The lamellar peritectic coupled growth in Fe-Ni peritectic system was investigated using the equilibrium Boettinger-Jackson-Hunt model.It was found that the slope of the undercooling vs.lamellar spacing is very near z...The lamellar peritectic coupled growth in Fe-Ni peritectic system was investigated using the equilibrium Boettinger-Jackson-Hunt model.It was found that the slope of the undercooling vs.lamellar spacing is very near zero around the minimum overheating,and the coupled growth can exist under this condition even if the slope of the undercooling vs.lamellar spacing curve is slightly smaller than zero.In addition,the peritectic reaction can never reach completion during the peritectic coupled growth.So the equilibrium peritectic coupled growth was modified by considering the incompletion of the peritectic reaction.It was shown that when the fractions of the peritectic reaction reach 60%-80% completion,the calculated undercooling vs.lamellar spacing curves agree well with the experimental obser-vations in the directionally solidified Fe-Ni alloys.展开更多
The electromagnetic levitation melting of the rare earth giant magnetostrictive materials Tb 0.27 Dy 0.73 Fe 1.90 alloys is realized. The compound is difficult to realize levitation melting at terrestrial environment ...The electromagnetic levitation melting of the rare earth giant magnetostrictive materials Tb 0.27 Dy 0.73 Fe 1.90 alloys is realized. The compound is difficult to realize levitation melting at terrestrial environment because of its high density and low electric conductivity. The microstructure of the sample near peritectic composition obtained by this process contains REFe 2 matrix phase, a large amount of rod like REFe 3 phase embedded in the matrix phase, rare earth rich phase enriching around the REFe 3 phase and a small amount of rare earth rich phase in the REFe 2 matrix phase far from the REFe 3 phase, which is significantly different from that of the sample obtained by general melting casting process with the same composition,which contains almost complete REFe 2 phase and a small amount of RE rich phase in the REFe 2 matrix phase. The formation of the microstructure can be attributed to the coupled growth of the peritectic phase—REFe 2 and the primary phase—REFe 3 , and the subsequent eutectic reaction under this experimental condition.展开更多
Laser remelting experiments were performed by a 1.0?kW continuous CO 2 laser to investigate the rapid solidification behavior of Zn rich Zn Ag peritectic alloys. Three kinds of microstructures occurrs with the varying...Laser remelting experiments were performed by a 1.0?kW continuous CO 2 laser to investigate the rapid solidification behavior of Zn rich Zn Ag peritectic alloys. Three kinds of microstructures occurrs with the varying of laser scanning speed and Ag content in the alloys. It is mainly plate like single phase cellular η when the Ag content was lower than 1.8% (mole fraction). As the Ag content increased, instead of typical structure of primary dendrites of ε surrounded by peritectic η , a two phase plate like η+ε with primary dendrites of ε is found when the laser scanning speed was higher than a critical value. Intercellular spacing of cellular η or interphase spacing of two phase couple growth η+ε decreases with increasing laser scanning speed.展开更多
This paper focuses on the research of the bioconversion of 1,3-propanediol by Klebsiella pneumoniae. The linear correlation of cell growth and 1,3-propanediol synthesis was found. An equation of the relationship betwe...This paper focuses on the research of the bioconversion of 1,3-propanediol by Klebsiella pneumoniae. The linear correlation of cell growth and 1,3-propanediol synthesis was found. An equation of the relationship between cell growth and biocatalysis was given.With the analysis of metabolism, it was discovered that the cell regulated the NADH production by cell growth in order to supply enough reductive equivalent for enzyme catalysis. A conclusion was drawn that the cell growth was coupled with the reactivation of a key-enzyme which catalyzes 1,3-propanediol production in Klebsiella pneumoniae.展开更多
基金the National Natural Science Foundation of China (Grant Nos. 50395102 and 50271020) the Program for New Century Excellent Talents in University (Grant No. 05-0530)
文摘The lamellar peritectic coupled growth in Fe-Ni peritectic system was investigated using the equilibrium Boettinger-Jackson-Hunt model.It was found that the slope of the undercooling vs.lamellar spacing is very near zero around the minimum overheating,and the coupled growth can exist under this condition even if the slope of the undercooling vs.lamellar spacing curve is slightly smaller than zero.In addition,the peritectic reaction can never reach completion during the peritectic coupled growth.So the equilibrium peritectic coupled growth was modified by considering the incompletion of the peritectic reaction.It was shown that when the fractions of the peritectic reaction reach 60%-80% completion,the calculated undercooling vs.lamellar spacing curves agree well with the experimental obser-vations in the directionally solidified Fe-Ni alloys.
文摘The electromagnetic levitation melting of the rare earth giant magnetostrictive materials Tb 0.27 Dy 0.73 Fe 1.90 alloys is realized. The compound is difficult to realize levitation melting at terrestrial environment because of its high density and low electric conductivity. The microstructure of the sample near peritectic composition obtained by this process contains REFe 2 matrix phase, a large amount of rod like REFe 3 phase embedded in the matrix phase, rare earth rich phase enriching around the REFe 3 phase and a small amount of rare earth rich phase in the REFe 2 matrix phase far from the REFe 3 phase, which is significantly different from that of the sample obtained by general melting casting process with the same composition,which contains almost complete REFe 2 phase and a small amount of RE rich phase in the REFe 2 matrix phase. The formation of the microstructure can be attributed to the coupled growth of the peritectic phase—REFe 2 and the primary phase—REFe 3 , and the subsequent eutectic reaction under this experimental condition.
文摘Laser remelting experiments were performed by a 1.0?kW continuous CO 2 laser to investigate the rapid solidification behavior of Zn rich Zn Ag peritectic alloys. Three kinds of microstructures occurrs with the varying of laser scanning speed and Ag content in the alloys. It is mainly plate like single phase cellular η when the Ag content was lower than 1.8% (mole fraction). As the Ag content increased, instead of typical structure of primary dendrites of ε surrounded by peritectic η , a two phase plate like η+ε with primary dendrites of ε is found when the laser scanning speed was higher than a critical value. Intercellular spacing of cellular η or interphase spacing of two phase couple growth η+ε decreases with increasing laser scanning speed.
文摘This paper focuses on the research of the bioconversion of 1,3-propanediol by Klebsiella pneumoniae. The linear correlation of cell growth and 1,3-propanediol synthesis was found. An equation of the relationship between cell growth and biocatalysis was given.With the analysis of metabolism, it was discovered that the cell regulated the NADH production by cell growth in order to supply enough reductive equivalent for enzyme catalysis. A conclusion was drawn that the cell growth was coupled with the reactivation of a key-enzyme which catalyzes 1,3-propanediol production in Klebsiella pneumoniae.
