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Dissipation and adhesion in collisions between amorphous FeO nanoparticles
Journal of Aerosol Science ( IF 4.5 ) Pub Date : 2021-01-22 , DOI: 10.1016/j.jaerosci.2020.105742
Baochi D. Doan , Adrienne R. Dove , Patrick K. Schelling

How dust grains aggregate into planetesimals is still an open question. It is experimentally observed that binary collisions between micron-sized dust grains result in adhesion for collisions up to 1 ms−1. However, aggregates at scales 1 mm and above have been shown to exhibit fragmentation or bouncing at relevant collision velocities, resulting in a barrier preventing the formation of larger aggregates. One key factor is the weak adhesion observed between dust particles in aggregates leading to ruptures even in low-velocity collisions. To better understand the structure and strength of the adhered interface resulting from collisions, we performed molecular-dynamics simulations of head-on collisions between amorphous FeO nanoparticles. The results demonstrate several important phenomena which indicate how bonding between aggregates might become stronger than is often observed in experiments. For nanograins, it is shown that strong attractive interactions result in a minimum relative collision speed vc determined just before impact. The values of vc for particle radii 7 nm and below are computed to be in the range 40100 ms−1. This high collision speed is shown to result in strong bond reordering at the interface. Moreover, increasing the incident collision speed vrel is shown to increase the work of adhesion Wadh, which is correlated to substantial bond rearrangement. Specifically, for values of vrel in the range between 1090 ms−1, the interface between adhered grains is structured very closely to perfectly coordinated FeO amorphous solid. The reported results suggest stronger bonding results from collisions between particles with unpassivated surfaces, especially when particles are small, have amorphous surface structures, or when collisions occur at higher relative speeds. These factors should generate aggregates with stronger bonds that are less easily broken in subsequent collisions, and hence might be responsible for aggregates less likely to fragment at larger length scales.



中文翻译:

非晶态FeO纳米粒子之间碰撞中的耗散和粘附

尘粒如何聚集成小行星仍然是一个悬而未决的问题。实验观察到,微米级尘埃颗粒之间的二元碰撞导致粘附力达到1个ms -1。但是,规模聚合1个已经表明,mm以上的材料在相关的碰撞速度下显示出碎裂或弹跳,从而形成阻挡层,防止形成较大的聚集体。一个关键因素是,即使在低速碰撞中,在集料中的尘埃颗粒之间观察到的较弱的粘附力也会导致破裂。为了更好地了解碰撞产生的粘附界面的结构和强度,我们进行了分子动力学模拟,研究了非晶态FeO纳米颗粒之间正面碰撞的情况。结果表明了几个重要现象,这些现象表明聚集体之间的键合可能比实验中经常观察到的更牢固。对于纳米颗粒,显示出强大的吸引力相互作用导致最小的相对碰撞速度vC在冲击之前确定。的值vC 半径为7 nm及以下的粒子的计算范围为 40100ms -1。如此高的碰撞速度显示出可导致界面处强烈的键重排。此外,提高入射碰撞速度v[RË 被证明可以增加粘附力 w ^一个dH,这与大量的键重排有关。具体来说,对于v[RË 介于 1090ms -1,粘附晶粒之间的界面非常紧密地与完美配位的FeO非晶态固体紧密结合。报告的结果表明,具有未钝化表面的粒子之间的碰撞会产生更强的键合效果,尤其是当粒子较小,具有无定形的表面结构时,或者当以较高的相对速度发生碰撞时。这些因素应生成具有更强键合的聚集体,这些聚集体在随后的碰撞中不易断裂,因此可能导致聚集体在较大的长度范围内不太可能破碎。

更新日期:2021-02-02
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