Structure of coke powder heat-treated with boron

Coal tar pitch-based coke powder with a fine mosaic texture was heat-treated with various concentrations of boron powder at 2900°C. Increasing the boron amount led to smaller d₀₀₂ and larger d₁₁₀, and made the original fine texture coarser. Some small particles showed specific structures of polyhedrons, of which surfaces are 002 planes of graphite lattice, after heat treatment with boron. The size of the polyhedron increased with boron content. Boron concentration was lower at the surface than at the inner portions of particles for a powder heat-treated with a higher amount of boron, while it depended less on the depth for that heat-treated with a lower amount of boron. The formation mechanism of the polyhedron particle is discussed.