Polishing liquid and polishing method for zinc selenide crystal

Abstract

The present application relates to polishing technology field of zinc selenide crystal. Disclosed are a polishing liquid and a polishing method for zinc selenide crystal. The polishing liquid for zinc selenide crystal comprises ammonium chromate, citric acid and pure water in a mass ratio of 4-6:2-4:100, and the pH value of the polishing liquid is 5-7. The polishing method for zinc selenide crystal comprises polishing the zinc selenide crystal with the polishing liquid. The polishing liquid has good chemical corrosion effect on the surface and subsurface damage layer of the polished ZnSe, can accelerate the removal of the damage layer, improve the polishing efficiency, and is not prone to causing orange peel phenomenon.

Description

Technical Field

[0001] This invention relates to the field of polishing technology for zinc selenide crystals, and more specifically, to polishing solutions and polishing methods for zinc selenide crystals. Background Technology

[0002] ZnSe is an infrared optical material with high transmittance and low absorption coefficient. It exhibits minimal absorption of light at a wavelength of 10.6 μm and possesses high thermal shock resistance, making it the preferred material for optical components in high-power CO2 laser systems. It is widely used in infrared lenses, laser windows, and infrared night vision devices. However, ZnSe has low hardness, making it prone to scratches and chipping during processing. Minimally destructive polishing methods are generally employed, and current processing methods mainly suffer from two problems:

[0003] 1. Low polishing efficiency, poor surface finish, incomplete polishing, or serious scratches and pits;

[0004] 2. Polishing with a polyurethane polishing pad results in fewer scratches, but the aperture cannot be modified; and during the polishing process, the polishing fluid accumulates on the polyurethane pad, resulting in a deeper subsurface damage layer, producing a large amount of orange peel effect and edge collapse.

[0005] 3. Currently, most polishing is done using an alkaline polishing solution made of alumina, hydrogen peroxide, and NaOH, which is inefficient and results in a large number of scratches.

[0006] Therefore, this application is hereby submitted. Summary of the Invention

[0007] The purpose of this invention is to provide a polishing solution and polishing method for zinc selenide crystals.

[0008] This invention is implemented as follows:

[0009] In a first aspect, the present invention provides a polishing solution for zinc selenide crystals, the components of which include ammonium chromate, citric acid and pure water in a mass ratio of 4-6:2-4:100, and the pH value of the polishing solution is 5-7.

[0010] In an optional embodiment, sodium citrate is also included to adjust the pH of the polishing solution to 5-7.

[0011] Secondly, the present invention provides a polishing method for zinc selenide crystals, comprising polishing the zinc selenide crystals with a polishing solution as described in the foregoing embodiments.

[0012] In optional implementations, the following are included:

[0013] Grinding: Abrasive material is obtained by grinding zinc selenide crystal material with boron carbide abrasive;

[0014] First polishing: The abrasive material is white corundum micro powder of specification W1, and the polishing liquid is added. The abrasive material is polished on an asphalt polishing pad for 3-5 hours to obtain the first polishing material.

[0015] Second polishing: The first polishing material is obtained by adding chromium oxide micro powder with a specification of W0.05 to the polishing liquid and polishing on an asphalt polishing pad for 6-8 hours;

[0016] Third polishing: Polish the second polishing material on the asphalt polishing pad for 30-60 minutes by adding the polishing liquid dropwise.

[0017] In an optional implementation, the tar polishing pad is made of tar of type 1 and type 2.

[0018] In an optional implementation, the mass ratio of asphalt of type 1# to type 2# is 1 to 2:1.

[0019] In an optional implementation, the droplet acceleration rate for the first polishing process is 6 to 7 drops / second;

[0020] The droplet acceleration rate during the second polishing process is 6–7 drops / second;

[0021] During the third polishing process, the dripping rate of the polishing slurry is 8-9 drops / second.

[0022] In an optional implementation, the component disk is moved vertically throughout the grinding and polishing process.

[0023] In an optional embodiment, the zinc selenide crystal is a deformable strip. Before grinding, the strip is glued to the component disk with wax. During grinding and the first to third polishing processes, the flatness is controlled within 1λ. After polishing, the lower plate of the component disk is baked to melt the wax.

[0024] After removing the strip and cleaning it, flip it over and apply glue to the plate. Then, continue to grind and polish the unpolished side in the same way.

[0025] In an optional implementation, the baking temperature is 80–90°C.

[0026] The present invention has the following beneficial effects:

[0027] The polishing slurry provided in this application has a good chemical corrosion effect on the ZnSe surface and subsurface damage layer after grinding, which can accelerate the removal of the damage layer, improve polishing efficiency, and prevent orange peel phenomenon. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a photograph showing the surface smoothness of the tar polishing pad involved in the embodiments of this application;

[0030] Figure 2 This is a photograph of the surface of the zinc selenide crystal obtained after polishing in Example 1;

[0031] Figure 3 This is a photograph of the surface of the zinc selenide crystal obtained after polishing in Comparative Example 1.

[0032] Figure 4 This is a photograph of the surface of the zinc selenide crystals obtained after polishing in Comparative Example 2.

[0033] Figure 5 A photograph of the surface of zinc selenide crystals obtained after polishing in Comparative Example 3;

[0034] Figure 6 This is a photograph of the surface of the zinc selenide crystal obtained after polishing in Comparative Example 4.

[0035] Figure 7 A photograph of the surface of zinc selenide crystals obtained after polishing in Comparative Example 5;

[0036] Figure 8 A photograph of the surface of zinc selenide crystals obtained after polishing in Comparative Example 6;

[0037] Figure 9 A photograph of the surface of zinc selenide crystals obtained after polishing in Comparative Example 7;

[0038] Figure 10 A photograph showing the surface smoothness of a typical asphalt disc in Comparative Example 8;

[0039] Figure 11 This is a photograph of the surface of the zinc selenide crystal obtained after polishing, as shown in Comparative Example 8. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0041] The polishing solution and polishing method for zinc selenide crystals provided in the embodiments of the present invention will be described in detail below.

[0042] The polishing solution for zinc selenide crystals provided in this embodiment of the invention comprises ammonium chromate, citric acid, and pure water in a mass ratio of 4-6:2-4:100, and the pH value of the polishing solution is 5-7.

[0043] Ammonium chromate is a corrosion inhibitor that effectively slows down corrosion. Citric acid (C6H8O7) is corrosive and can corrode the surface of zinc selenide, accelerating surface removal efficiency: ZnSe + 2C6H8O7 == Zn3(C6H5O7)2 + 3H2Se↑. H2Se is soluble in water, and pure water is free of impurities, so it will not introduce impurities when used to prepare polishing solutions. Chemical polishing solutions have a good chemical corrosion effect on the surface and subsurface damage layer of ZnSe after grinding, which can accelerate the removal of the damage layer, improve polishing efficiency, and avoid causing orange peel effect.

[0044] Furthermore, the polishing solution also includes sodium citrate to adjust the pH value of the polishing solution to 5-7.

[0045] The polishing method for zinc selenide crystals provided in this application includes polishing the zinc selenide crystals using the polishing solution provided in this application.

[0046] This polishing method has high polishing efficiency because it uses the polishing liquid provided in the embodiments of this application to polish the zinc selenide crystal.

[0047] Preferably, the polishing disc used in the polishing process is an asphalt polishing disc, which is made of asphalt of type 1 and type 2.

[0048] Preferably, the asphalt polishing disc is made of asphalt of type 1# and type 2# in a mass ratio of 1 to 2:1.

[0049] Using high-purity, smooth-surfaced tar of type 1 and type 2, a polishing tar disc is prepared according to the above example. Polishing with the tar disc can effectively modify the aperture and is less likely to cause edge collapse. The polishing disc, together with the polishing liquid provided in the embodiments of this application, can polish zinc selenide crystals, which can effectively improve polishing efficiency, reduce surface roughness, and reduce the depth and range of subsurface damage layer.

[0050] The polishing method is as follows:

[0051] S1, Grinding

[0052] Abrasives are obtained by grinding zinc selenide crystal materials using boron carbide abrasives using existing grinding methods.

[0053] Furthermore, the grinding process is as follows: pre-chamfering → grinding W40 boron carbide 0.04mm to remove tool marks → grinding W20 boron carbide 0.03mm to remove coarse sand holes left by grinding W40 boron carbide → grinding W10 boron carbide 0.02mm to remove coarse sand holes left by grinding W20 boron carbide.

[0054] Polishing with polishing slurry after grinding can increase polishing efficiency by about 20% compared to polishing with polishing slurry alone.

[0055] S2, First Polishing

[0056] The first polishing material is obtained by adding polishing liquid to white corundum micro powder of specification W1 at a rate of 6-7 drops / second on an asphalt polishing pad and polishing for 3-5 hours.

[0057] S3, Second Polishing

[0058] The first polishing material is chromium oxide micro powder with a specification of W0.05, which is added to the polishing liquid at a rate of 6-7 drops / second and polished on the asphalt polishing pad for 6-8 hours to obtain the second polishing material.

[0059] At this point, the surface pitting of the ZnSe material meets the surface finish requirements.

[0060] S4, Third Polishing

[0061] The second polishing material is applied to the asphalt polishing pad by adding polishing liquid at a dripping rate of 8-9 drops / second for 30-60 minutes.

[0062] The polishing method provided in this application adds a third, purely chemical polishing step compared to existing technologies. After the surface pitting reaches the required smoothness, polishing continues using a polishing tar disc. At this point, no polishing powder is added; only the chemical polishing liquid is used for polishing for more than half an hour. This effectively removes fine surface scratches caused by polishing powder, improves surface smoothness, and reduces the likelihood of orange peel texture and edge collapse. The polishing liquid also has good lubrication and heat dissipation properties, which can further improve the surface roughness of the crystal.

[0063] Preferably, during the entire grinding and polishing process, in order to avoid scratches caused by dragging the component disk on the polishing disk, the component disk is picked up vertically.

[0064] Furthermore, a method for polishing small, easily deformable ZnSe strips:

[0065] D1. Use wax to attach the strips to the component tray;

[0066] The small-sized ZnSe strip is processed using the steps S1 to S4 described above. It should be noted that during the grinding and polishing process, the flatness of the strip should be controlled within 1λ. Then, the strip is heated to 80-90℃ in an oven to melt the wax, thereby allowing the strip to detach from the component tray.

[0067] D2. Remove the slats, and protect the surface finish of the slats during this process;

[0068] D3. Clean the slats, flip them over, and then apply glue to the tray.

[0069] D4. Continue to process the unpolished side of the small-sized ZnSe strip using steps S1 to S4 above. Note that during the polishing process, the flatness of the strip should be controlled within 1λ.

[0070] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0071] Example 1

[0072] This embodiment provides a polishing liquid and a polishing method for polishing zinc selenide crystals with a diameter of Ф30×3mm.

[0073] The polishing solution consists of ammonium chromate, citric acid, pure water, and sodium citrate. The solution has a pH of approximately 6, and the mass ratio of ammonium chromate, citric acid, and pure water is 5:3:100.

[0074] The tar polishing pad is made of tar of type 1 and type 2 in a mass ratio of 1.5:1. A photo of its outer surface is shown below. Figure 1 As shown.

[0075] The polishing method is as follows:

[0076] S1, Grinding

[0077] Pre-chamfering → Grinding W40 boron carbide 0.04mm to remove tool marks → Grinding W20 boron carbide 0.03mm to remove coarse sand holes left by grinding W40 boron carbide → Grinding W10 boron carbide 0.02mm to remove coarse sand holes left by grinding W20 boron carbide.

[0078] S2, First Polishing

[0079] The first polishing material was obtained by adding polishing liquid to white corundum micro powder of specification W1 on an asphalt polishing pad at a rate of 6-7 drops / second and polishing for 4 hours.

[0080] S3, Second Polishing

[0081] The first polishing material is chromium oxide micro powder with a specification of W0.05, which is added to the polishing liquid at a rate of 6-7 drops / second and polished on an asphalt polishing pad for 7 hours to obtain the second polishing material.

[0082] At this point, the surface pitting of the ZnSe material meets the surface finish requirements.

[0083] S4, Third Polishing

[0084] The second polishing material was applied to the asphalt polishing pad by adding polishing liquid at a dripping rate of 8-9 drops / second for 30 minutes.

[0085] The component tray is handled vertically throughout the polishing process.

[0086] Zinc selenide crystals obtained after polishing, such as Figure 2 As shown, its surface is free of orange peel, scratches, and spots.

[0087] Example 2

[0088] This embodiment provides a polishing liquid and a polishing method for polishing square zinc selenide crystals with dimensions of 30×30×3mm.

[0089] The polishing solution consists of ammonium chromate, citric acid, pure water, and sodium citrate. The solution has a pH of approximately 5, and the mass ratio of ammonium chromate, citric acid, and pure water is 4:4:100.

[0090] The tar polishing disc is made from tar of type 1 and type 2 in a 1:1 mass ratio.

[0091] The specific preparation method is as follows:

[0092] S1, Grinding

[0093] Pre-chamfering → Grinding W40 boron carbide 0.04mm to remove tool marks → Grinding W20 boron carbide 0.03mm to remove coarse sand holes left by grinding W40 boron carbide → Grinding W10 boron carbide 0.02mm to remove coarse sand holes left by grinding W20 boron carbide.

[0094] S2, First Polishing

[0095] The first polishing material was obtained by adding polishing liquid to white corundum micro powder of specification W1 on an asphalt polishing pad at a rate of 6-7 drops / second and polishing for 3 hours.

[0096] S3, Second Polishing

[0097] The first polishing material is chromium oxide micro powder with a specification of W0.05, which is added to the polishing liquid at a rate of 6-7 drops / second and polished on an asphalt polishing pad for 6 hours to obtain the second polishing material.

[0098] At this point, the surface pitting of the ZnSe material meets the surface finish requirements.

[0099] S4, Third Polishing

[0100] The second polishing material was applied to the asphalt polishing pad at a dripping rate of 8-9 drops per second for 60 minutes.

[0101] The component tray is handled vertically throughout the polishing process.

[0102] The zinc selenide crystals obtained after polishing are the same as those obtained in Example 1, with no orange peel, scratches, or spots on their surface.

[0103] Example 3

[0104] This embodiment provides a polishing fluid and a polishing method for polishing zinc selenide crystal strips with dimensions of 70×25×2.5mm (small size).

[0105] The polishing solution consists of ammonium chromate, citric acid, pure water, and sodium citrate. The solution has a pH of approximately 7, and the mass ratio of ammonium chromate, citric acid, and pure water is 6:2:100.

[0106] The tar polishing disc is made from tar of type 1 and type 2 in a 1:1 mass ratio.

[0107] The specific polishing method in this embodiment is as follows:

[0108] D1:

[0109] Attach the strips to the component tray with wax;

[0110] S1, Grinding

[0111] Pre-chamfering → Grinding W40 boron carbide 0.04mm to remove tool marks → Grinding W20 boron carbide 0.03mm to remove coarse sand holes left by grinding W40 boron carbide → Grinding W10 boron carbide 0.02mm to remove coarse sand holes left by grinding W20 boron carbide.

[0112] S2, First Polishing

[0113] The first polishing material was obtained by adding white corundum micro powder of specification W1 to the polishing slurry at a rate of 6-7 drops / second on an asphalt polishing pad and polishing for 5 hours.

[0114] S3, Second Polishing

[0115] The first polishing material is chromium oxide micro powder with a specification of W0.05, which is added to the polishing liquid at a rate of 6-7 drops / second and polished on an asphalt polishing pad for 8 hours to obtain the second polishing material.

[0116] At this point, the surface pitting of the ZnSe material meets the surface finish requirements.

[0117] S4, Third Polishing

[0118] The second polishing material was applied to the asphalt polishing pad at a dripping rate of 8-9 drops per second for 60 minutes.

[0119] In steps S1 to S3, the flatness of the slats is controlled within 1λ.

[0120] After polishing, bake the lower part of the component tray in an oven at about 80°C to completely melt the wax.

[0121] D2: Remove the slats and apply a surface finish protection to the slats;

[0122] D3: Clean the slats, flip them over, and then apply glue to the tray;

[0123] D4: Continue to process the unpolished side of the small-sized ZnSe strip using steps S1 to S4 above. It should be noted that during the polishing process, the flatness of the strip should be controlled within 1λ.

[0124] The zinc selenide crystals obtained after polishing are the same as those obtained in Example 1, with no orange peel, scratches, or spots on their surface.

[0125] Comparative Example 1

[0126] This comparative example is essentially the same as Example 1, except that the mass ratio of ammonium chromate, citric acid, and pure water is 10:5:100, and the pH value is approximately 4. The polished zinc selenide crystals are as follows: Figure 3 As shown, the crystal surface exhibits orange peel-like texture and pitting.

[0127] Comparative Example 2

[0128] This comparative example is essentially the same as Example 1, except that the mass ratio of ammonium chromate, citric acid, and pure water is 3:10:100, sodium citrate was not used to adjust the pH, and the pH of the solution is approximately 2. The polished zinc selenide crystals are as follows: Figure 4 As shown, the crystal surface is severely corroded, with pits and scratches.

[0129] Comparative Example 3

[0130] This comparative example is basically the same as Example 1, except that: this comparative example uses a polishing pad made of No. 1 tar for polishing. The zinc selenide crystals obtained by polishing are as follows: Figure 5 As shown, shallow scratches and pits are present on the crystal surface.

[0131] Comparative Example 4

[0132] This comparative example is basically the same as Example 1, except that: this comparative example uses a polishing pad made of No. 2 tar for polishing. The zinc selenide crystals obtained by polishing are as follows: Figure 6 As shown, the crystal surface has deep scratches and a small number of pits.

[0133] Comparative Example 5

[0134] This comparative example is basically the same as Example 1, except that the third polishing step (S4) is replaced with a 30-minute polishing step (S3). The zinc selenide crystals obtained from polishing are as follows: Figure 7 As shown, due to the short polishing time, the scratches were not completely removed.

[0135] Comparative Example 6

[0136] Existing methods were used, and the zinc selenide crystals were polished using a polyurethane polishing pad. The resulting zinc selenide crystals are shown below. Figure 8 As shown, the crystal surface exhibits orange peel texture, scratches, and pitting.

[0137] Comparative Example 7

[0138] Polishing was performed using existing methods and an alkaline polishing solution with a pH of 8. The resulting zinc selenide crystals were as follows: Figure 9 As shown, the crystal surface exhibits orange peel texture and scratches.

[0139] Comparative Example 8

[0140] Provide a common asphalt pad, such as Figure 10 As shown.

[0141] Polishing was performed using the same method as in Example 1, but with a standard tar pad as in this example. The resulting zinc selenide crystals were as follows: Figure 11 As shown, the surface of the zinc selenide crystal is covered with deep scratches.

[0142] In summary, the polishing slurry provided in this application embodiment has a good chemical corrosion effect on the ZnSe surface and subsurface damage layer after grinding, which can accelerate the removal of the damage layer, improve polishing efficiency, and prevent orange peel phenomenon.

[0143] In the preferred technical solution, the zinc selenide crystal is first ground, and then polished with the polishing liquid provided in this application. Compared with polishing liquid alone, the polishing efficiency can be increased by 20%.

[0144] In the preferred embodiment, polishing with tar polishing pads made of tar of type 1# and type 2# can effectively modify the aperture and is less likely to cause edge collapse; the polishing pads, together with the polishing liquid provided in the embodiments of this application, can effectively improve polishing efficiency, reduce surface roughness, and reduce the depth and range of the subsurface damage layer.

[0145] In the preferred embodiment, the addition of a chemical polishing slurry-only polishing step effectively removes fine surface scratches caused by polishing powder, improves surface smoothness, and reduces the likelihood of orange peel texture and edge collapse. This polishing slurry also has good lubrication and heat dissipation properties, further enhancing the surface smoothness of the crystal.

[0146] The ZnSe crystal polished by the method provided in this embodiment of the invention can have 0-2 surface scratches (compared to 5-6 scratches by traditional processing methods). Processing with this method will not produce orange peel or collapsed edges.

[0147] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A polishing method for zinc selenide crystals, characterized in that, The method includes polishing zinc selenide crystals with a polishing slurry, wherein the polishing slurry comprises ammonium chromate, citric acid and pure water in a mass ratio of 4~6:2~4:100, and sodium citrate for adjusting the pH value of the polishing slurry to 5~7; Polishing methods include: Grinding: Abrasive material is obtained by grinding zinc selenide crystal material with boron carbide abrasive; First polishing: The abrasive material is white corundum micro powder of specification W1, and the polishing liquid is added. Polishing is carried out on an asphalt polishing pad for 3-5 hours to obtain the first polishing material; Second polishing: The first polishing material is obtained by adding chromium oxide micro powder with a specification of W0.05 to the polishing liquid and polishing on an asphalt polishing pad for 6-8 hours; Third polishing: Apply the second polishing material to the asphalt polishing pad by dripping the polishing liquid for 30-60 minutes; The tar polishing disc is made of tar of type 1 and type 2.

2. The polishing method according to claim 1, characterized in that, The mass ratio of asphalt of type 1# to type 2# is 1~2:

1.

3. The polishing method according to claim 1, characterized in that, The droplet acceleration rate for the first polishing process is 6-7 drops / second; The droplet acceleration rate for the second polishing process is 6-7 drops / second; During the third polishing process, the dripping rate of the polishing fluid is 8-9 drops / second.

4. The polishing method according to claim 1, characterized in that, Throughout the grinding and polishing process, the component disk is moved vertically.

5. The polishing method according to claim 1, characterized in that, The zinc selenide crystal is a deformable strip. Before grinding, wax is used to stick the strip to the component disk. During grinding and the first to third polishing processes, the flatness is controlled within 1λ. After polishing, the lower plate of the component disk is baked to melt the wax. After removing the strip and cleaning it, flip it over and apply glue to the plate. Then, continue to grind and polish the unpolished side in the same way.

6. The polishing method according to claim 5, characterized in that, The baking temperature is 80~90℃.

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