Effects of pottery stone and firing rate on microstructure and thermal properties of porcelain tableware by single fast–firing

Abstract

The application of pottery stone as the main raw materials in the ceramic manufacturing process was based on the investigation of raw materials for porcelain tableware products of a small ceramic industry in Lampang Province, Thailand. This research aimed to study the effects of pottery stone, feldspar, Lampang clay and quartz on the microstructure, and the physical and thermal properties of porcelain tableware produced by single fast firing. The effects of particle size, packing density, and firing rate on the phase composition and its impact on thermal expansion and thermal shock resistance of porcelain tableware produced by single fast firing were also studied. This research, raw materials from local area such as Lampang pottery stone, Lampang clay, feldspar, and quartz were used. The characterization of the raw materials, in the study, consisted the particle size analysis, chemical and mineral composition, and thermal behavior. To study the mixture ratio of the porcelain body, the ratio was designed as following in wt% of 60-70 of Lampang pottery stone, 0-20 Lampang clay, 0-20 of feldspar, and 0-40% for quartz in nine component ratios. The particle size of each batch was ground at 8, 16, and 24 h. The firing properties were fired at 1,200C with different firing times at 2, 4, and 8 h in an oxidation atmosphere. The effects of the physical properties, mechanical properties, microstructures, translucency, density before and after the firing, thermal expansion coefficient, thermal shock resistance, and cracking resistance of the porcelain body following the simulation method of the production process, and samples from the Ban Nam Jo Ceramic Factory were determined. As the results, the batch was ground at 24 h and was fired at 4-8 h representing the suitable condition. The achieve component consisted in wt% of 60 Lampang pottery stone, 15-20 Lampang clay and feldspar, and 10 silica. The chemical composition was composed in wt% of 70.51-74.72 silicon dioxide, 9.98-10.97 aluminum oxide, and 9.35-11.35 potassium oxide. Mullite and quartz were also found as the main constituents due to the formation of mullite crystal (>40%) and quartz crystal (>50%). The mixture ratio present the shrinkage at 13.5%, water absorption at 0.14 %, bulk density at 2.03 g/cm3, apparent porosity at 0.3%, and a flexural strength at 1, 198 kg/cm2. The coefficient of the thermal expansion resistance, thermal shock, and cracking resistance of the products were achieved. The coefficient of the thermal expansion of the body was similar to the glaze of the Ban Nam Jo Ceramic factory with a difference about 20% approximately. The thermal shock resistance of the body showed that all ratios were able to withstand heat up to 200°C. The cracking resistance showed that the glaze present cracked layer for 80wto quartz content. The porcelain body from the experiment was improved according to the requirements of the Thai Industrial Standards (TIS 564-2546).