Papers by Author: Won Kyu Han

Abstract: Lanthanum hydroxide and oxide were prepared by the precipitation method in an aqueous medium at room temperature. The precipitate was examined using thermal analysis, X-ray diffraction and Scanning Electron Microscopy to investigate the phase evaluation and the thermal transformation by decomposition. The as-precipitated powder from the precipitation method was hexagonal La(OH)3. The lanthanum hydroxide was decomposed to oxide in two-steps as La(OH)3 → LaOOH + H2O and 2LaOOH → La2O3 + H2O.

Abstract: Ag deposited Si/C composite was studied as the anode. In order to enhance the electrochemical properties of Si electrodes, which show poor cyclability as an anode in lithium ion secondary battery, the deposition of Ag prepared by electroless deposition method on the surface of the Si/C composite powder produced by high energy ball milling. Si/C composite shows overall fade in capacity which is caused by Si pulverization. However, The Ag deposited Si/C composite improves cyclability and exhibits capacity of ~590mAh/g after 30th cycle. Scanning electron microscopy(SEM) and X-ray diffraction(XRD) measurement are adapted to inspect the deposition process.

Abstract: Platinum/Palladium modified aluminide coatings prepared by aluminide pack cementation on the nickel base superalloy Inconnel 738. The platinum/palladium modified aluminide coating of cyclic oxidation behavior at 1200°C was investigated by TGA, XRD and SEM/EDS. Platinum/Palladium modified aluminide coatings showed better cyclic oxidation resistance than Platinum modified aluminide coating and palladium modified aluminide coating compared. Pt and Pd alloy played an enough role in alumina stabilization and in delaying the degradation of β-phase.