The Nb-Ru system is of interest because the ∼NbRu phase has potential for high temperature shape memory alloys. Previous workers have identified the phase transformation variously as involving twinning, of cubic-to-tetragonal and tetragonal–to-orthorhombic (or monoclinic) transformations. As well as the terminal (Nb) and (Ru) solid solutions, two intermetallic phases have been identified: ∼NbRu and ∼NbRu3 / ∼Nb3Ru5 / ∼NbRu2, but the boundaries between the different phases are still not fully established. This investigation looked at six as-cast alloys of different compositions across the Nb-Ru system, which were made from 99.95 % purity Nb and Ru. The samples were made by arc-melting under an argon atmosphere, using titanium as an oxygen-getter. These samples were sectioned and prepared metallographically for optical microscopy, SEM and XRD analyses, the latter using an X’pert database. The phases found were (Nb), (Ru), ∼NbRu and “∼NbRu3”, as expected. Although the samples were mainly homogeneous, there was porosity in the (Ru) phase between the “∼NbRu3” dendrites in the Nb28.5:Ru71.5 at.% sample. The Nb14.2:Ru85.8 at.% sample was mainly single-phase (Ru).

The reprocessing of tailings or gold mine waste dumps to extract gold has become an attractive proposition for mining houses worldwide because of the availability of gold which was not easily recovered using old technologies. This study seeks to exploit the novel properties of nanostructured materials in enhancing gold extraction from gold mine tailings. The beneficiation of slimes or tailings involved taking samples for mineralogical studies, synthesis of a novel adsorbent medium (nano C-MgO) prepared by using both chemical and mechano-synthesis methods, oxidative pre-treatment of flotation concentrates, cyanidation and final recovery of the precious metal from solution in a Carbon in Column (CIC) system. The nanocomposite adsorbent was studied by powder X-ray Diffraction (XRD) for structural analysis, Field Emission Scanning Electronic Microscopy (FESEM) for surface morphology, Energy-dispersive X-ray spectroscopy (EDX) for elemental analysis and Fourier Transform Infrared (FTIR) spectroscopy for chemical structure analysis. The Brunauer-Emmett-Teller (BET) Surface Area Analysis procedure was employed to determine the total specific surface area of the nano-adsorbent. Representative tailings samples of 100-500 g were obtained for different analytical investigations using a riffle splitter. The tailings grade was analysed using the Atomic Absorption Spectroscopy (AAS) technique and was found to be an average of 0.5 g/tonne. A comparative Pseudo-Equilibrium test showed that the novel C-MgO nano adsorbent had an average of 84% recovery against 70 % for convectional activated carbon. The average crystalline size of 4.5 -11nm for the majority of MgO nanoparticles was obtained using Debye-Scherrer formula. FESEM confirmed that nano MgO was porous in nature and highly agglomerated whilst EDX exhibited the successful synthesis of the nano-composite product. This work also shows that the nano-adsorbent presents a huge potential for application in the conventional processes for gold adsorption.

LIBS is a developing analytical technique, which is used to perform qualitative and semi-quantitative elemental analysis of materials (solid, liquid and gas). Recently LIBS became an attractive technique to be used for geological samples, due to its advantages such as fast data collection and the lack of sample preparation. This study is done to improve analytical methods for geochemical analysis of samples during different exploration phases (Mining, filed analysis, etc.), to be used in the future as a real-time analysis method to save money and time spent in labs. In this work, LIBS has been used to differentiate between some geological samples gathered from different areas: South Africa and Namibia. Using principal component analysis (PCA), it was found that LIBS was able to differentiate between the samples even those of the same area. The results from the LIBS technique were correlated with subsequent analysis of the same samples by Particle-Induced X-ray emission (PIXE).

Multi-pass compression tests were carried out on the Gleeble-1500D® and Gleeble-3800TM® thermo-mechanical simulators to investigate the effect of temperature, strain rate and inter-pass time on the development of the texture in ferritic stainless steels (FSS) AISI 430 and 433, the latter an Al-containing variant. Orientation Distribution Functions (ODFs) through the electron backscattered diffraction (EBSD) technique was employed to characterise and study the texture present in the steels after hot working. The mean flow stress analysis showed that, the dynamic recrystallization to dynamic recovery transition temperature decreases with an increase in strain rate in both grades of stainless steels possibly allowing texture optimisation at lower hot rolling temperatures. Higher finishing rolling temperatures, lower strain rates and longer inter-pass times led to improvement in the formation of the desired γ-fibre texture which contributes to ductility or drawability in these steels. Dynamic recrystallization which promotes the formation of the desired γ-fibre texture was found to occur in both AISI 430 and 433 at temperatures above 1000 °C and strain rates less than 5 s-1. Generally AISI 433 develops a stronger gamma texture than the AISI 430 when hot rolled under similar conditions.

Vanadium carbide has outstanding tribological behaviour, superior to other similar carbides in Groups IVB and VB, except TiC. Most research on vanadium carbide uses it as an additive to enhance wear performance, inhibit grain growth and decrease density, and it has also been used as a partial replacement for WC in WC-Co. This work is on alloys of VC-Ni to provide potential lighter and more corrosion-resistant materials, and VC-Ni alloys were made by this method for the first time, and evaluated. Three alloys of compositions VC-4Ni, VC-10Ni and VC-22.1Ni (at.%) were produced by spark plasma sintering (SPS). The mixed powders were sintered at different temperatures and pressures to optimize the sintered density and hardness of the alloys. The best alloy was VC-10Ni (at.%), which had the highest density and the highest hardness.

Earth stabilization, using two by-products available in Burkina Faso: Calcium Carbide Residue (CCR) and Rice Husk Ash (RHA), improved the performance of compressed earth blocks (CEBs). The effect of adding CCR or CCR: RHA (in various ratios) to the clayey earth was investigated. CEBs were molded by manually compressing moisturized mixtures of earthen materials and 0-15 % CCR or CCR: RHA (various ratios) with respect to the weight of earthen material. The results showed that, with 15 % CCR: RHA in 7: 3 ratio, the compressive strength of CEBs (6.6 MPa) is three times that of the CEBs containing 15 % CCR alone (2.2 MPa). This improvement was related to the pozzolanic reaction between CCR, clay and RHA. These CEBs comply with the requirement for wall construction of two-storey housing.

Demand for newer, stronger, stiffer, yet lighter-weight and environmental friendly (biodegradable) materials in the fields such as automobile for non-structural applications are ever increasing. The principal reasons for using natural (cellulosic) fibers is they possess several attractive properties such their economic feasibility, enhanced sustainability, good specific mechanical properties, and desirable aspect ratio for good performance after melt-processing. Natural fiber composite materials are now being rapidly utilized in automobile industries, and they have become the forefront of research and development activity. An interesting alternative for reinforcing soft polymeric matrices with short fibers is the use of cellulose fibers which show remarkable reinforcing effects in thermoplastics such as polypropylene. The current study made an attempt to investigate the suitability of sisal fibers for automobile industry for non-structural and low-strength interior applications. In this work native sisal fibers were extracted and the effect of alkali treatment on their morphological, tensile, moisture absorption and thermal properties were studied. Scanning electron micrographs indicated roughening of the surface of the fiber strands due to the removal of the hemicellulose layer on alkali treatment. The maximum weight-gain for the composite prepared from treated fibers was 2.12 %, while that for the composite prepared from untreated fiber was 4.33 %. From the thermograms, the results indicate initial degradation for the treated fiber to have improved from 174 °C to 230 °C (56 °C shift) when compared to the untreated fiber. This fiber has competitive advantages when evaluated with other natural fibers. A polymer composite was processed from the chemically modified fiber, profiled against equivalent material systems in Ashby material property charts exhibited its suitability for light, low strength and low flexure material applications which can use a potential replacement of fibres being used currently.

The use of waste is rapidly becoming a supra-disciplinary field in most parts of the world where the use of industrial wastes like fly ash, granulated steel slag, silica fume, and waste fibers in construction has become very popular since the last half of the 20th century. Other forms of industrial wastes are also re-used even for more sensitive applications on soils to upgrade soil texture. For example, waste from bauxite refining (red mud) is known to be extensively re-utilised. These concepts are yet to take tangible hold in Africa, despite the huge resources available. Electric-Arc Furnace Steel slag is a major waste product from the steel industry involving the melting of scrap to make steel in an electric arc furnace. Use of such waste materials in construction alleviates the huge environmental pollution problem which often exists in areas where they are produced and/or dumped. Currently, the material is mainly used in construction works as unbound aggregate for asphalt concrete pavements, or as road base in many countries. However, it consists predominantly of oxides and silicates of magnesium, calcium, aluminium, iron and thus can be used as substitute for cement. This paper compares the effect of utilising this type of Steel slag and Granulated Blast Furness Slag, as partial replacement for Portland cement. The influence of the physical and chemical characteristics of the two materials on the setting time, compressive strength, total porosity and pore-size distribution of cement pastes have been evaluated. For the experimental conditions studied, the result reveal adequate properties for high levels of replacement but suggests that superior qualities, compared with Portland cement concrete is possible only if replacement levels do not exceed about 10%.

An effective way to reduce the impact of cement production on the environment is to use supplementary cementitious materials (SCM) as a partial substitution to cement. In addition to the reduction in cost and energy saving, the use of SCM in cement for the manufacture of mortar and concrete offers technical advantages. In this paper, cement was partially substituted by fines obtained from crushed recycled bricks recovered from a brick plant. The level of substitution was either 0%, 5%, 10% or 15% by weight of cement. The results show that cement substitution by brick fines resulted in a slight loss of workability with the increase of the substitution rate. Substitutions rates of 5% and 10% produced at long-term comparable strength as control mortars. The differential thermal analysis (DTA) and thermo-gravimetric analysis (TGA) results show cement hydration improved significantly with different rates of substitutions at 28 and 180 days of age.

The hydration of cement is an exothermic reaction which generates around 300 kJ/kg of cement hydrated. In mass concrete structures such as dams and large foundations, this heat of hydration causes a significant rise in temperature in the internal sections of the concrete. If thermal gradients between the internal sections and the near-surface zone of the concrete element are sufficiently large, the thermal stress can cause cracking of the concrete. This cracking may cause functional or structural problems in the operation of the structure. In order to minimise the potential for such cracking, it is necessary to minimise the rate and amount of heat that is evolved, particularly during the early period of the hydration process. This can be achieved by design engineers and concrete technologists through judicious selection and processing of concrete-making materials. This paper presents the observations and results obtained over a number of years from adiabatic testing of concretes, computational modelling of temperature development in large concrete structures and direct temperature measurements in actual structures, with a view to understanding the effects of concrete-making materials on temperature development in concrete. The paper considers the effects of different types of rock aggregates, different types of Portland cement, fineness of grinding of the cement, the addition of supplementary cementitious materials and variations in the concrete starting temperature on temperature development in a large concrete element over time. The results indicate that using a coarser ground cement, adding significant amounts of supplementary cementitious materials and cooling the concrete mixture before placing has a more significant effect in reducing the risk of cracking than varying the aggregate type of the Portland cement type.

Before 2008, it was common knowledge around the world that insulation always saved air conditioning energy in buildings. In 2008 a phenomenon called anti-insulation was brought to light by Masoso & Grobler. They demonstrated that there are instances when insulation materials in a building directly increase building energy use. Researchers around the world then echoed the message. Recent work by some of the authors investigated the anti-insulation phenomenon in summer and winter for both hot climatic regions (Botswana) and cold climatic regions (Canada). Their study concluded that there is still a mystery of exaggerated sources of heat inside the building aggravating the anti-insulation phenomenon. They hypothesized that incident solar radiation through the windows could be one of the causes. This paper therefore focuses on eliminating direct solar radiation through windows by applying external shadings on a previously anti-insulation building. The energy saved is evaluated and the possible reversal of anti-insulation studied. The study is useful to energy policy makers and the building industry as it showcases the existence of a possible silent killer (anti-insulation) and demonstrates that investing large sums of money on insulation in buildings may not be the most economic thing to do in building design decisions.