Method for the synthesis of large particles of diamond

Abstract

The application discloses a synthesis method of large-granularity diamond. The method comprises the following steps: S1: after placing a diamond assembling block in a top pressure machine, the pressure of the top pressure machine is increased to 90-95 MPa, and the heating power is increased to 8.5-9.7 kW; S2: the pressure and the power are kept constant for h1; S3: for h2, the pressure is uniformly decreased to 84-90 MPa, and the power is uniformly increased to 9.3-9.9 kW; S4: for h3, the pressure is uniformly increased to 95-100 MPa, and the power is kept constant; S5: for h4, the pressure is uniformly decreased to 85-90 MPa, and the power is uniformly decreased to 8.3-9 kW; and S6: the heating is stopped and the pressure is released. The method can solve the problems of pressure and temperature drift caused by long-time synthesis of large-granularity diamond, and improves the purity of the large-granularity diamond rough.

Description

Technical Field

[0001] This invention relates to the field of diamond synthesis technology, and more particularly to a method for synthesizing large diamond particles. Background Technology

[0002] Diamond, as a superhard material possessing excellent properties such as ultra-high hardness, ultra-high thermal conductivity, and wide light transmission band, has irreplaceable application value in fields such as industrial processing, electronic devices, optical windows, and jewelry. With the rapid development of modern technology and high-end manufacturing, the market demand for large-particle, high-quality gem-grade diamond single crystals is becoming increasingly urgent.

[0003] Current conventional high-temperature, high-pressure (HTHP) lab-grown diamond growth processes are isothermal and pressure-controlled processes because diamond growth requires a stable and unchanging environment. Therefore, this method has long been widely adopted. However, as diamonds become larger, the problem of poor clarity remains unresolved, becoming the biggest challenge for high-end industrial applications of diamonds. While the pressure gauge and power output appear constant, leading to the assumption of a stable internal temperature, the actual internal chamber may already exhibit abnormal impurity concentrations or temperature field drift. Since there is no means to measure the actual pressure and temperature inside the reaction chamber, the true internal temperature and pressure can only be estimated. This can result in substandard clarity in the final product, and the lack of comparability between different batches of process conditions makes it difficult to build an effective process database. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a method for synthesizing large diamonds, which can solve the problem of pressure and temperature drift caused by long-term synthesis of large diamonds and improve the clarity of large diamond roughs.

[0005] The present invention achieves the above-mentioned technical objectives through the following technical solutions.

[0006] On one hand, the present invention provides a method for synthesizing large diamond particles, comprising the following steps: S1: After placing the diamond assembly block in the top press, the pressure of the top press is increased to 90-95 MPa, and the heating power is increased to 8.5-9.7 kW; S2: Keep the pressure and power constant within h1; S3: Within h2, the pressure is reduced to 84-90 MPa at a constant rate, while the power is increased to 9.3-9.9 kW at a constant rate. S4: Within h3, the pressure is increased at a constant rate to 95-100 MPa, while the power remains constant. S5: Within h4, the pressure drops uniformly to 85-90 MPa, while the power drops uniformly to 8.3-9 kW. S6: Stop heating and release pressure.

[0007] The synthesis method of this invention is suitable for large-particle diamonds. The synthesis steps mainly include a seed crystal formation stage, an initial formation stage, a slow, high-quality growth stage, a rapid shell solidification stage, and a withdrawal from the growth zone stage. In the seed crystal formation stage, high pressure and low temperature are used to ensure the seed crystal is not burned. In the initial formation stage, the pressure is slowly reduced while the internal temperature is uniformly increased, ensuring internal clarity in the early stages of slow growth. In the slow, high-quality growth stage, due to the gradual interpenetration of carbon and metal, the internal pressure drifts downwards. At this point, the pressure needs to be slowly increased to counteract the pressure drift, and the power needs to remain constant as heat generation and heat dissipation reach equilibrium. The rapid shell solidification stage is a preparatory step towards the end of growth, requiring a rapid reduction in pressure and power to bring growth to a standstill and prevent impurities from penetrating the interior. Withdrawing from the growth zone requires an even faster reduction in pressure and power to end growth and seal the growth zone. This solves the problem of pressure and temperature drift caused by long-term synthesis of large-particle lab-grown diamonds, ensuring the clarity of the large-particle diamond rough.

[0008] According to the synthesis method of the present invention, preferably, in step S2, h1 ranges from 8 to 15 h.

[0009] In step S2 of this invention, h1 represents the time during which the pressure and power remain constant. The range of h1 can be 8 to 15 hours, preferably 9 to 13 hours, and more preferably 10 to 12 hours. Within this range, it is beneficial for seed crystal formation while ensuring that the seed crystal is not burned by the specific pressure and power.

[0010] According to the synthesis method of the present invention, preferably, in step S1, the pressure is 91-94 MPa and the power is 8.7-9.5 kW.

[0011] Step S1 of this invention is the seed crystal forming stage, which employs high pressure and low temperature. The pressure can be 90-95 MPa, preferably 91-94 MPa; the heating power can be 8.5-9.7 kW, preferably 8.7-9.5 kW, and more preferably 9.0-9.3 kW. Within the scope of this invention, it can be ensured that the seeds are not burned.

[0012] According to the synthesis method of the present invention, preferably, in step S3, the range of h2 is 16 to 25 h.

[0013] In step S3 of this invention, h2 represents the time during which the pressure is slowly reduced while the internal temperature is uniformly increased. The range of h2 can be 16 to 25 hours, preferably 18 to 23 hours, and more preferably 20 to 22 hours. Within this time range, specific pressure and power are used to ensure slow seed growth and maintain internal purity in the early stages.

[0014] According to the synthesis method of the present invention, preferably, in step S3, the pressure is 85-88 MPa and the power is 9.4-9.7 kW.

[0015] In step S3 of this invention, the pressure can be 84-90 MPa, preferably 85-88 MPa, more preferably 86-87 MPa; the heating power can be 9.3-9.9 kW, preferably 9.4-9.7 kW, more preferably 9.5-9.6 kW. Within the scope of this invention, the initial internal cleanliness can be guaranteed.

[0016] According to the synthesis method of the present invention, preferably, in step S4, the range of h3 is 140-160h.

[0017] In step S4 of this invention, h3 represents the time during which the pressure is increased while the power remains constant. The range of h3 can be 140–160 h, preferably 145–158 h, and more preferably 150–155 h. Within this time range, specific pressure and power can be used to achieve slow, high-quality seed growth.

[0018] According to the synthesis method of the present invention, preferably, in step S4, the pressure is 95-98 MPa.

[0019] In step S4 of this invention, the pressure can be 95-100 MPa, preferably 95-98 MPa, and more preferably 95-96 MPa. During this stage, the internal pressure will drift downwards; a slow pressurization can counteract this drift. Simultaneously, as heat generation and heat dissipation reach equilibrium, the power output remains consistent, achieving slow, high-quality growth.

[0020] According to the synthesis method of the present invention, preferably, in step S5, h4 ranges from 3 to 6h.

[0021] In step S5 of this invention, h4 represents the time during which the pressure and power are reduced. The range of h4 can be 3 to 6 hours, preferably 4 to 5.5 hours, and more preferably 5 to 5.5 hours. Within this time range, specific pressure and power can be used to achieve rapid seed husk formation.

[0022] According to the synthesis method of the present invention, preferably, in step S5, the pressure is 85-88 MPa, while the power is uniformly reduced to 8.4-8.8 kW.

[0023] In step S5 of this invention, the pressure can be 85-90 MPa, preferably 85-88 MPa, more preferably 85-86 MPa; the power can be 8.3-9 kW, preferably 8.4-8.8 kW, more preferably 8.5-8.6 kW. At this stage, which is the final stage of growth, the pressure and power are rapidly reduced to stop growth and prevent impurities from penetrating the interior.

[0024] In step S6 of the present invention, the growth zone is withdrawn, and the pressure and power are reduced to 0 at a faster rate within 1 to 3 hours, thereby ending the growth and closing the growth zone.

[0025] According to the synthesis method of the present invention, preferably, the average weight of a single large diamond is 10 to 11 carats.

[0026] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention targets large diamonds and controls the growth rate at different stages by matching pressure and power at different stages. Furthermore, by adjusting process parameters, it offsets the drift phenomenon caused by the actual internal pressure due to volume shrinkage, effectively solving the problem of poor clarity in large synthetic diamonds.

[0027] (2) The diamonds cultivated by the synthesis method of the present invention have an average weight of 10.6 carats, a clarity grade of A, a maximum diameter of 15 mm, and a maximum height of 13 mm, which increases the overall output value by 120-150% compared with the traditional process. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0029] Example 1 On the 900 model, a 220*80 carbide top hammer is used, along with 97*72 pyrophyllite blocks to assemble the composite block. After placing the diamond assembly block in the top press, the pressure of the top press is increased to 91MPa, and the heating power is increased to 9.2kW.

[0030] Seed crystal formation stage: Keep the pressure and power constant for 10 hours.

[0031] Initial molding stage: During the first 10 to 30 hours (20 hours), the pressure was reduced from 91 MPa to 87 MPa at a constant rate, while the power was increased from 9.2 kW to 9.5 kW at a constant rate.

[0032] Slow, high-quality growth stage: During the period from 30 to 180 hours (150 hours), the pressure is increased from 87 MPa to 95 MPa at a constant rate, while the power is kept constant at 9.5 kW.

[0033] Rapid solidification stage: During the period from 180 to 185 hours (5 hours), the pressure decreased from 95 MPa to 85 MPa at a constant rate, while the power decreased from 9.5 kW to 8.5 kW at a constant rate.

[0034] Withdrawal from growth stage: During the period from 185h to 187h (2h), the pressure was reduced from 85 MPa to 0 at a constant rate, and the power was reduced from 8.5kW to 0 at a constant rate.

[0035] Example 2 On the 900 model, a 220*80 carbide top hammer and a 97*72 pyrophyllite block are used to assemble the composite block. After placing the diamond assembly block in the top press, the pressure of the top press is increased to 95MPa, and the heating power is increased to 9.7kW.

[0036] Seed crystal formation stage: Keep the pressure and power constant for 10 hours.

[0037] Initial molding stage: During the first 10 to 30 hours (20 hours), the pressure is reduced from 95 MPa to 90 MPa at a constant rate, while the power is increased from 9.7 kW to 9.9 kW at a constant rate.

[0038] Slow, high-quality growth stage: During the period from 30 to 180 hours (150 hours), the pressure is increased from 90 MPa to 98 MPa at a constant rate, while the power is kept constant at 9.9 kW.

[0039] Rapid solidification stage: During the period from 180 to 185 hours (5 hours), the pressure decreased from 98 MPa to 88 MPa at a constant rate, while the power decreased from 9.9 kW to 8.9 kW at a constant rate.

[0040] Withdrawal from growth stage: During the period from 185h to 187h (2h), the pressure was reduced from 88 MPa to 0 at a constant rate, and the power was reduced from 8.9kW to 0 at a constant rate.

[0041] Example 3 On the 900 model, a 220*80 carbide top hammer and a 97*72 pyrophyllite block are used to assemble the composite block. After placing the diamond assembly block in the top press, the pressure of the top press is increased to 93MPa, and the heating power is increased to 9.3kW.

[0042] Seed crystal formation stage: Keep the pressure and power constant for 10 hours.

[0043] Initial molding stage: During the first 10 to 30 hours (20 hours), the pressure was reduced from 93 MPa to 88 MPa at a constant rate, while the power was increased from 9.3 kW to 9.6 kW at a constant rate.

[0044] Slow, high-quality growth stage: During the period from 30 to 180 hours (150 hours), the pressure is increased from 88 MPa to 96 MPa at a constant rate, while the power is kept constant at 9.6 kW.

[0045] Rapid solidification stage: During the period from 180 to 185 hours (5 hours), the pressure decreased from 96 MPa to 86 MPa at a constant rate, while the power decreased from 9.6 kW to 8.6 kW at a constant rate.

[0046] Withdrawal from growth stage: During the period from 185h to 187h (2h), the pressure was reduced from 86MPa to 0 at a constant rate, and the power was reduced from 8.6kW to 0 at a constant rate.

[0047] Example 4 On the 900 model, a 220*80 carbide top hammer is used, along with 97*72 pyrophyllite blocks to assemble the composite block. After placing the diamond assembly block in the top press, the pressure of the top press is increased to 91MPa, and the heating power is increased to 9.2kW.

[0048] Seed crystal forming stage: Keep the pressure and power constant for 9 hours.

[0049] Initial molding stage: During the period from 9 to 27 hours (18 hours), the pressure was reduced from 91 MPa to 87 MPa at a constant rate, while the power was increased from 9.2 kW to 9.5 kW at a constant rate.

[0050] Slow, high-quality growth stage: During the period from 27 to 182 hours (155 hours), the pressure was increased from 87 MPa to 95 MPa at a constant rate, while the power was kept constant at 9.5 kW.

[0051] Rapid solidification stage: During the period from 182 to 186 hours (4 hours), the pressure decreased from 95 MPa to 85 MPa at a constant rate, while the power decreased from 9.5 kW to 8.5 kW at a constant rate.

[0052] Withdrawal from growth stage: During the period from 186h to 188h (2h), the pressure was reduced from 85 MPa to 0 at a constant rate, and the power was reduced from 8.5kW to 0 at a constant rate.

[0053] Example 5 On the 900 model, a 220*80 carbide top hammer is used, along with 97*72 pyrophyllite blocks to assemble the composite block. After placing the diamond assembly block in the top press, the pressure of the top press is increased to 91MPa, and the heating power is increased to 9.2kW.

[0054] Seed crystal formation stage: Keep the pressure and power constant for 12 hours.

[0055] Initial molding stage: During the 12th to 35th hour (23 hours), the pressure was uniformly reduced from 91 MPa to 87 MPa, while the power was uniformly increased from 9.2 kW to 9.5 kW.

[0056] Slow, high-quality growth stage: During the period from 35 to 180 hours (145 hours), the pressure is increased from 87 MPa to 95 MPa at a constant rate, while the power is kept constant at 9.5 kW.

[0057] Rapid solidification stage: During the period from 180 to 184 hours (4 hours), the pressure decreased from 95 MPa to 85 MPa at a constant rate, while the power decreased from 9.5 kW to 8.5 kW at a constant rate.

[0058] Withdrawal from growth stage: During the period from 184h to 186h (2h), the pressure was reduced from 85 MPa to 0 at a constant rate, and the power was reduced from 8.5kW to 0 at a constant rate.

[0059] Comparative Example 1 After the diamond assembly block is placed in the top press, the pressure of the top press is increased to 95 MPa within 2 minutes. After reaching the maximum pressure, the power is increased to 9.5 kW within 2 hours.

[0060] Maintaining constant power and pressure, the diamond seed crystal grows. Once growth is complete, heating is stopped and the pressure is slowly released.

[0061] In Examples 1-5 and Comparative Example 1, diamonds were grown from 15 seeds. The results of diamond clarity, average weight per seed, maximum diameter and height are shown in Table 1.

[0062] Table 1. Diamond Measurement Results As shown in the table above, the diamonds synthesized in Examples 1-5 have an average weight of over 10 carats per diamond, with over 80% achieving Grade A clarity. The largest diamond diameter reaches 15mm, and the largest height reaches 13mm, indicating high quality. Comparative Example 1, which uses a constant temperature and pressure process, produced larger diamonds with poorer clarity.

[0063] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for synthesizing large diamond particles, characterized in that, Includes the following steps: S1: After placing the diamond assembly block in the top press, the pressure of the top press is increased to 90-95 MPa, and the heating power is increased to 8.5-9.7 kW; S2: Keep the pressure and power constant within h1; S3: Within h2, the pressure is reduced to 84-90 MPa at a constant rate, while the power is increased to 9.3-9.9 kW at a constant rate. S4: Within h3, the pressure is increased at a constant rate to 95-100 MPa, while the power remains constant. S5: Within h4, the pressure drops uniformly to 85-90 MPa, while the power drops uniformly to 8.3-9 kW. S6: Stop heating and release pressure.

2. The synthesis method according to claim 1, characterized in that, In step S2, h1 ranges from 8 to 15h.

3. The synthesis method according to claim 1, characterized in that, In step S1, the pressure is 91-94 MPa and the power is 8.7-9.5 kW.

4. The synthesis method according to claim 1, characterized in that, In step S3, the range of h2 is 16 to 25 h.

5. The synthesis method according to claim 1, characterized in that, In step S3, the pressure is 85-88 MPa and the power is 9.4-9.7 kW.

6. The synthesis method according to claim 1, characterized in that, In step S4, h3 ranges from 140 to 160h.

7. The synthesis method according to claim 3, characterized in that, In step S4, the pressure is 95-98 MPa.

8. The synthesis method according to any one of claims 1 to 7, characterized in that, In step S5, h4 ranges from 3 to 6h.

9. The synthesis method according to claim 8, characterized in that, In step S5, the pressure is 85-88 MPa, while the power decreases at a constant rate to 8.4-8.8 kW.

10. The synthesis method according to any one of claims 1 to 9, characterized in that, Large diamonds typically weigh between 10 and 11 carats each.

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