糸井 貴臣

TiC-Ti coatings were successfully formed on alumina (Al2O3) balls by the mechanical coating technique (MCT) using Ti and TiC powders. The influence of the added amount of TiC powder in MCT on the coating formation of the TiC-Ti coatings was investigated, and the results revealed that Ti powder is easier to coat on Al2O3 balls than TiC powder. The effect of the added amount of TiC powder on the thickness of the TiC-Ti coatings could be considered to be with three stages. After heat treatment in carbon powder for the TiC-Ti coatings, rutile TiO2 formed on the surface of the TiC-Ti coatings to be the photocatalyst composite coatings of TiO2/TiC-Ti. When the added amount of TiC powder was lower than 60%, the relative X-ray diffraction (XRD) intensity of rutile TiO2 peaks obviously became stronger with increasing the added amount of TiC powder. The photocatalytic activity of the TiO2/TiC-Ti coatings under visible light irradiation first increased and then decreased with increasing the added amount of TiC powder, and the photocatalytic activity showed highest when the added amount of TiC powder was 60%. (C) 2016 Elsevier B.V. All rights reserved.

The growth kinetics and properties of nominally 1-ML (monolayer)-thick InN wells on/in +c-GaN matrix fabricated using dynamic atomic layer epitaxy (D-ALEp) by plasma-assisted molecular beam epitaxy were systematically studied, with particular attention given to the effects of growth temperature. Attention was also given to how and where the similar to 1-ML-thick InN layers were frozen or embedded on/in the +c-GaN matrix. The D-ALEp of InN on GaN was a two-stage process; in the 1st stage, an "In+N" bilayer/monolayer was formed on the GaN surface, while in the 2nd, this was capped by a GaN barrier layer. Each process was monitored in-situ using spectroscopic ellipsometry. The target growth temperature was above 620 degrees C and much higher than the upper critical epitaxy temperature of InN (similar to 500 degrees C). The "In+N" bilayer/monolayer tended to be an incommensurate phase, and the growth of InN layers was possible only when they were capped with a GaN layer. The InN layers could be coherently inserted into the GaN matrix under self-organizing and self-limiting epitaxy modes. The growth temperature was the most dominant growth parameter on both the growth process and the structure of the InN layers. Reflecting the inherent growth behavior of D-ALEp grown InN on/in +c-GaN at high growth temperature, the embedded InN layers in the GaN matrix were basically not full-ML in coverage, and the thickness of sheet-island-like InN layers was essentially either 1-ML or 2-ML. It was found that these InN layers tended to be frozen at the step edges on the GaN and around screw-type threading dislocations. The InN wells formed type-I band line-up heterostructures with GaN barriers, with exciton localization energies of about 300 and 500 meV at 15 K for the 1-ML and 2-ML InN wells, respectively. (C) 2016 Author(s).

An Al sheet and a Ni-coated Cu sheet were lap joined by using magnetic pulse welding (MPW). Tensile tests were performed on the joined sheets, and a good lap joint was achieved at a discharge energy of >0.9 kJ. The weld interface exhibited a wavy morphology and an intermediate layer along the weld interface. Microstructure observations of the intermediate layer revealed that the Ni coating region consisted of a Ni-Al binary amorphous alloy and that the Al sheet region contained very fine Al nanograins. Ni fragments indicative of unmelted residual Ni from the coating were also observed in parts of the intermediate layer. Formation of these features can be attributed to localize melting and a subsequent high rate cooling of molten Al and Ni confined to the interface during the MPW process. In the absence of an oxide film, atomic-scale bonding was also achieved between the intermediate layer and the sheet surfaces after the collision. MPW utilises impact energy, which affects the sheet surfaces. From the obtained results, good lap joint is attributed to an increased contact area, the anchor effect, work hardening, the absence of an oxide film, and suppressed formation of intermetallic compounds at the interface. (C) 2016 Elsevier Inc. All rights reserved.

We have examined vanadium nitride (VN) films as a candidate material for the low-resistivity diffusion barrier of Cu interconnects in Si-LSI technology, aimed at reducing the interconnect resistance. We successfully prepared a continuous and uniform VN film as thin as 5 nm with a nanocrystalline texture with grains 2-5 nm in size. The VN barrier applied to the model system of Cu/VN/SiO2/Si and Cu/VN/SiOC/Si shows excellent barrier properties; the ultrathin barrier shows a negligible structural change and the absence of Cu penetration and/or interfacial reaction in the systems after annealing at 500 degrees C. The properties of an ultrathin VN barrier, such as low resistivity (50 mu Ocm) and high density (5.8 g/cm(3)), are attributed to the formation of a stable d-VN phase in a nanocrystalline texture with grains of size smaller than or equal to the barrier thickness that stands high in a structurally stable and chemically inert barrier. (C) 2016 The Japan Society of Applied Physics

Superplastic behavior of a Zn 22 mass % Al eutectoid alloy (SPZ) with small addition of Sn (SPZSn) was investigated. Granular grain size of about 0.3 μm was obtained by water quench after annealing SPZ and SPZ05Sn (addition of 0.05 mass % Sn into the SPZ) at 653 K for 2 h. The fundamental microstructure of the SPZ05Sn was similar to that of the SPZ, but, microstructure observation by Scanning Transmission Electron Microscope (STEM) showed additive Sn was present at the α’ grain boundary in the SPZ05Sn. Excellent high strain rate superplasticity was achieved in the SPZ05Sn, with elongation of more than 1300% at 523 K at strain rate of 10-1 S-1. Furthermore, large elongation of about 1100% was recorded at 473 K at strain rate of 10-1 S-1. The large elongation and high strain rate sensitivity value of the SPZ05Sn tend to shift to higher strain rate region as compared to those of the SPZ. It was considered that the small addition of Sn into the SPZ effectively suppressed the grain growth of α and β phase during the superplastic deformation, because granular grains less than 2 μm is maintained after superplastic deformation at 523 K.

This study optimized photocatalytic hydrogen purification using the preferential oxidation (PROX) of CO impurities among nanoscale disk-like, spheroidal, and rod-like ZnO promoted by adsorbed Cu ions. Four key factors were examined.

The design and synthesis of nanoscale zinc oxides (ZnOs) and their applications to photocatalysis are widely explored. However, the photocatalytic controls needed to design appropriate crystalline faces and promoter sites for each catalytic reaction step using ZnO have been rarely reported. This study optimized photocatalytic hydrogen purification using the preferential oxidation (PROX) of CO impurities among nanoscale disk-like, spheroidal, and rod-like ZnO promoted by adsorbed Cu ions. Four key factors were examined: (1) the diffusion length to the surface of separated electrons and holes induced by light; (2) the crystalline face where formate was formed from CO and its stability; (3) the crystalline face where Cu ions adsorbed for trapping electrons and reducing O-2; and (4) the frequency factor of "charge recombination as cations and anions" derived from photogenerated holes and electrons, respectively, at the boundary of crystalline faces. The optimal photocatalyst for hydrogen purification (CO PROX) was determined to be Cu-spheroidal ZnO. An efficient photocatalytic cycle was obtained by increasing the frequency factor between unstable unidentate formate on the (000 (1) over bar) face and Cu ions adsorbed on neighboring unsaturated {10 (1) over bar1} faces.

Solar cells and fuel cells have been extensively investigated. However, the need for sustainability, durability, and an electromotive force greater than 1.5 V per cell has not yet been fully realized. Herein, a photofuel cell (PFC) comprising two photocatalysts TiO2 and BiOCl that uses acidic water as a fuel is described. The PFC is designed such that water can be regenerated from the photogenerated O2 in the cell, and the electromotive force is as high as the difference between the conduction band minimum of TiO2 and the valence band maximum of BiOCl (theoretical: 2.75 V, experimental: 1.76 V). The photocurrents were in accordance with a kinetic model based on the combination of the excited electron concentration at TiO2 and the hole concentration at BiOCl. The reaction between the surface sites of O and/or Cl-deficient BiO1-xCl1-y species formed by ultraviolet-visible light irradiation with O-2 was in situ monitored using Bi L3-edge extended X-ray absorption fine structure and X-ray photoelectron spectroscopy supported by Raman and UV-visible spectroscopy and could be involved in the cathodic O2 photoreduction in the PFC. Furthermore, amorphous-like BiO1-xCl species were observed on the surface of the BiOCl crystallites in high-resolution transmission electron microscopy. Importantly, this PFC that comprises TiO2 and BiOCl is sustainable, recyclable, and has a series resistance that can be controlled by adjusting the BiOCl particle size, and exhibits a more efficient charge flow because of band bending than that of a previously reported PFC based on the rectification of the Schottky barrier.

Using electric-field-assisted solid-state ion exchange, we formed a buried silver nanowire network in borosilicate glass. This procedure had two stages: a silver doping stage by applying voltage with silver as the anode (referred to as forward) and a silver precipitation stage by applying voltage in the opposite direction (referred to as reverse). Microscopic observations revealed many needle-like precipitates (100-300 nm in diameter) linked to each other, forming a thin layer at the bottom of the silver-doped area. The configuration of the layer formed in the glass matrix was precisely transferred from that of the dopant, silver foil in the present study. The embedded electrical wiring in the glass slide was tested using a patterned circuit-like silver foil as a dopant. Measuring the electrical resistance between two ends of the formed wire, we found that the embedded layer had high conductivity and acted as an electrical circuit. (C) 2014 AIP Publishing LLC.

Piezoelectric energy harvesters can be used to convert ambient energy into electrical energy and power small autonomous devices. In recent years, massive effort has been made to improve the energy harvesting ability in piezoelectric materials. In this study, reduced graphene oxide was added into poly(vinylidene fluoride) to fabricate the piezoelectric nanocomposite films. Open-circuit voltage and electrical power harvesting experiments showed remarkable enhancement in the piezoelectricity of the fabricated poly(vinylidene fluoride)/reduced graphene oxide nanocomposite, especially at an optimal reduced graphene oxide content of 0.05 wt%. Compared to pristine poly(vinylidene fluoride) films, the open-circuit voltage, the density of harvested power of alternating current, and direct current of the poly(vinylidene fluoride)/reduced graphene oxide nanocomposite films increased by 105%, 153%, and 233%, respectively, indicating a great potential for a broad range of applications.

A photofuel cell comprising two photocatalysts TiO2 and Ag-TiO2 is demonstrated. The open circuit voltage, short circuit current, and maximum electric power of the PFC were 1.59 V, 74 mu A, and 14 mu W, respectively. The electron flow was rectified due to the Schottky barrier between TiO2 and Ag nanoparticles.

In this study, the microstructure and mechanical properties of Mg-Zn-Y alloy sheets were investigated. Tensile tests at room temperature were performed along the rolling direction of Mg98Zn1Y1-, Mg96Zn2Y2-, and Mg94Zn3Y3- alloy sheets and their annealed states (773 K for 0.6 ks). These alloy sheets exhibited yield strengths of 261, 317, and 380 MPa, and elongations of 12, 10, and 6%, respectively. The yield strength of a Mg-Zn-Y alloy sheet with Zn and Y contents greater than 2 at% was higher than 300 MPa. The microstructure observations suggested that the alloy sheet strength mainly resulted from (i) the formation of basal texture in the long period stacking ordered (LPSO) phase and (ii) the uniform dispersion of a fine Mg3Zn3Y2 phase. In the annealed state, the yield strength tended to decrease, while the elongation tended to increase. Large elongations of 20% or more were achieved in the Mg98Zn1Y1- and Mg96Zn2Y2 -alloy annealed sheets. The cold workability of the Mg-Zn-Y alloy sheets and an AZ31-O sheet were evaluated, using a V-bending test at room temperature. Both Mg98Zn1Y1- and Mg96Zn2Y2- annealed sheets could be bent without cracking with a minimum bending radius per thickness of 3.3, which was less than that of the AZ31-O sheet. Texture randomization occurred in the Mg-Zn-Y alloy annealed sheets owing to recrystallization of the Mg phase, which was confirmed by electron backscattering diffraction (EBSD) analysis. Large elongations and good cold workability of the Mg-Zn-Y annealed sheets are presumably attributed to an increase in the randomness of the Mg phase owing to re-crystallization. These results suggested that a Mg alloy sheet of high yield strength or good cold workability could be prepared by controlling the alloy composition and its microstructure in the Mg-Zn-Y alloy system. (C) 2012 Elsevier B.V. All rights reserved.

A set of resistance-type strain sensors has been fabricated from metal-coated carbon nanofiller (CNF)/epoxy composites. To nanofillers, i.e., multi-walled carbon nanotubes and vapor growth carbon fibers (VGCFs) with nickel, copper and silver coatings were used. The ultrahigh strain sensitivity was observed in these novel sensors as compared to the sensors made from the CNFs without metal-coating, and conventional strain gauges. In terms of gauge factor, the sensor made of VGCFs with silver coating is estimated to be 155, which is around 80 times higher than that in a metal-foil strain gauge. The possible mechanism responsible for the high sensitivity and its dependence with the networks of the CNFs with and without metal-coating and the geometries of the CNFs were thoroughly investigated. (C) 2012 Elsevier Ltd. All rights reserved.

Mg96Zn2Y2 (at.%) extruded alloy was fabricated by hot-extrusion of the Mg96Zn2Y2 machined chip. The Mg96Zn2Y2 extruded alloy consisted of a long period stacking ordered (LPSO)-, Mg3Zn3Y2- and Mg- phases. The Mg phase with mean grain size of 450 am was confirmed by TEM. However, the LPSO- and Mg3Zn3Y2- phases had relatively large grain size compared with Mg phase. The Mg96Zn2Y2 extruded alloy also showed superplasticity at temperatures of 623 K and 723 K with initial strain rates from 2x10(-1) s(-1) to 2x10(-3) s(-1). The maximum elongation of 450 % was achieved at 723 K with an initial strain rate of 2x10(-3) s(-1). From TEM observation, it is considered that grain boundary sliding of Mg grains was dominant deformation mechanism of the Mg96Zn2Y2 extruded alloy at high temperature range.

Preferential oxidation of CO (63 Pa) and O-2 (76 Pa) in H-2 (6.3 kPa) using spheroidal ZnO nanoparticles (22 nm x 47 nm) converted 52% of CO into CO2, and selectivity to CO2 was 92 mol% under UV-visible light for 5 h. When 0.5 wt.% of Cu2+ was adsorbed on ZnO, 91% of CO was converted into CO2 with a selectivity of 99 mol% under UV-visible light for 3 h. CO (63 Pa) was photocatalytically decreased to 2.3 mPa (0.35 ppm) in O-2 (150 Pa) and H-2 (63 kPa) for 5 h with a selectivity of 94 mol%. As evident from a XANES peak at 8983.1 eV, the surface Cu-II sites trapped photogenerated electrons. Furthermore, O-2-derived species were reduced by accepting electrons from Cu-I and protons from the neighboring formate species, as indicated by the FT-IR peaks at 2985, 2879, 1627, 1587, and 1297 cm(-1). (C) 2011 Elsevier Inc. All rights reserved.

The unique properties of carbon nanotube (CNT) have made it very attractive as reinforcement in polymer nanocomposites in the hope of effectively improving the mechanical properties. In order to explore the effects of three appealing influencing factors, i.e., acid treatment, pressured curing, and liquid rubber (LR) on mechanical properties of nanocomposites, tensile tests, and single-edge notched bending (SENB) tests are carried out for four types of CNT-reinforced nanocomposites. Compared with type I of nanocomposites using pristine multiwalled carbon nanotube (MWCNT) as reinforcement for epoxy, which are termed as Epoxy/MWCNT, type II of Epoxy/MWCNT-COOH nanocomposites with acid-treated MWCNTs as reinforcement, show obvious improvement on tensile properties and fracture toughness. This positive effect of acid treatment can be attributed to better dispersion of CNTs and stronger interface based on the corresponding fracture surfaces. For type III of P-Epoxy/MWCNT-COOH nanocomposites under pressured curing, although the voids in samples are decreased effectively and the interface is strengthened, there is no expected positive results because of severe CNTs agglomeration. For type IV of P-Epoxy/LR/MWCNT-COOH nanocomposites, addition of LR results in at least around a threefold increase in fracture toughness compared with that of P-Epoxy/MWCNT-COOH, indicating the amazing effect of LR. The present work provides much more choices for fabricating specific CNT-reinforced nanocomposites with desired properties by reasonably combining proper fabrication conditions including acid treatment, pressured curing, liquid rubber with polymer matrix, and reinforcement loading. © 2012 American Society of Mechanical Engineers.

Microstructures of the long period stacking ordered (LPSO) phase deformed by compression test or rolling at room temperature were investigated. The Mg85Ni6Y9(at.%) alloy was composed mostly of plate-type phase with 10H-type LPSO structure. The Mg85Ni6Y9 alloy exhibited compression yield stress of 365 MPa and fracture strain of 30 % at room temperature. After compression test with applied stress of 25 %, a bend, delamination between basal planes and crack initiation at boundary of the LPSO phase were observed. From these microstructural features, it was considered that the deformation of the LPSO phase significantly influenced by a kink deformation. The Mg85Ni6Y9 alloy could be rolled with 30 % reduction at room temperature. The kink deformation was frequently observed in the LPSO phase of the alloy sheet. The basal plane texture was formed in plane sheet of the alloy sheet. However, it was more difficult to form basal plane texture in the LPSO phase than in the pure-Mg due to introduce the kink deformation. Therefore, it was considered that better rollability of the Mg85Ni6Y9 alloy compared with the pure-Mg was brought for the kink deformation.

The wear properties of pure-Mg, AZ31 extruded alloy, AZ91 cast alloy, and Mg90.5Cu3.25Y6.25 (at.%) cast alloy consisting of Mg and long-period-ordered (LPO) phases were investigated by pin-on-disk-type wear tests under dry sliding. The wear loss of the Mg90.5Cu3.25Y6.25 cast alloy at high-applied loads over 147 N was less than those of AZ Mg alloys, and about two-thirds of the AZ31 extruded alloy, which indicated that the Mg90.5Cu3.25Y6.25 cast alloy has superior wear-resistance. The basal planes (0 0 0 2) and (1 0 (1) over bar 1) were apparent in the X-ray diffraction patterns of worn surfaces of pure-Mg and Mg alloys. This XRD result indicated that basal planes in both the Mg and LPO phases were aligned to worn surfaces for the pure-Mg and Mg alloys, and this result was also supported by EBSD analysis. Because slip deformation tends to easily occur on the Mg basal plane at a low critical resolved shear stress (CRSS), formation of the basal-plane alignment on the wear surface negatively affects the wear-resistance properties. After the wear test of the Mg90.5Cu3.25Y6.25 cast alloy, a kink deformation in the LPO phase was frequently observed in the worn edge section. The kink deformation in the LPO phase contributes to improve wear-resistance properties by suppression of the basal-plane alignment. (C) 2011 Elsevier B.V. All rights reserved.

A series of structural polytypes formed in an Mg-1 at.% Zn-2 at.% Y alloy has been identified, which are reasonably viewed as long-period stacking derivatives of the hexagonal-close-packed Mg structure with alternate AB stacking of the close-packed atomic layers. Atomic-resolution Z-contrast imaging clearly revealed that the structures are long-period chemical-ordered as well as stacking-ordered; unique chemical order along the stacking direction occurs as being synchronized with a local faulted stacking of AB'C'A, where B' and C' layers are commonly enriched by Zn/Y atoms.

The tensile property and cold formability of a Mg96Zn2Y2 alloy sheet containing Mg-, long-period ordered (LPO)-, and Mg3Zn3Y2-phases were investigated. The Mg96Zn2Y2 alloy sheet exhibited a high yield stress of 320 MPa and elongations of 11% at room temperature and could be prepared by hot-rolling. After, annealing at 773 K for 0.6 ks, although the yield stress decreased to 200 MPa, elongation increased to 20%. Texture randomization due to re-crystallization of the Mg phase that occurred in the annealed Mg96Zn2Y2 alloy sheet was confirmed by EBSD analysis. The formability of a Mg96Zn2Y2 alloy sheet and an AZ31-O sheet was evaluated via a 90 degrees V-bending test at room temperature. The annealed Mg96Zn2Y2 alloy sheet could be bent without cracking with a minimum bending radius per thickness of R/t = 3.3, which is less than that of the as-rolled Mg96Zn2Y2 alloy sheet and the AZ31-O sheet. This improvement in the cold formability of the Mg96Zn2Y2 alloy sheet is considered due to an increase in randomness of the Mg phase that results from re-crystallization of the Mg phase. (C) 2010 Elsevier B.V. All rights reserved.

Microstructures and wear properties of a recycled Fe3Al-based alloy made from high-carbon Cr steel sludge and Al can scraps were first investigated in this study The alloy was composed of D0(3)-type Fe3Al matrix and Fe3AlC05 dispersions (kappa phase). Carbon in the steel sludge and Al can scraps contributes to the formation of the kappa phase Next, the recycled Fe3Al-based composites reinforced by transition metal carbides (TMC = TiC, NbC. V4C3, and ZrC) were fabricated by in-situ reactions between transition metals (TM = Ti, Nb, V. and Zr) and carbon when these transition metals are added to the molten Fe3Al-based alloy The (Fe,Al)(2)Nb intermetallic compound and a Fe-Al-Zr-C carbide are also formed in the Nb- and Zr-added Fe3Al-based composites with NbC and ZrC, respectively The Vickers hardness values of the recycled Fe3Al-based composites reinforced by TMC were higher than that reinforced only by the kappa phase Abrasive wear behavior is observed for these composites The carbides of the kappa phase, TiC, NbC, V4C3 and ZrC are still embedded in the matrix after abrasive wear without delamination or destruction. This result indicates that the carbides significantly affect the wear resistance of these composites. The wear resistance of the composites reinforced by TMCs is higher than that reinforced by the kappa phase Moreover, the wear resistance of the recycled Fe3Al-based composites reinforced by TiC is much higher than that of gray cast iron: the former value is comparable to that of high-carbon Cr steels Thus, carbon in the steel sludge and Al can scraps is useful to synthesize hard carbides with transition metals. We have succeeded in preparing the valuable recycled Fe3Al-based composites with excellent wear resistance from the industrial steel and Al scraps. (C) 2010 Elsevier Ltd All rights reserved.

Ternary Mg Zn Y alloy sheets with several volume fractions of a Mg12ZnY phase were prepared by hot rolling at 623 K Volume fraction of the Mg12ZnY phase was increased with increasing of Zn and Y contents in the Mg(100-\-\)ZN(x)Y(\) (\ = 1 similar to 6 v = 2 similar to 9 at%) alloys and achieved more than 85% in an Mg85Zn6Y9 alloy (002) pole figures showed both of basal planes of the Mg12ZnY and Mg phases have a tendency to incline toward parallel to the sheet surface However it it was considered that the formation of a basal plane texture in the Mg12ZnY phase is difficult compared with that in the Mg phase due to a kink deformation An Mg90 5Zn3 Y-25(6) (25) alloy sheet exhibited a 0 2% proof strength an ultimate tensile strength and an elongation of 353 MPa 400 MPa and 5% respectively at room temperature and 279 MPa 375 MPa and 12% respectively at 523 K Although elongation was slightly less than those in the commercial Mg sheets the Mg-90 Zn-5(3) Y-25(6) (25) alloy sheet showed high strength over a wide temperature range compared to those in commercial Mg alloys [doi 10 2320/matertrans L-M2010816]

Recycle-typed Fe3Al composites reinforced by Fe3AlC0.5 or TIC phases with several volume fractions were prepared from high-carbon Cr steel sludge. Al can scraps and pure-Ti metal. The feasibility of recycle-typed Fe3Al composites for practical use as cutting tools was investigated by conducting cutting tests under dry conditions using, as work materials, an Al alloy (A5056) for rough machining and pure-Cu (C1020) for finish machining. In the cutting tests of A5056 by rough machining, adhesive wear was the dominant wear mechanism. The ranking of tool life was inconsistent with that of tool hardness, and the tool life of recycle-typed Fe3Al(3.3Ti) was longer than that of high-speed steel (HSS). In the cutting tests of C1020 by finish machining, the tool lives of recycle-typed Fe3Al composites were longer than that of HSS. After a 9 min cutting test with a recycle-typed Fe3Al (1.9Ti) tool, the surface roughness of C1020 was 0.8 mu m, about half of that cut with the HSS tool. These results suggested that recycle-typed Fe3Al composites have potential as cutting tools, and showed promise as viable alternatives to HSS. (C) 2010 Elsevier Ltd. All rights reserved.

We have investigated the evolution of microstructures in a nanocrystalline VN barrier of similar to 10 nm thickness to clarify the failure mechanism in a Cu/VN/SiO2/Si system owing to high-temperature annealing. Transmission electron microscopy observation reveals that the as-deposited VN barrier shows a uniform layer with a columnar structure composed of grains no larger than 10 nm in size. A negligible change in the morphology of the VN barrier is evident even after annealing at 600 degrees C for 1 h. Annealing at 800 degrees C brings about noticeable growth of VN grains in the lateral direction without any solid-phase reaction at each interface, resulting in a failure of the VN barrier owing to local discontinuity of the layer. This result is also consistent with the result obtained by Auger electron spectroscopy. It is revealed that the thin VN barrier fails after annealing at 800 degrees C for 1 h owing to the loss of the continuity in the lateral direction without chemical reaction and intermixing at barrier interfaces. (C) 2010 The Japan Society of Applied Physics

The composition dependence of yield strength and elongation of the Mg-Zn-Y ternary alloy system were investigated. Yield strength was found to increase with the increasing Zn and Y contents, while elongation decreased in Zn- and Y- rich- regions in the system. The composition ratio of Zn to Y, both of which shows large elongation and comparatively high yield strength, was 1:1 in the Mg-rich region of the alloy system. Mg98Zn1Y1 Mg96Zn2Y2, and Mg94Zn3Y3 (at.%) cast alloys exhibited yield strength of 107, 129, and 173 MPa, and elongations of 17, 8, and 12%, respectively. These alloys consist of Mg-, LPO-, and Mg3Zn3Y2- phases. We also prepared Mg-Zn-Y alloy sheets by hot rolling using cast alloys, and we investigated their microstructure and mechanical properties. The Mg98Zn1Y1, Mg96Zn2Y2, and Mg94Zn3Y3, alloy sheets exhibited yield strength of 276, 319, and 379 MPa, and elongations of 12, 11, and 8%, respectively. After annealing at 673 K for 3 h, large elongations above 20 % were achieved both of the Mg98Zn1Y1 and Mg96Zn2Y2 alloy sheets.

Platinum nanoparticles have been reported with mean sizes between 1.5 and 7 nm supported on carbon, The contact between Pt nanoparticles and C has never been controlled and monitored nanoscopically. In this paper, stable Pt nanoparticles with a mean size of 1.2 nm were synthesized embedded on/in a C matrix catalytically produced from acetylene over the Pt nanoparticles. The replica Pt-C composite was synthesized inside of the ordered mesopores (2.7 nm) of Al-MCM-41 followed by removal of the template. The contact between the Pt nanoparticle and C was experimentally observed by high-energy resolution Pt L(2)-edge XANES spectra tuned to 11065.7 eV, at a lower energy by 5 eV than the Pt L beta(1) peak top for the replica Pt-C pressed to electrolyte polymer (Nafion). The spectra were nicely reproduced in a theoretical spectrum using ab initio multiple scattering calculations for the interface Pt site between cuboctahedral Pt(38) and graphite layers. Other Pt sites detected in state-selective Pt L(2)-edge XANES were exclusively metallic for replica Pt-C/Nafion either in air or in H, The thus-characterized replica Pt-C composite was tentatively tested as a cathode of H(2)-air polymer electrolyte fuel cell in comparison to commercial 20 wt % Pt/Vulcan XC-72 as the cathode. The improvement of Pt dispersion stabilized on/in a C matrix, effective contact of Pt with C, and diffusion of O(2) in a few nanometers of replica Pt-C powder was suggested,

Anion doping to titanium oxide (TiO(2)) has been extensively studied to explore visible light-responsive photocatalysts. Among them, sulfur doping was most effective; however, the site structure and the implication to promoted photocatalysis have not been reported yet, except for valence state information based on X-ray photoelectron spectroscopy. Sulfur and/or nitrogen was doped to TiO(2) with a narrow pore size distribution, at 3 nm, using thiourea or urea. They were compared to the uniform mesoporous TiO(2) modified via the chemical vapor deposition (CVD) of hydrogen sulfide and the titanate/TiO(2) nanotube synthesized hydrothermally using TiS(2). In ethanol and O(2) under visible light (wavelengths of >370, >420, >480, >520, or >580 nm), water formation was promoted by a factor of 12, in clear contrast to the only 2.3x enhancement for acetaldehyde formation by doping sulfur. These anion-doped mesoporous TiO(2) catalysts were characterized using Ti and S K-edge extended X-ray absorption fine structure for the first time. The Ti-S bonds were detected at 2.283-2.44 angstrom for sulfur-doped mesoporous TiO(2) using thiourea and sulfur-doped mesoporous TiO(2) via CVD, demonstrating the presence of substitutional anionic S on the O sites. The doped anionic sulfur created impurity level(s) at 0.8-2.2 eV below the conduction band (CB) minimum of mesoporous TiO(2). It enabled the electron excitation to the CB and then to O(2) to convert to water under visible light. In contrast, the impurity level(s) at 0.8-2.2 eV below the CB minimum was/were not effective to (directly or indirectly) receive electrons from the substrate (ethanol/ethoxyl). Preferential water formation under visible light was also observed for TiO(2) nanotubes that were synthesized hydrothermally from TiS(2).

Hot extrusion of machined chips of Mg96Zn2Y2 (at%) alloy was carried out at 623 K, and microstructures and mechanical properties of the extruded Mg96Zn2Y2 alloy were investigated. The alloy consisted of alpha-Mg, Mg12ZnY, and Mg3Zn3Y2 phases, and the Mg grains had a mean grain size of 450 nm. The Mg12ZnY phase was frequently observed inside the fine Mg grains. In addition, oxidation occurred around cavities remaining after extrusion, The extruded alloy exhibited a high 0.2% proof strength of 495 MPa and elongation of 3% at room temperature. The Mg grain refinement and dispersion of Mg12ZnY and Mg3Zn3Y2 phases caused by hot extrusion led to high strength at room temperature. Further, the extruded alloy also exhibited superplasticity at temperatures of 623 and 723 K with initial strain rates from 2 x 10(-1) S-1 to 2 x 10(-3) S-1. The maximum elongation was 450% at 723 K with an initial strain rate of 2 x 10(-3) S-1. Grain boundary sliding of Mg grains is the dominant deformation mechanism for the alloy at high temperature ranges. [doi: 10.2320/matertrans.L-MRA2008842]

Ternary M90.5Ni3.25Y6.25 (at.%) cast alloy consisting of a long-period ordered (LPO) phase and alpha-Mg was rolled to 70% thickness reduction at 623K. After annealing at 673K for 6 h, kink bands of the LPO phase and alpha-Mg grains of about 700 nm were observed in the Mg90.5Ni3.25Y6.25 alloy sheet. The alloy sheet exhibited a yield stress, an ultimate tensile strength and an elongation of 460 MPa, 526 MPa and 8%, respectively, at room temperature, and 301 MPa, 345 MPa and 12%, respectively, at 523K. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Microstructure evolutions of rapidly-solidified (RS) ribbon and conventionally cast bulk Mg-1 at%Zn-2 at%Y alloys have been studied by transmission electron microscopy (TEM), particularly focusing on formation process and phase stability of the long-period structures. It is found that there are significant differences in microstructural evolutions between the RS ribbon and the cast-bulk alloys, in terms of thermal stability of the long-period phases at temperatures higher than 673 K. For both the as-quench ribbon and the as-cast bulk specimens, 18R-type long-period phase is dominantly observed at grain boundaries. After annealing at temperatures higher than 673 K, the long-period phases at grain boundaries in the RS ribbon almost disappear to form Mg24Y5 and Mg3Zn3Y2 compounds within the grain interiors, while the long-period phases remained stable in the cast-bulk alloy even at temperatures higher than 673 K.

The crystal structure of a new phase with an approximate composition of Mg91Ce7Zn2, which is formed as a main phase in an Mg91Ce6Zn3 alloy, has been determined by atomic-scale observations of high-resolution transmission electron microscopy (HRTEM) and high-angle annular detector dark-field scanning transmission electron microscopy (HAADF-STEM). The structure of this phase can be described as a one-dimensional incommensurate structure with an orthorhombic unit cell of a = 1.03 nm, b = 1.03 nm and c = 3.7 nm, formed by insertion of anti-phase boundaries in the fundamental Mg12Ce (Mn12Th-type) structure with a tetragonal unit cell of a(0) = 1.03 nm and c(0) = 0.60 nm. The anti-phase boundaries are parallel to the (001) plane of the fundamental tetragonal structure, and an average interval of the boundaries along the [001] direction is about 3.1 c(0). Also, a commensurate structure with an interval of 5.5c(0) is observed as a coexisting phase with the incommensurate structure.

Single-wall carbon nanohorn (SWNH), which is a tubular particle with a cone cap, was oxidized in an oxygen flow at various temperatures. N-2 adsorption at 77 K, thermogravinietry (TG), differential thermal analysis (DTA), transmission electron microscopy, and Raman spectroscopy measurements were carried out on the oxidized SWNHs. The specific surface area of the oxidized SWNHs can be controlled by oxidation temperature, giving the maximum value of 1420 m(2)/g. The pore size distribution by the BJH method and the comparison plot of the N2 adsorption isotherms of SWNH oxidized at different temperatures against that of as-grown SWNH revealed the minimum oxidation temperature for opening internal nanopores. TG-DTA analyses determined the components of as-grown SWNH: amorphous carbon 2.5 wt %, defective carbon at the cone part 15 wt %, tubular carbon 70 wt %, and graphitic carbon 12 wt %. These systematic analyses provided the exact internal nanopore volume of 0.49 mL/g for pure SWNH particles.

Thin nanocrystalline vanadium nitride (VN) films of low resistivity were examined as an extremely thin diffusion barrier to provide thermal stability in Cu/VN/SiO2/Si systems. A 10-nm-thick VN barrier with grains ranging from several to similar to10 nm in diameter provided excellent barrier properties. After annealing at 600 degreesC for 1 h, the barrier showed scarcely any change in structure and absence of Cu diffusion and/or decisive interfacial reaction in the system. This was interpreted to mean that the present barrier, which is made of a thermochemically stable delta-VN compound phase with a slightly nitrogen-rich composition and a nanocrystalline structure, was preferable to suppress the solid-phase reaction and/or diffusion, as well as the structural change upon annealing. It was revealed that the nanocrystalline VN barrier is an excellent candidate as a barrier in a forthcoming Cu metallization scheme. (C) 2004 American Vacuum Society.

A long period stacking (LPS) structure with 18R-type has been observed in Mg97Zn1Y2 (at%) alloy prepared by Cu-mold casting and induction melting methods. The 18R-type LPS structure is also found in the Mg97Zn1Er2 alloy prepared by the induction melting method. After annealing at 773 K for 5 h, the 18R-type LPS structure in the Mg97Zn1Y2 alloy is transformed to a 14H-type LPS structure. (C) 2004 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Ternary nitride TiZrN films with nano-crystalline grains of 2-10 nm in size and similar to90 muOmega cm in resistivity were successfully prepared as a material applicable to a thin diffusion barrier of low electrical resistivity. In the Cu/TiZrN/Si contact system, a TiZrN film with similar to10 nm thickness is the barrier adequate to suppress the extremely small quantity of Cu penetration into the Si substrate upon annealing at 600 degreesC for 1 h without significant structural change and solid-phase reaction. The observed stable nano-crystalline structure and chemically inert characteristic of TiZrN were the dominant features for the successful demonstration of high performance barrier properties of thin TiZrN films. (C) 2003 Elsevier Science B.V. All rights reserved.

The microstructure and Vickers hardness of the Mg97Zn1Y2 RS P/M alloys extruded at several temperatures (573Ksimilar to723K) have been investigated. Transmission electron microscopy (TEM) observations indicated that the 6 periodic hexagonal (6H) structure was formed in these RS P/M alloys. With increasing the extrusion temperature from 573 to 723K, the average grain size increased from 180 to 490nm. The Mg grains of the Mg97Zn1Y2 RS P/M alloy consolidated at 723K grew form 490nm to 1.3 mu m, in diameter by annealing at 773K for 5h. However, the 6H structure existed without any apparent structural change due to its high thermal stability. The Vickers hardness decreased from 136 to 69 with increasing of the grain size. However, the Vickers hardness of the Mg97Zn1Y2 RS P/M alloys estimated on the Hall-Petch relation was much higher than that of pure Mg. The results indicated that a remarkable gap between the Hall-Petch relations of the Mg97Zn1Y2 RS P/M alloys and pure Mg was originated from 6H structure in the Mg97Zn1Y2 RS P/M alloys. The present results demonstrate the 6H structure improved the strength of the Mg97Zn1Y2 RS P/M alloys as well as the fine grains.