1. Characterization and Mechanical Properties of Sintered Clay MineralsSara Tominc, Vilma Ducman, Jakob Koenig, Srečo D. Škapin, Matjaž Spreitzer, 2024, published scientific conference contribution Abstract: The need to reduce energy consumption and the carbon footprint generated by firing ceramics has stimulated research to develop sintering processes carried out at lower temperatures(ideally not above 300 °C) and high pressures (up to 600 MPa), the so-called cold sintering process (CSP) (Grasso et al., 2020, Maria et al., 2017). To evaluate the applicability of CSP to clays, we focused on two representative clay minerals, kaolinite and illite, and on the natural clay material obtained from a Slovenian brick manufacturer. The selected clay materials were characterized on the basis of mineralogical-chemical composition (XRD, XRF) and particle size distribution (SEM analysis, PSD, BET). The powders of clay minerals and natural clay material were first sintered in a heating microscope to determine the sintering conditions and then in a laboratory furnace at 1100 °C for 2 hours and additionally at 1300 °C for kaolinites. The effect of compression of the initial powders on their final properties was also investigated.
Keywords: conventional sintering, cold sintering, clay minerals, characterization, mechanical properties
Published in DiRROS: 29.03.2024; Views: 101; Downloads: 45
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2. Evaluation of fly ash-based alkali activated foams at room and elevated temperaturesKatja Traven, Mark Češnovar, Srečo D. Škapin, Vilma Ducman, 2020, published scientific conference contribution Abstract: Alkali activated materials (AAM) are, in their broadest classification, any binder systems derived by the reaction of an alkali metal source (silicates, alkali hydroxides, carbonates , sulphates) with a solid, amorphous alumosilicate powder (found in precursors such as slag, fly ash and bottom ash). A wide variety of products can be obtained by the alkali activation process and could replace traditional construction products. Among the se, alkali activated foams (AAF) represent one of the most promising materials, owing to their economically accessible alumosilicate rich source materials, including industrial waste materials, clean processing, higher added value and most importantly, pro ducts with competitive properties. In the present study, the properties of alkali activated fly ash - based foam materials were studied at room temperature as well as at elevated temperatures (up to 1200 °C ) in order to develop a durable material in terms o f mechanical properties and suitability for high temperature applications.
Keywords: lightweight porous insulating material, alkali activated materials, microstructural analysis
Published in DiRROS: 05.03.2024; Views: 103; Downloads: 42
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4. The role of relative humidity on crystallization of calcium carbonate from calcium acetoacetate precursorAndreja Pondelak, Francesca Rosi, Celeste Maurich, Costanza Miliani, Srečo D. Škapin, Andrijana Sever Škapin, 2019, original scientific article Abstract: Calcium acetoacetate, Ca(OAcAc)2, was exposed 7, 30 and 365 days to different values of relative humidity (33%, 48%, 75% and 96%) at 40 °C in order to study its transformation to CaCO3. The resulting Ca(OAcAc)2 decomposition and the time dependence of the phase transformations were monitored and critically evaluated by Fourier transform infrared spectroscopy, field emission scanning electron microscopy and X-ray powder diffraction. The impact of relative humidity on CaCO3 polymorph formation was thoroughly assessed. In all of the conditions used and for all ageing periods, the formed crystal structure is found to be vaterite. At the lowest relative humidity (33%), the amorphous CaCO3 remains more or less almost untransformed even after one year of exposure. It is proposed that the reason for the stability of amorphous CaCO3 is due to the limited amount of physisorbed water on the surfaces of the particles, which is considered the driving force for its transformation. However, the carbonation process is faster in the case of the highest humidity (96%). The findings are not only important for better solutions in the field of cultural heritage, but also shed new light on the fundamental mechanism of CaCO3 crystallization.
Keywords: calcium acetoacetate, relative humidity, carbonation, amorphous carbonate, vaterite, mechanism
Published in DiRROS: 22.11.2023; Views: 286; Downloads: 135
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5. High temperature resistant fly-ash and metakaolin-based alkali-activated foamsKatja Traven, Mark Češnovar, Srečo D. Škapin, Vilma Ducman, 2021, original scientific article Abstract: Alkali-activated foams (AAFs) present one of the most promising materials for use in the construction sector. Their main advantages lie in their utilization of waste material and their ability to form at temperatures well below 100 °C, while still competing in performance with foamed glass or ceramics. The present body of research has focused on improving the thermal stability of fly-ash foams by i) adding metakaolin, and ii) changing the activator from sodium-based to potassium-based components. It has been confirmed that a certain increase in thermal resistance is achieved through the addition of metakaolin while changing activators played a crucial role. While sodium-based AAFs without metakaolin start to shrink at approximately 600 °C, samples that have had metakaolin added start to shrink at approximately 700 °C. Samples without metakaolin that have used a potassium activator start to shrink at approximately 800 °C, whereas potassium-based samples with the addition of metakaolin start to shrink at approximately 900 °C.
Keywords: alkali activated materials, geopolymers, high temperature, resistance, foams
Published in DiRROS: 01.08.2023; Views: 247; Downloads: 190
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7. Slovenska priporočila za obravnavo odraslih bolnikov s kronično odpovedjo prebavilNada Rotovnik-Kozjek, Tajda Božič, Katja Kogovšek, Borut Štabuc, Laura Petrica, Karla Berlec, Nataša Puzić Ravnjak, Erik Brecelj, Aleš Tomažič, Sanela Banović, Rada Franko, Milena Kovač-Blaž, Janez Breznik, Davorin Ćeranić, David Drobne, Mojca Gašperin, Tomaž Jurca, Maja Ebert Moltara, Rado Janša, Marjana Turk Jerovšek, Taja Jordan, Tina Kamhi, Primož Karner, Milena Kerin-Povšič, Neža Majdič, Denis Mlakar-Mastnak, Andreja Ocepek, Tadeja Pintar, Stojan Potrč, Nataša Smrekar, Monika Sonc, Maja Šeruga, Petra Tavčar, Igor Virant, 2021, professional article Keywords: kronična odpoved prebavil, zdravljenje, onkološko zdravljenje
Published in DiRROS: 11.06.2021; Views: 1311; Downloads: 350
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9. Go for Mura : upravljanje poplavnih gozdov v območjih Natura 2000 ob MuriŠpela Ambrožič, Gregor Božič, Maarten De Groot, Andreja Ferreira, Tatjana Gregorc, Marjana Hönigsfeld Adamič, Anže Japelj, Andrej Kapla, Marko Kovač, Štefan Kovač, Lado Kutnar, Tom Levanič, Boštjan Mali, Aleksander Marinšek, Zdenka Mazej, Nikica Ogris, Špela Planinšek, Mitja Skudnik, Gabrijela Triglav Brežnik, Saša Vochl, Al Vrezec, 2017, professional monograph Abstract: Vsebina publikacije na kratko povzema izsledke projekta Go for Mura. Predstavljeni so poplavni in močvirni gozdovi ob Muri, njihov pomen ter različni vidiki omenjenih gozdov, ki so bili raziskani tekom projekta. Predstavljene so ostale aktivnosti projekta .
Keywords: Natura 2000, gospodarjenje, poškodovanost gozdov, poplavni gozd, Slovenija
Published in DiRROS: 18.01.2021; Views: 1566; Downloads: 465
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10. Decision support tool for the management of dynamic genetic conservation unitsA. Rudow, Marjana Westergren, J. Buiteveld, Václav Buriánek, B. Cengel, Joan Cottrell, G. de Dato, K. Järve, Davorin Kajba, Colin Kelleher, François Lefèvre, M. Liesebach, L. Nagy, Srđan Stojnić, M. Villar, L. Yrjänä, Michele Bozzano, 2020, final research report Keywords: decision support tool, genetic conservation
Published in DiRROS: 14.01.2021; Views: 1155; Downloads: 539
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