الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The goal of this study is to develop and characterize Fe-Ni alloy/Polyamide 6 (PA6)
nanocomposites in order to explore the potential of this new metal-polymer nanocomposite in
automotive applications, in an effort to replace higher priced fiber-reinforced PA6 composites
and reduce part weight in any of the automotive components.
The study is as follows. First, nanocrystalline (nc) Fe-Ni alloys with different compositions
were synthesized by chemical reduction of the corresponding metal ions with hydrazine in
aqueous solution. Process variables of reaction temperature, pH of the hydrazine solution and
total concentration of metal ions were varied in order to determine the optimum synthesis
conditions and alloy composition, regarding quality, productivity and cost. Then. the optimum
nc Fe-Ni alloy particles were surface capped (modified) with self-assembled monolayer of
hexadecanethiol (HDT) in order to reduce the average particle size of alloy particles and
improve their dispersability which, in turn, enlarge the nanofiller-polymer matrix contact area
and thus good interfacial interactions and efficient stress transfer are manifested between the
two phases, leading to remarkable performance of the prepared Fe-Ni alloyIPA6
nanocomposites. In addition. the adsorbed hexadecanethiolate (HDTE) molecules onto the
surface of nc Fe-Ni particles can form many entanglements with PA6 molecules, leading to
further improvement in the interfacial interactions between alloy particles and polymer matrix.
A new technique was employed for surface capping nc Fe-Ni particles with HDT molecules.
Finally, the unmodified, pristine (P-), nc Fe-Ni particles were compounded with PA6, using
various techniques, to prepare p-Fe-Ni alloylP A6 nanocomposites of different compositions.
The employed compounding techniques include direct melt mixing, solution mixing, and
ultrasound-assisted master batch. The surface-modified Fe-Ni nanoparticles (m-Fe-Ni) with
two different contents of HDTE were compounded with P A6 via the optimum compounding
technique to prepare 3 wfllo m-Fe-Ni alloyIPA6 nanocomposites. The morphology, crystalline
structure, mechanical and thermomechanical properties of the resultant nanocomposites were
investigated.
Considering XRD, SEM and EDS results, the prepared alloy at [Fe2J/[Ni2J ratio in the
reaction solution = 4/6, a reaction temperature of 80 DC, pH of the hydrazine solution of 12.5
and total concentration of metal ions of 0.6 M, is considered the optimum alloy as it is
nanocrystalline, highly pure and its particle size is not that much out of the nanosize range. It
is coded p-Fe4oNi60. FTIR, TGA and FE-SEM analyses reveal that long shaking time and sub-
ambient temperature of ultrasonic water bath are necessary for deposition and adsorption of
significant amount of HDTE molecules on the surface of alloy particles and, as a consequence,
for adequate reduced particle size and improved particle dispersibility and thermal oxidation
stability of the m-Fe40Ni60 particles as compared with p-Fe40Ni6Q particles. Moreover, the
increase of HDT concentration in the HDT -ethanol solution greatly increases the HDTE
content within m-Fe4oNi6Q particles which, in turn. greatly reduces the average particle size
and improves particle dispersibility and thermal oxidation stability of the resultant m-Fe4oNi6Q
particles. The study also reveals that the new technique can have great potential among the
currently used techniques for surface modification of metal nanoparticles with alkanethiol
molecules.
SM and UMB nanocomposites have better mechanical and thennomechanical properties than
MM ones and UMB nanocomposites exhibit the most enhanced performance. In addition,
morphological and crystalline structure analyses indicate that there is good interfacial
interaction between p-Fe40N~ particles and P A6 in SM and UMB nanocomposites but not in
MM ones. This can be attributed to the intensive mixing applied in SM and UMB techniques,
which broke up particle agglomerates, improved the distribution of alloy particles within the
polymer matrix and resulted in good nanoparticle wetting with P A6 molecules. Therefore,
good interfacial interaction and thus efficient stress transfer are manifested between the two
phases. However, unlike storage modulus and flexural properties, the impact strengths of SM
and UMB nanocomposites are less than that of neat PA6. Interestingly, 3 wt% m-
Fe40Ni6()ll> A6 nanocomposites prepared by UMB process exhibit significantly improved
impact strength as well as other mechanical and thennomechanical properties, compared to
neat PA6. This is mainly owing to three reasons a) m-Fe4oN~ nanoparticles are much smaller
and better distributed within P A6 matrix than p-Fe4oNi60 nanoparticles do, b) HDTE molecules
act as plasticizer and therefore improve the toughness of the nanocomposite, c) The
tremendous increase ofy-phase (%) with respect to the total crystalline phase ofPA6 within 3
wt”10 m-Fe4oNi6()ll> A6 nanocomposites as compared with 3 wt% P-Fe40Ni6()ll> A6
nanocomposite. It is concluded that there are five competing factors playing a critical role in
determining the overall performance of nanocomposites: i) the degree of agglomeration and
particle distribution within P A6 matrix; ii) the degree of crystallinity; iii) the relative fraction
ofy-form to o-form crystals; and iv) the Tg ofPA6 phase as compared to neat PA6; and v) the
content ofHDTE within the nanocomposite. Overall, 3 wt% m-Fe4oNi6ofPA6 nanocomposites
show great promise and their performance is found to be close to that of 15 wt”/o short OF IP A6
composite. Thus, they can replace a commercial 14 wt”10 OFIPA6 composite (Chernion® 214
OH) in automotive components, which achieves cost and weight savings and improves the
fuel-consumption efficiency. However, accurate visibility study should be carried out to
precisely estimate the production costs of 3 wt% m-Fe4oNi6ofPA6 nanocomposites and the
commercial 14 wt”/o GFIPA6 composite. Hence it can be decided whether or not the 3 wt% m-
Fe4oNi6()ll>A6 nanocomposites can be economical alternatives to commercial 14 wt”10 OFIPA6
composite in automotive industry.