Preparation of Silica-Coated Co-Pt Alloy Nanoparticles
Preparation of Silica-Coated Co-Pt Alloy Nanoparticles
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DOI：
10.1016/j.matlet.2005.12.078
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发表时间：
2006-07
影响因子：
3
通讯作者：
Yoshio Kobayashi;M. Horie;D. Nagao;Y. Ando;T. Miyazaki;M. Konno
中科院分区：
文献类型：
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作者：
Yoshio Kobayashi;M. Horie;D. Nagao;Y. Ando;T. Miyazaki;M. Konno
将先前提出的Co纳米粒子的二氧化硅包覆方法扩展到Co-铂合金纳米粒子的二氧化硅包覆。以CoCl2(1.2×10−·3M)、H2PtCl6(1.2×10−·3M)、柠檬酸(4×10−·4M)、NaBH4(1.2×10−·2M)为原料制备了合金纳米粒子。在硅烷偶联剂3-氨丙基三甲氧基硅烷(8×10−5M)和硅源正硅酸乙酯(7.2×10−(4M))存在下，在水/乙醇溶液中进行了二氧化硅包覆。透射电子显微镜观察和X-射线衍射仪分析表明，合金纳米粒子表面包覆了二氧化硅，由面心立方结构的Co-铂合金微晶组成，晶粒度为4.6~10.7 nm。SiO_2包覆颗粒的磁性强烈依赖于热处理温度。300℃以上退火后，合金的饱和磁化强度为1.4emu/g样品，矫顽场为450Oe，这可能是由于合金中钴的氧化使合金中的微晶转变为纯的铂，从而降低了合金的饱和磁化强度和矫顽场。
A previously proposed method for silica-coating of Co nanoparticles was extended to silica-coating of Co–Pt alloy nanoparticles. The alloy nanoparticles were prepared from CoCl2(1.2×10− 3M), H2PtCl6(1.2×10− 3M), citric acid (4×10− 4M) and NaBH4(1.2×10− 2M). The silica-coating was performed in aqueous/ethanolic solution with a silane coupling agent, 3-aminopropyltrimethoxysilane (8×10−5M), and a silica source, tetraethoxyorthosilicate (7.2×10− 4M) in the presence of the alloy nanoparticles. TEM observation and X-ray diffraction measurements revealed that the alloy nanoparticles were coated with silica and consisted of fcc Co–Pt alloy crystallites with crystal sizes of 4.6–10.7 nm. Magnetic properties of the silica-coated particles were strongly dependent on annealing temperature. Maximum values of 1.4 emu/g-sample for saturation magnetization and 450 Oe for coercive field were obtained for the particles annealed at 300 °C. Annealing above 300 °C transformed the crystallite from the alloy to pure Pt probably through oxidation of cobalt in the alloy, resulting in reductions in saturation magnetization and coercive field.