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        • Interactions of Dimethoxy Ethane with Li<sub>2</sub>O<sub>2</sub> Clusters and Likely Decomposition Mechanisms for Li–O<sub>2</sub> Batteries

          Assary, Rajeev S.,Lau, Kah Chun,Amine, Khalil,Sun, Yang-Kook,Curtiss, Larry A. American Chemical Society 2013 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.117 No.16

          <P>One of the major problems facing the successful development of Li–O<SUB>2</SUB> batteries is the decomposition of nonaqueous electrolytes, where the decomposition can be chemical or electrochemical during discharge or charge. In this paper, the decomposition pathways of dimethoxy ethane (DME) by the chemical reaction with the major discharge product, Li<SUB>2</SUB>O<SUB>2</SUB>, are investigated using theoretical methods. The computations were carried out using small Li<SUB>2</SUB>O<SUB>2</SUB> clusters as models for potential sites on Li<SUB>2</SUB>O<SUB>2</SUB> surfaces. Both hydrogen and proton abstraction mechanisms were considered. The computations suggest that the most favorable decomposition of ether solvents occurs on certain sites on the lithium peroxide surfaces involving hydrogen abstraction followed by reaction with oxygen, which leads to oxidized species such as aldehydes and carboxylates as well as LiOH on the surface of the lithium peroxide. The most favorable site is a Li–O–Li site that may be present on small nanoparticles or as a defect site on a surface. The decomposition route initiated by the proton abstraction from the secondary position of DME by the singlet cluster (O–O site) requires a much larger enthalpy of activation, and subsequent reactions may require the presence of oxygen or superoxide. Thus, pathways involving proton abstraction are less likely than that involving hydrogen abstraction. This type of electrolyte decomposition (electrolyte with hydrogen atoms) may influence the cell performance including the crystal growth, nanomorphologies of the discharge products, and charge overpotential.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2013/jpccck.2013.117.issue-16/jp400229n/production/images/medium/jp-2013-00229n_0004.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp400229n'>ACS Electronic Supporting Info</A></P>

        • Increased Stability Toward Oxygen Reduction Products for Lithium-Air Batteries with Oligoether-Functionalized Silane Electrolytes

          Zhang, Zhengcheng,Lu, Jun,Assary, Rajeev S.,Du, Peng,Wang, Hsien-Hau,Sun, Yang-Kook,Qin, Yan,Lau, Kah Chun,Greeley, Jeffrey,Redfern, Paul C.,Iddir, Hakim,Curtiss, Larry A.,Amine, Khalil American Chemical Society 2011 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.115 No.51

          <P>The successful development of Li-air batteries would significantly increase the possibility of extending the range of electric vehicles. There is much evidence that typical organic carbonate based electrolytes used in lithium ion batteries form lithium carbonates from reaction with oxygen reduction products during discharge in lithium-air cells so more stable electrolytes need to be found. This combined experimental and computational study of an electrolyte based on a tri(ethylene glycol)-substituted trimethylsilane (<ext-link xlink:type='simple'>1NM3</ext-link>) provides evidence that the ethers are more stable toward oxygen reduction discharge species. X-ray photoelectron spectroscopy (XPS) and FTIR experiments show that only lithium oxides and no carbonates are formed when <ext-link xlink:type='simple'>1NM3</ext-link> electrolyte is used. In contrast XPS shows that propylene carbonate (PC) in the same cell configuration decomposes to form lithium carbonates during discharge. Density functional calculations of probable decomposition reaction pathways involving solvated oxygen reduction species confirm that oligoether substituted silanes, as well as other ethers, are more stable to the oxygen reduction products than propylene carbonate. These results indicate that the choice of electrolyte plays a key role in the performance of Li-air batteries.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2011/jpccck.2011.115.issue-51/jp2087412/production/images/medium/jp-2011-087412_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp2087412'>ACS Electronic Supporting Info</A></P>

        • Lithium Superoxide Hydrolysis and Relevance to Li–O<sub>2</sub> Batteries

          Wang, Hsien-Hau,Lee, Yun Jung,Assary, Rajeev S.,Zhang, Chengji,Luo, Xiangyi,Redfern, Paul C.,Lu, Jun,Lee, Young Joo,Kim, Do Hyung,Kang, Tae-Geun,Indacochea, Ernesto,Lau, Kah Chun,Amine, Khalil,Curtiss American Chemical Society 2017 The Journal of Physical Chemistry Part C Vol.121 No.18

          <P>Fundamental understanding;of reactions, of lithium peroxides and superoxides is this for :the development of Li-O-2 batteries. In context, an investigation is reported of the hydrolysis of lithium superoxide, which has recently been synthesized in a Li-O-2 battery. Surprisingly, the hydrolysis of solid LiO2 is significantly different from that of NaO2 and KO2. Unlike KO2 and NaO2, the hydrolysis of LiO2 does not produce H2O2. Similarly, the reactivity of Li2O2 toward water differs from LiO2 in that Li2O2 results in H2O2 as a product. The difference in the LiO2 reactivity with water due to the more exothermic nature of the formation of LiOH and O-2 compared with the corresponding reactions, of NaO2 and KO2. We also show that a titration method used in this study, based on reaction of the discharge product with a Ti(IV)OSO4 solution; provides a useful diagnostic technique to provide information Oh the composition of a,discharge product in a Li-O-2 battery.</P>

        • Magnetism in lithium-oxygen discharge product.

          Lu, Jun,Jung, Hun-Ji,Lau, Kah Chun,Zhang, Zhengcheng,Schlueter, John A,Du, Peng,Assary, Rajeev S,Greeley, Jeffrey,Ferguson, Glen A,Wang, Hsien-Hau,Hassoun, Jusef,Iddir, Hakim,Zhou, Jigang,Zuin, Lucia Wiley-VCH 2013 ChemSusChem Vol.6 No.7

          <P>Nonaqueous lithium-oxygen batteries have a much superior theoretical gravimetric energy density compared to conventional lithium-ion batteries, and thus could render long-range electric vehicles a reality. A molecular-level understanding of the reversible formation of lithium peroxide in these batteries, the properties of major/minor discharge products, and the stability of the nonaqueous electrolytes is required to achieve successful lithium-oxygen batteries. We demonstrate that the major discharge product formed in the lithium-oxygen cell, lithium peroxide, exhibits a magnetic moment. These results are based on dc-magnetization measurements and a lithium-oxygen cell containing an ether-based electrolyte. The results are unexpected because bulk lithium peroxide has a significant band gap. Density functional calculations predict that superoxide-type surface oxygen groups with unpaired electrons exist on stoichiometric lithium peroxide crystalline surfaces and on nanoparticle surfaces; these computational results are consistent with the magnetic measurement of the discharged lithium peroxide product as well as EPR measurements on commercial lithium peroxide. The presence of superoxide-type surface oxygen groups with spin can play a role in the reversible formation and decomposition of lithium peroxide as well as the reversible formation and decomposition of electrolyte molecules.</P>


          <i>In Situ</i> Formed Ir<sub>3</sub>Li Nanoparticles as Active Cathode Material in Li-Oxygen Batteries

          Halder, Avik,Ngo, Anh T.,Luo, Xiangyi,Wang, Hsien-Hau,Wen, J. G.,Abbasi, Pedram,Asadi, Mohammad,Zhang, Chengji,Miller, Dean,Zhang, Dongzhou,Lu, Jun,Redfern, Paul C.,Lau, Kah Chun,Amine, Rachid,Assary, American Chemical Society [etc.] 2019 The Journal of physical chemistry A Vol.123 No.46

          <P>Lithium-oxygen (Li-O<SUB>2</SUB>) batteries are a promising class of rechargeable Li batteries with a potentially very high achievable energy density. One of the major challenges for Li-O<SUB>2</SUB> batteries is the high charge overpotential, which results in a low energy efficiency. In this work size-selected subnanometer Ir clusters are used to investigate cathode materials that can help control lithium superoxide formation during discharge, which has good electronic conductivity needed for low charge potentials. It is found that Ir particles can lead to lithium superoxide formation as the discharge product with Ir particle sizes of ∼1.5 nm giving the lowest charge potentials. During discharge these 1.5 nm Ir nanoparticles surprisingly evolve to larger ones while incorporating Li to form core-shell structures with Ir<SUB>3</SUB>Li shells, which probably act as templates for growth of lithium superoxide during discharge. Various characterization techniques including DEMS, Raman, titration, and HRTEM are used to characterize the LiO<SUB>2</SUB> discharge product and the evolution of the Ir nanoparticles. Density functional calculations are used to provide insight into the mechanism for formation of the core-shell Ir<SUB>3</SUB>Li particles. The <I>in situ</I> formed Ir<SUB>3</SUB>Li core-shell nanoparticles discovered here provide a new direction for active cathode materials that can reduce charge overpotentials in Li-O<SUB>2</SUB> batteries.</P> [FIG OMISSION]</BR>

        • KCI등재

          Interfacial Layers Evolution During Annealing in Ti-Al Multi-Laminated Composite Processed Using Hot Press and Roll Bonding

          A. H. Assari,B. Eghbali 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5

          Ti-Al multi-laminated composites have great potential in high strength and low weight structures. In the present study, tri-layer Ti-Al composite was synthesized by hot press bonding under 40 MPa at 570 °C for 1 h and subsequent hot roll bonding at about 450 °C. This process was conducted in two accumulative passes to 30% and to 67% thickness reduction in initial and final passes, respectively. Then, the final annealing treatments were done at 550, 600, 650, 700 and 750 °C for 2, 4 and 6 h. Investigations on microstructural evolution and thickening of interfacial layers were performed by scanning electron microscopes, energy dispersive spectrometer, X-ray diffraction and micro-hardness tests. The results showed that the thickening of diffusion layers corresponds to amount of deformation. In addition to thickening of the diffusion layers, the thickness of aluminum layers decreased and after annealing treatment at 750 °С for 6 h the aluminum layers were consumed entirely, which occurred because of the enhanced interdiffusion of Ti and Al elements. Scanning electron microscope equipped with energy dispersive spectrometer showed that the sequence of interfacial layers as Ti3Al-TiAl-TiAl2-TiAl3 which are believed to be the result of thermodynamic and kinetic of phase formation. Micro-hardness results presented the variation profile in accordance with the sequence of intermetallic phases and their different structures.

        • KCI우수등재

          Cognitive Impairments and Associated Structural Brain Changes in Metabolic Syndrome and Implications of Neurocognitive Intervention

          Kordestani-Moghadam Parastou,Assari Shervin,Nouriyengejeh Sarah,Mohammadipour Fatemeh,Pourabbasi Ata 대한비만학회 2020 The Korean journal of obesity Vol.29 No.3

          Currently, metabolic syndrome has become a global health problem. Alterations in neurocognitive functions among patients with metabolic syndrome are important issues in this disorder. In this paper, studies on metabolic syndrome were reviewed and their importance emphasized for the benefit of experts and policy makers. Metabolic syndrome activates inflammatory mediators that disrupt brain metabolism. These mediators can be activated by metabolic inflammation and microvascular disorders and may further cause damage to the white matter and impair cognitive function. These alterations can result in serious changes in cognitive abilities. The association between cognitive changes and metabolic syndrome has been independently evaluated in several studies. In addition, some areas of research in the field of metabolic syndrome include the effectiveness of neurocognitive interventions to enhance normal behaviors or reduce risky behaviors in patients. Structural brain correlates of health-related behaviors provide a basis for designing more effective behavioral interventions by identifying the corresponding brain regions and using behavioral interventions.

        • KCI등재

          Experimental study on the water inlet and outlet position of a solar collector reservoir for maximum efficiency

          S. Khodadadi,A. Ghanavati,M. R. Assari,M. Hatami,D. D. Ganji 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.5

          An experimental study is conducted on the heat transfer in the reservoir of a solar water-heater flat-plate solar collector to obtain itstemperature distribution. A total of 29 temperature sensors are placed inside the reservoir, and 2 sensors in the water inlet and outlet passages. The effect of the inlet and outlet positions on the temperature distribution inside the reservoir is studied to obtain the best locationfor the maximum temperature range. When the inlet position is II and the outlet position is B (Fig. 3(c)), the reservoir exhibits the bestperformance because of the high temperature range and areas inside it.

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