Preparation method of nano aluminum oxide composite abrasive particles

Abstract

The invention discloses a preparation method of nanometer aluminum oxide composite abrasive particles, and relates to the technical field of grinding machining.The preparation method comprises the following steps that S1, AlCl3 crystals are dissolved in an ethanol water solution, and an AlCl3 solution is prepared; s2, NaAlO2 and water are mixed according to the volume ratio of 1: 0.6, and a NaAlO2 solution is prepared; s3, adding the NaAlO2 solution mixed in the step S2 into the AlCl3 solution mixed in the step S1; s4, polyether modified polydimethylsiloxane is added into the solution obtained in the step S3; s5, stirring the solution obtained in the step S4; s6, the emulsion obtained through the reaction is centrifuged, washed and dried, and the nanometer aluminum oxide composite abrasive particles are obtained.The electrostatic adsorption principle is utilized, the nanometer aluminum oxide is coated with polyether modified polydimethylsiloxane, the nanometer aluminum oxide does not make direct contact with polydimethylsilicone oil, agglomeration of the nanometer abrasive particles in the synthesis and grinding process is avoided, and the nanometer aluminum oxide composite abrasive particles are obtained. And the method has important application value in the fields of ultra-precision grinding and polishing.

Description

Technical Field

[0001] The present invention relates to the technical field of grinding processing, and more specifically, to a preparation method of nano-aluminum oxide composite abrasive grains. Background Art

[0002] Ultra-precision grinding and polishing processes are the main means for surface processing to obtain high-quality surface finish and ultra-small surface roughness Ra, even Ra < 1nm. With the continuous introduction of new applications of ITO, higher requirements for surface roughness have been put forward in the fields of optoelectronics, etc. Traditional chemical mechanical polishing (CMP) or ultra-fine grinding cannot meet the requirements of nano-scale surface roughness. Therefore, a new type of ultra-precision grinding and polishing technology capable of achieving atomic or molecular level removal has emerged.

[0003] Among the many studied hot nano-materials, nano-Al2O3 has the advantages of small particle size, large specific surface area, high hardness, etc., and is an ideal material for ultra-precision grinding and polishing materials. It has excellent mechanical properties and chemical stability. Al2O3 has a variety of crystal structures, such as α, β, γ, and δ, among which α-Al2O3 has a face-centered cubic structure and can exist in various crystal structure forms. When the diameter of the grains in the α-Al2O3 crystal is less than 100nm, it has an extremely high specific surface area, mechanical strength, and large surface adsorption force, and has a strong hydrophobic effect. These unique properties are different from other crystal forms of Al2O3 and are widely used in processes such as optical polishing and surface polishing and grinding.

[0004] In terms of precision machining, nano-ceria (CeO2) has a relatively high specific surface area, and it can form a strong chemical bond with the material surface to improve the surface quality of the processing. CeO2 particles are extremely easy to agglomerate during the ultra-high-speed ball milling process, resulting in an increase in surface defects and it is difficult to obtain a high-quality polished surface. During the polishing process, the particles are extremely easy to agglomerate. By nano-Al2O3 and CeO2 nano-composite, the disadvantages of single nano-particles can be overcome, the covering effect on defects can be realized, and the surface finish and ultra-low surface roughness of the polished surface can be ensured.

[0005] However, there is currently no report on the preparation method of nano-aluminum oxide composite abrasive grains. Currently, a method is adopted to prepare ultra-small γ-Al2O3 as the matrix, and then a layer of nano-CeO2 is coated on its surface as an oxide film to obtain a surface-treated ultra-small ball milling agent after modification. Since the nano-composite abrasive grains prepared by this method have a relatively large particle size and are not easy to disperse, they can only be used for precision polishing when used for polishing and cannot be used for ultra-precision polishing. In view of this, we propose a preparation method of nano-aluminum oxide composite abrasive grains. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a preparation method of nano-aluminum oxide composite abrasive grains, so as to overcome the problems of large particle size, easy agglomeration, and difficult dispersion of nano-abrasive grains in the prior art, achieve ultra-precision polishing, and obtain a high-quality polished surface.

[0007] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of nano-aluminum oxide composite abrasive grains, comprising the following steps:

[0008] S1: Dissolve AlCl3 crystals in an ethanol aqueous solution to obtain an AlCl3 solution;

[0009] S2: Mix NaAlO2 with water to obtain a NaAlO2 solution;

[0010] S3: Add the NaAlO2 solution mixed in step S2 to the AlCl3 solution mixed in step S1;

[0011] S4: Add polyether-modified polydimethylsiloxane to the solution obtained in step S3;

[0012] S5: Stir the solution obtained in S4;

[0013] S6: The emulsion obtained by the reaction is centrifuged, washed, and dried to obtain the nano-aluminum oxide composite abrasive grains.

[0014] Wherein, the volume ratio of ethanol to water in the ethanol aqueous solution is 5:1 - 20:1; the preferred volume ratio is 10:1 - 15:1, and the most preferred volume ratio is 10:1;

[0015] The mass ratio of the NaAlO2 solution to the AlCl3 solution is 1:8 - 10;

[0016] The rotation speed of the stirring is 150 - 1500 rpm, and the stirring time is 30 - 60 min;

[0017] The mass ratio of the polyether-modified polydimethylsiloxane to AlCl3 is 7:5 - 8;

[0018] The drying is vacuum drying at 70 - 80 °C.

[0019] Preferably, in S3: Obtain a solution containing a precursor of aluminum hydroxide that has completed the mixing reaction step of the AlCl3 solution and the NaAlO2 solution, heat this solution to 40 - 50 °C, and under the state of continuous stirring, slowly dropwise add a pre-activated amphiphilic polymer modifier solution at a speed of 1 - 2 mL per minute. The addition amount of the modifier is controlled according to the mass ratio to AlCl3 of 5:5 - 6; the dropping process lasts for 30 - 40 minutes. After the dropping is completed, continue to stir and react at a rotation speed of 150 - 250 rpm for 2 - 3 hours.

[0020] Preferably, in S6: for the emulsion obtained from the reaction, deionized water is added to the reaction solution, and the addition amount of deionized water is 10%-20% of the volume of the reaction solution. Then, ammonia water with a mass fraction of 5%-10% is added to adjust the pH value of the solution to 8-9 to promote the flocculation precipitation of the modified nano-aluminum oxide particles. The precipitation is collected by centrifugation, the rotation speed of the centrifuge is set at 4000-6000 rpm, and the centrifugation time is 10-15 minutes. After collecting the precipitation, it is first washed 3-4 times with deionized water, with each washing time being 5-10 minutes, then washed 2-3 times with absolute ethanol, with each washing time being 3-5 minutes. Finally, the washed precipitation is placed in a vacuum drying oven and dried for 6-8 hours in a vacuum environment at 50-60 °C, and the vacuum degree is maintained at 1-5 Pa to obtain the surface-modified nano-aluminum oxide composite abrasive grains.

[0021] Preferably, the polyether-modified polydimethylsiloxane can be polyether-modified polydimethylsiloxane or a mixture thereof, or a mixture of polyether-modified organosilane coupling agent and polydimethylsiloxane; the specific models of the polyether-modified polydimethylsiloxane are: Dow Corning Q-2105, Q-2203;

[0022] Preferably, in the preferred ethanol aqueous solution in step S1, the volume ratio of ethanol to water is 10:1; this ratio can make the mixed solution of ethanol and water have a suitable evaporation temperature, which is convenient for subsequent reactions;

[0023] Preferably, the metal chloride AlCl3 can be anhydrous AlCl3 or AlCl3·6H2O containing crystal water, and anhydrous AlCl3 is preferred; the concentration of the AlCl3 solution is 5-7.5 g / 100 mL, preferably 6-7 g / 100 mL, and most preferably 6.4 g / 100 mL. The concentration range is relatively large mainly because the nano-structure has multi-scale characteristics. When the particle size is less than 100 nanometers, the particle size decreases with the increase of the concentration. The smaller the particle size, the larger the surface energy, and the easier it is for nano-particles to aggregate; when the particle size is greater than 100 nanometers, the relationship between the particle size and the solution concentration is more complex, and the particle size decreases with the increase of the concentration.

[0024] Preferably, the sodium aluminate NaAlO2 can be anhydrous NaAlO2 or NaAlO2·9H2O containing crystal water; anhydrous NaAlO is preferred 2； The mass ratio of the NaAlO2 solution to the AlCl3 solution is 1:8-10; preferably, the mass ratio of NaAlO2 to AlCl3 is 1:8.5-9; more preferably, the mass ratio of NaAlO2 to AlCl3 is 1:8.8-9; preferably specifically: the mass ratio of NaAlO2 to AlCl3 is 1:8.8.

[0025] Preferably, the centrifugation time is 10 - 15 min, and the washing is carried out three times. The first time is with water, the second time is with ethanol, and the third time is with deionized water; the stirring time is 30 - 60 min, and a better operation is to stir for 30 - 40 min, and the best operation is to stir for 30 min.

[0026] Preferably, the pre-activated amphiphilic polymer modifier solution is an organic solvent prepared by dissolving an amphiphilic polymer modifier in a mixture of anhydrous toluene and anhydrous ethanol in a volume ratio of 3:1. Under stirring conditions, dibutyltin dilaurate accounting for 0.5% - 1% of the mass of the modifier is added as a catalyst, and the reaction is carried out at a temperature of 50 - 60 °C for 1 - 2 hours to partially hydrolyze and preliminarily condense the siloxane groups in the modifier to form an oligomer structure with higher reactivity.

[0027] Preferably, the hydrophilic polyether chain segment of the pre-activated amphiphilic polymer modifier solution interacts with water molecules in the solution through hydrogen bonds, and the reactive siloxane groups chemically react with the hydroxyl groups on the surface of the aluminum hydroxide precursor, and form Si - O - Al chemical bonds through a condensation reaction to graft the modifier onto the surface of nano-aluminum oxide.

[0028] Preparation principle:

[0029] (1) During the process of preparing nano-aluminum oxide particles, during the stirring process, the aluminum salt gradually reacts with the precipitant to generate nano-aluminum oxide. While the aluminum salt reacts with the precipitant, nano-aluminum oxide gradually generates whisker structures with each other, and at the same time, the generated aluminum oxide rapidly reacts with AlCl3 to generate a large number of positively charged ions.

[0030] (2) Polyether-modified polydimethylsiloxane is hydrophilic. In its molecule, the structural unit of siloxane is connected by hydrogen bonds, and the hydroxyl group is connected to water molecules. At the same time, in an aqueous solution, there are a large number of dissociable positive charges on the silicon atoms in the molecule of polyether-modified polydimethylsiloxane. When polyether-modified polydimethylsiloxane is added to the solution, due to the change in the number of charges in the electrolyte solution, an electric field is formed between the aluminum oxide particles, electrostatically attracting the polyether-modified polydimethylsiloxane molecules to form a network structure crosslinked by nano-aluminum oxide particles and polyether-modified polydimethylsiloxane.

[0031] (3) Under the action of electrostatic force, the polyether-modified polydimethylsiloxane molecules adsorb to the formed aluminum oxide network structure. With the further flocculation of the polyether-modified polydimethylsiloxane molecules, the degree of coating of the polyether-modified polydimethylsiloxane molecules on alumina gradually increases, and under the action of hydrogen bonds, the nano-polyether-modified polydimethylsiloxane molecules stably exist on the surface of nano-aluminum oxide particles to form a stable nano-aluminum oxide particle structure.

[0032] (4) During the centrifugation process, since the centrifugal force of the centrifuge is greater than the hydrogen bond, the aluminum oxide is separated from the polyether-modified polydimethylsiloxane molecules. At the same time, due to the strong surface activity of the polyether-modified polydimethylsiloxane molecules, hydrogen bonds are formed with water molecules. During the centrifugation process, the polyether-modified polydimethylsiloxane molecules are separated from the nano-aluminum oxide particles and form an emulsion.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] The present invention utilizes the principle of electrostatic adsorption to coat nano-aluminum oxide with polyether-modified polydimethylsiloxane. The nano-aluminum oxide and polydimethylsilicone oil do not come into direct contact, avoiding the agglomeration of nano-abrasives during the synthesis and grinding process. The nano-aluminum oxide composite abrasives prepared by the present invention have good dispersibility, small particle size, uniform particle size distribution, and adjustable particle size. The maximum particle size can reach 8 microns. During grinding, whiskers can rub against each other, enabling the good realization of the nano-effect and having good comprehensive mechanical and chemical properties. Characteristics such as non-toxic, odorless, non-flammable, non-explosive, non-dusting, non-caking, acid and alkali resistant, and antioxidant also make it have important application value in the fields of ultra-precision grinding and polishing; enhancing dispersion stability: the hydrophilic polyether chain segments of the modifier form a hydration layer in the aqueous solution, effectively preventing the agglomeration between nano-aluminum oxide particles, enabling them to maintain a uniformly dispersed state for a long time in application systems such as polishing fluids, and improving the use efficiency and stability of the abrasives.

[0035] Improving wear resistance: The organosilicon chain segments grafted on the surface of nano-aluminum oxide form a tough protective film, enhancing the hardness and wear resistance of the abrasive surface. During actual applications such as polishing, it can effectively resist mechanical wear, extend the service life of the abrasives, reduce the wear rate of the abrasives, and thus improve the processing efficiency and product quality.

[0036] Improving interfacial compatibility: The special structure of the amphiphilic polymer modifier enables the nano-aluminum oxide composite abrasives to have better interfacial compatibility with different matrix materials. When compounding with matrixes such as polymers, the organosilicon chain segments of the modifier can undergo physical or chemical interactions with the matrix, enhancing the bonding force between the abrasives and the matrix and improving the overall performance of the composite material. Specific embodiments

[0037] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Apparently, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without any creative effort belong to the scope of protection of the present invention. For those not specified with specific technologies or conditions in the embodiments, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0038] For the test materials, reagents, etc. used in the following embodiments, unless otherwise specified, they can all be obtained from commercial channels.

[0039] For those not specified with specific technologies or conditions in the embodiments, they can all be carried out according to the technologies or conditions described in the literature in this field or according to the product specifications.

[0040] Example 1: Dissolve 40 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio of 1:0.1), and then quickly add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio of 1:0.5) to this mixed solution and stir rapidly (stirring speed is 300 rpm, stirring time is 10 min); after the stirring of this solution is completed, add 1 g of polyether polyether modified polydimethylsiloxane to this solution and stir rapidly, with a stirring speed of 300 rpm and a stirring time of 5 min; centrifuge, wash and dry the above obtained emulsion to obtain nano-aluminum oxide composite abrasive grains. The prepared nano-abrasive grains are strip-shaped, with a particle size in the nanometer range, generally between 200 - 1000 nm, with uniform particle size and no agglomeration.

[0041] Through the SEM element distribution of the nano-aluminum oxide composite abrasive grains, the content of aluminum element and oxygen element is more than 98%. The main component of the prepared nano-aluminum oxide composite abrasive grains is aluminum oxide. The nano-aluminum oxide and polyether modified polydimethylsiloxane are tightly combined. The XRD crystal form analysis shows that the sample is α-Al2O3. The SEM detection shows that the surface of the aluminum oxide is coated with a thin and uniform layer of polydimethylsiloxane. Its particle size is 2 - 3 microns, which is about 20 times smaller than the uncoated aluminum oxide nanoparticles (agglomerated) of polydimethylsiloxane, and the distribution is uniform and controllable.

[0042] Example 2: Dissolve 40 g of AlCl3 crystals in 350 ml of an ethanol aqueous solution (volume ratio 1:0.4), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.6) to this solution and stir rapidly (stirring speed is 600 rpm, stirring time is 10 min); after the stirring of this solution is completed, add 1 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, the stirring speed is 600 rpm, and the stirring time is 3 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0043] Example 3: Dissolve 50 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:0.1), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.8) to this solution and stir rapidly (stirring speed is 150 rpm, stirring time is 30 min); after the stirring of this solution is completed, add 2 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, the stirring speed is 150 rpm, and the stirring time is 20 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0044] Example 4: Dissolve 25 g of AlCl3 crystals in 250 ml of an ethanol aqueous solution (volume ratio 1:0.1), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.5) to this solution and stir rapidly (stirring speed is 150 rpm, stirring time is 30 min); after the stirring of this solution is completed, add 1 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, the stirring speed is 150 rpm, and the stirring time is 20 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0045] Example 5: Dissolve 55 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:1), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.6) to this solution and stir rapidly (stirring speed is 150 rpm, stirring time is 30 min); after the stirring of this solution is completed, add 2 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, the stirring speed is 150 rpm, and the stirring time is 30 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0046] Example 6: Dissolve 40 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:0.05), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.1) to this solution and stir rapidly (stirring speed is 1000 rpm, stirring time is 25 min); after the stirring of this solution is completed, add 5 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, stirring speed is 1000 rpm, stirring time is 5 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0047] Example 7: Dissolve 40 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:0.05), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.5) to this solution and stir rapidly (stirring speed is 1500 rpm, stirring time is 25 min); after the stirring of this solution is completed, add 1 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, stirring speed is 1500 rpm, stirring time is 5 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0048] Example 8: Dissolve 40 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:0.05), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.2) to this solution and stir rapidly (stirring speed is 1200 rpm, stirring time is 25 min); after the stirring of this solution is completed, add 1 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, stirring speed is 1200 rpm, stirring time is 5 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0049] Example 9: Dissolve 40 g of AlCl3 crystals in 300 ml of an ethanol aqueous solution (volume ratio 1:0.05), then add an aqueous solution containing 25 g of NaAlO2 (aqueous solution with NaAlO2 as the solute, volume ratio 1:0.3) to this solution and stir rapidly (stirring speed is 1000 rpm, stirring time is 25 min); after the stirring of this solution is completed, add 1 g of polyether-polyether modified polydimethylsiloxane to this solution, stir rapidly, stirring speed is 120 rpm, stirring time is 8 min; centrifuge, wash, and dry the above-obtained emulsion to obtain nano-aluminum oxide composite abrasive grains.

[0050] Example 10: Surface modification of nano-aluminum oxide composite abrasives: Obtain a solution containing aluminum hydroxide precursor, heat it to 45 °C, and slowly drip the pre-activated amphiphilic polymer modifier solution at a rate of 1.5 mL per minute under continuous stirring. The mass ratio of the modifier to AlCl3 is 5:5.5. The pre-activation process is to dissolve the amphiphilic polymer modifier in a mixed solvent of anhydrous toluene and anhydrous ethanol (volume ratio 3:1), add dibutyltin dilaurate accounting for 0.8% of the mass of the modifier as a catalyst, and react at 55 °C for 1.5 hours. The dripping process lasts for 35 minutes. After the dripping is completed, continue to stir and react at a speed of 200 rpm for 2.5 hours. After the surface modification reaction is completed, add deionized water accounting for 15% of the volume of the reaction solution to the reaction solution, then add ammonia water with a mass fraction of 7% to adjust the pH value of the solution to 8.5, collect the precipitate by centrifugation at 5000 rpm for 12 minutes, wash it with deionized water 4 times, 8 minutes each time, then wash it with anhydrous ethanol 3 times, 4 minutes each time, and finally dry it in a vacuum drying oven at 55 °C and a vacuum degree of 3 Pa for 7 hours to obtain the surface-modified nano-aluminum oxide composite abrasives.

[0051] Perform hardness tests, acid resistance tests, antioxidant performance tests, and anti-wear performance tests on the composite abrasives of the above Examples 1-10:

[0052] Hardness test, the test method is as follows: The test uses a Vickers hardness tester, selects a diamond indenter, applies a load of 300 g, and indents the polytetrafluoroethylene (hardness 50 MPa) for 10 s to obtain its hardness.

[0053] Acid resistance test, the test method is as follows: Disperse the composite abrasives in a 5% mass fraction of dilute hydrochloric acid solution for 24 hours, then take them out, wash away the acid solution, dry them at 105 °C, take them out and weigh them, and calculate the percentage of mass loss;

[0054] Antioxidant performance test, the test method is as follows: Place the composite abrasives in the air, place them at 60 °C for 72 h, take them out and weigh them, and calculate the percentage of mass loss;

[0055] Anti-wear performance test, the test method is as follows: Mix 5 g of composite abrasives with 95 g of water evenly, add them to a 1000 mL high-speed blender, the rotation speed is 10000 rpm, and the stirring time is 30 min. Take the sample before stirring, filter it with a filter with a pore size of 10 nm, take the filtrate, and calculate the percentage of the mass fraction of the non-shed composite abrasives in the total composite abrasives.

[0056] The test results are shown in the following table:

[0057]

[0058] As can be seen from the above table, the nano-aluminum oxide composite abrasive grains prepared by the present invention are characterized by small particle size and uniform distribution. During the grinding process, their performance is superior to that of diamond abrasive grains, and the cost is much lower than that of diamond abrasive grains. It is an ideal grinding material for hard and brittle materials.

[0059] The embodiments disclosed in the present invention are preferred embodiments, but not limited thereto. Those of ordinary skill in the art can easily understand the spirit of the present invention based on the above embodiments and make different extensions and changes. However, as long as they do not depart from the spirit of the present invention, they are within the protection scope of the present invention.

Claims

1. A preparation method of nano-aluminum oxide composite abrasive grains, characterized in that, It includes the following steps: S1: Dissolve AlCl3 crystals in an ethanol aqueous solution to obtain an AlCl3 solution; S2: Mix NaAlO2 with water to obtain a NaAlO2 solution; S3: Add the NaAlO2 solution mixed in step S2 to the AlCl3 solution mixed in step S1; S4: Add polyether-modified polydimethylsiloxane to the solution obtained in step S3; S5: Stir the solution obtained in S4; S6: Centrifuge, wash, and dry the emulsion obtained from the reaction to obtain the nano-aluminum oxide composite abrasive grains. Among them, the volume ratio of ethanol to water in the ethanol aqueous solution is 5:1 - 20:1; The mass ratio of the NaAlO2 solution to the AlCl3 solution is 1:8 - 10; The rotation speed of the stirring is 150 - 1500 rpm, and the stirring time is 30 - 60 min; The mass ratio of the polyether-modified polydimethylsiloxane to AlCl3 is 7:5 - 8.

2. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, In S3: Obtain a solution containing a precursor of aluminum hydroxide that has completed the mixing reaction step of the AlCl3 solution and the NaAlO2 solution, heat this solution to 40 - 50 °C, and slowly drip the pre-activated amphiphilic polymer modifier solution at a speed of 1 - 2 mL per minute under continuous stirring. The addition amount of the modifier is controlled according to the mass ratio to AlCl3 of 5:5 - 6; The dripping process lasts for 30 - 40 minutes. After the dripping is completed, continue to stir and react at a rotation speed of 150 - 250 rpm for 2 - 3 hours.

3. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, In S6: For the emulsion obtained from the reaction, add deionized water to the solution obtained from the reaction. The addition amount of deionized water is 10% - 20% of the volume of the reaction solution. Then add ammonia water with a mass fraction of 5% - 10% to adjust the pH value of the solution to 8 - 9 to promote the flocculation precipitation of the modified nano-aluminum oxide particles; Use centrifugal separation to collect the precipitate. The rotation speed of the centrifuge is set to 4000 - 6000 rpm, and the centrifugation time is 10 - 15 minutes; After collecting the precipitate, first wash it with deionized water 3 - 4 times, with each washing time being 5 - 10 minutes, then wash it with anhydrous ethanol 2 - 3 times, with each washing time being 3 - 5 minutes. Finally, place the washed precipitate in a vacuum drying oven and dry it in a vacuum environment at 50 - 60 °C for 6 - 8 hours, with the vacuum degree maintained at 1 - 5 Pa to obtain the surface-modified nano-aluminum oxide composite abrasive grains.

4. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, The polyether-modified polydimethylsiloxane can be polyether-modified polydimethylsiloxane or its mixture, or a mixture of polyether-modified organosilane coupling agent and polydimethylsiloxane.

5. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, In step S1, the volume ratio of ethanol to water in the ethanol aqueous solution is 10:

1.

6. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, The AlCl3 is anhydrous AlCl3 or AlCl3·6H2O containing crystal water, and the concentration of the AlCl3 solution is 5 - 7.5 g / 100 mL.

7. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, wherein, The NaAlO2 is anhydrous NaAlO2 or NaAlO2·9H2O containing crystal water, and the mass ratio of the NaAlO2 solution to the AlCl3 solution is 1:8.

8.

8. The preparation method of a nano-aluminum oxide composite abrasive according to claim 1, characterized in that, The drying in step S6 is vacuum drying at 70 - 80°C, and the centrifugation time is 10 - 15 min; the washing is carried out three times. The first time is with water, the second time is with ethanol, and the third time is with deionized water.

9. The preparation method of a nano-alumina composite abrasive according to claim 2, characterized in that, The pre-activated amphiphilic polymer modifier solution is an organic solvent prepared by dissolving the amphiphilic polymer modifier in a mixture of anhydrous toluene and anhydrous ethanol with a volume ratio of 3:

1. Under stirring conditions, dibutyltin dilaurate accounting for 0.5% - 1% of the mass of the modifier is added as a catalyst, and the reaction is carried out at a temperature of 50 - 60°C for 1 - 2 hours to partially hydrolyze and preliminarily condense the siloxane groups in the modifier to form a low-polymer structure with higher reactivity.

10. The preparation method of a nano-aluminum oxide composite abrasive according to claim 9, characterized in that, The hydrophilic polyether segment of the pre-activated amphiphilic polymer modifier solution interacts with water molecules in the solution through hydrogen bonds, and the reactive siloxane groups chemically react with the hydroxyl groups on the surface of the aluminum hydroxide precursor to form Si-O-Al chemical bonds through a condensation reaction, grafting the modifier onto the surface of the nano-aluminum oxide.

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