Passive Behavior of Ultra-Fine-Grained 1050 Aluminum Alloy Produced by Accumulative Roll Bonding in a Borate Buffer Solution

In this study, the effect of the ARB process on the passive behavior of ultra-fine-grained 1050 aluminum alloy in a borate buffer solution(p H 6.0) has been investigated. The result of the microhardness tests revealed that the microhardness values increase with an increasing number of ARB cycles. The potentiodynamic polarization plots revealed that the higher number of cycles for the specimens proceeds with the ARB process rather than annealing yield to lower corrosion and passive current densities and more noble corrosion potential values. Moreover, electrochemical impedance spectroscopy measurements showed that increasing the number of ARB cycles offers better conditions for forming the passive films.     

Carbon nanotubes growth on sub-surface catalyst layer of Cu–Ni nanoparticles thin film

Cu–Ni nanoparticles (NPs) thin films were prepared by Direct Current (DC) magnetron sputtering with Cu and Ni targets. The products were used as catalysts for Thermal CVD (TCVD) growing of carbon nanotubes (CNTs) from acetylene gas at 825°C. In order to characterize the nano catalysts, X-ray Diffraction (XRD) and Atomic Force Microscopy (AFM) and to study the synthesized CNTs Scanning Electron Microscopy (SEM) and Raman Spectroscopy were applied. A remarkable CNT grown on the sub-surface of catalyst layer compared to its top is deduced from SEM images. Despite the poor catalytic activity of the top-surface, these considerations led us to conclude more catalytic activity of the sub-surface.     

Hydrodynamics characterization of the Maxblend impeller

The hydrodynamic characteristics of the Maxblend^TM impeller have been investigated in the case of viscous Newtonian fluids. Both laboratory experiments and 3D finite element based computational fluid dynamics (CFD) simulations have been carried out. The power consumption, the mixing evolution yielding the mixing time, and the effect of baffles in the laminar and transition flow regimes have been determined. It was found that the limit Reynolds number between the laminar and transition regimes is approximately 25 and 38 for the unbaffled and baffled configurations, respectively. Based on the range of Reynolds numbers studied in this work, the best window performance of the Maxblend^TM mixer where fast and homogenous mixing is achieved is the end of the laminar regime and the early transition regime with baffles.     

Study of a novel and simple method of generating binary mask for microprism fabrication

A new and simple method for generating binary masks for fabrication of gray scale micro-optical elements is proposed and examined. In this technique the main idea is superimposing two or more gratings with slightly different pitches that depend on the considered gray tone level. This causes generation of a chirped binary mask in which the openings widths are changed from a maximum to minimum through considered steps. Furthermore, to show its capability, it was applied to fabricate some microprisms. In addition, influence of proximity gap, and designation parameters on the surface quality were studied. It is shown that surface deterioration is effectively modified by optimizing the designation parameters. In comparison to other techniques, one of the advantages of this method is to have an assortment of pulse modulated masks that are able to create a variety of gray tone levels. Other advantages are ease in designation and implementation, and the fact that surface roughness could be smoothed effectively by aptly optimized parameters. Theoretical approach, simulation works, and experimental results are presented.     

Periodically focused modes in chains of dielectric spheres

We show that, theoretically, Brewster angle conditions for transverse magnetic polarized rays can be periodically reproduced in chains of spheres with index n?=?[Formula: see text] giving rise to lossless periodically focused modes with 2D period, where D is the sphere diameter. Using ray tracing for a spherical emitter with the diameter D we show that chains of spheres work as filters of such modes at 1.72?相似文献   

Shake table response and analysis of a concrete-filled FRP tube bridge column

The seismic performance of a concrete filled fiber reinforced polymer (FRP) tube (CFFT) bridge column was studied through shake table testing and nonlinear dynamic analyses of a one-fifth scale two-column bridge pier that also incorporated a conventional RC column. The FRP tube in the CFFT column was a prefabricated composite pipe with glass fibers aligned in ±55° with respect to the tube axis to provide both hoop and longitudinal strengths. The columns had nearly the same flexural capacities. The accumulated dissipated hysteresis energy of the CFFT column normalized by steel ratio was 1.6 times larger than that of the RC column; yet, it remained visibly damage free up to a drift ratio of 7%. The CFFT column failed due to FRP tube rupture under 8.4% drift ratio. The equivalent plastic hinge length of CFFT column was found to be more than twice that of the RC column, which implies larger spread of plasticity and smaller local ductility demands. The nonlinear dynamic modeling of the pier response using OpenSees led to very good agreement with the measured response of the pier under moderate and large-amplitude motions.     

Intrinsically high-Q dynamic AFM imaging in liquid with a significantly extended needle tip

Atomic force microscope (AFM) probe with a long and rigid needle tip was fabricated and studied for high Q factor dynamic (tapping mode) AFM imaging of samples submersed in liquid. The extended needle tip over a regular commercially available tapping-mode AFM cantilever was sufficiently long to keep the AFM cantilever from submersed in liquid, which significantly minimized the hydrodynamic damping involved in dynamic AFM imaging of samples in liquid. Dynamic AFM imaging of samples in liquid at an intrinsic Q factor of over 100 and an operational frequency of over 200?kHz was demonstrated. The method has the potential to be extended to acquire viscoelastic material properties and provide truly gentle imaging of soft biological samples in physiological environments.