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[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.
[en] Highlights: • Nanolaminate thin films of Al2O3/TiO2 with different bilayer density were prepared by ALD method. • A new multidimensional reconstruction method was implemented to analyze the nanomechanical response of the samples. • Mechanical response of the nanolaminates showed to be improved by layer thickness and follow the behavior of a nanocomposite coating. • The method implemented allows the reconstruction of 4D mechanical data at the nanoscale. A novel method of nanomechanical testing of multilayered Al2O3/TiO2 nanolaminates was implemented by the nanoindentation technique. The indentation data were reconstructed and filtered by a statistical analysis algorithm and presented as a function of the penetration depth of the indenter. Results show the increment of mechanical properties on the laminates as a function of the amorphous interfaces of the individual layers and the effective control of the wear rate of the structures for further applications. The results presented show both important insights on the mechanical behavior of nanolaminates and the further applicability of the reconstruction model for error reduction on mechanical testing of nanolaminate samples.
[en] Highlights: • Humic acid-HA, NaHCO3, MgSO4, KCl and CaCl2 change the stability and oxidation state of silver nanoparticle-AgNPs surface. • Ag3+ is formed on AgNPs surface mainly in presence of NaHCO3, MgSO4 and HA. • Toxicological endpoints in zebrafish embryos exposed to Ag3+ were not significant for acute exposure. • HA coated on AgNPs surface reduces the concentration of Ag ions released and the toxicity in zebrafish embryos. • HA acts as a natural attenuator/remediator of polluted water with AgNPs. - Abstract: The use of silver nanoparticles (AgNPs) result in an inevitable contact with aquatic environments. Here we study the behavior of AgNPs and the developmental toxicity in zebrafish embryos exposed to these nanoparticles (0–10 mg/L) with and without the presence of HA (20 mg/L), using zebrafish facility water (ZFW) and zebrafish growing media (ZGM). The presence of cations and HA gave rise to a decrease in Ag ion release and ζ-potential, an increase in the hydrodynamic diameter and oxidation of the AgNP surface. The results show that the presence of HA and cations in the media, as well as the silver speciation, i.e., the unusual presence of Ag3+, decreases the toxicity of AgNPs (LC50AgNPs: 1.19 mg/L; LC50AgNPs+HA: 3.56 mg/L), as well as silver bioavailability and toxicity in zebrafish embryos. Developmental alterations and the LC50 (1.19 mg/L) of AgNPs in ZFW were more relevant (p ≤ 0.05) than for AgNPs in ZGM (LC50 > 10 mg/L). It was demonstrated that the bioaccumulation and toxicity of AgNPs depends on several factors including AgNPs concentration, nanoparticle aggregation, dissolved silver ions, speciation of silver ions, the amount of salt in the environment, the presence of humic substances and others, and different combinations of all of these factors.