The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed b...The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.展开更多
YSZ/（Ni, Al） composite coatings with different Ni：Al mole ratios were deposited on superalloy Inconel 600 by electrophoretic deposition（EPD） technique, followed by sintering in CH_4 atmosphere at 1 100 ℃for 2 h ...YSZ/（Ni, Al） composite coatings with different Ni：Al mole ratios were deposited on superalloy Inconel 600 by electrophoretic deposition（EPD） technique, followed by sintering in CH_4 atmosphere at 1 100 ℃for 2 h and isothermally oxidation at 1000 ℃ for 50 h. After sintering at 1100 ℃ for 2 h in CH_4 atmosphere, besides ZrC and t-ZrO_2 phases, the phase constitutes of Ni：Al mole ratios with 1：3, 1：2, and 1：1 were（Zr, Al）C, AlNi_3 and Ni phases, respectively. A remarkable difference in the oxidation behaviors of YSZ/（Ni, Al） composite coatings with different Ni：Al mole ratios was observed. For YSZ（Ni：Al=1：3） coated sample, oxidation at 1000 ℃ causes decomposition of the（Zr,Al）C solid solution to metallic Al, and then most of the Al is oxidized to Al_2O_3. For the YSZ（Ni：Al=1：2） coated sample, oxidation at 1000 ℃ mainly causes decomposition of the AlNi_3 phase. For YSZ（Ni：Al=1：1） coated sample, after oxidation at 1000 ℃, most of the Ni is oxidized to Ni O phase, and tolerated 50 h of oxidation and finally cracked and spalled from the specimen. YSZ（Ni：Al=1：3） and YSZ（Ni：Al=1：2） coated samples show superior oxidation resistance than that of YSZ coating. The different oxidation resistance mechanisms of YSZ/（Ni, Al） composite coatings sintered in CH_4 atmosphere were discussed.展开更多
The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of appare...The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy（Ea）were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction（G（α）=1-（1-α）~2,whereαis the conversion degree）plays an important role in the whole oxidation process.At the first stage（α=0.05-0.30）,the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage（α=0.30-0.50）,the oxidation process is completely controlled by the secondary chemical reaction（G（α）=1-（1-α）~2）.At the third stage（α=0.50-0.95）,the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G（α）=（1-α）^（-1）（β=10K·min^（-1）,whereβis heating rate）,G（α）=（1-α）^（-1/2）（β=15-20K·min^（-1））,and G（α）=（1-α）^（-2）（β=25K·min^（-1））,respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^（-1）.展开更多
基金financial support by the Fundamental Research Funds for the Central Universities (No. N130602003)National High Technology Research and Development Program of China (No. 2012AA062302)the National Natural Science Foundation of China (No. 51574067)
文摘The effects of MgO and TiO_2 on the viscosity, activation energy for viscous flow, and break-point temperature of titanium-bearing slag were studied. The correlation between viscosity and slag structure was analyzed by Fourier transform infrared（FTIR） spectroscopy. Subsequently, main phases in the slag and their content changes were investigated by X-ray diffraction and Factsage 6.4 software package. The results show that the viscosity decreases when the MgO content increases from 10.00wt% to 14.00wt%. Moreover, the break-point temperature increases, and the activation energy for viscous flow initially increases and subsequently decreases. In addition, with increasing TiO_2 content from 5.00wt% to 9.00wt%, the viscosity decreases, and the break-point temperature and activation energy for viscous flow initially decrease and subsequently increase. FTIR analyses reveal that the polymerization degree of complex viscous units in titanium-bearing slag decreases with increasing MgO and TiO_2 contents. The mechanism of viscosity variation was elucidated. The basic phase in experimental slags is melilite. Besides, as the MgO content increases, the amount of magnesia–alumina spinel in the slag increases. Similarly, the sum of pyroxene and perovskite phases in the slag increases with increasing TiO_2 content.
基金Funded by the Science and Technology Key Fund Project of Shanghai University of Engineering Science(cs1405015)the Graduate Research and Innovation Special Projects of Shanghai University of Engineering Science(15KY0501 and 14KY0515)
文摘YSZ/（Ni, Al） composite coatings with different Ni：Al mole ratios were deposited on superalloy Inconel 600 by electrophoretic deposition（EPD） technique, followed by sintering in CH_4 atmosphere at 1 100 ℃for 2 h and isothermally oxidation at 1000 ℃ for 50 h. After sintering at 1100 ℃ for 2 h in CH_4 atmosphere, besides ZrC and t-ZrO_2 phases, the phase constitutes of Ni：Al mole ratios with 1：3, 1：2, and 1：1 were（Zr, Al）C, AlNi_3 and Ni phases, respectively. A remarkable difference in the oxidation behaviors of YSZ/（Ni, Al） composite coatings with different Ni：Al mole ratios was observed. For YSZ（Ni：Al=1：3） coated sample, oxidation at 1000 ℃ causes decomposition of the（Zr,Al）C solid solution to metallic Al, and then most of the Al is oxidized to Al_2O_3. For the YSZ（Ni：Al=1：2） coated sample, oxidation at 1000 ℃ mainly causes decomposition of the AlNi_3 phase. For YSZ（Ni：Al=1：1） coated sample, after oxidation at 1000 ℃, most of the Ni is oxidized to Ni O phase, and tolerated 50 h of oxidation and finally cracked and spalled from the specimen. YSZ（Ni：Al=1：3） and YSZ（Ni：Al=1：2） coated samples show superior oxidation resistance than that of YSZ coating. The different oxidation resistance mechanisms of YSZ/（Ni, Al） composite coatings sintered in CH_4 atmosphere were discussed.
基金supported by the National Natural Science Foundation of China(Grant No.51234010)Special Fund for Basic Scientific Research in Colleges and Universities of the Central Business (No.0903005203413)
文摘The non-isothermal oxidation experiments of ilmenite concentrate were carried out at various heating rates under air atmosphere by thermogravimetry.The oxidation kinetic model function and kinetic parameters of apparent activation energy（Ea）were evaluated by Málek and Starink methods.The results show that under air atmosphere,the oxidation process of ilmenite concentrate is composed of three stages,and the chemical reaction（G（α）=1-（1-α）~2,whereαis the conversion degree）plays an important role in the whole oxidation process.At the first stage（α=0.05-0.30）,the oxidation process is controlled gradually by secondary chemical reaction with increasing conversion degree.At the second stage（α=0.30-0.50）,the oxidation process is completely controlled by the secondary chemical reaction（G（α）=1-（1-α）~2）.At the third stage（α=0.50-0.95）,the secondary chemical reaction weakens gradually with increasing conversion degree,and the oxidation process is controlled gradually by a variety of functions;the kinetic equations are G（α）=（1-α）^（-1）（β=10K·min^（-1）,whereβis heating rate）,G（α）=（1-α）^（-1/2）（β=15-20K·min^（-1））,and G（α）=（1-α）^（-2）（β=25K·min^（-1））,respectively.For the whole oxidation process,the activation energies follow a parabolic law with increasing conversion degree,and the average activation energy is 160.56kJ·mol^（-1）.
