By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures w...By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.展开更多
The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and ...The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.展开更多
The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel sp...The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel speed is 26 and 42 m/s, the as-spun ribbons are completely crystallized to the Ti-Ni B2 phase. The Ti-rich plate precipitates lying on {100} planes are observed in the as-spun ribbon fabricated with a wheel speed of 26 m/s. The spherical Ti2Ni precipitates are observed at grain boundaries in the as-spun ribbons fabricated with a wheel speed of 42 m/s. Amorphous and B2 phases coexist in the as-spun ribbon fabricated with a wheel speed of 52 m/s. The uniformity of grain size in heat treated ribbons decreases with increasing wheel speed.展开更多
The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbo...The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.展开更多
The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the tempera...The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the temperature dependence of their electrical resistivity as well as the typical transport properties of the amorphous alloys with comparatively high values of electrical resistivity, ρ. The normalized temperature coefficient of the resistivity (TCR ≡ 1/ρ300K·dρ/dT) tended to increase with increasing x in the temperature range of 100-300 K. These behaviors would suggest that the transport properties of the present amorphous ribbons were governed by temperature variation of the Debye-Waller factor, not by electron-phonon scattering. The hydrogen charged ribbons obtained by an electrochemical method also showed similar electrical resistivity behaviors as a function of the temperature. However, TCR of x = 40 with hydrogen charged ribbon, in which the amount of absorbed hydrogen was about 14 at%, increased about three times more than that of the pre-charged amorphous ribbon.展开更多
基金Projects(51271149,50901060)supported by the National Natural Science Foundation of ChinaProject(NPU-310201401007JCY01007)supported by the Nothwestern Polytechnical University(NPU)Foundations for Fundamental Research,ChinaProject(2012-0009451)supported by the National Research Foundation of Korea
文摘By using the melt spinning techniques, the Fe63Co32Gd5 alloy ribbons with 15-50 m in thickness and 3-7 mm in width were prepared at the wheel speeds of 15, 20, 25 and 35 m/s. The rapid solidification microstructures were characterized by three layers, the middle layer of which reaches 80% thickness and forms the column grain of(Fe,Co) solid with Gd solution. Grain refinement takes place with the increase of the wheel speed. And after 0.5 h heat treatment at 823 K, the ribbon thickness becomes larger and the middle layer of column grain is very orderly perpendicular to the ribbon plane. The coercivity of quenched and annealed Fe63Co32Gd5 ribbons both have the inflection point at the wheel speed of 20 m/s, and the tendency is declining. The heat treatment processing makes the coercivity become lower by improving the order of(Fe,Co)17Gd2 compound. The saturation magnetization of quenched ribbons increases with the enhancement of wheel speed, whereas that of annealed ones decreases firstly and then increases. The minimum coercivity is 5.30×103 A/m and the maximum saturation magnetization is 163.62 A·m2/kg, which is obtained in the conditions of the wheel speed of 35 m/s and 0.5 h heat treatment at the temperature of 823 K.
文摘The effects of Co as a substituent for Ni on microstructure and electrochemical capacity of hydrogen storage alloys MI（NiCoMnAl）5.4 at -30- ＋80 ℃, in which the content of Co was 0, 1.31%, 2.63%, 3.94%, 5.25%, and 6.56% （mass fraction）, respectively, were reported. All of the alloys were prepared by vacuum induction melting followed by melt-spinning. It is found that the electrochemical capacity of alloys at different temperature depends upon the compositions and preparation methods. The electrochemical capacity of alloys increases at higher temperature （40 - 80 ℃ ） and decreases at lower temperature （ - 30 - 0 ℃ ） with an increasing cobalt content. With an increasing temperature, melt-spinning is more favorable for improved capacity of the alloys than casting. Analyses of the charging/discharging potential curves illustrate that higher cobalt content and melt-spinning techniques are more effective to increase the capacity at higher temperature because of the higher hydrogen evolution potential. On the contrary, the capacity of alloys at lower temperature can be increased by decreasing cobalt content and casting, which is ascribed to higher hydrogen evolution potential and delayed hydrogen evolution reaction, as well as reduced potential drop in the charging/discharging process. XRD patterns confirm that all of the specimens present a single hexagonal CaCu5-type structure and an increased lattice parameters with increasing Co content. The FWHM of the main peak of melt-spun ribbons reduces because of more homogeneous composition and less lattice strain defects.
文摘The effect of wheel speed on microstructures of Ti-48%Ni (mole fraction) melt-spun ribbons was investigated by X-ray diffractometry, scanning electron microscopy and transmission electron microscopy. When the wheel speed is 26 and 42 m/s, the as-spun ribbons are completely crystallized to the Ti-Ni B2 phase. The Ti-rich plate precipitates lying on {100} planes are observed in the as-spun ribbon fabricated with a wheel speed of 26 m/s. The spherical Ti2Ni precipitates are observed at grain boundaries in the as-spun ribbons fabricated with a wheel speed of 42 m/s. Amorphous and B2 phases coexist in the as-spun ribbon fabricated with a wheel speed of 52 m/s. The uniformity of grain size in heat treated ribbons decreases with increasing wheel speed.
基金Supported by the National High Technology Research and Development Programme of China under Grant No 2003AA327010, and the National Natural Science Foundation of China under Grant No 60271028.
文摘The microstructure of CosoNi22Ga28 ribbon with the L10 structure is examined. The band-like morphology is observed. These bands with the width in a range of 40-200 nm appear along the transverse direction of the ribbon. The giant magnetoimpedance （GMI） effect in this alloy is measured. The results show that Co5oNi22Ga28 exhibits a sharp peak of the GAI effect. The maximum GAH ratio up to 360% is detected. The GMI effect measured versus temperature shows large jumps of the magnetoimpedance amplitude at the reversal martensitic transformation temperature 240℃ and Curie temperature 375℃C respectively. The jump ratios of the magnetoimpedance amplitude examined at these temperatures are about 5 and 10, respectively.
文摘The electrical transport properties of (Ni0.8Nb0.2)100-xZrx (x = 30, 40 and 50) amorphous ribbons and hydrogen charged specimens were investigated. The amorphous ribbons indicated a negative coefficient in the temperature dependence of their electrical resistivity as well as the typical transport properties of the amorphous alloys with comparatively high values of electrical resistivity, ρ. The normalized temperature coefficient of the resistivity (TCR ≡ 1/ρ300K·dρ/dT) tended to increase with increasing x in the temperature range of 100-300 K. These behaviors would suggest that the transport properties of the present amorphous ribbons were governed by temperature variation of the Debye-Waller factor, not by electron-phonon scattering. The hydrogen charged ribbons obtained by an electrochemical method also showed similar electrical resistivity behaviors as a function of the temperature. However, TCR of x = 40 with hydrogen charged ribbon, in which the amount of absorbed hydrogen was about 14 at%, increased about three times more than that of the pre-charged amorphous ribbon.
