Mod processing of epitaxial ferroelectric films

Abstract

Ferroelectric thin films have been receiving great attention for the applications in emerging areas. The MOD(Metal-Organic Deposition) processing could be successfully applied for processing the well controlled epitaxial ferroelectric films at relatively low temperatures. Examples are K(Ta, Nb)O₃ and LiNbO₃ film processings. Epitaxial films of K(Ta, Nb)O₃ could be synthesized by the reaction control of metal alkoxides on Pt(100)/MgO(100) substrates. The structures of the precursor solutions were analyzed to control the crystallization. The chemically modified metal alkoxide precursor with a chelate ligand could be utilized for micro-patterned LiNbO₃ epitaxial films using ultra-violet irradiation. The combination of micro-patterning will afford the novel break-through to the development of the integrated functional materials.     

Relationship between histological complexity and elemental composition of the cuspal enamels among human deciduous teeth

The purpose of this study is to clear the difference of histology and elemental composition of the cuspal enamels among the human deciduous teeth. The reground surfaces at the cuspal enamels of them were observed under SEM. The contents of seven elements were analyzed quantitatively with EPMA. It is thought that not only the first zone but also the second zone of the inner enamel in the deciduous molar causes the lateral enlargement of the dental caries along the dento-enamel junction because the second zone of the inner enamel in the deciduous molar was more porous than that in the permanent premolar. It is thought that the cuspal enamel in the deciduous teeth is low calcified than that in the permanent teeth because the contents of calcium and phosphorus in the former were significantly lower than those in the latter. It is considered that the cuspal enamel in the deciduous teeth may include less magnesian whitlockite than that in the permanent teeth because the content of magnesium in the former was significantly lower than those in the latter. A relationship was recognized between the complexity level in the histological structure and the elemental composition of the cuspal enamels among the human deciduous teeth.     

Relationship between histological complexity and elemental composition of the cuspal enamels among human deciduous teeth

The purpose of this study is to clear the difference of histology and elemental composition of the cuspal enamels among the human deciduous teeth. The reground surfaces at the cuspal enamels of them were observed under SEM. The contents of seven elements were analyzed quantitatively with EPMA. It is thought that not only the first zone but also the second zone of the inner enamel in the deciduous molar causes the lateral enlargement of the dental caries along the dento-enamel junction because the second zone of the inner enamel in the deciduous molar was more porous than that in the permanent premolar. It is thought that the cuspal enamel in the deciduous teeth is low calcified than that in the permanent teeth because the contents of calcium and phosphorus in the former were significantly lower than those in the latter. It is considered that the cuspal enamel in the deciduous teeth may include less magnesian whitlocki-te than that in the permanent teeth because the content of magnesium in the former was significantly lower than those in the latter. A relationship was recognized between the complexity level in the histological structure and the elemental composition of the cuspal enamels among the human deciduous teeth.     

Cementite dispersed in carbons from ferrocene,vinylferrocene, divinylbenzene systems

Cementite-dispersed carbon was synthesized by pressure pyrolysis of divinylbenzene-vinylferrocene and divinylbenzene-ferrocene below 600° C. The magnetization of divinylbenzeneferrocene polymer was higher than that of divinylbenzene-vinylferrocene copolymer at temperatures from 300 to 400° C. The saturation magnetization of cementite-dispersed carbon formed above 500° C was dependent only on the iron concentration in the carbon matrix. The coercive force of cementite-dispersed carbon synthesized from divinylbenzene -vinylferrocene copolymer was about 900 Oe as a maximum value, whereas divinylbenzene-ferrocene polymer gave cementite-dispersed carbon with lower coercive force of 200 Oe. The size of cementite particles dispersed in the carbon from divinylbenzene-vinylferrocene copolymer was less than 50 nm diameter, while divinylbenzene-ferrocene (DVB-Fc) polymer gave a carbon containing larger particles up to 130 nm. The feasible initial aggregation of paramagnetic species in DVB-Fc polymer gave large particles of cementite with multiple magnetic domain. Fixation of ferrocene by the carbon-carbon bond to the parent polymer matrix was found to be effective for fine dispersion of cementite particles in the resultant carbon.     

Hybrid microfabricated device for field measurement of atmospheric sulfur dioxide

A miniaturized planar-membrane-based gas collector of 800 nL internal liquid volume was integrated with a microfabricated conductivity detector to measure atmospheric SO2. This device is operated with a dilute H2SO4/ H202/2-propanol absorber for a finite integration period (typically, 1.5 min) without liquid flow. During this period, sulfuric acid is formed from SO2 that diffuses into the liquid and accumulates therein. The increase in conductivity with ongoing sampling is measured. The absorber is then replaced with fresh solution, and the process starts anew. The most important factors that govern sensitivity and the detection limit are the choice of the membrane, the nature of the internal collector solution, and the thickness of the solution layer. A porous polypropylene membrane with some 2-propanol (IPA) incorporated in the internal solution was found to be the best combination. The sensitivity was inversely proportional to the solution layer thickness, and a layer thickness of 100 microm resulted in a practical device with good performance characteristics. Greater applied pressure on the gas phase relative to the liquid side also can improve device performance. The system is operated with 12 V DC and does not require a liquid pump. Under optimized conditions, the LOD is 0.7-1.0 ppbv for a sampling period of 1.5 min. The device was field-tested around Mt. Aso in Japan. Changes in ambient SO2 concentrations could be followed with good time resolution. The results are compared with data obtained by a collocated macroscale instrument.     

Synthesis of iron-dispersed carbons by pressure pyrolysis of divinylbenzene-vinylferrocene copolymer

Versatile carbons with finely dispersed iron were synthesized by pressure pyrolysis of a copolymer prepared from divinylbenzene and vinylferrocene at temperatures below 680? C and pressures of 125 MPa. The pyrolysis conditions of the copolymer were found to influence the final morphology of carbons to give fibrils, spheres and polyhedra. The resulting carbons contained uniformly fine particles of cementite (Fe₃C) which were less than 30 nm in size, whereas the magnetite was dispersed in the carbon matrix by pressure pyrolysis in the presence of water. Highly dispersed cementite in carbon was found to decompose into metallic iron by further heat treatment above 850? C. Porous spherulitic carbons were also synthesized by heat treatment of magnetite containing carbon spherulites.     

Synthesis and properties of magnetite-dispersed carbon by pressure pyrolysis of divinylbenzene-vinylferrocene with water

Magnetite-dispersed carbon was synthesized by pressure pyrolysis of the divinylbenzene-vinylferrocene system in the presence of water at 125 MPa below 700°C. Supercritical water influenced the phase separation of oligomers formed during the pyrolysis to give carbons with various morphologies, such as spherulitic, coalescing spherulitic and polyhedral carbon, depending upon the concentration of water. Carbon spherulites from 5 to 10 μm diameter dispersed with magnetite particles (<100 nm) were synthesized by pyrolysis of divinylbenzene-5.1 mol% vinylferrocene and 20.0 wt% water at 550°C and 125 MPa. The specific area of magnetite-dispersed carbon synthesized at 600°C and 125 MPa was 92 m²g⁻¹ after heat treatment at 800°C for 1 h. The specific area of the carbon specimen increased with decreasing pyrolysis temperature of the parent copolymers from 700 to 550°C. The Curie temperature of magnetite-dispersed carbon was 585°C. Magnetite dispersed in the carbon matrix was reduced to wüstite during the further heat treatment in vacuum. The saturation magnetization of magnetite-dispersed carbon was 79% of the theoretical value, and changed in proportion to the concentration of iron in the carbon matrix.     

Bifunctional nanotube scaffolds for diverse ligands are purified simply from Escherichia coli strains coexpressing two functionalized flagellar genes

We functionalized Escherichia coli FliC flagellin proteins to form tailored nanotubes binding single types or pairs of ligands, including divalent cations, fluorescent antibodies, or biotin-avidin-linked moieties such as ferritins. The ratio of each tag in bifunctionalized flagella could be toggled extending their sophistication as nanoscaffolds. Tobacco Etch Virus (TEV) protease site-containing FliCs were cleaved by the cognate protease without filament disintegration, potentiating their use as removable nanolithography masks to deposit attached ligands by protease cleavage.     

Electrical and mechanical properties of coaxial cable for use under high temperature and radioactive conditions

This research examines the effect of γ-ray irradiation at different temperatures (room temperature and 250°C) and atmospheric conditions (air and N₂) on the electrical and mechanical characteristics of thermoplastic polyimide (TPI) insulated and sheathed coaxial cable, which is designed for high-temperature, radioactive use. It was found that the TPI insulated and sheathed coaxial cable had good radiation resistance at 250°C under N₂, γ-ray irradiation of 75 MGy under air and electron beam irradiation of approximately 100 MGy under He. It was also found that both crosslinking and crystallization of TPI was accelerated by the synergistic effect of heat and γ-ray irradiation. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (2): 1–9, 1997