Short-range and Middle-range Ordering

在金属铁腐蚀过程中，溶解在水溶液中的Fe(II)离子和Fe(III)离子以聚阳离子形式析出，形成腐蚀产物。在这些过程中，形成了结构复杂的氢氧化铁和氧化物。本文采用EXAFS和定量X-射线衍射法系统地研究了外加离子对铁化合物中短程有序化的影响。除了这些实验外，还利用电化学电位和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。本工作专门合成了含亚铁离子的绿色铁锈，在控制温度等条件下，将其氧化成氢氧化铁和氧化铁。结果表明，绿锈向不同铁氧化物和羟基氧化物的转化强烈依赖于反应温度、反应速度和水溶液的pH等条件。此外，还进行了固体颗粒的X射线反常散射测量，以考察外来阳离子如锰对铁氧化物结构的影响。这一结果表明，在磁铁矿的尖晶石结构中，锰几乎均匀地分布在不同的位置。此外，还对外加阴离子氧化的氢氧化铁的中短程有序结构进行了表征。认为在GR的结构变化过程中，硅酸盐离子等外来离子被引入到固体颗粒中，从而扭曲了GR的结构。因此，外来阴离子的掺入可能会导致原子排列的扭曲，这似乎不仅会导致粒子的形态变化，还会导致离子选择性等性质的变化。

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.