Structural transformations for a subbituminous coal, impact of temperature on gold-tube pyrolysis chars evaluated using HRTEM

•The distributions of a subbituminous coal fringes were quantified by HRTEM.•The evolution of size of the coal chars aromatic sheet were investigated.•Impact of temperature on gold-tube pyrolysis chars was evaluated.•Coal thermoplastic behavior was present between ∼450 and 500 °C by fringe lengths.•The pyrolysis could be divided into three stages by the fringe orientation.