Preparation method of ellipsoidal large-size diamond single crystal

Abstract

The invention is suitable for the technical field of diamond single crystal preparation, and provides a preparation method of an ellipsoidal large-size diamond single crystal, which comprises the following steps: using a large-size diamond single crystal with clear edges as a crystal; placing in a high-pressure assembly block, and drying; the high-pressure assembly block is placed in a cavity of a cubic press device, corrosion operation is carried out, the pressure is 3-6 GPa, the temperature is 1200-2000 DEG C, and the time is 5 min to 48 h; and after finishing, taking out the crystal, removing impurities on the surface, and cleaning to obtain the ellipsoidal large-size diamond single crystal. According to the method, the large-size diamond buried in the metal catalyst is treated through cubic high-pressure equipment, the preparation of diamond single crystals with different sizes from edge-corner clear crystals to slightly round to sphere-like shapes to ellipsoidal shapes can be realized by regulating and controlling the temperature and the heat preservation time, and the method is simple and easy to operate; the technical problem of large-size ellipsoidal diamond single crystal preparation is solved, the production cost is low, good repeatability is achieved, and the requirement for batch production can be met.

Description

Technical Field

[0001] The invention belongs to the technical field of diamond single crystal preparation, and in particular relates to a method for preparing an ellipsoidal large-size diamond single crystal. Background Art

[0002] Diamond is widely used in many fields such as cutting, grinding, drilling, electronic devices, optical devices and biomedicine due to its excellent physical and chemical properties, such as extremely high hardness, excellent thermal conductivity and chemical stability. With the advancement of science and technology, the demand for diamond morphology and performance has become more diversified. Among the many diamond shapes, ellipsoidal and spherical diamonds have shown superiority in grinding efficiency, material strength and processing tools such as ultra-precision drills, dressers and molds due to their unique geometric properties, and have therefore received widespread attention.

[0003] At present, a variety of methods have been proposed for synthesizing diamonds, among which high temperature and high pressure (HPHT) and chemical vapor deposition (CVD) are the most commonly used technologies. However, existing technologies still face many challenges in directly growing and preparing large-sized ellipsoidal diamonds; although CVD technology can relatively flexibly adjust deposition parameters, in actual operation, achieving uniform and controllable ellipsoidal diamonds still has certain technical difficulties, and the operation is complex and difficult to mass produce. Summary of the invention

[0004] The purpose of the embodiments of the present invention is to provide a method for preparing an ellipsoidal large-size diamond single crystal, aiming to solve the problems raised in the above background technology.

[0005] The embodiment of the present invention is implemented as follows: a method for preparing an ellipsoidal large-size diamond single crystal comprises the following steps: S1. Use large-sized, angular diamond single crystals as crystals to eliminate metal and impurities on the surface of the crystals; S2, placing the crystal in a high-voltage assembly block, and then drying the high-voltage assembly block; S3, placing the high-pressure assembly block in the cavity of a six-sided top press device, and performing a dissolution operation at a pressure of 3-6 GPa, a temperature of 1200-2000 °C, and a time of 5 min-48 h; S4. After the dissolution 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 the crystal is cleaned to obtain the ellipsoidal large-size diamond single crystal.

[0006] Preferably, in S1, the operation of eliminating metal and impurities on the surface of the crystal is specifically: acid washing and ultrasonic treatment of 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.

[0007] Preferably, in S2, the assembling process of placing the crystal in the high-pressure assembly block comprises the following steps: Use the pyrophyllite block as the outer container, and then put the conductive steel cap, pyrophyllite ring, conductive metal sheet, graphite sheet and sodium chloride + zirconium oxide liner in order from bottom to top; Then put the graphite heating tube in close contact with the inner wall of the sodium chloride + zirconium oxide liner, and then put the magnesium oxide + zirconium oxide plug and the insulating tube in sequence. Put the metal catalyst as a dissolving agent in the insulating tube, and bury the diamond single crystal in the middle; Then put in another magnesia + zirconia plug, just flush with the liner; Finally, another graphite sheet, a conductive metal sheet, a pyrophyllite ring, and a conductive steel cap are placed in sequence to obtain an assembly structure that is symmetrical up and down.

[0008] Preferably, the metal catalyst is one of Fe, Ni, Co, Mn or an alloy thereof.

[0009] Preferably, in S2, the operation of drying the high-pressure assembly block is specifically: placing the high-pressure assembly block in an oven at 120° C. for 30 minutes.

[0010] Preferably, in S4, the operation of removing the metal alloy and graphite on the surface of the crystal is specifically: 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 in a volume ratio of 1:3 and heating it again to remove the graphite on the surface of the crystal.

[0011] Preferably, in S4, the cleaning operation is specifically: performing ultrasonic cleaning for 10 minutes.

[0012] The embodiment of the present invention provides a method for preparing an ellipsoidal large-sized diamond single crystal, which uses HPHT technology to process large-sized diamonds buried in various elemental metals or alloys such as Fe, Ni, Co, and Mn through a six-sided top high-pressure device, and the preparation of spherical and ellipsoidal diamond single crystals of different sizes can be achieved by regulating the temperature and the holding time, wherein the high pressure prevents the diamond from rapid graphitization caused by high temperature and maintains the original strength and hardness, thereby achieving efficient preparation of large-sized ellipsoidal diamonds, and the prepared crystals are of excellent quality, and the size can also be dynamically adjusted. The preparation method is not only simple and easy to operate, but also reduces the production cost to a certain extent, and has good repeatability, can meet production requirements, can greatly promote the application of diamond in the field of processing tools such as ultra-precision drill bits, trimmers, and molds, and also provides a more reliable solution for the industrial application and research and development of diamonds in the future. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the structure of a high-voltage assembly block provided by an embodiment of the present invention; Figure 2 Optical photographs of diamond single crystals before and after dissolution provided in Examples 1-3 of the present invention; Figure 3 A scanned image of a diamond single crystal after dissolution provided in Examples 1-3 of the present invention; Figure 4 A positive flow chart of a method for preparing an ellipsoidal large-size diamond single crystal provided in an embodiment of the present invention.

[0014] In the attached figure, 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 DESCRIPTION

[0015] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0016] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments.

[0017] Example 1: A method for preparing a large-size ellipsoidal diamond single crystal, such as Figure 4 As shown, the specific steps include: S1. Pre-assembly treatment: Use large-sized, angular diamond single crystals as crystals. Before assembly, the crystals are pickled (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to eliminate residual metal and graphite impurities on the surface; S2, assembly block: Assemble the cleaned diamonds according to Figure 1 The assembly diagram is assembled, and the specific steps are: the phyllite block 3 is used as the external container, and the remaining materials are placed in the order of conductive steel cap 2, phyllite ring 1, conductive metal sheet 4, graphite sheet 5 and sodium chloride + zirconium oxide liner 6 from bottom to top; secondly, a graphite heating tube 7 with a thickness of 0.9 mm is placed to make it close to the inner wall of 6; then, magnesium oxide + zirconium oxide plug 8 and insulating tube are placed in sequence, and a metal catalyst 9 is placed in the insulating tube, and the metal catalyst 9 is Fe 70 Ni 30 and bury the large-sized angular diamond single crystal 10 in the middle, followed by the magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6; finally, the graphite sheet 5, the conductive metal sheet 4, the pyrophyllite ring 1, and the conductive steel cap 2 are placed in sequence, and finally a vertically symmetrical assembly structure is formed; S3, after the assembly is completed, the high pressure assembly block is placed in an oven at 120°C for 30 minutes to reduce the moisture in the assembly material; 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 ℃) to carry out the dissolution experiment. The dissolution time is 2 hours (the setting of the temperature in the cavity is related to the electric power, so the temperature in the cavity is set according to the relationship curve between the input power and the temperature measured by the double platinum-rhodium (Pt-30% RH / Pt-6% Rh) thermocouple. Similarly, the pressure is set according to the calibration curve between the oil pressure and the pressure inside the cavity established according to the high-pressure phase transition point of bismuth (Bi), barium (Ba) and thallium (Tl); S5. After the dissolution is completed, the assembly block is taken out and smashed open. The sample is taken out and placed in a dilute nitric acid solution and heated to remove the metal alloy around the crystal. The boiled crystal is then placed in a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1:3 and heated again to remove graphite on the crystal surface. Finally, the crystal is ultrasonically cleaned for 10 minutes.

[0018] Embodiment 2: A method for preparing an ellipsoidal large-size diamond single crystal, comprising the following steps: S1. Pre-assembly treatment: Use large-sized, angular diamond single crystals as crystals. Before assembly, the crystals are pickled (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to eliminate residual metal and graphite impurities on the surface; S2, assembly block: Assemble the cleaned diamonds according to Figure 1 The assembly diagram is assembled, and the specific steps are: the phyllite block 3 is used as the external container, and the remaining materials are placed in the order of conductive steel cap 2, phyllite ring 1, conductive metal sheet 4, graphite sheet 5 and sodium chloride + zirconium oxide liner 6 from bottom to top; secondly, a graphite heating tube 7 with a thickness of 0.9 mm is placed to make it close to the inner wall of 6; then, magnesium oxide + zirconium oxide plug 8 and insulating tube are placed in sequence, and a metal catalyst 9 is placed in the insulating tube, and the metal catalyst 9 is Fe 70 Ni 30 and bury the large-sized angular diamond single crystal 10 in the middle, followed by the magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6; finally, the graphite sheet 5, the conductive metal sheet 4, the pyrophyllite ring 1, and the conductive steel cap 2 are placed in sequence, and finally a vertically symmetrical assembly structure is formed; S3, after the assembly is completed, the high pressure assembly block is placed in an oven at 120°C for 30 minutes to reduce the moisture in the assembly material; S4, placing the high-pressure assembly block in the cavity of the six-sided top press device and setting the required pressure (5.4 GPa) and temperature (1340 °C) to carry out a dissolution experiment, and the dissolution time is 2 hours; S5. After the dissolution is completed, the assembly block is taken out and smashed open. The sample is taken out and placed in a dilute nitric acid solution and heated to remove the metal alloy around the crystal. The boiled crystal is then placed in a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1:3 and heated again to remove graphite on the crystal surface. Finally, the crystal is ultrasonically cleaned for 10 minutes.

[0019] Embodiment 3: A method for preparing an ellipsoidal large-size diamond single crystal, comprising the following steps: S1. Pre-assembly treatment: Use large-sized, angular diamond single crystals as crystals. Before assembly, the crystals are pickled (nitric acid: sulfuric acid = 1:3) and ultrasonically treated to eliminate residual metal and graphite impurities on the surface; S2, assembly block: Assemble the cleaned diamonds according to Figure 1 The assembly diagram is assembled, and the specific steps are: the phyllite block 3 is used as the external container, and the remaining materials are placed in the order of conductive steel cap 2, phyllite ring 1, conductive metal sheet 4, graphite sheet 5 and sodium chloride + zirconium oxide liner 6 from bottom to top; secondly, a graphite heating tube 7 with a thickness of 0.9 mm is placed to make it close to the inner wall of 6; then, magnesium oxide + zirconium oxide plug 8 and insulating tube are placed in sequence, and a metal catalyst 9 is placed in the insulating tube, and the metal catalyst 9 is Fe 70 Ni 30 and bury the large-sized angular diamond single crystal 10 in the middle, followed by the magnesium oxide + zirconium oxide plug 8, which is flush with the liner 6; finally, the graphite sheet 5, the conductive metal sheet 4, the pyrophyllite ring 1, and the conductive steel cap 2 are placed in sequence, and finally a vertically symmetrical assembly structure is formed; S3, after the assembly is completed, the high pressure assembly block is placed in an oven at 120°C for 30 minutes to reduce the moisture in the assembly material; S4, placing the high-pressure assembly block in the cavity of the six-sided top press device and setting the required pressure (5.4 GPa) and temperature (1420 °C) to carry out a dissolution experiment, and the dissolution time is 0.5 hours; S5. After the dissolution is completed, the assembly block is taken out and smashed open. The sample is taken out and placed in a dilute nitric acid solution and heated to remove the metal alloy around the crystal. The boiled crystal is then placed in a mixed solution of nitric acid and sulfuric acid in a volume ratio of 1:3 and heated again to remove graphite on the crystal surface. Finally, the crystal is ultrasonically cleaned for 10 minutes.

[0020] The surface morphology of the crystals prepared in Examples 1-3 was characterized by using a Leica M205c optical microscope (OM) to collect optical photographs and a scanning electron microscope (SEM; JSM-IT200A) to collect scanning images, and obtaining optical images before and after dissolution as shown in FIG. Figure 2 As shown, the scan image after dissolution is Figure 3 As shown; according to Figure 2 It can be seen that before dissolution, the crystal shape is a standard hexaoctahedron with clear edges and corners, and the color is yellow (a, b, c). After dissolution, the crystal color is bright yellow and more transparent (a1, b1, c1). The crystal shapes of a1 and b1 with dissolution temperatures of 1260 ℃ and 1340 ℃ are still hexaoctahedral crystals, and their {111} and {100} faces are also easy to distinguish. However, with the increase of temperature, the edges and corners of the crystal are obviously gradually rounded. When the dissolution temperature is 1420 ℃ and the time is only 0.5 h, the edges and corners of the crystal completely disappear, and the {111} and {100} faces of the crystal are difficult to distinguish, showing an ellipsoid shape (as shown in c1); according to Figure 3 It can be seen that the dissolution temperature of a is 1260 ℃, the crystal plane is obviously rough and uneven, and the edges and corners are still obvious; the dissolution temperature of b is 1340 ℃, the {100} crystal plane is no longer rough, and the {111} crystal plane is still partially rough and uneven, and the crystal planes can still be distinguished; the dissolution temperature of c reaches 1420 ℃, all crystal planes are no longer rough, but the crystal planes are also difficult to distinguish.

[0021] 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.

[0022] 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 in the protection scope of the present invention.

Claims

1. A method for preparing an ellipsoidal large-size diamond single crystal, characterized in that: The following steps are involved: S1. Use large-sized, angular diamond single crystals as crystals to eliminate metal and impurities on the surface of the crystals; S2, placing the crystal in a high-voltage assembly block, and then drying the high-voltage assembly block; S3, placing the high-pressure assembly block in the cavity of a six-sided top press device, and performing a dissolution operation at a pressure of 3-6 GPa, a temperature of 1200-2000 °C, and a time of 5 min-48 h; S4. After the dissolution 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 the crystal is cleaned to obtain the ellipsoidal large-size diamond single crystal.

2. The method for preparing an ellipsoidal large-size diamond single crystal according to claim 1, characterized in that: In S1, the operation of eliminating metal and impurities on the surface of the crystal is specifically: acid washing and ultrasonic treatment of 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 for preparing an ellipsoidal large-size diamond single crystal according to claim 1, characterized in that: In S2, the assembly process of placing the crystal in the high-pressure assembly block comprises the following steps: Use the phyllite block (3) as the outer container, and then put the conductive steel cap (2), the phyllite ring (1), the conductive metal sheet (4), the graphite sheet (5) and the sodium chloride + zirconium oxide liner (6) in order from bottom to top; Then, a graphite heating tube (7) is placed so that it is close to the inner wall of the sodium chloride + zirconium oxide liner (6), and then a magnesium oxide + zirconium oxide plug (8) and an insulating tube are placed in sequence. A metal catalyst (9) is placed in the insulating tube as a dissolving agent, and a diamond single crystal (10) is buried in the middle; Then insert another magnesium oxide + zirconium oxide plug (8) to be flush with the liner (6); Finally, another graphite sheet (5), a conductive metal sheet (4), a pyrophyllite ring (1), and a conductive steel cap (2) are placed in sequence, and finally an assembly structure that is symmetrical in top and bottom is obtained.

4. The method for preparing an ellipsoidal large-size diamond single crystal according to claim 3, characterized in that: The metal catalyst (9) is one of Fe, Ni, Co, and Mn, or an alloy thereof.

5. The method for preparing an ellipsoidal large-size diamond single crystal according to claim 1, characterized in that: In S2, the operation of drying the high-pressure assembly block is specifically: placing the high-pressure assembly block in an oven at 120° C. for 30 minutes.

6. The method for preparing an ellipsoidal large-size diamond single crystal according to claim 1, characterized in that: In S4, the operation of removing the metal alloy and graphite on the surface of the crystal is specifically: 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 in a volume ratio of 1:3 and heating it again to remove the graphite on the surface of the crystal.

7. The method for preparing an ellipsoidal large-size diamond single crystal according to claim 1, characterized in that: In S4, the cleaning operation is specifically: performing ultrasonic cleaning for 10 minutes.

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