One-dimensional analysis of supersonic two-stage HVOF process

The one-dimensional calculation of the gas/particle flows of a supersonic two-stage high-velocity oxy-fuel (HVOF) thermal spray process was performed. The internal gas flow was solved by numerically integrating the equations of the quasi-one-dimensional flow including the effects of pipe friction and heat transfer. As for the supersonic jet flow, semi-empirical equations were used to obtain the gas velocity and temperature along the center line. The velocity and temperature of the particle were obtained by an one-way coupling method. The material of the spray particle selected in this study is ultra high molecular weight polyethylene (UHMWPE). The temperature distributions in the spherical UHMWPE particles of 50 and 150μm accelerated and heated by the supersonic gas flow was clarified.     

Twenty-two percent efficiency HIT solar cell

We have achieved the world's highest solar cell conversion efficiency of 22.3% (V_oc: 0.725 V, I_sc: 3.909 A, FF: 0.791, total area: 100.5 cm², confirmed by AIST) by using a heterojunction with intrinsic thin layer (HIT) structure. This is the world's first practical-size (>100 cm²) silicon solar cell that exceeds a conversion efficiency of 22% as a confirmed value. This high efficiency has been achieved mainly due to improvements in a-Si:H/c-Si hetero-interface properties and optical confinement.The excellent a-Si:H/c-Si hetero-interface of the HIT structure enables a high V_oc of over 0.720 V and results in better temperature properties. In order to reduce the power-generating cost, we are now investigating numerous technologies to further improve the conversion efficiency, especially the V_oc, of HIT solar cells, with the aim of achieving 23% efficiency in the laboratory by 2010.     

The Chemical Adsorption Properties of Silanol to Metal-Oxide Surface Studied by Using Di(1-naphthyl)silanediol and Nano-porous Alumina Membranes

Silanols have a high bonding ability to the surface of metal oxides by forming Si–O-metal bonds, and can produce functional properties which originate in the organic moieties of them to the metal-oxide surface. In order to tune and to emphasize the functional properties, it is important to control the degree of surface modification and to increase the amount of modifiers on the metal-oxide surface. In this work, the chemical surface modification of nano-porous alumina membranes (NPAMs), which possess a regular honeycombed structure with sub-micrometer pores and a high shape stability, with a typical silanol compound of di(1-naphthyl)silanediol, (Nap)₂Si(OH)₂, by immersing NPAMs into its solutions in order to obtain quantitative information on the reaction conditions for the efficient surface modification. The NPAMs having chemically modified surface with (Nap)₂Si(OH)₂ were prepared successfully by the immersing method, and the amount of (Nap)₂Si(OH)₂ adsorbed on the NPAM surface was estimated quantitatively by UV absorption of the NPAM. The effects of the solvent, temperature, and concentration of (Nap)₂Si(OH)₂ solutions on the efficiency in the chemical surface modification were investigated precisely, and almost complete surface modification with the covering ratio of the NPAM surface by (Nap)₂Si(OH)₂ of ∼100% was achieved by using the solutions with non-polar solvents, higher temperatures, and a concentration of ∼1 mM.     

Differential effect of a PAF antagonist CV-3988 on active and passive anaphylactic shock in various mouse strains

To define the role of platelet-activating factor (PAF) in anaphylactic shock in the mouse, the suppressive effect of CV-3988, a PAF antagonist, on active and passive anaphylactic shock was studied. Various mouse strains treated or not treated withBordetella pertussis (B. pertussis) were used. We found that the effect of CV-3988 on anaphylactic shock in the mice that were actively sensitized with bovine serum albumin plusB. pertussis differed markedly according to mouse strain. CV-3988 suppressed the anaphylactic shock in C3H/He and CBA/JN mice at a low dose of 3 mg/kg, whereas antagonists to other mediators such as histamine, serotonin, thromboxane A₂ and leukotrienes did not show a suppressive effect. This suggests that PAF plays a major role in anaphylactic shock in these strains. On the other hand, CV-3988 did not suppress active anaphylactic shock in cataract Shionogi (CTS), NOD and DS strains even at a high dose of 30 mg/kg, which could be interpreted to suggest that PAF is not active in these strains. However, this possibility was ruled out based on the similar results obtained in passive anaphylactic shock and PAF-induced shock in these mice. Passive anaphylactic shock in CTS mice mediated by IgG₁ antibody was markedly suppressed by CV-3988 but not at all by antagonists to other mediators. Furthermore, the suppressive action of CV-3988 against passive anaphylactic shock, and PAF-induced shock was greatly attenuated when the mice were pretreated withB. pertussis. From these results, the conclusion can be drawn that PAF is the main mediator of active and passive anaphylactic shock in the mouse in general, even though the effect of CV-3988 differs depending on the mouse strain and on whether or notB. pertussis treatment is used. Based on a paper presented at the Third International Conference on Platelet-Activating Factor and Structurally Related Alkyl Ether Lipids, Tokyo, Japan, May 1989.     

Molten-Salt Synthesis and Characterization of Nickel-Doped Forsterite Nanocrystals

Nickel-doped forsterite (Ni²⁺:Mg₂SiO₄) nanocrystals have been synthesized by a facile molten-salt approach in the presence of NaCl and a surfactant (NP-7.5). The products were characterized by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, selected area electron diffraction (SAED), and luminescence spectra measurements. The crystal size could be controlled by tailoring the synthesis parameters. TEM, high-resolution TEM, and SAED results revealed the single crystalline character of Mg₂SiO₄ nanoparticles. A possible model for the growth of Ni²⁺:Mg₂SiO₄ nanocrystals was postulated. The obtained Ni²⁺:Mg₂SiO₄ nanocrystals show strong, super broad, near-infrared luminescence at room temperature. These doped Mg₂SiO₄ nanocrystals are promising gain mediums for super broadband optical amplification.     

Preparation of a crosslinked polyelectrolyte membrane for fuel cells with an allyl methacrylate based two‐step reaction

In this study, a proton‐exchange membrane for fuel cells was prepared via a two‐step reaction with an allyl methacrylate (AMA) as an asymmetric crosslinking agent. First, a linear‐chain polymer was synthesized, consisting of hydrophilic 2‐acrylamido‐2‐methylpropanesulfonic acid (AMPS), hydrophobic 2,2,2‐trifluoroethyl methacrylate (TFEMA), and AMA. Subsequently, we crosslinked the linear‐chain polymer by reacting the remaining allyl group during dry heating. The proton conductivity of the prepared membrane was 7 × 10^?2 S/cm at room temperature. The membrane was characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry, and atomic force microscopy. The polymer electrolyte membrane fuel cell (PEMFC) performance was evaluated for a membrane electrode assembly composed of the crosslinked AMPS–TFEMA–AMA/ fluoroalkyl graft polymer (FGP) membrane. As a result of a power‐generation test, a maximum power density of 174 mW/cm² at a current density of 400 mA/cm² was observed for a PEMFC single cell. Consequently, it was confirmed that the AMPS–TFEMA–AMA/FGP membrane for PEMFC could easily be prepared via a two‐step reaction at a low cost and that PEMFC exhibited a cell performance and that of cells with the Nafion membrane. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Direct Observation of Crack Tip Geometry of SiO2 Glass by High-Resolution Electron Microscopy

Crack tips in thin SiO₂ glass films were observed directly by high-resolution/high-voltage electron microscopy. An elliptical crack with radius of curvature ∼ 1.5 nm was observed. When the glass film with the crack was soaked in water at 90°C for 7 d, the crack tip became blunt by a process of dissolution and precipitation.     

Plasma polymerized membranes and gas permeability. I

Gas permeability of composite membrane prepared by plasma polymerization of various organic compounds was studied. In the membrane, a pinhole-free polymeric thin film was formed on a porous substrate. This film below 0.2 μm in thickness had sufficient mechanical strength for gas separation. The composite membranes were recognized to have high permeability and high permselectivity. Especially, the membranes prepared from hexamethyldisiloxane showed high permeation rate for oxygen, and those prepared from 1-hexene or cyclohexane showed high permselectivity between oxygen and nitrogen. chemical structure of plasma-polymerized film prepared from hexamethyldisiloxane was similar to that of dimethylpolysiloxane with a crosslinking of the polymer. The high permeability and high permselectivity of this film is considered to be due to its structure as mentioned above.