The properties of polymers near an interface are altered relative to their bulk value due both to chemical interaction and geometric confinement effects. For the past two decades, the dynamics of polymers in confined geometries (thin polymer film or nanocomposites with high-surface area particles) has been studied in detail, allowing progress to be made toward understanding the origin of the dynamic effects near interfaces. Observations of mechanical property enhancements in polymer nanocomposites have been attributed to similar origins. However, the existing measurement methods of these local mechanical properties have resulted in a variety of conflicting results on the change of mechanical properties of confined polymers. Here, an atomic force microscopy (AFM)-based method is demonstrated that directly measures the mechanical properties of polymers adjacent to a substrate with nanometer resolution. This method allows us to consistently observe the gradient in mechanical properties away from a substrate in various materials systems, and paves the way for a unified understanding of thermodynamic and mechanical response of polymers. This gradient is both longer (up to 170 nm) and of higher magnitude (50% increase) than expected from prior results. Through the use of this technique, we will be better able to understand how to design polymer nanocomposites and polymeric structures at the smallest length scale, which affects the fields of structures, electronics, and healthcare.

Rational design and understanding of the intrinsic mechanism are critical to develop highly active and durable electrocatalysts. In this study, a series of bi-metallic boride catalysts based on Ni and Co were prepared, and their activities were evaluated. The synthesised Co-10Ni-B catalyst exhibited excellent activity for water splitting in a 1 M KOH electrolyte. The overpotential was 330 mV at a current density of 10 mA cm-2, better than previously reported mono-metallic borides and even IrO2. The synergistic effect of Co and Ni was proved by X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy. The facile formation of critical intermediates CoOOH and NiOOH during the catalytic processes and a significant increase in surface area owing to the introduction of a second metal into mono-metallic boride were attributed to the superior catalytic performance of catalysts for the oxygen evolution reaction. A Co-10Ni-B-sp catalyst with a higher surface area than the Co-10Ni-B catalyst was also synthesised to evaluate the effect of a high surface area on the catalytic activity. A lower overpotential of 310 mV at a current density of 10 mA cm-2 was achieved.

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Although microarc oxidation is frequently used in producing wear‐ and corrosion‐resistant coatings on Ti and Ti alloys for biomedical applications, the formation of nonuniform microstructure of the coatings is still unavoidable. To overcome this drawback, this work adopts ultrasonic assistance in the microarc oxidation of Ti–6Al–4V and systematically investigates the influences of ultrasonic treatment with different durations on the coating microstructures and resultant properties. The positive effects of ultrasonic, such as cavitation effect, sound flow effect, and mechanical effect, accelerate the cooling rate of electrolyte and promote the homogeneity of the solute on the sample surface. Therefore, the ultrasonic‐assisted coatings exhibit uniform microstructures with fewer cracks and therefore improve performances. For instance, compared with the counterpart without ultrasonic assistance, the ultrasonic‐assisted coating with 15 min duration demonstrates 25.1% lower mass loss in the tribology test and half corrosion density in Hank's solution. Such results indicate that ultrasonic assistance in microarc oxidation of Ti–6Al–4V can homogenize the microstructures of coatings and enhance their corrosion resistance and wear resistance in human body.

The degradation of perfluorosulfonic acid (PFSA) membranes (e.g., Nafion membranes) in polymer electrolyte membrane fuel cells has caused wide widespread concern. However, their degradation behaviors, which lead to the damage of fuel cells, need to be investigated under alternative accelerating environments by the simulation of fuel‐cell operating conditions. Nafion membranes showed a homogeneous degradation behavior during hydrogen peroxide (H2O2) aging, whereas a nonhomogeneous (or crack‐type) degradation behavior occurs for Nafion membranes aged in an H2O2/Fe2+ system (Fenton's reagent), where plenty of the typical microcracks appeared. Interestingly, in the case of nonhomogeneous degradation, the membrane presented a lower fluoride emission rate than that with the homogeneous degradation; this indicates a possible selective attack model of free radicals to both CF2 and the defect end groups in PFSA membranes. In addition, the effects of the different degradation behaviors on the thermal stability and water uptake of membranes were examined by thermogravimetric analyses. H2 crossover and single‐fuel‐cell tests were carried out to evaluate the influence of the degradation behaviors on the fuel‐cell performance. These showed that the membrane with a nonhomogeneous degradation behavior had a higher hydrogen crossover and was more destructive than that with a homogeneous behavior. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013