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|Title: ||Synthesis of magnetic nanoparticles and nanocomposites via water-in-oil microemulsions|
|Authors: ||Lin, Mian|
|Issue Date: ||2006|
|Publisher: ||© Mian Lin|
|Abstract: ||The effects of surfactants, co-surfactants, aqueous phase and temperature on
the solubilisation capability of microemulsion systems were investigated.
Appropriate water-in-oil (w/o) microemulsion systems for the synthesis of
nanomaterials were selected in consideration of the higher solubilisation and
the better thermo-stability.
Mono-dispersed iron oxide nanoparticles with the size of 1-5 nm were
synthesised via Igepal CO-520/cyclohexane w/o microemulsion at 25°C. The
size of particles increased from 1 nm to 10 nm with the increase of the size of
water pools. The original particles as prepared were identified as magnetite,
which transformed into maghemite after 2-hour hydrothermal at 120°C and
into hematite after 2-hour hydrothermal at 140°C, accompanied with the
increased crystallite size. Precipitation was employed for basic studies of
starting materials, reaction time and temperature. Compared with
precipitation-derived particles, microemulsion-derived nanoparticles show
smaller particle size, are less aggregated and exhibit higher activities and a
lower saturation magnetisation and coercivity both at 5K and 300K.
Poly-(methacrylic acid) (PMAA), Polyacrylamide (PAM) nano-spheres were
synthesised via Triton X-114/cyclohexane and Brij 97/cyclohexane w/o
microemulsions at 60°C, respectively. The size of PMMA spheres is 30-100nm
while the size of PAM spheres increased from 50 nm to 200 nm with the
increase of surfactant concentration from 19.3% to 28.9%. The increased size of
water pools from 2.43 to 4.32 also resulted in the increased size of PAM from
50 nm to 500 nm. The effects of reaction time and temperature, and reagent
concentration on PAM polymerisation in microemulsion were investigated in
terms of the conversion, molecular weight and morphology of polymers produced.
Core-shell structured silica coated iron oxide nanoparticles were synthesised
via Igepal CO-520/cyclohexane systems at 25°C, with 5 nm core and 5 nm
shell. Nanocomposites of PAM embedded with iron oxide were synthesised in
Brij 97/cyclohexane at 60°C, with the size of 120 nm. The crystallinity of
magnetic nanoparticles was affected by the coating process.|
|Description: ||A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.|
|Appears in Collections:||PhD Theses (Materials)|
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