Key Engineering Materials Vol. 917

Abstract: Natural fibres have gained huge attention of researchers in the field of composite manufacturing due to its low cost, biodegradability, availability and high performance. However, due to its high hydroxyl content of cellulose, natural fibre is susceptible to water absorption which invariably adversely affects properties of the composite. Researchers have proved that nano-materials such as nanoclay mixed with the polymer composites can overcome the problem. This study investigates tensile strength and microstructural property of tigernut fibres reinforced polymer composites tailored to automotive application. Tigernut fibres mixed with nanoclay of size 50≤µm, were used to reinforce epoxy in three levels of loading 2, 4, 6 % respectively. The composite was prepared by shear mixing of polymer and the reinforcements, followed by lamination and curing of the composite. The tensile strength and microstructural property of the composites produced were examined. The results show that tensile strength increases as the percentage weight fraction of the reinforcement increases. The microstructures show good interfacial adhesion between reinforcement and polymer matrix. Tigernut fibre show a sustainable material useful for automotive applications.

Abstract: Conductive polymer composites (CPCs) based on polypropylene (PP)/epoxy (EP) and high-density polyethylene (HDPE)/EP blends filled with synthetic graphite (SG) were produced and characterized to explore their potential for high electrical conductivity applications. The polymer blends were chosen as matrices due to their immiscibility and potential to enable co-continuous morphology formation and preferential distribution of filler, which allows formation of maximized conducting networks. In-plane and through-plane resistivities of PP/EP/SG composites decreased from 0.083 Ω.cm to 0.015 Ω.cm and 10.16 Ω.cm to 0.31 Ω.cm, respectively, while for HDPE/EP/SG composites, in-plane and through-plane resistivities decreased from 0.086 Ω.cm to 0.014 Ω.cm and 5.02 Ω.cm to 0.24 Ω.cm, respectively, when SG content was increased from 30 to 80 wt%. The immiscible blend-based composites produced in this study have the potential to achieve significantly higher conductivity than filled single polymers due to concentration of filler in one of the polymer phases and the co-continuous structure of the blends. Also, resistivity anisotropy of the PP/EP/SG and HDPE/EP/SG composites generally decreased with increase in SG content, with HDPE/EP/SG composites showing lower resistivity anisotropy than PP/EP/SG composites at the same SG content.

Abstract: The application of short-term packaging plastics that are biodegradable and possess the same or even greater mechanical properties as regular synthetic plastics is on the rise. These plastics, when disposed, are acted upon by microorganisms that are present naturally in soil and primarily release water and carbon dioxide into the atmosphere. In this study bioplastics was created using banana peel starch and LDPE coupled with plasticizers such as palm oil and glycerol, mechanical properties of the newly created bioplastic were studied. Furthermore, the characterization of the starch particles derived from renewable source were carried out using EDX and SEM. The biodegradation studies using glycerol as a plasticizer showed that 95%-LDPE breakdown occurred by 4.27% after 7 days, 17.7% after 14 days, and finally 25.77% after 28 days. However, when Palm Oil was used as a plasticizer, 95% -LDPE degradation occurred at 1.16% after 7 days, 2.57% after 14 days, and 5.15% after 28 days. This indicated that glycerol-plasticized LDPE-Starch sheets degraded at a quicker pace than palm oil-plasticized LDPE-Starch sheets. Finally, this study revealed that glycerol-plasticized LDPE-Starch sheets have better physiochemical properties (compressive and tensile stress) than palm oil-plasticized LDPE-Starch sheets. Keywords: Biodegradable; Plastic Sheet; Polyethylene (LDPE); Banana; Starch;

Abstract: The utilization of environmentally sustainable agro-waste as Natural fibers (NF) for reinforcement in polymer bio-composites has opened up a new path for materials development. Investigation has advocated that alterations of fiber surface by either physical or chemical techniques, enhances the efficacy of NF reinforced polymer composite. plantain (Musa paradisiacal) fiber (PF) isolated from plantain pseudo steam was treated with potassium permanganate in acetone in this investigation. Using a manual lay-up and compression moulding approach, modified and unmodified fibers were employed to manufacture a NF/polyester resin bio-composite. Surface morphology shows surface roughness of PF surface after treatments. The plantain fiber bio-composites (PFB) reinforced with modified fiber shows improvement in mechanical strength under optimal conditions, providing possibilities and durability for use in technical and structural

Abstract: One valid way to access the state of knowledge in a specific research area is by assessing the availability of quality publications in that research area. In this work, we assess the level of high entropy research in Africa considering that it is a hot topic in the field of materials engineering. Precedent on the independent studies of Cantor and Yeh, the conventional alloying techniques are evolving towards the high entropy approach. To determine the extent of high entropy research in Africa, SCOPUS database was used following specific keywords searches. The result ranked South Africa as the most publisher of high entropy alloy-related articles in Africa followed by Egypt then Kenya, Nigeria and Algeria. Notably, most high entropy alloy articles published from South Africa and Egypt are within the last two years. In South Africa, the high entropy alloys are majorly fabricated via arc melting, spark plasma sintering and laser deposition techniques while Egypt shows proficiency in studies focusing on mechanical alloying, sintering and casting processes for high entropy alloys. Conclusively, the research output from Africa is still lagging when compared to those of other continents however, maximizing the limited infrastructure within Africa and improving collaborations will go a long way towards improving Africa’s research output on high entropy alloys.

Abstract: The structural integrity of ASTM P92 steel welded joints is of concern due to the Type IV cracking associated with the heat-affected zone (HAZ). Two HAZ treatments were done on P92 steel using a Gleeble^® 3500 thermo-mechanical simulator at 900°C (intercritical HAZ) and 950°C (fine-grained HAZ). Followed by post-weld heat treatment (PWHT) of the samples in two sets:: a conventional PWHT at 760°C for 2 hours followed by air cooling; or re-austenitisation at 1050°C for 40 minutes then air cooling, followed PWHT. After conventional PWHT, the HAZ simulated at 950°C had the lowest toughness (108J) than the base metal (130J). After the heat treatments, samples that underwent a 900°C HAZ simulation had higher Charpy toughness (improved from 130-208 ± 6J) and lower hardness (decreased from 234.4-222.3HV_0.5) than those at 950°C. The microstructures had lath martensite with differing precipitate densities depending on the thermal treatment. Keywords: P92 steel, heat affected zone, post-weld heat treatment, precipitates

Abstract: Critical investigation of strength properties of materials is required in Engineering practice to ensure an enhanced service life. Globally, industrialists are struggling to increase cost savings from lost production due to the failure of machine, while customers are concerned about the safety and reliability of the products. Hammer mills are prone to various modes of failure like chemical failure, erosive failure, abrasive failure and fatigue failure. The effect of these failure modes is always detrimental to the operation of the machine and its efficiency. Hence, forensic investigation is essential to determine the failure modes and their effects on hammer mills for bone crushing. Field investigation was carried out to monitor the hammer mill in operation for 12 months with a production of 20 bags per hour. The total production per day for 8 hours is expected to be 160 bags at a given speed. Thus, the cost of machine downtime on production is huge. The Pareto method was used to determine the effect of downtime on revenue and production for a period of one year. The hours of failure were between 1 to 2 hours per day. The loss in revenue was calculated using the variation of number of failure with time, as obtained from hammer mill. The outcome showed that hammers investigated failed as a result of abrasive wear, fatigue, impact, and chemical wear, respectively. The cost of downtime was found to be $ 37,745,809,920.00 CAD for the period of study. Based on findings, wide ranging factors are required to evaluate the performance of the hammer mill for improved productivity and efficiency. These are proper material selection, design and appropriate operational parameters. However, there is need for optimisation of the hammer material via heat treatment methods as this will reduce the yearly cost of production, downtime of the milling machine for bone crushing as well as improvement in productivity.

Abstract: Mild steel material has broad application in marine construction, due to their availability, low cost, and high tensile strength. Nevertheless, the major limitation of mild steel is its low corrosion resistance. The use of eco-friendly inhibitors in protecting mild steel from aggressive media is one of the cheap and practical means competing with conventional phosphate and chromate inhibitors. Herein, the synergism corrosion inhibition effects between key lime and chlorpheniramine drug were examined as sustainable inhibitors for mild steel in 24.5 M NaCl solutions through electrochemical measurement, and morphology of the same was characterized using scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy (SEM/EDX). The electrochemical investigations revealed that in the presence of 2ml key lime and 8ml chlorpheniramine drug the optimum inhibitive efficiency of 81.82% was achieved, this is connected to the protecting layer build-up on the surface of the mild steel, thus, blocking the harsh ion diffusion pathway. The polarization plot shows that the inhibitors complex the deposition led to the corrosion inhibition mixed-type mechanisms. The films formed on the mild steel surface were proved by the SEM/EDX result. The adsorption result shows that the inhibitors fit the Langmuir adsorption isotherm. Keywords: Synergistic effect, sustainable corrosion inhibition, NaCl solution, electrochemical techniques, mild steel

Abstract: The reinforced composite coating has been proven to offer outstanding properties and increased component life span in service. Thus, its development has found a significant place in advanced engineering applications. This study aims to reinforce Zinc-Zinc Oxide composite coatings with an organic and sustainable, eco-friendly product, scales of Micropogonias undulatus (M. undulatus) anti-corrosion composite coating, for mild steel protection in service. The coating was developed via the electrolytic deposition route. The effects of the process parameter, deposition time, on the morphology and electrochemical properties were reported. While the Optical Microscope (O.M.) and Scanning Electron microscopy (S.E.M.) equipped with Energy Dispersive Spectroscopy (E.D.S.) were used for structural study, the PGSTAT 30 potentiostat linked to the electrochemical software NOVA 1.8 was used for the corrosion polarisation studies. The result showed excellent coating adhesion, substrate protection and remarkable corrosion resistant attributes with the Zn-ZnO-M. undulatus scales nanoparticulate coatings. The result also revealed that the deposition done at 25 minutes had the best and most enhanced anti-corrosion attributes.