Gel abrasive tool based on photocatalysis-mechanical synergistic mechanism and polishing method

Abstract

The present application aims at solving the defects of the existing photocatalytic polishing technology, and provides a gel abrasive tool and a polishing method based on a photocatalysis-mechanical synergistic mechanism. The gel abrasive tool is prepared through four steps: firstly, Ni-TiO2 powder is prepared, then SiO2 / Ni-TiO2 core-shell structure catalyst powder is synthesized, then the SiO2 / Ni-TiO2 core-shell structure catalyst powder is mixed with binders, abrasives and other raw materials to prepare bubble-free slurry, and finally the target gel abrasive tool is obtained through freezing-thawing, sintering solidification and surface finishing. The Ni-TiO2 in the abrasive tool is coated with a SiO2 layer, which can effectively prevent the catalyst from being abnormally consumed, and prolong its service life by 3-5 times. In the polishing process, the SiO2 / Ni-TiO2 catalyst powder on the surface of the gel abrasive tool will have its SiO2 coating layer damaged by mechanical action, and the exposed Ni-TiO2 can maintain high catalytic activity under ultraviolet excitation, which is suitable for precision machining requirements, and can reduce processing cost and environmental burden, and provides reliable technical support for green precision machining of hard and brittle workpieces.

Description

Technical Field

[0001] This invention relates to the field of precision machining, grinding and polishing technology, and in particular to a gel abrasive and polishing method based on a photocatalytic-mechanical synergistic mechanism. Background Technology

[0002] In the field of precision polishing technology, the ultra-precision machining of high-hardness and high-strength materials has always been a core technological bottleneck restricting the high-quality development of related industries. Typical hard and brittle materials such as silicon carbide, sapphire, and engineering ceramics, due to their inherent characteristics of high hardness, high wear resistance, and strong chemical stability, generally face two major technical challenges when processed using traditional purely mechanical polishing methods: First, low processing efficiency. Conventional abrasive polishing processes have a low removal rate for these hard and brittle materials, making it difficult to meet the demands of high-end manufacturing for mass production efficiency. Second, difficulty in balancing processing quality and tool life. The intense mechanical friction between the abrasive and the workpiece surface during processing not only easily leads to scratches, subsurface damage, and other defects on the workpiece surface, causing deterioration of surface integrity, but also exacerbates the wear of polishing tools, significantly increasing processing costs.

[0003] Silicon carbide, as a core substrate material for third-generation semiconductors, directly determines the fabrication precision and performance stability of subsequent devices due to its surface roughness and flatness. Traditional polishing techniques have consistently struggled to achieve nanoscale surface roughness while simultaneously meeting the demands of high-efficiency processing, becoming a key obstacle to the industrial application of silicon carbide substrates. To address these technical challenges, domestic and international scholars have proposed solutions based on synergistic chemical-mechanical processes. Among these, photocatalytically assisted chemical mechanical polishing (CMP) technology has garnered widespread attention and research within the industry due to its combination of environmental advantages and superior processing efficiency.

[0004] For example, Chinese patent application CN118905731A discloses a high-precision and high-efficiency polishing method for hard and brittle ceramic materials. This method involves mixing nano-abrasive particles, nano-photocatalytic particles, an oxidant, nano-graphene oxide, a dispersant, and deionized water, and adjusting the pH value to prepare a photocatalytic nano-polishing liquid. Under ultraviolet light irradiation, this photocatalytic nano-polishing liquid is used to polish the hard and brittle ceramic material. This achieves high-efficiency polishing of hard and brittle ceramic materials by introducing photocatalysis to soften the workpiece surface and the lubrication effect of nanomaterials, in addition to abrasive removal. However, while such free abrasive photocatalytic polishing systems can achieve nanoscale surface roughness, they suffer from significant limitations due to their process characteristics, including long processing cycles and limited production efficiency. Specifically, the random distribution of abrasive particles leads to insufficient effective cutting point density, and the number of abrasive particles actually involved in material removal during free abrasive polishing is limited.

[0005] To overcome the aforementioned technical obstacles, researchers have developed a semi-bonded abrasive polishing tool—gel abrasive. This technology effectively improves the controllability of abrasive distribution by fixing functional components such as abrasives and catalysts within a three-dimensional polymer network, increasing chemical reaction efficiency by 2-3 times and material removal rate to 0.7-1.5 μm / h. For example, invention patent CN120038677A discloses a high-porosity ceramic-bonded diamond micron abrasive, its preparation method, and its application. This abrasive uses a gel casting method to prepare the ceramic-bonded diamond abrasive, which features high porosity, high self-sharpening properties, and low grinding resistance, enabling efficient processing of semiconductor materials.

[0006] However, two major unresolved technical challenges remain in photocatalytic chemimechanical polishing: First, the hydroxyl radicals generated by the photocatalytic reaction have an inherent short lifespan. They often undergo self-quenching before diffusing to the surface of the silicon carbide workpiece to participate in the polishing reaction. This not only causes a large amount of ineffective loss of oxidant but also significantly reduces polishing efficiency. Second, although the catalytic efficiency of composite photocatalysts is significantly improved compared to single catalysts, they are highly sensitive to ambient light and are easily excited by stray light, resulting in non-specific catalytic reactions. This causes some catalysts to be consumed prematurely before participating in the target polishing process, further increasing processing costs and reducing the economic efficiency of the process.

[0007] Based on this, an adaptable protective layer was designed and prepared. Through physical isolation and interface control, it can effectively reduce the abnormal loss of composite photocatalyst in non-processing areas and improve the dispersion stability of the catalyst in the mold. This is a feasible technical approach to solve the above problems and improve the economy and efficiency of the polishing process. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings and deficiencies of existing photocatalytic polishing technologies by providing a gel abrasive and polishing method based on a photocatalytic-mechanical synergistic mechanism.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A gel abrasive based on a photocatalytic-mechanical synergistic mechanism, wherein the gel abrasive is prepared by the following steps:

[0011] 1) Preparation of Ni-TiO2 powder: Tetrabutyl titanate was added to anhydrous ethanol, acetylacetone was added and stirred until homogeneous to obtain solution A; nickel nitrate hexahydrate was dissolved in anhydrous ethanol and stirred until completely dissolved to obtain solution B; under constant temperature water bath conditions, solution B was added dropwise to solution A and stirred continuously until a light green homogeneous sol was formed; deionized water was slowly added to the sol and stirred until the system was homogeneous, then baked to obtain a dry gel, which was then ground into powder and dried to obtain Ni-TiO2 powder. The specific working principle of this step is that when preparing solution A, tetrabutyl titanate is dissolved in anhydrous ethanol, and acetylacetone chelates with titanium ions to passivate its hydrolytic activity and avoid precipitation caused by subsequent water addition; when preparing solution B, nickel nitrate hexahydrate is dissolved in anhydrous ethanol to form a homogeneous Ni-TiO2 sol. 2+ Solution, ensuring uniform doping. Under constant temperature water bath conditions, solution B is added dropwise to solution A, Ni 2+ Slow dispersion allows the system to undergo pre-hydrolysis, complexation, and condensation reactions, forming a pale green, homogeneous sol. Deionized water is then slowly added to induce controlled hydrolysis and condensation of tetrabutyl titanate, further stabilizing the sol network through cross-linking. Baking removes the solvent and volatiles, solidifying the sol into a dry gel. Further grinding, drying, and calcination remove residual impurities, crystallizing TiO2 and Ni. 2+ By uniformly doping into the TiO2 lattice, Ni-TiO2 powder with excellent photocatalytic activity and good dispersion is finally obtained, which is suitable for subsequent photocatalytic-mechanical synergistic polishing requirements.

[0012] 2) Preparation of SiO2 / Ni-TiO2 catalyst powder: Ni-TiO2 powder was added to anhydrous ethanol and ultrasonically dispersed until no visible agglomerates were found. Then, hexadecyltrimethylammonium bromide was added and stirred to obtain solution C. Tetraethyl orthosilicate was dissolved in anhydrous ethanol and stirred evenly. Deionized water and ammonia were slowly added and stirred continuously until a uniform solution D was formed. Solution C was added to solution D, heated and reacted continuously. After the reaction was completed, the mixture was vacuum dried to obtain SiO2 / Ni-TiO2 catalyst powder for photocatalysis. This step involves adding solution C (Ni-TiO2 dispersion) to solution D (SiO2 colloid) and heating to accelerate the composite reaction, allowing Ni-TiO2 to be uniformly loaded on the surface of the SiO2 colloid and forming a stable composite system. Continuous stirring can prevent agglomeration caused by excessively high local concentrations and ensure that Ni-TiO2 is uniformly distributed on the SiO2 support. Vacuum drying thoroughly removes ethanol, water and residual impurities from the system, solidifies the composite structure, and finally obtains a SiO2 / Ni-TiO2 catalyst powder with stable photocatalytic activity and uniform dispersion.

[0013] 3) Preparation of slurry: Mix polyvinyl alcohol, phenolic resin, SiO2 / Ni-TiO2 catalyst powder, diamond powder, copper powder, talc powder, deionized water and dispersant evenly, and put the mixture into a vacuum defoamer and stir until there are no bubbles and the system is uniform to obtain the slurry;

[0014] 4) Preparation of gel polishing disc: After the slurry is sieved through a screen to remove large particle agglomerates, it is poured into a mold and the slurry is gelled by freezing-thawing method. The gel is placed in an oven for sintering and curing treatment. Finally, the surface of the cured product is trimmed to obtain the gel polishing disc.

[0015] Step 3) During slurry preparation, the raw materials work synergistically to form a uniform and stable molding system. Polyvinyl alcohol and phenolic resin act as binders, firmly bonding the components and ensuring subsequent molding and mold strength. SiO2 / Ni-TiO2 catalyst powder provides photocatalytic activity, meeting the requirements of photocatalytic-mechanical synergistic polishing. Diamond powder acts as the abrasive, undertaking the main mechanical cutting and polishing function, while copper powder enhances the mechanical properties and thermal conductivity of the mold. Deionized water serves as the dispersion medium, working with dispersants to prevent agglomeration of the powder components and ensure system uniformity. The mixture is then stirred in a vacuum defoamer to thoroughly remove air bubbles generated during mixing, preventing them from affecting the subsequent mold molding quality and performance, ultimately resulting in a uniform, bubble-free slurry. Step 4) When preparing the gel polishing disc, sieving through a sieve can remove large particle agglomerates, preventing unevenness on the surface of the molded abrasive and affecting polishing accuracy. After pouring the slurry into the mold, the freeze-thaw method allows the water in the slurry to crystallize and form a stable gel structure after thawing, laying the foundation for the basic shape of the abrasive. Oven sintering and curing can remove moisture and residual impurities from the system, cross-link and cure the binder, and enhance the mechanical strength and stability of the abrasive. Finally, surface finishing makes the working surface of the abrasive smooth and flat, ensuring uniform contact with the workpiece during polishing, and finally obtaining a gel abrasive adapted for photocatalytic-mechanical synergistic polishing.

[0016] According to the above scheme, the mass percentage of each raw material in step 1) is relative to the total mass of raw materials used to prepare Ni-TiO2 powder in step 1), as follows: tetrabutyl titanate 10wt%~30wt%, anhydrous ethanol 50wt%~80wt% (of which, the anhydrous ethanol used to prepare solution A is 40wt%~60wt%, and the anhydrous ethanol used to prepare solution B is 10wt%~20wt%), acetylacetone 0.1wt%~1wt%, nickel nitrate hexahydrate 1wt%~5wt%, and deionized water 10wt%~20wt%.

[0017] According to the above scheme, the preparation process of Ni-TiO2 powder in step 1) is as follows: Tetrabutyl titanate is slowly added to anhydrous ethanol and stirred for 30-60 min; then acetylacetone is added to inhibit the excessively rapid hydrolysis of tetrabutyl titanate, and stirring is continued for 10-30 min to obtain solution A; nickel nitrate hexahydrate is dissolved in anhydrous ethanol and ultrasonically dispersed for 30-50 min until the solution becomes transparent to obtain solution B; solution B is added dropwise to solution A and stirred for 1-2 minutes under a water bath at 60-80℃. After 3 hours, a uniform light green sol is formed. Deionized water is slowly added to the sol to adjust the pH of the system to 3-4. After stirring for 8-12 hours, the mixture is placed in an oven at 60-80℃ and baked for 12-24 hours to form a dry gel. The dry gel is ground into powder and dried at 80-90℃ for 8-12 hours. The dried powder is placed in an oven and heated to 450-500℃ at a heating rate of 2℃ / min. It is then calcined at this temperature for 2-3 hours and naturally cooled to obtain Ni-TiO2 powder.

[0018] According to the above scheme, the mass percentage of each raw material in step 2) is relative to the total mass of raw materials used to prepare SiO2 / Ni-TiO2 catalyst powder in step 2), specifically as follows: Ni-TiO2 powder is 15wt% to 25wt%, anhydrous ethanol is 60wt% to 80wt% (of which, the anhydrous ethanol used to prepare solution C is 40wt% to 50wt%, and the anhydrous ethanol used to prepare solution D is 20wt% to 30wt%), hexadecyltrimethylammonium bromide is 0.1wt% to 1wt%, tetraethyl orthosilicate is 1wt% to 10wt%, deionized water is 5wt% to 10wt%, and ammonia is 0.1wt% to 1wt%.

[0019] According to the above scheme, the preparation process of SiO2 / Ni-TiO2 catalyst powder in step 2) is as follows: Ni-TiO2 powder is added to anhydrous ethanol and ultrasonically dispersed for 30-50 min until no visible agglomerates are found; hexadecyltrimethylammonium bromide is added and stirred at 60-70℃ for 1-2 h to improve the surface hydrophilicity of Ni-TiO2 powder, which is denoted as solution C; tetraethyl orthosilicate is mixed with anhydrous ethanol and stirred for 10-30 min until the system is homogeneous; deionized water and ammonia are slowly added and stirred continuously for 30-60 min to form a homogeneous solution D; solution C is added to solution D and stirred continuously in a water bath at 40-60℃ for 6-8 h; after the reaction is completed, the mixture is washed 1-3 times alternately with anhydrous ethanol and deionized water, and vacuum dried at 60-80℃ for 8-12 h to obtain SiO2 / Ni-TiO2 catalyst powder for photocatalysis.

[0020] According to the above scheme, the mass percentage of each raw material in step 3) is relative to the total mass of raw materials used to prepare the slurry in step 3), specifically as follows: polyvinyl alcohol 5wt%~15wt%, phenolic resin 5wt%~15wt%, SiO2 / Ni-TiO2 catalyst powder 10wt%~20wt%, diamond powder with a particle size of 2.5μm 10wt%~20wt%, copper powder with a particle size of 3μm 20wt%~40wt%, talc powder with a particle size of 3μm 10wt%~20wt%, deionized water 5wt%~15wt%, and dispersant 0.1wt%~1wt%.

[0021] According to the above scheme, in step 4), the slurry is sieved through a 200-mesh sieve to filter out large particle agglomerates, and then the sieved slurry is poured into a mold.

[0022] According to the above scheme, in step 4), the mold after pouring the slurry is placed in a refrigerator and subjected to low-temperature gelation treatment at -20 to -30°C for 8 to 12 hours. After being taken out, it is naturally thawed at room temperature for 4 to 6 hours. The gel blank is taken out from the mold and soaked in anhydrous ethanol for 12 to 24 hours. Then it is placed in an oven and sintered in sections at 50 to 100°C and 120 to 180°C for 1 to 3 hours, respectively. Finally, the surface of the sintered product is polished to obtain the gel mold.

[0023] A polishing method based on a photocatalytic-mechanical synergistic mechanism, using the aforementioned gel abrasive, comprises the following specific steps:

[0024] 1) Fix the silicon carbide workpiece on the fixture and assemble the gel abrasive onto the surface of the rotating base plate;

[0025] 2) An ultraviolet light source is arranged around the rotating base disk, and the incident angle of the ultraviolet light is adjusted by an optical adjustment device to ensure that the ultraviolet light is uniformly irradiated onto the working surface of the gel mold;

[0026] 3) The contact pressure between the silicon carbide workpiece and the gel mold is adjusted by a precision displacement platform to ensure that the contact pressure is uniform and controllable;

[0027] 4) Start the motor drive system to drive the rotating base disk to rotate and drive the gel abrasive to rotate synchronously, so that a controllable relative sliding friction is formed between the silicon carbide workpiece and the working surface of the gel abrasive; during the polishing operation, a micro-pump is used to continuously supply polishing fluid to the polishing processing area. The polishing fluid is prepared by mixing 0.1-10wt% hydrogen peroxide and the balance water.

[0028] During silicon carbide polishing, the SiO2 shell of the SiO2 / Ni-TiO2 catalyst powder is controllably exfoliated under the mechanical friction of diamond abrasive grains, dynamically exposing the Ni-TiO2 active sites and thus maintaining the efficient and continuous catalytic reaction. Under ultraviolet irradiation, the Ni-TiO2 core layer undergoes a photocatalytic reaction, generating hydroxyl radicals. These radicals, in synergy with the polishing slurry, soften the surface of the silicon carbide workpiece and form an easily removable modified layer. Subsequently, the diamond abrasive grains precisely remove the modified layer using mechanical grinding force, achieving a synergistic coupling of chemical catalysis and mechanical grinding. Through this cycle of modified layer "generation-removal," efficient and high-precision polishing of the silicon carbide workpiece is achieved.

[0029] According to the above scheme, the wavelength of the ultraviolet light source is 365nm and the power is 10-50W; the rotation speed of the gel abrasive is 50-100rpm; and the flow rate of the polishing fluid is 20-30mL / min.

[0030] The beneficial effects of this invention are:

[0031] The gel abrasive of this invention is made by uniformly dispersing SiO2 / Ni-TiO2 catalyst powder in a polymer gel matrix, with the Ni-TiO2 catalyst inside coated with silica to form a core-shell structure. This core-shell structure effectively prevents abnormal loss of the Ni-TiO2 catalyst under natural light conditions, significantly improves the light resistance of Ni-TiO2 in non-processed areas, and thus prevents the loss and deactivation of Ni-TiO2 catalyst in non-processed areas under light source irradiation, extending the catalyst's lifespan by 3-5 times. Furthermore, even when the SiO2 protective layer of this core-shell structure is damaged by mechanical action, the internal Ni-TiO2 catalyst can still maintain high reactivity under ultraviolet light excitation, providing a novel technical approach for green manufacturing.

[0032] During the polishing process, when the surface of the grinding wheel is subjected to mechanical shearing, the SiO2 protective layer on the surface of the SiO2 / Ni-TiO2 catalyst powder is controllably exfoliated, exposing the Ni-TiO2 core layer. Under ultraviolet irradiation, the exposed catalytic sites generate hydroxyl radicals, which selectively oxidize the workpiece surface, forming a softening layer with a thickness of 10–300 nm, thus improving the mechanical removal efficiency of the material by 10–35%. Furthermore, the oxidation products are only CO2 and H2O. Compared with traditional polishing slurries, the chemical oxygen demand during the polishing process is reduced by more than 50%, and there is no need to use heavy metal polishing slurries. Test results show that the heavy metal ion content in the polishing wastewater is reduced by more than 45%, and organic pollutant emissions are reduced by 50%, providing a new technical solution for the green precision machining of hard and brittle workpieces. Attached Figure Description

[0033] Figure 1This is a schematic diagram of the surface morphology and structure of the SiO2 / Ni-TiO2 catalyst powder prepared in Example 1;

[0034] Figure 2 This is a comparison chart of the photocatalytic performance test results of the three catalytic powders in Example 2;

[0035] Figure 3 This is a schematic diagram of the polishing principle of the present invention;

[0036] Figure 4 This is a comparison chart of material removal rate and surface roughness of silicon carbide workpieces after polishing with different polishing discs;

[0037] Figure 5 The image shows the surface morphology of a silicon carbide workpiece after photocatalytic-mechanical synergistic polishing and the polishing apparatus.

[0038] Figure 6 This is a comparison of the surface morphology and surface roughness of silicon carbide workpieces under different catalyst concentrations. Detailed Implementation

[0039] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0040] Example 1

[0041] This embodiment describes the preparation of the gel abrasive based on the photocatalytic-mechanical synergistic mechanism of the present invention, specifically through the following steps:

[0042] 1) Preparation of Ni-TiO2 powder: 30 wt% tetrabutyl titanate was slowly added to 44 wt% anhydrous ethanol and magnetically stirred for 30 min; then 1 wt% acetylacetone was added to inhibit the excessively rapid hydrolysis of tetrabutyl titanate, and stirring was continued for 30 min to obtain solution A; 5 wt% nickel nitrate hexahydrate was dissolved in 10 wt% anhydrous ethanol and ultrasonically dispersed for 50 min until the solution became transparent to obtain solution B; solution B was added dropwise to solution A and incubated in a 60℃ water bath. Stirring under the specified conditions for 1 hour yields a uniform light green sol. 10 wt% deionized water is slowly added to the mixed sol to adjust the pH to 4. After stirring for another 8 hours, the mixture is placed in a 70°C oven and baked for 12 hours to form a dry gel. The dry gel is ground into powder and dried at 90°C for 8 hours. The dried powder is placed in an oven and heated to 450–500°C at a rate of 2°C / min, then calcined at this constant temperature for 3 hours. After natural cooling, Ni-TiO2 powder is obtained.

[0043] 2) Preparation of SiO2 / Ni-TiO2 catalyst powder: 24wt% Ni-TiO2 powder was added to 40wt% anhydrous ethanol and ultrasonically dispersed for 50 min until no visible agglomerates were found; 0.5wt% hexadecyltrimethylammonium bromide was added and stirred at 60℃ for 1 h to improve the hydrophilicity of the Ni-TiO2 surface, denoted as solution C; 10wt% tetraethyl orthosilicate was mixed with 20wt% anhydrous ethanol and magnetically stirred for 30 min; 5wt% deionized water and 0.5wt% ammonia (commercially available concentrated ammonia with a mass concentration of 25%–28% was used) were slowly added and stirred for 60 min to form solution D; solution C was added to solution D and stirred continuously in a water bath at 60℃ for 6 h; after the reaction, the mixture was washed three times alternately with anhydrous ethanol and deionized water, and then vacuum dried at 80℃ for 8 h to obtain SiO2 / Ni-TiO2 catalyst powder for photocatalysis. Figure 1 The prepared SiO2 / Ni-TiO2 catalyst powder has a core-shell structure and is uniformly coated with a silicon dioxide protective layer.

[0044] 3) Preparation of slurry: Mix 10wt% polyvinyl alcohol, 8wt% phenolic resin, 10wt% SiO2 / Ni-TiO2 catalyst powder, 20wt% diamond powder with a particle size of 2.5μm, 30wt% copper powder with a particle size of 3μm, 11wt% talc powder with a particle size of 3μm, 10wt% water and 1wt% dispersant 5040, and stir evenly in a vacuum defoamer to obtain slurry.

[0045] 4) Preparation of gel polishing disc: The slurry was filtered through a 200-mesh sieve to remove large particle agglomerates. The slurry was then poured into a mold and placed in a refrigerator at -20°C for 12 hours to gel at low temperature. After removal, it was allowed to thaw naturally at room temperature for 4 hours. The gel embryo was removed from the mold and immersed in anhydrous ethanol for 24 hours. Then it was placed in an oven at 60°C for 2 hours and sintered again at 180°C for 1 hour. Finally, the surface was polished smooth to obtain the gel polishing disc.

[0046] Example 2

[0047] This embodiment was used to verify the photocatalytic performance of SiO2 / Ni-TiO2 catalyst powder. Three types of catalyst powders—pure TiO2 (Group A), Ni-TiO2 (Group B), and SiO2 / Ni-TiO2 (Group C)—were selected for comparative photocatalytic degradation performance tests. The catalyst powders of Groups A, B, and C were dispersed in deionized water to prepare homogeneous suspensions. Methylene blue was added to each suspension as a photocatalytic degradation indicator, and the mixtures were subjected to continuous ultraviolet light irradiation for 1 hour. After the reaction, the supernatant of each group was collected and analyzed using a UV-Vis spectrophotometer. The intensity change of the characteristic absorption peak of methylene blue at 663 nm indirectly characterized the amount of hydroxyl radicals generated in the system, and the photocatalytic degradation efficiency of the three catalyst groups was compared and evaluated.

[0048] Depend on Figure 2 It can be seen that group B exhibited the highest methylene blue degradation rate and the largest decrease in absorbance, indicating that Ni doping enhanced the photocatalytic activity of TiO2 and promoted the generation of more hydroxyl radicals. Group A had the second highest degradation efficiency, suggesting that unmodified TiO2 still possesses some photocatalytic ability, but at a lower reaction rate. Group C had the lowest degradation efficiency, mainly attributed to the SiO2 coating layer initially suppressing the exposure of active sites on the catalyst. However, this phenomenon precisely verifies the effectiveness of the SiO2 protective layer—it can reduce unnecessary catalyst loss under non-processing conditions. In actual polishing, mechanical friction gradually removes the SiO2 layer, allowing Ni-TiO2 within the catalyst to participate in the reaction, thereby improving the long-term stability and utilization rate of the catalyst.

[0049] Example 3

[0050] This embodiment uses the gel abrasive prepared in Example 1, combined with the polishing method based on the photocatalytic-mechanical synergistic mechanism described in this invention, to polish silicon carbide workpieces. For the specific polishing principle, please refer to [link to relevant documentation]. Figure 3 .

[0051] The experimental parameters were set as follows: the polishing slurry was prepared by mixing 10 parts hydrogen peroxide and 90 parts water; the wavelength of the ultraviolet light source was 365nm and the power was 10W; the rotation speed of the gel abrasive was 90rpm; the flow rate of the polishing slurry was 24mL / min; the initial surface roughness Sa of the silicon carbide workpiece used in the experiment was 62±2nm, and the polishing time was 60min.

[0052] The specific polishing steps are as follows:

[0053] 1) Fix the silicon carbide workpiece on a special fixture, and assemble the above-mentioned gel abrasive mold onto the surface of the rotating base plate;

[0054] 2) Arrange ultraviolet light sources around the rotating base disk, and adjust the incident angle of ultraviolet light through an optical adjustment device to ensure that ultraviolet light is uniformly irradiated onto the working surface of the gel mold;

[0055] 3) The contact pressure between the silicon carbide workpiece and the gel abrasive is adjusted by a precision displacement platform to ensure that the contact pressure is uniform and controllable;

[0056] 4) Start the motor drive system to drive the rotating base disk to rotate and drive the gel abrasive to rotate synchronously, so that a controllable relative sliding friction is formed between the silicon carbide workpiece and the working surface of the gel abrasive; during the polishing process, polishing liquid is continuously supplied to the polishing processing area through a micro pump.

[0057] Comparative Example 1

[0058] This comparative example uses a common diamond gel abrasive to polish a silicon carbide workpiece, in order to compare it with Example 3.

[0059] Experimental parameters: The polishing slurry was prepared by mixing 10 parts hydrogen peroxide and 90 parts water; the grinding wheel rotation speed was 90 rpm; the polishing slurry flow rate was 24 mL / min; the initial surface roughness Sa of the silicon carbide workpiece used in the experiment was 62 ± 2 nm; and the polishing time was 60 min.

[0060] The polishing steps in this comparative example are completely the same as those in Example 3, except that the ultraviolet light source irradiation step is omitted and the photocatalytic-mechanical synergistic mechanism is not used.

[0061] The performance of the polished silicon carbide workpieces from Example 3 and Comparative Example 1 was compared, and the results are as follows: Figure 4 As shown. Compared to traditional diamond gel abrasives, the gel abrasive based on the photocatalytic-mechanical synergistic mechanism of this invention exhibits superior polishing performance: material removal rate is increased by 8%, reaching 0.98 μm / h; simultaneously, workpiece surface roughness is reduced by 32%. Figure 5 It can be seen that the silicon carbide workpiece surface polished by the gel abrasive of the present invention is flat and smooth, and the final surface roughness is reduced to 6.225nm, showing good surface finish.

[0062] Example 4

[0063] This embodiment uses a SiO2 / Ni-TiO2 catalyst. By adjusting the mass percentage of SiO2 / Ni-TiO2 catalyst powder, its effect on the polishing performance of gel abrasives and the surface quality of silicon carbide workpieces was investigated. Specifically, gel abrasives were prepared using SiO2 / Ni-TiO2 catalyst powder with mass percentages of 0 wt%, 5 wt%, 10 wt%, 15 wt%, and 20 wt%. The preparation steps were basically the same as in Example 1, with the only difference being the different mass percentages of SiO2 / Ni-TiO2 catalyst powder. Furthermore, the total mass of the system was adjusted by increasing or decreasing the amount of copper powder to ensure a consistent total proportion of each component.

[0064] Using the above five gel abrasives, all combined with the polishing method based on the photocatalytic-mechanical synergistic mechanism described in Example 3, silicon carbide workpieces with uniform initial surface roughness were polished to investigate the variation law of workpiece surface material removal rate and surface roughness with catalyst concentration.

[0065] Experimental results are as follows Figure 6 As shown, the material removal rate is positively correlated with the catalyst concentration, while the surface roughness decreases monotonically with increasing catalyst concentration. Specific test results are as follows: When the SiO2 / Ni-TiO2 catalyst concentration is in the range of 0–15 wt%, the material removal rate gradually increases with increasing concentration, reaching a maximum of 1.01 μm / h at a concentration of 15 wt%; the surface roughness of the silicon carbide workpiece reaches its optimal value of 6.225 nm when the SiO2 / Ni-TiO2 catalyst concentration is 10 wt%. However, when the SiO2 / Ni-TiO2 catalyst concentration exceeds 10 wt%, the rate of increase in material removal rate slows significantly, and the surface roughness of the workpiece gradually deteriorates.

[0066] The specific reasons for this phenomenon are as follows: An increased proportion of SiO2 / Ni-TiO2 catalyst leads to a corresponding decrease in the proportion of copper powder. Copper powder primarily enhances the mechanical properties and thermal conductivity of gel abrasives. Insufficient copper powder reduces the mechanical strength and wear resistance of the gel abrasive, making it prone to porosity or cracking. This results in uneven contact pressure between the abrasive and the workpiece during polishing, instability in the grinding process, and ultimately, deterioration of the workpiece's surface roughness. Therefore, considering both polishing efficiency and surface quality requirements, the mass proportion of SiO2 / Ni-TiO2 catalyst in the gel abrasive should not exceed 10 wt% in this invention.

[0067] The above description is only a preferred embodiment of the present invention. Therefore, all equivalent changes or modifications made to the structure, features and principles described in the claims of this patent application are included in the scope of this patent application.

Claims

1. A gel abrasive based on a photocatalytic-mechanical synergistic mechanism, characterized in that, The gel abrasive is prepared by the following steps: 1) Preparation of Ni-TiO2 powder: Tetrabutyl titanate was added to anhydrous ethanol, acetylacetone was added and stirred until homogeneous to obtain solution A; nickel nitrate hexahydrate was dissolved in anhydrous ethanol and stirred until completely dissolved to obtain solution B; under constant temperature water bath conditions, solution B was added dropwise to solution A and stirred continuously until a light green uniform sol was formed; deionized water was slowly added to the sol and stirred until the system was homogeneous, and then baked to obtain a dry gel. The dry gel was ground into powder and dried to obtain Ni-TiO2 powder. 2) Preparation of SiO2 / Ni-TiO2 catalyst powder: Ni-TiO2 powder was added to anhydrous ethanol and ultrasonically dispersed until no visible agglomerates were found. Then, hexadecyltrimethylammonium bromide was added and stirred to obtain solution C. Tetraethyl orthosilicate was dissolved in anhydrous ethanol and stirred until homogeneous. Deionized water and ammonia were slowly added and stirred continuously until a homogeneous solution D was formed. Solution C was added to solution D, heated and reacted continuously. After the reaction was completed, the mixture was vacuum dried to obtain SiO2 / Ni-TiO2 catalyst powder for photocatalysis. 3) Preparation of slurry: Mix polyvinyl alcohol, phenolic resin, SiO2 / Ni-TiO2 catalyst powder, diamond powder, copper powder, talc powder, deionized water and dispersant evenly, and put the mixture into a vacuum defoamer and stir until there are no bubbles and the system is uniform to obtain the slurry; 4) Preparation of gel polishing disc: After the slurry is sieved through a screen to remove large particle agglomerates, it is poured into a mold and the slurry is gelled by freezing-thawing method. The gel is placed in an oven for sintering and curing treatment. Finally, the surface of the cured product is trimmed to obtain the gel polishing disc.

2. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 1, characterized in that, The mass percentage of each raw material in step 1) is relative to the total mass of raw materials used to prepare Ni-TiO2 powder in step 1), as follows: tetrabutyl titanate 10wt%~30wt%, anhydrous ethanol 50wt%~80wt%, acetylacetone 0.1wt%~1wt%, nickel nitrate hexahydrate 1wt%~5wt%, and deionized water 10wt%~20wt%.

3. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 2, characterized in that, The preparation process of Ni-TiO2 powder in step 1) is as follows: Tetrabutyl titanate is slowly added to anhydrous ethanol and stirred for 30-60 min; then acetylacetone is added to inhibit the excessively rapid hydrolysis of tetrabutyl titanate, and stirring is continued for 10-30 min to obtain solution A; nickel nitrate hexahydrate is dissolved in anhydrous ethanol and ultrasonically dispersed for 30-50 min until the solution becomes transparent to obtain solution B; solution B is added dropwise to solution A and stirred in a water bath at 60-80℃ for 1-3 h. A uniform light green sol is formed; deionized water is slowly added to the sol to adjust the pH of the system to 3-4, and stirring is continued for 8-12 hours. The sol is then placed in an oven at 60-80℃ and baked for 12-24 hours to form a dry gel; the dry gel is ground into powder and dried at 80-90℃ for 8-12 hours; the dried powder is placed in an oven and heated to 450-500℃ at a heating rate of 2℃ / min, calcined at a constant temperature for 2-3 hours, and then naturally cooled to obtain Ni-TiO2 powder.

4. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 1, characterized in that, In step 2), the mass percentage of each raw material is relative to the total mass of raw materials used to prepare the SiO2 / Ni-TiO2 catalyst powder in step 2), as follows: Ni-TiO2 powder is 15wt% to 25wt%, anhydrous ethanol is 60wt% to 80wt%, hexadecyltrimethylammonium bromide is 0.1wt% to 1wt%, tetraethyl orthosilicate is 1wt% to 10wt%, deionized water is 5wt% to 10wt%, and ammonia is 0.1wt% to 1wt%.

5. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 4, characterized in that, The preparation process of SiO2 / Ni-TiO2 catalyst powder in step 2) is as follows: Ni-TiO2 powder is added to anhydrous ethanol and ultrasonically dispersed for 30-50 min until no visible agglomerates are found; hexadecyltrimethylammonium bromide is added and stirred at 60-70℃ for 1-2 h to improve the surface hydrophilicity of Ni-TiO2 powder, and this is denoted as solution C; tetraethyl orthosilicate is mixed with anhydrous ethanol and stirred for 10-30 min until the system is homogeneous; deionized water and ammonia are slowly added and stirred continuously for 30-60 min to form a homogeneous solution D; solution C is added to solution D and stirred continuously in a water bath at 40-60℃ for 6-8 h; after the reaction is completed, the mixture is washed 1-3 times alternately with anhydrous ethanol and deionized water, and then vacuum dried at 60-80℃ for 8-12 h to obtain SiO2 / Ni-TiO2 catalyst powder for photocatalysis.

6. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 1, characterized in that, In step 3), the mass percentage of each raw material is relative to the total mass of the raw materials used to prepare the slurry in step 3), and is as follows: polyvinyl alcohol 5wt%–15wt%, phenolic resin 5wt%–15wt%, SiO2 / Ni-TiO2 catalyst powder 10wt%–20wt%, diamond powder with a particle size of 2.5μm 10wt%–20wt%, copper powder with a particle size of 3μm 20wt%–40wt%, talc powder with a particle size of 3μm 10wt%–20wt%, deionized water 5wt%–15wt%, and dispersant 0.1wt%–1wt%.

7. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 1, characterized in that, In step 4), the slurry is sieved through a 200-mesh sieve to remove large particle agglomerates, and then the sieved slurry is poured into a mold.

8. The gel abrasive based on the photocatalytic-mechanical synergistic mechanism according to claim 1, characterized in that, In step 4), the mold after pouring the slurry is placed in a refrigerator and subjected to low-temperature gelation treatment at -20 to -30°C for 8 to 12 hours. After removal, it is allowed to thaw naturally at room temperature for 4 to 6 hours. The gel blank is removed from the mold and immersed in anhydrous ethanol for 12 to 24 hours. Then it is placed in an oven and sintered in sections at 50 to 100°C and 120 to 180°C for 1 to 3 hours, respectively. Finally, the surface of the sintered product is polished to obtain the gel mold.

9. A polishing method based on a photocatalytic-mechanical synergistic mechanism, characterized in that, The gel abrasive tool described in any one of claims 1-8 is used, and the specific steps are as follows: 1) Fix the silicon carbide workpiece on the fixture and assemble the gel abrasive onto the surface of the rotating base plate; 2) An ultraviolet light source is arranged around the rotating base disk, and the incident angle of the ultraviolet light is adjusted by an optical adjustment device to ensure that the ultraviolet light is uniformly irradiated onto the working surface of the gel mold; 3) The contact pressure between the silicon carbide workpiece and the gel mold is adjusted by a precision displacement platform to ensure that the contact pressure is uniform and controllable; 4) Start the motor drive system to drive the rotating base disk to rotate and drive the gel abrasive to rotate synchronously, so that a controllable relative sliding friction is formed between the silicon carbide workpiece and the working surface of the gel abrasive; during the polishing operation, a micro-pump is used to continuously supply polishing fluid to the polishing processing area. The polishing fluid is prepared by mixing 0.1-10wt% hydrogen peroxide and the balance water.

10. The polishing method based on the photocatalytic-mechanical synergistic mechanism according to claim 9, characterized in that, The wavelength of the ultraviolet light source is 365nm and the power is 10-50W; the rotation speed of the gel abrasive is 50-100rpm; and the flow rate of the polishing slurry is 20-30mL / min.

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