Currently, I am facing the unevenly distributed sample height under the nanoindentation experiment. How to apply the sample perfectly flat and reduce the uneven height as much as possible? (Sample is flat after polishing procedure, after applying the sample to the sample tray, the uneven height arises.)
Hello Dr. Cao,
It is advised to have a very flat specimen for nano indentation tests. If your sample is not flat after paper grinding and cloth polishing, then you may use some commercially available clay in between the specimen and sample holding stage . Then gently put it in a pressing machine (ram pressing) with some aluminum foil/butter paper on top of the sample and apply pressure from the top using piston/ram.
Hope this helps...
Thanks and regards
IIT Kanpur
Sample preparation and then sample clamping/glueing/holding during a nanoindentation test it is a complicate subject and it HIGHLY affects the nanoindentation results. It is even more complicate if the nanoindentation tests it is an high temperature test.
Preparation: if you need to cut a sample out of a solid piece, the way it is to use first a precise saw like Struers Accutom and then proceed with the grinding/polishing. Grinding Polishing needs to be done with precision to ensure the plan parallelity of the sample faces... To ensure parallelity we use the struers AccuStop and then grinding and polishing till mirror finishing , in this way the sample should be below 20/30 micrometres of height difference on the whole sample surface.
Clamping/Glueing on the sample holder: Use the sample holder provided by your nanoindenter producer and clamp or glue the sample on the top of it. This procedure highly influences the nanoindentation results in fact it can add comliance to the tests. For instance a small difference in the glue thickness (difference of few micrometres) can add compliance to the measurements and results in a Young modulus reduction of 50% and more... Calmping or glueing depends on the smaple thickness. I suggest glueing the sample with cyanoacrilate glue of really low viscosity ( sometimes commercially called Precision Max or similar), and apply a weight on the sample taking care of protecting the surface with an optical paper or similar... The glue thickness should be less than 10 micrometres once hardened...
Remember also that the indentation mark diameter of your measurements should not exceed 1/8 of the sample thickness...
Regards
A proper polishing procedure is critical.
Then there are various techniques for laying horizontally. A simple one is to assemble it in advance on a small layer of plasticine, so that the top surface is parallel to the base.
Good job
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