Journal
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
Volume 286, Issue 1, Pages 157-160Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/S0921-5093(00)00628-6
Keywords
carbon encapsulated nanoparticles; superparamagnetic; magnetic properities
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In the present work, experiments aim at the encapsulation of foreign materials within hollow graphitic cage have been carried out for iron group metals (Fe, Co, Ni) using a modified are-discharge (carbon arc) reactor. HRTEM (high resolution transmission electron miscroscope), and XRD (X-ray diffractometer) studies, for three carbon encapsulated materials, showing nanoparticles of both a metallic phase (alpha-Fe, gamma-Fe; hcp-Co, fcc-Co; fcc-Ni) and also a carbide phase (M3C, M = Fe, Co, Ni) are encapsulated in graphitic carbon. The magnetic measurement for the three as-made nanoparticles, indicating that the values of saturation magnetic moment of three nanoparticle are 37.6, 55.5 and 15.7% of the bulk ferromagnetic elements counterparts, respectively. The different comparison values (M-r/M-s) of remanent magnetization (M-r) and saturation magnetization (M-s) suggest, the encapsulated Fe and Co nanoparticles are shown to be ferromagnetic with a ratio of remnant to saturation magnetization M-r/M-s similar to 0.3; whereas, the encapsulated Ni nanoparticles exhibits superparamagnetic behavior at room temperature. (C) 2000 Elsevier Science S.A. All rights reserved.
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