Key Engineering Materials Vol. 841

Abstract: Effect of the plating thicknesses on tensile and fatigue properties of hot-dip galvanized steel at room temperature was evaluated. The galvanized steel with thickness of 100 μm and 200 μm were prepared. Both microstructures of η-phase and δ₁-phase were similar with each other. In the comparison with the galvanized steel with thickness of 100 μm, the microstructure of ζ-phase for the galvanized steel with thickness of 200 μm was blunt columnar structure due to long immersion time. Tensile and fatigue strengths for a galvanized steel are sensitive to the microstructure of the galvanized layer. The tensile strength and the strength of fatigue limit for the galvanized steel with thickness of 200 μm were smaller than that of 100 μm. In the galvanized steel with thickness of 200 μm, the peeling at plating layer easily occurred. The exfoliated sites have the potential to become subcracks. As the result, the main crack may propagate at early cycles.

Abstract: Nanotechnology is receiving widespread attention in many industrial sectors, including construction material industry. One of the nano-scale admixtures, which has the potential to enhance the performance of cement and concrete, is known as Nano-silica (n-SiO₂). In general, fly ash (FA) is currently used in cement and concrete industry for replacing the consumption of Portland cement (OPC) to reduce its production cost as well as to improve some specific required properties, e.g., workability or low internal heat liberation. However, the strength of hardened Portland cement is normally decreased when a higher amount of fly ash is presented. This research article is therefore pointed on the influence of nano-silica dosage on the properties of cement paste incorporating with high calcium fly ash. Seven different proportions of OPC:FA were prepared viz. 100:0, 80:20, 60:40, 50:50, 40:60, 20:80 and 0:100 by weight. The commercial grade nano-silica (in liquid form) was used as an admixture in those mixes by 0.0, 0.5, 1.0 and 1.5 wt% of the mixing water with a water-to-binder (w/b) ratio of 0.30. The results indicated that the addition of n-SiO₂ improved the compressive strength of all mixtures (with and without high calcium FA) as the presence of n-SiO₂ can be a source of silica and easily contribute to an additional formation of CSH in the cementing system, confirmed by the results of XRD analysis. The main findings show a potential approach of using n-SiO₂ as an admixture for cement and concrete construction.

Abstract: Repair mortar (RM) with dense texture and high anti-crack is cost-effective for application onto the surface of concrete structure to effectively delay the detachment of concrete protective layer and the corrosion of steel bars. Here, the effects of ductile fiber and polymer latex on the flexural strength (f_t), compressive strength (f_c), bond strength (f_b), and shrinkage rate (δ_r) of fiber-reinforced polymer repair mortar (FP-RM) were comprehensively studied. Results show, the individual doping of polymer latex can improve the f_t, f_b, and the toughness (the f_t/f_c ratio) of P-RM, and the f_b is increased by 75.78% with respect to the plain mortar, which imply polymer ingredient is essential to P-RM. Some ductile fibers individual dosage also can enhance the f_t, f_c, and δ_r of F-RM, respectively; When the polymer latex and ductile fiber are simultaneously doped into the FP-RM mortar together, the f_t and f_b of FP-RM can be increased up to 9.4MPa, and 2.52MPa, respectively, in tandem with 40.54% reduction of δ_r, showing superior synergy effect.

Abstract: In this study, a liquid gel bandage for wound treatment was synthesized using a combination of tannic acid and polyethylene glycol (TAPE). Agar was added as a stabilizer based on the physical properties of the formed product. Ethanol was chosen as solvent based on the resulting drying rate and mixing consistency. The liquid bandage was characterized in terms of its drying, adhesion, and swelling. Also, its antimicrobial and cytotoxic properties were evaluated. The final formulation had a drying time of 5 minutes, a T-peel adhesion yield point of 591.6 Pa, and a swelling ratio of 64%. The gel was also observed to be anti-microbial towards both S. aureus and E. coli, as well as exhibiting cytotoxic effects. Overall, the gel proved to have comparable properties to previously studied liquid bandages yet can be produced at a significantly lower cost.

Abstract: In this study, the graphene was prepared by chemical vapor deposition (CVD) method, and then through thermal annealing technique it was firmly coated on and partly diffused into the inner surfaces of journal bearings made from aluminum bronze CuAl10Fe3. The journal bearings without graphene coatings were also prepared with made from aluminum bronze CuAl10Fe3 and tested under the same conditions as the references of comparison. Through frequent start-stop test, the changing laws of coefficient of friction (COF), power consumption, and back temperature rise and wear loss for each journal bearing with or without graphene coating were obtained. The test results showed that graphene coating could significantly reduce the power consumption and wear loss during the start and stop phases.

Abstract: Given that the quality of water supplied to hot water supply systems must meet drinking water requirements, it is also important that the water preparation process is of great importance. The quality of that water is also important in terms of preventing the formation of heat in hot water systems. It is known that the main cause of the formation of water is the presence of calcium and magnesium cations and bicarbonate and sulfate anions in water. The traditional methods for preventing the limescale include the combination of calcium and magnesium cations from the water and replacing them with cations that are not easy to resolve at high temperatures. The quality of water treated by these methods does not meet drinking water requirements. Taking these into account, the Cl-anionizationprocess of drinking water has been developed in high-tech anionite technology. According to this technology, the first water from the city water gridis processed through anionite and activated carbon filters, which are mechanically charged with high anionite. The treated water is then cleaned out of microbes and bacteria through the ultraviolet disinfection equipment and delivered to the operator according to the quality requirements for drinking water. In the chlorine-anionization process, most of the sulfate and bicarbonate anions in water change to chlorine anions and their solidity remains constant. Thus, the density of the limescale-forming anions in the water decreases sharply and it meets the quality indicators of drinking water. High-grade anionite in the filter (8÷12) is regenerated by NaCl solution. The filtration rate of the solution from the anionite is determined depending on the concentration of calcium cations contained in the salt given for regeneration. Regeneration mode is such that the CaCO3 combination does not crumble when the anionite layer is formed. It is known that the temperature of the heated water in the hot water supply system does not exceed (60÷70)°C. In this case, the decomposition of limescale at Hc<2 mg-eq/l (carbonate hardness) is not observed. As carbonate hardness increases to 4 mg/l, the thin layer in the system shows a collapse. The basic element of the proposed technological schemeCl-anionite filter was applied at ADA University in Baku and positive results were obtained. Early observed collapse of pipes has been prevented and the working regime of hot water heaters has improved. A high-performance anionite such as A200EMBCl, which is a major ingredient of the UK's Purelite, and then the Russian-made AB-17-8 high-anionite anions have been used on the device.

Abstract: A portable non-enzymatic electrochemical sensor for malathion detection based on CuFe₂O₄ and reduced graphene oxide nanocomposites was developed. CuFe₂O₄-rGO nanocomposites were synthesized using a facile one-pot co-precipitation method. X-ray diffraction, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy confirmed successful synthesis of the nanocomposites. Square wave voltammetry was performed using a portable potentiostat (CheapStat) and a three-electrode setup in order to determine the electrochemical behavior of the nanocomposite and its interaction with malathion. Maximum inhibition was observed at conditions corresponding to 15% rGO loading, pH 4 buffer solution, and five-minute accumulation time. Calibration of the sensor established a linear detection range of 0.5-8 ppm and a detection limit of 0.992 ± 0.007 ppm. Altogether, the performance parameters indicate good selectivity and potential applicability of the system for malathion monitoring particularly in agricultural products.

Abstract: Slide-burnishing is one of the most powerful processes for microstructural evolution. Here slide-burnishing was performed by a cemented carbide ball loaded and fed on the flat surface of a rotating disk specimen of carbon steel using a lathe machine. This process provides many advantages: burnishing reduces the surface roughness, increases the surface hardness due to grain refinement, improves the wear resistance, and requires no special equipment. Transmission electron microscopy (TEM) observation revealed that nano-crystalline structures in the 10–300 nm grain size range were formed at the burnished sub-surface layer and that grain size increased approximately linearly with depth below the surface due to the strain gradient. High rotation speed in the burnishing process prompted further grain refinement, as evidenced by ultrafine and equiaxed grains in the 10 nm size range at the top surface layer of the specimen burnished at the highest rotational speed. Burnishing increased the indentation hardness of the nano-crystalline layer by a factor of 3.5. The expected linear relationship between hardness and inverse square root of grain size was identified.

Abstract: Production of multi-rifled seamless steel tubes employing cold draw process using multi-rifled mandrel is quite a modern technology. The important characteristic of the tube drawing process, unlike the tube with internal rifling, is the corner filling which influences the dimension accuracy of the internal shape of the tube. In this study, the influence of drawing tool dimensions and mandrel shape on to final rifling filling was investigated. Draw process has been simulated by using the three-dimensional rigid-plastic finite element method (FEM) by using DEFORM 3D software. The results of numerical simulation show that the shape of drawing tools and process conditions have a significant influence on the forming process and final shape and properties of the workpiece.