Oxidation Of Mg Alloys Research Articles

Cytocompatibility of porous P-containing coating prepared by plasma electrolytic oxidation of Mg alloy

Magnesium alloys are potential biodegradable hard-tissue implant materials because of their excellent biomechanical compatibility, biosafety, and absorbability. In order to further improve the biocompatibility of these alloys, a ceramic coating was prepared on the surface of a magnesium alloy specimen by plasma electrolytic oxidation (PEO) in a phosphate solution. The ceramic coating has a rough surface, porous structure, and no harmful elements in the ceramic membrane. Further, experiments with MG63 cells show that the PEO ceramic coating can promote cell adhesion and proliferation, and it causes no obvious cytotoxicity. In conclusion, PEO can be used to prepare a suitable ceramic coating on the surface of the magnesium alloy, thereby increasing its potential for clinical applications.

Phosphorous removal and high-purity struvite recovery from hydrolyzed urine with spontaneous electricity production in Mg-air fuel cell

Abstract In this study, a single-chamber Mg-air fuel cell (MAFC) is used to remove phosphorous (P) and to simultaneously recover struvite and electricity from synthetic hydrolyzed urine. The Mg2+ generated from the anodic oxidation of Mg alloy provides a source of Mg for struvite precipitation. Meanwhile, the cathodic oxygen reduction reaction through a four-electron pathway produces OH− to maintain suitable pH for struvite precipitation and the avoid the addition of exogenous chemical reagents. The P concentration in the effluent is lower than 0.5 mg L−1 after a 15-min treatment and meets the sewage grade A discharge standard in China. The P removal efficiency of urine reaches 99.48% with an effluent P concentration of 0.28 mg L−1 after a 25-min operation of MAFC, and the removed P can be completely recovered as high-purity struvite precipitation. The rate constant for P removal is calculated to be 0.46 min−1 by fitting a first-order kinetic model. The recovered precipitation is identified as struvite, and the chemical analysis reveals a struvite purity of 98.26%. The maximum power density of MAFC with P-containing urine as electrolyte reaches 552.32 mW m−3, which is 47.39% higher than that of MAFC with P-free electrolyte. The struvite precipitation reaction can promote the electricity production of MAFC. This work provides not only a novel method for purifying and recovering resources from urine but also a new perspective for enhancing the electrochemical performance of MAFC in the future.

Effect of Ca Additions on Ignition Temperature and Multi-Stage Oxidation Behavior of AZ80

AZ80, AZX801, and AZX802 alloys were prepared to investigate the ignition temperature and multi-stage oxidation behavior in air. Besides, the microstructures of alloys before and after oxidation were compared. The results reveal that AZX802 exhibits the characteristics of higher ignition temperature and best oxidation resistance compared to AZX801 and AZ80, which contributes to the increase of melting temperature of secondary phase in matrix due to the formation and increase of Al2Ca, with the addition of Ca in AZ80. In addition, the incubation periods before accelerated oxidation and the beginning of the accelerated oxidation temperatures of AZ80, AZX801, and AZX802 are different during multi-stage oxidation, which also contributes to the different onset melting temperature of the secondary phase. And the beginning of the accelerated oxidation of Mg alloys at high temperature is always accompanied by the onset melting of the low melting temperature of the secondary phase and the growth of oxide nodule on the surface.

CaO첨가가 마그네슘 합금의 고온산화에 미치는 영향

CaO첨가가 마그네슘 합금의 고온산화에 미치는 영향

Effect of Ca and Y on the Oxidation of Mg Alloys

The AZ91D magnesium alloys containing 1% Ca and 1% Y were cast and oxidized between 350 and 500oC in atmospheric air to study the effect of Ca and Y on the oxidation of Mg alloys. The Mg+1% Ca alloy consisted of α-Mg, Al12Mg17, and Al2Ca. The AZ91D+1% Y alloy consisted of α-Mg, Al12Mg17, and Al2Y. Al2Ca and Al2Y were present in the form of platelets or blocky particles along the boundaries of primary α–Mg grains.The oxidation rates observed for the three alloys in the study decreased in the following order: AZ91D, AZ91D+1% Y, and AZ91D+1% Ca. As the oxidation progressed, the compact MgO oxide scale became porous, non-adherent, thick, and fragile. Ca, in the AZ91D+1% Ca alloy, was the most active element, and it appeared to diffuse outward toward the oxide layer rather easily. The presence of CaO in the oxide layer retarded the oxidation of the Mg alloy. Both the oxide scale and the matrix of the AZ91D+1% Y alloy contained oxygen. The dissolution of oxygen beyond the oxide scale indicates that Y could not effectively deter the ingress of oxygen, although the 1% Y content did increase the oxidation resistance of the alloy. Acknowledgement. This work is the outcome of "Environment-friendly and Energy-efficient Manufacturing Technology of Eco-Mg" program (No. 10035292-2010-01) funded by the Korea government Ministry of Trade, Industry and Energy.

Effect of Ca and CaO on the High Temperature Oxidation of Mg Alloys

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