Processing of Fully-Dense Nanocomposites through Novel Design

燃烧合成是一种制造工艺，它利用加热过程中粉末之间的反应产生的化学能。这种内部产生的化学能可以避免使用高耗能的加热炉，从而减少制造过程中的能源消耗。燃烧合成法已被用于制备许多先进材料，包括陶瓷、金属间化合物和复合材料。到目前为止，除了在制造过程中压制材料和/或使用额外的制造步骤来完全形成材料外，这种燃烧合成的有利方法通常不能生产无气孔的高强度复合材料和纳米复合材料。这些都是额外的能源密集型步骤，成本也很高。该奖项支持基础研究，以设计粉末和粉末压坯，只需一个快速反应步骤就可以形成强大的无孔复合材料和更强的无孔纳米复合材料，从而消除了任何额外的昂贵和能源密集型制造步骤的需要。这将给社会带来巨大的好处，因为使用这种工艺可以生产许多材料，它们在航空航天、汽车、生物医学和能源行业都有应用。这项研究项目涉及代表不足和经济困难的学生参与研究和教育活动，因此工程教育也将受到积极和影响。本研究从新的基础科学角度解决了长期存在的残余孔隙率和不均匀的燃烧合成问题。具体地说，将研究粉末和粉末致密多尺度设计对燃烧合成中致密化和均化机理的影响。对于在反应过程中产生液相的材料，我们将从根本上理解缺陷浓度对纳米复合材料快速合成和均化的影响，无论有没有外场。这项研究将完成一项以前被认为不可能完成的任务，即通过燃烧合成制备全密度或接近全密度的均匀复合材料和纳米复合材料，而无需施加外压或后处理热处理。通过深入的表征和力学性能研究，本研究还将建立这些新材料的加工-组织-性能关系。

Combustion Synthesis is a manufacturing process that utilizes the chemical energy produced from a reaction between powders during heating. Such internally produced chemical energy can avoid the use of an energy-intensive heating furnace, thus reducing energy consumption during manufacturing. Combustion Synthesis has been used to form many advanced materials including ceramics, intermetallics and composites. So far, this advantageous process of combustion synthesis has generally not been capable of producing pore-free high-strength composites and nanocomposites, except by pressing the materials during manufacturing, and/or using an additional manufacturing step to fully form the material. These are extra energy-intensive and costly steps. This award supports fundamental research to design powders and powder compacts which can form strong pore-free composites and stronger pore-free nanocomposites in only one rapid reaction step, thus eliminating the need for any extra costly and energy-intensive manufacturing steps. The benefits to society will be significant, as there are many materials that can be produced using this process, and they have applications in the aerospace, automotive, biomedical and energy industries. The research project involves the participation of underrepresented and economically disadvantaged students in the research and educational activities, thus engineering education will also be positively impacted.  This research tackles the long-standing Combustion Synthesis problems of residual porosity and inhomogeneity from a new fundamental scientific standpoint. Specifically, the influence of powder and powder compact multi-scale design on the densification and homogenization mechanisms in combustion synthesis will be investigated. A fundamental understanding of the effects of defect concentrations on the rapid synthesis and homogenization of nanocomposites with or without external field will be established for materials that generate a liquid phase during the reaction. The research will fulfill a previously thought to be impossible task of producing full or near-full density homogeneous composites and nanocomposites via combustion synthesis without the application of external pressure or post processing heat treatments. Through in-depth characterization and mechanical properties investigations, the research will also establish the processing-microstructure-properties relations for these new materials.