Papers by Keyword: Electron Microscopy

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Authors: Igor Matko, Bernard Chenevier, M. Audier, Roland Madar, M. Diani, L. Simon, L. Kubler, D. Aubel
Authors: T. Walther, Colin J. Humphreys, A.G. Cullis, D.J. Robbins
Authors: Guo Qing Zhong, Qin Zhong, Hong Liang Zhou, Yu Qing Jia
Abstract: The Co–B alloy can be prepared facilely by a solid-solid reaction of CoCl2•6H2O and KBH4 powders at room temperature. Various characterizations, such as the chemical analysis, inductively coupled plasma-atomic emission spectroscopy (ICP), powder X-ray diffraction, electron diffraction and TEM have been performed. The results indicate that the Co-B alloy obtained by the solid-solid reaction is amorphous nanoparticles. The composition of the alloy is Co1.36B. The average diameter of the Co–B alloy nanoparticles is 30nm–50nm. The room temperature solid-solid reaction is mainly a surface reaction. The direct solid solid reaction between the borohydride and some metal-salts is thermodynamically possible. This simple preparation method may also be used for the large-scale production of the amorphous nanoparticles of some metal-boron alloys.
Authors: S.S. Campos, E. Valencia Morales, H.J. Kestenbach
Authors: K. Short, Richard Wuhrer, G. Collins, Wing Yiu Yeung
Authors: Wei Wen Liu, Tijjani Adam, Azizan Aziz, Siang Piao Chai, Abdul Rahman Mohamed, U. Hashim
Abstract: The effect of calcination temperature for Fe2O3/MgO catalysts on the formation of carbon nanotubes (CNTs) was examined. CNTs were synthesized over Fe2O3/MgO catalysts calcined at different temperatures by catalytic decomposition of methane at 1000°C. The synthesized CNTs were investigated by a combination of scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The results show that the effect of calcination temperatures greatly governed the diameter and the quality of the SWCNTs formed. The catalysts calcined at 500, 600 and 700°C produced CNTswith the diameters of 1.53, 1.95 and 2.97nm, respectively. Generally, an increase in the calcination temperature increases the average diameter and decreases the quality of the CNTs produced.
Authors: Chong Hong Zhang, Yue Sheng Wang, K.Q. Chen, Ji Guo Sun, J.M. Quan, Chang Qi Chen
Abstract: Low-activation Fe-Cr-Mn alloy and 316L stainless steel were irradiated with 92 MeV Ar ions at about 500°C, to fluences of 0.8~1.7×1021 ions m-2 .After irradiation, cross-sectional specimens were investigated with transmission electron microscopy.Cavities with high number density were observed in the peak dose regions. The cavity number density reaches maximum at Ar concentration peak, while cavity mean size is consistent with displacement damage profile. It is indicated that Ar atoms can enhance cavity formation in a manner similar to helium. There are thresholds of dose and dose rate for the bi-modal size distribution of cavities. The significant growth of a small portion of cavities in the peak damage region at the highest ion-fluence is ascribed to the effect of interactive sink strength of cavities.
Authors: Cléo Thomás Gabriel Vilela Menegaz Teixeira Pires, Júlio César Perin de Melo, Claudio Airoldi
Abstract: Organofunctionalized phyllosilicates containing both amino and mercapto groups were synthesized and used as support for silver nanoparticles in situ deposition. Depending on silver concentration in relation to phyllosilicate different amount of nanoparticles size and distributions were obtained, even with smallest silver used causes strong exfoliation of the phylosilicate lamella. Also such condition favors nanoparticles formation with homogeneous distribution with smaller diameters and narrower particle particles size distributions. With highest silver amounts preferential external phyllosilicate surface crystallization is obtained, as given by particle diameters up to 30 nm. Scanning and transmission electron microscopies were successfully employed to characterize morphological and structural features for these synthesized materials, enabling atomic visualization for the silver nanoparticles. These new phyllosilicates containing silver nanoparticles are extensively employed to design inorganic light emission diodes and also in applying in biological fields.
Authors: Stan T. Mandziej
Abstract: Thermal mechanical fatigue (TMF) was found to accelerate microstructure transformation in martensitic-bainitic Cr-Mo-V creep-resisting steels used in power generation. Particular role in this acceleration has been ascribed as being due to configurations of dislocations generated in the compression part of the TMF cycle, which dislocations in the tensile part of the cycle appeared to assist precipitation processes while important role in this acceleration is due to Bauschinger effect. Based on this finding an accelerated creep test (ACT) on Gleeble thermal mechanical simulator was developed to gain in a short time of less than 30 hours the microstructures and properties of steels and welds similar to these appearing after the long-term exposure in power plants. Investigations by scanning electron microscopy and transmission electron microscopy confirmed similarity of microstructure transformation after the ACT with this occurring after the multi-year real creep in power generating installations, in particular in these where premature failures occurred.
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