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The influence of grain size on degradation of electrical contacts during fretting wear was investigated. Copper polycrystals with grain sizes of 2–162 µm were used to examine friction, wear, and electrical contact resistance. The results showed that the electrical contact failure was caused by the compact oxide layer produced at the contact junction. Copper specimens with smaller grains had a longer lifecycle because of grain-size strengthening. However, this strengthening effect was limited to a critical grain size and, with further increase in grain size, plastic deformation underneath the contact surface played a major role in delaying the contact failure caused by oxide formation on the fretting surface.

The effect of displacement and humidity on fretting-induced instability of electrical contact resistance ( R c ) was studied. A fretting tester was used to examine R c in partial and gross slip modes. Under the partial slip regime the contact failure was susceptible to the displacement and moisture effectively increased contact stability, which was pronounced at smaller displacements. In the gross slip mode, however, humidity effect was relatively small. The early contact failure at low humidity was attributed to the wear debris agglomeration within the sliding interface, suggesting a high propensity of electrical contact failure at dry conditions.

Much remains unknown about the mammalian immune response to Giardia lamblia, a protozoan pathogen that causes diarrhoeal outbreaks. We fractionated protein extracts of G. lamblia trophozoites by Viva-spin centrifugation, DEAE ion exchange and gel filtration chromatography. Resultant fractions were screened for antigenic molecules by western blots analysis using anti-G. lamblia antibodies (Abs), resulting in identification of G. lamblia binding immunoglobulin protein (GlBiP). Maturation of mouse dendritic cells (DCs) in response to recombinant GlBiP (rGlBiP) was detected by increased expression of surface molecules such as CD80, CD86 and MHC class II; these mature DCs, produced pro-inflammatory cytokines (TNF-α, IL-12 and IL-6). Especially, the truncated rGlBiP containing the heat-shock protein 70 domain-induced cytokine production from mouse DCs. rGlBiP-induced DC activation was initiated by TLR4 in a MyD88-dependent way and occurred through activation of p38 and ERK1/2 MAPKs as well as increased activity of NF-κB and AP-1. Moreover, CD4(+) T cells stimulated with rGlBiP-treated DCs produced high levels of IL-2 and IFN-γ. Together, our results suggest that GlBiP contributes to maturation of DCs via activation of TLR4-MyD88-p38, ERK1/2 MAPK, NF-κB and AP-1.

We investigated the orbital anisotropy of LuFe(2)O(4) using the Fe L(2,3)- and O K-edge x-ray absorption spectroscopy (XAS) and cluster model calculations. X-ray magnetic circular dichroism reveals a surprisingly large orbital magnetic moment (m(o) approximately 0.8 micro(B)/f.u.), which originates the giant magnetic anisotropy. The polarization dependent XAS enables us to identify the orbital states and occupations, different from the band calculation predictions. These findings were examined by using the cluster model analysis, which also explains the orbital magnetic moment as well as the total moment (2.9 micro(B)/f.u.). Taking into account the charge order, we also determined the spin structure.

We have studied quasi-two-dimensional multiferroic LuFe2O4 with strong charge-spin-lattice coupling, in which low-temperature coercivity approaches an extraordinary value of 9 T in single crystals. The enhancement of the coercivity is connected to the collective freezing of nanoscale pancakelike ferrimagnetic domains with large uniaxial magnetic anisotropy ("Ising pancakes"). Our results suggest that collective freezing in low-dimensional magnets with large uniaxial anisotropy provides an effective mechanism to achieve enhanced coercivity. This observation may help identify novel approaches for synthesis of magnets with enhanced properties.

We investigated electronic structure of hexagonal multiferroic YMnO3 using the polarization dependent x-ray absorption spectroscopy (XAS) at O K and Mn L(2,3) edges. The spectra exhibit strong polarization dependence at both edges, reflecting anisotropic Mn 3d orbital occupation. Moreover, the O K edge spectra show that Y 4d states are strongly hybridized with O 2p ones, resulting in large anomalies in Born effective charges on off-centering Y and O ions. These results manifest that the Y d(0)-ness with rehybridization is the driving force for the ferroelectricity, and suggest a new approach to understand the multiferroicity in the hexagonal manganites.

We investigated electronic structure of hexagonal multiferroic YMnO3 using the polarization dependent x-ray absorption spectroscopy (XAS) at O K and Mn L(2,3) edges. The spectra exhibit strong polarization dependence at both edges, reflecting anisotropic Mn 3d orbital occupation. Moreover, the O K edge spectra show that Y 4d states are strongly hybridized with O 2p ones, resulting in large anomalies in Born effective charges on off-centering Y and O ions. These results manifest that the Y d(0)-ness with rehybridization is the driving force for the ferroelectricity, and suggest a new approach to understand the multiferroicity in the hexagonal manganites.

Irradiation with approximately 10 keV x rays or medium-energy electrons destroys long-range order of Ir spin dimers in CuIr2S4 while preserving the dimers locally. We find that as the order is destroyed, a new type of incommensurate structural correlations appears. This represents an intriguing example of order from disorder phenomenon, in which a previously unknown incommensurate order appears in the radiation-induced disordered state. These results suggest that two competing instabilities, one of which can be suppressed by radiation, are present in the system. Otherwise unrealized structural or electronic states can, therefore, be revealed in correlated systems by x-ray or electron irradiation.

We investigated the electronic structure of a layered ${\mathrm{Ca}}_{2\ensuremath{-}x}{\mathrm{Sr}}_{x}\mathrm{Ru}{\mathrm{O}}_{4}$ in a metallic regime $(0.15\ensuremath{\leqslant}x\ensuremath{\leqslant}2.0)$ using a polarization dependent O $1s$ x-ray absorption spectroscopy. The spectrum shows strong variations with the polarization especially in Ru $4d$ region, which enables us to identify the electronic states. The spectral line shape gradually changes with increase of Sr concentration, and agrees well with an unrestricted Hartree-Fock analysis, which suggests evolution of the orbital states and provides clues for how the lattice distortion affects the orbital occupations.

We investigated ferromagnetism of a newly discovered ferromagnetic semiconductor Co-doped anatase ${\mathrm{T}\mathrm{i}\mathrm{O}}_{2}$ thin film, using the magnetic circular dichroism (MCD) at the Co ${L}_{2,3}$ absorption edges. The magnetic moment was observed to be $\ensuremath{\sim}0.1{\ensuremath{\mu}}_{B}/\mathrm{C}\mathrm{o}$ in the measurements, but the MCD spectral line shape is nearly identical to that of Co metal, showing that the ferromagnetism is induced by a small amount of clustered Co. With thermal treatments at $\ensuremath{\sim}400\text{ }\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$, the MCD signal increases, and the moment reaches up to $\ensuremath{\sim}1.55{\ensuremath{\mu}}_{B}/\mathrm{C}\mathrm{o}$, which is $\ensuremath{\sim}90%$ of the moment in Co metal. In the latter case, the cluster size was observed to be 20--60 nm.

We investigated ferromagnetism of a newly discovered ferromagnetic semiconductor Co-doped anatase TiO2 thin film, using the magnetic circular dichroism (MCD) at the Co L(2,3) absorption edges. The magnetic moment was observed to be approximately 0.1 micro(B)/Co in the measurements, but the MCD spectral line shape is nearly identical to that of Co metal, showing that the ferromagnetism is induced by a small amount of clustered Co. With thermal treatments at approximately 400 degrees C, the MCD signal increases, and the moment reaches up to approximately 1.55 micro(B)/Co, which is approximately 90% of the moment in Co metal. In the latter case, the cluster size was observed to be 20-60 nm.

Introduction Nickel-rich cathode materials, such as Li[Ni1-xMx]O2 (x ≤ 0.2 and M = Co and Mn), are known to deliver high capacity of 200 mAh g-1.[1] However, the unstable structure at the highly delithiated state gives rise to reaction with the organic electrolyte and carbon anode, causing severe safety problems.[2] A great deal of research has been conducted to eliminate such catastrophic effects by developing flame-retardant additives, thermally stable anodes, and thermally stable cathodes.[3] One of the most effective ways to address the safety concern is to coordinate the Ni-rich materials with tetravalent Mn-containing oxide materials, like Li[Ni1/2Mn1/2]O2 or Li[Ni1/3Co1/3Mn1/3]O2, by forming a core-shell particle or a core-shell particle with concentration gradient in the shell.[4] Tomograms of these core-shell and core-shell concentration gradient particles revealed that Li[Ni0.8Co0.1Mn0.1]O2 appeared only in the core, and the delivered capacity was mainly due to the core because the outer shell usually possesses the rate-limiting properties (poor Li + diffusion). It was anticipated that, if the higher concentration of Ni can be maintained from the particle center to the surface, and at the same time the outer surface can be modified by tetravalent Mn, the resulting capacity can be further improved compared to the above two concepts. In addition, the tetravalent Mn in the surface part is responsible for the satisfactory thermal properties. Figure 1 represents the above hypothesis schematically: i) high concentration of Ni (80%) is maintained throughout the spherical particle and ii) the Co content at the center (10%) is gradually reduced to the outer surface (2%), but Mn replaces the reduced Co content, forming a solid solution in the particle. Experimental The Ni-fixed full gradient structure formation of [Ni0.8Co0.2](OH)2 inner particles, Co-free aqueous solution was prepared by mixing required amounts of NiSO4 and MnSO4 salt solutions (Ni:Mn = 0.8:0.2 in molar ratio) and Mn-free (Ni:Co = 0.8:0.2 in molar ratio) solution separately. Initially, Co-free aqueous solution was slowly pumped into the stoichiometric amount of Mn-free solution, and at the same time, the homogeneously mixed solution, containing Ni, Co, and Mn ions, was fed into the CSTR. After a certain reaction time, green Ni-fixed full gradient particles slowly accumulated. The coprecipitated precursor powders were filtered, washed, and dried at 110 oC And that compounds were thoroughly mixed with LiOH·H2O and heated at 750 oC for 10h in air, respectively. The chemical compositions of the resulting powders were determined by atomic absorption spectroscopy (AAS, Vario 6, Analyticjena). Line scans for the full-gradient materials were obtained with an electron probe X-ray microanalyzer (EPMA, JXA-8100, JEOL). Results and discussion Figure 2 shows a cross-sectional scanning electron microscopy (SEM) image of a single lithiated solid solution particle (SSP) Li[Ni0.80Co0.07Mn0.13]O2 oxide particle and the corresponding elemental distribution of Ni, Co, and Mn. Taken together, these results describe a solid solution with a composition between Li[Ni0.8Co0.1Mn0.1]O2 and Li[Ni0.8Co0.02Mn0.18]O2 (see tie line in Figure 2). The total average composition of the solid solution particle (SSP) was found to be Li[Ni0.8Co0.06Mn0.14]O2, determined by atomic absorption spectroscopy (AAS). References 1. S.-U. Woo , B.-C. Park , C. S. Yoon , S.-T. Myung , J. Prakash , Y.-K. Sun , J. Electrochem. Soc. 2007 , 154 , A649 . 2. H. Arai , S. Okada , Y. Sakurai , J. Yamaki , Solid State Ionics 1998 , 109 , 295. 3. Y. E. Hyung , D. R. Vissers , K. Amine , J. Power Sources. 2003 , 191–121 , 383 . 4. Y.-K. Sun , S.-T. Myung , M.-H. Kim , J. Prakash , K. Amine , J. Am. Chem. Soc. 2005 , 127 , 13411 .

To reduce the cost of the battery system and increase the driving range for the EVs, batteries with very high energy density and improved safety are needed (1). In the past, most of the work has been centered on developing high energy layered cathode materials. Among these materials, LiNi0.80Co0.15Al0.05O2 (2) and Li[Ni1-x-yCoxMny]O2 (3), where 1 – x – y≥0.6 have been investigated intensely in the past ten years because they offer higher capacity than existing cathode materials. However, they exhibit poor cycling and thermal characteristics, especially at high voltage and elevated temperatures, because of oxygen release from the charged electrode, which oxidizes the electrolyte and leads to a quick capacity fade and, in some cases, severe thermal runaway of the cell. We report a novel cathode material with full concentration gradients of Ni and Co ions and a fixed composition of Mn (FCG-Mn-F) extending throughout each secondary particle, which has long rod-shaped primary particles that span from the center to the surface. The constant Mn concentration across the particle provides outstanding cycle life and safety, and the linearly decrease in Ni concentration toward the particle outer surface results in high capacity. At the same time, the gradual increase of the Co concentration from the particle center to the surface increases the electronic conductivity, yielding excellent rate capability. This unique FCG-Mn-F morphology, reported here for the first time, could lead to 1) a highly densified particles, which can lead to high volumetric energy density at the cell level, 2) fast lithium diffusion across the particle, which improved the rate capability of the material, especially at low temperature, and 3) high thermal stability because of limited surface reactivity with the electrolyte. The positive electrode material FCG-Mn-F Li[Ni0.60Co0.15Mn0.25]O2, a Ni-poor aqueous solution (Ni:Co:Mn = 0.50:0.25:0.25 in molar ratio) from tank 2 made of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O was slowly pumped into a Ni-rich (Ni:Mn = 0.75:0.25 in molar ratio) stock solution in tank 1, after which the homogeneously mixed solution was fed into a continuously stirred tank reactor (CSTR). During the early stage of coprecipitation reaction, spherical [Ni0.75Mn0.25](OH)2 particles were formed first, and a transition-metal-containing hydroxide with different composition gradually accumulated on the surface of the spherical [Ni0.75Mn0.25](OH)2 particles via layer-by-layer assembly with a precipitation process. We increased the concentration of the ammonium hydroxide (molar ratio of ammonium hydroxide to transition metal = 1.0) and sodium hydroxide amounts (molar ratio of sodium hydroxide to transition metal = 2.0) to favor the growth the primary particles. The obtained FCG-Mn-F [Ni0.60Co0.15Mn0.25](OH)2 was mixed with LiOH·H2O, and the mixture was calcined at 825 °C for 10 h in air. Reference 1. J.-M. Tarascon, M. Armand, Nature, 414 (2001) 359 2. R. Kostecki, F. McLarnon, Electrochem. Solid State Lett. 7 (2004) A380 3. K.-S. Lee, S.-T. Myung, K. Amine, H. Yashiro, Y.-K. Sun, J. Electrochem. Soc., 154 (2007)A971

Lithium-ion batteries are an important power source owing to their high energy density, high voltage, and excellent cycle life. Common applications include portable electronic devices such as portable smart phones, notebook-style personal computers, plug-in hybrid vehicles (PHEVs), and electric vehicles (EVs). However, the energy density and safety of lithium-ion batteries is still insufficient for most applications. At present, the driving range of EVs is less than 160 km and is significantly reduced by the use of air conditioning. As a result, further increases in the energy density, cycle life, and safety are important for their successful application in the automobile industry. The development of new, high-capacity cathode materials is a prerequisite for the next generation of lithium-ion batteries intended for use in EV applications.[1–2] The layered Li[NixCoyMnz]O2 materials, only Li[Ni1/3Co1/3Mn1/3]O2 is used in automobile applications in conjunction with stabilized spinel Li1 + xMn2 - yAlyO4 in a composite form, resulting in a lower capacity and outstanding safety characteristics characteristics.[3] The capacity of Li[Ni1/3Co1/3Mn1/3]O2 (155 mAh g- 1) is so low that it limits the driving range of associated EVs to less than 160 km. Another promising cathode material is Li[Ni0.5Co0.2Mn0.3]O2, which delivers a capacity of 170 mAh g- 1. However, Li[Ni0.5Co0.2Mn0.3]O2 fails to satisfy requirements for EV applications owing to its poor capacity retention and safety, creating a need for cathode materials with the capacity of Li[Ni0.5Co0.2Mn0.3]O2 and the safety of Li[Ni1/3Co1/3Mn1/3]O2. We report a promising cathode material specifically engineered for EV applications: Li[Ni0.54Co0.16Mn0.30]O2 with a full concentration gradient (FCG) of Ni and Co ions at a fixed Mn content of 30% throughout the particle. We compared the electrochemical, structural, and thermal stabilities of the FCG material with those of conventional Li[Ni0.5Co0.2Mn0.3]O2 and Li[Ni1/3Co1/3Mn1/3]O2materials. Experimental Spherical FCG [NixCoyMnz](OH)2 precursors were synthesized through the co-precipitation method. A Ni-poor aqueous solution (molar ratio of Ni/Co/Mn = 0.50:0.20:0.30) consisting of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·5H2O was slowly pumped from tank 2 into a Ni-rich (molar ratio of Ni/Mn=0.7:0.3) stock solution in tank 1. The homogeneously mixed solution was then fed into a continuously stirred tank reactor (CSTR, 4 L) in a replenished N2 atmosphere. Concurrently, a NaOH solution (4.0 mol L- 1, aq) and the desired amount of a NH4OH chelating agent solution (aq) were pumped separately into the reactor. The concentration of the solution, pH value, temperature, and stirring speed of the mixture in the reactor were carefully controlled. During the early stage of the co-precipitation process, [Ni0.7Mn0.3](OH)2 (composition of the center of the particle) was first precipitated. Nickel–cobalt–manganese hydroxide at different compositions was then gradually piled onto the formed [Ni0.7Mn0.3](OH)2 particles to result in a linear composition change of Ni and Co toward the outer surface of the particles. The precursor powders were obtained through filtering, washing, and drying at 100 oC overnight. The obtained FCG [Ni0.54Co0.16Mn0.30](OH)2 was mixed with LiOH·H2O, and the mixture was calcined at 875 oC for 10 h in air. Electrochemical properties of the synthesized FCG [Ni0.54Co0.16Mn0.30]O2 were evaluated using a 2032-type coin type cell. Results and discussion Fig. 1 shows the change of concentrations of Co and Ni in the single rod-shaped primary particle was determined by means of energy-dispersive X-ray spectroscopy (EDS) along with the corresponding elemental distribution of Ni, Co, and Mn around the center region of the FCG particle; the results are shown superimposed on the TEM image. The EDS data show that the Co/Ni atomic ratio decreased from 0.375 to 0.323 along the 1.2 mm length toward particle core, a composition variation similar to that shown by the electron-probe X-ray microanalysis (EPMA) data in Figure 2. Note that the concentration gradient was observed within a single primary particle, which is a characteristic of the FCG particles synthesized by our unique co-precipitation method. Ni was depleted at the particle surface and became slowly enriched toward the particle center whereas Co levels gradually depleted. As expected, the elemental mapping shows that Mn was distributed uniformly throughout the center region of particle. References 1. J. B. Goodenough, Y. Kim, Chem. Mater. 22, 587 (2010). 2. Y.-K. Sun, S.-T. Myung, B.-C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 8, 320 (2009). 3. I. Belharouak, Y.-K. Sun, J. Liu, K. Amine, J. Power Sources 123, 247 (2003).

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The electrochemical properties and thermal stabilities of a new positive electrode material for Li-ion batteries, Li[Ni 0.55 Co 0.15 Mn 0.30 ]O 2 , were investigated over a wide potential window. This electrode material was synthesized via a coprecipitation method. X-ray diffraction studies indicated that the synthesized material crystallized into an α-NaFeO 2 layered structure (R3m). The Li[Ni 0.55 Co 0.15 Mn 0.30 ]O 2 positive electrode has a discharge capacity of 202 mAh g -1 in the voltage range of 2.7-4.5 V. This high capacity was retained throughout cycling. The thermal stability of Li[Ni 0.55 Co 0.15 Mn 0.30 ]O 2 was measured by differential thermal calorimetry and found to be comparable to that of Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 . This positive electrode material was also characterized in a full cell configuration (graphite negative electrode) by the hybrid pulse power characterization tests following the FreedomCAR battery test manual for plug-in hybrid electric vehicles (PHEVs). The pulse power capability and available energy met the goals for PHEVs.

A long-standing issue about the Cu valency in selenospinel CuCr2Se4 was investigated by soft X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD). Using the sensitivity of XAS and XMCD to the valence value of transition metal ion and its local symmetry, we checked the valence value of each cation in selenospinel CuCrxTi 2−xSe4 (x = 1.0, 1.1, 1.5, and 2.0) and obtained spectroscopic evidence that a small amount of the Cu cation changes the valency from Cu(I) to Cu(II) as the Cr concentration increases from 1.0 to 2.0. Dependence of the Cu(II) concentration and the mean field magnetic exchange energy on the Cr concentration suggests the Cu d-hole could play a crucial role in the intriguing magnetic/electrical properties of CuCr2Se4.