Publications (3)0 Total impact
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Article: Mechanochemical processing of refractory pyrite
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ABSTRACT: Mechanochemical reactions are those which are initiated by the application of a mechanical force. In recent times it has been shown that solid state mechanochemical reactions can be initiated by milling the reactants in a high energy ball mill — a process known as mechanical milling. Oxidation/reduction reactions have been shown to occur at room temperature during mechanical milling, and this has led to the idea that it may be possible to refine metallic ores via room temperature mechanochemical processes. In this study, it has been found that pyrite (FeS2) can be mechanochemically processed in a high energy ball mill. Pyrite is the most common sulfide host for gold, and in refractory pyrite samples gold is encapsulated in the pyrite matrix, so this matrix must be broken down prior to cyanidation. X-ray diffraction, Mössbauer spectroscopy and thermal analysis techniques have shown that pyrite can be oxidised mechanochemically, with the sulfur retained as a sulfate without the production of sulfur dioxide gas. Potential exists for this process to form the basis for an economically viable, environmentally friendly process for the treatment of refractory pyritic gold ores.Minerals Engineering. -
Article: Gas sensing properties of nanosized tin oxide synthesised by mechanochemical processing
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ABSTRACT: Tin oxide thin films have been prepared by mechanochemical processing and spin coating. Separated SnO2 nanoparticles, averaging 24 nm, were produced by mechanochemical processing. The powder consisted primarily of tetragonal SnO2, however, some orthorhombic SnO2 was also found to be present. SnO2 thin films were prepared by spin coating onto alumina transducers, followed by subsequent annealing. XPS analysis concluded the films were essentially stoichiometric with carbon being the main impurity. The average particle size of the SnO2 film was found to be approximately 34 nm. The electrical response of the sensor to O2, over the concentration range 1 ppm to 10%, was measured. The sensor was found to be extremely stable and repeatable, with a response and decay time of approximately 2 min. The response and decay times were found to decrease as the oxygen concentration increased.Sensors and Actuators B: Chemical. -
Article: Mechanical milling of magnesium powder
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ABSTRACT: The evolution of microstructure during mechanical milling of magnesium powder has been studied. Commercially pure (99.6%, −325 mesh) magnesium powder was mechanically milled in a modified SPEX 8000 shaker mill in an inert atmosphere. The optical microscopy of the powder in the early stage of milling showed deformation by twinning and re-twinning within the grains developing sub-grain boundaries, which eventually defined nanometre-sized grains. The grain size reduction examined using XRD revealed a rapid decrease and then saturation of the grain size at approximately 42 nm. A relatively large final grain size compared to other mechanically milled metals was obtained due to the high recovery rate of magnesium. The corresponding internal strain was also observed to be low, confirming that enhanced recovery had occurred during milling. The internal strain during milling showed inverse grain size dependence. Moiré fringe patterns of TEM micrographs showed absence of dislocations within the grains of as milled magnesium powder.Materials Science and Engineering: A.
