Biomedical Engineering Reference
In-Depth Information
electrospun metal precursor/polymer nanofiber mats in a hydrogen atmo-
sphere. However, calcination in an argon atmosphere has recently been
introduced as a safe, economically preferable and more effective alternative
strategy to produce silver, nickel and cobalt nanofibers.
Among the common ferromagnetic metals, cobalt has distinct magnetic
properties. The incorporation of cobalt nanoparticles in nickel nanofibers
results in better magnetic properties compared with the bulk.
Electrospinning of a colloidal solution rather than a sol-gel (which is
widely utilized in the conventional electrospinning technique) has been
suggested as a novel strategy to prepare cobalt nanoparticles/ nickel acetate/
poly(vinyl alcohol) and nanofiber mats. Calcination of the dried electrospun
mats in an argon atmosphere at 700
C for 5 h leads to the production of
cobalt-doped nickel nanofibers. Overall, the magnetic properties studied
point to an improvement in the magnetic parameters of synthesized cobalt-
doped nickel nanofibers compared with pristine ones.
Generally, the electrospun solution is either a polymer(s) dissolved in a
proper solvent or metallic precursor/polymer solution. The distinct feature
of these solutions is that they have to be completely miscible. In other
words, in the case of a metallic precursor, it should be soluble in a suitable
solvent because it has to hydrolyze and polycondensate in the final
precursor/polymer mixture to form the gel network.
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2.7.1 Assessing the magnetic properties of cobalt-doped
nickel nanofibers
Synthesized cobalt-doped nickel nanofibers revealed better magnetic
properties compared with pristine ones, using a gravimetric analyzer
(TGA, Pyris1, PerkinElmer Inc., USA). Information about the phase and
crystallinity was obtained by using a Rigaku x-ray diffractometer (XRD,
Rigaku, Japan) with Cu KR (
) (1.540A
˚
λ
) radiation over the Bragg angle
ranging from 30 to 100
. High-resolution images and selected area electron
diffraction patterns were obtained with a transmission electron microscope
(TEM, JEOL JEM-2010, Japan) operated at 200 kV.
The magnetic properties of the nanofibers were evaluated using
commercial superconducting quantum interface device (SQUID) magne-
tometery. The nanofibers were weighed and then placed into capsules in an
inert gas environment. After this, the capsules were sealed with paraffin wax
to prevent air oxidation of the nanofibers. The masses of the pristine and
cobalt-doped nickel nanofibers were 11.48 and 5.26mg respectively.
The mechanism of the spin-reorientation transition (SRT) in the Ni/Fe/
Ni/W(110) system has been investigated using in situ low-energy electron
microscopy, x-ray magnetic circular dichroism measurements and first-
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