Browsing by Subject "Transmission electron microscopy (TEM)"

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Open Access
Properties of high specific strength Al-4wt.% Al2O3/B4C nano-composite produced by accumulative roll bonding process
(Elsevier Ltd, 2013) Alizadeh, M.; beni H.A.; Ghaffari, M.; Amini, R.
The influence of nano-scale reinforcement on the mechanical and microstructural properties of ultrafine-grained composites was studied. Al matrix (pure aluminum) composites, with a grain size of 230nm and B4C and Al2O3 reinforcements with an average size of 50nm, were fabricated via the accumulative roll bonding (ARB) process. To evaluate structure and microstructure of the produced composites, X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM) were applied. Mechanical properties of the specimens were investigated by tensile and hardness tests. The result revealed that in comparison with monolithic Al (ARBed Al without ceramic particles), the presence of nano-particles enhances specific strength of composites. Also, the results showed that with increasing ARB cycles, the microhardness of the composites increases. In addition, the specific strength and microhardness of the composite samples are higher than those of the monolithic Al. The density of the composite samples and monolithic Al was measured by the Archimedes method showing that the density decreases in presence of ceramic particles. © 2013 Elsevier Ltd.
Open Access
Raman and TEM studies of Ge nanocrystal formation in SiOx: Ge/SiOx multilayers
(Wiley, 2007) Dana, Aykutlu; Aǧan, S.; Tokay, S.; Aydınlı, Atilla; Finstad, T. G.
Alternating germanosilicate-siliconoxide layers of 10-30 nm thickness were grown on Si substrates by plasma enhanced chemically vapor deposition (PECVD). The compositions of the grown films were determined by X-ray photoelectron spectroscopy measurements. The films were annealed at temperatures varying from 670 to 1000°C for 5 to 45 minutes under nitrogen atmosphere. High resolution cross section TEM images, electron diffraction and electron energy-loss spectroscopy as well as energy-dispersive X-ray analysis (EDAX) data confirm presence of Ge nanocrystals in each layer. The effect of annealing on the Ge nanocrystal formation in multilayers was investigated by Raman spectroscopy and Transmission Electron Microscopy (TEM). As the annealing temperature is raised to 850°C, single layer of Ge nanocrystals observed at lower annealing temperatures is transformed into a double layer with the smaller sized nanocrystals closer to the substrate SiO2 interface.