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As part of an effort to build a prototype flow battery system using a nano-suspension containing β-Ni（OH）2 nanoparticles as the cathode material, nano-sized β-Ni（OH）2 particles with well-controlled particle size and morphology were synthesized via the one-step precipitation of a NiCl2 precursor. The composition and morphology of the nanoparticles were characterized by scanning electronic microscopy （SEM） and X-ray diffraction （XRD）. The XRD patterns confirmed that β-Ni（OH）2 was successfully synthesized, while SEM results showed that the particle sizes range from 70 to 150 nm. To ensure that Ni（OH）2 could be employed in the nano-suspension flow battery, the electrochemical performance of the synthesized 13-Ni（OH）2 was initially tested in pouch cells through charge/discharge cycling. The phase transformations occurring during charge/discharge were investigated using in-situ X-ray absorption spectroscopy to obtain the shift in the oxidation state of Ni （X-ray adsorption near edge structure, XANES） and the distances between Ni and surrounding atoms in charged and discharged states （extended X-ray absorption fine structure, EXAFS）. XANES results indicated that the electrode in the discharged state was a mixture of phases because the edge position did not shift back completely. XAFS results further proved that the discharge capacity was provided by β-NiOOH and the ratio between β-Ni（OH）2 and γ-NiOOH in the electrode in the discharged state was 71：29. Preliminary nano-suspension tests in a lab-scale cell were conducted to understand the behavior of the nano-suspension during charge/discharge cycling and to optimize the operating conditions.

Co（Ⅱ）and Ni（Ⅱ）are two common toxic heavy metals,and may simultaneously exist in contaminated water,soil,and sediment systems in Earth’s surface environment.Under this circumstance,competitive adsorption between the two metals may influence their migration,toxicity,and bioavailability.In this research,the competitive sorption of Co（Ⅱ）and Ni（Ⅱ）on γ-Al2O3was studied using both macroscopic sorption experiments and extended X-ray absorption fine structure（EXAFS）spectroscopy.Results suggest that Ni（Ⅱ）reduced the amount of Co（Ⅱ）sorption in a binary-solute system at pH 6.0.This is because both Co（Ⅱ）and Ni（Ⅱ）form inner-sphere surface complexes during sorption on γ-Al2O3and compete for the surface reactive sites.However,Co（Ⅱ）exhibited a negligible influence on sorption amount of Ni（Ⅱ）under the same conditions,which suggests Ni（Ⅱ）has a stronger affinity to alumina surface.At pH 7.5,Co（Ⅱ）and Ni（Ⅱ）sorption density were much higher than that at pH 6.0,but there no mutual competitive effect was observed.EXAFS analysis further revealed that formation of layered double-hydrated precipitates was the dominant sorption mechanism for both Co（Ⅱ）and Ni（Ⅱ）at pH 7.5.Because this type of sorption does not rely on surface reactive sites,there was no competition between Co（Ⅱ）and Ni（Ⅱ）.This finding sheds light on risk assessment and remediation of Ni/Co pollution.

The local environment of Cu atoms in Fe73.5Cu1Nb3Si13.5B9 alloy was investigated by extended X-ray absorption fine structure （EXAFS）. Cu clusters began to order when the annealing temperature was around 733 K from the results of the Fourier trans- form curves. The fitting results showed that the first shell of the near fcc （face-centered cubic） Cu clusters only contained Cu atoms. The coordination number increased with the annealing temperature. Subsequently, the occupancy rate increased from 33.3% （annealed at 733 K） to 100% （annealed at 853 K）. This local structural change of Cu atoms could probably affect the distribution of the bcc（body-centered cubic） α-Fe in Fe73.5Cu1Nb3Si13.5B9 alloy.

The effects of pH,contact time and natural organic ligands on radionuclide Eu（Ⅲ） adsorption and mechanism on titanate nanotubes（TNTs） are studied by a combination of batch and extended X-ray absorption fine structure（EXAFS） techniques.Macroscopic measurements show that the adsorption is ionic strength dependent at pH 6.0,but ionic strength independent at pH 6.0.The presence of humic acid（HA） /fulvic acid（FA） increases Eu（Ⅲ） adsorption on TNTs at low pH,but reduces Eu（Ⅲ） adsorption at high pH.The results of EXAFS analysis indicate that Eu（Ⅲ） adsorption on TNTs is dominated by outer-sphere surface complexation at pH 6.0,whereas by inner-sphere surface complexation at pH 6.0.At pH 6.0,Eu（Ⅲ） consists of ～ 9 O atoms at REu？O ≈ 2.40  in the first coordination sphere,and a decrease in NEu-O with increasing pH indicates the introduction of more asymmetry in the first sphere of adsorbed Eu（Ⅲ）.At long contact time or high pH values,the Eu（Ⅲ） consists of ～2 Eu at REu-Eu ≈ 3.60  and ～ 1 Ti at REu-Ti ≈ 4.40 ,indicating the formation of inner-sphere surface complexation,surface precipitation or surface polymers.Surface adsorbed HA/FA on TNTs modifies the species of adsorbed Eu（Ⅲ） as well as the local atomic structures of adsorbed Eu（Ⅲ） on HA/FA-TNT hybrids.Adsorbed Eu（Ⅲ） on HA/FA-TNT hybrids forms both ligand-bridging ternary surface complexes（Eu-HA/FA-TNTs） as well as surface complexes in which Eu（Ⅲ） remains directly bound to TNT surface hydroxyl groups（i.e.,binary Eu-TNTs or Eu-bridging ternary surface complexes（HA/FA-Eu-TNTs））.The findings in this work are important to describe Eu（Ⅲ） interaction with nanomaterials at molecular level and will help to improve the understanding of Eu（Ⅲ） physicochemical behavior in the natural environment.

Local atomic structures of an amorphous Mg65Cu25Gd10 alloy and the structural changes by thermal annealing have been studied by extended X-ray absorption fine structure （EXAFS）. The correlation between structural changes and mechanical properties for the Mg65Cu25Gd10 alloy has also been discussed. Results showed that Cu atoms around Gd in Mg65Cu25Gd10 lost rapidly during annealing , resulting in the segregation of Cu atoms. The coordination number NGd-Mg of Mg65Cu25Gd10 annealed at 373 K first diminished and then augmented with the increase of annealing time. The formation of polyhedral short-range order unit with coordination number of nearly 12 around Gd atoms is in favor of the improvement of mechanical properties. The chemical short-range order, not topological short-range order in the amorphous Mg65Cu25Gd10 alloy had obvious changes during annealing.

To identify the re-arrangement of constituent atoms of an amorphous Mg65Cu25Gd10 alloy happened with annealing, structure relaxation of the alloy was investigated as a function of an- nealing time at 373 K through extended X-ray absorption fine structure （EXAFS） analysis procedures. To understand the effect of structure relaxation on strength, compression tests were conducted for both the as-cast and the annealed Mg65Cu25Gd10 samples. It is found that short range order around Cu and Gd atoms exhibits different variation trends with increasing annealing time at 373 K, though the structure of the alloy still remains to be amorphous. Based on the fact that the strength of the alloy first exhibits a reduction and then a recovery with annealing time, it is suggested that the enhancement of short range order around Cu should be responsible for the strength reduction, while the enhancement of short range order around Gd should be responsible for the strength recovery.