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1
المؤلفون: Yannick Descantes, Yann Fosse, G. Ehret
المصدر: Materials and Structures. 39:3-12
مصطلحات موضوعية: Aggregate (composite), Sample (material), Mineralogy, Building and Construction, Test method, Mechanics of Materials, Solid mechanics, Particle-size distribution, Flow coefficient, Rock types, General Materials Science, Alluvium, Civil and Structural Engineering, Mathematics
الوصف: A new image processing based test method has been developed, in order to assess the percentage of crushed and broken surfaces in alluvial coarse aggregate. This test method has been implemented into the VDG40 videograder and an effective test procedure has been set. Indeed, the analysis of a 1 kg 6/10-mm sample only requires less than three minutes and seems to be very repeatable, since the coefficients of variation are below 1%. Comparison analyses between VDG40, European crushed and broken surfaces reference test and flow coefficient test were proceeded with 6/10 alluvial gravel, using samples recombined in accordance with different European crushed and broken surfaces categories. Results showed very strong correlations between VDG40 values and coarse and broken surface values, with R2 factors above 92%. Moreover, strong correlation was established between VDG40 values and flow coefficient test results, with R2 factor above 93%. Further testing is now necessary with other rock types, in order to standardize the ANG criteria and to build specifications for 6/10 alluvial gravel characterization. Next steps should be to assess the method reproducibility and to test other aggregate fractions, namely sand fractions.
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2
المؤلفون: R. Halimi, G. Ehret, A Bouabellou, K. Mirouh, A Mosser, A. Karaali
المصدر: Materials Science and Engineering: B. :246-250
مصطلحات موضوعية: Materials science, Annealing (metallurgy), Mechanical Engineering, Doping, Metallurgy, Analytical chemistry, chemistry.chemical_element, Condensed Matter Physics, Microstructure, Ion, Monocrystalline silicon, chemistry.chemical_compound, Chromium, chemistry, Mechanics of Materials, Transmission electron microscopy, Silicide, General Materials Science
الوصف: The effect of the phosphorus on the microstructure and on the nature of the formed silicide in the annealed Cr/Si system is studied. The chromium layer is deposited by electron gun evaporation on the undoped and P + doped monocrystalline silicon. Cross-sectional transmission electron microscopy (XTEM) investigation of the samples, annealed at 475 °C for different times, shows that the presence of phosphorus leads to the formation of CrSi 2 disilicide, free of defects, and Cr 3 Si silicide for lower and higher annealing times, respectively. In the case of undoped substrate the formed CrSi 2 disilicide is stable and contains a high concentration of stacking faults when the chromium is partially consumed.
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3Microstructural study of annealed Cr/Si system using cross-sectional TEM combined with nano-analysis
المؤلفون: A Mosser, G. Ehret, K. Mirouh, A Bouabellou, R. Halimi
المصدر: Materials Science and Engineering: B. 102:80-83
مصطلحات موضوعية: Materials science, Silicon, Annealing (metallurgy), Mechanical Engineering, Metallurgy, Alloy, Analytical chemistry, chemistry.chemical_element, Substrate (electronics), engineering.material, Condensed Matter Physics, Semimetal, Atomic diffusion, Chromium, chemistry, Mechanics of Materials, Transmission electron microscopy, engineering, General Materials Science
الوصف: Among the various characterization methods generally used in the study of silicidation mechanisms, particularly interfaces structure, the cross-sectional transmission electron microscopy (XTEM) combined with nano-analysis were not much used. This work dealt with the study, by mean of this method, of interfacial atomic diffusion phenomena in thin Cr/Si system in dependence on heat treatment conditions. The chromium film of 850 A thickness was electron gun deposited onto (111) oriented phosphorus implanted Si substrate. The XTEM observations of samples annealed at 475 °C during 60 and 120 min showed that the chromium was partially consumed in opposite to the case where the Si substrate was not implanted. The thickness of formed chromium silicide was practically the same for 60 and 120 min. Nano-analysis revealed the presence of Si atoms at the surface and Cr atoms into the substrate leading to the formation of a crystalline Cr–Si alloy. However, after 500 °C during 5 min the obtained results showed that no reaction occurred between Si and Cr and Si atoms were present in the Cr film. This indicated that Si diffused towards the surface before silicidation.
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4
المؤلفون: R. Halimi, G. Ehret, A Bouabellou, K. Mirouh, J Werckman, A Mosser
المصدر: Materials Science and Engineering: B. 73:116-119
مصطلحات موضوعية: Materials science, Silicon, Mechanical Engineering, Metallurgy, Doping, technology, industry, and agriculture, Analytical chemistry, chemistry.chemical_element, Substrate (electronics), equipment and supplies, Condensed Matter Physics, Amorphous solid, chemistry.chemical_compound, Ion implantation, chemistry, Mechanics of Materials, Transmission electron microscopy, Silicide, General Materials Science, Thin film
الوصف: Cross-sectional transmission electron microscopy was used to study the effect of doped silicon substrate on the formation of CrSi 2 disilicide. A chromium film 800 A thick was electron gun deposited onto unimplanted and phosphorus implanted Si(111) substrates. The implanted dose was 5×10 15 at. cm −2 at 30 keV. The Cr–Si samples were heat treated in vacuum at 475°C for different times. Transmission electron microscopy investigations, performed on doped and undoped Si substrates, have shown that the presence of P + ions resulted in the delay of the CrSi 2 compound growth. In addition, the nanoanalysis of the samples with P + implanted silicon has revealed the apparition of a crystalline Si–Cr alloy in the Si substrate near the CrSi 2 –Si interface, the formation of an amorphous Si thin layer between the formed silicide and this alloy, and a diffusion of Si atoms towards the free surface.
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5
المؤلفون: L. Constant, F. Le Normand, G. Ehret, C. Speisser
المصدر: Journal of Materials Research. 14:560-564
مصطلحات موضوعية: Materials science, Hybrid physical-chemical vapor deposition, Mechanical Engineering, Nucleation, chemistry.chemical_element, Diamond, Chemical vapor deposition, Combustion chemical vapor deposition, engineering.material, Condensed Matter Physics, Electron beam physical vapor deposition, Chemical engineering, chemistry, Mechanics of Materials, engineering, General Materials Science, Graphite, Carbon
الوصف: We report the first observation of large graphitic capped clusters with threefold symmetry (tripods). They were generated under the diamond growth conditions by the chemical vapor deposition process activated by hot filaments on a Cu(111) surface while conditions of very poor diamond nucleation (104–105 cm-2) are fullfilled. They were characterized by direct high resolution imaging and selected area diffraction. Furthermore, a lot of them are connected. The behavior of hydrogen radicals to curl and to close limited-size graphitic planes is emphasized to explain their formation. These tripods appear to be readily stable carbon as they form only after other limited-size graphitic clusters such as graphite lumps or bucky onions. It is thus expected that the chemical vapor deposition process is a quite relevant preparation method to grow in a controlled way new forms of carbon with a narrow size distribution.
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::d1bf1eebabb211bdc14ad886b766c83e
https://doi.org/10.1557/jmr.1999.0080 -
6
المؤلفون: B.A. Gurney, H. Lefakis, P. Humbert, M. Benaissa, G. Ehret, Virgil Simon Speriosu
المصدر: Materials Science Forum. :697-700
مصطلحات موضوعية: Materials science, chemistry, Mechanics of Materials, Annealing (metallurgy), Mechanical Engineering, Metallurgy, chemistry.chemical_element, General Materials Science, Condensed Matter Physics, Magnetic thin film, Cobalt, Stacking fault
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_________::0b316acbd9eb30eb0b29ac8104296923
https://doi.org/10.4028/www.scientific.net/msf.207-209.697 -
7
المؤلفون: W. Saikaly, F. Le Normand, A. Charai, L. Constant, G. Ehret, C. Speisser, M. Romeo
المساهمون: Jung, Marie-Anne
المصدر: Scopus-Elsevier
مصطلحات موضوعية: Physics and Astronomy (miscellaneous), Hydrogen, Metals and Alloys, Nucleation, chemistry.chemical_element, Diamond, Mineralogy, Chemical vapor deposition, engineering.material, Condensed Matter Physics, Copper, Electronic, Optical and Magnetic Materials, chemistry, Chemical engineering, Phase (matter), engineering, General Materials Science, Reactivity (chemistry), Carbon, ComputingMilieux_MISCELLANEOUS
الوصف: We report further observations of graphitic carbon onions and polyhedra that are formed together with graphitic planes under the conditions of the chemical vapour deposition of diamond as previously described by Constant et al. (1997, Surf. Sci., 387, 28). The occurrence of such carbon onions is quite specific to the copper substrate. They were observed with various pre-treatments of the substrate. It is suggested that both the nucleation and the growth of such carbon onions occur on the copper surface rather than in the gas phase. It is believed that, instead of high-energy electron or ion beams as described elsewhere by Banhart (1997, J. appl. Phys., 81, 3440), the formation of carbon onions is due to the high reactivity of the atomic hydrogen present in the gas phase. These hydrogen radicals induce a curvature of the graphitic planes by preferential reactivity on the corner and edge sites. A dense phase in the core of few carbon onions was sometimes seen. We then measured an interplanar distan...
URL الوصول: https://explore.openaire.eu/search/publication?articleId=doi_dedup___::4ba2c75509d48fb04071460fc20563f0
https://hal.archives-ouvertes.fr/hal-00685225
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