Ni-TiO2 nanocomposite coating with high resistance to corrosion and wear

Ni-TiO₂ nanocomposite coatings with various contents of TiO₂ nanoparticles were prepared by electrodeposition in a Ni plating bath containing TiO₂ nanoparticles to be codeposited. The influences of the TiO₂ nanoparticle concentration in the plating bath, the current density and the stirring rate on the composition of nanocomposite coatings were investigated. The composition of coatings was studied by using energy dispersive X-ray system (EDX). The wear behavior of the pure Ni and Ni-TiO₂ nanocomposite coatings were evaluated by a pin-on-disc tribometer. The corrosion performance of coatings in 0.5 M NaCl, 1 M NaOH and 1 M HNO₃ as corrosive solutions was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy methods (EIS). The microhardness and wear resistance of the nanocomposite coatings increase with increasing of TiO₂ nanoparticle content in the coating. With increasing of TiO₂ nanoparticle content in the coating, the polarization resistance increases, the corrosion current decreases and the corrosion potential shifts to more positive values.     

Dung pads increase pasture production,soil nutrients and microbial biomass carbon in grazed dairy systems

In grazing systems dung is an important source of nutrients which can increase soil fertility and contribute to nutrient cycling through increased pasture production. Changes in soil chemical and biological properties and pasture production were measured below and around dung pads created in the field. Almost 65% of the total dung P remained after 45 days and about two-thirds of the pad fresh weight had disappeared in that time, indicating that physical degradation is the mechanism of incorporation of dung P. All the pads bar one were completely degraded by 112 days. At this time, soil pH and EC increased under dung pads as did Olsen extractable inorganic phosphorus (Pi) and total phosphorus (Pt), with these changes observed at 0–5 and 5–10 cm depths. Bicarbonate extractable soil organic phosphorus (Po) was not affected by dung and the observed differences in soil Po:Pi ratios were largely influenced by the substantial addition of inorganic P from dung. Dung increased the P buffering capacity of the 0–5 cm soil samples collected at the end of the experiment, potentially contributing to the increased extractable soil P measured under the pads. Dung also changed soil properties in 0–10 cm samples with increases in soil pH, EC, Colwell P and Colwell K recorded even long after the dung had completely disappeared. Microbial biomass carbon increased under dung pads in the 0–10 cm soil samples in the first 45 days after pads were applied. Total herbage production and ryegrass biomass increased significantly under and around the pads by 112 days after dung was applied. The botanical composition changed significantly with increased ryegrass contents observed, but only under the dung pads. This experiment demonstrated that increases in pasture around dung pads in the field are not solely due to animal rejection.     

A time‐dependent multiphysics,multiphase modeling framework for carbon nanotube synthesis using chemical vapor deposition

A time‐dependent multiphysics, multiphase model is proposed and fully developed here to describe carbon nanotubes (CNTs) fabrication using chemical vapor deposition (CVD). The fully integrated model accounts for chemical reaction as well as fluid, heat, and mass transport phenomena. The feed components for the CVD process are methane (CH₄), as the primary carbon source, and hydrogen (H₂). Numerous simulations are performed for a wide range of fabrication temperatures (973.15–1273.15 K) as well as different CH₄ (500–1000 sccm) and H₂ (250–750 sccm) flow rates. The effect of temperature, total flow rate, and feed mixture ratio on CNTs growth rate as well as the effect of amorphous carbon formation on the final product are calculated and compared with experimental results. The outcomes from this study provide a fundamental understanding and basis for the design of an efficient CNT fabrication process that is capable of producing a high yield of CNTs, with a minimum amount of amorphous carbon. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

An innovative approach to electro-oxidation of dopamine on titanium dioxide nanotubes electrode modified by gold particles

Au/TiO₂/Ti electrodes were prepared by galvanic deposition of gold particles from an acidic bath containing KAu(CN)₂ in the presence of a citrate buffer onto TiO₂ nanotubes layer on titanium substrates. Titanium oxide nanotubes were fabricated by anodizing titanium foil in a DMSO fluoride-containing electrolyte. The morphology and surface characteristics of Au/TiO₂/Ti electrodes were investigated using scanning electron microscopy and energy-dispersive X-ray, respectively. The results indicated that gold particles were homogeneously deposited on the surface of TiO₂ nanotubes. The nanotubular TiO₂ layers consist of individual tubes of about 40–80 nm diameters. The electro-catalytic behavior of Au/TiO₂/Ti electrodes for the dopamine electro-oxidation was studied by cyclic voltammetry and differential pulse voltammetry. The results showed that Au/TiO₂/Ti electrodes exhibit a considerably higher electro-catalytic activity toward the oxidation of dopamine. The catalytic oxidation peak current showed a linear dependence on dopamine concentration and a linear calibration curve was obtained in the concentration range of 0.5–2.5 mM of dopamine.     

Evaluation of the localized corrosion on Mg electrode surface by electrochemical noise technique

The symmetrical and asymmetrical electrodes made of Mg were studied in 0.1-M NaCl electrolyte adjusted at pH 12. The statistical and wavelet methods were employed for analyzing the electrochemical current noise (ECN) signals. The asymmetric configuration was used for electrochemical detection of filiform corrosion on Mg electrode. The real time scale of the dominant transients of the asymmetric electrodes was detected on the basis of the maximum peak in the SDPS plots. The SDPS values of the real time scale crystals of the ECN signals resulting from asymmetrical electrodes increased with the increase in immersion time due to the onset of filiform corrosion.     

Toughness Enhancement in Roll-Bonded Al6061-15 vol.% SiC Laminates via Controlled Interfacial Delamination

Researchers have examined different approaches to improve damage tolerance of discontinuously reinforced aluminum (DRA). In this study, three-layer DRA laminates containing two exterior layers of Al6061-15 vol.% SiCp and an interlayer of Al1050 were fabricated by hot roll bonding. Interfacial adhesion between the layers was controlled by means of rolling stain. The results of shear test revealed that, the bonding strength of laminates was influenced by number of rolling passes. Considering this effect, the role of interfacial bonding on the toughness of laminates was studied under three-point bending in the crack divider orientation. The quasi-static toughness of the laminates was greater than that of the monolithic DRA. Plastic deformation of the ductile interlayer and interfacial delamination were found as the major sources of energy absorption in this fracture process. It was shown that interfacial adhesion in these laminate does not alter the initiation energy in quasi-static test. Propagation energy under same loading condition, however, illustrated significant sensitivity to the interfacial bonding. The results of the current study reveal that improving the interfacial adhesion by means of rolling strain eliminates the ease of plastic deformation of the ductile interlayer and thus reduces the contribution of this mechanism in quasi-static toughness of the laminate.     

A hybrid computer simulation-adaptive neuro-fuzzy inference system algorithm for optimization of dispatching rule selection in job shop scheduling problems under uncertainty

The International Journal of Advanced Manufacturing Technology - Unstable environment of industrial systems is a source of various uncertainties in production features such as processing times....     

Modeling permeability of 3-D nanofiber media in slip flow regime

Over the last few decades, numerous analytical and/or numerical expressions have been developed for predicting the permeability of a fibrous medium. These expressions, however, are not accurate in predicting the permeability of media made up of nanofibers. This is because the previous expressions were mostly developed for coarse fibers, where using the so-called no-slip velocity boundary condition at the fiber surface is quite justified. Removing the no-slip velocity restriction in this work, we study the effect of slip flow on the permeability of fibrous materials made up of nanofibers. This has been accomplished by generating a large series of 3-D virtual geometries that resemble the microstructure of a nanofiber (e.g., electrospun) material. Stokes flow equations are solved numerically in the void space between the nanofibers, with the slip flow boundary condition developed based on the Maxwell first order model. The influence of fiber diameter and solid volume fraction (SVF) on the media's permeability is studied, and used to establish a correction factor for the existing permeability expressions when used for nanofiber media.