1,721,259 research outputs found
XPS investigation of 5N purity Al thin foils for MEMS devices
No full textThin Al foils are promising materials for applications in devices of microelectromechanical systems (MEMS). In this work, three foils of high purity (5N) Al with different thickness (10, 50, and 125 μm) were analyzed by means of X-ray photoelectron spectroscopy (XPS), before and after annealing (720 K for 30 min). XPS surface analysis and depth profiling of chemical composition were performed to investigate the distribution of Al oxide. Electron energy loss spectroscopy (EELS) measurements were also carried out in order to identify the plasmon losses and chemical state of Al. The loss peaks in the 5N-Al thin foils were compared with those of an Al foil of commercial purity (99.95 wt%). The thickness of the oxide layer on the sample surface of all the samples is not constant and oxide is thicker in the samples of high purity than in those of commercial quality. Moreover, the thinnest foils of 5N-Al (10 μm) exhibit the thinnest oxide layer. These findings have been discussed by considering the size effect, that is, mechanical properties of thin foils are improving as the thickness decreases. The complex morphology of the metal-oxide interface may contribute to enhance the mechanical performances of Al foils with a thickness below ~50 μm, because the free dislocations pile up against the interface which represents an obstacle for their motion hindering plastic deformation. Obtained results suggest that Al foils to be used in MEMS devices should be of high purity and annealed to get a surface completely covered by the oxide layer
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparison between roll diffusion bonding and hot isostatic pressing production processes of ti6al4v-sicf metal matrix composites
No full textStudy of steel-WC interface produced by solid-state capacitor discharge sinter-welding
No full textMultimaterial components are more suitable than monolithic materials to combine several mechanical and functional properties simultaneously. Bi-layer components made of WC-Co and steel can combine enhanced wear resistance and toughness, which are beneficial for a wide range of advanced tribo-structural applications. In this study, a new solid-state capacitor discharge sinter-welding (CDSW) process has been used to achieve an AISI M2 steel/WC–12% Co joint starting from green compacts. The CDSW process allows very short processing times, which help to prevent the coarsening of steel grains or WC particles, as well as avoid WC decomposition and minimize microstructural defects. The morphological, chemical, and structural characteristics of the phases and interface have been investigated. The results demonstrate an intimate bonding of the two joining materials and a significant diffusion of substitutional elements up to 100–150 μm apart from the interface. Copyright © 2016 John Wiley & Sons, Ltd
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Composition of plasma-sprayed tungsten coatings on CuCrZr alloy
No full textMock-ups for the International Thermonuclear Experimental Reactor(ITER) were manufactured by depositing W coatings on tubular substrates of CuCrZr alloy via plasma spraying. An appropriate interlayer (of Ni, Al and Si) was optimised to increase the adhesion of W on the Cu alloy and to provide a soft interface with intermediate thermal expansion coefficient for better thermo-mechanical compatibility.
The distribution of chemical elements in the layered interface and in the coating was investigated by energy dispersive spectroscopy (EDS), XPS and AES in the as-preparedmaterial and after heat treatment of 24 h at 823 K. Moreover, the external Wlayer was examined by inductively coupled plasma emission spectrometry(ICP-ES).
The results showed that the as-prepared material does not exhibit macro-porosity. The layers forming the interface do not exhibit any long-range diffusion of the chemical species from layer to layer during the deposition process. The heat treatment does not seem to cause long-rangemigration of Al and Ni into theWcoating.
The presence of Ni (0.4wt%) in the as-deposited externalWlayer as shown by ICP-ES is only due to the low purity (commercial grade) of W powders used in spraying operations. It can be eliminated by using W powders of higher purity in the deposition process
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
La distribution on the crater surface of W-1%La2O3 produced by a single laser pulse
No full textThe W-1%La2O3 alloy has been irradiated by a single laser pulse (λ = 1064 nm) to simulate transient thermal loads of high energy occurring in a tokamak under operative conditions. A zone with a diameter of ~2 mm, namely, much larger than the focal spot, results to be affected by the pulse, and a crater of about 300 μm is observed in its center. La2O3 particles are not present inside the crater. The change of surface morphology is accompanied by elemental redistribution. Multipoint XPS analysis evidenced that the concentration of La is very low in the crater and increases moving toward the border of the affected zone while that of W shows an opposite trend. The composition changes involve only the outmost 5 nm of the sample: through depth profiling, no differences of chemical composition were detected deeper in the alloy between the center and external border of the affected area
Ceria/stannate multilayer coatings on AZ91D Mg alloy
No full textIn this work, CeO2/stannate multilayer coatings on AZ91D magnesium alloy were successfully obtained by
chemical conversion and sol–gel dip coating. The stannate conversion coatings were prepared from a
stannate aqueous bath containing Na2SnO3, CH3COONa, Na3PO4 and NaOH at different temperatures and immersion
times. Ceria films were produced on stannate/AZ91D starting from Ce(III) nitrate solutions in H2O. In
some cases, the PVA was added as chelating agent. Ceria top coatings were fired at 200 °C for 1 h. Coating microstructure
was examined by FE-SEM. Finally, the corrosion resistance features of the coatings were tested
by the electrochemical impedance spectroscopy (EIS) in 3 wt.% NaCl solution. The effect of PVA addition was
evaluated in terms of microstructure and corrosion resistance features. CeO2/stannate multilayer films, 3 μm
thick, uniform, well adherent and nearly crack free were obtained. The formation of CeO2 phase was confirmed
by XRD and XPS analyses. The XPS depth profiles showed a limited diffusion of Mg towards the ceramic
film. The EIS tests showed a significant improvement of corrosion resistance of the multilayer coatings
(~16.6 kΩ after 48 h in NaCl solution) with respect to the blank alloy (~2.4 kΩ after 48 h in NaCl solution
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