A method for preparing porous single crystal diamond

Abstract

The method for preparing porous single crystal diamond provided by the present invention comprises the following steps: using a diamond seed as a growth substrate, and a mixture of diamond powder crystals and metal catalyst powders is wrapped around the diamond seed crystals and then sealed and formed; under high temperature and high pressure conditions in a diamond stable zone, the diamond powder crystals adjust the crystal orientation in a molten catalyst environment, and directional attachment and growth are performed with the diamond seed crystals as a substrate; the metal catalyst reduces the temperature and pressure conditions required for crystal growth, provides a suitable environment for the directional attachment of the diamond powder crystals, and increases the growth rate of the diamond. As the diamond seed crystals grow, due to the fast growth rate, gaps and other defects between the diamond powder crystals and at the attachment and bonding points with the seed crystal substrate, after the seed crystals grow up, the diamond powder crystals and the metal catalyst that are not involved in the growth are removed by pickling and vibration impact to obtain a porous single crystal diamond.

Description

Technical Field

[0001] The invention belongs to the technical field of crystal growth, and specifically relates to a method for preparing porous single-crystal diamond, in particular to a method for synthesizing a large porous diamond single crystal. Background Art

[0002] The synthesis of diamond usually involves adding a catalyst to graphite under high temperature and high pressure conditions to convert it into diamond. Currently, the commonly used methods for synthesizing large single crystals of diamond in the field of high temperature and high pressure are: temperature gradient method and thin film growth method.

[0003] Regarding the synthesis of porous diamonds, K. Honda et al. in Japan used plasma etching to prepare nanoporous honeycomb diamonds, but the synthetic diamonds were in the form of thin films with a pore size of only 400 nm. Varga et al. used the CVD method to grow porous diamond films of various shapes, but they were only thin films and small in size; Aleksei Chepurov et al. in Russia used iron nanoparticles to etch artificial single crystal diamond in a hydrogen atmosphere to obtain porous diamonds with a pore size of 0.5-0.7μm and a single pore depth of 3μm.

[0004] The porous diamonds synthesized above are all relatively small porous diamond film layers with low strength and small thickness of porous diamond layers, which are not suitable for wide applications. Summary of the invention

[0005] Based on the above problems, an object of the present invention is to provide a method for preparing porous single crystal diamond.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is: a method for preparing porous single crystal diamond, comprising the following steps:

[0007] Step 1, mixing diamond seed crystals, diamond powder crystals and metal catalyst powder, and then sealing and wrapping them to obtain a sealing block;

[0008] Step 2, treating the sealing block under high temperature and high pressure conditions of 5.2 to 8 GPa and 1200° C. to 1600° C., and removing the sealing package to obtain a diamond blank;

[0009] Step 3: Acid washing and vibration impact are used to remove diamond particles and metal catalyst particles that have not participated in the growth of the diamond block to obtain porous single crystal diamond.

[0010] The diamond seed is used as the growth matrix, and the mixture of diamond powder and metal catalyst powder is wrapped around the diamond seed and then sealed. Under the high temperature and high pressure conditions in the diamond growth stable zone, the diamond powder grows with the diamond seed as the matrix. Under the action of the catalyst, the diamond powder adjusts its own grain orientation and achieves directional attachment with the diamond seed to achieve the same grain orientation. The metal catalyst reduces the temperature and pressure conditions required for crystal growth, provides a suitable environment for the directional attachment of diamond powder, and increases the growth rate of diamond. As the diamond seed grows, due to the fast growth rate, there are gaps and other defects between the diamond powder and the attachment to the seed matrix. After the seed grows up, the diamond powder and metal catalyst that do not participate in the growth are removed by acid washing and vibration impact to obtain porous single crystal diamond. The particle size of the porous single crystal diamond is affected by the size of the diamond seed crystal grains, the temperature and pressure conditions, and the high temperature and high pressure treatment time. The larger the diamond seed crystal grain size and the longer the high temperature and high pressure treatment time, the larger the particle size of the porous single crystal diamond. Porous single crystal diamonds of different sizes can be obtained according to needs. Large-sized porous single crystal diamonds can be used to make cutting tools, and small-sized porous single crystal diamonds can be used to make adsorbents and abrasives. When made into cutting tools, due to its porous characteristics, the self-sharpening of the cutting tool is enhanced, and the holding force of the diamond and the handle base is enhanced, thereby improving the fit between the cutting tool and the handle and the cutting performance. When used as adsorption materials and electrode materials, since porous diamonds have a higher specific surface area and a larger contact area with the material, they will greatly improve the adsorption performance and electrolysis efficiency.

[0011] Specifically, in step 1, the diamond seed crystals are mixed with diamond powder crystals and metal catalyst powder and then placed in a mold for pre-pressing to obtain a block sample, which is then sealed and wrapped to obtain a sealed block. The pre-pressing into blocks facilitates sealing and wrapping, and at the same time removes oxygen in the raw material particles to avoid oxidation of the raw materials in step 2.

[0012] Specifically, in step 1, the block sample is first reduced with hydrogen at 300-1200° C. and then sealed and packaged. The hydrogen reduction is to further remove oxygen in the sample to ensure that no oxygen will oxidize the raw material during the sintering process in step 2.

[0013] Specifically, in step 1, the diamond seed is a single crystal diamond block with a grain size of more than 100 μm, and the grain size of the diamond powder crystal is preferably 3nm to 10 μm. In order to prepare a larger porous diamond single crystal, the diamond seed size can be selected to be larger, but due to the difference in interfacial energy, the larger the difference between the specific surface area of ​​the diamond seed and the diamond microcrystal within the above grain size range, the better, so the size of the diamond powder crystal should be smaller, maintaining about 1 μm, and the ratio of the grain size of the diamond seed to the grain size of the diamond powder crystal is (10 to 1000): 1. If the matching is unreasonable, for example: the diamond seed is selected to be 1 cm, and the diamond powder crystal is selected to be 1 nm, and the specific surface area difference between the two is too large, then the diamond powder crystal will self-nucleate and will not grow; the metal catalyst powder is at least one of iron powder, cobalt powder, nickel powder and alloy powder thereof, such as iron-nickel alloy powder. Specifically, in step 1, the diamond powder crystals and the metal catalyst powder are mixed in a volume / weight ratio of 1: (1-10). The ratio can grow within a certain range. If the ratio is too small, the diamond powder crystals will be completely melted into the catalyst and will not grow. If the ratio is too large, the diamond powder crystals will agglomerate or grow abnormally and will not adhere to and grow on the surface of the seed crystal.

[0014] Specifically, in step 1, the sample is sealed and wrapped in an assembly block, and the assembly block includes a magnesium oxide cavity, a carbon tube, a dolomite tube, and a phyllite block which are sequentially sleeved from the inside to the outside, wherein a dolomite ring and a molybdenum sheet are sequentially arranged at the upper and lower ends of the dolomite tube from the inside to the outside, respectively, through openings coaxial with the dolomite tube are arranged at the upper and lower ends of the phyllite block, a steel plug is arranged in the channel to abut the molybdenum sheet, a carbon sheet is arranged at the upper and lower ends of the carbon tube, a carbon column whose two ends are respectively abutted against the molybdenum sheet and the carbon sheet is arranged on the inner ring of the dolomite ring, and the diamond seed is mixed with the diamond powder crystal and the metal catalyst powder and then sealed and wrapped in the magnesium oxide cavity; in step 2, the assembled assembly block is placed in a six-sided top press for high temperature and high pressure treatment, the press is started, and the six top hammers of the press squeeze the six faces of the phyllite block, thereby generating high pressure at the sample in the magnesium oxide cavity, the upper and lower top hammers of the press are energized, and high temperature is generated in the assembly.

[0015] Specifically, in step 2, the sealing block is treated at 5.2-8 GPa and 1200° C.-1600° C. for 10 minutes or more.

[0016] Specifically, the operation of pickling the diamond block in step 3 is as follows: washing it in hot dilute nitric acid for a long time, then soaking it in aqua regia for washing, dissolving the metal catalyst in the pickling solution, and finally removing impurities by ultrasonic vibration.

[0017] The beneficial effects of the present invention are:

[0018] The diamond seed is used as the growth matrix, and the mixture of diamond powder and metal catalyst powder is wrapped around the diamond seed and then sealed. Under the high temperature and high pressure conditions in the diamond growth stable zone, the diamond powder grows with the diamond seed as the matrix. Under the action of the catalyst, the diamond powder adjusts its own grain orientation and achieves directional attachment with the diamond seed to achieve the same grain orientation. The metal catalyst reduces the temperature and pressure conditions required for crystal growth, provides a suitable environment for the directional attachment of diamond powder, and increases the growth rate of diamond. As the diamond seed grows, due to the fast growth rate, there are gaps and other defects between the diamond powder and the attachment to the seed matrix. After the seed grows up, the diamond powder and metal catalyst that do not participate in the growth are removed by acid washing and vibration impact to obtain porous single crystal diamond. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is an assembly diagram used in the embodiment;

[0020] Figure 2 This is an overall picture of the porous single crystal diamond block obtained in Example 1;

[0021] Figure 3 This is a partial SEM test image of the porous single crystal diamond block obtained in Example 1;

[0022] Figure 4 This is the Raman detection spectrum of the porous diamond single crystal obtained in Example 1;

[0023] Figure 5 is the Laue diffraction pattern of the porous diamond single crystal obtained in Example 1;

[0024] Figure 6 This is a SEM test image of the porous single crystal diamond block obtained in Example 2;

[0025] Figure 7 This is a SEM test image of the porous single crystal diamond block obtained in Example 3;

[0026] Figure 8 This is a SEM test image of the porous single crystal diamond block obtained in Example 4;

[0027] Fig. 9 This is a SEM test image of the porous single crystal diamond block obtained in Example 5;

[0028] Among them, 1 is a magnesium oxide cavity, 2 is a carbon tube, 3 is a dolomite tube, 4 is a pyrophyllite block, 5 is a dolomite ring, 6 is a molybdenum sheet, 7 is a steel plug, 8 is a carbon sheet, 9 is a carbon column, 10 is a block sample, 11 is, and 12 is. DETAILED DESCRIPTION

[0029] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0030] Example 1

[0031] This embodiment provides a method for preparing porous single crystal diamond, comprising the following steps:

[0032] Step 1: Place diamond powder with a grain size of 1 micron and metal catalyst powder in a three-dimensional mixer at a volume ratio of 1:4 and mix them evenly. Then wrap the mixed powder around an artificial single crystal diamond with a grain size of 590 microns and place it in a mold for pre-pressing to obtain a block sample. The block sample is hydrogen reduced at 900°C and then sealed and wrapped in an assembly block. Figure 1 As shown, the assembly block includes a magnesium oxide cavity, a carbon tube, a dolomite tube, and a pyrophyllite block which are sequentially sleeved from the inside to the outside, wherein a dolomite ring and a molybdenum sheet are sequentially arranged at the upper and lower ends of the dolomite tube from the inside to the outside, respectively, through openings coaxial with the dolomite tube are arranged at the upper and lower ends of the pyrophyllite block, a steel plug is arranged in the channel to abut against the molybdenum sheet, a carbon sheet is arranged at the upper and lower ends of the carbon tube, a carbon column whose two ends abut against the molybdenum sheet and the carbon sheet is arranged at the inner ring of the dolomite ring, and the block sample is sealed and wrapped in the magnesium oxide cavity;

[0033] Step 2, placing the assembled assembly block in a six-sided top press, sintering at 5.5 GPa and 1260° C. for 60 minutes, and removing the sealing package to obtain a diamond blank;

[0034] Step 3: The diamond block is cleaned in dilute nitric acid, and then soaked in aqua regia to remove diamond powder and metal catalyst powder that are not involved in the growth, and finally ultrasonically cleaned to obtain porous single crystal diamond.

[0035] The porous single crystal diamond obtained in this example was subjected to SEM scanning electron microscope test, and the test results are as follows Figure 2 , 3 As shown, the size of the porous single crystal diamond obtained is about 683 microns; Raman test was performed on it, and the test results are as follows Figure 4 As shown, the initial line represents the Raman peak of the artificial single crystal diamond sample, the convex line represents the Raman peak of the porous single crystal diamond surface, and the concave line represents the Raman peak of the porous single crystal diamond pores. The materials at the surface and pores of the porous single crystal diamond can both produce Raman spectra corresponding to the diamond material, proving that no other impurities grow on the sample; according to Figure 5 The Laue diffraction pattern shown shows that it is a single crystal sample.

[0036] Example 2

[0037] The difference between this embodiment and embodiment 1 is that the grain size of the artificial single crystal diamond used in step 1 is 620 microns, and in step 2, it is sintered at 5.5 GPa and 1260° C. for 30 minutes. Other operations are the same as in embodiment 1.

[0038] The porous single crystal diamond prepared in this embodiment was subjected to SEM scanning electron microscope test, and the test results are as follows: Figure 6 As shown, the size of the obtained porous single crystal diamond is about 660 microns.

[0039] Example 3

[0040] The difference between this embodiment and embodiment 1 is that the grain size of the artificial single crystal diamond used in step 1 is 625 microns, and in step 2, it is sintered at 5.5 GPa and 1260° C. for 15 minutes. Other operations are the same as in embodiment 1.

[0041] The porous single crystal diamond prepared in this embodiment was subjected to SEM scanning electron microscope test, and the test results are as follows: Figure 7 As shown, the size of the obtained porous single crystal diamond is about 650 microns.

[0042] Example 4

[0043] This embodiment provides a method for preparing porous single crystal diamond, comprising the following steps:

[0044] Step 1: Place diamond powder with a grain size of 100 nanometers and metal catalyst powder in a three-dimensional mixer at a volume ratio of 1:4 and mix them evenly. Then wrap the mixed powder around an artificial single crystal diamond with a grain size of 640 micrometers and place it in a mold for pre-pressing to obtain a block sample. The block sample is hydrogen reduced at 700°C and then sealed and wrapped in an assembly block. Figure 1 As shown, the assembly block includes a magnesium oxide cavity, a carbon tube, a dolomite tube, and a pyrophyllite block which are sequentially sleeved from the inside to the outside, wherein a dolomite ring and a molybdenum sheet are sequentially arranged at the upper and lower ends of the dolomite tube from the inside to the outside, respectively, through openings coaxial with the dolomite tube are arranged at the upper and lower ends of the pyrophyllite block, a steel plug is arranged in the channel to abut against the molybdenum sheet, a carbon sheet is arranged at the upper and lower ends of the carbon tube, a carbon column whose two ends abut against the molybdenum sheet and the carbon sheet is arranged at the inner ring of the dolomite ring, and the block sample is sealed and wrapped in the magnesium oxide cavity;

[0045] Step 2, placing the assembled assembly block in a six-sided top press, sintering at 6 GPa and 1300° C. for 15 minutes, and removing the sealing package to obtain a diamond blank;

[0046] Step 3: The diamond block is cleaned in dilute nitric acid, and then soaked in aqua regia to remove diamond powder and metal catalyst powder that are not involved in the growth, and finally ultrasonically cleaned to obtain porous single crystal diamond.

[0047] The porous single crystal diamond obtained in this example was tested by SEM scanning electron microscope. The test results are as follows: Figure 8 The obtained porous single crystal diamond has a size of about 680 microns.

[0048] Example 5

[0049] This embodiment provides a method for preparing porous single crystal diamond, comprising the following steps:

[0050] Step 1: put diamond powder with a grain size of 3 microns and metal catalyst powder into a three-dimensional mixer in a volume ratio of 1:4 and mix them evenly. Then wrap the mixed powder around an artificial single crystal diamond with a grain size of 640 microns and place it in a mold for pre-pressing to obtain a block sample. The block sample is hydrogen reduced at 600°C and then sealed and wrapped in an assembly block. Figure 1 As shown, the assembly block includes a magnesium oxide cavity, a carbon tube, a dolomite tube, and a pyrophyllite block which are sequentially sleeved from the inside to the outside, wherein a dolomite ring and a molybdenum sheet are sequentially arranged at the upper and lower ends of the dolomite tube from the inside to the outside, respectively, through openings coaxial with the dolomite tube are arranged at the upper and lower ends of the pyrophyllite block, a steel plug is arranged in the channel to abut against the molybdenum sheet, a carbon sheet is arranged at the upper and lower ends of the carbon tube, a carbon column whose two ends abut against the molybdenum sheet and the carbon sheet is arranged at the inner ring of the dolomite ring, and the block sample is sealed and wrapped in the magnesium oxide cavity;

[0051] Step 2, placing the assembled assembly block in a six-sided top press, sintering at 6.0 GPa and 1200° C. for 15 minutes, and removing the sealing package to obtain a diamond blank;

[0052] Step 3: The diamond block is cleaned in dilute nitric acid, and then soaked in aqua regia to remove diamond powder and metal catalyst powder that are not involved in the growth, and finally ultrasonically cleaned to obtain porous single crystal diamond.

[0053] The porous single crystal diamond obtained in this example was tested by SEM scanning electron microscope. The test results are as follows: Fig. 9 As shown, the size of the obtained porous single crystal diamond is about 660 microns.

[0054] The above embodiments 1 to 5 are combined with the attached Figures 2 to 9The results show that the method provided by the present invention can be used to repeatedly synthesize porous single crystal diamond. The crystals synthesized by the method have no obvious defects, irregular shapes, high porosity, large specific surface area, simple operation, low cost, repeatability, and can meet the requirements of mass production, and also meet the needs of some fields for porous diamonds. Figure 2 , 3 , 6, 7, 8, 9, it can be seen that the pores of the porous single crystal diamonds obtained in Examples 1 to 3 and 4 to 5 decrease respectively, indicating that under the same temperature and pressure conditions, the longer the sintering time, the more pores the porous single crystal diamond has; under the same sintering time, the higher the temperature and pressure conditions, the more pores the porous single crystal diamond has.

[0055] The above embodiments of the present invention are merely examples for illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes and modifications can be made based on the above description. It is impossible to list all the embodiments here. Any obvious changes or modifications derived from the technical solution of the present invention are still within the scope of protection of the present invention.

Claims

1. A method for preparing porous single crystal diamond, characterized in that: The following steps are involved: Step 1, sealing and wrapping a sample obtained by mixing diamond seed crystals with diamond powder crystals and metal catalyst powder to obtain a sealing block, wherein the mixture of the diamond powder crystals and the metal catalyst powder wraps the outside of the diamond seed crystals; Step 2, treating the sealing block under high temperature and high pressure conditions of 5.2 to 8 GPa and 1200° C. to 1600° C., and removing the sealing package to obtain a diamond blank; Step 3: Acid washing and vibration impact are used to remove diamond powder crystals and metal catalyst powder that do not participate in the growth of the diamond block to obtain porous single crystal diamond.

2. The method for preparing porous single crystal diamond according to claim 1, characterized in that: In the step 1, diamond seed crystals are mixed with diamond powder crystals and metal catalyst powder and then placed in a mold for pre-pressing to obtain a block sample, which is then sealed and wrapped to obtain a sealing block.

3. The method for preparing porous single crystal diamond according to claim 2, characterized in that: In the step 1, the block sample is first reduced with hydrogen at 300-1200° C. and then sealed and packaged.

4. The method for preparing porous single crystal diamond according to claim 1, characterized in that: In step 1, the diamond seed crystal is a single crystal diamond particle with a grain size of 100 μm or more, the diamond powder crystal has a grain size of 3 nm to 10 μm, and the metal catalyst powder is at least one of iron powder, cobalt powder and nickel powder.

5. The method for preparing porous single crystal diamond according to claim 1 or 4, characterized in that: The ratio of the grain size of the diamond seed crystal to the grain size of the diamond powder crystal is (10-1000):

1.

6. The method for preparing porous single crystal diamond according to claim 1 or 4, characterized in that: In step 1, the diamond powder and the metal catalyst powder are mixed in a volume / weight ratio of 1: (1-10).

7. The method for preparing porous single crystal diamond according to claim 1, characterized in that: In the step 1, the sample is sealed and wrapped in an assembly block, and the assembly block includes a magnesium oxide cavity, a carbon tube, a dolomite tube, and a phyllite block which are sequentially arranged from the inside to the outside, wherein a dolomite ring and a molybdenum sheet are arranged at the upper and lower ends of the dolomite tube respectively from the inside to the outside, and through openings coaxial with the dolomite tube are arranged at the upper and lower ends of the phyllite block respectively, and steel plugs are arranged in the channel to abut the molybdenum sheet, and carbon sheets are arranged at the upper and lower ends of the carbon tube respectively, and a carbon column is arranged on the inner circle of the dolomite ring, and the diamond seed crystals are mixed with diamond powder crystals and metal catalyst powder and then sealed and wrapped in the magnesium oxide cavity; in the step 2, the assembled assembly block is placed in a six-sided top press for high temperature and high pressure treatment.

8. The method for preparing porous single crystal diamond according to claim 1, characterized in that: In the step 2, the sealing block is treated at 5.2-8 GPa and 1200° C.-1600° C. for 10 minutes or more.

9. The method for preparing porous single crystal diamond according to claim 1, characterized in that: The operation of pickling the diamond block in step 3 is specifically: washing it in dilute nitric acid, and then soaking it in aqua regia for washing.

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