Inter-American Materials Collaboration (CIAM): A Novel Synthesis and Sintering Process for Nanostructured Oxide and Carbide Ceramic Composites

非技术说明：本项目由材料研究部（DMR）和国际科学与工程办公室（OISE）共同资助。它将为学生和高中教师提供制备先进纳米结构复合材料的实验和计算机建模经验。该工艺将用于形成这些复合材料的独特之处在于它能够制备极细的起始粉末，并在较低的温度和较低的压力下将粉末固化成有用的工程部件。较低的温度和压力可以防止粉末的过度生长。因此，复合材料的纳米结构特性可以保留，具有有益的工程意义。有了这样的结构，这些复合材料被假设具有独特的机械性能，这可能在工程应用中被证明是有用的，特别是在需要更强更轻的复合材料的航空航天工业中。通过这个项目，来自参与机构的学生将接受实验技术和计算机模型的培训，从而可以合成和烧结独特的材料。此外，来自当地一所高中的教师将在暑假期间在领导机构参与研究活动和课程计划的制定。技术细节：该项目的目的是研究完全致密的氧化物和碳化物纳米复合材料的独特合成和火花等离子烧结（SPS）。第一个要进行的活动将是使用反胶束工艺合成纳米结构粉末，并在广泛的实验条件下（即，煅烧温度，煅烧时间和水与表面活性剂的比例）对该工艺进行表征，以优化和扩大该工艺。作为实验工作的补充，将开发合成过程的计算机模型，用于预测所制备粉末的最终形状、粒度和晶粒尺寸。随后，将通过火花等离子烧结对纳米结构粉末进行致密化，并在广泛的实验条件下（即压力、温度和致密化时间）进行表征。在致密化过程中，将仔细检查微观结构的发展，以确定纳米粉末的晶粒生长。该项目将在三个方面区别于以往的实验研究：(1)这将是第一个使用超细氧化物和碳化物粉末（在1 - 5纳米范围内）通过SPS烧结获得晶粒尺寸为30纳米及以下的致密物的研究；(2)这将是第一个利用介观方法开发反胶束系统计算机模型的研究，这对于捕捉许多分子类型的特征具有重要价值，这些特征是使用连续介质力学方法或完全原子模型（后者由于计算限制）无法实现的；(3)这将是第一个描述晶粒尺寸小于30纳米的全致密纳米结构致密体的研究，这将允许确定这类材料的机械性能。

Non-technical Description:This project is jointly funded by the Division of Materials Research (DMR) and the Office of International Science and Engineering (OISE). It will provide experimental and computer-modeling experience to students and high school teachers in the preparation of advanced nanostructured composite materials. The uniqueness of the process that will be applied for the formation of these composites lies in its capacity to prepare extremely fine starting powders, and to consolidate the powders into useful engineering components using lower temperatures and lower pressures. The lower temperatures and pressures prevent exaggerated growth of the powders. Hence, the nanostructured character of the composites can be preserved with beneficial engineering implications. With such a structure, these composite materials are hypothesized to possess unique mechanical properties, which may prove useful in engineering applications, particularly in the aerospace industry, where the need for stronger and lighter composite materials is always present. Through this project, students from the participating institutions will be trained in experimental techniques and computer models that will allow the synthesis and sintering of unique materials. In addition, teachers from a local high school will be involved in research activities and development of lesson plans during the summer at the lead institution.Technical Details:The objective of this project is to study the unique synthesis and spark-plasma sintering (SPS) of fully-densified oxide and carbide nanocomposites. The first activity to be undertaken will be the synthesis of nanostructured powders using a reverse micelle process, and the characterization of the process over a wide range of experimental conditions (i.e., temperature of calcination, time of calcination, and water-to-surfactant ratio) in order to optimize and scale-up the process. As a complement to the experimental work, computer models for the synthesis process will be developed that can be used to predict the final shape, particle size, and crystallite size of the powders being prepared. Subsequently, densification of the nanostructured powders via spark-plasma sintering will be undertaken and characterized over a wide range of experimental conditions (i.e., pressure, temperature, and time of densification). The microstructural development during the densification process will be examined carefully to determine grain growth of the nanopowders. The project will distinguish itself from previous experimental studies in three ways: (1) this will be first study that will use ultra-fine oxide and carbide powders (in the 1 - 5 nm range) for sintering via SPS to obtain compacts with grain sizes 30 nm and lower; (2) this will be the first study that will utilize a mesoscopic approach for the development of a computer model of reverse micellar systems, which is of great value for capturing many molecular-type features that are not possible using continuum mechanics approaches or fully atomistic models, the latter due to computational restrictions; and (3) this will be the first study that will characterize fully dense nanostructured compacts with grain sizes below 30 nm, which will allow the determination of mechanical properties in these types of materials.