| Effect of Partial Substitution of K2O for Na2O on
Sintering, Crystallization and Mechanical Properties
of SiO2-CaO-K2O-Na2O-CaF2 Glass-Ceramics |
Mina Eilaghi,a,* Maziar Montazerianb and Bijan Eftekhari Yektab
pages: 1-6
DOI : 10.1080/0371750X.2015.1130650 |
| Abstract |
| In this work, the effects of partial substitution of K2O for Na2O on the sintering
and crystallization of a SiO2-CaO-K2O-Na2O-CaF2 glass have been studied. This
glass composition was close to the glass-forming composition of fluorocanasite
mineral. The glass-ceramics were made via sintering with concurrent
crystallization of glass-powder compacts. The samples were characterized by
hot stage microscopy, differential thermal analysis, X-ray diffraction and
scanning electron microscopy. CaF2 precipitated as a primary crystal in all studied
glasses and crystallization was predominant between 625o and 1000oC. All
glasses showed the best sinterability at 1000oC. By increasing the K2O content
from 7 to 13 mol% (at the expense of Na2O), the crystallization peaks shifted to
higher temperatures and the main crystalline phases at the best sintering
temperature were fluorocanasite, cuspidine, xonotlite and wollastonite. Vickers
microhardness, 3-point bending strength, fracture toughness and thermal
expansion coefficient were estimated to identify the optimum composition.
Measurements revealed that the addition of 10 mol% K2O to the base glass
improved the bending strength from 110±10 to 137±7 MPa. The maximum
achieved fracture toughness was 2.6±0.1 MPa.m1/2.
[Keywords: Glass-ceramics, Fluorocanasite, Sintering, Crystallization,
Mechanical Properties] |
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