Department of Physics, Astronomy and Materials Science, Missouri State University, Springfield, MO 65897, USA.
J Synchrotron Radiat. 2012 Sep;19(Pt 5):797-805. doi: 10.1107/S0909049512029093. Epub 2012 Jul 28.
Radiolysis-induced effects on aqueous tungsten ions are observed to form a precipitate within seconds upon exposure to a synchrotron X-ray micro-beam in a WO(3) + H(2)O system at 873 K and 200 MPa. In situ Fe K-edge energy-dispersive X-ray absorption spectroscopy (ED-XAS) measurements were made on Fe(II)Cl(2) aqueous solutions to 773 K in order to study the kinetics of high-temperature reactions of Fe(2+) and Fe(3+) ions with transient radiolysis species. The radiolytic reactions in a fluid sample within a hydrothermal diamond anvil cell result in oxidation of the Fe(2+) ion at 573 K and reduction of Fe(3+) at temperatures between 673 and 773 K and of the Fe(2+) ion at 773 K. The edge-energy drift evident in the ED-XAS data directly reflects the kinetics of reactions resulting in oxidation and/or reduction of the Fe(2+) and Fe(3+) ions in the aqueous solutions at high temperatures. The oxidation and reduction trends are found to be highly consistent, making reliable determinations of reaction kinetics possible.
在 873 K 和 200 MPa 的条件下，将 WO(3) + H(2)O 体系中的水合钨离子暴露于同步加速器 X 射线微束中，可在几秒钟内观察到辐照诱导效应形成沉淀。为了研究 Fe(2+)和 Fe(3+)离子与瞬态辐射分解产物在高温下反应的动力学，对 Fe(II)Cl(2)水溶液进行了原位 Fe K 边能量色散 X 射线吸收光谱（ED-XAS）测量，最高温度达 773 K。在高温下水热金刚石压腔中流体样品中的辐照反应导致 573 K 时 Fe(2+)离子氧化，673-773 K 时 Fe(3+)离子还原，773 K 时 Fe(2+)离子还原。ED-XAS 数据中明显的边缘能量漂移直接反映了水溶液中 Fe(2+)和 Fe(3+)离子氧化和/或还原反应的动力学。发现氧化和还原趋势非常一致，使得反应动力学的可靠测定成为可能。
