Preparation and characterization of date palm fibers and
polypropylene matrix composites
1,2
1
Omar Mortagy and 1,2Mahmoud Farag
The Mechanical Engineering Department, the American University in Cairo, Egypt
2
The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
Natural fibers, such as flax, hemp and jute, offer an environmentally more acceptable
alternative to man-made fibers, such as glass and carbon fibers, in reinforcing plastics.
This is because they need much less energy to grow, are renewable, and are biodegradable after use. In addition to satisfying the increasingly stringent environmental
criteria, natural fibers offer several other advantages, such as light weight and acoustic
and thermal insulation because of their hollow and cellular structure. Because of these
advantages, natural fiber reinforced plastics (NFRP) have replaced glass fiber
reinforced plastic components in vehicles such as the Mercedes Benz A-Class and the
Ford Model U hybrid-electric car.
This paper discusses the preparation and characterization of fibers extracted from date
palm fruit carrying bunches and explores their use in strengthening polypropylene
matrix composites. The fruit bunches are composed of predominantly cellulose fibers
held together by hemicellulose and lignin matrix. The fibers are extracted by first
mechanically crushing the fruit-bearing bunches, chemical treatment with NaOH at
90oC for two hours, and then separation of the fibers from the matrix using ultrasonic
treatment for one hour at 50 oC. The density of the fibers was approximately 1.1 g/cc
and diameter 180-270 μm. SEM studies showed that the fibers were made up of
axially oriented fibrils of 5-7 μm diameter as well as large axial pores of about 30 μm
diameter. Radial small pores of 3-6 μm diameter were also revealed.
The mechanical behavior of the fibers is being measured and compared with the
properties of other natural fibers in the published literature. Different volume fractions
of the fibers are also embedded in polypropylene matrix to determine the effect of
preparation method and fiber volume fraction on mechanical behavior and water
absorption.
If proved viable, the use of date palm fruit carrying bunches, which are currently
discarded as agricultural waste, would be of great economic value since we have more
than 7 million date palm trees in Egypt.
STRC. 1
Processing of CNT-reinforced aluminum matrix composites
1,2
1
Amal M. K. Esawi, 1,2Ahmed Abdel Gawad, 1,2Mostafa El Borady, and
1,2
Mohamed Emara
The Mechanical Engineering Department, the American University in Cairo, Egypt
2
The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
In spite of varying reports in the literature on the exact properties of carbon
nanotubes, both theoretical and experimental results confirm their possession of
remarkable mechanical properties. Such properties have earned them serious
consideration from both industry and research institutes as reinforcements for a
number of material systems. Aluminum matrix composites have numerous attractive
lightweight and structural applications. Reinforcing aluminum with nanotubes is
expected to lead to exceptional new composites. However, some processing problems
have first to be overcome; namely, (1) dispersion of the nanotubes within the matrix,
and (2) controlling their alignment in the matrix. This work aims to overcome these
problems by developing two novel techniques: one is the mechanical alloying of the
nanotube/Al matrix powders to overcome the first problem and the second is the use
of a powder rolling technique to produce thin strips of aligned CNT within the
aluminum matrix.
Although observations of the fracture surface of the samples show that the CNTs
are well dispersed and have not been damaged by the mechanical alloying process, the
results so far are showing limited enhancement in mechanical properties. This could
be attributed to two main reasons: (1) the use of catalytic CNTs of the cheapest
variety available commercially and (2) poor interfacial bonding between the CNTs
and the aluminum matrix. Further investigations are being carried out to: (1)
Understand the local interfacial mechanics. The interface will be modified to promote
bonding and the effect will be studied using nanoindentation techniques. (2) Study the
effect of the processing temperature on the strength of the composite. It has been
reported in the literature that higher processing temperatures result in the formation of
aluminum carbide Al4C3 at defect sites on the nanotubes which may lead to a stronger
interfacial bond between the nanotubes and the aluminum matrix. (3) Investigate the
effect of using different aspect ratio CNTs on the mechanical properties.
STRC. 2
Construction of consolidation maps for finite element material modeling
of equal channel angular extrusion of hot compact nano and micron
powders
1,2
1
Ahmed Sadek and 1,2Hanadi G. Salem
The Mechanical Engineering Department, the American University in Cairo, Egypt
2
The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
The Equal Channel Angular Extrusion (ECAE) process is one of the most promising
processes used for producing nanostructured consolidates making using of the severe
plastic conditions that the powder particles experience during the extrusion. The
intrinsic heat generated during extrusion in addition to 1.16 total strain imposed on the
powder per passes can substitute for the elevated temperature required for sintering.
The consolidation condition of the micro and nanopowders prior to ECAE influences
significantly the structural evolution and hence mechanical properties of the produced
bulk product. Building a model for such a process has become an essential
requirement to allow several iterations and runs for obtaining optimal forming
conditions that will produce best properties of the consolidate. Through the current
research work consolidation maps of hardness and density variation for microscale
and nanoscale Al-2124 powders hot compacts are obtained. The optimum
consolidation condition will be selected for subsequent ECAE processing compared to
the green compact condition. The consolidation behavior maps obtained for the micro
and nanoscale powders will be used for the development of a finite element materials
model of the ECAEed consolidates. A nanostructured microscale powders about
45µm and 87nm particle and internal structure average size, respectively hot compacts
of height to diameter (h/d) ratio of 4 were obtained by combinations of temperatures
(360, 420 and 480oC), durations (30, 60, and 90 minutes) ,and pressures (4, 5, and 6)
multiples of the yield strength (ys) of as received Al-2124. A nanostructured
nanoscale powders about 90nm and 15.6nm particle and internal structure average
size, respectively were obtained by 36 hours of high energy ball milling. The
nanoscale hot compacts were obtained using the same ranges of temperature and
durations used for microscale ones, but with higher values of pressure (6, 7, and 8)
multiples of the yield strength of as received Al-2124 powder. The nanoscale
compacts exhibited hardness-values 3 to 4 times higher than that of microscale ones.
For the microscale compacts, the optimal combination of compaction conditions was
achieved for 60 minutes duration at 420-to-480oC range of temperatures, and 5-to6ys range of stress. For the 30 and 90 minutes compaction durations the optimum
properties were limited to 480oC over a stress range of 5.2 to 5.8 ys.
STRC. 3
Effect of the compaction parameters and canning material of
nanostructured Al-Powder consolidated via intense plastic straining
process
1,2
1
Mohamed Shamma and 1,2Hanadi G. Salem
The Mechanical Engineering Department, the American University in Cairo, Egypt
2
The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
Research groups around the world have reached common and contradicting
conclusions regarding the behavior and properties of nanostructured materials. The
aim of this research is to affirm the common findings by previous research, and
support one of the currently proposed concepts of mechanical behavior based on indepth testing and characterization of consolidated micro and nanopowders of
aluminum processed by Equal Channel angular Extrusion (ECAE). The main
challenge faced in processing nanostructured powders or bulk products is the
retention of the internal nanoscale structures during the various processing stages.
ECAE is classified as one of the intense plastic straining processes that are capable of
producing bulk products with internal structure that is one order of magnitude smaller
(200nm) than the conventional processing techniques (2.0µm). The ongoing project
constitutes several activities such as (a) Design and manufacturing of the ECAE die
for the consolidation of the micro and nanopowders into bulk billets, (b) Variation of
the powder pre-extrusion condition including the powder canning materials, (c)
variation of the extrusion parameters, and (d) characterization of the produced bulk
consolidates before and after extrusion. Utilizing different "can" materials during
extrusion has been investigated. The effect of variation of the processing parameters
(compaction condition, extrusion temperature, strain rate) on the sample density, grain
size, and hardness is studied. Al-2124 micro-powders with 87nm internal structure
was consolidated through ECAE, which produced consolidated bulk rods with
internal structure of 37nm in average size. The present study shows that ECAE is
capable of producing consolidates form nanostructured-micro-powders, which opens
a new venue for extensive investigation of the consolidation parameters for improved
properties bulk nanocrystalline (NC) materials, as well as offering a new class of bulk
materials for practical engineering applications.
STRC. 4
Design of micro-lens arrays used for generation of diffractionlimited beams
1
Joumana El-Rifai and 1,2Amr Shaarawi
1
The Yousef Jameel, Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
2
The Physics Department and the American University in Cairo, Egypt
Diffraction-limited beams can be generated using various methods. They can be
produced using spherical lenses, conical lenses or annular slits that lie in the focal
plane of a positive lens. The use of conical lenses in the production and generation of
diffraction-limited beams is investigated in this work. The beam shaped by uniform
illumination of a single conical lens is investigated using numerical simulations. The
decay behavior and the focal depth of the beam are characterized in terms of the
wavelength of the illumination and the radius of the axicon lens. The single lens is
later expanded to an array of conical lenses packed in various shapes. The effects of
the array shape on the focal depth of the field will be presented.
In the case a single conical lens is uniformly illuminated two equations describing the
output beam were used to produce the simulations. The first equation was proposed
by R.M. Herman and T. A. Wiggins (“Production and uses of diffractionless beams.”
J. Opt. Soc. Am. A, 8 (6), 932-942 (1991)). The equation describes the production of a
Bessel beam of the first kind using a conical lens. In their joint paper Herman and
Wiggins adopted a mathematical approach, approximating their equation to prove that
the output equation has a Bessel function lateral profile and thus the conical lens
produces a Bessel beam. Within the scope of this study, we used a numerical
approach rather than a mathematical one, where Herman and Wiggins’ original exact
equation (before any approximations) was adopted
The simulations produced using the Herman and Wiggins approach only considered a
conical lens placed at an origin (i.e., at x  y  0 ). In order to obtain simulations for a
conical lens placed at any position on the xy-plane Herman and Wiggins expressions
were modified to simulate the radiation from a conic lens placed at any arbitrary
position ( x  xn and y  yn ). To examine the effect an array of conical lenses
simulations of the radiated field for different configurations of the axicon lenses were
carried out. It will be shown that the shape of the array has a direct influence on the
decay behavior of the generated beams.
STRC. 5
The preparation and characterization of catalytically viable
micro/mesoporous mixed metallic oxides
1,2
Jehane Ragai, 1,2Adham R. Ramadan, 1,2Nahed Yacoub, 2,3Christine Azer, 1,2Gehane
Ghali, 1,2Malak Issa, 1,2Haguer Amin
1
2
Chemistry Department, the American University in Cairo, Egypt
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
3
Chemistry Department, Ain Shams University, Cairo, Egypt
The preparation and characterization of metal oxides and mixed metal oxides are
carried out with the aim of investigating their catalytic and ion exchange properties.
This is achieved by:

Surface and bulk characterization using gas adsorption techniques for the
determination of extent of surface area as well as porosity

Measurement of acidic and basic properties of the prepared oxides and mixed
oxides using different techniques differentiating between Lewis and Bronsted
acidity/basicity.

X-ray diffraction for crystalinity and phase determination

Infrared spectrometry for the determination of different active groups in the
oxide/mixed oxide matrices

Thermal analyses for the establishment of the thermal behaviour of the
oxides/mixed oxides, an important parameter for catalysts

SEM imaging for shedding light on surface morphology
Doping is carried out with different cations and anions of different sizes and charges
as their presence within the oxides/mixed oxides matrices is seen to affect the above
parameters differently, with significant bearings on catalytic and ion exchange
properties.
STRC. 6
Enhancement design for a symmetrical decoupled MEMs-based
gyroscope
1,2
Abdelhameed Sharaf, 2,3Sherif Sedky, 1,4Mahmoud A. Ashour, 5Serag E.-D. Habib
1
NCRRT, EAEA, 3 Ahmed Alzomor st., Naser city, Cairo, Egypt
Yousef Jameel Science and Technology Research Center (STRC), Egypt
3
Physics Department, the American university in Cairo, Egypt
4
IC Design Center, EAEA, 3 Ahmed Alzomor st., Naser city Cairo, Egypt
5
Electronics and Communications Dept., Faculty of Engineering, Cairo University,
12613, Giza, Egypt
2
This paper introduces an efficient design for symmetrical and decoupled
micromachined gyroscope as shown in figure 1. The design utilizes all the silicon area
in a more efficient way as compared to previously suggested designs (S. E. Alpe, and
Tayfun Akin, “A single-crystal silicon symmetrical and decoupled MEMS gyroscope
on an insulating substrate,” J. of MEMS, Vol. 14, No. 4, August 2005, PP. 707-717),
increases the driving electrostatic force, and increases the sensing capacitance.
Decoupling between sense and drive modes is achieved by separating the drive and
sense masses. The decoupling is required to minimize the mechanical crosstalk,
whereas matching the resonance frequencies is essential to increase the sensor
sensitivities by the mechanical quality factor of the sense mode. A complete analytical
analysis, based on the equations of motion, is performed. The analysis shows a
resonance frequency of 4743 Hz for both modes, drive amplitude of 2.275 µm, and
sense mode amplitude of 7.64nm. The mechanical and electrical sensitivities are
0.008 µm/(º/s) and 1.9 mV/(º/s) respectively. The change in the output capacitance is
0.13 aF/(º/s). The numerical analysis is preformed using finite element analysis
(ANSYS). First a modal analysis is performed to extract the structure natural
frequency. The resonance frequencies are 5385 Hz and 5382 Hz for drive and sense
mode respectively, which has a frequency mismatch as low as 0.04%. The mode
shapes for sense mode is derived. The mismatch between analytical and numerical
results is 11.9%, which is mainly due to the higher accuracy of the numerical model
as compared to the approximated analytical model. The frequency response of the
drive mode indicates drive mode amplitude of 2.819 µm. Table I summarize the main
results of this work. It is clear from the table that the proposed design has similar
Fixed
values to those reported for decoupled micromachined
gyroscopes, but with more
Anchor
Electrodes
efficient use of area.
Table 1: Simulated results
Parameter
Target
2
Size (mm )
1
Thickness
10
Drive Freq. (Hz)
40650
Sense freq. (Hz)
41250
Sense Capacitance
130 fF
Proposed
1.44
20
5385
5382
0.319 pF
Proof
mass
Actuator
Sensor
Drive
Sensor
Figure 1: Schematic diagram for a symmetric
decoupled micromachined gyroscope.
STRC. 7
Drive amplitude
(µm)
Measurement range
(º/s)
Scale factor (mV/
(º/s))
2
2.275
± 300
± 312
17.6 ×10-3
1.9
STRC. 8
Surface stress measurements for the electropolymerization of aniline
1,2
Adham R. Ramadan, 2Malak Issa
1
2
The Chemistry Department, the American University in Cairo, Egypt
The Yousef Jameel, Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
Electrochemical reactions result is significant structural changes of the electrode
electrolyte interface, with a generation of considerable stress/strain forces. Atomic
Force Microscopy is used to detect these forces, using a set up where the AFM
cantilever is used as the working electrode in an electrochemical cell assembly. The
potential of this working electrode is controlled, using a potentionstat, to values where
the electropolymerization of aniline to polyaniline takes place. This is followed by a
cycling of the potential of the working electrode between values corresponding to the
oxidation (with a corresponding swelling/expansion) and reduction (with a
corresponding shrinking) of the polyaniline layer. The generated stress and strain
changes result in the deflection of the AFM cantilever, which is detected by the
reflection of the laser beam.
The synchronization of the electrochemical signals controlling the potential of the
working electrode with the detection of cantilever deflection has been a challenge for
this experimental set-up. In this respect, a Signal Access Module has been added to
the AFM allowing the access to the electrical signal from the AFM laser detector
system. This would facilitate keeping the detection of cantilever deflection in line
with the potential variation within the electrochemical cell assembly.
STRC. 9
Pulsed laser deposition for BiTe for energy scavengers
1
Ahmed Kamal, 1Hassan Bakr, 2Ziyang Wang, 2Paolo Fiorini, 1,3Sherif Sedky
1
The Yousef Jameel Science and Technology Research Center (STRC),
The American University in Cairo, Egypt
2
IMEC, 75 Kapledreef, B3001, Heverlee, Leuven, Belgium
3
Physics Department, the American University in Cairo, Egypt
Bismuth Telluride (Bi2Te3) is one of the most common materials which possess,
relatively, high thermoelectric figure of merits. Obviously, high quality thermoelectric
thin films, which are the basic component of efficient thermoelectric energy
scavengers operating in the vicinity of room temperature, help construct permanent,
clean, tiny and cheap batteries. The output power of a Bi2Te3 based thermoelectric
generator is very small, in the micro-Watt range; however, it is fairly enough to drive
transducers used in human body applications.
In this work, Pulsed Laser Deposition (PLD) technique is used to deposit uniform thin
films of Bi2Te3. It is well known that PLD has an advantage over all other techniques,
such as evaporation, molecular beam epitaxy (MBE), chemical vapor deposition
(CVD), and sputtering, which is stoichiometry. This is, simply, the ability to replicate
the target/reference material and this is maintained through out the whole deposition
process. In this optimization research, 8 samples of p-type (Bi0.25Sb0.75)2Te3 in
addition to 6 samples of n-type Bi2(Te0.94Se0.06)3 were, all, deposited and analyzed to
investigate the effect of substrate temperature, chamber pressure and substrate
composition on the physical properties of the deposited films, namely grain
microstructure, Seebeck coefficient and, electrical resistivity of the deposited films.
R esistivity (m  .cm )
   


-5
1 0 m b a rr


-1
1 0 m b a rr





-2
1 0 m b a rr





o

D ep o sitio n Tem p era tu re ( C )
Figure 1: Dependence of resistivity of p-type BiTe on deposition temperature.
STRC. 10
Nanodiagnostics
1,2,3
Hassan M. E. Azzazy
1
Chemistry Department, the American University in Cairo, Cairo, Egypt
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Cairo, Egypt
3
Graduate School of Biotechnology, University of Maryland University College, MD,
USA
2
Emerging nanotechnology tools and techniques show promise in meeting rigorous
demands of the clinical laboratory for early pre-symptomatic disease diagnosis and
realizing personalized medicine. Nanoparticles such as quantum dots (QDs), gold
nanoparticles, and paramagnetic nanoparticles have been used to extend the current
limits of medical diagnosis and develop new assay platforms for molecular as well as
point of care testing. QDs are among the most promising nanotools. These nanocrystal
fluorophores have several potential medical applications including in vitro
diagnostics, intracellular imaging, targeted drug delivery, and photodynamic therapy.
The diverse potential applications of the QDs are attributed to their unique optical
properties including broad-range excitation, size-tunable narrow emission, and high
photostability. The size and composition of QDs can be varied to obtain the desired
emission properties and make them amenable for simultaneous detection of multiple
targets. A QD-based immunoassay has been used to detect prostate-specific antigen at
0.38 ng/L. Color-coded nanoparticles have also been used for counting individual
biomolecules and intact virus particles in complex mixtures without target
amplification. Nanodiagnostics promise increased sensitivity, multiplexing
capabilities, and reduced cost for many diagnostic and imaging applications.
However, these diagnostic nanotechnologies need to be further optimized for routine
clinical use.
STRC. 11
Bulk and local mechanical behaviour of nanocomposites used as dental
restorative materials
1,2
Dalia Abdel Hamid, 1,3Amal Esawi, 2Inas Sami, and 2Randa Elsalawy
1
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Cairo,Egypt
2
Dental Material Department, Faculty of Oral and Dental Medicine, Cairo
University, Cairo, Egypt
3
Mechanical engineering Department, the American University in Cairo,
Cairo, Egypt
The development of resin -based composite technology is considered as one of the
most significant contributions to dentistry. Adhesively bonded resin composites have
the advantages of conserving sound tooth structure with the potential for tooth
reinforcement, while at the same time providing an aesthetically acceptable
restoration. However, no one composite material has been able to meet both the
functional needs of posterior restorations and the superior aesthetics required for
anterior restoration. In an attempt to develop a dental resin composite that had the
mechanical strength of hybrid composite material and the superior polish and gloss
retention associated with micro-filled materials, nano-filled resin composites have
been introduced in the market.
Although nanofillers are the most popular fillers utilized in current dental visible
light-activated resin composite and are claimed to be the solution for the most
challenging material limitations as a universal restorative material, the mechanisms by
which these fillers influence the resin composite properties are not well explained.
The aim of this research is to obtain a better understanding of the effect of introducing
nanofillers on the bulk behaviour of dental resin nanocomposites (visible lightactivated dental resin composite restorative materials) using nanoindentation
techniques, atomic force and field emission scanning electron microscopy. The local
interfacial mechanics as well as the reinforcement mechanisms of the nanocomposites
are studied and related to the bulk behaviour.
STRC. 12
Fabrication and characterization of carbon nanotube-reinforced polymer matrix
composites
1,3
1
Amal Esawi, 1,3Hanadi Salem, 2,3Adham Ramadan and 1,3Hanadi Hussein
Mechanical Engineering Department, the American university in Cairo, Egypt
2
Chemistry Department, the American university in Cairo, Egypt
3
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
Carbon Nanotubes have been receiving attention from researchers due to their
remarkable properties such as: High Young’s modulus, high rupture strength and
aspect ratio. This makes them ideal candidates for reinforcement in composite
materials. The main challenge faced in processing CNT-composites is that the CNTs
agglomerate due to attractive Van Der Waal interactions, and thus homogenous
dispersion of the nanotubes in many matrices is not straight forward. Several research
teams have attempted to fabricate CNT-polymer composites using different matrices,
weight fractions of the nanotubes and different fabrication techniques. The objective
of this work is to fabricate, process and characterize CNT-reinforced polymer matrix
nanocomposites (PMNC). Extrusion of the nanocomposite was one of the processing
techniques used currently for the production of bulk products suitable for
characterization. The processing and mechanical properties of the extrudates were
then investigated. In the current research, Polypropylene reinforced with CNT was
mixed by dry and solvent techniques aiming for the optimization of the mixing
process. The tensile properties of the produced extrudates were characterized. In
addition, CNT distribution and fracture morphology of the PMNC were investigated
using scanning electron microscopy. It was found that dry mixing produced PMNC
with highest yield strength (YS) for matrices reinforced with 0.5 % CNT, while
solvent mixing produced a highest YS for those reinforced with 1% CNT. However,
the matrix chain alignment strain for solvent mixing was twice that produced for dry
mixing with highest strain produced for the 2.5% CNT content.
STRC. 13
The use of DNA-chip technique in biotechnology
1,2
Hamza El Dorry
1
2
Biology Department, the American University in Cairo, Egypt
The Yousef Jameel Science and Technology Research Center (STRC)
The American University in Cairo, Egypt
The availability of complete genome sequences of human and model organisms
derived a major breakthrough in gene-wide expression profiles using DNA-chip
technology. This technique is designed to monitor the expression levels of thousands
of genes simultaneously. We used DNA-chip technique to understand the metabolic
differences between two model microorganisms- Saccharomyses cerevisiae and
Trichodrma reesei - in metabolizing glucose, and its polymer cellulose, to fuel
ethanol. The unicellular microorganism S. cerevisiae can metabolize glucose to
ethanol, but can not hydrolyse cellulose to glucose. In contrast, the multicellular
microorganism T. reesei metabolizes cellulose to glucose but does not reduce glucose
to ethanol. Analysis of the expression of 2000 genes of T. reesei revealed that, unlike
S. cerevisiae, the expression of the genes encoding the enzymes of the tricarboxylic
acid cycle and the proteins of the electron transport chain is programmed in a way that
favors the oxidation of pyruvate via the tricarboxylic acid cycle rather than its
reduction to ethanol by fermentation. Moreover, the results indicate that acetaldehyde
may be channeled into acetate rather than ethanol, thus preventing the regeneration of
NAD(+), a pivotal product required for anaerobic metabolism. The studies also point
out that the regulatory machinery controlled by glucose was most probably the target
of evolutionary pressure that directed the flow of metabolites into respiratory
metabolism rather than fermentation. This finding has significant implications for the
development of metabolically engineered cellulolytic microorganisms for fuel
production from cellulose biomass.
STRC. 14
Structure-property relationships of polymer/layered silicate
nanocomposites
1
Walid Awad, 2,3Amal Esawi, 3,4Adham Ramadan
1
2
Fire Protection Department, National Institute of Standards, Giza, Egypt
Mechanical Engineering Department, the American University in Cairo, Egypt
3
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
4
Chemistry Department, the American University in Cairo, Egypt
Polymer/clay nanocomposites currently give rise to a great deal of interest from both
academics and industries. By dispersing small amounts of clay, at the molecular level,
within a polymeric matrix, a large array of properties can be significantly improved.
The efficiency of the clay (layered silicates) in improving the properties of the
polymer materials is primarily determined by the degree of its dispersion in the
polymer matrix. To promote the molecular and stable dispersion of the clay layers, the
clays should be organically-modified with onium salts. Understanding the structureproperty relationships in these nanocomposite materials is of great importance in
designing materials with desired properties.
In this work, two approaches have been employed to prepare polymer/clay
nanocomposites; one involves the solution blending method while the other uses melt
compounding. A series of thermoplastic-based nanocomposites (polyamide-6 and
polystyrene) were prepared using different kinds of organically-modified clays. The
morphological characterization of these nanocomposites was carried out using x-ray
diffraction. Evaluation of their structural and thermal properties was carried out by
infrared spectroscopy, thermogravimetric analysis and differential scanning
calorimetry.
STRC. 15
Parameters influencing the consolidation behavior of AA2124-TiC micro and
nanocomposites
1,2
Hanadi G. Salem, 3Sherif El Eskandarany and 3Hassan Abdul Fattah
1
Department of Mechanical Engineering, the American University in Cairo, Egypt
2
The Yousef Jameel Science and Technology Research Center (STRC),
the American University in Cairo, Egypt
3
Department of Mining, Metallurgy and Petroleum Engineering Al-Azhar University
Optimization of the processing parameters of the nanostructured materials is of great
concerns due to the difficulty in retention of the nanoscale structure during the various
processing stages as well as the difficulties encountered in the production of a
homogeneous distribution of the reinforcement. In the current research, a top down
approach was employed for the refinement of a micron scale Al-2124 alloy powder 40
µm in average size using high energy ball milling up to 60 hours. Reinforcement of
the refined Al-2124 powders with 1 m powder of TiC with internal structure <100
nm was conducted to investigate the compaction and consolidation behavior of the
produced nanocomposite. X-ray diffraction was employed to determine the crystallite
size as a function of milling time. The milled powders were characterized in the green
and sintered conditions. Degree of densification and other mechanical properties were
investigated for the nanoscale consolidated powders versus the microscale one with
and without reinforcement. Various compaction and consolidation parameters (time,
pressure, h/d ratio and sintering temperatures) were employed to consolidate BNS
metal matrix nanocomposites of Al-2124 with variable content of nanocrystalline TiC
reinforcing powder compared to that of the bare Al-2124. Microstructural evolution
was investigated using a 1nm resolution field emission scanning electron microscope
as well as optical microscopy. Milling time of 36 hrs produced a 100 nm
nanopowders in average size with internal structure size of 16.8 nm. Increasing the
milling time beyond 36 hr resulted in the re-clustering of the fine particles, which was
associated with a slight increase in particle size and shape with an insignificant
change in structure size. An improved densification and hardness was produced with
the reinforcement of the nanoscale Al-2124 matrix by TiC compared to the microscale
one due to the relative particle size (RPS) ratio of the matrix-to-reinforcement. Water
quenching subsequent to sintering results in induced cracking and voiding of the
reinforced micro and nanoscale matrices, while air cooling produces a more sound
and dense consolidates.