Ultrasonic de-agglomeration and dispersion of oxides is important for a range of applications. In particular, in liquid metal, this is one of the ways to produce metal-matrix composites reinforced with micron and nano sized particles. The associated mechanism through which the de-agglomeration occurs has, however, only been conceptualized theoretically and not yet been validated with experimental observations. In this paper, the influence of ultrasonic cavitation on SiO₂ and MgO agglomerates (commonly found in lightweight alloys as reinforcements) with individual particle sizes ranging between 0.5 and 10 μm was observed for the first time in-situ using high-speed imaging. Owing to the opacity of liquid metals, a de-agglomeration imaging experiment was carried out in de-ionised water with sequences captured at frame rates up to 50 kfps. In-situ observations were further accompanied by synchronised acoustic measurements using an advanced calibrated cavitometer, to reveal the effect of pressure amplitude arising from oscillating microbubbles on oxide de-agglomeration. Results showed that ultrasound-induced microbubble clusters pulsating chaotically, were predominantly responsible for the breakage and dispersion of oxide agglomerates. Such oscillating cavitation clusters were seen to capture the floating agglomerates resulting in their immediate disintegration. De-agglomeration of oxides occurred from both the surface and within the bulk of the aggregate. Microbubble clusters oscillating with associated emission frequencies at the subharmonic, 1st harmonic and low order ultra-harmonics of the driving frequency were deemed responsible for the breakage of the agglomerates.

氧化物的超声波解聚和分散对于一系列应用很重要。特别是在液态金属中，这是生产用微米和纳米尺寸颗粒增强的金属基复合材料的方法之一。然而，发生解聚的相关机制仅在理论上被概念化，尚未通过实验观察得到验证。本文就超声空化对SiO _{2 的影响}和 MgO 团聚体（常见于轻质合金中作为增强材料），其单个粒径范围在 0.5 到 10 μm 之间，首次使用高速成像原位观察到。由于液态金属的不透明性，在去离子水中进行了解聚成像实验，以高达 50 kfps 的帧速率捕获序列。原位观察进一步伴随着使用高级校准空腔计的同步声学测量，以揭示振荡微泡产生的压力幅度对氧化物解聚的影响。结果表明，超声诱导的微泡簇混乱地脉动，是氧化物团聚体破裂和分散的主要原因。看到这种振荡的空化簇捕获了漂浮的团聚体，导致它们立即分解。氧化物的解聚发生在聚集体的表面和内部。在驱动频率的次谐波、一阶谐波和低阶超谐波处以相关发射频率振荡的微泡簇被认为是造成团聚体破裂的原因。