RESUMEN
In the present work, hydroxyapatite (HA)-titanium (Ti, 20 wt%) composite coating was coated on NiTi alloy substrate by EPD (electrophoretic deposition) process. Before applying the coating, the HA powder was composed with Ti powder using a ball milling process. Influence of the ball milling time on morphology and phase structure of HA-Ti powder was evaluated using TEM and XRD analysis. After composing the HA particles with Ti, the HA-Ti composite powders were coated on the NiTi substrate by the EPD process in an n-butanol medium for 2 min, with the applied voltage of 60 V. XRD and SEM analysis were utilized to evaluate the phase analysis and morphology of the coatings. Mechanical and electrochemical characteristic of the coatings were also assessed using the micro-indentation, micro-scratch, and polarization tests, respectively. The results revealed that the milling process time had a significant influence on reaction bonds and optimum mixing time was 4 hr. Micro-hardness of the HA-Ti composite coating (304 HV) was substantially higher than the HA coating (72 HV). Also, as the HA coating was composed with Ti particles, the amount of force (in the micro-scratch test) required for detaching the coating from the NiTi substrate increased from 7.1 to 17.8 N. The polarization results showed that the HA-Ti composite coating had a higher electrochemical resistance compared with the HA coating. Corrosion resistance of the NiTi alloy coated with HA increased from 133 kΩ.cm2 to 2,720 kΩ.cm2 after composed with the Ti particles.
Asunto(s)
Materiales Biocompatibles Revestidos/química , Durapatita/química , Níquel/química , Titanio/química , Materiales Biocompatibles Revestidos/metabolismo , Técnicas Electroquímicas , Dureza , Ensayo de Materiales , Fenómenos Mecánicos , Conformación Molecular , Relación Estructura-Actividad , Propiedades de SuperficieRESUMEN
In the present study, the different contents of tantalum pentoxide (Ta2O5: 10, 15, 20 and 30â¯wt%) nanoparticles were introduced into the natural hydroxyapatite (nHA) coating structure on NiTi substrate through electrophoretic deposition (EPD) method. The phase compositions of coatings were perused before and after the sintering at 800⯰C for 1â¯h by XRD. The incorporation of 30wt%Ta2O5 into nHA matrix induced the formation of undesirable soluble Ca3(PO4)2 phase in composite coating. The FESEM images showed that the density of continuous nHA coating increased by compositing with Ta2O5. The maximum adhesion strength of 28.3⯱â¯0.7â¯MPa accomplished from the nHA-20â¯wt%Ta2O5 composite coating. The Ni ions concentration measurement results from the passivated-NiTi with nHA and nHA-(10, 15 and 20)wt%Ta2O5 coatings during 30â¯days of immersion in PBS clarified the positive role of Ta2O5 in decreasing the Ni leaching due to the lowering the open porosities of nHA structure. The biological response of the coating surfaces was assessed in vitro by cell culturing and MTS assay. By considering the morphology and density of adsorbed cells on each coating, the improved biocompatibility of nHA coating in the presence of Ta2O5 was justified by scrutinizing the surface roughness, wettability and charge. The highest cell attachment and proliferation on nHA-20â¯wt%Ta2O5 coating was related to owning the lowest roughness, wetting angle of 34o⯱â¯0.5 and the highest negative surface charge density. Also, the concentration of the highest negative charge density on nHA-20â¯wt%Ta2O5 coating surface in the SBF solution caused to the enhancement of the amount of the apatite nuclei through providing more sites to calcium absorption.