Galvanic corrosion of carbon steel coupled to antimony

Galvanic corrosion of carbon steel coupled to antimony was studied in aerated and N₂-purged electrolytes at ambient and 60 °C temperatures. Free corrosion potential of antimony and carbon steel shifts to more active values with increasing temperature and N₂ purging of the electrolyte. Under all experimental conditions, antimony remains less electronegative than carbon steels. Aeration and temperature affect potentiodynamic behaviour of both materials. As a consequence, the corrosion current for the antimony–carbon steel couple increases with increasing temperature and with aeration. There was a good agreement between the corrosion currents obtained through the Evans’ experiment and super-imposed potentiodynamic scans.     

The magnetization reversal processes of Sm2Gd10.5Fe8Co64Zr2.5Cu13 alloy in the as-quenched state

The magnetization reversal processes of the as-quenched Sm₂Gd_10.5Fe₈Co₆₄Zr_2.5Cu₁₃ ribbons obtained by melt-spinning method have been investigated. From the analysis of the initial magnetization curve it was deduced that the main mechanism of magnetization reversal process is the pinning of domain walls at the grain's boundaries. From the dependence of the reversible magnetization components as a function of magnetic field it was found that reversible rotation of magnetic moment vector results in high initial values of this component. The presence of several maxima on the differential susceptibility curves derived from the irreversible magnetization component in both direction of magnetization implies existence of several pinning sites for domain walls. The interaction between the alloy grains have been examined by using the so-called δm(μ₀H_i) plot. The values of δm(μ₀H) for investigated alloy remains positive for an applied field up to 1.15 T and negative for higher fields. Such behavior of δm(μ₀H_i) dependence certifies that the dominant interaction between grains is the short range exchange interactions but low values of δm(μ₀H) implies that these interactions are week.     

Nano Si-coated graphite composite anode synthesized by semi-mass production ball milling for lithium secondary batteries

Nano-sized silicon particles were uniformly coated onto a natural graphite surface by a 1 ton/month-based semi-mass production ball milling method in order to prepare Si-based anodes for Li ion batteries. The structure, surface morphology and Si coating properties of the as-synthesized powders were analyzed by XRD, Raman, SEM, TEM and EDS mapping tools. The initial gravimetric discharge capacity of the Si-coated graphite measured using a half cell was 761 mAh/g at a rate of 0.2 C. Additionally, the discharge capacity retention of a full cell system was 71.4% at a 1 C rate even after 300 cycles as well as 96.6% of initial coulombic efficiency. The cycled composite powders were further analyzed by SEM and EDS mapping techniques. This method is proposed for commercial extension to the manufacture of lithium secondary batteries.     

Preliminary study on the tribology of an organic-molecule-coated touch panel display surface

The use of touch panel displays has been increasing due to the popularity of tablet PCs and smart phones. In order to protect the touch panel surface from scratches, contaminants from fingerprints and skin oils and so on, anti-contamination coating is necessary.One of the ways to protect the surface is to cover it with a thin and dense organic molecular layer. At the present time, the primary requirement for the coating is fingerprint-resistance or easy removal of contaminants. An adsorbed molecular layer of PFPE-derivatives is currently used for this purpose, in order to reduce the surface energy of the surface. Since the current major concern of panel makers is anti-fingerprint performance, degradation of the molecular layer by both tribological and environmental conditions is a major issue for the development of the coatings.Given the current priorities, however, tribological research into such subjects as the touch feeling of the panel and the friction characteristic has not been conducted. The touch feeling and its relation to the operation are very important but very difficult to study because it is very hard to express the touch feeling numerically. As a preliminary study, several different coated surfaces were prepared and their friction coefficients were measured by rubbing with a finger or a steel or glass ball to clarify the tribological characteristics of the surface.An Si wafer and a glass plate were used in this study as models of the solid substrate of a display. They were coated with an adsorbed organic molecular layer of two PFPE-derivatives with different molecular structures named Type-F and Type-D or several reference molecular layers, such as OTS-SAM and FDTE-SAM. In addition to the tribological data, degradation by UV irradiation was also examined to compare the performance. The results are discussed from the tribological and chemical points of view.     

Toughness of Sintered NdFeB Magnets

The failure mechanism of sintered NdFeB magnets was studied from the view of fracture model and fracture mechanism, and the effect of alloying on strength and toughness of the magnets was researched too. The results showed that intercrystalline fracture was the main fracture model and cracks elongated along the interface between 2–14–1 phase and Nd-rich phase. Generally, the methods for improving toughness include enhancing bond strength of the interface between the two phases mentioned just, refining grains of 2–14–1 phase and increasing the amount of particles of Nd-rich phase localized at grain boundary. The fracture model of the Nd_15.5Fe_76.5Al₁Ti_0.5B_6.5 magnets was transcrystalline cleavage fracture, whose value of fracture toughness increased about 30% compared to that of the Nd_15.5Fe₇₈B_6.5 magnets. Otherwise, the value of fracture toughness of the magnets with a proper amount of addition of Ag increased about 70% compared to that of the Nd_15.5Fe₇₈B_6.5 magnets. Moreover, the two sorts of modified magnet mentioned just could be drilled successfully. In addition, development of the research about increasing the strength and toughness of sintered NdFeB magnets is reviewed in this article.     

Investigation of voltage reduction in nanostructure-embedded organic light-emitting diodes

We investigated the reduction of the operating voltage in organic light-emitting diodes containing WO₃ nanoislands. The thickness of the organic layer and the periodicity of the nanoislands were varied in order to quantitatively analyze the electrical changes. The thickness of the N,N′-bis(naphthalen-1-yl)-N,N′-bis(phenyl)-benzidine (NPB) layer was varied from 150 nm to 600 nm, and various periodic nanoislands of 300 nm, 330 nm, and 370 nm were fabricated. Two geometric factors, which are the effective length and effective area, influence the operating voltage. The effective length is determined by the relative thickness of the nanoislands compared with the organic thickness, and the reduction of the operating voltage is linearly proportional to the relative thickness. The effective area is a nonlinear function of periodicity, and the voltage is reduced as the periodicity decreases.     

Magnetocaloric effect of La0.8Ce0.2Fe11.4−xMnxSi1.6 compounds

The effect of Mn addition on the magnetocaloric effect (MCE) of the La_0.8Ce_0.2Fe_11.4?xMn_xSi_1.6 (x = 0.0, 0.1, 0.2, 0.3) compounds was investigated. It was revealed that the transition temperatures of the compounds are sensitive to Mn composition. The temperatures are shifted from 177 to 121 K for Mn composition from 0.0 to 0.3. Moreover, thermal lag and magnetic hysteresis loss of the compounds are reduced largely due to Mn addition. A good MCE with a large and almost constant refrigerant capacity in a large temperature span over 50 K was achieved in the investigated compounds. The investigated compounds are promising magnetic entropy change materials.     

A novel lamellar coordination polymer incorporating partially overlapped helices,ladders and zigzag chains – Synthesis,crystal structure and magnetic property

The hydrothermal assembly of CoCl₂ · H₂O with benzene-1, 2, 3, 4-tetracarboxylic acid (H₄mpda) yielded a novel lamellar coordination polymeric complex, Co₂mpda(H₂O)₆ · H₂O (1), in which each layer presents an interesting multifold topology: both as partially overlapped helices with alternate chirality and as alternately arranged ladders and zigzag chains.     

Liquid–liquid demixing and microstructure of Co–Cu–Zr alloys with low Zr content

Liquid–liquid phase separation and its effect on the microstructure has been investigated along the quasi-binary line (Co₄₀Cu₆₀)_100−xZr_x with x = 2, 4, 6, 9 and additionally for (Co₅₀Cu₅₀)₉₄Zr₆ and (Co₆₀Cu₄₀)₉₄Zr₆. The elemental distributions and the microstructures were analyzed by scanning electron microscopy and energy dispersive X-ray spectroscopy for samples that were (i) processed by thermal cycling in alumina crucibles at 10, 20 and 30 K/min with simultaneous differential thermal analysis, (ii) rapidly quenched by single-roller melt spinning and (iii) quenched after having been electromagnetically levitated at various temperatures. The metastable miscibility gap of the binary Co–Cu system with phase separation into Co- and Cu-rich liquids transforms into a stable miscibility gap for Zr contents 3 < x < 7.5 with separation into Co/Zr-rich and Cu-rich liquids. In contrast to the binary Co–Cu system where the Cu-rich liquid phase always surrounds the Co-rich phase, the Zr addition modifies the surface tension energies and/or wetting behavior in a peculiar way so that the Co/Zr-rich phase always encloses the Cu-rich liquid phase concerning the ternary Co–Cu–Zr system in that compositional range. The macrosegregation morphologies of the liquid phase separation that built up via Ostwald ripening, gravity-driven convection, collision, coalescence and wetting effects proceed on a very short time scale and even samples that have been prepared by rapid quenching techniques still exhibit phase separated regions in the micrometer regime.