Combustion Synthesis of Nanocomposite Materials

本研究重点研究了燃烧条件、各种添加剂和前处理步骤对由纳米粉末反应物形成的完全致密、梯度和随机多孔结构的影响。研究了颗粒大小、混合过程和反应混合物中生成的颗粒的拓扑结构对反应动力学和产物微观结构的影响。这些研究选择了几个放热反应，包括铝/二氧化钛、铝/铌、铝/镍和铝/硅/氮。用热重分析/差示扫描量热法(TGA/DSC)和非等温技术研究了这些反应的反应动力学。此外，还使用了一种新的燃烧诊断方法，该方法使用了门控、增强型CCD摄像机和激光诱导击穿光谱(LIBS)仪器来分析动态温度分布。研究了由反应性纳米粉末组成的体系中的同时燃烧合成和单轴致密化，这些纳米粉末包括铝、硅、氧化镍或铌。全面研究了保护性涂层和其他粒子表面处理对其反应性、燃烧波特性和产物形貌的影响。此外，还对具有梯度组成和/或孔隙率的纳米结构材料的形成进行了基础研究。在外力和/或添加剂内部气化存在的情况下，对体积燃烧(VC)和自蔓延高温合成(SHS)区域的燃烧过程进行了数学建模。通过开发新的和更快的响应技术，应该有助于更好地理解凝聚相体系中的反应动力学。此外，这项研究还应加强对结构材料在强非等温条件下形成的认识。这些研究的结果应该有益于材料科学、燃烧和反应工程领域。该项目为现有的REU Sites项目提供了研究机会，该项目服务于部落学院。这也是与德国和波兰的合作努力的基础。

SUMMARYThis study focuses on the effects of combustion conditions, various additives, and pre-processing steps on the formation of fully dense, graded, and random porous structures derived from nanopowdered reactants. The investigation covers the effects of particle size, mixing procedure, and the topology of the resulting particles in the reacting mixture on reaction kinetics and the microstructure of products. Several exothermic reactions have been selected for these studies including aluminum/titania, aluminum/niobia, aluminum/nickel, and aluminum/silicon/nitrogen. Both thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and nonisothermal techniques are used to evaluate reaction kinetics of these reactions. In addition, a new combustion diagnostic method using a gated, intensified CCD camera and a laser-induced breakdown spectroscopy (LIBS) instrument is used to analyze dynamic temperature profiles. Simultaneous combustion synthesis and uniaxial densification in systems consisting of reactive nanopowders, such as aluminum, silicon, nickel oxide, or niobia, is investigated. Comprehensive studies of the effect of protective coatings and other particle surface treatments on their reactivity, combustion wave characteristics, and the morphology of resulting products are performed. Also done are fundamental studies of the formation of nanostructural materials with graded composition and/or porosity. The dynamics of combustion processes in both volume combustion (VC) and self-propagating high-temperature synthesis (SHS) regimes in the presence of external forces and/or internal gasification of additives are modeled mathematically.Broader impact Experimental research studies, by development of new and faster response techniques, should lead to better understanding of reaction kinetics in condensed phase systems. In addition, the research should enhance the knowledge of the formation of structural materials under strongly non-isothermal conditions. Findings from these research studies should be beneficial to materials science, combustion, and reaction engineering communities. This project provides research opportunities for an existing REU Sites program that serves tribal colleges. It also underlies cooperative efforts with Germany and Poland.