Key Engineering Materials Vol. 911

Abstract: Nanocomposites (NCs) (100-x) SrFe₁₂O₁₉/x Co (x = 10, 20, and 30 wt. %) were produced using the high energy ball-milling (HEBM) process. The effects of hard/semi-hard ratio and annealing temperature (800, 900, and 1000 °C) on the exchange-spring in magnetic NCs were discussed. X-ray diffraction examination showed the coexistence of M-type hexaferrite SrFe₁₂O₁₉ (SFO) as the hard phase and CoFe₂O₄ spinel ferrite (CFO) as the semi-hard phase. Using a scanning electron microscope (SEM), the morphology and elemental analysis of the NCs were analyzed. The magnetic performances were investigated via a vibrating sample magnetometer at room temperature. With increasing the CFO content and annealing temperature, the hysteresis loop became narrower and possessed semi-hard magnetic properties. The 10 wt. % Co NCs annealed at 800 °C had the highest coercivity of H_c = 4.2 kOe. These results are correlated with switching field distribution plots that have indicated the efficient exchange-spring between SFO and CFO phases NCs annealed at 800 °C. The studied samples can be a promising candidate in permanent magnets and magnetic recording media applications.

Abstract: Nb₂O₅ has recently been considered as one of the oxides thin films that attracts a noticeable attraction by scientific prospective aspects. Its usefulness in a wide practical applications range such as in optoelectronic devices, optical coatings, catalysis, gas sensors, photocell, electrochromics, photoelectrodes, Ec devices, microelectronics and in the medical field paid researchers attention to synthesize it by various methods like sol.gel, electrodeposition, chemical vapor deposition etc. Among those, Pulsed laser deposition technique has achieved an effective improvements. In this paper, we aim to revise increasing significance of Nb₂O₅ supported by previous applications and a further possible future outlook.

Abstract: Polarisation methods, and Open circuit potential measurements have been utilized to evaluate the impact of heat remediation on the corrosion characteristics of CuAlNi shape memory alloy in 3.5 percent NaCl solutions. CuAlNi alloy specimens were investigated in their as-sintered condition and following a thermal remediation processing that included annealing at 900 °C for 60 min associated with water quenching, and 200-degree centigrade for 30 hrs. and rapid cooling in iced water. The enhancement in polarisation resistance and reduction in corrosion rate of heat-treated CuAlNi alloy further suggests that heat remediation has a positive effect on CuAlNi alloy corrosion resistance. After measurements of polarisation, optical microscopy, SEM/EDX, and XRD examination of specimen surfaces reveal the presence of corrosion damage on the electrode surfaces, with CuCl2, AlCl3, and Cu2Cl (OH)3 compounds as surface corrosion products..

Abstract: In this study, an experimental investigation of the effect of addition of Alumina (Al₂O₃), Zinc Oxide (ZnO), and Silicon Oxide (SiO₂) particles powders on the mechanical behavior and crystallinity of the PLA films was carried. Granulated of Polylactic acid (PLA) and ceramic powders with different concentrations were prepared to form PLA/ZnO and PLA/ZnO-SiO₂-Al₂O₃ composites films using a solvent casting process. Morphology of PLA and composite films were examined by optical microscopy, chemical and crystal structures of composites are analyzed by (ATR-FTIR) spectroscopy and XRD techniques. Tensile strength and young modulus are determined by traction test. The obtained result by optical microscopy shows the micrograph of PLA samples with different composition are evenly distributed on the film surface. The intensity of the absorption band located at 754 cm^-1 which correspond to the crystalline phase of PLA is verified by the ATR-FTIR characterization. The XRD diffraction shows that the ceramic particles influence on the peaks intensity of PLA films localized at 19.5 ° C and 22.5 ° C, which indicate an augmentation in the crystallinity of the composite films. Mechanical tests show Tensile strength and Elasticity modulus are improved after the addition of Oxide Particles to Polylactic acid films.

Abstract: The sintering at (1.35x103) °C for 90 minutes under argon gas atmosphere formed a nickel aluminide NiAl-based composite strengthened with yttrium oxide Y₂O₃ with the addition of cobalt in the current sample. (ASTM E140 – 12b) was used to perform the Brinell hardness test. The addition of cobalt increases the hardness of the (NiAl-Y₂O₃) composite. The hardness of NiAl-30Y₂O₃ composite improved from 341HB to 359HB after 1.5 wt.% Co was added, although the hardness improved to (381-383)HB after 2-2.5 percent Co was added. According to the findings of the wear examination, the inclusion of cobalt decreases the wear intensity of NiAl-30Y₂O₃, according to the findings of the wear examination. The adhesion wear rate reduces from 7.61 * 10^-6 gr / cm to 6.72 * 10^-6 gr / cm when 1.5 wt. percent Co is added, thus inserting 2-2.5 wt. percent Co reduces the rate to 5.87* 10^-6 – 5.22* 10^-6 gr /cm.

Abstract: The present study has been conducted in order to obtain iron nitrides layer on AISI4140 steel by using plasma nitriding treatment. As one of several parameters of this process, the nitrogen rate ranging from 10 to 70% with a step of 20% was chosen. The structure, the morphology, the thickness and the hardness of iron nitrides layer were investigated. As a result, the improvement of surface hardness of nitrided steel was identified related with the increase of compound layer thickness due to the increase of activation rate. The steel substrate treated at high activation rate presents hardness 3 times higher than that of untreated steel.

Abstract: The use of zinc coatings deposited onto steel is one of the most important commercial processing techniques employed to protect steel components exposed to severe corrosive environments. Our objective is to improve the coated galvanizing steel used as irrigation tube in the agriculture field. After the best mechanical and chemical preparation, the substrates of this steel were galvanized by immersion in a molten zinc bath heated at 450°C during 15 min. the coated steel substrates underwent an annealing treatment in classical furnace heated at 350 °C for various holding times. This research work is to investigate the time effect of annealing treatment on intermetallic compounds of coatings obtained by hot dip galvanizing steel. For this purpose, several characterization means are used to evaluate the change effected by the annealing time on the phases of galvanizing coating. The kinetic growth of each layer relates the thickness to the annealing time by a simple power law. The treatment of annealing at temperature of 350 °C and holding time of 150 min can changed the structural and mechanical properties of coating phases. The gamma and delta layers presented the hard inner layers became relatively soft phases which would not lead to cracking and detachment of the coating.

Abstract: In this paper, the thermal behavior of concrete blocks with different rubber ratios was examined experimentally. The rubber of 0%, 5%, 10%, 15%, and 20% used instead of fine aggregate in a concrete block raw materials. The size of the rubber granules used in this study is between 0-1 mm. The concrete approved mixing ratios are 1:2:1. The indoor solar simulator with 700 w/m² light intensity was applied on the external surface of each block and thermocouples were used to measure the temperature on the external and internal surfaces. The other block surfaces are insulated. The results indicated that the use of rubber aggregate with the concrete block reduced the inner surface temperature by increasing the thermal resistance of the heat flux. ​For 20% rubber added, produce 8.5% low-weighted construction materials and with high thermal resistance that works to save energy consumed in the building sector.

Abstract: The article describes a new method to use biopolymers (Nano starch) as an alternative to mineral admixtures in improving concrete properties, producing sustainable concrete, and reducing CO₂ emissions in the atmosphere by partial replacement of cement with silica fume. The impact of nano starch as a biopolymer on certain properties of silica fume concrete In the fresh state (slump and fresh density) and In the hardened state (compressive strength, splitting tensile strength) at 7 and 28 days was researched. It has been added to silica fume concrete in various percentages of (0.5%, 1%, and 1.5%) by the weight of cement. The mix proportions were (1:2.3:2.3) (cement: sand: gravel) respectively, for all blends w/c equal 0.47, and constant percentage of ( silica fume of 15%, and superplasticizer of 0.75 percent) by the weight of cement. According to the findings, the optimal starch addition was 0.5%, which resulted in a 34% increase in compressive strength and a 31% and 21% increase in splitting tensile and flexural strength of concrete, respectively. Slump increased by 19%, and fresh density increased by 4% when the starch powder was added at a concentration of 1.5%.

Abstract: The tire manufacturing sector occupies a significant portion of the global economy. The production of vehicle tires requires the utilization of different raw and processed materials. Steel beads are one of these main ingredients, used to reinforce the treads and sidewalls of car tires. In this study, the effect of incorporating steel fibers cut from discarded bead wire (DBW) during the tire manufacturing process on the rheological, mechanical, and flexural toughness of high-strength self-compacting concrete (SCC) was investigated. Four SCC mixes were prepared with four discarded bead wires, at volume fractions of 0%, 0.3%, 0.6%, and 1%. Four lengths of the discarded bead wires were used in the term of hybridization: 10, 20, 30, and 35 mm. These were mixed together, with each length comprising 25% of the total. Investigations of fresh and hardened concrete properties were carried out. The results showed that discarded bead wires affected the rheological properties of the high-strength SCC adversely, causing a considerable reduction in slump flow and passing ability and an increase in T500 and V-funnel time, and enhancing segregation resistance. On the other hand, the mechanical properties, such as compressive strength and splitting tensile strength were improved significantly with the inclusion of the discarded bead wire. Moreover, investigations of flexural toughness based on ASTM requirements were conducted. Overall, the presence of different lengths of the discarded bead wire helped to transfer the load from the cementitious matrix to the short fibers, and then to the long ones, leading to the enhanced energy absorption capacity of high-strength SCC.