Acoustic Emission During Firing of the Illite-Based Ceramics with Fly Ash Addition

M. Knapeka, T. Húlan b, P. Dobroň a, F. Chmelík a, A. Trník b and I. Štubňa b aDept. of Physics of Materials, Charles University in Prague, Ke Karlovu 5, 121 16 Prague, Czech Republic bDept. of Physics, Constantine the Philosopher University in Nitra, Tr. A. Hlinku 1, 949 74 Nitra, Slovakia

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In this work, illite-based ceramic body with power plant fly ash addition (60 wt.% of illite, 30 wt.% of fly ash and 10 wt.% of illite fired at 1100°C) was investigated by the thermal analysis techniques (differential thermal analysis, thermodilatometry and thermogravimetry) and the acoustic emission technique. The green body was heated up to 1100°C at three different rates 2.5, 5, 10 K/min. The most intense acoustic emission was recorded at the highest rate 10 K/min. Mutual correlations between thermal analyses and acoustic emission data were also examined. The first acoustic emission response appears at 430°C, corresponding to a small endotherm on the DTA curve, where the thermal decomposition of mineral portlandite takes place. In the temperature range from 600 to 900°C, high acoustic emission activity correlates with dehydroxylation and expansion of the sample. At temperatures higher than 800°C, the source of acoustic emission signals is the thermal decomposition of calcite. The amorphous phase created from illite at 920°C becomes pyroplastic, therefore it is not documented by the acoustic emission technique.

DOI: 10.12693/APhysPolA.128.783 PACS numbers: 64.70.ph, 61.43.Fs, 65.60.+a, 81.70.Pg, 43.40.Le