Short-range and Middle-range Ordering

溶解在水溶液中的亚铁Fe（II）离子和三价铁Fe（III）离子在金属铁的腐蚀过程中以聚阳离子的形式沉淀，由此形成腐蚀产物。在这些过程中，形成具有复杂结构的铁羟基氧化物和氧化物。本文系统地采用EXAFS和定量X射线衍射方法研究了杂质离子对铁化合物短程有序和中程有序的影响。除了这些实验之外，还使用电化学电势和pH测量来分析水溶液的反应条件，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锈，在温度等控制条件下将其氧化为铁的氢氧化物和氧化物。结果表明，绿色锈转化为不同的铁氧化物和羟基氧化物的过程强烈地依赖于反应条件，如温度、速率和水溶液的pH值。此外，为了研究锰等外来阳离子对铁氧化物结构的影响，进行了固体粒子的X射线异常散射测量。这一结果表明，锰几乎均匀地分布在磁铁矿尖晶石结构的不同位置。此外，短程和中程有序的铁羟基氧化物的原子排列，这是与外来阴离子氧化的特点。在GR的结构变化过程中，硅酸盐离子等外来离子被认为掺入到固体颗粒中，从而使结构发生扭曲。结果，外来阴离子很可能通过它们的掺入引起原子排列的畸变，这似乎不仅引起形态变化，而且还引起颗粒的性质，如离子选择性。

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.