Microstructural differences and formation mechanisms of spark plasma sintered ceramics with or without boron nitride wrapping

Two different modes of placing powders in a graphite die were used in a spark plasma sintering system: loading a conductive green body (zirconium nitride, ZrN, or titanium nitride, TiN) into a non-conductive bed (boron nitride) or loading the ZrN or TiN powders into the die directly. The ceramics obtained, which had completely different morphologies, have been characterized in this work. Through experimental and theoretical analysis, possible formation mechanisms of microstructural differences have been proposed.