Abstract: Lightweight and efficient structures have the aim to
enhance the efficiency of the components in various industries.
Toward this end, composites are one of the most widely used
materials because of durability, high strength and modulus, and low
weight. One type of the advanced composites is grid-stiffened
composite (GSC) structures, which have been extensively considered
in aerospace, automotive, and aircraft industries. They are one of the
top candidates for replacing some of the traditional components,
which are used here. Although there are a good number of published
surveys on the design aspects and fabrication of GSC structures, little
systematic work has been reported on their material modification to
improve their properties, to our knowledge. Matrix modification
using nanoparticles is an effective method to enhance the flexural
properties of the fibrous composites. In the present study, a silanecoupling
agent (3-glycidoxypropyltrimethoxysilane/3-GPTS) was
introduced onto the silica (SiO2) nanoparticle surface and its effects
on the three-point flexural response of isogrid E-glass/epoxy
composites were assessed. Based on the Fourier Transform Infrared
Spectrometer (FTIR) spectra, it was inferred that the 3-GPTS
coupling agent was successfully grafted onto the surface of SiO2
nanoparticles after modification. Flexural test revealed an
improvement of 16%, 14%, and 36% in stiffness, maximum load and
energy absorption of the isogrid specimen filled with 3 wt.% 3-
GPTS/SiO2 compared to the neat one. It would be worth mentioning
that in these structures, considerable energy absorption was observed
after the primary failure related to the load peak. In addition, 3-
GPTMS functionalization had a positive effect on the flexural
behavior of the multiscale isogrid composites. In conclusion, this
study suggests that the addition of modified silica nanoparticles is a
promising method to improve the flexural properties of the gridstiffened
fibrous composite structures.
Abstract: Green concrete are generally composed of recycling
materials as hundred or partial percent substitutes for aggregate,
cement, and admixture in concrete. To reduce greenhouse gas
emissions, efforts are needed to develop environmentally friendly
construction materials. Using of fly ash based geopolymer as an
alternative binder can help reduce CO2 emission of concrete. The
binder of geopolymer concrete is different from the ordinary Portland
cement concrete. Geopolymer Concrete specimens were prepared
with different concentration of NaOH solution M10, M14, and, M16
and cured at 60ºC in duration of 24 hours and 8 hours, in addition to
the curing in direct sunlight. Thus, it is necessary to study the effects
of the geopolymer binder on the behavior of concrete. Concrete is
made by using geopolymer technology is environmental friendly and
could be considered as part of the sustainable development. In this
study, the Local Alkaline Activator in Egypt and crashed stone as
coarse aggregate in fly ash based-geopolymer concrete was
investigated. This paper illustrates the development of mechanical
properties. Since the gained compressive strength for geopolymer
concrete at 28 days was in the range of 22.5MPa – 43.9MPa.
Abstract: Local steel slag is produced as a by-product during the
oxidation of steel pellets in an electric arc furnace. Using local steel
slag waste as a hundred substitutes of crashed stone in construction
materials would resolve the environmental problems caused by the
large-scale depletion of the natural sources of crashed stone. This
paper reports the experimental study to investigate the influence of a
hundred replacement of crashed stone as a coarse aggregate with
local steel slag, on the fresh and hardened geopolymer concrete
properties. The investigation includes traditional testing of hardening
concrete, for selected mixes of cement and geopolymer concrete. It
was found that local steel slag as a coarse aggregate enhanced the
slump test of the fresh state of cement and geopolymer concretes.
Nevertheless, the unit weight of concretes was affected. Meanwhile,
the good performance was observed when fly ash used as geopolymer
concrete based.
Abstract: This study presents experimental and optimization of
nanoparticle mass concentration and heat input based on the total
thermal resistance (Rth) of loop heat pipe (LHP), employed for PCCPU
cooling. In this study, silica nanoparticles (SiO2) in water with
particle mass concentration ranged from 0% (pure water) to 1% is
considered as the working fluid within the LHP. The experimental
design and optimization is accomplished by the design of
experimental tool, Response Surface Methodology (RSM). The
results show that the nanoparticle mass concentration and the heat
input have significant effect on the Rth of LHP. For a given heat
input, the Rth is found to decrease with the increase of the
nanoparticle mass concentration up to 0.5% and increased thereafter.
It is also found that the Rth is decreased when the heat input is
increased from 20W to 60W. The results are optimized with the
objective of minimizing the Rth, using Design-Expert software, and
the optimized nanoparticle mass concentration and heat input are
0.48% and 59.97W, respectively, the minimum thermal resistance
being 2.66 (ºC/W).
Abstract: In present study, a large deposit of oolitic iron ore of
Late Carboniferous-Permotriassic-Lower Jurassic age was discovered
in Wadi Halfa and Argein areas, North Sudan. It seems that the iron
ore mineralization exists in the west and east bank of the River Nile
of the study area that are found on the Egyptian-Sudanese border.
The Carboniferous-Lower Jurassic age strata were covered by 67
sections and each section has been examined and carefully described.
The iron-ore in Wadi Halfa occurs as oolitic ironstone and contained
two horizons: (A) horizon and (B) horizon. Only horizon (A) was
observed in southern Argein area. The texture of the ore is variable
depending on the volume of the component. In thin sections, the
average of the ooids was ranged between 90%-80%. The matrix
varies between 10%-20% by volume and detritus quartz in other
component my reach up to 30% by volume in sandy massive ore.
Ooids size ranges from 0.2mm-1.00 mm on average in very coarse
ooids may attend up to 1 mm in size. The matrix around the ooids is
dominated by iron hydroxide, carbonate, fine, and amorphous silica.
The probable ore reserve estimate of 1.234 billion at a head grade of
41.29% Fe for the Wadi Halfa Oolitic Ironstone Formation. The iron
ore shows higher content of phosphorus ranges from 6.15% to 0.16%,
with mean 1.45%. The new technology Hatch–Ironstone Chloride
Segregation (HICS) can be used to produce commercial-quality of
iron and reduce phosphorus and silica to acceptable levels for steel
industry. The presence of infrastructures in addition to the presence
of massive quantities of iron ore would make exploitation
economically.
Abstract: Calcium Phosphate Cement (CPC) due to its high bioactivity and optimum bioresorbability shows excellent bone regeneration capability. Despite it has limited applications as bone implant due to its macro-porous microstructure causing its poor mechanical strength. The reinforcement of apatitic CPCs with biocompatible fibre glass phase is an attractive area of research to improve upon its mechanical strength. Here, we study the setting behaviour of Si-doped and un-doped α tri calcium phosphate (α - TCP) based CPC and its reinforcement with addition of E-glass fibre. Alpha Tri calcium phosphate powders were prepared by solid state sintering of CaCO3 , CaHPO4 and Tetra Ethyl Ortho Silicate (TEOS) was used as silicon source to synthesize Si doped α-TCP powders. Both initial and final setting time of the developed cement was delayed because of Si addition. Crystalline phases of HA (JCPDS 9- 432), α-TCP (JCPDS 29-359) and β-TCP (JCPDS 9-169) were detected in the X-ray diffraction (XRD) pattern after immersion of CPC in simulated body fluid (SBF) for 0 hours to 10 days. As Si incorporation in the crystal lattice stabilized the TCP phase, Si doped CPC showed little slower rate of conversion into HA phase as compared to un-doped CPC. The SEM image of the microstructure of hardened CPC showed lower grain size of HA in un-doped CPC because of premature setting and faster hydrolysis of un-doped CPC in SBF as compared that in Si-doped CPC. Premature setting caused generation of micro and macro porosity in un-doped CPC structure which resulted in its lower mechanical strength as compared to that in Si-doped CPC. It was found that addition of 10 wt% of E-glass fibre into Si-doped α-TCP increased the average DTS of CPC from 8 MPa to 15 MPa as the fibres could resists the propagation of crack by deflecting the crack tip. Our study shows that biocompatible E-glass fibre in optimum proportion in CPC matrix can enhance the mechanical strength of CPC without affecting its biocompatibility.
Abstract: The seriously damaged structures during earthquakes
show the need and importance of design of reinforced concrete
structures with high ductility. Reinforced concrete beam-column
joints have an important function in all structures. Under seismic
excitation, the beam column joint region is subjected to horizontal
and vertical shear forces whose magnitude is many times higher than
the adjacent beam and column. Strength and ductility of structures
depends mainly on proper detailing of the reinforcement in beamcolumn
joints and the old structures were found ductility deficient.
DSP materials are obtained by using high quantities of super
plasticizers and high volumes of micro silica. In the case of High
Performance Densified Small Particle Concrete (HPDSPC), since
concrete is dense even at the micro-structure level, tensile strain
would be much higher than that of the conventional SFRC, SIFCON
& SIMCON. This in turn will improve cracking behaviour, ductility
and energy absorption capacity of composites in addition to
durability. The fine fibers used in our mix are 0.3mm diameter and 10
mm which can be easily placed with high percentage. These fibers
easily transfer stresses and act as a composite concrete unit to take up
extremely high loads with high compressive strength. HPDSPC
placed in the beam column joints helps in safety of human life due to
prolonged failure.
Abstract: Erosion and abrasion are wear mechanisms reducing
the lifetime of machine elements like valves, pump and pipe systems.
Both wear mechanisms are acting at the same time, causing a
“Synergy” effect, which leads to a rapid damage of the surface.
Different parameters are effective on erosive abrasive wear rate. In
this study effect of particle impact angle on wear rate and wear
mechanism of ductile and brittle materials was investigated. A new
slurry pot was designed for experimental investigation. As abrasive
particle, silica sand was used. Particle size was ranking between 200-
500 μm. All tests were carried out in a sand-water mixture of 20%
concentration for four hours. Impact velocities of the particles were
4.76 m/s. As ductile material steel St 37 with Vickers Hardness
Number (VHN) of 245 and quenched St 37 with 510 VHN was used
as brittle material. After wear tests, morphology of the eroded
surfaces were investigated for better understanding of the wear
mechanisms acting at different impact angles by using Scanning
Electron Microscope. The results indicated that wear rate of ductile
material was higher than brittle material. Maximum wear rate was
observed by ductile material at a particle impact angle of 300 and
decreased further by an increase in attack angle. Maximum wear rate
by brittle materials was by impact angle of 450 and decreased further
up to 900. Ploughing was the dominant wear mechanism by ductile
material. Microcracks on the surface were detected by ductile
materials, which are nucleation centers for crater formation. Number
of craters decreased and depth of craters increased by ductile
materials by attack angle higher than 300. Deformation wear
mechanism was observed by brittle materials. Number and depth of
pits decreased by brittle materials by impact angles higher than 450.
At the end it is concluded that wear rate could not be directly related
to impact angle of particles due to the different reaction of ductile and
brittle materials.
Abstract: This paper investigates the effectiveness of two
natural zeolites in reducing expansion of concrete due to alkali-silica
reaction. These natural zeolites have different reactive silica content.
Three aggregates; two natural sands and one crushed stone aggregate
were used while preparing mortar bars in accordance with accelerated
mortar bar test method, ASTM C1260. Performances of natural
zeolites are compared by examining the expansions due to alkali
silica reaction. Natural zeolites added to the mixtures at 10% and
20% replacement levels by weight of cement. Natural zeolite with
high reactive silica content had better performance on reducing
expansions due to ASR. In this research, using high reactive zeolite at
20% replacement levels was effective in mitigating expansions.
Abstract: Low Temperature Matrix Isolation - Electron
Paramagnetic Resonance (LTMI-EPR) Spectroscopy was utilized to
identify the species of iron oxide nanoparticles generated during the
oxidative pyrolysis of 1-methylnaphthalene (1-MN). The otherwise
gas-phase reactions of 1--MN were impacted by a polypropylenimine
tetra-hexacontaamine dendrimer complexed with iron (III) nitrate
nonahydrate diluted in air under atmospheric conditions. The EPR
fine structure of Fe (III)2O3 nanoparticles clusters, characterized by gfactors
of 2.00, 2.28, 3.76 and 4.37 were detected on a cold finger
maintained at 77 K after accumulation over a multitude of
experiments. Additionally, a high valence Fe (IV) paramagnetic
intermediate and superoxide anion-radicals, O2•- adsorbed on
nanoparticle surfaces in the form of Fe (IV) --- O2•- were detected
from the quenching area of Zone 1 in the gas-phase.
Abstract: A bauxite ore can be utilized in Bayer Process, if the
mass ratio of Al2O3 to SiO2 is greater than 10. Otherwise, its FexOy
and SiO2 content should be removed. On the other hand, removal of
TiO2 from the bauxite ore would be beneficial because of both
lowering the red mud residue and obtaining a valuable raw material
containing TiO2 mineral. In this study, the low grade diasporic
bauxite ore of Yalvaç, Isparta, Turkey was roasted under reducing
atmosphere and subjected to magnetic separation. According to the
experimental results, 800°C for reduction temperature and 20000
Gauss of magnetic intensity were found to be the optimum
parameters for removal of iron oxide and rutile from the nonmagnetic
ore. On the other hand, 600°C and 5000 Gauss were
determined to be the optimum parameters for removal of silica from
the non-magnetic ore.
Abstract: In this study, the experiments were carried out to
determine the best coolant for the quenching process among waterbased
silica, alumina, titania and copper oxide nanofluids (0.1 vol%).
A sphere made up off brass material was used in the experiments.
When the spherical test specimen was heated at high temperatures, it
was suddenly immersed into the nanofluids. All experiments were
carried out at saturated conditions and under atmospheric pressure.
After the experiments, the cooling curves were obtained by using the
temperature-time data of the specimen. The experimental results
showed that the cooling performance of test specimen depended on
the type of nanofluids. The silica nanoparticles enhanced the
performance of boiling heat transfer and it is the best coolant for the
quenching among other nanoparticles.
Abstract: A dip-coating process has been used to form an
asymmetric silica membrane with improved membrane performance
and reproducibility. First, we deposited repeatedly silica on top of a
commercial alumina membrane support to improve its structural
make up. The membrane is further processed under clean room
conditions to avoid dust impurity and subsequent drying in an oven
for high thermal, chemical and physical stability. The resulting
asymmetric membrane exhibits a gradual change in the membrane
layer thickness. Compared to the support, the dual-layer process
improves the gas flow rates. For the scientific applications for natural
gas purification, CO2, CH4 and H2 gas flow rates were. In addition,
the membrane selectively separated hydrogen.
Abstract: Many water desalination technologies have been
developed but in general they are energy intensive and have high cost
and adverse environmental impact. Recently, adsorption technology
for water desalination has been investigated showing the potential of
using low temperature waste heat (50-85oC) thus reducing energy
consumption and CO2 emissions. This work mathematically
compares the performance of an adsorption cycle that produces two
useful effects namely, fresh water and cooling using two different
adsorbents, silica-gel and an advanced zeolite material AQSOA-ZO2,
produced by Mitsubishi plastics. It was found that at low chilled
water temperatures, typically below 20oC, the AQSOA-Z02 is more
efficient than silica-gel as the cycle can produce 5.8 m3 of fresh water
per day and 50.1 Rton of cooling per tonne of AQSOA-ZO2. Above
20oC silica-gel is still better as the cycle production reaches 8.4 m3
per day and 62.4 Rton per tonne of silica-gel. These results show the
potential of using the AQSOA-Z02 at low chilled water temperature
for water desalination and cooling applications.
Abstract: As the trend in automotive technology is fast moving
towards hybridization and electrification to curb emissions as well as
to improve the fuel efficiency, air-conditioning systems in passenger
cars have not caught up with this trend and still remain as the major
energy consumers amongst others. Adsorption based air-conditioning
systems, e.g. with silica-gel water pair, which are already in use for
residential and commercial applications, are now being considered as
a technology leap once proven feasible for the passenger cars. In this
paper we discuss a methodology, challenges and feasibility of
implementing an adsorption based air-conditioning system in a
passenger car utilizing the exhaust waste heat. We also propose an
optimized control strategy with interfaces to the engine control unit
of the vehicle for operating this system with reasonable efficiency
supported by our simulation and validation results in a prototype
vehicle, additionally comparing to existing implementations,
simulation based as well as experimental. Finally we discuss the
influence of start-stop and hybrid systems on the operation strategy of
the adsorption air-conditioning system.
Abstract: The effect of additional magnesium oxide (MgO) was
investigated by using the tungsten oxide supported on silica catalyst
(WOx/SiO2) physically mixed with MgO in a weight ratio 1:1. The
both fresh and spent catalysts were characterized by FT-Raman
spectrometer, UV-Vis spectrometer, X-Ray diffraction (XRD) and
temperature programmed oxidation (TPO). The results indicated that
the additional MgO could enhance the conversion of trans-2-butene
due to isomerization reaction. However, adding MgO would increase
the amount of coke deposit on the WOx/SiO2 catalyst. The TPO
profile presented two peaks when the WOx/SiO2 catalyst was
physically mixed with MgO. The further peak was suggested that
came from coke precursor could be produced by isomerization
reaction of undesired product. Then, the occurred coke precursor
could deposit and form coke on the acid catalyst.
Abstract: An unconventional composite inorganic ceramic
membrane capable of enhancing carbon dioxide emission decline was
fabricated and tested at laboratory scale in conformism to various
environmental guidelines and also to mitigate the effect of global
warming. A review of the existing membrane technologies for carbon
capture including the relevant gas transport mechanisms is presented.
Single gas permeation experiments using silica modified ceramic
membrane with internal diameter 20mm, outside diameter 25mm and
length of 368mm deposited on a macro porous support was carried
out to investigate individual gas permeation behaviours at different
pressures at room temperature. Membrane fabrication was achieved
using after a dip coating method. Nitrogen, Carbon dioxide, Argon,
Oxygen and Methane pure gases were used to investigate their
individual permeation rates at various pressures. Results show that
the gas flow rate increases with pressure drop. However above a
pressure of 3bar, CO2 permeability ratio to that of the other gases
indicated control of a more selective surface adsorptive transport
mechanism.
Abstract: Fly ash (FA) thanks to the significant presence of SiO2
and Al2O3 as the main components is a potential raw material for
geopolymers production. Mechanical activation is a method for
improving FA reactivity and also the porosity of final mixture; those
parameters can be analysed through sorption properties. They have
direct impact on the durability of fly ash based geopolymer mortars.
In the paper, effect of FA fineness on sorption properties of
geopolymers based on sodium silicate, as well as relationship
between fly ash fineness and apparent density, compressive and
flexural strength of geopolymers are presented. The best results in the
evaluated area reached the sample H1, which contents the highest
portion of particle under 20μm (100% of GFA). The interdependence
of individual tested properties was confirmed for geopolymer
mixtures corresponding to those in the cement based mixtures: higher
is portion of fine particles < 20μm, higher is strength, density and
lower are sorption properties. The compressive strength as well as
sorption parameters of the geopolymer can be reasonably controlled
by grinding process and also ensured by the higher share of fine
particle (to 20μm) in total mass of the material.
Abstract: Propylene self-metathesis to ethylene and butene was
studied over WOx/SiO2 catalysts at 450oC and atmospheric pressure.
The WOx/SiO2 catalysts were prepared by incipient wetness
impregnation of ammonium metatungstate aqueous solution. It was
found that, adding nano-sized extra supports (SiO2 and TiO2) by
physical mixing with the WOx/SiO2 enhanced propylene conversion.
The UV-Vis and FT-Raman results revealed that WOx could migrate
from the original silica support to the extra support, leading to a
better dispersion of WOx. The ICP-OES results also indicate that
WOx existed on the extra support. Coke formation was investigated
on the catalysts after 10 h time-on-stream by TPO. However, adding
nano-sized extra supports led to higher coke formation which may be
related to acidity as characterized by NH3-TPD.
Abstract: Nanofibers of PVA /nickel nitrate/silica/alumina
izopropoxide/boric acid composite were prepared by using sol-gel
processing and electrospinning technique. By high temperature
calcinations of the above precursor fibers, nanofibers of
NiO/Al2O3/B2O3/SiO2 composite with diameters about 500 nm
could be successfully obtained. The fibers were characterized by
XRD and SEM analyses.