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Iskalni niz: "ključne besede" (microtomography) .

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1.
Direct reconstruction of wet foam from sparse-view, dynamic X-ray CT scans
Jens Renders, Lucia Mancini, Jan De Beenhouwer, Jan Sijbers, 2024, izvirni znanstveni članek

Povzetek: X-ray imaging of wet foam dynamics with a high temporal resolution (e.g., 3D videos with a 10 Hz frame rate) requires fast rotation of either the foam sample or the X-ray gantry. This, however, strongly limits the number of X-ray projections per rotation that can be acquired. As a result, conventional computed tomography reconstruction methods generate 3D images with severe undersampling artefacts, complicating subsequent foam analysis. Herein, BubSub, a novel tomographic reconstruction approach that reconstructs a 4D (3D plus time) dynamic image of wet foam bubbles from sparse-view X-ray projections by leveraging prior knowledge about the evolving foam structure, is introduced. BubSub adapts a collection of subdivision surfaces with spherical topology to represent liquid–gas interfaces of foam bubbles. Estimation of bubble positions and shapes at each time point is achieved by minimizing the projection distance in relation to the measured projections. BubSub operates efficiently with minimal memory usage, exhibits robustness against noise, and provides accurate reconstructions, even when the available projections are limited, as evidenced by various experiments using both simulated and real wet foam X-ray data.
Ključne besede: redki pogledi, dinamika pene, rentgenska mikrotomografija, tomografska rekonstrukcija, sparse views, foam dynamics, X-ray microtomography, tomographic reconstruction
Objavljeno v DiRROS: 16.12.2024; Ogledov: 153; Prenosov: 86
.pdf Celotno besedilo (2,80 MB)
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2.
Identifying crystal nucleation mechanisms in a synthetic trachybasalt: a multimodal approach
Stefano Peres, Thomas A. Griffiths, Fabio Colle, Stefano Iannini Lelarge, Matteo Masotta, Alessio Pontesilli, Lucia Mancini, Rainer Abart, 2024, izvirni znanstveni članek

Povzetek: To develop new criteria to distinguish different crystal nucleation mechanisms in silicate melts, we performed crystallization experiments using a synthetic hydrous (2 wt% H2O) trachybasalt and combined three-dimensional information from synchrotron X-ray computed microtomography with two-dimensional mapping of crystallographic orientation relationships (CORs) using electron backscatter diffraction. Crystallization experiments were performed at 400 MPa by cooling the melt from 1300 °C to resting temperatures of 1150 and 1100 °C and maintaining isothermal conditions for 30 min and 8 h. Three distinct titanomagnetite (Tmt) populations formed: (1) skeletal crystals, isolated or partially embedded in clinopyroxene (Cpx); (2) anhedral crystals, always attached to Cpx; (3) flattened needle-shaped crystals, embedded in Cpx. These morphologically different Tmt populations formed in response to one cooling event, with varying nucleation mechanisms and at different undercooling conditions. The clustered three-dimensional distribution of population 2 and 3 Tmt grains and the high proportion of Tmt-Cpx interfaces sharing CORs indicate that these Tmt grains heterogeneously nucleated on Cpx. The near-random three-dimensional distribution of (often isolated) population 1 Tmt grains, together with the low proportion of Tmt-Cpx interfaces sharing CORs, imply their isolated, possibly homogeneous nucleation, potentially followed by heterogeneous nucleation of Cpx on population 1 Tmt. Heterogeneous nucleation in slightly to moderately undercooled magmas should affect the sequence of crystallization as well as morphology and clustering of crystals, which may actively contribute to the variation of rheological parameters like viscosity. Finally, observed intra- and inter-sample variations in Tmt-Cpx COR frequencies indicate the potential for this parameter to record further petrological information.
Ključne besede: experimental petrology, nucleation mechanisms, X-ray microtomography, crystal clustering, heterogeneous nucleation
Objavljeno v DiRROS: 16.12.2024; Ogledov: 149; Prenosov: 130
.pdf Celotno besedilo (5,45 MB)
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3.
Effects of different China and ball clays on traditional ceramic process : a multi-methodological approach
Andreas Bernasconi, Nicoletta Marinoni, Lucia Mancini, Marco Voltolini, Fernando Francescon, R. Sartori, Alessandro Pavese, 2024, izvirni znanstveni članek

Povzetek: A combination of technological properties, mineralogical composition and three-dimension (3D) imaging is proposed to get insights into sanitary-ware ceramic bodies of the Vitreous-China technology as a function of the different clay raw materials used in the formulation of slip. Particular attention is paid to the effects induced along the production chain, during casting, after drying (dried body) and after firing (fired body). The different combinations of China and ball clays lead to different casting behaviour, in first instance, and to different mechanical strength, then, due to variations in the particle size distribution rather than in the mineralogical composition. In particular, the finer the particle size, the finer the pore size and, in addition, the better the mechanical properties (with a maximum of 4.7 MPa), due to a better packing. However, fine particle size distribution worsens the slip’s behaviour into moulds, impacting negatively on productivity, with a 17 % reduction of casting thickness. Upon firing process, such differences are mitigated by the body densification and result in more similar pores’ distributions, though the importance of the mineralogical composition is revealed. In fact, differences in mineralogical phases’ contents and in kaolinite HI index guide the comprehension of high temperature phase evolution and technological properties like the fired body thermal expansion, foremost via residual quartz. These results are important for a plastic raw materials’s selection within the ceramic sanitary-ware process.
Ključne besede: clay raw materials, vitreous-China technology, synchrotron X-ray microtomography, X-ray diffraction, ceramic properties, phase analysis
Objavljeno v DiRROS: 16.12.2024; Ogledov: 146; Prenosov: 115
.pdf Celotno besedilo (3,59 MB)
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4.
An investigation into corrosion around voids at the steel-concrete interface
Miha Hren, Tadeja Kosec, Andraž Legat, 2024, izvirni znanstveni članek

Povzetek: In this study, the influence of voids on corrosion process at the steel-concrete interface was investigated, as the exact influence of these features on corrosion processes under various environmental conditions is not entirely understood. Coupled multi electrode arrays and electrical resistance probes were implemented to monitor the evolution of corrosion under cyclic exposure to chlorides and carbonation. MicroCT was used to determine the location and volume of corrosion damage. It was found that, in most cases, corrosion damage initiated outside the voids. During initiation and the early propagation phase, the steel beneath the voids rarely participated in the redox reaction. In following phases, various kinds of corrosion evolution were observed. Specific corrosion mechanisms were proposed and discussed to explain these corrosion processes.
Ključne besede: microtomography, corrosion, coupled multi-electrode array, steel-concrete interface
Objavljeno v DiRROS: 06.06.2024; Ogledov: 533; Prenosov: 508
.pdf Celotno besedilo (23,73 MB)
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5.
Multi-scale and multi-modal imaging study of mantle xenoliths and petrological implications
Marco Venier, Luca Ziberna, Lucia Mancini, Alexander P. Kao, Federico Bernardini, Giacomo Roncoroni, Sula Milani, Nasrrddine Youbi, Yondon Majigsuren, Angelo De Min, Davide Lenaz, 2024, izvirni znanstveni članek

Povzetek: 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.
Ključne besede: petrology, mantle xenoliths, X-ray microtomography, multi-scale image analysis
Objavljeno v DiRROS: 23.05.2024; Ogledov: 481; Prenosov: 97
.pdf Celotno besedilo (1,64 MB)
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6.
The microstructure, mechanical and electrochemical properties of 3D printed alloys with reusing powders
Mirjam Bajt Leban, Miha Hren, Tadeja Kosec, 2023, izvirni znanstveni članek

Povzetek: CoCrMo and Ti6Al4V are widely used in medical, dental and 3D printing technology, allowing the accurate fabrication of geometrically complicated structures. In order to reduce the costs of printed objects, the reuse of powder is common daily practice. AQ1 When using 3D printing technology, the direct impact of elevated temperatures and the influence of the laser beam may change the properties of the powder when it is reused, thus affecting the final properties of the printed object. The main aim of the present study was to investigate the impact of reused powder on the mechanical, microstructural and electrochemical properties of 3D printed objects. 3D printed objects fabricated from virgin and reused powder of both alloys were analyzed by metallographic observation, computed tomography, XRD and electrochemical methods. The main finding of the study was that the use of reused powder (recycled 3 times) does not detrimentally affect the mechanical and corrosion integrity of 3D printed CoCr and Ti6Al4V alloys, especially for the purpose of applications in dentistry.
Ključne besede: additive manufacturing, selective laser melting, virgin powder, reused powder, microtomography
Objavljeno v DiRROS: 08.01.2024; Ogledov: 880; Prenosov: 356
.pdf Celotno besedilo (2,93 MB)
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7.
Effect of undercooling on clinopyroxene crystallization in a high K basalt : implications for magma dynamics at Stromboli volcano
Fabio Colle, Matteo Masotta, S. Costa, Silvio Mollo, P. Landi, Alessio Pontesilli, S. Peres, Lucia Mancini, 2023, izvirni znanstveni članek

Povzetek: We present undercooling (∆T) experiments aimed at investigating the effect of growth kinetics on the textural and compositional evolution of clinopyroxene crystals growing from a high-K basalt erupted during the 2003 paroxysm of Stromboli volcano (Italy). The experiments were performed at P = 350 MPa, T = 1050–1210 °C, H2Omelt = 0–3 wt%, and fO2 = Ni-NiO + 1.5 buffer. An initial stage of supersaturation was imposed to the melt under nominally anhydrous (∆Tanh = 10–150 °C) and hydrous (∆Thyd = 25–125 °C) conditions. Afterwards, this supersaturation state was mitigated by melt relaxation phenomena over an annealing time of 24 h. Results show that plagioclase is the liquidus mineral phase of the high-K basalt at ∆Tanh = 10 °C and dominates the phase assemblage as the degree of undercooling increases. Conversely, clinopyroxene and spinel co-saturate the melt at ∆Thyd = 25 °C, followed by the subordinate formation of plagioclase. At ∆Tanh/hyd ≤ 50 °C, the textural maturation of clinopyroxene produces polyhedral crystals with {−111} (hourglass) and {hk0} (prism) sectors typical of a layer-by-layer growth mechanism governed by an interface-controlled crystallization regime. At ∆Tanh/hyd ≥ 75 °C, the attainment of dendritic and skeletal morphologies testifies to the establishment of diffusion-limited reactions at the crystal-melt interface. 3D reconstructions of synchrotron radiation X-ray microtomographic data reveal a composite growth history for clinopyroxene crystals obtained at ∆Tanh/hyd ≥ 95 °C. The early stage of melt supersaturation produces rosette-like structures composed of dendritic branches of clinopyroxene radiating from a common spinel grain, which acts as surface for heterogeneous nucleation. As diffusive relaxation phenomena progress over the annealing time, the elongate dendrites that constitute the inner crystal domain are partially infilled by the melt and develop skeletal overgrowths in the outer domain. With the increasing degree of undercooling, TAl and M1Ti cations are progressively incorporated in the lattice site of clinopyroxene at the expense of TSi and M1Mg cations. Because of the effect of H2Omelt on the liquidus depression and melt depolymerization, crystals obtained at ∆Thyd are also more enriched in TAl and M1Ti and depleted in TSi and M1Mg than those growing at ∆Tanh. The emerging picture is that the morphological and geochemical evolution of clinopyroxene is mutually controlled by the combined effects of melt supersaturation and relaxation phenomena. A new empirical relationship based on the cation exchange reactions in the lattice site of clinopyroxene is finally proposed to estimate the degree of undercooling governing the crystallization of augitic phenocrysts erupted during normal and violent explosions at Stromboli.
Ključne besede: clinopyroxene, undercooling, hourglass, crystallization, microtomography
Objavljeno v DiRROS: 27.10.2023; Ogledov: 1027; Prenosov: 598
.pdf Celotno besedilo (6,46 MB)
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8.
Electrochemical cycling behaviour and shape changes of Zn electrodes in mildly acidic aqueous electrolytes containing quaternary ammonium salts
Benedetto Bozzini, Marco Boniardi, Tommaso Caielli, Andrea Casaroli, Elisa Emanuele, Lucia Mancini, Nicola Sodini, Jacopo Strada, 2023, izvirni znanstveni članek

Povzetek: 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.
Ključne besede: battery, electrolyte, electrochemical measurements, quaternary Ammomium salt, X-ray computed microtomography, mobility
Objavljeno v DiRROS: 06.07.2023; Ogledov: 852; Prenosov: 467
.pdf Celotno besedilo (2,52 MB)
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9.
Characterizing steel corrosion in different alkali-activated mortars
Nina Gartner, Miha Hren, Tadeja Kosec, Andraž Legat, 2021, izvirni znanstveni članek

Povzetek: 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.
Ključne besede: corrosion, alkali-activated mortars, steel reinforcement, electrochemical impedance spectroscopy, X-ray computed microtomography, visual analysis
Objavljeno v DiRROS: 05.07.2023; Ogledov: 835; Prenosov: 431
.pdf Celotno besedilo (7,00 MB)
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10.
Production and characterization of lightweight aggregates from municipal solid waste incineration fly-ash through single- and double-step pelletization process
Alberto Ferraro, Vilma Ducman, Francesco Colangelo, Lidija Korat Bensa, Danilo Spasiano, Ilenia Farina, 2023, izvirni znanstveni članek

Povzetek: The performance of a cold-bonding pelletization process was investigated for lightweight aggregates (LWAs) production from municipal solid waste incineration (MSWI) fly-ash (FA), by including multiple waste materials in the aggregate mixture. Before pelletization, FA was pre-treated by washing with water, which led to a reduction of chloride (66.79%) and sulphate (25.30%) content. This was further confirmed by XRF and XRD analyses, which showed a reduction of chloride elements and the content of chlorine crystalline phases. The pelletization process was carried out using both single- and double-step methods. For single-step pelletization, all the mixtures contained 80% FA, combined with various compositions of cement (5, 10, and 15%) and granulated blast furnace slag (GBFS) (5, 10, and 15%). For the double-step pelletization 30% of cement and 70% of marble sludge (MS) were added to each of the previous mixtures. The apparent density of all the aggregates varied between 1.60 and 1.87 g cm 3, suggesting their suitability to be classified as LWAs. Aggregates produced from double-step pelletization showed improved characteristics, with water absorption capacity and open porosity generally lower compared to the corresponding aggregates from the single-step pelletization. The best values of compressive (crushing) strength (almost 11 MPa) were observed for double-step pelletization aggregates with initial cement: GBFS mixture of 15%:5%. Results from leaching tests showed an overall significant release of chloride and sulphate. Nevertheless, leaching from double-step pelletization aggregates was reduced by 1.73- 4.02 times for chloride and 1.58-5.67 times for sulphate, further suggesting that better performances are achievable through the addition of an aggregate second layer.
Ključne besede: MSWI fly ash, lightweight aggregate, microtomography, open access
Objavljeno v DiRROS: 03.05.2023; Ogledov: 802; Prenosov: 669
.pdf Celotno besedilo (8,90 MB)
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