By combining the α/γ interface migration and the carbon diffusion at the interface in Fe-C alloys, a mathematical model is constructed to describe the mixed-control mechanism for proeutectoid ferrite formation from ...By combining the α/γ interface migration and the carbon diffusion at the interface in Fe-C alloys, a mathematical model is constructed to describe the mixed-control mechanism for proeutectoid ferrite formation from austenite. In this model, the α/γ interface is treated as non-equilibrium interface, i.e., the carbon concentration of austenite at γ/α interface is obtained through theoretical calculation, instead of that assumed as the local equilibrium concentration. For isothermal precipitation of ferrite in Fe-C alloys, the calculated results show that the rate of interface migration decreases monotonically during the whole process, while the rate of carbon diffusion from γ/α interface into austenite increases to a peak value and then decreases. The process of ferrite growth may be considered as composed of three stages: the period of rapid growth, slow growth and finishing stage. The results also show that the carbon concentration of austenite at γ/α interface could not reach the thermodynamic equilibrium value even at the last stage of ferrite growth.展开更多
The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle ...The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle size on the process were explored.It is found that the recoveries of Sb and Fe reach86.1%and28.8%,respectively,when the reaction conditions are4.0mol/L HCl,900r/min stirring speed at85°C with<0.074mm particle size after50min leaching.XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model.The leaching of Sb corresponds to diffusion-controlled model at low temperature(15?45°C)and mixed-controlled model at high temperature(45?85°C),and the apparent activation energies are6.91and17.93kJ/mol,respectively.The leaching of Fe corresponds to diffusion-controlled model,and the apparent activation energy is1.99kJ/mol.Three semi-empirical rate equations are obtained to describe the leaching process.展开更多
基金This work was supported by the National Natural Science Foundation of China under grant No.50075053the Emphasized Item of Development Funds of Science and Technology of Shanghai City,China(No.03H201).
文摘By combining the α/γ interface migration and the carbon diffusion at the interface in Fe-C alloys, a mathematical model is constructed to describe the mixed-control mechanism for proeutectoid ferrite formation from austenite. In this model, the α/γ interface is treated as non-equilibrium interface, i.e., the carbon concentration of austenite at γ/α interface is obtained through theoretical calculation, instead of that assumed as the local equilibrium concentration. For isothermal precipitation of ferrite in Fe-C alloys, the calculated results show that the rate of interface migration decreases monotonically during the whole process, while the rate of carbon diffusion from γ/α interface into austenite increases to a peak value and then decreases. The process of ferrite growth may be considered as composed of three stages: the period of rapid growth, slow growth and finishing stage. The results also show that the carbon concentration of austenite at γ/α interface could not reach the thermodynamic equilibrium value even at the last stage of ferrite growth.
基金Project (51474257) supported by the National Natural Science Foundation of ChinaProject (2015zzts037) supported by the Postgraduate Research and Innovation Projects of Hunan Province,ChinaProject (2015JC3005) supported by the Key Technology Research and Development Program of Hunan Province,China
文摘The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle size on the process were explored.It is found that the recoveries of Sb and Fe reach86.1%and28.8%,respectively,when the reaction conditions are4.0mol/L HCl,900r/min stirring speed at85°C with<0.074mm particle size after50min leaching.XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model.The leaching of Sb corresponds to diffusion-controlled model at low temperature(15?45°C)and mixed-controlled model at high temperature(45?85°C),and the apparent activation energies are6.91and17.93kJ/mol,respectively.The leaching of Fe corresponds to diffusion-controlled model,and the apparent activation energy is1.99kJ/mol.Three semi-empirical rate equations are obtained to describe the leaching process.
