There are several studies in which they disperse magnetic nanoparticles in wax, talc, etc. in order to decrease their aggregation, but they generally do not show clear evidence of the deaggregation of the nanoparticles. It is normally inferred from changes in the magnetic measurements (coercivity, remanence, etc.), but I was wondering if there is an alternative method in order to really know how the nanoparticles are arranged inside the solid matrix (maybe ultramicrotomy + TEM?).
Hi Javier
For the best results you would probably have to cool your specimen and do cryosectioning to get decent sections for TEM. Then let them warm up and TEM. People looking at organic polymers do that often.
Hi,
the method we used in our lab is embedding the grinded sample (wax+MNPs) in an epoxy resin for microscopy (Epofix) and then UMT with a knife for soft materials and TEM. (see attached publication) During curing the resin can heat up slightly above the melting point of the wax so the aggregation of MNPs can change, although the viscosity of the liquid wax at that temperature is quite high so the particles are supposed to not move too much.
Another method we have tried with good results is directly making a solid block with the sample for UMT. Of course in this case you need a much higher amount of sample to prepare the block (although once the lamelles are cut, you can re-use the rest of the block). If you (or the UMT technician) are careful and patient, thin slices of wax without embedding in any other media can be cut.
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