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.
3D printed microfluidic chip design for diagnostic studies
(2024-12) Sekhwama, Masindi; Mpofu, Kelvin T; Mcoyi, Michael P; Sivarasu, S
In this study, additive manufacturing (3D printing) is utilised to fabricate lateral flow microfluidic chips (LFMC). Our chips were designed using Autodesk design software and printed using a Formlabs 3D printer. They are printed using Formlabs V4 resin polymer. In this work, the design process is highlighted in detail and shows an LFMC design that is made for potential applications in diagnostics studies. Our study also tested the performance of one of the chip designs in actual diagnostics experiment on an optical transmittance setup with a peristaltic pump. The LFMC was integrated onto a custom-built transmittance optical biosensor to measure the transmission intensity. A real-time kinetic study was conducted using an HIV-1 oligonucleotide probe. The study involved performing real-time transmittance analysis by pumping the HIV-1 oligonucleotide probe at different flow rates, ranging from 9. 5 μm/min to 13 μm/min with intervals of 0.5 μm/min. During the experiment, transmission intensity or transmitted light was measured in real time as the oligonucleotide HIV probe bound to neutravidin immobilised on the Au metal surface. These measurements were recorded using a USB400 spectrometer, with a broad- band UV light source that emits wavelengths ranging from 400 to 800 nm. The study underscored the significance of microfluidic chips as devices capable of enhancing the performance of biosensors as well as the use of 3D printing in the design and manufacture of these microfluidic chips.
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.
A comparison of two biosensing recognition elements using SPR for the detection of drug- resistant genes
(2025-07) Chauke, Sipho H; Tjale, Mabotse A; Maphanga, Charles P; Felix Dube, F; Ombinda-Lemboumba, Saturnin; Mthunzi-Kufa, P
The burden of tuberculosis (TB) infections is disproportionately high in low-income and resource-limited settings. This disparity exacerbates the emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) Mycobacterium tuberculosis (Mtb), the bacterium that causes TB. Early detection and treatment of TB remain key strategies to reduce the spread and disease progression, particularly for the detection of drug-resistant forms. Therefore, optical-based diagnostic devices could solve this problem. Surface plasmon resonance (SPR) biosensors offer various advantages, including rapid analysis, high specificity, and sensitivity, as well as requiring small amounts of samples for analysis. For this study, two multidrug-resistant genes, namely, catalase-peroxidase (KatG) and enoyl reductase (InhA), were detected using a custom-built surface plasmon resonance (SPR) setup. Biotinylated and thiolated deoxyribonucleic acid (DNA) probes, specific to the two genes (KatG and InhA), were used as biorecognition elements to capture KatG and InhA target DNA. The SPR setup was used for the analysis of the binding interactions occurring on the gold-coated slides. The SPR biosensor setup indicated binding interactions through the changes in reflected intensities. The reflected intensities indicated the differences in the resonance angle between each experimental test. This is the initial step to identifying the best characterization of DNA as biorecognition elements for detecting drug-resistant mutations using an SPR-based setup.
A comparison of weldability and mechanical properties of additive manufactured and bulk Ti6Al4V alloy
(2024-11) Akinlabi, ET; Omoniyi, PO; Mahamood, RM; Arthur, Nana KK; Pityana, Sisa L; Skhosane, Besabakhe S; Okamoto, Y; Shinonaga, T; Maina, MR; Akinlabi, SA; Jen, TC
Titanium and its alloys, especially the Ti6Al4V, have tremendous use in the aerospace and biomedical industries. Since conceptualizing additive manufacturing techniques, it has been one of the most popular manufacturing techniques used on Titanium and its alloys. However, building large parts of the Ti6Al4V through additive manufacturing can be cumbersome due to the multiphysics involved in the heating and cooling of the material and the limited building space. This article examines the weldability of additive manufactured Ti6Al4V, manufactured through laser metal deposition (LMD) technique, and bulk sheet metal of Ti6Al4V manufactured through the rolling process. The welds were characterized using hardness, tensile, X-ray diffraction (XRD), and the evolving microstructure. Results show martensitic microstructure within the fusion zone, resulting in high hardness within the zone, which is confirmed in the XRD results. Failure occurred at the LMD heat-affected zone side of the sample due to the martensitic microstructure within the zone. The research further affirms the feasibility of joining Ti6Al4V manufactured through different routes through laser welding.
A digital twin framework to support vehicle interaction risk management in the mining industry
(2023-08) Verster, Jacobus J; Roux, Pieter W; Magweregwede, Fleckson; De Ronde, Willis; Crafford, Gerrie; Mashaba, Mathews M; Turundu, Safiya L; Mpofu, Mvikel; Prinsloo, Jacobus V; Ferreira, Pieta; Brodner, Hartmut D
In recent years, transport-related accidents, notably those involving trackless mobile machinery (TMM), have consistently ranked among the top three causes of fatalities and injuries in the South African mining industry (SAMI) [1]. These accidents arise from a combination of mechanical and technical malfunctions, environmental factors, and human or machine operator errors. Remarkably, these incidents persist despite the existence of specific regulations, standards, and codes of practice for transportation and machinery. This paper introduces a digital twin framework for TMM, which employs a systems engineering approach combined with software tools and computational analysis. This framework aims to enhance the current regulations by offering a continuous, quantitative risk assessment. By modelling and detecting non-conformance and adverse vehicle interaction events, the framework provides a quantitative risk analysis that complements the prevailing qualitative methods reliant on historical data and operational experience. A case study conducted at the CSIR main campus in Pretoria showcases the potential of the TMM Digital Twin.
A predictive geometallurgical framework for flotation kinetics in complexes platinum group metal orebodies: Mode of occurrence-based modification of the Kelsall model using particle swarm optimization
(2025-06) Kabemba, AM; Mutombo, Kalenda; Waters, KE
Mineralogical variability exerts a profound influence on the flotation performance of Platinum Group Metal (PGM) ores, particularly those from the Platreef deposit, where complex associations and textures influence recovery, grade, and kinetics. This study integrates the Mode of Occurrence (MOC) and mineral associations into a modified Kelsall flotation kinetics model, optimized using a Particle Swarm Optimization (PSO) algorithm, to improve prediction accuracy. Batch flotation tests were conducted on eight samples from two lithologies—Pegmatoidal Feldspathic Pyroxenite (P-FPX) and Feldspathic Pyroxenite (FPX)—with mineralogical characterization performed using MLA, QEMSCAN, and XRD. PGMs in liberated (L) and sulfide-associated (SL) forms accounted for up to 90.6% (FPX1), exhibiting high fast-floating fractions (θf = 0.77–0.84) and fast flotation rate constants (Kf = 1.45–1.78 min−1). In contrast, PGMs locked in silicates (G class) showed suppressed kinetics (Kf < 0.09 min−1, Ks anomalies up to 8.67 min−1) and were associated with lower recovery (P-FPX3 = 83.25%) and increased model error (P-FPX4 = 57.3). FPX lithologies achieved the highest cumulative recovery (FPX4 = 90.35%) and the best concentrate grades (FPX3 = 116.5 g/t at 1 min), while P-FPX1 had the highest gold content (10.45%) and peak recovery (94.37%). Grade-recovery profiles showed steep declines after 7 min, particularly in slow-floating types (e.g., P-FPX2, FPX2), with fast-floating lithologies stabilizing above 85% recovery at 20 min. The model yielded R2 values above 0.97 across all samples. This validates the predictive power of MOC-integrated flotation kinetics for complex PGM ores and supports its application in geometallurgical plant design. Model limitations in capturing complex locked ore textures (SAG, G classes) highlight the need for reclassification based on floatability indices and further integration of machine learning methods.
A review of failure mechanisms and advanced remanufacturing technologies for gears and sprockets in mining machinery
(2026-03) Belete, MB; Omogbehin, GS; Regesa, AI; Setswalo, K; Leso, TP; Satya, PRV; Olakanmi, EO; Botes, A; Ndeda, R; Pityana, Sisa L; Ematang, NY
This review systematically identifies, quantifies, and synthesizes the failure modes of heavy-duty gears and sprockets in mining equipment, examines their underlying causes or contributing factors, and evaluates remanufacturing strategies to enhance component durability. Despite the critical role of these drivetrain components, the number of mining-specific studies is limited, making this synthesis essential for understanding trends, informing practical interventions, and proposing further research areas. Analysis of the literature indicates that tooth fracture dominates gear failures, representing approximately 75% of reported cases in open-pit mines, primarily due to extreme shock loads, and 50% in underground mines, driven by fatigue and contamination. In contrast, abrasive wear is the primary mode of sprocket degradation (> 60% in both mining environments), resulting from continuous exposure to abrasive particulates, moisture, and high-humidity conditions. Manufacturing-induced defects, particularly quenching micro-cracks and unfavorable residual tensile stresses from conventional heat treatments, emerge as a primary contributor to premature failures, independent of operational conditions. Advanced remanufacturing techniques provide targeted solutions for these recurring failures. Laser cladding using wear-resistant iron-based matrix metal composites (IMMCs) enables precision restoration of gear teeth, while wire-arc additive manufacturing (WAAM) is well-suited for repairing extensively fractured components. By integrating insights on failure mechanisms, operational environments, and remanufacturing effectiveness, this review bridges critical gaps in mining-specific knowledge of component degradation and restoration. The synthesis offers actionable guidance for extending the service life and improving the operational reliability of heavy-duty mining drivetrain components.
Achieving heterogeneous network microstructure in laser additively manufactured hybrid TiBw/TiC/Ti6Al4V
(2025) Masina, Bathusile N; tshela TH; Lekoadi, Paul M
Laser-directed energy deposition and in-situ alloying processes were used to manufacture hybrid in-situ TiBw/TiC/Ti6Al4V composites while varying the powder flow rate of both TiB2 and TiC. The optical microscopy (OM) and scanning electron microscopy (SEM) reveal that both in-situ TiB-whiskers and TiC particles precipitated at prior β boundaries. This led to the formation of a heterogeneous network and novel network microstructures. It was found that the heterogeneous network microstructure consisted of fine-grain zones with a network structure and coarse-grain zones with spherical structures. The effect of adding TiB2 and TiC on microstructure features and hardness was systemically investigated. It was found that the was no significant increase in the microhardness as the powder flow rate increased of both reinforcements.
Adapting SegMap: A LiDAR place recognition framework for standalone use in C++ applications
(2025-09) Maweni, Thabisa; Amayo, P
Autonomous mobile robots rely on accurate environmental mapping and continuous self-localisation for effective navigation, often achieved through complex algorithms that combine data from multiple sensors. Aru-SegMap is an adaptation of SegMap, a widely used 3D point cloud segment-based map representation, for modern ROS2-based and standalone C++ applications focused on localisation. SegMatch, a 3D point cloud segmentation and matching library integral to SegMap, reliably estimates a robot's position and detects loop closures. This adaptation involved modularising the original library, decoupling it from a deprecated TensorFlow C++ API and ROS1, and integrating visualisation capabilities, enabling greater flexibility and usability for continued robotics research and development. Aru_SegMap was validated using datasets of varied agricultural environments. It is functional, produces consistent segments, and provides reliable localisation.
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.
Advances in β-titanium Alloys for Applications in the Biomedical Fields
(Springer, 2025-01) Bolokang, Amogelang S; Mathabathe, Maria N
The advances in biocompatibility, structural properties, application and processing techniques of beta (β)-titanium alloys are presented. These alloys are promising future biomedical alloys due to their low modulus of elasticity (MOE), and non-toxic elements. The biocompatibility of these alloys exhibits a low modulus of elastic (MOE) closer to that of human bone ~ 30 GPa. On one hand, the best mechanical properties and performance of the alloys is found in porous materials. Particularly, porous Ti-24Nb, Ti-35Nb and Ti-42Nb alloys exhibit reduced hardness with elastic modulus values of 11, 18.0 and 11.2 GPa, respectively. Furthermore, advanced processes such as additive manufacturing including selective laser manufacturing (SLM) and directed energy deposition (DED) are gaining traction in the manufacturing industry.
An optical gas imaging technique based on strobed illumination
(2024-12) Chirindo, Mathews; Cox, Ettienne; Duness, Kahesh
Gas leakage from equipment poses undesirable safety, environmental and operational impacts. Many optimal gas imaging techniques exist which detect and visualize gas plumes. However, most of these techniques struggle to produce clear images when the temperature gradient between the scene background and the gas plume is small. This paper presents an optical gas imaging technique that is based on strobed illumination, wherein the strobing frequency of the illuminating device is associated with the camera frame rate. Experimental test results are presented to show the improved detection of volatile organic compound gases during strobed illumination under dark room laboratory conditions where the percentage contrast value of the illuminated gas relative to its background varies by 50.8% The test results for the detection of sulphur hexafluoride gas and liquid petroleum gas under an outside environment are also presented.
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.
Analysis of failure characteristics of screen plates of ring hammer crusher used in coal handling applications
(2024-08) Kyekyere, E; Olakanmi, EO; Prasad, RVS; Matshediso, B; Motimedi, T; Botes, A; Pityana, Sisa L
The screen plate, a critical component within a ring hammer crusher (also known as a ring granulator or rolling ring crusher), plays a vital role in the secondary crushing of coal. Functioning both as a platform for coal crushing and as a sieve to achieve the desired coal size, it is essential to understand and examine its failure characteristics to enhance its mechanical and wear resistance properties in coal handling applications. This study thoroughly explored the failure modes, mechanisms, and underlying causes of screen plate failures. Microscopic techniques such as optical microscopy (OM), scanning electron microscopy (SEM), Vickers microhardness test and spectrochemical analysis were utilised to identify the failure mechanism. Failure modes identified from the macroscopic analysis were discharged hole widening, hole wall break-off, plate edge crack, plate fracture, one-sided edge slimming, and general surface wear of the screen plate. The fractographic and wear track analysis identified the principal failure mechanisms of three-body abrasive wear, two-body sliding abrasion wear, shear-induced fatigue fracture and brittle shear fracture. The root causes of the failures are the rotor’s direct impact, defects in the parent material, the presence of hard materials in the coal and the use of unsuitable steel grade in the screen plate manufacturing. The service life of the screen plate can be improved through proper material selection, uniform crusher feeding, surface modification of the surface of the “as purchase” screen plate with appropriate wear-resistant materials, and adherence to good maintenance practices.
Analytical analysis of the beam propagation factor of elegant Hermite-Gaussian and elegant Laguerre-Gaussian beams with astigmatism
(2023-09) Mabena, Chemist M
The impact of astigmatism on the beam propagation factor (M2) of elegant Hermite–Gaussian and elegant Laguerre–Gaussian beams is examined. We derive closed-form expressions for M2 when the optical beams are aberrated with astigmatism. The analysis shows that the beam radius is crucial to the degree of impact astigmatism has on M2. To this extent, we derive the beam radius that separates the region where the M2 is negligibly affected and the region where it becomes severely affected. For the elegant Laguerre-Gaussian beams, we establish a parameter that determines a set of beams that are impacted equally by astigmatism. The analytical results are validated with numerical simulations.

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