High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content(≥10 wt%)because of the short slag-metal separation time.In this study,CaO and CaF2 are added to the melt to improve t...High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content(≥10 wt%)because of the short slag-metal separation time.In this study,CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation.The thermodynamics of the step-by-step reduction process of TiO2 in the Ti-Al-Fe-Si-O system whose composition is close to the alloy after melt separation were calculated.Samples of alloys and slags before and after melt separation were systematically analyzed.The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2.The O content of the alloys slightly decreases with temperature from 1873 to 2023 K,which agrees with the changes in the law of deoxidation limit.It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction.The addition of Al2 O3-CaO-CaF2 slag and high temperature promote the removal of Al2 O3 and titanium suboxides.The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%,respectively.展开更多
The complex fluoride, KNiF3, with perovskite structure was synthesized by refluxing KF and Ni（NO3）2·6H20 in ethanediol. The samples were characterized by X-ray diffraction（XRD）, transmission electron microsc...The complex fluoride, KNiF3, with perovskite structure was synthesized by refluxing KF and Ni（NO3）2·6H20 in ethanediol. The samples were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, X-ray photoelectron spectroscopy（XPS）, and ultraviolet-visible diffuse reflectance speetroseopy（UV-Vis DRS）. The results indicate that the mean diameter of KNiF3 particles is about 30-60 nm and the oxygen content in the samples is ≤5%. The prepared KNiF3 shows obvious absorption peaks at 400-830 nm.展开更多
The effects of the calcination temperature on the oxygen content and magnetic properties of the nano- crystalline perovskite manganite Lao.75Sro.25MnO3±δ pre- pared by the sol-gel method were investigated. The h...The effects of the calcination temperature on the oxygen content and magnetic properties of the nano- crystalline perovskite manganite Lao.75Sro.25MnO3±δ pre- pared by the sol-gel method were investigated. The highest temperatures at which the samples were calcined were 973, 1073, 1273, and 1473 K. The X-ray diffraction （XRD） analyses indicate that all the samples have only a single phase with the R3c perovskite structure. As the calcination temperature and calcination time increase, the oxygen content in the samples increases from being deficient to being in excess of that in the stoichiometric formula. The crystallite size also increases from 23 to 283 nm. Magnetic measurements indicate that the sample calcined at 1073 K has the highest Curie temperature. This is owing to the fact that the crystallite cores of this sample have stoichiometric oxygen content. The dependence of the Curie temperature and the saturation magnetization on the calcination tem- perature are successfully explained.展开更多
The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;h...The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;however,it is difficult to be studied in situ.Here,a new method of measuring the oxygen transfer rate at the gas-slag and slag-metal interfaces was reported based on electrochemical analyses.The interfacial oxygen transfer rate in the smelting process of Inconel 718 superalloy was investigated at 1723,1773,1823,and 1873 K.The experimental results show that the electrochemical method can measure the real-time oxygen content;hence,this method is promising in controlling the oxygen content in alloys.As the temperature increased,both the equilibrium oxygen content and the rate of oxygen absorption increased significantly,and the increase was the most obvious when the temperature was 1873 K.The possible reason is that the increase in temperature weakens the mass transfer resistance of the electric double layer at the interface,thus accelerating the oxygen transfer rate.展开更多
基金financially supported by the National Natural Science Foundation of China (Nos. 51422403, 51774078 and U1508217)the Fundamental Research Funds for the Central Universities (No. N162505002)
文摘High ferrotitanium prepared directly by the thermite method has a disadvantageously high O content(≥10 wt%)because of the short slag-metal separation time.In this study,CaO and CaF2 are added to the melt to improve the basicity of the slag and melt separation under heat preservation is performed to strengthen slag-metal separation.The thermodynamics of the step-by-step reduction process of TiO2 in the Ti-Al-Fe-Si-O system whose composition is close to the alloy after melt separation were calculated.Samples of alloys and slags before and after melt separation were systematically analyzed.The result indicates that the reaction that TiO is reduced by Al to Ti is the limited step in the reduction process of TiO2.The O content of the alloys slightly decreases with temperature from 1873 to 2023 K,which agrees with the changes in the law of deoxidation limit.It is mainly attributed to the movement of chemical reactions in the alloy melt at different temperatures and slag-metal interfacial reaction.The addition of Al2 O3-CaO-CaF2 slag and high temperature promote the removal of Al2 O3 and titanium suboxides.The minimum contents of O and Al in the alloy reach 1.84 wt% and 3.26 wt%,respectively.
基金Supported by the National Natural Science Foundation of China(No.20671069)
文摘The complex fluoride, KNiF3, with perovskite structure was synthesized by refluxing KF and Ni（NO3）2·6H20 in ethanediol. The samples were characterized by X-ray diffraction（XRD）, transmission electron microscopy（TEM）, X-ray photoelectron spectroscopy（XPS）, and ultraviolet-visible diffuse reflectance speetroseopy（UV-Vis DRS）. The results indicate that the mean diameter of KNiF3 particles is about 30-60 nm and the oxygen content in the samples is ≤5%. The prepared KNiF3 shows obvious absorption peaks at 400-830 nm.
基金financially supported by the National Natural Science Foundation of China(No.NSF-11174069)the Natural Science Foundation of Hebei Province(No.E2011205083)+1 种基金the Key Item Science Foundation of Hebei Province(No.10965125D)the Key Item Science Foundation of the Education Department of Hebei Province(No.ZD2010129)
文摘The effects of the calcination temperature on the oxygen content and magnetic properties of the nano- crystalline perovskite manganite Lao.75Sro.25MnO3±δ pre- pared by the sol-gel method were investigated. The highest temperatures at which the samples were calcined were 973, 1073, 1273, and 1473 K. The X-ray diffraction （XRD） analyses indicate that all the samples have only a single phase with the R3c perovskite structure. As the calcination temperature and calcination time increase, the oxygen content in the samples increases from being deficient to being in excess of that in the stoichiometric formula. The crystallite size also increases from 23 to 283 nm. Magnetic measurements indicate that the sample calcined at 1073 K has the highest Curie temperature. This is owing to the fact that the crystallite cores of this sample have stoichiometric oxygen content. The dependence of the Curie temperature and the saturation magnetization on the calcination tem- perature are successfully explained.
基金gratefully express their appreciation to National Natural Science Foundation of China(Nos.51974153 and U1960203)the Joint Fund of State Key Laboratory of Marine Engineering and University of Science and Technology Liaoning(SKLMEA-USTL-201707)the China Scholarship Council(201908210457).
文摘The interfacial oxygen transfer rate is one of the main factors to control the composition of alloys.The commonly employed method of studying the interfacial oxygen transfer rate is the chemical composition analysis;however,it is difficult to be studied in situ.Here,a new method of measuring the oxygen transfer rate at the gas-slag and slag-metal interfaces was reported based on electrochemical analyses.The interfacial oxygen transfer rate in the smelting process of Inconel 718 superalloy was investigated at 1723,1773,1823,and 1873 K.The experimental results show that the electrochemical method can measure the real-time oxygen content;hence,this method is promising in controlling the oxygen content in alloys.As the temperature increased,both the equilibrium oxygen content and the rate of oxygen absorption increased significantly,and the increase was the most obvious when the temperature was 1873 K.The possible reason is that the increase in temperature weakens the mass transfer resistance of the electric double layer at the interface,thus accelerating the oxygen transfer rate.
