Mechanisms of Nucleation and Crystal Growth of Metal Halide Networks

金属卤化物网络的成核和晶体生长机制

• 批准号: 0705190
• 负责人: James Martin
• 金额: $ 39万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-01-15 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0705190&HistoricalAwards=false
• 关键词: Mechanisms; Nucleation; Crystal; Growth; Metal

This project will use isothermal time and temperature resolved two-dimensional X-ray diffraction (2-D t/TRXRD) techniques to independently measure the rates of intrinsic, and extrinsic nucleation, and crystal growth, as well as to perform simultaneous pair distribution function (PDF) analysis of the crystalline and amorphous fractions. This will be accomplished using high energy X-rays, area detectors with up to 30 Hz time resolution, development of melt-quenching techniques with rates greater than 500/min, and data processing methods to accommodate collection and analysis of massive amounts of data. The studies will be conducted with a series of halide materials that exhibit melting points between room temperature and 350 C, which are temperatures that are readily amenable to the proposed experimental methods. Specifically, the crystallization of clathrated networks (our halozeotypes), probing the crystallization of parent binary condensed phases, and considering step-wise structural ordering through the formation of molecular plastic crystalline phases will be studied. This project will provide invaluable training of students in fundamental scientific discoveries with implications for the atmospheric and geologic sciences as well as for the design and function of advanced materials. %%%Fast time-resolved diffraction techniques are being developed, and facilities at Argonne and Brookhaven National Laboratories are being used to independently measure the rates of crystal nucleation and growth. This work is transforming classical understandings of the mechanisms by which crystals are formed from the molten state. Contrary to the assumptions of classical theory, this project will demonstrate that it is the organization of atomic and molecular level structure in the molten state, rather than surface energy that controls the rate of nucleation and crystal growth. New instrumentation and data processing tools will be developed, and series mechanistic studies performed to develop and refine a new structural-order-driven-crystallization (SODC) theory. Answers from these fundamental mechanistic studies of crystal growth will help decipher mysteries such as ice-crystal growth in clouds which dramatically impact global climates, and will be applicable to the design and function of advanced technologies such as phase change materials utilized for data storage for which understanding of the rapid amorphous-to-crystal transitions will lead to superior performance.

该项目将使用等温时间和温度分辨二维 X 射线衍射 (2-D t/TRXRD) 技术来独立测量内在和外在成核以及晶体生长的速率，并执行同步对分布函数(PDF) 结晶和非晶部分的分析。 这将通过使用高能 X 射线、时间分辨率高达 30 Hz 的区域探测器、速率大于 500/min 的熔化淬火技术的开发以及适应大量数据收集和分析的数据处理方法来实现。 该研究将使用一系列熔点在室温至 350°C 之间的卤化物材料进行，这些温度很容易适用于所提出的实验方法。具体来说，将研究包合物网络（我们的卤沸型）的结晶，探索母体二元凝聚相的结晶，并考虑通过形成分子塑性结晶相的逐步结构排序。该项目将为学生提供宝贵的基础科学发现培训，这些发现对大气和地质科学以及先进材料的设计和功能具有影响。 %%%快速时间分辨衍射技术正在开发中，阿贡国家实验室和布鲁克海文国家实验室的设施正在用于独立测量晶体成核和生长的速率。 这项工作正在改变对熔融态晶体形成机制的经典理解。 与经典理论的假设相反，该项目将证明，控制成核和晶体生长速率的是熔融状态下原子和分子水平结构的组织，而不是表面能。 将开发新的仪器和数据处理工具，并进行一系列机理研究，以开发和完善新的结构有序驱动结晶（SODC）理论。 这些晶体生长基本机制研究的答案将有助于解开诸如云中冰晶生长之类的谜团，这对全球气候产生巨大影响，并将适用于先进技术的设计和功能，例如用于数据存储的相变材料，了解非晶态到晶体的快速转变将带来卓越的性能。