To study the allergenic properties of titanium (Ti), the corrosion behaviors and following metal ions release of Ti and nickel (Ni) in simulated physiological environments were investigated. Anodic polarization tests and accelerated dissolution tests were performed in artificial saliva with and without fluorine, and in artificial sweat. Ti showed good corrosion resistance in the artificial saliva without fluorine even when the passive film was physically destroyed by mechanical wear. The concentration of Ti ions released into the solution showed relatively higher values in artificial saliva with fluorine and in artificial sweat, however, it remained to be below 10 ppm. On the other hand, Ni was not passivated in these solutions and the concentrations of the released Ni ions were about 100 ppm. Thus, Ti can be regarded as a considerably safer material than Ni from the viewpoint of corrosion engineering. The large differences in the corrosion characteristics and metal ion solubility between Ti and Ni under the experimental conditions are discussed.
We report an improved performance of a carbon-based supercapacitor using etched stainless steel (SS) current collector deposited with platinum nanoparticles (PtNs) over bare SS current collector/un-etched SS current collector deposited with PtNs. The PtNs grown on the etched surface of the current collectors provides a better contact with the surface of activated carbon monoliths electrode prepared from pre-carbonized fibres of oil palm empty fruit bunches. X-ray diffraction, field-emission scanning electron microscopy, the energy dispersive X-ray analysis, and X-ray photoelectron spectroscopy were employed to investigate the different properties of bare SS current collector and the modified current collector. Electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charge–discharge results consistently suggest that the deposition of PtNs on the etched surface of the current collector causes an increase in specific capacitance of 10% (from 105 to 115 F g−1), 4% (from 141 to 146 F g−1) and 6% (from 142 to 150 F g−1) respectively. Correspondingly, the specific energy increases from 4.12 to 4.51 Wh kg−1 and specific power from 173 to 196 W kg−1. Also EIS and GCD results respectively show a decrease of 47% (from 1.332 to 0.710 Ω) and 44% (from 1.75 to 0.974 Ω) in equivalent series resistance.
A new compound with the core luminescent dye unit diketopyrrolopyrrole (DPP), namely 3,6-dithiophen-2-yl-2,5-dihydropyrrole[3,4-c]pyrrole-1,4-dione (DTDPP), attached to 3,4-ethylenedioxythiophene (EDOT) was synthesized. From this monomer, polymer films were prepared on glassy carbon and indium tin oxide surfaces using cyclic voltammetry. The films were characterized using cyclic voltammetry, chronocoulometry, and atomic force microscopy. The electropolymerization of the monomer exhibits reversible electrochemistry that transitions to quasireversible electrochemistry. During electropolymerization, the overpotential for the reduction process exceeds the overpotential for the oxidation process and cyclic voltammetric characterization of the films demonstrates that oxidation is more favored than reduction. Spectroelectrochemical measurements confirm that the polymer films demonstrate electrochromic behavior that correlates to the electrochemical observations during characterization of the films.
Yolk-shell structured silicon-polypyrrole (Si-PPy) composite has been prepared by an in situ chemical polymerization approach. The designed parcel method significantly improves the cycling stability and rate capability compared to those of bare silicon. The Si-PPy composite exhibits a high specific capacity of 1400 mAh g−1 after 100 cycles, which is approximately 4 times higher than bare Si. Moreover, the Si-PPy composite delivers a high reversible capacity of ∼1200 mAh g−1 at a high current density of 10 A g−1, while the bare Si only achieves a low capacity of ∼490 mAh g−1 at the same current density. The outstanding electrochemical properties of the Si-PPy composites are attributed to the stability and conductivity of the PPy shell and the nanoscale structure of the composite.
Capacity and voltage retentions upon subsequent cycles for Li2RuO3 and Li2Mn0.4Ru0.6O3 (LMR) under various cut-off voltages have been investigated. The change in average and local structures upon electrochemical cycling were examined by ex-situ XRD and Ru L3-edge XANES measurements, and the relationship between the cyclic capabilities and the structural changes is discussed. The deteriorations of discharge capacity and average discharge voltage in the subsequent cycles of LMR with a charge cut-off voltage of 4.8 V vs. Li/Li+ are remarkably smaller than that with the voltage of 4.2 V. Moreover, LMR exhibits higher average discharge voltage than Li2RuO3 under a charge cut-off voltage of 4.8 V. The phase transition behavior of LMR was not similar to Li2RuO3 upon electrochemical cycling. Ru L3-edge XANES spectra measurements reveal that RuO6 octahedra in LMR charged at 4.2 V are much distorted. The local structure of RuO6 octahedra is associated with the cyclic capability of LMR and Li2RuO3.
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