Zheng Maosheng

The glass transition temperature and microstructure of polyurethane/epoxy resin interpenetrating polymer networks nanocomposites

Nanocomposites with various contents of organophilic montmorillonite (oMMT) have been prepared by adding oMMT to interpenetrating polymer networks (IPNs) of polyurethane and epoxy resin (PU/EP) which had been prepared by a sequential polymeric technique. DSC experiment indicates a novel phenomenon that the glass transition temperature (Tg) of the nanocomposites increases with the oMMT content up to 3 %, then decreases with further increasing oMMT content. In order to explain this phenomenon, crosslink density, hydrogen bonding in the hard segments, crystallization of the nanocomposites and the exfoliation degree of oMMT in the nanocomposites have been investigated by swelling method, FT-IR, XRD, SEM and TEM, respectively. The results indicate that the crosslink density and the hydrogen bonding index of the nanocomposites increase, but the crystallization degree of the nanocomposites decreases with increasing oMMT content. In addition, oMMT improves the network structure of PU/EP.

Influence of Combination of Casimir Force and Residual Stress on the Behaviour of Micro- and Nano-Electromechanical Systems

Casimir force and residual stresses actually appear in over-layers or films simultaneously. The study of the behaviour of micro- and nano-electromechanical systems in the presence of Casimir force and residual stress is of significance to the design of the relevant devices. We derive analytical expressions of the deflection of a bridge-shaped device under the mutual actions of Casimir force and residual stress in films. It is shown that the tensile residual stress enhances wavy behaviour of the deflection, while the compressive residual stress increases the deflection value and reduces the wavy behaviour.

Order-Disorder Transition of Ternary Ordered Alloy

Percolation transition model proposed previously for binary alloy is developed to study order-disorder transition of ternary ordered alloy. With the help of quasichemical approach of alloy thermodynamics, new expression for predicting order-disorder transition temperature of ternary ordered alloy is put forward. Good agreement of predictions and tests in available literature obtained.