11. Particle size manipulation as an influential parameter in the development of mechanical properties in electric arc furnace slag-based AAMKatja Traven, Mark Češnovar, Vilma Ducman, 2019, izvirni znanstveni članek Povzetek: Alkali-activated materials (AAM) have gained recognition as a promising alternative to technical ceramic and building materials owing to the lower energy demands for production and the potential to use slag as a precursor. In the present study, five sets of slag-based AAM pastes were prepared with different particle sizes (fractions d < 63, 63 < d < 90, and 90 < d < 125 μm in different mass ratios) under the same curing regime and using a fixed precursor to activator (water) mass ratio. Precursors and the hardened AAM are evaluated using BET, XRD, XRF, SEM, FTIR, reactivity of precursors by leaching, and mercury intrusion porosimetry (MIP). Chemical analysis indicated only marginal differences among the different-sized fractions of input materials, whereas the BET surface area and reactivity among the precursors differed significantly-smaller particles had the largest surface area, and thus, higher reactivity. The mineralogical differences between the precursors and hardened AAM were negligible. The results revealed that compressive strength was significantly influenced by particle size, i.e., a threefold increase in strength when the particle size was halved. Microstructural evaluation using MIP confirmed that the porosity was the lowest in AAM with the smallest particle size. The low porosity and high reactivity of the fine fractions led to the highest compressive strength, confirming that manipulation of particle size can significantly influence the mechanical properties.
Ključne besede: alkalijsko aktivirani materiali, žlindra iz obločne peči, mehanska aktivacija, mehanske lastnosti, poroznost, alkali-activated materials (AAM), electric arc furnace steel slag, mechanical activation, mechanical properties, porosity
Objavljeno v DiRROS: 22.11.2023; Ogledov: 266; Prenosov: 136
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12. Evaluation of locally available amorphous waste materials as a source for alternative alkali activatorsKatja Koenig, Katja Traven, Majda Pavlin, Vilma Ducman, 2021, izvirni znanstveni članek Povzetek: The production of alkali-activated materials with excellent mechanical performance requires the use of waterglass, which has a significant carbon footprint. Such materials can have a lower carbon footprint if we replace water glass with alternative activators sourced from waste. In this study, we assessed the suitability of locally available amorphous waste materials (stone wool, glass wool, bottle glass and cathode-ray tube glass) as a source for the preparation of alternative alkali activators. We quantified the amount of silicon and aluminium dissolved in the activator solutions via inductively coupled plasma-optical emission spectrometry. The alternative activators were then used to produce alkali-activated fly ash and slag. The compressive strength values of alkali-activated fly ash specimens upon the addition of NaOH, water glass and the most promising alternative activator were 38.98 MPa, 31.34 MPa and 40.37 MPa, respectively. The compressive strength of slag specimens activated with alternative activators with the highest concentration of dissolved silicon (21 g/L) was, however, 70% higher than the compressive strength of slag specimens activated with only 10 M sodium hydroxide. The compressive strength of slag specimens with the addition of the most promising alternative activator was significantly lower (3.5 MPa) than the compressive strength of those that had been activated by commercial water glass (34.3 MPa).
Ključne besede: alkalijsko aktivirani materiali, alternativni aktivatorji, lastnosti, alkali activated materials/geopolimers, alternative activators, properties
Objavljeno v DiRROS: 22.08.2023; Ogledov: 233; Prenosov: 154
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14. Optimizacija procesnih parametrov stiskanja termopastičnih materialov : magistrsko deloMarko Rožič, 2022, magistrsko delo Ključne besede: optimizacija procesnih parametrov, vakuumsko stiskanje, hidravlična stiskalnica, termoplastični materiali, simulacije, Autodesk Moldflow Insight (AMI), polietilen (PE), polipropilen (PP), mehanske lastnosti, magistrsko delo
Objavljeno v DiRROS: 29.03.2023; Ogledov: 437; Prenosov: 0
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20. Novel complex stacking of fully-ordered transition metal layers in Li [sub] 4 FeSbO [sub] 6 materialsEric McCalla, Bojan Budič, Robert Dominko, 2015, izvirni znanstveni članek Povzetek: As part of a broad project to explore Li4MM′O6 materials (with M and M′ being selected from a wide variety of metals) as positive electrode materials for Li-ion batteries, the structures of Li4FeSbO6 materials with both stoichiometric and slightly deficient lithium contents are studied here. For lithium content varying from 3.8 to 4.0, the color changes from yellow to black and extra superstructure peaks are seen in the XRD patterns. These extra peaks appear as satellites around the four superstructure peaks affected by the stacking of the transition metal atoms. Refinements of both XRD and neutron scattering patterns show a nearly perfect ordering of Li, Fe, and Sb in the transition metal layers of all samples, although these refinements must take the stacking faults into account in order to extract information about the structure of the TM layers. The structure of the most lithium rich sample, where the satellite superstructure peaks are seen, was determined with the help of HRTEM, XRD, and neutron scattering. The satellites arise due to a new stacking sequence where not all transition metal layers are identical but instead two slightly different compositions stack in an AABB sequence giving a unit cell that is four times larger than normal for such monoclinic layered materials. The more lithium deficient samples are found to contain metal site vacancies based on elemental analysis and Mössbauer spectroscopy results. The significant changes in physical properties are attributed to the presence of these vacancies. This study illustrates the great importance of carefully determining the final compositions in these materials, as very small differences in compositions may have large impacts on structures and properties.
Ključne besede: materiali, elektrokemija, spektrografija
Objavljeno v DiRROS: 31.03.2015; Ogledov: 4725; Prenosov: 781
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