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In this research project, a new OECD Test Guideline (TG) for the determination of “Particle Size and Particle Size Distributions of Nanomaterials” was developed as the existing OECD TG 110 is considered to be outdated in terms of applicable size range (not covering sizes <200 nm) and methods. By its scope with an applicable size range from 1 to 1000 nm the new Test Guideline (TG PSD) covers the whole nanoscale. The TG PSD is applicable for particulate and fibrous nanomaterials. The prescribed, pairwise measurement of fibre diameter and length in the TG PSD allows for the first time to differen-tiate fibres with regard to their size-dependent hazard properties. Measurement instructions for each included method were validated within two separated interlaboratory comparisons, as a distinction between near spherical particles and fibres when applying the methods has to be made.
Besides information on content and structure of the TG PSD, this final report outlines essential steps, considerations and organisational aspects during the development of the TG. Insights into the selec-tion, preparation and prevalidation of test materials used in the interlaboratory comparison are given. Finally, main results of the interlaboratory comparisons and their impacts on the TG PSD are pre-sented.
Typology of Inks
Archives and museums around the world contain a vast number of manuscripts that were written in different inks: carbon inks, plant inks, iron-gall inks and mixed inks. Yet most archaeometric studies of manuscripts focus on the palette of pigments found in illuminated manuscripts whereas identification of the inks is still largely based on cultural-historical studies and visual inspections. One of the reasons of this disproportion in the studies can be explained by the properties of Raman spectroscopy, the technique of choice for identification of pigments. In contrast, this technique is only partially viable when dealing with organic colourants. Brown and Clark discuss these difficulties and the uncertainties of identification of iron-gall inks by Raman spectroscopy in their pioneering work on early medieval Anglo-Saxon manuscripts (K. Brown and R. Clark 2004). To facilitate instrumental analysis of inks, we have developed a protocol that starts with the identification of the inks type (Rabin et al. 2012) which doesn’t require complicated instrumentation and can be carried out by paleographers and codicologists.
Three typological ink classes
The black writing materials used in manuscript production in Antiquity und Middle Ages can be sorted in three typologically different ink classes: soot, plant and iron-gall. Soot ink is a fine dispersion of carbon pigments in a water soluble binding agent; plant-based ink consists of a solution of the tannins extracted from gallnuts or tree bark; iron-gall ink, is produced by mixing a soluble compound of iron (II) with gallic or tannic acid extracted from gallnuts or tree bark. Therefore, iron-gall ink presents a boundary case between solution and dispersion ink, in which a water-soluble preliminary stage oxidizes and evolves into a black, insoluble precipitate similar to the carbon pigments when the writing is exposed to air (Krekel 1999). The additional category of mixed inks, i.e. inks produced by addition of various metals to the soot inks or intentional mixing of iron-gall and soot - based inks started attracting scholarly attention only recently because their significance was established only a short while ago (Brun et al. 2016, Colini 2018, Nehring et al. 2021). We suggest that plant and mixed inks build a bridge from the carbon ink of Antiquity to the properly formulated iron-gall ink that became a standard black ink from the late Middle Ages to the 19th century when it gave way to modern inks.
Gas adsorption is based on physical properties between gases and solid materials, enriching the surface with packed gas molecules with a higher density than in the bulk phase. For using this mechanism as a gas storage strategy, highly porous materials are necessary since large surfaces in small volumes can provide the storage system with a higher density than the gas phase. In the case of hydrogen gas, the interaction forces with solid surfaces are generally low at room temperature but can increase considerably at low operating temperatures. As a counterpart, the storage pressure is considerably lower than that necessary by traditional gas compression.
Amongst ultra-porous adsorbent materials for hydrogen cryoadsorption, metal-organic frameworks (MOFs) are a group of remarkable solids made from metallic nodes linked by organic molecules exhibiting a wide variety of composition, geometry, porous properties, and chemical functionality. The scientific community focused in the last years on enhancing both the specific area of materials and the interaction energy to extend the storage properties of cryoadsorption to ambient-temperature and use it as hydrogen storage mechanisms in vehicles. However, the found difficulty in achieving ultra-porous structures with high-enough interaction energies decreased this research interest in the last years.
However, for a stationary application like hydrogen refueling stations, where space and weight are not such limits as in vehicles, cryoadsorption can still be considered a feasible candidate for hydrogen storage. Cryoadsorption is the only fast and fully reversible approach to store hydrogen at similar density values as compressed gas. Cryogenic operation is a technological challenge, but first, liquid nitrogen is cheap, and second, it is less energy-demanding than hydrogen liquefaction, which is indeed considered as feasible for transportation and storage. Cryoadsorption involves lower pressure
than compressed gas, increasing safety in the storage facilities, but additional research on the construction materials properties is necessary to better understand their behavior in contact with hydrogen at cryogenic temperatures. However, the knowledge of all these mechanisms is important to identify the improvement opportunities based on, probably, the interphase between different solutions.
To achieve the set project goals, this internal research report describes the work packages realised within the framework of the project.