The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the s...The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the system, the reaction behaviors ofsilicate species were systematically investigated by thermodynamic analysis. The thermodynamic analysis shows that silicate in thetungstate clinker partly decomposes in the leaching process, with 150-160 mg/L silicon thermodynamically at 25 ℃. The dissolvedsilicon can be removed by magnesium salts via forming insoluble MgSiO3. The low carbonate and high ammonia concentrations inthe system are beneficial to the removal of silicon, with silicon concentration reaching 8-10 mg/L thermodynamically, whereasMgSiO3 precipitation is hardly formed when the concentration of total carbonate is more than 1.5 mol/L. The reaction behaviors ofcalcium and magnesium were also studied in the system. The results in the verification experiments consist with the theoreticalcalculation.展开更多
The effect of a salicylic Schiff base componnd （Salcn） on the corrosion of AZ91 alloy in 30% ethylene glycol aqueous solution （30% EG/W） was investigated by electrochemical methods. Scanning electron microscope wa...The effect of a salicylic Schiff base componnd （Salcn） on the corrosion of AZ91 alloy in 30% ethylene glycol aqueous solution （30% EG/W） was investigated by electrochemical methods. Scanning electron microscope was used to observe the alloy surface in corrosive solution before and after the addition of inhibitor. There was no significant corrosion inhibition at the room temperature but high inhibition efficiencies were obtained at elevated temperatures due to the formation of chemisorbed inhibitor monolayer. As the inhibitor concentration increased, the inhibition efficiency increased probably due to more inhibitor adsorption on the alloy surface.展开更多
The present work focuses on a new method combining cast-infiltration with thermal spraying technology to improve the surface corrosion resistance of magnesium alloy.A zinc-based alloy layer was fabricated on the surfa...The present work focuses on a new method combining cast-infiltration with thermal spraying technology to improve the surface corrosion resistance of magnesium alloy.A zinc-based alloy layer was fabricated on the surface of AZ91D magnesium alloy. The microstructure of the layer was characterized by scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy(EDS).The phase constituent of these alloys was identified by X-ray diffractometry(XRD).The analysis results reveal that a zinc-based alloy layer with a thickness of 700μm can form on the surface of AZ91 alloy matrix.The layer is composed of Mg7Zn3,MgZn and a small amount of α-Mg solid solution.The results indicate that the corrosion-resistance of the specimen with a zinc-based alloy layer is much better than that of the specimen without the layer after being immersed in 5%NaCl solution for 240 h, and the layer is more protective for the AZ91 alloy.展开更多
To promote the scale-up production and industrial application of magnesium oxide （MgO） whiskers, MgO whiskers were prepared by the calcination method of the precursor. The precursor MgSO4·5Mg（OH）2·2H2O ...To promote the scale-up production and industrial application of magnesium oxide （MgO） whiskers, MgO whiskers were prepared by the calcination method of the precursor. The precursor MgSO4·5Mg（OH）2·2H2O （152 MOS） single component was prepared by hydrothermal synthesis reaction in MgSO4 solution and NaOH solution. MgO whisker was prepared by heating treatment of the precursor at low heating speed to keep the structure of the precursor not be destroyed. The composition, the morphology and the structure of these whiskers were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicate that the MgO whisker was about 0.5-1.2 μm in diameter and 20-80 μm in length, with an aspect ratio no less than 100.展开更多
基金Project(51274243)supported by the National Natural Science Foundation of ChinaProject(2015CX001)supported by the Innovation-driven Plan of Central South University,China
文摘The reaction behaviors of silicate species in （NH4）2WO4-（NH4）2CO3-NH3-H2O system are crucial to developing a greenmanufacture technique for ammonium paratungstate. In order to efficiently remove silicon from the system, the reaction behaviors ofsilicate species were systematically investigated by thermodynamic analysis. The thermodynamic analysis shows that silicate in thetungstate clinker partly decomposes in the leaching process, with 150-160 mg/L silicon thermodynamically at 25 ℃. The dissolvedsilicon can be removed by magnesium salts via forming insoluble MgSiO3. The low carbonate and high ammonia concentrations inthe system are beneficial to the removal of silicon, with silicon concentration reaching 8-10 mg/L thermodynamically, whereasMgSiO3 precipitation is hardly formed when the concentration of total carbonate is more than 1.5 mol/L. The reaction behaviors ofcalcium and magnesium were also studied in the system. The results in the verification experiments consist with the theoreticalcalculation.
基金the Research Council of the University of Mohaghegh Ardabili for its financial support of this study
文摘The effect of a salicylic Schiff base componnd （Salcn） on the corrosion of AZ91 alloy in 30% ethylene glycol aqueous solution （30% EG/W） was investigated by electrochemical methods. Scanning electron microscope was used to observe the alloy surface in corrosive solution before and after the addition of inhibitor. There was no significant corrosion inhibition at the room temperature but high inhibition efficiencies were obtained at elevated temperatures due to the formation of chemisorbed inhibitor monolayer. As the inhibitor concentration increased, the inhibition efficiency increased probably due to more inhibitor adsorption on the alloy surface.
文摘The present work focuses on a new method combining cast-infiltration with thermal spraying technology to improve the surface corrosion resistance of magnesium alloy.A zinc-based alloy layer was fabricated on the surface of AZ91D magnesium alloy. The microstructure of the layer was characterized by scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy(EDS).The phase constituent of these alloys was identified by X-ray diffractometry(XRD).The analysis results reveal that a zinc-based alloy layer with a thickness of 700μm can form on the surface of AZ91 alloy matrix.The layer is composed of Mg7Zn3,MgZn and a small amount of α-Mg solid solution.The results indicate that the corrosion-resistance of the specimen with a zinc-based alloy layer is much better than that of the specimen without the layer after being immersed in 5%NaCl solution for 240 h, and the layer is more protective for the AZ91 alloy.
文摘To promote the scale-up production and industrial application of magnesium oxide （MgO） whiskers, MgO whiskers were prepared by the calcination method of the precursor. The precursor MgSO4·5Mg（OH）2·2H2O （152 MOS） single component was prepared by hydrothermal synthesis reaction in MgSO4 solution and NaOH solution. MgO whisker was prepared by heating treatment of the precursor at low heating speed to keep the structure of the precursor not be destroyed. The composition, the morphology and the structure of these whiskers were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results indicate that the MgO whisker was about 0.5-1.2 μm in diameter and 20-80 μm in length, with an aspect ratio no less than 100.
