Flexible polishing method for photoelectric selective catalysis of RB-SiC composite material

Abstract

The invention relates to a flexible polishing method for RB-SiC composite material photoelectric selective catalysis, and belongs to the field of ultra-precision machining.The method comprises the steps that an RB-SiC composite material workpiece is fixed to a clamp, then the workpiece clamp is connected to the positive electrode of a power source, and the RB-SiC composite material is polished; a polishing solution supply pipe mixed with light, electro-catalysis particles, an oxidizing agent and polishing abrasive particles is connected to the negative electrode, voltage is applied to the workpiece, the polishing solution is sprayed to the surface of the workpiece, and a closed loop is formed; ultraviolet light is used for fully irradiating the position where the polishing solution is sprayed on the surface of the workpiece; and finally, a flexible polishing tool rotating at a high speed is adopted, different phases of the RB-SiC composite material workpiece are selectively removed by adjusting the ultraviolet light intensity and the voltage, and multi-phase consistency machining of the RB-SiC composite material workpiece is achieved. The initial performance difference between the two phases is greatly weakened, high-efficiency and high-precision surface polishing is achieved, and the problems of surface scratches, subsurface damage and the like are avoided.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision machining, and in particular relates to a flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials. Background Technology

[0002] Composite materials are novel materials composed of two or more materials with different properties. Due to their significant advantages such as high specific strength, light weight, corrosion resistance, and fatigue resistance, and the good designability and controllability of their composition and structure, composite materials are widely used in aerospace, space mirrors, construction, electronic devices and other fields. They are especially advantageous in scenarios with high requirements for lightweight, high strength and multifunctional integration, showing advantages that traditional metals and inorganic materials cannot replace.

[0003] To address the challenge of achieving uniform surface processing of composite materials, various researchers have employed high-energy physical field-assisted methods, such as plasma-assisted processing and laser-assisted processing. These methods utilize high-energy physical fields to create localized high-temperature zones on the surface of composite workpieces, softening or melting the surface and reducing the initial property differences between different phases. This addresses the issue of hard phases being difficult to remove while soft phases are relatively easy to remove in traditional machining. While these methods have achieved some success in improving surface smoothness, the high temperatures can potentially cause thermal damage to the material substrate or lead to thermal stress cracks. Furthermore, high-energy physical field processing cannot achieve confined processing of the workpiece surface, easily damaging other areas and significantly impacting surface quality, often failing to achieve uniform removal of multiple phases.

[0004] The applicant's earlier application (publication number CN121018297A) discloses an electrocatalytic oxidation flexible polishing method for smoothing the surface of composite materials. The method connects the composite material workpiece to the positive terminal of a power supply and connects a polishing slurry supply pipe containing catalytic abrasive particles and oxidant to the negative terminal of the power supply. A voltage is applied to the composite material workpiece, and the polishing slurry is sprayed onto the surface of the composite material workpiece through the polishing slurry supply pipe to form a closed loop. Then, the surface of different phases of the composite material workpiece is modified into oxides with smaller performance differences through an electrocatalytic oxidation process. The oxides on the surface of the composite material workpiece are removed using a flexible polishing tool.

[0005] RB-SiC is a common composite material used in optical mirrors, formed by the reaction and sintering of SiC and Si phases. Due to the significant differences in hardness and mechanical properties between the two phases, the removal rates of the different phases during processing are inconsistent, increasing the step height difference between the two phases. The smoothing process of this step height difference during polishing directly affects subsequent coating processes, thus impacting the overall surface quality of the workpiece. Even using the method described in the applicant's prior application, it is impossible to remove SiC deeper than Si for RB-SiC materials. Therefore, a flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials is urgently needed. Summary of the Invention

[0006] The purpose of this invention is to provide a flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials, in order to solve the problem that existing RB-SiC composite material polishing methods cannot remove SiC deeper than Si, resulting in a height difference between the SiC and Si phases and poor overall surface smoothness.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: This invention relates to a flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials, comprising the following steps: S1. Fix the RB-SiC composite material workpiece on the fixture; S2. Connect the fixture to the positive terminal of the power supply, connect the polishing slurry supply pipe containing photocatalytic particles, oxidant and polishing abrasive grains to the negative terminal, apply voltage to the workpiece, and spray the polishing slurry onto the surface of the workpiece to form a closed circuit. S3. Use ultraviolet light to fully irradiate the polishing liquid sprayed onto the workpiece surface; S4. A high-speed rotating flexible polishing tool is used, combined with adjustments to the ultraviolet light intensity and voltage, to selectively remove different phases of the RB-SiC composite material workpiece, thereby achieving multi-phase consistency processing of the RB-SiC composite material workpiece.

[0008] Preferably, in step S1, conductive adhesive is used to fix the RB-SiC composite material workpiece onto the fixture.

[0009] Preferably, the photocatalytic particles mixed in the polishing slurry used in S2 are one of metal oxide particles, metal doped particles, or non-metal element doped particles. The metal oxide particles are one of TiO2, ZnO, and CeO2; The metal-doped particles are one of Fe, Cu, and Ag; The non-metallic element doped particles are one of N, C, and S.

[0010] Preferably, the electrocatalytic particles mixed in the polishing liquid used in S2 are one of the following: noble metal nanoparticles, transition metal nanoparticles, metal oxide particles, composite particles doped with non-metallic elements, or MOF particles. The noble metal nanoparticles mentioned are one of Pt, Pd, Au, and Ag particles; The transition metal nanoparticles mentioned are one of Ni, Fe, Cu, and Co particles; The metal oxide particles are one of NiO, Fe2O3, and Fe3O4 particles; The composite particles doped with non-metallic elements are composite particles doped with one or more of N, B, and S.

[0011] Preferably, the oxidant mixed in the polishing slurry used in S2 is a liquid oxidant, a gaseous oxidant, or a solid oxidant; The liquid oxidant is one of H2O2, HNO3, and NaClO; The gaseous oxidant is one of Cl2, F2, and O2; The solid oxidant is one of KMnO4 and MnO2.

[0012] Preferably, the polishing abrasive particles mixed in the polishing slurry used in S2 are one of diamond abrasive particles, silicon dioxide abrasive particles, and cerium dioxide abrasive particles. Different abrasive particles with different hardness and particle sizes are selected according to the hardness and initial roughness of the workpiece being polished.

[0013] Preferably, in step S2, a voltage of 0~20V is applied to the workpiece.

[0014] Preferably, the ultraviolet light used in S3 has a wavelength of 200~400nm, an irradiation distance of 5~50mm, and an optical power of 0~6000mW / cm². 2 .

[0015] If the ultraviolet light wavelength is too small, the photon energy will be too high, which will easily break the bonds and etch the material surface, thereby causing excessive local reaction and increasing the surface roughness of the workpiece. If the ultraviolet light wavelength is too large, it will not meet the excitation conditions of the photocatalyst band gap, and the electron-hole pair generation efficiency will be extremely low, resulting in insufficient surface modification and affecting the processing quality.

[0016] When the irradiation distance is too small, uneven light intensity distribution can easily lead to local overreaction, resulting in uneven oxide layer thickness, micro-pitting, or even increased roughness. When the irradiation distance is too large, the light intensity decreases sharply, resulting in insufficient modification of the workpiece surface and inadequate modification of the polished area, thus reducing the polishing quality.

[0017] Preferably, in step S4, the optimal values ​​of ultraviolet power and voltage are obtained by parameter optimization. The specific method of parameter optimization is as follows: multiple sets of corresponding ultraviolet power, voltage and two-phase height difference data are collected, and the ultraviolet power, voltage and two-phase height difference are used as x, y and z values ​​respectively for fitting. The intersection of the fitted surface and the z = 0 plane is the optimal value of ultraviolet power and voltage when the height difference is minimized.

[0018] Compared with the prior art, the technical solution provided by this invention has the following advantages: 1. The flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials involved in this invention connects the RB-SiC composite workpiece to the positive terminal of a power supply, and connects a polishing slurry supply pipe containing photocatalytic particles, electrocatalytic particles, oxidant, and polishing abrasive particles to the negative terminal. A voltage is applied to the workpiece, and the polishing slurry is sprayed onto the workpiece surface to form a closed loop. At the same time, ultraviolet light is used to fully irradiate the polishing slurry sprayed area on the workpiece surface. Through photoelectro-selective catalytic flexible polishing, the surface of the composite material is modified into oxides, which greatly weakens the initial performance difference between the two phases. Combined with the flexible polishing method, high-efficiency and high-precision surface polishing is achieved, and problems such as surface scratches and subsurface damage are avoided.

[0019] 2. The flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials involved in this invention can control the positive and negative changes in the height difference on the surface of the composite material by adjusting the intensity of the light and electric energy fields, thereby achieving selective removal. The optimal values ​​of ultraviolet light power and voltage are obtained by parameter optimization, realizing the multiphase consistency processing of RB-SiC composite materials. Moreover, the light and electric energy fields are relatively easy to obtain, and there is usually no need to select highly corrosive chemical polishing solutions, which meets the requirements of green manufacturing and environmentally friendly processing.

[0020] 3. The flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials involved in this invention connects a polishing slurry supply pipe containing photocatalytic particles and oxidant to a negative electrode connection, and sprays the polishing slurry onto the workpiece surface to form a closed loop. At the same time, ultraviolet light is used to fully irradiate the polishing slurry sprayed area on the workpiece surface. The two energy fields only act on the contact area of ​​the polishing slurry on the workpiece surface and do not affect other areas of the workpiece surface, thus realizing confined processing. Attached Figure Description

[0021] Figure 1 This is a diagram illustrating the mechanism of photoelectric synergistic catalytic flexible polishing removal. Figure 2 This is a schematic diagram of the fitting surface of ultraviolet light intensity-voltage-two-phase height difference; Figure 3 It is a white light image that selectively removes different phases. Detailed Implementation

[0022] To further understand the content of this invention, the invention will be described in detail with reference to the embodiments. The following embodiments are used to illustrate the invention, but are not intended to limit the scope of the invention.

[0023] See attached document Figure 1 As shown, this invention relates to a flexible polishing method for photoelectro-selective catalysis of RB-SiC composite materials, which includes the following steps: S1. Use conductive adhesive to fix the RB-SiC composite material workpiece on the fixture; S2. Connect the fixture to the positive terminal of the power supply, and connect the polishing slurry supply pipe containing photocatalytic particles, oxidant and polishing abrasive particles to the negative terminal.

[0024] The photocatalytic particles are one of metal oxide particles, metal-doped particles, or non-metal element-doped particles. The characteristics of different types of photocatalytic particles are shown in Table 1.

[0025] Table 1: Characteristics of Different Types of Photocatalytic Particles

[0026] The metal oxide particles are one of TiO2, ZnO, and CeO2; The metal-doped particles are one of Fe, Cu, and Ag; the non-metal-doped particles are one of N, C, and S. Metal oxide particles are typically wide-bandgap and highly efficient at generating electron-hole pairs, making them the preferred photocatalyst. Metal-doped particles, due to the presence of metal ions, can provide additional redox cycles, but may lead to aggregation. Non-metal-doped particles can significantly broaden the photoresponse range. Based on these characteristics of photocatalytic particles, metal oxide particles are preferred.

[0027] The electrocatalytic particles are selected from one of the following: noble metal nanoparticles, transition metal nanoparticles, metal oxide particles, composite particles doped with non-metallic elements, or MOF particles. The characteristics of different types of electrocatalytic particles are shown in Table 2.

[0028] Table 2: Characteristics of Different Types of Electrocatalytic Particles

[0029] The noble metal nanoparticles are one of Pt, Pd, Au, and Ag particles; the transition metal nanoparticles are one of Ni, Fe, Cu, and Co particles; the metal oxide particles are one of NiO, Fe2O3, and Fe3O4 particles; and the composite particles doped with non-metallic elements are composite particles doped with one or more of N, B, and S. Metal nanocatalysts possess high conductivity, high specific surface area, and abundant surface active sites, making them the preferred electrocatalysts. Metal oxide particles exhibit strong multi-valence state regulation capabilities and high chemical stability, but their conductivity is relatively weak. Doped particles can be custom-designed and have high structural controllability. Based on the characteristics of these different types of electrocatalytic particles, metal nanoparticles are preferentially selected as the electrocatalytic particles.

[0030] The oxidant can be a liquid oxidant, a gaseous oxidant, or a solid oxidant. The effects of different types of oxidants are shown in Table 3.

[0031] Table 3: Effects of Different Types of Oxidizing Agents

[0032] The liquid oxidant is one of H₂O₂, HNO₃, and NaClO; the gaseous oxidant is one of Cl₂, F₂, and O₂; and the solid oxidant is one of KMnO₄ and MnO₂. Liquid oxidants are often the preferred choice due to their simple preparation; gaseous oxidants have strong oxidizing properties but are prone to causing localized damage; solid oxidants exhibit uniform reaction and good stability. Based on the characteristics of different types of oxidants, liquid oxidants, which are easier to prepare, are preferred.

[0033] The polishing fluid contains polishing abrasive grains such as diamond abrasive grains, silicon dioxide abrasive grains, and cerium dioxide abrasive grains. Different abrasive grains with different hardness and particle size are selected according to the hardness and initial roughness of the workpiece being polished.

[0034] Apply a voltage of 0~20V to the workpiece and spray polishing liquid onto the workpiece surface to form a closed circuit; S3. Thoroughly irradiate the polishing liquid sprayed onto the workpiece surface with ultraviolet light. The wavelength of the ultraviolet light is 200~400nm, the irradiation distance is 5~50mm, and the optical power is 0~6000mW / cm². 2 .

[0035] If the ultraviolet light wavelength is too small, the photon energy will be too high, which will easily break the bonds and etch the material surface, thereby causing excessive local reaction and increasing the surface roughness of the workpiece. If the ultraviolet light wavelength is too large, it will not meet the excitation conditions of the photocatalyst band gap, and the electron-hole pair generation efficiency will be extremely low, resulting in insufficient surface modification and affecting the processing quality.

[0036] When the irradiation distance is too small, uneven light intensity distribution can easily lead to local overreaction, resulting in uneven oxide layer thickness, micro-pitting, or even increased roughness. When the irradiation distance is too large, the light intensity decreases sharply, resulting in insufficient modification of the workpiece surface and inadequate modification of the polished area, thus reducing the polishing quality.

[0037] S4. A high-speed rotating flexible polishing tool is used, combined with adjustments to the ultraviolet light intensity and voltage, to selectively remove different phases from the RB-SiC composite workpiece, achieving multi-phase uniform processing of the RB-SiC composite workpiece. The removal principle is as follows: Figure 1 As shown, the A phase of the RB-SiC composite workpiece is SiC, and the B phase is Si, with an initial height difference of Hd between the two phases. To achieve a highly smooth workpiece surface, the removal depth of SiC needs to be greater than that of Si. When the polishing slurry is sprayed onto the surface of the RB-SiC composite workpiece, a closed loop is formed between the slurry and the workpiece. Under electrolysis, the oxidant generates some hydroxyl radicals. Simultaneously, the metal catalyst in the polishing slurry undergoes a redox reaction with the oxidant, further increasing the concentration of hydroxyl radicals (·OH) in the slurry. Furthermore, under the influence of current, the metal catalyst reaction becomes more vigorous, and a large number of hydroxyl radicals catalytically modify the two phases on the composite surface to form an oxide layer, reducing the initial performance difference. However, the modification ability of a single electric field on the workpiece surface is limited, failing to achieve over-modification of the A phase to below the B phase, thus failing to achieve selective removal of both phases. Increasing the voltage continuously leads to overall oxidation, deteriorating the workpiece surface quality. Therefore, it is necessary to introduce an ultraviolet light field to further modify the A phase on the workpiece surface. After the polishing liquid on the workpiece surface is irradiated with ultraviolet light, the photocatalytic particles absorb photon energy, and their valence electrons are excited to the conduction band, thereby generating electron-hole pairs. The generated holes have strong oxidizing properties and first react with water molecules or hydroxyl groups (OH-) on the workpiece surface. - The reaction produces hydroxyl radicals; while the conduction band electrons can react with oxygen to produce superoxide ions (O2). - This further participates in the generation of hydroxyl radicals. Under the simultaneous presence of light and electric fields, phase A is over-modified, resulting in a change in the interphase height difference from positive to negative. Therefore, selective catalysis using light and electric fields can form oxide layers with similar hardness and chemical properties on the surfaces of phases A and B. A flexible polishing tool driven by a spindle can then be used to polish the surface of the RB-SiC composite workpiece, achieving mechanical removal. By controlling the ultraviolet light power and applied voltage, the removal rate difference between the two phases of the composite material can be effectively altered, thereby achieving bidirectional control of the surface height difference, i.e., selective removal under different process conditions, such as... Figure 3 The image shown is a surface morphology image after selective removal of different phases, measured using a white light interferometer. Figure 3 Image (a) shows the selective removal of phase B white light. Figure 3(b) is a white light image of selective removal of phase A. By adjusting the ultraviolet light power and voltage, selective removal of the two phases was achieved, and a reversible morphology of "one high and one low" or "one low and one high" on the surface of the composite material was obtained, providing a valid basis for selective removal of two phases in composite materials.

[0038] For composite materials with significant differences in properties between the two phases, the harder phase needs to be modified to a thickness greater than the other phase to achieve uniform removal of both phases. Unlike the case of a single electric field, the simultaneous presence of both light and electric fields allows for selective control of the height difference between the two phases. A pure electric field cannot excessively modify the harder phase A to below phase B, thus limiting the smooth removal of both phases. Therefore, the control over the height difference between the two phases is limited. The photoelectro-selective catalysis method in this invention theoretically allows the height difference between the two phases of the composite material to approach zero. (See attached document.) Figure 2 The figure shown is a graph of experimental data for photoelectro-selective catalysis. This invention uses parameter optimization to obtain the optimal values ​​of ultraviolet light power and voltage. The specific method of parameter optimization is as follows: multiple sets of corresponding ultraviolet light power, voltage and two-phase height difference data are collected. The ultraviolet light power, voltage and two-phase height difference are used as x, y and z values ​​respectively for fitting. The intersection of the fitted surface and the theoretical optimal plane (z = 0) is the optimal value of ultraviolet light power and voltage when the height difference is minimized. The optimal parameters are used to achieve smoothing of the interphase height difference, that is, Hd is infinitely close to 0.

[0039] It should be noted that the method of the present invention is not only applicable to RB-SiC composite materials, but also to silicon-based composite material workpieces, metal-based composite material workpieces, ceramic composite material workpieces, carbon-based composite material workpieces, polymer-based composite material workpieces, etc.

[0040] The present invention has been described in detail above with reference to the embodiments, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made in accordance with the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials, characterized in that, It includes the following steps: S1. Fix the RB-SiC composite material workpiece on the fixture; S2. Connect the fixture to the positive terminal of the power supply, connect the polishing slurry supply pipe containing photocatalytic particles, oxidant and polishing abrasive grains to the negative terminal, apply voltage to the workpiece, and spray the polishing slurry onto the surface of the workpiece to form a closed circuit. S3. Use ultraviolet light to fully irradiate the polishing liquid sprayed onto the workpiece surface; S4. A high-speed rotating flexible polishing tool is used, combined with adjustments to the ultraviolet light intensity and voltage, to selectively remove different phases of the RB-SiC composite material workpiece, thereby achieving multi-phase consistency processing of the RB-SiC composite material workpiece.

2. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: S1 uses conductive adhesive to fix the RB-SiC composite material workpiece onto the fixture.

3. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: The photocatalytic particles mixed in the polishing slurry used in S2 are one of the following: metal oxide particles, metal doped particles, or non-metal element doped particles. The metal oxide particles are one of TiO2, ZnO, and CeO2; The metal-doped particles are one of Fe, Cu, and Ag; The non-metallic element doped particles are one of N, C, and S.

4. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: The polishing liquid used in S2 contains electrocatalytic particles, which are one of the following: noble metal nanoparticles, transition metal nanoparticles, metal oxide particles, composite particles doped with non-metallic elements, or MOF particles. The noble metal nanoparticles mentioned are one of Pt, Pd, Au, and Ag particles; The transition metal nanoparticles mentioned are one of Ni, Fe, Cu, and Co particles; The metal oxide particles are one of NiO, Fe2O3, and Fe3O4 particles; The composite particles doped with non-metallic elements are composite particles doped with one or more of N, B, and S.

5. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: The oxidant mixed in the polishing slurry used in S2 is a liquid oxidant, a gaseous oxidant, or a solid oxidant; The liquid oxidant is one of H2O2, HNO3, and NaClO; The gaseous oxidant is one of Cl2, F2, and O2; The solid oxidant is one of KMnO4 and MnO2.

6. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: The polishing abrasive particles mixed in the polishing fluid used in S2 are one of diamond abrasive particles, silicon dioxide abrasive particles, and cerium dioxide abrasive particles.

7. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: In step S2, a voltage of 0~20V is applied to the workpiece.

8. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: The ultraviolet light used in S3 has a wavelength range of 200~400nm, an irradiation distance of 5~50mm, and an optical power of 0~6000mW / cm². 2 .

9. The flexible polishing method for photoelectroselective catalysis of RB-SiC composite materials according to claim 1, characterized in that: In step S4, the optimal values ​​of ultraviolet power and voltage are obtained by parameter optimization. The specific method of parameter optimization is as follows: multiple sets of corresponding ultraviolet power, voltage and two-phase height difference data are collected, and the ultraviolet power, voltage and two-phase height difference are used as x, y and z values ​​respectively for fitting. The intersection of the fitted surface and the z = 0 plane is the optimal value of ultraviolet power and voltage when the height difference is minimized.

Images