A method for preparing an ellipsoidal large-size diamond single crystal

Abstract

The application is suitable for the technical field of diamond single crystal preparation, and provides a preparation method of ellipsoidal large-size diamond single crystal, which comprises the following steps: using a large-size diamond single crystal with clear edges and corners as a crystal; placing the crystal in a high-pressure assembly block and drying; placing the high-pressure assembly block in a cavity of a six-surface top pressing machine device, performing a dissolution operation, the pressure is 3-6 GPa, the temperature is 1200-2000 DEG C, and the time is 5 min-48 h; after the operation is completed, the crystal is taken out, the impurities on the surface are removed, and then the crystal is cleaned to obtain an ellipsoidal large-size diamond single crystal. The large-size diamond buried in the metal catalyst is treated by the six-surface top high-pressure equipment, the preparation of the diamond single crystal from the crystal with clear edges and corners to slightly round to spherical to ellipsoidal can be realized by adjusting the temperature and the holding time, the method is simple and easy to operate, the technical problem of the preparation of the large-size ellipsoidal diamond single crystal is solved, the production cost is low, the method has good repeatability, and the batch production requirements can be met.

Description

Technical Field

[0001] This invention belongs to the field of diamond single crystal preparation technology, and particularly relates to a method for preparing large-size ellipsoidal diamond single crystals. Background Technology

[0002] Diamond, due to its excellent physicochemical properties, such as extremely high hardness, excellent thermal conductivity, and chemical stability, is widely used in various fields including cutting, grinding, drilling, electronic devices, optical instruments, and biomedicine. With technological advancements, the demands for diamond morphology and performance are becoming increasingly diverse. Among the many diamond shapes, ellipsoidal and spherical diamonds, due to their unique geometric characteristics, exhibit superior performance in grinding efficiency, material strength, and machining tools such as ultra-precision drills, dressers, and molds, and have therefore attracted widespread attention.

[0003] Currently, various methods have been proposed for the synthesis of diamond, among which high-temperature high-pressure (HPHT) and chemical vapor deposition (CVD) are the most commonly used techniques. However, existing technologies still face many challenges in directly growing large-sized ellipsoidal diamonds. Although CVD technology can relatively flexibly adjust deposition parameters, achieving uniform and controllable ellipsoidal diamonds in practice remains technically difficult, and the complex operation makes mass production challenging. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing large-size ellipsoidal diamond single crystals, aiming to solve the problems mentioned in the background art.

[0005] The present invention is implemented as follows: a method for preparing an ellipsoidal large-size diamond single crystal includes the following steps:

[0006] S1. Use large-sized, sharp-edged diamond single crystals as crystals to eliminate metals and impurities on the crystal surface;

[0007] S2. Place the crystal in the high voltage assembly block, and then dry the high voltage assembly block.

[0008] S3. Place the high-pressure assembly block in the cavity of the six-sided top press device and perform the etching operation at a pressure of 3-6 GPa, a temperature of 1200-2000 ℃, and a time of 5min-48h.

[0009] S4. After the etching operation is completed, the crystal in the high-pressure assembly block is taken out, the metal alloy and graphite on the surface of the crystal are removed, and then it is cleaned to obtain the ellipsoidal large-size diamond single crystal.

[0010] Preferably, in S1, the operation of removing metals and impurities from the crystal surface specifically involves: acid washing and ultrasonic treatment of the crystal, wherein the acid used is a mixture of nitric acid and sulfuric acid, and the volume ratio of nitric acid to sulfuric acid is 1:3.

[0011] Preferably, in step S2, the assembly process of placing the crystal in the high-voltage assembly block includes the following steps:

[0012] Use pyrophyllite blocks as the outer container, and then place the conductive steel cap, pyrophyllite ring, conductive metal sheet, graphite sheet and sodium chloride + zirconium oxide liner in order from bottom to top.

[0013] Then, a graphite heating tube is placed in place so that it is tightly attached to the inner wall of the sodium chloride + zirconium oxide liner. Then, a magnesium oxide + zirconium oxide plug and an insulating tube are placed in sequence. A metal catalyst is placed in the insulating tube as a solvent, and a diamond single crystal is buried in the center.

[0014] Then insert another magnesium oxide + zirconium oxide plug, which is flush with the liner.

[0015] Finally, another graphite sheet, a conductive metal sheet, a pyrophyllite ring, and a conductive steel cap are placed in sequence to obtain a symmetrical assembly structure.

[0016] Preferably, the metal catalyst is one or an alloy of Fe, Ni, Co, and Mn.

[0017] Preferably, in S2, the operation of drying the high-pressure assembly block specifically involves placing the high-pressure assembly block in an oven at 120°C for 30 minutes.

[0018] Preferably, in S4, the operation of removing the metal alloy and graphite from the crystal surface specifically involves: placing the crystal in a dilute nitric acid solution and heating it to remove the metal alloy around the crystal, and then placing the boiled crystal in a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:3 and heating it again to remove the graphite from the crystal surface.

[0019] Preferably, in S4, the cleaning operation specifically involves ultrasonic cleaning for 10 minutes.

[0020] This invention provides a method for preparing large-size ellipsoidal diamond single crystals. The method employs HPHT technology, using a six-sided high-pressure device to process large-size diamonds embedded in various elemental metals or alloys such as Fe, Ni, Co, and Mn. By controlling the temperature and holding time, spherical and ellipsoidal diamond single crystals of different sizes can be prepared. The high pressure prevents the diamond from rapid graphitization caused by high temperatures, while maintaining its original strength and hardness. This achieves efficient preparation of large-size ellipsoidal diamonds, resulting in crystals of excellent quality with dynamically adjustable size. This preparation method is not only simple and easy to operate but also reduces production costs to a certain extent. It also has good repeatability, meeting production requirements and greatly promoting the application of diamonds in ultra-precision drill bits, dressing tools, and molds. Furthermore, it provides a more reliable solution for future industrial applications and research and development of diamonds. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the high-voltage assembly block provided in an embodiment of the present invention;

[0022] Figure 2 Optical photographs of diamond single crystals before and after etching, provided in Examples 1-3 of this invention;

[0023] Figure 3 The scan images are of the diamond single crystals after etching provided in Examples 1-3 of this invention;

[0024] Figure 4 This is a flowchart illustrating a method for preparing an ellipsoidal large-size diamond single crystal, as provided in an embodiment of the present invention.

[0025] In the attached diagram, 1-pyrophyllite ring; 2-conductive steel cap; 3-pyrophyllite block; 4-conductive metal sheet; 5-graphite sheet; 6-sodium chloride + zirconium oxide liner; 7-graphite heating tube; 8-magnesium oxide + zirconium oxide plug; 9-metal catalyst; 10-diamond single crystal. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0027] The specific implementation of the present invention will be described in detail below with reference to specific embodiments.

[0028] Example 1: A method for preparing a large-size ellipsoidal diamond single crystal, such as... Figure 4 As shown, the specific steps include:

[0029] S1. Pre-assembly treatment: Large-sized, sharp-edged diamond single crystals are used as crystals. Before assembly, the crystals are acid-washed (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to remove residual metal and graphite impurities on the surface.

[0030] S2, Assembly Block: Arrange the cleaned diamonds according to... Figure 1 The assembly diagram is complete. The specific steps are as follows: Pyrophyllite block 3 serves as the outer container. The remaining materials are placed in the following order from bottom to top: conductive steel cap 2, pyrophyllite ring 1, conductive metal sheet 4, graphite sheet 5, and sodium chloride + zirconium oxide liner 6. Next, a 0.9mm thick graphite heating tube 7 is placed in, ensuring it is tightly attached to the inner wall of 6. Then, a magnesium oxide + zirconium oxide plug 8 and an insulating tube are placed in sequence. A metal catalyst 9, which is Fe, is placed inside the insulating tube. 70 Ni 30 A large, angular diamond single crystal 10 is buried in the center, followed by a magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6. Finally, graphite sheet 5, conductive metal sheet 4, pyrophyllite ring 1, and conductive steel cap 2 are placed in sequence, resulting in a symmetrical assembly structure.

[0031] S3. After assembly, place the high-pressure assembly block in a 120°C oven for 30 minutes to reduce the moisture in the assembly material.

[0032] S4. Place the high-pressure assembly block in the cavity of the six-sided top press device and set the required pressure (5.4 GPa) and temperature (1260 ℃) for a dissolution test. The dissolution time is 2 hours. (The temperature setting inside the cavity is related to the electric power. Therefore, the temperature inside the cavity is set according to the relationship curve between the input power and temperature measured by the double platinum-rhodium (Pt-30% RH / Pt-6% Rh) thermocouple. Similarly, the pressure setting is based on the calibration curve between the oil pressure and the internal pressure of the cavity established by the high-pressure phase transition point of bismuth (Bi), barium (Ba) and thallium (Tl).)

[0033] S5. After the etching is complete, remove the assembly block and break it open. Take out the sample and place it in a dilute nitric acid solution and heat it to remove the metal alloy around the crystal. Then, place the boiled crystal in a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:3 and heat it again to remove the graphite on the crystal surface. Finally, perform ultrasonic cleaning on the crystal for 10 minutes.

[0034] Example 2: A method for preparing a large-size ellipsoidal diamond single crystal, comprising the following steps:

[0035] S1. Pre-assembly treatment: Large-sized, sharp-edged diamond single crystals are used as crystals. Before assembly, the crystals are acid-washed (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to remove residual metal and graphite impurities on the surface.

[0036] S2, Assembly Block: Arrange the cleaned diamonds according to... Figure 1 The assembly diagram is complete. The specific steps are as follows: Pyrophyllite block 3 serves as the outer container. The remaining materials are placed in the following order from bottom to top: conductive steel cap 2, pyrophyllite ring 1, conductive metal sheet 4, graphite sheet 5, and sodium chloride + zirconium oxide liner 6. Next, a 0.9mm thick graphite heating tube 7 is placed in, ensuring it is tightly attached to the inner wall of 6. Then, a magnesium oxide + zirconium oxide plug 8 and an insulating tube are placed in sequence. A metal catalyst 9, which is Fe, is placed inside the insulating tube. 70 Ni 30 A large, angular diamond single crystal 10 is buried in the center, followed by a magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6. Finally, graphite sheet 5, conductive metal sheet 4, pyrophyllite ring 1, and conductive steel cap 2 are placed in sequence, resulting in a symmetrical assembly structure.

[0037] S3. After assembly, place the high-pressure assembly block in a 120°C oven for 30 minutes to reduce the moisture in the assembly material.

[0038] S4. Place the high-pressure assembly block in the cavity of the six-sided top press device and set the required pressure (5.4 GPa) and temperature (1340 ℃) for a dissolution test. The dissolution time is 2 hours.

[0039] S5. After the etching is complete, remove the assembly block and break it open. Take out the sample and place it in a dilute nitric acid solution and heat it to remove the metal alloy around the crystal. Then, place the boiled crystal in a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:3 and heat it again to remove the graphite on the crystal surface. Finally, perform ultrasonic cleaning on the crystal for 10 minutes.

[0040] Example 3: A method for preparing a large-size ellipsoidal diamond single crystal, comprising the following steps:

[0041] S1. Pre-assembly treatment: Large-sized, sharp-edged diamond single crystals are used as crystals. Before assembly, the crystals are acid-washed (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to remove residual metal and graphite impurities on the surface.

[0042] S2, Assembly Block: Arrange the cleaned diamonds according to... Figure 1 The assembly diagram is complete. The specific steps are as follows: Pyrophyllite block 3 serves as the outer container. The remaining materials are placed in the following order from bottom to top: conductive steel cap 2, pyrophyllite ring 1, conductive metal sheet 4, graphite sheet 5, and sodium chloride + zirconium oxide liner 6. Next, a 0.9mm thick graphite heating tube 7 is placed in, ensuring it is tightly attached to the inner wall of 6. Then, a magnesium oxide + zirconium oxide plug 8 and an insulating tube are placed in sequence. A metal catalyst 9, which is Fe, is placed inside the insulating tube.70 Ni 30 A large, angular diamond single crystal 10 is buried in the center, followed by a magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6. Finally, graphite sheet 5, conductive metal sheet 4, pyrophyllite ring 1, and conductive steel cap 2 are placed in sequence, resulting in a symmetrical assembly structure.

[0043] S3. After assembly, place the high-pressure assembly block in a 120°C oven for 30 minutes to reduce the moisture in the assembly material.

[0044] S4. Place the high-pressure assembly block in the cavity of the six-sided top press device and set the required pressure (5.4 GPa) and temperature (1420 ℃) ​​to conduct a dissolution test. The dissolution time is 0.5 hours.

[0045] S5. After the etching is complete, remove the assembly block and break it open. Take out the sample and place it in a dilute nitric acid solution and heat it to remove the metal alloy around the crystal. Then, place the boiled crystal in a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:3 and heat it again to remove the graphite on the crystal surface. Finally, perform ultrasonic cleaning on the crystal for 10 minutes.

[0046] The surface morphology of the crystals prepared in Examples 1-3 was characterized using optical photographs acquired with a Leica M205c optical microscope (OM) and scanning electron microscope (SEM; JSM-IT200A) to acquire scanning images, resulting in optical images before and after etching, as shown below. Figure 2 As shown, the scan image after etching is as follows: Figure 3 As shown;

[0047] according to Figure 2 It can be seen that before etching, the crystals are standard hexagonal octahedrals with sharp edges and are yellow (a, b, c). After etching, the crystals are bright yellow and more transparent (a1, b1, c1). Among them, the crystals of a1 and b1, which are etched at temperatures of 1260 ℃ and 1340 ℃ respectively, are still hexagonal octahedrals, and their {111} and {100} faces are easily distinguishable. However, as the temperature increases, the edges of the crystals gradually become more rounded. When the etching temperature is 1420 ℃ and the time is only 0.5 h, the edges of the crystals completely disappear, and the {111} and {100} faces of the crystals are not easily distinguishable, and they appear as ellipsoids (as shown in c1).

[0048] according to Figure 3It can be seen that the etch temperature of a is 1260 ℃, and the crystal face is obviously rough and uneven, with obvious edges and corners; the etch temperature of b is 1340 ℃, the {100} crystal face is no longer rough, the {111} crystal face is still partially rough and uneven, and the crystal face is still distinguishable; the etch temperature of c reaches 1420 ℃, all crystal faces are no longer rough, but the crystal faces are not easy to distinguish.

[0049] Based on the preparation methods of Examples 1-3, by changing parameters such as pressure, temperature, and time, diamond single crystals of different sizes and shapes can be obtained.

[0050] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for producing an ellipsoidal large-size diamond single crystal, characterized by, The method comprises the following steps: S1, using large-size angular diamond single crystal as crystal, eliminating metal and impurities on the surface of the crystal; S2, placing the crystal in a high-pressure assembly block, and then drying the high-pressure assembly block; S3, placing the high-pressure assembly block in a cavity of a six-surface press device, and performing dissolution operation, with a pressure of 3-6 GPa, a temperature of 1200-2000 ℃, and a time of 5 min-48 h; S4, taking out the crystal in the high-pressure assembly block after the dissolution operation, removing metal alloy and graphite on the surface of the crystal, and then cleaning to obtain the ellipsoidal large-size diamond single crystal; In S2, the assembly process of placing the crystal in the high-pressure assembly block comprises the following steps: Put the pyrophyllite block (3) as an external container, and then put the conductive steel cap (2), pyrophyllite ring (1), conductive metal sheet (4), graphite sheet (5), and sodium chloride+zirconia lining pipe (6) in order from bottom to top; Then put the graphite heating pipe (7) to tightly adhere to the inner wall of the sodium chloride+zirconia lining pipe (6), and then put the magnesium oxide+zirconia plug (8) and the insulating pipe in order, put the metal catalyst (9) as the dissolution agent in the insulating pipe, and bury the diamond single crystal (10) in the middle; Then put another magnesium oxide+zirconia plug (8) to be flush with the lining pipe (6); Finally, put another graphite sheet (5), conductive metal sheet (4), pyrophyllite ring (1), and conductive steel cap (2) in order, and finally get the symmetrical assembly structure.

2. The method of claim 1, wherein the method further comprises the step of: In S1, the operation of eliminating metal and impurities on the surface of the crystal is specifically: acid pickling and ultrasonic treatment are performed on the crystal, wherein the acid used is a mixed acid of nitric acid and sulfuric acid, and the volume ratio of nitric acid to sulfuric acid is 1:

3.

3. The method of claim 1, wherein the method further comprises the step of: The metal catalyst (9) is one of Fe, Ni, Co, and Mn or an alloy thereof.

4. The method of claim 1, wherein the method further comprises: In S2, the drying operation of the high-pressure assembly block is specifically: placing the high-pressure assembly block in a 120℃ oven for 30 min.

5. The method of claim 1, wherein the method further comprises the step of: In S4, the operation of removing metal alloy and graphite on the surface of the crystal is specifically: placing the crystal in a dilute nitric acid solution and heating to remove the metal alloy around the crystal, and then placing the boiled crystal in a mixed solution of nitric acid and sulfuric acid with a volume ratio of 1:3 and heating again to remove the graphite on the surface of the crystal.

6. The method of claim 1, wherein the method further comprises: In S4, the cleaning operation is specifically: ultrasonic cleaning for 10 min.

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