Isolation groove for cultivating diamonds and preparation method thereof

Abstract

The invention discloses an isolation groove for cultivating diamonds and a preparation method of the isolation groove, and relates to the technical field of artificial diamond cultivation through an HTHP temperature difference method, in particular to the isolation groove for cultivating the diamonds and the preparation method of the isolation groove. The specially-made mold comprises an outer mold frame and an upper pressing head slidably connected in the outer mold frame, a lower pressing head is fixedly connected to the bottom end of the inner circumferential face of the outer mold frame, a sleeve is fixedly connected to the inner circumferential face of the upper pressing head, an insulating pipe is placed on the lower surface of the fired isolation groove plate, and a crystal bed is fixedly connected to the bottom end of the inner circumferential face of the insulating pipe; the upper surface of the crystal bed is filled with the catalyst layer, the upper surface of the catalyst layer is filled with the graphite layer, the isolation groove plate is independent of the outer portion of the insulation tube and tightly attached to the insulation tube, the isolation effect is good, and the nickel sheets placed in the grooves are placed in the upper surface of the isolation groove plate, so that the effect of isolating and absorbing impurities can be achieved, and the internal pressure can be increased; and the pressure loss under high pressure is reduced.

Description

Technical Field

[0001] This invention relates to the field of lab-grown diamond technology, and more specifically, to a separation tank for lab-grown diamonds and its preparation method. Background Technology

[0002] With the continuous iteration of global science and technology and the upgrading of downstream industries such as jewelry and high-end electronics (e.g., heat sinks, semiconductor substrates), the global market demand for lab-grown diamonds is showing a continuous upward trend. Currently, the mainstream manufacturing processes for lab-grown diamonds are mainly divided into two categories: high-temperature high-pressure (HTHP) thermoelectric method and chemical vapor deposition (CVD). Among them, the HTHP thermoelectric method, due to its advantages of high synthesis efficiency, fast crystal growth speed, and greater suitability for commercial mass production, occupies a dominant position in global lab-grown diamond production capacity, accounting for more than 60%. Furthermore, related technologies surrounding the optimization of its reaction chamber structure, precise temperature and pressure control, and performance upgrades of core auxiliary components are constantly being iterated and updated to meet the synthesis needs of higher quality and larger size lab-grown diamonds. However, in existing HTHP (Heat-to-Heat) diamond growing technology, the traditional spacer, as a core auxiliary component, still has significant technical shortcomings: traditional spacers are mostly made of conventional ceramic materials such as alumina and magnesium oxide, and their installation methods are limited to only two single forms: "embedded inside the insulating tube" or "attached to the outside of the insulating tube". If placed inside the insulating tube, the spacer is prone to direct contact with the carbon source (graphite) and catalyst (iron-nickel alloy), and at high temperatures, it is easy to undergo interfacial reactions to generate low-melting-point compounds, which not only destroys the integrity of the isolation structure, but also causes impurity elements (such as Al and Mg) to dissolve and diffuse into the diamond growth area. If attached to the outside of the insulating tube, it is difficult to form a tight seal with the insulating tube, which can easily cause crosstalk in the temperature and pressure fields inside the reaction chamber, and cannot effectively isolate the material exchange between the carbon source area and the seed crystal area. More importantly, these traditional separators only have basic physical isolation functions and lack the design to actively adsorb or intercept impurities. The trace metal debris, ceramic powder and other impurities generated during the cultivation process are easily diffused with the carbon source and encapsulated by the diamond crystal. This ultimately leads to the presence of defects such as impurity points and inclusions in the synthesized lab-grown diamonds. Among them, products with a clarity grade lower than VS2 account for more than 40%, which seriously affects the optical transparency, mechanical stability and overall commercial quality of diamonds, and restricts the large-scale production of high-value-added lab-grown diamonds. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides an isolation tank for lab-grown diamonds and its preparation method, thus solving the problems mentioned in the background section.

[0004] The technical solution of this invention is as follows: To achieve the above objectives, the present invention provides the following technical solution: a separation tank for lab-grown diamonds and its preparation method, comprising the following steps: S1 Preparation: The required high-purity samarium oxide powder is calcined at high temperature to remove impurities from the incoming material, and then cooled naturally before use. S2 ingredients: Take samarium oxide powder that has been purified at high temperature, add graphite as a lubricant during pressing, and add methylcellulose as a binder for mixing; S3 Mixing: Mix all the above materials evenly in the mixer according to the proportions; S4 pressing: Using a special mold, the isolation groove plate of the required size is pressed; S5 firing: fired in a furnace; S6 Assembly: During assembly, the isolation slot plate is placed on the upper end of the insulating tube, and a nickel sheet is placed in the groove inside it.

[0005] Preferably, the samarium oxide powder is calcined at 800°C for 2 hours.

[0006] Preferably, the high-temperature purified samarium oxide powder comprises 85%, graphite is added as a lubricant during pressing, and methylcellulose is added as a binder for mixing.

[0007] Preferably, the pressed isolation trough plate is fired in a furnace at 1200°C.

[0008] Preferably, the upper surface of the isolation trough plate is provided with a placement groove.

[0009] Preferably, the special mold includes an outer mold frame and an upper pressure head slidably connected within the outer mold frame. A lower pressure head is fixedly connected to the bottom end of the inner circumferential surface of the outer mold frame, and a sleeve is fixedly connected to the inner circumferential surface of the upper pressure head.

[0010] Preferably, an insulating tube is placed on the lower surface of the fired isolation tank plate, a crystal bed is fixedly connected to the bottom end of the inner circumference of the insulating tube, a catalyst layer is filled on the upper surface of the crystal bed, and a graphite layer is filled on the upper surface of the catalyst layer.

[0011] Preferably, a nickel sheet is placed in the placement groove on the upper surface of the isolation groove plate.

[0012] Beneficial effects This invention provides a separation tank for lab-grown diamonds and its preparation method, which has the following beneficial effects: 1. The isolation tank for lab-grown diamonds and its preparation method. Samarium oxide is a high-performance rare earth ceramic material with excellent high temperature resistance (melting point up to 2345℃) and chemical corrosion resistance. In the extreme environment of high temperature and high pressure (HPHT) lab-grown diamonds (5-6GPa, 1200-1500℃), it can maintain a stable crystal structure and mechanical properties, and is not prone to cracking, deformation or chemical decomposition. This not only extends the service life of the isolation tank, but also prevents the dissolution of substrate impurities, providing a clean and constant growth microenvironment for lab-grown diamond crystals and reducing defects such as crystal inclusions and dislocations.

[0013] 2. The isolation trough for lab-grown diamonds and its preparation method have a good isolation effect because the isolation trough plate is independent of the outside of the insulating tube, yet it is tightly fitted to the insulating tube.

[0014] 3. The isolation tank for lab-grown diamonds and its preparation method, by placing nickel sheets in the grooves on the upper surface of the isolation tank plate, can not only isolate and absorb impurities, but also increase the internal pressure and reduce pressure loss under high pressure. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the preparation process of the present invention; Figure 2 This is a schematic diagram of the mating structure between the outer mold frame and the upper pressure head of the present invention; Figure 3 This is a frontal cross-sectional view of the outer mold frame of the present invention; Figure 4 This is a schematic diagram of the mating structure of the insulating tube and the isolation groove plate of the present invention; Figure 5 This is a frontal cross-sectional view of the insulating tube of the present invention.

[0016] In the diagram: 1. Outer mold frame; 2. Sleeve; 3. Upper pressure head; 4. Lower pressure head; 5. Isolation groove plate; 6. Nickel sheet; 7. Insulating tube; 8. Graphite layer; 9. Catalyst layer; 10. Crystal bed. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0018] Traditional separators only have basic physical isolation functions and lack the design to actively adsorb or intercept impurities. During the cultivation process, trace metal debris (such as Fe-Ni particles detached from the catalyst layer) and ceramic powder and other impurities are easily diffused with the carbon source and encapsulated by the diamond crystal. This ultimately leads to the presence of defects such as impurity points and inclusions in the synthesized lab-grown diamonds. Among them, products with a clarity grade lower than VS2 account for more than 40%, which seriously affects the optical transparency, mechanical stability and overall commercial quality of diamonds, and restricts the large-scale production of high-value-added lab-grown diamonds. This embodiment is invented to solve the above problems.

[0019] Please see Figures 1 to 5 This invention provides a technical solution: a separation tank for lab-grown diamonds and its preparation method, comprising the following steps: S1 Preparation: The required high-purity samarium oxide powder is calcined at high temperature to remove impurities from the incoming material, and then cooled naturally before use. Take high-purity samarium oxide powder (Sm2O3) with a purity ≥99.99%, median particle size D50 = 2-5 μm, and specific surface area 10-15 m². 2 / g), placed in a box atmosphere furnace for high-temperature impurity removal: Heating program: Increase from room temperature to 800℃ at a rate of 5℃ / min, and hold for 2 hours; Impurity removal mechanism: High-temperature volatilization removes adsorbed moisture (≤0.1wt%) and residual organic additives (such as dispersants in the powder synthesis process) from the powder. Cooling process: After the heat preservation is completed, turn off the heating device, place the powder in a clean quartz boat inside the furnace, and allow it to cool naturally to below 50°C in a dry air atmosphere (relative humidity ≤20%). Then transfer it to a glass bottle for later use (to avoid secondary moisture absorption). S2 ingredients: Take samarium oxide powder that has been purified at high temperature, add graphite as a lubricant during pressing, and add methylcellulose as a binder for mixing; Weigh the following raw materials by weight percentage: S1-treated samarium oxide powder: 85% (core substrate, providing high-temperature structural stability); Graphite powder: 5% (selected from natural flake graphite, with a carbon content ≥99.9% and a particle size of 200-500 mesh, used as a lubricant in the pressing process to reduce the coefficient of friction between the powder and the mold to ≤0.2). Methylcellulose: 10% (choose a low viscosity type; a 2% aqueous solution has a viscosity of 20-50 mPa·s. As a binder, it needs to be dissolved in anhydrous ethanol in advance to prepare a 10wt% solution to improve its dispersibility in the powder). The batching operation is carried out in an inert gas protective glove box (argon atmosphere, oxygen content ≤0.1%) to avoid moisture absorption or oxidation of the raw materials.

[0020] S3 Mixing: Mix all the above materials evenly in the mixer according to the proportions; Add the samarium oxide powder, graphite powder, and methylcellulose ethanol solution weighed in S2 to a planetary mixer (5L capacity, lined with a zirconia ball mill jar), and mix according to the following parameters: Rotational speed: 300 r / min; Mixing time: 2.5 hours (during which the machine is stopped every 30 minutes to take samples and check the particle size distribution uniformity using a laser particle size analyzer to ensure that the D50 deviation is ≤ ±0.5μm); Post-processing: After mixing, the material is transferred to a vacuum drying oven (vacuum degree -0.09MPa, temperature 60℃) and dried for 2 hours to remove ethanol solvent, resulting in a dry and loose mixed powder (flowability ≥45s / 50g, no lumps).

[0021] S4 pressing: Using a special mold, the isolation groove plate 5 of the required size is pressed; Cold isostatic pressing is performed on a four-column hydraulic press using a specially designed mold. The structure and parameters of the specially designed mold are as follows: Outer mold frame 1: The material is Cr12MoV mold steel (quenched, hardness HRC58-62), the inner circumferential surface is polished to Ra≤0.8μm, and the inner diameter is consistent with the outer diameter of the isolation groove plate 5 (tolerance ±0.02mm). Upper pressure head 3: It is slidably connected inside the outer mold frame 1, and its lower end face is provided with a boss (precision IT7 grade) that matches the groove on the upper surface of the isolation groove plate 5. The fit clearance with the outer mold frame is 0.01-0.03mm. The lower pressure head 4 is fixed to the bottom of the inner circumference of the outer mold frame 1, and the flatness of the upper surface is ≤0.01mm / m to ensure that the bottom of the blank is flat. Sleeve 2: Fixed to the inner circumferential surface of the upper pressure head 3, made of high-speed steel (W18Cr4V).

[0022] Pressing parameters: pressing pressure 15-20MPa, holding time 90-120 seconds, density of the formed blank ≥80%, no cracks, missing corners or other defects, dimensional deviation ≤±0.2mm.

[0023] S5 firing: fired in a furnace; The S4 pressed green body was placed in a high-temperature atmosphere furnace for sintering, and the process curve is as follows: Low-temperature degreasing stage: room temperature → 800℃, heating rate 5℃ / min, holding for 1 hour (to remove organic binders such as methylcellulose and avoid high-temperature decomposition and bubble generation). High-temperature sintering stage: 800℃→1200℃, heating rate 3℃ / min, holding time for 3 hours (to promote the diffusion sintering of samarium oxide particles and increase density); Cooling stage: 1200℃ → room temperature, cooling with the furnace (cooling rate ≤8℃ / min, to avoid cracking caused by thermal stress); Argon gas is introduced for protection during sintering (flow rate 1-2 L / min), and the oxygen partial pressure inside the furnace is ≤10⁻. 5 Pa. Performance indicators of the sintered isolation tank plate 5: bulk density ≥ 5.3 g / cm³ 3 Compressive strength ≥190MPa, high temperature resistance ≥1600℃, coefficient of thermal expansion (25-1000℃) is 8.5×10⁻ 6 / ℃.

[0024] S6 Assembly: During assembly, the isolation slot plate 5 is placed on the upper end of the insulating tube, and a nickel sheet 6 is placed in the groove inside it; Component pretreatment: Insulating tube 7: Ultrasonic cleaning with anhydrous ethanol for 15 minutes (power 300W) to remove surface oil, then dry at 60℃ for later use; Nickel sheet 6: Polish the surface oxide layer with 1000-grit sandpaper, clean with anhydrous ethanol and blow dry to ensure surface roughness Ra≤0.2μm; Graphite layer 8 and catalyst layer 9: large particulate impurities are removed by sieving (100 mesh sieve).

[0025] Layered assembly: First, fix the crystal bed 10 to the bottom of the inner end of the insulating tube 7 (using high-temperature ceramic adhesive for bonding, curing temperature 150℃×1h). A catalyst layer 9 and a graphite layer 8 are sequentially filled on the upper surface of the crystal bed 10. During the filling process, a vibration table (amplitude 0.5 mm, frequency 50 Hz) is used to compact the layers to ensure uniform density. Place the isolation groove plate 5 horizontally on the upper end of the insulating tube 7, and ensure that the coaxiality between the two is ≤0.1mm by using positioning fixtures; Finally, the nickel sheet 6 is embedded into the placement groove of the isolation plate 5, and the pressure block is used to gently press to ensure a proper fit (gap ≤ 0.01mm).

[0026] The upper surface of the isolation trough plate 5 is provided with a placement groove.

[0027] The special mold includes an outer mold frame 1 and an upper pressure head 3 that is slidably connected inside the outer mold frame 1. A lower pressure head 4 is fixedly connected to the bottom of the inner circumferential surface of the outer mold frame 1, and a sleeve 2 is fixedly connected to the inner circumferential surface of the upper pressure head 3.

[0028] An insulating tube 7 is placed on the lower surface of the fired isolation tank plate 5. A crystal bed 10 is fixedly connected to the bottom of the inner circumference of the insulating tube 7. A catalyst layer 9 is filled on the upper surface of the crystal bed 10. A graphite layer 8 is filled on the upper surface of the catalyst layer 9.

[0029] A nickel sheet 6 is placed in the placement groove on the upper surface of the isolation trough plate 5.

[0030] In summary, when using the isolation tank for lab-grown diamonds and its preparation method, the isolation tank assembled in step S6 is first placed into a high-temperature, high-pressure lab-grown diamond reaction chamber (such as a six-sided press chamber). This ensures that the outer wall of the insulating tube 7 is tightly fitted to the side wall of the chamber to stabilize pressure transmission. The upper surface of the nickel sheet 6 makes precise contact with the upper electrode of the chamber to achieve conductive connection. Simultaneously, it is confirmed that pre-treated diamond seed crystals (such as HPHT seed crystals with a particle size of 1-2 mm) have been placed in the seed crystal slot of the crystal bed 10. Then, the reaction equipment is started, and the temperature and pressure are increased according to the preset process: first, the chamber pressure is increased to 5-6 GPa, then the temperature is increased to 1200-1500℃ (the suitable temperature and pressure range for diamond growth) at a rate of 10℃ / min, and held at this temperature and pressure for 10-20 hours (adjusted according to the target diamond size). During this process, the isolation trough plate 5, with its high temperature resistance of ≥1600℃ and ≤8.5×10⁻ 6 The thermal expansion coefficient of / ℃ stabilizes and isolates the graphite layer 8 (carbon source region) from the seed crystal region, preventing carbon source impurities from directly contacting the seed crystal; the insulating tube 7 effectively blocks the transverse current, ensuring a uniform electric field in the reaction area; the catalyst layer 9 catalyzes the carbon elements in the graphite layer 8 to convert into the diamond phase under high temperature and pressure, and grows directionally along the seed crystal. After the growth cycle is completed, the temperature is lowered to room temperature at a rate of 5℃ / min, the pressure is slowly released, the isolation tank is removed, the nickel sheet 6 is disassembled and separated from the isolation tank plate 5, and high-quality grown diamond crystals with no inclusions and an integrity of ≥95% can be obtained from the crystal bed 10.

[0031] It should be noted that in the description of this invention, terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," which indicate direction or positional relationships, are based on the direction or positional relationships shown in the accompanying drawings. These are used merely for ease of description and do not indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0033] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an isolation tank for lab-grown diamonds, characterized in that... Includes the following steps: S1 Preparation: The required high-purity samarium oxide powder is calcined at high temperature to remove impurities from the incoming material, and then cooled naturally before use. S2 ingredients: Take samarium oxide powder that has been purified at high temperature, add graphite as a lubricant during pressing, and add methylcellulose as a binder for mixing; S3 Mixing: Mix all the above materials evenly in the mixer according to the proportions; S4 pressing: Using a special mold, press the isolation groove plate (5) of the required size; S5 firing: fired in a furnace; S6 Assembly: During assembly, the isolation slot plate (5) is placed on the upper end of the insulating tube, and a nickel plate (6) is placed in the groove inside it.

2. The method for preparing a separation tank for lab-grown diamonds according to claim 1, characterized in that: The samarium oxide powder was calcined at 800°C for 2 hours.

3. The method for preparing a separation tank for lab-grown diamonds according to claim 1, characterized in that: The high-temperature purified samarium oxide powder is 85%, graphite is added as a lubricant during pressing, and methylcellulose is added as a binder for mixing.

4. The method for preparing a separation tank for lab-grown diamonds according to claim 1, characterized in that: The pressed isolation trough plate (5) is placed in a furnace and fired at 1200°C.

5. A diamond isolation groove according to claim 1, characterized in that: It is prepared by the method described in claims 1-4.

6. A diamond isolation groove according to claim 5, characterized in that: The upper surface of the isolation trough plate (5) is provided with a placement groove.

7. The isolation tank for lab-grown diamonds according to claim 6, characterized in that: The special mold includes an outer mold frame (1) and an upper pressure head (3) slidably connected inside the outer mold frame (1). A lower pressure head (4) is fixedly connected to the bottom of the inner circumferential surface of the outer mold frame (1), and a sleeve (2) is fixedly connected to the inner circumferential surface of the upper pressure head (3).

8. The isolation tank for lab-grown diamonds according to claim 7, characterized in that: An insulating tube (7) is placed on the lower surface of the fired isolation trough plate (5). A crystal bed (10) is fixedly connected to the bottom of the inner circumference of the insulating tube (7). A catalyst layer (9) is filled on the upper surface of the crystal bed (10). A graphite layer (8) is filled on the upper surface of the catalyst layer (9).

9. The isolation tank for lab-grown diamonds according to claim 8, characterized in that: A nickel sheet (6) is placed in the placement groove on the upper surface of the isolation plate (5).

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