Abstract: In the past decade, the use of digital image correlation
(DIC) techniques has increased significantly in the area of
experimental mechanics, especially for materials behavior
characterization. This non-contact tool enables full field displacement
and strain measurements over a complete region of interest. The DIC
algorithm requires a random contrast pattern on the surface of the
specimen in order to perform properly. To create this pattern, the
specimen is usually first coated using a white matt paint. Next, a
black random speckle pattern is applied using any suitable method. If
the applied paint coating is too thick, its top surface may not be able
to exactly follow the deformation of the specimen, and consequently,
the strain measurement might be underestimated. In the present
article, a study of the influence of the paint thickness on the strain
underestimation is performed for different strain levels. The results
are then compared to typical paint coating thicknesses applied by
experienced DIC users. A slight strain underestimation was observed
for paint coatings thicker than about 30μm. On the other hand, this
value was found to be uncommonly high compared to coating
thicknesses applied by DIC users.
Abstract: Development of new generation bio-tribological,
multilayer coatings opens an avenue for fabrication of future hightech
functional surfaces. In the presented work, nano-composite,
Cr/CrN+[Cr/ a-C:H implanted by metallic nanocrystals] multilayer
coatings have been developed for surface protection of medical tools.
Thin films were fabricated by a hybrid Pulsed Laser Deposition
technique. Complex microstructure analysis of nanomultilayer
coatings, subjected to mechanical and biological tests, were
performed by means of transmission electron microscopy (TEM).
Microstructure characterization revealed the layered arrangement of
Cr23C6 nanoparticles in multilayer structure. Influence of deposition
conditions on bio-tribological properties of the coatings was studied.
The bio-tests were used as a screening tool for the analyzed
nanomultilayer coatings before they could be deposited on medical
tools. Bio-medical tests were done using fibroblasts. The mechanical
properties of the coatings were investigated by means of a ball-ondisc
mechanical test. The micro hardness was done using Berkovich
indenter. The scratch adhesion test was done using Rockwell
indenter. From the bio-tribological point of view, the optimal
properties had the C106_1 material.
Abstract: Electrodeposition is a simple and economic technique
for precision coating of different shaped substrates with pure metal,
alloy or composite films. Dc electrodeposition was used to produce
Cr, Co-Cr and Co-Cr/TiO2 nano-composite coatings from Cr(III)
based electrolytes onto 316L SS substrates. The effects of TiO2 nanoparticles
concentration on co-deposition of these particles along with
Cr content and microhardness of the coatings were investigated.
Morphology of the Cr, Co-Cr and Co-Cr/TiO2 coatings besides their
tribological behavior were studied. The results showed that increment
of TiO2 nanoparticles concentration from 0 to 30 g L-1 in the bath
increased their co-deposition and Cr content of the coatings from 0 to
3.5 wt.% and from 23.7 to 31.2 wt.%, respectively. Microhardness of
Cr coating was about 920 Hv which was higher than Co-Cr and even
Co-Cr/TiO2 films. Microhardness of Co-Cr and Co-Cr/TiO2 coatings
were improved by increasing their Cr and TiO2 content. All the
coatings had nodular morphology and contained microcracks.
Nodules sizes and the number of microcracks in the alloy and
composite coatings were lower than the Cr film. Wear results
revealed that the Co-Cr/TiO2 coating had the lowest wear loss
between all the samples, while the Cr film had the worst wear
resistance.
Abstract: Microstructural and electrical properties of
Cu-chromium alloy (Cu-Cr) dispersed with vapor-grown carbon fiber
(VGCF) prepared by powder metallurgy (P/M) process have been
investigated. Cu-0.7 mass% Cr pre-alloyed powder (Cu-Cr) made by
water atomization process was used as raw materials, which contained
solid solute Cr elements in Cu matrix. The alloy powder coated with
un-bundled VGCF by using oil coating process was consolidated at
1223 K in vacuum by spark plasma sintering, and then extruded at
1073 K. The extruded Cu-Cr alloy (monolithic alloy) had 209.3 MPa
YS and 80.4 IACS% conductivity. The extruded Cu-Cr with 0.1
mass% VGCF composites revealed a small decrease of YS compared
to the monolithic Cu-Cr alloy. On the other hand, the composite had a
higher electrical conductivity than that of the monolithic alloy. For
example, Cu-Cr with 0.1 mass% VGCF composite sintered for 5 h
showed 182.7 MPa YS and 89.7 IACS% conductivity. In the case of
Cu-Cr with VGCFs composites, the Cr concentration was observed
around VGCF by SEM-EDS analysis, where Cr23C6 compounds were
detected by TEM observation. The amount of Cr solid solution in the
matrix of the Cu-Cr composites alloy was about 50% compared to the
monolithic Cu-Cr sintered alloy, and resulted in the remarkable
increment of the electrical conductivity.
Abstract: Sol-enhanced Zn-Ni-Al2O3 nanocomposite coatings
were electroplated on mild steel by our newly developed solenhanced
electroplating method. In this method, transparent Al2O3 sol
was added into the acidic Zn-Ni bath to produced Zn-Ni-Al2O3nanocomposite
coatings. The chemical composition, microstructure and
mechanical properties of the composite and alloy coatings deposited
at two different agitation speed were investigated. The structure of all
coatings was single γ-Ni5Zn21 phase. The composite coatings possess
refined crystals with higher microhardness compared to Zn-Ni alloy
coatings. The wear resistance of Zn-Ni coatings was improved
significantly by incorporation of alumina nano particles into the
coatings. Higher agitation speed provided more uniform coatings
with smaller grain sized and slightly higher microhardness.
Considering composite coatings, high agitation speeds may facilitate
co-deposition of alumina in the coatings.
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: High pressure turbine (HPT) blades of DV – 2 jet
engines are made from Ni – based superalloy. This alloy was
originally manufactured in the Soviet Union and referred as ŽS6K.
For improving alloy’s high temperature resistance are blades coated
with Al – Si diffusion layer. A regular operation temperature of HPT
blades vary from 705°C to 750°C depending on jet engine regime.
An overcrossing working temperature range causes degradation of
the protective coating as well as base material which microstructure
is formed by the gamma matrix and strengthening phase gamma
prime (forming small particles in the microstructure). Diffusion
processes inside the material during exposition of the material to high
temperatures causes mainly coarsening of the gamma prime particles,
thus decreasing its strengthening effect. Degradation of the Al – Si
coating caused its thickness growth. All the microstructure changes
and coating layer thickness growth results in decreasing of the turbine
blade operation lifetime.
Abstract: Non contact evaluation of the thickness of paint
coatings can be attempted by different destructive and nondestructive
methods such as cross-section microscopy, gravimetric mass
measurement, magnetic gauges, Eddy current, ultrasound or
terahertz. Infrared thermography is a nondestructive and non-invasive
method that can be envisaged as a useful tool to measure the surface
thickness variations by analyzing the temperature response. In this
paper, the thermal quadrupole method for two layered samples heated
up with a pulsed excitation is firstly used. By analyzing the thermal
responses as a function of thermal properties and thicknesses of both
layers, optimal parameters for the excitation source can be identified.
Simulations show that a pulsed excitation with duration of ten
milliseconds allows obtaining a substrate-independent thermal
response. Based on this result, an experimental setup consisting of a
near-infrared laser diode and an Infrared camera was next used to
evaluate the variation of paint coating thickness between 60 μm and
130 μm on two samples. Results show that the parameters extracted
for thermal images are correlated with the estimated thicknesses by
the Eddy current methods. The laser pulsed thermography is thus an
interesting alternative nondestructive method that can be moreover
used for nonconductive substrates.
Abstract: In this study, ultrasonic assisted machining (UAM) technique is applied in side-surface milling experiment for glass-ceramic workpiece material. The tungsten carbide cutting-tool with diamond coating is used in conjunction with two kinds of cooling/lubrication mediums such as water-soluble (WS) cutting fluid and minimum quantity lubricant (MQL). Full factorial process parameter combinations on the milling experiments are planned to investigate the effect of process parameters on cutting performance. From the experimental results, it tries to search for the better process parameter combination which the edge-indentation and the surface roughness are acceptable. In the machining experiments, ultrasonic oscillator was used to excite a cutting-tool along the radial direction producing a very small amplitude of vibration frequency of 20KHz to assist the machining process. After processing, toolmaker microscope was used to detect the side-surface morphology, edge-indentation and cutting tool wear under different combination of cutting parameters, and analysis and discussion were also conducted for experimental results. The results show that the main leading parameters to edge-indentation of glass ceramic are cutting depth and feed rate. In order to reduce edge-indentation, it needs to use lower cutting depth and feed rate. Water-soluble cutting fluid provides a better cooling effect in the primary cutting area; it may effectively reduce the edge-indentation and improve the surface morphology of the glass ceramic. The use of ultrasonic assisted technique can effectively enhance the surface finish cleanness and reduce cutting tool wear and edge-indentation.
Abstract: Considering palm oil as non-drying oil owing to its
low iodine value, an attempt was taken to increase the unsaturation in
the fatty acid chains of palm oil for the preparation of alkyds. To
increase the unsaturation in the palm oil, sulphuric acid (SA) and
para-toluene sulphonic acid (PTSA) was used prior to alcoholysis for
the dehydration process. The iodine number of the oil samples was
checked for the unsaturation measurement by Wijs method. Alkyd
resin was prepared using the dehydrated palm oil by following
alcoholysis and esterification reaction. To improve the film properties
0.5wt.% multi-wall carbon nano tubes (MWCNTs) were used to
manufacture polymeric film. The properties of the resins were
characterized by various physico-chemical properties such as density,
viscosity, iodine value, saponification value, etc. Structural
elucidation was confirmed by Fourier transform of infrared
spectroscopy and proton nuclear magnetic resonance; surfaces of the
films were examined by field-emission scanning electron microscope.
In addition, pencil hardness and chemical resistivity was also
measured by using standard methods. The effect of enhancement of
the unsaturation in the fatty acid chain found significant and
motivational. The resin prepared with dehydrated palm oil showed
improved properties regarding hardness and chemical resistivity
testing. The incorporation of MWCNTs enhanced the thermal
stability and hardness of the films as well.
Abstract: Chemical vapor deposition (CVD) diamond coated
cutting tool has excellent cutting performance, it is the most ideal tool
for the processing of nonferrous metals and alloys, composites,
nonmetallic materials and other difficult-to-machine materials
efficiently and accurately. Depositing CVD diamond coating on the
cemented carbide with high cobalt content can improve its toughness
and strength, therefore, it is very important to research on the
preparation technology and cutting properties of CVD diamond coated
cemented carbide cutting tool with high cobalt content. The
preparation technology of boron-doped diamond (BDD) coating has
been studied and the coated drills were prepared. BDD coating were
deposited on the drills by using the optimized parameters and the SEM
results show that there are no cracks or collapses in the coating.
Cutting tests with the prepared drills against the silumin and aluminum
base printed circuit board (PCB) have been studied. The results show
that the wear amount of the coated drill is small and the machined
surface has a better precision. The coating does not come off during
the test, which shows good adhesion and cutting performance of the
drill.
Abstract: Paints are the most widely used methods of protection
against atmospheric corrosion of metals. The aim of this work was to
determine the protective performance of epoxy coating against sea
water before and after damage.
Investigations are conducted using stationary and non-stationary
electrochemical tools such as electrochemical impedance
spectroscopy has allowed us to characterize the protective qualities of
these films. The application of the EIS on our damaged in-situ
painting shows the existence of several capacitive loops which is an
indicator of the failure of our tested paint. Microscopic analysis
(micrograph) helped bring essential elements in understanding the
degradation of our paint condition and immersion training corrosion
products.
Abstract: Surface modification and functionalization has been
an important tool for scientists in order to open new frontiers in
nanoscience and nanotechnology. Desired surface characteristics for
the intended applications can be achieved with surface
functionalization.
In this work, the effect of water soluble ligands on the adsorption
capabilities of silver nanoparticles onto AC which was synthesized
from German beech wood was investigated. Sodium borohydride
(NaBH4) and polyvinyl alcohol (PVA) were used as the ligands.
Silver nanoparticles with different surface coatings have average
sizes range from 10 to 13 nm. They were synthesized in aqueous
media by reducing Ag (I) ion in the presence of ligands. These
particles displayed adsorption tendencies towards AC when they
were mixed together and shaken in distilled water.
Silver nanoparticles (NaBH4-AgNPs) reduced and stabilized by
NaBH4 adsorbed onto AC with a homogenous dispersion of
aggregates with sizes in the range of 100-400 nm. Beside, silver
nanoparticles, which were prepared in the presence of both NaBH4
and PVA (NaBH4/PVA-Ag NPs), demonstrated that NaBH4/PVA-Ag
NPs adsorbed and dispersed homogenously but, they aggregated with
larger sizes on the AC surface (range from 300 to 600 nm). In
addition, desorption resistance of Ag nanoparticles were investigated
in distilled water. According to the results AgNPs were not desorbed
on the AC surface in distilled water.
Abstract: In this study, an experiment was executed related to
the strength of wooden materials which have been commonly used
both in the past and present against pressure and whether fire
retardant materials used against fire have any effects or not. Totally
81 samples which included 3 different wood species, 3 different
sizes, 2 different fire retardants and 2 unprocessed samples were
prepared. Compressive pressure tests were applied to the prepared
samples, their variance analyses were executed in accordance with
the obtained results and it was aimed to determine the most
convenient wooden materials and fire-retardant coating material. It
was also determined that the species of wood and the species of
coating caused the decrease and/or increase in the resistance against
pressure.
Abstract: Thin ZnO films are deposited on glass substrates via
sol–gel method and dip-coating. The films are prepared from zinc
acetate dehydrate as a starting reagent. After that the as-prepared
ZnO sol is aged for different periods (0, 1, 3, 5, 10, 15 and 30 days).
Nanocrystalline thin films are deposited from various sols. The
effect ZnO sols aging time on the structural and photocatalytic
properties of the films is studied. The films surface is studied by
Scanning Electron Microscopy. The effect of the aging time of the
starting solution is studied in the photocatalytic degradation of
Reactive Black 5 (RB5) by UV-vis spectroscopy. The experiments
are conducted upon UV-light illumination and in complete darkness.
The variation of the absorption spectra shows the degradation of RB5
dissolved in water, as a result of the reaction, occurring on the surface
of the films and promoted by UV irradiation. The initial
concentrations of dye (5, 10 and 20 ppm) and the effect of the aging
time are varied during the experiments. The results show, that the
increasing aging time of starting solution with respect to ZnO
generally promotes photocatalytic activity. The thin films obtained
from ZnO sol, which is aged 30 days have best photocatalytic
degradation of the dye (97,22%) in comparison with the freshly
prepared ones (65,92%). The samples and photocatalytic
experimental results are reproducible. Nevertheless, all films exhibit
a substantial activity in both UV light and darkness, which is
promising for the development of new ZnO photocatalysts by sol-gel
method.
Abstract: Water contamination by toxic compound is one of the serious environmental problems today. These toxic compounds mostly originated from industrial effluents, agriculture, natural sources and human waste. These studies focus on modification of multiwalled carbon nanotube (MWCNTs) with nanoparticle of calixarene and explore the possibility of using this modification for the remediation of cadmium in water. The nanocomposites were prepared by dissolving calixarene in chloroform solution as solvent, followed by additional multiwalled carbon nanotube (MWCNTs) then sonication process for 3 hour and fabricated the nanocomposites on substrate by spin coating method. Finally, the nanocomposites were tested on cadmium ion (10 mg/ml). The morphology of nanocomposites was investigated by FESEM showing the formation of calixarene on the outer walls of carbon nanotube and cadmium ion also clearly seen from the micrograph. This formation was supported by using energy dispersive x-ray (EDX). The presence of cadmium ions in the films, leads to some changes in the surface potential and Fourier Transform Infrared spectroscopy (FTIR).The nanocomposites MWCNTs-calixarene have potential for development of sensor for pollutant monitoring and nanoelectronics devices applications.
Abstract: TiO2 thin films have been prepared by the sol-gel dipcoating
technique in order to elaborate antireflective thin films for
monocrystalline silicon (mono-Si). The titanium isopropoxyde was
chosen as a precursor with hydrochloric acid as a catalyser for
preparing a stable solution. The optical properties have been tailored
with varying the solution concentration, the withdrawn speed, and the
heat-treatment. We showed that using a TiO2 single layer with 64.5
nm in thickness, heat-treated at 450°C or 300°C reduces the mono-Si
reflection at a level lower than 3% over the broadband spectral
domains [669-834] nm and [786-1006] nm respectively. Those latter
performances are similar to the ones obtained with double layers of
low and high refractive index glasses respectively.
Abstract: To develop AZ91D magnesium alloys with improved
properties, we have applied TiN and VN/TiN multilayer coatings
using DC magnetron sputter technique. Coating structure, surface
morphology, chemical bonding and corrosion resistance of coatings
were analyzed by x-ray diffraction (XRD), scanning electron
microscope (SEM), x-ray photoelectron spectroscopy (XPS), and
tafel extrapolation method, respectively. XPS analysis reveal that VN
overlayer reacts with oxygen at the VN/TiN interface and forms more
stable TiN layer. Morphological investigations and the corrosion
results show that VN/TiN multilayer thin film coatings are quite
effective to optimize the corrosion resistance of Mg alloys.
Abstract: Yttrium oxide (Y2O3) films have been successfully
deposited with yttrium-ethylenediamine tetraacetic acid (EDTA·Y·H)
complexes prepared by various milling techniques. The effects of the
properties of the EDTA·Y·H complex on the properties of the
deposited Y2O3 films have been analyzed. Seven different types of the
raw EDTA·Y·H complexes were prepared by various commercial
milling techniques such as ball milling, hammer milling, commercial
milling, and mortar milling. The milled EDTA·Y·H complexes
exhibited various particle sizes and distributions, depending on the
milling method. Furthermore, we analyzed the crystal structure,
morphology and elemental distribution profile of the metal oxide films
deposited on stainless steel substrate with the milled EDTA·Y·H
complexes. Depending on the milling technique, the flow properties of
the raw powders differed. The X-ray diffraction pattern of all the
samples revealed the formation of Y2O3 crystalline phase, irrespective
of the milling technique. Of all the different milling techniques, the
hammer milling technique is considered suitable for fabricating dense
Y2O3 films.
Abstract: Stress Corrosion Crack (SCC) in pipeline is a type of
environmentally assisted cracking (EAC), since its discovery in 1965
as a possible cause of failure in pipeline, SCC has caused, on
average, one of two failures per year in the U.S, According to the
NACE SCC DA a pipe line segment is considered susceptible to SCC
if all of the following factors are met: The operating stress exceeds
60% of specified minimum yield strength (SMYS), the operating
temperature exceeds 38°C, the segment is less than 32 km
downstream from a compressor station, the age of the pipeline is
greater than 10 years and the coating type is other than Fusion
Bonded Epoxy(FBE). In this paper as a practical experience in
NISOC, Direct Assessment (DA) Method is used for identification
SCC defect in unpiggable pipeline located downstream of
compressor station.