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Soon, Jiyong,Lee, Tae Jin,Kim, Hyun-seung,Jung, Jiwon,Ryu, Ji Heon,Oh, Seung M. The Electrochemical Society 2017 Journal of the Electrochemical Society Vol.164 No.12
<P>A small amount of copper (II) oxide (CuO) powder is added into a nickel-doped manganese spinel (LiNi0.5Mn1.5O4, LNMO) positive electrode to function as a hydrogen fluoride (HF) scavenger. The direct contact experiment between CuO powder and HF solution shows that CuO reacts with HF and water to form copper (II) fluoride dihydrate (CuF2 center dot 2H(2)O). In the Li/LNMO cell prepared without added CuO, HF is generated as a product of electrolyte decomposition. HF attacks the LNMO electrode to dissolve the metal and/or inorganic film components, and both processes will enlarge the electrode surface area exposed to the electrolyte solution. Consequently, the electrolyte decomposition and concomitant film deposition are continued to cause cell polarization and eventually cell failure. In the cell fabricated with the CuO-added LNMO electrode, the HF concentration in the electrolyte solution is lower due to its scavenging by CuO, thereby protecting the metal from dissolution. As a result, the change in the electrode surface area is less significant, and the electrolyte decomposition and film deposition are mitigated. The low level of film deposition reduces the cell polarization and therefore improves the cell performance. (C) 2017 The Electrochemical Society. All rights reserved.</P>
가스터빈 블레이드의 에어포일 표면균열에 미치는 불소이온세정의 영향
김형익(Hyung-Ick Kim),박홍선(Hong-Sun Park),석창성(Chang-Sung Seok),김문영(Moon-Young Kim) 대한기계학회 2005 대한기계학회 춘추학술대회 Vol.2005 No.5
The blade of the gas turbine must withstand the most severe combination of temperature, stress and environment. After certain period operation, various types of damages are easily found and the damages are identified as due to the turbine operating mode. In order to have with initially similar mechanical properties, the blade of nickel-based superalloy components is passed by a replacement repair process. The fluoride ion cleaning (FIC) process is used to assist in the successful welding repair of nickel-based superalloy components. This work is to study the FIC influence for a gas turbine blade that was serviced 25,748 EOH after first overhaul. The conditions of blade samples were observed by optical microscope and SEM, and the chemical composition of flaws in the blade was investigated by EDS. The condition of the blade was examined from the gamma prime phase morphology and size, because the gamma prime phase coarsening rate depends largely on the exposure time and temperature.
Cho, Woosuk,Kim, Sang-Min,Song, Jun Ho,Yim, Taeeun,Woo, Sang-Gil,Lee, Ko-Woon,Kim, Jeom-Soo,Kim, Young-Jun Elsevier 2015 Journal of Power Sources Vol.282 No.-
<P><B>Abstract</B></P> <P>A surface coating of SiO<SUB>2</SUB> is applied to a Ni rich LiNi<SUB>0.6</SUB>Co<SUB>0.2</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> cathode material in a bid to improve its electrochemical and thermal properties. A uniform coating is achieved through a wet process using nano-sized SiO<SUB>2</SUB> powder, and though the coated electrode is found to exhibit a reduced rate capability, its cycle performance at a high temperature of 60 °C is greatly enhanced. The effect of this SiO<SUB>2</SUB> coating is further investigated by electrochemical impedance spectroscopy, which confirms that it suppresses the growth of interfacial impedance during progressive cycles. The SiO<SUB>2</SUB> coating also demonstrates good HF scavenging ability, producing a subsequent reduction in the degradation of the active core material. The thermal properties of LiNi<SUB>0.6</SUB>Co<SUB>0.2</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> are also improved by the SiO<SUB>2</SUB> coating due to a reduction in the direct contact between the electrode and electrolyte. On the basis of these results, SiO<SUB>2</SUB> coating is considered a viable surface modification method for improving the electrochemical and thermal properties of LiNi<SUB>0.6</SUB>Co<SUB>0.2</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nano-sized SiO<SUB>2</SUB> was uniformly coated on the surface of LiNi<SUB>0.6</SUB>Co<SUB>0.2</SUB>Mn<SUB>0.2</SUB>O<SUB>2</SUB> cathode. </LI> <LI> Thermal stability and cycle performance are improved by SiO<SUB>2</SUB> coating. </LI> <LI> EIS results suggest that side reaction on interface is suppressed by SiO<SUB>2</SUB> coating. </LI> <LI> SiO<SUB>2</SUB> coating shows significant HF scavenging effect. </LI> </UL> </P>