A research report submitted to the Faculty of Engineering and the Build Environment, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science in Engineering Johannesburg, 2014 / The South African power crisis and corresponding rising costs experienced since 2008, created a paradigm shift in terms of electricity use. The mining sector is the second highest consumer of electricity with metalliferous mines being accountable for 80% of the total power. Recent studies revealed that underground ventilation and cooling accounts for 30% to 40% of total electricity costs in an underground metalliferous mine. Hence the need to look at ways to reduce electricity consumption in ventilation and cooling. Work has been done on optimising efficiencies of ventilation and refrigeration systems of underground mines. Currently, the high energy consumption is driven by efforts to achieve a thermally acceptable environment for workers (manned) in deep metalliferous mines which is currently between 27ºC (wb) and 29ºC (wb). However, no detailed study has been done looking at increasing thermally acceptable environments for deep level metalliferous mine. In this study the impact of increasing rejection temperature to 40ºC (db) was assessed in the automated (unmanned) scenario at a maximum depth of 2811 metres. Then the power demand was compared with the manned scenario. The results proved that automation in an underground mine has the potential of reducing electricity cost of ventilation and cooling by more than 50%. For example, the production rate of about 200 kilo-tons per month yield an annual cost saving of R71 million on electricity. These cost savings can be used to justify automation systems. Automation removes workers from the hazardous environment and replaces them with equipment which can withstand harsher conditions. The introduction of an automation system in underground mines would not come risk-free. Currently, automation systems have not yet reached a level of removing workers completely from underground.There are instances that would require workers to enter production zones. A Bow-Tie risk analysis was used to show the hazards that workers would be exposed to and prevention controls and responses to mitigate the impact the risks. / MT2017

The participation of indigenous communities and use of indigenous knowledge systems (IKS) in environmental governance is provided for in several international and national environmental legislation and policies. In South Africa, the National Environmental Management Act 107 of 1998 (NEMA) in Chapter 1, Principle 4g requires that decisions must take into account the interests, needs and values of all interested and affected parties, and this includes recognising all forms of knowledge, including traditional and ordinary knowledge. This study investigated the Environmental Impact Assessment process (EIA) in mining developments in three rural communities in Limpopo Province, South Africa with regards to the effectiveness of public participation in fostering the incorporation of IKS. The qualitative research design used in this study employed several research methods through the utilisation of 3 villages as a case study. Semi-structured interviews, a focus group discussion and document analysis were used to collect information regarding the public participation process and the integration of IKS into EIAs. This report illustrates that IKS exists in rural communities and some of it is relevant to be incorporated in EIAs. This research study has shown that while expert knowledge dominates the EIA process, there is no indication that this is done deliberately to exclude IKS. This study has also revealed that the public participation process has a number of weaknesses such as in the selection and composition of community stakeholders and communication procedures. Suspicions also developed amongst the villagers of community representatives being bribed by the mine, and infighting started within community committees resulting in some community members losing trust in the committees. The disagreements with regards to the integrity of community committees created divisions and this negatively impacted on the public participation process. However, despite these weaknesses, if capacity building for both EIA experts and rural communities is done, the public participation process has potential as a tool to aid the integration of IKS into EIAs.

Low temperature plasma surface alloying with nitrogen (nitriding), carbon (carburising) and both (carbonitriding) has been successfully employed in hardening medical grade ASTM F138, ASTM F1586 and ASTM F2581 as well as engineering grade AISI 316 by the formation of a modified layer better known as S-phase or expanded austenite. In this study, systematic plasma treatments and characterisation were performed on medical grade stainless steel in order to establish the optimised treatment conditions, especially temperature, which can maximise the hardened case depth without any detriment in corrosion resistance. The surface of a biomaterial must not adversely affect its biological environment and return the material surface must not be adversely affected by the surrounding host tissue and fluids. Experimental results have shown that this duality of concern can be addressed by creating S-phase. It has been shown that low-temperature nitriding (430°C), carburising (500°C) and carbonitriding (430°C) improved the localised corrosion, corrosion-wear and fretting-wear resistance of these medical grade stainless. Also biocompatibility studies have proved that these hardened surfaces were biocompatible under the realms of the tests conducted in this study therefore the use of hardened medical grade austenitic stainless steel might be suitable in implant applications.

This thesis reports on an environmentally-friendly pultrusion technique for the production of fibre-reinforced composites, termed as “clean pultrusion”. In this new manufacturing technique, the resin bath used in the conventional pultrusion was replaced with a custom-built resin impregnator. The resin impregnator was designed and built to impregnate the rovings using a combination of pin, injection and capillary-based impregnation. An integral aspect of the clean pultrusion process was spreading of the filaments in the rovings, via mechanical means, prior to impregnation. An automated fibre spreading rig was designed and built based on “tension-release” process. The rig-design was optimised using Taguchi method. The physical, mechanical and thermo-mechanical properties of the composites pultruded using the clean and conventional techniques were compared. It was found that the composites manufactured using the clean pultrusion exhibited lower void and better mechanical properties. A life cycle assessment (LCA) was also performed to compare the environmental impact of the clean and conventional pultrusion processes. The LCA demonstrated conclusively that the clean pultrusion technique offers several environmental advantages over the conventional resin-bath pultrusion. The new pultrusion technique was demonstrated as being a viable method to pultrude composites without using a resin bath.

Microstructural analysis and mechanical property assessment have been carried out on hot isostatically pressed (HIPped) and heat treated samples of RR 1000 powder to assess Net Shape HIPping as a process-route for aero engine components. HIPping led to (Hf,Zr)-rich oxides and carbides on prior particle boundaries (PPBs) which could be coarsened, but not eliminated by changing the HIP procedure. HIPping above the γ′ solvus resulted in coarser grains with serrated boundaries and in the formation of irregular-shaped secondary γ′ and fan-type γ-γ′ structures. Factors which influence the growth and morphology of γ′ particles are considered and it is shown that particle impingement dominates in the formation of irregular γ′ during continuous cooling from supersolvus. Solution treatment near the HIPping temperature led to thermally induced pores (TIP) but lower temperatures avoided TIP and changed the γ′ size, distribution and morphology giving a large volume fraction of finer cuboidal secondary γ′ and medium-sized spherical tertiary γ′.

Between 50% and 70% of the total energy used in the extraction process may be attributed to comminution. Microwave pre-treatment has been suggested as a means to decrease the energy requirements. A variety of mineral ores have been investigated and the effects of microwave radiation quantified in terms of the mineralogy, changes in the Bond Work Index, flotability and magnetic separation. It has been shown that microwave pre-treatment is most effective for coarse grained ores with consistent mineralogy consisting of good microwave absorbers in a transparent gangue (up to a 90% decrease in Bond work index for Palabora copper ore) whereas fine grained ores consisting predominantly of good absorbers are not affected as well (a reduction of only 25% in work index for Mambula ore). Although the mineralogy of minerals are affected by exposure to microwave radiation, flotability and magnetic separation characteristics have been shown not to be adversely affected, unless the microstructure is completely destroyed after prolonged microwave exposure. Computer simulations have shown that significant changes to comminution circuits are possible as a result of microwave induced work index reductions (three mills reduced to one). Purpose-built microwave units may hold the solution for more efficient mineral extraction in the near future.

Linear friction welding (LFW) of two α - β titanium alloys, Ti-6Al-4V (Ti64) and Ti-6Al-2Sn-4Zr-6Mo (Ti6246) was studied, focusing on micro-hardness measurement, microstructure and texture characterisation. It has been found that in the as-welded condition Ti6246 has lower micro-hardness values in the weld region than in the base material, while for Ti64 the weld region is harder. The change in hardness is greatly related to the microstructures formed after welding. In cnetre weld zone (CWZ), in the autogenous Ti6246 weld, the microstructure consists of fine β grains with needle shape orthorhombic α″. In the autogenous Ti64 weld, relatively large acicular martensitic α′ phase was found. A very strong texture component, where the basal pole is concentrated in the sample normal direction and one of the {11 20}α poles is concentrated in the oscillation direction, is identified in both the CWZ and thermo-mechanically affected zone. Comparison between the α texture and the β texture suggests that the strong texture component T is the consequence of the deformation β texture developed at high temperature and the preferred variant selection during the β→α transformation. The texture was found to have significant influence on the fracture toughness of the weld region.

Lithium is considered a borderline strategically important metal for the UK due to the limited availability of primary deposits, of sufficient grade, for economic processing (Naden, 2012). The rising demand, of approximately 10% yearly, has promulgated investigations for the development of secondary sources of lithium in order to secure long term reserves for the UK and Europe (Jaskula, 2015). The British Geological Survey (1987) estimated that the St Austell granite contained up to 3.3 million tonnes of recoverable lithium. Imerys Ltd also identified lithium-bearing mineral in their kaolin waste material in Beauvoir, containing up to 0.89 wt.% Li2O. The lithium-bearing minerals identified were; lepidolite (K(Li,Al)3(Si,Al)4O10(F,OH)2) and zinnwaldite (KLiFeAl(AlSi3)O10(F,OH)2), which can contain between 3.0 to 7.7 wt.% Li2O and 2.0 to 5.0 wt.% Li2O, respectively (Garrett, 2004). Lithium flotation concentrates containing up to 5.0 wt.% Li2O were optimised for the Beauvoir waste material with up to 80% lithium recoveries, whereas a lower flotation grade of 0.5 wt.% Li2O was found for the St Austell material. The St Austell waste materials did not prove viable to process via conventional flotation routes hence a novel process route for the bio-recovery of lithium from lithium rich micas was developed. Extraction of lithium by bioleaching has demonstrated the ability of fungi, of Aspergillus niger group, to leach lithium from the lepidolite in significant quantity, achieving 125mg/L of lithium in solution after twelve weeks of bio-leaching, at a recovery of 45%. Following this research, Imerys are applying to build a pilot plant, securing funding through the Innovative UK grant.

Ti has been widely used in biomedical fields since the 1950s because of biocompatibility, corrosion resistance and suitable mechanical properties. However, corrosion-related failures of Ti implants are observed. Ti corrosion products are reported to induce unfavourable biological responses, which may lead to failures of Ti implants. Corrosion of three grades of Ti (CP-Ti Grade2, CP-Ti Grade4 and Ti6Al4V) in simulated peri-implant environments was investigated by solution analysis, surface analysis and electrochemical tests. Lipopolysaccharide, a component of bacterial cell walls and a mediator of peri-implant inflammation, was observed to enhance Ti corrosion in slightly acidic and neutral conditions (pH 4-7) whilst it inhibited Ti dissolution in highly acidic environments (pH 2). Both albumin, an abundant protein, and H₂O₂, an important inflammation product, influenced corrosion of Ti6Al4V and the co-existence of both species considerably enhanced Ti release than either species in isolation. The β phase of Ti6Al4V was preferentially attacked in H₂O₂. The presence of an early coloniser of dental implants Streptococcus sanguinis and human neutrophils, abundant immune cells, promoted Ti release. Mechanically-assisted crevice corrosion simulation was demonstrated with development of aggressive crevice chemistry. Albumin decreased the abrasion charge of Ti6Al4V while LPS and H2O2 did not show a measurable change.

Several unscheduled shut downs of the Cruas nuclear power plant in France have been caused by the deposition of corrosion products in flow broaches of the steam generator tube support sheets. The depositions are theorised to be the result of electrokinetically stimulated deposition. In this work, a hot water loop to replicate these depositions in the laboratory was built, along with rigs to characterise supporting phenomena – the corrosion rate of stainless steel and the solubility of the corrosion products. While the data obtained from the hot water loop did not provide conclusive proof of the existence or prevalence of the electrokinetically stimulated deposition mechanism, evidence of deposition caused by cavitation was found. The corrosion rate of stainless steel was measured at high temperatures in solutions of lithium hydroxide at various concentrations. Surface finish was found to have an effect on the corrosion rate, though the difference between mechanically ground surfaces with an order of magnitude difference in roughness was found to be minimal. The solubility of the corrosion products formed was measured and found to be of similar order to that reported in the literature, however the minor alloying elements were found to leach from the surface in substantial quantities.