الفهرس 
2.1 Electrospinning: Historical BackgroundOnly 14 pages are availabe for public view
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Abstract
Electrospinning is a unique process in that it is able to produce polymer fibers having diameters ranging over several orders of magnitude,
from the micrometer range typical of conventional fibers down to the
nanometer range.
Ultrafine fibers were electrospun from polyacrylonitrile (PAN) and
/N,N-dimethylformamide (DMF) solution to be used as a precursor for
carbon nanofibers. An electrospinning set-up was designed, constructed
used to collect fibers with diameter ranging from 104 nm to 434 nm.
Morphology of fibers and its distribution were investigated by varying
Berry’s number, charge density, spinning angle, spinneret diameter and
collector area. A more systematic understanding of process parameters was
obtained and a quantitative relationship between electrospinning
parameters and average fiber diameter was established by using response
surface methodology (RSM).
Optimum electrospinning conditions by using RSM have been
utilized to produce five MWCNTs/PAN nanofibril composites. The as
electrospun fabrics have been heat treated through two steps; stabilization
and carbonization assisted by using static pressure. Morphological
characterization via SEM showed a reduction in the electrospun nano fibril
average diameter due to hot-pressing from 180 nm to 130 nm. TEM
analysis showed a formation of 2-D graphitic structure for the hot-pressed
samples. Raman spectroscopy analysis showed an increase in the
crystallite size from 3.7 to 9.6 nm for the hot-pressed 5wt.%
MWCNTs/PAN samples. Electrical conductivity of the fabrics has been
investigated by using (H10K13532-50LCR meter). Analytical approach
has been applied based on Lichteneker formula to evaluate the electrical properties of MWCNTs, single nanofiber and single nanofibril composite
as a function in its fabric measured properties. The conductivity and
Dielectric values of hot-pressed fabrics proved the possibility of using it as
a good candidate for surface mounted components especially in biomedical
applications.
Finally, mechanical and tribological characterization of the hot
pressed fabrics by adding MWCNTs improved fabrics modulus of the
modulus of elasticity, coefficient of friction (from 1.7 to 0.15) and abrasive
mass loss (as low as 0.2 mg) have been achieved. The hot-pressed
electrospun MWCNTs/carbon nanofibril composite fabrics can be used, by
controlling MWCNTs wt%, as a good candidate for both journal bearings
(C.O.F. below 0.4 is required) and brake pads (C.O.F. from 0.4 to 0.7 are
required) applications.