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이규원,이철의,A. Gedanken,E. Sominski,Yu. Koltypin 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.6
We have studied the magnetic and the electric properties of La_(0.8)Sr_(0.2)MnO_3 (LSMO)nanoparticle-decorated carbon nanotubes (CNTs). The magnetic susceptibility showed a paramagnetic - superparamagnetic phase transition at TSP » 200 K with a blocking temperature of T_B ∼ 120 K, which can be attributed to the LSMO nanoparticles. At T_(SP), the charge transport taking place through the CNTs network showed a metal-insulator transition (MIT) characteristic of the LSMO nanoparticles, indicating a concomitant MIT in the CNTs triggered by the LSMO nanoparticles. In the metallic phase, the charge transport appears to be dominated by a 2D weak localization effect, which at temperatures below T_B was seen to be somewhat suppressed by the internal field. At temperatures below 50 K, a Kondo effect dominates the electric and the magnetic properties.
Sivakumar, Periyasamy,Jana, Milan,Jung, Min Gyu,Gedanken, Aharon,Park, Ho Seok The Royal Society of Chemistry 2019 Journal of materials chemistry. A, Materials for e Vol.7 No.18
<P>Nanostructured mixed multi-metal compounds (NCM) based on nickel (Ni), cobalt (Co), and manganese (Mn) are considered as promising electrode materials owing to their multiple valence states, facile accessibility to active sites, and low activation energy for electron transfer. Herein, we demonstrated the fabrication of a hexagonal nanoplate-like architecture of ternary NCM hydroxide with controlled size and composition by a facile one-pot hydrothermal process. The size and composition of the hexagonal NCM nanoplates were controlled by varying the ratio of Ni to (Co + Mn) sources. Accordingly, the maximum capacitance of the optimum NCM is 1188 F g<SUP>−1</SUP> at 1 A g<SUP>−1</SUP> with high rate capacitance due to abundant active sites of the Ni-rich phase and rapid charge transfer kinetics of the nanoplate architecture. By integrating high-capacity Ni-rich NCM hydroxide as a positive electrode with activated carbon as a negative electrode, a full cell of a hybrid supercapacitor (HSC) was configured in the enlarged voltage window of 0-1.5 V. Therefore, the HSC cells deliver the maximum energy and power densities of 42.56 W h kg<SUP>−1</SUP> and 17 791.56 W kg<SUP>−1</SUP>, respectively, showing good cycling stability with 78.8% capacity retention over 50 000 cycles and the coulombic efficiency of 100%.</P>
Rozenberg, E.,Tsindlekht, M.I.,Felner, I.,Sominski, E.,Gedanken, A.,Mukovskii, Ya.M.,Cheol Eui Lee IEEE 2009 IEEE transactions on magnetics Vol.45 No.6
<P>AC and dc magnetic measurements in temperature interval 5-350 K and at external magnetic field H les 5 T were employed to probe the finite-size and nonstoichiometry effects on magnetic ordering of La<SUB>0.5</SUB>Ca<SUB>0.5</SUB>MnO<SUB>3</SUB> half-doped manganite compound. It is shown that the complex mixed magnetic ordering in bulk samples appears to be unstable regarding the both effects. The strongest one is the size effect, suppressing the mixed order and inducing the ferromagnetic-like one, which is characteristic also for other half-doped manganites. The small variations in cation composition (nonstoichiometry), which don't influence the crystal structure, lead to strong perturbations in the mixed magnetic ordering of the bulk. The results obtained are discussed in the terms of pronounced competition of spin, charge and lattice degrees of freedom, characteristic for doped manganites.</P>
Sivakumar, Periyasamy,Jana, Milan,Kota, Manikantan,Jung, Min Gyu,Gedanken, Aharon,Park, Ho Seok Elsevier 2018 Journal of Power Sources Vol.402 No.-
<P><B>Abstract</B></P> <P>We demonstrate a facile and controllable synthesis of horn-like Co<SUB>3</SUB>O<SUB>4</SUB> nanostructures through a solvothermal process followed by calcination at different temperatures. The particle sizes and defects of the as-obtained Co<SUB>3</SUB>O<SUB>4</SUB> nanohorns are controlled with respect to calcining temperatures, while preserving the horn-like morphology. In particular, the Co<SUB>3</SUB>O<SUB>4</SUB> nanohorn electrodes prepared at 300 °C reveal the specific capacitance of ∼2751 F g<SUP>−1</SUP> and the rate capability of 46.8%, which is greater than those of materials obtained at 350, 400, and 450 °C. In order to enlarge the potential window, a hybrid supercapacitor is configured with the Co<SUB>3</SUB>O<SUB>4</SUB> nanohorn and activated carbon used as positive and negative electrodes, respectively. The as-fabricated hybrid supercapacitor shows high specific capacitance of ∼101 F g<SUP>−1</SUP> and the rate capability of 80.5%. The energy and power densities of hybrid supercapacitor are ∼31.70 W h kg<SUP>−1</SUP> and 16.71 kW kg<SUP>−1</SUP>, respectively, along with 91.37% of capacitance retention over 350,000 cycles. These energy and power densities of the hybrid supercapacitors are approximately 8.5 and 3.5 times greater than values of Co<SUB>3</SUB>O<SUB>4</SUB> symmetric supercapacitor.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Nanohorn-like Co<SUB>3</SUB>O<SUB>4</SUB> architectures are synthesized. </LI> <LI> The high specific capacitance of 2751 F g<SUP>−1</SUP> is obtained at the optimized temperature. </LI> <LI> Energy density of hybrid supercapacitor is ∼31.70 W h kg<SUP>−1</SUP>. </LI> <LI> Capacitance retention is 91.37% over 350,000 charge-discharge cycles. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kumar, V.B.,Sanetuntikul, J.,Ganesan, P.,Porat, Z.,Shanmugam, S.,Gedanken, A. Pergamon Press 2016 Electrochimica Acta Vol. No.
The formation of Ga-Pt particles and their simultaneous embedment in graphene layers was performed by sonication of molten gallium in an aqueous solution of H<SUB>2</SUB>PtCl<SUB>6</SUB> in the presence of graphene. X-ray analysis of the dry particles revealed that their composition was GaPt<SUB>3</SUB> and GaPt<SUB>2.</SUB> The synthesized Ga-Pt/G was examined as an electrode material for methanol oxidation reaction (MOR) and oxygen reduction reaction (ORR). This novel electrode showed better activity for MOR and ORR than a commercial Pt/C catalyst.
Nanometric Size Effect on Magnetic Ordering in Half-doped La0.5 Ca0.5 MnO3 Manganite: EPR Probing
M. Auslender,E. Rozenberg,A. I. Shames,D. Mogilyansky,E. Sominski,A. Gedanken,이철의 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.61
Measurements of the X-band electron paramagnetic resonance and the model fittings of the linewidth and intensity versus temperature dependences were employed to probe the finite-size effect on the magnetic ordering in half-doped La0.5 Ca0.5 MnO3 manganite. It is shown that complex mixed magnetic ordering in bulk samples, comprised of the antiferromagnetic and the charge-ordered (AFM/CO) component, together with the ferromagnetic one, appear to be unstable regarding this effect; the AFM/CO phase is suppressed in nano-samples, which agrees with the data of magnetic measurements. In addition, we have managed to show that the FM state, appearing in nano-grains, is frustrated due to (i) an AFM-like core-shell interaction and (ii) a strong spin disorder at the surfaces and core-shell transition layers.
Rozenberg, E.,Shames, A. I.,Jung, G.,Mukovskii, Ya. M.,Sominski, E.,Gedanken, A.,Lee, Cheol Eui Wiley - VCH Verlag GmbH & Co. KGaA 2007 Physica status solidi. B Vol. No.
<P>Electron spin resonance was studied on three (two bulk and one nanometer sized) samples of the same La<SUB>0.7</SUB>Ca<SUB>0.3</SUB>MnO<SUB>3</SUB> manganite compound aiming to compare their magnetic homogeneities. The results obtained show that both ceramic and single crystalline bulk samples are less homogeneous than nano-crystalline one. Except for higher homogeneity, the nano sample demonstrates also a weaker magnetic anisotropy. As a result, well pronounced coexistence of different magnetic phases (coexistence of ferromagnetic and paramagnetic resonance signals) is observed in bulk samples, while it is absent in nano. It is suggested that such strong difference is directly connected to the difference in structural state of the samples. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)</P>
Effect of water intercalation onVOxlayers in dodecylamine-intercalated vanadium oxide nanotubes
Kweon, Hyocheon,Lee, Kyu Won,Lee, Eun Mo,Park, Jitae,Kim, I-M.,Lee, Cheol Eui,Jung, G.,Gedanken, A.,Koltypin, Yu. American Physical Society 2007 Physical review. B, Condensed matter and materials Vol.76 No.4