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Stochastic approach to heterogeneous crystal nucleation in silicate glasses

硅酸盐玻璃异质晶体成核的随机方法

基本信息

批准号：
329439308
负责人：
Professor Dr.-Ing. Joachim Deubener
金额：
--
依托单位：
Institut für Nichtmetallische Werkstoffe
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2017
资助国家：
德国
起止时间：
2016-12-31 至 2019-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/329439308?language=en
关键词：
Stochastic approach heterogeneous crystal nucleation

项目摘要

The project aims at creating a deeper understanding of the heterogeneous nucleation in silicate glasses by studying the mean lag time, nucleation rates and site activities from the time average of single nucleation events under dynamic and isothermal conditions. In particular, calorimetric experiments of repeated cooling-heating cycles which start and end above liquidus temperature of an individual glass volume are proposed. To account for the stochastic nature of nucleation ca. 300 cycles will be conducted in each experiment. Different series of experiments are designed to explore the nature of the nucleation sites from changing their geometry and number of as well as the type of contact material. Numerical calculations and the comparison of their results with experimental data are intended to improve the theoretical description of underlying heterogeneous nucleation mechanisms which will help to make predictions on their crystallization kinetics more reliable. On the practical side the experimental data will provide statistical certainty in contrast to previous one-time cooling experiments and will allow to construct temperature-time-transformation (TTT) and continous-cooling-transformation (CCT) diagrams. These representations of the crystallization kinetics from which for example critical cooling rates can be deduced are most relevant to industrial practice since heterogeneous nucleation is the dominating mechanism to control crystallization in glass-ceramic manufacturing.

该项目旨在通过研究动态和等温条件下单次成核事件的时间平均值来研究硅酸盐玻璃中的平均滞后时间、成核速率和位置活度，从而加深对硅酸盐玻璃中非均相成核的理解。特别是，提出了在单个玻璃体积的液相线温度以上开始和结束的重复冷却-加热循环的量热实验。为了解释成核的随机性质，每个实验将进行大约300个循环。设计了一系列不同的实验，通过改变触头材料的几何形状和数量以及类型来探索成核点的性质。数值计算及其结果与实验数据的比较旨在完善对非均相成核机理的理论描述，这将有助于对其结晶动力学的预测更加可靠。在实际方面，与以前的一次性冷却实验相比，实验数据将提供统计上的确定性，并将允许建立温度-时间-转变(TTT)和连续冷却-转变(CCT)图。由于异相成核是微晶玻璃制造中控制析晶的主要机制，因此这些析晶动力学的表示法与工业实践最为相关，例如，临界冷却速率可以从这些表象中推导出来。