Maycon Ericles Macedo Barros, Gabriely Gonçalves Lima, Alberto Moreira Jorge, Diego Alfonso Godoy Pérez, Ramón Raudel Pena Garcia, Cleânio da Luz Lima, ANDERSON OLIVEIRA LOBO, Alexandre de Castro Maciel, Fernanda Roberta Marciano
Bioactive and electrically responsive coatings are promising approaches for improving the functionality of next-generation orthopedic and dental implants. In this study, biomimetic calcium phosphate and calcium phosphate/magnetite (Fe 3 O 4 ) composite coatings were deposited on Ti-35Nb-7Zr-5Ta alloy processed by high-pressure torsion (HPT) using a supersaturated simulated body fluid (SBF 5x) route. The influence of Fe 3 O 4 incorporation on the coatings' morphological, compositional, structural, and electrical properties was systematically investigated. Scanning electron microscopy revealed porous apatite-like coatings covering the alloy surface, while EDS analyses showed a progressive increase in the Ca/P ratio from 0.91 to 1.58 with increasing Fe 3 O 4 content. X-ray diffraction, Raman spectroscopy, and FTIR analyses consistently indicated the formation of calcium-deficient hydroxyapatite (CDHA)-like phases and their evolution toward a more ordered structure in the presence of magnetite. The addition of Fe3O4 also modified the coating morphology and roughness, with the highest roughness reaching 6.60 μm. Electrical characterization demonstrated a substantial enhancement in charge transport after Fe 3 O 4 incorporation. The effective resistance decreased from 2.52 × 10 6 Ω for the undoped coating to approximately (2.19–2.51) × 10 4 Ω for the Fe-containing coatings, corresponding to a reduction of nearly two orders of magnitude. Impedance spectroscopy revealed a transition from predominantly capacitive behavior to a resistive–capacitive response, indicating the formation of electrically active pathways associated with magnetite-containing regions within the composite coating. The combined microstructural, compositional, and electrical results demonstrate that Fe 3 O 4 influences the growth and maturation of biomimetically deposited calcium phosphate coatings while significantly enhancing their electrical responsiveness. These findings highlight the potential of CDHA/ Fe 3 O 4 composite coatings on low-modulus TNZT-HPT substrates as multifunctional surfaces for electrically responsive biomedical implant applications.