Synthesis, growth mechanism and magnetic properties of SiO2-coated Co nanocapsules

✍ Scribed by X.F. Zhang; X.L. Dong; H. Huang; B. Lv; X.G. Zhu; J.P. Lei; S. Ma; W. Liu; Z.D. Zhang

• Publisher: Elsevier Science
• Year: 2007
• Tongue: English
• Weight: 541 KB
• Volume: 55
• Category: Article
• ISSN: 1359-6454
• DOI: 10.1016/j.actamat.2007.02.019

✦ Synopsis

The growth mechanism and magnetic properties of SiO 2 -coated Co nanocapsules synthesized by the arc-discharge method were investigated. Most of the as-prepared products were nanocapsules with a core/shell structure consisting of a Co core and a SiO 2 shell, while some of them displayed a rod-like configuration. The formation of the SiO 2 nanorods was governed by an extended vapor-liquid-solid (VLS) mechanism and Co nanoparticles acted as a catalyst for the growth of the nanorods. The Co/SiO 2 nanocapsules were annealed at 300, 400 and 500 °C, respectively, for 30 min in air, in order to observe their oxidation behavior. The crystalline grains of the Co/SiO 2 nanocapsules clearly grew during annealing. After annealing at 500 °C, the ferrimagnetic Co 3 O 4 phase appeared. The grain size effect, oxidation behavior and magnetic properties are discussed in detail for the nanocapsules.