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19 results on '"Yücelen, Emrah"'

5. Surface evolution of a Pt–Pd–Au electrocatalyst for stable oxygen reduction

Author

Li, Jian, primary, Yin, Hui-Ming, additional, Li, Xi-Bo, additional, Okunishi, Eiji, additional, Shen, Yong-Li, additional, He, Jia, additional, Tang, Zhen-Kun, additional, Wang, Wen-Xin, additional, Yücelen, Emrah, additional, Li, Chao, additional, Gong, Yue, additional, Gu, Lin, additional, Miao, Shu, additional, Liu, Li-Min, additional, Luo, Jun, additional, and Ding, Yi, additional

Published
2017
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9. Aberration-corrected microscopy and spectroscopy analysis of pristine, nitrogen containing detonation nanodiamond

Author

Turner, Stuart, Shenderova, Olga, da Pieve, Fabiana, Lu, Yinggang, Yücelen, Emrah, Verbeeck, Johan, Lamoen, Dirk, and Van Tendeloo, Gustaaf

Subjects
Physics
Abstract

Aberration-corrected transmission electron microscopy, electron energy-loss spectroscopy, and density functional theory (DFT) calculations are used to solve several key questions about the surface structure, the particle morphology, and the distribution and nature of nitrogen impurities in detonation nanodiamond (DND) cleaned by a recently developed ozone treatment. All microscopy and spectroscopy measurements are performed at a lowered acceleration voltage (80/120kV), allowing prolonged and detailed experiments to be carried out while minimizing the risk of knock-on damage or surface graphitization of the nanodiamond. High-resolution TEM (HRTEM) demonstrates the stability of even the smallest nanodiamonds under electron illumination at low voltage and is used to image the surface structure of pristine DND. High resolution electron energy-loss spectroscopy (EELS) measurements on the fine structure of the carbon K-edge of nanodiamond demonstrate that the typical * pre-peak in fact consists of three sub-peaks that arise from the presence of, amongst others, minimal fullerene-like reconstructions at the nanoparticle surfaces and deviations from perfect sp(3) coordination at defects in the nanodiamonds. Spatially resolved EELS experiments evidence the presence of nitrogen within the core of DND particles. The nitrogen is present throughout the whole diamond core, and can be enriched at defect regions. By comparing the fine structure of the experimental nitrogen K-edge with calculated energy-loss near-edge structure (ELNES) spectra from DFT, the embedded nitrogen is most likely related to small amounts of single substitutional and/or A-center nitrogen, combined with larger nitrogen clusters.

Published
2013

13. Tanet al.Reply

Author

Tan, Haiyan, primary, Turner, Stuart, additional, Yücelen, Emrah, additional, Verbeeck, Jo, additional, and Van Tendeloo, Gustaaf, additional

Published
2012
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17. 2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy.

Author

Haiyan Tan, Turner, Stuart, Yücelen, Emrah, Verbeeck, Jo, and Van Tendeloo, Gustaaf

Subjects
*SCANNING transmission electron microscopy, *TRANSMISSION electron microscopy, *ELECTRON energy loss spectroscopy, *ATOMS
Abstract

Using a combination of high-angle annular dark-field scanning transmission electron microscopy and atomically resolved electron energy-loss spectroscopy in an aberration-corrected transmission electron microscope we demonstrate the possibility of 2D atom by atom valence mapping in the mixed valence compound Mn304. The Mn L23 energy-loss near-edge structures from Mn2+ and Mn3+ cation sites are similar to those of MnO and Mn2O3 references. Comparison with simulations shows that even though a local interpretation is valid here, intermixing of the inelastic signal plays a significant role. This type of experiment should be applicable to challenging topics in materials science, such as the investigation of charge ordering or single atom column oxidation states in, e.g., dislocations. [ABSTRACT FROM AUTHOR]

Published
2011
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18. Tan et al. Reply:.

Author

Tan, Haiyan, Turner, Stuart, Yücelen, Emrah, Verbeeck, Jo, and Van Tendeloo, Gustaaf

Subjects
*LETTERS to the editor, *TRANSITION metal oxides, *ELECTRON microscopy
Abstract

A response by H. Tan, S. Turner and J. Verbeeck to a letter to the editor about their article "2D Atomic Mapping of Oxidation States in Transition Metal Oxides by Scanning Transmission Electron Microscopy and Electron Energy-Loss Spectroscopy" in a previous issue is presented.

Published
2012
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19. Real-time atomic scale imaging of nanostructural evolution in aluminum alloys.

Author

Malladi SK, Xu Q, van Huis MA, Tichelaar FD, Batenburg KJ, Yücelen E, Dubiel B, Czyrska-Filemonowicz A, and Zandbergen HW

Abstract

We present a new approach to study the three-dimensional compositional and structural evolution of metal alloys during heat treatments such as commonly used for improving overall material properties. It relies on in situ heating in a high-resolution scanning transmission electron microscope (STEM). The approach is demonstrated using a commercial Al alloy AA2024 at 100-240 °C, showing in unparalleled detail where and how precipitates nucleate, grow, or dissolve. The observed size evolution of individual precipitates enables a separation between nucleation and growth phenomena, necessary for the development of refined growth models. We conclude that the in situ heating STEM approach opens a route to a much faster determination of the interplay between local compositions, heat treatments, microstructure, and mechanical properties of new alloys.

Published
2014
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