Ultrafine alumina powder, preparation method thereof and device for preparing ultrafine alumina powder

Abstract

The invention provides superfine aluminum oxide powder, a preparation method thereof and a device for preparing the superfine aluminum oxide powder, and relates to the field of metal oxides. The preparation method of the superfine aluminum oxide powder comprises the following steps: carrying out atomization treatment on an aluminum salt solution and an alkaline solution to form aluminum salt liquid drops and alkaline liquid drops; the aluminum salt liquid drops and the alkaline liquid drops are subjected to pulsating pressurization and aerial fog stirring, so that the aluminum salt liquid drops and the alkaline liquid drops are subjected to a chemical reaction, and an aluminum hydroxide precursor is obtained; the aluminum hydroxide precursor is subjected to microwave heating, the superfine aluminum oxide powder is obtained, and the superfine aluminum oxide powder is alpha-Al2O3. Pulsating pressurization and aerial fog stirring cooperate with each other, so that the formation of large aggregates is effectively inhibited, and the quality of the superfine aluminum oxide powder is remarkably improved. The aluminum oxide powder prepared through the method has the advantages of being good in dispersity, uniform in particle size distribution, small in grain size and the like, and the requirements for high-performance aluminum oxide powder in the fields of aviation, aerospace, chemical engineering, energy and the like can be met.

Description

Technical Field

[0001] The present application relates to the field of metal oxides, and in particular to an ultrafine aluminum oxide powder and a preparation method thereof, and a device for preparing the ultrafine aluminum oxide powder. Background Art

[0002] Alumina has the advantages of high strength, high hardness, wear resistance, corrosion resistance, high temperature resistance, oxidation resistance, good insulation, etc. It is one of the most widely used ceramic materials and is widely used in chemical, mechanical, metallurgical, aerospace and other fields. With the continuous development of technology and the continuous expansion of application fields, especially electronic and mechanical products, higher requirements are put forward for the particle size, purity and uniformity of alumina powder, and the demand for ultra-fine, high-purity, uniform particle size distribution and good dispersibility of high-quality alumina powder is increasing.

[0003] At present, the main method for preparing ultrafine alumina powder for industrial production is liquid phase precipitation. In the reaction process of the conventional liquid phase precipitation method, the area where the two solutions first contact generates crystal nuclei first. As the reaction continues, the first generated crystal nuclei continue to grow and become particles with larger particle sizes, while the area that contacts later generates fine particles and gradually grows. The fine particles generated later will be adsorbed on the surface of the large particles generated earlier. As time goes by, agglomerates are formed, and the product has poor dispersibility and uneven particle size. The liquid phase precipitation method is simple in equipment, low in cost, and high in yield for preparing ultrafine alumina powder. However, the precipitation agent is directly added to the solution during the precipitation process, and the precipitation process is unbalanced, with local over-concentration problems, which leads to the prepared alumina powder being prone to agglomeration, uneven particle size, and a wide particle size distribution range, which cannot meet the needs of high-end equipment for high-quality alumina powder materials.

[0004] Therefore, it is necessary to improve the preparation method of ultrafine alumina powder to meet the demand of high-end equipment for high-quality alumina powder materials. Summary of the invention

[0005] The purpose of the present application is to provide an ultrafine alumina powder and a preparation method thereof and an apparatus for preparing the ultrafine alumina powder to solve the above problems.

[0006] To achieve the above objectives, this application adopts the following technical solutions:

[0007] The present application provides a method for preparing ultrafine alumina powder, comprising:

[0008] Atomizing the aluminum salt solution and the alkaline solution to form aluminum salt droplets and alkaline droplets;

[0009] The aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring to allow the aluminum salt droplets and the alkaline droplets to undergo a chemical reaction to obtain an aluminum hydroxide precursor;

[0010] The aluminum hydroxide precursor is subjected to microwave heating to obtain ultrafine aluminum oxide powder, wherein the ultrafine aluminum oxide powder is α-Al2O3;

[0011] The aerosol stirring rate is 500-1000 r / min;

[0012] The frequency of the pulsating pressurization is 30-60 Hz, and the pressure amplitude of the pulsating pressurization is 0.3-0.8 MPa.

[0013] According to an embodiment of the present application, the aluminum salt solution includes at least one of an aluminum nitrate solution, an aluminum sulfate solution, and an aluminum chloride solution;

[0014] The alkaline solution includes at least one of aqueous ammonia and ammonium bicarbonate solution;

[0015] And / or, atomizing the aluminum salt solution and the alkaline solution includes: atomizing the aluminum salt solution and the alkaline solution using an atomizer array, wherein the frequency of the atomizer array is 5 to 10 MHz.

[0016] According to an embodiment of the present application, the chemical reaction is carried out in a reactor, the bottom of which is filled with a mixed solution of water and polyethylene glycol;

[0017] The preparation method further comprises: stirring the mixed solution; wherein the stirring rate of the mixed solution is 200 to 800 r / min;

[0018] And / or, the preparation method further comprises: subjecting the mixed solution to ultrasonic treatment.

[0019] According to an embodiment of the present application, the temperature of the microwave heating is 900-1100°C;

[0020] And / or, the microwave heating time is 20 to 60 minutes;

[0021] And / or, the average particle size of the ultrafine alumina powder is 20 to 50 nm.

[0022] The present application also provides an ultrafine alumina powder, which is prepared by the ultrafine alumina powder preparation method described above.

[0023] The present application also provides a device for preparing ultrafine alumina powder, the device for preparing ultrafine alumina powder is used to perform the method for preparing ultrafine alumina powder as described above, and the device for preparing ultrafine alumina powder comprises:

[0024] A reactor, wherein the reactor is used to chemically react aluminum salt droplets and alkaline droplets to obtain an aluminum hydroxide precursor; an atomizer array is installed on the reactor, and the atomizer array is used to atomize the aluminum salt solution and the alkaline solution into aluminum salt droplets and alkaline droplets; the reactor comprises a tank body and a pressure regulating component, the pressure regulating component is connected to the tank body, and the pressure regulating component is used to pulsate pressurize the reactor; a gas phase agitator is installed in the tank body, and the gas phase agitator is used to perform aerosol stirring on the aluminum salt droplets and the alkaline droplets;

[0025] A microwave reactor is used to perform microwave heating on the aluminum hydroxide precursor to obtain ultrafine aluminum oxide powder.

[0026] According to an embodiment of the present application, the pressure regulating component includes a piston; the reactor has an extrusion section and a mixing section; the piston is located in the extrusion section, and the gas phase agitator and the atomizer array are located in the mixing section.

[0027] According to an embodiment of the present application, a liquid phase agitator is provided at the bottom of the tank body for stirring the mixed solution;

[0028] And / or, an ultrasonic generator is also installed on the tank body for performing ultrasonic treatment on the mixed solution.

[0029] Compared with the prior art, the beneficial effects of this application include:

[0030] The present application adopts atomization to atomize aluminum salt solution and alkaline solution into uniform and fine droplets, and introduces them into the reactor container for chemical reaction; wherein, by pulsating and pressurizing aluminum salt droplets and alkaline droplets, the pressure in the reactor can produce rhythmic or random pulsating changes, which is conducive to accelerating its reaction rate; and the rhythmic or random pulsating process helps to prevent excessive aggregation of molecules to produce large-sized agglomerates. At the same time, the present application also performs aerosol stirring on aluminum salt droplets and alkaline droplets, and aerosol stirring helps to evenly diffuse different media, increase the probability of contact reaction of heterogeneous media, and evenly generate a large number of tiny crystal nuclei, and finally form uniform and fine precipitation particles. In general, pulsating pressurization and aerosol stirring cooperate with each other, effectively inhibit the formation of large agglomerates, and effectively improve the quality of ultrafine alumina powder. The alumina powder prepared by the method of the present application has the advantages of good dispersibility, uniform particle size distribution, and small grain size, which can meet the needs of aviation, aerospace, chemical industry, energy and other fields for high-performance alumina powder.

[0031] The aluminum oxide powder of the present application has the advantages of good dispersibility, uniform particle size distribution, small grain size, etc., and has high quality.

[0032] The device for preparing ultrafine alumina powder of the present application can be used to prepare high-quality alumina powder, which has good dispersibility, uniform particle size distribution, and fine grain size, and can meet the needs of high-performance alumina powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope of the present application.

[0034] Figure 1 It is a structural schematic diagram of the reactor in this application;

[0035] Figure 2 is a transmission electron microscope image of the ultrafine alumina powder prepared in Example 1;

[0036] Figure 3 This is the XRD spectrum of the ultrafine alumina powder prepared in Example 1, wherein the red line represents the characteristic peak of α-Al2O3.

[0037] Description of reference numerals:

[0038] 100 - reactor, 110 - atomizer array, 120 - tank body, 130 - pressure regulating component, 140 - gas phase agitator, 150 - liquid phase agitator. DETAILED DESCRIPTION

[0039] In order to better explain the technical solution provided by this application, before the embodiments, the technical solution is first described as a whole, as follows:

[0040] The present application provides a method for preparing ultrafine alumina powder, comprising:

[0041] Atomizing the aluminum salt solution and the alkaline solution to form aluminum salt droplets and alkaline droplets;

[0042] The aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring to allow the aluminum salt droplets and the alkaline droplets to undergo a chemical reaction to obtain an aluminum hydroxide precursor;

[0043] The aluminum hydroxide precursor is subjected to microwave heating to obtain ultrafine aluminum oxide powder, wherein the ultrafine aluminum oxide powder is α-Al2O3;

[0044] The aerosol stirring rate is 500-1000 r / min;

[0045] The frequency of the pulsating pressurization is 30-60 Hz, and the pressure amplitude of the pulsating pressurization is 0.3-0.8 MPa.

[0046] Through pulsating pressurization, the pressure in the reactor can produce rhythmic or random pulsating changes. When the pressure increases, it is accompanied by temperature changes, the molecular mean free path is shortened, and the reaction activity is increased, which helps to increase the reaction speed. On the other hand, the pressure increase will promote the contact and collision between the atomized droplets, which is also conducive to accelerating its reaction rate; and the rhythmic or random pulsating process helps to prevent the excessive aggregation of molecules to form large-sized agglomerates. Aerosol stirring helps to evenly diffuse different media and increase the probability of contact reaction of heterogeneous media. The formed cyclone produces partial centrifugal effect, which helps the reaction products to be scattered and thrown out, and then fall into the liquid phase at the bottom of the reactor, preventing them from meeting and agglomerating in a small radius to form large agglomerates. Through the synergistic effect of pulsating pressurization and aerosol stirring, the formation of large agglomerates is effectively suppressed, which is conducive to obtaining high-quality ultrafine alumina powder.

[0047] In general, the ultrafine alumina powder prepared in the present application has the advantages of good dispersibility, uniform particle size distribution, and small grain size, and can meet the demand for high-performance alumina powder in the fields of aviation, aerospace, chemical industry, energy, etc.

[0048] According to an embodiment of the present application, the rate of the aerosol stirring is 500 to 1000 r / min. Through aerosol stirring, the medium can be forced to convect, which is beneficial to the uniform mixing of aluminum salt droplets and alkaline droplets. When the aerosol stirring rate is within the above range, the atomized droplets can form a turbulent cyclone, and the Reynolds number is high, and the media of different components are mixed evenly. If the aerosol stirring rate is too low, the medium mixing uniformity deteriorates and cannot be fully mixed; too high a stirring rate may cause mechanical shear, increase the energy consumption of the system and the degree of wear of the equipment, and too high a stirring rate may also lead to poor stability of equipment operation.

[0049] Exemplarily, the rate of aerosol stirring may be 500 r / min, 600 r / min, 700 r / min, 800 r / min, 900 r / min, 1000 r / min or any value between 500 and 1000 r / min.

[0050] According to an embodiment of the present application, the frequency of the pulsating pressurization is 30 to 60 Hz, and the pressure amplitude of the pulsating pressurization is 0.3 to 0.8 MPa. During the pulsating pressurization process, when the pressure gradually increases, the number of molecular collisions per unit time increases, which speeds up the reaction rate and promotes the reaction. If the pressure amplitude is too small, it will affect the reaction rate. However, if the pressure is high for a long time or the pressure peak is not reached again before it is fully dispersed, the risk of producing large particles will increase. When the frequency and pressure amplitude of the pulsating pressurization are within the above range, a reasonable reaction speed can be generated without increasing the risk of producing large particles, which is conducive to the generation of ultrafine alumina powder with uniform particle size distribution.

[0051] For example, the frequency of the pulsating pressurization may be 30 Hz, 40 Hz, 50 Hz, 60 Hz, or any value between 30 and 60 Hz.

[0052] The pressure amplitude of the pulsating pressurization can be 0.3 MPa, 0.4 MPa, 0.5 MPa, 0.6 MPa, 0.7 MPa, 0.8 MPa or any value between 0.3 and 0.8 MPa.

[0053] According to an embodiment of the present application, the aluminum salt solution includes at least one of an aluminum nitrate solution, an aluminum sulfate solution, and an aluminum chloride solution;

[0054] The alkaline solution includes at least one of aqueous ammonia and ammonium bicarbonate solution;

[0055] And / or, atomizing the aluminum salt solution and the alkaline solution includes: atomizing the aluminum salt solution and the alkaline solution using an atomizer array, wherein the frequency of the atomizer array is 5 to 10 MHz. The atomizer array can use ultrasound to atomize the aluminum salt solution and the alkaline solution into uniform fine droplets, which is beneficial to improving the particle size uniformity of the final product aluminum oxide powder. If the frequency of the atomizer array is too low, the atomized droplet size will be larger, and small droplets cannot be obtained, resulting in poor particle size uniformity of the aluminum oxide powder. If the frequency of the atomizer array is too high, it may cause excessive volatilization of the liquid, increase energy consumption, and easily damage the equipment.

[0056] Furthermore, the nebulizer array is an ultrasonic nebulizer array.

[0057] Exemplarily, the frequency of the atomizer array may be 5 MHz, 6 MHz, 7 MHz, 8 MHz, 9 MHz, 10 MHz or any value between 5 and 10 MHz.

[0058] According to an embodiment of the present application, the chemical reaction is carried out in a reactor, and a mixed solution of water and polyethylene glycol is installed at the bottom of the reactor; the reaction products at the top of the reactor are collected at the bottom of the reactor, and the mixed solution is used to collect the reaction products. Specifically, the formed cyclone produces a partial centrifugal effect, which helps the reaction products to be scattered and thrown out, and then fall into the mixed solution at the bottom of the reactor, preventing them from meeting and agglomerating within a small radius to form large aggregates. It can also allow the unreacted fine droplets at the top of the reactor to enter the mixed solution and further react completely.

[0059] Furthermore, polyethylene glycol can act as a dispersant, which is beneficial to improving the dispersibility of the final product.

[0060] The preparation method also includes: stirring the mixed solution; wherein the stirring rate of the mixed solution is 200 to 800 r / min. Stirring the mixed solution is conducive to promoting the uniformity of the mixing of the reactants and inhibiting the formation of agglomerates, accelerating the reaction rate, and improving the particle size uniformity and dispersibility of the aluminum hydroxide precursor, thereby avoiding the problems of poor dispersibility and uneven particle size in the preparation of aluminum oxide powder by conventional liquid phase precipitation method. If the stirring rate of the mixed solution is too low, the product is prone to agglomeration; if the stirring rate of the mixed solution is too fast, the dispersion state of the product will not change significantly, and the energy consumption is relatively large.

[0061] Illustratively, the stirring rate of the mixed solution may be 200 r / min, 300 r / min, 400 r / min, 500 r / min, 600 r / min, 700 r / min, 800 r / min or any value between 200 and 800 r / min.

[0062] And / or, the preparation method further comprises: subjecting the mixed solution to ultrasonic treatment. The high-frequency vibration waves generated by the ultrasonic treatment can increase the kinetic energy of ions in the liquid in the reactor, promote the uniformity of the mixing of reactants and inhibit the formation of agglomerates, and the heat generated by the ultrasonic wave can indirectly increase the temperature of the material, accelerate the reaction rate, further improve the particle size uniformity and dispersibility of the obtained aluminum hydroxide precursor, and thus improve the quality of the aluminum oxide powder.

[0063] According to some embodiments of the present application, after obtaining the aluminum hydroxide precursor and before subjecting the aluminum hydroxide precursor to microwave heating, the preparation method further includes: washing and drying the aluminum hydroxide precursor.

[0064] The present application adopts microwave heating to heat the aluminum hydroxide precursor. Due to the strong penetrating ability of microwaves, the inside and outside of the material can be evenly and quickly heated as a whole, the heating is uniform, the heating time is shorter, and the local overheating or overcooling that may occur in traditional heating methods is avoided. The microwave heating method can make the particle size of the obtained product aluminum oxide powder more uniform and finer.

[0065] According to the embodiment of the present application, the temperature of the microwave heating is 900-1100°C; at the above temperature, it is conducive to obtaining a single phase of α-Al2O3, and the particle size of the generated alumina powder is small. If the temperature of the microwave heating is too low, in addition to α-Al2O3, other phases will be generated in the obtained product, and a single phase of α-Al2O3 cannot be obtained; if the temperature of the microwave heating is too high, the grains will grow.

[0066] Exemplarily, the temperature of microwave heating may be 900°C, 950°C, 1000°C, 1050°C, 1100°C or any value between 900 and 1100°C.

[0067] And / or, the microwave heating time is 20 to 60 minutes; within the above time, the aluminum hydroxide precursor can be completely reacted to generate ultrafine aluminum oxide powder. If the microwave heating time is too short, the aluminum hydroxide is not completely dehydrated, which will lead to a decrease in the quality of aluminum oxide; if the microwave heating time is too long, the grain size will become larger.

[0068] Exemplarily, the microwave heating time can be 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min, 60 min or any value between 20 and 60 min.

[0069] And / or, the average particle size of the ultrafine alumina powder is 20 to 50 nm.

[0070] The present application also provides an ultrafine alumina powder, which is prepared by the ultrafine alumina powder preparation method described above.

[0071] The present application also provides a device for preparing ultrafine alumina powder, the device for preparing ultrafine alumina powder is used to perform the method for preparing ultrafine alumina powder as described above, the device for preparing ultrafine alumina powder comprises: a microwave reactor and Figure 1 The reactor 100 shown is used to make the aluminum salt droplets and the alkaline droplets react chemically to obtain an aluminum hydroxide precursor; the reactor 100 is equipped with an atomizer array 110, and the atomizer array 110 is used to atomize the aluminum salt solution and the alkaline solution into aluminum salt droplets and alkaline droplets; the reactor 100 includes a tank body 120 and a pressure regulating component 130, and the pressure regulating component 130 is connected to the tank body 120, and the pressure regulating component 130 is used to pulsate pressurize the reactor 100; a gas phase agitator 140 is installed in the tank body 120, and the gas phase agitator 140 is used to perform aerosol stirring on the aluminum salt droplets and the alkaline droplets;

[0072] The microwave reactor is used to perform microwave heating on the aluminum hydroxide precursor to obtain ultrafine aluminum oxide powder.

[0073] Specifically, the pressure regulating component 130 can make the pressure in the reactor 100 produce rhythmic or random pulsating changes, and the process is similar to the pressure change of the cylinder of a stroke engine. When the pressure increases, it is accompanied by temperature changes, the molecular mean free path is shortened, and the reaction activity is increased, which helps to increase the reaction speed. On the other hand, the pressure increase will promote the contact and collision between the atomized droplets, which is also conducive to accelerating its reaction rate; and the rhythmic or random pulsating process helps to prevent the excessive aggregation of molecules to produce large-sized agglomerates. The gas phase agitator 140 helps to evenly diffuse different media and increase the probability of contact reaction of heterogeneous media. The formed cyclone produces partial centrifugal effect, which helps the reaction products to be scattered and thrown out, and then fall into the liquid phase at the bottom of the reactor 100, preventing them from meeting and agglomerating in a small radius to form large agglomerates. Through the synergistic effect of the pressure regulating component 130 and the gas phase agitator 140, the formation of large agglomerates is effectively suppressed, and high-quality ultrafine alumina powder can be obtained using the method of the present application.

[0074] According to an embodiment of the present application, the pressure regulating component 130 includes a piston; the reactor 100 has an extrusion section and a mixing section; the piston is located in the extrusion section, and the gas phase agitator 140 and the atomizer array 110 are located in the mixing section.

[0075] The extrusion section is located between the piston and the top of the reactor. Figure 1 The mixing section is located between the piston and the bottom of the reactor, that is, Figure 1 Below the middle pressure regulating component 130.

[0076] According to an embodiment of the present application, a liquid phase agitator 150 is provided at the bottom of the tank body 120, and the liquid phase agitator 150 is used to stir the mixed solution;

[0077] And / or, an ultrasonic generator is also installed on the tank body 120, and the ultrasonic generator is used to perform ultrasonic treatment on the mixed solution.

[0078] As used herein:

[0079] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0080] The embodiments of the present application will be described in detail below in conjunction with specific examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present application and should not be considered as limiting the scope of the present application. If specific conditions are not specified in the examples, they are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0081] Example 1

[0082] Embodiment 1 provides a method for preparing ultrafine alumina powder, comprising the following steps:

[0083] Atomizing an aluminum salt solution and an alkaline solution by using an atomizer array, wherein the aluminum salt solution is an aluminum sulfate solution, the concentration of the aluminum nitrate solution is 0.8 mol / L, the alkaline solution is an ammonium bicarbonate solution, and the frequency of the atomizer array is 10 MHz, to form aluminum salt droplets and alkaline droplets;

[0084] Aluminum salt droplets and alkaline droplets are introduced into a reaction kettle, and the aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring, wherein the aerosol stirring rate is 1000r / min, the pulsating pressurization frequency is 60Hz, and the pulsating pressurization pressure amplitude is 0.8MPa, so that the aluminum salt droplets and the alkaline droplets undergo a chemical reaction; a mixed solution of water and polyethylene glycol is placed at the bottom of the reaction kettle; the mixed solution is stirred; wherein the stirring rate of the mixed solution is 800r / min; after the reaction is completed, an aluminum hydroxide precursor is obtained;

[0085] The aluminum hydroxide precursor is subjected to microwave heating at a temperature of 1000° C. for 20 minutes to obtain ultrafine aluminum oxide powder.

[0086] Figure 2 The transmission electron microscope image of the ultrafine alumina powder prepared in Example 1 is shown in FIG. Figure 2 It can be seen that the ultrafine alumina powder obtained in Example 1 did not form large agglomerates, had a good dispersion effect, had small and uniform powder particle size, and had an average particle size of 30 to 50 nm.

[0087] Figure 3 : This is the XRD spectrum of the ultrafine alumina powder prepared in Example 1. The characteristic peak of α-Al2O3 appears in the XRD spectrum of the ultrafine alumina powder prepared in Example 1, indicating that the ultrafine alumina powder prepared in Example 1 is α-Al2O3.

[0088] Example 2

[0089] Embodiment 2 provides a method for preparing ultrafine alumina powder, comprising the following steps:

[0090] Atomizing an aluminum salt solution and an alkaline solution by using an atomizer array, wherein the aluminum salt solution is an aluminum nitrate solution, the concentration of the aluminum nitrate solution is 0.8 mol / L, the alkaline solution is ammonia water, and the frequency of the atomizer array is 5 MHz, to form aluminum salt droplets and alkaline droplets;

[0091] Aluminum salt droplets and alkaline droplets are introduced into a reaction kettle, and the aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring, wherein the aerosol stirring rate is 500r / min, the pulsating pressurization frequency is 30Hz, and the pulsating pressurization pressure amplitude is 0.3MPa, so that the aluminum salt droplets and the alkaline droplets undergo a chemical reaction; a mixed solution of water and polyethylene glycol is placed at the bottom of the reaction kettle; the mixed solution is stirred; wherein the stirring rate of the mixed solution is 200r / min; after the reaction is completed, an aluminum hydroxide precursor is obtained;

[0092] The aluminum hydroxide precursor is subjected to microwave heating at a temperature of 1000° C. for 30 minutes to obtain ultrafine aluminum oxide powder.

[0093] The ultrafine alumina powder obtained in Example 2 did not form large agglomerates, had a good dispersion effect, had fine and uniform powder particle size, and had an average particle size of 20 to 40 nm;

[0094] The ultrafine alumina powder obtained in Example 2 is α-Al2O3.

[0095] Example 3

[0096] Embodiment 3 provides a method for preparing ultrafine alumina powder, comprising the following steps:

[0097] Atomizing an aluminum salt solution and an alkaline solution using an atomizer array, wherein the aluminum salt solution is an aluminum chloride solution, the concentration of the aluminum chloride solution is 0.8 mol / L, the alkaline solution is an ammonium bicarbonate solution, and the frequency of the atomizer array is 7 MHz, to form aluminum salt droplets and alkaline droplets;

[0098] Aluminum salt droplets and alkaline droplets are introduced into a reactor, and the aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring, wherein the aerosol stirring rate is 750r / min, the pulsating pressurization frequency is 45Hz, and the pulsating pressurization pressure amplitude is 0.5MPa, so that the aluminum salt droplets and the alkaline droplets undergo a chemical reaction; a mixed solution of water and polyethylene glycol is placed at the bottom of the reactor; the mixed solution is stirred; wherein the stirring rate of the mixed solution is 500r / min; after the reaction is completed, an aluminum hydroxide precursor is obtained;

[0099] The aluminum hydroxide precursor is subjected to microwave heating at a temperature of 950° C. for a time of 25 min to obtain ultrafine aluminum oxide powder.

[0100] The ultrafine alumina powder obtained in Example 3 did not form large agglomerates, had a good dispersion effect, had fine and uniform powder particle size, and had an average particle size of 30 to 50 nm;

[0101] The ultrafine alumina powder obtained in Example 3 is α-Al2O3.

[0102] Comparative Example 1

[0103] Ultrafine alumina powder was prepared by referring to the method of Example 1. Other parameters were the same as those of Example 1, except that in Comparative Example 1, the rate of aerosol stirring was 450 r / min.

[0104] The average particle size of the ultrafine alumina powder obtained in Comparative Example 1 is 50 to 70 nm.

[0105] Comparative Example 2

[0106] Ultrafine alumina powder was prepared by referring to the method of Example 1. Other parameters were the same as those of Example 1, except that in Comparative Example 2, the frequency of pulsating pressurization was 65 Hz.

[0107] The average particle size of the ultrafine alumina powder obtained in Comparative Example 2 is 60 to 80 nm.

[0108] Comparative Example 3

[0109] Ultrafine alumina powder was prepared by referring to the method of Example 1, and other parameters were the same as those of Example 1, except that in Comparative Example 3, the pressure amplitude of the pulsating pressurization was 0.9 MPa.

[0110] The average particle size of the ultrafine alumina powder obtained in Comparative Example 3 is 70 to 90 nm.

[0111] Comparative Example 4

[0112] Ultrafine alumina powder was prepared by referring to the method of Example 1, and other parameters were the same as those of Example 1, except that in Comparative Example 4, the aluminum salt droplets and the alkaline droplets were not aerosol stirred.

[0113] The ultrafine alumina powder obtained in Comparative Example 4 formed relatively large agglomerates, the agglomeration phenomenon was relatively serious, and the average particle size of the powder was 100-120 nm.

[0114] Comparative Example 5

[0115] Ultrafine alumina powder was prepared by referring to the method of Example 1, and other parameters were the same as those of Example 1, except that: in Comparative Example 5, the aluminum salt droplets and the alkaline droplets were not subjected to pulsating pressurization.

[0116] The ultrafine alumina powder obtained in Comparative Example 5 formed larger agglomerates, and the agglomeration phenomenon was more serious. The average particle size of the powder was 90 to 110 nm.

[0117] Comparative Example 6

[0118] Ultrafine alumina powder was prepared by referring to the method of Example 1, and other parameters were the same as those of Example 1, except that in Comparative Example 6, the aluminum salt droplets and the alkaline droplets were not subjected to pulsating pressurization and aerosol stirring.

[0119] The ultrafine alumina powder obtained in Comparative Example 6 formed relatively large agglomerates, the agglomeration phenomenon was quite serious, and the average particle size of the powder was 110-130 nm.

[0120] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0121] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present application and form different embodiments. For example, in the above claims, any one of the claimed embodiments may be used in any combination. The information disclosed in this background technology section is intended only to deepen the understanding of the overall background technology of the present application and should not be regarded as an admission or in any form of implication that the information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing ultrafine alumina powder, characterized in that: include: Atomizing the aluminum salt solution and the alkaline solution to form aluminum salt droplets and alkaline droplets; The aluminum salt droplets and the alkaline droplets are subjected to pulsating pressurization and aerosol stirring to allow the aluminum salt droplets and the alkaline droplets to undergo a chemical reaction to obtain an aluminum hydroxide precursor; The aluminum hydroxide precursor is subjected to microwave heating to obtain ultrafine aluminum oxide powder, wherein the ultrafine aluminum oxide powder is α-Al2O3; The aerosol stirring rate is 500-1000 r / min; The frequency of the pulsating pressurization is 30-60 Hz, and the pressure amplitude of the pulsating pressurization is 0.3-0.8 MPa.

2. The method for preparing ultrafine alumina powder according to claim 1, characterized in that: The aluminum salt solution includes at least one of aluminum nitrate solution, aluminum sulfate solution, and aluminum chloride solution; The alkaline solution includes at least one of aqueous ammonia and ammonium bicarbonate solution; And / or, atomizing the aluminum salt solution and the alkaline solution includes: atomizing the aluminum salt solution and the alkaline solution using an atomizer array, wherein the frequency of the atomizer array is 5 to 10 MHz.

3. The method for preparing ultrafine alumina powder according to claim 1, characterized in that: The chemical reaction is carried out in a reactor, the bottom of which is filled with a mixed solution of water and polyethylene glycol; The preparation method further comprises: stirring the mixed solution; wherein the stirring rate of the mixed solution is 200 to 800 r / min; And / or, the preparation method further comprises: subjecting the mixed solution to ultrasonic treatment.

4. The method for preparing ultrafine alumina powder according to any one of claims 1 to 3, characterized in that: The temperature of the microwave heating is 900-1100°C; And / or, the microwave heating time is 20 to 60 minutes; And / or, the average particle size of the ultrafine alumina powder is 20 to 50 nm.

5. An ultrafine alumina powder, characterized in that: The ultrafine alumina powder is prepared by the method for preparing the ultrafine alumina powder according to any one of claims 1 to 4.

6. A device for preparing ultrafine alumina powder, characterized in that: The device for preparing ultrafine alumina powder is used to perform the method for preparing ultrafine alumina powder according to any one of claims 1 to 4, and the device for preparing ultrafine alumina powder comprises: A reactor, wherein the reactor is used to chemically react aluminum salt droplets and alkaline droplets to obtain an aluminum hydroxide precursor; an atomizer array is installed on the reactor, and the atomizer array is used to atomize the aluminum salt solution and the alkaline solution into aluminum salt droplets and alkaline droplets; the reactor comprises a tank body and a pressure regulating component, the pressure regulating component is connected to the tank body, and the pressure regulating component is used to pulsate pressurize the reactor; a gas phase agitator is installed in the tank body, and the gas phase agitator is used to perform aerosol stirring on the aluminum salt droplets and the alkaline droplets; A microwave reactor is used to perform microwave heating on the aluminum hydroxide precursor to obtain ultrafine aluminum oxide powder.

7. The device for preparing ultrafine alumina powder according to claim 6, characterized in that: The pressure regulating component comprises a piston; the reaction kettle comprises an extrusion section and a mixing section; the piston is located in the extrusion section, and the gas phase agitator and the atomizer array are located in the mixing section.

8. The device for preparing ultrafine alumina powder according to claim 6 or 7, characterized in that: A liquid phase agitator is provided at the bottom of the tank body, and the liquid phase agitator is used to stir the mixed solution; And / or, an ultrasonic generator is also installed on the tank body, and the ultrasonic generator is used to perform ultrasonic treatment on the mixed solution.

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