The behavior of hydroxyl units of synthetic goethite and its dehydroxylated product hematite.
The behavior of hydroxyl units of synthetic goethite and its dehydroxylated product hematite.
复制标题
DOI：
10.1016/s1386-1425(01)00445-0
复制
发表时间：
2001-11
期刊：
影响因子：
--
通讯作者：
H. Ruan;R. Frost;J. Kloprogge
中科院分区：
文献类型：
--
作者：
H. Ruan;R. Frost;J. Kloprogge
采用傅里叶红外光谱（FTIR）和x射线衍射（XRD）相结合的方法，对合成针铁矿及其脱羟基产物赤铁矿在180 ~ 270℃的热转变过程中羟基单元的行为进行了表征。在200℃以上的温度下，XRD检测到赤铁矿，而在230℃以上没有检测到针铁矿。针铁矿在3212 ~ 3194、1687 ~ 1674、1643 ~ 1640、888 ~ 884和800 ~ 798 cm−1处有5个强烈的OH振动，在3450 ~ 3445 cm−1处有1个H2O振动。羟基拉伸和弯曲振动强度随针铁矿脱羟基程度的减小而减小。红外吸收光谱清晰地显示出针铁矿与赤铁矿之间的相变；特别是过量羟基单位从针铁矿向赤铁矿的迁移。536 ~ 533和454 ~ 452 cm−1两个波段是铁O在赤铁矿结构中的低波数振动。红外光谱的波段成分分析数据支持羟基主要影响针铁矿的a面和赤铁矿的等效c面。
The behavior of the hydroxyl units of synthetic goethite and its dehydroxylated product hematite was characterized using a combination of Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) during the thermal transformation over a temperature range of 180–270°C. Hematite was detected at temperatures above 200°C by XRD while goethite was not observed above 230°C. Five intense OH vibrations at 3212–3194, 1687–1674, 1643–1640, 888–884 and 800–798 cm−1, and a H2O vibration at 3450–3445 cm−1were observed for goethite. The intensity of hydroxyl stretching and bending vibrations decreased with the extent of dehydroxylation of goethite. Infrared absorption bands clearly show the phase transformation between goethite and hematite; in particular, the migration of excess hydroxyl units from goethite to hematite. Two bands at 536–533 and 454–452 cm−1are the low wavenumber vibrations of FeO in the hematite structure. Band component analysis data of FTIR spectra support the fact that the hydroxyl units mainly affect the a plane in goethite and the equivalent c plane in hematite.