I am making hBN composites with epoxy and using different concentrations of hBN. However, in comparison to the literature, I don't see a sharp increase in thermal conductivity in my composites sample especially at higher hBN loading (after 15% hBN concentration). I am following the cold press and sintering process and always get a gradually increasing trend at higher hBN concentrations. What could be the possible reasons for not having a sharp increase in thermal conductivity at higher hBN concentration?
Dear Milon Hossain
I'm afraid you didn’t modify the surface of hBN by suitable coupling agent to enhance the adhesion between epoxy and hBN particles. So if you do such modification, you improve bonding and minimize thermal contact resistance at interfacial zones which surrounds the hBN particles and high thermal conductivity will be achieved at less filler content and will see a sharp increase in thermal conductivity with higher hBN loading. In [1] item 2.2.1 , you can stand on golden procedure related the modification by the saline coupling agent APTES.
Best regards
[1]https://onlinelibrary.wiley.com/doi/epdf/10.1002/pen.25841
Dear Milon Hussein! I agree with the previous answer. In addition, you can have a large number of pores (air bubbles) in your mixture. This will also seriously impair thermal conductivity. You did not write exactly how you inject hBn, but the best way to remove pores and obtain a homogeneous solution would be ultrasound.
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