Utsunomiya University

About: Utsunomiya University is a education organization based out in Utsunomiya, Japan. It is known for research contribution in the topics: Laser & Holography. The organization has 4139 authors who have published 6812 publications receiving 91975 citations. The organization is also known as: Utsunomiya daigaku.

Photoluminescence in hexagonal silicon carbide by direct femtosecond laser writing.

Abstract: Direct femtosecond laser writing has been used to produce localized regions of photo-luminescent emission in 4H- and 6H-silicon carbide (SiC). Arrays of active color centers were fabricated by different pulse laser energies in the sites of square grids at various depths (from surface level to 10 μm below surface). We optically characterized the fabricated color centers using confocal imaging with 532 and 780 nm excitation, photo-luminescence spectroscopy, and lifetime decay at room temperature. We show that the technique can produce specifically the silicon vacancy color center emitting in the range 850–950 nm and other emitters in the 700 nm. This method can be adopted to engineer color centers in (SiC) at different depths in the material for single-photon generation, sensing, display fabrication, and light emitting diodes.

A parallel object-oriented total architecture: A–NET

Abstract: A-NET is a parallel object-oriented total architecture for highly parallel computation. Starting with a computation model, this paper describes parallel constructs of the designed language, called A-NETL; the A-NETL oriented machine instruction set architecture; the hardware organization of a node processor, which consists of a 40-bit processing element and a router; and a local operating system on each of the node processors. Statistics for the designed language and the machine are derived from experimental results. Keywords: parallel object-oriented, total architecture, multicomputer, processing element, router, parallel operating system

The Active Phase of Nickel/Ordered Ce2Zr2OxCatalysts with a Discontinuity (x=7-8) in Methane Steam Reforming

Abstract: In recent years, there has been a surge in interest in syngas (H2/CO) and H2 production technologies, which utilize a wide variety of hydrocarbon feed stocks, such as gasoline, diesel, LPG, natural gas, methanol, and bio-ethanol. Among fossil fuels, natural gas ( 90 vol% CH4) is the ideal fuel, owing to its ready availability, high energy density, and wide distribution network; CH4 activation and reforming provide attractive ways to produce syngas, which can be transformed to useful larger hydrocarbons. Catalysts based on both noble metals and other metals have been extensively studied for CH4 steam reforming. [1, 2] Noble-metal (Rh, Ru, Ir, Pd, and Pt) catalysts are active and stable; however, because of the limited supply and high cost of noble metals, much attention has been paid to the development of non-noble metal catalysts, among which nickel-based catalysts have attracted particular attention because of their similar mechanistic features to noble-metal catalysts. The strong C H bonds of CH4 (439 kJmol ) and endothermic heat of reforming reactions necessitate high temperatures for practical CH4 conversion, and thus stable catalysts that resist sintering under extreme operating conditions. In CH4 steam reforming, coke formation that deactivates the catalyst is thermodynamically favored at a H2O/CH4 ratio less than 1.4. Thus, industrial CH4 steam reforming is usually carried out at a H2O/CH4 ratio of 1.4 or greater. Although catalytic CH4 steam reforming at low H2O/CH4 ratios have many advantages from operational and energy-consuming viewpoints, conventional nickel-based catalysts suffer from severe carbon deposition under such conditions. Supports and additives (for example, CeO2, ZrO2, CeO2-ZrO2, and La2O3) have been used to confer catalysts with kinetic resistance to carbon deposition and Ni sintering because they enhance redox activity and thermal stability, thereby promoting steam reforming. The efficient CH4 upgrading has long been a challenge in fundamental research. Herein, we report the unique properties and active phase of a new Ni/ordered Ce2Zr2Ox (x = 7–8) catalyst with a regular arrangement of Ce and Zr ions in CH4 steam reforming to produce H2 and CO at H2O/CH4 = 1. The catalytic performance of Ni/Ce2Zr2Ox (x = 7–8) strongly depends on the phase and oxygen content of Ce2Zr2Ox, and it shows a unique discontinuity in catalytic activity at x = 7.5. The 2 wt % Ni/pyrochlore-Ce2Zr2O7 catalyst showed a remarkable performance in CH4 steam reforming at 923 K at H2O/CH4 = 1 (Table 1). Ni/CeO2, Ni/ZrO2, and Ni/CeO2ZrO2 reduced by H2 were much less active and selective than Ni/Ce2Zr2O7, and significant deactivation was observed probably owing to Ni sintering and carbon deposition. On the other hand, the Ni/pyrochlore-Ce2Zr2O7 catalyst was stable, resulting in a remarkably high catalytic performance (for a typical 50 h performance, see the Supporting Information, Figure S4). At 973 K, the Ni/Ce2Zr2O7 catalyst exhibited high CO selectivity of 96–98% and high H2 selectivity of 96– 99% at CH4 and H2O conversions of 92–94% and > 96 %, respectively. Platinum, a typical noble metal active for CH4 steam reforming, was supported on CeO2, ZrO2, or Ce2Zr2O7, but the performance was not significantly enhanced by these types of supports, and the CH4 conversion on these Pt-based catalysts ranged between 29 % and 39 %. For Pt-based catalysts, CH4 steam reforming may be controlled by Pt rather than by the nature of the support. 8] In the presence of 0.8% O2 in the reaction feed, the Ni/ Ce2Zr2O7 catalyst also exhibited high H2 selectivity (97–99%) at a CH4 conversion of 93–94 % for at least 10 h. No significant deactivation was observed. These are great advan[*] Dr. M. Tada, Dr. S. Zhang, N. Ishiguro Institute for Molecular Science 38 Nishigo-naka, Myodaiji, Okazaki, Aichi 444-8585 (Japan) E-mail: mtada@ims.ac.jp