Microstructure of Fe-based and NiFe nanowires encapsulated by multiwalled carbon nanotube radial structures
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The crystalline iron-based nanowires encapsulated by multiwalled carbon nanotubes have
been the subject of numerous studies owing to the range of potential applications. The
presence of a-Fe (bcc)/y -Fe(fcc) junctions o ers the possibility of exploitation of the
exchange bias effect, an interfacial magnetic phenomenon that plays a major role in
magnetocaloric cooling, spintronic and high-density magnetic storage devices. This work
is concerned with the synthesis and microstructural characterization of Fe-based and NiFe
nanowires encapsulated by multiwall carbon nanotube radial structures. The known attributes
of these structures are well matched to the magnetocaloric application. The
primary aim of this work was to determine the unknown microstructural details of the
encapsulated nanowire that are of relevance to the magnetocaloric application (junction
types, location and orientation relative to the nanotube axis). The secondary aim was to
explore the modi cation of the synthesis route to promote desirable attributes. This is
the first report of a-Fe/y -Fe sequential junctions and a-Fe/Fe3C concentric junctions in
encapsulated Fe-based nanowires. The presence of a-Fe/y -Fe junctions was inferred from
the observation of a-Fe nanowires terminated by a ~100 nm length y-Fe crystallites of
larger diameter. The a-Fe/Fe3C junctions exhibit the Bagaryatski orientation relationship:
[110 ]bcck[100 ]orth. The degree of substrate roughness was found to be a means of
tailoring details of the structure and composition of the encapsulated nanowires. NiFe
encapsulated nanowires were found to contain crystallites of a-NiFe, y-NiFe and Ni3Fe
and the sequential junctions -NiFe/Ni3Fe and a-NiFe/y-NiFe junctions.
Authors
Ibrar, MuhammadCollections
- Theses [4201]