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Kim, HunUk,Sun, Yang-Kook,Shin, Kyung Hee,Jin, Chang Soo Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>In this work, Li<SUB>4</SUB>Mn<SUB>5</SUB>O<SUB>12</SUB> was synthesized by the solution combustion method at 300, 400, 500 and 600 °C for 3, 5 and 10 h using LiNO<SUB>3</SUB>, Li(CH<SUB>3</SUB>COO)ċ2H<SUB>2</SUB>O and Mn(CH<SUB>3</SUB>COO)<SUB>2</SUB>ċ4H<SUB>2</SUB>O.</P><P>We have investigated Li<SUB>4</SUB>Mn<SUB>5</SUB>O<SUB>12</SUB> as a positive electrode for the lithium ion battery and the hybrid capacitor. Li<SUB>4</SUB>Mn<SUB>5</SUB>O<SUB>12</SUB> calcined at 400 °C for 5 h shows higher specific capacity and a capacitance of 44.2 mAh g<SUP>−1</SUP> at 1C-rate in 3.7–4.4 V and 51.9 F g<SUP>−1</SUP> (33.6 F cc<SUP>−1</SUP>) at 1 mA cm<SUP>−2</SUP> in 1.0–2.5 V, respectively. It maintains a capacitance of 99.6% after 100 cycles.</P>
Plasmon effects on the Wannier threshold law in hot quantum plasmas
Kim, Sung-Han,Jung, Young-Dae Royal Swedish Academy of Sciences 2008 Physica scripta Vol.78 No.1
<P>The effects of plasmons and screening on the Wannier threshold law for the double-electron escape into the continuum states are investigated in hot quantum plasmas. The screened renormalized electron charge is obtained by considering the equation of motion in the Wannier configuration with the effective interaction potential, taking into account the plasmon and screening effects. In addition, the screened Wannier exponent for the double-electron escape is obtained as a function of the plasmon parameter, charge of the residual ion and Debye length. It is shown that the plasmon effect increases the renormalized electron charge, especially in the screened Coulomb zone. It is also shown that the plasmon effect enhances the Wannier exponent in the small-Debye-length domain.</P>
Different behaviors of half-metallic ferromagnetism of Cr-doped AlN and InN
Kang, ByungSub,Lee, HaengKi,Kim, KyeongSup,Kang, HeeJae Royal Swedish Academy of Sciences 2009 Physica scripta Vol.79 No.2
<P>The electronic structure and magnetism are studied for the zinc-blende and wurtzite (Al,Cr)N, (Ga,Cr)N and (In,Cr)N by using the full potential linear muffin-tin orbital method. The energy gap (quasi-gap) in Cr-doped wurtzite InN decreases exponentially with increasing the Cr concentration from 0.027 to 0.166. The half-metallicity is retained in the whole range of concentrations considered, whereas for (Al,Cr)N, the half-metallic character disappears at a concentration of 0.166. The Cr magnetic moment in AlN is about 2.12–2.40μ<SUB>B</SUB> Cr atom<SUP>−1</SUP> with changing the Cr concentration, and for Cr in InN, it is a nearly constant value of 3.0 μ<SUB>B</SUB> Cr atom<SUP>−1</SUP>.</P>
Kim, Min-Jung,Jang, Dae-Hwan,Choa, Yong-Ho Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles prepared by the co-precipitation of Fe<SUP>2+</SUP> and Fe<SUP>3+</SUP> with NH<SUB>4</SUB>OH were simply modified by the carboxylic acid group of 3-thiopheneacetic acid (3TA) and meso-2,3-dimercaptosuccinic acid (DMSA). These functionalized Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles when coated with 3TA and DMSA have increased hydrophilic properties, thus causing them to be well dispersed in aqueous solutions. Then oligonucleotides (5′-AGC T-Amine-3′) were immobilized on the carboxylic acid group-modified Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles. They were characterized by using FT-IR, XRD and TEM. The concentration of the oligonucleotide-modified Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles was investigated using a UV–vis spectrometer and compared to that of Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles without any surface modification. The Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles were spherical and the particle sizes were approximately 10 nm. The immobilizing efficiencies of the Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles modified with 3TA and DMSA were higher than those of the non-functionalized Fe<SUB>3</SUB>O<SUB>4</SUB> nanoparticles.</P>
Electronic transport properties of Fe-doped CoSb<sub>3</sub> prepared by hot pressing
Park, Kwan-Ho,Jung, Jae-Yong,Ur, Soon-Chul,Kim, Il-Ho Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Fe-doped CoSb<SUB>3</SUB> skutterudites were prepared by hot pressing, and their thermoelectric and electronic transport properties were examined. The positive signs of the Seebeck and Hall coefficients for all Fe-doped specimens showed that Fe atoms acted as <I>p</I>-type dopants by substituting for Co atoms. The carrier concentration increased with increasing Fe doping content, and the Fe generated excess holes. The Seebeck coefficient showed a positive value at all temperatures examined, and increased with increasing temperature. The temperature dependence of electrical resistivity suggests that Co<SUB>1−<I>x</I></SUB>Fe<SUB><I>x</I></SUB>Sb<SUB>3</SUB> is a highly degenerate semiconducting material. Fe doping reduced the thermal conductivity considerably, and the lattice contribution was dominant in Fe-doped CoSb<SUB>3</SUB> skutterudites.</P>
Discharge properties of a lithium/sulfur cell at body temperature
Kim, Ic-Pyo,Park, Jin-Woo,Ahn, Hyo-Jun,Ahn, In-Shup,Kim, Ki-Won,Ahn, Jou-Hyeon,Ryu, Ho-Suk Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>To investigate the feasibility of a Li/S cell for application to medical devices, the discharge properties of Li/S cells were investigated at 36.5 °C. A Li/S cell has the first discharge capacity 1158 mA h (g-S)<SUP>−1</SUP> at body temperature, whose cathode is composed of sulfur, carbon black and PVdF. The Li/S cells were discharged at various current densities to evaluate the rate capability, and the cycle performance at 100 mA g<SUP>−1</SUP> current density was also studied compared with previous reports.</P>
Zhao, Xiaohui,Kim, Dul-Sun,Raghavan, Prasanth,Ahn, Jou-Hyeon,Ahn, Hyo-Jun,Ryu, Ho-Suk,Cho, Gyu-Bong,Noh, Jung-Pil Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Porous polymer membranes based on poly(vinylidene fluoride-<I>co</I>-hexafluoropropylene) were prepared by the phase inversion process, and the effect of processing parameters, such as the type of solvent and concentration of the polymer solution, on the membrane morphology and electrochemical properties of a polymer electrolyte (PE) was investigated. The membranes prepared were characterized by scanning electron microscopy and differential scanning calorimetry. PEs were prepared by soaking the porous membrane in 1 M LiPF<SUB>6</SUB> in ethylene carbonate/dimethyl carbonate, and their electrochemical performance was studied. The polymer concentration and/or non-solvent greatly influenced the morphology and electrochemical performance of the PE. A conductivity of ∼10<SUP>−3</SUP> S cm<SUP>−1</SUP> and charge/discharge capacities of ∼140 mAh g<SUP>−1</SUP> for the Li/LiFePO<SUB>4</SUB> cell were obtained.</P>
Suk Ryu, Ho,Seon Kim, Jong,Guo, Zaiping,Liu, Huakun,Won Kim, Ki,Hyeon Ahn, Jou,Jun Ahn, Hyo Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P> Fe<SUB>2</SUB>O<SUB>3</SUB> thin films are important for the fabrication of rechargeable lithium microbatteries. Thin films of Fe<SUB>2</SUB>O<SUB>3</SUB> were prepared by the electrostatic spray deposition (ESD) technique by using iron chloride as the precursor. The thin film electrodes, without inert additives such as polymer binder and conducting material, can deliver a first discharge capacity of 912 mA h g<SUP>−1</SUP> and retain a discharge capacity of 537 mA h g<SUP>−1</SUP> at a current density of 200 mA g<SUP>−1</SUP> to the 100th cycle. The coulombic efficiency of the Fe<SUB>2</SUB>O<SUB>3</SUB> thin-film electrode was over 96% after several cycles.</P>
Cho, Kwon Koo,Cho, Gyu Bong,Kim, Ki Won,Ryu, Kwang Sun Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Various kinds of β-Ga<SUB>2</SUB>O<SUB>3</SUB> nanomaterials such as nanowires, nanorods, nanobelts, nanosheets and nanocolumns have been successfully synthesized by simple evaporation of gallium powder with no assisted catalyst in a flow of argon gas. The as-synthesized materials were pure, structurally uniform, single crystalline with monoclinic β-Ga<SUB>2</SUB>O<SUB>3</SUB> structure (space group: C2 m<SUP>−1</SUP>) and free from defects. The synthesized nanomaterials were deposited with a growth order of nanocolumn/nanorod, nanowire/nanobelt and nanosheet with synthesis time. The nucleation site was looked over in detail. We present evidence that the surface, edge and tip of previously grown β-Ga<SUB>2</SUB>O<SUB>3</SUB> nanomaterials again provide a nucleation site of new β-Ga<SUB>2</SUB>O<SUB>3</SUB> nanomaterials. Because no metal catalysts were introduced into our growth, a vapor–liquid–solid (VLS) growth is not the likely process in this work, indicating that the observed nanomaterials were grown via a vapor–solid (VS) mechanism.</P>
Heo, Yong Kang,Kim, Sung Min,Lee, Sang Yul Royal Swedish Academy of Sciences 2010 Physica scripta Vol.2010 No.t139
<P>Gold nanoparticles were synthesized with various discharge durations using solution plasma processing (SPP), and the effects of the discharge duration between 120 and 900 s on the size and shape of the gold nanoparticles were investigated using UV–Vis NIR spectrophotometry and transmission electron microscopy (TEM). The results showed that discharge duration had a strong effect on the formation of gold nanoparticles. The results from the UV–Vis NIR spectrophotometer showed that an absorption coefficient peak at a wavelength of approximately 520 nm was observed, which indicated the formation of gold nanoparticles. As the discharge duration increased, the average particle diameter and the size distribution became smaller. Especially for the discharge duration of 900 s, the average diameter of gold nanoparticles was measured to be the smallest, less than ⩽25 nm in diameter, and most uniform in size distribution. The particle shape became more spherical as the discharge duration increased. Possible mechanisms for the formation of nanoparticles in SPP were suggested in that electrons and electric energy provided from SPP are to increase the surface potential of nanoparticles and, consequently, the increment of electrons and electric energy produces many charged nanoparticles. The charged particles prevent or reduce particle aggregation strongly so that the diameter of the nanoparticles decreased.</P>