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

CAA：Li2O-2SiO2 玻璃中的瞬态成核行为：Q 形态的影响

• 批准号: 9506486
• 负责人: Hanna Nekvasil
• 金额: $ 4.9万
• 依托单位: SUNY at Stony Brook
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1995
• 资助国家: 美国
• 起止时间: 1995-07-15 至 1997-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9506486&HistoricalAwards=false
• 关键词: CAA; Transient; Nucleation; Behavior; Li2O

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.

9506486硅酸盐玻璃中的Nekvasil晶核在地质和材料系统中都具有重要意义。然而，关于预先存在的非晶相结构对硅酸盐熔体和玻璃中均匀成核过程的影响以及导致新的稳态物种分布的动态过程，仍然存在许多重要的问题。这项CAA被要求允许PI开始一个新的研究方向，专注于与熔融和玻璃硅酸盐结晶有关的依赖时间的过程的结构方面。这一方向有力地补充了她之前在熔融硅酸盐中平衡热力学的实验和理论工作。该项目将作为核磁共振光谱学和成核研究的入门，并将在她的第一次休假期间进行。这项拟议的研究特别侧重于评估结构调整的动力学及其对诱导时间的影响。玻璃状二硅酸锂的MAS和静态核磁共振实验将与成核研究相结合，其具体目标是确定结构扰动后“短”范围有序重新调整的动力学。当结合结构对诱导时间的影响时，QN物种重排的动力学也将表明团簇分布的重新调整的动力学(即“中等”范围顺序)。除了促进我们对预先存在的结构对诱导时间的影响的理解外，获得的数据应该提供一种手段来确定特定测量的QN物种分布在Tg或以下是否反映了平衡状态。这与文献中对玻璃的众多结构数据的解释直接相关，并应为今后结构研究的玻璃制备提供指导。该奖项的增刊将支持一位特别有才华的女性，非裔美国人。她将在该项目的各个方面与PI和一名女性化学教授密切合作。