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Verformung und Gefügetransformation bei Schwingungsverschleiß von austenitischen FeCrNi-Legierungen
(2004)
Open cell rigid foams made from polyurethane (PU) are frequently used in ceramic processing for preparation of porous ceramics by the so-called replica technique. This work presents data regarding the PU burnout, shrinkage characteristics as well as the morphology of the ceramic coated PU sponges during heating up. Shrinkage of the ceramic coated PU sponges closely follows the mass loss due to PU decomposition. Two temperatures (i) 267 °C and (ii) 380 °C were identified at which PU decomposition reaches local maxima. Shrinkage measurements on ceramic coated PU sponges reveal that both PU decomposition stages lead to similar extends of shrinkage in the ceramic coated PU sponge. Differential thermal analysis (DTA) showed that the two decomposition related temperatures (267 and 380 °C) differ concerning the energy release. While the low-temperature signal is endothermic, an exothermic signal was detected at 380 °C. The morphology of the ceramic coated PU sponges was investigated with scanning electron microscopy (SEM) which gave insight into the formation of hollow ceramic struts-a well known feature of ceramics being prepared by the replica technique.
Morphological and compositional features regarding blue and yellow pigments used in glazed ceramics from Portugal are investigated by means of a SEM/EDX system. Fragments of samples produced in the main pottery-making centres between the XVIXVIII centuries (Lisbon and Coimbra) were the objects of study. The main question to be answered is whether there are differences in the manufacturing procedures employed. For this purpose, two types of samples were analysed: faiences and wall-tiles (the famous 'Azulejos', in Portuguese). Differences between the manufacturing techniques of the two production centres were veritably found. The expected linkage between Fe–Co–Ni–As–Bi was challenging to investigate. Thus, Co was found in Fe- or Ni-rich structures, but with no structural connection to As or Bi. However, the As-needle-like structures were always identified in blue regions. One interesting finding related particularly to the blue pigment was the presence of SnO2 agglomerates throughout the whole glaze, which suggests its intentional addition for 'lightening' the well known dark Co blue. Concerning the yellow pigment differences established in the crystal shape and size are indicative of different firing temperatures used.
The synthesis of the polymorphic cocrystal caffeine:anthranilic acid was investigated to obtain a better understanding of the processes leading to the formation of different polymorphic forms. In the case of these cocrystal polymorphs synthesized by liquid-assisted grinding a distinct influence of the dipole moment of the solvent was found. A pre-coordination between the solvent molecules and the caffeine:anthranilic acid cocrystal could be identified in the formation of form II. In the case of form II the solvent can be regarded as a catalyst. The formation pathway of each polymorph was evaluated using synchrotron X-ray diffraction.