Abstract
This article reports the mechanical and biocorrosion behaviour of hollow silica nanosphere (SiO2) reinforced (0.5–2 vol.%) magnesium (Mg) syntactic foams. Room temperature tensile properties’ characterization suggests that the increased addition of hollow silica nanospheres resulted in a progressive increase in tensile yield strength (TYS) and ultimate tensile strength (UTS) with Mg-2 vol.% SiO2 exhibiting a maximum TYS of 167 MPa and a UTS of 217 MPa. The degradation behaviour of the developed Mg-SiO2 syntactic foams in four different simulated body fluids (SBFs): artificial blood plasma solution (ABPS), phosphate-buffered saline solution (PBS), artificial saliva solution (ASS) and Hanks’ balanced saline solution (HBSS) was investigated by using potentiodynamic polarization studies. Results indicate that corrosion resistance of the Mg-SiO2 syntactic foam decreases with increasing chloride ion concentration of the SBF. Mg-1.0 vol.% SiO2 displayed the best corrosion response and its corrosion susceptibility pertaining to corrosion rate and polarisation curves in different SBF solutions can be ranked in the following order: ABPS > PBS > HBSS > ASS. The surface microstructure demonstrated the presence of a better passivated layer on the syntactic foams compared to pure Mg. The observed increase in corrosion resistance is correlated with intrinsic changes in microstructure due to the presence of hollow silica nanospheres. Further, the effect of corrosive environment on the degradation behaviour of Mg has been elucidated.
Highlights
Benefitting from the advantages of being bioresorbable and having an elastic modulus, density and mechanical properties that closely match load bearing bones, magnesium (Mg)-based materials are emerging to play a crucial role in both basic research and clinical applications for orthopaedic and craniofacial fracture fixation [1,2]
The incorporation of hollow silica nanospheres into Mg led to the progressive enhancement in both 0.2% tensile yield strength (TYS) and ultimate tensile strength (UTS) whereas the tensile failure strain exhibited declining trend
Corrosion resistance of the Mg-SiO2 syntactic foams increased with decreasing presence of chloride, sulphate and dihydrogen phosphate concentrations and increasing carbonate concentration
Summary
Benefitting from the advantages of being bioresorbable and having an elastic modulus, density and mechanical properties that closely match load bearing bones, magnesium (Mg)-based materials are emerging to play a crucial role in both basic research and clinical applications for orthopaedic and craniofacial fracture fixation [1,2]. Metals 2020, 10, 1583 used permanent metallic implants made of titanium (Ti) alloys or stainless steel [4,5] These permanent metallic implants often result in stress-shielding at bone–implant interface due to mismatch in elastic modulus, osteolysis due to toxic metal ion release during wear and corrosion, tissue tear and other clinical complications during removal surgeries [6,7,8]. It is imperative to tailor the strength and degradation properties of Mg for successful clinical translation and various approaches like alloying [10], heat treatments [11], surface modifications [12], bioactive coatings [13]
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