Research Publications/Outputs

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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, O
In 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.
3D mapping and photogrammetry sensor payload for unmanned aerial vehicles
(2023-11) Purdon, Kyla; Van Niekerk, T; Phillips, R; Marais, Stephen T
Unmanned Aerial Vehicles (UAVs) have shown great potential for data collection and monitoring of areas. Sensors such as LiDARs and cameras can be used on UAVs for high-resolution data collection and used for various applications like Digital Surface Models (DSM), photogrammetry, inspection systems, and maintenance applications. This paper describes the design and implementation of a sensor payload for UAVs using a LiDAR sensor, camera, Inertial Measurement Unit (IMU), and Global Positioning System (GPS). The payload collects data that can be used to georeference LiDAR and camera data, which can later be used to generate a georeferenced map and perform object detection and classification.
4-RRS PKM for stabilisation on a mobile sensor platform
(2023-11) Ramruthan, Kshir; Kuchwa-Dube, C
Disturbances experienced by an inspection robot can reduce the quality of its sensor measurements, which can in turn negatively affect the robot’s functionality. This research aimed to design a Parallel Kinematic Mechanism (PKM) for use as a stabilisation mechanism. The research focused on designing, simulating, building, testing, and analysing the mechanism. The PKM was modelled and simulated using MATLAB®, designed and developed using NX CAD software, and it was tested using a custom-built test rig that could simulate rotational disturbances. Using the metric of absement, the PKM significantly reduced the disturbances, depending on the disturbance induced.
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 L
Laser 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.
The adsorption of halogen molecules on Ti (110) surface
(2021-01) Tshwane, David M; Modiba, Rosinah; Govender, Gonasagren; Ngoepe, PE; Chauke, R
Adsorption 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.
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 R
The 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.
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, HR
Fluorine 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.
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 L
Shafts, 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.
Anomaly detection monitoring system for healthcare
(2021-01) Boloka, Tlou J; Crafford, Gerhardus J; Mokuwe, Mamuku W; Van Eden, Beatrice
Most 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.
Applications of microfluidics in biosensing
(2024) Sekhwama, Masindi; Mpofu, Kelvin T; Sivarasu, S; Mthunzi-Kufa, Patience
Microfluidic devices have become a vastly popular technology, particularly because of the advantages they offer over their traditional counterparts. They have such a wide range of uses and can make complex tasks quite efficient. One area of research or work that has benefited greatly from the use of microfluidics is biosensing, where microfluidic chips are integrated into biosensor setups. There are growing numbers of applications of microfluidics in this area as researchers look for efficient ways to tackle disease diagnostics and drug discovery, which are critical in this era of recurring pandemics. In this work, the authors review the integration of microfluidic chips with biosensors, as well as microfluidic applications in biosensing, food security, molecular biology, cell diagnostics, and disease diagnostics, and look at some of the most recent research work in these areas. The work covers a wide range of applications including cellular diagnostics, life science research, agro-food processing, immunological diagnostics, molecular diagnostics, and veterinarian diagnostics. Microfluidics is a field which combines fundamental laws of physics and chemistry to solve miniaturization problems involving fluids at the nanoscale and microscale, and as such, the authors also examine some fundamental mathematical concepts in microfluidics and their applications to biosensing. Microfluidics has relatively new technologies with great potential in terms of applications.
Applying design for additive manufacturing to existing aerospace parts
(2023-11) Bester, Duwan C
Additive Manufacturing has widely been used in the aerospace industry. However, local uptake in the aerospace industry has been slow with mostly additively manufactured polymer parts being used. The Advanced High Performance Reconnaissance Light Aircraft (AHRLAC), which is a locally produced military aircraft, is well positioned to prove the local capabilities in Metal Additive Manufacturing to the local Aerospace industry. Two parts of this aircraft were identified through prior experience in Additive Manufacturing and taken through the Design for Additive Manufacturing process. The identified parts were a forward cockpit control cable mount and a canopy guide. The parts were redesigned using topology optimisation and, in both instances, a weight, cost, and lead time reduction was achieved.
ARGUS: A pole climbing surveillance robot
(2023-11) De Ronde, Wiilis; Bosscha, Peter A; Marais, Stephen T; Pretorius, A
Due to the high prevalence and unpredictability of violent protest action in South Africa, a need has arisen for rapidly deployable surveillance. This paper proposes an Automated Robotic Guardian for Urban Surveillance (ARGUS) platform, a wheeled, pole climbing robot as a potential solution. The platform is designed to attach to and traverse up existing cylindrically shaped infrastructure, such as light posts, enabling easy deployment in urban environments. The robot is intended for varioussurveillance needs, such as public safety at events, and periods of unrest or protest action. Following a detailed concept design stage, simulated results are presented for the proposed robot. This includes comprehensive CAD modelling, static force and torque calculations of the pole climbing robot, and finite element analysis of the component stresses while positioned on the pole. The robotic platform is currently in production and future work will include experimental validation of the simulated system.
Assembly line quality assurance through hand tracking and object detection
(2022-10) Mokuwe, Mamuku W; Goorun, Yurisha; Crafford, Gerhardus J
This work presents a vision-based quality assurance system that does assembly line monitoring. The system is developed using machine learning hand tracking and object detection methods to monitor the worker’s hand movement while evaluating the correctness of the assembly. Feedback about the order of the steps the worker has taken is continuously shown to the user. This work has the potential to reduce the amount of manual work required for quality assurance in assembly line.
Biosensing multidrug-resistant TB genes using SPR
(2024-01) Chauke, Sipho H; Ombinda-Lemboumba, Saturnin; Dube, FS; Mthunzi-Kufa, Patience
Tuberculosis (TB) is one of the most prevalent infectious diseases globally. Although it is curable, several factors, such as the inappropriate use of treatment drugs lead to drug-resistant strains of TB. The burden of infection is disproportionately high in low-income and resource-limited settings. Furthermore, this disparity is exacerbated in patients with already compromised immune systems. Therefore, early detection and treatment of TB play an important role in reducing the spread and progression to drug-resistant disease forms. There are currently a few rapid multi-drug resistant TB diagnostic tests available, however, most are limited due to costs and accessibility. Several genes, such as catalase-peroxidase (katG) and enoyl reductase (inhA) genes, contain mutations that are responsible for resistance to the TB drug, isoniazid. We therefore, aim to use a custom-built surface plasmon resonance (SPR) system to detect katG and inhA genes. Deoxyribonucleic acid (DNA) probes, specific for katG and inhA, were used as biorecognition elements to capture katG and inhA target DNA. The katG and inhA gene-specific DNA probes were immobilized on a gold-coated glass sensor chip before the target DNA was introduced for detection. As a negative control, a mismatched probe, unspecific to both genes was used for confirmation of the absence of the two genes in the experimental setup. The specificity and sensitivity of the capture probes to the target DNA were investigated using the gold-coated glass sensor chip on the SPR setup. The changes in the resonance angle dip indicated the hybridization of the target DNA and the capture probe. The results from this study will contribute to the optimization of an optical-based biosensor detecting drug-resistant mutations.
Challenges in machining of advanced materials
(CRC Press, 2022-05) Mathabathe, Maria N; Bolokang, Amogelang S; Gajrani, KK; Prasad, A; Kumar, A
Contemporary 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.
Chemical sensor nanotechnology in pharmaceutical drug research
(2022-08) Thobakgale, Setumo L; Ombinda-Lemboumba, Saturnin; Mthunzi-Kufa, Patience
The 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.
The Circular Economy as Development Opportunity: Exploring Circular Economy Opportunities across South Africa’s Economic Sectors
(CSIR, 2021-12) Godfrey, Linda K; Nahman, Anton; Oelofse, Suzanna HH; Trotter, Douglas; Khan, Sumaya; Nontso, Zintle; Magweregwede, Fleckson; Sereme, Busisiwe V; Okole, Blessed N; Gordon, Gregory ER; Brown, Bernadette; Pillay, Boyse; Schoeman, Chanel; Fazluddin, Shahed; Ojijo, Vincent O; Cooper, Antony K; Kruger, Daniel M; Napier, Mark; Mokoena, Refiloe; Steenkamp, Anton J; Msimanga, Xolile P; North, Brian C; Seetal, Ashwin R; Mathye, Salamina M; Godfrey, Linda K
The intention of this book is to present the CSIR’s position and interpretation of the circular economy, and to use it to drive discussions on where immediate circular economy opportunities are achievable in South Africa. Opportunities that can be harnessed by business, government and civil society. These circular economy opportunities are framed in this book within the context of the current challenges facing various economic sectors. The CSIR has selected seven, resource intensive sectors – mining, agriculture, manufacturing, human settlements, mobility, energy and water – for further assessment. Many of these economic sectors have seen significant declines over the past years, with agriculture, manufacturing, transport and construction all showing negative growth pre-COVID. These are all sectors under economic stress and in need of regeneration. South Africa stands on the threshold of profound choices regarding its future development path. Transitioning to a more circular economy provides the country with the opportunity to address many national priorities including manufacturing competitiveness, food security; sustainable, resilient and liveable cities; efficient transport and logistics systems; and energy and water security, while at the same time decarbonising the economy. The transition to a circular economy provides the country with an opportunity for green and inclusive development to be the cornerstone of a post-COVID economic recovery. The titles of this book chapters are the following: Chapter 1: Driving economic growth in South Africa through a low carbon, sustainable and inclusive circular economy. Chapter 2: Placing the South African mining sector in the context of a circular economy transition. Chapter 3: Supporting food security and economic development through circular agriculture. Chapter 4: Supporting the development of a globally competitive manufacturing sector through a more circular economy. Chapter 5: Creating resilient, inclusive, thriving human settlements through a more circular economy. Chapter 6: Facilitating sustainable economic development through circular mobility. Chapter 7: Decoupling South Africa’s development from energy demand through a more circular economy. Chapter 8: Decoupling South Africa’s development from water demand through a circular economy.
A cloud-based road infrastructure analysis system using machine learning
(2022-11) Naidoo, Thegaran; Verster, Jacobus J; Marais, Stephen T
A cloud-based road infrastructure analysis system was developed to assist as an information management system for detecting and managing information about road defects and road assets. The system uses computer vision and machine learning algorithms and is accessed through a web interface. The detection results are viewed through an online, account-based web interface.
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, Patience
Human 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.
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, O
Corrosion 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.

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