Properties of networks obtained by internal plasticization of epoxy resin with aromatic and aliphatic glycidyl compounds

In order to improve the fracture properties of p, p′-diaminodiphenylmethane-cured epoxy resin, various kinds of aromatic and aliphatic glycidyl compounds were investigated as a modifier at an amount of 30 wt %. Several compounds promoted the fracture toughness. In any glycidyl compounds, however, heat resistance was decreased by the modification. The dynamic mechanical properties of the modified epoxy resins were measured. The crosslinking density ρ was calculated from the theory of rubber elasticity, and the mechanical properties of the resins were discussed in regard to the crosslinking density. Tensile strength was scarcely affected by the crosslinking density. Elongation at break and Izod impact strength increased remarkably with decrease in crosslinking density. The fracture toughness K_Ic- increased with decrease in crosslinking density except at small ρ.     

Mid-infrared spectroscopic measurement of ionic dissociative materials in the metabolic pathway

We determine the pH dependency of the mid-infrared spectra in aqueous solution of the organic dissociative materials in the metabolic pathway: saccharide phosphates (G6P, F6P), adenosine, and its phosphates (ATP, ADP, AMP). The series of molar absorbance spectra for these reagents were obtained in a pH range of about 2 to 11 with a Fourier transform infrared (FT-IR) spectrometer equipped with a horizontal diamond attenuated total reflection (ATR) sampling accessory. We also provide a method of infrared spectral extraction of ionic dissociative materials by performing a linear least-square fitting utilizing the formulas of ionic dissociation equilibrium shift, and we obtain the infrared spectrum of each ionic species of the dissociative materials: G6P-, G6P2-; F6P-, F6P2-; ATP2-, ATP3-, ATP4-; ADP-, ADP2-, ADP3-; AMP, AMP-, AMP2-; and adenosine+, adenosine0. The infrared spectral structure of each ionic species of the dissociative materials in the metabolic pathway are discussed. Additionally, the possibility for a quantification system of the concentrations of the organic dissociative materials in varying pH is suggested.     

Corrosion of aluminium alloy A6061-T6 members embedded in alkaline materials

Owing to the corrosive conditions in coastal areas, aluminium alloy railings and similar structures are normally used on infrastructure works such as bridges and roads located in such areas because aluminium alloys are inherently corrosion resistant. However, to achieve rigid support, aluminium alloy members are often embedded in concrete. Consequently, the embedded parts undergo corrosion caused by the alkaline content of the cement used in the concrete. This research was carried out to study the corrosion behaviour on both the embedded and unembedded sides of aluminium alloy A6061-T6 members embedded in the concrete and also to investigate the ability of a combined coating of anodic oxide and organic film to inhibit corrosion. Additionally, the influence of scratch damage on the performance of this coating material was evaluated.     

Effect of weld line direction and paint orientation on corrosion and paint deterioration characteristics of welded part of steel

One thousand two hundred cycles of accelerated exposure experiment with combined salt water spray simulating atmospheric corrosion was performed for investigating the effect of weld line direction and paint orientation on the corrosion and paint deterioration characteristics of welded part of the steel. The corrosion depth of the weld toe of transverse weld line became 1.35 times as large as that of the base metal part because of the remained salt water on the weld toe. The coating thickness at the weld toe became thin by vertically painting on the transverse weld line. When the scribe line was installed at the thin painted weld toe under the transverse weld line, the paint blister area became 15% larger than that of the base metal part. The paint coating thickness at the weld toe in different weld line directions and paint orientations should be confirmed and ensured from the viewpoints of manufacturing and maintaining steel structures.     

Identification of factor determining strength under compressive loads of steel members corrected by heating/pressing

By using cruciform columns, factors dominating behavior under compressive loads of steel structural members, whose locally buckled part was corrected by heating/pressing, have been elucidated. They were geometric residual imperfection resulted from incomplete correction and increase of yield stress due to large plastic deformation caused by local buckling and its correction process. For soundness diagnosis of the corrected member, the importance of these factors was investigated based on the results of the numerical simulation. Although the increase of yield stress did not affect the ultimate strength, that changed the deformation mode of the member after the ultimate situation. As the result, it was elucidated that the increase of yield stress was not important in the soundness diagnosis. The residual imperfection affected the buckling and ultimate strength of the corrected member. Rather the size of the region than the absolute value in the out-of-plane direction of the residual imperfection should be controlled as small as possible for ensuring the soundness of the corrected member.     

Computer simulation study on the shear-induced phase separation in semidilute polymer solutions in 3-dimensional space

We investigated the shear-induced phase separation and/or concentration fluctuation phenomena in semidilute polymer solution by using computer simulation in 3-dimensional space with Doi-Onuki theory. The enhancement of the concentration fluctuations occurs under shear flow and the scattering function in q_x-q_z plane exhibits the so-called butterfly pattern as observed experimentally, where q_x and q_z are the components of the scattering vector for flow direction and neutral direction, respectively. The time changes in the peak position and the intensity at peak position in the scattering function in q_x-q_z plane can be divided into two regions: the peak position becomes smaller and the peak intensity increases with t, and then the peak position and intensity become constant and the system reaches its steady state. These agree with the experimental results qualitatively. However, the computer simulation results indicate that the peak position at the steady state is almost independent of the shear rate, while the decrease in the peak position at steady state with shear rate has been observed experimentally. This disagreement originates from the use of the simplest constitutive equation in the computer simulation.     

Manipulating spin current in the magnetic nanopillar

Because of the capability to switch the magnetization of a nanoscale magnet, the spin transfer effect is critical for the application of magnetic random access memory. For this purpose, it is important to enhance the spin current carried by the charge current. Calculations based on the diffusive spin-dependent transport equations reveal that the magnitude of spin current can be tuned by modifying the ferromagnetic layer and the spin relaxation process in the device. Increasing the ferromagnetic layer thickness is found to enhance both the spin current and the spin accumulation. On the other hand, a strong spin relaxation in the capping layer also increases the spin current but suppresses the spin accumulation. To demonstrate the theoretical results, nanopillar structures with the size of approximately 100 nm are fabricated and the current-induced magnetization switching behaviors are experimentally studied. When the ferromagnetic layer thickness is increased from 3 nm to 20 nm, the critical switching current for the current-induced magnetization switching is significantly reduced, indicating the enhancement of the spin current. When the Au capping layer with a short spin-diffusion length replaces the Cu capping layer with a long spin-diffusion length, the reduction of the critical switching current is also observed.