Time:2023.11.10Browse:1
Graphite is one of the substances with the highest melting and boiling points in nature, with a melting point of 3850 ± 50 ℃ and a boiling point of 4500 ℃. However, the boiling points of silicate minerals are all below 2750 ℃ (quartz boiling point), and the boiling point of graphite is much higher than the boiling point of the impurity silicate it contains. This characteristic is the theoretical basis for high-temperature purification of graphite. Fill the graphite powder directly into a graphite crucible and heat it in a purification furnace filled with inert gas and Freon protective gas to 2300-3000 ℃ for a period of time. Impurities in the graphite will overflow, thus achieving the purification of the graphite. The high-temperature method generally uses high carbon graphite containing over 99% carbon purified by flotation or chemical methods as the raw material, which can purify the graphite to 99% 99%. By further improving the process conditions and improving the quality of the crucible, the purity can reach 99% More than 995%.
The high-temperature method can produce over 99.99% ultra-high purity graphite, but it requires the fixed carbon of the raw material to be above 99%. Moreover, the equipment is expensive, the investment is huge, and the production scale is limited. The electric furnace heating technology requires strict isolation of air, otherwise the graphite will start to oxidize when heated to 450 ℃ in hot air. The higher the temperature, the greater the loss of graphite. Only special industries with very high requirements for graphite quality (such as national defense, aerospace, etc.) use high-temperature method to produce high-purity graphite in small batches.