Currently have a Zeiss Sigma SEM outfitted with a EDS and EBSD camera. I want to measure the volume fraction of Mg2Si particles in a small area, these particles may measure only a 20-30 nanometers in length. Is this possible to do with this setup, or will my samples need to be sent off to be measured using TEM or EPMA?
You cannot estimate a volume fraction with TEM. Period. The attached diagrams will tell you why.
But it's a well known fact that a volume fraction is equal to a surface fraction on a cross section. For phases big enough TEM specimens are very close to cross sections, so no problems in measuring a volume fraction (and I do not understand why do you need these pictures with cubical structures). Of course for features as small as 20 nm TEM foils are not equal to cross sections. It is quite possible that stereology now is developed good enough to include this particular case in its scope.
@ Sam Bacurin As for using EDS... I just wonder if you can estimate what part of alloying elements is still in solid solution and what part had already precipitated.
Vladimir Dusevich Yes, you are correct in theory - a surface fraction (if representative) will equate to a volume fraction. I can provide a reference for this. However, consider a group of monodisperse 500 nm diameter spheres. There is only one size in this material. Consider taking 100 nm thick slices with a microtome. You'll end up with a distribution of discs of which the largest (occasionally seen) will reflect the true diameter of 500 nm. The average size will be 250 nm in diameter with an incredibly wide spread. Sample preparation has created polydispersity from a monodisperse sample. Think it can't happen? Happened to NBS in the 1950's with polystyrene emulsion polymerized standards dispersed in epoxy resin and microtomed.
Another example. Consider you want to measure the % of the body occupied by the liver. A vertical slice will be totally different to a horizontal slice and, in the latter, some slices won't even show the liver.
Everything under TEM is an artifact of sample preparation and selection.
Alan F Rawle
What you said about spheres is a case well described by stereology. Nothing unusual. As for liver example, it is beyond the scope of stereology - it does not work with singular objects. However, it's volume fraction could be measured if enough randomly choosen dissection planes was used. Not really a problem.
Wafaa Alhashemi
No, EDS software cannot answer specific metallurgical questions.
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