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.

将通过自我传播的高温合成（SHS）过程对先进材料制备进行全面研究。 （SHS过程是一个基于粉末的过程，其中至少一种反应材料是一种细分的粉末。两种主要的sh反应是涉及两个固体（S/S）的反应，涉及固体和气体（g/s）的反应；在这两种情况下，两种情况下的反应是在两种情况下进行的，当反应剂的范围内，或者是一种自发性混合物，或者是“又一次的组合”。材料的床，将凝结的产品或产品混合物留在其之后。）增强和精确的产品微观结构是该程序的主要目标。预计该研究将识别和量化关键的微观力学过程，这些过程确定了合成材料中产物相的类型，大小和分布（以及孔隙率特征）。该程序中的活性将集中在具有明确定义的微结构的样品中的固有反应动力学上。样品将由嵌入SHS粉末混合物中的金属或双金属箔组成。粉末将以通常的方式点燃，以便粉末和箔纸参与SHS反应。因此，箔界面处的扩散，熔化和/或反应将在与常规SHS反应的相同温度和时间尺度上驱动。因此，将很容易表征的“微观结构”将被创建，并且在完全基于粉末的SHS反应中，理想化的大型平坦界面将经历与材料相同的温度病史。将获得扩散系数，反应动力学参数和产生的相分布。将研究固体和气体固体系统。将开发出相对简单的这种理想配置模型，以帮助提取基本动力学参数。预计这项研究将建立强大的处理 - 微观结构 - 材料关系。对SHS处理所涉及的相互关系的增强基本理解将导致开发具有控制/量身定制的微体系结构的材料的标准化方法。该特定程序的重点将放在涉及内在动力学的实验和理论研究上。有关SHS处理的其他方面的其他任务，特别是应用于“功能梯度”材料的生产，将在陆军研究办公室同时同时资助的平行计划上执行。需要对SHS加工所涉及的详细机制的基本研究来实现这种新型方法的全部潜力，以生产具有独特特性的高级材料。如果不理解这些机制，生产具有针对各种最终用途的属性的产品的生产将仍然非常困难和耗时，并且必须为每个新应用重复学习长时间的学习过程。 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.