A method of synthesizing colored cultivated diamonds

Abstract

A synthetic method of color cultured diamond, the catalyst uses FeCo alloy, and also includes trace elements of Ni, B, Ti, the mixture is added to the planetary ball mill for mixing, and n-heptane is added as a process control agent to obtain a mixed powder, the mixed powder is screened through a 120 mesh screening device to obtain undersize, the undersize is added to the graphite mold cavity for pressure heating to make an alloy rod, the alloy rod is further compressed by a rotary swaging machine, the compression rate is 25%, and the temperature is 1350 DEG C, a dense alloy rod is obtained, the dense alloy rod is cut to obtain a catalyst sheet, and the catalyst sheet and high-purity graphite are synthesized into a diamond through a top pressure machine. By using the catalyst, the element content is controllable, the grain is refined, the density is higher, the impurity content is less, the combination mode of different catalyst sheets is adjusted to control the trace elements into the diamond, and finally the color of the diamond can be artificially intervened.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diamond synthesis and cultivation process, and particularly relates to a synthesis method of color cultivation diamond. BACKGROUND

[0002] Color diamond is the focus of research in the jewelry field. The research methods for impurities, defects, color and other aspects of diamond crystal are diverse, which can effectively reveal the growth conditions and performance changes of diamond, and lay a solid theoretical foundation for the application of diamond in the fields of superhard materials, gem materials and semiconductor materials. With the development of artificial cultivation of diamond technology, more and more attention is paid to the synthesis of color diamond.

[0003] In order to reduce the dependence on the mining of natural diamonds, the industry has increased research on cultivated diamonds. Yellow Ib type, colorless IIa type and blue IIb type gem-grade diamonds are the three main types on the market, but they still cannot meet people's demand for the diversification of diamond color. At present, the color of diamond can be improved by technical means, such as green, blue, red, pink, etc. The cost of color treatment of natural diamond is high, the market acceptance is not high, and the price is very expensive. With the development of artificial cultivation of diamond technology, color treatment of synthetic diamond has gradually developed. The advantages of cultivated diamond are low cost, rich samples and controllable color. Compared with natural diamond, the controllable color of cultivated diamond is expected to realize large-scale production, making the color diamond marketable. Therefore, it is imperative to change the color and increase the variety of cultivated diamond by controlling the content of trace elements.

[0004] Whether it is a natural diamond or a HPHT or CVD synthetic diamond, the color of the diamond crystal after growth is mostly unsatisfactory, with yellow, brown or gray tones, etc. On the one hand, it has a great impact on the price of diamond, and color modification research is beneficial to improve the value of diamond; on the other hand, color modification experiments are based on material modification research. In the early stage, surface coating technology was mainly used to improve the color of diamond, but due to poor durability, easy peeling of the coating, and other reasons, this method was abandoned. With the development of science and technology, artificial cultivation of diamond is now mainly treated by HPHT, irradiation, annealing or composite process to produce or repair internal defects of diamond, so as to improve the color grade of diamond or make the diamond show more attractive colors such as green, pink, purple, red, etc., so as to improve the value and economic benefit of diamond. However, the current color control of diamond is high in cost, which is not conducive to commercial use. At the same time, the temperature field and pressure field of the synthetic diamond process fluctuate greatly, resulting in unstable quality of synthetic diamond. The quality of diamond is greatly different in different parts of the crystal bed of the same assembly block, and the diamond grade is also different between different synthetic blocks, resulting in poor quality of finished products. SUMMARY

[0005] In view of the above, in order to overcome the defects of the prior art, the purpose of the present application is to provide a synthetic method for color cultured diamond,

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme: a synthetic method for color cultured diamond,

[0007] Step one, preparing catalyst raw materials, the catalyst uses FeCo alloy, and also includes trace elements of Ni, B and Ti, so the catalyst raw material is a mixture of Fe and Co and trace elements of Ni, B and Ti;

[0008] Step two, grinding and mixing, the mixture obtained in step one is added to a planetary ball mill for mixing, and n-heptane is added as a process control agent to obtain mixed powder;

[0009] Step three, screening, the mixed powder obtained in step two is screened through a 120 mesh screening device to obtain undersize;

[0010] Step four, vacuum hot pressing and sintering, the undersize obtained in step three is added to a graphite mold cavity for pressure and heating to make an alloy rod;

[0011] Step five, spinning, the alloy rod obtained in step four is further compressed by a spinning machine, and the compression rate is 25%, and the temperature is 1350°C, to obtain a dense alloy rod;

[0012] Step six, cutting, the dense alloy rod obtained in step five is cut to obtain a catalyst sheet;

[0013] Step seven, synthesizing diamond, the catalyst sheet obtained in step six and high-purity graphite are synthesized into diamond by a top pressure machine.

[0014] As a preferred technical scheme of the present application, the purity of high-purity graphite is 99.99%, and the FeCo alloy in step one selects Fe powder with a purity of 99.99% and Co powder with a purity of 99.95%.

[0015] As a preferred technical scheme of the present application, the purity of high-purity graphite is 99.99%, and the FeCo alloy in step one selects Fe powder with a purity of 99.99% and Co powder with a purity of 99.95%.

[0016] As a preferred technical scheme of the present application, the Fe powder adopts spherical shape with a particle size of 1 μm, the Co powder adopts spherical shape with a particle size of 1-5 μm, the Ni powder adopts flaky shape with a particle size of 25 μm, the Ti powder adopts spherical shape with a particle size of 1-5 μm, and the B powder adopts flaky shape with a particle size of 5 μm.

[0017] By using different shapes for different substances, the efficiency and mixing uniformity in the grinding process can be improved.

[0018] As a preferred technical solution of the present application, the ball-to-material ratio in step two is 8:1, and the ball milling speed is 400 r / min, and the ball milling time is 30 h.

[0019] As a preferred technical solution of the present application, the proportion of n-heptane in step two is 1% by weight.

[0020] As a preferred technical solution of the present application, the process conditions in step four are as follows: heating to 600 DEG C in 30 min and axial pressure of 20 MPa, then heating to 900 DEG C in 20 min and axial pressure of 40 MPa, then heating to 950 DEG C in 10 min and axial pressure of 50 MPa, holding for 1 h, and naturally cooling.

[0021] As a preferred technical solution of the present application, the temperature of the rotary swaging in step five is 1350 DEG C.

[0022] As a preferred technical solution of the present application, the content of Ti is 0-2%, and controlling the content of Ti can realize the control of the color of the diamond.

[0023] When the content of Ti is between 0-0.99%, the color changes from deep yellow to light yellow, when the content of Ti is 1%, the color becomes colorless, and when the content of Ti is between 1.01%-2%, the color changes from light blue to deep blue, so the content of Ti can be controlled to realize the control of the color of the synthetic diamond.

[0024] As a preferred technical solution of the present application, the proportion of Ni and B added is 10% of Ti.

[0025] By adding Ni and B, the transparency, purity and impurities of the diamond during the synthesis of the diamond can be effectively controlled, and the quality of the diamond synthesis is improved.

[0026] Compared with the prior art, the present application has the following beneficial effects:

[0027] The existing diamond color changing method changes the diamond through HPHT, irradiation, annealing or composite process post-processing technology to produce or repair internal defects of the diamond, and then changes the color; the present application artificially intervenes the color of the diamond by adjusting the content of trace elements in the assembled block before the HPHT diamond synthesis, thereby saving the cost of the color changing link.

[0028] The catalyst commonly used in HPHT synthetic diamond is FeCo alloy, which is prepared by smelting method. The trace element distribution is uneven, the grain is coarse, and the gap is large. In the process of synthesizing diamond, due to the many internal parts of the synthesis block and the size is not strict, and the temperature field and pressure field of the six-surface pressure machine fluctuate greatly during the synthesis of diamond, which leads to unstable quality of synthetic diamond. The quality of diamond is greatly different in different parts of the crystal bed of the same assembly block, and the diamond grade is also different between different synthesis blocks. The element content of the catalyst can be controlled, the grain is refined, the impurity content is less, and different element ratio catalyst sheets can be made. By adjusting the combination mode of different catalyst sheets, the trace elements can enter the diamond or enter the diamond interior in a step-by-step manner, so that the C atoms in the diamond are replaced by other elements or defects are formed at different sites in the diamond, and finally the color of the diamond can be artificially intervened. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the whole process of the application.

[0030] Figure 2 It is a picture of diamond obtained by the application with Ti content from 0 to 0.99%.

[0031] Figure 3 It is a picture of diamond obtained by the application with Ti content from 10.01% to 2%. DETAILED DESCRIPTION

[0032] The technical solutions in the embodiments of the application will be clearly and completely described below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the application.

[0033] Please refer to Figures 1-3 A synthetic method of color cultivation diamond,

[0034] Step one, preparing catalyst raw materials, the catalyst uses FeCo alloy, and also includes trace elements of Ni, B and Ti, so the catalyst raw material is a mixture of Fe and Co and trace elements of Ni, B and Ti;

[0035] Step two, grinding and mixing, the mixture obtained in step one is added to a planetary ball mill for mixing, and n-heptane is added as a process control agent to obtain mixed powder;

[0036] Step three, screening, the mixed powder obtained in step two is screened through a 120 mesh screening device to obtain undersize;

[0037] Step four, vacuum hot-pressing sintering, the undersize obtained in step three is added into a graphite mold cavity for pressure heating to make an alloy rod;

[0038] Step five, rotary forging, the alloy rod obtained in step four is further compressed by a rotary forging machine at a compression rate of 25% and a temperature of 1350°C to obtain a dense alloy rod;

[0039] Step six, cutting, the dense alloy rod obtained in step five is cut to obtain a catalyst sheet;

[0040] Step seven, synthesizing diamond, the catalyst sheet obtained in step six and high-purity graphite are used to synthesize diamond by a top press machine.

[0041] The crystal bed, the catalyst, and the high-purity graphite are sequentially matched to form an assembly block, the assembly block is placed into a 850mm cylinder diameter six-surface press machine, the pressure is increased to 84MPa in 6min, pressure maintaining is started, heating is added at this time, the power is increased to 5900W in 2min, and temperature maintaining is started; the pressure is kept constant for 165h, the temperature is kept constant for 142h, heating is stopped, and the pressure is released to obtain synthetic diamond. The catalyst has controllable element content, refined grain, higher density, and less impurity content; meanwhile, catalyst sheets with different element proportions can be made, the combination mode of different catalyst sheets is adjusted, trace elements are controlled to enter the diamond or enter the diamond interior in a stepwise manner, the C atoms in the diamond interior are replaced by other elements, or defects are formed at different sites in the diamond interior, and finally the color of the diamond can be artificially intervened.

[0042] Referring to Figure 1 , the purity of the high-purity graphite is 99.99%, the Fe powder has a purity of 99.99%, and the Co powder has a purity of 99.95%.

[0043] Referring to Figure 1 , the purity of the Ni powder is 99.95%, the purity of the Ti powder is 99.99%, and the B is B4C, and the purity of the B is 99.95%.

[0044] Referring to Figure 1 , the Fe powder is spherical with a particle size of 1μm, the Co powder is spherical with a particle size of 1-5μm, the Ni powder is flaky with a particle size of 25μm, the Ti powder is spherical with a particle size of 1-5μm, and the B powder is flaky with a particle size of 5μm.

[0045] Different shapes of different substances can improve the efficiency and mixing uniformity in the grinding process.

[0046] Referring to Figure 1 , the ball-to-material ratio in step two is 8:1, the ball milling speed is 400r / min, and the ball milling time is 30h.

[0047] Referring to Figure 1The proportion of n-heptane in step two is 1% of the weight.

[0048] Referring to Figure 1 The process conditions in step four are as follows: 30 min for temperature rising to 600 DEG C and axial pressure 20 MPa, then 20 min for temperature rising to 900 DEG C and axial pressure 40 MPa, then 10 min for temperature rising to 950 DEG C and axial pressure to 50 MPa, 1 h for keeping temperature, and natural cooling.

[0049] Referring to Figure 1 The temperature of rotary forging in step five is 1350 DEG C.

[0050] Referring to Figure 1 The content of Ti is 0-2%, and controlling the content of Ti can realize the control of the color of diamond.

[0051] When the content of Ti is between 0-0.99%, the color changes from deep yellow to light yellow, when the content of Ti is 1%, the color becomes colorless, and when the content of Ti is between 1.01%-2%, the color changes from light blue to deep blue, so the content of Ti can be controlled to realize the control of the color of synthetic diamond.

[0052] The adding proportion of Ni and B is 10% of Ti.

[0053] By adding Ni and B, the transparency, purity and impurities of diamond in the process of synthesizing diamond can be effectively controlled, and the quality of diamond synthesis is improved.

[0054] Although the embodiments of the present application have been shown and described, it can be understood by those skilled in the art that various changes, modifications, replacements and variations can be made to the embodiments without departing from the principles and spirits of the present application, the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing colored lab-grown diamonds, characterized in that... ； Step 1: Prepare catalyst raw materials. The catalyst is an FeCo alloy and also includes trace elements such as Ni, B, and Ti. Therefore, the catalyst raw materials are Fe powder, Co powder, and Ni powder. A mixture of Ni powder and Ti powder; wherein the content of Ti powder is greater than 0 and less than or equal to 2%, and controlling the content of Ti powder can achieve control over the color of the diamond; the Ni powder and The powder addition ratio is 10% of the Ti powder; Step two, grinding and mixing: The mixture obtained in step one is added to a planetary ball mill for homogenization, and n-heptane is added as a process control agent to obtain a mixed powder; the proportion of n-heptane is 1% by weight. Step 3, sieving: The mixed powder obtained in step 2 is sieved through a 120-mesh sieve to obtain the undersize material; Step 4, vacuum hot pressing sintering: The sieved material obtained in step 3 is added into the graphite mold cavity and heated under pressure to form an alloy rod; the process conditions are: heating to 600℃ and axial pressure of 20MPa for 30 minutes, then heating to 900℃ and axial pressure of 40MPa for 20 minutes, then heating to 950℃ and axial pressure of 50MPa for 10 minutes, holding at the temperature for 1 hour, and then cooling naturally. Step 5, rotary forging: The alloy rod obtained in step 4 is further compressed using a rotary forging machine with a compression rate of 25% and a temperature of 1350℃ to obtain a dense alloy rod; the rotary forging temperature is 1350℃. Step six, cutting: the dense alloy rod obtained in step five is cut to obtain catalyst sheets; Step 7: Synthesize diamonds. The catalyst sheet obtained in Step 6 is combined with high-purity graphite to synthesize diamonds using a top press.

2. The method for synthesizing colored lab-grown diamonds according to claim 1, characterized in that, The high-purity graphite has a purity of 99.99%, and in step one, the Fe powder has a purity of 99.99%, and the Co powder has a purity of 99.95%.

3. The method for synthesizing colored lab-grown diamonds according to claim 1, characterized in that, The Ni powder has a purity of 99.95%, and the Ti powder has a purity of 99.99%. The powder purity is 99.95%.

4. The method for synthesizing colored lab-grown diamonds according to claim 1, characterized in that, The Fe powder is in spherical form with a particle size of 1 μm, the Co powder is in near-spherical form with a particle size of 1-5 μm, the Ni powder is in flake form with a particle size of 25 μm, and the Ti powder is in near-spherical form with a particle size of 1-5 μm. The powder is in flake form with a particle size of 5μm.

5. The method for synthesizing colored lab-grown diamonds according to claim 1, characterized in that, In step two, the ball-to-material ratio is 8:1, the ball milling speed is 400 r / min, and the ball milling time is 30 h.

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