What is the process of synthetic diamond? What else should I pay attention to?

1. Assembly of synthetic parts

  Generally, lump and flake molten (dissolved) medium metal or alloy are used. The way of assembly of synthetic parts is to arrange one layer of graphite and one layer of molten (dissolved) medium metal or alloy sheet (block) at intervals, and load it into the formed pyrophyllite block. In addition, there are powdery, tubular or columnar and other forms of molten (dissolved) metal or alloy, forming a variety of assembly methods. Is the synthesis of large single crystal diamond, the better two assembly methods.

2. Temperature-boosting mode

  Choosing proper pressure, temperature and time and controlling these parameters can solve the problems of increasing coarse-grain ratio and improving quality. There are two specific ways:

  (1) first pressurized and heated to the lowest pressure and temperature of diamond generated by melting (solution) media, and then insulation for several minutes to more than ten minutes, cooling and boosting pressure or constant temperature to the selected pressure, and rapidly heating to the corresponding balance temperature of pressure (to generate the inside of the diamond V-shaped area), insulation for a few minutes, then cooling and lowering pressure. Can also be cooled to the formation of diamond near the lowest limit, heat preservation for a period of time and then reduced to room temperature and atmospheric pressure. Abrasive grade diamonds are obtained by this process.

  (2) First pressurize to the lowest pressure of diamond generation by melting (solution) medium, heat up to the upper limit of equilibrium temperature    corresponding to the selected pressure, keep warm for a few minutes, quickly increase the pressure to the selected pressure, and cool down to the inside of the V-shaped zone of diamond generation (namely, the high temperature zone of diamond generation), keep warm for a few minutes, then reduce the temperature and reduce the pressure. It can also be cooled to the low temperature near the formation of diamond V-shaped area, and after insulation, it can be cooled and depressurized. High quality diamond crystal with large grain, complete crystal shape, less impurity and high compressive strength can be produced by heating and pressurizing this process.

3. Purification of synthetic diamonds

  Synthetic diamond products in addition to diamond, there are residual graphite, metal or alloy, pyrophyllite fragments and other things. So, it has to be treated to get a pure diamond.

(1) Remove metal or alloy

  Chemicals such as nitric acid and aqua regia can remove metals. In industrial production, a large number of metal removal methods to electrolysis is better, and low cost.

(2) remove graphite

  Generally, two steps are used. The first step is sodium carbonate treatment, the second step is perchloric acid treatment.

(3) Remove pyrophyllite

  Remove pyrophyllite By removing metal and graphite, what is left is diamond and pyrophyllite. At present, the most common method to remove pyrophyllite is sodium hydroxide treatment.