Honeycomb-layer structured Na3Ni2BiO6 as a high voltage and long life cathode material for sodium-ion batteries

Bhange, D.,Ali, G.,Kim, D. H.,Anang, D.,Shin, T.,Kim, M. G.,Kang, Y. M.,Chung, K.,Nam, K. W. Royal Society of Chemistry 2017 Journal of Materials Chemistry A Vol.5 No.3

<P>The need to find sodium ion battery (SIB) cathodes with high voltage, capacity and improved cycle life has stimulated research on sodium containing layered transition metal oxides. With this perspective, the electrochemical properties of highly ordered, honeycomb layered Na3Ni2BiO6 with a monoclinic superstructure are explored as a cathode material in SIBs. It has been demonstrated that Na3Ni2BiO6 delivers a discharge capacity of 106 mA h g(-1), having high voltage plateaus at 3.50 and 3.25 V, with marginal capacity fading after 50 cycles. Operando X-ray diffraction studies during charging/discharging reveal two reversible two-phase transition mechanisms (initial O3 phase -> P3 intermediate phase -> O1 final phase) during sodium extraction. Ex situ X-ray absorption spectroscopy reveals the charge compensation mechanism for the reversible Ni3+/Ni2+ as an active redox couple while Bi5+ being inactive during cycling. Extended X-ray absorption fine structure analysis shows highly reversible local structural changes around both Ni and Bi atoms occurring during electrochemical cycling. In addition, unique local structure changes especially around Ni atoms due to the honeycomb ordering and size mismatch between Ni2+ and Bi5+ ions are revealed by EXAFS analysis during charging and discharging, which is quite different from the local structure changes in regular layer structured NaMO2 (M = transition metals) cathode materials. The present results suggest that honeycomb layered metal oxides with the general formula, Na3M((II)) M-2(V) O-6, can be considered as candidates for high voltage and long life cathode materials for SIBs.</P>

Improving the sodium storage capacity of tunnel structured Na_xFe_xTi_2-xO₄ (x = 1, 0.9 & 0.8) anode materials by tuning sodium deficiency

Bhange, Deu S.,Ali, Ghulam,Kim, Ji-Young,Chung, Kyung Yoon,Nam, Kyung-Wan Elsevier 2017 Journal of Power Sources Vol.366 No.-

<P><B>Abstract</B></P> <P>Due to their abundance and environmentally benign nature, iron and titanium present as the most attractive potential elements for use in rechargeable sodium-ion batteries (SIBs). Accordingly, two structurally different Fe and Ti based compounds, stoichiometric NaFeTiO<SUB>4</SUB> and sodium deficient Na<SUB>x</SUB>Fe<SUB>x</SUB>Ti<SUB>2-x</SUB>O<SUB>4</SUB> (where x = 0.9, and 0.8), are explored as anode materials for SIBs. Their structure and sodium storage capacity are systematically investigated by using combined structural and electrochemical analysis. Rietveld refinement analysis reveals that the sodium deficiency leads to the structural transformation from a single-tunnel structure (NaFeTiO<SUB>4</SUB>) to a zigzag-type double-tunnel structure (Na<SUB>0.9</SUB>Fe<SUB>0.9</SUB>Ti<SUB>1.1</SUB>O<SUB>4</SUB> and Na<SUB>0.8</SUB>Fe<SUB>0.8</SUB>Ti<SUB>1.2</SUB>O<SUB>4</SUB>). The series of sodium deficient compounds bears systematic sodium ion vacancies in their structure up to 20%. Sodium deficiency in the Na<SUB>x</SUB>Fe<SUB>x</SUB>Ti<SUB>2-x</SUB>O<SUB>4</SUB> logically provides additional space for accommodating the excess sodium ions as such the Na<SUB>x</SUB>Fe<SUB>x</SUB>Ti<SUB>2-x</SUB>O<SUB>4</SUB> compounds with higher level of sodium deficiency show higher specific capacities than the stoichiometric NaFeTiO<SUB>4</SUB>. All the compounds exhibited very good electrochemical cycling stability, with minimal capacity loss during cycling. The present approach is a model example of improvement in the sodium storage capacity of the anode materials by tuning the chemical composition, and could facilitate the performance improvement of known or new electrode materials for SIBs.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Series of Na<SUB>x</SUB>Fe<SUB>x</SUB>Ti<SUB>2-x</SUB>O<SUB>4</SUB> compounds (x = 1, 0.9, and 0.8) are synthesized. </LI> <LI> Na deficiency leads to the structural change from single-to double-tunnel structure. </LI> <LI> Na deficiency logically provides an extra space for housing excess Na ions. </LI> <LI> Sodium storage capacity increases with increasing Na deficiency. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Structural characterization of various alkali cation forms of synthetic aluminosilicate natrolites

Shin, Jiho,Bhange, Deu S.,Park, Min Bum,Hong, Suk Bong Elsevier 2015 Microporous and mesoporous materials Vol.210 No.-

<P><B>Abstract</B></P> <P>The structures of the Na<SUP>+</SUP>, K<SUP>+</SUP>, Rb<SUP>+</SUP>, and Cs<SUP>+</SUP> forms of PST-3 and PST-4, two synthetic aluminosilicate natrolite zeolites with almost completely disordered and ordered distributions of framework Si and Al atoms, respectively, in both hydrated and dehydrated states have been determined using synchrotron powder X-ray diffraction and Rietveld analyses. It was found that the trivalent tetrahedral atom (T-atom) content, as well as the type of extraframework alkali metal cations and the hydration state, is a more important factor governing the framework flexibility of this family of small-pore zeolites than the T-atom distribution.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The structures of various alkali cation forms of PST-3 and PST-4 have been determined. </LI> <LI> Their framework flexibility is highly dependent on the extraframework composition. </LI> <LI> The degree of T-atom ordering alters, to a lesser extent, the framework flexibility. </LI> <LI> PST-3 and PST-4 are more flexible than TNU-3 and TNU-4, their gallosilicate analogs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Tetrahedral Atom Ordering in a Zeolite Framework: A Key Factor Affecting Its Physicochemical Properties

Shin, Jiho,Bhange, Deu S.,Camblor, Miguel A.,Lee, Yongjae,Kim, Wha Jung,Nam, In-Sik,Hong, Suk Bong American Chemical Society 2011 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.133 No.27

<P>Three gallosilicate natrolites with closely similar chemical composition but differing in the distribution of Si and Ga over crystallographically different tetrahedral sites (T-sites) show striking differences in their cation exchange performance. The ability to exchange Na<SUP>+</SUP> by the larger alkali metal cations decreases upon increasing the size of the cation, as expected, but also with the degree of T-atom ordering. To seek an insight into this phenomenon, the crystal structures of 11 different zeolites, which show variations in degree of T-atom ordering, nature of countercation, and hydration state, have been refined using synchrotron diffraction data. While the three as-made sodium materials were characterized to have a low, medium, and high degree of ordering, respectively, their pore sizes are close to the size of the bare Na<SUP>+</SUP> cation and much smaller than that of the larger alkali cations, which are nonetheless exchanged into the materials, each one at a different level. Interestingly, large differences are also manifested when the Na<SUP>+</SUP> back-exchange is performed on the dehydrated K<SUP>+</SUP> forms, with crystallographic pore sizes too small even to allow the passage of Na<SUP>+</SUP>. Although the thermodynamic data point to small differences in the enthalpy of the Na<SUP>+</SUP>/K<SUP>+</SUP> exchange in the three materials, comparison of the “static” crystallographic pore sizes and the diameter of the exchanged cations lead us to conclude that during the exchange process these zeolites undergo significant deformations that dynamically open the pores, allowing cation traffic even for Cs<SUP>+</SUP> in the case of the most disordered material. In addition to the very large topological flexibility typical of the natrolite framework, we propose as a hypothesis that there is an additional flexibility mechanism that decreases the rigidity of the natrolite chain itself and is dependent on preferential siting of Si or Ga on crystallographically different T-sites.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2011/jacsat.2011.133.issue-27/ja202739j/production/images/medium/ja-2011-02739j_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja202739j'>ACS Electronic Supporting Info</A></P>

Nickel-titanium oxide as a novel anode material for rechargeable sodium-ion batteries

Kalubarme, R.,Inamdar, A.,Bhange, D. S.,Im, H.,Gosavi, S.,Park, C. J. Royal Society of Chemistry 2016 Journal of Materials Chemistry A Vol.4 No.44

<P>Nickel-titanium oxide (NiTiO3; NTO) of an ilmenite structure that comprises a layered transition-metal octahedral structure, wherein the zigzag open tunnels are possible routes for Na intercalation, can be a potential anode material for sodium (Na) ion batteries (SIBs). In this study, nanocrystalline NTO particles that are of sizes 3 to 5 nm were prepared using a simple hydrothermal process followed by annealing, and the particles were then tested for SIB applications. The pure-NTO electrode that comprises a hexagonal crystal structure and mesoporous morphology demonstrated a reversible capacity of approximately 521 mA h g(-1) that corresponds to a coulombic efficiency of 67% in the first cycle, which further improved to similar to 98% in the following cycles, at an applied specific current of 50 mA g(-1), and stable cycling performance for 200 cycles. Further, due to the synergetic effect of the porous network structure and high surface area, the NTO electrode exhibited an exceptional rate capability, delivering a capacity of 192 mA h g(-1) at a high specific current of 4000 mA g(-1). The excellent cyclability and rate capability of the NTO electrode are attributed to the improved electronic conductivity and highly porous microstructure of the NTO material, whereby fast charge transfer and facile diffusion of the Na-ions to the active sites are enabled.</P>

Security, Vulnerability and Protection of Vehicular On-board Diagnostics

Aastha Yadav,Gaurav Bose,Radhika Bhange,Karan Kapoor,N.Ch.S.N Iyengar,Ronnie D. Caytiles 보안공학연구지원센터 2016 International Journal of Security and Its Applicat Vol.10 No.4

Recent studies have shown that ‘’hacktivists’’ can mount serious attacks on automobiles. The automotive On-Board Diagnostic (OBD) interface enables an efficient way to access information of the in-vehicle electronic system and leaves way for unauthorized access by an intruder. We discover that remote exploitation is feasible via a broad range of attack points such as mechanic tools, CD players, Bluetooth and Tire Pressure Monitoring System. Wireless communications channels allow long distance vehicle control. Finally, the paper discusses the drawbacks of Seed-Key Mechanism to authenticate and provide an extra layer of authentication to help build a safer automotive ecosystem.

新都市開發의 促進方案

申邦鉉 단국대학교 대학원 1983 學術論叢 Vol.7 No.-

The construction of a new city--which is pleasantly inhabitable-has been a human dream with the birth of city on this earth. It has become a more ardent passion than ever, since the existing city-system starts exerting ill effects and presenting injurious influence upon the agreeable inhabitation. However, the desire for new-city development, in the modern connotation, is stemmed out of the rapid urbanization, which followed the Industrial Revolution. In the mid-20-th century, nations in the world attained economic growth successfully, in various degrees, through industrialization in their economy. This resulted in the enormous population movement into industrialized city, and this intensified population concentration raised some critical issues such as the deterioration of city environment, the developmental distances between regions, and so on. In order to meet these needs and to readjust these injurious effects, a great deal of nations have adopted the new-city development as a remedy. As a promoting scheme for new-city development, the present study discusses ⅰ) the goal of development strategy, ⅱ) the expansion of housing-land, ⅲ) the reformation of city-life environment, and ⅳ) the institutional support. The goal of development strategy should notice the industrial, the commercial, the business, and the daily-living facility as well on the additionally developed building-site, and these facilities should be able to function systematically with one another through effectual population flow. As to the expansion of housing-land, this study suggests the establishment of development-pole in the collected development capacity with concentrated development strategy-rather than eith diffused development strategy. In addition, the spill-over effect from the development-pole should be taken into consideration at the same time. For the reformation of city-life environment, the completion of educational facility, the installation of commercial-business facility, and their comfortableness and security need to be supplemented in the planning. Finally, the institutional support for new-city development includes the finance for construction fund, the balanced unit-development by civilian investment. the higher priority for housing construction fund, the timely establishment of self-determining institution fro developmental administration, and the assistance by tax-benefit in the promoting scheme for new-city development proposed by this study.

비판적 사고 교육의 국내 연구동향과 시사점

방선희 한국방송통신대학교 미래원격교육연구원 2011 평생학습사회 Vol.7 No.1

비판적 사고 능력의 중요성은 교육에서 오랫동안 강조되어온 주제이다. 본 연구에서는 이에 대하여 지금까지 이루어진 국내연구의 동향을 살펴보고 이를 통해 비판적 사고 교육의 현황과 미래 연구에 대한 제안을 하고자 하였다. 연구의 대상은 2000년부터 2011년까지 12년간 이루어진 비판적 사고 교육 관련 논문 114편이며, 수집된 자료는 연구의 대상, 연구주제, 연구방법, 연구가 이루어진 환경, 연구가 적용된 전공영역의 5가지 기준에 따라 분석되었다. 본 연구에서는 이에 대한 연구 결과와 함께 비판적 사고 교육에 관한 연구의 방향을 제시하였다. 연구 결과, 첫째 주로 초등교육과 대학교육을 중심으로 다양한 연령에서 비판적 사고 교육에 대한 연구가 이루어지고 있으며 이에 따라 각 연령별 학제별 특징을 반영한 비판적 사고 교육 연구가 확충될 필요가 있다. 둘째, 비판적 사고 교육을 위한 교수방법, 수업모형과 정의 및 개념 정립에 대한 연구의 비율이 높았으며 특히 비판적 사고 능력 신장을 위한 특정 교수방법의 제안에 관한 연구가 많았다. 따라서 이에 대한 양적, 질적 검증 연구가 확충될 필요가 있으며 교수 방법 제시에 앞서 적용되는 영역의 특수성에 대한 고려가 필요하다. 셋째, 비판적 사고 성향 또는 비판적 사고 교육의 성과를 측정할 수 있는 평가 도구에 대한 연구가 확충될 필 요가 있다. 넷째, 현재까지의 비판적 사고 교육은 주로 오프라인 교육을 중심으로 연구 되었으며 따라서 온라인을 통한 비판적 사고 교육에 대한 연구가 확충될 필요가 있다. 다섯째, 다양한 교과목에서 비판적 사고 교육의 필요성을 제기하고 있으며 따라서 각 교과목별 비판적 사고 교육의 목적을 재고하고 비판적 사고 교육 방법에서 영역의 특수성 반영에 대한 논의가 필요하다. The importance of critical thinking has long been emphasized in education. This study attempts to examine the trends in Korean research so far on this subject and to present the current state of critical thinking education and future research proposals. For this, 114 papers related to critical thinking published for 12 years from 2000 to 2011 were analyzed and the collected materials were analyzed according to five standards such as the research subjects, research theme, research methodology, the environment in which research took place and the fields on which research was carried out. The study presents the results together with the future direction for research on critical thinking education. This study has found out, first, that research on critical thinking education for various age groups from primary school to universities is being carried out. Accordingly, more research on critical thinking education reflecting the characteristics of each age group and school system is necessary. Second, studies organizing the definition and concepts, teaching methodologies and class models for critical thinking education were most prevalent. In particular, much research has been carried out on proposing special teaching methodologies to foster the ability to critically think. As such, more research verifying quantitatively and qualitatively the studies so far carried out on critical thinking is necessary. Before presenting teaching methodologies, a consideration of the distinctive characteristics of the fields is necessary. Third, more research should be carried out on evaluation tools to measure the achievements of critical thinking education and the critical thinking trends. Fourth, research so far on critical thinking education has mostly been focused on off-line education and as such, more research needs to be carried out on on-line education for critical thinking. Fifth, various subjects have shown the need for critical thinking education. Therefore, the purpose of critical thinking education by subject should be surveyed and the distinctive characteristics of each field should be reflected when discussing teaching methodologies for critical thinking.

The Strong Three-body Weak Interaction Contribution in the Nonmesonic Weak Decay of p-shell Λ Hypernuclei

Bhang, H.,Ajimura, S.,Aoki, K.,Banu, A.,Fukuda, T.,Hashimoto, O.,Hwang, J. I.,Kameoka, S.,Kang, B. H.,Kim, E.,Kim, J. H.,Kim, M.,Maruta, T.,Miura, Y.,Miyake, Y.,Nagae, T.,Nakamura, M.,Nakamura, S. N. Springer-Verlag 2013 Few-body systems Vol.54 No.7

스마트 러닝 활성화를 위한 자기주도 학습 전략 연구

방선희 한국방송통신대학교 미래원격교육연구원 2012 평생학습사회 Vol.8 No.1

최근 스마트 러닝에 대한 관심이 증대됨에 따라 스마트 러닝 활성화를 위한 다양한 전략들이 제시되고 있다. 본 연구에서는 지금까지 제안된 스마트 러닝의 개념과 특징을 통해 자기주도 학습이 스마트 러닝 활성화를 위한 핵심적인 사항임을 제시하고자 하였다. 동시에 본 연구에서는 스마트 러닝 환경이 학습자의 자기주도 학습을 촉진하는 최적화된 환경이 될 수 있다고 보았다. 이를 위해 자기주도 학습의 개념과 전략을 살펴보고 이것이 현재까지 제안된 스마트 러닝 기술의 지원을 바탕으로 어떻게 구현될 수 있는지 생각해 보았다. 본 연구에서는 지금까지 제안된 자기주도 학습의 전략을 학습자의 자기주도 학습 수준에 따라 스마트 러닝 환경에서 지원하는 방안을 제시하였다. As recent interests in Smart Learning are growing, different strategies are suggested to vitalize the Smart Learning. Through concepts and features of Smart Learning suggested until now, this study shows that self-directed learning is the essence to invigorate the Smart Learning. And it confirms that Smart Learning environment is the optimum to facilitate learner’s self-directed learning experiences. To prove the aforementioned, it covers the concept of self-directed learning and its strategies and shows how they can materialize with technological supports of Smart Learning presented so far. The study shows how the Smart Learning environment supports of self-directed learning strategies according to the learner’s level of self-directed learning.