Papers by Keyword: Magnesium

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Authors: Tong Huan Zhang, Min Jian Yang, Peng Bo Li, Wei Xian Ran, Qian Qian Zhang, Chang Zhen Li, Chao Ding
Abstract: Mg-based hydrogen storage material was prepared by ball milling, and then the material was used to react with CS2. The morphology and hydrogen desorption properties of the hydrogen storage material as well as the CS2 hydrogenation product were analyzed. Results show that in situ hydrogenation and desulfurization of CS2 happens with the MgH2 in the hydrogen storage material as hydrogen donator and desulfurizer at 300 °C and ordinary pressure, and MgS, CH4 and H2S are generated from the reaction. There is a coupling relationship between dehydrogenation of the hydrogen storage material and hydrogenation of CS2. The addition of nickel and molybdenum show negative effect on the sulfur fixation capability of the Mg-based hydrogen storage material though they could decrease the dehydrogenation temperature of the material.
Authors: Jyotsna Dutta Majumdar
Abstract: Laser as a source of focused energy may be applied for the modification of microstructure and/or composition of the near surface region of a component. The technique may be applied for the development of a ceramic/intermetallics/interstitial compound dispersed metal matrix composite layer on the surface of metallic substrate by melting the substrate with a high power laser and simultaneous addition of alloy powders for the development of metal matrix composite layer by in-situ reactions. In the present contribution, development of metal-dispersed and intermetallic-dispersed matrix composite layer on the surface of metallic matrix has been discussed with a suitable example of its application.
Authors: Guo Chao Qi, Feng Jun Shan, Qiang Li, Jing Yuan Yu, Qu Kai Zhang
Abstract: Magnesium apatite (MA, (Ca9Mg)(PO4)6(OH)2) and Hydroxyapatite (HA) coatings were synthesized on Ti6Al4V substrates by a sol-gel dip coating method. Glucose and bovine serum albumin (BSA) were added to the standard simulated body fluid (SBF) separately to form organic-containing simulated body fluids. MA and HA coatings were immersed in standard and organic modified SBF for time periods of 4, 7, 14, 21 and 28 days at 37±1°C. The surface dissolution and deposition behavior of the coatings after soaking were examined with Scanning Electron Microscopy (SEM) and X-ray Photoelectron Spectroscopy (XPS). The results show that glucose in SBF has no apparent effect on the deposition of new apatite from the solution. BSA in SBF shows retardation effect on the deposition of apatite by forming a protein dominant globular layer. This layer inhibits the further deposition of apatite from SBF solution.
Authors: Ehsan Sharifi Sede, Shamsedin Mirdamadi, Hossein Arabi
Abstract: This study sought to create a biocomposite of Magnesium and Titanium via a powder metallurgy technique. Powder metallurgy technique was used to produce three different volume percentages of Magnesium (30% , 35% , 40%). Titanium powder was mixed with Magnesium, then the samples were compressed by 1800 Bar using a cold, isostatic press process. The samples were then sintered to 850 for 100 min. At this temperature, the compressive yield strength was increased to 210 Mpa and significantly depended on the volume percent of Magnesium present, the core size and temperature of sintering. The bioactivity of the samples in a simulated body fluid (SBF) was also investigated. When the samples were immersed in the simulated body fluid for a 14 and 28 days, calcium and other elements were found to be deposited on the surface. Additionally, it was found that TiO2 has the ability to induce the formation of bone-like apatite in the SBF. In addition, the degradation product of Magnesium in a biological system caused a rise in the pH and environment for the deposition of calcium and other element on the surface were enhanced. Finally, the samples were analyzed using XRD, EDS, and optical and scanning electron microscopy (SEM).
Authors: Paul Rosemann, Susanne Bender, Andreas Heyn, Jürgen Schmidt
Abstract: As bio-absorbable implant material the magnesium alloy Mg-1Ca is able to degrade in-vivo. The mechanical properties of this alloy are similar to those of human bone; both Mg and Ca are essential elements in human body. The main problem is the high corrosion rate of this alloy. Two coating systems based on plasma-chemical oxidation and an organic dip coating are applied onto MgCa1.0 magnesium alloy in order to slow down the corrosion rate. The corrosion behaviour of the coated alloys was investigated with electrochemical noise measurements. The influence of hydrogen evolution and increasing pH-value on the cytotoxicity was examined. The results of these investigations suggest that a combination of both coating systems leads to promising degradation properties.
Authors: Yu Bai, Fang Li Yu, Jun Du, Wen Xian Wang, Ze Qin Cui, Zhi Hai Han, Jian Feng Yang
Abstract: Due to the low density and high specific strength, magnesium and its alloys have been extensively used in the automobile and aerospace applications, where the weight reduction is critical. However, they are highly prone to corrosion, which has greatly limited their application in the automotive and aerospace industries. This paper briefly reviews the technologies for improving the corrosion and wear resistance of magnesium alloys and finds that the widespread application of magnesium alloys is still limited by the lack of proper protective coatings. Therefore, there is still a need to explore new materials and methods for the effective protection of magnesium and its alloys.
Authors: Luo Xing Li, Jia Zhou, X. He, Jie Zhou, Jurek Duczczyk
Abstract: The present case study addressed a practical problem of wall thickness attenuation during extrusion to produce a complex thin-walled hollow magnesium profile. A HyperWorks FEM software package was employed to aid in identifying the causes for the wall thickness attenuation. Recommendations were made to adjust the interspacing between the mandrels and the height of the welding chamber. The modified dies yielded much improved results in terms of velocity and hydrostatic pressure uniformity. The wall thickness of the extrudate predicted using FEM simulation was very close to experimental measurements. The case study demonstrated the feasibility of using FEM simulation as a useful tool to solve industrial problems encountered in the production of complex profiles.
Authors: Ting Ting Yan, Si Yu Wu, Qing Hua Chen, Qing Mei Liu, Jia Rong Yang
Abstract: Mg and its alloys draw more and more attentions to be used as biodegradable medical materials. But the rapid degradation of those materials limits their clinical applications. In this article, a phosphate coating was prepared on AZ31B magnesium alloy to improve its anti-corrosion property. Morphology, composition and corrosion resistance of the coating were studied. The SEM research showed that the coating that composed of rod-like phosphates with small amount of random distributed micro-voids was approximately10-20μm in thickness. The XRD analysis indicated that the coating was mainly composed of MgO, Mg3(PO4)2and Zn3(PO4)2·xH2O. Electrochemical test showed the phosphate treatment could significant improve the corrosion resistance of AZ31B.
Authors: Ping Yang, Li Meng, Q.G. Xie, F.E. Cui
Abstract: Basal slip and tension twinning are dominant deformation mechanisms of polycrystalline magnesium at low temperature. However, fracture originates mainly from compression twins or shear bands developed from compression twins. This work compared firstly the morphological difference of two types of twins. Then, the dependence of different deformation mechanisms on initial orientations is computed by Schmid factor analysis and compared with measured matrix orientations of twins. Finally, orientation relationships of compression twins with matrices are determined using EBSD technique and compared with theoretical value.
Authors: Ming Liu, Sandrine Zanna, Helene Ardelean, Isabelle Frateur, Patrik Schmutz, Guang Ling Song, Andrej Atrens, Philippe Marcus
Abstract: An XPS investigation was carried out on the surface film formed by exposure to high-purity water, on mechanically polished Mg and the two Mg-Al intermetallic compounds: Al3Mg2 and Mg17Al12. The result for mechanically polished pure Mg indicates that a film of MgO covered by a Mg(OH)2 layer, formed by the reaction of MgO with water vapour in the air. On immersion in distilled water, this film was hydrated to a duplex film with an inner MgO layer next to the Mg metal and an external porous layer of hydroxide. For both intermetallics, there was preferential dissolution of magnesium from the mechanically ground surface and also during aqueous immersion. After immersion, there was a 10 nm thick, stable film on the surface; the film composition on Al3Mg2 was whilst that on Mg17Al12 was .
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