Browsing by Author "Jonsson, Stefan"

Now showing 1 - 4 of 4
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    Beneficiation and Evaluation of Mutaka kaolin
    (In Proceedings of Second International Conference on Advances in Engineering and Technology, 2011) Kirabira, John Baptist; Jonsson, Stefan; Byaruhanga, Joseph K.
    Kaolin is an important industrial mineral which often needs upgrading for special applications. The upgrading process, commonly known as beneficiation, is aimed at removing impurities like feldspar, quartz, iron oxide, etc. In this study, a kaolin sample was collected from a deposit located at Mutaka, South-Western Uganda, – the biggest kaolin deposit in the country. With the aim of upgrading this sample, it was processed by a laboratory hydro cyclone to produce a kaolinite concentrate and this has been characterized to ascertain its use as an industrial raw material. Characterization of the beneficiated sample was carried out by XRD, SEM, particle-size distribution, density and volume measurements, chemical analysis, whiteness index test, thermal analysis (DTA/TG) and surface area measurements. Results show that the laboratory beneficiation exercise improves the kaolin sample to a very high grade with a chemical composition close to that of ideal kaolinite. The major impurity after beneficiation, iron oxide, was further reduced by acid leaching. Results show that the properties of the final product are close to that of ideal kaolin.
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    Development And Characterisation Of Triaxial Electrical Porcelains From Ugandan Ceramic Minerals
    (Ceramics International, 2010) Olupot, Peter W.; Jonsson, Stefan; Byaruhanga, Joseph K.
    Ten formulations of triaxial porcelain composed from 30–60% clay, 20–45% feldspar and 20–25% sand, were prepared from raw materials sourced from Ugandan deposits. Specimens were made using the plastic extrusion method and characterized in terms of constituent oxide composition, flexural strength, fracture toughness, dielectric strength, microstructure and phase properties using ICP-AES analyses, 4-point load strength test, Vicker's indentation, FEG-SEM and powder-XRD analyses, respectively. XRD studies revealed that the crystalline phases are mullite and quartz and their intensity is almost identical for all samples fired at 1250°C but there is a decrease in quartz content as temperature is increased. Samples with 20% sand content resulted in higher density, modulus of rupture and fracture toughness compared to those containing 25% sand. The major factor influencing bending strength was found to be porosity in samples as opposed to crystallinity. A sample with 67.3% SiO2, 20.2% Al2O3, 3.4% K2O and 6.3% others exhibited best properties.
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    Fireclay Refractories from Ugandan Kaolinitic Minerals
    (steel research international, 2006) Kirablra, John Baptist; Wijk, Gunnar; Jonsson, Stefan; Byaruhanga, Joseph Kadoma
    In the present work, two deposits, one of kaolin and the other of ball clay, located in Uganda were investigated for the possibility of manufacturing fireclay refractories. Kaolin from the Mutaka deposit was used as the main source of alumina while ball clay from Mukono was the main plasticizer and binder material. The formulated green body was consolidated by wet pressing and fired at 1350°C in a tunnel kiln. Characterization of the sintered articles was done by X-ray diffraction, scanning electron microscopy, and chemical composition (ICP-AES). In addition, technological properties related to thermal conductivity, thermal shock, alkali resistance, water absorption, porosity, shrinkage, permanent linear change, linear thermal expansion, refractoriness under load, and cold crushing strength were determined. The properties of the articles manufactured from these naturally occurring raw minerals reveal that they compare favorably with those of parallel types. Thus, the raw materials can be exploited for industrial production.
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    Study of Glazes and Their Effects on Properties of Triaxial Electrical Porcelains from Ugandan Minerals
    (Journal of Materials engineering and performance, 2010) Olupot, Peter W.; Jonsson, Stefan; Byaruhanga, Joseph K.
    Kaolin, ball clay, feldspar, and sand were collected from deposits in Uganda, milled and sieved to particle sizes of 45, 45, 53, and 25 μm, respectively. Three porcelain bodies and five glazes were formulated from them. The glazes were applied on porcelain specimens and subsequently evaluated for their effects on properties of porcelain samples. The formulated specimens were investigated using dilatometry, Steger test, FEG-SEM, XRD, 4-point bending, dielectric strength, and fracture toughness tests. A porcelain specimen consisting of 68% SiO2, 19% Al2O3, 4.7% K2O, and a glaze RO:0.57Al2O3:4.86SiO2 exhibited MOR of 105 MPa with Weibull modulus of 5.6 and a dielectric strength of 18 kV/mm upon firing at a heating rate of 6 °C/min to 1250 °C and holding for 2 h. The microstructure of the high-strength specimen exhibited round mullite needles, quartz, and glass. Holding samples for 2 h at peak temperature resulted in a 22% increase in MOR compared to 1 h holding. Glazing further improved strength by 67% for the best sample. Compressive stresses in glaze contributed to the strengthening effect. The dielectric and mechanical strength values obtained qualify the formulated sample for application in electrical insulation.