Dear Anbuthangam,

There is no industrial method to completely separate particles smaller than 1 microns from particles of 1 to 5 microns. Sieving does not work with such particles (small mesh size for industrial applications is 20 microns). Air centrifugal classifier also can not separate such fractions.

Only thing you can do - continue grinding the whole powder. With proper wet milling (small grinding ball, long time) you grind all your particles in the submicron size.

If it is possible to suspend the particles in liquid, there are two self-evident ways: filtration and centrifugation.

Good luck!

Dear Anbuthangam,

There is no industrial method to completely separate particles smaller than 1 microns from particles of 1 to 5 microns. Sieving does not work with such particles (small mesh size for industrial applications is 20 microns). Air centrifugal classifier also can not separate such fractions.

Only thing you can do - continue grinding the whole powder. With proper wet milling (small grinding ball, long time) you grind all your particles in the submicron size.

This is in addition to what said Denis above. Micron-sized particles are heavier than nanoparticles and therefore the former will sediment from the suspension faster than the latter. So, you need to find the moment when the former will be mainly precipitated on the bottom of the vessel while the latter will be mainly in the bulk of the suspension.

You can try the sedimentation process, decanting successively the top section after ultrasonic excitation or stirring and subsequently waiting for a few minutes, and then analsyse the individual fractions byt absorption spectroscopy and SEM to get an idea of their size distribution. This is rather laborious as it may have to be repeated several times until you are happy with the reminaing size distriution.