[en] Cerium-activated yttrium aluminate (Y_3Al_5O_12:Ce''3+)exhibiting a garnet structure has been widely utilized in the production of light emitting diodes (LEDs) as a yellow emitting phosphor. The commercialized yttrium aluminum garnet (YAG) phosphor is typically synthesized by a solid-state reaction, which produces irregular shape particles with a size of several tens of micrometers by using the top-down method. To control the shape and size of particles, which had been the primary disadvantage of top-down synthetic methods, we synthesized YAG:Ce nanoparticles with a diameter of 500 nm using a coprecipitation method under the atmospheric pressure without the use of template or special equipment. The precursor particles were formed by refluxing an aqueous solution of the nitrate salts of Y, Al, and Ce, urea, and polyvinylpyrrolidone (55 K) at 100 °C for 12 h. YAG:Ce nanoparticles were formed by the calcination of precursor particles at 1100 °C for 10 h under atmospheric conditions. The phase identification, microstructure, and photoluminescent properties of the products were evaluated by X-ray powder diffraction, scanning electron microscopy, absorption spectrum and photoluminescence analyses

[en] We report the development of multi-component filler metal with low melting point for joining Ti-Super STS metals based on the followings. - Design of filler metal alloys with low melting point - Design of filler metal alloys based on understanding of dissimilar joining - Effect of addition elements on the melting point of filter metals - Optimization of process parameters for fabrication of powder/ribbon type filler metal

[en] In this study, amphiphilic polymers such as poly(vinyl pyrrolidione) (PVP) were directly adsorbed onto the surface of semiconductor QDs to overcome the limitations described. The detection ability on latent fingerprints is expected to improve if nanomaterials are used, because they exhibit good emission and have functionalities that can interact with fingerprint residues, thereby leading to better sensitivity and selectivity in latent fingerprint detection. The limitations on the detection of latent fingerprint found in crime scenes can be overcome by the excellent emission of nanoparticles. Moreover, the detection sensitivity can be improved by in troducing new nanomaterials that can interact with the surface of fingerprint residues.

[en] Titania nanoparticles (TNPs) that are already in widespread used in our daily lives as white pigments and sunscreen materials have attracted much attention for their possible applications in various fields, such as photonic band materials, gas sensing, solar cells, batteries, and photocatalysts. We systemically investigated the factors controlling the size of TNPs in the presence of KCl. The amount of titanium precursor, the concentration of KCl, the reaction temperature, and the polarity of the solvent were all shown to affect the kinetics of the hydrolysis/condensation and to dictate the resulting particle size. We also showed that the prepared TNPs at room temperature could be effectively phase-transformed to anatase nanocrystals, which exhibited very effective photocatalytic activity comparable to that of commercialized TiO_2 photocatalysts. We believed that this simple preparation method, which allows for size control of our particles, along with easy surface modification could expand the usage of TNPs to various applications.

[en] Although Gd₂O₃ (gadolinia) nanoparticle is the subject of intense research interest due to its magnetic property as well as controllable emission wavelengths by doping of various lanthanide ions, it is known to be difficult to prepare monodisperse crystalline gadolinia nanoparticles because it requires high temperature thermal annealing process to enhance the crystallinity. In this article, we demonstrate the synthesis of hollow nanoparticles of crystalline Gd₂O₃ by employing poly(N-vinylpyrrolidone) (PVP) to stabilize the surface of Gd(OH)CO₃·H₂O nanoparticles and to successively form SiO₂ shell as a protecting layer to prevent aggregation during calcinations processes. Silica shells could be selectively removed after calcinations by a treatment with basic solution to give hollow nanoparticles of crystalline Gd₂O₃. The formation mechanism of hollow nanoparticles could be suggested based on several characterization results of the size and shape, and crystallinity of Gd₂O₃ nanoparticles by TEM, SEM, and XRD.

[en] This article deals with an investigation on the phase behavior of the pseudoternary AOT/cyclohexane/0.2M AgNO₃ aqueous solution and features of Water-in-Oil (W/O) microemulsions (MEs). The sizes and structures of water pools in the microemulsions were determined by Small-Angle Neutron Scattering (SANS). SANS spectra yielded that water pools of spheres with sizes 4-10 nm and of cylinders with lengths of 25-30 nm were formed at four different compositions inside the microemulsion region. Silver nanoparticles were prepared with the microemulsions and identified by the peaks at 400 nm wavelength and types of UV/Vis absorption spectra. TEM micrographs showed that the silver nanoparticles formed were spherical and rod-like, depending on the compositions of the microemulsions and reflecting the sizes and shapes of the water pools

[en] Free-standing nanoporous alumina membrane microtubes with different shapes (rectangular and cylindrical tubes) and variable dimensions were easily fabricated by direct anodization of the aluminum templates of the specified shapes (strip and wire) and dimensions during the electrochemical reaction

[en] The influence of heat treatments on the grain boundary morphology of alloy 690 (Ni-30Cr-9Fe) was studied. Serrated grain boundaries were produced by isothermal heat treatment at 800 .deg. C after solution heat treatment at 1150 .deg. C or by control cooling in the temperature range of 800 .deg. C and 400 .deg. C with a rate of 5 .deg. C/min or below. The amplitude and wavelength of serrated grain boundaries increased with longer isothermal heat treatment time or slower cooling rates, but showed maximum value at some extent, respectively. Precipitates on the serrated grain boundaries were revealed as Cr₂₃C₆ having semi-coherent cube-to-cube relationship - {100}_matrix//{100}_ppt, <100>_matrix//<100>_ppt - with one adjacent grain

[en] Stress corrosion cracking(SCC) tests have been performed on both thermal treated and serrated alloy 600 at 320 .deg. C, 8.65MPa in 40% NaOH solution for 500hr. Stress corrosion cracking resistance was improved to a great extent for caustic SCC in serrated alloy 600

[en] Fuel-storage tank is a representative example of liquid-structure interaction systems. In order to prevent the undesired structural failure by a variety of external loads, the reliable analysis of the dynamic response of such structural systems is of a great importance. In this paper, we address the analytical study on free vibration of axisymmetric cylindrical fuel-storage tanks together with the parametric investigation of Eigen-characteristics with respect to the relative fuel fill-height and the relative tank height. Numerical results illustrating theoretical results are also included