TY - JOUR
T1 - Large-scale synthesis, annealing, purification, and magnetic properties of crystalline helical carbon nanotubes with symmetrical structures
AU - Tang, Nujiang
AU - Zhong, Wei
AU - Au, Chaktong
AU - Gedanken, Aharon
AU - Yang, Yi
AU - Du, Yonwei
N1 - Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2007/6/18
Y1 - 2007/6/18
N2 - Crystalline helical carbon nanotubes (HCNTs) are synthesized as the main products in the pyrolysis of acetylene at 450°C over Fe nanoparticles generated by means of a combined sol-gel/reduction method. Transmission electron microscopy (TEM) images reveal that there are two HCNTs attached to each Fe3C nanoparticle, and that the two HCNTs are mirror images of each other. Annealing in Ar at 750°C and purification by immersion in hot (90°C) HCl solution do not significantly change the structure of the HCNTs, despite the partial removal of Fe nanoparticles by the latter treatment. The magnetic properties of the as-prepared, annealed, and purified HCNTs have been systematically examined. The annealed sample shows relatively high magnetization due to the ferromagnetic α-Fe nanoparticles encapsulated in the HCNT nodes. In the case of HCl treatment, relatively pure HCNTs are obtained by the removal of ferromagnetic nanoparticles from the double-HCNT nodes. The effects of the amount of catalyst used in the synthesis process on the morphology and yield of the carbon products have also been investigated.
AB - Crystalline helical carbon nanotubes (HCNTs) are synthesized as the main products in the pyrolysis of acetylene at 450°C over Fe nanoparticles generated by means of a combined sol-gel/reduction method. Transmission electron microscopy (TEM) images reveal that there are two HCNTs attached to each Fe3C nanoparticle, and that the two HCNTs are mirror images of each other. Annealing in Ar at 750°C and purification by immersion in hot (90°C) HCl solution do not significantly change the structure of the HCNTs, despite the partial removal of Fe nanoparticles by the latter treatment. The magnetic properties of the as-prepared, annealed, and purified HCNTs have been systematically examined. The annealed sample shows relatively high magnetization due to the ferromagnetic α-Fe nanoparticles encapsulated in the HCNT nodes. In the case of HCl treatment, relatively pure HCNTs are obtained by the removal of ferromagnetic nanoparticles from the double-HCNT nodes. The effects of the amount of catalyst used in the synthesis process on the morphology and yield of the carbon products have also been investigated.
UR - http://www.scopus.com/inward/record.url?scp=34250870033&partnerID=8YFLogxK
U2 - 10.1002/adfm.200600767
DO - 10.1002/adfm.200600767
M3 - Journal article
AN - SCOPUS:34250870033
SN - 1616-301X
VL - 17
SP - 1542
EP - 1550
JO - Advanced Functional Materials
JF - Advanced Functional Materials
IS - 9
ER -