In the early metal evaporation industry, the evaporation material used for evaporation of metals (such as aluminum) in the early days was stone
Ink material. Graphite material has the following characteristics:
(1) High melting point. At normal pressure, 3350+_ 25 ℃ 'sublimation, 3750+_ Melting at 50 ℃, greatly exceeding
The temperature required for vacuum coating is stable and reliable.
(2) The material has good conductivity, the resistivity of artificial graphite is generally 8 ¨ Q · m, and the carbon material
The resistivity of the graphite material is between 20-50 s · M. and the resistance of the graphite material changes very little with the increase of temperature
Relatively stable
(3) Graphite material has low coefficient of thermal expansion and good thermal shock resistance
It has good dimensional stability when used at high temperature and is not easy to be damaged during rapid heating and cooling.
(4) Graphite material is easy to process and has high strength, but it is brittle. Its mechanical strength increases with temperature
High and increased. Between 2000 and 2500 ℃, its strength is about twice that at room temperature. Therefore, it is suitable for high
Work under warm conditions.
(5) Compared with other materials, graphite has good chemical stability, but it is easy to be oxidized.