Abstract: Nonlinear evolution of broadband ultrasonic pulses
passed through the rock specimens is studied using the apparatus
“GEOSCAN-02M”. Ultrasonic pulses are excited by the pulses of Qswitched
Nd:YAG laser with the time duration of 10 ns and with the
energy of 260 mJ. This energy can be reduced to 20 mJ by some light
filters. The laser beam radius did not exceed 5 mm. As a result of the
absorption of the laser pulse in the special material – the optoacoustic
generator–the pulses of longitudinal ultrasonic waves are excited with
the time duration of 100 ns and with the maximum pressure
amplitude of 10 MPa. The immersion technique is used to measure
the parameters of these ultrasonic pulses passed through a specimen,
the immersion liquid is distilled water. The reference pulse passed
through the cell with water has the compression and the rarefaction
phases. The amplitude of the rarefaction phase is five times lower
than that of the compression phase. The spectral range of the
reference pulse reaches 10 MHz. The cubic-shaped specimens of the
Karelian gabbro are studied with the rib length 3 cm. The ultimate
strength of the specimens by the uniaxial compression is (300±10)
MPa. As the reference pulse passes through the area of the specimen
without cracks the compression phase decreases and the rarefaction
one increases due to diffraction and scattering of ultrasound, so the
ratio of these phases becomes 2.3:1. After preloading some horizontal
cracks appear in the specimens. Their location is found by one-sided
scanning of the specimen using the backward mode detection of the
ultrasonic pulses reflected from the structure defects. Using the
computer processing of these signals the images are obtained of the
cross-sections of the specimens with cracks. By the increase of the
reference pulse amplitude from 0.1 MPa to 5 MPa the nonlinear
transformation of the ultrasonic pulse passed through the specimen
with horizontal cracks results in the decrease by 2.5 times of the
amplitude of the rarefaction phase and in the increase of its duration
by 2.1 times. By the increase of the reference pulse amplitude from 5
MPa to 10 MPa the time splitting of the phases is observed for the
bipolar pulse passed through the specimen. The compression and
rarefaction phases propagate with different velocities. These features
of the powerful broadband ultrasonic pulses passed through the rock
specimens can be described by the hysteresis model of Preisach-
Mayergoyz and can be used for the location of cracks in the optically
opaque materials.
Abstract: Carbon nanotubes (CNTs) are known for having high elastic properties with high surface area that promote them as good candidates for reinforcing polymeric matrices. In composite materials, CNTs lack chemical bonding with the surrounding matrix which decreases the possibility of better stress transfer between the components. In this work, a chemical treatment for activating the surface of the multi-wall carbon nanotubes (MWCNT) was applied and the effect of this functionalization on the elastic properties of the epoxy nanocomposites was studied. Functional amino-groups were added to the surface of the CNTs and it was evaluated to be about 34% of the total weight of the CNTs. Elastic modulus was found to increase by about 40% of the neat epoxy resin at CNTs’ weight fraction of 0.5%. The elastic modulus was found to decrease after reaching a certain concentration of CNTs which was found to be 1% wt. The scanning electron microscopic pictures showed the effect of the CNTs on the crack propagation through the sample by forming stress concentrated spots at the nanocomposite samples.
Abstract: Rapid population growth, urbanization and
industrialization are known as the most important factors of
environment problems. Elimination and management of solid wastes
are also within the most important environment problems. One of the
main problems in solid waste management is the selection of the best
site for elimination of solid wastes. Lately, Geographical Information
System (GIS) has been used for easing selection of landfill area. GIS
has the ability of imitating necessary economic, environmental and
political limitations. They play an important role for the site selection
of landfill area as a decision support tool. In this study; map layers will be studied for minimum effect of
environmental, social and cultural factors and maximum effect for
engineering/economic factors for site selection of landfill areas and
using GIS for a decision support mechanism in solid waste landfill
areas site selection will be presented in Aksaray/Turkey city,
Güzelyurt district practice.
Abstract: Natural fibers are used in polymer composites to
improve mechanical properties to replace inorganic reinforcing
agents produced by non-renewable resources. The present study
investigates the tensile and flexural behaviors of palm fibers-high
density polyethylene (HDPE) composite as a function of volume
fraction. The surface of the fibers was treated by mercerization
treatments to improve the wetting behavior of the apolar HDPE. The
treatment characterization was obtained by scanning electron
microscopy, X-Ray diffraction and infrared spectroscopy. Results
evidences that a good adhesion interfacial between fibers-matrix
caused an increase strength and modulus flexural as well as tensile
strength in the modified fibers/HDPE composites when compared to
the pure HDPE and untreated fibers reinforced composites.
Abstract: The first laboratory synthesis of hard materials such as
diamond proceeded to attack of developing materials with high
hardness to compete diamond. Boron rich solids are good candidates
owing to their short interatomic bond lengths and strong covalent
character. Boron containing hard material was synthesized by modifiedmicrowave
method under nitrogen atmosphere by using a fuel
(glycine or urea), amorphous boron and/or boric acid in appropriate
molar ratio. Characterizations were done by x-ray diffraction (XRD),
Fourier transform infrared (FTIR) spectroscopy, scanning electron
microscopy/energy dispersive analyze (SEM/EDS), thermo
gravimetric/differential thermal analysis (TG/DTA).
Abstract: The aim of this study was to investigate the
photocatalytic activity of polycrystalline phases of bismuth tungstate
of formula Bi2WO6. Polycrystalline samples were elaborated using a
coprecipitation technique followed by a calcination process at
different temperatures (300, 400, 600 and 900°C). The obtained
polycrystalline phases have been characterized by X-ray diffraction
(XRD), scanning electron microscopy (SEM), and transmission
electron microscopy (TEM). Crystal cell parameters and cell volume
depend on elaboration temperature. High-resolution electron
microscopy images and image simulations, associated with X-ray
diffraction data, allowed confirming the lattices and space groups
Pca21. The photocatalytic activity of the as-prepared samples was
studied by irradiating aqueous solutions of Rhodamine B, associated
with Bi2WO6 additives having variable crystallite sizes. The
photocatalytic activity of such bismuth tungstates increased as the
crystallite sizes decreased. The high specific area of the
photocatalytic particles obtained at 300°C seems to condition the
degradation kinetics of RhB.
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: In this paper, we study the optical nonlinearities of
Silver sulfide (Ag2S) nanostructures dispersed in the Dimethyl
sulfoxide (DMSO) under exposure to 532 nm, 15 nanosecond (ns)
pulsed laser irradiation. Ultraviolet–visible absorption spectrometry
(UV-Vis), X-ray diffraction (XRD), and transmission electron
microscopy (TEM) are used to characterize the obtained nanocrystal
samples. The band gap energy of colloid is determined by analyzing
the UV–Vis absorption spectra of the Ag2S NPs using the band
theory of semiconductors. Z-scan technique is used to characterize
the optical nonlinear properties of the Ag2S nanoparticles (NPs).
Large enhancement of two photon absorption effect is observed with
increase in concentration of the Ag2S nanoparticles using open Zscan
measurements in the ns laser regime. The values of the nonlinear
absorption coefficients are determined based on the local nonlinear
responses including two photon absorption. The observed aperture
dependence of the Ag2S NP limiting performance indicates that the
nonlinear scattering plays an important role in the limiting action of
the sample. The concentration dependence of the optical liming is
also investigated. Our results demonstrate that the optical limiting
threshold decreases with increasing the silver sulfide NPs in DMSO.
Abstract: This study intends to show the influence of the
hydrolytic degradation on the properties of the e-PTFE/NOMEX®
membranes used in fire-protective clothing. The modification of
water vapour permeability, morphology and chemical structure was
examined by MOCON Permatran, electron microscopy scanning
(SEM), and ATR-FTIR, respectively. A decrease in permeability to
water vapour of the aged samples was observed following closure of
transpiration pores. Analysis of fiber morphology indicates the
appearance of defects at the fibers surface with the presence of micro
cavities. ATR-FTIR analysis reveals the presence of a new absorption
band attributed to carboxylic acid terminal groups generated during
the amide bond hydrolysis.
Abstract: Graphene was dispersed using a tip sonicator and the
effect of surfactants were analysed. Sodium Dodecyl Sulphate (SDS)
and Polyvinyl Alcohol (PVA) were compared to observe whether or
not they had any effect on any de-wrinkling, and secondly whether
they aided to achieve better dispersions. There is a huge demand for
wrinkle free graphene as this will greatly increase its usefulness in
various engineering applications. A comprehensive literature on dewrinkling
graphene has been discussed. Low magnification Scanning
Electronic Microscopy (SEM) was conducted to assess the quality of
graphene de-wrinkling. The utilization of the PVA has significant
effect on de-wrinkling whereas SDS had minimal effect on the dewrinkling
of graphene.
Abstract: In recent years, the use of the aluminum based alloys
in the industry and technology are increasing. Alloying elements in
aluminum have further been improving the strength and stiffness
properties that provide superior compared to other metals. In this
study, investigation of physical properties (microstructure,
microhardness, tensile strength, electrical conductivity and thermal
properties) in the Al-12.6wt.%Si-%2wt.Ni ternary alloy were
investigated. Al-Si-Ni alloy was prepared in vacuum atmosphere. The
samples were directionally solidified upwards with different growth
rate V (8.3−165.45 μm/s) at constant temperature gradient G (7.73
K/mm). The flake spacings (λ), microhardness (HV), ultimate tensile
strength (σ), electrical resistivity (ρ) and thermal properties (H, Cp,
Tm) of the samples were measured. Influence of the growth rate and
spacings on microhardness, ultimate tensile strength and electrical
resistivity were investigated and relationships between them were
obtained. According to results, λ values decrease with increasing V,
but HV, σ and ρ values increase with increasing V. Variations of
electrical resistivity (ρ) of solidified samples were also measured.
The enthalpy of fusion (H) and specific heat (Cp) for the alloy was
also determined by differential scanning calorimeter (DSC) from
heating trace during the transformation from liquid to solid. The
results in this work were compared with the previous similar
experimental results.
Abstract: In this research, thorium dioxide mesoporous
nanocrystalline powder was synthesized through the sol-gel method
using hydrated thorium nitrate and ammonium hydroxide as starting
materials and Triton X100 as surfactant. ThO2 gel was characterized
by thermogravimetric (TGA), and prepared ThO2 powder was
subjected to scanning electron microscopy (SEM), X-ray diffraction
(XRD), and Brunauer-Emett-Teller (BET) analyses studies. Detailed
analyses show that prepared powder consisted of phase with the
space group Fm3m of thoria and its crystalline size was 12.6 nm. The
thoria possesses 16.7 m2/g surface area and the pore volume and size
calculated to be 0.0423 cc/g and 1.947 nm, respectively.
Abstract: The use of titanium fluoride and iron fluoride
(TiF3/FeF3) catalysts in combination with polutetrafluoroethylene
(PTFE) in plain zinc- dialkyldithiophosphate (ZDDP) oil is important
for the study of engine tribocomponents and is increasingly a strategy
to improve the formation of tribofilm and provide low friction and
excellent wear protection in reduced phosphorus plain ZDDP oil. The
influence of surface roughness and the concentration of
TiF3/FeF3/PTFE were investigated using bearing steel samples
dipped in lubricant solution at 100°C for two different heating time
durations. This paper addresses the effects of water drop contact
angle using different surface; finishes after treating them with
different lubricant combination. The calculated water drop contact
angles were analyzed using Design of Experiment software (DOE)
and it was determined that a 0.05 μm Ra surface roughness would
provide an excellent TiF3/FeF3/PTFE coating for antiwear resistance
as reflected in the Scanning electron microscopy (SEM) images and
the tribological testing under extreme pressure conditions. Both
friction and wear performance depend greatly on the PTFE/and
catalysts in plain ZDDP oil with 0.05 % phosphorous and on the
surface finish of bearing steel. The friction and wear reducing effects,
which was observed in the tribological tests, indicated a better micro
lubrication effect of the 0.05 μm Ra surface roughness treated at
100°C for 24 hours when compared to the 0.1 μm Ra surface
roughness with the same treatment.
Abstract: This paper presents thermal annealing de-wetting
technique for the preparation of porous metal membrane for Thin
Film Encapsulation (TFE) application. Thermal annealing de-wetting
experimental results reveal that pore size formation in porous metal
membrane depend upon i.e. 1. The substrate at which metal is
deposited, 2. Melting point of metal used for porous metal cap layer
membrane formation, 3. Thickness of metal used for cap layer, 4.
Temperature used for formation of porous metal membrane. In order
to demonstrate this technique, Silver (Ag) was used as a metal for
preparation of porous metal membrane on amorphous silicon (a-Si)
and silicon oxide. The annealing of the silver thin film of various
thicknesses was performed at different temperature. Pores in porous
silver film were analyzed using Scanning Electron Microscope
(SEM). In order to check the usefulness of porous metal film for TFE
application, the porous silver film prepared on amorphous silicon (a-
Si) and silicon oxide was released using XeF2 and VHF, respectively.
Finally, guide line and structures are suggested to use this porous
membrane for robust TFE application.
Abstract: The synthesis of CuFe2O4 spinel powders by an
optimized combustion-like process followed by calcination is
described herein. The samples were characterized using X-ray
diffraction (XRD), differential thermal analysis (TG/DTA), scanning
electron microscopy (SEM), dilatometry and 4-probe DC methods.
Different glycine to nitrate (G/N) ratios of 1 (fuel-deficient), 1.48
(stoichiometric) and 2 (fuel-rich) were employed. Calcining the asprepared
powders at 800 and 1000°C for 5 hours showed that the G/N
ratio of 2 results in the formation of the desired copper spinel single
phase at both calcination temperatures. For G/N=1, formation of
CuFe2O4 takes place in three steps. First, iron and copper nitrates
decompose to iron oxide and pure copper. Then, copper transforms to
copper oxide and finally, copper and iron oxides react with each other
to form a copper ferrite spinel phase. The electrical conductivity and
the coefficient of thermal expansion of the sintered pelletized
samples were 2 S.cm-1 (800°C) and 11×10-6 °C-1 (25-800°C),
respectively.
Abstract: Polyaniline is an indispensible component in lightemitting
devices (LEDs), televisions, cellular telephones, automotive,
corrosion-resistant coatings, actuators etc. The electrical conductivity
properties was found be increased by introduction of metal nano
particles. In the present study, an attempt has been made to utilize
platinum nano particles to achieve the improved electrical properties.
Polyaniline and Pt-polyaniline composite are synthesized by
electrochemical routes. X-ray diffractometer confirms the amorphous
nature of polyaniline. The Bragg’s diffraction peaks correspond to
platinum nanoparticles in Pt-polyaniline composite and
thermogravimetric analyzer indicates its decomposition at certain
temperature. The Scanning Electron Micrographs of colloidal
platinum nanoparticles were spherical, uniform shape in the
composite. The current-voltage (I-V) characteristics of the PANI and
composites were also studied which indicate a significant decreasing
resistivity than PANI-Platinum after introduction of pt nanoparticles
in the matrix of polyaniline (PANI).
Abstract: In this study, to clarify the effectiveness of an
aluminum/chromium/tungsten-based-coated tool for cutting sintered
steel, tool wear was experimentally investigated. The sintered steel
was turned with the (Al60,Cr25,W15)N-, (Al60,Cr25,W15)(C,N)- and
(Al64,Cr28,W8)(C,N)-coated cemented carbide tools according to the
physical vapor deposition (PVD) method. Moreover, the tool wear of
the aluminum/chromium/tungsten-based-coated item was compared
with that of the (Al,Cr)N coated tool. Furthermore, to clarify the tool
wear mechanism of the aluminum/chromium/tungsten-coating film for
cutting sintered steel, Scanning Electron Microscope observation and
Energy Dispersive x-ray Spectroscopy mapping analysis were
conducted on the abraded surface. The following results were
obtained: (1) The wear progress of the (Al64,Cr28,W8)(C,N)-coated
tool was the slowest among that of the five coated tools. (2) Adding
carbon (C) to the aluminum/chromium/tungsten-based-coating film
was effective for improving the wear-resistance. (3) The main wear
mechanism of the (Al60,Cr25,W15)N-, the (Al60,Cr25,W15)(C,N)-
and the (Al64,Cr28,W8)(C,N)-coating films was abrasive wear.
Abstract: Superabsorbent polymers received much attention and
are used in many fields because of their superior characters to
traditional absorbents, e.g., sponge and cotton. So, it is very
important but challenging to prepare highly and fast-swelling
superabsorbents. A reliable, efficient and low-cost technique for
removing heavy metal ions from wastewater is the adsorption using
bio-adsorbents obtained from biological materials, such as
polysaccharides-based hydrogels superabsorbents. In this study, novel multi-functional superabsorbent composites
type semi-interpenetrating polymer networks (Semi-IPNs) were
prepared via graft polymerization of acrylamide onto chitosan
backbone in presence of gelatin, CTS-g-PAAm/Ge, using potassium
persulfate and N,N’-methylene bisacrylamide as initiator and
crosslinker, respectively. These hydrogels were also partially
hydrolyzed to achieve superabsorbents with ampholytic properties
and uppermost swelling capacity. The formation of the grafted
network was evidenced by Fourier Transform Infrared Spectroscopy
(ATR-FTIR) and Thermogravimetric Analysis (TGA). The porous
structures were observed by Scanning Electron Microscope (SEM).
From TGA analysis, it was concluded that the incorporation of the Ge
in the CTS-g-PAAm network has marginally affected its thermal
stability. The effect of gelatin content on the swelling capacities of
these superabsorbent composites was examined in various media
(distilled water, saline and pH-solutions). The water absorbency was
enhanced by adding Ge in the network, where the optimum value was
reached at 2 wt. % of Ge. Their hydrolysis has not only greatly
optimized their absorption capacity but also improved the swelling
kinetic.These materials have also showed reswelling ability. We
believe that these super-absorbing materials would be very effective
for the adsorption of harmful metal ions from wastewater.
Abstract: Processing of Al-19.4Si alloy by high intensive
electron beam has been carried out and multiple increases in fatigue
life of the material have been revealed. Investigations of structure and
surface modified layer destruction of Al-19.4Si alloy subjected to
multicycle fatigue tests to fracture have been carried out by methods
of scanning electron microscopy. The factors responsible for the
increase of fatigue life of Al-19.4Si alloy have been revealed and
analyzed.
Abstract: This study suggests the estimation method of stress
distribution for the beam structures based on TLS (Terrestrial Laser
Scanning). The main components of method are the creation of the
lattices of raw data from TLS to satisfy the suitable condition and
application of CSSI (Cubic Smoothing Spline Interpolation) for
estimating stress distribution. Estimation of stress distribution for the
structural member or the whole structure is one of the important
factors for safety evaluation of the structure. Existing sensors which
include ESG (Electric strain gauge) and LVDT (Linear Variable
Differential Transformer) can be categorized as contact type sensor
which should be installed on the structural members and also there are
various limitations such as the need of separate space where the
network cables are installed and the difficulty of access for sensor
installation in real buildings. To overcome these problems inherent in
the contact type sensors, TLS system of LiDAR (light detection and
ranging), which can measure the displacement of a target in a long
range without the influence of surrounding environment and also get
the whole shape of the structure, has been applied to the field of
structural health monitoring. The important characteristic of TLS
measuring is a formation of point clouds which has many points
including the local coordinate. Point clouds are not linear distribution
but dispersed shape. Thus, to analyze point clouds, the interpolation is
needed vitally. Through formation of averaged lattices and CSSI for
the raw data, the method which can estimate the displacement of
simple beam was developed. Also, the developed method can be
extended to calculate the strain and finally applicable to estimate a
stress distribution of a structural member. To verify the validity of the
method, the loading test on a simple beam was conducted and TLS
measured it. Through a comparison of the estimated stress and
reference stress, the validity of the method is confirmed.