Preparation and Characterisation of Y3fe5o12-Filled Polyvinylidene Fluoride Composite
This research project was undertaken with the main objective of preparing and characterising a wave absorbing material by utilising a magnetic material with polymer as the base material to provide the carrier template. Polyvinylidene fluoride (PVDF) was chosen as the polymer due to the well-estab...
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| Format: | Thesis |
| Language: | English English |
| Published: |
2007
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/5045/1/FS_2007_44.pdf |
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| Summary: | This research project was undertaken with the main objective of preparing and
characterising a wave absorbing material by utilising a magnetic material with polymer
as the base material to provide the carrier template. Polyvinylidene fluoride (PVDF) was
chosen as the polymer due to the well-established physical properties. Yttrium iron
garnet (YIG) was chosen as the magnetic filler due to its well known microwave
absorbing properties.
Preparation of YIG particles was carried out via a sol-gel method from nitrates raw
material with a citrate route. It was found that with this method employed, the sintering
temperature of YIG was minimised to 800ºC compared to 1300ºC for a normal solid
state reaction method. PVDF powder was supplied by manufacturer and its film was
prepared by dissolving it in cyclopentanone. This method was chosen to reduce the
heating cost of preparation as a normal preparation would require hot melting of the PVDF powder. It was found that up to 30 weight percent (wt%) of PVDF could be
dissolved in cyclopentanone successfully. Higher wt% hindered total dissolution of
PVDF. Dissolution of PVDF powder in cyclopentanone was carried out by magnetic
stirring at about 200 RPM for half an hour followed by another half an hour of stirring
and heating (200 RPM and 90ºC). The whole process was carried out under reflux
condition and the gel formed after the stirring was left to cool down for a few minutes.
The gel was cast onto a petri dish to form film. PVDF-YIG composite was prepared by
the same PVDF preparation method with additional YIG particles prepared as a raw
material component. The composition of YIG is limited to 20 wt%.
It was found that YIG particles prepared had an average crystallite size of about 51 nm
and YIG single phase was formed at sintering temperature as low as 600ºC. Temperature
of 800ºC was chosen as the sintering temperature for preparation of YIG filler particles
for the composite due to a better garnet phase formed as observed by XRD. PVDF with
10 wt% of PVDF dissolved in cyclopentanone was chosen for the composite
preparation. The PVDF film prepared was found to be highly crystalline with a major
XRD peak observed at 77.7º (2θ). This peak was never reported before for PVDF. The
PVDF film had leaf-like morphology with observable fibrils. FT-IR results confirmed
the YIG and PVDF prepared conformed to reported results. EDX analysis showed that
all elements were traceable although with some deviation from theoretical values. Magnetic analysis of YIG, PVDF and PVDF-YIG composites showed that all the
samples prepared were wave absorbing. It was found that the PVDF film without any
filler was a magnetic material and had a better wave absorbing property than the YIG
itself. It was also found that imaginary permeability of composite samples showed a
capacitive instead of inductive character. However, the best wave absorber was found to
be the composite with 1 wt% of YIG filled which can operate at a frequency range of 2
MHz – 1 GHz with a real permeability of about 200. |
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