GOALI: Fundamental Investigations of Nucleation Processes in Silicate Liquids and Glasses with a Goal of Developing Predictive Models for Glass Formation and Crystallization

非技术描述：数千年来，玻璃一直是重要的技术材料。 玻璃陶瓷（部分结晶玻璃）也很重要，填补了低技术应用，如炉灶和炊具，高技术应用，如光波导，望远镜镜，骨修复和牙科修复。用于复合装甲，陶瓷能够打破冲击弹丸，而金属背板吸收弹丸的动能。控制成核是液体或玻璃结晶的第一步，对于玻璃陶瓷的生产至关重要。然而，通常在上个世纪早期为气体中的液体形成而开发的模型的上下文中理解成核，并且在大约60年前扩展到液体的结晶。这种模式不足以满足当今所需的控制水平。 以前的假设现在是有问题的，所以预测往往不能同意定量与实验数据。这项研究的目的是发展一个更深入的了解晶体成核和制定一个更定量的模型。这种新模型为计算机模拟的发展提供了基础，可用于加速新玻璃和陶瓷的发现和设计。该项目为研究生提供了与康宁研发部的工业科学家互动的机会，并为毕业生在工业或学术界开辟了一条职业道路。技术专长：玻璃和玻璃陶瓷是无处不在的现代材料，是广泛应用的基础。了解成核和生长对于生产高质量玻璃和陶瓷以及发现新的玻璃和陶瓷至关重要。必须精确控制这些过程以产生所需的失透微结构，包括在玻璃中形成的微晶的数量、类型和尺寸。目前，获得这种控制权在很大程度上是经验性的，导致新产品的开发时间很长。因此，玻璃和玻璃陶瓷公司正在努力开发改进的测量和建模能力，并提高对成核和生长过程的基本理解，达到或超过该领域的最先进水平。这项研究是与康宁研发部的科学家一起进行的，重点是通过对两种模型硅酸盐玻璃进行协调的实验/建模方法，加深对晶体成核的了解（Ba 2 O-2SiO 2和Na 2 O-2CaO-3SiO 2）关键要素包括扫描量热测量以确定显著成核的温度范围，测量随时间变化的成核速率作为温度的函数，对玻璃和成核晶相进行X射线和弹性中子散射研究，以评估玻璃结构对成核屏障的重要性，扩展成核的经典理论，以包括核与液体/玻璃之间的扩散界面的影响，并考虑液体/玻璃中的有序性，并结合计算机模型和模拟来测试这些理论。获得的新见解为计算机模型奠定了基础，这些模型可以指导具有优化微观结构的新型玻璃和玻璃陶瓷的快速开发。这些活动反映了加速材料开发的广泛方法，这是国家的优先事项。美国正处于危机之中，寻求科学、技术、工程和数学（STEM）职业的学生人数越来越少。这项研究形成了研究生培养的一个组成部分，无论是在学术和工业环境。该项目使学生接触到尖端的玻璃生产和表征技术，并为毕业生提供最佳的职业道路。

NON-TECHNICAL DESCRIPTION: Glasses have been centrally important technological materials for thousands of years. Glass ceramics (partially crystallized glasses) are also important, filling low technology applications such as stove-tops and cookware, to high technology applications such as optical waveguides, telescope mirrors, bone prosthesis and dental restorations. Used in composite armor, ceramics are able to break up impacting projectiles while a metallic backing plate absorbs the kinetic energy of the projectile. Controlling nucleation, the first step in the crystallization of a liquid or glass, is critically important for the production of glass ceramics. However, nucleation is generally understood within the context of a model that was developed for liquid formation in a gas in the early years of the last century and extended to the crystallization of liquids about 60 years ago. This model is inadequate for the level of control needed today. The previous assumptions are now questionable and so predictions often fail to agree quantitatively with experimental data. This research is aimed at developing a deeper understanding of crystal nucleation and the formulation of a more quantitative model. This new model provides a foundation for the development of computer simulations that can be used to accelerate the discovery and design of new glasses and ceramics. The project provides opportunities for graduate students to interact with industrial scientists in Corning Research and Development and leads to a career path for graduates in either industry or academia.TECHNICAL DETAILS: Glasses and glass ceramics are ubiquitous modern materials, fundamental to a wide range of applications. Understanding nucleation and growth is critical in the production of high quality glasses and ceramics and the discovery of new ones. These processes must be precisely controlled to produce the desired devitrified microstructures, including the number, type, and size of crystallites formed in the glass. Currently, gaining this control is largely empirical, resulting in long development times for new products. Glass and glass ceramics companies are therefore working to develop improved measurement and modeling capabilities, and to increase the fundamental understanding of nucleation and growth processes at or beyond the state-of-the-art in the field. This research, carried out with scientists in Corning Research and Development, focuses on the development of a deeper understanding of crystal nucleation through a coordinated experimental/modeling approach for two model silicate glasses (Ba2O-2SiO2 and Na2O-2CaO-3SiO2) Key elements include scanning calorimetric surveys to determine the temperature range of significant nucleation, measurements of the time-dependent nucleation rates as a function of temperature, X-ray and elastic neutron scattering studies of the glass and nucleating crystal phases to assess the importance of glass structure on the nucleation barrier, extending the classical theory of nucleation to include the effects of the diffuse interface between the nucleus and the liquid/glass and to take into account ordering in the liquid/glass, and incorporating computer models and simulations to test these theories. The new insights gained lay the foundation for computer models that can guide the rapid development of new glasses and glass ceramics with an optimized microstructure. These activities mirror a broad approach for accelerated materials development that is a national priority. The US is in crisis, with a decreasing number of students seeking careers in science, technology, engineering and math (STEM). This research forms an integral part of graduate student training, both in an academic and industrial environment. This project exposes students to cutting edge glass production and characterization techniques and leads to an optimal career path for graduates.