17 Nanocomposites for Permanent Magnets
421
Fig. 17.17 FORC diagrams of FePd/Fe (44/56 vol.%) nanocomposites formed by annealing at
a 773 and b 823 K [49]
phase grains during the harsh reductive annealing step needed to form SmCo 5 . A
combined solution phase chemistry and calciothermic reduction approach, in which
Fe nanoparticles are temporarily coated to stabilize their size, has been successfully used to fabricate nanocomposites consisting of a high coercivity SmCo 5 matrix
phase containing nanosized Fe inclusions [57]. Details of this case study will now
be presented.
The complete synthesis route used to fabricate SmCo 5 − Fe nanocomposites is
illustrated in Fig. 17.18. Fe nanoparticles of 12 nm in diameter were synthesised by
decomposition of Fe(CO) 5 in the presence of oleyamine and hexadecylammonium
chloride at 180 °C. The Fe nanoparticles were then coated in a 7-nm-thick layer of
SiO 2 by controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS)
in the presence of ammonia. TEM images of the as-prepared Fe nanoparticles and
Fig. 17.18 Schematic illustration of the synthesis of SmCo 5 − Fe nanocomposites by assembling Sm(OH) 3 nanorods, Co(OH) 2 nanoplates, and Fe/SiO 2 nanoparticles, followed by reductive
annealing, NaOH solution washing and compaction [57]
421
Fig. 17.17 FORC diagrams of FePd/Fe (44/56 vol.%) nanocomposites formed by annealing at
a 773 and b 823 K [49]
phase grains during the harsh reductive annealing step needed to form SmCo 5 . A
combined solution phase chemistry and calciothermic reduction approach, in which
Fe nanoparticles are temporarily coated to stabilize their size, has been successfully used to fabricate nanocomposites consisting of a high coercivity SmCo 5 matrix
phase containing nanosized Fe inclusions [57]. Details of this case study will now
be presented.
The complete synthesis route used to fabricate SmCo 5 − Fe nanocomposites is
illustrated in Fig. 17.18. Fe nanoparticles of 12 nm in diameter were synthesised by
decomposition of Fe(CO) 5 in the presence of oleyamine and hexadecylammonium
chloride at 180 °C. The Fe nanoparticles were then coated in a 7-nm-thick layer of
SiO 2 by controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS)
in the presence of ammonia. TEM images of the as-prepared Fe nanoparticles and
Fig. 17.18 Schematic illustration of the synthesis of SmCo 5 − Fe nanocomposites by assembling Sm(OH) 3 nanorods, Co(OH) 2 nanoplates, and Fe/SiO 2 nanoparticles, followed by reductive
annealing, NaOH solution washing and compaction [57]