Microstructure and tensile strength of grade 2 titanium processed by equal-channel angular pressing and by rolling

Commercially pure titanium strengthened by severe plastic deformation constitutes an alternative to the use of complex Ti alloys in many medical or industrial applications. In this research, rods of grade 2 Ti were processed by up to six passes using Equal-channel angular pressing (ECAP) at 573 K followed by cold rolling at room or subzero temperatures. After four passes of ECAP, the grain size was refined down to the submicrometer scale and subsequent rolling led to further refinement. The microstructure was characterized by taking Vickers microhardness measurements and tensile testing was performed both at room temperature and in the temperature range of 573–773 K. The results show that at all temperatures the tensile strength is significantly improved by means of these processing techniques. At room temperature, the ultimate tensile strength of pure Ti after ECAP plus subzero rolling is close to that of the traditional Ti-6Al-4V alloy while maintaining adequate levels of elongation to failure.     

An evaluation of the shearing patterns introduced by different anvil alignments in high-pressure torsion

A two-phase duplex stainless steel was used to investigate the influence of different amounts of anvil misalignment on the shearing patterns produced during high-pressure torsion (HPT) and subsequently on the hardness distributions across the disc upper surfaces. The results show that for a perfect alignment of the anvils, to within <25 μm, the discs exhibit regular flow patterns as anticipated from conventional analysis whereas for anvil misalignments of 100 or 200 μm the discs develop double-swirl patterns on the upper surfaces. These double swirls increase in size with increasing anvil misalignments and decrease in size with increasing numbers of torsional turns. The origin of these double swirls is investigated by examining a model based on a buckling theory for loaded beams and the development of instabilities within the discs during HPT processing. It is demonstrated that this model provides a satisfactory explanation for the reports of swirls and vortices in samples processed by HPT.     

Pinched flow fractionation: continuous size separation of particles utilizing a laminar flow profile in a pinched microchannel

A concept of "pinched flow fractionation" for the continuous size separation and analysis of particles in microfabricated devices has been proposed and demonstrated. In this method, particles suspended in liquid were continuously introduced into a microchannel having a pinched segment and were aligned to one sidewall in the pinched segment by another liquid flow without particles. The particles were then separated perpendicularly to the flow direction according to their sizes by the spreading flow profile inside the microchannel. Polymer microbeads were successfully separated, and the effects of the flow rate and channel shapes on the separation performance were examined. Also, separated particles were collected independently by making branches at the end of the pinched segment. Since this method utilizes only the laminar flow profile inside a microchannel, complicated outer field control could be eliminated, which is usually required for other kinds of particle separation methods such as field flow fractionation. Also, this method can be applied both for particle size analysis and for preparation of monodispersed particles, since separation can be rapidly and continuously performed.     

High temperature thermal stability of ultrafine-grained silver processed by equal-channel angular pressing

The high temperature thermal stability of the ultrafine-grained (UFG) microstructures in low stacking-fault-energy silver was studied by differential scanning calorimetry (DSC). The UFG microstructures in two samples having purity levels of 99.995 and 99.99 at.% were achieved by four passes of equal-channel angular pressing at room temperature. The defect structure was studied by electron microscopy, X-ray line profile analysis, and positron annihilation spectroscopy before and after the exothermic DSC peak related to recovery and recrystallization. The heat released in the DSC peak was correlated to the change of defect structure during annealing. It was found for both compositions that a considerable fraction of stored energy (~15–20 %) was retained in the samples even after the DSC peak due to the remaining UFG regions and a large density of small dislocation loops in the recrystallized volumes. The larger impurity level in Ag yielded a higher temperature of recrystallization and a lower released heat. The latter observation is explained by the much lower vacancy concentration before the DSC peak which is attributed to the segregation of dopants at grain boundaries resulting in a smaller free volume in the interfaces.     

Bacterial cellulose/silica hybrid fabricated by mimicking biocomposites

In plants such as grasses, rice, and sugar cane, biomineralizatin occurs such that amorphous silica is drawn from soil, transferred and deposited on polysaccharide matrix. In this study, by mimicking natural biomineralization in plants, a cellulose/silica hybrid was produced using bacterial cellulose (BC). BC hydro-gel was immersed in an aqueous solution of silanol derived from tetraethoxysilane (TEOS), and silanol was then converted into silica in the BC hydro-gel matrix. By pressing the BC hydro-gels and hybrids at 120 °C and 1–2 MPa, water-free translucent sheets were obtained. In the leaves of rice plants, large silica bodies (μm order) were embedded in the polysaccharide matrix, whereas in the BC/silica hybrids, nano scale silica was embedded between the micro fibrils of the BC matrix. Reflecting this structure, the modulus of elasticity and tensile strength of dry BC/silica hybrid improved to 17 GPa at 25 °C and 185 MPa, respectively. In the case of rice plants, the modulus was 3.5 GPa at 25 °C and the tensile strength was 25–88 MPa, suggesting a weaker structure than in BC hybrid.     

Numerical analysis on the optical role of nano-randomness on the Morpho butterfly's scale

The blue coloration of Morpho butterflies has anomalously low angular dependence despite the production of color with a selected wavelength based on an interference effect. A key to the mechanism of the specific Morpho-color was suggested to be the randomness of its scale. Using finite-difference time-domain (FDTD) analysis, the role of different kinds of randomness in the structure of the Morpho butterfly's scale was investigated, which was impossible by conventional analytical calculations. The results revealed that incoherence in the incident light plays an essential role, which cannot be realized only by structural randomness. On the other hand, the lateral and vertical randomness, and the number of random components were found each to have an independent role to realize the specific Morpho-color preventing the sharp reflective angular dependence. The direction obtained by the numerical simulations to analyze optically complex random structures will serve not only to understand the scientific principles, but also to design the optical properties of artificial materials.     

Predictors of cardiovascular events in hemodialysis patients after stress myocardial perfusion imaging

Cardiovascular prognosis in patients under normal stress myocardial perfusion images (MPI) is generally excellent. However, this is not true for patients with chronic kidney disease (CKD) treated by hemodialysis. This study evaluated prognostic factors of adverse cardiovascular events in hemodialysis patients in whom stress MPI was performed. Pharmacological stress MPI was performed in 88 hemodialysis patients, and we retrospectively followed‐up for 26 months. Cardiovascular events included cardiac death, nonfatal myocardial infarction, and unstable angina. Cardiovascular events occurred in 16 patients (18%). Univariate Cox regression analysis revealed that peripheral artery disease (PAD) and parameters of stress MPI were significant predictors of cardiovascular events. Multivariate Cox regression analysis revealed that only PAD (hazard ratio = 6.54; P = 0.002), and abnormal stress MPI (hazard ratio = 8.26; P = 0.008) were independent and significant predictors of cardiovascular events. Kaplan–Meier analysis showed better prognosis in patients with normal stress MPI than in patients with abnormal stress MPI (P < 0.001, log–rank test). However, in patients with normal stress MPI, cardiovascular events occurred in 10 of the 76 patients (13%). Among patients with normal stress MPI, Kaplan–Meier analysis showed that patients with no PAD had better prognosis than patients with PAD (P = 0.001, log–rank test). In hemodialysis patients, both PAD and stress MPI were powerful cardiovascular predictors. Normal stress MPI alone cannot guarantee good prognosis in terms of cardiovascular events. Consideration of PAD may improve the predictive value of stress MPI in some patients.     

Transfer of caesium and potassium from Japanese apricot (Prunus mume Sieb.et Zucc.) to Japanese apricot liqueur (Ume liqueur)

The potential contamination with radionuclides released by the Fukushima Daiichi Nuclear Power Plant Accident following the great east Japan earthquake and tsunami in March 2011 of agricultural products and processed foods derived from them is a matter of on‐going concern. The stable ¹³³Cs is a useful indicator for predicting the behaviour of radioactive Cs, and potassium (K) is a congener of Cs. In this study, the distribution of ¹³³Cs and K in Ume fruit, and the transfer of ¹³³Cs and K from Ume fruit to Ume liqueur, were investigated. The concentrations of ¹³³Cs and K in Ume fruit were highest in the skin, followed by the kernel or flesh, and then the pit. About 80% of ¹³³Cs and K in all Ume fruits was distributed in the flesh. The transfer ratios of ¹³³Cs and K from Ume fruit to Ume liqueur were similar among all cultivars after 3 months, and they were similar to those of organic acids. The food retention factor (Fr = weight of ¹³³Cs in Ume liqueur/weight of ¹³³Cs in Ume fruit) was ca. 0.8, and the processing factor (Pf = concentration of ¹³³Cs in Ume liqueur/concentration of ¹³³Cs in Ume fruit) was 0.2–0.3. From the present study, the radioactivity of Ume liqueur would be below the legal limit if made using Ume fruits within the legal limit, thereby confirming the safety of Ume liqueur. Copyright © 2016 The Institute of Brewing & Distilling     

Determination of Activation Energies and Electric Dipole Moment of In‐Plane Highly Electrically Conductive Hetero‐C12TCNQ/C20 LB Films Using Thermally Stimulated Current

The activation energies of in‐plane highly electrically conductive 2‐dodecyl‐7,7,8,8‐tetracyanoquinodimethane (C₁₂ TCNQ)/arachidic acid (C₂₀) hetero‐LB films and C₁₂TCNQ homo‐LB films were determined by thermally stimulated current (TSC) measurement. The TSC curves for the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode were nearly of the same shape as those for the upper Al electrode/C₁₂TCNQ/lower Al electrode. The activation energies of the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode and upper Al electrode/C₁₂TCNQ/lower Al electrode were 0.9–1.3 eV at 55–80^°C and 1.6–1.8 eV at 105–120^°C, respectively. The TSC curves for the upper Al electrode/C₁₂TCNQ/C₂₀/lower Al electrode and upper Al electrode/C₁₂TCNQ/lower Al electrode had two peaks at 55–80^°C owing to the depolarization of the electric dipole and two peaks at 105–120^°C owing to the movement of space charges in the C₁₂TCNQ molecule. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Application of ion attachment mass spectrometry to evolved gas analysis for in situ monitoring of porous ceramic processing

Ion attachment mass spectrometry was applied to evolved gas analysis-mass spectrometry (EGA-MS), generally known as thermogravimetry-mass spectrometry. Characteristic species arising from poly(vinyl alcohol) (PVA) and poly(methyl methacrylate) (PMMA) resin, used as a binder and a porogen, respectively, in the starting materials for porous ceramics, were detected in the mass spectra. The EGA curves of the characteristic mass peaks from PVA and PMMA, when plotted against the programmed temperature, successfully showed the individual pyrolysis behavior of each polymer during the firing process.