Hydromaghemite, an intermediate in the hydrothermal transformation of 2-line ferrihydrite into hematite
Hydromaghemite, an intermediate in the hydrothermal transformation of 2-line ferrihydrite into hematite
复制标题
DOI：
10.2138/am-2003-11-1207
复制
发表时间：
2003-11-01
影响因子：
3.1
通讯作者：
de Grave, E
中科院分区：
文献类型：
--
作者：
Barrón, V;Torrent, J;de Grave, E
如果足够量的强吸附配体（例如磷酸盐或柠檬酸盐）被吸附在起始产物上，则2系水铁矿向赤铁矿的水热转变进行缓慢。在这项工作中，我们研究了在 125 至 200 摄氏度的温度范围、0-6% 的 P/Fe 摩尔比和 3% 的柠檬酸盐/Fe 摩尔比下的这种转变。通过 X 射线衍射 (XRD)、红外光谱、不同温度和 60 kOe 应用场的穆斯堡尔光谱 (MS)、磁力和热分析以及透射电子显微镜 (TEM) 对产物进行了表征。在150℃时，纯的2线水铁矿迅速转变为赤铁矿。 P/Fe=2.75%或柠檬酸盐/Fe=3%的2线水铁矿的转变产物磁化率>240x10(-6)m(3)/kg，根据XRD和MS数据，是具有结构P的赤铁矿、6线水铁矿和磁相的混合物。该相表现出磁赤铁矿的大部分特征反射和 MS 特征，并以 7-30 nm 亚圆形颗粒的形式出现，其晶格条纹对应于磁赤铁矿 (3 10) 和 (220) 平面。它被指定为“水磁赤铁矿”，因为它在 110 至 350 摄氏度之间失去 >3% 的水。 150℃时，完全转变为赤铁矿
The hydrothermal transformation of 2-line ferrihydrite into hematite proceeds slowly if a sufficient quantity of some strongly adsorbing ligand, such as phosphate or citrate, is sorbed on the starting product. In this work, we studied such transformation at temperatures ranging from 125 to 200degreesC, a molar P/Fe ratio of 0-6%, and a molar citrate/Fe ratio of 3%. The products were characterized by X-ray diffraction (XRD), infrared spectroscopy, Mossbauer spectroscopy (MS) at various temperatures and in an applied field of 60 kOe, magnetic and thermal analysis, and transmission electron microscopy (TEM). At 150degreesC, pure 2-line ferrihydrite transformed rapidly into hematite. The products of transformation of 2-line ferrihydrite with P/Fe=2.75% or citrate/Fe=3% had a magnetic susceptibility of >240x10(-6) m(3)/kg and were, according to XRD and MS data, mixtures of hematite with structural P, 6-line ferrihydrite, and a magnetic phase. This phase exhibited most of the characteristic reflections and MS features of maghemite, and occurred as 7-30 nm subrounded particles with lattice fringes corresponding to the maghemite (3 10) and (220) planes. It was designated "hydromaghemite" because it lost >3% water between 110 and similar to350degreesC. At 150degreesC, complete transformation into hematite occurred in