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，对材料科学的进步以及依赖固体配方的各种技术部门（从制药工业到光学和电子材料）至关重要。尽管如此，晶体生长仍然是一个知之甚少的现象。此外，从信息存储到能量转换的先进技术越来越依赖于纳米尺度的材料设计。该项目研究了超小纳米级孔隙中材料的结晶，这些孔隙将晶体的尺寸限制在关键技术领域的核心属性偏离普通的尺寸。耐火材料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性，镁盐被认为是火星上的水报告者。复合材料组成的大合奏的纳米晶体在独立的整料，可以很容易地处理，预计有不寻常的性能，将进行调查。该项目还将支持旨在为新兴的年轻科学家拓宽STEM管道的教育活动，包括创建纽约市初中和高中学生团队，他们将参加美国晶体生长竞赛，同时开设晶体结构和性质课程。首席研究员还将为少数民族服务机构的教师举办材料世界研讨会，旨在向大学课堂介绍新的跨学科课程，他将于2019年举办第24届半年度有机固态化学国际会议。这些活动将加强纽约大学材料研究科学与工程中心现有的大量STEM活动。技术摘要：本项目将研究惰性整料纳米级孔隙中的结晶，通过将结晶限制在通常无法穿透的长度尺度上来研究，提供一种缩小成核和生长知识差距的方法。孔尺寸与确定结晶结果的临界尺寸范围相当，提供了一个机会来检查结晶过程中尺寸对多晶型选择性的影响以及受限晶体的尺寸依赖性多晶型稳定性排名，有效地将尺寸作为相图上的变量。该项目将揭示尺寸依赖的热性能，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。纳米尺寸的孔提供了一个理想的环境来检查立体化学助剂对多晶型物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在初始核的特定晶面处的结合。表征镁盐水合物的行为，限制在孔隙中模仿共生体，可能会告知最近在火星上的水合阶段。也将探索基于大集合的对准功能纳米晶体（1010晶体/cm 2）的自立式复合材料，其可以消除对大块单晶的需要。总的来说，该项目将提供急需的洞察成核和晶体生长在临界长度尺度，结晶可以是确定性的，同时也提供了一种途径，以新的混合材料。 从事该项目的学生将获得先进的X射线衍射方法，晶体结构分析，多态性，分子建模，光谱学和近场显微镜的专业知识，他们将接受影响关键技术领域的材料概念的培训，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.