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Numazu, Japan

Zhu C.,Hokkaido University | Nobuta A.,Hokkaido University | Saito G.,Hokkaido University | Nakatsugawa I.,Combustion Synthesis Co. | Akiyama T.,Hokkaido University
Advanced Powder Technology | Year: 2014

In this work, fine powders of spinel-type LiMn2O4 as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn2O4 products were successfully prepared by SCS with a subsequent calcination treatment at 600-1000 C. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge-discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 C had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g-1 and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn2O4 sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g-1. © 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. Source

Niu J.,Hokkaido University | Akiyama T.,Hokkaido University | Yi X.,Northwest University, China | Nakatsugawa I.,Combustion Synthesis Co.
AIChE Journal | Year: 2013

Significance: Single-phase β-SiAlON particles with submicron size were prepared via combustion synthesis (CS) using natural kaolin, Si, and Al as raw materials under a nitrogen atmosphere of 1 MPa. Kaolin could not only act as the raw material to provide the source of oxygen, but also act as the diluent to reduce the reaction temperature by eliminating the structural water during reaction process. © 2012 American Institute of Chemical Engineers (AIChE). Source

Niu J.,Hokkaido University | Yi X.,Northwest University, China | Nakatsugawa I.,Combustion Synthesis Co. | Akiyama T.,Hokkaido University
Intermetallics | Year: 2013

A novel method of producing submicron-size β-SiAlON powders by combustion synthesis using NaCl as a diluent was proposed. The combustion synthesis was carried out with the raw materials Si, SiO2, and Al powders, and varying amounts of NaCl under a nitrogen pressure of 1 MPa. Phase compositions and particle morphologies of the synthesized powders were analyzed. The results revealed that as the z-values increased, the amount of NaCl needed to complete the reaction increased, which in turn decreased the particle size of the product. With small z-values, single-phase products were obtained; however, with large z-values, NaCl and unreacted Si remained in the products due to the large amount of liquid phase. NaCl acted not only as a diluent by absorbing the heat generated by the reaction but also as a diffusion barrier between β-SiAlON particles, which greatly limited the growth of β-SiAlON crystals.©2012 Elsevier Ltd. All rights reserved. Source

Niu J.,Hokkaido University | Nakamura T.,Hokkaido University | Nakatsugawa I.,Combustion Synthesis Co. | Akiyama T.,Hokkaido University
Chemical Engineering Journal | Year: 2014

Reaction characteristics of combustion synthesis (CS) of β-SiAlON powders in a horizontal CS chamber were compared by including two types of additives (β-SiAlON and NaCl) in Si, SiO2, and Al powder raw materials. The results showed that the reaction characteristics were influenced by the additives, which exerted a strong effect on the reaction rate and the morphology of the products. At the respective maximum combustion temperatures, a relatively slow conversion rate, with a reacted fraction (η) of 58.7%, was achieved with the addition of 12mass% NaCl to the raw materials, whereas the addition of 45mass% β-SiAlON powders afforded η=88%. The NaCl additive yielded rod-like crystals, which were well developed by a long after-burn time. However, self-sintering occurred in the presence of β-SiAlON powders. The results indicate that some degree of control over the conversion rate of the reaction and the microstructures of the product can be achieved by varying the type of additives. © 2013 Elsevier B.V. Source

Niu J.,Hokkaido University | Harada K.,Combustion Synthesis Co. | Nakatsugawa I.,Combustion Synthesis Co. | Akiyama T.,Hokkaido University
Ceramics International | Year: 2014

A facile salt-assisted combustion synthesis of β-SiAlON and systematic characterization of the endothermic effects of addition of KCl, MgCl 2, and CaCl2 were investigated under a nitrogen pressure of 1 MPa. Single-phase products containing crystals with different shapes were obtained. The results indicated that the metal chlorides act as perfect diluents that effectively absorb the reaction heat via their melting and evaporation, which occur in the same temperature ranges as the two stages of the exothermic processes. In addition, the products exhibited different morphologies when the type or amount of metal chlorides was changed. The results of this work suggest that single-phase β-SiAlON could be fabricated with the intended morphology by simply adding different kinds of metal chlorides. © 2013 Elsevier Ltd and Techna Group S.r.l. Source

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