期刊
JOURNAL OF NON-CRYSTALLINE SOLIDS
卷 356, 期 9-10, 页码 517-524出版社
ELSEVIER SCIENCE BV
DOI: 10.1016/j.jnoncrysol.2009.04.074
关键词
Bioglass; Biomaterials; Nuclear magnetic (and quadrupole) resonance; Alkali silicates; Silicates; Soda-lime-silica; NMR, MAS NMR and NQR; Short-range order; Thermal properties
资金
- EPIZSC [EP/C549309/1]
- Engineering and Physical Sciences Research Council [EP/G00465X/1] Funding Source: researchfish
- EPSRC [EP/G00465X/1] Funding Source: UKRI
Five bioactive glasses based on 49.5SiO(2)-1,1P(2)O(5)-(23.0(1 - x))CaO-xMgO-26.4Na(2)O Mol.% were synthesised where CaO was replaced progressively on a molar basis by MgO (where 0 <= x <= 1). The glasses were characterised by P-31 and Si-29 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, dilatometry, differential thermal analysis (DTA) and density measurements with the aim of gaining a comprehensive understanding of the structure-property relationships. The P-31 NMR spectra of the glasses exhibited well-defined resonances at ca. 9-14 ppm, corresponding to a T orthophosphate environment. Full substitution of MgO caused a downfield shift of ca. 5 ppm, implying the preferential association of sodium with the orthophosphate species. The Si-29 NMR spectra exhibited a peak at ca. -79 ppm, indicating a Q(2) silicon species, along with a shoulder at ca. -90 ppm, corresponding to a Q(2) species. On addition of MgO, the Q(2) shoulder was seen to progressively increase in magnitude. These results suggest that MgO, rather than depolymerising the silicate network by acting as a network modifier, is behaving in part, as an intermediate oxide. Deconvolution of the Si-29 NMR peaks suggest that, although 86% of the magnesium oxide is acting traditionally as a network modifying cation, up to 14% of the magnesium oxide is entering the silicate network as tetrahedral, MgO4, removing network modifying ions for charge compensation and resulting in the observed polymerisation of the silicate network. Correspondingly, both the glass transition temperature and dilatometric softening point values were seen to decrease whilst the thermal expansion coefficient values rose, with increasing MgO content. This was due to the significantly lower bond strength, of Mg-O compared to Si-O, weakening the glass network. (C) 2009 Elsevier B.V. All rights reserved.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据