Fundamental Studies of Controlled Microstructure Developmentby the Self-Propagating High-Temperature Synthesis Process

自蔓延高温合成过程控制微观结构发展的基础研究

• 批准号: 9114253
• 负责人: Gregory Stangle
• 金额: --
• 依托单位: Alfred University NY State College of Ceramics
• 依托单位国家: 美国
• 项目类别: Continuing grant
• 财政年份: 1992
• 资助国家: 美国
• 起止时间: 1992-02-15 至 1996-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9114253&HistoricalAwards=false
• 关键词: Fundamental; Studies; Controlled; Microstructure; Developmentby

A comprehensive investigation of the preparation of advanced materials by the Self-Propagating High-Temperature Synthesis (SHS) Process will be conducted. (The SHS process is a powder- based process, where at least one of the reactant materials is a finely-divided powder. Two primary classes of SHS reactions are those involving two solids (S/S) and those involving a solid and a gas (G/S); the reactions in both cases are characteristically exothermic. When the reactant mixture is "ignited" at one end, a self-sustaining or self-propagating "combustion wave" proceeds through the packed bed of material, leaving a condensed product or product mixture in its wake.) Enhanced and precise control of the product microstructure is a major goal of this program. The study is expected to identify and quantify key micromechanistic processes which determine the type, size, and distribution of the product phases (as well as the porosity characteristics) in the synthesized material. Activity in this program will focus on the intrinsic reaction kinetics in samples with a well-defined micro-structure. The samples will consist of a metallic or bimetallic foil embedded in an SHS powder mixture. The powder will be ignited in the usual fashion so that both the powder and the foil participate in the SHS reaction. The diffusion, melting, and/or reaction at the foil interface will thus be driven on the same temperature and time scales as a conventional SHS reaction. Thus, a "microstructure" which can be readily characterized will be created, and an idealized large, flat interface will be subjected to the same temperature history as material in a totally powder-based SHS reaction. Diffusion coefficients, reaction kinetic parameters, and resulting phase distributions will all be obtained. Both a solid-solid and a gas-solid system will be studied. A relatively simple model of this idealized configuration will be developed to aid in the extraction of the fundamental kinetic parameters. This study is expected to establish a strong processing-microstructure-material properties relationship; the enhanced fundamental understanding of the interrelationships involved in SHS processing will lead to development of standardized approaches for producing materials with a controlled/tailored microarchitecture. Emphasis in this particular program will be placed on experimental and theoretical studies of the intrinsic kinetics involved; additional tasks regarding other aspects of SHS processing, particularly as applied to production of "functionally gradient" materials will be carried out on a parallel program being funded concurrently by the Army Research Office. Fundamental studies of the detailed mechanisms involved in SHS processing are needed for attainment of the full potential of this novel method for production of advanced materials with unique properties; without such understanding of these mechanisms, production of products with properties optimized for various end uses will remain very difficult and time consuming, with a long learning process having to be repeated for each new application. Fine-tuning the SHS process to produce materials with well-defined (and controlled) composition gradients and/or pore structures will make major contributions to such widely varied applications as catalyst support materials, heat-engine components, porous preforms for composite materials fabrication, disk brakes, high-temperature filter media, high-surface area adsorption materials, piezoelectric devices, and shape-selective separation media.

将对自蔓延高温合成（SHS）工艺制备先进材料进行全面的研究。(The SHS工艺是一种基于粉末的工艺，其中至少一种反应物材料是细粉。SHS反应的两个主要类别是涉及两种固体（S/S）和涉及固体和气体（G/S）的反应;在这两种情况下的反应都是典型的放热反应。当反应物混合物在一端被“点燃”时，自持或自传播的“燃烧波”通过材料的填充床前进，在其尾流中留下冷凝的产物或产物混合物。产品微观结构的增强和精确控制是该计划的主要目标。该研究预计将确定和量化决定合成材料中产品相的类型，尺寸和分布（以及孔隙率特性）的关键微观机械过程。在这个程序中的活动将集中在具有明确的微观结构的样品的内在反应动力学。样品将由嵌入SHS粉末混合物中的金属箔或铝箔组成。粉末将以通常的方式点燃，以便粉末和箔都参与SHS反应。因此，箔界面处的扩散、熔化和/或反应将在与常规SHS反应相同的温度和时间尺度上被驱动。因此，可以容易地表征的“微观结构”将被创建，并且理想化的大的、平坦的界面将经受与完全基于粉末的SHS反应中的材料相同的温度历史。扩散系数，反应动力学参数，和由此产生的相分布都将获得。将研究固-固和气-固系统。一个相对简单的模型，这种理想化的配置将被开发，以帮助提取的基本动力学参数。这项研究预计将建立一个强大的处理微观结构材料性能的关系，加强基本的理解，在SHS处理所涉及的相互关系，将导致开发标准化的方法，生产材料与控制/定制的微结构。在这个特殊的计划的重点将放在实验和理论研究的内在动力学参与;额外的任务有关的SHS处理的其他方面，特别是应用到生产的“功能梯度”材料将进行一个并行的计划，同时由陆军研究办公室资助。需要对SHS处理中涉及的详细机制进行基础研究，以实现这种生产具有独特性能的先进材料的新方法的全部潜力;如果不了解这些机制，生产具有针对各种最终用途优化的性能的产品将仍然非常困难和耗时，必须为每个新应用重复长时间的学习过程。微调SHS工艺以生产具有良好定义的（和受控的）组成梯度和/或孔结构的材料将对诸如催化剂载体材料、热力发动机部件、用于复合材料制造的多孔预成型件、盘式制动器、高温过滤介质、高表面积吸附材料、压电器件和形状选择性分离介质等广泛不同的应用做出重大贡献。