[en] One-dimensional nanoparticles (1D NPs), such as single-wall carbon nanotubes (SWNTs) and metallic, semiconducting, and magnetic nanorods, have received great attention due to their unique anisotropic physical properties, which provide a wide range of potential applications such as optical and electronic devices, sensing and imaging, energy storage, and drug delivery. For practical realization of 1D NPs for a variety of potential applications, it is essential to fabricate a well-defined symmetric, directional, hierarchical structure using molecular self-assembly. Studies on the fabrication of hierarchical structures of 1D NPs have been successfully done by using various self-assembling method including solvent evaporation, electrostatic attraction, and DNA programming. However, 1D NP binary superlattice, which is expected to show emerging properties through collective interaction between different NPs, has not been reported so far. In this paper, first, a binary superlattice of 1D NPs has been developed for the first time using a hydrophillically functionalized SWNTs and a pre-foremd hexagonal phase of cylindrical micelles. The combination of small angle neutron and x-ray scattering measurements shows that a AB₂ type binary superlattice, in which the hexagonal structure of functionalized SWNTs are embedded in honeycomb lattice of cylindrical micelles, are formed. The AB₂ type binary superlattice of 1D NPs can be highly aligned into one direction under an oscillatory shear field. Theoretical calculation based on the cell theory shows that the AB₂ and AB₃ type binary superlattices can be formed to maximize the free volume entropy for both 1D NPs of two different diameters depending on the diameter and mixing ratios. Second, the self-assembly phenomenon of binary mixtures of cylindrical colloids with different diameters under the depletion attraction has been investigated. By varying on the diameter ratio, mixing ratio, and repulsive or attractive force between the different cylindrical colloids, it is proved that the weak attraction is necessary to form the hierarchical structure in addition to the diameter and mixing ratios. Third, based on the understanding of the interactions between different 1D NPs obtained above studies, a facile method to fabricate two-dimensional hexagonal monolayer superlattices of gold nanorods (GNRs) individually embedded in silica matrix on substrate has been developed. In this method, the cetyltrimethylammonium bromide (CTAB) bilayer-coated GNRs are self-assembled into a hexagonally packed monolayer superlattice on substrate by slow evaporation in the presence of silica precursors in the solution at a highly acidic condition. The GNR superlattices fabricated by this method show an excellent structural stability at high temperature as high as 500∘C and in solvents of a wide range of polarities including water, ethanol, toluene and cyclohexane. The structural stability makes the GNR superlattices highly reusable SERS active substrates for sensitive molecular detection, well-maintaining the SERS intensity over 10 cycles. The understanding of interparticle interactions between different 1D NPs and self-assembly of GNRs obtained in these studies may provide a new route to fabricate the binary superlattice of GNRs, which is highly stable, and thus, can be applied in various application fields

[en] Effects of the Nb addition on the strain induced ferrite transformation just above Ar₃ temperature were investigated. Hot compression tests were performed with varying the true strain up to 1.6 (80% reduction) using Gleeble 1500. After the hot deformation, samples were immediately water-quenched to examine ferrite formation characteristics. The grain boundary misorientation angles were measured by electron backscatter diffraction in order to observe evolution of the ferrite grains. For reheating temperatures such as 900 and 1000 deg. C, where Nb was mostly precipitated as NbC, strain induced ferrite grains of 1-2 μm were formed homogeneously within the austenite grain in Nb steel. In the cases of higher reheating temperatures 1100 and 1250 deg. C, where most of Nb was dissolved, the strain induced ferrite transformation was remarkably reduced and the ferrite morphology was changed to elongated grains. It was considered that the ferrite transformation during deformation was retarded by both the solute drag effect of Nb and the consumption of strain energy for the dynamic precipitation of NbC

[en] The synthesis of Si nanoparticles by ultrasonication processing of porous Si powder and a novel method for preparing a high-capacity Si/C composite using this technique is reported. The porous Si powder is prepared by selectively etching the silicide phase of a Ti₂₄Si₇₆ alloy consisting of Si and silicide phases. The particle size of the nanocrystalline Si is determined by the crystallite size of the Si and silicide phases in the alloy powder. Ultrasonication of the porous Si obtained from the mechanically alloyed Ti₂₄Si₇₆ alloy generates nanocrystalline Si particles of size about 5 nm. Growth of the Si and silicide phases in the alloy is induced by annealing of the mechanically alloyed sample, with a consequent increase in the size of the Si particles obtained after ultrasonication. Application of the ultrasonication process to the fabrication of Si/C composite anode materials generates nanometer-scale Si particles in situ that are distributed in the matrix. Analysis of the phases obtained and evaluation of the distribution of the nanometer-scale Si particles in the composites via XRD/TEM measurements show that the nanometer-scale Si particles are effectively synthesized and uniformly distributed in the carbon matrix, leading to enhanced electrochemical performance of the Si/C composites

[en] Hard carbon and microcrystalline graphite (MG) core-shell structured composite materials are prepared, and their electrochemical performances as an anode material for lithium-ion batteries are reported. The composite materials are obtained by coating a mixture of MG and pitch onto hard carbon particles, followed by heating at 1200 °C under an argon atmosphere for 1 h. The surface of the hard carbon is subsequently covered with a layer of the MG/pitch carbon composite. In the coating layer of the MG/pitch carbon composite, the MG particles are divided into nanoscale graphite sheets, and uniformly dispersed within the pitch of carbon matrix. The composite particles have a rounded shape, especially when the content of MG increases, which can improve their packing density compared to hard carbon having sharp edges. Anodes prepared from these composite materials exhibit enhanced electrochemical performances, including a high reversible capacity, high initial coulombic efficiency, high charging/discharging rate capability, and desirable cycling stability

[en] The cycling behaviors of Co-Si alloy and multilayered films, which were prepared by co-deposition from separate pure metal sources and by alternating deposition of different metals, respectively, are investigated. The alloy films with near stoichiometric compound composition of CoSi_2.06 and CoSi_2.2 exhibit an excellent cycling stability, but alloying with large excess Si results in capacity fading during cycling. The cycling stability of multilayers with average composition of CoSi_2.9 is improved significantly by post-annealing treatment at 350 deg. C. Nano-structured multilayer films are suggested as promising anode materials for thin-film batteries

[en] We investigated the experimental method that uses the homogeneous precipitation method to prepare mica flakes-coated rutile-type titania pearlescent pigment with urea as a precipitant. TiO_2 particles exhibit a high reflection of lights and optical properties with chemical stabilities, so they are appropriate for coating on luminescent pigments (mica). The coating principle of mica coated titania with various thicknesses was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and tested by spectrophotometer. Mica with a particle size in the range of 40-60 um was suspended in water, and metal sulphates and urea were added to the mixture, which was heated to boiling. The change in pH was continuously followed. The metal oxide and crystal structure were affected by the conditions of TiOSO_4 concentration and reaction time with a sintering temperature the range of 800-1100°C.

[en] This paper studies the experimental method that uses the homogeneous precipitation method to prepare mica flakes coated with anatase-type titania pearlescent pigment with urea as precipitant. The optimum technology parameters, the chemical composition, the microstructure, and the color property of resulting pigments are discussed. The coating principle of mica coated titania with various coating thickness is analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy(TEM) and tested by spectrophotometer analysis. The colored nanocrystalline pigments with different morphology and coating thickness 45-170 nm were prepared by homogeneous precipitation treatment of TiOSO_4(titanum oxysulfate) aqueous solutions. Characterizations on the pigments show that the pearlescent effects of the pigments depend mainly on mica size, thickness of the metal oxide deposit, its chemical composition, and crystal structure.

[en] The lamellar structure of two phases, the Zn-rich and Al-rich phases, is formed in a Zn-5 wt% Al eutectic alloy. In order to study the effect of microstructural changes on the tensile properties of eutectic Zn-Al binary alloy, Zn-Al and Zn-Al-Cu alloys were directionally solidified at a growth rate of 50 μm/s using a Bridgman-type method. The alloys were successively drawn until reaching area reductions of 50% and 80% at room temperature. The tensile strength of the Zn-Al alloy decreased with increasing drawing ratio. In the Zn-Al-Cu alloy, the tensile strength increased until the area reduction reached 50%, but decreased at an area reduction of 80%. The ductility of alloys prepared by directional solidification increased with increasing drawing ratio. The orientations of the lamellar structure and grains were aligned in the drawn direction. The inter-lamellar distance of the alloys also decreased with increasing drawing ratio. As a result, the trade-off between strength and ductility could be significantly reduced. The strength and ductility combination of 246 MPa-40% was achieved by cold drawing with 80% area reduction of the Zn-Al-Cu alloy.

[en] In this study, the solid and liquid oxidation behaviors of Al–Mg alloys that had a trace of Ca were investigated. With increasing Ca content, the grains of α-Al dendrites in Al–7.5mass%Mg alloys were refined by the formation of two Ca-containing particles at grain boundaries. Using thermal gravimetric analysis result at 515 °C for 24 h under O₂ atmosphere, Al–7.5mass%Mg alloy exhibited a parabolic behavior in its weight gain during oxidation. However, there was nearly no difference in the weight change during oxidation of the Al–7.5mass%Mg alloys that contained a trace of Ca. From the auger electron spectroscopy and transmission electron microscopy/energy-dispersive X-ray spectroscopy results for the oxidized surface, it is believed that the improvement in the oxidation resistance in Al–7.5mass%Mg alloys that contain Ca may be attributed to the formation of a mixed oxide layer that includes CaO, MgO, and Al₂O₃ on the surface. After a melt holding test for 3 h, there was no notable difference in Mg loss during oxidation between Al–7.5mass%Mg and Al–7.5mass%Mg–0.1mass%Ca alloys. However, for a melt oxidation time for 24 h, the Mg reduction of Al–7.5mass%Mg alloy reached approximately 15%, whereas in Ca added alloy, the reduction was controlled under 8%. The cross section of Al–10mass%Mg alloy that solidified after the melt holding test showed a significant contamination due to oxide inclusions. However, Ca added alloys had good internal soundness throughout all the conditions. It was confirmed that the protective layer formed by Ca-containing can suppress the formation of Mg-based oxide inclusions and result in an increase in the alloy internal soundness during the melting process.

[en] In order to study the effect of microstructural change on the tensile properties of discontinuous precipitated Al-Zn binary alloy, four different Al-Zn alloys(25, 30, 35, 45 wt%Zn) were aged at 160 ℃ for different aging times(0, 5, 15, 30, 60, 120, 360 min) after being solution treated at 400 ℃, and successively drawn at room and cryogenic temperatures(-197 ℃). Discontinuous precipitation was formed during aging in the Al matrix(which contained more than 30 wt%Zn) in Al alloys containing more than 30 wt%Zn. The tensile strength of continuous precipitated Al-35Zn alloy decreased with increasing drawing ratio, however, the tensile strength of discontinuous precipitated Al-35Zn alloy increased with further drawing. The strength and ductility combination, 350 MPa-36%was achieved by drawning discontinuous precipitated Al-Zn alloy at room temperature. The discontinuous precipitated Al-Zn alloy drawn at cryogenic temperature showed a higher value of tensile strength, over 500 MPa, although ductility decreased.