Lanthanum modification of crystalline phases and residual glass in augite glass ceramics produced with industrial solid wastes
Abstract
The effects of La2O3 on microstructure and properties of the CaO-MgO-SiO2-Al2O3 glass ceramics, made from Bayan Obo West Mine tailing and fly ash, were investigated. Results showed that La2O3 additions up to 2 wt% promoted augite crystallization. Above this concentration, La2O3 suppressed augite crystallization by rather forming lanthanum oxyapatite that acted as a barrier for the growth of augite. Also Cr ions, the key element for the augite nuclei, were enriched in lanthanum oxyapatite. The La3+ cations were found to partially substitute for Ca2+ at the M2 structural sites in clinopyroxene (augite). Nano crystalline clusters, containing La3+, Na+, Ca2+, Mg2+ and Fe3+ in augite-like proportions, were found uniformly dispersed in the residual glassy phase. The glass ceramic with 2 wt% La2O3 shows optimum mechanical properties and chemical durability. The bending strength and Vickers hardness are 238 MPa and 7.57 GPa, acid and alkali-resistance are 97.5% and 98.9%, respectively.
- Publication:
-
Journal of Non Crystalline Solids
- Pub Date:
- November 2019
- DOI:
- 10.1016/j.jnoncrysol.2019.119638
- Bibcode:
- 2019JNCS..52419638C
- Keywords:
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- <SUB>L</SUB>anthanum oxide;
- <SUB>A</SUB>ugite;
- <SUB>G</SUB>lass ceramics;
- <SUB>R</SUB>esidual glass;
- <SUB>C</SUB>rystallization