Tensile and Surface Mechanical Properties of Polyethersulphone (PES) and Polyvinylidene Fluoride (PVDF) Membranes

Mechanical properties of polymer membranes (strength, hardness and elasticity) are very important parameters for the application performance, e.g. water purification. We study the tensile and surface mechanical properties of hollow fiber and flat sheets mat membranes based on PES and PVDF polymers. Tensile test, nanoindentation and atom force microscopy are used for characterization at macro and nanoscale. Mechanical properties are correlated with pore structure of membranes. The reinforced PVDF HF hollow fiber membranes show 30-fold higher stiffness and 3-fold higher hardness compared to non-reinforced PES HF. Surface mechanical properties of flat sheet membranes are strongly improved by decreasing the pore size. The smoothest surface with 100–200 nm roughness has the best surface mechanical performance obtained by nanoindentation.

Fabrication of Highly Ordered Two-Dimensional Graphene Arrays on Patterned Substrate

We report a facial and straightforward method to fabricate highly ordered two-dimensional graphene arrays. A monolayer molecule pattern with alternative hydrophilic/hydrophobic wetting property was first formed by using micro-contact printing (μCP) and self-assembly techniques. Water droplets were condensed on the hydrophilic areas under saturated water atmosphere, which could be used to construct the ordered graphene arrays. The optical microscopy and atom force microscopy results indicate that ring and porous arrays of graphene can be obtained with low and high concentration of graphene solutions, respectively. Without the water droplet template, graphene patterns with square structure were produced.

The Study on Surface Morphology and Residual Stress of Al2O3 Film

The aluminum oxide (Al2O3) films are grown on n-type Si-(100) substrate by electron beam evaporation at substrate temperature 500°C~800°C. The Al2O3film surface morphology is characterized by atom force microscopy (AFM) to evaluate the grain microstructure, and the residual stress was investigated by wafer stress analyzer. The results show that different substrate temperature is important condition to the properties of Al2O3film. Microstructure characterization indicates that the film surface at low substrate temperature is smoother, and the surface roughness of these Al2O3films is in the range 1-6 nm. The residual stress increases with increasing the substrate temperature, while the stress decreases after annealing in N2condition. It also can be concluded that the microstructure is correlated with residual stress.