Magnetic Properties of Fe-alloy Catalyst Nanoparticles for Carbon Nanofiber Synthesis
ORAL
Abstract
The magnetic properties of Fe-alloy nanoparticles, used as catalysts in vertically-aligned carbon nanofiber (VACNF) growth, has been investigated. First, Fe and Co or Ni were co-sputtered onto Si substrates in order to make a catalyst alloy film. These substrates were then placed in a plasma-enhanced CVD chamber with a substrate temperature of 700$^{\circ}$C and a flowing mixture of acetylene (C$_2$H$_2$) and ammonia (NH$_3$) gas. During the PECVD, the catalyst film breaks into nanoparticles of 50--200~nm and VACNFs are grown. EDX shows that the catalyst nanoparticles nominally have the deposited alloy ratio. In addition, the nanoparticles are still magnetic and have a non-negligible remanence and hysteresis. Their magnetic properties are investigated by SQUID magnetometry in applied field of $|H| \le 50$~kOe and temperatures of 5--400~K. In addition, AC susceptibility studies give energy loss characteristics of the co-synthesized VACNF system.
*Part of this research was conducted at the Center for Nanophase Materials Sciences, which is sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, U.S. Department of Energy.
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