Yazar "Losego, Mark D." seçeneğine göre listele

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    Aqueous degradation and atomic layer deposition (ALD) stabilization of BaAl2O4: Eu2+, Dy3+long afterglow phosphors
    (Elsevier, 2023) Karacaoğlu, Erkul; Uyaner, Mesut; Okyay, Ali Kemal; Losego, Mark D.
    This paper presents the aqueous degradation mechanisms of BaAl2O4:Eu2+, Dy3+ phosphors and demonstrates an ability to prevent degradation via Al2O3 nano encapsulation of powders by atomic layer deposition (ALD) technique. Phosphor powder is synthesized from the solid-state reaction method. The aqueous degradation of this phosphor is systematically studied. This phosphor is found to hydrolyze and degrade within just 30 min of exposure in water. The degradation of BaAl2O4 host lattice directly affects the blue-green light emission at 497 nm, producing blue-and red-emissions that are peaked at 429 nm and 687 nm, respectively. Hydrated and structural decomposed BaAl2O4 reveals a continuous change in the phase assemblage over 30 days of immersion. To prevent this rapid degradation, use of a protective nanocoating was investigated. 10 nm Al2O3 coatings were applied to the surface of the phosphor powder via ALD. ALD coated BaAl2O4:Eu2+,Dy3+ phosphor retains its phosphorescence for at least 7 days of water exposure. Successful encapsulation of such phosphor particles will make them possible to use in aqueous applications or store in long-term humid environments.
  • Küçük Resim Yok
    Öğe
    Atomic layer deposition (ALD) of nanoscale coatings on SrAl2O4-based phosphor powders to prevent aqueous degradation
    (Wiley, 2020) Karacaoglu, Erkul; Ozturk, Esra; Uyaner, Mesut; Losego, Mark D.
    The aqueous degradation of Eu2+-activated and Dy3+-codoped strontium aluminate (SrAl2O4:Eu2+, Dy3+, SA2-Green) long afterglow phosphors synthesized from solid-state reaction and coated with nanoscale metal oxide protective layers (<= 12 nm) via atomic layer deposition (ALD) is investigated. Uncoated phosphor powders degrade rapidly upon water immersion and lose their green phosphorescence within 48 hours of water exposure. Postmortem investigations reveal hydration and decomposition of the SrAl2O4 phase. ALD of 10 nm Al2O3 or 12 nm TiO2 is found to significantly improve the powder's resistance to aqueous degradation. All ALD-coated powders show minimal structural and chemical degradation and retain phosphoresence after 48 hours of water immersion. This enhanced durability offers a new pathway for applying long afterglow phosphors to outdoor applications like roadway markings or safety signage and for their incorporation into more eco-friendly waterborne coatings.