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

非技术描述：纳米纤维陶瓷是快速增长的工程先进陶瓷的一部分，到2024年，其全球市场预计将达到1340亿美元。陶瓷纳米纤维的直径比通过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、卓越的强度和/或韧性，使它们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支撑、更高效的燃料电池和电池以及更强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，在具有竞争力的生产率和成本下获得多孔或致密的陶瓷结构，同时保持所需的性能。本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-性能关系来解决这些挑战，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，并推动可持续制造技术和商业产品的发展。不同层次（大学和高中）的学生参与了这项研究的各个方面，并正在培养在扩展先进陶瓷和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：本项目研究烧结过程中单个氧化陶瓷纳米纤维的初始孔隙度、结构和排列对微结构和机械性能的影响。正在解决的关键方面包括：如何在烧结过程中保持纳米纤维状态，并引入传统材料无法实现的独特而有用的性能。纳米纤维的结构、孔隙度和相互作用如何影响纤维陶瓷组件的性能。在保持纳米纤维结构的同时所能达到的最大密度。鉴定与纳米纤维形状相关的任何烧结现象。研究活动是用几种具有代表性的氧化陶瓷纳米纤维（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进行的。研究的重点是：(1)在煅烧/烧结过程中，纳米纤维组合中单个纤维行为和纤维-纤维相互作用的影响；（ii）纳米纤维的填充、烧结行为与纳米纤维基陶瓷的最终结构之间的关系；（iii）基于纳米纤维结构的结构/力学性能关系，以及（iv）适用于各种纳米纤维陶瓷系统的构建模型，以解释和预测材料行为。本研究采用一种先进的高产率自由表面静电纺丝方法，大量生产陶瓷前驱体纤维和纤维组件，具有其他方法无法实现的特性。该项目涉及两名攻读博士学位的研究生，每年为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.