Corrosion properties of materials coated with Cr2O3/NiCr and with Cr2O3+NiCr functionally gradient materials

This paper studied the corrosion properties of five kinds of Cr₂O₃ coated materials: the SUS316L austenitic stainless steels respectively coated with the Cr₂O₃ layer (Cr₂O₃/316), Cr₂O₃ and 80Ni‐ 20Cr layers (Cr₂O₃/80NiCr/316), Cr₂O₃ and 50Ni‐ 50Cr layers (Cr₂O₃/50NiCr/316), Cr₂O₃ + 80Ni‐ 20Cr functionally gradient materials (Cr₂O₃ + 80NiCr FGM), and Cr₂O₃ + 50Ni‐ 50Cr FGM (Cr₂O₃ + 50NiCr FGM). All the coatings were made by atmospheric pressure plasma spraying method (APPS). The corrosion resistance of the coated materials was analyzed by immersion tests and electrochemical evaluations. A mechanism of the corrosion failures for these kinds of coated structures was proposed. The different coating structures for improving the adhesion between ceramics and substrates were assessed, and the effect of Cr content in the NiCr coatings on the corrosion property was discussed. The ceramic coatings with the 50Ni‐ 50Cr intermediate layer possessed a better corrosion resistance than that with 80Ni‐ 20Cr. The FGM structures appeared to offer weaker resistance to corrosion attack than that with the intermediate layer in general. Under corrosion test conditions, the corrosion‐proof abilities of the coated structures were, respectively: the Cr₂O₃/50NiCr/316 in the best rank; the Cr₂O₃/316, Cr₂O₃/80NiCr/316, and Cr₂O₃ + 50NiCr FGM in the second rank; and the Cr₂O₃ + 80NiCr FGM in the last rank. This means that applying the 50NiCr intermediate layer under the Cr₂O₃ ceramic coating can further improve the corrosion resistance of Cr₂O₃/316. Porosity analysis was used to explain the difference of corrosion resistance between the Cr₂O₃/50NiCr coated material and the Cr₂O₃ + 50NiCr FGM. The porosity in each layer of the Cr₂O₃ + 50NiCr FGM was higher than that in the Cr₂O₃/50NiCr coating, and as a result the corrosion resistance of Cr₂O₃/50Ni Cr/316 is better than Cr₂O₃ + 50NiCr FGM.     

Effects of solvent addition to acetylation medium on cellulose triacetate prepared from low-grade hardwood dissolving pulp

As cellulose triacetate was prepared from low-grade hardwood-dissolving pulp, a considerable amount of the insoluble residue was present in the acetylation medium of the acetic acid/acetic anhydride/sulfuric acid system, and it consisted mainly of cellulose triacetate (CTA) and xylan diacetate (XDA). As one of the remedies for reducing the insoluble residue, a solvent was added to the acetylation medium and the effects of the solvent addition on the amount of insoluble residue formed were studied. To do so, 17 different solvents were selected so as to cover a wide range of solubility parameters. The obtained results clearly indicated that the addition of the solvent affects the amount of insoluble residue and that, excluding dichloroacetic acid, nitromethane was effective for its reduction, but that neither methylene chloride nor nitroethane were in spite of their effectiveness for softwood-dissolving pulp, which would be due to the intrinsic properties of XDA on the solubility in the acetylation medium. A new acetylation system with such an appropriate solvent would, therefore, provide a clue as to an industrial usage of the low-grade hardwood-dissolving pulps for cellulose acetate production. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1445–1449, 1998     

Recovery and restructuring induced by fission energy ions in high burnup nuclear fuel

In light water commercial reactors, extensive change of grain structure was found at high burnup ceramic fuels. The mechanism is driven by bombardment of fission energy fragments and studies were conducted by combining accelerator based experiments and computer-science. Specimen of CeO₂ was used as simulation material of fuel ceramics. With swift heavy ion (Xe) irradiation on CeO₂, with 210 MeV, change of valence charge and lattice deviation of cations were observed by XPS and XRD. Combined irradiations of Xe implantation and swift heavy ion irradiation successfully produced sub-micrometer sized sub-grains, similar as that observed in commercial fuels. Studying components of mechanism scenarios, with first principle calculations using the VASP code, we found stable hyper-stoichiometric defect structures of UO_2+x. Molecular dynamics studies revealed stability of Xe planar defects and also found rapid transport mode of oxygen-vacancy clusters.     

Morphological change in FePt nanogranular thin films induced by swift heavy ion irradiation

We have investigated morphology change of FePt nanogranular films (FePt)₄₇(Al₂O₃)₅₃ under irradiation with 210 MeV Xe ions. Here, electron tomography technique was extensively employed to clarify three-dimensional (3D) structure in irradiated specimens, in addition to conventional transmission electron microscopy (TEM) techniques such as bright-field observation and scanning TEM energy dispersive X-ray spectroscopy (STEM-EDX) analysis. The ion irradiation induces the coarsening of FePt nanoparticles with elongation along the beam direction. Electron tomography 3D reconstructed images clearly demonstrated that when the fluence achieves 5.0 × 10¹⁴ ions/cm², well-coarsened FePt balls have been formed on the irradiated surface, and the particles in the film interior have been deformed into rods along the ion trajectory. The alloy particles become inhomogeneous in composition after prolonged irradiation up to 1.0 × 10¹⁵ Xe ions/cm². The particle center is enriched with Pt, while Fe is slightly redistributed to the periphery.     

A Hexameric Ribozyme Nanostructure Formed by Double-Decker Assembly of a Pair of Triangular Ribozyme Trimers

The modular architecture of naturally occurring ribozymes makes them a promising class of structural platform for the design and assembly of three-dimensional (3D) RNA nanostructures, into which the catalytic ability of the platform ribozyme can be installed. We have constructed and analyzed RNA nanostructures with polygonal-shaped (closed) ribozyme oligomers by assembling unit RNAs derived from the Tetrahymena group I intron with a typical modular architecture. In this study, we dimerized ribozyme trimers with a triangular shape by introducing three pillar units. The resulting double-decker nanostructures containing six ribozyme units were characterized biochemically and their structures were observed by atomic force microscopy. The double-decker hexamers exhibited higher catalytic activity than the parent ribozyme trimers.     

Increase of inductance ratio of flat type fault current limiter with high‐Tc superconducting disk

Fault current limiters (FCLs) are expected to reduce fault current and improve stability of power systems. A flat type fault current limiter consisting of the pancake primary winding and a high‐T_c superconducting (HTS) disk was proposed as a modified version of a conventional magnetic shield type of the FCL with the superconducting cylinder. The flat type FCL has the advantage of being manufactured smaller than the cylinder type FCL. It is pointed out, from a magnetic field analysis, that the volume of the flat type FCL is smaller than that of the cylinder type FCL with same magnitude of the limiting inductance. Further, the magnetic field analysis suggests that a high inductance ratio can be realized by radially enlarging both the primary winding and the HTS disk, stacking the FCL modules in layers and sandwiching the primary winding with superconducting disks. © 2006 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Evaluation of the contents and ratios of five fractionated proteins to elucidate the protein composition in soybean seeds

Selecting suitable soybean cultivars is important for food processing and exploring their endowment with desirable physiological functions. We applied the fractionation method previously established to compare soy protein composition among cultivars to promote such a selection. More than 95% of the proteins in soybean cotyledons were extracted from 13 soybean cultivars using a high-concentration salt solution. The extracted proteins were fractionated into five fractions, namely oil body-associated protein (OBAP), polar lipid-associated protein (PLAP), globulins (11S and 7S), and whey by centrifugation after tuning the solubility behavior of the proteins with various solutions. Protein species in each fraction were analyzed by SDS-PAGE. Protein content in the total extract and five fractions was quantified to characterize the protein composition of soybean cultivars. The correlation between the protein content of each fraction and the total protein in cotyledon was investigated. A strong positive correlation was found only for the 11S fraction (r = 0.82), followed by a positive correlation in the 7S fraction (r = 0.65). Thus, we surmised that the increased protein content in soybean was due to increased globulin content. Furthermore, the calculation of the average ratio of protein content in each fraction indicated the globulin fraction (7S and 11S) to be 52%, the lipophilic protein fraction (OBAP and PLAP) to be 33%, and the whey fraction to be 13%. The preparation method employed in this study is a promising tool for efficiently comparing the protein composition of soybean cultivars to evaluate the potential use of cultivars for food production.