Ceramic Pellets made through Spark Plasma Sintering (SPS) use to be very brittle and hence removing graphite layer using Grinding & Polishing becomes challenging.
Hello Aditya Arun,
To the better of my experience working on SPS, ceramic samples consolidated by this technique must not be brittle but the contrary, they usually achieve quite good mechanical properties. Thus, usually removing the graphite layer by polishing is the best way. I recommend you first to check the sintering parameters and avoid consolidate brittle samples (some systems are more challenging to sinter than others, it depends on the conductivity and the starting powder particle size). I could not give you any recommendation about how to remove the graphite layer from a brittle pellet since, if it is brittle, then it has not been well sintered.
Such the case, try to start polishing gently with coarse grit sandpaper (the grit size of sandpaper is usually stated as a number that is inversely related to the particle size), for example a number of grit 300 or 400 and then you can switch to a finest grit, like 600 or 800 and so on successively (I generally finish the polishing of my samples with 1500 or even 2000 grit number).
I hope this to be useful for you.
Regards.
Depending on what ceramic you have you can burn off (via oxidation) graphite at about 600°C-700°C
Hello Aditya Arun,
To the better of my experience working on SPS, ceramic samples consolidated by this technique must not be brittle but the contrary, they usually achieve quite good mechanical properties. Thus, usually removing the graphite layer by polishing is the best way. I recommend you first to check the sintering parameters and avoid consolidate brittle samples (some systems are more challenging to sinter than others, it depends on the conductivity and the starting powder particle size). I could not give you any recommendation about how to remove the graphite layer from a brittle pellet since, if it is brittle, then it has not been well sintered.
Such the case, try to start polishing gently with coarse grit sandpaper (the grit size of sandpaper is usually stated as a number that is inversely related to the particle size), for example a number of grit 300 or 400 and then you can switch to a finest grit, like 600 or 800 and so on successively (I generally finish the polishing of my samples with 1500 or even 2000 grit number).
I hope this to be useful for you.
Regards.
You may find useful to check also this RG discussions: https://www.researchgate.net/post/Chemical_etchant_or_thermal_etching_condition_for_graphite https://www.researchgate.net/post/How_can_I_digest_graphite_powder_in_order_to_measure_the_nitrogen_content_impurity_levels_in_it https://www.researchgate.net/post/can_graphite_withstand_70_nitric_acid_at_temperature_150_to_160
What type of ceramic pellets you are sintering by SPS. Once you remove the sintered pellet from mold, it is easy to remove the graphite layer (in my experience, I have done so many experiments on SPS). You can polish gently on very smooth salt paper or use carborundum powder. If you have any doubts, please check my research papers on SPSP.
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