Microstructure and microtexture evolution of aluminum alloy 3003 under ultrasonic welding process for embedding SiC fibre

Ultrasonic welding process can be used for bonding metal foils which is the fundament of ultrasonic consolidation (UC). UC process can be used to embed reinforcement fibres such as SiC fibres within an aluminum matrix materials. In this research we are investigating the phenomena occurring in the microstructure of the parts during ultrasonic welding process to obtain better understanding about how and why the process works. High-resolution electron backscatter diffraction (EBSD) is used to study the effects of the vibration on the evolution of microstructure in AA3003. The inverse pole figures (IPF) and the correlated misorientation angle distribution of the mentioned samples are obtained. The characteristics of the crystallographic orientation, the grain structure and the grain boundary are analyzed to find the effect of ultrasonic vibration on the microstructure and microtexture of the bond. The ultrasonic vibration will lead to exceptional refinement of grains to a micron level along the bond area and affect the crystallographic orientation. Ultrasonic vibration results in a very weak texture. Plastic flow occurs in the grain after welding process and there is additional plastic flow around the fibre which leads to the fibre embedding. © 2009 Editorial Board of CHINA WELDING.

Ionography of Submicron Foils and Nanostructures Using Ion Flow Generated in FS-Laser Cluster Plasma

A novel type of submicron ion radiography designed to image low-contrast objects, including nanofoils, membranes and biological structures, is proposed. It is based on femtosecond-laser-driven-cluster- plasma source of multicharged ions and polymer dosimeter film CR-39. The intense isotropic ion flow was produced by femtosecond Ti:Sa laser pulses with intensity similar to 4x10(17) W/cm(2) absorbed in the supersonic jet of the mixed He and CO2 gases. Two Focusing Spectrometers with Spatial Resolution (FSSR) were used to measure X-ray spectra of H-and He-like multicharged oxygen ions. The spectra testify that ions with energy more than 300 keV were radiated in different directions from the plasma source. High contrast ion radiography images were obtained for 2000 dpi metal mesh, 1 mu m polypropylene and 100 nm Zr foils as well as for the different biological objects. Images were recorded on a 1 mm thick CR-39 detector, placed in contact with back surface of the imaged samples at the distances 140 -160 mm from the ion source. The spatial resolution of the image no worse than 600 nm was provided. A difference in object thickness of 100 nm was very well resolved for both Zr and polymer foils. The ion radiography images recorded at different angles from the source, demonstrated almost uniform spatial distribution of ion with total number of 10(8) per shot. (C) 2009 WILEY-VCH Vertag GmbH & Co. KGaA, Weinheim

Task-specific ionic liquid for solubilizing metal oxides

Protonated betaine bis(trifluoromethylsulfonyl) imide is an ionic liquid with the ability to dissolve large quantities of metal oxides. This metal-solubilizing power is selective. Soluble are oxides of the trivalent rare earths, uranium(VI) oxide, zinc(II) oxide, cadmium( II) oxide, mercury( II) oxide, nickel( II) oxide, copper(II) oxide, palladium(II) oxide, lead(II) oxide, manganese( II) oxide, and silver( I) oxide. Insoluble or very poorly soluble are iron(III), manganese(IV), and cobalt oxides, as well as aluminum oxide and silicon dioxide. The metals can be stripped from the ionic liquid by treatment of the ionic liquid with an acidic aqueous solution. After transfer of the metal ions to the aqueous phase, the ionic liquid can be recycled for reuse. Betainium bis( trifluoromethylsulfonyl) imide forms one phase with water at high temperatures, whereas phase separation occurs below 55.5 degrees C ( temperature switch behavior). The mixtures of the ionic liquid with water also show a pH-dependent phase behavior: two phases occur at low pH, whereas one phase is present under neutral or alkaline conditions. The structures, the energetics, and the charge distribution of the betaine cation and the bis( trifluoromethylsulfonyl) imide anion, as well as the cation-anion pairs, were studied by density functional theory calculations.

Comparison of Experimental PIV Data and CFD Simulations for Flow in a Diesel Particulate Filter Inlet Diffuser

Flow maldistribution of the exhaust gas entering a Diesel Particulate Filter (DPF) can cause uneven soot distribution during loading and excessive temperature gradients during the regeneration phase. Minimising the magnitude of this maldistribution is therefore an important consideration in the design of the inlet pipe and diffuser, particularly in situations where packaging constraints dictate bends in the inlet pipe close to the filter, or a sharp diffuser angle. This paper describes the use of Particle Image Velocimetry (PIV) to validate a Computational Fluid Dynamic (CFD) model of the flow within the inlet diffuser of a DPF so that CFD can be used with confidence as a tool to minimise this flow maldistribution. PIV is used to study the flow of gas into a DPF over a range of steady state flow conditions. The distribution of flow approaching the front face of the substrate was of particular interest to this study. Optically clear diffusing cones were designed and placed between pipe and substrate to allow PIV analysis to take place. Stereoscopic PIV was used to eliminate any error produced by the optical aberrations caused by looking through the curved wall of the inlet cone. In parallel to the experiments, numerical analysis was carried out using a CFD program with an incorporated DPF model. Boundary conditions for the CFD simulations were taken from the experimental data, allowing an experimental validation of the numerical results. The CFD model incorporated a DPF model, the cement layers seen in segmented filters and the intumescent matting that is commonly used to pack the filter into a metal casing. The mesh contained approximately 580,000 cells and used the realizable ?-e turbulence model. The CFD simulation predicted both pressure drop across the DPF and the velocity field within the cone and at the DPF face with reasonable accuracy, providing confidence in the use the CFD in future work to design new, more efficient cones.

Microwave-assisted Cu-catalyzed Ullmann ether synthesis in a continuous-flow milli-plant

The combination of milli-scale processing and microwave heating has been investigated for the Cu-catalyzed Ullmann etherification in fine-chemical synthesis, providing improved catalytic activity and selective catalyst heating. Wall-coated and fixed-bed milli-reactors were designed and applied in the Cu-catalyzed Ullmann-type CO coupling of phenol and 4-chloropyridine. In a batch reactor the results show clearly increased yields for the microwave heated process at low microwave powers, whereas high powers and catalyst loadings reduced the benefits of microwave heating. Slightly higher yields were found in the Cu/ZnO wall-coated as compared to the Cu/TiO fixed-bed flow-reactor. The benefit here is that the reaction occurs at the surface of the metal nanoparticles confined within a support film making the nano-copper equally accessible. Catalyst deactivation was mainly caused by Cu oxidation and coke formation; however, at longer process times leaching played a significant role. Catalyst activity could partially be recovered by removal of deposited by-product by means of calcination. After 6h on-stream the reactor productivities were 28.3 and 55.1kgprod/(mR3h) for the fresh Cu/ZnO wall-coated and Cu/TiO fixed-bed reactor, respectively. Comparison of single- and multimode microwaves showed a threefold yield increase for single-mode microwaves. Control of nanoparticles size and loading allows to avoid high temperatures in a single-mode microwave field and provides a novel solution to a major problem for combining metal catalysis and microwave heating. Catalyst stability appeared to be more important and provided twofold yield increase for the CuZn/TiO catalyst as compared to the Cu/TiO catalyst due to stabilized copper by preferential oxidation of the zinc. For this catalyst a threefold yield increase was observed in single-mode microwaves which, to the best of our knowledge, led to a not yet reported productivity of 172kgprod/(mR3h) for the microwave and flow Ullmann CO coupling. © 2012 Elsevier B.V.

Adsorption of metal ions on nitrogen surface functional groups in activated carbons

A commercially available coconut-shell-derived active carbon was oxidized with nitric acid, and both the original and oxidized active carbons were treated with ammonia at 1073 K to incorporate nitrogen functional groups into the carbon. An active carbon with very high nitrogen content (similar to9.4 wt % daf) was also prepared from a nitrogen-rich precursor, polyacrylonitrile (PAN). These nitrogen-rich carbons had points of zero charge (pH(pzc)) similar to H-type active carbons. X-ray absorption near-edge structure (XANES) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) were used to characterize the nitrogen functional groups in the carbons. The nitrogen functional groups present on the carbon surface were pyridinic, pyrrolic (or indolic), and pyridonic structures. The adsorption of transition metal cations Cd2+, Ni2+, and Cu2+ from aqueous solution on the suite of active carbons showed that adsorption was markedly higher for carbons with nitrogen functional groups present on the surface than for carbons with similar pH(pzc) values. In contrast, the adsorption characteristics of Ca2+ from aqueous solution were similar for all the carbons studied. Flow microcalorimetry (FMC) studies showed that the enthalpies of adsorption of Cd2+(aq) on the active carbons with high nitrogen contents were much higher than for nitric acid oxidized carbons studied previously, which also had enhanced adsorption characteristics for metal ion species. The enthalpies of adsorption of Cu2+ were similar to those obtained for Cd2+ for specific active carbons. The nitrogen functional groups in the carbons act as surface coordination sites for the adsorption of transition metal ions from aqueous solution. The adsorption characteristics of these carbons are compared with those of oxidized carbons.

An in situ spatially resolved analytical technique to simultaneously probe gas phase reactions and temperature within the packed bed of a plug flow reactor

This paper reports the detailed description and validation of a fully automated, computer controlled analytical method to spatially probe the gas composition and thermal characteristics in packed bed systems. As an exemplar, we have examined a heterogeneously catalysed gas phase reaction within the bed of a powdered oxide supported metal catalyst. The design of the gas sampling and the temperature recording systems are disclosed. A stationary capillary with holes drilled in its wall and a moveable reactor coupled with a mass spectrometer are used to enable sampling and analysis. This method has been designed to limit the invasiveness of the probe on the reactor by using the smallest combination of thermocouple and capillary which can be employed practically. An 80 mu m (O.D.) thermocouple has been inserted in a 250 mu m (O.D.) capillary. The thermocouple is aligned with the sampling holes to enable both the gas composition and temperature profiles to be simultaneously measured at equivalent spatially resolved positions. This analysis technique has been validated by studying CO oxidation over a 1% Pt/Al2O3 catalyst and the spatial resolution profiles of chemical species concentrations and temperature as a function of the axial position within the catalyst bed are reported.

Theoretical and FE analysis of ultrasonic welding of aluminum alloy 3003

Ultrasonic welding (consolidation) process is a rapid manufacturing process that is used to join thin layers of metal at low temperature and low energy consumption. Experimental results have shown that ultrasonic welding is a combination of both surface (friction) and volume (plasticity) softening effects. In the presented work, an attempt has been made to simulate the ultrasonic welding of metals by taking into account these effects (surface and volume). A phenomenological material model has been proposed, which incorporates these two effects (i.e., surface and volume). The thermal softening due to friction and ultrasonic (acoustic) softening has been included in the proposed material model. For surface effects, a friction law with variable coefficient of friction that is dependent on contact pressure, slip, temperature, and number of cycles has been derived from experimental friction tests. The results of the thermomechanical analyses of ultrasonic welding of aluminum alloy have been presented. The goal of this work is to study the effects of ultrasonic welding process parameters, such as applied load, amplitude of ultrasonic oscillation, and velocity of welding sonotrode on the friction work at the weld interface. The change in the friction work at the weld interface has been explained on the basis of softening (thermal and acoustic) of the specimen during the ultrasonic welding process. In the end, a comparison between experimental and simulated results has been presented, showing a good agreement. Copyright © 2009 by ASME.

Effects of particle/matrix interface and strengthening mechanisms on the mechanical properties of metal matrix composites

A randomly distributed multi-particle model considering the effects of particle/matrix interface and strengthening mechanisms introduced by the particles has been constructed. Particle shape, distribution, volume fraction and the particles/matrix interface due to the factors including element diffusion were considered in the model. The effects of strengthening mechanisms, caused by the introduction of particles on the mechanical properties of the composites, including grain refinement strengthening, dislocation strengthening and Orowan strengthening, are incorporated. In the model, the particles are assumed to have spheroidal shape, with uniform distribution of the centre, long axis length and inclination angle. The axis ratio follows a right half-normal distribution. Using Monte Carlo method, the location and shape parameters of the spheroids are randomly selected. The particle volume fraction is calculated using the area ratio of the spheroids. Then, the effects of particle/matrix interface and strengthening mechanism on the distribution of Mises stress and equivalent strain and the flow behaviour for the composites are discussed.