Development of macropores in calcium carbonate body using novel carbonation method of calcium hydroxide/sodium chloride composite

Calcium carbonate is one of the bioceramics and has been used clinically as a bone substitute in dental and orthopedic surgery. Introduction of macropores into the bioceramics is highly recommended because those pores enable tissue ingrowth and accelerated osteointegration. We tried to prepare calcium carbonate body with macropores through the new carbonation method of calcium hydroxide/sodium chloride composite. Sodium chloride acted as a water-soluble porogen in developing macropores in calcium carbonate body and was removed completely by washing with distilled water after carbonation. We investigated effects of sodium chloride content and molding pressure on the porosity and the mechanical strength of the calcium carbonate body. Through this study, it was found that the porosity of body increased with the sodium chloride content in composite and was hardly affected by molding pressure. On the other hand, the mechanical strength was increased with the molding pressure and reduced with the porosity. In addition, the increase in content of sodium chloride caused the enlargement of hole size as well as the enhancement of extent of interconnection among pores through hole. Especially, the calcium carbonate body with over 90% porosity could be prepared when 90 wt.% sodium chloride was used under 10 MPa molding pressure. Its average pore and hole size were 177 and 80 μm, respectively.     

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.     

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.     

Mechanism underlying specificity of proteins targeting inorganic materials

Adhesion force analysis using atomic force microscopy clearly revealed for the first time the mechanism underlying the specific binding between a titanium surface and ferritin possessing the sequence of Ti-binding peptide in its N-terminal domain. Our results proved that the specific binding is due to double electrostatic bonds between charged residue and surface groups of the substrate. Furthermore, it is also demonstrated that the accretion of surfactant reduces nonspecific interactions, dramatically enhancing the selectivity and specificity of Ti-binding peptide.     

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.