A method for producing porous diamond

Abstract

A method for preparing porous diamond is disclosed, aiming to address the problems of high cost and low efficiency in existing methods for preparing porous diamond. The preparation method includes: 1. Cleaning the diamond and then pre-treating it by hydrogen-oxygen plasma etching at 900-950℃; 2. Sequentially depositing a titanium film and an iron film onto the diamond using magnetron sputtering; 3. Placing the titanium-iron film-coated diamond in an MPCVD device, increasing the gas pressure and power, and performing metal-catalyzed hydrogen-oxygen plasma etching at 950-1000℃; 4. Immersing the etched diamond in a mixed acid solution for high-temperature acid washing. This invention directly prepares a porous structure on the diamond surface, resulting in a denser and more uniform porous structure with a three-dimensional etched structure. The diameter of ordinary pores in the porous structure is approximately 1-20 μm, and the diameter of macropores is approximately 50 μm or more, significantly increasing the specific surface area of ​​the diamond.

Description

Technical Field

[0001] This invention belongs to the field of diamond material preparation, specifically relating to a method for preparing porous diamond. Background Technology

[0002] Diamond is widely used in many industrial and social fields due to its excellent properties. However, to meet the many new and potential applications of diamond materials, it is necessary to form structures with specific morphology and roughness on the diamond surface. Porous diamond materials have attracted widespread attention due to their flexible surface functions, high surface area-to-volume ratio, and self-sharpening properties. Porous surface structures can significantly improve the electrical properties of boron-doped diamond (BDD), expanding its applications in electrochemical electrodes, supercapacitors, catalysts, and other fields. Simultaneously, porous surface structures can also significantly improve the adhesion of ordinary diamond, expanding its applications in ultra-precision grinding and polishing. Currently, the most effective methods for preparing porous diamonds are ICP, FIB plasma processing, or chemical vapor deposition heteroepitaxial diamond; however, these methods are costly and limited to experimental research, making them impractical for industrial production. Preparing porous diamond structures through transition metal etching is a simple and inexpensive method, but current transition metal etching methods produce porous diamonds with small pores and shallow depths, making it difficult to meet application requirements. Summary of the Invention

[0003] To address the problems of high cost and low efficiency in existing methods for preparing porous diamond, this invention provides a method for preparing porous diamond that can achieve the preparation of densely porous surface diamonds with pore sizes of 1-20 μm.

[0004] The method for preparing porous diamond according to the present invention is carried out according to the following steps:

[0005] I. Diamond Pretreatment: The surface roughness Ra of the diamond is reduced to less than 50 nm by laser cutting and tribomechanical polishing. Then, it is subjected to high-temperature acid washing with a mixed solution of concentrated sulfuric acid and concentrated nitric acid, followed by ultrasonic cleaning to obtain the cleaned diamond. The cleaned diamond is then placed in an MPCVD device, and 300 sccm of hydrogen and 5-7 sccm of oxygen are introduced. When the gas pressure reaches 10-15 mbar, the plasma is activated. The gas pressure is increased to 200-220 mbar, and hydrogen-oxygen plasma etching is performed at a temperature of 900-950℃ to obtain the pretreated diamond.

[0006] 2. Coating: The pretreated diamond is placed in a vacuum plasma cleaner for oxygen surface treatment for 40-90 seconds, and then placed in a magnetron sputtering coating device. After evacuation, argon gas with a flow rate of 15-30 sccm is introduced. A titanium target is used. After ignition, sputtering is performed at a pressure of 1-2 Pa and a power of 70-90 W for 3-4 minutes. Then, after evacuation again, argon gas with a flow rate of 30-40 sccm is introduced. An iron target is used. After ignition, an iron film is sputtered at a pressure of 1-2 Pa and a power of 90-110 W to obtain a diamond coated with a titanium-iron film.

[0007] III. Metal-catalyzed hydrogen-oxygen plasma etching: Diamond coated with a titanium-iron film is placed in an MPCVD apparatus. After evacuation, 400 sccm of hydrogen and 10-15 sccm of oxygen are introduced into the chamber. When the pressure reaches 10-15 mbar, 1500W microwaves are input to form plasma. Subsequently, the pressure is (rapidly) increased to 170-180 mbar and the power to 2200-2400W, and maintained at 750-780℃ for 15-30 minutes. Then, the pressure is adjusted to 250-260 mbar and the power to 3500-3700W, and metal-catalyzed hydrogen-oxygen plasma etching is performed at 950-1000℃. After etching, the pressure is adjusted to 50-60 mbar and the power to 1700-1900W, and maintained at 400-450℃ for 15-20 minutes to obtain the etched diamond.

[0008] IV. Residual Metal Cleaning: The etched diamond is immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for high-temperature acid washing to remove residual metal and obtain porous diamond.

[0009] This invention proposes a method for preparing porous diamond, improving upon the transition metal etching method. Unlike conventional pure transition metal etching methods that use high-temperature annealing to prepare porous diamond, this invention uses a titanium-iron catalytic hydrogen-oxygen plasma etching method to achieve simple and efficient porous diamond preparation. Before depositing the iron film, this invention first deposits a titanium transition layer. Relying on the strong bonding force between titanium and diamond, the adhesion of the iron film to the diamond surface is improved, preventing the iron film from detaching under vacuum and high temperature. During the etching process, this invention maintains a temperature of 750-780℃ for a period of time to promote uniform mixing of the titanium-iron metal film and its melting and uniform spreading on the diamond surface. This prevents uneven etching caused by directly raising the etching temperature, which could lead to the metal film shrinking to the center or excessive spreading, resulting in uneven distribution of the metal film on the diamond surface. This improves the uniformity of the final porous diamond surface structure. This invention utilizes a high-temperature hydrogen-oxygen plasma environment for metal-catalytic etching of diamond. The continuous reaction of hydrogen and oxygen groups with graphite carbon atoms generated on the diamond surface promotes continuous catalysis, enhancing the etching capability and resulting in a porous structure with larger pore sizes and deeper surface micropores. This produces porous diamonds with a larger specific surface area and higher surface roughness. During the final etching stage, the temperature is maintained at 400-450°C for a period during the cooling phase by adjusting the gas pressure and power. The hydrogen-oxygen plasma then removes any residual graphite generated during the metal-catalytic etching process. The three processes in the etching stage of this invention ensure that the metal film is uniformly etched onto the diamond surface to create a porous surface with larger pore size and greater depth, while simultaneously removing residual graphite. Compared to the uneven distribution of the porous structure caused by the uneven distribution of the metal film in conventional transition metal high-temperature annealing etching method, the low catalytic etching reaction rate caused by the accumulation of metal catalytic products, the short reaction process duration resulting in small surface pores and shallow depth, and the problem of the large amount of residual graphite generated by transition metal catalytic etching requiring additional treatment, this invention achieves efficient and superior preparation of porous structures on the diamond surface.

[0010] The method for preparing porous diamond according to the present invention has the following beneficial effects:

[0011] 1. Simple process and fast preparation speed. The iron-catalyzed plasma etching process is simple and can quickly prepare porous structures. The preparation of porous structures can be completed in 0.5-2 hours, and the longer the time, the denser the porous structure on the diamond surface.

[0012] 2. Excellent porous structure preparation effect. This invention directly prepares porous structures on the diamond surface. Compared with methods that prepare porous diamond through chemical vapor deposition heteroepitaxial growth on a heterostructure substrate with a porous surface or randomly arranged organic compounds, the method described in this invention does not introduce additional impurity elements or impurity substrates. Compared with ICP, FIB, and other plasma etching methods, this invention has lower costs, faster preparation speed, denser surface porous structures, and larger pore sizes. Compared with existing transition metal catalytic etching methods, the porous diamond structure prepared by this invention is superior, with a denser and more uniform porous structure distribution, exhibiting a three-dimensional etched structure rather than a simple two-dimensional planar porous etched structure. The diameter of ordinary pores in the porous structure is approximately 1-20 μm, and the diameter of macropores is approximately 50 μm or more, significantly increasing the specific surface area of ​​diamond.

[0013] 3. Wide applicability. The method described in this invention is applicable to single-crystal diamonds with 100, 111, and 110 crystal planes, as well as polycrystalline diamonds, avoiding the limitation of chemical vapor deposition heteroepitaxial growth, which can only prepare polycrystalline porous diamonds. Attached Figure Description

[0014] Figure 1 The image shown is an electron microscope image of the 100-facet single-crystal porous diamond surface obtained in the example.

[0015] Figure 2 The image shown is an electron microscope image of the 110-crystal plane single-crystal porous diamond surface obtained in the example.

[0016] Figure 3 The image shown is an electron microscope image of the polycrystalline porous diamond surface obtained in the example. Detailed Implementation

[0017] Specific Implementation Method 1: The preparation method of porous diamond in this implementation method is carried out according to the following steps:

[0018] I. Diamond Pretreatment: The surface roughness Ra of the diamond is reduced to less than 50 nm by laser cutting and tribomechanical polishing. Then, it is subjected to high-temperature acid washing with a mixed solution of concentrated sulfuric acid and concentrated nitric acid, followed by ultrasonic cleaning to obtain the cleaned diamond. The cleaned diamond is then placed in an MPCVD device, and 300 sccm of hydrogen and 5-7 sccm of oxygen are introduced. When the gas pressure reaches 10-15 mbar, the plasma is activated. The gas pressure is increased to 200-220 mbar, and hydrogen-oxygen plasma etching is performed at a temperature of 900-950℃ to obtain the pretreated diamond.

[0019] 2. Coating: The pretreated diamond is placed in a vacuum plasma cleaner for oxygen surface treatment for 40-90 seconds, and then placed in a magnetron sputtering coating device. After evacuation, argon gas with a flow rate of 15-30 sccm is introduced. A titanium target is used. After ignition, sputtering is performed at a pressure of 1-2 Pa and a power of 70-90 W for 3-4 minutes. Then, after evacuation again, argon gas with a flow rate of 30-40 sccm is introduced. An iron target is used. After ignition, an iron film is sputtered at a pressure of 1-2 Pa and a power of 90-110 W to obtain a diamond coated with a titanium-iron film.

[0020] III. Metal-catalyzed hydrogen-oxygen plasma etching: Diamond coated with a titanium-iron film is placed in an MPCVD apparatus. After evacuation, 400 sccm of hydrogen and 10-15 sccm of oxygen are introduced into the chamber. When the pressure reaches 10-15 mbar, 1500W microwaves are input to form plasma. Subsequently, the pressure is (rapidly) increased to 170-180 mbar and the power to 2200-2400W, and maintained at 750-780℃ for 15-30 minutes. Then, the pressure is adjusted to 250-260 mbar and the power to 3500-3700W, and metal-catalyzed hydrogen-oxygen plasma etching is performed at 950-1000℃. After etching, the pressure is adjusted to 50-60 mbar and the power to 1700-1900W, and maintained at 400-450℃ for 15-20 minutes to obtain the etched diamond.

[0021] IV. Residual Metal Cleaning: The etched diamond is immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for high-temperature acid washing to remove residual metal and obtain porous diamond.

[0022] In step two of this embodiment, the thickness of the magnetron sputtered titanium film is 10-20 nm, and the thickness of the iron film is 200-300 nm.

[0023] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the mixed solution of concentrated sulfuric acid and concentrated nitric acid in steps one and four is made by mixing concentrated sulfuric acid with a mass concentration of 98.3% and concentrated nitric acid with a mass concentration of 69% in a volume ratio of 1:1.

[0024] Specific Implementation Method 3: This implementation method differs from Specific Implementation Method 1 or 2 in that the temperature of high-temperature pickling in step 1 is 70-90℃, and the high-temperature pickling time is 20-30 minutes.

[0025] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the ultrasonic cleaning process described in step one uses acetone, deionized water, and alcohol in sequence for ultrasonic cleaning, with each cleaning session lasting 10-15 minutes.

[0026] Specific Implementation Method 5: This implementation method differs from Specific Implementation Methods 1 to 4 in that the diamond in step 1 is a single-crystal diamond or a polycrystalline diamond, and the diamond particle size is 100-500mm.

[0027] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that an iron target is used in step two, and the time for sputtering the iron film is 40-60 minutes under conditions of 1-2 Pa air pressure and 90-110 W power after ignition.

[0028] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that the vacuuming process described in step three, where the vacuum level reaches 3×10⁻⁶, is different. -6 -5×10 -6 mbar.

[0029] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that the metal-catalyzed hydrogen-oxygen plasma etching time in step three is 0.5-2 hours.

[0030] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that in step three, the gas pressure and power are subsequently adjusted to 260 mbar and 3600 W, and metal catalytic hydrogen-oxygen plasma etching is performed at a temperature of 1000°C; after etching, the gas pressure is adjusted to 60 mbar and the power to 1800 W, and the temperature is maintained at 450°C for 15 minutes.

[0031] Specific Implementation Method 10: This implementation method differs from Specific Implementation Methods 1 to 9 in that the temperature of the high-temperature pickling treatment in step 4 is 180-280℃.

[0032] Example: The preparation method of porous diamond in this example is carried out according to the following steps:

[0033] I. Diamond Pretreatment: The surface roughness Ra of the diamond is reduced to less than 50 nm by laser cutting and tribomechanical polishing. Then, it is acid-washed at 80°C for 20 min by a mixed solution of 98.3% concentrated sulfuric acid and 69% concentrated nitric acid (volume ratio 1:1). After ultrasonic cleaning, the cleaned diamond is obtained. The cleaned diamond is then placed in an MPCVD device, and 300 sccm of hydrogen and 6 sccm of oxygen are introduced. When the pressure reaches 12 mbar, the plasma is activated. The pressure is increased to 220 mbar, and the diamond is etched by hydrogen-oxygen plasma at 920°C for 10 min to obtain the pretreated diamond.

[0034] II. Coating: The pretreated diamond is placed in a vacuum plasma cleaner for oxygen surface treatment for 50 seconds, and then placed in a magnetron sputtering coating apparatus, where a molecular pump is used to evacuate the vacuum to 8.0 × 10⁻⁶.-4 Below Pa, argon gas at a flow rate of 20 sccm was introduced, and a titanium target was used. After ignition, sputtering was performed at 1 Pa pressure and 80 W power for 3 min, and then the vacuum was re-evacuated to 8.0 × 10⁻⁶ Pa. -4 Below Pa, argon gas with a flow rate of 40 sccm was introduced, and an iron target was used. After ignition at 6 Pa pressure, an iron film was sputtered at 2 Pa pressure and 100 W power for 50 min to obtain diamond with a titanium-iron film.

[0035] III. Metal-catalyzed hydrogen-oxygen plasma etching: Diamond coated with a titanium-iron film is placed in an MPCVD apparatus. After evacuation, 400 sccm of hydrogen and 10 sccm of oxygen are introduced into the chamber. When the pressure reaches 15 mbar, 1500 W of microwaves are input to form plasma. Subsequently, the pressure is (rapidly) increased to 180 mbar and the power to 2400 W, and maintained at 760°C for 20 min. Then, the pressure and power are adjusted to 260 mbar and the power to 3600 W, and metal-catalyzed hydrogen-oxygen plasma etching is performed at 1000°C. After etching, the pressure is adjusted to 60 mbar and the power to 1800 W, and maintained at 450°C for 15 min. Finally, the temperature is lowered to obtain the etched diamond.

[0036] IV. Residual Metal Cleaning: Immerse the etched diamond in a mixed solution of concentrated sulfuric acid and concentrated nitric acid. Heat the solution to 180°C on a heating platform and hold for 15 minutes. Then heat the solution to 280°C and hold for 1 hour to remove residual metal and obtain porous diamond.

[0037] In this embodiment, the diamond samples used were 100-faceted diamond, 110-faceted diamond, and polycrystalline diamond, respectively. Figure 1 It can be seen that the surface of the 100-faceted diamond has been etched with a uniform and dense three-dimensional porous structure with a pore size of about 1-20μm, which improves the surface roughness and significantly increases the specific surface area.

[0038] Depend on Figure 2 As can be seen, similar to the 100 crystal plane, the 110 crystal plane was etched with the same three-dimensional porous structure, indicating that the etching method of the present invention is applicable to all crystal planes of single-crystal diamond.

[0039] Depend on Figure 3 It is evident that the surface of polycrystalline diamond is similar to that of single-crystal diamond, with a three-dimensional porous surface structure etched out, and the pore diameter is about 10-30 μm. This indicates that the method of the present invention is equally applicable to both single-crystal and polycrystalline diamond, and is a porous diamond preparation method covering all types of diamond.

Claims

1. A method for preparing porous diamond, characterized in that... The preparation method is carried out according to the following steps: I. Diamond Pretreatment: The surface roughness Ra of the diamond is reduced to less than 50 nm by laser cutting and tribomechanical polishing. Then, it is subjected to high-temperature acid washing with a mixed solution of concentrated sulfuric acid and concentrated nitric acid, followed by ultrasonic cleaning to obtain the cleaned diamond. The cleaned diamond is then placed in an MPCVD device, and 300 sccm of hydrogen and 5-7 sccm of oxygen are introduced. When the gas pressure reaches 10-15 mbar, the plasma is activated. The gas pressure is increased to 200-220 mbar, and hydrogen-oxygen plasma etching is performed at a temperature of 900-950℃ to obtain the pretreated diamond.

2. Coating: The pretreated diamond is placed in a vacuum plasma cleaner for oxygen surface treatment for 40-90 seconds, and then placed in a magnetron sputtering coating device. After evacuation, argon gas with a flow rate of 15-30 sccm is introduced. A titanium target is used. After ignition, sputtering is performed at a pressure of 1-2 Pa and a power of 70-90 W for 3-4 minutes. Then, after evacuation again, argon gas with a flow rate of 30-40 sccm is introduced. An iron target is used. After ignition, an iron film is sputtered at a pressure of 1-2 Pa and a power of 90-110 W to obtain a diamond coated with a titanium-iron film. III. Metal-catalyzed hydrogen-oxygen plasma etching: Diamond coated with a titanium-iron film is placed in an MPCVD apparatus. After evacuation, 400 sccm of hydrogen and 10-15 sccm of oxygen are introduced into the chamber. When the pressure reaches 10-15 mbar, 1500W microwaves are input to form plasma. Then, the pressure is increased to 170-180 mbar and the power to 2200-2400W, and the temperature is maintained at 750-780℃ for 15-30 minutes. Subsequently, the pressure is adjusted to 250-260 mbar and the power to 3500-3700W, and metal-catalyzed hydrogen-oxygen plasma etching is performed at a temperature of 950-1000℃. After etching, adjust the air pressure to 50-60 mbar and the power to 1700-1900 W, and maintain the temperature at 400-450℃ for 15-20 minutes to obtain the etched diamond. IV. Residual Metal Cleaning: The etched diamond is immersed in a mixed solution of concentrated sulfuric acid and concentrated nitric acid for high-temperature acid washing to remove residual metal and obtain porous diamond.

2. The method for preparing porous diamond according to claim 1, characterized in that... The mixed solution of concentrated sulfuric acid and concentrated nitric acid in steps one and four is made by mixing concentrated sulfuric acid with a mass concentration of 98.3% and concentrated nitric acid with a mass concentration of 69% in a volume ratio of 1:

1.

3. The method for preparing porous diamond according to claim 1, characterized in that... In step one, the temperature for high-temperature pickling is 70-90℃, and the pickling time is 20-30 minutes.

4. The method for preparing porous diamond according to claim 1, characterized in that... The ultrasonic cleaning process described in step one involves sequentially using acetone, deionized water, and alcohol, with each cleaning session lasting 10-15 minutes.

5. The method for preparing porous diamond according to claim 1, characterized in that... In step one, the diamond can be either single-crystal diamond or polycrystalline diamond.

6. The method for preparing porous diamond according to claim 1, characterized in that... In step two, an iron target is used. After ignition, the iron film is sputtered at a pressure of 1-2 Pa and a power of 90-110 W for 40-60 minutes.

7. The method for preparing porous diamond according to claim 1, characterized in that... Step three involves evacuating the vacuum until the vacuum level reaches 3×10⁻⁶. -6 -5×10 -6 mbar.

8. The method for preparing porous diamond according to claim 1, characterized in that... In step three, the metal-catalyzed hydrogen-oxygen plasma etching time is 0.5-2 hours.

9. The method for preparing porous diamond according to claim 1, characterized in that... In step three, the gas pressure is then adjusted to 260 mbar, the power to 3600 W, and metal-catalyzed hydrogen-oxygen plasma etching is performed at a temperature of 1000 °C. After etching, adjust the air pressure to 60 mbar and the power to 1800 W, and maintain the temperature at 450℃ for 15 minutes.

10. The method for preparing porous diamond according to claim 1, characterized in that... The temperature for the high-temperature pickling process in step four is 180-280℃.

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