Colorless diamond and preparation method therefor

Abstract

Colorless diamond and a preparation method therefor. The preparation method comprises the following steps: 1) using seed crystals (30) to seed catalyst sheets (40); 2) alternately assembling the seeded catalyst sheets (40), graphite sheets (10) and nitrogen-removing sheets (20), so that each nitrogen-removing sheet (20) is located between a graphite sheet (10) and a catalyst sheet (40), so as to obtain a core column; 3) subjecting the core column to coating treatment to obtain a synthesis block; and 4) applying pressure and heat to the synthesis block to obtain colorless diamond.

Description

A colorless diamond and its preparation method Technical Field

[0001] This invention relates to the field of diamond synthesis technology, and in particular to a colorless diamond and its preparation method. Background Technology

[0002] Natural diamond reserves are extremely limited, so many companies both domestically and internationally are currently cultivating colorless diamonds to fill the industry's demand and gaps. Whether from an industrial or jewelry industry perspective, lab-grown diamonds are the best alternative to natural diamonds, making the lab-grown diamond industry's development prospects very promising. With the rapid development of domestic lab-grown diamond technology and increasingly fierce industry competition, the technology for producing synthetic colorless diamonds continues to improve and achieve breakthroughs.

[0003] In the international standard diamond color grading system, color is divided into 23 grades using the letters DZ, decreasing in color from D to Z. Grade D is the highest grade, pure and colorless. Currently, the main technology for synthesizing synthetic diamonds both domestically and internationally is the thermochemical method. The thermochemical method for synthesizing colorless diamonds has several drawbacks: firstly, the suitable temperature range is too small, generally below 30℃, making production stability difficult to control; secondly, the yield per unit is low, generally below 20ct, making economic efficiency difficult to guarantee; and thirdly, the synthesis time per block is long, generally over 24 hours. In addition, a few manufacturers use the traditional method of directly mixing catalyst, graphite, and seed crystals and pressing them into a core to synthesize colorless diamonds. This method has even more limitations: firstly, it is difficult to synthesize high-grade, large-particle colorless diamonds; while ensuring quality, the main particle size can only reach about 1.0mm, and the color grade of the colorless diamonds is low, all below F grade; secondly, particle size uniformity and crystal form uniformity are difficult to guarantee, and a large proportion of aggregated crystals and irregularly shaped materials are easily produced. Summary of the Invention

[0004] In view of the shortcomings of the prior art described above, the object of the present invention is to provide a colorless diamond, its preparation method, and its uses. The preparation method of colorless diamond described in this application solves the problem of difficulty in synthesizing uniform, high-quality colorless diamond in high yield in the prior art.

[0005] To achieve the above and other related objectives, the present invention is obtained through the following technical solution.

[0006] The first aspect of this invention discloses a method for preparing colorless diamond, the method comprising the following steps:

[0007] Seed crystals are used to seed the catalyst sheet;

[0008] The catalyst sheet, graphite sheet, and denitrification sheet are alternately assembled after seeding, such that any one of the denitrification sheets is located between the graphite sheet and the catalyst sheet, to obtain a core column;

[0009] The core column is then coated to obtain a composite block;

[0010] The synthetic block is pressurized and heated to obtain the colorless diamond.

[0011] Preferably, in step 1), the seed crystal has a particle size of 0.05~0.5mm. For example, the particle size of the seed crystal can be 0.05~0.2mm, 0.2~0.3mm, 0.3~0.4mm, or 0.4~0.5mm.

[0012] Preferably, in step 1), the seed crystal is synthetic diamond.

[0013] More preferably, the magnetic susceptibility of the seed crystal is less than 2*10. -5 SI. The magnetic susceptibility of the seed crystal can be 0.5*10. -5 SI~0.8*10 -5 SI, 0.8*10 -5 SI~1*10 -5 SI, 1*10 -5 SI~1.3*10 -5 SI, 1.3*10 -5 SI~1.5*10 -5 SI, 1.5*10 -5 SI~1.8*10 -5 SI, 1.8*10 -5 SI~2*10 -5 SI.

[0014] More preferably, the crystal form of the synthetic diamond is selected from one or more of hexahedral and hex-octahedral.

[0015] Preferably, in step 1), the raw materials of the catalyst sheet include Fe powder and Ni powder, and based on the mass of the catalyst sheet, the content of Fe powder is 30-80 wt%, and the content of Ni powder is 20-70 wt%.

[0016] The Fe powder content can be 30-40 wt%, 40-50 wt%, 50-60 wt%, 60-65 wt%, 65-70 wt%, 70-75 wt%, or 75-80 wt%.

[0017] The content of the Ni powder can be 20-25wt%, 25-28wt%, 28-30wt%, 30-40wt%, 40-50wt%, 50-60wt%, 60-65wt%, or 65-70wt%.

[0018] More preferably, the Fe powder content is 65-70 wt%.

[0019] More preferably, the content of the Ni powder is 25-28 wt%.

[0020] Preferably, the density of the catalyst sheet is 5.0~7.5 g / cm³. 3 .

[0021] The density of the catalyst sheet can be 5.0~6.5 g / cm³. 3 6.5~6.7g / cm 3 6.7~6.88g / cm 3 6.88~6.9g / cm 3 6.9~6.92g / cm 3 6.92~6.94 g / cm³ 3 6.94~7.2g / cm 3 7.2~7.5g / cm 3 .

[0022] More preferably, the density of the catalyst sheet is 6.5~6.94 g / cm³. 3 .

[0023] More preferably, the particle size of the Fe powder and Ni powder is 300-500 mesh. For example, the particle size of the Fe powder and Ni powder can be 300-350 mesh, 350-400 mesh, 400-450 mesh, or 450-500 mesh.

[0024] More preferably, the oxygen content of the Fe powder and Ni powder is less than 200 ppm. For example, the oxygen content of the Fe powder and Ni powder can be 50~100 ppm, 100~150 ppm, or 150~200 ppm.

[0025] More preferably, the raw materials of the catalyst sheet further include one or more of Co powder and Mn powder. Further, based on the mass of the catalyst sheet, the content of Co powder is 1-10 wt%, and the content of Mn powder is 0.1-5 wt%. Increasing the amount of Co powder and Mn powder can further improve the quality of the colorless diamond.

[0026] The content of Co powder can be 1-2 wt%, 2-4 wt%, 4-6 wt%, 6-8 wt%, or 8-10 wt%.

[0027] The content of Mn powder can be 1-2 wt%, 2-4 wt%, 4-6 wt%, 6-8 wt%, or 8-10 wt%.

[0028] Furthermore, the particle size of the Co powder and Mn powder is 300-500 mesh. For example, the particle size of the Co powder and Mn powder can be 300-350 mesh, 350-400 mesh, 400-450 mesh, or 450-500 mesh.

[0029] Furthermore, the oxygen content of the Co powder and Mn powder is less than 200 ppm. For example, the oxygen content of the Co powder and Mn powder can be 50~100 ppm, 100~150 ppm, or 150~200 ppm.

[0030] In practice, the thickness of the catalyst sheet can be adjusted arbitrarily according to the particle size of the target colorless diamond, as long as the growth space requirements of the colorless diamond are met. For example, if the particle size of the target diamond is 2.0 mm, the thickness of the catalyst sheet can be 6 mm.

[0031] In a preferred embodiment, the thickness of the catalyst sheet is 1-20 mm. For example, the thickness of the catalyst sheet can be 1-3 mm, 3-6 mm, 6-9 mm, 9-12 mm, 12-15 mm, 15-18 mm, or 18-20 mm.

[0032] In a more preferred embodiment, the thickness of the catalyst sheet is 1 to 13 mm.

[0033] Preferably, in step 2), the raw material for the graphite sheet is graphite powder, and the purity of the graphite powder is greater than or equal to 99.9%.

[0034] More preferably, the purity of the graphite powder is greater than or equal to 99.99%.

[0035] Preferably, the graphite powder has a particle size of 300-500 mesh. For example, the particle size of the graphite powder can be 300-350 mesh, 350-400 mesh, 400-450 mesh, or 450-500 mesh.

[0036] Preferably, the density of the graphite sheet is 1.5~2.0 g / cm³. 3 The density of the graphite sheets, as described, can be 1.5 ~ 1.8 g / cm³. 3 1.8 ~1.85 g / cm³ 3 1.85 ~1.88 g / cm³ 3 1.88 ~1.9 g / cm³ 3 1.9~1.91g / cm 3 1.91 ~1.93 g / cm³ 31.93 ~1.95 g / cm³ 3 1.95~2.0g / cm 3 .

[0037] More preferably, the density of the graphite sheet is 1.85 ~ 1.93 g / cm³. 3 .

[0038] In practice, the thickness of the graphite sheet can be adjusted arbitrarily according to the number of seed crystals and growth requirements, as long as it can support the growth of the seed crystals to the target colorless diamond particle size.

[0039] In a preferred embodiment, the thickness of the graphite sheet is 1-5 mm. For example, the thickness of the graphite sheet can be 1.5-3.5 mm.

[0040] Preferably, in step 2), the denitrification sheet is a metal sheet, and the metal includes one or more of Cu, Al, Ti, Zr, and Mg.

[0041] In practice, the thickness of the denitrification sheet can be adjusted arbitrarily according to the particle size and target quality requirements of the target colorless diamond, as long as it can support the colorless diamond to reach the target grade. In a preferred embodiment, the thickness of the denitrification sheet is 0.05-0.5 mm. For example, the thickness of the denitrification sheet can be 0.05~0.1 mm, 0.1~0.15 mm, 0.15~0.2 mm, 0.2~0.3 mm, 0.3~0.4 mm, or 0.4~0.5 mm.

[0042] In practice, the shape and size of the graphite sheet, the catalyst sheet, and the denitrification sheet can be adjusted according to the actual production of colorless diamond, the preparation conditions, and the preparation equipment.

[0043] In a preferred embodiment, the graphite sheet, the catalyst sheet, and the denitrification sheet all have circular cross-sections, and the diameters of the graphite sheet, the catalyst sheet, and the denitrification sheet are 20-40 mm. For example, the diameters of the graphite sheet, the catalyst sheet, and the denitrification sheet can be 37 mm.

[0044] In a more preferred embodiment, the graphite sheet, the catalyst sheet, and the denitrification sheet have the same diameter.

[0045] In practice, the preparation methods of the graphite sheet and the catalyst sheet can be chosen arbitrarily, as long as the density and component ratio requirements are met.

[0046] In a preferred embodiment, the graphite sheet and the catalyst sheet are prepared by pressing raw materials into sheets, wherein the pressing mold is a cemented carbide mold, and the pressing pressure is greater than or equal to 4 t / cm. 2The pressing time is 3-5 seconds.

[0047] In a more preferred embodiment, the pressing mold is cylindrical and the material of the pressing mold is tungsten carbide alloy.

[0048] In a more preferred embodiment, the method for preparing the catalyst sheet includes the following steps: mixing the raw materials evenly and then placing them into a granulator to obtain catalyst particles with a diameter of 1-3 mm; placing the catalyst particles into a mold and pressing them to obtain the catalyst sheet. For example, the diameter of the catalyst particles can be 1-1.5 mm, 1.5-2.0 mm, 2.0-2.5 mm, or 2.5-3 mm.

[0049] Preferably, in step 1), the step of selecting the fabric includes:

[0050] a1) Make a seed container, one part of which is a flat part, the flat part is provided with several through holes, and an adhesive layer is pasted on the side of the flat part away from the feed end;

[0051] a2) Place the seed crystal into the seed container, shake the seed container to allow the seed crystal to leak out from the through hole and stick to the adhesive layer;

[0052] a3) Peel the adhesive layer with the seed crystals from the planar portion and overlap it with the catalyst sheet, with the side of the adhesive layer with the seed crystals in contact with the catalyst sheet. After overlapping, apply pressure to the adhesive layer and / or the catalyst sheet so that the seed crystals are completely pressed into the catalyst sheet.

[0053] More preferably, the diameter of the through hole is 0.05~0.5mm. The diameter of the through hole is equal to the particle size of the desired seed crystal, such that only one seed crystal of the desired preparation leaks out from any one of the through holes.

[0054] The diameter of the through hole can be 0.05~0.2mm, 0.2~0.3mm, 0.3~0.4mm, or 0.4~0.5mm.

[0055] More preferably, the inlet end of the seeding container is detachably connected to a sealing cap. The sealing cap prevents the seeds from spilling out of the inlet end of the container during the seeding process.

[0056] More preferably, the adhesive layer is a material with adhesive on its surface. The material can be selected arbitrarily according to the actual situation, such as one or more of adhesive tape, paper, plastic and rubber.

[0057] More preferably, the thickness of the adhesive layer is less than or equal to 0.5 mm.

[0058] In practice, the material, shape, and size of the seed container can be arbitrarily selected according to actual needs, as long as the shape and size of the planar portion and the adhesive layer are equal to the catalyst sheet. For example, the material of the seed container can be metal and / or plastic.

[0059] In a preferred embodiment, the seed container is cylindrical, and the inner diameter of the seed container is the same as the diameter of the catalyst sheet.

[0060] More preferably, in step a2), the shaking time is 3~5s, until each of the through holes is filled with the seed crystals.

[0061] More preferably, in step a3), the peeling is done manually, during which the human body does not come into contact with the seed crystal and the seed crystal does not fall off the adhesive layer.

[0062] More preferably, before the alternating assembly, the fabric is repeated several times so that both sides of the catalyst sheet reach the required fabric density.

[0063] More preferably, in step a3), the applied pressure is 10~20 t / cm. 2 The pressure is applied for 2 to 5 seconds.

[0064] Preferably, in step 3), the coating process involves placing the core column into a pyrophyllite block.

[0065] More preferably, before placing the core column into the pyrophyllite block, the core column is first placed into an insulating tube, then into a heating tube, and finally into the pyrophyllite block.

[0066] In one specific embodiment, the insulating tube is made of dolomite or magnesium oxide and has a thickness of 0.8-1.5 mm; the heating tube is made of iron or graphite and has a thickness of 0.2-0.5 mm. The thickness of the insulating tube can be 0.8-1.0 mm, 1.0-1.2 mm, or 1.2-1.5 mm. The thickness of the heating tube can be 0.2-0.25 mm, 0.25-0.35 mm, 0.35-0.45 mm, or 0.45-0.5 mm.

[0067] Preferably, the coating process further includes a step of removing impurities from the core post.

[0068] Preferably, in step 4), the applied pressure is 5~6 GPa. For example, the applied pressure can be 5~5.2 GPa, 5.2~5.4 GPa, 5.4~5.5 GPa, 5.5~5.7 GPa, 5.7~5.9 GPa, or 5.9~6 GPa.

[0069] Preferably, in step 4), the heating temperature is 1300~1400℃. For example, the heating temperature can be 1300~1320℃, 1320~1350℃, 1350~1380℃, or 1380~1400℃.

[0070] Preferably, in step 4), the pressurization and heating time is 2-72 hours. The pressurization and heating time can be 2-7 hours, 7-15 hours, 15-25 hours, 25-35 hours, 35-45 hours, 45-55 hours, 55-65 hours, or 65-72 hours.

[0071] Preferably, after step 4), the step further includes extracting the colorless diamond.

[0072] More preferably, the extraction method is selected from one or more of acid-base purification and / or electrolytic purification.

[0073] Preferably, step 6) further includes a step of removing impurities from the core post.

[0074] More preferably, the device for removing impurities from the core column is a high-temperature vacuum furnace.

[0075] More preferably, the temperature for removing impurities from the core post is 1000~1100℃. The temperature for removing impurities from the core post can be 1000~1020℃, 1020~1040℃, 1040~1060℃, 1060~1080℃, or 1080~1100℃.

[0076] More preferably, the time for removing impurities from the core post is 4-8 hours. For example, the time for removing impurities from the core post can be 4-5 hours, 5-6 hours, 6-7 hours, or 7-8 hours.

[0077] More preferably, the vacuum degree for removing impurities from the core post is 1*10. -1 The vacuum degree required to remove impurities from the core post is as described above. -5 ~1*10 -4 1*10 -4 ~1*10 -3 1*10 -3 ~1*10 -2 1*10 -2 ~1*10 -1 .

[0078] In practice, the pressurization and heating device can be selected arbitrarily according to operational or economic needs.

[0079] In a preferred embodiment, the pressurizing and heating device is a six-sided press. The model of the six-sided press can be arbitrarily selected according to the specific size of the core column, such as a six-sided press with a diameter of Φ560mm-Φ850mm.

[0080] In a more preferred embodiment, the six-sided top press is Φ560mm.

[0081] The second aspect of this application discloses a colorless diamond prepared by the preparation method described above.

[0082] Preferably, the particle size of the colorless diamond is 0.3-5.0 mm. For example, the particle size of the colorless diamond can be 0.3-0.4 mm, 0.4-0.6 mm, 0.6-1.0 mm, 1.0-1.2 mm, 1.2-1.6 mm, 1.6-2.0 mm, 2.0-2.4 mm, 2.4-2.8 mm, 2.8-3.0 mm, 3.0-3.4 mm, 3.4-3.6 mm, 3.6-4.0 mm, 4.0-4.4 mm, 4.4-4.6 mm, or 4.6-5.0 mm.

[0083] Preferably, the colorless diamond has a color grade of D or E.

[0084] Preferably, the colorless diamond has a hexahedral crystal form.

[0085] In this application, the quality testing of the colorless diamond is carried out with reference to the testing methods in "Diamond Grading GB / T 16554-2003".

[0086] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0087] 1) This invention employs a method of separately pressing the carbon source and catalyst, and assembling them in alternating sheet-like forms, with a denitrification sheet placed between them. Compared to the method of directly mixing and pressing the catalyst and graphite, this invention can reduce the growth of spontaneous nuclei during the high-temperature and high-pressure synthesis process, and the synthesized colorless diamond has higher purity and significantly higher color grade, reaching D and E grades.

[0088] 2) This invention designs the number and distribution of seed crystals according to the required particle size of colorless diamond, and matches graphite sheets and catalyst sheets of appropriate thickness. While ensuring the grade and stability of colorless diamond, the synthesis time of colorless diamond is greatly shortened compared with the temperature difference method, the single yield is greatly increased, and the content of colorless diamond with color grade E or above is greater than 90wt%.

[0089] 3) Construct a simple seeding container and adopt a simple and efficient seeding method. Compared with the traditional manual seeding method, this method improves seeding efficiency while reducing the chance of seed contamination. Attached Figure Description

[0090] Figure 1 shows a longitudinal cross-sectional view of the core post described in this application.

[0091] Figure 2 shows a longitudinal cross-sectional view of the seed container described in this application.

[0092] Figure 3 shows a photograph of the colorless diamond described in Embodiment 1 of this application.

[0093] Figure 4 shows a photograph of the colorless diamond described in Embodiment 2 of this application.

[0094] Figure 5 shows a photograph of the colorless diamond described in Embodiment 3 of this application.

[0095] Figure 6 shows a photograph of the colorless diamond described in Embodiment 4 of this application.

[0096] Figure 7 shows a photograph of the colorless diamond described in Comparative Example 1 of this application.

[0097] Explanation of reference numerals in the attached figures

[0098] 10 Graphite sheet, 20 Nitrogen removal sheet, 30 Seed crystal, 40 Catalyst sheet, 50 Seed container, 51 Flat part, 52 Sealing cap, 60 Adhesive layer. Detailed Implementation

[0099] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0100] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0101] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in this invention, any of the two points within each numerical range, as well as any value between the two points, may be selected. Unless otherwise defined, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement this invention.

[0102] In this application, the applicant addresses the problem of difficulty in synthesizing high-grade colorless diamond in high-volume production using existing technologies. The applicant provides a method for preparing colorless diamond, which produces colorless diamond with high purity, reaching grades D and E. Compared with the temperature difference method for synthesizing colorless diamond, the synthesis time is significantly shortened and the yield per unit is significantly increased.

[0103] Figure 1 is a longitudinal cross-sectional view of the core column of this application. As shown in Figure 1, the seed crystal 30 is embedded in the catalyst sheet 40, and the denitrification sheet 20 is disposed between the catalyst sheet 40 and the graphite sheet 10.

[0104] It should be noted that the number of stacked layers of the denitrification sheet 20, the catalyst sheet 40 and the graphite sheet 10 can be adjusted according to the target particle size and the size of the synthesis block.

[0105] It should be noted that the material, shape, and size of the seed container 50 can be adjusted according to actual operation or economic needs.

[0106] In a specific embodiment shown in Figure 2, the seeding container 50 is cylindrical, with an inner diameter of 20-40 mm and a height of 10-30 mm. The planar portion 51 of the seeding container 50 is uniformly provided with several through holes. The seeding container 50 also includes a sealing cap 52, which prevents the seeds from spilling out during seeding. In actual operation, the diameter of the through holes is consistent with the particle size of the seeds, such as 0.05-0.5 mm. The number of through holes can be adjusted according to the required seeding density.

[0107] In a specific embodiment shown in Figure 2, the adhesive layer 60 is attached to the side of the flat portion 51 away from the feed inlet. The shape and size of the adhesive layer are the same as those of the flat portion 51, and the thickness of the adhesive layer 60 is less than or equal to 0.5 mm.

[0108] In practice, the shape, size, and material of the pressing mold described in this application can be arbitrarily selected according to actual needs. In the specific embodiments described below, the pressing mold is made of tungsten carbide cemented carbide, the pressing mold is cylindrical, the inner diameter of the pressing mold is 37mm, and the height is 30mm.

[0109] In the following specific embodiments, the differences between the seed containers in each embodiment are only in the diameter and number of through holes. Each seed container 50 is cylindrical, with an inner diameter of 37 mm and a height of 30 mm. The diameters of the through holes are 0.05 mm, 0.2 mm, and 0.5 mm, respectively. Each seed container 50 also includes a sealing cap 52. The adhesive layer 60 is adhered to the side of the flat portion 51 away from the feed inlet. The adhesive layer is a circular adhesive tape with a diameter of 37 mm and a thickness of 0.1 mm.

[0110] In the following embodiments of this application, the finished product refers to colorless diamonds with a color grade of D and E. The yield rate is calculated as the ratio of the mass of colorless diamonds with a color grade of D and E to the total mass of colorless diamonds.

[0111] Example 1

[0112] This embodiment provides a method for preparing colorless diamond, the method comprising the following steps:

[0113] 1) Pressing graphite sheets 10: Add high-purity graphite powder to the above pressing mold, use a four-column press, set the parameters, and press at 5t / cm 2 Under pressure, the high-purity graphite powder is pressed in a mold for 3 seconds to obtain 10 graphite sheets. This process is repeated 5 times to obtain 5 sheets with a thickness of 3 mm, a diameter of 37 mm, and a density of 1.9 g / cm³. 3 The graphite sheet 10, wherein the purity of the high-purity graphite powder is greater than or equal to 99.99%, and the particle size of the high-purity graphite powder is 300 mesh;

[0114] 2) Pressing Catalyst Sheets 40: Fe powder, Ni powder, Co powder, and Mn powder are mixed to obtain catalyst powder. The particle size of the Fe powder, Ni powder, Co powder, and Mn powder is 300 mesh, and the oxygen content of the Fe powder, Ni powder, Co powder, and Mn powder is 100 ppm. Based on the total mass of the catalyst powder, the content of Fe powder is 70 wt%, the content of Ni powder is 25 wt%, the content of Co powder is 4 wt%, and the content of Mn powder is 1 wt%. The mixing is carried out using a three-dimensional mixer at a speed of 15 r / min for 5 hours to obtain catalyst powder. Then, the catalyst powder is placed in a granulator to granulate into catalyst particles with a diameter of 2.5 mm. Finally, the catalyst particles are pressed into catalyst sheets. The steps of pressing the catalyst sheets include: adding the catalyst particles into the above-mentioned pressing mold, using a four-column press, setting the parameters, and pressing at 8 t / cm 2 Under pressure, the catalyst particles are pressed in a mold for 5 seconds to obtain catalyst sheet 40. The above steps are repeated 4 times to obtain 4 sheets with a thickness of 6 mm, a diameter of 37 mm, and a density of 6.9 g / cm³. 3 Catalyst tablet 40.

[0115] 3) Place the seed crystals 30 in the seeding container 50, which has 114 through holes with a diameter of 0.2 mm. Shake the seeding container 50 to allow the seed crystals 30 to leak out from the through holes and adhere evenly to the adhesive layer 60. Gently remove the adhesive layer 60, which is evenly coated with the seed crystals 30, from the seeding container 50 and attach it to the catalyst sheet 40. Use a four-column press at 10 t / cm 2 Under pressure, the seed crystal 30 is uniformly and completely pressed into the catalyst sheet 40, and then the adhesive layer 60 is gently removed to complete one seed placement. The seed crystal 30 is synthetic diamond with a particle size of 0.2 mm, a hexahedral crystal form, and a magnetic susceptibility of 1.0*10⁻⁶. -5 SI.

[0116] 4) Repeat step 3) to seed both sides of all catalyst sheets 40;

[0117] 5) Assemble the core column: Alternately assemble the graphite sheet 10, the catalyst sheet 40 after seeding, and the denitrification sheet 20 to obtain the core column shown in Figure 1; based on the total mass of the denitrification sheet 20, the content of Ti in the denitrification sheet 20 is 80wt%, the content of Al is 20wt%, and the thickness of the denitrification sheet 20 is 0.2mm.

[0118] 6) Place the core column in a high-temperature vacuum furnace for 6 hours, setting the temperature to 1000℃ and the vacuum degree to 1×10⁻⁶. -3 Remove impurities, and vacuum pack after baking for later use;

[0119] 7) Place the vacuum-treated core into a matching insulating tube, then into a matching heating tube, and finally into a pyrophyllite block to obtain a composite block. The insulating tube is made of dolomite with a thickness of 1.0 mm; the heating tube is made of iron with a thickness of 0.25 mm.

[0120] 8) The synthesized blocks were placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure was 6.0 GPa, and the temperature was 1350℃, determined by setting the process curve. The power curve control was set as follows: initial power 6800W, held for 550s, then power reduced to 6500W within 25s, held for 100s, then slowly reduced to 6300W within 23 hours, held for 80s, and finally allowed to cool naturally. The pressure curve control was set as follows: the six-sided press was increased from 0MPa to 55MPa at a rate greater than 2MPa / s to begin heating, then pressurized, held for 450s, then pressurized again, increasing the pressure to 70MPa within 20s, then stopped, held for 20s, then increased to 74MPa within 23 hours, held for 15s, and finally allowed to depressurize naturally.

[0121] 9) Purification to obtain the colorless diamond: The purification includes the following steps: the synthetic block is crushed into 5-10mm particles using a four-column press, and then the particles are placed in an electrolytic cell with hydrochloric acid as the electrolyte for electrolysis for 50-100 hours. The electrolysis voltage is 6V-12V DC voltage to obtain a diamond mixture; nitric acid and sulfuric acid are mixed in a certain proportion and added to the diamond mixture to completely submerge it. The mixture is then heated to 280℃ for 2-10 hours to obtain the treated diamond mixture; sodium hydroxide is added to the treated diamond mixture at a ratio of 1:5, and after thorough mixing, the mixture is heated to a molten state for 1-5 hours, and the liquid is discarded; the mixture is then soaked again in nitric acid to neutralize it, the liquid is discarded, and the diamond is dried at 150℃.

[0122] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0123] 1) Figure 3 was taken by a Raysun Optical Instruments Co., Ltd. RX-A4K measurable camera. As shown in Figure 3, the crystal form of the colorless diamond is hexahedral.

[0124] 2) The colorless diamond was obtained by sieving using the ES-04 electromagnetic vibrating screen of Shenzhen Ruichengjie Technology Co., Ltd., and the main particle size of the diamond was 7-10 mesh.

[0125] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond can reach the D and E grades;

[0126] 4) The yield of colorless diamonds in a single synthetic block is 69.5 ct;

[0127] 5) The yield of the colorless diamond is 91.2%.

[0128] Example 2

[0129] The difference from Example 1 is that, in this example, based on the total mass of the catalyst powder, the content of Fe powder is 65wt%, the content of Ni powder is 30wt%, the content of Co powder is 4wt%, and the content of Mn powder is 1wt%; 9 sheets with a thickness of 1.8mm, a diameter of 37mm, and a density of 1.85g / cm³ are obtained by pressing. 3 Eight graphite sheets, each 3.0 mm thick, 37 mm in diameter, and with a density of 6.5 g / cm³. 3 The catalyst sheet has a thickness of 0.1 mm; the seed crystal has a particle size of 0.05 mm; the seed container has a through-hole diameter of 0.05 mm and a number of 252 through-holes.

[0130] In step 8), the synthesized block is placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure is 6.0 GPa, and the temperature is 1300℃, determined by setting the process curve. The power curve control is set as follows: initial power is 6600W, held for 550s, then the power is reduced to 6300W within 25s, held for 100s, then slowly reduced to 6200W within 12 hours, held for 80s, and finally allowed to cool naturally. The pressure curve control is set as follows: the six-sided press is increased from 0MPa to 55MPa at a rate greater than 2MPa / s to begin heating, then the pressurization is stopped, held for 450s, then the pressurization is continued, increasing the pressure to 71MPa within 15s, stopping the pressurization, holding for 20s, increasing the pressure to 75.5MPa within 12 hours, holding for 20s, and finally allowing to depressurize naturally.

[0131] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0132] 1) Figure 4 was taken by a Raysun Optical Instruments Co., Ltd. RX-A4K measurable camera. As shown in Figure 4, the crystal form of the colorless diamond is hexahedral.

[0133] 2) The main particle size of the colorless diamond obtained by sieving using the ES-04 electromagnetic vibrating screen machine of Shenzhen Ruichengjie Technology Co., Ltd. is 14-16 mesh;

[0134] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond can reach the D and E grades;

[0135] 4) The yield of a single piece of the colorless diamond is 84.3 ct.

[0136] 5) The yield of the colorless diamond is 90.7%.

[0137] Example 3

[0138] The difference from Example 1 is that, in this example, based on the total mass of the catalyst powder, the content of Fe powder is 70wt%, the content of Ni powder is 28wt%, and the content of Co powder is 2wt%; four sheets with a thickness of 3.0mm, a diameter of 37mm, and a density of 1.91 g / cm³ are obtained by pressing. 3 Three graphite flakes, each 9.0 mm thick, 37 mm in diameter, and with a density of 6.92 g / cm³. 3 The catalyst sheet has a thickness of 0.15 mm. The seed container has 52 through holes with a diameter of 0.2 mm.

[0139] In step 8), the synthesized block is placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure is 5.5 GPa, and the temperature is 1400℃, determined by setting the process curve. The power curve control is set as follows: initial power is 6900W, held for 550s, then the power is reduced to 6650W within 25s, held for 100s, then slowly reduced to 6400W within 47.5h, held for 80s, and finally allowed to cool naturally. The pressure curve control is set as follows: the six-sided press is increased from 0MPa to 55MPa at a rate greater than 2MPa / s to begin heating, then the pressurization is stopped, held for 450s, then the pressure is increased to 70.5MPa within 15s, stopped, held for 20s, then the pressure is increased to 74.5MPa within 47.5h, held for 15s, and finally allowed to depressurize naturally.

[0140] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0141] 1) Figure 5 was taken by a Raysun Optical Instruments Co., Ltd. RX-A4K measurable camera. As shown in Figure 5, the crystal form of the colorless diamond is hexahedral.

[0142] 2) The colorless diamond was obtained by sieving using the ES-04 electromagnetic vibrating screen of Shenzhen Ruichengjie Technology Co., Ltd., and the main particle size of the diamond was 5-6 mesh.

[0143] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond can reach the D and E grades.

[0144] 4) The yield of a single piece of the colorless diamond is 50.6 ct.

[0145] 5) The yield of the colorless diamond is 90.3%.

[0146] Example 4

[0147] The difference from Example 1 is that 16 sheets with a thickness of 1.5 mm, a diameter of 37 mm, and a density of 1.93 g / cm³ were obtained by pressing. 3 Fifteen graphite flakes, each 1.0 mm thick, 37 mm in diameter, and with a density of 6.88 g / cm³. 3 The catalyst sheet has a thickness of 0.05 mm; the seed crystal has a particle size of 0.05 mm; the seed container has a through-hole diameter of 0.05 mm and a number of 1220 through-holes.

[0148] The synthetic blocks were placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure was determined to be 5.2 GPa and the temperature 1300℃ by setting the process curve. The power curve control was set as follows: initial power 6500W, held for 550s, then power reduced to 6300W within 25s, held for 50s, then slowly reduced to 6200W within 2 hours and held for 100s, finally allowing natural cooling. The pressure curve control was set as follows: the six-sided press was increased from 0MPa to 55MPa at a rate greater than 2MPa / s to begin heating, then pressurized, held for 400s, then pressurized again, increasing the pressure to 70MPa within 10s, stopping, holding for 20s, then increasing the pressure to 73MPa within 2 hours and holding for 15s, finally allowing natural depressurization.

[0149] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0150] 1) Figure 6 was taken by a Raysun Optical Instruments Co., Ltd. RX-A4K measurable camera. As shown in Figure 6, the crystal form of the colorless diamond is hexahedral.

[0151] 2) The main particle size of the colorless diamond obtained by sieving using the ES-04 electromagnetic vibrating screen machine of Shenzhen Ruichengjie Technology Co., Ltd. is 40-45 mesh.

[0152] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the color of the colorless diamond can reach grade D;

[0153] 4) The yield of a single piece of the colorless diamond is 98.4 ct.

[0154] 5) The yield of the colorless diamond is 92.5%;

[0155] Example 5

[0156] The difference from Example 1 is that, in this example, based on the total mass of the denitrification sheet, the denitrification sheet contains 80 wt% Ti, 10 wt% Al, and 10 wt% Zr; and is pressed to obtain three sheets with a thickness of 3.5 mm, a diameter of 37 mm, and a density of 1.88 g / cm³. 3 Two graphite flakes, each 13.0 mm thick, 37 mm in diameter, and with a density of 6.94 g / cm³. 3 The catalyst sheet has a thickness of 0.5 mm; the denitrification sheet has a particle size of 0.5 mm; the seed crystal has a through-hole diameter of 0.5 mm and a number of 24 through-holes.

[0157] The synthesized blocks were placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure was determined to be 5.0 GPa and the temperature 1300℃ by setting the process curve. The power curve control was set as follows: initial power 6400W, held for 1000s, then power reduced to 6300W within 100s, held for 50s, then slowly reduced to 6200W within 70 hours, held for 300s, and finally allowed to cool naturally. The pressure curve control was set as follows: the six-sided press was increased from 0MPa to 55MPa at a rate greater than 2MPa / s to begin heating, then pressurized, held for 1000s, then pressurized again, increasing the pressure to 70MPa within 10s, stopping, holding for 20s, then increasing the pressure to 73.5MPa within 70 hours, holding for 300s, and finally allowing to depressurize naturally.

[0158] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0159] 1) The colorless diamond was photographed using a Raysun Optical Instruments Co., Ltd. RX-A4K measurable camera, and its crystal form is hexahedral.

[0160] 2) The main particle size of the colorless diamond obtained by sieving using the ES-04 electromagnetic vibrating screen machine of Shenzhen Ruichengjie Technology Co., Ltd. is 4-5 mesh;

[0161] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond can reach the D and E grades.

[0162] 4) The yield of a single piece of the colorless diamond is 50.2 ct.

[0163] 5) The yield of the colorless diamond is 90%;

[0164] Comparative Example 1

[0165] The difference from Example 1 is that in this comparative example, the catalyst powder, the high-purity graphite powder, and the metal powder corresponding to the denitrification sheet are mixed for 5 hours at 15 r / min using a TD-9 three-dimensional mixer according to the dosage in Example 1. Then, the mixed powder is placed in a YC-100BX4 granulator to granulate into mixed particles with a diameter of 3.0 mm, and the seed crystal is embedded in them. Finally, it is pressed into a core column, and then the operations described in steps 6) to 9) of Example 1 are performed to obtain colorless diamond.

[0166] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0167] 1) As shown in Figure 7, it can be observed that the colorless diamond contains many internal impurities;

[0168] 2) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond has a yellowish-black hue, which does not meet the grading standard;

[0169] 3) The yield of the colorless diamond is 0;

[0170] 4) The yield of the colorless diamond is 78.4 ct.

[0171] Comparative Example 2

[0172] This comparative example provides a method for preparing colorless diamond using a temperature difference method. The temperature difference method used in this comparative example includes the following steps:

[0173] 1) Seed distribution: 114 seed crystals are evenly distributed and pressed into the crystal bed wafer. The seed crystals are the same as those in Example 1. The thickness of the crystal bed wafer is 2 mm, the diameter is 37 mm, and the material is magnesium oxide.

[0174] 2) Assemble the core column: Assemble the dolomite core, graphite sheet, catalyst sheet, denitrification sheet and seeded crystal bed sheet in sequence to obtain the core column. The thickness of the dolomite core is 15mm and the diameter is 37mm. In this comparative example, the graphite sheet, catalyst sheet and denitrification sheet are the same as in Example 1.

[0175] 3) Place the core column in a high-temperature vacuum furnace for 6 hours, setting the temperature to 1000℃ and the vacuum degree to 1×10⁻⁶. -3 Remove impurities, and vacuum pack after baking for later use;

[0176] 4) The vacuum-treated core is placed into a matching insulating tube, then into a matching heating tube, and finally into a pyrophyllite block to obtain a composite block. The insulating tube is made of dolomite with a thickness of 1.0 mm; the heating tube is made of iron with a thickness of 0.25 mm.

[0177] 5) The synthesized blocks were placed in a Φ560mm six-sided press for synthesis. The required synthesis pressure was 5.5 GPa, and the temperature was 1200℃, determined by setting the process curve. The power curve control was set as follows: initial power of 6000W, held for 1000s, then reduced to 5900W within 25s, held for 100s, then slowly reduced to 5700W within 47 hours, held for 80s, and finally allowed to cool naturally. The pressure curve control was set as follows: the six-sided press was increased from 0MPa to 50MPa at a rate greater than 2MPa / s to begin heating, then the pressurization was stopped, held for 1100s, and then the pressure was increased to 65MPa within 20s, stopped, held for 20s, then increased to 70MPa within 47 hours, held for 10s, and finally allowed to depressurize naturally.

[0178] The purification process is carried out using the same steps as step 9) described in Example 1.

[0179] The colorless diamond obtained in this embodiment, as determined by testing, is as follows:

[0180] 1) The colorless diamond was photographed using an RX-A4K measurable camera from Raysun Optical Instruments Co., Ltd., and its crystal form is hexahedral.

[0181] 2) The colorless diamond was obtained by sieving using the ES-04 electromagnetic vibrating screen of Shenzhen Ruichengjie Technology Co., Ltd., and the main particle size of the diamond was 8-12 mesh.

[0182] 3) According to the test results of "Diamond Grading GB / T 16554-2003", the colorless diamond can reach the D and E grades;

[0183] 4) The yield of colorless diamonds in a single synthetic block is 10.2 ct.

[0184] 5) The yield of the colorless diamond is 90.5%.

[0185] In summary, the method for preparing colorless diamond described in this invention employs separate pressing of the carbon source and catalyst, followed by alternating assembly in sheet form, with a denitrification sheet placed between them. This reduces spontaneous nucleation during the high-temperature, high-pressure synthesis of colorless diamond, resulting in higher purity and significantly higher color grade, reaching D and E levels. Compared to the temperature difference method for synthesizing colorless diamond, this method significantly shortens the synthesis time and greatly increases the yield per unit volume.

[0186] This invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0187] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for preparing colorless diamond, characterized in that, The preparation method includes the following steps: 1) Seeds are used to seed the catalyst sheet; 2) Assemble several graphite sheets, denitrification sheets, and the catalyst sheets after seeding in an alternating manner, such that a denitrification sheet is present between any graphite sheet and any catalyst sheet, to obtain a core column; 3) The core pillar is coated to obtain a composite block; 4) Pressurize and heat the synthetic block to obtain the colorless diamond.

2. The preparation method according to claim 1, characterized in that, In step 1), the seed crystal has a particle size of 0.05~0.5mm; And / or, in step 1), the seed crystal is synthetic diamond; And / or, in step 1), the raw materials of the catalyst sheet include Fe powder and Ni powder, and based on the mass of the catalyst sheet, the content of Fe powder is 30-80 wt% and the content of Ni powder is 20-70 wt%. And / or, the density of the catalyst sheet is 5.0~7.5 g / cm³. 3 ; And / or, in step 2), the raw material for the graphite sheet is graphite powder, the purity of the graphite powder is greater than or equal to 99.9%, and the particle size of the graphite powder is 300~500 mesh; And / or, the density of the graphite sheet is 1.5~2.0 g / cm³. 3 ; And / or, in step 2), the denitrification sheet is a metal sheet, and the metal includes one or more of Cu, Al, Ti, Zr, and Mg; And / or, the thickness of the nitrogen removal sheet is 0.05-0.5 mm.

3. The preparation method according to claim 2, characterized in that, The crystal form of the synthetic diamond is selected from one or more of hexahedral and hex-octahedral. And / or, the particle size of the Fe powder and Ni powder is 300~500 mesh; And / or, the oxygen content of the Fe powder and Ni powder is less than 200 ppm; And / or, the raw materials of the catalyst sheet also include one or more of Co powder and Mn powder, wherein the content of Co powder is 1-10 wt% and the content of Mn powder is 0.1-5 wt% based on the mass of the catalyst sheet.

4. The preparation method according to claim 3, characterized in that, The particle size of the Co powder and Mn powder is 300~500 mesh; And / or, the oxygen content of the Co powder and Mn powder is less than 200 ppm.

5. The preparation method according to claim 1, characterized in that, In step 1), the step of selecting the fabric type includes: a1) Make a seed container, one end of which is a flat part, and the flat part is provided with several through holes. An adhesive layer is pasted on the side of the flat part away from the feed end. a2) Place the seed crystal into the seed container, shake the seed container to allow the seed crystal to leak out from the through hole and stick to the adhesive layer; a3) Peel the adhesive layer with the seed crystals from the planar portion and overlap it with the catalyst sheet, with the side of the adhesive layer with the seed crystals in contact with the catalyst sheet. After overlapping, apply pressure to the adhesive layer and / or the catalyst sheet so that the seed crystals are completely pressed into the catalyst sheet.

6. The preparation method according to claim 5, characterized in that, The diameter of the through hole is 0.05~0.5mm; And / or, the feed end of the cloth seed container is connected to a removable sealing cap.

7. The preparation method according to claim 1, characterized in that, In step 3), the coating process involves placing the core column into a pyrophyllite block. And / or, the coating process further includes a step of removing impurities from the core post; And / or, in step 4), the pressure applied is 5~6 GPa; And / or, in step 4), the heating temperature is 1300~1400℃; And / or, in step 4), the pressurization and heating time is 2~72h; And / or, after step 4), the step of extracting the colorless diamond is also included.

8. The preparation method according to claim 7, characterized in that, The temperature for removing impurities from the core column is 1000~1100℃; And / or, the time for removing impurities from the core post is 4~8 hours; And / or, the vacuum degree for removing impurities from the core column is 1*10. -1 above; And / or, the extraction method is selected from one or more of acid-base purification and / or electrolytic purification.

9. A colorless diamond prepared by the preparation method according to any one of claims 1 to 8.

10. The colorless diamond according to claim 9, characterized in that, The colorless diamond has a particle size of 0.3-5.0 mm; And / or, the colorless diamond has a color grade of D or E; And / or, the colorless diamond has a hexahedral crystal form.

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