We demonstrate the remote detection method of oils in water by laser Raman spectroscopy. A frequency-doubled, Q-switched Nd:YAG laser at 532 nm was used as a light source, and oils in water were ...identified in the optical cells placed 2 and 4 m away in a water tank by using the Raman signals at 2910 cm−1 from oils. The results show that the configuration of underwater remote Raman spectroscopy can be a useful alternative method for detecting oil leaks from subsea pipelines, potentially providing more capability of target selectivity as compared with fluorescence detection
•Laser Raman spectroscopy is applied to the remote detection of oils in water.•Raman signals at 2910 cm−1 are detected from oils contained in a 5 mm cell.•Measurements at stand-off distances of 2 and 4 m in water are demonstrated.•The method will be useful for detecting subsea oil leaks from pipelines.
To develop more highly-efficient SOFCs, we have investigated the thickness of highly resistive layer which consist of solid solutions of CeO2–ZrO2 system generally observed between YSZ electrolyte ...and cathode-interlayer made of doped CeO2. In terms of the effect of the dopant in the CeO2-based interlayer materials on the thickness of the solid solution, the use of YDC or LDC for the interlayer results in a thinner solid solution compared to that obtained when a GDC interlayer was used. When adapted into SOFCs, I-V tests at 800°C indicated that the cell with a YDC interlayer exhibited substantially better performance than the cell with a GDC interlayer.
•The effect of dopants in the CeO2-based material on the thickness of (Ce,Zr)O2 in SOFC cells was examined.•Compared to GDC, the use of YDC and LDC can reduce the Ce diffusion distance into the YSZ electrolyte.•A cell with a YDC interlayer was confirmed to exhibit significantly improved cell performance compared to a cell with GDC.
Achievements of NEDO durability projects on SOFC mode are summarized with a focus on the physicochemical mechanisms characterized by diffusion properties of cell components and chemical reactions of ...cell components with gaseous impurities. Ni sintering and depletion including impurity (P, B, S) effects have been examined in terms of the surface/interface energies of Ni/oxide cermet anodes. The conductivity degradation due to the transformation of the cubic YSZ electrolyte was found to be characterized in terms of two time constants for the reductive and the oxidative regions to be determined by the Y‐diffusivity and its enhancement on NiO internal reduction in YSZ, while observed gaps in conductivity degradation behavior between stacks and button cells were ascribed to differences in those physicochemical properties involved, namely cation diffusion and kinetics associated with NiO internal reduction. The cathode performance degradation due to sulfur poisoning exhibits a variety of dependences on the microstructure (dense or porous) of doped‐ceria interlayers, the thickness of YSZ electrolyte and the humidity in the anode atmosphere, suggesting effects of protons in the cathode vicinity and the SrO activity changes during fabrication the LSCF/GDC/YSZ multilayers. Some defect chemical considerations were made on how such defects are affected by fabrication processes.
Direct-drive inertial confinement fusion (ICF), where a fuel capsule is imploded by high-power laser beams to cause ignition, is a promising energy production method that does not emit any greenhouse ...gases. Diamond is an ideal capsule material for direct-drive ICF. Its low compressibility and high density, which exceed those of conventional capsule materials (e.g., plastic), are advantageous for the robust implosion of fuel capsules. We are developing polycrystalline diamond capsules using the hot-filament chemical vapor deposition (HF-CVD) technique. HF-CVD is ideal for capsule fabrication for power plants of the future because it is inexpensive and amenable to mass production, as its deposition area can be extended by only increasing the number of filaments. In this study, we improved upon our previous fabrication process and obtained nanocrystalline diamond capsules of better quality. The capsules were comprehensively characterized, employing both the typical parameters (i.e., surface morphology and sp2 content) as well as parameters important for direct-drive ICF application (i.e., tungsten and hydrogen contents, capsule thickness, density, and mode amplitudes of surface roughness). The characterized hollow nanocrystalline diamond capsules were introduced into the laser experiment at the GEKKO laser facility at Osaka University, where a capsule can be spherically irradiated by 12 high-power laser beams. The experimental results showed successful implosion, and the implosion dynamics were well reproduced by radiation hydrodynamic simulation code calculations. These results verify the accurate characterization and quality of the nanocrystalline diamond capsules as being applicable to laser irradiation experiments.
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•Diamond capsule was fabricated by hot filament chemical vapor deposition.•Fabricated capsules were comprehensively characterized.•Laser experiment demonstrated successful implosion of the fabricated capsules.
As the substrate materials for segmented-in-series type solid oxide fuel cells (SOFCs), the mechanical characteristics, such as Young's modulus, of Al sub(2)O sub(3)-NiO-YSZ, TiO sub(2)-NiO-YSZ and ...MgO-NiO-YSZ were examined under SOFC operating conditions. The Young's modulus for all of the samples decreased at a high temperature. For the Al sub(2)O sub(3)-NiO-YSZ samples, the behaviours of the Young's modulus changed at each process including as-sintered, 100 h reduction and 2000 h reduction. For the TiO sub(2)-NiO-YSZ samples, the Young's modulus behaviour varied between the as-sintered and reduced samples. However, further reduction did not change the behaviour of the Young's modulus. For the MgO-NiO-YSZ samples, the Young's modulus of the samples exhibited a nearly constant behaviour through the sequence of processes from as-sintered to 100 h reduction and 2000 h reduction. Based on the microstructural analysis, the compositions of the framework of the samples and the sliding of the grain boundary stronelv affected the Young's modulus.
Laser induced breakdown spectroscopy (LIBS) based on femtosecond laser pulses has widely been used for analyzing chemical elements in samples. In this research, we achieved the double-pulse operation ...with a two-polarizer configuration, and the signal enhancement factor of 4–15 was observed as compared with the single pulse LIBS scheme. It is found that with the change in interpulse delay time between 0 and 150 ps, the laser-fluence dependence of the LIBS signal enhancement can be classified into three types that are characterized by the different behavior of linear and quadratic intensity increase, followed by the intensity saturation. Such different responses are presumably ascribable to the mechanisms of electron-ion relaxation and plasma reheating. Also, different behavior is seen for the signal enhancement with different laser intensity and beam diameter while the laser fluence is kept constant. This indicates that generally, the use of a larger beam diameter is recommended for increasing the signal enhancement factor.
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•The femtosecond double-pulse LIBS with a two-polarizer configuration.•Three types of laser-fluence dependence of the LIBS signal enhancement.•More signal enhancement using a larger beam diameter.
Residual stresses in the electrolytes of segmented-in-series solid oxide fuel cells (SIS-SOFCs) and anode-supported cells (ASCs) were estimated at room temperature by X-ray diffraction. In the ...SIS-SOFCs, the residual stresses in the electrolyte were smaller than in the ASCs and did not change significantly after redox cycling. For both designs, numerically calculated values of the residual stresses in the electrolyte were found to be comparable to the experimental results. Next, in order to simulate the reoxidation reaction, the anode was subjected to forced expansion, and the residual stresses were estimated at high temperatures. It was found that in the SIS-SOFC, the dimensional changes and residual stresses were smaller than those in the ASC. The high redox tolerance of the SIS-SOFC is considered to stem from the fact that the electrically insulated substrate prevents the expansion and deformation of the positive electrode–electrolyte–negative electrode structure.
Long‐term performance testes by CRIEPI (Central Research Institute for Electric Power Industry) on six industrial stacks have revealed an interesting correlation between cathode polarization loss and ...ohmic loss. To make clear the physicochemical meaning of this correlation, detailed analyses were made on the conductivity degradation of YSZ electrolyte in button cells and then on the ohmic losses in the industrial cells in terms of time constants which are determined from speed of the tetragonal transformation through the Y diffusion from the cubic phase to the tetragonal phase. In some cases, shorter time constants (faster degradations) were detected than those expected from the two‐time‐constant (with and without NiO reduction effects) model, suggesting that additional ohmic losses after subtracting the contribution from the tetragonal transformation must be caused from other sources such as cathode‐degradation inducing effects. Main cathode degradations can be ascribed to sulfur poisoning due to contamination in air in the CRIEPI test site. An important feature was extracted as this cathode degradations became more severe when the gadolinium‐doped ceria (GDC) interlayers were fabricated into dense film. Plausible mechanisms for cathode degradations were proposed based on the Sr/Co depletion on surface of lanthanum strontium cobalt ferrite (LSFC) in the active area. Peculiar cathode degradations found in stacks are interpreted in term of changes in surface concentration by reactions with sulfur oxide, electrochemical side reactions for water vapor emission or Sr volatilization, and diffusion of Sr/Co from inside LSCF.
The changes with time of the residual stress on the electrolyte were measured in situ during re-oxidation under solid oxide fuel cell (SOFC) operation conditions using a segmented-in-series ...(SIS)-type SOFC and a conventional anode-supported planar (ASP)-type SOFC to understand the mechanical behaviour of the materials in the SOFC. In situ X-ray residual stress measurement was successful, and the real-time change with time of the residual stress of the electrolyte was revealed under SOFC operating conditions. In the ASP-type SOFC, the residual stress changed from compression to tensile stress, and destruction of the cell was confirmed 20 min after the air introduction. In contrast, in the case of the SIS-type SOFC, the residual stress was almost constant, even when the anode material was exposed to oxidation conditions for more than 4 h. These results indicate that the SIS-type SOFC has a high tolerance against reduction and oxidation (redox) compared with the ASP-type SOFC, which requires a conductive support material with a high Ni content. This is because the SIS-type SOFC has an electrically insulated support material that does not require a high Ni content.
► We succeeded in making real-time observation of change with time of residual stress on electrolyte. ► Real-time changes with time of mechanical behaviour in anode during re-oxidation were revealed. ► In ASP-type SOFC, the destruction was observed 20 min after the beginning of re-oxidation. ► In the SIS-type SOFC, the residual stress was almost constant for more than 4 h.
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