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

定制的玻璃结晶可以合成一类特定的无机功能材料-玻璃陶瓷。例如，基于Li2O/Al2O3/SiO2 （LAS）的母玻璃陶瓷可以得到零热膨胀的微晶玻璃，后者被广泛用于灶台面板。另一方面，MgO/Al2O3/SiO2 （MAS）基玻璃的结晶可能导致具有高硬度和/或抗弯强度的微晶玻璃。提出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特性结合起来。尤其要努力使LAS微晶玻璃获得优异的力学性能，这是目前尚未实现的。坚固的LAS玻璃陶瓷是非常可取的，特别是与零热膨胀相结合。为了设计具有纳米级晶体相的微晶玻璃，对其成核和结晶机制的深刻理解是必不可少的。因此，只有基于对相关工艺的基本理解，才能实现高硬度和零热膨胀这两种矛盾特性的结合。对以ZrO2为成核剂的MAS母玻璃的初步研究表明，产生具有优异力学性能的微晶玻璃的机理是多方面的。除了相变之外，高热膨胀系数的晶相选择性析出也可以获得高硬度的微晶玻璃，而Y2O3的加入可以稳定残余的玻璃相，抑制石英的结晶，但仍然可以获得性能优异的微晶玻璃。这些发现将进一步深化，并与基于las的玻璃陶瓷中的成核和结晶现象进行直接比较。在这样做的过程中，计划的实验将被限制在只有少数组件的玻璃系统模型中，以抑制少数组件的影响。仅以ZrO2为成核剂，但具有高于通常成核剂浓度的确定的las基玻璃，应熔融、陶瓷化，并在物理性质和各自的微观结构方面进行表征。使用不同的纳米分析方法，比较非等化学的LAS和mas基玻璃的结晶时间演变，特别强调早期成核阶段。此外，在所选择的LAS母玻璃成分中加入Y2O3，分析其对晶相演化、残余玻璃相稳定以及所得微晶玻璃力学性能的影响。计划的研究将支持硅酸盐玻璃陶瓷结晶机制的全面图景。

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.