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Matsugi K.,Hiroshima University | Tomigahara K.,Hiroshima University | Choi Y.B.,Hiroshima University | Sasaki G.,Hiroshima University | Kuramoto H.,Hiroshima City Industrial Promotion Center
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy | Year: 2013

Spark sintering behaviors on mixed powders of Fe-B and Fe with low cost were investigated to develop the hard materials as substitution of WC-Co alloys. The cheap powders with mean composition of Fe-19.1 wt%B consisting of mixed phases of B, FeB, Fe2B and Fe were ball-milled for crushing the particles with 45/μm. The ball milled Fe-B powders with 10μm were 0, 10 and 50vol%Fe added (hereafter called, 100, 90 and 50FeB, respectively). The spark sintering technique was utilized to fabricate ubiquitously hard-materials compacts. The promising maximum temperatures in sintering were defined on three compacts on the basis of the optimization of their Rockwell hardness and relative density. Rockwell hardness number on C scale was changed 66 to 71 depending on Fe contents on three compacts with the densities of 92-97 %, and the value of 100 FeB compact was the same as that of WC-7.8Co. The 100, 90 and 50FeB compacts showed the fracture strain of 0.32, 0.43 and 0.53 %, or fracture stress of 345, 435 and 447 MPa, respectively, in three points bending tests at 293 K. The fracture stress and strain were 5-17% decreased and 7-9% increased, respectively, on three points bended samples at 773 K, compared with those at 293 K. Source


Miyaoka H.,Hiroshima University | Fujii H.,Hiroshima University | Fujii H.,Hiroshima City Industrial Promotion Center | Yamamoto H.,Hiroshima University | And 4 more authors.
International Journal of Hydrogen Energy | Year: 2012

Ammonia NH3 and lithium hydride LiH system releases hydrogen even at room temperature to form lithium amide LiNH2. LiNH 2 is recycled back to NH3 and LiH below 300 °C under hydrogen H2 flow condition. However, the reaction rate of the system is slow for a practical application. In this work, various kinds of transition metal chlorides were examined as a potential catalyst to improve the kinetics. For hydrogen desorption reaction, the reaction kinetics of titanium chloride TiCl3 dispersing LiH was about 8 times faster than the raw LiH, suggesting that TiCl3 possessed an excellent catalytic effect. In the case of the regeneration reaction, the reaction kinetics was also improved by the addition of TiCl3. It was mainly caused by physical effects in contrast to the hydrogen desorption process, in other words, the small crystallite and/or particle were formed by the milling with the additive. Copyright © 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Source


Matsugi K.,Hiroshima University | Tomigahara K.,Hiroshima University | Choi Y.B.,Hiroshima University | Sasaki G.,Hiroshima University | And 3 more authors.
Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy | Year: 2011

The spark sintering technique was utilized to fabricate ubiquitously hard-materials compacts which were 0, 10 and 50vol% Fe added (hereafter called, 100, 90 and 50%FeB, respectively) in as-received powders with mean composition of Fe-19.1 wt%B. Rockwell hardness number on C scale was changed 63 to 70 depending on Fe contents, and the value of 100%FeB compact was the same as that of WC-7.8Co. The 100 and 90%FeB compacts showed the fracture strain of 0.32 and 0.41 %, or fracture stress of 212 and 133 MPa, respectively, in three points bending tests at room temperature. The 100%FeB compacts had the same level in fracture stress and increment of 0.1 % in fracture strain at 773 K, compared with those obtained from the bending tests at room temperature. Dynamic friction coefficient of 90 and 100%FeB compacts was lower than that of WC-7.8%Co in pin (SK2) on disk configuration. Same values were shown in both wear loss on specimens (100%FeB or WC-7.8%Co), and SK2, which meant the similar level in these compacts for the cutting performance as the tool materials. The value of flank wear width (V B) was 0.26 mm at cutting distance of 30 m for the work material of Ti-6A1-4V using the cutting tool of 100% FeB, which meant the satisfaction for its standard value of 0.3 mm as the life of tools. Source


Matsugi K.,Hiroshima University | Hiraiwa A.,Hiroshima University | Choi Y.-B.,Hiroshima University | Sasaki G.,Hiroshima University | Kuramoto H.,Hiroshima City Industrial Promotion Center
Materials Transactions | Year: 2013

Neck-seeds among pure titanium powders were homogeneously caused by the pulse discharge as an early stage in spark sintering. Their compacts showed some characteristic microstructures by the adjustment of process parameters such as temperature-history, -amplitude and applied pressure in the following continuous current discharge. Such property-controls might be carried out on the basis of the micro phenomena caused in or between powders. The allotropic transformation of α and β phases was utilized for achievement of full density and microstructure control, as case study of property-controls on Ti compacts. Both nearly full density and characteristic microstructures were achieved by the control of heat and cool cycles in temperature-ranges below and above β transus, due to excellent thermal and load control-ability in the spark sintering equipment. The 0.2% proof and tensile strength were increased, only by rising of relative densities. In contrast, the tensile elongation and reduction of area were affected by both relative densities and microstructures. The relation among mechanical properties, density and microstructures was investigated on obtained compacts, and one method for their property-controls was proposed on the basis of this result. © 2013 The Japan Institute of Metals. Source


Tsubota M.,Hiroshima University | Hino S.,Hiroshima University | Fujii H.,Hiroshima City Industrial Promotion Center | Oomatsu C.,Hiroshima University | And 3 more authors.
International Journal of Hydrogen Energy | Year: 2010

The possibility of using ammonia as a hydrogen carrier is examined for the reaction between magnesium ammine complex MgCl2(NH3)6 and lithium hydride LiH. Sample was milled at low temperature of -40 °C to avoid decomposition of MgCl2(NH3)6 during the milling. The effects of milling time, milling speed (revolutions per minute), and catalysts on hydrogen storage properties were investigated by thermogravimetry, thermal desorption mass spectroscopy, and X-ray diffraction experiments. Experimental results indicated that a milled composite of Mg(NH3)6Cl2 and catalyzed-LiH desorbed the ∼100% H2 gas even at 125 °C in a closed system. The reverse reaction also proceeded by separately cooling MgCl2 at lower temperature than 100 °C and heating LiNH2 at 300 °C in the closed system. © 2010 Professor T. Nejat Veziroglu. Source

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