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The localized breakdown behavior of AA7055 alloy, and an Al-Zn-Mg alloy having no Cu, with different tempers was studied in 3.5 wt% NaCl solution by an in situ observation system during polarization. Three potentials at which the current increased rapidly were found for AA7055-T6 (peak-aged) samples. The first breakdown potential corresponded to the transient dissolution of an active surface layer formed during surface preparation by abrading with grinding paper. The second potential at which the current increased rapidly was associated with crevice corrosion and was not a true breakdown potential. The second breakdown potential was associated with pitting of the underlying bulk alloy. However, no surface layer attack and a single breakdown potential were observed for AA7055-T73 (over-aged) samples and for the Cu-free Al-Zn-Mg samples in the peak-aged condition. All three samples contained surface layers consisting of nano-grains with the solute-rich bands formed by surface preparation. Both the Zn-rich bands in the surface layer and the Cu content in matrix solid solution of the underlying bulk alloy are responsible for surface layer attack. The change in pitting potential with over-aged tempers could be rationalized based on the Cu content in the matrix. Precipitation-hardenable aluminum alloys are main structural materials for aircrafts due to their high strength-to-density ratio. The AlZn-Mg(-Cu) alloys form precipitates following the general precipitation sequence of supersaturated solid solution, GP zones, metastable η , and stable η.1,2 Metastable η phase is believed to be the main hardening phase and responsible for the peak hardening in Al-ZnMg(-Cu) alloys.2 The equilibrium phase η has the hexagonal structure of MgZn 2 , but Al and Cu can substitute for Zn, and the stoichiometry of this phase can be described as Mg(Zn,Al,Cu) 2 in Cu containing 7××× series Al alloys.3,4 Aging treatments produce changes in the morphology, chemistry, size and density of precipitates and the composition of the solid solution. In the past decade, much research effort has been put into evaluating the composition of nanoscale precipitates in Al alloys due to the development of advanced characterization tools such as atom probe tomography (APT).2,5-7 Sha and Cerezo studied the chemistry evolution of the early-stage precipitates in 7050 Al alloy using transmission electron microscopy (TEM) and APT.2 Marlaud and Deschamps investigated the composition of precipitates and the solid solution in Al-Zn-Mg-Cu alloys in peak-aged and over-aged conditions by combining APT and systematic anomalous small-angle X-ray scattering (ASAXS) techniques.7 This microstructural information has also facilitated a better understanding of corrosion behavior in 7××× series Al alloys with different heat treatments.The localized breakdown behavior of 7××× series Al alloys has been studied extensively. 4,[8][9][10][11][12] The anodic polarization curve for 7×××-T6 Al alloys in NaCl solution exhibits two breakdown potentials. However, only one breakdown pot...

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It is a great challenge to obtain high performance carbon fluoride (CF x ) cathodes with high specific capacity and good rate performance due to the electronic conductivity of CF x being known to decrease with an increase in the specific capacity. Herein, we propose a novel fluorinated graphene (FG)/sulfur hybrid cathode to enhance both the energy density and power density of lithium/carbon fluoride (Li/CF x ) batteries. Impressive enhancements of the specific capacity, discharge voltage, and rate capability are demonstrated with the novel FG/sulfur hybrid cathode. In comparison with the pristine FG cathode, the hybrid cathode exhibits higher electrochemical activity, lower overpotential, and faster ion transfer over the main discharge range. Furthermore, when the melt-diffusion method is used to prepare the hybrid cathode, the uncommon monoclinic sulfur is presented under ambient temperature. A significant synergistic effect which reduces the reaction resistance effectively is demonstrated with the presence of monoclinic sulfur, leading to the highest energy density of 2341 W h kg À1 and a power density up to 13 621 W kg À1 at 8.0 A g À1 . Our results are expected to introduce a new generation of high energy and high power density lithium primary cells, based on a simple and effective strategy employing FG/S hybrid cathodes.