Method for preparing diamond by taking BaCO3 as raw material and diamond

Abstract

The invention discloses a method for preparing a diamond by taking BaCO3 as a raw material and the diamond. The method comprises the following steps: pre-pressing and forming barium carbonate powder, and drying to obtain a formed sample; wrapping the formed sample with a metal wrapping body, putting the formed sample wrapped by the metal wrapping body into a high-pressure sintering unit, and then drying; carrying out high-pressure and high-temperature sintering on the high-pressure sintering unit filled with the formed sample, and firstly pressurizing and then heating; and the metal inclusion is removed, and the formed sample is subjected to acid pickling to obtain the monocrystal diamond. According to the method, C in BaCO3 can be simply, efficiently and completely converted into diamond.

Description

Technical Field

[0001] The invention belongs to the field of inorganic non-metallic materials, and specifically relates to a method for preparing diamond using BaCO3 as a raw material. Background Art

[0002] Synthetic diamond is a well-known durable material that can have different characteristics, such as variable color, luminescence and semiconductor properties depending on admixtures (B, N, Ni, etc.) and / or structural defects. Currently available high pressure and high temperature (HPHT) synthesis methods can obtain large (up to 8-10 mm) gem-quality diamond crystals. In theory, synthetic diamond can be doped with an unlimited number of isotopes. 14 C, or even completely by 14 C. This carbon isotope is a β-emitter with a half-life of 5730±40 years and a decay energy of 0.156 MeV. Reprocessing of spent nuclear fuel provides an almost unlimited supply of BaCO3. 14 C source, 14 C in solid compound Ba 14 It is easy to store in CO3 and 14 CO3 has a high specific activity. 14 The synthesis of C diamond single crystals is very complex. Recently, experiments have demonstrated the technology of converting BaCO3 powder into diamond single crystals using high temperature. Secondly, if you use real 14 Such research could be substantially optimized by selecting promising diamond types and the most efficient synthesis methods in advance before C.

[0003] At present, HPHT and CVD are the main technologies for synthesizing artificial diamonds. With the progress of high temperature and high pressure technology (HPHT) and chemical vapor deposition technology (CVD) to synthesize artificial diamonds, the development and application of diamonds have been greatly promoted. However, for the process of synthesizing diamonds by CVD, point defects caused by impurities and line defects introduced by surface processing technology affect the quality of diamonds; for the HTHP method, the long-term high temperature and high pressure make the production cost expensive and the equipment requirements are stringent. In addition, HPHT diamond uses metal catalysts, which leaves trace metal particles in the diamond, so it is still difficult to obtain pure diamonds. At present, the preparation technology of high-quality single-crystal diamond materials is a bottleneck problem that restricts the large-scale application of diamond detectors. Summary of the invention

[0004] The invention provides a method for preparing diamond by taking BaCO3 as a raw material. The method can simply and efficiently convert C in BaCO3 completely into diamond.

[0005] The present invention provides a method for preparing diamond using BaCO3 as a raw material, comprising:

[0006] (1) pre-pressing and drying barium carbonate powder to obtain a molded sample;

[0007] (2) wrapping the molded sample of step (1) with a metal inclusion, placing the wrapped molded sample into a high pressure sintering unit and drying it;

[0008] (3) a high pressure sintering unit containing the molded sample of the high pressure and high temperature sintering step (2), wherein the high pressure and high temperature sintering temperature is 1400-2000° C. and the pressure is 8-20 GPa;

[0009] (4) Remove the metal inclusions and pickle the molded sample to obtain single crystal diamond.

[0010] Preferably, in step (1), the particle size of the barium carbonate powder is 300 nm-4 μm. The present invention can achieve better compaction and easier pre-pressing by providing a suitable particle size.

[0011] Preferably, the pre-pressing pressure is 400-500 MPa, and the holding time is 10s-30s.

[0012] Preferably, in step (2), the material of the metal inclusion is one or more of Mo, Ta, and Zr. The metal inclusion provided by the present invention has the function of wrapping the raw material powder without contamination, and is not easily oxidized under high temperature and high pressure and does not react with the raw material powder.

[0013] Preferably, in step (2), the drying temperature is 100-120°C.

[0014] Preferably, the high pressure sintering unit is a cube assembly, and the material of the cube assembly is composed of pyrophyllite, dolomite blocks and the like.

[0015] Preferably, in step (3), the process of high pressure and high temperature sintering is as follows: start increasing the pressure, and after reaching the set pressure, heat up and keep the temperature for a period of time. After the heat preservation is completed, stop heating, keep the pressure for a period of time, and then start reducing the pressure.

[0016] Preferably, in step (3), the temperature of the high pressure and high temperature sintering is 1400-2000°C, the set pressure is 8-20GPa, and the holding time and pressure holding time are 15s-4min respectively. The present invention controls the appropriate sintering temperature and pressure so that the C in BaCO3 can be converted into diamond.

[0017] Preferably, in step (3), the pressure increasing rate of the high pressure and high temperature sintering is 50-100 MPa / s, the temperature increasing rate is 2-5°C / s, and the pressure reducing rate is 50-100 MPa / s.

[0018] Preferably, in step (4), the pickling solution is one or more of HCl, HNO3, HF, H2SO4.

[0019] On the other hand, the present invention also provides a diamond, which is prepared by the method for preparing diamond using BaCO3 as raw material.

[0020] Preferably, the diamond is 14 C Diamond or 12 C diamond, the size of the diamond is 200nm-200μm.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The method for preparing diamond provided by the present invention does not require the introduction of a reducing agent, and directly synthesizes BaCO3 into single crystal diamond through the temperature and pressure of high temperature and high pressure sintering. The preparation method is simple and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A process flow chart provided for a specific embodiment of the present invention;

[0024] Figure 2 The scanning electron microscope images of the raw material barium carbonate powder used in Examples 1, 2 and Comparative Example 1;

[0025] Figure 3 XRD patterns of the raw material barium carbonate powder used in Examples 1, 2 and Comparative Example 1;

[0026] Figure 4 This is a scanning electron microscope analysis image of the synthetic block of Example 1;

[0027] Figure 5 This is the XRD pattern of the block synthesized in Example 1;

[0028] Figure 6 This is a Raman spectrum analysis diagram of the synthetic block of Example 1;

[0029] Figure 7 This is a scanning electron microscope analysis image of the synthetic block of Example 2;

[0030] Figure 8 This is the Raman spectrum analysis diagram of the synthetic block in Example 2. DETAILED DESCRIPTION

[0031] The present invention is further described below through the accompanying drawings and specific implementation methods. It is necessary to point out here that this embodiment is for further explanation of the present invention and cannot be understood as limiting the scope of protection of the present invention. Technical personnel skilled in the art can make some non-essential improvements and adjustments based on the content of the above invention.

[0032] Example 1

[0033] This embodiment provides a method for synthesizing diamond, such as Figure 1 As shown, including:

[0034] a. Assemble the sintering unit: Take 0.866 g of BaCO3 powder with a purity of 99.99% and a grain size of 300 nm-4 μm, pre-press the BaCO3 powder into a shape, and dry the molded sample in a vacuum drying oven.

[0035] b. Treat the metal inclusion Ta cup used to wrap the raw materials, grind and polish, then degrease, ultrasonically clean, and vacuum dry. Put the pre-pressed BaCO3 powder into the metal inclusion to prevent the sample from being contaminated under high temperature and high pressure; put the wrapped sample into the high-pressure assembly sintering unit, and put the assembled sintering unit into a drying oven at a constant temperature of 120℃ to dry it for use.

[0036] c. High temperature and high pressure sintering: Use a six-sided top press for high temperature and high pressure sintering. The pressure is set to 15GPa, the temperature is set to 1600℃, the pressure increase rate is 100MPa / s, and the heating rate is 2℃ / s. When the power reaches the set value, keep the temperature and pressure for 30s. After the temperature and pressure are completed, slowly reduce the pressure.

[0037] d. Sample processing: Take out the sample from the synthesis chamber, remove the metal wrapped around the sample, grind the synthetic sample into powder, and then remove impurities through acid washing to obtain diamond.

[0038] Sample performance test: Figure 2 As shown in (a)-(f), the raw material BaCO3 powder used is mostly irregular spherical or flaky particles, and small particles with a particle size of 300-800nm ​​are agglomerated on large particles with a particle size of 1-4μm.

[0039] like Figure 3 As shown in the figure, the XRD results of the raw material BaCO3 powder show that the position and peak intensity of each diffraction peak are consistent with the diffraction data of the standard card orthorhombic phase BaCO3, which is an orthorhombic crystal structure. The characteristic peak of the sample is sharp and the half-peak width is very narrow, indicating that the sample is fully crystallized.

[0040] After high temperature and high pressure experiments, the BaCO3 powder reacted with some substances in the synthetic block, that is, the high-pressure sintering unit, to form a block.

[0041] like Figure 4-Figure 6 As shown, Figure 4 (a), (c) and (e) are the surface morphologies of synthetic blocks of different sizes; Figure 4 (b), (d) and (f) correspond to Figure 4From the C element mapping diagrams of (a), (c) and (e), it can be seen from the EDS results of the scanning electron microscope that diamond single crystals have been formed, and the diamond grain size is between 400nm-10μm. From the EDS Map results, it can be found that except for the diamond particles, no C is detected anywhere else, proving that the C in BaCO3 can be completely converted into diamond. In addition, peaks related to diamond are detected in both the XRD spectrum and the Raman spectrum.

[0042] Example 2

[0043] a. Assemble the sintering unit: Take 0.754 g of BaCO3 powder with a purity of 99.99% and a grain size of 300 nm-4 μm, pre-press the BaCO3 powder into a shape, and dry the molded sample in a vacuum drying oven.

[0044] b. Treat the metal inclusion Ta cup used to wrap the raw materials, grind and polish, then degrease, ultrasonically clean, and vacuum dry. Put the pre-pressed BaCO3 powder into the metal inclusion to prevent the sample from being contaminated under high temperature and high pressure; put the wrapped sample into the high-pressure assembly sintering unit, and put the assembled sintering unit into a drying oven at a constant temperature of 120℃ to dry it for use.

[0045] c. High temperature and high pressure sintering: Use a six-sided top press for high temperature and high pressure sintering. The pressure is set to 10GPa, the temperature is set to 1400℃, the pressure increase rate is 100MPa / s, and the heating rate is 2℃ / s. When the power reaches the set value, keep the temperature and pressure for 4 minutes. After the temperature and pressure are completed, slowly reduce the pressure.

[0046] d. Sample processing: Take out the sample from the synthesis chamber, remove the metal wrapped around the sample, grind the synthetic sample into powder, and then remove impurities through acid washing to obtain diamond.

[0047] Sample performance test: Figure 7 As shown, Figure 7 (a), (c) and (e) are the surface morphologies of synthetic blocks of different sizes; Figure 7 (b), (d) and (f) correspond to Figure 4 The C element mapping of (a), (c) and (e) shows that large diamonds are formed, and the diamonds are irregular blocks with uniform luster, with a size greater than 30μm and up to 200μm, buried under other impurity phases. Raman detection of the sample also shows peaks related to diamonds, such as Figure 8 shown.

[0048] Comparative Example 1

[0049] a. Assemble the sintering unit: Take 0.936g of BaCO3 powder with a purity of 99.99% and a grain size of 300nm-4μm, pre-press the BaCO3 powder into a shape, and dry the molded sample in a vacuum drying oven;

[0050] b. Treat the metal inclusion Ta cup used to wrap the raw materials, grind and polish, then degrease, ultrasonically clean, and vacuum dry. Put the pre-pressed BaCO3 powder into the metal inclusion to prevent the sample from being contaminated under high temperature and high pressure environment; put the wrapped sample into the high pressure assembly sintering unit, and put the assembled sintering unit into a drying oven at a constant temperature of 120℃ to dry for use;

[0051] b. High temperature and high pressure sintering: Use a six-sided top press for high temperature and high pressure sintering. The pressure is set to 5 GPa, the temperature is set to 2000 °C, the pressure increase rate is 100 MPa / s, and the heating rate is 2 °C / s. When the power reaches the set value, keep the temperature and pressure for 3 minutes. After the temperature and pressure are completed, slowly reduce the pressure.

[0052] c. Sample processing: Take out the sample in the synthesis cavity, remove the metal wrapped around the sample, grind the synthetic sample into powder, and then remove impurities through acid washing.

[0053] Sample performance test: No diamond-related peaks were detected in the XRD spectrum and Raman spectrum, proving that diamond cannot be formed directly through BaCO3 at lower pressures.

Claims

1. A method for preparing diamond using BaCO3 as raw material, characterized in that: include: (1) pre-pressing and drying barium carbonate powder to obtain a molded sample; (2) wrapping the molded sample of step (1) with a metal inclusion, placing the wrapped molded sample into a high pressure sintering unit and drying it; (3) a high pressure sintering unit containing the molded sample of the high pressure and high temperature sintering step (2), wherein the high pressure and high temperature sintering temperature is 1400-2000° C. and the pressure is 8-20 GPa; (4) Remove the metal inclusions and pickle the molded sample to obtain single crystal diamond.

2. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (1), the particle size of the barium carbonate powder is 300 nm-4 μm.

3. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: The pre-pressing pressure is 400-500 MPa, and the holding time is 10s-30s.

4. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (2), the material of the metal inclusion is one or more of Mo, Ta, and Zr.

5. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (2), the drying temperature is 100-120°C.

6. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (3), the heat preservation time and pressure preservation time are 15s-4min respectively.

7. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (3), the pressure increase rate of the high pressure and high temperature sintering is 50-100 MPa / s, the temperature increase rate is 2°C / s, and the pressure reduction rate is 50-100 MPa / s.

8. The method for preparing diamond using BaCO3 as raw material according to claim 1, characterized in that: In step (4), the pickling solution is one or more of HCl, HNO3, HF, and H2SO4.

9. A diamond, characterized in that: The diamond is prepared by the method for preparing diamond using BaCO3 as raw material as described in any one of claims 1-8.

10. The diamond according to claim 9, characterized in that The diamond is 14 C Diamond or 12 C diamond, the size of the diamond is 200nm-200μm.

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