Effect of orientation of two-dimensional filler on dynamic mechanical properties of cured epoxy resin

Dynamic mechanical properties of cured epoxy resin filled with mica flake, as two-dimensional filler, were investigated over the temperature range from room temperature to 200°C. Two series of composite specimens were examined. One is series RM, containing ill-oriented mica flakes, and another is RMB, containing mica flakes oriented in the direction parallel to the specimen surface. Both tensile and shear moduli for RMB series were determined by dynamic mechanical experiments. The tensile modulus for RMB series was always higher than that for RM series over the whole temperature range. The shear modulus for RMB series was low, compared with that of the tensile modulus in the rubbery state. The behavior of the modulus reinforcement, observed both in the glassy and rubbery states, was compared with recently proposed theories of Wu and Padawer and Beecher. In the glassy state, the tensile modulus of RM series follows Wu's theory, while that of the RMB series agrees with Padawer and Beecher's theory. In the rubbery state, the tensile modulus of each series cannot be well explained by either theory. It was proposed that the tensile stress applied to the specimen was converted to shear stress in a thin resinous layer sandwiched by two mica flakes. The modulus behavior of the RMB series can be fully explained by this model.     

Development of a radon trap device using a corona discharge

Radon is one of the noble gases, which are chemically inert and do not make any reactants under normal conditions. In this experiment we demonstrated an enigmatic reaction between radon and fluorine when a corona discharge is used as a promoter. Distinctive changes in radon concentrations were caused by the discharge and a trap efficiency of >99.5% was estimated. The mass balance between the trapped and the released radon was found to be reasonable. This indicates the existence of chemical reactions with radon. This trap phenomenon has application as a technique for reducing radon concentration in radon-contaminated air. It is possible that this technique will be applicable to other noble gases.     

Wave-optical evaluation of interference fringes and wavefront phase in a hard-x-ray beam totally reflected by mirror optics

The intensity flatness and wavefront shape in a coherent hard-x-ray beam totally reflected by flat mirrors that have surface bumps modeled by Gaussian functions were investigated by use of a wave-optical simulation code. Simulated results revealed the necessity for peak-to-valley height accuracy of better than 1 nm at a lateral resolution near 0.1 mm to remove high-contrast interference fringes and appreciable wavefront phase errors. Three mirrors that had different surface qualities were tested at the 1 km-long beam line at the SPring-8/Japan Synchrotron Radiation Research Institute. Interference fringes faded when the surface figure was corrected below the subnanometer level to a spatial resolution close to 0.1 mm, as indicated by the simulated results.     

An explanation of the wetting and the mutual diffusion mechanisms of liquid metals using ab-initio atomic orbital calculation

In this report, in order to clarify fundamentally the wetting phenomenon between pure material surfaces, we propose a new method for the experimental evaluation and consider quantitatively the wetting mechanism from the microscopic standpoint of the chemical reaction between interfacial atoms. Ab-initio molecular orbital calculation was performed to explain the wetting and the mutual diffusion mechanisms. It was found that the calculated binding energies were in good agreement with the interaction energies estimated from measured contact angles, and it was also cleared that the hybridization of the interfacial d-orbitals was one of the most important elements of the mutual diffusion.     

水/水乳液的形成、稳定及功能特性研究进展

水/水乳液是一种新型胶体分散体系，目前已成为胶体与界面科学领域的研究热点。本文综述水/水乳液的形成机制、影响因素和特性，归纳总结典型天然高分子的水/水乳液体系；介绍利用颗粒、嵌段聚合物、聚电解质等3种物质稳定水/水乳液的方法，其中，重点介绍颗粒稳定水/水乳液的机理和影响因素，以及水/水乳液在活性物质荷载和淀粉消化中的应用。指出水/水乳液的未来发展方向，特别是应开发更多的食品级水/水乳液体系，以拓展在食品中的应用范围。     

Swallowing profiles of food polysaccharide gels in relation to bolus rheology

Swallowing profiles of food polysaccharide gels were investigated in relation to bolus rheology. Polysaccharide gel from either gellan gum or a mixture of gellan gum and psyllium seed gum was used as a model food. Acoustic analysis and sensory evaluation were carried out to investigate the swallowing profiles using the same human subjects. Model bolus was prepared through instrumental mastication using a mechanical simulator to mimic the action of the human jaw in the presence or absence of artificial saliva and was subjected to dynamic viscoelasticity measurements to investigate the rheological properties. Bolus from the binary gel was shorter in time required to transfer through the pharyngeal phase due to mass flow and was scored higher in sensory perceived cohesiveness (bolus forming) than that from gellan gum gel. Model bolus from the binary gel showed a rheologically weak gel (or structured fluid) behavior and was higher in structural homogeneity than that from gellan gum gel. Also, dynamic viscoelasticity parameters of the binary gel were less dependent on the addition level of saliva. Results indicate that the viscoelasticity balance is a key for texture design of dysphagia foods in relation to the saliva miscibility.     

Quantitative evaluation of initial galvanic corrosion behavior of CNTs reinforced Mg–Al alloy

The macroscopic corrosion phenomenon of the CNTs reinforced Mg composites remarkably occurred in the moist environment, due to a large potential of the galvanic cells formed between α-Mg matrix and CNTs. Therefore, it is necessary to reduce the potential difference at their interfaces in order to obstruct the galvanic corrosion phenomenon. In this study, AZ61B alloy composites reinforced with CNTs (CNT/AZ61B) were fabricated by powder metallurgy method, and their potential differences between CNTs and the α-Mg matrix were reduced by concentration of Al atoms around CNTs via heat treatment. The potential distribution around CNTs was measured by using scanning Kelvin probe force microscopy (SKPFM). Heat treatment of CNT/AZ61B composites at 823 K for 10 h caused the obvious concentration of Al atoms around CNTs, and resulted in the remarkable decrease of the potential difference at the interface between the α-Mg matrix and CNTs. Additionally, the salt water immersion test results indicated that the corrosion rate of CNTs/AZ61B composite materials after heat treatment was obviously reduced to less than about 30% of the non-treated composite material. Thus, the changes of α-Mg matrix potential by concentrating Al atoms around CNTs was effective to improve initial galvanic corrosion resistance of CNTs reinforced Mg composites.