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首页> 外文期刊>Journal of Non-Crystalline Solids: A Journal Devoted to Oxide, Halide, Chalcogenide and Metallic Glasses, Amorphous Semiconductors, Non-Crystalline Films, Glass-Ceramics and Glassy Composites >Influence of magnesia on the structure and properties of bioactive glasses
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Influence of magnesia on the structure and properties of bioactive glasses

机译：氧化镁对生物活性玻璃结构和性能的影响

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摘要

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.
机译：合成了五种基于49.5SiO（2）-1,1P（2）O（5）-（23.0（1-x））CaO-xMgO-26.4Na（2）O摩尔％的生物活性玻璃，其中CaO逐渐被替换以摩尔计基于MgO（其中0 <= x <= 1）。通过对P-31和Si-29魔角旋转核磁共振（MAS NMR）光谱，膨胀计，差热分析（​​DTA）和密度测量进行表征，以全面了解结构-特性之间的关系。眼镜的P-31 NMR光谱在大约200nm处表现出明确的共振。 9-14 ppm，对应于正磷酸T环境。 MgO的完全替代引起大约90nm的低场偏移。 5 ppm，暗示钠与正磷酸盐物种的优先结合。 Si-29 NMR谱图显示一个峰。 -79 ppm，表示存在Q（2）硅物种，以及大约在20英寸处的肩部。 -90 ppm，对应于Q（2）物质。在添加MgO时，可以看到Q（2）肩的大小逐渐增加。这些结果表明，MgO而不是通过充当网络改性剂来解聚硅酸盐网络，而部分地表现为中间氧化物。 Si-29 NMR峰的解卷积表明，尽管传统上86％的氧化镁起着网络改性阳离子的作用，但高达14％的氧化镁作为四面体MgO4进入硅酸盐网络，从而除去了电荷补偿并导致观察到的硅酸盐网络聚合。相应地，随着MgO含量的增加，玻璃化转变温度和膨胀软化点值均下降，而热膨胀系数值则上升。这是由于Mg-O的结合强度明显低于Si-O，从而削弱了玻璃网络。

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