Tahmineh Ahmadi

In the present study, polycaprolactone fumarate (PCLF) and polycaprolactone fumarate/silicon and magnesium codoped fluorapatite nanoparticles (PCLF/Si–Mg–FA nanocomposite) were deposited on the surface of Ti–6Al–4V alloy via dip-coating technique. The adhesion test, scanning electron microscopy (SEM) equipped with energy dispersive spectrometer (EDS), X-ray diffraction (XRD) technique, Fourier transform infrared spectroscopy (FTIR), electrochemical, and in vitro biocompatibility evaluations were utilized to characterize coated and uncoated specimens. The results show that uniform nanocomposite coating (thickness of about 6.65 µm) with appropriate adhesion strength and a homogeneous distribution of Si-Mg-FA nanoparticles throughout the PCLF matrix was coated on the substrate. The potentiodynamic polarization and electrochemical impedance tests, in agreement with each other, indicated higher corrosion resistance of nanocomposite coating in comparison to uncoated and PCLF-coated specimens. Cell cytotoxicity (MTT) evaluation and cell adhesion examinations show no toxicity and represent a good cell attachment with flattened sheet morphologies for nanocomposite coating.

In this research, using the manual shielded metal arc welding (SMAW) process, a wear-resistant layer was created by AMA1600v, AMA1622v, and AMA1623v hard coating electrodes on the St37 carbon mild steel, and the effect of the number of welding passes on the microstructure and corrosion resistance of the coatings was evaluated. For this purpose, optical microscope, scanning electron microscope (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) were used. The results showed a distribution of different carbide deposits in the microstructure of the coating metals. The deposits were complexs of the carbides of chromium, molybdenum, and vanadium. The results of the XRD demostrated the presence of martensite, austenite, chromium carbide, and molybdenum carbide phases in all three coating metals. Tungsten carbide (W2C) was observed only in the AMA1623v sample. The results of the Tafel polarization test showed that the bare and the 1622v samples had the highest corrosion current density (15.23 µA/cm2 and 7.06 µA/cm2, rspectively) among the under-studied samples, and therefore had the highest corrosion rate and the lowest corrosion resistance. Also, the results of the test showed that the corrosion current density of the 1600v sample (6.29 µA/cm2) was higher than that obtained for the 1623v sample (4.80 µA/cm2), which revealed the lower corrosion resistance of the 1600v sample. In addition, according to the results of the electrochemical impedance spectroscopy (EIS) analysis, the highest charge transfer resistance and coating resistance with the values of 6.3 kOhm.cm2 and 68.5 Ohm.cm2, respectively, belonged to the 1623v sample, which was also proven by the polarization test. Moreover, the lowest charge transfer resistance and coating resistance among the coated samples with the values of 2.73 kOhm.cm2 and 42.5 Ohm.cm2, respectively, belonged to the 1622v sample.

Due to its high deterioration rate in the physiological environment, the clinical application of magnesium (Mg) in bone repair has been restricted. Graphene oxide (GO)-plasma electrolytic oxidation (PEO) coatings were effectively applied to Mg alloy to enhance corrosion resistance and biocompatibility. The structure, biocompatibility, electrochemical characteristics, and long-term corrosion performance of composite coatings were studied in the present paper. The incorporation of GO to the PEO layer decreased wettability of all samples, resulting in hydrophobic behavior. The amount of GO incorporated in the PEO layer had a minor effect on the film thickness, but the pore size of the PEO coating decreased as the amount of GO increased. PEO/GO coatings have better corrosion resistance than counterpart PEO coatings and bare samples, according to electrochemical tests. The results also demonstrated that corrosion resistance increases significantly as GO concentration increases, owing to the fact that GO nanosheets in the coating operate as a barrier to the electrolyte diffusion route, preventing aggressive electrolytes from accessing the substrate. Because of dramatically decreased Mg ion release and changes in pH value in the culture medium, all of the PEO and PEO/GO coatings could improve MG63 cell attachment and differentiation compared to the bare Mg alloy sample. The as-prepared PEO/GO coating on Mg alloy is attractive for medical applications due to its satisfactory corrosion resistance and biocompatibility.

Design of a scaffold with convenient mechanical properties to emulate bone structure is a major challenge for bone tissue engineers. In this study, porous ceramic scaffolds containing various weight fractions of nano β-tricalcium phosphate (nβ-TCP) (with a particle size of about 50-70 nm) were prepared by the replication method. Synthesised scaffolds were then coated with poly(3‐hydroxybutyrate) (PHB) for 30 and 60 sec. According to the morphological and mechanical tests, it was determined that synthesised scaffold containing 50 wt.% of nβ-TCP with a coating time of 30 sec showed desirable properties in bone tissue engineering. The bioactivity of this scaffold indicated that the bone-like apatite layers were well formed on the nanocomposite scaffold. Cell culture study showed a significant increase in cell proliferation between the coated, uncoated and control sample after 5 days of cell culturing. The results confirm that this nanocomposite scaffold has good potential for bone tissue engineering applications.

In this study, a nano-composite composed of gelatin as the matrix and Si-Mg-FA nano-particles as an additive was deposited on the AZ31 Mg alloy via dip coating method. In addition, a coating composed...