CN108854850B

CN108854850B - Synthesis process of personalized precious stone grade diamond

Info

Publication number: CN108854850B
Application number: CN201810763853.9A
Authority: CN
Inventors: 张建华; 胡碧涌; 杨晋中; 黄茂; 齐仁太; 邵静茹; 郝静; 张智超; 李毛毛
Original assignee: Zhengzhou Sino Crystal Diamond Joint Stock Co ltd
Current assignee: Zhengzhou Sino Crystal Diamond Joint Stock Co ltd
Priority date: 2018-07-12
Filing date: 2018-07-12
Publication date: 2023-06-23
Anticipated expiration: 2038-07-12
Also published as: CN108854850A

Abstract

The invention discloses a synthesis process of personalized precious stone grade diamond, which comprises the following steps: pressurizing and heating; continuously heating, preserving heat, pressurizing and maintaining pressure; then the pressure is increased to be 1-3MPa/h, the pressure is increased to the final synthesis pressure of 65-70MPa, and after the heating power is increased to 7-8KW for 1-3h, the heat preservation and pressure maintaining are continued for 8-12h; stopping heating and cooling to room temperature, and starting to release pressure when the temperature is reduced to half, until the pressure is relieved to normal pressure. By adopting the synthesis process, personalized pattern customization can be realized, the grown diamond crystal is controlled to be colorless and transparent, the diamond can be comparable to precious stone grade diamond, and patterns with different shapes can be controlled to be grown at the center of the diamond crystal, such as: spherical, pine needle, etc., and simultaneously, eliminates the cracks of the finished product and improves the cleanliness of the diamond, thereby meeting the personalized demands of customers.

Description

Synthesis process of personalized precious stone grade diamond

Technical Field

The invention belongs to the technical field of diamond synthesis, and particularly relates to a synthesis process of personalized precious stone grade diamond.

Background

The technology of artificially synthesizing diamond monocrystal is from the high temperature and high pressure temperature gradient method adopted by general electric company in 1970, and the Ib type diamond monocrystal is synthesized by means of metal catalyst method. Most of foreign parts adopt a double-sided hydraulic press for high-temperature and high-pressure synthesis of diamond single crystals, while the domestic parts almost adopt a hinge type hexahedral hydraulic press for high-temperature and high-pressure synthesis of diamond single crystals, and the hinge type hexahedral hydraulic press is high-temperature and high-pressure equipment which is independently researched and produced in China and has the advantages of an ultrahigh-pressure die, simple structure, simple production operation, easy control of press technological parameters, balanced pressure, low cost and the like, so the hinge type hexahedral hydraulic press is always the main equipment for synthesizing superhard materials in China from 60 s. The ultrahigh pressure synthesis die of the hexahedral hydraulic press consists of 6 hammers with three-dimensional axes perpendicular to each other, and in the working process, the top hammer of the hexahedral hydraulic press applies pressure to 6 faces of the regular hexahedral high Wen Zu synthetic block, and an ultrahigh pressure synthesis cavity is formed by 12 sealing edges formed by flowing of sealing materials on the outer layer of the synthetic block and the 6 faces of the top hammer. The multi-pressure source hinge type hexahedral top press is widely used in China, and the driving of the top hammer by the multi-pressure source hinge type press is realized by utilizing pistons of 6 oil cylinders. The anvil is pushed to move by the oil pressure system, pressurized and pressure-maintaining, and a precise electric control automatic system is adopted to be connected with the anvil in a matched way, so that proper pressure can be controlled.

The precious stone grade diamond monocrystal has larger granularity (granularity is more than 1 mm) and higher cleanliness (the interior of the crystal is almost colorless and transparent), and most of the monocrystal is used as artware or jewelry. Meanwhile, the diamond has very excellent performances in the aspects of sound, light, electricity, heat and the like, so that the diamond has irreplaceable effects in the fields of aerospace, medicine, military, electronics and the like. The existing method for artificially synthesizing the precious stone-grade diamond mainly adopts a high-temperature high-pressure temperature gradient method. The method can not only stably convey carbon atoms in the carbon source to the crystal, but also reasonably control the growth of the crystal. For assembling the assembled block, the composite medium of pyrophyllite and dolomite is usually selected for sealing and pressure transmission outside, steel caps are selected for heating and heat preservation at the top, diamond monocrystal is selected as seed crystal inside to be arranged on a zirconium dioxide crystal bed and is ensured to be arranged at a low-temperature end, high-purity graphite is required to be used as a carbon source to be ensured to be positioned at a high-temperature end, a metal alloy catalyst is arranged in the middle, and materials such as a graphite tube, sodium chloride and the like are respectively selected as heating and heat preservation mediums. And selecting proper pressure and temperature, wherein the pressure is about 5-6 GPa, and the temperature is not more than 1500 ℃.

The existing synthesis process mainly comprises the following steps: and (3) raising the pressure to 70-80% of the synthesis pressure of the diamond by using a high-pressure oil pump, maintaining the pressure for tens to more than ten minutes, raising the pressure to 60-80 MPa, and maintaining the pressure for tens to hundreds of hours according to the pressure requirement. And heating by adopting constant heating power generally, when the diamond synthesis pressure reaches 70-80%, starting heating, wherein the heating power is 7-8kW, and after the heating power reaches a preset value, heating constantly for tens to hundreds of hours.

However, when the precious stone-grade diamond is used as an artwork and a jewelry, the existing technology is difficult to synthesize the personalized precious stone-grade diamond, i.e. the shape of the internal pattern of the crystal cannot be controlled. The personalized precious stone grade diamond is specifically expressed as: and controlling the center of the diamond crystal to grow patterns with different shapes, such as: the ball shape and the pine needle are adopted, and the grown diamond crystal is controlled to have no crack and high cleanliness, and can be compared with precious stone grade diamond, thereby meeting the individual demands of customers. Amorphous carbon (also known as transition carbon, converted from a carbon source, which is a broad class of allotropes of carbon) can be introduced into the interior of large-sized diamond crystals by changing the raw materials, assembly and synthesis processes of diamond.

Compared with personalized precious diamond, the existing diamond synthesis process can not synthesize, and has the following problems: 1. in the initial stage of synthesis, the existing synthesis process adopts a method of directly heating to the final synthesis temperature of the diamond, the heat preservation and pressure maintaining are not carried out in a temperature range which is 20-30% lower than the final synthesis temperature of the diamond, the carbon source cannot form amorphous carbon, and the carbon source can be nucleated due to the too fast temperature increase; 2. in the pressurizing and heating process, the pressure is slightly increased, and the temperature is gradually increased until reaching a temperature interval suitable for the growth of the diamond, and the pressure is not increased to the synthesis pressure of the diamond at the moment, so that a good nucleation temperature-pressure interval of the diamond is missed; 3. in the constant pressure and heat preservation process of the diamond synthesis pressure, the current technology keeps the power almost unchanged, and the constant temperature and the constant pressure can lead to the difficulty in continuously transferring carbon elements in a carbon source to a seed crystal for a long time, reduce the growth speed of the diamond and influence the crystal quality of the diamond; 4. the amorphous carbon cannot enter the inside of the diamond crystal without proper pressurizing and heating operations in the later stage of synthesis. The above problems will lead to the difficulty in achieving a personalized production with current diamond synthesis processes.

Disclosure of Invention

The invention aims to provide a synthesis process of personalized precious stone grade diamond.

Based on the above purpose, the invention adopts the following technical scheme:

a process for synthesizing personalized precious stone grade diamond, comprising the steps of:

(1) Pressurizing and heating process: placing the assembled synthetic block into a high-pressure cavity of a hexahedral top press, pressurizing to an initial synthetic pressure of 45-50MPa for one time, maintaining the pressure for 2-4 hours, pressurizing to a middle synthetic pressure of 60-65MPa at 3.5-7.5MPa/h, and maintaining the pressure for 5-10 hours; when the pressure rises to 30-35% of the final synthesis pressure of 65-70MPa, heating is started, the heating power rises to 3-4KW of initial power through 5-10s, the temperature is kept for 2-4h, the heating power rises to 5-6KW of middle power through 5-10s, and the heating power is kept for 5-10h;

(2) Continuously heating, preserving heat, pressurizing and maintaining pressure;

(3) Then the pressure is increased to be 1-3MPa/h, the pressure is increased to the final synthesis pressure of 65-70MPa through 2-3h, and the heating power is increased to the final power of 7-8KW through 1-3h, and then the heat preservation and pressure maintaining are carried out continuously for 8-12h;

(4) Stopping heating and cooling to room temperature, and starting to release pressure when the temperature is reduced to half, until the pressure is relieved to normal pressure.

In the step (1), the pressurizing speed during one pressurizing is 3.5-7.5MPa/h; the hexahedral press is a multi-pressure source hinge hexahedral press.

In the step (2), the specific operation of heating and preserving heat is as follows: heating for 10-15h at a speed of 0.03-0.05 KW/h, and preserving heat for 5-10h; the specific operation of pressurizing and pressure maintaining is as follows: pressurizing at a speed of 0.05-0.08MPa/h for 10-15h and maintaining the pressure for 5-10h.

In the step (2), the times of continuous temperature rise, heat preservation and pressurization and pressure maintaining are respectively 1-2 times (the times of temperature rise, heat preservation and pressurization and pressure maintaining are 1-2 times).

In the step (4), the heating power is reduced at a speed of 0.005-0.01KW/s in the process of stopping heating and reducing temperature; the pressure relief speed is 0.05-0.06MPa/s.

The principle of the invention: in the interior of the assembled synthetic block, the carbon source and the seed crystal are respectively positioned at a high temperature end and a low temperature end, and due to the temperature difference, the solubility of diamond and graphite in the catalyst solvent is different, so that concentration gradient is generated, and the migration of carbon elements from the high temperature end to the low temperature end is promoted. When the carbon element in the metal catalyst solution is supersaturated with diamond or graphite, the carbon element will precipitate in the form of diamond to start homoepitaxial growth and gradually start growing. The initial synthesis temperature of the invention is lower than the prior art, and the method of multistage boosting pressure maintaining, temperature rising and heat preserving is adopted, so that the continuous boosting pressure maintaining, temperature rising and heat preserving can be realized in the synthesis process, and the time of the invention can be shortened by nearly one third compared with the prior synthesis time. Amorphous carbon can be obtained in a pressure-temperature environment with a pressure of 40-50MPa and a temperature of 800-100 ℃ by adopting a multi-stage heating method, because the synthesis process is carried out in a stable region of a diamond phase, graphite is in a metastable state in the region, the internal heating amplitude of an assembled synthesis block is reduced in the initial heating stage of synthesis, the temperature of the synthesis of the final diamond (1200-1300 ℃) can lead to the deviation of crystal growth from the phase stable region of graphite-to-diamond conversion, and at the moment, the synthesis condition is near the diamond-graphite equilibrium curve, so that the graphite is converted into sp contained in the sp ² 、sp ³ Amorphous carbon of carbon structure, while at a good nucleation zone for diamond in a slightly higher pressure-temperature environment. At different temperature-pressure stages, the synthesis pressure is 40-50MPa, the temperature is 800-1000 ℃, the conversion of carbon source into a small amount of amorphous carbon is facilitated, and the nucleation of diamond is facilitated at higher temperature and pressure. With the continuous growth of the seed crystal, the surface area is larger and larger, the demand for carbon sources is higher and higher, and the continuous small-amplitude pressurization and heat preservation are beneficial to the continuous growth of the seed crystal. And (3) continuously pressurizing and maintaining the pressure for one half of the full time period (20-25 h from the beginning of synthesis), and enabling the diamond to enter the diamond crystal. And then the amorphous carbon shape in the crystal is controlled by lifting to different temperature ranges. Heating to synthesis temperature and maintaining the temperature in the middle of synthesis, the amorphous carbon shape can be fixed, i.e. the amorphous carbon gradually starts to form into sphere, due to the increase of temperatureHigh, amorphous carbon has a tendency to change towards the sphere and agglomerate each part under the action of surface tension, and the sphere has the least surface energy and a more stable morphology. Due to amorphous carbon, i.e. having graphite crystals sp ² And has a structure of diamond crystal sp ³ The density of the diamond-like carbon is obviously different from that of diamond, and the diamond-like carbon can be acted by the action of the force in diamond crystal under the action of high temperature and high pressure, amorphous carbon is in the form of a very regular sphere due to surface tension on the one hand and surrounding diamond crystals on the other hand. At the final synthesis temperature of 1200-1500 ℃, carbon atoms are continuously conveyed from a high temperature end to a low temperature end, the carbon atoms are gradually adsorbed by a seed crystal at the low temperature end in the conveying process, and after the high temperature high pressure synthesis time is prolonged, the diamond seed crystal can gradually grow into diamond crystals with larger size.

Compared with the prior art, the invention has the following beneficial effects:

by adopting the synthesis process, personalized pattern customization can be realized, the grown diamond crystal is controlled to be colorless and transparent, the diamond can be comparable to precious stone grade diamond, and patterns with different shapes can be controlled to be grown at the center of the diamond crystal, such as: spherical and pine needles, and meanwhile, eliminates cracks of finished products and improves the cleanliness of diamond, and can meet the personalized demands of customers.

Drawings

FIG. 1 is a graph of an existing precious stone grade diamond synthesis process;

FIG. 2 is a graph of a personalized gem-grade diamond synthesis process of the present invention;

FIG. 3 is an assembled composite block internal block diagram;

FIG. 4 diamond seed;

FIG. 5 a spherical pattern inside the crystal;

FIG. 6 personalized precious stone grade bare drill;

FIG. 7 is a Raman spectrum of a prior art precious stone grade diamond;

FIG. 8 is a Raman spectrum of the personalized precious stone grade diamond prepared in example 1 of the present invention;

wherein: in fig. 3, 1, a steel cap; 2. a pyrophyllite sealing block; 3. a dolomite liner; 4. a high purity graphite rod; 5. a thermal insulation material; 6. a graphite tube; 7. steel sheet, graphite sheet heat transfer medium; 8. pyrophyllite plugging rings; 9. pyrophyllite ring; 10. dolomite blocking rings; 11. a filler material; 12. an isolation tube; 13. alloy catalyst sheet; 14. diamond seed crystal; 15. a crystal bed; 16. a dolomitic stone ring.

Detailed Description

Example 1

(1) Pressurizing and heating process: placing the assembled synthetic block into a high-pressure cavity of a multi-pressure-source hinge type hexahedral top press, pressurizing at a pressurizing speed of 6.5MPa/h for one time until the initial synthetic pressure is 48MPa, maintaining the pressure for 3 hours, and pressurizing at a pressurizing speed of 6.5MPa/h until the intermediate synthetic pressure is 61MPa, and maintaining the pressure for 7 hours; when the pressure rises to 35% of the final synthesis pressure of 67MPa, heating is started, the heating power rises to 3.6KW at the initial power for 8s, the temperature is kept for 2h, the heating power rises to 5.5KW at the middle power for 8s, and the temperature is kept for 8h;

(2) Continuously heating and preserving heat, pressurizing and maintaining pressure for 2 times (heating and preserving heat for 2 times, pressurizing and maintaining pressure for 2 times); the specific operation of heating and preserving heat is as follows: raising the temperature for 11h at the speed of 0.03KW/h and preserving the heat for 8h; the specific operation of pressurizing and pressure maintaining is as follows: pressurizing at a speed of 0.05MPa/h for 11h and maintaining the pressure for 8h;

(3) Then the pressure is increased to 2.5MPa/h, the pressure is increased to 67MPa of final synthetic pressure after 3h, and the heating power is increased to 7KW of final power after 3h, the heat preservation and pressure maintaining are carried out continuously for 12h;

(4) Stopping heating and cooling to room temperature, and starting to relieve pressure when the temperature is reduced to half, and ending until the pressure is relieved to normal pressure; the heating power is reduced at a speed of 0.01KW/s in the process of stopping heating and reducing temperature; the pressure relief rate was 0.06MPa/s.

Example 2

(1) Pressurizing and heating process: placing the assembled synthetic block into a high-pressure cavity of a multi-pressure-source hinge type hexahedral top press, pressurizing at a pressurizing speed of 3.5MPa/h for one time until the initial synthetic pressure is 45MPa, maintaining the pressure for 2 hours, and pressurizing at a pressurizing speed of 3.5MPa/h until the intermediate synthetic pressure is 60MPa, and maintaining the pressure for 10 hours; when the pressure rises to 30% of the final synthesis pressure of 65MPa, heating is started, the heating power rises to 3KW at the initial power after 5s, the temperature is kept for 2h, and the heating power rises to 5KW at the middle power after 5s, and the temperature is kept for 10h;

(2) Continuously heating, preserving heat, pressurizing and maintaining pressure for 2 times respectively; the specific operation of heating and preserving heat is as follows: raising the temperature for 15h at the speed of 0.03KW/h and preserving the temperature for 5h; the specific operation of pressurizing and pressure maintaining is as follows: pressurizing at a speed of 0.05MPa/h for 15h and maintaining the pressure for 5h;

(3) Then the pressure is increased to be 1MPa/h, the pressure is increased to the final synthesis pressure of 65MPa through 3h, and the heating power is increased to the final power of 8KW through 3h, and then the heat preservation and pressure maintaining are carried out continuously for 8h;

(4) Stopping heating and cooling to room temperature, and starting to relieve pressure when the temperature is reduced to half, and ending until the pressure is relieved to normal pressure; the heating power is reduced at the speed of 0.005KW/s in the process of stopping heating and reducing temperature; the pressure relief rate was 0.05MPa/s.

Example 3

(1) Pressurizing and heating process: placing the assembled synthetic block into a high-pressure cavity of a multi-pressure-source hinge type hexahedral top press, pressurizing at a pressurizing speed of 7.5MPa/h for one time until the initial synthetic pressure is 50MPa, maintaining the pressure for 4 hours, and pressurizing at a pressurizing speed of 7.5MPa/h until the intermediate synthetic pressure is 65MPa, and maintaining the pressure for 5 hours; when the pressure rises to 35% of the final synthesis pressure of 70MPa, heating is started, the heating power rises to 4KW at the initial power after 10s, the temperature is kept for 4 hours, the heating power rises to 6KW at the middle power after 10s, and the temperature is kept for 5 hours;

(2) Continuously heating, preserving heat, pressurizing and maintaining pressure for 2 times respectively; the specific operation of heating and preserving heat is as follows: heating for 10h at the speed of 0.05KW/h, and preserving heat for 10h; the specific operation of pressurizing and pressure maintaining is as follows: pressurizing at the speed of 0.08MPa/h for 10h and maintaining the pressure for 10h;

(3) Then the pressure is increased to 3MPa/h, the pressure is increased to the final synthetic pressure of 70MPa through 2h, and the heating power is increased to the final power of 7KW through 1h, and then the heat preservation and pressure maintaining are carried out continuously for 12h;

The combined synthetic block adopted in the embodiment selects high-purity graphite with the mass fraction of 99.999% to prepare a graphite rod core as a carbon source in the personalized jewel-grade diamond synthesis process. The catalyst is prepared by taking an alloy mainly comprising iron, cobalt and nickel as the catalyst, adding titanium powder and aluminum powder which account for 1-2% of the catalyst by mass and have the mass fraction of 99.99% as a nitrogen removing agent, and mixing iron powder, cobalt powder, nickel powder, aluminum powder and titanium powder according to the mass ratio of 1:4, and smelting, casting and pressing the powder into a catalyst tablet, wherein the iron content is 60% -70%, the cobalt content is 20% -30%, the nickel content is 10% -15%, the aluminum content is 0.5% -1%, and the titanium content is 0.5% -1%. The metal aluminum and titanium can react with nitrogen element under high temperature and high pressure melting state to generate very stable aluminum nitride and titanium nitride, thereby achieving the purpose of removing the dispersed nitrogen impurity in the diamond crystal. Thus, the absorption of yellow light by the diamond crystal can be greatly reduced, and the inside of the crystal is colorless and transparent.

The assembled block is made of pyrophyllite and dolomite composite medium, and is of a cubic structure, the exterior is provided with a pyrophyllite sealing block 2 and an embedded dolomite ring 16, the top and the bottom are provided with steel caps 1, and the top and the bottom are provided with the pyrophyllite ring 9 and the dolomite ring 16 as plugs. The dolomite blocking ring 10 is tightly attached to the dolomite liner tube 3, and the sealing and heat insulating properties of the synthetic block can be improved by tightly attaching the pyrophyllite blocking ring 8 to the dolomite blocking ring 10 up and down. The steel sheet and graphite sheet heat transfer medium 7 is placed at the contact position of the bottom of the plug and the graphite tube, so that the heat transfer area can be increased, and the internal temperature of the synthetic block can be increased. The structure serves as an assembled composite block for sealing, pressure transfer and heat conduction. The internal cavity is a heat insulation material 5 with a tubular structure, and is internally provided with an annular liner tube of a composite medium of sodium chloride, zirconium dioxide and magnesium oxide, wherein the content of sodium chloride is 40-50%, the content of zirconium dioxide is 30-40% and the content of magnesium oxide is 30-20%. The composite medium annular liner tube has the functions of stabilizing temperature and uniformly transmitting pressure. And secondly, a high-purity graphite tube 6 is selected as a heat transfer device to be assembled in the annular heat insulation layer, wherein the heating tube is generally prepared from 99.99-99.999% high-purity graphite. An annular insulating material mainly comprising zirconium dioxide is selected as a separation tube 12 to cover the inner wall of the graphite tube 6, so that the effect of isolating external gas and solid impurities is achieved, and a filling material 11 is arranged in a space between the graphite tube 6 and the separation tube 12. The high purity graphite rod 4, the alloy catalyst sheet 13 and the crystal bed 15 are respectively arranged in the isolation tube 12 from top to bottom (the diamond seed crystal 14 is arranged on the crystal bed 15). The internal structure of the assembled composite block is shown in fig. 3.

High-quality hexa-octahedral pure crystals are selected as seed crystals and are arranged on a composite crystal bed of zirconium dioxide and magnesium oxide, wherein the crystal granularity is usually 0.35-0.40 mm, as shown in fig. 4 (color pictures in other documents). Ensuring that the seed crystal and the carbon source are respectively arranged at the low temperature end and the high temperature end, and placing the alloy catalyst in the seed crystal and the carbon source. The carbon source, the catalyst and the outside of the crystal bed are wrapped by insulating materials, so that impurities in the external materials are prevented from entering the diamond crystal in the growth process. The diamond monocrystal particles grown by the continuity of the seed crystal are transparent and clean, the interior of the crystal is provided with a spherical pattern as shown in figure 5 (amorphous carbon in A in the figure), the diamond monocrystal particles are synthesized by the embodiment 1, and the cut and ground finished product personalized bare drill is as shown in figure 6.

Because of the different structures of diamond, graphite crystals and amorphous carbon, laser raman spectroscopy (laser Raman spectrometer) is generally used to analyze whether diamond grade diamond contains carbon structure impurities such as graphite in other non-diamond phases. Fig. 7 is a raman spectrum of a gemstone-grade diamond, and fig. 8 is a raman spectrum of a personalized gemstone-grade diamond manufactured in example 1 of the present invention. As can be seen from fig. 7 and 8, the precious stone-grade diamond and the personalized precious stone-grade diamond are each 1331.43cm ^-1 And 1331.87cm ^-1 Has obvious vibration peak, and full width at half maximum (FWHM) of 3.1 cm ^-1 、3.2 cm ^-1 . The standard Raman peak of natural IIa type diamond is 1332cm ^-1 At the location, the full width at half maximum (FWHM) is 2cm ^-1 . So that the vibration peak position of the two is equal to the Raman standard peak 1332 and cm of the natural IIa diamond ^-1 Very close and with small half-width differences. The content of diamond crystal structure is extremely high. Differently, a precious stone is personalizedThe grade diamond is 1428.35cm ^-1 The amorphous carbon peak is determined to be amorphous carbon peak after the comparison of the literature at home and abroad, and the standard peak is 1400-1500 cm ^-1 Between them. Amorphous carbon contains two-dimensional graphite layers or three-dimensional graphite crystallites with extremely small diameters (less than 30 nm), and the three-dimensional crystallite structure and diamond sp ³ Structurally similar, two-dimensional layer and graphite crystal sp ² The structures are similar. The peaks of the polycrystalline and single crystal graphites are not shown, indicating that the graphite impurity is not contained.

Claims

1. A process for synthesizing personalized precious stone grade diamond, comprising the steps of:

(1) Pressurizing and heating process: placing the assembled synthetic block into a high-pressure cavity of a hexahedral top press, pressurizing for 2-4 hours after primary pressurizing to an initial synthetic pressure of 45-50MPa, pressurizing to a middle synthetic pressure of 60-65MPa at a pressurizing speed of 3.5-7.5MPa/h, and maintaining for 5-10 hours; when the pressure rises to 30-35% of the final synthesis pressure of 65-70MPa, heating is started, the heating power rises to 3-4KW of initial power through 5-10s, the temperature is kept for 2-4h, the heating power rises to 5-6KW of middle power through 5-10s, and the heating power is kept for 5-10h;

(2) Continuously heating, preserving heat, pressurizing and maintaining pressure; the specific operation of heating and preserving heat is as follows: heating for 10-15h at a speed of 0.03-0.05 KW/h, and preserving heat for 5-10h; the specific operation of pressurizing and pressure maintaining is as follows: pressurizing at a speed of 0.05-0.08MPa/h for 10-15h and maintaining the pressure for 5-10h;

2. The process for synthesizing personalized gem-grade diamond according to claim 1, wherein in the step (1), the pressurizing speed at the time of one pressurizing is 3.5-7.5MPa/h; the hexahedral press is a multi-pressure source hinge hexahedral press.

3. The process for synthesizing personalized gem-grade diamond according to claim 1, wherein in the step (2), the number of times of continuous heating, heat preservation, pressurization and pressure maintaining is 1-2 times.

4. The process for synthesizing personalized gem-grade diamond according to claim 1, wherein in the step (4), the heating power is reduced at a rate of 0.005-0.01KW/s in the process of stopping heating and cooling; the pressure relief speed is 0.05-0.06MPa/s.