NiO纳米片和多孔纳米片自组装的空心微球的无模板水热法制备与磁学性质

报道一种非常简单的制备NiO和Ni(OH)₂空心微球的无模板水热法, 即通过NiCl₂与氨水在140 ℃水热反应12 h, 制备了Ni(OH)₂纳米片自组装的空心微球, 经400 ℃热处理2 h得到了NiO空心微球. 采用X射线衍射仪、扫描电镜和透射电子显微镜对产物进行表征, 并在室温下测试了它的磁学性能, 结果表明, Ni(OH)₂空心微球的直径约为3～4 μm, 它是由尺寸1.1～1.3 μm左右的六方相结构的Ni(OH)₂纳米片组装而成; NiO空心微球是由立方相纳米片和多孔纳米片组装而成, 它具有弱的铁磁性, 其矫顽力为583 Oe, 剩余磁化强度为0.213 emu/g. 研究了氨在Ni(OH)₂纳米片的形成与组装过程中的作用, 提出了可能的生长机理.

Template-free Hydrothermal Synthesis and Magnetic Properties of Hollow Microspheres Co-constructed with NiO Nanosheets and Porous Nanosheets

In this work, we report a very simple template-free hydrothermal approach to prepare hollow Ni(OH)₂ and NiO microspheres. The hollow Ni(OH)₂ microspheres were prepared via the hydrothermal reaction of NiCl₂ with aqueous ammonia at 140 ℃ for 12 h. Subsequently, the similar microstructured NiO hollow microspheres were obtained by calcining the above precursor at 400 ℃ for 2 h. The as-synthesized products were characterized by means of powder X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The results showed that the hollow Ni(OH)₂ microspheres with the diameters of 3～4 μm are constructed from 2-dimensional Ni(OH)₂ nanosheets with the hexagonal structure and dimensions of 1.1～1.3 μm. The hollow NiO microspheres are co-constructed from NiO nanosheets and porous nanosheets with the cubic structure. Magnetic properties of the hollow NiO microspheres have been detected by a vibrating sample magnetometer at room temperature. It was found that the NiO microspheres exhibit weak ferromagnetism. The coercive force and remanent magnetization are 583 Oe and 0.213 emu/g respectively. The role of the ammonia in the growth and self-assembly of Ni(OH)₂ nanosheets was investigated, and a possible mechanism was also proposed to account for the formation and conversion of Ni(OH)₂ nanosheet-based hollow microspheres into NiO hollow microspheres.