CAA: Transient Nucleation Behavior in Li2O-2SiO2 Glasses: The Effects of Q Speciation

小行星9506486 硅酸盐玻璃中的晶体成核在地质和材料系统中都具有重要意义。然而，许多重要的问题仍然存在关于预先存在的非晶相结构的影响，在硅酸盐熔体和玻璃的均匀成核过程和动态过程导致新的稳态物种分布。 要求CAA允许PI开始一个新的研究方向，重点关注与熔融和玻璃态硅酸盐结晶有关的时间依赖性过程的结构方面。 这一方向有力地补充了她以前在熔融硅酸盐平衡热力学方面的实验和理论工作。 这个项目将作为核磁共振光谱学以及成核研究的介绍，并将在她的第一个休假期间进行。 拟议的研究重点特别是评价结构调整的动力学及其对诱导时间的影响。 MAS和静态核磁共振实验玻璃二硅酸锂将与成核研究相结合，其具体目标是确定结构扰动后的“短”程有序再调整的动力学。 当与结构对诱导时间的影响结合时，Qn物质重排的动力学也将指示簇分布的重新调整的动力学（即，“中等”范围顺序）。 除了推进我们的理解的影响，预先存在的结构上的诱导时间，所获得的数据应该提供一种手段，以确定是否或不具体测量的Qn物种分布在或低于Tg反映了平衡状态。 这是直接相关的众多结构数据的玻璃在文献中的解释，并应提供一个指导玻璃的制备，为未来的结构研究。 该奖项的补充将支持一个特别有才华的女性，非洲裔美国大学毕业生。 她将与PI和一位女化学教授就该项目的各个方面密切合作。

9506486 Nekvasil Crystal nucleation in silicate glasses is of great importance in both geological and materials systems. Yet, many important questions still remain regarding the effects of pre-existing amorphous phase structure on the homogeneous nucleation process in silicate melts and glasses and the dynamic processes leading to new steady-state species distributions. This CAA is requested to permit the PI to begin a new research direction focused on the structural aspects of time-dependent processes relating to crystallization from molten and glassy silicates. This direction strongly complements her previous experimental and theoretical work on equilibrium thermodynamics in molten silicates. This project would serve as an introduction to NMR spectroscopy as well as nucleation studies and would be conducted during her first sabbatical leave. The proposed study focuses specifically on evaluating the kinetics of structural readjustments and its effect on induction times. MAS and static NMR experiments on glassy lithium disilicate will be coupled with nucleation studies with the specific goal of determining the kinetics of "short" range order readjustments after structural perturbation. The kinetics of Qn species rearrangements when coupled with the effects of structure on induction times will also indicate the kinetics of the readjustment of cluster distributions (i.e., "medium" range order). In addition to advancing our understanding of the effect of pre-existing structure on induction times, the data obtained should provide a means of determining whether or not a specific measured Qn species distribution at or below Tg reflects an equilibrium state. This is of immediate relevance to the interpretation of the numerous structural data of glasses in the literature and should provide a guide to the preparation of glasses for future structural studies. The award supplement will support a particularly talented female, African-American underg raduate. She will work closely with the PI and a female chemistry professor on all aspects of the project.