Nanofiber-Based Ceramic Structures: The Roles of Initial Phases and Microarchitecture

非技术描述：基于纳米纤维的陶瓷是迅速增长的工程高级陶瓷类别的一部分，其市场预计到2024年全球将达到1340亿美元。陶瓷纳米纤维的直径比机械拉伸生产的传统微纤维小一到四个数量级。这些纳米纤维可以表现出独特的特性，如超塑性、增强的可加工性以及优异的强度和/或韧性，使其在下一代陶瓷基复合材料、对各种有害气体和挥发性有机化合物具有高灵敏度和选择性的传感器、改进的催化剂和催化剂载体、更高效的燃料电池和电池以及更强大的牙科复合材料中具有吸引力。然而，纳米纤维基陶瓷技术面临着巨大的挑战，如何在保持所需性能的同时，以具有竞争力的生产率和成本获得多孔或致密的陶瓷结构。该项目通过为选定的纳米纤维陶瓷结构建立关键的工艺-结构-性能-性能关系来应对这些挑战，并建立可应用于各种纳米纤维陶瓷系统的现实模型，以解释和预测材料性能，促进可持续制造技术和商业产品的发展。不同层次的学生(大学和高中)参与了这项研究的方方面面，并正在发展在扩展高级陶瓷及相关研究和制造领域的高度专业化工作所需的动手技能。技术细节：本项目研究了单个氧化物陶瓷纳米纤维在烧结过程中的初始孔隙率、结构和有序性对所产生的微结构和机械性能的影响。正在讨论的关键方面包括：如何在烧结过程中保留纳米纤维状态，以及如何获得传统材料无法实现的独特和有用的性能。纳米纤维的结构、孔隙率和相互作用如何影响纤维状陶瓷组件的性能。在保持纳米纤维结构的同时可以达到的最大密度。识别任何专门与纳米纤维形状相关的烧结现象。研究活动是通过将几种典型的氧化物陶瓷纳米纤维(氧化铝、二氧化硅、氧化锆、镁铝尖晶石及其组合)排列成二维和三维纳米纤维结构来进行的。这项研究的重点是：(I)在烧成/烧结过程中纳米纤维组装过程中单个纤维行为和纤维-纤维相互作用的影响；(Ii)纳米纤维陶瓷的陶瓷纳米纤维填充、烧结行为和最终结构之间的关系；(Iii)所制备的纳米纤维基构件中的结构/力学性能关系；以及(Iv)适用于各种纳米纤维陶瓷系统的建筑模型来解释和预测材料行为。本研究采用一种先进的高产量自由表面电纺丝方法，大量生产陶瓷前驱体纤维和纤维组件，其性能是其他方法所不能达到的。该项目涉及两名博士研究生，每年向至少三名本科生和三名对科学感兴趣的当地高中生提供研究机会。

NON-TECHNICAL DESCRIPTION: Nanofiber-based ceramics are part of a rapidly growing class of engineered advanced ceramics whose market is projected to reach $134 billion worldwide by the year 2024. Ceramic nanofibers have diameters from one to four orders of magnitude smaller than conventional microfibers produced by mechanical drawing. These nanofibers can exhibit unique characteristics such as superplasticity, enhanced machinability, and superior strength and/or toughness that make them attractive for applications in next generation ceramic matrix composites, sensors with high sensitivity and selectivity to various deleterious gases and volatile organic compounds, improved catalysts and catalyst supports, more efficient fuel cells and batteries, and stronger dental composites. However, the technology of nanofiber-based ceramics faces significant challenges in obtaining porous or dense ceramic structures at competitive productivity and cost while preserving the desired properties. This project addresses those challenges through establishing the crucial process-structure-property-performance relationships for selected nanofiber-based ceramic structures, and building the realistic models which can be applied to various nanofibrous ceramic systems to explain and predict the material performance and to advance development of sustainable manufacturing technology and commercial products. Students at different levels (university and high-school) are involved in every aspect of this study and are developing hands-on skills needed for highly specialized jobs in expanding advanced ceramics and associated research and manufacturing domains. TECHNICAL DETAILS: This project investigates the roles of initial porosity, structure and ordering of individual oxide ceramic nanofibers during sintering on the resulting microarchitecture and mechanical properties. The key aspects being addressed include: How the nanofibrous state can be preserved during sintering and lead unique and useful properties not otherwise achievable in traditional materials. How structure, porosity, and interaction of nanofibers affect the properties of a fibrous ceramic assemblies. The maximum density that can be achieved while maintaining the nanofibrous structure. Identification of any sintering phenomena associated exclusively with the nanofiber shape. The research activities are carried out with several representative oxide ceramic nanofibers (alumina, silica, zirconia, Mg-Al spinel, and combinations thereof) arranged into 2-D and 3-D nanofibrous constructs. The research is centered on the investigation of (i) effects of the individual fiber behavior and fiber-fiber interaction in the nanofibrous assembly during calcination/sintering; (ii) relationships between the ceramic nanofiber packing, sintering behavior and final structure of nanofiber-based ceramics; (iii) structure /mechanical property relationships in fabricated nanofiber-based constructs, and (iv) building models that are applicable to various nanofibrous ceramic systems to explain and predict material behavior. An advanced high-yield free-surface electrospinning method is employed in this study to produce the ceramic precursor fibers and fibrous assemblies in sizeable quantities with characteristics not achievable by other methods. The project involves two graduate students on the Ph.D. track and provides the research opportunities on a yearly basis to at least three undergraduate students and three local high-school students interested in science.