i had prepared a Al2O3 nano particles by Planetary ball milling process. The SEM images show the lumped particles therefore morphology of particles is not much clear. somebody suggest to make a suspension solution followed by sonication process. i want to know what suspended solution i should use and what is the detail procedure of sonication process. for reference i am attaching the SEM images of Al2o3 what i got actually.
That is a Nano-crystal NOT a Nanoparticle. Nanoparticles and quantum dots are single particles of nanometer size. Nanoparticle can be huge agglomerations having nanocrystalline characteristics.
Very true... the image is probably large agglomerate of nano-particle. To resolve the individual particle under SEM I would go for sub-kV imaging.
To be pedantic, this is an aggregate (tightly/chemically bound) and not an agglomerate (loosely bound/can be disrupted by sonication). See:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
One should also Google 'comminution limit' . My recollection for alumina is that this is in the order of 2 - 3 microns. So it's not possible to produce nano-Al2O3 from a top down process. See slides 32 and onwards in:
October 6th, 2016 Controlling powder bulk density by optimizing particle size and shape distribution
https://www.brainshark.com/malvern/vu?pi=271602698&b=1&tx=120486&c1=22
You cannot see nanocrystals on SEM. Even if you are able to obtain better images, you cannot say for sure whether the submicronic particles are cold welded or just agglomerates.
@ Horea They are not agglomerates....Submicron (solid) materials diffuse into one another and generate solid bridges between the primary particles...
@ Horea. OK, then, by definition, they can be disrupted by sonication by your conjecture........ However, the comminution limit for alumina is around 2 - 3 microns....
What I wanted to point out, it it difficult from the SEM image to conclude whether the large aggregate is an agglomeration, a large particle formed by cold welding during milling or even by diffusion.
Dear Vibu Sharma,
If you synthesized the Al2O3 nanoparticle using bottom up approach i.e solid state reaction among the chemical reagents (stoichiometric mixture) sometime the reaction could be incomplete. if you use any salt as inert phase, please wash out. To check whether it is nanoparticle or nanocrystral please disperse the washed sample in aqueous media , allow them to dry up at room temperature. if it is nanocrystal you will able to see the deposited Al2O3 crystals at bottom. However to avoid such phenomenon you could simply heat the as milled powder. the limit of heating temperature could be determined from DSC analysis. However, the image you have provided looks as the image of as milled powder. the magnification is only 1000X. it is not possible to investigate surface morphology with this magnification. You have to try at higher magnification. for obtaining clear image you just simply check zeta potential at different pH, then add the washed powder in water fixed the suspension pH resposnible for higher zeta potential value, sonicate for 30 min. check SEM image. if it does not work or zeta potential value below 30 mV, you could also add some electrolyte as NaCl or Na-hexametaphosphate, then sonicate and check with SEM.
The magnification is too low and there is a self-evident charging on the picture. Al2O3 is an insulator and it is necessary to use some special modes (low tension, VP, etc.) or coat it with a thin layer of gold or another metal. The simplest way is a conventional 5 nm gold coating by a sputter system.
Good luck!
Dear friends
i made a DLS test on the al203 planetary ball milled for nano particles. i am attaching the report here with. the avg size of the particles i got is 0.5 micron.how can i interpreted the DLS graph..i think i call my powder as nearly nano structured al203 powder
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