Preparation and Characterization of Ring-Shaped Co Nanomaterials

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• 作者：Lin Guo ; Fang Liang ; Ning Wang ; Desheng Kong ; Siming Wang ; Lin He ; Chinping Chen ; Xiangmin Meng ; Ziyu Wu
• 刊名：Chemistry of Materials
• 出版年：2008
• 出版时间：August 26, 2008
• 年：2008
• 卷：20
• 期：16
• 页码：5163-5168
• 全文大小：330K
• 年卷期：v.20,no.16(August 26, 2008)
• ISSN：1520-5002

文摘

Donut- or ring-shaped Co nanomaterials were successfully synthesized using the polymer-modified method, by which PVP is used as a surface modifier reagent. The synthesized products were structurally and morphologically characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), whereas the magnetic characterization was performed by temperature- and field-dependent magnetization measurements. The results show that the rings have a h-Co nanostructure. The outer diameter is about 400−500 nm, inner diameter 150−250 nm, and the ring plane thickness ∼120 nm. The magnetization measurements show a typical coercivity of about 112 Oe at 300 K and an almost vanishing coercivity, H_C ≈ 0 at T = 5 K. Numerical calculations using the packeage of object oriented micromagnetic framework (OOMMF) reveal a magnetization ground-state of flux closure structure, as expected for the geometric structure of the submicrometer-sized Co rings. This explains the observed hysteresis loops at low temperature with a vanishing small coercivity. A possible reaction process for the formation of the donut-shaped Co nanostructure is presented.