Papers by Author: Ke Yang

Abstract: Microstructure and bio-corrosion properties of as-cast Mg-Zn-Mn-Y alloys are investigated in detail to reveal the effect of the precipitate on the biocorrosion properties for biomedical application by scanning electronic microscopy electrochemical measurement and immersion tests. Alloy I is composed of primary Mg, Mg7Zn3 and I-phase, while there is only one secondary phase (W-phase) in alloy II. Alloy with W-phase exhibits a higher corrosion resistance and a lower corrosion current density. W-phase acts as a cathode and Mg matrix as an anode at the interface between W-phase and Mg matrix, while I-phase acts as an anode and Mg matrix as a cathode. The standard electrode potentials of secondsry phases are in the following order: W-phase>Mg>I-phase.

Abstract: Nano-sized nitrogen-doped Ti-W mixed oxides (N-TiO2-x%WO3) were prepared by soft chemical method, and their intrinsic characteristics were investigated using XRD, TEM, N2 adsorption and desorption isotherms, UV-Vis diffuse reflectance spectra and XPS. Experiments on photodegradation of Methylene Blue (MB) under visible light irradiation were carried out to evaluate the photocatalytic abilities of N-TiO2-x%WO3. Chemical Oxygen Demand (COD) analysis was also performed to evaluate the mineralization abilities of N-TiO2-x%WO3. It is shown that the N-TiO2-x%WO3 exhibited higher COD removing rates compared with Degussa P25. The color bleaching rates of N-TiO2-x%WO3 were equal to that of Degussa P25. The enhanced photocatalytic activities were probably related to the strong absorption abilities of the N-TiO2-x%WO3.

Abstract: The in vitro blood compatibility of a new nickel free high nitrogen austenitic stainless steel Fe-Cr-Mn-Mo-N (BIOSSN4) was studied by the kinetic clotting time test and the platelet rich plasma adhesion test in this paper. In comparison with 316L stainless steel, the kinetic clotting time of BIOSSN4 steel are longer, and only causes less activation of platelets in platelet adhesion test, which was indicated by their morphology and low spreading. The experimental results reveals that the BIOSSN4 stainless steel has better blood compatibility, the blood compatibility mechanism of steels was analyzed based on surface tension and interfacial tension between the steels and blood.

Abstract: Magnesium and its alloys are possible to develop new type of biodegradable medical magnesium alloys by using their active corrosion potential. The bio-corrosion properties of the high pure magnesium in the Hank’s solution were investigated in this paper, the results showed that high pure magnesium had a low corrosion rate and hydrogen release in Hank’s solution, when the pH value of solution was controlled at 7.5, the corrosion rate was under 0.2mm/year, the production of hydrogen was about 0.15ml/cm2, and if the solution wasn’t controlled on pH value, the corrosion rate was about 0.02 mm/year, production of hydrogen was about 0.1ml/cm2 . Result of in vitro Kinetic clotting time test and animal implant prep-test showed that High pure magnesium had good thromboresistant property and tissue compatibility, pure magnesium can biodegrade lowly in animal body and formed surface apatite, which proportion of Ca/P was similar with bone tissue.

Abstract: Tantalum dioxide and nitrogen co-doped titanium dioxide nanopowders, denoted as (Ta2O5, N) co-doped TiO2, were fabricated by a high-energy ball miller using TiO2, Ta2O5 and urea as raw materials. Experiments on the photocatalytic activities of the (Ta2O5, N) co-doped TiO2 were carried out in the form of photodegradation of methylene blue (MB) in aqueous solution under visible light irradiation. Enhanced photocatalytic activities were observed for the (Ta2O5, N) co-doped TiO2 than commercial Degussa P25. Besides, physical, chemical and optical properties, including XRD, DRS, and XPS were detected to analyze the origins for the enhanced photocatalytic activities of the prepared samples.

Abstract: Nitrogen-doped titania nanoparticles were co-prepared by sol-gel and mechanical-alloying method. Raman spectroscopy was used to investigate the microstructure information of the nitrogen-doped titania nanoparticles. Besides, XPS, ESR and UV-vis absorption spectra were also analyzed as supplementary means. At first blue then red shift of 142 cm-1 peak was observed as the annealing temperatures increased. The possible reasons for the shift were discussed.

Abstract: Surface Nanocrystallization(SNC) is a new method of fabricating nanostructured materials while thermal stability is an important problem for the application of nanostructured materials. A nanostructured layer was fabricated on the surface of 40Cr steel by Supersonic Particles Bombarding method, and the variation of microstructure and microhardness of nanostructured layer was studied. Nanostructured surface layer showed high thermal stability.

Abstract: Mullite-alumina porous ceramics were fabricated by polymer-aided extrusion through using natural kaolin and alumina as starting materials. The physical and chemical properties of porous ceramics were investigated. The results showed that the approach of using kaolin as starting material offers many benefits such as low cost, big processing capacities, low mullitization temperature and unique microstructure. The porous ceramics with high strength, high porosity, narrow pore size distribution, high permeability and good thermal-shock behavior was obtained by modifying preparation conditions.

Abstract: Implantation of drug releasing coronary stents has been developed as an useful method for prevention of the restenosis in blood vessels. Copolymers of methyl methacrylate (MMA), butyl methacrylate (BMA) and methacrylic acid (MAA) were prepared as the coating polymer for drug releasing stent. The adhesion of the polymer with metal substrate and the biocompatibility were studied. Effect of the polymer composition on the adhesion between polymer coatings and metal substrate, as well as the effect of the polymer purification method on biocompatibility of the polymer, was studied. The results showed that the copolymer coating has good dry and wet adhesion properties, which can be improved by control of the polymer compositions. Biocompatibility of the prepared copolymer comes within the permission limit.

Abstract: The deformation behavior of Inconel718 at room temperature was studied by tensile tests. Three kinds of specimens were tested, including cold rolled, heat treated with grain size ASTM5 and heat treated with grain size ASTM7. The true stress-strain curves were obtained based on the tensile test records. The true stress-strain relation can express the room temperature deformation behavior, which can be described by equations similar to the Voce equation. The limit value of the work-hardening rate θ0 is very sensitive to the microstructure of the alloy.