Mamookho Elizabeth Makhatha

• Ph.D Polymer chemistry
• Professor (Full) at University of Johannesburg

This study investigated the role of valence electron orbital filling ( e/a ratio) on the reported corrosion resistance performance of Ti-Pt and Ti- Au binary alloys containing less than 10 atomic percent (at. %) precious metal. The valence electron orbital filling enabled us to determine the oxidation states of these binary Ti alloys, and thus esta...

Purpose In response to the growing demand for a polymer with improved chemical and thermal stability in the construction sector, this study aims to thoroughly explore the characteristics of silver nanoparticles (AgNP) and their various concentrations. The primary goal is to determine the effect of these nanoparticles on the chemical and thermal sta...

Natural fibers (NFs) are becoming more and more interesting to research, because of their numerous benefits, sensitivity, biodegradability, and capacity to provide sustainable products that encourage technological innovation and a variety of industrial applications. In this study, a two-step treatment approach was adopted to chemically modify NF ob...

This paper uses a modified dynamic material modeling (MDMM) suggested by Murty and Rao to develop processing maps (PM) of 2205 duplex stainless steels (DSS). Gleeble 1500D, a thermo-mechanical simulator was used to conduct single hit compression tests at a temperature between 850 and 1050 °C and strain rates of 0.001-5 s ⁻¹ . Additionally hot compr...

This work predicts, hot flow curves of 2205 DSS using strain-compensated Arrhenius rate-type constitutive model. Twenty-five (25) × Ø10 diameter × 15 mm height cylindrical samples were hot compressed at a temperature between 850 and 1050 °C at an interval of 50 °C and strain rates between 0.001 and 5 s⁻¹, using Gleeble 1500D. After the tests, corre...

Background Owing to the promising characteristics— high strength-to-weight ratio, acoustic and thermal insulation, renewable and biodegradable, sisal fiber-based composites have been explored. Including patents, interesting literature is available on sisal fiber-based composites. Method The materials under investigation were sisal fiber (SF), poly...

The influence of solution treatment on the phase evolution and tensile properties of Ti-Mo alloys was investigated to assess their potential use in biomedical applications. Phase formation and microstructural evolution were studied using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), and electron backscatter d...

This research aimed to investigate the sustainability of grade V Titanium alloy (Ti-6Al-4V) in NaCl, as well as its mechanical properties for biomedical applications. Improving titanium alloys is critical for producing alloys with minimal side effects. The impacts of structure, indentation test, corrosion resistance, and wear resistance of six tita...

The high corrosion resistance of Al 6061 has made the material for wide applications. However, for its sustainability in applications, the mechanical properties and corrosion resistance have to be improved through modifications such as heat treatment. Therefore, the study investigates the influence of the aging time on the corrosion resistance, mec...

For several decades, mild steel has been an ideal mandated material in many industrial applications. However, unlike stainless steel and other special steel alloys, mild steel is prone to corrosion attack, leading to devastating failures of equipment and metallic structures over time, causing losses worth billions. This situation has spurred resear...

In this study, Natural fibres (NF) from bamboo bundles was modified by first pre-treated with Ethanol, followed by potassium permanganate (KMnO 4 ) in Acetone solution at varied concentrations and time durations. To optimize the influence of ethanol pre-treatment and KmnO 4 treatment at varied concentration and duration on the tensile strength (TS)...

The removal of Fe 2+ and Mn 2+ from cobalt sulfate-saturated solutions is frequently problematic for Cu-Co hydrometallurgical process performance. Among the applied and developed methods for the removal of these metals, adsorption has drawn less attention. This study investigates on the removal of Fe 2+ and Mn 2+ in industrial cobalt solutions know...

Although fossil fuel continues to play a dominant role in global energy system unfortunately their life span is threatened as the fossil reserves are running out. Except for the fact that they are readily available, tried and tested, unfortunately they bring about a negative environmental and climate impact. When the fossil fuels are burned, they p...

Demands for energy are rising as the world's population expands. To meet these demands, fossil fuels have been overused, yet this over reliance on them has led to their depletion. The usage of fossil fuels has also significantly contributed to the release of greenhouse gases, which is a serious environmental concern. Sustainable energy is therefore...

The present study conducts the phase analysis, microstructural characteristics, and mechanical property evaluation on the as-cast and quenched Ti-15Mo-xFe alloys with high iron content ranging from 4 to 12 weight percent. All the four alloys were produced in a button-arc melting furnace. Heat treatment in the form of solution treatment was performe...

The aluminum 5754 alloy is one of the widely used engineering materials in shipping, rivet making, tread plates and automotive industries. These engineering structures envisage variable loading conditions during their service. In addition to it, it is also experiencing seismic vibrations. Hence, the engineering components made from such aluminum al...

Polymer nanocomposites have been of great interest to packaging, energy, molding, and transportation industries due to several favorable properties including a higher resistance to stress and cracking even under flexed conditions, and also a chemical resistance to water, acids, and alkalis. The current work disseminates the studies on the mechanica...

This study presents the analysis of the microstructure and Vickers micro-hardness of β-Ti type Ti-15.05Mo alloy obtained by different cooling rates. The alloy was fabricated using an arc-melting furnace, solution treated in a muffle furnace and cooled using different cooling medium such as ice water, furnace cool and air cooling. The X-ray analysis...

Shape Memory Alloys (SMAs) are popular due to their ability to regain their original shape after plastic deformation. Binary TiPt alloys have low shape memory effects and as such, alloying elements are added to improve these properties. The effect of alloying and increasing the Hf in binary Ti50Pt50 to form ternary Ti50Pt50−xHfx (x=6.25,12.5 and 18...

Jute fiber is one of the most extensively used eco-friendly natural fibers that are hydrophilic. The performance of natural fiber-reinforced composites is affected by the diffusion of heat and moisture from the environment in addition to the exposure time. In the present investigation, the ultimate tensile strength, displacement at fracture, and en...

Plastic bags are one of the most widely used packaging materials in industries. Lower production cost, lightweight and high strength envisage its use in food packaging, carrier, and transportation industries. However, these plastic bags are non-biodegradable and cause serious water and soil pollution. It is one of the most thrust areas of research...

The casting of metal alloys followed by hot forging is a widely used manufacturing technology to produce a homogeneous microstructure. The combination of mechanical and thermal energy envisages the microstructural properties of metal alloys. In the present investigation, a metal alloy of composition 0.05C-1.52Cu-1.51Mn (in weight %) was cast in an...

While recent research has used organic coatings to replace chromium‐based coatings, the ability of a coating material to repeat its chemical properties on different substrates is still under investigation. The Repellix superhydrophobic compound was developed and deposited on three different substrates using the atomic layer deposition method under...

Normalizing is a widely used heat treatment process for steel to induce desired mechanical and microstructural properties. In the present investigation, P91 martensitic steel was subjected to normalizing, followed by deep cryogenic soaking (DCS) using a muffle furnace and liquid nitrogen chamber. The specimens were reheated in the temperature range...

The P91 martensitic steel is one of the most extensively used materials in engineering applications which is used to completely transform into martensite during normalizing. In the present investigation, P91 martensitic steel samples were subjected to “tempering” using a muffle furnace. The X-ray diffraction (XRD) spectra showed an increased peak i...

2205 duplex stainless steel suffers poor hot workability, especially whe1981hot-deformed. This investigation aims to determine the strain rate’s effect on the material’s dynamic recrystallization after heat treatment. Secondly, to ascertain the critical strain at which the recrystallization occurs. The as-rolled material was subjected to heat treat...

The detrimental precipitation at the 2205 duplex stainless steel (DSS) grain boundaries has characterized the material to have poor workability after being hot-rolled. However, the detrimental precipitation in the microstructure is largely influenced by the cooling rate or method. There is an insufficient investigation of this steel's grade interfa...

The current study investigates the influence Mo on the microstructure and bending properties of solution treated Ti-xMo alloys (x= 10.00, 12.89, and 15.05 wt%). The fundamental objective of the study is to attain the correlation between the composition, processing, microstructure, and bending properties of β Ti after the solution treatment process....

Current research is focused on development of β-type titanium alloys for biomedical applications as substitutes of the undesirable Ti6Al4V alloy. Ti6Al4V alloy has a higher elastic modulus (110 GPa) than that of the human bone (10-30 GPa) and this mismatch in elastic moduli can cause stress shielding effect, which can cause bone resorption and impl...

The effects of operating conditions on copper, iron, and cobalt dissolution from sulfide ores in sulfuric acid–sodium chloride media are predicted using an artificial neural network (ANN) model. The artificial neural network model was developed, trained, and predicted using the feed-forward back-propagation (BP) algorithm. The sulfuric acid concent...

This paper studies the inhibition efficiency of mild steel in 1 molar hydrochloric acid in the presence and absence of an inhibitor by means of potentiodynamic polarization and electrochemical impedance spectroscopy. The immersion time and temperature were 3 h and 25 °C, respectively. The inhibitor concentration was 25, 100, 300, 500 and 700 ppm, r...

Over the years, the use of new alternative lixiviants for gold extraction has been investigated to overcome the environmental concerns resulting from the cyanidation process. Moreover, with global economic factors causing a decline in gold prices, it is crucial that novel hydrometallurgical methods of extracting gold minimise operational costs by u...

This study investigated the operating parameters that affect the kinetic dissolution of copper and cobalt from sulfidic ores. The sulfuric acid concentration, temperature, sodium chloride concentration, particle size range, and leaching time were selected to deduce the kinetic mechanism of the leaching reaction. Other parameters, such as a stirring...

The low carbon copper-bearing steel exhibits high toughness and better weldability. In the present investigation, 0.05C–1.52Cu–1.45Mn stainless steel and its titanium added counterpart which is 0.05C–0.05Ti–1.52Cu–1.45Mn stainless steel were subjected to hot rolling. The hot rolling test followed by quenching to retain the microstructure was done u...

The author in order to solve the problem of optimizing the accuracy of mechanical equipment failure detection proposes a vibration signal collection and computer simulation detection for mechanical equipment failure. Using wavelet domain Wiener filtering-based mechanical equipment fault detection method, the author first combined Wiener filtering a...

The reduction of surface roughness on additively manufactured components has become a critical factor in engineering applications. This paper reports the electropolishing of additively manufactured Ti-6Al-4V by powder bed selective laser melting (SLM) using a nontoxic electrolyte solution. The results have shown that the salt-based electrolyte can...

The application of machine learning (ML) techniques to metal-based nanomaterials has contributed greatly to understanding the interaction of nanoparticles, properties prediction, and new materials discovery. However, the prediction accuracy and efficiency of distinctive ML algorithms differ with different metal-based nanomaterials problems. This, a...

In this work, the inhibitive capability of Cysteine-doped Polyvinylpyrrolidone (PVPC) in 1.0 M HCl solution was investigated using mild steel as the reference material. To elucidate the effect of concentration on the corrosion inhibition efficiency, the synthesized PVPC via solution polymerization method was added to the acidic solution at differen...

The effect of Nb in the glue site of the cluster-plus-glue atom model formula on the microstructure and mechanical properties of Ti-Mo alloy was investigated. Phase and microstructural analysis were performed by X-ray diffraction and electron backscatter diffraction. Tensile properties were also examined. A small amount of secondary martensitic α”...

To solve the problems of large mechanical powertrain such as complex structure, serious accident, strong nonlinear characteristics of running state, bad operating environment, non-Gaussian noise, and various uncertain factors, it is difficult to make an accurate fault diagnosis. This paper proposes a method for dealing with nonlinear characteristic...

RF Magnetron sputtering is a distinctive deposition process that has applicability for growing thin film coatings on the surface of any materials such as biomedical implants without the formation of excessive heat and alteration of the overall properties of the materials. In this research study, a 99.5% purity nanostructured titanium carbide (TiC)...

In the modern construction industry, there is a need for environment friendly energy efficient buildings to support the idea of sustainability. This article investigates the numerical simulation of air distribution of central air conditioning in tall atrium using the CFD technology to simulate the air distribution in the atrium of the large hotel b...

The aim of this study is to investigate the effect of niobium on the microstructure and mechanical properties of Ti-Mo-Nb alloys, which include Ti-11.1Mo-10.8Nb (TMN1), Ti-10.2Mo-19.5Nb (TMN2), and Ti-9.2Mo-26.7Nb (TMN3) alloys designed using the cluster-plus-glue-atom model. The molybdenum equivalence, average electron concentration ratio, and d-e...

Two poly (ethylene glycol)-tyrosine hybrid polymers (PEGT1% and PEGT3%) were used to inhibit the corrosion of mild steel in 1 M HCl. In this work, surface plot investigations which employed several mapped sites, pixel coordinates, ideal spread function, and 3D-luminance plots were used to monitor the corrosion performances of the two green hybrid p...

In present investigation, an attempt was made to optimise the peak stress for paper laminate composite using FRANC2D software. It was observed that the laminate having the triangular geometry supposed to be most appropriate as it has the lowest value of peak stress contour compared to other models like parallel strip, up-down tapered and down-up ta...

Uni-axial compression (UAC) tests and further post deformation annealing (PDA) were done for 23Cr-6Ni-3Mo duplex stainless steel (DSS). The initial morphology was equiaxed (EQ) in nature. In the first stage of PDA, austenite showed limited static recrystallization (SRX) followed by static recovery (SRV); however ferrite showed static recovery (SRV)...

Nanocellulose has been reported to be a very useful biomaterial with applications in biomedical, pharmaceutical, built industry, automobile, aerospace and many more. Its advantages over synthetic fibers include renewability, energy efficiency, cost effectiveness, biodegradability and good mechanical and thermal properties. However, the production o...

The effect of Mo content on the microstructural evolution and the tensile properties of as-cast binary Ti-Mo alloys is designed by using the cluster-plus-glue atomic model and the β prediction method, such as the Moeq, e/a ratio and the d-electron, which were used to predict the stability of the β phase. The designed (Ti-10.02 wt % Mo, Ti-10.83 wt...

Aim Develop machine learning models for the performance of refrigerator and airconditioning system. Background The Coefficient Of Performance (COP) of Refrigerator and Air-Conditioning (RAC) is a complex function of evaporative temperature and concentration of nano-particle in lubricants. In recent years, researchers focus on experimental study fo...

Monolithic aluminium alloy lacks adequate mechanical and tribological properties necessary for optimal functionality in the industry. As a consequence, industrialists and manufacturers have experienced its frequent failures in service. This has necessitated the switch to Al matrix composites which possess better mechanical and tribological characte...

There is an increase in demand for durable and efficient organic nanoscale coatings for modern manufacturing systems and/or components for various applications. In wake of this demand, a new superhydrophobic silane compound was deposited on mild steel, stainless steel and titanium substrates which were pre-treated with alumina via the atomic layer...

Solar photovoltaic (PV) technologies are now considered viable options to fulfill the electricity demand for end-users worldwide. However, these PV technologies need to be technically analyzed in terms of pre-feasibility and performance assessment by utilizing the available solar radiation and ambient temperature of the PV system installation site....

The synthesis and corrosion inhibition performance of poly(butylene-succinate)-L-proline (PBSLP) prepared by solution polymerization are reported. PBSLP was characterized by FTIR, XRD, and SEM/energy dispersive X-ray (EDX). PBSLP was used to protect mild steel in 1 M hydrochloric acid. An SEM and an atomic force microscope (AFM) were used to charac...

β-type titanium alloys are acquiring research interest in orthopaedic applications because of their exceptional properties such as moderate strength, good biocompatibility and corrosion resistance, high ductility and low elastic modulus. The study aims at designing a series of binary Ti-Mo alloys (Ti-8.71 Mo, Ti-10.02 Mo, Ti-11.78 Mo and Ti-15.05 M...

The renewable energy sector in a developing country can play a vital role in socio-economic development. With proper utilization of renewable energy resources (RESs) such as photovoltaic (PV) energy system, wind energy system, hydrogen fuel cell (HFC) energy system, etc. may be accepted for renewable electricity generation for urban or rural popula...

Shea nut shell (SNS) is an agrowaste obtained from Vitellaria paradoxa tree and discarded by burning. The extraction of nanocellulose from this agrowaste is expected to be a value addition to Shea farming and processing. However, the isolation of quality nanocellulose begins with optimal pretreatment of the agrowaste material. In this work, the mer...

Mining of minerals such as gold, copper, and platinum has been one of several activities sustaining the economy of South Africa. However, the mining sector has contributed significantly to environmental contamination through the improper disposal of mine tailings which covers vast areas of land. Therefore, this study utilised a vitrification proces...

The problem of environmental pollution is a global concern as it affects the entire ecosystem. There is a cyclic revolution of pollutants from industrial waste or anthropogenic sources into the environment, farmlands, plants, livestock and subsequently humans through the food chain. Most of the toxic metal cases in Africa and other developing natio...

The environmental consciousness and consumer pressure have forced manufacturing industries to use natural fibres as a substitute for conventional non-renewable reinforcing materials. In the present investigation, the effect of rate of loading on jute fibre-reinforced polymer composite was studied. The mechanical properties (in three-point bend test...

In the present investigation, the effect of substructures on hardness and conductivity during partial annealing of cold-rolled copper was studied. Substructures were observed after annealing at lower temperature; however, the annealed sample (at higher temperature) was mostly free from substructures. Therefore, it is proposed that the restoration m...

In the present study, microstructural analysis of post-deformation annealed sample has been carried out for 23Cr–6Ni–3Mo duplex stainless steel. It was observed that the restoration mechanism and substructural characteristics were different for austenite and ferrite during post-deformation annealing. In the initial stage of post-deformation anneali...

The pipes are subjected to different load conditions such as internal stress, compression, tension, bending and/or any combination thereof. These various types of load conditions induce new cracks and/or cause propagation of the existing cracks. In this study, a TP316L stainless steel pipe subjected to four-point bend testing was examined to predic...

In this study, the selected streams within the Blesbokspruit located in South Africa were characterised in this study. Because of prolonged mining activities coupled with ineffective management practices, several mine tailing (MT) dumps are widely distributed in this area. Metals and metalloid contamination from these tailing facilities have been r...

The mining of gold is associated with several environmental challenges such as acid mine drainage, release of toxic metals which are associated to tailing sediments and have adversely impacted human health and the ecosystem. With increasing global population that is faced with limited land resources for agricultural activities, there is need for la...

In this study, the conventional powder metallurgy route of pressing and sintering was employed to study the effects of the particle size of blended elemental Ti-6Al-4V powders on the properties of powder mixtures, green and sintered densities. The -45 μm and -150 μm 60Al-40V master alloy powder were blended with the titanium powder to produce the -...

In the Blesbokspruit area of Ekuhurleni, South Africa, previous gold mining activities resulted in many tailings dump sites. 20 representative soil samples were used in describing the distribution of metals. The soils were very strongly acidic ranging from 3.86 to 4.34 with a low cation exchange capacity (CEC). Based on X-ray fluorescence (XRF) ana...

Conductive polymer nanocomposites are receiving lots of research attention in the field of material science due to their fascinating properties and potentials in many areas of applications. In this work, reduced graphene oxide (RGO); a highly conducting nanofiller was synthesized and incorporated into the matrix of insulating expanded polystyrene (...

Food security remains an important aspect of human lives and the vital role of soil in the global agricultural and food crops production is obvious. The quality of agricultural products which is being consumed by human through the food chain is dependent on the condition of the soil. Previous gold mining activities resulted in the discharge of tail...

Corrosion inhibitor has been successfully used for the protection of 3CR12 stainless steel surface against corrosion in 1–2.5 M HCl. The performance of this inhibitor was correlated to the chemical composition and microscopic structures in accordance with the adsorption on the metal surface. Deoxyribonucleic acid (DNA) was extracted from the thymus...

The ecofriendly poly(butylene succinate) extended with 1,6-diisocynatohexane composted with L-histidine (PBSLH) polymer composite was synthesized by condensation polymerization. The polymer composite was characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), and scanning electron microscope (SEM-EDX). The inhibition action of...

The development of laboratory work on friction stir welding (FSW) and friction stir spot welding (FSSW) FSW of dissimilar materials should provide a good insight into their possible industrial applications; and therefore, enhance their industrial development. Many applications in various industries, especially in the manufacturing sector, have led...

Friction stir welding (FSW) and friction stir spot welding are solid state joining processes employed for the joining of similar and dissimilar materials. The processes are used by many researchers; because these processes produce sound welds; and they do not have common welding problems, such as solidification and liquefaction cracking related to...

Friction stir spot welding (FSSW) is a solid state welding process; and it is used to overcome the difficulties of joining aluminium and copper alloys. Dissimilar joining of AA1060 and C11000 using friction stir welding was carried out. The microhardness profile analyses were carried out and the probability distribution function (PDF) of the measur...

The Friction stir spot welding technique was used to produce lap spot welds of AA1060 and C11000. Various process parameters and tool geometries were used to fabricate the welds. The microstructures of the produced spot welds produced were examined by using optical microscopy (OM) and scanning electron microscopy (SEM). The chemical analysis of the...

Aluminium and copper are widely used in engineering structures, due to their unique performances, such as higher electrical conductivity, heat conductivity, corrosion resistance and mechanical properties even though they have considerable differences in their melting points. In this study, the microstructure of the friction stir spot welds of alumi...

The joining technology of similar and dissimilar materials plays a crucial role in various areas, include manufacturing. Many conventional welding techniques have been used over the years to successfully join various materials. Friction stir welding (FSW) and friction stir spot welding (FSSW) are solid state welding processes. This introduction giv...

This study explored the synthesis of activated carbon from olive seeds by chemical and thermal activation, and evaluated the energy efficiency of the process. The oilseed samples were carbonized at varying temperature (600–840 °C). The produced activated carbons were used for dye removal, studying the effect of temperature. The materials were analy...

Occurrences of over 44 economic minerals has been reported in Nigeria including copper ores found in Bauchi and Zamfara states. Now that the Nigeria petroleum industry which is the mainstay of her economy is experiencing downturn due to the global instability in oil price, it hence become imperative to diversify the economic to solid minerals parti...

Alloys of titanium in various forms are employed in engineering applications due to superior strength and performance than its pure form. Ti-6Al-4V alloy is highly viable in the aerospace, marine and automotive industries. Since it contains a combination of alpha-and beta-stabilizers, and it also maintains its specific strength within wide range of...

Jarosite wastes are produced daily from the refineries and contain toxic elements. In this study, the characterization of jarosite/clay/fly ash admixture is carried out to explore the possibility of using the produced bricks in the construction industry. The XRD results showed that the major phases in jarosite are Coesite and Mackinawite while Kaol...

Various evolving applications in power generation and the chemical, petrochemical, nuclear, aerospace, industries and manufacturing led to the development of techniques such as friction stir welding (FSW) and friction stir spot welding (FSSW) for similar and dissimilar materials. Many challenges include different melting temperatures arise during t...

Press and sinter is considered to be the most cost effective powder metallurgy process for producing parts. However, loose powder sintering shows to be a more promising cost effective powder metallurgy process as it entails pouring powder into a mould followed by sintering. The differences in their behaviour with respect to densification, maintaini...

Direct powder rolling (DPR) is an unconventional powder metallurgy technique for fabricating flat mill products. It offers significant cost reduction by using low processing temperatures and reduced fabrication steps compared to ingot metallurgy. Roll compaction is the first stage in the DPR process, hence proper selection of roll compaction parame...

An investigation was carried out on a high grade copper oxide ore to determine the optimum recovery rate of copper from the pregnant leached solution obtained from leaching the ore in a sulfuric acid lixiviant. The copper oxide ore occur in coarse grains locked in a porphyritic fine grain alumina and silica. 800 g of copper oxide ore was obtained a...

Mining is a strategic sector of the global economy. However, the effects of mining and mineral processing activities on human health and environment cannot be overemphasized. The prevailing areas of concern include: air quality, water quality, water quantity and the ecological impacts of these activities. Mines activities bring about the release of...

The local South African foundry industry discharges large volumes of waste sand each year, with estimates for silica and chromite sands of 250,000 and 25,000 tons, respectively. As a developing country, South Africa is moving toward a greener environment, so the management of industrial waste is an imperative area of study. In this work, we present...