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Your search keyword '"Yoo, Bung Uk"' showing total 38 results
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38 results on '"Yoo, Bung Uk"'

36. Self-templated synthesis of hollow silica microspheres using Na2SiO3 precursor.

Author

Yoo, Bung Uk, Han, Moon Hee, Nersisyan, Hayk H., Yoon, Jong Hyun, Lee, Ki Jin, and Lee, Jong Hyeon

Subjects
*CHEMICAL templates, *MICROSPHERES, *CHEMICAL precursors, *SILICON oxide, *CHEMICAL synthesis, *PRECIPITATION (Chemistry)
Abstract

Highlights: [•] A facile synthesis has been developed to convert directly solid Na2SiO3. [•] The synthesis has been carried out at ambient pressure and temperature. [•] Hydrolysis was performed using ethanol, Na2SiO3 particles and HCl solution. [•] Other precipitants (NH4Cl, (NH4)2SO4, B2O3) were tested. [•] The particle characteristics were investigated by TGA, FE-SEM, XRD, and BET. [Copyright &y& Elsevier]

Published
2014
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37. Morphological diversity of AlN nano- and microstructures: synthesis, growth orientations and theoretical modelling.

Author

Nersisyan, Hayk H., Lee, Jong Hyeon, Kim, Hyun You, Ryu, Seunhwa, and Yoo, Bung Uk

Subjects
*ACOUSTIC surface waves, *NANOSTRUCTURES, *LIGHT emitting diodes, *MICROSTRUCTURE, *CRYSTAL symmetry, *DENSITY functional theory
Abstract

Recent developments have seen breakthroughs in zero-, one-, two-, and three-dimensional AlN micro- and nanostructures, such as nanoparticles, nanowires, nanotubes, thin films and 3D multifold symmetry crystals. The attractive electrical, optical, and thermal properties of AlN make these materials irreplaceable for microelectrochemical systems (MEMS), surface acoustic waves (SAWs) and light emitting diodes (LED). The significant interest in the field of AlN nanostructure synthesis and application encouraged us to summarise the reported data to better understand the physical and chemical aspects of AlN crystal growth processes. Four main topics are covered in this review article: (1) the morphological diversity of AlN nano- and microstructures; (2) formation mechanisms and growth dynamics; (3) theoretical simulation of growth processes based on density functional theory (DFT) and phase field (PF) modelling approaches; (4) application and devices. This article also provides a perspective on future research relevant to AlN micro- and nanostructures. [ABSTRACT FROM AUTHOR]

Published
2020
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38. Shape-controlled synthesis of titanium microparticles using calciothermic reduction concept.

Author

Kwon, Suk Cheol, Lee, Young Jun, Nersisyan, Hayk, Lee, Jong Hyeon, Ri, Vladislav, and Yoo, Bung Uk

Subjects
*TITANIUM dioxide, *SELF-propagating high-temperature synthesis, *NOBLE gases, *ACTIVATION energy, *OXIDATION-reduction reaction
Abstract

Abstract This paper reports the preparation of Ti microparticles that are angular and spherical in shape through the combustion of a TiO 2 + αCa (where α is moles of Ca) exothermic mixture in an inert atmosphere. The relationship between the combustion parameters and the properties of the resultant Ti particles is discussed with consideration of the effect of Ca concentration. Using excess amounts of Ca in the experiment was effective in modifying the shape of the particles from angular to spherical. The Ti powder was found to be well-dispersed and the diameter of individual particles ranged from 5 µm to 50 µm. Based on the combustion parameters, the activation energy for the redox reaction was calculated as ∼ 138 kJ/mol. This paper discusses the chemistry of the reduction process and highlights the effects of combustion temperature and the amount of liquid calcium on the characteristics of the Ti particles. Graphical abstract The combustion process in TiO 2 + Ca mixture developed a maximum temperature of about 1820 °C and resulted in Ti spherical particles. fx1 [ABSTRACT FROM AUTHOR]

Published
2018
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