Modulating the phases of iron carbide nanoparticles: from a perspective of interfering with the carbon penetration of Fe@Fe3O4 by selectively adsorbed halide ions

Ziyu Yang; Tianshan Zhao; Xiaoxiao Huang; Xin Chu; Tianyu Tang; Yanmin Ju; Qian Wang; Yanglong Hou; Song Gao

doi:10.1039/c6sc01819j

Modulating the phases of iron carbide nanoparticles: from a perspective of interfering with the carbon penetration of Fe@Fe₃O₄ by selectively adsorbed halide ions

Chem Sci. 2017 Jan 1;8(1):473-481. doi: 10.1039/c6sc01819j. Epub 2016 Aug 18.

Authors

Ziyu Yang¹, Tianshan Zhao², Xiaoxiao Huang¹, Xin Chu¹, Tianyu Tang¹, Yanmin Ju¹, Qian Wang², Yanglong Hou¹, Song Gao³

Affiliations

¹ Department of Materials Science and Engineering , College of Engineering , Peking University , Beijing 100871 , China . Email: hou@pku.edu.cn.
² Center for Applied Physics and Technology , College of Engineering , Peking University , Beijing 100871 , China.
³ College of Chemistry and Molecular Engineering , Peking University , Beijing 100871 , China.

Abstract

Iron carbide nanoparticles (ICNPs) are considered to have great potential in new energy conversion, nanomagnets and biomedical applications due to their intrinsically peculiar magnetic and catalytic properties. However, the synthetic routes were greatly limited in morphology and phase controlled synthesis. In this article, we present a versatile solution chemistry route towards colloidal ICNPs (Fe₂C-hexagonal and monoclinic syngony, Fe₅C₂-monoclinic syngony and Fe₃C-orthorhombic syngony) derived from body centered cubic Fe@Fe₃O₄ by introducing heteroatoms to restrain their phase transformation. We found that the phases of Fe₂C NPs could be controlled by direct phase transformation in the drastic thermally driven procedure (defined as thermodynamical manner). Meanwhile, the selective adsorption of Cl ions weakened the bonding between Fe and C atoms, thus interfering with the penetration of C atoms to form lower carbon content Fe₅C₂ and Fe₃C NPs. The kinetic mechanisms were evaluated using density functional theory (DFT) simulations focusing on the bonding energy between Fe-C and Fe-Cl atoms. All the obtained ICNPs exhibited typically soft ferromagnetic properties with the highest saturation magnetization value of 101.2 emu g^-1 and the highest Curie temperature of 497.8 K.