Fabrication of vertically aligned Pd nanowire array in AAO template by electrodeposition using neutral electrolyte

A vertically aligned Pd nanowire array was successfully fabricated on an Au/Ti substrate using an anodic aluminum oxide (AAO) template by a direct voltage electrodeposition method at room temperature using diluted neutral electrolyte. The fabrication of Pd nanowires was controlled by analyzing the current–time transient during electrodeposition using potentiostat. The AAO template and the Pd nanowires were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) methods and X-Ray diffraction (XRD). It was observed that the Pd nanowire array was standing freely on an Au-coated Ti substrate after removing the AAO template in a relatively large area of about 5 cm², approximately 50 nm in diameter and 2.5 μm in length with a high aspect ratio. The nucleation rate and the number of atoms in the critical nucleus were determined from the analysis of current transients. Pd nuclei density was calculated as 3.55 × 10⁸ cm⁻². Usage of diluted neutral electrolyte enables slower growing of Pd nanowires owing to increase in the electrodeposition potential and thus obtained Pd nanowires have higher crystallinity with lower dislocations. In fact, this high crystallinity of Pd nanowires provides them positive effect for sensor performances especially.     

Fabrication of Pd-Fe nanowires with a high aspect ratio by AAO template-assisted electrodeposition

In this study, vertically oriented Pd_0.86Fe_0.14 nanowires have been fabricated using an anodized aluminum oxide (AAO) template by direct voltage electrodeposition at room temperature. AAO template-assisted electrodeposition of Pd-Fe was carried out in Pd(NH₃)₂Cl₂:FeSO₄·7H₂O solution. The AAO template and the Pd_0.86Fe_0.14 nanowires were characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) methods and X-ray diffraction (XRD). It was observed that the Pd_0.86Fe_0.14 nanowires were approximately 65 nm in diameter and 10 μm in length with an aspect ratio of 153 in a relatively large area of about 4 cm². The nucleation rate and the number of atoms in the critical nucleus are determined from the analysis of current transients.     

Hydrogen sensing properties of ZnO nanorods: Effects of annealing,temperature and electrode structure

In this study, the hydrogen (H₂) sensing properties of vertically aligned zinc oxide (ZnO) nanorods were investigated depending on annealing, Pd coating, temperature and electrode structure. ZnO nanorods were fabricated by using hydrothermal method on a glass substrate and an indium tin oxide (ITO) coated glass substrate. In order to determine the effects of annealing on the H₂ sensor performance, the nanorods were heated at 500 °C in dry air. H₂ sensing measurements were done in the temperature range of 25–200 °C. It was found that, the sensor response of Pd coated ZnO nanorods were much higher than the un-coated nanorods due to the catalytic effect of Pd thin film. Moreover, the un-annealed samples showed better sensor response than the annealed samples due to the number of oxygen deficiency. In addition, the lateral electrode structure showed higher sensor response than the sandwich electrode structure.     

Simulation of the effect of elastic precipitates in SMA materials based on a micromechanical model

This paper deals with the modeling of Shape Memory Alloys (SMA) with embedded precipitates, and describes the effect of these precipitates on the phase transformation properties. It is based on a micromechanical constitutive model and uses a double scale transition technique. The first scale transition considers elastic inclusions embedded in an SMA matrix. It uses the Mori–Tanaka homogenization technique to determine the equivalent behavior of an SMA single crystal. The second scale transition leads to the effective behavior of an SMA polycrystalline aggregate. It is based on the behavior of each grain and uses a self-consistent homogenization technique. The constitutive non-linear equations of this model are then numerically solved. The results obtained under different loadings are detailed and discussed at the grain and at the sample (macroscopic) scales. Finally the effect of the volume fraction of precipitates on the transformation properties are discussed.     

Determination of thermo-electrical properties in Sn based alloys

The variation of thermal conductivity of solid phase versus temperature for Sn-21 wt.% Bi, Sn-25 wt.% In and Sn-35 wt.% In-26 wt.% Bi alloys were measured with a radial heat flow apparatus. From the graphs of thermal conductivity versus temperature, the thermal conductivity of the solid phases at their melting temperatures and the thermal temperature coefficients for the same alloys were obtained. The ratios of thermal conductivity of liquid phase to solid phase for the same materials were measured with a Bridgman type directional solidification apparatus. The variations of electrical conductivity of solid phases versus temperature for the same alloys were determined from the Wiedemann-Franz law by using the measured values of thermal conductivity. From the graphs of electrical conductivity versus temperature, the electrical temperature coefficients for the same alloys were also determined. According to present experimental results it can be concluded that the thermal and electrical conductivity of Sn based alloys depend on the thermal and electrical conductivity of the alloying elements. If the thermal and electrical conductivity of the alloying elements are lower than the thermal conductivity of Sn, the thermal conductivity of Sn based alloys decreases, whereas, otherwise, it increases.     

An experimental study on the heat recovery from the exhaust air of stenters with a packed bed column

Stenters are the dryers that are commonly used in textile finishing mills. The exhaust air of the stenters is of great potential of energy saving via heat recovery mainly using the latent heat of condensation of the water vapour involved. This study reveals the usage possibility of a packed bed column for the heat recovery from the exhaust air of the stenter. An experimental investigation was carried out with a laboratory‐scale counter flow packed bed column. Additionally, an exergetic evaluation of the system was performed. Water inlet temperature and relative humidity ratio of the exhaust air are the main factors that affect the water outlet temperatures and efficiency of the system. It was observed that a decrease in the water inlet temperature increases the recovered exergy; however, water outlet temperature is not significantly affected by the inlet temperature of the water. The exergy efficiency of the system increases with the increase in the relative humidity ratio of the exhaust air. Copyright © 2007 John Wiley & Sons, Ltd.     

Robust Adaptive Control for Mobile Manipulators

This paper addresses the trajectory tracking control of a nonholonomic wheeled mobile manipulator with parameter uncertainties and disturbances. The proposed algorithm adopts a robust adaptive control strategy where parametric uncertainties are compensated by adaptive update techniques and the disturbances are suppressed. A kinematic controller is first designed to make the robot follow a desired end-effector and platform trajectories in task space coordinates simultaneously. Then, an adaptive control scheme is proposed, which ensures that the trajectories are accurately tracked even in the presence of external disturbances and uncertainties. The system stability and thc convergence of tracking errors to zero are rigorously proven using Lyapunov theory. Simulations results are given to illustrate the effectiveness of the proposed robust adaptive control law in comparison with a sliding mode controller.