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

Abstract

In this work, illite-based ceramic body with power plant y ash addition (60 wt.% of illite, 30 wt.% of y ash and 10 wt.% of illite red at 1100• C) was investigated by the thermal analysis techniques (dierential thermal analysis, thermodilatometry and thermogravimetry) and the acoustic emission technique. The green body was heated up to 1100• C at three dierent 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 rst 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.

Development of stress on quartz grain in illite ceramics during cooling stage of firing

“…Below this temperature, the signals of the AE appear, 6),8) Young's modulus begins to decrease slowly, 1) and the thermodilatometric curve changes its slope slightly. 8) The temperature T g is the natural starting temperature below which the stress is created in the grain and surrounding glassy phase. Since the elastic modulus, Poisson's ratio, and CLTE of the quartz grain and glassy phase are temperature dependent (Figs.…”

Mechanical properties of illite‐based ceramics with controlled porosity studied by modern in situ techniques

“…Therefore, it allows to study the properties of illite in a relatively pure form, devoid of the influence of other phases such as kaolinite, quartz, and feldspars, which are typically present in natural clays in considerably high quantities. There are only a limited number of works investigating this material and these studies focus primarily on the thermo‐physical properties of illite …”

“…. The AE technique has also been successfully employed for the examination of microcracking, which takes place during thermal loading of ceramic materials, primarily as a result of various phase transformations …”

“…There are only a limited number of works investigating this material and these studies focus primarily on the thermo-physical properties of illite. 2,15,16,[18][19][20][21][22][23][24][25][26][27][28] Moreover in this work, a controlled porosity was introduced into IRC using a sacrificial template method, thus obtaining sample sets with various degrees of porosity. Mechanical properties of IRC and their dependence on the level of porosity were investigated using conventional compression tests combined with modern in situ acoustic emission (AE) and digital image correlation (DIC) techniques, which proved to be particularly effective for the examination of deformation dynamics, investigated up to now mostly in porous or dense metallic and composite materials, see Refs.…”

“…The AE technique has also been successfully employed for the examination of microcracking, which takes place during thermal loading of ceramic materials, primarily as a result of various phase transformations. 2,19,33,34 The main objective of this work was, therefore, twofold. First, as there is an absence of related investigations, we aim to contribute to the understanding of deformation behavior of illite-based ceramic materials and of the effect of controlled porosity on its mechanical parameters.…”