Structural evolution of WO3 nanoclusters on ZrO2

2006 ◽  
Vol 21 (4) ◽  
pp. 807-810 ◽  
Author(s):  
C. Angeles-Chavez ◽  
M.A. Cortes-Jácome ◽  
E. Torres-Garcia ◽  
J.A. Toledo-Antonio
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
High Resolution ◽  
Crystal Size ◽  
Direct Evidence ◽  
Structural Evolution ◽  
Precipitation Method ◽  
Orthorhombic Structure ◽  
Transmission Electron

Direct evidence of the transformation of WOx species in WO3 nanoclusters on WOx–ZrO2 system was achieved by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy on samples obtained by a conventional precipitation method and annealed from 560 to 800 °C. WO3 Nanoclusters with 2-nm crystal size orthorhombic structure were identified on the ZrO2 surface after annealing at 800 °C.

Study of Triangle-Shaped Defects on Nearly On-Axis 4H-SiC Substrates

2016 ◽  
Vol 858 ◽  
pp. 225-228 ◽  
Author(s):  
Ren Wei Zhou ◽  
Xue Chao Liu ◽  
Hui Jun Guo ◽  
H.K. Kong ◽  
Er Wei Shi
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
High Resolution ◽  
Optical Microscopy ◽  
Epitaxial Growth ◽  
Surface Defects ◽  
Micro Raman Spectroscopy ◽  
Transmission Electron

Triangle-shaped defects are one of the most common surface defects on epitaxial growth of 4H-SiC epilayer on nearly on-axis SiC substrate. In this paper, we investigate the feature and structure of such defects using Nomarski optical microscopy (NOM), micro-Raman spectroscopy and high resolution transmission electron microscopy (HR-TEM). It is found that triangle-shaped defects were composed of a thick 3C-SiC polytype, as well as 4H-SiC epilayer.

HRTEM study of crystal structures and microstructures of High-Te superconductors YBa2−xSrxCu3Oy (x=0-1.2)

1990 ◽  
Vol 48 (4) ◽  
pp. 58-59
Author(s):  
Yoshio Matsui ◽  
Uk Lee ◽  
Akira Ono ◽  
Shigeo Horiuchi ◽  
Chusei Tsuruta
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Crystal Structures ◽  
Twin Plane ◽  
Orthorhombic Structure ◽  
High Tc ◽  
Domain Structures ◽  
Transmission Electron ◽  
Cation Sites

High-Tc superconducting oxide YBa2Cu3Oy has an orthorhombic structure (a=0. 382, b=0. 389 and c=1. 17nm) with layer sequences of (..BaO CuOx BaO CuO2 Y CuO2 BaO CuOx BaO..) along the c-axis. It usually has twinned microstructure with twin plane {110}, causing associated splitting of some of the diffraction spots. It is well known that these characteristic structures of YBa2Cu3Oy can be affected by partial substitutions of cation sites. For instance, tetragonal structure with a=b is stabilized in the compounds Ba2−xLa1+xCu3Oy and Ba2−xNd1+xCu3Oy . Formations of 90-degree domain structures are also observed in these compounds. Recently, Ono et al. prepared a series of compounds, YBa2−xSrxCu3Oy (x=0 to 1.2), to study the effects of substituting Ba by Sr and found the gradual decrease of Tc with increase of x. In the present study, change of the crystal structures and the microstructures in a series of compounds are examined by means of high-resolution transmission electron microscopy.

Correlation Between Electrical Properties and Composition / Microstructure of Si-C-N Ceramics

1997 ◽  
Vol 500 ◽  
Author(s):  
C. Haluschka ◽  
C. Engel ◽  
R. Riedel ◽  
H.-J. Kleebe ◽  
R. Franke
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Chemical Composition ◽  
High Resolution ◽  
Electrical Properties ◽  
Microstructural Characteristics ◽  
X Ray ◽  
Transmission Electron ◽  
X Ray Absorption

ABSTRACTIn this paper we report on the measurement of electrical properties of multielement ceramics in the ternary Si-C-N system using the impedance spectroscopy. The results were correlated to the chemical composition, the hybridization state and the microstructural characteristics investigated by chemical analysis, X-Ray absorption near edge spectroscopy (XANES), Raman Spectroscopy, high resolution transmission electron microscopy (HRTEM) and X-Ray powder diffraction (XRD).

Electron beam-induced surface modification and nano-engineering of carbon nanotubes: Single-walled and multiwalled

2006 ◽  
Vol 21 (12) ◽  
pp. 3109-3123 ◽  
Author(s):  
S. Gupta ◽  
R.J. Patel ◽  
R.E. Giedd
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Raman Spectroscopy ◽  
Electron Beam ◽  
Electron Microscope ◽  
High Resolution ◽  
Band Intensity ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

Influence of low and medium energy electron beam (E-beam) irradiation on the single-walled (SW) and multiwalled (MW) carbon nanotube films grown by microwave chemical vapor deposition are investigated. These films were subjected to electron beam energy of 50 keV from scanning electron microscope for 2.5, 5.5, 8.0, and 15 h and 100, 200, and 300 keV from transmission electron microscope electron gun for a few minutes to approximately 2 h continuously. To assess the surface modifications/structural degradation, the films were analyzed prior to and post-irradiation using x-ray diffraction and micro-Raman spectroscopy in addition to in situ monitoring by scanning and high-resolution transmission electron microscopy. A minimal increase in intertube or interplanar spacing (i.e., d002) for MW nanotubes ranging from 3.25–3.29 Å (∼3%) can be analogized to change in c-axis of graphite lattice due to thermal effects measured using x-ray diffraction. Resonance Raman spectroscopy revealed that irradiation generated defects in the lattice evaluated through variation of: the intensity of radial breathing mode (RBM), intensity ratio of D to G band (ID/IG), position of D and G bands and their harmonics (D* and G*). The increase in the defect-induced D band intensity, quenching of RBM intensity, and only a slight increase in G band intensity are some of the implications. The MW nanotubes tend to reach a state of saturation for prolonged exposures, while SW transforming semiconducting to quasi-metallic character. Softening of the q = 0 selection rule is suggested as a possible way to explain these results. It is also suggestive that knock-on collision may not be the primary cause of structural degradation, rather a local gradual reorganization, i.e., sp2+δ ⇔ sp2+δ, sp2 C seems quite possible. Experiments showed that with extended exposures, both kinds of nanotubes displayed various local structural instabilities including pinching, graphitization/amorphization, and forming intra-molecular junction (IMJ) within the area of electron beam focus possibly through amorphous carbon aggregates. They also displayed curling and closure forming nano-ring and helix-like structures while mending their dangling bonds. High-resolution transmission electron microscopy electrons corroborated these conclusions. Manufacturing of nanoscale structures “nano-engineering” of carbon-based systems is tentatively ascribed to irradiation-induced solid-state phase transformation, in contrast to conventional nanotube synthesis from the gas phase.

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