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.

High-resolution Electron Microscopy Observation of Grain-boundary Films in Superplastically Deformed Silicon Nitride

2000 ◽  
Vol 15 (7) ◽  
pp. 1551-1555 ◽  
Author(s):  
Guo-Dong Zhan ◽  
Mamoru Mitomo ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
High Resolution ◽  
Grain Boundary ◽  
Applied Stress ◽  
Thickness Distribution ◽  
High Resolution Electron Microscopy ◽  
Stress Axis ◽  
Resolution Electron ◽  
Boundary Films

The thickness distribution of grain-boundary films during the superplastic deformation of fine-grained β–silicon nitride was investigated by high-resolution electron microscopy. In particular, grain-boundary thickness was considered with respect to the stress axis in two orientations; namely, parallel and perpendicular to the direction of applied stress. The results showed that the thickness distribution in boundaries perpendicular to the direction of applied stress was unimodal, whereas in parallel boundaries it was bimodal. Moreover, it was found that the majority of film-free boundaries were parallel to the direction of applied stress in the extremely deformed sample. The variation in spacing reflects distribution of stresses within the material due to irregular shape of the grains and the existence of percolating load-bearing paths through the microstructure.

High-Resolution Electron Microscopy Observations of Grain-Boundary Films in Silicon Nitride Ceramics

1992 ◽  
Vol 287 ◽  
Author(s):  
H.-J. Kleebe ◽  
M. K. Cinibulk ◽  
I. Tanaka ◽  
J. Bruley ◽  
R. M. Cannon ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
High Resolution ◽  
Grain Boundary ◽  
Film Thickness ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Nitride Ceramics ◽  
Boundary Films ◽  
Repulsive Forces

ABSTRACTCharacterization of silicon nitride ceramics by transmission electron microscopy (TEM) provides structural and compositional information on intergranular phases necessary to elucidate the factors that can influence the presence and thickness of grain-boundary films. Different TEM techniques can be used for the detection and determination of intergranular-film thickness, however, the most accurate results are obtained by high-resolution electron microscopy (HREM). HREM studies were applied, in conjunction with analytical electron microscopy, to investigate the correlation between intergranular-phase composition and film thickness. Statistical analyses of a number of grain-boundary films provided experimental verification of a theoretical equilibrium film thickness. Model experiments on a high-purity Si3N4 material, doped with low amounts of Ca, suggest the presence of two repulsive forces, a steric force and a force produced by an electrical double layer, that may act to balance the attractive van der Waals force necessary to establish an equilibrium film thickness.

Cubic silicon nitride embedded in amorphous silicon dioxide

2001 ◽  
Vol 16 (8) ◽  
pp. 2179-2181
Author(s):  
Ming Zhang ◽  
Hongliang He ◽  
F. F. Xu ◽  
T. Sekine ◽  
T. Kobayashi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Silicon Nitride ◽  
High Resolution ◽  
Analytical Electron Microscopy ◽  
High Resolution Electron Microscopy ◽  
Cubic Symmetry ◽  
Resolution Electron ◽  
Microscopy Image ◽  
Wave Compression ◽  
Small Crystallite

A cubic silicon nitride embedded in amorphous SiO2 compound has been characterized by means of high-resolution analytical electron microscopy. The specimen was prepared from β–Si3N4 powders at a high pressure and temperature by shock wave compression. The typical high-resolution electron microscopy image from one small crystallite together with its diffractodiagram pattern indicated that the Si3N4 crystallites had a cubic symmetry. The electron energy loss spectrum from the small crystallite is very different from those of outside amorphous SiO2 phase and raw β–Si3N4 particles, and there are more N elements that were detected in this small crystallite than those in standard Si3N4.

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.

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