Microstructural and mechanical properties of plasma sprayed boron nitride nanotubes reinforced alumina coating

Boron Nitride Nanotube (BNNT) has emerged as a potential reinforcement for ceramic and metal matrices due to its excellent mechanical, chemical, and thermal properties. We have reinforced 5 vol % BNNT into the alumina (Al2O3) matrix using the atmospheric plasma spraying technique in the present study. BNNTs have been successfully retained after experiencing extreme temperatures of the plasma plume. Reinforcement of BNNTs has improved the relative density of pure Al2O3 coating from 90% to 94%, whereas the hardness, elastic modulus, and fracture toughness enhanced by 117%, 35% and 51%, respectively for the BNNTs reinforced coatings. The critical energy release rate increased from 3.90 +/- 1.18 J/m(2) to 6.50 +/- 1.22 J/m(2) with BNNT addition. The property enhancement reasons are attributed to improved densification, uniform distribution of BNNTs into the matrix, and toughening mechanisms, such as BNNT truss, nanotube pull-out, and crack bridging. This BNNT strengthened Al2O3 coating could be a successful candidate for highly durable and strong structural material for automobile and aviation sector, high speed cutting tools and in bioimplant sectors.