PSI - Issue 10

A. Hein et al. / Procedia Structural Integrity 10 (2018) 219–226 A. Hein and V. Kilikoglou / Structural Integrity Procedia 00 (2018) 000 – 000

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Fig. 1. SEM micrographs of polished sections of Late Minoan crucibles tempered with different types of organic fibers: (left) straw; (right) animal hair. Investigations of different types of functional ceramics in general indicate a relation between microstructure, in terms of micromorphology, inclusions and pore structure, and the presumed function or rather preferred performance. Amphorae, for example, had to withstand considerable mechanical loads during their primary use as transport con tainers. In cargo ships or storing places they were commonly stacked in several layers by placing their bases in the spaces between the shoulders of the amphorae in the respective lower layer. Thus, substantial weight load emerged, requiring sufficient strength and toughness to avoid potential damages in the contact areas. Furthermore, the ceramic body should have exhibited adequate impermeability, when being used for transport and storage of liquid commodities. Indeed, amphorae were commonly produced from fine-grained clay pastes which were fired at com parably high temperatures. Thus, the ceramic matrix was typically clearly vitrified, presenting different levels of the development of glassy connections among the clay particles (Fig.2), which are expected to have affected after all also the material performance (Hein et al. (2008a)).

Fig. 2. Microstructures of Aegean transport amphorae (left) initial vitrification; (b) extensive vitrification.

Ceramics, which were used in pyrotechnical processing, such as metallurgy or glass making, on the other hand had to withstand predominantly substantial thermal loads. Apart from basic refractoriness, in terms of material integrity and inertness at temperatures of above 1200 °C, the ceramics had to withstand thermal shock due to rapid temperature changes and depending on their specific function they had either to support or to reduce heat transfer through the ceramic matrix. This depended, however, also on knowledge and availability of raw materials. For example, kaolinitic clays, necessary for the production of sufficiently temperature-resistant crucibles, were commonly used only from