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2 Archives of Metallurgy and Materials

2 2017

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Reaction Kinetics and Morphological Study of TiNb2O7 Synthesized by Solid-State Reaction

Choi S. H., Ali B., Choi K. S., Hyun S. K., Sim J. J., Choi W. J., Joo W., Lim J. H., Lee T. H., Kim T. S., Park K. T.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2B

1051--1056

Although TiNb2O7 is regarded as a material with high application potential in lithium-ion batteries (LIBs) and solid-oxide fuel cells (SOFCs), it has been difficult to find suitable cost-effective conditions for synthesizing it on a commercial scale. In this study, TiNb2O7 compounds were synthesized by a solid state synthesis process. For stoichiometrically precise synthesis of the TiNb2O7 phase, the starting materials, TiO2 and Nb2O5 were taken in a 1:1 molar ratio. Activation energy and reaction kinetics of the system were investigated at various synthesis temperatures (800,1000,1200, and 1400°C) and for various holding durations (1,5,10, and 20 h). Furthermore, change in the product morphology and particle size distribution were also evaluated as a function of synthesis temperature and duration. Additionally, quantitative phase analysis was conducted using the Rietveld refinement method. It was found that increases in the synthesis temperature and holding time lead to increase in the mean particle size from 1 to 4.5 μm. The reaction rate constant for the synthesis reaction was also calculated.

Fabrication of a Spherical Titanium Powder by Combined Combustion Synthesis and DC Plasma Treatment

Choi S. H., Ali B., Hyun S. K., Sim J. J., Choi W. J., Joo W., Lim J. H., Lee Y. J., Kim T. S., Park K. T.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2B

1057--1062

Combustion synthesis is capable of producing many types of refractory and ceramic materials, as well as metals, with a relatively lower cost and shorter time frame than other solid state synthetic techniques. TiO2 with Mg as reductant were dry mixed and hand compacted into a 60 mm diameter mold and then combusted under an Ar atmosphere. Depending on the reaction parameters (Mg concentration 2 ≤ α ≤ 4), the thermocouples registered temperatures between 1160°C and 1710°C . 3 mol of Mg gave the optimum results with combustion temperature (Tc) and combustion velocity (Uc) values of 1372°C and 0.26 cm/s respectively. Furthermore, this ratio also had the lowest oxygen concentration in this study (0.8 wt%). After combustion, DC plasma treatment was carried out to spheroidize the Ti powder for use in 3D printing. The characterization of the final product was performed using X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and N/O analysis.