Six-sided top press
Structure and principle: The six-sided top press is a commonly used device for preparing single crystal diamond by high temperature and high pressure method. It is mainly composed of six top hammers, which apply pressure to the synthesis cavity from six directions and can generate very high hydrostatic pressure. During the synthesis process, carbon source materials such as graphite and metal catalysts are placed in the synthesis cavity, and the cavity is heated by an external heating device. At the same time, the six-sided top hammers apply pressure to create a high temperature and high pressure environment, so that carbon atoms crystallize under the action of the catalyst to form diamond.
Application characteristics: This equipment can control pressure and temperature more accurately, and the quality of synthesized diamond is relatively stable. For example, my country has achieved many results in the research and development and application of six-sided top presses. It can generate sufficiently high pressure and temperature in a relatively small space, which is suitable for the synthesis of single crystal diamonds with small to medium particle sizes, and can achieve a certain degree of mass production in industrial production.
Two-sided top press
Structure and principle: The two-sided top press applies pressure to the sample through two opposing pressure heads. Its structure is relatively simple, mainly consisting of two upper and lower pressure heads and a support device. During operation, the pressure is transmitted to the sample in the synthesis mold through the pressure head, and the sample is brought to a high temperature state by external heating. Carbon source and catalyst are placed inside the mold to promote diamond growth under high temperature and high pressure environment.
Application features: The two-sided top press can generate higher pressure and is suitable for some synthetic experiments with particularly high pressure requirements or diamond preparation for specific processes. However, due to its relatively single pressure direction, the uniformity of pressure may not be as good as that of the six-sided top press. When synthesizing large-grained single-crystal diamond, uneven crystal growth may occur due to uneven pressure.
High temperature heating system
Components: In high temperature and high pressure equipment, the high temperature heating system is indispensable. It mainly includes heating elements (such as graphite heating tubes, metal heating wires, etc.) and temperature measurement and control devices. For systems with graphite as the heating element, when current passes through graphite, graphite will heat up, thereby providing heat for the synthesis cavity. Temperature measurement devices (such as thermocouples, etc.) can monitor the temperature in real time and feedback to the control system to ensure that the temperature remains within the required range for synthetic diamond.
Function: Accurate temperature control is essential for the growth of diamond. Different carbon source and catalyst combinations, as well as different growth stages, may require different temperature conditions. For example, in some synthesis processes, the temperature needs to be controlled at around 1300-1500℃. The high-temperature heating system can meet this precise control requirement and ensure the growth quality and growth rate of diamond.
Pressure control system
Components: The pressure control system mainly includes a pressure sensor and a pressure regulating device. The pressure sensor can detect the pressure inside the synthesis chamber in real time, convert the pressure signal into an electrical signal and transmit it to the control system. The pressure regulating device adjusts the pressure by adjusting the degree of advancement of the top hammer (for six-sided top presses, etc.) or other pressure-applying methods according to the instructions of the control system.
Function: In the diamond synthesis process, the stability and accuracy of the pressure have a great influence on the growth of the crystal. For example, in the diamond nucleation and growth stages, the pressure needs to be stably controlled at around 5-10GPa. The pressure control system can effectively avoid crystal defects or growth failures caused by pressure fluctuations, ensuring the smooth progress of the synthesis process.
