Magnetic properties of fully dense Sm 2Fe 17N x magnets prepared by shock compression

Abstract

Fully dense Sm 2Fe 17N x bulk bodies with the porosities of 2–10% were prepared by shock compression combined with a propellent gun in a certain low-pressure region, using the magnetically aligned powder pellets without binder. The consolidated state and porosity of the shock-consolidated bulk bodies mainly depended on the driving shock pressure, while the vacuum atmosphere was slightly effective to consolidation. Doping of Zn (2 wt%) was also effective to consolidation. The magnetic properties of the shock-consolidated bulk bodies were dominated mainly by driving shock pressure. The coercivity and maximum energy product (( BH) max) were almost constant in the driving shock pressure range up to about 16 GPa in a copper standard capsule, and began to decrease beyond it due to partial decomposition by the residual temperature. As a result, it was found that if we chose the appropriate shock conditions, the decrease rate of (( BH) max) from the starting material could be suppressed to less than 20–30%, which may be mainly caused by the decrease in remanent magnetization, probably due to the scattering effect of particle alignment in the process of shock consolidation. The values of ( BH) max of the bulk bodies prepared in a certain low-pressure region were stable over 20 MGOe. A large bulk body of cm scale with a ( BH) max of 22.5 MGOe was prepared by using an explosive system.