Preparation method of double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive

Abstract

The invention discloses a method for preparing a double-layer core-shell structured PS / TiO2 / CeO2 nanocomposite abrasive, belonging to the technical field of nanocomposite materials. The composite abrasive prepared by the method comprises polystyrene microspheres as the inner core, which are double-coated with titanium oxide as the middle layer and cerium oxide as the outer layer. The composite abrasive combines the advantages of organic polymers and metal oxides, and during the polishing process, the synergistic effect of titanium oxide and cerium oxide can improve the material removal rate. In addition, the core-shell structure of the composite abrasive, which is soft inside and hard outside, can exert a special polishing effect. Specifically, during the polishing process, the soft polystyrene inner core can buffer the polishing pressure borne by the KDP crystal, reducing excessive mechanical damage to the polished surface caused by the coating layer, thereby achieving better surface quality of the polished surface.

Description

Technical Field

[0001] The invention belongs to the technical field of nano-composite materials, and in particular relates to a method for preparing a double-layer core-shell structured PS / TiO2 / CeO2 nano-composite abrasive. Background Art

[0002] Potassium dihydrogen phosphate (KDP) crystals, as excellent nonlinear optical crystals, are widely used in inertial confinement fusion devices, high-power laser weapons, tunable acousto-optic filters, electro-optic switches, and other fields. However, due to their soft and brittle properties, hygroscopicity, and anisotropy, they are prone to damage such as edge collapse and small waviness, making them one of the most difficult materials to process. Their surface quality significantly affects their optical properties, and polishing methods and abrasive types directly impact the polished surface quality.

[0003] Chemical mechanical polishing (CMP) technology is a polishing process that achieves a globally flat surface through the dual coupling effects of chemical corrosion and mechanical grinding by chemical reagents in the polishing liquid. It is currently a technology that is widely used in the field of ultra-precision machining.

[0004] Abrasives are a crucial component of polishing fluids. The abrasive's material, morphology, particle size, and particle size distribution are key factors in determining polishing effectiveness. Because KDP crystals demand high polishing quality, existing single abrasives are unable to meet these requirements. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive. The composite abrasive prepared by this method has a good polishing effect on KDP crystals.

[0006] In order to solve the above problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a method for preparing a double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive, comprising the following steps:

[0008] Step 1, preparing polystyrene (PS) microspheres: adding styrene and methacryloyloxyethyltrimethylammonium chloride to a polyvinylpyrrolidone aqueous solution, heating to boiling, and then adding 2,2-azobis(2-methylpropylimidazole) dihydrochloride to react to obtain a polystyrene emulsion, and drying and grinding the emulsion to obtain PS microspheres.

[0009] Step 2, preparing PS / TiO2 composite microspheres: dispersing the PS microspheres prepared in step 1 into anhydrous ethanol to prepare a PS ethanol solution, and ultrasonically dispersing it evenly; then adjusting the pH value of the mixed solution to 6-9 with ammonia water and heating it; then adding an ethanol solution of an organic titanate and stirring the reaction; after the reaction is completed, centrifuging the product and repeatedly washing it with deionized water and anhydrous ethanol; then drying and grinding it to obtain PS / TiO2 composite microspheres.

[0010] Step 3, preparing PS / TiO2 / CeO2 composite abrasive: disperse the PS / TiO2 composite microspheres prepared in step 2 into deionized water to prepare a PS / TiO2 aqueous solution, and ultrasonically disperse it evenly; then add soluble cerium salt and hexamethylenetetramine; stir the reaction under heating conditions; after the reaction is completed, centrifuge the final product and repeatedly wash it with deionized water and anhydrous ethanol; finally, dry and grind it to obtain the PS / TiO2 / CeO2 composite abrasive.

[0011] Furthermore, in step 1, the concentration of the polyvinyl pyrrolidone aqueous solution is 0.5 g / L to 6 g / L; the amount of styrene and the polyvinyl pyrrolidone aqueous solution is 45 g to 150 g: 1 L; the amount of methacryloyloxyethyltrimethylammonium chloride and the polyvinyl pyrrolidone aqueous solution is 0.5 g to 5.5 g: 1 L; the amount of 2,2-azobis(2-methylpropylimidamide) dihydrochloride and the polyvinyl pyrrolidone aqueous solution is 0.5 g to 2.5 g: 1 L; in step 1, a constant temperature oil bath is used for heating at a temperature of 100 to 110° C., and 2,2-azobis(2-methylpropylimidamide) dihydrochloride is added and the reaction is carried out for 5 to 8 hours.

[0012] Furthermore, in step 2, the organic titanate is any one of tetrabutyl titanate, isopropyl titanate, and titanium isopropoxide, or a combination thereof.

[0013] Furthermore, in step 2, the concentration of the PS ethanol solution is 5 g / L to 30 g / L, and the concentration of the organic titanate ethanol solution is 10 g / L to 100 g / L; in step 2, a constant temperature oil bath is used for heating at a temperature of 70 to 90° C., and the reaction time is 2 to 4 hours.

[0014] Furthermore, in step 3, the soluble cerium salt is any one of cerium nitrate, cerium sulfate, cerium chloride, or a combination thereof.

[0015] Furthermore, in step 3, the concentration of the PS / TiO2 aqueous solution is 2.5g / L~15g / L, the dosage relationship between the soluble cerium salt and the PS / TiO2 aqueous solution is 20g-100g:1L; the molar ratio of the soluble cerium salt to hexamethylenetetramine is 1:5; in step 3, a constant temperature oil bath is used for heating, the heating temperature is 60~85°C, and the reaction time is 2~4h.

[0016] The beneficial effects of the present invention are as follows: the present invention provides a method for preparing a double-layer core-shell structured PS / TiO2 / CeO2 nano-composite abrasive, wherein the core of the composite abrasive prepared by the method is a polystyrene microsphere, which is double-coated with titanium oxide as an intermediate layer and cerium oxide as an outer layer; the composite abrasive combines the advantages of organic polymers and metal oxides, and during the polishing process, the synergistic effect of titanium oxide and cerium oxide can improve the material removal rate; in addition, the core-shell structure of the composite abrasive, which is soft inside and hard outside, can exert a special polishing effect; specifically, during the polishing process, the soft polystyrene core can buffer the polishing pressure borne by the KDP crystal, reduce excessive mechanical damage to the polished surface caused by the coating layer, and thus enable the polished surface to obtain better surface quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 Shown is the SEM image of the PS microspheres prepared in Example 1 of the present invention.

[0018] Figure 2 Shown are FTIR images of PS microspheres, PS / TiO2 composite microspheres and PS / TiO2 / CeO2 composite abrasives prepared in Example 1 of the present invention.

[0019] Figure 3 Shown are the XRD patterns of the PS / TiO2 composite microspheres and PS / TiO2 / CeO2 composite abrasives prepared in Example 1 of the present invention.

[0020] Figure 4 Shown are SEM images of PS microspheres prepared with three different DMC dosages of the present invention.

[0021] Figure 5 Shown are TEM images of PS / TiO2 / CeO2 composite abrasives prepared at three different cerium nitrate dosages of the present invention.

[0022] Figure 6 Shown are AFM images of the PS / TiO2 / CeO2 composite abrasive, CeO2 and PS / CeO2 abrasives after polishing KDP crystals prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0023] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to specific embodiments. The following description is only used to illustrate the technical solutions of the present invention and is not intended to limit the present invention. The experimental methods used in the examples are conventional methods unless otherwise specified. The materials, reagents, etc. used are all commercially available unless otherwise specified.

[0024] Example 1

[0025] A method for preparing a double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive comprises the following steps:

[0026] Step 1: Preparation of polystyrene (PS) microspheres:

[0027] Prepare a polyvinylpyrrolidone (PVP) aqueous solution with a concentration of 1.25 g / L, stir evenly, pour it into a flask and place it in a constant temperature oil bath; add styrene and methacryloyloxyethyltrimethylammonium chloride (DMC); the dosage relationship of styrene to PVP aqueous solution is 90 g:1 L; the dosage relationship of DMC to PVP aqueous solution is 1.4 g:1 L; then start stirring and heat to 105°C; keep warm at 105°C for 5 minutes, then add 2,2-azobis(2-methylpropylimidazole) dihydrochloride (AIBA) and stir to react for 6 hours; the dosage relationship of AIBA to PVP aqueous solution is 1 g:1 L; the emulsion obtained by the reaction is placed in a drying oven at 60-90°C for drying, and after drying, it is ground to obtain PS microspheres.

[0028] like Figure 1 Shown is the SEM image of PS microspheres prepared in Example 1 of the present invention. Figure 1 It can be seen from the figure that the PS microspheres prepared in this example are spherical, without adhesion, agglomeration, or rupture, and have uniform particle size and good monodispersity. The average particle size of the PS microspheres was found to be 131 nm.

[0029] Step 2: Preparation of PS / TiO2 composite microspheres:

[0030] The PS microspheres prepared in step 1 were dispersed in anhydrous ethanol to a concentration of 16 g / L PS ethanol solution, and ultrasonically dispersed uniformly. The pH of the mixed solution was then adjusted to 7 with aqueous ammonia and poured into a flask. The flask was placed in an oil bath, stirred, and heated to 80°C. A 30 g / L tetrabutyl titanate ethanol solution was then added dropwise to the flask, and the mixture was stirred for 3 hours. After the reaction, the mixture was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. The mixture was then dried in a drying oven at 60-90°C and ground to obtain PS / TiO2 composite microspheres.

[0031] Step 3: Preparation of PS / TiO2 / CeO2 composite abrasive:

[0032] The PS / TiO2 composite microspheres prepared in step 2 were dispersed into a 5g / L PS / TiO2 aqueous solution in deionized water and uniformly dispersed by ultrasonication. Cerium nitrate and hexamethylenetetramine were then added. The amount of cerium nitrate to the PS / TiO2 aqueous solution was 50g:1L, and the molar ratio of cerium nitrate to hexamethylenetetramine was 1:5. After complete dissolution, the microspheres were poured into a flask, which was then placed in an oil bath. The reactants in the flask were stirred evenly and heated to 75°C for 3 hours. After the reaction was completed, the final product was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. Finally, the product was dried in a drying oven at 60-90°C and ground to obtain a PS / TiO2 / CeO2 composite abrasive.

[0033] like Figure 2 Shown are FTIR images of PS microspheres, PS / TiO2 composite microspheres and PS / TiO2 / CeO2 composite abrasives prepared in Example 1 of the present invention. Figure 3 Shown are the XRD patterns of the PS / TiO2 composite microspheres and PS / TiO2 / CeO2 composite abrasives prepared in Example 1 of the present invention.

[0034] from Figure 2 It can be seen from the FTIR curve of PS microspheres that at 1603.2 cm -1 、1494.6cm -1 and 1450cm -1 The characteristic peak at 1070.9cm is the stretching vibration peak of C=C on the benzene ring; -1 and 1026.4cm -1 The characteristic peak at 755.4cm is the in-plane bending vibration peak of the monosubstituted benzene ring CH; -1 and 697.9cm -1 The characteristic peak at 3387cm is the out-of-plane bending vibration peak of the monosubstituted benzene ring CH. These characteristic peaks indicate that styrene undergoes polymerization to form polystyrene. For PS / TiO2 composite microspheres, the peak at 3387cm -1 The broad characteristic peak near the microsphere is the stretching vibration band of hydroxyl-OH formed by water on the surface of the microsphere; the infrared absorption peak of amorphous TiO2 is between 400 and 800 cm -1 From the figure, it can be clearly seen that at 540cm -1 There is an obvious characteristic peak at 1026.4cm, which is the characteristic peak of Ti-O-Ti, indicating that TiO2 exists on the surface of PS microspheres. -1 The characteristic peak at 699.3 cm is the characteristic peak of Ce-O. -1 The characteristic peak at is the asymmetric stretching vibration peak of Ce-O-Ce metal oxide in the lattice, indicating the presence of CeO2 in the sample.

[0035] from Figure 3 It can be seen that the PS / TiO2 composite microspheres prepared in Example 1 of the present invention have only one obvious amorphous diffraction peak near 2θ=21°. Combined with the TEM image of the PS / TiO2 composite microspheres, it is shown that TiO2 exists in the composite microspheres in an amorphous structure. The PS / TiO2 / CeO2 composite abrasive exhibits characteristic diffraction peaks of CeO2 with a cubic fluorite structure at 2θ=28.7°, 33.2°, 47.5°, 56.4°, 59°, 69.5°, 76.6° and 78.8°, and a weak TiO2 amorphous diffraction peak appears near 2θ=21°, which indicates that the cerium oxide grain layer has completely coated the titanium oxide layer, and the PS / TiO2 / CeO2 composite abrasive forms a double-layer core-shell structure.

[0036] Example 2

[0037] A method for preparing a double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive comprises the following steps:

[0038] Step 1: Preparation of polystyrene (PS) microspheres:

[0039] Prepare a polyvinylpyrrolidone (PVP) aqueous solution with a concentration of 0.5 g / L, stir evenly, pour it into a flask and place it in a constant temperature oil bath; add styrene and methacryloyloxyethyltrimethylammonium chloride (DMC); the dosage relationship of styrene to PVP aqueous solution is 45 g:1 L; the dosage relationship of DMC to PVP aqueous solution is 0.5 g:1 L; then start stirring and heat to 100°C; keep warm at 100°C for 5 minutes, then add 2,2-azobis(2-methylpropylimidazole) dihydrochloride (AIBA) and stir to react for 5 hours; the dosage relationship of AIBA to PVP aqueous solution is 0.5 g:1 L; the emulsion obtained by the reaction is placed in a drying oven at 60-90°C for drying, and after drying, it is ground to obtain PS microspheres.

[0040] Step 2: Preparation of PS / TiO2 composite microspheres:

[0041] The PS microspheres prepared in step 1 were dispersed in anhydrous ethanol to a concentration of 5g / L PS ethanol solution, and ultrasonically dispersed uniformly. The pH of the mixed solution was then adjusted to 6 with aqueous ammonia and poured into a flask. The flask was placed in an oil bath, stirred, and heated to 70°C. A 10g / L tetrabutyl titanate ethanol solution was then added dropwise to the flask, and the mixture was stirred for 2 hours. After the reaction, the mixture was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. The mixture was then dried in a drying oven at 60-90°C and ground to obtain PS / TiO2 composite microspheres.

[0042] Step 3: Preparation of PS / TiO2 / CeO2 composite abrasive:

[0043] The PS / TiO2 composite microspheres prepared in step 2 were dispersed into a 2.5g / L PS / TiO2 aqueous solution in deionized water and uniformly dispersed by ultrasonication. Cerium nitrate and hexamethylenetetramine were then added. The amount of cerium nitrate to the PS / TiO2 aqueous solution was 20g:1L, and the molar ratio of cerium nitrate to hexamethylenetetramine was 1:5. After complete dissolution, the microspheres were poured into a flask, which was then placed in an oil bath. The reactants in the flask were stirred evenly and heated to 60°C for 2 hours. After the reaction, the final product was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. Finally, the product was dried in a drying oven at 60-90°C and ground to obtain a PS / TiO2 / CeO2 composite abrasive.

[0044] Example 3

[0045] A method for preparing a double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive comprises the following steps:

[0046] Step 1: Preparation of polystyrene (PS) microspheres:

[0047] Prepare a polyvinylpyrrolidone (PVP) aqueous solution with a concentration of 6 g / L, stir evenly, pour it into a flask and place it in a constant temperature oil bath; add styrene and methacryloyloxyethyltrimethylammonium chloride (DMC); the dosage relationship of styrene to PVP aqueous solution is 150 g:1 L; the dosage relationship of DMC to PVP aqueous solution is 5.5 g:1 L; then start stirring and heat to 110°C; keep warm at 110°C for 5 minutes, then add 2,2-azobis(2-methylpropylimidazole) dihydrochloride (AIBA) and stir to react for 8 hours; the dosage relationship of AIBA to PVP aqueous solution is 2.5 g:1 L; the emulsion obtained by the reaction is placed in a drying oven at 60-90°C for drying, and after drying, it is ground to obtain PS microspheres.

[0048] Step 2: Preparation of PS / TiO2 composite microspheres:

[0049] The PS microspheres prepared in step 1 were dispersed in anhydrous ethanol to a concentration of 30 g / L PS ethanol solution, and ultrasonically dispersed uniformly. The pH of the mixed solution was then adjusted to 9 with aqueous ammonia and poured into a flask. The flask was placed in an oil bath, stirred, and heated to 90°C. A 100 g / L tetrabutyl titanate ethanol solution was then added dropwise to the flask, and the mixture was stirred and reacted for 4 hours. After the reaction, the mixture was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. The mixture was then dried in a drying oven at 60-90°C and ground to obtain PS / TiO2 composite microspheres.

[0050] Step 3: Preparation of PS / TiO2 / CeO2 composite abrasive:

[0051] The PS / TiO2 composite microspheres prepared in step 2 were dispersed into a 15g / L PS / TiO2 aqueous solution in deionized water and uniformly dispersed by ultrasonication. Cerium nitrate and hexamethylenetetramine were then added. The amount of cerium nitrate to the PS / TiO2 aqueous solution was 100g:1L, and the molar ratio of cerium nitrate to hexamethylenetetramine was 1:5. After complete dissolution, the mixture was poured into a flask, which was then placed in an oil bath. The reactants in the flask were stirred evenly and heated to 85°C for 4 hours. After the reaction was completed, the final product was centrifuged and repeatedly washed with deionized water and anhydrous ethanol. Finally, the product was dried in a drying oven at 60-90°C and ground to obtain a PS / TiO2 / CeO2 composite abrasive.

[0052] According to tests, the particle size of the polystyrene microspheres prepared by the method of the present invention is 100-200 nm; the thickness of the titanium oxide layer is 10-30 nm; and the thickness of the cerium oxide layer is 5-30 nm.

[0053] Comparative Experiment 1

[0054] Based on Example 1, only the amount of DMC in step 1 was changed to study its effect on the material of the present invention. Specifically, DMC was not added in one of the preparation methods, and the amount ratio of DMC to PVP aqueous solution was 4.2 g:1 L.

[0055] like Figure 4 Shown are SEM images of PS microspheres prepared with three different DMC dosages. From left to right, the DMC dosages are: no DMC, a DMC:PVP aqueous solution dosage ratio of 1.4 g:1 L, and a DMC:PVP aqueous solution dosage ratio of 4.2 g:1 L.

[0056] from Figure 4 As can be seen in (a), when DMC is not added, the particle size of the prepared PS microspheres is very uneven and the surface morphology is rough. After adding DMC, the particle size of the PS microspheres is significantly reduced, and the particle size distribution becomes uniform (e.g. Figure 4 (b)). When the amount of DMC increases to a certain value, the particle size of PS microspheres will decrease (as shown in Figure 4 (c)). This is because the addition of DMC accelerates the nucleation rate of PS and increases the number of nuclei, which leads to a decrease in the average particle size.

[0057] Comparative Experiment 2

[0058] Based on Example 1, only the concentration of the tetrabutyl titanate ethanol solution in Step 2 was varied to investigate its effect on the material of the present invention. Specifically, the tetrabutyl titanate ethanol solution concentrations were 15, 20, 25, 30, 35, and 40 g / L. This experiment yielded a series of PS / TiO2 composite microspheres with varying TiO2 layer thicknesses, as shown in Table 1 below.

[0059] Table 1. Statistical table of the effects of different concentrations of tetrabutyl titanate ethanol (TBOT) solution on the thickness of the TiO2 layer in PS / TiO2 composite microspheres.

[0060]

[0061] The data in Table 1 show that the thickness of the TiO2 layer in the PS / TiO2 composite microspheres increases with increasing TBOT concentration. This is because the concentration of TiO2 particles produced by hydrolysis of TBOT increases. Under the action of electrostatic force, more TiO2 particles are coated on the surface of the PS microspheres, thereby increasing the thickness of the TiO2 layer.

[0062] Comparative Experiment 3

[0063] Based on Example 1, only the amount of cerium nitrate in Step 3 was varied to investigate its effect on the material of the present invention. Specifically, the ratios of cerium nitrate to PS / TiO₂ aqueous solution were 10 g:1 L and 25 g:40 L, respectively. This experiment yielded a series of PS / TiO₂ / CeO₂ composite abrasives with varying CeO₂ layer thicknesses.

[0064] like Figure 5 The following are TEM images of PS / TiO2 / CeO2 composite abrasives prepared at three different cerium nitrate dosages. As can be seen from the figure, when the cerium nitrate dosage is 10g:1L, the number of CeO2 particles generated is very small, and ultimately only discretely distributed on the surface of the PS microspheres ( Figure 5 (a)). When the amount of cerium nitrate was 25g:1L, the number of CeO2 particles generated increased significantly, and a CeO2 layer was formed on the surface of the PS microspheres, but a complete coating layer was not formed ( Figure 5 (b)). When the amount of cerium nitrate was increased to 40 g / L, a complete CeO2 layer was formed ( Figure 5 As shown in (c), when the amount of cerium nitrate continued to increase, the CeO2 shell became thicker.

[0065] Comparative Experiment 4

[0066] The PS / TiO2 / CeO2 composite abrasive was prepared using Example 1 and polished in comparison with CeO2 abrasive and PS / CeO2 composite abrasive. The specific method is as follows:

[0067] CeO2 abrasive, PS / CeO2 and PS / TiO2 / CeO2 composite abrasive were made into polishing liquids with the same concentration and used to polish KDP crystals.

[0068] Polishing conditions are as follows:

[0069] The polishing machine is a UNIPOL-1502 precision grinding and polishing machine, and the polishing pad is a polyurethane polishing pad.

[0070] The polishing pressure is 13.1 kPa, the polishing disc speed is 90 r / min, the polishing liquid flow rate is 0.1 L / min, and the polishing time is 10 min.

[0071] The microstructure of the polished KDP crystal surface was observed using a Dimension Edge atomic force microscope (AFM) from Bruker, Germany. Figure 6 Shown are AFM images of the PS / TiO2 / CeO2 composite abrasive, CeO2 and PS / CeO2 abrasives after polishing KDP crystals prepared in Example 1 of the present invention.

[0072] After testing and analysis, the crystal surface roughness R a 1.12nm( Figure 6 (a)), the material removal rate is 185nm / min; after polishing with PS / CeO2 composite abrasive, the crystal surface roughness R a 0.39nm( Figure 6 (b)), the material removal rate is 137nm / min; after polishing with PS / TiO2 / CeO2 composite abrasive, the crystal surface roughness R a 0.34nm( Figure 6 (c)), MRR is 176nm / min. Compared with CeO2 abrasive, PS / CeO2 composite abrasive significantly improves the surface finish of the crystal, but the material removal rate is reduced. The PS / TiO2 / CeO2 composite abrasive prepared by the present invention can not only reduce the surface roughness of the crystal, but also obtain a high material removal rate, thereby improving the polishing effect. This is because the elastic modulus of the PS microsphere core is about 3GPa, which is much lower than the elastic modulus of the CeO2 grain (200GPa). The compression elastic modulus of the PS / TiO2 / CeO2 composite abrasive prepared by the present invention is measured by nanoindentation method to be about 9GPa, which greatly reduces the scratches on the KDP crystal surface. At the same time, the synergistic effect of TiO2 and CeO2 improves the polishing efficiency.

[0073] The above embodiments are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments. For those skilled in the art, other variations in different forms can be made based on the above description. Obvious variations derived therefrom fall within the scope of protection of the present invention. Finally, it should be noted that the terms "comprise," "include," or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article, or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article, or device.

Claims

1. A double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive for chemical mechanical polishing of KDP crystals. The preparation method of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive comprises the following steps: Step 1: Preparation of polystyrene (PS) microspheres: Styrene and methacryloyloxyethyltrimethylammonium chloride were added to a polyvinylpyrrolidone aqueous solution, and the mixture was heated to boiling. 2,2-azobis(2-methylpropylimidazole) dihydrochloride was then added to react to obtain a polystyrene emulsion. The emulsion was then dried and ground to obtain PS microspheres. Step 2: Preparation of PS / TiO2 composite microspheres: The PS microspheres prepared in step 1 are dispersed in anhydrous ethanol to prepare a PS ethanol solution, and ultrasonically dispersed uniformly; the pH value of the mixed solution is then adjusted to 6-9 with ammonia water and heated; the ethanol solution of the organic titanate is then added and stirred for reaction; after the reaction is completed, the product is centrifuged and repeatedly washed with deionized water and anhydrous ethanol; and then dried and ground to obtain PS / TiO2 composite microspheres; Step 3: Preparation of PS / TiO2 / CeO2 composite abrasive: The PS / TiO2 composite microspheres prepared in step 2 are dispersed in deionized water to prepare a PS / TiO2 aqueous solution, and ultrasonically dispersed uniformly; then, soluble cerium salt and hexamethylenetetramine are added; the reaction is stirred under heating conditions; after the reaction is completed, the final product is centrifuged and repeatedly washed with deionized water and anhydrous ethanol; finally, the PS / TiO2 / CeO2 composite abrasive is obtained by drying and grinding.

2. The use of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive according to claim 1 for chemical mechanical polishing of KDP crystals, characterized in that: In step 1, the concentration of the polyvinyl pyrrolidone aqueous solution is 0.5 g / L~6 g / L; the amount of styrene and the polyvinyl pyrrolidone aqueous solution is 45 g~150 g:1L; the amount of methacryloyloxyethyltrimethylammonium chloride and the polyvinyl pyrrolidone aqueous solution is 0.5 g~5.5 g:1L; the amount of 2,2-azobis(2-methylpropylimidazole) dihydrochloride and the polyvinyl pyrrolidone aqueous solution is 0.5 g~2.5 g:1L; in step 1, a constant temperature oil bath is used for heating at a temperature of 100~110°C, and the reaction is carried out for 5~8 hours after the addition of 2,2-azobis(2-methylpropylimidazole) dihydrochloride.

3. The use of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive according to claim 1 for chemical mechanical polishing of KDP crystals, characterized in that: In step 2, the organic titanate is any one of tetrabutyl titanate, isopropyl titanate, and titanium isopropoxide, or a combination thereof.

4. The use of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive according to claim 1 for chemical mechanical polishing of KDP crystals, characterized in that: In step 2, the concentration of the PS ethanol solution is 5 g / L~30 g / L, and the concentration of the organic titanate ethanol solution is 10 g / L~100 g / L; in step 2, a constant temperature oil bath is used for heating at a temperature of 70~90°C, and the reaction time is 2~4 h.

5. Use of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive according to claim 1 for chemical mechanical polishing of KDP crystals, characterized in that: In step 3, the soluble cerium salt is any one of cerium nitrate, cerium sulfate, cerium chloride, or a combination thereof.

6. Use of the double-layer core-shell structure PS / TiO2 / CeO2 nanocomposite abrasive according to claim 1 for chemical mechanical polishing of KDP crystals, characterized in that: In step 3, the concentration of the PS / TiO2 aqueous solution is 2.5 g / L~15 g / L, the amount of the soluble cerium salt and the PS / TiO2 aqueous solution is 20 g-100 g:1L; the molar ratio of the soluble cerium salt to hexamethylenetetramine is 1:5; in step 3, a constant temperature oil bath is used for heating, the heating temperature is 60~85°C, and the reaction time is 2~4 h.

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