Thermal instability of Bi-Pb-Sr-Ca-Cu-O superconductor around 650δC

Bi_0.85Pb_0.15Sr_0.8CaCu_1.4O _y superconductor was quenched to room temperature after annealing at several temperatures in air. From the initial magnetization curve measurement for the annealed samples, it was found that the volume fraction of superconducting phases of the sample annealed at 650°C greatly decreased. TEM observation revealed that a second phase often appeared in the grain-boundary region for the sample annealed at 700°C. The second phase was identified as Bi₁Pb₂Sr_2.6Ca_1.6O _y by energy dispersive spectroscopy.     

A reconfigurable VLSI-based double-lens tracking camera

Watching and tracking an object while seeing a much wider view is one of advantages of the eye system. We proposed and developed a tracking camera system that mimics the eyes by using double-lens modules. In the system, a wide view is captured through the wide-lens module, while the target in it is tracked and magnified through the telescopic lens module. Electronic circuits for tracking control are implemented onto the reconfigurable VLSI or FPGA in order to embed the parallelism in the tracking algorithm into the hardware. A successfully developed FPGA-based prototype performs high-speed tracking at the video-rate. This work was present in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Current collecting efficiency of micro tubular SOFCs

In this study, current collecting efficiency of the micro tubular solid oxide fuel cell (SOFC) was estimated to determine optimum size of the micro tubular SOFC. Two models for collecting current from single terminal (ST) and double terminal (DT) of anode tube were proposed and used to calculate the current collecting efficiency as functions of anode thickness, tube length and operating temperature. It was shown that design of the cell geometry and current correcting method are significantly important to achieve high performance micro tubular SOFC stacks. The efficiency loss estimated from the DT model was about 2–4-fold lower than those of obtained from the ST model. The DT model was shown to be more effective for higher operating temperature and the tube length.     

Effect of Microstructural Control on Thermoelectric Properties of Hot-Pressed Aluminum-Doped Zinc Oxide

The thermal conductivity of polycrystalline Al-doped ZnO was controlled through the fabrication of nanostructured polycrystalline materials, by hot-pressing nanosized Zn_{1– x} Al _x O ( x = 0.01, 0.02) particles, which were synthesized by a coprecipitation and spray-drying method. This process resulted in an improved thermoelectric power factor because of the nanosized Zn_0.99Al_0.01O particles of the polycrystalline products. The thermal conductivity also was decreased as a result of the formation of nanocrystalline Zn_0.99Al_0.01O.     

Hydrothermal Synthesis and Formation Mechanisms of Lanthanum Tin Pyrochlore Oxide

Well-defined La₂Sn₂O₇ with a phase-pure pyrochlore structure was produced by hydrothermal synthesis at temperatures as low as 200°C. Production of phase-pure La₂Sn₂O₇ requires a pH above 10, and higher pH accelerates the crystallization process. The synthesis produced spherical particles of average particle size ∼0.59 μm (±0.12) and surface area ∼14.1 m²/g. SEM and TEM observation for morphologic evolution and kinetic analysis during crystallization indicated that La₂Sn₂O₇ formation probably proceeds via a two-step reaction. First a transient dissolution–precipitation occurs. Then the primary crystallites aggregate because of their colloidal instability, and heterocoagulation with the lanthanum hydrous oxide precursor particles also occurs. The sluggish reaction rate at the later stage of reaction is characterized by an in situ transformation, where the soluble tin species is diffused through the porous La₂Sn₂O₇ aggregates to react with entrapped lanthanum precursors.     

Direct Formation of Crystalline Gadolinium-Doped Ceria Powder via Polymerized Precursor Solution

Synthesis of Ce_0.9Gd_0.1O_1.95 (CGO) powder from a polymeric precursor solution containing a mixture of nitrates, nitric acid, and ethylene glycol was investigated with emphasis on the effect of polymerization of the precursor solution on the crystallization and morphology of the derived solid intermediate and the final oxide powder. It is shown for the first time in this work that the solid intermediate derived from the polymerized solution is present in the form of well-crystallized cerium-gadolinium formate solid solution, Ce_{1− x} Gd _x (HCOO)₃, exhibiting anisotropic growth. Further polymerization of the precursor solution resulted in the direct formation of loosely agglomerated nanoscaled CGO oxide powder from the polymerized solution at temperatures as low as 130°C.     

Preparation and characterization of the Sb-doped TiO2 photocatalysts

Doped TiO₂ photocatalysts have been prepared by a coprecipitation method. Uniformly doped nanocrystalline TiO₂ of 10–20 nm sizes was synthesized by calcinating the coprecipitated gels at 400–650°C. Photocatalytic characterization along with the microstructural investigation for each catalyst provides better understanding of the photocatalytic behavior. It was found that the photodegradation of methylene blue (MB) was a complex function of the doping type and its concentration and the microstructural characteristics of the catalysts. Antimony doing significantly improved photocatalytic performance as compared to the undoped TiO₂. Post-treatment of the as-precipitated wet doped Ti gels in an organic solvent also increased the surface area, forming approximately 8 nm size doped TiO₂ with surface area 149 m²/g. Superior catalytic activity was observed in the Sb-doped TiO₂ samples at a doping concentration ranging from 1 to 5 at%. Using the 5 at% Sb-doped TiO₂ catalyst treated in butanol, 100 ppm of MB could be decomposed completely within 1 h, which was better than the commercial Degussa P-25.     

New transverse-domain formation mechanism in aquarter-micrometre-gate HEMT

Studies a quarter-micrometre-gate HEMT by a two-dimensional Monte Carlo particle simulation to gain a deeper insight into the device operation. A new transverse-domain formation due to intervalley electron transfer is predicted. The effect of domain formation on device performance and current saturation characteristics is also discussed     

Monte Carlo particle simulation of a GaAs short-channel MESFET

A Monte Carlo particle simulation of a 0.25 ?m-long gate (and 0.25 ?m-long channel) GaAs MESFET having a practical doping density and sitting on a substrate is carried out. Extremely high values of gm and Idss of 643 mS/mm and 5.35 mA/20 ?m were obtained. The near-ballistic nature of the electron transport in the FET was confirmed.     

Design and Fabrication of a Novel Electrode-Supported Honeycomb SOFC

We report the design and fabrication of a novel electrode-supported honeycomb solid oxide fuel cell (SOFC), that can generate high volumetric power density. Among various cell designs, honeycomb SOFCs are suitable for compact SOFC modules because they have a large surface electrode area per unit volume. We have succeeded in fabricating a cathode-supported honeycomb SOFC via extrusion of a LaSrMnO₃ honeycomb monolith and through the use of a new slurry injection method for the channel surface coating using electrolyte/anode bi-layers. The fabricated honeycomb SOFCs exhibited high volumetric power densities of approximately 1.2 W/cm³ at 600°C under a wet H₂ fuel flow.