da Costa Geraldo Magela, Blanco-Andujar Cristina, De Grave Eddy, Pankhurst Quentin A
Chemistry Department, Federal University of Ouro Preto , Ouro Preto, Brazil.
J Phys Chem B. 2014 Oct 9;118(40):11738-46. doi: 10.1021/jp5055765. Epub 2014 Sep 30.
Three different magnetic samples with particle sizes ranging from 10 to 30 nm were prepared by wet chemical methods. The powders were heated at 100, 150, 200, and 250 °C during 30 min under air. Ferrous and total iron contents were determined immediately after the synthesis and after the thermal treatments. All samples were characterized by X-ray diffraction, transmission and integral low-energy electron Mössbauer spectroscopy (ILEEMS) at 298 K. These samples are composed of a mixture of individual particles of maghemite and magnetite, which implies that once oxidation starts in this kind of material, it occurs throughout the entire particle volume. The existence of a maghemite/magnetite core-shell model was ruled out. A linear correlation between the average isomer shift and the magnetite content was found, allowing the estimation of the amounts of magnetite and maghemite in an unknown sample without the need of performing chemical analysis.
通过湿化学方法制备了三种不同粒径范围为10至30纳米的磁性样品。将这些粉末在空气中于100、150、200和250°C下加热30分钟。在合成后和热处理后立即测定亚铁和总铁含量。所有样品在298 K下通过X射线衍射、透射和积分低能电子穆斯堡尔谱（ILEEMS）进行表征。这些样品由磁赤铁矿和磁铁矿的单个颗粒混合物组成，这意味着一旦这种材料开始氧化，氧化会在整个颗粒体积内发生。排除了磁赤铁矿/磁铁矿核壳模型的存在。发现平均同质异能位移与磁铁矿含量之间存在线性相关性，无需进行化学分析即可估计未知样品中磁铁矿和磁赤铁矿的含量。
