Noriyuki Kuwano

Green Synthesis of Magnetite (Fe3O4) Nanoparticles Using Seaweed (Kappaphycus alvarezii) Extract.

In this study, a simple, rapid, and eco-friendly green method was introduced to synthesize magnetite nanoparticles (Fe3O4-NPs) successfully. Seaweed Kappaphycus alvarezii (K. alvarezii) was employed as a green reducing and stabilizing agents. The synthesized Fe3O4-NPs were characterized with X-ray diffraction (XRD), ultraviolet-visible spectroscopy (UV-Vis), Fourier transform infrared (FT-IR), and transmission electron microscopy (TEM) techniques. The X-ray diffraction planes at (220), (311), (400), (422), (511), (440), and (533) were corresponding to the standard Fe3O4 patterns, which showed the high purity and crystallinity of Fe3O4-NPs had been synthesized. Based on FT-IR analysis, two characteristic absorption peaks were observed at 556 and 423xa0cm−1, which proved the existence of Fe3O4 in the prepared nanoparticles. TEM image displayed the synthesized Fe3O4-NPs were mostly in spherical shape with an average size of 14.7xa0nm.

Annealing of an AlN buffer layer in N2–CO for growth of a high-quality AlN film on sapphire

The annealing of an AlN buffer layer in a carbon-saturated N2–CO gas on a sapphire substrate was investigated. The crystal quality of the buffer layer was significantly improved by annealing at 1650–1700 °C. An AlN buffer layer with a thickness of 300 nm was grown by metalorganic vapor phase epitaxy (MOVPE), and was annealed at 1700 °C for 1 h. We fabricated a 2-µm-thick AlN layer on the annealed AlN buffer layer by MOVPE. The full widths at half maximum of the (0002)- and (

Green Synthesis of Gold Nanoparticles Using Aqueous Extract of Garcinia mangostana Fruit Peels

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Electron microscopy analysis of microstructure of postannealed aluminum nitride template

)-plane X-ray rocking curves were 16 and 154 arcsec, respectively, and the threading dislocation density was 4.7 × 108 cm−2.

Electron Microscopy Study of Grain Boundary Behavior in Pb-Free Solder Materials for Mitigation of Whiskers

The synthesis of gold nanoparticles (Au-NPs) is performed by the reduction of aqueous gold metal ions in contact with the aqueous peel extract of plant, Garcinia mangostana (G. mangostana). An absorption peak of the gold nanoparticles is observed at the range of 540–550źnm using UV-visible spectroscopy. All the diffraction peaks at 2ź = 38.48°, 44.85°, 66.05°, and 78.00° that index to (111), (200), (220), and (311) planes confirm the successful synthesis of Au-NPs. Mostly spherical shape particles with size range of 32.96 ± 5.25źnm are measured using transmission electron microscopy (TEM). From the FTIR results, the peaks obtained are closely related to phenols, flavonoids, benzophenones, and anthocyanins which suggest that they may act as the reducing agent. This method is environmentally safe without the usage of synthetic materials which is highly potential in biomedical applications.

Electron microscopy determination of crystallographic polarity of aluminum nitride thin films

The microstructure of an AlN template after high-temperature annealing was investigated by transmission electron microscopy (TEM). The AlN template was prepared by depositing an AlN layer of about 200 nm thickness on a sapphire (0001) substrate by metal–organic vapor phase epitaxy. The AlN template was annealed under (N2 + CO) atmosphere at 1500–1650 °C. TEM characterization was conducted to investigate the microstructural evolution, revealing that the postannealed AlN has a two-layer structure, the upper and lower layers of which exhibit Al and N polarities, respectively. It has been confirmed that postannealing is an effective treatment for controlling the microstructure.

Preliminary Study on Deformation and Recrystallization Behavior of Pure Tin for Mitigation of Whisker Growth

The changes of microstructure in pure-Sn after deformation were investigated by electron microscopy. Two types of specimens were prepared: Sample-1; pure-Sn/Fe-42Ni, Sample-2; single crystalline pure-Sn. The growth of curling whiskers on Sample-1 was observed in-situ in a scanning electron microscope (SEM). A thin foil specimen of the curling whisker was made with a focused ion beam (FIB) mill. Transmission electron microscope (TEM) analysis confirmed that the curling whisker was of a single crystal regardless of its external shape. New models for growth process of a bent single-crystalline whisker were proposed. The models are composed of epitaxial growth and recrystallization. Electron back scatter diffraction (EBSD) analysis was performed for Sample-2. The results of EBSD strongly suggested that recrystallization proceeds even at room temperature. These experimental results are very important to understand the behavior of dynamical deformation and recrystallization of Sn metal, and useful in consideration the mitigation of whiskers.

Electron Microscopy of the Tin-oxide Nanolayer Formed on the Surface of Sn-Ag-Cu Alloys

Aluminum nitride (AlN) crystallizes usually in the wurtzite structure (P63mc) and it has a crystallographic polarity. In this work, the polarity in AlN was characterized by using several methods of transmission electron microscopy (TEM) in order to examine their applicability. AlN was deposited by metalorganic vapor phase epitaxy (MOVPE), followed by annealing at 1550u2009°C. TEM samples were prepared by using a focused ion beam (FIB) mill. Observation was performed with microscopes of JEM-2100, JEM-ARM200u2009F and FEI Titan Cubed G2 at Kyushu University (Japan), and the following results were obtained. (1) Conventional TEM imaging: Under a diffraction condition with hkilu2009=u20090002, inversion domains or an inversion domain boundary (IDB) was observed. (2) Scanning TEM (STEM) High-Angle Annular Dark Field (HAADF) imaging: Even when atomic column images of Al and N are not resolved completely from each other, the polarity was determined from the shape of atomic column images. (3) Scanning moire fringe imaging: The moire fringe pattern indicated the position of IDB and determine the direction of polarity. (4) Convergent beam electron diffraction (CBED): CBED was applicable for determination of the polarity in AlN at the acceleration voltage of 120u2009kV. Hence the polarity, direction of polarity and inversion domain boundary was determined using advanced TEM methods.

Piezoelectric element and its manufacturing method

Since the mechanism of Sn-whisker growth is closely related with the behavior of deformation and recrystallization, understanding of the behavior is very important to establish the measure for mitigation of whisker growth. In this work, microstructural changes after heavy deformation by scratching were characterized by EBSD for a single crystal of β-Sn, and the following results were obtained. Three types of crystal grains appear immediately after the deformation; small grains in aggregation, large serrated grains and rim-grains. The small grains are considered to be formed by dynamic recrystallization. They continue to grow at a room temperature over a lengthy period of time. The large grain has a certain crystallographic relationship with the matrix where <100> axes of the large grain and the matrix are almost parallel to each other. The serrated boundaries of large grain are so stable that the large grain does not show a grain growth process. The stable boundary is considered to promote a continuous growth of whiskers.

METHOD OF MANUFACTURING IRON SOFT MAGNETIC POWDER COATED WITH SPINEL FERRITE FILM CONTAINING ZINC AND SOFT MAGNETIC SINTERED COMPOSITE MATERIAL PRODUCED BY THIS METHOD

Sn-Ag-Cu alloy used in the present study is commercial Sn-3.0Ag-0.5Cu solder ball alloys with a diameter of 400 and 300 μm which were long term atmospheric oxidized for about 6 years (specimen-1) and under high temperature/humidity at 85°C and relative humidity of 85% for 2140 h, respectively. Morphologies and nanostructure of the oxide nanolayers formed on the surface of Sn-Ag-Cu alloys were studied from the interface of the oxide film and the tin substrate by transmission electron microscopy (TEM) to verify the oxidation mechanism. Cross-sectional TEM specimens were prepared using a focused-ion-beam (FIB) micro-sampling technique. Before the FIB fabrication, the specimen surface was coated with carbon (C) and tungsten (W) films. Inhomogeneous thickness of tin-oxide nanolayer formed on specimen-1 and specimen-2 were fluctuated between 20-40 nm and 40-50 nm, respectively. The nanolayer on specimen-1, however, consists of polycrystalline SnO and SnO2, whereas the one on the specimen-2 comprises of polycrystalline SnO2. High resolution (HRTEM) image and fast Fourier transformation (FFT) spectra corresponding to the interface and the substrate areas have confirmed those results. The results verify that at very long atmospheric oxidation Sn was gradually oxidized to be SnO (Sn2+) and then SnO2 (Sn4+), in which SnO is present at the region closed to interface between Sn-substrate and the tin-oxide layer. At high temperature oxidation, however, Sn was completely oxidized to be SnO2.