Fabrication of porous low crystalline calcite block by carbonation of calcium hydroxide compact

Calcium carbonate (CaCO₃) has been widely used as a bone substitute material because of its excellent tissue response and good resorbability. In this experimental study, we propose a new method obtaining porous CaCO₃ monolith for an artificial bone substitute. In the method, calcium hydroxide compacts were exposed to carbon dioxide saturated with water vapor at room temperature. Carbonation completed within 3 days and calcite was the only product. The mechanical strength of CaCO₃ monolith increased with carbonation period and molding pressure. Development of mechanical strength proceeded through two steps; the first rapid increase by bonding with calcite layer formed at the surface of calcium hydroxide particles and the latter increase by the full conversion of calcium hydroxide to calcite. The latter process was thought to be controlled by the diffusion of CO₂ through micropores in the surface calcite layer. Porosity of calcite blocks thus prepared had 36.8–48.1% depending on molding pressure between 1 MPa and 5 MPa. We concluded that the present method may be useful for the preparation of bone substitutes or the preparation of source material for bone substitutes since this method succeeded in fabricating a low-crystalline, and thus a highly reactive, porous calcite block.     

Temperature Dependence of Novel Single-Photon Detectors in the Long-Wavelength Infrared Range

Novel single-photon detectors, called Charge-sensitive Infrared Phototransistor (CSIP), have been developed in the long wavelength infrared (LWIR) range. The devices are fabricated in GaAs/AlGaAs double-quantum-well (DQW) structure, and do not require ultralow temperatures (T < 1 K) for operation. Figures of merit are determined in a T-range of 4.2 K∼30 K by using a homemade all-cryogenic spectrometer. We found that the photo-signal persists up to around 30 K. Excellent specific detectivity D ^* = 9.6 × 10¹⁴ cm Hz^1/2/W and noise equivalent power NEP = 8.3 × 10⁻¹⁹ W/Hz^1/2 are derived up to T = 23 K. The dynamic range of detection exceeds 10⁶, roughly ranging from attowatt to picowatt levels. These values are by a few orders of magnitude higher than that of the state-of-the-art values of other detectors. Simple planar structure of CSIPs is feasible for array fabrication and will make it possible to monolithically integrate with reading circuit. CSIPs are, therefore, not only extremely sensitive but also suitable for practical use in wide ranging applications.     

Al-laminated film packaged organic radical battery for high-power applications

A 100-mAh class of aluminum-laminated film packaged organic radical battery with a poly(2,2,6,6-tetramethyl-1-piperidinyloxy-4-yl methacrylate) (PTMA) composite cathode and a graphite anode has been fabricated. Its total weight was 22 g and the thickness was 4.3 mm. Because PTMA comprised only 6.2% of the total cell weight, the energy density was considerably less than that of a lithium ion battery. However, the power density per active material weight was found to be better than that of lithium ion battery. The applications which require high-power capability rather than high-energy density, such as the sub-battery in electronic devices and motor drive assistance in electric vehicles, would be appropriate for organic radical batteries in the future.     

Dual mode diffusion of NaCl in Japanese radish under cooking conditions

ABSTRACT:  Sorption and diffusion of NaCl in Japanese radish have been studied. The sorption isotherm was obtained at 98 °C by the conventional method. The concentration profile by the 1-dimensional diffusion of NaCl in Japanese radish from the 3.0% solution was measured at 98 °C with the FRITRUC method involving a foodstuff rod in a thin rubber casing. Fick's diffusion coefficient, D , calculated therefrom showed a threefold variation with a maximum. This variation was quantitatively interpreted by applying a dual-mode sorption and diffusion theory under an assumption that the rate determining step of the diffusion is that in the cell wall. Two thermodynamic diffusion coefficients, D_T ( p ) and D_T ( L ), where p and L are the species of NaCl sorbed by partition and Langmuir modes, respectively, a parameter, α, derived from the local equilibrium relations between the p and L species, and S , the concentration of the Langmuir adsorption site in the cell wall of the radish, were estimated. D_T ( p ) was found to be smaller than D_T ( L ). As an explanation of the larger D_T ( L ), we invoked the higher hydration state of the adsorption site of the L species, being ascribed to residual anionic pectin in the radish than the local environment of the p species. The sorption isotherm showed a convex upward deviation from the linear relation. By using the parameters for the local equilibrium and some assumed parameters, the isotherm was found to be explainable. We suggest possible applications of the present method and interpretation to the diffusion study on the cooking systems comprising varieties of seasoning components and foodstuffs.     

Fabrication of multilayered photochromic memory media using pressure-sensitive adhesives

We fabricated a multilayered medium by a laminating process with pressure-sensitive adhesives. It was possible to reduce the thickness variations of both photosensitive layers and transparent layers by applying laminating films. This method is easy to use to pile up many layers for a multilayered medium. We fabricated twenty recording layers and demonstrated the capability to record with significant reading results. The recorded data in each layer were read out without crosstalk. We evaluated the signal-to-noise ratio and crosstalk between neighboring layers. It was found that the signal-to-noise ratio of a multilayered medium was higher than 50 dB.     

Magnetic field analysis of a squirrel cage induction motor considering rotor skew and higher harmonics in the secondary current

This paper describes a method to analyze harmonic magnetic fields of squirrel cage induction motors considering rotor skew and higher harmonics in the secondary current. The proposed method is based on a two‐dimensional finite element method. The rotor skew structure is expressed by multiple 2D finite element mesh models, produced in suitable axial positions, and the magnetic field in each mesh model is calculated by the revised secondary current taking into account the skew effect. The secondary currents, magnetic flux densities, and electromotive forces are calculated by the proposed method. Then the differences between a skewed rotor and a nonskewed rotor are discussed. From the comparison between the calculated and the experimental results, the proposed method is shown to be appropriate and useful for quantitative estimation of harmonic components of induction motors. © 1999 Scripta Technica, Electr Eng Jpn, 129(2): 98–109, 1999     

Highly selective hydrogen production from propane by Ru–Ni core–shell nanocatalyst deposited on reduced graphene oxide by sequential chemical vapor deposition

A narrow temperature window (160°C-190°C) was identified for the selective deposition of Ru on Ni supported on reduced graphene oxide (rGO) through a sequential chemical vapor deposition (CVD) method. Cyclopentadiene and cyclopentene were identified as decomposition products of nickelocene CVD on rGO, whereas only methane was detected in gaseous products from ruthenocene CVD. Heat treatment converted the selectively deposited Ru on Ni/rGO into Ru–Ni core–shell bimetallic system on the surface of rGO as confirmed by high-resolution transmission electron microscopy. The Ru–Ni/rGO thus prepared produced hydrogen with high selectivity in propane steam reforming performed in the temperature range of 350°C to 850°C. Addition of 3.6% Ru against Ni supported on rGO improved the turnover frequency (TOF) of propane up to 70% to 100% compared to the Ni/rGO catalyst at lower temperatures (350°C-450°C). The presence of Ru lowered the activation energy of propane SR from 65.7 kJ mol⁻¹ for Ni/rGO to 48.7 kJ mol⁻¹ for Ru–Ni/rGO catalyst.     

New macromolecular silane coupling agents synthesized by living anionic polymerization; grafting of these polymers onto inorganic particles and metals

New macromolecular silane coupling agents, which are end-triethoxysilylated poly(styrene) and poly(tert-butylmethacrylate), were investigated as possible inorganic particle and metal surface treatment agents. These polymers containing poly(styrene) and poly(tert-butylmethacrylate) as the main chain, were prepared by living anionic polymerization. Grafting of the polymers onto inorganic particles and metals was performed via the hydrolysis of the triethoxysilyl group using either acidic or basic catalyst. n-Butylphosphate was used as the catalyst for grafting onto inorganic substances having an acidic surface such as silica. However, in the case of grafting onto inorganic substances having a basic surface, tetrabutylammoniumhydroxide was employed as the catalyst. Contrary to expectations, grafting onto titania was successful even in the absence of a catalyst. Particles grafted with these polymers showed excellent dispersibility in organic medium, in which the polymers are soluble. This phenomenon is in contrast to that for particles treated with polymers possessing triethoxysilyl groups at random positions of the chain or those treated with trimethylsilyl groups. Surface tension measurements of metal substrates coated with the grafted polymers, were found to be identical to the values obtained for the bulk polymers.