Suitability of strontium and cobalt-free perovskite cathodes with La9.67Si5AlO26 apatite electrolyte for intermediate temperature solid oxide fuel cells.

Aluminium-doped lanthanum silicate (LSAO) apatite-type compounds have been considered as promising candidates for substituting yttria-stabilized zirconia (YSZ) as electrolytes for intermediate temperature solid oxide fuel cells (IT-SOFC). Nevertheless, not many materials have been reported to work as cathodes in a LSAO apatite-based cell. In the present work, eight different strontium and cobalt-free compounds with a perovskite-type structure and the general composition LaM1-xNxO3-δ (where M = Fe, Cr, Mn; N = Cu, Ni; and x = 0.2, 0.3) have been tested. This study includes the synthesis and structural characterization of the compounds, as well as thermomechanical and chemical compatibility tests between them. Functional characterization of the individual components has been performed by electrochemical impedance spectroscopy (EIS). Apatite/perovskite symmetrical cells were used to measure area-specific resistance (ASR) of the half cell in an intermediate temperature range (500-850 °C) both with and without DC bias. According to its electrochemical behaviour, LaFe0.8Cu0.2O3-δ is the most promising material for IT-SOFC among the compositions tested since its ASR is similar to that of the traditional (LaxSr1-x)MnO3 (LSM) cathode.

Measuring Membrane Permeation Rates through the Optical Visualization of a Single Pore.

Membranes are a critical technology for energy-efficient separation processes. The routine method of evaluating membrane performance is a permeation measurement. However, such measurements can be limited in terms of their utility: membrane microstructure is often poorly characterized; membranes or sealants leak; and conditions in the gas phase are poorly controlled and frequently far-removed from the conditions employed in the majority of real processes. Here, we demonstrate a new integrated approach to determine permeation rates, using two novel supported molten-salt membrane geometries. In both cases, the membranes comprise a solid support with laser-drilled pores, which are infiltrated with a highly CO2-selective molten carbonate salt. First, we fabricate an optically transparent single-crystal, single-pore model membrane by local laser drilling. By infiltrating the single pore with molten carbonate, monitoring the gas-liquid interface optically, and using image analysis on gas bubbles within the molten carbonate (because they change volume upon controlled changes in gas composition), we extract CO2 permeation rates with exceptional speed and precision. Additionally, in this arrangement, microstructural characterization is more straightforward and a sealant is not required, eliminating a major source of leakage. Furthermore, we demonstrate that the technique can be used to probe a previously unexplored driving force region, too low to access with conventional methods. Subsequently, we fabricate a leak-free tubular-supported molten-salt membrane with 1000 laser-drilled pores (infiltrated with molten carbonate) and employ a CO2-containing sweep gas to obtain permeation rates in a system that can be described with unprecedented precision. Together, the two approaches provide new ways to measure permeation rates with increased speed and at previously inaccesible conditions.

Interacting plasmon and phonon polaritons in aligned nano- and microwires.

The availability of macroscopic, nearly periodic structures known as eutectics opens a new path for controlling light at wavelength scales determined by the geometrical parameters of these materials and the intrinsic properties of their component phases. Here, we analyze the optical waveguiding properties of eutectic mixtures of alkali halides, formed by close-packed arrangements of aligned cylindrical inclusions. The wavelengths of phonon polaritons in these constituents are conveniently situated in the infrared and are slightly larger than the diameter and separation of the inclusions, typically consisting on single-crystal wires down to submicrometer diameter. We first discuss the gap mode and the guiding properties of metallic cylindrical waveguides in the visible and near-infrared, and in particular we investigate the transition between cylinder touching and non-touching regimes. Then, we demonstrate that these properties can be extended to the mid infrared by means of phonon polaritons. Finally, we analyze the guiding properties of an actual eutectic. For typical eutectic dimensions, we conclude that crosstalk between neighboring cylindrical wires is small, thus providing a promising platform for signal propagation and image analysis in the mid infrared.

Broadband laser tunability of Nd3+ ions in 0.8CaSiO3-0.2Ca3(PO4)2 eutectic glass.

Site-selective spectroscopy and stimulated emission experiments performed in the (4)F(3/2)-->(4)I(11/2) laser transition of Nd(3+)-doped 0.8CaSiO(3-) 0.2Ca(3)(PO(4))(2) eutectic glass are presented. The spectral features of the excitation spectra and those of spontaneous and stimulated emissions reveal the existence of a very complex crystal field site distribution for Nd(3+) ions. As a consequence, the stimulated emission of Nd(3+) in this glass shows a tunability of about 10 nm as a function of excitation wavelength.

Synthesis of Heteronuclear Pt-Tl Complexes with Donor-Acceptor Bonds. X-ray Structures of cis-[Tl(&mgr;(2)-OOCCH(3))Pt(PPh(3))(C(6)F(5))(2)] and (NBu(4))(2)[{Pt(C(6)F(5))(3)}(2){(&mgr;(2)-O,&mgr;(3)-O'CCH(3))Tl}(2)].

Reactions of the anionic platinum complexes (NBu(4))[Pt(PPh(3))(C(6)F(5))(2)(OCOCH(3))] (1) and (NBu(4))(2)[Pt(C(6)F(5))(3)(S)] (S = methanol or acetone) with Tl(I) salts afford the heterometallic neutral cis-[(C(6)F(5))(2)(PPh(3))Pt(&mgr;(2)-OOCCH(3))Tl] (2) and the dimeric dianionic (NBu(4))(2)[{(C(6)F(5))(3)Pt}(2){(&mgr;(2)-O,&mgr;(3)-O'CCH(3))Tl}(2)] (3). Both complexes display Pt-Tl bonds with bond lengths of 2.994(1) Å and 2.884(1) Å, respectively, the latter being the shortest Pt-Tl(I) distance reported so far. The structure of both compounds has been established by X-ray studies.