Journal of Powder Materials

C.K. Rhee

4 Articles

Stability and Sedimentation Properties of TiO₂ Nanoparticles: S.H. Woo, M.K. Lee, C.K. Rhee; J Korean Powder Metall Inst. 2006;13(4):263-268.; DOI: https://doi.org/10.4150/KPMI.2006.13.4.263

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In this study, the colloidal stability and sedimentation behavior of crystalline TiO_2 particles (300nm) in various organic solvents have been investigated by means of a backscattered light flux profile (Turbiscan). The backscattered light flux profiles revealed that the TiO_2 nanoparticles were readily sedimented in water, methyl alcohol, and ethyl alcohol due to a flocculation-induced particle growth, while a particle coalescence and a sedimentation of the TiO_2 nanoparticles were hardly observed in isopropyl alcohol. The migration velocities of the TiO_2 particle were measured as around 6.15/min, 12.53 m/min, 6.51m/min, and 0.18m/min for water, methyl alcohol, ethyl alcohol, and isopropyl alcohol, respectively, showing a remarkably slow migration of the TiO_2 particles in isopropyl alcohol.

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Effects of Viscosity on Dispersion Stability of Nano CoAl₂O₄ Ceramic Ink
Ji-Hyeon Lee, Hae-Jin Hwang, Jin-Ho Kim, Kwang-Taek Hwang, Kyu-Sung Han
Journal of the Korean Ceramic Society.2015; 52(6): 497. CrossRef

Synthesis of Aluminum Hydroxide Nanofiber by Electrolysis of Aluminum Plates: S.H. Woo, M.K. Lee, C.K. Rhee; J Korean Powder Metall Inst. 2006;13(2):108-111.; DOI: https://doi.org/10.4150/KPMI.2006.13.2.108

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Aluminum hydroxides were synthesized by a simple electrolytic reaction of aluminum plates. The aluminum hydroxide, boehmite (AlO(OH)), was predominantly formed in the application of electrical potential at and above 30V, while the mixture of bayerite (Al(OH)_3) and boehmite (AlO(OH)) phases were formed below 20V. The boehmite has a clear fibrous structure controlled on nanometer scale. On the contrary, the bayerite consists of the typical hourglass or semi-hourglass shaped coarse crystals as a result of aggregation of various crystals stacked together. The specific surface area of the boehmite nanofiber was markedly high, approaching at about 302;m2/g.

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Experimental Study on Microwave Drying Aluminum Hydroxide
Xuemei Zheng, Fuqin Yuan, Aiyuan Ma, Shihong Tian
Coatings.2024; 14(6): 687. CrossRef

Photocatalytic Behaviors of Transition Metal Ions Doped TiO₂ Synthesized by Mechanical Alloying: S.H. Woo, W.W. Kim, S.J. Kim, C.K. Rhee; J Korean Powder Metall Inst. 2005;12(4):266-272.; DOI: https://doi.org/10.4150/KPMI.2005.12.4.266

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Transition metal ions(Ni2+, Cr3+ and V5+) doped TiO_2 nanostructured powders were synthesized by mechanical alloying(MA) to shift the adsorption threshold into the visible light region. The synthesized powders were characterized by XRD, SEM, TEM and BET for structural analysis, UV-Vis and photoluminescence spectrum for the optical study. Also, photocatalytic abilities were evaluated by decomposition of 4-chlorophenol(4CP) under ultraviolet and visible light irradiations. Optical studies showed that the absorption wavelength of transition metal ions doped TiO_2 powders moved to visible light range, which was believed to be induced by the energy level change due to the doping. Among the prepared TiO_2 powders, NiO2+ doped TiO_2 powders, showed excellent photooxidative ability in 4CP decomposition.

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Influence of Cu modified surface states by sol gel Technique on Photocatalytic Activity of Titanium dioxide
Zulfiqar Ali, Atta ullah Shah, Zahid Ali, Arshad Mahmood
Materials Chemistry and Physics.2020; 249: 123169. CrossRef

Tribological Properties of Cu-Ni Alloy Nanopowders Synthesized by Pulsed Wire Evaporation (PWE) Method: J.S. Oh, J.H. Park, W.W. Kim, C.K. Rhee; J Korean Powder Metall Inst. 2004;11(5):376-382.; DOI: https://doi.org/10.4150/KPMI.2004.11.5.376

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Nanoscale Cu-Ni alloy nanopowders have been produced by a pulsed wire evaporation method in an inert gas. The effect of Cu-Ni alloy nanopowders as additives to motor oil on the tribological properties was studied at room temperature. The worn surfaces were characterized by Scanning Electron Microscopy (SEM) and Energy-Dispersive X-ray Spectroscopy (EDS). Cu-Ni alloy nanopowders as additives lowered coefficient of friction and wear rate. It was found that a copper containing layer on the worn surface was formed, and deposited layers of the metal cladding acted as lubricant on the worn surface, reducing the friction coefficient. It was clearly demonstrated that Cu-Ni alloy nanopowders as additives are able to restore the worn surface and to preserve the friction surfaces from wear.

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A Study on the Thermal Conductivity of Thermal Grease According to Cu-Ni Content
Haneul Kang, Hyunji Kim, Sunghoon Im, Jinho Yang, Sunchul Huh
Key Engineering Materials.2021; 880: 71. CrossRef

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