Formation of three-dimensional Al₄C₃ nano-round-combs with nanorod branches by catalytic thermal evaporation

Three-dimensional Al₄C₃ nanowires have been synthesized by thermal evaporation process using CaO as an auxiliary agent. Morphologies, chemical composition and crystal structure of Al₄C₃ nanowires were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM) and x-ray diffractometer(XRD). The process yields a large fraction of long round-comb like Al₄C₃ nanowires of 300–500 nm in diameter. High-resolution transmission electron microscopy(HRTEM) shows that the Al₄C₃ nanowires are single crystals and the growth direction of nanowire trunk is [0001] axis of Al₄C₃ crystal. There are many Al₄C₃ nanorod branches of 500–1000 nm length on the nanowire trunk. The liquid reaction products of CaO and Al₂O₃ have contributed to the growth of round-comb like Al₄C₃ nanowires. A round-comb like growth model based on the vapor-liquid-solid (V-L-S) growth mechanism is proposed to explain the growth of Al₄C₃ nanowires, which reveals that the reason for this shape is that the liquid products of CaO and Al₂O₃ are dispersed in the nanowire trunk.