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In this study, the corrosion behavior and microstructural transformations of 1000 series aluminum and copper tubes after an explosive welding process were investigated. Welding was performed with a fixed stand-off distance and various explosion thicknesses. Explosive welding was carried out using a consistent stand-off distance of 2 mm while varying the thickness of the explosive material of 60 mm (sample 1) and 80 mm (sample 2). The explosion velocity employed during the process was measured at 2504 m/s. Optical and electron microscopy images revealed that the thickness of the melting layer at the interface increases proportionally with the thickness of the explosive charge. Specifically, as the explosive thickness increased from 60 to 80 mm, the thickness of the melting layer increased as well. Also, the resuls of the potentiodynamic polarization test indicated a decrease in the corrosion potential from –670 mV (sample 1) to –665 mV (sample 2) as the explosive material thicknesses increased. At the same time, the corrosion current density rose from 52.34 µA/cm2 (sample 1) to 78.32 μA/cm2 (sample 2). An analysis of the Nyquist diagram for explosive welding samples revealed that the curve radius of sample 2 exceeded that of sample 1, suggesting a higher corrosion resistance in sample 1 compared to that in sample 2. [ABSTRACT FROM AUTHOR]

In this study, the effect of the compaction velocity as well as the size and volume content of the reinforcing particles on the thermal properties of Mg-B4C composites were evaluated. B4C reinforcing particles at various percentages (0, 5, 10%) and two sizes (micron-scale and nanoscale) were added to the magnesium matrix using a planetary ball mill and compacted at 450 °C and three different compaction velocities. The Instron device was utilized for the quasi-static compaction of the powder particles while a drop-hammer and a Split-Hopkinson bar were used for the dynamic compaction of composite powders at medium and high strain rates, respectively. The thermal behavior of the composites was studied by measuring their thermal conductivity and coefficient of thermal expansion. The results showed improvement in dimensional stability of the composites with increasing the volume percentage of the reinforcing particles. Higher compaction velocities led to higher thermal conductivity and coefficient of thermal expansion. Besides, further addition of the reinforcing particles to the matrix resulted in a decrease in the thermal properties. Magnesium samples reinforced with B4C nanoparticles exhibited superior thermal properties compared to those reinforced with micron-sized particles. [ABSTRACT FROM AUTHOR]

One of the important living organisms in stagnant waters, surface waters, water reservoirs, pools and dams is microalgae. Various methods have been developed and studied for the removal of these microscopic organisms from drinking water, of which the sedimentation or flocculation is one of the significant methods. The method is based on using sediments substance or flocculants. This study aimed to introduce feasible, harmless and suitable biological flocculants and evaluate their ability to precipitate Cyclotella diatoms. The presence of a large number of Cyclotella diatoms in water creates an unpleasant color and odor in the water. For this purpose, autoflocculation–sedimentation and bioflocculation processes were used to harvest Cyclotella. The effect of pH, mixing speed and time on harvest efficiency for autoflocculation–sedimentation and bioflocculation processes was investigated. The autoflocculation results showed that the removal efficiency increased with increasing pH, decreasing mixing speed and increasing settling time. For bioflocculation, Scenedesmus microalgae were used to isolate Cyclotella diatoms, and by examining the parameters affecting the rate of microalgae isolation, the optimal conditions have been determined. The ratio of 1:1 combination of microalgae–diatomaceous earth and pH = 10 and residence time of 120 min can yield up to 83% isolation and sedimentation of Cyclotella microalgae, which is a very efficient and inexpensive environmentally friendly method for the separation of infected microalgae from used drinking water. [ABSTRACT FROM AUTHOR]

The composites consisting of similar or dissimilar metallic layers with different physical properties are vastly applicable. Among various methods for producing these composites, cold roll bonding (CRB) is considered to be more efficient and more cost-effective than other bonding processes. Nowadays, Al-Cu layer composite bonds are favorable in different industries due to their low price, well conductibility, high corrosion resistance, high deformation, and good electrical conduction. This review paper deals with the investigations of the Al-Cu cold rolling process, of the bonding mechanism of metallic layers during CRB, and of the effect of the roll bond strength parameters such as initial thickness, for one. Roll bonding has three levels: (1) physical touch; (2) activating surfaces in touch; (3) interaction between bonding metals. CRB is supposed to be an in-plane strain, and the normal stress distributed on the top and bottom rollers is homogeneous. Annealing before and after rolling, the direction and speed of rolling, the amount of thickness reduction, and the lubrication conditions on the Al–Cu bond through the roll bonding process were studied. The effect of different annealing conditions on the produced intermetallic compounds at the Al–Cu rolling bond interface and the growth of the intermetallic phases and their impact on the CRB parameters was examined. The thickness of intermetallic compounds, thickness reduction under the rolling process, the rolling speed, the annealing temperature, and time affected the bond strength. The effect of the rolling speed on the bond strength depends on the touching time between the sheets during rolling, which means that the touching time between two surfaces of Al and Cu sheets reduces at higher rolling speeds. As a result, the chance for proper bonding is lost, and, therefore, the bond strength is decreased. [ABSTRACT FROM AUTHOR]

In the present study, the effect of temperature and duration of hot-dipping on structural properties, hardness, and corrosion resistance of Zn–5% Al coatings on ST13 low-carbon steel has been investigated. The samples were dipped in a molten metal bath at temperatures of 440, 480 and 520°C, during 20, 50 and 70 seconds. To investigate the microstructure and properties of samples, scanning electron microscopy, energy dispersive X-ray spectrometry, microhardness measurements, and potentiodynamic polarization corrosion tests were used. The results showed that the coating structure is an eutectic layer at 440°C, and at the interface of the substrate and the coating a thin inhibitory layer is formed that prevents the diffusion of the substrate atoms into the coating and from the molten bath into the substrate. With an increase of temperature to 480 and 520°C, with the diffusion of iron atoms of the substrate and of the molten bath, a triple metallic layer of Al–Fe–Zn forms, and the thickness of the coating increases. As the dipping time increases, the number of intermetallic particles in the coating also increases. At higher temperatures, the hardness went up from 86 to 121.73 Hv and the corrosion rate—from 7.381 to 37.53 Mpy. Keywords: hot dip, Zn–5% Al coating, microstructure, intermetallic, corrosion [ABSTRACT FROM AUTHOR]

In the present study, the corrosion behavior and microstructure changes of copper sheets joined with martensitic stainless steel AISI 410 in the salt environment after the explosive welding process have been investigated. An explosive loading and explosive material thickness were considered as variables. In the investigation, potentiodynamic polarization tests, electrochemical impedance spectroscopy, and metallographic tests were used through optical microscopy and scanning electron microscopy. The results of dynamic potential polarization curves showed that the corrosion density decreased with increasing the explosive load and decreasing the concentration at the interface. The results of metallography indicate a wave-eddy of the interface due to an increase in the thickness of the explosive load. According to the polarization test, the corrosion density increased with increasing the stand-off distance and the explosive load; an increase in the energy of the interface resulted from increasing the stand-off distance and the explosive loading, which exacerbates corrosion. [ABSTRACT FROM AUTHOR]

In the present study, the influence of the pin rotating speed on corrosion behavior and mechanical properties of the friction stir welded (FSW) 6063 aluminum alloy joints was investigated. The welding process was performed at rotating speeds of 800, 1000, and 1200 rpm and a constant traverse speed of 50 mm/min. The joints were analyzed via optical microscopy, scanning electron microscopy, and microhardness test. A cyclic polarization test and electrochemical impedance spectroscopy (EIS) were performed so as to study the effect of the pin rotating speed on corrosion behavior of joints in the solution of sodium chloride (3.5%). Microhardness results showed that the maximum amount of hardness is related to the sample with 1000 rpm rotating speed because of optimized input heat, which caused an increase in the grain refinement and dynamic recrystallization. The cyclic polarization test demonstrated that the corrosion rate in the heat affected zone (HAZ) was higher than that of the base and weld metals; this is due to grain coarsening and an increase of secondary phase particles, which causes intensification of galvanic corrosion. It was found that the higher the pin rotating speed, the higher the corrosion rate. The growth of secondary phase particles was identified due to an input heat increase. Also, EIS results indicated that increasing the pin rotating speed at FSW reduces the polarization resistance (RP) amount at the Nyquist diagram, followed by a decrease of corrosion resistance. A lower amount of RP and corrosion resistance verified in the HAZ was compared to those of the weld metal. [ABSTRACT FROM AUTHOR]

Yttrium oxysulfide nanoparticles doped with trivalent europium have been synthesized using urea homogen precipitation and followed by sulfurization at 800 °C under argon atmosphere. Structural and morphological of synthesized phosphore nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transform infrared spectrometry. Hexagonal structure was confirmed by XRD and TEM. Compositional analysis were carried out by energy dispersive X-ray and particle induced X-ray emission. Photoluminescence emission spectra was measured by fluorescent spectrometer. The effect of doped europium concentration (0.1, 0.2, 0.5 mol%) on particle size of yttrium oxysulfide was investigated. The results showed that dopant concentration in these levels did not change crystal structure of the host, but influenced brightness, as with increasing concentrations of europium, luminescence emission increases. Moreover, obtained particle sizes by SEM were 49, 50 and 60 nm respectively which are in agreement with TEM results. [ABSTRACT FROM AUTHOR]

This paper describes the synthesis of Al7075 metal matrix composites reinforced with SiC, and the characterization of their microstructure and mechanical behavior. The mechanically milled Al7075 micron-sized powder and SiC nanoparticles are dynamically compacted using a drop hammer device. This compaction is performed at different temperatures and for various volume fractions of SiC nanoparticles. The relative density is directly related to the compaction temperature rise and indirectly related to the content of SiC nanoparticle reinforcement, respectively. Furthermore, increasing the amount of SiC nanoparticles improves the strength, stiffness, and hardness of the compacted specimens. The increase in hardness and strength may be attributed to the inherent hardness of the nanoparticles, and other phenomena such as thermal mismatch and crack shielding. Nevertheless, clustering of the nanoparticles at aluminum particle boundaries make these regions become a source of concentrated stress, which reduces the load carrying capacity of the compacted nanocomposite. [ABSTRACT FROM AUTHOR]

Effective stress is one of the most important parameters which strongly affects pore volume compressibility curve, which is used in assessing the reservoir rock properties. It causes change in porosity as well as permeability of the reservoir rocks. In the present study, pore volume compressibility characteristics of the reservoir rocks at different effective stresses were used to derive the relationship of porosity and permeability with the effective stress. To this end, analytical processes for deriving the porosity-stress and permeability-stress relationships are discussed in relation to the reservoir rocks. As a result, a porosity-stress formulation is proposed which is in good agreement with the experimental data. Also, two formulas are proposed for permeability-stress relationship; one on the base of Kozeny-Carman permeability-porosity model and the other one is based on a differential form of permeability-porosity relationship. After calibrating the required coefficients for one sandstone and three limestones, it was concluded that the first permeability-stress model is the upper bound correlation while the latter is the lower bound. Furthermore, it is shown that the latter has better agreement to the real experimental data of the sansdstone samples, while the first one is close to the experimental observations from limestone samples. Also, it is concluded that structure of pores is a key factor on permeability-stress relationship, so that there is a significant difference between the experimental data and the proposed relationship for a limestone sample with vuggy pore spaces. [ABSTRACT FROM AUTHOR]

The purposes of this study were to determine normal value of glycated hemoglobin in Persian cats and to investigate its relation to fasting plasma glucose. Blood samples were collected from 67 clinically healthy adult Persian cats (32 males and 35 females). After separation and washing of red blood cells, hemolysate was prepared and subjected to weak cation exchange chromatography for determination of glycosylated hemoglobin. Glucose was measured in fasting plasma samples (after 10-12 h of fasting) using glucose oxidase method. Glycosylated hemoglobin % in the studied cats was 1.56 ± 0.47 in males and 1.61 ± 0.52 in females. Fasting plasma glucoses were 88.3 ± 10.2 and 90.8 ± 11.5 mg/dl in males and females, respectively. Glycosylated hemoglobin % and plasma glucose strongly correlated together ( r = 0.79, p < 0.001). Three cats with persistent high fasting plasma glucose showing glycosylated hemoglobin percentage of 2.6, 2.8, and 2.9 % which exceeded the upper limit of the normal value obtained in this study were found. We concluded that glycosylated hemoglobin % is a good indicator of fasting plasma glucose, and its determination can be considered as a method for diabetes screening in Persian cats. Considering three cats with persistent high fasting plasma glucose and glycosylated hemoglobin percent, we concluded that glycosylated hemoglobin percent could be a good biochemical test for screening or diagnosis diabetes in cats. [ABSTRACT FROM AUTHOR]