Fabrication of electrical porcelain insulator from ceramic raw materials of Oromia region, Ethiopia

Abstract

Electrical porcelain insulator was fabricated from local ceramic raw materials, Bombowha kaolin/clay, Arero feldspar and Arero quartz available in Ethiopia. The raw materials mineralogy, chemical composition, and thermal properties were characterized by using x-ray diffractometer (XRD), atomic absorption spectrometer (AAS) and thermogravimetry (TGA), respectively. Plasticity of clay was determined according to Atterberg plasticity test. Based on the raw materials chemical composition, five different porcelain insulator test bodies were prepared at firing temperature of 1000 °C, 1100 °C, 1200 °C and 1300 °C. Water absorbance, apparent porosity, bulk density, dielectric strength and microstructure of fired porcelain insulators were studied as a function of firing temperature. The XRD and AAS results revealed that in Bombowha clay, kaolinite mineral was found to be a major mineral constituent with appreciable silica (46.84 wt%) and alumina (36.74 wt%) content with moderate plasticity (PI = 19–21%). The Arero feldspar belongs to anorthoclase feldspar minerals with less alkali content (Na2O + K20) of <7wt %. Among the tested porcelain insulator bodies, the test body with composition of 45% kaolin, 45% feldspar and 10 % quartz exhibited superior properties of having a water absorbance of 0.010%, porosity of 0.088%, density of 2.466 g/cm3, dielectric strength of 8 Kv/mm at firing temperature of 1300 °C with mullite and quartz phase embedded in sufficient glassy phase. Therefore, the experimental result confirmed that standard porcelain insulator can be fabricated from locally available ceramic raw materials (clay and quartz) in Ethiopia at optimized condition.