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| - Structural and Magnetic Properties of Oxidatively Stable CobaltNanoparticles Encapsulated in Graphite Shells
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| - Oxidatively stable magnetic cobalt nanoparticles were prepared by annealing cobalt nanoparticles coatedwith poly(styrene-b-4-vinylphenoxyphthalonitrile) block copolymers. An oxygen-impermeable graphiticcoating around the cobalt nanoparticles was created during thermal treatment at 700 °C owing to thethermal decomposition/cross-linking of a polymer with a highly aromatic character. A variety of analyticaltechniques were used to elucidate the physical properties of the pre-heat-treated and heat-treated samples.The cobalt-specific saturation magnetization (σs) increased from 81 to 173 emu g-1 Co upon heating ofthe polymer-coated cobalt nanoparticles. The pre-heat-treated sample readily oxidized, as revealed bylow-temperature magnetic susceptometry studies, whereas the heat-treated sample showed oxidativestability for over 1 year. The mean cobalt particle size increased from 18.5 to 36.1 nm during thermaltreatment. Electron diffraction and X-ray diffraction revealed that the pre-heat-treated particles were weaklycrystalline, while the heat-treated particles were strongly crystalline. The dominant phase of the heat-treated sample was determined to be face-centered cubic with other minor phases present (hexagonalclose packed and epsilon).
- Oxidatively stable, magnetic cobalt nanoparticles were prepared by annealing cobalt nanoparticles coated with poly(styrene-b-4-vinylphenoxyphthalonitrile) block copolymers. An oxygen-impermeable graphitic coating around the cobalt nanoparticles was created during thermal treatment at 700 °C owing to the thermal decomposition/cross-linking of a polymer with a highly aromatic character.
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