Why should graphitic refractory materials be used now that graphite can burn?
C is inactive in nature. Carbon will not burn unless the temperature is about 2000℃, so it can't be lit generally. Coal can be lit because it contains other combustible substance which ignite carbon indirectly. While graphite, carbon black, is more pure and dense than coal., so it is hard to oxidize.Their molecular structures are also different, just like diamond is harder than graphite.
Materials for refractory must have the following characteristics and properties: 1, high stability: Anti-oxidation, anti-reduction, thermal decomposition; 2, high melting point : 2800℃; 3, low price. Graphite has all three characteristics and properties, especially melting point and stability.
In theory, any substance can burn as long as certain temperature is reached. Graphite is turned from diamond under anaerobic condition and at high temperature of 2 000 ~ 3 000 ℃. that is to say, ignition point of graphite (lamellar graphite ) under anaerobic condition will be at least above 3 000 ℃. There are many types of graphite, and their ignition points are also different. Ignition point of pyrolytic graphite is much low. Except for a few cutting-edge areas, fire endurance demand for most areas in daily life (eg. brake pad will add a certain amount of graphite) is under 1000 ℃. Therefore, graphite can be used as refractory material. That is, graphite can both burn and can be used as refractory material, which are not contradictory.
