Short-range and Middle-range Ordering

在金属铁腐蚀过程中，溶解在水溶液中的亚铁（II）离子和三铁（III）离子以聚阳离子的形式析出，形成腐蚀产物。在这些过程中，形成了铁的氢氧化物和结构复杂的氧化物。在这项工作中，系统地使用了EXAFS和定量x射线衍射方法来表征外来离子对其铁化合物的中短程有序的影响。除了这些实验外，还通过电化学电位和pH测量分析了水溶液的反应条件，以澄清这些铁化合物的形成条件。本研究专门合成了含铁离子的绿锈，并在温度等可控条件下将其氧化为铁的氢氧化物和氧化物。结果表明，绿锈向不同氧化铁和氢氧化物的转化与反应温度、反应速率和水溶液pH等条件密切相关。此外，为了研究锰等外源阳离子对氧化铁结构的影响，对固体颗粒进行了x射线异常散射测量。结果表明，锰在磁铁矿尖晶石结构中几乎均匀分布于不同位置。此外，还对铁氢氧化物在外源阴离子氧化作用下的中短程有序原子排列进行了表征。认为在GR的结构变化过程中，硅酸盐离子等外来离子被掺入固体颗粒中，使GR的结构发生扭曲。因此，外源阴离子的掺入很可能引起原子排列的扭曲，这似乎不仅引起粒子的形态变化，而且引起离子选择性等特性的变化。

Ferrous Fe(II) ions and ferric Fe(III) ions dissolved in aqueous solution are precipitated as polycations during corrosion of metallic iron, by which corrosion products are formed. In these processes, iron oxyhydroxides and oxides with complicated structure are formed. In this work, the EXAFS and quantitative X-ray diffraction methods were systematically used for characterizing influences of foreign ions on the short range and middle range ordering of their iron compounds. In addition to these experiments, reaction conditions of the aqueous solution were also analyzed using electrochemical potential and pH measurements, in order to clarifying the formation conditions of these iron compounds. In this works, green rust containing ferrous ions was specially synthesized, which was oxidized to iron oxyhydroxides and oxides under controlled conditions such as temperature. The results showed that the transformation from green rust to different iron oxides and oxyhydroxides strongly depend on reaction conditions such as temperature rate and pH of aqueous solution. In addition, X-ray anomalous scattering measurement of solid particles was carried out in order to investigate an influence of foreign cations such as manganese on the structure of iron oxides. This result indicated that manganese was almost equally distributed to different sites in the spinel structure of magnetite. Furthermore, the short range and middle range ordering the atomic arrangements of iron oxyhydroxides, which were oxidized with foreign anions was also characterized. Foreign ions like silicate ions were considered to be incorporated into the solid particles during structural changes of GR, by which the structure was distorted. As a result, foreign anions are likely to induce the distortion of the atomic arrangement by their incorporation, and this appears to cause not only the morphological changes and also properties of particles such as ion selectivity.