Mechanical properties and fracture behaviour of SiTiCO fibre/SiAlON composite

Unidirectional SiTiCO fibre (Tyranno fibre®) reinforced SiAlON (Si₂Al₄O₄N₄) was fabricated by the filament winding method. The fibre/matrix green sheets were stacked and hot-pressed at 1773 K for 1.8 ks under a nitrogen atmosphere. The composite with a fibre content of 42 vol% showed significantly higher flexural strength (800 MPa) than that of monolithic SiAlON ceramics (570 MPa). A strength decrease due to the matrix degradation was observed at high temperature (1273 K and 1473 K). The fracture toughness of the composite measured by SENB (single edge notched beam) method was 8.0 MPa·m^0.5, being two times higher than that of monolithic ceramics (4.0 MPa·m^0.5). The work-of-fracture of the composite measured by static and dynamic methods was 9.62 kJ/m² and 8.29 kJ/m², respectively. 1998 Elsevier Science Limited and Techna S.r.l.     

Environmental effect on mechanical properties of aluminide matrix composites

This paper investigates the validity of the toughness measurement with a variation of the loading rate for distinguishing the fracture mechanism of aluminide intermetallics and their composites. The ductility and fracture toughness of Ni₃Al alloys and their composites are governed by inherent grain boundary brittleness and moisture-induced embrittlement at ambient temperatures. Although B doping is effective in suppressing both factors, remarkable improvement of toughness mainly depends on grain boundary strengthening. The toughness of the alloys is influenced by the dislocation locking mechanism and the extrinsic embrittlement promoted by diffusion of oxygen at intermediate temperatures. Extrinsic embrittlement is the predominant mechanism in determining the toughness at 673 K. Restriction of the dislocation motion is the predominant factor in determining toughness at 873 and 1073 K. The composites reinforced with TiC particles exhibit exceptionally constant toughness at 300 to 900 K.     

Immunoassay using poly-tetrafluoroethylene microstructure in organic solvent

This paper reports the first application of poly-tetrafluoroethylene (PTFE) microstructure, which fabricated by synchrotron radiation induced photo-evaporation process, to enzyme-linked immunosorbent assay. The advantages of PTFE microstructure for the development of lab-on-a-chip due to the extremely high-aspect ratio microstructure and chemical stability of PTFE is discussed. The results of immunoassay shows the successful detection of analyte (mouse IgG) with detection range with 0–100 ng/ml. This result suggests the successful immobilization of antibody (anti-mouse IgG goat antibody) onto the X-ray exposed surface of PTFE microstructure and successful demonstration of antigen–antibody reaction in the PTFE microstructure. We also demonstrated the detection of polychlorinated biphenyl (PCB). As the result of demonstration, we successfully detected PCB with ranging analyte concentration of 0.1–10 ng/ml.     

Grain growth prediction based on data assimilation by implementing 4DVar on multi-phase-field model

We propose a method to predict grain growth based on data assimilation by using a four-dimensional variational method (4DVar). When implemented on a multi-phase-field model, the proposed method allows us to calculate the predicted grain structures and uncertainties in them that depend on the quality and quantity of the observational data. We confirm through numerical tests involving synthetic data that the proposed method correctly reproduces the true phase-field assumed in advance. Furthermore, it successfully quantifies uncertainties in the predicted grain structures, where such uncertainty quantifications provide valuable information to optimize the experimental design.     

Structure-properties of super-tough PLA alloy with excellent heat resistance

Poly(lactic acid) (PLA) was toughed by blending hydrogenated styrene-butadiene-styrene block copolymer (SEBS) with the aid of reactive compatibilizer, poly(ethylene-co-glycidyl methacrylate) (EGMA). The high temperature property and thermal aging resistance were improved by further incorporating polycarbonate (PC), the ductile polymer with high glass transition temperature. On the basis of transmission electron microscopy, differential scanning calorimetry, and dynamic mechanical analysis, the outstanding toughness and aging resistance of the 4 component alloy; e.g., PLA/PC/SEBS/EGMA = 40/40/5/5 (wt. ratio), seems to come from the negative pressure effect of SEBS that dilates the plastic matrix consisting of PLA and PC to enhance the local segment motions.     

Hydrogen generation by water radiolysis with immersion of oxidation products of Zircaloy-4

In order to predict the hydrogen gas generation from seawater or water in which debris would be included by the severe accident of nuclear power plant, we investigated the effect of ZrO₂ and the oxidation products of Zircaloy-4 on hydrogen gas generation by radiolysis of water since the radiolytic generation could be affected by materials immersed in water. Powders of well-characterized oxides and oxidation products were immersed in either seawater or distilled water, and irradiated by gamma ray from a Co-60 source. The observed hydrogen yield, G(H₂), was measured as a function of the weight fraction of oxide in water up to 50 wt%. The enhancement of the hydrogen generation by radiolysis of water with the commercial oxides and the oxidation products of Zircaloy-4 was quite small or absent in seawater. But the enhancement was observed in the presence of the oxides or the oxidation products at low weight fraction in distilled water. This enhancement in distilled water seemed to be dependent on specific surface area or particle size, but its dependence on the crystal structure was not apparent in the experimental results. The enhancement was saturated at higher ZrO₂ weight fractions and it was not apparent in the seawater.     

Optimum design of a regenerative braking system for electric vehicles based on fuzzy control strategy

A regenerative braking system (RBS) can prolong the driving distance of electric vehicles by converting mechanical energy into electric energy. In this paper, an RBS based on fuzzy control strategy is proposed. By analyzing the characteristics of all factors, under the assurance of safety and stability during braking conditions, a fuzzy control model was established in the MATLAB/SIMULINK environment and verified by using simulation software Advisor2002. In order to recover more energy, the control model was optimized by the Taguchi method, and a new fuzzy control model was established and simulated. The simulation results show that by using the optimized fuzzy control system, more braking energy can be recovered and that the energy recovery efficiency can be increased. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Effect of the solvent on growth of titania nanotubes prepared by anodization of Ti in HCl

The effect of the solvent on the anodic growth of titania nanotubes in HCl dissolved in water, ethylene glycol and 2-propanol was studied. These nanotubes grow with locally rapid breakdown of the passive TiO₂ film forming a forest of nanotubes-bearing microtowers with the background of passive TiO₂ Film. These bundles of assembled-groups of titania nanotubes look like Pillars corals. The low relative permittivity of the 2-propanol led to lowering of dissociation of HCl and hence lowering the activity of H⁺ and Cl⁻ ions which in turn led to suppress of dissolution of titania and increasing the growth rate of the titania nanotubes. The X-ray diffraction pattern showed that the titania nanotubes after annealing change to the crystalline anatase phase. The anodic films showed characteristic coloration with intensity and color that changes (qualitatively) with time of anodization.     

Copper‐ion adsorption and gold‐ion reduction by polyphenols prepared by the enzymatic reaction of horseradish peroxidase

Polyphenols were synthesized via a horseradish peroxidase reaction from phenol, catechol, and pyrogallol for use as copper‐ion adsorbents. The molecular weights of the polyphenols ranged from about 1000 to 3000 g/mol. The hydroxyl group contents in the polyphenols from phenol, catechol, and pyrogallol were 5.9, 4.0, and 0.94 mol/kg, respectively, as determined by titration. The saturation binding capacity for copper ions of the polyphenols from phenol, catechol, and pyrogallol were calculated to be 1.44, 0.88, and 0.22 mol/kg, respectively, at pH 4.5. Copper ions were efficiently adsorbed via an ion‐exchange interaction by the synthesized polyphenols with vicinal hydroxyl groups, and those polyphenols could be applied to metal adsorption. Gold ions were selectively reduced by the phenol group in polypyrogallol in acid media to form gold particles. The reduced gold particles were eluted with a solution of 1.0M thiourea plus 0.5M HCl. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Comonomer-unit compositional distribution and its effect on thermal and crystallization behavior of bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

In order to clarify the relationships between comonomer-unit compositional distribution and physical properties of bacterial poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)], the comonomer-unit composition and its distribution as well as their effects on the physical properties of P(3HB-co-3HHx) have been studied. A series of fractions with very different comonomer-unit composition but very narrow distribution were obtained by repeated fractionation and re-fractionation. It was found the as-bacterially synthesized P(3HB-co-3HHx) had very broad comonomer-unit compositional distribution. The solvent/non-solvent fractionation of P(3HB-co-3HHx) was found to be firstly regulated by the comonomer-unit composition and then by the molecular weight. Significant effect of the comonomer-unit compositional distribution on thermal and crystallization behavior as well as crystalline morphology of P(3HB-co-3HHx) was observed. It was concluded that as-bacterially synthesized P(3HB-co-3HHx) samples should be considered as polymer blends of component polymers with different 3HHx unit content, whose physical properties considerably depend on the comonomer-unit composition as well as comonomer-unit compositional distribution.