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Preparation and Superparamagnetism of Nano-Ni/mesoporous SiO2 Composites
Fan Sanqiang1, Cai Weili1, Mou Jimei1, Chen Huiyu2
1.Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230026;2.Department of Physics, University of Science and Technology of China, Hefei 230026
Abstract:
Nano-Ni/mesoporous SiO2 composites were obtained by reducing Ni2+-doped SiO2 xerogels in H2, which were prepared via a sol-gel route. The average size of nano-Ni particles in mesoporous composites was estimated at 11~12nm from TEM (Transmission Electron Microscope) photographs. The results of magnetic measurements show that compared with the conventional nano-Ni particles, the Ni particles in nano-Ni/mesoporous SiO2 composites remain superparamagnetic state when their particle size is larger than the critical size of Ni calculated theoretically. Elevation of the reduction temperature promotes transformation of nano-Ni particles in mesoporous composites into the superparamagnetic state within a certain range of temperature.
Key words:  Superparamagnetism, Mesoporous composites, Magnetic anisotropy
FundProject:国家自然科学基金资助项目(19974041)
纳米Ni/SiO2介孔复合体的制备与超顺磁性
樊三强1, 蔡维理*1, 牟季美1, 陈慧余2
1.中国科学技术大学材料科学与工程系, 合肥 230026;2.中国科学技术大学物理系, 合肥 230026
摘要:
采用溶胶—凝胶法制备了含Ni2+的SiO2干凝胶,再通过化学还原得到了纳米Ni/SiO2介孔复合体。从样品的透射电子显微镜观测结果可估算出,介孔复合体中Ni粒子的尺寸约为11~12nm。样品的磁性测量结果表明,与通常的Ni纳米颗粒相比,纳米Ni/SiO2介孔复合体中纳米Ni粒子的粒径在大于理论计算的纳米Ni粒子的临界尺寸时,仍能够保持超顺磁状态。在一定温度范围内,提高还原温度有利于复合体中纳米Ni粒子向超顺磁状态转变。
关键词:  超顺磁性  介孔复合体  磁各向异性
DOI:10.1088/1674-0068/14/2/205-210
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