The effect of mineralogy, microstructure and firing temperature on the effective thermal conductivity of traditional hot processing ceramics

• Published in: Applied clay science Vol. 135; pp. 260 - 270
• Main Authors: Allegretta, Ignazio, Eramo, Giacomo, Pinto, Daniela, Hein, Anno
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.01.2017
• Subjects: Cooking pots; Firing temperature; Glass crucibles; Sifnos; Thermal conductivity; Thermal conductivity; Cooking pots; Sifnos; Glass crucibles; Firing temperature
• ISSN: 0169-1317; 1872-9053
• DOI: 10.1016/j.clay.2016.10.001

The present work analyses the effect of mineralogy, microstructure and firing temperature on the effective thermal conductivity of traditional hot processing ceramics. Samples prepared with two quartz-rich kaolinitic clays (BAR1 and BAR2), a fine kaolinitic clay (ARG) and a glaucophane-rich clay (SIF), were fired in the range between 950 and 1350°C. The effective thermal conductivity is principally affected by the porosity of the body. Mullite further improves the thermal conductivity of BAR1 and BAR2 ceramics, while in ARG samples cristobalite is correlated with the increase in thermal conductivity. In SIF ceramics, the higher densification and the formation of spinel, pyroxene and hematite results in a higher conductivity compared to the other samples. The amorphous phase improves the ceramics' thermal conductivity since it seals voids between particles. In samples in which quartz exceeds 50wt%, the ceramics' thermal conductivity decreases because of fissures and detachment zones formed after the α-β quartz phase transition. Finally, functional conclusions are drawn on traditional cooking pot and Medieval glass crucibles. •Porosity is the main factor affecting the ceramic effective thermal conductivity.•New formed mullite, cristobalite, spinel, pyroxenes and hematite further improve keff.•Densification and thermal properties explain the wide use of Siphinian cooking pots.•High quartz amounts reduce the effective thermal conductivity of glass crucibles.•Matrix composition, quartz amount and texture control body densification.