Center for Materials Engineering

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Browsing Center for Materials Engineering by Subject "Alkaline-Rich Material"

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    Investigating the Effect of Partial Substitution of Feldspar by Alkaline-rich Material on the Processing Temperature of Locally Produced Electrical Porcelain Insulator
    (Addis Ababa University, 2020-09) Eaba, Beyene; Sintayehu, Nibret (PhD)
    The demand for electric power supply has been significantly increasing in the world and particularly in Ethiopia. In the power generation sector, it is crucial to develop a high quality insulation material to transmit and distribute the generated power, such as porcelain insulator. Therefore, in this study, we produced an electrical porcelain insulator from locally available clay (Bombowha clay), feldspar (Arero feldspar) and quartz (Arero quartz) and achieved reduced processing temperature without compromising insulator properties. The physical and dielectric properties such as apparent porosity, water absorption, bulk density, and dielectric strength of the as prepared samples were performed. Furthermore, XRD and FE-SEM analysis were utilized to analyze the phase formation and morphology of the phases after firing. The Arero feldspar was partially substituted with alkaline rich materials (sodium carbonate, sodium chloride and glass powder). These preliminary samples were then fired at 1000 oC and the best substitute and processing technique were compared and the one with good dielectric strength was chosen for further study. Reasonable dielectric strength was achieved from the samples containing sodium carbonate as a substitute which was chosen for further study. Experiments were performed using different concentration of sodium carbonate (5%, 7.5% , and 10% of the feldspar composition in the porcelain), and firing temperature of 1000 oC, 1100 oC, and 1200 oC. The XRD and FE-SEM results showed that sufficient amount of the required phase, i.e., mullite phase, formed at 1100 oC and 1200 oC with the addition of the sodium carbonate as a substitute. Furthermore, relatively good dielectric strength values for porcelain insulator were achieved by the samples prepared at a lower temperature of 1200 oC compared to previous studies. The maximum dielectric strength which was achieved by substituting 10% of the feldspar with Na2CO3 is 7.51 kV/mm; the standard for low voltage overhead line porcelain insulator being in the range of 6.1 - 13 kV/mm. Moreover, substituting values of 5% and 7.5 % at 1200 oC exhibited comparable dielectric strength values with the 10 % substitute.