Abstract: This study focuses on a novel method for dispersion
and distribution of reinforcement under high intensive shear stress to
produce metal composites. The polyacrylonitrile (PAN)-based short
carbon fiber (Csf) and Nextel 610 alumina fiber were dispersed under
high intensive shearing at mushy zone in semi-solid of A356 by a
novel method. The bundles and clusters were embedded by
infiltration of slurry into the clusters, thus leading to a uniform
microstructure. The fibers were embedded homogenously into the
aluminum around 576-580°C with around 46% of solid fraction.
Other experiments at 615°C and 568°C which are contained 0% and
90% solid respectively were not successful for dispersion and
infiltration of aluminum into bundles of Csf. The alumina fiber has
been cracked by high shearing load. The morphologies and
crystalline phase were evaluated by SEM and XRD. The adopted
thixo-process effectively improved the adherence and distribution of
Csf into Al that can be developed to produce various composites by
thixomixing.
Abstract: We present a gas-liquid microfluidic system as a
reactor to obtain magnetite nanoparticles with an excellent degree of
control regarding their crystalline phase, shape and size. Several
types of microflow approaches were selected to prevent nanomaterial
aggregation and to promote homogenous size distribution. The
selected reactor consists of a mixer stage aided by ultrasound waves
and a reaction stage using a N2-liquid segmented flow to prevent
magnetite oxidation to non-magnetic phases. A milli-fluidic reactor
was developed to increase the production rate where a magnetite
throughput close to 450 mg/h in a continuous fashion was obtained.
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: The nanoindentation behaviour and phase
transformation of annealed single-crystal silicon wafers are examined.
The silicon specimens are annealed at temperatures of 250, 350 and
450ºC, respectively, for 15 minutes and are then indented to maximum
loads of 30, 50 and 70 mN. The phase changes induced in the indented
specimens are observed using transmission electron microscopy
(TEM) and micro-Raman scattering spectroscopy (RSS). For all
annealing temperatures, an elbow feature is observed in the unloading
curve following indentation to a maximum load of 30 mN. Under
higher loads of 50 mN and 70 mN, respectively, the elbow feature is
replaced by a pop-out event. The elbow feature reveals a complete
amorphous phase transformation within the indented zone, whereas
the pop-out event indicates the formation of Si XII and Si III phases.
The experimental results show that the formation of these crystalline
silicon phases increases with an increasing annealing temperature and
indentation load. The hardness and Young’s modulus both decrease as
the annealing temperature and indentation load are increased.
Abstract: Aluminium matrix composites with alumina
reinforcements give superior mechanical & physical properties. Their
applications in several fields like automobile, aerospace, defense,
sports, electronics, bio-medical and other industrial purposes are
becoming essential for the last several decades. In the present work,
fabrication of hybrid composite was done by Stir casting technique
using Al 6061 as a matrix with alumina and silicon carbide (SiC) as
reinforcement materials. The weight percentage of alumina is varied
from 2 to 4% and the silicon carbide weight percentage is maintained
constant at 2%. Hardness and wear tests are performed in the as cast
and heat treated conditions. Age hardening treatment was performed
on the specimen with solutionizing at 550°C, aging at two
temperatures (150 and 200°C) for different time durations. Hardness
distribution curves are drawn and peak hardness values are recorded.
Hardness increase was very sensitive with respect to the decrease in
aging temperature. There was an improvement in wear resistance of
the peak aged material when aged at lower temperature. Also
increase in weight percent of alumina, increases wear resistance at
lower temperature but opposite behavior was seen when aged at
higher temperature.
Abstract: It is the worldwide problem that the recycled PVB is
not recycled and it is wildly stored in landfills. However, PVB has
similar chemical properties such as PVC. Moreover, both of these
polymers are plasticized. Therefore, the study of thermal properties
of plasticized PVC and the recycled PVB obtained by recycling of
windshields is carried out. This work has done in order to find nondegradable
processing conditions applicable for both polymers.
Tested PVC contained 38% of plasticizer diisononyl phthalate
(DINP) and PVB was plasticized with 28% of triethylene glycol,
bis(2-ethylhexanoate) (3GO). The thermal and thermo-oxidative
decomposition of both vinyl polymers are compared by calorimetric
analysis and by tensile strength analysis.
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: 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: Submerged arc welding is a very complex process. It
is a very efficient and high performance welding process. In this
present study an attempt have been done to reduce the welding
distortion by increased amount of oxide flux through TiO2 in
submerged arc welding process. Care has been taken to avoid the
excessiveness of the adding agent for attainment of significant
results. Data Envelopment Analysis (DEA) based BAT algorithm is
used for the parametric optimization purpose in which DEA is used
to convert multi response parameters into a single response
parameter. The present study also helps to know the effectiveness of
the addition of TiO2 in active flux during submerged arc welding
process.
Abstract: We report herein the development and preliminary mechanical characterization of fully-dense multi-wall carbon nanotube (MWCNT)-reinforced ceramics and glasses based on a completely new methodology termed High Shear Compaction (HSC). The tubes are introduced and bound to the matrix grains by aid of polymeric binders to form flexible green bodies which are sintered and densified by spark plasma sintering to unprecedentedly high densities of 100% of the pure-matrix value. The strategy was validated across a PyrexTM glass / MWCNT composite while no identifiable factors limit application to other types of matrices. Nondestructive evaluation, based on ultrasonics, of the dynamic mechanical properties of the materials including elastic, shear and bulk modulus as well as Poisson’s ratio showed optimum property improvement at 0.5 %wt tube loading while evidence of nanoscalespecific energy dissipative characteristics acting complementary to nanotube bridging and pull-out indicate a high potential in a wide range of reinforcing and multifunctional applications.
Abstract: When printing a plate (or dish) by an FDM 3D printer,
the process normally requires support material, which causes several
problems. This paper proposes a method for forming thin plates
without using wasteful support material. This method requires several
extraordinary parameter values when slicing plates. The experiments
show that the plates can, for the most part, be successfully formed
using a conventional slicer and a 3D printer; however, seams between
layers spoil them and the quality of printed objects strongly depends
on the slicer.
Abstract: HZSM-5 zeolites modified by iron and phosphorus
were applied in catalytic cracking of butene. N2 adsorption and
NH3-TPD were employed to measure the structure and acidity of
catalysts. The results indicate that increasing phosphorus loading
decreased surface area, pore volume and strong acidity of catalysts.
The addition of phosphorus significantly decreased butene conversion
and promoted propylene selectivity. The catalytic performance of
catalyst was strongly dependent on the reaction conditions.
Appropriate reaction conditions could suppress side reactions and
enhance propylene selectivity.
Abstract: It is an established fact that polymers have several
physical limitations such as low stiffness and low resistance to
impact on loading. Hence, polymers do not usually have requisite
mechanical strength for application in various fields. The
reinforcement by high strength fibers provides the polymer
substantially enhanced mechanical properties and makes them more
suitable for a large number of diverse applications. This research
evaluates the effects of particulate Cow bone and Groundnut shell
additions on the mechanical properties and microstructure of cow
bone and groundnut shell reinforced epoxy composite in order to
assess the possibility of using it as a material for engineering
applications. Cow bone and groundnut shell particles reinforced with
epoxy (CBRPC and GSRPC) was prepared by varying the cow bone
and groundnut shell particles from 0-25 wt% with 5 wt% intervals. A
Hybrid of the Cow bone and Groundnut shell (HGSCB) reinforce
with epoxy was also prepared. The mechanical properties of the
developed composites were investigated. Optical microscopy was
used to examine the microstructure of the composites. The results
revealed that mechanical properties did not increase uniformly with
additions in filler but exhibited maximum properties at specific
percentages of filler additions. From the Microscopic evaluation, it
was discovered that homogeneity decreases with increase in % filler,
this could be due to poor interfacial bonding.
Abstract: Haynes 25 alloy (also known as L-605 alloy) is cobalt
based super alloy which has widely applications such as aerospace
industry, turbine and furnace parts, power generators and heat
exchangers and petroleum refining components due to its excellent
characteristics. However, the workability of this alloy is more
difficult compared to normal steels or even stainless. In present work,
an experimental investigation was performed under cryogenic
cooling to determine cutting tool wear patterns and obtain optimal
cutting parameters in turning of cobalt based superalloy Haynes 25.
In experiments, uncoated carbide tool was used and cutting speed (V)
and feed rate (f) were considered as test parameters. Tool wear
(VBmax) were measured for process performance indicators.
Analysis of variance (ANOVA) was performed to determine the
importance of machining parameters.
Abstract: This paper aims to study the effect of cold work
condition on the microstructure of Cu-1.5wt%Ti, and Cu-3.5wt%Ti
and hence mechanical properties. The samples under investigation
were machined, and solution heat treated. X-ray diffraction technique
is used to identify the different phases present after cold deformation
by compression and also different heat treatment and also measuring
the relative quantities of phases present. The metallographic
examination is used to study the microstructure of the samples. The
hardness measurements were used to indicate the change in
mechanical properties. The results are compared with the mechanical
properties obtained by previous workers. Experiments on cold
compression followed by aging of Cu-Ti alloys have indicated that
the most efficient hardening of the material results from continuous
precipitation of very fine particles within the matrix. These particles
were reported to be β`-type, Cu4Ti phase. The β`-β transformation
and particles coarsening within the matrix as well as long grain
boundaries were responsible for the overaging of Cu-1.5wt%Ti and
Cu-3.5wt%Ti alloys. It is well known that plate-like particles are β –
type, Cu3Ti phase. Discontinuous precipitation was found to start at
the grain boundaries and expand into grain interior. At the higher
aging temperature, a classic Widmanstätten morphology forms giving
rise to a coarse microstructure comprised of α and the equilibrium
phase β. Those results were confirmed by X-ray analysis, which
found that a few percent of Cu3Ti, β precipitates are formed during
aging at high temperature for long time for both Cu- Ti alloys (i.e.
Cu-1.5wt%Ti and Cu-3.5wt%Ti).
Abstract: This work studies the effect of chemical composition
on the activity and selectivity of γ–alumina supported CuO/
MnO2/Cr2O3 catalysts toward deep oxidation of CO, dimethyl ether
(DME) and methanol. The catalysts were prepared by impregnation
of the support with an aqueous solution of copper nitrate, manganese
nitrate and CrO3 under different conditions. Thermal, XRD and TPR
analysis were performed. The catalytic measurements of single
compounds oxidation were carried out on continuous flow equipment
with a four-channel isothermal stainless steel reactor. Flow-line
equipment with an adiabatic reactor for simultaneous oxidation of all
compounds under the conditions that mimic closely the industrial
ones was used. The reactant and product gases were analyzed by
means of on-line gas chromatographs.
On the basis of XRD analysis it can be concluded that the active
component of the mixed Cu-Mn-Cr/γ–alumina catalysts consists of at
least six compounds – CuO, Cr2O3, MnO2, Cu1.5Mn1.5O4,
Cu1.5Cr1.5O4 and CuCr2O4, depending on the Cu/Mn/Cr molar ratio.
Chemical composition strongly influences catalytic properties, this
influence being quite variable with regards to the different processes.
The rate of CO oxidation rapidly decrease with increasing of
chromium content in the active component while for the DME was
observed the reverse trend. It was concluded that the best
compromise are the catalysts with Cu/(Mn + Cr) molar ratio 1:5 and
Mn/Cr molar ratio from 1:3 to 1:4.
Abstract: Effect of sprue/metal head height on mould filling,
microstructure and mechanical properties of TWDI casting is studied.
Results show that metal/sprue height of 50 mm is not sufficient to
push the melt through the gating channel, but as it is increased from
100-350 mm, proper mould filling is achieved. However at higher
heights between 200 mm and 350 mm, defects associated with
incomplete solidification, carbide precipitation and turbulent flow are
evident. This research shows that superior UTS, hardness, nodularity
and nodule count are obtained at 100 mm sprue height.
Abstract: Cemented carbides, owing to their excellent
mechanical properties, have been of immense interest in the field of
hard materials for the past few decades. A number of processing
techniques have been developed to obtain high quality carbide tools,
with a wide range of grain size depending on the application and
requirements. Microwave sintering is one of the heating processes,
which has been used to prepare a wide range of materials including
ceramics. A deep understanding of microwave sintering and its
contribution towards control of grain growth and on deformation of
the resulting carbide materials requires further studies and attention.
In addition, the effect of binder materials and their behavior during
microwave sintering is another area that requires clear understanding.
This review aims to focus on microwave sintering, providing
information of how the process works and what type of materials it is
best suited for. In addition, a closer look at some microwave sintered
Tungsten Carbide-Cobalt samples will be taken and discussed,
highlighting some of the key issues and challenges faced in this
research area.
Abstract: Zn alloy and composite coatings are widely used in
buildings and structures, automobile and fasteners industries to
protect steel component from corrosion. In this paper, Zn-Ni-Al2O3
nanocomposite coatings were electrodeposited on mild steel using a
novel sol enhanced electroplating method. In this method, transparent
Al2O3 sol was added into the acidic Zn-Ni bath to produced Zn-Ni-
Al2O3 nanocomposite coatings. The effect of alumina sol on the
electrodeposition process, and coating properties was investigated
using cyclic voltammetry, XRD, ESEM and Tafel test. Results from
XRD tests showed that the structure of all coatings was single γ-
Ni5Zn21 phase. Cyclic voltammetry results showed that the
electrodeposition overpotential was lower in the presence of alumina
sol in the bath, and caused the reduction potential of Zn-Ni to shift to
more positive values. Zn-Ni-Al2O3 nanocomposite coatings produced
more uniform and compact deposits, with fine grained microstructure
when compared to Zn-Ni coatings. The corrosion resistance of Zn-Ni
coatings was improved significantly by incorporation of alumina
nanoparticles into the coatings.
Abstract: In present global scenario, aluminum alloys are
coining the attention of many innovators as competing structural
materials for automotive and space applications. Comparing to other
challenging alloys, especially, 7xxx series aluminum alloys have
been studied seriously because of benefits such as moderate strength;
better deforming characteristics and affordable cost. It is expected
that substitution of aluminum alloys for steels will result in great
improvements in energy economy, durability and recyclability.
However, it is necessary to improve the strength and the formability
levels at low temperatures in aluminum alloys for still better
applications. Aluminum–Zinc–Magnesium with or without other
wetting agent denoted as 7XXX series alloys are medium strength
heat treatable alloys. In addition to Zn, Mg as major alloying
additions, Cu, Mn and Si are the other solute elements which
contribute for the improvement in mechanical properties by suitable
heat treatment process. Subjecting to suitable treatments like age
hardening or cold deformation assisted heat treatments; known as low
temperature thermomechanical treatments (LTMT) the challenging
properties might be incorporated. T6 is the age hardening or
precipitation hardening process with artificial aging cycle whereas T8
comprises of LTMT treatment aged artificially with X% cold
deformation. When the cold deformation is provided after solution
treatment, there is increase in hardness related properties such as
wear resistance, yield and ultimate strength, toughness with the
expense of ductility. During precipitation hardening both hardness
and strength of the samples are increasing. The hardness value may
further improve when room temperature deformation is positively
supported with age hardening known as thermomechanical treatment.
It is intended to perform heat treatment and evaluate hardness, tensile
strength, wear resistance and distribution pattern of reinforcement in
the matrix. 2 to 2.5 and 3 to 3.5 times increase in hardness is reported
in age hardening and LTMT treatments respectively as compared to
as-cast composite. There was better distribution of reinforcements in
the matrix, nearly two fold increase in strength levels and up to 5
times increase in wear resistance are also observed in the present
study.