Preservation of York Minster historic limestone by hydrophobic surface coatings

Magnesian limestone is a key construction component of many historic buildings that is under constant attack from environmental pollutants notably by oxides of sulfur via acid rain, particulate matter sulfate and gaseous SO 2 emissions. Hydrophobic surface coatings offer a potential route to protect existing stonework in cultural heritage sites, however, many available coatings act by blocking the stone microstructure, preventing it from 'breathing' and promoting mould growth and salt efflorescence. Here we report on a conformal surface modification method using self-assembled monolayers of naturally sourced free fatty acids combined with sub-monolayer fluorinated alkyl silanes to generate hydrophobic (HP) and super hydrophobic (SHP) coatings on calcite. We demonstrate the efficacy of these HP and SHP surface coatings for increasing limestone resistance to sulfation, and thus retarding gypsum formation under SO/H O and model acid rain environments. SHP treatment of 19th century stone from York Minster suppresses sulfuric acid permeation

Magnetic and Electronic Structure Studies of Nanocrystalline (Co 2 Mn) 4 0 Ni 60 Alloy

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Temperature dependence of the electrical resistivity and absolute thermoelectric power of amorphous metallic glass Ni33.3Zr66.7

International audienceElectron transport properties and thermal stability of Ni33.3Zr66.7 metallic glass (MG) have been studied using an original device for simultaneous measurements of electrical resistivity and absolute thermoelectric power (ATP) controlled by a LabView software written by one of us. The electrical resistivity and absolute thermoelectric power were measured simultaneously and very accurately over a temperature range from 25 to 400 °C with a nominal heating rate of 0.5 K min− 1. The electronic thermal conductivity was also determined using the Wiedemann–Franz law in the same temperature range. Due to its high efficiency, this technique is more and more used because it is characterized by a high sensitivity to detection of the phase transitions related to electronic transport, which is the aim of this study. Analysis of the temperature dependence of the resistivity and ATP of the Ni33.3Zr66.7 glassy ribbons proves the potential of this characterization method to study the thermal behavior of metallic glasses. The crystal structure and the morphology of Ni33.3Zr66.7 metallic glass in the as-quenched state and after heat treatments were studied using X-ray diffraction (XRD), and scanning electron microscope (SEM)