Boron-doped alumina for smart lubricants: Theory and experiment

We have carried out atomistic modeling of ceramic alumina (Al₂O₃) doped with boron oxide (B₂O₃) using density functional theory (DFT). Alumina exhibits excellent material properties, including a high melting point, hardness, and corrosion resistance. Alumina also possesses good tribological properties that can be enhanced with the addition of solid lubricants. In this study we investigated structural changes of alumina with respect to boron weight percentages (wt%) between 5% to 20% in order to understand the role of boron, introducing tribological properties to a mechanically favorable structure. Increasing amounts of boron oxide doping were added by substitution to an alumina unit cell and optimized using DFT. The most energetically favorable structures at each boron wt% were identified and were directly compared to experimental x-ray diffraction (XRD) patterns, finding agreement between theoretical and experimental patterns for stable aluminum borate phase (9Al₂O₃ 2B₂O₃). Further investigation into theoretically produced structures can then be carried out to determine properties favorable to lubrication.