The mechanisms by which titanium carbide （TiC） improves the properties of tungsten carbide （WC） coatings deposited on duplex stainless steels using laser particle injection technique were investigated. The relatio...The mechanisms by which titanium carbide （TiC） improves the properties of tungsten carbide （WC） coatings deposited on duplex stainless steels using laser particle injection technique were investigated. The relationships between laser process parameters and the synthesized composite were studied. The morphologies and microstructures of the feedstock powders and composite coatings were characterized using scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX） techniques. Surface hardness of the composite layers was determined using the Vickers microhardness tester while its corrosion behaviour in 3.5%NaCl solution was investigated by potentiodynamic polarization curve measurement method. As a result of the laser treatment, microstructures characterized by hard ceramic particles with strong bonding to substrate were formed on the surface layer of the steels. The addition of TiC to WC resulted in microstructures free from cracks, pores and intermetallics which could be detrimental to the properties of the composites. High microhardness was observed and most of the coatings shifted the corrosion potential to more noble values with the pseudo-passive curve.展开更多
The interplay of mineralogical variation and mineral phase distribution within varying particle sizes on the dissolution behaviour of a low grade complex sulphide ore was investigated through bioleaching experiments a...The interplay of mineralogical variation and mineral phase distribution within varying particle sizes on the dissolution behaviour of a low grade complex sulphide ore was investigated through bioleaching experiments and electrochemical technique. Investigations were carried out utilizing mineralogical data on the variations in mineral and phase distribution within particle sizes of <53μm,53-75μm,75-106μm and 106-150μm in mixed mesophilic cultures of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans.Electrochemical behaviour was studied using particulate electrodes from the four varying particle sizes and from massive electrodes prepared from the two major sulphide mineral rich phases(sphalerite-rich and galena-rich)and a complex mineralogical phase of the bulk ore.Bioleaching studies reveal the highest recoveries at a particle size of 75μm,while electrochemical investigations reveal the highest dissolution at particle size of 106μm.Electrochemical results show that sphalerite rich phase has the highest dissolution rate while galena-rich complex phase has the least.SEM studies confirm the highest bacterial attack at the sphalerite-rich phase.The discrepancies between the dissolutions within particle sizes obtained from bioleaching experiments and electrochemical studies are consistent with and attributed both to the physical and mineralogical influences.Electrochemical behaviour is influenced and controlled by galvanic interaction resulting from mineralogical variation, while bioleaching behaviour is influenced by mineralogical variation as well as physical effect of particle size.展开更多
The role that ore mineralogy plays in understanding and optimizing the conditions favouring the bioleaching of complex sulphide ore containing high amounts of siderite was studied using mixed cultures of mesophilic ba...The role that ore mineralogy plays in understanding and optimizing the conditions favouring the bioleaching of complex sulphide ore containing high amounts of siderite was studied using mixed cultures of mesophilic bacteria,with emphasis on zinc,lead and copper recoveries.The influencing parameters investigated include particle size,stirring speed,volume of inoculum,pulp density,and pH.The results show that the mixed mesophilic cultures can extract about two and a half times the amount of zinc than copper over an equivalent period of time.The highest zinc and copper recoveries of 89.2% and 36.4% respectively are obtained at particle size of 75 μm,stirring speed of 150 r/min,pulp density of 10% (w/v),12% (v/v) inoculum concentration,and a pH of 1.6.Variations in elemental composition within different particle sizes resulting from the mineralogy of the ore account for the bioleaching behaviour at varying particle sizes.The dissolution at varying pulp density,volume of inoculum,solution pH and the low solution potential observed are also influenced by ore mineralogy.展开更多
基金the National Research Foundation (NRF) under the National Nanotechnology Equipment Program(NNEP)(74407)The financial support received from Tshwane University of Technology and the African Laser Centre( ALC) for Babatunde Abiodun Obadele during the course of this study is also acknowledged
文摘The mechanisms by which titanium carbide （TiC） improves the properties of tungsten carbide （WC） coatings deposited on duplex stainless steels using laser particle injection technique were investigated. The relationships between laser process parameters and the synthesized composite were studied. The morphologies and microstructures of the feedstock powders and composite coatings were characterized using scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDX） techniques. Surface hardness of the composite layers was determined using the Vickers microhardness tester while its corrosion behaviour in 3.5%NaCl solution was investigated by potentiodynamic polarization curve measurement method. As a result of the laser treatment, microstructures characterized by hard ceramic particles with strong bonding to substrate were formed on the surface layer of the steels. The addition of TiC to WC resulted in microstructures free from cracks, pores and intermetallics which could be detrimental to the properties of the composites. High microhardness was observed and most of the coatings shifted the corrosion potential to more noble values with the pseudo-passive curve.
文摘The interplay of mineralogical variation and mineral phase distribution within varying particle sizes on the dissolution behaviour of a low grade complex sulphide ore was investigated through bioleaching experiments and electrochemical technique. Investigations were carried out utilizing mineralogical data on the variations in mineral and phase distribution within particle sizes of <53μm,53-75μm,75-106μm and 106-150μm in mixed mesophilic cultures of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans.Electrochemical behaviour was studied using particulate electrodes from the four varying particle sizes and from massive electrodes prepared from the two major sulphide mineral rich phases(sphalerite-rich and galena-rich)and a complex mineralogical phase of the bulk ore.Bioleaching studies reveal the highest recoveries at a particle size of 75μm,while electrochemical investigations reveal the highest dissolution at particle size of 106μm.Electrochemical results show that sphalerite rich phase has the highest dissolution rate while galena-rich complex phase has the least.SEM studies confirm the highest bacterial attack at the sphalerite-rich phase.The discrepancies between the dissolutions within particle sizes obtained from bioleaching experiments and electrochemical studies are consistent with and attributed both to the physical and mineralogical influences.Electrochemical behaviour is influenced and controlled by galvanic interaction resulting from mineralogical variation, while bioleaching behaviour is influenced by mineralogical variation as well as physical effect of particle size.
文摘The role that ore mineralogy plays in understanding and optimizing the conditions favouring the bioleaching of complex sulphide ore containing high amounts of siderite was studied using mixed cultures of mesophilic bacteria,with emphasis on zinc,lead and copper recoveries.The influencing parameters investigated include particle size,stirring speed,volume of inoculum,pulp density,and pH.The results show that the mixed mesophilic cultures can extract about two and a half times the amount of zinc than copper over an equivalent period of time.The highest zinc and copper recoveries of 89.2% and 36.4% respectively are obtained at particle size of 75 μm,stirring speed of 150 r/min,pulp density of 10% (w/v),12% (v/v) inoculum concentration,and a pH of 1.6.Variations in elemental composition within different particle sizes resulting from the mineralogy of the ore account for the bioleaching behaviour at varying particle sizes.The dissolution at varying pulp density,volume of inoculum,solution pH and the low solution potential observed are also influenced by ore mineralogy.
