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Kim, Sun Jae,Choi, Moon-Bong,Park, Mansoo,Kim, Hyoungchul,Son, Ji-Won,Lee, Jong-Ho,Kim, Byung-Kook,Lee, Hae-Weon,Kim, Seung-Goo,Yoon, Kyung Joong Elsevier 2017 Journal of Power Sources Vol.360 No.-
<P><B>Abstract</B></P> <P>As the solid oxide fuel cell (SOFC) technology matures, durability under real operating conditions is considered as one of the most critical issues for commercialization. The severe conditions encountered in practical operation include a large temperature gradient and generation of local hot spots within stacks. Herein, we report the degradation mechanisms of anode-supported planar SOFCs supplied by Posco Energy at elevated operating temperatures. A simple comparison of the voltage reduction rates at different operating temperatures does not appropriately represent the degree of degradation, because the rapid deterioration of the cell components at high temperatures is compensated for by the fast reaction and transport kinetics. A combination of impedance interpretation and post-mortem analysis reveals the major degradation processes that are distinctively accelerated by increasing temperature, including the chemical interaction between the cathode and electrolyte, the enlargement of the interfacial pores, the coarsening of the fine particles in the composite electrodes, the formation of interfacial cracks and Cr poisoning. Systematic analysis presented in this study provides guidelines for counteracting the unexpected temperature increase, and the database established under various extreme conditions would form the groundwork for achieving the lifetime goals of commercial SOFC systems.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Long-term stability of solid oxide fuel cells are evaluated at various temperatures. </LI> <LI> The impedance spectra are analyzed using the distribution of the relaxation time technique. </LI> <LI> The major degradation processes accelerated by increasing temperature are clarified. </LI> </UL> </P>
Kim, Si-Won,Kim, Hyoungchul,Yoon, Kyung Joong,Lee, Jong-Ho,Kim, Byung-Kook,Choi, Wonjoon,Lee, Jong-Heun,Hong, Jongsup Elsevier 2015 Journal of Power Sources Vol.280 No.-
<P><B>Abstract</B></P> <P>High temperature co-electrolysis of steam/CO<SUB>2</SUB> mixtures using solid oxide cells has been proposed as a promising technology to mitigate climate change and power fluctuation of renewable energy. To make it viable, it is essential to control the complex reacting environment in their fuel electrode. In this study, dominant reaction pathway and species transport taking place in the fuel electrode and their effect on the cell performance are elucidated. Results show that steam is a primary reactant in electrolysis, and CO<SUB>2</SUB> contributes to the electrochemical performance subsequently in addition to the effect of steam. CO<SUB>2</SUB> reduction is predominantly governed by thermochemical reactions, whose influence to the electrochemical performance is evident near limiting currents. Chemical kinetics and mass transport play a significant role in co-electrolysis, given that the reduction reactions and diffusion of steam/CO<SUB>2</SUB> mixtures are slow. The characteristic time scales determined by the kinetics, diffusion and materials dictate the cell performance and product compositions. The fuel electrode design should account for microstructure and catalysts for steam electrolysis and thermochemical CO<SUB>2</SUB> reduction in order to optimize syngas production and store electrical energy effectively and efficiently. Syngas yield and selectivity are discussed, showing that they are substantially influenced by operating conditions, fuel electrode materials and its microstructure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Steam is the primary reactant in co-electrolysis of steam/CO<SUB>2</SUB> mixtures. </LI> <LI> CO<SUB>2</SUB> contributes to the electrochemical performance near limiting currents. </LI> <LI> CO<SUB>2</SUB> reduction is predominantly governed by thermochemical reactions. </LI> <LI> Chemical kinetics and mass transport play a significant role in co-electrolysis. </LI> <LI> Syngas yield and selectivity are largely dependent on operating conditions. </LI> </UL> </P>
Ultralow thermal conductivity of β -Cu<sub>2</sub>Se by atomic fluidity and structure distortion
Kim, Hyoungchul,Ballikaya, Sedat,Chi, Hang,Ahn, Jae-Pyung,Ahn, Kiyong,Uher, Ctirad,Kaviany, Massoud Elsevier 2015 Acta materialia Vol.86 No.-
<P><B>Abstract</B></P> <P>We demonstrate a prototype thermal evolution path for liquid thermal conductivity in solids. Thermal evolution of β -Cu<SUB>2</SUB>Se shows large interstitial displacement of constituent atoms marked by glass-like transitions and an asymptotic liquid thermal transport. Using ab initio molecular dynamics (AIMD), we identify these transitions, and confirm them with in situ transmission electron microscopy and electron energy loss spectroscopy. The thermal disorder of the Cu<SUP>+</SUP> ions forms homopolar Cu–Cu bonds under a rigid Se framework, and at yet higher temperatures the Se framework undergoes thermal distortion. The non-equilibrium AIMD prediction of lattice thermal conductivity shows significant suppression of the phonon transport, in agreement with experiments and molecular behavior.</P>
Atomistic Assessments of Lithium-Ion Conduction Behavior in Glass-Ceramic Lithium Thiophosphates
Kim, Ji-Su,Jung, Wo Dum,Son, Ji-Won,Lee, Jong-Ho,Kim, Byung-Kook,Chung, Kyung-Yoon,Jung, Hun-Gi,Kim, Hyoungchul American Chemical Society 2019 ACS APPLIED MATERIALS & INTERFACES Vol.11 No.1
<P>We determined the interatomic potentials of the Li-[PS<SUB>4</SUB><SUP>3-</SUP>] building block in (Li<SUB>2</SUB>S)<SUB>0.75</SUB>(P<SUB>2</SUB>S<SUB>5</SUB>)<SUB>0.25</SUB> (LPS) and predicted the Li-ion conductivity (σ<SUB>Li</SUB>) of glass-ceramic LPS from molecular dynamics. The Li-ion conduction characteristics in the crystalline/interfacial/glassy structure were decomposed by considering the structural ordering differences. The superior σ<SUB>Li</SUB> of the glassy LPS could be attributed to the fact that ∼40% of its structure consists of the short-ranged cubic S-sublattice instead of the hexagonally close-packed γ-phase. This glassy LPS has a σ<SUB>Li</SUB> of 4.08 × 10<SUP>-1</SUP> mS cm<SUP>-1</SUP>, an improvement of ∼100 times relative to that of the γ-phase, which is in agreement with the experiments.</P> [FIG OMISSION]</BR>
Kim, Jeong Hun,Shin, Sung Soo,Noh, Ho Sung,Son, Ji-Won,Choi, Mansoo,Kim, Hyoungchul Elsevier 2017 Journal of membrane science Vol.544 No.-
<P><B>Abstract</B></P> <P>A versatile and robust process was developed for the fabrication of ceramic films in solid oxide fuel cells (SOFCs), allowing the microstructures of the films to be tailored from porous to dense. This nanoscale spray process was assisted by electrospray ionization and specific polymer additives such as polyvinyl pyrrolidone and polyvinyl butyral, and it provided a large degree of freedom for controlling the membrane microstructures of the cathode and electrolyte. The final spray-deposition-based SOFC cell, which consisted of a dense, thin electrolyte (thickness: ~4µm) and a crack-free porous cathode layer (thickness: ~10µm), exhibited notable reliability, an open-circuit voltage of ~1.11V (approaching the theoretical value), and a maximum power density of ~805mW/cm<SUP>2</SUP> at 650°C, which is substantially higher than the power-generating performances of previously reported spray-deposition-based SOFCs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The polymer-assisted electrospray deposition (PA-ESD) was developed for the ceramic membranes in solid oxide fuel cells. </LI> <LI> Applying the electrospray and polymer additives, the membranes were successfully tailored from porous to dense structures. </LI> <LI> Open-circuit voltage of ~1.11 V and peak power density of 805mW/cm<SUP>2</SUP> at 650 °C were recorded. </LI> <LI> The PA-ESD cell exhibited good durability with a degradation rate of 1.5% under constant current load at 650 °C for 100h. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
외식기업의 회복 공정성과 회복만족, 고객감정 재방문의도 간의 관계
김윤서 ( Yoonseo Kim ),김양숙 ( Yangsuk Kim ),신형철 ( Hyoungchul Shin ) 관광경영학회 2021 관광경영연구 Vol.101 No.-
The purpose of this study is to study the fairness of recovery, satisfaction of recovery, customer sentiment, and intention of revisit to consumers who have experience in recovering products and services of restaurant companies. From February 1 to March 1, 2020, the survey was conducted through the Google Online Survey. A total of 280 copies were used for the study for the results. As a result, Hypothesis 1 shows that "procedural fairness and interaction fairness will have a positive effect on recovery satisfaction." Thus, hypothesis 1 was partially adopted. For Hypothesis 2, it was shown that "distributional fairness and interaction fairness will have a positive effect on customer sentiment." Thus, Hypothesis 2 was partially adopted. For Hypothesis 3, the hypothesis was adopted that "Recovery satisfaction will have a positive effect on customer sentiment." In the case of Hypothesis 4, the hypothesis was adopted that "Recovery satisfaction will have an effect of positive on the intention of re-visiting." For Hypothesis 5, the hypothesis that "customer sentiment will have a positive effect on the intention of the revisit" was adopted. Accordingly, we understood customer needs. Therefore, we strengthen the theory of consumers' behavioral rationale for service failures. It also presents suggestions for seeking practical measures for restaurant businesses.