Spray-flame synthesis uses low-cost precursors dissolved in organic solvents to produce functional metaloxide nanoparticles. In the spray flame, the precursor-laden droplets show frequent and intense thermally-induced disruption, so-called puffing and micro-explosion. This process is often correlated with high uniformity of particle sizes. Whether puffing and micro-explosion are also directly associated with the formation or release of iron oxide nanoparticles is not clear. Also, the spatiotemporal evolution of nanoparticles in the turbulent flow field of the flame is largely unknown from experiments. We performed simultaneous high-speed microscopic imaging of droplet shadowgraphs at 360 kHz as well as elastic light scattering (ELS) and laser-induced emission (LIE) of nanoparticles at 40 kHz. Comparing ELS and LIE images allows distinguishing signals from droplets, flame, and nanoparticles, as only the nanoparticles will appear in images from both methods. ELS and LIE show nanoparticles as thin narrow filaments, presumably following the local flow. Nanoparticle filaments are found at a height of 50 mm and more above the burner in the spray flame. The filaments show increasing LIE signal and higher confinement with increasing height above the burner. The appearance of LIE and thus nanoparticles does not directly correlate with the presence of droplets or their disruption.

喷雾火焰合成使用溶解在有机溶剂中的低成本前体来生产功能性金属氧化物纳米颗粒。在喷射火焰中，充满前体的液滴表现出频繁而强烈的热诱导破坏，即所谓的膨化和微爆炸。该过程通常与颗粒尺寸的高度均匀性相关。膨化和微爆炸是否也与氧化铁纳米颗粒的形成或释放直接相关尚不清楚。此外，实验中很大程度上未知纳米颗粒在火焰湍流场中的时空演化。我们在 360 kHz 下对液滴阴影图进行同步高速显微成像，并在 40 kHz 下对纳米颗粒进行弹性光散射 (ELS) 和激光诱导发射 (LIE)。比较 ELS 和 LIE 图像可以区分来自液滴、火焰和纳米颗粒的信号，因为两种方法的图像中只会出现纳米颗粒。 ELS 和 LIE 显示纳米颗粒为细窄丝状，可能遵循局部流动。在喷射火焰中，纳米颗粒细丝位于燃烧器上方 50 毫米及以上的高度。随着燃烧器上方高度的增加，灯丝显示出增强的 LIE 信号和更高的限制。 LIE 和纳米颗粒的出现与液滴的存在或其破坏没有直接关系。