Synthesizing synthetic diamonds imposes extremely demanding physical, process, and control reliability requirements on the pressure measurement and control system. Any failure or malfunction in the system can lead to severe physical destruction, catastrophic equipment damage, and heavy economic losses.
Strict Requirements for Pressure Measurement and Control Reliability
Maintaining Ultra-High Temperature and Pressure Thermodynamic Boundaries: Synthetic diamond synthesis (HPHT method) relies on graphite transforming in the presence of catalysts under extreme conditions of approximately $2000^\circ\text{C}$ and hydraulic pressures up to $100\text{ MPa}$ (with actual chamber pressures exceeding $5\text{ to }6\text{ GPa}$). The system must ensure that the entire reaction remains strictly within the "diamond stable zone" of the carbon phase diagram; any pressure fluctuations will deviate from the crystal growth window.
Precision in Multi-Stage Gradient Pressurization and Command Dispatch: The synthesis process in a cubic press involves critical transition nodes across multiple stages, including pre-pressing, pressurization, high-pressure holding, and gradual decompression (such as the 7 command dispatch points configured in the system). The control system must guarantee zero drift and zero misjudgment at each set pressure threshold to maintain synchronized hydraulic valve switching and command execution.
Immunity to Strong Electromagnetic and Industrial Noise Interference: Synthesis plants operate continuously for extended periods, where strong surge currents and severe electromagnetic noise are generated by high-power heating power supplies, frequently cycling high-pressure hydraulic solenoid valves, and motor startups. The measuring instrument must possess robust anti-interference redundancy to prevent program crashes or runaway code execution.
Severe Consequences of System Malfunctions or False Operations
Decompression in Molten State and Explosive Blowouts: When the metal catalyst and carbon source inside the synthesis capsule are in a high-pressure, high-temperature molten eutectic state, any false pressure-relief command triggered by heavy interference will cause a sudden chamber pressure drop. This triggers an instantaneous volumetric expansion of the molten material, resulting in a violent blowout/explosion that destroys the tungsten carbide anvils, shatters the press frame, and severely endangers personnel safety.
Failure of Overtravel Protection and Anvil Fractures: If the pressure feedback fails, reads falsely low, or fails to trigger overtravel protection, the hydraulic system will continue to apply excessive stroke and over-limit tonnage. This can cause direct collision interference and catastrophic stress-induced fracturing of the expensive cemented carbide anvils.
Batch Crystal Defects and Material Scrapping: Fluctuations or delays in pressure control disrupt the nucleation rate and step-growth of the diamond crystals, causing heavy metal inclusions, polycrystallinity, structural cracking, or graphitization reversal, leading to the complete loss of costly raw materials and high-energy-consuming operating cycles.