Cellular microstructure modification and high temperature performance enhancement for Sm2Co17-based magnets with different Zr contents

Influence of Zr contents on high-temperature magnetic performance of Sm(CoFeCuZr)(x=0.025,0.03,0.035,0.04) magnets were investigated.As x increases from 0.025 to 0.04,the temperature coefficient of intrinsic coercivity(H) is optimized from-0.1673% K^(-1)to-0.1382% K^(-1)and the Hat 773 K gradually increases from 556.32 kA m^(-1)to 667 kA m^(-1).The microstructure and microchemistry of different Zr-content magnets were revealed by a transmission electron microscope equipped with EDS.The increasing Zr content induces that the average size of cells decreases from ~76 nm to ~56 nm and the weight fraction of 1:5 H cell boundary phase increases from ~25% to ~37% as well,resulting decreasing of the average Cu content at cell boundaries from 13.59 at% to ~8.52 at%.It is found that the Cu-lean characteristic at cell boundary phase is the reason that gives rise to higher magnetic properties at elevated temperatures for x=0.04 magnet.

Observational connection between local high-temperature phenomena within magnetic clouds and the Sun

Magnetic clouds(MCs) frequently show abnormal high-ionization states of heavy ions. The abnormal high-charge distributions are related to the coronal temperature of their source regions. We examined the plasma and magnetic field data of 74 MCs observed by the Advanced Composition Explorer from February 1998 to December 2008. We determined that 14 of the 74 events showed local high-temperature phenomena. We analyzed the correlation between proton temperature and O7/O6ratio(or high mean Fe charge state ?Fe?) within the local high-temperature regions in the 14 MCs. Results show that proton temperature and O7/O6 ratio(or high mean Fe charge state) had good correlations in nine MCs, but had no evident correlation in the other five MCs. The local high-temperature phenomena within the nine MCs have resulted from the Sun.

Review on thermal-related measurement methods for superconducting devices and prospect for high-speed maglev transportation application

High‐temperature superconducting(HTS)bulks can not only be self‐stable when levitated above a permanent magnet(PM)but also can be used as quasi PM with higher magnetic energy product due to their magnetic flux pinning characteristics.Therefore,HTS bulks have wide application potentials in maglev trains,maglev bearings,flywheel energy storage,drug delivery,and high field magnets.In the external magnetic field of common application scenarios,HTS bulks have no external input current,so it is difficult to achieve the overall quench.However,local quenching in the bulk is still possible in the harsh fluctuating external field environment.Although it is difficult to reach the total quench,its critical parameters like Jc will inevitably deteriorate,which may collapse the application system.Therefore,in contrast to superconducting wires and tapes that are more concerned with quench detection,HTS bulks with a 3D volume effect are more focused on internal sensitive temperature locations,the impacts of volume and scale,and the coupling influence on application parameters such as magnetism and force.Therefore,for efficient thermal‐related measurement of HTS bulk applications,this paper investigates and discusses 12 commonly‐used temperature measurement or quench detection methods in all superconducting application fields.These methods primarily refer to the current quench detection technologies used in HTS tapes and wires.From the standpoint of practical temperature measurement requirements of HTS bulks and technological limitations of maglev application scenarios,working characteristics and service conditions of the 12 methods,and 4 temperature detection methods are selected through a comprehensive understanding and comparison of basic principles.They are expected to be used in real‐time monitoring and early warning schemes for onboard superconducting levitation devices of HTS maglev transportation or other applications in the future.