The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0~2.0 MP...The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0~2.0 MPa H2 pressure for several hours at room temperature for decrepitation. After disproportionation were high hydrogen pressures, the bulk alloys were disproportionated into particles with a size of 200. Investigations by powder X-ray diffractometer (XRD) showed, the after HD sample crystallized in the hexagonal CaCu5-type structure. The temperature dependence of pressure analysis (TPA) curve of the SmCo5 alloy showed that the hydrogen absorption temperature was about 150 ℃. Cylindrical sintered magnets of composition Sm36Co64 were prepared using HD ball milled, isostatic pressing, vacuum sintering and subsequent heat treatment. The demagnetization curves showed that the HD processes could improve the magnetic properties and squareness factor of the SmCo5 sintered magnet.展开更多
In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties ...In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).展开更多
The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the ...The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-east alloy with the thickness of 10 mm shows better activation property, higher 1C discharge capacity and better cyclic stability than others. It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloy with the thickness of 3 mm shows much better comprehensive electrochemical properties than as-east one; The cyclic. stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3 similar to 6 mm are improved after annealing. It is mainly owing to the great release of internal stress and the decrease of the segregation of Mn in the alloys.展开更多
In order to reduce the cost of LaNi5 based hydrogen storage alloys, effect of substitution of Mn for Ni on structural and electrochemical properties of LaNi4-xFeMnx (x=0-0.8) hydrogen storage alloys was studied system...In order to reduce the cost of LaNi5 based hydrogen storage alloys, effect of substitution of Mn for Ni on structural and electrochemical properties of LaNi4-xFeMnx (x=0-0.8) hydrogen storage alloys was studied systematically. X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that LaNi5 and La2Ni7 phases were invariably present in all alloy samples, and when x >= 0.4, (Fe, Ni) phase was observed. Electrochemical studies revealed that the discharge capacity reached a maximum value of 306.4 mAh/g when x=0.2 and the cycling stability decreased with the increase of x. With the increase of Mn content, hydrogen diffusion coefficient decreased, whereas high rate discharge-ability (HRD) and exchange current density first increased slowly when x <= 0.2 and then decreased markedly when x=0.8, indicating that electrochemical reaction on the surface of alloy electrodes had strong influence on kinetic property.展开更多
The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage allo...The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.展开更多
LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was ...LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was found that the 0.2 C discharge capacity increased with the increase of the thickness (from 1 mm to 10 mm) of the ingots, mainly due to the enlargement of the unit cell volume; Among the thickness of the ingots in our study, 10 mm sample showed a better activation property; LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 alloy with 10mm showed higher comprehensive properties than those with other thickness under 1C rate.展开更多
The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi_5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argo...The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi_5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argon atmosphere. The results showed that for LaNi_(5-x)M_x(M = Al, Fe, or Co) alloys, the lattice constants and unit cell volumes increased with an increasing amount of Al and Fe. On the other hand, these parameters decreased upon partial substitution of La by Ce. In addition, the lattice constant remained almost constant in the La_(0.6)Ce_(0.4)Ni_(5–x)Cox alloys regardless of the value of x(x = 0.3, 0.6, or 0.9), as Ce might enhance the homogeneity of the CaCu_5-type phase in Co-containing alloys. The hydrogen storage properties of the alloys were investigated using pressure, composition, and temperature isotherms. The experimental results showed that the plateau pressure decreased with an increasing content of Al, Fe, or Co, but it increased with Ce addition. Furthermore, the plateau pressures of all Co-containing alloys were almost identical upon substitution with Ce. Finally, the enthalpy(ΔH) and entropy(ΔS) values for all alloys were calculated using van't Hoff plots. The relationship between the lattice parameters and enthalpy changes for hydrogenation will be discussed.展开更多
The Cu-Ti-Si alloys containing in-situ formed Ti5Si3 are prepared. In order to clarify the Ti5Si3 formation processes and its microstructure characteristics, the as-cast and deeply etched Cu-Ti-Si alloys with differen...The Cu-Ti-Si alloys containing in-situ formed Ti5Si3 are prepared. In order to clarify the Ti5Si3 formation processes and its microstructure characteristics, the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that the eutectic Ti5Si3 phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix. In addition, there is Cu in the center of many Ti5Si3 rods, resulting in a core-shell structure. With the increase of the cooling rate, Ti5Si3 distributes more uniformly, and the diameter of Ti5Si3 significantly decreases, with a minimum size of less than 100 nm, while the aspect ratio of Ti5Si3 increases.展开更多
In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been in...In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been investigated by means of XRD, PCT, and measurement of electrochemical capacity and cycle life.The test results show that the effect of these two kinds of substituting elements on discharge capacity is Cu > Fe, and the cycle life is on the contrary.Both of them have no distinct influence on activity speed, but activity speed increases with the decrease of Co.By the order way, the high discharge rate characteristics rise with the addition of Cu and decreasing of Co.展开更多
Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereform...Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.展开更多
Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master...Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.展开更多
The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the ...The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the wetting angle of the liquid alloy raising in steel substrate surface and enhances the adhesive power and wettability between them.It is concluded that the mischmetal addition in baths influences the reac- tion between steel sheet and liquid Zn+5 wt%Al alloy and thus improves the wettability of them.展开更多
The electronic structures are calculated by the DV-Xa molecular orbital method employing small model clusters in order to clarify the roles of the hydride forming elements, A, (e.g., La, Zr Ti, Mg) and non-forming e...The electronic structures are calculated by the DV-Xa molecular orbital method employing small model clusters in order to clarify the roles of the hydride forming elements, A, (e.g., La, Zr Ti, Mg) and non-forming elements, B, (e.g., Ni, Mn, Fe) in hydrogen storage alloys. It is confirmed from this calculation that hydrogen interacts more strongly with hydride non-forming elements, B, than hydride forming elements, A, in agreement with our previous calculations. However,the B-H interaction is enhanced only when some A element exists in the neighborhood. Otherwise, such a B-H interaction never operates in the alloy. In this sense,the coexistence of A and B elements are essential in the constitution of hydrogen storage alloys. Also, it is shown that the A/B compositional ratio of hydrogen storage alloys is understood in terms of a simple parameter, 2Bo(A - B) / /Bo(A - A)+ Bo(B-B)], where the Bo(A-B), Bo(A-A) and the Bo(B-B) are the bond strengths between atoms given in the parentheses.展开更多
For hypereutectic Nb-Si based alloys,primary Nb_(5)Si_(3)phases typically grow in a faceted mode during equilibrium or near-equilibrium solidification,which damages the ductility and toughness.To address this issue,he...For hypereutectic Nb-Si based alloys,primary Nb_(5)Si_(3)phases typically grow in a faceted mode during equilibrium or near-equilibrium solidification,which damages the ductility and toughness.To address this issue,here we artificially manipulate the growth morphology of Nb_(5)Si_(3)using electron beam surface melting(EBSM)and subsequent annealing treatments.Results show that such a non-equilibrium solidification pathway enables the transition from faceted growth to non-faceted dendritic growth of Nb_(5)Si_(3),along with evident microstructure refinement,generation of metastableβ-Nb_(5)Si_(3)phases and elimination of chemical segregation.The transformation fromβ-Nb_(5)Si_(3)toα-Nb_(5)Si_(3)and Nb solid solution(Nbss)particles is triggered by the annealing treatment at 1450°C for 5 h.Also,we find the annealing-mediated formation of inherited Nb_(5)Si_(3)dendrites that maintain the dendritic morphology of the original as-solidifiedβ-Nb_(5)Si_(3)dendrites.This work thus provides a feasible routine to obtain thermally stable and refinedα-Nb_(5)Si_(3)dendrites in hypereutectic Nb-Si based alloys.展开更多
Negative electrodes of the Ni-metal hydride battery were made from hydrogen storage alloy Mm0.9Ti0. 1Ni3. 9Mn0.4Co0.4Al0.3 mod fied by coating with Ni or mixing with Co powder. The cell volume expansion of hexagonal s...Negative electrodes of the Ni-metal hydride battery were made from hydrogen storage alloy Mm0.9Ti0. 1Ni3. 9Mn0.4Co0.4Al0.3 mod fied by coating with Ni or mixing with Co powder. The cell volume expansion of hexagonal structure was about 12 % after coating with 11 % Ni on the alloy Surface,When this alloy was mixed with Co powder. the discharge capacity and the utilization efficiency of the hydrogen storage alloy increased. When the alloy was coated with 11 wt-% Ni and also mixed with 10 wt-% Co powder. the capacity decay for a small sealed cylindrical cell (AA size. 1 Ah) was only about 4 % after 200 cycles展开更多
基金the National Natural Science Foundation of ChinaBeijing Municipal Science &Technology Commission for financial support for the study
文摘The application of ‘extreme’ hydrogen-decrepitation (HD) process using high-pressure disproportionation was extended to Sm-Co5-type-alloy. The alloy with nominal composition of Sm36Co64 was treated under 1.0~2.0 MPa H2 pressure for several hours at room temperature for decrepitation. After disproportionation were high hydrogen pressures, the bulk alloys were disproportionated into particles with a size of 200. Investigations by powder X-ray diffractometer (XRD) showed, the after HD sample crystallized in the hexagonal CaCu5-type structure. The temperature dependence of pressure analysis (TPA) curve of the SmCo5 alloy showed that the hydrogen absorption temperature was about 150 ℃. Cylindrical sintered magnets of composition Sm36Co64 were prepared using HD ball milled, isostatic pressing, vacuum sintering and subsequent heat treatment. The demagnetization curves showed that the HD processes could improve the magnetic properties and squareness factor of the SmCo5 sintered magnet.
文摘In this study, the mechanical properties of aluminum-5%magnesium doped with rare earth metal neodymium were evaluated. Fuzzy logic (FL) and artificial neural network (ANN) were used to model the mechanical properties of aluminum-5%magnesium (0-0.9 wt%) neodymium. The single input (SI) to the fuzzy logic and artificial neural network models was the percentage weight of neodymium, while the multiple outputs (MO) were average grain size, ultimate tensile strength, yield strength elongation and hardness. The fuzzy logic-based model showed more accurate prediction than the artificial neutral network-based model in terms of the correlation coefficient values (R).
文摘The effect of thickness (1 similar to 10 mm) of the ingots on the electrochemical properties of as-cast and annealed strip cast LPCNi3.55Co0.75Mn0.4Al0.3 hydrogen storage alloys was investigated. It is found that the 0.2 C discharge capacity of as-cast LPCNi3.55Co0.75Mn0.4Al0.3 alloy increases with the increase of the thickness of the ingots. As-east alloy with the thickness of 10 mm shows better activation property, higher 1C discharge capacity and better cyclic stability than others. It is mainly contributed to its larger unit cell volume and less internal stress. Annealed LPCNi3.55Co0.75Mn0.4Al0.3 alloy with the thickness of 3 mm shows much better comprehensive electrochemical properties than as-east one; The cyclic. stability of the alloy with the thickness of 6 mm and the activation properties of the alloys with the thickness of 3 similar to 6 mm are improved after annealing. It is mainly owing to the great release of internal stress and the decrease of the segregation of Mn in the alloys.
基金Project supported by the National Nature Science Foundation of China (NSFC50571072)GD-MOE Coordination Project of Industry Academic and Research (2008B090500274)
文摘In order to reduce the cost of LaNi5 based hydrogen storage alloys, effect of substitution of Mn for Ni on structural and electrochemical properties of LaNi4-xFeMnx (x=0-0.8) hydrogen storage alloys was studied systematically. X-ray diffraction (XRD) and scanning electron microscope (SEM) showed that LaNi5 and La2Ni7 phases were invariably present in all alloy samples, and when x >= 0.4, (Fe, Ni) phase was observed. Electrochemical studies revealed that the discharge capacity reached a maximum value of 306.4 mAh/g when x=0.2 and the cycling stability decreased with the increase of x. With the increase of Mn content, hydrogen diffusion coefficient decreased, whereas high rate discharge-ability (HRD) and exchange current density first increased slowly when x <= 0.2 and then decreased markedly when x=0.8, indicating that electrochemical reaction on the surface of alloy electrodes had strong influence on kinetic property.
文摘The effects of low-Co AB_5 type hydrogen storage alloys prepared by quenchingand annealing on the performances of MH-Ni batteries were investigated, and the characteristics ofthe low-Co AB_5 type hydrogen storage alloys were compared with those of the high-Co AB_5 typehydrogen storage alloy as well. The results showed that the faster the cooling of the low-Cohydrogen storage alloy is, the better homogeneity of the chemical composition for the alloy and thelonger cycle life of the battery are, but the electrochemical discharge capacity and high-ratedischarge ability are reduced. The high-rate discharge ability and charge retention of MH-Nibatteries for the conventional as-cast annealed low-Co hydrogen storage alloy were superior to thosefor the rapidly quenched low-Co hydrogen storage alloy and the high-Co hydrogen storage alloy, buta little inferior in the cycle life.
文摘LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 hydrogen storage alloy was investigated, and the effects of thickness of its strip casting ingots(as cast) on the electrochemical performances were discussed. It was found that the 0.2 C discharge capacity increased with the increase of the thickness (from 1 mm to 10 mm) of the ingots, mainly due to the enlargement of the unit cell volume; Among the thickness of the ingots in our study, 10 mm sample showed a better activation property; LPCNi 3.55 Co 0.75 Mn 0.4 Al 0.3 alloy with 10mm showed higher comprehensive properties than those with other thickness under 1C rate.
基金partially supported by International Academic Exchange Program of Muroran Institute of Technology,Muroran(Japan)University of Science and Technology Beijing,Beijing(China)+1 种基金Environmentally Friendly Materials Education Program provided by Muroran MATERIAsupported by Beijing Key Laboratory of Energy Conservation and Emission Reduction for Metallurgical Industry,Beijing,China
文摘The effects of partial substitution of La by Ce and Ni by Al, Fe, or Co in LaNi_5-based alloys on hydrogen storage performance were systematically studied. All samples were prepared using vacuum arc melting in an argon atmosphere. The results showed that for LaNi_(5-x)M_x(M = Al, Fe, or Co) alloys, the lattice constants and unit cell volumes increased with an increasing amount of Al and Fe. On the other hand, these parameters decreased upon partial substitution of La by Ce. In addition, the lattice constant remained almost constant in the La_(0.6)Ce_(0.4)Ni_(5–x)Cox alloys regardless of the value of x(x = 0.3, 0.6, or 0.9), as Ce might enhance the homogeneity of the CaCu_5-type phase in Co-containing alloys. The hydrogen storage properties of the alloys were investigated using pressure, composition, and temperature isotherms. The experimental results showed that the plateau pressure decreased with an increasing content of Al, Fe, or Co, but it increased with Ce addition. Furthermore, the plateau pressures of all Co-containing alloys were almost identical upon substitution with Ce. Finally, the enthalpy(ΔH) and entropy(ΔS) values for all alloys were calculated using van't Hoff plots. The relationship between the lattice parameters and enthalpy changes for hydrogenation will be discussed.
基金This work was financially supported by the Natural Science Foundation of Hebei Province of China(Grant No.E2019502057)the Fundamental Research Funds for the Central Universities,China(Grant No.2018MS120).
文摘The Cu-Ti-Si alloys containing in-situ formed Ti5Si3 are prepared. In order to clarify the Ti5Si3 formation processes and its microstructure characteristics, the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that the eutectic Ti5Si3 phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix. In addition, there is Cu in the center of many Ti5Si3 rods, resulting in a core-shell structure. With the increase of the cooling rate, Ti5Si3 distributes more uniformly, and the diameter of Ti5Si3 significantly decreases, with a minimum size of less than 100 nm, while the aspect ratio of Ti5Si3 increases.
文摘In order to further reduce the cost of AB5 type rare earth-based hydrogen storage alloy, a low-Co AB5 type hydrogen storage alloy were by substituting Co with Cu and Fe.The characteristics of these alloys have been investigated by means of XRD, PCT, and measurement of electrochemical capacity and cycle life.The test results show that the effect of these two kinds of substituting elements on discharge capacity is Cu > Fe, and the cycle life is on the contrary.Both of them have no distinct influence on activity speed, but activity speed increases with the decrease of Co.By the order way, the high discharge rate characteristics rise with the addition of Cu and decreasing of Co.
文摘Magnetic properties and microstructure of SmCo_5 alloys were examined. It is found that the coercivity ofthe alloy is strongly influenced by its microstructure. If more non- 1 : 5 phase precipitated particles wereformed, which are properly due to the existing of oxygen in the alloys introduced during the heat treatment process, the magnetic properties of the alloy decrease.
文摘Al5Ti1B master alloy was produced by two-step method. Experimental results show that the structure of Al5TilB master alloy depends on that of AlTi and AlB master alloys, the morphologies of TiAl3 depend on AlTi master alloy and the boride phases depend on AlB master alloy. There are remarkable structure heredity between Al5Ti1B master alloy and AlTi, AlB master alloys. Theoretical analyses show that AlTi and Al-B master alloys can change the melt structure of Al5Ti1B master alloy, then affect the solid structure of the master alloy.
文摘The wetting of steel sheet by liquid Zn+5 wt%Al alloy has been measured by the Meniscograph. The result shows that the addition of mischmetal in Zn+5 wt%Al alloy decreases the surface tension of the alloy,reduces the wetting angle of the liquid alloy raising in steel substrate surface and enhances the adhesive power and wettability between them.It is concluded that the mischmetal addition in baths influences the reac- tion between steel sheet and liquid Zn+5 wt%Al alloy and thus improves the wettability of them.
文摘The electronic structures are calculated by the DV-Xa molecular orbital method employing small model clusters in order to clarify the roles of the hydride forming elements, A, (e.g., La, Zr Ti, Mg) and non-forming elements, B, (e.g., Ni, Mn, Fe) in hydrogen storage alloys. It is confirmed from this calculation that hydrogen interacts more strongly with hydride non-forming elements, B, than hydride forming elements, A, in agreement with our previous calculations. However,the B-H interaction is enhanced only when some A element exists in the neighborhood. Otherwise, such a B-H interaction never operates in the alloy. In this sense,the coexistence of A and B elements are essential in the constitution of hydrogen storage alloys. Also, it is shown that the A/B compositional ratio of hydrogen storage alloys is understood in terms of a simple parameter, 2Bo(A - B) / /Bo(A - A)+ Bo(B-B)], where the Bo(A-B), Bo(A-A) and the Bo(B-B) are the bond strengths between atoms given in the parentheses.
基金National Natural Science Foundation of China(Grant No.51571004).
文摘For hypereutectic Nb-Si based alloys,primary Nb_(5)Si_(3)phases typically grow in a faceted mode during equilibrium or near-equilibrium solidification,which damages the ductility and toughness.To address this issue,here we artificially manipulate the growth morphology of Nb_(5)Si_(3)using electron beam surface melting(EBSM)and subsequent annealing treatments.Results show that such a non-equilibrium solidification pathway enables the transition from faceted growth to non-faceted dendritic growth of Nb_(5)Si_(3),along with evident microstructure refinement,generation of metastableβ-Nb_(5)Si_(3)phases and elimination of chemical segregation.The transformation fromβ-Nb_(5)Si_(3)toα-Nb_(5)Si_(3)and Nb solid solution(Nbss)particles is triggered by the annealing treatment at 1450°C for 5 h.Also,we find the annealing-mediated formation of inherited Nb_(5)Si_(3)dendrites that maintain the dendritic morphology of the original as-solidifiedβ-Nb_(5)Si_(3)dendrites.This work thus provides a feasible routine to obtain thermally stable and refinedα-Nb_(5)Si_(3)dendrites in hypereutectic Nb-Si based alloys.
文摘Negative electrodes of the Ni-metal hydride battery were made from hydrogen storage alloy Mm0.9Ti0. 1Ni3. 9Mn0.4Co0.4Al0.3 mod fied by coating with Ni or mixing with Co powder. The cell volume expansion of hexagonal structure was about 12 % after coating with 11 % Ni on the alloy Surface,When this alloy was mixed with Co powder. the discharge capacity and the utilization efficiency of the hydrogen storage alloy increased. When the alloy was coated with 11 wt-% Ni and also mixed with 10 wt-% Co powder. the capacity decay for a small sealed cylindrical cell (AA size. 1 Ah) was only about 4 % after 200 cycles