Abstract: This paper investigates the effectiveness of two
natural zeolites in reducing expansion of concrete due to alkali-silica
reaction. These natural zeolites have different reactive silica content.
Three aggregates; two natural sands and one crushed stone aggregate
were used while preparing mortar bars in accordance with accelerated
mortar bar test method, ASTM C1260. Performances of natural
zeolites are compared by examining the expansions due to alkali
silica reaction. Natural zeolites added to the mixtures at 10% and
20% replacement levels by weight of cement. Natural zeolite with
high reactive silica content had better performance on reducing
expansions due to ASR. In this research, using high reactive zeolite at
20% replacement levels was effective in mitigating expansions.
Abstract: The main idea of this work is to investigate the effect
of knitted fabrics characteristics on moisture management properties.
Wetting and transport properties of single jersey, Rib 1&1 and
English Rib fabrics made out of cotton and blended Cotton/Polyester
yarns were studied. The dynamic water sorption of fabrics was
investigated under same isothermal and terrestrial conditions at
20±2°C-65±4% by using the Moisture Management Tester (MMT)
which can be used to quantitatively measure liquid moisture transfer
in one step in a fabric in multidirections: Absorption rate, moisture
absorbing time of the fabric's inner and outer surfaces, one-way
transportation capability, the spreading/drying rate, the speed of
liquid moisture spreading on fabric's inner and outer surfaces are
measured, recorded and discussed. The results show that fabric’s
composition and knit’s structure have a significant influence on those
phenomena.
Abstract: The conventional ceramic route was utilized to
prepare a hard magnetic powder (M-type strontium ferrite,
SrFe12O19). The stoichiometric mixture of iron oxide and strontium
carbonate were calcined at 1000oC and then fired at various
temperatures. The influence of various reaction parameters such as
mixing ratio, calcination temperature, firing temperature and firing
time on the magnetic behaviors of the synthesized magnetic powder
were investigated. The magnetic properties including Coercivity
(Hc), Magnetic saturation (Ms), and Magnetic remnance (Mr) were
measured by vibrating sample magnetometer. Morphologically the
produced magnetic powder has a dense hexagonal grain shape
structure.
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: Effect of alloying on the microstructure and mechanical properties of heat-resisting duplex stainless steel (DSS) for Mg production was investigated in this study. 25Cr-8Ni based DSS’s were cast into rectangular ingots of which the dimension was 350×350×100 mm3 . Nitrogen and Yttrium were added in the range within 0.3 in weight percent. Phase equilibrium was calculated using the FactSage®, thermodynamic software. Hot exposure, high temperature tensile and compression tests were conducted on the ingots at 1230oC, which is operation temperature employed for Mg production by Silico-thermic reduction. The steel with N and Y showed much higher strength than 310S alloy in both tensile and compression tests. By thermal exposition at 1230oC for 200 hrs, hardness of DSS containing N and Y was found to increase. Hot workability of the heat-resisting DSS was evaluated by employing hot rolling at 1230 oC. Hot shortness was observed in the ingot with N and found to disappear after addition of Y.
Abstract: Biomass treatment through densification is very suitable and helpful technology before its effective energy recovery. Densification process of biomass is significantly influenced by various technological and material variables, which are ultimately reflected on the final solid biofuels quality. The paper deals with the experimental research of the relationship between technological and material variables during densification of fast-growing trees, roundly fast-growing willows. The main goal of presented experimental research is to determine the relationship between compression pressure and raw material particle size from a final briquettes density point of view. Experimental research was realized by single-axis densification. The impact of particle size with interaction of compression pressure and stabilization time on the quality properties of briquettes was determined. These variables interaction affects the final solid biofuels (briquettes) quality. From briquettes production point of view and from densification machines constructions point of view is very important to know about mutual interaction of these variables on final briquettes quality. The experimental findings presented here are showing the importance of mentioned variables during the densification process.
Abstract: This paper reports the viability of developing Zn-27Al
alloy matrix hybrid composites reinforced with alumina, graphite and
fly ash (solid waste bye product of coal in thermal power plants).
This research work was aimed at developing low cost-high
performance Zn-27Al matrix composite with low density. Alumina
particulates (Al2O3), graphite added with 0, 2, 3, 4 and 5 wt% fly ash
were utilized to prepare 10wt% reinforcing phase with Zn-27Al alloy
as matrix using two-step stir casting method. Density measurement,
estimated percentage porosity, tensile testing, micro hardness
measurement and optical microscopy were used to assess the
performance of the composites produced. The results show that the
hardness, ultimate tensile strength, and percent elongation of the
hybrid composites decrease with increase in fly ash content. The
maximum decrease in hardness and ultimate tensile strength of
13.72% and 15.25% respectively were observed for composite grade
containing 5wt% fly ash. The percentage elongation of composite
sample without fly ash is 8.9% which is comparable with that of the
sample containing 2wt% fly ash with percentage elongation of 8.8%.
The fracture toughness of the fly ash containing composites was
however superior to those of composites without fly ash with 5wt%
fly ash containing composite exhibiting the highest fracture
toughness. The results show that fly ash can be utilized as
complementary reinforcement in ZA-27 alloy matrix composite to
reduce cost.
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: The effect of molybdate addition to chloride
environment on resistance of AISI 316Ti stainless steel to pitting
corrosion was studied. Potentiodynamic polarisation tests were
performed in 1 M and 0.1 M chloride acidified solutions with various
additions of sodium molybdate at room temperature. The presented
results compare the effect of molybdate anions on quality of passive
film (expressed by the pitting potential) in both chloride solutions.
The pitting potential increases with the increase inhibitor
concentration. The inhibitive effect of molybdate ions is stronger in
chloride solution of lower aggressiveness (0.1M).
Abstract: The knitted fabric suffers a deformation in its
dimensions due to stretching and tension factors, transverse and
longitudinal respectively, during the process in rectilinear knitting
machines so it performs a dry relaxation shrinkage procedure and
thermal action of prefixed to obtain stable conditions in the knitting.
This paper presents a dry relaxation shrinkage prediction of Bordeaux
fiber using a feed forward neural network and linear regression
models. Six operational alternatives of shrinkage were predicted. A
comparison of the results was performed finding neural network
models with higher levels of explanation of the variability and
prediction. The presence of different reposes is included. The models
were obtained through a neural toolbox of Matlab and Minitab
software with real data in a knitting company of Southern
Guanajuato. The results allow predicting dry relaxation shrinkage of
each alternative operation.
Abstract: Ceramic obtained on the base of aluminum oxide has
wide application range, because it has unique properties, for example,
wear-resistance, dielectric characteristics, and exploitation ability at
high temperatures and in corrosive atmosphere. Low temperature
synthesis of α-Al2O3 is energo-economical process and it is topical
for developing technologies of corundum ceramics fabrication. In the present work possibilities of low temperature transformation
of oxyhydroxides in α-Al2O3, during the presence of small amount of
rare–earth elements compounds (also Th, Re), have been discussed.
Aluminum unstable oxyhydroxides have been obtained by hydrolysis
of aluminium isopropoxide, nitrates, sulphate, and chloride in
alkaline environment at 80-90ºC temperatures. β-Al(OH)3 has been
received from aluminum powder by ultrasonic development. Drying
of oxyhydroxide sol has been conducted with presence of various
types seeds, which amount reaches 0,1-0,2% (mas). Neodymium,
holmium, thorium, lanthanum, cerium, gadolinium, disprosium
nitrates and rhenium carbonyls have been used as seeds and they
have been added to the sol specimens in amount of 0.1-0.2% (mas)
calculated on metals. Annealing of obtained gels is carried out at 70–
1100ºC for 2 hrs. The same specimen transforms in α-Al2O3 at
1100ºC. At this temperature in case of presence of lanthanum and
gadolinium transformation takes place by 70-85%. In case of
presence of thorium stabilization of γ-and θ-phases takes place. It is
established, that thorium causes inhibition of α-phase generation at
1100ºC, and at the time when in all other doped specimens α-phase is
generated at lower temperatures (1000-1050ºC). Synthesis of various
type compounds and simultaneous consolidation has developed in the
furnace of OXY-GON. Composite materials containing oxide and
non-oxide components close to theoretical data have been obtained in
this furnace respectively. During the work the following devices have
been used: X-ray diffractometer DRON-3M (Cu-Kα, Ni filter,
2º/min), High temperature vacuum furnace OXY-GON, electronic
scanning microscopes Nikon ECLIPSE LV 150, NMM-800TRF,
planetary mill Pulverisette 7 premium line, SHIMADZU Dynamic
Ultra Micro Hardness Tester, DUH-211S, Analysette 12 Dyna sizer.
Abstract: Processing of high-silicon bauxite on the base of the
traditional clinkering method is related to high power consumption
and capital investments, which makes production of alumina from
those ores non-competitive in terms of basic economic showings. For
these reasons, development of technological solutions enabling to
process bauxites with various chemical and mineralogical structures
efficiently with low level of thermal power consumption is important.
Flow sheet of the studies on washability of ores from the Timanskoe
and the Severo-Onezhskoe deposits is on the base of the flotation
method.
Abstract: A problem of complex mineral resources development is urgent and priority, it is aimed at realization of the processes of their ecologically safe development, one of its components is revealing the influence of the forms of element compounds in raw materials and in the processing products. In view of depletion of the precious metal reserves at the traditional deposits in the XXI century the large-size open cast deposits, localized in black shale strata begin to play the leading role. Carbonaceous (black) shales carry a heightened metallogenic potential. Black shales with high content of carbon are widely distributed within the scope of Bureinsky massif. According to academician Hanchuk`s data black shales of Sutirskaya series contain generally PGEs native form. The presence of high absorptive towards carbonaceous matter gold and PGEs compounds in crude ore results in decrease of valuable components extraction because of their sorption into dissipated carbonaceous matter.
Abstract: The development of composite materials and the
related design and manufacturing technologies is one of the most
important advances in the history of materials. Composites are
multifunctional materials having unprecedented mechanical and
physical properties that can be tailored to meet the requirements of a
particular application. Some composites also exhibit great resistance
to high-temperature corrosion, oxidation, and wear. Polymers are
widely used indoors and outdoors, therefore they are exposed to a
chemical environment which may include atmospheric oxygen, acidic
fumes, acidic rain, moisture heat and thermal shock, ultra-violet light,
high energy radiation, etc. Different polymers are affected differently
by these factors even though the amorphous polymers are more
sensitive. Ageing is also important and it is defined as the process of
deterioration of engineering materials resulting from the combined
effects of atmospheric radiation, heat, oxygen, water, microorganisms
and other atmospheric factors.
Abstract: The present study deals with the characterization of
CrSiN coatings obtained by PVD magnetron sputtering systems.
CrSiN films were deposited with different Si contents, in order to
check the effect of at.% variation on the different properties of the
Cr–N system. Coatings were characterized by scanning electron
microscopy (SEM) for thickness measurements, X-ray diffraction.
Surface morphology and the roughness characteristics were explored
using AFM, Mechanicals properties, elastic and plastic deformation
resistance of thin films were investigated using nanoindentation test. We observed that the Si addition improved the hardness and the
Young’s modulus of the Cr–N system. Indeed, the hardness value is
18,56 GPa for CrSiN coatings. Besides, the Young’s modulus value
is 224,22 GPa for CrSiN coatings for Si content of 1.2 at.%.
Abstract: Polylactic acid (PLA) is the most commercially
available bio-based and biodegradable plastic at present. PLA has
been used in plastic related industries including single-used
containers, disposable and environmentally friendly packaging owing
to its renewability, compostability, biodegradability, and safety.
Although PLA demonstrates reasonably good optical, physical,
mechanical and barrier properties comparable to the existing
petroleum-based plastics, its brittleness and mold shrinkage as well as
its price are the points to be concerned for the production of rigid and
semi-rigid packaging. Blending PLA with other bio-based polymers
including thermoplastic starch (TPS) is an alternative not only to
achieve a complete bio-based plastic, but also to reduce the
brittleness, shrinkage during molding and production cost of the
PLA-based products. TPS is a material produced mainly from starch
which is cheap, renewable, biodegradable, compostable, and nontoxic.
It is commonly prepared by a plasticization of starch under
applying heat and shear force. Although glycerol has been reported as
one of the most plasticizers used for preparing TPS, its migration
caused the surface stickiness of the TPS products. In some cases,
mixed plasticizers or natural fibers have been applied to impede the
retrogradation of starch or reduce the migration of glycerol. The
introduction of fibers into TPS-based materials could reinforce the
polymer matrix as well. Therefore, the objective of the present
research is to study the effect of starch type (i.e. native starch and
phosphate starch), plasticizer type (i.e. glycerol and xylitol with a
weight ratio of glycerol to xylitol of 100:0, 75:25, 50:50, 25:75 and
0:100) and fiber content (i.e. in the range of 1-25 %wt) on properties
of PLA/TPS blend and composite. PLA/TPS blends and composites
were prepared using a twin-screw extruder and then converted into
dumbbell-shaped specimens using an injection molding machine. The
PLA/TPS blends prepared by using phosphate starch showed higher
tensile strength and stiffness than the blends prepared by using native
one. In contrast, the blends from native starch exhibited higher
extensibility and heat distortion temperature (HDT) than those from
the modified starch. Increasing xylitol content resulted in enhanced
tensile strength, stiffness and water resistance, but decreased
extensibility and HDT of the PLA/TPS blend. Tensile properties and
hydrophobicity of the blend could be improved by incorporating
silane treated-jute fibers.
Abstract: Here, we have shown the reaction of [Cr(ArN(CH2)3NAr)2Cl2] (1) where (Ar = 2,6-Pri
2C6H3) and in presence of NaCp (2) (Cp= C5H5 = cyclopentadien), with a center
coordination η5 interaction between Cp as co-ligand and chromium
metal center, for optimization we used density functional theory
(DFT), under methods, explicitly including electrons correlations, for
the final calculations as MB3LYP (Becke) (Lee–Yang–Parr) level of
theory we used to obtain more exact results. This complex was
calculated as electronic energy for molecular system, because the
calculation accounting all electrons correlations interactions. The
optimised of [Cr(ArN(CH2)3NAr)2(η5-Cp)] (Ar = 2,6-Pri2C6H3 and Cp = C5H5) was found to be thermally stable. By using Dewar-Chatt-Duncanson model, as a basis of the molecular orbital (MO) analysis
and showed the highest occupied molecular orbital (HOMO) and
lowest occupied molecular orbital LUMO.
Abstract: At the present work, highly transparent strip type
quasi-solid state dye-sensitized solar cells (DSSCs) were fabricated
through inkjet printing using nanocomposite TiO2 inks as raw
materials and tested under outdoor illumination conditions. The cells,
which can be considered as the structural units of large area modules,
were fully characterized electrically and electrochemically and after
the evaluation of the received results a large area DSSC module was
manufactured. The module design was a sandwich Z-interconnection
where the working electrode is deposited on one conductive glass and
the counter electrode on a second glass. Silver current collective
fingers were printed on the conductive glasses to make the internal
electrical connections and the adjacent cells were connected in series
and finally insulated using a UV curing resin to protect them from the
corrosive (I-/I3-) redox couple of the electrolyte. Finally, outdoor tests
were carried out to the fabricated dye-sensitized solar module and its
performance data were collected and assessed.
Abstract: In this work, repaired crack in 6061- T6 aluminum
plate with composite patches presented, firstly we determine the
displacement, strain and stress, also the first six mode shape of the
plate, secondly we took the same model adding central crack
initiation, which is located in the center of the plate, its seize vary
from 20 mm to 60 mm and we compare the first results with second.
Thirdly we repair various cracks with composite patch (carbon/
epoxy) and for (2 layers, 4 layers). Finally the comparison of stress,
strain, displacement and six first natural frequencies between un-cracked
specimen, crack propagation and composite patch repair.
Abstract: Pure nickel coatings have been successfully
electrodeposited on copper substrates by the pulse plating technique.
The influence of current density, duty cycle and pulse frequency on
the surface morphology, crystal orientation, and microhardness was
determined. It was found that the crystallite size of the deposit
increases with increasing current density and duty cycle. The crystal
orientation progressively changed from a random texture at 1 A/dm2
to (200) texture at 10 A/dm2. Increasing pulse frequency resulted in
increased texture coefficient and peak intensity of (111) reflection.
An increase in duty cycle resulted in considerable increase in texture
coefficient and peak intensity of (311) reflection. Coatings obtained
at high current densities and duty cycle present a mixed morphology
of small and large grains. Maximum microhardness of 193 Hv was
achieved at 4 A/dm2, 10 Hz and duty cycle of 50%. Nickel coatings
with (200) texture are ductile while (111) texture improves the
microhardness of the coatings.