Diamond has many special excellent properties: ① high thermal conductivity, ② low thermal expansion coefficient, ③ low friction coefficient, ④ high hardness, ⑤ high transparency of visible light and infrared light, ⑤ high refractive index, ⑤ chemical and radioactive inertness, etc. Therefore, it is widely used in special fields of industry and scientific research, such as cutting tools, abrasives, thermal probes in unfavorable environments, radioactive detectors, pressure sensors, fluorescence intensifiers, optical windows, micromechanical components, high-density and high-energy electronic components, etc.