Corrosion behavior and in-vitro bioactivity of porous Mg/Al2O3 and Mg/Si3N4 metal matrix composites fabricated using microwave sintering process

In the present work the corrosion behavior and in-vitro bioactivity of two kinds of porous Mg-metal matrix nanocomposites separately reinforced with Al(2)O(3 )whiskers and Si3N4 particles were reported. 10 wt% of reinforcement was mixed with magnesium using high-energy ball milling and ethanol media for 10 min. After that, 10 ml ethylene glycol was added to milled mixture at the final stage of drying on a heater/stirrer at 70 degrees C. After stirring for 12 h, the powder mixtures were uniaxially pressed at 300 MPa to produce bar-shaped green specimens. The microwave sintering was performed at 650 degrees C without soaking time in a graphite bed. Porosity of about 50% was measured for both sintered composites using Archimedes principle. The XRD investigations revealed Mg2Al3 and MgO phases as the result of reaction between Mg and Al2O3. Moreover, the reaction products in Mg- Si3N4 composite were Mg2Si, Mg3N2 and Si. The corrosion tests showed that the polarization resistance of both prepared composites is higher than that of pure Mg. Mg-Al2O3 composite also showed lower corrosion current density compared to Mg- Si(3)N(4 )composite (1.42E(-4) and 1.36E(-3) A cm(-2), respectively). In-vitro bioactivity analysis of composites showed high level of needle-shaped CA-P inside porosities of Mg-Si3N4 composite; while in the case of Mg-Al2O3 composite a lower amount and smaller needle-shaped particles were found.