Biodegradable metal foams have been studied as potential materials for bone scaffolds. Their mechanical properties largely depend on the relative density and micro-structural geometry. In this work, mechanical behavior of iron foams with different cell sizes was investigated under various compression tests in dry and wet conditions and after subjected to degradation in Hanks' solution. Statistical analysis was performed using hypothesis and non-parametric tests. The deformation behavior of the foams under compression was also evaluated. Results show that the mechanical properties of the foams under dry compression tests had a "V-type" variation, which is explained as a function of different geometrical properties by using a simple tabular method. The wet environment did not change the compression behavior of the iron foams significantly while degradation decreased the elastic modulus, yield and compression strengths and the energy absorbability of the specimens. The deformation of open cell iron foams under compression is viewed as a complex phenomenon which could be the product of multiple mechanism such as bending, buckling and torsion.
Despite its high structural strength and degradability, the potentiality of pure iron foam for bone scaffolds is low due to its lack of surface bioactivity. This work aims to provide a surface bioactivity to the iron foam by developing a calcium phosphate (CaP) conversion coating. Silver (Ag), known for its antibacterial property, was then incorporated onto the CaP coating via co-deposition (Ag/CaP-c) and post-treatment (Ag/CaP-p). By tuning the Ca/P ion ratio and Ag concentration during the coating process, an optimum coating parameter was obtained. All coatings were found to enhance mineralization ability and mechanical integrity of the iron foam over time. Electrochemical and immersion tests indicated that the coatings regulated the degradation rate of the iron foam via a variation of coating resistance and capacitance. Silver ions were released slowly from the Ag/CaP coating during the immersion test indicating a potential long-term antibacterial property of the coating. Details on the coating design and process optimization, the effects of three different simulated physiological solutions, and the mechanical property of the coated iron foam are discussed in this report.
Diazonium salts coupled with vinylic monomers were able to functionalize carpets of carbon nanotubes by electro-activation in aqueous media. Hence, nano-sized carbon surfaces were shown to react with active radical species in solution through a new covalent grafting process called Surface Electroinitiated Emulsion Polymerization (SEEP), where diazonium salts are used both to initiate the polymerization of vinylic monomers in solution and to form a primer grafted polyphenylene-like layer on the carbon surface. SEM and TEM analyses revealed that ultrathin polymer films are grafted on the sidewalls of carbon nanotubes. XPS spectroscopy further confirmed the functionalization of multi-walled carbon nanotubes
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