Author Topic: Finding density from Continuum  (Read 62 times)

emma_fisi

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Finding density from Continuum
« on: May 10, 2019, 07:40:19 am »
Hi Probe Hive-mind,

I have a question about obtaining density from probe/SEM data.

We've been doing large grids of analyses using Probe Software and the Thermo EDS system (Pathfinder), in order to try and determine the bulk composition of some meteorites. In order to get at the true bulk composition, we need to know the density of each phase, in addition to its chemistry. Whereas olivine/sulfide/metal grains are easy - the densities for different compositions have already been determined - the meteorite matrix is made up of clay-like stuff, and the density of this material is not known.

Does anyone out there know of any method that can take the EDS spectra that we have collected, and, using the chemistry, calculate the density? I have heard of methods of using the EDS background to determine density, but I am not sure of how to do this in practice.

As always, any help is greatly appreciated.
Em

Probeman

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Re: Finding density from Continuum
« Reply #1 on: May 16, 2019, 10:35:39 am »
We've been doing large grids of analyses using Probe Software and the Thermo EDS system (Pathfinder), in order to try and determine the bulk composition of some meteorites. In order to get at the true bulk composition, we need to know the density of each phase, in addition to its chemistry. Whereas olivine/sulfide/metal grains are easy - the densities for different compositions have already been determined - the meteorite matrix is made up of clay-like stuff, and the density of this material is not known.

Does anyone out there know of any method that can take the EDS spectra that we have collected, and, using the chemistry, calculate the density? I have heard of methods of using the EDS background to determine density, but I am not sure of how to do this in practice.

As always, any help is greatly appreciated.
Em

Hi Emma,
I've been thinking about this for a few days and I'm drawing a blank on what physics would allow a determination of density at the micro scale.

You mentioned a method using EDS continuum spectra, but do you have any more info about this method?

Unless the sample was a film of known composition and thickness, I can't think of a way one might determine density.  Because if one knows the mass thickness and linear thickness, the density falls out nicely, but otherwise I can't think of anything.
john
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emma_fisi

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Re: Finding density from Continuum
« Reply #2 on: May 16, 2019, 12:39:43 pm »
Hi John,

I have found a paper by Zanetta (see attached) that claims to be able to do such a thing, but to be honest, I am not sure I understand what they are doing. It looks to involve modeling of the continuum, combined with point analyses to check the chemistry of particular phases.

Cheers,
Em