Search results for "Metallurgy"
showing 10 items of 1419 documents
Non-destructive Approach to Multilayer Objects: XRF Analysis of Gilt and Enamelled Metals of the Medieval Cross of Rosciolo
2013
Abstract The penetration of X-rays is usually a limitation to the application of XRF analysis to multilayered materials, however it is possible, by software tools based on the fundamental parameters method, to overcome this problem and estimate thickness and composition of each layer. The cross of Rosciolo is a significant example of multilayer object: it is made of a wood core with attached gilt silver sheets and decorated with enamels. Measurements were carried out in situ and the PyMCA software was employed. The values of gilding thickness, Au/Hg ratios and Cu content in the silver sheets, and enamel's composition are discussed.
Improvement of the electrochemical behaviour of Zn-electroplated steel using regenerated Cr(III) passivation baths
2014
[EN] Conversion coatings based on trivalent chromium are more sensitive to the presence of zinc and iron impurities than the chromate formulations. This fact contributes to a decrease in the quality of passivation and to the generation of a significant amount of hazardous liquid waste. Recently, a new eco-innovative process based on Emulsion Pertraction Technology (EPT) is being implemented at industrial scale for selectively removing Zn and Fe from spent passivation baths in order to enhance the lifetime of the Cr (III) baths. In this study, the effect of Zn and Fe removal on the electrochemical behaviour of Zn-electroplated steel samples was evaluated by means of polarisation curves and e…
Pulsed laser deposition of Sr2FeMoO6 thin films
2005
Abstract The effect of various deposition conditions and after-growth protocols on the magnetic and transport properties of Sr 2 FeMoO 6 films has been explored. It is found that the saturation magnetization and the magnetoresistance (MR) are dominated by the degree of cationic order, and the strain effects are clearly evidenced in a lower T C . The after-growth annealing of the films and the deposition of a buffer layer has been found to relax the film strains. This translates into a clear increase of the measured low-field magnetoresistance ratios.
Synthesis of nanostructured amorphous carbon-copper composite films by plasma-enhanced chemical vapour deposition
2016
Abstract Nanostructured amorphous carbon-copper composite films were formed by plasma-enhanced chemical vapour deposition. The formation was done on copper-silicon substrates at 25 °C, 300 °C, 520 °C, and 700 °C temperatures using an acetylene gas at 40–70 Pa pressure. The heating of the Cu Si substrate induced formation of Cu nanospheres with 50–500 nm size depending on the substrate temperature. The microstructure and composition of nanostructured carbon-copper composite films were investigated. The SEM views showed formation of amorphous carbon films with the randomly distributed nanostructures. The oxygen concentration in the composite films decreased with the increased heating temperat…
Mechanical behavior of polylactic acid/polycaprolactone porous layered functional composites
2016
Abstract Biopolymeric porous devices exhibiting graded properties can play a crucial role in several fields, such as tissue engineering or controlled drugs release. In this context, the gradient of a specific property can be achieved by developing porous laminates composed by different types of materials. This work presents for the first time a multi-phasic porous laminate based on polycaprolactone (PCL) and polylactic acid (PLA) prepared by combining melt mixing, compression molding and particle leaching. All the materials were characterized from a morphological and a mechanical point of view. The results put into evidence the possibility to tune and to predict the mechanical properties by…
Numerical simulation of linear fiction welding (LFW) processes
2011
Solid state welding processes are becoming increasingly important due to a large number of advantages related to joining ''unweldable'' materials and in particular light weight alloys. Linear friction welding (LFW) has been used successfully to bond non-axisymmetric components of a range of materials including titanium alloys, steels, aluminum alloys, nickel, copper, and also dissimilar material combinations. The technique is useful in the research of quality of the joints and in reducing costs of components and parts of the aeronautic and automotive industries.LFW involves parts to be welded through the relative reciprocating motion of two components under an axial force. In such process t…
On the Solid Bonding Phenomena in Linear Friction Welding and Accumulative Roll Bonding Processes: Numerical Simulation Insights
2015
Solid Bonding based welding processes allow to obtain defect free joints with low residual stress and low distortion. However, the engineering and optimization of solid bonding processes is difficult and requires a large number of time and cost consuming test trials. In this way, proper numerical models are essential tools permitting effective process design. The aim of this research was the comparison of the material process conditions during two different manufacturing processes taking advantage of the same metallurgical phenomenon, namely solid bonding. Linear Friction Welding, used to weld non-axisymmetric components and Accumulative Roll Bonding, used to increase the mechanical propert…
Metallurgical Evolutions in Hot Forging of Dual Phase Titanium Alloys: Numerical Simulation and Experiments
2015
Titanium forging has been encountering a growing interest in the scientific and industrial communities because of the distinct advantages it provides with respect to machining, in terms of both mechanical properties of the product and material waste, thus significantly reducing the Buy to Fly ratio. In the paper, a numerical FE model, based on a tri-coupled approach and able to predict the microstructural evolutions of the workpiece during the process, is developed and set up. Calculated results are compared to experiments for a few industrial case studies. The final phases distribution in the forged parts is experimentally measured and compared to the FE model output finding satisfying ove…
Reduction of low-frequency 1/f noise in Al-AlOx-Al tunnel junctions by thermal annealing
2010
We report that annealing Al-AlOx-Al tunnel junctions in a vacuum chamber at temperature of 400C reduces the characteristic 1/f noise in the junctions, in some cases by an order of magnitude. Both ultra high vacuum and high vacuum fabricated samples demonstrated a significant reduction in the 1/f noise level. Temperature dependence of the noise was studied between 4.2 and 340 Kelvin, with a linear dependence below 100 K, but a faster increase above. The results are consistent with a model where the density of charge trapping two level-systems within the tunneling barrier is reduced by the annealing process.
Polymerization and Damage of C60 Single Crystals under Low Fluency Laser Irradiation
2001
Photo-induced hardening, substructure formation and damage of C 60 single crystals under the 632.8 nm He-Ne laser irradiation in air at a power density of 1.47 mW/mm 2 was investigated by microhardness and AFM methods. Photo-induced formation of the dislocation substructure and crystallographically oriented crack patterns on the (111) face due to lattice contraction on polymerization were observed. Two phototransformed states: soft (400-450 MPa) and hard (650-1000 MPa) are found to appear under laser-irradiation. Hard fullerite is created in the subsurface layer < 1 μm at the saturation stage of phototransformation. It softens to 400-450 MPa at 340 K and reverts to non-polymerized state at …