Papers by Keyword: TEM Analysis

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Authors: Andrea Severino, Corrado Bongiorno, Stefano Leone, Marco Mauceri, Giuseppe Pistone, Giuseppe Condorelli, Giuseppe Abbondanza, F. Portuese, Gaetano Foti, Francesco La Via
Abstract: 3C-SiC/Si heteroepitaxy is hampered by large mismatches in lattice parameters (19.7%) and thermal expansion coefficient (8%) leading to 3C-SiC films containing high defects density. To reduce the presence of defects, a multi-step growth process in a CVD reactor is used. The aim of the work is to study the effect of carbonization on differently oriented Si surfaces, experiencing a 200°C-wide temperature range in a CVD reactor, to improve the crystalline quality. TEM analysis are carried out to evaluate thickness, crystal orientations and defects of carbonized layers with respect to the time-dependence of the process and to the different orientations of the Si substrate. It will be shown that process-related defects are strictly correlated to the substrate orientation either for size, density, occupied area, shape or thickness. Uniform, flat and crystalline thin SiC films are obtained with a low defect density.
Authors: Manuel Gómez, S.F. Medina, Pilar Valles, Alberto Quispe
Abstract: Excellent mechanical properties (high strength and toughness) of microalloyed steels are mainly caused by induced precipitation during thermomechanical treatment (TMT) and grain refinement. It has been recently found that TMT of Nb-microalloyed steels can give rise to two different kinds of precipitates, manifested by the double plateau in the statically recrystallised fraction (Xa) against time curves. This work presents an electron diffraction study performed in a transmission electron microscope, equipped with an EDS analytical system. Lattice parameters of a great deal of particles, smaller than 200 nm and with face cubic centred structure, have been measured. Frequency distribution of the values of lattice parameters shows that these are grouped in two sets whose mean values are close. Comparison of these values with those found in the literature for carbides, nitrides and carbonitrides usually present in microalloyed steels demonstrates that they are Nb carbonitrides with slight stoichiometric differences (NbCxNy).
Authors: Lu Yang Ren, Mohsen Masoumi, Henry Hu
Abstract: Metallographic analyses on microstructure of squeeze cast magnesium alloy AM50 with different levels of calcium addition are performed via optical microscopy (OM), and scanning electron microscopy (SEM). The OM results show the calcium has a grain refining effect on the base alloy AM50 with the level of Ca addition up to 2 wt.%. As the Ca content further increases, its grain refining effect becomes limited. The SEM observation reveals the addition of 2 wt.% Ca to the AM50 alloy leads to the formation of a continuous network of eutectic phases along grain boundaries while the discontinuous divorced secondary eutectic β-Mg12Al17 is present in the microstructure of AM50 containing also the primary α-Mg, and Mn-Al intermetallic particles. The elemental mapping by the energy dispersive spectroscopy (EDS) indicates the presence of the major alloying elements of Al and Ca along grain boundaries in the squeeze cast AM50 alloy with Ca addition.
Authors: C.K. Jung, I.S. Bae, Y.H. Song, S.J. Cho, Jin Hyo Boo
Abstract: Titanium oxynitride (TiOxNy) films were prepared by RF PECVD on Si(100) and glass substrates using nitrogen and argon mixture gas. Titanium iso-propoxide (Ti[OCH(CH3) 2] 4, 97%) was used as precursor with different nitrogen flow rate to control oxygen and nitrogen contents in the films. Changes of chemical states of constituent elements in the deposited films were examined by X-ray photoelectron spectroscopy (XPS) analysis. With increasing nitrogen flow rate the total amount of nitrogen was increased while that of oxygen was decreased. The film growth orientation and N-H peak intensity characteristics were also analyzed by X-ray diffraction (XRD), atomic force microscopy (AFM), and infrared spectroscopy (FT-IR). Through refractive index as well as contact angle analysis, we can suggest that relationship to surface energy and optical property. Moreover, transmission electron microscopy (TEM) was also used to investigate the morphology of TiOxNy thin film and the phase of the TiOxNy thin film different nitrogen flow rate.
Authors: Karl Otto Dohnke, Korbinian Kaspar, Dirk Lewke
Abstract: Mechanical blade dicing is a state-of-the-art technique for the chip separation of SiC devices. Due to the hardness of SiC this technique suffers from low feed rate and high wear of the diamond coated dicing blade, resulting in the risk of uncontrolled tool breakage during the dicing process. With the upcoming transition to 150 mm diameter of SiC wafers this technique will most probably reach its limit. For dicing SiC wafers of those diameters on a productive scale three alternative dicing technologies are considered in this paper: ablation laser dicing, Stealth Dicing and Thermal Laser Separation. All these methods are based on laser processing. The benefits of these technologies are discussed in detail and compared to the classical mechanical diamond blade dicing, including a brief summary of first experimental results on each of the three laser dicing technologies.
Authors: C. Salmon, D. Tiberghien, Régine Molins, Christian Colin, Francis Delannay
Authors: Oleg L. Khasanov, Yury F. Ivanov, Edgar S. Dvilis, Oleg S. Tolkachev
Abstract: Commercial nanopowder of the partially yttrium-stabilized zirconia (ZrO2+3 mol.% Y2O3) was treated by the non-cavitational powerful ultrasonic action (PUA). Influence of PUA on the microstructure and phase composition of the powder has been investigated by scanning and transmission electron microscopy. Investigated powder before and after PUA has polycrystalline structure. It was found that TZ-3YS particles after PU-treatment have tetragonal and cubic zirconia phases; some of the particles consist of a mixture of monoclinic, tetragonal and cubic phases, but these particles have substructure with random orientation of fragments.
Authors: Yang Soo Kim, David Sudol, Victoria Dimonie, Mohammed El-Aasser
Abstract: Hollow polystyrene nanocapsules with sizes of ~100 nm have been prepared via a miniemulsion polymerization process by applying the encapsulation of a nonsolvent (i.e., isooctane). Divinylbenzene has been added to styrene as a cross-linking comonomer in order to improve a structural stability of the hollow polymer capsules. Morphology variation of nanocapsules with concentrations of divinylbenzene and also isooctane has been studied using transmission electron microscopy analysis. Kinetic study on the miniemulsion polymerization of styrene in the presence of divinylbenzene and isooctane has been carried out using fractional conversion data determined by the gravimetric analysis.
Authors: Michal Besterci, Oksana Velgosová, Ladislav Kovác, Jozef Ivan
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