Structure and magnetic properties of mono- and bi-layer graphene films on ultraprecision figured 4H-SiC(0001) surfaces

Monolayer and bilayer graphene films with a few hundred nm domain size were grown on ultraprecision figured 4H-SiC(0001) on-axis and 8 degrees -off surfaces by annealing in ultra-high vacuum. Using X-ray photoelectron spectroscopy (XPS), atomic force microscopy, reflection high-energy electron diffraction, low-energy electron diffraction (LEED), Raman spectroscopy, and scanning tunneling microscopy, we investigated the structure, number of graphene layers, and chemical bonding of the graphene surfaces. Moreover, the magnetic property of the monolayer graphene was studied using in-situ surface magneto-optic Kerr effect at 40 K. LEED spots intensity distribution and XPS spectra for monolayer and bilayer graphene films could become an obvious and accurate fingerprint for the determination of graphene film thickness on SiC surface.     

Low temperature formation of Si1 − x − yGexSny-on-insulator structures by using solid-phase mixing of Ge1 − zSnz/Si-on-insulator substrates

We proposed the low temperature formation technique of strain-relaxed Si_{1 − x − y}Ge_xSn_y-on-insulator (SGTOI) structures. We found that the solid-phase reaction and the formation of single and uniform Si_{1 − x − y}Ge_xSn_y layer on an insulator after annealing SiO₂/Ge_1 − zSn_z/SOI structures even at a temperature as low as 400 °C. We characterized the crystalline structure of SGTOI, and investigated the effects of annealing, Sn incorporation, and a SiO₂ cap layer on the solid-phase reaction between Ge_1 − zSn_z and SOI layers. The solid-phase reaction is enhanced with a higher Sn content and a thicker SiO₂ cap layer, and then Si_{1 − x − y}Ge_xSn_y layers are more rapidly formed. The SGTOI layer exhibits very low mosaicity and have good crystallinity.     

Quantum size effect in TiO2 nanoparticles prepared by finely controlled metal assembly on dendrimer templates

The use of dendrimer templates to make metal-based nanoparticles of controlled size has attracted much interest. These highly branched macromolecules have well-defined structures that enable them to bind metal ions to generate precursors that can be converted into nanoparticles. We describe the sub-nanometre size control of both anatase and rutile forms of TiO2 particles with phenylazomethine dendrimers, leading to samples with very narrow size distributions. Such fine tuning is possible because both the number and location of metal ions can be precisely controlled in these templates. Quantum size effects are observed in the particles, and the energy gap between the conduction and valence bands exhibits a blueshift with decreasing particle size and is dependent on the crystal form of the material. The dependency of the bandgap energy on these factors is explained using a semi-empirical effective mass approximation.     

New leak element using sintered stainless steel filter for in-situ calibration of ionization gauges and quadrupole mass spectrometers

A new leak element using a sintered stainless steel filter with a pore size of less than 1 μm has been developed for in-situ calibrations of ionization gauges (IGs) and quadruple mass spectrometers (QMSs). The gas flow through this leak element realizes molecular flow at an upstream pressure of less than 10⁴ Pa. This new leak element, which is a kind of open-type standard leak, has four advantages. (1) Calibrations for various gas species are available only with this single leak element because the conductance is easily compensated for gas species by molecular mass. (2) Calibrations with multiple pressure points are easily available because the conductance is constant against changing upstream pressure. (3) Calibrations for a gas mixture are available because the interference effect between gas molecules in a gas mixture is negligible. (4) The dependence of flow rate on temperature is small and is compensated theoretically. These advantages were experimentally demonstrated. The stability and uncertainty of the leak element were also evaluated. The changes in the conductance of this leak element were less than 3% over one year. Since the conductance is typically 10⁻¹⁰ · m³/s, the reference gas flow in the range from 10⁻⁸ Pa · m³/s to 10⁻⁶ Pa m³ is obtained by changing the upstream pressure from 10² Pa to 10⁴ Pa with an uncertainty of approximately 6%.     

Effect of adsorption behaviour of polyelectrolytes on fluidity and packing ability of aqueous graphite slurries

The effect of surface hydrophobicity on the adsorption behaviour of polyelectrolytes is investigated using graphite and alumina powder slurries. Graphite slurries containing carboxymethylcellulose (CMC) have a relatively low apparent viscosity and afford a sediment with a relatively high packing fraction as compared to that obtained when using sodium polyacrylate (Na-PAA) as a dispersant, although both have the same functional group. As a greater amount of CMC is adsorbed, it is concluded that its adsorption mechanism involves hydrophobic interaction, thus making it a better dispersant for hydrophobic powders in aqueous media. In contrast, Na-PAA is more effective in dispersing relatively hydrophilic powders such as alumina, as it adsorbs mainly through electrostatic interactions.     

On the damping analysis of FRP laminated composite plates

This paper presents the damping analysis of fiber reinforced plastics laminated composite plates. For this purpose, the maximum strain and kinetic energies of a cross-ply laminated plate are evaluated analytically based on the three-dimensional theory of elasticity. The displacements of the simply supported rectangular plates are expanded into the polynomial forms with respect to a thickness coordinate, and then governing equations are formulated by using the Ritz's method. In the numerical calculations, natural frequencies and modal damping ratios are calculated for the plates with different stacking sequence and thickness ratios. The validity of the assumption of deformations and the applicability of the other plate theories (e.g. classical lamination theory (CLT), first-order shear deformation theory (FSDT) and higher-order shear deformation theory) to the laminated thick plates are discussed by comparing the numerical results obtained by the present method with the CLT and the FSDT solutions.     

Origin of Significant Grain Refinement in Co-Cr-Mo Alloys Without Severe Plastic Deformation

We have previously reported that ultrafine-grained (UFG) microstructures can be obtained in a Co-29Cr-6Mo (wt pct) alloy by utilizing dynamic recrystallization (DRX) that occurs during conventional hot deformation (Yamanaka et al.: Metall. Mater. Trans. A, 2009, vol. 40A, pp. 1980?94). The present study investigates the novel DRX mechanism of this alloy in detail. The microstructure evolution during hot deformation under relatively high Zener?CHollomon (Z) parameter conditions for which ultrafine grains can develop was systematically investigated by electron backscatter diffraction (EBSD) and transmission electron microscopy. This alloy exhibited a different flow stress behavior and microstructural development from conventional DRX mechanisms. The deformation microstructure contained a large number of stacking faults, which implies that planar dislocation slip is the primary deformation mechanism in the hot deformation of the Co-29Cr-6Mo alloy due to its abnormally low stacking fault energy (SFE) at elevated temperatures. Inhomogeneities in local strain distributions induced by planar slip will enhance grain subdivision by geometrically necessary (GN) dislocation boundaries. Deformation twinning may also contribute to grain refinement. The DRX mechanism operating in the Co-29Cr-6Mo alloy is discussed by considering the relationships between anomalous dislocation structures, flow stress behavior, texture development, and nucleation behavior.     

抗晶间腐蚀奥氏体不锈钢的晶界工程

Sensitization by chromium depletion due to chromium carbide precipitation at grain boundaries in austenitic stainless steels can not be prevented perfectly only by previous conventional techniques, such as reduction of carbon content, stabilization-treatment, local solution-heat-treatment, etc. Recent studies on grain boundary structure have revealed that the sensitization depends strongly on grain boundary character and atomic structure, and that low energy grain boundaries such a~ coincidence-site-lattice (CSL) boundaries have strong resistance to intergranular corrosion. The concept of grain boundary design and control has been developed as grain boundary engineering (GBE). GBEed materials are characterized by high frequencies of CSL boundaries which are resistant to intergranular deterioration of materials, such as intergranular corrosion. A thermomechanical treatment was tried to improve the resistance to the sensitization by GBE. A type 304 austenitic stainless steel was cold-rolled and solution-heat-treated, and then sensitization-heat-treated. The grain boundary character distribution was examined by orientation imaging microscopy (OIM). The intergranular corrosion resistance was evaluated by electrochemical potentiokinetic reactivation (EPR) and ferric sulfate-sulfuric acid tests. The sensitivity to intergranular corrosion was reduced by the thermomechanical treatment and indicated a minimum at a small roll-reduction The frequency of CSL boundaries indicated a maximum at the small reduction. The ferric sulfate-sulfuric acid test showed much smaller corrosion rate in the thermomechanical-treated specimen than in the base material. A high density of annealing twins were observed in the thermomechanical-treated specimen. The results suggdst that the therrmomechanical treatment can introduce low energy segments in the grain boundary network by annealing twins and can arrest the percolation of intergranular corrosion from the surface. The effects of carbon content and other minor elements on optimization in grain boundary character distribution (GBCD) and thermomechanical parameters were also examined during GBE.     

Prevention of accomplishing synchronous multi-modal human–robot cooperation by using visual rhythms

Effective rhythm expression (ERE) from a robot to a human performing a multi-modal physical-cooperation (MMPC) task was accomplished. During MMPC, the participant and the robot can exchange various rhythms between themselves. To accomplish ERE, it is important to appropriately select the modalities in which the robot expresses its desired rhythm. Accordingly, a hypothesis that selecting the visual rhythm for RE prevents MMPC was tested and confirmed. This hypothesis was preliminarily confirmed in regard to MMPC between two humans. Moreover, to confirm the hypothesis in regard to human–robot cooperation, an experimental system (including a rope-turning robot) was developed. This experimental system allowed experimenters to evaluate the synchronization during MMPC between a human and a robot by measuring the norm of angular velocities. The results of several experiments (namely, a comparison of norms), in which several combinations of visual and auditory rhythmic stimuli were presented to the subjects, strongly supported the hypothesis.