Investigation about iron(III) incorporation into layered double hydroxides: Compositional and structural properties of Mg2FeyAl(1−y)(OH)6-Cl and Zn2FeyAl(1−y)(OH)6-Cl

International audienceLayered Double Hydroxides (LDH) and related nanocomposites have attracted much attention for biomedical applications and the development of LDH drug carriers composed by endogenous metals such as iron is of obvious interest. However, most of the studies reported so far on iron-containing LDH, mainly focusing on the applications, suffer from insufficient data about the synthesis and the characterization of these materials. In this study, it is addressed compositional and structural properties of two series of LDH materials, Mg2FeyAl(1−y)-Cl and Zn2FeyAl(1−y)-Cl with a M2+/M3+ molar ratio (R) equal to 2 and 0 ≤ y ≤ 1. By combining crystal-chemical reasoning, Rietveld refinements and pair distribution function analysis (PDF), it was possible to differentiate between contributions from crystalline and amorphous components. Concerning Mg-series, for y > 0.5, the compositions were found to slightly deviate from those expected with an increase in the value of R tending to 3. For Zn-series, more heterogeneous samples were obtained with the presence of amorphous 2-line ferrihydrite clearly demonstrated by PDF analysis. As well as providing a reliable approach to the characterization of Fe-LDH, this study gives useful elements for better understanding and interpreting the results reported in the literature regarding these phases

Electrochemical Behavior of Morphology-Controlled Copper (II) Hydroxide Nitrate Nanostructures

International audienceNanostructure control is an important issue when using electroactive materials in energy conversion and storage devices. In this study, we report various methods of synthesis of nanostructured copper (II) hydroxide nitrate (Cu-2(OH)(3)NO3) with a layered hydroxide salt (LHS) structure using various synthesis methods and investigate the correlation between nanostructure, morphology, and their pseudocapacitive electrochemical behavior. The variations in nanostructure size and morphology were comprehensively explored by combining X-ray diffraction (XRD) and scanning electron microscopy (SEM), while the electrochemical activity was characterized using cyclic voltammetry. We demonstrate that Cu-2(OH)(3)NO3-LHS nanostructured submicron particles produced by alkaline precipitation with 88% of the copper cations can cycle with a two-electron redox process. Unfortunately, the electroactivity decreases rapidly from the first cycle due to the occurrence of structural transformations and subsequent electrochemical grinding. However, samples obtained by ultrasonication and microwave synthesis, two original synthesis methods for LHS materials, formed of nanosized crystalline domains agglomerated in micron-sized particles, represent a good compromise between capacity and cyclability. Moreover, by using pair distribution function analysis on electrode materials after repeated cycling, we were able to follow the chemical and structural changes occurring in Cu-2(OH)(3)NO3 materials during electrochemical cycling with first a quick transformation to Cu2O and then the appearance of Cu metal and copper acetate Cu(II)(2)(O2CCH3)(4)center dot 2H(2)O

Temperature stability of a pure metakaolin based K‐geopolymer: Part 1. Variations in the amorphous mineral network

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