Key Engineering Materials Vol. 962

Abstract: In this study, the 2024 Al powder with different weight fractions of graphite is mechanically milled using a high-energy ball mill for 3 hours each in the nitrogen environment. The milled powder is compacted at an elevated temperature. X-ray diffraction is used to phase analysis of milled powder as well as compacted specimens. Optical microscopy is used for microstructural analysis and hardness measurements are done for the evaluation of mechanical properties. The hot compacted specimens are also tested for their wear properties. Results show that there is no new phase formed during mechanical milling. But, after hot compaction of the milled powder, Al₂Cu formed due to precipitation. No reaction is observed between the aluminum and the carbon (graphite) after milling as well as hot compaction. Microstructures of all hot compacted specimens are not showing pores, which, signifies full density after compaction. The formation of Al₄C₃ is not observed at any stage of processing. Therefore, graphite is uniformly distributed in all specimens, and the same is observed at grain boundaries of α-Al grains in the microstructures. Hardness increases with the addition of 1 wt.% graphite but it decreases with a further increase in graphite. The wear resistance of 2024 Al with 1 wt% graphite is the highest among all the compositions. The high hardness and wear resistance of 2024Al with 1 wt% graphite is the consequence of precipitation of Al₂Cu during hot compaction and the presence of graphite which creates hindrances in the metal matrix. The presence of free graphite in the vicinity of grain boundaries acts as a solid lubricant which improves wear resistance of 2024 Al.

Abstract: Due to the combination of its numerous excellent mechanical qualities, the flexible iron has been used more and more since its invention in 1948. To develop significantly improved characteristics, the unnecessary investigation is being done. The most recent development in the field of flexible iron, or SG iron, is Austempererd malleable iron. At four different temperatures, two different types of spheroidal graphite (SG) cast iron samples with varying copper weight levels were austempered. The temperatures used for austempering were 200°C, 300°C, 350°C, and 400°C. As a component of the austempering time and temperature, the effect of the austempering process (i.e. time and temperature) on the mechanical characteristics of spheroidal graphite iron was investigated. The progress of spheroidal graphite iron's properties was significantly influenced by the pace of cooling and the extinguishing process. The organisation of different stages during isothermal change under varied austempering settings has also been the focus of XRD analysis. By using SEM, graphite morphology has been focused on. For this investigation, samples were obtained from the castings' focal point for XRD analysis. It was discovered that virtually always, it is possible to discriminate between the ferrite (110) and austenite (111) lines. The ferrite (110) line is growing with expanding austempering time and declining with increasing austempering temperature, whereas the highest power of the austenite (111) line is expanding with expanding temperature. Thus, very precise control of the interaction components (austempering duration and temperature) is required for austempering. The results showed that, when compared to other grades (N1) through the various austempering processes used in this evaluation, ADI containing the alloying component copper (grade N2) achieved crucial mechanical qualities.

Abstract: Microstructure fabrication and chemical surface functionalization with low-surface-energy materials are the key steps to achieve hydrophobic surfaces with high water droplet contact angles (CA). In this work we employed wire Electric Discharge Machining (EDM) as a way to induce microstructure topography on stainless steel 304 coupons. The resulting topography was rendered hydrophobic using trichloro-1H,1H,2H,2H-perfluorooctyl silane (PFOTS) via gas phase deposition. The channels created by machining and PFOTS functionalization facilitate water condensation by increasing nucleation sites and enhancing droplet coalescence. The resulting surface is hydrophobic (CA~140^o) in contrast to the bare stainless steel 304, which is hydrophilic (CA~76^o).

Abstract: In the transportation industry, seat cushions are crucial since they are directly responsible for the comfort and safety of the occupant. In this study, recently developed deproteinized natural rubber (DPNR) latex foam is used to make seat cushions for the first time through the Dunlop batch foaming process. A CONFORMat™ pressure sensor system and a mannequin were used to investigate the pressure-relief performance of seat cushions made from DPNR latex foam. Flexible polyurethane (PU) and memory foam (PM) were used as a comparison. The study found that DPNR latex foam has a lower peak pressure value than PU foam, comparable to PM foam. The vibration transmissibility properties of the foam samples were examined using a UCON VT-9008 vibration machine according to ASTM D3580-95. DPNR latex foam has the lowest attenuation frequency, which could be related to the low stiffness and high resilience properties of the material. Overall, the findings suggest that the novel DPNR latex foam has both excellent pressure-relief and vibration isolation performance, making it an ideal candidate material for seat cushions intended for the transportation industry.

Abstract: Deproteinized natural rubber (DPNR) latex is a modified version of natural rubber (NR) latex that is hypoallergenic and odorless when used in products. However, due to the lack of studies in this field, there are relatively few DPNR latex foam products to date. Our laboratory has developed a novel manufacturing technique that involves a heat-enzymatic reaction followed by a concentration procedure to generate DPNR latex directly from freshly tapped latex and to manufacture a novel DPNR latex foam using the Dunlop batch foaming procedure. To investigate the mechanical properties of the foam, ball-rebound resilience studies and compression tests were conducted on DPNR latex, commercial grade polyurethane (PU) and polyurethane memory (PM) foams as a comparison. Compressive stress-strain study revealed that the hysteresis loss ratio of DPNR latex foam, PU foam, and PM foam is 0.19, 0.66, and 0.86, respectively. DPNR latex foam exhibits the lowest hysteresis loss ratio due to its elastic behavior thus able to store a high amount of energy when under compressed. On the other hand, the rebound resilience of DPNR latex foam, PU foam, and PM foam is 74%, 29%, and 9%, respectively, indicating that DPNR latex foam has the highest rebound resilience. The resilience property is correlated with the elasticity, dimensional stability and durability of foam materials. Thus, DPNR latex foam is suitable for heavy-duty cushion applications including seats for transportation industry.

Abstract: The discovery of Carbon Nanotubes (CNT) has opened the doors for revolutionary applications in the mechanical, aerospace, and electrical sectors. However, to fully utilize the potential of carbon nanotubes, there is a persisting need to identify all sorts of structural modifications that can be observed in any type of manufacturing procedure for CNTs. Thus, the presented study investigates the mechanical properties of CNTs with variable waviness and defect density. Furthermore, the study is performed using classical Molecular Dynamics simulations (MD). The structures are then characterized with single or multiple vacancy defects along the axis of the nanotube structure, which is modeled as wavy structures to replicate their natural structure. After the simulation results were analyzed, it was observed that the increase in the surrounding temperature from 300K to 1500K reduces the overall tensile strength of the CNT sample from 89-47 GPa. However, introducing a single vacancy defect to the same structures was shown to reduce the tensile strength to 41 GPa at 1500K and 62 GPa at 300K.

Abstract: Main initiative of this study is to report the changes occurred in the particle size and distribution of nano-hydroxyapatite powders due to the novel effect of Plant Leaf Mediated Natural Extracts (PLMNEs). Wet-Chemical precipitation method is used to obtain homogeneous nano-hydroxyapatite powders. These nano-hydroxyapatite powders have been synthesized by using different precursors and relative concentrations. The natural extracts used as Natural Stabilizers (NSs) are derived from Soya Leaves (SL) and Spinach Leaves (SpL) for the preparation of nano-hydroxyapatite. Present study reports the morphological changes in nano-hydroxyapatite and has been characterized using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Small Angle X-Ray Scattering (SAXS). Till now no studies have been reported on synthesis of nano-hydroxyapatite using Plant Leaf Mediated Natural Extracts as precursors. The Natural Stabilizers used have been found to show evidence of several medicinal effects.

Abstract: Here in, we report the synthesis and effect of solvents on photoluminescence properties of 1-(2-Methoxy-phenoxymethyl)-benzo[f]chromen-3-one (2-MPBC) and 1-(3-Methoxy-phenoxymethyl)–benzo[f]chromen-3-one (3-MPBC) molecules through Pechmann cyclisation method. The optical properties of coumarins are studied by employing a various solvents with different polarity and refractive index. The values of ground state dipole moment is 0.71D and 0.49D for 2-MPBC and 3-MPBC respectively. It is found that the ground state dipole moments (μ_g) comparatively smaller than excited state dipole moments (μ_e) for the both molecules because of more polar in nature of the excited state. Further, on the basis of solvent polarity parameter ( ), the change in dipole moments (Δμ) is found to 052D and 0.60D for by solvatochromic shift method and 0.61D and 1.23D from theoretical calculation for 2-MPBC and 3-MPBC respectively.

Abstract: In recent years, the EU policy identified the hydrogen as one of the main energy vectors to support the power production from renewable sources. Coherently, electrolysis is suitable to convert energy in hydrogen with no carbon emission and high purity level. Among the electrolysis technologies, the anion exchange membrane (AEM) seems to be promising for the performance and the development potential at relatively high cost. In the present work, AEM electrolysers, and their technological bottlenecks, have been investigated, in comparison with other electrolysers’ technology such as alkaline water electrolysis and proton exchange membranes. Major efforts and improvements are investigated about innovative materials design and the corresponding novel approach as main focus of the present review. In particular, this work evaluated new materials design studies, to enhance membrane resistance due to working cycles at temperatures close to 80 °C in alkaline environment, avoiding the employment of toxic and expensive compounds, such as fluorinated polymers. Different strategies have been explored, as tailored membranes could be designed as, for example, the inclusion of inorganic nanoparticles or the employment of not-fluorinated copolymers could improve membranes resistance and limit their environmental impact and cost. The comparison among materials’ membrane is actually limited by differences in the environmental conditions in which tests have been conducted, thereafter, this work aims to derive reliable information useful to improve the AEM cell efficiency among long-term working periods.