High-purity alumina nano-powder and preparation method thereof

Abstract

The invention provides high-purity aluminum oxide nano powder and a preparation method thereof, and belongs to the technical field of nano material preparation. The preparation method comprises the following steps: by taking aluminum sulfate octadecahydrate and aluminum chloride hexahydrate as aluminum salts and polyethylene glycol and fumaric acid as admixtures, slowly adding an aluminum salt solution into an ammonium carbonate solution to react, washing, centrifuging, filtering, drying and sieving to obtain precursor powder, adding ethanol into the precursor powder to prepare slurry, then adding behenic acid into the slurry, and carrying out ball milling to obtain a finished product. And carrying out ball milling, sieving, drying and calcining to obtain the high-purity aluminum oxide nano powder. The prepared aluminum oxide nano powder is uniform in particle size distribution and good in dispersity, the purity is larger than 99.99%, and the requirement of the high-end aluminum oxide nano powder industry can be met.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, specifically to a high-purity alumina nanopowder and its preparation method. Background Technology

[0002] High-purity alumina generally refers to powder materials with a purity greater than or equal to 99.99% and a uniform particle size distribution. High-purity alumina powder possesses unique physical, chemical, electrical, optical, thermal, and mechanical properties, giving it excellent characteristics such as high-temperature resistance, chemical corrosion resistance, resistance to rapid heating and cooling, and resistance to cracking. It has gradually become an important inorganic non-metallic material. High-purity alumina can be widely used in LED artificial sapphire crystals, advanced ceramics, PDP phosphors, high-pressure sodium lamps, new luminescent materials, special ceramics, advanced coatings, tri-color materials, catalysts, and some high-performance materials. It belongs to one of the high-end materials with large output, high output value, and wide application in the new materials industry since the 20th century.

[0003] As is well known, the particle size and purity of nano-alumina materials depend on the preparation method. Existing methods for preparing nano-alumina mainly include the pyrolysis of ammonium aluminum carbonate, the hydrolysis of aluminum isopropoxide, the pyrolysis of ammonium aluminum sulfate, and the modified Bayer process. Currently, the main method for preparing high-purity alumina nanopowder using ammonium aluminum sulfate as a raw material is the pyrolysis of ammonium aluminum sulfate. However, while this method has advantages such as inexpensive raw materials and the ability to recycle the mother liquor, it easily generates large amounts of sulfur trioxide and ammonia during the preparation process, severely polluting the environment. Furthermore, this method suffers from the defect of insufficient calcination leading to unsatisfactory purity of the alumina nanopowder. In addition, although existing technologies can also prepare nano-sized alumina powder, the large specific surface area and high atomic ratio of nano-sized alumina powder result in extremely high surface energy. To reduce this surface energy, nano-sized alumina powder is prone to agglomeration, leading to uneven particle size distribution. Furthermore, interparticle interactions, influencing factors during preparation and processing, and environmental factors can all contribute to the agglomeration of nano-sized alumina powder. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing high-purity alumina nanopowder, comprising the following steps:

[0005] (1) Dissolve aluminum sulfate octadeca and aluminum chloride hexahydrate in deionized water to obtain an aluminum salt aqueous solution; dissolve ammonium carbonate in deionized water, and then add polyethylene glycol and fumaric acid to obtain an ammonium carbonate solution;

[0006] (2) The aluminum salt aqueous solution is slowly added dropwise to the ammonium carbonate solution to carry out the reaction. After the reaction is completed, the product is washed, centrifuged, filtered, dried and sieved to obtain the precursor powder.

[0007] (3) Ethanol was added to the precursor powder to prepare a slurry, then behenic acid was added to the slurry, and the mixture was ball-milled, sieved, dried and calcined to obtain high-purity alumina nanopowder.

[0008] In some embodiments of the present invention, the mass ratio of aluminum sulfate octadecahydrate and aluminum chloride hexahydrate in step (1) is 1:1-2.

[0009] In some embodiments of the present invention, the concentration of the aluminum salt aqueous solution in step (1) is 1-2 mol / L, and the concentration of the ammonium carbonate solution is 0.5-1 mol / L.

[0010] In some embodiments of the present invention, the amount of fumaric acid added in step (1) is 1%-8% of the total mass of aluminum sulfate octadecahydrate and aluminum chloride hexahydrate.

[0011] In some embodiments of the present invention, the polyethylene glycol in step (1) is PEG400.

[0012] In some embodiments of the present invention, the amount of polyethylene glycol added in step (1) is 0.5%-3% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate.

[0013] In some embodiments of the present invention, the dropping rate in step (2) is 8-15 mL / min.

[0014] In some embodiments of the present invention, the reaction temperature in step (2) is 5-25 °C, the reaction time is 1-5 h, and the pH of the system at the reaction endpoint is 8-9.

[0015] In some embodiments of the present invention, step (2) involves washing three times with deionized water.

[0016] In some embodiments of the present invention, the drying temperature in steps (2) and (3) is 80-90 °C, the drying time is 5-10 h, and the material is passed through an 80-150 mesh sieve.

[0017] In some embodiments of the present invention, the mass ratio of behenic acid to precursor powder in step (3) is 0.5-3.5:100.

[0018] In some embodiments of the present invention, the solid content of the slurry in step (3) is 20-50 wt%.

[0019] In some embodiments of the present invention, the ball milling speed in step (3) is 300-500 rpm and the ball milling time is 1-3 h.

[0020] In some embodiments of the present invention, the ball milling in step (3) is carried out in a ball milling device, which includes a ball milling jar and a ball milling medium, wherein the ball milling jar and the ball milling medium are made of alumina with a purity greater than 99.99%.

[0021] In some embodiments of the present invention, the calcination temperature in step (3) is 900-1200 ℃, the calcination time is 1-3h, and the heating rate during the calcination process is 4-8 ℃ / min.

[0022] This invention also improves the high-purity alumina nanopowder prepared according to the method.

[0023] In some embodiments of the present invention, the purity of the high-purity alumina nanoparticles is greater than 99.99%.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] In the process of preparing high-purity alumina nanopowder, this invention introduces polyethylene glycol and fumaric acid, which utilize steric hindrance and chemical coordination to synergistically inhibit particle agglomeration and regulate the morphology of alumina nanopowder.

[0026] This invention adds behenic acid to the slurry, which combines with other raw materials to form steric hindrance, preventing powder agglomeration and improving powder dispersibility.

[0027] In existing technologies, aluminum chloride is typically used as the aluminum source to prepare alumina nanoparticles. However, the inventors discovered during their research that while aluminum chloride as an aluminum salt can yield precursors with small particle sizes, the precursors produced by this method are in colloidal form, exhibiting severe particle agglomeration and poor dispersion, which is detrimental to subsequent processing steps such as filtration and drying. Therefore, this invention uses a combination of aluminum chloride and aluminum sulfate as the aluminum source for preparing alumina. The two complement each other, achieving improved dispersibility and finer powder particles. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] Unless otherwise specified, the test methods or experimental methods described in the following examples are all conventional methods; unless otherwise specified, the raw materials and additives are obtained from conventional commercial sources or prepared by conventional methods.

[0030] Example 1

[0031] A method for preparing high-purity alumina nanopowder, the specific steps of which are as follows:

[0032] (1) Dissolve aluminum sulfate octahydrate and aluminum chloride hexahydrate in deionized water, wherein the mass ratio of aluminum sulfate octahydrate and aluminum chloride hexahydrate is 1:2, to obtain an aluminum salt aqueous solution with a concentration of 1 mol / L; dissolve ammonium carbonate in deionized water, and then add PEG400 and fumaric acid, wherein the amount of fumaric acid added accounts for 5% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, and the amount of polyethylene glycol added accounts for 1.5% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, to obtain an ammonium carbonate solution with a concentration of 0.7 mol / L;

[0033] (2) The aluminum salt aqueous solution was slowly added to the ammonium carbonate solution at a rate of 10 mL / min, and the reaction was carried out at 15 °C for 3 h. The pH of the system at the end of the reaction was 8. After the reaction was completed, the product was washed three times with deionized water, centrifuged at 5000 rpm / min for 10 min, filtered, dried at 80 °C for 6 h, and passed through a 150 mesh sieve to obtain the precursor powder.

[0034] (3) Ethanol was added to the precursor powder to prepare a slurry with a solid content of 35wt%. Then, behenic acid was added to the slurry. The mass ratio of behenic acid to precursor powder was 2.5:100. The mixture was ball-milled at 400 rpm for 2 hours. The ball milling was carried out in a ball milling device, which included a ball milling jar and a ball milling media. The ball milling jar and the ball milling media were made of alumina with a purity greater than 99.99%. The alumina was passed through a 150-mesh sieve, dried at 90 ℃ for 5 hours, heated to 1000 ℃ at a heating rate of 4 ℃ / min, and calcined for 2 hours to obtain high-purity alumina nanopowder.

[0035] Example 2

[0036] A method for preparing high-purity alumina nanopowder, the specific steps of which are as follows:

[0037] (1) Dissolve aluminum sulfate octahydrate and aluminum chloride hexahydrate in deionized water, wherein the mass ratio of aluminum sulfate octahydrate and aluminum chloride hexahydrate is 1:1, to obtain an aluminum salt aqueous solution with a concentration of 2 mol / L; dissolve ammonium carbonate in deionized water, and then add PEG400 and fumaric acid, wherein the amount of fumaric acid added is 1% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, and the amount of polyethylene glycol added is 0.5% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, to obtain an ammonium carbonate solution with a concentration of 0.5 mol / L;

[0038] (2) The aluminum salt aqueous solution was slowly added to the ammonium carbonate solution at a rate of 8 mL / min, and the reaction was carried out at 5 °C for 1 h. The pH of the system at the end of the reaction was 8. After the reaction was completed, the product was washed three times with deionized water, centrifuged at 5000 rpm / min for 10 min, filtered, dried at 80 °C for 5 h, and passed through an 80-mesh sieve to obtain the precursor powder.

[0039] (3) Ethanol was added to the precursor powder to prepare a slurry with a solid content of 20wt%. Then, behenic acid was added to the slurry. The mass ratio of behenic acid to precursor powder was 0.5:100. The mixture was ball-milled at 300rpm for 1h. The ball milling was carried out in a ball milling device, which included a ball milling jar and a ball milling media. The ball milling jar and the ball milling media were made of alumina with a purity greater than 99.99%. The alumina was passed through an 80-mesh sieve, dried at 80℃ for 5h, heated to 900℃ at a heating rate of 4℃ / min, and calcined for 1h to obtain high-purity alumina nanopowder.

[0040] Example 3

[0041] A method for preparing high-purity alumina nanopowder, the specific steps of which are as follows:

[0042] (1) Dissolve aluminum sulfate octahydrate and aluminum chloride hexahydrate in deionized water, wherein the mass ratio of aluminum sulfate octahydrate and aluminum chloride hexahydrate is 1:2, to obtain an aluminum salt aqueous solution with a concentration of 2 mol / L; dissolve ammonium carbonate in deionized water, and then add PEG400 and fumaric acid, wherein the amount of fumaric acid added accounts for 8% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, and the amount of polyethylene glycol added accounts for 3% of the total mass of aluminum sulfate octahydrate and aluminum chloride hexahydrate, to obtain an ammonium carbonate solution with a concentration of 1 mol / L;

[0043] (2) The aluminum salt aqueous solution was slowly added to the ammonium carbonate solution at a rate of 15 mL / min, and the reaction was carried out at 25 °C for 5 h. The pH of the system at the end of the reaction was 9. After the reaction was completed, the product was washed three times with deionized water, centrifuged at 5000 rpm / min for 10 min, filtered, dried at 90 °C for 10 h, and passed through a 150 mesh sieve to obtain the precursor powder.

[0044] (3) Ethanol was added to the precursor powder to prepare a slurry with a solid content of 50 wt%. Then, behenic acid was added to the slurry. The mass ratio of behenic acid to precursor powder was 3.5:100. The mixture was ball-milled at 500 rpm for 3 h. The ball milling was carried out in a ball milling device, which included a ball milling jar and a ball milling media. The ball milling jar and the ball milling media were made of alumina with a purity greater than 99.99%. The alumina was passed through a 150-mesh sieve, dried at 90 ℃ for 10 h, heated to 1200 ℃ at a heating rate of 8 ℃ / min, and calcined for 3 h to obtain high-purity alumina nanopowder.

[0045] Comparative Example 1

[0046] The difference from Example 1 is that aluminum sulfate octadecahydrate was not added, but the rest of the steps are the same as in Example 1.

[0047] Comparative Example 2

[0048] The difference from Example 1 is that aluminum chloride hexahydrate was not added, but the rest of the steps are the same as in Example 1.

[0049] Comparative Example 3

[0050] The difference from Example 1 is that fumaric acid was not added, but the rest of the steps are the same as in Example 1.

[0051] Comparative Example 4

[0052] The difference from Example 1 is that behenicol was not added, but the rest of the steps are the same as in Example 1.

[0053] Performance testing:

[0054] The particle size and purity of the alumina nanopowders prepared in the test examples and comparative examples are shown in Table 1.

[0055] Table 1

[0056] Group D10 (nm) D50 (nm) D90 (nm) purity(%) Example 1 58 126 293 99.99 Example 2 61 132 305 99.99 Example 3 63 137 318 99.99 Comparative Example 1 259 730 1726 99.72 Comparative Example 2 382 817 2890 99.31 Comparative Example 3 275 752 1942 99.85 Comparative Example 4 296 803 2417 99.46

[0057] As shown in Table 1, the alumina nanoparticles prepared in Examples 1-3 of this invention have smaller particle sizes, with D50 between 126-137 nm, while the D50 of Comparative Examples 1-4 is between 730-817 nm, a difference of one order of magnitude.

[0058] The D90-D10 difference of the alumina nanoparticles prepared in Examples 1-3 of this invention is within the range of 235-255 nm, showing a very narrow distribution. In contrast, the D90-D10 difference of the alumina nanoparticles prepared in Comparative Examples 1-4 is within the range of 1467-2508 nm, showing a very wide distribution. This indicates that this invention, by adjusting the raw material composition and using the preparation process, effectively controls the size of the alumina nanoparticles, prevents nanoparticle agglomeration, and obtains alumina nanoparticles with a uniform particle size distribution. The wider particle size distribution of Comparative Examples 1-4 indicates a serious agglomeration problem. Furthermore, the purity of the alumina nanoparticles prepared in the comparative examples is lower than that of this invention.

[0059] In summary, the alumina nanopowder prepared by the method provided by this invention has good dispersibility, uniform particle size distribution, and high product purity, which can meet the requirements of the high-end alumina nanopowder industry.

[0060] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity alumina nanopowder, characterized in that, Includes the following steps: (1) Dissolve aluminum sulfate octadeca and aluminum chloride hexahydrate in deionized water to obtain an aluminum salt aqueous solution; dissolve ammonium carbonate in deionized water, and then add polyethylene glycol and fumaric acid to obtain an ammonium carbonate solution; (2) The aluminum salt aqueous solution is slowly added dropwise to the ammonium carbonate solution to carry out the reaction. After the reaction is completed, the product is washed, centrifuged, filtered, dried and sieved to obtain the precursor powder. (3) Ethanol was added to the precursor powder to prepare a slurry, then behenic acid was added to the slurry, and the mixture was ball-milled, sieved, dried and calcined to obtain high-purity alumina nanopowder.

2. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, In step (1), the mass ratio of aluminum sulfate octadecahydrate to aluminum chloride hexahydrate is 1:1-2.

3. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The concentration of the aluminum salt aqueous solution in step (1) is 1-2 mol / L, and the concentration of the ammonium carbonate solution is 0.5-1 mol / L.

4. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The amount of fumaric acid added in step (1) is 1%-8% of the total mass of aluminum sulfate octadecahydrate and aluminum chloride hexahydrate.

5. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The amount of polyethylene glycol added in step (1) is 0.5%-3% of the total mass of aluminum sulfate octadecahydrate and aluminum chloride hexahydrate.

6. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The dropping rate in step (2) is 8-15 mL / min, the reaction temperature in step (2) is 5-25 ℃, the reaction time is 1-5 h, and the pH of the system at the reaction endpoint is 8-9.

7. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The mass ratio of behenic acid to precursor powder in step (3) is 0.5-3.5:

100.

8. The method for preparing high-purity alumina nanopowder according to claim 1, characterized in that, The calcination temperature in step (3) is 900-1200 ℃, the calcination time is 1-3h, and the heating rate during the calcination process is 4-8 ℃ / min.

9. High-purity alumina nanopowder prepared by the method according to any one of claims 1-8.

10. The high-purity alumina nanopowder according to claim 9, characterized in that, The purity of the high-purity alumina nanopowder is greater than 99.99%.