Changes in the dielectric properties during the thermochromic transition of commercial VO(2) powders were determined in situ, by analyzing the low-loss region of the electron energy-loss spectroscopy ...(EELS) spectra in a transmission electron microscope at room temperature (insulator phase) and 100 degrees C (metallic phase). A comparison of experimental EELS spectra and ab initio density-functional theory calculations (WIEN2k code) within the generalized gradient approximation (GGA) is presented. A characteristic peak around 5.6 eV appears in the energy-loss function in metallic phase, which is absent in insulator phase. The origin of the characteristic peak is analyzed by means of energy-band structure calculations.
Ferromagnetism is observed in LiNiO sub(3) nanocrystals exposed to a reducing atmosphere intended to create oxygen vacancies. The existence of vacancies is confirmed by measuring the oxygen depletion ...across the selected nanoparticles by TEM. The magnetism shows no temperature dependence in the range of 4300 K. The density functional theory was used to perform spin polarized electronic structure calculations for LiNiO sub(3) with and without oxygen vacancies. The calculated magnetic data qualitatively support the observed magnetic behavior.
The dielectric properties of cubic spinel-type LiMn(2)O(4), used as cathode material in lithium ion secondary batteries, are studied by analyzing the low-loss region of the electron energy loss ...spectroscopy (EELS) spectrum in a transmission electron microscope. A comparison of experimental EELS spectra and ab initio density-functional theory calculations (WIEN2k code) within the generalized gradient approximation (GGA) is presented. The origins of interband transitions are identified in the electronic band structure, by calculating the partial imaginary part of the dielectric function and the partial density of states of Li, Mn and O. Good agreement with experimental spectra is observed which allowed interpreting main features of the EELS spectrum.
A comparative study was carried out for an alloy of Al50(Ni75Mo23)50 processed by two different high energy ball mills. A SPEX and Simoloyer mill were used. The milled products were characterized ...using X-Ray Diffraction and Scanning Electron Microscopy. A different morphology and microstructural evolution were found with each mill used. It was evident that prolonged milling time induced the formation of two different intermetallic compounds (AlNi or AlMo3). Furthermore, the milling intensity had an important effect on its microstructural evolution and phase formation sequence.
A sensor based on random connections of single-crystalline SnO
nanowires (NWs) has been fabricated for ethanol detection. The NW length of ∼10 μm leads to the formation of several random node ...connections between the Ag electrodes. The samples were subjected to thermal treatments under a reducing atmosphere of H
/Ar, to generate oxygen vacancies at the surface of the NWs. As a result, the core conduction channel of the NWs, where the conduction is based on electron hopping through the potential barriers at the contact nodes, switch to the surface of the NWs by the creation of an impurity band of shallow donors located at 0.347 eV below the conduction band. We suggest that the H
-rich atmosphere of the thermal treatments induced the formation of interstitial hydrogen (H
) and substitutional hydrogen (H
), which are shallow donors with low formation energy.
Novel cathode electrocatalysts based on Pd and cerium oxide nanorods (CeO2-NR), supported on home-obtained graphene (G) and N-doped graphene (GD1, GD2), were synthesized. The electrocatalysts were ...identified as PdCeO2-NR/G, PdCeO2-NR/GD1 and PdCeO2-NR/GD2. In half cell measurements in 0.5 mol L−1 KOH, these electrocatalysts showed higher mass and specific activity for the Oxygen Reduction Reaction (ORR) than Vulcan-supported Pd/C and comparable to PdCeO2-NR/C. Tests in a dual-chamber Microbial Fuel Cell (MFC) were performed using pharmaceutical residual water (PRW) as anode substrate, while KOH (pH = 9.6) was the electrolyte in the cathode compartment. The bioanode was formed by commercial Pt/C electrocatalyst and Bacillus subtilis as the microorganism grown as a biofilm. Meanwhile, the gas diffusion electrode (GDE) cathode contained the above-mentioned Pd-based electrocatalysts. The MFC equipped with the PdCeO2-NR/GD1 electrocatalyst as cathode delivered an Open Circuit Voltage of 0.308 V and a maximum power density of 12.47 mW m−2. This performance was higher than those of the MFC with Pd/C (0.21 V and 4.50 mW m−2) and commercial Pt/C (0.21 V and 5.43 mW m−2) cathodes. Thus, PdCeO2-NR/GD1 is a promising cathode for MFCs. Moreover, B. subtilis demonstrated to be an active microorganism to generate electrical energy from PRW.
Display omitted
•Application of cerium oxide nanorods (CeO2-NR) as cathode co-catalyst.•CeO2-NR and N-doped graphene enhance the performance of Pd for the ORR in KOH.•B. subtilis is an active microorganism to generate energy.•Pharmaceutical Residual Water is a suitable substrate for Microbial Fuel Cells.•PdCeO2-NR/GD1 cathode shows the higher performance in a Microbial Fuel Cell.
