Electron Microscopy Study of Fatigue Crack Initiation in Ni3Al Single Crystals

1988 ◽  
Vol 133 ◽  
Author(s):  
L. M. Hsiung ◽  
N. S. Stoloff
Keyword(s):  
Electron Microscopy ◽  
Fatigue Crack ◽  
Crack Initiation ◽  
Single Crystals ◽  
Room Temperature ◽  
Fatigue Crack Initiation ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Dislocation Loops ◽  
Defect Clusters

ABSTRACTTransmission electron microscopy of single-slip oriented Ni3Al single crystals cyclically deformed at room temperature revealed a high density of dislocation dipoles and point defect clusters. The majority of the defect clusters were identified by weak-beam TEM to be of vacancy type. The observations of circular perfect dislocation loops, Frank loops, and spherical voids revealed the evidence of vacancy condensation during fatigue cycling at room temperature. Together with SEM observations of surface topography, it is suggested that fatigue crack initiation in Ni3Al single crystals can be rationalized by formation of microvoids at PSB/matrix interfaces.

Transmission Electron Microscopy study of Bi-based superconducting phases

1990 ◽  
Vol 48 (4) ◽  
pp. 50-51
Author(s):  
J.G. Wen ◽  
K.K. Fung
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystals ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Space Groups ◽  
Superconducting Phases ◽  
Ceramic Samples ◽  
Transmission Electron ◽  
Modulated Structures

Bi-based superconducting phases have been found to be members of a structural series represented by Bi2Sr2Can−1Cun−1On+4, n=1,2,3, and are referred to as 2201, 2212, 2223 phases. All these phases are incommensurate modulated structures. The super space groups are P2/b, NBbmb 2201, 2212 phases respectively. Pb-doped ceramic samples and single crystals and Y-doped single crystals have been studied by transmission electron microscopy.Modulated structures of all Bi-based superconducting phases are in b-c plane, therefore, it is the best way to determine modulated structure and c parameter in diffraction pattern. FIG. 1,2,3 show diffraction patterns of three kinds of modulations in Pb-doped ceramic samples. Energy dispersive X-ray analysis (EDAX) confirms the presence of Pb in the three modulated structures. Parameters c are 3 0.06, 38.29, 30.24Å, ie 2212, 2223, 2212 phases for FIG. 1,2,3 respectively. Their average space groups are all Bbmb.

Electron Microscopy Study of Submicron Size Antiferromagnetic KMnF3 Nanoparticles and Their Self-assembly

2003 ◽  
Vol 775 ◽  
Author(s):  
Jeffrey Anderson ◽  
Rubi Garcia ◽  
Weilie L. Zhou
Keyword(s):  
Electron Microscopy ◽  
Self Assembly ◽  
Room Temperature ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Submicron Particles ◽  
Spherical Particles ◽  
Large Area ◽  
Homogeneous Crystal ◽  
Field Emission Electron Microscopy

AbstractSubmicron KMnF3 cubic and spherical nanoparticles were synthesized using the reverse micelle method. The nanostructures of the nanocrystals were studied by field emission electron microscopy and transmission electron microscopy. KMnF3 nanocrystals synthesized at room temperature started with cubic submicron particles (∼100 nm) and consisted of KMnF3 nanocrystallites (10-15 nm). As the reaction continued, the nanocrystals fused together and transformed into perfect cubic nanocrystals. Spherical beads composed of KMnF3 nanocrystallites were observed at low temperature synthesis. As the reaction continued, the spherical particles grew larger, however, no characteristic cubic shape of KMnF3 nanoparticles were observed. Even as they grew larger, there was no evidence of homogeneous crystal morphology as seen in the room temperature samples. Cubic shape KMnF3 nanocrystals were self-assembled into large area self-assembling patterns.

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