Bone regeneration demands biomaterials capable of supporting tissue integration and mimicking the native piezodynamic properties of bone. In this study, hydroxyapatite–barium titanate (HA-BT) composite coatings with varying BT content (10, 30, and 50 wt%) were developed to enhance the piezoelectric response and corrosion resistance of Ti6Al4V implants. The coatings were synthesized via high-energy ball milling and atmospheric plasma spraying (APS). XRD analysis with Rietveld refinement confirmed the presence of HA along with secondary phases (TTCP, β-TCP, CaO). Electrochemical tests revealed lower corrosion current densities for the coatings containing ≤30% BT, indicating improved stability in physiological environments. Cytotoxicity assays (MTT) demonstrated biocompatibility across all formulations. Piezoresponse force microscopy (DART-SS-PFM) confirmed enhanced d₃₃-eff values for the 50% BT coating (>15 pm/V); however, biological assays under low-intensity pulsed ultrasound (LIPUS) stimulation showed increased osteocalcin expression for ≤30% BT, while 50% BT induced cellular stress. Overall, HA-BT coatings with up to 30% BT exhibited optimal electrochemical stability, favorable piezoelectric performance, and enhanced biological response, underscoring their potential for orthopedic implant applications and regenerative tissue engineering.

In the present manuscript, the influence of reaction time on the hexagonal-to-monoclinic phase transition in hydroxyapatite (HAp) nanofibers synthesized via a low-temperature modified hydrothermal method at 100 °C is investigated. The resulting nanofibers were highly crystalline and stoichiometric, with a Ca/P ratio of approximately 1.67. Comprehensive structural and functional characterization, combining X-ray diffraction with Rietveld refinement, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, transmission electron microscopy (TEM), and resonance-tracking piezoresponse force microscopy (RT-PFM), was employed to elucidate the role of the non-centrosymmetric monoclinic P2₁/b phase in governing HAp’s structural and piezoelectric properties. The analyses indicated a time-dependent phase evolution from hexagonal (P6₃/m) to monoclinic (P2₁/b), with exclusive formation of the hexagonal phase at 6 h and a clearly dominant monoclinic fraction (73.56%) after 24 h. Nanofibers synthesized for 48 h comprised approximately 98% monoclinic HAp and exhibited elongated morphologies with an average length of 354.82 nm and diameter of 45 nm. RT-PFM measurements confirmed a pronounced piezoelectric response associated with the monoclinic phase, yielding an effective piezoelectric coefficient (d_eff) of 19.85 pm/V. In vitro MTT assays demonstrated that the high monoclinic content did not compromise biocompatibility, as cell viability and cytotoxicity met the requirements of ISO 10993 and ASTM F895 standards. These findings offer new insights into how monoclinic ordering governs the piezoelectric behavior of HAp and suggest a promising strategy for enhancing its performance in biomedical applications.

Manganese oxides, especially birnessite-type $$\delta$$ -MnO $$_2$$ , are promising pseudocapacitive materials as electrodes in supercapacitors due to thei

In this study, the synthesis of a long-chain aliphatic amino compound and its sour corrosion inhibition properties were reported. Oleylamine was obtained through the reaction of 4-(Aminomethyl) pyridine with 1-chloro-octadecane. The identification and characterization of reaction products were carried out through Fourier transform infrared spectroscopy (FTIR) and gas chromatography/mass spectroscopy (GC-MS). Oleylamine was tested as a sour corrosion inhibitor for steels. Different concentrations of oleylamine (0, 5, 10, 25, and 100 ppm) in a sour saline electrolyte were analyzed. The dynamic anticorrosive behavior of oleylamine on carbon mild steel (AISI 1018) surfaces was evaluated using a laminar flow of 100 rpm and tested with potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. After electrochemical testing, the surface of the steel specimens that were used was characterized with Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The electrochemical results of the anticorrosive efficiency of oleylamine for steel showed an exponential behavior as a function of inhibitor concentration. At a concentration of 20 ppm of the inhibitor, the anticorrosive efficiency did not show any significant changes. However, at 100 ppm of the inhibitor, an efficiency of over 95% was achieved. After the electrochemical tests, the surface of the steel samples with the inhibitor revealed the formation of an inhibitor layer that prevented the corrosion of the steel.

Infection associated with orthopedic implants remains a major challenge in the development of biomimetic materials for bone tissue engineering. Surface modification strategies are widely employed to transform bioinert metallic substrates into bioactive interfaces that promote tissue integration while preventing bacterial colonization. This study investigated the effect of incorporating silver nanoparticles (nAg) into hydroxyapatite–barium titanate (HA–BT) coatings on their structural, mechanical, piezoelectric, biological, and antibacterial properties. Raw materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), whereas coatings were evaluated by XRD, scanning electron microscopy (SEM), tensile adhesion testing, electrochemical analysis, piezoresponse force microscopy (PFM), cell viability, and antibacterial assays. The coatings exhibited secondary phases, including β-tricalcium phosphate (β-TCP), tetracalcium phosphate (TTCP), and calcium oxide (CaO), generated during atmospheric plasma spraying (APS), while no silver oxide phases were detected after nAg incorporation. SEM observations revealed homogeneous phase distribution and strong coating–substrate adhesion. The addition of nAg did not significantly affect adhesive strength (44.58 ± 2.2 MPa for HA30BT and 43.28 ± 2.8 MPa for HA30BT–nAg). Protein adsorption studies indicated moderate albumin affinity (K_ads = 0.45) for nAg-containing coatings. Both coatings exhibited piezodynamic activity with d₃₃ values of approximately 13 pm/V. MTT assays confirmed non-cytotoxic behavior, with viability reductions below 2%. Osteocalcin expression demonstrated comparable osteogenic activity in coatings with and without nAg, regardless of low-intensity pulsed ultrasound stimulation. These findings highlight the potential of HA–BT–nAg coatings as multifunctional surfaces for bone regeneration and infection prevention.