Effect of cullet on firing temperature and dielectric properties of porcelain insulator

Abstract

Porcelain insulators prepared from locally available ceramic materials, such as Hosaena clay, quartz, partially replaced feldspar by cullet (rich in alkaline materials). The physical and electrical properties, such as water absorption, apparent porosity, bulk density, linear shrinkage, and dielectric strength as a function of firing temperature, were evaluated. The XRD and AAS measurement results show Hosaenna clay mainly belongs to kaolinite minerals with a sufficient SiO2 (45.60wt. %), Al2O3 (35.52wt. %), and it possesses reasonable plasticity nature. The SEM and Electrical properties measurement shows the porcelain insulators fired at 1150 C & 1200 C showed homogenized primary and secondary mullite with optimum glassy phase and good dielectric strength for practical applications. The primary & secondary mullite and glassy phases were grown early at a firing temperature of 1150 and 1200 C, due to the partial replacement of feldspar by cullet. The porcelain insulator prepared from the composition of 45%clay, 35%feldspar, 10%quartz and 10%cullet and fired at 1200 C showed dielectric strength 8.9kv/mm, water absorption (0.459%), apparent porosity (1.530%), bulk density (4.29 g/cm 3 ), and linear shrinkage (4.18%). Therefore, incorporating economic alkaline materials such as cullet to improve the alkalinity of the locally available clay materials, Hosaenna clay, Arero feldspar, and Arero quartz reduces the firing temperature with excellent dielectric strength.

Flux potentials of local talc in low voltage electro-porcelain insulator production

“…In addition, water absorption was reduced from 6.88 % in the Feldspar-rich recipe to 1.49 % in the 10 % Talc substitution resulting in a 78.29 % reduction in water absorption. This trend in reduction of both apparent porosity and water absorption at higher temperatures is consistent with previous studies [7,19].…”

“…This result of chemical composition (see Table 2) shows that silica (SiO2) and alumina (Al2O3) are the principal oxides found in the raw materials while other oxides were present in negligible quantities. This result agrees with findings in [7] and [18]. Remarkably, flux content in Feldspar (K2O-Na2O) sums up to 13.21% which is greater than the 12% threshold [18] for porcelain insulators.…”

“…𝐴𝑝𝑝𝑎𝑟𝑒𝑛𝑡 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 (%) = 𝑊 𝑑 𝑊 𝑑 − 𝑊 𝑠 𝑥 100 (7) 𝐵𝑢𝑙𝑘 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 (%) = 𝑊 𝑑 𝑊 𝑤 − 𝑊 𝑠 𝑥 100 (8) Where Wd, Ws and Ww are previously defined in sections 2.4.2 and 2.4.3.…”

“…At 1000 o C, the linear shrinkage increased until 6% Talc but then decreased as the Talc content approached 10 % (see Figure 4 (a)). As temperature increased, release of glassy crystallites occurred along with entrapped gases [7] and this caused the steady increase in linear shrinkage. However, as the Talc content increased from 2 %, reduction of sintering temperature occurs and this inhibits shrinkage, although this phenomenon does not apply to Talc contents above 6%.…”

“…Their findings showed improvements in microhardness and dielectric properties. Remarkably, [7] in their use of cullet to substitute the Feldspar component found that this measure offered excellent dielectric strength at a lower kiln temperature. Similarly, the partial replacement of Feldspar with sodium bicarbonate has also been reported in [8], which reduced sintering temperature and improve dielectric performance of porcelain insulators.…”