Results 1 - 2 of 2
Results 1 - 2 of 2. Search took: 0.013 seconds
|Sort by: date | relevance|
[en] Highlights: • Novel nanocomposite thin films consisting of nanocrystalline chromium embedded in an amorphous chromium carbide matrix are reported for the first time. • The novel nanocomposite films show ultra low nanowear and a relatively high hardness of around 22 GPa. • The nanocomposite films show a strong correlation between the macro and nano-tribological properties. - Abstract: In this work, we report the first observation of novel nanocomposite thin films consisting of nanocrystalline chromium embedded in an amorphous chromium carbide matrix (nc-Cr/a-CrC) with relatively high hardness (∼22,3 GPa) and ultra low nanowear. The films were deposited onto silicon substrates using a magnetic filtered cathodic arc deposition system at various negative bias voltages, from 50 to 450 V. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) suggested the co-existence of chromium and chromium carbide phases, while high resolution transmission electron microscopy (HRTEM) confirmed the presence of the nc-Cr/a-CrC structure. The friction coefficient measured with the ball-on disk technique and the nanowear results showed a strong correlation between the macro and nano-tribological properties of the samples. These novel nanocomposite films show promising properties as solid lubricant and wear resistant coatings with relatively high hardness, low friction coefficient and ultra low nanowear.
[en] Highlights: • Importance of mixing intensity for aqueous LiFePO4 cathode slurries is demonstrated. • Fe3+ rich layer formation on intensively mixed LiFePO4 electrode surface is detected. • C/LiFePO4 pouch cells with aqueous processed electrodes show outstanding cyclability. • Aqueous cathode slurry processing is viable approach toward cheaper and greener LIBs. - Abstract: The positive electrodes based on nano- and micrometric carbon coated LiFePO4 (LFP) powders are prepared via aqueous slurry processing using “normal” and “intensive” mixing procedures. The XRD, XPS, and electrochemical characterization reveal that the “intensive” mixing process improves the discharge C-rate capability of the n-LFP cathode however provokes formation of an undesirable thin surface layer enriched by Fe3+ species. The waterborne graphite anodes and LiFePO4 cathodes for the energy and power cells are being developed, upscaled and manufactured on a pilot plant. Energy LiFePO4/C pouch cells demonstrate outstanding durability maintaining 80% of initial discharge capacity (IDC) after 7450 and 2400 full cycles under 1D and 4D discharge currents, respectively. Moreover, further cycling of the energy cell working under 1C/4D protocol reveals its extra-long secondary life (70% of IDC on 9200th cycle). Power LiFePO4/C pouch cell shows long lasting cycle life retaining 80% of IDC after 3350 cycles under harsh cycling conditions (3C/8D). The reported results are being achieved despite confirmed water release from lithium iron phosphate cathodes to the electrolyte. Finally, viability of aqueous processing of the electrodes without sacrificing electrochemical performance of LiFePO4/C batteries is clearly proven.