Studies on the nature of primary surface crystallization in bioactive glasses of SiO2-P2O5-CaO-Na2O-K2O-CaF2 composition.

SiO2-P2O5-CaO-Na2O-K2O-CaF2 组合物生物活性玻璃初级表面结晶性质的研究。

• 批准号: 506582091
• 负责人: Dr.-Ing. Carsten Blaeß
• 金额: --
• 依托单位: Abteilung 5: Werkstofftechnik
• 依托单位国家: 德国
• 项目类别: WBP Fellowship
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/506582091?language=en
• 关键词: Studies; nature; primary; surface; crystallization

The processability of bioactive glasses is significantly limited by their high tendency to surface crystallization. The clinical use of individually manufactured three-dimensional bone replacement implants made of bioactive glass has therefore only been established in isolated cases so far. Moreover, because processability and bioactivity, in particular solubility in body fluid, are diametrically opposed. A promising compromise seems to be the fluoride-containing glass "F3" (mol%: 44.8SiO2-2.5P2O5-36.5CaO-6.6Na2O-6.6K2O-3.0CaF2). Preliminary studies have shown that its sintering ability depends on grain size. The competing primary detectable surface crystallization is assigned to Combeit (Na6-2xCac+xSi6O18 (0 ≤ x ≤ 1)). This crystal phase is also typical for the clinically used Bioglass® 45S5 and Biosilicate® and prevents crystallization-free sintering there. The primary surface crystallization is thus the greatest danger for the chemical and physical homogeneity of the sintered body with regard to segregation, depletion of the residual glass phase and irregular residual porosity. However, a crystalline framework forming along the former grain boundaries equally has the potential to freeze sintered additively manufactured green bodies at defined porosity and thus prevent the loss of structural integrity of the specimen bodies or even create a complex, hierarchical, and fine-particle void architecture. To elucidate the fundamental influence factors of these phenomena and their applicative potential, also for comparably crystallizing glass compositions, it is necessary to investigate the mechanism and kinetics of primary surface nucleation in glass F3 in more detail. The underlying nucleation mechanism and the technological possibilities for influencing it, for example in the context of powder production or preparation, are largely unknown to date. Since the primary crystal phase is most likely to be oriented to the composition of the Combeit according to the current findings, the variation of the sodium content in the glass as well as on the glass surface appears to be the most targeted. The influence of the surface sodium concentration on the crystallization, the sintering behavior and the resulting microstructure of the sintered bodies will be investigated by comparing surface chemically leached or enriched as well as fractured, fire-polished, and annealed surfaces. DTA, microscopy, XRD, XPS, spectroscopy (IR, Raman) and NMR will be used for the planned work. The planned investigations will take place on powders as well as on bulk materials.

生物活性玻璃的可加工性受到其表面结晶性的限制。因此，迄今为止，单独制造的由生物活性玻璃制成的三维骨替代植入物的临床应用仅在个别病例中建立。此外，因为加工性和生物活性，特别是在体液中的溶解度，是截然相反的。一个有希望的折中方案似乎是含氟玻璃“F3”（摩尔百分比：44.8 sio2 -2.5 p2o5 -36.5 cao -6.6 na20 -6.6 k20 -3.0 caf2）。初步研究表明，其烧结性能与晶粒尺寸有关。可检测到的主要表面结晶为Combeit （Na6-2xCac+xSi6O18(0≤x≤1)）。这种晶体相也是临床上使用的生物玻璃®45S5和生物硅酸盐®的典型晶体相，可以防止无结晶烧结。因此，初级表面结晶对于烧结体的化学和物理均匀性是最大的危险，涉及偏析，残余玻璃相的耗尽和不规则的残余孔隙。然而，沿着前晶界形成的晶体框架同样有可能将烧结的增材制造的生坯冻结在规定的孔隙率下，从而防止试样体结构完整性的丧失，甚至产生复杂的、分层的、细颗粒的空隙结构。为了阐明这些现象的基本影响因素及其应用潜力，以及对玻璃成分的类似结晶化，有必要更详细地研究F3玻璃初生表面成核的机理和动力学。迄今为止，基本的成核机制和影响成核机制的技术可能性，例如在粉末生产或制备方面，在很大程度上是未知的。根据目前的研究结果，由于初晶相最有可能与孔珠的组成有关，因此玻璃中钠含量的变化以及玻璃表面的钠含量的变化似乎是最有针对性的。表面钠浓度对结晶、烧结行为和烧结体的微观结构的影响将通过比较表面化学浸出或富集以及断裂、火抛光和退火表面来研究。DTA，显微镜，XRD， XPS，光谱（IR, Raman）和NMR将用于计划的工作。计划中的调查将在粉末和散装材料上进行。