Browsing by Author "Ikuma, Y"

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    Photosensitive oxide semiconductors for solar hydrogen fuel and water disinfection
    (Taylor and Francis Online, 2014-01-01) Nowotny, J; Atanacio, AJ; Bak, T; Belova, S; Fiechter, S; Ikuma, Y; Ionescu, M; Kennedy, BJ; Majewski, PJ; Murch, GE; Wachsman, ED
    Hydrogen is expected to become a commonly used energy carrier on the global scale in the near future. However, hydrogen as a fuel is environmentally friendly only when generated from water using renewable energy, such as solar energy. Therefore, intensive research aims to develop a new generation of solar materials, which may be used for the production of hydrogen fuel from water using solar energy. The highly promising candidates for solar energy conversion are photosensitive oxide semiconductors (POSs), particularly the TiO2-based semiconductors, which may be used for converting solar energy into the chemical energy required for hydrogen generation from water, as well as water purification (removal of microbial agents and toxic contaminants from water). The present work considers an R&D strategy for developing TiO2-based systems capable of converting solar energy into the chemical energy via water oxidation. The effect of surface versus bulk semiconducting properties on the performance of POSs is considered in terms of partial and total water oxidation. The progress requires modification of the key performance-related properties (KPPs) in order to enhance the light-induced reactivity of the POSs with water. The most recent approach in the development of POSs with enhanced performance is deposition of metallic islets of different size and shape in order to induce a plasmonic effect. The development of high-performance POSs can be achieved through a multidisciplinary approach. It is shown that defect disorder has a critical effect on the light-induced reactivity of POSs and the solar energy conversion. Therefore, defect engineering may be applied in the development of high-performance POSs. This work considers the hurdles in the development of high-performance POSs for specific applications and formulates the key questions that must be addressed to overcome these hurdles. The concepts developed for TiO2 may be expanded for other metal oxides. © 2014, Institute of Materials, Minerals and Mining and ASM International.
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    Surface segregation of niobium and tantalum in titanium dioxide. Overview
    (John Wiley & Sons, 2016-02-15) Atanacio, AJ; Ikuma, Y
    Segregation in crystals results in surface layer enrichment of selected lattice elements. The present work considers the phenomenon of segregation in solid solutions of TiO2 doped with donor-type elements, such as niobium and tantalum. The focus is on the effect of oxygen activity on segregation at elevated temperatures. It is shown that the effect of oxygen activity on the segregation-induced enrichment may be used for engineering of oxide materials in general and TiO2-based materials in particular with controlled surface composition that is required to achieve the desired reactivity and photoreactivity for energy conversion in general and solar energy conversion in particular. The development of the related surface engineering procedures requires correct determination of oxygen activity during processing and the segregation-induced concentration gradients within the surface layer.© The American Ceramic Society, 2016.Copyright © 1999-2020 John Wiley & Sons, Inc