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Photocatalytic CO2 reduction over mesoporous TiO2 photocatalysts
Martin Reli, Peter Nadrah, Miroslava Filip Edelmannová, Rudolf Ricka, Andrijana Sever Škapin, Urška Lavrenčič Štangar, Kamila Kočí, 2024, izvirni znanstveni članek

Povzetek: In this study, we investigated different synthesis methods (template-free and template-based) using copolymers of poly(ethylene oxide) and poly(propylene oxide) to enhance the CO2 reduction activity of mesoporous TiO2. Our main goal was to identify key factors affecting photocatalyst efficiency and selectivity. We compared the newly synthesized TiO2 photocatalysts with the commercial photocatalyst P25. Among the materials studied, TiO2-P123 in its pure anatase form demonstrated the highest photoreduction efficiency and CO2 selectivity. In contrast, TiO2-EG, TiO2-F127, and P25, which contained both rutile and anatase phases, exhibited decreased photoactivity due to the formation of a type II heterojunction between the phases and higher oxygen adsorption on rutile's surface. Additionally, we observed that the choice of chemicals for photocatalyst preparation significantly influenced the specific surface area. TiO2-P123, the most active photocatalyst, had the highest specific surface area, providing more reactive sites for improved light absorption efficiency and prolonged electron-hole pair lifetimes, resulting in enhanced photocatalytic activity. We also calculated apparent quantum yields to support our findings.
Ključne besede: CO2 reduction, TiO2, photocatalysis, mesoporous material, Sol-gel method
Objavljeno v DiRROS: 14.11.2023; Ogledov: 68; Prenosov: 9
.pdf Celotno besedilo (2,42 MB)
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UV light causes structural changes in microplastics exposed in bio-solids
S. S. Alavian Petroody, Seyed Hossein Hashemi, Luka Škrlep, Branka Mušič, Cornelis A. M. van Gestel, Andrijana Sever Škapin, 2023, izvirni znanstveni članek

Povzetek: Bio-solids (biological sludge) from wastewater treatment plants are a significant source of the emission of microplastics (MPs) into the environment. Weakening the structure of MPs before they enter the environment may accelerate their degradation and reduce the environmental exposure time. Therefore, we studied the effect of UV-A and UV-C, applied at 70 °C, on three types of MPs, polypropylene (PP), polyethylene (PE), and polyethylene terephthalate (PET), that are commonly found in sewage sludge, using three shapes (fibers, lines, granules). The MPs were exposed to UV radiation in bio-solid suspensions, and to air and water as control. The structural changes in and degradation of the MPs were investigated using Attenuated Total Reflectance–Fourier Transform Infrared Spectrometry (ATR-FTIR) and surface morphology was performed with SEM analysis. UV exposure led to the emergence of carbonyl and hydroxyl groups in all of the PP samples. In PE and PET, these groups were formed only in the bio-solid suspensions. The presence of carbonyl and hydroxyl groups increased with an increasing exposure time. Overall, UV radiation had the greatest impact on the MPs in the bio-solids suspension. Due to the surface-to-volume ratio of the tested samples, which influences the degradation rate, the fibers were more degraded than the other two plastic shapes. UV-A was slightly more effective at degrading the MPs than UV-C. These findings show that ultraviolet radiation in combination with an elevated temperature affects the structure of polymers in wastewater bio-solids, which can accelerate their degradation.
Ključne besede: microplastics, degradation, hydroxyl, carbonyl, ultraviolet light
Objavljeno v DiRROS: 14.11.2023; Ogledov: 73; Prenosov: 43
.pdf Celotno besedilo (2,27 MB)
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Strižna trdnost spojev z ribjim klejem lepljenega lesa ovrednotena z metodo ABES
Matic Sitar, Andreja Pondelak, Samo Grbec, Milan Šernek, 2023, izvirni znanstveni članek

Povzetek: V prispevku smo s pomočjo sistema za avtomatizirano vrednotenje zlepljenosti (ABES) ugotavljali razvoj strižne trdnosti ribjega kleja pri lepljenju lesa. Uporabili smo bukov (Fagus sylvatica L.) furnir, ki smo ga lepili pri konstantnem tlaku 12 barov, medtem ko smo spreminjali temperaturo in čas stiskanja. Temperatura je znašala med25 °C in 100 °C, z intervalom 25 °C, čas stiskanja pa od 1 minute do 60 minut. Dosežena maksimalna strižna trdnost je znašala okoli 10 N/mm², dosegli smo jo pri vseh štirih proučevanih temperaturah stiskanja. Na podlagi rezultatov študije smo ugotovili, da strižna trdnost ribjega kleja pri različnih temperaturah segrevanja neenakomerno narašča. Pri višjih temperaturah segrevanja hitreje dosežemo maksimalne strižne trdnosti. Strižne trdnosti spoja lepila iz ribjega kleja smo ugotavljali tudi po standardih EN 204 in EN 205.
Ključne besede: wood
Objavljeno v DiRROS: 14.11.2023; Ogledov: 62; Prenosov: 43
.pdf Celotno besedilo (2,41 MB)
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Closing data gaps and paving the way for pan-European fire safety efforts : Terminology of fire statistical variables
Martina Manes, Ana Sauca, Mohamad El Houssami, Petra Andersson, Colin McIntyre, Richard Campbell, David Rush, Anja Hofmann, Peter Wagner, Sergei Sokolov, Mindel Leene, Margrethe Kobes, Dirk Oberhagemann, Nicola Rupp, Grunde Jomaas, Friedrich Grone, Eric Guillaume, 2023, izvirni znanstveni članek

Povzetek: A well-defined terminology of fire-related variables is important for correct analyses and supporting knowledge-based decisions regarding the evaluation of building fires at the European level. After developing an overview of current practices for fire statistics in Part I, the terminology used and the data collected by the EU Member States and eight other countries regarding fire incidents, property damage and human losses were mapped to increase awareness of their practice and support a comprehensive assessment of several fire statistical datasets. A questionnaire was distributed to relevant authorities responsible for the collection, elaboration/analysis, and fire statistical data publications to define and select the essential variables for an appropriate fire assessment and fire incident description. Based on the results of the questionnaire able to identify the essential fire statistical variables and a detailed analysis of current definitions adopted in the fire statistics of the EU Member States and other countries, a common terminology is proposed to collect the necessary data in the EU Member States and obtain meaningful datasets based on standardised terms and definitions. The results will generate essential outputs to move towards harmonised fire statistics at the EU level and contribute to an appropriate analysis able to improve fire prevention and fire mitigation in building fires.
Ključne besede: fire statistics, fire incidents, building fires, fire statistical variables, terminology
Objavljeno v DiRROS: 13.11.2023; Ogledov: 82; Prenosov: 47
.pdf Celotno besedilo (1,11 MB)
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Defining the fire decay and the cooling phase of post-flashover compartment fires
Andrea Lucherini, Jose L. Torero, 2023, izvirni znanstveni članek

Povzetek: The current research study discusses and characterises the fire decay and cooling phase of post-flashover compartment fires, as they are often mixed up despite their important heat transfer differences. The two pha- ses are defined according to the fire heat release rate time-history. The fire decay represents the phase in which the fire heat release rate decreases from the ventilation- or fuel-limited steady-state value of the fully-developed phase to fire extinguishment. This phase is highly influenced by the fuel characteristics, ranging from fast decays for hydrocarbon and liquid fuels to slow decays for charring cellulosic fuels (wood). Once the fuel is consumed, the compartment volume enters the cooling phase, where the cooling in the gas-phase and solid-phase happens with significantly different modes and characteristic times. The thermal boundary conditions at the structural elements are then defined according to physical characteristics and dynamics within the compartment. The research study also underlines how the existing performance-based methodologies lack explicit definitions of the decay and cooling phases and the corresponding thermal boundary conditions for the design of fire-safe struc- tural elements under realistic fire conditions.
Ključne besede: razpadanje ognja, hlajenje, izgorevanje, naravna izpostavljenost ognju, dinamika požara, požari v oddelkih, požarno inženirstvo, učinkovitost, požarna varnost, fire decay, cooling, burnout, natural fire exposure, fire dynamics, compartment fires, structural fire engineering, performance-based, fire safety
Objavljeno v DiRROS: 13.11.2023; Ogledov: 85; Prenosov: 35
.pdf Celotno besedilo (4,91 MB)
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A historical overview of experimental solid combustion research in microgravity
Wilson Ulises Rojas Alva, Grunde Jomaas, 2022, izvirni znanstveni članek

Povzetek: Studying solid combustion phenomena in microgravity environments can be complex, and this is furthered by many limitations and constraints in the available microgravity research platforms. Consequently, fire safety in spacecraft is also a complex subject. The main limitations found in the field are related to the microgravity quality, the duration of microgravity conditions, the rig capabilities in volume and size, time scales, length scales and the diagnostic systems, and these are therefore the focus in the current investigation. The laboratory capacity of ground-based platforms has remained somewhat stalled since 1990s, some drop towers have recently been upgraded to extend their performance. New space-based platforms have been or are being established and could extend the windows-of-opportunity to perform research. In addition, a discussion is provided on the implications of the fact that the phenomena studied in the experimental investigations and the type of material employed covers both programmatic and scientific needs. It is found that a handful of materials are most widely studied to quantify and characterise some of the phenomena, while some materials have been employed even in single experimental efforts. The current literature review provides a very comprehensive overview of previous experimental studies and the experimental methodologies utilised. Thus, this study can become an aid to planning for future studies.
Ključne besede: Microgravity, research platforms, solid combustion, fire safety, spacecraft
Objavljeno v DiRROS: 13.11.2023; Ogledov: 84; Prenosov: 11
.pdf Celotno besedilo (965,67 KB)
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Flame spread behaviour of Polydimethylsiloxane (PDMS) membranes in 1 g and µg environments
Wilson Ulises Rojas Alva, Frederik Møller-Poulsen, Sze Lok Man, Cameron Creamer, David Hanna, Grunde Jomaas, 2022, izvirni znanstveni članek

Povzetek: Diffusion flame behaviour and silica ash (SiO2) production were experimentally studied for various Polydimethylsiloxane (PDMS) membrane thicknesses (0.125 mm to 1.0 mm) in normal gravity and during microgravity flight experiments. The flames were established on vertical samples (300 mm in length) and subjected to either opposed or concurrent forced flows (both laminar and turbulent), assimilating the NASA Test 1 that is in use for spacecraft material selection. The opposed flame spread rate was observed to be steady and could be estimated using classical theory. Under concurrent flow, the flame spread rate was only steady for very high forced flows. The opposed flame-spread rate ranged from 0.5 to 1.5 mm/s, while the concurrent case ranged between 0.1 and 12 mm/s. The transport of silica ash (SiO2) was found to affect the heat balance of the concurrent flame spread in a manner that resulted in unsteady flame spread. For opposed flame spread, on the other hand, the transport of silica ash showed to be irrelevant. The extinction behaviour for the concurrent flame spread was heavily dominated by the transport of silica-ash, while for opposed flames, extinction was due to kinetics (at high forced flows). In microgravity environments, the transport and deposition of silica ash is anticipated to dominate flame spread and near-limit as well. These results suggest that silica-based products might be less flammable in microgravity than other similar materials such as common thermoplastics (PP or PE) used as wire jackets.
Ključne besede: silicone burning, spacecraft fire safety, flame spread, near-limit, silica-ash
Objavljeno v DiRROS: 13.11.2023; Ogledov: 92; Prenosov: 12
.pdf Celotno besedilo (1,61 MB)
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Recovery of phosphorus and metals from the ash of sewage sludge, municipal solid waste, or wood biomass : a review and proposals for further use
Sara Tominc, Vilma Ducman, Wolfgang Wisniewski, Terttu Luukkonen, Kirkelund Gunvor M., Ottosen Lisbeth M., 2023, izvirni znanstveni članek

Povzetek: This review provides an overview of methods to extract valuable resources from the ash fractions of sewage sludge, municipal solid waste, and wood biomass combustion. The resources addressed here include critical raw materials, such as phosphorus, base and precious metals, and rare earth elements for which it is increasingly important to tap into secondary sources in addition to the mining of primary raw materials. The extraction technologies prioritized in this review are based on recycled acids or excess renewable energy to achieve an optimum environmental profile for the extracted resources and provide benefits in the form of local industrial symbioses. The extraction methods cover all scarce and valuable chemical elements contained in the ashes above certain concentration limits. Another important part of this review is defining potential applications for the mineral residues remaining after extraction. Therefore, the aim of this review is to combine the knowledge of resource extraction technology from ashes with possible applications of mineral residues in construction and related sectors to fully close material cycle loops.
Ključne besede: critical raw materials, extraction, sewage sludge ash, municipal solid waste incineration ash, wood biomass ash
Objavljeno v DiRROS: 03.11.2023; Ogledov: 141; Prenosov: 53
.pdf Celotno besedilo (1,12 MB)
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Effect of undercooling on clinopyroxene crystallization in a high K basalt : implications for magma dynamics at Stromboli volcano
F. Colle, Matteo Masotta, S. Costa, Silvio Mollo, P. Landi, A. 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: 199; Prenosov: 131
.pdf Celotno besedilo (6,46 MB)
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Use of fly ash and phosphogypsum for the synthesis of belite-sulfoaluminate clinker
Sabina Dolenec, Lea Žibret, Emilija Fidanchevska, V. Jovanov, Biljana Angjusheva, Vilma Ducman, 2019, izvirni znanstveni članek

Povzetek: Fly ash and phosphogypsum were used as Naturally Occurring Radioactive Materials (NORM) by-products for the synthesis of belite-sulfoaluminate clinkers. The influence of raw mixture composition and firing temperature was investigated. Clinkers and cements were examined by X-ray powder diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy. The compressive strength of the cements was determined after 28 days. Clinker phases identified included ye’elimite, ß-phase of belite, ternesite and gehlenite, while the main hydration product of the cement pastes was ettringite. The results showed that belite-sulfoaluminate cements can be fabricated with a compressive strength of 45.9 N/mm2 by firing the raw mixture (70 wt.% marl, 10 wt.% bauxite and 20 wt.% phosphogypsum) at a temperature of 1320°C/1h.
Ključne besede: clinker, microstructure, fly ash, gypsum, calcium sulphoaluminate
Objavljeno v DiRROS: 27.10.2023; Ogledov: 183; Prenosov: 80
.pdf Celotno besedilo (2,01 MB)
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