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Hu H.E.,Wuhan University | Zhen L.,Harbin Institute of Technology | Imai T.,Japan National Industrial Research Institute of Nagoya
Journal of Materials Processing Technology | Year: 2010

The effects of deformation temperature and strain in hot rolling deformation on strain rate sensitivity of the TiNp/2014 Al composite were studied by tensile tests conducted out at 773, 798, 818 and 838 K with the strain rates from 1.7 ×10-3 to 1.7 × 100 s-1. It is shown that the curves of m value of the TiNp/2014Al composite deformed at different temperatures can be divided into two stages with the variation of strain rate, and the critical strain rates are 10-1 s-1. The optimum deformation temperature of the TiNp/2014 Al composite is near incipient melting temperature of 816 K and the optimum strain rate is a little higher than the critical strain rate. The effect of deformation temperature on strain rate sensitivity is relative to liquid phase helper accommodation. The effect of strain in hot rolling deformation on strain rate sensitivity attributes to change of microstructure and deformation mechanism. © 2010 Elsevier B.V. All rights reserved. Source


Osaki T.,Japan National Industrial Research Institute of Nagoya
Catalysis Letters | Year: 2015

The effect of Ni diameter on the rates of individual steps involved in CH4-CO2 reforming was examined on Ni/Al2O3 catalysts in the diameter range of ca. 4-22 nm. It was revealed that CO2 dissociation to give CO and Oads was improved by decreasing the diameter. This may result in increasing the number of adsorbed oxygen species per active site of catalyst, which may consequently enhance the oxidation of CHx,ads to CHxOads. Furthermore subsequent rate-determining step, CHxOads → CO + x/2H2, was also promoted by decreasing the diameter. The enhancement of these elementary steps was considered a cause for the increase of turnover frequency with decreasing nickel diameter. Gasification of deposited carbons by CO2, i.e., the reverse Boudouard reaction, was also improved by decreasing the size of nickel. Although suppression of coking on fine nickel may primarily be due to the retardation of graphite nucleation, improvement of the reverse Boudouard reaction may also contribute to the carbon-free reforming to a certain degree. (Chemical Equation Presented). © 2015 Springer Science+Business Media. Source


Osaki T.,Japan National Industrial Research Institute of Nagoya
Catalysis Letters | Year: 2015

Abstract: The effect of Ni diameter on the rates of individual steps involved in CH4–CO2 reforming was examined on Ni/Al2O3 catalysts in the diameter range of ca. 4–22 nm. It was revealed that CO2 dissociation to give CO and Oads was improved by decreasing the diameter. This may result in increasing the number of adsorbed oxygen species per active site of catalyst, which may consequently enhance the oxidation of CHx,ads to CHxOads. Furthermore subsequent rate-determining step, CHxOads → CO + x/2H2, was also promoted by decreasing the diameter. The enhancement of these elementary steps was considered a cause for the increase of turnover frequency with decreasing nickel diameter. Gasification of deposited carbons by CO2, i.e., the reverse Boudouard reaction, was also improved by decreasing the size of nickel. Although suppression of coking on fine nickel may primarily be due to the retardation of graphite nucleation, improvement of the reverse Boudouard reaction may also contribute to the carbon-free reforming to a certain degree. Graphical Abstract: [Figure not available: see fulltext.] © 2015 Springer Science+Business Media New York Source


Hu H.E.,Wuhan University | Zhen L.,Harbin Institute of Technology | Imai T.,Japan National Industrial Research Institute of Nagoya
Materials Science and Technology | Year: 2011

Superplasticity of the TiN p/2014Al composite prepared by powder metallurgy method was investigated by tensile tests conducted at different temperatures (773, 798, 818 and 838 K) with different strain rates range from 1.7 × 10 0 to 1.7 × 10 -3 s -1. Results show that a maximum elongation of 351% is achieved at 818 K and 3×3610 -1 s -1. At different deformation temperatures, the curves of m value can be divided into two stages with the variation of strain rate and the critical strain rate is 10 -1 s -1. Superplastic deformation activation energy in the TiNp/ 2014Al composite is 417 kJ mol -1, which is related to liquid phase formation at triple points of grain boundaries and interfaces between the matrix and the reinforcement. Superplastic deformation mechanism of the TiN p/2014Al composite is grain boundary sliding accommodate mechanism when the strain rate is lower than 10 -1 s -1, and transfers to grain boundary sliding accommodation mechanism plus liquid phase helper accommodation mechanism when the strain rate is higher than 10 -1 s -1. © 2011. Source


Sakai T.,Fukuoka Dental College | Okamura K.,Fukuoka Dental College | Watazu A.,Japan National Industrial Research Institute of Nagoya | Teraoka K.,Japan National Industrial Research Institute of Nagoya | Kido H.,Fukuoka Dental College
Journal of Hard Tissue Biology | Year: 2013

The aim of this study was to develop experimental titanium implants sputter-coated from a hydroxyapatite target and to evaluate peri-implant tissue responses in an animal experiment. The experimental implants were prepared from plastic rods, each of which was 1.6 mm in diameter and 7 mm in length. A thin titanium film was deposited onto the rods by DC magnetron sputtering. The surface of each rod was subsequently sputter-coated from a hydroxyapatite target by RF magnetron sputtering. The experimental implants were placed in the tibiae of 8-week-old male SD rats. Titanium-coated implants were placed as controls using the same method. Tissue samples were obtained 3, 5, 7, 10, 14, and 28 days after implant placement. Histological evaluation was performed using a light microscope, and the bone-implant contact ratios (BICs) were measured. Microstructural observations of implant-bone interfaces were made using a transmission electron microscope (TEM). Peri-implant osteoblastic activity was evaluated using samples obtained 5, 7, and 10 days after implant placement. Immunohistochemical evaluation of type I collagen, osteopontin, and osteocalcin was performed. Uniform smoothness of experimental implant surfaces was confirmed by scanning electron microscope(SEM) images. In the calcium phosphate layer, the compositional ratio of the experimental implant surface was Ca:P:O=1.0:0.79:2.8 based on the results of X-ray photoelectron spectroscopy(XPS). In the trabecular bone region, the BIC ratio was significantly higher in the experimental group than in the control group at 5, 7, 10, and 28 days after implant placement. Type I collagen, osteopontin, and osteocalcin immunostaining revealed that the experimental group tended to show positive results earlier than the control group. The results of this study suggest that surface treatment using a hydroxyapatite target and RF magnetron sputtering can enhance new bone formation during implant osseointegration. © 2013 The Hard Tissue Biology Network Association Printed in Japan, All rights reserved. Source

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