Advances in Science and Technology Vol. 151

Abstract: Strip casting of Al–25%Si was tested using an unequal-diameter twin-roll caster equipped with steel rolls. To increase the cooling ability, the shell thickness was decreased to 6 mm. The solidification length was 180 mm to solidify Al–25%Si, which has large latent heat. 4% Mg was added to Al–25%Si to prevent the strip sticking to the roll without using parting material. A grooved roll was adopted for the upper roll to prevent solidification shrinkage and strip cracking during rolling. Al–25%Si–4%Mg strip could be cast at a roll speed of 10 m/min by these enhancements. The as-cast strip could be hot rolled down to 1 mm. A cross section of the strip was investigated using optical microscopy, and the primary Si and eutectic Si were found to be very fine.

Abstract: A three-wheel caster for the fabrication of thin aluminum alloy wire was designed, assembled and tested. The first aim was to develop a caster more compact than the Properzi continuous caster. The second was to cast thin wires without burrs. The third was for the cast wire to have a cross-sectional area of less than 80 mm². The casting of Al–Mg alloy wire was tested using the developed three-wheel caster, consisting of a large lower casting wheel and two small upper forming wheels whose positions could be independently adjusted. Two types of upper wheels were tested. The casting speed was 6 m/min, and the diameter of lower and upper wheels were 600 and 200 mm, respectively. The wheels were made from copper for the rapid solidification of the molten metal. The focus of this study was on the forming of the semisolid wire by the two upper forming wheels and the ability of the device to cast wire without burrs. The influence of the position of the upper wheels on the wire properties was investigated.

Abstract: SACM 645 nitriding steel is a commercial Cr-M0-Al medium carbon low alloy steel. Due to its good balance of strength, toughness and wear resistance the steel has been widely used for several general-purpose parts. Hot forging is a heat treatment method commonly used to increase the hardness of steel. The temperature and strain rate used in hot forging of steel results in changes in grain shape and size through a mechanism known as recovery, recrystallization and grain growth. There are common problems such as defect, net shape and cracked. The designer lacked of knowledge and understanding of the behavior of materials in hot forging process. This research aimed to study material properties under Hot forging at high temperature and effect of times annealing. Experiment, it was found that at 5 temperature levels, which were 850, 950, 1,050, 1,150 and 1,200 °C and annealing test in furnace temperature constant 800°C, holding time in furnace for 6 different times (1-6 hour). Therefore hot forging and the annealing test after hot forging concluded low temperatures, annealing time less result in small grain sizes and high hardness values. On the other hand, the higher temperature, annealing time long the larger the grain size and the lower the hardness. Consequently, the designer can use the information to improve the hot forging process, annealing determines the material properties of the finished products to the design of the part fabrication process.

Abstract: Inadequate handling and disposal of contaminated industrial waste significantly contribute to environmental pollution. The presence of pollutants, including dyes, in wastewater necessitates the development of innovative remediation techniques. Metal oxide-catalyzed photodegradation capitalizes on the capacity of a dye to absorb light energy, offering a rapid method to break down the dye into less harmful, colorless byproducts. In this work, bimetallic copper-iron oxides with various copper to iron were synthesized for the photodegradation of fuchsine. The photocatalysts were prepared through oxalate precipitation followed by thermal decomposition. Structural analysis revealed a MOF-like structure of the bimetallic oxalate precursors. Thermal decomposition of the oxalates yielded photocatalytic bimetallic copper-iron oxides. Photodegradation studies demonstrated that the addition of copper-iron oxides accelerated the degradation of fuchsine and a higher concentration of CuO enhances the performance of the photocatalyst. Notably, the copper-iron oxide with a 1:1 (CuFe) ratio proved to be the most effective catalyst for the photodegradation of fuchsine. Furthermore, the photodegradation of fuchsine conforms to a pseudo-first order model and exhibits characteristics of a first-order reaction. Our findings emphasize that simple and high-efficiency bimetallic oxide catalysts can be used for water decontamination applications.

Abstract: The water-in-salt method, recognized for regulating metal ion solvation structure, garners attention in secondary batteries for its potential to broaden the electrolyte's operational range and reduce side reactions. However, the understanding of how anion size variations impact metal ion solvation structure remains limited. This study addresses the gap by employing mixed electrolytes with diverse anion sizes, investigating the effects of electrolyte concentration and anion size on the solvation structure of zinc cations crucial in electrochemical reactions. Various analytical techniques, including FT-IR, Raman, and NMR spectroscopy, are utilized. Mixed electrolytes are formulated by dissolving ZnCl₂ and Zn (NO₃)₂ in water (1.0 mol kg^‒1), with the addition of LiCl and LiNO₃ (0.1 to 19.0 mol kg^‒1). FT-IR and Raman analyses reveal weakened hydrogen bonds with increasing electrolyte concentration. Elevated concentration disrupts bonds between Li⁺ ions and water molecules, resulting in alterations in solvation structure. NMR and FT-IR spectra exhibit distinct behaviors, suggesting influences from molecular bonding structure and anion size, intricately linked to the specific salt used in electrolyte preparation.

Abstract: This study investigates the influence of lithium salt on the interfacial reactions that occur between SiO and ethylene carbonate-based solutions in lithium secondary batteries. Electrochemical reactions occurring at a SiO electrode were examined to gain insights into the effects of lithium salts, such as LiPF₆, LiBF₄, LiClO₄, and LiCF₃SO₃, on the interfacial resistance. The SiO electrode exhibited a relatively high reversible capacity and Coulomb efficiency in an electrolyte solution containing LiCF₃SO₃. The interfacial resistance was the highest in the solution containing LiPF₆ and the lowest in the solution containing LiBF₄. The findings from this investigation are expected to offer valuable insights for optimizing the design and performance of lithium secondary batteries by manipulating interfacial reactions.

Abstract: This work evaluates the shear stress in concrete beams with the addition of reinforcing fibers. Since there is no established standard in Peru, it was proposed to use the "JSCE-SF6" test method recommended by the Japanese Society of Civil Engineers and an analytical model to determine the shear strength of concrete with fibers. For this purpose, steel and polypropylene fibers were used in the proportions of 3kg, 5kg, 7kg and 9kg for each design. The main test was the shear test based on Japanese standards, however, secondary tests such as compression and flexural tests were also performed. The results obtained showed the contribution of the fibers in the three tests performed. In the shear test, the polypropylene fibers obtained a higher shear strength in all their mix designs in the same proportions. Additionally, an analytical model is proposed to determine the shear stress in concrete with fibers, which includes as variables the compressive strength, the mass fraction of fibers and the tensile strength of the fibers, which generates acceptable values close to those obtained experimentally with the Japanese Standard Shear Test.

Abstract: Reinforced concrete exposed to high temperatures, such as in a fire, poses a serious threat to buildings by weakening the concrete and reducing the structure's stiffness. Therefore, the article investigated the structural behavior of reinforced concrete when subjected to elevated temperatures in Peru, where many structures are not designed to withstand high temperatures, leading to irreparable damages such as loss of human lives and changes in material properties. To enhance the heat resistance of reinforced concrete, carbon fibers were added, and a percentage of ultra-high-strength concrete was incorporated. The material was analyzed using the finite element method. Different frames were evaluated, focusing on the use of matrices and nodes. The proposal involved adding new materials; carbon fibers were added at 0.06%, and ultra-high-strength concrete at 20%. These quantities were chosen based on the researched articles. First, the properties of each material were defined and input into the software. Then, a temperature ranges from 100°C to 1000°C was defined. The results were evaluated, and improvement percentages regarding displacements due to applied loads were determined. The findings indicate a 33.05% improvement in distributed load and temperature-induced loads between 100°C to 1000°C, varying between 17% and 6.56% respectively. It was concluded that higher temperatures result in more significant damages such as changes in color, deflections, and loss of stiffness, increasing the probability of collapse in a shorter time frame. In conclusion, the use of the proposed materials enhances resistance and reduces deflections when subjected to various types of loads.

Abstract: In structural columns, honeycombs are very common in small and big works. This problem is caused by poor consolidation of the concrete that increases the probability of honeycombs (voids left in concrete). These imply costs incurred and affect the work schedule. An exhaustive search is carried out regarding methods in the scientific literature and materials with respect to their availability in the market related to the problem. In this way, it was found that the design of a self-compacting concrete using the ACI 237R-07 with the use of a supplementary cementitious material aims to be a solution to this problem. Rice husk ashes contain silicon oxide and aluminates. These elements improve or increase the strength of the concrete, offer workability and fluidity properties. It was found that with a 5% replacement, 735 mm and 730 mm of slump flow and J-ring were obtained, respectively. Additionally, the V-funnel time was 9.58 seconds. The use of RHA positively increased the values of the measured tests with respect to the standard, thereby improving the workability and stability properties.