Research Initiation Award: Single Particle Studies of Particle Morphology Evolution During Spray Processing of Inorganic Materials

Timothy Ward CTS-9509394本研究的目的是：(1)促进对由喷涂工艺生产的无机（陶瓷或金属）粉末的物理和化学过程的理解，这些过程控制着颗粒形态（如致密、空心颗粒或多孔）和微观结构（如寻粒或单晶）；(2)利用这种理解来开发和测试策略，以生产几种代表性材料和前驱体类型所需的或避免不需要的形态。基本的实验方法将是利用电动平衡来悬浮单个溶液前体颗粒，然后观察单个颗粒的形态演变，因为温度和/或湿度以受控的方式改变。随着温度的变化（在某些情况下可达800℃或更高），溶剂蒸发、前驱体分解、气体析出、熔化、烧结、蒸发/冷凝等过程有助于最终的形貌和微观结构。利用摄像机和光散射直观跟踪形貌演变，利用摄像机和光散射监测质量变化，利用粒子悬浮电压监测质量变化。将研究单相和多组分/多相颗粒，利用已报道的在喷雾热解合成粉末中产生不同颗粒形态的前驱体。具体来说，将使用硝酸盐、氯化物、有机金属和胶体前体研究金属银和氧化锆。将研究金属/陶瓷复合颗粒（氧化锆/银）和含有挥发性成分（PbO）的多组分混合物。这个项目的结果将能够更好地控制由喷雾工艺生产的材料的颗粒特性。应用喷雾工艺生产的无机材料包括：电子陶瓷（如超导体和铁电体）、富勒烯、纳米材料和复合材料以及金属粉末。＊＊＊

ABSTRACT Timothy Ward CTS-9509394 The objectives of this research are: (1) to advance the understanding of the physical and chemical processes which govern the particle morphology (e.g. dense, hollow particles or porous) and microstructure (e.g. find-grained or single crystal) of inorganic (ceramic or metal) powders produced by spray processes, and (2) to utilize that understanding to develop and test strategies for producing desired, or avoiding undesired, morphologies for several representative materials and precursor types. The basic experimental approach will be to utilize an electrodynamic balance to levitate individual solution precursor particles, and then observe the morphology evolution of the individual particle as the temperature and/or humidity are changed in a controlled fashion. As the temperature is changed (up to 800{SYMBOL 176 \f "Symbol"}C or higher in some cases), solvent evaporation, precursor decomposition, gas evolution, melting, sintering, evaporation/condensation and other processes contribute to the final morphology and microstructure. Morphology evolution will be followed visually using a video camera and light scattering, and mass changes will be monitored using a video camera and light scattering, and mass changes will be monitored using the particle levitation voltage. Both single-phase and multicomponent/multiphase particles will be investigated utilizing precursors which have been reported to yield different particle morphologies in powder synthesis by spray pyrolysis. Specifically, metallic Ag and zirconia will be studied using nitrate, chloride, organometallic and colloidal precursors. Metal/ceramic composite particles (zirconia/silver) and multicomponent mixtures containing a volatile component (PbO) will be investigated. The results of this project will enable better control over particle characteristics in materials produced by spray processes. Inorganic materials which might be good candidates for production by spray processes include: elec tronic ceramics such as superconductors and ferroelectrics, fullerenes, nanophase materials and composites, and metal powders. ***