CN112169707A

CN112169707A - Preparation method and reaction system of high-grade artificial diamond

Info

Publication number: CN112169707A
Application number: CN201910643247.8A
Authority: CN
Inventors: 彭靖; 彭英利; 马承愚; 周玉
Original assignee: Shenzhen Zhihe Carbon Silicon Technology Co ltd
Current assignee: Shenzhen Zhihe Carbon Silicon Technology Co ltd
Priority date: 2019-07-02
Filing date: 2019-07-02
Publication date: 2021-01-05

Abstract

The invention relates to a preparation method and a reaction system of high-grade artificial diamond, which can continuously prepare the high-grade artificial diamond with high quality for 1 to 10 days by adopting supercritical water as a preparation medium and taking various carbon sources as raw materials under the catalysis of hydrogen at the temperature and the pressure of the supercritical state. The reaction system is the core for preparing the high-grade artificial diamond, and the key for preparing the high-grade artificial diamond by the reaction device is the double heating control and the suspension type master batch hanging rail positioning structure design.

Description

Preparation method and reaction system of high-grade artificial diamond

Technical Field

The invention relates to the field of new materials, in particular to a preparation method and a reaction system of high-grade artificial diamond.

Background

The high-grade artificial diamond refers to large single crystal artificial diamond of 1 carat and more than 10 carat, and is also called gem grade artificial diamond. High-grade artificial diamond is rapidly developed in recent years due to market demands, and professional manufacturers at home and abroad compete for research, development and production. The currently used production methods include a high-temperature high-pressure method (HPHT method) and a vapor deposition method (CVD method).

The HPHT process, also known as the differential temperature process, is essentially a physical high pressure process using a metal as the catalyst medium. The method is firstly proposed by GE company in 1967, and 5mm (about 1 carat) yellow single crystal diamond (Ib) is synthesized in 1971, and then colorless (Ia type) and blue (Ib type) large single crystal diamond growth technologies are developed. But cannot be industrialized due to excessive production cost and unstable product quality. Later, Sumitomo electricians produced large yellow single crystals of 7-8mm or less by batch production using the HPHT method. A small high-pressure HPHT method production device and a process are developed at the university of Florida in the United states, and the growth speed of large crystals is 3 days and half 2.8 carats.

The CVD method is a method of producing diamond using vapor deposition on a diamond seed or a metal metalloid sheet. Apollo Diamond Inc. in the United states first created a technique for producing high grade diamond by CVD. The growth rate was 5 carats per week (1 carat net drill). The canary physical laboratory in the united states in 2005 developed single-channel diamond wafers capable of reaching growth rates of 100um/h to 300 um/h. The transparent single crystal diamond with the weight of 10 gram can be obtained, and nearly colorless, blue and yellow large single crystals can be directly grown without high-temperature and high-pressure post-treatment. The intradiscal geophysical laboratory obtains us patent 2005.

The HPHT process has the disadvantage that diamond grows in the molten catalyst, and metal atoms in the catalyst more or less enter the diamond lattice, forming metal residues. The method also limits the growth of large single crystal diamonds due to the limited space of the high pressure chamber of the apparatus. Manufacturing larger equipment increases investment and costs.

The CVD method has the advantages of high purity of diamond and no metal residue in preparation. But has the disadvantages of slow growth speed, complex process and difficult realization of industrialization.

The supercritical hydrothermal method (SCW method) of the invention is a novel technology taking supercritical water as a catalyst, has the advantages of both the HPHT method and the CVD method, and abandons the defects. The method has the main advantages that the diamond can grow rapidly, the single crystal can achieve high purity, the high quality degree cannot be achieved by other methods, and industrialization is easy to realize.

Disclosure of Invention

The invention provides a preparation method and a reaction system of high-grade artificial diamond, which adopts supercritical water as a catalyst, selects a plurality of carbon sources as raw materials and continuously prepares the high-grade artificial diamond under the supercritical state and the catalytic action of hydrogen; the reaction system adopts double heating control and is provided with a suspension type master batch (seed crystal) hanging fence in the reaction device so as to realize the growth of the large single crystal diamond.

In order to achieve the purpose, the technical route adopted by the invention is as follows:

(1) the filtered water is pressurized to 25-30MPa, heated to 400 ℃ at 300 ℃, added with carbon source gas and hydrogen gas, reacted and deposited to obtain the large single crystal diamond.

(2) The reaction system is provided with a single heating device and a reactor auxiliary heating sleeve, temperature control and regulation are performed, a suspended master batch hanging fence is arranged at the middle upper part of the reactor, and seed crystal growth is performed.

The carbon source selected by the invention comprises: natural gas, argon, coal gas, methanol, ethanol and graphite.

The principle of the invention is as follows:

supercritical water (T > 374.3 ℃, P > 22.1MPa) is the best catalyst for preparing high-grade artificial diamond due to high density, high viscosity, high thermal conductivity and strong diffusion. If the thermal conductivity of supercritical water at high temperature and high pressure is 0.418W/(m.k), which is equivalent to the normal thermal conductivity value, the temperature can be rapidly transmitted to the C source target object at H₂Under the action of the C element and the pressure matching, the C element can be quickly reacted and converted into diamond crystal particles and deposited on the diamond seed crystal to continuously grow large single crystal diamond.

The reaction system of the invention adopts double heating devices, greatly ensures the heating efficiency and can better control the reaction temperature. The suspension type master batch hanging fence arranged in the reactor ensures that the seed crystal master batch is accurately fixed at the optimal reaction position, and ensures the effective deposition target of crystal preparation.

The high-grade artificial diamond prepared by the invention has the indexes of hardness, refractive index, purity, chromaticity and the like which are all close to those of natural diamond, and the maximum single crystal mass can reach more than 10 carats. Can be applied to the jewelry electronic industry, the aerospace industry and a plurality of high-tech fields. The high-grade artificial diamond becomes the modern industrial new material which is most suitable for the modern time with the highest thermal conductivity, excellent optical property, semiconductor property and chemical stability.

Drawings

FIG. 1 is a schematic diagram of the process flow and reaction principle of the present invention.

FIG. 2 is a schematic view of a reaction system of the present invention.

Detailed Description

Referring to fig. 1, in the process flow and reaction principle schematic diagram of the present invention, (1) is a charging process, in which treated purified water (H) is added₂O) is conveyed to a pressurizing step (2) and is pressurized to a pressure of 1 to 35MPa to obtain (H)₂O) reaching the supercritical pressure condition, entering a heating section (3) for preheating to 1-300 ℃, entering a reaction process (4), and simultaneously adding a carbon source gas (4-1-1): CH4 or Ar, CO, etc., and is pressurized to 1-35MPa by a gas pressurizing device (4-1); adding catalyst hydrogen: h₂Pressurizing by a gas pressurizing device (4-2) to 1-35 MPa. The conditions of the diamond preparation reaction are as follows: pc: 30-35MPa, Tc: 500 ℃ and 600 ℃; conversion reaction time: 10-60S; crystal growth time: 3-10 d; the reaction process is as follows:

(5) is a cooling process, supercritical water and CH after reaction₄、 H₂The mixed gas enters a separation process (6) through a heating device (3) under the separation conditions that: t is less than 200 ℃, and P is less than 9 MPa. After the pressure and the temperature are reduced H₂O is deposited and separated and discharged, and gas H₂、CO、CO₂Is recovered by (7) and H is separated₂After purification, the product is sent to a hydrogen storage step (4-2-2).

Referring to FIG. 2, a reaction system of the present invention is schematically illustrated. High pressure H as catalyst₂O enters a preheater 2 through 1, enters a reaction device 3 after heat exchange, is subjected to auxiliary heating, is heated by 3-1 starting, simultaneously starts a carbon source gas storage tank 4-1 and a booster pump 4 as well as a hydrogen storage tank 5-1 and a booster pump 5, and enters the reaction device together with pressurized gas, and under the supercritical state, supercritical water and the carbon source gas (CH) are mixed in the closed reaction device₄Or Ar, CO, etc.),Hydrogen (H)₂) Are homogeneously mixed and reacted. Under proper temperature and pressure, C in the carbon source gas is converted into diamond particles rapidly (30-60S) to be deposited on the diamond wood hanging fence crystal, and the diamond particles are grown by continuous deposition for about 3-10 days to prepare the large single crystal artificial diamond. The supercritical water mixed gas after the preparation reaction enters a preheater 2 from a pipeline 6 at the upper part of a reaction device 3 and is mixed with a new material (H)₂O) heat exchange and then sending to a separation device.

After 3-10 days of continuous preparation, the generated large single crystal diamond and the small particle diamond are both discharged from the bottom of the reaction device. Through detection, the hardness, the refractive index, the cleanliness and the color of the artificial diamond product all meet the design requirements.

Claims

1. A preparation method and a reaction system of high-grade artificial diamond are characterized in that: supercritical water is adopted as a preparation medium, and various probing sources are selected as raw materials to continuously prepare the high-grade artificial diamond under the supercritical state and the hydrogen catalysis.

2. The method for preparing a high-grade synthetic diamond according to claim 1, wherein: the selected multipurpose detecting source raw materials comprise natural gas, argon, coal gas, methanol, ethanol and graphite.

3. The method for preparing a high-grade synthetic diamond according to claim 1, wherein: the supercritical state is the state of water at a temperature of > 400 ℃ and a pressure of > 25MPa during the preparation reaction.

4. The method for preparing a high-grade synthetic diamond according to claim 1, wherein: the continuous preparation of high-grade artificial diamond means that the reaction time for preparation is more than 1 day.

5. The reaction system for producing a high-grade synthetic diamond according to claim 1, wherein: the reaction system consists of a heating device, a reaction device and a gas supercharging device.

6. The reaction system for producing a high-grade synthetic diamond according to claim 5, wherein: the heating jacket is arranged outside the reaction device to improve and control the preparation reaction temperature.

7. The reaction system for producing a high-grade synthetic diamond according to claim 5, wherein: the reaction device is internally provided with a suspension type master batch hanging fence and is positioned at the middle upper part in the device.

8. The reaction system for producing a high-grade synthetic diamond according to claim 5, wherein: the gas booster consists of two booster pumps and an auxiliary gas storage tank.