The microwave dielectric properties and microstructures of the (1-x)(Mg0.95Zn0.05)2TiO4-x (Ca0.8Sr0.2)TiO3 ceramics prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At x = 0.07, a dielectric constant (εr) of ~17.86, a quality factor (Q×f) value of ~ Q×f~133,600 Hz (at 10 GHz), and a temperature coefficient of resonant frequency (τf) of ~ –5ppm/°Cwere obtained for 0.93(Mg0.95Zn0.05)2TiO4-0.07(Ca0.8Sr0.2)TiO3 ceramic sintered at 1240°C for 4 hr. The dielectric is proposed as a candidate material for low-loss microwave and millimeter wave applications.
A composite phosphate film was formed on magnesium aluminum (Mg-Al) alloy which was impregnated in phosphating solution containing phosphate, cerium salt, organic ammonium and corrosion inhibitor. The sample was examined by scanning electron microscope (SEM), X-ray diffraction (XRD), and Energy Dispersive Spectrometer (EDS) to analyze the organization and structure of the film. Additionally, the corrosion resistance of the film of composite phosphate was also investigated by salt spray test. As a result, it shows that the components of the film formed on Mg-Al alloy contain phosphates and elemental zinc. On the other hand, the composite phosphate film possessing photo-absorption property can be used for protective layer and laser pretreatment of Mg-Al alloy.
In order to improve the anticorrosion ability of a Mg-5Zn-1.5Ca alloy used as a bone replacement material, this study prepared the MnCaP conversion coating, which was formed from a phosphating solution mixed with a MnCl2 solution of 0.05 molarity, on a magnesium (Mg) alloy. After forming a MnCaP conversion coating on a Mg alloy, micro-arc oxidation (MAO) proceeded for improving the anticorrosion ability of the sample. As a result, when the 0.05MnCaP coating on a Mg alloy was immersed in the simulated body fluid (SBF), the corrosion current, pH value change, and hydrogen evolution volume of the SBF solution are lower than a uncoated Mg alloy. From the SEM and EDS analyses for a corroded 0.05MnCaP coating on a Mg alloy, the manganese (Mn) phosphate in a lumpy-rock form and the calcium (Ca) phosphate in a flake form alternate to each other densely, so that the coating can effectively prevent a Mg alloy from corrosion.
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