Oxidation behavior of low-grade vanadiferous titanomagnetite concentrate with high titanium

In order to clarify the oxidation mechanisms and make better use of the low-grade vanadiferous titanomagnetite concentrate with high titanium(LVTC),the oxidation behavior of LVTC was investigated.The results showed that oxidation degree was achieved within 90 min when temperature was not lower than 700°C,and the main phases of the oxidized LVTC consisted of Fe9TiO15,Fe2O3,CaSiTiO5 and a small amount of Fe2.75Ti0.25O4.Increasing temperature is favorable to the formation of Fe2TiO5.The surface of LVTC gradually becomes rough,with fine particles of needle-like and granular shape appearing on the surface,which finally turn from laminar to creamy,spread out,and are interspersed with many tiny holes.The phase oxidation paths in LVTC were as follows:(1)Fe2.75Ti0.25O4→Fe9TiO15+Fe2O3;(2)Fe2.75Ti0.25O4→Fe2O3+FeTiO3→Fe2TiO5;(3)FeTiO3→Fe2O3+Fe2Ti3O9→Fe2TiO5.LVTC is predominantly mesoporous whether oxidized or not,with the pores mainly distributed in the range of 2–40 nm,and the specific surface area of LVTC decreases significantly with increasing temperature.

A polyphenol-induced hydroxyapatite coating modulates corrosion resistance and biocompatibility of magnesium alloys

In order to solve the problem of excessive degradation rate and insufficient biocom-patibility of magnesium-based bone implants,a polyphenol(EGCG)induced hydroxy-apatite(HA)coating was prepared on the surface of AZ31 alloy.The physical and chemical properties and corrosion resistance of the coating were analysed in depth,and its biocompatibility was preliminarily explored in vitro.The results showed that the polyphenol(EGCG)conversion coating constructed on the AZ31 could successfully induce the formation of HA by complexing the phenolic hydroxyl group with calcium ions.The electrochemical and long-term immersion experiments showed that the corrosion resistance of EGCG/HA composite coating was significantly improved.The self-corrosion current density,hydrogen evolution and the increase of pH value of AZ31-EGCG/HA were significantly lower than those of AZ31.On the basis of inhibiting the excessive corrosion of the substrate,the composite coating significantly improves the compatibility of pre-osteoblasts,supports the adhesion and spreading and effectively reduces the haemolysis rate to less than 5%.The preparation method of the coating is simple,low cost and suitable for complex shape surfaces,which can significantly improve the corrosion resistance and biocompatibility of the AZ31 substrate.It is expected to provide a solution for the surface modification of magnesium-based bone implants.

A Study on the Biocompatibility of MgO Coating Prepared by Anodic Oxidation Method on Magnesium Metal

Magnesium(Mg),is widely used for the bone repair in oral and orthopedic application due to excellent bioactivity,degradation and biocompatibility.However,the range of application is greatly limited because of the rapid degradation of Mg metal in the body.Surface modification is an effective method to enhance the corrosion resistance and reduce the degradation rate of Mg metal.In the present study,pure Mg metal(P-Mg)was subjected to alkali-heat treatment(AT-Mg)or anodic oxidation-heat treatment(AO-HT-Mg).Both AT-Mg and AO-HT-Mg had a layer of MgO on their surfaces after treatment.Then the effects of MgO coating on corrosion resistance,bioactivity,Mesenchymal Stem Cells’(MSCs)proliferation,adhesion and osteogenic differentiation,and the bone repair capability of Mg metal were investigated.We found both AT-Mg and AO-HT-Mg had stronger corrosion resistance than P-Mg.MSCs on both AT-Mg and AO-HT-Mg had higher expression of proteins and genes of ALP,OCN,Col-I and Runx2 than those on P-Mg.They also showed better bone repair property than P-Mg in vivo.In general,MgO layer formed by anodic oxidation-heat treatment had better resistance and biocompatibility than that produced by alkali-heat treatment.This study indicated the MgO coating not only improved the corrosion resistance of Mg metal,but also promoted the osteogenic differentiation of MSCs and bone regeneration.