The growth of submillimeter spherules on a graphite surface under prolonged heating

The process of formation and growth of carbon protrusions of various shapes up to $0.3$ mm in size on the surface of graphite samples kept at a temperature of $\sim3$ kK for $\sim10^3$ s in argon at a pressure of $\sim50$ kPa is described. Possible mechanisms for the formation of protrusions (spherules) are discussed; it is assumed that an important role in these processes can be played by the emission of carbon microparticles from the sample.