Formation of highly crystalline maghemite nanoparticles from ferrihydrite in the liquid phase
Formation of highly crystalline maghemite nanoparticles from ferrihydrite in the liquid phase
复制标题
液相中水铁矿形成高结晶磁赤铁矿纳米粒子
DOI：
10.1007/s11434-014-0520-2
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发表时间：
2014-10-01
影响因子：
--
通讯作者：
Li, Decai
中科院分区：
文献类型：
--
作者：
Gong, Xiaomin;Li, Jian;Li, Decai
Fe_5O_7（OH）中心点4 H（2）O水铁矿是一种低结晶度的反铁磁材料。以水铁矿为前驱体，在FeCl 2/NaOH溶液中，通过化学诱导转化法制备了γ-Fe 2 O3（磁赤铁矿）磁性纳米粒子。采用振动样品磁强计、透射电子显微镜、X射线衍射仪（XRD）、X射线能谱仪（EDS）和X射线光电子能谱仪（XPS）对产物的磁化强度、形貌、晶体结构和化学组成进行了表征。水铁矿经历聚集生长并转化为α-FeO（OH）（针铁矿）颗粒，其随后转化为γ-Fe 2 O3纳米颗粒，其被NaCl包覆。γ-Fe 2 O3颗粒具有片状形态，当从0.01 mol/L FeCl 2和FeCl 2：NaOH摩尔比为0.4制备时。γ-Fe 2 O3颗粒更球形，当从FeCl 2：NaOH摩尔比为0.6制备时。片状颗粒的Fe含量低于球形颗粒。它们的磁化强度相似，但片状颗粒的磁化强度较大。形貌和磁化强度的差异归因于表面效应，而磁性的差异归因于形状效应。
Fe5O7(OH)center dot 4H(2)O ferrihydrite is a low-crystallinity antiferromagnetic material. gamma-Fe2O3 (maghemite) magnetic nanoparticles were prepared from a ferrihydrite precursor, by chemically induced transformation in FeCl2/NaOH solution. The magnetization, morphology, crystal structure and chemical composition of the products were determined by vibrating sample magnetometry, transmission electron microscopy, X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy (XPS). Ferrihydrite underwent aggregation growth and transformed into alpha-FeO(OH) (goethite) particles, which subsequently transformed into gamma-Fe2O3 nanoparticles, that became coated with NaCl. The gamma-Fe2O3 particles had a flake-like morphology, when prepared from 0.01 mol/L FeCl2 and a FeCl2:NaOH molar ratio of 0.4. The gamma-Fe2O3 particles were more spherical, when prepared from a FeCl2:NaOH molar ratio of 0.6. The Fe content of the flake-like particles was lower than that of the spherical particles. Their magnetizations were similar, and the coercivity of the flake-like particles was larger. The differences in morphology and magnetization were attributed to the surface effect, and the difference in coercivity to the shape effect.