A method for preparing polycrystalline diamond particles with high recovery rate

Abstract

This invention relates to a method for preparing polycrystalline diamond microparticles with high recovery rate. The main propellant column preparation involves: mixing explosive with graphite and placing the mixture into a cylindrical mold with a bottom diameter of 20-40 mm; pressurizing the mixture at a rate of 8-10 MPa / min to 80-100 MPa and holding the pressure for 3-5 min; then pressurizing it at a rate of 2-5 MPa / min to 200-220 MPa and holding the pressure for 20-30 min; resulting in a main propellant column with a height-to-diameter ratio of 1.0-1.5 and a density of 1.50-1.52 g / cm³. 3 Current technology suggests that the density of the active pharmaceutical ingredient (API) column should be between 1.60 and 1.65 g / cm³. 3 The optimization was carried out within the specified range, but this invention found that the density of the main drug column was within the range of 1.50-1.52 g / cm³. 3 Within a lower range, the final recovery rate of diamond microparticles can be increased to 11-13%.

Description

Technical Field

[0001] This invention relates to a method for preparing polycrystalline diamond microparticles, and more particularly to a method for preparing polycrystalline diamond microparticles with high recovery rate. Background Technology

[0002] Diamond microparticles, especially polycrystalline diamond aggregates at the nano and submicron scales, possess the combined properties of diamond (superhardness, high thermal conductivity, and high chemical stability) and micro / nano materials (high specific surface area and easy dispersibility), demonstrating enormous application potential in fields such as precision polishing, composite coatings, thermally conductive fillers, drug carriers, and quantum information.

[0003] Currently, the mainstream methods for preparing micro / nano diamond particles mainly include detonation, high-temperature and high-pressure (HTHP), and chemical vapor deposition (CVD). Among these, detonation is the primary method for industrial production of micro / nano diamond particles due to its high production efficiency and relatively low cost. This method utilizes carbon-rich explosives detonated in an inert medium to generate an instantaneous high-temperature and high-pressure environment, causing free carbon atoms to directly transform into nanoscale diamond phases. Although this method is relatively mature, its final diamond particle yield is typically only 5-8% of the total explosive mass. Therefore, improving the final diamond particle recovery rate remains a technical challenge that has been sought to be solved but has yet to be successfully achieved. Summary of the Invention

[0004] This invention solves the technical problem of how to improve the final recovery rate of diamond microparticles.

[0005] This invention provides a method for preparing polycrystalline diamond microparticles. The preparation of the main propellant column involves mixing explosive with graphite and placing the mixture into a cylindrical mold with a bottom diameter of 20-40 mm. The pressure is increased to 80-100 MPa at a rate of 8-10 MPa / min and held for 3-5 min. Then, the pressure is increased to 200-220 MPa at a rate of 2-5 MPa / min and held for 20-30 min. After pressing, the ratio of the height to the diameter of the main propellant column is 1.0-1.5, resulting in a density of 1.50-1.52 g / cm³.

[0006] Furthermore, the density of the main drug column is 1.50-1.51 g / cm3.

[0007] Furthermore, the explosive has a mass percentage of 70-80 wt% and the graphite has a mass percentage of 20-30 wt%.

[0008] Furthermore, the explosive is trinitrotoluene and cyclotrimethylenetrinitramine, and the mass ratio of trinitrotoluene to cyclotrimethylenetrinitramine is 40:60 or 50:50.

[0009] Furthermore, after compression, the pressure is released to atmospheric pressure at a rate not exceeding 3 MPa / min.

[0010] Further, the explosive and graphite are pretreated: the explosive and graphite are ball-milled and mixed at below 40°C under an inert atmosphere for 4-6 hours, and then passed through a 200-mesh sieve.

[0011] Furthermore, the detonator, initiating charge, and main charge are assembled and suspended inside the explosive container, creating an oxygen-deficient environment for the main charge to detonate.

[0012] Further, the post-detonation mixture is washed, filtered, settled, and dried to obtain detonation ash.

[0013] Further, after reacting the detonation ash with acid, the ash is washed and dried to obtain polycrystalline diamond microparticles.

[0014] The beneficial effects of this invention are as follows:

[0015] Existing technologies suggest that the density of the main drug column should be optimized within the range of 1.60-1.65 g / cm3. However, this invention has found that a lower main drug column density of 1.50-1.52 g / cm3 can increase the final recovery rate of diamond microparticles to 11-13%. Detailed Implementation

[0016] The following non-limiting embodiments are intended to enable those skilled in the art to more fully understand the invention, but do not limit the invention in any way. Example 1

[0017] A method for preparing polycrystalline diamond microparticles, the method comprising the following steps:

[0018] TNT and RDX are mixed at a mass ratio of 50:50 to obtain the explosive.

[0019] According to the mass percentage, 80wt% of explosives and 20wt% of graphite are added to a fully enclosed planetary ball mill. High-purity nitrogen is filled into the fully enclosed planetary ball mill. The ball mill is carried out in an intermittent mode for 15 minutes, followed by a 5-minute pause for cooling to keep the temperature inside the fully enclosed planetary ball mill below 40°C throughout the process. The mixture is then ball-milled for 4 hours and passed through a 200-mesh sieve to ensure uniform mixing.

[0020] After the explosive and graphite are mixed evenly, they are placed in a cylindrical mold with a bottom diameter of 40 mm. The pressure is increased to 100 MPa at a rate of 8 MPa / min and held for 4 min to initially compact the material and complete particle rearrangement. Then, the pressure is increased to 210 MPa at a rate of 4 MPa / min and held for 20 min to achieve omnidirectional uniform compaction. Finally, the pressure is released to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main explosive column. After compression, the ratio of the height to the diameter of the main explosive column is 1.43, and the density of the main explosive column is 1.502 g / cm3.

[0021] The detonator, initiating charge, and main charge are tightly bound together with tape, placed in a plastic bag filled with deionized water, and then suspended inside the explosive container to detonate the main charge.

[0022] The detonation mixture is washed, filtered, settled, and dried to obtain detonation ash;

[0023] Detonation ash and concentrated sulfuric acid were reacted at 180℃ for 6 hours at a solid-liquid ratio of 1 g / 30 mL. After washing and drying, polycrystalline diamond microparticles were obtained. Example 2

[0024] The difference from Example 1 is as follows: the pressure is increased to 100 MPa at a rate of 8 MPa / min and held for 4 min, then increased to 200 MPa at a rate of 4 MPa / min and held for 20 min, and then depressurized to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main drug column. After compression, the ratio of the height to the diameter of the main drug column is 1.24, making the density of the main drug column 1.507 g / cm3.

[0025] Comparative Example 1

[0026] The difference from Example 1 is as follows: the pressure is increased to 100 MPa at a rate of 8 MPa / min and held for 4 min, then increased to 220 MPa at a rate of 4 MPa / min and held for 20 min, and then depressurized to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main drug column. After compression, the ratio of the height to the diameter of the main drug column is 1.03, making the density of the main drug column 1.615 g / cm3.

[0027] Comparative Example 2

[0028] The difference from Example 1 is as follows: the pressure is increased to 100 MPa at a rate of 8 MPa / min and held for 4 min, then increased to 210 MPa at a rate of 4 MPa / min and held for 20 min, and then depressurized to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main drug column. After compression, the ratio of the height to the diameter of the main drug column is 1.02, making the density of the main drug column 1.603 g / cm3.

[0029] Comparative Example 3

[0030] The difference from Example 1 is that the pressure was increased to 220 MPa at a rate of 4 MPa / min and held for 20 min, and then depressurized to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main drug column. After compression, the ratio of the height to the diameter of the main drug column was 1.39, and the density of the main drug column was 1.516 g / cm3.

[0031] Comparative Example 4

[0032] The difference from Example 1 is that the ball milling process does not pass through a 200-mesh sieve. The pressing process is as follows: the pressure is increased to 100 MPa at a rate of 8 MPa / min and held for 4 min, then increased to 210 MPa at a rate of 4 MPa / min and held for 20 min, and then depressurized to atmospheric pressure at a rate of 2.5 MPa / min to obtain the main drug column. After pressing, the ratio of the height to the diameter of the main drug column is 1.06, making the density of the main drug column 1.541 g / cm3.

[0033] The results of diamond purity and final recovery rate in Examples 1-2 and Comparative Examples 1-4 are shown in Table 1 below:

[0034]

[0035] Based on Examples 1 and 2, and Comparative Examples 1 and 2, the prior art considers the main drug column density to be in the range of 1.60-1.65 g / cm³. This invention uses a lower main drug column density, which improves the diamond recovery rate significantly beyond the expected range. Based on Examples 1 and 2, and Comparative Example 3, Comparative Example 3, without the first stage of compression, shows a significant decrease in diamond recovery rate due to poor uniformity of main drug column density. Based on Examples 1 and 2, and Comparative Example 4, Comparative Example 4, without a 200-mesh sieve, suffers from poor uniformity of main drug column density and component distribution due to particle size differences, resulting in a significant decrease in diamond recovery rate.

Claims

1. A method for preparing polycrystalline diamond microparticles, characterized in that: Pretreatment of explosives and graphite: The explosives and graphite are ball-milled together at below 40℃ under an inert atmosphere for 4-6 hours, and then passed through a 200-mesh sieve. Preparation of the main explosive column: After the explosives and graphite are mixed evenly, they are placed in a cylindrical mold with a bottom diameter of 20-40 mm. The pressure is increased to 80-100 MPa at a rate of 8-10 MPa / min and held for 3-5 minutes. Then, the pressure is increased to 200-220 MPa at a rate of 2-5 MPa / min and held for 20-30 minutes. After pressing, the pressure is released to atmospheric pressure at a rate not exceeding 3 MPa / min. The height-to-diameter ratio of the main explosive column after pressing is 1.0-1.5, and the density of the main explosive column is 1.50-1.52 g / cm³. 3 .

2. The preparation method according to claim 1, characterized in that: The density of the main drug column is 1.50-1.51 g / cm³. 3 .

3. The preparation method according to claim 1, characterized in that: The explosive has a mass percentage of 70-80 wt% and the graphite has a mass percentage of 20-30 wt%.

4. The preparation method according to claim 1, characterized in that: The explosive is trinitrotoluene and cyclotrimethylenetrinitramine, and the mass ratio of trinitrotoluene to cyclotrimethylenetrinitramine is 40:60 or 50:

50.

5. The preparation method according to claim 1, characterized in that: The detonator, initiating charge, and main charge are assembled and suspended inside the explosive container, creating an oxygen-deficient environment for the main charge, which is then detonated.

6. The preparation method according to claim 5, characterized in that: The detonation mixture is washed, filtered, settled, and dried to obtain detonation ash.

7. The preparation method according to claim 6, characterized in that: After reacting the detonation ash with acid, the ash is washed and dried to obtain polycrystalline diamond microparticles.

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