Tailored synthesis in nanoparticle permanent magnets (NPPMs)

Milled and unmilled: 1 GPa at 100C. ~50% density and XRD showed no change in lattice. Note that the milled powder heated much more quickly than the unmilled powder, indicating better interparticle connectivity due to reducing the large agglomerates.
Milled and unmilled: 1 GPa at 100C. ~50% density and XRD showed no change in lattice. Note that the milled powder heated much more quickly than the unmilled powder, indicating better interparticle connectivity due to reducing the large agglomerates.

CMI researchers from Ames National Laboratory conducted the activity for this highlight

Innovation
Demonstrated Spark Plasma Sintering (SPS) of α”-Fe16N2 without decomposition of the magnetic phase.

Achievement
Demonstrated that SPS can be used to compact α”-Fe16N2 powders and that the behavior of the compaction changes with agglomerate size (as received vs low energy ball milling). The density of the part is enhanced using ~15% of a low temperature sintering aid.

Significance and Impact

  • The α”-Fe16N2 is a truly critical element free magnetic compound.
  • The challenge is to form the nanoscale compound into a dense monolithic part without degrading the magnetic phase.

Hub Targets Addressed 

  • Developing critical material free Iron Nitride based magnets.
  • Accelerated magnet discovery and maturation.
     
SPS of unmilled powder + ~15 wt% In. XRD of the α”-Fe16N2 +In SPS sample shows the In is textured and the α” shows no obvious decomposition. SEM shown that the α” phase agglomerates are fully encapsulated by the In.
SPS of unmilled powder + ~15 wt% In. XRD of the α”-Fe16N2 +In SPS sample shows the In is textured and the α” shows no obvious decomposition. SEM shown that the α” phase agglomerates are fully encapsulated by the In.