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To study the reaction kinetics at the anode of solid-oxide fuel cells, a nickel stripe pattern was prepared on the surface of yttria-stabilized zirconia (YSZ) [8 mole percent (m/o) Y 2 O 3 -doped ZrO 2 ] by an ionized cluster beam (ICB) method and photolithography. Due to grain growth of nickel film at high temperatures, the minimum possible width of the stripes was found to be ca. 5 μm. By impedance measurements in H 2 -H 2 O atmospheres at 100 to 850 o C, it was shown that the reaction proceeds through the triple-phase boundary (TPB) of H 2 -H 1 O/Ni/YSZ and the mechanism of the rate-determining reaction is different from that at the TPB of H 2 -H 2 O/Pt/YSZ

Energy-dispersive X-ray signals calibrated by Rutherford backscattering indicated the generation of Al13/24Ga11/24N in Ga-rich stripes in a nonflat Al0.58Ga0.42N layer. Also, the CL peak wavelengths of ∼259 and 272 nm also showed the generation of Al15/24Ga9/24N and Al13/24Ga11/24N in Al-rich zones and Ga-rich stripes, respectively. The wavelength of a strong CL peak at ∼246 nm, which was observed from the Al0.7Ga0.3N layer in our previous study, is also considered to correspond to the near-band-emission wavelengths of Al17/24Ga7/24N. In particular, the stronger reproducibility of metastable Al15/24Ga9/24N generation was confirmed, in agreement with the computed predictions by other research groups.

Towards a Gbps-class outdoor mobile optical wireless communication (OWC), we experimentally investigate an up-to 292-Mbps diffuse-line-of-sight OWC in the solar-blind band based on an AIGaN-LED and a Silicon photo multiplier array under a typical indoor illumination condition.

The metastability of Al n /12Ga1-n/12N (n = 2, 3, and 4) was investigated by the statistical analysis of electroluminescence (EL) spectra having dual peaks with a peak-to-peak distance (pp) of >10 nm generated from nonflat Al x Ga1- x N (x ∼ 0.2) quantum wells (QWs) fabricated on c(0001) sapphire substrates with a miscut of 1.0° towards the m[1 1 ˉ 00] axis. To explain the origins of the dual-peak EL (DPEL) spectra, which are often observed for AlGaN-QWs with Ga content of greater than 0.7, a nonflat QW model incorporating two metastable compositions, Al(n-1)/12Ga1-(n-1)/12N and Al n /12Ga1-n/12N (n: integer), is proposed. By the statistical analysis of peak wavelengths in DPEL spectra and the verification of EL spectral shapes, two series of featured EL peak wavelengths with intervals of 2–3 nm were obtained from five out of six LED wafers. The two series of featured EL peak wavelengths were assigned by comparison with the calculated EL wavelengths. Then, Al2/12Ga10/12N and Al3/12Ga9/12N were determined to be the origins of peaks with the longer and shorter wavelengths in the DPEL, respectively, in addition to the metastable Al n /12Ga1-n/12N (n= 4–9) compositions observed in our previous studies. When DPEL (pp> 10 nm) appeared, the difference in QW thickness between Al2/12Ga10/12N and Al3/12Ga9/12N tended to be larger than one monolayer (ML), indicating a significant amount of Ga or GaN mass transport. Furthermore, the Al2/12Ga10/12N and Al3/12Ga9/12N QWs are considered to have thicknesses of m ML (m: consecutive integers), suggesting the 1 ML configuration of Al and Ga atoms on the c(0001) plane. In addition, the DPEL obtained from nonflat Al x Ga1- x N (x ∼ 0.25) QWs by another research group was shown to be related to two metastable Al n /12Ga1-n/12N (n = 3, 4), similarly to our one exceptional LED wafer, which also agreed with the model proposed in this work.

Trifluoroethylene (HFO-1123) and its mixtures are useful as the next generation refrigerants because their global warming potential (GWP) are lower than that of those ordinarily used. HFO-1123, however, has the potential to disproportionate explosively as does tetrafluoroethylene. In this report, the explosive disproportionation of mixed gases of HFO-1123 and other gases were investigated by the fusing of Pt wires ignition method at 10 MPa and 488 K which was the upper limit of the conditions in typical refrigerant usage. It was found that there was a roughly linear correlation between the lower limit of HFO-1123 concentration at which disproportionation occurred and the molar heat capacity at a constant volume of mixed gas. This experimental finding strongly suggests that an explosive disproportionation consists of a thermal explosion process.

Trifluoroethylene and its mixtures are useful as next generation refrigerants because of their lower global warming potential (GWP) than that of those ordinarily used. Trifluoroethylene, however, has the potential to disproportionate explosively, as does tetrafluoroethylene. In the present research, we quantitatively searched for conditions in which trifluoroethylene undergoes disproportionation. We modified the ignition apparatus as so it could be performed using electromagnetic force, we simulated spark phenomena in air conditioners and analyzed the disproportionation process of trifluoroethylene using that equipment. The spark energy yielding 1% probability of disproportionation was found to be 6.33 J, at which pressure was 1 MPa and temperature was 373 K. It was revealed that trifluoroethylene had much higher minimum ignition energy than that of ordinary combustible materials such as methane and hydrogen. The reason for the high ignition energy needed to initiate disproportionation of trifluoroethylene was considered to be that the flame kernel needed to have a large size and a long lifetime to propagate the disproportionation reaction because of its lower frequency factor of producing solid graphite. The fact that the delay time of trifluoroethylene disproportionation was 0.1 s also explained the lower frequency factor of producing solid graphite.

Ga-rich zones created along macrosteps in n-AlGaN plausibly function as electron pathways of AlGaN-based deep-ultraviolet (DUV) LEDs fabricated on AlN templates using 1.0°-miscut c(0001) sapphire substrates toward the m[1-100] axis. This work was performed to clarify AlN mole fractions (xAl) of Ga-rich zones. xAl ≃ (7/12, 6/12, and 5/12) was observed in Ga-rich zones in AlαGa1−αN (α ≃ 0.63, 0.55, and 0.43, respectively) by the method proposed in our previous article in which we showed that Ga-rich zones of Al8/12Ga4/12N were created in Al0.7Ga0.3N. xAl in the Ga-rich zones obtained from an energy-dispersive x-ray signal by scanning transmission electron microscopy calibrated by Rutherford backscattering well agreed with xAl obtained by cross-sectional cathodoluminescence (CL) spectroscopy using scanning electron microscopy. A weak CL shoulder peak corresponding to Al4/12Ga8/12N was also observed for Al0.43Ga0.57N. In addition, xAl ≃ n/12 (n = 6–9) in Al-rich zones appeared in the rest of the Ga-rich zones. Furthermore, nanobeam electron diffraction patterns of the Ga-rich zones indicated a high possibility of a regular configuration of Ga and Al atoms on the c(0001) plane in our samples. Consequently, xAl values in nonflat AlGaN layers with macrosteps were often determined to be near n/12 (n: integer). Thus, Ga-rich zones (xAl = n/12: n = 4–8) formed in our nonflat AlGaN layers, which originated from the macrosteps along [11–20] edgelines normal to the m[1–100] axis, are suggested to be metastable. The creation of discrete xAl in Ga-rich zones should contribute to the stable production of DUV-LEDs using high-miscut sapphire substrates.

To clarify the behavior of the AlGaN in 20 nm wide Ga-rich current pathways in an n-AlGaN layer, which assists carrier localization in AlGaN-based light-emitting diodes, we performed a detailed analysis using an n-Al0.7Ga0.3N layer on AlN with dense macrosteps on a 1.0° miscut sapphire substrate. Energy-dispersive X-ray spectra, obtained using cross-sectional scanning transmission electron microscopy calibrated by Rutherford backscattering and cross-sectional cathodoluminescence spectra, indicated that AlN mole fraction in the Ga-rich current pathways was nearly ~2/3. This result is consistent with those of other research groups, suggesting that metastable Al2/3Ga1/3N is created in Ga-rich current pathways.

The origin of the fast modulation characteristics of deep ultraviolet (DUV) AlGaN light-emitting diodes (LEDs) grown on AlN/sapphire templates with vicinal off-angles is reported by employing time-resolved electroluminescence (EL) and micro-imaging experiments. The LEDs have recently demonstrated Gbps-class optical wireless communication (OWC) under both room-lighting and direct-sun. The frequency response (f3dB) of the LED reached 184 MHz, which is far beyond expectations by considering the size of the LEDs. Since self-organized micro-LED structures with a low electric capacitance (C) are observed by the EL experiments, the compatibility of high efficiency and fast modulation nature of the AlGaN LEDs is explained. Our approach can overcome the dilemma, where micro-LEDs can be modulated fast but have low power, and therefore, the self-organized micro-LED structure is an ideal solution to realize practical DUV OWCs.

AlGaN-based deep-ultraviolet light-emitting diodes (LEDs) incorporating uneven multiple quantum wells (MQWs) with inclined and terrace zones, which were fabricated on an AlN template with dense macrosteps, have exhibited a high internal quantum efficiency (IQE). To investigate the microscopic structure of uneven MQWs, cathodoluminescence (CL) mapping characterization was carried out, and the maps of the CL intensity at 300 K relative to that at 38 K were obtained for uneven MQWs that targeted 265 and 285 nm LEDs. At an electron beam current of less than 1.0 nA, the signals from inclined and terrace zones of the uneven MQWs were confirmed to satisfy the nonsaturated excitation condition at 300 K. Nonradiative recombination (NR) was insufficiently frozen even at 38 K, specifically on the terraces in the 265 nm MQW, suggesting high concentrations of NR centers due to point defects (PDs). In contrast, NR in the 285 nm MQW at 38 K was closer to freeze-out. The concentration of PDs in the 285 nm MQW was likely to be lower than that in the 265 nm MQW. Finally, the ratios of the CL intensity at 300 K to those at 38 K were mapped, demonstrating an approach to creating an approximate map of IQE. The values in the CL intensity ratio maps are discussed by considering the analytical error factors. The results support the model of localized current injection through Ga-rich stripe zones in the n-AlGaN cladding layer.

The microscopic structural and optical characteristics of AlGaN-based light-emitting diodes grown on AlN templates with macrosteps were evaluated. Cross-sectional transmission electron microscopy in the high-angle annular dark field scanning mode and microscopic energy dispersive X-ray spectroscopy reveal that the AlGaN cladding layer under the AlGaN quantum wells (QWs) has microscopic compositional modulations originating from the macrosteps at the AlN template surface. The Ga-rich oblique zones in the cladding layer likely behave as current micropaths. These micropaths are connected to the carrier localization structure, which is formed by the modulation of both the well widths and the compositions of the QWs. In-plane spatially-resolved cathodoluminescence (CL) spectroscopy indicated significant inhomogeneity of the CL characteristics: the brighter emission with a lower peak photon energy confirms the existence of the carrier localization structure in the QWs. Carrier localization in the QWs along with the current micropaths in the AlGaN cladding layer appears to increase the external quantum efficiency of AlGaN LEDs.

Reproducible fabrication of the hierarchically porous monolithic silica in a large volume exceeding 1000 mL has been established. By the hydrothermal enlargement of the fully accessible small pores to exceed 50 nm in diameter, the capillary force emerged on solvent evaporation was dramatically reduced, which allowed the preparation of crack-free monoliths with evaporative solvent removal under an ambient pressure. The local temperature inhomogeneity within a reaction vessel in a large volume was precisely controlled to cancel the heat evolved by the hydrolysis reaction of tetramethoxysilane and that consumed to melt ice cubes dispersed in the solution, resulting in large monolithic silica pieces with improved structural homogeneity. Homogeneity of the pore structure was confirmed, both on macro- and mesoscales, using SEM, mercury intrusion, and nitrogen adsorption/desorption measurements. Furthermore, the deviations in chromatographic performance were examined by evaluating multiple smaller monolithic columns prepared from the monolithic silica pieces cut from different parts of a large monolith. All the daughter columns thus prepared exhibited comparable performances to each other to prove the overall homogeneity of the mother monolith. Preliminary results on high-speed separation of peptides and proteins by the octadecylsilylated silica monolith of the above production have also been demonstrated.

This paper describes the performance of a dry low-NOx gas turbine combustor designed with a new fuel supply concept. This concept uses automatic fuel distribution achieved by an interaction between the fuel jet and the airflow. At high loads, most of the fuel is supplied to the lean premixed combustion region for low-NOx, while at low loads, it is supplied to the pilot combustion region for stable combustion. A numerical simulation was carried out to estimate the equivalence ratio in the fuel supply unit. Next, through the pressurized combustion experiments on the combustor with this fuel supply unit using natural gas as fuel, it was confirmed that NOx emissions were reduced and stable combustion was achieved over a wide equivalence ratio range.

AlGaN-based LEDs (λ < 300 nm) fabricated on n-AlGaN templates with a threading dislocation density larger than 5 × 108/cm2, which were grown on (0001) sapphire with a 1.0° miscut relative to the m-plane, showed external quantum efficiencies (EQEs) of 3.5, 3.9, 6.1, and 6.0% at 266, 271, 283, and 298 nm, respectively. These EQE values reveal significantly high internal quantum efficiencies (IQEs). This performance was obtained using an uneven multiple quantum well (MQW) grown on the AlGaN template with macrosteps having height larger than the well thickness. The electroluminescence spectra of the fabricated LEDs using this MQW structure shifts to a longer wavelength compared with those on sapphire with a miscut angle of 0.3° relative to the m-plane. Furthermore, the LEDs with this MQW show no deleterious effect on the lifetime, broader electroluminescence spectral widths, and higher output powers when using sapphire with a miscut of 1.0°.

We report on the fabrication and characterization of high efficiency ultraviolet (UV) light emitting diodes (LEDs) with emission wavelength ranging from 255 to 355 nm. Epi-layers of UV LEDs were grown on AlGaN templates with sapphire substrates. Flip-chip configuration without removing sapphire is used for characterization of the UV LEDs. External quantum efficiencies (EQEs) over 3% were obtained for all the investigated wavelengths with maximum value reaching 5.1% for 280 nm LED. Under RT DC operation at a current of 500 mA, output powers of 38, 77, and 64 mW were measured for 257, 280, and 354 nm, respectively. By using enhanced light extraction technologies, such as, moth-eye structure on the back side of the sapphire substrate, we expect to improve these values by up to 50%.

We report on development for commercial production of 50mW class AlGaN based deep ultraviolet light-emitting diodes (DUVLED) with wave length ranging 255 to 355 nm. DUVLED have about 10% EQE and over 10000 hours life time.

Reproducible fabrication of the hierarchically porous monolithic silica in a large volume exceeding 1000 mL has been established. By the hydrothermal enlargement of the fully accessible small pores to exceed 50 nm in diameter, the capillary force emerged on solvent evaporation was dramatically reduced, which allowed the preparation of crack-free monoliths with evaporative solvent removal under an ambient pressure. The local temperature inhomogeneity within a reaction vessel in a large volume was precisely controlled to cancel the heat evolved by the hydrolysis reaction of tetramethoxysilane and that consumed to melt ice cubes dispersed in the solution, resulting in large monolithic silica pieces with improved structural homogeneity. Homogeneity of the pore structure was confirmed, both on macro- and mesoscales, using SEM, mercury intrusion, and nitrogen adsorption/desorption measurements. Furthermore, the deviations in chromatographic performance were examined by evaluating multiple smaller monolithic columns prepared from the monolithic silica pieces cut from different parts of a large monolith. All the daughter columns thus prepared exhibited comparable performances to each other to prove the overall homogeneity of the mother monolith. Preliminary results on high-speed separation of peptides and proteins by the octadecylsilylated silica monolith of the above production have also been demonstrated.

A-site deficient La(Sr)CrO 3 − δ thin film interconnectors were successfully fabricated on porous La(Sr)MnO x tubes using high deposition rate laser ablation. The La(Sr)CrO 3 − δ films obtained by this method are dense and void-free. The film deposition rate was about 10 μm/min. The substrate could easily be masked in order to deposit the films in the desired shape. The substrate tube was heated at 873–1073 K. As the substrate temperature was much lower than the sintering temperature of the substrate tube, the porous micro-structures of the substrate tube were maintained. The difference in chemical composition between the film and the target was negligible.

To replace mercury lamps with AlGaN-based deep-ultraviolet (DUV) LEDs, a simple and low-cost package with increased light extraction efficiency (LEE) is indispensable. Therefore, resin encapsulation is considered to be a key technology. However, the photochemical reactions induced by DUV light cause serious problems, and conventional resins cannot be used. In the former part of this study, a comparison of a silicone resin and fluorine polymers was carried out in terms of their suitability for encapsulation, and we concluded that only one of the fluorine polymers can be used for encapsulation. In the latter part, the endurance of encapsulation using the selected fluorine polymer was investigated, and we confirmed that the selected fluorine polymer can guarantee a lifetime of over 6,000 h at a wavelength of 265 nm. Furthermore, a 3 × 4 array module of encapsulated dies on a simple AlN submount was fabricated, demonstrating the possibility of W/cm2-class lighting.

La−xSrxCrO3−δ films were fabricated on yttria stabilized zirconia (YSZ) and La(Sr)MnO3 polycrystal substrates using the laser ablation method. At a substrate temperature of 973 K and an oxygen pressure of 10−4 Torr, the resultant films were porefree and contained no detectable oxygen vacancy. The chemical composition of the films almost agreed with the target. Film crystallinity depended on the crystal structure of the substrates. The film formed on YSZ substrate showed remarkable primary particle growth resulting from heat-treatment at 1473 K for 5 h in air. When a film was formed on the LaMnO3 substrate, which has a crystal structure similar to that of LaCrO3, under the same conditions as above, neither crystal structure change nor particle growth was observed from heat-treatment at 1473 K.

Tubular-type solid oxide fuel cell (SOFC) with interconnector has been successfully fabricated, with a maximum single cell power density of 0.9 W/cm2, the highest value reported so far. A self supporting La(Sr)MnOx tube was used for the cathode. The La(Sr)CrOx interconnector was made using the laser oblation method. The yttria-stabilized zirconia (YSZ) electrolyte and Ru/YSZ cermet anode were fabricated by the electrochemical vapor deposition (EVD) process.

La(Sr)MnO[sub 3] cathodes have been investigated as high temperature oxygen reduction electrodes in the solid oxide fuel cells (SOFCs). The cathodes consist of 10 mole percent of yttria stabilized zirconia (YSZ) thin film electrolyte layer deposited on a porous La[sub 0.81]Sr[sub 0.09]MnO[sub 3] tube using the electrochemical vapor deposition method. The La(Sr)MnO[sub 3]/YSZ cathodes have different electrochemical properties from those fabricated with the sintering method. The cathode polarization was about 1 mV at a current density of 1.5 A/cm[sup 2] in oxygen at 1,000 C. This type of cathode has an extremely large phase boundary and large interfacial capacitance (more than 1 F/cm[sup 2]) which is approximately proportional to the oxygen partial pressure.

In order to elucidate the reaction mechanism at the anode of solid oxide fuel cells (SOFC) in H2H2O atmospheres, instead of conventional nickel-zirconia cermet anodes, we employed nickel stripe patten electrodes prepared on the surface of 8m/o Y2O3- doped ZrO2 (YSZ), which have well-defined length and morphology of the gas/nickel/YSZ triplet phase boundary (TPB). On the surface of single crystalline YSZ-plates, compact nickel layer was prepared by ICB (ionized cluster beam) method. By photolithography, the stripe patterns of alternative nickel and YSZ lines were prepared. Electrochemical measurements were made on the electrode impedence and steady-state polarization current using a terminal method in the H2H2OAr gas mixtures with hydrogen partial pressure, PH2 = 102−104 Pa and water vapor pressure, pH20=3×10su2−2×103 Pa at 700°C. It was shown that the rate of electrode reaction at 700°C can be approximately expressed by I=kPH2aO−k′PH2O12aO−12 (k, k′: rate constant), where aO is the oxygen activity at the TPB which is related to the electrode potential E versus 1.013×105 Pa O2 (g) by RTO=2EF. The rate of anodic reaction was found to be essentially determined by the reaction of H2(g) and the adsorbed oxygen on the nickel surface, while the rate of cathodic reaction seems to be determined by the first order reaction or surface diffusion process of adsorbed hydrogen, Had, which may take place after the reaction of H2O(g)→H2Oad→Had+OHad.

Seeding particles for laser Doppler velocimeter (LDV) measurement have been developed which are of uniform diameter, spherical shape, low loose weight and high melting temperature. Evaluation test results show that the use of the particles can increase the signal quality substantially and extend the measurable field of the LDV, which can hardly be accessed by conventional measurement methods.

An H2D2 isotope effect on an external magnetic field effect on the hydrogen-oxygen reaction on an SnO2 surface at 775 K was observed. The rate of increase for the external magnetic field effect on the H2O2 reaction was 1.5 times as large as on the D2O2 reaction. This effect strongly suggests that the H2O2 reaction on the SnO2 surface is an Eley-Rideal type reaction. The present results strongly suggest that only the H2O2 reaction via the activated complex OH2− was accelerated by an external magnetic field and that the activated complex of this reaction has a structure in which there is only a weak interaction between undissociated hydrogen molecules and surface-adsorbed O2−. A model is proposed in which the magnetic field affects the electron spin of the quasi-radical pair H · · H in activated complexes, and the recombination of H · · H is inhibited by the singlet-triplet conversion caused by applying an external magnetic field.

The reaction mechanism for electrochemical‐vapor deposition of yttria‐stabilized zirconia was studied. Yttria‐stabilized zirconia films were deposited on porous La(Sr)MnOx using the electrochemical‐vapor‐deposition process. The distribution of yttria concentration through the film was investigated by means of secondary‐ion‐mass spectroscopy and x‐ray microanalysis and found to be nearly constant. The deposition rate was approximately proportional to the minus two‐thirds power of the film thickness, the one‐third power of the partial pressure of ZrCl4/YCl3 mixed gas, and the two‐thirds power of the product of the reaction temperature and the electronic conductivity of yttria‐stabilized zirconia film. These experimental results were explained by a model for electron transport through the YSZ film and reaction between the surface oxygen and the metal chloride on the chloride side of the film, both of which affect the deposition rate. If the film thickness is very small, the deposition rate is thought to be c...

Ru/YSZ cermet SOFC anodes were fabricated using the EVD method. Ru has high sintering resistivity compared with Ni. During the power generation tests at 1273 K the Ru/YSZ cermet anode showed high activity for hydrogen oxidation compared with conventional Ni/YSZ cermet anodes. Especially in the high current density of a maximum of 3200 mA/cm2 the ac polarization value was reduced to approximately 200 mV. Tubular type SOFCs were made by depositing 10 micro m thick 10 mol% yttriastabilized zirconia (YSZ) electrolyte films on porous La(Sr)MnOx cathode tubes using the EVD process and then making a Ru/YSZ cermet anode on YSZ. The cells had the highest power generation density with a maximum density of 1550 mW/cm2. After the power generation test of approximately one week including several thermal cycles, the anode polarization was unchanged and there was no change in the Ru metal grain size.

The oxidation states of manganese in the La1−xMnO3−δ (x = 0.09–0.11) were investigated by electron spin resonance (ESR) and iodometry. The ESR analysis carried out at room temperature for the samples prepared in air revealed the presence of broad peaks at g = 2.0, considered to be relevant to Mn2+. It was also found that the intensity of the peak increased as lanthanum vacancy content increased. The average valence state of manganese, determined by iodometry, was approximately 3.2, and decreased by 1 as the lanthanum vacancy increased by 1. Similar trends were observed with the samples prepared at Po2 = 1×10−7. The results indicated that Mn2+ is stably present in the La1−xMnO3−δ having an average valence number exceeding 3.0. A series of experimental results with respect to the non-stoichiometry of La1−xMnO3−δ can be explained by assuming that Mn2+ is stabilized after forming a complex with a lanthanum vacancy and two oxygen vacancies.

This paper reports that, the authors succeeded in fabricating a solid-oxide-electrolyte fuel cell, with the highest power-generation density, with a maximum single-cell-level density of 1550 mW/cm{sup 2}. This cell was made by depositing a 10{mu}m thick 10 mol% (m/o) yttria stabilized zirconia (YSZ) electrolyte layer on a porous La(Sr)MnO{sub x} cathode tube using the electrochemical vapor deposition method and then making a Ru/YSZ cermet anode on top of it.

La(Sr)MnO[sub 3] cathodes have been investigated as high temperature oxygen reduction electrodes in the solid oxide fuel cells (SOFCs). The cathodes consist of 10 mole percent of yttria stabilized zirconia (YSZ) thin film electrolyte layer deposited on a porous La[sub 0.81]Sr[sub 0.09]MnO[sub 3] tube using the electrochemical vapor deposition method. The La(Sr)MnO[sub 3]/YSZ cathodes have different electrochemical properties from those fabricated with the sintering method. The cathode polarization was about 1 mV at a current density of 1.5 A/cm[sup 2] in oxygen at 1,000 C. This type of cathode has an extremely large phase boundary and large interfacial capacitance (more than 1 F/cm[sup 2]) which is approximately proportional to the oxygen partial pressure.

This paper introduces a new solid oxide fuel cell system using a tubular cell. This authors have developed a computer program for a tubular solid oxide fuel cell incorporating an inner reforming process. This program enables us to estimate the distribution of the output current density, the gas density, and the temperature distribution of bulk and gases. This program has been applied to the conventional solid oxide fuel cell power generation system proposed by Westinghouse Electric Corporation wherein the cell is cooled by air. The calculated results conform to the measured data of a test run in a 3 KW module made by Westinghouse Electric Corporation. This program has also been applied to a high speed fuel recycling system in which pure oxygen is used. Attempts to estimate the maximum current take-out of both systems have been made. The calculations based on published data have indicated that a 300 mm cell attached to a conventional air cooling system would output an average of 370 mA/cm[sup 2] given the conditions that the fuel utilization factor is 80% and the air utilization factor is 25%. The potential between cell contacts was 0. 606 V. Anything over this output is limited by themore » temperature tolerance of the cell. Moreover, the fuel recycling system composed of self-supporting tubular cells was very capable of cooling under the conditions of 10% fuel utilization per cycle, 100% oxidant utilization, and average current output of 926 mA/cm[sup 2], and 0. 811 V.« less

Measurements were made on the Hall effect of SnO2 thin‐film inflammable gas sensors prepared by using the reactive sputtering method. The results revealed that when the electrical conductivity of the sensors changed with a change in the flammable gas concentration in air, the apparent carrier density changed significantly while apparent mobility hardly changed at all. However, detailed analysis revealed that these experimental results could not be explained by using the double Schottky model or the neck model that had been proposed. In order to provide satisfactory explanation of the experimental results, the authors clarified that for SnO2 thin films there exists no distinction between bulk and surface of the grain while the carrier densities of bulk and surface of the grain simultaneously change with a change in oxygen absorption of the SnO2 surface in the presence of flammable gas. This model was in good agreement with the results of transmission electron microscopy observations.

Studies have been made of the gas sensing properties of both steady and unsteady state SnO2 thin film gas sensors in contact with CH4 and H2 in air from 400 to 500° C. The results suggest a new sensing mechanism model for SnO2 semiconductor flammable gas sensors. This model is based on the following points: (i) Sensor conductivity is determined by the concentration of carrier electrons. (ii) Carrier concentration is controlled by surface unsaturated oxygen adsorption site concentration which is decided by the balance between oxygen adsorption and the surface reaction between oxygen adsorbate and flammable gases. (iii) The activation energy of the reaction is changed by the Fermi energy change for any change in sensor conductivity. This model explains all experimental results.

The currently available resins for underfilling and encapsulation are limited to wavelengths longer than approximately 330 nm because almost all resins are decomposed by deep-ultraviolet light. Fluorine resins are possible materials for underfilling and encapsulation in deep-ultraviolet LEDs, and we have investigated methods of underfilling and encapsulation using such resins. Also, their durability at wavelengths of 265 and 285 nm has been studied from the photochemical viewpoint, and we propose a stable amorphous fluorine resin that is optically isotropic. Also, a trial of encapsulation using the resin has been made.

In a steady state, the dependence of an external magnetic field effect on the H 2 -O 2 reaction on the SnO 2 surface upon field direction, field intensity, temperatures, and hydrogen concentration was measured. Measurements made of the dependence upon the magnetic field direction confirmed that the magnetic field effects resulted not from changes in the mobility of the carrier electrons but from the increased rate of the reaction between hydrogen and surface-adsorbed oxygen. Magnetic field effects were found to be higher in the 573-623 K temperature range than in the 673-773 K range

We studied the transcient response properties of external magnetic field effects on SnO 2 surface H 2 -O 2 reactions by measuring the transcient response of conductivity for SnO 2 thin films at 773 K in air containing 0.35 vol % H 2 .

An increase in the conductivity of SnO{sub 2} thin film by applying a strong magnetic field was observed when a H{sub 2}-O{sub 2} reaction was proceeding on the SnO{sub 2} surface in an oxygen atmosphere at 773 K. The rate of increase in the conductivity was proportional to the square of the magnetic field intensity and was independent of H{sub 2} concentration. The rate was approximately 2.3% at 5 T. The conductivity remains unchanged when no reaction or a CH{sub 4}-O{sub 2} reaction occurred on the SnO{sub 2}. Hence, it can be concluded that this phenomenon was caused by the external magnetic field effect characteristics of the H{sub 2}-O{sub 2} reaction on the SnO{sub 2} surface.

AlGaN-based deep ultraviolet light-emitting diodes (LEDs) with aluminum reflective electrodes deposited to cover both p- and n-mesh contact electrodes have been fabricated. A 1.55-fold increase in light extraction efficiency has been demonstrated. Despite their reduced contact area, the LEDs exhibited only a slight increase in forward voltage of 0.45 V at 20 mA. Also, their 50% lifetime was estimated to be about 10,000 h at 20 mA DC at room temperature by extrapolation. Owing to the reflective electrodes, a 288 nm LED with external quantum efficiency as high as 5.4% was achieved. The light output power was 4.6 mW at 20 mA.