A functional material of carbon nano-composite is investigated to be utilised as a Thermal Interface Material (TIM) in the Low Voltage Power Supply (LVPS) bricks as part of the upgrade of the large Hardron Collider (LHC) accelerator at CERN. The TIM is a composite in a pasty form, based on carbon nanomaterials (CNMs) and Silicone heat transfer compound. The goal behind the implementation of...
The Vacuum Arc Thruster (VAT) is an unconventional plasma propulsion system with unique advantages for small satellite applications. The relevant literature and figures of merit were presented. An inductive energy storage pulsed power circuit was built which delivered triangular submillisecond current pulses to a coaxial VAT. The dense copper plasma, the expansion of the macroparticle plume,...
The DC discharge microthruster concept is a simple, energy efficient plasma micropropulsion system that operates using an ionisation-acceleration coupling mechanism. This system was developed in the hopes of addressing some of the shortcomings of many state-of-the art electric micropropulsion systems. Preliminary studies have been conducted on the thruster from which the stable operating...
Measuring phase differences between orthogonal polarisations has become a common industry practice. In food and drug production the circular birefringence exhibited by chiral molecules has been used to identify and measure the concentrations of enantiomers, while linear birefringence has been used in stress and biological imaging. Conventional techniques regularly rely on stressing...
The gold industry in South Africa, mainly based on the metal extraction through cyanide leaching and the use of microorganisms, has been among the top 10% country's main source of income. This results in a strong economy, emergence of new towns and new financial structures. The use of cyanide as a lixiviant raises serious environmental concerns as it negatively impacts on the biodiversity,...
Kimberlite rock has been activated with a high energy photon beam, following which high energy resolution spectra have been acquired in time differential mode. This enables a lifetime analysis of the isotopes that have been activated. An isotope identification is then performed using the dual information of characteristic gamma rays and lifetimes. This enables an unambiguous assignment of the...
During the early high-level lockdown linked to the COVID-19 pandemic in 2020 much of the South African industrial and economic sectors ground to a halt. This provided an opportunity to identify the role human activities have on the local contribution to aerosol emissions in Gauteng by comparing the 2020 atmospheric turbidity during that time of the year with the levels observed in prior years....
Food drying is an energy-intensive operation that results in the removal or reduction of the moisture content of different foods for storage, quality retention, and enhancement purposes. In developing countries, open solar drying is one of the major methods adopted for the preservation of agricultural products due to the availability of solar energy at little or no cost, especially in Africa....
Abstract.
In this work, thin films of dip coated CuO nanoparticles were prepared on fluorine-doped tin oxide (FTO) substrates and the film’s processing parameters which includes the withdrawal rate, film thickness and annealing temperature were optimized for photoelectrochemical (PEC) water splitting. CuO films were prepared at withdrawal speeds ranging from 50-200 mm/min, with thicknesses...
In this paper, a combined solar cooker with a sunflower oil storage tank is presented. The solar cooker consists of a 1.8 m parabolic dish that has an oil circulating copper spiral coil receiver embedded to a metallic cooking plate. The receiver is connected to a 50 L sunflower oil storage tank for the dual purpose of heat storage and cooking. A DC pump is used to circulate the oil during...
A novel cavity type solar receiver for solar trough thermal plants was developed. Previously, the theory for such a receiver was developed, and a simulation written based on it. Some results from the simulation were compared to an indoors experiment to encouraging agreement. In this talk, I present a version that was developed for a ~20kW solar plant and is tested in the open using an in-house...
The determination of the dark electrical characteristics of each cell within a PV module enables the simulation of the complete PV modules electrical performance when in operation. It is, therefore, possible to estimate the power output of a PV module in operation. In a previous study, a method was developed that used injection dependent Electroluminescence (EL) images to characterise...
Thin-film photovoltaic (PV) technology has been around for quite some time with varying performance for the different technologies. A major shortcoming of thin-film PV modules compared to crystalline PV technology is their shorter guaranteed operational lifespan as they degrade faster. In this study, the performance of thin-film technology operating in an outdoor environment is monitored and...
Carbon based nanostructures have a long history, dating back to the 30ies and 40ies of the 20th century. They got a strong boost with the discovery of the fullerenes and nanotubes, and they were crowned by the research on graphene. The investigations on these nanostructures are of both fundamental and technological interest due to the interesting electronic and physical properties...
Diphenylaniline dyes are important sets of organic dyes that has stirred many research interest as photosensitizers in TiO2 semiconductor based dye sensitized solar cells (DSSCs). The advantages of organic dyes over metal based complexes are higher extinction coefficient, low cost, good environmental compatibility and electrochemical properties. The diphenylaniline organic dyes with basic...
Recently, carbonaceous nanomaterials such as carbon nanotubes and two-dimensional graphene have attracted the attention of the scientific community in probe to improve energy conversion and storage technologies. The graphene sheet is more preferred due to its large specific area, flexible structure, high transparency, excellent mobility of charge carriers and is expected to be able to slow the...
Rechargeable sodium-ion batteries (SIBs) have attracted great attention for large-scale electric energy storage applications and smart grid owing to the abundance of Na resources and comparable performance with lithium-ion batteries. The use of organic electrode materials enables a sodium storage system with high energy/power density, metal-free, environmental friendliness, flexibility,...
The University of the Witwatersrand will be producing over 1200 Low Voltage Power Supplies (LVPS) to power the on-detector electronics of the Tile Calorimeter (TileCal) ATLAS detector in preparation for the Phase II upgrade. Two burn-in type test stations are currently being developed in the high-throughput electronics laboratory. The Load readout board is used to read and control/adjust...
With University of the Witwatersrand responsible for producing 50% of the Low Voltage Power Supplies (LVPS) bricks for powering on-detector electronics of the Handronic Tile Calorimeter (TileCal). The Burn-in testing station is used to detect early failures in components of the LVPS bricks, thereby increasing component reliability, detect early failures in components. The LVPS bricks that...
Time coincidence detection of annihilation photon pairs is used to determine the instantaneous position of point-like particles used as flow following tracers in dynamic systems. Locations are calculated by a minimisation approach applied to a small number of reconstructed pairs assuming a fixed signal to noise ratio. Consecutive locations define the particle trajectory, and hence the dynamic...
Instrumental neutron activation analysis (INAA) is a non-destructive technique used for qualitative and quantitative elemental analysis in a range of contexts, including the food, coal and minerals processing industries, and the detection of contraband. Broadly, INAA requires the irradiation of a sample in a neutron field, and the neutron interactions within the sample to produce radioactive...
The Positron Emission Particle Tracking (PEPT) technique enables the tracking of a moving
radioactive tracer particle at high spatial and temporal resolution, from which its trajectory can
be accurately reconstructed. The uncertainty budget is complex and poorly understood,
particularly for derived quantities such as momenta, energies, and forces, which are typically
calculated using...
Structure light beams that are tailored in the polarisation and transverse spatial degrees of freedom are ubiquitous to numerous applications and emerging technologies ranging from laser cutting, particle tracking, to high dimensional classical and quantum secure communication. Imperfections in optical elements or perturbations in a propagation medium can degrade the quality of spatial modes...
This study examined changes in the properties of poly-crystalline hexagonal boron nitride (h-BN) samples implanted with light ions (He+, Li+, B+, and Ne+) at 150 keV and at a fluence of 1x1015 ions/cm2. We have previously reported the production of cubic boron nitride nanoparticles in a subsurface layer, accompanied by a measurable hardening. The GIXRD findings show a new peak at 46.45°...
Abstract
At nanoscale, the electrical, optical, and catalytic properties of metal nanoparticles depend on shape and size. In this study, gold nanoparticles (AuNPs) were synthesized using the seed-mediated growth method. Au nanospheres, nanoprisms and nanorods with average sizes of 6 and 68 nm, (70 nm length, 40 nm width) and grain sizes of 14, 20 and 130 nm, respectively; obtained by SEM and...
PEPT Cape Town has established the development of Gallium-68 based tracer particle analogues for use in positron emission particle tracking studies of granular and multiphase systems. The accuracy of the measured data relies strongly on how representative the tracer particle analogue is to the media of interest in these dynamic systems. The ability to control and manipulate the tracer particle...
Positron Emission Particle Tracking (PEPT) is a radioactive tracer technique used to determine the trajectory of a positron emitting macroscopic particle used as a flow follower. The nearly collinear 511 keV gamma ray pairs resulting from positron annihilation are detected in dedicated arrays. The tracking efficiency and performance is dependent on the physical properties of the tracer,...
Fast neutron fields are found in a wide variety of contexts, for example at accelerator and medical radiation facilities, around nuclear power plants, in aviation and space flight. The essence of neutron metrology is to quantify both the fluence and energy of these fields, which is complicated by the large range of energies, intensities and directional characteristics in each unique scenario...
The upgrade of the ATLAS hadronic tile-calorimeter (TileCal) Low-Voltage Power
Supply (LVPS) falls under the high-luminosity LHC upgrade project. This presentation serves
to provide a detailed overview of the development of an endurance (Burn-in) test station for
use on an upgraded LVPS component known as a Brick. These Bricks are radiation hard
transformer-coupled buck converters that...
Abstract
Food is the most essential need for both human and animal survival. During food production, and in high harvesting times, the food supply can be greater than food demand. This will result in more food wastage. The use of a solar dryer will reduce food wastage and preserve food for a longer time before consumption. Solar drying improves the quality of the dried products significantly,...
The monitoring of volatile organic compounds (VOCs) in the atmosphere can yield useful information regarding environmental processes, such as the degradation of pesticides or the composition of natural gas seeps. The VOCs in air are easily monitored by trapping on silicone multi-channel traps (MCTs) followed by gas-chromatographic analysis. However, MCTs are not passive devices and require...
Abstract. Selective detection of gases such as Nitrogen Dioxide (NO2), Carbon Monoxide (CO), Carbon Dioxide (CO2), and various other volatile organic gases is necessary for air quality monitoring. In this project we are focusing on Zinc Oxide (ZnO) as a gas-sensor and the test gas considered is Nitrogen Oxide, an oxidising gas. The conductivity of ZnO gas sensor increases when the sensor is...
X-ray Computed tomography (XCT) is a technique that is used to generate 3D images of a sample which allows the observation of the internal structure [1]. Projections are collected as the sample rotates through 360 degrees followed by a reconstruction step using algorithms such as the filtered back-projection. This technique has found widespread applications in fields such as medical...
CORROSION BEHAVIOUR OF SPARK PLASMA SINTERED TI-AL ALLOYS
M. T. Sinthumule, T. Tshephe
Faculty of Engineering and Built Environment, University of Johannesburg, P.O. box 524, Auckland Park 2006, Johannesburg, South Africa
Tel.: +27 (65) 864 5787 E-mail: sinthumulemukzz@gmail.com
Abstract
The research study focusses on the corrosion characteristic of titanium-aluminum (Ti-Al) sintered...
Thermal Infrared (TIR) imaging identifies abnormal thermal signatures in photovoltaic (PV) modules as cell areas operating at elevated temperature. Contaminants on a PV module glass can cause mismatch in operation of PV cells connected in series and can result in hotspots. The hotspots can occur due to different thermal emissivity of the module glass and contaminants and current mismatch...
Since, for some years now, with the rapid development of industrialization and urbanization, severe pollution primarily attributed to automobile exhaust and factory emission has become major threat to human survival and development. A leakage of flammable and explosive gases may end in a loss of life and property damage. Thus uplifting the concern for researchers to seek a high sensitive,...
The maximum photovoltaic (PV) power output is not always achieved in real time measurement due to the unsteady weather conditions. Local solar irradiance plays a critical role in the performance of solar panels. Therefore, the site assessment of weather conditions is necessary for a better forecasting of potential PV power output and recommendation of the suitable solar panel. Due to limited...
In this study, copper zinc tin sulphide (CZTS) and copper zinc tin sulphur selenide (CZTSSe) thin films were deposited on molybdenum (Mo), indium tin oxide (ITO) and fluorine-doped tin oxide (FTO) by sputtering deposition and were annealed in nitrogen at 500°C for 60 minutes. The XRD patterns on all substrates showed tetragonal kesterite CZTS with I4 ̅ space group and tetragonal kesterite...
In this study we used high resolution Laplace Deep-Level Transient Spectroscopy (L-DLTS) to study the electrical properties of the E and Eˊ defects in germanium (Ge) which are introduced by alpha particle radiation. Current-voltage and capacitance-voltage measurements reveal a decrease in the quality of the devices fabricated on the radiated samples. The activation energies for these defects...
Abstract
The research study will be focusing on the improvement of white cast iron hammer mill beaters that will be manufactured by casting and additions of alloying elements, such as carbide formers, i.e. molybdenum (Mo) and titanium (Ti) into the liquid melt. White cast iron, ASTM A532, Class I, Type A, material designation, NiCrHC alloy. A supplied hammer mill beater (HMB) of white cast...
Improvement of Abrasive Wear Resistance and Toughness on Hammer Mill Beaters by Additions of Molybdenum and Vanadium-Ferroalloys in White Cast Iron
F. Nyambi, M. Ngqase, W. Nheta
Faculty of Engineering and Built Environment, University of Johannesburg, P.O. box 524, Auckland Park 2006, Johannesburg, South Africa
Tel.: +27 (0) 76 875 5938 E-mail:...
Adiel Holtzhausen, Mmantsae Diale
Department of Physics, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa
Abstract
In this study, hematite (α-Fe2O3) thin films were synthesized, on fluorine-doped tin oxide (FTO) glass substrates, using dip coating and spray pyrolysis. This was done to study the morphological, optical and structural properties of the hematite. Six...
The Tile Calorimeter (TileCal) is currently preparing for the Run 3 data-taking period. As part of the ongoing Phase I upgrades, TileCal is replacing a part of the Timing, Trigger and Control (TTC) system. The legacy TTC system is being replaced with a new advanced electronic board, designed for the ATLAS experiment at CERN. The new ATLAS Local Trigger Interface (ALTI) module, is a 6U VME...
Solid carbon nanospheres of about 4 nm diameter have been prepared and then doped by ion implantation, using a specialized end-station adapted for the uniform implantation of powders. Boron, nitrogen and neon ions were chosen initially, the latter for control purposes. Herein, the dependence of the physicochemical properties of solid carbon spheres on the fluence of the implanted ions was...
The properties of noble metals are different when these materials are reduced to nano-scale dimensions (1 – 100 nm), dependent on shape and size of the particle. In this research gold nanorods were synthesized using the mediated-seed method. The absorption spectrum of these nanorods showed two bands; the transverse and longitudinal band. Transmission Electron Microscopy (TEM) images show...
A major upgrade to the High Luminosity Large Hardon Collider (HL-LHC) will increase the instantaneous luminosity by a factor 5 compared to the LHC. A complete redesign of the electronic system is required for new radiation levels, data bandwidth as well as the clock distribution. The upgrade of this electronic system is an integration of front-end and back-end electronics to acquire physics...
