Browsing by Author "Linkov, V.M."

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    Composite low temperate hydrogen storage material on the basis of iron-titanium alloy ; synthesis and structure
    (University of the Western Cape, 2006) Onyegbule, Nkele; Linkov, V.M.; Nechaev, A.; Dept. of Chemistry; Faculty of Science
    It is widely believed that hydrogen will within a few tens of years become the means of storing and transporting energy. The reason is the depletion of hydrocarbons and the relatively facile production of hydrogen from various renewable sources of energy. Hydrogen can be combusted in an efficient way in a fuel cell with water as emission product. As concerns over air pollution and global warming increase, the incentive to switch to clean and efficient hydrogen economy becomes greater and the transition may occur well before hydrocarbon reserves are extinct. The overall goal of the project is to develop the knowledge base for solid-state hydrogen storage technology suitable for stationary and mobile applications. In order to accomplish this goal, the project will have a dual focus which includes the synthesis of novel nano-structured hydrogen storage materials and systems that can accurately analyze the materials. The aim of this research is to develop a novel composite hydrogen storage material with high wt% storage capacity, high intrinsic safety, appropriate thermodynamics, high mechanical strength, reversibility of the system and fast kinetics based on a well known “low temperature” intermetallic alloy (Ti/Fe) as the core. In the course of achieving this objective, the structural, thermal, chemisorptive and physisorptive attributes of this material on a nanoscale have been evaluated considering that nano-structuring is a potentially promising approach for controlling bond strength, kinetics, and sorption temperatures and pressures. By combining different materials with suitable catalytic and thermodynamic properties, a new class of hybrid hydrogen storage material has been developed. More importantly, the focus was to increase the capacity of hydrogen sorption in this material. This goal was achieved with the mechano-chemical pre-treatment of Ti/Fe alloy and surface modification with carbon nanotubes, binary palladium and magnesium metals via a layer-by-layer modification technique. The chemical and mechanical stability of hydrogen storage materials is of great importance because hydrogen storage materials must withstand repeated adsorption and desorption cycles. The layer by layer approach that was used in this project allowed the investigation of the chemical and mechanical stability of the materials as each layer was added. Through this layer by layer approach suitable nano-particles were introduced that are chemically and mechanically stable. The knowledge emanating from this investigation is expected to allow the directed design of new, higher-efficiency, recyclable hydride-based materials in pursuance of the 6.0 wt% goal set forth by the US Department of Energy.
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    Hydrogen selective properties of cesium-hydrogensulphate membranes
    (University of the Western Cape, 2006) Meyer, Faiek; Linkov, V.M.; Bladergroen, B.J.; Dept. of Chemistry; Faculty of Science
    Over the past 40 years, research pertaining to membrane technology has lead to the development of a wide range of applications including beverage production, water purification and the separation of dairy products. For the separation of gases, membrane technology is not as widely applied since the production of suitable gas separation membranes is far more challenging than the production of membranes for eg. water purification. Hydrogen is currently produced by recovery technologies incorporated in various chemical processes. Hydrogen is mainly sourced from fossil fuels via steam reformation and coal gasification. Special attention will be given to Underground Coal Gasification since it may be of great importance for the future of South Africa. The main aim of this study was to develop low temperature CsHSO4/SiO2 composite membranes that show significant Idea selectivity towards H2:CO2 and H2:CH4.
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    Palladium surface-modified rare earth metal-based ab5 type hydride-forming materials
    (University of the Western Cape, 2008) Williams, Mario; Linkov, V.M.; Nechaev, A.N.
    Driven by mounting standards of living and a growing population, South African energy consumption is expected to increase dramatically within the next decade. The increased demand for more energy will require enormous growth in the capacity for energy generation, more secure and diversified energy sources, and a successful strategy to reduce greenhouse gas emissions. The wellbeing of the South African economy depends on reliable and affordable supplies of energy; whilst environmental wellbeing, from improving urban air quality to abating the risk of global warming, requires energy resources that emit less greenhouse gases compared to petrochemicals. Amongst the various alternative energy strategies, building an energy infrastructure that utilises hydrogen as the primary energy carrier may enable a non-polluting energy security in the future, when it is produce using renewable energy sources (e.g. water electrolysis). Hydrogen has been acknowledged as a key element in the future generation of energy and will be essential in increasing and maintaining economic growth. The significance of hydrogen as a future energy source is due to its large abundance and an energy density that is three times greater than that of an average hydrocarbon fuel. Roughly 80% of hydrogen is produced by natural gas reforming, partial oxidation of light alcohols, and autothermal reforming. In addition, a number of alternative technologies exist in which hydrogen can be generated from starting materials such as coal; biomass; and water, including electrolysis, fossil fuel processing, and coal gasification. However, most of these technologies produce a hydrogen product which is of poor purity. Purification is achievable considering equipment costs are extremely high and the process is therefore mostly economically unfeasible.
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    Preparation and physico-chemical properties of nickel nanostructured materials deposited in etched ion-track membrane
    (University of the Western Cape, 2005) Nkosi, Mlungisi Moses; Linkov, V.M.; Nechaev, A.; Theron, C.C.; Dept. of Chemistry; Faculty of Science
    The development of finely dispersed powders and superfine-grained materials intended for application in various areas of science and engineering is one of the challenges facing modern nanotechnology. Thus, specific fundamental and applied research was required in order to consolidate advancement made in preparing nano- and submicron crystalline composite materials. Useful templates for electrochemical deposition of nanowires include porous alumina films formed by anodic oxidation of aluminium, nuclear track-etched porous membranes, nanochannel array-glass and mesoporous channel hosts. The properties of the nanowires are directly related to the properties of the nanoporous templates such as, the relative pore orientations in the assembly, the pore size distribution, and the surface roughness of the pores. The template synthesis method, based on the use of porous polymeric and inorganic matrixes, is now actively used for synthesis of such composite materials. The method allows the chemical and/or electrochemical synthesis of nano- and microstructured tubes and wires consisting of conducting polymers, metals and semiconductors.In this study various technological challenges relating to template synthesis and development of nickel nano- and microstructures on adequately strong and durable substrates were investigated. The two methods used were the electrochemical and chemical deposition. “Hard nickel” bath solution was used for optimal nickel deposition. This optimization included investigating variables such as the template structure, type of electrolyte and form of electrolytic deposition. Scanning Electron Microscopy was used to investigate the structures of template matrixes and the resultant materials. The cyclic voltammetry method was applied for the analysis of electrochemical properties and hydrogen evaluation reaction of nano- and microstructured nickel based electrodes. The activity of composite nano- and microstructured materials in various configurations resulting from pore filling of template matrices by nickel was explored. Studies of the physical structure and chemical properties of the nanostructured materials included investigating the necessary parameters of template matrices. The optimum conditions of synthesis, which allowed development of materials with the highest catalytic activity, were determined.  The effect of the template structure on microcrystallinity of the catalyst particles was established using the XRD method. Different new types of non-commercial asymmetric ion track membranes has been tested for nanostructure preparation. The catalytic activity of the new developed nanomaterials is higher as compared to materials using commercial templates. The procedures to modify the newly developed nickel catalyst with Pt, Pd and Pt-Pd alloy have been developed. The Pt and Pt-Pd alloy containing catalyst showed the best performance in water electrolysis. In this work, the promising role for specific application of the new materials in hydrogen economy has been demonstrated.
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    Synthesis and characterization of nanofluids for cooling applications
    (University of the Western Cape, 2006) Botha, Subelia Senara; Linkov, V.M.; Bladergroen, B.J.; Dept. of Chemistry; Faculty of Science
    Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in numerous industrial sectors. Recently submicron and high aspect ratio particles (nanoparticles and nanotubes) were introduced into the heat transfer fluids to enhance the thermal conductivity of the resulting nanofluids. The aim of this project was to investigate the physico-chemical properties of nanofluids synthesized using submicron and high aspect ratio particles suspended in heat transfer fluids.