Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigate...Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.展开更多
1 INTRODUCTIONThe concentration distribution of reactant in porouscatalyst pellet not only is the basis of calculating theeffectiveness factor,but also has a great significancein investigating the reaction and mass tr...1 INTRODUCTIONThe concentration distribution of reactant in porouscatalyst pellet not only is the basis of calculating theeffectiveness factor,but also has a great significancein investigating the reaction and mass transfer in thecatalyst pellet.In principle,the concentration distri-bution and the effectiveness factor of a catalyst pelletcan be obtained by solving the reaction-diffusion equation.However,most of the differential equations haveno analytical solution except for some simple cases.The previous investigators have made great efforts to calculate the effectiveness factors of catalysts.They first obtained asymptotic solutions of effective-ness factor in the cases of the Thiele modulus φ→Oand φ→oo by means of perturbation method,thensynthesized the information of the asymptotic solu-展开更多
Magnesium and its alloys have attracted great attention as biocompatible and degradable biomaterials recent years.But their corrosion rate has been proved to be too high,which limits their biomedical application great...Magnesium and its alloys have attracted great attention as biocompatible and degradable biomaterials recent years.But their corrosion rate has been proved to be too high,which limits their biomedical application greatly.In order to improve the corrosion resistance,nano-fluoridated apatite(FA) coating was prepared on ZK60 magnesium alloy by a simple chemical conversion method.The FA coating showed a needle-like morphology.The polarization curves and EIS plots indicated that the FA coating improved the corrosion potential by 125 mV and doubled the polarization resistance of the magnesium alloy,meanwhile decreasing the corrosion current by two orders of magnitude of the substrate in simulated body fluid.The MTT assay indicated good cytocompatibility of L-929 cells with the fluoridated apatite coated magnesium alloy.展开更多
基金Projects(51874071,52022019,51734005)supported by the National Natural Science Foundation of ChinaProject(161045)supported by the Fok Ying Tung Education Foundation for Yong Teachers in the Higher Education Institutions of China。
文摘Siderite,as an abundant iron ore,has not been effectively utilized,with a low utilization rate.In this study,the in-situ kinetics and mechanism of siderite during suspension magnetization roasting(SMR)were investigated to improve the selective conversion of siderite to magnetite and CO,enriching the theoretical system of green SMR using siderite as a reductant.According to the gas products analyses,the peak value of the reaction rate increased with increasing temperature,and its curves presented the feature of an early peak and long tail.The mechanism function of the siderite pyrolysis was the contraction sphere model(R_(3)):f(α)=3(1−α)2/3;E_(α)was 46.4653 kJ/mol;A was 0.5938 s^(−1);the kinetics equation was k=0.5938exp[−46.4653/(RT)].The in-situ HT-XRD results indicated that siderite was converted into magnetite and wüstite that exhibited a good crystallinity in SMR under a N_(2) atmosphere.At 620℃,the saturation magnetization(M_(s)),remanence magnetization(Mr),and coercivity(Hc)of the product peaked at 53.63×10^(-3)A·m^(2)/g,10.23×10^(-3)A·m^(2)/g,and 12.40×10^(3)A/m,respectively.Meanwhile,the initial particles with a smooth surface were transformed into particles with a porous and loose structure in the roasting process,which would contribute to reducing the grinding cost.
基金Supported by the Natural Science Foundation of Fujian Province.
文摘1 INTRODUCTIONThe concentration distribution of reactant in porouscatalyst pellet not only is the basis of calculating theeffectiveness factor,but also has a great significancein investigating the reaction and mass transfer in thecatalyst pellet.In principle,the concentration distri-bution and the effectiveness factor of a catalyst pelletcan be obtained by solving the reaction-diffusion equation.However,most of the differential equations haveno analytical solution except for some simple cases.The previous investigators have made great efforts to calculate the effectiveness factors of catalysts.They first obtained asymptotic solutions of effective-ness factor in the cases of the Thiele modulus φ→Oand φ→oo by means of perturbation method,thensynthesized the information of the asymptotic solu-
基金supported by the Program for Young Excellent Talents in Tongji University (Grant No. 2009KJ003)"Chen Guang" project(Grant No. 10CG21) supported by Shanghai Municipal Education Commission and Shanghai Education Development Foundation
文摘Magnesium and its alloys have attracted great attention as biocompatible and degradable biomaterials recent years.But their corrosion rate has been proved to be too high,which limits their biomedical application greatly.In order to improve the corrosion resistance,nano-fluoridated apatite(FA) coating was prepared on ZK60 magnesium alloy by a simple chemical conversion method.The FA coating showed a needle-like morphology.The polarization curves and EIS plots indicated that the FA coating improved the corrosion potential by 125 mV and doubled the polarization resistance of the magnesium alloy,meanwhile decreasing the corrosion current by two orders of magnitude of the substrate in simulated body fluid.The MTT assay indicated good cytocompatibility of L-929 cells with the fluoridated apatite coated magnesium alloy.
