Papers by Author: Yong Wang

Abstract: The corrosion and degradation behavior of Mg-Ca binary alloy in simulated body fluid (SBF) were studied by immersion of pure Mg and Mg-Ca alloys with different Ca contents in SBF. The corrosion process was carried out by real-time measurement of sample weight, pH value of SBF and the microstructures of the immersed samples at different immersion time observed by electron microscopy. The result shows that Mg-Ca alloy with 0.7% Ca has better corrosion resistance than the one with 2.0% Ca. The product generated on the surface of Mg-0.7Ca during the immersion was identified by X-ray diffraction and energy spectrum analysis.

Abstract: Nano-TiO2 synthesized by hydrolysis of TiCl4 demonstrated high reactivity in presence of peroxide hydrogen under visible light (λ>420nm).The nano-TiO2 powders were characterized by XRD, Uv-Vis, FT-IR. The results showed that the TiO2 nanocatalyst sensitized with peroxide hydrogen could absorb visible light up to 550nm, and Vis absorption could be extended to 600 nm for the sulfated TiO2 .Photocatylytic degradations of methyl orange and methylene blue were above 90% for sulfated TiO2 in 180min. The inorganic sulfate species absorbing on the surface of titania were mainly responsible for the high activity of the TiO2 under visible light regions．

Abstract: The specific gravity and elastic modulus of magnesium alloys are similar to that of human bone. Magnesium is one of the most important elements in the human body and plays a key role in the metabolic process. But the application of magnesium is seriously limited as a biomaterial since it corrodes easily in the physiological environment of the body. In order to reduce the corrosion, we developed protective films using rare earth (RE) conversion processing. The surface of magnesium samples was modified by contact with different rare-earth salt solutions; then the samples were dipped in SBF to test their corrosion resistance. The change of mass and the pH of the solutions were measured continuously using an electronic scale and a pH micrometer. The surface microstructure of the samples was observed by XRD and metallomicroscope. Corrosion rates of the samples in SBF were determined using Taffier curve. The preliminary results show that the conversion treatment with CeCl3 or Y(NO3)3 can improve the corrosion resistance of magnesium in SBF. The relationship of the RE salts concentration and the corrosion properties were studied,the best combination of parameters was determined, and the formation mechanism of rare-earth conversion film has been also elaborated.

Abstract: Recently, there has been an increasing interest in magnesium as biomaterials due to its similar elastic modulus, density and strength to that of human bone than other currently popularly used metallic biomaterials. However, the knowledge of its biocompatibility is lacking. This paper reports the results of testing the cytotoxicity, haemolysis and acute toxicity on untreated and treated magnesium samples. The results showed that no cytotoxicity was detected on untreated magnesium samples. However, samples of alkali-treated magnesium caused distinct morphological changes on cells with a reduction in cell number vs the control group. In haemolysis tests, untreated magnesium showed a haemolytic effect, whereas there was a small haemolytic effect (2.2%) on alkali heat-treated metal; this is less than the allowable 5%. Magnesium samples coated with an organic film show the lowest haemolytic effect. No acute toxicity was observed; no animal deaths occurred and we observed no obvious weight differences in untreated magnesium vs organic coated samples compared to the control group.