The samples were grinded in pestle mortar and then heat treated at 1100 degree Celcius. The size of particles was in nano range. With passage of time, the agglomeration has been observed in the samples. The size of particles is no longer in nano range.
How to remove the agglomeration?
either by heat treatment at low temperature or grinding
or I have to prepare fresh samples?
Hi,
You should specify the material and provide enough information when you post a question to answer properly. Anyway, metal oxide contain large no of hydroxyl groups and in their colloidal suspensions they tend to aggregate very fast and form aggregates and later agglomerates. Surface passivization with suitable surfactants of the nanoparticles is a solution to prevent aggregation of the particles. Solid state aggregation will depend upon the properties of the particles (fo. eg. magnetic metal oxide nanoparticles.) Grinding or heat treatment will not prevent the aggregation you will initially get nanoparticles with such methods but they will again aggregate. So surface treatment is the best way. The choice of the modifier will depend upon targeted applications. It will also depend upon the state (suspension/solid powder) in which you are intended to use the nanoparticles in the target application/s.
good luck.
Even a surface modification will not help if you have to sinter the material by 1100°C. The material fuse together and to not form aggreagtes which are seperable.
You can easily distinct between aggregation and fusing(sintering). In both case the particles may be large but the crystallite size will in general be small in the first case and large in the second. (XRD and TEM or XRD and DLS)
Refer this link:www.ifam.fraunhofer.de/.../WorldPM_2014_Walther_PROPERTIES_A...
Refer this link:https://books.google.co.in/books?isbn=162708018X
Refer this link:https://books.google.co.in/books?isbn=1490100962
Refer this link:www.google.co.in/patents/US20060269436
Go for wet grinding , Heat treat at lower temperature for a longer time preferably in an inert atmosphere.
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