In this work we studied the possibility of using
Fe+6
“super iron” compounds, including
BaFenormalO4,normalK2FenormalO4,CuFenormalO4
, and
SrFenormalO4
as potential cathode materials for rechargeable Li batteries, and their behavior in several nonaqueous Li salt solutions. Classic electrochemical techniques, such as cyclic voltammetry and chronopotentiometry combined with X-ray photoelectron spectroscopy, X-ray diffraction, Mössbauer spectroscopy, atomic adsorption, atomic emission, in situ and ex situ atomic force microscopy imaging, and diffuse reflectance Fourier Transform infrared spectroscopy were used in order to obtain a full picture of the electrochemical behavior of these compounds.
Fe6+
compounds such as
normalK2FenormalO4
and
BaFenormalO4
are reduced in the presence of Li ions to
Fe3+
compounds.
Fe2normalO3,Li2O
, and
normalK2O
or BaO are formed in amorphous or nanocrystalline structures. The reaction is partially reversible, i.e.,
Fe6+
compounds can be reformed by oxidation. The mechanisms of the lithiation–delithiation of these systems and what limited their reversibility are discussed.
Degradation of polymers by hyperthermal species (e.g. atomic oxygen (ATOX)) occurs in a variety of practical systems including external surfaces of spacecraft in low earth orbits (LEO), for which the impact with the residual atomic oxygen (impact energy 3-7 eV) results in significant erosion. In the present work the effects of hyperthermal species on two polymers commonly used for space applications (Kapton H and Teflon FEP) were investigated. The polymers were exposed to 30 eV 0' and Ne+ fluences of 10'5-10'9 ionscm-2. The phenomena investigated included total mass loss and changes of surface morphology (SEM and AFM) and surface chemical composition (XPS). The relative significance of the collisional and chemical degradation processes was evaluated by comparing the effects of 0' and Ne' bombardment. AFM analysis was found very powerful in studying the damage from its initial atomic scale (roughness of -1 nm) to its final macroscopic scale (roughness > 1 am).
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