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Due to the reduced thickness of thin films formed via atomic layer deposition, analyzing their true mechanical properties is difficult. To overcome this drawback, tensile tests on free-standing alumina thin films floating on water were conducted to measure their mechanical properties. Tensile tests on alumina thin films formed at different deposition temperatures were also conducted; the results indicated that higher Young's modulus and the strength were obtained from thin films formed at higher deposition temperatures. Factors responsible for the variations in mechanical properties were investigated through analyses of the structure, density, and composition of the films.

Aerogels have the lowest thermal conductivity (

This study evaluates the performance and stability of Pt cathodes, which are treated by infiltrating cerium oxide (CeOx) onto their surfaces, in polymer electrolyte membrane fuel cells. The concentration of CeOx on the surface of Pt is adjusted by varying the concentration of the cerium precursor in the infiltration solution. The peak power density of the cell using the Pt cathode featuring the optimal amount of infiltrated CeOx is as high as 400 mW cm−2 at 70 °C, which is approximately 40% higher than that of the cell using the untreated Pt cathode under identical test conditions. Electrochemical impedance analysis confirms that this increase in peak power density is clearly attributed to the decrease in cathodic polarization impedance, which implies that the CeOx deposited on the surface of Pt enhances the catalytic performance of Pt. The infiltration of CeOx on the surface of Pt is also confirmed to be truly effective for improving the stability of Pt. Accelerated degradation tests demonstrate that the degradation rates of the cells using CeOx-Pt cathodes are significantly lower than that of the cell using the untreated Pt cathode because of the preservation of electrochemically active sites, as revealed by cyclic voltammetry.

Recently, atomic layer deposition (ALD) has drawn much attention as a suitable tool for fabrication and engineering of high performance fuel cell catalysts and electrodes. Intrinsic merits of ALD enable synthesis of conformal and uniform film even at a sub-nm scale with excellent stoichiometry control and reproducibility. Leveraging the unique characteristics, ALD has proven its promising potential as a solution to achieve two major challenges of solid oxide fuel cell research: sluggish kinetics at low operational temperatures and long-term stability. In this review, recent efforts to address the challenges by the use of ALD-based functionalization of surfaces and interfaces of cell components are discussed.

In this study, wind-battery hybrid power systems are designed, evaluated, and optimized for regular supply of electrical power at a designated minimum load level with no shortage. Our simulation uses lead-acid batteries and vanadium redox flow batteries (VRBs) for storage, and utilizes hourly wind speed data measured in 2012 at Mt. Taegi in South Korea. Twenty Vestas V80 wind turbines, each rated at 2 MW, are used as power generators, on the basis of an actual wind turbine project recently installed at Mt. Taegi. Sale to the main grid of electricity generated in excess of the minimum load offset the initial capital costs for installation of the wind turbines and batteries. Results show that the optimized wind-VRB hybrid system can supply more than 9 MW of regular electrical power at no cost. Even higher levels of production are profitable with sale of the wind-generated electricity directly to a demand site at a price greater than the price of sales to the main grid. A reduction in the VRB electrolyte costs and an increase in carbon taxes can also increase profitability.

Highly c-axis-oriented (Sr,Ba)Nb2O6 (SBN) films were grown on a seeded MgO(100) substrate via sol-gel method. The substrate was preseeded with epitaxial islands of SBN made by breaking up a continuous film into single-crystal islands by pores. Since the number of epitaxial nuclei was increased at the interface between the film and the substrate, the film on a seeded substrate had better highly orientation than that on unseeded substrate. The film having low Sr content exhibited better epitaxial growth because of the distorted unit-cell network and the change of lattice parameters of SBN thin film. For obtaining excellent optical properties, SBN:75 film was prepared on MgO substrate with SBN:25 composition seed layer. Because of low birefringence of refractive indices in the film having high Sr content, the optical scattering loss by the anisotropy of refractive indices was suppressed.

Highly oriented lead lanthanum titanate (PLT) thin films on MgO (100) and c-plane sapphire single-crystal substrates have been prepared using the sol-gel process. The orientation and the mechanism of the highly preferred oriented PLT films derived sol-gel process have been investigated. The sol-gel PLT films fabricated on MgO (100) and c-plane sapphire substrates grow preferentially with (100) and (111) crystallographic orientations respectively, regardless of the film thickness and La content. In addition, it is confirmed that the tetragonality of the PLT perovskite structure decreases with an increase of La content. The a-axis orientation of the sol-gel PLT film on MgO (100) substrate is controlled only by formation of the intrinsic tensile stress during the crystallization of the film.

Lead lanthanum titanate [(Pb,La)TiO{sub 3}] sol-gel films have been prepared to investigate the effect of heat treatment on the fabrication of uniform and crack-free thick films by applying different heating schedules. The surface morphology as well as the optical properties such as refractive index, optical transmission, and optical propagation loss of the films was examined depending on the film thickness. Because the slower and longer heating is enough to remove the organic and nitrate residues and diminish the thermal shock during heating the films, the slower and longer heating can produce the uniform and crack-free thick films having higher refractive index as well as lower optical propagation loss. Also, the drying and heating the films on hot plate in every coating resulted in the fabrication of thick films having above 8000 {Angstrom} without any defects and microcracks. This film presented the highest refractive index as well as the lowest optical propagation loss which grows exponentially with increasing the film thickness due to the scattering of defects in the film. {copyright} {ital 1997 Materials Research Society.}

Photobleaching of the optical absorption band in the 5-eV region of sol-gel-derived germanium oxide glass thin films was examined with the irradiation of the 5-eV light. The photobleaching represented by the saturated absorption coefficient change (−Δα) and the ratio of the neutral oxygen monovacancies to neutral oxygen divacancies concentrations for the germanium oxide were 175 cm−1 and 0.113, respectively. These values are larger than those of the pure germanium oxide bulk glass as well as germanosilicate thin films. The changes in bonding configuration around Ge atom by ultraviolet illumination were analyzed using x-ray photoelectron spectroscopy.