• Journal of Powder Materials
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• v.25 no.1
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• pp.48-53
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• 2018

One-dimensional rutile $TiO_2$ is an important inorganic compound with applicability in sensors, solar cells, and Li-based batteries. However, conventional synthesis methods for $TiO_2$ nanowires are complicated and entail risks of environmental contamination. In this work, we report the growth of $TiO_2$ nanowires on a Ti alloy powder (Ti-6wt%Al-4wt%V, Ti64) using simple thermal oxidation under a limited supply of $O_2$. The optimum condition for $TiO_2$ nanowire synthesis is studied for variables including temperature, time, and pressure. $TiO_2$ nanowires of ${\sim}5{\mu}m$ in length and 100 nm in thickness are richly synthesized under the optimum condition with single-crystalline rutile phases. The formation of $TiO_2$ nanowires is greatly influenced by synthesis temperature and pressure. The synthesized $TiO_2$ nanowires are characterized using field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM).

• Journal of Powder Materials
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• v.26 no.4
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• pp.319-326
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• 2019

Additive manufacturing (AM) is a highly innovative method for joining dissimilar materials for industrial applications. In the present work, AM of STS630 and Ti-6Al-4V powder alloys on medium entropy alloys (MEAs) NiCrCo and NiCrCoMn is studied. The STS630 and Ti64 powders are deposited on the MEAs. Joint delamination and cracks are observed after the deposition of Ti64 on the MEAs, whereas the deposition of STS630 on the MEAs is successful, without any cracks and joint delamination. The microstructure around the fusion zone interface is characterized by scanning electron microscopy and X-ray diffraction. Intermetallic compounds are formed at the interfacial regions of MEA-Ti64 samples. In addition, Vicker's hardness value increased dramatically at the joint interface between MEAs and Ti-6Al-4V compared to that between MEAs and STS630. This result is attributed to the brittle nature of the joint, which can lead to a decrease in the joint strength.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2002.11a
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• pp.64-66
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• 2002

• Journal of Powder Materials
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• v.17 no.1
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• pp.59-64
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• 2010

8 mol% Y-doped $SrTiO_3$ powder was synthesized by Pechini method from titanium isopropoxide, strontium nitrate, yttrium nitrate, citric acid and ethylene glycol. A $Y_2Ti_2O_7$ pyrochlore phase-free perovskite powder was obtained by calcining a polymeric resin, which was prepared from a precursor solution, at $500^{\circ}C$ in an air atmosphere. Low temperature calcination could lead to a fine-grained microstructure. In the case of a solid-state reaction, an extended heat-treatment at high temperature in a reduced atmosphere needed to obtain a single phase perovskite $SrTiO_3$.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.04a
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• pp.64-65
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• 2006

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2005.11a
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• pp.64-65
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• 2005

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.11
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• pp.1587-1591
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• 2015

For a higher definition discharge cell, the method of high speed addressing is necessary. In order to modify the surface charges, the liquefied $TiO_2$ or MgO powder is added on MgO layer in front glass and on the phosphor in rear glass in micro barrier discharge. Both the electro-optical properties and the discharge time lag characteristics are measured from 4 inch. test panel, such as the discharge voltage, current, luminance, luminous efficacy and discharge time lag. As the results, the statistic time lag is improved by about 40 %.

• Clean Technology
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• v.24 no.4
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• pp.280-286
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• 2018

In this study, the adsorption performance of vapor phase VOCs under dry conditions was evaluated by using two metal oxides, $TiO_2$ powder and $Al_2O_3$ powder. BET analysis and ammonia in-situ FT-IR analysis were used to analyze specific surface area and surface acid site. As a result, $TiO_2$ powder and $Al_2O_3$ powder had a specific surface area of $317.6m^2\;g^{-1}$ and $64m^2\;g^{-1}$, respectively. In the case of $TiO_2$ powder, many acid sites were observed on the surface. As a result of evaluating the vapor phase VOCs adsorption performance using two metal oxide powders, $TiO_2$ powder having a relatively large specific surface area and a large number of acid sites exhibited relatively good adsorption performance. In particular, it is considered that the specific surface area directly affects the adsorption performance, and further study on the effect of the acid site is required. Based on the $TiO_2$ exhibited excellent adsorption performance, it manufactured into various forms of honeycomb, hollow fiber and disc. As a result, the adsorption performance was lower than that of the powder, but it is advantageous in view of applicability. In addition, it was confirmed that the disc adsorbent having excellent thermal durability due to the characteristics of the manufacturing process stably maintains adsorption performance even at a high temperature desorption process several times.

• Journal of Powder Materials
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• v.9 no.2
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• pp.96-102
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• 2002

In the present study, equiatomic porous TiNi shape-memory alloys have been successfully prepared by self-propagating high-temperature synthesis (SHS) using elemental titanium and nickel powders. The porous TiNi alloys thus obtained have an open porous structure with about 64 vol.% porosity, and the pore size is about 1.8 mm. The effect of preheating temperature on the microstructure have been investigated. It is found that the pore size increases with increasing preheating temperature. Moreover, the preheating temperature was shown to have a significant effect on the microstructrue of the SHS-synthesized porous TiNi shape memory alloys.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2007.11a
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• pp.61-62
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• 2007

HVOF thermal spray coating of micron size Co-alloy powder has been studied for the durability improvement of high velocity spindle (HVS). Optimal coating process of this system for the best surface properties is hydrogen flow rate 75 FMR, oxygen flow rate 38-42 FMR, feed rate 30 g/min at spray distance 5 inch. Friction coefficient (FC) and wear trace (WT) decrease increasing coating surface temperature from 25$^{\circ}$C to 538$^{\circ}$C due to the higher lubricant effects of the oxides at the higher temperature. At the study of adhesion of T800 coating on a light metal alloy Ti-6Al-4V (Ti64) tensile bond strength (TBS) and tensile fracture location (TFL) of Ti64/T800 are 8,740 psi and near middle of T800 coating respectively. This shows that adhesion of Ti64/T800 is higher than the cohesion strength (8,740 psi) of T800 coating. Therefore T800 coating is strongly advisable for the surface coating on HVS such as high speed air-bearing spindle.