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Item 2D numerical model for heat transfer on a laser deposited high entropy alloy baseplate using Comsol Multiphysics(2021-12) Dada, A; Popoola, P; Mathe, Ntombizodwa R; Adeosun, S; Aramide, OIn an optimization study, cracks were observed in the microstructures of laser-deposited HEAs on a steel baseplate from residual stresses, thus, the optimization of crack-free microstructures was achieved by the optimization of the laser parameters by baseplate preheating attributed to the lowering of the thermal gradients of the deposition process. This study reports the finite element analysis on the temperature distribution by the moving laser modelled to achieve process optimization with the necessary boundary conditions. Simulation has been reported as a facilitating tool in predicting the behaviour of materials during process optimization. Comsol Multiphysics 4.4, was used to create a 2D transient heat transfer time-dependent model to simulate the temperature distribution and the laser heating of the A301 steel baseplate surface and determine the effect of temperature on the optimization process of the alloys. Gaussian profiles were used as the heat source distributed per time. The results are presented in terms of thermal fields and Gaussian temperature profiles. Which show the temperature distribution that occurred in the steel baseplate during fabrication and the high cooling rate of the laser additive manufacturing technique restricted thermal stresses, improving adhesion and facilitating the optimization process.Item Addition of Chromium and its effect on the microstructure and mechanical properties of laser- coated high carbon ferrochrome alloy on mild steel(2021-08) Aramide, BP; Popoola, P; Sadiku, R; Jamiru, T; Pityana, Sisa LLaser cladding is an additive manufacturing technology that can be utilized in surface strengthening, modification, and repair of components that are subjected to adverse working conditions. This can be accomplished by the addition of functionally graded material with a remarkable limit to enhancing an engaged credited property of monolithic material that is superior and better than its monolithic counterparts. Chromium addition to the microstructure of components has been found to increase the electrochemical stability, high-temperature strength and corrosion resistance of laser additive manufactured components. The current study investigates the effect of the extra addition of chromium on the hardness and microstructure of laser coated high carbon ferrochrome FeCrV15 on steel baseplate.Item The adsorption of halogen molecules on Ti (110) surface(2021-01) Tshwane, David M; Modiba, Rosinah; Govender, Gonasagren; Ngoepe, PE; Chauke, RAdsorption of halogen on the metal surface has received much attention due to its technological applications and major relevance for material surface processing, corrosion protection and etching. In this work, first-principle approach was used to investigate the interaction of halogen molecules on Ti (110) surface. The present results revealed that adsorption of the halogen molecule is exothermic and occurs by dissociation bonding. The HF molecule was found to be more thermodynamically stable than the HI molecule. In addition, our results revealed that the adsorption of halogen ions on Ti (110) surface is energetically favourable than the adsorption of halogen molecule. The possible adsorption sites were tested, and the top site position was found to be the most favourable followed by the hollow and bridging site for both halogens. Furthermore, the results showed the linear relationship between adsorption energy strength and charge transfer. Also, the density of states and charge density difference was studied to investigate the electronic interaction. The charge redistribution showed an electron depletion on Ti atom and charge accumulation on the halogen region.Item Adsorption of NH3 and NO2 molecules on sn-doped and undoped ZnO (101) surfaces using density functional theory(2022) Dima, Ratshilumela S; Tshwane, David M; Shingange, Katekani; Modiba, Rosinah; Maluta, NE; Maphanga, Rapela RThe adsorption and interaction mechanisms of gaseous molecules on ZnO surfaces have received considerable attention because of their technological applications in gas sensing. The adsorption behavior of NH3 and NO2 molecules on undoped and Sn-doped ZnO (101) surfaces was investigated using density functional theory. The current findings revealed that both molecules adsorb via chemisorption rather than physisorption, with all the adsorption energy values found to be negative. The calculated adsorption energy revealed that the adsorption of the NH3 molecule on the bare ZnO surface is more energetically favorable than the adsorption of the NO2 molecule. However, a stable adsorption configuration was discovered for the NO2 molecule on the surface of the Sn-doped ZnO surface. Furthermore, the adsorption on the undoped surface increased the work function, while the adsorption on the doped surface decreased. The charge density redistribution showed charge accumulation and depletion on both adsorbent and adsorbate. In addition, the density of states and band structures were studied to investigate the electronic behavior of NH3 and NO2 molecules adsorbed on undoped and Sn-doped ZnO (101) surfaces.Item Adsorption-desorption of F2 diatomic molecule on Ti (100) surface at different coverages(2021-12) Tshwane, David M; Modiba, Rosinah; Govender, Gonasagren; Ngoepe, PE; Chauke, HRFluorine molecules and ions are used as an etchant for metal surface processing. The presence of fluorine significantly influences the electrochemical behaviour on a metal surface, which has major relevance for etching, corrosion, electro-catalysis and galvanic deposition processes. Although the fluorine ions play an important role in metal surface etching, the studies remain limited and unclear, especially at the atomistic scale. In this work, density functional theory is used to investigate the structural and electronic properties of F2 diatomic molecule adsorption on Ti (100) surface at different coverages. Results revealed a dissociative adsorption mechanism of F2 on the Ti (100) surface. Adsorption energy analysis of F2 on Ti (100) surface denotes an exothermic process. Moreover, increasing F2 coverage resulted in the formation of TiF4 and Ti2F6 molecules on the surface. In addition, the calculated heat of formation for TiF4 was found to be more favourable than Ti2F6 species. Calculated desorption energies for TiF4 and Ti2F6 is 11.73 eV/atom and 9.04 eV/atom, suggesting non-spontaneous.Item Analysis of dry sliding wear performance of tribaloy T-800/Tungsten carbide coating deposited via laser cladding assisted with preheating(2022-10) Nyadongo, ST; Olakanmi, EO; Pityana, Sisa LShafts, gears, axles and crankshafts, which are exposed to severe sliding wear environment, are made from wear resistant EN8 medium carbon steel. The wear resistance of EN8 can be enhanced by depositing it with laser cladding assisted with preheat (LCAP) fabricated T-800/WC composite coating. A systematic study via accurate, reproducible ball on disk tests which explores how extreme sliding force and velocity influence wear resistance and mechanism of the coating and the uncoated EN8 is carried out. It was revealed that EN8 substrate has up to six (6) times more special specific wear rate (SSWR) relative to T-800/WC coating. An increase in sliding force increased the SSWR whilst an increase in sliding velocity reduced the SSWR for the LCAP coating. Alumina (Al2O3) counter wear body exhibited the highest SSWR compared to silicon carbide (SiC) and silicon nitride (Si3N4) counter wear body on both T-800/WC and EN8. Oxidative and abrasive wear mechanisms were evident on the coating. A wear mechanism for the T-800/WC was deduced which showed abrasive wear, oxide layer formation, breaking of the formed oxide layer and back to abrasive wear during dry sliding wear.Item Anomaly detection monitoring system for healthcare(2021-01) Boloka, Tlou J; Crafford, Gerhardus J; Mokuwe, Mamuku W; Van Eden, BeatriceMost developing countries suffer from inadequate health care facilities and a lack of medical practitioners as most of them emigrate to developed countries. The outbreak of the COVID-19 pandemic has left these countries more vulnerable to facing the worse outcome of the pandemic. This necessitates the need for a system that continuously monitors patient status and detects how their physiological variables will change over time. As a result, it will reduce the rate of mortality and mitigate the need for medical practitioners to monitor patients continuously. In this work, we show how an autoencoder and extreme gradient boosting can be merged to forecast physiological variables of a patient and detect anomalies and their level of divergence. An accurate detection of current and future anomalies will enable remedial action to be taken by medical practitioners at the right time and possibly save lives.Item Challenges in machining of advanced materials(CRC Press, 2022-05) Mathabathe, Maria N; Bolokang, Amogelang S; Gajrani, KK; Prasad, A; Kumar, AContemporary ways of employing and combining existing materials are a requisite for meeting tomorrow’s engineering applications. This is upscaled by the potent attributes of remaining competitive by keeping costs effective while advancing the fabrication of new material technologies. Thus, moderation of the tool condition and machining process, for example, is becoming successively critical to achieving more eminent yields, exceptional machine automation, better product quality, and reduced labor-intensive costs. Owing to the intricate nature of advanced materials, such as ceramic matrix composites, their brittle and heterogeneous structure and their anisotropic mechanical and thermal behavior render a variety of material removal mechanisms that result in surface defects. Therefore, this chapter’s objective is to focally evaluate how dissimilar machining techniques influence the machined surfaces of advanced materials. Furthermore, the study aims to pioneer the fundamental technologies and trendsetting development for machining process monitoring, namely, contemporary industrial practice inclusive of general workpiece surface integrity parameters, fluid consignment systems, wheel preparation options, and machine tool design/alignments. Similarly, academic research on the conventional and nonconventional machinability of advanced materials in the aerospace industry is deeply investigated. This is achieved by assessing new, various material characterization methods to identify and quantify the mechanical and thermal surface/subsurface damages and highlight their governing removal/grinding-process mechanisms.Item Chemical sensor nanotechnology in pharmaceutical drug research(2022-08) Thobakgale, Setumo L; Ombinda-Lemboumba, Saturnin; Mthunzi-Kufa, PatienceThe increase in demand for pharmaceutical treatments due to pandemic-related illnesses has created a need for improved quality control in drug manufacturing. Understanding the physical, biological, and chemical properties of APIs is an important area of health-related research. As such, research into enhanced chemical sensing and analysis of pharmaceutical ingredients (APIs) for drug development, delivery and monitoring has become immensely popular in the nanotechnology space. Nanomaterial-based chemical sensors have been used to detect and analyze APIs related to the treatment of various illnesses pre and post administration. Furthermore, electrical and optical techniques are often coupled with nano-chemical sensors to produce data for various applications which relate to the efficiencies of the APIs. In this review, we focus on the latest nanotechnology applied to probing the chemical and biochemical properties of pharmaceutical drugs, placing specific interest on several types of nanomaterial-based chemical sensors, their characteristics, detection methods, and applications. This study offers insight into the progress in drug development and monitoring research for designing improved quality control methods for pharmaceutical and healthrelated research.Item The combination of low level laser therapy and efavirenz drastically reduces HIV infection in TZM-bl cells(2020-06) Lugongolo, Masixole Y; Manoto, Sello L; Ombinda-Lemboumba, Saturnin; Maaza, M; Mthunzi-Kufa, PatienceHuman immunodeficiency virus (HIV) infection remains a global health challenge despite the use of antiretroviral therapy, which has led to a significant decline in the mortality rates. Owing to the unavailability of an effective treatment to completely eradicate the virus, researchers continue to explore new methods. Low level laser therapy (LLLT) has been widely used to treat different medical conditions and involves the exposure of cells or tissues to low levels of red and near infrared light. The study aimed to determine the effect of combining two unrelated therapies on HIV infection in TZM-bl cells.Item The comparative study of the microstructural and corrosion behaviour of laser-deposited high entropy alloys(2021-06) Dada, M; Popoola, P; Mathe, Ntombizodwa R; Pityana, Sisa L; Adeosun, S; Aramide, OCorrosion is a conservational occurrence that has a large economic impact on most metals and its alloys because it destroys and deteriorates most materials by an electrochemical process through the reaction of these materials with the environment. High Entropy Alloys in aerospace applications react with the environment in applications such as jet engines, especially at elevated temperatures. Thus, the capacity of high entropy alloys to resist corrosion must be investigated to expand the application of this advanced material in the aerospace industry. In this comparative study, AlCoCrFeNiCu and AlCoCrFeNiTi High Entropy Alloy samples were fabricated by Laser Additive Manufacturing, particularly direct energy deposition and the corrosion behaviour of both alloys were examined and compared. The influence of the laser processing parameters on the microstructure and corrosion responses of the high entropy alloys in 3.5 wt% NaCl solution was also investigated. The microstructural morphologies were examined using an X-ray diffraction system (XRD) and Scanning electron microscope (SEM) equipped with Energy Dispersion Spectroscopy (EDS). The results showed that the Scan speed had the most influence on the microstructure and corrosion behaviour of the alloys. There was a strong relationship between the phase structure of the alloys and their susceptibility to localized corrosion. Therefore, it has been proposed in this study that the phase distribution within the alloys also influences the corrosion behaviour of laser deposited high entropy alloys.Item Conceptual design framework for setting up aluminum alloy powder production system for Selective Laser Melting (SLM) process(2019-05) Matsagopane, G; Olakanmi, EO; Botes, Annelize; Kutua, SDocumentation on the correct process and component requirements for setting up efficient aluminum powder production systems capable of manufacturing powder that meets the requirements for the selective laser melting (SLM) process is not available due to its proprietary nature. This hinders powder metallurgy (PM) trainees in acquiring knowledge and skills needed in setting up such metal powder production systems. To address this challenge, powder requirements for the SLM process and powder production techniques for manufacturing powder that meets SLM requirements were identified and defined via literature review. User-value analysis and cost–benefit analysis techniques were applied as evaluation tools to identify the best components and process parameters for an aluminum powder production system. A conceptual design framework for setting up an aluminum powder gas atomizing system which meets SLM requirements is developed. This review improves the delivery of PM education in developing countries as trainees gain knowledge and skills for setting up powder production systems.Item Coupled heat transfer, fluid flow and solidification kinetics for laser additive manufacturing applications(2021-07) Khomenko, MD; Makoana, Nkutwane W; Pityana, Sisa L; Mirzade, FKHA new coupled heat transfer and solidification kinetics model is developed for the optimization of microstructure during laser additive manufacturing applications. The Johnson–Mehl–Avrami–Kolmogorov equation is applied in a self-consistent manner for modeling of the rapid phase change on the substrate. The numerical simulations using the OpenFOAM framework are conducted for Ni-based superalloy single track laser cladding. Single track laser cladding experiments were carried out to verify the results of our calculations. A rather good coincidence with the experimental data is shown for the developed model. The influence of processing parameters on the macro and micro parameters of the tracks is analyzed. A method for changing the average crystalline size and simultaneous preservation of the height and width of the track is presented. The possibility of controlling the microstructure of similar tracks gives an opportunity to preserve the scanning strategy for building parts with a defined quality.Item Crack mitigation in laser engineered net shaping of WC-10wt%FeCr cemented carbides(2022-04) Molobi, E; Sacks, N; Theron, MarithaLaser engineered net shaping of a WC-10wt%FeCr cemented carbide showed cracking during deposition despite using a full factorial design of experiments matrix along with single and multiple objective optimization models to establish an optimal parameter set. In this study four techniques namely, laser re-melting, use of FeCr and Ni-alloy butter layers, and substrate preheating, were used in an effort to reduce the crack susceptibility of deposited samples and the resultant effects on microstructure and hardness were studied. Laser re-melting improved the surface morphology of the deposited samples and reduced the number of primary and secondary cracks, however the hardness decreased. The Ni-alloy butter layer reduced the formation of secondary cracking and led to an increase in hardness, while the FeCr butter layer resulted in increased primary cracks and a reduced hardness. Substrate preheating reduced crack formation and led to an increase in the hardness with the reduction in cracking being attributed to a reduction of the initial thermal gradient.Item Design and manufacturing of an aggregate abrasion test device for testing in high acceleration field(2021-11) Xungu, Sipho; Mgangira, Martin B; Giani, John CThis paper describes the design and manufacturing of a mechanical system, the Aggregate Abrasion Test Device (AATD), which comprises of a rolling model drum, with the purpose of obtaining experimental data that is subsequently used to quantify the abrasion behaviour of aggregate particles. The study of the abrasion behaviour of geomaterials is complex due to among other factors, non-linear mechanical properties that depend on stress levels and stress history. In this case the aggregate assemblage is subjected to different stress levels by operating the system within the geotechnical centrifuge environment. The system was tested up to a maximum gravitational force of 25-G. The paper focuses on the design, manufacturing, construction, testing of the system and the experimental lessons or findings observed during the prototype testing. The system provides an alternative experimental way for determining the durability of the aggregate solely dominated by particle-to-particle interaction mechanism.Item Design and simulation of a bearing housing aerospace component from titanium alloy (TI6AL4V) for additive manufacturing(2022-12) Oyesola, M; Mpofu, K; Daniyan, I; Mathe, Ntombizodwa RIn evaluating emerging technology, such as additive manufacturing, it is important to analyse the impact of the manufacturing process on efficiency in an objective and quantifiable manner. This study deals with the design and simulation of a bearing housing made from titanium alloy (Ti6Al4V) using the selective laser melting (SLM) technique. The Finite Element Analysis (FEA) method was used for assessing the suitability of Ti6Al4V for aerospace application. The choice of Ti6Al4V is due to the comparative advantage of its strength-to-weight ratio. The implicit and explicit modules of the Abaqus software were employed for the non-linear and linear analyses of the component part. The results obtained revealed that the titanium alloy (Ti6Al4V) sufficiently meets the design, functional and service requirements of the bearing housing component produced for aerospace application. The designed bearing is suitable for a high speed and temperature application beyond 1900 K, while the maximum stress induced in the component during loading was 521 kPa. It is evident that the developed stresses do not result in a distortion or deformation of the material with yield strength in the region of 820 MPa. This work provides design data for the development of a bearing housing for AM under the technique of SLM using Ti6Al4V by reflecting the knowledge of the material behaviour under the operating conditions.Item Designing a Sn-slag composite with possible non-toxic applications to provide a pure metal casting environment(2019-02) Bolokang, Amogelang SFoundry slag formed during the production of medium carbon steel was milled into powder which was then compacted into blocks to form heat treatment furnace refractory materials. The foundry slag was ball-milled into powders which were further heat-treated at 300, 400, 500, 600 and 700 °C for 1 h. XRD pattern of ball-milled and heat-treated slag powder showed the rhombohedral and face-centred cubic (FCC) eta-phase. The dominating phase detected through the XRD is the a-Al2O3 with a rhombohedral crystal structure. The corresponding lattice parameters for therhombohedral crystal structure are a = 0.476 nm; c = 0.129 nm with R-3c # 167 space group and number. The density of the milled slag was measured at 3.325 ± 0.085 g/cm3, which is lower than pure alumina (3.69 g/cm3). After mixing the slag powder with Sn, a good microstructural bonding yielding alumina and tin oxide phases formed after sintering. Recycling of the waste foundry slag into a usable product provides an opportunity not only for value addition but eliviates the burden of slag disposal to preserve the environment.Item Detection of mycobacterium tuberculosis using gold nanoparticles conjugated to TB antibodies(2021-03) Maphanga, Charles P; Manoto, Sello L; Ombinda-Lemboumba, Saturnin; Mthunzi-Kufa, PatienceIn recent years, conjugated nanoparticles have gained significant applications in diagnostics, particularly gold nanoparticles (AuNPs). When functionalized with antibodies, AuNPs can selectively interact with cells and biomolecules. The conjugation of biomolecules to AuNPs has been achieved using a variety of techniques, one such approach is the covalent coupling method used in the current study. Generally, in diagnostics, the conjugation of different moieties such as antibodies to the AuNPs widens their applications and provides them with new or enhanced properties. Due to their high specificity and diversity, antibodies are widely used to provide specificity and bioactivity to AuNPs, particularly for biosensor applications. Localized surface plasmon resonance (LSPR) has emerged as a leader among label-free biosensing techniques because it offers sensitive, robust, and rapid detection of biological analytes. Biomolecular adsorptions on AuNPs surface increases the dielectric constant and change the intensities and the wavelengths of the LSPR band associated with AuNPs. As a result, the adsorptions of biomolecules onto surfaces of this AuNPs can be monitored by measuring the absorption spectra of the AuNPs. In this study, TB antibodies were covalently conjugated to AuNPs and used to detect mycolic acid TB antigens at various concentrations. Characterization of the AuNPs was done using transmission electron microscopy (TEM) while the biomolecular interaction between TB antibodies and the antigen was measured using LSPR. From our findings, it was realised that the use of antibodyconjugated AuNPs enhanced the detection of the analyte even at low concentrations of the analyte.Item Development of ideal processing parameters for powder bed fusion system processing of AlSi10Mg using design of experiments(2021-08) Mathe, Ntombizodwa RThe additive manufacturing of aluminium alloys has gained great interest in the transport industry in the past 10 years. This is mainly due to the lightweight and good strength that these alloys offer especially for applications in aerospace and other related industries. However, there is a drawback in using these alloys especially the parts produced by additive manufacturing as they have to be heat treated before application to relieve residual stresses caused by the fast heating and cooling experienced during powder bed fusion (PBF) fabrication. Most of the current PBF metal system offer a variety of processing parameters for part building, however AM uptake and industrial implementation is still slow due to restrictions of the laser power and laser interaction time that are slow and thus the parts take long to produce. Seeing this lag in the market, the CSIR has produced a high speed and high power PBF machine with a build platform larger than the currently available commercial systems. This system allows for the faster production of parts due to its higher consolidation rate and it has already been validated for aluminium alloys, specifically AlSi10Mg. The properties evaluated were microstructure and hardness, which found to be comparable to commercial PBF machines. The samples were analysed for microstructure, mechanical properties using tensile testing procedure. In order to determine that ideal processing window, the response surface methods was used on the Stat-Ease Design Expert software using ultimate tensile strength, elongation and hardness as outputs. Based on the data analysed, the processing window was narrowed to 1400 W laser power and 1.63 – 1.95 s interaction time.Item Directed energy deposition of a cemented tungsten carbide rotary burr prototype(2021-11) Molobi, E; Sacks, N; Theron, MarithaIn this study a cemented tungsten carbide rotary burr prototype was fabricated using directed energy deposition based on an optimal parameter set which was previously derived from a full factorial design of experiments matrix approach. Finite element analysis under static conditions was carried out on the burr to understand the possible geometric stress raisers and stresses during assimilated operation. Initial field tests were done to assess the functional performance of the prototype, and comparisons were made against a conventionally manufactured burr.