The interaction of fully dense 45S5-bioglass derived samples produced by Spark Plasma Sintering (SPS) with simulated body fluid (SBF) solution was investigated in detail taking advantage of the Rietveld refinement method to quantitatively evidence the corresponding microstructural and compositional changes. It is observed that, when the original amorphous nature is mostly (75 wt%) preserved in the material during sintering (550°C, 2 minutes), the resulting specimens dissolve faster and determine relatively higher pH increase and ions release in the SBF solution. Correspondingly, a relatively lower amount of hydroxycarbonate apatite (HCA) is formed on their surface. In contrast, a more extensive apatite layer with trabecular structure is generated within 3 days storage on the surface of fully crystallized samples obtained at 600°C by SPS, which only consists of Na–Ca silicate grains (20 nm). Moreover, as the sintering temperature and dwell time were increased to 700°C and 20 minutes, respectively, a rhenanite-like phase was also formed (about 15 wt%), other than crystallites growth to 90 nm. Interestingly, the presence of rhenanite provides a beneficial contribution for the production of the HCA layer, which was found the largest for this system when considering storage periods of 7 and 14 days, respectively.

中文翻译：

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暴露于模拟体液的45S5生物玻璃产品成分和结构变化的综合研究

利用Rietveld精炼方法定量研究了相应的微观结构和组成变化，详细研究了火花等离子体烧结（SPS）生产的完全致密的45S5生物玻璃样品与模拟体液（SBF）溶液之间的相互作用。可以观察到，在烧结（550°C，2分钟）过程中，当原始非晶态大部分保留在材料中时（75 wt％），所得样品会更快溶解，并确定相对较高的pH值增加和SBF溶液中的离子释放。相应地，在它们的表面上形成了相对较少量的碳酸羟基磷灰石（HCA）。相比之下，在600℃下通过SPS获得的完全结晶的样品表面上存储3天之内，会生成具有小梁结构的更广泛的磷灰石层，它仅由Na-Ca硅酸盐晶粒（20 nm）组成。此外，随着烧结温度和停留时间分别增加到700℃和20分钟，除了微晶生长到90nm之外，还形成了类菱锰矿相（约15wt％）。有趣的是，菱锰矿的存在为HCA层的生产提供了有益的贡献，当分别考虑7天和14天的存储时间时，发现该体系的HCA层最大。