Preparation method of magnesium fluoride nano-powder

Abstract

The invention provides a preparation method of magnesium fluoride nano-powder, which comprises the following steps: dissolving magnesium salt in water to obtain a magnesium salt solution; dissolving villiaumite in water to obtain a villiaumite solution; the magnesium salt solution and the villiaumite solution are placed in a freezer to be refrigerated, the temperature of the refrigerated magnesium salt solution and villiaumite solution ranges from 0 DEG C to 4 DEG C, the refrigerated villiaumite solution and the refrigerated magnesium salt solution react, and magnesium fluoride precipitation liquid is obtained; and placing the magnesium fluoride precipitation solution in an ice-water mixture for static aging, and carrying out centrifugal separation to obtain the magnesium fluoride nano-powder. The magnesium salt solution and the villiaumite solution are refrigerated to reduce the temperature of the solution, so that the reaction speed of the magnesium salt solution and the villiaumite solution can be effectively reduced, and magnesium fluoride with smaller grain size can be obtained; and the magnesium fluoride particles are subjected to static aging in an ice-water mixture, so that the Brownian motion rate is reduced, the collision probability is reduced, and the agglomeration degree of the magnesium fluoride nano powder is reduced, thereby achieving the purpose of reducing the particle size of the magnesium fluoride powder.

Description

Technical Field

[0001] This invention relates to the field of fine magnesium fluoride technology, specifically to a method for preparing magnesium fluoride nanopowder. Background Technology

[0002] Magnesium fluoride (MgF2), belonging to the tetragonal crystal system, is colorless and has a melting point of 1248℃. It is a very important and widely used inorganic material. Magnesium fluoride possesses excellent optical properties, exhibiting a wide transmission range, high transmittance, and high refractive index, making it a crucial optical component in optical systems. It is widely used in mirrors, lenses, and polarizing elements in the ultraviolet and infrared bands. Simultaneously, magnesium fluoride also possesses excellent mechanical properties, chemical stability, and thermal shock resistance, allowing it to withstand the impact of high-energy-density laser beams. Therefore, magnesium fluoride is suitable for use in harsh environments and high-power laser systems. Furthermore, magnesium fluoride can be used as an additive in the ceramics and glass industries to improve the hardness and wear resistance of ceramic materials, lower the melting point and viscosity of glass, improve production efficiency, and enhance the chemical stability of glass. In particular, polycrystalline magnesium fluoride is resistant to acid and alkali corrosion, seawater, and rainwater erosion, and offers advantages such as low cost and ease of processing. Therefore, polycrystalline magnesium fluoride is also widely used in the manufacture of radomes and other dome materials for infrared-guided missiles to protect electronic sensors or detectors from external environmental factors.

[0003] Currently, the main method for preparing polycrystalline magnesium fluoride is vacuum hot pressing. This method typically uses magnesium fluoride powder with high sintering activity as the sintering raw material. By applying pressure during high-temperature sintering, residual pores in the ceramic are eliminated, resulting in high-density polycrystalline magnesium fluoride ceramics. Highly sintering-active magnesium fluoride powder is the foundation and prerequisite for hot-pressed magnesium fluoride ceramics. In particular, hot-pressing technology places high demands on the purity, particle size and distribution, morphology, and agglomeration degree of the magnesium fluoride powder. Therefore, effectively reducing the particle size of hot-pressed magnesium fluoride powder and improving its sintering activity is one of the main problems currently hindering the development of high-optical-quality polycrystalline magnesium fluoride ceramics.

[0004] Chinese invention patent document CN115010153A discloses a nano-magnesium fluoride powder, its preparation method, and its application. The method involves dissolving magnesium oxide in nitric acid to obtain magnesium nitrate, reacting magnesium nitrate with sodium carbonate to obtain magnesium carbonate precipitate, and then reacting magnesium carbonate with hydrofluoric acid to prepare magnesium fluoride precipitate. This method involves three reaction processes, and requires the use of two highly corrosive acids, concentrated nitric acid and hydrofluoric acid, which poses significant risks. Furthermore, the magnesium fluoride powder has a particle size of approximately 1μm to 40μm, which is relatively coarse and cannot meet the requirements for vacuum hot pressing of high-optical-quality polycrystalline magnesium fluoride. Summary of the Invention

[0005] The technical problem to be solved by this invention is how to reduce the particle size of magnesium fluoride powder.

[0006] The present invention solves the above-mentioned technical problems through the following technical means: This invention provides a method for preparing magnesium fluoride nanopowder, comprising the following steps: Magnesium salts were dissolved in water to obtain a magnesium salt solution; fluoride salts were dissolved in water to obtain a fluoride solution; the magnesium salt solution and the fluoride solution were placed in a freezer and refrigerated at a temperature of 0–4°C; the refrigerated fluoride solution reacted with the refrigerated magnesium salt solution to obtain a magnesium fluoride precipitate; the magnesium fluoride precipitate was placed in an ice-water mixture for static aging, and after centrifugation, magnesium fluoride nanoparticles were obtained.

[0007] Beneficial effects: This invention lowers the temperature of magnesium salt and fluoride salt solutions by refrigerating them to 0-4°C, effectively slowing down the reaction rate and facilitating the production of magnesium fluoride with smaller grain sizes. Magnesium fluoride has numerous surface defects and a large specific surface area, making it prone to agglomeration. Static aging in an ice-water mixture reduces the Brownian motion rate of magnesium fluoride particles, decreasing the probability of collisions and further reducing the agglomeration of magnesium fluoride nanoparticles, thereby achieving the goal of reducing the particle size of magnesium fluoride powder.

[0008] Preferably, the magnesium salt includes one or more of magnesium nitrate, magnesium chloride, or magnesium acetate.

[0009] Preferably, the fluoride salt includes one or more of ammonium fluoride or sodium fluoride.

[0010] Preferably, the concentration of magnesium ions in the magnesium salt solution is 0.05 mol / L to 5 mol / L.

[0011] Preferably, the concentration of fluoride ions in the fluoride salt solution is 0.1 mol / L to 10 mol / L.

[0012] Preferably, the refrigeration time is 20 min to 60 min.

[0013] Preferably, the static aging time is 40 min to 60 min.

[0014] Preferably, the centrifugation is performed multiple times, and the water added during the centrifugation is zero-degree Celsius water.

[0015] Beneficial effects: This invention further improves the purity of magnesium fluoride powder through multiple centrifugal separations and further reduces the agglomeration degree of magnesium fluoride powder by using zero-degree Celsius water.

[0016] Preferably, the magnesium fluoride after centrifugation is frozen to obtain magnesium fluoride blocks.

[0017] Preferably, the freezing temperature is 0 to -18°C, and the freezing time is 12 to 48 hours.

[0018] Preferably, magnesium fluoride bulk material is subjected to vacuum freeze-drying to obtain magnesium fluoride nanoparticles.

[0019] Preferably, the freeze-drying time is 12h to 48h, the freeze-drying temperature is -40 to -60℃, and the vacuum degree is 1Pa to 10Pa.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The raw materials used in this invention are commercially available magnesium salts and fluoride salts. Magnesium fluoride precipitate is generated by the reaction of magnesium salts and fluoride salts. After static aging, centrifugation, freezing and vacuum freeze drying, magnesium fluoride nanoparticles are obtained. The process is simple, has a high yield, and is very suitable for large-scale industrial production.

[0021] This invention reduces the particle size and agglomeration of magnesium fluoride nanoparticles by lowering the temperature of the reaction solution, avoiding the use of organic substances such as surfactants and dispersants, and also reducing the difficulty of purifying magnesium fluoride nanoparticles.

[0022] Compared with existing magnesium fluoride nanopowders, the magnesium fluoride nanopowders of the present invention have smaller particle size, lower agglomeration degree, and higher sintering activity, making them very suitable as sintering raw materials for polycrystalline magnesium fluoride ceramics. Attached Figure Description

[0023] Figure 1 This is an X-ray diffraction pattern of magnesium fluoride nanoparticles in Example 1 of the present invention; Figure 2 This is a transmission electron microscope (TEM) image of magnesium fluoride nanoparticles in Example 1 of the present invention. Figure 3 This is a transmission electron microscope (TEM) image of magnesium fluoride nanoparticles in Example 2 of the present invention. Figure 4 This is a transmission electron microscope (TEM) image of magnesium fluoride nanoparticles in Example 3 of the present invention. Figure 5 This is a transmission electron microscope (TEM) image of magnesium fluoride nanoparticles in Example 4 of the present invention. Figure 6 This is a transmission electron microscope image of magnesium fluoride nanoparticles in Comparative Example 1 of the present invention; Figure 7 This is a transmission electron microscope image of magnesium fluoride nanoparticles in Comparative Example 2 of the present invention; Figure 8 This is a transmission electron microscope (TEM) image of magnesium fluoride nanoparticles in Comparative Example 3 of the present invention. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0026] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0027] Example 1 This embodiment provides a method for preparing magnesium fluoride nanopowder, specifically including the following steps: Weigh 256g of magnesium nitrate with a purity of not less than 99% and add it to 1 liter of primary deionized water with a resistivity of 18.25 MΩ / cm. Stir at 100 rpm for 20 minutes using a magnetic stirrer to obtain a magnesium nitrate solution with a magnesium ion concentration of 1 mol / L. Weigh 81g of ammonium fluoride with a purity of not less than 99% and dissolve it in 2 liters of deionized water with a resistivity of 18.25 MΩ / cm at the same stirring speed for 20 minutes to obtain an ammonium fluoride solution with a fluoride ion concentration of 2.18 mol / L.

[0028] Magnesium nitrate and ammonium fluoride solutions were refrigerated in a freezer for 60 minutes, at which point their temperature was 0°C. The refrigerated magnesium nitrate solution was then placed in a water bath equipped with a magnetic stirrer, with an ice-water mixture added to maintain a consistently low temperature. The refrigerated ammonium fluoride solution was precisely dripped into the magnesium nitrate solution in the water bath using a peristaltic pump at a speed of 60 rpm. Simultaneously, the ammonium fluoride solution was rapidly stirred magnetically at a speed of 200 rpm over a dripping time of 40 minutes. After the ammonium fluoride solution had completely dissolved into the magnesium nitrate solution, forming a magnesium fluoride precipitate, the solution was left to stand and age in the ice-water mixture water bath for another 40 minutes.

[0029] Pour the aged magnesium fluoride precipitate into a centrifuge tube and centrifuge at 11,000 rpm for 20 minutes. Scoop the magnesium fluoride gel that has settled at the bottom of the centrifuge tube into a beaker, add deionized water at 0 degrees Celsius to the beaker, and stir continuously with a glass rod while sonicating until the magnesium fluoride gel is completely dissolved in the deionized water at 0 degrees Celsius to obtain a magnesium fluoride solution.

[0030] The magnesium fluoride solution was centrifuged again at 11,000 rpm for 40 minutes. The magnesium fluoride gel was then transferred to a beaker and sonicated and stirred in deionized water at 0°C to dissolve it. This process was repeated four times by centrifugation and three times by washing with deionized water at 0°C to remove residual nitrate and ammonium ions from the magnesium fluoride solution. The resulting magnesium fluoride gel was then frozen at -18°C for 12 hours to form magnesium fluoride blocks.

[0031] Magnesium fluoride bulk material was placed in a vacuum freeze dryer and freeze-dried for 12 hours under a vacuum of 1 Pa and a temperature of -60°C to obtain magnesium fluoride nanoparticles. The weight of the magnesium fluoride nanoparticles was 61 g, with a yield of approximately 98% and minimal loss.

[0032] according to Figure 1 It can be seen that the magnesium fluoride nanopowder is a pure magnesium fluoride phase, and no other impurity phases are generated during the synthesis process. Based on... Figure 2 It can be seen that the particle size of magnesium fluoride powder is about 10.9 nm, which is small and has good dispersibility.

[0033] Example 2 This embodiment provides a method for preparing magnesium fluoride nanopowder, specifically including the following steps: Weigh 214g of magnesium acetate with a purity of not less than 99% and add it to 0.4 liters of primary deionized water with a resistivity of 18.25 MΩ / cm. Stir at 200 rpm for 20 minutes using a magnetic stirrer to obtain a magnesium acetate solution with a magnesium ion concentration of 4 mol / L. Weigh 81g of ammonium fluoride with a purity of not less than 99% and dissolve it in 0.5 liters of deionized water with a resistivity of 18.25 MΩ / cm at the same stirring speed for 20 minutes to obtain an ammonium fluoride solution with a fluoride ion concentration of 4.36 mol / L.

[0034] Magnesium acetate and ammonium fluoride solutions were refrigerated for 40 minutes, at which point their temperature was 4°C. The refrigerated magnesium acetate solution was then placed in a water bath equipped with a magnetic stirrer, with an ice-water mixture added to maintain a consistently low temperature. Ammonium fluoride solution was precisely added dropwise to the magnesium acetate solution using a peristaltic pump at 30 rpm. Simultaneously, the solution was rapidly stirred magnetically at 200 rpm over a period of 20 minutes. After the ammonium fluoride solution had completely precipitated in the magnesium acetate solution, the precipitate was allowed to stand and age in the ice-water mixture water bath for another 60 minutes.

[0035] Pour the aged magnesium fluoride precipitate into a centrifuge tube and centrifuge at 9000 rpm for 80 min. Scoop the magnesium fluoride gel that has settled at the bottom of the centrifuge tube into a beaker, add deionized water at 8°C to the beaker, and stir continuously with a glass rod while sonicating until the magnesium fluoride gel is completely dissolved in the deionized water at 8°C to obtain a magnesium fluoride solution.

[0036] The magnesium fluoride solution was centrifuged again at 9000 rpm for 80 min. The magnesium fluoride gel was then transferred to a beaker and dissolved by stirring and sonication in deionized water at 8°C. This process was repeated three times by centrifugation and twice by washing with deionized water to remove residual acetate and ammonium ions from the magnesium fluoride solution. The resulting magnesium fluoride gel was then frozen at -10°C for 48 h to form magnesium fluoride blocks.

[0037] Magnesium fluoride bulk material was placed in a vacuum freeze dryer and freeze-dried for 48 hours under a vacuum of 1 Pa and a temperature of -60℃ to obtain magnesium fluoride nanopowder. According to... Figure 3 It can be seen that the particle size of the magnesium fluoride nanopowder in this embodiment is 13nm, the weight of the magnesium fluoride nanopowder is 60.1g, the yield is about 96.4%, and the loss is small.

[0038] Example 3 This embodiment provides a method for preparing magnesium fluoride nanopowder, specifically including the following steps: Weigh 256g of magnesium nitrate with a purity of not less than 99% and add it to 0.2 liters of primary deionized water with a resistivity of 18.25 MΩ / cm. Stir at 100 rpm for 20 minutes using a magnetic stirrer to obtain a magnesium nitrate solution with a magnesium ion concentration of 5 mol / L. Weigh 92g of sodium fluoride with a purity of not less than 99% and dissolve it in 0.25 liters of deionized water with a resistivity of 18.25 MΩ / cm at the same stirring speed for 20 minutes to obtain a sodium fluoride solution with a fluoride ion concentration of 8.8 mol / L.

[0039] Magnesium nitrate solution and sodium fluoride solution were refrigerated in a freezer for 50 minutes, at which point their temperature was 3°C. The refrigerated magnesium nitrate solution was then placed in a water bath equipped with a magnetic stirrer, with an ice-water mixture added to maintain a consistently low temperature. Sodium fluoride solution was precisely added dropwise to the magnesium nitrate solution using a peristaltic pump at a speed of 40 rpm. Simultaneously, the solution was rapidly stirred magnetically at 200 rpm over a period of 25 minutes. After the sodium fluoride solution had completely added to the magnesium nitrate solution, forming a magnesium fluoride precipitate, the precipitate was allowed to stand and age in the ice-water mixture water bath for another 50 minutes.

[0040] Pour the aged magnesium fluoride precipitate into a centrifuge tube and centrifuge at 10,000 rpm for 30 minutes. Scoop the magnesium fluoride gel that has settled at the bottom of the centrifuge tube into a beaker, add 5°C deionized water to the beaker, and stir continuously with a glass rod while sonicating until the magnesium fluoride gel is completely dissolved in the 5°C deionized water to obtain a magnesium fluoride solution.

[0041] The magnesium fluoride solution was centrifuged again at 10,000 rpm for 30 min. The magnesium fluoride gel was then transferred to a beaker and dissolved by stirring and sonication in deionized water at 5°C. This process was repeated 6 times by centrifugation and 5 times by washing with deionized water to remove residual nitrate and sodium ions from the magnesium fluoride solution. The resulting magnesium fluoride gel was then frozen at -15°C for 48 h to form magnesium fluoride blocks.

[0042] Magnesium fluoride bulk material was placed in a vacuum freeze dryer and freeze-dried for 48 hours under a vacuum of 10 Pa and a temperature of -50 °C to obtain magnesium fluoride nanoparticles. According to... Figure 4 It can be seen that the magnesium fluoride nanoparticles in this embodiment have a particle size of 13.4 nm, a weight of 61.5 g, a yield of approximately 98%, and minimal loss.

[0043] Example 4 This embodiment provides a method for preparing magnesium fluoride nanopowder, specifically including the following steps: Weigh 95g of magnesium chloride with a purity of not less than 99% and add it to 5 liters of primary deionized water with a resistivity of 18.25 MΩ / cm. Stir at 100 rpm for 20 minutes using a magnetic stirrer to obtain a magnesium chloride solution with a magnesium ion concentration of 0.2 mol / L. Weigh 92g of sodium fluoride with a purity of not less than 99% and dissolve it in 5.5 liters of deionized water with a resistivity of 18.25 MΩ / cm at the same stirring speed for 20 minutes to obtain a sodium fluoride solution with a fluoride ion concentration of 0.4 mol / L.

[0044] Magnesium chloride and sodium fluoride solutions were refrigerated in a freezer for 60 minutes, at which point their temperature was 0°C. The refrigerated magnesium chloride solution was then placed in a water bath equipped with a magnetic stirrer, with an ice-water mixture added to maintain the low temperature. Sodium fluoride solution was precisely added dropwise to the magnesium chloride solution using a peristaltic pump at a speed of 45 rpm. Simultaneously, ammonium fluoride solution was added dropwise to the magnesium nitrate solution, while the mixture was rapidly stirred magnetically at a speed of 200 rpm over a period of 27 minutes. After the sodium fluoride solution had completely dissolved into the magnesium chloride solution, forming a magnesium fluoride precipitate, the precipitate was allowed to stand and age in the ice-water mixture water bath for another 40 minutes.

[0045] Pour the aged magnesium fluoride precipitate into a centrifuge tube and centrifuge at 11,000 rpm for 30 minutes. Scoop the magnesium fluoride gel that has settled at the bottom of the centrifuge tube into a beaker, add 0°C deionized water to the beaker, and stir continuously with a glass rod while sonicating until the magnesium fluoride gel is completely dissolved in the 0°C deionized water to obtain a magnesium fluoride solution.

[0046] The magnesium fluoride solution was centrifuged again at 11,000 rpm for 40 min. The magnesium fluoride gel was then transferred to a beaker and dissolved by sonication in deionized water at 0°C. This process was repeated 5 times by centrifugation and 4 times by washing with deionized water to remove residual chloride and sodium ions from the magnesium fluoride solution. The resulting magnesium fluoride gel was then frozen in a freezer at -5°C for 12 h to form magnesium fluoride blocks.

[0047] Magnesium fluoride bulk material was placed in a vacuum freeze dryer and freeze-dried for 12 hours under a vacuum of 5 Pa and a temperature of -50℃ to obtain magnesium fluoride nanoparticles. Figure 5 As shown, the particle size of the magnesium fluoride nanoparticles in this embodiment is 16.5 nm, the weight of the magnesium fluoride nanoparticles is 58 g, and the yield is approximately 93%.

[0048] Comparative Example 1 This comparative example provides a method for preparing magnesium fluoride nanopowder. The difference between this comparative example and Example 1 is that the magnesium nitrate solution and ammonium fluoride solution were not refrigerated. Instead, the ammonium fluoride solution was dripped into the magnesium nitrate solution using a peristaltic pump. The entire reaction process was carried out at room temperature. All other aspects were the same.

[0049] according to Figure 6 It can be seen that the magnesium fluoride nanoparticles in Comparative Example 1 have a particle size of about 90 nm, which is significantly larger than that in Comparative Example 1, and there is obvious agglomeration.

[0050] Comparative Example 2 This comparative example provides a method for preparing magnesium fluoride nanopowder. The difference between this comparative example and Example 1 is that the magnesium fluoride precipitate was not aged statically in a water bath of ice and water mixture, but was aged statically at room temperature. All other aspects are the same.

[0051] according to Figure 7 It can be seen that the magnesium fluoride nanoparticles of Comparative Example 2 have a particle size of about 14 nm, which is similar to the magnesium fluoride nanoparticles of Example 1, but the degree of agglomeration is much more serious than that of Example 1.

[0052] Comparative Example 3 This comparative example provides a method for preparing magnesium fluoride nanopowder. The difference between this comparative example and Example 1 is that the temperature of the magnesium nitrate solution and ammonium fluoride solution after refrigeration is 10°C.

[0053] according to Figure 8 It can be seen that the magnesium fluoride nanoparticles of Comparative Example 3 have a particle size of about 62 nm, which is larger than that of the magnesium fluoride nanoparticles of Example 1.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing magnesium fluoride nanopowder, characterized in that, Includes the following steps: Magnesium salts are dissolved in water to obtain magnesium salt solutions; fluoride salts are dissolved in water to obtain fluoride salt solutions; the magnesium salt solutions and fluoride solutions are refrigerated at a temperature of 0–4°C; the refrigerated fluoride solutions react with the refrigerated magnesium salt solutions to obtain magnesium fluoride precipitate. Magnesium fluoride precipitate was placed in an ice-water mixture for static aging, and then centrifuged to obtain magnesium fluoride nanoparticles.

2. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, The refrigeration time is 20 to 60 minutes.

3. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, The centrifugation process is repeated multiple times, and the water added during centrifugation is at zero degrees Celsius.

4. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, The static aging time is 40 to 60 minutes.

5. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, The magnesium fluoride nanoparticles after centrifugation were frozen to obtain magnesium fluoride bulk.

6. The method for preparing magnesium fluoride nanopowder according to claim 5, characterized in that, The freezing temperature is 0 to -18°C, and the freezing time is 12 to 48 hours.

7. The method for preparing magnesium fluoride nanopowder according to claim 5, characterized in that, Magnesium fluoride bulk material was freeze-dried under vacuum to obtain magnesium fluoride nanoparticles.

8. In the method for preparing magnesium fluoride nanopowder according to claim 7, the freeze-drying time is 12h to 48h, the freeze-drying temperature is -40℃ to -60℃, and the vacuum degree is 1Pa to 10Pa.

9. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, Magnesium salts include one or more of magnesium nitrate, magnesium chloride, or magnesium acetate; fluoride salts include one or more of ammonium fluoride or sodium fluoride.

10. The method for preparing magnesium fluoride nanopowder according to claim 1, characterized in that, The concentration of magnesium ions in magnesium salt solutions ranges from 0.05 mol / L to 5 mol / L; the concentration of fluoride ions in fluoride salt solutions ranges from 0.1 mol / L to 10 mol / L.

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