SmCo7块状纳米晶烧结磁体的制备和性能

采用放电等离子烧结技术制备了致密纳米晶SmCo6.6Nb0.4烧结磁体,研究了磁体的结构和磁性能.结果表明,烧结磁体具有TbCu7结构,说明通过SPS过程可以获得稳定的1:7相;磁体由平均晶粒尺寸约为30 nm的1:7相构成,磁体的室温矫顽力高达2.8 T,而剩磁比高达0.74,说明在纳米晶之间存在强烈的晶间交换耦合作用.烧结磁体具有良好的高温性能,773K时的矫顽力为0.48 T,矫顽力温度系数β为-0.169%/K.     

块状纳米晶Sm2Co17烧结磁体的研究

采用高能球磨和放电等离子烧结技术制备了致密纳米晶Sm2Co17烧结磁体,研究了粉末和烧结磁体的结构和磁性能.球磨粉末在低温退火(<1023K)时,主相为TbCu7结构;高温退火(>1023K)时,主相为Th2Zn17结构.退火温度从923K增加到1223K,粉末的矫顽力从0.99T下降到0.12T.烧结磁体也具有TbCu7结构,磁体平均晶粒尺寸约为35nm.室温时磁体的剩磁为0.65T,矫顽力达0.87T.烧结磁体具有较好的高温性能,573K时的剩磁为0.6T,矫顽力为0.32T.     

SmCo6.6Nb0．4块状纳米晶烧结磁体的结构和磁性能

采用SPS技术制备了纳米晶SmCo6．6Nb0.4烧结磁体，研究了磁体的结构和磁性能．X衍射结果表．4明烧结磁体具有TbCu7结构，说明SPS过程可以获得稳定的1：7相．TEM观察显示，磁体由平均晶粒尺寸约为30nm的1：7相构成．室温时磁体的矫顽力高达2．8T，而剩磁比高达0．74，说明在纳米晶之间存在强烈的晶间交换耦合作用．烧结磁体具有良好的高温性能，矫顽力温度系数β为-0.169％/K。     

放电等离子烧结制备块状纳米晶SmCo5烧结磁体

采用放电等离子烧结（SPS）技术制备了致密纳米晶SmCo5烧结磁体，研究了磁体的结构和磁性能。X衍射结果表明，烧结磁体具有CaCu5结构，说明SPS过程可以获得稳定的1：5相。TEM观察显示，磁体由平均晶粒尺寸约为30nm的1：5相构成。室温时磁体的矫顽力高达2208kA/m，而剩磁比高达0，7，说明在纳米晶之间存在强烈的晶间交换耦合作用。烧结磁体具有良好的高温性能，773K时的矫顽力为456kA/m，矫顽力温度系数β为-0．212％/K。     

SmCo7-xFex块状纳米晶烧结磁体的研究

采用放电等离子烧结技术制备了块状纳米晶SmCo7-xFex（x=0，0．4，1，2）烧结磁体，对磁体的微观结构扣磁性能进行了观察扣测试．X衍射结果表明，烧结磁体具有TbCu7结构，说明SPS过程可以获得稳定的1：7相．TEM观察显示，磁体晶粒尺寸在20～50nm．磁体具有较好的磁性能，x=0．4时，矫顽力为992．8kA/m，剩磁为0．634T（BH）max为69．75kJ/m^3。     

放电等离子烧结温度对热压/热变形NdFeB纳米晶永磁体磁性能的影响

采用放电等离子烧结技术制备了热压/热变形NdFeB磁体。研究了不同烧结温度对热压磁体、热变形磁体微观结构及磁性能的影响。结果表明,随烧结温度的升高,磁体密度上升,680℃时已达理论密度的99.7%;另一方面,晶粒则随温度的增加发生长大。剩磁和最大磁能积受密度和晶粒大小的交互作用,在650℃时达最大:(BH)m=129kJ/m3,Br=0.87T,Hci=914kA/m。热变形后,磁体主相晶粒的c轴逐渐转向与压力平行的方向,形成磁晶各向异性,使磁体的剩磁和最大磁能积大幅增加。热压烧结温度对热变形磁体的磁性能有着极大影响,其剩磁和最大磁能积随热压温度的升高先升高后降低,620℃热压后,热变形磁体磁性能达最大:(BH)m=339kJ/m3,Br=1.49T,Hci=576kA/m。     

热处理工艺对块体纳米晶Fe3B/Nd2Fe14B复合磁体性能的影响

采用放电等离子烧结技术(Spark Plasma Sintering,简称SPS技术)将快淬Nd4.5Fe77B18.5薄带制备成块状纳米晶复合磁体.着重研究了热处理工艺对磁体密度、微观结构和磁性能的影响.结果表明,通过直接烧结得到的磁体具有超细纳米晶结构,合适的热处理可以消除残余非晶,得到较好的晶体结构和磁性能.但过高的热处理温度和较长的保温时间的增大会造成晶粒长大,结果导致磁性能的恶化.在最佳热处理条件下得到的磁体的磁性能为Br=1.014T,JHc=237.21 kA/m,(BH)max=61.85 kJ/m3.     

NdH纳米助剂回收制备烧结钕铁硼永磁体的研究

采用NdH纳米掺杂的方法对废旧烧结钕铁硼磁体进行了回收制备。研究了不同NdH纳米粉掺杂量对再制造烧结钕铁硼磁性能的影响。随着NdH纳米粉末掺杂量的增多,烧结磁体矫顽力从926.54 kA/m增加到1 299.87 kA/m;剩磁首先相对稳定在1.296 T,在掺杂量2.0%(质量分数)后,剩磁逐渐下降。与原始磁体相比,2.0%(质量分数)NdH纳米粉掺杂磁体性能最佳,矫顽力回复97.5%,剩磁回复95.9%,磁能积回复89.7%。通过计算,掺杂3.0%(质量分数)NdH纳米粉后,再制造烧结磁体中富钕相体积分数从3.03%增加到5.70%,然而其晶粒尺寸从8.18μm增长至11.68μm。结合微观分析与磁性能,2.0%(质量分数)NdH纳米粉掺杂磁体性能最好。     

回收制备烧结Nd-Fe-B磁体的磁性能与耐热性能

以废旧钕铁硼磁体为原料,采用短流程回收制备技术制备了烧结Nd-Fe-B磁体,通过添加镨钕混合稀土研究了磁体的磁性能和耐热性能.结果表明,在回收磁体中添加2％ PrNd,制备的烧结Nd-Fe-B磁体的剩磁为1.31T、矫顽力为1 474.86 kA/m、磁能积为353.90 kJ/m3.与一次成品相比矫顽力恢复到102％,剩磁恢复到95％,磁能积恢复到90％.在293～393 K范围内未掺杂PrNd磁体的矫顽力温度系数为-0.589 9％/K,掺杂2％PrNd磁体的矫顽力温度系数为-0.556 4％/K,提高了磁体在高温下的耐热性能.这是由于添加混合稀土PrNd增强了主相晶粒间的去磁交换耦合作用,提高了主相的磁晶各向异性场,从而提高了磁体的矫顽力和耐热性能.     

烧结温度对稀土永磁Sm(Co0.72Fe0.15Cu0.1Zr0.03)7.5的磁性能的影响

采用粉末冶金法制备稀土永磁Sm(Co0.72Fe0.15Cu0.1Zr0.03)7.5,研究烧结温度对磁体的磁性能的影响.结果表明:随着烧结温度的提高,剩磁Br、内禀矫顽力Hci及最大磁能积(BH)max都先增加后降低.虽然Br在烧结温度为1220℃时获得最大值0.95T,但磁体的综合磁性能在烧结温度为1215℃时最优,Br、Hci和(BH)max分别达到0.94T、2276.6kA·m-1和171.9kJ·m-3.1215℃烧结的磁体的温度稳定性较好,有望应用到550℃环境中.     

放电等离子烧结NdFeB磁体的磁化特征

利用放电等离子烧结技术(SPS)制备烧结钕铁硼磁体SPS NdFeB。为了更好地理解SPS Nd-FeB磁体的磁硬化机理,利用振动样品磁强计研究了SPS NdFeB磁体在室温下的磁化和反磁化过程。结果表明,在强度为800kA/m的较低外加磁场和强度为1760kA/m的较高外加磁场下的磁化特征明显不同,前者可称为形核控制模式,后者则为钉扎控制模式。比较样品的磁化过程和反磁化过程的曲线,发现样品的矫顽力大小等于样品磁化过程钉扎场的大小。     

SmCo_5/α-Fe双相复合纳米晶磁体的结构与磁性研究

超声波分解Fe（CO）5的产物Fe纳米颗粒,通过非均相沉淀获得包覆型SmCo5/α-Fe双相复合磁粉,采用放电等离子快速热压技术（Spark Plasma Sintering,SPS）制备出全致密的各向同性Sm-Co5/α-Fe双相复合纳米晶磁体,研究发现,软磁相α-Fe添加后,磁体的剩磁Mr有所提高,矫顽力Hci则有所减小,随后通过对各向同性磁体进行热变形制备出各向异性磁体,形成了较好的C轴晶体织构。软磁相α-Fe名义含量为10%时,磁体磁性能为：μ0Ms=1.01T、μ0Mr=0.86T、Hci=0.1708T。     

Large aperture superconducting magnet (benkei)

Benkei, which was a large window frame conventional magnet at KEK has been converted to a superconducting magnet. In the conversion, the pole gap has been doubled from 0.5 m to 1.0 m retaining an analysing power at 2 T m. Several new techniques were applied to coil windings and cryostat fabrication. The superconducting Benkei has shown satisfactory performances for long term operation.     

Bulk Nanocrystalline SmCo6.6Nb0.4 Sintered Magnet With TbCu7-Type Structure Prepared by Spark Plasma Sintering

We prepared bulk nanocrystalline SmCo_6.6Nb_0.4 sintered magnet material by spark plasma sintering technique. X-ray diffraction patterns show that the magnet exhibits a stable TbCu₇ structure. Transmission electron microscopy indicates that the microstructure of the magnet is composed of SmCo_6.6Nb_0.4 single-phase grains with an average grain size of 30 nm. Magnetic measurement shows that under a 7 T magnetic field, the coercivity of the magnet reaches as high as 2.8 T; the saturation magnetization and the remanence are 69.6 and 51.4 emu/g, respectively. The magnet exhibits good thermal stability with the coercivity of 0.48 T at 773 K, and the coercivity temperature coefficient beta of -0.169%/K.     

放电等离子烧结NdFeB磁体的氧化和腐蚀行为

采用放电等离子烧结技术制备了新型NdFeB磁体,研究了NdFeB磁体在湿热环境下的氧化行为和在电解质溶液中的电化学特性.在扫描电子显微镜下分析了磁体的显微组织结构和成分.结果表明,与传统烧结NdFeB磁体相比,新型磁体的显微组织特征为:主相Nd2Fe14B晶粒细小、均匀,富钕相在主相晶粒边界上分布较少,主要集中在三角晶界处.这种组织结构有效抑制了磁体沿富钕相发生的晶间腐蚀的过程,使磁体具有良好的耐腐蚀性能.     

Electric-magnetic field-induced aligned electrospun poly (ethylene oxide) (PEO) nanofibers

In this work, we report our attempt on the production of well-aligned nanofibers of poly (ethylene oxide) (PEO) by the introduction of magnetic field in the electric field by placing a cylindrical magnet within the electric field. Well-aligned nanofibers were obtained on top of the magnet. No particular structure could be associated with the other sides of the magnet. The aligned nanofibers were characterized by a host of characterization techniques such as optical and scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The diameter of the PEO nanofibers ranged between 500 and 1000 nm.     

Design of an energy storage flywheel system using permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB)

We propose a new energy storage flywheel system using a superconducting magnetic bearing (SMB) and a permanent magnet bearing (PMB). The superconducting magnetic bearing (SMB) suppresses the vibrations of the flywheel rotor. And the permanent magnet bearing (PMB) passively controls the rotor position. The energy storage flywheel system is characterized by using the two different type magnetic bearings of permanent magnet bearing (PMB) and superconducting magnetic bearing (SMB). This paper, discusses the design of the permanent magnet bearing (PMB) and the dynamics of the new energy storage flywheel system.     

AC loss in YBCO coated conductors at high dB/dt measured using a spinning magnet calorimeter (stator testbed environment)

A new facility for the measurement of AC loss in superconductors at high dB/dt has been developed. The test device has a spinning rotor consisting of permanent magnets arranged in a Halbach array; the sample, positioned outside of this, is exposed to a time varying AC field with a peak radial field of 0.566 T. At a rotor speed of 3600 RPM the frequency of the AC field is 240 Hz, the radial dB/dt is 543 T/s and the tangential dB/dt is 249 T/s. Loss is measured using nitrogen boiloff from a double wall calorimeter feeding a gas flow meter. The system is calibrated using power from a known resistor. YBCO tape losses were measured in the new device and compared to the results from a solenoidal magnet AC loss system measurement of the same samples (in this latter case measurements were limited to a field of amplitude 0.1 T and a dB/dt of 100 T/s). Solenoidal magnet system AC loss measurements taken on a YBCO sample agreed with the Brandt loss expression associated with a 0–0.1 T I_c of 128 A. Subsequently, losses for two more YBCO tapes nominally identical to the first were individually measured in this spinning magnet calorimeter (SMC) machine with a B_max of 0.566 T and dB/dt of up to 272 T/s. The losses, compared to a simplified version of the Brandt expression, were consistent with the average I_c expected for the tape in the 0–0.5 T range at 77 K. The eddy current contribution was consistent with a 77 K residual resistance ratio, RR, of 4.0. The SMC results for these samples agreed to within 5%. Good agreement was also obtained between the results of the SMC AC loss measurement and the solenoidal magnet AC loss measurement on the same samples.