79 5 Tokiwadai

Hodogaya, Japan

79 5 Tokiwadai

Hodogaya, Japan

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Sato N.,Japan National Institute of Materials Science | Sato N.,Kyushu University | Ojima M.,University of Tokyo | Morooka S.,79 5 Tokiwadai | And 3 more authors.
Advanced Materials Research | Year: 2012

Martensite morphology such as connectivity or dispersivity in ferrite (F)/martensite (M) dual-phase (DP) steels was investigated from topological viewpoint to reveal the effect of the martensite morphology on the mechanical properties. Topological analysis permits evaluation of the microstructural connectivity and dispersivity by measuring the number of handles, independent bodies and genus, etc. The topological analysis was performed on three-dimensional (3D) reconstructed images of the microstructure with different connectivity, dispersivity, volume fraction and hardness of martensite in DP steels that were prepared by changing the intercritical annealing temperature. The connectivity and the volume fraction of martensite increased while the dispersivity and hardness of it decreased with increasing annealing temperature. The effect of connectivity and dispersivity as well as volume fraction and hardness, in particular, on work hardening behavior was individually evaluated at a given strain. © (2012) Trans Tech Publications, Switzerland.


Okazaki S.,79 5 Tokiwadai | Nakagawa H.,79 5 Tokiwadai | Murata K.,79 5 Tokiwadai | Fukuda K.,79 5 Tokiwadai
Sensor Letters | Year: 2011

A fiber-optic gas sensor device, which can detect hydrogen leakage along the fiber, was developed. The sensor device was composed of bismuth-based optical fiber (core) and sol-gel derived platinum-supported tungsten trioxide thin film (Pt/WO3 sensing clad). Operating principle is based on the absorption of evanescent-wave leaking from the fiber core into the clad region. Since the refractive index of the bismuth-based optical fiber is higher than that of tungsten trioxide, realization of the low loss evanescent-type hydrogen sensor is expected. The propagation loss of the fabricated sensor in air condition was about 0.25 dB/m. The value should be enough to realize the distributed hydrogen sensing in the range of several tens of meters. The light power propagating through the device of 5 cm length decreased by about 10% with the exposure to 10% H2/N2 gas and relatively good reproducibility was obtained. Copyright © 2011 American Scientific Publishers. All rights reserved.

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