Syntactic foams with fly ash cenospheres or commercial microballoons as fillers have been widely used in various applications ranging from aerospace to marine fields and the automotive industry. However, these two extensively adopted fillers possess multiple shortcomings, such as variations in the composition, material degeneration and distinct structural heterogeneity, which will inevitably hamper accurate prediction of the structure–property relationship and the corresponding design of the syntactic foams, reducing material utilization. Here, we present a microfluidic-based approach integrated with a subsequent heat treatment process to engineer syntactic foam fillers with a predefined composition, specified dimensional scope and reduced structural heterogeneity. These fillers are fully guaranteed by the synergy of the flexible and controllable generation of droplet templates with hydrodynamic regulation and rational selection of the nanoparticle dynamic response with respect to the heating temperature. In addition, two distinct surface morphologies have been observed with a temperature demarcation point of 1473 K, further endowing the fillers with multiplicity and optionality, simultaneously laying the foundation to regulate the properties of the syntactic foams through the diversity of the filler selection. Then, we fabricated a syntactic foam specimen by mold casting, and the integrity of the fillers inside was verified using an elaborate buoyancy comparison experiment, exhibiting its potential value in lightweight related applications. As the fillers derived from our approach show significant advantages over conventional ones, they will provide considerable benefits for the regulation and improvement of syntactic foam fillers in many practical applications.

中文翻译：

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通过操纵片上准同心纳米颗粒壳液滴模板制备复合泡沫填料

以粉煤灰空心球或商用微气球为填充剂的复合泡沫塑料已广泛用于从航空航天到海洋领域和汽车工业的各种应用中。但是，这两种被广泛采用的填料具有多个缺点，例如组成变化，材料变性和明显的结构异质性，这将不可避免地妨碍对结构-性能关系的准确预测以及句法泡沫的相应设计，从而降低了材料利用率。在这里，我们提出了一种基于微流体的方法，该方法与后续的热处理工艺相结合，以设计具有预定组成，指定尺寸范围和降低的结构异质性的复合泡沫填料。这些填充物通过液滴模板的灵活可控生成与流体动力学调节的协同作用得到了充分保证，并且相对于加热温度合理选择了纳米颗粒的动力学响应。此外，观察到两种不同的表面形貌，温度分界点为1473 K，进一步赋予了填料多种多样的选择性，同时为通过选择填料的多样性调节复合泡沫的性能奠定了基础。然后，我们通过模铸法制造了一种复合泡沫样品，并通过精心设计的浮力对比实验验证了填充物的完整性，在轻型相关应用中展现了其潜在价值。