Metal Catalysts and Resin Beads

[houstontx]

I was wondering if there was any possible way to analyze the surfaces of various metal catalyst powders and resin beads with a compound light microscope. This is normally done with electron microscope but could any useful data be determined with polarizing light, phase or oblique illumination? The metal powder particles will not transmit light but maybe surface edges could be visible? Polystyrene resin beads are amber colored and will transmit light or could be fractured/crushed to increase transmittance.

The goal is to be able to compare clean unused catalyst with full activity to used/spent catalyst with little to no activity. Essentially we want to be able to examine the surfaces of the catalyst after being used in a reaction and washed with various solvents.

Thanks,

[JimT]

My scientific advice is "Try it"

Can't help but as this is a hobby that's how I learn stuff. Maybe somebody else with more knowledge will chime in.

[gekko]

I agree with JimT. You may want to illuminate it from above the stage; in that case, a cover glass may give undesirable reflections, so you may need to avoid covering it, but in that case you will be limited to objectives with numerical apertures of less than 2.5 or 3 (10x or less) if you want to obtain good quality images. As JimT said, try it and see what you get.

[zzffnn]

houstontx,

You may need to use epi illumination (epi light source, polarizer/analyzer and epi objectives). Adding that to your personal Olympus scope will be expensive.

I am guessing you need to look at pores of your metal catalyst (unoccupied pore = available catalyst site, occupied = not usuable)?

The power of epi objectives required will depend on the resolution (pore size) needed and depth of focus (thickness of your catalyst particles). You may need objectives of over 20x and NA of over 0.4 for that resolution, but I am guessing here.

If you cannot get help here, maybe go to photomacrography dot net and ask in their forum. Rik, the admin there, and a few other guys are very good at optical math. If this is a professional question, you may want to consult Olympus' or Nikon's tech support.

At 10x objective or higher, your working distance may be too short to allow DIY (you may have to use epi objective which pass light to sample and collects reflected light back).

With a regular biological 4x objective, you would have enough working distance to shine LED torch light from above ( this DIY would be easy to try and you don't need any extra epi equipment). But 40x-60x total magnification may not be enough for your metal pores?

You can deal with reflection using polarized light and analyzer.

gekko, I think you made a typo there. A 10x objective usually has a NA of 0.25. Not 2.5. And pores of catalyst particles may not be resolved well with 10x objective. But I am guessing here.

[houstontx]

zzffnn,

Thats great help, this is for semi work & fun. I definitely think polarizing light would be necessary for solid metal catalysts which is in powder form. I'm sure olympus or other manufacturers have a solution for this which is extremely expensive. There is literature in journal articles. But I have yet to delve too deep.

I do have a long working distance 40x which would allow room for light from above...I have the samples sitting in front of me just need to try something.

Will look into photomacography,

Thanks,

Chris

[zzffnn]

Well, please give it a try with what you have plus a LED flashlight or diffused camera flash. That way, at least you would be able to guesstimate if your LWD 40x can resolve the pores of catalyst?

And does your LWD 40x says 0.17 (that means you need to put on cover slip)? Maybe suspend metal powers in a thin layer of water or immersion oil, if particles are fine enough?

Edit: I did a quick Google and read that most catalysts have pore size of less than 100 nm. If that is the case with your catalyst, conventional light microscopes probably won't be resolving enough (not even with 100x oil objectives, epi or not).

[gekko]

gekko, I think you made a typo there. A 10x objective usually has a NA of 0.25. Not 2.5

You are right, of course, but for one who cannot count beyond 5, a factor of 10 error may be par for the course . I concur with your advice of first trying above stage illumination of some kind to see what can be seen and determine if going to the expense of epi-illumination would be warranted.

[The QCC]

zzffnn is quite right.
The resolution of the best light microscopes are approx. 400-200 nm.

A polarizing microscope will not do much good for opaque crystals.
This is my attempt at using a polarizing microscope on crushed, ground, smashed and hammered play sand. 40x obj., crossed polars, plus a 1000 lumen LED flash light providing ambient light.
Looks pretty, but not an awful lot of light passed through the grains.

sand- 400x, crossed polares

PlaySand1_PWA_3i.jpg (49.52 KiB) Viewed 6485 times

[zzffnn]

QCC, polarizer/analyzer can be used to reduce surface light glare of metal particles. In that case, your overhead reflective light source should have one polarized filter and the other filter should be placed after objective and before eyes.

[The QCC]

All my experience with polarizers is with my microscope. It has a removable analyzer and a polarizer that is part of the condenser, thus not removable from the light path.
The light travels through the very thin, 30-90 micron slice. At 30 microns the crystal thickness is 150 times too thick to see the cavities.
It may be possible to make a thin section of the catalyst powders as thin as 10 microns with very expensive equipment..

Even using a basic compound microscope with an external polarizer and analyzer, the light microscope will not show the cavities in the crystals. That is why an electron microscope is used to view the cavities.

You will get pretty pictures of the crystals, but not the cavities.