Crystallization kinetics of Ni-doped Ca 2 Al 2 SiO 7 glass microspheres
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Crystallization kinetics of Ni‑doped Ca2Al2SiO7 glass microspheres Melinda Majerová1 · Anna Prnová2,3 · Alfonz Plško2,3 · Branislav Hruška3 · Jana Valúchová2,3 · Jozef Kraxner3 · Els Bruneel4 · Klaartje De Buysser4 · Dušan Galusek2,3 Received: 29 November 2019 / Accepted: 4 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract The Ni-doped C a2Al2SiO7 glass systems were prepared by flame synthesis. Solid-state reaction was used to prepare the powder precursors. The concentration of Ni was 0.5, 1 and 3 mol%. Polydisperse systems were prepared with diameters between 5 and 140 μm. Detailed examination of morphology of the glass microbeads by SEM revealed no features indicating the presence of crystalline phases. However, X-ray diffraction analysis showed that the samples GNi0.5 (0.5 mol% of Ni) and GNi1.0 (1.0 mol% of Ni) contained traces of crystalline gehlenite. HT-XRD was used to determine the temperature dependence of phase composition. For all prepared compositions, only one crystalline phase ( Ca2Al2SiO7) was observed. DSC measurements in the temperature range 30–1200 °C at five different heating rates were carried out to study the thermal behavior. The DSC curves of all glasses contained one exothermic peak, which was attributed to crystallization of the gehlenite. The maximum of the peak decreased with increasing Ni content in the microspheres. The kinetic parameters (frequency factor A, apparent activation energy Eapp and the Avrami coefficient m) of the crystallization were determined using the Johnson–Mehl–Avrami–Kolgomorov model. In case of GNi0.5 and GNi1.0 glasses, the nucleation’s rate had linear temperature dependence, the crystal growth interface is controlled by chemical boundary and the crystal growth is one-dimensional. The rate of nucleation is linear, the crystal interface growth is controlled by diffusion and one-dimensional crystal growth prevails in crystallization of the GNi3.0 (3.0 mol% of Ni). Keywords Flame synthesis · Glass microspheres · Ni-doped glass · Gehlenite · Crystallization kinetics
Introduction A number of silicates form solid solutions, which in terms of composition belong to solid solution join Åkermanite (Ca2MgSi2O7) and gehlenite (Ca2Al2Si2O7) and crystallize with the melilite structure. Silicates as possible hosts for optically active additives are characteristic by very good
* Melinda Majerová [email protected] 1
Department of Magnetometry, Institute of Measurement Science, Slovak Academy of Sciences, Dúbravská cesta 9, 842 19 Bratislava, Slovakia
2
Joint Glass Centre (Vitrum Laugaricio) of the IIC SAS, TnUAD and FChPT STU, Študentska 2, 911 50 Trenčin, Slovakia
3
Centre for Functional and Surface Functionalized Glass, TnUAD, Študentska 2, 911 50 Trenčin, Slovakia
4
Department of Chemistry, Gent University, Krijgslaan 281 S3, 9000 Ghent, Belgium
chemical stability, low phonon energy, high thermal stability, good hydrolytic resistance and mean costing. The structure of gehlenite can be described by the space group P 4̄ 21m. The
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