3D Frameworks with Variable Magnetic and Electrical Features from Sintered Cobalt-Modified Carbon Nanotubes

Serguei V Savilov; Sergei A Chernyak; Maria S Paslova; Anton S Ivanov; Tolganay B Egorova; Konstantin I Maslakov; Petr A Chernavskii; Li Lu; Valery V Lunin

doi:10.1021/acsami.8b04367

3D Frameworks with Variable Magnetic and Electrical Features from Sintered Cobalt-Modified Carbon Nanotubes

ACS Appl Mater Interfaces. 2018 Jun 20;10(24):20983-20994. doi: 10.1021/acsami.8b04367. Epub 2018 Jun 8.

Authors

Affiliations

¹ Department of Chemistry , Lomonosov Moscow State University , Leninskie Gory 1-3 , Moscow 119991 , Russia.
² A. V. Topchiev Institute of Petrochemical Synthesis , Russian Academy of Sciences , Leninsky Prospect 29 , Moscow 119991 , Russia.
³ National University of Singapore , 21 Lower Kent Ridge Road , 119077 , Singapore.

PMID: 29847909
DOI: 10.1021/acsami.8b04367

Abstract

3D frameworks of carbon nanotubes (CNTs) uniformly decorated by cobalt oxide or carbon-encapsulated cobalt nanoparticles were obtained by spark plasma sintering for the first time. The influence of the sintering temperature ( T_S) and Co content on the morphology, structure, and electrical and magnetic properties of the obtained materials was investigated by Raman spectroscopy, electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and in situ magnetometry. It was shown that application of the SPS technique allowed simultaneous compaction of the material, formation of CNT framework, and Co oxide reduction. The appearance of the carbon shell around 4-10 nm Co particles was observed at T_S > 600 °C. At higher T_S, the Co particle size increased (up to 300 nm at 1400 °C), whereas the carbon shell ordered and thickened. The formation of large-size few-layers graphene sheets was observed at T_S = 1400 °C. Electrical conductivity of the composites was found to be higher than that of sintered pristine CNTs and varied in the range of 500-12 500 Sm/m. Magnetic experiments demonstrated soft magnetization of the samples and the coercivity of 200-300 Oe. Thus, the obtained CNT-based material is simultaneously compact, formable, electroconductive, and ferromagnetic. Its properties can be tuned by variation of the sintering parameters. Synthesized cobalt-modified carbon 3D structures are promising for the application in magnetic separation, catalysis, fuel cells, and electromagnetic shielding.

Keywords: 3D frameworks; carbon nanotubes; cobalt-encapsulated particles; compaction; magnetic materials; magnetic separation; spark plasma sintering.