ABSTRACT
Nano-hydroxyapatite (nHA)-matrix coatings containing graphene nanosheets (GNS)-nHA were coated on Ti6Al7Nb alloys by plasma electrolytic oxidation (PEO) treatment for the improvement of their surface properties. Crystallographic properties, functional groups, and elemental analysis of coatings were characterized by XRD, ATR-FTIR, and EDS analysis. Surface morphological changes of the coated surfaces were investigated by AFM and SEM. The electrochemical corrosion behavior of the coatings was examined by using the potentiodynamic scanning (PDS) tests under in-vitro conditions in simulated body fluid (SBF). The results showed that the GNS was successfully deposited in ceramic matrix coatings on Ti6Al7Nb alloys. Also, the microstructural observations revealed that the coatings have a porous and rough structure. The XRD and ATR-FTIR quantitative analysis have proved the appearance of HA and GNS in the coating layers. An increase in the coating thickness, surface hardness, and anatase/rutile transformation rate was determined, while the GNS ratio in the coating layers was increased. The microhardness of the nHA coating reinforced with 1.5 wt% GNS was measured at 862 HV, which was significantly higher than that of GNS-free (only nHA) coating (584 HV). The best in-vitro resistance to corrosion in SBF was observed in the nHA/1.5GNS wt% coating.
ABSTRACT
The hybrid coatings containing the graphene nano-sheet (GNS) and nano-hydroxyapatite (nHA) phases have been successfully synthesized on Ti6Al7Nb alloys by a one-step hydrothermal method. The hydrothermal reaction was carried out for 24 h at 200 °C. The GNS ratio has been altered as 1, 3, 5 and 7 wt.% in the coatings and, the results have compared with non- GNS containing coatings. The effect of the GNS ratio on the microstructure, hardness, and in vitro corrosion responses has been investigated in detail. The characterizations of the coatings were carried out by SEM, EDS, AFM, XRD and, FTIR. The corrosion behavior of the hybrid coatings was compared in Kokubo's solution at 37 °C by using potentiodynamic polarization tests. The results showed that the hydroxyapatite phases were deposed on the graphene layers with nano-size nucleation with its Ca/P stoichiometric ratio. The best hydrophilicity (~52°) property has been obtained in nHA/3GNS coatings. In addition, the corrosion rates of coatings increased in the following order: nHA/3GNS < nHA/1GNS < nHA/7GNS < nHA/5GNS < only nHA.
Subject(s)
Durapatite/chemistry , Graphite/chemistry , Materials Testing , Nanoparticles/chemistry , Nanostructures/chemistry , Titanium/chemistry , Alloys/chemistry , Coated Materials, Biocompatible/chemistry , Corrosion , Electrochemistry , Hardness , In Vitro Techniques , Microscopy, Electron, Scanning , Potentiometry , Spectroscopy, Fourier Transform Infrared , Stress, Mechanical , Temperature , Wettability , X-Ray DiffractionABSTRACT
In this study, we examined whether the resistance of peritoneal catheters against the retraction force changed over time following shunt placement, and the role of this resistance in shunt fracture is discussed. We investigated peritoneal catheters removed from patients treated with a ventriculoperitoneal shunt because of hydrocephalus; previously, patients underwent shunt revision. The maximum tension, maximum elongation and elongation percentages of the peritoneal catheters were measured. The mean and maximum tension values of the revised peritoneal catheters were increased compared to the unused catheters. The maximum elongation and elongation rates were significantly decreased. The changes in the maximum elongation, elongation rate and tension values were unrelated to the time elapsed after catheter insertion. This finding indicates that the time elapsed following peritoneal catheter placement was not an individual factor based on the strength of the response of the organism to the foreign body and the mechanical trauma exposed in shunt fractures.
