A platelet-shaped alumina nanoparticle, a method of preparation and use thereof in geothermal circulating media

Abstract

The application discloses a preparation method of sheet-shaped alumina nanoparticles, which comprises the following steps: dissolving an aluminum source in a solvent to obtain a precursor solution, adjusting the pH value to 8-10, adding a molecular sieve template agent into the precursor solution and stirring and dispersing uniformly, depositing the aluminum source precursor on the surface of the molecular sieve template agent at room temperature, filtering, washing and drying the product after high-temperature aging treatment, calcining the obtained product at high temperature to remove the remaining organic matter and promote the crystallization of alumina, and then removing the molecular sieve template agent by using a template scavenger to obtain the sheet-shaped alumina nanoparticles; the prepared nanofluid does not appear precipitation and flocculation phenomenon after standing for 48 hours, has excellent dispersion stability, has low viscosity, is less affected by the temperature gradient change, is not easy to precipitate and block in the geothermal reservoir cracks, and thus has a wide application prospect in the development of geothermal energy, and is helpful to improve the utilization efficiency of geothermal energy and reduce energy consumption and environmental pollution.

Description

Technical Field

[0001] The present invention belongs to the field of material technology, and in particular relates to flaky aluminum oxide nanoparticles and a preparation method and application thereof. Background Art

[0002] Geothermal energy development is limited by the low heat transfer efficiency of traditional circulating media. Al2O3 nanoparticles have been widely studied due to their high specific surface area and thermal stability, but the specific surface area of ​​conventional spherical or rod-shaped particles is limited. Flaky Al2O3 nanoparticles have a large specific surface area and can significantly improve the heat transfer performance of fluids, but existing preparation methods are complex and costly. In addition, nanofluids are prone to microcracks clogging in geothermal reservoirs due to increased viscosity. Therefore, there is an urgent need to develop a nanofluid with high dispersibility, high thermal conductivity, low cost, and suitable for geothermal extraction.

[0003] Chinese patent document CN119192949A discloses a one-component waterborne epoxy dip coating for a fin-type radiator, which utilizes the efficient thermal conductivity of nanomaterials, but does not involve improvements in the preparation method of nanoparticles and is applied in the field of coating technology.

[0004] Chinese patent document CN119076937A discloses a molecular sieve-loaded high-entropy alloy nanoparticle material and a preparation method thereof, which relates to the preparation of molecular sieves and nanomaterials, but does not involve the fields of geothermal energy and heat transfer.

[0005] Chinese patent CN119309336A discloses a nanofluid-enhanced urban geothermal extraction system and method, which addresses the heat exchange efficiency of nanofluids in geothermal circulation systems, but does not involve improvements in the preparation method of nanoparticles. Summary of the Invention

[0006] The present invention aims to provide a flaky aluminum oxide nanoparticle and a preparation method thereof, and to develop a nanofluid with stable dispersion and excellent heat transfer performance based on the particles, so as to improve the heat exchange efficiency of the geothermal circulation system.

[0007] A method for preparing flaky aluminum oxide nanoparticles comprises the following steps:

[0008] (1) Dissolve the aluminum source in a solvent to obtain a precursor solution, adjust the pH value to 8-10, add the molecular sieve template agent to the precursor solution and stir to disperse it evenly;

[0009] (2) standing at room temperature to allow the aluminum source precursor to deposit on the surface of the molecular sieve template, and filtering, washing and drying the product after high-temperature aging treatment;

[0010] (3) The obtained product is calcined at high temperature to remove the remaining organic matter and promote the crystallization of alumina. Subsequently, a template scavenger is used to remove the molecular sieve template to obtain flaky alumina nanoparticles.

[0011] According to the above scheme, the molecular sieve template in step 1 is TPH-6 molecular sieve, specifically a silicon-based mesoporous molecular sieve with a two-dimensional hexagonal pore structure, the pore size of which is regulated by the synthesis conditions and varies in the range of 2-50nm.

[0012] According to the above scheme, the concentration of the aluminum source in step 1 is 0.04~0.06 mol / L.

[0013] According to the above scheme, the mass ratio of the molecular sieve template to the aluminum source in step 1 is (0.4~0.6):1.

[0014] According to the above scheme, the standing time in step 2 is 12~14h, the high temperature aging temperature is 80~85℃, and the high temperature aging time is 6~7h.

[0015] According to the above scheme, the high temperature calcination temperature in step 3 is 550~560℃.

[0016] According to the above scheme, the particle size of the flaky aluminum oxide nanoparticles obtained in step 3 ranges from 20 to 60 nm.

[0017] According to the above scheme, the molecular sieve template is prepared in the following manner:

[0018] (1) Dissolve the structure-directing agent in a solvent and add an acid catalyst to adjust the pH value of the solution to 1.4-1.6;

[0019] (2) Slowly add the silicon source reagent dropwise to 0.02~0.03 mol / L while stirring, and make the molar ratio of structure directing agent to silicon source reagent be (0.02~0.03):1 to form a uniform solution;

[0020] (3) The solution was transferred to an autoclave, and pre-hydrolyzed first, and then hydrothermally crystallized; the pre-hydrolysis temperature was 37-39°C, the pre-hydrolysis time was 2-3 h, the hydrothermal crystallization temperature was 120-125°C, and the hydrothermal crystallization time was 48-50 h;

[0021] (4) The product is filtered, washed, and dried, and then calcined in a muffle furnace to remove the structure-directing agent.

[0022] According to the above scheme, the raw materials used are calculated by weight as follows: 100 parts of solvent, 4-8 parts of silicon source reagent, 0.2-0.4 parts of structure directing agent, and an appropriate amount of acid catalyst; the solvent is one or more of water, ethanol, and methanol; the silicon source reagent is one or more of tetraethyl orthosilicate (TEOS), sodium silicate, silica sol, and tetramethylsilane; the structure directing agent is one or more of P123 (PEO-PPO-PEO triblock copolymer), F127 (PEO-PPO-PEO triblock copolymer), P65 (PEO-PP-PEO diblock copolymer), and cetyltrimethylammonium bromide (CTAB); and the acid catalyst is one or more of hydrochloric acid (HCl), sulfuric acid, nitric acid, and acetic acid.

[0023] A flaky aluminum oxide nanoparticle is prepared by adopting the above scheme.

[0024] A geothermal circulation medium, the composition of which is as follows in parts by weight:

[0025] 2-4 parts of the above-mentioned flaky aluminum oxide nanoparticles; 100 parts of solvent; 2-4 parts of dispersant.

[0026] The method for preparing the geothermal circulation medium comprises the following steps:

[0027] (1) adding the flaky aluminum oxide nanoparticles to the solvent under stirring conditions to achieve preliminary uniform dispersion;

[0028] (2) Under stirring conditions, the dispersant is continuously added to uniformly mix the flaky aluminum oxide nanoparticles and the dispersant;

[0029] (3) Continue stirring and then perform ultrasonic oscillation. After the treatment is completed, a dispersed and stable flaky alumina nanofluid is obtained.

[0030] According to the above scheme, the stirring speed is 1000~2000RPM, the stirring time is 30~40min; the ultrasonic oscillation frequency is 45~55kHz, and the ultrasonic oscillation time is 30~40min.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1. The present invention utilizes molecular sieves to prepare flaky Al2O3 nanoparticles with small particle size and large specific surface area, providing a new method for the preparation of nanoparticles with specific particle size and shape.

[0033] 2. Through comparative geothermal cycle testing, the inventors discovered that nanofluids containing flaky nanoparticles with the largest specific surface area within the same particle size range exhibit the best heat transfer performance in geothermal circulation systems. Compared to rod-shaped and spherical Al2O3 nanofluids of the same particle size, the present flaky alumina nanofluid exhibited 7.4% and 18.5% higher heat transfer coefficients and 5.3% and 13.3% higher heat transfer rates, respectively. This provides a new solution for the efficient utilization of geothermal energy.

[0034] 3. The preparation method of the flaky aluminum oxide nanoparticles and nanofluid of the present invention is simple, low-cost, and easy to realize industrial production. The prepared nanofluid does not show precipitation and flocculation after standing for 48 hours, and has excellent dispersion stability.

[0035] 4. The viscosity of the flaky alumina nanofluid involved in the present invention is less affected by temperature gradient changes and is not easy to precipitate and clog in geothermal reservoir cracks. Therefore, it has broad application prospects in geothermal energy development, helps to improve the utilization efficiency of geothermal energy, and reduce energy consumption and environmental pollution. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 : SEM image of flaky Al2O3 nanoparticles prepared in Example 1.

[0037] Figure 2 : Graph showing the experimental effect of the flaky Al2O3 nanofluid prepared in Example 1 after 48 hours of static sedimentation.

[0038] Figure 3 : Diagram showing the aggregation effect of flaky Al2O3 nanoparticles in dry hot rock cracks in Experimental Example 1. DETAILED DESCRIPTION

[0039] The following examples further illustrate the technical solutions of the present invention but are not intended to limit the scope of protection of the present invention.

[0040] Specific implementation method The molecular sieve template agent used is TPH-6 molecular sieve. TPH-6 molecular sieve is a silicon-based mesoporous molecular sieve with a highly ordered two-dimensional hexagonal pore structure, and its pore size can be controlled by synthetic conditions and can usually vary within the range of 2-50nm.

[0041] The specific embodiment provides a method for preparing TPH-6 molecular sieve:

[0042] S1. Dissolve the structure-directing agent in a solvent and add an acid catalyst to adjust the solution pH to 1.4-1.6;

[0043] S2. Slowly add the silicon source reagent dropwise to a concentration of 0.02-0.03 mol / L while stirring, with a molar ratio of structure-directing agent to silicon source reagent of (0.02-0.03):1, to form a uniform solution.

[0044] S3. The solution was transferred to an autoclave, first subjected to pre-hydrolysis, and then to hydrothermal crystallization; the pre-hydrolysis temperature was 37-39°C, the pre-hydrolysis time was 2-3 h, the hydrothermal crystallization temperature was 120-125°C, and the hydrothermal crystallization time was 48-50 h;

[0045] S4. The product is filtered, washed and dried, and then calcined in a muffle furnace to remove the structure directing agent.

[0046] Furthermore, the raw materials used are calculated by weight as follows: 100 parts of solvent, 4-8 parts of silicon source reagent, 0.2-0.4 parts of structure directing agent, and an appropriate amount of acid catalyst; the solvent is one or more of water, ethanol, and methanol; the silicon source reagent is one or more of tetraethyl orthosilicate (TEOS), sodium silicate, silica sol, and tetramethylsilane; the structure directing agent is one or more of P123 (PEO-PPO-PEO triblock copolymer), F127 (PEO-PPO-PEO triblock copolymer), P65 (PEO-PP-PEO diblock copolymer), and cetyltrimethylammonium bromide (CTAB); and the acid catalyst is one or more of hydrochloric acid (HCl), sulfuric acid, nitric acid, and acetic acid.

[0047] A specific embodiment provides a method for preparing flaky aluminum oxide nanoparticles, comprising the following steps:

[0048] (1) Dissolve the aluminum source in a solvent to obtain a 0.04-0.06 mol / L precursor solution, adjust the pH value to 8-10, add the molecular sieve template to the precursor solution and stir to disperse it evenly. The mass ratio of the molecular sieve template to the aluminum source is (0.4-0.6):1;

[0049] (2) standing at room temperature to allow the aluminum source precursor to deposit on the surface of the molecular sieve template, and filtering, washing and drying the product after high-temperature aging treatment; the standing time is 12~14h, the high-temperature aging temperature is 80~85℃, and the high-temperature aging time is 6~7h;

[0050] (3) The obtained product is calcined at a high temperature of 550-560°C to remove the remaining organic matter and promote the crystallization of alumina. Subsequently, a template scavenger is used to remove the molecular sieve template agent to obtain flaky alumina nanoparticles with a particle size range of 20-60 nm.

[0051] The specific embodiment also provides a method for preparing a geothermal circulation medium using flaky Al2O3 nanoparticles, comprising the steps of:

[0052] (1) Add flaky Al2O3 nanoparticles into the solvent while magnetically stirring. The magnetic stirring speed is set to 1000 RPM to ensure that the flaky Al2O3 nanoparticles are initially evenly dispersed.

[0053] (2) Dispersant (sodium dodecylbenzenesulfonate) was added while magnetic stirring was performed. The speed of magnetic stirring was set to 1000 RPM to ensure that the flaky Al2O3 nanoparticles and the dispersant were evenly mixed.

[0054] (3) The mixed nanofluid was further subjected to magnetic stirring at a speed of 1000 RPM for 30 to 40 minutes. The mixture was then subjected to water bath ultrasonic oscillation at a frequency of 45 kHz for 30 minutes. After the treatment, a dispersed and stable flaky Al2O3 nanofluid was obtained.

[0055] Example 1

[0056] In this embodiment, the molecular sieve template agent used is TPH-6 molecular sieve, which is prepared from the following raw materials in parts by weight: 100 parts of solvent, 4 parts of silicon source reagent, 0.2 parts of structure directing agent, and an appropriate amount of acid catalyst; wherein the solvent is water; the silicon source reagent is tetraethyl orthosilicate (TEOS); the structure directing agent is P123 (PEO-PPO-PEO triblock copolymer); and the acid catalyst is hydrochloric acid (HCl).

[0057] Flaky Al2O3 nanoparticles prepared using molecular sieves are prepared from the following raw materials in parts by weight: 100 parts solvent, 4 parts aluminum source, 2 parts molecular sieve template, an appropriate amount of pH adjuster, and an appropriate amount of template scavenger. The solvent is water; the aluminum source is aluminum nitrate; the pH adjuster is ammonia water; and the template scavenger is sodium hydroxide (NaOH). Flaky aluminum oxide nanoparticles with a particle size range of 20-40 nm and a specific surface area of ​​160-180 m2 are prepared using the preparation method provided in the detailed description. 2 / g.

[0058] The SEM images of the flaky Al2O3 nanoparticles prepared in this example are shown in the attached Figure 1 shown.

[0059] The flaky Al2O3 nanoparticles obtained in this example were used to prepare a flaky Al2O3 nanofluid with a concentration of 2%. The results of the static sedimentation experiment within 48 hours are shown in the attached Figure 2 shown.

[0060] Example 2

[0061] In this embodiment, the molecular sieve template agent used is TPH-6 molecular sieve, which is prepared from the following raw materials in parts by weight: 100 parts of solvent, 4 parts of silicon source reagent, 0.2 parts of structure directing agent, and an appropriate amount of acid catalyst; wherein the solvent is water; the silicon source reagent is sodium silicate; the structure directing agent is F127 (PEO-PPO-PEO triblock copolymer); and the acid catalyst is hydrochloric acid (HCl).

[0062] Flaky Al2O3 nanoparticles prepared using molecular sieves are prepared from the following raw materials in parts by weight: 100 parts solvent, 4 parts aluminum source, 2 parts molecular sieve template, an appropriate amount of pH adjuster, and an appropriate amount of template scavenger. The solvent is water; the aluminum source is aluminum hydroxide (Al(OH)3); the pH adjuster is sodium carbonate (Na2CO3); and the template scavenger is sodium hydroxide (NaOH). Using the preparation method provided in the detailed description, flaky aluminum oxide nanoparticles with a particle size range of 20-50 nm and a specific surface area of ​​150-170 m 2 / g.

[0063] Example 3

[0064] In this embodiment, the molecular sieve template agent used is TPH-6 molecular sieve, which is prepared from the following raw materials in parts by weight: 100 parts of solvent, 4 parts of silicon source reagent, 0.2 parts of structure directing agent, and an appropriate amount of acid catalyst; wherein the solvent is water; the silicon source reagent is silica sol; the structure directing agent is P65 (PEO-PP-PEO diblock copolymer); and the acid catalyst is sulfuric acid.

[0065] Flaky Al2O3 nanoparticles prepared using molecular sieves are prepared from the following raw materials in parts by weight: 100 parts solvent, 4 parts aluminum source, 2 parts molecular sieve template, an appropriate amount of pH adjuster, and an appropriate amount of template scavenger. The solvent is water; the aluminum source is aluminum nitrate; the pH adjuster is sodium hydroxide (NaOH); and the template scavenger is sulfuric acid. The preparation method provided in the detailed description is used to prepare flaky aluminum oxide nanoparticles with a particle size range of 30-60 nm and a specific surface area of ​​140-170 m 2 / g.

[0066] Example 4

[0067] In this embodiment, the molecular sieve template used is TPH-6 molecular sieve, which is prepared from the following raw materials in parts by weight: 100 parts of solvent, 4 parts of silicon source reagent, 0.2 parts of structure directing agent, and an appropriate amount of acid catalyst; wherein the solvent is water; the silicon source reagent is tetramethylsilane; the structure directing agent is cetyltrimethylammonium bromide (CTAB); and the acid catalyst is hydrochloric acid (HCl).

[0068] Flaky Al2O3 nanoparticles prepared using molecular sieves are prepared from the following raw materials in parts by weight: 100 parts of solvent, 4 parts of aluminum source, 2 parts of molecular sieve template, an appropriate amount of pH adjuster, and an appropriate amount of template scavenger; wherein the solvent is water; the aluminum source is aluminum hydroxide (Al(OH)3); the pH adjuster is ammonia water (NH3·H2O); and the template scavenger is sodium hydroxide (NaOH). The flaky aluminum oxide nanoparticles with a particle size range of 30-50 nm and a specific surface area of ​​160-180 m2 are prepared using the preparation method provided in the detailed embodiment. 2 / g.

[0069] The specific implementation method also uses a nanofluid circulation heat transfer experimental device to test the heat transfer performance of nanofluids under medium-deep geothermal reservoir conditions, exploring the influence of flow rate on the heat transfer performance of nanofluids below the actual heat source boundary. The test site is located in Yingshan County, Huanggang City, Hubei Province, with a well depth of 230m and a wellhead geothermal water temperature of approximately 70°C. The test steps include the following:

[0070] (1) Inject the prepared nanofluid into the reservoir;

[0071] (2) Place the heating section pipeline in the geothermal well so that the heating section pipeline is completely immersed in the geothermal water in the well and keep the pipeline 0.3m below the geothermal water level;

[0072] (3) Set the peristaltic pump flow rate and turn on the peristaltic pump to provide power for the nanofluid;

[0073] (4) When the fluid temperature at the outlet of the heating section begins to change, start recording the fluid temperature change data at the inlet and outlet of the heating section and continue for 30 minutes;

[0074] (5) After 30 minutes, turn off the peristaltic pump and retract the heating section pipeline from the well, ending the test. Specific test conditions are shown in the following test example.

[0075] The following test examples all use the flaky Al2O3 nanoparticles prepared in Example 1. The rod-shaped nanoparticles used have a microscopic size of 20-40 nm and a specific surface area of ​​160-180 m 2 / g. The spherical nanoparticles used are 20-40nm in size and have a specific surface area of ​​90-110m 2 / g.

[0076] 2 wt% nanofluid was prepared by using the flaky Al2O3 nanoparticles, rod-shaped nanoparticles and spherical nanoparticles prepared in Example 1. Sodium dodecylbenzenesulfonate was used as the dispersant. The results were tested at a shear rate of 170.3s -1 The viscosity of the product changes with temperature. The results are shown in Table 1.

[0077] Table 1

[0078]

[0079] From the data in Table 1, it can be seen that the viscosity of flake Al2O3 nanoparticles is slightly higher than that of rod-shaped and spherical nanoparticles at the same temperature, but the viscosity change in the range of 20℃-90℃ is only 0.5 mPa·s. Compared with rod-shaped nanoparticles and spherical nanoparticles, they are less affected by temperature gradient changes and have more beneficial temperature stability.

[0080] Test Example 1

[0081] Step 1: Set the flow rate of the peristaltic pump to 0.2 m / s.

[0082] Step 2: Increase the concentration of flaky nanoparticles from 0.25% to 0.5%, and the heat transfer coefficient of the nanofluid is tested from 124.8W / (m 2 K) increased to 125.33W / (m 2 ·K), the heat transfer coefficient increased by 0.4%.

[0083] Step 3: Increase the concentration of flaky nanoparticles from 0.5% to 1%, and the heat transfer coefficient of the nanofluid is tested from 125.33W / (m 2 K) increased to 142.34W / (m 2 ·K), the heat transfer coefficient increased by 13%.

[0084] Step 4: Increase the concentration of flaky nanoparticles from 1% to 2%, and the test results show that the heat transfer coefficient of nanofluid increases from 142.34W / (m 2 K) increased to 153.41W / (m 2 ·K), the heat transfer coefficient increased by 7%.

[0085] The aggregation effect of flaky Al2O3 nanoparticles in the cracks of hot dry rocks in this test example is shown in the attached figure. Figure 3 shown.

[0086] Test Example 2

[0087] Step 1: Set the flow rate of the peristaltic pump to 0.6 m / s.

[0088] Step 2: Increase the concentration of nanoparticles from 0.25% to 0.5%, and the heat transfer coefficient of the nanofluid is tested from 293.72W / (m 2 K) increased to 318.33W / (m 2 ·K), the heat transfer coefficient increased by 8%.

[0089] Step 3: Increase the concentration of nanoparticles from 0.5% to 1%, and the heat transfer coefficient of the nanofluid is tested from 318.33W / (m2 K) increased to 328.72W / (m 2 ·K), the heat transfer coefficient increased by 3%.

[0090] Step 4: Increase the concentration of nanoparticles from 1% to 2%, and the heat transfer coefficient of the nanofluid is tested from 328.72W / (m 2 K) increased to 343.14W / (m 2 ·K), the heat transfer coefficient increased by 4%.

[0091] Test Example 3

[0092] Step 1: Set the flow rate of the peristaltic pump to 0.6 m / s.

[0093] Step 2: The concentration of the flaky nanoparticles was set to 2%, and the maximum heat transfer coefficient of the nanofluid was 343.14 W / (m 2 ·K), the maximum heat transfer is 693.4W.

[0094] Step 3: The concentration of rod-shaped nanoparticles was set to 2%, and the maximum heat transfer coefficient of the nanofluid was 337.54 W / (m 2 ·K), and the maximum heat transfer is 685.9W. Compared with the sheet nanofluid, the heat transfer coefficient and heat transfer are reduced by 1.7% and 1.1%, respectively.

[0095] Step 4: Set the concentration of spherical nanoparticles to 2% and test the maximum heat transfer coefficient of the nanofluid to be 332.91W / (m 2 ·K), and the maximum heat transfer is 675.2W. Compared with the sheet nanofluid, the heat transfer coefficient and heat transfer are reduced by 3.1% and 2.7%, respectively.

[0096] Test Example 4

[0097] Step 1: Set the flow rate of the peristaltic pump to 0.8 m / s.

[0098] Step 2: The concentration of the flaky nanoparticles was set to 1%, and the maximum heat transfer coefficient of the nanofluid was 413.37 W / (m 2 ·K), the maximum heat transfer is 810.9W.

[0099] Step 3: The concentration of rod-shaped nanoparticles was set to 1%, and the maximum heat transfer coefficient of the nanofluid was 384.89W / (m 2 ·K), and the maximum heat transfer is 770.1W. Compared with the sheet nanofluid, the heat transfer coefficient and heat transfer are reduced by 7.4% and 5.3%, respectively.

[0100] Step 4: Set the concentration of spherical nanoparticles to 1% and test the maximum heat transfer coefficient of the nanofluid to be 348.84W / (m 2 ·K), and the maximum heat transfer is 715.7W. Compared with the sheet nanofluid, the heat transfer coefficient and heat transfer are reduced by 18.5% and 13.3%, respectively.

[0101] Furthermore, compared with rod-shaped nanofluids and spherical nanofluids, sheet-shaped nanofluids have the best heat transfer enhancement effect in geothermal circulation systems.

[0102] Test Example 5

[0103] Step 1: Set the flow rate of the peristaltic pump to 0.2m / s, 0.6m / s, 0.8m / s, and 1.2m / s in sequence.

[0104] Step 2: At four different flow rates, the heat transfer effects of geothermal cycles were compared using flaky Al2O3 nanofluid with a mass fraction of 2wt% and water.

[0105] Furthermore, the actual heat transfer coefficient comparison between nanofluids and water in geothermal reservoirs is shown in Table 2.

[0106] Table 2

[0107]

[0108] The comparative test results in Table 1 show that the nanofluid provided by the present invention exhibits a 20% increase in heat transfer coefficient compared to water at a flow rate of 0.2 m / s. This flow rate is consistent with the actual flow state of the fluid in geothermal reservoir fractures. Furthermore, the nanofluid was operated for 72 hours without nanoparticle deposition or pipe blockage. Therefore, these test results demonstrate that the nanofluid provided by the present invention significantly improves geothermal energy utilization efficiency when used as a geothermal circulation medium.

[0109] The above describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various modifications can be made within the scope of knowledge possessed by ordinary technicians in the relevant technical field without departing from the spirit of the present invention.

Claims

1. A method for preparing flaky aluminum oxide nanoparticles, characterized in that The following steps are involved: (1) dissolving an aluminum source in a solvent to obtain a precursor solution, adjusting the pH value to 8-10, and adding a molecular sieve template to the precursor solution and stirring to disperse it evenly; the molecular sieve template is TPH-6 molecular sieve, specifically a silicon-based mesoporous molecular sieve with a two-dimensional hexagonal pore structure, the pore size of which is regulated by the synthesis conditions and varies within the range of 2-50 nm; (2) standing at room temperature to allow the aluminum source precursor to deposit on the surface of the molecular sieve template, and filtering, washing and drying the product after high-temperature aging treatment; (3) The obtained product is calcined at high temperature to remove the remaining organic matter and promote the crystallization of alumina. Subsequently, a template scavenger is used to remove the molecular sieve template to obtain flaky alumina nanoparticles.

2. The method for preparing flaky aluminum oxide nanoparticles according to claim 1, wherein The concentration of the aluminum source in step 1 is 0.04-0.06 mol / L; the mass ratio of the molecular sieve template to the aluminum source is (0.4-0.6):

1.

3. The method for preparing flaky aluminum oxide nanoparticles according to claim 1, wherein In step 2, the standing time is 12 to 14 hours, the high-temperature aging temperature is 80 to 85° C., and the high-temperature aging time is 6 to 7 hours.

4. The method for preparing flaky aluminum oxide nanoparticles according to claim 1, wherein The high temperature calcination temperature in step 3 is 550-560°C.

5. The method for preparing flaky aluminum oxide nanoparticles according to claim 1, wherein The particle size of the flaky aluminum oxide nanoparticles obtained in step 3 ranges from 20 to 60 nm.

6. The method for preparing flaky aluminum oxide nanoparticles according to claim 1, wherein The molecular sieve template is prepared in the following manner: (1) dissolving a structure directing agent in a solvent, and adding an acid catalyst to adjust the pH value of the solution to 1.4-1.6; the structure directing agent is one or more of P123 triblock copolymer, F127 triblock copolymer, P65 diblock copolymer, and cetyltrimethylammonium bromide; (2) Slowly add the silicon source reagent dropwise to 0.02~0.03 mol / L while stirring, and make the molar ratio of structure directing agent to silicon source reagent be (0.02~0.03):1 to form a uniform solution; (3) The solution was transferred to an autoclave, and pre-hydrolyzed first, and then hydrothermally crystallized; the pre-hydrolysis temperature was 37-39°C, the pre-hydrolysis time was 2-3 h, the hydrothermal crystallization temperature was 120-125°C, and the hydrothermal crystallization time was 48-50 h; (4) The product is filtered, washed, and dried, and then calcined in a muffle furnace to remove the structure-directing agent.

7. The method for preparing flaky aluminum oxide nanoparticles according to claim 6, characterized in that The raw materials used in the preparation method of the molecular sieve template agent are 100 parts of solvent, 4-8 parts of silicon source reagent, and 0.2-0.4 parts of structure directing agent in parts by weight; the solvent used in the preparation method of the molecular sieve template agent is one or more of water, ethanol, and methanol; the silicon source reagent is one or more of ethyl orthosilicate, sodium silicate, silica sol, and tetramethylsilane; and the acid catalyst is one or more of hydrochloric acid, sulfuric acid, nitric acid, and acetic acid.

Images