Artifacts in Transmission Electron Microscopy - Sample Preparation Topic for Transmission Electron Microscopy - page 132

Selective dissolution : Chemical or electrolytic polishing or etching can reveal
phases if one of them dissolves more slowly than another. Selective dissolu-
tion can create an undulating surface if the flow of the dissolution layer or
bath agitation are not correctly ensured. It can cause roughness if the bath
reveals dense atomic planes and form peaks if precipitates or segregation
zones (grain boundaries, dislocations, etc.) are sensitive to the bath.
Techniques involved: electropolishing, chemical polishing, twin-jet electrolytic
thinning, full-bath electrolytic thinning, twin-jet chemical thinning, full-bath
chemical thinning, and extractive replica.
Composition change : Change in the elemental chemical composition of the
sample due to a loss or addition of chemical elements tied to contamination
or dissolution during preparation.
Techniques involved: electropolishing, chemical polishing, twin-jet electrolytic
thinning, full-bath electrolytic thinning, twin-jet chemical thinning, full-bath
chemical thinning, and extractive replica.
Structural change : Partial or total change of the crystallographic and chemi-
cal organization of a sample, caused by chemical effects. It can result in a
change in form, amorphization of the crystal network, a change in network,
or crystallization or re-crystallization.
Techniques involved: electropolishing, chemical polishing, twin-jet electrolytic
thinning, full-bath electrolytic thinning, twin-jet chemical thinning, full-bath
chemical thinning, and extractive replica.
Microstructural change : Partial or total change of the structural organization of
microstructure components, caused by ionic effects. It can result in morphol-
ogy changes, phase distribution, changes in crystal structure, precipitation,
chemical gradients, formation of new phases, etc.
Techniques involved: electropolishing, chemical polishing, twin-jet electrolytic
thinning, full-bath electrolytic thinning, twin-jet chemical thinning, full-bath
chemical thinning, and extractive replica.
2.3.1 Changes Specific to Biological Materials
Structural change : Alterations of structure at different scales, leading to the
observation of a sample that is different from the living material.
- Volume change
- Denaturing of components leading to textural changes
- Transformation of the protein gel into a reticulated structure
Techniques involved: chemical fixation.
- Transformation of membrane phospholipids into unbroken lines