Browsing by Author "Lupyana, Samwel Daud"

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    Effect of Nano-SiO2, Nano-TiO2 and Nano-Al2O3 addition on fluid loss in oil-well cement slurry
    (Springer Open, 2019) Maagi, Mtaki Thomas; Lupyana, Samwel Daud; Gu, Jun
    In this article, incorporation of nano-SiO2 (NS), nano-TiO2 (NT ) and nano-Al2O3 (NA) particles and their binary and ternary blends on water filtration in oil-well cement slurry was examined. The nanoparticle contents were chosen at proportions corresponding to 1, 2, 3 and 4% based on the weight of cement. The experimental specimens were tested at three various temperatures of 70, 80 and 90 °C using a gas pressure of 1000 psi. The quantity of water filtrate collected was measured in milliliter (mL) at 30 min after the test begins. The results consistently indicate that an additional of NS, NT and NA particles independently, reduced the loss of liquid in cement, and its performance varies with temperature and the nanoparticle dosages. The 3% NS usage delivered strong evidence in lessening fluid loss compared to the other results by reducing the loss up to 72%. When collective impact of nanomaterials was deter-mined, the fluid retainment was also improved. The replacement of 4% NST reduced fluid loss by the most compared to NSA and NTA binary groups. In-case of ternary combination, NSTA showed a highest reduction of the water loss by 58–60% likened to the plain samples at the concentration of 4%. The key investigation of this paper clearly suggested that the efficacy of Class G cement having nanoparticles to trap its water is dependent on the nanoparticle contents. The lessening of water filtration might be explicated by the filling capability of nano-scale particles. Nanoparticles can plug the openings within the oil-well cement slurry matrix, thus promoting the retainability of water. Besides, nano-particles quickens the hydration products by creating dense interlocking C–S–H gels for bridging cement grains and forming enclosed structure which can stop the liquid from escaping the slurry.
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    Perspective and control of cation interdiffusion and interface reactions in solid oxide fuel cells (SOFCs)
    (Elsevier, 2023) Sahini, Mtabazi Geofrey; Lupyana, Samwel Daud
    The occurrence of cation interdiffusion during sintering and operation of Solid Oxide Fuel Cells (SOFCs) is inevitable, due to high temperatures and chemical potential gradients. Cation interdiffusion may be followed by solid state reaction, resulting into the formation of secondary phases. Understanding of the factors that trigger the occurrence of cation interdiffusion and interface reactions is crucial towards controlling their occurrences. Here, we have discussed the phenomena associated with cation interdiffusion in solid oxide fuel cells. We have established that cation interdiffusion and interface reactions occur both during the high temperature sintering and during SOFC operations. Case examples where cation interdiffusion and subsequent interface reactions form secondary phases are discussed. The various methods that can be used to minimize or control the occurrence of cation interdiffusion are discussed: the use of diffusion barriers, fabrication of strontium free cathode materials, lowering the sintering temperature and the SOFC operating temperature
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    Use of phyto-based polymeric material as chemical admixture in well cement slurry formulation
    (Elsevier, 2021) Lupyana, Samwel Daud; Sahini, Mtabazi Geofrey; Kattiba, Saada Msafiri; Gu, Jun
    Plants extracts contain a wide range of organic components and have been used as admixtures in modifying different cement properties. In this study, aqueous extract of Euphorbia Tirucalli (ET) as bio-admixture was characterized and tested for potential use in the preparation of well cement slurry. Several tests such as setting time tests, fluid loss tests, rheological properties of well cement slurries incorporating different proportions of the ET and the reference slurries without ET were conducted and evaluated. Phytochemical composition of ET was investigated by using Gas Chromatography-Mass Spectrometer (GCMS) analytical technique. Interactions between the bio-admixture and cement components during hydration were also characterized by Fourier Transform-Infrared (FT-IR) spectroscopic technique. GC–MS analysis indicates the presence of the palmitic acid groups such as hexadecanoic acid, methyl ester, n-Hexadecanoic acid and 9-Hexadecanoilc acid and the fatty acid components commonly known as linoleic acid. Incorporation of the bio-admixture shows to enhance fluid loss properties and slurry rheology. Also, the bio-admixture indicates promoting retardation of cement hydration due to increase in setting times with increase in mix proportions. These properties indicated to be dependent to the bio-admixture concentration. FT-IR spectroscopic investigations suggests possible interaction between bio-admixture and the ionic species in the cement slurry.