Department of Materials Science and Engineering

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    Who is marginalized in energy justice? Amplifying community leader perspectives of energy transitions in Ghana
    (Energy Research & Social Science, 2021) Baker, E.; Nock, D.; Dodoo-Arhin, D.; et al.
    There is a divide in energy access studies, between technologically-focused modeling papers in engineering and economics, and energy justice frameworks and principles grounded in social sciences. Quantitative computational models are necessary when analyzing energy, and more specifically electricity, systems, as they are technologically-complex systems that can diverge from intuitive patterns. To assure energy justice, these models must be reflective of, and informative to, a wide range of stakeholders, including households and communities alongside utilities, governments, and others. Yet, moving from a qualitative understanding of pref erences to quantitative modeling is challenging. In this perspective piece, we pilot the use of the value-focused thinking framework to inform stakeholder engagement. The result is a strategic objective hierarchy that highlights the tradeoffs and the social, economic and technological factors that need to be measured in models. We apply the process in Ghana, using a survey, stakeholder workshops, and follow-up interviews to uncover key tradeoffs and stakeholder-derived ob jectives. We discuss three key areas that have been rarely, if ever, well-represented in energy models: (1) the relationship between the dynamics of electricity end-use and the technology and economic structure of the system; (2) explicit tradeoffs between electricity access, cost, and reliability as defined by stakeholders; and (3) the definition of new objectives, such as minimizing hazards related to theft. We conclude that this model of engagement provides an opportunity to tie together rigorous qualitative analysis and stakeholder engagement with crucial quantitative models of the electricity system.
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    Multicomponent Photocatalytic-Dispersant System for Oil Spill Remediation
    (ACS Omega, 2024) Gbogbo, S.; Nyankson, E.; Agyei-Tuffour, B.; et al.
    In the present work, the potential application of a fabricated halloysite nanotubes-Ag-TiO2 (HNT-Ag-TiO2) compo site loaded with a binary surfactant mixture made up of lecithin and Tween 80 (LT80) in remediating oil spillages was examined. The as-prepared Ag-TiO2 that was used in the fabrication of the HNT-Ag-TiO2-LT80 composite was characterized by X-ray diffraction, Raman spectroscopy, UV−vis and diffuse reflectance spectroscopy, CV analyses, and SEM-EDX. The synthesized composite was also characterized by thermogravimetric analysis, Fourier-transform infrared spectroscopy, and scanning electron microscopy-energy dispersive X-ray spectroscopy. The synthesized composite was active in both the UV and visible light regions of the electromagnetic spectrum. The oil-remediating potential of the as-prepared composite was examined on crude oil, and aromatics and asphaltene fractions of crude oil. The composite was able to reduce the surface tension, form stable emulsions and smaller oil droplet sizes, and achieve a high dispersion effectiveness of 91.5%. A mixture of each of the crude oil and its fractions and HNT-Ag-TiO2-LT80 was subjected to photodegradation under UV light irradiation. The results from the GC-MS and UV−vis analysis of the photodegraded crude oil revealed that the photocatal composite was able to photodegrade the crude oil, aromatics, and asphaltene fractions of crude oil with the formation of intermediate photodegradation products depicting that the HNT-Ag-TiO2-LT80 has a potential as an oil spill remediation material.
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    Recent Trends in The Use of Nanomaterials for Wastewater Treatment: A Minireview
    (The 2nd International Conference on Multidisciplinary Engineering and Applied Sciences, 2023) Saliu, H.; Annan, E.; Bello, A.
    Man’s life depends on water in many ways. Worldwide industrialization and water resource exploitation have accelerated during the past few decades. Heavy metals and other pollutants, including effluent wastewater, are released into water streams as a result of industrial activity all over the world. Due to their toxicity, these contaminants are thought to be hazardous to both man and the environment and lower the quality of water. Even in low concentrations, heavy metals can be extremely harmful to living things. Numerous methods have been investigated for treating wastewater for many years. However, the discipline of nanotechnology has recently shown the world how to solve the issue of wastewater treatment using creative and practical methods.
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    Vulcanization kinetics and reinforcement behaviour of natural rubber-carbon black composites Addition of Shea-butter versus aromatic oil as plasticizers
    (Heliyon, 2024) Mensah, B.; Onwona-Agyeman, B.; Nsaful, F.; et.al;
    This work is a comparative study between Shea butter (SB) and treated distillate aromatic extract oil (TDAE) as plasticizers in the vulcanization of natural rubber (NR)- carbon black (CB) vulcanizates (—CB—S—NR—). The plasticized CB—S—NR composites extended scorch (Ts2) and optimum (T90) curing times. The delays in crosslinking reaction were suspected to be due to the increased viscosity (ML) and insulation of the reacting species (NR, CB, Sulfur and other curing aids) by the films of plasticizers. This effect increased the activation energy (Ea (KJ/mol)) for vulcanization. The CB—S—NR— without plasticizer SB (SBO) showed higher ML, crosslinking density index (ΔM), rheological strength (MH) and low cure reversion properties than others. In comparison, the SB-loaded CB-S—NR— composites showed improvement in ML, ΔM, T90, with lower Ea (KJ/mol) than TDAE samples. Also, the SB compounds exhibited higher Young’s modulus Eo (MPa) than SBO and TDAE compounds. For instance, the Eo (MPa) of SB5 was over 7 and 1200 % higher than SBO and STD5, respectively. However, —CB—S—NR— filled with TDAE generally showed higher strength (MPa), attributed to stronger CB-NR interactions. Therefore, environmentally friendly SB could replace petroleum-based oils for compounding rubbers.
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    The Use of Recycled Polyethylene in Water-Oil Emulsion for Lightweight Concrete
    (International Journal of Polymer Science, 2024) Nangor, E.; Annan, E.; Konadu, D.S.; Damoah, L.N.W.; et al.
    This study was to determine the suitability of recycled waste polyethylene (WPE) processed into water-oil emulsion for lightweight concrete applications. The processed WPE in the form of polyethylene emulsion (PE-e) is to promote physical interaction between the polymeric material and the cementitious matrix. The PE-e used was also to partially replace concrete mix composition by PE-e_1, PE-e_2.5, PE-e_5, and PE-e_10 percents for reference concrete and to introduce plasticity into the mechanical behaviour of the concrete. The PE was processed into PE-e to promote affinity for water, and this hydrophilicity was prominent in PE-e_1 and PE-e_2.5 percent concretes. Concretes with PE-e_1 and PE-e_2.5 percent formed good miscibility with the cementitious matrix. The density of the PE-e concrete decreased to 13.68% with 10% PE-e at 28 days. The replacement of mix constituents of PE-e_1, PE-e_2.5, and PE-e_5 percent induced elastic to plastic behaviour in the concrete coupled with low water absorption. The FTIR data showed characteristic peaks of 3378 cm-1, 1740 cm-1, and 1148 cm-1 in the PE-e. Using optical microscopy, it was shown that the PE particles were homogenously dispersed in the concrete matrix. The study shows the feasibility of using PE-e_1 percent to produce structural lightweight concrete and up to PE-e_10 percent for nonstructural applications mainly for light, non-load-bearing partitions
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    Fracture and Toughening of Mycelium-based Biocomposites
    (Materials & Design, 2024) Etinosa, P.O.; Salifu, A.A.; Osafo, S.; et al.
    This study presents a combined experimental and analytical study of the fracture behavior and toughening mechanisms of bioprocessed mycelium-based biocomposites. The composites comprise hemicellulose hemp ducts (as nutritional and reinforcing components) intertwined with increasing weight percentages of laterite particles. Single-edge notched fracture experiments and in-situ observations of crack growth were used to explore the ef fects of varying proportions of laterite on the composite resistance-curve behavior. The toughening mechanisms, fracture modes, and crack-microstructure interactions were also elucidated. Since crack-bridging and crack deflection were observed to be the dominant toughening mechanisms, they were modeled using fracture me chanics approaches. Crack-bridging was shown to dominate the toughening at lower weight fractions of laterite (0–20 wt%). However, as the laterite content increases (20–40 wt%), a combination of crack-bridging and crack deflection was observed. Finally, at higher laterite weight fractions (>40 wt%), crack-tip shielding occurred primarily via crack deflection. The fracture mechanics predictions of resistance-curve behavior are shown to be consistent with the experimental measurements. The results suggest that mycelium-based and mycelium-laterite composites can be engineered with tunable fracture toughness. The implications of the results are also discussed for the development of sustainable building materials.
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    Ultrasonic–biogenic synthesis of silver on anodized aluminum with superior antibacterial properties
    (Materials Advances, 2023) Agbe, H.; Sarkar, D.K.; Dodoo-Arhin, D.; et al.
    The design and fabrication of high-touch surfaces with antibacterial properties can reduce microbial burden and subsequent nosocomial infections in a hygiene-critical environment. In the present study, biogenic silver nanoparticles (biogenic Ag-NPs) have been synthesized and deposited in situ on an anodized aluminum oxide surface using an ultrasound-assisted onion extract synthesis process. Morphological features and chemical composition have been characterized using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) spectroscopy, UV-Vis absorption spectroscopy and attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopy. The biogenic Ag-NP-coated anodized aluminum exhibited 100% E. coli bacteria inactivation under 60 minutes of contact
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    Chicken Feather Protein Dispersant for Effective Crude Oil Dispersion in the Marine Environment
    (American Chemical Society, 2023) Adofo, Y.K.; Nyankson, E.; Agyei-Tuffour, B.; et al.
    Various studies report that aside from the adverse impact of crude oil on the marine environment, there is the likelihood that chemical dispersants used on the surface of water as oil-treating agents themselves possess a degree of toxicity, which have additional effects on the environment. To eliminate the subject of toxicity, there are several materials in nature that have the ability to form good emulsions, and such products include protein molecules. In In this study, chicken feathers, which are known to contain ≥90% protein, were used to formulate a novel dispersant to disperse crude oil in seawater (35 ppt). Protein from chicken feathers was extracted and synthesized into the chicken feather protein (CFP) dispersant using deionized water as a solvent. Emulsions formed from CFP-synthesized dispersants were stable over a considerably long period of time, whereas the droplet sizes of the emulsion formed were on the average very small in diameter, making droplet coalescence very slow. The CFP dispersants exhibited moderate surface and interfacial activity at normal seawater salinity. Using the US EPA’s baffled flask test, at 800 and 1000 mg/ml CFP surfactant-to-oil ratios, dispersion effectiveness values of 56.92 and 68.64 vol % were obtained, respectively, which show that CFP has a great potential in crude oil dispersion. Moreover, the acute toxicity test performed on Nile tilapia showed that CFP was practically nontoxic with an LC50 value of more than 100 mg/L after 96 hours of exposure. The results obtained showed that the CFP dispersant is environmentally friendly.
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    Managing Excess Lead Iodide with Functionalized Oxo-Graphene Nanosheets for Stable Perovskite Solar Cells
    (Angewandte Chemie International Edition, 2023) Li, G.; Li, M.; Agyei-Tuffour, B.; et al.
    Stability issues could prevent lead halide perovskite solar cells (PSCs) from commercialization despite it having a comparable power conversion efficiency (PCE) to silicon solar cells. Overcoming drawbacks affecting their long-term stability is gaining incremental importance. Excess lead iodide (PbI2) causes perovskite degradation, although it aids in crystal growth and defect passivation. Herein, we synthesized functionalized oxo-graphene nanosheets (Dec-oxoG NSs) to effectively manage the excess PbI2. Dec-oxoG NSs provide anchoring sites to bind the excess PbI2 and passivate perovskite grain boundaries, thereby reducing charge recombination loss and significantly boosting the extraction of free electrons. The inclusion of Dec-oxoG NSs leads to a PCE of 23.7% in inverted (p-i-n) PSCs. The devices retain 93.8% of their initial efficiency after 1,000 hours of tracking at maximum power points under continuous one-sun illumination and exhibit high stability under thermal and ambient conditions. [*] Dr. G. Li,+ Prof. Dr. M. Li, Y. Tang, Z. Zhang Key Lab for Special Functional Materials of Ministry of Education, National & Local Joint Engineering Research Center for High efficiency Display and Lighting Technology, School of Materials Science and Engineering, Collaborative Innovation Center of Nano Functional Materials and Applications, Henan University Kaifeng 475004 (China) E-mail: mengli@henu.edu.cn Dr. G. Li,+ Prof. Dr. M. Li, Dr. A. Musiienko, F. Akhundova, J. Li, K. Prashanthan, Dr. F. Yang, S. Trofimov, S. Zuo, L. Wu, L. Wang, Dr. Y. Yang, Dr. B. Agyei-Tuffour, Dr. R. W. MacQueen, Dr. B. Naydenov, Dr. T. Unold, Prof. Dr. E. Unger, Prof. Dr. A. Abate Helmholtz-Zentrum Berlin für Materialien und Energie GmbH Hahn-Meitner-Platz 1, 14109 Berlin (Germany) E-mail: antonio.abate@helmholtz-berlin.de Dr. G. Li,+ Prof. Dr. A. Abate Department of Chemistry, Bielefeld University Universitätsstraße 25, 33615 Bielefeld (Germany) Dr. G. Li+ Present address: Institute of Chemical Sciences and Engineering, École Polytechnique Fédérale de Lausanne (EPFL) 1015 Lausanne (Switzerland) Dr. Y. Hu,+ Q. Cao, Prof. Dr. S. Eigler Institute of Chemistry and Biochemistry, Freie Universität Berlin Altensteinstraße 23a, 14195 Berlin (Germany) E-mail: siegfried.eigler@fu-berlin.de Dr. Y. Hu+ CNRS, Immunology, Immunopathology and Therapeutic Chemistry, UPR3572, University of Strasbourg, ISIS 67000 Strasbourg (France) K. Prashanthan Department of Physics, University of Jaffn
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    Flow Improvers and Pipeline Internal Coating Benefits and Limitations with Respect to Pipeline Capacity Enhancement
    (Journal of Advanced Research in Fluid Mechanics and Thermal Sciences, 2023) Okyere, M.S.; Damoah, L.N.W.; Nyankson, E.; Konadu, D.B.
    This article illustrates the outcome of a theoretical examination of applying internal coating and flow improver to gas and liquid pipeline systems. A test case of a 12-inches, 18-inches, 24-inches, 30-inches, 36-inches, and 42-inches diameter gas and liquid transmission pipelines evaluates hypothetically, synergistic use of pipeline internal coating with flow improver to enhance flow rate of a pipeline and minimize internal friction. The improvements in pipeline hydraulics are recognized and the enhancement of pipeline capacity calculated over a broad range of parameters. The hydraulic benefits are presented as percentage increase in pipeline capacity using flow equations. Analysis shows that internal coating of pipelines plus injection of flow improver is hydraulically and economically viable for both gas and liquid pipelines with a typical capacity increase greater than 116%. Corrosion protection and safety is improved with low operating cost.
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    Structure and diffuseness model of solid-liquid interface for binary alloys
    (Results in Physics, 2023) Bensah, Y.D.
    Using the morphological instability at the solid–liquid interface as a basis by the maximum entropy production rate principle (MEPR), a model is presented on the morphological structure and diffuseness of the interface during directional solidification of binary alloys. It is shown that, the independent diffuseness theory of Cahn and the Jackson roughness criterion can be unified at a limiting condition under this new MEPR solidification model. The model under the principle of MEPR is applied to describe the evolution of atomistically smooth and rough interfaces through the evaluation of the size of the solid–liquid interface and the of number atomic layers. The model is tested with data for binary alloys of aluminium, lead, and tin at varying solute concentrations. The results showed strong agreement with available data from experimental measurements.
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    Physico- and biochemical properties of alginates extracted from Ecklonia maxima and Sargassum fluitans using a simple cascade process
    (Springer Science and Business, 2023) Agyei-Tuffour, B.; Darko, C. N.S.; Premarathna, A. D.; et al.
    Alginate fractions from the pelagic Sargassum fluitans (Børgesen) Børgesen and kelp, Ecklonia maxima (Osbeck) Papenfuss sourced from the coastal waters of Ghana and South Africa respectively, were extracted by a simple sequential protocol different from the conventional methods. A total of six different phycocolloids were obtained, with two extracted under ambient conditions (fractions 1A) and the remaining four under hot conditions (fractions 2A and 3A) using ethanol and CaCl2, respectively, for precipitation. These extracts were assessed for variations in their physicochemical properties, tyrosinase inhibition, antioxidation and anticoagulation activities. Molecular weights of the extracts were ~ 58–1506 kDa with their yields ranging between 4.8 to 11.1%. A sequential reduction (up to tenfold) was observed in their total phenolic compounds, proteins and sulphate contents. 1H-NMR analysis of their uronic acid block structure revealed M/G ratios less than 1 for all extracts with dominant FGG and FGGG units depicting guluronic acid rich alginate fractions. Extracts from S. fluitans, notably, showed distinct antioxidation activity comparable to the well-known antioxidants like ascorbic acid. For tyrosinase inhibition, the highest was from S. fluitans fraction 1A (~ 37.1 ± 4.38%). The variations in properties of extracts reported herein, elucidates the possibility of obtaining series of relatively desirable alginate fractions from E. maxima and Ghanaian sourced S. fluitans via this modified extraction process.
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    Comparative analyses of the mechanical and microstructural properties of the weld region of LPG cylinder materials
    (Informa UK Limited, trading as Taylor & Francis Group, 2023) Ardayfio, B.; Ampah-Essel, J.E.; Tetteh, W.; et al.
    Abstract: This paper presents the numerical and experimental results of the mechanical and microstructural properties of liquefied petroleum gas cylinders from local sources. The tensile strength, burst and fracture toughness of the materials were also investigated. The results show that the carbon content for all samples averaged ~0.22 wt% and manganese ~0.76 wt% and the microstructure was largely pearlitic. The tensile strength showed that LPG-C3 recorded high tensile strength of ~ 611 MPa and hardness of ~ 200 HV while LPG-C5 recorded low tensile strength of ~ 450 MPa. The finite element analysis (FEA) showed fracture toughness of ,5 � 105MPa.mm0.5 for LPG-C2 and the energy release rate of ~2 � 106J/m2 for LPG-C5. All samples exhibited high resilience to crack propagation which showed ductile fracture after tensile test. The implications of the results are discussed to elaborate on the influence of carefully controlling the alloying elements of LPG cylinder materials on their mechanical and microstructures during fabrication.
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    A review of prospects and challenges of photocatalytic decomposition of volatile organic compounds (VOCs) under humid environment
    (John Wiley and Sons Inc, 2023) Doo-Arhin, D.; Masresha, G.; Jabasingh, S.A.; et al.
    Abstract Volatile organic compounds (VOCs) are harmful for humans and the surrounding ecosystem. Emissions from these pollutants have caused a signifi cant reduction in air quality, which has an effect on people’s health. Alkanes, alkenes, alcohols, aromatics, and other VOC pollutants have all been broken down by TiO2 photocatalytic processes. Due to several operating inefficiencies and deactivation issues in humid environments, the practical application of photocatalysis has not been realized on a broader scale. The effectiveness of photo-oxidation of VOCs is impacted by a variety of environmental conditions. In the photocatalytic oxidation of the VOCs, relative humidity (RH) is critical. Therefore, it is important to review the recent findings on how humidity affects the photocatalytic breakdown of VOCs in air. To satisfy this need, this work provides a critical review of the related literature with focus on the fun damentals of photocatalysis, photocatalytic degradation of air pollutants, and the influence of humidity on the photocatalytic process degradation for selected air pollutants. It also highlights the kinetic models and typical photocatalytic reactor and supports for VOC removal.
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    Eco-friendly green composites reinforced with recycled polyethylene for engineering applications
    (Springer link, 2023) Annan, E.; Mensah, J.K.; Arthur, E.K.; et al.
    Abstract Polyethylene (PE) and cement are industrial products that promote environmental pollution. These products when exposed on the landfill have tremendous effects on the lives of humanity and other living creatures, including animals. Therefore, this research presents the results of experimental and theoretical modeling of green composites (without the inclusion of cement) reinforced with recycled polyethylene waste for applications in the Mechanical and Civil Engineering industry. The composites are produced using different weight fractions of laterite and molten PE mixed homogeneously to produce unique green composites with excellent mechanical properties. The green composite with 40 wt.% laterites and 60 wt.% PE exhibited the highest compressive strength, flexural strength and fracture toughness of 25 MPa, 7.3 MPa and 0.6M Pa√m, respectively. Additionally, the green composite recorded maximum yield stress of ∼2MP. The maximum yield stress of the green composites falls under the minimum range of yield stress for traditional concrete structures. The SEM images reveal evidence of bonding and ligament bridging in the green composites reinforced with 40 wt.% laterites and 60 wt.% PE. The probability distribution plots show that the polyethylene in the green composites follows the Weibull distribution with low Anderson Darling Statics and p-values greater than significance level of 5%.
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    Electronic and Magnetic Properties of Transition Metal-Doped MoS2 Monolayer: First-Principles Calculations
    (Physica Status Solidi b, 2023) Boakye, D.; Martin, H.; Labik, L.K.; Yaya, A.
    Density functional theory in the framework of generalized gradient approximation (GGA) of Perdew–Burke–Ernzerhof to investigate the effects of some selected transition metal (TM) and rare-earth metal (RE) dopants on the electronic and magnetic properties of a 2D molybdenum disulfide (MoS2) monolayer is reported. The results demonstrate that it is energetically stable to incorporate Ni and Cu in MoS2 structure under Mo-rich conditions. The pristine MoS2 monolayer has a calculated direct bandgap of 1.70 eV and experiences significant reduction in the gap due to the defects. There is observed induced magnetic behavior due to the tight binding effect originating from the localized dopants and the nearest-neighbor Mo atoms, with magnetic moments ranging between 0.82 and 3.00 μB. Some of the dopants result in 100% spin polarization which is useful for engineering spin filter devices on magnetic MoS2 nanostructures.
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    Nanowires for Electrochemical Energy Storage Applications
    (Taylor and Francis Group an Informa Business, 2023) Darkwa, K.M.; Ampong, D.N.; Boamah, R.; et al.
    Electrochemical reactions involve the exchange of electrons and ions at the interfaces between electrodes and an electrolyte allowing supercapacitors to store energy by separating positive and negative charges. Over the past few years, nanowires, as one of the representative one dimensional (1D) nanomaterials, have demonstrated excellent capability for realizing a variety of applications in the fields of energy storage. Moreover, they offer 1D electronic pathways, which are key in charge transport, a large active interface between the electrolyte and electrode, etc. The high aspect ratio property of nanowires provides high surface area thereby enhancing electrolyte interaction with active electrode sites, resulting in increased material utilization, continuous electron transport, reduced resistance to charge flow, and improving electrode conductivity and kinetics. This chapter presents the theory, synthesis, and application of nanowires for electrochemical energy storage (EES) devices. It also highlights the scientific challenges associated with nanowires’ integration into energy storage devices, including reduced coulombic efficiency, capacity decay, and poor cycling, with possible solutions. Finally, a projection into the future direction of nanowire’s appli cation in energy storage devices is presented and discussedElectrochemical reactions involve the exchange of electrons and ions at the interfaces between electrodes and an electrolyte allowing supercapacitors to store energy by separating positive and negative charges. Over the past few years, nanowires, as one of the representative one dimensional (1D) nanomaterials, have demonstrated excellent capability for realizing a variety of applications in the fields of energy storage. Moreover, they offer 1D electronic pathways, which are key in charge transport, a large active interface between the electrolyte and electrode, etc. The high aspect ratio property of nanowires provides high surface area thereby enhancing electrolyte interaction with active electrode sites, resulting in increased material utilization, continuous electron transport, reduced resistance to charge flow, and improving electrode conductivity and kinetics. This chapter presents the theory, synthesis, and application of nanowires for electrochemical energy storage (EES) devices. It also highlights the scientific challenges associated with nanowires’ integration into energy storage devices, including reduced coulombic efficiency, capacity decay, and poor cycling, with possible solutions. Finally, a projection into the future direction of nanowire’s application in energy storage devices is presented and discussed
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    Nanowires for Photonic Applications
    (Taylor and Francis Group an Informa Business, 2023) Agyei-Tuffour, B.; Adzo, E.; Amedalor, R.; et al.
    Nanowires have the potential to be easily integrated into nanoelectronics and nanophotonic systems, which could lead to improved industry performance. Their chemical compositions, lengths, and diameters (structural properties) significantly influence their electronic and optical characteristics. Based on their applications, plasmonic and photonic devices often use dielectric and metallic nanowires. For sensing and light-emitting devices, semiconducting nanowires are used. These characteristics are due to the fact that there are quantum restrictions of the electron in nanowires, which results in inhibition in the energy levels different from in bulk materials. This chapter presents the theory, synthesis, and fabrication of nanowires for use in the photonic industry. Also presented are efforts being made to integrate nanowires as components in photonic structures while highlighting the scientific and technological challenges with their possible solutions. Finally, a projection into the future direction of nanowire application in the photonic industry is also presented and discussed
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    Investigating the Effect of Curing Activators on the Cure Kinetics of Acrylonitrile–Butadiene Rubber Filled with Graphene Oxide and Reduced Graphene Oxides Nanocomposites
    (International Journal of Polymer Science, 2023) Mensah, B.; Onwona-Agyeman, B.; Efav, J.K.; Ofor, R.A.; Zigah, M.; Koranteng, J.; Karikari, M.; Nsaful, F.; Addo, D.A.
    For the first time, acrylonitrile–butadiene rubber (NBR)–graphene oxide (GO) and reduced graphene oxide (rGO) composites were prepared without cure activators: zinc oxide/stearic acid (ZnO/SA) and studied. The vulcanization characteristics of the compounds were systematically studied at 160–190° C, with the aid of rheometer and differential scanning calorimetry (DSC) techniques. NBR revealed rapid curing time (t90) with greater cure rate index compared with NBR–GO/rGO composites for the rheometer measurement. This results were in correspondence with the activation energies Ea (kJ/mol) calculated by Ozawa and Kissinger models of vulcanization kinetics. NBR–rGO obtained reduced t90 and Ea (kJ/mol) than NBR–GO, perhaps due to lower oxygenated groups: epoxide (–C–O–C–), carboxyl (–O–C=O), and hydroxyl (–OH) present. Although, the composites delayed in curing, they significantly recorded high tensile properties with high reinforcing factors than NBR. The order of increasing mechanical properties: NBR < NBR–rGO < NBR–GO followed the same order of increasing crosslinking density. In terms of tensile strength, NBR–GO-1 obtained 62.5% and 18.2% increment than NBR and NBR–rGO-1, respectively. The findings from this study indicate that the absence of ZnO/SA in rubber compounds may slow down curing of rubber–GO/rGO composites and lower networks compared with those containing activators ZnO/SA. However, optimization of ZnO/SA and with desired functional groups on graphene and derivative graphene sheets (GDS) including other proposed factors may enhance the curing speed of rubber–GDS based systems, without compromising their mechanical integrity for advanced applications.
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    Explainable machine learning for predicting the band gaps of ABX3 perovskites
    (Materials Science in Semiconductor Processing, 2023) Obada, D.O.; Dodoo-Arhin, D.; et al.
    In this study, we trained and compared explainable machine learning algorithms for predicting the band gaps of perovskite materials that have the formula ABX3 containing both zero and non-zero band gaps. Six supervised learning models: 5 ensemble learning methods and 1 neural network (CompoundNet) were employed to study the non-linear relationship that exists between the band gap and the characteristics of its constituent elements such as electronegativity, covalent radius, first ionization energy, and row in the periodic table. The machine learning (ML) models were trained on datasets obtained from density functional theory (DFT) calculations. The results show that CatBoost and XGBoost models yielded the least predictive errors and the highest coefficient of determination of R2 ≥ 88% than other approaches in the testing phase. Furthermore, the Shapley Additive Explanation (SHAP) was used for explaining the model based on the elemental composition of each perovskite compound from the physics standpoint, and a novel holistic feature ranking of the explained models was proposed. One key insight gained from the SHAP analysis is that the Pauling electronegativity of the B site cation in the cubic perovskites which characteristically plays an important role in the electronic properties of this class of materials is the feature that contributes most to the prediction of the band gaps. These results reveal the potential of ML to predict materials properties quickly and accurately with datasets useful in the engineering of efficient solar cell devices.