Dual Coating of Calcium Titanate and High-Entropy Alloy for Improved Mechanical and Bioactive Properties of ZTA Implants

In this study, we developed a dual-coating approach to enhance the mechanical and bioactive properties of zirconia-toughened alumina (ZTA) bioceramics for biomedical implant applications. The method applies a two-step coating process: a calcium titanate (CaTiO₃) layer on the tissue-contacting region to promote bioactivity and osseointegration, and a high-entropy alloy (HEA, Fe_0.25Pt_0.25Zr_0.25Mg_0.25) coating on the remaining surface to improve mechanical strength and durability. ZTA substrates were synthesized through high-energy ball milling and sintering at 1400 °C, yielding a baseline hardness of 2.97 GPa and an elastic modulus of 79.2 GPa, as measured by nanoindentation. Molecular dynamics (MD) simulations, performed using LAMMPS with a hybrid Embedded Atom Method, Buckingham, and Lennard-Jones potential framework, produced a hardness range of 2.49-2.95 GPa, consistent with experimental results. The HEA coating increased the composite hardness to 2.63 GPa, reduced principal stresses from 1330 to 546 MPa, and improved thermal conductivity with a <i>z</i>-axis heat flux of 80 eV/fs·Å², minimizing localized overheating. The CaTiO₃ coating slightly increased hardness to 2.49 GPa while enhancing bioactivity through improved apatite formation and cell proliferation. Stress and thermal analyses confirmed the HEA's mechanical stability and the CaTiO₃'s contribution to biological integration. This dual-coating method addresses ZTA's challenges, including low-temperature degradation and limited bone bonding, providing a framework for high-performance, biocompatible dental implants.