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1.
Y2O3-Al2O3 microsphere crystallization analyzed by electron backscatter diffraction (EBSD)
Wolfgang Wisniewski, Anna Prnová, Peter Švančárek, Milan Parchovianský, Dušan Galusek, 2020, izvirni znanstveni članek

Povzetek: The crystallization of glass microspheres in the Y2O3–Al2O3-system produced from precursor powders of four different nominal compositions via flame synthesis is analyzed in detail by electron microscopy with a focus on electron backscatter diffraction (EBSD). Growth models are formulated for individual microspheres crystallized during flame synthesis as well as after an additional heat treatment step. 16 different types of crystallized bodies are cataloged for future reference. They are presented without regard for their relative occurrence; some are extremely rare but illustrate the possibilities of flame synthesis in the analyzed system. All three phases in the binary Y2O3–Al2O3-phase diagram (Y3Al5O12, YAlO3 and Y4Al2O9) and α-alumina are located by EBSD. Energy dispersive X-ray spectrometry results obtained from these microspheres show that their chemical composition can deviate from the nominal composition of the precursor powder. The multitude of differing microsphere types showing polygon and dendritic crystal growth as well as phase separation indicate that flame synthesis can lead to a wide variety of parameters during microsphere production, e.g. via irregular flight paths through the flame, contaminants or irregular cooling rates.
Ključne besede: Y2O3-Al2O3, microsphere crystallization, flame synthesis, EBSD
Objavljeno v DiRROS: 23.07.2024; Ogledov: 110; Prenosov: 91
.pdf Celotno besedilo (6,57 MB)
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2.
Increasing the amorphous content in river sediments intended for supplementary cementitious materials using flame synthesis
Wolfgang Wisniewski, Jozef Kraxner, Lea Žibret, Dušan Galusek, Vilma Ducman, 2024, izvirni znanstveni članek

Povzetek: Dredged river sediments are currently a waste material which is mainly landfilled or reintegrated into rivers. They can also be used as a renewable resource for the construction sector. Pre- treatments at high temperatures allow their use for more advanced applications such as supplementary cementitious materials (SCMs) or as a precursor for alkali activated materials (AAMs). The work presented here shows that flame synthesis can be used to almost completely vitrify such sediments and increase their leachability for Al and Si beyond the levels achieved by conventional calcination at 750–950 ◦C for 1h. The reactivity of the prepared samples was analyzed via the Si and Al solubility in 10 M NaOH and was generally increased by the applied treatments but maximized by flame synthesis. Their microstructure was analyzed using scanning electron microscopy and their phase composition was monitored using X-ray diffraction. The results show an almost complete amorphization of the sediments by flame synthesis, however their reactivity does not increase at the same rate.
Ključne besede: sediments, SCM, vitrification, properties
Objavljeno v DiRROS: 23.05.2024; Ogledov: 282; Prenosov: 250
.pdf Celotno besedilo (2,50 MB)
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