Papers by Author: Sang Woo Lee

Abstract: A study on the refining of nickel sulfate solution from sulfuric acid leached solution of spent lithium ion battery and fabrication of nickel nanopowders from the nickel sulfate solution was investigated. the nickel sulfate solution with high purity (>99.9%) was refined by precipitation method and solvent extraction method. the nickel nanopowders were synthesized by liquid phase reduction method with hydrazine and sodium hydroxide. the purity of nickel sulfate solution and nickel nanopowders were measured by EDTA(ethylenediaminetetraacetic) titration method with ICP-OES(inductively coupled plasma optical emission spectrometer). morphology, particle size and crystal structure of the nickel nanopowder was observed using transmission electron microscopy and x-ray diffraction spectroscopy.

Abstract: An investigation is reported by coating BaMgAl10O17:Eu2+ phosphor by silicon oxide using catalyzed atomic layer deposition. Nanoscaled SiO2 films were prepared at room temperature using tetraethoxysilane (TEOS), H2O and NH3 as precursors, reactant gas and catalyst, respectively. AES analysis showed the surface composition of coated phosphor was silicon oxide. In TEM and FE-SEM analysis, the growth rate was about 0.7 Å/cycle and the surface morphology became smoother and clearer than that of uncoated phosphor. The photoluminescence intensity (PL) increased up to 11.04% as ALD cycle increased up to 200 ALD cycle. This means that the reactive surface of uncoated phosphors is uniformly grown with stable silicon oxide to reduce the dead surface layer without change of bulk properties. Moreover, it is found that nanoscaled SiO2 films are quite effective for the improvement of the aging characteristics of photoluminescence.