Electrical conductivity of BaCe0.9Nd0.1O3−α in H2+H2O+Ar gas mixture

Electroconductivity of BaCe_0.9Nd_0.1O_3−α was studied as a function of the composition of the H₂+H₂O+Ar mixture and temperature in the interval from 873 to 1173 K. It was shown that the electroconductivity was independent of P_H2 (0.97 to 0.10 atm) and P_O2 (10⁻²¹ to 10⁻²⁶ atm), but depended on P_H2O (0.08 to 0.005 atm). A mathematical processing of the P_H2O dependencies of the electroconductivity, which was performed in terms of a classical model of defect formation in high-temperature proton-conducting solid electrolytes, yielded equilibrium constants of the reaction of water dissolution in BaCe_0.9Nd_0.1O_3−α and mobilities of protons and oxygen ions. The temperature dependencies of these quantities were used to determine the mobility activation energies of protons (E_a=34±7 kJ/mole) and oxygen ions (E_a=72±8 kJ/mole), and also the enthalpy (ΔH=−150±25 kJ/mole) and the entropy (ΔS=153±26 kJ/mole·K) of the reaction of water dissolution in BaCe_0.9Nd_0.1O_3−α.     

Nickel-cermet anode for fuel cells with the LSGM electrolyte

The effect of some technological parameters (firing temperature, thickness of an interphase layer made of solid electrolyte Ce_0.82Gd_0.18O_1.91 (GDC), the GDC electrolyte amount in nickel-cermet) on the electrochemical and electric properties of a nickel-cermet (Ni-GDC) anode intended for fuel cells with the La_0.88Sr_0.12Ga_0.82Mg_0.18O_2.85 (LSGM) electrolyte is studied. The polarization resistance of such an electrode is shown to hardly depend on the thickness of the interphase layer (4.5–23.5 μm) and the GDC electrolyte amount in nickel-cermet and to increase with the anode firing temperature. It is established that the contact resistance is concentrated in cells with the developed nickel-cermet electrode at the GDC/LSGM interface. At a temperature of 700°C the developed anodes may ensure a current density of 1 A cm^?2 at an overvoltage of less than 100 mV when using both moist hydrogen and a methane-oxygen mixture as the fuel.     

Electroconductivity,Nature of Conduction,Thermodynamic Stability of the BaPr1 –xYxO3 – αCeramics

The electroconductivity and the nature of conduction of vacuum-dense ceramics BaPr_{1 – x} Y _x O_{3 –} (x= 0.05–0.15) is studied at temperatures of 373 to 985°C, of 2.1 × 10⁴to 10^–11Pa, and of 40 to 2400 Pa. The coefficient of linear thermal expansion is measured. The ceramics have a perovskite structure and are practically p-type semiconductors with a maximum conductivity of 0.26 S cm^–1at x= 0.10 and 800°C, in air. The share of ionic (proton) conductivity of the ceramics does not exceed 0.2–0.4%. The conductivity is weakly dependent on the air humidity. In a hydrogen-containing atmosphere, the ceramics undergoes reduction with destruction. Boundaries of thermodynamic stability of BaPr_0.9Y_0.1O_{3 –} at 500–900°C are determined.     

Scattering of an atomic beam by a short light pulse

The observation of the scattering of sodium atoms by a short light pulse (≈ 10^?8 s) is treated. The pulse has the spatial structure of a standing wave. The particles are scattered at the expense of the forces of the stimulated light pressure (gradient forces). In a resonance field of the order of 10³ V/cm, the scattering angle is of the order of 0.01 rad.     

Fiber laser mode locked by a Sagnac interferometer with nonlinear polarization rotation

We describe a new fiber laser configuration based on a nonlinear optical loop mirror with a symmetrical coupler, a quarter-wave retarder, and highly twisted, birefringent fiber in the loop. The nonlinear optical loop mirror configuration operates by nonlinear polarization rotation. We have achieved stable generation of subpicosecond pulses with milliwatts of average output power.     

Two-dimensional image magnification in an asymmetric-reflection X-ray microscope

The experimental results on the two-dimensional 20× magnification of an x-ray image obtained in an asymmetric-reflection x-ray microscope with the use of a laboratory source of x rays are discussed. The field of view is determined by the linear sizes of the detector and is equal to 0.5 × 0.5 mm in our experiment for an exposure time of 600 s.     

Wavelength tunable high power laser using a double-clad Er:Yb doped fiber

We experimentally demonstrated a stable, wavelength-tunable fiber laser using a polarization-maintaining, double-clad Er:Yb doped fiber amplifier in the cavity. The output wavelength is tunable over the range from 1535 to 1567 nm using a fixed grating and the dichroic mirror placed on a rotational mount; under rotation of the dichroic mirror the tuning ratio of 50 nm/deg was found. We studied the wavelength tuning range dependence on the amplifier fiber length and achieved a maximal output power of 850 mW. This configuration can be Q-switched for high peak power and its narrow bandwidth is suitable for nonlinear optics applications, such as parametric teraherthz generator.     

Tunable dual-wavelength fiber laser based on a polarization-maintaining fiber Bragg grating and a Hi-Bi fiber optical loop mirror

We demonstrate experimentally the operation of a linear cavity dual-wavelength fiber laser using a polarization maintaining fiber Bragg grating (PM-FBG) as an end mirror that defines two closely spaced laser emission lines. The PM-FBG is also used to tune the laser wavelengths. The total tuning range is ∼8 nm. The laser operates in a stable dual-wavelength mode for an appropriate adjustment of the cavity losses for the generated wavelengths. The high birefringence (Hi-Bi) fiber optical loop mirror (FOLM) is used as a tunable spectral filter to adjust the losses. The FOLM adjustment was performed by the temperature control of the Hi-Bi fiber.     

Nickel Reinforced Catalysts Over a Heat-Exchanging Surface for Benzene Hydrogenation

X-ray technique, mercury porosimetry and electron microscopy were used to study the regularities of formation of porous metallic nickel-aluminium supports reinforced with a steel grid and distributed over a heat-exchanging surface, and of nickel catalysts supported on them. Such catalysts are active in gas phase benzene hydrogenation and also possess high heat conductivity.