Protective coating based on manganese–copper oxide for solid oxide fuel cell interconnects: Plasma spray coating and performance evaluation

A solid oxide fuel cell (SOFC) stack requires metallic interconnects to electrically connect unit cells, while preventing fuel from mixing with oxidant. During SOFC operations, chromia scales continue to grow on the interconnect surfaces, resulting in a considerable increase of interfacial resistance, and at the same time, gaseous Cr species released from the chromia scales degrades the cathode performance. To address these problems, in this study, protective Mn₂CuO₄ coatings are fabricated on metallic interconnects (Crofer 22 APU) via a plasma spray (PS) process. The PS technique involves direct spray deposition of molten Mn₂CuO₄ onto the interconnect substrate and leads to the formation of high-density Mn₂CuO₄ coatings without the need for post-heat-treatment. The thickness, morphology, and porosity of the PS-Mn₂CuO₄ coating are found to depend on the processing parameters, including plasma arc power, gas flow rate, and substrate temperature. The PS-Mn₂CuO₄ coating fabricated with optimized parameters is completely impermeable to gases and has high adhesion strength on the interconnect substrate. Furthermore, no resistive chromia scales are formed at the coating/substrate interface during the PS process. As a result, the PS-Mn₂CuO₄-coated interconnects show a very low area-specific resistance below 10?mΩ?cm² at 800?°C in air and excellent stability during both continuous operation and repeated thermal cycling. This work suggests that an appropriate combination of the material and coating process provides a highly effective protective layer for SOFC interconnects.     

Genetically Modified Ferritin Nanoparticles with Bone-Targeting Peptides for Bone Imaging

Bone homeostasis plays a major role in supporting and protecting various organs as well as a body structure by maintaining the balance of activities of the osteoblasts and osteoclasts. Unbalanced differentiation and functions of these cells result in various skeletal diseases, such as osteoporosis, osteopetrosis, and Paget’s disease. Although various synthetic nanomaterials have been developed for bone imaging and therapy through the chemical conjugation, they are associated with serious drawbacks, including heterogeneity and random orientation, in turn resulting in low efficiency. Here, we report the synthesis of bone-targeting ferritin nanoparticles for bone imaging. Ferritin, which is a globular protein composed of 24 subunits, was employed as a carrier molecule. Bone-targeting peptides that have been reported to specifically bind to osteoblast and hydroxyapatite were genetically fused to the N-terminus of the heavy subunit of human ferritin in such a way that the peptides faced outwards. Ferritin nanoparticles with fused bone-targeting peptides were also conjugated with fluorescent dyes to assess their binding ability using osteoblast imaging and a hydroxyapatite binding assay; the results showed their specific binding with osteoblasts and hydroxyapatite. Using in vivo analysis, a specific fluorescent signal from the lower limb was observed, demonstrating a highly selective affinity of the modified nanoparticles for the bone tissue. These promising results indicate a specific binding ability of the nanoscale targeting system to the bone tissue, which might potentially be used for bone disease therapy in future clinical applications.     

Microwave-assisted synthesis of CaMoO4 nano-powders by a citrate complex method and its photoluminescence property

Nano-sized CaMoO₄ powders, which have scheelite type structure, were successfully synthesized at low temperatures by a modified citrate complex method using microwave irradiation. The citrate complex precursors were heat-treated at temperatures from 300 to 700 °C for 3 h. Crystallizations of the CaMoO₄ nano-sized powders were detected at 400 °C, and entirely completed at a temperature of 500 °C. Almost nano-powders of CaMoO₄ heat-treated between 400 and 600 °C showed primarily spherical and homogeneous morphology. The average crystalline sizes of CaMoO₄ were 12–27 nm at temperatures of 400–700 °C, showing an ordinary tendency to increase with the temperatures. The CaMoO₄ powders prepared at 600 °C showed the strongest photoluminescence intensity.     

Efficient and robust ceramic interconnects based on a mixed-cation perovskite for solid oxide fuel cells

To achieve a required output voltage, a solid oxide fuel cell (SOFC) stack has multiple unit cells connected in series through interconnects (ICs). A dual-layer IC film comprising p- and n-type conducting perovskite oxides is considered to be a promising design in terms of electrical properties and stability; however, its fabrication is materials-intensive and time-consuming. Here, we propose an advanced design of a single-layer IC film inspired by the interfacial nature of the dual-layer IC film. Based on an understanding of cross-diffusion phenomena across the interface between Sr_0.7La_0.2TiO₃ and La_0.8Sr_0.2MnO₃ during the co-sintering process revealed by secondary ion mass spectroscopy, we design and synthesize mixed-cation perovskite oxides, (Sr_0.6La_0.4)_0.9(Ti_1–xMn_x)O₃ (SLTM), for IC applications in SOFCs. Among various compositions, Ti-rich SLTM (x?=?0.25) shows high sinterability, leading to the formation of a thin, gas-tight IC film on a porous anode support via simple screen printing and sintering. When exposed to both reducing and oxidizing atmospheres, the fabricated SLTM-IC film is highly conductive and remains stable during continuous operation. The ceramic IC design proposed in this work may provide great benefits in terms of reduced costs of IC materials and fabrication, while maintaining the IC performance required for SOFCs.     

Kinetic behaviors of CO2 hydrates in porous media and effect of kinetic promoter on the formation kinetics

Formation behaviors of CO₂ hydrate in silica gels are investigated at various pressure and temperature conditions. In addition, a kinetic promoter of sodium dodecyl sulfate (SDS) is used in order to evaluate promotional effect on the formation behaviors in porous media. Formation rates and hydrate conversions are found to be large when higher pressure or lower temperature is used at a given temperature or at a given pressure, respectively. The formation rates are found to be affected more significantly when driving force larger than 1.0 MPa is applied. In addition, when the kinetic promoter is used, initial hydrate formation rates are found to increase so as to reach the final gas consumption more rapidly. Obtained results are expected to provide useful information for designing or evaluating a hydrate-based process using porous media.     

A review of gas diffusion layer in PEM fuel cells: Materials and designs

The gas diffusion layer (GDL) plays a key role on reactant gas diffusion and water management in proton exchange membrane (PEM) fuel cells. This paper reviews recent developments of single- and dual-layer GDLs for PEM fuel cells and various materials and approaches used for development of novel GDL. A variety of carbon- and metal-based macroporous substrates are presented. Hydrophobic treatments using different fluorinated polymers are addressed. Engineering parameters which control the performance of microporous layer such as carbon treatment, wettability, thickness, and microstructure are also reviewed. In addition, future prospects for development of new GDL development are discussed.     

A study on the potentiostatic current transient and linear sweep voltammogram simulated from fractal intercalation electrode: diffusion coupled with interfacial charge transfer

Potentiostatic current transient and linear sweep voltammogram, theoretically calculated from the well-defined fractal profiles were analysed, with particular emphasis on hydrogen transport under the condition where hydrogen diffusion in the electrode is kinetically coupled with the charge-transfer reaction at the electrode/electrolyte interface. Under such a constraint of mixed control, the simulated current transient from the fractal electrode hardly exhibited the generalised Cottrell behaviour, and, especially, it displayed an inflexion point at the time that corresponds to the temporal outer cut-off of fractality (crossover time required for the fractal to flat transition). In the case of the linear sweep voltammogram computed from the fractal electrode, moreover, the power dependence of the peak current on the scan rate deviated negatively from the generalised Randles-Sev?ik behaviour, above the slow threshold scan rate (crossover scan rate needed for the fractal to flat transition). From the analyses of the current transients and the linear sweep voltammograms calculated with various values of the simulation parameters, it was further recognised that during the potential jump as well as the potential scan, the temporal cut-off ranges of fractality under the constraint of mixed control are crucially determined by the interfacial charge-transfer kinetics, even though the spatial cut-off range and the hydrogen diffusivity in the electrode are maintained constant.     

NO2 adsorption behaviour on LaFeO3 electrodes of YSZ-based non-nernstian electrochemical sensors

X-ray photoelectron spectroscopy (XPS) was used to examine the NO₂ adsorption behaviour on the LaFeO₃ and Pt electrodes of planar yttria stabilized zirconia non-Nernstian gas sensors. The electrochemical sensors were exposed to the same gas atmosphere containing 1000 ppm NO₂ at 650°C. XPS of the as-prepared sensors and sensors after exposure to NO₂ revealed bonded nitrogen peaks on the surface of the semiconducting oxide but no nitrogen peaks on the Pt electrode. Therefore, NO₂ adsorption on a LaFeO₃ electrode plays an important role in the NO₂ detection mechanism.     

Pure color and stable blue-light emission-alternating copolymer based on fluorene and dialkoxynaphthalene

A new blue-light emitting polymer that alternates between fluorene and alkoxynaphthalene structure has been developed. The fluorene and naphthalene units were highly distorted with an angle of 76.22° according to theoretical calculations. The obtained polymer has a weight average molecular weight of 273,800 with a polydispersity index of 2.35, good solubility and high thermal stability with a T_g of 176 °C. The film photoluminescence (PL) spectrum (405 nm) is consistent with that of solution and the PL spectra of the polymer did not show any peak in the long wavelength region even after annealing for 24 h at 100 °C. The double-layered device with an ITO/PEDOT/polymer/LiF/Al structure has a turn-on voltage of about 5.4 V, maximum brightness of 110 cd/m² and an electroluminescent efficiency of 0.09 cd/A. The OLED generates pure blue EL emission (λ_max = 405 nm) with excellent CIE coordinates (x = 0.15, y = 0.10) as well as stable blue EL emission that is not altered by voltage increase.     

Adaptive mixture-of-experts models for data glove interface with multiple users

Hand gestures have great potential to act as a computer interface in the entertainment environment. However, there are two major problems when implementing the hand gesture-based interface for multiple users, the complexity problem and the personalization problem. In order to solve these problems and implement multi-user data glove interface successfully, we propose an adaptive mixture-of-experts model for data-glove based hand gesture recognition models which can solve both the problems.The proposed model consists of the mixture-of-experts used to recognize the gestures of an individual user, and a teacher network trained with the gesture data from multiple users. The mixture-of-experts model is trained with an expectation-maximization (EM) algorithm and an on-line learning rule. The model parameters are adjusted based on the feedback received from the real-time recognition of the teacher network.The model is applied to a musical performance game with the data glove (5DT Inc.) as a practical example. Comparison experiments using several representative classifiers showed both outstanding performance and adaptability of the proposed method. Usability assessment completed by the users while playing the musical performance game revealed the usefulness of the data glove interface system with the proposed method.