Size of plastic region owing to blunting of the precrack tip andJ lc value in several types of structural steels

In this study, a three-point bendJ _lc fracture-toughness test was carried out using four types of structural steels at room temperature. The values of (γ _p)V, which represent the width of the region where the voids are located just ahead of the crack tip, were measured by Beacham's method [9] with the help of a scanning electron microscope (SEM). The experimental (γ _p) values and the theoretical values obtained using the finite element method (FEM) or calculated fromK at initiation are in good agreement. It was found that there is a certain linear relationship between (γ _p)Vand the stretched zone width (SZW), and an experimental relationship betweenJ _lc andσ _flow·(γ _p)V which may be expressed by the following equation: $$J_{lc} = 44.1 + 0.35\sigma _{{\text{flow}}} \cdot (\gamma _{\text{p}} )V_c KJ$$ whereσ _flow is the average value of the yield stress and the ultimate tensile strength. (γ _p)V _c represents the critical value of (γ _p)V. The numerical constant 44.1 kJ m^?2 is considered to be aJ _lc value for brittle fracture of the material tested, according to the authors' previous results. It is possible to calculateJ _lc if (γ _p)V _c can be measured.     

Crystallite size distribution and the lattice distortions in highly γ-irradiated linear polyethylene

Crystallite size distributions and lattice distortions have been analysed for highly-irradiated linear polyethylene in the direction normal to 1 1 0 and 0 0 1 lattice planes through X-ray line profile analysis. It has been found that the lateral crystallite size is little affected irradiation greater than 1000 Mrad, whereas that in the chain direction decreases almost linearly with the dose of irradiation. A minor difference in the crystallite size between irradiation atmospheres, i.e. irradiation in air or in vacuum, has been disclosed at a very high dose of irradiation. The above degradation behaviour of crystallites and the change in lattice distortions have proved that radiation cross-links are mainly formed in the amorphous region near the lamellar surface of polyethylene.     

A facile synthesis of hydro- and vinyl-functionalized di- and tetrasiloxanes and polyaddition via hydrosilylation

Summary Hydro- and vinyl-bifunctionalized di- or tetrasiloxane were synthesized by degradative cleavage of functional cyclic siloxanes with methyllithium followed by quenching with a functional chlorosilane, or by ring-opening of hexamethylcyclotrisiloxane (D₃) by functional alkyllithium followed by quenching with a functional chlorosilane. These bifunctionalized siloxanes were used as monomers in polyaddition with transition metal catalysts.     

Formation of Zirconia Solid Solutions Containing Alumina Prepared by New Preparation Method

In the system ZrO₂–Al₂O₃, a new method for preparing ZrO₂ solid solutions from ZrCl₄ and AlCl₃ using hydrazine monohydrate is investigated. c -ZrO₂ solid solutions containing up to ∼40 mol% Al₂O₃ crystallize at low temperatures from amorphous materials. The formation mechanism is discussed from IR spectral data. The values of the lattice parameter α increase linearly from 0.5072 to 0.5105 nm with increasing Al₂O₃ content. At higher temperatures, transformation of the solid solutions proceeds as follows: c ( SS ) → t ( ss ) → t ( ss ) +α-Al₂O₃→ m +α-Al₂O₃. m -ZrO₂–α-Al₂O₃ composite ceramics are fabricated by hot isostatic pressing for 2 h at 1250°C and 196 MPa. Microstructures and mechanical properties are examined, in connection with increasing Al₂O₃ content.     

Agglomeration control of hydroxyapatite nano-crystals grown in phase-separated microenvironments

Materials synthesis processes that require high temperatures consume large quantities of energy that generate an environmental burden. We attempted to synthesize hydroxyapatite (HAp) nano-crystals without firing or melting. “Water in oil” (W/O) emulsions were employed as microreactors for HAp formation. The surfactant-bounded water mediated HAp crystal nucleation, and HAp nano-crystallites were obtained. The obtained particles were aggregates composed of plate-like nano-crystals and monodisperse tiny crystals. Utilization of the W/O emulsions resulted in tunable nucleation frequency and the reactant provision, and yielded HAp nano-crystals with characteristic agglomeration properties.     

Measurements of gamma-ray emission probabilities of 241, 243Am and 239Np

Gamma-ray emission probabilities of ^{241, 243}Am and ²³⁹Np have been precisely measured with gamma- and alpha-ray spectroscopic methods. The activities of the samples were determined by measuring alpha particles using a Si semiconductor detector. Gamma rays emitted from the samples were measured with a planar type High-Purity Germanium (HPGe) detector. An efficiency curve of the HPGe detector was derived with uncertainties from 0.7% to 2.5% by combining measured efficiencies and Monte Carlo simulation. The gamma-ray emission probabilities for the major gamma rays of these nuclides were determined with uncertainties less than 1.2%.     

Experimental Evaluation of Characteristics of SR Motor Made of Permendur

A switched reluctance (SR) motor has a doubly salient pole structure. The performance of the SR motor strongly depends on the magnetic properties of the core material, since it consists only of an iron core and copper windings. This study experimentally evaluates the performance of an SR motor made of permendur (Fe–49% Co alloy), which has very high saturation flux density and low core loss. Two types of SR motors that have the same dimensions but different core materials are used: one motor is made of the conventional nonoriented Si steel, and the other is made of permendur. Comparison of the characteristics of the two motors shows that the performance of the permendur SR motor surpasses that of the conventional one in terms of output power and efficiency. © 2014 Wiley Periodicals, Inc. Electr Eng Jpn, 187(1): 51–57, 2014; Published online in Wiley Online Library ( wileyonlinelibrary.com ). DOI 10.1002/eej.22431     

Laser Photolysis Study on Mechanism and Efficiency of Electron Transfer Between Fullerenes (C60 and C70) and Tetraselenafulvalenes

Abstract

Efficient electron-transfer reactions from three kind of tetraselenafulvalenes (TSeF's) to photoexcited triplet state of C₆₀ or C₇₀ in polar solvents have been confirmed by transient absorption spectroscopy observing the decay of ³C₆₀*/³C₇₀* and rise of C₆₀ ^??/C₇₀ ^??. Growth of single crystal seems to be stimulated by laser irradiation of the solution containing C₆₀ and bis(ethylenedithio)tetraselena-fulvalene (BEDT-TSeF), in which C₆₀ ^?? was effectively formed.     

Optically and electrically excited emissions from organic semiconducting oligomer crystals

This paper reviews optically and electrically excited emissions from organic semiconducting oligomers in the form of their single crystals. Of the semiconducting oligomers, the review focuses on thiophene/phenylene co‐oligomers (TPCOs). The topics cover crystal growth and laser oscillation along with related spectrally narrowed emissions of TPCO crystals. Aside from the strong excitation with a laser beam, weak excitation using a mercury lamp produces optical fringes superimposed on broadband emission spectra. The laser oscillation spectra accompanied by longitudinal multimode and optical fringes observed from the weak excitation have the same origin. This enables us to determine optical constants (i.e. refractive indices) and their dispersion of the crystals and provides sufficient information for the construction of optoelectronic devices based on the organic crystals. As a typical example, the review outlines the improved device constitution and performance as well as device operation methods with light‐emitting field‐effect transistors (LEFETs), because the device configuration is suited for cutting‐edge devices including lasers. Finally the review presents device performance of LEFETs having a diffraction grating. These devices are suited for exploring the possibility of constructing a next‐generation current‐injected laser device. © 2016 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.