The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd Fe B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process ...The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd Fe B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0 0015% at 1073 K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523~723 K for 1 h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet.展开更多
Hydrogen decrepitation and desorption of the Nd16Fe76B8 magnet are studied by X-ray diffraction analysis and Fe Mossbauer spectroscopy. The results of the as-cast alloy samples treated under various hydrogen gas press...Hydrogen decrepitation and desorption of the Nd16Fe76B8 magnet are studied by X-ray diffraction analysis and Fe Mossbauer spectroscopy. The results of the as-cast alloy samples treated under various hydrogen gas pressures at various temperatures are reported. A special hydrogenation- dehydrogenation treatment of the Nd- Fe- B cast alloy can produce excellent isotropic magnet powders and the treated sample has passed a hydrogenation- disproportion- recombination process. The effect of the presence of α- Fe in magnet powders is discussed.展开更多
1.IntroductionThe rhombohedral compoundSmFeN(x=1~3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N material...1.IntroductionThe rhombohedral compoundSmFeN(x=1~3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N materials with quite good mag-展开更多
The technical parameters of HD process were studied, including the effects of temperature and neodymium contents on the incubation period of hydrogen absorption, hydrogen concentration and the rate of hydrogen absorbe...The technical parameters of HD process were studied, including the effects of temperature and neodymium contents on the incubation period of hydrogen absorption, hydrogen concentration and the rate of hydrogen absorbed. The results show that the incubation period is shortened and the rate of hydrogen absorbed is accelerated with rising temperature and surface area. These are attributed to the rising rate of hydrogen diffusion at higher temperature. The change of the incubation period and the rate of hydrogen absorbed have the similar trend resulted from the increasing content of the Nd-rich phase owing to the rising temperature. Moreover, the percent of the Nd-rich phase in the ingot can be calculated according to the total hydrogen weight gain.展开更多
The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than...The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than that of traditional ball milling (BM) magnet, while the remanence and the maximum energy product of HD magnet are lower. Microstructure analysis shows that some fine un sintered powders are distributed at the grain boundaries of HD magnet. X ray diffraction (XRD) analysis reveals that the degree of easy axis alignment of HD magnet is lower. Some ideas to improve the current HD process were proposed.展开更多
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
文摘The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd Fe B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0 0015% at 1073 K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523~723 K for 1 h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet.
文摘Hydrogen decrepitation and desorption of the Nd16Fe76B8 magnet are studied by X-ray diffraction analysis and Fe Mossbauer spectroscopy. The results of the as-cast alloy samples treated under various hydrogen gas pressures at various temperatures are reported. A special hydrogenation- dehydrogenation treatment of the Nd- Fe- B cast alloy can produce excellent isotropic magnet powders and the treated sample has passed a hydrogenation- disproportion- recombination process. The effect of the presence of α- Fe in magnet powders is discussed.
文摘1.IntroductionThe rhombohedral compoundSmFeN(x=1~3)is currently attractinginterest due to its promise as a new perma-nent magnet material.Its magnetic proper-ties have been investigated in details.TheSm-Fe-N materials with quite good mag-
文摘The technical parameters of HD process were studied, including the effects of temperature and neodymium contents on the incubation period of hydrogen absorption, hydrogen concentration and the rate of hydrogen absorbed. The results show that the incubation period is shortened and the rate of hydrogen absorbed is accelerated with rising temperature and surface area. These are attributed to the rising rate of hydrogen diffusion at higher temperature. The change of the incubation period and the rate of hydrogen absorbed have the similar trend resulted from the increasing content of the Nd-rich phase owing to the rising temperature. Moreover, the percent of the Nd-rich phase in the ingot can be calculated according to the total hydrogen weight gain.
文摘The effect of Hydrogen Decrepitation (HD) process on the magnetic properties and microstructure of sintered NdFeAlB magnet (HD magnet) was investigated. The results show that the coercivity of HD magnet is higher than that of traditional ball milling (BM) magnet, while the remanence and the maximum energy product of HD magnet are lower. Microstructure analysis shows that some fine un sintered powders are distributed at the grain boundaries of HD magnet. X ray diffraction (XRD) analysis reveals that the degree of easy axis alignment of HD magnet is lower. Some ideas to improve the current HD process were proposed.
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.