1. Tailoring the crystalline and amorphous phase ratios of TiO2 through the use of organic additives during hydrothermal synthesisNejc Rozman, Andrijana Sever Škapin, David Maria Tobaldi, Goran Dražić, Peter Nadrah, 2024, original scientific article Abstract: The photocatalytic properties of TiO2 are primarily determined by its crystallinity and crystalline phase ratios. To improve the photocatalytic properties of TiO2, greater control over the formation of crystalline and amorphous phases during synthesis is therefore required. In this study, we demonstrate how the addition of minute amounts of three organic compounds (isopropanol, acetone and acetic acid) during hydrothermal treatment affects the amorphous and crystalline phase ratios: the addition of isopropanol or acetone accelerates the phase transition from anatase and brookite to rutile, whereas the addition of acetic acid inhibits the transformation of anatase to rutile, increasing the content of amorphous phase compared to samples where no organic compound was added. We show that the combination of the organic compound added, along with the duration of the hydrothermal treatment, can be used to tailor the phase composition of TiO2, so as to obtain either: i) TiO2 with a high content of both rutile and amorphous phase, ii) TiO2 with a high rutile content and iii) TiO2 with different ratios of all four phases, when the duration of synthesis is short (2–4 h). The materials synthesized exhibited high photocatalytic activity (in most cases higher than P25), which is attributed to the beneficial phase composition and high specific surface area. Keywords: sol-gel processes, X-ray methods, chemical properties, TiO2, photocatalysis Published in DiRROS: 14.08.2024; Views: 44; Downloads: 87
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2. Multi-scale and multi-modal imaging study of mantle xenoliths and petrological implicationsMarco Venier, Luca Ziberna, Lucia Mancini, Alexander P. Kao, Federico Bernardini, Giacomo Roncoroni, Sula Milani, Nasrrddine Youbi, Yondon Majigsuren, Angelo De Min, Davide Lenaz, 2024, original scientific article Abstract: The accurate textural characterization of mantle xenoliths is one of the fundamental steps to understanding the main processes occurring in the upper mantle, such as sub-solidus recrystallization, magmatic crystallization, and metasomatism. Texture, composition, and mineralogy reflect the temperature, pressure, stress conditions, melting, and/or contamination events undergone before and during the entrapment in the host magma. For these reasons, characterizing the three-dimensional (3D) texture of silicate, oxide, sulfide, and glass phases has great importance in the study of mantle xenoliths. We performed a multi-scale and multi-modal 3D textural analysis based on X-ray computed microtomography (µ-CT) data of three mantle xenoliths from different geodynamic settings (i.e., mobile belt zone, pericraton, oceanic hotspot). The samples were selected to represent different, variably complex internal structures composed of grains of different phases, fractures, voids, and fluid inclusions of different sizes. We used an approach structured in increasing steps of spatial and contrast resolution, starting with in-house X-ray µ-CT imaging (spatial resolution from 30 µm down to 6.25 µm) and moving to high-resolution synchrotron X-ray µ-CT at the micrometer scale. We performed a 3D characterization of mantle xenoliths, comparing the results with the analysis of conventional 2D images (thin sections) obtained by optical microscopy and simulating the random sectioning of several thin sections to estimate the probability of correct modal classification. The 3D models allow the extraction of textural information that cannot be quantified solely from thin sections: spinel layering, distribution of silicic glass, and related vesicles. Moreover, high-density volumes identified as sulfides were detected in two xenoliths, showing no relation with the spinel layering in one case and a preferential concentration along fractures in the other. Given the variety of textures and mineral assemblages of mantle xenoliths worldwide, the results are used to suggest experimental and analytical protocols for the characterization of these materials. Keywords: petrology, mantle xenoliths, X-ray microtomography, multi-scale image analysis Published in DiRROS: 23.05.2024; Views: 187; Downloads: 41
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3. Alternative alkali activators based on waste bottle glass and waste cathode-ray tube glassKatja Koenig, Katja Traven, Vilma Ducman, 2021, published scientific conference contribution Abstract: Alkali-activated binders are an environmentally friendly alternative to Portland cement, particularly when locally-available raw materials are used. It is well known that alkali activation with a sodium silicate activator generates a hardened binder with higher compressive strength than a binder hardened with sodium hydroxide. As the alkali-silicate activators are produced through energy extensive processes, and their use can significantly increase the carbon footprint of the final products, it is of great significance to develop alternative alkaline activators based on locally-available waste materials. This article assesses the potential to apply waste bottle glass and waste cathode-ray tube (CRT) glass to synthesise alternative alkali activators by the hydrothermal method. Inductively coupled plasma-optical emission spectrometry (ICP-OES) was used to determine silicon and aluminium content in the alternative activators. The influence of dissolution process parameters (time, temperature, particle size) on the concentrations of silicon and aluminium in the alternative activators was investigated. The alternative activators with silicon concentration up to 19 g/L and aluminium concentration up to 0.9 g/L were prepared at T = 120 °C and boiling time 24 h. The alternative alkali activators and, for comparison, also commercial sodium silicate were used in the alkali activation of fly ash powder. The formed pastes were cured at 70 °C for 72 h. Mechanical strength measurements indicated that alkali activation of fly ash with the optimal alternative activator yielded hardened paste with compressive strength of 33 MPa. However, the compressive strength of hardened paste prepared from fly ash and commercial sodium silicate reached 70 MPa. Part of this difference can be ascribed to the lower density of hardened pastes prepared with alternative activators. Keywords: alkali -activated materials, alternative alkali activators, waste bottle glass, waste cathode -ray tube glass, fly ash, hydrothermal method Published in DiRROS: 25.01.2024; Views: 382; Downloads: 239
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4. Electrochemical cycling behaviour and shape changes of Zn electrodes in mildly acidic aqueous electrolytes containing quaternary ammonium saltsBenedetto Bozzini, Marco Boniardi, Tommaso Caielli, Andrea Casaroli, Elisa Emanuele, Lucia Mancini, Nicola Sodini, Jacopo Strada, 2023, original scientific article Abstract: Secondary Zn–based batteries are a valid alternative to Li for stationary storage, but commercial devices are not yet available, chiefly owing to anode shape-change and passivation issues. Mildly acidic aqueous solutions are actively studied, since they seem to limit unstable growth of Zn, with respect to the alkaline ones, customary for primary batteries. Additives can further improve the performance of mildly acidic electrolytes. In this work we focus on the impact of a series of quaternary ammonium salts (TBAB, CTAB, DMDTDAB, BDMPAC, BPPEI, PDADMAC), selected to represent a comprehensive range of molecular functionalities. Electrochemical measurements (cyclic voltammetry, chronopotentiometry and galvanostatic-cycling in split-cells), combined with 2D and 3D imaging techniques (SEM, stereomicroscopy and in situ tomography) were adopted for the assessment Zn behaviour. This multi-technique approach pinpointed TBAB as the single most effective additive for low-current density operation, while at high current densities the additive-free electrolyte allows better cycling performance, coherently with similar results for alkaline electrolytes. Keywords: battery, electrolyte, electrochemical measurements, quaternary Ammomium salt, X-ray computed microtomography, mobility Published in DiRROS: 06.07.2023; Views: 560; Downloads: 289
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5. Characterizing steel corrosion in different alkali-activated mortarsNina Gartner, Miha Hren, Tadeja Kosec, Andraž Legat, 2021, original scientific article Abstract: Alkali-activated materials (AAMs) present a promising potential alternative to ordinary Portland cement (OPC). The service life of reinforced concrete structures depends greatly on the corrosion resistance of the steel used for reinforcement. Due to the wide range and diverse properties of AAMs, the corrosion processes of steel in these materials is still relatively unknown. Three different alkali-activated mortar mixes, based on fly ash, slag, or metakaolin, were prepared for this research. An ordinary carbon-steel reinforcing bar was installed in each of the mortar mixes. In order to study the corrosion properties of steel in the selected mortars, the specimens were exposed to a saline solution in wet/dry cycles for 17 weeks, and periodic electrochemical impedance spectroscopy (EIS) measurements were performed. The propagation of corrosion damage on the embedded steel bars was followed using X-ray computed microtomography (XCT). Periodic EIS measurements of the AAMs showed different impedance response in individual AAMs. Moreover, these impedance responses also changed over the time of exposure. Interpretation of the results was based on visual and numerical analysis of the corrosion damages obtained by XCT, which confirmed corrosion damage of varying type and extent on steel bars embedded in the tested AAMs. Keywords: corrosion, alkali-activated mortars, steel reinforcement, electrochemical impedance spectroscopy, X-ray computed microtomography, visual analysis Published in DiRROS: 05.07.2023; Views: 574; Downloads: 271
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6. Quantitative in situ X-ray diffraction analysis of early hydration of belite-calcium sulfoaluminate cement at various defined temperaturesMaruša Mrak, Christian L. Lengauer, Sabina Dolenec, 2021, original scientific article Abstract: The influence of temperature on the early hydration of belite-calcium sulfoaluminate cements with two different calcium sulfate to calcium sulfoaluminate molar ratios was investigated. The phase composition and phase assemblage development of cements prepared using molar ratios of 1 and 2.5 were studied at 25, 40 and 60 ◦C by in situ X-ray powder diffraction. The Rietveld refinement method was used for quantification. The degree of hydration after 24 h was highest at ambient temperatures, but early hydration was significantly accelerated at elevated temperatures. These differences were more noticeable when we increased the temperature from 25 ◦C to 40 ◦C, than it was increased from 40 ◦C to 60 ◦C. The amount of calcium sulfate added controls the amount of the precipitated ettringite, namely, the amount of ettringite increased in the cement with a higher molar ratio. The results showed that temperature also affects full width at half maximum of ettringite peaks, which indicates a decrease in crystallite size of ettringite at elevated temperatures due to faster precipitation of ettringite. When using a calcium sulfate to calcium sulfoaluminate molar ratio of 1, higher d-values of ettringite peaks were observed at elevated temperatures, suggesting that more ions were released from the cement clinker at elevated temperatures, allowing a higher ion uptake in the ettringite structure. At a molar ratio of 2.5, less clinker is available in the cement, therefore these differences were not observed. Keywords: in situ X-ray diffraction, hydration, temperature, cement, rietveld analysis Published in DiRROS: 26.06.2023; Views: 518; Downloads: 294
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7. Multiscale femoral neck imaging and multimodal trabeculae quality characterization in an osteoporotic bone sampleEnrico Soldati, Flavy Roseren, Daphne Guenoun, Lucia Mancini, Emilio Catelli, Silvia Prati, Giorgia Sciutto, Jerome Vicente, Stefano Iotti, David Bendahan, Emil Malucelli, Martine Pithioux, 2022, original scientific article Abstract: Although multiple structural, mechanical, and molecular factors are definitely involved in osteoporosis, the assessment of subregional bone mineral density remains the most commonly used diagnostic index. In this study, we characterized bone quality in the femoral neck of one osteoporotic patients as compared to an age-matched control subject, and so used a multiscale and multimodal approach including X-ray computed microtomography at different spatial resolutions (pixel size: 51.0, 4.95 and 0.9 µm), microindentation and Fourier transform infrared spectroscopy. Our results showed abnormalities in the osteocytes lacunae volume (358.08 ± 165.00 for the osteoporotic sample vs. 287.10 ± 160.00 for the control), whereas a statistical difference was found neither for shape nor for density. The osteoporotic femoral head and great trochanter reported reduced elastic modulus (Es) and hardness (H) compared to the control reference (−48% (p < 0.0001) and −34% (p < 0.0001), respectively for Es and H in the femoral head and −29% (p < 0.01) and −22% (p < 0.05), respectively for Es and H in the great trochanter), whereas the corresponding values in the femoral neck were in the same range. The spectral analysis could distinguish neither subregional differences in the osteoporotic sample nor between the osteoporotic and healthy samples. Although, infrared spectroscopic measurements were comparable among subregions, and so regardless of the bone osteoporotic status, the trabecular mechanical properties were comparable only in the femoral neck. These results illustrate that bone remodeling in osteoporosis is a non-uniform process with different rates in different bone anatomical regions, hence showing the interest of a clear analysis of the bone microarchitecture in the case of patients’ osteoporotic evaluation Keywords: synchrotron X-ray microtomography, bone, trabecular struicture, osteons, osteoporosis, phase-contrast imaging, open access Published in DiRROS: 28.04.2023; Views: 512; Downloads: 267
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8. The effect of cultivation practices on agronomic performance, elemental composition and isotopic signature of spring oat (Avena sativa L.)Aleš Kolmanič, Lovro Sinkovič, Marijan Nečemer, Nives Ogrinc, Vladimir Meglič, original scientific article Keywords: oat, cultivation practice, yield, energy dispersive X-ray fluorescence (EDXRF), elements, isotopic signature Published in DiRROS: 06.09.2022; Views: 738; Downloads: 273
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9. Structural and CO [sub] 2 capture properties of ethylenediamine-modified HKUST-1 metal-organic frameworkNika Vrtovec, Matjaž Mazaj, Gianpiero Buscarino, Angela Terracina, Simonpietro Agnello, Iztok Arčon, Janez Kovač, Nataša Zabukovec Logar, 2020, original scientific article Keywords: functionalization, modification, adsorption, extended X-ray absorption fine structure, materials Published in DiRROS: 25.11.2020; Views: 2585; Downloads: 1061
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10. RNA-dependent cysteine biosynthesis in bacteria and archaeaTakahito Mukai, Ana Crnković, Takuya Umehara, Natalia N. Ivanova, Nikos C. Kyrpides, Dieter Söll, 2017, original scientific article Keywords: amino acyl-tRNA synthetases, archaea, archaeal proteins, bacteria, computational biology, crystallography, X-ray, genetic code, genome, archaeal, genome, bacterial, phosphoserine, protein binding, protein biosynthesis, RNA, archaeal, RNA, bacterial, RNA, transfer, amino acyl, RNA, transfer, cys, sulfur/metabolism, biochemistry, bioinformatics, cysteine biosynthesis, genetic code, translation Published in DiRROS: 07.05.2020; Views: 1950; Downloads: 1417
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