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  • Author or Editor: H. Wiedemann x
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Abstract  

A new instrument for DSC in combination with thermomicroscopy in transmitted light is described, where a DSC device is in corporated within a commercially available hot stage.

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Abstract  

Egyptian mural paintings, polychromatic sculptures and mummy coffins exhibit a remarkable durability, ranging over millennia. This phenomenon can be explained by the dry, non-corrosive climate of the Nile valley and/or by the knowledge and experience with which Egyptian craftsmen developed skills to conserve items and materials for eternity. Investigations concerning the timber and covering or protecting layers of mummy coffins are reported. The experimental results were obtained by means of thermal analysis and X-ray diffraction. The interpretation sheds light on the ancient techniques applied.

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Abstract  

The thermal reactivity of fossilized/petrified dinosaur eggshells excavated in China, Argentina and France has been studied by means of thermal analysis/mass spectrometry (TG-MS), X-ray diffractometry (XRD) and analytical scanning electron microscopy (SEM-EDX). The results provide more detailed information on the properties of these fossil materials and therefore allow an improved typology of this most remarkable family of creatures.

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Abstract  

Thermal analysis has been used to study the composition of paper and paper-like materials for some decades. The application of these techniques permits to distinguish between the original paper which was used by the artists and possible forgeries. Quite often, however, the identification of the differences demands the simultaneous application of several other techniques. The present investigation includes Asiatic wood-prints from China and Japan, and lithographs of European artists, such as Pablo Picasso, Salvador Dali, and Marc Chagall. Utamaro (1753–1806) is one of the most celebrated artists in the history of the Japanese woodblock print. He became one of the famous painters of ‘Ukiyo-e’ (Ukiyo-e means transitory world). In China Utamaro's pictures were also produced. The differences are found in the kind of paper: The Japanese used Mitsumata paper, while the Chinese printed on Bamboo paper mixed with silk fibers. Hu-j-zong (Nanking, 1619) and a group of famous Chinese painters created the book of the ‘Ten Bamboo Studio’ which contains woodblock prints as visual aids for young artists. A reprint of these woodblock prints appeared in 1717. Later, a bootleg of this book appeared in Japan (1817). The differentiation is possible by thermogravimetric investigation of the used papers. Statistic evaluations in Europe show that more than 1 000 000 bootleg copies of lithographs of Pablo Picasso, Salvador Dali, and Marc Chagall exist. Thermoanalytical measurements allow the distinction between the original artifacts and the bootlegs. Raman spectroscopy gives an additional possibility for the distinction between the applied color pigments.

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Abstract  

A new pressure DSC module (Mettler DSC27HP) and its abilities for vapor pressure determination in the range of subambient pressure to 7 MPa are presented. To compare the new to an established method, vapor pressures of caffeine, naphthalene and o-phenacetin have been determined both by pressure DSC and the Knudsen effusion cell method. These results, including the derived heats of evaporation and heats of sublimation, are compared to literature values.

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The application of thermal analysis and other techniques to determine the thermal and mechanical history of an object is extended to investigate the method of manufacturing of ancient papers. The Humboldt Fragment number six of the Codex Huamantla and other Mexican papers are analyzed by means of Differential Scanning Calorimetry (DSC) and Thermogravimetry-Mass Spectroscopy (TG-MS). The results reveal mechanical treatment or beating of the raw material and also indicate, that the two cultures exchanged knowledge about the paper making. The simplicity and speed of thermoanalytical methods make them a good choice to screen samples for composition and origin. With the addition of more elaborate techniques, such as X-ray analysis, IR spectroscopy, evolved gas analysis by mass spectrometry and microscopy, a definitive classification can be reached easily.

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The correlation between morphological changes and DSC recordings gives valuable information on the mechanism of phase transformations. The present paper describes a new instrument for simultaneous DSC and thermomicroscopy in transmitted light, where a DSC device is placed in a commercially available hot-stage. The application of this DSC/thermomicroscopy is exemplified by study of the phase diagrams for KNO3-NaNO3, diphenylamine-benzophenone and a liquid crystal system.

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The experimental conditions influencing thermoanalytical results are summarized and subdivided into three groups: sample properties, experimental parameters, apparative parameters. By means of selected examples, some experimental conditions are discussed, mainly for TG and DTA. Special care is given to particle size, the atmosphere as part of the reacting system and as experimental parameter, the buoyancy problem, dynamic re-impact phenomena of molecules, heat transfer and supercooling problems in melting, and DTA under different isobaric conditions. In quantitative thermal analysis, experimental conditions need careful control. Standard reference materials as well as automatic data collection and processing techniques help in achieving better thermoanalytical results.

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