A core-shell structure doped cerium oxide-based abrasive and its preparation method and application

Abstract

The invention discloses a core-shell structure doped cerium oxide-based abrasive and its preparation method and application, which belongs to the technical field of polishing materials. The preparation method of the core-shell structure doped cerium oxide-based abrasive comprises the following steps: (1) using a soap-free emulsion polymerization method, under a protective atmosphere, using a polymer monomer, a cross-linking agent, an initiator and water as raw materials to stir and react at 60-80°C for at least 7h to obtain a polymer colloid solution; (2) uniformly dispersing the polymer colloid solution into water, adding a first rare earth salt and a second rare earth salt, or adding the first rare earth salt and a transition metal salt, and then adding a precipitant, heating the reaction, washing, filtering, and drying to obtain the core-shell structure doped cerium oxide-based abrasive. The method of the present invention is simple in steps, and the obtained core-shell structure doped cerium oxide-based abrasive has good dispersibility, can achieve the effect of mitigating polishing, reduce surface damage, and has good polishing effect and high polishing efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of polishing materials, and in particular to a core-shell structure-doped cerium oxide-based abrasive, a preparation method thereof, and an application thereof. Background Art

[0002] The rapid development of communications technology in recent years has driven screen display systems toward ultra-thin and flexible designs. Ultra-thin glass (UTG) holds considerable market potential and scientific research value in applications such as organic light-emitting semiconductor (OLED) substrates, photovoltaic cells, wearable electronic devices, and foldable / curved cover glass. To achieve flexibility, glass substrates must be polished to achieve efficient thinning and a precisely flat surface, posing a significant challenge to the cover glass polishing process. Chemical mechanical polishing (CMP), the only global planarization technology, has been widely used in ultra-precision optical components, ultra-large-scale integrated circuit devices, and liquid crystal glass substrates.

[0003] In a typical glass CMP process, material removal and flattening are achieved through the synergistic effect of abrasive mechanical friction and chemical corrosion. The core process point of CMP technology is the abrasive system, and its characteristics directly determine the quality of polishing. At present, most commercial abrasives are single inorganic abrasives such as aluminum oxide, silicon oxide, cerium oxide, diamond, etc. Cerium oxide is considered to be the most promising CMP polishing powder because of its chemical corrosion to glass. However, commercial cerium oxide polishing powder on the market is often calcined, with a small particle size and poor dispersion stability. The polishing efficiency is low, and the removal of surface scratches is poor.

[0004] Chinese patent publication number CN101818047A discloses a silicon oxide-cerium oxide core-shell composite abrasive particle, which has a spherical silicon oxide core and a cerium oxide coating. The silicon oxide abrasive in the core has high dispersibility, and a composite abrasive with higher dispersibility than a single cerium oxide abrasive can be obtained, thereby improving the poor dispersibility of the single cerium oxide abrasive. Chinese patent publication number CN113563843A discloses a core-shell structured cerium dioxide / nanodiamond composite abrasive. The composite abrasive comprises cerium dioxide nanorods grown with nanodiamond particles, and the weight ratio of cerium dioxide nanorods to nanodiamond particles is 3:1 to 1:1. The composite abrasive can improve polishing efficiency.

[0005] Chinese patent publication CN116062786A discloses a method for preparing monodisperse, quasi-spherical micron-sized cerium oxide. The method involves first preparing a chitosan solution, then adding a cerium salt to the chitosan solution, stirring and dissolving it, and subjecting it to a hydrothermal reaction. After centrifugation, the precipitate is removed, washed, and dried to obtain a cerium complex. The cerium complex is then heated in a muffle furnace for a reaction, yielding monodisperse, quasi-spherical micron-sized cerium oxide. The method utilizes chitosan as both a complexing agent and a reducing agent. While the hydrothermal reaction reduces the cerium salt, the reduced product is fully dispersed and complexed to prevent aggregation.

[0006] However, the above method may have the problems of complicated steps, high cost, and the performance of the abrasive particles produced needs to be further improved. Therefore, it is very important to develop a composite abrasive with a simple preparation method that can improve polishing efficiency and polishing quality. Summary of the Invention

[0007] The invention provides a method for preparing a core-shell structure doped cerium oxide-based abrasive. The steps are simple, and the prepared core-shell structure doped cerium oxide-based abrasive has good dispersibility, can achieve a mild polishing effect, reduce surface damage, and has good polishing effect and high polishing efficiency.

[0008] The specific technical solutions adopted are as follows:

[0009] A method for preparing a core-shell structure-doped cerium oxide-based abrasive comprises the following steps:

[0010] (1) using a soap-free emulsion polymerization method, under a protective atmosphere, with polymer monomers, a crosslinking agent, an initiator and deionized water as raw materials, stirring and reacting at 60-80° C. for at least 7 hours to obtain a polymer colloidal solution;

[0011] (2) uniformly dispersing the polymer colloid solution in water, adding the first rare earth salt and the second rare earth salt, or adding the first rare earth salt and the transition metal salt; then adding a precipitant, heating for reaction, washing, filtering, and drying to obtain the core-shell structure doped cerium oxide-based abrasive;

[0012] The polymer monomer is styrene or methyl methacrylate;

[0013] The first rare earth salt is a trivalent cerium salt.

[0014] The present invention uses a soap-free emulsion polymerization method to first prepare polymer microspheres. Then, using the principle of electrostatic attraction, a doped cerium oxide-based shell is coated on the polymer microspheres to form a core-shell composite abrasive. The present invention designs the composite abrasive structure, combining a specific core-shell structure with trivalent rare earth ion / high-valent transition metal ion doping to increase the abrasive particle size and chemical activity, increase the number of active abrasive particles, improve the dispersibility of the abrasive particles, enhance polishing efficiency, achieve high-efficiency polishing, reduce surface damage, and improve polishing precision.

[0015] Preferably, the polymer monomer is treated with a sodium hydroxide solution having a mass fraction of 5% to remove the polymerization inhibitor.

[0016] The cross-linking agent includes methylene bisacrylamide, sodium lauryl sulfate, divinyl benzene or diisocyanate.

[0017] The initiator is dibenzoyl peroxide, potassium persulfate or azobisisobutyronitrile.

[0018] Preferably, in the soap-free emulsion polymerization reaction system, the concentration of the polymer monomer is 5-20 wt %, the concentration of the cross-linking agent is 0.15-0.35 wt %, and the concentration of the initiator is 0.2-0.5 wt %.

[0019] Under the above reaction conditions, polymer microspheres with an average diameter of 300nm-370nm can be prepared, and the surface of the corresponding polymer microspheres is negatively charged, which is conducive to the coating of the doped cerium oxide-based shell in the subsequent step, giving the composite abrasive a low Young's modulus and spring-like properties.

[0020] Preferably, the second rare earth salt is a trivalent lanthanum salt, a trivalent ytterbium salt, a trivalent neodymium salt, a trivalent gadolinium salt, a trivalent promethium salt or a trivalent europium salt.

[0021] Preferably, the transition metal salt is a tetravalent zirconium salt, a pentavalent niobium salt or a hexavalent molybdenum salt.

[0022] In the homogeneous precipitation method, a second rare earth salt or transition metal salt is used to achieve doping of rare earth elements or transition metal elements in the shell layer. During the polishing application process, Ce in cerium oxide 3+ It helps to break the Si-O bond during the CMP process. Trivalent rare earth ions or high-valent transition metal ions with large ionic radius can easily achieve Ce 4+ substitution and regulation of lattice oxygen defects, thereby promoting Ce 3+ Increasing the concentration further improves the polishing efficiency.

[0023] Further preferably, the first rare earth salt is cerium nitrate hexahydrate, the second rare earth salt is lanthanum nitrate hexahydrate, and the transition metal salt is zirconium nitrate pentahydrate.

[0024] In step (2), each milliliter of polymer colloid solution corresponds to 0.2-0.3 mmol of the first rare earth salt and 0.005-0.05 mmol of the second rare earth salt; or each milliliter of polymer colloid solution corresponds to 0.2-0.3 mmol of the first rare earth salt and 0.005-0.05 mmol of the transition metal salt.

[0025] Preferably, the precipitant is hexamethylenetetramine; the molar ratio of the total amount of the first rare earth salt and the second rare earth salt to the amount of the precipitant is 1:10, or the molar ratio of the total amount of the first rare earth salt and the transition metal salt to the amount of the precipitant is 1:10.

[0026] In step (2), the heating reaction conditions are 70-90° C. for 1-4 h.

[0027] The present invention also provides the core-shell structure doped cerium oxide based abrasive material prepared by the preparation method of the core-shell structure doped cerium oxide based abrasive material.

[0028] The core-shell structure doped cerium oxide-based abrasive comprises a polymer microsphere core and a doped cerium oxide-based shell, wherein the mass fraction of the polymer microsphere core is 40% to 60% and the mass fraction of the doped cerium oxide-based shell is 40% to 60%.

[0029] Preferably, the average diameter of the core-shell structure doped cerium oxide-based abrasive is 360-420 nm, the average diameter of the core of the polymer microsphere is 300-370 nm, and the average particle size of the grains in the doped cerium oxide-based shell is 5-10 nm.

[0030] The present invention also provides a polishing liquid, which is composed of the core-shell structure doped cerium oxide-based abrasive, water and a pH regulator; the pH value of the polishing liquid is 6-8, and the mass fraction of the core-shell structure doped cerium oxide-based abrasive in the polishing liquid is 0.25%-5%.

[0031] In the polishing liquid, the surface potential of the core-shell structure doped cerium oxide-based abrasive is positive, which is opposite to the surface charge of glass and silicon oxide hydrate layer at the same pH. By strengthening the electrostatic attraction between the abrasive and the glass surface, the removal efficiency of the silicon oxide material is accelerated.

[0032] The invention also provides application of the core-shell structure doped cerium oxide-based abrasive in the field of polishing.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] (1) The core-shell structure doped cerium oxide-based abrasive provided by the present invention forms a multi-element polishing system through the synergistic effect of the flexible polymer microsphere core, the inorganic abrasive shell with mechanical and chemical removal capabilities, and the doping of rare earth elements or transition metal elements to enhance the chemical tooth effect, thereby improving the dispersion and polishing performance of the abrasive. On the one hand, the core-shell structure can increase the particle size of the abrasive particles, increase the number of active abrasive particles, improve the dispersibility of the polishing liquid slurry, improve the polishing efficiency, reduce the damage to the polishing surface, improve the accuracy, and reduce the roughness of the polished surface. On the other hand, the Ce in cerium oxide 3+ It helps to break the Si-O bond during the CMP process. Trivalent rare earth ions or high-valent transition metal ions with large ionic radius can easily achieve Ce 4+ substitution and regulation of lattice oxygen defects, thereby promoting Ce 3+ Increasing the concentration further improves the polishing efficiency.

[0035] (2) The core-shell structure doped cerium oxide-based abrasive provided by the present invention has a "spring-like" effect in the polishing process, which can achieve a gentle polishing effect, reduce surface damage, and has a high polishing rate on the surface of the glass substrate, and greatly improves the sub-nanometer surface flatness.

[0036] (3) The preparation method of the core-shell structure doped cerium oxide-based abrasive is simple, helps to save rare earth resources and production raw material costs, is economical and green, and has a high yield.

[0037] (4) The polishing liquid provided by the present invention has simple components and does not contain any other corrosion inhibitors, oxidants, or dispersants. It has low raw material cost and low solid content. By controlling the pH to adjust the Zeta potential of the abrasive particle surface, the charge of the abrasive particles in the polishing liquid is opposite to the charge of the glass and silicon oxide surfaces. By strengthening the electrostatic attraction between the abrasive and the glass surface, the removal efficiency of the silicon oxide material is accelerated, and the polishing effect is high and effective. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a transmission electron microscope image of the core-shell structure doped cerium oxide-based abrasive prepared in Example 1.

[0039] Figure 2 This is an AFM image of the surface of a soda-lime glass substrate before polishing.

[0040] Figure 3 This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing liquid in Application Example 1.

[0041] Figure 4 This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing liquid in Application Example 2.

[0042] Figure 5This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing liquid in Application Example 3. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the examples and accompanying drawings. It should be understood that these examples are intended to illustrate the present invention only and are not intended to limit the scope of the invention. The operating methods in the following examples where no specific conditions are specified are generally performed under conventional conditions or as recommended by the manufacturer.

[0044] Example 1

[0045] (1) Using a soap-free emulsion polymerization method, 10 g of styrene and 0.32 g of a crosslinker, methylenebisacrylamide, were dispersed in 150 ml of water under continuous stirring. The mixture was continuously deoxygenated by nitrogen bubbling and stirred for 0.5 h, then gradually heated to 70°C and maintained for 30 min. Then, 30 ml of an aqueous solution containing 0.41 g of potassium persulfate was added under a high nitrogen flow rate to initiate polymerization. The resulting mixed solution was maintained at 70°C under nitrogen protection for 7 hours, and then cooled to room temperature to stop the polymerization, thereby obtaining a polymer colloidal solution.

[0046] (2) 4 ml of the polymer colloid solution obtained in step (1) was dispersed into 200 ml of water and evenly separated using a cell crusher for 10 min; 50 ml of 0.0192 mol·L -1 Cerium nitrate hexahydrate and 0.0008 mol·L -1 Lanthanum nitrate hexahydrate aqueous solution and 50ml 0.2mol·L -1 A hexamethylenetetramine aqueous solution is added to obtain a mixed solution; the mixed solution is reacted in a magnetic stirrer at 80° C. for 2 hours, and further washed, filtered, and dried to obtain the core-shell structure doped cerium oxide-based abrasive.

[0047] The TEM image of the core-shell structure doped cerium oxide-based abrasive prepared in Example 1 is as follows: Figure 1 As shown, the mass fraction of the polymer microsphere core is about 53.82%, and the mass fraction of the doped cerium oxide-based shell is about 46.18%. The average diameter of the core-shell structure doped cerium oxide-based abrasive is 360-420nm, the average diameter of the polymer microsphere core is 300-370nm, and the average particle size of the grains in the doped cerium oxide-based shell is 5-10nm.

[0048] Comparative Example 1

[0049] In this comparative example, the preparation method of the core-shell structure abrasive is different from that in Example 1 only in that, in step (2), 50 ml of 0.02 mol·L -1 Cerium nitrate hexahydrate aqueous solution and 50ml 0.2mol·L -1A hexamethylenetetramine aqueous solution is prepared to obtain a mixed solution; and the shell of the core-shell structure abrasive obtained does not contain the doping element lanthanum.

[0050] Example 2

[0051] The preparation method of the core-shell structure abrasive in this embodiment is different from that in embodiment 1 only in that, in step (2), 50 ml of 0.0192 mol·L -1 Cerium nitrate hexahydrate and 0.0008 mol·L -1 Aqueous solution of neodymium nitrate hexahydrate and 50ml of 0.2mol·L -1 A hexamethylenetetramine aqueous solution is prepared to obtain a mixed solution; the shell of the core-shell structure abrasive obtained further contains the doping element neodymium.

[0052] Example 3

[0053] The preparation method of the core-shell structure abrasive in this embodiment is different from that in embodiment 1 only in that, in step (2), 50 ml of 0.0192 mol·L -1 Cerium nitrate hexahydrate and 0.0008 mol·L -1 Ytterbium nitrate hexahydrate aqueous solution and 50ml 0.2mol·L -1 A hexamethylenetetramine aqueous solution is prepared to obtain a mixed solution; and the shell of the core-shell structure abrasive obtained further contains the doping element ytterbium.

[0054] Example 4

[0055] The preparation method of the core-shell structure abrasive in this embodiment is different from that in embodiment 1 only in that, in step (2), 50 ml of 0.016 mol·L -1 Cerium nitrate hexahydrate and 0.004 mol·L -1 Manganese nitrate aqueous solution and 50ml0.2mol·L -1 A hexamethylenetetramine aqueous solution is prepared to obtain a mixed solution; and the shell of the core-shell structure abrasive obtained further contains the doping element manganese.

[0056] Example 5

[0057] The preparation method of the core-shell structure abrasive in this embodiment is different from that in embodiment 1 only in that, in step (2), 50 ml of 0.018 mol·L -1 Cerium nitrate hexahydrate and 0.002 mol·L -1 Aqueous solution of zirconyl nitrate and 50ml 0.2mol·L -1 A hexamethylenetetramine aqueous solution is prepared to obtain a mixed solution; the shell of the core-shell structure abrasive obtained further contains the doping element zirconium.

[0058] Application Example 1

[0059] The core-shell structure doped cerium oxide-based abrasive in Example 1 was placed in deionized water, the mass fraction of the abrasive was controlled to be 1%, and the pH was adjusted to 7 with a 2% mass fraction sodium hydroxide solution to prepare a polishing liquid.

[0060] Application Example 2

[0061] The core-shell structure abrasive in Comparative Example 1 was placed in deionized water, the mass fraction of the abrasive was controlled to be 1%, and the pH was adjusted to 7 with a sodium hydroxide solution with a mass fraction of 2%, to prepare a polishing liquid.

[0062] Application Example 3

[0063] Commercial CeO2 abrasive (particle size 50 nm) was added to deionized water, the mass fraction of CeO2 was controlled to be 1%, and the pH was adjusted to 7 with a 2% mass fraction sodium hydroxide solution to prepare a polishing liquid.

[0064] Sample analysis

[0065] The polishing liquids of Application Example 1, Application Example 2, and Application Example 3 were used to perform polishing tests on soda-lime glass substrates under the following conditions. The polishing conditions include:

[0066] Polishing machine: Alpha-600; workpiece: 20 mm × 20 mm soda-lime glass sheet; polishing pad: polyurethane material, Henan Moao; polishing pressure: 5 N; lower platen speed: 150 rpm; indenter speed: 100 rpm; polishing time: 1.5 min; polishing fluid flow rate: 31 ml / min;

[0067] After polishing, the glass substrate was cleaned and dried, and the surface quality of the substrate was measured using an atomic force microscope (AFM). The results were as follows: Figure 2-Figure 5 As shown, Figure 2 This is an AFM image of the surface of a soda-lime glass substrate before polishing. Figure 3 This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing solution in Example 1. Figure 4 This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing solution in Example 2. Figure 5 This is an AFM image of the surface of a soda-lime glass substrate after polishing with the polishing liquid in Application Example 3.

[0068] At the same time, the surface roughness test results show that when the polishing liquid in Application Example 1 is used for fine polishing of the surface of soda-lime glass, a surface with Ra of 0.318nm can be obtained; when the polishing liquid in Application Example 2 is used for fine polishing of the surface of soda-lime glass, a surface with Ra of 0.431nm can be obtained; when the polishing liquid in Application Example 3 is used for fine polishing of the surface of soda-lime glass, a surface with Ra of 1.33nm can be obtained. Figure 2-Figure 5 As can be seen from the surface roughness test results, the polishing liquid prepared by the core-shell structure doped cerium oxide-based abrasive of the present invention shows lower surface roughness and better flattening ability than the commercial cerium oxide abrasive polishing liquid on the market.

[0069] The embodiments described above provide a detailed description of the technical solutions of the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, supplements or similar substitutions made within the scope of the principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a core-shell structure doped cerium oxide-based abrasive, characterized in that: The following steps are involved: (1) using a soap-free emulsion polymerization method, under a protective atmosphere, with polymer monomer, cross-linking agent methylene bisacrylamide, initiator and water as raw materials, stirring and reacting at 60-80° C. for at least 7 hours to obtain a polymer colloidal solution; in the soap-free emulsion polymerization reaction system, the concentration of the polymer monomer is 5-20 wt %, the concentration of the cross-linking agent is 0.15-0.35 wt %, and the concentration of the initiator is 0.2-0.5 wt %; (2) uniformly dispersing the polymer colloid solution in water, adding the first rare earth salt and the second rare earth salt, or adding the first rare earth salt and the transition metal salt; then adding a precipitant, heating for reaction, washing, filtering, and drying to obtain the core-shell structure doped cerium oxide-based abrasive; The polymer monomer is styrene or methyl methacrylate; The first rare earth salt is cerium nitrate hexahydrate; the second rare earth salt is lanthanum nitrate hexahydrate, and the transition metal salt is zirconium nitrate pentahydrate; In step (2), each milliliter of the polymer colloid solution corresponds to 0.2-0.3 mmol of the first rare earth salt and 0.005-0.05 mmol of the second rare earth salt; or each milliliter of the polymer colloid solution corresponds to 0.2-0.3 mmol of the first rare earth salt and 0.005-0.05 mmol of the transition metal salt; The average diameter of the core-shell structure doped cerium oxide-based abrasive is 360-420 nm, the average diameter of the core of the polymer microsphere is 300-370 nm, and the average particle size of the grains in the doped cerium oxide-based shell is 5-10 nm.

2. The method for preparing the core-shell structure doped cerium oxide-based abrasive according to claim 1, characterized in that: The initiator is dibenzoyl peroxide, potassium persulfate or azobisisobutyronitrile.

3. The method for preparing the core-shell structure doped cerium oxide-based abrasive according to claim 1, characterized in that: The precipitant is hexamethylenetetramine.

4. The method for preparing a core-shell structure doped cerium oxide-based abrasive according to claim 1, characterized in that: The heating reaction conditions are 70-90°C for 1-4h. 5 . The core-shell structure doped cerium oxide-based abrasive prepared according to the method for preparing the core-shell structure doped cerium oxide-based abrasive according to claim 1 .

6. A polishing liquid, characterized in that: The polishing liquid comprises the core-shell structure doped cerium oxide-based abrasive according to claim 5, water and a pH regulator; the pH value of the polishing liquid is 6-8; and the mass fraction of the core-shell structure doped cerium oxide-based abrasive in the polishing liquid is 0.25%-5%.

7. Use of the core-shell structure doped cerium oxide-based abrasive according to claim 5 in the field of polishing.

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