Observation of GaAs—AlxGa1 — x as heterostructures and quantum-well-wire structures using backscattered electron image

As a microscale tool for observing GaAs-Al_x Ga_1–xAs heterostructures, backscattered electron (BE) images in the scanning electron microscope (SEM) were compared with conventional secondary electron (SE) images. BE images were found to be more sensitive to compositional differences between GaAs and Al_xGa_1–xAs and less sensitive to surface roughness. BE images have a spatial resolution of 10 nm or better. This method enables the nondestructive observation of ultrafine lateral periodic structures, such as quantum-well-wire (QWW) structures, fabricated by compositional disordering technology using focused Ga ion-beam (Ga-FIB) implantation into GaAs-Al_xGa_1–xAs material.     

Fabrication of Flexible and Transparent Conductive Nanosheets by the UV‐Irradiation of Gold Nanoparticle Monolayers

Conductive films that are highly transparent and flexible are extremely attractive for emerging optoelectronic applications. Currently, indium‐doped tin oxide films are the most widely used transparent conductive films and much research effort is devoted to developing alternative transparent conductive materials to overcome their drawbacks. In this work, a novel and facile approach for fabricating transparent conductive Au nanosheets from Au nanoparticles (AuNPs) is proposed. Irradiating an AuNP monolayer at the air–water interface with UV light results in a nanosheet with ≈3.5 nm thickness and ≈80% transparency in the UV–visible region. Further, the so‐fabricated nanosheets are highly flexible and can maintain their electrical conductivity even when they are bent to a radius of curvature of 0.6 mm. Fourier‐transform infrared and X‐ray photoelectron spectroscopy characterizations reveal that the transformation of the monolayer of AuNPs into the nanosheet is induced by the photodecomposition and/or photodetachment of the dodecanethiol ligands capping the AuNPs. Further, the UV‐irradiation of a hybrid monolayer consisting of AuNPs and silica particles affords the patterning of Au nanosheets with periodic hole arrays.     

Fabrication of lead-free piezoelectric (Bi<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>)TiO<Subscript>3</Subscript>–BaTiO<Subscript>3</Subscript> ceramics using electrophoretic deposition

Electrophoretic deposition (EPD) process has certain advantages such as it can be applied for a mass production and also can be combined with magnetic crystal alignment technique. In this work, we prepared lead-free 85(Bi_0.5Na_0.5)TiO₃–15BaTiO₃ (85BNT–15BT) piezoelectric ceramics by conventional uniaxial pressing and EPD process. Various conditions were optimized such as suspension media, applied electrical field, and deposition time in order to yield dense green ceramics of 85BNT–15BT composition using EPD process. 85BNT–15BT ceramics prepared using EPD process revealed the Curie temperature of about 250 °C, coercive field of about 30 kV/cm, and piezoelectric constant (d ₃₃) of 75 pC/N. The EPD-processed samples exhibited structural and electrical properties similar to that of the conventionally processed one suggesting the successful fabrication of 85BNT–15BT piezoelectric ceramics by EPD method without composition deviation. This study lays a foundation on the fabrication of Bi-based lead-free piezoelectric ceramics by an alternative route other than the conventionally practiced solid-state reaction method maintaining the similar chemical composition, moreover, leaving a large space to explore more in the future.     

Bending fracture rule for 3D-printed curved continuous-fiber composite

Three-dimensional (3D) printing is an attractive technology to produce complex structures without the need for expensive tools and molds. Additives are usually incorporated with the plastic materials used in 3D printing to increase their strength and rigidity. In particular, carbon fiber-reinforced plastic (CFRP) shows promise as a material for use in 3D printing. However, the strength of CFRP after printing is still unclear, although it is known that its strength is affected by the plastic melting during printing. In this study, we analyzed the fracture behavior of CFRP specimens before and after bending to different curvature radii. From the experimental results, a fracture criterion that described the behavior of the materials by considering tensile and compressive loads was developed. The fracture mechanism was the same for CFRP specimens with different curvature radii. These results increase our understanding of the mechanical properties of CFRP materials used in 3D printing.     

Syntheses and properties of tetramethyl-p-silphenylenesiloxanealkenylmethyl-siloxane copolymers and their derivatives

$\text{Tetramethyl}\text{-p-}\text{silphenylenesiloxane}\text{alkenylmethylsiloxane}$ (TMPS/AMS) copolymers were snyhtesized from p-bis-dimethylhydroxysilylbenzene and a series of alkenylmethyldichlorosilanes as the starting materials. The alkenyl groups of the copolymers were vinyl, allyl, 2-(3-cyclohexenyl)ethyl, methacryloxypropyl and 3-bicycloheptenyl groups. The composition ranged from TMPS/AMS mole% ratio of $\text{92}\text{8}$ to $\text{83}\text{17}$ and the molecular weights were in the range 10⁴ to 10⁵. These copolymers were confirmed to have two compositions, one a certain length of TMPS segment and the other an AMS monomer unit, and that they could form films on the basis of the crystallization character of the TMPS segment. The melting temperatures of these copolymers decreased as the TMPS mole content decreased and as the alkenyl group contents were increased. The epoxidation reactions of these copolymers with m-chloroperbenzoic acid were carried out and the proportions of conversions of the alkenyl groups into epoxy groups varied depending upon the types of alkenyl groups involved. Cyclic olefin groups such as the 2-(3-cyclohexenyl)ethyl or the 3-bicycloheptenyl group were more easily epoxidized than the vinyl or allyl groups. The TMPS/dimethylsiloxane (DMS) graft copolymer could also be synthesized by the reaction of TMPS/vinylmethylsiloxane copolymer with dimethylhydrosilyl-terminated DMS oligomer in the presence of chloroplatinic acid acting as the catalyst.     

Modification of poly(vinyl chloride). XIX. Electroplating of poly(vinyl chloride)

As a preliminary treatment in the PVC-electroplating procedure, treatment with dimethylformamide followed by sensitization leads to a finely roughened and a highly hydrophilic surface with reducing power. This is caused by the formation of an ionic complex compound between dimethylformamide and tin(II) chloride absorbed in the PVC surface. A much more finely and deeply etched surface which exhibits higher adhesion through the mechanical interlocking effect is obtained with the PVC blends containing the plasticizer with a low value of interaction parameter and with a solubility parameter approximate to that of PVC. Adhesion of the metal layer to the PVC surface thus obtained is improved about 1.5 times by thermal aging at 120°C for 20 min.     

Multiple evaluations of the removal of pollutants in road runoff by soil infiltration

Groundwater replenishment by infiltration of road runoff is expected to be a promising option for ensuring a sustainable urban water cycle. In this study, we performed a soil infiltration column test using artificial road runoff equivalent to approximately 11-12 years of rainfall to evaluate the removal of pollutants by using various chemical analyses and bioassay tests. These results indicated that soil infiltration treatment works effectively to remove most of the pollutants such as organic matter (chemical oxygen demand (CODMn) and dissolved organic carbon (DOC)), P species, polycyclic aromatic hydrocarbons (PAHs), numerous heavy metals and oestrogenic activities. Bioassay tests, including algal growth inhibition test, Microtox and mutagen formation potential (MFP) test, also revealed effective removal of toxicities by the soils. However, limited amounts of NO3, Mn, Ni, alkaline earth metals, perfluorooctane sulphonate (PFOS) and perfluorooctane sulphonamide (FOSA) were removed by the soils and they possibly reach the groundwater and cause contamination.     

Highly elongated,low‐aspect‐ratio tokamak produced by negative‐biased theta pinch

Ultra Low Aspect Ratio Tokamaks (ULART) are produced by using a negative‐biased theta‐pinch device. A slender conducting rod which serves as a toroidal field coil is newly installed along a geometrical center axis of the theta‐pinch coil. The ULART is quickly formed for about 10 μs by applying programmed current flows from three sets of fast banks and a slow bank to these coils and is sustained for about 100 μs. The plasma diagnosed from a magnetic probe array has a low aspect ratio A = 1.1 and a poloidal surface with a high elongation ratio κ = 10. The safety factor reaches about 30 near the separatrix edge when I_p = 280 kA flows in the plasma and I_tfc = 30 kA in the conducting rod. A preliminary result on global MHD characteristics of the ULART is also given. The plasma is unstable with respect to a vertical displacement and a toroidal n = 1 mode. The amplitudes of these modes depend on the values of I_tfc and κ. © 2001 Scripta Technica, Electr Eng Jpn, 134(4): 19–27, 2001     

Effect of crosslinking structure on sorption of CO2 in photocrosslinked PVCA film

The sorption behavior of CO₂ gas in photocrosslinked poly(vinyl cinnamate) film was examined under atmospheric pressure. The sorption isotherm was well described by the Langmuir equation, suggesting that sorption of CO₂ is mainly governed by adsorption in the microvoids. The amount of sorbed CO₂ was significantly affected by the degree of crosslinking. The CO₂ sorption was enhanced at a lower degree of crosslinking but was decreased at a higher degree of crosslinking. The unexpected increase in the amount of adsorbed CO₂ correlated with the increase in the number of microvoids that occurred as a result of the crosslinking reaction. However, further crosslinking led to a decrease in the mean size of the microvoids. The smaller microvoids, in comparison to CO₂ molecules, did not act as adsorption sites, so that the amount of sorbed CO₂ decreased. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 1744–1750, 2000     

Development of a simulator to calculate an optimal slab heating pattern for reheat furnaces

To improve energy consumption and to meet quality requirements for the slab heating process of reheat furnaces in hot strip mills, a new optimal slab heat pattern calculation simulator has been developed. The simulator consists of the following functions; (1) two-dimensional (slab thickness direction and slab length direction) slab temperature calculation function, which is capable of calculating skidmarks along the length of a slab, (2) furnace heat balance calculation function, (3) optimizing calculation function of slab heat pattern using a linear programming method. The simulator developed has been installed into a furnace computer control system for an actual plant. This paper describes the functions of the simulator and simulation results using the simulator. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120 (3): 42–53, 1997