Morphology analysis of tracks in the aerogels impacted by hypervelocity irregular particles

Ai Du,Ling Wang,Peijian Si,Zhihua Zhang,Hongwei Li,Jun Shen,Bin Zhou,Mingfang Liu,Guangwei Cao,Yi Ma

doi:10.1017/hpl.2020.54

Abstract

Abstract As an attractive collector medium for hypervelocity particles, combined with outstanding physical properties and suitable compositional characteristics, SiO2 aerogel has been deployed on outer space missions and laser shock-loaded collection experiments. In this paper, impact experiments were conducted to understand the penetration process of irregular grains, irregular Al2O3 grains with two different sizes and speeds (~110 μm@7 km/s, ~251 μm@2.3 km/s) at various density silica aerogels. By classifying the shapes of projectile residues and tracks, the morphology of tracks was analyzed. It was observed that there were several kinds of typical tracks in the penetration of irregular grains, accompanied by residues with the shapes of near-sphere, polyhedron, streamlined body wedge, and rotator. The rotational behavior was demonstrated by the final status of one flake projectile as direct evidence. In addition, there was no obvious relationship between the track length and experimental parameters, which may be caused by the uncertain interaction between aerogels and irregular particles. In addition, it confirmed the existence of fragmentation, melting situation by observing the shape of the impact entrance hole. At the same time, optical coherence tomography was used to observe the detail of tracks clearly, which provided a method to characterize the tracks nondestructively.

Highlights

Owing to a hierarchical, nanoporous microstructure and unique properties, aerogel is different from ordinary materials and even considered to be a new state of matter[1]
Filtered by isolation tube, scattering hypervelocity particles were shot by plasma and vertically impacted on aerogel targets with velocities of 2.3 and 7 km/s (Figure 2)
The Stardust track shapes could be classified into three types[10] and quantified according to typical limiting dimensions[12]

Summary

Introduction

Nanoporous microstructure and unique properties, aerogel is different from ordinary materials and even considered to be a new state of matter[1]. Silica aerogel capture cells had been deployed in space missions[4,5]. On the Mir space station, silica aerogels were exposed to and captured successfully hypervelocity particles from both man-made and natural. Kearsley et al.[4] considered the differences may be derived from the complex impactor behavior and aerogel response, so they carried out ground experiments with a diverse suite of projectile particles to demonstrate their hypothesis. The gently curving carrot-shaped tracks observed in aerogel were assigned as being due to the irregular shape of projectiles. This is closer to the actual situation whereby many items of space debris have irregular shapes. It is worthwhile to analyze track morphology of hypervelocity irregular grains in silica aerogel

Results

Discussion

Conclusion