Structure-Properties-Relationships in Lithiumaluminosilicate Glass Ceramics Containing High Concentrations of Nucleation Agents

定制的玻璃结晶允许合成特定类别的无机功能材料-玻璃陶瓷。例如，基于Li 2 O/Al 2 O3/SiO2（LAS）的母体玻璃的陶瓷化可导致具有零热膨胀的玻璃陶瓷，后一种材料广泛用于炉灶面板。另一方面，MgO/Al 2 O3/SiO2（MAS）基玻璃的结晶可产生具有高硬度和/或抗弯强度的玻璃陶瓷。拟议的研究项目旨在通过精确控制其微观和纳米结构，将商业上最相关的LAS和MAS硅酸盐玻璃陶瓷的有用宏观性能联合收割机结合起来。特别是，应尝试在LAS玻璃陶瓷中获得优异的机械性能，这仍然是未实现的热塑性。坚固的LAS玻璃-陶瓷是非常理想的，尤其是与零热膨胀结合。为了设计具有纳米级晶相的玻璃陶瓷以用于所需的应用，对潜在的成核和结晶机制的深刻理解是必要的。因此，只有在对相关工艺有了基本了解的基础上，才能实现高硬度和零热膨胀这两种矛盾特性的结合。对以ZrO 2为成核剂的MAS母玻璃的综合初步研究表明，可能导致具有优异机械性能的玻璃陶瓷的机制是多种多样的。除了相变之外，具有高热膨胀系数的结晶相的选择性沉淀也可以导致高硬度的玻璃陶瓷，而添加Y2 O3可以稳定残余玻璃相并抑制石英结晶，但仍然导致具有优异性能的玻璃陶瓷。这些发现应深化，并直接比较LAS基玻璃陶瓷的成核和结晶现象。在此过程中，计划中的实验将仅限于模拟只有几个组件的玻璃系统，以抑制少数组件的影响。仅以ZrO 2作为成核剂，但具有规定的但高于通常的成核剂浓度的LAS基玻璃应熔融、陶瓷化并在物理性质和相应微观结构方面进行表征。使用不同的nanoanalytical方法，在非等化学LAS和MAS为基础的玻璃的结晶的时间演变的比较应绘制，特别强调的早期成核阶段。此外，Y2 O3应添加到选定的LAS母玻璃组合物中，以分析其对晶相演变、残余玻璃相的稳定化以及所得玻璃-陶瓷的机械性能的影响。计划中的研究应支持硅酸盐玻璃陶瓷结晶机制的全面描述。

Tailored crystallization of glasses allows synthesis of a specific class of inorganic functional materials - glass-ceramics. As an example, ceramming of parent glasses based on Li2O/Al2O3/SiO2 (LAS) may lead to glass-ceramics with zero thermal expansion, the latter material is widely used in cooktop panels. A crystallization of MgO/Al2O3/SiO2 (MAS)-based glasses, on the other hand, may lead to glass-ceramics with high hardness and/or bending strength. The proposed research project is aimed to combine the useful macroscopic properties of the commercially most relevant LAS- and MAS-silicate glass-ceramics by precise control of their micro- and nanostructure. In particular, it shall be tried to gain excellent mechanical properties in LAS glass-ceramics that remain unrealized thitherto. Robust LAS glass-ceramics are very desirable, especially in combination with zero thermal expansion. To design glass-ceramics with nanoscaled crystalline phases for applications as desired, a profound understanding of the underlying nucleation and crystallization mechanisms is imperative. As such, especially a combination of contradictory properties - high hardness and zero thermal expansion - will only be realized based on a fundamental understanding of the associated processes. Comprehensive initial studies concerning MAS parent glasses with ZrO2 as nucleation agent have shown that the mechanisms which may lead to glass-ceramics with excellent mechanical properties are manifold. Besides phase changes, selective precipitation of crystalline phases with high coefficient of thermal expansion may also result in glass-ceramics of high hardness, whereas the addition of Y2O3 can stabilize the residual vitreous phase and suppress a quartz crystallization, yet still lead to glass-ceramics with excellent properties. These findings shall be deepened, and a direct comparison to nucleation- and crystallization phenomena in LAS-based glass-ceramics shall be drawn. In doing so, the planned experiments will be restricted to model glass systems with only a few components, to suppress the influence of minority components. LAS-based glasses with ZrO2 as nucleation agent only, but with defined, yet higher-than-usual nucleation agent concentration, shall be molten, cerammed and characterized in terms of physical properties and respective microstructure. Using distinct nanoanalytical methods, a comparison of the temporal evolution of crystallization in non-isochemical LAS- and MAS-based glasses shall be drawn, with a special emphasize on the early nucleation stages. Additionally, Y2O3 shall be added to chosen LAS parent glass compositions, to analyze its influence on crystal phase evolution, stabilization of the residual vitreous phase, and the mechanical properties of the resulting glass-ceramics. The planned investigations shall support a comprehensive picture of the crystallization mechanisms in silicate glass-ceramics.