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In this study, a planetary ball mill was used for mechanical activation of phosphate concentrate by dry milling in argon atmosphere. To investigate the structural changes of fluorapatite, amorphization degree, crystallite size, micro-strain, particles size, specific surface area changes and new phase formation were investigated. The crystallite size and micro-strain were estimated using Williamson-Hall method. To investigate the influence of effective parameters on mechanical activation, the ball to powder ratio of 20:1 and 40:1 with two types of balls of 9.4 and 20 mm and speeds of 200 and 500 rpm was used. The results showed that agglomeration of particles occur at higher intensities of mechanical activation, but no phase change occurs during high intensity ball milling. The most variations in crystallite size, micro-strain, surface area, amorphization degree and XRD line broadening were for samples that were activated by smaller balls for longer time. The results of the Williamson-Hall plots showed that the maximum effect of mechanical activation on phosphate concentrate was in the first 20 minutes with small balls and the crystallite size, micro-strain and amorphization degree was changed from 225 nm, 0.09% and 0% for initial sample to 64.29 nm, 0.9% and 80.081% for mechanically activated sample, respectively. Also the results showed that changes in cell parameter at c direction had larger effect on unit cell volume. The maximum unit cell volume variations were corresponding to mechanically activated sample with 9.4 mm balls that changed from 525.4 (A³) for initial sample to 528 (A³) for activated one after 90 min.
 

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  Studying dough microstructure is considered as a useful and effective tool to understand the effect of different process parameters on dough and the final product characteristics. In this study, sample preparation and staining protocols were established to study the dough micro-structure with epi-fluorescence light microscope (EFLM). For this purpose, dough sample preparation and staining conditions with respect to the type of staining dye, solvent, dye concentration, staining time and the type of filter used for EFLM were studied. The results showed that sodium Fluorescein (1% w/v) and Rhodamine B (0.1% w/v) in 2-methoxyethanol solvent give the best staining results. The double staining technique used enabled us to simultaneously and successfully observe the starch granules and protein network in the dough. The resting time after the addition of the dye had an impact on the quality of microscopic images. Among different resting times investigated, 60 min time gave the best results. Among the different EFLM filters, the MWBV2 filter for 420 nm spectrum gave the best results. Using image processing software and the specialized plug-ins the quality of EFLM images was improved. When a suitable protocol and methodology was established, the microstructure of dough was studied under different mixing regimes (under-mixing, optimal mixing and over-mixing). Overall, the results indicated that EFLM can be successfully used for studying the dough microstructure and this technique gives comparable results to well-known CSLM technique.

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In this study effects of flour hydration was investigated on gluten development in bread dough. For this purpose, zero-mechanical energy developed (ZD) doughs, which prepared and hydrated outside conventional mixers were used. Effects of fridge and room temperatures for different durations (1.5, 4 and 24 h) was studied on dough hydration extent and gluten development. Epi-fluorescence light microscopic (EFLM) observations revealed positive effect of holding time in both temperatures on protein distribution extent in dough microstructure. However, increasing temperature for durations studied showed strong effect on hydration and hence gluten development extent. So, treatments carried out at room temperature for 24 h compared to those accomplished at fridge temperature for the same duration showed the best gluten development patterns. Concluding, flour hydration leads to development of gluten structures in the dough. Gluten self-aggregation caused by hydration accounts for this phenomenon. However, the structures observed for ZD doughs in this study were different from those reported for optimally-mixed doughs, which show coarse interconnected gluten network surrounding starch granules.  

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This study is concerned with a correlation between the microstructure and mechanical properties of 42CrMo4 steel which was subjected quenched-tempered and step-quenching heat treatment. Quench tempering and step quenching heat treatment produced a tempered martensite and an equiaxed Ferrite-Bainite-Martensite (F-B-M) microstructure, respectively. Tensile test results indicated a yield drop effect in F-B-M microstructure with ferritic matrix. This effect was not observed on the specimens with tempered martensite and F-B-M microstructure with hard phase B-M matrix. This effect can be attributed to dislocation generation in ferrite phase during bainitic and martensitic transformations. Fractographic investigations indicated intergranular cleavage in F-B-M microstructure and micro-void coalescence in tempered martensite microstructure can be attributed to carbide formation in martensitic structure during tempering micro-void coalescence in tempered martensite microstructure

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  In this research the effect of microwave thermal treatment with power of 600 w on Longissimus.dorsi (L.d) muscle of camel by 1-3 years were examined. Chemical analysis, mechanical properties and proteins behavior of raw and microwaved samples were compared. Also the cook loss changes in three powers of 300, 600 and 900 w were measured which all of them were followed a zero-order kinetic model. The percentage of fat, protein and ash increased because of high cook loss. Sodium reduced while iron and zinc increased. Shear force and compression force increased in comparison with raw sample. Both Shear force and compression force followed a three-phase curve :(1) rapid toughening, (2) rapid softening, (3) slow toughening. The microstructures of raw and heated samples were also studied. The micrographs showed the rupture of meat structure and connective tissue coagulation. DSC was performed to assess protein denaturation.  

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Abstract: The influence of cement content increase on corrosion resistant behavior in concretes containing nano-SiO2 was experimentally studied. For comparison, the chloride diffusion of plain concrete and the concrete containing nano-SiO2 was also experimentally studied. The test results indicated that the corrosion resistance of concretes containing nano-particles is significantly improved. However, the index of diffusion chloride ion in the concretes containing nano-SiO2 is directly related to cement content in the mix. The SEM oservations revealed that the microstructure of concrete with nano-SiO2 is more uniform and compact than that of normal concrete, but higher pore size distribution was observed when cement content is increased, which in turn leads to the increase in the diffusion of choloride ion.

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The present study was conducted with the aim of protein isolate production from the muscle of grass carp (Ctenopharyngodon idella) and investigation of the effect of extraction pH on different properties of isolated protein. Proteins were produced by pH-shift method in two treatments including dissolution in alkaline pH (11.5), and acidic pH (3), and then evaluated in terms of nutritional value, functional properties, and structural changes. According to the results, the yield of protein production was significantly higher in alkaline conditions than in acidic conditions. The evaluation of emulsifying and foaming capacity and water absorption capacity showed that the protein obtained from alkaline pH was better than acidic treatment. Also, the extracted proteins contained all essential amino acids within the recommended limit for daily consumption of adults. The evaluation of color indices showed that the protein obtained from acidic pH had a brighter and whiter color than alkaline pH. The images obtained from the scanning electron microscope and the FTIR spectra of samples showed that the pH-shift method did not lead to extensive destruction of the protein structure and both protein isolates had all the absorption peaks related to the main bonds of the proteins structure. In general, it can be concluded that the pH-shift method is an efficient method for extracting high quality protein from grass carp tissue, and different alkaline and acidic conditions lead to the production of proteins with different characteristics that can be used based on the application that is intended for the final product.

 

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Metal foams are a new class of materials with interesting structural properties; however no comprehensive understanding of their inelastic behavior has been established yet. Since the experimental studies of these materials have their own limitations, there is a growing research interest towards the mesostructural modeling of these materials. Accordingly many researchers have been trying to generate realistic and representative numerical models of the foams and prepare computational labs in which different aspects of foams mechanical behavior can be thoroughly investigated. The following three kinds of mesostructures have been commonly employed: (1) models based on a unit cell or a building block, (2) random Voronoi diagrams, and (3) CAD structures provided by the X-ray micro-computed tomography. In the current study, the physically representative circle set Voronoi diagrams are employed to define the geometry of 2D metallic foams. It is assumed that the minimum and maximum radii of the circular generators are 0.5 and 1.5 mm, respectively. The first sample is generated using linear distribution of cell size while, compared to the first sample, the second and third specimens have less and more small cells. An extra specimen (the forth sample) is also created with the same structure of the first one unless its edges are straight. In the next step, the FE models of the specimens are created using second order Timoshenko beam elements. Finally, the effects of microstructural features (e.g. strut curvature and cell size distribution) on the initial yield surface, elastic properties, and failure modes of the foams are numerically investigated under various biaxial loading conditions. Displacement-controlled loading is used. A newly energy-based approach developed for the identification of initial yield points has been incorporated. The results show that: (a) the size of the initial yield surface is significantly influenced by the curvature of the cell struts, (b) in the principal stresses space, the initial yield surface is bigger in the tension-tension region, (c) for a constant relative density, the presence of more big cells in a sample increases the size of the yield envelope, and (d) the macroscopic yield properties of the specimens can be interpreted according the microscopic failure mechanisms of the plastic yielding, elasto-plastic buckling, and plastic hinging of the struts. Furthermore, it is found that the previously proposed energy-based method for the identification of yield initiation under multiaxial loading conditions has serious shortcomings and needs revision.

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In this paper, the process of joining Ti-3Al-2.5V titanium alloy thin sheets by means of micro-plasma arc welding (MPAW) is reported. An experimental set-up was developed using traditional gas tungsten arc welding apparatus and a home-built torch for butt welding of coupon specimens. The specimens were welded under controlled welding parameters, such as voltage, current, travel speed and shielding gas flow rate. An appropriate set of parameters for MPAW process was examined by mechanical properties tests and microstructure characterization. Mechanical tests including tensile test, bending test and micro-hardness evaluation across the weld line generally show that if suitable welding parameters are used, the tensile strength of the welded specimen is well comparable with that of the base metal while its hardness increased at the fusion zone (FZ). The bending test revealed that using appropriate welding parameters, no crack or notch appeared at the welded joint. Fractography, X-ray diffraction and metallograpghy were also performed to study the microstructure evolution. SEM images of the fracture surface presented characteristics of ductile rupture. Studies on microstructure morphology of the specimens at the FZ and HAZ reveal occurrence of phase transformation from high temperature phase to acicular phase

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Metal foams as a new class of materials with interesting properties such as high stiffness and strength to density ratios, capacity to absorb impact energy, and reproducibility, are rapidly growing their share in advanced materials market. However, due to their porous microstructure, experimental investigations of their properties are not trivial and normally need rigorous procedures and high end equipments. Accordingly, there is a growing research interest towards the numerical modeling of their cellular structure in which the following three kinds of models have been commonly employed: (1) structures based on a unit cell or a building block, (2) random Voronoi diagrams, and (3) CAD data provided by Xray micro-computed tomography. In the current study, the mesostructure of aluminum foam produced by the brazing technique is simulated as a connected assembly of spherical shells. The latest inward packing scheme from the set of constructive algorithms is incorporated to efficiently pack the spheres in space. The Gamma distribution is used to control the cell diameters. Three mean values of 3, 4, and 5 mm and two variances of 0.5 and 1.0 mm are assumed for the radii of spheres and cubic specimens of 50 mm are generated. Two assumptions of constant thickness and constant thickness to radius ratio have been applied to the spherical shells. Two relative densities of 0.05 and 0.1 have been examined in the current study. A code is written to automatically transfer these geometrical data to ABAQUS FE program. The models are then meshed in 1 mm S4R shell elements. Tie contacts are defined between neighbor spheres. Furthermore, self contact is used to prevent any probable penetrations in the models. The foaming material is assumed to be AL 3003 H12 with elastic-perfectly plastic behavior. Next, the uniaxial load is applied by means of two rigid planes and the stress-strain curves are extracted. Main attention has been paid to the elastic modulus and initial yield stress of foam. It is observed that keeping the mean value of the radius and increasing its variance lead to the generation of more small spheres within the microstructure which itself increases the number of interactions inside the foam and thus increases elastic modulus and yield stress. The results also show that, for both thickness assumptions made here, increasing the mean radius of spheres decreases the number of spheres and their interaction points and subsequently weakens their uniaxial mechanical properties. Furthermore, compared to foams generated based on the constant thickness to radius ratio assumption, the presence of thick small spheres in foams with cells of constant thickness makes them stiffer and stronger. This effect is more pronounced in foam with higher densities

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This paper investigates the effects of constructional elements on the biomechanical behavior of desert locust hind wing. First, the microstructure of the insect wing is investigated using scanning electron microscope. The results of the scanning electron microscopy are used to develop finite element models of the wing with different constructional elements. The presented models are studied under the inertial and aerodynamic loads applied during flight and the obtained stresses and displacements are assessed. The results show that longitudinal veins, longitudinal and cross veins, corrugations, corrugations and longitudinal veins and finally a combination of corrugations and longitudinal and cross veins cause averagely 4, 25.75, 4.34, 184.54, 768.5 times decrease of the achieved principal stresses in comparison with a wing without the mentioned constructional elements. Constructional elements of the locust wing play an important role to uniform the pattern of stress distribution in the wing during flight. Further, the existence of the mentioned constructional elements causes a decrease in the variation of the stress within a stroke-cycle. In addition, it is shown that the inertia and aerodynamic forces have less effect on the wing deformation than the elastic ones. The results of this research may be helpful in the development of lightweight structures with high strength.

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Friction stir welding (FSW) has become a technology of widespread interest because of its numerous advantages, most important of which is its ability to weld otherwise unweldable alloys. In this study, friction stir welding process has been used to join A441 AISI steel and AA1100 aluminum alloy. Optical microscopy, X-ray diffraction analysis (XRD), Energy-dispersive X-ray spectroscopy (EDS) and Vickers microhardness tests were employed to study on the joint microstructure evolution and hardness. The results showed that after welding process, head affected zone (HAZ) and stir zone (SZ) were formed in steel base metal side and head affected zone (HAZ), thermo-mechanical affected zone (TMAZ) and stir zone (SZ) were formed in aluminum alloy side. Mg2Al3 spherical particles formed with the ferrite and pearlite constituents in the junction. These particles were formed between the aluminum grain boundaries and due to the difference in contraction coefficient with aluminum base metal, were causing hot cracks in stir zone during solidification. Due to the generated frictional heat, small grains of ferrite and pearlite with very fine grain size of aluminum were formed in stir zone. Base metals dynamic recrystallization and formation of intermetallic compounds led to stir zone microhardness became higher than other areas.

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Engineering components during service are exposed to destructive phenomena such as wear which may lead to their destruction. For their protection and reduction of costs of replacement of these defective components and also increasing productivity, attention is given to welding processes for depositing a wear-resistant layer on the components. In this research, the effect of welding current on last layer weld quality deposited on carbon steel by shielded metal arc welding process using Fe-based hardfacing electrodes is investigated. The chemical composition of the weld deposit layers was studied by quantometery. Optical and scanning electron microscopes, energy dispersive X-ray fluorescence and X-ray diffraction were used for microstructural studies. Microhardness and pin on disk wear tests were also employed for microhardness and wear resistance evaluations. The metallography and X-ray diffraction results show presence of martensite and retained austenite in the microstructure of the last deposited weld layer. The results of chemical analysis and microhardness and wear-resistant tests show that increasing the current increases weld dilution which leads to reduction of alloying elements affecting hardness and wear resistance of the weld deposit and hence these properties decrease slightly. Evaluation of the worn surfaces shows that the wear mechanism on the last deposited layer is of abrasive wear type.

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In this study, particulate nanocomposites with A356 aluminum alloy as a matrix reinforced with 1 and 1.5 wt.% SiCnanoparticles with 50 nm average grain size were fabricated by stir casting method and then the obtained composites were subjected to T6 heat treatment. The mechanical properties such as Hardness Test and Tensile Test of composites Samples were investigated. Microstructures of the samples were also investigated by using optical microscope (OM) and scanning electron microscope (SEM). The results show that T6 heat treated nanocomposites have significantly higher Hardness and tensile Strength compared to the nanocomposites without heat treatment. The enhancement in the mechanical propertiecanis due to the formation of Mg2Si phase and globular silicon particles.Also, increasing in the concentration of SiC nanoparticles led to improve the hardness and tensile strength, So that the highest tensile strength and hardness was obtained for the 1.5 wt.%SiCnanocomposite. Tensile strength and hardness of 1.5 wt% SiCnanocompositesbefore and afterT6 heat treatmentachieved 177MPa and 236MPa and 80 HBN and 123 HBN, respectively.Fracture surfaces were studied using SEM show that failureof all samples is brittle fracture.

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The electrokinetic (EK) approach is one of the popular choices for the extraction of inorganic contaminants (e.g. heavy metals) from a soil matrix. On the other hand, many factors can affect the performance of EK contaminant remediation. Therefore, in the present study a series of macro and micro level tests including electrokinetic experiments, pH and electrical conductivity (EC), adsorption and desorption, X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses were performed to investigate the effects of time and pore fluid characteristics on the efficiency of EK remediation. For this purpose, the kaolinite clay was separately infected with different solutions containing zinc nitrate and lead nitrate in concentrations of 20 and 40 cmol/kg and then electrokinetic experiments on a laboratory scale were conducted at 2 V/cm voltage gradient in time periods of 3, 6, 12, 24 and 48 days. Nitric acid was also used as a catholyte solution to enhance the soil remediation process. The results obtained show that the soil response to the EK remediation is a function of the contaminant characteristics, the pH of soil-electrolyte system and the time of testing. In EK contaminant remediation from a soil matrix, it is significant to pay particular attention to the effect of the concentration and type of contaminant on the applicability and efficiency of this method. The results reveal that under the same conditions, especially in the low times, extraction efficiency from samples containing lead was measured approximately 70 percent of the samples containing zinc. This is because the lead tends to more adsorbe on the clay surface and has a greater tendency to form precipitate. In addition to the type of contaminants, it was found that the increase in concentration of contaminants in the soil through a series of physical-chemical reactions accelerates clean up capabilities, particularly in the initial time period of the EK experiments. Catholyte conditioning with acidic solution enhanced the removal of heavy metals, which is mainly due to microstructural changes and an increase in the mobility of pollutants. In fact, based on the X-ray diffraction and scanning electron microscope analyses, the microstructural characteristics and the arrangement of the clay particles have an important role in the process of electrokinetic soil remediation. The formation of flocculated structure decreases the retention capacity of the clay particles and also increases the flow path, which enhance the efficiency of pollutant extraction. It was found that the soil remediation, especially in the parts close to the anode, greatly enhanced with increase the time of EK test; however, the further increase in time had a limited impact on results, especially in the samples containing high concentrations of zinc. This indicates that there is an optimum time in the process of cleaning up heavy metals from the soil by EK method, which depends on the type and concentration of contaminant. Moreover, it was seen that the extent of contaminant removal from anode side towards the cathode side is considerable when catholyte conditioning with acidic solution is used. In other words, reducing the pH of soil-electrolyte system has a significant impact in increasing the efficiency of pollutant extraction.

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In this study, A356 aluminum alloy matrixcomposites reinforced with different weight percentages of SiC nano- and microparticles respectively with 50 nm and 5 µm average particle sizes were fabricated by stir casting method. Due to the effect of T6 heat treatment on the strength and hardness of A356alloy, the obtained composites were subjected to the T6 heat treatment. The mechanical properties such as hardness and compressive properties of the composites were investigated. Microstructures of the samples were also investigated by an optical microscope (OM), scanning electron microscope (SEM) and field emission scanning electron microscope (FESEM). Microstructural investigation indicated that T6 heat treatment led to thechange of eutectic silicon morphology and formation of theMg2Si precipitates during age hardening stage, leading to increase the hardness and compressive strength. The results showed that an increase in wt.% of nanoparticles led to an increase in hardness and compressive strength. The results of microstructural investigationshowedthe relatively uniform distribution of reinforcement particles. Also, the strength and hardness of the composites reinforced with nanoparticleswere greater than those of the composite reinforced with microparticles, even with higher weight percent of reinforcement particles. Hardness and compressive strength at 35% strain for the composite reinforced with 1.5 wt.% nanoparticles were respectively obtained 62 HBN and 252MPa, which are improved compared to the base alloy.

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In the present study, AM60 magnesium alloy was casting and then subjected to hot extrusion process. Next, Multi Directional Forging (MDF) experiments with six pass numbers were conducted to investigate the influence of the operation on the microstructure and mechanical properties of these alloys. The shear punch test (SPT) and Vickers microhardness test were employed to evaluate the mechanical properties of the extruded and MDFed samples. Both the shear yield stress (SYS) and ultimate shear strength (USS) obtained from the shear punch test increased just after two passes but decreased with further pressing, although it was expected that the grains became finer with increasing the pass number. After two passes USS increased from 121.58 MPa to 142.42 MPa. This rise and fall indicates that texture softening overcame the strengthening effects of the grain refinement. The Vickers microhardness was measured across the cross sections of the extruded and MDFed samples, the results of this test also confirms that rise and fall procedure. The average microhardness of the extruded and MDFed samples were found to be respectively 73.50, 85.93, 82.26 and 77.83 HV for the extruded and 2,4 and 6 passes of MDFed, which confirms SPT results. Optical micrographs showed that processing by MDF reduces the grain size from 11.22 to 1.91 µm after 6 passes.

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Nowadays, multilayered sheet metals are used in order to achieve a wide range of favorite mechanical, physical, thermal and electrical properties. The laser beam passage over the sheet creates extreme temperature changes which can lead to a change in chemical properties and microstructures. Due to the wide application of these materials in chemical and corrosive environments, corrosion tests were carried out on two-layered SUS304L/copper C11000 and three-layered SUS430/copper C11000/steel SUS430 sheets subjected to various laser passes. Ytterbium fiber laser is used and the governor mechanism during the process is TGM. The changes of microstructures were revealed by metallography. Corrosion resistance of steel layer in three-layered sheet subjected to laser was dropped due to the martensite and oriented ferrite grain size reduction in HAZ. There is no change in microstructure and corrosion behavior of copper layer and the second steel layer due to the HAZ low penetration depth. There is no change in microstructure and corrosion behavior of steel layer in two layered sheet due to the austenitic microstructure. Penetration depth of HAZ in two-layered sheet is limited to a small part of its steel cross section. So, there is no change in microstructure and corrosion behavior of copper, and corrosion is the same all over the copper layer in all specimens.

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The propose of  this study was to investigate the production of biodegradable edible film............