Stacking Faults in SiC Nanowires

2008 ◽  
Vol 8 (7) ◽  
pp. 3504-3510 ◽  
Author(s):  
K. L. Wallis ◽  
M. Wieligor ◽  
T. W. Zerda ◽  
S. Stelmakh ◽  
S. Gierlotka ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Stacking Faults ◽  
Multiwall Carbon Nanotubes ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
Ir Spectrometry ◽  
X Ray ◽  
Sic Nanowires ◽  
Transmission Electron ◽  
Multiwall Carbon

SiC nanowires were obtained by a reaction between vapor silicon and multiwall carbon nanotubes, CNT, in vacuum at 1200 °C. Raman and IR spectrometry, X-ray diffraction and high resolution transmission electron microscopy, HRTEM, were used to characterize properties of SiC nanowires. Morphology and chemical composition of the nanowires was similar for all samples, but concentration of structural defects varied and depended on the origin of CNT. Stacking faults were characterized by HRTEM and Raman spectroscopy, and both techniques provided complementary results. Raman microscopy allowed studying structural defects inside individual nanowires. A thin layer of amorphous silicon carbide was detected on the surface of nanowires.

Formation of U-type hexaferrites

2004 ◽  
Vol 19 (8) ◽  
pp. 2462-2470 ◽  
Author(s):  
Darja Lisjak ◽  
Darko Makovec ◽  
Miha Drofenik
Keyword(s):  
Crystal Structure ◽  
Electron Microscopy ◽  
Stacking Faults ◽  
High Energy ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Calcination Temperatures ◽  
Intermediate Phases ◽  
Transmission Electron

The formation of U-type hexaferrites with the composition Ba4B2Fe36O60 (B = Co, Ni, Zn) was studied. Samples were characterized by means of x-ray diffraction, electron microscopy (with energy-dispersive spectroscopy), and thermogravimetric and thermomagnetic analyses. U-hexaferrites are formed from the intermediate phases M-hexaferrite (BaFe12O19) and Y-hexaferrite (Ba2B2Fe12O22), which at the same time represent units in the U-hexaferrites’ crystal structure. The preparation of monophase U-hexaferrites was made possible by combining high-energy milling or chemical coprecipitation with a calcination at 1250–1300 °C. Structural defects, such as stacking faults, were observed in monophase samples with a high-resolution transmission electron microscope. The observed defects can be regarded as seeds for the formation of other hexaferrite phases after prolonged calcination times or higher calcination temperatures.

Comparison of Cobalt Based Catalysts Supported on MWCNT and SBA-15 Supporters for Fischer-Tropsch Synthesis by Using Autoclave Type Reactor

2011 ◽  
Vol 364 ◽  
pp. 70-75 ◽  
Author(s):  
Adkham Yakubov ◽  
M.G. Kutty ◽  
Pei Lee Siew ◽  
Maizatul S. Shaharun ◽  
S.B. Abd Hamid ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Multiwall Carbon Nanotubes ◽  
Incipient Wetness Impregnation ◽  
Impregnation Method ◽  
Santa Barbara ◽  
X Ray ◽  
Transmission Electron ◽  
Temperature Programmed ◽  
Multiwall Carbon ◽  
Autoclave Reactor

10 and 40 wt% Co/Multiwall Carbon Nanotubes (MWCNT) and 10 and 40 wt% Co/Santa Barbara Amorphous-15 (SBA-15) catalysts were prepared via incipient wetness impregnation method. It was characterized by Scanning Electron Microscopy, BET, X-ray Diffractometry (XRD), Transmission Electron Microscopy (TEM), Temperature-Programmed Reduction and H2Desorption. A 200 ml hastelloy autoclave reactor was implemented to see the performance of the catalysts. It was observed that the performance of 40 wt% Co/SBA-15 was higher that other catalysts in terms of production of longer chain paraffins.

scholarly journals Sol-Gel Derived Eu3+-Doped Gd2Ti2O7Pyrochlore Nanopowders

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Sanja Ćulubrk ◽  
Željka Antić ◽  
Vesna Lojpur ◽  
Milena Marinović-Cincović ◽  
Miroslav D. Dramićanin
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Structural Changes ◽  
Sol Gel ◽  
Pyrochlore Phase ◽  
Structural Defects ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Sol Gel Synthesis

Herein we presented hydrolytic sol-gel synthesis and photoluminescent properties of Eu3+-doped Gd2Ti2O7pyrochlore nanopowders. According to Gd2Ti2O7precursor gel thermal analysis a temperature of 840°C is identified for the formation of the crystalline pyrochlore phase. Obtained samples were systematically characterized by powder X-ray diffraction, scanning and transmission electron microscopy, and photoluminescence spectroscopy. The powders consist of well-crystalline cubic nanocrystallites of approximately 20 nm in size as evidenced from X-ray diffraction. The scanning and transmission electron microscopy shows that investigated Eu3+-doped Gd2Ti2O7nanopowders consist of compact, dense aggregates composed entirely of nanoparticles with variable both shape and dimension. The influence of Eu3+ions concentration on the optical properties, namely, photoluminescence emission and decay time, is measured and discussed. Emission intensity as a function of Eu3+ions concentration shows that Gd2Ti2O7host can accept Eu3+ions in concentrations up to 10 at.%. On the other hand, lifetime values are similar up to 3 at.% (~2.7 ms) and experience decrease at higher concentrations (2.4 ms for 10 at.% Eu3+). Moreover, photoluminescent spectra and lifetime values clearly revealed presence of structural defects in sol-gel derived materials proposing photoluminescent spectroscopy as a sensitive tool for monitoring structural changes in both steady state and lifetime domains.

scholarly journals Composite Nanofibers Containing Multiwall Carbon Nanotubes as Biodegradable Membranes in Reconstructive Medicine

Nanomaterials ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 63 ◽  
Author(s):  
Andrzej Hudecki ◽  
Dorota Łyko-Morawska ◽  
Wirginia Likus ◽  
Magdalena Skonieczna ◽  
Jarosław Markowski ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Maxillofacial Surgery ◽  
Multiwall Carbon Nanotubes ◽  
Dermal Fibroblasts ◽  
Hydroxyl Groups ◽  
X Ray ◽  
Biological Responses ◽  
Transmission Electron ◽  
Multiwall Carbon

We have tested titanium (Ti) plates that are used for bone reconstruction in maxillofacial surgery, in combination with five types of novel long-resorbable biomaterials: (i) PCL0—polycaprolactone without additives, (ii) PCLMWCNT—polycaprolactone with the addition of multiwall carbon nanotubes (MWCNT), (iii) PCLOH—polycaprolactone doped with multiwall carbon nanotubes (MWCNT) containing –OH hydroxyl groups, (iv) PCLCOOH—polycaprolactone with the addition of multiwall carbon nanotubes (MWCNT) containing carboxyl groups, and (v) PCLTI—polycaprolactone with the addition of Ti nanoparticles. The structure and properties of the obtained materials have been examined with the use of Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and/or X-ray powder diffraction (XRD). Titanium BR plates have been covered with: (i) PCL0 fibers (PCL0BR—connection plates), (ii) PCLMWCNT fibers (PCLMWCNTBR—plates), (iii) PCLOH fibers (PCLOHBR—plates), (iv) PCLCOOH (PCLCOOHBR—plates), (v) PCLTI fiber (PCLTIBR—connection plates). Such modified titanium plates were exposed to X-ray doses corresponding to those applied in head and neck tumor treatment. The potential leaching of toxic materials upon the irradiation of such modified titanium plates, and their effect on normal human dermal fibroblasts (NHDF) have been assessed by MTT assay. The presented results show variable biological responses depending on the modifications to titanium plates.

High-density stacking faults in a supersaturated nitrided layer on austenitic stainless steel

2016 ◽  
Vol 49 (6) ◽  
pp. 1967-1971 ◽  
Author(s):  
Ke Tong ◽  
Fei Ye ◽  
Honglong Che ◽  
Ming Kai Lei ◽  
Shu Miao ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Nitrided Layer ◽  
Stacking Faults ◽  
High Density ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron

The nitrogen-supersaturated phase produced by low-temperature plasma-assisted nitriding of austenitic stainless steel usually contains a high density of stacking faults. However, the stacking fault density observed in previous studies was considerably lower than that determined by fitting the X-ray diffraction pattern. In this work, it has been confirmed by high-resolution transmission electron microscopy that the strip-shaped regions of about 3–25 nm in width observed at relatively low magnification essentially consist of a series of stacking faults on every second {111} atomic plane. A microstructure model of the clustered stacking faults embedded in a face-centred cubic structure was built for these regions. The simulated X-ray diffraction and transmission electron microscopy results based on this model are consistent with the observations.

Microstructure of Carbon Encapsulated Superparamagnetic Co Nanoparticles

2001 ◽  
Vol 704 ◽  
Author(s):  
Xiang-Cheng Sun ◽  
J. Reyes-Gasga ◽  
X. L. Dong
Keyword(s):  
Electron Microscopy ◽  
Arc Discharge ◽  
Stacking Faults ◽  
Good Evidence ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Lattice Images ◽  
Co Nanoparticles ◽  
Discharge Method

AbstractCarbon encapsulated magnetic Co nanoparticles have been synthesized by modified arc-discharge method. Both high-resolution transmission electron microscopy (HREM) and powder x-ray diffraction (XRD) profiles reveal the presence of 8-15nm diameter crystallites coated with 1-3 carbon layers. Specially, HREM images indicate that the intimate and contiguous carbon fringe around those Co nanoparticles is good evidence for complete encapsulation by carbon shell layers. The encapsulated phases are identified as hcp (α)-Co, fcc (β)-Co and cobalt carbide (Co3C) nanocrystals by using x-ray diffraction, electron diffraction and energy dispersive x-ray analysis. However, some fcc (β)-Co particles with a significant fraction of stacking faults are observed by HREM and confirmed by means of numerical Fourier transform (FFT) of HREM lattice images. In particular, the carbon encapsulation formation and growth mechanism are also reviewed.

Reduction of Structural Defects in Ge Epitaxially Grown on Nano-Structured Si Islands on SOI Substrate

2013 ◽  
Vol 205-206 ◽  
pp. 400-405
Author(s):  
Peter Zaumseil ◽  
Yuji Yamamoto ◽  
Markus Andreas Schubert ◽  
Thomas Schroeder ◽  
Bernd Tillack
Keyword(s):  
Electron Microscopy ◽  
Vapor Deposition ◽  
Strain State ◽  
Chemical Vapor ◽  
Structural Defects ◽  
Misfit Dislocations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Nanostructured Si

One way to further increase performance and/or functionality of Si micro-and nanoelectronics is the integration of alternative semiconductors on silicon (Si). We studied the Ge/Si heterosystem with the aim to realize a Ge deposition free of misfit dislocations and with low content of other structural defects. Ge nanostructures were selectively grown by chemical vapor deposition on periodic Si nanoislands (dots and lines) on SOI substrate either directly or with a thin (about 10 nm) SiGe buffer layer. The strain state of the structures was measured by different laboratory-based x-ray diffraction techniques. It was found that a suited SiGe buffer improves the compliance of the Si compared to direct Ge deposition; plastic relaxation during growth can be prevented, and fully elastic relaxation of the structure can be achieved. Transmission electron microscopy confirms that the epitaxial growth of Ge on nanostructured Si is free of misfit dislocations.

Growth and Photoluminescence of β-SiC Nanowires on Porous Silicon Array

2013 ◽  
Vol 662 ◽  
pp. 11-15
Author(s):  
Hai Yan Wang ◽  
Li Ping Kang ◽  
Yong Qiang Wang ◽  
Zi Jiong Li
Keyword(s):  
Electron Microscopy ◽  
Porous Silicon ◽  
Chemical Vapor ◽  
Chemical Vapor Deposition Method ◽  
Fluorescent Light ◽  
X Ray Diffraction ◽  
X Ray ◽  
Sic Nanowires ◽  
Quantum Confinement Effects ◽  
Transmission Electron

Nonaligned and curly β-SiC nanowires (nw-SiC) were grown on porous silicon array (PSA) by a chemical vapor deposition method with nickel as the catalyst. The morphology, structure and the composition of the nw-SiC/PSA and the SiC-SiO2core-shell fibers which is the semi-product were characterized by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. Based on the experimental results a possible growth mechanism of nw-SiC was explained. Two broad photoluminescence peaks located around ~409 and ~494 nm were observed in nw-SiC/PSA in the PL measurement when utilizing 300 nm ultraviolet fluorescent light excited at room temperature. The excellent luminescent performances are ascribed to the quantum confinement effects in nw-SiC. The optical merits of nw-SiC/PSA made it a promising material in the fields of ultraviolet-blue emitting devices.

Effect of Urea on the Shape and Structure of Carbon Nanotubes

2018 ◽  
Vol 73 (2) ◽  
pp. 113-120 ◽  
Author(s):  
M. R. Elamin ◽  
Babiker Y. Abdulkhair ◽  
Kamal K. Taha
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Chemical Vapour ◽  
Multiwall Carbon Nanotubes ◽  
Nitrogen Adsorption ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Adsorption Analysis ◽  
Bet Analysis ◽  
Multiwall Carbon

AbstractCoiled multiwall carbon nanotubes (MWCNTs) were prepared on Fe, Co, and Ni metal oxides supported on α-Al2O3 using urea as fuel and catalyst surface modifying agent by catalytic chemical vapour deposition (CCVD). The shape of the nanotubes was influenced by the addition of urea, where coiled and uncoiled tubes were obtained in the presence and absence of urea, respectively. The MWCNTs were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and nitrogen adsorption analysis. The coiling/uncoiling of the nanotubes was visualized from the SEM and TEM images of the prepared specimens. The XRD data showed the characteristic peaks of the nanotubes. BET analysis of the coiled tubes revealed 85.57 m2 g−1 surface area with a pore diameter 102.2–110.8 Å. A mechanism for the nanotubes coiling is suggested.

Manifestation of structural defects in photoluminescence from GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
M. A. Reshchikov ◽  
J. Jasinski ◽  
F. Yun ◽  
L. He ◽  
Z. Liliental-Weber ◽  
...  
Keyword(s):  
Point Defects ◽  
Molecular Beam ◽  
Stacking Faults ◽  
Structural Defects ◽  
Large Set ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
X Ray ◽  
Transmission Electron ◽  
Gan Crystal

ABSTRACTSharp peaks of unidentified nature are detected in the low-temperature photoluminescence (PL) spectrum of undoped GaN in the photon energy range between 3.0 and 3.46 eV. These PL lines are commonly attributed to excitons bound to yet unidentified structural defects. We analyzed X-ray diffraction data in a large set of GaN samples grown by molecular beam epitaxy in order to find any correlation between these unusual PL peaks and the GaN crystal structure. Moreover, in selected samples exhibiting such peaks, cross-sectional transmission electron microscopy was taken in an effort to detect the presence and density of various structural defects. The preliminarily results indicate that most of unusual PL lines in GaN (Y lines) are not directly related to the observed structural defects, such as edge, screw, mixed dislocations, or stacking faults. However, there exists the possibility that point defects trapped at dislocations or other structural defects are responsible for these PL lines.

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