3d Transition Metals and Oxides within Carbon Nanotubes by Co-Pyrolysis of Metallocene & Camphor: High Filling Efficiency and Self-Organized Structures

TL;DR

This paper presents a simplified single-zone furnace method for synthesizing high-quality, metal-filled carbon nanotubes with high efficiency and controlled morphology, including novel Ni@CNT and Co@CNT samples with enhanced magnetic properties.

Contribution

Introduces a single-zone furnace pyrolysis technique using sublimed metallocenes and camphor to produce high-quality, metal-filled CNTs, including first-time synthesis of Ni@CNT and Co@CNT with superior magnetic properties.

Findings

High filling efficiency of metal-filled CNTs achieved.

First synthesis of Ni@CNT and Co@CNT with high saturation magnetization.

Controlled morphology and aligned Fe2O3@CNT structures demonstrated.

Abstract

We demonstrate that a single zone furnace with a modified synthesis chamber design is sufficient to obtain metal (Fe, Co or Ni) filled carbon nanotubes (CNT) with high filling efficiency and controlled morphology. Samples are formed by pyrolysis of metallocenes, a synthesis technique that otherwise requires a dual zone furnace. Respective metallocene in all three cases are sublimed in powder form, a crucial factor for obtaining high filling efficiency. While Fe@CNT is routinely produced using this technique, well-formed Ni@CNT or Co@CNT samples are reported for the first time. This is achieved by sublimation of nickelocene (or cobaltocene) in combination with 'camphor'. These samples exhibit some of the highest saturation magnetization (Ms) values, at least an order of magnitude higher than that reported for Ni or Co filled CNT, by aerosol assisted pyrolysis. The results also elucidate on why Ni or Co@CNT are relatively difficult to obtain by pyrolyzing powder metallocene alone. Overall, a systematic variation of synthesis parameters provides insights for obtaining narrow length and diameter distribution and reduced residue particles outside filled CNT - factors which are important for device related applications. Finally, the utility of this technique is demonstrated by obtaining highly aligned forest of Fe2O3@CNT, wherein Fe2O3 is a functional magnetic oxide relevant to spintronics and battery applications.