Various kinds of clusters such as hydrogen, ionic, and metallic bonding clusters were generated using several unique methods such as the nozzle beam, high-electric-field, and evaporation-on-liquid methods. The size and structure of these clusters were analyzed by time-of-flight (TOF), high-energy electron diffraction (HEED), transmission electron microscopy (TEM), and small-angle X-ray scattering (SAXS). In addition, the impact of the cluster ions on a solid surface was investigated, and unique irradiation effects were found, such as the low-energy irradiation effect and the high-density irradiation effect. The kinetic energy of the cluster ion was converted to thermal energy, resulting in extremely high temperatures. Furthermore, the simultaneous use of chemical sputtering and thermal annealing processes was demonstrated with ethanol cluster ion beams. As a result, low irradiation damage and high-rate sputtering of Si surfaces was performed by the retardation potential method.
A novel homogeneous transition-metal catalyst, a polymer-supported terpyridine–palladium(II) complex, was found to promote the aminocarbonylation of aryl iodines using methoxylamine under phosphine-free conditions in water with good yield. The catalyst was recovered and reused several times without loss of catalytic activity. To our knowledge, this is the first example of polymer-supported, palladium-catalyzed synthesis of primary amides by aminocarbonylation of aryl iodides and methoxylamine under phosphine-free conditions in water.
We synthesized carbon nanowalls on a Si substrate by microwave surface-wave plasma chemical vapor deposition. The Raman scattering ID/IG ratio was changed by altering the DC bias applied to the growth substrate and the decrease in ID/IG with increasing DC bias appears to arise from the growing length of the carbon nanowalls. The ultrasonically separated carbon nanowalls in ethanol exhibited strong 2D-peak intensity and significant graphitization. A graphite layer of approximately 10 nm grew parallel to the substrate initially, and the carbon nanowalls grew on top of that. When the nanowalls were dispersed in ethanol and spin-coated onto PET, they exhibited a transmittance of 81% and a sheet resistance of 52 kΩ/□ without reduction treatment used in the graphene oxide.
In dispersion-type inorganic electroluminescence (EL) devices, a high-voltage drive is required to achieve high luminescence, as the thickness of the phosphor layer is 20 μm or more. Transparent electrodes such as indium tin oxide (ITO) are required, because light emission from the phosphor layer is necessary. To solve these issues, we developed a circular comb-type metal electrode with several narrow gaps on a glass substrate that produces a strong electric field, which is impossible to achieve with conventional structures. A comb-type metal (Au) electrode and a comb-type ITO electrode were used in the experiments. The luminance from the phosphor layer side at 30 V/μm was 26.9 cd/m2 for the Au electrode, which was twice that for the ITO electrode (19.9 cd/m2). Thus, it is possible to fabricate a light-emitting device without transmissive electrodes by using a lustrous metallic material such as Au with a circular comb-type design.
Large vacancy clusters in aluminum single crystals with low dislocation density, which show up as black dots in X-ray topographs, generate new dislocations and stacking faults during heat treatments. In order to obtain dislocation-free or low-dislocation-density metal single crystals, it is necessary to suppress the formation of large vacancy clusters. To this end, our starting material was either (1) ultrahigh-purity aluminum, intended to minimize the number of nucleation sites for large vacancy clusters, or (2) a dilute alloy of Zn in Al, intended to block the migration of excess vacancies by binding them with zinc atoms during slow cooling. Single crystals of the Al-Zn dilute alloy failed to improve the perfection unless a large vacancy cluster was formed. Upon cyclic annealing, however, the number density of black dots in X-ray topographs of ultrahigh-purity aluminum crystals decreased rapidly and significantly. It was thus confirmed that using a high-purity starting material was effective in suppressing the formation of large vacancy clusters.
The fungi Botrytis cinerea and Colletotrichum acutatum were used to convert acetophenone to 1-phenylethanol. B. cinerea produced a 98.5% yield of 1-phenylethanol with an enantiomeric excess of 93.8%. Conversely, addition of 1-phenylethanol did not change the reaction rate or product composition. In contrast, the reaction catalyzed by C. acutatum was markedly slower, commencing only after an approximately three-day delay. The concentration of substrate decreased gradually over approximately 14 days, coinciding with increased production of 1-phenylethanol. Phenol was produced after 18 days, and the final yields of 1-phenylethanol and phenol were 38.1% and 61.5%, respectively.
(Na0.50K0.45Li0.05)NbO3 (NKLN) powder was synthesized by the malic acid complex solution method, and NKLN solid solutions were then fabricated at firing temperatures of 900−1050℃ using a conventional solid-state reaction technique. The piezoelectric properties of the resulting materials were measured, and samples produced at 950℃ were found to exhibit the maximum d33 and kp values of 151 pC/N and 32%, respectively. On the basis of a local structural analysis using high-energy X-ray diffraction, the distortion of NbO6 octahedra, which is the origin of the ferroelectric properties, also exhibited a maximum at 950℃. Thus, this is the optimal firing temperature for fabricating NKLN samples with excellent piezoelectric properties and the largest NbO6 octahedral distortion.
Zn-rich CuxZnyS is a transparent p-type semiconductor. In this study, we fabricated CuxZnyS thin films by electrochemical deposition and investigated changes in properties due to annealing in a sulfur atmosphere. The sample before annealing was amorphous with composition Cu : Zn : S : O = 0.03 : 0.29 : 0.57 : 0.11. After one hour annealing at 400℃, we observed formation of the ZnS phase by X-ray diffraction and Raman measurements. Although the sample exhibited p-type conductivity before the annealing, it did not clearly show p-type conductivity after the annealing at temperatures higher than 300℃. Those results indicate that CuxZnyS is a metastable phase and is believed to separate into the ZnS phase and a phase including Cu by the annealing at temperatures higher than 300℃.
To develop high-performance materials for high-power piezoelectric applications, ternary high-density solid solutions with compositions of xPb(Zr0.52Ti0.48)O3−yPb(Mn1/3Sb2/3)O3−zPb(Zn1/3Nb2/3)O3 (PZTxPMSyPZnNz) with x = 0.82−0.96, y = 0.02−0.16, and z = 0.02−0.16, were fabricated by a conventional solid-state reaction method. A detailed investigation was carried out into the microstructure and crystal structure of the samples, together with their piezo- and ferroelectric properties. It was found that a solid solution with x = 0.86, y = 0.085, and z = 0.055 and a rhombohedral structure exhibited excellent piezo- and ferroelectric properties. These included piezoelectric coefficients d33 (longitudinal length mode) = 170 pC/N and -d31 (transverse length mode) = 69 pC/N, a mechanical quality factor Qm(p) (radial mode) = 2218, d33⋅Qm(p) = 376×103 pC/N, -d31⋅Qm(p) = 133×103 pC/N, electromechanical coupling factors kp (radial mode) = 46% and k31 (transverse length mode) = 28%, a Curie temperature Tc = 259℃ a remanent polarization 2Pr = 53 μC/cm2, and a coercive field 2Ec = 34 kV/cm. Thus, this is a highly promising piezoelectric material for high-power ultrasonic vibrators and piezoelectric transformers.
The BiFe1-xMnxO3(BFMO) film shows monoclinic structure distorted along the <110> direction, while high quality [CaFeO3(CFO)/BFMO] superlattice grows with tetragonal structure, lattice parameter of which in-plane is fit to that of Nb doped SrTiO3(001) substrate. The BFMO film and the [CFO/BFMO] superlattice show similar M-H curves and saturation magnetic moment as a function of temperature. Magnetic moment rapidly increases in low magnetic field region and then gradually develops and saturated in high field region at 10 K. At 300 K, magnetic moment saturates in low magnetic field. As a temperature increases, saturation magnetic moment per magnetic ion rapidly decreases above 10K, and then gradually reduces. The magnetic moment at 300K of BFMO is 0.107μB higher than 0.034μB detected in the [CFO/BFMO] superlattice, probably due to the thin BFMO layer in the superlattice. Estimated TC of the BFMO film and the superlattice is 600 K and 500K, much higher than room temperature. Leakage current behavior indicates the Fowler-Nordheim tunneling and Schottky emission at Au/BFMO interface and Poole-Frenkel hopping conduction in the BFMO layer.
Fermi level and valence state were investigated in RFe2O4 (R = Y, Dy, Ho, Er, Tm, Yb, Lu, Sc, or In), which shows magnetoelectric effect originating from charge and magnetic orders of Fe2+ and Fe3+. We succeeded in controlling the Fermi level of YbFe2O4 system by Ti4+ substitution for Yb3+. The variation in the ratio of Fe2+ to Fe3+ is suggested to the origin of the Fermi level variation. This report suggests the possibility of simple selection of conduction type in functional oxide.
The influence of intrinsic defects and hydrogen-defect complexes on the properties of n-type ZnO crystals has been studied in terms of annealing and hydrogen plasma irradiation. Electrical and optical properties have been found to be dependent on annealing conditions and hydrogen plasma irradiation. When an as-polished sample was annealed in Ar atmosphere containing Zn vapor at 800°C for 2 h, the color of the sample changed into orange because of the formation of oxygen vacancies (VO). In spite of the VO formation, Hall mobility of the sample increased from 162 to 210 cm2V−1s−1. Carrier concentration also increased by about four orders of magnitude. The simultaneous increases in carrier concentration and Hall mobility indicate that zinc vacancy (VZn) concentration, which acts as a compensation acceptor, are decreased by supplying Zn vapor during the annealing. Hydrogen plasma irradiation did not affect electrical properties of the sample annealed in Ar atmosphere containing Zn vapor, but improved those of the sample annealed in pure Ar atmosphere. The carrier concentration and Hall mobility increased by hydrogen plasma irradiation decreased with increasing post-annealing temperature. The post-annealing temperature dependence suggests that VZn passivated by hydrogen starts to dissociate at temperatures around 400°C.
Lead (Pb)-free piezoelectric films formed on metallic substrates are of interest for advanced piezoelectric devices. BaTiO3 films with a thickness of 10 μm were deposited on Fe-Cr-Al based heat-resistant stainless-steel substrates using aerosol deposition at room temperature. The BT film annealed at 1473 K for 1h had 1.2μm-diameter grains, of which crystal phase was the perovskite single phase of the tetragonal crystal system. The dielectric constant was 2200, and the dielectric loss was 0.02. Piezoelectric displacement of the cantilevers with annealed BT films on stainless-steel substrates improved with increased annealing temperature. The piezoelectric constant d31 of film annealed at 1473 K was -56 pm/V.
The pulley-type heat-engine using a shape memory alloy (SMA), which is consisted of pulleys and a coil or a liner shaped SMA element, is one of the representative SMA heat-engines for recovering low-temperature exhaust heat energy. However, the output-power of pulley-type SMA engines tends to reduce due to the cooling insufficiency of the SMA element because the main cooling method of this engine is air cooling. Furthermore, the reduction in size of the mechanism of this engine is incompatible with augmentation of the power output. For improvement of the cooling efficiency and output power, we propose the use of a tape-shaped SMA element and invented a new cooling system contained in the pulley. By using this system, the mechanism of pulley-type SMA heat-engine can be made compact and temperature stability of the SMA elements during operation is achieved. Results of the experiment show the peak output power to be approximately equal regardless of the presence/absence of operation of the cooling system. However, the output power of the engine without cooling decreases to less than half of the maximum power due to overheating during operating. On the other hand, the decrement of engine output during operation is suppressed by approximately 10 %, by the operation of cooling system. Furthermore, the optimal inter-shaft distance of pulleys is shortened by the cooling system. This tendency is caused by the transformation ability improvement of the SMA element due to the improvement in cooling efficiency.
Raman measurements and uncertainty evaluations were conducted for C60 fullerene nanowhiskers (C60FNWs) synthesized using the liquid-liquid interfacial precipitation (LLIP) method and for a vacuum-deposited C60 thin film. No photopolymerization was observed for the C60 molecules when the specimens were irradiated by a green laser of 532 nm wavelength at a power density of 5.7×103 mW/mm2. It is demonstrated that the 1469.95 ± 0.42 cm-1 can be used as a standard peak position of the Ag(2) mode of C60FNWs.
Amphiphilic graft hydrogel containing hydrophobic poly(trimethylene carbonate) (PTMC) oligo segments was synthesized. The graft gel had PTMC segments with a degree of polymerization of either 11 or 21, and the in-feed composition ratio of the graft segments was 2 mol%. Three types of graft gels containing different hydrophilic monomer units as the main chain were synthesized by photo radical polymerization, and their swelling ratios and loading efficiencies of a model drug molecule were examined. The swelling ratio of the hydrogel decreased with increasing feed ratio of PTMC segments and was altered by the presence of hydrophilic monomer units. The hydrogel is cross-linked not only by the chemical cross-linker but also by the hydrophobic domain of the PTMC graft segment. Furthermore, the hydrophobic domain could be used to incorporate molecules such as a model drug. Two types of molecules such as hydrophobic and amphiphilic molecules were used, and the selectivity of the molecular incorporation in each graft gel was evaluated by UV–Vis spectroscopy. Both model drug molecules were incorporated into the graft gel, and an amphiphilic molecule was released from the shrunken gels; however, the hydrophobic molecule remained incorporated. These features are important for hydrophobic drug loading, and hence, the functional graft gels are expected to be useful for selective molecular incorporation.
This article describes a simple procedure to fabricate magnetically-responsive particles from as-prepared particles. Firstly, a magnetically-responsive, holmium-containing surfactant (DDAH) was prepared by mixing a commercially available surfactant and holmium(III) chloride hexahydrate. Subsequently, polydopamine (PDA) particles, which exhibit beautiful structural colors, were modified using the DDAH to afford PDA/DDAH particles. The magnetic behavior of the obtained PDA/DDAH particles was investigated. Furthermore, structural color changes of the materials prepared by PDA/DDAH particles under magnetic fields were also investigated.
Low-voltage electroluminescence (EL) at 390 nm was obtained in a MIS structure at applied voltage of 15-30 V from 3 at.% Ge-implanted 50-nm SiO2 layer samples after the successive two-stage annealing. From the optical emission, Ge-related oxygen deficiency centers (Ge-ODCs) are speculated to exist at a shallow depth. To clarify the creation depth of Ge-ODCs and roles of nanoparticles (NPs), Ge-oxidation states in the SiO2 layer and Ge NP were measured by two methods, i.e., X-ray photoelectron spectrometry (XPS) and 3-dimensional atom probe (3D-AP) after annealing: (1) in nitrogen gas flow at 700℃ for 1h and (2) in air flow at 700℃ for 1h. In XPS with Ar-etching, a significant increase of Ge-O bonds was shown at 15 - 30 nm in depth. Ge-Ge bonds decreased in the whole depth region. In 3D-AP, relatively large four Ge NPs were detected in the Ge-implanted SiO2 layer. The shallowest NP was spherical with at diameter of 5 nm and had a Ge-core at 2 nm in diameter and Ge-oxide shell of with 1 - 2 in thickness. So Ge-O bonds were surely created between core and shell. The role of Ge NP is to ensure forming G-ODCs in NP and interrupting progress of Ge oxidation to the deeper side.
Secondary ion mass spectrometry (SIMS) is powerful method for obtaining component information from solid samples, such as semiconductor devices and biological tissue. Moreover, SIMS has high surface sensitivity because of the use of a primary ion probe. The keV-energy ion probe is, however, unstable under low vacuum conditions and this makes evaluation of volatile liquid samples difficult. A new SIMS technique that uses an MeV-energy heavy ion probe, called ambient SIMS, enables measuring volatile liquid samples under ambient conditions by high transmission capability of the primary probe. In this study, water in liquid form, which has a relatively high vapor pressure (2,339 Pa at 20℃), was evaluated by ambient SIMS and gave some cluster ions with high intensity. This result suggests that ambient SIMS has significant potential for evaluating both solid and liquid samples with high sensitivity.
Fe and Co films are prepared on glass substrates by DC magnetron sputtering and N ion implantation is carried out by a bipolar-type plasma based ion implantation (PBII) technique. Some samples are annealed at 150℃ in vacuum after N ion implantation. The structural and compositional changes are examined by thin film X-ray diffraction (XRD) measurements, scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX). The changes of magnetic properties are also examined by vibrating sample magnetometer (VSM). It is found that surface morphology is not changed significantly by N ion implantation and subsequently annealing as far as SEM observation, although N content is surely increased in the both films. XRD measurements reveal that nitride phases, ε-Fe3-xN and γ-Co3N, may be formed by N implantation. The results of VSM measurements indicate that the saturation magnetization of Fe films are slightly increased by N ion implantation. However, the saturation magnetization of Co films are decreased. After annealing at 150℃, the magnetic properties are deteriorated significantly for the both samples.
Yttria stabilized cubic zirconia (YSZ) is one of the potential matrices to be used in hostile radiation environment. In the present study, the evolution of dislocation loops in sintered YSZ specimens was investigated in situ in high voltage electron microscopes under irradiation with high energy electrons as functions of electron energy from 1.25 to 3.0 MeV and irradiation temperature from 300 to 773 K. In situ microstructure observation reveals that under 1.25 MeV electron irradiation at 300 to 673 K, no dislocation loops were formed up to a fluence of 4.5×1026 m-2. Under irradiation with 2.0 and 3.0 MeV electrons, the microstructure evolution was strongly dependent on electron energy and irradiation temperature, resulting the formation of perfect dislocation loops and/or oxygen-type dislocation loops. Results reveal an importance of the ratio of displacement damage rate between oxygen sublattice and cation sublattice, and their mobility on the nucleation-and-growth of defects in YSZ.
In this paper, the inelastic thermal spike model extended to multilayered systems was applied to Cu/a-Ge system and compared to the experimental results available in literature. Evidence of molten phase formation from both sides of the interface has been identified for both the irradiations at room temperature and 77 K. However, comparison with the experimental results reveals, in addition to liquid diffusion, a further unknown contribution to mixing for room temperature irradiations. We suggested that solid state diffusion of Cu atoms was enhanced in radiation-induced porous-structure in a-Ge at room temperature.
Crater formations with gas cluster ion beam (GCIB) were used for non-contact hardness measurement of various films. The crater diameter formed with size-selected Ar cluster ions decreased with inverse cube root of film hardness. When the total acceleration energy was constant, the cluster size did not affect the average crater diameter. In addition, high ionization electron voltage caused wide distribution of crater depth and diameter due to the formation of multiply charged GCIB.