Photochemical reaction and shear thickening combined polishing method for diamond workpiece

Abstract

This invention discloses a photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces. The method involves processing the diamond workpiece using a specific shear thickening polishing fluid. During polishing, ultraviolet light is continuously irradiated into the polishing fluid. The photocatalyst microparticles in the polishing fluid absorb the energy of the ultraviolet light, generating photogenerated holes to form hydroxyl radicals. On one hand, the hydroxyl radicals combine with the Si dangling bonds on the surface of nano-silica to form -Si-OH groups. On the other hand, the hydroxyl radicals in the shear thickening polishing fluid contact the rough surface of the workpiece, forming a large number of -OH functional groups on its surface. During polishing, the friction between the workpiece surface and the shear thickening polishing fluid causes a local temperature increase in the fluid, promoting a condensation reaction to form C-O-Si chemical bonds. Then, under the action of strong shear force, the C-C back bonds on the surface of the diamond workpiece are broken, removing the C-O-Si chemical bonds and achieving efficient and high-quality polishing.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision polishing technology, specifically to a photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces. Background Technology

[0002] Diamond, due to its unique physical and chemical properties, possesses advantages such as high hardness, high strength, good wear resistance, good thermal conductivity, and excellent chemical stability. It is widely used in many fields, including machining, semiconductor materials, and electronics manufacturing. With the rapid development of ultra-precision polishing and semiconductor technology, diamond has become one of the most promising materials in modern industry. However, precisely because of these excellent properties, diamond is also an extremely difficult material to process. Traditional polishing methods for diamond workpieces mainly include laser melting, mechanical polishing, and chemical mechanical polishing. Laser melting polishing is highly efficient, effectively removing surface materials from diamonds. However, it suffers from low polishing precision and is prone to forming a thermal damage layer on the diamond surface / subsurface. Vaporized residual impurities can easily adhere to the machined surface, affecting the diamond's properties. Furthermore, laser melting equipment is expensive, leading to high production costs. Mechanical polishing offers low production costs, high flexibility, and fast polishing speeds, but it can only perform rough polishing, failing to meet the requirements of ultra-precision workpieces. It also easily causes significant damage to the diamond and polishing wheel (defects and lattice distortion). Chemical mechanical polishing utilizes etchants to improve polishing efficiency, achieving smooth surfaces, ultra-low surface / subsurface damage, large polishing area, and low cost. However, it can only polish planar workpieces and is unsuitable for complex-shaped diamond workpieces. It is also environmentally unfriendly, exhibiting a very low MRR value, and requires high temperatures during processing.

[0003] Shear thickening polishing is a novel polishing technology developed in recent years, suitable for polishing complex curved surfaces. During polishing, the relative motion between the workpiece and the polishing slurry causes the shear thickening effect of the slurry, which has shear thickening properties, to increase its viscosity dramatically. This increases the holding force on the abrasive grains, thus forming a flexible "fixed abrasive" that adheres to the workpiece surface in the processing area, enabling high-quality polishing of complex curved surfaces. However, for diamond workpieces (e.g., diamond tools), their high hardness and wear resistance make surface material removal extremely difficult. Ordinary shear thickening polishing processes are insufficient to effectively remove the micro-peaks on the surface of diamond workpieces, failing to achieve efficient and high-precision polishing. Adding strong oxidants to the shear thickening polishing slurry can improve material removal efficiency, but it can also damage and oxidize other parts of the diamond workpiece. Without treatment, this reduces the polishing consistency of the interconnected heterogeneous surfaces (interconnection surfaces between diamond material and substrate material) on the workpiece surface. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a photochemical reaction and shear thickening composite polishing method. The shear thickening polishing fluid used in this method contains specific components. During polishing, ultraviolet light is continuously irradiated into the polishing fluid. During the polishing process, the photochemical reaction, tribochemical reaction and shear thickening effect work synergistically to achieve efficient and high-quality polishing of the diamond workpiece surface.

[0005] This invention provides the following technical solutions:

[0006] A photochemical reaction and shear thickening composite polishing method is applicable to diamond workpieces. This method utilizes a shear thickening polishing device to polish the diamond workpiece. During polishing, a relative shearing action occurs between the diamond workpiece and the shear thickening polishing fluid in the polishing tank, achieving material removal. The shear thickening polishing fluid contains hydrogen peroxide, nano-silica, and photocatalyst microparticles. During polishing, ultraviolet light is irradiated into the shear thickening polishing fluid. The photocatalyst microparticles in the polishing fluid absorb the energy of the ultraviolet light, exciting electrons from the valence band to the conduction band, forming free electrons and holes. The holes have strong oxidizing properties, catalyzing the H2O or H2O2 adsorbed on the surface of the photocatalyst microparticles to generate highly oxidizing hydroxyl radicals. Hydroxyl radicals combine with Si dangling bonds on the surface of nano-silica to form -Si-OH groups, which coat the surface of nano-silica and make it superhydrophilic. Another group of hydroxyl radicals combines with C dangling bonds on the diamond surface to generate -OH functional groups. During polishing, the friction between the diamond workpiece and the shear-thickened polishing fluid raises the temperature of the system, causing the -OH functional groups on the diamond workpiece surface to undergo a condensation reaction with the -Si-OH groups on the nano-silica surface to form CO-Si chemical bonds. During polishing, the strong shear force on the diamond workpiece breaks the C-C back bonds, thereby removing the CO-Si chemical bonds on the surface of the diamond workpiece, thus achieving the purpose of polishing.

[0007] Compared with existing technologies, the polishing method of this invention utilizes the synergistic effect of chemical reaction, tribochemical reaction, and shear thickening effect to achieve efficient and high-quality polishing of diamond workpiece surfaces, demonstrating significant progress. The specific beneficial effects are as follows: Diamond workpieces are processed using a specific shear-thickening polishing fluid. During polishing, the polishing fluid is continuously irradiated with ultraviolet light. The photocatalyst micropowder in the polishing fluid absorbs the energy of the ultraviolet light, generating numerous hydroxyl radicals through photogenerated holes. On one hand, these hydroxyl radicals combine with the Si dangling bonds on the surface of nano-silica to form -Si-OH groups, covering the surface of the nano-silica and making it superhydrophilic. On the other hand… In the process of polishing, the shear-thickening agglomerates formed by the relative motion between the shear-thickening polishing fluid and the workpiece carry a large number of hydroxyl radicals and come into contact with the rough surface of the workpiece, forming a large number of -OH functional groups on its surface. During polishing, the friction between the workpiece surface and the shear-thickening polishing fluid causes the local temperature of the shear-thickening polishing fluid to rise, which promotes the condensation reaction between the -Si-OH functional groups on the surface of nano-silica and the -OH functional groups on the surface of diamond workpiece to form CO-Si chemical bonds. Then, under the action of strong shear force, the C-C back bonds on the surface of diamond workpiece are broken, thereby removing the CO-Si chemical bonds on the surface of diamond workpiece, achieving the purpose of efficient and high-quality polishing.

[0008] As an optimization, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the polishing tank is made of a light-transmitting material, and during polishing, the ultraviolet light source is positioned below or to the side of the polishing tank. Thus, during polishing, the ultraviolet light source shines through the polishing tank onto the shear-thickening polishing fluid, and positioning the ultraviolet light source below or to the side of the polishing tank avoids interference from the ultraviolet light source equipment to other equipment during the processing operation.

[0009] As an optimization, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the ultraviolet light preferably uses short-wave ultraviolet light with a wavelength of 150-450nm and an ultraviolet intensity preferably of 1000-3000mW / cm². 2 The distance between the ultraviolet light source and the bottom of the polishing tank can be 2-5 mm. Under this wavelength range and ultraviolet intensity, the photocatalytic micropowder in the shear-thickened polishing fluid undergoes a good photochemical reaction with ultraviolet light, which is beneficial to improving polishing efficiency.

[0010] As an optimized approach, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the shear thickening polishing liquid contains hydrogen peroxide at a mass fraction of 1%-3%, nano-silica at a mass fraction of 45%-55%, and photocatalyst micropowder at a mass fraction of 2%-4%.

[0011] As an optimized approach, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the shear thickening polishing fluid also contains an adsorbent corrosion inhibitor. During polishing, the adsorbent corrosion inhibitor acts on the surface of the diamond workpiece to form a corrosion-inhibiting film. As the diamond workpiece is continuously polished, the surface roughness peaks decrease, the surface tends to stabilize, and the thickness of the corrosion-inhibiting film tends to stabilize, thereby reducing surface damage to the diamond workpiece substrate material caused by nano-silica and photocatalyst micropowder. Further, preferably, the mass ratio of hydrogen peroxide reagent to adsorbent corrosion inhibitor in the shear thickening polishing fluid is 3-5:1.

[0012] As an optimized approach, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the photocatalyst micropowder is nano-zinc oxide. Nano-zinc oxide has good biocompatibility and low toxicity, and has minimal environmental impact.

[0013] As an optimization, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the diamond workpiece can be a part made of polycrystalline diamond, single-crystal diamond, or diamond coating material.

[0014] As an optimized approach, in the aforementioned photochemical reaction and shear thickening composite polishing method for diamond workpieces, the diamond workpiece is a diamond tool. During polishing, the tool holder is clamped and fixed using a fixture corresponding to the lower end of the workpiece shaft, exposing the surface to be machined. The height is controlled to immerse the surface in the shear thickening polishing fluid. The rotation of the workpiece shaft drives the diamond tool to rotate, while the polishing groove rotates in the opposite direction. When the diamond workpiece is a diamond tool, the above polishing setup can achieve higher polishing efficiency and quality.

[0015] As an optimized approach, in the aforementioned photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, the polishing tank rotates at 80-110 rpm, and the workpiece shaft rotates at 2-10 rpm. Polishing efficiency is high and polishing effect is good at these speeds, which is beneficial for industrial implementation. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the photochemical reaction and shear thickening composite polishing process of the present invention;

[0017] Figure 2 This is a schematic diagram of the photochemical reaction and shear thickening composite polishing principle of the present invention;

[0018] Figure 3 This is a schematic diagram of the microscopic removal process of the photochemical reaction and shear thickening composite polishing of the present invention;

[0019] The labels in the attached diagram are as follows: 1-polishing tank; 2-workpiece shaft; 3-main driver; 4-ultraviolet light generator; 5-polycrystalline diamond micro-drill; 6-ultraviolet light; 7-nano silica; 8-shear-thickening polishing fluid; 9-adsorption type corrosion inhibitor; 10-shear-thickening agglomerate; 11-modified nano silica. Detailed Implementation

[0020] The technical solution of the present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials and equipment used in this invention can be purchased from the market or are commonly used in the field.

[0021] The photochemical reaction and shear thickening composite polishing method for diamond workpieces of the present invention primarily belongs to the shear thickening polishing method. This method utilizes a shear thickening polishing device to polish the diamond workpiece. During polishing, a relative shearing action occurs between the diamond workpiece and the shear thickening polishing fluid in the polishing tank, achieving material removal.

[0022] Unlike existing technologies, the present invention uses a shear-thickening polishing slurry containing hydrogen peroxide, nano-silica, and photocatalyst micropowder. During polishing, ultraviolet light is irradiated into the shear-thickening polishing slurry. The photocatalyst micropowder in the slurry absorbs the energy of the ultraviolet light, exciting electrons from the valence band to the conduction band, forming free electrons and holes. The holes have strong oxidizing properties, catalyzing the H2O or H2O2 adsorbed on the surface of the photocatalyst micropowder to generate hydroxyl radicals with strong oxidizing properties. Some of the hydroxyl radicals combine with the Si dangling bonds on the surface of the nano-silica to form -Si-OH groups, covering the surface of the nano-silica and modifying it to be superhydrophilic. Other hydroxyl radicals combine with the C dangling bonds on the surface of diamond. During polishing, the friction between the diamond workpiece and the shear-thickened polishing fluid raises the temperature of the system, causing the -OH functional groups on the surface of the diamond workpiece to undergo a condensation reaction with the -Si-OH groups on the surface of nano-silica to form CO-Si chemical bonds. During polishing, the strong shear force on the diamond workpiece breaks the C-C back bonds, thereby removing the CO-Si chemical bonds on the surface of the diamond workpiece (the polishing fluid with the shear-thickening effect wraps the CO-Si chemical bonds and pulls them off the surface of the diamond workpiece, removing the outermost C atoms of the rough diamond surface). The micro-roughness peaks on the workpiece surface are effectively removed under the mutual coupling of friction and chemistry, thus achieving the purpose of polishing.

[0023] During processing, the shear friction between the shear-thickened agglomerates and the workpiece surface generates a large amount of heat locally, causing a significant rise in local temperature. Temperatures between 70-100℃ are more conducive to the condensation reaction. In implementing this invention, the relative shear rate between the workpiece and the polishing fluid is controlled between 60-300 s. -1 The middle range is more suitable.

[0024] Example (see) Figure 1-3 )

[0025] In this embodiment, the diamond workpiece is a polycrystalline diamond micro-drill 5. The shear-thickening polishing machine used for processing includes a polishing tank 1, a workpiece shaft 2, a main driver 3, and an ultraviolet light generator 4. The main driver 3 is located below the polishing tank 1, driving the polishing tank 1 to rotate. The workpiece shaft 2 is located above the right side of the polishing tank 1. The handle of the polycrystalline diamond micro-drill 5 is inserted into the corresponding clamping hole at the lower end of the workpiece shaft 2 to achieve clamping, exposing the surface to be processed. The height is controlled so that the surface to be processed is immersed in the shear-thickening polishing fluid 8. The rotation of the workpiece shaft 2 drives the polycrystalline diamond micro-drill 5 to rotate. At the same time, the polishing tank 1 rotates in the opposite direction. The polishing tank 1 is made of quartz material. The ultraviolet light generator 4 is located below the bottom end of the polishing tank 1. The ultraviolet light generator 4 emits ultraviolet light 6, which shines through the polishing tank 1 and irradiates the shear-thickening polishing fluid 8.

[0026] In this embodiment, the shear-thickening polishing fluid 8 contains hydrogen peroxide (2% by mass of the polishing fluid), nano-silica 7 (50% by mass of the polishing fluid), photocatalyst micropowder (nano-zinc oxide, 3% by mass of the polishing fluid), and adsorbent corrosion inhibitor 9 (with a mass ratio of 1:4 to hydrogen peroxide). By utilizing the rheological effect of the polishing fluid under shear stress, and in conjunction with the photochemical reaction in the polishing fluid, efficient and ultra-precision polishing of the surface of the polycrystalline diamond micro-drill 5 is achieved. Specifically, during the polishing process, ultraviolet light passes through the polishing tank 1 and irradiates the flowing shear-thickened polishing fluid 8. After absorbing the energy of the ultraviolet light 6, the photocatalyst micropowder (nano zinc oxide) in the polishing fluid excites electrons from the valence band to the conduction band, forming free electrons and holes. The holes have strong oxidizing properties and catalyze the H2O or H2O2 adsorbed on the surface of nano zinc oxide to generate hydroxyl radicals with strong oxidizing properties. Some of the hydroxyl radicals combine with the Si dangling bonds on the surface of nano silica 7 to form -Si-OH groups, which cover the surface of nano silica 7 and modify its surface, making it superhydrophilic.

[0027] During rotation, the shear-thickening polishing fluid 8 moves relative to the polycrystalline diamond micro-drill 5, forming shear-thickening aggregates 10. Another portion of hydroxyl radicals are encapsulated by these aggregates 10 and come into contact with the rough surface of the polycrystalline diamond micro-drill 5. The original diamond surface contains numerous rough peak-valley structures and a large number of C dangling bonds, which readily combine with hydroxyl radicals to generate -OH functional groups. Simultaneously, the relative motion between the shear-thickening polishing fluid 8 and the polycrystalline diamond micro-drill 5 generates heat through shear friction, raising the local system temperature. The -OH functional groups on the surface of the polycrystalline diamond micro-drill 5 come into contact with the -Si-OH groups on the surface of the nano-silica 7, generating heat. A condensation reaction occurs, where oxygen atoms combine to release an H2O molecule, forming a CO-Si chemical bond. Then, the shear force generated by the relative motion between the modified nano-silica 11 in the shear-thickened polishing fluid 8 and the polycrystalline diamond micro-drill 5 breaks the CC back bond, thereby removing the CO-Si chemical bond on the surface of the polycrystalline diamond micro-drill 5 (the CC bond is longer than the CO bond and is more easily broken by shear force). The micro-roughness peaks on the surface of the polycrystalline diamond micro-drill 5 are effectively removed under the mutual coupling of friction and chemistry, achieving the purpose of polishing. This series of reactions is repeated continuously during the polishing process to achieve high-efficiency ultra-precision polishing.

[0028] The adsorbent corrosion inhibitor 9 in the shear-thickening polishing fluid 8 forms a corrosion-inhibiting film on the surface of the polycrystalline diamond micro-drill 5 matrix material (diamond workpieces are generally composed of matrix material and diamond; the polycrystalline diamond micro-drill 5 uses cemented carbide as the matrix material and is obtained by welding polycrystalline diamond onto the matrix material). As the polycrystalline diamond micro-drill 5 is continuously polished, the roughness peaks of the matrix material decrease, the surface tends to stabilize, and the thickness of the corrosion-inhibiting film tends to stabilize, reducing the surface damage of nano-silica 7 and nano-zinc oxide to the polycrystalline diamond micro-drill 5 matrix material.

[0029] Polishing parameters:

[0030] Processing parameters numerical values Ultraviolet light wavelength 350nm Ultraviolet light intensity <![CDATA[1800mW / cm 2 <!-- 4 -->]]> Distance between ultraviolet light generator and bottom of polishing tank 2mm Polishing tank speed 100rpm Workpiece shaft speed 5rpm Polishing time 20min

[0031] Under the above processing parameters, the surface roughness near the cutting edge of the polycrystalline diamond micro-drill in this embodiment decreased from 230±20nm to below 20nm, and the cutting edge surface was smooth and undamaged, achieving the high efficiency, high quality, and damage-free surface quality requirements of diamond material cutting tool edges.

[0032] The foregoing general description of the invention and its specific embodiments should not be construed as limiting the technical solution of the invention. Those skilled in the art, based on the disclosure of this application, can add, reduce, or combine the disclosed technical features in the foregoing general description and / or embodiments without departing from the constituent elements of the invention, to form other technical solutions within the scope of protection of this application.

Claims

1. A photochemical reaction and shear thickening composite polishing method applicable to diamond workpieces, characterized in that: This method uses a shear-thickening polishing device to polish diamond workpieces. During polishing, there is a relative shearing action between the diamond workpiece and the shear-thickening polishing fluid in the polishing tank, thereby achieving material removal. The shear-thickening polishing fluid contains hydrogen peroxide, nano-silica, and photocatalyst microparticles. During polishing, ultraviolet light is irradiated into the shear-thickening polishing fluid. The photocatalyst microparticles in the polishing fluid absorb the energy of the ultraviolet light, exciting electrons from the valence band to the conduction band, forming free electrons and holes. The holes have strong oxidizing properties, catalyzing the H2O or H2O2 adsorbed on the surface of the photocatalyst microparticles to generate hydroxyl radicals with strong oxidizing properties. Some of the hydroxyl radicals combine with the Si dangling bonds on the surface of the nano-silica to form -Si-OH groups, covering the surface of the nano-silica and modifying it to be superhydrophilic. Another... Some hydroxyl radicals combine with the C dangling bonds on the diamond surface to generate -OH functional groups. During polishing, the friction between the diamond workpiece and the shear-thickened polishing fluid raises the temperature of the system, causing the -OH functional groups on the diamond workpiece surface to undergo a condensation reaction with the -Si-OH groups on the nano-silica surface to form CO-Si chemical bonds. During polishing, the strong shear force on the diamond workpiece breaks the C-C back bonds, thereby removing the CO-Si chemical bonds on the diamond workpiece surface. The micro-roughness peaks on the workpiece surface are effectively removed under the mutual coupling of friction and chemistry, thus achieving the purpose of polishing.

2. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 1, characterized in that: The polishing tank is made of a light-transmitting material. During polishing, an ultraviolet light source is placed below or to the side of the bottom of the polishing tank.

3. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 2, characterized in that: The ultraviolet light used is short-wave ultraviolet light with a wavelength of 150-450nm and an ultraviolet intensity of 1000-3000mW / cm². 2 The distance between the ultraviolet light source and the bottom of the polishing tank is 2-5mm.

4. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 3, characterized in that: In the shear-thickening polishing slurry, hydrogen peroxide accounts for 1%-3% of the slurry's mass fraction, nano-silica accounts for 45%-55% of the slurry's mass fraction, and photocatalyst micropowder accounts for 2%-4% of the slurry's mass fraction.

5. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 1, characterized in that: The shear-thickening polishing fluid also contains an adsorption-type corrosion inhibitor. During polishing, the adsorption-type corrosion inhibitor acts on the surface of the diamond workpiece to form a corrosion-inhibiting film. As the diamond workpiece is continuously polished, the roughness peaks of the matrix material decrease, the surface tends to stabilize, and the thickness of the corrosion-inhibiting film tends to stabilize, thereby reducing the surface damage of nano-silica and photocatalytic micropowder to the matrix material of the diamond workpiece.

6. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 5, characterized in that: In the shear-thickening polishing fluid, the mass ratio of hydrogen peroxide reagent to adsorption-type corrosion inhibitor is 3-5:

1.

7. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 1, characterized in that: The photocatalyst micropowder is nano zinc oxide.

8. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 1, characterized in that: The diamond workpiece is a part made of polycrystalline diamond, single-crystal diamond, or diamond coating material.

9. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 8, characterized in that: The diamond workpiece is a diamond tool. During polishing, the shank of the diamond tool is inserted into the corresponding fixture hole at the lower end of the workpiece shaft to achieve clamping, exposing the surface to be machined. The height is controlled so that the surface to be machined is immersed in the shear-thickening polishing fluid. The rotation of the workpiece shaft drives the diamond tool to rotate, while the polishing groove rotates in the opposite direction.

10. The photochemical reaction and shear thickening composite polishing method for diamond workpieces according to claim 9, characterized in that: During polishing, the polishing tank rotates at 80-110 rpm, and the workpiece shaft rotates at 2-10 rpm.

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