on the surface and surroundings of nano-alumina particles, during subsequent calcination, nano-MgO (magnesium acetate decomposition) is directly generated on the surface of the alumina particles in situ, and then MgO and the adjacent Al2O3 directly undergo solid phase reaction, which greatly shortens the Mg 2+ and Al 3+ The mutual diffusion distance realizes short-range interface diffusion, which is conducive to the precise control of the stoichiometric ratio in the local micro-region, and the resulting phase purity is higher; in addition, the in-situ generated high-activity nano-MgO can reduce the reaction activation energy, greatly shorten the reaction time, and reduce energy consumption.

[0047] The preparation method of the magnesium aluminum spinel nano infrared transparent ceramics proposed by the present invention is further described below with reference to specific examples:

[0048] Example 1

[0049] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0050] After dissolving magnesium acetate tetrahydrate (purity not less than 99.9%) in deionized water, nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed (in the course of the experiment, it was found that although nano-MgAl2O4 powder can also be prepared using various salts, in industrial production, the amount of raw materials used is much larger than that of nano-alumina powder, and the amount of product obtained is much smaller than that of nano-alumina powder, while the performance of the prepared powder is essentially the same) to obtain a mixed solution, in which the molar ratio of Mg to Al in the mixed solution is 1:2; the mixed solution is placed in an alumina crucible and calcined at 400°C for 1 hour to obtain MgAl2O4 nano-powder;

[0051] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 8 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to obtain a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 200 MPa for 30 minutes to obtain a MgAl2O4 ceramic green body.

[0052] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1500℃ and a pressure of 100MPa for 3 hours to obtain MgAl2O4 ceramics. The sample was annealed at 800℃ for 5 hours and then double-sided high-precision polished to a sample roughness Ra <2nm. Finally, MgAl2O4 infrared transparent ceramics with an average particle size of 240nm were obtained.

[0053] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 1 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 88%.

[0054] Example 2

[0055] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0056] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 400°C for 2 hours to obtain MgAl2O4 nanopowder;

[0057] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 10 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to obtain a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 250 MPa for a holding time of 45 minutes to obtain a MgAl2O4 ceramic green body.

[0058] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1700°C and a pressure of 125MPa for 3 hours to obtain MgAl2O4 ceramics. The sample was annealed at 950°C for 15 hours and then double-sided high-precision polished to a sample roughness Ra <2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0059] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 2 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 86%.

[0060] Example 3

[0061] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0062] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 400°C for 3 hours to obtain MgAl2O4 nanopowder;

[0063] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 12 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to prepare a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 300 MPa for 60 minutes to obtain a MgAl2O4 ceramic green body.

[0064] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1900°C and a pressure of 150 MPa for 4.5 hours to obtain MgAl2O4 ceramics. The sample was annealed at 800°C for 15 hours and then double-sided high-precision polished to a sample roughness Ra < 2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0065] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 3 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 87%.

[0066] Example 4

[0067] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0068] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 600°C for 2 hours to obtain MgAl2O4 nanopowder;

[0069] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 10 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to prepare a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 200 MPa for 45 minutes to obtain a MgAl2O4 ceramic green body.

[0070] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1700°C and a pressure of 125 MPa for 6 hours to obtain MgAl2O4 ceramics. The sample was annealed at 1100°C for 10 hours and then double-sided high-precision polished to a sample roughness Ra < 2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0071] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 4 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 87%.

[0072] Example 5

[0073] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0074] Dissolving magnesium acetate tetrahydrate (purity not less than 99.9%) in deionized water, adding nano-alumina powder (purity not less than 99.9%), and thoroughly mixing to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution is 1:2; placing the mixed solution in an alumina crucible, and calcining at 600°C for 1 hour to obtain MgAl2O4 nanopowder;

[0075] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 8 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to obtain a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 250 MPa for 30 minutes to obtain a MgAl2O4 ceramic green body.

[0076] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1900°C and a pressure of 100 MPa for 6 hours to obtain MgAl2O4 ceramics. The sample was annealed at 950°C for 15 hours and then double-sided high-precision polished to a sample roughness Ra < 2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0077] The average infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 5 As shown in the results, the average transmittance of the ceramic in the infrared 3-5μm is greater than 85%; the XRD of MgAl2O4 infrared transparent ceramic is as follows Figure 6 As shown in Figure 2, it has the same diffraction peaks as the standard PDF card of MgAl2O4. Figure 7 The results show that the grains are small and round, with a particle size distribution between 180-270nm, the ceramic is dense inside, and there is no gap between the grains. Figure 8 As shown in the figure, it has the same diffraction peak as the standard XRD card of MgAl2O4. Figure 9 As shown in the results, the particle size of the powder particles is uniform, and the particle size distribution histogram of MgAl2O4 nanopowder is as follows Figure 10 As shown, the particle size is 40-90nm.

[0078] Example 6

[0079] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0080] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 600°C for 2 hours to obtain MgAl2O4 nanopowder;

[0081] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 12 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to prepare a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 300 MPa for 60 minutes to obtain a MgAl2O4 ceramic green body.

[0082] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1500℃ and a pressure of 150MPa for 4.5 hours to obtain MgAl2O4 ceramics. The sample was annealed at 1100℃ for 5 hours and then double-sided high-precision polished to a sample roughness Ra <2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0083] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 11 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 86%.

[0084] Example 7

[0085] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0086] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 800°C for 3 hours to obtain MgAl2O4 nanopowder;

[0087] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 10 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to prepare a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 200 MPa for 45 minutes to obtain a MgAl2O4 ceramic green body.

[0088] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1900°C and a pressure of 125 MPa for 4.5 hours to obtain MgAl2O4 ceramics. The sample was annealed at 950°C for 5 hours and then double-sided high-precision polished to a sample roughness Ra < 2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0089] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 12 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 84%.

[0090] Example 8

[0091] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0092] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 800°C for 1 hour to obtain MgAl2O4 nanopowder;

[0093] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 8 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to obtain a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 250 MPa for 30 minutes to obtain a MgAl2O4 ceramic green body.

[0094] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1500℃ and a pressure of 100MPa for 4.5h to obtain MgAl2O4 ceramics. The sample was annealed at 1100℃ for 15h and then double-sided high-precision polished to a sample roughness Ra <2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0095] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 13 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 84%.

[0096] Example 9

[0097] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0098] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 800°C for 2 hours to obtain MgAl2O4 nanopowder;

[0099] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 10 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to obtain a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 300 MPa for a holding time of 45 minutes to obtain a MgAl2O4 ceramic green body.

[0100] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1700°C and a pressure of 125MPa for 6 hours to obtain MgAl2O4 ceramics. The sample was annealed at 800°C for 10 hours and then double-sided high-precision polished to a sample roughness Ra <2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0101] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 14 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 82%.

[0102] Table 1 Mechanical properties of infrared transparent ceramics prepared in Examples 1, 3, 5, 7, and 9

[0103] project Flexural strength (MPa) HV3 hardness (GPa) Example 1 180 11.92 Example 3 177 11.98 Example 5 178 12.15 Example 7 185 12.05 Example 9 187 12.45

[0104] Example 10

[0105] This embodiment prepares a magnesium aluminum spinel nano infrared transparent ceramic, and the preparation method thereof includes the following steps:

[0106] Magnesium acetate tetrahydrate (purity not less than 99.9%) was dissolved in deionized water, and nano-alumina powder (purity not less than 99.9%) was added and thoroughly mixed to obtain a mixed solution, wherein the molar ratio of Mg to Al in the mixed solution was 1:2; the mixed solution was placed in an alumina crucible and calcined at 800°C for 3 hours to obtain MgAl2O4 nanopowder;

[0107] The MgAl2O4 nanopowder was placed in a zirconia ball mill, milled for 12 hours using 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant to prepare a slurry. The slurry was spray granulated to obtain spherical particles with a particle size of approximately 200 μm. The spherical particles were poured into a mold and dry-pressed at a pressure of 8 MPa. The spherical particles were then cold isostatically pressed at a pressure of 300 MPa for 60 minutes to obtain a MgAl2O4 ceramic green body.

[0108] The above-mentioned green body was placed in a hot isostatic pressing furnace and sintered at a temperature of 1700°C and a pressure of 150 MPa for 4.5 hours to obtain MgAl2O4 ceramics. The sample was annealed at 1100°C for 5 hours and then double-sided high-precision polished to a sample roughness Ra < 2nm, finally obtaining MgAl2O4 infrared transparent ceramics.

[0109] The infrared transmittance curve of the MgAl2O4 infrared transparent ceramic prepared in this embodiment is as follows: Figure 15 As shown, the results show that the maximum transmittance of the ceramic in the infrared 3-5μm is greater than 82%.

[0110] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing magnesium aluminum spinel nano infrared transparent ceramics, characterized in that: The steps include: The MgAl2O4 nano powder is ball-milled and granulated, then pressed into a shape, and then subjected to sintering and annealing treatments in sequence to obtain the MgAl2O4 nano infrared transparent ceramic. The MgAl2O4 nanopowder is obtained by calcining a mixed solution containing a magnesium source and an aluminum source. The aluminum source is nano-alumina powder with a particle size of 20-50 nm.

2. The preparation method according to claim 1, characterized in that The calcination temperature is 400-800°C and the calcination time is 1-3 hours.

3. The preparation method according to claim 1, characterized in that The pressing molding adopts an isostatic pressing method, and its process parameters are: pressure 200-300 MPa, time 30-60 min.

4. The preparation method according to claim 1, characterized in that The sintering treatment adopts hot isostatic pressing sintering, and its process parameters are: temperature 1500-1900° C., pressure 100-150 MPa, heating rate 3-5° C. / min, and time 3-6 hours.

5. The preparation method according to claim 1, characterized in that The annealing treatment is performed at a temperature of 1100-1220° C. and for a time of 5-15 hours.

6. The preparation method according to claim 1, characterized in that The magnesium source is one of magnesium sulfate, magnesium acetate and magnesium nitrate.

7. The preparation method according to claim 6, characterized in that The magnesium source is magnesium acetate.

8. The preparation method according to claim 1, characterized in that The ball mill uses 1-3 mm zirconia balls as a medium and anhydrous ethanol as a dispersant.

9. The preparation method according to claim 1, characterized in that The ball milling time is 8-12h.

10. A magnesium-aluminum spinel nano-infrared transparent ceramic prepared by the preparation method according to any one of claims 1 to 9.

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