Search

Highly porous NiO–gadolinium-doped ceria (GDC) nano-composite powders are synthesized by a one-pot glycine nitrate process and applied to the fabrication of Ni–YSZ (yttria-stabilized zirconia)-supported tubular solid oxide fuel cells (SOFCs) with a cell configuration of Ni–YSZ/Ni/Ni–GDC/GDC/LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ)–GDC/LSCF. The power density of the cell is as high as 413 mW cm−2 at 600 °C, which is 1.37 times higher than that of an identically configured cell fabricated using ball milling-derived NiO–GDC powders (301 mW cm−2). The high porosity of the powders and the good mixing between the NiO and GDC primary nanoparticles due to the abrupt combustion of the precursors effectively suppress the densification, coarsening, and agglomeration of NiO and GDC particles during sintering, resulting in a highly porous Ni–GDC anode layer with good dispersion of Ni and GDC particles and a cell with significantly enhanced power density.

Strategies for the enhancement of gas sensing properties, and specifically the improvement of gas selectivity of metal oxide semiconductor nanowire (NW) networks grown by chemical vapor deposition and thermal evaporation, are reviewed. Highly crystalline NWs grown by vapor-phase routes have various advantages, and thus have been applied in the field of gas sensors over the years. In particular, n-type NWs such as SnO2, ZnO, and In2O3 are widely studied because of their simple synthetic preparation and high gas response. However, due to their usually high responses to C2H5OH and NO2, the selective detection of other harmful and toxic gases using oxide NWs remains a challenging issue. Various strategies—such as doping/loading of noble metals, decorating/doping of catalytic metal oxides, and the formation of core–shell structures—have been explored to enhance gas selectivity and sensitivity, and are discussed herein. Additional methods such as the transformation of n-type into p-type NWs and the formation of catalyst-doped hierarchical structures by branch growth have also proven to be promising for the enhancement of gas selectivity. Accordingly, the physicochemical modification of oxide NWs via various methods provides new strategies to achieve the selective detection of a specific gas, and after further investigations, this approach could pave a new way in the field of NW-based semiconductor-type gas sensors.

A study synthesized exclusively single-crystalline Cd(< 10%)-doped alpha-manganese sulphide (MnS) nanowires (NWs), with a controlled Cd content, by the chemical vapor deposition method. Results indicate that the distinctive magnetic properties of the nanowires have a strong correlation with their photoluminescence, which could be influenced by the nanosize effect and the Cd doping.

[Cd.sub.1-x][Mn.sub.x]S (x=0.1-0.3) nanowires were synthesized by using the chemical vapor deposition method. The nanowires consist of single-crystalline wurtzite structured CdS with a [010] or [011] growth direction, while the XRD pattern shows the concentration of the lattice constants, confirming the incorporation of Mn into the CdS lattices.

The Sn-doped In2O3(ZnO)4 and In2O3(ZnO)5 nanowires are synthesized by thermal evaporation method. The diameter of nanowires is periodically modulated in the range of 50-90 nm.

Rh-loaded In2O3hollow spheres with diameters of ∼2 μm were prepared by a one-pot hydrothermal reaction of aqueous solution containing indium nitrate, rhodium chloride, and glucose and subsequent heat treatment at 500 °C for 2 h. The response to 100 ppm C2H5OH (Ra/Rg, Ra: resistance in air, Rg: resistance in gas) of 1.67 at% Rh-loaded In2O3hollow spheres was 4748, which was ∼180 times higher than that of pure In2O3hollow spheres. Rh loading decreased the temperature for maximum gas response from 475 °C to 371 °C, which also enhanced the selectivity to C2H5OH 15.1–24.7 times and recovery speed. The ultrahigh sensitivity and selectivity to C2H5OH, the lower sensing temperature, and the reduced recovery time were attributed to electronic interactions between Rh and In2O3and the promotion of catalytic dissociation of C2H5OH into reactive gases. [ABSTRACT FROM AUTHOR]

Magnetite (Fe3O4) hollow spheres were prepared by solvothermal reaction of ethanol solution containing Fe-acetate and l-lysine, and were subsequently transformed into hematite (Fe2O3) hollow spheres with nanoscale (20–30 nm) thin shells by heat treatment at 500 °C for 2 h. Both the as-prepared and heat-treated hollow spheres contained another small sphere within each shell, which was attributed to the following solvothermal self-assembly reactions: (1) the nucleation of Fe3O4spheres, (2) lysine capping on the nuclei, (3) the growth of lysine-capped particles by cross-linking between lysine molecules, and (4) the formation of Fe shell layers by the interaction between Fe ions and outer lysine molecules. In the assembly reaction, l-lysine with amino and carboxyl radicals played the key role. The heat-treated Fe2O3hollow spheres showed significantly enhanced C2H5OH sensing characteristics and promising Li-ion intercalation behaviors. [ABSTRACT FROM AUTHOR]

Cd1-xMnxS (x = 0.1−0.3) nanowires were synthesized by using the chemical vapor deposition method. They all consist of a single-crystalline wurtzite CdS structure with a [010] or [011] growth direction. The X-ray diffraction pattern reveals the contraction of the lattice constants due to the incorporation of Mn. The Mn2+ emission at ∼2.15 eV, originating from the d−d (4T1 → 6A1) transition, appears below 50−80 K. Its decay time is in the range of 0.55−1 ms, showing a decrease with increasing Mn content. The Mn doping reduces significantly the decay time of band-edge emission from 590 ps to 20−30 ps. Upon applying magnetic field (up to 7 T), the Mn2+ emission is suppressed and donor−acceptor pair emission becomes dominant, suggesting the energy transfer from the band electrons to the Mn2+ ions. [ABSTRACT FROM AUTHOR]

High-density Zn0.85In0.15O and Zn0.75In0.25O nanowires were synthesized by thermal evaporation method. They consist of single-crystalline wurtzite ZnO structure with uniform [010] growth direction. X-ray diffraction (XRD) reveals the structural defects caused by the In incorporation. X-ray photoelectron spectrum (XPS) analysis suggests that In withdraw the electrons from Zn and increase the dangling-bond O 2p states. The lower energy shift and green-band enhancement of photoluminescence are well correlated with the results of XRD and XPS. [ABSTRACT FROM AUTHOR]

Highly sinterable gadolinia doped ceria (GDC) powders are prepared by carbonate coprecipitation and applied to the GDC interlayer in Ni–YSZ (yttria stabilized zirconia)-supported tubular solid oxide fuel cell in order to prevent the reaction between YSZ electrolyte and LSCF (La0.6Sr0.4Co0.2Fe0.8O3−δ) cathode materials. The formation of highly resistive phase at the YSZ/LSCF interface was effectively blocked by the low-temperature densification of GDC interlayer using carbonate-derived active GDC powders and the suppression of Sr diffusion toward YSZ electrolyte via GDC interlayer by tuning the heat-treatment temperature for cathode fabrication. The power density of the cell with the configuration of Ni–YSZ/YSZ/GDC/LSCF–GDC/LSCF was as high as 906 mW cm−2, which was 2.0 times higher than that (455 mW cm−2) of the cell with the configuration of Ni–YSZ/YSZ/LSM(La0.8Sr0.2MnO3−δ)–YSZ/LSM at 750 °C. [ABSTRACT FROM AUTHOR]