Abstract: Nanofibers are effective materials which have
frequently been investigated to produce high quality air filters. As an
environmental approach our aim is to achieve nanofibers by melting.
In spun-bond systems extruder, spin-pump, nozzle package and
attenuator are used. Molten polymer which flows from extruder is
made steady by spin-pump. Regular melt passes through nozzle holes
and forms fibers under high pressure. The fibers pulled from nozzle
are shrunk to micron size by an attenuator; after solidification, they
are collected on a conveyor. In this research different designs of
attenuator system have been studied; and also CFD analysis has been
done on these different designs. Afterwards, one of these designs
tested and finally some optimizations have been done to reduce
pressure loss and increase air velocity.
Abstract: Poly vinyl acetate (PVA)-based titania (TiO2)–carbon
nanotube composite nanofibers (PVA-TCCNs) with various
PVA-to-solvent ratios and PVA-based TiO2 composite nanofibers
(PVA-TN) were synthesized using an electrospinning process,
followed by thermal treatment. The photocatalytic activities of these
nanofibers in the degradation of airborne monocyclic aromatics under
visible-light irradiation were examined. This study focuses on the
application of these photocatalysts to the degradation of the target
compounds at sub-part-per-million indoor air concentrations. The
characteristics of the photocatalysts were examined using scanning
electron microscopy, X-ray diffraction, ultraviolet-visible
spectroscopy, and Fourier-transform infrared spectroscopy. For all the
target compounds, the PVA-TCCNs showed photocatalytic
degradation efficiencies superior to those of the reference PVA-TN.
Specifically, the average photocatalytic degradation efficiencies for
benzene, toluene, ethyl benzene, and o-xylene (BTEX) obtained using
the PVA-TCCNs with a PVA-to-solvent ratio of 0.3 (PVA-TCCN-0.3)
were 11%, 59%, 89%, and 92%, respectively, whereas those observed
using PVA-TNs were 5%, 9%, 28%, and 32%, respectively.
PVA-TCCN-0.3 displayed the highest photocatalytic degradation
efficiency for BTEX, suggesting the presence of an optimal
PVA-to-solvent ratio for the synthesis of PVA-TCCNs. The average
photocatalytic efficiencies for BTEX decreased from 11% to 4%, 59%
to 18%, 89% to 37%, and 92% to 53%, respectively, when the flow
rate was increased from 1.0 to 4.0 L min1. In addition, the average
photocatalytic efficiencies for BTEX increased 11% to ~0%, 59% to
3%, 89% to 7%, and 92% to 13%, respectively, when the input
concentration increased from 0.1 to 1.0 ppm. The prepared
PVA-TCCNs were effective for the purification of airborne aromatics
at indoor concentration levels, particularly when the operating
conditions were optimized.
Abstract: Co metal supported on SiO2 and Al2O3 catalysts with
a metal loading varied from 30 of 70 wt.% were evaluated for
decomposition of methane to COx free hydrogen and carbon
nanomaterials. The catalytic runs were carried out from 550-800oC
under atmospheric pressure using fixed bed vertical flow reactor. The
fresh and spent catalysts were characterized by BET surface area
analyzer, XRD, SEM, TEM and TG analysis. The data showed that
50% Co/Al2O3 catalyst exhibited remarkable higher activity at 800oC
with respect to H2 production compared to rest of the catalysts.
However, the catalytic activity and durability was greatly declined at
higher temperature. The main reason for the catalytic inhibition of Co
containing SiO2 catalysts is the higher reduction temperature of
Co2SiO4. TEM images illustrate that the carbon materials with
various morphologies, carbon nanofibers (CNFs), helical-shaped
CNFs and branched CNFs depending on the catalyst composition and
reaction temperature were obtained.
Abstract: Polysulfone (PSU) is a specialty engineering polymer
having various industrial applications. PSU is especially used in
waste water treatment membranes due to its good mechanical
properties, structural and chemical stability. But it is a hydrophobic
material and therefore its surface aim to pollute easily. In order to
resolve this problem and extend the properties of membrane, PSU
surface is rendered hydrophilic by addition of the sepiolite
nanofibers. Sepiolite is one of the natural clays, which is a hydrate
magnesium silicate fiber, also one of the well known layered clays of
the montmorillonites where has several unique channels and pores
within. It has also moisture durability, strength and low price.
Sepiolite channels give great capacity of absorption and good surface
properties. In this study, nanocomposites of commercial PSU and
Sepiolite were prepared by solvent mixing method. Different organic
solvents and their mixtures were used. Rheological characteristics of
PSU-Sepiolite solvent mixtures were analyzed, the solubility of
nanocomposite content in those mixtures were studied.
Abstract: The main objective of this paper is study the influence
of carbon nano-tubes fibers and nano silica fibers on the
characteristic compressive strength and flexural strength on concrete
and cement mortar. Twelve tested specimens were tested with square
section its dimensions (4040 160) mm, divided into four groups.
The first and second group studied the effect of carbon nano-tubes
(CNTs) fibers with different percentage equal to 0.0, 0.11%, 0.22%,
and 0.33% by weight of cement and effect of nano-silica (nS) fibers
with different percentages equal to 0.0, 1.0%, 2.0%, and 3.0% by
weight of cement on the cement mortar. The third and fourth groups
studied the effect of CNTs fiber with different percentage equal to
0.0%, 0.11%, and 0.22% by weight of cement, and effect of nS fibers
with different percentages were equal to 0.0%, 1.0%, and 2.0% by
weight of cement on the concrete. The compressive strength and
flexural strength at 7, 28, and 90 days is determined. From analysis of
tested results concluded that the nano-fibers is more effective when
used with cement mortar more than used with concrete because of
increasing the surface area, decreasing the pore and the collection of
nano-fibers. And also by adding nano-fibers the improvement of
flexural strength of concrete and cement mortar is more than
improvement of compressive strength.
Abstract: In this research, waterglass based aerogel powder was
prepared by sol–gel process and ambient pressure drying. Inspired by
limited dust releasing, aerogel powder was introduced to the PET
electrospinning solution in an attempt to create required bulk and
surface structure for the nanofibers to improve their hydrophobic and
insulation properties. The samples evaluation was carried out by
measuring density, porosity, contact angle, heat transfer, FTIR, BET,
and SEM. According to the results, porous silica aerogel powder was
fabricated with mean pore diameter of 24 nm and contact angle of
145.9º. The results indicated the usefulness of the aerogel powder
confined into nanofibers to control surface roughness for
manipulating superhydrophobic nanowebs with water contact angle
of 147º. It can be due to a multi-scale surface roughness which was
created by nanowebs structure itself and nanofibers surface
irregularity in presence of the aerogels while a layer of fluorocarbon
created low surface energy. The wettability of a solid substrate is an
important property that is controlled by both the chemical
composition and geometry of the surface. Also, a decreasing trend in
the heat transfer was observed from 22% for the nanofibers without
any aerogel powder to 8% for the nanofibers with 4% aerogel
powder. The development of thermal insulating materials has become
increasingly more important than ever in view of the fossil energy
depletion and global warming that call for more demanding energysaving
practices.
Abstract: The main purpose of this work was verify the
influence of the accelerated carbonation in the physical and
mechanical properties of the hybrid composites, reinforced with
micro and nanofibers and composites with microfibers. The
composites were produced by the slurry vacuum dewatering method,
followed by pressing. It was produced using two formulations: 8% of
eucalyptus pulp + 1% of the nanofibrillated cellulose and 9% of
eucalyptus pulp, both were subjected to accelerated carbonation. The
results showed that the accelerated carbonation contributed to
improve the physical and mechanical properties of the hybrid
composites and of the composites reinforced with microfibers
(eucalyptus pulp).
Abstract: PAN nanofibers reinforced with amine functionalized
carbon nanotubes. The effect of amine functionalization and the
effect of concentration of CNT on the conductivity and mechanical
and morphological properties of composite nanofibers were
examined. 1%CNT-NH2 loaded PAN/CNT nanofiber showed the best
mechanical properties. Conductivity increased with the incorporation
of carbon nanotubes. While an increase of concentration of CNT
increases the diameter of nanofiber, the use of functionalized CNT
results to decrease of diameter of nanofiber.
Abstract: The main goal of this study was to find simple and industrially applicable production of ion exchangers based on nanofibrous polystyrene matrix and characterization of prepared material. Starting polystyrene nanofibers were sulfonated and crosslinked under appropriate conditions at the same time by sulfuric acid. Strongly acidic cation exchanger was obtained in such a way. The polymer matrix was made from polystyrene nanofibers prepared by NanospiderTM technology.
Various types postpolymerization reactions and other methods of crosslinking were studied. Greatly different behavior between nano- and microsize materials was observed. The final nanofibrous material was characterized and compared to common granular ion exchangers and available microfibrous ion exchangers. The sorption properties of nanofibrous ion exchangers were compared with the granular ion exchangers. For nanofibrous ion exchangers of comparable ion exchange capacity was observed considerably faster adsorption kinetics.
Abstract: A proton exchange membrane has been developed for
direct methanol fuel cell (DMFC). The nanofiber network composite
membranes were prepared by interconnected network of Nafion
(perfuorosulfonic acid) nanofibers that have been embedded in an
uncharged and inert polymer matrix, by electro-spinning. The
spinning solution of Nafion with a low concentration (1 wt%
compared to Nafion) of high molecular weight poly(ethylene oxide),
as a carrier polymer. The interconnected network of Nafion
nanofibers with average fiber diameter in the range of 160-700nm,
were used to make the membranes, with the nanofiber occupying up
to 85% of the membrane volume. The matrix polymer was
crosslinked with Norland Optical Adhesive 63 under UV. The
resulting membranes showed proton conductivity of 0.10 S/cm at
25°C and 80% RH; and methanol permeability of 3.6 x 10-6 cm2/s.
Abstract: Montmorillonite (MMT) is a very abundant clay mineral and is versatile such that it can be chemically or physically altered by changing the ions between the sheets of its layered structure. This clay mineral can be prepared into functional nanoparticles that can be used as fillers in other nanomaterials such as nanofibers to achieve special properties. In this study, two types of iron-modified MMT, Iron-MMT (FeMMT) and Zero Valent Iron-MMT (ZVIMMT) were synthesized via ion exchange technique. The modified clay was incorporated in polymer nanofibers which were produced using a process called electrospinning. ICP analysis confirmed that clay modification was successful where there is an observed decrease in the concentration of Na and an increase in the concentration of Fe after ion exchange. XRD analysis also confirmed that modification took place because of the changes in the d-spacing of Na-MMT from 11.5 Å to 13.6 Å and 12.6 Å after synthesis of FeMMT and ZVIMMT, respectively. SEM images of the electrospun nanofibers revealed that the ZVIMMT-filled fibers have a smaller average diameter than the FeMMT-filled fibers because of the lower resistance of the suspensions of the former to the elongation force from the applied electric field. The resistance to the electric field was measured by getting the bulk voltage of the suspensions.
Abstract: The negative Poisson’s ratios can be described in terms of models based on the geometry of the system and the way this geometry changes due to applied loads. As the Poisson’s ratio does not depend on scale hence deformation can take place at the nano to macro level the only requirement is the right combination of the geometry. Our thrust in this paper is to combine our knowledge of tailored enhanced mechanical properties of the materials having negative Poisson’s ratio with the micromachining and electrospining technology to develop a novel stent carrying a drug delivery system. Therefore, the objective of this paper includes (i) fabrication of a micromachined metal sheet tailored with structure having negative Poisson’s ratio through rotating solid squares geometry using femtosecond laser ablation; (ii) rolling fabricated structure and welding to make a tubular structure (iii) wrapping it with nanofibers of biocompatible polymer PCL (polycaprolactone) for drug delivery (iv) analysis of the functional and mechanical performance of fabricated structure analytically and experimentally. Further, as the applications concerned, tubular structures have potential in biomedical for example hollow tubes called stents are placed inside to provide mechanical support to a damaged artery or diseased region and to open a blocked esophagus thus allowing feeding capacity and improving quality of life.
Abstract: Interlaminar shear strength (ILSS) of fiber reinforced polymer composite is an important property for most of the structural applications. Matrix modification is an effective method used to improve the interlaminar shear strength of composite. In this paper, EPON 862/w epoxy system was modified using Tetraethyl orthosilicate (TEOS) electrospun nanofibers (ENFs) which were produced using electrospinning method. Unmodified and nanofibers modified resins were used to fabricate glass fiber reinforced polymer composite (GFRP) using H-VARTM method. The ILSS of the Glass Fiber Reinforced Polymeric Composites (GFRP) was investigated. The study shows that introduction of TEOS ENFs in the epoxy resin enhanced the ILSS of GFRPby 15% with 0.6% wt. fraction of TEOS ENFs.
Abstract: The effect of carbon materials on TiO2 for the photocatalytic hydrogen gas production from water / alcohol mixtures was investigated. Single walled carbon nanotubes (SWNTs), multi walled carbon nanotubes (MWNTs), carbon nanofiber (CNF), fullerene (FLN), graphite (GP), and graphite silica (GS) were used as co-catalysts by directly mixing with TiO2. Drastic synergy effects were found with increase in the amount of hydrogen gas by a factor of ca. 150 and 100 for SWNTs and GS with TiO2, respectively. Moreover, the increment factor of hydrogen production reached to 180, when the mixture of SWNTs and TiO2 were smashed in an agate mortar before photocatalytic reactions. The order of H2 gas production for these carbon materials was SWNTs > GS >> MWNTs > FLN > CNF > GP. To maximize the hydrogen production from SWNTs/TiO2, various parameters of experimental condition were changed. Also, a comparison between Pt/TiO2, SWNTs/TiO2 and GS/TiO2 was made for the amount of H2 gas production. Finally, the recyclability of SWNTs/TiO2or GS/TiO2 was tested.
Abstract: In this manuscript, we produced neat electrospun poly(o-methoxyaniline) (POMA) fibers and utilized it for applying the growth of neural stem cells. The transparency and morphology of as-prepared POMA fibers was characterized by UV-visible spectroscopy and scanning electron microscopy, respectively. It was found to have no adverse effects on the long-term proliferation of the neural stem cells (NSCs), retained the ability to self-renew, and exhibit multipotentiality. Results of immunofluorescence staining studies confirmed that POMA electrospun fibers could provide a great environment for NSCs and enhance its differentiation.
Abstract: A numerical simulation of optimization all of electrospinning processing parameters to obtain smallest nanofiber diameter have been performed by employing genetic algorithm (GA). Fitness function in genetic algorithm methods, which was different for each parameter, was determined by simulation approach based on the Reneker’s model. Moreover, others genetic algorithm parameter, namely length of population, crossover and mutation were applied to get the optimum electrospinning processing parameters. In addition, minimum fiber diameter, 32 nm, was achieved from a simulation by applied the optimum parameters of electrospinning. This finding may be useful for process control and prediction of electrospun fiber production. In this paper, it is also compared between predicted parameters with some experimental results.
Abstract: Nowadays due to globalization of economy and
competition environment, innovation and technology plays key role
at creation of wealth and economic growth of countries. In fact
prompt growth of practical and technologic knowledge may results in
social benefits for countries when changes into effective innovation.
Considering the importance of innovation for the development of
countries, this study addresses the radical technological innovation
introduced by nanopapers at different stages of producing paper
including stock preparation, using authorized additives, fillers and
pigments, using retention, calender, stages of producing conductive
paper, porous nanopaper and Layer by layer self-assembly. Research
results show that in coming years the jungle related products will lose
considerable portion of their market share, unless embracing radical
innovation. Although incremental innovations can make this industry
still competitive in mid-term, but to have economic growth and
competitive advantage in long term, radical innovations are
necessary. Radical innovations can lead to new products and
materials which their applications in packaging industry can produce
value added. However application of nanotechnology in this industry
can be costly, it can be done in cooperation with other industries to
make the maximum use of nanotechnology possible. Therefore this
technology can be used in all the production process resulting in the
mass production of simple and flexible papers with low cost and
special properties such as facility at shape, form, easy transportation,
light weight, recovery and recycle marketing abilities, and sealing.
Improving the resistance of the packaging materials without reducing
the performance of packaging materials enhances the quality and the
value added of packaging. Improving the cellulose at nano scale can
have considerable electron optical and magnetic effects leading to
improvement in packaging and value added. Comparing to the
specifications of thermoplastic products and ordinary papers,
nanopapers show much better performance in terms of effective
mechanical indexes such as the modulus of elasticity, tensile strength,
and strain-stress. In densities lower than 640 kgm -3, due to the
network structure of nanofibers and the balanced and randomized
distribution of NFC in flat space, these specifications will even
improve more. For nanopapers, strains are 1,4Gpa, 84Mpa and 17%,
13,3 Gpa, 214Mpa and 10% respectively. In layer by layer self
assembly method (LbL) the tensile strength of nanopaper with Tio3
particles and Sio2 and halloysite clay nanotube are 30,4 ±7.6Nm/g
and 13,6 ±0.8Nm/g and 14±0.3,3Nm/g respectively that fall within
acceptable range of similar samples with virgin fiber. The usage of
improved brightness and porosity index in nanopapers can create
more competitive advantages at packaging industry.
Abstract: High purity hydrogen and the valuable by-product of carbon nanotubes (CNTs) can be produced by the methane catalytic decomposition. The methane conversion and the performance of CNTs were determined by the choices of catalysts and the condition of decomposition reaction. In this paper, Ni/MgO and Ni/O-D (oxidized diamond) catalysts were prepared by wetness impregnation method. The effects of reaction temperature and space velocity of methane on the methane conversion were investigated in a fixed-bed. The surface area, structure and micrography were characterized with BET, XPS, SEM, EDS technology. The results showed that the conversion of methane was above 8% within 150 min (T=500) for 33Ni/O-D catalyst and higher than 25% within 120 min (T=650) for 41Ni/MgO catalyst. The initial conversion increased with the increasing temperature of the decomposition reaction, but their catalytic activities decreased rapidly while at too higher temperature. To decrease the space velocity of methane was propitious to promote the methane conversion, but not favor of the hydrogen yields. The appearance of carbon resulted from the methane decomposition lied on the support type and the condition of catalytic reaction. It presented as fiber shape on the surface of Ni/O-D at the relatively lower temperature such as 500 and 550, but as grain shape stacked on and overlayed on the surface of the metal nickel while at 650. The carbon fiber can form on the Ni/MgO surface at 650 and the diameter of the carbon fiber increased with the decreasing space velocity.
Abstract: Cement, the most widely used construction material
is very brittle and characterized by low tensile strength and strain
capacity. Macro to nano fibers are added to cement to provide
tensile strength and ductility to it. Carbon Nanotube (CNT), one of
the nanofibers, has proven to be a promising reinforcing material in
the cement composites because of its outstanding mechanical
properties and its ability to close cracks at the nano level. The
experimental investigations for CNT reinforced cement is costly,
time consuming and involves huge number of trials. Mathematical
modeling of CNT reinforced cement can be done effectively and
efficiently to arrive at the mechanical properties and to reduce the
number of trials in the experiments. Hence, an attempt is made to
numerically study the effective mechanical properties of CNT
reinforced cement numerically using Representative Volume
Element (RVE) method. The enhancement in its mechanical
properties for different percentage of CNTs is studied in detail.
Abstract: Intermetallic Ni3Al – based alloys belong to a group
of advanced materials characterized by good chemical and physical
properties (such as structural stability, corrosion resistance) which
offer advenced technological applications. The paper presents the
study of catalytic properties of Ni3Al foils (thickness approximately
50 &m) in the methanol and hexane decomposition. The egzamined
material posses microcrystalline structure without any additional
catalysts on the surface. The better catalytic activity of Ni3Al foils
with respect to quartz plates in both methanol and hexane
decomposition was confirmed. On thin Ni3Al foils the methanol
conversion reaches approximately 100% above 480 oC while the
hexane conversion reaches approximately 100% (98,5%) at 500 oC.
Deposit formed during the methanol decomposition is built up of
carbon nanofibers decorated with metal-like nanoparticles.