Morphology of Nanometric Boron Nitride Powders Produced by Laser Pyrolysis

1994 ◽  
Vol 359 ◽  
Author(s):  
F. Willaime ◽  
L. Boulanger ◽  
M. Cauchetier
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
High Resolution ◽  
Boron Nitride ◽  
Carbon Materials ◽  
High Resolution Electron Microscopy ◽  
Nitrogen Atmosphere ◽  
Major Constituent ◽  
Structure And Morphology ◽  
Resolution Electron

ABSTRACTUltrafine boron nitride powders were synthesized by laser driven reactions in BC13-NH3 mixtures. The structure and morphology of the graphitic nanoparticles generated in this process were investigated by high-resolution electron microscopy. Polyhedral concentric shells (ranging in size from 30 nm to more than 100 nm) are a major constituent of the as-pyrolyzed powder. This onion-like configuration is very similar to that observed in carbon materials. After heat treatment at 1650°C under nitrogen atmosphere, plate-like particles with a few perfectly flat graphitic sheets (10 to 50 layer thick, 50 nm in diameter) are formed.

Fine structure of crack in ceramics

1984 ◽  
Vol 42 ◽  
pp. 402-403
Author(s):  
Hiroshi Kakibayashi ◽  
Fumio Nagata
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Heat Conduction ◽  
Silicon Nitride ◽  
High Resolution ◽  
High Resolution Electron Microscopy ◽  
Nitrogen Atmosphere ◽  
Ion Etching ◽  
Resolution Electron ◽  
Shock Resistance

Many kinds of ceramics have been developed providing enough insulation, heat conduction or shock resistance. For the characteristics of strong toughness of the ceramics, movements of cracks by applying a force are noteworthy, because most ceramics are hardly distorted.In the present works, behavior of cracks in ceramics is observed with high resolution electron microscopy. Silicon nitride (Si3N4) ceramics were made by sintering in nitrogen atmosphere at 1800°C. Some Y2O3 and AlN were added to assist the sintering. A piece of the ceramics was sliced and polished mechanically untill 20μm in thickness. The specimen was mounted on a single hole grid, and was thinned with an ion etching equipment to be thin enough to observe.

Grain Boundary Transformations in Bi-Doped Copper

1991 ◽  
Vol 238 ◽  
Author(s):  
Elsie C. Urdaneta ◽  
David E. Luzzi ◽  
Charles J. McMahon
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Treatment Time ◽  
High Resolution Electron Microscopy ◽  
Transmission Electron ◽  
Resolution Electron

ABSTRACTBismuth-induced grain boundary faceting in Cu-12 at ppm Bi polycrystals was studied using transmission electron microscopy (TEM). The population of faceted grain boundaries in samples aged at 600°C was observed to increase with heat treatment time from 15min to 24h; aging for 72h resulted in de-faceting, presumably due to loss of Bi from the specimen. The majority of completely faceted boundaries were found between grains with misorientation Σ=3. About 65% of the facets of these boundaries were found to lie parallel to crystal plane pairs of the type {111}1/{111]2- The significance of these findings in light of recent high resolution electron microscopy experiments is discussed.

High Resolution Electron Microscopy studies of the degradation process of the calcium A zeolite

1986 ◽  
Vol 44 ◽  
pp. 852-853
Author(s):  
D.R. Acosta N.
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Thermal Treatment ◽  
Amorphous State ◽  
High Resolution Electron Microscopy ◽  
Degradation Process ◽  
Auger Spectroscopy ◽  
Nitrogen Atmosphere ◽  
Vacuum Line ◽  
Resolution Electron

The change from the crystalline to the amorphous state of the sodium A zeolite, has been investigated by Bursill and by Thomas. From individual HREM pictures those authors suggest three different mechanisms responsible for the degradation process. In the present work the degradation of the calcium A zeolite, characterized also by Auger spectroscopy, was studied by HREM methods. The sample was under thermal treatment at 450°C during four hours in a vacuum line after which it was mounted in the microscope in a nitrogen atmosphere.

Catalyst-Free Synthesis of Single-Wall Boron Nitride Nanotubes via Laser Ablation

2000 ◽  
Vol 633 ◽  
Author(s):  
Roland S. Lee ◽  
Julie Gavillet ◽  
Marc Lamy de la Chapelle ◽  
Jean-Lou Cochon ◽  
Daniel Pigache ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Laser Ablation ◽  
Chemical Composition ◽  
High Resolution ◽  
Boron Nitride ◽  
Energy Loss ◽  
High Resolution Electron Microscopy ◽  
Boron Nitride Nanotubes ◽  
Resolution Electron ◽  
Electron Energy Loss

AbstractBoron nitride nanotubes (BN-NTs) were synthesized in “mass” quantities (∼0.6 g/h) using a continuous CO2 laser ablation reactor described in the literature [1]. High-resolution electron microscopy (HRTEM) analyses have shown the nanotubes to be organized in “ropes” comprising ∼10 tubes. Analysis of HRTEM images indicate that the majority of the tubes are zig-zag. The chemical composition of the tubes was confirmed using electron energy loss spectroscopy (EELS) analysis, which also determined that nanoparticles terminating tube ends were composed of pure boron covered by BN fullerene-like “cages”. The growth mechanism of the nanotubes seems to be “root-based” with tubes growing from boron nanoparticles dispersed throughout the samples; the non-particle-terminated ends of the tubes exhibit flat “caps” characteristic of BN-NTs [2].

Multi-and Single-Walled Boron Nitride Nanotubes Produced From Carbon Nanotubes by a Substitution Reaction

1999 ◽  
Vol 593 ◽  
Author(s):  
D. Golberg ◽  
Y. Bando ◽  
W. Han ◽  
L. Bourgeois ◽  
K. Kurashima ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Boron Nitride ◽  
High Resolution Electron Microscopy ◽  
Nitrogen Atmosphere ◽  
Boron Nitride Nanotubes ◽  
Boron Trioxide ◽  
Resolution Electron ◽  
Electron Energy Loss ◽  
C Nanotubes

ABSTRACTBoron nitride (BN) multi-walled (MWNT) or single-walled (SWNT) nanotubes were synthesized from carbon MWNT and SWNT templates, respectively, under heating of C nanotubes together with boron trioxide in a flowing nitrogen atmosphere. B and N atom substitution for C atoms in the nanotubular shells during C oxidation by the B2O3 vapor in the N2 flow is thought to underlie the formation mechanism. Structural and chemical BN MWNT/SWNT analyses were performed by means of high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS), respectively. In particular, BN MWNT shell structure and defects, and electron irradiation stability were studied. Finally, the prospects of using the substitution technique for the synthesis of other advanced nanostructures made of BN (nanorods, nanoplates and nanocones) are discussed.

Sign in / Sign up

Export Citation Format

Share Document