Synthesis of Composite Particles by Liquid Aerosol Thermolysis

液体气溶胶热解(LAT)是指将液体前体溶液雾化成离散的液滴，然后通过时间/温度/大气调节的反应器传输的一般类型的颗粒合成过程。该计划的总体目标是为液体气溶胶热解合成亚微米复合粒子建立一门基础工程科学。设计了颗粒合成和溶解实验，以确定影响固体复合颗粒形成和化学分布的因素。将使用原位技术监测蒸发阶段液滴的产生和收缩，以此作为雾化、前体溶液特性和蒸发条件的函数。在蒸发阶段之后，将使用在线采样来获得颗粒并表征其随时间和温度的变化。将使用在上述实验中产生的信息对每个工艺步骤进行数学分析，并对照这些工艺的现有或派生模型进行评估。选择了以氧化铝前驱体为基质相的模型体系，首先考察了纳米晶相均匀分散的均匀复合体系的合成，其次考察了一个相包裹另一个相的合成。氧化铝中的氧化锌和铂可以用来研究与均匀沉淀相关的问题，而氧化铝-碳化硅允许我们研究一种相(碳化硅)在另一种相(即晶内)中的分离。所提出的技术旨在生产组成范围宽、结晶度为100 nm、具有所需的均匀性和第二相分布的纳米晶材料。

Liquid aerosol thermolysis (LAT) refers to the general class of particle synthesis processes in which a liquid precursor solution is atomized into discrete droplets and subsequently transported through a time/temperature/atmosphere-regulated reactor. The overall objective of the proposed program is to establish a fundamental engineering science for the synthesis of submicron, composite particles by liquid aerosol thermolysis. Particle synthesis and solution experiments are designed to identify those factors affecting solid composite particle formation and chemical distribution. In situ technique will be used to monitor droplets generation and shrinkage during the evaporation stage as a function of atomization, precursor solution characteristics and evaporation conditions. After the evaporation stage, on-line sampling will be used to obtain and characterize particles as a function of time and temperature. Each process step will be mathematically analyzed using information generated in the above experiments and evaluated against existing or derived models for those processes. Model systems, based on alumina precursors as the matrix phase, have been selected examine first the synthesis of homogeneous composite systems in which the nanocrystalline phases are uniformly dispersed and second, those in which one phase encapsulates the other. Zinconia and platinum in alumina allow use to examine issues associated with uniform precipitation whereas alumina-SiC allows us the possibility to examine the isolation of one phase (SiC) within another (i.e. intragranular). The proposed techniques aim to production of nanocrystalline materials of a wide compositional range and having 100 nm crystallinity, of desired uniformity and second phase distribution.