Structure,properties and corrosion resistivity of polymeric nanocomposite coatings based on layered silicates

This paper reviews the recent research and development of polymeric nanocomposite coatings based on layered silicates. In the past few decades, extensive research activities have been conducted on clay minerals due to their unique layered structure, rich intercalation chemistry and availability at low cost, environmental stability, and good processability. One of the most important categories of layered silicates is nanoclays. The nanoclay is considered as reinforcement for polymers in the manufacture of low-cost, lightweight and high performance nanocomposite coatings. In this paper, we try to introduce the structure, properties, and surface modification of clay minerals. Different properties of polymer clay nanocomposite coatings consisting of different polymers are also reviewed. These coatings may consist of conductive and nonconductive polymers. The corrosion resistance of each type is discussed separately. Some novel properties can be observed from the interaction of two dissimilar chemical components at the molecular level that posses enhancements in corrosion inhibition on metallic substrates. Finally, the prospective problems of industrial usage of these materials are mentioned.     

High‐performance doubly fed induction machine drive system using predictive direct torque control drive system fed by indirect matrix converters

This paper presents a novel predictive direct torque control for doubly fed induction machine based on indirect matrix converter (IMC), which is characterized by its simple structure, minimal‐torque ripple, and constant switching frequency. Nowadays, the control strategies based on predictive methods have proved their efficiency to improve drive systems capabilities. So, in this paper, one of the best predictive methods that have recently been suggested for doubly fed induction machine drive systems is applied to IMC. The purpose of this combination is to modify the control parameters and size/volume reduction of drive system structure, which is difficult to achieve in conventional systems based on voltage source inverters. The good tracking behavior with reduced torque and flux ripple for both motoring and generating modes as well as removing bulky electrolytic capacitor from the DC link of a converter resulted by using three vectors, two active vectors together with one zero vector per switching period, and applying these vectors to the inverter stage of IMC. To improve the motor drive system performance and reduce losses caused by snubber circuits, the rectifier four‐step commutation method in rectifier bridge is used. In the inverter stage, the predictive direct torque control method is employed. The simulation results of the proposed model confirm its effectiveness and accuracy. Copyright © 2013 John Wiley & Sons, Ltd.     

Chirality dependence of carbon single-walled nanotube material properties: axial Young's modulus

The potential use of individual carbon nanotubes as nano devices warrants detailed investigation of their mechanical behavior based on structural and geometrical configurations. The objective of this paper is to unravel the structural and chirality dependence of the axial Young's modulus of a carbon single-walled nanotube by analytical and numerical approaches. In this work, we employ the general homogenization composite shell model developed based on the asymptotic homogenization technique for analytical modeling of single-walled nanotubes. We derive the working formulae for the effective elastic properties of carbon single-walled nanotube of any chirality and predict the structural and chiral dependence of the effective axial Young's modulus of the nanotube. Also, a finite element analysis on the chirality dependence of the axial Young's modulus of the carbon nanotube is reported. The outcomes of our analyses are compared with available experimental and simulation results.