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基于水溶性前驱物的火焰合成和生长路径激光诊断
王述浩
学位类型博士
导师丁玉龙
2016-07
学位授予单位中国科学院研究生院
学位授予地点北京
学位专业化学工程
关键词火焰气溶胶法 氧化钨 合成路径 激光诊断 Libs
摘要

火焰气溶胶合成是高效制备纳米材料的典型方法,涉及多相复杂系统反应过程。本文搭建基于水溶性前驱物的火焰气溶胶平台和激光诊断平台,以系列钨基纳米氧化物为合成目标产物,探讨了水溶性前驱物火焰气溶胶合成路径的关键控制因素,并使用激光诊断方法对合成路径予以确认。论文的主要内容和研究结果如下:(1)基于同轴扩散火焰和超声雾化装置,建立基于水溶性前驱物的火焰气溶胶合成平台。通过CFD的模拟,计算优化了温度、停留时间等关键参数,使用PDI修正的Lang公式测算液滴尺寸。对多元金属酸铵盐和硝酸盐等水溶性前驱物进行了热分析以研究分解过程。为了在线检测颗粒生成过程,将光谱仪和ICCD组合,搭建激光诊断平台。(2)采用高温火焰合成了系列氧化钨粉体,研究了前驱物浓度、进料速率、火焰温度和冷却速率等因素对产物形貌、晶型和结晶度的影响,综合前驱物热分解特性,推导液滴在火焰合成中的历程,揭示了扩散速率对高温气相合成中颗粒生长的影响。合成多种氧化物单体及复合材料,证实基于水溶性前驱物的火焰气溶胶平台可靠性。(3)设计不同火焰温度,合成不同形貌的氧化物单体及复合材料,将颗粒的演变过程处理为有限时间升华动力学问题,揭示火焰温度和物质的热物性(饱和蒸气压)的竞争关系对路径选择和产物粒径分布的决定作用。通过密相辅助低通量LIBS方法,认定液滴分别经历“液滴-颗粒”低温路径和“液滴-蒸气-粉体”高温路径。(4)采用火焰气溶胶法直接沉积氧化钨薄膜。通过调整沉积高度,改变液滴到达基板状态,实现不同形态薄膜的快速制备。基于火焰沉积不同阶段的低通量LIBS信号显著不同,设计和预测薄膜结构,揭示了薄膜沉积过程中物质状态于薄膜生长机制。

其他摘要

One of the most promising methods for cost- and material-effective manufacture of nanoparticles is flame aerosol synthesis, which is a complex multiphase process involving many scientific issues. The present work focuses on the synthesis route and the governing factors in flame aerosol synthesis from aqueous solution, via producing nanostructured tungsten-based materials. The contents and conclusion are listed as below:(1) Flame aerosol synthesis reactor was assembled by coupling a co-flow burner and an ultrasonic atomizer. The temperature profile and residence time were determined by CFD method. The droplet size was calculated by Lang’s model and further corrected by measurement with PDI. The thermal analysis of hydrosoluble salt, e.g. ammonium polyoxometalates and nitrate, was carried out to determine the possible transformation of precursors in high temperature environment. To detect the nanoparticles formation process, a laser-based diagnostics system which combines spectrometer and ICCD was built up.(2) A high temperature flame was employed to prepare a series of WO3 powders and to study the effect of precursor concentration, feed rate, and cooling rate on morphology and crystallography. The formation mechanism within the high temperature environment is discussed. The impact of precursor concentration on particle morphology suggested the key role of the competition between nucleation and particle growth.(3) Unitary oxide and composite material were flexibly fabricated by flames with different temperatures. The evolution of particle was considered as an issue of finite-time sublimation dynamics. The competition between flame temperature and vapor pressure determined the selection of pathways and the size distribution of final particles. The dense phase assisted low-fluence LIBS based on oxygen atomic spectrum distinguished the synthesis route between “droplet-particle” and “droplet-vapor-powder”.(4) WO3 films were deposited by flame aerosol synthesis. The structured pattern depended on the stage of the droplet-particle, which could be controlled by adjusting the substrate height above the burner. Experiments show that the low-fluence LIBS signal depending on the droplet-particle stage could be employed to predict films morphologies. The work revealed the relevance among processing conditions, low-fluence LIBS signal, formation mechanism and the film morphology. 

语种中文
文献类型学位论文
条目标识符http://ir.ipe.ac.cn/handle/122111/22878
专题研究所(批量导入)
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GB/T 7714
王述浩. 基于水溶性前驱物的火焰合成和生长路径激光诊断[D]. 北京. 中国科学院研究生院,2016.
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