在气相燃烧合成纳米颗粒过程中,温度分布对化学反应、颗粒的团聚和烧结有重要作用;速度分布对前驱体和颗粒的输运、颗粒的温度经历效应和停留时间有不可忽视的影响.为了研究纳米颗粒在火焰中形成和演变的过程以及化学反应和颗粒运动所依赖的温度分布、速度分布,本文在传统热泳取样的基础上提出了一种新的热泳取样 电镜分析方法.该方法在火焰内部同一测点采用热电偶测温和两次时间间隔不同的热泳取样,通过电子显微镜对样品的颗粒沉积状态进行统计和分析,能够得到火焰的温度分布、流动速度分布、颗粒体积分数和颗粒尺度分布.
Multiple parameters from temperature and flow velocity are thus measured in detail to provide the information required for understanding chemistry and particle dynamics processes that include combustion,particle agglomerate/coalescence and diffusion.In order to investigate the temperature and flow velocity of flame more easily and flexibly,this paper puts forward a new method of thermophoretic sampling-scanning electron microscopy image analysis.This method can attain the flame temperature distribution,the velocity distribution,particle volume fraction and the aggregate particle size distribution simultaneously.The basic principle is to measure flame temperature using a fine-wire thermocouple,then to sample particles in the same position of flame for two different exposure time intervals by a thermophoresis probe,then to analyze the SEM images of these samples.
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