I need the particle size and the shape of graphene oxide in epoxy powder as shown in the following FESEM morphology
Dear Dina Raheem, It is challenging to identify with certainty the shape of the graphene oxide nanoparticles in the epoxy powder based on the image you sent.
The nanoparticles, likely sub-micron in size, have an irregular, plate-like shape. They are well dispersed within the epoxy powder, although some agglomeration is visible.
What sort of contrast would you expect to see? You are mixing particles of carbon with some oxygen (GO) into a matrix of carbon with some oxygen and hydrogen (epoxy). Where will the contrast come from?
The atomic number is about the same, so there will be little or no contrast in the BSE image.
The particles are supposedly embedded or encapsulated by the epoxy so you may not have much topographical contrast in SE or BSE.
The composition is virtually the same, so Thomas Breuer
, there will be nothing to see in an x-ray map. That will be all the more true given the small feature size and that you are using 30 kV. The excitation volume is over 4 um deep in C. How will you see something smaller than 100 nm.Two other things.
Your sample appears to be coated with a metal. I would guess Au but maybe Pt. The texture you see on the surface is from the coating. Once we got our field-emission FEI Quanta, we switched to using Ir as the metal. It has MUCH smaller grain size. We now use 5 nm or less for a thickness.
Your mag value is misleading. Your scale bar is definitely accurate. Your raster was about 2.5 um wide. We run our Quanta with a 5-inch Polaroid print as the mag reference. That is, we assume the printed image will be 5 inches wide. On our SEM, that image would be labeled as 48 kx, not 120 kx. Your screen must be 13 inches wide. If you had a bigger screen, your mag would have been even higher.
I agree that the contrast between graphene oxide and embedding material must be increased to distinguish between the particles and filler.
A standard method in electron microscopy of hydrocarbon-based materials (polymers, biological samples) is heavy metal staining to enhance contrast (differences). For polymers see here (There are serious safety issues!):
These methods will work on the polymer bonds (crosslinking) of the embedding material, not for GO itself, but may be in BSE imaging you would see dark GO particles in a brighter matrix.
A 2nd way may be using a different embedding material: In the field of battery research, a silicon rubber was used: “Wacker (ELASTOSIL RT 675) was found suitable to provide the necessary contrast between carbon black and porosity.” (M. Ender PhD thesis 2014 http://digbib.ubka.uni-karlsruhe.de/volltexte/documents/3073727; in German!)
Thomas Breuer
, my point still stands. Yes, a lower voltage could allow mapping to work in a different system, say GO in silicone. The lower voltage would help keep the interaction volume inside the GO. However, without staining, I don't expect there would be any contrast to be seen between GO and epoxy. Maps just aren't that sensitive.I also meant to add that this situation is rather analogous to trying to see glass beads in water. With very little difference in refractive index between the phases, the beads practically disappear. That is like the GO in epoxy. What would be the source of contrast?
I have also added one of our images of a sample of nano-silica with and without 15 nm of gold coating. The texture that I used to be so interested in was nothing more than the gold.
Finally, I forgot to mention that there appears to be a phase in your image with a prismatic shape. I hazard to guess that that is the GO. Do you have images of the GO apart from the epoxy?
- Badges
- Science topic
- Similar topics
- Physical Sciences
- Materials Science
- Materials Chemistry
- Polymer Chemistry