21. Use of fly ash and phosphogypsum for the synthesis of belite-sulfoaluminate clinkerSabina 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: 381; Prenosov: 148
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22. The corrosion resistance of dental Ti6Al4V with differing microstructures in oral environmentsMirjam Bajt Leban, Tadeja Kosec, Matjaž Finšgar, 2023, izvirni znanstveni članek Povzetek: The impact of the microstructural properties of a Ti6Al4V alloy on its electrochemical properties, as well as the effect of the α- and β-phases present within it, is still unclear. With the introduction of new, emerging technologies, such as selective laser melting and post heat treatments, the effect of the microstructure on an alloy's corrosion properties has become increasingly interesting from a scientific perspective. When these alloys are produced through different methods, despite an identical chemical composition they have diverse microstructures, and consequently display varying resistance to corrosion. In the present research study, Ti–6Al–4V alloy specimens produced by three different processes, leading to the formation of three different microstructures were investigated: heat treated specimen fabricated by selective laser melting, wrought and cast specimens. The impact of the microstructure of these alloys when immersed in artificial saliva was studied through the use of various electrochemical techniques, by microscopical examinations, and time-of-flight secondary ion mass spectrometry. Corrosion properties were investigated by the measurement of open circuit potential, linear polarization, and potentiodynamic curve measurements followed by microscopical examinations, and time-of-flight secondary ion mass spectrometry examination was conducted to reveal spatial distribution of alloying species on oxide film. It was found that the difference between specimens containing an α+β microstructure was small and not dependent on the aspect ratio of the β-phase, alloy grain size, and vanadium partitioning coefficient, but rather on the size, shape, and content of this phase.
Ključne besede: Ti6Al4V, dental alloy, microstructure, corrosion resistance, heat treatment, ToF-SIMS
Objavljeno v DiRROS: 26.10.2023; Ogledov: 466; Prenosov: 233
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23. Effect of deep cryogenic treatment on corrosion properties of various high-speed steelsJure Voglar, Živa Novak, Patricia Jovičević Klug, Bojan Podgornik, Tadeja Kosec, 2021, izvirni znanstveni članek Povzetek: The aim of the study was to evaluate the corrosion properties of three different grades of high-speed steel following a heat treatment procedure involving deep cryogenic treatment after quenching and to investigate how these properties are connected to the microstructure and hard- ness of the material. The hardness of steels was measured, and microstructural properties were determined through observation of the metallographically prepared steels using scanning electron microscopy. These studies were complemented corrosion evaluation by the use of corrosion potential measurement and linear polarization measurement of steels in a sodium tetraborate buffer at pH 10. The results showed that the deep cryogenic procedure of high-speed steel changed the microstructure and consequently affected the hardness of the investigated steels to different extents, depending on their chemical composition. Corrosion studies have confirmed that some high-speed steels have improved corrosion properties after deep cryogenic treatment. The most important improvement in corrosion resistance was observed for deep cryogenically treated high-speed steel EN 1.3395 (M3:2) by 31% when hardened to high hardness values and by 116% under lower hardness conditions. The test procedure for differentiating corrosion properties of differently heat-treated tool steels was established alongside the investigation.
Ključne besede: deep cryogenic treatment, corrosion, microstructure, hardness
Objavljeno v DiRROS: 01.08.2023; Ogledov: 278; Prenosov: 145
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24. The Incorporation of steel slag into belite-sulfoaluminate cement clinkersLea Žibret, Katarina Šter, Maruša Mrak, Mojca Loncnar, Sabina Dolenec, 2021, izvirni znanstveni članek Povzetek: The potential use of steel slag from treated steel slag in belite-sulfoaluminate cements was investigated in this study. Cement clinkers with two phase compositions were synthesized, allowing the incorporation of different amounts of steel slag. The phase composition and microstructure of cement clinkers at three different sintering temperatures were studied by X-ray powder diffraction and the Rietveld method, as well as scanning electron microscopy with energy dispersive spectrometry. The results showed that the targeted phase composition of clinkers was achieved at a sintering temperature of 1250%C. However, a higher amount of perovskite instead of ferrite was detected in the clinker with a higher content of Ti-bearing bauxite. Apart from the main phases, such asbelite, calcium sulfoaluminate, and ferrite, several minor phases were identified, including mayenite, perovskite, periclase, and alkali sulfates. In both clinker mixtures, a higher content of MgO in the steelslags resulted in the formation of periclase. Furthermore, the hydration kinetics and compressive strength at 7 and 28 days were studied in two cements prepared from clinkers sintered at 1250%C. As evidenced by the results of isothermal calorimetry, the hydration kinetics were also influenced by the minor clinker phases. Cement with a higher content of calcium sulfoaluminate phase developed a higher compressive strength.
Ključne besede: cements, BCSA, steel slag, secundary row materials, microstructure, clinker phase
Objavljeno v DiRROS: 01.08.2023; Ogledov: 268; Prenosov: 124
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25. Microstructural characteristics of belite–sulfoaluminate cement clinkers with bottom ashLea Žibret, Andrej Ipavec, Sabina Dolenec, 2022, izvirni znanstveni članek Povzetek: The incorporation mechanism of impurities derived from raw materials into a belite-sulfoaluminate cement clinker with bottom ash was investigated in two raw mixtures. Alkalis lowered the sintering temperature by 50 °C. Ti stabilized β belite and prevented the formation of γ-belite. Sodalite solid solution showed an incomplete substitution of Si by Al. At a higher Ti content ferrite solid solution trended towards perovskite composition. Although calcium sulfoaluminate only fully developted at 1300 °C, the clinkers sintered at 1200 °C were the most reactive, as the presence of anhydrite at 1200 °C accelerated early hydration. Clinker reactivity decreased with an increase in sintering temperature.
Ključne besede: BSCA clinker, belite, calcium sulfoaluminate, secondary raw materials, microstructure, reactivity
Objavljeno v DiRROS: 03.07.2023; Ogledov: 403; Prenosov: 190
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26. Thermal-deformation model of a SR-modified A356 aluminum alloyYongyue Liu, Xianglai Xu, Jiangxiong Cheng, Hongwei Sun, Xueping Ren, Peng Jiang, 2022, izvirni znanstveni članek Ključne besede: A356 aluminum alloy, Sr modification, microstructure, thermal-deformation model
Objavljeno v DiRROS: 22.06.2022; Ogledov: 531; Prenosov: 155
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