福室 直樹

Proton-exchange-membrane hydrogen fuel cells (PEMFCs) are an important energy device for achieving a sustainable hydrogen society. Carbon-based catalysts used in PEMFCs’ cathode can degrade significantly during operation-voltage shifts due to the carbon deterioration. The longer lifetime of the system is necessary for the further wide commercialization of PEMFCs. Therefore, carbon-free catalysts are required for PEMFCs. In this study, highly crystallized conducting Sb-doped SnO2 (Sb-SnO2) nanoparticles (smaller than 7 nm in size) were synthesized using an ozone-assisted hydrothermal synthesis. Pt nanoparticles were loaded on Sb-SnO2 supporting particles by polyol method to be “Pt/Sb-SnO2 catalyst”. The Pt/Sb-SnO2 catalyst showed a high oxygen reduction reaction (ORR) mass activity (178.3 A g−1-Pt @ 0.9 V), compared to Pt/C (149.3 A g−1-Pt @ 0.9 V). In addition, the retention ratio from the initial value of electrochemical surface area (ECSA) during 100,000-voltage cycles tests between 1.0 V and 1.5 V, Pt/SnO2 and Pt/Sb-SnO2 catalyst exhibited higher stability (90% and 80%), respectively, than that of Pt/C catalyst (47%). Therefore, the SnO2 and Sb-SnO2 nanoparticles synthesized using this new ozone-assisted hydrothermal method are promising as carbon-free catalyst supports for PEMFCs.

Fully printable carbon-based multiporous-layered-electrode perovskite solar cells (MPLE-PSCs) are easy to fabricate and have excellent durability. In this study, the porosity of the mesoporous TiO2 layer as the electron transport layer in MPLE-PSCs was controlled by varying the particle diameter of TiO2 nanoparticles from 14 nm to 98 nm. Furthermore, the results of absorbed photon-to-current conversion efficiency, visible light reflectance spectroscopy, pore-size distribution, X-ray diffraction, field emission scanning electron microscopy, and photovoltaic parameters of MPLE-PSCs are discussed. Although the porous TiO2 layer with smaller nanoparticles showed higher photoabsorption, it was found that the more voids of perovskite crystals created in the TiO2 porous layer, the smaller the particle size (<18 nm). The porous TiO2 layers with particles over 26 nm are well filled with perovskite crystals, resulting in a higher photovoltaic capacity with TiO2 particles over 26 nm. As a result, the short-circuit current density (JSC) showed a maximum value using 43 nm TiO2 particles, with an average power conversion efficiency (PCE) of 10.56 ± 1.42%. Moreover, the PCE showed a maximum value of 12.20% by using 26 nm TiO2 nanoparticles.

We found that an AAA-type battery (min. 750 mAh) pressurized with Ar or N₂ at pressures of up to 5 MPa exhibited a significant durability enhancement even under high-current conditions.

In electroless nickel-phosphorus plating (ENPP), growth of the plated layer under high pressure was found to be faster than under ambient pressure. To quantitatively elucidate the effect of high pressure on the mechanism of the ENPP reaction, we propose a kinetic model that takes into account both mass transfer and reaction of the chemical species present in the plating solution. We solved the mass balance equations between the chemical species to calculate the transient changes in the thickness of the plated layer as well as the concentrations of the chemical species in the plating solution. By fitting the calculated results to the experimentally acquired results based on the nonlinear least square method, we determined such parameters as the film mass transfer coefficient, the adsorption constants, and the reaction rate constants of the chemical species in the model. As a result, we found that the film mass transfer coefficient under high pressure was greater than that under ambient pressure and revealed the dependence of the coefficient on pressure. The transient changes in the concentrations of the chemical species in the plating solution that we calculated based on the kinetic model employing our estimated parameters closely modeled the experimental results with the determination coefficients being mostly over 99%.

Ferromagnetic magnetite (Fe<inf>3</inf>O<inf>4</inf>) thin films for magnetoelectric multiferroic applications were deposited on (200) (Bi<inf>3.25</inf>Nd<inf>0.65</inf>Eu<inf>0.10</inf>)Ti<inf>3</inf>O<inf>12</inf>(BNEuT)/(101) Nb:TiO<inf>2</inf>substrates by metalorganic chemical vapor deposition (MOCVD) using an iron(III) tris(2,2,6,6-tetramethyl-3,5-heptanedionato) precursor as the iron source. The BNEuT film utilized as a ferroelectric template material was in the form of freestanding nanoplates with narrow spaces between them. The effects of deposition conditions such as the deposition time and substrate temperature on the magnetic and structural characteristics of the Fe<inf>3</inf>O<inf>4</inf>/BNEuT composite films were investigated. All the films consisted of mostly single-phase Fe<inf>3</inf>O<inf>4</inf>with a cubic inverse-spinel structure. When deposition was carried out at temperatures of 400–420 °C, the filling rates of particles introduced into the narrow spaces between the BNEuT nanoplates exhibited high values of 76–89% including the amorphous phase. This suggested that the deposition in this temperature range made progress according to the growth mechanism of MOCVD in the surface reaction rate determining state. Room-temperature magnetic moment–magnetic field curves for Fe<inf>3</inf>O<inf>4</inf>thin films deposited at 400–500 °C for 60 min exhibited narrow rectangular hysteresis loops, indicating typical soft magnetic characteristics.

&emsp;日本金属学会誌 第79巻 第 3 号(2015)78&ndash;81<br> <br> &emsp;80頁Fig. 2(f)のプロットが誤っておりましたので，訂正いたします． <br>

By immersion of silicon into a solution containing metal-salt and hydrofluoric acid, fine metal particles are deposited onto the silicon surface by electroless displacement reaction. The particle density of deposited metal varies widely depending on the kind of metal and the surface condition of silicon substrates. The platinum particle density changes to an especially large degree according to silicon surface conditions. This study revealed the relation of deposition time to platinum particle density deposited by electroless displacement deposition on argonplasma-etched Si surfaces. Single-crystalline n-Si（100）wafers were chemically pretreated and were then etched with argon plasma using a radiofrequency glow discharge spectrometer. The electroless displacement deposition of platinum particles onto the silicon surface proceeds by immersion of silicon wafers into a hexachloroplatinic（IV）acid solution containing hydrofluoric acid. Platinum particles were deposited in the progressive mode until 450 s, and reached 10¹¹ cm^－2. The particle density was decreased by immersion longer than 450 s, and was maintained at 10¹⁰ cm^－2 after 900 s. Dimples appeared on the silicon surface by immersion for 600 s and longer. Dimples were formed by local anodic dissolution of silicon under the platinum particles. The initial increase and posterior decrease in the particle density are explained, respectively, as the influence of argon-plasma etching and the dissolution of the influenced region of a silicon wafer.