Crystallization under Nanoscale Confinement

非技术摘要：结晶是美国工业中最大的单元操作之一，对材料科学以及从制药工业到光学和电子材料等依赖固体配方的各种技术部门的进步至关重要。尽管如此，晶体生长仍然是一个鲜为人知的现象。此外，先进技术--从信息存储到能源转换--越来越依赖于纳米尺度的材料设计。这个项目研究了材料在超小纳米尺度孔隙中的结晶，这种孔隙将晶体的大小限制在对关键技术部门至关重要的属性不同于普通的维度。耐火整体中的纳米孔提供的独特环境将用于评估镁盐的性质和反应活性，这些镁盐被认为是火星上的水记录器。由大量纳米晶体组成的独立整体组成的复合材料将被研究，这些材料可以很容易地处理，并预计具有不寻常的性能。该项目还将支持旨在为新兴年轻科学家拓宽STEM渠道的教育活动，包括创建纽约市初中生和高中生团队，他们将参加美国晶体生长大赛，同时开设晶体结构和性能课程。这位首席研究员还将为少数族裔服务机构的教职员工举办一个材料世界研讨会，旨在将新的跨学科课程引入大学课堂，他还将于2019年主办第24届国际有机固态化学会议。这些活动将增强纽约大学材料研究科学与工程中心现有的STEM活动。技术摘要：该项目将研究惰性整体的纳米级孔隙中的结晶，提供一种方法，通过将结晶限制在通常难以研究的长度范围内，缩小成核和生长方面的知识差距。孔尺寸与决定结晶结果的临界尺寸区域相当，提供了一个机会来检查尺寸对结晶过程中多晶型选择性的影响，以及受限晶体的尺寸依赖的多晶型稳定性排名，从而有效地将尺寸作为相图上的变量。该项目将揭开尺寸依赖的热性质、多晶型稳定性排名和从2D X射线衍射估计的临界尺寸之间的对应关系。纳米孔提供了一个理想的环境来研究立体化学助剂对多晶型选择性和稳定性的作用，这被认为涉及在晶体生长的早期阶段结合在初始核的特定晶面上。表征水合镁盐的行为，被限制在孔隙中以模拟相互生长，可能会为火星上最近的水合阶段提供信息。还将探索基于大的定向功能纳米晶体(1010晶体/cm2)系综的独立复合材料，这可以消除对大块单晶的需要。总而言之，该项目将提供急需的洞察成核和晶体生长的关键长度尺度，其中结晶可以是决定性的，同时也提供了一条途径，新的杂化材料。从事这个项目的学生将获得先进的X射线衍射方法、晶体结构分析、多态、分子建模、光谱学和近场显微镜方面的专业知识，他们将接受影响关键技术部门的材料概念方面的培训，包括制药和电子材料。

Non-technical Abstract:Crystallization, one of the largest unit operations in U.S. industry, is critical to the advancement of materials science as well as various technical sectors that rely on solid formulations, from the pharmaceutical industry to optical and electronic materials. Nonetheless, crystal growth remains a poorly understood phenomenon. Moreover, advanced technologies - from information storage to energy conversion - increasingly rely on materials design at the nanometer length scale. This project examines crystallization of materials in ultrasmall nanometer-scale pores that constrain the size of crystals to dimensions where properties that are central to key technological sectors depart from the ordinary. The unique environment provided by the nanopores in refractory monoliths will be used to evaluate the properties and reactivity of magnesium salts, which have been implicated as water reporters on Mars. Composites consisting of large ensembles of nanocrystals in free-standing monoliths that can be handled readily and are anticipated to have unusual properties, will be investigated. The project also will support education activities aimed at widening the STEM pipeline for emerging young scientists, including the creation of teams of NYC middle and high-school students who will compete in the US Crystal Growth Competition, concurrent with a curriculum on structure and properties of crystals. The principal investigator also will operate a Material World workshop for faculty from minority-serving institutions designed to introduce new interdisciplinary curricula to college classrooms, and he will host the 24th biannual International Conference on the Chemistry of the Organic Solid State in 2019. These activities will augment substantial existing STEM activities at the New York University Materials Research Science and Engineering Center.Technical Abstract:This project will investigate crystallization in nanoscale pores of inert monoliths, providing an approach to narrow the knowledge gap in nucleation and growth by confining crystallization at a length scale that typically is impenetrable to study. The pore dimensions are comparable to the critical size regime where crystallization outcomes are determined, providing an opportunity to examine the influence of size on polymorph selectivity during crystallization as well as size-dependent polymorph stability rankings for confined crystals, effectively adding size as a variable on the phase diagram. The project will unravel the correspondence between size-dependent thermal properties, polymorph stability ranking, and critical sizes estimated from 2D X-ray diffraction. The nanosized pores provide an ideal environment to examine the role of stereochemical auxiliaries on polymorph selectivity and stability, which is thought to involve binding at specific crystal faces of incipient nuclei at the early stages of crystal growth. Characterizing the behavior of magnesium salt hydrates, confined in pores to emulate intergrowths, may inform on recent hydrated phases on Mars. Free-standing composite materials based on large ensembles of aligned functional nanocrystals ( 1010 crystals/cm2), which can obviate the need for bulk single crystals, also will be explored. Collectively, the project will provide much-needed insight into nucleation and crystal growth at critical length scales where crystallization can be deterministic while also providing a pathway to new hybrid materials. Students working on this project will acquire expertise in advanced X-ray diffraction methods, crystal structure analysis, polymorphism, molecular modeling, spectroscopy and near-field microscopies, and they will be trained in materials concepts that impact critical technological sectors, including pharmaceutical and electronic materials.