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I. de Moraes and N. M. Dempsey
17.2 Chemical Synthesis of Hard-Soft Nanocomposites
Chemical synthesis, using a range of solution chemistry techniques (precipitation,
hydride reduction, hydrothermal, reverse micelles, polyol, sol–gel, thermolysis,
photolysis, sonolysis, electrochemical/electrodeposition…) is applied to the fabrication of a wide range of magnetic nanoparticles, including core-shell nanoparticles [36–39]. These bottom-up fabrication approaches allow to tune the size, shape
and composition of the magnetic nanoparticles. Chemically synthesised magnetic
nanoparticles are now used to make ferrofluids for applications in seals, bearings,
dampers, stepper motors, loudspeakers and sensors [40]. In the field of bio-medicine,
they are used as contrast agents in magnetic resonance imaging and for magnetic separation in diagnostic kits, while their potential use in drug delivery and magnetic hyperthermia in cancer treatment are being extensively explored [37–39]. Self-assembled
periodic arrays of magnetic nanoparticles are being studied for use as magnetic
recording media [39, 41], while they are also being considered for use in the ferrite
cores of high frequency electronic components [40] and in microwave devices [38].
Our interest in chemical synthesis lies in the fact that it offers the possibility to
produce hard and soft magnetic nanoparticles or core-shell nanoparticles that can be
used as building blocks to fabricate bulk hard-soft nanocomposites. The potential to
upscale chemical synthesis routes opens the possibility to fabricate bulk nanocomposite magnets on an industrial scale. A number of excellent review articles have
dealt with the chemical synthesis of hard-soft magnetic nanocomposites [21, 38, 39,
42]. Here, we have selected three case studies to highlight advances made and the
great potential which this approach holds for the fabrication of high-performance
permanent magnets.
17.2.1 Case Study #1—FePt/Fe 3 Pt Nanocomposites
This case study concerns the fabrication of FePt/Fe 3 Pt nanocomposites [43] and is
a follow on from the pioneering work by Sun and co-workers on the preparation
of monodisperse nanoparticles of FePt [41] and magnetite (Fe 3 O 4 ) [44]. We will
begin by recalling the main results from these studies and will then describe the
self-assembly of these precursors and further processing steps developed to fabricate
hard-soft nanocomposites.
FePt nanoparticles were prepared from a mixture containing platinum acetylacetonate and iron pentacarbonyl. Reduction of the Pt(acac) 2 (acac = acetylacetonate, CH 3 COCHCOCH 3 ) by a diol and thermal decomposition of iron pentacarbonyl followed by addition of a flocculent (ethanol) led to the preceipitation of FePt
nanoparticles [41]. The addition of oleic acid and oleyl amine in the mixture served
to stabilise monodisperse nanoparticles of diameter 3 nm. The size of the nanoparticles could be increased by adding additional reagents to 3 nm seed particles while
the composition of the nanoparticles could be tuned by adjusting the molar ratio of
I. de Moraes and N. M. Dempsey
17.2 Chemical Synthesis of Hard-Soft Nanocomposites
Chemical synthesis, using a range of solution chemistry techniques (precipitation,
hydride reduction, hydrothermal, reverse micelles, polyol, sol–gel, thermolysis,
photolysis, sonolysis, electrochemical/electrodeposition…) is applied to the fabrication of a wide range of magnetic nanoparticles, including core-shell nanoparticles [36–39]. These bottom-up fabrication approaches allow to tune the size, shape
and composition of the magnetic nanoparticles. Chemically synthesised magnetic
nanoparticles are now used to make ferrofluids for applications in seals, bearings,
dampers, stepper motors, loudspeakers and sensors [40]. In the field of bio-medicine,
they are used as contrast agents in magnetic resonance imaging and for magnetic separation in diagnostic kits, while their potential use in drug delivery and magnetic hyperthermia in cancer treatment are being extensively explored [37–39]. Self-assembled
periodic arrays of magnetic nanoparticles are being studied for use as magnetic
recording media [39, 41], while they are also being considered for use in the ferrite
cores of high frequency electronic components [40] and in microwave devices [38].
Our interest in chemical synthesis lies in the fact that it offers the possibility to
produce hard and soft magnetic nanoparticles or core-shell nanoparticles that can be
used as building blocks to fabricate bulk hard-soft nanocomposites. The potential to
upscale chemical synthesis routes opens the possibility to fabricate bulk nanocomposite magnets on an industrial scale. A number of excellent review articles have
dealt with the chemical synthesis of hard-soft magnetic nanocomposites [21, 38, 39,
42]. Here, we have selected three case studies to highlight advances made and the
great potential which this approach holds for the fabrication of high-performance
permanent magnets.
17.2.1 Case Study #1—FePt/Fe 3 Pt Nanocomposites
This case study concerns the fabrication of FePt/Fe 3 Pt nanocomposites [43] and is
a follow on from the pioneering work by Sun and co-workers on the preparation
of monodisperse nanoparticles of FePt [41] and magnetite (Fe 3 O 4 ) [44]. We will
begin by recalling the main results from these studies and will then describe the
self-assembly of these precursors and further processing steps developed to fabricate
hard-soft nanocomposites.
FePt nanoparticles were prepared from a mixture containing platinum acetylacetonate and iron pentacarbonyl. Reduction of the Pt(acac) 2 (acac = acetylacetonate, CH 3 COCHCOCH 3 ) by a diol and thermal decomposition of iron pentacarbonyl followed by addition of a flocculent (ethanol) led to the preceipitation of FePt
nanoparticles [41]. The addition of oleic acid and oleyl amine in the mixture served
to stabilise monodisperse nanoparticles of diameter 3 nm. The size of the nanoparticles could be increased by adding additional reagents to 3 nm seed particles while
the composition of the nanoparticles could be tuned by adjusting the molar ratio of