Synthesis mechanism of carbon nanotube fibers using reactor design principles

•Quality of the CNT fibers and continuity of the synthesis of CNT fibers were improved by applying reactor design principles.•Identification of decomposition temperature and reaction sequence of chemicals in direct spinning process.•Understanding on the effect of water on the decomposition of chemicals in the synthesis of CNT fibers.•Increase of the quality of CNT fiber by controlling the injection position of water in the vertical reactor.