Suber Lorenza, Imperatori Patrizia, Ausanio Giovanni, Fabbri Fabio, Hofmeister Herbert
CNR-ISM, 00016 Monterotondo Stazione, Roma, Italy.
J Phys Chem B. 2005 Apr 21;109(15):7103-9. doi: 10.1021/jp045737f.
We have explored the synthesis of iron oxide particles, tubes, and fibrils within the pores of nanoporous polycarbonate and alumina membranes. The membranes contain uniformly distributed cylindrical pores with monodispersed diameters (varying between 20 and 200 nm) and thicknesses of 6 and 60 microm, respectively. By hydrolysis and polymerization of iron salts, particles of different sizes and phases were formed in the pores, building iron oxide particle nanowires. Alternatively, by the sol-gel technique, using as reagents metalloorganic compounds, fibrils and tubes of different iron oxide phases were prepared. Structural and morphological investigations performed using scanning electron microscopy and transmission electron microscopy revealed ordered iron oxide particle wires, tubes, and fibrils formed inside the membrane nanopores. Magnetic characterization was accomplished with a vibrating sample magnetometer. Below the blocking temperature (T(B)), the magnetic behavior of the nanowires was governed by dipolar interaction between nearest-neighbor nanoparticles inside the pore, whereas the energy barrier, and therefore the T(B) value, was mainly governed by dipolar interaction between magnetic moments over larger (interpore) distances. As expected, crystalline iron oxide nanotubes exhibited magnetic perpendicular anisotropy due to their magnetocrystalline and shape anisotropy.
我们已经探索了在纳米多孔聚碳酸酯和氧化铝膜的孔隙内合成氧化铁颗粒、管和纤维。这些膜含有直径均匀分布（在20至200纳米之间变化）且厚度分别为6和60微米的圆柱形孔隙。通过铁盐的水解和聚合，在孔隙中形成了不同尺寸和相的颗粒，构建了氧化铁颗粒纳米线。另外，通过溶胶 - 凝胶技术，使用金属有机化合物作为试剂，制备了不同氧化铁相的纤维和管。使用扫描电子显微镜和透射电子显微镜进行的结构和形态研究揭示了在膜纳米孔内形成的有序氧化铁颗粒线、管和纤维。用振动样品磁强计完成了磁性表征。在阻塞温度（T(B)）以下，纳米线的磁行为由孔隙内最近邻纳米颗粒之间的偶极相互作用控制，而能垒以及因此的T(B)值主要由较大（孔间）距离上磁矩之间的偶极相互作用控制。正如预期的那样，由于其磁晶各向异性和形状各向异性，结晶氧化铁纳米管表现出磁垂直各向异性。
